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Find video protocols related to scientific articles indexed in Pubmed.
Air etalon facilitated simultaneous measurement of group refractive index and thickness using spectral interferometry.
Appl Opt
PUBLISHED: 11-18-2014
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A simple method based on air etalons of a transparent cavity is proposed to simultaneously measure the group refractive index and thickness of a transparent optical plate by spectral domain low coherence interferometry. In this method, only a single beam path is needed in contrast to the two beam paths, the reference and sample arms, of the conventional Michelson interferometer. An empty cavity is first constructed in the beam path by two glass plates. Then the transparent plate under test is inserted into the cavity, so that two air gaps are formed in the cavity. A beam of light of low coherence length is then transmitted through the cavity in the normal direction. Measurements of the reflected waves by the air gaps before and after the sample plate is put into the cavity allow us to determine the group refractive index (ng) and thickness (d) of the sample simultaneously. The relative precision of the results for d and ng are both approximately 7×10-4.
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On the non-closure of particle backscattering coefficient in oligotrophic oceans.
Opt Express
PUBLISHED: 11-18-2014
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Many studies have consistently found that the particle backscattering coefficient (bbp) in oligotrophic oceans estimated from remote-sensing reflectance (Rrs) using semi-analytical algorithms is higher than that from in situ measurements. This overestimation can be as high as ~300% for some oligotrophic ocean regions. Various sources potentially responsible for this discrepancy are examined. Further, after applying an empirical algorithm to correct the impact from Raman scattering, it is found that bbp from analytical inversion of Rrs is in good agreement with that from in situ measurements, and that a closure is achieved.
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Ligand replacement induced chemiluminescence for selective detection of an organophosphorus pesticide using bifunctional Au-Fe3O4 dumbbell-like nanoparticles.
Chem. Commun. (Camb.)
PUBLISHED: 11-07-2014
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A facile ligand replacement induced chemiluminescence method is developed for selective detection of the organophosphorus pesticide parathion-methyl based on the use of bifunctional Au-Fe3O4 dumbbell-like nanoparticles to overcome the interference from coexisting substances in a real sample.
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Total Synthesis of Tricladins A and B and Identification of Their Absolute Configuration.
J. Org. Chem.
PUBLISHED: 11-07-2014
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A concise synthesis of both (S)- and (R)-enantiomers of tricladins A and B from l-Boc alanine was achieved. The diastereomeric intermediates were separated by chiral column chromatography, and the absolute configuration of the 2-position was assigned by observed NOE interactions with the known stereogenic center at the 5-position. By comparison of all synthesized final enantiomers with the corresponding natural products, we concluded that the natural tricladins A and B must have the (R)-configuration.
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Label-Free Surface-Enhanced Raman Scattering Imaging to Monitor the Metabolism of Antitumor Drug 6-Mercaptopurine in Living Cells.
Anal. Chem.
PUBLISHED: 11-06-2014
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The molecular processes of drugs from cellular uptake to intracellular distribution as well as the intracellular interaction with the target molecule are critically important for the development of new antitumor drugs. In this work, we have successfully developed a label-free surface-enhanced Raman scattering (SERS) technique to monitor and visualize the metabolism of antitumor drug 6-mercaptopurine in living cells. It has been clearly demonstrated that Au@Ag NPs exhibit an excellent Raman enhancement effect to both 6-mercaptopurine and its metabolic product 6-mercaptopurine-ribose. Their different ways to absorb at the surface of Au@Ag NPs lead to the obvious spectral difference for distinguishing the antitumor drug and its metabolite by SERS spectra. The Au@Ag NPs can easily pass through cell membranes in a large amount and sensitively respond to the biological conversion of 6-mercaptopurine in tumor cells. The Raman imaging can visualize the real-time distribution of 6-mercaptopurine and its biotransformation with the concentrations in tumor cells. The SERS-based method reported here is simple and efficient for the assessments of drug efficacy and the understanding of the molecular therapeutic mechanism of antitumor drugs at the cellular level.
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Selective Fluorescence Turn-On and Ratiometric Detection of Organophosphate Using Dual-Emitting Mn-Doped ZnS Nanocrystal Probe.
Anal. Chem.
PUBLISHED: 10-31-2014
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Semiconductor nanocrystals (NCs) possess unique photoluminescent properties which can be used to design fluorescence probes for chemo/biosensing applications. Several have recently emerged that offer excellent turn-on or ratiometric fluorescence chemosensory protocols by sophisticated procedures, but it has been challenging to realize all of these advantages in a single construct. Herein, we develop an intrinsic dual-emitting Mn-doped ZnS nanocrystal-based probe that achieves this goal with turn-on and ratiometric fluorescence response for the determination of organophosphate (diethylphosphorothioate, DEP). The probe relies on the modification of dopamine dithiocarbamate on the surface of NCs and the modulation of dual emission through a photoinduced electron transfer process, which makes use of red fluorescence of Mn(2+) ions doped in the NCs as specific recognition for the target analyte and blue defect emission of the NCs as stable internal reference. In presence of DEP, the red emission of the probe is thus enhanced by switching off the electron transfer pathway, while the blue emission is almost unchanged. With the addition of different amounts DEP, the two emission intensity ratios gradually vary and display color changes from dark-blue to purple to red. Thus, this method generates turn-on and ratiometric fluorescence signals for quantitative and visual detection of the analyte. Significantly, the dual-emitting probe has been used to fabricate paper-based test strips for visual detection of DEP residues, which validate the method for its rapid, on-site, and visual identification.
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Fluorescent Nanohybrid of Gold Nanoclusters and Quantum Dots for Visual Determination of Lead Ions.
ACS Appl Mater Interfaces
PUBLISHED: 10-31-2014
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Highly green emissive gold nanoclusters (Au NCs) are synthesized using glutathione as a stabilizing agent and mercaptopropionic acid as a ligand, and the intensity of fluorescence is specifically sensitive to lead ions. We then fabricated a ratiometric fluorescence nanohybrid by covalently linking the green Au NCs to the surface of silica nanoparticles embedded with red quantum dots (QDs) for on-site visual determination of lead ions. The green fluorescence can be selectively quenched by lead ions, whereas the red fluorescence is inert to lead ions as internal reference. The different response of the two emissions results in a continuous fluorescence color change from green to yellow that can be clearly observed by the naked eyes. The nanohybrid sensor exhibits high sensitivity to lead ions with a detection limit of 3.5 nM and has been demonstrated for determination of lead ions in real water samples including tap water, mineral water, groundwater, and seawater. For practical application, we dope the Au NCs in poly(vinyl alcohol) (PVA) film and fabricate fluorescence test strips to directly detect lead ions in water. The PVA-film method has a visual detection limit of 0.1 ?M, showing its promising application for on-site identification of lead ions without the need for elaborate equipment.
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Interference enhancement in spectral domain interferometric measurements on transparent plate.
Appl Opt
PUBLISHED: 10-17-2014
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In spectral domain interferometry, the interference signal generated by directly reflected waves from the two surfaces of a sample plate under test is greatly enhanced by the blockage of those light waves reflected by the two arm mirrors in the Michelson interferometer. This sample surface-reflected interference signal, being the optical path length of the plate, is therefore identifiable directly from the Fourier-transformed interference spectrum. Consequently, the group refractive index and physical thickness of the plate can be obtained simultaneously without any prior information of them. Moreover, subsequent in situ angular scanning on the interference spectra helps to retrieve the wavelength-dependent phase refractive index and first-order dispersion. The order of magnitude of the relative error for the group refractive index is 10-4, while that for the phase refractive index and the physical thickness is 10-3.
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Intervention of death-associated protein kinase 1-p53 interaction exerts the therapeutic effects against stroke.
Stroke
PUBLISHED: 08-19-2014
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Death-associated protein kinase 1 (DAPK1) interacts with the tumor suppressor gene p53 via a direct binding of a death domain of DAPK1 to a DNA-binding motif (DM) of p53 (p53DM) and converges multiple cell death pathways in stroke. The goals of this study are to determine whether disruption of DAPK1-p53 interaction is therapeutically effective against stroke.
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Optical imaging in an Alzheimer's mouse model reveals amyloid-?-dependent vascular impairment.
Neurophotonics
PUBLISHED: 08-19-2014
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Alzheimer's disease (AD) and cerebrovascular disease are often comorbid conditions, but the relationship between amyloid-? and in vivo vascular pathophysiology is poorly understood. We utilized a multimodal, multiscale optical imaging approach, including spatial frequency domain imaging, Doppler optical coherence tomography, and confocal microscopy, to quantify AD-dependent changes in a triple transgenic mouse model (3xTg-AD) and age-matched controls. From three months of age (naïve) to 20 months (severe AD), the brain tissue concentration of total and oxy-hemoglobin (Total Hb, ctO2Hb) decreased 50 and 70%, respectively, in 3xTg-AD mice. Compared to age-matched controls, significant differences in brain hemoglobin concentrations occurred as early as eight months (Total Hb: 126 ± 5 ?M versus 108 ± 4 ?M; ctO2Hb: 86 ± 5 ?M versus 70 ± 3 ?M; for control and AD, respectively). These changes were linked to a 29% vascular volume fraction decrease and 35% vessel density reduction in the 20-month-old 3xTg-AD versus age-matched controls. Vascular reduction coincided with increased brain concentration of amyloid-? protein, vascular endothelial growth factor (VEGF), and endothelial nitric oxide synthase (eNOS) at eight and 20 months compared to the three-month baseline. Our results suggest that amyloid-? blocks the normally reparative effects of upregulated VEGF and eNOS, and may accelerate in vivo vascular pathophysiology in AD.
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Neo-Fused Hexaphyrin: A Molecular Puzzle Containing an N-Linked Pentaphyrin.
Angew. Chem. Int. Ed. Engl.
PUBLISHED: 08-15-2014
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The first neo-confused hexaphyrin(1.1.1.1.1.0) was synthesized by oxidative ring closure of a hexapyrrane bearing two terminal "confused" pyrroles. The new compound displays a folded conformation with a short interpyrrolic C???N distance of 3.102 Å, and thus it readily underwent ring fusion to afford a neo-fused hexaphyrin with an unprecedented 5,5,5,7-tetracyclic ring structure. Furthermore, coordination of Cu(II) triggered a ring opening/contracting reaction to afford a Cu(II) complex of an N-linked pentaphyrin derivative. The roles of reactive N?C bonds in the porphyrinoid macrocycles were demonstrated.
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Impact of sludge cation distribution pattern on its filterability in membrane bioreactor.
Bioresour. Technol.
PUBLISHED: 08-15-2014
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The distributions of cations of various valences (Na(+), Ca(2+) and Fe(3+)) in the outer layers of extracellular polymeric substances (EPSs) to pellet have a significant impact on the stratification structure of polysaccharides (PS) or proteins (PN) in activated sludge. Comparison with the control showed that the monovalent Na(+) reduced flocculability slightly (about 9.75%), whereas Ca(2+) and Fe(3+) increased flocculability significantly. The modified fouling index (MFI) had a significant correlation with PN in the supernatant (rp=0.8593), slime (rp=0.7218) and loosely bound EPS (LB, rp=0.8012). However, it had a moderate correlation with PS in supernatant (rp=0.5842), and weak correlation to slime (rp=0.3785) or LB (rp=0.3219). There was an ignored correlation with PN or PS in the tightly bound EPS (TB) or pellet. The lower amount of PN or PS in the supernatant would have positive impact on improving the activated sludge filterability.
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Electrochemistry and catalytic properties for dioxygen reduction using ferrocene-substituted cobalt porphyrins.
Inorg Chem
PUBLISHED: 07-28-2014
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Cobalt porphyrins having 0-4 meso-substituted ferrocenyl groups were synthesized and examined as to their electrochemical properties in N,N'-dimethylformamide (DMF) containing 0.1 M tetra-n-butylammonium perchlorate as a supporting electrolyte. The examined compounds are represented as (Fc)n(CH3Ph)(4-n)PorCo, where Por is a dianion of the substituted porphyrin, Fc and CH3Ph represent ferrocenyl and/or p-CH3C6H4 groups linked at the four meso-positions of the macrocycle, and n varies from 0 to 4. Each porphyrin undergoes two reversible one-electron reductions and two to six one-electron oxidations in DMF, with the exact number depending upon the number of Fc groups on the compound. The first electron addition is metal-centered to generate a Co(I) porphyrin. The second is porphyrin ring-centered and leads to formation of a Co(I) ?-anion radical. The first oxidation of each Co(II) porphyrin is metal-centered to generate a Co(III) derivative under the given solution conditions. Each ferrocenyl substituent can also be oxidized by one electron, and this occurs at more positive potentials. Each compound was investigated as a catalyst for the electoreduction of dioxygen when adsorbed on a graphite electrode in 1.0 M HClO4. The number of electrons transferred (n) during the catalytic reduction was 2.0 for the three ferrocenyl substituted compounds, consistent with only H2O2 being produced as a product of the reaction. Most monomeric cobalt porphyrins exhibit n values between 2.6 and 3.1 under the same solution conditions, giving a mixture of H2O and H2O2 as a reduction product, although some monomeric porphyrins can give an n value of 4.0. Our results in the current study indicate that appending ferrocene groups directly to the meso positions of a porphyrin macrocycle will increase the selectivity of the oxygen reduction, resulting in formation of only H2O2 as a reaction product. This selectivity of the electrocatalytic oxygen reduction reaction is explained on the basis of steric hindrance by the ferrocene substituents which prevent dimerization.
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High-speed Intravascular Photoacoustic Imaging of Lipid-laden Atherosclerotic Plaque Enabled by a 2-kHz Barium Nitrite Raman Laser.
Sci Rep
PUBLISHED: 07-09-2014
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Lipid deposition inside the arterial wall is a key indicator of plaque vulnerability. An intravascular photoacoustic (IVPA) catheter is considered a promising device for quantifying the amount of lipid inside the arterial wall. Thus far, IVPA systems suffered from slow imaging speed (~50?s per frame) due to the lack of a suitable laser source for high-speed excitation of molecular overtone vibrations. Here, we report an improvement in IVPA imaging speed by two orders of magnitude, to 1.0?s per frame, enabled by a custom-built, 2-kHz master oscillator power amplifier (MOPA)-pumped, barium nitrite [Ba(NO3)2] Raman laser. This advancement narrows the gap in translating the IVPA technology to the clinical setting.
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Sulindac attenuates valproic acid-induced oxidative stress levels in primary cultured cortical neurons and ameliorates repetitive/stereotypic-like movement disorders in Wistar rats prenatally exposed to valproic acid.
Int. J. Mol. Med.
PUBLISHED: 07-06-2014
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Accumulating evidence suggests that anti-inflammatory agents and antioxidants have neuroprotective properties and may be beneficial in the treatment of neurodevelopental disorders, such as autism. In the present study, the possible neuroprotective properties of sulindac, a non-steroidal anti-inflammatory drug (NSAID), were investigated in vitro using cultured cortical neurons with valproic acid (VPA)-induced neurotoxicity, as well as in vivo through the behavioral analysis of rats prenatally exposed to VPA as a model of autism. VPA induced 4-hydroxynonenal (4-HNE) expression, reactive oxygen species (ROS) generation and decreased cell viability in primary cultured cortical neurons established from timed-pregnant (embryonic day 18) Wistar rat pups. However, co-incubation of the neurons with VPA and sulindac reduced oxidative stress and increased cell viability. The rats were administered an intraperitoneal injection with one of the following: VPA, sulindac, VPA and sulindac, or physiological saline, and their offspring were subjected to the open field test. During the test trials, repetitive/stereotypic-like movements for each rat were recorded and analyzed. The results revealed that treatment with both sulindac and VPA reduced the VPA-induced repetitive/stereotypic-like activity and the sulindac and VPA-treated animals responded better in the open field test compared to the VPA-treated animals. The results from the present study demonstrate that the antioxidant properties of sulindac may prove to be beneficial in the treatment of autism, suggesting that the upregulation of the Wnt/?-catenin signaling pathway disrupts oxidative homeostasis and facilitates susceptibility to autism.
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cRGD-conjugated magnetic-fluorescent liposomes for targeted dual-modality imaging of bone metastasis from prostate cancer.
J Liposome Res
PUBLISHED: 06-25-2014
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Abstract We reported the development of multifunctional liposomes as a dual-modality probe to facilitate targeted magnetic resonance and fluorescent imaging of bone metastasis from advanced cancer. Multifunctional liposomes consisted of liposomes as a carrier, hydrophobic CdSe QDs in phospholipid bilayer, hydrophilic iron oxide nanoparticles in interior vesicle, lipid-PEG derivative on the surface and cRGDyk peptide conjugated to distal ends of lipid-PEG derivative. Excellent stability, effective detection signal, low toxicity, high resistance to phagocytosis by macrophages and good specificity to tumor of multifunctional liposomes were confirmed by in vitro characterization. The in vivo results demonstrated that multifunctional liposomes accumulated mainly in tumor and liver, indicating that targeted dual-modality imaging was achieved, and the results from two kinds of modalities were consistent and complementary. These findings provide a helpful strategy for detection of bone metastases in a more effective manner for initiation of appropriate therapy.
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Spectral interdependence of remote-sensing reflectance and its implications on the design of ocean color satellite sensors.
Appl Opt
PUBLISHED: 06-13-2014
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Using 901 remote-sensing reflectance spectra (R(rs)(?), sr?¹, ? from 400 to 700 nm with a 5 nm resolution), we evaluated the correlations of R(rs)(?) between neighboring spectral bands in order to characterize (1) the spectral interdependence of R(rs)(?) at different bands and (2) to what extent hyperspectral R(rs)(?) can be reconstructed from multiband measurements. The 901 R(rs) spectra were measured over a wide variety of aquatic environments in which water color varied from oceanic blue to coastal green or brown, with chlorophyll-a concentrations ranging from ~0.02 to >100??mg??m?³, bottom depths from ~1??m to >1000??m, and bottom substrates including sand, coral reef, and seagrass. The correlation coefficient of R(rs)(?) between neighboring bands at center wavelengths ?(k) and ?(l), r(??)(?(k), ?(l)), was evaluated systematically, with the spectral gap (??=?(l)-?(k)) changing between 5, 10, 15, 20, 25, and 30 nm, respectively. It was found that r(??) decreased with increasing ??, but remained >0.97 for ???20??nm for all spectral bands. Further, using 15 spectral bands between 400 and 710 nm, we reconstructed, via multivariant linear regression, hyperspectral R(rs)(?) (from 400 to 700 nm with a 5 nm resolution). The percentage difference between measured and reconstructed R(rs) for each band in the 400-700 nm range was generally less than 1%, with a correlation coefficient close to 1.0. The mean absolute error between measured and reconstructed R(rs) was about 0.00002??sr?¹ for each band, which is significantly smaller than the R(rs) uncertainties from all past and current ocean color satellite radiometric products. These results echo findings of earlier studies that R(rs) measurements at ~15 spectral bands in the visible domain can provide nearly identical spectral information as with hyperspectral (contiguous bands at 5 nm spectral resolution) measurements. Such results provide insights for data storage and handling of large volume hyperspectral data as well as for the design of future ocean color satellite sensors.
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?-conjugated carbon radicals at graphene oxide to initiate ultrastrong chemiluminescence.
Angew. Chem. Int. Ed. Engl.
PUBLISHED: 05-15-2014
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Graphene oxide has widely been employed in various fields, but its structure and composition has still not been fully understood. Here we report that freshly prepared graphene oxide exhibits a large number of ?-conjugated carbon radicals at its ?-network plane, which result from the addition reaction of hydroxyl radicals from H2O2 onto the conjugated double bonds of graphene oxide. The ?-conjugated carbon radicals can directly initiate the long-lasting visible chemiluminescence of luminol, which is even stronger than that obtained when horseradish peroxidase and H2O2 are used. Previously, graphene oxide was mainly reported to be a quencher of chemiluminescence instead. Remarkably, the reacted radicals can be regenerated, thereby enabling the repetitive initiation of chemiluminescence by re-treatment of graphene oxide. The results reported here provide a new understanding of the structure, properties, and applications of graphene oxide.
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Upconversion nanoparticles for ratiometric fluorescence detection of nitrite.
Analyst
PUBLISHED: 05-07-2014
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We have developed a selective upconversion switching method for the ratiometric fluorescence detection of nitrite using upconversion nanoparticles (UCNPs) and an efficient nitrite reaction. The green emission (?(em) = 539 nm) of NaYF4:Yb(3+),Er(3+) nanoparticles can be selectively quenched by the neutral red (NR) dye due to the spectral overlap between the emission at 539 nm and the absorption of NR, while its red emission (?(em) = 654 nm) remains unchanged. Nitrite reacts specifically and strongly with NR to form diazonium salt and lose the diazonium group, which sharply decreases the absorption of NR. Thus, the green emission of NaYF4:Yb(3+),Er(3+) can be recovered by increasing the amount of nitrite, leading to visible color changes from red to orange-yellow and finally green under excitation at 980 nm. The increase in the ratio of emission intensities (I539/I654) is quantitatively correlated to the concentration of nitrite ions. Moreover, the developed method has been successfully applied to nitrite detection in real samples such as drinking water, natural water and meat foods. In particular, the upconversion sensors can efficiently avoid background optical interference and thus show potential for the detection of nitrite salts in complex samples.
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Integrated IVUS-OCT Imaging for Atherosclerotic Plaque Characterization.
IEEE J Sel Top Quantum Electron
PUBLISHED: 04-29-2014
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For the diagnosis of atherosclerosis, biomedical imaging techniques such as intravascular ultrasound (IVUS) and optical coherence tomography (OCT) have been developed. The combined use of IVUS and OCT is hypothesized to remarkably increase diagnostic accuracy of vulnerable plaques. We have developed an integrated IVUS-OCT imaging apparatus, which includes the integrated catheter, motor drive unit, and imaging system. The dual-function imaging catheter has the same diameter of current clinical standard. The imaging system is capable for simultaneous IVUS and OCT imaging in real time. Ex vivo and in vivo experiments on rabbits with atherosclerosis were conducted to demonstrate the feasibility and superiority of the integrated intravascular imaging modality.
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MicroRNA-1 in Cardiac Diseases and Cancers.
Korean J. Physiol. Pharmacol.
PUBLISHED: 04-15-2014
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MicroRNAs (miRs) are endogenous ?22-nt non-coding RNAs that participate in the regulation of gene expression at post-transcriptional level. MiR-1 is one of the muscle-specific miRs, aberrant expression of miR-1 plays important roles in many physiological and pathological processes. In this review, we focus on the recent studies about miR-1 in cardiac diseases and cancers. The findings indicate that miR-1 may be a novel, important biomarker, and a potential therapeutic target in cardiac diseases and cancers.
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Speckle reduction in optical coherence tomography images based on wave atoms.
J Biomed Opt
PUBLISHED: 04-09-2014
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Optical coherence tomography (OCT) is an emerging noninvasive imaging technique, which is based on low-coherence interferometry. OCT images suffer from speckle noise, which reduces image contrast. A shrinkage filter based on wave atoms transform is proposed for speckle reduction in OCT images. Wave atoms transform is a new multiscale geometric analysis tool that offers sparser expansion and better representation for images containing oscillatory patterns and textures than other traditional transforms, such as wavelet and curvelet transforms. Cycle spinning-based technology is introduced to avoid visual artifacts, such as Gibbs-like phenomenon, and to develop a translation invariant wave atoms denoising scheme. The speckle suppression degree in the denoised images is controlled by an adjustable parameter that determines the threshold in the wave atoms domain. The experimental results show that the proposed method can effectively remove the speckle noise and improve the OCT image quality. The signal-to-noise ratio, contrast-to-noise ratio, average equivalent number of looks, and cross-correlation (XCOR) values are obtained, and the results are also compared with the wavelet and curvelet thresholding techniques.
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Selective visual detection of trace trinitrotoluene residues based on dual-color fluorescence of graphene oxide-nanocrystals hybrid probe.
Analyst
PUBLISHED: 03-27-2014
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Herein, for the detection of highly explosive 2,4,6-trinitrotoluene (TNT) instantly and on-site, a fluorescence ratiometric probe using a dual-emission nanohybrid has been developed. The nanohybrid comprises blue-colored fluorescent graphene oxide (FGO) being conjugated with red-emitting manganese-doped ZnS nanocrystals (ZnS:Mn NCs), the latter being functionalized with hexamethylenediamine. The blue fluorescence of FGO is insensitive to TNT and is used as an internal reference, whereas the red fluorescence of ZnS:Mn NCs can be selectively quenched by TNT through electron transfer, resulting in a unique red-purple-blue color response as the amount of TNT is increased. Thus, the probe could be used for the quantitative measurement of TNT based on the fluorescence ratiometric method. We demonstrated that the nanohybrid probe exhibited high visual detection sensitivity and reliability in comparison with single-color fluorescence quenching probes. A fluorescence test paper was prepared using the nanohybrid probe and was demonstrated to detect TNT residues directly on various surfaces including rubber, a person's fingers and manila envelopes with a visual detection limit as low as 5.68 ng mm(-2), showing its promising application for security screening.
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Highly sensitive and selective fluorescence detection of copper (II) ion based on multi-ligand metal chelation.
Talanta
PUBLISHED: 03-22-2014
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A fluorescent probe was synthesized and demonstrated to be highly selective and sensitive in the reaction with copper (II) ion, generating a large variation of the fluorescence intensity in a dose-response manner. The probe contains a dansyl moiety as fluorophore and a multidentate ligand for copper (II) ion recognition. The reaction of the molecular probe with copper (II) ion proceeds rapidly and irreversibly in a 1 to 1 stoichiometric way, leading to the production of stable copper (II) complex, which subsequently results in the quenching of fluorescence. The detection limit for copper (II) ion was measured to be about 2ppb. It was also shown that the probe has high selectivity for copper (II) ion and good anti-interference ability against other transition metal ions. The herein reported very simple and reliable fluorescence probe could be employed for copper (II) ion detection in many aspects.
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Inkjet-printed silver nanoparticle paper detects airborne species from crystalline explosives and their ultratrace residues in open environment.
Anal. Chem.
PUBLISHED: 03-18-2014
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An electronic nose can detect highly volatile chemicals in foods, drugs, and environments, but it is still very much a challenge to detect the odors from crystalline compounds (e.g., solid explosives) with a low vapor pressure using the present chemosensing techniques in such way as a dog's olfactory system can do. Here, we inkjet printed silver nanoparticles (AgNPs) on cellulose paper and established a Raman spectroscopic approach to detect the odors of explosive trinitrotoluene (TNT) crystals and residues in the open environment. The layer-by-layer printed AgNP paper was modified with p-aminobenzenethiol (PABT) for efficiently collecting airborne TNT via a charge-transfer reaction and for greatly enhancing the Raman scattering of PABT by multiple spectral resonances. Thus, a Raman switch concept by the Raman readout of PABT for the detection of TNT was proposed. The AgNPs paper at different sites exhibited a highly uniform sensitivity to TNT due to the layer-by-layer printing, and the sensitive limit could reach 1.6 × 10(-17) g/cm(2) TNT. Experimentally, upon applying a beam of near-infrared low-energy laser to slightly heat (but not destruct) TNT crystals, the resulting airborne TNT in the open environment was probed at the height of 5 cm, in which the concentration of airborne species was lower than 10 ppt by a theoretical analysis. Similarly, the odors from 1.4 ppm TNT in soil and 7.2, 2.9, and 5.7 ng/cm(2) TNT on clothing, leather, and envelope, respectively, were also quickly sensed for 2 s without destoying these inspected objects.
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Assessment of early occlusal caries pre- and post-sealant application--an imaging approach.
Lasers Surg Med
PUBLISHED: 03-16-2014
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Clinicians have difficulty assessing and monitoring early occlusal caries. Traditional clinical exam and radiographs are unable to detect the subtle alterations in enamel indicative of de- or re-mineralization, particularly under dental sealants. Although clinicians have used laser fluorescence (LF) to address this gap, this modality has demonstrated weak correlation with histology. The International Caries Detection and Assessment System (ICDAS-II) has demonstrated high sensitivity and specificity for caries detection, but since it is based on visual assessment, it is of no use in areas beneath the most commonly used dental sealants which are opaque. Optical coherence tomography (OCT) is an emergent assessment tool which has demonstrated great promise in detecting and quantifying caries, including areas beneath commonly used dental sealants and composites. However, OCT has not yet been widely integrated into clinical dental practice, perhaps because OCT imaging does not provide an easily accessible diagnostic outcome for clinicians. The objective of this ex vivo study was to use OCT-images of sound and carious occlusal surfaces in combination with a simple algorithm to compare the caries detection ability of OCT with tools clinicians may be more familiar with (LF and radiography), and with an established valid and reliable clinical assessment tool (ICDAS-II).
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Confocal acoustic radiation force optical coherence elastography using a ring ultrasonic transducer.
Appl Phys Lett
PUBLISHED: 03-13-2014
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We designed and developed a confocal acoustic radiation force optical coherence elastography system. A ring ultrasound transducer was used to achieve reflection mode excitation and generate an oscillating acoustic radiation force in order to generate displacements within the tissue, which were detected using the phase-resolved optical coherence elastography method. Both phantom and human tissue tests indicate that this system is able to sense the stiffness difference of samples and quantitatively map the elastic property of materials. Our confocal setup promises a great potential for point by point elastic imaging in vivo and differentiation of diseased tissues from normal tissue.
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MRI quantification of non-Gaussian water diffusion in normal human kidney: a diffusional kurtosis imaging study.
NMR Biomed
PUBLISHED: 03-11-2014
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Our aim was to prospectively evaluate the feasibility of diffusional kurtosis imaging (DKI) in normal human kidney and to report preliminary DKI measurements. Institutional review board approval and informed consent were obtained. Forty-two healthy volunteers underwent diffusion-weighted imaging (DWI) scans with a 3-T MR scanner. b values of 0, 500 and 1000?s/mm(2) were adopted. Maps of fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (D? ), axial diffusivity (D|| ), mean kurtosis (MK), radial kurtosis (K? ) and axial kurtosis (K|| ) were produced. Three representative axial slices in the upper pole, mid-zone and lower pole were selected in the left and right kidney. On each selected slice, three regions of interest were drawn on the renal cortex and another three on the medulla. Statistical comparison was performed with t-test and analysis of variance. Thirty-seven volunteers successfully completed the scans. No statistically significant differences were observed between the left and right kidney for all metrics (p values in the cortex: FA, 0.114; MD, 0.531; D? , 0.576; D|| , 0.691; MK, 0.934; K? , 0.722; K|| , 0.891; p values in the medulla: FA, 0.348; MD, 0.732; D? , 0.470; D|| , 0.289; MK, 0.959; K? , 0.780; K|| , 0.287). Kurtosis metrics (MK, K|| , K? ) obtained in the renal medulla were significantly (p <0.001) higher than those in the cortex (0.552?±?0.04, 0.637?±?0.07 and 0.530?±?0.08 in the medulla and 0.373?±?0.04, 0.492?±?0.06 and 0.295?±?0.06 in the cortex, respectively). For the diffusivity measures, FA of the medulla (0.356?±?0.03) was higher than that of the cortex (0.179?±?0.03), whereas MD, D? and D|| (mm(2) /ms) were lower in the medulla than in the cortex (3.88?±?0.09, 3.50?±?0.23 and 4.65?±?0.29 in the cortex and 2.88?±?0.11, 2.32?±?0.20 and 3.47?±?0.31 in the medulla, respectively). Our results indicate that DKI is feasible in the human kidney. We have reported the preliminary DKI measurements of normal human kidney that demonstrate well the non-Gaussian behavior of water diffusion, especially in the renal medulla. Copyright © 2014 John Wiley & Sons, Ltd.
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In vivo detection of inhalation injury in large airway using three-dimensional long-range swept-source optical coherence tomography.
J Biomed Opt
PUBLISHED: 02-28-2014
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We report on the feasibility of using long-range swept-source optical coherence tomography (OCT) to detect airway changes following smoke inhalation in a sheep model. The long-range OCT system (with axial imaging range of 25 mm) and probe are capable of rapidly obtaining a series of high-resolution full cross-sectional images and three-dimensional reconstructions covering 20-cm length of tracheal and bronchial airways with airway diameter up to 25 mm, regardless of the position of the probe within the airway lumen. Measurements of airway thickness were performed at baseline and postinjury to show mucosal thickness changes following smoke inhalation.
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Structure-selective hot-spot Raman enhancement for direct identification and detection of trace penicilloic acid allergen in penicillin.
Biosens Bioelectron
PUBLISHED: 02-14-2014
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Trace penicilloic acid allergen frequently leads to various fatal immune responses to many patients, but it is still a challenge to directly discriminate and detect its residue in penicillin by a chemosensing way. Here, we report that silver-coated gold nanoparticles (Au@Ag NPs) exhibit a structure-selective hot-spot Raman enhancement capability for direct identification and detection of trace penicilloic acid in penicillin. It has been demonstrated that penicilloic acid can very easily link Au@Ag NPs together by its two carboxyl groups, locating itself spontaneously at the interparticle of Au@Ag NPs to form strong Raman hot-spot. At the critical concentration inducing the nanoparticle aggregation, Raman-enhanced effect of penicilloic acid is ~60,000 folds higher than that of penicillin. In particular, the selective Raman enhancement to the two carboxyl groups makes the peak of carboxyl group at C6 of penicilloic acid appear as a new Raman signal due to the opening of ?-lactam ring of penicillin. The surface-enhanced Raman scattering (SERS) nanoparticle sensor reaches a sensitive limit lower than the prescribed 1.0‰ penicilloic acid residue in penicillin. The novel strategy to examine allergen is more rapid, convenient and inexpensive than the conventional separation-based assay methods.
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Diurnal remote sensing of coastal/oceanic waters: a radiometric analysis for Geostationary Coastal and Air Pollution Events.
Appl Opt
PUBLISHED: 02-12-2014
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Optical remote sensing systems aboard geostationary platforms can provide high-frequency observations of bio-optical properties in dynamical coastal/oceanic waters. From the end-user standpoint, it is recognized that the fidelity of daily science products relies heavily on the radiometric sensitivity/performance of the imaging system. This study aims to determine the theoretical detection limits for bio-optical properties observed diurnally from a geostationary orbit. The analysis is based upon coupled radiative transfer simulations and the minimum radiometric requirements defined for the GEOstationary Coastal and Air Pollution Events (GEO-CAPE) mission. The diurnal detection limits are found for the optically active constituents of water, including near-surface concentrations of chlorophyll-a (CHL) and total suspended solids (TSS), and the absorption of colored dissolved organic matter (aCDOM). The diurnal top-of-atmosphere radiance (Lt) is modeled for several locations across the field of regard (FOR) to investigate the radiometric sensitivity at different imaging geometries. It is found that, in oceanic waters (CHL=0.07??mg/m3), detecting changes smaller than 0.01??mg/m3 in CHL is feasible for all locations and hours except for late afternoon observations on the edge of the FOR. For more trophic/turbid waters (0.6
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Ion-exchange chromatography combined with direct current amperometric detection at CuNPs/reduced graphene oxide-chitosan composite film modified electrode for determination of monosaccharide composition of polysaccharides from Phellinus igniarius.
Talanta
PUBLISHED: 01-10-2014
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A novel Cu nanoparticles/reduced graphene oxide-chitosan (CuNPs/r-GO-chitosan) composite film modified glassy carbon electrode (GCE) was fabricated by dispersing CuNPs uniformly on a stable r-GO-chitosan thin film through electrodeposition process. The modified electrode was characterized by cyclic voltammetry, scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS), and exhibited efficiently electrocatalytic oxidation toward monosaccharides with high stability. The good electrocatalytic activity of this modified electrode might be attributed to the synergistic effect of r-GO and CuNPs, and the stability might be attributed to the r-GO and chitosan thin matrix film. When the CuNPs/r-GO-chitosan/GCE was used as an electrochemical sensor in high performance anion exchange chromatography-direct current amperometric detection (HPAEC-DC) flowing system for the determination of monosaccharides under constant working potential of +0.55 V, the detection limits (S/N=3) ranged from 0.006 to 0.02 mg L(-1) for the analyzed sugars, and the dynamic linear ranges spanned from 0.02 to 500 mg L(-1). The proposed method has been applied for the determination of monosaccharide composition of crude polysaccharides from phellinus igniarius real samples, and the results were satisfactory.
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Mechanical analysis of arterial plaques in native geometry with OCT wall motion analysis.
J Biomech
PUBLISHED: 01-07-2014
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The mechanical behavior of an atherosclerotic plaque may encode information about the type, composition, and vulnerability to rupture. Human arterial segments with varying plaque burden were analyzed ex vivo with optical coherence tomography (OCT) to determine plaque type and to determine compliance during pulsatile inflation in their native geometry. Calcifications and lipid filled plaques showed markedly different compliance when analyzed with OCT wall motion analysis. There was also a trend towards increased circumferential variation in arterial compliance with increasing plaque burden.
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Comparative analysis of P2X1, P2X2, P2X3, and P2X4 receptor subunits in rat nodose ganglion neurons.
PLoS ONE
PUBLISHED: 01-01-2014
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Nodose ganglion (NG) neurons are visceral primary sensory neurons. The transmission and regulation of visceral sensation is mediated mainly by the P2X purinoceptor (P2X receptor). Although the characteristics of different P2X receptor subunits in the NG have been studied previously, comprehensive analyses have not been performed. In this study, we used immunohistochemistry, immunocytochemistry, and whole cell patch clamp techniques to compare the expression and function of P2X1, P2X2, P2X3, and P2X4 receptor subunits in adult rat NG neurons. Polyclonal antibodies against the four P2X subunits labeled different subpopulations of NG neurons. P2X1 and P2X3 were expressed mainly in small-to-medium sized NG neurons, whereas P2X2 and P2X4 were located mostly in medium- and larger-sized NG neurons. Over 36% of NG neurons were P2X3 positive, which was higher than the other three P2X subunits. In addition, different types of currents were recorded from neurons expressing different P2X subunits. The fast type of ATP current was recorded from neurons containing P2X1-4 subunits, the intermediate type of current was recorded from neurons containing the P2X1, P2X3, and P2X4 subunits, the slow type was recorded from neurons expressing P2X1-3, and/or P2X4 subunits, whereas the very slow type was recorded from neurons containing the P2X2 and P2X3 subunits. These comparative results provide an anatomical verification of the different subunits in NG neurons, and offer direct support for the idea that various functional NG populations have distinct responses to ATP, which might be in part due to the different expression profiles of diverse P2X subunits.
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Retrospective study of prenatal diagnosed pulmonary sequestration.
Pediatr. Surg. Int.
PUBLISHED: 11-01-2013
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To describe the prenatal findings, treatments and outcomes of fetuses with pulmonary sequestrations (PS), which were retrospectively studied.
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In vivo, high-resolution, three-dimensional imaging of port wine stain microvasculature in human skin.
Lasers Surg Med
PUBLISHED: 10-01-2013
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Port-wine stain (PWS) is a congenital, progressive vascular malformation of the dermis. The use of optical coherence tomography (OCT) for the characterization of blood vessels in PWS skin has been demonstrated by several groups. In the past few years, advances in OCT technology have greatly increased imaging speed. Sophisticated numerical algorithms have improved the sensitivity of Doppler OCT dramatically. These improvements have enabled the noninvasive, high-resolution, three-dimensional functional imaging of PWS skin. Here, we demonstrate high-resolution, three-dimensional, microvasculature imaging of PWS and normal skin using Doppler OCT technique.
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Lens-free endoscopy probe for optical coherence tomography.
Opt Lett
PUBLISHED: 08-14-2013
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We present an ultrathin fiber-optic endoscopy probe for optical coherence tomography (OCT), which is made of a series of fused optical fibers instead of the conventional scheme based on an objective lens. The large-core fiber with a core diameter of 20 ?m was utilized for the probe, while a single-mode fiber of core diameter 8.2 ?m mainly delivered the OCT light. Those fibers were spliced with a bridge fiber of an intermediate core size. The guided light was stepwise converted to a beam of a large mode-field diameter to be radiated with a larger depth of focus. We obtained a 125 ?m thick all-fiber endoscopy probe with a side-viewing capability implemented by an angled fiber end. Successful OCT imaging was demonstrated with a swept-source OCT system and showed the practical applicability of our lens-free endoscopy probe.
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Planar and Nonplanar Free-Base Tetraarylporphyrins: ?-Pyrrole Substituents and Geometric Effects on Electrochemistry, Spectroelectrochemistry, and Protonation/Deprotonation Reactions in Nonaqueous Media.
Chemistry
PUBLISHED: 08-08-2013
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A series of planar and nonplanar free-base ?-pyrrole substituted meso-tetraarylporphyrins were characterized by electrochemistry, spectroelectrochemistry, and protonation or deprotonation reactions in neutral, acidic, and basic solutions of CH2 Cl2 . The neutral compounds are represented as H2 (P), in which P represents a porphyrin dianion with one of several different sets of electron-withdrawing or -donating substituents at the messo and/or ?-pyrrole positions of the macrocycle. The conversion of H2 (P) to [H4 (P)](2+) in CH2 Cl2 was accomplished by titration of the neutral porphyrin with trifluoroacetic acid (TFA) while the progress of the protonation was monitored by UV/Vis spectroscopy, which was also used to calculate log?2 for proton addition to the core nitrogen atoms of the macrocycle. Cyclic voltammetry was performed after each addition of TFA or TBAOH to CH2 Cl2 solutions of the porphyrin and half-wave potentials for reduction were evaluated as a function of the added acid or base concentration. Thin-layer spectroelectrochemistry was used to obtain UV/Vis spectra of the neutral and protonated or deprotonated porphyrins under the application of an applied reducing potential. The magnitude of the protonation constants, the positions of ?max in the UV/Vis spectra and the half-wave or peak potentials for reduction are then related to the electronic properties of the porphyrin and the data evaluated as a function of the planarity or nonplanarity of the porphyrin macrocycle. Surprisingly, the electroreduction of the diprotonated nonplanar porphyrins in acid media leads to H2 (P), whereas the nonplanar H2 (P) derivatives are reduced to [(P)](2-) in CH2 Cl2 containing 0.1?M tetra-n-butylammonium perchlorate (TBAP). Thus, in both cases an electrochemically initiated deprotonation is observed.
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Influence of Raman scattering on ocean color inversion models.
Appl Opt
PUBLISHED: 08-06-2013
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Raman scattering can be a significant contributor to the emergent radiance spectrum from the surface ocean. Here, we present an analytical approach to directly estimate the Raman contribution to remote sensing reflectance, and evaluate its effects on optical properties estimated from two common semianalytical inversion models. For application of the method to ocean color remote sensing, spectral irradiance products in the ultraviolet from the OMI instrument are merged with MODerate-resolution Imaging Spectroradiometer (MODIS) data in the visible. The resulting global fields of Raman-corrected optical properties show significant differences from standard retrievals, particularly for the particulate backscattering coefficient, b(bp), where average errors in clear ocean waters are ~50%. Given the interest in transforming b(bp) into biogeochemical quantities, Raman scattering must be accounted for in semianalytical inversion schemes.
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Capturing the vital vascular fingerprint with optical coherence tomography.
Appl Opt
PUBLISHED: 08-06-2013
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Using fingerprints as a method to identify an individual has been accepted in forensics since the nineteenth century, and the fingerprint has become one of the most widely used biometric characteristics. Most of the modern fingerprint recognition systems are based on the print pattern of the finger surface and are not robust against spoof attaching. We demonstrate a novel vital vascular fingerprint system using Doppler optical coherence tomography that provides highly sensitive and reliable personal identification. Because the system is based on blood flow, which only exists in a livng person, the technique is robust against spoof attaching.
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Miniature optical coherence tomography-ultrasound probe for automatically coregistered three-dimensional intracoronary imaging with real-time display.
J Biomed Opt
PUBLISHED: 07-24-2013
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We have developed a novel miniature integrated optical coherence tomography (OCT)-intravascular ultrasound (IVUS) probe, with a 1.5-mm-long rigid part and 0.9-mm outer diameter, for real-time intracoronary imaging of atherosclerotic plaques and guiding of interventional procedures. By placing the OCT ball lens and IVUS transducer back-to-back at the same axial position, this probe can provide automatically coregistered, coaxial OCT-IVUS imaging. To demonstrate its real-time capability, three-dimensional OCT-IVUS imaging of a pigs coronary artery displaying in polar coordinates, as well as images of three major types of atherosclerotic plaques in human cadaver coronary segments, were obtained using this probe and our upgraded system. Histology validation is also presented.
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A chemically reactive Raman probe for ultrasensitively monitoring and imaging the in vivo generation of femtomolar oxidative species as induced by anti-tumor drugs in living cells.
Chem. Commun. (Camb.)
PUBLISHED: 06-17-2013
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A chemically reactive Raman probe has been developed for ultrasensitively monitoring and imaging the in vivo generation of femtomolar oxidative species as induced by anti-tumor drugs in living cells.
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Resonant acoustic radiation force optical coherence elastography.
Appl Phys Lett
PUBLISHED: 06-14-2013
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We report on a resonant acoustic radiation force optical coherence elastography (ARF-OCE) technique that uses mechanical resonant frequency to characterize and identify tissues of different types. The linear dependency of the resonant frequency on the square root of Youngs modulus was validated on silicone phantoms. Both the frequency response spectrum and the 3D imaging results from the agar phantoms with hard inclusions confirmed the feasibility of deploying the resonant frequency as a mechanical contrast for tissue imaging. Furthermore, the results of resonant ARF-OCE imaging of a post-mortem human coronary artery with atherosclerosis demonstrate the potential of the resonant ARF-OCE as a non-invasive method for imaging and characterizing vulnerable plaques.
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Simultaneous determination of peroxydisulfate and conventional inorganic anions by ion chromatography with the column-switching technique.
J Sep Sci
PUBLISHED: 06-03-2013
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The application of ion chromatography with the column-switching technique for the simultaneous analysis of peroxydisulfate and conventional inorganic anions in a single run is described. With this method, conventional inorganic anions were separated by consecutive elution through both the guard column and separation column, but peroxydisulfate that only passed through the guard column had a good peak shape and short retention time. A series of standard solutions consisting of target anions of various concentrations from 0.01 to 75 mg/L were analyzed, with a correlation coefficient (r) ? 0.9990. The limits of detection were in the range of 0.49-9.84 ?g/L based on the S/N of 3 and a 25 ?L injection volume. RSDs for retention time, peak area, and peak height were all <1.77%. A spiking study was performed with satisfactory recoveries between 97.6 and 103.4% for all anions. The quantitative determination of peroxydisulfate and conventional inorganic anions in surface waters was accomplished within 18 min by this column-switching technique.
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Inkjet printing lanthanide doped nanorods test paper for visual assays of nitroaromatic explosives.
Anal. Chim. Acta
PUBLISHED: 06-03-2013
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The facile and sensitive strategies for detections of nitroaromatic explosives are highly desirable in many challenging environments, especially for homeland security against terrorism. Here, we inkjet printed polyethylenimine (PEI)-coated Ce, Tb co-doped NaGdF4 nanorods (NaGdF4:Ce/Tb NRs) onto common filter paper to construct test paper for visual and instant detections of a typical explosive 2,4,6-trinitrophenol (TNP). Polyethylenimine molecules not only facilitate the formation of uniform NaGdF4 nanorods but also provide specific recognized sites for TNP by the acid-base pairing interaction. The resultant TNP bound at the surface of PEI-coated NaGdF4:Ce/Tb NRs can strongly quench the phosphorescence with a remarkably high quenching constant by the charge transfer mechanism from NaGdF4:Ce/Tb NRs to TNP. By printing of the probe on a piece of filter paper, trace amounts of TNP can be visually detected by the appearance of a dark color against a bright green background under a UV lamp. This test paper can detect TNP as low as 0.45 ng mm(-2) by the naked eye, which provides a potential application in the rapid, on-line detections of explosives.
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Real-time subglottic stenosis imaging using optical coherence tomography in the rabbit.
JAMA Otolaryngol Head Neck Surg
PUBLISHED: 05-18-2013
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Subglottic stenosis (SGS) is a severe, acquired, potentially life-threatening disease that can be caused by endotracheal tube intubation. Newborns and neonates are particularly susceptible to SGS owing to the small caliber of their airway.
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Analysis of hexavalent chromium in Colla corii asini with on-line sample pretreatment valve-switching ion chromatography.
J Chromatogr A
PUBLISHED: 05-12-2013
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An ion chromatography (IC) system with on-line sample pretreatment using valve-switching technique was developed for the determination of hexavalent chromium (Cr(VI)) in Colla corii asini. Colla corii asini is a complicated sample with organics as main matrix. In this work, a polymer-based reversed-phase column was used as a pretreatment column. Via valve-switching technique, sample solution with target ions were eluted from a collection loop to analytical columns, with matrix eliminated on-line. Under the optimized separation conditions, the method showed good linearity (r=0.9998) in the range of 0.004-1.0mg/L and satisfactory repeatability (RSD<3%, n=6). The limit of detection (LOD) was 1.4?g/L (S/N=3). The average spiked recoveries of Cr(VI) were 93.4-102.0%. The result showed that the on-line sample pretreatment IC system was convenient and practical for the determination of trace Cr(VI) in Colla corii asini samples.
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The phase transition of W-doped VO2 nanoparticles synthesized by an improved thermolysis method.
J Nanosci Nanotechnol
PUBLISHED: 05-08-2013
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High-quality thermochromic monoclinic VO2(M) and series of W-doped V(1-x)W(x)O2(M) nanoparticles were successfully synthesized by an improved thermolysis method. The products were investigated using X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) technologies. The measurement of DSC revealed that the metal-insulator phase transition (MIT) of 2.0% W-doped VO2 sample occurred at 25.6 degrees C, which was much lower than the MIT of host VO2(M) nanoparticles at 67.6 degrees C. The results showed that the proportion of the transmittance of tetragonal phase reached only about 29% of that of monoclinic phase for 0.5% W-doped VO2 at the wavenumber 900 cm(-1), which indicated W-doped VO2(M) was an intelligent window and optical switch materials.
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High frequency of the X-chromosome inactivation in young female patients with high-grade glioma.
Diagn Pathol
PUBLISHED: 04-30-2013
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Gliomas are common tumors and high-grade ones account for 62% of primary malignant brain tumors. Though current evidence have suggested that inherited risks play a role in glioma susceptibility, it was conveyed that glioma was such a complex disease, and the direct genetic contribution to glioma risk factors and its relation to other factors should be discussed more deeply. X-chromosome inactivation (XCI) is the mechanism by which gene dosage equivalence is achieved between female mammals with two X chromosomes and male mammals with a single X chromosome. As skewed XCI has been linked to development of some solid tumors, including ovarian, breast, and pulmonary and esophageal carcinomas, it is challenging to elucidate the relation of skewed XCI to high-grade gliomas development.
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Neuregulin1beta1 antagonizes apoptosis via ErbB4-dependent activation of PI3-kinase/Akt in APP/PS1 transgenic mice.
Neurochem. Res.
PUBLISHED: 04-09-2013
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Alzheimers disease (AD) is characterized by the deposition of beta-amyloid protein (A?) and extensive neuronal cell death. Apoptosis plays a crucial role in loss of neurons in AD. Neuregulin1 (NRG1) has been found to protect neurons from oxygen glucose deprivation induced apoptosis and hypoxia ischemia induced apoptosis. However, the relationship between NRG1 and apoptosis related protein expression in AD and its mechanism remain uncertain. The present study explores the effects of NRG1 on A?-induced apoptosis in AD. In this study, extracellular domain of NRG1beta1 (NRG1?1-ECD) promoted the expression of p-ErbB4 receptor, p-Akt and increased the level of Bcl-2 both in APP/PS1 transgenic mice and in vitro. In primary culture of neurons, the level of Bcl-2 protein decreased significantly after A? treatment. These changes were inhibited by pretreatment of neurons with NRG1?1-ECD. A specific inhibitor of PI3-kinase/Akt pathway, wortmannin, significantly abrogated the effects of NRG1?1-ECD on p-Akt and Bcl-2 levels. Furthermore, the expression of PI3-kinase/Akt by NRG1?1-ECD was ErbB4-dependent. Our data demonstrated that NRG1?1-ECD might serve as an obvious neuroprotection in AD, and the possible protective mechanism occurs most likely via ErbB4-dependent activation of PI3-kinase/Akt pathway.
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Generalized ocean color inversion model for retrieving marine inherent optical properties.
Appl Opt
PUBLISHED: 04-03-2013
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Ocean color measured from satellites provides daily, global estimates of marine inherent optical properties (IOPs). Semi-analytical algorithms (SAAs) provide one mechanism for inverting the color of the water observed by the satellite into IOPs. While numerous SAAs exist, most are similarly constructed and few are appropriately parameterized for all water masses for all seasons. To initiate community-wide discussion of these limitations, NASA organized two workshops that deconstructed SAAs to identify similarities and uniqueness and to progress toward consensus on a unified SAA. This effort resulted in the development of the generalized IOP (GIOP) model software that allows for the construction of different SAAs at runtime by selection from an assortment of model parameterizations. As such, GIOP permits isolation and evaluation of specific modeling assumptions, construction of SAAs, development of regionally tuned SAAs, and execution of ensemble inversion modeling. Working groups associated with the workshops proposed a preliminary default configuration for GIOP (GIOP-DC), with alternative model parameterizations and features defined for subsequent evaluation. In this paper, we: (1) describe the theoretical basis of GIOP; (2) present GIOP-DC and verify its comparable performance to other popular SAAs using both in situ and synthetic data sets; and, (3) quantify the sensitivities of their output to their parameterization. We use the latter to develop a hierarchical sensitivity of SAAs to various model parameterizations, to identify components of SAAs that merit focus in future research, and to provide material for discussion on algorithm uncertainties and future emsemble applications.
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Graphene oxide embedded sandwich nanostructures for enhanced Raman readout and their applications in pesticide monitoring.
Nanoscale
PUBLISHED: 03-27-2013
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Analytical techniques based on surface-enhanced Raman scattering (SERS) suffer from a lack of reproducibility and reliability, thus hampering their practical applications. Herein, we have developed a SERS-active substrate based on a graphene oxide embedded sandwich nanostructure for ultrasensitive Raman signal readout. By using this novel Au@Ag NPs/GO/Au@Ag NPs sandwich nanostructure as a SERS substrate, the Raman signals of analytes were dramatically enhanced due to having plenty of hot spots on their surfaces and the unique structure of the graphene oxide sheets. These features make the sandwich nanostructured film an ideal SERS substrate to improve the sensitivity, reproducibility and reliability of the Raman readout. The sandwich nanostructure film can be applied to detect rhodamine-6G (R6G) with an enhancement factor (EF) of ?7.0 × 10(7) and the pesticide thiram in commercial grape juice with a detection limit of as low as 0.1 ?M (0.03 ppm), which is much lower than the maximal residue limit (MRL) of 7 ppm in fruit prescribed by the U.S. Environmental Protection Agency (EPA). The GO embedded sandwich nanostructure also has the ability to selectively detect dithiocarbamate compounds over other types of agricultural chemical. Furthermore, spiked tests show that the sandwich nanostructure can be used to monitor thiram in natural lake water and commercial grape juice without further treatment. In addition, the GO enhanced Raman spectroscopic technique offers potential practical applications for the on-site monitoring and assessment of pesticide residues in agricultural products and environments.
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Imaging and quantifying Brownian motion of micro- and nanoparticles using phase-resolved Doppler variance optical coherence tomography.
J Biomed Opt
PUBLISHED: 03-22-2013
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Different types and sizes of micro- and nanoparticles have been synthesized and developed for numerous applications. It is crucial to characterize the particle sizes. Traditional dynamic light scattering, a predominant method used to characterize particle size, is unable to provide depth resolved information or imaging functions. Doppler variance optical coherence tomography (OCT) measures the spectral bandwidth of the Doppler frequency shift due to the Brownian motion of the particles utilizing the phase-resolved approach and can provide quantitative information about particle size. Spectral bandwidths of Doppler frequency shifts for various sized particles were quantified and were demonstrated to be inversely proportional to the diameter of the particles. The study demonstrates the phase-resolved Doppler variance spectral domain OCT technique has the potential to be used to investigate the properties of particles in highly scattering media.
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Simultaneous determination of imidacloprid and carbendazim in water samples by ion chromatography with fluorescence detector and post-column photochemical reactor.
Talanta
PUBLISHED: 03-13-2013
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A new analytical method has been developed and validated for the simultaneous determination of pesticides from different classes using ion chromatography-online photochemical derivatisation-fluorescence detector (IC-hv-FD). Fluorimetric detection was performed at ?ex/?em=332 nm/367 nm for imidacloprid and then detector was set at ?ex/?em=247 nm/470 nm for carbendazim. The two pesticides imidacloprid and carbendazim were successfully separated isocratically on an IonPac(®) AS11 (250 mm × 4 mm i.d; 13 µm particle size, Dionex) anion-exchange column using 40 mM KOH with 10% (v/v) acetonitrile and pumped at a flow rate of 1.0 mL min(-1). Under the optimized conditions, the limit of detection (LOD, S/N=3) of imidacloprid and carbendazim were 7.8 µg L(-1) and 67 µg L(-1), respectively. The experimental results showed that there was good linearity with a correlation coefficient (r)?0.9966 over the range of 0.05-10 mg L(-1) for imidacloprid and 0.2-15 mg L(-1) for carbendazim. Good reproducibility with a relative standard deviation (RSD, n=7) less than 4.5%. Finally, the proposed method was applied with satisfactory results to the analysis of these pesticides in ground water, lake water and river water without any pre-treatment of samples. The average spiked recoveries were in the range of 90-104%.
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Robust approach to directly measuring water-leaving radiance in the field.
Appl Opt
PUBLISHED: 03-13-2013
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It has been a long-standing goal to precisely measure water-leaving radiance (L(w), or its equivalent property, remote-sensing reflectance) in the field, but reaching this goal is quite a challenge. This is because conventional approaches do not provide a direct measurement of L(w), but rather measure various related components and subsequently derive this core property from these components. Due to many uncontrollable factors in the measurement procedure and imprecise post-measurement processing routines, the resulting L(w) is inherently associated with various levels of uncertainties. Here we present a methodology called the skylight-blocked approach (SBA) to measure L(w) directly in the field, along with results obtained recently in the Laurentian Great Lakes. These results indicate that SBA can measure L(w) in high precision. In particular, there is no limitation of water types for the deployment of SBA, and the requirement of post-measurement processing is minimum; thus high-quality L(w) for a wide range of aquatic environments can be acquired.
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Surface-enhanced Raman scattering chip for femtomolar detection of mercuric ion (II) by ligand exchange.
Anal. Chem.
PUBLISHED: 03-11-2013
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The chemical sensing for the convenient detection of mercuric ion (II) (Hg(2+)) have been widely explored with the use of various sensing materials and techniques. It still remains a challenge to achieve ultrasensitive but simple, rapid, and inexpensive detection to metal ions. Here we report a surface-enhanced Raman scattering (SERS) chip for the femtomolar (fM) detection of Hg(2+) by employing silver-coated gold nanoparticles (Au@Ag NPs) together with an organic ligand. 4,4-Dipyridyl (Dpy) can control the aggregation of Au@Ag NPs via its dual interacting sites to Ag nanoshells to generate strong Raman hot spots and SERS readouts. However, the presence of Hg(2+) can inhibit the aggregation of Au@Ag NPs by the coordination with Dpy, and as a result the SERS signals of Dpy are quenched. On the basis of these findings, a SERS chip has been fabricated by the assembly of Au@Ag NPs on a piece of silicon wafer and the further modification with Dpy. The exchange of Dpy from the chip into the aqueous Hg(2+) droplet results in the quenching of Raman signals of Dpy, responding to 10 fM Hg(2+) that is about 6 orders of magnitude lower than the limit defined by the U.S. Environmental Protection Agency in drinkable water. Each test using the SERS chip only needs a droplet of 20 ?L sample and is accomplished within ?4 min. The SERS chip has also been applied to the quantification of Hg(2+) in milk, juice, and lake water.
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Simultaneous determination of glucose, D-gluconic, 2-keto-D-gluconic and 5-keto-D-gluconic acids by ion chromatography-pulsed amperometric detection with column-switching technique.
Talanta
PUBLISHED: 03-06-2013
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A simple ion chromatographic (IC) method for simultaneous determination of glucose, D-gluconic acid (DGA), 2-keto-D-gluconic acid (2-KDG) and 5-keto D-gluconic acid (5-KDG) was proposed, with pulsed amperometric detection (PAD) and column-switching technique. Using this technique, the four compounds were detected simultaneously in a short time with strongly retained compounds (2-KDG and 5-KDG) eluted out prior to weakly retained compounds (glucose and DGA). Under the optimized conditions, the method showed good linearity in the range of 0.01-20 mg L(-1) with determination coefficients (R(2))? 99.84%. Low detection limits (LODs) in the range of 0.87-2.59 ?g L(-1) and good repeatability (RSD<3%, n=6) were obtained. The proposed method has been successfully applied to the analysis of the four compounds in the fermentation broth, in which Gluconobacter oxydans was used to produce gluconic acids from glucose.
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Hybrid POSS-containing brush on gold surfaces for protein resistance.
Macromol Biosci
PUBLISHED: 02-23-2013
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A hybrid polymer brush containing poly(ethylene glycol) (PEG) chains and polyhedral oligosilsesquioxane (POSS) on a gold surface is presented that exhibits an excellent protein resistance and long-term stability. A series of hybrid polymer brushes with different length and numbers of PEG chains are fabricated through chemisorption of PEG-POSS-SH on the gold surface. Protein adsorption of these hybrid brushes is investigated. The amount of protein adsorption decreases with increasing lengths and numbers of PEG chains. After immersion in BSA solution for two months, the PPS4 brushes retain their protein resistance, while a PEG-SH layer loses its non-fouling performance. These POSS-containing hybrid polymer brushes might offer an alternative for modification of gold surface with an excellent protein resistance for long-term applications.
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Evaluation of optical coherence tomography for the measurement of the effects of activators and anticoagulants on the blood coagulation in vitro.
IEEE Trans Biomed Eng
PUBLISHED: 02-06-2013
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Optical properties of human blood during coagulation were studied using optical coherence tomography (OCT) and the parameter of clotting time derived from the 1/e light penetration depth (d(1/e)) versus time was developed in our previous work. In this study, in order to know if a new OCT test can characterize the blood-coagulation process under different treatments in vitro, the effects of two different activators (calcium ions and thrombin) and anticoagulants, i.e., acetylsalicylic acid (ASA, a well-known drug aspirin) and melagatran (a direct thrombin inhibitor), at various concentrations are evaluated. A swept-source OCT system with a 1300 nm center wavelength is used for detecting the blood-coagulation process in vitro under a static condition. A dynamic study of d1/e reveals a typical behavior due to coagulation induced by both calcium ions and thrombin, and the clotting time is concentration-dependent. Dose-dependent ASA and melagatran prolong the clotting times. ASA and melagatran have different effects on blood coagulation. As expected, melagatran is much more effective than ASA in anticoagulation by the OCT measurements. The OCT assay appears to be a simple method for the measurement of blood coagulation to assess the effects of activators and anticoagulants, which can be used for activator and anticoagulant screening.
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A single pump cycling-column-switching technique coupled with homemade high exchange capacity columns for the determination of iodate in iodized edible salt by ion chromatography with UV detection.
Food Chem
PUBLISHED: 01-27-2013
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A single pump cycling-column-switching technique has been developed for the iodate analysis in edible salt. Homemade high exchange capacity columns were adopted for the separation of iodate and chloride. Iodate could be retained and concentrated in a homemade concentrator column after eluents passing through the suppressor. With UV detection, iodate exhibited satisfactory linearity in the range of 0.1-10.0 mg/L with a correlation coefficient of 0.9996. The detection limit (LOD) was 45.53 ?g/L, based on the signal-to-noise ratio of 3 (S/N=3) and a 100 ?L injection volume. Relative standard deviations (RSDs) for retention time, peak area and peak height were all less than 2.1%. Recoveries of added iodate were in the range of 98.4-101.6% for the spiked samples. The quantitative determination of iodate in edible salt was accomplished by this column-switching technique, without any pretreatment and interference. The results on six samples were statistically compared with results determined by conventional titrimetric method.
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Polystyrene-divinylbenzene stationary phases agglomerated with quaternized multi-walled carbon nanotubes for anion exchange chromatography.
J Chromatogr A
PUBLISHED: 01-22-2013
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This work explores the potential of multi-walled carbon nanotubes as an agglomerated material for ion chromatography stationary phases for the separation of inorganic anions. Polyelectrolytes with quaternary ammonium groups were introduced onto the carbon nanotube surface, based on condensation polymerization of 1,4-butanediol diglycidyl ether (BDDE) and methylamine (MA). Quaternized multi-walled carbon nanotubes (Q-MWCNTs) were electrostatically adsorbed onto the surface of sulfonated polystyrene-divinylbenzene (PS-DVB) beads to generate the anion exchanger, which were confirmed by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). A 100mm×4.0mm i.d. column was packed with Q-MWCNTs agglomerated PS-DVB particles, with a capacity of 56?equiv./column. Separation of inorganic anions, such as F(-), Cl(-), NO2(-), Br(-), NO3(-), SO4(2-) and PO4(3-) were performed. The stationary phase was rigid, chemically stable and showed good ion-exchange characteristics.
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Determination of methotrexate and folic acid by ion chromatography with electrochemical detection on a functionalized multi-wall carbon nanotube modified electrode.
J Chromatogr A
PUBLISHED: 01-16-2013
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A simple and sensitive method was developed for simultaneous determination of methotrexate (MTX) and folic acid (FA) by ion chromatography with electrochemical detection (IC-ECD). Quaternary amine functionalized multi-wall carbon nanotubes (q-MWNTs) modified glassy carbon electrode (GCE) was used as an amperometric sensor to determine MTX and FA. The electrochemical behaviors of MTX and FA at the q-MWNTs/GCE were studied by cyclic voltammetry (CV). Results indicated that this modified electrode exhibited electrocatalytic oxidation toward MTX and FA with high sensitivity, stability and long life. Good separation of MTX and FA was demonstrated by IC on an anion-exchange column with phosphate buffer solution (PBS) as eluent. Under the optimal conditions, the linear ranges were from 0.01 to 20mg/L for both MTX and FA with correlation coefficients r ? 0.9994. The obtained detection limits (LODs) for MTX and FA were 0.2 and 0.4 ?g/L (S/N=3), respectively. The method has been successfully applied to the determination of MTX and FA in plasma and urine of patients of rheumatoid arthritis.
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Polarization-maintaining buffered Fourier domain mode-locked swept source for optical coherence tomography.
Opt Lett
PUBLISHED: 12-20-2011
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A polarization-maintaining buffered Fourier domain mode-locked (FDML) swept source with a center wavelength of 1300 nm is demonstrated. The scanning rate of the buffered FDML swept source is doubled without sacrificing the output power of the swept source by combining two orthogonally polarized outputs with a polarization beam combiner. The stability of the swept source is improved because the polarization state of the laser beam inside the laser cavity is maintained without the use of any polarization controllers. The swept source is capable of an edge-to-edge tuning range of more than 150 nm and a FWHM range of 95 nm at a 102 kHz sweeping rate and with an average power of 12 mW. A swept source optical coherence tomography (SSOCT) system is developed utilizing this buffered FDML swept source. The axial resolution of the SSOCT system is measured to be 9.4 µm in air. The sensitivity of the SSOCT system is 107.5 dB at a depth of 0.25 mm with a 6 dB roll-off at a depth of 2.25 mm.
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Shell thickness-dependent Raman enhancement for rapid identification and detection of pesticide residues at fruit peels.
Anal. Chem.
PUBLISHED: 12-15-2011
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Here, we report the shell thickness-dependent Raman enhancement of silver-coated gold nanoparticles (Au@Ag NPs) for the identification and detection of pesticide residues at various fruit peels. The Raman enhancement of Au@Ag NPs to a large family of sulfur-containing pesticides is ~2 orders of magnitude stronger than those of bare Au and Ag NPs, and there is a strong dependence of the Raman enhancement on the Ag shell thickness. It has been shown for the first time that the huge Raman enhancement is contributed by individual Au@Ag NPs rather than aggregated Au@Ag NPs with "hot spots" among the neighboring NPs. Therefore, the Au@Ag NPs with excellent individual-particle enhancement can be exploited as stand-alone-particle Raman amplifiers for the surface identification and detection of pesticide residues at various peels of fruits, such as apple, grape, mango, pear, and peach. By casting the particle sensors onto fruit peels, several types of pesticide residues (e.g., thiocarbamate and organophosphorous compounds) have been reliably/rapidly detected, for example, 1.5 nanograms of thiram per square centimeter at apple peel under the current unoptimized condition. The surface-lifting spectroscopic technique offers great practical potentials for the on-site assessment and identification of pesticide residues in agricultural products.
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Unusual multi-step sequential Au(III)/Au(II) processes of gold(III) quinoxalinoporphyrins in acidic non-aqueous media.
Inorg Chem
PUBLISHED: 11-09-2011
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The electrochemistry of gold(III) mono- and bis-quinoxalinoporphyrins was examined in CH(2)Cl(2) or PhCN containing 0.1 M tetra-n-butylammonium perchlorate (TBAP) before and after the addition of trifluoroacetic acid to solution. The investigated porphyrins are represented as Au(PQ)PF(6) and Au(QPQ)PF(6), where P is the dianion of the 5,10,15,20-tetrakis(3,5-di-tert-butylphenyl)porphyrin and Q is a quinoxaline group fused to a ?,?-pyrrolic position of the porphyrin macrocycle; in Au(QPQ)PF(6) there is a linear arrangement where the quinoxalines are fused to pyrrolic positions that are opposite each other. The porphyrin without the fused quinoxaline groups, Au(P)PF(6), was also investigated under the same solution conditions. In the absence of acid, all three gold(III) porphyrins undergo a single reversible Au(III)/Au(II) process leading to the formation of a Au(II) porphyrin which can be further reduced at more negative potentials to give stepwise the Au(II) porphyrin ?-anion radical and dianion, respectively. However, in the presence of acid, the initial Au(III)/Au(II) processes of Au(PQ)PF(6) and Au(QPQ)PF(6) are followed by an internal electron transfer and protonation to regenerate new Au(III) porphyrins assigned as Au(III)(PQH)(+) and Au(III)(QPQH)(+). Both protonated gold(III) quinoxalinoporphyrins then undergo a second Au(III)/Au(II) process at more negative potentials. The electrogenerated monoprotonated monoquinoxalinoporphyrin, Au(II)(PQH), is then further reduced to its ?-anion radical and dianion forms, but this is not the case for the monoprotonated bis-quinoxalinoporphyrin, Au(II)(QPQH), which accepts a second proton and is rapidly converted to Au(III)(HQPQH)(+) before undergoing a third Au(III)/Au(II) process to produce Au(II)(HQPQH) as a final product. Thus, Au(P)PF(6) undergoes one metal-centered reduction while Au(PQ)PF(6) and Au(QPQ)PF(6) exhibit two and three Au(III)/Au(II) processes, respectively. These unusual multistep sequential Au(III)/Au(II) processes were monitored by thin-layer spectroelectrochemistry and a reduction/oxidation mechanism for Au(PQ)PF(6) and Au(QPQ)PF(6) in acidic media is proposed.
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Investigating in vivo airway wall mechanics during tidal breathing with optical coherence tomography.
J Biomed Opt
PUBLISHED: 10-28-2011
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Optical coherence tomography (OCT) is a nondestructive imaging technique offering high temporal and spatial resolution, which makes it a natural choice for assessing tissue mechanical properties. We have developed methods to mechanically analyze the compliance of the rabbit trachea in vivo using tissue deformations induced by tidal breathing, offering a unique tool to assess the behavior of the airways during their normal function. Four-hundred images were acquired during tidal breathing with a custom-built endoscopic OCT system. The surface of the tissue was extracted from a set of these images via image processing algorithms, filtered with a bandpass filter set at respiration frequency to remove cardiac and probe motion, and compared to ventilatory pressure to calculate wall compliance. These algorithms were tested on elastic phantoms to establish reliability and reproducibility. The mean tracheal wall compliance (in five animals) was 1.3±0.3×10(-5) (mm Pa)(-1). Unlike previous work evaluating airway mechanics, this new method is applicable in vivo, noncontact, and loads the trachea in a physiological manner. The technique may have applications in assessing airway mechanics in diseases such as asthma that are characterized by significant airway remodeling.
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Integrated ultrasound and photoacoustic probe for co-registered intravascular imaging.
J Biomed Opt
PUBLISHED: 10-28-2011
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We report on the synergy of an integrated ultrasound (US) and photoacoustic (PA) probe system for intravascular imaging. The combined dual-modality probe is based on a 39 MHz ring-shaped US transducer which detects both US echoes and laser-generated PA signals. By combining optical fiber, US transducer, and micromirror, we can obtain intravascular cross-sectional B-scan images by internal illumination of the sample. The performance of the probe is evaluated in a phantom study. Moreover, the coaxially designed probe also provides co-registered US and PA images of a normal rabbit aorta, which demonstrates the imaging ability of the dual-functional system, implying future clinical applications.
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Recent advances in optical coherence tomography for the diagnoses of lung disorders.
Expert Rev Respir Med
PUBLISHED: 09-30-2011
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There have been many advances in the field of diagnostic and therapeutic pulmonary medicine in the past several years, with major progress in the field of imaging. Optical coherence tomography (OCT) is a high-resolution (micron level) imaging modality currently being advanced with the potential to image airway wall structures in real time and at higher resolution than previously possible. OCT has the potential to increase the sensitivity and specificity of biopsies, create 3D images of the airway to guide diagnostics, and may have a future role in diverse areas such as the evaluation and treatment of patients with obstructive sleep apnea, tracheal stenosis, airway remodeling and inhalation injury. OCT has recently been investigated to monitor airway compliance in chronic obstructive pulmonary disease and asthma patients as well as differentiate causes of pulmonary hypertension. In future clinical and research applications, OCT will likely be combined with other endoscopic based modalities such as ultrasound, spectroscopy, confocal, and/or photoacoustic tomography to determine functional and biomolecular properties. This article discusses the current uses of OCT, its potential applications, as it relates to specific pulmonary diseases, and the future directions for OCT.
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Mode-filtered large-core fiber for short-pulse delivery with reduced nonlinear effects.
Opt Lett
PUBLISHED: 09-03-2011
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We present a large-core fiber (LCF) with a reduced nonlinear property for a single-mode beam delivery of intense ultrashort pulses. A tapered-fiber mode filter was fabricated in an LCF with the core diameter decreased from 20??m to 6??m at the tapered waist region surrounded by index-matched liquid. By the tapered geometry, the high-order mode was rejected so that our mode-filtered LCF acted as a single-mode fiber despite the multimode property of the original LCF. It has been found that this fiber class is suitable for applications, such as an endoscopic multiphoton microscope, that demand a flexible short-distance (<4?m) delivery medium of ultrashort pulses.
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