JoVE Visualize What is visualize?
Stop Reading. Start Watching.
Advanced Search
Stop Reading. Start Watching.
Regular Search
Find video protocols related to scientific articles indexed in Pubmed.
Probing the structural and electronic properties of small aluminum dideuteride clusters.
J. Mol. Graph. Model.
PUBLISHED: 08-07-2014
Show Abstract
Hide Abstract
Adsorption of deuterium on the neutral and anionic Aln(?) (n=1-9, 13; ?=0, -1) clusters has been investigated systematically using density functional theory. The comparisons between the Franck-Condon factor simulated spectra and the measured photoelectron spectroscopy (PES) of Cui and co-workers help to search for the ground-state structures. The results showed that D2 molecule tends to be dissociated on aluminum clusters and forms the radial AlD bond with one aluminum atom. By studying the evolution of the binding energies, second difference energies and HOMO-LUMO gaps as a function of cluster size, we found Al2D2, Al6D2 and Al7D2(?) clusters have the stronger relative stability and enhanced chemical stability. Also, considering the larger adsorption energies of these three clusters, we surmised that Al2, Al6 and Al7(?) may be the better candidates for dissociative adsorption of D2 molecule among the clusters we studied. Furthermore, the natural population analysis (NPA) and difference electron density were performed and discussed to probe into the localization of the charges and reliable charge-transfer information in AlnD2 and AlnD2(?) clusters.
Related JoVE Video
[Neurobehavioral development in preterm infants: a retrospective study of 181 cases].
Zhongguo Dang Dai Er Ke Za Zhi
PUBLISHED: 07-11-2014
Show Abstract
Hide Abstract
To investigate the results of Gesell Developmental Scale in follow-up of preterm infants and to determine possible high-risk factors for poor long-term neurological outcome.
Related JoVE Video
Hydrothermal synthesis of core-shell structured TbPO4:Ce(3+)@TbPO4:Gd(3+) nanocomposites for magnetic resonance and optical imaging.
Dalton Trans
PUBLISHED: 07-03-2014
Show Abstract
Hide Abstract
Multi-modal imaging based on multifunctional nanoparticles provides deep, non-invasive and highly sensitive imaging and is a promising alternative approach that can improve the sensitivity of early cancer diagnosis. In this study, two nanoparticles, TbPO4:Ce(3+) and TbPO4:Ce(3+)@TbPO4:Gd(3+), were synthesized via the citric-acid-mediated hydrothermal route, and then systematically characterized by means of microstructure, photoluminescence, magnetic resonance imaging (MRI), biocompatibility, and bioimaging. The results of energy dispersive X-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS) line scans indicated that TbPO4:Gd(3+) nanoshells about 5 nm in thickness were successfully coated on the TbPO4:Ce(3+) nanocores. X-ray diffraction (XRD) and Fourier transforms of high-resolution transmission electron microscopy (TEM) images indicated that the core-shell nanocomposites had a single crystal structure. The photoluminescence of the TbPO4:Ce(3+)@TbPO4:Gd(3+) and TbPO4:Ce(3+) nanoparticles was greatly intensified by 200 times and 100 times, respectively, compared with pure TbPO4 nanoparticles. In vitro cytotoxicity tests based on the methyl thiazolyl tetrazolium (MTT) assay demonstrated that the monodispersed nanoparticles of TbPO4:Ce(3+)@TbPO4:Gd(3+) had low toxicity. The intracellular luminescence of the nanoparticles after being internalized by HeLa cells was also observed using confocal fluorescence microscopes. MRI showed that the nanoshells of Gd-doped TbPO4 possessed a longitudinal relaxivity of 4.067 s(-1) mM(-1), which is comparable to that of the commercial MRI contrast Gd-TDPA. As a result, the core-shell structured TbPO4:Ce(3+)@TbPO4:Gd(3+) nanoparticles can potentially serve as multifunctional nanoprobes for both optical biolabels and MRI contrast agents.
Related JoVE Video
Chemisorption-induced two- to three-dimensions structural transformations in gold pentamer (CO)nAu 5 (-) (n =0-5).
J Mol Model
PUBLISHED: 05-08-2014
Show Abstract
Hide Abstract
Understanding the geometry structures of gold clusters, especially with adsorbates, is essential for designing highly active gold nanocatalysts. Here, CO chemisorption onto the Au5 (-) cluster is investigated using the density functional calculations. It is found that chemisorption of CO molecules can induce previously unreported two- to three-dimensions (3D) structural changes. Even a single CO chemisorption induces a major structural change to explain the huge blue-shift in photoelectron spectroscopy (PES). The apex site in the parent Au5 (-) cluster is not always the most preferred site for the chemisorption, and two bridged adsorption CO molecules are observed in the lowest-energy (CO)3Au5 (-) cluster. A clear splitting is observed in the first PES of (CO)4Au5 (-), and calculated planar and 3D geometries are likely coexisting in the cluster beam. The fifth CO adsorption leads to the structural transformation of Au5 skeleton to create more apex sites to accommodate five CO molecules. The structural properties, together with the vertical electron detachment energy (VDE) and binding energies calculations indicate that the chemisorption-saturated number is 5.
Related JoVE Video
Probing the geometries, relative stabilities, and electronic properties of neutral and anionic Ag(n)S(m) (n?+?m???7) clusters.
J Mol Model
PUBLISHED: 04-11-2014
Show Abstract
Hide Abstract
The geometry structures, relative stabilities, and electronic properties of neutral and anionic Ag(n)S(m) (n?+?m???7) clusters have been investigated systematically by means of density function theory (DFT). The results of geometry optimization show that the most stable configurations of binary Ag(n)S(m)?/? clusters have an early appearance of 3D structure at n?=?3, m?=?1, differing from those of pure silver and sulfur clusters. Moreover, the ground-state structures prefer low spin multiplicity (singlet or doublet) except for S?, Ag?S?, Ag?S?, Ag?S?, and Ag?S?. The calculated electron detachment energies (both vertical and adiabatic) are in good agreement with experimental data. This further lends considerable credence for the lowest-energy structures and the chosen computational method. By calculating the binding energies, fragmentation energies, second-order difference of energies and HOMO-LUMO energy gaps of neutral and anionic Ag n S m clusters, the relative stability and electronic property as a function of cluster size are discussed in detail. Further, in order to understand the nature of the bond in doped clusters and pure clusters, we have performed the contour maps of their HOMOs and analyzed their composition.
Related JoVE Video
Structural and relative stabilities, electronic properties, and hardness of iron tetraborides from first prinicples.
Inorg Chem
PUBLISHED: 03-07-2014
Show Abstract
Hide Abstract
First-principles calculations were carried out to investigate the structure, phase stability, electronic property, and roles of metallicity in the hardness for recently synthesized FeB4 with various different structures. Our calculation indicates that the orthorhombic phase with Pnnm symmetry is the most energetically stable one. The other four new dynamically stable phases belong to space groups monoclinic C2/m, orthorhombic Pmmn, trigonal R3?m, and hexagonal P63/mmc. Their mechanical and thermodynamic stabilities are verified by calculating elastic constants, formation enthalpies, and phonon dispersions. We found that all phases are stabilized further under pressure. Above the pressure of about 50 GPa, the formation enthalpy of Pmmn is almost equal to that of P63/mmc phase. The analysis on density of states not only demonstrates that formation of strong covalent bonding in these compounds contributes greatly to their stabilities but also that they all exhibit metallic behavior which does not relate to the approach used. By considering metallic contributions, the estimated Vickers hardness values based on the semiempirical model show that the OsB4-structured FeB4, with a hardness of 48.1 GPa, well exceeding the limitation of superhardness (40 GPa), is more hard than the most stable phase. The others are predicted to be potential hard materials. Moreover, the atomic configuration and strong B-B covalent bonds are found to play important roles in the hardness of materials.
Related JoVE Video
Probing the structural and electronic properties of bimetallic chromium-gold clusters CrmAun(m+n?6): comparison with pure chromium and gold clusters.
J Mol Model
PUBLISHED: 02-22-2014
Show Abstract
Hide Abstract
Bimetallic chromium-gold CrmAun(m+n?6) clusters are systematically investigated using the density functional theory at PW91P86 level with LanL2TZ basis set to understand the evolution of various structural, electronic, magnetic, and energetic properties as a function of size (m+n) and composition (m/n) of the system. Theoretical results show a logical evolution of the properties depending on the size and the composition of the system. Cr m clusters clearly prefer 3D structures while Au n clusters favor planar configurations. The geometry of the bimetallic Cr m Au n clusters mainly depends on their composition, i.e., clusters enriched in Cr atoms prefer 3D structures while increasing Au contents promotes planar configurations. The stability is maximized when the composition of binary Cr m Au n clusters is nearly balanced. Meanwhile, the number of hetero Cr-Au bonds and charge transfer from Cr to Au are maximized for clusters with m?n. The most probable dissociation channels of the Cr m Au n clusters are calculated and analyzed. Natural population analysis reveals that Au atoms tend to be negatively charged while Cr atoms tend to be positively charged. Combined with the trend that Au atoms favor the surface/edges/vertices and Cr atoms tend to be inside, the outer part of the cluster tends to be negatively charged, and the inner part tends to be positively charged.
Related JoVE Video
Terrimicrobium sacchariphilum gen. nov., sp. nov., an anaerobic bacterium of the class 'Spartobacteria' in the phylum Verrucomicrobia, isolated from a rice paddy field.
Int. J. Syst. Evol. Microbiol.
PUBLISHED: 02-17-2014
Show Abstract
Hide Abstract
A strictly anaerobic, mesophilic, carbohydrate-fermenting bacterium, designated NM-5T, was isolated from a rice paddy field. Cells of strain NM-5(T) were Gram-stain-negative, non-motile, non-spore-forming, short rods (0.5-0.7 µm×0.6-1.2 µm). The strain grew optimally at 37 °C (growth range 20-40 °C) and pH 7.0 (pH 5.5-8.0). The strain could grow fermentatively on arabinose, xylose, fructose, galactose, glucose, ribose, mannose, cellobiose, lactose, maltose and sucrose. The main end-products of glucose fermentation were acetate and propionate. Organic acids, alcohols and amino acids were not utilized for growth. Yeast extract was not required but stimulated the growth. Nitrate, sulfate, thiosulfate, elemental sulfur, sulfite, and Fe (III) nitrilotriacetate were not used as terminal electron acceptors. The DNA G+C content was 46.3 mol%. The major cellular fatty acids were iso-C14:0, C18:0 and C16:0. 16S rRNA gene sequence analysis revealed that strain NM-5T belongs to the class 'Spartobacteria', subdivision 2 of the bacterial phylum Verrucomicrobia. Phylogenetically, the closest species was 'Chthoniobacter flavus' (89.6% similarity in 16S rRNA gene sequence). A novel genus and species, Terrimicrobium sacchariphilum gen. nov., sp. nov., is proposed. The type strain of the type species is NM-5T (=JCM 17479T=CGMCC 1.5168T).
Related JoVE Video
Paludibacter jiangxiensis sp. nov., a strictly anaerobic, propionate-producing bacterium isolated from rice paddy field.
Arch. Microbiol.
PUBLISHED: 01-14-2014
Show Abstract
Hide Abstract
A mesophilic, obligately anaerobic, propionate-producing fermentative bacterium, designated strain NM7(T), was isolated from rural rice paddy field. Cells of strain NM7(T) are Gram-negative, non-motile, non-spore-forming, short rods, and negative for catalase. The strain grew optimally at 37 °C (the range for growth 15-40 °C) and pH 7.0 (pH 5.0-7.5). The strain could grow fermentatively on various sugars, including arabinose, xylose, fructose, galactose, glucose, mannose, cellobiose, lactose, maltose, sucrose, pectin and starch. The main end products of glucose fermentation were acetate and propionate. Yeast extract was not required but stimulated the growth. Nitrate, sulfate, thiosulfate, elemental sulfur, sulfite, and Fe(III) nitrilotriacetate were not used as terminal electron acceptors. The G+C content of genomic DNA was 42.8 mol%. The major cellular fatty acids were C15:0, anteiso-C15:0, C16:0, and C17:0. The most abundant polar lipid of strain NM7(T) was phosphatidylethanolamine. 16S rRNA gene sequence analysis revealed that it belongs to the family Porphyromonadaceae of the phylum Bacteroidetes. The closest recognized species was Paludibacter propionicigenes (91.4 % similarity in 16S rRNA gene sequence). A novel species, Paludibacter jiangxiensis sp. nov., is proposed to accommodate strain NM7(T) (=JCM 17480(T) = CGMCC 1.5150(T) = KCTC 5844(T)).
Related JoVE Video
Phase stability, mechanical properties, hardness, and possible reactive routing of chromium triboride from first-principle investigations.
J Chem Phys
PUBLISHED: 12-24-2013
Show Abstract
Hide Abstract
The first-principles calculations are employed to provide a fundamental understanding of the structural features and relative stability, mechanical and electronic properties, and possible reactive route for chromium triboride. The predicted new phase of CrB3 belongs to the rhombohedral phase with R-3m symmetry and it transforms into a hexagonal phase with P-6m2 symmetry at 64 GPa. The mechanical and thermodynamic stabilities of CrB3 are verified by the calculated elastic constants and formation enthalpies. Also, the full phonon dispersion calculations confirm the dynamic stability of predicted CrB3. Considering the role of metallic contributions, the calculated hardness values from our semiempirical method for rhombohedral and hexagonal phases are 23.8 GPa and 22.1 GPa, respectively. In addition, the large shear moduli, Youngs moduli, low Poissons ratios, and small B?G ratios indicate that they are potential hard materials. Relative enthalpy calculations with respect to possible constituents are also investigated to assess the prospects for phase formation and an attempt at high-pressure synthesis is suggested to obtain chromium triboride.
Related JoVE Video
Probing the structural, bonding, and magnetic properties of cobalt coordination complexes: co-benzene, co-pyridine, and co-pyrimidine.
J Phys Chem A
PUBLISHED: 11-20-2013
Show Abstract
Hide Abstract
Neutral and anionic Co1,2(benzene)1,2, Co1,2(pyridine)1,2, and Co1,2(pyrimidine)1,2 complexes have been investigated within the framework of an all-electron gradient-corrected density functional theory. The ground-state structures for each size clusters were identified based on the geometry optimization. Meanwhile, their electron affinities and vertical detachment energies were predicted and compared with the experimental values. By analyzing the pattern of highest occupied molecular orbitals (HOMOs), we found that the bond formation of these Co-organic complexes mainly arises from the 3d/4s electrons of the cobalt atoms and the ?-cloud of the organic molecules. More importantly, we presented an approach to map and analyze the Co-organic interactions from another perspective. The scatter plots of the reduced density gradient (RDG) versus ? allow us to identify the different types of interactions, and the maps of the gradient isosurfaces show a rich visualization of chemical bond and steric effects. Their magnetic properties were studied by determining the spin magnetic moments and visualizing the spin density distributions. Finally, the natural population analysis (NPA) charge was calculated to achieve a deep insight into the distribution of electron density and the reliable charge-transfer information.
Related JoVE Video
Formation and properties of iron-based magnetic superhalogens: a theoretical study.
J Chem Phys
PUBLISHED: 09-21-2013
Show Abstract
Hide Abstract
In order to explore new magnetic superhalogens, we have systematically investigated the structures, electrophilic properties, stabilities, magnetic properties, and fragmentation channels of neutral and anionic Fe(m)F(n) (m = 1, 2; n = 1-7) clusters using density functional theory. Our results show that a maximum of six F atoms can be bound atomically to one Fe atom, and the Fe-Fe bonding is not preferred in Fe2F(n)(0/-) clusters. The computed electron affinities (EAs) indicate that FeF(n) with n ? 3 are superhalogens, while Fe2F(n) can be classified as superhalogens for n ? 5. To further understand their superhalogen characteristic, the natural population analysis charge distribution and the HOMOs of anionic clusters were also analyzed. When the extra negative charge and the content of HOMO are mainly located on F atoms, the clusters could be classified as superhalogens with EAs substantially surpass that of Cl. By calculating the binding energies per atom and the HOMO-LUMO gaps, FeF3, FeF4(-), Fe2F4, Fe2F5(-), and Fe2F7(-) clusters were found to have higher stabilities, corresponding to the Fe atoms that are attained at their favorite +2 and +3 oxidation states. Furthermore, we also predicted the most preferred fragmentation channel and product for all the ground state clusters. Even more striking is the fact that both neutral and anionic Fe(m)F(n) (m = 1, 2; n = 1-7) clusters carry large magnetic moments which mainly come from 3d orbital of iron atom.
Related JoVE Video
[Research on human enterovirus 71 infectivity assay based on A real-time cell Analysis].
Bing Du Xue Bao
PUBLISHED: 07-31-2013
Show Abstract
Hide Abstract
This research aims to evaluate the application of Real - time cell assay (RTCA) based on microelectronics sensor technology in the detection of HEV71 induced cell lesion. Growth indexes of RD cells at different stages were observed dynamically, appropriate cell concentration was selected to test HEV71 infectivity and to determine the HEV71 neutralizing antibody titer in serum. The traditional microplate test was used as methodology comparison and results validation at the same time. Cell impedance was transformed to cell index (CI) value and visual dynamic curve through software, and the result showed that the observation of HEV71 infectivity was more than 5d when the RD cells concentration was 1. 5 X 10(4) hole on the 96 electronic orifice plate. Compared with the traditional cytopathic effect (CPE) through microscope observation method, the end point judgment results were consistent between these two methods at 132h (about 5. 5d) post virus inoculation. In the neutralization tests, three CI values of neutralizing antibody titers against HEV71 in human serum were correspond to those obtained from traditional 96 microplate microscopy. RTCA also suggested that the presentation time of CPE induced by the i virus could be different even the end point judgment was the same with the same neutralization antibody titer. Compared with the traditional microplate monitoring method, RTCA can save labor and eliminate the hands-on error in the monitoring HEV71 infectivity and antibody titer detection in serum. RTCA can be served as one of the supplementary methods of traditional detection method, with the advantages of dynamically observing the occurrence and development of cell pathological changes, and the variation of virus infectivity and serum neutralizing antibodies.
Related JoVE Video
Structures, electrophilic properties, and hydrogen bonds of cytidine, uridine, and their radical anions: Microhydration effects.
J Chem Phys
PUBLISHED: 07-19-2013
Show Abstract
Hide Abstract
Structures, electrophilic properties, and hydrogen bonds of the neutral and anionic monohydrated nucleoside, (cytidine)H2O, and (uridine)H2O have been systematically investigated using density functional theory. Various water-binding sites were predicted by explicitly considering the optimized monohydrated structures. Meanwhile, predictions of electron affinities and vertical detachment energies were also carried out to investigate their electrophilic properties. By examining the singly occupied molecular orbital and natural population analysis, we found the excess negative charge is localized on the cytidine and uridine moiety in anionic monohydrates. This may be the reason why the strength of hydrogen bonding undergoes an obvious change upon the extra electron attachment. Based on the electron density (?) and reduced density gradient (RDG), we present an approach to map and analyze the weak interaction (especially hydrogen bond) in monohydrated cytidine and uridine. The scatter plots of RDG versus ? allow us to identify the different type interactions. Meanwhile, the maps of the gradient isosurfaces show a rich visualization of hydrogen bond, van der Waals interaction, and steric effect.
Related JoVE Video
Evolution of structure and properties of neutral and negatively charged transition metal-coronene complexes: a comprehensive analysis.
Dalton Trans
PUBLISHED: 04-30-2013
Show Abstract
Hide Abstract
The geometries, electronic and magnetic properties of neutral and negatively charged Mn(coronene)m (M = V and Ti; n, m = 1, 2) complexes were investigated using density functional theory. The results show that one V or Ti atom prefers to occupy the ?(6)-site in M(coronene)(0/-) complexes and to be sandwiched between the two coronene molecules in M(coronene)2(0/-) complexes. Two metal atoms always form a dimer and interact with one coronene molecule. The calculated vertical electron affinities and transition energies are in good agreement with experimental values. This lends considerable credence to the obtained ground state structure and validates the chosen computational method. The bond formation between metal atom and coronene is accounted for by 3d/4s-? bonds, as revealed by the molecular orbitals plots. The reason why the peripheral ring site binds metal most effectively has been analyzed systematically by ? electron content, aromaticity and average charge on carbon atoms. The electron localization function shows that there is perfect electron delocalization in these complexes. Furthermore, the magnetic moments of V(coronene)(0/-) and Ti(coronene)(-) are found to be substantially enhanced over the corresponding free metal atom; the magnetic moment of the neutral Ti(coronene) remains unchanged; while the larger size clusters experience a reduction.
Related JoVE Video
Novel function of N,N-bis(2-chloroethyl)docos-13-enamide for reversal of multidrug resistance in tongue cancer.
Eur. J. Pharmacol.
PUBLISHED: 04-01-2013
Show Abstract
Hide Abstract
Multidrug resistance (MDR) is a key element in the failure of chemotherapies, and development of agents to overcome MDR is crucial to improving cancer treatments. The overexpression of glutathione-S-transferases (GSTs) is one of the major mechanisms of MDR. Because some agents used in traditional Chinese medicine have strong antitumor effects coupled with low toxicity; we investigated the ability of N,N-bis(2-chloroethyl)docos-13-enamide (compound J), the synthesized analog of a highly unsaturated fatty acid from Isatis tinctoria L., to reverse the MDR induced by adriamycin (ADM) in TCA8113/ADM cells. We found that compound J significantly increased the cytotoxicity of ADM in TCA8113/ADM cells, with a reversal fold of 2.461. Analysis of the mechanisms through which compound J reversed MDR indicated that compound J significantly decreased the activity of GSTs and enhanced the depletion of GSH in TCA8113/ADM cells, but did not affect the P-glycoprotein (P-gp) efflux. Taken together, our data suggested that compound J was an excellent candidate for reversing MDR in cancer therapy.
Related JoVE Video
Density functional study on size-dependent structures, stabilities, electronic and magnetic properties of Au(n)M (M = Al and Si, n = 1-9) clusters: comparison with pure gold clusters.
J Mol Model
PUBLISHED: 09-08-2011
Show Abstract
Hide Abstract
The density functional theory (DFT) method has been employed to systematically investigate the geometrical structures, relative stabilities, and electronic and magnetic properties of Au(n)M (M = Al and Si, n = 1-9) clusters for clarifying the effect of Al(Si) modulation on the gold nanostructures. Of all the clusters studied, the most stable configurations adopt a three-dimensional structure for Au(n)Al at n = 4-8 and Au(n)Si at n = 3-9, while for pure gold systems, no three-dimensional lowest energy structures are obtained. Through a careful analysis of the fragmentation energy, second-order difference of energy, HOMO-LUMO energy gap, and magnetic moment as a function of cluster size, an odd-even alternative phenomenon has been observed. The results show that the clusters with even-number valence electrons have a higher relative stability, but lower magnetic moments. Furthermore, Al(Si) doping is found to enhance the stabilities of gold frameworks. In addition, the charge analysis has been given to understand the different effects of individual doped atom on electronic properties and compared further.
Related JoVE Video
Determination of structures, stabilities, and electronic properties for bimetallic cesium-doped gold clusters: a density functional theory study.
J Phys Chem A
PUBLISHED: 08-03-2011
Show Abstract
Hide Abstract
The equilibrium geometric structures, stabilities, and electronic properties of bimetallic Au(n)Cs (n = 1-10) and pure gold Au(n) (n ? 11) clusters have been systematically investigated by using density functional theory with meta-generalized gradient approximation. The optimized geometries show that one Au atom capped on Au(n-1)Cs structures and Cs atom capped Au(n) structures for different sized Au(n)Cs (n = 1-10) clusters are two dominant growth patterns. Theoretical calculated results indicate that the most stable isomers have three-dimensional structures at n = 4 and 6-10. Averaged atomic binding energies, fragmentation energies, and second-order difference of energies exhibit a pronounced even-odd alternations phenomenon. The same even-odd alternations are found in the highest occupied-lowest unoccupied molecular orbital gaps, vertical ionization potential, vertical electron affinity, and hardnesses. In addition, it is found that the charge in corresponding Au(n)Cs clusters transfers from the Cs atom to the Au(n) host in the range of 0.851-1.036 electrons.
Related JoVE Video
Structural, electronic and magnetic effects of Al-doped niobium clusters: a density functional theory study.
J Mol Model
PUBLISHED: 07-12-2011
Show Abstract
Hide Abstract
The application of the ab initio stochastic search procedure with Saunders "kick" method has been carried out for the elucidation of global minimum structures of a series of Al-doped clusters, Nb(n)Al (1 ? n ? 10). We have studied the structural characters, growth behaviors, electronic and magnetic properties of Nb(n)Al by the density functional theory calculations. Unlike the previous literature reported on Al-doped systems where ground state structures undergo a structural transition from the Al-capped frame to Al-encapsulated structure, we found that Al atom always occupies the surface of Nb(n)Al clusters and structural transition does not take place until n = 10. Note that the fragmentation proceeds preferably by the ejection of an aluminum atom other than niobium atom. According to the natural population analysis, charges always transfer from aluminum to niobium atoms. Furthermore, the magnetic moments of the Nb(n)Al clusters are mainly located on the 4d orbital of niobium atoms, and aluminum atom possesses very small magnetic moments.
Related JoVE Video
Hyperthyroidism-associated coronary spasm: A case of non-ST segment elevation myocardial infarction with thyrotoxicosis.
J Geriatr Cardiol
PUBLISHED: 06-27-2011
Show Abstract
Hide Abstract
Hyperthyroidism is associated with many heart diseases. Thyrotoxic state has a relationship with coronary spasm. We present a case of a non-menopausal woman with hyperthyroidism who complained of chest pain. The diagnosis of coronary spasm was confirmed by coronary angiography (CAG). She is treated well with anti-thyrotoxicosis and anti-anginal medication. We recommend not use CAG as the first diagnostic choice among the patients with medication-uncontrolled hyperthyroidism and chest pain.
Related JoVE Video
Geometries, stabilities, and electronic properties of Pt-group-doped gold clusters, their relationship to cluster size, and comparison with pure gold clusters.
Phys Chem Chem Phys
PUBLISHED: 04-26-2011
Show Abstract
Hide Abstract
A systematic study of bimetallic Au(n)M(2) (n = 1-6, M = Ni, Pd, and Pt) clusters is performed by using density functional theory at the B3LYP level. The geometric structures, relative stabilities, HOMO-LUMO gaps, natural charges and electronic magnetic moments of these clusters are investigated, and compared with pure gold clusters. The results indicate that the properties of Au(n)M(2) clusters for n = 1-3 diverge more from pure gold clusters, while those for n = 4-6 show good agreement with Au(n) clusters. The dissociation energies, the second-order difference of energies, and HOMO-LUMO energy gaps, exhibiting an odd-even alternation, indicate that the Au(4)M(2) clusters are the most stable structures for Au(n)M(2) (n = 1-6, M = Ni, Pd, and Pt) clusters. Moreover, we predict that the average atomic binding energies of these clusters should tend to a limit in the range 1.56-2.00 eV.
Related JoVE Video
Probing the structural and magnetic properties of transition metal-benzene anion complexes.
Dalton Trans
PUBLISHED: 03-24-2011
Show Abstract
Hide Abstract
Two types of transition metal-benzene anion complexes, (titanium)(n)(benzene)(m)? and (cobalt)(n)(benzene)(m)? (n ? 2, m ? 3) have been determined using density functional theory. The photoelectron spectra of Ti(n)Bz(m)? and Co(n)Bz(m)? (n ? 2, m ? 3) were discussed from the perspective of quantum chemical calculations of the vertical detachment energies (VDEs) of several low-energy isomers obtained by the structural optimization procedure. The binding of Ti and Co atoms to benzene molecules is accounted by 3d-? bonds, as revealed by the molecular orbitals. The topology of the electronic density has been analyzed, suggesting that the C-C bonds were weakened in the transition metal-benzene complexes in comparison to those in free benzene. Spin density distribution results show the spin densities for Ti(n)Bz(m)? and Co(n)Bz(m)? (n ? 2, m ? 3) reside mainly on the metal Ti and Co centers (70%-90%). A shift to lower magnetic moment with respect to the pure titanium/cobalt cluster anions indicates the solvent benzene molecule acts to demagnetize the bare titanium/cobalt cluster anions.
Related JoVE Video
Ab initio calculation of the geometries, stabilities, and electronic properties for the bimetallic Be2Au(n) (n = 1-9) clusters: comparison with pure gold clusters.
J Mol Model
PUBLISHED: 03-18-2011
Show Abstract
Hide Abstract
Ab initio methods based on density functional theory at BP86 level were applied to the study of the geometrical structures, relative stabilities, and electronic properties of small bimetallic Be(2)Au(n) (n = 1-9) clusters. The optimized geometries reveal that the most stable isomers have 3D structures at n = 3, 5, 7, 8, and 9. Here, the relative stabilities were investigated in terms of the averaged atomic binding energies, fragmentation energies and second-order difference of energies. The results show that the planar Be(2)Au(4) structure is the most stable structure for Be(2)Au(n) clusters. The HOMO-LUMO gap, vertical ionization potential, vertical electron affinity and chemical hardness exhibit a pronounced even-odd alternating phenomenon. In addition, charge transfer and natural electron configuration were analyzed and compared.
Related JoVE Video
A systematic search for the structures, stabilities, and electronic properties of bimetallic Ca?-doped gold clusters: comparison with pure gold clusters.
J Mol Model
PUBLISHED: 03-14-2011
Show Abstract
Hide Abstract
The local meta-GGA exchange correlation density functional (TPSS) with a relativistic effective core potential was employed to systematically investigate the geometric structures, stabilities, and electronic properties of bimetallic Ca(2)Au( n ) (n?=?1-9) and pure gold Au( n ) (n???11) clusters. The optimized geometries show that the most stable isomers for Ca(2)Au( n ) clusters have 3D structure when n?>?2, and that one Au atom capping the Ca(2)Au( n-1) structure for different-sized Ca(2)Au( n ) (n?=?1-9) clusters is the dominant growth pattern. The average atomic binding energies and second-order difference in energies show that the Ca(2)Au(4) isomer is the most stable among the Ca(2)Au( n ) clusters. The same pronounced even-odd alternations are found in the HOMO-LUMO gaps, VIPs, and hardnesses. The polarizabilities of the Ca(2)Au( n ) clusters show an obvious local minimum at n?=?4. Moreover, the inverse corrections to the polarizabilities versus the ionization potential and hardness were found for the gold clusters.
Related JoVE Video
A DFT study on equilibrium geometries, stabilities, and electronic properties of small bimetallic Na-doped Au(n) (n = 1-9) clusters: comparison with pure gold clusters.
J Mol Model
PUBLISHED: 02-18-2011
Show Abstract
Hide Abstract
A systematic study on the geometric structures, relative stabilities, and electronic properties of small bimetallic Au(n)Na (n = 1-9) clusters has been performed by means of first-principle density functional theory calculations at the PW91PW91 level. The results show that the optimized ground-state isomers adopt planar structures up to n = 5, and the Na-capped geometries are dominant growth patterns for n = 6-9. Dramatic odd-even alternative behaviors are obtained in the second-order difference of energies, fragmentation energies, highest occupied-lowest unoccupied molecular orbital energy gaps, and chemical hardness for both Au(n)Na and Au(n+1) clusters. It is found that Au(5)Na and Au(6) have the most enhanced stability. Here, the size evolutions of the theoretical ionization potentials are in agreement with available experimental data, suggesting a good prediction of the lowest energy structures in the present study. In addition, the charge transfer has been analyzed on the basis of natural population analysis.
Related JoVE Video
Equilibrium geometries, stabilities, and electronic properties of the bimetallic M2-doped Au(n) (M = Ag, Cu; n = 1-10) clusters: comparison with pure gold clusters.
J Phys Chem A
PUBLISHED: 12-30-2010
Show Abstract
Hide Abstract
The density functional method with relativistic effective core potential has been employed to investigate systematically the geometrical structures, relative stabilities, growth-pattern behaviors, and electronic properties of small bimetallic M(2)Au(n) (M = Ag, Cu; n = 1-10) and pure gold Au(n) (n ? 12) clusters. The optimized geometries reveal that M(2) substituted Au(n+2) clusters and one Au atom capped M(2)Au(n-1) structures are dominant growth patterns of the stable alloyed M(2)Au(n) clusters. The calculated averaged atomic binding energies, fragmentation energies, and the second-order difference of energies as a function of the cluster size exhibit a pronounced even-odd alternation phenomenon. The analytic results exhibit that the planar structure Ag(2)Au(4) and Cu(2)Au(2) isomers are the most stable geometries of Ag(2)Au(n) and Cu(2)Au(n) clusters, respectively. In addition, the HOMO-LUMO gaps, charge transfers, chemical hardnesses and polarizabilities have been analyzed and compared further.
Related JoVE Video
[Epidemiology and etiology of hand-foot-and-mouth disease in Shanghai, 2009].
Bing Du Xue Bao
PUBLISHED: 11-24-2010
Show Abstract
Hide Abstract
To analyze the epidemiological and etiological characteristics of Hand-Foot-and-Mouth disease (HFMD) in Shanghai in 2009, epidemiological data was retrieved from the National Notifiable Disease Report System (NNDRS). Nucleic acid of enterovirus (EV) was detected by real-time RT-PCR from 799 HFMD cases from 15 districts/counties in Shanghai; the complete sequences of VP1 encoding region of several identified EV71 strains and sequences of VP4 encoding region of several untyped EV were determined and analyzed. Analysis and summary of the epidemiological data was conducted with Microsoft Excel, and sequence analyses were conducted with both BioEdit and MEGA software. Untyped EV was identified through comparing the VP4 sequence to sequence database using BLAST online service. It was showed that all the 18 districts/counties had reported HFMD cases; children less than 6 years old were the most susceptible population group; the peak of epidemics of HFMD was from April to July; EV71 and Coxsackievirus A16 (CA16) were the major pathogens for this epidemic, but the constituent ratio of EV71 and CA16 was different in different months and regions; CA16 infection was mainly responsible for the mild HFMD, but EV71 for most of the severe cases; EV71 strains of Shanghai were clustered with representatives of subgenotype C4a and showed the highest identity to them, based on the sequence analyses of VP1 encoding region; 2 of the untyped EV were identified as CA2 and CA10 respectively. All the results indicated that EV71 and CA16 were the major pathogens for the epidemic of HFMD in Shanghai, 2009; the circulating EV71 belonged to subgenotype C4a. Besides, other types of EV (for example: CA2 and CA10) were also responsible for a few of the HFMD cases.
Related JoVE Video
Geometries, stabilities, and electronic properties of small anion Mg-doped gold clusters: a density functional theory study.
J Phys Chem A
PUBLISHED: 10-13-2010
Show Abstract
Hide Abstract
First-principle density functional theory is used for studying the anion gold clusters doped with magnesium atom. By performing geometry optimizations, the equilibrium geometries, relative stabilities, and electronic and magnetic properties of [Au(n)Mg]? (n = 1-8) clusters have been investigated systematically in comparison with pure gold clusters. The results show that doping with a single Mg atom dramatically affects the geometries of the ground-state Au(n+1)? clusters for n = 2-7. Here, the relative stabilities are investigated in terms of the calculated fragmentation energies, second-order difference of energies, and highest occupied?lowest unoccupied molecular orbital energy gaps, manifesting that the ground-state [Au(n)Mg]? and Au(n+1)? clusters with odd-number gold atoms have a higher relative stability. In particular, it should be noted that the [Au?Mg]? cluster has the most enhanced chemical stability. The natural population analysis reveals that the charges in [Au(n)Mg]? (n = 2-8) clusters transfer from the Mg atom to the Au frames. In addition, the total magnetic moments of [Au(n)Mg]? clusters exhibit an odd-even oscillation as a function of cluster size, and the magnetic effects mainly come from the Au atoms.
Related JoVE Video
Preparation and characterization of ceria-zirconia composite for enrichment and identification of phosphopeptides.
J Sep Sci
PUBLISHED: 06-25-2010
Show Abstract
Hide Abstract
Ceria-zirconia composites at different molar ratios were synthesized. Several methods were used to characterize these composites, including X-ray photoelectron spectroscopy, surface area and surface acid-base property detection. A one-step method for isolation and identification of phosphopeptides from peptide mixture was created using these ceria-zirconia composites. Using tryptic digest of standard phosphorylated protein, we have shown that these enrichment and dephosphorylation activities are effective. The adsorption capacity and catalytic property of ceria-zirconia composites at different molar ratios and calcinated temperatures were studied. In combination with MALDI-TOF-based peptide mass finger printing technique, we have established a method to utilize the enrichment/dephosphorylation dual properties of these ceria-zirconia composites for the analysis of phosphoprotein in nonfat milk successfully.
Related JoVE Video
The use of liquid phase deposition prepared phosphonate grafted silica nanoparticle-deposited capillaries in the enrichment of phosphopeptides.
J Sep Sci
PUBLISHED: 05-15-2010
Show Abstract
Hide Abstract
In our current work, we describe how open tubular-immobilized metal-ion affinity chromatography (OT-IMAC) capillary columns connected to a solid phase microextraction (in-tube SPME) device can be used for the enrichment of phosphopeptides. A phosphonate modified silica nanoparticle (NP)-deposited capillary was prepared by liquid phase deposition (LPD), and used for the immobilization of Fe(3+), Zr(4+) or Ti(4+). The enrichment capacities of three different OT-IMAC capillary columns were compared by using tryptically digested alpha-casein as sample. The improved extraction efficiency in our technique was demonstrated by comparing to a directly modified capillary, and a comparison of phosphopeptide extraction from simple and complex samples was tested for both modes. Our results show that the NP-IMAC-Zr(4+) capillary column can be used to selectively isolate phosphopeptides from real samples, and can enrich for beta-casein phosphopeptides from concentrations as low as 1.7x10(-9) M.
Related JoVE Video
Density functional study of structural and electronic properties of bimetallic copper-gold clusters: comparison with pure and doped gold clusters.
Phys Chem Chem Phys
PUBLISHED: 04-01-2010
Show Abstract
Hide Abstract
The geometrical structures, relative stabilities, and electronic properties of small bare gold clusters Au(n)(lambda) and bimetallic complexes of bare metal clusters with one copper atom Au(n-1)Cu(lambda) (charge lambda = 0, +1, -1; 2 < or = n < or = 9) have been systematically investigated by means of first-principles density functional calculations at the B3LYP level. The results show that the most stable isomers have a planar structure and resemble pure gold clusters in shape, and no three-dimensional isomers were obtained for neutral and anionic doped gold clusters. However, the geometries of Au(n-1)Cu(+) are found to undergo a structural change from two dimensional to three dimensional when the cluster contains 7 atoms. The calculated dissociation energy and second difference energy as a function of the cluster size exhibit a pronounced even-odd alternation phenomenon. Ionization potentials and electron detachment energies (both vertical and adiabatic) of Au(n)(lambda) and Au(n-1)Cu(lambda) clusters are discussed and compared with available experimental results. A good agreement between experimental and theoretical results suggests good prediction of the lowest energy structures for all clusters calculated in the present study.
Related JoVE Video
Real-time detection of single-living pancreatic beta-cell by laser tweezers Raman spectroscopy: high glucose stimulation.
Biopolymers
PUBLISHED: 01-22-2010
Show Abstract
Hide Abstract
Glucose acts as a beta-cell stimulus factor and leads to cellular responses that involve a large amount of biomolecule formation, relocation, and transformation. We hypothesize that information about these changes can be obtained in real-time by laser tweezers Raman spectroscopy. To test this hypothesis, repeated measurements designs in accordance with the application of Raman spectroscopy detection were used in the current experiment. Single rat beta-cells were measured by Raman spectroscopy in 2.8 mmol/l glucose culture medium as a basal condition. After stimulation with high glucose (20 mmol/l), the same cells were measured continuously. Each cell was monitored over a total time span of 25 min, in 5 min intervals. During this period of time, cells were maintained at an appropriate temperature controlled by an automatic heater, to provide near-physiological conditions. It was found that some significant spectral changes induced by glucose were taking place during the stimulation time course. The most noticeable changes were the increase of spectral intensity at the 1002, 1085, 1445, and 1655 cm(-1) peaks, mainly corresponding to protein and lipid. We speculate that these changes might have to do with beta-cell protein and lipid synthesis. Using laser tweezers Raman spectroscopy in combination with glucose stimulation, optical spectral information from rat beta-cells was received and analyzed.
Related JoVE Video
Theoretical studies of EPR spectra and defect structure for Er3+ center in lithium niobate.
Spectrochim Acta A Mol Biomol Spectrosc
PUBLISHED: 01-04-2010
Show Abstract
Hide Abstract
The optical and EPR spectra of octahedral Er(3+) center in LiNbO(3) have been studied by diagonalizing 364 x 364 complete energy matrices. The new set of crystal-field parameters that can well account for the Stark levels and EPR parameters have been obtained for Er(3+) ions in LiNbO(3). Simultaneously, by simulating the most reliable six-order parameter B(60) obtained, we have presented the evidence that the Er(3+) ions do not occupy the actual Li(+) site, but have a displacement along the C(3)-axis away from the Li(+) center by about 0.0454 nm. The conclusion is well in accord with that drawn by earlier workers.
Related JoVE Video
Structural, electronic, and magnetic properties of gold cluster anions doped with zinc: Au(n)Zn- (2 < or = n < or = 10).
J Phys Chem A
PUBLISHED: 10-31-2009
Show Abstract
Hide Abstract
The geometrical structures, relative stabilities, electronic, and magnetic properties of zinc-doped gold cluster anions Au(n)Zn(-) (2 < or = n < or = 10) have been systematically investigated by means of first-principles density functional calculations at the B3LYP level. The results show that the most stable isomers have a planar structure and resemble pure gold cluster anions in shape, and no 3D isomers were obtained. Calculated dissociation energy, the second difference energy, and the highest occupied-lowest unoccupied molecular orbital gaps as a function of the cluster size exhibit a pronounced even-odd alternation phenomenon. The first vertical detachment energy of the anion clusters were calculated and compared with available experimental results. A good agreement between experimental and theoretical results suggests good prediction of the lowest-energy structures for all clusters calculated in the present study. Furthermore, both the local and total magnetic moments display a pronounced odd-even oscillation with the number of gold atoms.
Related JoVE Video
Theoretical study on local defect structure of (FeO4)(5-) clusters in YGG and LGG crystals.
Spectrochim Acta A Mol Biomol Spectrosc
PUBLISHED: 02-11-2009
Show Abstract
Hide Abstract
The optical spectrum and the local defect structure of tetrahedral (FeO4)(5-) clusters are investigated in yttrium gallium garnet (YGG) and lutetium gallium garnet (LGG) crystals by means of the 252x252 complete energy matrices for d(5) configuration ions in tetragonal ligand field. The results show that the local defect structures around tetrahedral Fe3+ centers display an expansion effect. Simultaneously, the (FeO4(5-) clusters in the two different crystals have very similar local structures, which are close to those in YIG garnet crystal. Finally the relative curves of the zero-field splitting energies DeltaE1 and DeltaE2 in the ground state (6)A(1) varying with the structure parameter theta are plotted.
Related JoVE Video
Rapid determination of Delta9-Tetrahydrocannabinol in saliva by polymer monolith microextraction combined with gas chromatography-mass spectrometry.
Talanta
PUBLISHED: 01-23-2009
Show Abstract
Hide Abstract
A method was developed for the determination of Delta(9)-Tetrahydrocannabinol (THC) in saliva by polymer monolith microextraction (PMME) combined with gas chromatography-mass spectrometry. The poly(methacrylic acid-co-ethylene glycol dimethacrylate) (p(MAA-co-EGDMA)) monolithic capillary column was selected as the extraction medium of PMME, which showed high extraction capacity towards THC in saliva. To reach optimum PMME extraction performance, several PMME parameters were investigated, including matrix pH, flow rate for extraction, sampling volume and elution solvent. Under the optimal conditions, good extraction efficiency was obtained with no matrix interference in the process of extraction and the subsequent GC-MS analysis. In the selected-ion monitoring (SIM) mode, the limit of detection (LOD) for THC was 0.68 ng/mL. The linearity range of the method was 3-300 ng/mL. Excellent reproducibility of the method was exhibited by intra- and inter-day precisions, yielding the relative standard deviations (R.S.D.s) less than 12%; recoveries higher than 89%. The proposed method was proved to be rapid, sensitive, and competently applied to the determination of THC in saliva samples.
Related JoVE Video
Probing the structural, electronic and magnetic properties of multicenter Fe?S??/?, Fe?S??/? and Fe?S??/? clusters.
J Mol Model
Show Abstract
Hide Abstract
The structural, electronic and magnetic properties of neutral and anion Fe2S2, Fe3S4 and Fe4S4 have been investigated with the aid of previous photoelectron spectroscopy and density functional theory calculations. Theoretical electron detachment energies (both vertical and adiabatic) of anion clusters for the lowest energy structure were computed and compared with the experimental results to verify the ground states. The optimized structures show that the ground state structures of Fe2S2(0/-), Fe3S4(0/-) and Fe4S4(0/-) favor high spin state and are similar to their structures in proteins. The electron delocalization pattern for all the clusters and the nature of bonding between Fe and S atoms were studied by analyzing molecular orbitals. Natural population analysis demonstrates that Fe atoms act as an electron donor in all clusters, and the electron density difference map clearly shows the direction of the electron flow over the whole complex. Furthermore, the investigated magnetism shows that the Fe atoms carried most of the magnetic moments, which is due mainly to the 3d state, while only very small magnetic moments are found on S atoms.
Related JoVE Video
Studies of EPR spectra and defect structure for Er³? ions in BaF? and SrF? crystals.
Spectrochim Acta A Mol Biomol Spectrosc
Show Abstract
Hide Abstract
The local lattice structure and electron paramagnetic resonance (EPR) spectra have been studied systematically by diagonalizing 364 × 364 complete energy matrices for a f(11) ion in a trigonal ligand-field. By simulating the calculated Stark levels and EPR parameters to the experimental results, the shift parameters are determined for Er(3+) ions in BaF(2) and SrF(2). The results show that the trigonal center is attributed to an interstitial F(-) ion located at the [111] axis of the cube, and the nearest ligand close to the charge compensator has a displacement towards central ion by 0.042Å for L center in BaF(2):Er(3+) and 0.026Å for J center in SrF(2):Er(3+), respectively. Moreover, the relationships between g-factors and shift parameter ?Z as well as orbit reduction factor k are discussed.
Related JoVE Video
Constructions of two polycatenanes and one polypseudo-rotaxane by discrete tetrahedral cages and stool-like building units.
Sci Rep
Show Abstract
Hide Abstract
Mechanically Interlocked molecules, such as catenanes and rotaxanes, are of great interest due to their fascinating structures and potential applications, while such molecules have been mainly restricted to comprising components of interlocked rings or polygons. The constructions of infinite polycatenanes and polyrotaxanes by discrete cages remain great challenge, and only two infinite polycatenanes fabricated by discrete cages have been reported so far, while the structures of polyrotaxanes and polypseudo-rotaxanes fabricated by discrete build units have not been documented to date. Herein we report the first example of a two-dimensional (2D) polypseudo-rotaxane fabricated by stool-like build units, the second example of a one-dimensional (1D) polycatenane, and the second example of a three-dimensional (3D) polycatenane, which were assemblied by discrete tetrahedral cages. The pores of dehydrated 3D polycatenane are dynamic, and display size-dependent adsorption/desorption behaviors of alcohols.
Related JoVE Video
Two hybrid polyoxometalate-pillared metal-organic frameworks.
Dalton Trans
Show Abstract
Hide Abstract
Two polyoxometalate-pillared 3D compounds, {Cu(5)(2-ptz)(6)(H(2)O)(4)(SiW(12)O(40))}·4H(2)O 1 and {Cu(9)(2-ptz)(12)(H(2)O)(6)(PMo(12)O(40))(2)}·H(2)O 2 (2-ptz = 5-(2-pyridyl)tetrazole) have been constructed based on different polyoxometalate anions, and copper-organic coordination polymer sheets by a hydrothermal method. Magnetic investigations reveal that both 1 and 2 exhibit antiferromagnetic coupling between the Cu(II) ions. Structural studies show the compound 1 exhibits a typical pcu-type net with the Schälfli symbol of {4(12)·6(3)}, and that compound 2 is a (3,4,6)-connected framework with novel {4(4)·6(10)·10}{6(3)}(2){6(5)·8} topology which has not been reported to date.
Related JoVE Video
Probing the structural and electronic properties of aluminum-sulfur AlnSm (2?n+m?6) clusters and their oxides.
J Mol Model
Show Abstract
Hide Abstract
Using the first-principle density functional calculations, the equilibrium geometries and electronic properties of anionic and neutral aluminum-sulfur AlnSm (2?n+m?6) clusters have been systematically investigated at B3PW91 level. The optimized results indicate that the lowest-energy structures of the anionic and neutral AlnSm clusters prefer the low spin multiplicities (singlet or doublet) except the Al2?, Al2, S2, Al4 and Al2S4 clusters. A significant odd-even oscillation of the highest occupied-lowest unoccupied molecular orbital (HOMO-LUMO) energy gaps for the AlnSm? clusters is observed. Electron detachment energies (both vertical and adiabatic) are discussed and compared with the photoelectron spectra observations. Furthermore, a good agreement between experimental and theoretical results gives confidence in the most stable clusters considered in the present study and validates the chosen computational method. In addition, the variation trend of chemical hardness is in keeping with that of HOMO-LUMO energy gaps for the AlnSm clusters. Upon the interaction of oxygen with the stable AlSm? clusters, the dissociative chemisorptions are favorable in energy. The binding energy and Gibbs free energy change show completely opposite oscillating behaviors as the cluster size increases.
Related JoVE Video
Theoretical investigation on the structural and thermodynamic properties of FeSe at high pressure and high temperature.
Dalton Trans
Show Abstract
Hide Abstract
A theoretical investigation on structural and thermodynamic properties of 11-type iron-based superconductor FeSe at high pressure and high temperature was performed by employing the first-principles method based on the density functional theory. Some structural parameters of FeSe in both tetragonal and hexagonal phases are reported. According to the fourth-order Birch-Murnaghan equation of states, the transition pressure P(t) of FeSe from the PbO-type phase to the NiAs-type phase was determined. The calculated results are found to be in good agreement with the available experimental data. Based on the quasi-harmonic Debye model, the pressure and temperature dependence of the thermodynamic properties for hexagonal phase FeSe were investigated. Our theoretical calculations suggest that the pressure and temperature have significant effects on the heat capacity, vibrational internal energy, vibrational entropy, vibrational Helmholtz free energy, thermal expansion coefficient and Debye temperature. Even though few theoretical reports on the structural properties of FeSe are found in the current literature, to our knowledge, this is a novel theoretical investigation on the structural and thermodynamic properties of FeSe at high temperature. We hope that the theoretical results reported here can give more insight into the structural and thermodynamic properties of other iron-based superconductors at high temperature.
Related JoVE Video
Probing the structural and electronic properties of small vanadium monoxide clusters.
Phys Chem Chem Phys
Show Abstract
Hide Abstract
The structural evolution and bonding of a series of early transition-metal oxide clusters, V(n)O(q) (n = 3-9, q = 0,-1), have been investigated with the aid of previous photoelectron spectroscopy (PES) and theoretical calculations. For each vanadium monoxide cluster, many low-lying isomers are generated using the Saunders "Kick" global minimum stochastic search method. Theoretical electron detachment energies (both vertical and adiabatic) were compared with the experimental measurements to verify the ground states of the vanadium monoxide clusters obtained from the DFT calculations. The results demonstrate that the combination of photoelectron spectroscopy experiments and DFT calculation is not only powerful for obtaining the electronic and atomic structures of size-selected clusters, but also valuable in resolving structurally and energetically close isomers. The second difference energies and adsorption energies as a function of the cluster size exhibit a pronounced even-odd alternation phenomenon. The adsorption energies of one O atom on the anionic (6.64 ? 8.16 eV) and neutral (6.41 ? 8.13 eV) host vanadium clusters are shown to be surprisingly high, suggesting strong capabilities to activate O by structural defects in vanadium oxides.
Related JoVE Video
Promising oxonitridosilicate phosphor host Sr3Si2O4N2: synthesis, structure, and luminescence properties activated by Eu2+ and Ce3+/Li+ for pc-LEDs.
Inorg Chem
Show Abstract
Hide Abstract
A novel oxonitridosilicate phosphor host Sr(3)Si(2)O(4)N(2) was synthesized in N(2)/H(2) (6%) atmosphere by solid state reaction at high temperature using SrCO(3), SiO(2), and Si(3)N(4) as starting materials. The crystal structure was determined by a Rietveld analysis on powder X-ray and neutron diffraction data. Sr(3)Si(2)O(4)N(2) crystallizes in cubic symmetry with space group Pa ?3, Z = 24, and cell parameter a = 15.6593(1) Å. The structure of Sr(3)Si(2)O(4)N(2) is constructed by isolated and highly corrugated 12 rings which are composed of 12 vertex-sharing [SiO(2)N(2)] tetrahedra with bridging N and terminal O to form three-dimensional tunnels to accommodate the Sr(2+) ions. The calculated band structure shows that Sr(3)Si(2)O(4)N(2) is an indirect semiconductor with a band gap ? 2.84 eV, which is close to the experimental value ? 2.71 eV from linear extrapolation of the diffuse reflection spectrum. Sr(3-x)Si(2)O(4)N(2):xEu(2+) shows a typical emission band peaking at ~600 nm under 460 nm excitation, which perfectly matches the emission of blue InGaN light-emitting diodes. For Ce(3+)/Li(+)-codoped Sr(3)Si(2)O(4)N(2), one excitation band is in the UV range (280-350 nm) and the other in the UV blue range (380-420 nm), which matches emission of near-UV light-emitting diodes. Emission of Sr(3-2x)Si(2)O(4)N(2):xCe(3+),xLi(+) shows a asymmetric broad band peaking at ~520 nm. The long-wavelength excitation and emission of Eu(2+) and Ce(3+)/Li(+)-doped Sr(3)Si(2)O(4)N(2) make them attractive for applications in phosphor-converted white light-emitting diodes.
Related JoVE Video
Equilibrium geometries, stabilities, and electronic properties of the cationic Au n Be + (n?=?1-8) clusters: comparison with pure gold clusters.
J Mol Model
Show Abstract
Hide Abstract
Ab initio method based on density functional theory at PW91PW91 level has been applied in studying the geometrical structures, relative stabilities, and electronic properties of small bimetallic Au(n)Be(+) (n?=?1-8) cluster cations. The geometrical optimizations indicate that a transition point from preferentially planar (two-dimensional) to three-dimensional (3D) structures occurs at n?=?6. The relative stabilities of Au(n)Be(+) clusters for the ground-state structures are analyzed based on the averaged binding energies, fragmentation energies, and second-order difference of energies. The calculated results reveal that the AuBe(+) and Au(5)Be(+) clusters possess higher relative stability for small size Au(n)Be(+) (n?=?1-8) clusters. The HOMO-LUMO energy gaps as a function of the cluster size exhibit a pronounced even-odd alternation phenomenon. Sequently, the natural population analysis and polarizability for our systems have been analyzed and compared further.
Related JoVE Video

What is Visualize?

JoVE Visualize is a tool created to match the last 5 years of PubMed publications to methods in JoVE's video library.

How does it work?

We use abstracts found on PubMed and match them to JoVE videos to create a list of 10 to 30 related methods videos.

Video X seems to be unrelated to Abstract Y...

In developing our video relationships, we compare around 5 million PubMed articles to our library of over 4,500 methods videos. In some cases the language used in the PubMed abstracts makes matching that content to a JoVE video difficult. In other cases, there happens not to be any content in our video library that is relevant to the topic of a given abstract. In these cases, our algorithms are trying their best to display videos with relevant content, which can sometimes result in matched videos with only a slight relation.