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.
Intermolecular interactions of trifluorohalomethanes with Lewis bases in the gas phase: An ab initio study.
J Chem Phys
PUBLISHED: 10-10-2014
Show Abstract
Hide Abstract
We perform an ab initio computational study of molecular complexes with the general formula CF3X-B that involve one trifluorohalomethane CF3X (X = Cl or Br) and one of a series of Lewis bases B in the gas phase. The Lewis bases are so chosen that they provide a range of electron-donating abilities for comparison. Based on the characteristics of their electron pairs, we consider the Lewis bases with a single n-pair (NH3 and PH3), two n-pairs (H2O and H2S), two n-pairs with an unsaturated bond (H2CO and H2CS), and a single ?-pair (C2H4) and two ?-pairs (C2H2). The aim is to systematically investigate the influence of the electron pair characteristics and the central atom substitution effects on the geometries and energetics of the formed complexes. The counterpoise-corrected supermolecule MP2 and coupled-cluster single double with perturbative triple [CCSD(T)] levels of theory have been employed, together with a series of basis sets up to aug-cc-pVTZ. The angular and radial configurations, the binding energies, and the electrostatic potentials of the stable complexes have been compared and discussed as the Lewis base varies. For those complexes where halogen bonding plays a significant role, the calculated geometries and energetics are consistent with the ?-hole model. Upon formation of stable complexes, the C-X bond lengths shorten, while the C-X vibrational frequencies increase, thus rendering blueshifting halogen bonds. The central atom substitution usually enlarges the intermolecular bond distances while it reduces the net charge transfers, thus weakening the bond strengths. The analysis based on the ?-hole model is grossly reliable but requires suitable modifications incorporating the central atom substitution effects, in particular, when interaction components other than electrostatic contributions are involved.
Related JoVE Video
Evolution of microstructure and residual stress under various vibration modes in 304 stainless steel welds.
ScientificWorldJournal
PUBLISHED: 01-01-2014
Show Abstract
Hide Abstract
Simultaneous vibration welding of 304 stainless steel was carried out with an eccentric circulating vibrator and a magnetic telescopic vibrator at subresonant (362?Hz and 59.3?Hz) and resonant (376?Hz and 60.9?Hz) frequencies. The experimental results indicate that the temperature gradient can be increased, accelerating nucleation and causing grain refinement during this process. During simultaneous vibration welding primary ? -ferrite can be refined and the morphologies of retained ?-ferrite become discontinuous so that ?-ferrite contents decrease. The smallest content of ?-ferrite (5.5%) occurred using the eccentric circulating vibrator. The diffraction intensities decreased and the FWHM widened with both vibration and no vibration. A residual stress can obviously be increased, producing an excellent effect on stress relief at a resonant frequency. The stress relief effect with an eccentric circulating vibrator was better than that obtained using a magnetic telescopic vibrator.
Related JoVE Video
Removal of ciprofloxacin from water by birnessite.
J. Hazard. Mater.
PUBLISHED: 02-04-2013
Show Abstract
Hide Abstract
With more pharmaceuticals and personal care products detected in the surface and waste waters, studies on interactions between these contaminants and soils or sediments have attracted great attention. In this study, the removal of ciprofloxacin (CIP), a fluoroquinolone antibiotic, by birnessite, a layered manganese oxide, in aqueous solution was investigated by batch studies supplemented by X-ray diffraction (XRD) and Fourier transform infrared analyses. Stoichiometric release of exchangeable cations accompanying CIP removal from water confirmed cation exchange as the major mechanism for CIP uptake by birnessite. Interlayer expansion after CIP adsorption on birnessite as revealed by XRD analyses indicated that intercalation contributed significantly to CIP uptake in addition to external surface adsorption. Correlation of CIP adsorption to specific surface area and cation exchange capacity suggested that the former was the limiting factor for CIP uptake. At the adsorption maximum, CIP molecules formed a monolayer on the birnessite surfaces. The adsorbed CIP could be partially removed using a cationic surfactant at a low initial concentration and mostly removed by AlCl3 at a higher initial concentration, which further supported the cation exchange mechanism for CIP removal by birnessite. The results indicated that the presence of layered Mn-oxide in the soil and waste water treatment systems may provide host for CIP accumulation.
Related JoVE Video
Quantitation of sudomotor innervation in skin biopsies of patients with diabetic neuropathy.
J. Neuropathol. Exp. Neurol.
PUBLISHED: 09-23-2011
Show Abstract
Hide Abstract
Previous assessments of the sudomotor system have depended on functional tests, and only a few studies document the pathologic findings of postganglionic nerve degeneration quantitatively and at the ultrastructural level. We developed a quantitative system of sudomotor innervation in skin biopsies of the distal leg by immunostaining of nerve fibers with anti-protein gene product 9.5 (PGP9.5) and by counterstaining with Congo red. A computerized area-based morphometric analysis was used to quantify the sweat gland innervation index (SGII), defined as the area of nerve fibers normalized to the area of sweat glands. This approach reduced the variations in measurements of sweat gland areas compared to the commonly used method by ?5.6-fold (2.47% ± 2.54% vs 13.97% ± 14.24%, p < 0.001); hence, variations in SGII were also reduced. We examined 35 Type 2 diabetic patients (24 men and 11 women; mean age, 56.5 ± 12.8 years), with symmetrical length-dependent neuropathy and reduced intraepidermal nerve fiber density (0.76 ± 0.95 fibers/mm). By light and electron microscopy, PGP9.5-positive nerve terminals surrounded Congo red-positive sweat gland secretory coils in controls; these periglandular nerve terminals were either absent or markedly reduced in diabetic patients. Diabetic patients had lower SGII values than age- and sex-matched controls (2.60% ± 1.96% vs 4.84% ± 1.51%, p < 0.0001). The SGII values were lower in patients with anhidrosis of the feet versus those with normal sweating of the feet (0.89% ± 0.71% vs 3.10% ± 1.94%, p < 0.01). Thus, skin biopsy offers combined assessment of sudomotor innervation.
Related JoVE Video
Structures and energetics of neutral and ionic silicon-germanium clusters: density functional theory and coupled cluster studies.
J Phys Chem A
PUBLISHED: 02-15-2011
Show Abstract
Hide Abstract
We have calculated the structural and energetic properties of neutral and ionic (singly charged anionic and cationic) semiconductor binary silicon-germanium clusters Si(m)Ge(n) for s = m + n ? 12 using the density functional theory (DFT-B3LYP) and coupled cluster [CCSD(T)] methods with Poples 6-311++G(3df, 3pd) basis set. Neutral and anionic clusters share similar ground state structures for s = 3-7, independent of the stoichiometry and atom locations, but start to deviate at s = 8. The relative energetic stability of the calculated ground state structures among possible isomers has been analyzed through a bond strength propensity model where the pair interactions of Si-Si, Si-Ge, and Ge-Ge are competing. Electron affinities, ionization potentials, energy gaps between the highest and lowest occupied molecular orbitals (HOMO-LUMO gaps), and cluster mixing energies were calculated and analyzed. Overall, for a fixed s, the vertical ionization potential increases as the number of silicon atoms m increases, while the vertical electron affinity shows a dip at m = 2. As s increases, the ionization potentials increase from s = 2 to s = 3 and then decrease slowly to s = 8. The mixing energies for neutral and ionic clusters are all negative, indicating that the binary clusters are more stable than pure elemental clusters. Except for s = 4 and 8, cationic clusters are more stable than anionic ones and, thus, are more likely to be observed in experiments.
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.