Persistence of covalent bonding in liquid silicon probed by inelastic x-ray scattering

Metallic liquid silicon at 1787 K is investigated using x-ray Compton scattering. An excellent agreement is found between the measurements and the corresponding Car-Parrinello molecular dynamics simulations. Our results show persistence of covalent bonding in liquid silicon and provide support for the occurrence of theoretically predicted liquid-liquid phase transition in supercooled liquid states. The population of covalent bond pairs in liquid silicon is estimated to be 17% via a maximally localized Wannier function analysis. Compton scattering is shown to be a sensitive probe of bonding effects in the liquid state.     

Relaxation phenomena of binary polar liquid mixture in C6H6 from conductivity of solution measured at 10 GHz electric field

The dielectric relaxation times τ _jk ’s and dipole moments μ _jk ’s of the binary (jk) polar mixtures of N,N-dimethyl formamide (DMF) and pyridine dissolved in benzene (i) are estimated using linear slope of σ _jk ″ − σ _ijk ′ curves as well as ratio of slopes of σ _ijk ″ − w _jk and σ _ijk ″ − w _jk curves at w _jk → 0 for different mole fractions τ _jk ’s of pyridine and experimental temperatures under 9.875 GHz electric field. The measured μ _jk ’s and τ _jk ’s agree well with the reported values validating the proposed methods. The solute-solute (dimer) molecular associations are inferred from the plot of τ _jk − x _j and μ _jk − x _j curves for x _j = 0.0 to 0.5 of pyridine and thereafter solute-solvent (monomer) molecular association occurs. The theoretical μ_theo’s are calculated to predict solute-solute and solute-solvent molecular association. The μ _jk − T curves are drawn to show elongation of bond angles and bond moments with temperatures. The thermodynamic energy parameters are calculated from Eyring’s rate theory equations to know the molecular dynamics as well as to ascertain Debye-Smyth relaxation mechanism of the systems.     

Optical activity of chiral thin film and liquid crystal hybrids

Using the glancing angle deposition (GLAD) technique, we have fabricated porous, chiral thin films with optically anisotropic helical microstructures that exhibit optical phenomena such as wavelength specific rotation of linearly polarized light. Initial research has shown that the porosity of the films allows for the addition of nematic liquid crystals (NLCs) to the films for promising applications in dynamically switchable devices, while simultaneously enhancing the optical properties of the film. This study describes the fundamental optical behaviour of LC-filled chiral thin films in relation to material, porosity, structure and thickness. It was found that for SiO₂ films, the addition of NLCs increased the effective rotatory power by two-fold when compared with results from the film without added LCs. The rotatory power of Al₂O₃ and MgF₂ films, while being similarly increased by the addition of LCs, exhibited a reversal in sign, or direction of rotation, for the visible wavelength spectrum investigated. The effects of film porosity and structure were studied by varying the angle of incidence from 83° to 86°; it was found that the greater porosity of the films deposited at larger angles allowed for more filling by the LCs and thus a larger increase in rotatory power. Finally, the addition of LCs was observed to shift the wavelength of peak rotation towards smaller values.     

Investigating the role of c-Jun N-terminal kinases in the proliferation of Werner syndrome fibroblasts using diaminopyridine inhibitors

To develop more potent small molecules with enhanced free radical scavenger properties, a series of N-substituted isatin derivatives was synthesized, and the cytoprotective effect on the apoptosis of PC12 cells induced by H₂O₂ was screened. All these compounds were found to be active, and N-ethyl isatin was found with the most potent activity of 69.7% protective effect on PC12 cells. Structure-activity relationship analyses showed the bioactivity of N-alkyl isatins decline as the increasing of the chain of the alkyl group, furthermore odd-even effect was found in the activity, which is interesting for further investigation.     

Formation and aqueous surface wettability of polysiloxane nanofibers prepared via surface initiated, vapor-phase polymerization of organotrichlorosilanes

The formation of high aspect ratio organosiloxane fibers of nanodimensionality via the surface-induced vapor-phase polymerization of vinyltrichlorosilane is reported. We also demonstrate the versatility of our method by producing fibers of various densities, polydispersities, and lengths. Nanofibers were characterized using SEM, EDX, XPS, TOF-SIMS, and variable-angle FTIR. Advancing aqueous contact angle measurements were used to evaluate the nanofiber surface wettability.     

H-transfer rates in ion-neutral complexes versus those in intact aliphatic ions

The relative rates of H-transfer between partners in ion-neutral complexes were compared with those in intramolecular rearrangements using results of first differential photoionization mass spectrometry measurements. Complex-mediated H-transfers are inferred to have rates of the same order as those for intramolecular hydrogen rearrangements, suggesting a similar range of motion of the reactive sites in both types of reactions. It is also concluded that at their fastest H-transfers take place between the partners in ion-neutral complexes within at most the time of several rotations of the partners in the complexes. Copyright 1999 John Wiley & Sons, Ltd.     

Disentangling the effects of phonation and articulation: Hemispheric asymmetries in the auditory N1m response of the human brain

Background  

The cortical activity underlying the perception of vowel identity has typically been addressed by manipulating the first and second formant frequency (F1 & F2) of the speech stimuli. These two values, originating from articulation, are already sufficient for the phonetic characterization of vowel category. In the present study, we investigated how the spectral cues caused by articulation are reflected in cortical speech processing when combined with phonation, the other major part of speech production manifested as the fundamental frequency (F0) and its harmonic integer multiples. To study the combined effects of articulation and phonation we presented vowels with either high (/a/) or low (/u/) formant frequencies which were driven by three different types of excitation: a natural periodic pulseform reflecting the vibration of the vocal folds, an aperiodic noise excitation, or a tonal waveform. The auditory N1m response was recorded with whole-head magnetoencephalography (MEG) from ten human subjects in order to resolve whether brain events reflecting articulation and phonation are specific to the left or right hemisphere of the human brain.