DFT-SCRF Calculations of Nitrogen Isotopic Reduced Partition Function Ratios for Amino Acids in Aqueous Solution at pH 7.4.

Using the self-consistent reaction field (SCRF) method, the nitrogen isotopic reduction partition function ratio (RPFR), a fundamental physical quantity for theoretical consideration of equilibrium isotope effects, was evaluated by density functional theory (DFT) for 20 proteinogenic and two related amino acids under physiological conditions at pH 7.4. At this pH value, all amino acids were of the zwitterion-type form with α-NH and α-COO groups, regardless of the net charge of -1 (monoanion), 0 (zwitterion), or +1 (monocation).

Applicability of self-consistent reaction field (SCRF) method to DFT estimation of hydrogen isotope separation factors in reversible processes.

In earlier quantum chemical calculations of isotope effects, chemical species in the liquid phase were generally treated as existing in the gas phase. In recent years, however, advances in computational programs have made it easier for the self-consistent reaction field (SCRF) method to handle chemical species in the liquid phase, and as a result, it has become easier to apply the SCRF method to isotope effect calculations. This paper concerns the scope of application of the DFT-SCRF method to reversible processes for hydrogen isotope enrichment.

DFT analysis of nitrogen isotopic reduction partition function ratios in proton exchange equilibria of glutamic acid species in water and its application to the estimation of nitrogen isotope fractionation.

L-Glutamic acid (Glu) plays a pivotal role in amino acid metabolism in living organisms. Theoretical knowledge of how metabolism propagates the nitrogen isotope composition (δN) is essential for elucidating the mechanism of amino acid metabolism . In this paper, to estimate the nitrogen isotope fractionation involving Glu and its protonated/deprotonated species, their nitrogen isotopic reduction partition function ratios (RPFRs) were calculated at the apfd/6-311+G(2d,p) level of theory by the SCRF method.

Temperature-independent lasing wavelength of highly stacked InAs quantum dot laser fabricated on InP(311)B substrate with Bi irradiation.

In this study, the effects of bismuth (Bi) irradiation on InAs quantum dot (QD) lasers operating in the telecommunication wavelength band were investigated. Highly stacked InAs QDs were grown on an InP(311)B substrate under Bi irradiation, and a broad-area laser was fabricated. In the lasing operation, the threshold currents were almost the same, regardless of Bi irradiation at room temperature.

Polarization transformation and destructive interference on subwavelength magnetic domains in magneto-plasmonic systems.

We demonstrate magneto-optical (MO) polarization transformation due to surface plasmons in CoPt perpendicular magnetic films in the polar Kerr geometry. An extraordinary Kerr rotation angle (θ =  ± 88.9°) that almost reaches the upper limit of polarization is produced in the attenuated total reflection (Kretschmann) configuration.

A density functional theory (DFT) study on reduced partition function ratios of oxygen species adsorbed on a Pt cluster and oxygen isotope effects.

A density functional theory (DFT) computation on oxygen species adsorbed on platinum (Pt) catalyst surfaces has been carried out to elucidate oxygen isotope fractionation observed at the cathode of a polymer electrolyte membrane fuel cell (PEMFC). The Pt(111) catalyst surface was modelled by a Pt cluster, and O, OH, OHH, OO, OOH, OHOH and HOHOH were assumed to be the oxygen species adsorbed on the Pt(111) surface. The oxygen isotope reduced partition function ratios (RPFRs) of the adsorbed species were calculated using the vibrational frequencies obtained by normal mode analyses performed on the optimized structures.

Nitrogen Isotopic Reduced Partition Function Ratios of Glycine and Serine in Water.

The nitrogen isotopic reduced partition function ratio (RPFR) of glycine (Gly) and serine (Ser) in water has been evaluated by a couple of methods. The experimental fact that those amino acids are present in the zwitterionic form in water has been best reproduced when trihydrated Gly and Ser molecules were treated by the discrete microsolvation method coupled with the self-consistent reaction field (SCRF) approach. The RPFR values of Gly and Ser in water at 25 °C are evaluated as 1.

Observation of O/O isotope effects at the cathode of a polymer electrolyte membrane fuel cell.

O/O isotope effects were observed at the cathode of a polymer electrolyte membrane fuel cell at 25 and 35°C. Results of experiments in which the O/O isotope ratios of the oxygen gases supplied to and exhausted from the cell were measured revealed that the lighter isotope O reacted more preferentially to form water molecules at the cathode than the heavier one, O. The value of the oxygen isotope separation factor, S, defined as the ratio of the O/O isotope ratios of the oxygen gases supplied to and exhausted from the cell, ranged from 1.

Focus tuning by liquid crystal lens in imaging system.

A quantitative study of the focus tuning by a liquid crystal lens in an imaging system composed of a camera module and the liquid crystal lens that performs the focusing function is reported. The resolving capability of the imaging system is investigated by analyzing the image of an ISO12233 chart formed by the system. Measurements show that with the focus tuning by the liquid crystal lens, the resolving power of the system can be very close to that of the camera module.

Liquid-crystal variable-focus lenses with a spatially-distributed tilt angles.

A pretilt angle controlling method by the density of rubbings using a tiny stylus is proposed. The control of the surface pretilt angle is achieved by rubbing a side-chain type polyimide film for a homeotropic alignment. Smooth liquid crystal (LC) director distribution in the bulk layer is successfully obtained even though the rough surface orientation.