High-Power, Highly Efficient Second-Harmonic Generation in a Periodically Poled ${hbox {MgO}}{:}{hbox {LiNbO}}_{3}$ Planar Waveguide

We designed a single-pass quasi-phase-matched second-harmonic generation (SHG) device with a planar waveguide; the device comprised a Y-cut 5 mol% MgO-doped LiNbO₃ (MgO:LiNbO₃)crystal core that was 3 mum thick and SiO₂ cladding. The waveguide provided a high coupling efficiency of 95% between an incident Gaussian beam and the fundamental guided mode of a fundamental wave; it also provided high electric-field confinement in the case of both the fundamental and SHG waves in the core. Thus, a high overlap between nonlinear polarization and an SHG-guided mode was attained. The bonding of the device with the waveguide side positioned downward to a heat sink provided a large heat radiation area when pumping with a near-collimated Gaussian beam, which reduced the temperature rise and its gradient along the waveguide to minimize the phase mismatch. We demonstrated the green light generation of 1.6 W with 40% conversion efficiency using a 7-mm-long sample and 1.2-W SHG with 60% efficiency using an 18-mm-long sample.     

The Combination of Cigarette Smoking and Alcohol Consumption Synergistically Increases Reactive Carbonyl Species in Human Male Plasma

Cigarette smoking and alcohol consumption are major risk factors for lifestyle-related diseases. Although it has been reported that the combination of these habits worsens risks, the underlying mechanism remains elusive. Reactive carbonyl species (RCS) cause chemical modifications of biological molecules, leading to alterations in cellular signaling pathways, and total RCS levels have been used as a lipid peroxidation marker linked to lifestyle-related diseases. In this study, at least 41 types of RCS were identified in the lipophilic fraction of plasma samples from 40 subjects using liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS). Higher levels of 10 alkanals, 5 trans-2-alkenals, 1 cis-4-alkenal, and 3 alkadienals were detected in the smoking/drinking group (N = 10) as compared to those with either habit (N = 10 each) or without both habits (N = 10) in the analysis of covariances adjusted for age and BMI. The levels of 3 alkanals, 1 trans-2-alkenal, 1 alkadienal, and 1 4-hydroxy-2-alkenal in the smoking/drinking group were significantly higher than those in the no-smoking/drinking and no-smoking/no-drinking groups. These results strongly indicate that the combination of cigarette smoking and alcohol drinking synergistically increases the level and variety of RCS in the circulating blood, and may further jeopardize cellular function.     

High-capacity organic positive-electrode material based on a benzoquinone derivative for use in rechargeable lithium batteries

The performance of 2,5-dimethoxy-1,4-benzoquinone (DMBQ) as an active material for rechargeable lithium batteries was investigated. A positive-electrode that incorporated DMBQ showed an initial discharge capacity of 312 mAh g⁻¹ with an average voltage of 2.6 V vs. Li⁺/Li. This discharge capacity corresponds to a benzoquinone-based two-electron redox behavior, and is more than twice that of the conventional positive-electrode material lithium cobalt oxide (LiCoO₂). Furthermore, the positive-electrode with DMBQ showed fair cycle-life performance. Theoretical quantum calculations based on the density functional theory (DFT) were also performed to clarify the mechanism of the electrochemical properties of the solid state of DMBQ.     

Pyroxene LiVSi2O6 as an electrode material for Li-ion batteries

Lithium vanadium metasilicate (LiVSi₂O₆) with pyroxene structure has been exploited as an electrode material for Li-ion batteries. Galvanostatic charge and discharge tests show that LiVSi₂O₆ is able to deliver a capacity of 85 mAh g⁻¹ at 30 °C, and a high capacity of 181 mAh g⁻¹ at 60 °C. The high capacity is believed to be due to the reactions of V³⁺/V⁴⁺ and V²⁺/V³⁺redox couples, accompanied by the excess 0.42 Li⁺ insertion into the lattice forming a Li-rich phase Li_1.42VSi₂O₆. High-energy synchrotron XRD combined with the Rietveld refinement analysis confirms that the electrochemical delithiation-lithiation reaction proceeds by a single phase redox mechanism with an overall volume variation of 1.9% between LiVSi₂O₆ and its delithiated state, indicating a very stable framework of LiVSi₂O₆ for Li⁺ ions extraction-insertion.     

AgBr nanocrystal-dispersed silsesquioxane-titania hybrid films for holographic materials

AgBr-doped silsesquioxane-titania films with a thickness of approximately 5 μm were prepared using a sol-gel technique. The dopant AgBr crystals were converted into very small Ag nanoparticles (mainly several nanometers) upon blue laser irradiation, leading to an increase in the absorption of the film in the visible region. An excess of Ag⁺ ions in the film was required for the conversion of AgBr into Ag upon blue laser irradiation. A maximum diffraction efficiency of 0.03% was achieved after two-beam interference exposure with a blue laser for 1300 s. These results imply that the films are suitable for use as holographic materials.     

Dimer Interface in Natural Variant NK1 Is Dispensable for HGF-Dependent Met Receptor Activation

NK1, a splicing variant of hepatocyte growth factor (HGF), binds to and activates Met receptor by forming an NK1 dimer and 2:2 complex with Met. Although the structural mechanism underlying Met activation by HGF remains incompletely resolved, it has been proposed that the NK1 dimer structure participates in this activation. We investigated the NK1 dimer interface’s role in Met activation by HGF. Because N127, V140, and K144 are closely involved in the head-to-tail NK1 dimer formation, mutant NK1 proteins with replacement of these residues by alanine were prepared. In Met tyrosine phosphorylation assays, N127-NK1, V140-NK1, and K144-NK1 showed 8.3%, 23.8%, and 52.2% activity, respectively, compared with wild-type NK1. Although wild-type NK1 promoted cell migration and scattering, N127-NK1, V140-NK1, and K144-NK1 hardly or marginally promoted them, indicating loss of activity of these mutant NK1 proteins to activate Met. In contrast, mutant HGFs (N127-HGF, V140-HGF, and K144-HGF) with the same amino acid replacements as in NK1 induced Met tyrosine phosphorylation and biological responses at levels comparable to those of wild-type HGF. These results indicate that the structural basis responsible for NK1-dependent Met dimer formation and activation differs from, or is at least distinguishable from, the structural basis responsible for HGF-dependent Met activation.     

Open L-lactic acid fermentation of food refuse using thermophilic Bacillus coagulans and fluorescence in situ hybridization analysis of microflora

In the production of commercially useful poly-L-lactic acid plastic from biomass wastes, a feasible fermentation process to produce optically active L-lactic acid would be required. Here, model kitchen refuse (MKR) was inoculated with Bacillus coagulans NBRC12583 under nonsterilized openculture conditions. At temperatures below 45 degrees C, a racemic mixture of D- and L-lactic acids was accumulated, whereas only L-lactic acid was selectively accumulated by incubation at 50-65 degrees C. At 45 degrees C, the results of fermentation could not be consistently reproduced. To analyze microflora in this type of mixed culture system, whole-cell fluorescence in situ hybridization (FISH) using 16S rRNA-targeted oligonucleotide probes for B. coagulans, Bcoa191, and LAC722(L), a group-specific probe for a wide range of mesophilic lactic acid bacteria was applied. The dominancy of mesophilic lactic acid bacteria at lower temperatures, and that of B. coagulans at higher temperatures were confirmed. By using a saccharified liquid of collected kitchen refuse, 86 g/l of L-lactic acid was accumulated under nonsterile conditions by a 5-d incubation at 55 degrees C, pH 6.5, with 53% carbon yield and 97% optical purity. To conclude, high temperature open lactic acid fermentation is a simple and promising method for producing high-grade L-lactic acid from biomass waste, and FISH analysis of such mixed-culture systems is helpful for monitoring the microflora in these cultures.     

Thermotolerant Bacillus licheniformis TY7 produces optically active l-lactic acid from kitchen refuse under open condition

A thermotolerant l-lactic-acid-producing bacterium was isolated and identified as Bacillus licheniformis TY7. TY7 shows optimum growth at pH 6.5 at 30 degrees C and normal growth up to 65 degrees C. Using nonsterile kitchen refuse at 50 degrees C, the strain produced 40 g/ll-lactic acid with 97% optical activity and 2.5 g/lxh productivity.     

Facilitation of shape-from-shading perception by random textures

Most natural objects have a texture on their surface, so the segregation between shading and texture is crucial for the robust perception of three-dimensional structure: The visual system has to decide whether shading or texture evoked the luminance change. We found that the contextual pop-out that results from shading was not suppressed, but was even facilitated, when random texture was added to the luminance of the entire stimulus, indicating the functional segregation and facilitative interaction between shading and texture cues. The local contrast evoked by random texture within a figure or at a boundary was a major factor in the facilitation, suggesting the crucial role of early vision in the interaction between the cues.     

Time-Dependent Unitary Transformation Method in the Strong-Field-Ionization Regime with the Kramers-Henneberger Picture

Time evolution operators of a strongly ionizing medium are calculated by a time-dependent unitary transformation (TDUT) method. The TDUT method has been employed in a quantum mechanical system composed of discrete states. This method is especially helpful for solving molecular rotational dynamics in quasi-adiabatic regimes because the strict unitary nature of the propagation operator allows us to set the temporal step size to large; a tight limitation on the temporal step size (δt<<1) can be circumvented by the strict unitary nature. On the other hand, in a strongly ionizing system where the Hamiltonian is not Hermitian, the same approach cannot be directly applied because it is demanding to define a set of field-dressed eigenstates. In this study, the TDUT method was applied to the ionizing regime using the Kramers-Henneberger frame, in which the strong-field-dressed discrete eigenstates are given by the field-free discrete eigenstates in a moving frame. Although the present work verifies the method for a one-dimensional atom as a prototype, the method can be applied to three-dimensional atoms, and molecules exposed to strong laser fields.