Interface dynamics of the Fisher equation with degenerate diffusion

We consider a degenerate parabolic reaction-diffusion equation with a monostable nonlinearity arising in population dynamics. In some suitable scaling limit, we prove the generation and propagation of an interface with constant normal velocity in the case that the initial condition has a convex compact support.     

Observable N-N oscillation in high scale seesaw models

We discuss a realistic high scale (nu(B-L) approximately 10(12) GeV) supersymmetric seesaw model based on the gauge group SU(2)L x SU(2)R x SU(4)c where neutron-antineutron oscillation can be in the observable range. This is contrary to the naive dimensional arguments which say that tau(N-N) is proportional to nu(B-L)5 and should therefore be unobservable for seesaw scale nu(B-L) > or = 10(5) GeV. Two reasons for this enhancement are (i) accidental symmetries which keep some of the diquark Higgs masses at the weak scale and (ii) a new supersymmetric contribution from a lower dimensional operator. The net result is that tau(N-N) is proportional to nu(B-L)2 nu(wk)3 rather than nu(B-L)5. The model also can explain the origin of matter via the leptogenesis mechanism and predicts light diquark states which can be produced at LHC.     

Oxidative dehydrogenation of ethane over Cr/ZSM-5 catalysts using CO2 as an oxidant

Highly active catalysts for oxidative dehydrogenation of ethane with CO2 were characterized by temperature-programmed reduction (TPR), temperature-programmed oxidation (TPO), Fourier transform infrared (FTIR) spectroscopy, and X-ray absorption fine-structure (XAFS) analysis. In the active catalysts, Cr/H-ZSM-5 (SiO2/Al2O3 > 190), Cr6+ = O, or possibly Cr5+ = O was the catalytic species on the zeolite support. In contrast, little Cr6+ (or Cr5+) was detected in the less-active catalysts. The Cr6+ (or Cr5+) species was reduced to an octahedral Cr3+ species by treatment with ethane at 773 K, and the reduced Cr species was reoxidized to the Cr6+ (or Cr5+) species by treatment with CO2 at 673-773 K. The Cr redox cycle played an important role in the catalyst's high activity.     

Optical properties of transparent barium titanate nanoparticle/polymer hybrid synthesized from metal alkoxides

A transparent BaTiO₃ particle/polymer hybrid was synthesized from a Ba–Ti double alkoxide modified with an organic ligand and its refractive index and second harmonic generation were studied. BaTiO₃ particles modified with 2-vinyloxyethanol (ethylene glycol monovinyl ether, EGMVE) were polymerized with methyl methacrylate (MMA) yielding the transparent BaTiO₃ particle/poly MMA hybrid. X-ray photoelectron spectra indicated that the formation of chemical bonds between BaTiO₃ nanoparticles and the organic matrix. The refractive indexes of the hybrid films depended on the crystallite size of BaTiO₃ nanoparticles and the volume fractions of BaTiO₃ and polymer phases. The hybrid film synthesized at BaTiO₃/8EGMVE/30H₂O/PMMA revealed a refractive index of 1.65 at 589 nm with an Abbe number of 54. The hybrid film exhibited a second harmonic wave of 532 nm on irradiation with a fundamental wave of 1,064 nm.     

Elemental mapping of frozen‐hydrated cells with cryo‐scanning X‐ray fluorescence microscopy

Visualizing the elemental distributions of cells and tissues is of growing importance in biology and medical science because such data deepen our understanding of the behavior of metal‐binding proteins and ions. Elemental mapping by X‐ray fluorescence analysis with a hard X‐ray nanobeam is very well suited for this purpose owing to its high sensitivity and high resolution. Using this technique, samples must be prepared without artifacts that are caused by treatments such as chemical fixation and staining procedures. In many studies of elemental mapping, sample preparation is not explicitly considered. To overcome this deficiency, we developed a cryo‐scanning X‐ray fluorescence microscope and installed it in the second experimental hutch of BL29XUL of SPring‐8. We used it to observe frozen‐hydrated cells that had been fixed by a quick‐freezing technique to preserve elemental data of the living state at an X‐ray energy of 11.5 keV. The distributions of K, Ca, Fe, Cu and Zn were successfully visualized. The distributions of these elements (especially those of K, Ca and Fe) differed from those in cells fixed with paraformaldehyde. Copyright © 2010 John Wiley & Sons, Ltd.     

Effect of UV lamp irradiation during oxidation of Zr/Pt/Si structure on electrical properties of Pt/ZrO2/Pt/Si structure

Metal-insulator-metal (MIM) capacitors were fabricated using ZrO₂ films and the effects of structural and native defects of the ZrO₂ films on the electrical and dielectric properties were investigated. For preparing ZrO₂ films, Zr films were deposited on Pt/Si substrates by ion beam deposition (IBD) system with/without substrate bias voltages and oxidized at 200 °C for 60 min under 0.1 MPa O₂ atmosphere with/without UV light irradiation (λ = 193 nm, Deep UV lamp). The ZrO₂(∼12 nm) films on Pt(∼100 nm)/Si were characterized by X-ray diffraction pattern (XRD), field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HRTEM), capacitance-voltage (C-V) and current-voltage (I-V) measurements were carried out on MIM structures. ZrO₂ films, fabricated by oxidizing the Zr film deposited with substrate bias voltage under UV light irradiation, show the highest capacitance (784 pF) and the lowest leakage current density. The active oxygen species formed by UV irradiation are considered to play an important role in the reduction of the leakage current density, because they can reduce the density of oxygen vacancies.     

Correction of Nonuniform Response in the Reconstruction for Single Photon Emission Computed Tomography with a Spatially Varying Focal Length Collimator

SPECT (single photon emission computed tomography) images can visualize physiological functions directly and are diagnostically useful. The reconstruction methods based on the Continuous-Discrete (C-D) mapping model have an immediate effect on SPECT imaging because they employ photon detection kernels describing the photon transport from the body to the detector. However, in a spatially varying focal length geometry, the concentration of the sensitivity around the center of rotation of the detector causes a change in the response from the original image to the reconstructed image. As a result, a false hot spot often appears around the center of rotation. This paper presents a convenient method to repress the change by correcting the resolving kernels. Numerical simulations show that the method can reduce the false hot spots.     

Formulation study for orally disintegrating tablet using partly pregelatinized starch binder

In this study, we aimed to design orally disintegrating tablets by employing a formulation design approach that enables the production of such tablets in the same facilities used for the production of solid dosage forms on an industrial scale. First, we examined the relationships between the types of binders used in the tablets and the properties of orally disintegrating tablets prepared by the wet granulation method. Results revealed that partly pregelatinized starch is a relatively suitable binder for orally disintegrating tablets as it also serves as a disintegrant. Next, we employed a central composite design for 2 factors, namely, corn starch and partly pregelatinized starch, in order to design granules suited for orally disintegrating tablets composed of D-mannitol, corn starch or partly pregelatinized starch. The effects of these 2 factors on 3 types of responses, namely, 50% granule size, compressing index and disintegrating index, were analyzed with a software package, and responses to changes in the factors were predicted. This study investigated the effects of binder type and binder content in orally disintegrating tablets, and provided evidence that the binder exerts a strong influence on tablet properties, and is therefore an important component of orally disintegrating tablets.     

Oxidation of an Internal-Edge-Substituted [5]Helicene-Derived Phosphine Synchronously Enhances Circularly Polarized Luminescence

Small chiral organic molecules with CD properties are in high demanded due to their potential use in promising electronic and biological applications. Herein, we reveal a system in which the oxidation of a phosphino group to the corresponding phosphine oxide on the inner rim of a helicene derivative induces a CPL response. Laterally π-extended 7,8-dihydro[5]helicenes bearing phosphine and phosphine oxide groups on their inner helical rims (i. e., the C1 position) were synthesized, and their helical structures were unambiguously determined by X-ray crystallography. The photophysical (UV/visible and emission) and chiroptical properties of these compounds were investigated in various solvents. Despite their structural similarities, phosphine oxide showed a significantly better CPL response than phosphine, with a high dissymmetry factor for emission (|g_lum|=(1.3–1.9)×10⁻³) that can be attributed to structural changes in the interior of the helicene helix.