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Notes: Deep levels in Si-doped In0.49Ga0.51P grown by compound-source molecular beam epitaxy (MBE) have been investigated by deep level transient spectroscopy. In0.49Ga0.51P samples were grown by compound-source MBE with V/III ratios of 4, 10, and 17. Depending upon the V/III ratio three major deep levels with activation energies of 0.26±0.02, 0.36±0.02, and 0.82±0.05 eV were observed. The effect of thermal annealing on the behavior of deep levels was also investigated. The deep levels in InGaP grown by compound-source MBE showed behavior of phosphorus antisites and related complexes unlike those found in solid-source MBE-grown InGaP that showed behavior of phosphorus vacancies and related complexes. Si-doped InGaP layers grown with a V/III ratio of 4 showed trap concentration and capture cross section as low as 1.38×1014 cm−3 and 2.9×10−16 cm2, respectively. The results indicate the potential of InGaP grown by compound-source MBE for use in improved low-frequency noise applications. © 2001 American Institute of Physics.

Notes: Average crystallite size and mean-square strain of illite in rock specimens and clay separates were measured independently in TEM images and by single-line Fourier (Voigt method) profile analysis of the c. 1 nm peak of XRD patterns for a prograde sequence of pelitic rocks (illite crystallinity indices=0.17–0.58°Δ2θ) from the Gaspé Peninsula, Quebec. The TEM-determined crystallite sizes in clay separates approximate those determined by Fourier profile analyses and those calculated from illite crystallinity indices by the Scherrer equation, with the exception of the diagenetic sample. The crystallite sizes and mean-square strains of illite in rock samples exhibit a trend similar to that determined by profile analyses, but the average crystallite sizes are up to five times larger than those measured for clay separates.TEM images show that all rock samples have a wide range of crystallite sizes, and the proportions of larger crystallites increase with metamorphic grade. The diagenetic illite is defect-rich, fine-grained (mean thickness by volume=c. 70 nm), 1Md material. Anchizonal illite tends to occur as separate aggregates of small 1Md and larger 2M1 crystals (c. 200 nm), comprising arrays of subparallel coalescing packets. The epizone sample has thick (c. 400 nm), defect-free crystals of muscovite occurring in stacks of parallel layers, or subhedral crystals intergrown with large-angle boundaries. Cleaved crystals that are free of intracrystalline layer terminations are dominant in clay separates of all samples, having ranges of smaller sizes with volume-average thicknesses of c. 43, 43, and 81 nm (c. 14, 28, 67 nm by the Voigt method), respectively, for the three zones.The results suggest that illite crystallinity indices do not provide a direct measure of a single microstructural state of illite in rocks, although they yield consistent limits for average crystallite sizes for the anchizone (23 & 48 nm here). Therefore, they serve as a general parameter of the degree of recrystallization on a relative basis, in part because the contributions of all peak-broadening variables (mixed layering, size and strain) decrease regularly with prograde regional metamorphism of pelites. The microstructural changes caused by rock disaggregation are probably a function of those variables as well. The data collectively demonstrate a trend from metastable, defect-rich, small crystals towards a stable assemblage of larger, defect-free crystals, through dissolution of strained crystals and neocrystallization, consistent with the Ostwald step rule.

Notes: Background  Human skin colour shows variations throughout life, and many extrinsic and intrinsic factors influence melanogenesis. Facultative pigmentation of sun-exposed skin has been suggested to reflect cumulative lifetime ultraviolet (UV) exposure in caucasians. However, pigmentary changes due to various regulatory factors may be different in dark-skinned peoples. Objectives  To observe the variations in skin colour due to ageing, gender differences and seasonal changes in Koreans with skin type IV or V. Methods  Skin pigmentation was measured at five body sites (buttock, glabella, the V of the neck area, inner arm and dorsal forearm) using skin reflectance spectroscopy in 497 subjects (age range 0–87 years) in winter and 311 subjects (age range 0–84 years) in summer. Among these subjects, 110 were assessed in both seasons. Three independent measurements at each site were done and the average value was used as the pigmentation level. Results  Constitutive pigmentation of the buttock was highest in the first decade of life. It then decreased during the second decade and this decreased level was maintained after the third decade. In contrast to caucasians, facultative pigmentation and sun exposure index did not increase with ageing. Gender differences were significant at all body sites after the first decade. Seasonal changes were apparent in dorsal forearm pigmentation. Little difference was seen in forehead pigmentation between summer and winter. Conclusions  Basal melanogenic regulation might not be different between Asians and caucasians. However, the sun exposure index may not represent lifelong cumulative UV exposure in Koreans. Age-, gender- and season-related characteristics of skin pigmentation in Koreans imply that genetically determined basal skin colour plays an important part in characterizing later responsiveness to UV radiation and sex hormones. Understanding differences between races will be helpful in studying the regulatory mechanisms of melanogenesis.

Notes: ZnSe epilayers were grown on GaAs (100) substrates by atomic layer epitaxy modified from chemical-vapor deposition with thicknesses ranging from 600 to 6000 A(ring). X-ray-diffraction and micro-Raman scattering measurements were carried out to study the effects of strain in the ZnSe epilayers with different thicknesses. The increase in full width at half-maximum of double-crystal x-ray rocking curves was observed for layers thicker than the critical thickness, which indicates that the crystallinity gets strongly degraded when the layers are grown over the critical thickness. The critical thickness estimated by x-ray rocking curves is 1500 A(ring), while that obtained by micro-Raman scattering is 1000 A(ring). This difference suggests that the elastic strain depends on the layer depth for ZnSe epilayers around the critical thickness.

Notes: We present an observation of the Wannier–Stark effect in a strained InGaAs/InGaP superlattice grown on a GaAs substrate. A blueshift of the effective absorption edge is observed in room and low-temperature photocurrent and transmission measurements. A ∼2000 cm−1 absorption change due to the transition of the absorption edge from a broad to a sharp quantum well-like excitonic shape was obtained for as little as a 2 V change in bias voltage. © 1996 American Institute of Physics.

Notes: This study presents a new approach that can stabilize effectively l-ascorbic acid in water-in-oil-in-water (w/o/w) double emulsions. Basically, the behavior of l-ascorbic acid in the aqueous phase was observed, considering its molecular deformation. Then, it was found that the stability determined in the aqueous phase by high-performance liquid chromatography (HPLC) showed that the collapse of ionization of l-ascorbic acid played a crucial role in protecting the molecular deformation. Then, the stable aqueous system was incorporated into the internal aqueous phase of the double emulsions. From the PLC analysis, it was observed that the l-ascorbic acid in an appropriate system showed high molecular stability for a long time. Moreover, in the measurement of in vitro skin permeation, the l-ascorbic acid stabilized in this study showed considerable skin permeation ability, indicating its potential applicability in pharmaceutics and cosmetics.

Notes: A novel simple method to detect vitamins in cosmetic products by gas chromatography-mass spectrometry (GC-MS) has been developed. Three vitamins (panthenol, cholecalciferol and tocopherol) were used for this study. Vitamins were prepared by dissolving in tetrahydrofuran (ThF), and silylated with bis-trimethylsilyltri-fluoroacetamide- trichloromethylsilane (BSTFA). Silylated vitamins were separated on a fused-silica capillary column coated with DB-5. The identification of each vitamin was accomplished by retention time and mass spectrum library search with a computer, and the quantitation was made in the selected-ion monitoring (SIM) mode of GC-MS. SIM mode had given sensitivity to determine 50 pg of panthenol, 285 pg of cholecalciferol and 130 pg of tocopherol. Linearity was maintained over the range 0.005–0.20% for each vitamin. Each cosmetic product (i.e. hair tonic and lotion) was found to contain amounts of the vitamins. This method was sensitive and gave 77.5–99.9% recovery of each vitamin from these cosmetic products. From these results, we concluded that silylation with BSTFA followed by GC-MS analysis allows the simple, convenient and exact determination of panthenol, cholecalciferol and tocopherol.

Notes: The trim coil system of a superconducting ring cyclotron currently under design at RIKEN is composed of five sets of superconducting and twenty sets of normal-conducting coils. A major correction for isochronization of the magnetic field is accomplished by the superconducting coils, and a fine correction by the normal-conducting coils. For an optimal design of the system, a numerical procedure was developed to generate isochronous fields for design nuclei and consequently current settings on the main and trim coils, employing an iteration of a least-squares fitting to minimize orbital frequency errors. The main and normal-conducting coils can also be used to correct unwanted harmonic fields with sector dependent and/or radially localized excitations. The correction schemes were conceived for presumed error fields, alignment tolerances being estimated based upon beam optics requirements. On the other hand, a new trim coil design was envisaged, which comprises only superconducting trim coils. The subcoils in the present five-set design can be independently excited to replace the normal-conducting coils. This option may be more economical, but complications on the superconducting coil system raise a reliability concern. © 1999 American Institute of Physics.

Notes: We present an in situ synchrotron x-ray scattering study on the thermal oxidation of epitaxial AlN/Sapphire(0001) films. During annealing to 700 °C, an epitaxial AlN film transforms progressively into a planar epitaxial γ-Al2O3 layer. The oxidation proceeds through the γ-Al2O3/AlN interfacial motion that is observed directly from the intensity fringes near the AlN(0002) Bragg reflection. The oxidation rate, deduced from the interfacial motion, exhibits repeating transitions from a linear to a parabolic oxidation behavior. This suggests that the oxide break down periodically. During the oxidation the strain in the remaining AlN reverts to the value measured at the same thickness during the growth of the AlN film. © 2002 American Institute of Physics.