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Notes: Abstract A chitinase gene (chiA) from Pseudomonas sp. YHS-A2 was cloned into Escherichia coli using pUC19. The nucleotide sequence determination revealed a single open reading frame of chiA comprised of 1902 nucleotide base pairs and 633 deduced amino acids with a molecular weight of 67,452 Da. Amino acid sequence alignment showed that ChiA contains two putative chitin-binding domains and a single catalytic domain. Two proline-threonine repeat regions, which are linkers between catalytic and substrate-binding domains in some cellulases and xylanases, were also found. From E. coli, ChiA was purified 12.8-fold relative to the periplasmic fraction. The Michaelis constant and maximum initial velocity for p-nitrophenyl-N,N′-diacetylchitobiose were 1.06 mM and 44.4 μmol/h per mg protein, respectively. The purified ChiA binds not only to colloidal chitin but also to other substrates (avicel, chitosan, and xylan), but the binding affinity of avicel, chitosan, and xylan is around 10 times lower than that of colloidal chitin. The reaction of ChiA with colloidal chitin and chitooligosaccharides (trimer-hexamer) produced an end product of N,N′-diacetylchitobiose, indicating that ChiA is a chitobiosidase.

Notes: Photoluminescence (PL) in PbWO4 single crystals doped with Pr3+, Sm3+, and Er3+ ion, which were grown by the Czochralski method, was studied. By investigating the PL for incident radiation with wavelength of 325 nm (He–Cd Laser), the energy levels of the PL centers were found: The PL levels in the Pr doped single crystal are 3Po and 1D2, that in the Sm-doped one is 4G5/2, and those in the Er doped one are 2H11/2, 4S3/2, and 4F9/2. In conclusion, the characteristics of these single crystals are governed solely by those of the rare-earth dopants, not by the lead tungstate. © 2002 American Institute of Physics.

Notes: We report optical properties of AlxGa1−xP (0≤x≤0.52) alloys grown by gas source molecular-beam epitaxy on S-doped GaP(001) substrates. Room-temperature pseudodielectric function spectra from 1.5 to 6.0 eV were obtained by spectroscopic ellipsometry. By applying the parabolic-band critical point model to numerically calculated second energy derivatives of these spectra, we obtained accurate room-temperature values of the E1, E0′, E2, and E2′ critical point energies and their dependence on composition x. © 2000 American Institute of Physics.

Notes: Time-domain reflectometry (TDR) is being used increasingly for measuring the moisture content of porous media. However, successful application for measuring water in soil has been limited to non-deformable soils, and it would be a valuable extension of the technique if it could be used for soils that shrink on drying. We have recently investigated its application to soils rich in clay and organic matter and peats. Here we propose a method for determining moisture content in deformable soils based on the relation between the dielectric constant, K, and the volumetric moisture content, Θ, measured by TDR.Parallel TDR probes with a length of 15 cm and a spacing of 2 cm were placed horizontally in soil cores with a diameter of 20 cm and height of 10 cm taken from a forest. The soil is very porous with large proportions of both silt and clay. The sample weight and travel time of the electromagnetic wave guided by parallel TDR probes were simultaneously measured as a function of time, from saturation to oven-dryness during which the core samples shrank considerably. Vertical and horizontal components of shrinkage were also measured to take the air-exposed region of TDR probe into account in the determination of K. The effect of deformation on volumetric moisture content was formulated for two different expressions, namely actual volumetric moisture content (AVMC) and fictitious (uncorrected) volumetric moisture content (FVMC). The effects of air-exposure and expressions of volumetric moisture content on the relation between K andΘ were examined by fitting the observations with a third-order polynomial. Neglecting the travel time in the air-exposed part or use of the FVMC underestimated the Θ for a given K. The difference was more pronounced between AVMC and FVMC than between two different dielectric constants, i.e. accounting for air-exposure, Kac, and not accounting for air-exposure, Kau. When the existing empirical models were compared with the fitted results, most underestimated the relation based on the AVMC. This indicates that published empirical models do not reflect the effect of deformation on the determination of Θ in our forest soil. Correct use of the Θ expression has more impact on determining moisture content of a deformable soil than the accommodation of travel time through the air-exposed region of TDR probe.

Notes: We have produced nanotube-in-oil suspensions and measured their effective thermal conductivity. The measured thermal conductivity is anomalously greater than theoretical predictions and is nonlinear with nanotube loadings. The anomalous phenomena show the fundamental limits of conventional heat conduction models for solid/liquid suspensions. We have suggested physical concepts for understanding the anomalous thermal behavior of nanotube suspensions. In comparison with other nanostructured materials dispersed in fluids, the nanotubes provide the highest thermal conductivity enhancement, opening the door to a wide range of nanotube applications. © 2001 American Institute of Physics.

Notes: We report pseudodielectric function data 〈ε〉=〈ε1〉+i〈ε2〉 of ZnSexTe1−x samples grown on GaAs substrates. The data were obtained from 1.5 to 6.5 eV using spectroscopic ellipsometry. Critical-point parameters were obtained by fitting model line shapes to numerically calculated second-energy derivatives of 〈ε〉. The bowing parameters of E0, E1, and E1+Δ1 were determined and were comparable to that of E0 quoted from the literature. We observed a monotonic increase of the linewidth of the E1 gap up to x=0.85, whereas that of E1+Δ1 showed a maximum value near x=0.5. We attribute this anomalous broadening of the E1 gap to sample microstructures developed in the low-Te composition alloys. © 2000 American Institute of Physics.

Notes: The application of atomic-force-microscope (AFM) direct patterning to the selective positioning of InAs quantum dots (QDs) on a (100) GaAs substrate has been proposed and experimentally implemented. The AFM direct patterning was used to generate various patterns of several tens of nanometers in size, and InAs QDs were subsequently grown by a metalorganic chemical vapor deposition technique. A nonuniform distribution of the QDs was observed near the patterns. The detailed shape of the QD distribution and the size of the QDs depended on the geometrical properties such as the sidewall angle, the spacing, and the width of the patterns. We have been able to ascertain, through our work, what growth conditions are necessary for QDs' alignment along the patterns. © 2000 American Institute of Physics.

Notes: Fluorinated silicon-oxide (SiOF) films were produced by electron-cyclotron-resonance plasma-enhanced chemical-vapor deposition. The effect of water absorption on the film properties was studied by measuring the residual stress as a function of exposure time to room air. The residual stress shows an increase of the compressive component as the film absorbs water. However, the chemical bonding structure does not change after the water absorption. The residual stress returns to the initial value when the film is dried. It is suggested that the water absorption occurs entirely by physical adsorption of H2O molecules to Si–F bonds. © 2001 American Institute of Physics.

Notes: The variation of residual stress with the water absorption was reduced drastically by the N2O plasma treatment for fluorinated silicon-oxide thin films. Fourier transformed infrared spectroscopy analysis showed that the film was oxidized by the plasma treatment. It was also determined that the oxidation occurred on the film surface from the P-etch rate and x-ray photoelectron spectroscopy analysis. The experimental results show that the stabilization results from the oxidation of the surface by the N2O plasma treatment. © 2002 American Institute of Physics.

Notes: Summary Skin hyperpigmentation is caused by the overproduction of melanin pigment, which is synthesized by the action of tyrosinase. We recently reported that aloesin inhibits tyrosinase activity. The present study was undertaken to test the inhibitory effect of aloesin on pigmentation in human skin after UV radiation. Experimental subjects were UV-irradiated (210 mJ) on the inner forearm. UV-irradiated regions were assigned to four groups: vehicle control, aloesin treated, arbutin treated, and aloesin and arbutin treated. Aloesin and/or arbutin were administered four times a day for 15 days. Aloesin treatment suppressed pigmentation by 34%, arbutin by 43.5%, and the cotreatment by 63.3% compared with the control (n = 15; P 〈 0.05). Moreover, aloesin treatment showed pigmentation suppression in a dose-dependent manner (n = 7; P 〈 0.05). These results raise the possibility that aloesin may be used as an agent that inhibits melanin formation induced by UV radiation.