Influence of sodium impurities on arf excimer-laser-induced absorption in CaF2 crystals

The formation of color centers induced by irradiation with ArF excimer lasers in CaF(2) crystals was found to depend strongly on the sodium impurity concentration. Sodium-related color centers were generated by two-photon absorption because the slope of the induced absorption coefficient just after irradiation started was proportional to the square of the laser fluence. The saturation absorption also depended on laser fluence, and a photobleaching induced absorption phenomenon was observed. We concluded that the saturation absorption level was determined by the equilibrium between two-photon excitation and one-photon reverse reaction.     

Expression of mRNA encoding IFN alpha in macrophages stimulated with Lactobacillus gasseri

The N7 of guanine is thought to be the primary target for adduct and crosslink formation between cisplatin and DNA. However, reactive sites in DNA other than the N7 of guanine may also participate in the formation of adducts with cisplatin. The possibility that these interactions arise and form DNA polymerase blocking lesions was investigated by primer extension reactions with Taq DNA polymerase. To differentiate between damage produced at relatively weak sites from those formed at the N7 of guanine, a modified DNA template was synthesised with the N7 of guanine replaced with a carbon atom. This was achieved in a PCR designed to incorporate 7-deazaguanine instead of normal guanine. The sequence specificity of cisplatin damage in the modified and unmodified DNA substrates was compared (after linear amplification) by DNA sequencing gel analysis. For concentrations of cisplatin (1 to 5 microM) that induce blocking lesions in normal DNA, no significant damage was observed in the modified DNA. This confirmed that the N7 of guanine is the major site of adduct formation in normal DNA. At higher concentrations of cisplatin (50 microM and 100 microM), lesions were found at AA dinucleotides and other novel sites in the modified DNA. These results indicate that the N7 of guanine is not required in the formation of some cisplatin adducts.     

Metabolism of 12-ketooctadecanoic acid byEscherichia coli K-12 andCandida tropicalis

The mode of degradation of long chain keto acids by two microorganisms was investigated.Escherichia coli K-12 converted 12-ketooctadecanoic acid to 4-ketodecanoic acid, accumulating some amounts of intermediates, 10-ketohexadecanoic, 8-ketotetradecanoic and 6-ketododecanoic acids. In contrast,Candida tropicalis completely metabolized the keto acid with transient accumulation of the metabolites mentioned above. The difference between the metabolism byE. coli of hydroxy acid and keto acid is that 12-hydroxyoctadecanoic acid is degraded as far as 6-hydroxydodecanoic acid, while 12-ketooctadecanoic acid can be degraded as far as 4-ketodecanoic acid.     

Magnetically enhanced terahertz response of Josephson junctions

We investigate the magnetic field effects on the terahertz (THz) response of grain boundary Josephson junctions. First, we show some experimental results of the THz response enhanced by a dc magnetic field. The experimental results and device configuration indicate that the THz RF magnetic field plays a role in enhancing the response. Second, we numerically simulate the current-voltage characteristics and obtain the power dependence of Shapiro steps. Since the junctions are wide compared to the inferred Josephson penetration depth, multiple current paths within a junction are possible and superconducting quantum interference device (SQUID) models should be used. Two kinds of SQUID models are used: an RF-current drive model and an RF-field activation model. Shapiro step enhancement by a dc magnetic field can be reproduced with the use of the RF-field activation model. Finally, we discuss step-height dependence on SQUID parameters as well as give a qualitative explanation for the different predictions of two SQUID models     

Dimethylaminoethylated hydroxypropyl‐chitosan: Preparation and application as polymeric ligand to form Rh6 cluster complexes for the reduction of benzaldehyde and nitrobenzene

Hydroxypropyl chitosan and its dimethylaminoethylated derivative were prepared in different conditions. Experimental results indicated that the degree of substitution (DS) of hydroxypropyl chitosan was strongly related to the molar ratio of propylene oxide to the glucosamine unit of chitosan, the used solvent, the reaction temperature and the amount of sodium hydroxide. Moreover, the obtained hydroxypropyl chitosan could be effectively dimethylaminoethylated by the reaction with dimethylaminoethyl chloride in the presence of NaH under DMAC solution. By the combination of dimethylaminoethylated hydroxypropyl chitosan and Rh₆(CO)₁₆, benzaldehyde and nitrobenzene could be converted into correspondingly reductive products in high yields under the WGSR condition. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 447–453, 2001     

4 Pro-R hydrogen of NADPH was abstracted for enzymatic hydride transfer by N-ethylmaleimide-reductase of Yarrowia lipolytica

We studied the steric course of the reaction catalyzed by the N-ethylmaleimide (NEM) reductase of Yarrowia (Candida) lipolytica (Y. lipolytica), using 4R-[4-2H1]NADPH and 4S-[4-2H1]NADPH as cofactors and N-ethylcitraconimide as substrate. Active substrates and inhibitors of NEM reductase and its subcellular distribution were also investigated to clarify the biochemical properties of this enzyme. NEM reductase catalyzes the reduction of N-ethylmaleimide to N-ethylsuccinimide with NAD(P)H as the cofactor. Several maleimide and cyclopentenone derivatives tested were also active substrates for NEM reductase of Y. lipolytica. Some pyrazolone derivatives, particularly 1-phenyl-5-pyrazolone, were found to be effective inhibitors of NEM reductase. Subcellular localization of NEM reductase was carried out using protoplast formation and differential centrifugation. Ninety-eight percent of the NEM reductase activity was recovered in the cytosolic fraction, indicating that NEM reductase in Y. lipolytica was the cytosolic enzyme. We also determined the stereochemical specificity of the reduction of N-ethylcitraconimide by NEM reductase in Y. lipolytica, showing that 4 Pro-R hydrogen of NADPH was abstracted for enzymatic hydride transfer by NEM reductase, and two hydrogen atoms from NADPH and H2O added to opposite faces of the double bond of N-ethylcitraconimide.     

Activities of superoxide dismutase and glutathione peroxidase in the red cells of Japanese acatalasemia blood

Trichophyton violaceum was cultured on a Sabouraud's dextrose agar slants for freeze-fracture replication. It was cryoprotected with glycerol and sucrose. The surface structure of the cell wall showed a rodlet pattern. Invagination-like craters were observed in the plasmalemma. The nuclear envelope with pores, mitochondria, and vacuoles were clearly shown. Three-dimensional views of the fine structure were presented.     

Implementation of new superconducting neural circuits using coupledSQUIDs

A novel superconducting neuron circuit and two types of variable synapses, which are based on superconducting quantum interferometer devices (SQUIDs), are presented. A neuron circuit with good input-output isolation and steep threshold characteristics is accomplished using a combination of a single-junction SQUID coupled to a double-junction SQUID. The quantum state of the single-junction SQUID represents the neuron state, and the output voltage of the double-junction SQUID, which is operated in a nonlatching mode with shunt resistors, is a sigmoid-shaped function of the input. Both variable synapse circuits are composed of multiple shunted double-junction SQUIDs. The first type changes its conductance value by using both superconducting and voltage states. The second variable synapse circuit changes its output current digitally by switching its bias currents. Besides numerical simulations of the circuit characteristics, we have fabricated superconducting neural chips in a Nb/AlO_x/Nb Josephson junction technology. The fundamental operation of each element and a 2-bit neural-based A/D converter have been successfully tested. A learning system with a variable synapse is also discussed     

Analysis of the thromboxane/prostacyclin balance in human urine by gas chromatography/selected ion monitoring: abnormalities in diabetics

Mouse fibroblasts (B-6) were cultured on agar-coated dishes. After cells grew for 2-3 generations relatively rapidly in suspension, they began to grow very slowly (stationary phase). Electron microscopic studies showed that cells in a stationary phase developed intracellular organella: membranous structures (endoplasmic reticulum and Golgi apparatus) became manifest and the number of mitochondria increased. The specific activities of succiniccytochrome c reductase and 5'-nucleotidase were three and five times higher, respectively, than those of cells on the dish.     

Switching delay of a nonlatching Josephson gate evaluated from ringoscillator operation

The authors present the experimental results for the switching delay of a dc-biased nonlatching Josephson gate (a coupled-superconducting quantum interference device gate). The measurement is executed by the use of a ring oscillator (RO) method. A frequency-to-voltage converter is used to evaluate the oscillation frequency of the RO. The circuit is designed and fabricated using a 2.5-kA/cm² Nb/AlO_x/Nb Josephson junction technology. The results show the minimum switching delay of 18 ps