Evolution and epidemiology of influenza A viruses]

Influenza A viruses are suitable for the analysis of virus evolution because the genes of the viruses are well analyzed. The origin of the present human influenza A viruses are deduced to be direct descendent of the viruses which caused Spanish flu in 1918. The analysis of NS gene shows the branching point between avian and human viruses are early 1900. By comparison of the amino acid sequences, HA serotypes could be divided into two groups, i.e., an H1 and an H3 groups. The branching between subtypes H1 and H2 occurred fairly recently. The HA genes of influenza A viruses evolve causing two kinds of antigenic variation, saift and drift, which are caused by different mechanisms.     

Cyclooxygenase-2-dependent delayed prostaglandin D2 generation is initiated by nerve growth factor in rat peritoneal mast cells: its augmentation by extracellular type II secretory phospholipase A2

When rat serosal connective tissue mast cells (CTMC) were stimulated with nerve growth factor (NGF), the immediate prostaglandin D2 (PGD2) generation was followed by delayed PGD2 generation that occurred between 2 and 24 h, reaching levels as high as 50 ng and 260 ng/10(6) cells in the absence or presence of lysophosphatidylserine (lysoPS), respectively. This delayed PGD2 generation was accompanied by de novo induction of cyclooxygenase (COX)-2, with NGF and lysoPS acting as inducer and enhancer, respectively. COX-2 induction and the attendant delayed PGD2 generation in CTMC were modestly induced by c-kit ligand, but not by Fc epsilonRI cross-linking. This indicated that the stimulus specificity differed from that observed in the immediate phase, in which NGF, c-kit ligand, and Fc epsilonRI cross-linking, either in combination with each other or with lysoPS as a cofactor, elicited comparable levels of PGD2 generation within 10 min, reaching 10 to 20 ng/10(6) cells. Addition of type II secretory phospholipase A2 (sPLA2), a PLA2 isoform that is detected in microg/ml levels in inflammatory exudates, to NGF-stimulated CTMC significantly augmented delayed, but not immediate, PGD2 generation, and this augmentative effect was mediated in part by the enhancement of COX-2 expression by sPLA2. These results suggest that CTMC have the capacity to produce PGD2 over a prolonged period in the presence of tissue-derived cytokines and sPLA2 in a COX-2-dependent manner.     

Ultra-fast optical switching operation of DBR lasers using anelectro-optical tuning section

For the first time, a DBR laser with an electro-optical Bragg section is reported for fast wavelength tuning operation. Using voltage to tune the wavelength, we measured on this device, the shortest switching time between different wavelength channels ever reported on DBR lasers: 500 ps, independently of the wavelength shift     

Conductivity of Tazheranite Ceramics Synthesized by Controlling Composition

Tazheranite ceramics with controlled compositions were synthesized by solid-phase reaction, and their conductivity was measured using the complex impedance method. The CaO content in tazheranite compositions showed the highest conductivity at around 15 mol%. In particular, Ca_0.81Ti_0.04O_y sintered bodies revealed the highest conductivity, and this value agreed very closely with that of 15 mol% CaO-stabilized ZrO₂.     

Aluminum-germanium-copper multilevel damascene process usinglow-temperature reflow sputtering and chemical mechanical polishing

A low-temperature multilevel aluminum-germanium-copper (Al-Ge-Cu) damascene technology was developed using reflow sputtering and chemical mechanical polishing (CMP). The maximum processing temperature for the fabrication of multilevel interconnections could be reduced to 420°C using Al-1%Ge-0.5%Cu, whereas the conventional reflow temperature was not less than 500°C. No degradation due to reflow heat cycles was observed in terms of Al-Ge-Cu wiring resistance. Electromigration test results indicated that the mean time to failure (MTTF) of Al-1%Ge-0.5%Cu was longer than 10 years at the operating condition, which was equivalent to that of Al-1%Si-0.5%Cu. The Al-1%Ge-0.5%Cu triple-level interconnection was fabricated using reflow sputtering to fill vias and wiring trenches and subsequent CMP for Al-Ge-Cu films     

Preparation of Zirconia-Toughened Bioactive Glass-Ceramic Composite by Sinter–Hot Isostatic Pressing

High-strength bioactive ceramics, MgO-CaO-SiO₂-P₂O₅ glass-ceramic composites toughened by zirconia, were prepared by sinter-hot isostatic pressing (sinter-HIPing) to achieve easier mass production and higher reliability. Raw materials for preparing a dense presintered body were investigated to obtain almost complete densification by sinter-HIPing. It was found that the densification of a presintered body was influenced by residual glassy phases in the crystallized glass particles. By using a controlled crystallized glass powder and a zirconia powder as raw materials, a presintered body with a relative density higher than 94% was prepared, and then it was densified to near its theoretical density by sinter-HIPing. This bioceramic exhibited an extremely high bending strength of 400 to 1000 MPa and fracture toughness of 3 to 5 MPa.m^1/2 for 30 to 80 vol% of zirconia.     

Release of nitrogen from SiOxNy films during RBS measurement

We have found that nitrogen atoms are released very rapidly from ultrathin SiO_xN_y films (2.6 nm) during RBS measurement with 500 keV He⁺ ions. The release behavior strongly depends on the preparation technique of the SiO_xN_y films. There is no release from the film prepared by thermal nitridation of SiO₂, while 80% of the nitrogen atoms are released from the film prepared by plasma nitridation at a fluence of 1×10¹⁶ cm⁻². The release cross-section for plasma SiO_xN_y films is of the order of 10⁻¹⁶ cm². This large cross-section cannot be explained by a simple recoil mechanism. The nitrogen release is also observed under irradiation with 5–10 keV electrons though the cross-section is of the order of 10⁻¹⁹ cm². These findings suggest that the observed nitrogen release is an electronic excitation induced process.     

Interferometric measurement of the linewidth enhancement factor ofa 1.55-μm strained multiquantum-well InGaAs/InGaAsP amplifier

The linewidth enhancement factor of an InGaAs/InGaAsP strained multiquantum well optical amplifier was measured interferometrically. It varied from 3 to 18 over the wavelength range from 1500 to 1600 nm with injection currents varying from one to four times the lasing threshold of the uncoated device. A rate equation model gave differential gain and refractive index change per carrier, respectively, in the range 0.3 to 2.5×10^-15 cm² and -5 to -8×10^-20 cm³     

Fabrication and characterization of high-performance InP/InGaAsdouble-heterojunction bipolar transistors

This paper is on high-performance InP/InGaAs double-heterojunction bipolar transistors (DHBT's) utilizing compositionally step-graded InGaAsP layers between the InGaAs base and InP collector to suppress the current blocking effect. These DHBT's exhibit current gains of 200 and excellent breakdown behavior. Moreover, the DHBT's permit collector current density levels J_C up to 3×10⁵ A/cm ² at V_CE=1.5 V. A current gain cutoff frequency of 155 GHz and a maximum oscillation frequency of 90 GHz have been successfully obtained at J_C=1.6×10⁵ A/cm². We have also investigated electron transport properties in the InP collector using a set of DHBT's with different injection energies into the InP collector. By increasing the injection energies, electron velocity is found to decrease from 3.5×10⁷ cm/s to 1.6×10⁷ cm/s, due to increased population of upper valleys. This result clearly demonstrates the significant role of nonequilibrium Γ-valley transport in determining the high-speed performance of InP/InGaAs DHBT's