Reflectivity dependence of threshold current in GaInAsP/InP surface emitting laser

A systematic study of changing the reflectivity of a Si/SiO/sub 2/ mirror for 1.3- mu m GaInAsP/InP surface-emitting lasers is discussed. An effective threshold current of 4.5 mA at 77 K continuous operation has been obtained. This indicates a possibility of a submilliampere threshold at 77 K and approximately=20 mA at 300 K by optimizing the mirror reflectivity.<>     

Paramagnetic meissner effect in superconducting single crystals of Ba1−x KxBiO3

The paramagnetic Meissner effect (PME) in the field cooled susceptibility has been observed in superconducting single crystals of Ba_1–xK_xBiO₃ using magnetometers of Quantum-Design Co. The PME is similar to that observed in cuprates and Nb superconductors. For the Ba_0.63K_0.37BiO₃ crystal the PME is observed in cooling process under the field up to 750 Oe. The PME was not found in the virgin-charged superconducting magnet. The PME is found in a superconductor with trapped flux and may arise from a remnant field, a temperature inhomogeneity near T_c, and a potassium-concentration inhomogeneity.We would like to thank Dr. Kwon-Sang Ryu at KRISS in Korea for the standardization of a Hall sensor. The Hall sensor was kindly provided by Asihi Chemical Co.     

Mesh waveguide optical star coupler

A new multimode optical star coupler with a mesh waveguide configuration is proposed to reduce the device length by stimulating light mixing in a short waveguide. A 4×4 optical star coupler has been fabricated and its branching variation of 2.8 dB is realised with the device length as short as 14.5 mm.     

Population pharmacokinetics of vancomycin in Japanese adult patients

MICA is a new polymorphic gene in the HLA region expressed in epithelial cell lines and gastrointestinal epithelium. Little is yet known about the MICA protein, and the pattern of its expression by freshly isolated cells has not been established. In the present experiments, we used antibodies raised in rabbits against alpha1 and alpha2 domain-peptides to study the expression of MICA. By western blot and immunoprecipitation, we detected a band of 62 000 Mr in various cell lines (THP-1, U937, HeLa, A431, Raji, MOLT-4, and HUV-EC-C) and in freshly isolated keratinocytes, endothelial cells, and monocytes but not in CD4+ and CD8+ T cells, and CD19+ cells (B lymphocytes). It was not possible to up-regulate the expression of MICA in different cells by stimulation with gamma-interferon, but the expression of MICA was induced in phytohemagglutinin-stimulated T cells. We confirmed that MICA is expressed at the cell surface by flow cytometry. Results of immunoprecipitation studies of beta2-microglobulin (beta2m)- or MICA-depleted, metabolically labeled HeLa cells indicated that MICA was not associated with beta2m. Although the function of MICA is still unknown, its restricted pattern of tissue expression, the fact that it is expressed on the cell surface, and its polymorphic nature suggest that this new molecule, encoded close to HLA class I, may play a role in the interaction between epithelial cells and cells of the immune system.     

Scalable rank-mapping algorithm for an icosahedral grid system on the massive parallel computer with a 3-D torus network

In this paper, we develop a rank-mapping algorithm for an icosahedral grid system on a massive parallel computer with the 3-D torus network topology, specifically on the K computer. Our aim is to improve the weak scaling performance of the point-to-point communications for exchanging grid-point values between adjacent grid regions on a sphere. We formulate a new rank-mapping algorithm to reduce the maximum number of hops for the point-to-point communications. We evaluate both the new algorithm and the standard ones on the K computer, using the communication kernel of the Nonhydrostatic Icosahedral Atmospheric Model (NICAM), a global atmospheric model with an icosahedral grid system. We confirm that, unlike the standard algorithms, the new one achieves almost perfect performance in the weak scaling on the K computer, even for 10,240 nodes. Results of additional experiments imply that the high scalability of the new rank-mapping algorithm on the K computer is achieved by reducing network congestion in the links between adjacent nodes.     

Simple optical wavelength-division multiplexer component that uses the lateral focusing scheme of a planar microlens

A planar microlens beam guide that is based on the lateral focusing property of gradient-index planar microlenses is realized for a wavelength-division multiplexer (WDM) component without precision alignment. By stacking two planar microlenses, we obtain a nearly circular focused spot of ~5-μm diameter by lateral focusing, which is comparable with that of a single-mode fibers. A fabricated WDM component that consists of four stacked lenses and microfilters inserted into the slits made in a substrate is demonstrated. The port-to-port coupling loss is 3-5 dB, and an extinction ratio of larger than 20 dB for multiplexed-demultiplexed wavelengths of 780 and 633 nm, respectively, is achieved.     

Sour beer production: impact of pitching sequence of yeast and lactic acid bacteria

Lactic acid bacteria have long been used in brewing to acidify mash or wort and in the production of traditional sour beer styles (Lambic, Gueuze) using spontaneous fermentation. This approach is time consuming (some sour beers are matured for three years to obtain the appropriate flavour), so many brewers choose a faster approach using mixed cultures (yeast and bacteria). In this study, the influence of the pitching sequence of bacteria and yeast on the fermentation process was evaluated (by rate of fermentation and acidification, attenuation degree and ethanol concentration). The trials were performed using three procedures: (i) the addition of bacteria followed by the yeast; (ii) the addition of the yeast followed by the bacteria and (iii) the simultaneous addition of yeast and bacteria. In each trial the following time intervals were applied: 24, 48 and 72 h. Weight loss of samples and drop in pH were measured daily, and ethanol content, real extract and lactic acid concentration measured at the end of the process. It was shown that the order of addition of yeast and bacteria determines the success of the lactic acid fermentation. The appropriate yield of lactic acid (ca. 6 g/L) and the drop in pH (<3.6) can be achieved by inoculating the bacteria prior to the inoculation of yeast. When yeast was pitched before the bacteria, the lactic acid content was ca. 2 g/L and pH was 3.9–4.2. © 2019 The Institute of Brewing & Distilling     

An InGaAs-GaAs vertical-cavity surface-emitting laser grown on GaAs(311)A substrate having low threshold and stable polarization

We have fabricated an InGaAs-GaAs vertical-cavity surface-emitting laser (VCSEL) grown on a GaAs(311)A substrate by molecular beam epitaxy (MBE) and demonstrated continuous wave operation at room temperature. A threshold current density of 80 A/cm/sup 2//well and very stable polarization characteristics up to 2.7 times the threshold were achieved. The polarization state with the highest optical intensity was oriented along the [2~33] direction, which is the crystallographic axis exhibiting the maximum gain. An extinction ratio of more than 12.7 dB was obtained between two orthogonal polarization states. The high and anisotropic gain of a (311)A-oriented VCSEL will drastically improve the device performance by optimization and process engineering.     

Single-transverse mode and stable-polarization operation underhigh-speed modulation of InGaAs-GaAs vertical-cavity surface-emittinglaser grown on GaAs (311) B substrate

We have demonstrated an oxide confinement vertical-cavity surface-emitting laser grown on a GaAs (311)B substrate, and achieved single-transverse mode and single-polarization operation in the entire tested current range. The threshold was 0.6 mA for a 2.7 μm×2.9 μm oxide aperture. Even under high-speed modulation up to 5 GHz, the device showed stable single-transverse mode and polarization. Sidemode suppression ratio and orthogonal polarization suppression ratio were over 30 and 10 dB, respectively     

A 1.9-GHz single chip IF transceiver for digital cordless phones

A 1.9 GHz IF transceiver for the Japanese standard personal handy-phone system (PHS) is fabricated in a 0.8-μm BiCMOS process with 20 GHz npn. A down-mixer, up-mixer, variable attenuator, quadrature modulator, first and second PLL, and second VCO are included in the 3.4×3.0 mm² chip. The chip draws 24 mA in receive mode and 44 mA in transmit mode, operating from 3.0 V. A total vector error of 4% for the π/4 QPSK PN9 pattern includes the up-mixer and the dual PLLs