Multichannel fiber ferrule for a stable laser-diode array module

We developed a multichannel fiber ferrule for a stable laser-diode array module. To apply YAG laser welding to parallel butt couple between the laser-diode and the single-mode fiber arrays, hermetically sealed and precisely aligned equi-interval fibers are required. We describe a V-grooved ceramic ferrule for embedding fibers. Fibers are fixed by soldering, using a flat ceramic lid and aligned with a 250 μm pitch. Our ferrule allowed a metallic, stem mounting laser-diode, to be fixed by YAG laser welding. All 30 samples tested have a leak rate of less than 1×10^-10 atm·cc/s. Optical coupling of fabricated modules was 9.7±0.2 dB and coupling loss change from 25°C to 115°C was within 0.5 dB     

Ultrahigh Electrical Resistance of Poly(cyclohexyl methacrylate)/Carbon Nanotube Composites Prepared Using Surface‐Initiated Polymerization

Multiwalled carbon nanotubes on which poly(cyclohexyl methacrylate)s are densely grafted (PCHMA‐CNTs), are synthesized using a modified surface‐initiated atom transfer radical polymerization technique. The electrical resistance of PCHMA‐CNT is systematically characterized under direct current (DC) and alternating current and compared to that of conventional nanocomposites prepared by blending PCHMA with the CNT (PCHMA/CNT). At a comparable volume fraction of CNT, DC volume resistivity of PCHMA‐CNT is 14 orders of magnitude higher than that of PCHMA/CNT. This is because the grafted polymer with a combination of the high molecular weight and the high grafting density isolates individual CNTs at a long distance in the PCHMA‐CNT system. In addition, impedance analysis reveals that the highly insulated PCHMA‐CNT has the same electrical nature as neat PCHMA, i.e., it is a dielectric. Furthermore, dynamic mechanical analysis shows PCHMA‐CNT has a good mechanical properties as well as ultrahigh electrical resistance.     

Screening of lactic acid bacteria for bile salt hydrolase activity

Bile salt hydrolysis is an important metabolic reaction in the bile salt metabolism of mammals. This reaction has a facilitating effect for bile salt excretion but can also be involved in various illnesses. In recent years interest has increased to use bile salt hydrolysis to influence the cholesterol metabolism of humans and farm animals. To understand the distribution and range of bile salt hydrolase activity in lactic acid bacteria, we screened more than 300 strains of the genera Bifidobacterium and Lactobacillus and the species Lactococcus lactis, Leuconostoc mesenteroides, and Streptococcus thermophilus. Results obtained for 273 strains showed that bile salt hydrolase activity is common in Bifidobacterium and Lactobacillus but absent in L. lactis, Leu. mesenteroides, and S. thermophilus. Nearly all bifidobacteria species and strains have bile salt hydrolase activity, whereas this activity can only be found in selected species of lactobacilli. A strong correlation can be observed between the habitat of a genus or species and the presence of bile salt hydrolase activity. Most often bile salt hydrolase activity is found in strains that have been isolated from the intestines or from feces from mammals--an environment rich in conjugated and unconjugated bile acids. Strains and species from other habitats like milk or vegetables--environments from which bile salts are absent--do normally not have bile salt hydrolase activity. In two independent assays, we established that bile salt hydrolase activity in bifidobacteria is, in general, much higher than in lactobacilli.     

Optimization of L-lactic acid feeding for the production of poly-D-3-hydroxybutyric acid by Alcaligenes eutrophus in fed-batch culture

We investigated optimization of the feeding of L-lactic acid for the production of poly-D-3-hydroxybutyric acid [P(3HB)] by Alcaligenes eutrophus in a fed-batch culture system. An acidic substrate solution was fed automatically so as to maintain the pH of the culture liquid at 7.0. Feeding of a substrate solution containing 45% (w/v) L-lactic acid, 6.2% (w/v) sodium L-lactate, 5.8% (w/v) ammonia water and 1.8% (w/v) potassium phosphate [at a molar ratio of carbon to nitrogen (C/N molar ratio) of 10], allowed the L-lactate concentration in the culture liquid to be maintained at approximately 2 g/l and the cell concentration reached 27.4 g/l after 15 h of cultivation. To promote P(3HB) production, a two-stage fed-batch culture consisting of a culture for cell growth and one for P(3HB) accumulation was carried out. When the substrate solution, whose C N molar ratio was 23, was fed during the P(3HB) accumulation phase, the cell concentration and the P(3HB) content in the cells reached 103 g/l and 57.6% (w/w), respectively, in 51.5 h.     

Isolation and characterization of the ATF2 gene encoding alcohol acetyltransferase II in the bottom fermenting yeast Saccharomyces pastorianus

The ATF2 gene encodes alcohol acetyltransferase II, which catalyses the synthesis of isoamyl acetate from acetyl coenzyme A and isoamyl alcohol. To characterize the ATF2 gene from the bottom fermenting yeast Saccharomyces pastorianus, the S. pastorianus ATF2 gene was cloned by colony hybridization using the S. cerevisiae ATF2 gene as a probe. When an atf1 null mutant strain was transformed with a multi-copy plasmid carrying the S. pastorianus ATF2 gene, the AATase activity of this strain was increased by 2.5-fold compared to the control. The S. pastorianus ATF2 gene has 99% nucleic acid homology in the coding region and 100% amino acid homology with the S. cerevisiae ATF2 gene. Southern blot analysis of chromosomes separated by pulse-field gel electrophoresis indicated that the ATF2 gene probe hybridized to chromosome VII in S. cerevisiae and to the 1100 kb chromosome in S. pastorianus. As S. pastorianus is thought to be a hybrid of S. cerevisiae and S. bayanus, the S. bayanus-type gene, which has a relatively low level of homology with the S. cerevisiae-type gene, is also usually detected. Interestingly, an S. bayanus-type ATF2 gene could not be detected. These results suggested that the cloned ATF2 gene was derived from S. cerevisiae. Analysis using an ATF2-lacZ fusion gene in S. pastorianus showed that expression of the ATF2 gene was relatively lower than that of the ATF1 gene and that it is repressed by aeration but activated by the addition of unsaturated fatty acids. The S. pastorianus ATF1, Lg-ATF1 and ATF2 Accession Numbers in the DDBJ Nucleotide Sequence Database are D63449, D63450 and D86480, respectively.     

An 8.1-ns Column-Access 1.6-Gb/s/pin DDR3 SDRAM With an 8:4 Multiplexed Data-Transfer Scheme

Three circuit techniques for an 8.1-ns column-access 1.6-Gb/s/pin 512-Mb DDR3 SDRAM using 90-nm dual-gate CMOS technology were developed. First, an 8:4 multiplexed data-transfer scheme, which operates in a quasi-4-bit prefetch mode, achieves a 3.17-ns reduction in column-access time, i.e., from 11.3 to 8.13 ns. Second, a dual-clock latency counter reduces standby power by 22% and cycle time from 1.7 to 1.2 ns. Third, a multiple-ODT-merged output buffer enables selection of five effective-resistance values Rtt (20, 30, 40, 60, and 120 Omega) without increasing I/O capacitance. Based on these techniques, 1.6-Gb/s/pin operation with a 1.36-V power supply and a column latency of 7 was accomplished     

Thiamine pyrophosphatase activity in the Golgi apparatus of calcitonin-treated osteoclasts.

The thiamine pyrophosphatase (TPPase) activity described by Novikoff and Goldfisher was examined in osteoclasts affected by calcitonin in order to elucidate whether the morphological and functional changes of the osteoclasts have an influence over the secretion function of their Golgi apparatus. The Golgi apparatus of osteoclasts of which the ruffled border had disappeared and bone resorption discontinued as the result of treatment with calcitonin showed a slight TPPase activity. The reaction products of the enzyme in these inactive osteoclasts were distinctly fewer than that of control osteoclasts, which were not affected by calcitonin. From these results, it is suggested that there may be a connection between the morphological and functional changes of osteoclasts and the secretion function of the Golgi apparatus.     

Practical model for gas temperature effects on CO2lasers

An analytical and experimental investigation on the effect of gas temperature on convection flow CO₂ lasers is presented. A simple and practical model neglecting the population of lower laser levels is proposed and examined by experiments. The model indicates simply that the gas temperature affects the `inherent threshold discharge power'. Appropriateness of the model has been proven regardless of the schemes of cross flow or axial flow     

A 62-ns 16-Mb CMOS EPROM with voltage stress relaxation technique

To meet the increasing demand for higher-density and faster EPROMs, a 16-Mb CMOS EPROM has been developed based on 0.6-μm N-well CMOS technology. In scaled EPROMs, it is important to guarantee device reliability under high-voltage operation during programming. By employing internal programming-voltage reduction and new stress relaxation circuits, it is possible to keep an external programming voltage V_pp of 12.5 V. The device achieves a 62-ns access time with a 12-mA operating current. A sense-line equalization and data-out latching scheme, made possible by address transition detection (ATD), and a bit-line bias circuit with two types of depletion load led to the fast access time with high noise immunity. This 16-Mb EPROM has pin compatibility with a standard 16-Mb mask-programmable ROM (MROM) and is operative in either word-wide or byte-wide READ mode. Cell size and chip size are 2.2 μm×1.75 μm and 7.18 mm×17.39 mm, respectively     

Organic field-effect transistors based on J-aggregate thin films of a bisazomethine dye

We report on the fabrication and the characterization of p-type organic field-effect transistors based on vapor-deposited J-aggregate bisazomethine dye thin films. The absorption spectra of this non-ionic organic semiconductor in the solid state show a strong influence of the film thickness on the J-aggregate formation. However, the electrical characteristics of the devices demonstrate that the hole transport properties do not vary significantly in films thicker than 100 nm. This is due to the fact that the J-aggregates are formed in this material at the surface of the crystalline grains and do not influence the semiconductor/gate dielectric interface and the charge transport properties of the devices. Hole field-effect mobilities as high as 2.4 × 10^?4 cm² V^?1 s^?1 were obtained and could be slightly improved by a solvent vapor treatment due to changes in the film crystallinity. Overall, this study demonstrates that J-aggregate bisazomethine dye thin films are good candidates for the realization of organic electronic devices.