Band-tail model and temperature-induced blue-shift in photoluminescence spectra of InxGa1-xN grown on sapphire

A band-tail model of inhomogeneously broadened radiative recombination is presented and applied to interpret experimental data on photoluminescence of various bulk and quantum-well epitaxial InGaN/GaN structures grown by MOCVD. The temperature dependence of the spectral peak position is analyzed according to the model, explaining the anomalous temperature-induced blue spectral shift. Significant differences are observed between epilayers grown on sapphire substrates and on GaN substrates prepared by the sublimation method. No apparent evidence of band tails in homoepitaxial structures indicates their higher crystalline quality.     

Inhibition of immunoglobulin production stimulating activity of glyceraldehyde-3-phosphate dehydrogenase by nucleotides

We have previously identified glyceraldehyde-3-phosphate dehydrogenase as an immunoglobulin production stimulating factor (IPSF) which facilitated immunoglobulin production by hybridomas and lymphocytes. The IPSF activity of this enzyme was suppressed by the coexistence of some sorts of nucleotides. We now report that the IPSF effect of GAPDH was suppressed by the coexistence of DNA, the inhibiting effect of degraded DNA being inferior to that of long-chain DNA. Both single-stranded and double-stranded synthetic polyribonucleotides also inhibited the IPSF activity of GAPDH. Moreover, nicotinamide adenine dinucleotide (NAD+) repressed the IPSF effect.     

100-Gb/s multiplexing and demultiplexing IC operations in InP HEMT technology

This paper describes the 100-Gb/s multiplexing operation of a selector IC and demultiplexing operation of a D-type flip-flop (D-FF) using production-level 0.1-/spl mu/m-gate-length InP HEMT IC technology. To boost the operating speed of the selector IC, a selector core circuit directly drives an external 50-/spl Omega/ load, and is included in the output stage. In addition, a test chip containing the selector and a D-FF to confirm error-free operation of these circuits was designed. The fabricated selector IC exhibited clear eye openings at 100 Gb/s, and its error-free operation was confirmed by using the test chip.     

Assessment of glycosaminoglycan-protein linkage tetrasaccharides as acceptors for GalNAc- and GlcNAc-transferases from mouse mastocytoma

Two glycosaminoglycan-protein linkage tetrasaccharide-serine compounds, GlcAbeta1-3Galbeta1-3Galbeta1-4Xylbeta1-O-Ser and GlcAbeta1-3Gal(4-O-sulfate)beta1-3Galbeta1-4Xylbeta1-O -Ser, were tested as hexosamine acceptors, using UDP-[3H]GlcNAc and UDP-[3H]GalNAc as sugar donors, and solubilized mouse mastocytoma microsomes as enzyme source. The nonsulfated Ser-tetrasaccharide was found to function as an acceptor for a GalNAc residue, whereas the Ser-tetrasaccharide containing a sulfated galactose unit was inactive. Characterization of the radio-labelled product by digestion with alpha-N-acetylgalactosaminidase and beta-N-acetylhexosaminidase revealed that the [3H]GalNAc unit was alpha-linked, as in the product previously synthesized using serum enzymes, and not beta-linked as found in the chondroitin sulfate polymer. Heparan sulfate/heparin biosynthesis could not be primed by either of the two linkage Ser-tetrasaccharides, since no transfer of [3H]GlcNAc from UDP-[3H]GlcNAc could be detected. By contrast, transfer of a [3H]GlcNAc unit to a [GlcAbeta1-4GlcNAcalpha1-4]2-GlcAbeta1-4-aMan hexasaccharide acceptor used to assay the GlcNAc transferase involved in chain elongation, was readily detected. These results are in agreement with the recent proposal that two different N-acetylglucosaminyl transferases catalyse the biosynthesis of heparan sulfate. Although the mastocytoma system contains both the heparan sulfate/heparin and chondroitin sulfate biosynthetic enzymes the Ser-tetrasaccharides do not seem to fulfil the requirements to serve as acceptors for the first HexNAc transfer reactions involved in the formation of these polysaccharides.     

Decrease of the obese gene expression in bovine subcutaneous adipose tissue by fasting

The expression of mRNA of leptin, the product of the obese gene, in bovine adipose tissue was analyzed by a lysate RNase protection assay. The mRNA level was significantly decreased by food deprivation for two days and partially recovered after 3 hr of refeeding, indicating that obese gene expression in the ruminant was regulated by feeding.     

Growth-supporting activities of fibronectin on hematopoietic stem/progenitor cells in vitro and in vivo: structural requirement for fibronectin activities of CS1 and cell-binding domains

Fibronectin (FN) is supposed to play important roles in various aspects of hematopoiesis through binding to very late antigen 4 (VLA4) and VLA5. However, effects of FN on hematopoietic stem cells are largely unknown. In an effort to determine if FN had a growth-supporting activity on hematopoietic stem cells, human CD34(+)/VLA4(bright)/VLA5(dull) hematopoietic stem cells and a murine stem cell factor (SCF)-dependent multipotent cell line, EML-C1, were treated with or without FN in a serum and growth-factor-deprived medium, and then subjected to clonogenic assay in the presence of hematopoietic growth factors. The pretreatment of the CD34(+) cells with FN gave rise to significantly increased numbers of granulocyte-macrophage colony-forming units (CFU-GM), erythroid burst colony-forming units, and mixed erythroid-myeloid colony-forming units. In addition, the numbers of blast colony-forming units and CFU-GM that developed after culture of EML-C1 cells with SCF and the combination of SCF and interleukin-3, respectively, were augmented by the pretreatment with FN. The augmented colony formation by FN was completely abrogated by the addition of CS1 fragment, but not of GRGDSP peptide, suggesting an essential role of FN-VLA4 interaction in the FN effects. Furthermore, the effects of various FN fragments consisting of RGDS-containing cell-binding domain (CBD), heparin-binding domain (HBD), and/or CS1 portion were tested on clonogenic growth of CD34(+) cells. Increased colony formation was induced by CBD-CS1 and CBD-HBD-CS1 fragments, but not with other fragments lacking CBD or CS1 domains, suggesting that both CS1 and CBD of FN were required for the augmentation of clonogenic growth of hematopoietic stem/progenitor cells in vitro. In addition to the in vitro effects, the in vivo administration of CBD-CS1 fragment into mice was found to increase the numbers of hematopoietic progenitor cells in bone marrow and spleen in a dose-dependent manner. Thus, FN may function on hematopoietic stem/progenitor cells as a growth-supporting factor in vitro and in vivo.     

Early start on continuous hemodialysis therapy improves survival rate in patients with acute renal failure following coronary bypass surgery

Acute renal failure requiring dialysis therapy after cardiac surgery occurs in 1% to 5% of patients; however, the optimal timing for initiation of dialysis therapy still remains undetermined. To assess the validity of early start of dialysis therapy, we studied the comparative survival between 14 patients who started to receive dialysis therapy when urine volume decreased to less than 30 mL/hr and another group of 14 patients who waited to begin dialysis therapy until the level of urine volume was less than 20 mL/hr for 14 days following coronary bypass graft surgery. Twelve of 14 patients who received early intervention survived. In contrast, only 2 of 14 patients in the late‐dialysis group survived. There was a significant difference in survival between the two groups (p < 0.01). There were no significant differences between the two groups with respect to age, sex ratio, the APACHE (Acute Physiologic and Chronic Health Evaluation) II score, and the levels of serum creatinine at the start of dialysis therapy (2.9 ± 0.2 mg/dL vs. 3.1 ± 0.2 mg/dL), as well as the levels of serum creatinine at admission. We propose that the timing of the start for treatment of acute renal failure following cardiac surgery should be determined by the decrease of urine volume and not the levels of serum creatinine. Early start of dialysis therapy may help improve the survival of patients with acute renal failure following cardiac surgery.     

Synaptic density of the prefrontal cortex regulated by dopamine instead of serotonin in rats

Recent findings indicate that monoamine contributes to synaptic plasticity. We examined the synaptic density of the prefrontal cortex and parietal cortex of rats using dopamine (DA) antagonists and agonists, as well as serotonin (5-HT) depleters and found a reduction in synaptic density in the prefrontal cortex lamina V-VI at a maximum of 20% with administration of a D1 antagonist (SCH23390) and at a maximum of 30% with a D2 antagonist (YM09151). Further, with the administration of D1+D2 antagonists there was a 27% decrease in synaptic density, which was a larger reduction than the total of the single dosages of each DA antagonist at equal levels. Increase in synaptic density was seen at a maximum of 8.5% with dosage of a D1 agonist (SKF38390) and 14.5% with dosage of a D2 agonist (PPHT). The dosage of D1+D2 agonists showed a 27.1% increase in synaptic density. There was no change in synaptic density of the parietal cortex with either DA antagonist or agonist administration. Administration of 5-HT depleter pCPA resulted in a 13.8% reduction of synaptic density in the parietal cortex, though there was no change identified in the synaptic density in the prefrontal cortex. Based on these results, it was suggested that the area of the brain with affected synaptic plasticity could differ, depending on the type of monoamine.     

Mitigation of Sn Whisker Growth by Small Bi Additions

In this study, the morphological development of electroplated matte Sn and Sn-xBi (x = 0.5 wt.%, 1.0 wt.%, 2.0 wt.%) film surfaces was investigated under diverse testing conditions: 1-year room-temperature storage, high temperature and humidity (HTH), mechanical loading by indentation, and thermal cycling. These small Bi additions prevented Sn whisker formation; no whisker growth was observed on any Sn-xBi surface during either the room-temperature storage or HTH testing. In the indentation loading and thermal cycling tests, short (<5 μm) surface extrusions were occasionally observed, but only on x = 0.5 wt.% and 1.0 wt.% plated samples. In all test cases, Sn-2Bi plated samples exhibited excellent whisker mitigation, while pure Sn samples always generated many whiskers on the surface. We confirmed that the addition of Bi into Sn refined the grain size of the as-plated films and altered the columnar structure to form equiaxed grains. The storage conditions allowed the formation of intermetallic compounds between the plated layer and the substrate regardless of the Bi addition. However, the growth patterns became more uniform with increasing amounts of Bi. These microstructural improvements with Bi addition effectively released the internal stress from Sn plating, thus mitigating whisker formation on the surface under various environments.     

Icosahedron cage occupancy of structure-H hydrate helped by Xe -1,1-, cis -1,2-, trans-1,2-, and cis-1,4-dimethylcyclohexanes

Four mixtures of 1,1-, cis-1,2-, trans-1,2-, and cis-1,4-dimethylcyclohexanes (hereafter abbreviated DMCH) including H₂O and Xe have been investigated in a temperature range over 274.5 K and a pressure range up to 2.7 MPa. The 1,1-DMCH and cis-1,2-DMCH generate the structure-H hydrate in the temperature range up to 295.2 and 280.2 K, respectively. Especially, very large depression of equilibrium pressure has been observed in the structure-H 1,1-DMCH hydrate system. On the other hand, neither trans-1,2-DMCH nor cis-1,4-DMCH generates the structure-H hydrate in the present temperature range. It is an important finding that the cis-1,4-DMCH does not generate the structure-H hydrate in the presence of Xe, while the mixture of cis-1,4-DMCH and methane generates the structure-H hydrate.