Direct dispersion measurement of highly-erbium-doped optical amplifiers using a low coherence reflectometer coupled with dispersive fourier spectroscopy

The group delay and dispersion, including the erbium ion contributions, of the highly erbium-doped silica planar waveguide amplifier and multicomponent glass fibre amplifiers are directly measured at different pump powers using a low coherence reflectometer and dispersive Fourier spectroscopy. This method derives the refractive index spectra of these amplifiers directly from the produced reflectograms without any physical or mathematical assumptions. The dispersion of the planar waveguide amplifier at 500 mW pumping changes between +300 and -200 ps/km/nm with a 0.4 wt.% erbium concentration.<>     

Deterioration of connectin/titin and nebulin filaments by an excess of protease inhibitors

OBJECTIVE: To investigate HLA class II allele associations with autoantibody responses to Ro/SS-A and La/SS-B among Japanese subjects. METHODS: Haplotype and allele distributions, along with molecular polymorphisms, of HLA class II genes were analyzed by polymerase chain reaction-restriction fragment length polymorphism in 41 Japanese women with precipitating autoantibodies to Ro/SS-A and/or La/SS-B. RESULTS: Among women with both Ro/SS-A and La/SS-B antibodies, the HLA class II haplotype DRB1*08032/DQA1*0103/DQB1*0601 and DRB1*08032 allele showed significantly increased frequencies compared with patients with anti-Ro/SS-A alone or with normal controls. All women with both anti-Ro/SS-A and anti-La/SS-B, but not those with anti-Ro/SS-A alone, carried DRB1 alleles that shared the same amino acid residues at positions 14-31 and 71 of the hypervariable regions of the DRB1 chain. All anti-Ro/SS-A positive women carried 1 or 2 alleles of DQB1*06 and DQB1*03 subtypes that shared the same amino acid residues at positions 71-77 of the DQB1 chain. HLA class II allele distributions did not differ among 3 anti-Ro/SS-A positive groups with different disease expressions, i.e., patients with systemic lupus erythematosus, patients with primary Sj?gren's syndrome, and women with no apparent symptoms of rheumatic disease. CONCLUSION: HLA class II allele distributions differ among anti-Ro/SS-A positive subjects according to the presence or absence of coexisting anti-La/SS-B antibodies, but not according to disease expression. Our findings suggest that different HLA class II molecules might control the development of anti-Ro/SS-A and/or anti-La/SS-B antibodies in the autoimmune response to the Ro/SS-A-La/SS-B complex.     

Tyrosine phosphorylation as a convergent pathway of heterotrimeric G protein- and rho protein-mediated Ca2+ sensitization of smooth muscle of rabbit mesenteric artery

1. The aim of this study was to determine whether different signal transduction mechanisms underlie the Ca2+ sensitizing effects of guanosine 5'-O-(3-thiotriphosphate) (GTP(gamma)S) and receptor agonists on beta-escin-skinned smooth muscle of rabbit mesenteric artery. 2. In the homogenate of the beta-escin-skinned arterial strip, C3 exoenzyme of Clostridium botulinum catalyzed the [32P]-ADP-ribosylation of only one protein that had the same molecular mass as the protein detected in Western blots with anti-rho p21 antibody. Pretreatment of preparations with C3 resulted in great inhibition of GTP(gamma)S-induced Ca2+ sensitization, although the effect of GTP(gamma)S at higher concentrations (> or = 30 microM) was not completely blocked by this treatment. In contrast, the enhancement by phenylephrine and histamine, in the presence of guanosine 5'-triphosphate, of the Ca2+-induced contraction was not affected by C3 pretreatment. 3. The protein kinase C (PKC) inhibitors calphostin C and staurosporine completely eliminated the enhancement by phorbol ester 12,13-dibutyrate of the Ca2+-induced contraction. However, these PKC inhibitors had no effect on GTP(gamma)S- and receptor agonist-induced Ca2+ sensitization. 4. The tyrosine kinase inhibitors genistein and tyrphostin 25 caused an irreversible and complete block of the enhancement by GTP(gamma)S of the Ca2+-induced contraction without affecting this Ca2+ contraction. The inactive genistein analogue daidzein did not modify the effect of GTP(gamma)S. The Ca2+ sensitizing effects of phenylephrine and histamine were also blocked by these tyrosine kinase inhibitors. 5. These results suggest that rho p21 predominantly mediates GTP(gamma)S-induced Ca2+ sensitization of beta-escin-skinned smooth muscle of rabbit mesenteric artery, while the Ca2+ sensitizing actions of heterotrimeric G protein-coupled receptor agonists do not involve this small G protein. However, it seems that tyrosine phosphorylation, but not PKC activation, plays an important role in both of the rho p21 protein- and heterotrimeric G protein-mediated Ca2+ sensitization mechanisms.     

Modeling of the pharyngeal muscle in Caenorhabditis elegans based on FitzHugh-Nagumo equations

The pharyngeal pumping motion to send food to the bowel is a rhythmic movement in Caenorhabditis elegans. This paper proposes a simulation-based approach to investigate the mechanisms of rhythm phenomena in the pharyngeal pumping motion. To conduct the simulations, first, we developed a pharyngeal muscle model including 29 cell models which simulate the activity of each cell as a membrane potential based on FitzHugh-Nagumo equations. Then, to compare the response of the model with that of C. elegans, we calculated the electropharyngeogram (EPG), which represents the electrophysiological responses of the pharyngeal cells, using the simulated membrane potentials. The results confirmed that our model could generate the EPG similar to that measured from C. elegans. We proposed a computer simulation of the pumping motion to investigate the mechanisms of rhythm phenomena in living organisms.     

Siliconizing of molybdenum plate using Si2Cl6 and some of its properties

Molybdenum plate was siliconized using Si₂Cl₆ as a silicon source, and the siliconizing conditions and some of its properties were examined. The siliconizing of the molybdenum plate began by the deposition here and there of island-like MoSi₂ deposits 4 to 6m thick in the initial stage (after 10 min induction time), and then coalescence of the deposits proceeded to form a uniform MoSi₂ layer all over the molybdenum plate after 30 min siliconizing time. The weight decrease of the siliconized plate by anodic dissolution in 0.2 M sulphuric acid reduced exponentially with increasing thickness of the MOSi₂ layer, and no weight decrease was observed at all above 16m thickness. The sea water corrosion and sea sand abrasion resistivities of the siliconized molybdenum plate increased with increasing siliconizing temperature and Si₂Cl₆ flow rate.     

Effects of support and additive on oxidation state and activity of Pt catalyst in propane combustion

The effects of support and additive on the oxidation state and catalytic activity of Pt catalyst in the low temperature propane combustion were systematically investigated on Pt/MgO, Pt/Al₂O₃ and Pt/SiO₂–Al₂O₃. The catalytic activity varied much with both support materials and additives. The catalyst on the more acidic support showed higher activity, and the catalytic activity on every support materials increased as the electronegativity of additives increased, while some additives decreased the activity. The oxidation state of platinum, estimated by white line intensity of Pt L_III-edge XANES spectrum, also varied with the support and additives, and additives with higher electronegativity greatly prevented the platinum from its oxidation under oxidising atmosphere. Among almost all the catalysts with various supports and various additives, a clear relationship was observed between the oxidation state of platinum and the catalytic activity; the more metallic platinum showed higher activity. Thus, it was concluded that the total electrophilic/electrophobic property derived from those of the support and additive controls the oxidation state of platinum, which intensively affects the catalytic activity; i.e. higher electrophilic property provides less oxidised platinum, resulting in high catalytic activity. The mechanism of this effect was also discussed on the basis of thermochemical data, and it was proposed that the electrophobic materials promote the noble metal oxidation since the noble metal oxo-anion such as PtO^δ− is more stabilised with electrophobic cation.     

Polymerization via zwitterion 25. Alternating copolymerizations of cyclic acyl phosphorite and phosphite with vinyl monomers having an electron withdrawing group

Summary Spontaneous copolymerizations of cyclic acyl phosphonite (SPO) and phosphite (SPI) with an electron-deficient vinyl monomer such as methyl acrylate (MA), methyl vinyl ketone (MVK), and acrolein (AL), gave the corresponding alternating copolymers. These copolymerizations took place without added initiator and proceeded through zwitterion intermediates. Copolymer structures 1a, 1b, 2 and 3 have been established, all of which were derived in a regiospecific manner of ambident anions. The scheme of the copolymerizations is presented.     

Cationic ring-opening polymerization of 2-phenyl-1,3,6,2-trioxaphosphocane

Summary The ring-opening polymerization of 2-phenyl-1,3,-6,2-trioxaphosphocane (4), an eight-membered cyclic phosphonite, has been investigated. Cationic initiators of PhCH₂-Cl and MeOTf gave polymers, whereas anionic and radical initiators did not yield polymer. The structure of polymer was examined by IR, ¹H, ³¹P, and ³¹C NMR spectroscopy of polymers and elemental analysis as well as the alkaline hydrolysis products. The polymer consisted of two different units, i.e., the major part is the normal phosphinate structure 5 and the minor part is the isomerized unit 6 in 7% with PhCH₂Cl initiation and in 34% with MeOTf initiator. The difference in nature of propagating species from these two initiators are discussed in connection with their reactivities.On leave from the Institute of Chemistry, Academia Sinica, Beijing, China