Temper embrittlement of Ni-Cr steel by antimony:II. Effects of addition of titanium

It is shown that the addition of 0.1 pct Ti to a low carbon Ni-Cr steel can eliminate most of the susceptibility to temper embrittlement due to both step cooling and isothermal aging. The mechanism by which Ti acts is complex and not yet clear. It suppresses carbide formation during the embrittlement heat treatment, which should retard the rate of embrittlement (cf. Part I). However, it also appears to interact with Ni and Sb by enhancing the segregation of Ni to grain boundaries and by mitigating the embrittling effect of Sb.     

DC electric-field-induced DNA stretching for AFM and SNOM studies

An effective method of DNA stretching on mica surfaces is proposed for an extremely low concentration of DNA. The method is based on an electric field and well applied on the concentration range from 57 x 10(-3) to 57 x 10(-6) ng/ml. The stretching exists in a gap between positive and negative electrodes. The difference in the stretching efficiency among the different surfaces of bare mica, Mg2+ soaked mica and AP-mica is discussed. The best performance of the stretching is found from the surface of AP-mica for the same experimental condition of sample concentration and applied voltage. Finally, from a Scanning near-field optical microscope image, it is found that well-stretched DNA molecules have shown more similar optical resolution, which is inferred from an optical fiber probe, itself.     

Local interaction of prostaglandin F 2alpha with endothelin-1 and tumor necrosis factor-alpha on the release of progesterone and oxytocin in ovine corpora lutea in vivo: a possible implication for a luteolytic cascade

Endothelin-1 (ET-1) and tumor necrosis factor-alpha (TNFalpha) participate in the cascade of luteolysis. Thus, in the present study the interactions of ET-1 and TNFalpha with prostaglandin F(2alpha) (PGF(2alpha)) on the release of progesterone and oxytocin (OT) within the corpus luteum (CL) were investigated. A microdialysis system (MDS) was surgically implanted in ovine CL (one MDS line/CL; 5-10 lines/ewe) formed after super-ovulation. A 4-h perfusion with PGF(2alpha) (0.01-1 micromol l (-1)) induced no clear effect on progesterone release, but acutely stimulated OT release in a dose-dependent manner. A perfusion of PGF(2alpha) (1 micromol l (-1)) increased ET-1 release over a period of 12 h. Two perfusions of ET-1 (0.1 micromol l(-1)) or a perfusion of ET-1 followed by TNFalpha (200 ng ml(-1)) decreased progesterone release (56-64% at 36-48 h). When the CL were pre-perfused with PGF(2alpha) (1 micromol l(-1)), two consecutive perfusions of ET-1 decreased progesterone release more rapidly. Similarly, a pre-perfusion with PGF(2alpha) followed by consecutive perfusions of ET-1 and then TNFalpha rapidly decreased progesterone release, with the inhibition most pronounced (35%) at 36-48 h. The simultaneous infusion of ET-1 with PGF(2alpha) induced a rapid decrease in progesterone release (36% at 36-48 h). In a further study, the possible second messenger systems involved in PGF(2alpha) action on the release of progesterone, OT and ET-1 were investigated. A perfusion with 12-O-tetradecanoyl-phorbol-13-acetate (TPA; 10 micromol l(-1)), A23187 (10 micromol l(-1)), or PGF(2alpha) + A23187 increased progesterone release during infusion, but decreased it after perfusion. All treatments induced a massive release of OT during infusion, and increased ET-1 release after infusion. These results show that ET-1 is capable of suppressing progesterone release in the PGF(2alpha)-primed ovine CL in vivo and thus ET-1 works as a local luteolysin together with PGF(2alpha) during the process of functional luteolysis. During structural luteolysis, TNFalpha may interact with PGF(2alpha) and ET-1 to cause a rapid drop in progesterone release and accelerate the process of luteolysis. This result supports the contention that ET-1 and TNFalpha interact with PGF(2alpha) as local luteolytic mediators in the ewe as previously suggested.     

Purification and characterization of myonase from X-chromosome linked muscular dystrophic mouse skeletal muscle

A chymotrypsin-like proteinase, designated myonase, was successfully purified to homogeneity from X-chromosome linked muscular dystrophic mouse skeletal muscle by affinity chromatography on agarose conjugated with lima bean trypsin inhibitor as ligand. The molecular mass of the purified myonase was determined to be 26 kDa by SDS-PAGE and to be 25,187 Da by mass spectrometry. The native enzyme is a single chain molecule and a monomeric protein without sugar side-chains. The nucleotide sequence of myonase mRNA is similar to mouse mast cell proteinase 4 (MMCP-4) cDNA. This is the first report of a native enzyme whose amino acid sequence closely corresponds to MMCP-4 cDNA. Myonase has chymotrypsin-like activities and hydrolyzes the amide bonds of synthetic substrates having Tyr and Phe residues at the P1 position. Myonase is most active at pH 9 and at high concentration of salts. Myonase preferentially hydrolyzes the Tyr4-Ile5 bond of angiotensin I and the Phe20-Ala21 bond of amyloid beta-protein, and it is less active towards the Phe8-His9 bond of angiotensin I and the Phe4-Ala5 and Tyr10-Glu11 bonds of amyloid beta-protein. Myonase is completely inhibited by such serine proteinase inhibitors as chymostatin, diisopropylfluorophosphate and phenylmethylsulfonyl fluoride, but not by p-tosyl-L-phenylalanine chloromethyl ketone, p-tosyl-L-lysine chloromethyl ketone, pepstatin, E-64, EDTA, and o-phenanthroline. It is also inhibited by lima bean trypsin inhibitor, soy bean trypsin inhibitor, and human plasma alpha1-antichymotrysin. These properties match those of chymase, but unlike chymase, myonase does not interact with heparin in the regulation of its activity. Myonase was immunohistochemically localized in myocytes, but not in mast cells.     

Finite-difference time-domain calculation with all parameters ofSellmeier's fitting equation for 12-fs laser pulse propagation in asilica fiber

In order to both experimentally and numerically investigate nonlinear femtosecond ultrabroadband-pulse propagation in a silica fiber, we have extended the finite-difference time-domain (FDTD) calculation of Maxwell's equations with nonlinear terms to that including all exact Sellmeier-fitting values. We have compared results of this extended FDTD method with experimental results, as well as with the solution of the generalized nonlinear Schrodinger equation by the split-step Fourier method with a slowly varying-envelope approximation. To the best of our knowledge, this is the first comparison between FDTD calculation and experimental results for nonlinear propagation of a very short (12 fs) laser pulse in a silica fiber     

Flame retarding mechanism of polycarbonate containing trifunctional phenylsilicone additive studied by analytical pyrolysis techniques

Summary The flame retarding mechanism for polycarbonate (PC) by a trifunctional phenyl-rich silicone additive was studied by analytical pyrolysis techniques. In order to clarify the actions of the silicone-based flame retardant for PC substrate during combustion, the change in the chemical structure of the flame retarded PC with the silicone additive (FR-PC) after thermal treatment at 380 °C was investigated by pyrolysis-gas chromatography (Py-GC) in the presence of organic alkali. On the pyrogram of the thermally treated FR-PC, which exhibited highly insoluble nature, the peaks reflecting the abnormal structures, formed through the reaction between a silyl radical originating from the additive and an ether like oxygen atom in the carbonate linkage of the PC chain accompanied by decarboxylation or Fries rearrangement, were clearly observed in much larger intensity than those on the pyrogram of the thermally treated PC. On the basis of the observed results for the thermally treated FR-PC, it was suggested that the formation of a char barrier on the surface of the FR-PC material was promoted during combustion to reduce the radiant heat of flame and to restrict the diffusion of flammable degradation products into the combustion zone. Thus formed cross-linking structure might surpress the thermal decomposition and confine the movements of the degradation products. Received: 20 May 2002 / Accepted: 10 June 2002     

Cerebral fat embolism studied by magnetic resonance imaging, transcranial Doppler sonography, and single photon emission computed tomography: case report

Cerebral fat embolism syndrome is an uncommon complication of trauma. We present a patient who developed cerebral fat embolism syndrome secondary to long-bone fractures. Although computed tomography of the brain failed to show any intracranial lesion, magnetic resonance imaging (MRI) detected scattered, high-signal-intensity lesions on T2-weighted images. 99mTc-d, 1-hexamethyl-propylene amine oxine single photon emission computed tomography (99mTc-HMPAO SPECT) and transcranial Doppler sonography (TCD) demonstrated low cerebral blood flow in the acute stage. MRI, 99mTc-HMPAO SPECT, and TCD correlated well with the clinical course of cerebral fat embolism syndrome.