Ti-13Nb-13Zr合金力学性能和显微组织的研究

研究了Ti—13Nb—13Zr合金在β相区和(α β)两相区固溶和时效处理后其合金力学性能及组织变化规律。分析发现在β相区固溶的合金，水冷时生成针状马氏体α′，空冷时生成亚稳定β相和少量αp，在(α β)两相区固溶生成β转和αp。在β相区和(α β)两相区固溶试样经时效后，晶粒内部主要析出点状和棒状αs。在750℃/1h固溶(WQ)和低温510℃/6h时效的合金抗拉强度高、塑性较高、弹性模量低，可以满足人体植入要求。     

(13C)-substituted sucrose: 13C-1H and 13C-13C spin coupling constants to assess furanose ring and glycosidic bond conformations in aqueous solution

Sucrose (beta-D-fructofuranosyl alpha-D-glucopyranoside, 1), methyl alpha-D-fructofuranoside (2), and methyl beta-D-fructofuranoside (3) have been prepared by chemical and/or enzymic methods with single sites of 13C-substitution at C-1, C-2, C-3, and C-6 of the fructofuranosyl ring. 1H (500 MHz) and 13C (75 and 125 MHz) NMR spectra of 1-3 have been obtained, yielding 1H-1H, 13C-1H, and 13C-13C spin coupling constants that were used to assess furanose ring and glycoside bond conformations in aqueous (2H2O) solution. Results show that the conformational mobility of the furanosyl ring in 3 is altered when incorporated into 1. Furthermore, 13C-13C and 13C-1H spin couplings across the glycosidic linkage suggest a psi torsion angle different from that observed in the crystal (phi appears similar). Interplay between the strength of the exoanomeric effect and hydrogen bonding in solution may be responsible, in part, for the apparent conformational flexibility of 1. In addition, spin couplings in 2 and 3 have been compared to those measured previously in alpha-D-threo-pentulofuranose (4) and beta-D-threo-pentulofuranose (5), respectively, as a means to study the effect of glycosidation and hydroxymethyl substitution on the solution conformation of the 2-ketofuranose ring. The conversion of 4 to 2 is accompanied by minimal conformational change, whereas a significant change accompanies the conversion of 5 to 3, showing that the effect of substitution on ring conformation depends highly on ring configuration before and after substitution.     

Preparation of monoiodotyrosine-13-glucagon

Glucagon was iodinated with the lactoperoxidase method at pH 10.0 in the presence of propylene glycol using a substitution of 0.3 g-atom I/mol glucagon. Under these conditions the reactivity of the iodine to tyrosine at position 13 is found to be 4-fold that of the tyrosine at position 10. The amount of diiodotyrosine was less than one-twentieth that of the monoiodotyrosine at either tyrosine residue. Relatively pure monoiodo[125I]tyrosine-13-glucagon can be separated from other iodoglucagons by means of DEAE-chromatography. Such a homogeneous preparation with a known position of the iodine makes it possible to study a specific interaction between the monoiodoglucagon and the glucagon antisera or the glucagon receptor.     

The Stimulated Raman Spectrum of Symmetric 13C Cyanogen, 13C2N2

BACKGROUND: The authors examined the interaction of ketamine with recombinant mu, kappa, and delta opioid receptors and recombinant orphan opioid receptors expressed in Chinese hamster ovary cells (CHO-mu, CHO-kappa, CHO-delta, and CHO(ORL1), respectively). METHODS: CHO-mu, CHO-kappa, and CHO-delta membranes were incubated with the opioid receptor radioligand [3H]diprenorphine at room temperature. Ketamine (racemic, R(-) and S(+)) was included at concentrations covering the clinical range. CHO(ORL1) membranes were incubated with [125I]Tyr(14)nociceptin and racemic ketamine at room temperature. The effects of racemic ketamine and selective opioid receptor agonists (mu: [D-Ala2, MePhe4, Gly(ol)5] enkephalin (DAMGO); kappa: spiradoline or delta: [D-pen2, D-pen5] enkephalin (DPDPE)) on forskolin-stimulated cyclic adenosine monophosphate formation also were examined. Data are mean +/- SEM. RESULTS: Racemic ketamine increased the radioligand equilibrium dissociation constant for [3H]diprenorphine from 85+/-5 to 273+/-11, 91+/-6 to 154+/-16, and 372+/-15 to 855+/-42 pM in CHO-mu, CHO-kappa, and CHO-delta, respectively. The concentration of radioligand bound at saturation was unaffected. In CHO-mu and CHO-kappa cells, racemic ketamine did not slow the rate of naloxone-induced [3H]diprenorphine dissociation. Ketamine and its isomers also displaced [3H]diprenorphine binding to mu, kappa, and delta receptors in a dose-dependent manner, with pKi values for racemic ketamine of 4.38+/-0.02, 4.55+/-0.04, and 3.57+/-0.02, respectively. S(+)-ketamine was two to three times more potent than R(-)-ketamine at mu and kappa receptors. Racemic ketamine displaced [125I]Tyr(14)nociceptin with an estimated affinity constant of 0.5 mM. Racemic ketamine inhibited the formation of cyclic adenosine monophosphate (naloxone insensitive) in a dose-dependent manner (concentration producing 50% inhibition approximately 2 mM) in all cell lines, including untransfected CHO cells. Ketamine (100 microM) reversed DAMGO (mu) and spiradoline (kappa) inhibition of formation of cyclic adenosine monophosphate. CONCLUSIONS: Ketamine interacts stereoselectively with recombinant mu and kappa opioid receptors.     

Studies of androgen production and binding in 13 male pseudohermaphrodites and 13 males with micropenis

We studied androgen production by morphologic and biochemical criteria plus androgen binding by skin fibroblasts in 13 male pseudohermaphrodites and 13 males with micropenis, none of whom had evidence of androgen insensitivity. Seventeen of the 26 patients had evidence of deficient androgen production, suggesting this as the cause of their incomplete virilization in utero. Fibroblasts from all 26 patients demonstrated normal androgen binding and affinity of the steroid for the receptor. Although these results exclude a deficiency of androgen binding in these individuals, other end organ defects are possible. Guidelines for diagnosis and management of such patients are presented.     

Biosynthesis of bikaverin in Fusarium oxysporum. Use of 13C nuclear magnetic resonance with homonuclear 13C decoupling to locate adjacent 13C labels

Bikaverin obtained by supplementing cultures of Fusarium oxysporum with singly and doubly 13C labeled acetate was enriched by approximately 0.5 atom percent with the 13C isotope. At this low enrichment 13C NMR spectra of samples labeled from (1-13C)- and (2-13C) acetate did not show, unequivocally, the pattern of isotopic incorporation. Small sample size, poor solubility and difficulties in the assignment of resonances also restricted the amount of information thacetate. The difficulty was overcome by using 13C homonuclear single-frequency decoupling in conjunction with 1H heteronuclear decoupling to locate bonded 13C-13C pairs. The carbon skeleton of bikaverin was shown to be biosynthesized entirely by condensation of acetate units and the pattern of assembly was established.     

Oxidation of exogenous [13C]galactose and [13C]glucose during exercise

The present study examined the oxidation of exogenous galactose or glucose during prolonged submaximal cycling exercise. Eight highly trained volunteers exercised on two occasions on a cycle ergometer at 65% of maximal workload for 120 min, followed by a 60-min rest period and a second exercise bout of 30 min at 60% maximal workload. At random, subjects ingested a 8% galactose solution to which an [1-13C]galactose tracer was added or a 8% glucose solution to which an [U-13C]glucose tracer was added. Drinks were provided at the end of the warm-up period (8 ml/kg) and every 15 min (2 ml/kg) during the first 120 min of the test. Blood and breath samples were collected every 30 and 15 min, respectively, during the test. The exogenous carbohydrate (CHO) oxidation was calculated from the 13CO2/12CO2 ratio and CO2 production of the expired air. Peak exogenous CHO oxidation during exercise for galactose and glucose was 0.41 +/- 0.03 and 0.85 +/- 0.04 g/min, respectively. Total CHO and fat oxidation were not significantly different between the treatments. Forty-six percent of the ingested glucose was oxidized, whereas only 21% of the ingested galactose was oxidized. As a consequence, more endogenous CHO was utilized with galactose than with glucose (124.4 +/- 6.7 and 100.1 +/- 3.6 g, respectively). These results indicate that the oxidation rate of orally ingested galactose is maximally approximately 50% of the oxidation rate of a comparable amount of orally ingested glucose during 120 min of exercise.     

Gaseous complexes formed between trichlorides (A1C13 and FeC13) and dichlorides

It has been found that in general the volatility of dichlorides is much enhanced in the presence of gaseous A1C1₃ and FeCl₃, and the existence of the complexes MA1₂C1₈, MAl₃Cl₁₁, and MFe₂Cl₈ is postulated. ΔH _T, ΔS _T, andT for MCl₂(s) + 2AlCl₃(g) = MAl₂Cl₈(g) are CaCl₂: −17.8 kcal, −25.7 cal K⁻¹ at 900 °K; CoCl₂: −15.2, −19.4 at 750°K; MgCl₂: −13.8, −17.9 at 800°K; MnCl₂: −15.8, −20.9 at 750°K; NiCl₂: −16.3, −24.2 at 750°K. For MCl₂(s) + 3AlCl₃(g) = MAl₃Cl₁₁(g) − CaCl₂: −30.0, −40.5 at 900°K; CoCl₂: −36.6, −47.4 at 700°K; MgCl₂: −42.6, −55.4 at 750°K; MnCl₂: −33.3, −42.0 at 750°K. For MCl₂(s) + 2FeCl₃(g) = MFe₂Cl₈(g) − CdCl₂: −19.4, −20.9 at 700°K: CoCl₂: −16.5, −17.2 at 800°K, MnCl₂: −19.1, −21.2 at 750°K; NiCl₂: −19.7, −24.4 at 800°K. Enhanced volatility was also found for ZnCl₂, PbCl₂, and CuCl, but since the condensed phase was liquid of unknown composition no calculations could be made. Owing to the interplay of the above equilibria with the dimerization equilibria for A1C1₃ and FeCl₃ the effective vapor pressures of the dichlorides in the presence of the trichlorides pass through maxima in the region 600° to 700°C.     

Corrosion resistance of laser nitrided commercially pure titanium and Ti-13Nb-13Zr biomedical alloys

C.P. Titanium and Ti-13Nb-13Zr alloys are widely used in biomedical applications as dental and orthopedic implants. However these materials are vulnerable to Surface corrosion. The aim of this investigation is to enhance the corrosion resistance of the above alloys through laser nitriding technique. Laser nitriding was performed using Nd: YAG laser. The Electrochemical properties of nitrided layer will be investigated in simulated body solution using potentiodynamic polarization technique. The results will be compared with those obtained on untreated alloys tested in same conditions. The laser nitrided and the corroded samples will also be characterized using XRD and SEM. The enhancement of wear resistance of the above samples will also be presented in this paper.