[en] The Metals Melting Skylab Experiment consisted of selectively melting, in sequence, three rotating discs made of aluminum alloy, stainless steel, and tantalum alloy. For comparison, three other discs of the same three materials were similarly melted or welded on the ground. The power source of the melting was an electron beam unit. Results are presented which support the concept that the major difference between ground-base and Skylab samples (i.e., large elongated grains in ground base samples versus nearly equiaxed and equal sized grains in Skylab samples) can be explained on the basis of constitutional supercooling, and not on the basis of surface phenomena. Microstructural observations on the weld samples and present explanations for some of these observations are examined. In particular, ripples and their implications to weld solidification were studied. Evidence of pronounced copper segregation in the Skylab A1 weld samples, and the tantalum samples studied, indicates a weld microhardness (and hence strength) that is uniformly higher than the ground base results, a finding which is in agreement with previous predictions. Photographs are shown of the microstructure of the various alloys

[en] Using a gauged flavor SU(3)-invariant hadronic Lagrangian, we study Ξ production from Kbar induced reactions on Λ and Σ in a coupled-channel approach. Including the four channels of KbarΛ, KbarΣ, πΞ, and ηΞ, we solve the Bethe-Salpeter equation in the K-matrix approximation by neglecting the off-shell contribution in the intermediate states. For the transition potential which drives the higher-order contribution, we consider all allowed Born diagrams in the s, t, and u channels. With coupling constants determined from the SU(3) symmetry using empirical input, we find that the cross sections for the reactions KbarΛ→πΞ, KbarΣ→πΞ, KbarΛ→ηΞ, and KbarΣ→ηΞ all have values of a few mb. In contrast to the results from the lowest-order Born approximation, the magnitude of these cross sections is less sensitive to the values of the cut-off parameters in the form factors. From the transition matrix in the coupled-channel approach, we have further evaluated the cross sections for the elastic process KbarΛ→KbarΛ, KbarΣ→KbarΣ, πΞ→πΞ, and ηΞ→ηΞ as well as for the inelastic processes KbarΛ→KbarΣ and πΞ→ηΞ. Implications of the reactions studied here in Ξ production from relativistic heavy ion collisions are discussed

[en] The ¹H NMR spectra of human β-endorphin indicate that the peptide exists in random-coil form in aqueous solution but becomes helical in mixed solvent. Thermal denaturation NMR experiments show that in water there is no transition between 24 and 75⁰C, while a slow noncooperative thermal unfolding is observed in a 60% methanol-40% water mixed solvent in the same temperature range. These findings are consistent with circular dichroism studies by other workers concluding that β-endorphin is a random coil in water but that it forms 50% α-helix or more in mixed solvents. The peptide in the mixed water-methanol solvent was further studied by correlated spectroscopy (COSY) and nuclear Overhauser effect spectroscopy (NOESY) experiments. These allow a complete set of assignments to be made and establish two distinct stretches over which the solvent induces formation of α-helices: the first occurs between Tyr-1 and Thr-12 and the second between Leu-14 and extending to Lys-28. There is evidence that the latter is capped by a turn occurring between Lys-28 and Glu-31. These helices form at the enkephalin receptor binding site, which is at the amino terminus, and at the morphine receptor binding site, located at the carboxyl terminus. The findings suggest that these two receptors may specifically recognize α-helices

[en] Opioid receptors have been solubilized from human striatal and rat whole-brain membranes by use of 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS). Tritiated human β-endorphin (³H-β/sub h/-EP) binding revealed high-affinity competition by morphine, naloxone, and various β-EP analogues. Lack of high-affinity competition by (+/-)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]benzeneacetamide methanesulfonate (U50-488, Upjohn) indicated that k sites were not labeled by ³H-β-/sub h/-EP under these conditions. Affinities were similar in both soluble and membrane preparations except for [Met]enkephalin, which appears to be rapidly degraded by the solubilized extract. Size differences between human and rat solubilized ³H-β/sub h/-EP-receptor complexes were revealed by exclusion chromatography

[en] The potent opioid peptide β-endorphin is found in the brain and pituitary with two related fragments, β-endorphin-(1-27) and β-endorphin-(1-26). The fragments, retain substantial opioid-receptor binding activity but are virtually inactive analgesically. β-Endorphin-(1-27) inhibits β-endorphin-induced and etorphine-induced analgesia when coinjected intracerebroventricularly into mice. Antagonism by competition at the same site(s) is suggested from parallel shifts of the dose-response curves of etorphine or β-endorphin in the presence of β-endorphin-(1-27). Its potency is 4-5 times greater than that of the opiate antagonist naloxone. β-Endorphin-(1-26) does not antagonize the antinociceptive action of etorphine or β-endorphin in doses up to 500 pmol per animal

[en] The authors investigated the binding of ¹²⁵I-labeled α-inhibin-92 (a 92-residue peptide) to human pituitary membrane preparations. Unlabeled α-inhibin-92 competed effectively with the labeled peptide for binding to the membranes. Binding was also inhibited by both α-inhibin-52 and α-inhibin-31, but less effectively. Scatchard analysis of the α-inhibin-92 binding data indicated the presence of high-affinity binding sites (1.35 nM/mg of membrane protein) with an apparent K/sub d/ of 0.37 nM. When ¹²⁵I-labeled α-inhibin-92 was covalently crosslinked to the pituitary membrane preparation with disuccinimidyl suberate and the solubilized labeled receptor complex was analyzed by NaDodSO₄/PAGE under either reducing or nonreducing conditions, a single radioactive band at an apparent molecular weight of 90,000 +/- 5000 observed. These data suggest that human pituitary has specific binding sites for α-inhibins

[en] Human granulosa cells cultured with calf serum actively proliferated for 18-20 generations and secreted progesterone into the medium; progesterone levels appeared to decline with increase in generation number. Cells cultured under serum-free conditions secreted significant amounts of progesterone and insulin-like growth factor II (IGF-II). The progesterone secretion was enhanced by the addition of human follitropin, lutropin, and chorionic gonadotropin but not by growth hormone. These cells, when challenged to varying concentrations of human growth hormone, human chorionic somatomammotropin, human prolactin, chorionic gonadotropin, follitropin, and lutropin, secreted IGF-II into the medium as measured by specific IGF-II RIA. Among these human hormones, chorionic gonadotropin, follitropin, and lutropin were most effective in inducing IGF-II secretion from these cells. When synthetic lutropin-releasing hormone and α-inhibin-92 were tested, only lutropin-releasing hormone was effective in releasing IGF-II. The results described suggest that cultured human granulosa cells can proliferate and actively secrete progesterone and IGF-II into the medium. IGF-II production in human granulosa cells was influenced by a multi-hormonal complex including human growth hormone, human chorionic somatomammotropin, and prolactin

[en] A sensitive and specific radioimmunoassay for human β-lipotropin (β/sub h/-LPH) in unextracted plasma was developed using pure β/sub h/-LPH as tracer and standard and an antiserum not cross-reacting with human β-MSH and hACTH. In healthy volunteers plasma β/sub h/-LPH ranged from <20 to 150 pg/ml at 8:00 a.m. and rose after metyrapone administration. β/sub h/-LPH was very low in panhypopituitarism, normal in most patients with untreated Cushing's disease, elevated in acromegaly and extremely high in Nelson's syndrome

[en] MoSi₂ has been used as an electrical heating element for approximately 40 years because of its high electrical and thermal conductivity and its excellent oxidation resistance at high temperatures. Recently, there has been increasing interest in the development of MoSi₂ as a high temperature structural material. However, its low fracture toughness at ambient temperatures and low creep resistance at elevated temperature limits its application. Efforts have been devoted to the improvement of the mechanical properties of MoSi₂. It has been reported that sintered MoSi₂ containing 1% of Mo₅Si₃ exhibits strength of about 400 Mpa even at around 1,400 C. A recent study also shows that Si depletion from MoSi₂ leads to the formation of the Mo₅Si₃ precipitates with a body-centered tetragonal crystal structure, which can affect the mechanical properties of MoSi₂. In the present experiment, another type of precipitate, (Mo, Fe)₅Si₃, was found in the MoSi₂ based material

[en] With an antiserum against human β-endorphin (β-EP) crossreacting <2% with human β-lipotropin (β-LPH) by weight we have developed a radioimmunoassay that can detect 1 pg β-EP in diluted raw plasma. In a.m. fasting plasma of 14 normal subjects β-EP ranged from <5 to 45 pg/ml. β-EP was elevated in untreated, but normal in successfully treated Cushing's disease; undetectable in a patient with adrenal adenoma; extremely high in Nelson's syndrome; and elevated in a patient with bronchogenic carcinoma before, but undetectable after tumor resection. In subjects with intact hypothalamic-pituitary-adrenal axis, β-EP was undectectable after dexamethasone and increased after metyrapone administration and insulin-induced hypoglycemia. β-EP concentration was considerably lower in serum than in simultaneously collected plasma, but increased in serum left unfrozen for several hours after clot removal. Thus, β-EP behaves like a hormone responding to the same stimuli as ACTH and β-LPH and blood appears to contain enzymes both generating and destroying immunoreactive β-EP