Structural stability of methane hydrate at high pressures

The structural stability of methane hydrate under pressure at room temperature was examined by both in-situ single-crystal and powder X-ray diffraction techniques on samples with structure types I,II, and H in diamond-anvil cells. The diffraction data for types II (slI) and H (sH) were refined to the known structures with space groups Fd3m and P63/mmc, respectively. Upon compression, sl methane hydrate transforms to the sll phase at 120 MPa, and then to the sH phase at 600 MPa. The sil methane hydrate was found to coexist locally with sl phase up to 500 MPa and with sH phase up to 600 MPa. The pure sH structure was found to be stable between 600 and 900 MPa. Methane hydrate decomposes at pressures above 3 GPa to form methane with the orientationally disordered Fm3m structure and ice VII (Pn3m). The results highlight the role of guest (CH4)-host (H20) interactions in the stabilization of the hydrate structures under pressure.     

Regulation of acetylcholine synthesis: does cytoplasmic acetylcholine control high affinity choline uptake?

When brain synaptosomes are obtained from animals that have been injected intravenously with [2H4]choline 1 minute before being killed, their high affinity [3H] choline uptake is correlated inversely with their acetylcholine content and directly with the rate at which they synthesize [2H4]acetylcholine. The control of such choline uptake by the cytoplasmic acetylcholine concentration is proposed as a mechanism regulating acetylcholine synthesis in cholinergic nerve terminals.     

Functional characterization of mongoose nicotinic acetylcholine receptor alpha-subunit: resistance to alpha-bungarotoxin and high sensitivity to acetylcholine

Temporary scapho-trapezoidal joint fixation with Kirschner wires was performed for stage IIIB Kienb?ck's disease in a 12-year-old girl. Preoperative evaluation with radiographs and magnetic resonance imaging confirmed the diagnosis. After 4 months of fixation, wrist range of motion was improved and pain was decreased. Postoperative magnetic resonance imaging revealed revascularization and fracture healing. Temporary scapho-trapezoidal fixation may be useful in the treatment of selected cases of Kienb?ck's disease in children.     

Hydrolysis of fused calcium chloride at high temperature

The hydrolysis of fused calcium chloride occurs at the initial step in the nickel segregation. This reaction was studied at 1113, 1173 and 1223 K under the experimental condition that equilibrium was attained at the gas-melt interface and the overall rate of the reaction was controlled by the gas diffusion to and from the gas-melt interface by using a slender platinum container. The weight loss of the sample and the amount of the evolved HC1 gas were continuously measured. The overall rate of the reaction was raised at higher temperature and higher moisture content in the mixed feed gas of N₂ and H₂O. It was found that CaO was formed above 1170 K. It was also formed at 1113 K when the moisture content of the feed gas was 19 pct or less. When the moisture content is higher than 24 pct at 1113 K, however, the reaction becomes more complicated; Ca(OH)₂ is formed in addition to CaO both of which are dissolved in the melt. A theoretical calculation was made regarding the hydrolysis in which only CaO is formed in order to verify that the overall rate is controlled by the gas diffusion; it was assumed that the equilibrium is attained at the gas-melt interface and the theoretical weight loss was calculated from the rate of counter-diffusion of H₂O and HC1 in the stagnant N₂ gas. The theoretical value was in excellent agreement with the measurement.     

Hydrolysis of fused calcium chloride at high temperature

The hydrolysis of fused calcium chloride occurs at the initial step in the nickel segregation. This reaction was studied at 1113, 1173 and 1223 K under the experimental condition that equilibrium was attained at the gas-melt interface and the overall rate of the reaction was controlled by the gas diffusion to and from the gas-melt interface by using a slender platinum container. The weight loss of the sample and the amount of the evolved HC1 gas were continuously measured. The overall rate of the reaction was raised at higher temperature and higher moisture content in the mixed feed gas of N₂ and H₂O. It was found that CaO was formed above 1170 K. It was also formed at 1113 K when the moisture content of the feed gas was 19 pct or less. When the moisture content is higher than 24 pct at 1113 K, however, the reaction becomes more complicated; Ca(OH)₂ is formed in addition to CaO both of which are dissolved in the melt. A theoretical calculation was made regarding the hydrolysis in which only CaO is formed in order to verify that the overall rate is controlled by the gas diffusion; it was assumed that the equilibrium is attained at the gas-melt interface and the theoretical weight loss was calculated from the rate of counter-diffusion of H₂O and HC1 in the stagnant N₂ gas. The theoretical value was in excellent agreement with the measurement. H. KONDO formerly a Graduate Student with the Department of Metallurgy, Kyoto University.     

高价稀土氧化矿物中氯离子的测定

文中对分析测定高价稀土氧化矿物中痕量氯离子时介质条件的影响进行了探索，从中得出了分析测定的最佳条件，并利用紫外分光光度计间接测定了高价氧化镨矿物中氯离子的含量，为生产单位提供了一种简便、经济的分析检验方法。     

A detergent-solubilized nicotinic acetylcholine receptor of Caenorhabditis elegans

We have used a spin column assay to study the detergent-solubilized levamisole receptor, a nicotinic acetylcholine receptor of the nematode Caenorhabditis elegans. The receptor can be successfully solubilized in detergent solutions of Triton X-100, Lubrol PX, or sodium cholate. Centrifugal gel filtration assay using the tritiated ligand [3H]meta-aminolevamisole ([3H]MAL) provides a greater signal and a better signal-to-noise ratio for soluble levamisole receptor binding than either polyethylene glycol precipitation or DEAE filter assay with the same ligand. As for membrane-bound receptor, the detergent-solubilized levamisole receptor consists of more than one affinity state. Detergent solubilization appears to increase the affinity of all states for [3H]MAL (Kd for the highest affinity solubilized [3H]MAL binding state, 41 +/- 5 pM). Data is presented on the equilibrium binding and the association and dissociation reaction rates of the receptor. The similar relative efficacy with which various compounds inhibit specific [3H]MAL binding and deficiencies in solubilizable high affinity specific [3H]MAL binding in two receptor mutants show that the solubilized receptor is the same nicotinic acetylcholine receptor that is detected by assaying membrane-bound specific [3H]MAL binding. The detergent-solubilized levamisole receptor is stable at 0 degree to 4 degrees C, making receptor purification feasible.     

A case of zinc chloride ingestion

Zinc chloride is a powerful corrosive agent. Reports of zinc chloride ingestion are uncommon, and there is little information about its toxicity and management. The authors report the clinical course of a 10-year-old girl who accidentally ingested an acid soldering flux solution (pH, 3.0; zinc chloride, 30% to < 60%). Systemic effects after the ingestion were unremarkable except for lethargy. Thus, chelation therapy was not considered. Severe gastric corrosion was caused by local caustic action. An antral stricture of the stomach approximately 3 weeks after the ingestion developed, and she underwent a modified Heineke-Mikulicz antropyloroplasty. Postoperatively, she made an uneventful recovery. On follow-up, although she was tolerating a normal diet, results of a barium meal showed her stomach to be totally aperistaltic. Results of a nuclear medicine study showed moderately delayed gastric emptying. Careful long-term follow-up is necessary, because there is potential risk for malignancy in the damaged stomach.     

A review of laboratory animal anesthesia with chloral hydrate and chloralose

Chloral hydrate (CH) and alpha-chloralose (CS) are often used to anesthetize laboratory animals although, to our knowledge, there have been no controlled studies of their anesthetic or analgesic effects. Induction of and recovery from anesthesia can be stressful, and anesthesia and analgesic quality have been questioned. Intraperitoneal (i.p.) administration of CH has resulted in adynamic ileus and peritonitis in rats, gastric ulcers in rats, and peritonitis in swine. Light anesthesia is induced in rats. In dogs, CH induces sedation to deep anesthesia when given intravenously. Gastric irritation in dogs can occur when CH is given orally. Chloral hydrate is considered a good sedative-hypnotic for farm animals. Intravenously administered CS anesthetizes dogs and cats for 5 to 10 hours, but the animals may require respiratory support. Chloralose appears to be a satisfactory anesthetic for dogs when stage III thiobarbiturate anesthesia is first induced. It is difficult to gauge the depth of anesthesia and analgesia with CS. In our clinical experience with swine and calves, CH given i.p. leads to adynamic ileus. We have found that CS given i.p. causes an inflammatory response in guinea pigs, rats, and calves. We observed that CS analgesia varies with the type of surgical procedure performed. Based on a literature review and our clinical experience, we suggest that CH or CS anesthesia should be preceded by administration of barbiturates, opioids, alpha-2 agonists, or phenothiazine tranquilizers. Chloral hydrate should only be used as a sedative or hypnotic for dogs; CS should not be used as a sole anesthetic agent. Neither drug should be used i.p. for survival surgery.     

Properties of electrolyte solutions relevant to high concentration chloride leaching I. Mixed aqueous solutions of hydrochloric acid and magnesium chloride

A computer code based on a Pitzer model has been developed for the comprehensive prediction of the thermodynamic properties of MgCl₂–HCl aqueous solutions over a wide range of conditions from 25 to 120 °C and from 0–350 g L^− 1 chloride. This code was applied to the calculation of (i) water activities and mean ionic activity coefficients for mixed aqueous solutions of hydrochloric acid and magnesium chloride over a wide range of concentrations and to 100 °C, (ii) solubilities of MgCl₂·6H₂O in MgCl₂–HCl solutions to 80 °C, (iii) partial pressures of HCl(g) and H₂O(g) over MgCl₂–HCl aqueous solutions at various temperatures and (iv) partial pressures of HCl(g) at the normal boiling point of these mixed electrolyte solutions. The model predictions are in excellent agreement with available experimental data and confirm evidence from the literature that MgCl₂(aq) and HCl(aq) mix almost ideally at constant water activity.     

The high temperature behavior of superalloys exposed to sodium chloride: II. corrosion

The corrosion behavior of various superalloys in molten NaCl has been examined by weight loss measurements, analysis of corrosion products, and potentiostatic polarization curves. Corrosion rates were higher in platinum than in quartz crucibles, relatively independent of alloy composition, but highly dependent on oxygen pressure. The high corrosion rates and the shape of the polarization curves indicate that the oxides formed in molten NaCl are not protective. Analysis of the sodium content in the alloy after exposure to molten NaCl indicates diffusion of sodium into the bulk of the metal. The effect of oxygen and the highercorrosion rates in platinum crucibles are explained by thermodynamic and kinetic considerations.     

Occlusion and ion exchange in the molten (lithium chloride+potassium chloride+alkaline-earth chloride) salt+zeolite 4A system with alkaline-earth chlorides of calcium and strontium and in the molten (lithium chloride+potassium chloride+actinide chloride) salt+zeolite 4A system with the actinide chloride of uranium

The interaction between molten salts of the type LiCl-KCl-MeCl _n (Me=Ca, Sr, U; = to 0.45; and x _KCl/x _LiCl=0.69) and zeolite 4A have been studied at 823 K. The main interactions between these salts and zeolite are molten salt occlusion to form salt-loaded zeolite and ion exchange between the molten salt and salt-loaded zeolite. An irreversible chemical reaction has been observed in the LiCl-KCl-UCl₃+zeolite system. The extent of occlusion is a function of the concentration of MeCl _n in the zeolite and is equal to 10±1 Cl⁻ per zeolite unit cell, (AlSiO₄)₁₂, at infinite MeCl _n dilution. The ion-exchange mole-fraction equilibrium constants (separation factors) with respect to Li are decreasing functions of the concentration of SrCl₂ and UCl₃, but an increasing function of the concentration of CaCl₂ in the zeolite. At infinite MeCl _n dilution, they are equal to 0.9, 11.9, and 13 for CaCl₂, SrCl₂, and UCl₃, respectively. The standard ion-exchange chemical potentials are equal to −50.0, −84, and −101.1 kJ·mol⁻¹ for Ca²⁺, Sr²⁺, and U³⁺, respectively.     

Cyclosporin A affects functions concerning acetylcholine release of cholinergic Torpedo synaptosomes

The effect of cyclosporin A was investigated on Torpedo synaptosomes. Cyclosporin A inhibits KCl-evoked acetylcholine release (up to 50% at 1 mu M) and was inactive on acetylcholine release induced by a Ca2+ ionophore, A23187. Interestingly, when the synaptosomes were pretreated with cyclosporin A, this immunosuppressor did abolish the modulation of A23187-induced acetylcholine release produced by two other drugs, cetiedil (alpha-cyclohexyl-3-thienyl acetic acid 2-(hexahydro-1H-azepin-1-yl) ethyl ester, citrate salt) and MR16728 (N-(N'-hexamethylene imino)-propyl-phenyl-cyclohexyl-methyl acetamide, chlorhydrate), which were previously shown to be inhibitory and stimulatory, respectively. Moreover, cyclosporin A and MR16728 are competitive inhibitors of [3H]cetiedil binding to purified synaptosomal presynaptic membranes (dissociation constant of 181.9 nM). These results suggest that presynaptic proteins involved in acetylcholine release (directly or indirectly through cyclophilin) are potential targets of cyclosporin A in Torpedo synaptosomes.     

A role of tyrosine phosphatase in acetylcholine receptor cluster dispersal and formation

Innervation of the skeletal muscle involves local signaling, leading to acetylcholine receptor (AChR) clustering, and global signaling, manifested by the dispersal of preexisting AChR clusters (hot spots). Receptor tyrosine kinase (RTK) activation has been shown to mediate AChR clustering. In this study, the role of tyrosine phosphatase (PTPase) in the dispersal of hot spots was examined. Hot spot dispersal in cultured Xenopus muscle cells was initiated immediately upon the presentation of growth factor-coated beads that induce both AChR cluster formation and dispersal. Whereas the density of AChRs decreased with time, the fine structure of the hot spot remained relatively constant. Although AChR, rapsyn, and phosphotyrosine disappeared, a large part of the original hot spot-associated cytoskeleton remained. This suggests that the dispersal involves the removal of a key linkage between the receptor and its cytoskeletal infrastructure. The rate of hot spot dispersal is inversely related to its distance from the site of synaptic stimulation, implicating the diffusible nature of the signal. PTPase inhibitors, such as pervanadate or phenylarsine oxide, inhibited hot spot dispersal. In addition, they also affected the formation of new clusters in such a way that AChR microclusters extended beyond the boundary set by the clustering stimuli. Furthermore, by introducing a constitutively active PTPase into cultured muscle cells, hot spots were dispersed in a stimulus- independent fashion. This effect of exogenous PTPase was also blocked by pervanadate. These results implicate a role of PTPase in AChR cluster dispersal and formation. In addition to RTK activation, synaptic stimulation may also activate PTPase which acts globally to destabilize preexisting AChR hot spots and locally to facilitate AChR clustering in a spatially discrete manner by countering the action of RTKs.     

银盐沉淀-铬酸盐法测定高氯离子水样中化学需氧量

在用铬酸盐法测定水样的化学需氧量(COD)时,氯离子的干扰是通过加入HgSO4,使其与氯离子结合成可溶性的氯汞络合物而部分除去。本文在分析氯离子干扰机理的基础上,提出了用硝酸银代替硫酸汞消除氯离子干扰,铬酸盐法测定高氯离子水样COD的分析方法。该法应用于废水中COD测定,所得结果与硫酸汞掩蔽法相符,6次测定样品的相对标准偏差为2.2%。同时对COD废液的处理及回收利用进行了研究,给出了银、铬、铁的回收和银纯化的方法。本法测定COD的结果准确,避免了汞盐的二次污染,且节约试剂,是值得推广的清洁分析方法。     

机械磨在氢氧化铝粉碎中的应用

本就机械磨生产氢氧化铝填料，与其它两种粉碎设备进行了比较，并指出机械磨不仅能保证产品质量，而且具有产量高、能耗低的优点，应大力推广应用。     

Positive cooperativity of acetylcholine and other agonists with allosteric ligands on muscarinic acetylcholine receptors

At fertilization periodic Ca2+ oscillations release oocytes from meiotic arrest. The present study examined whether these oscillations have a long-term role in pre- and postimplantation development, independent of their immediate effect. Sr(2+)-containing medium was used to induce oscillations during exit from meiosis and first embryonic mitosis and Sr(2+)-activated parthenotes were compared to ethanol-activated parthenotes and embryos generated by in vitro fertilization. After embryo culture, blastocysts were differentially stained for the inner cell mass and trophectoderm. It was found that oscillations both during exit from meiosis and during mitosis acted to increase the number of inner cell mass cells. In contrast, the trophectoderm cell number was largest in ethanol-activated parthenotes and smallest in fertilized embryos. Postimplantation development was also modestly improved by extending the time of exposure to Sr(2+)-containing medium. Together these data suggest that Ca2+ oscillations have a role in long-term embryonic events and that they provide more than merely a stimulus for meiotic resumption.