Solubilities of Pb+2, Bi+3, Sb+3, and Cu+1 sulfides in (NaCl+KCl+Na2S) melts

Solubilities of common metal sulfides have been determined in the (NaCl+KCl) eutectic melt with and without Na₂S. A novel gas-phase equilibrium technique has been used for PbS, Bi₂S₃, and So₂S₃, and an improved liquid phase equilibrium technique for Cu₂S, which eliminates the errors due to physical entrapment of the sulfide phase and segregation on quenching, enabling precise measurements to be made. Solubilities in the (NaCl+KCl) eutectic melt were determined as a function of temperature in the rante 700° to 950°C, and were found to be small. The partial molar heats of mixing of the sulfides in the eutectic melt have been calculated from the solubility measurements, to be 13.3, 31.4, 37.1, and 49.0 kcal for PbSs), Sb₂S₂(l), and Cu₂S(s), respectively. Sodium sulfide addition was observed to enhance these solubilities, the effect being largest for Cu₂S followed by Sb₂S₃, Bi₂S₃, and PbS. This effect is explained qualitatively. It was observed that PbS and Sb₂S₃ obey Henry's law up to saturation in (NaCl+KCl+Na₂S) melts. O. P. MOHAPATRA, formerly Graduate Student, University of Toronto     

Infrared Spectrum of Ozone in the 4600 and 5300 cm-1 Regions: High Order Accidental Resonances through the Analysis of nu1 + 2nu2 + 3nu3 - nu2, nu1 + 2nu2 + 3nu3, and 4nu1 + nu3 Bands

The very weak bands nu1 + 2nu2 + 3nu3 and 4nu1 + nu3 of 16O3 have been observed for the first time, using the Fourier transform spectrometer (FTS) of Reims and the usual experimental setup providing a large product p x l of approximately 38 Torr x 36 m. The upper levels of these A-type bands which are rather close in energy (they appear respectively at 5291.722 and 5307.790 cm-1) belong to two different sets of interacting polyads. To correctly reproduce the rotation-vibration energy levels and account for the observed perturbations, both bands are treated in a dyad approximation: the (123) state in the Coriolis resonance with the (330) state, and the (401) state in the Coriolis resonance with the (024) state. The assignments of the rotation-vibration levels of the (123) state are confirmed by measurements of line positions of the hot band nu1 + 2nu2 + 3nu3 - nu2 which has also been observed for the first time. The fits are very satisfactory: the r.m.s. deviation for 249 energy levels of the (123) state is 2.4 x 10(-3) cm-1 and is 2.0 x 10(-3) cm-1 for 266 levels of the (401) state. These r.m.s. are near experimental accuracy. Transition moments for the three observed bands are determined from measured line intensities. Copyright 1997 Academic Press. Copyright 1997Academic Press     

Arrestin-independent internalization of the m1, m3, and m4 subtypes of muscarinic cholinergic receptors

To understand what processes contribute to the agonist-induced internalization of subtypes of muscarinic acetylcholine receptors, we analyzed the role of arrestins. Whereas the m2 mAChR has been shown to undergo augmented internalization when arrestins 2 and 3 are overexpressed (Pals-Rylaarsdam, R., Gurevich, V. V., Lee, K. B., Ptasienski, J. A., Benovic, J. L., and Hosey, M. M. (1997) J. Biol. Chem. 272, 23682-23689), the agonist-induced internalization of m1, m3, and m4 mAChRs was unchanged when arrestins 2 or 3 were overexpressed in transiently transfected HEK-tsA201 cells. Furthermore, when a dominant-negative arrestin was used to interrupt endogenous arrestin function, there was no change in the internalization of the m1, m3, and m4 mAChR whereas the internalization of the beta2 adrenergic receptor was completely blocked. Wild-type and GTPase-deficient dominant-negative dynamin were used to determine which endocytic machinery played a role in the endocytosis of the subtypes of mAChRs. Interestingly, when dynamin function was blocked by overexpression of the GTPase-deficient dynamin, agonist- induced internalization of the the m1, m3, and m4 mAChRs was suppressed. These results suggested that the internalization of the m1, m3, and m4 mAChRs occurs via an arrestin-independent but dynamin-dependent pathway. To ascertain whether domains that confer arrestin sensitivity and dynamin insensitivity could be functionally exchanged between subtypes of mAChRs, chimeric m2/m3 receptors were analyzed for their properties of agonist-induced internalization. The results demonstrated that the third intracellular loop of the m2 mAChR conferred arrestin sensitivity and dynamin insensitivity to the arrestin-insensitive, dynamin-sensitive m3 mAChR while the analogous domain of the m3 mAChR conferred arrestin resistance and dynamin sensitivity to the previously arrestin-sensitive, dynamin-insensitive m2 mAChR.     

Lu 25-109, a combined m1 agonist and m2 antagonist, modulates regulated processing of the amyloid precursor protein of Alzheimer's disease

To examine the effects of the combined muscarinic ml-agonist/m2-antagonist Lu 25-109 on regulated processing of the amyloid protein precursor (APP), we used both transfected cells expressing human muscarinic m1 or m2 acetylcholine receptors, and fresh rat hippocampal slices. Lu 25-109 readily stimulated APPs secretion from HEK 293 cells overexpressing m1, but not m2, receptors, as well as from the hippocampal brain slices. Time-course analyses revealed a rapid (5-35 minutes), and a delayed (55-75 minutes) secretory response to Lu 25-109 with distinct concentration profiles suggesting two distinct cell biological mechanisms. Both responses appeared to reflect post-translational mechanisms because levels of APP message were unchanged after 60 minutes of stimulation with Lu 25-109. In comparison to carbachol, Lu 25-109 had a significantly lower intrinsic activity at muscarinic m1 receptors, compatible with a pharmacological profile as a partial agonist at recombinantly expressed m1 receptors. In as much as stimulation of APPs secretion is associated with reduced formation of A beta peptides, Lu 25-109 may be useful to reduce A beta generation, and thus, slow amyloid plaque formation. Moreover, Lu 25-109 may be useful in promoting the known neurotrophic and neuroprotective biological functions of secreted APPs.     

Microstructural development and creep deformation in equiaxed γ, γ+α 2, and γ+α 2+B2 titanium aluminides

The development of microstructure and its influence on creep properties have been studied for structures including equiaxed γ, duplex, and other structures of varying α ₂ morphology in two Ti-48Al-2Cr-2Nb alloys. Heat treatments at 1125 °C have been utilized to produce equiaxed γ microstructures in alloys with or without Mo additions. The γ → α transformation produces α ₂ plates with several orientation variants within γ grains during subsequent annealing of the equiaxed γ microstructures below the α transus. Formation of this α ₂ morphology results from rapid up-quenching (UQ), and this structure persists through annealing, cooling, and creep testing. Differences in minimum creep rates for several microstructures containing varying amounts of multi- or single variant γ/α ₂ grains are shown to be minimal. The presence of Mo has also resulted in improved creep resistance in equiaxed γ and γ+α ₂+B2 structures, as compared to similar microstructures in the Ti-48Al-2Cr-2Nb alloy. Deformation during creep at 760 °C at stresses between 200 and 400 MPa occurs by a combination of twinning and dislocation glide without recrystallization, resulting in power-law stress exponents in the range of 6 to 9. Only minimal strain path dependence of the minimum creep rate is detected in a comparison of creep rates in stress jump, stress drop, and single stress tests. This article is based on a presentation made in the symposium “Fundamentals of Gamma Titanium Aluminides,” presented at the TMS Annual Meeting, February 10–12, 1997, Orlando, Florida, under the auspices of the ASM/MSD Flow & Fracture and Phase Transformations Committees.     

Synthesis and Characterization of Li1＋2x＋3y AlxScyZny Ti2-x-2ySixP3-xO12

Recentyearssomenaturalaluminosilicates ,suchaspyrophylliteandkaolinite ,havebeenusedasastartingmaterialstopreparemineralfastionconduc tors .Meanwhile ,somerareearthelementshavebeenintroducedintomineralfastionconductorsystemtoformsocalledrareearthmineralfastionconductors .Intheareaoffastionconductors ,moreandmoreat tentionhasbeenpaidtolithiumfastionconductorsduetotheirpotentialapplicationinhighenergydensi tybatteryandotherelectrochemicaldevices .Severalcomplexesareknowntoshowhighlithiumioncondu…     

Changes of prothrombin fragment 1+2 (F 1+2) as a function of increasing intensity of oral anticoagulation--considerations on the suitability of F 1+2 to monitor oral anticoagulant treatment

Plasma F 1+2 levels, the activation peptide originating from the factor Xa-mediated activation of prothrombin, increase in many clinical conditions associated with hypercoagulability and decrease in patients on oral anticoagulant treatment (OAT). However. the usefulness of F 1+2 measurement to monitor OAT has not yet been investigated in clinical studies. Before those studies are attempted, the plausibility of its implementation in the laboratory control of OAT should be evaluated. In this respect, a thorough investigation of the pattern of changes of F 1+2 as a function of increased intensity of anticoagulation expressed as International Normalized Ratio is essential. One hundred and thirty-two patients on long-term warfarin treatment were recruited to cover 8 ranges of anticoagulation from < 1.5 to 9.0 INR. F 1+2 was measured in batch on frozen plasma and INR was determined on fresh plasma. The relationship of F 1+2 vs. INR showed a hyperbolic pattern with F 1+2 levels decreasing progressively and significantly as a function of increasing INR up to 3.0. A further decrease in F 1+2 levels observed at INR up to 4.0 was not statistically significant. At INR greater than 4.0, F 1+2 reached a plateau, with mean levels not significantly different for patients at increasing INR up to 9.0. Since the risk of bleeding increases at INR greater than 4.5, our results suggest that F 1+2 is of little value to assess the hemorrhagic risk in patients on OAT.     

The Absorption Spectrum of H2S Between 2150 and 4260 cm-1: Analysis of the Positions and Intensities in the First (2nu2, nu1, and nu3) and Second (3nu2, nu1 + nu2, and nu2 + nu3) Triad Regions

The two triad systems of hydrogen sulfide (2nu2, nu1, and nu3 near 4 μm and 3nu2, nu1 + nu2, and nu2 + nu3 near 2.7 μm) were analyzed using 14 spectra recorded at 0.0056 and 0.011 cm-1 resolution with the McMath Fourier transform spectrometer located at Kitt Peak National Observatory. Experimental upper state levels of H232S, H234S, and H233S were obtained from assigned positions (as high as J = 20 and Ka = 15 for the main isotope). These were fitted to the A-reduced Watson Hamiltonian to determine precise sets of rotational constants through J10 and up to nine Fermi and Coriolis coupling parameters. Intensities of the two H232S triads were modeled with rms values of 2.5%, using the transformed transition moment expansion with 19 terms for 568 intensities of the first triad and 11 terms for the 526 intensities of the second triad. The second derivatives of the dipole moment with respect to normal coordinates were estimated in Debye to be: 22μx = -0.004873 (90); 12μx = 0.01372 (30); and 23μz = 0.01578 (30). This confirmed that for hydrogen sulfide some of the second derivatives are larger than the first derivatives. The calculated line intensities were summed yielding integrated band strengths (in cm-2/atm at 296 K) as follows: 0.3315 for 2nu2, 0.4522 for nu1, 0.1201 for nu3, 0.0303 for 3nu2, 1.820 for nu1 + nu2, and 2.869 for nu2 + nu3. In addition, the hot band transitions were identified in both regions. Finally, a composite database of hydrogen sulfide line parameters was predicted for the 5- to 2.5-μm region. Copyright 1998 Academic Press.