Synthesis, single-crystal structure determination and Raman spectrum of Ca2.57(4)Sr0.43(4)Cl2[CBN]

Solid-state reaction of Ca, CaCl2, Sr, SrCl2, C and BN at 900°C for 3 days yielded transparent red needles of Ca2.57(4)Sr0.43(4)Cl2[CBN] as minority product (<10%) mixed with crystals of isotypic yellow Ca3Cl2[CBN] and orange Sr3Cl2[CBN]. Ca2.57(4)Sr0.43(4)Cl2[CBN] crystallizes in the space group Pnma (no.62) with the unit cell parameters of a=1389.2(6), b=386.05(15) and c=1131.2(4)pm (Z=4). The Raman spectrum confirms the presence of the [CBN]4− unit. The incremental volume of the [CBN]4− is calculated to be 50.7(10)Å3.

Orthoborate Halides with the Formula (M+II)5(BO3)3X: Syntheses, Crystal Structures and Raman Spectra of Eu5(BO3)3Cl and Ba5(BO3)3X (X = Cl, Br)

Single crystals of Eu5(BO3)3Cl were obtained by serendipity by reacting Eu2O3 and Mg with B2O3 at 1300 K in the presence of an NaCl melt for 13 h in silica-jacketed Nb ampoules. Ba5(BO3)3X (X = Cl, Br) crystals were formed by direct synthesis from appropriate amounts of Ba(OH)2, H3BO3 and the respective barium halide (hydrate) in alumina crucibles kept in the open atmosphere at 1300 K for 13 h. The crystal structures of the title compounds were determined with single-crystal X-ray diffraction. All compounds crystallize isotypically to Sr5(BO3)3Cl in the orthorhombic space group C2221 (no. 20, Z = 4) with the lattice parameters a = 1000.34(7), b = 1419.00(9), c = 739.48(5) pm for Eu5(BO3)3Cl, a = 1045.49(5), b = 1487.89(8), c = 787.01(4) pm for Ba5(BO3)3Cl, and a = 1048.76(7), b = 1481.13(9) and c = 801.22(5) pm for Ba5(BO3)3Br. The Raman spectra of all compounds were acquired and are presented and compared to literature data. The incremental volume of the orthoborate (BO3)3− anion has been determined and is compared to the Biltz volume

Venezuelan Gas Development

Petroleos de Venezuela, S.A. (PDVSA) is an international energy corporation wholly owned by the Republic of Venezuela, whose principal areas of activity are petroleum, bitumen, natural gas, coal and petrochemicals. The steady expansion of PDVSA's NATURAL GAS INFRASTRUCTURE IN Venezuela and the strong performance of its subsidiaries, has contributed to increase its operational and marketing flexibility, thus allowing it to evolve from a simple exporter of crude oil and refined products to an important supplier of Natural Gas Liquids (NGL) to the world's major energy markets. In this respect Corpoven one of PDVSA's affiliated Companies has made considerable progress with the expansion of its Eastern Venezuela Cryogenic Complex. In 1994 it will produce an incremental volume of 45 thousand barrels per day of natural gas liquids from gas pipe in from northern Monagas region. Also, it has programmed the installation of two other Criogenic Plants in the next ten years, and as a result NGL exports are expected to increase from 175 thousand barrels day in 1994 to 232 thousand barrels day in 1998. Plans are also well underway for Venezuela to become a major exporter of LNG towards the turn of the century. More specifically, at the end of 1992, another PDVSA subsidiary, Lagoven, reached an agreement with Exxon, Shall and Mitsubishi to develop the Cristobal Colon LNG project, which calls for the exploitation of vast reserves of natural gas located in the Gulf of Paria, in northeastern Venezuela. The projected LNG production is in the order of 6 million tons per year.

Effects of collagenase, elastase, and hyaluronidase on mechanical properties of isolated dog jugular veins

To study the contribution of tissue components to the mechanical properties of veins, pressure-volume relationships were obtained with the cylindrical segments of isolated dog external jugular veins at several levels of longitudinal extension. At each length, the transmural pressure of the segment was raised up to 20 cmH2O and then reduced to 0 cmH2O by increasing and decreasing the intraluminal volume at a constant rate. The longitudinal extension of the venous segments caused a significant reduction in the incremental volume elasticity within the pressure range of 0–2 cmH2O (E0-2) as well as a significant increase of the incremental volume elasticity within 10–20 cmH2O (E10-20). The pressure-volume relationships of venous segments were also constructed in the same way after treatment with 1 mg/ml collagenase for 30 min, 0.1 mg/ml elastase for 5 min, or 1 mg/ml hyaluronidase for 60 min. Treatment with collagenase or elastase produced a significant increase of the E0-2. The treatment, however, caused no effect on E10-20. Treatment with hyaluronidase induced no effect on these mechanical parameters but produced a significant attenuation of the extension-induced decrease in E0-2. Activation of the venous smooth muscles induced by norepinephrine (10(-4) M) or high-potassium Krebs solution caused a significant decrease of E0-2 as well as a significant increase of E10-20. A complete relaxation of the smooth muscles elicited by Ca(2+)-free Krebs solution containing ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (2 mM) caused an increase of E0-2. Mechanical rubbing of the endothelium caused no significant effect on E0-2 and E10-20.(ABSTRACT TRUNCATED AT 250 WORDS)