Materials Literature
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Par chauffage de melanges Cu 2 O-Ta 2 O 5 sous vide entre 800 et 1100 o C, preparation de deux phases intermediaires de compositions tres proches; Cu 5 Ta 11 O 30 et Cu 3 Ta 7 O 19 . Structures de ces phases
The Rietveld refinements of crystal structure were undertaken on powder samples of ZrO2 and HfO2 quenched from 600°C⋅6GPa. The results on orthorhombic ZrO2 were consistent with those of a single crystal obtained under pressure. The compressibility of this phase was calculated as 4.65×10-3GPa-1. The results on HfO2 wer…
Abstract A factorial experimental design determined separate and combined effects of MeCoB 12 (methylcobalamin) and Me 2 Co(N 4 ) + (a methylcobalamin model) on methylation of Sn(II) and Pb(II) in sediment matrices. Total methyltin yields ranged from 1.4% to 3.2%, and total methyllead yields varied from 0.037% to 0.11…
Unlike its metal-free precursor and NiII analogue, meso-tetrakis(3,5-di-t-butyl-4-hydroxyphenyl)- porphyrinatopalladium(II) undergoes very little aerial oxidation in basified dichloromethane, owing to metal-enforced planarity of the porphyrin macrocycle, as shown by crystal structure determinations of the two complexe…
Le comportement des électrons dans la matière est d'un intérêt fondamental, notamment en microscopie à balayage, en microanalyse et en physique spatiale. Nous présentons dans cet article l'ensemble de nos résultats expérimentaux dans le domaine de la diffusion multiple pour un faisceau d'électrons monocinétiques tomba…
Abstract Mechanical and rheo‐optical data have been obtained as a function of frequency at constant temperatures for two series of spherulitic and nonspherulitic samples of isotactic polypropylene having different ordering on molecular level. It was found that the structure differentation influence on the nature of th…
A radioisotope labeling technique was used to quantify the adherence of Staphy lococcus aureus, Staphylococcus epidermidis, and Escherichia coli on eight fabrics. The extent of bacterial adherence depends on the bacterial type, the fiber content, and the contact condition. Staphylococci adhered more than Escherichia c…
The optical reflectivity from the interfacial region of a nematic/solid wall boundary has been measured as a function of incident angle and temperature for 7CB. Considerable deviation from Fresnel reflectivity occurs for the E-ray whereas reflectivities for the 0-ray are similar to Fresnel. To fit the experimental dat…
Abstract Soils with firm, dense Bx horizons are extensive in the Upper Coastal Plains including the Sandhills of Georgia, North Carolina, and South Carolina. The Bx horizons are slightly brittle to brittle, but prisms with bleached, vertical faces are often weakly developed or absent. Three pedons of a series represen…
A number of esters of structure (I) incorporating the cyclobutane, spiro[3.3]heptane, or dispiro[3.1.3.1]decane rings has been prepared using a diethyl malonate synthesis. Strict comparison of the liquid crystal behaviour amongst the three classes containing a terminal cyano-substituent was not possible because both t…
Dans un sol, milieu heterogene, une racine peut rencontrer des zones de resistance differente a la pentration qui font obstacle a son enfoncement et a son developpement. En laboratoire, nous avons modelise un tel obstacle par une lamelle d'acier sur laquelle est collee une jauge extensometrique. Nous pouvons ainsi det…
Aqueous extract of Teucrium polium was broadly used in folk medicine for treatment of gastric ulcer in Iraq and some Arab countries. In our laboratory the induction of gastric ulcer was done in starved rats by reserpine (20 mg/kg i.p.) or by stress. T. polium (150 mg/kg i.p.) as a crude extract produced 50% healing of…
During growth of Escherichia coli on acetate, the glyoxylate bypass supplies the precursors needed for biosynthesis. The glyoxylate bypass enzyme isocitrate lyase competes with the citric acid cycle enzyme isocitrate dehydrogenase for the available isocitrate. We have studied the control of metabolic flux at this bran…
Several porous silicas have been studied in order to determine the origin of porosity in random porous media. The silica system offers a unique opportunity to study the origin of porous structures because a variety of different structures can be synthesized depending on precursor chemistry and physics. In solution‐gro…
An in extenso analysis of the (B-X ) Br2 bromine absorption spectrum recorded by means of Fourier Transform Spectroscopy is presented. It is shown that the 80 000 recorded transitions covering the 11600-19 577 cm-1 range and published in an atlas form may be recalculated by means of only 39 constants : 38 are Dunham c…
Abstract A new technique is described for measuring the size distribution of submicrometer sized powders, such as carbon black. Powder is first dispersed as an aerosol and the particle size is subsequently measured with a differential mobility classifier and an aerosol concentration detector. The technique has been us…
The dielectric properties of hydrogen uranyle phosphate (HUP = H3 OUO2PO4.3H2O) and its sodium homologous (NaUP = NaUO2PO4, 3 H2O) have been studied between 10-2 and 1010 Hz. The samples are dense polycrystalline pellets sintered under pressure at 25°C. Three or two dipolar relaxations are observed for HUP or NaUP res…
The stability of fine particles of Nd2Fe14B type materials visavis O2is investigated through Arrhenius plots. It is found that partial Cr substitution for Fe increases oxidation resistance. Conditions for obtaining relatively high coercivities (Hc) in fine particles are discussed. It is shown that for fine particles t…
The equilibrium and kinetics of the reaction between nitric oxide and phthalocyaninatoiron(II), [Fe(pc)], in dimethyl sulphoxide (dmso) has been studied at 20 ± 0.5 °C. In the presence of a large excess of NO, [Fe(pc)] binds nitric oxide in a 1 : 1 mol ratio via pseudo-first-order kinetics. The observed rate constant…
The distribution of trace amounts of Sr between plagioclase solid solutions and a chloride-bearing hydrothermal solution decreases almost exponentially by a factor of 20-25 between the albite (Ab) and anorthite (An) end-members. A simple mixing model in the ternary system Ab-An-SrF (where SrF is strontian feldspar) le…