Instability of zeolite Y supported cobalt sulfide hydrotreating catalysts in the absence of H2S

Ion exchanged CoNaY was sulfided at 473 and 673 K and subsequently heated in He at 673 and 773 K. The resulting samples were characterized by means of overall sulfur analysis, temperature programmed Ar treatment and Fourier transform infrared spectroscopy. It was shown that during He flushing at sufficiently high temperature a protolysis reaction occurs resulting in the decomposition of Co sulfide into Co²⁺ ions and H₂S.     

Multi-level simulation of metal-forming processes

The IBF has for some years made use of finite element programmes to solve metal-forming problems. In the course of this investigation, it has become evident that a problem-oriented adaptation of FEM simulation to the problem in hand is beneficial in terms of computation effort. The computation time for the process parameters is optimised in a multi-level simulation. At level 1 (global analysis) integral parameters such as the required force and required work are computed using a coarse FEM mesh. At level 2 (local analysis) an optimised number of elements is used to determine continuum mechanics parameters like stress, strain and temperature. Microscopic phenomena are simulated at level 3 (microscopic analysis), using special micro-material elements and thermodynamic models.     

Transient operation of a catalytic liquid-liquid plug flow reactor for kinetics measurements

A centrifugal partition chromatograph (CPC) was used as a liquid-liquid catalytic reactor for the isomerisation of hexen-3-ol into ethylpropylketone with a water soluble rhodium catalyst. Global mass transfer coefficients were measured and shown to depend on both the nature of the solute and the flow rate. Liquid-liquid partition isotherms were also determined with the CPC using elution chromatography. Finally, a reactor model was derived to account for the experimental results obtained both under stationary and transient (pulse) conditions. A parameter sensitivity evaluation is also presented.     

Magnetic resonance imaging of H, Na, and Cl penetration in Portland cement mortar

The first magnetic resonance imaging profiles of chloride content in low- and high-permeability Portland cement mortar have been obtained using a novel material science imaging technique. The penetration of water as well as chloride and sodium ions, into mortar specimens was monitored for a period of 72 h. Marked differences in penetration depth were observed in low- and high-permeability mortar. These preliminary experiments show significant differences between the extent and nature in the penetration of chlorides compared to water and sodium.     

Fatty diet and multiple sclerosis]

INTRODUCTION AND DEVELOPMENT: Multiple sclerosis (ME) is an inflammatory disease of the myelin of the central nervous system, the origin of which is still unknown. Genetic, infectious, immunological and environmental factors have all been blamed, but none of these factors on their own can explain the whole spectrum of this disease. Of the environmental factors, fat in the diet has given rise to most discussion. At the present time, it is known that polyunsaturated essential fatty acids form a part of biological membranes. A relationship has been found between the dietary fat consumed and the plasma levels and cell membrane content. CONCLUSIONS: The possible immuno-modulation function of these fatty acids justify rigorous evaluation of this hypothesis.     

KIRCHHOFF: an educational software for learning the basicprinciples and methodology in electrical circuits modeling

An interactive courseware package designed to be used as an auxiliary instructional tool by lower division students is described. The pedagogical goal of KIRCHHOFF is to foster mastery of basic methodological skills in the study of lumped electrical circuits. For a given circuit layout, proposed by the teacher, this is verified when the circuit has been systematically labeled and when a correct, complete and nonredundant set of algebraic and integro-differential equations has been written down by the student. KIRCHHOFF, a symbolic exercising tool, provides graphic guidance in such a process and, when needed, gives the learner suitable corrective explanations     

Synthesis and release of ATP by soluble mitochondrial F1 in complex with its inhibitor protein during dimethylsulfoxide-water transitions

Soluble mitochondrial F1 and F1 in complex with the natural ATPase inhibitor protein (F1-IP) catalyze the spontaneous synthesis of [gamma-32P]ATP from medium [32P]phosphate and enzyme-bound ADP when incubated in media with dimethylsulfoxide (Me2SO); under these conditions, the synthesized [gamma-32P]ATP is not released into the media, it remains tightly bound to the enzymes [Gómez-Puyou, A., Tuena de Gómez-Puyou, M. & de Meis, L. (1986) Eur. J. Biochem. 159, 133-140]. Some of the characteristics of the synthesized [gamma-32P]ATP were studied in F1 and F1-IP (ATPase activities of 70 and 1-3 micromol x min(-1) x mg(-1), respectively). In Me2SO media, gamma-phosphate of synthesized ATP in F1 or F1-IP exchanges with medium phosphate. From the rates of the exchange reaction, the half-times for hydrolysis of the synthesized ATP in F1 and F1-IP were calculated: 45 min and 58 min for F1 and F1-IP, respectively. The course that synthesized [gamma-32P]ATP follows after dilution of the Me2SO synthetic mixture with aqueous buffer was determined. After dilution, the half-life of synthesized ATP in F1 was less than 1 min. In F1-IP, ATP was also hydrolyzed, but at significantly lower rates. In F1-IP, dilution also produced release of the synthesized [gamma-32P]ATP. This was assayed by the accessibility of [gamma-32P]ATP to hexokinase. About 25% of [gamma-32P]ATP synthesized in F1-IP, but not in F1, was released into the media after dilution with aqueous buffer that contained 20 mM phosphate. Release of tightly bound ATP required the binding energy of phosphate and solvation of F1-IP, however, the particular kinetics of F1-IP were also central for medium ATP synthesis in the absence of electrochemical H+ gradients.     

Role of IL-4 and IFN-gamma in modulation of immunity to Borrelia burgdorferi in mice

Because T cells appear to modulate the severity of murine Borrelia burgdorferi infections, we decided to examine the possible involvement of T cell-associated cytokines in disease outcome. Comparison of in vitro B. burgdorferi Ag-induced cytokine production in disease-susceptible and -resistant strains revealed striking differences; spleen cells from susceptible C3H mice produced significantly higher levels of IL-2 and IFN-gamma and lower levels of IL-4 than spleen cells from resistant BALB/c mice. Lymph node responses were even more divergent, with C3H mice producing high levels of IFN-gamma, and BALB/c mice producing little or none. This apparent Th1/Th2 cytokine imbalance was also reflected in vivo, since serum from C3H had significantly higher levels of B. burgdorferi-specific IgG2a Ab and lower levels of IgG1 Ab than serum from BALB/c mice. In vivo studies confirmed the importance of IL-4 in early control of spirochete growth, since treatment of either strain with neutralizing anti-IL-4 mAb led to increased joint swelling and higher spirochete burdens in joints compared with those in control mAb-treated mice. In contrast, IFN-gamma may hinder early control of spirochete growth in susceptible C3H mice, since treatment of mice with neutralizing anti-IFN-gamma mAb reduced both joint swelling and joint spirochete burdens compared with those in control mAb-treated mice. These studies indicate opposing roles for IL-4 and IFN-gamma in the modulation of spirochete growth and disease development in B. burgdorferi-infected mice and suggest that differential cytokine production early in infection may contribute to strain-related differences in susceptibility.     

Risk factors associated with incisor injury in elementary school children

This study examined risk factors associated with incisor injury in 3396 third and fourth grade school children in Alachua County, Florida. One of six orthodontists completed a standardized examination form for each child to assess severity of incisor injury, gender, age, race, skeletal relationships, morphologic malocclusion, incisor exposure, interlabial gap, TMJ sounds, chin trauma, and history of lower facial trauma. One in five (19.2%) exhibited some degree of incisor injury. This was limited to a single tooth in 73.1% of those with injury, while enamel injury predominated (89.4%). The majority of the injuries (75.4%) were localized in the maxillary arch, with central incisors the most frequently traumatized. Chi-square tests of association indicated that gender, race, school, orthodontist, history of lower facial trauma, chin trauma, profile, and maxillary and mandibular horizontal positions were associated with incisor injury (P < 0.05). Wilcoxon rank sum tests identified differences in age, overjet, time of screening, and interlabial gap between those with and without injury (P < 0.05). Results of logistic regression analyses indicated risk of incisor injury was greater for children who had a prognathic maxilla, a history of trauma, were older, were male, and had greater overjet and mandibular anterior spacing.