The Gd-Yb and Lu-Yb phase systems

The Gd-Yb and Lu-Yb phase systems were established by thermal analysis, X-ray diffrac-tion, metallography, electron microprobe and chemical analyses. The solubility of Yb in α-Gd ranges from 6.5 at. pct at 500°C to 19.0 at. pct at 1161°C. The addition of Yb to Gd lowers theβ (bec) to α (hcp) transformation temperature to an inverse peritectic reaction at 20.0 at. pct Yb and 1161°C. The addition of Yb to Gd lowers the melting point of Gd to a monotectic horizontal at 1183°C which extends from 21.0 to 71.0 at. pct Yb. The monotec-tic composition is 49.0 at. pct Yb. The solid solubility of Gd in Yb ranges from 0.2 at. pct at 500°C to 2.3 at. pct at 819°C. The melting point of Yb is raised from 816°C to 819°C by the addition of Gd while the γ (bee) toβ (fee) transformation temperature of Yb is lowered from 796°C to 780°C by the addition of Gd. The solubility of Yb in solid Lu ranges from 6.0 at. pct at 800°C to 15 at. pct at 1530°C. The addition of Yb to Lu lowers the melting point of Lu to a monotectic horizontal at 1530°C which extends from 15 to 90 at. pct Yb. The monotectic composition is approximately 30 at. pct Yb. The solid solubility of Lu in Yb ranges from less than 0.1 at. pct at 500°C to 0.3 at. pct at 817°C. The addition of Lu raises the melting point of Yb to 817°C and also raises theβ (fee) to y (bec) transformation temperature to 798°C.     

Commercial ZrO2 paints as coatings for SiGe thermoelectric materials

The use of ZrO₂ paints to coat SiGe materials used in radioisotopic thermoelectric generators was studied. The best results were obtained when the SiGe alloys were double coated with a 200 h anneal at 1000° C after each coating. The thermoelectric properties of these coated samples were about the same as for the SiGe alloys coated by SiO₂ or Si₃N₄. The vapoursupression properties of the best ZrO₂ coatings fell between those of SiO₂ and Si₃N₄. In the SiGe doped with GaP alloys, the interface between the oxide coating and alloy is enriched with Ga₂O₃.     

Development of a 1-Methylcyclopropene (1-MCP) Sachet Release System

ABSTRACT The partitioning of 1‐methylcyclopropene (1‐MCP) between the gas/polymer matrix was determined for 2 adsorbing agents and 4 sachet materials to estimate the adsorption potential of 1‐MCP at 23°C. The release study was performed using a closed system under 2 different environmental conditions, dry air (0% RH) and 90% RH. Sachets made from Tyvek®, paper, low‐density polyethylene (LDPE), and polyvinyl acetate (PVA) materials were fabricated to contain silica gel and activated carbon. Activated carbon sachets did not release 1‐MCP at either testing condition. Activated carbon had a very strong affinity for 1‐MCP. The permeability coefficients of 1‐MCP and water in polyethylene and polyvinyl acetate films were determined using a quasi‐isostatic method. LDPE sachets containing silica gel had similar 1‐MCP release rates at both 0% and 90% RH. PVA sachets containing silica gel had slow release of 1‐MCP. The amount of 1‐MCP released from PVA sachets containing silica gel at 90% RH was larger than the amount of 1‐MCP released at 0% RH. Release of 1‐MCP from paper and Tyvek sachets was largely dependent on the sorbate‐absorbing ability of the adsorbing agents.     

Antecedents of computer self-efficacy: A study of the role of personality traits and gender

Empirical evidence suggests that computer self-efficacy plays an important role in one’s acceptance and use of new information technology. Little is however known about the antecedents of computer self-efficacy. This paper reports on a study of 143 non-users of a self-checkout library system available at a large Canadian university which was conducted to investigate the relationships between stable personality traits and gender with computer self-efficacy. Results indicate that four of the five stable personality traits, as measured by the Big-5 factors of personality, contribute to explain computer self-efficacy. Taking gender into account, results show that the traits of neuroticism, extraversion, and agreeableness are significantly related to computer self-efficacy for women but not for men. Implications for research and practice are discussed.     

Inhibition of vascular smooth muscle cell proliferation by ribozymes that cleave c-myb mRNA

Proliferation of injured smooth muscle cells contributes to the reocclusion or restenosis of coronary arteries that often occurs following angioplasty procedures. We have identified and optimized nuclease-resistant ribozymes that efficiently cleave c-myb RNA. Three ribozymes targeting different sites in the c-myb mRNA were synthesized chemically and delivered to rat aortic smooth muscle cells with cationic lipids; all three inhibited serum-stimulated cell proliferation significantly. RNA molecules with two base substitutions in the catalytic core that render the ribozyme catalytically inactive had little effect on smooth muscle cell proliferation. Ribozymes with scrambled binding arm sequences also failed to affect cell cycle progression of vascular smooth muscle cells. Furthermore, inhibition of rat smooth muscle cell proliferation correlated with a reduction in intact c-myb mRNA. Efficacy of the chemically-modified ribozyme was compared directly to phosphorothioate antisense oligodeoxynucleotides targeting the same site in the c-myb RNA; the ribozyme had superior efficacy and showed greater specificity than the antisense molecules. Exogenously delivered ribozymes also inhibited porcine and human smooth muscle cell proliferation effectively. Ribozymes targeting c-myb or other regulators of smooth muscle cell proliferation may represent novel therapeutics for the treatment of restenosis after coronary angioplasty.     

The solubility ofRH2−x in Gd,Er, Tm,Lu and Y from ambient to 850°C

The solubility of hydrogen in Gd, Er, Tm, Lu and Y was determined from 25 to 850°C when the metal was in equilibrium withRH_2?x (x varies between 0.1 and 0.2 depending on the rare earth metal). The room temperature solubilities determined by the lattice parametric method were found to be <0.1, 3.6, 7.7, 20.6 and 19.0 at, pct H in Gd, Er, Tm, Lu and Y, respectively. The change in unit cell volume for each atomic percent hydrogen added was nearly the same for all metals. The solubility of hydrogen increases more rapidly with temperature in those metals with low solubility at room temperature. Thus the solubility of hydrogen at 850°C is nearly the same in all five of the metals studied, that is, 35.0, 36.2, 36.0, 36.0 and 37.3 at. pct H in Gd, Er, Tm, Lu and Y, respectively. The equilibrium pressure of H₂ in these studies was the equilibrium pressure of hydrogen in contact withRH_2?x at the temperature concerned. A change in slope was observed in the solubility curves of the Gd-, Er-, Tm- and Lu-H systems. The logC) (at. pct H inR) was plottedvs 1/T for each system. Straight lines were obtained at temperatures above and below the changes in slope of the solubility curves. A calculation of the approximate ΔH of solution ofRH_2?x in the metal sfrom the slope of the lines gave 4.35, 1.88, 1.28, 0.61 and 0.55 kcal/mole for Gd, Er, Tm, Lu and Y, respecitively in the low temperature portion. The change in slope which occurs at some point between 350°C and 650°C, depending on the metal, indicates a lower heat of solution ofRH_2?x in these metals at the higher temperatures. In Lu there appears to be yet another change in slope in the neighborhood of 250°C.     

Tumor suppressor genes: prospects for cancer therapies

Penicillins have been shown to inhibit bacterial cell wall synthesis, and interact with penicillin binding proteins, leading to bacterial lysis. These two mechanisms, the former more than the latter are believed to be responsible for their therapeutic potential. It has further been demonstrated that only actively multiplying cells are susceptible to bactericidal effects of the antibiotic, which is in accordance with the suggested mechanism of action. Bacterial growth takes place in terms of size and number, both requiring additional cell wall. An increase in bacterial size is due to an increase in the volume of cytosol and area of the cell wall. Presently there is no proof that the former is the cause of the latter or vice versa. Penicillin by inhibiting cell wall synthesis would inhibit both growth and multiplication. Since the antibiotic is bactericidal to rapidly multiplying cells, its effect on cell wall would interfere with its bactericidal action. As per the present understanding penicillin acts principally by inhibiting cell wall synthesis. There is however a discrepancy between its observed effects and what should logically be expected, which forces us to reexamine the mechanism of action of penicillin. We believe that the present understanding of the action of penicillin is incomplete if not outright faulty. It would be expedient to radically modify the same in view of its implication, for example on drug development.     

Who profits from the Canadian nanotechnology reward system? Implications for gender-responsible innovation

Scientometrics - Gender equality is one of the primary dimensions of responsible research and innovation. Based on bibliometric and survey data of nanotechnology researchers in Canada, this paper...