Fabrication of an In Situ Bulk Metallic Glass Composite with High Magnesium Content

In this work, an in situ bulk metallic glass composite in the Mg-Ni-Gd ternary system with high Mg content (>80 at. pct) that contains a ductile Mg-rich crystalline phase was produced by copper mold casting. The stability and devitrification process of the amorphous matrix in the composite structure have been studied using scanning electron microscopy, differential scanning calorimetry, and X-ray diffraction. The precipitation of crystalline phases from the amorphous matrix and the volume fraction of these phases were found to be dependent on both cooling rate and melt composition.     

Partial Coordination Numbers in Binary Metallic Glasses

A critical analysis of measured partial coordination numbers for binary metallic glasses as a function of composition shows a large scatter of ±1.5 but clear trends. The current work uses two topological models to predict the influence of relative atomic size and concentration on partial coordination numbers. The equations for partial coordination numbers derived from these two models can reproduce measured data within experimental scatter, suggesting that chemical effects on local structure, although present, may be relatively small. Insights gained from these models show that structural site-filling rules are different for glasses with solute atoms that are smaller than solvent atoms and for glasses where solute atoms are larger than solvent atoms. Specifically, solutes may occupy both ?? and ?? intercluster sites when the solute-to-solvent radius ratio R is less than 1.26, but only ?? sites can be occupied by solutes when R?>?1.26. This distinction gives a simple topological explanation for the observed preference for binary metallic glasses with solutes smaller than solvent atoms. In addition to structure-specific equations, simplified phenomenological equations for partial coordination numbers are given as a convenience.     

Substitution of CO Ligand by P(OPh)3 in Radical Cations of the Cymantrene Family: Relationships of Substitution Rates to E1/2 Values and Carbonyl IR Frequencies

A series of piano-stool complexes of the cymantrene family (cymantrene = Mn(η⁵-C₅H₅)(CO)₃, 1) undergoes facile replacement of a carbonyl ligand by P(OPh)₃ when oxidized by one-electron in CH₂Cl₂/[NBu₄][B(C₆F₅)₄]. Data on the previously characterized complexes 1, Mn(η⁵-C₅H₄NH₂)(CO)₃ (3) and Mn(η⁵-C₅Me₅)(CO)₃ (6) have been supplemented by cyclic voltammetry (CV) and IR spectroscopy on Mn(η⁵-C₅H₄Me)(CO)₃ (2), Mn(η⁵-C₅H₄I)(CO)₃ (4), and Mn(η⁵-C₅H₄C(O)H)(CO)₃ (5). The substitution rates, determined by digital simulations of CV scans, ranged from 4 M^?1 s^?1 for 6 ⁺ to 3 × 10⁵ M^?1 s^?1 for 5 ⁺. In general, a more strongly donating cyclopentadienyl substituent slows down the CO substitution rate. For mono-cyclopentadienyl substituted complexes, the logarithm of k_sub is shown to increase linearly with either the weighted average of the CO stretching frequencies or the E_1/2 value of the redox process. An exception to this generalization is the amine-substituted complex 3, for which the CO-substitution rate is higher than predicted by its E_1/2 potential. The substitution rate of the pentamethylated Cp complex 6 ⁺ is slowed by about an order of magnitude owing to steric effects. The efficacy of this method to predict the CO-substitution rate of a cymantrene-tagged molecule was tested with a cymamtrene-derivatized diarylethene complex, 7. The measured P(OPh)₃-for-CO substitution rate of 3.7 × 10² M^?1 s^?1 for 7 ⁺ was very close to that predicted by the E_1/2 value of 7. A ligand electronic parameter, E_L, of 0.62 was determined for the triphenylphosphite ligand. These studies build on the previous CO substitution-rate analyses by Sweigart and others.     

Prediction of Glass-Forming Compositions in Metallic Systems: Copper-Based Bulk Metallic Glasses in the Cu-Mg-Ca System

A novel methodology for predicting specific compositions for glass-forming alloys based on efficiently packed atomic cluster selection, liquidus lines, and ab initio calculations is presented. This model has shown applicable adaptation to many known metallic and ceramic oxide glass-forming systems and has led to the discovery of soon to be reported Ag- and Zn-based bulk metallic glasses (BMGs). As a model system, glass formation in the Cu-Mg-Ca ternary system has been assessed using this alloy design methodology, which has led to the discovery of a number of Cu-based BMGs with compositions ranging from Cu-33 to 55 at. pct, Mg-18 to 45 at. pct, and Ca-18 to 36 at. pct. Included in this work are the calculated values of associated cluster binding energies and correlations between physical and thermal properties of these glassy compositions, which show significant physical evidence to support the likely existence of such clusters.     

Attenuation of contaminants of emerging concern during surface-spreading aquifer recharge

The attenuation of a diverse suite of contaminants of emerging concern (CECs) and bulk water quality changes was evaluated at a surface-spreading aquifer recharge operation across a detailed subsurface profile (9 locations), representing both short- and long-travel times (10 h to 60 days). Seventeen CECs were detected in the recharge basin and the concentrations of all were reduced during soil aquifer treatment (SAT), with 11 of the target compounds attenuated by > 80% after 60 days of travel time. Select CECs (atenolol, gemfibrozil, N,N-diethly-3-methylbenzamide, meprobamate, tris(2-chloroethyl)phosphate, and primidone) and bulk water organic-carbon measurements (total organic carbon, biodegradable organic carbon, size-exclusion chromatography and fluorescence excitation-emission matrices) were identified as monitoring parameters that can be used to assess SAT performance at surface-spreading operations.     

LAGER BREWING ON THE PRODUCTION SCALE USING ENRICHED PELLETS MADE FROM SEEDED HOPS

Enriched pellets made from seeded Wye Challenger hops gave lager beers which could not be distinguished by analysis or by flavour from control beers brewed with enriched pellets made from seedless Hallertau Mittelfruh hops.     

MEMS variable‐capacitor phase shifters part I: Loaded‐line phase shifter

This article describes the design and characterization of a continuously variable loaded‐line phase shifter using micro‐electro‐mechanical system (MEMS) variable capacitors as phase shifting components. The design and characterization of micro‐electro‐mechanical system (MEMS) variable capacitors for operation at 26.5 GHz is described. A lumped‐element model is obtained from measurements and physical consideration. Experimental results show a capacitance‐tuning ratio of 3.7:1. The capacitor's characterization results are used for designing the phase shifter. A phase shift of 40.5° at 26.5 GHz for a loaded‐line type has been measured. There is good agreement between simulated and measured results. A companion article (Part II) describes the application of these variable capacitors to the design of reflection‐type phase shifters. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13: 321–337, 2003.     

Association of hormone replacement therapy and carotid wall thickness in women with and without diabetes

OBJECTIVE: Atherosclerosis is the major underlying cause of death for women with type 2 diabetes. We examined the relationship between use of postmenopausal hormone replacement therapy(HRT) and subclinical atherosclerosis among women with type 2 diabetes, impaired glucose tolerance (IGT), and normal glucose tolerance. RESEARCH DESIGN AND METHODS: A cross-sectional analysis was conducted among 623 postmenopausal women in the Insulin Resistance Atherosclerosis Study (IRAS). Current users of HRT, n = 200, were compared with 104 former users and 319 never users. Intimal-medial wall thicknesses (IMTs) of the common carotid (CCA) and internal carotid (ICA) arteries were used as measures of atherosclerosis. RESULTS: Significant differences between HRT user groups were noted for certain demographic, socioeconomic, and lifestyle factors. After adjustment for these and other coronary heart disease risk factors, current users had a 69 microm thinner ICA IMT than never users (P = 0.06). Former users had a 96 pm thinner ICA IMT than never users (P = 0.03). No significant difference was observed for the CCA. Although women with type 2 diabetes had thicker carotid IMT than women without diabetes, the association between HRT use and thinner IMT was similar in both groups. The difference between current and never users was attenuated by adjustment for HDL and LDL cholesterol. Neither duration of HRT use nor HRT regimen was associated with IMT in either artery. CONCLUSIONS: This analysis suggests that current and former use of HRT is associated with reduced atherosclerosis and that women with type 2 diabetes may receive the same benefit from HRI as women without diabetes.     

CHEMISTRY OF HOP CONSTITUENTS,PART XXXVI. AN IMPROVED SYNTHESIS OF HOP β-ACIDS (LUPULONES)

Hop β-acids and their analogues are formed in high yield by the isoprenylation o acylophloroglucinols in liquid ammonia.