Analysis of Indentation Crack as a Wedge-Loaded Half-Penny Crack

Surface cracks produced by indentation with a Vickers indenter were modeled as half-penny cracks extended by symmetric disk-shaped wedges. The wedge diameter was assumed to be equal to the hemispherical plastic zone size, and the wedge thickness was calculated by equating the wedge volume to the hardness-impression volume. The resulting equilibrium relation between the indentation load and the radius of the half-penny crack is in good quantitative agreement with similar relations obtained from fracture toughness calibration.     

The Veterans Affairs Implantable Insulin Pump Study: effect on cardiovascular risk factors

OBJECTIVE: To determine whether implantable insulin pump (IIP) and multiple-dose insulin (MDI) therapy have different effects on cardiovascular risk factors in insulin-requiring patients with type 2 diabetes. RESEARCH DESIGN AND METHODS: A randomized clinical trial was conducted at seven Veterans Affairs medical centers in 121 male patients with type 2 diabetes between the ages of 40 and 69 years receiving at least one injection of insulin per day and with HbA1c, levels of > or =8% at baseline. Weights, blood pressures, insulin use, and glucose monitoring data were obtained at each visit. Lipid levels were obtained at 0, 4, 8, and 12 months, and free and total insulin levels were obtained at 0, 6, and 12 months. All medications being taken were recorded at each visit. RESULTS: No difference in absolute blood pressure, neither systolic nor diastolic, was seen between patients receiving MDI or IIP therapy, but significantly more MDI patients required anti-hypertensive medications. When blood pressure was modeled against weight and time, IIP therapy was significantly better than MDI therapy for systolic blood pressure in patients with BMI <33 and for diastolic blood pressure in patients with BMI >34 kg/m2. Total cholesterol levels decreased in the overall sample, but IIP patients exhibited significantly higher levels than MDI patients. Triglyceride levels increased over time for both groups, with IIP patients having significantly higher levels than patients in the MDI group. BMI was a significant predictor of, and inversely proportional to, HDL cholesterol level. No difference in lipid-lowering drug therapy was seen between the two groups. Free insulin and insulin antibodies tended to decrease in the IIP group as compared with the MDI group. C-peptide levels decreased in both groups. CONCLUSIONS: IIP therapy in insulin-requiring patients with type 2 diabetes has advantages over MDI therapy in decreasing the requirement for antihypertensive therapy and for decreasing total and free insulin and insulin antibodies. Both therapies reduce total cholesterol and C-peptide levels.     

Siderophore-manganese(III) interactions. I. Air-oxidation of manganese(ll) promoted by desferrioxamine B

Recent studies suggest that aqueous Mn(ll) complexes, particularly those with non-carboxylated ligands such as microbial siderophores, may be stable in soil and aquatic environments. In this paper, we determine the stability constants for Mn(ll) and Mn(lll) complexes with the common trihydroxamate siderophore, desferrioxamine B (DFOB). Base and redox titrations were conducted to determine DFOB conditional protonation constants and conditional stability constants for 1:1 DFOB complexes with Mn(ll) and Mn(lll). The conditional protonation constants agree well with literature values. We determined stability constants for three Mn(ll)-DFOB species and one Mn(lll)-DFOB species at 25 degrees C in 0.1 M NaCl. The Mn(lll) HDFOB+ complex can be formed readily by air-oxidation of Mn(ll)-DFOB. This reaction exhibits pseudo first-order kinetics with a rate coefficient that can be characterized as the product of oxygen concentration with a linear combination of the concentrations of the three Mn(ll)-DFOB complexes. The second-order rate coefficients appearing in this linear combination are 1 to 2 orders of magnitude smaller than that associated with oxidation of the hydrolytic species Mn(OH)(0)2. The Mn(lll)HDFOB+ complex is stable for pH in the range of 7.0-11.3; but, at pH < 7.0 it decomposes by internal electron transfer, yielding oxidized DFOB products and Mn(ll). For p[H+] > 11.3, the complex degrades by disproportionation, yielding Mn(ll) and solid MnO2. This range of pH stability supports the hypothesis that aqueous Mn(lll) may play a vital role in the biogeochemical cycling of not only manganese, but also other elements, such as carbon, sulfur, nitrogen, oxygen, and redox-active metals.     

Inhibition of insulin degradation by nonsuppressible insulin-like activity

Nonsuppressible insulin-like activity, provided by three sources, was evaluated for its effect on the proteolytic degradation of insulin utilizing insulin protease obtained from rat liver homogenate as well as liver cell membranes. All three preparations of nonsuppressible insulin-like activity were found to be competitive inhibitors of insulin degradation. In addition human plasma was fractionated yielding an acetone precipitate which was found to have nonsuppressible insulin-like activity and to be a competitive inhibitor of insulin protease.     

America's urban challenge: fiscal crisis or entrepreneurial opportunity

This paper briefly discusses the new urban ‘entrepreneurial’ dynamics occurring in city arenas across the USA. These new urban dynamics are already changing the way US cities are addressing their urban demands. In this process they are having far reaching consequences on the future shape and condition of urban America.     

Taxonomies and correlates of physique.

"Subjective" and "objective" taxonomies of human physique are more or less correlated among themselves and in different degrees with an array of nonanthropometric variables of interest to psychologists. There is probably closer corespondence between anthropometric data and function than is reported in the literature. The most advanced taxonomies can be improved, principally by: greater differentiation of predictive anatomical variables; increasing the scope of the systems to include such elements as internal body organs, the differential influences of nutrition, and age; and through use of refined multivariate statistical techniques for representing and analyzing complex data. (3-p. ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Selective labeling of proteins by using protein farnesyltransferase

The challenging task of identifying and studying protein function has been greatly aided by labeling proteins with reporter groups. Here, we present a strategy that utilizes an enzyme that labels a four-residue sequence appended onto the C terminus of a protein, with an alkyne-containing substrate. By using a bio-orthogonal cycloaddition reaction, a fluorophore that carried an azide moiety was then covalently coupled to the alkyne appended on the protein. FRET was used to calculate a F?rster (R) distance of 40 A between the eGFP chromophore and the newly appended Texas Red fluorophore. This experimental value is in good agreement with the predicted R value determined by using molecular modeling. The small recognition tag, the high specificity of the enzyme, and the orthogonal nature of the derivatization reaction will make this approach highly useful in protein chemistry.