Measurements of single chain form factors by small-angle neutron scattering from polystyrene blends containing high concentrations of labelled molecules

A series of small angle neutron scattering measurements on blends of normal polystyrene (PSH) and labelled (deuterated) polystyrene (PSD) have been made with concentrations of PSD from 5 to 50 mol %. It is shown that the single chain form factor of the polymer in bulk can be obtained from a single concentration measurement for any concentration of labelled molecules, providing the molecular weights of the parent and labelled molecules are the same and the molecular weight distributions are narrow.     

Characterization and Reconstitution of Human Lipoyl Synthase (LIAS) Supports ISCA2 and ISCU as Primary Cluster Donors and an Ordered Mechanism of Cluster Assembly

Lipoyl synthase (LIAS) is an iron–sulfur cluster protein and a member of the radical S-adenosylmethionine (SAM) superfamily that catalyzes the final step of lipoic acid biosynthesis. The enzyme contains two [4Fe–4S] centers (reducing and auxiliary clusters) that promote radical formation and sulfur transfer, respectively. Most information concerning LIAS and its mechanism has been determined from prokaryotic enzymes. Herein, we detail the expression, isolation, and characterization of human LIAS, its reactivity, and evaluation of natural iron–sulfur (Fe–S) cluster reconstitution mechanisms. Cluster donation by a number of possible cluster donor proteins and heterodimeric complexes has been evaluated. [2Fe–2S]-cluster-bound forms of human ISCU and ISCA2 were found capable of reconstituting human LIAS, such that complete product turnover was enabled for LIAS, as monitored via a liquid chromatography–mass spectrometry (LC–MS) assay. Electron paramagnetic resonance (EPR) studies of native LIAS and substituted derivatives that lacked the ability to bind one or the other of LIAS’s two [4Fe–4S] clusters revealed a likely order of cluster addition, with the auxiliary cluster preceding the reducing [4Fe–4S] center. These results detail the trafficking of Fe–S clusters in human cells and highlight differences with respect to bacterial LIAS analogs. Likely in vivo Fe–S cluster donors to LIAS are identified, with possible connections to human disease states, and a mechanistic ordering of [4Fe–4S] cluster reconstitution is evident.     

Electric Field Enhanced Coalescence of Drops in Liquid Emulsions

Electrical coalescers offer an effective means for decontaminating distillate fuels. Some of the charging mechanisms occurring in this type of coalescer are described.     

Microsomal cytochrome P450-3A4 (CYP3A4) nanobiosensor for the determination of 2,4-dichlorophenol—An endocrine disruptor compound

Cytochrome P450-3A4 (CYP3A4) is a monooxygenase enzyme that plays a major role in the detoxification of bioactive compounds and hydrophobic xenobiotics (e.g. medicines, drugs, environmental pollutants, food supplements and steroids). Physiologically the monooxygenation reactions of this class II, microsomal, b-type heme enzyme, usually requires cytochrome P450 reductase, NADPH. A novel CYP3A4 biosensor system that essentially simplified the enzymatic redox processes by allowing electron transfer between the electrode and the enzyme redox centre to occur, without any need for the physiological redox partners, was developed for the detection of 2,4-dichlorophenol (2,4-DCP), a priority environmental pollutant and an endocrine disruptor. The biosensor, GC/Naf-Co(Sep)³⁺/CYP3A4/Naf, was constructed by encapsulating CYP3A4 in a Nafion-cobalt (III) sepulchrate (Naf-Co(Sep)³⁺) composite film on a glassy carbon (GC) electrode. The responses of the biosensor to 2,4-dichlorophenol, erythromycin (CYP3A4 native substrate) and ketoconazole (CYP 3A4 natural inhibitor) were studied by cyclic and square wave voltammetric techniques. The detection limit (DL) of the biosensor for 2,4-dichlorophenol was 0.043 μg L⁻¹, which is by an order of magnitude lower than the EU limit (0.3 μg L⁻¹) for any pesticide compound in ground water. The biosensor's DL is lower than the U.S. Environmental Protection Agency's drinking water equivalent level (DWEL) value for 2,4-DCP, which is 2 μg L⁻¹.     

Randomized trial of a gatekeeper program for suicide prevention: 1-year impact on secondary school staff.

Gatekeeper-training programs, designed to increase identification and referral of suicidal individuals, are widespread but largely untested. A group-based randomized trial with 32 schools examined impact of Question, Persuade, Refer (QPR) training on a stratified random sample of 249 staff with 1-year average follow-up. To test QPR impact, the authors introduced and contrasted 2 models of gatekeeper-training effects in a population: gatekeeper surveillance and gatekeeper communication. Intent-to-treat analyses showed that training increased self-reported knowledge (effect size [ES] = 0.41), appraisals of efficacy (ES = 1.22), and service access (ES = 1.07). Training effects varied dramatically. Appraisals increased most for staff with lowest baseline appraisals, and suicide identification behaviors increased most for staff already communicating with students about suicide and distress. Consistent with the communication model, increased knowledge and appraisals were not sufficient to increase suicide identification behaviors. Also consistent with the communication model were results from 2,059 8th and 10th graders surveyed showing that fewer students with prior suicide attempts endorsed talking to adults about distress. Skill training for staff serving as "natural gatekeepers" plus interventions that modify students' help-seeking behaviors are recommended to supplement universal gatekeeper training. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Phase separation in a Ni-12.7 at. pct Al alloy at 550 °C

The phase separation at 550 °C in a Ni-12.7 at. pct Al alloy was investigated by means of small angle X-ray scattering, large angle X-ray scattering, electrical resistivity, and transmission electron microscopy. It was found that an abrupt change in the electrical resistivity and small angle scattering occurred within 15 seconds at 550 °C, following quenching from 1060 °C, and transmission electron microscopy confirmed the presence of small nuclei. However, after this period of rapid change, there was an incubation period of about ten hours in which there was minimal net growth of the nuclei. After the incubation period, growth was accelerated. High angle side bands were observed after a few minutes annealing, and their development closely paralleled the growth of the nuclei and precipitate particles at this temperature. For times beyond the incubation period, small angle X-ray scattering diagrams from single crystals became markedly anisotropic, indicating a quasi-regular spatial distribution of particles. The large and rapid change, in both electrical resistivity and in X-ray small angle scattering, observed after annealing at 550 °C of samples quenched from 1060 °C was attributed to the formation of tiny regions of short range ordered Ni₃Al which constitute subcritical nuclei.     

Evidence for different clinical subtypes of type 1 diabetes mellitus: a prospective study

Goal of this study was to compare the quantitative coronary arteriographic (QCA) results obtained with the Philips DCI/ACA analytical software package with those from postmortem casts in an animal experimental setting. Standard digital coronary arteriograms were obtained from 6 mongrel dogs. After the imaging procedure, the dogs were sacrificed and casts were made of the coronary trees by filling the vessels with a mixture of radio-opaque barium and silicone gel at a fixed pressure of 100 mmHg. Vessel diameters were measured from the digital arteriograms at a total of 118 selected locations with the ACA package. Thin slices were cut from the casts at these same measurement locations and the areas of the cross sections were obtained by manual tracing of the outline of each slice in an approximately 40 x magnified image. From these cross-sectional areas, cast diameters were derived using the formula for circular cross-sections. Cast diameters ranged in size from 0.69 to 3.30 mm. The systematic error between the measurements was found to be 0.058 mm; (p < 0.015) and the standard deviation of the signed difference 0.255 mm; the correlation coefficient was r = 0.91. The largest error sources are supposed to be the slight differences in the selection of identical positions in the X-ray images and on the casts, and the 'out-of-plane' magnification for a number of vessel locations. This postmortem study demonstrates that the diameters of coronary vessels can be measured from digital arteriograms with the DCI/ACA package with a high degree of accuracy and precision.     

Nursing diagnosis: language antithetical to nursing's ontology

The term nursing diagnosis is constructed in male, medical language. As such, it is proposed that it has no legitimacy in nursing discourse as it is antithetical to notions claimed foremost in nursing's ontology. It is also posited that the term 'nursing diagnosis', whilst reinforcing biomedicine, has little or no meaning to many nurses, is not understood by patients and has no justifiable place in health care discourse.     

The delayed anovulation syndrome: influence of hormones and correlation with behaviour

Experiments were conducted to assess the influence of the ovary and various steroid treatments on the development of the delayed anovulatory syndrome (DAS) in female rats. The influence of neonatally administered androgen on the development of ovarian function and female sexual behaviour was studied. It was found that neither the presence of the ovary nor the administration of oestrogen or androgen affected the time-course of the DAS. Doses of androgen which produced the DAS had little effect on female sexual behaviour and there was no evidence of time-dependent changes in sexual behaviour comparable to the time-dependent changes of ovarian physiology observed during the DAS.