Dynamics and mechanics below the glass transition: The non-equilibrium state

There is much interest in the dynamics of glass-forming systems above the glass transition temperature. However, in many applications the behavior of the systems needs to be understood in the glass-transition T_g range and particularly in the non-equilibrium state. We present a set of empirical observations for the dynamics of material behaviors near to, but below the glass transition for polymer glass formers and outline a “minimal” set of requirements that might be expected of computer simulations in the non-equilibrium glass near to T_g. The survey includes the kinetics and nonlinearity of the structural (volume or enthalpy) recovery of the glass and its impact on the mechanical response (physical aging). These are presented with the thought that computer simulations may well be able to provide insights to the origins of an extremely complicated set of experimental observations.

Additionally, we present some results of glass formation of simple liquids constrained to nanometer size pores with the expectation that such experiments may be readily simulated because of the small number of molecules in such pores.     

A Web-Based Instructional Module for Teaching Middle School Students Engineering Design with Simple Machines*

The current work describes an instructional module that emphasizes integrative design using six simple machines: the lever, the wheel and axle, the pulley, the inclined plane, the screw, and the gear. The emphasis of this module is to have students investigate the underlying scientific and mathematical properties of the “machines,” and then integrate this knowledge to design creative solutions to problems. This simple machines module makes use of an original web-based multimedia learning environment as well as off-line, hands-on building activities with the LEGO^TM Technic I set. The current instructional module was used in a pilot study in an Introduction to Engineering class, and we include preliminary results from this study.     

Assessment of the dysexecutive syndrome in schizophrenia

BACKGROUND: Cognitive neuropsychological theories hypothesize a role for frontal lobe executive deficits in the aetiology of schizophrenic symptoms. The study examined the performance of a schizophrenic group on the Behavioural Assessment of the Dysexecutive Syndrome (BADS; Wilson et al. 1996), a test battery which assesses the 'everyday' difficulties associated with the dysexecutive syndrome. Performance of the schizophrenics was contrasted with that of brain injured and healthy volunteer groups. METHODS: Matched groups of 31 schizophrenic patients, 35 patients with brain injuries and 26 healthy volunteers were administered the BADS. Patients were also given tests of general intelligence and memory. Patients and their relatives/carers also completed a questionnaire rating day-to-day failures of executive functioning. RESULTS: Schizophrenic and brain-injured patients showed impairment on the BADS, compared to healthy controls. There were no significant differences between the two patient groups. Significant impairment was found in a subgroup of 16 schizophrenics who showed otherwise intact general intellectual functioning, suggesting the existence of a specific executive deficit. Among the schizophrenic patient group there was evidence of a dissociation between executive and memory impairments. A significant correlation existed between performance on the BADS and relatives ratings of executive problems for the brain injured group, but not for the schizophrenic group. CONCLUSIONS: The BADS is a useful tool for identifying executive deficits in people with a diagnosis of schizophrenia, especially those who are otherwise generally intellectually intact. This is particularly important in the context of rehabilitation and community transition programmes.     

Trends in cancer mortality in Kanawha County, West Virginia, 1950-1984.

There has been much concern recently about possible adverse health effects related to exposure to toxic chemicals among residents of Kanawha County in southern West Virginia. An epidemiological study of trends in cancer mortality from 1950-1984 among the general population of Kanawha County in southern West Virginia was mounted. Cabell County, West Virginia was chosen to be a comparison county for Kanawha in addition to West Virginia and the total United States. The cancer mortality rates for white males and females were calculated using NCHS mortality data and Census Bureau population data available on the Mortality and Population Data System (MPDS) at the University of Pittsburgh. Mortality rates for cancer in Kanawha and Cabell Counties were evaluated over the time period 1950-1984 with an age-period-cohort (APC) analysis. In this analysis, poisson regression models were fit using the statistical program GLIM (Generalized Linear Models) to determine the separate effects of age, period of death, and birth cohort on the specific cancers of interest (lung, liver, bladder, CNS, leukemia, lympho-reticulosarcoma, all cancers). There were no significant county differences for cancer death rates between Kanawha and Cabell Counties except for leukemia among white males [O.R. = 1.27, 95% (C.I. = 1.03-1.6)], and for lympho-reticulosarcoma [O.R. = 1.66(1.24-2.07)], suggesting a possible occupational exposure. For leukemia, aleukemia, the effect observed seems to have declined. In contrast, the elevation of lympho-reticulosarcoma rates has remained in recent years (1970-1984).     

QT dispersion and risk factors for sudden cardiac death in patients with hypertrophic cardiomyopathy

Growth hormone (GH) treatment is associated with a reduction in fat mass in healthy and GH-deficient (GHD) subjects. This is mainly mediated via a direct GH action on adipose cells and stimulation of lipolysis. Leptin is secreted from adipose tissue and may be involved in signaling information about adipose tissue stores to the brain. Hormonal regulation of leptin is still not fully elucidated, and in the present study, we investigated both the long-term (4-month) and short-term (28-hour) GH effects on serum leptin and leptin gene expression in subcutaneous adipose tissue. In GHD adults (n = 24), leptin correlated with most estimates of adiposity (r = .62 to .86), as previously found in healthy subjects. However, no correlation was observed with intraabdominal fat determined by computed tomographic (CT) scan (INTRA-CT). GH treatment for 4 months had no independent effect on either serum leptin or leptin gene expression. In a short-term study, we found that fasting gradually reduced leptin levels in both healthy men and GHD adults, with a maximum reduction of 58% to 60% (P < .01) after 31 hours. No independent effect of GH suppression or GH substitution on serum leptin was found during fasting. Adipose tissue leptin mRNA correlated with serum leptin (r = .51, P < .01) and the body mass index ([BMI] r = .55, P < .05). Serum leptin levels and gene expression were significantly higher in women compared with men (26.6 +/- 5.8 v 10.0 +/- 1.30 ng/mL, P < .05). However, in regression analysis accounting for the gender differences in subcutaneous femoral adipose tissue (FEM-CT), the difference in serum leptin disappeared, indicating that subcutaneous femoral fat or factors closely related to femoral fat (eg, sex hormones) may be causal factors for the gender difference in leptin.     

ABT-089 [2-methyl-3-(2-(S)-pyrrolidinylmethoxy)pyridine]: I. A potent and selective cholinergic channel modulator with neuroprotective properties

Lactate dehydrogenase from the malarial parasite Plasmodium falciparum has many amino acid residues that are unique compared to any other known lactate dehydrogenase. This includes residues that define the substrate and cofactor binding sites. Nevertheless, parasite lactate dehydrogenase exhibits high specificity for pyruvic acid, even more restricted than the specificity of human lactate dehydrogenases M4 and H4. Parasite lactate dehydrogenase exhibits high catalytic efficiency in the reduction of pyruvate, kcat/Km = 9.0 x 10(8) min(-1) M(-1). Parasite lactate dehydrogenase also exhibits similar cofactor specificity to the human isoforms in the oxidation of L-lactate with NAD+ and with a series of NAD+ analogs, suggesting a similar cofactor binding environment in spite of the numerous amino acid differences. Parasite lactate dehydrogenase exhibits an enhanced kcat with the analog 3-acetylpyridine adenine dinucleotide (APAD+) whereas the human isoforms exhibit a lower kcat. This differential response to APAD+ provides the kinetic basis for the enzyme-based detection of malarial parasites. A series of inhibitors structurally related to the natural product gossypol were shown to be competitive inhibitors of the binding of NADH. Slight changes in structure produced marked changes in selectivity of inhibition of lactate dehydrogenase. 7-p-Trifluoromethylbenzyl-8-deoxyhemigossylic acid inhibited parasite lactate dehydrogenase, Ki = 0.2 microM, which was 65- and 400-fold tighter binding compared to the M4 and H4 isoforms of human lactate dehydrogenase. The results suggest that the cofactor site of parasite lactate dehydrogenase may be a potential target for structure-based drug design.     

Feminine dimension in the play fighting of rats (Rattus norvegicus) and its defeminization neonatally by androgens.

In rats, juvenile males engage in more play fighting (a male-typical behavior) than do juvenile females, and this difference is based on perinatal influences of androgens. The authors show that there are qualitative and quantitative differences between the sexes in the type of defensive responses and their manner of execution. In defensive responses, rats try to avoid having their napes contacted by their partner's snout. The sex differences arise from females' greater response distance; that is, females responded to an approach when the partner's snout was further from the nape. This permits females to use different defensive responses and to use them more successfully. This greater response distance is defeminized by the neonatal administration of testosterone propionate. Findings suggest that play fighting in rats has both male- and female-typical features and that these are, at least in part, influenced perinatally by androgens. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An adaptive feed strategy for a center-break reduction cell

An adaptive estimator of alumina concentration was developed for an industrial 140 kA prebake center-break fed aluminum reduction cell. The estimator employs a simple nonlinear model of an aluminum cell based on a mass balance of alumina and the correlation between alumina concentration and ohmic resistance. An extended Kalman filter is used to provide a best estimate of alumina concentration, and the covariance of the measurement noise is recursively updated using a forgetting factor. The estimator was tested using both simulated and real data, and it was shown that the estimator could be used as the basis of a feed-control strategy for similar cells.     

Mechanism of laser assisted field evaporation from insulating oxides

To explain the recent successful three-dimensional atom probe (3DAP) analyses of insulating oxides by laser assisted field evaporation, we investigated the mechanism of the laser-induced field evaporation of oxides by ab initio calculations. The calculated potential energy surfaces (PESs) for the ground and excited states indicated that the activation barrier height for field evaporation is substantially reduced by the accumulation of holes near the tip apex. This would make the direct electronic excitation possible to promote field evaporation along with thermal excitation. These theoretical calculations are supported by experimental observations.