Strong stability of elastic control systems with dissipative saturating feedback

We will consider, with a focus on saturating feedback control laws, two problems associated with damping in a bounded acoustic cavity . Our objective is to verify (compare (Discrete Continuous Dynamical Systems 7 (2001) 319, Math. Control Signals Systems 2 (1989) 265) that these are strongly stable: for every finite-energy solution, the acoustic energy goes to zero as t→∞. We will, in each case, formulate the problem in terms of a contraction semigroup of nonlinear operators on an appropriate Hilbert space and compare this with the corresponding semigroups without saturation—following Avalos and Lasiecka (Semigroup Forum 57 (1998) 278) in using the spectral methods of Arendt and Batty (Trans. Amer. Math. Soc. 8 (1988) 837) to show strong stabilization for those linear semigroups.     

Sex differences in olfactory identification and Wisconsin Card Sorting performance in schizophrenia: relationship to attention and verbal ability

We investigated the hypothesis that different prefrontal brain systems (i.e., dorsal vs. ventral) and sex contribute differentially to cognitive deficit in schizophrenia. Performance was assessed among clinically stable, chronic schizophrenic outpatients and matched normal control subjects on olfactory identification [on the University of Pennsylvania Smell Identification Test (UPSIT)] and on executive functions [using the Wisconsin Card Sorting Test (WCST)]. Patients were impaired on both tests compared to controls, and male schizophrenics were impaired on the WCST compared to female schizophrenics. The pattern of results suggests that gender differences on the UPSIT are mildly accentuated in schizophrenia. The data support our previous study indicating that UPSIT performance is largely independent of the executive or attentional deficits typically associated with schizophrenia, with the exception of verbal ability. Further research with larger samples is required to test the hypothesis that there is a severely impaired subgroup of male patients with diffuse prefrontal dysfunctions.     

An Atomistic Tomographic Study of Oxygen and Hydrogen Atoms and their Molecules in CVD Grown Graphene

The properties and growth processes of graphene are greatly influenced by the elemental distributions of impurity atoms and their functional groups within or on the hexagonal carbon lattice. Oxygen and hydrogen atoms and their functional molecules (OH, CO, and CO₂) positions' and chemical identities are tomographically mapped in three dimensions in a graphene monolayer film grown on a copper substrate, at the atomic part‐per‐million (atomic ppm) detection level, employing laser assisted atom‐probe tomography. The atomistic plan and cross‐sectional views of graphene indicate that oxygen, hydrogen, and their co‐functionalities, OH, CO, and CO₂, which are locally clustered under or within the graphene lattice. The experimental 3D atomistic portrait of the chemistry is combined with computational density‐functional theory (DFT) calculations to enhance the understanding of the surface state of graphene, the positions of the chemical functional groups, their interactions with the underlying Cu substrate, and their influences on the growth of graphene.     

Dynamic instabilities and stabilization methods in distributedreal-time scheduling of manufacturing systems

The paper concerns policies for sequencing material through a flexible manufacturing system to meet desired production goals for each part type. The authors demonstrate by examples that cyclic material flow and certain distributed scheduling policies can lead to instability in the sense that the required buffer levels are unbounded. This can be the case even when the set-up times for changing part types are zero. Sufficient conditions are then derived under which a class of distributed policies is stable. Finally, a general supervisory mechanism is presented which will stabilize any scheduling policy (i.e. maintain bounded buffer sizes at all machines) while satisfying the desired production rates     

Preventive services in a Medicare managed care environment

The results of a four year demonstration project of preventive services for Medicare managed care enrollees suggest that health promotion programs can impact health behaviors and outcomes. The study provided selected preventive services to 1,800 Medicare enrollees in a managed care environment. Participants were randomly assigned to control and experimental groups with the experimental group receiving an intervention service package and the control group usual care. The results included enhanced health behavior practices, lower depression, and higher immunization rates among those individuals in the experimental group. This study suggests that selected preventive services can be provided in a managed care environment to Medicare enrollees with likely positive health status and utilization outcomes.     

Diastolic dysfunction and altered energetics in the alphaMHC403/+ mouse model of familial hypertrophic cardiomyopathy

An arginine to glutamine missense mutation at position 403 of the beta-cardiac myosin heavy chain causes familial hypertrophic cardiomyopathy. Here we study mice which have this same missense mutation (alphaMHC403/+) using an isolated, isovolumic heart preparation where cardiac performance is measured simultaneously with cardiac energetics using 31P nuclear magnetic resonance spectroscopy. We observed three major alterations in the physiology and bioenergetics of the alphaMHC403/+ mouse hearts. First, while there was no evidence of systolic dysfunction, diastolic function was impaired during inotropic stimulation. Diastolic dysfunction was manifest as both a decreased rate of left ventricular relaxation and an increase in end-diastolic pressure. Second, under baseline conditions alphaMHC403/+ hearts had lower phosphocreatine and increased inorganic phosphate contents resulting in a decrease in the calculated value for the free energy released from ATP hydrolysis. Third, hearts from alphaMHC403/+ hearts that were studied unpaced responded to increased perfusate calcium by decreasing heart rate approximately twice as much as wild types. We conclude that hearts from alphaMHC403/+ mice demonstrate work load-dependent diastolic dysfunction resembling the human form of familial hypertrophic cardiomyopathy. Changes in high-energy phosphate content suggest that an energy-requiring process may contribute to the observed diastolic dysfunction.     

Are there sex differences in neuropsychological functions among patients with schizophrenia?

OBJECTIVE: Studies of sex differences in neuropsychological performance in schizophrenia report inconsistent results, due in part to methodological artifacts. The study presented here was specifically designed to examine sex differences in neuropsychological performance. It was hypothesized that schizophrenic women would exhibit fewer neuropsychological deficits than schizophrenic men and that their performance would be more similar to that of normal women than schizophrenic men's performance would be to that of normal men. METHOD: Thirty-one outpatients with DSM-III-R-defined schizophrenia were systematically sampled from an extensive service network serving a large urban catchment area for seriously mentally ill persons. Twenty-seven normal comparison subjects were matched within sex on the basis of age, parental socioeconomic status, ethnicity, and handedness. An extensive neuropsychological test battery was administered, and multivariate analysis of variance was used to test for the effects of sex and group and sex-by-group interactions. RESULTS: Male patients were significantly impaired across all functions in comparison with normal male subjects and on tests of attention, verbal memory, and executive functions in comparison with female patients. Female patients performed significantly worse than female normal comparison subjects only on tests of attention, executive functions, visual memory, and motor functions. CONCLUSIONS: The findings suggest that women with schizophrenia may be less vulnerable to particular cognitive deficits, especially those involving verbal processing, than schizophrenic men.     

The Bjornstad syndrome (sensorineural hearing loss and pili torti) disease gene maps to chromosome 2q34-36

We report that the Bjornstad syndrome gene maps to chromosome 2q34-36. The clinical association of sensorineural hearing loss with pili torti (broken, twisted hairs) was described >30 years ago by Bjornstad; subsequently, several small families have been studied. We evaluated a large kindred with Bjornstad syndrome in which eight members inherited pili torti and prelingual sensorineural hearing loss as autosomal recessive traits. A genomewide search using polymorphic loci demonstrated linkage between the disease gene segregating in this kindred and D2S434 (maximum two-point LOD score = 4.98 at theta = 0). Haplotype analysis of recombination events located the disease gene in a 3-cM region between loci D2S1371 and D2S163. We speculate that intermediate filament and intermediate filament-associated proteins are good candidate genes for causing Bjornstad syndrome.