Direct observation of charge inversion by multivalent ions as a universal electrostatic phenomenon

We have directly observed reversal of the polarity of charged surfaces in water upon the addition of tri- and quadrivalent ions using atomic force microscopy. The bulk concentration of multivalent ions at which charge inversion reversibly occurs depends only very weakly on the chemical composition, surface structure, size and lipophilicity of the ions, but is dominated by their valence. These results support the theoretical proposal that spatial correlations between ions are the driving mechanism behind charge inversion.Comment: submitted to PRL, 26-04-2004 Changed the presentation of the theory at the end of the paper. Changed small error in estimate of prefactor ("w" in first version) of equation

Spin-orbit coupling and ESR theory for carbon nanotubes

A theoretical description of ESR in 1D interacting metals is given, with primary emphasis on carbon nanotubes. The spin-orbit coupling is derived, and the resulting ESR spectrum is analyzed by field theory and exact diagonalization. Drastic differences in the ESR spectra of single-wall and multi-wall nanotubes are found. For single-wall tubes, the predicted double peak spectrum could reveal spin-charge separation.Comment: 4 pages, 1 figure, final version to appear in PR

Dissemination of Evidence-based Atypical Antipsychotic Information to Nursing Homes

Background: Accumulating evidence demonstrates minimal benefit and increased risk of off-label use of atypical antipsychotic medications for dementia-related behaviors. Optimal strategy for disseminating evidence-based guides to nursing home (NH) stakeholders is unclear. Our objective is to describe the impact of differing dissemination efforts in Connecticut NHs. Methods: Forty-three Connecticut NHs were randomized to one of 3 arms receiving incrementally intensive dissemination strategies of the Agency for Healthcare Research and Quality Comparative Effectiveness Review Summary Guide on the off-label use of atypical antipsychotic drugs, which was included in a toolkit informed by a needs assessment of NHs. All NHs received the paper-based toolkit and notifications regarding the online toolkit. Additionally, Arm 2 received individualized quarterly audit and feedback reports with atypical antipsychotic prescribing rates; Arm 3 received in-person educational visits and audit and feedback reports. Toolkit reach was assessed using interviews with NH leadership and staff. Online toolkit use was assessed using Google analytics. Results: Eighty leaders and 222 direct care staff were interviewed. Leadership and direct care staff in Arm 3 NHs were more likely to be familiar with the toolkit that those in Arm 1 (p=0.008) and Arm 2 (p Conclusions: Intensive dissemination, using multi-pronged approach including academic detailing and direct care staff trainings, appeared to be associated with higher familiarity with paper-based toolkit, but not Internet-based use of the toolkit in the NH setting

Direct measurement of antiferromagnetic domain fluctuations

Measurements of magnetic noise emanating from ferromagnets due to domain motion were first carried out nearly 100 years ago and have underpinned much science and technology. Antiferromagnets, which carry no net external magnetic dipole moment, yet have a periodic arrangement of the electron spins extending over macroscopic distances, should also display magnetic noise, but this must be sampled at spatial wavelengths of order several interatomic spacings, rather than the macroscopic scales characteristic of ferromagnets. Here we present the first direct measurement of the fluctuations in the nanometre-scale spin- (charge-) density wave superstructure associated with antiferromagnetism in elemental Chromium. The technique used is X-ray Photon Correlation Spectroscopy, where coherent x-ray diffraction produces a speckle pattern that serves as a "fingerprint" of a particular magnetic domain configuration. The temporal evolution of the patterns corresponds to domain walls advancing and retreating over micron distances. While the domain wall motion is thermally activated at temperatures above 100K, it is not so at lower temperatures, and indeed has a rate which saturates at a finite value - consistent with quantum fluctuations - on cooling below 40K. Our work is important because it provides an important new measurement tool for antiferromagnetic domain engineering as well as revealing a fundamental new fact about spin dynamics in the simplest antiferromagnet.Comment: 19 pages, 4 figure

Quantum Interference Effects in Electronic Transport through Nanotube Contacts

Quantum interference has dramatic effects on electronic transport through nanotube contacts. In optimal configuration the intertube conductance can approach that of a perfect nanotube ($4e^2/h$). The maximum conductance increases rapidly with the contact length up to 10 nm, beyond which it exhibits long wavelength oscillations. This is attributed to the resonant cavity-like interference phenomena in the contact region. For two concentric nanotubes symmetry breaking reduces the maximum intertube conductance from $4e^2/h$ to $2e^2/h$. The phenomena discussed here can serve as a foundation for building nanotube electronic circuits and high speed nanoscale electromechanical devices

Viscoelastic Depinning of Driven Systems: Mean-Field Plastic Scallops

We have investigated the mean field dynamics of an overdamped viscoelastic medium driven through quenched disorder. The model introduced incorporates coexistence of pinned and sliding degrees of freedom and can exhibit continuous elastic depinning or first order hysteretic depinning. Numerical simulations indicate mean field instabilities that correspond to macroscopic stick-slip events and lead to premature switching. The model is relevant for the dynamics of driven vortex arrays in superconductors and other extended disordered systems.Comment: 4 pages, 2 figure

Wave function mapping conditions in Open Quantum Dots structures

We discuss the minimal conditions for wave function spectroscopy, in which resonant tunneling is the measurement tool. Two systems are addressed: resonant tunneling diodes, as a toy model, and open quantum dots. The toy model is used to analyze the crucial tunning between the necessary resolution in current-voltage characteristics and the breakdown of the wave functions probing potentials into a level splitting characteristic of double quantum wells. The present results establish a parameter region where the wavefunction spectroscopy by resonant tunneling could be achieved. In the case of open quantum dots, a breakdown of the mapping condition is related to a change into a double quantum dot structure induced by the local probing potential. The analogy between the toy model and open quantum dots show that a precise control over shape and extention of the potential probes is irrelevant for wave function mapping. Moreover, the present system is a realization of a tunable Fano system in the wave function mapping regime.Comment: 6 pages, 6 figure

Understanding Antipsychotic Drug Use in the Nursing Home Setting

Introduction: The increasing prevalence of antipsychotic medication use in residents of nursing homes (NH) in the absence of psychiatric diagnoses is concerning. To address these concerns, it is essential to explore how these medications are being prescribed and managed in the NH setting. Our objectives were to understand the decision-making process that influences prescribing and factors that trigger administration of antipsychotic medications to residents with dementia in NHs and to explore why residents remain on antipsychotic medications over an extended period of time. Methods: Interviews with prescribers, caregivers, and family members, on-site observations in study facilities, and review of NH resident medical records. Facilities were selected to obtain a diverse sample of NHs. Results: 204 NH residents with dementia in 26 facilities distributed across five selected Centers for Medicaid and Medicare Services regions were included. Problematic behaviors were the dominant reasons offered as influencing prescribing of antipsychotic medications. Providers indicated that they chose an antipsychotic, rather than another drug class, because they believed that antipsychotic medications were more likely to be effective. There was no standard approach to taper attempts. Family members identified a lack of communication as a barrier to their involvement in decision-making. Conclusions: There is widespread perception that antipsychotic medications are effective and beneficial in managing problematic behaviors in NH residents with dementia. Little attention is given to planning for antipsychotic tapering or discontinuation. There may be opportunities to involve family members more fully in decision-making around the use of antipsychotic medications

Resveratrol Reverses Endothelial Colony-Forming Cell Dysfunction in Adulthood in a Rat Model of Intrauterine Growth Restriction.

Individuals born after intrauterine growth restriction (IUGR) are at risk of developing cardiovascular diseases (CVDs). Endothelial dysfunction plays a role in the pathogenesis of CVDs; and endothelial colony-forming cells (ECFCs) have been identified as key factors in endothelial repair. In a rat model of IUGR induced by a maternal low-protein diet, we observed an altered functionality of ECFCs in 6-month-old males, which was associated with arterial hypertension related to oxidative stress and stress-induced premature senescence (SIPS). Resveratrol (R), a polyphenol compound, was found to improve cardiovascular function. In this study, we investigated whether resveratrol could reverse ECFC dysfunctions in the IUGR group. ECFCs were isolated from IUGR and control (CTRL) males and were treated with R (1 μM) or dimethylsulfoxide (DMSO) for 48 h. In the IUGR-ECFCs, R increased proliferation (5'-bromo-2'-deoxyuridine (BrdU) incorporation, p < 0.001) and improved capillary-like outgrowth sprout formation (in Matrigel), nitric oxide (NO) production (fluorescent dye, p < 0.01), and endothelial nitric oxide synthase (eNOS) expression (immunofluorescence, p < 0.001). In addition, R decreased oxidative stress with reduced superoxide anion production (fluorescent dye, p < 0.001); increased Cu/Zn superoxide dismutase expression (Western blot, p < 0.05); and reversed SIPS with decreased beta-galactosidase activity (p < 0.001), and decreased p16 <sup>ink4a</sup> (p < 0.05) and increased Sirtuin-1 (p < 0.05) expressions (Western blot). No effects of R were observed in the CTRL-ECFCs. These results suggest that R reverses long-term ECFC dysfunctions related to IUGR

Knowledge of and perceived need for evidence-based educational materials about antipsychotic medication safety by nursing home staff

Background: Given the widespread overuse of antipsychotic medications among US nursing home (NH) residents, we sought to identify knowledge of and perceived need for the AHRQ Comparative Effectiveness Research Summary Guide (CERSG) “Off-Label Use of Atypical Antipsychotic Drugs”. Methods: We conducted a baseline needs assessment with 12 NHs participating in a randomized controlled trail evaluating evidence dissemination strategies. Using a mixed method approach, we conducted in-depth assessments of knowledge, attitudes, and practice behavior using telephone interviews with NH leadership (administrators, directors of nursing [DON], and medical directors), and questionnaires with NH leadership, consultant pharmacists and direct care staff. Interviews were transcribed, verbatim responses were coded independently by 2 project staff. The coding scheme was revised after each round until substantial agreement (85%) was reached. Results: Interviews revealed that 70% of medical directors and 46% of DON and administrators believed that antipsychotics decreased agitation and controlled harmful behavior; 50% of medical directors and 7% of DONs & administrators reported knowledge of the increased risk of morbidity and mortality due to atypical antipsychotics. Half of administrators and DONs expressed interest in receiving information for NH staff pertaining to understanding dementia and dementia-related behaviors, 42% believed families would benefit from information about antipsychotic use for dementia-related behaviors. Questionnaire results were similar. When leaders were asked to list any risks associated with antipsychotic use for residents with dementia, only 17% reported death as a possible adverse event; licensed nursing staff (RN and LPNs) reported death 5% of the time. Over half of consultant pharmacists identified that their biggest barrier to improving medication use in challenging NHs was physician resistance to accepting recommendations. Conclusions: The responses of the NH leaders, staff and consultant pharmacists suggest widespread knowledge gaps regarding antipsychotic benefits and risks, and suggest a need for increase evidence dissemination and broad organizational change