Enhancement of proton acceleration by hot-electron recirculation in thin foils irradiated by ultraintense laser pulses.

MeV-proton production from solid targets irradiated by 100-fs laser pulses at intensities above 1x10(20) W cm(-2) has been studied as a function of initial target thickness. For foils 100 microm thick the proton beam was characterized by an energy spectrum of temperature 1.4 MeV with a cutoff at 6.5 MeV. When the target thickness was reduced to 3 microm the temperature was 3.2+/-0.3 MeV with a cutoff at 24 MeV. These observations are consistent with modeling showing an enhanced density of MeV electrons at the rear surface for the thinnest targets, which predicts an increased acceleration and higher proton energies.

Molecular wires, switches, and memories.

Design and measurements of molecular wires, switches, and memories offer an increased device capability with reduced elements. We report: Measurements on through-bond electronic transport properties of nanoscale metal-1,4-phenylene diisocyanide-metal junctions are reported, where nonohmic thermionic emission is the dominant process, with isocyanide-Pd showing the lowest thermionic barrier of 0.22 eV; robust and large reversible switching behavior in an electronic device that utilizes molecules containing redox centers as the active component, exhibiting negative differential resistance (NDR) and large on-off peak-to-valley ratio (PVR) are realized; erasable storage of higher conductivity states in these redox-center-containing molecular devices are observed; and a two-terminal electronically programmable and erasable molecular memory cell with long bit retention time is demonstrated.

Conductance switching in single molecules through conformational changes.

We tracked over time the conductance switching of single and bundled phenylene ethynylene oligomers isolated in matrices of alkanethiolate monolayers. The persistence times for isolated and bundled molecules in either the ON or OFF switch state range from seconds to tens of hours. When the surrounding matrix is well ordered, the rate at which the inserted molecules switch is low. Conversely, when the surrounding matrix is poorly ordered, the inserted molecules switch more often. We conclude that the switching is a result of conformational changes in the molecules or bundles, rather than electrostatic effects of charge transfer.

Synthesis and preliminary testing of molecular wires and devices.

Presented here are several convergent synthetic routes to conjugated oligo(phenylene ethynylene)s. Some of these oligomers are free of functional groups, while others possess donor groups, acceptor groups, porphyrin interiors, and other heterocyclic interiors for various potential transmission and digital device applications. The syntheses of oligo(phenylene ethynylene)s with a variety of end groups for attachment to numerous metal probes and surfaces are presented. Some of the functionalized molecular systems showed linear, wire-like, current versus voltage (I(V)) responses, while others exhibited nonlinear I(V) curves for negative differential resistance (NDR) and molecular random access memory effects. Finally, the syntheses of functionalized oligomers are described that can form self-assembled monolayers on metallic electrodes that reduce the Schottky barriers. Information from the Schottky barrier studies can provide useful insight into molecular alligator clip optimizations for molecular electronics.

Seeking care for nonurgent medical conditions in the emergency department: through the eyes of the patient.

INTRODUCTION: The policy goal of shifting nonurgent visits from the emergency department to nonemergency health care settings is commonly devised, planned, and implemented without considering patients' perspectives. The purpose of this study was to gain an understanding of the context in which patients choose to seek health care in an emergency department. Human science provided the framework for this exploratory descriptive research study. METHODS: This study was conducted at an urban, university emergency department in Denver, Colo. Uninsured adult patients triaged as nonurgent who were being discharged home were eligible to participate. Eligible patients from 15 randomly selected shifts were asked to participate. Following their ED visit, open-ended interviews began with the question, "Can you tell me the story, or the chain of events, that led to your coming to the emergency department today?" Each interview was audiotaped. Transcripts were analyzed to identify common themes. Patients also rated their severity of illness from 1 (not severe) to 5 (life-threatening), and they rated their satisfaction with the health care they received from 1 (not satisfied) to 5 (extremely satisfied). RESULTS: The 30 study participants ranged in age from 17 to 60 years; 22 participants (73%) were women. Most patients (73%) rated their severity of illness as 3 or less and their satisfaction with the health care they received as 4 or more (83%). Five themes for seeking care were identified: (1) toughing it out, (2) symptoms overwhelming self-care measures, (3) calling a friend, (4) nowhere else to go, and (5) convenience. Despite the fact that the patients had nonurgent medical problems, their stories revealed that distress in their lives had influenced their need for emergency care. CONCLUSIONS: Access was prominent in the minds of uninsured patients seeking ED care for nonurgent medical diagnoses. Typically, patients did not perceive themselves as having an urgent problem, had been unsuccessful in gaining access to alternative non-ED health care settings, and found the emergency department to be a convenient and quality source of health care. The patients' stories relayed a context for ED visits that goes beyond medical diagnoses. This perspective has important implications for quality care delivery and for including patients in planning ways to access emergency health care.

The Chatt-Dewar-Duncanson model revisited: X-ray, DFT and NMR studies of rhodium-alkene binding--deviations from structural ideality.

An analysis has been made of deviations from ideal centrosymmetric bonding of alkenes to transition metals in square-planar complexes. Three separate approaches have been employed. Firstly, the geometries obtained for a series of X-ray crystal structures of monosubstituted rhodium-alkene complexes have been obtained. Secondly, DFT computations on closely related rhodium-alkene complexes are reported. Thirdly. the data have been augmented by recourse to the crystal structure serach and retrieval file (CSSR) database to retrieve the X-ray data for square-planar ethene and monosubstituted alkene complexes. The results obtained from these analyses provide a consistent picture. Two distortions from ideality are important: twisting of the alkene about the axis between the metal (M) and the alkene centroid and rolling of the alkene around a cylinder enclosing the metal, such that the two C-M bonds remain equal in length. The presence of both of these is verified through both X-ray structure determinations and DFT calculations. For the rolling distortion, there is a relationship between the electronic character of the substituent on the alkene and the direction of roll. The net effect of this is to place the more nucleophilic carbon of the alkene closer to the square plane. The significance of this for the regiochemistry of the Heck reaction is briefly discussed.

Managed care for the medically uninsured: the preliminary experience of CU CARE.

Uninsured Americans often face barriers to or lack continuity of care. Care for this population is often fragmented, expensive and undercompensated. University Hospital in Denver, in partnership with Kaiser Permanente of Colorado, sought to address this problem by developing CU CARE, a managed care demonstration program for the medically uninsured within the University of Colorado Health Sciences Center. This paper describes the evolution and preliminary experience of the CU CARE program. Policy implications for the future of health care delivery to this population are also briefly discussed.

The hypertensive patient in family practice.

BACKGROUND: Hypertension is one of the commonest reasons for visits to family physicians. Left untreated, hypertension and its sequelae can lead to serious morbidity and mortality. Most hypertensive patients have essential hypertension. METHODS: MEDLINE and Index Medicus literature searches of original studies, meta-analyses, and clinical reviews were conducted for the years 1987 to the present to review the latest recommendations on the diagnosis and treatment of hypertension. Background information from articles written before 1987, accessed from cross-reference of the more recent articles, is occasionally cited. RESULTS AND CONCLUSIONS: Based on the reviewed literature, an approach to the diagnosis and treatment of hypertension for the family physician is presented with an emphasis on cost-effectiveness and nonpharmacologic treatment. Nonpharmacologic measures and lifestyle modification should always be part of the treatment plan, especially given the presence or risks of other comorbid conditions (i.e., diabetes and stroke). Coexisting conditions, side-effects, ease of adherence, cost of medication and monitoring, and anti-left ventricular hypertrophy properties should be considered in selecting a pharmaceutical agent to treat hypertension. Several areas of further research, particularly in the areas of cost-effectiveness and outcomes, are needed to refine further the treatment of hypertension.

Visiting the wizard: children's memory for a recurring event.

The development of children's scripts for a recurring event was examined. 24 girls--2.5, 4, and 5.5 years of age--repeatedly experienced an initially novel episode (a trip to the "wizard's room") in a laboratory setting. Based on parents' ratings, the episode was defined as consisting of 26 actions organized into 7 activities. The sequential, spatial, and causal relations among the activities remained constant across episodes. Each child's knowledge of the recurring event was assessed by 4 probe conditions: free recall, prop reenactment, in-context reenactment, and in-context deviations. Results support conclusions that during early stages of script formation: (a) more actions and activities are included with age in children's scripts, (b) causally related activities are sequenced at all ages but temporal ordering is age-related, (c) hierarchical organization of actions within activities emerges gradually over the preschool years, and (d) probe conditions strongly influence performance for the younger but not for the older children.