Experimental Evidence of Plasmoids in High-ß Magnetic Reconnection.

Magnetic reconnection is a ubiquitous and fundamental process in plasmas by which magnetic fields change their topology and release magnetic energy. Despite decades of research, the physics governing the reconnection process in many parameter regimes remains controversial. Contemporary reconnection theories predict that long, narrow current sheets are susceptible to the tearing instability and split into isolated magnetic islands (or plasmoids), resulting in an enhanced reconnection rate. While several experimental observations of plasmoids in the regime of low-to-intermediate ß (where ß is the ratio of plasma thermal pressure to magnetic pressure) have been made, there is a relative lack of experimental evidence for plasmoids in the high-ß reconnection environments which are typical in many space and astrophysical contexts. Here, we report strong experimental evidence for plasmoid formation in laser-driven high-ß reconnection experiments.

Determining spectral response of the National Ignition Facility particle time of flight diagnostic to x rays.

The Particle Time of Flight (PTOF) diagnostic is a chemical vapor deposition diamond detector used for measuring multiple nuclear bang times at the National Ignition Facility. Due to the non-trivial, polycrystalline structure of these detectors, individual characterization and measurement are required to interrogate the sensitivity and behavior of charge carriers. In this paper, a process is developed for determining the x-ray sensitivity of PTOF detectors and relating it to the intrinsic properties of the detector. We demonstrate that the diamond sample measured has a significant non-homogeneity in its properties, with the charge collection well described by a linear model ax + b, where a = 0.63 ± 0.16 V-1 mm-1 and b = 0.00 ± 0.04 V-1. We also use this method to confirm an electron to hole mobility ratio of 1.5 ± 1.0 and an effective bandgap of 1.8 eV rather than the theoretical 5.5 eV, leading to a large sensitivity increase.

In situ calibration of charged particle spectrometers on the OMEGA Laser Facility using 241Am and 226Ra sources.

Charged particle spectrometry is a critical diagnostic to study inertial-confinement-fusion plasmas and high energy density plasmas. The OMEGA Laser Facility has two fixed magnetic charged particle spectrometers (CPSs) to measure MeV-ions. In situ calibration of these spectrometers was carried out using 241Am and 226Ra alpha emitters. The alpha emission spectrum from the sources was measured independently using surface-barrier detectors (SBDs). The energy dispersion and broadening of the CPS systems were determined by comparing the CPS measured alpha spectrum to that of the SBD. The calibration method significantly constrains the energy dispersion, which was previously obtained through the measurement of charged particle fusion products. Overall, a small shift of 100 keV was observed between previous and the calibration done in this work.

The phase-2 particle x-ray temporal diagnostic for simultaneous measurement of multiple x-ray and nuclear emission histories from OMEGA implosions (invited).

Electron-temperature (Te) measurements in implosions provide valuable diagnostic information, as Te is negligibly affected by residual flows and other non-thermal effects unlike ion-temperature inferred from a fusion product spectrum. In OMEGA cryogenic implosions, measurement of Te(t) can be used to investigate effects related to time-resolved hot-spot energy balance. The newly implemented phase-2 Particle X-ray Temporal Diagnostic (PXTD) utilizes four fast-rise (∼15 ps) scintillator-channels with distinct x-ray filtering. Titanium and stepped aluminum filtering were chosen to maximize detector sensitivity in the 10-20 keV range, as it has been shown that these x rays have similar density and temperature weighting to the emitted deuterium-tritium fusion neutrons (DTn) from OMEGA Cryo-DT implosions. High quality data have been collected from warm implosions at OMEGA. These data have been used to infer spatially integrated Te(t) with <10% uncertainty at peak emission. Nuclear and x-ray emission histories are measured with 10 ps relative timing uncertainty for x rays and DTn and 12 ps for x rays and deuterium-He3 protons (D3Hep). A future upgrade to the system will enable spatially integrated Te(t) with 40 ps time-resolution from cryogenic DT implosions.

Experiments on the dynamics and scaling of spontaneous-magnetic-field saturation in laser-produced plasmas.

In laser-produced high-energy-density plasmas, large-scale strong magnetic fields are spontaneously generated by the Biermann battery effects when temperature and density gradients are misaligned. Saturation of the magnetic field takes place when convection and dissipation balance field generation. While theoretical and numerical modeling provide useful insight into the saturation mechanisms, experimental demonstration remains elusive. In this letter, we report an experiment on the saturation dynamics and scaling of Biermann battery magnetic field in the regime where plasma convection dominates. With time-gated charged-particle radiography and time-resolved Thomson scattering, the field structure and evolution as well as corresponding plasma conditions are measured. In these conditions, the spatially resolved magnetic fields are reconstructed, leading to a picture of field saturation with a scaling of B∼1/L_{T} for a convectively dominated plasma, a regime where the temperature gradient scale (L_{T}) exceeds the ion skin depth.

Extension of charged-particle spectrometer capabilities for diagnosing implosions on OMEGA, Z, and the NIF.

New designs and a new analysis technique have been developed for an existing compact charged-particle spectrometer on the NIF and OMEGA. The new analysis technique extends the capabilities of this diagnostic to measure arbitrarily shaped ion spectra down to 1 MeV with yields as low as 106. Three different designs are provided optimized for the measurement of DD protons, T3He deuterons, and 3He3He protons. The designs are highly customizable, and a generalized framework is provided for optimizing the design for alternative applications. Additionally, the understanding of the detector's response and uncertainties is greatly expanded upon. A new calibration procedure is also developed to increase the precision of the measurements.

Characterizing x-ray transmission through filters used in high energy density physics diagnostics.

We report on the design and implementation of a new system used to characterize the energy-dependent x-ray transmission curve, Θ(E), through filters used in high-energy density physics diagnostics. Using an Amptek X-123-CdTe x-ray spectrometer together with a partially depleted silicon surface barrier detector, both the energy spectrum and total emission of an x-ray source have been accurately measured. By coupling these detectors with a custom PROTO-XRD x-ray source with interchangeable cathodes, accurate characterizations of Θ(E) for filters of varying materials and thicknesses have been obtained. The validity of the technique has been confirmed by accurately reproducing areal densities for high-purity filters with known x-ray transmission properties. In this paper, the experimental setup is described and the results of absorption calibrations performed on a variety of different filters are presented.

A multi-channel x-ray temporal diagnostic for measurement of time-resolved electron temperature in cryogenic deuterium-tritium implosions at OMEGA.

Electron-temperature (Te) measurements in implosions provide valuable diagnostic information, as Te is unaffected by residual flows and other non-thermal effects unlike ion temperature inferred from a fusion product spectrum. In OMEGA cryogenic implosions, measurement of Te(t) can be used to investigate effects related to time-resolved hot-spot energy balance. The proposed diagnostic utilizes five fast-rise (∼15 ps) scintillator channels with distinct x-ray filtering. Titanium and stepped aluminum filtering were chosen to maximize detector sensitivity in the 10 keV-20 keV range, as it has been shown that these x rays have similar density and temperature weighting to the emitted deuterium-tritium fusion neutrons. Initial data collected using a prototype nosecone on the existing neutron temporal diagnostic demonstrate the validity of this diagnostic technique. The proposed system will be capable of measuring spatially integrated Te(t) with 20 ps time resolution and <10% uncertainty at peak emission in cryogenic DT implosions.

Response of CR-39 nuclear track detectors to protons with non-normal incidence.

This paper presents data from experiments with protons at non-normal incidence to CR-39 nuclear track detectors, analyzing the properties of detection efficiency, proton track diameter, track contrast, and track eccentricity. Understanding the CR-39 response to protons incident at an angle is important for designing charged particle detectors for inertial confinement fusion (ICF) applications. This study considers protons with incident energies less than 3 MeV. In this regime, an incident angle of 10° has no effect on CR-39 detection efficiency, and >85% detection efficiency is preserved up through 25° in the range of 1.0 MeV-2.1 MeV. For ICF applications, incident angles above 30° are deemed impractical for detector design due to significant drops in proton detection at all energies. We observe significant reductions in detection efficiency compared to theoretical predictions, particularly at low energies where proton tracks are etched away. The proton track diameter measured by the scan system is observed to decrease with higher incident angles. The track diameters are analyzed with two fitting models, and it is shown that the diameter-energy relation can be fit with the existing models at angles up to 30°. The optical contrast of the tracks tends to increase with the angle, meaning that the tracks are fainter, and a larger increase is observed for higher energies. Eccentricity, a measure of how elongated proton tracks are, increases with the incident angle and drops after the critical angle. The lowest energy tracks remain nearly circular even at higher angles.

MoWeD, a computer program to rapidly deconvolute low resolution electrospray liquid chromatography/mass spectrometry runs to determine component molecular weights.

A computer program is described that can rapidly process low-resolution electrospray liquid chromatography/mass spectrometry (LC/MS) for peptides and proteins and assign molecular weights for observed components. The program first analyzes individual scans using a deconvolution algorithm similar to that previously described by Zhang and Marshall. Results for the entire run are then sorted by mass and those values found in adjacent scans are grouped together. The list of found components can also be compared to a user defined list of target molecular weight values making it easy to compare the results from different analyses. The program also has the capability to process a rolling average of scans that improves the performance when analyzing high molecular weight components. Other program features facilitate closer examination of selected spectra or regions of the chromatogram to check the MoWeD mass assignments. The utility of the program was demonstrated by the analysis of LC/MS data derived from a complex mixture of proteins derived from a bacterial whole cell lysate that had previously been analyzed manually. The MoWeD analysis was 30 times faster and provided a more comprehensive list of the components present.

Healthy People 2000: an assessment based on the Health Status Indicators for the United States and each state.

The Health Status Indicators (HSIs) were developed as part of the Healthy People 2000 process to facilitate the comparison of health status measures at national, State and local levels. In this report, the number of HSIs where the national target has been attained and the number of HSIs that have improved significantly are enumerated for the United States, the District of Columbia, and each State. Based on data for 1998, the United States had attained targets for 6 of the 17 HSIs with national targets. Twenty-three States had attained targets for 9 or more of the HSIs and 37 States had either attained the target for, or had made significant progress on, at least 12 of the indicators. Substantial progress has therefore been made since the Healthy People 2000 National Health Promotion and Disease Prevention Objectives were published in 1991.

An expert virtual instrument approach to the automated, data dependent MS/MS and LC/MS/MS analysis of proteins.

Mass spectrometry has become an indispensable analytical tool for studies related to the structure and function of peptides and proteins. The variety of analytical methods, the range of instrument capabilities, and the complexity of the data obtained make it difficult for most laboratories to acquire the necessary expertise to make optimal use of their instrumentation.We describe an expert system approach to automating specific types of analyses in a way that makes it easier to transfer the capability to do specific experiments to other laboratories. Central to the approach is the creation of a computer program (ie, a virtual instrument) that controls the operation of physical components, analyzes incoming data, automatically adjusts instrument parameters to achieve the goal of the analysis, and reports the results. By interacting with the mass spectrometer through the computer operating system, it is possible to add useful functions to the system without altering any of the manufacturer-controlled data system software. The usefulness of this approach is illustrated by the automation of experiments to confirm the sequences of synthetic peptides and perform LC/MS/MS peak parking experiments and real-time database searches.

Meta-analysis of the effects of psychoeducational care in adults with chronic obstructive pulmonary disease.

Meta-analysis, a quantitative research review, was conducted on 65 studies of the effect of education, exercise and/or psychosocial support (hereafter called psychoeducational care) in adults with chronic obstructive pulmonary disease (COPD). Studies ranged in publication date from 1954 to 1994. Only 34% of studies had subjects that were randomly assigned to treatment condition, and only 15% of studies had a placebo-type control group. Analyses by type of treatment showed that pulmonary rehabilitation (large muscle exercise and education plus a variety of psychosocial or behavioral interventions) had statistically significant beneficial effects on psychological well-being (d+ = 0.58, n = 13), endurance (d+ = 0.77, n = 13), functional status (d+ = 0.63, n = 8), VO2 (d+ = 0.56, n = 5), dyspnea (d+ = 0.71, n = 10), and adherence (d+ = 1.76, n = 2). A statistically significant beneficial effect of pulmonary rehabilitation was not found on Forced Expiratory Volume at 1 s. Across 7 outcomes examined, treatments including education-alone had significant beneficial effect on the accuracy of performing inhaler skills (d+ = 1.27, n = 7). Based on a very small sample of studies, a non-significant but small or medium sized effect of education-alone was evident on health care utilization (d+ = 0.26, n = 3) and on adherence to treatment regimen (d+ = 0.50, n = 2). Such results are inconclusive, suggesting that further research may be indicated. Relaxation-alone had statistically significant beneficial effects on both dyspnea (d+ = 0.91, n = 3) and psychological well-being (d+ = 0.39, n = 6). The research base has methodological weaknesses that should be rectified in future research. Nonetheless, based on the best evidence available to date, identified types of psychoeducational care have been shown to improve the functioning and well-being of adults with COPD.

Models and processes of research utilization.

The proliferation of research in nursing is greater today than at any other time in the history of nursing. In order for this research to be meaningful for practice, research utilization efforts are imperative. This article reviews three prominent research utilization models spanning three decades of development. Future challenges and suggestions for improving the process are identified. Through research utilization efforts, nurses are given the power to make informed choices regarding implementation of research-based assessments, diagnoses, interventions, and outcome measures that ultimately will result in improved patient outcomes.

Using clinical innovations for research-based practice.

Making choices about patient-care interventions pervades critical care nursing practice. Research utilization activities provide the reasoning by which assessment parameters are established, preventative actions are identified, and interventions are evaluated in the clinical setting for positive effects on patient outcomes. For research results to be directly applicable, they must be transformed into clinical innovations specific to a patient population, clinical situation, or institutional setting. A brief summary of using research findings to design clinical innovations is provided. Examples of selected clinical innovations are included to illustrate the steps of the research utilization process. Clinical innovations are intended to improve or validate patient outcomes and are considered the key to quality patient care.