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The Ogallala Aquifer, a primary irrigation water source in the High Plains region of the United States, is declining, thereby necessitating new water conservation strategies. This paper investigates the impact of mixed wettability on the evaporation dynamics of a 10-µl sessile water droplet placed within simulated soil pores comprised of hydrophobic Teflon beads (CA ∼ 108°) and hydrophilic glass (CA ∼ 41°) beads with 2.38-mm diameters, where homogeneous and heterogenous (i.e., mixed hydrophobicity and hydrophilicity) wettability configurations were investigated. Experiments were performed in an environmental chamber where the relative humidity and temperature were 60% ± 0.1% RH and 20 ± 0.4 °C, respectively. Wettability influenced evaporation times, with homogeneous hydrophobic pores (i.e., three Teflon beads) and heterogenous one glass, two Teflon pores having the longest average evaporation times of 40 and 39 min, respectively. Homogeneous hydrophilic pores (i.e., three glass beads) and heterogenous two glass, one Teflon pores exhibited evaporation times of 34 min. Evaporation times for heterogenous combinations trended based on the predominant wettability. Contact angles and the projected length of contact were analyzed from videos to capture pinning and depinning during evaporation. For many cases including hydrophobicity, contact angles were less than 90°, and in some configurations, water would be pinned on a Teflon bead, whereas depinning (i.e., moving) on a glass bead. Stick-slip evaporation was observed, where the evaporating droplet switched between constant contact radius and constant contact area evaporative modes to minimize droplet surface energy. The results suggest wettability alterations in agricultural settings may reduce evaporation. [ABSTRACT FROM AUTHOR]

Modeling environmental sound levels over continental scales is difficult due to the variety of geospatial environments. Moreover, current continental-scale models depend upon machine learning and therefore face additional challenges due to limited acoustic training data. In previous work, an ensemble of machine learning models was used to predict environmental sound levels in the contiguous United States using a training set composed of 51 geospatial layers (downselected from 120) and acoustic data from 496 geographic sites from Pedersen, Transtrum, Gee, Lympany, James, and Salton [JASA Express Lett. 1(12), 122401 (2021)]. In this paper, the downselection process, which is based on factors such as data quality and inter-feature correlations, is described in further detail. To investigate additional dimensionality reduction, four different feature selection methods are applied to the 51 layers. Leave-one-out median absolute deviation cross-validation errors suggest that the number of geospatial features can be reduced to 15 without significant degradation of the model's predictive error. However, ensemble predictions demonstrate that feature selection results are sensitive to variations in details of the problem formulation and, therefore, should elicit some skepticism. These results suggest that more sophisticated dimensionality reduction techniques are necessary for problems with limited training data and different training and testing distributions. [ABSTRACT FROM AUTHOR]

This paper applies new and recently introduced approaches to study trends in gun violence in the United States. We use techniques in both the time and frequency domain to provide a more complete understanding of gun violence dynamics. We analyze gun violence incidents on a state-by-state basis as recorded by the Gun Violence Archive. We have numerous specific phenomena of focus, including periodicity of incidents, locations in time where behavioral changes occur, and shifts in gun violence patterns since April 2020. First, we implement a recently introduced method of spectral density estimation for nonstationary time series to investigate periodicity on a state-by-state basis, including revealing where periodic behaviors change with time. We can also classify different patterns of behavioral changes among the states. We then aim to understand the most significant shifts in gun violence since numerous key events in 2020, including the COVID-19 pandemic, lockdowns, and periods of civil unrest. Our dual-domain analysis provides a more thorough understanding and challenges numerous widely held conceptions regarding the prevalence of gun violence incidents. [ABSTRACT FROM AUTHOR]

Pulp suspensions possess a yield stress that varies with concentration and fibre type, and understanding of this property is important to the pulp and paper industry. Unfortunately, pulp suspensions are highly susceptible to wall slip, which greatly complicates many rheological measurements including determination of the apparent yield stress. Using the vane method as a starting point, a slip-free method for measuring the apparent yield stress of pulp suspensions is developed. The findings from this method development are also used to assess the likelihood of slip having interfered with previous pulp rheometry studies and to offer some guidelines for the design of future experiments. Finally, the apparent yield stresses of suspensions of two National Institute of Standards and Technology reference pulps are determined for concentrations between 1% and 5% w/w, and the results contrasted with previous studies. [ABSTRACT FROM AUTHOR]

We present in this Special Issue of Physics of Plasmas the review, tutorial, and invited papers of the 2010 Annual Meeting of the American Physical Society's (APS) Division of Plasma Physics. This was the 52nd year of this meeting, and it was held in Chicago, Illinois on 8-12 November 2010. The meeting program was made up of over 100 review, tutorial, and invited oral presentations, and a significant fraction of these speakers prepared manuscripts which were peer-reviewed and are contained in this Special Issue. [ABSTRACT FROM AUTHOR]

Each year, the annual meeting of the APS Division of Plasma Physics (DPP) brings together a broad representation of the many active subfields of plasma physics and enjoys an audience that is equally diverse. The meeting was well attended and largely went as planned despite the interventions of hurricane Sandy which caused the city of Providence to shut-down during the first day of the conference. The meeting began on Monday morning with a review of the physics of cosmic rays, 2012 being the 100th year since their discovery, which illustrated the central importance of plasma physics to astrophysical problems. Subsequent reviews covered the importance of tokamak plasma boundaries, progress towards ignition on the National Ignition Facility (NIF), and magnetized plasma turbulence. The Maxwell prize address, by Professor Liu Chen, covered the field of nonlinear Alfvén wave physics. Tutorial lectures were presented on the verification of gyrokinetics, new capabilities in laboratory astrophysics, magnetic flux compression, and tokamak plasma start-up. [ABSTRACT FROM AUTHOR]

This paper introduces a mathematical framework for determining second surge behavior of COVID-19 cases in the United States. Within this framework, a flexible algorithmic approach selects a set of turning points for each state, computes distances between them, and determines whether each state is in (or over) a first or second surge. Then, appropriate distances between normalized time series are used to further analyze the relationships between case trajectories on a month-by-month basis. Our algorithm shows that 31 states are experiencing second surges, while four of the 10 largest states are still in their first surge, with case counts that have never decreased. This analysis can aid in highlighting the most and least successful state responses to COVID-19. [ABSTRACT FROM AUTHOR]

Until recently, most hearing conservation programs, including those in the military, have used permanent shifts in the pure-tone audiometric threshold as the gold standard for measuring hearing impairment in noise-exposed populations. However, recent results from animal studies suggest that high-level noise exposures can cause the permanent destruction of synapses between the inner hair cells and auditory nerve fibers, even in cases where pure-tone audiometric thresholds eventually return to their normal pre-exposure baselines. This has created a dilemma for researchers, who are now increasingly interested in studying the long-term effects that temporary hearing shifts might have on hearing function, but are also concerned about the ethical considerations of exposing human listeners to high levels of noise for research purposes. One method that remains viable to study the effects of high noise exposures on human listeners, or to evaluate the efficacy of interventions designed to prevent noise-related inner ear damage, is to identify individuals in occupations with unavoidable noise exposures and measure hearing before and as soon as possible after exposure. This paper discusses some of the important factors to be considered in studies that attempt to measure acute hearing changes in noise-exposed military populations. [ABSTRACT FROM AUTHOR]

This Resource Letter is a supplement to the earlier Resource Letters MP-1 and MP-2, and provides further sources on the Manhattan Project and related research. Books, review papers, journal articles, videos, and websites are cited for the following topics: general works, technical works, biographical and autobiographical works, foreign wartime nuclear programs and related allied intelligence, the use of the bombs against Hiroshima and Nagasaki, technical papers of historical interest, postwar policy and technical developments, and educational materials. Together, these three Resource Letters describe nearly 400 sources of information on the Manhattan Project. [ABSTRACT FROM AUTHOR]

Although the United States is becoming racially diverse, the representation of marginalized groups in physics still remains low. Historically Black Colleges and Universities (HBCUs) have been successful in graduating Black physicists, such that HBCUs are nine of the top 10 physics departments in the United States that produce bachelor degrees. Despite these outcomes, Black women are disproportionately underrepresented in physics. In 2016, only 4% and 3% of Black women earned bachelor's degrees and doctorate degrees in physics, respectively. Among faculty, Black women made up only 2% in physics doctorate programs and 3% in bachelor's-only physics departments in 2016. Though the percentage of Latinas in physics has increased, the percentage of Black women in physics has not grown. Therefore, Black female physics faculty are often tokenized and experience gendered racism (intersection of racism and sexism). In this paper, we used an intersectional approach to examine the psychological discourse on Black female physics faculty's experiences of gendered racism, identity shifting as a coping strategy, and we provide recommendations for creating an inclusive physics environment. [ABSTRACT FROM AUTHOR]

The genesis of this paper was notification to the author that he would receive the 2010 Rossing Prize in Acoustics Education, which carried the responsibility of giving a lecture at a meeting of the Acoustical Society of America. He decided to draw on his remembrances of writing several textbooks during a 40 year career as a professor to discuss the facets of writing that a faculty member might encounter. This paper is an expanded version of that lecture [J. H. Ginsberg, J. Acoust. Soc. Am. 128, 2389 (2010)]. An opening section elucidating the author's experiences as an author is followed by a discussion intended to motivate and encourage those who are undecided about taking on this activity. Suggestions are offered as to how to organize and proceed through a writing project as well as what elements should be included. An explanation of the author's role in the process of producing a printed textbook is provided. Guidance is offered as to how one can focus on writing a book in the face of teaching, research, and personal responsibilities. The closure discusses current trends that endanger the ongoing flow of high quality textbooks. [ABSTRACT FROM AUTHOR]

This paper first shows experimentally that the distribution of modal spacings in a reverberation room is well modeled by the Rayleigh or Wigner distribution. Since the Rayleigh or Wigner distribution is a good approximation to the Gaussian orthogonal ensemble (GOE) distribution, this paper confirms the current wisdom that the GOE distribution is a good model for the distribution of modal spacings. Next this paper gives the technical arguments that the author used successfully to support the pragmatic arguments of Baade and the Air-conditioning and Refrigeration Institute of USA for retention of the pure tone qualification procedure and to modify a constant in the International Standard ISO 3741:1999(E) for measurement of sound power in a reverberation room. [ABSTRACT FROM AUTHOR]

Floods are known to exhibit self-similarity and follow scaling laws that form the basis of regional flood frequency analysis. However, the relationship between basin attributes and the scaling behavior of floods is still not fully understood. Identifying these relationships is essential for drawing connections between hydrological processes in a basin and the flood response of the basin. The existing studies mostly rely on simulation models to draw these connections. This paper proposes a new methodology that draws connections between basin attributes and the flood scaling exponents by using observed data. In the proposed methodology, region-of-influence approach is used to delineate homogeneous regions for each gaging station. Ordinary least squares regression is then applied to estimate flood scaling exponents for each homogeneous region, and finally stepwise regression is used to identify basin attributes that affect flood scaling exponents. The effectiveness of the proposed methodology is tested by applying it to data from river basins in the United States. The results suggest that flood scaling exponent is small for regions having (i) large abstractions from precipitation in the form of large soil moisture storages and high evapotranspiration losses, and (ii) large fractions of overland flow compared to base flow, i.e., regions having fast-responding basins. Analysis of simple scaling and multiscaling of floods showed evidence of simple scaling for regions in which the snowfall dominates the total precipitation. [ABSTRACT FROM AUTHOR]

In 2009, the National Research Council issued Electricity from Renewables: Status, Prospects, and Impediments the study report of the Panel on Electricity from Renewable Sources. As part of the larger America's Energy Future study undertaken by the National Academies, the panel was asked to examine the technical potential for development and deployment of renewable electricity technologies. This paper summarizes the report by this panel. The panel noted that renewable electricity generation technologies represent a tremendous opportunity to provide low net carbon dioxide (CO2)-emitting electricity generation from domestic resources and to generate new economic opportunities for the United States. The panel found that there are sufficient domestic renewable resources and technologies to allow renewable electricity to play a significant role in future electricity generation. However, although wind and solar electricity in particular have exhibited very large growth rates, non-hydropower renewables still provide a small percentage of total US electricity generation. The study considered the size and distribution of the resource base; the status of renewable electricity technologies; the economics of renewable electricity in light of various policy options; the environmental impacts of electricity from renewable resources; and the issues related to scaling up deployment. The panel concluded that an aggressive but achievable future for renewables could have non-hydroelectric renewables contributing 10% of the nation's electricity generation by 2020 and 20% or more by 2035. To reach these levels, significant and sustained actions, involving a combination and coordination of policy, technology, and capital, will be essential. The panel emphasizes policy, technology, and capital equally because the scale of the effort required to reach such levels brings significant challenges beyond simple resource availability or technical capabilities. [ABSTRACT FROM AUTHOR]

This Resource Letter is a supplement to my earlier Resource Letter MP-1 and provides further sources on the Manhattan Project and related nuclear research. Books and journal articles are cited for the following topics: General works, technical works, biographical and autobiographical works, foreign wartime programs and allied intelligence, technical papers of historical interest, and postwar policy and technical developments. I also give a list of videos and websites dealing with the Manhattan Project, nuclear weapons, and nuclear issues. [ABSTRACT FROM AUTHOR]

The challenges associated with the development of innovative energy efficient technology require a new generation of skilled and creative scientists and engineers. Moreover, it is vital that they possess the ability to communicate their expertise to the general public and to serve as advisors and participants in the development of science policy. This paper describes a curriculum for a course in optics that. investigates the physical principles and policy aspects of solid state lighting. Recent legislation places stringent efficiency and reliability requirements on lighting, promoting the development of new commercial lighting options. The physics of solid state lighting fits naturally into the undergraduate optics curriculum, and the policy aspects provide students with an engaging connection between science and society. [ABSTRACT FROM AUTHOR]

Experiments on the National Ignition Facility (NIF) will require bright, short duration, near-monochromatic x-ray backlighters for radiographic diagnosis of many high-energy density systems. This paper details a vanadium pinhole backlighter producing (1.8±0.5)×1015 x-ray photons into 4π sr near the vanadium He-like characteristic x-ray energy of 5.18 keV. The x-ray yield was quantified from a set of Ross filters imaged to a calibrated image plate, with the Dante diagnostic used to confirm the quasimonochromatic nature of the spectrum produced. Additionally, an x-ray film image shows a source-limited image resolution of 26 μm from a 20 μm diameter pinhole. [ABSTRACT FROM AUTHOR]

This paper describes a common-view disciplined oscillator (CVDO) that locks to a reference time scale through the use of common-view global positioning system (GPS) satellite measurements. The CVDO employs a proportional-integral-derivative controller that obtains near real-time common-view GPS measurements from the internet and provides steering corrections to a local oscillator. A CVDO can be locked to any time scale that makes real-time common-view data available and can serve as a high-accuracy, self-calibrating frequency and time standard. Measurement results are presented where a CVDO is locked to UTC(NIST), the coordinated universal time scale maintained at the National Institute of Standards and Technology in Boulder, Colorado. [ABSTRACT FROM AUTHOR]

This paper presents a quantitative and comprehensive study of the lip movements of a given speaker in different speech/nonspeech contexts, with a particular focus on silences (i.e., when no sound is produced by the speaker). The aim is to characterize the relationship between 'lip activity' and 'speech activity' and then to use visual speech information as a voice activity detector (VAD). To this aim, an original audiovisual corpus was recorded with two speakers involved in a face-to-face spontaneous dialog, although being in separate rooms. Each speaker communicated with the other using a microphone, a camera, a screen, and headphones. This system was used to capture separate audio stimuli for each speaker and to synchronously monitor the speaker's lip movements. A comprehensive analysis was carried out on the lip shapes and lip movements in either silence or nonsilence (i.e., speech+nonspeech audible events). A single visual parameter, defined to characterize the lip movements, was shown to be efficient for the detection of silence sections. This results in a visual VAD that can be used in any kind of environment noise, including intricate and highly nonstationary noises, e.g., multiple and/or moving noise sources or competing speech signals. [ABSTRACT FROM AUTHOR]

We revisit a series of papers on science and society issues by David Hafemeister in the 1970s and 1980s. The emphasis in the present work is on world oil production limits and some consequences of various possible scenarios for the near future. Some of the data and scenarios used by Hafemeister are updated for U.S. oil production in the past two decades, and extended to an analysis of a peak in world oil production in the future. We discuss some simple scenarios for future energy use patterns and look at the consequence of these scenarios as world oil production begins to decline. We also provide a list of resources for critical investigations of natural resource extraction and depletion patterns. [ABSTRACT FROM AUTHOR]

A survey of the approaches which have been developed for mitigating transport in stellarators is presented. A primary deficiency of stellarators has been elevated transport levels due to their nonaxisymmetry. Since the early 1980s, stellarator research has addressed this difficulty, developing a range of techniques for reducing transport, both neoclassical and, more recently, also anomalous. Several of these approaches are now being implemented in a new generation of experiments in the United States and abroad. This paper describes the fundamental physics of these methods for transport reduction. [ABSTRACT FROM AUTHOR]

Absolute pitch is extremely rare in the U.S. and Europe; this rarity has so far been unexplained. This paper reports a substantial difference in the prevalence of absolute pitch in two normal populations, in a large-scale study employing an on-site test, without self-selection from within the target populations. Music conservatory students in the U.S. and China were tested. The Chinese subjects spoke the tone language Mandarin, in which pitch is involved in conveying the meaning of words. The American subjects were nontone language speakers. The earlier the age of onset of musical training, the greater the prevalence of absolute pitch; however, its prevalence was far greater among the Chinese than the U.S. students for each level of age of onset of musical training. The findings suggest that the potential for acquiring absolute pitch may be universal, and may be realized by enabling infants to associate pitches with verbal labels during the critical period for acquisition of features of their native language. [ABSTRACT FROM AUTHOR]

This paper develops a theoretical background for the interpretation of the time reversal (TR) processes applied to the refocalization of acoustic waves in dispersive media with multimode propagation of waves. Two parameters are introduced in order to measure the efficiency of signal recompression in TR processes: spatial and temporal efficiencies. It is demonstrated that the signal recompression enhances when the medium is highly dispersive, when there are several modes involved in the process, and when the angular aperture of the TR mirror is appreciable. These results are applied to Lamb waves recompression in thin plates and focalization efficiencies in longitudinal and transversal directions are deduced. Finally, these theoretical results are compared with the experimental ones obtained for different plate thicknesses. 2005 Acoustical Society of America. [ABSTRACT FROM AUTHOR]

In this paper, the propagation of a broadband sound pulse in three-dimensional (3D) shallow water waveguides is investigated numerically. Two cases are examined: (i) the 3D ASA benchmark wedge, and (ii) the 3D Gaussian canyon. The numerical method used to solve the four-dimensional acoustic problem is based on a Fourier synthesis technique. The frequency-domain calculations are carried out using the fully 3D parabolic equation based model 3DWAPE, recently modified to include a wide-angle paraxial approximation for the azimuthal component. A broadband sound pulse with a central frequency of 25 Hz and a bandwith of 40 Hz is considered. For both test cases, 3D results corresponding to a 25 Hz cw point source are first presented and compared with predictions from a 3D adiabatic modal model. Then, the acoustic problem is solved considering the broadband source pulse. The modal structure of the received signals is analyzed and exhibits multiple mode arrivals of the propagating signal. 2005 Acoustical Society of America. [ABSTRACT FROM AUTHOR]

Ring doves (Streptopelia risoria) produce a coo vocalization that is essentially a pure-tone sound at a frequency of about 600 Hz and with a duration of about 1.5 s. While making this vocalization, the dove inflates the upper part of its esophagus to form a thin-walled sac structure that radiates sound to the surroundings. It is a reasonable assumption that the combined influence of the trachea, glottis and inflated upper esophagus acts as an effective band-pass filter to eliminate higher harmonics generated by the vibrating syringeal valve. Calculations reported here indicate that this is indeed the case. The tracheal tube, terminated by a glottal constriction, is the initial resonant structure, and subsequent resonant filtering takes place through the action of the inflated esophageal sac. The inflated esophagus proves to be a more efficient sound radiating mechanism than an open beak. The action of this sac is only moderately affected by the degree of inflation, although an uninflated esophagus is inactive as a sound radiator. These conclusions are supported by measurements and observations that have been reported in a companion paper. 2004 Acoustical Society of America. [ABSTRACT FROM AUTHOR]

This paper presents a new method for robust and accurate fundamental frequency (F0) estimation in the presence of background noise and spectral distortion. Degree of dominance and dominance spectrum are defined based on instantaneous frequencies. The degree of dominance allows one to evaluate the magnitude of individual harmonic components of the speech signals relative to background noise while reducing the influence of spectral distortion. The fundamental frequency is more accurately estimated from reliable harmonic components which are easy to select given the dominance spectra. Experiments are performed using white and babble background noise with and without spectral distortion as produced by a SRAEN filter. The results show that the present method is better than previously reported methods in terms of both gross and fine F0 errors. 2004 Acoustical Society of America. [ABSTRACT FROM AUTHOR]

In order to examine the role of noise sensitivity in response to environmental noise, this paper presents detailed comparisons of socio-acoustic studies conducted around international airports in Amsterdam, Sydney, and London. Earlier findings that noise sensitivity moderates the effect of noise on annoyance were examined to see if they could be replicated in each of the datasets, independent of the technique of measuring noise sensitivity. The relation between exposure to aircraft noise and noise annoyance was studied separately for groups of individuals with low, medium, and high noise sensitivity, with statistical adjustment for relevant confounders. Results support the previous findings that noise sensitivity is an independent predictor of annoyance and adds to the prediction of noise annoyance afforded by noise exposure level by up to 26% of explained variance. There is no evidence of a moderating effect, whereby the covariation between noise exposure level and annoyance is weak for people who score at the extreme high or low end of the sensitivity scale, and strong for people who score in the middle of the sensitivity scale. Generally, noise sensitivity appears to increase annoyance independently of the level of noise exposure after adjustment for relevant confounders. These findings were consistent across the three datasets. 2004 Acoustical Society of America. [ABSTRACT FROM AUTHOR]

Traditionally, multiple listener room equalization is performed to improve sound quality at all listeners, during audio playback, in a multiple listener environment (e.g., movie theaters, automobiles, etc.). A typical way of doing multiple listener equalization is through spatial averaging, where the room responses are averaged spatially between positions and an inverse equalization filter is found from the spatially averaged result. However, the equalization performance, will be affected if there is a mismatch between the position of the microphones (which are used for measuring the room responses for designing the equalization filter) and the actual center of listener head position (during playback). In this paper, we will present results on the effects of microphone-listener mismatch on spatial average equalization performance. The results indicate that, for the analyzed rectangular configuration, the region of effective equalization depends on (i) the distance of a listener from the source, (ii) the amount of mismatch between the responses, and (iii) the frequency of the audio signal. We also present some convergence analysis to interpret the results. 2004 Acoustical Society of America. [ABSTRACT FROM AUTHOR]

Distortion product otoacoustic emission (DPOAE) suppression tuning curves (STCs) typically are constructed using suppression criteria of 3 or 6 dB. This paper describes a technique for generating DPOAE STCs using criteria ranging from 3 dB to complete suppression. The criterion effect was examined at various primary levels (f2=4 kHz) in normal-hearing ears. As expected, QERB and tip-to-tail differences decreased as probe level (L2) increased. QERB values were not systematically dependent on criterion. For low L2s, tip-to-tail differences decreased as criterion increased. Given similarities in methodology, DPOAE STCs constructed from completely suppressed responses might be most appropriate for comparison to psychophysical tuning curves. 2004 Acoustical Society of America. [ABSTRACT FROM AUTHOR]

Examines the effects of using computer simulations in teaching science to students in the United States. Differences in the performance of students using simulation and students using paper and pencil; Problems associated with students relying on the computer for answers; Details and method of implementation of the program.

We suggest that in the recent papers [J. Chem. Phys. 113, 2873 (2000)] and [J. Chem. Phys. 115, 11299 (2001)] an incorrect expression was used to obtain the diffusion coefficient of water in fully hydrated vermiculite clay from the Q dependence of the quasielastic neutron scattering data. This has led to underestimating the mean square jump length and the translational diffusion coefficient by a factor of 3. We discuss the correct way to extract the diffusion parameters and their properly estimated values. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The potential of an x-ray magnifier prepared from a pair of asymmetrically cut crystals is studied to explore high energy x-ray imaging capabilities at high intensity laser facilities. OMEGA-EP and NIF when irradiating mid and high Z targets can be a source of high-energy x-rays whose production mechanisms and use as backlighters are a subject of active research. This paper studies the properties and potential of existing asymmetric cut crystal pairs from the National Institute of Standards and Technology (NIST) built in a new enclosure for imaging x-ray sources. The technique of the x-ray magnifier has been described previously. This new approach is aimed to find a design that could be used at laser facilities by magnifying the x-ray source into a screen far away from the target chamber center, with fixed magnification defined by the crystals' lattice spacing and the asymmetry angles. The magnified image is monochromatic and the imaging wavelength is set by crystal asymmetry and incidence angles. First laboratory results are presented and discussed. [ABSTRACT FROM AUTHOR]

This paper compares the results from a GEANT4 simulation of the gas Cherenkov detector 1 (GCD1) with previous simulations and experimental data from the Omega laser facility. The GCD1 collects gammas emitted during a deuterium-tritium capsule implosion and converts them, through several processes, to Cherenkov light. Photon signals are recorded using subnanosecond photomultiplier tubes, producing burn reaction histories. The GEANT4 GCD1 simulation is first benchmarked against ACCEPT, an integrated tiger series code, with good agreement. The simulation is subsequently compared with data from the Omega laser facility, where experiments have been performed to measure the effects of Hohlraum materials on reaction history signals, in preparation for experiments at the National Ignition Facility. [ABSTRACT FROM AUTHOR]

Bang time and reaction history measurements are fundamental components of diagnosing inertial confinement fusion (ICF) implosions and will be essential contributors to diagnosing attempts at ignition on the National Ignition Facility (NIF). Fusion gammas provide a direct measure of fusion interaction rate without being compromised by Doppler spreading. Gamma-based gas Cherenkov detectors that convert fusion gamma rays to optical Cherenkov photons for collection by fast recording systems have been developed and fielded at Omega. These systems have established their usefulness in illuminating ICF physics in several experimental campaigns. Bang time precision better than 25 ps has been demonstrated, well below the 50 ps accuracy requirement defined by the NIF system design requirements. A comprehensive, validated numerical study of candidate systems is providing essential information needed to make a down selection based on optimization of sensitivity, bandwidth, dynamic range, cost, and NIF logistics. This paper presents basic design considerations arising from the two-step conversion process from γ rays to relativistic electrons to UV/visible Cherenkov radiation. [ABSTRACT FROM AUTHOR]

Breast cancer is a serious potential health problem for all women and is the second leading cause of cancer deaths in the United States. The current screening procedures and imaging techniques, including x-ray mammography, clinical biopsy, ultrasound imaging, and magnetic resonance imaging, provide only 73% accuracy in detecting breast cancer. This gives the impetus to explore alternate techniques for imaging the breast and detecting early stage tumors. Among the complementary methods, the noninvasive biomagnetic breast imaging is attractive and promising, because both ionizing radiation and breast compressions that the prevalent x-ray mammography suffers from are avoided. It furthermore offers very high contrast because of the significant electromagnetic properties' differences between the cancerous, benign, and normal breast tissues. In this paper, a hybrid and accurate modeling tool for biomagnetic breast imaging is developed, which couples the electromagnetic and ultrasonic energies, and initial validations between the model predication and experimental findings are conducted. [ABSTRACT FROM AUTHOR]

The article presents an updated transportation statistics for automobile and light truck usage in the U.S. in continuation to statistics presented in the paper titled "A Physicist's View of the Automobile Engine." Topics discussed include factors involved in data analysis such as average miles per gallon of automobiles, number of light trucks, and gasoline usage, classification of sport utility vehicles and minivans as light trucks, and increasing trends of using automobiles by students.

Introduces this issue as a special issue which is a collection of articles based on invited presentations at the 41st Annual Meeting of the Division of Plasma Physics (DPP) of the American Physical Society held in Seattle, Washington, in November 1999. Details of the program which involved several papers and a mini-conferences on Turbulence in the Interstellar Medium and Solar Wind, Plasma Propulsion Physics, Dusty Plasmas, and Computational Studies of Complexity in Turbulent Plasma; Coverage of a broad variety of research in plasma physics and highlighting of areas of intense interest and investigation, such as the basic physics of waves, instabilities, turbulence and transport and the properties of non-neutral plasmas and matter under very high pressures; Details of tutorial papers and presentations which are meant to be understood by non-experts.

Describes a simple method for creating a paper replica of the `Bighorn Medicine Wheel,' a celestial calendar wheel located in Sheridan, Wyoming. Materials needed; Procedures.

A two-dimensional axisymmetric electromagnetic particle-in-cell code with Monte Carlo collision conditions has been developed for an applied-field magnetoplasmadynamic thruster simulation. This theoretical approach establishes a particle acceleration model to investigate the microscopic and macroscopic characteristics of particles. This new simulation code was used to study the physical processes associated with applied magnetic fields. In this paper (I), detail of the computation procedure and results of predictions of local plasma and field properties are presented. The numerical model was applied to the configuration of a NASA Lewis Research Center 100-kW magnetoplasmadynamic thruster which has well documented experimental results. The applied magnetic field strength was varied from 0 to 0.12 T, and the effects on thrust were calculated as a basis for verification of the theoretical approach. With this confirmation, the changes in the distributions of ion density, velocity, and temperature throughout the acceleration region related to the applied magnetic fields were investigated. Using these results, the effects of applied field on physical processes in the thruster discharge region could be represented in detail, and those results are reported. [ABSTRACT FROM AUTHOR]

The article reports on the effort of the American Institute of Physics to minimize costs to authors in the U.S. It is stated that the American Institute of Physics is reducing the fee for color figures in print. The reduced rates eliminated the surcharge placed on the first color figure printed in the published paper.

An analysis of x-ray data from two series of Z-pinch shots taken on the short current-risetime Saturn accelerator at Sandia National Laboratories [Proceedings of 6th International IEEE Pulsed Power Conference, Arlington, VA, edited by P. J. Turchi and B. H. Bernstein (IEEE, New York, 1987), p. 310] is presented. In one series, the array radius was held constant and the array mass was varied; in the other series, the array mass was held constant and its radius varied. In both sets of experiments, large wire-number loads (N>=93) of aluminum were used in contrast to earlier small wire-number aluminum array experiments on Saturn where N≤42. Average electron temperatures and ion densities were inferred from the data. In addition, from the measured size of the emission region of K-shell x rays and from the inferred ion density, a fraction of the total array mass that participated in the K-shell emission was inferred and found to be directly correlated to the K-shell yields that were measured. This paper also demonstrates that the yields varied as a function of array mass and radius in much closer agreement with predictions [J. Appl. Phys. 67, 1725 (1990)] than had been observed in the earlier small wire-number experiments. Thus, a serious misperception that the reason for the early disagreement was in the calculations and not in the experiments is corrected. These predictions were made using one-dimensional (1D) magnetohydrodynamics calculations. The density and temperature trends inferred from the data analysis are well-behaved and consistent with the 1D calculations. This data analysis confirms the importance of achieving uniform plasma initial conditions and implosion symmetry when comparing computer code calculations with experiment. When the wire number of an array load is increased, a more uniform shell of plasma is calculated initially as the wires explode and, as the plasma stagnates on axis, the x-ray powers and yields are found experimentally to appro... [ABSTRACT FROM AUTHOR]