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Top 20 Most Read Articles
August 2008
The 20 articles with the most full-text downloads during the month, in descending order.
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Topic 1: Attracting Girls Into Physics AIP Conf. Proc. 628, pp. 9-12; doi:http://dx.doi.org/10.1063/1.1505270 (4 pages) Online Publication Date: 20 August 2002
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We discuss the problems in attracting girls into physics. We present some of the projects undertaken in various countries to ameliorate the problem, and we conclude with some follow‐up suggestions that can be implemented in all countries. © 2002 American Institute of Physics |
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Quantum Geometry and Quantum Gravity AIP Conf. Proc. 1023, pp. 3-33; doi:http://dx.doi.org/10.1063/1.2958178 (31 pages) Online Publication Date: 30 June 2008
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The purpose of this contribution is to give an introduction to quantum geometry and loop quantum gravity for a wide audience of both physicists and mathematicians. From a physical point of view the emphasis will be on conceptual issues concerning the relationship of the formalism with other more traditional approaches inspired in the treatment of the fundamental interactions in the standard model. Mathematically I will pay special attention to functional analytic issues, the construction of the relevant Hilbert spaces and the definition and properties of geometric operators: areas and volumes. |
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Modeling Laser Wake Field Acceleration with the Quasi‐Static PIC Code QuickPIC AIP Conf. Proc. 877, pp. 235-240; doi:http://dx.doi.org/10.1063/1.2409140 (6 pages) Online Publication Date: 8 December 2006
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We use the Quasi‐static Particle‐In‐Cell code QuickPIC to model laser wake field acceleration, in both uniform and parabolic plasma channels within current state of the art experimental laser and plasma parameters. QuickPIC uses the quasi‐static approximation, which allows the separation of the plasma and laser evolution, as they respond in different time scales. The laser is evolved with a larger time step, that correctly resolves distances of the order of the Rayleigh length, according to the ponderomotive guiding center approximation, while the plasma response is calculated through a quasi‐static field solver for each transverse 2d slice. We have performed simulations that show very good agreement between QuickPIC and three dimensional simulations using the full PIC code OSIRIS. We have scanned laser intensities from those for which linear plasma waves are excited to those for which the plasma response is highly nonlinear. For these simulations, QuickPIC was 2–3 orders of magnitude faster than OSIRIS. © 2006 American Institute of Physics |
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Status of Swift GRB Observations AIP Conf. Proc. 1000, pp. 3-8; doi:http://dx.doi.org/10.1063/1.2943494 (6 pages) Online Publication Date: 22 May 2008
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Since its launch on 20 November 2004, the Swift mission has been detecting ∼ 100 gamma‐ray bursts (GRBs) each year, and immediately (within ∼ 90 s) starting X‐ray and UV∕optical observations of the afterglow. It has already collected an impressive database including prompt emission to higher sensitivities than BATSE, uniform monitoring of afterglows, and rapid followup by other observatories notified through the GCN. The X‐ray afterglows have been found to have complex temporal shapes, including tails emission from the prompt phase and bright flares. X‐ray and optical afterglow detections from short bursts have led to accurate localizations. It is found that they can occur in non‐star forming galaxies or regions, whereas long GRBs are strongly concentrated within star forming regions. This is consistent with the NS merger model. Swift has greatly increased the redshift range of GRB detection. The highest redshift GRBs, at z ∼ 5–6, are approaching the era of reionization. Ground‐based deep optical spectroscopy of high redshift bursts is giving metallicity measurements and other information on the source environment to much greater distance than other techniques. The localization of GRB 060218 in a nearby galaxy, and association with SN 2006aj, added a valuable member to the class of GRBs with detected supernova. The prospects for future progress are excellent given the >10 year orbital lifetime of the Swift satellite. |
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A ROTATING HEAT PIPE FOR COOLING OF SUPERCONDUCTING MACHINES AIP Conf. Proc. 985, pp. 1333-1340; doi:http://dx.doi.org/10.1063/1.2908491 (8 pages) Online Publication Date: 27 March 2008
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A curved rotating heat pipe for use in superconducting motor and generator applications is introduced here. The heat pipe shown here is built so that both the condenser and evaporator sections are parallel to the axis of rotation. The condenser section is concentric with the axis of rotation while the evaporator section can be placed in contact with off-axis heat sources in the rotating machine. The geometry is achieved by incorporating an S-shaped curve between the on-axis rotating condenser section and the off-axis revolving evaporator section. We show that because the heat pipe is a sealed, passive heat transfer device with nearly isothermal operation, the heat pipe concept may be advantageous when considering the overall refrigeration system used with the superconducting machine. High-speed, room temperature test data with this heat pipe geometry indicate that the working fluid in the heat pipe continued to circulate, resulting in heat transfer with a high effective thermal conductivity, with the heat pipe operating under the influence of centrifugal accelerations approaching 400 g. |
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Fast Particle Interaction With Waves In Fusion Plasmas AIP Conf. Proc. 871, pp. 15-26; doi:http://dx.doi.org/10.1063/1.2404536 (12 pages) Online Publication Date: 30 November 2006
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There are two well‐known motivations for theoretical studies of fast particle interaction with waves in magnetic confinement devices. One is the challenge of avoiding strong collective losses of alpha particles and beam ions in future burning plasma experiments. The other one is the compelling need to quantitatively interpret the large amount of experimental data from JET, TFTR, JT‐60U, DIII‐D, and other machines. Such interpretation involves unique diagnostic opportunities offered by MHD spectroscopy. This report discusses how the present theory responds to the stated challenges and what theoretical and computational advances are required to address the outstanding problems. More specifically, this paper deals with the following topics: predictive capabilities of linear theory and simulations; theory of Alfvén cascades; diagnostic opportunities based on linear and nonlinear properties of unstable modes; interplay of kinetic and fluid nonlinearities; fast chirping phenomena for non‐perturbative modes; and global transport of fast particles. Recent results are presented on some of the listed topics, although the main goal is to identify critical issues for future work. © 2006 American Institute of Physics |
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The Quest for Elementary Particles AIP Conf. Proc. 1006, pp. 3-11; doi:http://dx.doi.org/10.1063/1.2927617 (9 pages) Online Publication Date: 25 April 2008
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This talk describes past progress in probing the structure of matter and the content of the Universe, which has led to the Standard Model of elementary particles, and the prospects for establishing new physics beyond the Standard Model using the LHC particle collider at CERN. |
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Views About Science and physics achievement: The VASS story AIP Conf. Proc. 399, pp. 605-614; doi:http://dx.doi.org/10.1063/1.53156 (10 pages) Online Publication Date: 9 July 2008
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The Views About Sciences Survey (VASS) is a paper-and-pencil instrument to characterize student views about knowing and learning science and assess the relation of these views to achievement in science courses. VASS shows that: (a) high school and college students have views about physics that often diverge from physicists’ views, (b) student views can be grouped into four distinct profiles: expert, high transitional, low transitional, and folk, (c) profile distributions are similar in college and high school, and (d) student profiles correlate significantly with physics achievement. © 1997 American Institute of Physics. |
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Velocity bunching in photo-injectors AIP Conf. Proc. 581, pp. 87-106; doi:http://dx.doi.org/10.1063/1.1401564 (20 pages)
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We describe here a new method to increase the peak current of high brightness electron beams as those required to drive X-ray SASE FEL’s, that is based on a rectilinear compressor scheme utilizing the bunching properties of slow waves. It is shown that whenever a beam, slower than the synchronous velocity, is injected into a RF wave at the zero acceleration phase and slips back in phase up to the peak acceleration phase, it can be compressed as far as the extraction happens at the synchronous velocity. In fact, the bunch undergoes a quarter of synchrotron oscillation that induces a net compression (i.e. a bunch length reduction) up to a factor of 20 when proper care is taken to preserve the longitudinal emittance. A few examples are presented to demonstrate the potentialities of this method, by which multi-kA beams at very low emittance can be generated at moderate energies (about 100 MeV). © 2001 American Institute of Physics. |
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The test facility for the short prototypes of the LHC superconducting magnets AIP Conf. Proc. 613, pp. 106-113; doi:http://dx.doi.org/10.1063/1.1472011 (8 pages) Online Publication Date: 15 May 2002
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The LHC development program relies on cryogenic tests of prototype and model magnets. This vigorous program is pursued in a dedicated test facility based on several vertical cryostats working at superfluid helium temperatures. The performance of the facility is detailed. Goals and test equipment for currently performed studies are reviewed: quench analysis and magnet protection studies, measurement of the field quality, test of ancillary electrical equipment like diodes and busbars. The paper covers the equipment available for tests of prototypes and some special series of LHC magnets to come. © 2002 American Institute of Physics. |
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Topic 2: Launching A Successful Physics Career AIP Conf. Proc. 628, pp. 13-16; doi:http://dx.doi.org/10.1063/1.1505271 (4 pages) Online Publication Date: 20 August 2002
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The facts that there are few women in physics and their presence decreases at each higher level in the hierarchy are evidence that women physicists face challenges in launching and pursuing a successful physics career. In four parallel discussion groups led and recorded by the coauthors, about 80 of the conference participants discussed the issues involved, shared proven solutions, and brainstormed other possible strategies. This paper summarizes the results of the discussions, emphasizing useful advice for aspiring women physicists and those interested in facilitating their retention and advancement. © 2002 American Institute of Physics |
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The Nuclear Renaissance — Implications on Quantitative Nondestructive Evaluations AIP Conf. Proc. 894, pp. 3-16; doi:http://dx.doi.org/10.1063/1.2717949 (14 pages) Online Publication Date: 28 March 2007
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The world demand for energy is growing rapidly, particularly in developing countries that are trying to raise the standard of living for billions of people, many of whom do not even have access to electricity. With this increased energy demand and the high and volatile price of fossil fuels, nuclear energy is experiencing resurgence. This so‐called nuclear renaissance is broad based, reaching across Asia, the United States, Europe, as well as selected countries in Africa and South America. Some countries, such as Italy, that have actually turned away from nuclear energy are reconsidering the advisability of this design. This renaissance provides the opportunity to deploy more advanced reactor designs that are operating today, with improved safety, economy, and operations. In this keynote address, I will briefly present three such advanced reactor designs in whose development Westinghouse is participating. These designs include the advanced passive PWR, AP1000, which recently received design certification for the US Nuclear Regulatory Commission; the Pebble Bed Modular reactor (PBMR) which is being demonstrated in South Africa; and the International Reactor Innovative and Secure (IRIS), which was showcased in the US Department of Energy’s recently announced Global Nuclear Energy Partnership (GNEP), program. The salient features of these designs that impact future requirements on quantitative nondestructive evaluations will be discussed. Such features as reactor vessel materials, operating temperature regimes, and new geometric configurations will be described, and mention will be made of the impact on quantitative nondestructive evaluation (NDE) approaches. © 2007 American Institute of Physics |
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Modeling of Entropy Producing Processes AIP Conf. Proc. 1029, pp. 3-10; doi:http://dx.doi.org/10.1063/1.2971993 (8 pages) Online Publication Date: 31 July 2008
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In all processes concerning real materials, entropy is produced. While undergoing such processes, the natural configuration of a body (the configuration that the body would take on the removal of all external stimuli) changes. It is also possible that the material symmetry of the body in these various natural configurations could be different. Usually, one requires that all processes meet the second law of thermodynamics namely that the rate of entropy production is non‐negative. In this study we make a more stringent requirement, namely that the rate of entropy production is maximized. A framework is developed wherein knowing how the material stores energy, produces entropy, conducts heat, absorbs or emits radiation, etc., allows one to determine the constitutive equation for the stress and other relevant quantities. |
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DRY DILUTION REFRIGERATOR WITH HIGH COOLING POWER AIP Conf. Proc. 985, pp. 1287-1291; doi:http://dx.doi.org/10.1063/1.2908485 (5 pages) Online Publication Date: 27 March 2008
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We present the construction concept and cooling capacity measurements of a 3,4He dilution refrigerator (DR), which was pre-cooled by a commercial pulse tube refrigerator (PTR). No cryogens are needed for the operation of this type of cryostat. The condensation of the helium mash was done in an integrated Joule-Thomson circuit, which was part of the dilution unit. The composition of the dilution unit was standard, but its components (still, heat exchangers, mixing chamber) were designed for high 3He flow. For thermometry, calibrated RuO chip resistance thermometers were available. In order to condense the mixture before an experiment, the fridge was operated like a Joule-Thomson liquefier with a relatively high inlet pressure (4 bar), where the liquid fraction of the circulating 3,4He mixture was accumulated in the dilution unit. The condensation took about 2 hours, and after 2 more hours of running, the temperature of the mixing chamber approached its minimum temperature of 10 mK. The maximum flow rate of the fridge was 1 mmol/s, and the refrigeration capacity of the mixing chamber was 700 μW at 100 mK. High cooling capacity, ease of operation and reliability distinguish this type of milli-Kelvin cooler. |
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DESIGN AND ANALYSIS OF A SMALL-SCALE BIOGAS LIQUEFACTION CYCLE AIP Conf. Proc. 985, pp. 1166-1174; doi:http://dx.doi.org/10.1063/1.2908468 (9 pages) Online Publication Date: 27 March 2008
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The biogas has practical significance in helping to solve the energy crisis. This paper provides a small-scale biogas liquefaction scheme, the liquefaction flow diagram, and analysis of the impacts of key parameters. The thermal parameters of the liquefaction cycle are presented. The results provide guidelines for the design of small-scale biogas liquefaction systems. |
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Investigation of the Influence of Different Boundary Conditions on Helicon Discharges AIP Conf. Proc. 669, pp. 26-29; doi:http://dx.doi.org/10.1063/1.1593857 (4 pages) Online Publication Date: 8 July 2003
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In this paper we present investigations on the influence of boundary conditions on helicon discharges. This is done using two approaches: Firstly, the influence of the plasma size is studied by excitation of whistler waves with different wavelengths (frequency range 100 – 1000 MHz). For wavelengths much smaller than the plasma dimensions (4.5 m in length and up to 40 cm in diameter), the unbounded whistler dispersion relation turns out to be appropriate. For increasing wavelengths, the measured dispersion deviates more and more from the predictions of unbounded plasma theory and the helicon wave dispersion relation must be used. Secondly, the boundary condition between the antenna and the plasma is investigated. Standard right‐helical antennae are used to operate an rf helicon plasma at a typical frequency of 13.56 MHz. In the linear magnetised plasma experiment VINETA, two different setups for the RF plasma source are available: a standard helicon setup with a glass cylinder attached to one end of the chamber, and a helicon antenna inserted into the stainless steel chamber. The spatial distribution of magnetic fluctuations as well as the plasma parameters are measured with high resolution in a plane perpendicular to the magnetic field as well as in a parallel plane. The influence of the different electric boundaries in the two setups is studied extensively under different operational conditions. This is done by studying the transitions between the capacitive, the inductive and the helicon mode operation. © 2003 American Institute of Physics |
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A Study on the Status of Women Faculty in Science at MIT AIP Conf. Proc. 628, pp. 103-106; doi:http://dx.doi.org/10.1063/1.1505288 (4 pages) Online Publication Date: 20 August 2002
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Signal processing for beam position monitors AIP Conf. Proc. 546, pp. 36-60; doi:http://dx.doi.org/10.1063/1.1342578 (25 pages)
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At the first sight the problem to determine the beam position from the ratio of the induced charges of the opposite electrodes of a beam monitor seems trivial, but up to now no unique solution has been found that fits the various demands of all particle accelerators. The purpose of this paper is to help “instrumentalists” to choose the best processing system for their particular application, depending on the machine size, the input dynamic range, the required resolution and the acquisition speed. After a general introduction and an analysis of the electrical signals to be treated (frequency and time domain), the definition of the electronic specifications will be reviewed. The tutorial will present the different families in which the processing systems can be grouped. A general description of the operating principles with relative advantages and disadvantages for the most employed processing systems is presented. Special emphasis will be put on recent technological developments based on telecommunication circuitry. In conclusion, an application example will show how to choose the correct solution for a particular case. © 2000 American Institute of Physics. |
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Enhancing Plasma Wakefield and E‐cloud Simulation Performance Using a Pipelining Algorithm AIP Conf. Proc. 877, pp. 201-207; doi:http://dx.doi.org/10.1063/1.2409135 (7 pages) Online Publication Date: 8 December 2006
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Modeling long timescale propagation of beams in plasma wakefield accelerators at the energy frontier and in electron clouds in circular accelerators such as CERN‐LHC requires faster and more efficient simulation codes. Simply increasing the number of processors does not scale beyond one‐fifth of the number of cells in the decomposition direction. A pipelining algorithm applied on fully parallelized code QuickPIC is suggested to overcome this limit. The pipelining algorithm uses many groups of processors and optimizes the job allocation on the processors in parallel computing. With the new algorithm, it is possible to use on the order of 102 groups of processors, expanding the scale and speed of simulations with QuickPIC by a similar factor. © 2006 American Institute of Physics |
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Nilpotent Orbits in Simple Lie Algebras and their Transverse Poisson Structures AIP Conf. Proc. 1023, pp. 148-152; doi:http://dx.doi.org/10.1063/1.2958166 (5 pages) Online Publication Date: 30 June 2008
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We consider nilpotent adjoint orbits in complex simple Lie algebras and we examine their transverse Poisson structures. We specialize to the two extreme and most interesting cases, i.e. the subregular and minimal orbits. |
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GBR - Devon
Chair and Lecturer (2 posts)
Sandia National Laboratories
US - NM - Albuquerque
Post Doc – Nuclear/ Nanoparticle Materials
Syracuse University
US - NY - Syracuse
Postdoc in Experimental CM Physics
University of Rochester
US - NY - Rochester
Biomedical Optics
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