Sample records for acceleration exposure limit

  1. Hypothetical exposure limits for oil-based metalworking fluids and cardiovascular mortality in a cohort of autoworkers: structural accelerated failure time models in a public health framework.

    PubMed

    Picciotto, Sally; Peters, Annette; Eisen, Ellen A

    2015-04-15

    Occupational exposure to aerosolized particles of oil-based metalworking fluid was recently linked to deaths from ischemic heart disease. The current recommended exposure limits might be insufficient. Studying cardiovascular mortality is challenging because symptoms can induce sicker workers to reduce their exposure, causing healthy-worker survivor bias. G-estimation of accelerated failure time models reduces this bias and permits comparison of multiple exposure interventions. Michigan autoworkers from the United AutoWorkers-General Motors cohort (n = 38,666) were followed from 1941 through 1994. Separate binary variables indicated whether annual exposure exceeded a series of potential limits. Separate g-estimation analyses for each limit yielded the total number of life-years that could have been saved among persons who died from specific cardiovascular causes by enforcing that exposure limit. Banning oil-based fluids would have saved an estimated 4,003 (95% confidence interval: 2,200, 5,807) life-years among those who died of ischemic heart disease. Estimates for cardiovascular disease overall, acute myocardial infarction, and cerebrovascular disease were 3,500 (95% confidence interval: 1,350, 5,651), 2,932 (95% confidence interval: 1,587, 4,277), and 917 (95% confidence interval: -80, 1,913) life-years, respectively. A limit of 0.01 mg/m(3) would have had a similar impact on cerebrovascular disease but one only half as great on ischemic heart disease. Analyses suggest that limiting exposure to metalworking fluids could have saved many life-years lost to cardiovascular diseases in this cohort. PMID:25816818

  2. Hypothetical Exposure Limits for Oil-Based Metalworking Fluids and Cardiovascular Mortality in a Cohort of Autoworkers: Structural Accelerated Failure Time Models in a Public Health Framework

    PubMed Central

    Picciotto, Sally; Peters, Annette; Eisen, Ellen A.

    2015-01-01

    Occupational exposure to aerosolized particles of oil-based metalworking fluid was recently linked to deaths from ischemic heart disease. The current recommended exposure limits might be insufficient. Studying cardiovascular mortality is challenging because symptoms can induce sicker workers to reduce their exposure, causing healthy-worker survivor bias. G-estimation of accelerated failure time models reduces this bias and permits comparison of multiple exposure interventions. Michigan autoworkers from the United AutoWorkers–General Motors cohort (n = 38,666) were followed from 1941 through 1994. Separate binary variables indicated whether annual exposure exceeded a series of potential limits. Separate g-estimation analyses for each limit yielded the total number of life-years that could have been saved among persons who died from specific cardiovascular causes by enforcing that exposure limit. Banning oil-based fluids would have saved an estimated 4,003 (95% confidence interval: 2,200, 5,807) life-years among those who died of ischemic heart disease. Estimates for cardiovascular disease overall, acute myocardial infarction, and cerebrovascular disease were 3,500 (95% confidence interval: 1,350, 5,651), 2,932 (95% confidence interval: 1,587, 4,277), and 917 (95% confidence interval: ?80, 1,913) life-years, respectively. A limit of 0.01 mg/m3 would have had a similar impact on cerebrovascular disease but one only half as great on ischemic heart disease. Analyses suggest that limiting exposure to metalworking fluids could have saved many life-years lost to cardiovascular diseases in this cohort. PMID:25816818

  3. Ultra-accelerated natural sunlight exposure testing

    DOEpatents

    Jorgensen, Gary J. (Pine, CO); Bingham, Carl (Lakewood, CO); Goggin, Rita (Englewood, CO); Lewandowski, Allan A. (Evergreen, CO); Netter, Judy C. (Westminster, CO)

    2000-06-13

    Process and apparatus for providing ultra accelerated natural sunlight exposure testing of samples under controlled weathering without introducing unrealistic failure mechanisms in exposed materials and without breaking reciprocity relationships between flux exposure levels and cumulative dose that includes multiple concurrent levels of temperature and relative humidity at high levels of natural sunlight comprising: a) concentrating solar flux uniformly; b) directing the controlled uniform sunlight onto sample materials in a chamber enclosing multiple concurrent levels of temperature and relative humidity to allow the sample materials to be subjected to accelerated irradiance exposure factors for a sufficient period of time in days to provide a corresponding time of about at least a years worth of representative weathering of the sample materials.

  4. Improving tritium exposure reconstructions using accelerator mass spectrometry

    PubMed Central

    Hunt, J. R.; Vogel, J. S.; Knezovich, J. P.

    2010-01-01

    Direct measurement of tritium atoms by accelerator mass spectrometry (AMS) enables rapid low-activity tritium measurements from milligram-sized samples and permits greater ease of sample collection, faster throughput, and increased spatial and/or temporal resolution. Because existing methodologies for quantifying tritium have some significant limitations, the development of tritium AMS has allowed improvements in reconstructing tritium exposure concentrations from environmental measurements and provides an important additional tool in assessing the temporal and spatial distribution of chronic exposure. Tritium exposure reconstructions using AMS were previously demonstrated for a tree growing on known levels of tritiated water and for trees exposed to atmospheric releases of tritiated water vapor. In these analyses, tritium levels were measured from milligram-sized samples with sample preparation times of a few days. Hundreds of samples were analyzed within a few months of sample collection and resulted in the reconstruction of spatial and temporal exposure from tritium releases. Although the current quantification limit of tritium AMS is not adequate to determine natural environmental variations in tritium concentrations, it is expected to be sufficient for studies assessing possible health effects from chronic environmental tritium exposure. PMID:14735274

  5. Count rate limitations in pulsed accelerator fields

    SciTech Connect

    Justus, Alan L [Los Alamos National Laboratory

    2010-12-15

    This paper discusses various concepts involved in the counting losses of pulse-counting health physics instrumentation when used within the pulsed radiation environments of typical accelerator fields, in order to pre-establish appropriate limitations in use. Discussed are the 'narrow' pulse and the 'wide' pulse cases, the special effect of neutron moderating assemblies, and the effect of pulse microstructure on the counting losses of the pulse-counting instrumentation. Examples are provided which highlight the various concepts and limitations.

  6. Occupational noise exposure limits for developing countries

    Microsoft Academic Search

    G. H Shaikh

    1999-01-01

    Occupational noise is one of the major environmental problems in industrial plants. Therefore, in order to limit high level occupational noise, maximum permissible occupational noise exposure limit in the range of 90–85dB(A) Leq for 8h\\/day (40h\\/week) have been allowed by the International Standards Organization (ISO), EEC and other developed countries. But in developing countries, most of the industrial plants work

  7. 30 CFR 56.5001 - Exposure limits for airborne contaminants.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...false Exposure limits for airborne contaminants. 56.5001 Section 56.5001...5001 Exposure limits for airborne contaminants. Except as permitted by § 56.5005...this section, the exposure to airborne contaminants shall not exceed, on the...

  8. 30 CFR 57.5001 - Exposure limits for airborne contaminants.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...false Exposure limits for airborne contaminants. 57.5001 Section 57.5001...5001 Exposure limits for airborne contaminants. Except as permitted by § 57.5005...paragraph (b), the exposure to airborne contaminants shall not exceed, on the...

  9. Timescale Correlation between Marine Atmospheric Exposure and Accelerated Corrosion Testing

    NASA Technical Reports Server (NTRS)

    Montgomery, Eliza L.; Calle, Luz Marina; Curran, Jerone C.; Kolody, Mark R.

    2011-01-01

    Evaluation of metal-based structures has long relied on atmospheric exposure test sites to determine corrosion resistance in marine environments. Traditional accelerated corrosion testing relies on mimicking the exposure conditions, often incorporating salt spray and ultraviolet (UV) radiation, and exposing the metal to continuous or cyclic conditions of the corrosive environment. Their success for correlation to atmospheric exposure is often a concern when determining the timescale to which the accelerated tests can be related. Accelerated laboratory testing, which often focuses on the electrochemical reactions that occur during corrosion conditions, has yet to be universally accepted as a useful tool in predicting the long term service life of a metal despite its ability to rapidly induce corrosion. Although visual and mass loss methods of evaluating corrosion are the standard and their use is imperative, a method that correlates timescales from atmospheric exposure to accelerated testing would be very valuable. This work uses surface chemistry to interpret the chemical changes occurring on low carbon steel during atmospheric and accelerated corrosion conditions with the objective of finding a correlation between its accelerated and long-term corrosion performance. The current results of correlating data from marine atmospheric exposure conditions at the Kennedy Space Center beachside corrosion test site, alternating seawater spray, and immersion in typical electrochemical laboratory conditions, will be presented. Key words: atmospheric exposure, accelerated corrosion testing, alternating seawater spray, marine, correlation, seawater, carbon steel, long-term corrosion performance prediction, X-ray photoelectron spectroscopy.

  10. LIMITS OF Nb3Sn ACCELERATOR MAGNETS

    SciTech Connect

    Caspi, Shlomo; Ferracin, Paolo

    2005-05-01

    Pushing accelerator magnets beyond 10 T holds a promise of future upgrades to machines like the Tevatron at Fermilab and the LHC at CERN. Exceeding the current density limits of NbTi superconductor, Nb{sub 3}Sn is at present the only practical superconductor capable of generating fields beyond 10 T. Several Nb{sub 3}Sn pilot magnets, with fields as high as 16 T, have been built and tested, paving the way for future attempts at fields approaching 20 T. High current density conductor is required to generate high fields with reduced conductor volume. However this significantly increases the Lorentz force and stress. Future designs of coils and structures will require managing stresses of several 100's of MPa and forces of 10's of MN/m. The combined engineering requirements on size and cost of accelerator magnets will involve magnet technology that diverges from the one currently used with NbTi conductor. In this paper we shall address how far the engineering of high field magnets can be pushed, and what are the issues and limitations before such magnets can be used in particle accelerators.

  11. Ultra-accelerated natural sunlight exposure testing facilities

    DOEpatents

    Lewandowski, Allan A.; Jorgensen, Gary J.

    2003-08-12

    A multi-faceted concentrator apparatus for providing ultra-accelerated natural sunlight exposure testing for sample materials under controlled weathering conditions comprising: facets that receive incident natural sunlight, transmits VIS/NIR and reflects UV/VIS to deliver a uniform flux of UV/VIS onto a sample exposure plane located near a center of a facet array in chamber means that provide concurrent levels of temperature and/or relative humidity at high levels of up to 100.times. of natural sunlight that allow sample materials to be subjected to accelerated irradiance exposure factors for a significant period of time of about 3 to 10 days to provide a corresponding time of about at least a years worth representative weathering of sample materials.

  12. Ultra-Accelerated Natural Sunlight Exposure Testing Facilities

    DOEpatents

    Lewandowski, Allan A. (Evergreen, CO); Jorgensen, Gary J. (Pine, CO)

    2004-11-23

    A multi-faceted concentrator apparatus for providing ultra-accelerated natural sunlight exposure testing for sample materials under controlled weathering conditions comprising: facets that receive incident natural sunlight, transmits VIS/NIR and reflects UV/VIS onto a secondary reflector that delivers a uniform flux of UV/VIS onto a sample exposure plane located near a center of a facet array in a chamber that provide concurrent levels of temperature and/or relative humidity at high levels of up to 100.times. of natural sunlight that allow sample materials to be subjected to accelerated irradiance exposure factors for a significant period of time of about 3 to 10 days to provide a corresponding time of about at least a years worth representative weathering of sample materials.

  13. Proposed maximum permissible exposure limits for ultrashort laser pulses.

    PubMed

    Roach, W P; Johnson, T E; Rockwell, B A

    1999-04-01

    Recent studies have provided considerable ED50 data for both visible and near infrared wavelengths from single laser pulses below one nanosecond of exposure. The current ANSI Z136.1 standard does not offer an approved maximum permissible exposure limit for subnanosecond single laser pulses and the current suggested maximum permissible exposure limit may be overly conservative. Lacking an approved standard industrial, medical, educational, and military uses of these types of laser systems may be limited or prohibited. A new set of laser maximum permissible exposure limits for subnanosecond visible and near infrared single laser pulses is recommended, along with the steps taken to develop the proposed standard. PMID:10086595

  14. Nonlinear dynamics of autonomous vehicles with limits on acceleration

    NASA Astrophysics Data System (ADS)

    Davis, L. C.

    2014-07-01

    The stability of autonomous vehicle platoons with limits on acceleration and deceleration is determined. If the leading-vehicle acceleration remains within the limits, all vehicles in the platoon remain within the limits when the relative-velocity feedback coefficient is equal to the headway time constant [k=1/h]. Furthermore, if the sensitivity ?>1/h, no collisions occur. String stability for small perturbations is assumed and the initial condition is taken as the equilibrium state. Other values of k and ? that give stability with no collisions are found from simulations. For vehicles with non-negligible mechanical response, simulations indicate that the acceleration-feedback-control gain might have to be dynamically adjusted to obtain optimal performance as the response time changes with engine speed. Stability is demonstrated for some perturbations that cause initial acceleration or deceleration greater than the limits, yet do not cause collisions.

  15. Threshold limit values, permissible exposure limits, and feasibility: The bases for exposure limits in the United States

    SciTech Connect

    Rappaport, S.M. (Univ. of North Carolina, Chapel Hill (United States))

    1993-01-01

    The development of exposure limits in the United States has always relied heavily upon the threshold limit values (TLVs) developed by the American Conference of Governmental Industrial Hygienists (ACGIH). In fact, the TLVs were adopted as official exposure limits by the Occupational Safety and Health Administration (OSHA) in 1972 and 1989. Given the continuing importance of the ACGIH limits, this paper compares the basis of the TLVs with that employed by OSHA de novo in its 12 new permissible exposure limits (PELs). Using benzene as an example, it is shown that OSHA's new PELs have been established following a rigorous assessment of the inherent risks and the feasibility of instituting the limit. The TLVs, on the other hand, have been developed by ad hoc procedures and appear to have traditionally reflected levels thought to be achievable at the time. However, this might be changing. Analysis of the historical reductions of TLVs, for 27 substances on the 1991-1992 list of intended changes, indicates smaller reductions in the past (median reduction of 2.0-2.5-fold between 1946 and 1988) compared to those currently being observed (median reduction of 7.5-fold between 1989 and 1991). Further analysis suggests a more aggressive policy of the ACGIH regarding TLVs for carcinogens but not for substances that produce effects other than cancer. Regardless of whether the basis of the TLVs has changed recently, it would take a relatively long time for the impact of any change to be felt, since the median age of the 1991-1992 TLVs is 16.5 years, and 75% of these limits are more than 10 years old. The implications of OSHA's continued reliance on the TLVs as a means of updating its PELs are discussed, and four alternatives are presented to the ACGIH regarding the future of its activities related to exposure limits. It is concluded that new mechanisms are needed for OSHA to update its PELs in a timely fashion so that the TLVs will not be adopted by default in the future.

  16. ELRA: The exposure limiting robotic apparatus

    SciTech Connect

    Knighton, G.C.; Rosenberg, K.E.; Henslee, S.P.; Michelbacher, J.A.; Wilkes, C.W.

    1992-09-01

    A problem situation involving the handling of radioactive material at Argonne National Laboratory -- West (ANL-W) was solved through the use of remote handling techniques, providing significant exposure reduction to personnel. Robotic devices can be useful, but the cost of a robot is often prohibitive for many jobs. A low cost, disposable robot was built which successfully removed a highly radioactive and potentially explosive system from a hot cell at ANL-W.

  17. Neutron Exposure Accelerator System For Biological Effect Experiments (NASBEE)

    SciTech Connect

    Takada, Masashi; Suda, Mitsuo; Kamada, So; Hagiwara, Takuya; Imaseki, Hitoshi; Hamano, Tsuyoshi [National Institute of Radiological Sciences, 4-9-1, Anagawa, Inage-ku Chiba, Japan 263-8555 (Japan)

    2011-06-01

    The neutron exposure accelerator system for biological effect experiments (NASBEE) was developed to study biological effects of fast neutrons. We have characterized the NASBEE neutron beams with neutron energy spectrum, absorbed dose energy distributions, and space distributions. The neutron energy spectrum shows 2.3 MeV as mean energy and 3.0 MeV as kerma of tissue-equivalent-plastic (A150) weighted mean energy, and the maximum neutron energy was determined to be 9 MeV. Neutron absorbed doses occupy 82% of the NASBEE neutron beam. NASBEE has been used to learn some of the outcomes of the biological effects of fast neutrons.

  18. Pushing the Limits of Accelerator Mass Spectrometry

    SciTech Connect

    Galindo-Uribarri, Alfredo {nmn} [ORNL; Beene, James R [ORNL; Danchev, M. [University of Tennessee, Knoxville (UTK); Doupe, J. [University of Toronto; Fuentes Madariaga, Beatriz E [ORNL; Gomez Del Campo, Jorge [ORNL; Hausladen, Paul [ORNL; Juras, Raymond C [ORNL; Liang, J Felix [ORNL; Litherland, Albert E [ORNL; Liu, Yuan [ORNL; Meigs, Martha J [ORNL; Mills, Gerald D [ORNL; Mueller, Paul Edward [ORNL; Padilla-Rodal, Elizabeth [ORNL; Pavan, John R [ORNL; Sinclair IV, John W [ORNL; Stracener, Daniel W [ORNL

    2007-01-01

    A renewed interest in Accelerator Mass Spectrometry (AMS) from nuclear physics laboratories is emerging in connection with Radioactive Ion Beams (RIBs). At the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory (ORNL) we are exploring the AMS capabilities of the 25-MV Tandem acclerator. Behind this effort is the realization that two fields of research - AMS and RIBs - complement each other in techniques. Development of effective and efficient beam purification techniques is of common interest to both AMS and the RIB program. Two main characteristics of the 25-MV Tandem provide unique opportunities for performing the highest sensitivity measurements of AMS; namely i) the highest operating voltage in the world, and ii) a folded geometry which involves a 180 degree magnet in the terminal. For the RIB program, we have used AMS techniques to improve the sensitivity of detection of some radioactive species in the measurement of unknown massses of n-rich nuclei. For AMS, we have concentrated in exploring two important isotopes, 14C and 36Cl, for applications that require the highest sensitivity. We have successfully measured 36Cl/Cl ratios as low as a few times 10-16 in seawater samples demonstrating that our set has the highest sensitivity for this isotope and proving that 36Cl can be measured at the levels required for a tracer in oceanography.

  19. OSHA's permissible exposure limits: Regulatory compliance versus health risk

    Microsoft Academic Search

    Robert C. Spear; Steve Selvin

    1989-01-01

    Workplace exposures to airborne chemicals are regulated in the U.S. by the Occupational Safety and Health Administration (OSHA) via the promulgation of permissible exposure limits (PELs). These limits, usually defined as eight-hour time-weighted average values, are enforced as concentrations never to be exceeded. In the case of chronic or delayed toxicants, the PEL is determined from epidemiological evidence and\\/or quantitative

  20. Gradient limitations in room temperature and superconducting acceleration structures

    SciTech Connect

    Solyak, N.A.; /Fermilab

    2008-10-01

    Accelerating gradient is a key parameter of the accelerating structure in large linac facilities, like future Linear Collider. In room temperature accelerating structures the gradient is limited mostly by breakdown phenomena, caused by high surface electric fields or pulse surface heating. High power processing is a necessary procedure to clean surface and improve the gradient. In the best tested X-band structures the achieved gradient is exceed 100 MV/m in of {approx}200 ns pulses for breakdown rate of {approx} 10{sup -7}. Gradient limit depends on number of factors and no one theory which can explain all sets of experimental results and predict gradient in new accelerating structure. In paper we briefly overview the recent experimental results of breakdown studies, progress in understanding of gradient limitations and scaling laws. Although superconducting rf technology has been adopted throughout the world for ILC, it has frequently been difficult to reach the predicted performance in these structures due to a number of factors: multipactoring, field emission, Q-slope, thermal breakdown. In paper we are discussing all these phenomena and the ways to increase accelerating gradient in SC cavity, which are a part of worldwide R&D program.

  1. Maximal Acceleration Limits on the Mass of the Higgs Boson

    E-print Network

    G. Lambiase; G. Papini; G. Scarpetta

    1998-08-28

    Caianiello's quantum geometrical model with maximal acceleration places the upper limit $\\mu\\leq 719.5$ GeV on the mass of the Higgs boson. The model also provides an equation linking the mass of the W boson to the Higgs mass $\\mu$ and independent symmetry breaking and mass generating mechanisms. These may further restrict the value of $\\mu$.

  2. Issues for Simulation of Galactic Cosmic Ray Exposures for Radiobiological Research at Ground-Based Accelerators

    PubMed Central

    Kim, Myung-Hee Y.; Rusek, Adam; Cucinotta, Francis A.

    2015-01-01

    For radiobiology research on the health risks of galactic cosmic rays (GCR) ground-based accelerators have been used with mono-energetic beams of single high charge, Z and energy, E (HZE) particles. In this paper, we consider the pros and cons of a GCR reference field at a particle accelerator. At the NASA Space Radiation Laboratory (NSRL), we have proposed a GCR simulator, which implements a new rapid switching mode and higher energy beam extraction to 1.5 GeV/u, in order to integrate multiple ions into a single simulation within hours or longer for chronic exposures. After considering the GCR environment and energy limitations of NSRL, we performed extensive simulation studies using the stochastic transport code, GERMcode (GCR Event Risk Model) to define a GCR reference field using 9 HZE particle beam–energy combinations each with a unique absorber thickness to provide fragmentation and 10 or more energies of proton and 4He beams. The reference field is shown to well represent the charge dependence of GCR dose in several energy bins behind shielding compared to a simulated GCR environment. However, a more significant challenge for space radiobiology research is to consider chronic GCR exposure of up to 3 years in relation to simulations with animal models of human risks. We discuss issues in approaches to map important biological time scales in experimental models using ground-based simulation, with extended exposure of up to a few weeks using chronic or fractionation exposures. A kinetics model of HZE particle hit probabilities suggests that experimental simulations of several weeks will be needed to avoid high fluence rate artifacts, which places limitations on the experiments to be performed. Ultimately risk estimates are limited by theoretical understanding, and focus on improving knowledge of mechanisms and development of experimental models to improve this understanding should remain the highest priority for space radiobiology research. PMID:26090339

  3. Issues for Simulation of Galactic Cosmic Ray Exposures for Radiobiological Research at Ground-Based Accelerators.

    PubMed

    Kim, Myung-Hee Y; Rusek, Adam; Cucinotta, Francis A

    2015-01-01

    For radiobiology research on the health risks of galactic cosmic rays (GCR) ground-based accelerators have been used with mono-energetic beams of single high charge, Z and energy, E (HZE) particles. In this paper, we consider the pros and cons of a GCR reference field at a particle accelerator. At the NASA Space Radiation Laboratory (NSRL), we have proposed a GCR simulator, which implements a new rapid switching mode and higher energy beam extraction to 1.5 GeV/u, in order to integrate multiple ions into a single simulation within hours or longer for chronic exposures. After considering the GCR environment and energy limitations of NSRL, we performed extensive simulation studies using the stochastic transport code, GERMcode (GCR Event Risk Model) to define a GCR reference field using 9 HZE particle beam-energy combinations each with a unique absorber thickness to provide fragmentation and 10 or more energies of proton and (4)He beams. The reference field is shown to well represent the charge dependence of GCR dose in several energy bins behind shielding compared to a simulated GCR environment. However, a more significant challenge for space radiobiology research is to consider chronic GCR exposure of up to 3 years in relation to simulations with animal models of human risks. We discuss issues in approaches to map important biological time scales in experimental models using ground-based simulation, with extended exposure of up to a few weeks using chronic or fractionation exposures. A kinetics model of HZE particle hit probabilities suggests that experimental simulations of several weeks will be needed to avoid high fluence rate artifacts, which places limitations on the experiments to be performed. Ultimately risk estimates are limited by theoretical understanding, and focus on improving knowledge of mechanisms and development of experimental models to improve this understanding should remain the highest priority for space radiobiology research. PMID:26090339

  4. Young Children's Limited and Narrow Exposure to Informational Text

    ERIC Educational Resources Information Center

    Yopp, Ruth Helen; Yopp, Hallie Kay

    2012-01-01

    Despite arguments for more fully including informational text in early childhood classrooms, research suggests that young children's exposure to the genre is quite limited. This article focuses on the informational books that children do encounter, specifically through read-alouds, and describes the narrow focus of those books. Informational…

  5. LIMITATIONS ON THE USES OF MULTIMEDIA EXPOSURE MEASUREMENTS FOR MULTIPATHWAY EXPOSURE ASSESSMENT - PART I: HANDLING OBSERVATIONS BELOW DETECTION LIMITS

    EPA Science Inventory

    Multimedia data from two probability-based exposure studies were investigated in terms of how censoring of non-detects affected estimation of population parameters and associations. Appropriate methods for handling censored below-detection-limit (BDL) values in this context were...

  6. Cumulative exposure to dust causes accelerated decline in lung function in tunnel workers

    PubMed Central

    Ulvestad, B; Bakke, B; Eduard, W; Kongerud, J; Lund, M

    2001-01-01

    OBJECTIVES—To examine whether underground construction workers exposed to tunnelling pollutants over a follow up period of 8 years have an increased risk of decline in lung function and respiratory symptoms compared with reference subjects working outside the tunnel atmosphere, and relate the findings to job groups and cumulative exposure to dust and gases.?METHODS—96 Tunnel workers and a reference group of 249 other heavy construction workers were examined in 1991 and re-examined in 1999. Exposure measurements were carried out to estimate personal cumulative exposure to total dust, respirable dust, ?-quartz, oil mist, and nitrogen dioxide. The subjects answered a questionnaire on respiratory symptoms and smoking habits, performed spirometry, and had chest radiographs taken. Radiological signs of silicosis were evaluated (International Labour Organisation (ILO) classification). Atopy was determined by a multiple radioallergosorbent test (RAST).?RESULTS—The mean exposure to respirable dust and ?-quartz in tunnel workers varied from 1.2-3.6 mg/m3 (respirable dust) and 0.019-0.044 mg/m3 (?-quartz) depending on job task performed. Decrease in forced expiratory volume in 1 second (FEV1) was associated with cumulative exposure to respirable dust (p<0.001) and ?-quartz (p=0.02). The multiple regression model predicted that in a worker 40 years of age, the annual decrease in FEV1 would be 25 ml in a non-exposed non-smoker, 35 ml in a non-exposed smoker, and 50-63 ml in a non-smoking tunnel worker (depending on job). Compared with the reference group the odds ratio for the occurrence of new respiratory symptoms during the follow up period was increased in the tunnel workers and associated with cumulative exposure to respirable dust.?CONCLUSIONS—Cumulative exposures to respirable dust and ?-quartz are the most important risk factors for airflow limitation in underground heavy construction workers, and cumulative exposure to respirable dust is the most important risk factor for respiratory symptoms. The finding of accelerated decline in lung function in tunnel workers suggests that better control of exposures is needed.???Keywords: heavy construction; respirable dust; lung function PMID:11555688

  7. The Occupational Exposure Limit for Fluid Aerosol Generated in Metalworking Operations: Limitations and Recommendations

    PubMed Central

    2012-01-01

    The aim of this review was to assess current knowledge related to the occupational exposure limit (OEL) for fluid aerosols including either mineral or chemical oil that are generated in metalworking operations, and to discuss whether their OEL can be appropriately used to prevent several health risks that may vary among metalworking fluid (MWF) types. The OEL (time-weighted average; 5 mg/m3, short-term exposure limit ; 15 mg/m3) has been applied to MWF aerosols without consideration of different fluid aerosol-size fractions. The OEL, is also based on the assumption that there are no significant differences in risk among fluid types, which may be contentious. Particularly, the health risks from exposure to water-soluble fluids may not have been sufficiently considered. Although adoption of The National Institute for Occupational Safety and Health's recommended exposure limit for MWF aerosol (0.5 mg/m3) would be an effective step towards minimizing and evaluating the upper respiratory irritation that may be caused by neat or diluted MWF, this would fail to address the hazards (e.g., asthma and hypersensitivity pneumonitis) caused by microbial contaminants generated only by the use of water-soluble fluids. The absence of an OEL for the water-soluble fluids used in approximately 80-90 % of all applicants may result in limitations of the protection from health risks caused by exposure to those fluids. PMID:22953224

  8. The occupational exposure limit for fluid aerosol generated in metalworking operations: limitations and recommendations.

    PubMed

    Park, Donguk

    2012-03-01

    The aim of this review was to assess current knowledge related to the occupational exposure limit (OEL) for fluid aerosols including either mineral or chemical oil that are generated in metalworking operations, and to discuss whether their OEL can be appropriately used to prevent several health risks that may vary among metalworking fluid (MWF) types. The OEL (time-weighted average; 5 mg/m(3), short-term exposure limit ; 15 mg/m(3)) has been applied to MWF aerosols without consideration of different fluid aerosol-size fractions. The OEL, is also based on the assumption that there are no significant differences in risk among fluid types, which may be contentious. Particularly, the health risks from exposure to water-soluble fluids may not have been sufficiently considered. Although adoption of The National Institute for Occupational Safety and Health's recommended exposure limit for MWF aerosol (0.5 mg/m(3)) would be an effective step towards minimizing and evaluating the upper respiratory irritation that may be caused by neat or diluted MWF, this would fail to address the hazards (e.g., asthma and hypersensitivity pneumonitis) caused by microbial contaminants generated only by the use of water-soluble fluids. The absence of an OEL for the water-soluble fluids used in approximately 80-90 % of all applicants may result in limitations of the protection from health risks caused by exposure to those fluids. PMID:22953224

  9. Tumor promotion by exposure to radiofrequency electromagnetic fields below exposure limits for humans.

    PubMed

    Lerchl, Alexander; Klose, Melanie; Grote, Karen; Wilhelm, Adalbert F X; Spathmann, Oliver; Fiedler, Thomas; Streckert, Joachim; Hansen, Volkert; Clemens, Markus

    2015-04-17

    The vast majority of in vitro and in vivo studies did not find cancerogenic effects of exposure to electromagnetic fields (RF-EMF), i.e. emitted by mobile phones and base stations. Previously published results from a pilot study with carcinogen-treated mice, however, suggested tumor-promoting effects of RF-EMF (Tillmann et al., 2010). We have performed a replication study using higher numbers of animals per group and including two additional exposure levels (0 (sham), 0.04, 0.4 and 2 W/kg SAR). We could confirm and extend the originally reported findings. Numbers of tumors of the lungs and livers in exposed animals were significantly higher than in sham-exposed controls. In addition, lymphomas were also found to be significantly elevated by exposure. A clear dose-response effect is absent. We hypothesize that these tumor-promoting effects may be caused by metabolic changes due to exposure. Since many of the tumor-promoting effects in our study were seen at low to moderate exposure levels (0.04 and 0.4 W/kg SAR), thus well below exposure limits for the users of mobile phones, further studies are warranted to investigate the underlying mechanisms. Our findings may help to understand the repeatedly reported increased incidences of brain tumors in heavy users of mobile phones. PMID:25749340

  10. "Quasi nonparametric" upper tolerance limits for occupational exposure evaluations.

    PubMed

    Davis, Charles B; Wambach, Paul F

    2015-01-01

    Upper tolerance limits (UTLs) are often used in comparing exposure data sets with an occupational exposure limit (OEL) or other regulatory criterion (RC): if the 95%-95% UTL does not exceed the OEL, one is 95% confident that at most 5% of exposures exceed the OEL, and the comparison "passes." The largest of 59 observations is a nonparametric (distribution-free) 95%-95% UTL (NPUTL); the chance that this largest value equals or exceeds the actual 95th percentile is at least 95%, regardless of the underlying data distribution. That many observations may seem excessive in clean environments or small studies, though, and one would like to "pass" using UTLs based on fewer observations sufficiently far below the OEL or RC. "Quasi-nonparametric" UTLs (QNP UTLs) accomplish this. QNP UTLs assign a "pass" so long as one has "59 [values] less than the RC" (the NPUTL itself), "30 less than 1/2 [of the RC]," "21 less than 1/3," and on down to "8 less than 1/10," the last matching a rule-of-thumb given in 2006 American Industrial Hygiene Association (AIHA) guidance. They are derived using the conservative, experience-based assumption that the data distribution is lognormal with log-scale standard deviation ? at most 2.0 (geometric standard deviation at most 7.39). Although based on this assumption, their statistical performance is reasonably unaffected or conservative when data come from other distributions often assumed for contaminant concentrations; moreover, their performance is insensitive to analytical variation. This conservative robustness merits the description "quasi-nonparametric." QNP UTLs are very easy to use. Reporting Limit (RL) issues do not arise. QNP UTLs reduce the numbers of observations needed to support conservative risk management decisions when sampling from compliant working conditions. PMID:25647534

  11. Timescale Correlation between Marine Atmospheric Exposure and Accelerated Corrosion Testing - Part 2

    NASA Technical Reports Server (NTRS)

    Montgomery, Eliza L.; Calle, Luz Marina; Curran, Jerome C.; Kolody, Mark R.

    2012-01-01

    Evaluation of metals to predict service life of metal-based structures in corrosive environments has long relied on atmospheric exposure test sites. Traditional accelerated corrosion testing relies on mimicking the exposure conditions, often incorporating salt spray and ultraviolet (UV) radiation, and exposing the metal to continuous or cyclic conditions similar to those of the corrosive environment. Their reliability to correlate to atmospheric exposure test results is often a concern when determining the timescale to which the accelerated tests can be related. Accelerated corrosion testing has yet to be universally accepted as a useful tool in predicting the long-term service life of a metal, despite its ability to rapidly induce corrosion. Although visual and mass loss methods of evaluating corrosion are the standard, and their use is crucial, a method that correlates timescales from accelerated testing to atmospheric exposure would be very valuable. This paper presents work that began with the characterization of the atmospheric environment at the Kennedy Space Center (KSC) Beachside Corrosion Test Site. The chemical changes that occur on low carbon steel, during atmospheric and accelerated corrosion conditions, were investigated using surface chemistry analytical methods. The corrosion rates and behaviors of panels subjected to long-term and accelerated corrosion conditions, involving neutral salt fog and alternating seawater spray, were compared to identify possible timescale correlations between accelerated and long-term corrosion performance. The results, as well as preliminary findings on the correlation investigation, are presented.

  12. 76 FR 60500 - Request for Information: Announcement of Carcinogen and Recommended Exposure Limit (REL) Policy...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-29

    ...Number NIOSH-240] Request for Information: Announcement of Carcinogen and Recommended Exposure Limit (REL) Policy Assessment...announcing its intent to ``review its approach to classifying carcinogens and establishing recommended exposure limits (RELs)...

  13. Extensive changes to occupational exposure limits in Korea.

    PubMed

    Jeong, Jee Yeon; Choi, Sangjun; Kho, Young Lim; Kim, Pan Gyi

    2010-11-01

    Occupational exposure limits (OELs) are used as an important tool to protect workers from adverse chemical exposures and its detrimental effects on their health. The Ministry of Labor (MOL) can establish and publish OELs based on the Industrial Safety and Health Act in Korea. The first set of OELs was announced by the MOL in 1986. At that time, it was identical to the Threshold Limit Values of the American Conference of Governmental Industrial Hygienists. Until 2006, none the first OELs except for those of three chemicals (asbestos, benzene, and 2-bromopropane) were updated during the last twenty years. The Hazardous Agents Review Committee established under the MOL selected 126 chemicals from 698 chemicals covered by OELs using several criteria. From 2005 to 2006, the MOL provided research funds for academic institutions and toxicological laboratories to gather the evidence documenting the need to revise the outdated OELs. Finally, the MOL notified the revised OELs for 126 chemicals from 2007 to 2008. The revised OELs of 58 substances from among these chemicals were lowered to equal or less than half the value of the original OELs. This is the most substantial change in the history of OEL revisions in Korea. PMID:20709131

  14. The development and regulation of occupational exposure limits in Korea.

    PubMed

    Paek, Domyung; Park, Doo Yong

    2006-11-01

    With the institution of the new chemical regulatory framework in 2003, chemicals at the workplace have been classified into five categories; banned substances, permission-required substances, regulated substances, occupational exposure limit set substances, and other generally controlled substances. Currently, there are 698 substances with OELs. As we have come to gain our own experiences in the study and control of chemical hazards at the workplace such as the 2-bromopropane poisoning, OEL setting process has been streamlined. The OELs in Korea, however, remain merely as a recommendation, which does not require all the substances with OELs to be measured at the workplace. Coordination of whole program for hazardous chemicals including workplace measurement, OEL setting process, and enforcement activities is still needed in Korea. PMID:16564609

  15. Sensory irritation as a basis for setting occupational exposure limits.

    PubMed

    Brüning, Thomas; Bartsch, Rüdiger; Bolt, Hermann Maximillian; Desel, Herbert; Drexler, Hans; Gundert-Remy, Ursula; Hartwig, Andrea; Jäckh, Rudolf; Leibold, Edgar; Pallapies, Dirk; Rettenmeier, Albert W; Schlüter, Gerhard; Stropp, Gisela; Sucker, Kirsten; Triebig, Gerhard; Westphal, Götz; van Thriel, Christoph

    2014-10-01

    There is a need of guidance on how local irritancy data should be incorporated into risk assessment procedures, particularly with respect to the derivation of occupational exposure limits (OELs). Therefore, a board of experts from German committees in charge of the derivation of OELs discussed the major challenges of this particular end point for regulatory toxicology. As a result, this overview deals with the question of integrating results of local toxicity at the eyes and the upper respiratory tract (URT). Part 1 describes the morphology and physiology of the relevant target sites, i.e., the outer eye, nasal cavity, and larynx/pharynx in humans. Special emphasis is placed on sensory innervation, species differences between humans and rodents, and possible effects of obnoxious odor in humans. Based on this physiological basis, Part 2 describes a conceptual model for the causation of adverse health effects at these targets that is composed of two pathways. The first, "sensory irritation" pathway is initiated by the interaction of local irritants with receptors of the nervous system (e.g., trigeminal nerve endings) and a downstream cascade of reflexes and defense mechanisms (e.g., eyeblinks, coughing). While the first stages of this pathway are thought to be completely reversible, high or prolonged exposure can lead to neurogenic inflammation and subsequently tissue damage. The second, "tissue irritation" pathway starts with the interaction of the local irritant with the epithelial cell layers of the eyes and the URT. Adaptive changes are the first response on that pathway followed by inflammation and irreversible damages. Regardless of these initial steps, at high concentrations and prolonged exposures, the two pathways converge to the adverse effect of morphologically and biochemically ascertainable changes. Experimental exposure studies with human volunteers provide the empirical basis for effects along the sensory irritation pathway and thus, "sensory NOAEChuman" can be derived. In contrast, inhalation studies with rodents investigate the second pathway that yields an "irritative NOAECanimal." Usually the data for both pathways is not available and extrapolation across species is necessary. Part 3 comprises an empirical approach for the derivation of a default factor for interspecies differences. Therefore, from those substances under discussion in German scientific and regulatory bodies, 19 substances were identified known to be human irritants with available human and animal data. The evaluation started with three substances: ethyl acrylate, formaldehyde, and methyl methacrylate. For these substances, appropriate chronic animal and a controlled human exposure studies were available. The comparison of the sensory NOAEChuman with the irritative NOAECanimal (chronic) resulted in an interspecies extrapolation factor (iEF) of 3 for extrapolating animal data concerning local sensory irritating effects. The adequacy of this iEF was confirmed by its application to additional substances with lower data density (acetaldehyde, ammonia, n-butyl acetate, hydrogen sulfide, and 2-ethylhexanol). Thus, extrapolating from animal studies, an iEF of 3 should be applied for local sensory irritants without reliable human data, unless individual data argue for a substance-specific approach. PMID:25182421

  16. Acceleration of Key Reactions as a Strategy to Elucidate the Rate-Limiting Chemistry Underlying

    E-print Network

    Wensel, Theodore G.

    Acceleration of Key Reactions as a Strategy to Elucidate the Rate-Limiting Chemistry Underlying of accelerating each step separately, while monitoring the rate of formation of the end product of the series of phototransduction turn-off. These reactions were accelerated separately and to- gether by adding hydroxylamine and

  17. Association of occupational pesticide exposure with accelerated longitudinal decline in lung function.

    PubMed

    de Jong, Kim; Boezen, H Marike; Kromhout, Hans; Vermeulen, Roel; Postma, Dirkje S; Vonk, Judith M

    2014-06-01

    Cross-sectional studies have shown that occupational exposure to vapors, gases, dusts, and fumes (VGDF) and pesticides is associated with a lower level of lung function. These associations seem to be stronger in ever smokers. In the current study, we aimed to assess whether occupational exposure to VGDF and pesticides is associated with longitudinal decline in lung function. We used 12,772 observations from 2,527 participants in the Vlagtwedde-Vlaardingen Study, a general-population-based cohort study that followed subjects for 25 years, from 1965 to the last survey in 1989/1990. Job-specific exposure was estimated with the ALOHA+ job exposure matrix. Associations between exposures and annual changes in forced expiratory volume in 1 second (FEV1) and FEV1 as a percentage of inspiratory vital capacity (FEV1%VC) were assessed with linear mixed-effect models including sex, age, and level of lung function at the first measurement and pack-years of smoking at the last measurement. We tested for interaction between smoking and occupational exposure and assessed associations separately for never smokers and ever smokers. Exposure to VGDF was not associated with accelerated lung function decline after adjustment for co-exposure to pesticides. Exposure to pesticides, both in the last-held job and as a cumulative measure, was associated with accelerated decline in FEV1 and FEV1%VC, especially among ever smokers, where we found an excess change in FEV1 of -6.9 mL/year (95% confidence interval: -10.2, -3.7) associated with high pesticide exposure. PMID:24780843

  18. An accelerated exposure and testing apparatus for building joint sealants

    NASA Astrophysics Data System (ADS)

    White, C. C.; Hunston, D. L.; Tan, K. T.; Hettenhouser, J.; Garver, J. D.

    2013-09-01

    The design, fabrication, and implementation of a computer-controlled exposure and testing apparatus for building joint sealants are described in this paper. This apparatus is unique in its ability to independently control and monitor temperature, relative humidity, ultraviolet (UV) radiation, and mechanical deformation. Each of these environmental factors can be controlled precisely over a wide range of conditions during periods of a month or more. Moreover, as controlled mechanical deformations can be generated, in situ mechanical characterization tests can be performed without removing specimens from the chamber. Temperature and humidity were controlled during our experiments via a precision temperature regulator and proportional mixing of dry and moisture-saturated air; while highly uniform UV radiation was attained by attaching the chamber to an integrating sphere-based radiation source. A computer-controlled stepper motor and a transmission system were used to provide precise movement control. The reliability and effectiveness of the apparatus were demonstrated on a model sealant material. The results clearly show that this apparatus provides an excellent platform to study the long-term durability of building joint sealants.

  19. Accelerator mass spectrometry in the biomedical sciences: Applications in low-exposure biomedical and environmental dosimetry

    SciTech Connect

    Felton, J.S.; Turteltaub, K.W.; Vogel, J.S.; Balhorn, R.; Gledhill, B.L.; Southon, J.R.; Caffee, M.W.; Finkel, R.C.; Nelson, D.E.; Proctor, I.D.; Davis, J.C.

    1990-05-10

    We are utilizing Accelerator Mass Spectrometry (AMS) as a sensitive detector for tracking the disposition of radio-isotope labeled molecules in the biomedical sciences. These applications have shown the effectiveness of AMS as a tool to quantify biologically important molecules at extremely low levels. For example, AMS is being used to determine the amount of carcinogen covalently bound to animal DNA (DNA adduct) at levels relevent to human exposure. Studies have been undertaken in our laboratory utilizing heterocyclic amine food-borne carcinogens and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a potent environmental carcinogen, to study the metabolism of carcinogens at low doses. In addition, AMS is being used to detect the presence of rare proteins (mutant forms of protamine) in human sperm. Problems in the life sciences where detection sensitivity or sample sizes are limitations should also benefit from AMS. Studies are underway to measure the molecular targeting of cancer chemotherapeutics in human tissue and to pursue applications for receptor biology. We are also applying other candidate isotopes, such as {sup 3}H (double labeling with {sup 14}C) and {sup 41}Ca (bone absorption) to problems in biology. The results described here with {sup 14}C-labeled molecules coupled with new isotope applications clearly show AMS technology to be an important new tool for the biomedical sciences community. 29 refs., 5 figs., 2 tabs.

  20. Overcomingthe Dephasing Limit in the Bubble Regime by Synergybetween Direct Laser Acceleration and Laser Wakefield Acceleration

    NASA Astrophysics Data System (ADS)

    Zhang, Xi; Khudik, Vladimir; Shvets, Gennady

    2014-10-01

    Direct Laser Acceleration (DLA) in the bubble regime is an acceleration mechanism that combines the traditional plasma wakefield acceleration inside the plasma bubble with energy gain directly from the laser pulse. Recent experiments demonstrated one of the signatures of the DLA: highly efficient gamma-rays from resonantly excited betatron oscillations of accelerated electrons inside the plasma bubble. Here we propose another potential benefit of DLA: the reduction of dephasing between the accelerated electrons and accelerating field of the bubble. A simple semi-analytic model is developed to investigate the synergy between DLA and LWA acceleration mechanisms. We propose to enhance the DLA by adding a second time-delayed weak laser pulse capable of interacting with bubble electrons right after self-injection. This scenario is validated by direct PIC modeling using the 2D VLPL code. The prospects for achieving high-energy electrons at the Texas Petawatt laser are discussed. This work is supported by the US DOE grant DE-SC0007889.

  1. Photothermal stability of encapsulated Si solar cells and encapsulation materials upon accelerated exposures

    Microsoft Academic Search

    F. J. Pern; S. H. Glick

    2000-01-01

    We have conducted a series of accelerated exposure test (AET) studies for various samples of crystalline-Si (c-Si) and amorphous-Si (a-Si) cells that were encapsulated with different superstrates, pottants, and substrates. Transmittance, fluorescence, color indices, impedance spectroscopy, laser optical beam induced current (OBIC), and light and dark current–voltage (I–V) measurements were used to characterize the samples. Nonuniform browning patterns of ethylene

  2. Acceleration and modulation of facial nerve regeneration by exposure to a moderate hypergravitic field

    NASA Astrophysics Data System (ADS)

    Rozenzweig, E.; Ishay, J. S.

    Quantitative histological study revealed that regeneration of sectioned guinea pig facial nerve is accelerated by exposure to a moderate hypergravitic field of 1.6g. A two fold increase in rate of regeneration and in sprouting was observed. Scar tissue formation was significantly reduced in animals exposed to the hypergravitic field. The results confirm a previous study in which regeneration was evaluated clinically and by qualitative histology.

  3. Exposure to light at night accelerates aging and spontaneous uterine carcinogenesis in female 129/Sv mice

    PubMed Central

    Popovich, Irina G.; Zabezhinski, Mark A.; Panchenko, Andrei V.; Piskunova, Tatiana S.; Semenchenko, Anna V.; Tyndyk, Maragriata L.; Yurova, Maria N.; Anisimov, Vladimir N.

    2013-01-01

    The effect of the constant illumination on the development of spontaneous tumors in female 129/Sv mice was investigated. Forty-six female 129/Sv mice starting from the age of 2 mo were kept under standard light/dark regimen [12 h light (70 lx):12hr dark; LD, control group], and 46 of 129/Sv mice were kept under constant illumination (24 h a day, 2,500 lx, LL) from the age of 5 mo until to natural death. The exposure to the LL regimen significantly accelerated body weight gain, increased body temperature as well as acceleration of age-related disturbances in estrous function, followed by significant acceleration of the development of the spontaneous uterine tumors in female 129/Sv mice. Total tumor incidence as well as a total number of total or malignant tumors was similar in LL and LD group (p > 0.05). The mice from the LL groups survived less than those from the LD group (?2 = 8.5; p = 0.00351, log-rank test). According to the estimated parameters of the Cox’s regression model, constant light regimen increased the relative risk of death in female mice compared with the control (LD) group (p = 0.0041). The data demonstrate in the first time that the exposure to constant illumination was followed by the acceleration of aging and spontaneous uterine tumorigenesis in female 129/Sv mice. PMID:23656779

  4. A Proposed Control Limit for Exposure to Airborne Erionite Fibers

    Microsoft Academic Search

    Joseph B. Jurinski; Neil B. Jurinski

    1997-01-01

    The unique physical and chemical properties of the zeolite minerals have resulted in their use in many industrial processes. Environmental exposures to erionite, a commonly fibrous zeolite, have been linked to elevated incidence of malignant pleural mesotheliomas and associated pleural disorders through epidemiological investigations. The presence of erionite in the workplace, with its documented relationship to elevated rates of pleural

  5. Accelerator physics and technology limitations to ultimate energy and luminosity in very large hadron colliders

    Microsoft Academic Search

    P. Bauer

    2002-01-01

    The following presents a study of the accelerator physics and technology limitations to ultimate energy and luminosity in very large hadron colliders (VLHCs). The main accelerator physics limitations to ultimate energy and luminosity in future energy frontier hadron colliders are synchrotron radiation (SR) power, proton-collision debris power in the interaction regions (IR), number of events-per-crossing, stored energy per beam and

  6. Safe human exposure limits for airborne linear siloxanes during spaceflight

    PubMed Central

    García, Hector D.; McMullin, Tami S.; Tobin, Joseph M.; James, John T.

    2013-01-01

    Background Low molecular weight siloxanes are used in industrial processes and consumer products, and their vapors have been detected in the atmospheres of the Space Shuttle and International Space Station. Therefore, the National Aeronautics and Space Administration (NASA) developed spacecraft maximum allowable concentrations (SMACs) for siloxane vapors to protect astronaut health. Since publication of these original SMACs, new studies and new risk assessment approaches have been published that warrant re-examination of the SMACs. Objective To reevaluate SMACs published for octamethyltrisiloxane (L3) for exposures ranging from 1 hour to 180 days, to develop a 1000-day SMAC, and to expand the applicability of those values to the family of linear siloxanes. Methods A literature review was conducted to identify studies conducted since the SMACs for L3 were set in 1994. The updated data were reviewed to determine the sensitive toxicity endpoints, and current risk assessment approaches and methods for dosimetric adjustments were evaluated. Results Recent data were used to update the original 1-hour, 24-hour, 30-day, and 180-day SMACs for L3, and a 1000-day SMAC was developed to protect crewmembers during future exploration beyond Earth orbit. Group SMACs for the linear siloxane family, including hexamethyldisiloxane (L2), L3, decamethyltetrasiloxane (L4), and dodecamethylpentasiloxane (L5), were set for exposures of 1-hour to 1000 days. Conclusion New SMACs, based on acute pulmonary and neurotoxicity at high doses only achievable with L2 and potential liver effects following longer-term exposures to L2 and L3, were established to protect crewmembers from the adverse effects of exposure to linear siloxanes. PMID:24255951

  7. BEHAVIORAL MECHANISMS OF MATING ACCELERATION AFTER EXPOSURE OF MALE C. CAPITATA (DIPTERA: TEPHRITIDAE) TO GINGER AND ORANGE OIL

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The behavioral mechanism of mating acceleration after exposure of male Mediterranean fruit flies to ginger root oil (GO) or to orange peel oil (OO) was studied in the laboratory. Exposure to both oils increased the frequency of sexual signaling. In a wind tunnel females were attracted at similar rat...

  8. Analysis of Biological Effects and Limits of Exposure to Weak Magnetic Fields

    E-print Network

    Halgamuge, Malka N.

    Analysis of Biological Effects and Limits of Exposure to Weak Magnetic Fields Chathurika D,malka.nisha}@unimelb.edu.au Abstract--Adverse biological outcomes due to thermal effects of exposure to high power magnetic fields to weak, low frequency magnetic fields. This paper involves a critical analysis of the voluminous

  9. Accelerated 20-year sunlight exposure simulation of a photochromic foldable intraocular lens in a rabbit model

    PubMed Central

    Werner, Liliana; Abdel-Aziz, Salwa; Peck, Carolee Cutler; Monson, Bryan; Espandar, Ladan; Zaugg, Brian; Stringham, Jack; Wilcox, Chris; Mamalis, Nick

    2011-01-01

    PURPOSE To assess the long-term biocompatibility and photochromic stability of a new photochromic hydrophobic acrylic intraocular lens (IOL) under extended ultraviolet (UV) light exposure. SETTING John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA. DESIGN Experimental study. METHODS A Matrix Aurium photochromic IOL was implanted in right eyes and a Matrix Acrylic IOL without photochromic properties (n = 6) or a single-piece AcrySof Natural SN60AT (N = 5) IOL in left eyes of 11 New Zealand rabbits. The rabbits were exposed to a UV light source of 5 mW/cm2 for 3 hours during every 8-hour period, equivalent to 9 hours a day, and followed for up to 12 months. The photochromic changes were evaluated during slitlamp examination by shining a penlight UV source in the right eye. After the rabbits were humanely killed and the eyes enucleated, study and control IOLs were explanted and evaluated in vitro on UV exposure and studied histopathologically. RESULTS The photochromic IOL was as biocompatible as the control IOLs after 12 months under conditions simulating at least 20 years of UV exposure. In vitro evaluation confirmed the retained optical properties, with photochromic changes observed within 7 seconds of UV exposure. The rabbit eyes had clinical and histopathological changes expected in this model with a 12-month follow-up. CONCLUSIONS The new photochromic IOL turned yellow only on exposure to UV light. The photochromic changes were reversible, reproducible, and stable over time. The IOL was biocompatible with up to 12 months of accelerated UV exposure simulation. PMID:21241924

  10. Accelerator physics and technology limitations to ultimate energy and luminosity in very large hadron colliders

    SciTech Connect

    P. Bauer et al.

    2002-12-05

    The following presents a study of the accelerator physics and technology limitations to ultimate energy and luminosity in very large hadron colliders (VLHCs). The main accelerator physics limitations to ultimate energy and luminosity in future energy frontier hadron colliders are synchrotron radiation (SR) power, proton-collision debris power in the interaction regions (IR), number of events-per-crossing, stored energy per beam and beam-stability [1]. Quantitative estimates of these limits were made and translated into scaling laws that could be inscribed into the particle energy versus machine size plane to delimit the boundaries for possible VLHCs. Eventually, accelerator simulations were performed to obtain the maximum achievable luminosities within these boundaries. Although this study aimed at investigating a general VLHC, it was unavoidable to refer in some instances to the recently studied, [2], 200 TeV center-of-mass energy VLHC stage-2 design (VLHC-2). A more thorough rendering of this work can be found in [3].

  11. The NREL outdoor accelerated-weathering tracking system and photovoltaic module exposure results

    SciTech Connect

    Basso, T.S. [National Renewable Energy Laboratory (NREL), 1617 Cole Blvd., Golden, Colorado, 80401-3393 (United States)

    1999-03-01

    This paper describes the Outdoor Accelerated-weathering Tracking System (OATS) and interim results for the first OATS study on photovoltaic (PV) modules. With two test planes measuring 1.52{times}1.83&hthinsp;m, OATS provides a unique solar-concentrating exposure capability. Test sample temperatures are moderated by air blowers. Water spray capability exists for wetting samples. The OATS two-axis tracker points to the sun using software calculations. Non-imaging aluminum reflectors give a nominal clear-sky optical concentration ratio of three. Field-qualification measurements in the test plane under reflector conditions showed its relative irradiance non-uniformity was {plus_minus}15{percent} for a clear-sky summer day with {plus_minus} 75 mm as the smallest distance for that non-uniformity. Exposure studies began in November 1997 on seven pairs of commercially available ribbon silicon, crystalline silicon and amorphous silicon PV modules kept at constant resistive load. The modules were periodically removed from OATS for visual inspection and solar simulator performance measurements. There were no module failures. This PV module study is ongoing and later results will be compared to other testing techniques. Through July 1998, the modules under reflector conditions received 392 MJ/m{sup 2} of total ultraviolet (TUV) exposure. That was 2.07 times the TUV exposure compared to a south-facing fixed array tilted 40{degree} up from horizontal at NREL. Similarly, the modules in the test plane under the covered reflectors received 1.04 times the fixed array TUV exposure. For the test plane under the covered reflectors there was a loss of 13{percent} TUV exposure attributed to the reflectors blocking some of the diffuse-sky UV light. Also through July 1998, the OATS sunlight availability measured 95{percent} compared to the cumulative global normal exposure at the NREL Solar Radiation Research Laboratory (SRRL). The OATS sunlight availability losses included downtime when the PV modules were removed, and when there were OATS tracking problems, maintenance, and repair. For December 1997 through July 1998, the SRRL cumulative exposure was 99{percent} compared to the respective monthly averages from years 1961 through 1990 at Boulder, Colorado. {copyright} {ital 1999 American Institute of Physics.}

  12. The NREL Outdoor Accelerated-weathering Tracking System and Photovoltaic Module Exposure Results

    SciTech Connect

    Basso, T. S.

    1998-10-31

    This paper describes the Outdoor Accelerated-weathering Tracking System (OATS) and interim results for the first OATS study on photovoltaic (PV) modules. With two test planes measuring 1.52 x 1.83 m, OATS provides a unique solar-concentrating exposure capability. Test sample temperatures are moderated by air blowers. Water spray capability exists for wetting samples. The OATS two-axis tracker points to the sun using software calculations. Non-imaging aluminum reflectors give a nominal clear-sky optical concentration ratio of three. Field-qualification measurements in the test plane under reflector conditions showed its relative irradiance non-uniformity was '' 15% for a clear-sky summer day with '' 75 mm as the smallest distance for that non-uniformity. Exposure studies began in November 1997 on seven pairs of commercially available ribbon silicon, crystalline silicon and amorphous silicon PV modules kept at constant resistive load. The modules were periodically removed from OATS for visual inspection and solar simulator performance measurements. There were no module failures. This PV module study is ongoing and later results will be compared to other testing techniques. Through July 1998, the modules under reflector conditions received 392 MJ/m2 of total ultraviolet (TUV) exposure. That was 2.07 times the TUV exposure compared to a south-facing fixed array tilted 40{sup o} up from horizontal at NREL. Similarly, the modules in the test plane under the covered reflectors received 1.04 times the fixed array TUV exposure. For the test plane under the covered reflectors there was a loss of 13% TUV exposure attributed to the reflectors blocking some of the diffuse-sky UV light. Also through July 1998, the OATS sunlight availability measured 95% compared to the cumulative global normal exposure at the NREL Solar Radiation Research Laboratory (SRRL). The OATS sunlight availability losses included downtime when the PV modules were removed, and when there were OAT S tracking problems, maintenance, and repair. For December 1997 through July 1998, the SRRL cumulative exposure was 99% compared to the respective monthly averages from years 1961 through 1990 at Boulder, Colorado.

  13. The NREL outdoor accelerated-weathering tracking system and photovoltaic module exposure results

    NASA Astrophysics Data System (ADS)

    Basso, Thomas S.

    1999-03-01

    This paper describes the Outdoor Accelerated-weathering Tracking System (OATS) and interim results for the first OATS study on photovoltaic (PV) modules. With two test planes measuring 1.52×1.83 m, OATS provides a unique solar-concentrating exposure capability. Test sample temperatures are moderated by air blowers. Water spray capability exists for wetting samples. The OATS two-axis tracker points to the sun using software calculations. Non-imaging aluminum reflectors give a nominal clear-sky optical concentration ratio of three. Field-qualification measurements in the test plane under reflector conditions showed its relative irradiance non-uniformity was ±15% for a clear-sky summer day with ± 75 mm as the smallest distance for that non-uniformity. Exposure studies began in November 1997 on seven pairs of commercially available ribbon silicon, crystalline silicon and amorphous silicon PV modules kept at constant resistive load. The modules were periodically removed from OATS for visual inspection and solar simulator performance measurements. There were no module failures. This PV module study is ongoing and later results will be compared to other testing techniques. Through July 1998, the modules under reflector conditions received 392 MJ/m2 of total ultraviolet (TUV) exposure. That was 2.07 times the TUV exposure compared to a south-facing fixed array tilted 40° up from horizontal at NREL. Similarly, the modules in the test plane under the covered reflectors received 1.04 times the fixed array TUV exposure. For the test plane under the covered reflectors there was a loss of 13% TUV exposure attributed to the reflectors blocking some of the diffuse-sky UV light. Also through July 1998, the OATS sunlight availability measured 95% compared to the cumulative global normal exposure at the NREL Solar Radiation Research Laboratory (SRRL). The OATS sunlight availability losses included downtime when the PV modules were removed, and when there were OATS tracking problems, maintenance, and repair. For December 1997 through July 1998, the SRRL cumulative exposure was 99% compared to the respective monthly averages from years 1961 through 1990 at Boulder, Colorado.

  14. Indirectly sensing accelerator beam currents for limiting maximum beam current magnitude

    DOEpatents

    Bogaty, John M. (Lombard, IL); Clifft, Benny E. (Park Forest, IL); Bollinger, Lowell M. (Downers Grove, IL)

    1995-01-01

    A beam current limiter for sensing and limiting the beam current in a particle accelerator, such as a cyclotron or linear accelerator, used in scientific research and medical treatment. A pair of independently operable capacitive electrodes sense the passage of charged particle bunches to develop an RF signal indicative of the beam current magnitude produced at the output of a bunched beam accelerator. The RF signal produced by each sensing electrode is converted to a variable DC voltage indicative of the beam current magnitude. The variable DC voltages thus developed are compared to each other to verify proper system function and are further compared to known references to detect beam currents in excess of pre-established limits. In the event of a system malfunction, or if the detected beam current exceeds pre-established limits, the beam current limiter automatically inhibits further accelerator operation. A high Q tank circuit associated with each sensing electrode provides a narrow system bandwidth to reduce noise and enhance dynamic range. System linearity is provided by injecting, into each sensing electrode, an RF signal that is offset from the bunching frequency by a pre-determined beat frequency to ensure that subsequent rectifying diodes operate in a linear response region. The system thus provides a large dynamic range in combination with good linearity.

  15. Indirectly sensing accelerator beam currents for limiting maximum beam current magnitude

    DOEpatents

    Bogaty, J.M.; Clifft, B.E.; Bollinger, L.M.

    1995-08-08

    A beam current limiter is disclosed for sensing and limiting the beam current in a particle accelerator, such as a cyclotron or linear accelerator, used in scientific research and medical treatment. A pair of independently operable capacitive electrodes sense the passage of charged particle bunches to develop an RF signal indicative of the beam current magnitude produced at the output of a bunched beam accelerator. The RF signal produced by each sensing electrode is converted to a variable DC voltage indicative of the beam current magnitude. The variable DC voltages thus developed are compared to each other to verify proper system function and are further compared to known references to detect beam currents in excess of pre-established limits. In the event of a system malfunction, or if the detected beam current exceeds pre-established limits, the beam current limiter automatically inhibits further accelerator operation. A high Q tank circuit associated with each sensing electrode provides a narrow system bandwidth to reduce noise and enhance dynamic range. System linearity is provided by injecting, into each sensing electrode, an RF signal that is offset from the bunching frequency by a pre-determined beat frequency to ensure that subsequent rectifying diodes operate in a linear response region. The system thus provides a large dynamic range in combination with good linearity. 6 figs.

  16. The Newtonian limit of spacetimes for accelerated particles and black holes

    E-print Network

    Jiri Bicak; David Kofron

    2009-01-26

    Solutions of vacuum Einstein's field equations describing uniformly accelerated particles or black holes belong to the class of boost-rotation symmetric spacetimes. They are the only explicit solutions known which represent moving finite objects. Their Newtonian limit is analyzed using the Ehlers frame theory. Generic spacetimes with axial and boost symmetries are first studied from the Newtonian perspective. The results are then illustrated by specific examples such as C-metric, Bonnor-Swaminarayan solutions, self-accelerating "dipole particles", and generalized boost-rotation symmetric solutions describing freely falling particles in an external field. In contrast to some previous discussions, our results are physically plausible in the sense that the Newtonian limit corresponds to the fields of classical point masses accelerated uniformly in classical mechanics. This corroborates the physical significance of the boost-rotation symmetric spacetimes.

  17. Setting occupational exposure limits in humans: contributions from the field of experimental psychology

    Microsoft Academic Search

    Monique A. M. Smeets; Jan H. A. Kroeze; Pamela H. Dalton

    2006-01-01

    Psychophysical methods from the field of experimental psychology are evaluated for their utility in the derivation of occupational\\u000a exposure limits (OELs) for volatile chemicals based on acute sensory irritation in humans. The lateralization threshold method,\\u000a which involves the localization of trigeminal vapor to the stimulated nostril, is evaluated for its underlying assumptions,\\u000a reliability and validity. Whole body exposures, on the

  18. Application of pharmacokinetics to derive biological exposure indexes from threshold limit values

    SciTech Connect

    Leung, H.W.; Paustenbach, D.J.

    1988-09-01

    The importance of incorporating the fundamental concepts of pharmacokinetics into biological monitoring program that involve the collection of various body fluid and tissue specimens is discussed. The application of these principles to establish biological exposures indexes bioequivalent to airborne exposure limits is described. Specific illustrative examples involving acetone, aniline, benzene, carbon tetrachloride, dieldrin, ethylbenzene, hexane, lead, methylene chloride, pentachlorophenol, phenol, styrene, toluene and xylene are presented.

  19. Accelerating the Early Numeracy Development of Kindergartners with Limited Working Memory Skills through Remedial Education

    ERIC Educational Resources Information Center

    Toll, Sylke W. M.; Van Luit, Johannes E. H.

    2013-01-01

    Background: Young children with limited working memory skills are a special interest group among all children that score below average on early numeracy tests. This study examines the effect of accelerating the early numeracy development of these children through remedial education, by comparing them with children with typically working memory…

  20. Effects of limited acceleration-deceleration capabilities and state of brake light on traffic flow

    Microsoft Academic Search

    Shiyong Lan; Xin Zhou; Tao Wang

    2010-01-01

    We present a new combined cellular automaton (CA) model for one-lane traffic flow. In this model, we consider the driver prejudgment according to the state (velocity and brake light) of the leading vehicle. We also consider the mechanical restrictions of vehicles realized by limited acceleration and deceleration capabilities, which is not considered in most models. Further more, comfortable driving is

  1. Potential Distribution for Space-Charge Limited Current between a Plane Accelerating Grid and Parallel Anode

    Microsoft Academic Search

    E. G. Ramberg; L. Malter

    1952-01-01

    Expressions are derived for the potential distribution between a plane accelerating grid and parallel anode under conditions of space-charge limitation, taking account of the Maxwellian velocity distribution of the electrons. The distribution is determined by Langmuir's diode functions in combination with a function depending on the current transmission of the grid-anode space, which is represented graphically.

  2. [Microclimatic indexes and limits of safe exposure in work activity at risk of thermal stress].

    PubMed

    Marcaletti, G; Terzi, R; Catenacci, G

    1984-03-30

    The working time in work places thermically uncomfortable must be limited in order to prevent the risk of thermal stress. In a previous study we have demonstrated that the best method for calculation of the safe exposure times is based on the required sweat rate index. In the present work we verified in different work places termically uncomfortable, grouped for equivalent values of WBGT index, the variability of the safe exposure times calculated by means of a method just now mentioned for various levels of energetic expenditure. The results point out the possibility of a mathematical relation between energetic expenditure, WBGT index and mean of safe exposure times. PMID:6712822

  3. Formate in serum and urine after controlled methanol exposure at the threshold limit value

    SciTech Connect

    d'Alessandro, A. (Univ. of Perugia (Italy)); Osterloh, J.D.; Chuwers, P.; Quinlan, P.J.; Kelly, T.J.; Becker, C.E. (Univ. of California, San Francisco, CA (United States))

    1994-02-01

    Methanol will be present as a new air pollutant when methanol-powered vehicles are introduced in the United States. Little is known about the effect of low-dose methanol exposure. It is controversial whether or not formate, the main metabolite responsible for methanol's acute toxicity, is a sensitive biological marker of toxicity or exposure. We studied the effect of a 4-hr exposure at rest to 200 ppm of methanol vapors on endogenous serum formate and on urinary formic acid excretion. A randomized, double-blind study of human exposure to a constant concentration of methanol was performed in a whole-body exposure chamber. Twenty-six healthy volunteers, each serving as his or her own control, participated in sham and methanol exposures. Urine (at 0, 4, 8 hr) and serum specimens (15 time points over 8 hr) collected before, during, and after the exposure were measured for formate. We found no significant differences in serum formate concentration between exposure and control conditions either at any time point or for area under the curve. Mean concentrations at the end of the exposure were: exposed 14.28 [+-] 8.90 mg/l and control 12.68 [+-] 6.43 mg/l. A slight, but nonsignificant (p = 0.08), increase in urine formate excretion rate was found at 4 hr (exposed 2.17 [+-] 1.69 mg/4 hr and control 1.67 [+-] 1.02 mg/4 hr). Age, sex, folic acid level, and smoking were not significant covariates. At 200 ppm, methanol exposure does not contribute substantially to endogenous formate quantities. Serum and urine formate determinations are not sensitive biological markers of methanol exposure at the threshold limit value. 24 refs., 4 tabs.

  4. Limited utility of Birkhoff's theorem in modified Newtonian dynamics: Nonzero accelerations inside a shell

    SciTech Connect

    Dai Dechang [Department of Physics, SUNY at Buffalo, Buffalo, New York 14260-1500 (United States); Matsuo, Reijiro; Starkman, Glenn [CERCA, Department of Physics, Case Western Reserve University, Cleveland, Ohio 44106-7079 (United States)

    2010-01-15

    We investigate the consequences of Birkhoff's theorem in general relativity (GR) and in modified Newtonian dynamics (MOND). We study, in particular, the system of a finite-mass test particle inside a spherical shell. In both GR and MOND, we find nonvanishing acceleration for that test particle. The direction of the acceleration is such that it pushes the test particle toward the center of the shell. In GR, the acceleration is found analytically in the case of a small test mass with a small displacement from the center of the shell. In MOND, the acceleration is found analytically in the limit of large test mass and small displacement, and a comparison to numerical values is made. Numerical simulations are done for more general cases with parameters that mimic the system of a galaxy in a cluster. In GR, the acceleration is highly suppressed and physically insignificant. In MOND, on the contrary, the acceleration of the point particle can be a significant fraction of the field just outside of the spherical shell.

  5. Note on the assessment of exposure using one-sided tolerance limits

    SciTech Connect

    Selvin, S.; Rappaport, S.; Spear, R.; Schulman, J.; Francis, M.

    1987-02-01

    Conceptual problems with OSHA's use of an absolute standard have led to alternative methods of assessing exposures to toxic materials in the workplace. One of these methods employs a one-sided tolerance limit. This statistical approach is explored from three points of view--identifiability, sampling strategies and statistical power. In general, assessing risk in the work environment with tolerance limits is found to give inadequate answers in several important respects.

  6. Metalworking fluid mist occupational exposure limits: a discussion of alternative methods.

    PubMed

    Cohen, Howard; White, Eugene M

    2006-09-01

    NIOSH published a recommended exposure limit (REL) for metalworking fluids (MWF) in 1998 that was designed to prevent respiratory disorders associated with these industrial lubricants. The REL of 0.4 mg/m(3) (as a time-weighted average for up to 10 hours) was for the fraction of aerosol corresponding to deposition in the thoracic region of the lungs. This nonregulatory occupational exposure limit (OEL) corresponded to approximately 0.5 mg/m(3) for total particulate mass. Although this REL was designed to prevent respiratory disorders from MWF exposures, NIOSH acknowledged that exposures below the REL may still result in occupational asthma and hypersensitivity pneumonitis--two of the most significant respiratory illnesses associated with MWF. In the 8 years since the publication of the NIOSH MWF REL, neither the Occupational Safety and Health Administration (OSHA) nor the American Conference of Governmental Industrial Hygienists (ACGIH) has recommended an exposure limit for water-soluble MWF specifically, other than their previous exposure limits for mineral oil. An informal effort to benchmark companies involved in the manufacture of automobiles and automotive parts in North America indicated that most companies are using the NIOSH MWF REL as a guide for the purchase of new equipment. Furthermore, most companies have adopted a goal to limit exposures to below 1.0 mg/m3. We failed to find any company that has strictly enforced an OEL of 1.0 mg/m(3) through the use of either administrative controls or personal protective equipment, when engineering controls failed to bring the exposures to below this limit. We also found that most companies have failed to implement specific medical surveillance programs for those employees exposed to MWF mist above 1.0 mg/m(3). Organization Resources Counselors (ORC) published in 1999 (on their website) a "best practices" manual for maintaining MWF systems and reducing the likelihood of MWF-related illnesses. The emphasis of this approach was on control techniques, and there was no assignment of a specific OEL for MWF due to the wide variety of fluids that exist. The ORC did suggest that maintaining exposure levels to below 2.0 mg/m(3) would assist in minimizing upper respiratory complaints associated with MWF. Although the ORC manual indicated that MWF vary in composition and no single OEL is likely to be appropriate for all such fluids, it adopted a very similar concept to control banding, placing all MWF operations into a single band using similar (if not identical) controls. OSHA, in lieu of adopting a 6B health standard for MWF, has also published a voluntary "best practices" manual on their website. Their document drew heavily from the work of ORC and also incorporated information from the 1998 NIOSH MWF criteria document. Industrial users of MWF need to have guidance, such as an OEL, to determine when either engineering, administrative controls, or personal protective equipment must be implemented to protect their employees. The purpose of this article is to explore various approaches that might be taken to result in a single or multiple limits for exposures to MWF and its components. Approaches such as control banding are discussed in terms of an alternative to the use of an OEL. PMID:16857649

  7. Tungsten damage and melt losses under plasma accelerator exposure with ITER ELM relevant conditions

    NASA Astrophysics Data System (ADS)

    Makhlaj, V. A.; Garkusha, I. E.; Aksenov, N. N.; Bazylev, B.; Landman, I.; Linke, J.; Malykhin, S. V.; Pugachov, A. T.; Sadowski, M. J.; Skladnik-Sadowska, E.; Wirtz, M.

    2014-04-01

    Experimental simulations of ITER edge-localized mode have been performed with a Kh-50 quasi-stationary plasma accelerator. Heat loads exceeded the tungsten melting threshold. Droplet splashing and the solid dust ejection were observed. Droplets were emitted during the plasma exposure and dust generation dominated after the end of a plasma pulse, at the time of the material cooling. A decrease in the droplet velocity at an increase in the surface heat load was observed. It could be attributed to growing sizes of the droplets at higher energy loads. After one hundred pulses were performed at loads below the tungsten melting and above the cracking threshold, some porosity appeared. Such defects achieved dimensions of several tens of ?m. A heat load amounting to half the cracking threshold (0.3 MJ m-2) could lead to the appearance of fatigue cracks after 100 plasma pulses. In this case the appearance of cracks could be caused by the accumulation and redistribution of linear defects (dislocations) in the affected tungsten layer.

  8. Accelerators

    NSDL National Science Digital Library

    Lawrence Berkeley National Laboratory. Particle Data Group

    2002-01-01

    What is the purpose of particle accelerators? On this web page, part of a particle physics tutorial, students read that accelerators solve two problems. The accelerators provide an increase in momentum to produce particles of small wavelength, and the fast-moving particles can create new particles when smashed together. A photograph of the inside of a particle accelerator is provided. Copyright 2005 Eisenhower National Clearinghouse

  9. Proposal for the assessment to quantitative dermal exposure limits in occupational environments: Part 2. Feasibility study for application in an exposure scenario for MDA by two different dermal exposure sampling methods

    Microsoft Academic Search

    D. H. Brouwer; L. Hoogendoorn; P. M. Bos; P. J. Boogaard; J. J. van Hemmen

    1998-01-01

    OBJECTIVE: To evaluate two different techniques for assessing dermal exposure to 4,4'-methylene dianiline (MDA) in a field study. The results were used to test the applicability of a recently proposed quantitative dermal occupational exposure limit (DOEL) for MDA in a workplace scenario. METHODS: For two consecutive weeks six workers were monitored for exposure to MDA in a factory that made

  10. The beryllium quandary: will the lower exposure limits spur new developments in sampling and analysis?

    SciTech Connect

    Brisson, Michael

    2013-06-03

    At the time this article was written, new rulemakings were under consideration at OSHA and the U.S. Department of Energy (DOE) that would propose changes to occupational exposure limits for beryllium. Given these developments, it’s a good time to review the tools and methods available to IHs for assessing beryllium air and surface contamination in the workplace—what’s new and different, and what’s tried and true. The article discusses limit values and action levels for beryllium, problematic aspects of beryllium air sampling, sample preparation, sample analysis, and data evaluation.

  11. Abrasion and fatigue resistance of PDMS containing multiblock polyurethanes after accelerated water exposure at elevated temperature.

    PubMed

    Chaffin, Kimberly A; Wilson, Charles L; Himes, Adam K; Dawson, James W; Haddad, Tarek D; Buckalew, Adam J; Miller, Jennifer P; Untereker, Darrel F; Simha, Narendra K

    2013-11-01

    Segmented polyurethane multiblock polymers containing polydimethylsiloxane and polyether soft segments form tough and easily processed thermoplastic elastomers (PDMS-urethanes). Two commercially available examples, PurSil 35 (denoted as P35) and Elast-Eon E2A (denoted as E2A), were evaluated for abrasion and fatigue resistance after immersion in 85 °C buffered water for up to 80 weeks. We previously reported that water exposure in these experiments resulted in a molar mass reduction, where the kinetics of the hydrolysis reaction is supported by a straight forward Arrhenius analysis over a range of accelerated temperatures (37-85 °C). We also showed that the ultimate tensile properties of P35 and E2A were significantly compromised when the molar mass was reduced. Here, we show that the reduction in molar mass also correlated with a reduction in both the abrasion and fatigue resistance. The instantaneous wear rate of both P35 and E2A, when exposed to the reciprocating motion of an ethylene tetrafluoroethylene (ETFE) jacketed cable, increased with the inverse of the number averaged molar mass (1/Mn). Both materials showed a change in the wear surface when the number-averaged molar mass was reduced to ? 16 kg/mole, where a smooth wear surface transitioned to a 'spalling-like' pattern, leaving the wear surface with ? 0.3 mm cracks that propagated beyond the contact surface. The fatigue crack growth rate for P35 and E2A also increased in proportion to 1/Mn, after the molar mass was reduced below a critical value of ?30 kg/mole. Interestingly, this critical molar mass coincided with that at which the single cycle stress-strain response changed from strain hardening to strain softening. The changes in both abrasion and fatigue resistance, key predictors for long term reliability of cardiac leads, after exposure of this class of PDMS-urethanes to water suggests that these materials are susceptible to mechanical compromise in vivo. PMID:23871543

  12. Approach to setting occupational exposure limits for sensory irritants in The Netherlands.

    PubMed

    Feron, V J; Art, J H; Mojet, J

    2001-01-01

    This article describes how scientists in the Netherlands set occupational exposure limits (OELs) for sensory irritants. When they tackle this issue, a number of key questions need to be answered. For example, did the studies indeed measure sensory irritation and not cytotoxicity? When the irritant is an odorant, can interference of olfactory stimulation be excluded? In the case of subjective measurements, can psychological irritation be excluded? When adaptation is an issue, did the studies indeed measure adaptation and not habituation? When OELs are established in the Netherlands, each of these issues is carefully addressed before a value is suggested. When setting an OEL in the Netherlands, human data carry more weight than animal data of comparable quality. As in the United States, documentation for the recommended OEL is written and a discussion of all available relevant and reliable data culminating in the selection of the key study for deriving the health-based recommended occupational exposure limit is provided. Special effort is dedicated to reconciling differences between the animal and human data. If the toxicological database is considered to be inadequate, the committee acknowledges this limitation and will not recommend a limit value due to insufficient data. PMID:11767940

  13. Rules and recent trends for setting health-based occupational exposure limits for chemicals.

    PubMed

    Skowro?, Jolanta; Czerczak, S?awomir

    2015-01-01

    The working environment is the special case of the non-natural environment created by man in which the increased production activity brings about the concentration of stimulators particularly aggressive to the human organism, such as chemical hazards, noise, vibration, extreme temperatures, and finally, intensified psychological and emotional stress. Depending on the nature and intensity, working environment factors have been classified into dangerous, harmful and annoying. The workers are more and more frequently exposed to dangerous chemicals in the working environment. The chemicals cause many diseases including, in the 1st place, respiratory insufficiency, inflammatory skin conditions, psychoneurological disorders and neoplastic diseases. Occupational exposure limit values (OELs), the main criteria for occupational exposure assessment, constitute an important factor for the safe use of chemicals in the working environment. In Poland, to date there are 524 chemical substances and 19 dusts for which maximum admissible concentrations (MAC) have been established. PMID:26182920

  14. Acceleration

    Microsoft Academic Search

    Edward Geoghegan

    1897-01-01

    IN NATURE, NO. 1415, p. 125, Prof. Lodge asserts that the subject of acceleration is at the root of the perennial debate between engineers and teachers of mechanics; and he urges clearness of idea and accuracy of speech on all who deal with the junior student. Towards this end I would suggest that the too common phrase ``acceleration of velocity''

  15. Cadmium exposure and phosphorus limitation increases metal content in the freshwater alga Chlamydomonas reinhardtii.

    PubMed

    Webster, Rachel E; Dean, Andrew P; Pittman, Jon K

    2011-09-01

    The characteristics of metal accumulation in freshwater microalgae are important to elucidate for a full understanding of metal cycling and toxicity in a freshwater system. This study has utilized an elemental profiling approach to investigate the impacts of Cd exposure and phosphorus (P) availability on metal accumulation after 7 days in batch culture-grown Chlamydomonas reinhardtii. Multivariate statistical analysis of the elemental data demonstrated distinct responses between both stresses. Sublethal concentrations of Cd (up to 15 ?M) caused increased accumulation of Co. Cu, Fe, and Zn content also increased in response to enhanced Cd concentrations but only when P availability was low. While Cd exposure effected the accumulation of a few specific metals, P limitation increased the accumulation of all essential trace metals and macronutrients analyzed including Co, Fe, K, Na, and Zn but not Mn. The accumulation of Cd also markedly increased in response to P limitation. The impact of P availability on essential metal accumulation was the same when either inorganic P or an organic P source (glycerophosphate) was used. These results highlight the potential risks of metal toxicity for freshwater microalgae and aquatic food chains when P availability is limiting and which can be exacerbated by Cd pollution. PMID:21809879

  16. Evaluation of the toxicity data for peracetic acid in deriving occupational exposure limits: a minireview.

    PubMed

    Pechacek, Nathan; Osorio, Magdalena; Caudill, Jeff; Peterson, Bridget

    2015-02-17

    Peracetic acid (PAA) is a peroxide-based chemistry that is highly reactive and can produce strong local effects upon direct contact with the eyes, skin and respiratory tract. Given its increasing prominence in industry, attention has focused on health hazards and associated risks for PAA in the workplace. Occupational exposure limits (OEL) are one means to mitigate risks associated with chemical hazards in the workplace. A mini-review of the toxicity data for PAA was conducted in order to determine if the data were sufficient to derive health-based OELs. The available data for PAA frequently come from unpublished studies that lack sufficient study details, suffer from gaps in available information and often follow unconventional testing methodology. Despite these limitations, animal and human data suggest sensory irritation as the most sensitive endpoint associated with inhalation of PAA. Rodent RD50 data (the concentration estimated to cause a 50% depression in respiratory rate) were selected as the critical studies in deriving OELs. Based on these data, a range of 0.36-0.51mg/m(3) (0.1-0.2ppm) was calculated for a time-weighted average (TWA), and 1.2-1.7mg/m(3) (0.4-0.5ppm) as a range for a short-term exposure limit (STEL). These ranges compare favorably to other published OELs for PAA. Considering the applicable health hazards for this chemistry, a joint TWA/STEL OEL approach for PAA is deemed the most appropriate in assessing workplace exposures to PAA, and the selection of specific values within these proposed ranges represents a risk management decision. PMID:25542141

  17. Limitations and problems in deriving risk estimates for low-level radiation exposure.

    PubMed Central

    Cohen, B. L.

    1981-01-01

    Some of the problems in determining the cancer risk of low-level radiation from studies of exposed groups are reviewed and applied to the study of Hanford workers by Mancuso, Stewart, and Kneale. Problems considered are statistical limitations, variation of cancer rates with geography and race, the "healthy worker effect," calendar year and age variation of cancer mortality, choosing from long lists, use of proportional mortality rates, cigarette smoking-cancer correlations, use of averages to represent data distributions, ignoring other data, and correlations between radiation exposure and other factors that may cause cancer. The current status of studies of the Hanford workers is reviewed. PMID:7336763

  18. Exposure limits for nanoparticles: report of an international workshop on nano reference values.

    PubMed

    van Broekhuizen, Pieter; van Veelen, Wim; Streekstra, Willem-Henk; Schulte, Paul; Reijnders, Lucas

    2012-07-01

    This article summarizes the outcome of the discussions at the international workshop on nano reference values (NRVs), which was organized by the Dutch trade unions and employers' organizations and hosted by the Social Economic Council in The Hague in September 2011. It reflects the discussions of 80 international participants representing small- and medium-size enterprises (SMEs), large companies, trade unions, governmental authorities, research institutions, and non-governmental organizations (NGOs) from many European countries, USA, India, and Brazil. Issues that were discussed concerned the usefulness and acceptability of precaution-based NRVs as a substitute for health-based occupational exposure limits (OELs) and derived no-effect levels (DNELs) for manufactured nanoparticles (NPs). Topics concerned the metrics for measuring NPs, the combined exposure to manufactured nanomaterials (MNMs) and process-generated NPs, the use of the precautionary principle, the lack of information about the presence of nanomaterials, and the appropriateness of soft regulation for exposure control. The workshop concluded that the NRV, as an 8-h time-weighted average, is a comprehensible and useful instrument for risk management of professional use of MNMs with a dispersible character. The question remains whether NRVs, as advised for risk management by the Dutch employers' organization and trade unions, should be under soft regulation or that a more binding regulation is preferable. PMID:22752096

  19. Silica-associated limited systemic sclerosis after occupational exposure to calcined diatomaceous earth.

    PubMed

    Moisan, Stéphanie; Rucay, Pierre; Ghali, Alaa; Penneau-Fontbonne, Dominique; Lavigne, Christian

    2010-10-01

    Silica-associated systemic sclerosis can occur in persons using calcined diatomaceous earth for filtration purpose. A limited systemic sclerosis was diagnosed in a 52-year-old male winegrower who had a combination of Raynaud's phenomenon, oesophageal dysfunction, sclerodactyly and telangectasia. The anti-centromere antibodies titre was 1/5000. The patient was frequently exposed to high atmospheric concentrations of calcined diatomaceous earth when performing the filtration of wines. Calcined diatomaceous earth is almost pure crystalline silica under the cristobalite form. The diagnosis of silica-associated limited systemic sclerosis after exposure to calcined diatomaceous earth was made. The patient's disease met the medical, administrative and occupational criteria given in the occupational diseases list 22 bis of the agriculture Social Security scheme and thence was presumed to be occupational in origin, without need to be proved. The diagnosis of occupational disease had been recognized by the compensation system of the agricultural health insurance. PMID:20605509

  20. Theory of factors limiting high gradient operation of warm accelerating structures

    SciTech Connect

    Nusinovich, Gregory S. [University of Maryland; Antonsen, Thomas M. [University of Maryland; Kishek, Rami [University of Maryland

    2014-07-25

    This final report summarizes the research performed during the time period from 8/1/2010 to 7/31/2013. It consists of two parts describing our studies in two directions: (a) analysis of factors limiting operation of dielectric-loaded accelerating (DLA) structures where the main problem is the occurrence of multipactor on dielectric surfaces, and (b) studies of effects associated with either RF magnetic or RF electric fields which may cause the RF breakdown in high-gradient metallic accelerating structures. In the studies of DLA structures, at least, two accomplishments should be mentioned: the development of a 3D non-stationary, self-consistent code describing the multipactor phenomena and yielding very good agreement with some experimental data obtained in joint ANL/NRL experiments. In the metallic structures, such phenomena as the heating and melting of micro-particles (metallic dust) by RF electric and magnetic fields in single-shot and rep-rate regimes is analyzed. Also, such processes in micro-protrusions on the structure surfaces as heating and melting due to the field emitted current and the Nottingham effect are thoroughly investigated with the account for space charge of emitted current on the field emission from the tip.

  1. Study of anticipated impact on DOE programs from proposed reductions to the external occupational radiation exposure limit

    SciTech Connect

    Clusen, Ruth C.

    1981-02-01

    A study of the impact of reducing the occupational radiation exposure limit from 5 rem/yr to 2.5, 1.0 and 0.5 rem/yr, respectively produced the following conclusions: reduction of the occupational exposure limit would result in significant increase in total accumulated exposure to the current radiation worker population and could require an increase in the work force; important programs would have to be abandoned at a planned exposure limit of 0.5 rem/yr; some engineering technology is not sufficiently developed to design or operate at the 0.5 rem/yr limit; even a factor of 2 reduction (2.5 rem/yr) would significantly increase costs and would result in an increase in total exposure to the work force; in addition to a significant one-time initial capital cost resulting from a 0.5 rem/yr limit, there would be a significant increase in annual costs; the major emphasis in controlling occupational exposure should be on further reduction of total man-rem; and current standards are used only as a limit. For example, 97% of the employees receive less than 0.5 rem/yr.

  2. Anomalous resistivity due to low-frequency turbulence. [of collisionless plasma with limited acceleration of high velocity runaway electrons

    NASA Technical Reports Server (NTRS)

    Rowland, H. L.; Palmadesso, P. J.

    1983-01-01

    Large amplitude ion cyclotron waves have been observed on auroral field lines. In the presence of an electric field parallel to the ambient magnetic field these waves prevent the acceleration of the bulk of the plasma electrons leading to the formation of a runaway tail. It is shown that low-frequency turbulence can also limit the acceleration of high-velocity runaway electrons via pitch angle scattering at the anomalous Doppler resonance.

  3. Asbestos exposure, cigarette smoking, and airflow limitation in long-term Canadian chrysotile miners and millers

    SciTech Connect

    Begin, R.; Boileau, R.; Peloquin, S.

    1987-01-01

    To investigate further the relationships of asbestos exposure, cigarette smoking, and airflow limitation, we have obtained detailed pulmonary function tests (PFT) in 331 long-term Canadian chrysotile workers, 34 of whom were lifetime nonsmokers. Three disease categories were defined on the bases of standard diagnostic criteria, gallium-67 lung uptake, and the lung pressure-volume curve. Category A was composed of workers without changes suggestive of alveolitis or asbestosis. There were eight nonsmokers (ns), among whom we found a statistically significant 30% reduction in airflow conductance (Gus) at low lung volume, which is consistent with the concept of an asbestos airway lesion. The 85 smokers (sm) of category A had reduction of Gus at both high and low lung volumes. Category B was composed of workers without asbestosis but with evidence of asbestos alveolitis. In the six ns, Gus was significantly reduced to 50% normal at low lung volume. The 59 sm had reduction of Gus at both high and low lung volumes but less severely than sm in category A. Category C was composed of workers with asbestosis. The 20 ns had restrictive pattern of lung function, and Gus was decreased to 39% normal at 50% TLC. The 153 sm in C had airflow reduction comparable to sm in B. We concluded that asbestos exposure, which leads to asbestos airway disease, asbestos peribronchiolar alveolitis, and asbestosis, causes airflow limitation at low lung volume but does not reduce the expiratory flow rates on the flow-volume curve in lifetime nonsmokers. In the smoking asbestos workers with alveolitis or asbestosis, the major component of airflow limitation is a smoking effect. In these smoking workers, rigidity of the lung lessens airflow obstruction associated with smoking at the expense of increased work of breathing.

  4. Multi-walled carbon nanotubes (Baytubes): approach for derivation of occupational exposure limit.

    PubMed

    Pauluhn, Jürgen

    2010-06-01

    Carbon nanotubes come in a variety of types, but one of the most common forms is multi-walled carbon nanotubes (MWCNT). This paper focuses on the dose-response and time course of pulmonary toxicity of Baytubes, a more flexible MWCNT type with the tendency to form assemblages of nanotubes. This MWCNT has been examined in previous single and repeated exposure 13-week rat inhalation studies. Kinetic endpoints and the potential to translocate to extrapulmonary organs have been examined during postexposure periods of 3 and 6 months, respectively. The focus of both studies was to compare dosimetric endpoints and the time course of pulmonary inflammation characterized by repeated bronchoalveolar lavage and histopathology during the respective follow-up periods. To better understand the etiopathology of pulmonary inflammation and time-related lung remodeling, two metrics of retained lung dose were compared. The first used the mass metric based on the exposure concentration obtained by filter analyses and aerodynamic particle size of airborne MWCNT. The second was based on calculated volumetric lung burdens of retained MWCNT. Kinetic analyses of lung burdens support the conclusion that Baytubes, in principal, act like poorly soluble agglomerated carbonaceous particulates. However, the difference in pulmonary toxic potency (mass-based) appears to be associated with the low-density (approximately 0.1-0.3g/m(3)) of the MWCNT assemblages. Of note is that assemblages of MWCNT were found predominantly both in the exposure atmosphere and in digested alveolar macrophages. Isolated fibers were not observed in exposure atmospheres or biological specimens. All findings support the conclusion that the low specific density of microstructures was conducive to attaining the volumetric lung overload-related inflammatory response conditions earlier than conventional particles. Evidence of extrapulmonary translocation or toxicity was not found in any study. Thus, pulmonary overload is believed to trigger the cascade of events leading to a stasis of clearance and consequently increased MWCNT doses high enough to trigger sustained pulmonary inflammation. This mechanism served as conceptual basis for the calculation of the human equivalent concentration. Accordingly, multiple interspecies adjustments were necessary which included species-specific differences in alveolar deposition, differences in ventilation, and the time-dependent particle accumulation accounting for the known species-specific differences in particle clearance half-times in rats and humans. Based on this rationale and the NOAEL (no-observed adverse effect level) from the 13-week subchronic inhalation study on rats, an occupational exposure limit (OEL) of 0.05 mg Baytubes/m(3) (time weighted average) is considered to be reasonably protective to prevent lung injury to occur in the workplace environment. PMID:20074606

  5. An evaluation of compliance with occupational exposure limits for crystalline silica (quartz) in ten Georgia granite sheds.

    PubMed

    Wickman, Arthur R; Middendorf, Paul J

    2002-06-01

    Since the 1920s, industrial hygiene studies have documented granite shed workers' exposures to crystalline silica, and the data from these studies have contributed to a better understanding of the relationship between silica exposures and adverse health effects, such as silicosis. The majority of these studies were conducted in the Barre, Vermont, granite sheds. However, a second major granite processing region is located in Elberton, Georgia, where approximately 1800 workers are employed in 150 granite sheds and 45 quarries. The current study reports the exposures of 40 workers in 10 granite sheds in Elberton, Georgia. The arithmetic mean exposure to silica for all monitored employees was 0.052 mg/m3. Employees were classified into one of seven job task groups. The job task group with the greatest exposure was the top polish group, which had a mean exposure of 0.085 mg/m3. Among the top polish workers, the greatest percentage of exposures above the Occupational Safety and Health Administration's permissible exposure limit (OSHA PEL) occurred among the workers who used dry grinders. Wet methods were effective in reducing these exposures to below the OSHA PEL. The mean exposure of Elberton granite shed workers was less than the OSHA PEL, but was not below the threshold limit value of the American Conference of Industrial Hygienists (ACGIH TLV), which was lowered in the year 2000 to 0.05 mg/m3. The Elberton granite shed workers provide a valuable cohort for research on the effects of exposure to crystalline silica at levels between the ACGIH TLV and the OSHA PEL. They are a relatively permanent worker population, are concentrated geographically, and have a quantitatively documented exposure to crystalline silica over the past twenty years. PMID:12049432

  6. Derivation of an occupational exposure limit for inorganic borates using a weight of evidence approach.

    PubMed

    Maier, A; Vincent, M; Hack, E; Nance, P; Ball, W

    2014-04-01

    Inorganic borates are encountered in many settings worldwide, spurring international efforts to develop exposure guidance (US EPA, 2004; WHO, 2009; ATSDR, 2010) and occupational exposure limits (OEL) (ACGIH, 2005; MAK, 2011). We derived an updated OEL to reflect new data and current international risk assessment frameworks. We assessed toxicity and epidemiology data on inorganic borates to identify relevant adverse effects. International risk assessment frameworks (IPCS, 2005, 2007) were used to evaluate endpoint candidates: reproductive toxicity, developmental toxicity, and sensory irritation. For each endpoint, a preliminary OEL was derived and adjusted based on consideration of toxicokinetics, toxicodynamics, and other uncertainties. Selection of the endpoint point of departures (PODs) is supported by dose-response modeling. Developmental toxicity was the most sensitive systemic effect. An OEL of 1.6mgB/m(3) was estimated for this effect based on a POD of 63mgB/m(3) with an uncertainty factor (UF) of 40. Sensory irritation was considered to be the most sensitive effect for the portal of entry. An OEL of 1.4mgB/m(3) was estimated for this effect based on the identified POD and an UF of 1. An OEL of 1.4mgB/m(3) as an 8-h time-weighted average (TWA) is recommended. PMID:24525063

  7. An Operating Economic Exposure - Australian Case Study: Foster’s Group Limited Beer

    Microsoft Academic Search

    Scott McCarthy; Adelina Ispriani

    2004-01-01

    This paper uses a large Australian multinational corporation as a case study examining foreign exchange operating exposure. We firstly review the importance of operating exposure for a business and then examine in detail the company’s exposure and policies to manage the exposure. A sensitivity analysis is also conducted to examine how movements in the value of exchange rates affect the

  8. New trends in the development of occupational exposure limits for airborne chemicals in China.

    PubMed

    Liang, You-xin; Su, Zhi; Wu, Wei-ai; Lu, Bo-qin; Fu, Wei-zu; Yang, Lei; Gu, Jin-yu

    2003-10-01

    Occupational exposure limits (OELs) are well established in many countries, which serve occupational professionals as benchmarks of industrial hygiene practice at workplaces worldwide. Starting in the mid-1950s, the central government of China began promulgating OELs for hazardous substances at workplaces. This paper discusses the historical basis, philosophical principles and schematic protocols of developing and setting OELs in China. The underlying principles include: (1) protection of human health being the first and the most important criterion; (2) the use of quantitative epidemiological studies in humans being given top priority; (3) integration and full use of all information sources, including animal experimental data for new chemicals or chemicals with new toxicity concerns; (4) considerations of socioeconomic and technological feasibilities in the country; and (5) amending existing standards based on new evidence. The strategy of the World Health Organization's "Two-step Procedure" is applied to convert health-based recommendations to law-based operational OELs, with considerations for national technological and socioeconomic conditions and priorities. As a result of the recent passage of the new law Occupational Diseases Prevention and Control Act of the People's Republic of China (ODPCAct), an official document Occupational Exposure Limits for Hazardous Agents in the Workplace containing a comprehensive list of new and amended OELs has been issued, which has now become one of the most essential regulations affiliated with the ODPCAct. This paper provides a brief summary of the salient features of the new law ODPCAct and the principles and processes of developing or amending OELs. This paper also discusses the challenges that lie ahead in enforcing the new regulations in China. PMID:14550754

  9. Accelerator mass spectrometry in the biomedical sciences: applications in low-exposure biomedical and environmental dosimetry

    Microsoft Academic Search

    J. S. Felton; K. W. Turteltaub; J. S. Vogel; R. Balhorn; B. L. Gledhill; J. R. Southon; M. W. Caffee; R. C. Finkel; D. E. Nelson; I. D. Proctor; J. C. Davis

    1990-01-01

    We are utilizing accelerator mass spectrometry as a sensitive detector for tracking the disposition of radioisotopically labeled molecules in the biomedical sciences. These applications have shown the effectiveness of AMS as a tool to quantify biologically important molecules at extremely low levels. For example, AMS is being used to determine the amount of carcinogen covalently bound to animal DNA (DNA

  10. Accelerator mass spectrometry in the biomedical sciences: Applications in low-exposure biomedical and environmental dosimetry

    Microsoft Academic Search

    J. S. Felton; K. W. Turteltaub; J. S. Vogel; R. Balhorn; B. L. Gledhill; J. R. Southon; M. W. Caffee; R. C. Finkel; D. E. Nelson; I. D. Proctor; J. C. Davis

    1990-01-01

    We are utilizing Accelerator Mass Spectrometry (AMS) as a sensitive detector for tracking the disposition of radio-isotope labeled molecules in the biomedical sciences. These applications have shown the effectiveness of AMS as a tool to quantify biologically important molecules at extremely low levels. For example, AMS is being used to determine the amount of carcinogen covalently bound to animal DNA

  11. The NREL Outdoor Accelerated-Weathering Tracking System Photovoltaic Module Exposure Results

    SciTech Connect

    Basso, T. S.

    2000-01-01

    Status results are presented for the Outdoor Accelerated-Weathering Tracking System (OATS) first study on photovoltaic (PV) modules. Studies began in November 1997 on pairs of commercially available crystalline silicon and amorphous silicon (a-Si) PV modules kept at constant resistive load.

  12. Fast Model Based Approximation of the Closed-loop Performance Limits of Gas/Liquid Inline Separators for Accelerated Design

    E-print Network

    Van den Hof, Paul

    Fast Model Based Approximation of the Closed-loop Performance Limits of Gas/Liquid Inline Separators for Accelerated Design M. Leskens, A. Huesman, P.M.J. Van den Hof* S. Belfroid, E. Nennie** P called inline separators (ILS). Unlike their large conventional counterparts, the operation

  13. Acceleration of Age-Related Hearing Loss by Early Noise Exposure: Evidence of a Misspent Youth

    PubMed Central

    Kujawa, Sharon G.; Liberman, M. Charles

    2007-01-01

    Age-related and noise-induced hearing losses in humans are multifactorial, with contributions from, and potential interactions among, numerous variables that can shape final outcome. A recent retrospective clinical study suggests an age-noise interaction that exacerbates age-related hearing loss in previously noise-damaged ears (Gates et al., 2000). Here, we address the issue in an animal model by comparing noise-induced and age-related hearing loss (NIHL; AHL) in groups of CBA/CaJ mice exposed identically (8-16 kHz noise band at 100 dB sound pressure level for 2 h) but at different ages (4-124 weeks) and held with unexposed cohorts for different postexposure times (2-96 weeks). When evaluated 2 weeks after exposure, maximum threshold shifts in young-exposed animals (4-8 weeks) were 40-50 dB; older-exposed animals (? 16 weeks) showed essentially no shift at the same postexposure time. However, when held for long postexposure times, animals with previous exposure demonstrated AHL and histopathology fundamentally unlike unexposed, aging animals or old-exposed animals held for 2 weeks only. Specifically, they showed substantial, ongoing deterioration of cochlear neural responses, without additional change in preneural responses, and corresponding histologic evidence of primary neural degeneration throughout the cochlea. This was true particularly for young-exposed animals; however, delayed neuropathy was observed in all noise-exposed animals held 96 weeks after exposure, even those that showed no NIHL 2 weeks after exposure. Data suggest that pathologic but sublethal changes initiated by early noise exposure render the inner ears significantly more vulnerable to aging. PMID:16481444

  14. Body composition changes in monkeys during long-term exposure to high acceleration fields

    NASA Technical Reports Server (NTRS)

    Pace, N.; Rahlmann, D. F.; Kodama, A. M.; Smith, A. H.

    1977-01-01

    Adult male pig-tailed monkeys, weighing 10-14 kg, were subjected to continuous centrifuging stress for 7 months in acceleration fields up to 2.5 g. In vivo analytical techniques were used to evaluate parameters of body composition, body-fluid distribution, and hematology. Statistically significant losses in total body mass, lean body mass, total body water, extracellular water content and interstitial water content proportional to the level of high g were demonstrated.

  15. Effect of Accelerated Ultra Violet and Thermal Exposure on Nano Scale Mechanical Properties of Nylon Fibers

    Microsoft Academic Search

    Nandula Wanasekara; Vijaya Chalivendra; Paul Calvert

    \\u000a Nano-characterization studies using atomic force microscopy (AFM) was conducted to study the effect of accelerated ultra violet\\u000a (UV) and thermal degradation on mechanical properties of Nylon textile fibers. Nylon fibers were exposed to UV radiation for\\u000a six different hours using Q-UV Panel Weatherometer. The exposed fibers were molded in an epoxy plug for nanaoindentation using\\u000a AFM. Progressive nanoindentation from surface

  16. Bioreactivity of the crystalline silica polymorphs, quartz and cristobalite, and implications for occupational exposure limits (OELs).

    PubMed

    Mossman, Brooke T; Glenn, Robert E

    2013-09-01

    Silica or silicon dioxides (SiO?) are naturally occurring substances that comprise the vast majority of the earth's crust. Because of their prevalence and commercial applications, they have been widely studied for their potential to induce pulmonary fibrosis and other disorders. Historically, the focus in the workplace has been on the development of inflammation and fibrotic lung disease, the basis for promulgating workplace standards to protect workers. Crystalline silica (CS) polymorphs, predominantly quartz and cristobalite, are used in industry but are different in their mineralogy, chemistry, surface features, size dimensions and association with other elements naturally and during industrial applications. Epidemiologic, clinical and experimental studies in the literature historically have predominantly focused on quartz polymorphs. Thus, in this review, we summarize past scientific evaluations and recent peer-reviewed literature with an emphasis on cristobalite, in an attempt to determine whether quartz and cristobalite polymorphs differ in their health effects, toxicity and other properties that may dictate the need for various standards of protection in the workplace. In addition to current epidemiological and clinical reports, we review in vivo studies in rodents as well as cell culture studies that shed light on mechanisms intrinsic to the toxicity, altered cell responses and protective or defense mechanisms in response to these minerals. The medical and scientific literature indicates that the mechanisms of injury and potential causation of inflammation and fibrotic lung disease are similar for quartz and cristobalite. Our analysis of these data suggests similar occupational exposure limits (OELs) for these minerals in the workplace. PMID:23863112

  17. Prior exposure to acrolein accelerates pulmonary inflammation in influenza A-infected mice.

    PubMed

    Ong, Ferrer H C; Henry, Peter J; Burcham, Philip C

    2012-08-01

    The combustion product acrolein contributes to several smoke-related health disorders, but whether this immunomodulatory toxicant alters pulmonary susceptibility to viruses has received little attention. To study the effects of prior acrolein dosing on the severity of influenza A viral infection, male BALB/c mice received acrolein (1mg/kg) or saline (control) via oropharyngeal aspiration either 4- or 7-days prior to intranasal inoculation with either influenza A/PR/8/34 virus or vehicle. At 0, 2, 4 and 7 days post-inoculation, lung samples were assessed for histological changes while pulmonary inflammation was monitored by estimating immune cell numbers and cytokine levels in bronchoalveolar lavage fluid (BALF). After viral challenge, animals that were exposed to acrolein 4 days previously experienced greater weight loss and exhibited an accelerated inflammatory response at 2 days after viral inoculation. Thus compared to saline-pretreated, virus-challenged controls, BALF recovered from these mice contained higher numbers of macrophages and neutrophils in addition to increased levels of several inflammatory cytokines, including IL-1?, IL-1?, IL-6, TNF, IFN-?, KC, and MCP-1. The acrolein-induced increase in viral susceptibility was suppressed by the carbonyl scavenger bisulphite. These findings suggest acute acrolein intoxication "primes" the lung to mount an accelerated immune response to inhaled viruses. PMID:22705057

  18. Exposure of PC12 cells to NGF/ethanol results in accelerated differentiation and altered gene expression

    SciTech Connect

    White, K.R.; Wooten, M.W. (Auburn Univ., AL (United States))

    1991-03-11

    The role of alcohols in affecting neuromorphogenesis was investigated in the pheochromocytoma cell line, PC12. The effect of ethanol at physiological concentrations in this system leads to accelerated neurite extension in the presence of suboptimal concentrations of NGF. Accelerated morphological differentiation was dependent upon the side chain length of the alcohol and not inhibited by pyrazole. Ethanol/NGF induced neurite extension can be blocked with 50nM of K252a, but not sphingozine, H7, H89, genistein or okadaic acid. Changes in the expression of 17 NGF-induced and/or neuronal transcripts were examined in relationship to time of NGF/ethanol exposure; dose of NGF/ethanol; and side-chain length of NFG/alcohol. The authors studies indicate that ethanol potentiates the effects of NFG and subsequent neurogenesis through both protein kinase C and cAMP-independent pathways. In addition, these data show that ethanol is capable of altering gene expression in a specific manner.

  19. Formate in serum and urine after controlled methanol exposure at the threshold limit value

    Microsoft Academic Search

    A. dAlessandro; J. D. Osterloh; P. Chuwers; P. J. Quinlan; T. J. Kelly; C. E. Becker

    1994-01-01

    Methanol will be present as a new air pollutant when methanol-powered vehicles are introduced in the United States. Little is known about the effect of low-dose methanol exposure. It is controversial whether or not formate, the main metabolite responsible for methanol's acute toxicity, is a sensitive biological marker of toxicity or exposure. We studied the effect of a 4-hr exposure

  20. Historical limitations of determinant based exposure groupings in the rubber manufacturing industry

    PubMed Central

    Vermeulen, R; Kromhout, H

    2005-01-01

    Aims: To study the validity of using a cross-sectional industry-wide exposure survey to develop exposure groupings for epidemiological purposes that extend beyond the time period in which the exposure data were collected. Methods: Exposure determinants were used to group workers into high, medium, and low exposure groups. The contrast of this grouping and other commonly used grouping schemes based on plant and department within this exposure survey and a previously conducted survey within the same industry (and factories) were estimated and compared. Results: Grouping of inhalable and dermal exposure based on exposure determinants resulted in the highest, but still modest, contrast (? ? 0.3). Classifying subjects based on a combination of plant and department resulted in a slightly lower contrast (? ? 0.2). If the determinant based grouping derived from the 1997 exposure survey was used to classify workers in the 1988 survey the average contrast decreased significantly for both exposures (? ? 0.1). On the contrary, the exposure classification based on plant and department increased in contrast (from ? ? 0.2 to ? ? 0.3) and retained its relative ranking overtime. Conclusions: Although determinant based groupings seem to result in more efficient groupings within a cross-sectional survey, they have to be used with caution as they might result in significant less contrast beyond the studied population or time period. It is concluded that a classification based on plant and department might be more desirable for retrospective studies in the rubber manufacturing industry, as they seem to have more historical relevance and are most likely more accurately recorded historically than information on exposure determinants in a particular industry. PMID:16234406

  1. Impulse noise exposure in early adulthood accelerates age-related hearing loss.

    PubMed

    Xiong, Min; Yang, Chuanhong; Lai, Huangwen; Wang, Jian

    2014-06-01

    The aim of this study was to investigate the influence of impulse noise on age-related hearing loss. The study consisted of two groups. Each group contained 109 men. Group I comprised veterans with normal hearing at the end of 1979 sino-vietnamese war. All these veterans were randomly selected from Guangzhou Military Command. Group II were men with no military experience randomly chosen from the health examination center of Guangzhou General Hospital of Guangzhou Military Command. Pure-tone thresholds of these two groups were measured and compared. The pure-tone thresholds of Group I were poorer than those of Group II at the frequencies of 4, 6 and 8 kHz. Thus, impulse noise accelerates age-related hearing loss. PMID:23842602

  2. Plasma exposure of different tungsten grades with plasma accelerators under ITER-relevant conditions

    NASA Astrophysics Data System (ADS)

    Makhlaj, Vadym A.; Garkusha, Igor E.; Aksenov, Nikolay N.; Bazylev, Boris; Byrka, Oleg V.; Landman, Igor; Linke, Jochen; Malykhin, Sergey V.; Pugachov, Anatoliy T.; Sadowski, Marek J.; Skladnik-Sadowska, Elzbieta; Wirtz, Marius

    2014-05-01

    This paper presents the results of tungsten irradiation experiments performed with three plasma facilities: the QSPA Kh-50 quasi-steady-state plasma accelerator, the PPA pulsed plasma gun and the magneto-plasma compressor. Targets made of different kinds of tungsten (sintered, rolled and deformed) were irradiated with powerful plasma streams at heat fluxes relevant to edge-localized modes in ITER. The irradiated targets were analyzed and two different meshes of cracks were identified. It has been shown that the major cracks do not depend on the tungsten grade. This has been attributed to ductile-to-brittle transition effects. Meshes of inter-granular micro-cracks were detected for energy loads above the melting threshold and these were probably caused by the re-solidification process. The blister-like and cellular-like structures were observed on sample surfaces exposed to helium and hydrogen plasmas.

  3. Acute Ozone (O3) Exposure Accelerates Diet-Induced Pulmonary Injury and Metabolic Alterations in a Rat Model of Type II Diabetes

    EPA Science Inventory

    Abstract for Society of Toxicology, March 22-25, 2015, San Diego, CAAcute Ozone (O3) Exposure Accelerates Diet-Induced Pulmonary Injury and Metabolic Alterations in a Rat Model of Type II DiabetesS.J. Snow1,3, D. Miller2, V. Bass2, M. Schladweiler3, A. Ledbetter3, J. Richards3, C...

  4. Relative Humidity in Limited Streamer Tubes for Stanford Linear Accelerator Center's BaBar Detector

    SciTech Connect

    Lang, M.I.; /MIT; Convery, M.; /SLAC; Menges, W.; /Queen Mary, U. of London

    2005-12-15

    The BABAR Detector at the Stanford Linear Accelerator Center studies the decay of B mesons created in e{sup +}e{sup -} collisions. The outermost layer of the detector, used to detect muons and neutral hadrons created during this process, is being upgraded from Resistive Plate Chambers (RPCs) to Limited Streamer Tubes (LSTs). The standard-size LST tube consists of eight cells, where a silver-plated wire runs down the center of each. A large potential difference is placed between the wires and ground. Gas flows through a series of modules connected with tubing, typically four. LSTs must be carefully tested before installation, as it will be extremely difficult to repair any damage once installed in the detector. In the testing process, the count rate in most modules showed was stable and consistent with cosmic ray rate over an approximately 500 V operating range between 5400 to 5900 V. The count in some modules, however, was shown to unexpectedly spike near the operation point. In general, the modules through which the gas first flows did not show this problem, but those further along the gas chain were much more likely to do so. The suggestion was that this spike was due to higher humidity in the modules furthest from the fresh, dry inflowing gas, and that the water molecules in more humid modules were adversely affecting the modules' performance. This project studied the effect of humidity in the modules, using a small capacitive humidity sensor (Honeywell). The sensor provided a humidity-dependent output voltage, as well as a temperature measurement from a thermistor. A full-size hygrometer (Panametrics) was used for testing and calibrating the Honeywell sensors. First the relative humidity of the air was measured. For the full calibration, a special gas-mixing setup was used, where relative humidity of the LST gas mixture could be varied from almost dry to almost fully saturated. With the sensor calibrated, a set of sensors was used to measure humidity vs. time in the LSTs. The sensors were placed in two sets of LST modules, one gas line flowing through each set. These modules were tested for count rate v. voltage while simultaneously measuring relative humidity in each module. One set produced expected readings, while the other showed the spike in count rate. The relative humidity in the two sets of modules looked very similar, but it rose significantly for modules further along the gas chain.

  5. Minimum-Time Travel for a Vehicle with Acceleration Limits: Theoretical Analysis and Receding-Horizon Implementation

    Microsoft Academic Search

    Efstathios Velenis; Panagiotis Tsiotras

    2008-01-01

    A methodology is proposed to generate minimum-time optimal velocity profiles for a vehicle with prescribed acceleration limits\\u000a along a specified path. The necessary optimality conditions are explicitly derived, allowing the construction of the optimal\\u000a solution semianalytically. A receding horizon implementation is also proposed for the on-line implementation of the velocity\\u000a optimizer. Robustness of the receding horizon algorithm is guaranteed by

  6. Raising gradient limitations in 2.1?GHz superconducting photonic band gap accelerator cavities

    SciTech Connect

    Simakov, Evgenya I., E-mail: smirnova@lanl.gov; Arsenyev, Sergey A.; Haynes, W. Brian; Shchegolkov, Dmitry Yu.; Suvorova, Natalya A.; Tajima, Tsuyoshi [Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, New Mexico 87545 (United States); Boulware, Chase H.; Grimm, Terry L. [Niowave, Inc., 1012 North Walnut Street, Lansing, Michigan 48906 (United States)

    2014-06-16

    We report results from recent 2.1?GHz superconducting radio frequency (SRF) photonic band gap (PBG) resonator experiments at Los Alamos. Two 2.1?GHz PBG cells with elliptical rods were fabricated and tested at high power in a liquid helium bath at the temperatures of 4?K and below 2?K. The described SRF PBG cells were designed with a particular emphasis on changing the shape of the PBG rods to reduce peak surface magnetic fields and at the same time to preserve its effectiveness at damping higher-order-modes. The superconducting PBG cavities have great potential for damping long-range wakefields in SRF accelerator structures without affecting the fundamental accelerating mode. The cells performed in accordance with simulation's predictions and the maximum achieved accelerating gradient was 18.3 MV/m. This represents a 30% increase over gradients previously demonstrated in superconducting PBG cavities with round rods.

  7. Raising gradient limitations in 2.1 GHz superconducting photonic band gap accelerator cavities

    NASA Astrophysics Data System (ADS)

    Simakov, Evgenya I.; Arsenyev, Sergey A.; Haynes, W. Brian; Shchegolkov, Dmitry Yu.; Suvorova, Natalya A.; Tajima, Tsuyoshi; Boulware, Chase H.; Grimm, Terry L.

    2014-06-01

    We report results from recent 2.1 GHz superconducting radio frequency (SRF) photonic band gap (PBG) resonator experiments at Los Alamos. Two 2.1 GHz PBG cells with elliptical rods were fabricated and tested at high power in a liquid helium bath at the temperatures of 4 K and below 2 K. The described SRF PBG cells were designed with a particular emphasis on changing the shape of the PBG rods to reduce peak surface magnetic fields and at the same time to preserve its effectiveness at damping higher-order-modes. The superconducting PBG cavities have great potential for damping long-range wakefields in SRF accelerator structures without affecting the fundamental accelerating mode. The cells performed in accordance with simulation's predictions and the maximum achieved accelerating gradient was 18.3 MV/m. This represents a 30% increase over gradients previously demonstrated in superconducting PBG cavities with round rods.

  8. Screening values for Non-Carcinogenic Hanford Waste Tank Vapor Chemicals that Lack Established Occupational Exposure Limits

    SciTech Connect

    Poet, Torka S.; Mast, Terryl J.; Huckaby, James L.

    2006-02-06

    Over 1,500 different volatile chemicals have been reported in the headspaces of tanks used to store high-level radioactive waste at the U.S. Department of Energy's Hanford Site. Concern about potential exposure of tank farm workers to these chemicals has prompted efforts to evaluate their toxicity, identify chemicals that pose the greatest risk, and incorporate that information into the tank farms industrial hygiene worker protection program. Established occupation exposure limits for individual chemicals and petroleum hydrocarbon mixtures have been used elsewhere to evaluate about 900 of the chemicals. In this report headspace concentration screening values were established for the remaining 600 chemicals using available industrial hygiene and toxicological data. Screening values were intended to be more than an order of magnitude below concentrations that may cause adverse health effects in workers, assuming a 40-hour/week occupational exposure. Screening values were compared to the maximum reported headspace concentrations.

  9. The Acceleration of Foam Aging by Thin-Slicing: Some Interpretations and Limitations

    Microsoft Academic Search

    D. Bhattacharjee; P. W. Irwin; J. R. Booth; J. T. Grimes

    1994-01-01

    Thin-slice accelerated aging methodologies have not been ag gressively pursued because of concerns about the reliability and applicability of the results. The use of gases such as helium, nitrogen and carbon dioxide, which diffuse rapidly and are only sparingly soluble in the polymer, may be used to obtain a diffu sion measurement in the foam matrix. These diffusion measurements provide

  10. Accelerated appearance of skin tumors in hairless mice by repeated UV irradiation with initial intense exposure and characterization of the tumors.

    PubMed

    Nishigori, C; Tanaka, M; Moriwaki, S; Imamura, S; Takebe, H

    1992-11-01

    Skin tumors were produced on the back of hairless mice, HOS (HR/De), by exposure to ultraviolet B light (UVB, 290-320 nm) with 4 different protocols. The first tumors appeared earlier (in 10 weeks in group I and 7 weeks in group III) when initial intense exposure was given, followed by repeated lower-level exposures, than when the mice were exposed to the repeated UV only (in 16 weeks both in group II and group IV). All mice developed skin tumors earlier in the groups given the repeated UV exposures three times a week than in the groups given the exposures twice a week. Most of the skin tumors produced by the UVB exposure were histologically malignant, being transplantable to nude mice, and the cultured cells grown from the tumors were capable of producing tumors when injected into nude mice. The accelerated development of skin tumors by initial intense exposure and short intervals of repeated exposure observed in this study may have implications for humans who expose themselves to intense sunbathing and UV tanning (burning) by fluorescent sun lamps. PMID:1483932

  11. Limits of NbTi and Nb3Sn, and development of W& R Bi-2212 High Field Accelerator Magnets

    SciTech Connect

    Cheng, Daniel; Dietderich, Daniel; Ferrracin, Paolo; Prestemon, Soren; Sabbi, GianLuca; Scanlan, Ron; Godeke, A.

    2007-06-01

    NbTi accelerator dipoles are limited to magnetic fields (H) of about 10 T, due to an intrinsic upper critical field (H{sub c2}) limitation of 14 T. To surpass this restriction, prototype Nb{sub 3}Sn magnets are being developed which have reached 16 T. We show that Nb{sub 3}Sn dipole technology is practically limited to 17 to 18 T due to insufficient high field pinning, and intrinsically to 20 to 22 T due to H{sub c2} limitations. Therefore, to obtain magnetic fields approaching 20 T and higher, a material is required with a higher H{sub c2} and sufficient high field pinning capacity. A realistic candidate for this purpose is Bi-2212, which is available in round wires and sufficient lengths for the fabrication of coils based on Rutherford-type cables. We initiated a program to develop the required technology to construct accelerator magnets from 'wind-and-react' (W&R) Bi-2212 coils. We outline the complications that arise through the use of Bi-2212, describe the development paths to address these issues, and conclude with the design of W&R Bi-2212 sub-scale magnets.

  12. The role of home smoking bans in limiting exposure to secondhand tobacco smoke in Hungary

    PubMed Central

    Paulik, Edit; Maróti-Nagy, Á.; Nagymajtényi, L.; Rogers, T.; Easterling, D.

    2013-01-01

    Our objective was to assess how exposure to secondhand tobacco smoke occurs in Hungarian homes, particularly among non-smokers, and to examine the effectiveness of home smoking bans in eliminating exposure to secondhand smoke at home. In 2009, 2286 non-smokers and smokers aged 16–70 years, who were selected randomly from a nationally representative sample of 48 Hungarian settlements, completed paper-and-pencil self-administered questionnaires addressing tobacco-related attitudes, opinions and behaviors. Chi-square tests, one-way analysis of variance and multivariate logistic regression models were used to assess the effect of demographics, socio-economic characteristics and home smoking policies on the risk of exposure to secondhand tobacco smoke at home. Significantly higher risk of exposure was found among younger, lower educated and poorer people and among those having no or partial home smoking restrictions. There was a significant interaction between education level and home smoking policies: the effect of a smoking ban on exposure to secondhand tobacco smoke was stronger for the lower educated group than the higher educated group. The results suggest that Hungarians are making good progress in implementing home smoking bans, and that in the majority of population these bans are working. More can be done to promote the uptake of home smoking bans among poorer and less educated subpopulations. PMID:22653684

  13. Cetacean noise criteria revisited in the light of proposed exposure limits for harbour porpoises.

    PubMed

    Tougaard, Jakob; Wright, Andrew J; Madsen, Peter T

    2015-01-15

    The impact of underwater noise on marine life calls for identification of exposure criteria to inform mitigation. Here we review recent experimental evidence with focus on the high-frequency cetaceans and discuss scientifically-based initial exposure criteria. A range of new TTS experiments suggest that harbour and finless porpoises are more sensitive to sound than expected from extrapolations based on results from bottlenose dolphins. Furthermore, the results from TTS experiments and field studies of behavioural reactions to noise, suggest that response thresholds and TTS critically depend on stimulus frequency. Sound exposure levels for pure tones that induce TTS are reasonably consistent at about 100 dB above the hearing threshold for pure tones and sound pressure thresholds for avoidance reactions are in the range of 40-50 dB above the hearing threshold. We propose that frequency weighting with a filter function approximating the inversed audiogram might be appropriate when assessing impact. PMID:25467877

  14. Behavioral Flexibility and Response Selection Are Impaired after Limited Exposure to Oxycodone

    ERIC Educational Resources Information Center

    Seip-Cammack, Katharine M.; Shapiro, Matthew L.

    2014-01-01

    Behavioral flexibility allows individuals to adapt to situations in which rewards and goals change. Potentially addictive drugs may impair flexible decision-making by altering brain mechanisms that compute reward expectancies, thereby facilitating maladaptive drug use. To investigate this hypothesis, we tested the effects of oxycodone exposure on…

  15. Airborne asbestos concentration from brake changing does not exceed permissible exposure limit

    Microsoft Academic Search

    Charles L. Blake; Drew R. Van Orden; Marek Banasik; Raymond D. Harbison

    2003-01-01

    The use in the past, and to a lesser extent today, of chrysotile asbestos in automobile brake systems causes health concerns among professional mechanics. Therefore, we conducted four separate tests in order to evaluate an auto mechanic’s exposure to airborne asbestos fibers while performing routine brake maintenance. Four nearly identical automobiles from 1960s having four wheel drum brakes were used.

  16. Early Postnatal Sound Exposure Induces Lasting Neuronal Changes in the Inferior Colliculus of Senescence Accelerated Mice (SAMP8): A Morphometric Study on GABAergic Neurons and NMDA Expression

    Microsoft Academic Search

    Dietrich Ernst Lorke; Lai Yung Wong; Helen W. L. Lai; Paul W. F. Poon; Aiqun Zhang; Wood Yee Chan; David Tai Wai Yew

    2003-01-01

    Senescence-acceleration-prone mice (SAMP8) provide a model to study the influence of early postnatal sound exposure upon the aging auditory midbrain. SAMP8 were exposed to a 9-kHz monotone of either 53- or 65-dB sound pressure level during the first 30 postnatal days, the neurons in the auditory midbrain responding selectively to 9 kHz were localized by c-fos immunohistochemistry and the following

  17. Extremely Low Frequency Exposure Limits Relative To Military Electrical\\/electronic System Environments

    Microsoft Academic Search

    R. P. Corcoran

    1992-01-01

    Military electrical and electronic equipment inherently radiate extremely low frequency (ELF) (30 to 300 Hz) fields. In this paper, ELF magnetic field limits from several national and international agencies are compared to MIL-STD-461C radiated emission (REO1) limits which some military electrical and electronic equipments must meet to maintain electromagnetic compatibility. The comparison shows that by meeting the REOl limits, military

  18. Gaussian convergence for stochastic acceleration of $\\cN$ particles in the dense spectrum limit

    E-print Network

    Yves Elskens

    2012-07-10

    The velocity of a passive particle in a one-dimensional wave field is shown to converge in law to a Wiener process, in the limit of a dense wave spectrum with independent complex amplitudes, where the random phases distribution is invariant modulo $\\pi/2$ and the power spectrum expectation is uniform. The proof provides a full probabilistic foundation to the quasilinear approximation in this limit. The result extends to an arbitrary number of particles, founding the use of the ensemble picture for their behaviour in a single realization of the stochastic wave field.

  19. 78 FR 33654 - Reassessment of Exposure to Radiofrequency Electromagnetic Fields Limits and Policies

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-04

    ...Radiofrequency Electromagnetic Fields Limits and Policies AGENCY...515120 (updated for inflation in 2010). \\187\\ See...not be dominant in its field of operation. We are...515112 (updated for inflation in 2010...not be dominant in its field of...

  20. Diffusion limit for many particles in a periodic stochastic acceleration field

    E-print Network

    Yves Elskens; Etienne Pardoux

    2008-11-05

    The one-dimensional motion of any number $\\cN$ of particles in the field of many independent waves (with strong spatial correlation) is formulated as a second-order system of stochastic differential equations, driven by two Wiener processes. In the limit of vanishing particle mass ${\\mathfrak{m}} \\to 0$, or equivalently of large noise intensity, we show that the momenta of all $N$ particles converge weakly to $N$ independent Brownian motions, and this convergence holds even if the noise is periodic. This justifies the usual application of the diffusion equation to a family of particles in a unique stochastic force field. The proof rests on the ergodic properties of the relative velocity of two particles in the scaling limit.

  1. Prey choice and habitat use drive sea otter pathogen exposure in a resource-limited coastal system

    USGS Publications Warehouse

    Johnson, Christine K.; Tinker, M. Tim; Estes, James A.; Conrad, Patricia A.; Staedler, Michelle M.; Miller, Melissa A.; Jessup, David A.; Mazet, Jonna A.K.

    2014-01-01

    The processes promoting disease in wild animal populations are highly complex, yet identifying these processes is critically important for conservation when disease is limiting a population. By combining field studies with epidemiologic tools, we evaluated the relationship between key factors impeding southern sea otter (Enhydra lutris nereis) population growth: disease and resource limitation. This threatened population has struggled to recover despite protection, so we followed radio-tagged sea otters and evaluated infection with 2 disease-causing protozoal pathogens, Toxoplasma gondii and Sarcocystis neurona, to reveal risks that increased the likelihood of pathogen exposure. We identified patterns of pathogen infection that are linked to individual animal behavior, prey choice, and habitat use. We detected a high-risk spatial cluster of S. neurona infections in otters with home ranges in southern Monterey Bay and a coastal segment near San Simeon and Cambria where otters had high levels of infection with T. gondii. We found that otters feeding on abalone, which is the preferred prey in a resource-abundant marine ecosystem, had a very low risk of infection with either pathogen, whereas otters consuming small marine snails were more likely to be infected with T. gondii. Individual dietary specialization in sea otters is an adaptive mechanism for coping with limited food resources along central coastal California. High levels of infection with protozoal pathogens may be an adverse consequence of dietary specialization in this threatened species, with both depleted resources and disease working synergistically to limit recovery.

  2. INTERACTION OF A MAGNETIZED SHELL WITH AN AMBIENT MEDIUM: LIMITS ON IMPULSIVE MAGNETIC ACCELERATION

    SciTech Connect

    Levinson, Amir, E-mail: Levinson@wise.tau.ac.i [School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978 (Israel)

    2010-09-10

    The interaction of relativistic magnetized ejecta with an ambient medium is studied for a range of structures and magnetization of the unshocked ejecta. We particularly focus on the effect of the ambient medium on the dynamics of an impulsive, high-sigma shell. It is found that for sufficiently high values of the initial magnetization {sigma}{sub 0} the evolution of the system is significantly altered by the ambient medium well before the shell reaches its coasting phase. The maximum Lorentz factor of the shell is limited to values well below {sigma}{sub 0}; for a shell of initial energy E = 10{sup 52} E{sub 52} erg and size r{sub 0} = 10{sup 12} T{sub 30} cm expelled into a medium having a uniform density n{sub i} , we obtain {Gamma}{sub max} {approx_equal} 180(E{sub 52}/T {sup 3}{sub 30} n{sub i}){sup 1/8} in the high-sigma limit. The reverse shock and any internal shocks that might form if the source is fluctuating are shown to be very weak. The restriction on the Lorentz factor is more severe for shells propagating in a stellar wind. Intermittent ejection of small sub-shells does not seem to help, as the shells merge while still highly magnetized. Lower sigma shells start decelerating after reaching the coasting phase and spreading away. The properties of the reverse shock then depend on the density profiles of the coasting shell and the ambient medium. For a self-similar cold shell the reverse shock becomes strong as it propagates inward, and the system eventually approaches the self-similar solution recently derived by Nakamura and Shigeyama.

  3. Highly accelerated simulations of glassy dynamics using GPUs: caveats on limited floating-point precision

    E-print Network

    Peter H. Colberg; Felix Höfling

    2011-01-17

    Modern graphics processing units (GPUs) provide impressive computing resources, which can be accessed conveniently through the CUDA programming interface. We describe how GPUs can be used to considerably speed up molecular dynamics (MD) simulations for system sizes ranging up to about 1 million particles. Particular emphasis is put on the numerical long-time stability in terms of energy and momentum conservation, and caveats on limited floating-point precision are issued. Strict energy conservation over 10^8 MD steps is obtained by double-single emulation of the floating-point arithmetic in accuracy-critical parts of the algorithm. For the slow dynamics of a supercooled binary Lennard-Jones mixture, we demonstrate that the use of single-floating point precision may result in quantitatively and even physically wrong results. For simulations of a Lennard-Jones fluid, the described implementation shows speedup factors of up to 80 compared to a serial implementation for the CPU, and a single GPU was found to compare with a parallelised MD simulation using 64 distributed cores.

  4. Multi-tissue analyses reveal limited inter-annual and seasonal variation in mercury exposure in an Antarctic penguin community.

    PubMed

    Brasso, Rebecka L; Polito, Michael J; Emslie, Steven D

    2014-10-01

    Inter-annual variation in tissue mercury concentrations in birds can result from annual changes in the bioavailability of mercury or shifts in dietary composition and/or trophic level. We investigated potential annual variability in mercury dynamics in the Antarctic marine food web using Pygoscelis penguins as biomonitors. Eggshell membrane, chick down, and adult feathers were collected from three species of sympatrically breeding Pygoscelis penguins during the austral summers of 2006/2007-2010/2011. To evaluate the hypothesis that mercury concentrations in penguins exhibit significant inter-annual variation and to determine the potential source of such variation (dietary or environmental), we compared tissue mercury concentrations with trophic levels as indicated by ?(15)N values from all species and tissues. Overall, no inter-annual variation in mercury was observed in adult feathers suggesting that mercury exposure, on an annual scale, was consistent for Pygoscelis penguins. However, when examining tissues that reflected more discrete time periods (chick down and eggshell membrane) relative to adult feathers, we found some evidence of inter-annual variation in mercury exposure during penguins' pre-breeding and chick rearing periods. Evidence of inter-annual variation in penguin trophic level was also limited suggesting that foraging ecology and environmental factors related to the bioavailability of mercury may provide more explanatory power for mercury exposure compared to trophic level alone. Even so, the variable strength of relationships observed between trophic level and tissue mercury concentrations across and within Pygoscelis penguin species suggest that caution is required when selecting appropriate species and tissue combinations for environmental biomonitoring studies in Antarctica. PMID:25085270

  5. Limits

    NSDL National Science Digital Library

    David Liao

    Students will see how the idea of a limit can be presented both in formal epsilon-delta-style terms, and using corresponding animations. After calculating a limit for a simple example function, we point out that limits do not always exist.

  6. “Nuisance Dust”: Unprotective Limits for Exposure to Coal Mine Dust in the United States, 1934–1969

    PubMed Central

    2013-01-01

    I examine the dismissal of coal mine dust as a mere nuisance, not a potentially serious threat to extractive workers who inhaled it. In the 1930s, the US Public Health Service played a major role in conceptualizing coal mine dust as virtually harmless. Dissent from this position by some federal officials failed to dislodge either that view or the recommendation of minimal limitations on workplace exposure that flowed from it. Privatization of regulatory authority after 1940 ensured that miners would lack protection against respiratory disease. The reform effort that overturned the established misunderstanding in the late 1960s critically depended upon both the production of scientific findings and the emergence of a subaltern movement in the coalfields. This episode illuminates the steep challenges often facing advocates of stronger workplace health standards. PMID:23237176

  7. Vitamin D Intake Determines Vitamin D Status of Postmenopausal Women, Particularly Those with Limited Sun Exposure123

    PubMed Central

    Cheng, Ting-Yuan David; Millen, Amy E.; Wactawski-Wende, Jean; Beresford, Shirley A. A.; LaCroix, Andrea Z.; Zheng, Yingye; Goodman, Gary E.; Thornquist, Mark D.; Neuhouser, Marian L.

    2014-01-01

    Few detailed data are available on the wide range of determinants of vitamin D status among postmenopausal women, and it is also unclear whether there may be undiscovered determinants. The objective of this study was to comprehensively evaluate determinants of serum 25-hydroxyvitamin D [25(OH)D] concentrations in a large cohort of postmenopausal women. Data from a subset of the Women’s Health Initiative Observational Study were analyzed (50–79 y; n = 3345). Information on diet, lifestyle behaviors, secondhand smoke, use of dietary supplements and medication, chronic diseases, and anthropometry was collected at baseline (1993–1998) and on sun exposure at year 4 follow-up. Linear regression was performed to estimate regression coefficients (?). Significant determinants were total vitamin D intake (food plus supplements per 100 IU/d, ? = 2.08), years of supplemental vitamin D use (? = 0.15), total fat intake (grams per day, ? = –0.03), smoking status (? = –2.64, current vs. never), regional solar irradiance (? = 6.26, 475–500 vs. 300–325 Langleys), daylight time spent outdoors in summer (? = 5.15, >2 h vs. <30 min/d), recreational physical activity (metabolic equivalent task per hour per week, ? = 0.13), waist circumference (centimeters, ? = –0.26), and race/ethnicity (? = –11.94, black vs. white). Total vitamin D intake (partial R2 = 0.09) explained the most variance in serum 25(OH)D concentrations (total R2 = 0.29). The association between total vitamin D intake and serum 25(OH)D concentrations was stronger among participants who spent less rather than more daylight time outdoors in summer (P-interaction = 0.026). History and medications for hypertension, hyperlipidemia, and type 2 diabetes and secondhand smoke exposure were not associated with serum 25(OH)D. In conclusion, dietary factors and sun exposure remain important determinants of vitamin D status in postmenopausal women. Vitamin D intake should be emphasized for those with limited sun exposure. PMID:24598886

  8. Prey choice and habitat use drive sea otter pathogen exposure in a resource-limited coastal system

    USGS Publications Warehouse

    Johnson, Christine K.; Tinker, M.T.; Estes, J.A.; Conrad, P.A.; Staedler, M.; Miller, M.A.; Jessup, David A.; Mazet, J.A.K.

    2009-01-01

    The processes promoting disease in wild animal populations are highly complex, yet identifying these processes is critically important for conservation when disease is limiting a population. By combining field studies with epidemiologic tools, we evaluated the relationship between key factors impeding southern sea otter (Enhydra lutris nereis) population growth: disease and resource limitation. This threatened population has struggled to recover despite protection, so we followed radio-tagged sea otters and evaluated infection with 2 disease-causing protozoal pathogens, Toxoplasma gondii and Sarcocystis neurona, to reveal risks that increased the likelihood of pathogen exposure. We identified patterns of pathogen infection that are linked to individual animal behavior, prey choice, and habitat use. We detected a high-risk spatial cluster of S. neurona infections in otters with home ranges in southern Monterey Bay and a coastal segment near San Simeon and Cambria where otters had high levels of infection with T. gondii. We found that otters feeding on abalone, which is the preferred prey in a resource-abundant marine ecosystem, had a very low risk of infection with either pathogen, whereas otters consuming small marine snails were more likely to be infected with T. gondii. Individual dietary specialization in sea otters is an adaptive mechanism for coping with limited food resources along central coastal California. High levels of infection with protozoal pathogens may be an adverse consequence of dietary specialization in this threatened species, with both depleted resources and disease working synergistically to limit recovery. ?? 2009 by The National Academy of Sciences of the USA.

  9. First-order Fermi acceleration in the two-stream limit. [for cosmic rays at relativistic and non-relativistic shocks

    NASA Technical Reports Server (NTRS)

    Bogdan, T. J.; Webb, G. M.

    1987-01-01

    A study of the first-order Fermi mechanism for accelerating cosmic-rays at relativistic and nonrelativistic shocks is carried out by using the two-stream approximation. Exact steady-state analytic solutions illustrating the shock acceleration process in the test-particle limit in which monoenergetic (relativistic) seed particles enter the shock through an upstream free-escape boundary are obtained. The momentum spectrum of the shock accelerated particles consists of a series of Dirac delta distributions corresponding to particles that have undergone an integral number of acceleration cycles. Since particles in the model have a finite fixed escape probability from the shock and the particle momenta p are equally spaced in log p, the envelope of the delta functions series is a power law in momentum. The solutions are used to discuss time-dependent aspects of the shock acceleration process in terms of the finite cycle time, escape probability, and momentum change per cycle that can be deduced from the steady-state model. The length-scale over which the accelerated particles extend upstream of the shock is shown to depend upon the particle energy, with the higher energy particles extending further upstream. This effect is shown to be intimately related to the kinematic threshold requirement that the particle speed exceed the fluid speed in order for particles to swim upstream of the shock and participate in the shock acceleration process.

  10. Limits of NbTi and Nb3Sn, and Development of W&R Bi2212 HighField Accelerator Magnets

    Microsoft Academic Search

    A. Godeke; D. Cheng; D. R. Dietderich; P. Ferracin; S. O. Prestemon; G. Sa bbi; R. M. Scanlan

    2006-01-01

    NbTi accelerator dipoles are limited to magneticfields (H)of about 10 T, due to an intrinsic upper critical field (Hc2) limitationof 14 T. To surpass this restriction, prototype Nb3Sn magnets are beingdeveloped which have reached 16 T. We show that Nb3Sn dipole technologyis practically limited to 17 to 18 T due to insufficient high fieldpinning, and intrinsically to 20 to 22

  11. Limitations of current dosimetry for intracavitary accelerated partial breast irradiation with high dose rate iridium-192 and electronic brachytherapy sources

    NASA Astrophysics Data System (ADS)

    Raffi, Julie A.

    Intracavitary accelerated partial breast irradiation (APBI) is a method of treating early stage breast cancer using a high dose rate (HDR) brachytherapy source positioned within the lumpectomy cavity. An expandable applicator stretches the surrounding tissue into a roughly spherical or elliptical shape and the dose is prescribed to 1 cm beyond the edge of the cavity. Currently, dosimetry for these treatments is most often performed using the American Association of Physicists in Medicine Task Group No. 43 (TG-43) formalism. The TG-43 dose-rate equation determines the dose delivered to a homogeneous water medium by scaling the measured source strength with standardized parameters that describe the radial and angular features of the dose distribution. Since TG-43 parameters for each source model are measured or calculated in a homogeneous water medium, the dosimetric effects of the patient's dimensions and composition are not accounted for. Therefore, the accuracy of TG-43 calculations for intracavitary APBI is limited by the presence of inhomogeneities in and around the target volume. Specifically, the breast is smaller than the phantoms used to determine TG-43 parameters and is surrounded by air, ribs, and lung tissue. Also, the composition of the breast tissue itself can affect the dose distribution. This dissertation is focused on investigating the limitations of TG-43 dosimetry for intracavitary APBI for two HDR brachytherapy sources: the VariSource TM VS2000 192Ir source and the AxxentRTM miniature x-ray source. The dose for various conditions was determined using thermoluminescent dosimeters (TLDs) and Monte Carlo (MC) calculations. Accurate measurements and calculations were achieved through the implementation of new measurement and simulation techniques and a novel breast phantom was developed to enable anthropomorphic phantom measurements. Measured and calculated doses for phantom and patient geometries were compared with TG-43 calculated doses to illustrate the limitations of TG-43 dosimetry for intracavitary APBI. TG-43 dose calculations overestimate the dose for regions approaching the lung and breast surface and underestimate the dose for regions in and beyond less-attenuating media such as lung tissue, and for lower energies, breast tissue as well.

  12. Cell inactivation, repair and mutation induction in bacteria after heavy ion exposure: Results from experiments at accelerators and in space

    NASA Astrophysics Data System (ADS)

    Horneck, G.; Schäfer, M.; Baltschukat, K.; Weisbrod, U.; Micke, U.; Facius, R.; Bücker, H.

    To understand the mechanisms of accelerated heavy ions on biological matter, the responses of spores of B. subtilis to this structured high LET radiation was investigated applying two different approaches. 1) By the use of the Biostack concept, the inactivation probability as a function of radial distance to single particles' trajectory (i.e. impact parameter) was determined in space experiments as well as at accelerators using low fluences of heavy ions. It was found that spores can survive even a central hit and that the effective range of inactivation extends far beyond impact parameters where inactivation by ?-ray dose would be effective. Concerning the space exeriment, the inactivation cross section exceeds those from comparable accelerator experiments by roughly a factor of 20. 2) From fluence effect curves, cross sections for inactivation and mutation induction, and the efficiency of repair processes were determined. They are influenced by the ions characteristics in a complex manner. According to dependence on LET, at least 3 LET ranges can be differentiated: A low LET range (app. < 200 keV/?m), where cross sections for inactivation and mutation induction follow a common curve for different ions and where repair processes are effective; an intermediate LET range of the so-called saturation cross section with negligible mutagenic and repair efficiency; and a high LET range (> 1000 keV/?m) where the biological endpoints are majorly dependent on atomic mass and energy of the ion under consideration.

  13. Replacing effective spectral radiance by temperature in occupational exposure limits to protect against retinal thermal injury from light and near IR radiation.

    PubMed

    Madjidi, Faramarz; Behroozy, Ali

    2014-01-01

    Exposure to visible light and near infrared (NIR) radiation in the wavelength region of 380 to 1400 nm may cause thermal retinal injury. In this analysis, the effective spectral radiance of a hot source is replaced by its temperature in the exposure limit values in the region of 380-1400 nm. This article describes the development and implementation of a computer code to predict those temperatures, corresponding to the exposure limits proposed by the American Conference of Governmental Industrial Hygienists (ACGIH). Viewing duration and apparent diameter of the source were inputs for the computer code. At the first stage, an infinite series was created for calculation of spectral radiance by integration with Planck's law. At the second stage for calculation of effective spectral radiance, the initial terms of this infinite series were selected and integration was performed by multiplying these terms by a weighting factor R(?) in the wavelength region 380-1400 nm. At the third stage, using a computer code, the source temperature that can emit the same effective spectral radiance was found. As a result, based only on measuring the source temperature and accounting for the exposure time and the apparent diameter of the source, it is possible to decide whether the exposure to visible and NIR in any 8-hr workday is permissible. The substitution of source temperature for effective spectral radiance provides a convenient way to evaluate exposure to visible light and NIR. PMID:25175283

  14. Asymmetric otolith function and increased susceptibility to motion sickness during exposure to variations in gravitoinertial acceleration level

    NASA Technical Reports Server (NTRS)

    Lackner, James R.; Graybiel, Ashton; Johnson, Walter H.; Money, Kenneth E.

    1987-01-01

    Von Baumgarten and coworkers (1979, 1981) have suggested that asymmetries in otolith function between the left and right labyrinths may result from differences in otoconial mass and could play a role in space motion sickness. Such asymmetries would be centrally compensated for under terrestrial conditions, but on exposure to weightlessness the persisting central compensation would produce a central imbalance that could lead to motion sickness. In this work ocular counterrolling was used as a way of measuring the relative 'efficiency' of the left and right otoliths; the ocular counterrolling scores of individuals were compared with their susceptibility to motion sickness during passive exposure to variations in Gz in parabolic flight maneuvers. The experimental findings indicate that large asymmetries in counterrolling for leftward and rightward body tilts are associated with greater susceptibility to motion sickness in parabolic flight.

  15. An Evaluation of Compliance with Occupational Exposure Limits for Crystalline Silica (Quartz) in Ten Georgia Granite Sheds

    Microsoft Academic Search

    Arthur R. Wickman; Paul J. Middendorf

    2002-01-01

    Since the 1920s, industrial hygiene studies have documented granite shed workers' exposures to crystalline silica, and the data from these studies have contributed to a better understanding of the relationship between silica exposures and adverse health effects, such as silicosis. The majority of these studies were conducted in the Barre, Vermont, granite sheds. However, a second major granite processing region

  16. Minimum exposure limits and measured relationships between the vitamin D, erythema and international commission on non-ionizing radiation protection solar ultraviolet.

    PubMed

    Downs, Nathan; Parisi, Alfio; Butler, Harry; Turner, Joanna; Wainwright, Lisa

    2015-01-01

    The International Commission on Non-Ionizing Radiation Protection (ICNIRP) has established guidelines for exposure to ultraviolet radiation in outdoor occupational settings. Spectrally weighted ICNIRP ultraviolet exposures received by the skin or eye in an 8 h period are limited to 30 J m(-2). In this study, the time required to reach the ICNIRP exposure limit was measured daily in 10 min intervals upon a horizontal plane at a subtropical Australian latitude over a full year and compared with the effective Vitamin D dose received to one-quarter of the available skin surface area for all six Fitzpatrick skin types. The comparison of measured solar ultraviolet exposures for the full range of sky conditions in the 2009 measurement period, including a major September continental dust event, show a clear relationship between the weighted ICNIRP and the effective vitamin D dose. Our results show that the horizontal plane ICNIRP ultraviolet exposure may be used under these conditions to provide minimum guidelines for the healthy moderation of vitamin D, scalable to each of the six Fitzpatrick skin types. PMID:25407011

  17. Language-Dependent Pitch Encoding Advantage in the Brainstem Is Not Limited to Acceleration Rates that Occur in Natural Speech

    ERIC Educational Resources Information Center

    Krishnan, Ananthanarayan; Gandour, Jackson T.; Smalt, Christopher J.; Bidelman, Gavin M.

    2010-01-01

    Experience-dependent enhancement of neural encoding of pitch in the auditory brainstem has been observed for only specific portions of native pitch contours exhibiting high rates of pitch acceleration, irrespective of speech or nonspeech contexts. This experiment allows us to determine whether this language-dependent advantage transfers to…

  18. Degradation of ZnO-based window layers for thin-film CIGS by accelerated stress exposures

    NASA Astrophysics Data System (ADS)

    Pern, F. J.; Noufi, R.; To, B.; DeHart, C.; Li, X.; Glick, S. H.

    2008-08-01

    The reliability of ZnO-based window layer for CuInGaSe2 (CIGS) solar cells was investigated. Samples of RF magnetron-sputtered, single-layer intrinsic and Al-doped ZnO and their combined bilayer on glass substrates were exposed in a weatherometer (WOM) and damp heat (DH) conditions with or without acetic acid vapor. Some preliminary samples of single-layer Al-doped Zn1-xMgxO (ZMO) alloy, a potential replacement for Al:ZnO with a wider bandgap, were also evaluated in the DH. The Al-doped ZnO and ZMO films showed irreversible loss in the conducting properties, free carrier mobility, and characteristic absorption band feature after <500-h DH exposure, with the originally clear transparent films turned into white hazy insulating films and the degradation rate follows the trend of (DH + acetic acid) > DH > WOM. The degradation rate was also reduced by higher film thickness, higher deposition substrate temperature, and dry-out intervals. The results of X-ray diffraction analysis indicate that the ZnO-based films underwent structural degeneration by losing their highly (002) preferential orientation with possible transformation from hexagonal into cubic and formation of Zn(OH)2. Periodic optical micro-imaging observations suggested a temporal process that involves initial hydrolysis of the oxides at sporadic weak spots, swelling and popping of the hydrolyzed spots due to volume increase, segregation of hydrolyzed regions causing discontinuity of electrical path, hydrolysis of the oxide-glass interface, and finally, formation of insulating oxides/hydroxides with visible delamination over larger areas.

  19. Degradation of ZnO-Based Window Layers for Thin-Film CIGS by Accelerated Stress Exposures

    SciTech Connect

    Pern, F. J.; Noufi, R.; To, B.; DeHart, C.; Li, X.; Glick, S. H.

    2008-01-01

    The reliability of ZnO-based window layer for CuInGaSe{sub 2} (CIGS) solar cells was investigated. Samples of RF magnetron-sputtered, single-layer intrinsic and Al-doped ZnO and their combined bilayer on glass substrates were exposed in a weatherometer (WOM) and damp heat (DH) conditions with or without acetic acid vapor. Some preliminary samples of single-layer Al-doped Zn{sub 1-x}Mg{sub x}O (ZMO) alloy, a potential replacement for Al:ZnO with a wider bandgap, were also evaluated in the DH. The Al-doped ZnO and ZMO films showed irreversible loss in the conducting properties, free carrier mobility, and characteristic absorption band feature after <500-h DH exposure, with the originally clear transparent films turned into white hazy insulating films and the degradation rate follows the trend of (DH + acetic acid) > DH > WOM. The degradation rate was also reduced by higher film thickness, higher deposition substrate temperature, and dry-out intervals. The results of X-ray diffraction analysis indicate that the ZnO-based films underwent structural degeneration by losing their highly (002) preferential orientation with possible transformation from hexagonal into cubic and formation of Zn(OH){sub 2}. Periodic optical micro-imaging observations suggested a temporal process that involves initial hydrolysis of the oxides at sporadic weak spots, swelling and popping of the hydrolyzed spots due to volume increase, segregation of hydrolyzed regions causing discontinuity of electrical path, hydrolysis of the oxide-glass interface, and finally, formation of insulating oxides/hydroxides with visible delamination over larger areas.

  20. Work to save dose: contrasting effective dose rates from radon exposure in workplaces and residences against the backdrop of public and occupational limits

    SciTech Connect

    Whicker, Jeffrey J [Los Alamos National Laboratory; Mcnaughton, Michael W [Los Alamos National Laboratory

    2009-01-01

    Office workers are exposed to radon while at work and at home. Though there has been a multitude of studies reporting the measurements of radon concentrations and potential lung and effective doses associated with radon and progeny exposure in homes, similar studies on the concentrations and subsequent effective dose rates in the non-mine workplaces are lacking. Additionally, there are few, if any, comparative analyses of radon exposures at more 'typical' workplace with residential exposures within the same county. The purposes of this study were to measure radon concentrations in office and residential spaces in the same county and explore the radiation dose implications. Sixty-five track-etch detectors were deployed in office spaces and 47 were deployed in residences, all within Los Alamos County, New Mexico, USA. The sampling periods for these measurements were generally about three months. The measured concentrations were used to calculate and compare effective dose rates resulting from exposure while at work and at home. Results showed that full-time office workers receive on average about 8 times greater exposure at home than while in the office (2.3 mSv yr-! versus 0.3 mSv yr-!). The estimated effective dose rate for a more homebound person was about 3 mSv yr-!. Estimating effective doses from background radon exposure in the same county as Los Alamos National Laboratory, with thousands of'radiological workers,' highlights interesting contrasts in radiation protection standards that span public and occupational settings. For example, the effective dose rate from background radon exposure in unregulated office spaces ranged up to 1.1 mSv yr-!, which is similar to the 1 mSv yr-! threshold for regulation ofa 'radiological worker,' as defined in the Department of Energy regulations for occupational exposure. Additionally, the estimated average effective dose total of> 3 mSv yf! from radon background exposure in homes stands in contrast to the 0.1 mSv yr-! air pathway effective public dose limit regulated by the Environmental Protection Agency for radioactive air emissions.

  1. Daily Exposure to Di(2-ethylhexyl) Phthalate Alters Estrous Cyclicity and Accelerates Primordial Follicle Recruitment Potentially Via Dysregulation of the Phosphatidylinositol 3-Kinase Signaling Pathway in Adult Mice1

    PubMed Central

    Hannon, Patrick R.; Peretz, Jackye; Flaws, Jodi A.

    2014-01-01

    ABSTRACT Humans are exposed daily to di(2-ethylhexyl) phthalate (DEHP), a plasticizer found in many consumer, medical, and building products containing polyvinyl chloride. Large doses of DEHP disrupt normal ovarian function; however, the effects of DEHP at environmentally relevant levels, the effects of DEHP on folliculogenesis, and the mechanisms by which DEHP disrupts ovarian function are unclear. The present study tested the hypothesis that relatively low levels of DEHP disrupt estrous cyclicity as well as accelerate primordial follicle recruitment by dysregulating phosphatidylinositol 3-kinase (PI3K) signaling. Adult CD-1 mice were orally dosed with DEHP (20 ?g/kg/day–750 mg/kg/day) daily for 10 and 30 days. Following dosing, the effects on estrous cyclicity were examined, and follicle numbers were histologically quantified. Further, the ovarian mRNA and protein levels of PI3K signaling factors that are associated with early folliculogenesis were quantified. The data indicate that 10- and 30-day exposure to DEHP prolonged the duration of estrus and accelerated primordial follicle recruitment. Specifically, DEHP exposure decreased the percentage of primordial follicles and increased the percentage of primary follicles counted following 10-day exposure and increased the percentage of primary follicles counted following 30-day exposure. DEHP exposure, at doses that accelerate folliculogenesis, increased the levels of 3-phosphoinositide-dependent protein kinase-1, mammalian target of rapamycin complex 1, and protein kinase B and decreased the levels of phosphatase and tensin homolog, potentially driving PI3K signaling. Collectively, relatively low levels of DEHP disrupt estrous cyclicity and accelerate primordial follicle recruitment potentially via a mechanism involving dysregulation of PI3K signaling. PMID:24804967

  2. Limits of NbTi and Nb3Sn, and Development of W&R Bi-2212 HighField Accelerator Magnets

    SciTech Connect

    Godeke, A.; Cheng, D.; Dietderich, D.R.; Ferracin, P.; Prestemon,S.O.; Sa bbi, G.; Scanlan, R.M.

    2006-09-01

    NbTi accelerator dipoles are limited to magneticfields (H)of about 10 T, due to an intrinsic upper critical field (Hc2) limitationof 14 T. To surpass this restriction, prototype Nb3Sn magnets are beingdeveloped which have reached 16 T. We show that Nb3Sn dipole technologyis practically limited to 17 to 18 T due to insufficient high fieldpinning, and intrinsically to 20 to 22 T due to Hc2 limitations.Therefore, to obtain magnetic fields approaching 20 T and higher, amaterial is required with a higher Hc2 and sufficient high field pinningcapacity. A realistic candidate for this purpose is Bi-2212, which isavailable in roundwires and sufficient lengths for the fabrication ofcoils based on Rutherford-type cables. We initiated a program to developthe required technology to construct accelerator magnets from'windand-react' (W&R) Bi-2212 coils. We outline the complicationsthat arise through the use of Bi-2212, describe the development paths toaddress these issues, and conclude with the design of W&R Bi-2212sub-scale magnets.

  3. Limits of NbTi and Nb3Sn, and Development of W&R Bi-2212 HighField Accelerator Magnets

    SciTech Connect

    Godeke, A.; Cheng, D.; Dietderich, D.R.; Ferracin, P.; Prestemon,S.O.; Sabbi, G.; Scanlan, R.M.

    2006-12-01

    NbTi accelerator dipoles are limited to magnetic fields (H)of about 10 T, due to an intrinsic upper critical field(Hc2) limitationof 14 T. To surpass this restriction, prototype Nb3Sn magnets are beingdeveloped which have reached 16 T. We show that Nb3Sn dipole technologyis practically limited to 17 to 18 T due to insufficient high fieldpinning, and intrinsically to 20 to 22 T due to Hc2 limitations.Therefore, to obtain magnetic fields approaching 20 T and higher, amaterial is required with a higher Hc2 and sufficient high field pinningcapacity. A realistic candidate for this purpose is Bi-2212, which isavailable in roundwires and sufficient lengths for the fabrication ofcoils based on Rutherford-type cables. We initiated a program to developthe required technology to construct accelerator magnets from'windand-react' (W&R) Bi-2212 coils. We outline the complicationsthat arise through the use of Bi-2212, describe the development paths toaddress these issues, and conclude with the design of W&R Bi-2212sub-scale magnets.

  4. A comparison of important international and national standards for limiting exposure to EMF including the scientific rationale.

    PubMed

    Roy, Colin R; Martin, Lindsay J

    2007-06-01

    A comparison of Eastern (from Russia, Hungary, Bulgaria, Poland, and the Czech Republic) and Western (represented by the International Commission on Non-Ionizing Radiation Protection guidelines and the Institute of Electrical and Electronic Engineers standards) radiofrequency standards reveals key differences. The Eastern approach is to protect against non-thermal effects caused by chronic exposure to low level exposure, and the occupational basic restriction is power load (the product of intensity and exposure duration). In contrast, the Western approach is to protect against established acute biological effects that could signal an adverse health effect, and the principal basic restriction is the specific absorption rate to protect against thermal effects. All of the standards are science-based, but a fundamental difference arises from a lack of agreement on the composition of the reference scientific database and of which adverse effect needs to be protected against. However, differences also exist between the ICNIRP and IEEE standards. An additional complication arises when standards are derived or modified using a precautionary approach. For ELF the differences between ICNIRP and IEEE are more fundamental; namely, differences in the basic restriction used (induced current; in-situ electric field) and the location of breakpoints in the strength-frequency curves result in large differences. In 2006, ICNIRP will initiate the review of their ELF and radiofrequency guidelines, and this will provide an opportunity to address differences in standards and the move towards harmonization of EMF standards and guidelines. PMID:17495666

  5. Sub-diffraction-limited multilayer coatings for the 0.3 numerical aperture micro-exposure tool for extreme ultraviolet lithography.

    PubMed

    Soufli, Regina; Hudyma, Russell M; Spiller, Eberhard; Gullikson, Eric M; Schmidt, Mark A; Robinson, Jeff C; Baker, Sherry L; Walton, Christopher C; Taylor, John S

    2007-06-20

    Multilayer coating results are discussed for the primary and secondary mirrors of the micro-exposure tool (MET): a 0.30 NA lithographic imaging system with a 200 microm x 600 microm field of view at the wafer plane, operating in the extreme ultraviolet (EUV) region at an illumination wavelength around 13.4 nm. Mo/Si multilayers were deposited by DC-magnetron sputtering on large-area, curved MET camera substrates. A velocity modulation technique was implemented to consistently achieve multilayer thickness profiles with added figure errors below 0.1 nm rms demonstrating sub-diffraction-limited performance, as defined by the classical diffraction limit of Rayleigh (0.25 waves peak to valley) or Marechal (0.07 waves rms). This work is an experimental demonstration of sub-diffraction- limited multilayer coatings for high-NA EUV imaging systems, which resulted in the highest resolution microfield EUV images to date. PMID:17538670

  6. Gaussian Convergence for Stochastic Acceleration of [InlineEquation not available: see fulltext.] Particles in the Dense Spectrum Limit

    NASA Astrophysics Data System (ADS)

    Elskens, Yves

    2012-08-01

    The velocity of a passive particle in a one-dimensional wave field is shown to converge in law to a Wiener process, in the limit of a dense wave spectrum with independent complex amplitudes, where the random phases distribution is invariant modulo ?/2 and the power spectrum expectation is uniform. The proof provides a full probabilistic foundation to the quasilinear approximation in this limit. The result extends to an arbitrary number of particles, founding the use of the ensemble picture for their behaviour in a single realization of the stochastic wave field.

  7. Acceleration without Horizons

    E-print Network

    Alaric Doria; Gerardo Munoz

    2015-02-18

    We derive the metric of an accelerating observer moving with non-constant proper acceleration in flat spacetime. With the exception of a limiting case representing a Rindler observer, there are no horizons. In our solution, observers can accelerate to any desired terminal speed $v_{\\infty} accelerating observer is completely determined by the distance of closest approach and terminal velocity or, equivalently, by an acceleration parameter and terminal velocity.

  8. IN VIVO COMPARISON OF EPITHELIAL RESPONSES FOR S-8 VERSUS JP-8 JET FUELS BELOW PERMISSIBLE EXPOSURE LIMIT

    PubMed Central

    Wong, Simon S.; Vargas, Jason; Thomas, Alana; Fastje, Cindy; McLaughlin, Michael; Camponovo, Ryan; Lantz, R. Clark; Heys, Jeffrey; Witten, Mark L.

    2010-01-01

    This study was designed to characterize and compare the pulmonary effects in distal lung from a low-level exposure to jet propellant-8 fuel (JP-8) and a new synthetic-8 fuel (S-8). It is hypothesized that both fuels have different airway epithelial deposition and responses. Consequently, male C57BL/6 mice were nose-only exposed to S-8 and JP-8 at average concentrations of 53 mg/m3 for 1 hour/day for 7 days. A pulmonary function test performed 24 hr after the final exposure indicated that there was a significant increase in expiratory lung resistance in the S-8 mice, whereas JP-8 mice had significant increases in both inspiratory and expiratory lung resistance compared to control values. Neither significant S-8 nor JP-8 respiratory permeability changes were observed compared to controls, suggesting no loss of epithelial barrier integrity. Morphological examination and morphometric analysis of airway tissue demonstrated that both fuels showed different patterns of targeted epithelial cells: bronchioles in S-8 and alveoli/terminal bronchioles in JP-8. Collectively, our data suggest that both fuels may have partially different deposition patterns, which may possibly contribute to specific different adverse effects in lung ventilatory function. PMID:18930109

  9. The LDCE Particle Impact Experiment as flown on STS-46. [limited duration space environment candidate materials exposure (LDCE)

    NASA Technical Reports Server (NTRS)

    Maag, Carl R.; Tanner, William G.; Borg, Janet; Bibring, Jean-Pierre; Alexander, W. Merle; Maag, Andrew J.

    1992-01-01

    Many materials and techniques have been developed by the authors to sample the flux of particles in Low Earth Orbit (LEO). Though regular in-site sampling of the flux in LEO the materials and techniques have produced data which compliment the data now being amassed by the Long Duration Exposure Facility (LDEF) research activities. Orbital debris models have not been able to describe the flux of particles with d sub p less than or = 0.05 cm, because of the lack of data. Even though LDEF will provide a much needed baseline flux measurement, the continuous monitoring of micron and sub-micron size particles must be carried out. A flight experiment was conducted on the Space Shuttle as part of the LDCE payload to develop an understanding of the Spatial Density (concentration) as a function of size (mass) for particle sizes 1 x 10(exp 6) cm and larger. In addition to the enumeration of particle impacts, it is the intent of the experiment that hypervelocity particles be captured and returned intact. Measurements will be performed post flight to determine the flux density, diameters, and subsequent effects on various optical, thermal control and structural materials. In addition to these principal measurements, the Particle Impact Experiment (PIE) also provides a structure and sample holders for the exposure of passive material samples to the space environment, e.g., thermal cycling, and atomic oxygen, etc. The experiment will measure the optical property changes of mirrors and will provide the fluence of the ambient atomic oxygen environment to other payload experimenters. In order to augment the amount of material returned in a form which can be analyzed, the survivability of the experiment as well as the captured particles will be assessed. Using Sandia National Laboratory's hydrodynamic computer code CTH, hypervelocity impacts on the materials which comprise the experiments have been investigated and the progress of these studies are reported.

  10. Acceleration-Induced Nonlocality

    E-print Network

    Bahram Mashhoon

    2003-01-17

    The standard relativistic theory of accelerated reference frames in Minkowski spacetime is described. The measurements of accelerated observers are considered and the limitations of the standard theory, based on the hypothesis of locality, are pointed out. The physical principles of the nonlocal theory of accelerated observers are presented. The implications of the nonlocal theory are briefly discussed.

  11. Exposure–response relationships for the ACGIH threshold limit value for hand-activity level: results from a pooled data study of carpal tunnel syndrome

    PubMed Central

    Kapellusch, Jay M; Gerr, Frederic E; Malloy, Elizabeth J; Garg, Arun; Harris-Adamson, Carisa; Bao, Stephen S; Burt, Susan E; Dale, Ann Marie; Eisen, Ellen A; Evanoff, Bradley A; Hegmann, Kurt T; Silverstein, Barbara A; Theise, Matthew S; Rempel, David M

    2014-01-01

    Objective This paper aimed to quantify exposure–response relationships between the American Conference of Governmental Industrial Hygienists’ (ACGIH) threshold limit value (TLV) for hand-activity level (HAL) and incidence of carpal tunnel syndrome (CTS). Methods Manufacturing and service workers previously studied by six research institutions had their data combined and re-analyzed. CTS cases were defined by symptoms and abnormal nerve conduction. Hazard ratios (HR) were calculated using proportional hazards regression after adjusting for age, gender, body mass index, and CTS predisposing conditions. Results The longitudinal study comprised 2751 incident-eligible workers, followed prospectively for up to 6.4 years and contributing 6243 person-years of data. Associations were found between CTS and TLV for HAL both as a continuous variable [HR 1.32 per unit, 95% confidence interval (95% CI) 1.11–1.57] and when categorized using the ACGIH action limit (AL) and TLV. Those between the AL and TLV and above the TLV had HR of 1.7 (95% CI 1.2–2.5) and 1.5 (95% CI 1.0–2.1), respectively. As independent variables (in the same adjusted model) the HR for peak force (PF) and HAL were 1.14 per unit (95% CI 1.05–1.25), and 1.04 per unit (95% CI 0.93–1.15), respectively. Conclusion Those with exposures above the AL were at increased risk of CTS, but there was no further increase in risk for workers above the TLV. This suggests that the current AL may not be sufficiently protective of workers. Combinations of PF and HAL are useful for predicting risk of CTS. PMID:25266844

  12. Long-term cadmium exposure accelerates oxidant injury: significance of bound/free water states during long-term metal stress.

    PubMed

    Czuba, M; Kraszewski, A

    1994-12-01

    Lepidium sativum (cress) and Lycopersicon esculentum (tomato) plants were grown in peatlite in controlled environments with or without long-term (4 weeks) cadmium stress (Cd) (100 micrograms/ml every fourth day) and with a single exposure (6 hr at 35 parts per hundred million (pphm)) or no exposure to the oxidant ozone (O3). Cress plants which received Cd wilted faster during O3 exposure and became a gray-green color by the end of a 6-hr O3 exposure. Those receiving O3 alone also wilted but were normal in color during wilting. Leaf water content (percentage) significantly declined in both O3 + Cd- and O3-treated plants. However, leaves after Cd + O3 exposure were severely dessicated and necrotic, whereas O3-treated plants recovered their water content completely but had some injury. Increased stomatal aperture in cress but not tomato before O3 exposure and significantly lower water content at 1 and 24 hr after the end of O3 exposure were associated with the higher Cd content of leaves before and subsequent to O3 exposure. These factors contributed to a greater injury and cell death observed in the leaves of combined cadmium-oxidant stress. Dielectric properties of Thlaspi arvense (field penny cress) leaves grown at continuous exposure to Cd and/or nickel (Ni) indicated that there were measurable differences between metal-containing vs control leaves with regard to bound/unbound water status. This indicated that there was more free water under metal stress, and that the bound water content significantly declined in the leaves of these plants. PMID:7534690

  13. NIOSH comments to DOL on the Occupational Safety and Health Administration's proposed rule; limited reopening of the rulemaking record on occupational exposure to formaldehyde by R. A. Lemen, February 9, 1987

    SciTech Connect

    Not Available

    1987-02-09

    The testimony concerns the position of NIOSH regarding occupational exposures to formaldehyde (50000). The testimony contains a letter sent from NIOSH regarding the NCI epidemiologic and industrial hygiene studies of workers exposed to formaldehyde. While statistically significant findings were not observed in some of the studies, both the report of the occupational epidemiologic study and the companion residential epidemiologic study indicate that the analyses demonstrated elevated risk estimates for cancer sites of the upper respiratory system associated with exposure potential to formaldehyde. This was strongest for individuals with long residence times in mobile homes. NIOSH indicates additional research should be conducted to assess the cancer risk associated with a combined exposure to formaldehyde on particulates. NIOSH is not aware of data that describe a safe exposure concentration to a carcinogen and thereby urges that the exposure limits to formaldehyde be for as low a level as possible.

  14. Induction of genomic instability in TK6 human lymphoblasts exposed to 137Cs gamma radiation: comparison to the induction by exposure to accelerated 56Fe particles

    NASA Technical Reports Server (NTRS)

    Evans, Helen H.; Horng, Min-Fen; Ricanati, Marlene; Diaz-Insua, M.; Jordan, Robert; Schwartz, Jeffrey L.

    2003-01-01

    The induction of genomic instability in TK6 human lymphoblasts by exposure to (137)Cs gamma radiation was investigated by measuring the frequency and characteristics of unstable clones isolated approximately 36 generations after exposure. Clones surviving irradiation and control clones were analyzed for 17 characteristics including chromosomal aberrations, growth defects, alterations in response to a second irradiation, and mutant frequencies at the thymidine kinase and Na(+)/K(+) ATPase loci. Putative unstable clones were defined as those that exhibited a significant alteration in one or more characteristics compared to the controls. The frequency and characteristics of the unstable clones were compared in clones exposed to (137)Cs gamma rays or (56)Fe particles. The majority of the unstable clones isolated after exposure to either gamma rays or (56)Fe particles exhibited chromosomal instability. Alterations in growth characteristics, radiation response and mutant frequencies occurred much less often than cytogenetic alterations in these unstable clones. The frequency and complexity of the unstable clones were greater after exposure to (56)Fe particles than to gamma rays. Unstable clones that survived 36 generations after exposure to gamma rays exhibited increases in the incidence of dicentric chromosomes but not of chromatid breaks, whereas unstable clones that survived 36 generations after exposure to (56)Fe particles exhibited increases in both chromatid and chromosome aberrations.

  15. Laser acceleration with open waveguides

    SciTech Connect

    Xie, Ming

    1999-03-01

    A unified framework based on solid-state open waveguides is developed to overcome all three major limitations on acceleration distance and hence on the feasibility of two classes of laser acceleration. The three limitations are due to laser diffraction, acceleration phase slippage, and damage of waveguide structure by high power laser. The two classes of laser acceleration are direct-field acceleration and ponderomotive-driven acceleration. Thus the solutions provided here encompass all mainstream approaches for laser acceleration, either in vacuum, gases or plasmas.

  16. Switched matrix accelerator

    SciTech Connect

    Whittum, David H.; Tantawi, Sami G.

    2001-01-01

    We describe a new concept for a microwave circuit functioning as a charged-particle accelerator at mm wavelengths, permitting an accelerating gradient higher than conventional passive circuits can withstand consistent with cyclic fatigue. The device provides acceleration for multiple bunches in parallel channels, and permits a short exposure time for the conducting surface of the accelerating cavities. Our analysis includes scalings based on a smooth transmission line model and a complementary treatment with a coupled-cavity simulation. We also provide an electromagnetic design for the accelerating structure, arriving at rough dimensions for a seven-cell accelerator matched to standard waveguide and suitable for bench tests at low power in air at 91.392 GHz. A critical element in the concept is a fast mm-wave switch suitable for operation at high power, and we present the considerations for implementation in an H-plane tee. We discuss the use of diamond as the photoconductor switch medium.

  17. Administration of Diethylnitrosamine in the Immediate Postnatal Period Coupled with Exposure to a Choline Deficient Diet Accelerates Hepatocarcinogenesis in the Rat

    Microsoft Academic Search

    Susan Hemmings; Judee Strickland

    2002-01-01

    The objectives of this study were to determine if the combination of: i. neonatal administration of diethylnitrosamine and ii. subsequent feeding of a choline deficient diet could accelerate hepatic premalignancy in the rat. The presence and size of premalignant nodules and the activity of the liver cancer enzyme marker g-glutamyltranspeptidase (gGT) were used as indicators of hepatic premalignancy. Three day

  18. Limited Awareness and Low Immediate Uptake of Pre-Exposure Prophylaxis among Men Who Have Sex with Men Using an Internet Social Networking Site

    PubMed Central

    Krakower, Douglas S.; Mimiaga, Matthew J.; Rosenberger, Joshua G.; Novak, David S.; Mitty, Jennifer A.; White, Jaclyn M.; Mayer, Kenneth H.

    2012-01-01

    Background In 2010, the iPrEx trial demonstrated that oral antiretroviral pre-exposure prophylaxis (PrEP) reduced the risk of HIV acquisition among high-risk men who have sex with men (MSM). The impact of iPrEx on PrEP knowledge and actual use among at-risk MSM is unknown. Online surveys were conducted to assess PrEP awareness, interest and experience among at-risk MSM before and after iPrEx, and to determine demographic and behavioral factors associated with these measures. Methods and Findings Cross-sectional, national, internet-based surveys were administered to U.S. based members of the most popular American MSM social networking site 2 months before (n?=?398) and 1 month after (n?=?4 558) publication of iPrEx results. Comparisons were made between these samples with regards to PrEP knowledge, interest, and experience. Data were collected on demographics, sexual risk, and experience with post-exposure prophylaxis (PEP). Regression analyses were performed to identify factors associated with PrEP awareness, interest, and experience post-iPrEx. Most participants were white, educated, and indicated high-risk sexual behaviors. Awareness of PrEP was limited pre- and post-iPrEx (13% vs. 19%), whereas interest levels after being provided with a description of PrEP remained high (76% vs. 79%). PrEP use remained uncommon (0.7% vs. 0.9%). PrEP use was associated with PEP awareness (OR 7.46; CI 1.52–36.6) and PEP experience (OR 34.2; CI 13.3–88.4). PrEP interest was associated with older age (OR 1.01; CI 1.00–1.02), unprotected anal intercourse with ?1 male partner in the prior 3 months (OR 1.40; CI 1.10–1.77), and perceiving oneself at increased risk for HIV acquisition (OR 1.20; CI 1.13–1.27). Conclusions Among MSM engaged in online networking, awareness of PrEP was limited 1 month after the iPrEx data were released. Utilization was low, although some MSM who reported high-risk behaviors were interested in using PrEP. Studies are needed to understand barriers to PrEP utilization by at-risk MSM. PMID:22470438

  19. The low-level radial velocity variability in Barnard's star (= GJ 699). Secular acceleration, indications for convective redshift, and planet mass limits

    NASA Astrophysics Data System (ADS)

    Kürster, M.; Endl, M.; Rouesnel, F.; Els, S.; Kaufer, A.; Brillant, S.; Hatzes, A. P.; Saar, S. H.; Cochran, W. D.

    2003-06-01

    We report results from 2 1/2 yr of high precision radial velocity (RV) monitoring of Barnard's star. The high RV measurement precision of the VLT-UT2+UVES of 2.65 m s-1 made the following findings possible. (1) The first detection of the change in the RV of a star caused by its space motion (RV secular acceleration). (2) An anti-correlation of the measured RV with the strength of the filling-in of the H_alpha line by emission. (3) Very stringent mass upper limits to planetary companions. Using only data from the first 2 years, we obtain a best-fit value for the RV secular acceleration of 5.15+/- 0.89 m s-1 yr-1. This agrees within 0.95sigma with the predicted value of 4.50 m s-1 yr-1 based on the Hipparcos proper motion and parallax combined with the known absolute radial velocity of the star. When the RV data of the last half-year are added the best-fit slope is strongly reduced to 2.97+/- 0.51 m s-1 yr-1 (3.0sigma away from the predicted value), clearly suggesting the presence of additional RV variability in the star. Part of it can be attributed to stellar activity as we demonstrate by correlating the residual RVs with an index that describes the filling-in of the H_alpha line by emission. A correlation coefficient of -0.50 indicates that the appearance of active regions causes a blueshift of photospheric absorption lines. Assuming that active regions basically inhibit convection we discuss the possibility that the fundamental (inactive) convection pattern in this M4V star produces a convective redshift which would indicate that the majority of the absorption lines relevant for our RV measurements is formed in a region of convective overshoot. This interpretation could possibly extend a trend indicated in the behaviour of earlier spectral types that exhibit convective blueshift, but with decreasing line asymmetries and blueshifts as one goes from G to K dwarfs. Based on this assumption, we estimate that the variation of the visible plage coverage is about 20%. We also determine upper limits to the projected mass msin i and to the true mass m of hypothetical planetary companions in circular orbits. For the separation range 0.017-0.98 AU we exclude any planet with msin i> 0.12 MJupiter and m> 0.86 MJupiter. Throughout the habitable zone around Barnard's star, i.e. 0.034-0.082 AU, we exclude planets with msin i> 7.5 MEarth and m> 3.1 MNeptune. Based on observations collected at the European Southern Observatory, Paranal, Chile (ESO programmes 65.L-0428, 66.C-0446, 267.C-5700, 68.C-0415, and 69.C-0722).

  20. The Use of a Vehicle Acceleration Exposure Limit Model and a Finite Element Crash Test Dummy Model to Evaluate the Risk of Injuries During Orion Crew Module Landings

    NASA Technical Reports Server (NTRS)

    Lawrence, Charles; Fasanella, Edwin L.; Tabiei, Ala; Brinkley, James W.; Shemwell, David M.

    2008-01-01

    A review of astronaut whole body impact tolerance is discussed for land or water landings of the next generation manned space capsule named Orion. LS-DYNA simulations of Orion capsule landings are performed to produce a low, moderate, and high probability of injury. The paper evaluates finite element (FE) seat and occupant simulations for assessing injury risk for the Orion crew and compares these simulations to whole body injury models commonly referred to as the Brinkley criteria. The FE seat and crash dummy models allow for varying the occupant restraint systems, cushion materials, side constraints, flailing of limbs, and detailed seat/occupant interactions to minimize landing injuries to the crew. The FE crash test dummies used in conjunction with the Brinkley criteria provides a useful set of tools for predicting potential crew injuries during vehicle landings.

  1. The Influence of an Air Exposure on the Secondary Electron Yield of Copper

    Microsoft Academic Search

    C Scheuerlein; Noël Hilleret

    1997-01-01

    Abstract The influence of different air exposure times on the secondary electron emission of clean copper surfaces as well as on technical copper surfaces has been studied in the context of the phenomenon of multipacting, which can limit the performance of superconducting radio-frequency (RF) cavities for particle acceleration. The copper samples were prepared by heat treatments and in situ sputter-etching

  2. Limited sampling strategies for tacrolimus exposure (AUC0-24) prediction after Prograf(®) and Advagraf(®) administration in children and adolescents with liver or kidney transplants.

    PubMed

    Almeida-Paulo, Gonzalo N; Lubomirov, Rubin; Alonso-Sanchez, Nazareth Laura; Espinosa-Román, Laura; Fernández Camblor, Carlota; Díaz, Carmen; Muñoz Bartola, Gema; Carcas-Sansuán, Antonio J

    2014-09-01

    To develop limited sampling strategies (LSSs) to predict total tacrolimus exposure (AUC0-24 ) after the administration of Advagraf(®) and Prograf(®) (Astellas Pharma S.A, Madrid, Spain) to pediatric patients with stable liver or kidney transplants. Forty-one pharmacokinetic profiles were obtained after Prograf(®) and Advagraf(®) administration. LSSs predicting AUC0-24 were developed by linear regression using three extraction time points. Selection of the most accurate LSS was made based on the r(2) , mean error, and mean absolute error. All selected LSSs had higher correlation with AUC0-24 than the correlation found between C0 and AUC0-24 . Best LSS for Prograf(®) in liver transplants was C0_1.5_4 (r(2)  = 0.939) and for kidney transplants C0_1_3 (r(2)  = 0.925). For Advagraf(®) , the best LSS in liver transplants was C0_1_2.5 (r(2)  = 0.938) and for kidney transplants was C0_0.5_4 (r(2)  = 0.931). Excluding transplant type variable, the best LSS for Prograf(®) is C0-1-3 (r(2)  = 0.920) and the best LSS for Advagraf(®) was C0_0.5_4 (r(2)  = 0.926). Considering transplant type irrespective of the formulation used, the best LSS for liver transplants was C0_2_3 (r(2)  = 0.913) and for kidney transplants was C0_0.5_4 (r(2)  = 0.898). Best LSS, considering all data together, was C0_1_4 (r(2)  = 0.898). We developed several LSSs to predict AUC0-24 for tacrolimus in children and adolescents with kidney or liver transplants after Prograf(®) and/or Advagraf(®) treatment. PMID:24861353

  3. Effects of limited exposure of rabbit chondrocyte cultures to parathyroid hormone and dibutyryl adenosine 3',5'-monophosphate on cartilage-characteristic proteoglycan synthesis

    SciTech Connect

    Kato, Y.; Koike, T.; Iwamoto, M.; Kinoshita, M.; Sato, K.; Hiraki, Y.; Suzuki, F.

    1988-05-01

    Treatment of rabbit chondrocyte cultures with PTH or (Bu)2cAMP for 30 h increased by 2- to 3-fold the incorporation of (35S)sulfate and 3H radioactivity with glucosamine as the precursor into large chondroitin sulfate proteoglycans characteristically found in cartilage matrix. However, PTH and (Bu)2cAMP did not increase either (35S)sulfate incorporation into small proteoglycans or the incorporation of 3H radioactivity into hyaluronic acid and other glycosaminoglycans. PTH and (Bu)2cAMP also increased the incorporation of (3H) serine into both proteoglycans and total protein. In all cultures described above, the stimulation of (3H)serine incorporation into proteoglycans exceeded that of (3H)serine incorporation into total protein. These data indicate that PTH and (Bu)2cAMP selectively stimulate cartilage proteoglycan synthesis while they increase total protein synthesis. Since cAMP seems to play a mediatory role in the action of PTH, we elected to examine the effects of a limited exposure of chondrocytes to PTH or (Bu)2cAMP on the synthesis of proteoglycans. Treatment with PTH or (Bu)2cAMP for only the initial 2-7 h did not increase the rates of incorporation of (35S)sulfate, the 3H radioactivity with glucosamine, and (3H)serine into proteoglycans, as measured at 30 h, despite the fact that this treatment brought about a rapid and transient rise in the cAMP level. Furthermore, the application of prostaglandin I2 at concentrations that increased cAMP levels in a similar fashion as did PTH did not affect (35S) sulfate incorporation into proteoglycans.

  4. Accelerators (3/5)

    ScienceCinema

    None

    2011-10-06

    1a) Introduction and motivation 1b) History and accelerator types 2) Transverse beam dynamics 3a) Longitudinal beam dynamics 3b) Figure of merit of a synchrotron/collider 3c) Beam control 4) Main limiting factors 5) Technical challenges Prerequisite knowledge: Previous knowledge of accelerators is not required.

  5. Accelerators (4/5)

    ScienceCinema

    None

    2011-10-06

    1a) Introduction and motivation 1b) History and accelerator types 2) Transverse beam dynamics 3a) Longitudinal beam dynamics 3b) Figure of merit of a synchrotron/collider 3c) Beam control 4) Main limiting factors 5) Technical challenges Prerequisite knowledge: Previous knowledge of accelerators is not required.

  6. AN OVERVIEW OF THE ADVANTAGES AND LIMITATIONS OF PROBABILISTIC EXPOSURE AND RISK ASSESSMENT METHODS USED IN EVALUATING HEALTH IMPACTS OF ENVIRONMENTAL CHEMICALS

    EPA Science Inventory

    Human exposures to environmental pollutants widely vary depending on the emission patterns that result in microenvironmental pollutant concentrations, as well as behavioral factors that determine the extent of an individual's contact with these pollutants. Each component of the s...

  7. The role of reported tobacco-specific media exposure on adult attitudes towards proposed policies to limit the portrayal of smoking in movies

    PubMed Central

    Blake, Kelly D; Viswanath, K; Blendon, Robert J; Vallone, Donna

    2011-01-01

    Objective To assess the relative, independent contribution of reported tobacco-specific media exposure (pro-tobacco advertising, anti-tobacco advertising, and news coverage of tobacco issues) to US adults’ support for policy efforts that aim to regulate the portrayal of smoking in movies. Methods Using the American Legacy Foundation’s 2003 American Smoking and Health Survey (ASHES-2), multivariable logistic regression was used to model the predicted probability that US adults support movie-specific tobacco control policies, by reported exposure to tobacco-specific media messages, controlling for smoking status, education, income, race/ethnicity, age, sex, knowledge of the negative effects of tobacco and state. Results Across most outcome variables under study, findings reveal that reported exposure to tobacco-specific media messages is associated with adult attitudes towards movie-specific policy measures. Most exposure to tobacco information in the media (with the exception of pro-tobacco advertising on the internet) contributes independently to the prediction of adult support for movie-specific policies. The direction of effect follows an expected pattern, with reported exposure to anti-tobacco advertising and news coverage of tobacco predicting supportive attitudes towards movie policies, and reported exposure to pro-tobacco advertising lessening support for some movie policies, though the medium of delivery makes a difference. Conclusion Media campaigns to prevent tobacco use and exposure to secondhand smoke have had value beyond the intended impact of single-issue campaigns; exposure to anti-tobacco campaigns and public dialogue about the dangers of tobacco seem also to be associated with shaping perceptions of the social world related to norms about tobacco, and ideas about regulating the portrayal of smoking in movies. PMID:20008152

  8. Prenatal exposure to escitalopram and/or stress in rats produces limited effects on endocrine, behavioral, or gene expression measures in adult male rats

    PubMed Central

    Bourke, Chase H.; Stowe, Zachary N.; Neigh, Gretchen N.; Olson, Darin E.; Owens, Michael J.

    2013-01-01

    Stress and/or antidepressants during pregnancy have been implicated in a wide range of long-term effects in the offspring. We investigated the long-term effects of prenatal stress and/or clinically relevant antidepressant exposure on male adult offspring in a model of the pharmacotherapy of maternal depression. Female Sprague-Dawley rats were implanted with osmotic minipumps that delivered clinically relevant exposure to the antidepressant escitalopram throughout gestation. Subsequently, pregnant females were exposed on gestational days 10–20 to a chronic unpredictable mild stress paradigm. The male offspring were analyzed in adulthood. Baseline physiological measurements were largely unaltered by prenatal manipulations. Behavioral characterization of the male offspring, with or without pre-exposure to an acute stressor, did not reveal any group differences. Prenatal stress exposure resulted in a faster return towards baseline following the peak response to an acute restraint stressor, but not an airpuff startle stressor, in adulthood. Microarray analysis of the hippocampus and hypothalamus comparing all treatment groups revealed no significantly-altered transcripts. Real time PCR of the hippocampus confirmed that several transcripts in the CRFergic, serotonergic, and neural plasticity pathways were unaffected by prenatal exposures. This stress model of maternal depression and its treatment indicate that escitalopram use and/or stress during pregnancy produced no alterations in our measures of male adult behavior or the transcriptome, however prenatal stress exposure resulted in some evidence for increased glucocorticoid negative feedback following an acute restraint stress. Study design should be carefully considered before implications for human health are ascribed to prenatal exposure to stress or antidepressant medication. PMID:23906943

  9. Accelerated Testing of Epoxy-FRP Composites for Civil Infrastructure Applications: Property Changes and Mechanisms of Degradation

    Microsoft Academic Search

    Andrew Stewart; Elliot P. Douglas

    2012-01-01

    Accelerated testing of FRP systems is frequently performed due to the long service life of these materials used to repair damaged civil structures. This testing typically involves exposure to common environmental conditions seen in the field. However, the main limitation of these experiments is that the testing protocols typically do not consider a change in the failure mechanism as a

  10. Occupational exposure in MRI

    PubMed Central

    Mcrobbie, D W

    2012-01-01

    This article reviews occupational exposure in clinical MRI; it specifically considers units of exposure, basic physical interactions, health effects, guideline limits, dosimetry, results of exposure surveys, calculation of induced fields and the status of the European Physical Agents Directive. Electromagnetic field exposure in MRI from the static field B0, imaging gradients and radiofrequency transmission fields induces electric fields and currents in tissue, which are responsible for various acute sensory effects. The underlying theory and its application to the formulation of incident and induced field limits are presented. The recent International Commission on Non-Ionizing Radiation Protection (ICNIRP) Bundesministerium für Arbeit und Soziales and Institute of Electrical and Electronics Engineers limits for incident field exposure are interpreted in a manner applicable to MRI. Field measurements show that exposure from movement within the B0 fringe field can exceed ICNIRP reference levels within 0.5 m of the bore entrance. Rate of change of field dB/dt from the imaging gradients is unlikely to exceed the new limits, although incident field limits can be exceeded for radiofrequency (RF) exposure within 0.2–0.5 m of the bore entrance. Dosimetric surveys of routine clinical practice show that staff are exposed to peak values of 42±24% of B0, with time-averaged exposures of 5.2±2.8 mT for magnets in the range 0.6–4 T. Exposure to time-varying fields arising from movement within the B0 fringe resulted in peak dB/dt of approximately 2 T s?1. Modelling of induced electric fields from the imaging gradients shows that ICNIRP-induced field limits are unlikely to be exceeded in most situations; however, movement through the static field may still present a problem. The likely application of the limits is discussed with respect to the reformulation of the European Union (EU) directive and its possible implications for MRI. PMID:22457400

  11. Length measurement in accelerated systems

    E-print Network

    Bahram Mashhoon; Uwe Muench

    2002-06-27

    We investigate the limitations of length measurements by accelerated observers in Minkowski spacetime brought about via the hypothesis of locality, namely, the assumption that an accelerated observer at each instant is equivalent to an otherwise identical momentarily comoving inertial observer. We find that consistency can be achieved only in a rather limited neighborhood around the observer with linear dimensions that are negligibly small compared to the characteristic acceleration length of the observer.

  12. Collinear wake field acceleration

    SciTech Connect

    Bane, K.L.F.; Chen, P.; Wilson, P.B.

    1985-04-01

    In the Voss-Weiland scheme of wake field acceleration a high current, ring-shaped driving bunch is used to accelerate a low current beam following along on axis. In such a structure, the transformer ratio, i.e., the ratio of maximum voltage that can be gained by the on-axis beam and the voltage lost by the driving beam, can be large. In contrast, it has been observed that for an arrangement in which driving and driven bunches follow the same path, and where the current distribution of both bunches is gaussian, the transformer ratio is not normally greater than two. This paper explores some of the possibilities and limitations of a collinear acceleration scheme. In addition to its application to wake field acceleration in structures, this study is also of interest for the understanding of the plasma wake field accelerator. 11 refs., 4 figs.

  13. The role of reported tobacco-specific media exposure on adult attitudes towards proposed policies to limit the portrayal of smoking in movies

    Microsoft Academic Search

    Kelly D Blake; K. Viswanath; Robert J Blendon; Donna Vallone

    2010-01-01

    ObjectiveTo assess the relative, independent contribution of reported tobacco-specific media exposure (pro-tobacco advertising, anti-tobacco advertising, and news coverage of tobacco issues) to US adults' support for policy efforts that aim to regulate the portrayal of smoking in movies.MethodsUsing the American Legacy Foundation's 2003 American Smoking and Health Survey (ASHES-2), multivariable logistic regression was used to model the predicted probability that

  14. Fetal dose estimates and the ICRP abdominal dose limit for occupational exposure of pregnant staff to technetium-99m and iodine-131 patients

    Microsoft Academic Search

    P. J. Mountford; H. R. Steele

    1995-01-01

    The International Commission on Radiological Protection has recently recommended a supplementary dose limit of 2 mSv to the abdominal surface of a pregnant member of staff in order to provide protection to her fetus comparable to that in members of the public, whose annual limit is recommended to be 1 mSv. In order to determine whether this apparent attenuation factor

  15. Occupational exposure to crystalline silica and autoimmune disease.

    PubMed Central

    Parks, C G; Conrad, K; Cooper, G S

    1999-01-01

    Occupational exposure to silica dust has been examined as a possible risk factor with respect to several systemic autoimmune diseases, including scleroderma, rheumatoid arthritis, systemic lupus erythematosus, and some of the small vessel vasculitidies with renal involvement (e.g., Wegener granulomatosis). Crystalline silica, or quartz, is an abundant mineral found in sand, rock, and soil. High-level exposure to respirable silica dust can cause chronic inflammation and fibrosis in the lung and other organs. Studies of specific occupational groups with high-level silica exposure (e.g., miners) have shown increased rates of autoimmune diseases compared to the expected rates in the general population. However, some clinic- and population-based studies have not demonstrated an association between silica exposure and risk of autoimmune diseases. This lack of effect may be due to the limited statistical power of these studies to examine this association or because the lower- or moderate-level exposures that may be more common in the general population were not considered. Experimental studies demonstrate that silica can act as an adjuvant to nonspecifically enhance the immune response. This is one mechanism by which silica might be involved in the development of autoimmune diseases. Given that several different autoimmune diseases may be associated with silica dust exposure, silica dust may act to promote or accelerate disease development, requiring some other factor to break immune tolerance or initiate autoimmunity. The specific manifestation of this effect may depend on underlying differences in genetic susceptibility or other environmental exposures. PMID:10970168

  16. Accelerated rotation with orbital angular momentum modes

    NASA Astrophysics Data System (ADS)

    Schulze, Christian; Roux, Filippus S.; Dudley, Angela; Rop, Ronald; Duparré, Michael; Forbes, Andrew

    2015-04-01

    We introduce a class of light field that angularly accelerates during propagation. We show that the acceleration (deceleration) may be controlled by adjustment of a single parameter, and tuned continuously, down to no acceleration at all. As the angular acceleration takes place in a bounded space, the azimuthal degree of freedom, such fields accelerate periodically as they propagate. Notably, the amount of angular acceleration is not limited by paraxial considerations, may be tailored for large accelerations over arbitrarily long distances, and can be engineered independently of the beam's spatial extent. We discuss how such angularly accelerating light fields can maintain the conservation of angular momentum through an energy exchange mechanism across the field.

  17. Dermal exposure assessment techniques.

    PubMed

    Fenske, R A

    1993-12-01

    Exposure of the skin to chemical substances can contribute significantly to total dose in many workplace situations, and its relative importance will increase when airborne occupational exposure limits are reduced, unless steps to reduce skin exposure are undertaken simultaneously. Its assessment employs personal sampling techniques to measure skin loading rates, and combines these measurements with models of percutaneous absorption to estimate absorbed dose. Knowledge of dermal exposure pathways is in many cases fundamental to hazard evaluation and control. When the skin is the primary contributor to absorbed dose, dermal exposure measurements and biological monitoring play complementary roles in defining occupational exposures. Exposure normally occurs by one of three pathways: (i) immersion (direct contact with a liquid or solid chemical substance); (ii) deposition of aerosol or uptake of vapour through the skin; or (iii) surface contact (residue transfer from contaminated surfaces). Sampling methods fall into three categories: surrogate skin; chemical removal; and fluorescent tracers. Surface sampling represents a supplementary approach, providing an estimate of dermal exposure potential. Surrogate skin techniques involve placing a chemical collection medium on the skin. Whole-body garment samplers do not require assumptions relating to distribution, an inherent limitation of patch sampling. The validity of these techniques rests on the ability of the sampling medium to capture and retain chemicals in a manner similar to skin. Removal techniques include skin washing and wiping, but these measure only what can be removed from the skin, not exposure: laboratory removal efficiency studies are required for proper interpretation of data. Fluorescent tracer techniques exploit the visual properties of fluorescent compounds, and combined with video imaging make quantification of dermal exposure patterns possible, but the need to introduce a chemical substance (tracer) into production processes represents an important limitation of this approach. Surface sampling techniques provide a measure of workplace chemical contamination. Wipe sampling has been used extensively, but is susceptible to high variability. Surface sampling requires definition of dermal transfer coefficients for specific work activities. A preliminary dermal exposure sampling strategy which addresses such issues as sampling method, representativeness and sample duration is proposed. Despite the limitations of current assessment techniques, it appears feasible to consider developing dermal occupational exposure limits (DOELs) for selected workplaces and chemical agents. Initial development of DOELs would be most practical where dermal exposure is from surface contact primarily, and where the work closely follows a routine. Improvement in the techniques of dermal exposure assessment is an important goal for occupational hygiene research, and is likely to lead to better health for worker populations. PMID:8304685

  18. SN 1987A - The impact of greater than 50 MeV gamma-ray luminosity limits on theories of particle acceleration

    NASA Technical Reports Server (NTRS)

    Sood, R. K.; Waldron, L.; Rochester, G. K.; Sumner, T. J.; Frye, G.; Jenkins, T.; Staubert, R.; Kendziorra, E.; Ubertini, P.; Bazzano, A.

    1992-01-01

    Analysis of the data obtained from two flights of a balloonborne gamma-ray detector to observe SN 1987A was completed. The detector, which included a spark chamber to determine the arrival directions of the photons, was sensitive in the energy range 50-500 MeV. The 95 percent confidence upper limit to the flux on day 55 after the explosion has been established to be 1.1 x 10 exp -5 photons/sq cm/s and on day 407 to be 3.4 x 10 exp -5 photons/sq cm/s. These limits are compared with various theoretical predictions.

  19. High-dose vitamin D3 reduces deficiency caused by low UVB exposure and limits HIV-1 replication in urban Southern Africans.

    PubMed

    Coussens, Anna K; Naude, Celeste E; Goliath, Rene; Chaplin, George; Wilkinson, Robert J; Jablonski, Nina G

    2015-06-30

    Cape Town, South Africa, has a seasonal pattern of UVB radiation and a predominantly dark-skinned urban population who suffer high HIV-1 prevalence. This coexistent environmental and phenotypic scenario puts residents at risk for vitamin D deficiency, which may potentiate HIV-1 disease progression. We conducted a longitudinal study in two ethnically distinct groups of healthy young adults in Cape Town, supplemented with vitamin D3 in winter, to determine whether vitamin D status modifies the response to HIV-1 infection and to identify the major determinants of vitamin D status (UVB exposure, diet, pigmentation, and genetics). Vitamin D deficiency was observed in the majority of subjects in winter and in a proportion of individuals in summer, was highly correlated with UVB exposure, and was associated with greater HIV-1 replication in peripheral blood cells. High-dosage oral vitamin D3 supplementation attenuated HIV-1 replication, increased circulating leukocytes, and reversed winter-associated anemia. Vitamin D3 therefore presents as a low-cost supplementation to improve HIV-associated immunity. PMID:26080414

  20. High-dose vitamin D3 reduces deficiency caused by low UVB exposure and limits HIV-1 replication in urban Southern Africans

    PubMed Central

    Coussens, Anna K.; Naude, Celeste E.; Goliath, Rene; Chaplin, George; Wilkinson, Robert J.; Jablonski, Nina G.

    2015-01-01

    Cape Town, South Africa, has a seasonal pattern of UVB radiation and a predominantly dark-skinned urban population who suffer high HIV-1 prevalence. This coexistent environmental and phenotypic scenario puts residents at risk for vitamin D deficiency, which may potentiate HIV-1 disease progression. We conducted a longitudinal study in two ethnically distinct groups of healthy young adults in Cape Town, supplemented with vitamin D3 in winter, to determine whether vitamin D status modifies the response to HIV-1 infection and to identify the major determinants of vitamin D status (UVB exposure, diet, pigmentation, and genetics). Vitamin D deficiency was observed in the majority of subjects in winter and in a proportion of individuals in summer, was highly correlated with UVB exposure, and was associated with greater HIV-1 replication in peripheral blood cells. High-dosage oral vitamin D3 supplementation attenuated HIV-1 replication, increased circulating leukocytes, and reversed winter-associated anemia. Vitamin D3 therefore presents as a low-cost supplementation to improve HIV-associated immunity. PMID:26080414

  1. Radionuclide production for positron emission tomography: Choosing an appropriate accelerator

    NASA Astrophysics Data System (ADS)

    Votaw, John R.; Nickles, R. Jerome

    1989-04-01

    The appropriate accelerator for producing 18F, 15O, 13N and 11C depends upon the existing conditions at the intended installation site. The existence of limited resources (e.g. financial, space, etc.) require that the relationship between the accelerator beam energy ( E) and beam current ( I), the yield ( Y) and the external radiation burden be known for each of the reactions leading to the above end products. The interdependence of these parameters is calculated using published cross section data. Isoexposure curves I = D( E) trace the locus of points ( I, E) that cause the radiation exposure, outside a concrete shield of given thickness, to equal a set value. Similarly, isoyield curves I = Y( E) trace the production of the desired radionuclide. The appropriate accelerator must have operating parameters within the region of ( I, E) space bounded by the critical yield and exposure isocontours. The final choice among the candidates within this region is then governed by the particular constraints of an institution (e.g. technical support, manpower requirements, cost, etc.). Factors leading to the purchase of an accelerator at the University of Wisconsin-Madison are presented.

  2. Muon acceleration in cosmic-ray sources

    SciTech Connect

    Klein, Spencer R.; Mikkelsen, Rune E. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Becker Tjus, Julia [Fakultät für Physik and Astronomie, Theoretische Physik I, Ruhr-Universität Bochum, D-44780 Bochum (Germany)

    2013-12-20

    Many models of ultra-high energy cosmic-ray production involve acceleration in linear accelerators located in gamma-ray bursts, magnetars, or other sources. These transient sources have short lifetimes, which necessitate very high accelerating gradients, up to 10{sup 13} keV cm{sup –1}. At gradients above 1.6 keV cm{sup –1}, muons produced by hadronic interactions undergo significant acceleration before they decay. This muon acceleration hardens the neutrino energy spectrum and greatly increases the high-energy neutrino flux. Using the IceCube high-energy diffuse neutrino flux limits, we set two-dimensional limits on the source opacity and matter density, as a function of accelerating gradient. These limits put strong constraints on different models of particle acceleration, particularly those based on plasma wake-field acceleration, and limit models for sources like gamma-ray bursts and magnetars.

  3. Muon Acceleration in Cosmic-Ray Sources

    NASA Astrophysics Data System (ADS)

    Klein, Spencer R.; Mikkelsen, Rune E.; Becker Tjus, Julia

    2013-12-01

    Many models of ultra-high energy cosmic-ray production involve acceleration in linear accelerators located in gamma-ray bursts, magnetars, or other sources. These transient sources have short lifetimes, which necessitate very high accelerating gradients, up to 1013 keV cm-1. At gradients above 1.6 keV cm-1, muons produced by hadronic interactions undergo significant acceleration before they decay. This muon acceleration hardens the neutrino energy spectrum and greatly increases the high-energy neutrino flux. Using the IceCube high-energy diffuse neutrino flux limits, we set two-dimensional limits on the source opacity and matter density, as a function of accelerating gradient. These limits put strong constraints on different models of particle acceleration, particularly those based on plasma wake-field acceleration, and limit models for sources like gamma-ray bursts and magnetars.

  4. Exposure to MIV-150 from a High-Dose Intravaginal Ring Results in Limited Emergence of Drug Resistance Mutations in SHIV-RT Infected Rhesus Macaques

    PubMed Central

    Hsu, Mayla; Keele, Brandon F.; Aravantinou, Meropi; Krawczyk, Noa; Seidor, Samantha; Abraham, Ciby J.; Zhang, Shimin; Rodriguez, Aixa; Kizima, Larisa; Derby, Nina; Jean-Pierre, Ninochka; Mizenina, Olga; Gettie, Agegnehu; Grasperge, Brooke; Blanchard, James; Piatak, Michael J.; Lifson, Jeffrey D.; Fernández-Romero, José A.; Zydowsky, Thomas M.; Robbiani, Melissa

    2014-01-01

    When microbicides used for HIV prevention contain antiretroviral drugs, there is concern for the potential emergence of drug-resistant HIV following use in infected individuals who are either unaware of their HIV infection status or who are aware but still choose to use the microbicide. Resistant virus could ultimately impact their responsiveness to treatment and/or result in subsequent transmission of drug-resistant virus. We tested whether drug resistance mutations (DRMs) would emerge in macaques infected with simian immunodeficiency virus expressing HIV reverse transcriptase (SHIV-RT) after sustained exposure to the potent non-nucleoside reverse transcriptase inhibitor (NNRTI) MIV-150 delivered via an intravaginal ring (IVR). We first treated 4 SHIV-RT-infected animals with daily intramuscular injections of MIV-150 over two 21 day (d) intervals separated by a 7 d drug hiatus. In all 4 animals, NNRTI DRMs (single and combinations) were detected within 14 d and expanded in proportion and diversity with time. Knowing that we could detect in vivo emergence of NNRTI DRMs in response to MIV-150, we then tested whether a high-dose MIV-150 IVR (loaded with >10 times the amount being used in a combination microbicide IVR in development) would select for resistance in 6 infected animals, modeling use of this prevention method by an HIV-infected woman. We previously demonstrated that this MIV-150 IVR provides significant protection against vaginal SHIV-RT challenge. Wearing the MIV-150 IVR for 56 d led to only 2 single DRMs in 2 of 6 animals (430 RT sequences analyzed total, 0.46%) from plasma and lymph nodes despite MIV-150 persisting in the plasma, vaginal fluids, and genital tissues. Only wild type virus sequences were detected in the genital tissues. These findings indicate a low probability for the emergence of DRMs after topical MIV-150 exposure and support the advancement of MIV-150-containing microbicides. PMID:24586674

  5. Acceleration in de Sitter spacetimes

    E-print Network

    Ion I. Cotaescu

    2015-02-23

    We propose a definition of uniform accelerated frames in de Sitter spacetimes applying the Nachtmann method of introducing coordinates using suitable point-dependent isometries. In order to recover the well-known Rindler approach in the flat limit, we require the transformation between the static frame and the accelerated one to depend continuously on acceleration, obtaining thus the natural generalization of the Rindler transformation to the de Sitter spacetimes of any dimensions.

  6. Asynchronous accelerator with RFQ injection for active longitudinal compression of accelerated bunches

    Microsoft Academic Search

    A. R. Tumanyan; Yu. L. Martirosyan; V. C. Nikhogosyan; N. Z. Akopov; Z. G. Guiragossian; R. M Martirosov; Z. N. Akopov

    2000-01-01

    An asynchronous accelerator is described, in which the principle of its operation permits the active longitudinal bunch compression of accelerated proton beams, to overcome the space charge limitation effects of intense bunches. It is shown that accelerated bunches from an RFQ linac can be adapted for Asynchronac injection for a multiple of choices in the acceleration frequencies of the RFQ

  7. Exposure Pathways

    MedlinePLUS

    ... to decay, the exposure continues. For radionuclides that decay slowly, the exposure continues over a very long time. Inhalation is of most concern for radionuclides that are alpha or beta particle emitters. Alpha and beta particles can transfer ...

  8. Exposure Nomographs

    NASA Astrophysics Data System (ADS)

    Zissell, Ronald E.

    Correct exposure times may be determined from nomographs relating signal-to-noise ratio, exposure time, color, seeing, and magnitude. The equations needed to construct the nomographs are developed. Calibration techniques are discussed.

  9. Extremely low frequency (ELF) electric and magnetic field exposure limits: rationale for basic restrictions used in the development of an Australian standard.

    PubMed

    Wood, Andrew W

    2008-09-01

    There are large disparities between basic restrictions for exposure to extremely low-frequency (0-3 kHz) Electric and Magnetic Fields set by two major international bodies. Both bodies agree that these basic restrictions should prevent neuro-stimulatory effects: the retinal phosphene at frequencies up to a few hundred Hertz and peripheral nervous stimulation (PNS) at higher frequencies. The disparity arises from differences in estimated thresholds and frequency dependence, and whether restrictions should be of tissue induced current density or electric field. This paper argues that the latter metric more directly relates to neurostimulatory processes. By analysing available literature, a threshold for retinal phosphenes occurrence is found to be 56 mV/m (95% Confidence Interval 2-1330 mV/m), with a characteristic frequency of 20 Hz. Similarly, the smallest PNS sensation threshold is identified at 2 V/m (characteristic frequency above 3 kHz). In the case of the former, the large range of uncertainty suggests a 'power of ten' value of 100 mV/m. For the latter, because of the small margin between sensation and pain threshold, and because of the large individual variation, the smallest estimate of sensation threshold (2 V/m) represents a basic restriction with precaution incorporated. PMID:18381600

  10. Plasma based accelerators

    SciTech Connect

    Evans, R.G.

    1987-05-05

    A plasma medium can support a variety of wave motions which may be useful for accelerating charged particles. For highly relativistic beams the longitudinal electrostatic wave is most suitable and may be driven by laser or by particle beams. The basic principles, limitations and prospects for these devices are discussed.

  11. Repeated exposure to 5D9, an inhibitor of 3D polymerase, effectively limits the replication of foot-and-mouth disease virus in host cells

    PubMed Central

    Rai, Devendra K.; Schafer, Elizabeth; Singh, Kamalendra; McIntosh, Mark A.; Sarafianos, Stefan G.; Rieder, Elizabeth

    2014-01-01

    Foot-and-mouth disease (FMD) is a highly contagious disease of livestock caused by a highly variable RNA virus (FMDV) that has seven serotypes and more than sixty subtypes. Both prophylactic and post-infection means of controlling the disease outbreak, including universally applicable vaccines and emergency response measures such as therapeutic treatments, are on high demand. In this study, we analyzed the long-term exposure outcome to a previously identified inhibitor of 3D polymerase (FMDV 3Dpol) for controlling FMDV infection and for the selection of resistance mutants. The results showed that no escape mutant viruses were isolated from FMDV A24 Cruzeiro infections in cell culture treated with gradually increasing concentrations of the antiviral compound 5D9 (4-chloro-N?-thieno, [2,3-d]pyrimidin-4-ylbenzenesulfonohydrazide) over ten passages. Biochemical and plaque assays revealed that when 5D9 was used at concentrations within a non-toxic range in cells, it drove the virus to undetectable levels at passage eight to ten. This is in contrast with observations made on parallel control (untreated) passages exhibiting fully viable and stable virus progenies. Collectively, the results demonstrated that under the experimental conditions, treatment with 5D9 does not confer a resistant phenotype and the virus is unable to evade the antiviral effect of the inhibitor. Further efforts using quantitative structure-property relationship (QSPR) based modifications of the 5D9 compound may result in the successful development of an effective in vivo antiviral drug targeting FMDV. PMID:23578728

  12. Accelerated degradation studies of MEH-PPV

    SciTech Connect

    Radousky, H.B.; Madden, A.D.; Pakbaz, K.; Hagler, T.W.; Lee, H.W.H.; Lorenzana, H.E.; Fox, G.A.; Elliker, P.R.

    1995-07-01

    MEH-PPV, which normally has a reddish color, is well known to show photobleaching problems. The photobleaching can be greatly accelerated by exposure to laser light while in air. For example, shining 457 mn light of relatively low intensity (0.06 W/cm{sup 2}) on the MEH-PPV causes the photoluminescence to decrease by a factor of two within a few seconds of exposure, and to show a nearly complete bleaching of the material within 30 minutes. The degradation rate is strongly influenced by laser power, sample thickness, oxygen exposure during preparation and spinning, as well as the oxygen environment during the measurement. The photobleach is indicative of one class of degradation mechanisms limiting the usefulness of PPV based polymers in electroluminescent devices. MEH-PPV which was spin coated in a nitrogen environment and measured in vacuum showed no measurable photo-chemical degradation for measuring times of up to several hours. A dramatic decrease in PL intensity was observed, however, in the presence of oxygen, as well as in samples spin coated in air, but measured in vacuum. We present data on the PL of MEH-PPV, as a function of oxygen concentration.

  13. Dose limits for astronauts

    NASA Technical Reports Server (NTRS)

    Sinclair, W. K.

    2000-01-01

    Radiation exposures to individuals in space can greatly exceed natural radiation exposure on Earth and possibly normal occupational radiation exposures as well. Consequently, procedures limiting exposures would be necessary. Limitations were proposed by the Radiobiological Advisory Panel of the National Academy of Sciences/National Research Council in 1970. This panel recommended short-term limits to avoid deterministic effects and a single career limit (of 4 Sv) based on a doubling of the cancer risk in men aged 35 to 55. Later, when risk estimates for cancer had increased and were recognized to be age and sex dependent, the NCRP, in Report No. 98 in 1989, recommended a range of career limits based on age and sex from 1 to 4 Sv. NCRP is again in the process of revising recommendations for astronaut exposure, partly because risk estimates have increased further and partly to recognize trends in limiting radiation exposure occupationally on the ground. The result of these considerations is likely to be similar short-term limits for deterministic effects but modified career limits.

  14. Pre-Exposure Antiretroviral Prophylaxis (PrEP) attitudes in high risk Boston area MSM: Limited knowledge and experience, but potential for increased utilization after education

    PubMed Central

    Mimiaga, Matthew J.; Case, Patricia; Johnson, Carey V.; Safren, Steven A.; Mayer, Kenneth H.

    2009-01-01

    Background Pre-exposure prophylaxis (PrEP) could protect individuals engaging in repeated high-risk behaviors from HIV infection. Understanding the demographic and behavioral predictors of intent to use PrEP may prove useful to identify clinical trial participants. Methods In 2007, 227 HIV-uninfected MSM recruited through modified respondent-driven sampling completed an interviewer-administered survey assessing prior PrEP use and awareness, future intent to use PrEP, demographics, sexual risk, psychosocial variables, and drug/alcohol use. Bivariate and multivariable logistic regression procedures examined predictors of intention to use PrEP. Results Mean age of participants was 41 (SD=9.1); 54% were non-white. One participant reported prior off-label PrEP use (medication obtained from his HIV-infected brother). Nineteen percent had previously heard of PrEP, while 74% reported intent to use PrEP if available after being educated about its potential. In multivariable analysis controlling for age and race/ethnicity, significant predictors of intent to use PrEP included: less education (OR=7.7; p=0.04), moderate income (OR=13.0; p=0.04), no perceived side effects from taking PrEP (OR=3.5; p=0.001), and not having to pay for PrEP (OR=4.2; p=0.05). Discussion Many New England MSM indicated an interest in using PrEP after learning about its potential, particularly if they could obtain PrEP at no expense and if PrEP had no side effects. Less educated MSM and those who knew less about PrEP and antiretroviral therapy (ART) before entering the study were more open to using ART for prevention once they had received some information suggesting its potential value. Findings suggest careful educational messages are necessary to ensure appropriate PrEP use if clinical trials reveal partial efficacy. PMID:19295337

  15. Phase II Study of Accelerated High-Dose Radiotherapy With Concurrent Chemotherapy for Patients With Limited Small-Cell Lung Cancer: Radiation Therapy Oncology Group Protocol 0239

    SciTech Connect

    Komaki, Ritsuko, E-mail: rkomaki@mdanderson.org [Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, Texas (United States); Paulus, Rebecca [Radiation Therapy Oncology Group Statistical Center, Philadelphia, Pennsylvania (United States); Ettinger, David S. [Department of Oncology, Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, Maryland (United States); Videtic, Gregory M.M. [Department of Radiation Oncology, Cleveland Clinic, Cleveland, Ohio (United States); Bradley, Jeffrey D. [Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri (United States); Glisson, Bonnie S. [Department of Thoracic/Head and Neck Oncology, University of Texas MD Anderson Cancer Center, Houston, Texas (United States); Langer, Corey J. [Thoracic Oncology, Abramson Cancer Center, University of Pennsylvania, Philadelphia, Pennsylvania (United States); Sause, William T. [Radiation Center, LDS Hospital, Salt Lake City, Utah (United States); Curran, Walter J. [Department of Radiation Oncology, Jefferson Medical College, Philadelphia, Pennsylvania (United States); Choy, Hak [Department of Radiation Oncology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas (United States)

    2012-07-15

    Purpose: To investigate whether high-dose thoracic radiation given twice daily during cisplatin-etoposide chemotherapy for limited small-cell lung cancer (LSCLC) improves survival, acute esophagitis, and local control rates relative to findings from Intergroup trial 0096 (47%, 27%, and 64%). Patients and Methods: Patients were accrued over a 3-year period from 22 US and Canadian institutions. Patients with LSCLC and good performance status were given thoracic radiation to 61.2 Gy over 5 weeks (daily 1.8-Gy fractions on days 1-22, then twice-daily 1.8-Gy fractions on days 23-33). Cisplatin (60 mg/m{sup 2} IV) was given on day 1 and etoposide (120 mg/m{sup 2} IV) on days 1-3 and days 22-24, followed by 2 cycles of cisplatin plus etoposide alone. Patients who achieved complete response were offered prophylactic cranial irradiation. Endpoints included overall and progression-free survival; severe esophagitis (Common Toxicity Criteria v 2.0) and treatment-related fatalities; response (Response Evaluation Criteria in Solid Tumors); and local control. Results: Seventy-two patients were accrued from June 2003 through May 2006; 71 were evaluable (median age 63 years; 52% female; 58% Zubrod 0). Median survival time was 19 months; at 2 years, the overall survival rate was 36.6% (95% confidence interval [CI] 25.6%-47.7%), and progression-free survival 19.7% (95% CI 11.4%-29.6%). Thirteen patients (18%) experienced severe acute esophagitis, and 2 (3%) died of treatment-related causes; 41% achieved complete response, 39% partial response, 10% stable disease, and 6% progressive disease. The local control rate was 73%. Forty-three patients (61%) received prophylactic cranial irradiation. Conclusions: The overall survival rate did not reach the projected goal; however, rates of esophagitis were lower, and local control higher, than projected. This treatment strategy is now one of three arms of a prospective trial of chemoradiation for LSCLC (Radiation Therapy Oncology Group 0538/Cancer and Leukemia Group B 30610).

  16. Wakefield accelerators

    SciTech Connect

    Simpson, J.D.

    1990-01-01

    The search for new methods to accelerate particle beams to high energy using high gradients has resulted in a number of candidate schemes. One of these, wakefield acceleration, has been the subject of considerable R D in recent years. This effort has resulted in successful proof of principle experiments and in increased understanding of many of the practical aspects of the technique. Some wakefield basics plus the status of existing and proposed experimental work is discussed, along with speculations on the future of wake field acceleration. 10 refs., 6 figs.

  17. Regulating the introduction of new chemicals under section 5 of TSCA: improving the efficiency of the process and reducing potential injury in the workplace through the use of operational MSDS and exposure limits.

    PubMed

    Rosenthal, I; Jayjock, M A; Keener, R L; Plamondon, J E

    1991-10-01

    The Toxic Substances Control Act (TSCA) authorizes the EPA to take appropriate actions to ensure that new and existing chemicals do not pose "unreasonable risk" to health or the environment. Section 2(b)(3) of the Act directs the Agency to accomplish this objective in a manner that does "not impede unduly or create unnecessary economic barriers to technological innovation." In recent years, critics have felt that the EPA has failed to achieve these primary goals of TSCA. This paper considers some of the reasons for this criticism and advocates an alternate approach of exposure limits and operationally sufficient controls to assist in achieving these goals. An illustration of how this alternate approach might work under practical conditions is presented, using as an example a new chemical substance from the class of acrylate monomers. These concepts and risk assessments provide data for a better design of future studies according to good laboratory practice and quality assurance. PMID:1669965

  18. Accelerated molecular dynamics methods

    SciTech Connect

    Perez, Danny [Los Alamos National Laboratory

    2011-01-04

    The molecular dynamics method, although extremely powerful for materials simulations, is limited to times scales of roughly one microsecond or less. On longer time scales, dynamical evolution typically consists of infrequent events, which are usually activated processes. This course is focused on understanding infrequent-event dynamics, on methods for characterizing infrequent-event mechanisms and rate constants, and on methods for simulating long time scales in infrequent-event systems, emphasizing the recently developed accelerated molecular dynamics methods (hyperdynamics, parallel replica dynamics, and temperature accelerated dynamics). Some familiarity with basic statistical mechanics and molecular dynamics methods will be assumed.

  19. Tandem electrostatic accelerators for BNCT

    SciTech Connect

    Ma, J.C. [Yanch and W.B. Howard Massachusetts Inst. of Technology, Cambridge, MA (United States)

    1994-12-31

    The development of boron neutron capture therapy (BNCT) into a viable therapeutic modality will depend, in part, on the availability of suitable neutron sources compatible with installation in a hospital environment. Low-energy accelerator-based intense neutron sources, using electrostatic or radio frequency quadrupole proton accelerators have been suggested for this purpose and are underdevelopment at several laboratories. New advances in tandem electrostatic accelerator technology now allow acceleration of the multi-milliampere proton beams required to produce therapeutic neutron fluxes for BNCT. The relatively compact size, low weight and high power efficiency of these machines make them particularly attractive for installation in a clinical or research facility. The authors will describe the limitations on ion beam current and available neutron flux from tandem accelerators relative to the requirements for BNCT research and therapy. Preliminary designs and shielding requirements for a tandern accelerator-based BNCT research facility will also be presented.

  20. Acceleration switch

    DOEpatents

    Abbin, Jr., Joseph P. (Albuquerque, NM); Devaney, Howard F. (Cedar Crest, NM); Hake, Lewis W. (Albuquerque, NM)

    1982-08-17

    The disclosure relates to an improved integrating acceleration switch of the type having a mass suspended within a fluid filled chamber, with the motion of the mass initially opposed by a spring and subsequently not so opposed.

  1. Nonlocal electrodynamics of linearly accelerated systems

    SciTech Connect

    Mashhoon, Bahram [Department of Physics and Astronomy, University of Missouri-Columbia, Columbia, Missouri 65211 (United States)

    2004-12-01

    The measurement of an electromagnetic radiation field by a linearly accelerated observer is discussed. The nonlocality of this process is emphasized. The nonlocal theory of accelerated observers is briefly described and the consequences of this theory are illustrated using a concrete example involving the measurement of an incident pulse of radiation by an observer that experiences uniform acceleration during a limited interval of time.

  2. Nonlocal Electrodynamics of Linearly Accelerated Systems

    E-print Network

    Bahram Mashhoon

    2004-10-05

    The measurement of an electromagnetic radiation field by a linearly accelerated observer is discussed. The nonlocality of this process is emphasized. The nonlocal theory of accelerated observers is briefly described and the consequences of this theory are illustrated using a concrete example involving the measurement of an incident pulse of radiation by an observer that experiences uniform acceleration during a limited interval of time.

  3. Impact of expert versus measurement-based occupational noise exposure estimates on exposure-response relationships

    Microsoft Academic Search

    Melissa C. Friesen; Hugh W. Davies; Aleck Ostry; Kay Teschke; Paul A. Demers

    2008-01-01

    Objective  Expert-judgment has frequently been used to assess quantitative exposure for epidemiologic studies, but accuracy varies widely\\u000a dependent on the type of exposure and the availability of measurements to anchor estimates. There is limited empirical evidence\\u000a of the sensitivity of exposure-response relationships to expert- versus measurement-based exposure assessment strategies.\\u000a We examined the sensitivity of the exposure-response relationship between occupational noise exposure

  4. Particle Acceleration by MHD Turbulence

    E-print Network

    Jungyeon Cho; A. Lazarian

    2005-10-21

    Recent advances in understanding of magnetohydrodynamic (MHD) turbulence call for revisions in the picture of particle acceleration. We make use of the recently established scaling of slow and fast MHD modes in strong and weak MHD turbulence to provide a systematic study of particle acceleration in magnetic pressure (low-$\\beta$) and gaseous pressure (high-$\\beta$) dominated plasmas. We consider the acceleration by large scale compressions in both slow and fast particle diffusion limits. We compare the results with the acceleration rate that arises from resonance scattering and Transit-Time Damping (TTD). We establish that fast modes accelerate particles more efficiently than slow modes. We find that particle acceleration by pitch-angle scattering and TTD dominates acceleration by slow or fast modes when the spatial diffusion rate is small. When the rate of spatial diffusion of particles is high, we establish an enhancement of the efficiency of particle acceleration by slow and fast modes in weak turbulence. We show that highly supersonic turbulence is an efficient agent for particle acceleration. We find that even incompressible turbulence can accelerate particles on the scales comparable with the particle mean free path.

  5. Antimutagenicity of WR-1065 in L5178Y cells exposed to accelerated (56)Fe ions

    NASA Technical Reports Server (NTRS)

    Evans, H. H.; Evans, T. E.; Horng, M. F.

    2002-01-01

    The ability of the aminothiol WR-1065 [N-(2-mercaptoethyl)-1,3-diaminopropane] to protect L5178Y (LY) cells against the cytotoxic and mutagenic effects of exposure to accelerated (56)Fe ions (1.08 GeV/nucleon) was determined. It was found that while WR-1065 reduced the mutagenicity in both cell lines when it was present during the irradiation, the addition of WR-1065 after the exposure had no effect on the mutagenicity of the radiation in either cell line. No marked protection against the cytotoxic effects of exposure to (56)Fe ions was provided by WR-1065 when added either during or after irradiation in either cell line. We reported previously that WR-1065 protected the LY-S1 and LY-SR1 cell lines against both the cytotoxicity and mutagenicity of X radiation when present during exposure, but that its protection when administered after exposure was limited to the mutagenic effects in the radiation-hypersensitive cell line, LY-S1. The results indicate that the mechanisms involved differ in the protection against cytotoxic compared to mutagenic effects and in the protection against damage caused by accelerated (56)Fe ions compared to X radiation.

  6. Acceleration Studies

    NASA Technical Reports Server (NTRS)

    Rogers, Melissa J. B.

    1993-01-01

    Work to support the NASA MSFC Acceleration Characterization and Analysis Project (ACAP) was performed. Four tasks (analysis development, analysis research, analysis documentation, and acceleration analysis) were addressed by parallel projects. Work concentrated on preparation for and implementation of near real-time SAMS data analysis during the USMP-1 mission. User support documents and case specific software documentation and tutorials were developed. Information and results were presented to microgravity users. ACAP computer facilities need to be fully implemented and networked, data resources must be cataloged and accessible, future microgravity missions must be coordinated, and continued Orbiter characterization is necessary.

  7. Radiation exposure limits for Japanese astronauts

    Microsoft Academic Search

    Takahiro Abe; Tatsuto Komiyama; Tatsunori Suemitsu

    1999-01-01

    Starting in 2001, Japanese astronauts will live aboard the International Space Station (ISS) for 3 to 6 months a year. For astronauts, space radiation is primarily hazardous. Therefore, the National Space Development Agency of Japan (NASDA) is developing a system for Space Radiation Safety Operations. This report describes our overall image of Space Radiation Safety Operations aboard the ISS, especially

  8. Accelerated Achievement

    ERIC Educational Resources Information Center

    Ford, William J.

    2010-01-01

    This article focuses on the accelerated associate degree program at Ivy Tech Community College (Indiana) in which low-income students will receive an associate degree in one year. The three-year pilot program is funded by a $2.3 million grant from the Lumina Foundation for Education in Indianapolis and a $270,000 grant from the Indiana Commission…

  9. Electrothermal accelerators

    Microsoft Academic Search

    M. D. Driga; M. W. Ingram; W. F. Weldon

    1989-01-01

    In electrothermal (ET) guns, the projectile acceleration is governed by gas dynamics as in explosively-driven guns. In a conventional gun, however, both the energy for heating and the material to be heated are contained in the solid propellant. Electrothermal launchers allow an external electric power supply to be used to provide the necessary energy; hence, lower atomic weight propellants may

  10. Plasma accelerator

    DOEpatents

    Wang, Zhehui (Los Alamos, NM); Barnes, Cris W. (Santa Fe, NM)

    2002-01-01

    There has been invented an apparatus for acceleration of a plasma having coaxially positioned, constant diameter, cylindrical electrodes which are modified to converge (for a positive polarity inner electrode and a negatively charged outer electrode) at the plasma output end of the annulus between the electrodes to achieve improved particle flux per unit of power.

  11. Particle acceleration

    NASA Technical Reports Server (NTRS)

    Vlahos, L.; Machado, M. E.; Ramaty, R.; Murphy, R. J.; Alissandrakis, C.; Bai, T.; Batchelor, D.; Benz, A. O.; Chupp, E.; Ellison, D.

    1986-01-01

    Data is compiled from Solar Maximum Mission and Hinothori satellites, particle detectors in several satellites, ground based instruments, and balloon flights in order to answer fundamental questions relating to: (1) the requirements for the coronal magnetic field structure in the vicinity of the energization source; (2) the height (above the photosphere) of the energization source; (3) the time of energization; (4) transistion between coronal heating and flares; (5) evidence for purely thermal, purely nonthermal and hybrid type flares; (6) the time characteristics of the energization source; (7) whether every flare accelerates protons; (8) the location of the interaction site of the ions and relativistic electrons; (9) the energy spectra for ions and relativistic electrons; (10) the relationship between particles at the Sun and interplanetary space; (11) evidence for more than one acceleration mechanism; (12) whether there is single mechanism that will accelerate particles to all energies and also heat the plasma; and (13) how fast the existing mechanisms accelerate electrons up to several MeV and ions to 1 GeV.

  12. Laser Acceleration in Vacuum and Gases with Capillary Waveguide

    SciTech Connect

    Xie, Ming

    1999-02-01

    A unified framework is developed to overcome all three major limitations on acceleration and distance and hence on the feasibility of two classes of laser acceleration. The three limitations are due to laser diffraction, acceleration phase slippage, and structure damage by high power laser if solid-state optical waveguide is used. The two classes of laser acceleration are direct-field acceleration and ponderomotive-driven acceleration. Thus this letter and its companion [1] provide solutions that are crucial to all mainstream approaches for laser acceleration, either in vacuum, gases or plasmas.

  13. Suppressing Parasitic Effects in a Long Dielectric Wakefield Accelerator

    SciTech Connect

    Shchegolkov, Dmitry [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Simakov, Evgenya Ivanovna [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Jing, Chunguang [Euclid Techlabs LLC., Cleveland, OH (United States); Argonne National Lab. (ANL), Argonne, IL (United States); Li, Chen [Argonne National Lab. (ANL), Argonne, IL (United States); Zholents, Alexander A. [Argonne National Lab. (ANL), Argonne, IL (United States); Power, John G. [Argonne National Lab. (ANL), Argonne, IL (United States)

    2014-08-27

    Dielectric wakefield acceleration is a promising concept for increasing the accelerating gradient above the limits of conventional accelerators. Although superior gradients are reported in short dielectric wakefield accelerator tubes, problems arise when it comes to efficiency and multi-meter long interaction lengths. Here we discuss possible issues and provide some solutions backed by simulations.

  14. Unruh temperature with maximal acceleration

    NASA Astrophysics Data System (ADS)

    Benedetto, Elmo; Feoli, Antonio

    2015-04-01

    In this paper, we modify the geometry of Rindler space so as to include an upper limit on the acceleration. Caianiello and his collaborators, in a series of papers, have analyzed the corrections to the classical spacetime metrics due to the existence of a maximal acceleration. Our goal is to derive, in this context, in a very simple way, the so-called Unruh temperature.

  15. INFLUENCE OF EXPOSURE ASSESSMENT METHOD IN AN EPIDEMIOLOGIC STUDY OF TRIHALOMETHANE EXPOSURE AND SPONTANEOUS ABORTION

    EPA Science Inventory

    Trihalomethanes are common contaminants of chlorinated drinking water. Studies of their health effects have been hampered by exposure misclassification, due in part to limitations inherent in using utility sampling records. We used two exposure assessment methods, one based on ut...

  16. LANSCE beam current limiter

    SciTech Connect

    Gallegos, F.R.

    1996-06-01

    The Radiation Security System (RSS) at the Los Alamos Neutron Science Center (LANSCE) provides personnel protection from prompt radiation due to accelerated beam. Active instrumentation, such as the Beam Current Limiter, is a component of the RSS. The current limiter is designed to limit the average current in a beam line below a specific level, thus minimizing the maximum current available for a beam spill accident. The beam current limiter is a self-contained, electrically isolated toroidal beam transformer which continuously monitors beam current. It is designed as fail-safe instrumentation. The design philosophy, hardware design, operation, and limitations of the device are described.

  17. Accelerated Stress-Corrosion Testing

    NASA Technical Reports Server (NTRS)

    1986-01-01

    Test procedures for accelerated stress-corrosion testing of high-strength aluminum alloys faster and provide more quantitative information than traditional pass/fail tests. Method uses data from tests on specimen sets exposed to corrosive environment at several levels of applied static tensile stress for selected exposure times then subsequently tensile tested to failure. Method potentially applicable to other degrading phenomena (such as fatigue, corrosion fatigue, fretting, wear, and creep) that promote development and growth of cracklike flaws within material.

  18. BICEP's acceleration

    E-print Network

    Carlo R. Contaldi

    2014-07-24

    The recent BICEP2 detection of, what is claimed to be primordial $B$-modes, opens up the possibility of constraining not only the energy scale of inflation but also the detailed acceleration history that occurred during inflation. In turn this can be used to determine the shape of the inflaton potential $V(\\phi)$ for the first time - if a single, scalar inflaton is assumed to be driving the acceleration. We carry out a Monte Carlo exploration of inflationary trajectories given the current data. Using this method we obtain a posterior distribution of possible acceleration profiles $\\epsilon(N)$ as a function of $e$-fold $N$ and derived posterior distributions of the primordial power spectrum $P(k)$ and potential $V(\\phi)$. We find that the BICEP2 result, in combination with Planck measurements of total intensity Cosmic Microwave Background (CMB) anisotropies, induces a significant feature in the scalar primordial spectrum at scales $k\\sim 10^{-3}$ Mpc$^{-1}$. This is in agreement with a previous detection of a suppression in the scalar power.

  19. Immunological Priming Requires Tregs and Interleukin-10-Producing Macrophages to Accelerate Resolution from Severe Lung Inflammation

    PubMed Central

    Eto, Yoshiki; Tripathi, Ashutosh; Mandke, Pooja; Mock, Jason R.; Garibaldi, Brian T.; Singer, Benjamin D.; Sidhaye, Venkataramana K.; Horton, Maureen R.; King, Landon S.; D'Alessio, Franco R.

    2014-01-01

    Overwhelming lung inflammation frequently occurs following exposure to both direct infectious and non-infectious agents, and is a leading cause of mortality world-wide. In that context, immunomodulatory strategies may be utilized to limit severity of impending organ damage. We sought to determine whether priming the lung by activating the immune system, or immunological priming, could accelerate resolution of severe lung inflammation. We assessed the importance of alveolar macrophages, regulatory T cells, and their potential interaction during immunological priming. We demonstrate that oropharyngeal delivery of low-dose lipopolysaccharide can immunologically prime the lung to augment alveolar macrophage production of interleukin-10 and enhance resolution of lung inflammation induced by a lethal dose of lipopolysaccharide or by pseudomonas bacterial pneumonia. Interleukin-10 deficient mice did not achieve priming and were unable to accelerate lung injury resolution. Depletion of lung macrophages or regulatory T cells during the priming response completely abrogated the positive effect of immunological priming on resolution of lung inflammation and significantly reduced alveolar macrophage interleukin-10 production. Finally, we demonstrated that oropharyngeal delivery of synthetic CpG-oligonucleotides elicited minimal lung inflammation compared to low-dose lipopolysaccharide, but nonetheless primed the lung to accelerate resolution of lung injury following subsequent lethal lipopolysaccharide exposure. Immunological priming is a viable immunomodulatory strategy used to enhance resolution in an experimental acute lung injury model with the potential for therapeutic benefit against a wide array of injurious exposures. PMID:24688024

  20. Pesticide exposure in children.

    PubMed

    Roberts, James R; Karr, Catherine J

    2012-12-01

    Pesticides are a collective term for a wide array of chemicals intended to kill unwanted insects, plants, molds, and rodents. Food, water, and treatment in the home, yard, and school are all potential sources of children's exposure. Exposures to pesticides may be overt or subacute, and effects range from acute to chronic toxicity. In 2008, pesticides were the ninth most common substance reported to poison control centers, and approximately 45% of all reports of pesticide poisoning were for children. Organophosphate and carbamate poisoning are perhaps the most widely known acute poisoning syndromes, can be diagnosed by depressed red blood cell cholinesterase levels, and have available antidotal therapy. However, numerous other pesticides that may cause acute toxicity, such as pyrethroid and neonicotinoid insecticides, herbicides, fungicides, and rodenticides, also have specific toxic effects; recognition of these effects may help identify acute exposures. Evidence is increasingly emerging about chronic health implications from both acute and chronic exposure. A growing body of epidemiological evidence demonstrates associations between parental use of pesticides, particularly insecticides, with acute lymphocytic leukemia and brain tumors. Prenatal, household, and occupational exposures (maternal and paternal) appear to be the largest risks. Prospective cohort studies link early-life exposure to organophosphates and organochlorine pesticides (primarily DDT) with adverse effects on neurodevelopment and behavior. Among the findings associated with increased pesticide levels are poorer mental development by using the Bayley index and increased scores on measures assessing pervasive developmental disorder, inattention, and attention-deficit/hyperactivity disorder. Related animal toxicology studies provide supportive biological plausibility for these findings. Additional data suggest that there may also be an association between parental pesticide use and adverse birth outcomes including physical birth defects, low birth weight, and fetal death, although the data are less robust than for cancer and neurodevelopmental effects. Children's exposures to pesticides should be limited as much as possible. PMID:23184105

  1. Asbestos Exposure Assessment Database

    NASA Technical Reports Server (NTRS)

    Arcot, Divya K.

    2010-01-01

    Exposure to particular hazardous materials in a work environment is dangerous to the employees who work directly with or around the materials as well as those who come in contact with them indirectly. In order to maintain a national standard for safe working environments and protect worker health, the Occupational Safety and Health Administration (OSHA) has set forth numerous precautionary regulations. NASA has been proactive in adhering to these regulations by implementing standards which are often stricter than regulation limits and administering frequent health risk assessments. The primary objective of this project is to create the infrastructure for an Asbestos Exposure Assessment Database specific to NASA Johnson Space Center (JSC) which will compile all of the exposure assessment data into a well-organized, navigable format. The data includes Sample Types, Samples Durations, Crafts of those from whom samples were collected, Job Performance Requirements (JPR) numbers, Phased Contrast Microscopy (PCM) and Transmission Electron Microscopy (TEM) results and qualifiers, Personal Protective Equipment (PPE), and names of industrial hygienists who performed the monitoring. This database will allow NASA to provide OSHA with specific information demonstrating that JSC s work procedures are protective enough to minimize the risk of future disease from the exposures. The data has been collected by the NASA contractors Computer Sciences Corporation (CSC) and Wyle Laboratories. The personal exposure samples were collected from devices worn by laborers working at JSC and by building occupants located in asbestos-containing buildings.

  2. Accelerators and the Accelerator Community

    SciTech Connect

    Malamud, Ernest; Sessler, Andrew

    2008-06-01

    In this paper, standing back--looking from afar--and adopting a historical perspective, the field of accelerator science is examined. How it grew, what are the forces that made it what it is, where it is now, and what it is likely to be in the future are the subjects explored. Clearly, a great deal of personal opinion is invoked in this process.

  3. [Accelerated titration design].

    PubMed

    Minami, H

    2000-09-01

    To reduce the number of patients treated at low and biologically inactive doses in phase I trials of anticancer agents, attempts to decrease the number of patients per dose level and to conduct a larger dose escalation have been made. Among them, accelerated titration designs were proposed and evaluated by simulation; designs 2 and 4 were reported to be acceptable (J Natl Cancer Inst 89: 1138-1147, 1997). Both designs 2 and 4 included only one patient per cohort during the initial accelerated phase. Dosage steps for the accelerated phase were defined using the modified Fibonacci method for design 2 and 100% escalation for design 4, respectively. The accelerated phase continued until one patient experienced dose-limiting toxicity or two patients experienced grade 2 toxicities. Dose escalation was conducted based on the information from the first course in design 2 and from the first three courses in design 4. In the simulation, both designs successfully reduced the total number of patients and the number of undertreated patients without increasing the number of overtreated patients. However, the safety of design 4 was assured as long as all patients received three courses of chemotherapy, which is unusual in phase I studies in Japan. Decision-making on dose escalation based on the information on toxicity in three courses might be cumbersome. Therefore, in Japan, design 2 would be recommended among the proposed accelerated designs. The performance of the design should be investigated by applying it to actual phase I studies and by evaluating the number of undertreated and overtreated patients. PMID:11016010

  4. Criminal exposure.

    PubMed

    1999-08-01

    A 39-year-old man who had sex with a 16-year-old boy, was sentenced to five years in prison. The defendant pleaded guilty to statutory rape and criminal exposure to HIV. The boy discovered that the man was taking HIV medications, and the man subsequently disclosed his treatment after being arrested. PMID:11367003

  5. Accelerator system and method of accelerating particles

    NASA Technical Reports Server (NTRS)

    Wirz, Richard E. (Inventor)

    2010-01-01

    An accelerator system and method that utilize dust as the primary mass flux for generating thrust are provided. The accelerator system can include an accelerator capable of operating in a self-neutralizing mode and having a discharge chamber and at least one ionizer capable of charging dust particles. The system can also include a dust particle feeder that is capable of introducing the dust particles into the accelerator. By applying a pulsed positive and negative charge voltage to the accelerator, the charged dust particles can be accelerated thereby generating thrust and neutralizing the accelerator system.

  6. Tritium Exposure Reconstruction Using Tree Rings at Lawrence Berkeley National Laboratory

    NASA Astrophysics Data System (ADS)

    Love, A. H.; Hunt, J. R.; Knezovich, J. P.

    2002-12-01

    There are numerous instances where historical exposures to contaminants can determine future health impacts, but limited means exist to reconstruct those exposures from current measurements and models. The National Tritium Labeling Facility at Lawrence Berkeley National Laboratory (LBNL) has released tritiated water into the atmosphere through an adjacent stack since 1969. Some members of the surrounding community are concerned about potential health effects from the emissions and have questioned the accuracy and thoroughness of reported historical release quantities and environmental monitoring. A grove of Eucalyptus globulus surround the emission stack and were used to reconstruct historical exposure levels. Previous studies have demonstrated that plants can be reliably used as passive monitors for tritiated water, as well as many other contaminants. Because trees can sequester tritium into wood during photosynthesis, a tree provides a temporal variation of exposure at least on an annual basis. Milligram-sized samples of wood from cores were measured for carbon-14 and tritium using accelerator mass spectrometry. The carbon-14 measurements were matched with bomb curve levels of carbon-14 to independently assess the age of the wood used for organically bound tritium measurements. The tritium exposure reconstruction was consistent with annual exposure monitoring and release quantities reported by LBNL over the last 30 years. Because this location has an episodic release pattern and complex topographic and meteorological variation, the historical assessment from these environmental measurements is likely to have less uncertainty than mathematical modeling efforts.

  7. Domestic Asbestos Exposure: A Review of Epidemiologic and Exposure Data

    PubMed Central

    Goswami, Emily; Craven, Valerie; Dahlstrom, David L.; Alexander, Dominik; Mowat, Fionna

    2013-01-01

    Inhalation of asbestos resulting from living with and handling the clothing of workers directly exposed to asbestos has been established as a possible contributor to disease. This review evaluates epidemiologic studies of asbestos-related disease or conditions (mesothelioma, lung cancer, and pleural and interstitial abnormalities) among domestically exposed individuals and exposure studies that provide either direct exposure measurements or surrogate measures of asbestos exposure. A meta-analysis of studies providing relative risk estimates (n = 12) of mesothelioma was performed, resulting in a summary relative risk estimate (SRRE) of 5.02 (95% confidence interval [CI]: 2.48–10.13). This SRRE pertains to persons domestically exposed via workers involved in occupations with a traditionally high risk of disease from exposure to asbestos (i.e., asbestos product manufacturing workers, insulators, shipyard workers, and asbestos miners). The epidemiologic studies also show an elevated risk of interstitial, but more likely pleural, abnormalities (n = 6), though only half accounted for confounding exposures. The studies are limited with regard to lung cancer (n = 2). Several exposure-related studies describe results from airborne samples collected within the home (n = 3), during laundering of contaminated clothing (n = 1) or in controlled exposure simulations (n = 5) of domestic exposures, the latter of which were generally associated with low-level chrysotile-exposed workers. Lung burden studies (n = 6) were also evaluated as a surrogate of exposure. In general, available results for domestic exposures are lower than the workers’ exposures. Recent simulations of low-level chrysotile-exposed workers indicate asbestos levels commensurate with background concentrations in those exposed domestically. PMID:24185840

  8. High average power induction accelerators

    SciTech Connect

    Swingle, J.C. (ed.)

    1985-10-01

    The induction accelerator is discussed with respect to general background and concept, beam transport, scaling, pulse power technology, and the electron beam injector. A discussion of the factors which affect the scaling of the intensity of the beam is given. Limiting factors include collective forces in the beam, virtual cathode formation, surroundings, and beam breakup instability. 24 refs., 11 figs. (WRF)

  9. FERMI ACCELERATION. DMITRY DOLGOPYAT

    E-print Network

    Dolgopyat, Dmitry

    FERMI ACCELERATION. DMITRY DOLGOPYAT Abstract. Fermi acceleration is a mechanism, first suggested, on average, be accelerated. Since then Fermi acceleration has been used to explain a number of natural phenomena and sev- eral simple mathematical models demonstrating Fermi acceleration have been proposed. We

  10. Progress on plasma accelerators

    SciTech Connect

    Chen, P.

    1986-05-01

    Several plasma accelerator concepts are reviewed, with emphasis on the Plasma Beat Wave Accelerator (PBWA) and the Plasma Wake Field Accelerator (PWFA). Various accelerator physics issues regarding these schemes are discussed, and numerical examples on laboratory scale experiments are given. The efficiency of plasma accelerators is then revealed with suggestions on improvements. Sources that cause emittance growth are discussed briefly.

  11. The Muon Accelerator Program

    SciTech Connect

    Geer, Steve; /Fermilab; Zisman, Mike; /LBL, Berkeley

    2011-08-01

    Multi-TeV Muon Colliders and high intensity Neutrino Factories have captured the imagination of the particle physics community. These new types of facility both require an advanced muon source capable of producing O(10{sup 21}) muons per year. The muons must be captured within bunches, and their phase space manipulated so that they fit within the acceptance of an accelerator. In a Neutrino Factory (NF), muons from this 'front end' are accelerated to a few GeV or a few tens of GeV, and then injected into a storage ring with long straight sections. Muon decays in the straight sections produce an intense neutrino beam. In a Muon Collider (MC) the muons must be cooled by a factor O(10{sup 6}) to produce beams that are sufficiently bright to give high luminosity in the collider. Bunches of positive and negative muons are then accelerated to high energy, and injected in opposite directions into a collider ring in which they collide at one or more interaction points. Over the last decade our understanding of the concepts and technologies needed for Muon Colliders and Neutrino Factories has advanced, and it is now believed that, within a few years, with a well focused R&D effort (i) a Neutrino Factory could be proposed, and (ii) enough could be known about the technologies needed for a Muon Collider to assess the feasibility and cost of this new type of facility, and to make a detailed plan for the remaining R&D. Although these next NF and MC steps are achievable, they are also ambitious, and will require an efficient and dedicated organization to accomplish the desired goals with limited resources. The Muon Accelerator Program (MAP) has recently been created to propose and execute this R&D program.

  12. Nonlocality of Accelerated Systems

    E-print Network

    Bahram Mashhoon

    2003-05-11

    The conceptual basis for the nonlocality of accelerated systems is presented. The nonlocal theory of accelerated observers and its consequences are briefly described. Nonlocal field equations are developed for the case of the electrodynamics of linearly accelerated systems.

  13. Ion Induction Accelerators

    Microsoft Academic Search

    John J. Barnard; Kazuhiko Horioka

    2011-01-01

    \\u000a The description of beams in RF and induction accelerators share many common features. Likewise, there is considerable commonality\\u000a between electron induction accelerators (see Chap. 7) and ion induction accelerators. However, in contrast to electron induction\\u000a accelerators, there are fewer ion induction accelerators that have been operated as application-driven user facilities. Ion\\u000a induction accelerators are envisioned for applications (see Chap. 10)

  14. Head-to-head, randomised, crossover study of oral versus subcutaneous methotrexate in patients with rheumatoid arthritis: drug-exposure limitations of oral methotrexate at doses ?15?mg may be overcome with subcutaneous administration

    PubMed Central

    Schiff, Michael H; Jaffe, Jonathan S; Freundlich, Bruce

    2014-01-01

    Objective To compare the relative bioavailability, safety and tolerability of oral methotrexate (MTX) and subcutaneous (SC) MTX administered via an auto-injector (MTXAI) in patients with rheumatoid arthritis (RA). Methods In this randomised, multicenter, open-label, three-way crossover study, patients ?18?years with adult RA undergoing treatment with MTX for ?3?months were assigned to receive MTX 10, 15, 20 and 25?mg weekly in a random sequence of three treatments: oral, SC into the abdomen and SC into the thigh. For 24?h after administration of each treatment, blood samples were collected for pharmacokinetic analysis and injection sites were assessed. Results Forty-seven patients completed the study. Systemic exposure of oral MTX plateaued at doses ?15?mg/week. In contrast, SC MTX demonstrated a linear increase in systemic exposure that was greater than oral MTX at each dose. No unexpected AEs were noted for either formulation. Conclusions Unlike oral MTX, the systemic exposure of SC MTX did not plateau over the doses studied, particularly at doses ?15?mg/week. In this study, higher systemic MTX exposure was not associated with increases in AEs. Patients with an inadequate clinical response to oral MTX may benefit from higher drug exposure by switching to SC MTX. Trial registration number NCT01618968. PMID:24728329

  15. Repair of overheating linear accelerator

    SciTech Connect

    Barkley, Walter; Baldwin, William; Bennett, Gloria; Bitteker, Leo; Borden, Michael; Casados, Jeff; Fitzgerald, Daniel; Gorman, Fred; Johnson, Kenneth; Kurennoy, Sergey; Martinez, Alberto; O’Hara, James; Perez, Edward; Roller, Brandon; Rybarcyk, Lawrence; Stark, Peter; Stockton, Jerry

    2004-01-01

    Los Alamos Neutron Science Center (LANSCE) is a proton accelerator that produces high energy particle beams for experiments. These beams include neutrons and protons for diverse uses including radiography, isotope production, small feature study, lattice vibrations and material science. The Drift Tube Linear Accelerator (DTL) is the first portion of a half mile long linear section of accelerator that raises the beam energy from 750 keV to 100 MeV. In its 31st year of operation (2003), the DTL experienced serious issues. The first problem was the inability to maintain resonant frequency at full power. The second problem was increased occurrences of over-temperature failure of cooling hoses. These shortcomings led to an investigation during the 2003 yearly preventative maintenance shutdown that showed evidence of excessive heating: discolored interior tank walls and coper oxide deposition in the cooling circuits. Since overheating was suspected to be caused by compromised heat transfer, improving that was the focus of the repair effort. Investigations revealed copper oxide flow inhibition and iron oxide scale build up. Acid cleaning was implemented with careful attention to protection of the base metal, selection of components to clean and minimization of exposure times. The effort has been very successful in bringing the accelerator through a complete eight month run cycle allowing an incredible array of scientific experiments to be completed this year (2003-2004). This paper will describe the systems, investigation analysis, repair, return to production and conclusion.

  16. Radiation Safety System of the B-Factory at the Stanford Linear Accelerator Center

    SciTech Connect

    Liu, James C

    1998-10-12

    The radiation safety system (RSS) of the B-Factory accelerator facility at the Stanford Linear Accelerator Center (SLAC) is described. The RSS, which is designed to protect people from prompt radiation exposure due to beam operation, consists of the access control system (ACS) and the radiation containment system (RCS). The ACS prevents people from being exposed to the very high radiation levels inside a beamline shielding housing. The ACS consists of barriers, a standard entry module at every entrance, and beam stoppers. The RCS prevents people from being exposed to the radiation outside a shielding housing, due to either normal or abnormal operation. The RCS consists of power limiting devices, shielding, dump/collimator, and an active radiation monitor system. The inter-related system elements for the ACS and RCS, as well as the associated interlock network, are described. The policies and practices in setting up the RSS are also compared with the regulatory requirements.

  17. Laser driven acceleration in vacuum and gases

    SciTech Connect

    Sprangle, P.; Esarey, E. [Beam Physics Branch, Plasma Physics Division Naval Research Laboratory, Washington, District of Columbia (United States) 20375; Hafizi, B. [Icarus Research, Inc., P.O. Box 30780, Bethesda, Maryland (United States) 20824-0780; Hubbard, R.; Krall, J.; Ting, A. [Beam Physics Branch, Plasma Physics Division Naval Research Laboratory, Washington, District of Columbia (United States) 20375

    1997-03-01

    Several important issues pertaining to particle acceleration in vacuum and gases are discussed. The limitations of laser vacuum acceleration as they relate to electron slippage, laser diffraction, material damage, and electron aperture effects are presented. Limitations on the laser intensity and particle self-fields due to material breakdown are quantified. In addition, the reflection of the self-fields associated with the accelerated particles places a limit on the number of particles. Two configurations for the inverse Cherenkov accelerator (ICA) are considered, in which the electromagnetic driver is propagated in a waveguide that is (i) lined with a dielectric material or (ii) filled with a neutral gas. The acceleration gradient in the ICA is limited by tunneling and collisional ionization in the dielectric liner or gas. Ionization can lead to significant modification of the optical properties of the waveguide, altering the phase velocity and causing particle slippage, thus disrupting the acceleration process. Maximum accelerating gradients and pulse durations are presented for a 10 {mu}m and a 1 mm wavelength driver. We show that the use of an unguided Bessel (axicon) beam can enhance the energy gain compared to a higher order Gaussian beam. The enhancement factor is N{sup 1/2}, where N is the number of lobes in the Bessel beam. {copyright} {ital 1997 American Institute of Physics.}

  18. Criminal exposure.

    PubMed

    1999-10-29

    [Name removed] was sentenced to 17 years in prison after he pleaded guilty in Knox County (Tennessee) Criminal Court to exposing three women to HIV through sex. One of the women is a 17-year-old who became infected and pregnant. The other two women came forward after learning that [name removed] was being investigated for rape involving the 17-year-old. [Name removed] could have been sentenced to up to 60 years for nine counts of criminal exposure to HIV and three counts of statutory rape. In 1994, [name removed] was charged in Michigan with having unprotected sex with HIV; those charges were dropped when the woman involved declined to pursue the case. PMID:11367055

  19. High-powered pulsed-ion-beam acceleration and transport

    SciTech Connect

    Humphries, S. Jr.; Lockner, T.R.

    1981-11-01

    The state of research on intense ion beam acceleration and transport is reviewed. The limitations imposed on ion beam transport by space charge effects and methods available for neutralization are summarized. The general problem of ion beam neutralization in regions free of applied electric fields is treated. The physics of acceleration gaps is described. Finally, experiments on multi-stage ion acceleration are summarized.

  20. Particle acceleration in solar flares: observations versus numerical simulations

    E-print Network

    Particle acceleration in solar flares: observations versus numerical simulations A O Benz, P C processes such as isotropization and magnetic trapping are made. Keywords: Particle acceleration, hard X. As the electric field of reconnection with possible parallel component capable of particle acceleration is limited

  1. PERSONAL EXPOSURE TO PARTICLES IN BANSKA BYSTRICA, SLOVAKIA

    EPA Science Inventory

    Epidemiological studies have associated adverse health impacts with ambient concentrations of particulate matter (PM), though these studies have been limited in their characterization of personal exposure to PM. An exposure study of healthy nonsmoking adults and children was cond...

  2. Biological effects from electromagnetic field exposure and public exposure standards.

    PubMed

    Hardell, Lennart; Sage, Cindy

    2008-02-01

    During recent years there has been increasing public concern on potential health risks from power-frequency fields (extremely low frequency electromagnetic fields; ELF) and from radiofrequency/microwave radiation emissions (RF) from wireless communications. Non-thermal (low-intensity) biological effects have not been considered for regulation of microwave exposure, although numerous scientific reports indicate such effects. The BioInitiative Report is based on an international research and public policy initiative to give an overview of what is known of biological effects that occur at low-intensity electromagnetic fields (EMFs) exposure. Health endpoints reported to be associated with ELF and/or RF include childhood leukaemia, brain tumours, genotoxic effects, neurological effects and neurodegenerative diseases, immune system deregulation, allergic and inflammatory responses, breast cancer, miscarriage and some cardiovascular effects. The BioInitiative Report concluded that a reasonable suspicion of risk exists based on clear evidence of bioeffects at environmentally relevant levels, which, with prolonged exposures may reasonably be presumed to result in health impacts. Regarding ELF a new lower public safety limit for habitable space adjacent to all new or upgraded power lines and for all other new constructions should be applied. A new lower limit should also be used for existing habitable space for children and/or women who are pregnant. A precautionary limit should be adopted for outdoor, cumulative RF exposure and for cumulative indoor RF fields with considerably lower limits than existing guidelines, see the BioInitiative Report. The current guidelines for the US and European microwave exposure from mobile phones, for the brain are 1.6 W/Kg and 2 W/Kg, respectively. Since use of mobile phones is associated with an increased risk for brain tumour after 10 years, a new biologically based guideline is warranted. Other health impacts associated with exposure to electromagnetic fields not summarized here may be found in the BioInitiative Report at www.bioinitiative.org. PMID:18242044

  3. Environmental Exposure Effects on Composite Materials for Commercial Aircraft

    NASA Technical Reports Server (NTRS)

    Hoffman, D. J.

    1980-01-01

    The test program concentrates on three major areas: flight exposure; ground based exposure; and accelerated environmental effects and data correlation. Among the parameters investigated were: geographic location, flight profiles, solar heating effects, ultraviolet degradation, retrieval times, and test temperatures. Data from the tests can be used to effectively plan the cost of production and viable alternatives in materials selection.

  4. Limited list: limited effects?

    PubMed

    Taylor, R J; Bond, C M

    1985-08-24

    During the first month after the limited National Health Service drug list came into effect 17 cooperative general practitioners recorded the actions taken when a now prohibited drug would formerly have been prescribed. An average of 6% of direct surgery contacts with patients and 8% of indirect contacts with patients were affected by the new regulations, but in 2% and 4% of cases respectively the patient received the same pharmacological substance under a different (generic or approved) name. Where a real change in pharmacological constitution or formulation had been required four fifths of these substitutes were considered by the doctors to result in less effective treatment. In 1% of contacts no drug was issued or recommended where one would formerly have been given. PMID:3928035

  5. Acceleration of runaway electrons and Joule heating in solar flares

    NASA Technical Reports Server (NTRS)

    Holman, G. D.

    1984-01-01

    The electric field acceleration of electrons out of a thermal plasma and the simultaneous Joule heating of the plasma are studied. Acceleration and heating timescales are derived and compared, and upper limits are obtained on the acceleration volume and the rate at which electrons can be accelerated. These upper limits, determined by the maximum magnetic field strength observed in flaring regions, place stringent restrictions upon the acceleration process. The role of the plasma resistivity in these processes is examined, and possible sources of anomalous resistivity are summarized. The implications of these results for the microwave and hard X-ray emission from solar flares are examined.

  6. Report on accelerated corrosion studies.

    SciTech Connect

    Mowry, Curtis Dale; Glass, Sarah Jill; Sorensen, Neil Robert

    2011-03-01

    Sandia National Laboratories (SNL) conducted accelerated atmospheric corrosion testing for the U.S. Consumer Product Safety Commission (CPSC) to help further the understanding of the development of corrosion products on conductor materials in household electrical components exposed to environmental conditions representative of homes constructed with problem drywall. The conditions of the accelerated testing were chosen to produce corrosion product growth that would be consistent with long-term exposure to environments containing humidity and parts per billion (ppb) levels of hydrogen sulfide (H{sub 2}S) that are thought to have been the source of corrosion in electrical components from affected homes. This report documents the test set-up, monitoring of electrical performance of powered electrical components during the exposure, and the materials characterization conducted on wires, screws, and contact plates from selected electrical components. No degradation in electrical performance (measured via voltage drop) was measured during the course of the 8-week exposure, which was approximately equivalent to 40 years of exposure in a light industrial environment. Analyses show that corrosion products consisting of various phases of copper sulfide, copper sulfate, and copper oxide are found on exposed surfaces of the conductor materials including wires, screws, and contact plates. The morphology and the thickness of the corrosion products showed a range of character. In some of the copper wires that were observed, corrosion product had flaked or spalled off the surface, exposing fresh metal to the reaction with the contaminant gasses; however, there was no significant change in the wire cross-sectional area.

  7. COMPARATIVE STUDIES OF PROTON ACCELERATORS FOR HIGH POWER APPLICATIONS.

    SciTech Connect

    WENG, W.T.

    2006-05-29

    There are many applications requiring high power proton accelerators of various kinds. However, each type of proton accelerator can only provide beam with certain characteristics, hence the match of accelerators and their applications need careful evaluation. In this talk, the beam parameters and performance limitations of linac, cyclotron, synchrotron, and FFAG accelerators are studied and their relative merits for application in neutron, muon, neutrino, and ADS will be assessed in terms of beam energy, intensity, bunch length, repetition rate, and beam power requirements. A possible match between the applications and the accelerator of choice is presented in a matrix form. The accelerator physics and technology issues and challenges involved will also be discussed.

  8. Covariant Uniform Acceleration

    E-print Network

    Yaakov Friedman; Tzvi Scarr

    2013-04-29

    We show that standard Relativistic Dynamics Equation F=dp/d\\tau is only partially covariant. To achieve full Lorentz covariance, we replace the four-force F by a rank 2 antisymmetric tensor acting on the four-velocity. By taking this tensor to be constant, we obtain a covariant definition of uniformly accelerated motion. We compute explicit solutions for uniformly accelerated motion which are divided into four types: null, linear, rotational, and general. For null acceleration, the worldline is cubic in the time. Linear acceleration covariantly extends 1D hyperbolic motion, while rotational acceleration covariantly extends pure rotational motion. We use Generalized Fermi-Walker transport to construct a uniformly accelerated family of inertial frames which are instantaneously comoving to a uniformly accelerated observer. We explain the connection between our approach and that of Mashhoon. We show that our solutions of uniformly accelerated motion have constant acceleration in the comoving frame. Assuming the Weak Hypothesis of Locality, we obtain local spacetime transformations from a uniformly accelerated frame K' to an inertial frame K. The spacetime transformations between two uniformly accelerated frames with the same acceleration are Lorentz. We compute the metric at an arbitrary point of a uniformly accelerated frame. We obtain velocity and acceleration transformations from a uniformly accelerated system K' to an inertial frame K. We derive the general formula for the time dilation between accelerated clocks. We obtain a formula for the angular velocity of a uniformly accelerated object. Every rest point of K' is uniformly accelerated, and its acceleration is a function of the observer's acceleration and its position. We obtain an interpretation of the Lorentz-Abraham-Dirac equation as an acceleration transformation from K' to K.

  9. Ocular toxicity from pesticide exposure: A recent review

    Microsoft Academic Search

    Kushik Jaga; Chandrabhan Dharmani

    2006-01-01

    Toxic effects on eyes result from exposure to pesticides via inhalation, ingestion, dermal contact and ocular exposure. Exposure\\u000a of unprotected eyes to pesticides results in the absorption in ocular tissue and potential ocular toxicity. Recent literature\\u000a on the risks of ocular toxicity from pesticide exposure is limited.\\u000a \\u000a Ocular toxicity from pesticide exposure, including the dose-response relationship, has been studied in

  10. Laser acceleration in novel media

    NASA Astrophysics Data System (ADS)

    Tajima, T.

    2014-05-01

    With newly available compact laser technology [1] we are capable of producing 100 PW-class laser pulses with a single-cycle duration on the femtosecond timescale. With this fs intense laser we can produce a coherent X-ray pulse that is also compressed, well into the hard X-ray regime (˜10 keV) and with a power up to as much as 10 Exawatts. We suggest utilizing these coherent X-rays to drive the acceleration of particles. Such X-rays are focusable far beyond the diffraction limit of the original laser wavelength and when injected into a crystal it forms a metallic-density electron plasma ideally suited for laser wakefield acceleration. If the X-ray field is limited by the Schwinger field at the focal size of ˜100 nm, the achievable energy is 1 PeV over 50 m. (If the X-rays are focused further, much higher energies beyond this are possible). These processes are not limited to only electron acceleration, and if ions are pre-accelerated to beyond GeV they are capable of being further accelerated using a LWFA scheme [2] to similar energies as electrons over the same distance-scales. Such high energy proton (and ion) beams can induce copious neutrons, which can also give rise to intense compact muon beams and neutrino beams that may be portable. High-energy gamma rays can also be efficiently emitted with a bril- liance many orders of magnitude above the brightest X-ray sources by this accelerating process, from both the betatron radiation as well as the dominant radiative-damping dynamics. With the exceptional conditions enabled by this technology we envision a whole scope of new physical phenomena, including: the possibility of laser self-focus in the vacuum, neutron manipulation by the beat of such lasers, zeptosecond spectroscopy of nuclei, etc. Further, we now introduce along with the idea of vacuum as a nonlinear medium, the Schwinger Fiber Accelerator. This is a self-organized vacuum fiber acceleration concept, in which the repeated process of self-focusing and defocusing for the X-ray pulse in vacuum forms a modulated fiber that guides the intense X-rays.

  11. I. ACCELERATION A. Introduction

    E-print Network

    McDonald, Kirk

    I. ACCELERATION A. Introduction Following cooling and initial bunch compression, the beams must be rapidly accelerated. The acceleration needed for a Higgs collider is probably the most conventional part undertaken. A sequence of linacs would work, but would be expensive. Some form of circulating acceleration

  12. Future accelerator technology

    SciTech Connect

    Sessler, A.M.

    1986-05-01

    A general discussion is presented of the acceleration of particles. Upon this foundation is built a categorization scheme into which all accelerators can be placed. Special attention is devoted to accelerators which employ a wake-field mechanism and a restricting theorem is examined. It is shown how the theorem may be circumvented. Comments are made on various acceleration schemes.

  13. Combined first and second order Fermi acceleration at comets

    Microsoft Academic Search

    T. I. Gombosi; K. Lorencz; J. R. Jokipii

    1989-01-01

    Two-dimensional, time-dependent model calculations indicate that an interplay between velocity and spatial diffusion may be responsible for the acceleration of implanted heavy ions in the cometary preshock region. Velocity diffusion (second order Fermi acceleration) accelerates the pickup ions to moderate energies thus creating a seed population for the more efficient diffusive-compressive shock acceleration. Solar wind convection limits the time available

  14. Stealth Acceleration and Modified Gravity

    E-print Network

    Charmousis, Christos; Padilla, Antonio

    2007-01-01

    We show how to construct consistent braneworld models which exhibit late time acceleration. Unlike self-acceleration, which has a de Sitter vacuum state, our models have the standard Minkowski vacuum and accelerate only in the presence of matter, which we dub ``stealth-acceleration''. We use an effective action for the brane which includes an induced gravity term, and allow for an asymmetric set-up. We study the linear stability of flat brane vacua and find the regions of parameter space where the set-up is stable. The 4-dimensional graviton is only quasi-localised in this set-up and as a result gravity is modified at late times. One of the two regions is strongly coupled and the scalar mode is eaten up by an extra symmetry that arises in this limit. Having filtered the well-defined theories we then focus on their cosmology. When the graviton is quasi-localised we find two main examples of acceleration. In each case, we provide an illustrative model and compare it to LambdaCDM.

  15. Stealth Acceleration and Modified Gravity

    E-print Network

    Christos Charmousis; Ruth Gregory; Antonio Padilla

    2007-06-06

    We show how to construct consistent braneworld models which exhibit late time acceleration. Unlike self-acceleration, which has a de Sitter vacuum state, our models have the standard Minkowski vacuum and accelerate only in the presence of matter, which we dub ``stealth-acceleration''. We use an effective action for the brane which includes an induced gravity term, and allow for an asymmetric set-up. We study the linear stability of flat brane vacua and find the regions of parameter space where the set-up is stable. The 4-dimensional graviton is only quasi-localised in this set-up and as a result gravity is modified at late times. One of the two regions is strongly coupled and the scalar mode is eaten up by an extra symmetry that arises in this limit. Having filtered the well-defined theories we then focus on their cosmology. When the graviton is quasi-localised we find two main examples of acceleration. In each case, we provide an illustrative model and compare it to LambdaCDM.

  16. Intrauterine exposures and risk of endometriosis

    Microsoft Academic Search

    Germaine M. Buck Louis; Mary L. Hediger; Josefa B. Pena

    2007-01-01

    BACKGROUND: Intrauterine environmental exposures have been adversely associated with male reproductive health in contrast to limited investigation of such exposures and female reproductive health. METHODS: To address this research gap, a cohort comprising 84 women aged 18-40 years undergoing laparoscopy was recruited prior to surgery and followed through the post-operative period for endometriosis diagnosis. Women were inter- viewed about environmental

  17. Remote handling and accelerators

    NASA Astrophysics Data System (ADS)

    Wilson, M. T.

    The high-current levels of contemporary and proposed accelerator facilities induce radiation levels into components, requiring consideration be given to maintenance techniques that reduce personnel exposure. Typical components involved include beamstops, targets, collimators, windows, and instrumentation that intercepts the direct beam. Also included are beam extraction, injection, splitting, and kicking regions, as well as purposeful spill areas where beam tails are trimmed and neutral particles are deposited. Scattered beam and secondary particles activate components all along a beamline such as vacuum pipes, magnets, and shielding. Maintenance techniques vary from hands-on to TV-viewed operation using state-of-the-art servomanipulators. Bottom- or side-entry casks are used with thimble-type target and diagnostic assemblies. Long-handled tools are operated from behind shadow shields. Swinging shield doors, unstacking block, and horizontally rolling shield roofs are all used to provide access. Common to all techniques is the need to make operations simple and to provide a means of seeing and reaching the area.

  18. Flavoring exposure in food manufacturing.

    PubMed

    Curwin, Brian D; Deddens, Jim A; McKernan, Lauralynn T

    2015-05-01

    Flavorings are substances that alter or enhance the taste of food. Workers in the food-manufacturing industry, where flavorings are added to many products, may be exposed to any number of flavoring compounds. Although thousands of flavoring substances are in use, little is known about most of these in terms of worker health effects, and few have occupational exposure guidelines. Exposure assessment surveys were conducted at nine food production facilities and one flavor manufacturer where a total of 105 area and 74 personal samples were collected for 13 flavoring compounds including five ketones, five aldehydes, and three acids. The majority of the samples were below the limit of detection (LOD) for most compounds. Diacetyl had eight area and four personal samples above the LOD, whereas 2,3-pentanedione had three area samples above the LOD. The detectable values ranged from 25-3124 ppb and 15-172 ppb for diacetyl and 2,3-pentanedione respectively. These values exceed the proposed National Institute for Occupational Safety and Health (NIOSH) recommended exposure limit for these compounds. The aldehydes had the most detectable samples, with each of them having >50% of the samples above the LOD. Acetaldehyde had all but two samples above the LOD, however, these samples were below the OSHA PEL. It appears that in the food-manufacturing facilities surveyed here, exposure to the ketones occurs infrequently, however levels above the proposed NIOSH REL were found. Conversely, aldehyde exposure appears to be ubiquitous. PMID:25052692

  19. Command Shaping for Flexible Systems with Constant Acceleration

    Microsoft Academic Search

    Jon Danielson; Jason Lawrence; William Singhose

    2007-01-01

    Input shaping is an effective means of eliminating vibration in many types of flexible systems. This paper discusses how input shaper performance is affected by systems with a fixed acceleration limit, a common occurrence in many mechanical drive systems. It is shown that some input shapers are not affected by an acceleration limit under certain conditions. A test criteria is

  20. Accelerator mass spectrometry of plutonium isotopes

    Microsoft Academic Search

    L. K. Fifield; R. G. Cresswell; M. L. di Tada; T. R. Ophel; J. P. Day; A. P. Clacher; S. J. King; N. D. Priest

    1996-01-01

    The feasibility of measuring plutonium isotope ratios by accelerator mass spectrometry has been demonstrated. Measurements on a test sample of known composition and on a blank showed that isotope ratios could be determined quantitatively, and that the present limit of detection by AMS is ? 106 atoms of plutonium. For 239Pu, this limit is at least two orders of magnitude

  1. Enhancing proton acceleration by using composite targets

    E-print Network

    Bulanov, S S; Schroeder, C B; Bulanov, S V; Esirkepov, T Zh; Kando, M; Pegoraro, F; Leemans, W P

    2015-01-01

    Efficient laser ion acceleration requires high laser intensities, which can only be obtained by tightly focusing laser radiation. In the radiation pressure acceleration regime, where the tightly focused laser driver leads to the appearance of the fundamental limit for the maximum attainable ion energy, this limit corresponds to the laser pulse group velocity as well as to another limit connected with the transverse expansion of the accelerated foil and consequent onset of the foil transparency. These limits can be relaxed by using composite targets, consisting of a thin foil followed by a near critical density slab. Such targets provide guiding of a laser pulse inside a self-generated channel and background electrons, being snowplowed by the pulse, compensate for the transverse expansion. The use of composite targets results in a significant increase in maximum ion energy, compared to a single foil target case.

  2. Acceleration Environment of the International Space Station

    NASA Technical Reports Server (NTRS)

    McPherson, Kevin; Kelly, Eric; Keller, Jennifer

    2009-01-01

    Measurement of the microgravity acceleration environment on the International Space Station has been accomplished by two accelerometer systems since 2001. The Microgravity Acceleration Measurement System records the quasi-steady microgravity environment, including the influences of aerodynamic drag, vehicle rotation, and venting effects. Measurement of the vibratory/transient regime, comprised of vehicle, crew, and equipment disturbances, has been accomplished by the Space Acceleration Measurement System-II. Until the arrival of the Columbus Orbital Facility and the Japanese Experiment Module, the location of these sensors, and therefore, the measurement of the microgravity acceleration environment, has been limited to within the United States Laboratory. Japanese Aerospace Exploration Agency has developed a vibratory acceleration measurement system called the Microgravity Measurement Apparatus which will be deployed within the Japanese Experiment Module to make distributed measurements of the Japanese Experiment Module's vibratory acceleration environment. Two Space Acceleration Measurement System sensors from the United States Laboratory will be re-deployed to support vibratory acceleration data measurement within the Columbus Orbital Facility. The additional measurement opportunities resulting from the arrival of these new laboratories allows Principal Investigators with facilities located in these International Space Station research laboratories to obtain microgravity acceleration data in support of their sensitive experiments. The Principal Investigator Microgravity Services project, at NASA Glenn Research Center, in Cleveland, Ohio, has supported acceleration measurement systems and the microgravity scientific community through the processing, characterization, distribution, and archival of the microgravity acceleration data obtained from the International Space Station acceleration measurement systems. This paper summarizes the PIMS capabilities available to the International Space Station scientific community, introduces plans for extending microgravity analysis results to the newly arrived scientific laboratories, and provides summary information for known microgravity environment disturbers.

  3. The accelerated testing of cements in brines

    SciTech Connect

    Krumhansl, J.L.

    1993-12-31

    Cementitious materials may be employed in settings where they face prolonged exposure to Mg-rich brines. This study evaluated the possibility of using high temperatures to accelerate brine-cement reaction rates. Class-H cement coupons were tested in Mg-K-Na-C1- SO{sub 4} brines to 100{degrees}C. MgC1{sub 2}-NaC1 solutions were also employed in a test sequence that extended to 200{degrees}C. It was found that accelerated testing could be used successfully to evaluate the compatability of cementitious materials with such brines.

  4. TURBULENT SHEAR ACCELERATION

    SciTech Connect

    Ohira, Yutaka, E-mail: ohira@phys.aoyama.ac.jp [Department of Physics and Mathematics, Aoyama Gakuin University, 5-10-1 Fuchinobe, Sagamihara 252-5258 (Japan)

    2013-04-10

    We consider particle acceleration by large-scale incompressible turbulence with a length scale larger than the particle mean free path. We derive an ensemble-averaged transport equation of energetic charged particles from an extended transport equation that contains the shear acceleration. The ensemble-averaged transport equation describes particle acceleration by incompressible turbulence (turbulent shear acceleration). We find that for Kolmogorov turbulence, the turbulent shear acceleration becomes important on small scales. Moreover, using Monte Carlo simulations, we confirm that the ensemble-averaged transport equation describes the turbulent shear acceleration.

  5. Assessing compliance with 60-hertz magnetic-field exposure guidelines.

    PubMed

    Patterson, Robert; Bracken, T; Alldredge, J

    2005-02-01

    Exposure limits for magnetic fields in the extremely low frequency range (3 to 3000 hertz) have been established by a number of organizations. The limits are generally intended to prevent overstimulation of electrically sensitive tissue and are expressed as ceiling values-levels not to be exceeded even momentarily. Exposures near or above the limits occur around high-current equipment and often have large spatial and temporal variability. The combination of variable exposures and ceiling-value exposure limits means that a practical exposure assessment must be statistically based. Practical guidance for assessing compliance for these exposures is limited. To fill this gap, this work develops a statistically based sampling and analysis methodology for evaluating compliance with magnetic-field exposure guidelines, using 60-hertz exposures in the electric utility industry as a model. The resulting methodology relies on (1) defining a scenario that includes tasks with similar high-field exposures for a group of workers, (2) having appropriate protocols for performing magnetic-field personal exposure measurements or having an exposure data set corresponding to that scenario, (3) assuming that the measured peak field is consistent with the exposure limit, (4) assuming that the peak exposure values follow a lognormal distribution, and (5) collecting sufficient measurements to determine the probability of compliance with a desired degree of statistical confidence. As examples, specific compliance probabilities and their confidence intervals are estimated for electric utility scenarios from available personal exposure measurements. This specific application demonstrates the general methodology and indicates that compliance with existing exposure limits may become an issue for certain tasks. PMID:15764528

  6. Nonparaxial Mathieu and Weber accelerating beams

    E-print Network

    Zhang, Peng; Li, Tongcang; Cannan, Drake; Yin, Xiaobo; Morandotti, Roberto; Chen, Zhigang; Zhang, Xiang

    2012-01-01

    We demonstrate both theoretically and experimentally nonparaxial Mathieu and Weber accelerating beams, generalizing the concept of previously found accelerating beams. We show that such beams bend into large angles along circular, elliptical or parabolic trajectories but still retain nondiffracting and self-healing capabilities. The circular nonparaxial accelerating beams can be considered as a special case of the Mathieu accelerating beams, while an Airy beam is only a special case of the Weber beams at the paraxial limit. Not only generalized nonparaxial accelerating beams open up many possibilities of beam engineering for applications, but the fundamental concept developed here can be applied to other linear wave systems in nature, ranging from electromagnetic and elastic waves to matter waves.

  7. Accelerated large-scale multiple sequence alignment

    PubMed Central

    2011-01-01

    Background Multiple sequence alignment (MSA) is a fundamental analysis method used in bioinformatics and many comparative genomic applications. Prior MSA acceleration attempts with reconfigurable computing have only addressed the first stage of progressive alignment and consequently exhibit performance limitations according to Amdahl's Law. This work is the first known to accelerate the third stage of progressive alignment on reconfigurable hardware. Results We reduce subgroups of aligned sequences into discrete profiles before they are pairwise aligned on the accelerator. Using an FPGA accelerator, an overall speedup of up to 150 has been demonstrated on a large data set when compared to a 2.4 GHz Core2 processor. Conclusions Our parallel algorithm and architecture accelerates large-scale MSA with reconfigurable computing and allows researchers to solve the larger problems that confront biologists today. Program source is available from http://dna.cs.byu.edu/msa/. PMID:22151470

  8. Residual acceleration data analysis for Spacelab missions

    NASA Technical Reports Server (NTRS)

    Rogers, Melissa J. B.; Alexander, J. I. D.

    1992-01-01

    A two-level reduction plan is developed analytically with references to existing experimental data that can be used to develop accelerometer databases for postflight experiment analyses. Residual-acceleration data from previous experiments are studied with attention given to the differences in magnitude among the databases. First-level processing is based on the identification of instances in which tolerable acceleration levels are exceeded so that the time intervals requiring further scrutiny are found. Acceleration time histories including magnitude and orientation are utilized with frequency data for the second level of processing, and the data required for a given time window are reduced by means of data decimation. The identification and processing of limited windows of acceleration data facilitates the characterization of the acceleration environment. These characterizations are of use in the design, location, and utilization of low-gravity laboratory equipment.

  9. Harmonic ratcheting for fast acceleration

    NASA Astrophysics Data System (ADS)

    Cook, N.; Brennan, J. M.; Peggs, S.

    2014-04-01

    A major challenge in the design of rf cavities for the acceleration of medium-energy charged ions is the need to rapidly sweep the radio frequency over a large range. From low-power medical synchrotrons to high-power accelerator driven subcritical reactor systems, and from fixed focus alternating gradient accelerators to rapid cycling synchrotrons, there is a strong need for more efficient, and faster, acceleration of protons and light ions in the semirelativistic range of hundreds of MeV/u. A conventional way to achieve a large, rapid frequency sweep (perhaps over a range of a factor of 6) is to use custom-designed ferrite-loaded cavities. Ferrite rings enable the precise tuning of the resonant frequency of a cavity, through the control of the incremental permeability that is possible by introducing a pseudoconstant azimuthal magnetic field. However, rapid changes over large permeability ranges incur anomalous behavior such as the "Q-loss" and "f-dot" loss phenomena that limit performance while requiring high bias currents. Notwithstanding the incomplete understanding of these phenomena, they can be ameliorated by introducing a "harmonic ratcheting" acceleration scheme in which two or more rf cavities take turns accelerating the beam—one turns on when the other turns off, at different harmonics—so that the radio frequency can be constrained to remain in a smaller range. Harmonic ratcheting also has straightforward performance advantages, depending on the particular parameter set at hand. In some typical cases it is possible to halve the length of the cavities, or to double the effective gap voltage, or to double the repetition rate. This paper discusses and quantifies the advantages of harmonic ratcheting in general. Simulation results for the particular case of a rapid cycling medical synchrotron ratcheting from harmonic number 9 to 2 show that stability and performance criteria are met even when realistic engineering details are taken into consideration.

  10. Linear Accelerator (LINAC)

    MedlinePLUS

    ... equipment? How is safety ensured? What is this equipment used for? A linear accelerator (LINAC) is the ... pg=stereotactic) . top of page How does the equipment work? View larger with caption The linear accelerator ...

  11. Accelerator Technology Division

    NASA Astrophysics Data System (ADS)

    1992-04-01

    In fiscal year (FY) 1991, the Accelerator Technology (AT) division continued fulfilling its mission to pursue accelerator science and technology and to develop new accelerator concepts for application to research, defense, energy, industry, and other areas of national interest. This report discusses the following programs: The Ground Test Accelerator Program; APLE Free-Electron Laser Program; Accelerator Transmutation of Waste; JAERI, OMEGA Project, and Intense Neutron Source for Materials Testing; Advanced Free-Electron Laser Initiative; Superconducting Super Collider; The High-Power Microwave Program; (Phi) Factory Collaboration; Neutral Particle Beam Power System Highlights; Accelerator Physics and Special Projects; Magnetic Optics and Beam Diagnostics; Accelerator Design and Engineering; Radio-Frequency Technology; Free-Electron Laser Technology; Accelerator Controls and Automation; Very High-Power Microwave Sources and Effects; and GTA Installation, Commissioning, and Operations.

  12. Acceleration of Gravity 1

    NSDL National Science Digital Library

    Michael Horton

    2009-05-30

    This lab is a Level 2 inquiry activity that should be taught after students understand acceleration but before they learn the equations for calculating the acceleration of a body dropped from a certain height. After this activity, students should understa

  13. Improved plasma accelerator

    NASA Technical Reports Server (NTRS)

    Cheng, D. Y.

    1971-01-01

    Converging, coaxial accelerator electrode configuration operates in vacuum as plasma gun. Plasma forms by periodic injections of high pressure gas that is ionized by electrical discharges. Deflagration mode of discharge provides acceleration, and converging contours of plasma gun provide focusing.

  14. Accelerating Particles with Plasma

    SciTech Connect

    Litos, Michael; Hogan, Mark

    2014-11-05

    Researchers at SLAC explain how they use plasma wakefields to accelerate bunches of electrons to very high energies over only a short distance. Their experiments offer a possible path for the future of particle accelerators.

  15. Quantum Theory in Accelerated Frames of Reference

    E-print Network

    Bahram Mashhoon

    2005-07-15

    The observational basis of quantum theory in accelerated systems is studied. The extension of Lorentz invariance to accelerated systems via the hypothesis of locality is discussed and the limitations of this hypothesis are pointed out. The nonlocal theory of accelerated observers is briefly described. Moreover, the main observational aspects of Dirac's equation in noninertial frames of reference are presented. The Galilean invariance of nonrelativistic quantum mechanics and the mass superselection rule are examined in the light of the invariance of physical laws under inhomogeneous Lorentz transformations.

  16. Force, mass and acceleration

    Microsoft Academic Search

    Phil Dalrymple; Richard Griffiths

    2005-01-01

    Force, mass and acceleration are everyday words but often used inaccurately. Force is a physical influence, which when applied to an object causes it to accelerate in the direction from which it was applied. Mass is the amount of matter in an object and is expressed in kilograms. Acceleration is the rate of change of velocity of an object in

  17. Multistage induction mass accelerator

    Microsoft Academic Search

    T. J. Burgess; M. Cowan

    1984-01-01

    The present investigation has the objective to discuss considerations which define the design and performance of a multistage, coaxial induction mass accelerator operating at high magnetic energy density. A review is presented of the magnetohydrodynamic computational model required to design, in detail, a high energy density, coaxial, magnetic induction mass accelerator. Attention is given to the derivation of the accelerator

  18. Direction of Acceleration

    NSDL National Science Digital Library

    Mary Spaulding, Clearbrook-Gonvick Public School, Clearbrook Minnesota, based on an original activity from Physics Principles and Problems (1995) page 75.

    In this short lab, students observe the movement of an air bubble in a small level, attached to a toy truck, as it is moved from a stop, to a steady speed and back to a stop. This gives a visual to the concepts positive acceleration, zero acceleration and negative acceleration.

  19. Acceleration: It's Elementary

    ERIC Educational Resources Information Center

    Willis, Mariam

    2012-01-01

    Acceleration is one tool for providing high-ability students the opportunity to learn something new every day. Some people talk about acceleration as taking a student out of step. In actuality, what one is doing is putting a student in step with the right curriculum. Whole-grade acceleration, also called grade-skipping, usually happens between…

  20. Angular Acceleration without Torque?

    ERIC Educational Resources Information Center

    Kaufman, Richard D.

    2012-01-01

    Hardly. Just as Robert Johns qualitatively describes angular acceleration by an internal force in his article "Acceleration Without Force?" here we will extend the discussion to consider angular acceleration by an internal torque. As we will see, this internal torque is due to an internal force acting at a distance from an instantaneous center.

  1. Prior Trauma Exposure for Youth in Treatment Foster Care

    ERIC Educational Resources Information Center

    Dorsey, Shannon; Burns, Barbara J.; Southerland, Dannia G.; Cox, Julia Revillion; Wagner, H. Ryan; Farmer, Elizabeth M. Z.

    2012-01-01

    Very little research has focused on rates of trauma exposure for youth in treatment foster care (TFC). Available research has utilized record review for assessing exposure, which presents limitations for the range of trauma types examined, as records are predominantly focused on abuse and neglect. The current study examines exposure rates and…

  2. Environmental tobacco smoke exposure in women with lung cancer

    Microsoft Academic Search

    M de Andrade; J. O Ebbert; J. A Wampfler; D. L Miller; R. S Marks; G. A Croghan; A Jatoi; E. E Finke; T. A Sellers; P Yang

    2004-01-01

    Background: Investigations on environmental tobacco smoke (ETS) exposure that include source intensity, childhood exposure, and association with histologic subtypes among never smoking lung cancer cases are limited. We report the patterns of ETS exposure history in a clinical cohort of women with newly diagnosed lung cancer. Methods: From 1997 to 2001, 810 women with lung cancer were interviewed to obtain

  3. Personal exposure to particles in Banská Bystrica, Slovakia

    Microsoft Academic Search

    MICHAEL BRAUER; FRANTIŠKA HRUBÁ; EVA MIHALÍKOVÁ; ELEONÓRA FABIÁNOVÁ; PETER MISKOVIC; ALENA PLZIKOVÁ; MARIE LENDACKÁ; JOHN VANDENBERG; ALISON CULLEN

    2000-01-01

    Epidemiological studies have associated adverse health impacts with ambient concentrations of particulate matter (PM), though these studies have been limited in their characterization of personal exposure to PM. An exposure study of healthy nonsmoking adults and children was conducted in Banska Bystrica, Slovakia, to characterize the range of personal exposures to air pollutants and to determine the influence of occupation,

  4. Solvent exposures in screen printing shops.

    PubMed

    Horstman, S W; Browning, S R; Szeluga, R; Burzycki, J; Stebbins, A

    2001-01-01

    A comprehensive description of working conditions, exposure patterns for organic solvents, and related health symptoms among workers in ten small screen printing companies located in Seattle, Washington, is presented. Sampling methods included continuous area monitoring, grab sampling, personal sampling, and time study observation. A total of 27 workers were observed and monitored for solvent exposure. Short-term peak exposures were characterized in terms of magnitude, duration and repetition, and their contribution to time weighted average (TWA) exposures were evaluated. A health questionnaire addressing the symptoms potentially attributable to solvents was used to investigate the possible health effects from exposure. Significant differences in the prevalence of headaches, dizziness, intoxication, and dry skin (p < 0.01) were reported among workers who had some solvent exposure compared with the referent group that was not exposed. Exposed workers were also more likely to report fatigue, loss of strength in the arms and hands, difficulty concentrating, sore throat, and a low alcohol tolerance. The study documented highly variable levels of solvent exposures. Screen printing workers in different companies, while performing the same basic tasks, had time weighted average (TWA) exposures ranging from 2% to 100% of the recommended threshold limit value (TLV) for mixtures. Continuous monitoring indicated that high short-term exposures are responsible for the bulk of TWA exposures. Grab samples and continuous monitoring verified that recommended Short Term Exposure Limits (STEL) for individual solvents may be exceeded on a routine basis. Frequent skin contact with solvents was also observed. Health problems in this industry and other small industries using organic solvents may result from these complex patterns of exposure. PMID:11759907

  5. 10 CFR 835.207 - Occupational dose limits for minors.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...2012-01-01 2012-01-01 false Occupational dose limits for minors. 835.207 Section 835...and External Exposure § 835.207 Occupational dose limits for minors. The dose limits for minors occupationally exposed to...

  6. 10 CFR 835.207 - Occupational dose limits for minors.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ...2010-01-01 2010-01-01 false Occupational dose limits for minors. 835.207 Section 835...and External Exposure § 835.207 Occupational dose limits for minors. The dose limits for minors occupationally exposed to...

  7. 10 CFR 835.207 - Occupational dose limits for minors.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...2014-01-01 2014-01-01 false Occupational dose limits for minors. 835.207 Section 835...and External Exposure § 835.207 Occupational dose limits for minors. The dose limits for minors occupationally exposed to...

  8. 10 CFR 835.207 - Occupational dose limits for minors.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ...2013-01-01 2013-01-01 false Occupational dose limits for minors. 835.207 Section 835...and External Exposure § 835.207 Occupational dose limits for minors. The dose limits for minors occupationally exposed to...

  9. 10 CFR 835.207 - Occupational dose limits for minors.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...2011-01-01 2011-01-01 false Occupational dose limits for minors. 835.207 Section 835...and External Exposure § 835.207 Occupational dose limits for minors. The dose limits for minors occupationally exposed to...

  10. Exposure assessment in the occupational setting.

    PubMed

    Stewart, P; Stenzel, M

    2000-05-01

    Exposure assessment, the first step in risk assessment, has traditionally been performed for a variety of purposes. These include compliance determinations; management of specific programs that are implemented by comparison with an occupational exposure limit (such as medical surveillance, training, and respiratory protection programs); task/source investigations for determination of exposure control strategies; epidemiologic studies; worker compensation/toxic tort cases; health complaint or problem investigations; risk assessment and management; and evaluation of future changes in the workplace (e.g., introduction of a new chemical). Each purpose requires slightly different approaches, but there are also many similarities. The goal of this paper is to identify a general approach to assessing exposures that can be used for all purposes with only slight modifications. Five components of exposure assessments are identified: collection of data, identification of the hazard, selection of exposure metrics, definition of exposure groups and estimation of the exposures. The characteristics of these components for each type of assessment are discussed. From this review, it is clear that there is substantial overlap across the types of assessment. A single exposure assessment program is suggested that encompasses all the needs of these assessments and incorporates assessment of exposures for an entire workforce at a site at minimal cost by using prediction models and validation with measurements. PMID:10808266

  11. Accelerated Aging Tests of Bubble Devices

    Microsoft Academic Search

    W. J. Tabor; R. Zappulla; A. W. Anderson

    1980-01-01

    Bubble devices are being manufactured by Western Electric Company, as well as a number of other companies, and have been used in the Bell System since 1978. Accelerated aging tests which include temperature-humidity-voltage bias exposure, temperature cycling, vibration and shock, and electromigration degradation of the Al-4.5% Cu conductors have been performed since the earliest bubble device was constructed. Many of

  12. Development of Accelerated Net Nitrate Uptake 1

    PubMed Central

    MacKown, Charles T.; McClure, Peter R.

    1988-01-01

    Upon initial nitrate exposure, net nitrate uptake rates in roots of a wide variety of plants accelerate within 6 to 8 hours to substantially greater rates. Effects of solution nitrate concentrations and short pulses of nitrate (?1 hour) upon `nitrate-induced' acceleration of nitrate uptake in maize (Zea mays L.) were determined. Root cultures of dark-grown seedlings, grown without nitrate, were exposed to 250 micromolar nitrate for 0.25 to 1 hour or to various solution nitrate concentrations (10-250 micromolar) for 1 hour before returning them to a nitrate-free solution. Net nitrate uptake rates were assayed at various periods following nitrate exposure and compared to rates of roots grown either in the absence of nitrate (CaSO4-grown) or with continuous nitrate for at least 20 hours. Three hours after initial nitrate exposure, nitrate pulse treatments increased nitrate uptake rates three- to four-fold compared to the rates of CaSO4-grown roots. When cycloheximide (5 micrograms per milliliter) was included during a 1-hour pulse with 250 micromolar nitrate, development of the accelerated nitrate uptake state was delayed. Otherwise, nitrate uptake rates reached maximum values within 6 hours before declining. Maximum rates, however, were significantly less than those of roots exposed continuously for 20, 32, or 44 hours. Pulsing for only 0.25 hour with 250 micromolar nitrate and for 1 hour with 10 micromolar caused acceleration of nitrate uptake, but the rates attained were either less than or not sustained for a duration comparable to those of roots pulsed for 1 hour with 250 micromolar nitrate. These results indicate that substantial development of the nitrate-induced accelerated nitrate uptake state can be achieved by small endogenous accumulations of nitrate, which appear to moderate the activity or level of root nitrate uptake. PMID:16666094

  13. Turbulent Particle Acceleration in the Diffuse Cluster Plasma

    E-print Network

    J. A. Eilek; J. C. Weatherall

    1999-06-30

    In situ particle acceleration is probably occuring in cluster radio haloes. This is suggested by the uniformity and extent of the haloes, given that spatial diffusion is slow and that radiative losses limit particle lifetimes. Stochastic acceleration by plasma turbulence is the most likely mechanism. Alfven wave turbulence has been suggested as the means of acceleration, but it is too slow to be important in the cluster environment. We propose, instead, that acceleration occurs via strong lower-hybrid wave turbulence. We find that particle acceleration will be effective in clusters if only a small fraction of the cluster energy density is in this form.

  14. Laser driven electron acceleration in vacuum, gases and plasmas

    SciTech Connect

    Sprangle, P.; Esarey, E.; Krall, J.

    1996-04-19

    This paper discusses some of the important issues pertaining to laser acceleration in vacuum, neutral gases and plasmas. The limitations of laser vacuum acceleration as they relate to electron slippage, laser diffraction, material damage and electron aperture effects, are discussed. An inverse Cherenkov laser acceleration configuration is presented in which a laser beam is self guided in a partially ionized gas. Optical self guiding is the result of a balance between the nonlinear self focusing properties of neutral gases and the diffraction effects of ionization. The stability of self guided beams is analyzed and discussed. In addition, aspects of the laser wakefield accelerator are presented and laser driven accelerator experiments are briefly discussed.

  15. Accelerated corrosion of stainless steel in thiocyanate-containing solutions

    SciTech Connect

    Pistorius, P Chris; Li, Wen

    2012-09-19

    It is known that reduced sulfur compounds (such as thiocyanate and thiosulfate) can accelerate active corrosion of austenitic stainless steel in acid solutions, but before we started this project the mechanism of acceleration was largely unclear. This work combined electrochemical measurements and analysis using scanning electron microscopy (SEM) and X-ray photo-electron spectroscopy (XPS), which provided a comprehensive understanding of the catalytic effect of reduced sulfur species on the active corrosion of stainless steel. Both the behavior of the pure elements and the steel were studied and the work focused on the interaction between the pure elements of the steel, which is the least understood area. Upon completion of this work, several aspects are now much clearer. The main results from this work can be summarized as follows: The presence of low concentrations (around 0.1 mM) of thiocyanate or tetrathionate in dilute sulfuric acid greatly accelerates the anodic dissolution of chromium and nickel, but has an even stronger effect on stainless steels (iron-chromium-nickel alloys). Electrochemical measurements and surface analyses are in agreement with the suggestion that accelerated dissolution really results from suppressed passivation. Even well below the passivation potential, the electrochemical signature of passivation is evident in the electrode impedance; the electrode impedance shows clearly that this pre-passivation is suppressed in the presence of thiocyanate. For the stainless steels, remarkable changes in the morphology of the corroded metal surface and in the surface concentration of chromium support the suggestion that pre-passivation of stainless steels is suppressed because dissolution of chromium is accelerated. Surface analysis confirmed that adsorbed sulfur / sulfide forms on the metal surfaces upon exposure to solutions containing thiocyanate or thiosulfate. For pure nickel, and steels containing nickel (and residual copper), bulk sulfide (visible as a black corrosion product) forms during anodic dissolution. The sulfide is electronically conductive, and gives an increase of several orders of magnitude in the electrode capacitance; the sulfide also causes anodic activation to persist after the pure metals and steels were removed from the thiocyanate-containing electrolyte and transferred to a thiocyanate-free electrolyte. The main practical implications of this work are that low concentrations of reduced sulfur compounds strongly affect anodic dissolution of stainless steels, and that selecting steels with elevated concentrations of chromium, nickel or molybdenum would serve to limit the anodic dissolution rate in the presence of reduced sulfur compounds.

  16. Medium wave exposure characterisation using exposure quotients.

    PubMed

    Paniagua, Jesús M; Rufo, Montaña; Jiménez, Antonio; Antolín, Alicia; Pinar, Iván

    2010-06-01

    One of the aspects considered in the International Commission on Non-Ionizing Radiation Protection guidelines is that, in situations of simultaneous exposure to fields of different frequencies, exposure quotients for thermal and electrical stimulation effects should be examined. The aim of the present work was to analyse the electromagnetic radiation levels and exposure quotients for exposure to multiple-frequency sources in the vicinity of medium wave radio broadcasting antennas. The measurements were made with a spectrum analyser and a monopole antenna. Kriging interpolation was used to prepare contour maps and to estimate the levels in the towns and villages of the zone. The results showed that the exposure quotient criterion based on electrical stimulation effects to be more stringent than those based on thermal effects or power density levels. Improvement of dosimetry evaluations requires the spectral components of the radiation to be quantified, followed by application of the criteria for exposure to multiple-frequency sources. PMID:20159912

  17. Compact Plasma Accelerator

    NASA Technical Reports Server (NTRS)

    Foster, John E.

    2004-01-01

    A plasma accelerator has been conceived for both material-processing and spacecraft-propulsion applications. This accelerator generates and accelerates ions within a very small volume. Because of its compactness, this accelerator could be nearly ideal for primary or station-keeping propulsion for spacecraft having masses between 1 and 20 kg. Because this accelerator is designed to generate beams of ions having energies between 50 and 200 eV, it could also be used for surface modification or activation of thin films.

  18. Entanglement of Accelerating Particles

    E-print Network

    W. L. Ku; M. -C. Chu

    2007-09-03

    We study how the entanglement of a maximally entangled pair of particles is affected when one or both of the pair are uniformly accelerated, while the detector remains in an inertial frame. We find that the entanglement is unchanged if all degrees of freedom are considered. However, particle pairs are produced, and the entanglements of different bipartite systems may change with the acceleration. In particular, the entanglement between accelerating fermions is transferred preferentially to the produced antiparticles when the acceleration is large, and the entanglement transfer is complete when the acceleration approaches infinity. However, for scalar particles, no entanglement transfer to the antiparticles is observed.

  19. 10 CFR 20.1206 - Planned special exposures.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...PROTECTION AGAINST RADIATION Occupational Dose Limits § 20.1206 Planned special exposures...licensee may authorize an adult worker to receive doses in addition to and accounted for separately from the doses received under the limits specified...

  20. 10 CFR 20.1206 - Planned special exposures.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...PROTECTION AGAINST RADIATION Occupational Dose Limits § 20.1206 Planned special exposures...licensee may authorize an adult worker to receive doses in addition to and accounted for separately from the doses received under the limits specified...

  1. 10 CFR 20.1206 - Planned special exposures.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ...PROTECTION AGAINST RADIATION Occupational Dose Limits § 20.1206 Planned special exposures...licensee may authorize an adult worker to receive doses in addition to and accounted for separately from the doses received under the limits specified...

  2. 10 CFR 20.1204 - Determination of internal exposure.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ...PROTECTION AGAINST RADIATION Occupational Dose Limits § 20.1204 Determination of internal exposure. (a) For purposes of assessing dose used to determine compliance with occupational dose equivalent limits, the licensee shall,...

  3. 10 CFR 20.1206 - Planned special exposures.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...PROTECTION AGAINST RADIATION Occupational Dose Limits § 20.1206 Planned special exposures...licensee may authorize an adult worker to receive doses in addition to and accounted for separately from the doses received under the limits specified...

  4. 10 CFR 20.1204 - Determination of internal exposure.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ...PROTECTION AGAINST RADIATION Occupational Dose Limits § 20.1204 Determination of internal exposure. (a) For purposes of assessing dose used to determine compliance with occupational dose equivalent limits, the licensee shall,...

  5. 10 CFR 20.1204 - Determination of internal exposure.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...PROTECTION AGAINST RADIATION Occupational Dose Limits § 20.1204 Determination of internal exposure. (a) For purposes of assessing dose used to determine compliance with occupational dose equivalent limits, the licensee shall,...

  6. 10 CFR 20.1206 - Planned special exposures.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ...PROTECTION AGAINST RADIATION Occupational Dose Limits § 20.1206 Planned special exposures...licensee may authorize an adult worker to receive doses in addition to and accounted for separately from the doses received under the limits specified...

  7. 10 CFR 20.1204 - Determination of internal exposure.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...PROTECTION AGAINST RADIATION Occupational Dose Limits § 20.1204 Determination of internal exposure. (a) For purposes of assessing dose used to determine compliance with occupational dose equivalent limits, the licensee shall,...

  8. 10 CFR 20.1204 - Determination of internal exposure.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...PROTECTION AGAINST RADIATION Occupational Dose Limits § 20.1204 Determination of internal exposure. (a) For purposes of assessing dose used to determine compliance with occupational dose equivalent limits, the licensee shall,...

  9. Occupational exposure and malignant lymphoma.

    PubMed

    Persson, B

    1996-01-01

    The incidence of malignant lymphoma, especially non-Hodgkin's lymphoma has increased over the last few decades. This statement is true despite the fact that methods for diagnosing malignant lymphoma have changed and misclassification has become a problem. The present review is mainly concerned with occupational aspects of malignant lymphoma. Several subsequent studies have dealt with malignant lymphoma among woodworkers and pulp and paper mill workers pointing to increased risks. Exposure to phenoxy herbicides have provided reasonable evidence to be connected with an increased risk of non-Hodgkin's lymphoma, whereas there is limited information regarding Hodgkin's disease. The relationship between solvent exposure and malignant lymphoma has been observed in a great number of studies. It is, however, still hard to identify specific solvent compounds responsible for the increased risk. Other occupational exposures i.e. wood preservatives, welding, asbestos, hair dyes and exposure to animal viruses among meatworkers and veterinarians have also been studied in relation to malignant lymphoma. This review shows that occupational factors, especially exposure to solvents and phenoxy herbicides and also to wood, play a role in the epidemiology of malignant lymphoma. PMID:9117190

  10. Spacecraft Water Exposure Guidelines (SWEGs)

    NASA Technical Reports Server (NTRS)

    James, John T.

    2008-01-01

    As the protection of crew health is a primary focus of the National Aeronautics and Space Administration, the Space and Life Sciences Directorate (SLSD) is vigilant in setting potable water limits for spaceflight that are health protective. Additional it is important that exposure limits not be set so stringently that water purification systems are unnecessarily over designed. With these considerations in mind, NASA has partnered with the National Research Council on Toxicology (NRCCOT) to develop spacecraft water exposure guidelines (SWEGs) for application in spaceflight systems. Based on documented guidance (NRC, 2000) NASA has established 28 SWEGs for chemical components that are particularly relevant to water systems on the International Space Station, the Shuttle and looking forward to Constellation.

  11. Challenges in Linear Accelerator Radiotherapy for Chordomas and Chondrosarcomas of the Skull Base: Focus on Complications

    SciTech Connect

    Hauptman, Jason S., E-mail: jhauptman@mednet.ucla.edu [Division of Stereotactic and Functional Neurosurgery, Department of Neurosurgery, University of California, Los Angeles, David Geffen School of Medicine, Los Angeles, CA (United States); Barkhoudarian, Garni; Safaee, Michael; Gorgulho, Alessandra [Division of Stereotactic and Functional Neurosurgery, Department of Neurosurgery, University of California, Los Angeles, David Geffen School of Medicine, Los Angeles, CA (United States); Tenn, Steven; Agazaryan, Nzhde; Selch, Michael [Department of Radiation Oncology, University of California, Los Angeles, David Geffen School of Medicine, Los Angeles, CA (United States); De Salles, Antonio A.F. [Division of Stereotactic and Functional Neurosurgery, Department of Neurosurgery, University of California, Los Angeles, David Geffen School of Medicine, Los Angeles, CA (United States); Department of Radiation Oncology, University of California, Los Angeles, David Geffen School of Medicine, Los Angeles, CA (United States)

    2012-06-01

    Purpose: Intracranial chordomas and chondrosarcomas are histologically low-grade, locally invasive tumors that infiltrate the skull base. Currently, consensus therapy includes surgical resection and adjuvant radiotherapy. Radiation delivery is typically limited by the proximity of these tumors to critical skull base structures. Methods: This is a retrospective review of 13 cases of chordomas and 2 cases of chondroid chondrosarcomas of the skull based treated with linear accelerator stereotactic radiotherapy (SRT, n = 10) or stereotactic radiosurgery (SRS, n = 5). The average time to the most recent follow-up visit was 4.5 years. The tumor characteristics, treatment details, and outcomes were recorded. Each radiation plan was reviewed, and the dosage received by the brainstem, optic apparatus, and pituitary was calculated. Results: Of the 10 patients treated with SRT, 6 were found to have unchanged or decreased tumor size as determined from radiographic follow-up. Of the 5 patients treated with SRS, 3 were found to have stable or unchanged tumors at follow-up. The complications included 1 SRT patient who developed endocrinopathy, 2 patients (1 treated with SRS and the other with SRT), who developed cranial neuropathy, and 1 SRS patient who developed visual deficits. Additionally, 1 patient who received both SRS and SRT within 2 years for recurrence experienced transient medial temporal lobe radiation changes that resolved. Conclusions: Where proton beam therapy is unavailable, linear accelerator-based SRT or radiosurgery remains a safe option for adjuvant therapy of chordomas and chondrosarcomas of the skull base. The exposure of the optic apparatus, pituitary stalk, and brainstem must be considered during planning to minimize complications. If the optic apparatus is included in the 80% isodose line, it might be best to fractionate therapy. Exposure of the pituitary stalk should be kept to <30 Gy to minimize endocrine dysfunction. Brainstem exposure should be limited to <60 Gy in fractions.

  12. Accelerations in Flight

    NASA Technical Reports Server (NTRS)

    Doolittle, J H

    1925-01-01

    This work on accelerometry was done at McCook Field for the purpose of continuing the work done by other investigators and obtaining the accelerations which occur when a high-speed pursuit airplane is subjected to the more common maneuvers. The accelerations obtained in suddenly pulling out of a dive with well-balanced elevators are shown to be within 3 or 4 per cent of the theoretically possible accelerations. The maximum acceleration which a pilot can withstand depends upon the length of time the acceleration is continued. It is shown that he experiences no difficulty under the instantaneous accelerations as high as 7.8 G., but when under accelerations in excess of 4.5 G., continued for several seconds, he quickly loses his faculties.

  13. High brightness electron accelerator

    DOEpatents

    Sheffield, Richard L. (Los Alamos, NM); Carlsten, Bruce E. (Los Alamos, NM); Young, Lloyd M. (Los Alamos, NM)

    1994-01-01

    A compact high brightness linear accelerator is provided for use, e.g., in a free electron laser. The accelerator has a first plurality of acclerating cavities having end walls with four coupling slots for accelerating electrons to high velocities in the absence of quadrupole fields. A second plurality of cavities receives the high velocity electrons for further acceleration, where each of the second cavities has end walls with two coupling slots for acceleration in the absence of dipole fields. The accelerator also includes a first cavity with an extended length to provide for phase matching the electron beam along the accelerating cavities. A solenoid is provided about the photocathode that emits the electons, where the solenoid is configured to provide a substantially uniform magnetic field over the photocathode surface to minimize emittance of the electons as the electrons enter the first cavity.

  14. DEMONSTRATION OF HUMAN EXPOSURE TOOLS

    EPA Science Inventory

    The Human Exposure and Atmospheric Sciences Division (HEASD) of the National Exposure Research Laboratory (NERL) conducts research on exposure measurements, human activity patterns, exposure and dose models, and cumulative exposures critical for the Agency to make scientificall...

  15. Ionization and pulse lethargy effects in inverse Cherenkov accelerators

    SciTech Connect

    Sprangle, P.; Hubbard, R.F., [Beam Physics Branch, Plasma Physics Division, Naval Research Laboratory, Washington, D.C. 20375 (United States); Hafizi, B., [Icarus Research, Inc., P.O. Box 30780, Bethesda, Maryland 20824-0780 (United States)] [Icarus Research, Inc., P.O. Box 30780, Bethesda, Maryland 20824-0780 (United States)

    1997-05-01

    Ionization processes limit the accelerating gradient and place an upper limit on the pulse duration of the electromagnetic driver in the inverse Cherenkov accelerator (ICA). Group velocity slippage, i.e., pulse lethargy, on the other hand, imposes a lower limit on the pulse duration. These limits are obtained for two ICA configurations in which the electromagnetic driver (e.g., laser or millimeter wave source) is propagated in a waveguide that is (i) lined with a dielectric material or (ii) filled with a neutral gas. In either configuration the electromagnetic driving field is guided and has an axial electric field with phase velocity equal to the speed of light in vacuum, c. The intensity of the driver in the ICA, and therefore the acceleration gradient, is limited by tunneling and collisional ionization effects. Partial ionization of the dielectric liner or gas can lead to significant modification of the dispersive properties of the waveguide, altering the phase velocity of the accelerating field and causing particle slippage, thus disrupting the acceleration process. An additional limitation on the pulse duration is imposed since the group velocity of the driving pulse is less than c and the pulse slips behind the accelerated electrons. Hence for sufficiently short pulses the electrons outrun the pulse, terminating the acceleration. Limitations on the driver pulse duration and accelerating gradient, due to ionization and pulse lethargy, are estimated for the two ICA configurations. Maximum accelerating gradients and pulse durations are presented for a 10 {mu}m, 1 mm, and 1 cm wavelength electromagnetic driver. The combination of ionization and pulse lethargy effects impose severe limitations on the maximum energy gain in inverse Cherenkov accelerators. {copyright} {ital 1997} {ital The American Physical Society}

  16. Stochastic relativistic shock-surfing acceleration

    E-print Network

    Benjamin D. G. Chandran; Naoki Bessho

    2004-08-03

    We study relativistic particles undergoing surfing acceleration at perpendicular shocks. We assume that particles undergo diffusion in the component of momentum perpendicular to the shock plane due to moderate fluctuations in the shock electric and magnetic fields. We show that dN/dE, the number of surfing-accelerated particles per unit energy, attains a power-law form, dN/dE \\propto E^{-b}. We calculate b analytically in the limit of weak momentum diffusion, and use Monte Carlo test-particle calculations to evaluate b in the weak, moderate, and strong momentum-diffusion limits.

  17. Critical Acceleration and Quantum Vacuum

    E-print Network

    Johann Rafelski; Lance Labun

    2012-04-22

    Little is known about the physics frontier of strong acceleration; both classical and quantum physics need further development in order to be able to address this newly accessible area of physics. In this lecture we discuss what strong acceleration means and possible experiments using electron-laser collisions and, data available from ultra-relativistic heavy ion collisions. We review the foundations of the current understanding of charged particle dynamics in presence of critical forces and discuss the radiation reaction inconsistency in electromagnetic theory and the apparent relation with quantum physics and strong field particle production phenomena. The role of the quantum vacuum as an inertial reference frame is emphasized, as well as the absence of such a `Machian' reference frame in the conventional classical limit of quantum field theory.

  18. Accelerated leach test development program

    SciTech Connect

    Fuhrmann, M.; Pietrzak, R.F.; Heiser, J.; Franz, E.M.; Colombo, P.

    1990-11-01

    In FY 1989, a draft accelerated leach test for solidified waste was written. Combined test conditions that accelerate leaching were validated through experimental and modeling efforts. A computer program was developed that calculates test results and models leaching mechanisms. This program allows the user to determine if diffusion controls leaching and, if this is the case, to make projections of releases. Leaching mechanisms other than diffusion (diffusion plus source term partitioning and solubility limited leaching) are included in the program is indicators of other processes that may control leaching. Leach test data are presented and modeling results are discussed for laboratory scale waste forms composed of portland cement containing sodium sulfate salt, portland cement containing incinerator ash, and vinyl ester-styrene containing sodium sulfate. 16 refs., 38 figs., 5 tabs.

  19. Head Impact Exposure in Collegiate Football Players

    PubMed Central

    Crisco, Joseph J.; Wilcox, Bethany J.; Beckwith, Jonathan G.; Chu, Jeffrey J.; Duhaime, Ann-Christine; Rowson, Steve; Duma, Stefan M.; Maerlender, Arthur C.; McAllister, Thomas W.; Greenwald, Richard M.

    2011-01-01

    In American football, impacts to the helmet and the resulting head accelerations are the primary cause of concussion injury and potentially chronic brain injury. The purpose of this study was to quantify exposures to impacts to the head (frequency, location and magnitude) for individual collegiate football players and to investigate differences in head impact exposure by player position. A total of 314 players were enrolled at three institutions and 286,636 head impacts were recorded over three seasons. The 95th percentile peak linear and rotational acceleration and HITsp (a composite severity measure) were 62.7g, 4378 rad/s2, and 32.6, respectively. These exposure measures as well as the frequency of impacts varied significantly by player position and by helmet impact location. Running backs (RB) and quarter backs (QB) received the greatest magnitude head impacts, while defensive line (DL), offensive line (OL) and line backers (LB) received the most frequent head impacts (more than twice as many than any other position). Impacts to the top of the helmet had the lowest peak rotational acceleration (2387 rad/s2), but the greatest peak linear acceleration (72.4 g), and were the least frequent of all locations (13.7%) among all positions. OL and QB had the highest (49.2%) and the lowest (23%.7%) frequency, respectively, of front impacts. QB received the greatest magnitude (70.8g and 5428 rad/s2) and the most frequent (44% and 38.9%) impacts to the back of the helmet. This study quantified head impact exposure in collegiate football, providing data that is critical to advancing the understanding of the biomechanics of concussive injuries and sub-concussive head impacts. PMID:21872862

  20. Diffusive Compression Acceleration of Energetic Particles with an Application to Shock Acceleration near Injection Energies

    NASA Astrophysics Data System (ADS)

    Zhang, Ming

    2007-08-01

    The behavior of energetic charged particles accelerated by a continuous plasma compression profile is explored in the framework of diffusion. At high enough energies, the accelerated particles have a power-law spectrum with a slope generally steeper than a shock spectrum with the same compression ratio. The spectral slope depends on the ratio of the diffusion coefficient to the product of the upstream plasma speed and the thickness of the compression region. In the limit of large diffusion, the spectrum becomes identical to that of diffusive shock acceleration, and when diffusion is small enough, it is consistent with adiabatic acceleration by a single passage through the compression region. For particles with a diffusion coefficient that increases with energy, the spectral shape of the accelerated particles changes from an adiabatic compressional acceleration spectrum at low energies to a shock spectrum at high energies. The flux level of the high-energy asymptotic shock spectrum is generally lower than that from a calculation with diffusive shock acceleration. When this result is applied to particles accelerated to high energies by shocks, the particle injection energy and efficiency can be determined once the energy dependence of the diffusion coefficient and the spectrum of the source particles are known. A threshold criterion for particle injection to shock acceleration can be set from the injection efficiency calculation.

  1. BRIDGE LIFECYCLE ANALYSIS AND DURABILITY EVALUATION USING ACCELERATED EXPOSURE TEST

    Microsoft Academic Search

    Yoshito Itoh; Tetsuya Kitagawa

    In recent years, new types of bridges have continued to appear with the development of construction technologies and functional requirements in Japan. However, lifecycle analysis was rare to be used to evaluate such new types of civil infrastructures. In this research, the general lifecycle assessment methodology is modified for evaluating the new types of civil infrastructures. Furthermore, this modified methodology

  2. Exposure to stallion accelerates the onset of mares' cyclicity.

    PubMed

    Wespi, B; Sieme, H; Wedekind, C; Burger, D

    2014-07-15

    Horses (Equus caballus) belong to the group of seasonally polyestrous mammals. Estrous cycles typically start with increasing daylight length after winter, but mares can differ greatly in the timing of onset of regular estrus cycles. Here, we test whether spatial proximity to a stallion also plays a role. Twenty-two anestrous mares were either exposed to one of two stallions (without direct physical contact) or not exposed (controls) under experimental conditions during two consecutive springs (February to April). Ovarian activity was monitored via transrectal ultrasound and stallion's direct contact time with each mare was determined three times per week for one hour each. We found that mares exposed to a stallion ovulated earlier and more often during the observational period than mares that were not exposed to stallions. Neither stallion identity nor direct contact time, mare age, body condition, size of her largest follicle at the onset of the experiment, or parasite burden significantly affected the onset of cyclicity. In conclusion, the timing of estrous cycles and cycle frequency, i.e., crucial aspects of female reproductive strategy, strongly depend on how the mares perceive their social environment. Exposing mares to the proximity of a stallion can therefore be an alternative to, for example, light programs or elaborated hormonal therapies to start the breeding season earlier and increase the number of estrous cycles in horses. PMID:24815602

  3. EXOTIC MAGNETS FOR ACCELERATORS.

    SciTech Connect

    WANDERER, P.

    2005-09-18

    Over the last few years, several novel magnet designs have been introduced to meet the requirements of new, high performance accelerators and beam lines. For example, the FAIR project at GSI requires superconducting magnets ramped at high rates ({approx} 4 T/s) in order to achieve the design intensity. Magnets for the RIA and FAIR projects and for the next generation of LHC interaction regions will need to withstand high doses of radiation. Helical magnets are required to maintain and control the polarization of high energy protons at RHIC. In other cases, novel magnets have been designed in response to limited budgets and space. For example, it is planned to use combined function superconducting magnets for the 50 GeV proton transport line at J-PARC to satisfy both budget and performance requirements. Novel coil winding methods have been developed for short, large aperture magnets such as those used in the insertion region upgrade at BEPC. This paper will highlight the novel features of these exotic magnets.

  4. Photonic Crystal Laser-Driven Accelerator Structures

    SciTech Connect

    Cowan, Benjamin M.

    2007-08-22

    Laser-driven acceleration holds great promise for significantly improving accelerating gradient. However, scaling the conventional process of structure-based acceleration in vacuum down to optical wavelengths requires a substantially different kind of structure. We require an optical waveguide that (1) is constructed out of dielectric materials, (2) has transverse size on the order of a wavelength, and (3) supports a mode with speed-of-light phase velocity in vacuum. Photonic crystals---structures whose electromagnetic properties are spatially periodic---can meet these requirements. We discuss simulated photonic crystal accelerator structures and describe their properties. We begin with a class of two-dimensional structures which serves to illustrate the design considerations and trade-offs involved. We then present a three-dimensional structure, and describe its performance in terms of accelerating gradient and efficiency. We discuss particle beam dynamics in this structure, demonstrating a method for keeping a beam confined to the waveguide. We also discuss material and fabrication considerations. Since accelerating gradient is limited by optical damage to the structure, the damage threshold of the dielectric is a critical parameter. We experimentally measure the damage threshold of silicon for picosecond pulses in the infrared, and determine that our structure is capable of sustaining an accelerating gradient of 300 MV/m at 1550 nm. Finally, we discuss possibilities for manufacturing these structures using common microfabrication techniques.

  5. Leaky Fermi accelerators

    NASA Astrophysics Data System (ADS)

    Shah, Kushal; Gelfreich, Vassili; Rom-Kedar, Vered; Turaev, Dmitry

    2015-06-01

    A Fermi accelerator is a billiard with oscillating walls. A leaky accelerator interacts with an environment of an ideal gas at equilibrium by exchange of particles through a small hole on its boundary. Such interaction may heat the gas: we estimate the net energy flow through the hole under the assumption that the particles inside the billiard do not collide with each other and remain in the accelerator for a sufficiently long time. The heat production is found to depend strongly on the type of Fermi accelerator. An ergodic accelerator, i.e., one that has a single ergodic component, produces a weaker energy flow than a multicomponent accelerator. Specifically, in the ergodic case the energy gain is independent of the hole size, whereas in the multicomponent case the energy flow may be significantly increased by shrinking the hole size.

  6. Relativistic Fermi acceleration with shock compressed turbulence

    E-print Network

    Lemoine, M; Lemoine, Martin; Revenu, Benoit

    2006-01-01

    This paper presents numerical simulations of test particle Fermi acceleration at relativistic shocks of Lorentz factor Gamma_sh = 2-60, using a realistic downstream magnetic structure obtained from the shock jump conditions. The upstream magnetic field is described as pure Kolmogorov turbulence; the corresponding downstream magnetic field lies predominantly in the plane tangential to the shock surface and the coherence length is smaller along the shock normal than in the tangential plane. Acceleration is nonetheless efficient and leads to powerlaw spectra with index s = 2.6-2.7 at large shock Lorentz factor Gamma_sh >> 1, markedly steeper than for isotropic scattering downstream. The acceleration timescale t_acc in the upstream rest frame becomes a fraction of Larmor time t_L in the ultra-relativistic limit, t_acc ~ 10 t_L/Gamma_sh. Astrophysical applications are discussed, in particular the acceleration in gamma-ray bursts internal and external shocks.

  7. Relativistic Fermi acceleration with shock compressed turbulence

    NASA Astrophysics Data System (ADS)

    Lemoine, Martin; Revenu, Benoît

    2006-02-01

    In this paper we present numerical simulations of test particle Fermi acceleration at relativistic shocks of the Lorentz factor ?sh= 2-60, using a realistic downstream magnetic structure obtained from the shock jump conditions. The upstream magnetic field is described as pure Kolmogorov turbulence; the corresponding downstream magnetic field lies predominantly in the plane tangential to the shock surface and the coherence length is smaller along the shock normal than in the tangential plane. Acceleration is none the less efficient and leads to power-law spectra with index ~= 2.6-2.7 at a large shock Lorentz factor ?sh>> 1, markedly steeper than for isotropic scattering downstream. The acceleration time-scale tacc in the upstream rest frame becomes a fraction of Larmor time tL in the ultrarelativistic limit, tacc~ 10 tL/?sh. Astrophysical applications are discussed, in particular the acceleration in ?-ray bursts internal and external shocks.

  8. Radiation Safety Systems for Accelerator Facilities

    SciTech Connect

    Liu, James C

    2001-10-17

    The Radiation Safety System (RSS) of an accelerator facility is used to protect people from prompt radiation hazards associated with accelerator operation. The RSS is a fully interlocked, engineered system with a combination of passive and active elements that are reliable, redundant, and fail-safe. The RSS consists of the Access Control System (ACS) and the Radiation Containment System (RCS). The ACS is to keep people away from the dangerous radiation inside the shielding enclosure. The RCS limits and contains the beam/radiation conditions to protect people from the prompt radiation hazards outside the shielding enclosure in both normal and abnormal operations. The complexity of a RSS depends on the accelerator and its operation, as well as associated hazard conditions. The approaches of RSS among different facilities can be different. This report gives a review of the RSS for accelerator facilities.

  9. Radiation Safety Systems for Accelerator Facilities

    SciTech Connect

    James C. Liu; Jeffrey S. Bull; John Drozdoff; Robert May; Vaclav Vylet

    2001-10-01

    The Radiation Safety System (RSS) of an accelerator facility is used to protect people from prompt radiation hazards associated with accelerator operation. The RSS is a fully interlocked, engineered system with a combination of passive and active elements that are reliable, redundant, and fail-safe. The RSS consists of the Access Control System (ACS) and the Radiation Containment System (RCS). The ACS is to keep people away from the dangerous radiation inside the shielding enclosure. The RCS limits and contains the beam/radiation conditions to protect people from the prompt radiation hazards outside the shielding enclosure in both normal and abnormal operations. The complexity of a RSS depends on the accelerator and its operation, as well as associated hazard conditions. The approaches of RSS among different facilities can be different. This report gives a review of the RSS for accelerator facilities.

  10. DESIGN CRITERIA OF A PROTON FFAG ACCELERATOR.

    SciTech Connect

    RUGGIERO, A.G.

    2004-10-13

    There are two major issues that are to be confronted in the design of a Fixed-Field Alternating-Gradient (FFAG) accelerator, namely: (1) the stability of motion over the large momentum range needed for the beam acceleration, and (2) the compactness of the trajectories over the same momentum range to limit the dimensions of the magnets. There are a numbers of rules that need to be followed to resolve these issues. In particular, the magnet arrangement in the accelerator lattice and the distribution of the bending and focusing fields are to be set properly in accordance with these rules. In this report they describe four of these rules that ought to be applied for the optimum design of a FFAG accelerator, especially in the case of proton beams.

  11. Dimethylacetamide pharmacokinetics following inhalation exposures to rats and mice.

    PubMed

    Hundley, S G; Lieder, P H; Valentine, R; McCooey, K T; Kennedy, G L

    1994-09-01

    Whole-body inhalation exposures to N,N-dimethylacetamide (DMAC) were conducted with male rats (Crl:CD BR) and mice (Crl:CD-1 (ICR)BR). Exposure concentrations were 50, 150, 300 and 500 ppm. The exposure routines consisted of single 1-, 3-, or 6-h exposures and ten 6-h exposures (10 exposure days in 2 weeks). Area under the plasma concentration curve (AUC) values were determined for DMAC and its metabolite N-methylacetamide (NMAC), following 6-h exposures (single exposure or last in a series of 10 exposures). The range of exposures was chosen to assess the exposure-dependent nature of DMAC pharmacokinetics in rats and mice. Plasma profiles indicated mice metabolized DMAC rapidly with plasma half-lives from 0.3 to 0.5 h for DMAC. The DMAC AUC values from mice were underestimated due to the required time (< 30 min) between termination of exposure and the initial blood sample. DMAC plasma half-life in rats ranged from 0.6 to 1.5 h. The AUC values for DMAC in rats increased approximately 5-fold and 3-fold as exposure concentrations increased from 150 to 300 ppm and 300 to 500 ppm, respectively. NMAC persisted in plasma for at least 24 h after the 150, 300 and 500 ppm exposures to rats. NMAC was not detected in plasma from mice beyond the 12-h post-exposure timepoint for the 300 and 500 ppm exposures. Regardless of exposure level, repeated DMAC exposures to both rats and mice resulted in plasma profiles of DMAC and NMAC similar to those from a single exposure. The dose-dependent nature of the DMAC AUC data and the absence of effects of repeated 300 and 500 ppm DMAC exposures supported a toxicity-driven upper limit of 350 ppm for a chronic inhalation study. PMID:8091430

  12. Biological Response to SPE Exposures

    NASA Technical Reports Server (NTRS)

    Wilson, J. W.; Cucinotta, F. A.; Kim, M.; Shinn, J. L.; Jones, T. D.; Chang, C. K.

    2004-01-01

    It has long been recognized that a single solar particle event (SPE) can produce, over a short period of time, exposures on the order of LD50 for humans under normal physiological conditions. It is further recognized that recovery from injury over the period of exposure would greatly increase the chances of survival (dose rate effects) although such effects were left unquantified. In the present report we use the bioresponse model derived from a broad range of animal and human exposure data for evaluation of troop readiness in tactical nuclear warfare to evaluate the biological risk posed by the solar event of 4 August 1972. The astronaut blood forming organ (BFO) exposure in deep space would have been 2.2 Sv (1.6 Gy) in a space suit, 1.8 Sv (1.3 Gy) in an aluminum pressure vessel, and 0.7 Sv (0.5 Gy) in an equipment room compared to an X-ray mortality threshold of 1.5 Gy (assuming high dose rate). We find BFO dose rate effectiveness factors for this SPE on the order of 3 to 4, greatly reducing the mortality risks for this event. There is an approximate 3 percent chance that an even larger event may occur for which exposures could be 2-4 times higher. Assured survival of the astronaut requires added shelter shielding and a warning system for this event. The required mass of the shelter shield can be greatly reduced by using hydrogenous materials such as polymers, water, food, and other biological materials in its construction. Limitations of the current bioresponse model arise from the exposures taking place in the microgravity environment wherein the immune system is already challenged and the effective mortality threshold may be reduced by a factor of two. Such microgravity effects could greatly affect astronaut risks.

  13. Spin, Acceleration and Gravity

    E-print Network

    Donato Bini; Christian Cherubini; Bahram Mashhoon

    2004-06-14

    The massless field perturbations of the accelerating Minkowski and Schwarzschild spacetimes are studied. The results are extended to the propagation of the Proca field in Rindler spacetime. We examine critically the possibility of existence of a general spin-acceleration coupling in complete analogy with the well-known spin-rotation coupling. We argue that such a direct coupling between spin and linear acceleration does not exist.

  14. Optically pulsed electron accelerator

    DOEpatents

    Fraser, J.S.; Sheffield, R.L.

    1985-05-20

    An optically pulsed electron accelerator can be used as an injector for a free electron laser and comprises a pulsed light source, such as a laser, for providing discrete incident light pulses. A photoemissive electron source emits electron bursts having the same duration as the incident light pulses when impinged upon by same. The photoemissive electron source is located on an inside wall of a radiofrequency-powered accelerator cell which accelerates the electron burst emitted by the photoemissive electron source.

  15. Arsenic exposure and cardiovascular disorders: an overview.

    PubMed

    Balakumar, Pitchai; Kaur, Jagdeep

    2009-12-01

    The incidence of arsenic toxicity has been observed in various countries including Taiwan, Bangladesh, India, Argentina, Australia, Chile, China, Hungary, Peru, Thailand, Mexico and United States of America. Arsenic is a ubiquitous element present in drinking water, and its exposure is associated with various cardiovascular disorders. Arsenic exposure plays a key role in the pathogenesis of vascular endothelial dysfunction as it inactivates endothelial nitric oxide synthase, leading to reduction in the generation and bioavailability of nitric oxide. In addition, the chronic arsenic exposure induces high oxidative stress, which may affect the structure and function of cardiovascular system. Further, the arsenic exposure has been noted to induce atherosclerosis by increasing the platelet aggregation and reducing fibrinolysis. Moreover, arsenic exposure may cause arrhythmia by increasing the QT interval and accelerating the cellular calcium overload. The chronic exposure to arsenic upregulates the expression of tumor necrosis factor-alpha, interleukin-1, vascular cell adhesion molecule and vascular endothelial growth factor to induce cardiovascular pathogenesis. The present review critically discussed the detrimental role of arsenic in the cardiovascular system. PMID:19787300

  16. Integrated Exposure Assessment Monitoring.

    ERIC Educational Resources Information Center

    Behar, Joseph V.; And Others

    1979-01-01

    Integrated Exposure Assessment Monitoring is the coordination of environmental (air, water, land, and crops) monitoring networks to collect systematically pollutant exposure data for a specific receptor, usually man. (Author/BB)

  17. EPIDEMIOLOGY AND EXPOSURE ASSESSMENT

    EPA Science Inventory

    Research collaborations between the National Health and Environmental Effects Research Laboratory (NHEERL) and the National Exposure Research Laboratory (NERL) centered on the development and application of exposure analysis tools in environmental epidemiology include the El Paso...

  18. Occupational Noise Exposure

    MedlinePLUS

    ... reduce worker exposure to noise in a workplace. Engineering controls that reduce sound exposure levels are available and technologically feasible for most noise sources. Engineering controls involve modifying or replacing equipment, or making ...

  19. Exposure Analysis Modeling System

    EPA Science Inventory

    The Exposure Analysis Modeling System (EXAMS) is an interactive software application for formulating aquatic ecosystem models and evaluating the fate, transport, and exposure concentrations of synthetic organic chemicals including pesticides, industrial materials, and leachates f...

  20. CHAPTER ONE: EXPOSURE MEASUREMENTS.

    EPA Science Inventory

    Determining human exposure to suspended particualte concentrations requires measurements that quantify different particle properties in microenvironments where people live, work, and play. Particle mass, size, and chemical composition are important exposure variables, and these ...

  1. Generating entangled fermions by accelerated measurements on the vacuum

    E-print Network

    David C. M. Ostapchuk; Robert B. Mann

    2009-03-02

    It is shown that accelerated projective measurements on the vacuum of a free Dirac spinor field results in an entangled state for an inertial observer. The physical mechanism at work is the Davies-Unruh effect. The produced state is always entangled and its entanglement increases as a function of the acceleration, reaching maximal entanglement in the asymptotic limit of infinite acceleration where Bell states are produced.

  2. Particle acceleration in flares

    NASA Technical Reports Server (NTRS)

    Benz, Arnold O.; Kosugi, Takeo; Aschwanden, Markus J.; Benka, Steve G.; Chupp, Edward L.; Enome, Shinzo; Garcia, Howard; Holman, Gordon D.; Kurt, Victoria G.; Sakao, Taro

    1994-01-01

    Particle acceleration is intrinsic to the primary energy release in the impulsive phase of solar flares, and we cannot understand flares without understanding acceleration. New observations in soft and hard X-rays, gamma-rays and coherent radio emissions are presented, suggesting flare fragmentation in time and space. X-ray and radio measurements exhibit at least five different time scales in flares. In addition, some new observations of delayed acceleration signatures are also presented. The theory of acceleration by parallel electric fields is used to model the spectral shape and evolution of hard X-rays. The possibility of the appearance of double layers is further investigated.

  3. Accelerator Control Middle Layer

    SciTech Connect

    Corbett, J.

    2004-09-15

    This paper reviews an efficient implementation of the software ''middle layer'' that resides between high-level accelerator control applications and the low-level accelerator control system. The middle layer software is written in MATLAB and includes links to the EPICS Channel Access Library. Functionally, the middle layer syntax closely parallels the Family/Index naming scheme used in many accelerator simulation codes and uses the same convention to communicate with both the online machine and the accelerator model. Hence, machine control, machine simulation and data analysis tools are integrated into a single, easy-to-use software package.

  4. Accelerators and Nobel Laureates

    NSDL National Science Digital Library

    Kullander, Sven

    This online article written by Sven Kullander at the Nobel e-Museum discusses the importance of particle accelerators to physics in a historical context. After studying their basic operatation, users can then learn about the many accelerator inventions and their assistance in various discoveries such as x-rays and electrons. The website provides links to descriptions of the many Nobel Prize winners who have utilized accelerators in their important work. Users can view images of the large accelerators from all over the world including the United Kingdom, Sweden, and the United State.

  5. Charged particle accelerator grating

    DOEpatents

    Palmer, Robert B. (Shoreham, NY)

    1986-01-01

    A readily disposable and replaceable accelerator grating for a relativistic particle accelerator. The grating is formed for a plurality of liquid droplets that are directed in precisely positioned jet streams to periodically dispose rows of droplets along the borders of a predetermined particle beam path. A plurality of lasers are used to direct laser beams into the droplets, at predetermined angles, thereby to excite the droplets to support electromagnetic accelerating resonances on their surfaces. Those resonances operate to accelerate and focus particles moving along the beam path. As the droplets are distorted or destroyed by the incoming radiation, they are replaced at a predetermined frequency by other droplets supplied through the jet streams.

  6. Accelerator-based BNCT.

    PubMed

    Kreiner, A J; Baldo, M; Bergueiro, J R; Cartelli, D; Castell, W; Thatar Vento, V; Gomez Asoia, J; Mercuri, D; Padulo, J; Suarez Sandin, J C; Erhardt, J; Kesque, J M; Valda, A A; Debray, M E; Somacal, H R; Igarzabal, M; Minsky, D M; Herrera, M S; Capoulat, M E; Gonzalez, S J; del Grosso, M F; Gagetti, L; Suarez Anzorena, M; Gun, M; Carranza, O

    2014-06-01

    The activity in accelerator development for accelerator-based BNCT (AB-BNCT) both worldwide and in Argentina is described. Projects in Russia, UK, Italy, Japan, Israel, and Argentina to develop AB-BNCT around different types of accelerators are briefly presented. In particular, the present status and recent progress of the Argentine project will be reviewed. The topics will cover: intense ion sources, accelerator tubes, transport of intense beams, beam diagnostics, the (9)Be(d,n) reaction as a possible neutron source, Beam Shaping Assemblies (BSA), a treatment room, and treatment planning in realistic cases. PMID:24365468

  7. Energy sweep compensation of induction accelerators

    SciTech Connect

    Sampayan, S.E.; Caporaso, G.J.; Chen, Y-J; Decker, T.A.; Turner, W.C.

    1990-09-12

    The ETA-II linear induction accelerator (LIA) is designed to drive a microwave free electron laser (FEL). Beam energy sweep must be limited to {plus minus}1% for 50 ns to limit beam corkscrew motion and ensure high power FEL output over the full duration of the beam flattop. To achieve this energy sweep requirement, we have implemented a pulse distribution system and are planning implementation of a tapered pulse forming line (PFL) in the pulse generators driving acceleration gaps. The pulse distribution system assures proper phasing of the high voltage pulse to the electron beam. Additionally, cell-to-cell coupling of beam induced transients is reduced. The tapered PFL compensates for accelerator cell and loading nonlinearities. Circuit simulations show good agreement with preliminary data and predict the required energy sweep requirement can be met.

  8. Swimmer Exposure Assessment Model

    EPA Science Inventory

    The SWIMODEL is a screening tool for conducting an exposure assessment of pesticides found in indoor swimming pools and spas. The SWIMODEL uses well-accepted screening exposure assessment equations to calculate the total worst-case exposure for swimmers expressed as a mass-based...

  9. Opioid Antagonist Impedes Exposure.

    ERIC Educational Resources Information Center

    Merluzzi, Thomas V.; And Others

    1991-01-01

    Thirty spider-phobic adults underwent exposure to 17 phobic-related, graded performance tests. Fifteen subjects were assigned to naltrexone, an opioid antagonist, and 15 were assigned to placebo. Naltrexone had a significant effect on exposure, with naltrexone subjects taking significantly longer to complete first 10 steps of exposure and with…

  10. DIETARY EXPOSURE MEASUREMENTS

    EPA Science Inventory

    This research constitutes the MCEARD base dietary exposure research program and is conducted to complement the NERL total human exposure program. The research builds on previous work to reduce the level of uncertainty in exposure assessment by improving NERL's ability to evaluat...

  11. GUIDELINES FOR EXPOSURE ASSESSMENT

    EPA Science Inventory

    The Guidelines for Exposure Assessment describe the general concepts of exposure assessment including definitions and associated units, and by providing guidance on the planning and conducting of an exposure assessment. Guidance is also provided on presenting the results of the e...

  12. HUMAN EXPOSURE ACTIVITY PATTERNS

    EPA Science Inventory

    Human activity/uptake rate data are necessary to estimate potential human exposure and intake dose to environmental pollutants and to refine human exposure models. Personal exposure monitoring studies have demonstrated the critical role that activities play in explaining and pre...

  13. Acceleration Worksheet 8/24/2011 ACCELERATION WORKSHEET

    E-print Network

    Davis, H. Floyd

    Acceleration Worksheet 8/24/2011 ACCELERATION WORKSHEET College of Arts and Sciences Name _____________ TO _____________ month/year month/year II. I meet the requirements for acceleration under [fill out either a) or b;Acceleration Worksheet 8/24/2011 Acceleration 2011-2012 Courses of Study The faculty of the college desires

  14. Exposure to Nanoparticles and Hormesis

    PubMed Central

    Iavicoli, Ivo; Calabrese, Edward J.; Nascarella, Marc A.

    2010-01-01

    Nanoparticles are particles with lengths that range from 1 to 100 nm. They are increasingly being manufactured and used for commercial purpose because of their novel and unique physicochemical properties. Although nanotechnology-based products are generally thought to be at a pre-competitive stage, an increasing number of products and materials are becoming commercially available. Human exposure to nanoparticles is therefore inevitable as they become more widely used and, as a result, nanotoxicology research is now gaining attention. However, there are many uncertainties as to whether the unique properties of nanoparticles also pose occupational health risks. These uncertainties arise because of gaps in knowledge about the factors that are essential for predicting health risks such as routes of exposure, distribution, accumulation, excretion and dose-response relationship of the nanoparticles. In particular, uncertainty remains with regard to the nature of the dose-response curve at low level exposures below the toxic threshold. In fact, in the literature, some studies that investigated the biological effects of nanoparticles, observed a hormetic dose-response. However, currently available data regarding this topic are extremely limited and fragmentary. It therefore seems clear that future studies need to focus on this issue by studying the potential adverse health effects caused by low-level exposures to nanoparticles. PMID:21191487

  15. Accelerated Hypertension after Venlafaxine Usage

    PubMed Central

    K?vrak, Yüksel; Güvenç, Tolga Sinan; Akbulut, Nurcihan; Ya?c?, ?brahim; Ç???ar, Gül?en; Gündüz, Süleyman; Balc?, Bahattin

    2014-01-01

    Venlafaxine is the first antidepressant that acts via inhibiting serotonin and noradrenaline reuptake. Hypertension is observed in doses exceeding 300?mg/day and is the most feared complication. We report a patient with accelerated hypertension after venlafaxine use observed at a dose of 150?mg/day. A 23-year-old patient with symptoms of insomnia, depression, anhedonia, fatigue admitted our clinic. Venlafaxine at a dose of 75?mg/day was initiated after he was diagnosed with major depressive disorder. After 5 months, venlafaxine dose was uptitrated to 150?mg/day due to inadequate response to drug. After using venlafaxine for ten months at the dose of 150?mg/day, he admitted our clinic with headache and epistaxis. He was hospitalized after his blood pressure was measured as 210/170?mmHg. No secondary causes for hypertension were found, and venlafaxine treatment was considered possible etiologic factor. After stopping venlafaxine treatment, his blood pressure was reverted back to normal limits. While mild elevation of blood pressure could be observed after venlafaxine treatment, this case shows that accelerated hypertension with a diastolic blood pressure rise above 120?mmHg could be observed at relatively low doses of venlafaxine. Close monitoring of blood pressure is necessary after initiation of treatment, as accelerated hypertension could cause endorgan damage with potentially catastrophic results. PMID:25328745

  16. Twisted acceleration-enlarged Newton-Hooke Hopf algebras

    E-print Network

    Marcin Daszkiewicz

    2010-07-27

    Ten Abelian twist deformations of acceleration-enlarged Newton-Hooke Hopf algebra are considered. The corresponding quantum space-times are derived as well. It is demonstrate that their contraction limit $\\tau \\to \\infty$ leads to the new twisted acceleration-enlarged Galilei spaces.

  17. Studies on longitudinal beam compression in induction accelerator drivers

    Microsoft Academic Search

    J. W.-K. Mark; D. D.-M. Ho; S. T. Brandon; C.-L. Chang; A. T. Drobot; A. Faltens; E. P. Lee; G. A. Krafft

    1986-01-01

    Longitudinal beam compression is an integral part of the U.S. induction accelerator development effort for heavy ion fusion. It occurs before final focus and fusion chamber beam transport and is a key process determining initial conditions for final focus hardware. Determining the limits for maximal performance of key accelerator components is an essential element of the effort to reduce driver

  18. Neck Forces and Moments and Head Accelerations in Side Impact

    Microsoft Academic Search

    Narayan Yoganandan; Frank A. Pintar; Dennis J. Maiman; Mat Philippens; Jac Wismans

    2009-01-01

    Objectives: Although side-impact sled studies have investigated chest, abdomen, and pelvic injury mechanics, determination of head accelerations and the associated neck forces and moments is very limited. The purpose of the present study was therefore to determine the temporal forces and moments at the upper neck region and head angular accelerations and angular velocities using postmortem human subjects (PMHS).Methods: Anthropometric

  19. The phase of particle acceleration in the flare development

    Microsoft Academic Search

    Z. Švestka

    1970-01-01

    Evidence is given that the particle acceleration in flares is confined to the initial phase of the flare development preceding the Ha flare maximum and lasting for less than 10 min. The impulsive acceleration process is confined to a relatively small limited volume of about 5 × 1027 cm3 in the region of highest magnetic gradient in the flare, and

  20. Employing Multiple CUDA Devices to Accelerate LTL Model Checking

    Microsoft Academic Search

    Jiri Barnat; Petr Bauch; Lubos Brim; Milan Ceska

    2010-01-01

    Recently, the CUDA technology has been used to accelerate many computation demanding tasks. For example, in our previous work we have shown how CUDA technology can be employed to accelerate the process of Linear Temporal Logic (LTL) Model Checking. While the raw computing power of a CUDA enabled device is tremendous, the applicability of the technology is quite often limited

  1. DANE TECHNICAL NOTE INFN -LNF, Accelerator Division

    E-print Network

    Istituto Nazionale di Fisica Nucleare (INFN)

    loop from Cavity Probe To Tuner System PowerAmplifier Forward Reverse To RF Cavity RF Phase Phase Amplifier LimiterRF Amplifier Low Pass Filter Forward RF Amplifier fc90MHzfc90MHz fc90MHz fc5MHz BufferKKKK KKKK DANE TECHNICAL NOTE INFN - LNF, Accelerator Division Frascati, May 20, 1994 Note: RF-11

  2. Improving Rural Teachers' Attitudes towards Acceleration

    ERIC Educational Resources Information Center

    Olthouse, Jill M.

    2015-01-01

    Gifted students see both educational benefits and barriers as a result of living in rural communities. Benefits include increased individual attention and community engagement; barriers include limited curricular options (Lawrence, 2009). Acceleration is an option that has positive academic outcomes but is underused, especially in rural areas.…

  3. SHOCK EMERGENCE IN SUPERNOVAE: LIMITING CASES AND ACCURATE APPROXIMATIONS

    SciTech Connect

    Ro, Stephen; Matzner, Christopher D. [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George St., Toronto, ON M5S 3H4 (Canada)

    2013-08-10

    We examine the dynamics of accelerating normal shocks in stratified planar atmospheres, providing accurate fitting formulae for the scaling index relating shock velocity to the initial density and for the post-shock acceleration factor as functions of the polytropic and adiabatic indices which parameterize the problem. In the limit of a uniform initial atmosphere, there are analytical formulae for these quantities. In the opposite limit of a very steep density gradient, the solutions match the outcome of shock acceleration in exponential atmospheres.

  4. EXHAUST MAIN PERSONNEL EXPOSURE CALCULATION

    SciTech Connect

    S. Su

    1999-09-29

    The purpose of this activity is to identify and determine potential radiation hazards in the service exhaust main due to a waste package leakage from an emplacement drift. This work supports the subsurface ventilation system design for the EDA II, which consists of an accessible service exhaust main for personnel, and an exhaust main for hot air flow. The objective is to provide the necessary radiation exposure calculations to determine if the service exhaust main is accessible following a waste package leak. This work includes the following items responsive to the stated purpose and objective: Calculate the limiting transient radiation exposure of personnel in the service exhaust main due to the passage of airborne radioactive material through the ventilation raise and connecting horizontal raise to the exhaust main in the event of a leaking waste package Calculate the potential exposures to maintenance workers in the service exhaust main from residual radioactive material deposited inside of the ventilation raise and connecting horizontal raise This calculation is limited to external radiation only, since the airborne and contamination sources will be contained in the ventilation raise and connecting horizontal raise.

  5. Amalgam exposure and neurological function.

    PubMed

    Kingman, Albert; Albers, James W; Arezzo, Joseph C; Garabrant, David H; Michalek, Joel E

    2005-03-01

    Concerns regarding the safety of silver-mercury amalgam fillings continue to be raised in the absence of any direct evidence of harm. The widespread population exposure to amalgam mandated that a thorough investigation be conducted of its potential effects on the nervous system. The National Institute of Dental and Craniofacial Research and U.S. Air Force investigators collaborated in the ongoing Air Force Health Study (AFHS) of Vietnam era veterans. The primary study question involved adverse health effects associated with exposure to herbicides or dioxin. An assessment of exposure to dental amalgam fillings was added to the 1997-1998 health examination to investigate possible associations between amalgam exposure and neurological abnormalities. Our study population consisted of 1663 dentate AFHS participants, comprised of 986 AFHS controls and 677 Ranch Hand veterans who were exposed to dioxin in Vietnam. Two hundred and fifty-two of the participants had confirmed diabetes mellitus. Study outcomes included clinical neurological signs, vibrotactile thresholds, and summary variables for different levels of peripheral neuropathy. A limitation of our study is that our database did not include more sensitive continuous measures such as nerve conduction studies. No significant associations were found between amalgam exposure and clinical neurological signs of abnormal tremor, coordination, station or gait, strength, sensation, or muscle stretch reflexes or for any level of peripheral neuropathy among our study participants. A statistically significant association was detected between amalgam exposure and the continuous vibrotactile sensation response for the combined non-diabetic participants and separately for non-diabetic AFHS controls. No significant association in this measure was detectable for non-diabetic Ranch Hand veterans or among the combined diabetic participants. The association is a sub-clinical finding that was not associated with symptoms, clinically evident signs of neuropathy, or any functional impairment. Overall, we found no association between amalgam exposure and neurological signs or clinically evident peripheral neuropathy. Our findings do not support the hypothesis that exposure to amalgam produces adverse, clinically evident neurological effects. PMID:15713345

  6. W-band millimeter wave exposure system for studying non-thermal effects on skeletal muscle contraction

    Microsoft Academic Search

    Jihwan Yoon; Stephanie Luongo; Robert Wiese; Pete Mastin; Lev Sadovnik; Gale L. Craviso; Indira Chatterjee

    2011-01-01

    A novel W-band (75-110 GHz) exposure system was designed, characterized and tested to be used for identifying millimeter wave (MMW) exposure parameters (frequency, modulation schemes and electric field magnitude) that could accelerate recovery from fatigue in skeletal muscle. The system designed allows electrical stimulation of muscle and measurement of contractile force during MMW exposure within an organ bath under conditions

  7. Semiconductor acceleration sensor

    NASA Astrophysics Data System (ADS)

    Ueyanagi, Katsumichi; Kobayashi, Mitsuo; Goto, Tomoaki

    1996-09-01

    This paper reports a practical semiconductor acceleration sensor especially suited for automotive air bag systems. The acceleration sensor includes four beams arranged in a swastika structure. Two piezoresistors are formed on each beam. These eight piezoresistors constitute a Wheatstone bridge. The swastika structure of the sensing elements, an upper glass plate and a lower glass plate exhibit the squeeze film effect which enhances air dumping, by which the constituent silicon is prevented from breakdown. The present acceleration sensor has the following features. The acceleration force component perpendicular to the sensing direction can be cancelled. The cross-axis sensitivity is less than 3 percent. And, the erroneous offset caused by the differences between the thermal expansion coefficients of the constituent materials can be canceled. The high aspect ratio configuration realized by plasma etching facilitates reducing the dimensions and improving the sensitivity of the acceleration sensor. The present acceleration sensor is 3.9 mm by 3.9 mm in area and 1.2 mm in thickness. The present acceleration sensor can measure from -50 to +50 G with sensitivity of 0.275 mV/G and with non-linearity of less than 1 percent. The acceleration sensor withstands shock of 3000 G.

  8. Accelerating Research with

    E-print Network

    Bernstein, Phil

    -for- use basis. Software and data are hosted on remote computers "in the cloud," and users connect throughAccelerating Academic Research with Cloud Computing Published: September 2014 For the latest information, please see www.microsoft.com/education #12;Accelerating Academic Research with Cloud Computing

  9. Electromagnetic mass accelerators

    Microsoft Academic Search

    Pavel V. Kasyanenko; Vasily A. Efremov; Sergey A. Kharitonov

    2010-01-01

    The powerful power supplies system (up to 3 - 4 GW in impulse) was developed for the electromagnetic mass accelerator. Unique blocks of repeated switching rated on high currents (up to 1.2MA and voltage up to 5KV) are considered. In this paper various designs of the mass accelerator system and its power supplies are described.

  10. Exploring acceleration through vectors

    NSDL National Science Digital Library

    This in class worksheet is designed to get students to think about and manipulate different accelerations in their head. Students work together with written descriptions of velocity and acceleration and draw the vectors in part one, and then turn that around in part two where they write descriptions of a car's motion based on the vector pictures they are given.

  11. J-PARC Accelerator

    SciTech Connect

    Yamazaki, Yoshishige [J-PARC Center High Energy Accelerator Research Organization (KEK) and Japan Atomic Energy Organization (JAEA) Shirakata-Shirane, Tokai-Mura, Naka-Gun, Ibaraki-Ken (Japan)

    2008-02-21

    The Japan Proton Accelerator Research Complex (J-PARC) is under construction in Tokai site. The linac beam commissioning started last fall, while the beam commissioning of the 3-GeV Rapid-Cycling Synchrotron (RCS) will start this fall. The status of the J-PARC accelerator is reported with emphasis on the technical development accomplished for the J-PARC.

  12. Particle Acceleration in Jets

    NASA Technical Reports Server (NTRS)

    Nishikawa, Ken-Ichi

    2005-01-01

    Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., active galactic nuclei (AGNs), gamma ray burst (GRBs), and Galactic microquasar systems usually have power-law emission spectra. Fermi acceleration is the mechanism usually assumed for the acceleration of particles in astrophysical environments.

  13. Acceleration of Gravity 2

    NSDL National Science Digital Library

    Michael Horton

    2009-05-30

    This lab is between a Level 2 and Level 3 inquiry activity in that it should be assigned after students understand acceleration but before they learn about the acceleration gravity. Because there are many sources of error when using a pendulum, students c

  14. ACCELERATOR RESEARCH STUDIES

    SciTech Connect

    P.G. O'Shea, M. Reiser, V. L. Granatstein, W. Lawson, I. Haber, R. Kishek

    2004-01-23

    ACCELERATOR RESEARCH STUDIES Task A: Study of the Physics of Space-Charge Dominated Beams for Advanced Accelerator Applications Task B: Studies of High-Power Gyroklystrons and Application to Linear Colliders Task C: Theory and Simulation of the Physics Space-Charge Dominated Beams Annual Report for the Period June 1, 2003 to May 31, 2004

  15. Diagnostics for induction accelerators

    SciTech Connect

    Fessenden, T.J.

    1996-04-01

    The induction accelerator was conceived by N. C. Christofilos and first realized as the Astron accelerator that operated at LLNL from the early 1960`s to the end of 1975. This accelerator generated electron beams at energies near 6 MeV with typical currents of 600 Amperes in 400 ns pulses. The Advanced Test Accelerator (ATA) built at Livermore`s Site 300 produced 10,000 Ampere beams with pulse widths of 70 ns at energies approaching 50 MeV. Several other electron and ion induction accelerators have been fabricated at LLNL and LBNL. This paper reviews the principal diagnostics developed through efforts by scientists at both laboratories for measuring the current, position, energy, and emittance of beams generated by these high current, short pulse accelerators. Many of these diagnostics are closely related to those developed for other accelerators. However, the very fast and intense current pulses often require special diagnostic techniques and considerations. The physics and design of the more unique diagnostics developed for electron induction accelerators are presented and discussed in detail.

  16. The contributions to solvent uptake by skin and inhalation exposure

    SciTech Connect

    Daniell, W.; Stebbins, A.; Kalman, D.; O'Donnell, J.F.; Horstman, S.W. (Department of Environmental Health, University of Washington, Seattle (United States))

    1992-02-01

    Solvent exposures were assessed among 97 auto body repair workers in order to determine whether skin contact represented a significant route of exposure. Each subject's cumulative skin exposure was ranked categorically based on simple observation: 49 none, 33 incidental or low, and 15 moderate or high. The median time-weighted average air exposure to solvents was 8.4% of the American Conference of Governmental Industrial Hygienists (ACGIH) combined solvent threshold limit value (TLV) with a range of 0-62% TLV, including toluene (median 4 ppm) and xylenes (median 0.9 ppm). Urine methyl hippuric acids (MHAs, metabolites of xylenes) were low compared to the ACGIH biological exposure index (BEI) with a median of 2% and a range of 0-12% BEI but were strongly correlated with both the level of airborne xylenes and skin exposure when considered simultaneously by using analysis of covariance (R = 0.91, p less than 0.0001). MHA excretion attributable to skin exposure for 15 min or more generally was comparable to or greater than that from associated air exposure over the full work shift. This study had limited ability to assess quantitatively the contributions of toluene exposures, but there was evidence that skin exposures also contributed significantly to toluene absorption. Air sampling will substantially underestimate a worker's total solvent dose in the setting of moderate or high skin exposure. Simple observation was effective in identifying workers in this sample who appeared to have sufficient skin exposure to produce a measurable increase in solvent uptake.

  17. Exposure monitoring and risk assessment of biphenyl in the workplace.

    PubMed

    Kim, Hyeon-Yeong; Shin, Sae-Mi; Ham, Miran; Lim, Cheol-Hong; Byeon, Sang-Hoon

    2015-01-01

    This study was performed to assess exposure to and the risk caused by biphenyl in the workplace. Biphenyl is widely used as a heat transfer medium and as an emulsifier and polish in industry. Vapor or high levels of dust inhalation and dermal exposure to biphenyl can cause eye inflammation, irritation of respiratory organs, and permanent lesions in the liver and nervous system. In this study, the workplace environment concentrations were assessed as central tendency exposure and reasonable maximum exposure and were shown to be 0.03 and 0.12 mg/m3, respectively. In addition, the carcinogenic risk of biphenyl as determined by risk assessment was 0.14 × 10-4 (central tendency exposure) and 0.56 × 10-4 (reasonable maximum exposure), which is below the acceptable risk value of 1.0 × 10-4. Furthermore, the central tendency exposure and reasonable maximum exposure hazard quotients were 0.01 and 0.06 for oral toxicity, 0.05 and 0.23 for inhalation toxicity, and 0.08 and 0.39 for reproduction toxicity, respectively, which are all lower than the acceptable hazard quotient of 1.0. Therefore, exposure to biphenyl was found to be safe in current workplace environments. Because occupational exposure limits are based on socioeconomic assessment, they are generally higher than true values seen in toxicity experiments. Based on the results of exposure monitoring of biphenyl, the current occupational exposure limits in Korea could be reviewed. PMID:25985312

  18. Exposure Monitoring and Risk Assessment of Biphenyl in the Workplace

    PubMed Central

    Kim, Hyeon-Yeong; Shin, Sae-Mi; Ham, Miran; Lim, Cheol-Hong; Byeon, Sang-Hoon

    2015-01-01

    This study was performed to assess exposure to and the risk caused by biphenyl in the workplace. Biphenyl is widely used as a heat transfer medium and as an emulsifier and polish in industry. Vapor or high levels of dust inhalation and dermal exposure to biphenyl can cause eye inflammation, irritation of respiratory organs, and permanent lesions in the liver and nervous system. In this study, the workplace environment concentrations were assessed as central tendency exposure and reasonable maximum exposure and were shown to be 0.03 and 0.12 mg/m3, respectively. In addition, the carcinogenic risk of biphenyl as determined by risk assessment was 0.14 × 10?4 (central tendency exposure) and 0.56 × 10?4 (reasonable maximum exposure), which is below the acceptable risk value of 1.0 × 10?4. Furthermore, the central tendency exposure and reasonable maximum exposure hazard quotients were 0.01 and 0.06 for oral toxicity, 0.05 and 0.23 for inhalation toxicity, and 0.08 and 0.39 for reproduction toxicity, respectively, which are all lower than the acceptable hazard quotient of 1.0. Therefore, exposure to biphenyl was found to be safe in current workplace environments. Because occupational exposure limits are based on socioeconomic assessment, they are generally higher than true values seen in toxicity experiments. Based on the results of exposure monitoring of biphenyl, the current occupational exposure limits in Korea could be reviewed. PMID:25985312

  19. Human occupational and nonoccupational exposure to fibers.

    PubMed Central

    Esmen, N A; Erdal, S

    1990-01-01

    Human exposure to fibers in occupational and nonoccupational environments has been a health concern for nearly a century. In this review, selected results from the literature are presented to highlight the availability, limitations, and interpretive difficulties associated with the past and current human fiber exposure data sets. In the traditionally defined asbestos fibers, large amounts of the data available suffer from the diversity of sample collection and analysis methods. Two simple generalizations suggest that occupational exposures are several orders of magnitude higher than that of environmental exposures; and currently extant data and the current routine measurement practices present significant difficulties in the consistent interpretation of the data with respect to health effects. The data on the human exposures to man-made vitreous fibers are much more complete than the data on asbestos exposure, while exposure data on other man-made fibrous materials are lacking. The human exposure data to many minerals which, at times, exist in fibrous habit, are very scanty, and in view of the biological activity of some of these fibers, this lack may be of significant concern. PMID:2272324

  20. Angular velocities, angular accelerations, and coriolis accelerations

    NASA Technical Reports Server (NTRS)

    Graybiel, A.

    1975-01-01

    Weightlessness, rotating environment, and mathematical analysis of Coriolis acceleration is described for man's biological effective force environments. Effects on the vestibular system are summarized, including the end organs, functional neurology, and input-output relations. Ground-based studies in preparation for space missions are examined, including functional tests, provocative tests, adaptive capacity tests, simulation studies, and antimotion sickness.

  1. Symmetry Restoration By Acceleration

    E-print Network

    P. Castorina; M. Finocchiaro

    2012-07-16

    The restoration of spontaneous symmetry breaking for a scalar field theory for an accelerated observer is discussed by the one-loop effective potential calculation and by considering the effective potential for composite operators. Above a critical acceleration, corresponding to the critical restoration temperature,T_c, for a Minkowski observer by Unruh relation, i.e. a_c/2\\pi=T_c, the symmetry is restored. This result confirms other recent calculations in effective field theories that symmetry restoration can occur for an observer with an acceleration larger than some critical value. From the physical point of view, a constant acceleration is locally equivalent to a gravitational field and the critical acceleration to restore the spontaneous symmetry breaking corresponds to a huge gravitational effect which, therefore, prevents boson condensation.

  2. Exposure assessment methods for a study of mortality and cancer morbidity in relation to specific petroleum industry exposures.

    PubMed

    Drummond, Ian; Murray, Neil; Armstrong, Thomas; Schnatter, A Robert; Lewis, R Jeffrey

    2006-10-01

    In 1987 a Canadian company implemented an exposure tracking and health information system. The exposure tracking method aligned closely with published concepts for describing workplace exposure, with over 1800 similar exposure groups being used to describe occupational exposures. The database has been actively maintained and is subject to a number of quality checks. Recently, the company initiated a cancer morbidity study, with one objective being to examine whether the exposure tracking data could be used to reconstruct exposure estimates for the cohort. Five agents--hydrogen sulfide, petroleum coke/spent catalyst, hydrocarbon solvents and fuels, hydrocarbon lubricants, and an index for exposure to operations derived from noise exposure--were selected for development of occupational exposure estimates for each cohort member. The cohort consisted of workers first employed between January 1964 and December 1994 and who were employed for at least 1 year. Work history records were associated with a similar exposure group, using human resources data and knowledge of local industrial hygienists. Only employees with >90% duration of their work history assigned were kept in the cohort (25,292 people out of a possible 25,617). For each similar exposure group inventory, the substances were identified that contributed to each of the five agents being studied. Exposure estimates before 1987 were modified using historic occupational exposure limits. Rules were created to sum the exposure from multiple substances found in any one similar exposure group. The validity of exposure estimates was tested via comparison with results documented in industrial hygiene survey reports. Industrial hygienists who were unaware of the derived exposure estimates evaluated several hundred industrial hygiene surveys and prepared benchmark information. The two lists were then evaluated for concordance, which was found to be significantly different from that occurring by chance. We conclude that the process described can create valid exposure estimates for use in epidemiology studies. PMID:16908452

  3. Use of dielectric material in muon accelerator RF cavities

    E-print Network

    French, Katheryn Decker

    2011-01-01

    The building of a muon collider is motivated by the desire to collide point-like particles while reducing the limitations imposed by synchrotron radiation. The many challenges unique to muon accelerators are derived from ...

  4. Formaldehyde exposure in nonoccupational environments.

    PubMed

    Dally, K A; Hanrahan, L P; Woodbury, M A; Kanarek, M S

    1981-01-01

    Free formaldehyde may be released from wood products and foam insulation where urea-formaldehyde resins have been used. From January, 1978 to November, 1979, 100 structures were investigated by the Wisconsin Division of Health after receiving complaints of health problems from occupants. Air samples were collected in midget impingers and analyzed for formaldehyde content by the chromotropic acid procedure. Health information was obtained from the occupants via questionnaires. Mean formaldehyde concentration observed ranged from below the limit of detection to 3.68 ppm. Eye irritation, burning eyes, runny nose, dry or sore throat, headache, and cough were the primary symptoms which were reported by the occupants. Statistically significant associations were seen between formaldehyde levels and age of home/building materials. Observations presented suggest nonoccupational, indoor environmental exposure to formaldehyde is significant and may reach levels which exceed occupational exposure standards. PMID:7316564

  5. EXAMPLE EXPOSURE SCENARIOS ASSESSMENT TOOL

    EPA Science Inventory

    Exposure scenarios are a tool to help the assessor develop estimates of exposure, dose, and risk. An exposure scenario generally includes facts, data, assumptions, inferences, and sometimes professional judgment about how the exposure takes place. The human physiological and beh...

  6. Design of accelerated corrosion tests for electronic components in automotive applications

    Microsoft Academic Search

    Peter Eriksson; Bo Carlsson; I. O. Wallinder

    2001-01-01

    Two new accelerated laboratory corrosion tests for electronic components in automotive applications have been developed, based on the use of metallic copper as a meter for corrosivity. The accelerated tests are designed so that they reproduce the same kind of corrosion effects as observed with exposure of copper in real vehicle environments. The test cycle that best simulates the corrosion

  7. Canonical Particle Acceleration in FRI Radio Galaxies

    E-print Network

    Andrew Young; Lawrence Rudnick; Debora Katz; Tracey DeLaney; Namir E. Kassim; Kazuo Makishima

    2005-02-26

    Matched resolution multi-frequency VLA observations of four radio galaxies are used to derive the asymptotic low energy slope of the relativistic electron distribution. Where available, low energy slopes are also determined for other sources in the literature. They provide information on the acceleration physics independent of radiative and other losses, which confuse measurements of the synchrotron spectra in most radio, optical and X-ray studies. We find a narrow range of inferred low energy electron energy slopes, n(E)=const*E^-2.1 for the currently small sample of lower luminosity sources classified as FRI (not classical doubles). This distribution is close to, but apparently inconsistent with, the test particle limit of n(E)=const*E^-2.0 expected from strong diffusive shock acceleration in the non-relativistic limit. Relativistic shocks or those modified by the back-pressure of efficiently accelerated cosmic rays are two alternatives to produce somewhat steeper spectra. We note for further study the possiblity of acceleration through shocks, turbulence or shear in the flaring/brightening regions in FRI jets as they move away from the nucleus. Jets on pc scales and the collimated jets and hot spots of FRII (classical double) sources would be governed by different acceleration sites and mechanisms; they appear to show a much wider range of spectra than for FRI sources.

  8. Media Exposure and Marijuana and Alcohol Use Among Adolescents

    PubMed Central

    PRIMACK, BRIAN A.; KRAEMER, KEVIN L.; FINE, MICHAEL J.; DALTON, MADELINE A.

    2010-01-01

    We aimed to determine which media exposures are most strongly associated with marijuana and alcohol use among adolescents. In 2004, we surveyed 1,211 students at a large high school in suburban Pittsburgh regarding substance use, exposure to entertainment media, and covariates. Of the respondents, 52% were female, 8% were non-White, 27% reported smoking marijuana, and 60% reported using alcohol. They reported average exposure to 8.6 hr of media daily. In adjusted models, exposure to music was independently associated with marijuana use, but exposure to movies was independently associated with alcohol use. Implications, limitations, and suggestions for further research are discussed. PMID:19306219

  9. Exposure assessment in auto collision repair shops.

    PubMed

    Bejan, Anca; Brosseau, Lisa M; Parker, David L

    2011-07-01

    Workers in auto collision shops are exposed to a variety of chemical and physical hazards. Previous studies have focused on measuring levels of isocyanates, but little is known about exposures to dust, noise, and solvents. In preparation for an intervention effectiveness study in small collision repair businesses, sampling was conducted on 3 consecutive days in four representative businesses with three to seven employees. Full-shift and task-specific exposures were measured for dust and solvents (for operations other than painting and spray gun cleaning). Full-shift personal exposures and tool-specific noise levels were also evaluated. Samples of banded earplugs were distributed to employees and feedback was collected after 1 week of wear time. Dust and solvent exposures did not exceed the OSHA PELs. Noise exposure doses were below the OSHA PEL; however, 4 of the 18 measurements were in excess of the ACGIH® threshold limit value. The majority of tools generated noise levels above 85 dBA. Air guns, wrenches, cutoff wheels, and air drills generated noise levels with the 5th percentile above 90 dBA. Mean noise levels generated by hammers, grinders, and ratchets were also above 95 dBA. Three pairs of banded earplugs had the best reviews in terms of comfort of use. This study was conducted during a time when all shops reported relatively low production levels. Noise exposure results suggest that it is likely that technicians' 8-hr time-weighted average exposures may be in excess of 85 dBA during periods of higher production, but exposures to dust and solvents are unlikely to approach OSHA exposure limits. These pilot test results will be useful when developing recommendations and technical assistance materials for health and safety interventions in auto collision repair businesses. PMID:21660833

  10. Large electrostatic accelerators

    SciTech Connect

    Jones, C.M.

    1984-01-01

    The increasing importance of energetic heavy ion beams in the study of atomic physics, nuclear physics, and materials science has partially or wholly motivated the construction of a new generation of large electrostatic accelerators designed to operate at terminal potentials of 20 MV or above. In this paper, the author briefly discusses the status of these new accelerators and also discusses several recent technological advances which may be expected to further improve their performance. The paper is divided into four parts: (1) a discussion of the motivation for the construction of large electrostatic accelerators, (2) a description and discussion of several large electrostatic accelerators which have been recently completed or are under construction, (3) a description of several recent innovations which may be expected to improve the performance of large electrostatic accelerators in the future, and (4) a description of an innovative new large electrostatic accelerator whose construction is scheduled to begin next year. Due to time and space constraints, discussion is restricted to consideration of only tandem accelerators.

  11. Amps particle accelerator definition study

    NASA Technical Reports Server (NTRS)

    Sellen, J. M., Jr.

    1975-01-01

    The Particle Accelerator System of the AMPS (Atmospheric, Magnetospheric, and Plasmas in Space) payload is a series of charged particle accelerators to be flown with the Space Transportation System Shuttle on Spacelab missions. In the configuration presented, the total particle accelerator system consists of an energetic electron beam, an energetic ion accelerator, and both low voltage and high voltage plasma acceleration devices. The Orbiter is illustrated with such a particle accelerator system.

  12. [Tolerance of +Gz accelerations in chronic compensated cardiac muscle disease].

    PubMed

    Suvorov, P M; Bykova, Iu I

    1975-01-01

    The functional potentialities of the cardiovascular system were investigated during an exposure of people with compensated chronic diseases of the cardiac muscle to acceleration (+Gz). The test subjects were exposed to acceleration of 3 and 5 g for 30 sec with an interval of 5 min. The parameters of hemodynamics, ECG and visual perception were recorded. The systolic blood volume, cardiac output and specific peripheral resistance were derived from the Bremser-Ranke formula. Seventy one subjects with heart diseases and 23 healthy subjects were examined. The subjects with myocardiodystrophy and myocarditic cardiosclerosis (12+/-16) showed a reduced tolerance to accelerations. During an exposure the subjects with atherosclerotic cardiosclerosis showed a higher pressure in vessels of ear conch than the healthy subjects. The myocardiodystrophic subjects frequently (20%) exhibited an inversion of electrocardiographic T2. The subjects with heart diseases (27-33%) showed extrasystolic disturbances. The results may be used in medical expertise of pilots. PMID:1214489

  13. Stress and adaptation responses to repeated acute acceleration.

    NASA Technical Reports Server (NTRS)

    Burton, R. R.; Smith, A. H.

    1972-01-01

    Study in which groups of adult male chickens (single-comb white leghorn) were exposed daily to acceleration (centrifugation) of 2 or 3 G for 10 min, 1, 4, 8, 12, 16, and 24 hr (continuously), or 0 time (controls). After approximately five months of this intermittent treatment (training), the birds were exposed to continuous accelerations of the same G force (intensity). The degree of stress and adaptation of each bird was determined by survival and relative lymphocyte count criteria. Intermittent training exposures of 2 G developed levels of adaptation in birds directly proportional to the duration of their daily exposure. Intermittent training periods at 3 G, however, produced a physiological deterioration in birds receiving daily exposures of 8 hr or more. Adaptive benefits were found only in the 1- and 4-hr-daily intermittent 3-G exposure groups. Exposure to 3 G produced an immediate stress response as indicated by a low relative lymphocyte count which returned to control (preexposed) values prior to the next daily acceleration period in the 10-min, 1-hr, and 4-hr groups. This daily recovery period from stress appeared to be necessary for adaptation as opposed to deterioration for the more severe environmental (3 G) alteration.

  14. Ion beam accelerator system

    NASA Technical Reports Server (NTRS)

    Aston, Graeme (Inventor)

    1984-01-01

    A system is described that combines geometrical and electrostatic focusing to provide high ion extraction efficiency and good focusing of an accelerated ion beam. The apparatus includes a pair of curved extraction grids (16, 18) with multiple pairs of aligned holes positioned to direct a group of beamlets (20) along converging paths. The extraction grids are closely spaced and maintained at a moderate potential to efficiently extract beamlets of ions and allow them to combine into a single beam (14). An accelerator electrode device (22) downstream from the extraction grids, is at a much lower potential than the grids to accelerate the combined beam.

  15. The MESA accelerator

    SciTech Connect

    Aulenbacher, Kurt [Institut für Kernphysik, Johannnes-Gutenberg-Universität Mainz (Germany)

    2013-11-07

    The MESA accelerator will operate for particle and nuclear physics experiments in two different modes. A first option is conventional c.w. acceleration yielding 150-200MeV spin-polarized external beam. Second, MESA will be operated as a superconducting multi-turn energy recovery linac (ERL), opening the opportunity to perform experiments with a windowless target with beam current of up to 10 mA. The perspectives for innovative experiments with such a machine are discussed together with a sketch of the accelerator physics issues that have to be solved.

  16. Pulmonary function and clearance after prolonged sulfuric acid aerosol exposure

    SciTech Connect

    Ives, P.J. (ABB Environmental, Chapel Hill, NC (United States)); Gerrity, T.R.; DeWitt, P.; Folinsbee, L.J. (Environmental Protection Agency, Chapel Hill, NC (United States))

    1991-03-15

    The authors studied pulmonary function and clearance responses after a 4 H exposure to 75-100 {mu}g/m{sup 3} sulfuric acid aerosol (SAA). Healthy subjects, who exercised for 30 min/H at ventilation of about 25 L/min, were exposed once to clean air and once to SAA. Oral hygiene and acidic juice gargle were used to minimize oral ammonia. Lung function tests, including spirometry, plethysmography, and partial flow-volume (PEFV) curves were performed before and after exposure. Clearance of 99m-Technetium labeled iron oxide was assessed after each exposure. The first moment of fractional tracheobronchial retention (M1TBR), after correcting for 24 H retention and normalizing to time zero, was used as an index of clearance. There were no significant changes in lung volumes, airways resistance, or maximum expiratory flows after SAA exposure. Flow at 40% of total lung capacity on PEFV curves decreased 17% (NS) after SAA exposure. Tracheobronchial clearance was accelerated after a single exposure to SAA; M1TBR decreased from 73 {plus minus} 5 min (air) to 69 {plus minus} 5 min (SAA). These results suggest that acute prolonged exposure to low levels of SAA has minimal effects on lung mechanics in healthy subjects but does produce a modest acceleration of particle clearance.

  17. LANSCE Beam Current Limiter (XL)

    SciTech Connect

    Gallegos, F.R.; Hall, M.J.

    1997-01-01

    The Radiation Security System (RSS) at the Los Alamos Neutron Science Center (LANSCE) is an engineered safety system that provides personnel protection from prompt radiation due to accelerated proton beams. The Beam Current Limiter (XL), as an active component of the RSS, limits the maximum average current in a beamline, thus the current available for a beam spill accident. Exceeding the pre-set limit initiates action by the RSS to mitigate the hazard (insertion of beam stoppers in the low energy beam transport). The beam limiter is an electrically isolated, toroidal transformer and associated electronics. The device was designed to continuously monitor beamline currents independent of any external timing. Fail-safe operation was a prime consideration in its development. Fail-safe operation is defined as functioning as intended (due to redundant circuitry), functioning with a more sensitive fault threshold, or generating a fault condition. This report describes the design philosophy, hardware, implementation, operation, and limitations of the device.

  18. ON PARTICLE ACCELERATION RATE IN GAMMA-RAY BURST AFTERGLOWS

    SciTech Connect

    Sagi, Eran; Nakar, Ehud [Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978 (Israel)

    2012-04-10

    It is well known that collisionless shocks are major sites of particle acceleration in the universe, but the details of the acceleration process are still not well understood. The particle acceleration rate, which can shed light on the acceleration process, is rarely measured in astrophysical environments. Here, we use observations of gamma-ray burst (GRB) afterglows, which are weakly magnetized relativistic collisionless shocks in ion-electron plasma, to constrain the rate of particle acceleration in such shocks. We find, based on X-ray and GeV afterglows, an acceleration rate that is most likely very fast, approaching the Bohm limit, when the shock Lorentz factor is in the range of {Gamma} {approx} 10-100. In that case X-ray observations may be consistent with no amplification of the magnetic field in the shock upstream region. We examine the X-ray afterglow of GRB 060729, which is observed for 642 days showing a sharp decay in the flux starting about 400 days after the burst, when the shock Lorentz factor is {approx}5. We find that inability to accelerate X-ray-emitting electrons at late time provides a natural explanation for the sharp decay, and that also in that case acceleration must be rather fast, and cannot be more than a 100 times slower than the Bohm limit. We conclude that particle acceleration is most likely fast in GRB afterglows, at least as long as the blast wave is ultrarelativistic.

  19. Deflation acceleration of lattice QCD simulations

    E-print Network

    Martin Lüscher

    2007-10-29

    Close to the chiral limit, many calculations in numerical lattice QCD can potentially be accelerated using low-mode deflation techniques. In this paper it is shown that the recently introduced domain-decomposed deflation subspaces can be propagated along the field trajectories generated by the Hybrid Monte Carlo (HMC) algorithm with a modest effort. The quark forces that drive the simulation may then be computed using a deflation-accelerated solver for the lattice Dirac equation. As a consequence, the computer time required for the simulations is significantly reduced and an improved scaling behaviour of the simulation algorithm with respect to the quark mass is achieved.

  20. Energetic particle acceleration in shear layers

    E-print Network

    M. Ostrowski

    1999-11-05

    A plasma velocity shear layer and/or a tangential flow discontinuity provide conditions allowing for energetic particle acceleration. We review such acceleration processes acting both in non-relativistic and in relativistic flows. In heliospheric conditions shear layers can provide particles with energies compatible with the observed values (from several keV up to MeV), while in relativistic extragalactic jets proton energies even in excess of 10^{19} eV can be obtained. Application of the discussed theory to particular astrophysical objects is severely limited by inadequate knowledge of local physical conditions.

  1. Stability of non-linear integrable accelerator

    SciTech Connect

    Batalov, I.; /Moscow, MIPT; Valishev, A.; /Fermilab

    2011-09-01

    The stability of non-linear Integrable Optics Test Accelerator (IOTA) model developed in [1] was tested. The area of the stable region in transverse coordinates and the maximum attainable tune spread were found as a function of non-linear lens strength. Particle loss as a function of turn number was analyzed to determine whether a dynamic aperture limitation present in the system. The system was also tested with sextupoles included in the machine for chromaticity compensation. A method of evaluation of the beam size in the linear part of the accelerator was proposed.

  2. Tracking of Acceleration with HNJ Method

    SciTech Connect

    Ruggiero,A.

    2008-02-01

    After reviewing the principle of operation of acceleration with the method of Harmonic Number Jump (HNJ) in a Fixed-Field Alternating Gradient (FFAG) accelerator for protons and heavy ions, we report in this talk the results of computer simulations performed to assess the capability and the limits of the method in a variety of practical situations. Though the study is not yet completed, and there still remain other cases to be investigated, nonetheless the tracking results so far obtained are very encouraging, and confirm the validity of the method.

  3. Effects of an active accelerator pedal on driver behaviour and traffic safety after long-term use in urban areas

    Microsoft Academic Search

    András Várhelyi; Magnus Hjälmdahl; Christer Hydén; Magda Draskóczy

    2004-01-01

    The long-term effects of the active accelerator pedal (AAP) were evaluated in the city of Lund in 2000 and 2001. The system, installed in 284 vehicles, produced a counterforce in the accelerator pedal at the speed limit. It could, however be overridden by pressing the accelerator pedal harder. The results showed that test drivers’ compliance with the speed limits improved

  4. Perchloroethylene exposure assessment among dry cleaning workers

    SciTech Connect

    Solet, D.; Robins, T.G.; Sampaio, C. (Univ. of Michigan, Ann Arbor (USA))

    1990-10-01

    Perchloroethylene (Perc), the most widely used solvent in dry cleaning, is toxic to the liver, kidneys, and central nervous system and may be a human carcinogen. In the Detroit area, as part of a project investigating the health status of dry cleaning workers, an exposure assessment was carried out in dry cleaning plants using perchloroethylene. Breath samples were obtained from each participant, and time-weighted average (TWA) breathing zone air samples were obtained using passive dosimeters on a subset expected to experience a range of exposures. Perc in breath and Perc in air were highly correlated (r2 = 0.75, p less than 0.0001). On average, operators of dry cleaning equipment experienced significantly more exposure than nonoperators. Also, employees working in shops that use transfer equipment (requiring physical transfer of Perc-saturated clothing from washers to dryers) showed significantly higher exposure than those in shops utilizing dry-to-dry machinery (permitting washing and drying in one machine in a single cycle). One or more air samples in every transfer shop exceeded the recently revised Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) of 25 ppm, while no air samples in dry-to-dry shops exceeded this limit. The results suggest concern for exposures to operators in transfer shops and that compliance with the PEL is achievable by engineering controls with presently existing technology.

  5. eavy Ion Accelerator Technology: Eighth International Conference. Proceedings

    SciTech Connect

    Shepard, K.W. [Physics Division, Argonne National Laboratory, Argonne, IL 60439 (United States)

    1999-04-01

    These proceedings represent papers presented at the 8th International Conference on Heavy Ion Accelerator Technology, held at Argonne National Laboratory, Argonne, Illinois, USA, in October, 1998. The opening session was dedicated to the memory of the late Ray Herb of the University of Wisconsin and National Electrostatics Corporation of the USA. Many aspects of research and developments in superconducting ion accelerators and ECR ion sources were discussed. Specific topics included voltage limitations of electrostatic accelerators, tandem accelerators, electrical stress, accelerator control linac boosters, beam extraction systems, accelerator mass spectroscopy and fission fragments. Several applications were reviewed including the technology needed for beams of exotic, radioactive nuclei. There were 58 papers presented at the conference, out of which 18 have been abstracted for the Energy,Science and Technology database.(AIP)

  6. A faster scaling in acceleration-sensitive atom interferometers

    NASA Astrophysics Data System (ADS)

    McDonald, G. D.; Kuhn, C. C. N.; Bennetts, S.; Debs, J. E.; Hardman, K. S.; Close, J. D.; Robins, N. P.

    2014-03-01

    Atom interferometers have been used to measure acceleration with at best a T2 scaling in sensitivity as the interferometer time T is increased. This limits the sensitivity to acceleration which is theoretically achievable by these configurations for a given frequency of acceleration. We predict and experimentally measure the acceleration-sensitive phase shift of a large-momentum-transfer atom interferometer based upon Bloch oscillations. Using this novel interferometric scheme we demonstrate an improved scaling of sensitivity which will scale as T3. This enhanced scaling will allow an increase in achievable sensitivity for any given frequency of an oscillatory acceleration signal, which will be of particular use for inertial and navigational sensors, and proposed gravitational wave detectors. A straightforward extension should allow a T4 scaling in acceleration sensitivity.

  7. Biomarkers of xenobiotic exposures

    SciTech Connect

    Brewster, M.A.

    1988-07-01

    Direct measurement of xenobiotic (foreign) chemicals is not always feasible as an exposure assessment,--owing to rapid metabolism, sequestration into fatty tissues, or lack of suitable assay methods. Furthermore, suspect exposures often involve complex mixtures of organics. In these circumstances, indirect biomarkers of exposure can be most helpful. This paper reviews four urinary parameters that hold promise as biomarkers of exposure in occupational and environmental settings: glucaric acid (end-product of the glucuronidation pathway), thioethers (end-product of glutathione reaction with electrophilic or alkylating agents), porphyrin pattern (altered with disruption in heme biosynthesis), and the Ames mutagenicity test. 112 references.

  8. Radiation exposure to anaesthetists during endovascular procedures.

    PubMed

    Arii, T; Uchino, S; Kubo, Y; Kiyama, S; Uezono, S

    2015-01-01

    Medical radiation exposure increases the likelihood of cataract formation. A personal dosimeter was attached to the left temple of 77 anaesthetists during 45 endovascular aortic aneurysm repairs and 32 interventional neuroradiology procedures. Compared with interventional neuroradiology, the median (IQR [range]) total radiation dose emitted by fluoroscopic equipment was significantly lower during endovascular aortic aneurysm repair (4175 (3127-5091 [644-9761]) mGy than interventional neuroradiology (1420 (613-2424 [165-10,840]) mGy, p < 0.001). However, radiation exposure to the anaesthetist's temple was significantly greater during endovascular aortic aneurysm repair (15 (6-41 [1-109]) ?Sv) than interventional neuroradiology (4 (2-8 [0-67]) ?Sv, p < 0.001). These data suggest that anaesthetists at our institution would have to deliver anaesthesia for ~1300 endovascular aortic aneurysm repairs and ~5000 interventional neuroradiology cases annually to exceed the general occupational limits, and ~10,000 endovascular aortic aneurysm repairs and ~37,500 interventional neuroradiology cases to exceed the ocular exposure limits recommended by the International Commission on Radiological Protection. Nevertheless, anaesthetists should be aware of the risk of ocular radiation exposure, and reduce this by limiting the time of exposure, increasing the distance from the source of radiation, and shielding. PMID:25267714

  9. Accelerator on a Chip

    SciTech Connect

    England, Joel

    2014-06-30

    SLAC's Joel England explains how the same fabrication techniques used for silicon computer microchips allowed their team to create the new laser-driven particle accelerator chips. (SLAC Multimedia Communications)

  10. Accelerator on a Chip

    ScienceCinema

    England, Joel

    2014-07-16

    SLAC's Joel England explains how the same fabrication techniques used for silicon computer microchips allowed their team to create the new laser-driven particle accelerator chips. (SLAC Multimedia Communications)

  11. Acceleration of Logarithmic Convergence

    NASA Technical Reports Server (NTRS)

    Gaskin, J. G.; Ford, W. F.

    1998-01-01

    In this paper, we shall give a characterization of all monotonically decreasing sequence of positive terms, whose sum converge and then introduce a Transformation which can be used to accelerate the convergence of a large class of logarithmically convergent series.

  12. Charged particle accelerator grating

    DOEpatents

    Palmer, R.B.

    1985-09-09

    A readily disposable and replaceable accelerator grating for a relativistic particle accelerator is described. The grating is formed for a plurality of liquid droplets that are directed in precisely positioned jet streams to periodically dispose rows of droplets along the borders of a predetermined particle beam path. A plurality of lasers are used to direct laser beams onto the droplets, at predetermined angles, thereby to excite the droplets to support electromagnetic accelerating resonances on their surfaces. Those resonances operate to accelerate and focus particles moving along the beam path. As the droplets are distorted or destroyed by the incoming radiation, they are replaced at a predetermined frequency by other droplets supplied through the jet streams.

  13. Vibration control in accelerators

    SciTech Connect

    Montag, C.

    2011-01-01

    In the vast majority of accelerator applications, ground vibration amplitudes are well below tolerable magnet jitter amplitudes. In these cases, it is necessary and sufficient to design a rigid magnet support structure that does not amplify ground vibration. Since accelerator beam lines are typically installed at an elevation of 1-2m above ground level, special care has to be taken in order to avoid designing a support structure that acts like an inverted pendulum with a low resonance frequency, resulting in untolerable lateral vibration amplitudes of the accelerator components when excited by either ambient ground motion or vibration sources within the accelerator itself, such as cooling water pumps or helium flow in superconducting magnets. In cases where ground motion amplitudes already exceed the required jiter tolerances, for instance in future linear colliders, passive vibration damping or active stabilization may be considered.

  14. Direct Acceleration of Electrons in a Corrugated Plasma Waveguide A. G. York* and H. M. Milchberg

    E-print Network

    Milchberg, Howard

    Direct Acceleration of Electrons in a Corrugated Plasma Waveguide A. G. York* and H. M. Milchberg) Historically, direct acceleration of charged particles by electromagnetic fields has been limited- field acceleration of electrons over many centimeters using relatively small femtosecond lasers. We

  15. A practical target system for accelerator-based BNCT which may effectively double the dose rate

    E-print Network

    Brenner, David Jonathan

    March 1998 A dose-limiting component of a proton accelerator-based source of epithermal neutrons, accelerator, BNCT, beryllium, lithium If boron neutron capture therapy BNCT is to become a practical option, accelerator-based sources of high fluxes of epithermal neutrons are essential.1­4 Much work has been performed

  16. Heave compensation and formation strength evaluation from downhole acceleration measurements while coring

    Microsoft Academic Search

    G. Guerin; D. Goldberg

    2002-01-01

    In order to evaluate the efficiency of heave compensation in the Ocean Drilling Program, we developed a device measuring the acceleration of the core barrels. First results show that heave compensation limits bit motion to 10% of the surface heave. We also use the acceleration data to characterize the formation. On rotary corers, acceleration amplitudes decrease with increasing hardness of

  17. DELAYED REPRODUCTIVE EFFECTS FOLLOWING EXPOSURE TO TOXIC CHEMICALS DURING CRITICAL DEVELOPMENTAL PERIODS

    EPA Science Inventory

    The studies presented in this review indicate that perinatal exposure of the fetal or neonatal rodent to a toxicant can adversely affect reproductive development, reduce fertility.and accelerate reproductive senescence. n rodents and humans exposure to DES, estrogens, androgens a...

  18. Motion with Constant Acceleration

    NSDL National Science Digital Library

    Dr. Russell Herman

    The purpose of this experiment is to track the motion for an air cart on a sloped track to fall a distance x with constant acceleration a = g sinq. You will verify that the distance and velocity along the incline are given by the parabola x = xo + vo t +1/2at2 and the line v = vo +at. Finally, you will determine the acceleration due to gravity.

  19. An active particle accelerator

    SciTech Connect

    Goldman, T.

    1991-01-01

    Although a static charge is difficult to maintain on macroscopic particles, it is straightforward to construct a small object with a regularly oscillating electric dipole moment. For objects of a given size, one may then construct an accelerator by appropriately matching the frequency and separations of an external array of electrodes to this size. Physically feasible size ranges, an accelerator design, and possible applications of such systems are discussed. 8 refs., 9 figs.

  20. CEBAF accelerator achievements

    SciTech Connect

    Y.C. Chao, M. Drury, C. Hovater, A. Hutton, G.A. Krafft, M. Poelker, C. Reece, M. Tiefenback

    2011-06-01

    In the past decade, nuclear physics users of Jefferson Lab's Continuous Electron Beam Accelerator Facility (CEBAF) have benefited from accelerator physics advances and machine improvements. As of early 2011, CEBAF operates routinely at 6 GeV, with a 12 GeV upgrade underway. This article reports highlights of CEBAF's scientific and technological evolution in the areas of cryomodule refurbishment, RF control, polarized source development, beam transport for parity experiments, magnets and hysteresis handling, beam breakup, and helium refrigerator operational optimization.

  1. Breakthrough: Fermilab Accelerator Technology

    ScienceCinema

    None

    2014-08-12

    There are more than 30,000 particle accelerators in operation around the world. At Fermilab, scientists are collaborating with other laboratories and industry to optimize the manufacturing processes for a new type of powerful accelerator that uses superconducting niobium cavities. Experimenting with unique polishing materials, a Fermilab team has now developed an efficient and environmentally friendly way of creating cavities that can propel particles with more than 30 million volts per meter.

  2. Case of accelerated silicosis in a sandblaster

    PubMed Central

    HUTYROVÁ, Beáta; SMOLKOVÁ, Petra; NAKLÁDALOVÁ, Marie; TICHÝ, Tomáš; KOLEK, Vít?zslav

    2014-01-01

    Sandblasting is traditionally known as a high-risk profession for potential development of lung silicosis. Reported is a case of a sandblaster with confirmed accelerated silicosis, a condition rather rarely diagnosed in the Czech Republic. Initially, the patient presented with progressive dry cough and exertional dyspnoea. In the early diagnostic process, a possible occupational aetiology was considered given his occupational history and known high-risk exposure to respirable silica particles confirmed by industrial hygiene assessment at the patient’s workplace. The condition was confirmed by clinical, histological and autopsy findings. The patient died during lung transplantation, less than five years from diagnosis. PMID:25567156

  3. Combined Toxic Exposures and Human Health: Biomarkers of Exposure and Effect

    PubMed Central

    Silins, Ilona; Högberg, Johan

    2011-01-01

    Procedures for risk assessment of chemical mixtures, combined and cumulative exposures are under development, but the scientific database needs considerable expansion. In particular, there is a lack of knowledge on how to monitor effects of complex exposures, and there are few reviews on biomonitoring complex exposures. In this review we summarize articles in which biomonitoring techniques have been developed and used. Most examples describe techniques for biomonitoring effects which may detect early changes induced by many chemical stressors and which have the potential to accelerate data gathering. Some emphasis is put on endocrine disrupters acting via epigenetic mechanisms and on carcinogens. Solid evidence shows that these groups of chemicals can interact and even produce synergistic effects. They may act during sensitive time windows and biomonitoring their effects in epidemiological studies is a challenging task. PMID:21556171

  4. On the evolving nature of exposure therapy.

    PubMed

    Schare, Mitchell L; Wyatt, Kristin P

    2013-03-01

    Four articles examining methodological applications of exposure therapy and its limited dissemination were briefly reviewed. Methodological articles included those by Abramowitz et al., Gryczkowski et al., and Weiner and McKay, which addressed couple treatment of obsessive-compulsive disorder (OCD), modification of evidence-based anxiety treatments for children, and novel exposure methods for depersonalization and derealization, respectively. The creative aspects of these innovations are highlighted as well as historical parallels in the empirical literature for both anxiety and other clinical phenomena. Underutilization and limited dissemination concerns are discussed in the context of the fourth article by Hipol and Deacon and as related to the field as a whole. A unique concept, exposaphobia, is hypothesized to explain the lack of clinicians' utilization of this technique, due to their own anxiety-driven inhibitions in using it. Suggestions for the future of exposure research and dissemination are made. PMID:23460592

  5. Computer subroutines for estimation of human exposure to radiation in low Earth orbit

    NASA Technical Reports Server (NTRS)

    Cucinotta, F. A.; Wilson, J. W.

    1985-01-01

    Computer subroutines to calculate human exposure to trapped radiations in low Earth orbit (LEO) on the basis of a simple approximation of the human geometry by spherical shell shields of varying thickness are presented and detailed. The subroutines calculate the dose to critical body organs and the fraction of exposure limit reached as a function of altitude of orbit, degree of inclination, shield thickness, and days in mission. Exposure rates are compared with current exposure limits.

  6. Radiation from charges in the continuum limit

    SciTech Connect

    Ianconescu, Reuven [Shenkar College of Engineering and Design, Ramat Gan 52526 (Israel)

    2013-06-15

    It is known that an accelerating charge radiates according to Larmor formula. On the other hand, any DC current following a curvilinear path, consists of accelerating charges, but in such case the radiated power is 0. The scope of this paper is to analyze and quantify how a system of charges goes from a radiating state to a non radiating state when the charges distribution goes to the continuum limit. Understanding this is important from the theoretical point of view and the results of this work are applicable to particle accelerator, cyclotron and other high energy devices.

  7. Environmental Residues and Biomonitoring Estimates of Human Insecticide Exposure from Treated Residential Turf

    Microsoft Academic Search

    C. E. Bernard; H. Nuygen; D. Truong; R. I. Krieger

    2001-01-01

    Intentional and unavoidable human exposure is a consequence of using pesticides to nurture and protect residential turf. Limited\\u000a exposure studies have been conducted for assessing potential human exposure of turf residues. Exposure was measured in persons\\u000a who performed a 20-minute structured activity (Jazzercise®) on chlorpyrifos (CP)-treated Kentucky bluegrass (12 ± 4 ?g CP\\/cm2). CP exposure was measured by determining urine

  8. The Limits of Quintessence

    SciTech Connect

    Caldwell, R.R.; Linder, Eric V.

    2005-05-24

    We present evidence that the simplest particle-physics scalar-field models of dynamical dark energy can be separated into distinct behaviors based on the acceleration or deceleration of the field as it evolves down its potential towards a zero minimum. We show that these models occupy narrow regions in the phase-plane of w and w', the dark energy equation-of-state and its time-derivative in units of the Hubble time. Restricting an energy scale of the dark energy microphysics limits how closely a scalar field can resemble a cosmological constant. These results, indicating a desired measurement resolution of order \\sigma(w')\\approx (1+w), define firm targets for observational tests of the physics of dark energy.

  9. HUMAN EXPOSURE DATABASES DEVELOPMENT AND APPLICATIONS

    EPA Science Inventory

    In the past, data from human exposure research studies often resided with the study investigators and the only way the data were disseminated was by publication in EPA reports or peer-reviewed journal manuscripts. Data were often published only as summary statistics with limited...

  10. MODEL DEVELOPMENT - EXPOSURE MODELS

    EPA Science Inventory

    Humans are exposed to mixtures of chemicals from multiple pathways and routes. These exposures may result from a single event or may accumulate over time if multiple exposure events occur. The traditional approach of assessing risk from a single chemical and a single route of e...

  11. EXPOSURE MODELING - SHEDS

    EPA Science Inventory

    This presentation provides a general overview of SHEDS model features, describes algorithms in the SHEDS-Air Toxics model that focus on mobile source exposures and multipathway exposures, and presents examples of results from application of the SHEDS-Air Toxics model to benzene i...

  12. Physically Based Rendering Intersection Acceleration

    E-print Network

    Kazhdan, Michael

    Physically Based Rendering (600.657) Intersection Acceleration #12;Intersection Testing Accelerated partitions: Group objects into clusters Cluster volumes may overlap #12;Uniform (Voxel) Grid Acceleration Acceleration · Trace rays through grid cells ­ Fast ­ Incremental A B C D E F Only check primitives

  13. Plasma-based accelerator structures

    SciTech Connect

    Schroeder, Carl B.

    1999-12-01

    Plasma-based accelerators have the ability to sustain extremely large accelerating gradients, with possible high-energy physics applications. This dissertation further develops the theory of plasma-based accelerators by addressing three topics: the performance of a hollow plasma channel as an accelerating structure, the generation of ultrashort electron bunches, and the propagation of laser pulses is underdense plasmas.

  14. Period measurement by accelerating observers

    E-print Network

    Bernhard Rothenstein; Stefan Popescu

    2006-07-04

    We consider the problem of the period measurement in the case of the following scenarios: stationary source of successive light signals and accelerating receiver, stationary receiver and accelerating source of successive light signals and stationary machine gun that fires successive bullets received by an accelerating receiver. The accelerated motion is the hyperbolic one.

  15. Solar Flares and particle acceleration

    E-print Network

    Solar Flares and particle acceleration Eduard Kontar School of Physics and Astronomy University and accelerated particles #12;Solar flares and accelerated particles From Emslie et al., 2004, 2005 Free magnetic Spectroscopic Imager RHESSI is designed to investigate particle acceleration and energy release in solar flares

  16. Deuterium accelerator experiments for APT.

    SciTech Connect

    Causey, Rion A. (Sandia National Laboratories, Livermore, CA); Hertz, Kristin L. (Sandia National Laboratories, Livermore, CA); Cowgill, Donald F. (Sandia National Laboratories, Livermore, CA)

    2005-08-01

    Sandia National Laboratories in California initiated an experimental program to determine whether tritium retention in the tube walls and permeation through the tubes into the surrounding coolant water would be a problem for the Accelerator Production of Tritium (APT), and to find ways to mitigate the problem, if it existed. Significant holdup in the tube walls would limit the ability of APT to meet its production goals, and high levels of permeation would require a costly cleanup system for the cooling water. To simulate tritium implantation, a 200 keV accelerator was used to implant deuterium into Al 6061-T and SS3 16L samples at temperatures and particle fluxes appropriate for APT, for times varying between one week and five months. The implanted samples were characterized to determine the deuterium retention and Permeation. During the implantation, the D(d,p)T nuclear reaction was used to monitor the build-up of deuterium in the implant region of the samples. These experiments increased in sophistication, from mono-energetic deuteron implants to multi-energetic deuteron and proton implants, to more accurately reproduce the conditions expected in APT. Micron-thick copper, nickel, and anodized aluminum coatings were applied to the front surface of the samples (inside of the APT walls) in an attempt to lower retention and permeation. The reduction in both retention and permeation produced by the nickel coatings, and the ability to apply them to the inside of the APT tubes, indicate that both nickel-coated Al 6061-T6 and nickel-coated SS3 16L tubes would be effective for use in APT. The results of this work were submitted to the Accelerator Production of Tritium project in document number TPO-E29-Z-TNS-X-00050, APT-MP-01-17.

  17. Acceleration of ampere class H{sup -} ion beam by MeV accelerator

    SciTech Connect

    Taniguchi, M.; Inoue, T.; Umeda, N.; Kashiwagi, M.; Watanabe, K.; Tobari, H.; Dairaku, M.; Sakamoto, K. [Fusion Research and Development Directorate, Japan Atomic Energy Agency, 801-1 Mukouyama, Naka 311-0193 (Japan)

    2008-02-15

    The H{sup -} ion accelerator R and D to realize the international thermonuclear experimental reactor neutral beam is ongoing at Japan Atomic Energy Agency (JAEA). The required performance for the prototype MeV accelerator developed at JAEA is 1 MeV, 500 mA (current density of 200 A/m{sup 2}) H{sup -} ion beam at the beamlet divergence angle of less than 7 mrad. Up to 2005, 836 keV, 146 A/m{sup 2} H{sup -} ion beam was successfully accelerated as the highest record of the current density at MeV class energy beams. In the present work, high current negative ion beam acceleration test was performed by increasing the beam extraction apertures from 3x3 (9 apertures) to 3x5 (15 apertures). By fixing the air leak at the source chamber due to backstream ions as well as the improvement of voltage holding capability by a new fiber reinforced plastic insulator ring, the performance of the MeV accelerator was improved. So far, H{sup -} ion beam of 320 mA was successfully accelerated up to 796 keV with the beam divergence angle of 5.5 mrad. The accelerated drain current including the electron reaches close to the power supply limit for the MeV test facility. The heat flux by the backstream ion during the above beam acceleration was estimated to be 360 W/cm{sup 2}. The Cs leakage to the accelerator during the test campaign (Cs total input of 5.0 g) was 0.26 mg (7.0 {mu}g/cm{sup 2}). This is considered to be the allowable level from the viewpoint of voltage holding.

  18. From dust to dose: Effects of forest disturbance on increased inhalation exposure.

    PubMed

    Whicker, Jeffrey J; Pinder, John E; Breshears, David D; Eberhart, Craig F

    2006-09-15

    Ecosystem disturbances that remove vegetation and disturb surface soils are major causes of excessive soil erosion and can result in accelerated transport of soils contaminated with hazardous materials. Accelerated wind erosion in disturbed lands that are contaminated is of particular concern because of potential increased inhalation exposure, yet measurements regarding these relationships are lacking. The importance of this was highlighted when, in May of 2000, the Cerro Grande fire burned over roughly 30% of Los Alamos National Laboratory (LANL), mostly in ponderosa pine (Pinus ponderosa) forest, and through areas with soils containing contaminants, particularly excess depleted and natural uranium. Additionally, post-fire thinning was performed in burned and unburned forests on about 25% of LANL land. The first goal of this study was to assess the potential for increased inhalation dose from uranium contaminated soils via wind-driven resuspension of soil following the Cerro Grande Fire and subsequent forest thinning. This was done through analysis of post-disturbance measurements of uranium air concentrations and their relationships with wind velocity and seasonal vegetation cover. We found a 14% average increase in uranium air concentrations at LANL perimeter locations after the fire, and the greatest air concentrations occurred during the months of April-June when wind velocities are highest, no snow cover, and low vegetation cover. The second goal was to develop a methodology to assess the relative contribution of each disturbance type towards increasing public and worker exposure to these resuspended soils. Measurements of wind-driven dust flux in severely burned, moderately burned, thinned, and unburned/unthinned forest areas were used to assess horizontal dust flux (HDF) in these areas. Using empirically derived relationships between measurements of HDF and respirible dust, coupled with onsite uranium soil concentrations, we estimate relative increases in inhalation doses for workers ranging from 15% to 38%. Despite the potential for increased doses resulting from these forest disturbances, the estimated annual dose rate for the public was <1 microSv yr(-1), which is far below the dose limits for public exposures, and the upper-bound dose rate for a LANL worker was estimated to be 140 microSv yr(-1), far below the 5 x 10(4) microSv yr(-1) occupational dose limit. These results show the importance of ecosystem disturbance in increasing mobility of soil-bound contaminants, which can ultimately increase exposure. However, it is important to investigate the magnitude of the increases when deciding appropriate strategies for management and long-term stewardship of contaminated lands. PMID:16618498

  19. Photon acceleration in laser wakefield accelerators

    NASA Astrophysics Data System (ADS)

    Trines, R. M. G. M.

    2007-07-01

    If the index of a refraction of a dispersive medium, such as a plasma, changes in time, it can be used to change the frequency of light propagating through the medium. This effect is called photon acceleration. It has been predicted in both theory and simulations, and also been demonstrated experimentally for the case of moving ionization fronts in gases (the so-called ionization blueshift) as well as for laser-driven wakefields. Here, we present studies of photon acceleration in laser-driven plasma wakefields. The unique spectral characteristics of this process will be discussed, to distinguish it from e.g. photon acceleration by ionization fronts, frequency domain interferometry or self-phase modulation. The dynamics of the photons in laser-wakefield interaction are studied through both regular particle-in-cell and wave-kinetic simulations. The latter approach provides a powerful, versatile, and easy-to-use method to track the propagation of individual spectral components, providing new insight into the physics of laser-plasma interaction. Theory, simulations and experimental results will be brought together to provide a full understanding of the dynamics of a laser pulse in its own wakefield. Even though the wave-kinetic approach mentioned above has mainly been developed for the description of laser-plasma interaction, it can be applied to a much wider range of fast wave-slow wave interaction processes: Langmuir waves-ion acoustic waves, drift waves-zonal flow, Rossby waves-zonal flow, or even photons-gravitational waves. Several recent results in these areas will be shown, often with surprising results.

  20. Fermi acceleration in astrophysical jets

    E-print Network

    Frank M. Rieger; Valenti Bosch-Ramon; Peter Duffy

    2006-10-05

    We consider the acceleration of energetic particles by Fermi processes (i.e., diffusive shock acceleration, second order Fermi acceleration, and gradual shear acceleration) in relativistic astrophysical jets, with particular attention given to recent progress in the field of viscous shear acceleration. We analyze the associated acceleration timescales and the resulting particle distributions, and discuss the relevance of these processes for the acceleration of charged particles in the jets of AGNs, GRBs and microquasars, showing that multi-component powerlaw-type particle distributions are likely to occur.

  1. Issues regarding acceleration in crystals

    SciTech Connect

    Chen, P. [Stanford Linear Accelerator Center, Menlo Park, CA (United States); Cline, D.B.; Gabella, W.E. [California Univ., Los Angeles, CA (United States). Dept. of Physics

    1992-12-01

    Both self-acceleration and laser-acoustic acceleration in crystals are considered. The conduction electrons in the crystal are treated as a plasma and are the medium through which the acceleration takes place. Self-acceleration is the possible acceleration of part of a bunch due to plasma oscillations driven by the leading part. Laser- acoustic acceleration uses a laser in quasi-resonance with an acoustic wave to pump up the plasma oscillation to accelerate a beam. Self-driven schemes though experimentally simple seem problematic because single bunch densities must be large.

  2. Biomarkers of exposure, sensitivity and disease

    NASA Technical Reports Server (NTRS)

    Brooks, A. L.

    1999-01-01

    PURPOSE: This review is to evaluate the use of biomarkers as an indication of past exposure to radiation or other environmental insults, individual sensitivity and risk for the development of late occurring disease. OVERVIEW: Biomarkers can be subdivided depending on their applications. Markers of exposure and dose can be used to reconstruct and predict past accidental or occupational exposures when limited or no physical measurements were available. Markers of risk or susceptibility can help identify sensitivity individuals that are at increased risk for development of spontaneous disease and may help predict the increased risk in sensitive individuals associated with environmental or therapeutic radiation exposures. Markers of disease represent the initial cellular or molecular changes that occur during disease development. Each of these types of biomarkers serves a unique purpose. OUTLINE: This paper concentrates on biomarkers of dose and exposure and provides a brief review of biomarkers of sensitivity and disease. The review of biomarkers of dose and exposure will demonstrate the usefulness of biomarkers in evaluation of physical factors associated with radiation exposure, such as LET, doserate and dose distribution. It will also evaluate the use of biomarkers to establish relationships that exist between exposure parameters such as energy deposition, environmental concentration of radioactive materials, alpha traversals and dose. In addition, the importance of biological factors on the magnitude of the biomarker response will be reviewed. Some of the factors evaluated will be the influence of species, tissue, cell types and genetic background. The review will demonstrate that markers of sensitivity and disease often have little usefulness in dose-reconstruction and, by the same token, many markers of dose or exposure may not be applicable for prediction of sensitivity or risk.

  3. Personal exposure of children to air pollution

    NASA Astrophysics Data System (ADS)

    Ashmore, M. R.; Dimitroulopoulou, C.

    Changes over recent decades in outdoor concentrations of air pollutants are well documented. However, the impacts of air pollution on an individual's health actually relate not to these outdoor concentrations but to their personal exposure in the different locations in which they spend time. Assessing how personal exposures differ from outdoor concentrations, and how they have changed over recent decades, is challenging. This review focuses on the exposure of children, since they are a particularly sensitive group. Much of children's time is spent indoors, and childhood exposure is closely related to concentrations in the home, at school, and in transport. For this reason, children's personal exposures to air pollutants differ significantly from both those of adults and from outdoor concentrations. They depend on a range of factors, including urbanisation, energy use, building design, travel patterns, and activity profiles; analysis of these factors can identify a wider range of policy measures to reduce children's exposure than direct emission control. There is a very large variation in personal exposure between individual children, caused by differences in building design, indoor and outdoor sources, and activity patterns. Identifying groups of children with high personal exposure, and their underlying causes, is particularly important in regions of the world where emissions are increasing, but there are limited resources for environmental and health protection. Although the science of personal exposure assessment, with the associated measurement and modelling techniques, has developed to maturity in North America and western Europe over the last 50 years, there is an urgent need to apply this science in other parts of the world where the effects of air pollution are now much more serious.

  4. Studies of accelerated compact toruses

    SciTech Connect

    Hartman, C.W.; Eddleman, J.; Hammer, J.H.

    1983-01-04

    In an earlier publication we considered acceleration of plasma rings (Compact Torus). Several possible accelerator configurations were suggested and the possibility of focusing the accelerated rings was discussed. In this paper we consider one scheme, acceleration of a ring between coaxial electrodes by a B/sub theta/ field as in a coaxial rail-gun. If the electrodes are conical, a ring accelerated towards the apex of the cone undergoes self-similar compression (focusing) during acceleration. Because the allowable acceleration force, F/sub a/ = kappaU/sub m//R where (kappa < 1), increases as R/sup -2/, the accelerating distance for conical electrodes is considerably shortened over that required for coaxial electrodes. In either case, however, since the accelerating flux can expand as the ring moves, most of the accelerating field energy can be converted into kinetic energy of the ring leading to high efficiency.

  5. Microelectromechanical acceleration-sensing apparatus

    DOEpatents

    Lee, Robb M. (Albuquerque, NM); Shul, Randy J. (Albuquerque, NM); Polosky, Marc A. (Albuquerque, NM); Hoke, Darren A. (Albuquerque, NM); Vernon, George E. (Rio Rancho, NM)

    2006-12-12

    An acceleration-sensing apparatus is disclosed which includes a moveable shuttle (i.e. a suspended mass) and a latch for capturing and holding the shuttle when an acceleration event is sensed above a predetermined threshold level. The acceleration-sensing apparatus provides a switch closure upon sensing the acceleration event and remains latched in place thereafter. Examples of the acceleration-sensing apparatus are provided which are responsive to an acceleration component in a single direction (i.e. a single-sided device) or to two oppositely-directed acceleration components (i.e. a dual-sided device). A two-stage acceleration-sensing apparatus is also disclosed which can sense two acceleration events separated in time. The acceleration-sensing apparatus of the present invention has applications, for example, in an automotive airbag deployment system.

  6. Risk factors for increased BTEX exposure in four Australian cities

    Microsoft Academic Search

    Andrea L. Hinwood; Clemencia Rodriguez; Tina Runnion; Drew Farrar; Frank Murray; Anthony Horton; Deborah Glass; Vicky Sheppeard; John W. Edwards; Lynnette Denison; Tom Whitworth; Chris Eiser; Max K Bulsara; Rob W. Gillett; Jenny Powell; S. Lawson; Ian Galbally

    2007-01-01

    Benzene, toluene, ethylbenzene and xylenes (BTEX) are common volatile organic compounds (VOCs) found in urban airsheds. Elevated levels of VOCs have been reported in many airsheds at many locations, particularly those associated with industrial activity, wood heater use and heavy traffic. Exposure to some VOCs has been associated with health risks. There have been limited investigations into community exposures to

  7. Exposure assessment at the workplace: Implications of biological variability

    Microsoft Academic Search

    Paola Manini; Giuseppe De Palma; Antonio Mutti

    2007-01-01

    Biological monitoring (BM) and biomarkers are widely applied in occupational toxicology. BM is mainly aimed at (i) defining the existence of an occupational exposure; (ii) quantifying the level of internal dose; (iii) verifying that exposure limits (BEI®, BAT, BLV) are respected. As compared to ambient monitoring, BM is more expensive and complex. Several biomarkers are available for the same chemical

  8. Baseline Measurements of Smoke Exposure Among Wildland Firefighters

    Microsoft Academic Search

    Timothy E. Reinhardt; Roger D. Ottmar

    2004-01-01

    Extensive measurements of smoke exposure among wildland firefighters are summarized, showing that firefighters can be exposed to significant levels of carbon monoxide and respiratory irritants, including formaldehyde, acrolein, and respirable particulate matter. Benzene was also measured and found to be well below permissible exposure limits, with the highest concentrations occurring among firefighters working with engines and torches burning petroleum-based fuel.

  9. Task-based Dermal Exposure Models for Regulatory Risk Assessment

    Microsoft Academic Search

    NICHOLAS D. WARREN; HANS MARQUART; YVETTE CHRISTOPHER; JUHA LAITINEN; JOOP J. VAN HEMMEN

    2006-01-01

    The regulatory risk assessment of chemicals requires the estimation of occupational dermal exposure. Until recently, the models used were either based on limited data or were specific to a particular class of chemical or application. The EU project RISKOFDERM has gathered a considerable number of new measurements of dermal exposure together with detailed contex- tual information. This article describes the

  10. Some considerations in choosing an occupational noise exposure regulation

    Microsoft Academic Search

    N. A. Ashford; D. Hattis; G. Heaton

    1976-01-01

    Some issues in conflict regarding the proposed OSHA standard for occupational exposure to noise are examined. These include material impairment, the extent of possible hearing loss, nonauditory effects, and the nature of social and economic costs benefits of regulation at 85 dBA and 90 dBA exposure limits. A preliminary analysis of the methodology and difficulties in arriving at cost benefit

  11. A Conditional Exposure Control Method for Multidimensional Adaptive Testing

    ERIC Educational Resources Information Center

    Finkelman, Matthew; Nering, Michael L.; Roussos, Louis A.

    2009-01-01

    In computerized adaptive testing (CAT), ensuring the security of test items is a crucial practical consideration. A common approach to reducing item theft is to define maximum item exposure rates, i.e., to limit the proportion of examinees to whom a given item can be administered. Numerous methods for controlling exposure rates have been proposed…

  12. Hexavalent Chromium Exposure and Control in Welding Tasks

    Microsoft Academic Search

    John D. Meeker; Pam Susi; Michael R. Flynn

    2010-01-01

    Studies of exposure to the lung carcinogen hexavalent chromium (CrVI) from welding tasks are limited, especially within the construction industry where overexposure may be common. In addition, despite the OSHA requirement that the use of engineering controls such as local exhaust ventilation (LEV) first be considered before relying on other strategies to reduce worker exposure to CrVI, data on the

  13. Particle Acceleration at High-$?$ Shock Waves

    E-print Network

    Jacek Niemiec

    2005-09-22

    First-order Fermi acceleration processes at ultrarelativistic shocks are studied with Monte Carlo simulations. The accelerated particle spectra are obtained by integrating the exact particle trajectories in a turbulent magnetic field near the shock, with a few ``realistic'' features of the field structure included. We show that the main acceleration process at oblique shocks is the particle compression at the shock. Formation of energetic spectral tails is possible in a limited energy range for highly perturbed magnetic fields. Cut-offs in the spectra occur at low energies in the resonance range considered. We relate this feature to the structure of the magnetic field downstream of the shock, where field compression produces effectively 2D turbulence in which cross-field diffusion is very small. Because of the field compression downstream, the acceleration process is inefficient also in parallel high-$\\gamma$ shocks for larger turbulence amplitudes, and features observed in oblique shocks are recovered. For small-amplitude perturbations, particle spectra are formed in a wide energy range and modifications of the acceleration process due to the existence of long-wave perturbations are observed. The critical turbulence amplitude for efficient acceleration at parallel shocks decreases with shock Lorentz factor. We also study the influence of strong short-wave perturbations downstream of the shock on the particle acceleration processes. The spectral indices obtained do not converge to the ``universal'' value . Our results indicate inefficiency of the first-order Fermi process to generate high-energy cosmic rays at ultrarelativistic shocks with the considered perturbed magnetic field structures.

  14. The evolution of high energy accelerators

    SciTech Connect

    Courant, E.D.

    1994-08-01

    Accelerators have been devised and built for two reasons: In the first place, by physicists who needed high energy particles in order to have a means to explore the interactions between particles that probe the fundamental elementary forces of nature. And conversely, sometimes accelerator builders produce new machines for higher energy than ever before just because it can be done, and then challenge potential users to make new discoveries with the new means at hand. These two approaches or motivations have gone hand in hand. This lecture traces how high energy particle accelerators have grown from tools used for esoteric small-scale experiments to the gigantic projects of today. So far all the really high-energy machines built and planned in the world--except the SLC--have been ring accelerators and storage rings using the strong-focusing method. But this method has not removed the energy limit, it has only pushed it higher. It would seem unlikely that one can go beyond the Large Hadron Collider (LHC)--but in fact a workshop was held in Sicily in November 1991, concerned with the question of extrapolating to 100 TeV. Other acceleration and beam-forming methods are now being discussed--collective fields, laser acceleration, wake-field accelerators etc., all aimed primarily at making linear colliders possible and more attractive than with present radiofrequency methods. So far it is not entirely clear which of these schemes will dominate particle physics in the future--maybe something that has not been thought of as yet.

  15. Speeds and accelerations of coronal mass ejections

    NASA Technical Reports Server (NTRS)

    St.cyr, O. Chris; Hundhausen, A. J.; Burkepile, J. T.

    1992-01-01

    More than 1300 coronal mass ejections have been detected in observations made by the coronagraph aboard SMM during 1980 and 1984-1989. The speed (projected onto the plane of the sky) for at least one morphoplogical feature in about half of these mass ejections could be measured. The average speed of all mass ejection features was about 350 km/s, but speeds range from a few 10s of km/s to more than 2000 km/s. There also appear to be significant variations between the speed distributions for different years. When a mass ejection feature appeared in three or more sequential images, its acceleration could also be calculated. But, because of the limited time a mass ejection remained in the SMM field of view, the ability to detect any given acceleration diminished with increasing mass ejection speed. In fact, the SMM observations do not reveal a discernable acceleration for most mass ejections. A modest yet credible acceleration was detected in 136 cases, while a deceleration was detected in only 7 cases. The LASCO coronagraph will have a more extensive field of view than the SMM instrument; hence, with these new SOHO (Solar and Heliospheric Observatory) observations, some of the challenging questions concerning mass ejection dynamics can be addressed. How far away from the Sun does the material in a mass ejection continue being accelerated? At what radial distance is the motion of the mass ejection dominated by deceleration as it interacts with the ambient interplanetary material?

  16. Dielectric laser accelerators

    NASA Astrophysics Data System (ADS)

    England, R. Joel; Noble, Robert J.; Bane, Karl; Dowell, David H.; Ng, Cho-Kuen; Spencer, James E.; Tantawi, Sami; Wu, Ziran; Byer, Robert L.; Peralta, Edgar; Soong, Ken; Chang, Chia-Ming; Montazeri, Behnam; Wolf, Stephen J.; Cowan, Benjamin; Dawson, Jay; Gai, Wei; Hommelhoff, Peter; Huang, Yen-Chieh; Jing, Chunguang; McGuinness, Christopher; Palmer, Robert B.; Naranjo, Brian; Rosenzweig, James; Travish, Gil; Mizrahi, Amit; Schachter, Levi; Sears, Christopher; Werner, Gregory R.; Yoder, Rodney B.

    2014-10-01

    The use of infrared lasers to power optical-scale lithographically fabricated particle accelerators is a developing area of research that has garnered increasing interest in recent years. The physics and technology of this approach is reviewed, which is referred to as dielectric laser acceleration (DLA). In the DLA scheme operating at typical laser pulse lengths of 0.1 to 1 ps, the laser damage fluences for robust dielectric materials correspond to peak surface electric fields in the GV /m regime. The corresponding accelerating field enhancement represents a potential reduction in active length of the accelerator between 1 and 2 orders of magnitude. Power sources for DLA-based accelerators (lasers) are less costly than microwave sources (klystrons) for equivalent average power levels due to wider availability and private sector investment. Because of the high laser-to-particle coupling efficiency, required pulse energies are consistent with tabletop microJoule class lasers. Combined with the very high (MHz) repetition rates these lasers can provide, the DLA approach appears promising for a variety of applications, including future high-energy physics colliders, compact light sources, and portable medical scanners and radiative therapy machines.

  17. Advanced accelerator theory development

    SciTech Connect

    Sampayan, S.E.; Houck, T.L.; Poole, B.; Tishchenko, N.; Vitello, P.A.; Wang, I.

    1998-02-09

    A new accelerator technology, the dielectric wall accelerator (DWA), is potentially an ultra compact accelerator/pulsed power driver. This new accelerator relies on three new components: the ultra-high gradient insulator, the asymmetric Blumlein and low jitter switches. In this report, we focused our attention on the first two components of the DWA system the insulators and the asymmetric Blumlein. First, we sought to develop the necessary design tools to model and scale the behavior of the high gradient insulator. To perform this task we concentrated on modeling the discharge processes (i.e., initiation and creation of the surface discharge). In addition, because these high gradient structures exhibit favorable microwave properties in certain accelerator configurations, we performed experiments and calculations to determine the relevant electromagnetic properties. Second, we performed circuit modeling to understand energy coupling to dynamic loads by the asymmetric Blumlein. Further, we have experimentally observed a non-linear coupling effect in certain asymmetric Blumlein configurations. That is, as these structures are stacked into a complete module, the output voltage does not sum linearly and a lower than expected output voltage results. Although we solved this effect experimentally, we performed calculations to understand this effect more fully to allow better optimization of this DWA pulse-forming line system.

  18. Acoustic particle acceleration sensors

    SciTech Connect

    Franklin, J.B. [Franklin Scientific Services (work performed while Mr. Franklin was employed by Defence Research Establishment Atlantic); Barry, P.J. [Defence Research Establishment Atlantic, P.O. Box 1012, Dartmouth, B2Y 3Z7 (CANADA)

    1996-04-01

    A crossed dipole array provides a directional receiving capability in a relatively small sensor package and is therefore very attractive for many applications in acoustics. Particle velocity measurements on two axes perpendicular to each other are required to provide the dipole signals. These can be obtained directly using particle velocity sensors or via simple transfer functions using acceleration and displacement sensors. Also, the derivative of the acoustic pressure with respect to space provides a signal proportional to the particle acceleration and gives rise to the pressure gradient sensor. Each of these sensors has strengths and drawbacks depending on the frequency regime of interest, the noise background, and whether a point or a line configuration of dipole sensors is desired. In this paper, the performance of acceleration sensors is addressed using a sensor concept developed at DREA. These sensors exploit bending stresses in a cantilever beam of piezoelectric material to obtain wide bandwidth and high sensitivity. Models which predict the acceleration sensitivity, pressure sensitivity, and natural frequency for this type of sensor are described. Experimental results obtained using several different versions of these sensors are presented and compared with theory. The predicted performance of acceleration sensors are compared with that of pressure gradient arrays and particle velocity sensors. {copyright} {ital 1996 American Institute of Physics.}

  19. Test particle acceleration by rotating jet magnetospheres

    E-print Network

    F. M. Rieger; K. Mannheim

    2000-11-01

    Centrifugal acceleration of charged test particles at the base of a rotating jet magnetosphere is considered. Based on an analysis of forces we derive the equation for the radial accelerated motion and present an analytical solution. It is shown that for particles moving outwards along rotating magnetic field lines, the energy gain is in particular limited by the breakdown of the bead-on-the-wire approximation which occurs in the vicinity of the light cylinder $r_{L}$. The corresponding upper limit for the maximum Lorentz factor $\\gamma_{max}$ for electrons scales $\\propto B^{2/3} r_{L}^{2/3}$, with $B$ the magnetic field strength at $r_{L}$, and is at most of the order of a $10^2-10^3$ for the conditions regarded to be typical for BL Lac objects. Such values suggest that this mechanism may provide pre-accelerated seed particles which are required for efficient Fermi-type particle acceleration at larger scales in radio jets.

  20. Lucky exposures: diffraction limited astronomical imaging through the atmosphere

    E-print Network

    Tubbs, Robert Nigel

    2003-11-25

    European Astronomers’ access to the European Northern Observatory, in the Canary Islands. This research has also made use of the SIMBAD database, operated at CDS, Strasbourg, France, and NASA’s Astrophysics Data System. This document was typeset... months. Thanks to Graham Cox for assisting with arrangements on La Palma, and to Richard Wilson and Peter Tuthill for useful conversations and data which helped in understanding the atmosphere. I am grateful to the whole COAST team for providing all...

  1. 79 FR 61383 - Chemical Management and Permissible Exposure Limits (PELs)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2014-10-10

    ...conducted a CFD study to model the potential for spontaneous heating in particular areas of underground coal...underground coal mines that face both methane control and spontaneous combustion issues. NIOSH looked at the rate of flame...

  2. ENVIRONMENTAL MONITORING AND HUMAN EXPOSURE ASSESSMENT USING IMMUNOCHEMICAL TECHNIQUES

    EPA Science Inventory

    The use of immunochemical technologies including, but not limited to, immunoassays is expanding to include various aspects of environmental analysis. Ultimately, the basis for environmental investigations is concern about human and ecological exposure to potentially toxic compoun...

  3. REPLICATION OF STUDY ON SPONTANEOUS AND BY-PRODUCT EXPOSURES

    EPA Science Inventory

    A limited number of epidemiological studies have evaluated the potential association between exposure to DBPs in drinking water and adverse reproductive outcomes. Reproductive effects that have been reported include spontaneous abortions, congenital defects, low birth weight, pre...

  4. Accelerator based coal positron beams

    SciTech Connect

    Schoessow, P.; Simpson, J.

    1987-01-01

    Cold positron beams produced using solid state moderators have been used profitably for condensed matter and positronium research. The low emittance and energy spread of these beams make the technique attractive as a potential positron source for future linear colliders, reducing or eliminating the need for damping rings. However, the intensities attained so far fall short of the requirements of a high energy linear collider. (approx.10/sup 11/ positrons/pulse at 10 kHz was taken as the positron flux necessary for a linear collider-B anti B factory). This report briefly reviews the state of the art in accelerator produced coal positron beams and indicates some areas in which yields might be improved. The discussion here is limited to electroproduced positrons.

  5. Supernovae and the Accelerating Universe

    NASA Technical Reports Server (NTRS)

    Wood, H. John

    2003-01-01

    Orbiting high above the turbulence of the earth's atmosphere, the Hubble Space Telescope (HST) has provided breathtaking views of astronomical objects never before seen in such detail. The steady diffraction-limited images allow this medium-size telescope to reach faint galaxies of 30th stellar magnitude. Some of these galaxies are seen as early as 2 billion years after the Big Bang in a 15 billion year old universe. Up until recently, astronomers assumed that all of the laws of physics and astronomy applied back then as they do today. Now, using the discovery that certain supernovae are standard candles, astronomers have found that the universe is expanding faster today than it was back then: the universe is accelerating in its expansion.

  6. Comparative Benchmark Dose Modeling as a Tool to Make the First Estimate of Safe Human Exposure Levels to Lunar Dust

    NASA Technical Reports Server (NTRS)

    James, John T.; Lam, Chiu-wing; Scully, Robert R.

    2013-01-01

    Brief exposures of Apollo Astronauts to lunar dust occasionally elicited upper respiratory irritation; however, no limits were ever set for prolonged exposure ot lunar dust. Habitats for exploration, whether mobile of fixed must be designed to limit human exposure to lunar dust to safe levels. We have used a new technique we call Comparative Benchmark Dose Modeling to estimate safe exposure limits for lunar dust collected during the Apollo 14 mission.

  7. Design and testing of electrostatic aerosol in vitro exposure system (EAVES): An alternative exposure system for particles

    EPA Science Inventory

    Conventional in vitro exposure methods for cultured human lung cells rely on prior suspension of particles in a liquid medium; these have limitations for exposure intensity and may modify the particle composition. Here electrostatic precipitation was used as an effective method f...

  8. Chemical process-based reconstruction of exposures for an epidemiological study. Part II. Estimated exposures to chloroprene and vinyl chloride.

    PubMed

    Esmen, Nurtan A; Hall, Thomas A; Phillips, Margaret L; Jones, E Paige; Basara, Heather; Marsh, Gary M; Buchanich, Jeanine M

    2007-03-20

    In a four-facility occupational epidemiology study of chloroprene monomer and polymer production workers, the chloroprene (CD) and vinyl chloride monomer (VCM) exposures were modeled for plant specific job title classes. In two facilities an acetylene-based process was used and in the other two plants only a butadiene-based process was used in the monomer synthesis. In the Acetylene process VCM was an undesirable by-product to be removed. In the newer butadiene-based process, VCM was not involved and the exposures to CD were considerably lower than they were in the earlier years. One of the limiting factors was the operator rotation within a number of job titles. This rotation and inability to differentiate between job titles subsumed in job classifications recorded in the work histories required an exposure classification scheme based on an order of magnitude separation of exposure classes. In the four facilities with considerable variation in the mix of the production methods, the CD exposures were remarkably similar in both calculated and measured values. The reductions in exposures were much more dependent upon the improvement of the production methods, rather than deliberate exposure control for occupational hygiene considerations. This is reasonable since the exposures were generally lower than the coeval exposure limits and/or guidelines. The estimated exposures were less than 100 ppm in the pre-1960 era and less than 10 ppm in the 1960-1980 era, less than 1 ppm 1980-1990 era and less than 0.5 ppm thereafter. The exposures were categorized in four classes for VCM and six classes for CD. The characteristic class exposure values were used to cumulate individual exposures over time with a quantification of the potential range for exposures that are reasonably certain to ascribe correct ranking to job classes. PMID:16989794

  9. Human mutagens: evidence from paternal exposure

    SciTech Connect

    Narod, S.A.; Douglas, G.R.; Nestmann, E.R.; Blakey, D.H.

    1988-01-01

    The importance of inherited mutations as a cause of human disease has been established clearly through examples of well-defined genetic anomalies, such as Down syndrome and retinoblastoma. Furthermore, it is suspected that environmental contaminants induce mutations resulting in increased risk for such defects in subsequent generations of persons exposed. The present lack of direct evidence for induced inherited genetic disorders in human beings hampers the development of risk estimation techniques for extrapolation from animal models. The most extensive prospective epidemiologic studies of inherited genetic effects have involved survivors of atomic bomb detonations and patients treated with cancer chemotherapy. In neither case has a significant elevation in inherited genetic effects or cancer been detected in the offspring of exposed individuals. Epidemiologic studies of subjects receiving chronic exposure may be confounded by the effect of maternal exposure during pregnancy. Consideration of only paternal exposure can minimize the confounding influence of teratogenicity, enhancing the resolving power of studies for inherited effects. Using this approach, retrospective (case-control) studies of childhood cancer patients have provided limited but suggestive evidence for inheritance of induced effects. Endpoints, such as congenital malformations and spontaneous abortion following paternal exposure, can also be considered as indicators of heritable mutagenic effects. For example, there is limited evidence suggesting that paternal exposure to anaesthetic gases may cause miscarriage and congenital abnormalities as a result of induced male germ cell mutations. 104 references.

  10. Perturbations for transient acceleration

    SciTech Connect

    Vargas, Cristofher Zuñiga; Zimdahl, Winfried [Universidade Federal do Espírito Santo, Departamento de Física, Av. Fernando Ferrari, 514, Campus de Goiabeiras, CEP 29075-910, Vitória, Espírito Santo (Brazil); Hipólito-Ricaldi, Wiliam S., E-mail: win_unac@hotmail.com, E-mail: hipolito@ceunes.ufes.br, E-mail: winfried.zimdahl@pq.cnpq.br [Universidade Federal do Espírito Santo, Departamento de Ciências Naturais, Grupo de Física Teórica, Rodovia BR 101 Norte, km 60, Campus de São Mateus, CEP 29932-540, São Mateus, Espírito Santo (Brazil)

    2012-04-01

    According to the standard ?CDM model, the accelerated expansion of the Universe will go on forever. Motivated by recent observational results, we explore the possibility of a finite phase of acceleration which asymptotically approaches another period of decelerated expansion. Extending an earlier study on a corresponding homogeneous and isotropic dynamics, in which interactions between dark matter and dark energy are crucial, the present paper also investigates the dynamics of the matter perturbations both on the Newtonian and General Relativistic (GR) levels and quantifies the potential relevance of perturbations of the dark-energy component. In the background, the model is tested against the Supernova type Ia (SNIa) data of the Constitution set and on the perturbative level against growth rate data, among them those of the WiggleZ survey, and the data of the 2dFGRS project. Our results indicate that a transient phase of accelerated expansion is not excluded by current observations.

  11. Medical uses of accelerators

    SciTech Connect

    Bradbury, J.N.

    1981-01-01

    A variety of particle accelerators have either potential or already demonstrated uses in connection with medically-related research, diagnosis, and treatment. For cancer radiotherapy, nuclear particles including protons, neutrons, heavy ions, and negative pi mesons have advantages compared to conventional radiations in terms of dose localization and/or biological effectiveness. Clinical evaluations of these particles are underway at a number of institutions. Accelerator-produced radionuclides are in widespread use for research and routine diagnostic purposes. Elemental analysis techniques with charged particles and neutrons are being applied to bone, blood, and other tissues. Finally, low-dose medical imaging can be accomplished with accelerated protons and heavy ions. The status and future of these programs are discussed.

  12. Nuclear Energy: Radiation Exposure

    NSDL National Science Digital Library

    John Pratte

    This lesson provides an overview of the sources and potential effects of radiation exposure. Topics include the history of the United States' domestic nuclear power program, the concept of ionizing radiation, and how radiation dosage is measured. There is also discussion of what constitutes a lethal dose of radiation and potential sources of exposure. The lesson includes an activity in which students measure their individual yearly exposures to radiation by making an inventory of lifestyle factors that affect their potential dosage and using an online calculator to sum up the contributions from the various sources.

  13. Diffusive Shock Acceleration

    NASA Astrophysics Data System (ADS)

    Baring, Matthew

    2003-04-01

    The process of diffusive acceleration of charged particles in shocked plasmas is widely invoked in astrophysics to account for the ubiquitous presence of signatures of non-thermal relativistic electrons and ions in the universe. This statistical energization mechanism, manifested in turbulent media, was first posited by Enrico Fermi in 1949 to explain the observed cosmic ray population, which exhibits an almost power-law distribution in rigidity. The absence of a momentum scale is a key characteristic of diffusive shock acceleration, and astrophysical systems generally only impose scales at the injection (low energy) and loss (high energy) ends of the particle spectrum. The existence of structure in the cosmic ray spectrum (the "knee") at around 3000 TeV has promoted contentions that there are at least two origins for cosmic rays, a galactic one supplying those up to the knee, and perhaps an extragalactic one that can explain even the ultra-high energy cosmic rays (UHECRs) seen at 1-300 EeV. Accounting for the UHECRs with familiar astrophysical sites of acceleration has historically proven difficult due to the need to assume high magnetic fields in order to reduce the shortest diffusive acceleration timescale, the ion gyroperiod, to meaningful values. Yet active galaxies and gamma-ray bursts remain strong and interesting candidate sources for UHECRs, turning the theoretical focus to relativistic shocks. This review summarizes properties of diffusive shock acceleration that are salient to the issue of UHECR generation. These include spectral indices, anisotropies, acceleration efficencies and timescales, as functions of the shock speed and mean field orientation, and also the degree of field turbulence. Astrophysical sites for UHECR production are also critiqued.

  14. Patterns of barbell acceleration during the snatch in weightlifting competition.

    PubMed

    Kipp, Kristof; Harris, Chad

    2015-07-01

    The purpose of this study was to determine the association between weightlifting performance and vertical barbell acceleration patterns. Barbell kinematic time-series data were tracked from 18 snatches from six weightlifters during a regional weightlifting competition. These data were used to calculate vertical barbell accelerations. Time-series data were normalised to 100% of lift phase, defined as the time interval between barbell lift-off and maximum height of the barbell during each snatch lift. The time-series data were then entered into a pattern recognition algorithm that extracted principal patterns and calculated principal pattern scores. Body mass-normalised lift weight, which was used to quantify weightlifting performance, was significantly correlated (r = 0.673; P = 0.033) with a pattern that captured a difference in peak vertical barbell acceleration between the transition and the second pull phase. This correlation indicated that barbell acceleration profiles of higher weight snatch lifts were characterised by smaller decreases in acceleration during the second knee bend and smaller peak acceleration during the second pull phase. Weightlifting coaches and sports scientist should monitor and track vertical acceleration of the barbell, with focus on acceleration profiles that limit (1) deceleration during the transition phase between the first and second pull and (2) peak acceleration during the second pull phase of the snatch. PMID:25530037

  15. Laser driven ion acceleration

    NASA Astrophysics Data System (ADS)

    Mora, P.

    2007-07-01

    The different acceleration mechanisms of ion acceleration from a foil irradiated by a short-pulse laser are briefly discussed, i.e., the backward and forward ion acceleration from the front side, the forward ion acceleration from the rear side, and the shock acceleration inside the target itself. A particular attention is then given to the forward ion acceleration from the rear side, as it appears presently as the most efficient mechanism. Fast electrons are first created at the front side of a thin foil by the laser-plasma interaction, then propagate through the target and build a charge separation field at the rear side. The corresponding electric field ionizes atoms and accelerates ions. The paradigm for the plasma expansion is the self-similar quasi-neutral expansion of an isothermal semi-infinite plasma into a vacuum that is first presented together with the resultant energy spectrum. The analysis of the conditions of validity of the quasi-neutrality assumption enables to determine the structure of the ion front and the maximum ion velocity as a function of time. Various effects are then discussed which may modify the ion spectrum with respect to the simple model : (i) Electron cooling (finite plasma slab case) : the thermal electron energy is progressively converted into the kinetic energy of the ions. The ion spectrum now converges when time goes to infinity in contrast with the isothermal semi-infinite plasma case. (ii) Two-phase model : a refined model is presented, where the electron temperature first rises together with the laser pulse intensity, and then decreases adiabatically while the energy is transferred to the ions. (iii) Two-temperature electron distribution function : as expected, the high energy part of the spectrum is governed by the hot electron component (iv) Existence of a finite initial ion density gradient : a wave breaking of the ion flow occurs after a finite time, with the formation of an ion front. When electron cooling is taken into account, and when the initial ion density scale length lss is larger than a few percent of the total plasma slab width, the final maximum ion velocity decreases with lss. (v) Multispecies ions: optimisation of the target structure can lead to the acceleration of quasi-monoenergetic light ions (especially protons).

  16. A Smoother Acceleration

    NSDL National Science Digital Library

    Christine Chapman

    2009-03-01

    Some may argue that gifted children have many education options, but these options do not always help gifted students learn science. Unfortunately, gifted students often do not reach their full academic potential--they are frequently less motivated to succeed because they are not being academically challenged in regular classrooms (McCoach and Siegle 2003). To counter these problems, a strong option for educating gifted students is acceleration. This article describes the challenges that more and more gifted students face when accelerating, particularly when skipping an entire academic year. Strategies to lessen their intensity and duration and, ultimately, help gifted students to succeed are also included.

  17. HIGH GRADIENT INDUCTION ACCELERATOR

    SciTech Connect

    Caporaso, G J; Sampayan, S; Chen, Y; Blackfield, D; Harris, J; Hawkins, S; Holmes, C; Krogh, M; Nelson, S; Nunnally, W; Paul, A; Poole, B; Rhodes, M; Sanders, D; Selenes, K; Sullivan, J; Wang, L; Watson, J

    2007-06-21

    A new type of compact induction accelerator is under development at the Lawrence Livermore National Laboratory that promises to increase the average accelerating gradient by at least an order of magnitude over that of existing induction machines. The machine is based on the use of high gradient vacuum insulators, advanced dielectric materials and switches and is stimulated by the desire for compact flash x-ray radiography sources. Research describing an extreme variant of this technology aimed at proton therapy for cancer will be described. Progress in applying this technology to several applications will be reviewed.

  18. An accelerator technology legacy

    SciTech Connect

    Heighway, E.A.

    1994-11-01

    Accelerator technology has been a major beneficiary of the investment made over the last decade. It is the intention of this paper to provide the reader with a glimpse of the broad nature of those advances. Development has been on a broad front and this paper can highlight only a few of those. Two spin-off applications will be outlined -- a concept for a compact, active, beam probe for solar body exploration and the concept for an accelerator-driven transmutation system for energy production.

  19. Interfacing to accelerator instrumentation

    SciTech Connect

    Shea, T.J.

    1995-12-31

    As the sensory system for an accelerator, the beam instrumentation provides a tremendous amount of diagnostic information. Access to this information can vary from periodic spot checks by operators to high bandwidth data acquisition during studies. In this paper, example applications will illustrate the requirements on interfaces between the control system and the instrumentation hardware. A survey of the major accelerator facilities will identify the most popular interface standards. The impact of developments such as isochronous protocols and embedded digital signal processing will also be discussed.

  20. Photocathodes in accelerator applications

    SciTech Connect

    Fraser, J.S.; Sheffield, R.L.; Gray, E.R.; Giles, P.M.; Springer, R.W.; Loebs, V.A.

    1987-01-01

    Some electron accelerator applications require bursts of short pulses at high microscopic repetition rates and high peak brightness. A photocathode, illuminated by a mode-locked laser, is well suited to filling this need. The intrinsic brightness of a photoemitter beam is high; experiments are under way at Los Alamos to study the brightness of short bunches with high space charge after acceleration. A laser-illuminated Cs/sub 3/Sb photoemitter is located in the first rf cavity of an injector linac. Diagnostics include a pepper-pot emittance analyzer, a magnetic spectrometer, and a streak camera.

  1. Operational plasma density and laser parameters for future colliders based on laser-plasma accelerators

    SciTech Connect

    Schroeder, C. B.; Esarey, E.; Leemans, W. P. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

    2012-12-21

    The operational plasma density and laser parameters for future colliders based on laser-plasma accelerators are discussed. Beamstrahlung limits the charge per bunch at low plasma densities. Reduced laser intensity is examined to improve accelerator efficiency in the beamstrahlung-limited regime.

  2. DOE occupational radiation exposure 1996 report

    SciTech Connect

    NONE

    1996-12-31

    The goal of the US Department of Energy (DOE) is to conduct its radiological operations to ensure the health and safety of all DOE employees including contractors and subcontractors. The DOE strives to maintain radiation exposures to its workers below administrative control levels and DOE limits and to further reduce these exposures and releases to levels that are ``As Low As Reasonably Achievable`` (ALARA). The DOE Occupational Radiation Exposure Report, 1996 provides summary and analysis of the occupational radiation exposure received by individuals associated with DOE activities. The DOE mission includes stewardship of the nuclear weapons stockpile and the associated facilities, environmental restoration of DOE and precursor agency sites, and energy research. Collective exposure at DOE has declined by 80% over the past decade due to a cessation in opportunities for exposure during the transition in DOE mission from weapons production to cleanup, deactivation and decommissioning, and changes in reporting requirements and dose calculation methodology. In 1996, the collective dose decreased by 10% from the 1995 value due to decreased doses at five of the seven highest-dose DOE sites. For 1996, these sites attributed the reduction in collective dose to the completion of several decontamination and decommissioning projects, reduced spent fuel storage activities, and effective ALARA practices. This report is intended to be a valuable tool for managers in their management of radiological safety programs and commitment of resources.

  3. High-Level, but Not Low-Level, Occupational Exposure to Inhaled Anesthetics Is Associated with Genotoxicity in the Micronucleus Assay

    Microsoft Academic Search

    Gunther Wiesner; Klaus Hoerauf; Klaus Schroegendorfer; Pawel Sobczynski; Marion Harth; Hugo W. Ruediger

    2001-01-01

    To minimize the possible health risks posed by waste anesthetic gases, the National Institute of Occupational Safety and Health (NIOSH) recommends exposure lim- its. We investigated the genotoxicity of a previously es- tablished occupational exposure exceeding these limits (high-level exposure) and of one within these limits (low-level exposure). Genotoxicity was assessed by the formation of micronucleated lymphocytes in 25 anes-

  4. Indoor aerosols: from personal exposure to risk assessment.

    PubMed

    Morawska, L; Afshari, A; Bae, G N; Buonanno, G; Chao, C Y H; Hänninen, O; Hofmann, W; Isaxon, C; Jayaratne, E R; Pasanen, P; Salthammer, T; Waring, M; Wierzbicka, A

    2013-12-01

    Motivated by growing considerations of the scale, severity, and risks associated with human exposure to indoor particulate matter, this work reviewed existing literature to: (i) identify state-of-the-art experimental techniques used for personal exposure assessment; (ii) compare exposure levels reported for domestic/school settings in different countries (excluding exposure to environmental tobacco smoke and particulate matter from biomass cooking in developing countries); (iii) assess the contribution of outdoor background vs indoor sources to personal exposure; and (iv) examine scientific understanding of the risks posed by personal exposure to indoor aerosols. Limited studies assessing integrated daily residential exposure to just one particle size fraction, ultrafine particles, show that the contribution of indoor sources ranged from 19% to 76%. This indicates a strong dependence on resident activities, source events and site specificity, and highlights the importance of indoor sources for total personal exposure. Further, it was assessed that 10-30% of the total burden of disease from particulate matter exposure was due to indoor-generated particles, signifying that indoor environments are likely to be a dominant environmental factor affecting human health. However, due to challenges associated with conducting epidemiological assessments, the role of indoor-generated particles has not been fully acknowledged, and improved exposure/risk assessment methods are still needed, together with a serious focus on exposure control. PMID:23574389

  5. Estimating exposure using kriging: a simulation study.

    PubMed Central

    Wartenberg, D; Uchrin, C; Coogan, P

    1991-01-01

    Retrospective studies of disease often are limited by the resolution of the exposure measurements. For example, in a typical study of adverse health effects from contaminated groundwater, the number of wells sampled may range from only a few to as many as several dozen, while the number of cases and controls may be in the hundreds or more. To derive individual estimates of exposure for wells that were not sampled, investigators must extrapolate. In this study, we compare three methods of extrapolating from a limited number of observations to estimate individual exposures. Using two naive models of groundwater contamination, we compare nearest neighbor interpolation, inverse distance squared weighting, and kriging for estimating exposure based on a limited number of measurements. Our results show that although kriging is a statistically optimal method, it is not markedly better than simpler interpolation algorithms, though it is considerably more complex to use. Aberrant well measurements and discontinuities are problematic for all methods. We provide some guidance in interpolating data and outline a more comprehensive comparison of methodology. PMID:1954944

  6. Pesticide-Exposure Matrix

    Cancer.gov

    The "Pesticide-exposure Matrix" was developed to help epidemiologists and other researchers identify the active ingredients to which people were likely exposed when their homes and gardens were treated for pests in past years.

  7. Persuasion Via Mere Exposure

    ERIC Educational Resources Information Center

    Tucker, Raymond K.; Ware, Paul D.

    1971-01-01

    Describes an experiment which sought to effect persuasion by merely exposing subjects to the name of a stimulus object for a specified number of times. Through illustration, explains the theoretical basis and methodology employed in a mere exposure experiment. (Author)

  8. Nanotechnology and Exposure Science

    PubMed Central

    LIOY, PAUL J.; NAZARENKO, YEVGEN; HAN, TAE WON; LIOY, MARY JEAN; MAINELIS, GEDIMINAS

    2014-01-01

    This article discusses the gaps in our understanding of human exposures to nanoparticles stemming from the use of nanotechnology-based consumer products by the general public. It also describes a series of steps that could be taken to characterize such exposures. The suggested steps include classification of the nanotechnology-based products, simulation of realistic exposure patterns, characterization of emissions, analysis of the duration of activities resulting in exposures, and consideration of the bioaccessibility of nanoparticles. In addition, we present a preliminary study with nanotechnology-based cosmetic powders where particle release was studied under realistic powder application conditions. The data demonstrated that when nanotechnology-based cosmetic powders were used, there was a potential for inhaling airborne particles ranging in size from tens of nanometers to tens of micrometers. PMID:21222382

  9. Pesticide exposure in children.

    PubMed

    2012-12-01

    This statement presents the position of the American Academy of Pediatrics on pesticides. Pesticides are a collective term for chemicals intended to kill unwanted insects, plants, molds, and rodents. Children encounter pesticides daily and have unique susceptibilities to their potential toxicity. Acute poisoning risks are clear, and understanding of chronic health implications from both acute and chronic exposure are emerging. Epidemiologic evidence demonstrates associations between early life exposure to pesticides and pediatric cancers, decreased cognitive function, and behavioral problems. Related animal toxicology studies provide supportive biological plausibility for these findings. Recognizing and reducing problematic exposures will require attention to current inadequacies in medical training, public health tracking, and regulatory action on pesticides. Ongoing research describing toxicologic vulnerabilities and exposure factors across the life span are needed to inform regulatory needs and appropriate interventions. Policies that promote integrated pest management, comprehensive pesticide labeling, and marketing practices that incorporate child health considerations will enhance safe use. PMID:23184103

  10. NATIONAL EXPOSURE REGISTRY (NER)

    EPA Science Inventory

    This system is a listing of persons (general population) with documented exposure to select hazardous substances (superfund related). All adverse health outcomes are monitored prospectively. Retrospective identification of adverse health outcomes (usually verified by medical reco...

  11. Pregnancy and Radiation Exposure

    MedlinePLUS

    ... Exposure to the Embryo or Fetus from Diagnostic Nuclear Medicine Pregnant women may be administered radioactive materials ... determination be obtained from the health physicist, a nuclear medicine physician, or a radiation oncologist associated with ...

  12. Testing a combined vibration and acceleration environment.

    SciTech Connect

    Jepsen, Richard Alan; Romero, Edward F.

    2005-01-01

    Sandia National Laboratories has previously tested a capability to impose a 7.5 g-rms (30 g peak) radial vibration load up to 2 kHz on a 25 lb object with superimposed 50 g acceleration at its centrifuge facility. This was accomplished by attaching a 3,000 lb Unholtz-Dickie mechanical shaker at the end of the centrifuge arm to create a 'Vibrafuge'. However, the combination of non-radial vibration directions, and linear accelerations higher than 50g's are currently not possible because of the load capabilities of the shaker and the stresses on the internal shaker components due to the combined centrifuge acceleration. Therefore, a new technique using amplified piezo-electric actuators has been developed to surpass the limitations of the mechanical shaker system. They are lightweight, modular and would overcome several limitations presented by the current shaker. They are 'scalable', that is, adding more piezo-electric units in parallel or in series can support larger-weight test articles or displacement/frequency regimes. In addition, the units could be mounted on the centrifuge arm in various configurations to provide a variety of input directions. The design along with test results will be presented to demonstrate the capabilities and limitations of the new piezo-electric Vibrafuge.

  13. Assessment of mechanical exposure in ergonomic epidemiology

    PubMed Central

    van der Beek, A. J.; Frings-Dresen, M. H.

    1998-01-01

    In recent years several different methods have been developed to assess mechanical exposures, which are related to musculoskeletal disorders in ergonomic epidemiology. Each of these methods is capable of measuring one or more aspects of risk factors, but has drawbacks as well. Improper application of methods might result in biased exposure estimates, which has serious consequences for risk estimates arising from epidemiological studies. The aim of this paper was to systematically evaluate the usefulness of different measurement methods in terms of accuracy and applicability. Assessment of external exposure measures by subjective judgements (from experts or self reports from workers), observational methods (on site or afterwards from video recordings), and direct measurements methods (at work or during laboratory simulations) are discussed for each of the dimensions of exposure level, duration, and frequency. It is concluded that expert judgements and self reports give only limited insight into the occurrence of tasks and activities. Further information can be obtained from observations, which can best be combined with direct measurements of exposure to posture, movement, and exerted forces to achieve exposure profiles by occupational task. Internal exposures estimated by biomechanical modelling mostly consider the low back and require information on postures of the different body segments and exerted forces, completed with movement data in the case of dynamic models. Moreover, electromyography (EMG) and measurements of intra-abdominal pressure might be used for this purpose. Both biomechanical models and EMG are useful methods to assess internal exposure, but biomechanical models should not be restricted to the level of compressive forces on the lower back. Finally, current problems and future directions in measurement strategies and methods are discussed.   PMID:9764106

  14. Assessment of mechanical exposure in ergonomic epidemiology.

    PubMed

    van der Beek, A J; Frings-Dresen, M H

    1998-05-01

    In recent years several different methods have been developed to assess mechanical exposures, which are related to musculoskeletal disorders in ergonomic epidemiology. Each of these methods is capable of measuring one or more aspects of risk factors, but has drawbacks as well. Improper application of methods might result in biased exposure estimates, which has serious consequences for risk estimates arising from epidemiological studies. The aim of this paper was to systematically evaluate the usefulness of different measurement methods in terms of accuracy and applicability. Assessment of external exposure measures by subjective judgements (from experts or self reports from workers), observational methods (on site or afterwards from video recordings), and direct measurements methods (at work or during laboratory simulations) are discussed for each of the dimensions of exposure level, duration, and frequency. It is concluded that expert judgements and self reports give only limited insight into the occurrence of tasks and activities. Further information can be obtained from observations, which can best be combined with direct measurements of exposure to posture, movement, and exerted forces to achieve exposure profiles by occupational task. Internal exposures estimated by biomechanical modelling mostly consider the low back and require information on postures of the different body segments and exerted forces, completed with movement data in the case of dynamic models. Moreover, electromyography (EMG) and measurements of intra-abdominal pressure might be used for this purpose. Both biomechanical models and EMG are useful methods to assess internal exposure, but biomechanical models should not be restricted to the level of compressive forces on the lower back. Finally, current problems and future directions in measurement strategies and methods are discussed. PMID:9764106

  15. Stacked insulator induction accelerator gaps

    SciTech Connect

    Houck, T.I.; Westenskow, G.A.; Kim, J.S.; Eylon, S.; Henestroza, E.; Yu, S.S.; Vanecek, D.

    1997-05-01

    Stacked insulators, with alternating layers of insulating material and conducting film, have been shown to support high surface electrical field stresses. We have investigated the application of the stacked insulator technology to the design of induction accelerator modules for the Relativistic-Klystron Two-Beam Accelerator program. The rf properties of the accelerating gaps using stacked insulators, particularly the impedance at frequencies above the beam pipe cutoff frequency, are investigated. Low impedance is critical for Relativistic-Klystron Two-Beam Accelerator applications where a high current, bunched beam is trsnsported through many accelerating gaps. An induction accelerator module designs using a stacked insulator is presented.

  16. Autoimmunity and Asbestos Exposure

    PubMed Central

    Pfau, Jean C.; Serve, Kinta M.; Noonan, Curtis W.

    2014-01-01

    Despite a body of evidence supporting an association between asbestos exposure and autoantibodies indicative of systemic autoimmunity, such as antinuclear antibodies (ANA), a strong epidemiological link has never been made to specific autoimmune diseases. This is in contrast with another silicate dust, crystalline silica, for which there is considerable evidence linking exposure to diseases such as systemic lupus erythematosus, systemic sclerosis, and rheumatoid arthritis. Instead, the asbestos literature is heavily focused on cancer, including mesothelioma and pulmonary carcinoma. Possible contributing factors to the absence of a stronger epidemiological association between asbestos and autoimmune disease include (a) a lack of statistical power due to relatively small or diffuse exposure cohorts, (b) exposure misclassification, (c) latency of clinical disease, (d) mild or subclinical entities that remain undetected or masked by other pathologies, or (e) effects that are specific to certain fiber types, so that analyses on mixed exposures do not reach statistical significance. This review summarizes epidemiological, animal model, and in vitro data related to asbestos exposures and autoimmunity. These combined data help build toward a better understanding of the fiber-associated factors contributing to immune dysfunction that may raise the risk of autoimmunity and the possible contribution to asbestos-related pulmonary disease. PMID:24876951

  17. Auditory localization under sustained +Gz acceleration.

    PubMed

    Nelson, W T; Bolia, R S; Tripp, L D

    2001-01-01

    The ability to localize a virtual sound source in the horizontal plane was evaluated under varying levels of sustained (+Gz) acceleration. Participants were required to judge the locations of spatialized noise bursts in the horizontal plane (elevation 0 degrees) during exposure to 1.0, 1.5, 2.5, 4.0, 5.5, and 7.0 +Gz. The experiment was conducted at the U.S. Air Force Research Laboratory's Dynamic Environment Simulator, a three-axis centrifuge. No significant increases in localization error were found between 1.0 and 5.5 +Gz; however, a significant increase did occur at the 7.0 +Gz level. In addition, the percentage of front/back confusions did not vary as a function of +Gz level. Collectively, these results indicate that the ability to localize virtual sound sources is well maintained at various levels of sustained acceleration. Actual or potential applications include the incorporation of spatial audio displays into the human-computer interface for vehicles that are operated in acceleration environments. PMID:11592670

  18. An objective determination of +Gz acceleration tolerance

    NASA Technical Reports Server (NTRS)

    Sandler, H.; Rositano, S. A.; McCutcheon, E. P.

    1977-01-01

    Until recently, human +Gz acceleration tolerance has relied solely on subjective criteria relating to loss of vision. By use of newly developed noninvasive instrumentation using a transcutaneous Doppler flow system, objective end point criteria have been developed based on measured blood flow to the head. The system consists of miniature 8 MHz Doppler sensors (2 x 1 x 0.5 cm) placed on the forehead over both frontal branches of the temporal arteries to detect blood flow velocity from back scattered ultrasound. Its use has allowed for correlation of altered, decreased and actual reversal of eye level blood flow with subsequent central light loss. Over 100 subjects have now been studied during more than 2,000 centrifuge runs. Objective changes in temporal artery flow velocity consistently preceded visual degradation for each subject during all acceleration profiles. No subject has gone unconscious without first exhibiting a minimum 6 sec of total flow cessation. Retrograde flow followed by complete flow cessation always preceded central light loss. Results indicate that this method can be successfully used with a wide variety of tasks during exposure to +Gz acceleration. It is recommended for use during evaluation of protective maneuvers or devices on the centrifuge or during actual flight in high performance aircraft. It may also serve as a potential safety monitor during space Shuttle re-entry if there is doubt about a passenger's cardiovascular status.

  19. European particle accelerator conference

    SciTech Connect

    Tazzari, S.

    1988-01-01

    This book contains the following topics: The LEP project, Superconducting RF cavities for accelerator application, Commissioning of super-ACO, Pulsed high-power beams, RF Power sources, Astrid, A storage ring for ions and electrons, Linear collider studies in Europe.

  20. Acceleration and Mass

    NSDL National Science Digital Library

    Michael Horton

    2009-05-30

    Although this lab is not an inquiry activity, it is very important in learning about acceleration and mass. It is a deeply held misconception among students that objects of different masses fall at different rates. Simply explaining that this is not true