Science.gov

Sample records for acceleration exposure limit

  1. Accelerated GLAS exposure station

    SciTech Connect

    Dallas, J.L.; Afzal, R.S.; Stephen, M.A. [NASA Selker, M.D.

    1995-12-31

    The Geoscience Laser Altimeter System (GLAS) is being developed by NASA/GSFC to measure the dynamics of the ice sheet mass balance, land, and cloud and atmospheric properties. An instrument altimetric resolution of 10 cm per shot is required. The laser transmitter will be a diode pumped, Q-switched, Nd:YAG laser producing 1064 nm, 100 mJ, 4 ns pulses at 40 Hz repetition rate in a TEM{infinity} mode. A minimum lifetime goal of 2 billion shots is required per laser transmitter. The performance of the GLAS laser can be limited by physical damage to the optical components caused by the interaction of intense laser energy with the optical coatings and substrates. Very little data exists describing the effects of long duration laser exposure, of 4 ns pulses, on an optical component. An Accelerated GLAS Exposure Station (AGES) is being developed which will autonomously operate and monitor the GLAS laser at an accelerated rate of 500 Hz. The effects of a large number of laser shots will be recorded. Parameters to be monitored include: laser power, pulsewidth, beam size, laser diode drive current and power, Q-switch drive voltage, temperature, and humidity. For comparison, one set of AGES-sister optical components will be used in the non-accelerated GLAS laser and another will be evaluated by a commercial optical damage test facility.

  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 AutoWorkersGeneral 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. Deriving exposure limits

    NASA Astrophysics Data System (ADS)

    Sliney, David H.

    1990-07-01

    Historically many different agencies and standards organizations have proposed laser occupational exposure limits (EL1s) or maximum permissible exposure (MPE) levels. Although some safety standards have been limited in scope to manufacturer system safety performance standards or to codes of practice most have included occupational EL''s. Initially in the 1960''s attention was drawn to setting EL''s however as greater experience accumulated in the use of lasers and some accident experience had been gained safety procedures were developed. It became clear by 1971 after the first decade of laser use that detailed hazard evaluation of each laser environment was too complex for most users and a scheme of hazard classification evolved. Today most countries follow a scheme of four major hazard classifications as defined in Document WS 825 of the International Electrotechnical Commission (IEC). The classifications and the associated accessible emission limits (AEL''s) were based upon the EL''s. The EL and AEL values today are in surprisingly good agreement worldwide. There exists a greater range of safety requirements for the user for each class of laser. The current MPE''s (i. e. EL''s) and their basis are highlighted in this presentation. 2. 0

  4. Voltage limitations of electrostatic accelerators

    SciTech Connect

    Hyder, H.R. )

    1999-04-01

    The history of electrostatic accelerators has been punctuated by a series of projects in which innovative designs have failed to meet the expectations of their designers. From the early, air-insulated Van de Graaffs at Round Hill to certain of the large pressurized heavy ion accelerators of the 1970s and 1980s, increases in size or changes in design and materials have not always led to the maximum voltages expected or extrapolated. Since these failures have continued beyond childhood into a mature technology, it is reasonable to assume that the causes of voltage limitation are varied and complex. They have remained poorly understood for a number of reasons: resources for an extended program of research into breakdown and failure of electrostatic generators have always been meager, especially for large machines devoted to nuclear research; the inaccessibility of pressurized generators makes instrumentation difficult and testing slow; the calculation of transient and dynamic effects is laborious and the results difficult to verify; voltage test experiments on operating accelerators are inhibited by the significant risk of damage due to energy release on breakdown: and the total voltages (though not the local fields) achieved in many electrostatic accelerators exceed those produced in any other man-made environment. In this review, the behavior of several generators of different designs is examined in order to assess the importance of the various design features and operating conditions that control the maximum voltage achievable in a working machine. [copyright] [ital 1999 American Institute of Physics.

  5. Voltage limitations of electrostatic accelerators

    SciTech Connect

    Hyder, H. R. McK.

    1999-04-26

    The history of electrostatic accelerators has been punctuated by a series of projects in which innovative designs have failed to meet the expectations of their designers. From the early, air-insulated Van de Graaffs at Round Hill to certain of the large pressurized heavy ion accelerators of the 1970s and 1980s, increases in size or changes in design and materials have not always led to the maximum voltages expected or extrapolated. Since these failures have continued beyond childhood into a mature technology, it is reasonable to assume that the causes of voltage limitation are varied and complex. They have remained poorly understood for a number of reasons: resources for an extended program of research into breakdown and failure of electrostatic generators have always been meager, especially for large machines devoted to nuclear research; the inaccessibility of pressurized generators makes instrumentation difficult and testing slow; the calculation of transient and dynamic effects is laborious and the results difficult to verify; voltage test experiments on operating accelerators are inhibited by the significant risk of damage due to energy release on breakdown: and the total voltages (though not the local fields) achieved in many electrostatic accelerators exceed those produced in any other man-made environment. In this review, the behavior of several generators of different designs is examined in order to assess the importance of the various design features and operating conditions that control the maximum voltage achievable in a working machine.

  6. Ultra-accelerated natural sunlight exposure testing

    SciTech Connect

    Jorgensen, G.J.; Bingham, C.; Goggin, R.; Lewandowski, A.A.; Netter, J.C.

    2000-06-13

    Process and apparatus are disclosed 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.

  7. Ultra-accelerated natural sunlight exposure testing

    DOEpatents

    Jorgensen, Gary J.; Bingham, Carl; Goggin, Rita; Lewandowski, Allan A.; Netter, Judy C.

    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.

  8. Microdosimetric basis for exposure limits.

    PubMed

    Brackenbush, L W; Braby, L A

    1988-08-01

    Consideration of the energy deposited by ionizing radiation in microscopic volumes has led to new insights into dosimetric concepts at the levels of interest in radiation protection. Large amounts of energy are deposited by the passage of low linear-energy-transfer (LET)-charged particles through small volumes. If a typical cell nucleus is considered to be about 7 micron, at an exposure rate of 2.5 X 10(-1) C kg-1 h-1 (1 mR hr-1) from a 60Co irradiation, the average cell nucleus receives one energy deposition event every 12.5 d. Biological processes, which modify radiation damage, typically occur in a few minutes to a few hours. Thus, at occupational exposure levels it is probably the irreparable or misrepaired effects of irradiation that determine the biological consequences. One goal of dosimetry is to measure the incident radiation, making it possible to predict biological risk and set meaningful exposure limits. These measurements must relate to the energy depositions that are responsible for radiation effects at low dose rates, yet the dosimetry system must not be excessively complex to allow use by operational health physicists. Furthermore, our description of the irradiation should be directly measurable. The use of quality factors based upon the energy deposition in a 1-micron-diameter volume of tissue as prescribed in International Commission on Radiation Units Report No. 40 (Joint Task Group 1986) satisfies these requirements. Instrumentation based upon measurement of lineal energy has already been successfully used in health-physics applications. Future changes in the quality factor can be accommodated by changing the algorithm in these microprocessor-based instruments. PMID:3410692

  9. Count rate limitations in pulsed accelerator fields

    SciTech Connect

    Justus, Alan L

    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.

  10. Space-charge limits in linear accelerators

    SciTech Connect

    Wangler, T.P.

    1980-12-01

    This report presents equations that allow an approximate evaluation of the limiting beam current for a large class of radio-frequency linear accelerators, which use quadrupole strong focusing. Included are the Alvarez, the Wideroe, and the radio-frequency quadrupole linacs. The limiting-current formulas are presented for both the longitudinal and the transverse degrees of freedom by assuming that the average space-charge force in the beam bunch arises from a uniformly distributed charge within an azimuthally symmetric three-dimensional ellipsoid. The Mathieu equation is obtained as an approximate, but general, form for the transverse equation of motion. The smooth-approximation method is used to obtain a solution and an expression for the transverse current limit. The form of the current-limit formulas for different linac constraints is discussed.

  11. Accelerator limitations to ion beam analysis

    NASA Astrophysics Data System (ADS)

    Klatt, Ch.; Hartmann, B.; Kalbitzer, S.

    1997-02-01

    Energy spread of ion beams is an important limitation of nuclear reaction analysis. While in single-stage electrostatic accelerators ion source or high voltage instabilities predominate, tandem type machines exhibit the stripping process as an additional and rather complex source of energy broadening. We have investigated the energy widths of the ions 1H and 15N for resonance reactions and 4He from a 3 MV tandem accelerator operated with a gas stripping column. Major differences between the final energy spread of injected atomic and molecular negative ions have been observed. Molecular break-up and energy-loss straggling may easily amount to a few keV, whereas the contribution by high voltage ripple is negligible in most cases. The results will be discussed in view of their impact on different analytical techniques for high-resolution analysis of thin solid films.

  12. [Nanosilver--Occupational exposure limits].

    PubMed

    ?widwi?ska-Gajewska, Anna Maria; Czerczak, S?awomir

    2015-01-01

    Historically, nanosilver has been known as colloidal silver composed of particles with a size below 100 nm. Silver nanoparticles are used in many technologies, creating a wide range of products. Due to antibacterial properties nanosilver is used, among others, in medical devices (wound dressings), textiles (sport clothes, socks), plastics and building materials (paints). Colloidal silver is considered by many as an ideal agent in the fight against pathogenic microorganisms, unlike antibiotics, without side effects. However, in light of toxicological research, nanosilver is not inert to the body. The inhalation of silver nanoparticles have an adverse effect mainly on the liver and lung of rats. The oxidative stress caused by reactive oxygen species is responsible for the toxicity of nanoparticles, contributing to cytotoxic and genotoxic effects. The activity of the readily oxidized nanosilver surface underlies the molecular mechanism of toxicity. This leads to the release of silver ions, a known harmful agent. Occupational exposure to silver nanoparticles may occur in the process of its manufacture, formulation and also usage during spraying, in particular. In Poland, as well as in other countries of the world, there is no separate hygiene standards applicable to nanomaterials. The present study attempts to estimate the value of MAC-TWA (maximum admissible concentration--the time-weighted average) for silver--a nano-objects fraction, which amounted to 0.01 mg/m3. The authors are of the opinion that the current value of the MAC-TWA for silver metallic--inhalable fraction (0.05 mg/m3) does not provide sufficient protection against the harmful effects of silver in the form of nano-objects. PMID:26325054

  13. 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.

  14. Exposure of Polymeric Glazing Materials Using NREL's Ultra-Accelerated Weathering System (UAWS)

    SciTech Connect

    Bingham, C.; Jorgensen, G.; Wylie, A.

    2010-01-01

    NREL's Ultra-Accelerated Weathering System (UAWS) selectively reflects and concentrates natural sunlight ultraviolet irradiance below 475 nm onto exposed samples to provide accelerated weathering of materials while keeping samples within realistic temperature limits. This paper will explain the design and implementation of the UAWS which allow it to simulate the effect of years of weathering in weeks of exposure. Exposure chamber design and instrumentation will be discussed for both a prototype UAWS used to test glazing samples as well as a commercial version of UAWS. Candidate polymeric glazing materials have been subjected to accelerated exposure testing at a light intensity level of up to 50 UV suns for an equivalent outdoor exposure in Miami, FL exceeding 15 years. Samples include an impact modified acrylic, fiberglass, and polycarbonate having several thin UV-screening coatings. Concurrent exposure is carried out for identical sample sets at two different temperatures to allow thermal effects to be quantified along with resistance to UV.

  15. Regulating under uncertainty: newsboy for exposure limits.

    PubMed

    Cooke, Roger M; Macdonell, Margaret

    2008-06-01

    Setting action levels or limits for health protection is complicated by uncertainty in the dose-response relation across a range of hazards and exposures. To address this issue, we consider the classic newsboy problem. The principles used to manage uncertainty for that case are applied to two stylized exposure examples, one for high dose and high dose rate radiation and the other for ammonia. Both incorporate expert judgment on uncertainty quantification in the dose-response relationship. The mathematical technique of probabilistic inversion also plays a key role. We propose a coupled approach, whereby scientists quantify the dose-response uncertainty using techniques such as structured expert judgment with performance weights and probabilistic inversion, and stakeholders quantify associated loss rates. PMID:18643816

  16. Ultra-Accelerated Natural Sunlight Exposure Testing Facilities

    DOEpatents

    Lewandowski, Allan A.; Jorgensen, Gary J.

    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.

  17. 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.

  18. Gradient Limitations in Room Temperature and Superconducting Acceleration Structures

    SciTech Connect

    Solyak, N. A.

    2009-01-22

    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 and D program.

  19. 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.

  20. 30 CFR 57.5038 - Annual exposure limits.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Annual exposure limits. 57.5038 Section 57.5038..., Physical Agents, and Diesel Particulate Matter Radiation-Underground Only 57.5038 Annual exposure limits. No person shall be permitted to receive an exposure in excess of 4 WLM in any calendar year....

  1. Human exposure limits to hypergolic fuels

    NASA Technical Reports Server (NTRS)

    Garcia, H. D.; James, J. T.; Limero, T. F.

    1992-01-01

    Over the past four decades, many studies have been conducted on the toxicities of the rocket propellants hydrazine (HZ) and monomethylhydrazine (MH). Numerous technical challenges have made it difficult to unambiguously interpret the results of these studies, and there is considerable divergence between results obtained by different investigators on the inhalation concentrations (MAC's) for each toxic effect inducible by exposure to hypergolic fuels in spacecraft atmospheres, NASA undertook a critical review of published and unpublished investigations on the toxicities of these compounds. The current state of the art practices for similar studies. While many questions remain unanswered, MAC's were determined using the best available data for a variety of toxic endpoints for potential continuous exposure durations ranging from 1 hour to 180 days. Spacecraft MAC's (SMAC's) were set for each compound based on the most sensitive toxic endpoint at each exposure duration.

  2. 47 CFR 1.1310 - Radiofrequency radiation exposure limits.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... exercise control over their exposure. Limits for occupational/controlled exposure also apply in situations... or can not exercise control over their exposure. ... and 17.4.3. Copyright NCRP, 1986, Bethesda, Maryland 20814. In the frequency range from 100 MHz...

  3. 47 CFR 1.1310 - Radiofrequency radiation exposure limits.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... exposure limits. The criteria listed in table 1 shall be used to evaluate the environmental impact of human..., “Evaluating Compliance with FCC-Specified Guidelines for Human Exposure to Radiofrequency Radiation.” Note to... Levels with Respect to Human Exposure to Radio Frequency Electromagnetic Fields, 3 kHz to 300 GHz,”...

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

    SciTech Connect

    Takada, Masashi; Suda, Mitsuo; Kamada, So; Hagiwara, Takuya; Imaseki, Hitoshi; Hamano, Tsuyoshi

    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.

  5. 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.

  6. 30 CFR 56.5001 - Exposure limits for airborne contaminants.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... asbestos standard found in 29 CFR 1910.1001, Appendix A, or a method at least equivalent to that method in... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Exposure limits for airborne contaminants. 56... Quality and Physical Agents Air Quality § 56.5001 Exposure limits for airborne contaminants. Except...

  7. 30 CFR 57.5001 - Exposure limits for airborne contaminants.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... contrast microscopy (PCM) using the OSHA Reference Method in OSHA's asbestos standard found in 29 CFR 1910... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Exposure limits for airborne contaminants. 57... Underground § 57.5001 Exposure limits for airborne contaminants. Except as permitted by § 57.5005— (a)...

  8. 10 CFR 850.22 - Permissible exposure limit.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... concentration of beryllium greater than the permissible exposure limit established in 29 CFR 1910.1000, as... 10 Energy 4 2013-01-01 2013-01-01 false Permissible exposure limit. 850.22 Section 850.22 Energy DEPARTMENT OF ENERGY CHRONIC BERYLLIUM DISEASE PREVENTION PROGRAM Specific Program Requirements §...

  9. 10 CFR 850.22 - Permissible exposure limit.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... concentration of beryllium greater than the permissible exposure limit established in 29 CFR 1910.1000, as... 10 Energy 4 2012-01-01 2012-01-01 false Permissible exposure limit. 850.22 Section 850.22 Energy DEPARTMENT OF ENERGY CHRONIC BERYLLIUM DISEASE PREVENTION PROGRAM Specific Program Requirements §...

  10. 10 CFR 850.22 - Permissible exposure limit.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... concentration of beryllium greater than the permissible exposure limit established in 29 CFR 1910.1000, as... 10 Energy 4 2011-01-01 2011-01-01 false Permissible exposure limit. 850.22 Section 850.22 Energy DEPARTMENT OF ENERGY CHRONIC BERYLLIUM DISEASE PREVENTION PROGRAM Specific Program Requirements §...

  11. 10 CFR 850.22 - Permissible exposure limit.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... concentration of beryllium greater than the permissible exposure limit established in 29 CFR 1910.1000, as... 10 Energy 4 2010-01-01 2010-01-01 false Permissible exposure limit. 850.22 Section 850.22 Energy DEPARTMENT OF ENERGY CHRONIC BERYLLIUM DISEASE PREVENTION PROGRAM Specific Program Requirements §...

  12. 10 CFR 850.22 - Permissible exposure limit.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... concentration of beryllium greater than the permissible exposure limit established in 29 CFR 1910.1000, as... 10 Energy 4 2014-01-01 2014-01-01 false Permissible exposure limit. 850.22 Section 850.22 Energy DEPARTMENT OF ENERGY CHRONIC BERYLLIUM DISEASE PREVENTION PROGRAM Specific Program Requirements §...

  13. 46 CFR 197.515 - Permissible exposure limits (PELs).

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 7 2014-10-01 2014-10-01 false Permissible exposure limits (PELs). 197.515 Section 197.515 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE OCCUPATIONAL SAFETY AND HEALTH STANDARDS GENERAL PROVISIONS Benzene 197.515 Permissible exposure limits (PELs). The...

  14. 46 CFR 197.515 - Permissible exposure limits (PELs).

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 7 2013-10-01 2013-10-01 false Permissible exposure limits (PELs). 197.515 Section 197.515 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE OCCUPATIONAL SAFETY AND HEALTH STANDARDS GENERAL PROVISIONS Benzene 197.515 Permissible exposure limits (PELs). The...

  15. 46 CFR 197.515 - Permissible exposure limits (PELs).

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 7 2012-10-01 2012-10-01 false Permissible exposure limits (PELs). 197.515 Section 197.515 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE OCCUPATIONAL SAFETY AND HEALTH STANDARDS GENERAL PROVISIONS Benzene 197.515 Permissible exposure limits (PELs). The...

  16. 46 CFR 197.515 - Permissible exposure limits (PELs).

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 7 2010-10-01 2010-10-01 false Permissible exposure limits (PELs). 197.515 Section 197.515 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE OCCUPATIONAL SAFETY AND HEALTH STANDARDS GENERAL PROVISIONS Benzene § 197.515 Permissible exposure limits (PELs). The...

  17. 46 CFR 197.515 - Permissible exposure limits (PELs).

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 7 2011-10-01 2011-10-01 false Permissible exposure limits (PELs). 197.515 Section 197.515 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE OCCUPATIONAL SAFETY AND HEALTH STANDARDS GENERAL PROVISIONS Benzene § 197.515 Permissible exposure limits (PELs). The...

  18. Diffusive shock acceleration - Acceleration rate, magnetic-field direction and the diffusion limit

    NASA Technical Reports Server (NTRS)

    Jokipii, J. R.

    1992-01-01

    This paper reviews the concept of diffusive shock acceleration, showing that the acceleration of charged particles at a collisionless shock is a straightforward consequence of the standard cosmic-ray transport equation, provided that one treats the discontinuity at the shock correctly. This is true for arbitrary direction of the upstream magnetic field. Within this framework, it is shown that acceleration at perpendicular or quasi-perpendicular shocks is generally much faster than for parallel shocks. Paradoxically, it follows also that, for a simple scattering law, the acceleration is faster for less scattering or larger mean free path. Obviously, the mean free path can not become too large or the diffusion limit becomes inapplicable. Gradient and curvature drifts caused by the magnetic-field change at the shock play a major role in the acceleration process in most cases. Recent observations of the charge state of the anomalous component are shown to require the faster acceleration at the quasi-perpendicular solar-wind termination shock.

  19. [Titanium dioxide nanoparticles: occupational exposure limits].

    PubMed

    Swidwi?ska-Gajewska, Anna Maria; Czerczak, S?awomir

    2014-01-01

    Titanium dioxide (TiO2) is produced in Poland as a high production volume chemical (HPVC). It is used mainly as a pigment for paints and coatings, plastics, paper, and also as additives to food and pharmaceuticals. Titanium dioxide nanoparticles are increasingly applied in cosmetics, textiles and plastics as the ultraviolet light blocker. This contributes to a growing occupational exposure to TiO2 nanoparticles. Nanoparticles are potentially responsible for the most adverse effects of titanium dioxide. Due to the absence of separate fraction of nanoobjects and appropriate measurement methods the maximum admissible concentrations (MAC) for particles < 100 nm and nano-TiO2 cannot be established. In the world there are 2 proposals of occupational exposure levels for titanium dioxide nanoparticles: 0.3 mg/m3, proposed by the National Institute for Occupational Safety and Health (NIOSH), and 0.6 mg/m3, proposed by experts of the New Energy and Industrial Technology Development Organization (NEDO). The authors of this article, based on the available data and existing methods for hygiene standards binding in Poland, concluded that the MAC value of 0.3 mg/m3 for nanoparticles TiO2 in the workplace air can be accepted. PMID:25230569

  20. Opportunities and limits of AMS with 3-MV tandem accelerators

    NASA Astrophysics Data System (ADS)

    Steier, Peter; Golser, Robin; Liechtenstein, Vitaly; Kutschera, Walter; Priller, Alfred; Vockenhuber, Christof; Wallner, Anton

    2005-10-01

    With the Vienna Environmental Research Accelerator (VERA, based on a 3-MV tandem accelerator) we have systematically explored the limitations due to terminal voltage, both by modelling and by experiments. If no stable atomic isobars exist, e.g. for 236U or 244Pu, the same detection limits as for large machines have been achieved. In cases where isobar separation is required, the achievable energy is the limitation. To study isobar separation experimentally, we use a new method called ?TOF: the different energy loss in a foil is measured with a time-of-flight (TOF) detector. Separation of 36Cl from 36S is possible. With diamond like carbon (DLC) stripper foils (0.6 ?g/cm2) and by pushing our Pelletron tandem to 3.6 MV, we achieved a significant increase in energy compared to gas stripping at 3 MV: e.g. 36Cl7+ at 28.8 MeV instead of 36Cl5+ at 18 MeV can be used.

  1. 47 CFR 1.1310 - Radiofrequency radiation exposure limits.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 1 2012-10-01 2012-10-01 false Radiofrequency radiation exposure limits. 1.1310 Section 1.1310 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL PRACTICE AND PROCEDURE Grants by Random Selection Procedures Implementing the National Environmental Policy Act of 1969 § 1.1310 Radiofrequency radiation exposure...

  2. Historical Context and Recent Advances in Exposure-Response Estimation for Deriving Occupational Exposure Limits

    PubMed Central

    Wheeler, M.W.; Park, R. M.; Bailer, A. J.; Whittaker, C.

    2015-01-01

    Virtually no occupational exposure standards specify the level of risk for the prescribed exposure, and most occupational exposure limits are not based on quantitative risk assessment (QRA) at all. Wider use of QRA could improve understanding of occupational risks while increasing focus on identifying exposure concentrations conferring acceptably low levels of risk to workers. Exposure-response modeling between a defined hazard and the biological response of interest is necessary to provide a quantitative foundation for risk-based occupational exposure limits; and there has been considerable work devoted to establishing reliable methods quantifying the exposure-response relationship including methods of extrapolation below the observed responses. We review several exposure-response modeling methods available for QRA, and demonstrate their utility with simulated data sets. PMID:26252067

  3. 30 CFR 57.5001 - Exposure limits for airborne contaminants.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... contrast microscopy (PCM) using the OSHA Reference Method in OSHA's asbestos standard found in 29 CFR 1910... exposure exceeding the 0.1 f/cc full-shift limit or the 1 f/cc excursion limit. When PCM results indicate...

  4. 30 CFR 56.5001 - Exposure limits for airborne contaminants.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... concentration shall be determined by phase contrast microscopy (PCM) using the OSHA Reference Method in OSHA's asbestos standard found in 29 CFR 1910.1001, Appendix A, or a method at least equivalent to that method in... limit. When PCM results indicate a potential exposure exceeding the 0.1 f/cc full-shift limit or the 1...

  5. 30 CFR 56.5001 - Exposure limits for airborne contaminants.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... concentration shall be determined by phase contrast microscopy (PCM) using the OSHA Reference Method in OSHA's asbestos standard found in 29 CFR 1910.1001, Appendix A, or a method at least equivalent to that method in... limit. When PCM results indicate a potential exposure exceeding the 0.1 f/cc full-shift limit or the 1...

  6. 30 CFR 57.5001 - Exposure limits for airborne contaminants.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... contrast microscopy (PCM) using the OSHA Reference Method in OSHA's asbestos standard found in 29 CFR 1910... exposure exceeding the 0.1 f/cc full-shift limit or the 1 f/cc excursion limit. When PCM results indicate...

  7. 30 CFR 57.5001 - Exposure limits for airborne contaminants.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... contrast microscopy (PCM) using the OSHA Reference Method in OSHA's asbestos standard found in 29 CFR 1910... exposure exceeding the 0.1 f/cc full-shift limit or the 1 f/cc excursion limit. When PCM results indicate...

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

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... contrast microscopy (PCM) using the OSHA Reference Method in OSHA's asbestos standard found in 29 CFR 1910... exposure exceeding the 0.1 f/cc full-shift limit or the 1 f/cc excursion limit. When PCM results indicate...

  9. 30 CFR 56.5001 - Exposure limits for airborne contaminants.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... concentration shall be determined by phase contrast microscopy (PCM) using the OSHA Reference Method in OSHA's asbestos standard found in 29 CFR 1910.1001, Appendix A, or a method at least equivalent to that method in... limit. When PCM results indicate a potential exposure exceeding the 0.1 f/cc full-shift limit or the 1...

  10. 30 CFR 56.5001 - Exposure limits for airborne contaminants.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... concentration shall be determined by phase contrast microscopy (PCM) using the OSHA Reference Method in OSHA's asbestos standard found in 29 CFR 1910.1001, Appendix A, or a method at least equivalent to that method in... limit. When PCM results indicate a potential exposure exceeding the 0.1 f/cc full-shift limit or the 1...

  11. 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

  12. 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

  13. Surfatron laser-plasma accelerator: prospects and limitations

    SciTech Connect

    Joshi, C.

    1983-01-01

    The surfatron laser-plasma accelerator is an extension of the plasma beat wave accelerator scheme. It utilizes very intense electric fields, 10/sup 9/ to 10/sup 10/ V/cm, associated with focussed laser beams to accelerate particles. (GHT)

  14. Accelerated Fatigue of Dentin with Exposure to Lactic Acid

    PubMed Central

    Majd, H.; Ryou, H.; Mutluay, M. M.; Xu, Hockin H. K.; Arola, D.

    2013-01-01

    Composite restorations accumulate more biofilm than other dental materials. This increases the likelihood for the hard tissues supporting a restoration (i.e. dentin and enamel) to be exposed to acidic conditions beyond that resulting from dietary variations. In this investigation the fatigue strength and fatigue crack growth resistance of human coronal dentin were characterized within a lactic acid solution (with pH=5) and compared to that of controls evaluated in neutral conditions (pH=7). A comparison of the fatigue life distributions showed that the lactic acid exposure resulted in a significant reduction in the fatigue strength (p?0.001), and nearly 30% reduction in the apparent endurance limit (from 44 MPa to 32 MPa). The reduction in pH also caused a significant decrease (p?0.05) in the threshold stress intensity range required for the initiation of cyclic crack growth, and significant increase in the incremental rate of crack extension. Exposure of tooth structure to lactic acid may cause demineralization, but it also increases the likelihood of restored tooth failures via fatigue, and after short time periods. PMID:23948166

  15. 76 FR 52664 - Request for Information: Announcement of Carcinogen and Recommended Exposure Limit (REL) Policy...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-23

    ... Carcinogen and Recommended Exposure Limit (REL) Policy Assessment AGENCY: National Institute for Occupational... review its approach to classifying carcinogens and establishing recommended exposure limits (RELs) for... recommended exposure limit (REL) for carcinogens or should lower targets be considered? (4) In...

  16. 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

  17. 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...

  18. Allowable exposure limits for carbon dioxide during extravehicular activity

    NASA Technical Reports Server (NTRS)

    Seter, Andrew J.

    1993-01-01

    The intent was to review the research pertaining to human exposure to carbon dioxide (CO2) and to recommend allowable exposure limits for extravehicular activity (EVA). Respiratory, renal, and gastrointestinal systems may be adversely affected by chronic low dose CO2 exposure. Ventilation was increased 15 percent with 1 percent CO2 and 50 percent with 2 percent CO2. Chronic exposure to less than 2 percent CO2 led to 20 day cycles of uncompensated and compensated respiratory acidosis. Acid-base changes were small. Histopathologic changes in guinea pig lungs have been noted with long term exposure to 1 percent CO2. No changes were seen with exposure to 0.5 percent CO2. Cycling of bone calcium stores with associated changes in blood and urinary calcium levels occurs with long term CO2 exposure. Histologic changes in bone have been noted in guinea pigs exposed to 1 percent CO2. Renal calcification has been noted in guinea pigs with exposure to as low as 0.5 percent CO2. An increase in gastric acidity was noted in subjects with long term exposure to 1 percent CO2. Cardiovascular and neurologic function were largely unaffected. A decrease in the incidence of respiratory, renal, and gastrointestinal disease was noted in submariners coincident with a decrease in ambient CO2 from 1.2 percent to 0.8-0.9 percent. Oxygen (O2) and CO2 stimulate respiration independently and cumulatively. The addition of CO2 to high dose O2 led to the faster onset of seizure activity in mice. Experiments evaluating the physiologic responses to intermittent, repetitive exposures to low dose CO2 and 100 percent O2 mixtures should be performed. A reduction in the current NASA standard for CO2 exposure during EVA of 1 percent (7.6 mmHg) for nominal and 2 percent (15.2 mmHg) for heavy exertion to 0.5 percent (3.8 mmHg) for nominal and 1 percent (7.6 mmHg) for heavy exertion may be prudent. At a minimum, the current NASA standard should not be liberalized.

  19. 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

  20. FETAL DEXAMETHASONE EXPOSURE ACCELERATES DEVELOPMENT OF RENAL FUNCTION: RELATIONSHIP TO DOSE, CELL DIFFERENTIATION AND GROWTH INHIBITION

    EPA Science Inventory

    Fetal exposure to high doses of glucocorticoids slows cellular development and impairs organ performance, in association with growth retardation. evertheless, low doses of glucocorticoids may enhance cell differentiation and accelerate specific functions. he current study examine...

  1. Optical properties of dyes affected by accelerating UV light exposure

    NASA Astrophysics Data System (ADS)

    Huang, Der-Ray; Chen, Yi-An; Liou, Run-Lin; Lin, Jing-Xuan; Tsai, Chih-Hung

    2015-09-01

    The optical characteristics of dyes are very important factors either for optical recording media or for dye sensitized solar cells (DSSC). The purpose of this paper is to study the stability of the dye in room temperature under the UV light exposure. Different dyes for different applications have different effect on the optical properties of dyes under the UV light exposures. Generally the dyes for recording media are very sensitive to the UV light exposure, while the dyes for DSSC applications are not so sensitive to the UV light exposure. After UV light exposure for 20-50 h, the intensities of main absorption peaks for recordable media are degraded obviously, while the intensities of main absorption peaks for dye sensitized solar cells are not degraded obviously.

  2. Strategies for setting occupational exposure limits for particles.

    PubMed Central

    Greim, H A; Ziegler-Skylakakis, K

    1997-01-01

    To set occupational exposure limits (OELs) for aerosol particles, dusts, or chemicals, one has to evaluate whether mechanistic considerations permit identification of a no observed effect level (NOEL). In the case of carcinogenic effects, this can be assumed if no genotoxicity is involved, and exposure is considered safe if it does not exceed the NOEL. If tumor induction is associated with genotoxicity, any exposure is considered to be of risk, although a NOEL may be identified in the animal or human exposure studies. This must also be assumed when no information on the carcinogenic mechanism, including genotoxicity, is available. Aerosol particles, especially fibrous dusts, which include man-made mineral fiber(s) (MMMF), present a challenge for toxicological evaluation. Many MMMF that have been investigated have induced tumors in animals and genotoxicity in vitro. Since these effects have been associated with long-thin fiber geometry and high durability in vivo, all fibers meeting such criteria are considered carcinogenic unless the opposite has been demonstrated. This approach is practicable. Investigations on fiber tumorigenicity/genotoxicity should include information on dose response, pathobiochemistry, particle clearance, and persistence of the material in the target organ. Such information will introduce quantitative aspects into the qualitative approach that has so far been used to classify fibrous dusts as carcinogens. The rationales for classifying the potential carcinogenicity of MMMF and for setting OELs used by the different European committees and regulatory agencies are described. PMID:9400750

  3. 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.

  4. Accelerator Mass Spectrometry of 129I towards its lower limits

    NASA Astrophysics Data System (ADS)

    Vockenhuber, Christof; Casacuberta, Nuria; Christl, Marcus; Synal, Hans-Arno

    2015-10-01

    We present the performance of Accelerator Mass Spectrometry (AMS) of 129I using the low energy facility TANDY of the Laboratory of Ion Beam Physics at ETH Zurich, Switzerland. Running the tandem accelerator at 300 kV in combination with helium as a stripper gas we obtain high transmission of >50% trough the accelerator for 129I ions in charge state 2+, molecules at mass 129 are sufficiently suppressed at appropriate stripper-gas pressures. While the high-energy spectrometer provides excellent suppression of the stable isotope 127I, mass-to-charge state (m/q) interferences are significantly reduced in 2+, allowing for measurements essentially free of background from other masses (isotopes and m/q interferences). The main challenge in the AMS of 129I comes from cross talk between samples in the ion source. With sufficient care low-level samples (129I/127I < 10-13) can be well measured, e.g. Woodward iodine was measured to 129I/127I = (3.4 0.3) 10-14, demonstrating that low-energy AMS of 129I provides both high overall efficiency and very low background.

  5. "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

  6. The Challenges of Limiting Exposure to THS in Vulnerable Populations.

    PubMed

    Samet, Jonathan M; Chanson, Dayana; Wipfli, Heather

    2015-09-01

    Research on active smoking and secondhand smoke exposure has led to policy changes to protect individuals from the adverse health impacts of tobacco smoke. Despite the extensive literature on tobacco, only recently has there been recognition that long-lived tobacco smoke components (known as "thirdhand smoke" or THS) in indoor environments where smoking has taken place may have adverse health consequences. This paper describes THS and addresses the challenges of limiting exposure to THS in vulnerable populations (e.g., nonsmokers and young children). We conducted a limited survey of key stakeholders in the Los Angeles area to better understand approaches to address THS in the real estate and automobile industries. Most respondents indicated concerns about past smoking for property value and reported using various techniques to eliminate THS. We consider examples of other pollutants as case studies, including radon, asbestos, and lead, to help frame policy directions for THS. Based on the information collected from stakeholders and the case studies, we offer policy approaches to managing THS. PMID:26231499

  7. Development of Occupational Exposure Limits for the Hanford Tank Farms

    SciTech Connect

    Still, Kenneth; Gardner, Donald; Snyder, Robert; Anderson, Thomas; Honeyman, James; Timchalk, Charles

    2010-04-01

    Production of plutonium for the United States nuclear weapons program from the 1940s to the 1980s generated 53 million gallons of radioactive chemical waste, which is storedin 177 underground tanks at the Hanford Site in southeastern W 18 ashington State. Recent 19 attempts to begin the retrieval and treatment of these wastes require moving the waste to 20 more modern tanks results in potential exposure of the workers to unfamiliar odors 21 emanating from headspace in the tanks. Given the unknown risks involved, workers 22 were placed on supplied air respiratory protection. CH2M HILL, the managers of the 23 Hanford Site Tank Farms, asked an Independent Toxicology Panel (ITP) to assist them in issues relating to an Industrial Hygiene and risk assessment problem. The ITP was called upon to help determine the risk of exposure to vapors from the tanks, and in general develop a strategy for solution of the problem. This paper presents the methods used to determine the chemicals of potential concern (COPC) and the resultant development of screening values and Acceptable Occupational Exposure Limits (AOELs) for these COPCs. A total of 1,826 chemicals were inventoried and evaluated. Over 1,500 chemicals were identified in the waste tanks headspaces and more than 600 of these were assigned screening values; 72 of these compounds were recommended for AOEL development. Included in this list of 72 were 57 COPCs identified by the ITP and of these 47 were subsequently assigned AOELs. An exhaustive exposure assessment strategy was developed by the CH2M HILL industrial hygiene department to evaluate these COPCs.

  8. Airborne Isocyanate Exposures in the Collision Repair Industry and a Comparison to Occupational Exposure Limits

    PubMed Central

    Reeb-Whitaker, Carolyn; Whittaker, Stephen G.; Ceballos, Diana M.; Weiland, Elisa C.; Flack, Sheila L.; Fent, Kenneth W.; Thomasen, Jennifer M.; Gaines, Linda G. Trelles; Nylander-French, Leena A.

    2014-01-01

    Isocyanate exposure was evaluated in 33 spray painters from 25 Washington State autobody shops. Personal breathing zone samples (n = 228) were analyzed for isophorone diisocyanate (IPDI) monomer, 1,6-hexamethylene diisocyanate (HDI) monomer, IPDI polyisocyanate, and three polyisocyanate forms of HDI. The objective was to describe exposures to isocyanates while spray painting, compare them with short-term exposure limits (STELs), and describe the isocyanate composition in the samples. The composition of polyisocyanates (IPDI and HDI) in the samples varied greatly, with maximum amounts ranging from up to 58% for HDI biuret to 96% for HDI isocyanurate. There was a significant inverse relationship between the percentage composition of HDI isocyanurate to IPDI and to HDI uretdione. Two 15-min STELs were compared: (1) Oregon's Occupational Safety and Health Administration (OR-OSHA) STEL of 1000 ?g/m3 for HDI polyisocyanate, and (2) the United Kingdom's Health and Safety Executive (UK-HSE) STEL of 70 ?g NCO/m3 for all isocyanates. Eighty percent of samples containing HDI polyisocyanate exceeded the OR-OSHA STEL while 98% of samples exceeded the UKHSE STEL. The majority of painters (67%) wore half-face air-purifying respirators while spray painting. Using the OROSHA and the UK-HSE STELs as benchmarks, 21% and 67% of painters, respectively, had at least one exposure that exceeded the respirator's OSHA-assigned protection factor. A critical review of the STELs revealed the following limitations: (1) the OR-OSHA STEL does not include all polyisocyanates, and (2) the UK-HSE STEL is derived from monomeric isocyanates, whereas the species present in typical spray coatings are polyisocyanates. In conclusion, the variable mixtures of isocyanates used by autobody painters suggest that an occupational exposure limit is required that includes all polyisocyanates. Despite the limitations of the STELs, we determined that a respirator with an assigned protection factor of 25 or greater is required to protect against isocyanate exposures during spray painting. Consequently, half-face air-purifying respirators, which are most commonly used and have an assigned protection factor of 10, do not afford adequate respiratory protection. PMID:22500941

  9. Limiting electron beam current for cyclic induction acceleration in a constant guide field

    SciTech Connect

    Kanunnikov, V.N.

    1982-09-01

    Theoretical relations are derived for the limiting beam current in a cyclic induction accelerator (CIA) with a constant guide field. The calculations are in agreement with the available experimental data. It is shown that the limiting average beam current in a CIA is of the order of 100 microamperes, i.e., the level attained in microtrons and linear accelerators. The CIA may find industrial applications.

  10. Scalar speed limits and cosmology: Acceleration from D-cceleration

    NASA Astrophysics Data System (ADS)

    Silverstein, Eva; Tong, David

    2004-11-01

    Causality on the gravity side of the AdS/CFT correspondence restricts motion on the moduli space of the N=4 super Yang-Mills theory by imposing a speed limit on how fast the scalar field may roll. This effect can be traced to higher-derivative operators arising from integrating out light degrees of freedom near the origin. In the strong coupling limit of the theory, the dynamics is well approximated by the Dirac-Born-Infeld Lagrangian for a probe D3-brane moving toward the horizon of the AdS Poincar patch, combined with an estimate of the (ultimately suppressed) rate of particle and string production in the system. We analyze the motion of a rolling scalar field explicitly in the strong coupling regime of the field theory and extend the analysis to cosmological systems obtained by coupling this type of field theory to four-dimensional gravity. This leads to a mechanism for slow roll inflation for a massive scalar at sub-Planckian vacuum expectation value without need for a flat potential (realizing a version of k inflation in a microphysical framework). It also leads to a variety of novel Friedman-Roberston-Walker cosmologies, some of which are related to those obtained with tachyon matter.

  11. 76 FR 71346 - Public Meeting and Request for Information: Carcinogen and Recommended Exposure Limit (REL...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-17

    ...: Carcinogen and Recommended Exposure Limit (REL) Policy Assessment AGENCY: The National Institute for... review its approach to classifying carcinogens and establishing recommended exposure limits (RELs) for... occupationally exposed) be the target level for a recommended exposure limit (REL) for carcinogens or...

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

    PubMed

    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. PMID:24089872

  13. 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.

  14. Quantify landslide exposure in areas with limited hazard information

    NASA Astrophysics Data System (ADS)

    Pellicani, R.; Spilotro, G.; Van Westen, C. J.

    2012-04-01

    In Daunia region, located in the North-western part of Apulia (Southern Italy), landslides are the main source of damage to properties in the urban centers of the area, involving especially transportation system and the foundation stability of buildings. In the last 50 years, the growing demand for physical development of these unstable minor hillside and mountain centers has produced a very rapid expansion of built-up areas, often with poor planning of urban and territorial infrastructures, and invasion of the agricultural soil. Because of the expansion of the built-up towards not safe areas, human activities such as deforestation or excavation of slopes for road cuts and building sites, etc., have become important triggers for landslide occurrence. In the study area, the probability of occurrence of landslides is very difficult to predict, as well as the expected magnitude of events, due to the limited data availability on past landslide activity. Because the main limitations concern the availability of temporal data on landslides and triggering events (frequency), run-out distance and landslide magnitude, it was not possible to produce a reliable landslide hazard map and, consequently, a risk map. Given these limitations in data availability and details, a qualitative exposure map has been produced and combined with a landslide susceptibility map, both generated using a spatial multi-criteria evaluation (SMCE) procedure in a GIS system, for obtaining the qualitative landslide risk map. The qualitative analysis has been provided the spatial distribution of the exposure level in the study area; this information could be used in a preliminary stage of regional planning. In order to have a better definition of the risk level in the Daunia territory, the quantification of the economic losses at municipal level was carried out. For transforming these information on economic consequences into landslide risk quantification, it was necessary to assume the temporal probability of landslides, on the basis of the expert knowledge on the landslide phenomena. For each of twenty-five municipalities included in the study area, the expected losses (or consequences), in monetary terms, due to different hazard scenarios have been evaluated. After calculating the economic losses, the total risk at municipal level was evaluated, by generating the risk curves and calculating the area under the curves. The analysis of the risk curves related to the 25 municipalities has showed that the total risk values, expressed in monetary terms, is higher for the bigger municipal areas located in the southern part of the study area where the elevation is lower, as are more numerous the elements at risk distributed on the municipal territory. Finally, this quantitative risk assessment procedure, which calculates the exposure in monetary terms of elements at risk, allows to establish the changes in risk in future with urban development and monetary inflation.

  15. Limits of fetal thyroid risk from radioiodine exposure

    SciTech Connect

    Lloyd, R.D.; Tripp, D.A.; Kerber, R.A.

    1996-04-01

    An incident in which a young women became pregnant soon after being treated with 444 MBq {sup 131}I for Graves disease prompted us to search local records for the occurrence of thyroid abnormalities among people exposed in utero to fallout radioiodine. The data base from the Utah Fallout Study indicated that there had been 480 cohort subjects for whom dose to thyroid from fallout radioiodine had been calculated and who could have received any thyroid dose before birth (2473 subjects had been re-examined in 1985-86 of the 4818 examined in 1965-70). Of these 480 subjects in this category, 403 of them could be located in the 1980`s and were examined for abnormalities. Although nodules, thyroiditis, hypothyroidism and goiter were seen among the 375 persons with in utero thyroid doses from fallout radioiodine below 0.42 Gy, no thyroid abnormalities of any kind occurred in the 4 persons with in utero thyroid doses of 0.5 to 2.6 Gy. In addition, no neoplasia was found in any of the 403 subjects examined about 3 decades after in utero fallout exposure. These limited data do not indicate that the fetal thyroid is more sensitive than the postnatal thyroid by more than about a factor of about 4 when thyroid dose is considered and by not much more than unity when the comparison is based on dose equivalent (x-ray vs. radioiodine). 21 refs., 1 tab.

  16. Preliminary results of accelerated exposure testing of solar cell system components

    NASA Technical Reports Server (NTRS)

    Anagnostou, E.; Forestieri, A. F.

    1977-01-01

    Plastic samples and solar cell sub modules were exposed to an accelerated outdoor environment in Arizona and an accelerated simulated environment in a cyclic ultraviolet exposure tester which included humidity exposure. These tests were for preliminary screening of materials suitable for use in the manufacture of solar cell modules which are to have a 20-year lifetime. The samples were exposed for various times up to six months, equivalent to a real time exposure of four years. Suitable materials were found to be FEP-A, FEP-C, PFA, acrylic, silicone compounds and adhesives and possibly parylene. The method of packaging the sub modules was also found to be important to their performance.

  17. 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.

  18. Arsenite exposure accelerates aging process regulated by the transcription factor DAF-16/FOXO in Caenorhabditis elegans.

    PubMed

    Yu, Chan-Wei; How, Chun Ming; Liao, Vivian Hsiu-Chuan

    2016-05-01

    Arsenic is a known human carcinogen and high levels of arsenic contamination in food, soils, water, and air are of toxicology concerns. Nowadays, arsenic is still a contaminant of emerging interest, yet the effects of arsenic on aging process have received little attention. In this study, we investigated the effects and the underlying mechanisms of chronic arsenite exposure on the aging process in Caenorhabditis elegans. The results showed that prolonged arsenite exposure caused significantly decreased lifespan compared to non-exposed ones. In addition, arsenite exposure (100 μM) caused significant changes of age-dependent biomarkers, including a decrease of defecation frequency, accumulations of intestinal lipofuscin and lipid peroxidation in an age-dependent manner in C. elegans. Further evidence revealed that intracellular reactive oxygen species (ROS) level was significantly increased in an age-dependent manner upon 100 μM arsenite exposure. Moreover, the mRNA levels of transcriptional makers of aging (hsp-16.1, hsp-16.49, and hsp-70) were increased in aged worms under arsenite exposure (100 μM). Finally, we showed that daf-16 mutant worms were more sensitive to arsenite exposure (100 μM) on lifespan and failed to induce the expression of its target gene sod-3 in aged daf-16 mutant under arsenite exposure (100 μM). Our study demonstrated that chronic arsenite exposure resulted in accelerated aging process in C. elegans. The overproduction of intracellular ROS and the transcription factor DAF-16/FOXO play roles in mediating the accelerated aging process by arsenite exposure in C. elegans. This study implicates a potential ecotoxicological and health risk of arsenic in the environment. PMID:26796881

  19. 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.

  20. 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.

  1. 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

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

    NASA Astrophysics Data System (ADS)

    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.

    1990-12-01

    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 adduct) at levels relevent to human exposure. Detection sensitivities are 1 carcinogen molecule bound in 1011 to 1012 DNA bases, depending on the specific activity of the radiolabeled carcinogen. 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. Approximately l per 106 sperm analyzed contain the rare form of the protamine. Protamine isolated from this small number of cells is being analyzed by AMS, following 14C labeling. Thus, AMS can be used to verify the identity of an extremely small amount of biological material. Furthermore, an additional improvement of 2 orders of magnitude in the sensitivity of biomdical tracer studies is suggested by preliminary work with bacterial hosts depleted in radiocarbon. Other 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 3H (double labeling with 14C) and 41Ca (bone absorption) to problems in biology. The detection of 36Cl and 26Al have applications for determination of human neutron exposure and understanding neurological toxicity, respectively. The results described here with 14C-labeled molecules coupled with new isotope applications clearly show AMS technology to be an important new tool for the biomedical sciences community.

  3. Aging after noise exposure: acceleration of cochlear synaptopathy in "recovered" ears.

    PubMed

    Fernandez, Katharine A; Jeffers, Penelope W C; Lall, Kumud; Liberman, M Charles; Kujawa, Sharon G

    2015-05-13

    Cochlear synaptic loss, rather than hair cell death, is the earliest sign of damage in both noise- and age-related hearing impairment (Kujawa and Liberman, 2009; Sergeyenko et al., 2013). Here, we compare cochlear aging after two types of noise exposure: one producing permanent synaptic damage without hair cell loss and another producing neither synaptopathy nor hair cell loss. Adult mice were exposed (8-16 kHz, 100 or 91 dB SPL for 2 h) and then evaluated from 1 h to ? 20 months after exposure. Cochlear function was assessed via distortion product otoacoustic emissions and auditory brainstem responses (ABRs). Cochlear whole mounts and plastic sections were studied to quantify hair cells, cochlear neurons, and the synapses connecting them. The synaptopathic noise (100 dB) caused 35-50 dB threshold shifts at 24 h. By 2 weeks, thresholds had recovered, but synaptic counts and ABR amplitudes at high frequencies were reduced by up to ? 45%. As exposed animals aged, synaptopathy was exacerbated compared with controls and spread to lower frequencies. Proportional ganglion cell losses followed. Threshold shifts first appeared >1 year after exposure and, by ? 20 months, were up to 18 dB greater in the synaptopathic noise group. Outer hair cell losses were exacerbated in the same time frame (? 10% at 32 kHz). In contrast, the 91 dB exposure, producing transient threshold shift without acute synaptopathy, showed no acceleration of synaptic loss or cochlear dysfunction as animals aged, at least to ? 1 year after exposure. Therefore, interactions between noise and aging may require an acute synaptopathy, but a single synaptopathic exposure can accelerate cochlear aging. PMID:25972177

  4. Aging after Noise Exposure: Acceleration of Cochlear Synaptopathy in Recovered Ears

    PubMed Central

    Fernandez, Katharine A.; Jeffers, Penelope W.C.; Lall, Kumud; Liberman, M. Charles

    2015-01-01

    Cochlear synaptic loss, rather than hair cell death, is the earliest sign of damage in both noise- and age-related hearing impairment (Kujawa and Liberman, 2009; Sergeyenko et al., 2013). Here, we compare cochlear aging after two types of noise exposure: one producing permanent synaptic damage without hair cell loss and another producing neither synaptopathy nor hair cell loss. Adult mice were exposed (816 kHz, 100 or 91 dB SPL for 2 h) and then evaluated from 1 h to ?20 months after exposure. Cochlear function was assessed via distortion product otoacoustic emissions and auditory brainstem responses (ABRs). Cochlear whole mounts and plastic sections were studied to quantify hair cells, cochlear neurons, and the synapses connecting them. The synaptopathic noise (100 dB) caused 3550 dB threshold shifts at 24 h. By 2 weeks, thresholds had recovered, but synaptic counts and ABR amplitudes at high frequencies were reduced by up to ?45%. As exposed animals aged, synaptopathy was exacerbated compared with controls and spread to lower frequencies. Proportional ganglion cell losses followed. Threshold shifts first appeared >1 year after exposure and, by ?20 months, were up to 18 dB greater in the synaptopathic noise group. Outer hair cell losses were exacerbated in the same time frame (?10% at 32 kHz). In contrast, the 91 dB exposure, producing transient threshold shift without acute synaptopathy, showed no acceleration of synaptic loss or cochlear dysfunction as animals aged, at least to ?1 year after exposure. Therefore, interactions between noise and aging may require an acute synaptopathy, but a single synaptopathic exposure can accelerate cochlear aging. PMID:25972177

  5. Research of the optical properties of solar-reflective materials subjected to accelerated and nonaccelerated exposure tests. Final report

    SciTech Connect

    Rausch, R A

    1980-10-01

    Research on candidate reflective materials for use in solar thermal power applications is reported. The candidate materials have been subjected to exposure tests conducted previously at the Phoenix, Arizona test site. The samples have been exposed to each of three test conditions - one non-accelerated and two different accelerated tests (nominally 8 suns). Post-exposure optical measurements of spectral reflectance were then conducted for the exposure test samples. Reflectance specularity data for the subject materials are obtained from optical measurements performed by Battelle-PNL. Summarized is an investigation of the accumulated reflectance data for correlations using three of the various materials included in the exposure test sample set. (LEW)

  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. 47 CFR 1.1310 - Radiofrequency radiation exposure limits.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... any 1 gram of tissue (defined as a tissue volume in the shape of a cube). Exceptions are the parts of... tissue (defined as a tissue volume in the shape of a cube). Exposure may be averaged over a time period... peak spatial-average SAR of 1.6 W/kg, averaged over any 1 gram of tissue (defined as a tissue volume...

  8. 47 CFR 1.1310 - Radiofrequency radiation exposure limits.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... any 1 gram of tissue (defined as a tissue volume in the shape of a cube). Exceptions are the parts of... tissue (defined as a tissue volume in the shape of a cube). Exposure may be averaged over a time period... peak spatial-average SAR of 1.6 W/kg, averaged over any 1 gram of tissue (defined as a tissue volume...

  9. Bisphenol A exposure accelerated the aging process in the nematode Caenorhabditis elegans.

    PubMed

    Tan, Ling; Wang, Shunchang; Wang, Yun; He, Mei; Liu, Dahai

    2015-06-01

    Bisphenol A (BPA) is a well-known environmental estrogenic disruptor that causes adverse effects. Recent studies have found that chronic exposure to BPA is associated with a high incidence of several age-related diseases. Aging is characterized by progressive function decline, which affects quality of life. However, the effects of BPA on the aging process are largely unknown. In the present study, by using the nematode Caenorhabditis elegans as a model, we investigated the influence of BPA exposure on the aging process. The decrease in body length, fecundity, and population size and the increased egg laying defection suggested that BPA exposure resulted in fitness loss and reproduction aging in this animal. Lifetime exposure of worms to BPA shortened the lifespan in a dose-dependant manner. Moreover, prolonged BPA exposure resulted in age-related behavior degeneration and the accumulation of lipofuscin and lipid peroxide products. The expression of mitochondria-specific HSP-6 and endoplasmic reticulum (ER)-related HSP-70 exhibited hormetic decrease. The expression of ER-related HSP-4 decreased significantly while HSP-16.2 showed a dose-dependent increase. The decreased expression of GCS-1 and GST-4 implicated the reduced antioxidant ability under BPA exposure, and the increase in SOD-3 expression might be caused by elevated levels of reactive oxygen species (ROS) production. Finally, BPA exposure increased the generation of hydrogen peroxide-related ROS and superoxide anions. Our results suggest that BPA exposure resulted in an accelerated aging process in C. elegans mediated by the induction of oxidative stress. PMID:25819108

  10. Long-term bisphenol A exposure accelerates insulitis development in diabetes-prone NOD mice.

    PubMed

    Bodin, Johanna; Bølling, Anette Kocbach; Samuelsen, Mari; Becher, Rune; Løvik, Martinus; Nygaard, Unni Cecilie

    2013-06-01

    Exposure to the endocrine disruptor (ED) bisphenol A (BPA) used in polycarbonate plastic and epoxy resins appears ubiquitous since BPA can be found in over 90% of analyzed urine samples from all age groups. There is a parallel occurrence of increased prevalence in type 1 diabetes mellitus (T1DM) and an increased exposure to EDs the last decades. T1DM is caused by insulin deficiency due to autoimmune destruction of insulin producing pancreatic beta cells and has been suggested to be induced by various environmental factors acting together with a genetic predisposition. The objective of the present study was to investigate the effect of BPA (0, 1 and 100 mg/l BPA in the drinking water) on T1DM development in nonobese diabetic (NOD) mice, spontaneously developing T1DM. Histological evaluation of pancreas from 12-weeks-old female mice revealed significantly increased insulitis in mice exposed to 1 mg/l BPA, while the insulitis was less severe at the higher BPA exposure. Serum glucose levels in the 1 mg/ml BPA group tended to be hyperglycaemic, also indicating an accelerated onset of T1DM. The high BPA exposure seemed to counteract the diabetes development in females and also in male NOD mice for both BPA concentrations. Prior to insulitis, both BPA concentrations resulted in increased apoptosis and reduced numbers of tissue resident macrophages in pancreatic islets. In conclusion, long-term BPA exposure at a dose three times higher than the tolerable daily intake of 50 µg/kg, appeared to accelerate spontaneous insulitis and diabetes development in NOD mice. PMID:23496298

  11. 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

  12. Optimal proton acceleration from lateral limited foil sections and different laser pulse durations at relativistic intensity

    SciTech Connect

    Toncian, T.; Swantusch, M.; Toncian, M.; Willi, O.; Andreev, A. A.; Platonov, K. Y.

    2011-04-15

    The proton acceleration from a thin foil irradiated by a laser pulse at relativistic intensities is a process highly dependent on the electron dynamic at the rear side of the foil. By reducing the lateral size of the laser irradiated foil the hot electrons are confined in a small volume leading to an enhancement of both the maximum proton energy and the conversion efficiency in the target normal sheath acceleration regime. In this paper we demonstrate that an optimal lateral size of the target can be found. While a smaller target surface leads to a better hot electron confinement and enhances the Debye sheath accelerating the protons, it also leads to an increase of preplasma formation due to limited laser contrast available experimentally and hence to a decrease of the proton acceleration. The experimentally found optimum is in good agreement with analytic theory and 2D particle in cell simulations. In addition, the maximum proton energy as a function of pulse duration has been investigated. The experimental results fit to an analytical model.

  13. Further Analysis of Accelerated Exposure Testing of Thin-Glass Mirror Matrix

    SciTech Connect

    Kennedy, C. E.; Terwilliger, K.; Jorgensen, G. J.

    2007-01-01

    Concentrating solar power (CSP) companies have deployed thin-glass mirrors produced by wet-silver processes on {approx}1-mmthick, relatively lightweight glass. These mirrors are bonded to metal substrates in commercial installations and have the confidence of the CSP industry. Initial hemispherical reflectance is {approx}93%-96%, and the cost is {approx}$16.1/m{sup 2}-$43.0/m{sup 2}. However, corrosion was observed in mirror elements of operational solar systems deployed outdoors for 2 years. National Renewable Energy Laboratory (NREL) Advanced Materials Team has been investigating this problem. First, it was noted that this corrosion is very similar to the corrosion bands and spots observed on small (45 mm x 67 mm) thin-glass mirrors laminated to metal substrates with several different types of adhesives and subjected to accelerated exposure testing (AET) at NREL. The corrosion appears as dark splotches in the center of the mirror, with a corresponding 5%-20% loss in reflectivity. Secondly, two significant changes in mirror manufacture have occurred in the wet-chemistry process because of environmental concerns. The first is the method of forming a copper-free reflective mirror, and the second is the use of lead-free paints. However, the copper-free process requires stringent quality control and the lead-free paints were developed for interior applications. A test matrix of 84 combinations of sample constructions (mirror type/backprotective paint/adhesive/substrate) was devised for AET as a designed experiment to identify the most-promising mirrors, paints, and adhesives for use with concentrator designs. Two types of accelerated exposure were used: an Atlas Ci5000 WeatherOmeter (CI5000) and a BlueM damp-heat chamber. Based on an analysis of variance (ANOVA), the various factors and interactions were modeled. These samples now have more than 36 months of accelerated exposure, and most samples have completed their test cycle. We will discuss the results of the final exposure testing of these mirror samples. Glass mirrors with copper back-layers and heavily leaded paints have been considered robust for outdoor use. However, the basic mirror composition of the new mirrors is radically different from that of historically durable solar mirrors, and the outdoor durability must be determined.

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

    SciTech Connect

    Basso, T.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{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.}

  15. 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.

  16. 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.

  17. Prenatal Exposure to Low Levels of Androgen Accelerates Female Puberty Onset and Reproductive Senescence in Mice

    PubMed Central

    Witham, Emily A.; Meadows, Jason D.; Shojaei, Shadi; Kauffman, Alexander S.

    2012-01-01

    Sex steroid hormone production and feedback mechanisms are critical components of the hypothalamic-pituitary-gonadal (HPG) axis and regulate fetal development, puberty, fertility, and menopause. In female mammals, developmental exposure to excess androgens alters the development of the HPG axis and has pathophysiological effects on adult reproductive function. This study presents an in-depth reproductive analysis of a murine model of prenatal androgenization (PNA) in which females are exposed to a low dose of dihydrotestosterone during late prenatal development on embryonic d 16.518.5. We determined that PNA females had advanced pubertal onset and a delay in the time to first litter, compared with vehicle-treated controls. The PNA mice also had elevated testosterone, irregular estrous cyclicity, and advanced reproductive senescence. To assess the importance of the window of androgen exposure, dihydrotestosterone was administered to a separate cohort of female mice on postnatal d 2123 [prepubertal androgenization (PPA)]. PPA significantly advanced the timing of pubertal onset, as observed by age of the vaginal opening, yet had no effects on testosterone or estrous cycling in adulthood. The absence of kisspeptin receptor in Kiss1r-null mice did not change the acceleration of puberty by the PNA and PPA paradigms, indicating that kisspeptin signaling is not required for androgens to advance puberty. Thus, prenatal, but not prepubertal, exposure to low levels of androgens disrupts normal reproductive function throughout life from puberty to reproductive senescence. PMID:22778229

  18. Threshold limits for biological indication of prolonged radiation exposure using mFISH.

    PubMed

    Osovets, Sergey V; Sotnik, Natalia V; Meineke, Viktor; Scherthan, Harry; Drr, Harald; Azizova, Tamara V

    2014-06-01

    Chromosome aberration (translocation) yield was investigated by mFISH in peripheral blood lymphocytes of Mayak Production Association (PA) workers with prolonged occupational exposure to ionizing radiation (IR). A dose threshold for cytogenetic indication of a prolonged occupational radiation exposure was estimated for Mayak PA workers using functions of dose distributions. Two limits were estimated for the indication of IR exposure to workers with a prolonged external gamma-ray exposure: These are a background translocation yield of N? = 0.812 0.149% and a dose threshold of indication D? estimated to be approximately 1 Gy. PMID:24776899

  19. Uses and limits of empirical data in measuring and modeling human lead exposure.

    PubMed Central

    Mushak, P

    1998-01-01

    This paper examines the uses and limits of empirical data in evaluating measurement and modeling approaches to human lead exposure. Empirical data from experiment or observation or both have been used in studies of lead exposure. For example, experimental studies have elucidated and quantified physiologic or biokinetic parameters of lead exposure under controlled conditions. Observation, i.e., epidemiology, has been widely applied to study population exposures to lead. There is growing interest in the use of lead exposure prediction models and their evaluation before use in risk assessment. Empirical studies of lead exposure must be fully understood, especially their limits, before they are applied as "standards" or reference information for evaluation of exposure models, especially the U.S. Environmental Protection Agency's lead biokinetic model that is a focus of this article. Empirical and modeled datasets for lead exposure may not agree due to a) problems with the observational data or b) problems with the model; caution should be exercised before either a model or observational data are rejected. There are at least three sources of discordance in cases where there is lack of agreement: a) empirical data are accurate but the model is flawed; b) the model is valid but reference empirical data are inaccurate; or c) neither empirical data nor model is accurate, and each is inaccurate in different ways. This paper evaluates some of the critical empirical input to biokinetic models, especially lead bioavailability. Images Figure 3 PMID:9860906

  20. Derivation of safe health-based exposure limits for potential consumer exposure to styrene migrating into food from food containers.

    PubMed

    Gelbke, Heinz-Peter; Banton, Marcy; Faes, Eric; Leibold, Edgar; Pemberton, Mark; Duhayon, Sophie

    2014-02-01

    Residual styrene present in polystyrene food packaging may migrate into food at low levels. To assure safe use, safe exposure levels are derived for consumers potentially exposed via food using No/Low Adverse Effect Levels from animal and human studies and assessment factors proposed by European organisations (EFSA, ECHA, ECETOC). Ototoxicity and developmental toxicity in rats and human ototoxicity and effects on colour discrimination have been identified as the most relevant toxicological properties for styrene health assessments. Safe exposure levels derived from animal studies with assessment factors of EFSA and ECHA were expectedly much lower than those using the ECETOC approach. Comparable safe exposure levels were obtained from human data with all sets of assessment factors while ototoxicity in rats led to major differences. The safe exposure levels finally selected based on criteria of science and health protection converged to the range of 90-120 mg/person/d. Assuming a consumption of 1 kg food/d for an adult, this translates to 90 mg styrene migration into 1 kg food as safe for consumers. This assessment supports a health based Specific Migration Limit of 90 ppm, a value somewhat higher than the current overall migration limit of 60 ppm in the European Union. PMID:24316211

  1. Accelerated exposure tests of encapsulated Si solar cells and encapsulation materials

    SciTech Connect

    Pern, F.J.; Glick, S.H.

    1999-03-01

    We have conducted a series of accelerated exposure test (AET) studies for various crystalline-Si (c-Si) and amorphous-Si (a-Si) cell samples that were encapsulated with different superstrates, pottants, and substrates. Nonuniform browning patterns of ethylene vinyl acetate (EVA) pottants were observed for glass/EVA/glass-encapsulated c-Si cell samples under solar simulator exposures at elevated temperatures. The polymer/polymer-configured laminates with Tedlar or Tefzel did not discolor because of photobleaching reactions, but yellowed with polyester or nylon top films. Delamination was observed for the polyester/EVE layers on a-Si minimodules and for a polyolefin-based thermoplastic pottant at high temperatures. For all tested c-Si cell samples, irregular changes in the current-voltage parameters were observed that could not be accounted for simply by the transmittance changes of the superstrate/pottant layers. Silicone-type adhesives used under UV-transmitting polymer top films were observed to cause greater cell current/efficiency loss than EVA or polyethylene pottants. {copyright} {ital 1999 American Institute of Physics.}

  2. Accelerated Exposure Tests of Encapsulated Si Solar Cells and Encapsulation Materials

    SciTech Connect

    Pern, F. J.; Glick, S. H.

    1998-10-08

    We have conducted a series of accelerated exposure test (AET) studies for various crystalline-Si (c-Si) and amorphous-Si (a-Si) cell samples that were encapsulated with different superstrates, pottants, and substrates. Nonuniform browning patterns of ethylene vinyl acetate (EVA) pottants were observed for glass/EVA/glass-encapsulated c-Si cell samples under solar simulator exposures at elevated temperatures. The polymer/polymer-configured laminates with Tedlar or Tefzel did not discolor because of photobleaching reactions, but yellowed with polyester or nylon top films. Delamination was observed for the polyester/EVA layers on a-Si minimodules and for a polyolefin-based thermoplastic pottant at high temperatures. For all tested c-Si cell samples, irregular changes in the current-voltage parameters were observed that could not be accounted for simply by the transmittance changes of the superstrate/pottant layers. Silicone-type adhesives used under UV-transmitting polymer top films were observed to cause greater cell current/efficiency loss than EVA or polyethylene pottants.

  3. Medical considerations for human exposure to acceleration-induced loss of consciousness.

    PubMed

    Whinnery, J E

    1991-07-01

    Unconsciousness in humans has probably been occurring since before recorded history. Acceleration-induced loss of consciousness (G-LOC) in flight has been occurring since 1919. Loss of consciousness and syncope are common occurrences in clinical medicine with G-LOC, occurring in a large number of aircrew and research subjects during centrifuge exposures. Although the major risk to humans exposed to centrifuge-induced G-LOC is related directly to the central nervous, cardiac, and musculoskeletal (neck and back) systems, other risks are also present. Human exposure to G-LOC is required to help solve the G-LOC problem in aviators. To perform such human research, the benefits must clearly outweigh the risks to the human. Even if the risk-benefit ratio is considered favorably balanced, continued monitoring of individuals exposed to G-LOC is mandatory. To facilitate monitoring of humans exposed to G-LOC, a central nervous system (CNS) insult classification system would be of significant value. A suggested classification scheme which considers the type of CNS insult, the history of exposure to G-LOC, and the temporal evolution of potential CNS insult is developed. To date there is no indication that G-LOC episodes have any associated long term or persistent psychophysiological sequelae. Improved acute and long term evaluation of humans exposed to G-LOC are, however, important aspects of conducting G-LOC research with humans. Such research and careful monitoring are necessary to understand and eventually solve the G-LOC problem in aviators. PMID:1898295

  4. Workshop report: strategies for setting occupational exposure limits for engineered nanomaterials.

    PubMed

    Gordon, Steven C; Butala, John H; Carter, Janet M; Elder, Alison; Gordon, Terry; Gray, George; Sayre, Philip G; Schulte, Paul A; Tsai, Candace S; West, Jay

    2014-04-01

    Occupational exposure limits (OELs) are important tools for managing worker exposures to chemicals; however, hazard data for many engineered nanomaterials (ENMs) are insufficient for deriving OELs by traditional methods. Technical challenges and questions about how best to measure worker exposures to ENMs also pose barriers to implementing OELs. New varieties of ENMs are being developed and introduced into commerce at a rapid pace, further compounding the issue of OEL development for ENMs. A Workshop on Strategies for Setting Occupational Exposure Limits for Engineered Nanomaterials, held in September 2012, provided an opportunity for occupational health experts from various stakeholder groups to discuss possible alternative approaches for setting OELs for ENMs and issues related to their implementation. This report summarizes the workshop proceedings and findings, identifies areas for additional research, and suggests potential avenues for further progress on this important topic. PMID:24462629

  5. Quantification of volatile organic compounds in smoke from prescribed burning and comparison with occupational exposure limits

    NASA Astrophysics Data System (ADS)

    Romagnoli, E.; Barboni, T.; Santoni, P.-A.; Chiaramonti, N.

    2014-05-01

    Prescribed burning represents a serious threat to personnel fighting fires due to smoke inhalation. The aim of this study was to investigate exposure by foresters to smoke from prescribed burning, focusing on exposure to volatile organic compounds (VOCs). The methodology for smoke sampling was first evaluated. Potentially dangerous compounds were identified among the VOCs emitted by smoke fires at four prescribed burning plots located around Corsica. The measured mass concentrations for several toxic VOCs were generally higher than those measured in previous studies due to the experimental framework (short sampling distance between the foresters and the flame, low combustion, wet vegetation). In particular, benzene, phenol and furfural exceeded the legal short-term exposure limits published in Europe and/or the United States. Other VOCs such as toluene, ethybenzene or styrene remained below the exposure limits. In conclusion, clear and necessary recommendations were made for protection of personnel involved in fighting fires.

  6. Flame acceleration due to wall friction: Accuracy and intrinsic limitations of the formulations

    NASA Astrophysics Data System (ADS)

    Demirgok, Berk; Sezer, Hayri; Akkerman, V.Yacheslav

    2015-11-01

    The analytical formulations on the premixed flame acceleration induced by wall friction in two-dimensional (2D) channels [Bychkov etal., Phys. Rev. E 72 (2005) 046307] and cylindrical tubes [Akkerman etal., Combust. Flame 145 (2006) 206] are revisited. Specifically, pipes with one end closed are considered, with a flame front propagating from the closed pipe end to the open one. The original studies provide the analytical formulas for the basic flame and fluid characteristics such as the flame acceleration rate, the flame shape and its propagation speed, as well as the flame-generated flow velocity profile. In the present work, the accuracy of these approaches is verified, computationally, and the intrinsic limitations and validity domains of the formulations are identified. Specifically, the error diagrams are presented to demonstrate how the accuracy of the formulations depends on the thermal expansion in the combustion process and the Reynolds number associated with the flame propagation. It is shown that the 2D theory is accurate enough for a wide range of parameters. In contrast, the zeroth-order approximation for the cylindrical configuration appeared to be quite inaccurate and had to be revisited. It is subsequently demonstrated that the first-order approximation for the cylindrical geometry is very accurate for realistically large thermal expansions and Reynolds numbers. Consequently, unlike the zeroth-order approach, the first-order formulation can constitute a backbone for the comprehensive theory of the flame acceleration and detonation initiation in cylindrical tubes. Cumulatively, the accuracy of the formulations deteriorates with the reduction of the Reynolds number and thermal expansion.

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

    SciTech Connect

    Nusinovich, Gregory S.; Antonsen, Thomas M.; Kishek, Rami

    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.

  8. Ultrasonication: An Efficient Agitation for Accelerating the Supersaturation-Limited Amyloid Fibrillation of Proteins

    NASA Astrophysics Data System (ADS)

    Yoshimura, Yuichi; So, Masatomo; Yagi, Hisashi; Goto, Yuji

    2013-07-01

    Amyloid fibrils are self-assemblies of proteins with an ordered cross-? architecture. Because they are associated with serious disorders, understanding their structure and mechanism of fibrillation is important. Irradiation with ultrasonication leads to fragmentation of amyloid fibrils, useful for seeding experiments. Recently, ultrasonication has been found to trigger the spontaneous formation of fibrils in solutions of monomeric amyloidogenic proteins. The results indicate that amyloid fibrillation is similar to the crystallization of solutes from a supersaturated solution. The accelerating effects of ultrasonication on amyloid fibrillation suggest that cavitation microbubbles play a key role in effectively converting the metastable state of supersaturation to the labile state, leading to spontaneous fibrillation. Moreover, ultrasonic irradiation would be promising for a high-throughput screening assay of amyloid fibrillation, advancing the study of supersaturation-limited amyloidogenesis.

  9. A limited-memory acceleration strategy for MCMC sampling in hierarchical Bayesian calibration of hydrological models

    NASA Astrophysics Data System (ADS)

    Kuczera, George; Kavetski, Dmitri; Renard, Benjamin; Thyer, Mark

    2010-07-01

    Hydrological calibration and prediction using conceptual models is affected by forcing/response data uncertainty and structural model error. The Bayesian Total Error Analysis methodology uses a hierarchical representation of individual sources of uncertainty. However, it is shown that standard multiblock "Metropolis-within-Gibbs" Markov chain Monte Carlo (MCMC) samplers commonly used in Bayesian hierarchical inference are exceedingly computationally expensive when applied to hydrologic models, which use recursive numerical solutions of coupled nonlinear differential equations to describe the evolution of catchment states such as soil and groundwater storages. This note develops a "limited-memory" algorithm for accelerating multiblock MCMC sampling from the posterior distributions of such models using low-dimensional jump distributions. The new algorithm exploits the decaying memory of hydrological systems to provide accurate tolerance-based approximations of traditional "full-memory" MCMC methods and is orders of magnitude more efficient than the latter.

  10. Setting Occupational Exposure Limits for Chemical Allergens—Understanding the Challenges

    PubMed Central

    Dotson, G. S.; Maier, A.; Siegel, P. D.; Anderson, S. E.; Green, B. J.; Stefaniak, A. B.; Codispoti, C. D.; Kimber, I.

    2015-01-01

    Chemical allergens represent a significant health burden in the workplace. Exposures to such chemicals can cause the onset of a diverse group of adverse health effects triggered by immune-mediated responses. Common responses associated with workplace exposures to low molecular weight (LMW) chemical allergens range from allergic contact dermatitis to life-threatening cases of asthma. Establishing occupational exposure limits (OELs) for chemical allergens presents numerous difficulties for occupational hygiene professionals. Few OELs have been developed for LMW allergens because of the unique biological mechanisms that govern the immune-mediated responses. The purpose of this article is to explore the primary challenges confronting the establishment of OELs for LMW allergens. Specific topics include: (1) understanding the biology of LMW chemical allergies as it applies to setting OELs; (2) selecting the appropriate immune-mediated response (i.e., sensitization versus elicitation); (3) characterizing the dose (concentration)-response relationship of immune-mediated responses; (4) determining the impact of temporal exposure patterns (i.e., cumulative versus acute exposures); and (5) understanding the role of individual susceptibility and exposure route. Additional information is presented on the importance of using alternative exposure recommendations and risk management practices, including medical surveillance, to aid in protecting workers from exposures to LMW allergens when OELs cannot be established. PMID:26583909

  11. Setting Occupational Exposure Limits for Chemical Allergens--Understanding the Challenges.

    PubMed

    Dotson, G S; Maier, A; Siegel, P D; Anderson, S E; Green, B J; Stefaniak, A B; Codispoti, C D; Kimber, I

    2015-01-01

    Chemical allergens represent a significant health burden in the workplace. Exposures to such chemicals can cause the onset of a diverse group of adverse health effects triggered by immune-mediated responses. Common responses associated with workplace exposures to low molecular weight (LMW) chemical allergens range from allergic contact dermatitis to life-threatening cases of asthma. Establishing occupational exposure limits (OELs) for chemical allergens presents numerous difficulties for occupational hygiene professionals. Few OELs have been developed for LMW allergens because of the unique biological mechanisms that govern the immune-mediated responses. The purpose of this article is to explore the primary challenges confronting the establishment of OELs for LMW allergens. Specific topics include: (1) understanding the biology of LMW chemical allergies as it applies to setting OELs; (2) selecting the appropriate immune-mediated response (i.e., sensitization versus elicitation); (3) characterizing the dose (concentration)-response relationship of immune-mediated responses; (4) determining the impact of temporal exposure patterns (i.e., cumulative versus acute exposures); and (5) understanding the role of individual susceptibility and exposure route. Additional information is presented on the importance of using alternative exposure recommendations and risk management practices, including medical surveillance, to aid in protecting workers from exposures to LMW allergens when OELs cannot be established. PMID:26583909

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

    SciTech Connect

    d'Alessandro, A. ); Osterloh, J.D.; Chuwers, P.; Quinlan, P.J.; Kelly, T.J.; Becker, C.E. )

    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.

  13. A proposed occupational exposure limit for 2,3,7,8-tetrachlorodibenzo-p-dioxin.

    PubMed

    Leung, H W; Murray, F J; Paustenbach, D J

    1988-09-01

    One contaminant produced unintentionally during the manufacture of chlorophenols and phenoxy herbicides is 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The resulting TCDD-containing wastes have been detected at many hazardous waste sites which in recent years have been in the process of remediation. Concerns about worker exposure to TCDD-contaminated soil (dust) during remediation of hazardous waste sites have produced a need for an occupational exposure limit (OEL) for TCDD. The animal toxicology data and human experience with TCDD are reviewed, and an occupational exposure limit for TCDD is proposed. The animal data support risk estimations which are based on TCDD as a nongenotoxic carcinogen. Studies on human populations have failed to demonstrate clearly any significant long-term health effects at levels to which humans have been exposed. The data indicate that an 8-hr time-weighted average limit of 2 ng/m3 is appropriate, and the associated risk would be consistent with other carcinogens at their corresponding OELs. A preliminary OEL of 0.2 ng/m3 (200 pg/m3) is recommended, however, in light of other sources of exposure because of TCDD's ubiquitousness in the environment, its unclear mechanism of action, and its rather long biological half-life in humans. This limit provides an ample margin of safety to prevent chloracne following repeated, acute exposure, and it addresses those chronic effects of TCDD observed in animal studies as well as those observed after accidental human exposure. The resulting body burden caused by chronic exposure to TCDD at the proposed OEL is examined. Its toxicological significance is compared with human tissue data and with other similarly persistent chemicals.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2972183

  14. Proposed occupational exposure limit for 2,3,7,8-tetrachlorodibenzo-p-dioxin

    SciTech Connect

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

    1988-09-01

    One contaminant produced unintentionally during the manufacture of chlorophenols and phenoxy herbicides is 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The resulting TCDD-containing wastes have been detected at many hazardous waste sites which in recent years have been in the process of remediation. Concerns about worker exposure to TCDD-contaminated soil (dust) during remediation of hazardous waste sites have produced a need for an occupational exposure limit (OEL) for TCDD. The animal toxicology data and human experience with TCDD are reviewed, and an occupational exposure limit for TCDD is proposed. The animal data support risk estimations which are based on TCDD as a nongenotoxic carcinogen. Studies on human populations have failed to demonstrate clearly any significant long-term health effects at levels to which humans have been exposed. The data indicate that an 8-hr time-weighted average limit of 2 ng/m3 is appropriate, and the associated risk would be consistent with other carcinogens at their corresponding OELs. A preliminary OEL of 0.2 ng/m3 (200 pg/m3) is recommended, however, in light of other sources of exposure because of TCDD's ubiquitousness in the environment, its unclear mechanism of action, and its rather long biological half-life in humans. This limit provides an ample margin of safety to prevent chloracne following repeated, acute exposure, and it addresses those chronic effects of TCDD observed in animal studies as well as those observed after accidental human exposure. The resulting body burden caused by chronic exposure to TCDD at the proposed OEL is examined. Its toxicological significance is compared with human tissue data and with other similarly persistent chemicals. 74 references.

  15. The Impact of Different Permissible Exposure Limits on Hearing Threshold Levels Beyond 25 dBA

    PubMed Central

    Sayapathi, Balachandar S; Su, Anselm Ting; Koh, David

    2014-01-01

    Background: Development of noise-induced hearing loss is reliant on a few factors such as frequency, intensity, and duration of noise exposure. The occurrence of this occupational malady has doubled from 120 million to 250 million in a decade. Countries such as Malaysia, India, and the US have adopted 90 dBA as the permissible exposure limit. According to the US Occupational Safety and Health Administration (OSHA), the exposure limit for noise is 90 dBA, while that of the US National Institute of Occupational Safety and Health (NIOSH) is 85 dBA for 8 hours of noise exposure. Objectives: This study aimed to assess the development of hearing threshold levels beyond 25 dBA on adoption of 85 dBA as the permissible exposure limit compared to 90 dBA. Patients and Methods: This is an intervention study done on two automobile factories. There were 203 employees exposed to noise levels beyond the action level. Hearing protection devices were distributed to reduce noise levels to a level between the permissible exposure limit and action level. The permissible exposure limits were 90 and 85 dBA in factories 1 and 2, respectively, while the action levels were 85 and 80 dBA, respectively. The hearing threshold levels of participants were measured at baseline and at first month of postshift exposure of noise. The outcome was measured by a manual audiometer. McNemar and chi-square tests were used in the statistical analysis. Results: We found that hearing threshold levels of more than 25 dBA has changed significantly from pre-intervention to post-intervention among participants from both factories (3000 Hz for the right ear and 2000 Hz for the left ear). There was a statistically significant association between participants at 3000 Hz on the right ear at ‘deteriorated’ level ( χ² (1) = 4.08, φ = - 0.142, P = 0.043), whereas there was worsening of hearing threshold beyond 25 dBA among those embraced 90 dBA. Conclusions: The adoption of 85 dBA as the permissible exposure limit has preserved hearing threshold level among participants at 3000 Hz compared to those who embraced 90 dBA. PMID:25763196

  16. Perceived benefits and challenges of repeated exposure to high fidelity simulation experiences of first degree accelerated bachelor nursing students.

    PubMed

    Kaddoura, Mahmoud; Vandyke, Olga; Smallwood, Christopher; Gonzalez, Kristen Mathieu

    2016-01-01

    This study explored perceptions of first-degree entry-level accelerated bachelor nursing students regarding benefits and challenges of exposure to multiple high fidelity simulation (HFS) scenarios, which has not been studied to date. These perceptions conformed to some research findings among Associate Degree, traditional non-accelerated, and second-degree accelerated Bachelor of Science in Nursing (BSN) students faced with one to two simulations. However, first-degree accelerated BSN students faced with multiple complex simulations perceived improvements on all outcomes, including critical thinking, confidence, competence, and theory-practice integration. On the negative side, some reported feeling overwhelmed by the multiple HFS scenarios. Evidence from this study supports HFS as an effective teaching and learning method for nursing students, along with valuable implications for many other fields. PMID:26260522

  17. The Scientific Basis of Uncertainty Factors Used in Setting Occupational Exposure Limits

    PubMed Central

    Dankovic, D. A.; Naumann, B. D.; Maier, A.; Dourson, M. L.; Levy, L. S.

    2015-01-01

    The uncertainty factor concept is integrated into health risk assessments for all aspects of public health practice, including by most organizations that derive occupational exposure limits. The use of uncertainty factors is predicated on the assumption that a sufficient reduction in exposure from those at the boundary for the onset of adverse effects will yield a safe exposure level for at least the great majority of the exposed population, including vulnerable subgroups. There are differences in the application of the uncertainty factor approach among groups that conduct occupational assessments; however, there are common areas of uncertainty which are considered by all or nearly all occupational exposure limit-setting organizations. Five key uncertainties that are often examined include interspecies variability in response when extrapolating from animal studies to humans, response variability in humans, uncertainty in estimating a no-effect level from a dose where effects were observed, extrapolation from shorter duration studies to a full life-time exposure, and other insufficiencies in the overall health effects database indicating that the most sensitive adverse effect may not have been evaluated. In addition, a modifying factor is used by some organizations to account for other remaining uncertainties—typically related to exposure scenarios or accounting for the interplay among the five areas noted above. Consideration of uncertainties in occupational exposure limit derivation is a systematic process whereby the factors applied are not arbitrary, although they are mathematically imprecise. As the scientific basis for uncertainty factor application has improved, default uncertainty factors are now used only in the absence of chemical-specific data, and the trend is to replace them with chemical-specific adjustment factors whenever possible. The increased application of scientific data in the development of uncertainty factors for individual chemicals also has the benefit of increasing the transparency of occupational exposure limit derivation. Improved characterization of the scientific basis for uncertainty factors has led to increasing rigor and transparency in their application as part of the overall occupational exposure limit derivation process. PMID:26097979

  18. Development of a limited-sampling model for prediction of doxorubicin exposure in dogs.

    PubMed

    Wittenburg, L A; Thamm, D H; Gustafson, D L

    2014-06-01

    Understanding the relationship between drug dose and exposure (pharmacokinetics, PK) and the relationship between exposure and effect (pharmacodynamics) is an important component of pharmacology when attempting to predict clinical effects of anticancer drugs. PK studies can provide a better understanding of these relationships; however, they often involve intensive sampling over an extended period of time, resulting in increased cost and decreased compliance. Doxorubicin (DOX), one of the most widely used antineoplastic agents in veterinary cancer therapy, is characterized by large interpatient variability in overall drug exposure and the development and degree of myelosuppression following equivalent dosages. We have developed and validated a limited-sampling strategy for DOX, in which three blood samples are obtained over 1 h post-treatment, that accurately predicts patient exposure. This strategy could allow for refining of dosing variables and utilization of therapeutic drug monitoring to ensure optimized dosing. PMID:22747489

  19. Proposed Occupational Exposure Limits for Non-Carcinogenic Hanford Waste Tank Vapor Chemicals

    SciTech Connect

    Poet, Torka S.; Timchalk, Chuck

    2006-03-24

    A large number of volatile chemicals have been identified in the headspaces of tanks used to store mixed chemical and radioactive waste at the U.S. Department of Energy (DOE) Hanford Site, and there is concern that vapor releases from the tanks may be hazardous to workers. Contractually established occupational exposure limits (OELs) established by the Occupational Safety and Health Administration (OSHA) and American Conference of Governmental Industrial Hygienists (ACGIH) do not exist for all chemicals of interest. To address the need for worker exposure guidelines for those chemicals that lack OSHA or ACGIH OELs, a procedure for assigning Acceptable Occupational Exposure Limits (AOELs) for Hanford Site tank farm workers has been developed and applied to a selected group of 57 headspace chemicals.

  20. Chronic lead exposure accelerates decay of long-term potentiation in rat dentate gyrus in vivo.

    PubMed

    Gilbert, M E; Mack, C M

    1998-04-01

    Long-term potentiation (LTP) is a model of synaptic plasticity believed to encompass the underlying neurobiological mechanisms that support memory function. Chronic developmental lead (Pb) exposure is known to be associated with cognitive dysfunction in children and animals. Disruption of the induction of long-term potentiation (LTP) has been reported in the hippocampus following chronic exposure to environmentally relevant levels of Pb in rats. Under urethane anesthesia, we have previously observed Pb-induced increases in the threshold for LTP induction. With higher train intensities, LTP was induced and no declines in the amplitude of responses within a 60-min posttrain period were evident. The present study was designed to assess the effects of Pb on the more enduring forms of LTP in the dentate gyrus of the conscious rat. Beginning in the late gestational period, rats were chronically exposed to 0.2% Pb(2+)-acetate through the drinking water of the pregnant dam, and directly through their own water supply at weaning. As adults, electrodes were permanently implanted in male offspring and field potentials evoked by perforant path stimulation were recorded from the dentate gyrus over several weeks. LTP was induced by delivering theta-burst patterned stimulation at a maximal stimulus intensity through the perforant path electrode, and input/output (I/O) functions were monitored for 1 month. Population spike (PS) amplitude was increased maximally 1 h after train delivery. The time constant of decay (tau) calculated from pooled data for each group yielded declines in PS amplitude by 63% in 17.4 days in controls and 13.4 days in Pb-exposed animals. Quantitative estimates of decay in individual animals were achieved in two ways: (1) by calculating difference scores in I/O functions from the maximal LTP at 1 h, and (2) by interpolating day to decay by 63% from declines from maximal LTP. The interpolated values were used to compare the incidence of animals showing decay of 63% within 1 week posttrain. Both analyses revealed a more accelerated rate of decay of LTP in animals developmentally exposed to Pb relative to controls. Endurance of potentiated responses for days to weeks is believed to be supported by structural modifications and synaptic growth. The reported effects of Pb on growth-related processes may thus contribute to a reduced persistence of LTP and the resulting cognitive deficits engendered by developmental Pb exposure. PMID:9602098

  1. 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

    ... for Disease Control and Prevention (CDC) published a notice in the Federal Register (76 FR 52664) announcing its intent to ``review its approach to classifying carcinogens and establishing recommended... Carcinogen and Recommended Exposure Limit (REL) Policy Assessment AGENCY: National Institute for...

  2. Defining occupational and consumer exposure limits for enzyme protein respiratory allergens under REACH.

    PubMed

    Basketter, D A; Broekhuizen, C; Fieldsend, M; Kirkwood, S; Mascarenhas, R; Maurer, K; Pedersen, C; Rodriguez, C; Schiff, H-E

    2010-02-01

    A wide range of substances have been recognized as sensitizing, either to the skin and/or to the respiratory tract. Many of these are useful materials, so to ensure that they can be used safely it is necessary to characterize the hazards and establish appropriate exposure limits. Under new EU legislation (REACH), there is a requirement to define a derived no effect level (DNEL). Where a DNEL cannot be established, e.g. for sensitizing substances, then a derived minimal effect level (DMEL) is recommended. For the bacterial and fungal enzymes which are well recognized respiratory sensitizers and have widespread use industrially as well as in a range of consumer products, a DMEL can be established by thorough retrospective review of occupational and consumer experience. In particular, setting the validated employee medical surveillance data against exposure records generated over an extended period of time is vital in informing the occupational DMEL. This experience shows that a long established limit of 60 ng/m(3) for pure enzyme protein has been a successful starting point for the definition of occupational health limits for sensitization in the detergent industry. Application to this of adjustment factors has limited sensitization induction, avoided any meaningful risk of the elicitation of symptoms with known enzymes and provided an appropriate level of security for new enzymes whose potency has not been fully characterized. For example, in the detergent industry, this has led to general use of occupational exposure limits 3-10 times lower than the 60 ng/m(3) starting point. In contrast, consumer exposure limits vary because the types of exposure themselves cover a wide range. The highest levels shown to be safe in use, 15 ng/m(3), are associated with laundry trigger sprays, but very much lower levels (e.g. 0.01 ng/m(3)) are commonly associated with other types of safe exposure. Consumer limits typically will lie between these values and depend on the actual exposure associated with product use. PMID:20026217

  3. 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

  4. 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

  5. An improved limit on the charge of antihydrogen from stochastic acceleration.

    PubMed

    Ahmadi, M; Baquero-Ruiz, M; Bertsche, W; Butler, E; Capra, A; Carruth, C; Cesar, C L; Charlton, M; Charman, A E; Eriksson, S; Evans, L T; Evetts, N; Fajans, J; Friesen, T; Fujiwara, M C; Gill, D R; Gutierrez, A; Hangst, J S; Hardy, W N; Hayden, M E; Isaac, C A; Ishida, A; Jones, S A; Jonsell, S; Kurchaninov, L; Madsen, N; Maxwell, D; McKenna, J T K; Menary, S; Michan, J M; Momose, T; Munich, J J; Nolan, P; Olchanski, K; Olin, A; Povilus, A; Pusa, P; Rasmussen, C Ø; Robicheaux, F; Sacramento, R L; Sameed, M; Sarid, E; Silveira, D M; So, C; Tharp, T D; Thompson, R I; van der Werf, D P; Wurtele, J S; Zhmoginov, A I

    2016-01-21

    Antimatter continues to intrigue physicists because of its apparent absence in the observable Universe. Current theory requires that matter and antimatter appeared in equal quantities after the Big Bang, but the Standard Model of particle physics offers no quantitative explanation for the apparent disappearance of half the Universe. It has recently become possible to study trapped atoms of antihydrogen to search for possible, as yet unobserved, differences in the physical behaviour of matter and antimatter. Here we consider the charge neutrality of the antihydrogen atom. By applying stochastic acceleration to trapped antihydrogen atoms, we determine an experimental bound on the antihydrogen charge, Qe, of |Q| < 0.71 parts per billion (one standard deviation), in which e is the elementary charge. This bound is a factor of 20 less than that determined from the best previous measurement of the antihydrogen charge. The electrical charge of atoms and molecules of normal matter is known to be no greater than about 10(-21)e for a diverse range of species including H2, He and SF6. Charge-parity-time symmetry and quantum anomaly cancellation demand that the charge of antihydrogen be similarly small. Thus, our measurement constitutes an improved limit and a test of fundamental aspects of the Standard Model. If we assume charge superposition and use the best measured value of the antiproton charge, then we can place a new limit on the positron charge anomaly (the relative difference between the positron and elementary charge) of about one part per billion (one standard deviation), a 25-fold reduction compared to the current best measurement. PMID:26791725

  6. An improved limit on the charge of antihydrogen from stochastic acceleration

    NASA Astrophysics Data System (ADS)

    Ahmadi, M.; Baquero-Ruiz, M.; Bertsche, W.; Butler, E.; Capra, A.; Carruth, C.; Cesar, C. L.; Charlton, M.; Charman, A. E.; Eriksson, S.; Evans, L. T.; Evetts, N.; Fajans, J.; Friesen, T.; Fujiwara, M. C.; Gill, D. R.; Gutierrez, A.; Hangst, J. S.; Hardy, W. N.; Hayden, M. E.; Isaac, C. A.; Ishida, A.; Jones, S. A.; Jonsell, S.; Kurchaninov, L.; Madsen, N.; Maxwell, D.; McKenna, J. T. K.; Menary, S.; Michan, J. M.; Momose, T.; Munich, J. J.; Nolan, P.; Olchanski, K.; Olin, A.; Povilus, A.; Pusa, P.; Rasmussen, C. Ø.; Robicheaux, F.; Sacramento, R. L.; Sameed, M.; Sarid, E.; Silveira, D. M.; So, C.; Tharp, T. D.; Thompson, R. I.; van der Werf, D. P.; Wurtele, J. S.; Zhmoginov, A. I.

    2016-01-01

    Antimatter continues to intrigue physicists because of its apparent absence in the observable Universe. Current theory requires that matter and antimatter appeared in equal quantities after the Big Bang, but the Standard Model of particle physics offers no quantitative explanation for the apparent disappearance of half the Universe. It has recently become possible to study trapped atoms– of antihydrogen to search for possible, as yet unobserved, differences in the physical behaviour of matter and antimatter. Here we consider the charge neutrality of the antihydrogen atom. By applying stochastic acceleration to trapped antihydrogen atoms, we determine an experimental bound on the antihydrogen charge, Qe, of |Q| < 0.71 parts per billion (one standard deviation), in which e is the elementary charge. This bound is a factor of 20 less than that determined from the best previous measurement of the antihydrogen charge. The electrical charge of atoms and molecules of normal matter is known to be no greater than about 10‑21e for a diverse range of species including H2, He and SF6. Charge–parity–time symmetry and quantum anomaly cancellation demand that the charge of antihydrogen be similarly small. Thus, our measurement constitutes an improved limit and a test of fundamental aspects of the Standard Model. If we assume charge superposition and use the best measured value of the antiproton charge, then we can place a new limit on the positron charge anomaly (the relative difference between the positron and elementary charge) of about one part per billion (one standard deviation), a 25-fold reduction compared to the current best measurement.

  7. Identifying an indoor air exposure limit for formaldehyde considering both irritation and cancer hazards

    PubMed Central

    Golden, Robert

    2011-01-01

    Formaldehyde is a well-studied chemical and effects from inhalation exposures have been extensively characterized in numerous controlled studies with human volunteers, including asthmatics and other sensitive individuals, which provide a rich database on exposure concentrations that can reliably produce the symptoms of sensory irritation. Although individuals can differ in their sensitivity to odor and eye irritation, the majority of authoritative reviews of the formaldehyde literature have concluded that an air concentration of 0.3 ppm will provide protection from eye irritation for virtually everyone. A weight of evidence-based formaldehyde exposure limit of 0.1 ppm (100 ppb) is recommended as an indoor air level for all individuals for odor detection and sensory irritation. It has recently been suggested by the International Agency for Research on Cancer (IARC), the National Toxicology Program (NTP), and the US Environmental Protection Agency (US EPA) that formaldehyde is causally associated with nasopharyngeal cancer (NPC) and leukemia. This has led US EPA to conclude that irritation is not the most sensitive toxic endpoint and that carcinogenicity should dictate how to establish exposure limits for formaldehyde. In this review, a number of lines of reasoning and substantial scientific evidence are described and discussed, which leads to a conclusion that neither point of contact nor systemic effects of any type, including NPC or leukemia, are causally associated with exposure to formaldehyde. This conclusion supports the view that the equivocal epidemiology studies that suggest otherwise are almost certainly flawed by identified or yet to be unidentified confounding variables. Thus, this assessment concludes that a formaldehyde indoor air limit of 0.1 ppm should protect even particularly susceptible individuals from both irritation effects and any potential cancer hazard. PMID:21635194

  8. Short-term metal particulate exposures decrease cardiac acceleration and deceleration capacities in welders: a repeated-measures panel study

    PubMed Central

    Cavallari, Jennifer M; Fang, Shona C; Lu, Chensheng; Lin, Xihong; Mittleman, Murray A; Christiani, David C

    2016-01-01

    Objective Acceleration (AC) and deceleration (DC) capacities measure heart rate variability during speeding up and slowing down of the heart, respectively. We investigated associations between AC and DC with occupational short-term metal PM2.5 exposures. Methods A panel of 48 male welders had particulate matter less than 2.5 microns in diameter (PM2.5) exposure measurements over 4–6 h repeated over 5 sampling periods between January 2010 and June 2012. We simultaneously obtained continuous recordings of digital ECG using a Holter monitor. We analysed ECG data in the time domain to obtain hourly AC and DC. Linear mixed models were used to assess the associations between hourly PM2.5 exposure and each of hourly AC and DC, controlling for age, smoking status, active smoking, exposure to secondhand smoke, season/time of day when ECG reading was obtained and baseline AC or DC. We also ran lagged exposure response models for each successive hour up to 3 h after onset of exposure. Results Mean (SD) shift PM2.5 exposure during welding was 0.47 (0.43) mg/m3. Significant exposure–response associations were found for AC and DC with increased PM2.5 exposure. In our adjusted models without any lag between exposure and response, a 1 mg/m3 increase of PM2.5 was associated with a decrease of 1.46 (95% CI 1.00 to 1.92) ms in AC and a decrease of 1.00 (95% CI 0.53 to 1.46) ms in DC. The effect of PM2.5 on AC and DC was maximal immediately postexposure and lasted 1 h following exposure. Conclusions There are short-term effects of metal particulates on AC and DC. PMID:26644456

  9. Epidemiologic link between tuberculosis and cigarette/biomass smoke exposure: Limitations despite the vast literature.

    PubMed

    Bishwakarma, Raju; Kinney, William H; Honda, Jennifer R; Mya, Jenny; Strand, Matthew J; Gangavelli, Avani; Bai, Xiyuan; Ordway, Diane J; Iseman, Michael D; Chan, Edward D

    2015-05-01

    The geographic overlap between the prevalence of cigarette smoke (CS) exposure and tuberculosis (TB) in the world is striking. In recent years, relatively large number of studies has linked cigarette or biomass fuel smoke exposure and various aspects of TB. Our goals are to summarize the significance of the known published studies, graphically represent reports that quantified the association and discuss their potential limitations. PubMed searches were performed using the key words 'tuberculosis' with 'cigarette', 'tobacco', 'smoke' or 'biomass fuel smoke.' The references of relevant articles were examined for additional pertinent papers. A large number of mostly case-control and cross-sectional studies significantly associate both direct and second-hand smoke exposure with tuberculous infection, active TB, and/or more severe and lethal TB. Fewer link biomass fuel smoke exposure and TB. While a number of studies interpreted the association with multivariate analysis, other confounders are often not accounted for in these analyses. It is also important to emphasize that these retrospective studies can only show an association and not any causal link. We further explored the possibility that even if CS exposure is a risk factor for TB, several mechanisms may be responsible. Numerous studies associate cigarette and biomass smoke exposure with TB but the mechanism(s) remains largely unknown. While the associative link of these two health maladies is well established, more definitive, mechanistic studies are needed to cement the effect of smoke exposure on TB pathogenesis and to utilize this knowledge in empowering public health policies. PMID:25808744

  10. Limitations of waterborne exposure of fish early life stages to BDE-47.

    PubMed

    Gonzlez-Doncel, Miguel; Torija, Carlos Fernndez; Beltrn, Eulalia Mara; Garca-Maurio, Jos Enrique; Sastre, Salvador; Carbonell, Gregoria

    2014-03-01

    2,2',4,4'-Tetrabromodiphenyl ether (BDE-47) is acknowledged as the most abundant congener of all polybrominated diphenyl ethers (PBDEs). Despite its limited residence in the water column, most ecotoxicological research using fish early life stages (ELS) has focused on its waterborne bioavailability. These studies have been supported either by chemical analysis in solutions or in tissues after ? 168 h exposures to relatively high waterborne concentrations with dimethyl sulfoxide (DMSO) as solvent carrier (? 0.5%). Using noninvasive physiological and anatomical features in medaka ELS, we investigated the viability of waterborne BDE-47 exposures (100-10,000 ?g/L; 1% DMSO) and evaluated the developmental effects in relation to the actual BDE-47 present in water. Embryos were exposed for 10 days under semi-static (24-h renewal) conditions and waterborne BDE-47 concentrations (i.e., dissolved) were quantitated daily and their accumulation in eleutheroembryonic tissues was analyzed 4 days after exposures finished. BDE-47 in solution rapidly decreased after each renewal by >50% in 24h. This was confirmed by discernible precipitation occurring at ? 5,000 ?g/L on the bottom of the container and attached to the chorionic filaments of eggshell. The fast dissipation from water may explain why, besides the subtle, yet significant effects on post-hatching growth (short length at ?5000?g/L), no other significant deleterious developmental effects were observed despite the fact that BDE-47 accumulated in tissues in response to BDE-47 treatment. Waterborne BDE-47 exposure was unachievable under traditional semi-static exposure conditions, but was achievable in repeated pulse exposures lasting a few hours whenever the medium was renewed. Hence, this research encourages the use of alternate - more realistic - exposure routes (e.g., particulate matter or sediments) when evaluating early developmental toxicity of BDE-47 or any other PBDE sharing similar properties. PMID:24508762

  11. 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.

  12. Fullerene c60: inhalation hazard assessment and derivation of a period-limited acceptable exposure level.

    PubMed

    Shinohara, Naohide; Gamo, Masashi; Nakanishi, Junko

    2011-10-01

    Fullerene C(60) has great potential for use in many industry and medical nanotechnology applications. Although the use of nanomaterials has been increasing in the recent years, limited information about its potential hazardous effects is available. Therefore, safety of nanomaterials is a world concern. Before health effects arise in workers and the general population, development and use under appropriate management are desirable. Therefore, we aimed to determine an acceptable exposure level for humans by reviewing the limited animal toxicity data available. Here, we present an initial hazard assessment, including a review of the available toxicity information of the effects of C(60) on the lungs. We then estimated the no-observed-adverse-effect level (NOAEL) of C(60) on rat lung toxicity by using lung retention of C(60) in inhalation exposure and intratracheal instillation tests. The NOAEL of C(60) on rat lung toxicity was estimated to be 3.1 mg/m(3). Because this is the NOAEL for subchronic toxicity, a period-limited acceptable exposure level (AEL(PL)) for humans was proposed, which assumed 15 years of exposure and modification within the next 10 years since more knowledge will be gained in the future. The AEL(PL) of C(60) particles with a geometric mean of 96 nm and a geometric standard deviation (GSD) of 2.0 was estimated to be 0.39 mg/m(3) for healthy workers and 1.4 10(-2) mg/m(3) for the general human population. The AEL(PL) of C(60) particles with different sizes was estimated to be for healthy workers and for the general human population. PMID:21856993

  13. MDI Biological Laboratory Arsenic Summit: Approaches to Limiting Human Exposure to Arsenic.

    PubMed

    Stanton, Bruce A; Caldwell, Kathleen; Congdon, Clare Bates; Disney, Jane; Donahue, Maria; Ferguson, Elizabeth; Flemings, Elsie; Golden, Meredith; Guerinot, Mary Lou; Highman, Jay; James, Karen; Kim, Carol; Lantz, R Clark; Marvinney, Robert G; Mayer, Greg; Miller, David; Navas-Acien, Ana; Nordstrom, D Kirk; Postema, Sonia; Rardin, Laurie; Rosen, Barry; SenGupta, Arup; Shaw, Joseph; Stanton, Elizabeth; Susca, Paul

    2015-09-01

    This report is the outcome of the meeting "Environmental and Human Health Consequences of Arsenic" held at the MDI Biological Laboratory in Salisbury Cove, Maine, August 13-15, 2014. Human exposure to arsenic represents a significant health problem worldwide that requires immediate attention according to the World Health Organization (WHO). One billion people are exposed to arsenic in food, and more than 200 million people ingest arsenic via drinking water at concentrations greater than international standards. Although the US Environmental Protection Agency (EPA) has set a limit of 10 μg/L in public water supplies and the WHO has recommended an upper limit of 10 μg/L, recent studies indicate that these limits are not protective enough. In addition, there are currently few standards for arsenic in food. Those who participated in the Summit support citizens, scientists, policymakers, industry, and educators at the local, state, national, and international levels to (1) establish science-based evidence for setting standards at the local, state, national, and global levels for arsenic in water and food; (2) work with government agencies to set regulations for arsenic in water and food, to establish and strengthen non-regulatory programs, and to strengthen collaboration among government agencies, NGOs, academia, the private sector, industry, and others; (3) develop novel and cost-effective technologies for identification and reduction of exposure to arsenic in water; (4) develop novel and cost-effective approaches to reduce arsenic exposure in juice, rice, and other relevant foods; and (5) develop an Arsenic Education Plan to guide the development of science curricula as well as community outreach and education programs that serve to inform students and consumers about arsenic exposure and engage them in well water testing and development of remediation strategies. PMID:26231509

  14. Advances in Inhalation Dosimetry Models and Methods for Occupational Risk Assessment and Exposure Limit Derivation

    PubMed Central

    Kuempel, Eileen D.; Sweeney, Lisa M.; Morris, John B.; Jarabek, Annie M.

    2015-01-01

    The purpose of this article is to provide an overview and practical guide to occupational health professionals concerning the derivation and use of dose estimates in risk assessment for development of occupational exposure limits (OELs) for inhaled substances. Dosimetry is the study and practice of measuring or estimating the internal dose of a substance in individuals or a population. Dosimetry thus provides an essential link to understanding the relationship between an external exposure and a biological response. Use of dosimetry principles and tools can improve the accuracy of risk assessment, and reduce the uncertainty, by providing reliable estimates of the internal dose at the target tissue. This is accomplished through specific measurement data or predictive models, when available, or the use of basic dosimetry principles for broad classes of materials. Accurate dose estimation is essential not only for dose-response assessment, but also for interspecies extrapolation and for risk characterization at given exposures. Inhalation dosimetry is the focus of this paper since it is a major route of exposure in the workplace. Practical examples of dose estimation and OEL derivation are provided for inhaled gases and particulates. PMID:26551218

  15. Advances in Inhalation Dosimetry Models and Methods for Occupational Risk Assessment and Exposure Limit Derivation.

    PubMed

    Kuempel, Eileen D; Sweeney, Lisa M; Morris, John B; Jarabek, Annie M

    2015-01-01

    The purpose of this article is to provide an overview and practical guide to occupational health professionals concerning the derivation and use of dose estimates in risk assessment for development of occupational exposure limits (OELs) for inhaled substances. Dosimetry is the study and practice of measuring or estimating the internal dose of a substance in individuals or a population. Dosimetry thus provides an essential link to understanding the relationship between an external exposure and a biological response. Use of dosimetry principles and tools can improve the accuracy of risk assessment, and reduce the uncertainty, by providing reliable estimates of the internal dose at the target tissue. This is accomplished through specific measurement data or predictive models, when available, or the use of basic dosimetry principles for broad classes of materials. Accurate dose estimation is essential not only for dose-response assessment, but also for interspecies extrapolation and for risk characterization at given exposures. Inhalation dosimetry is the focus of this paper since it is a major route of exposure in the workplace. Practical examples of dose estimation and OEL derivation are provided for inhaled gases and particulates. PMID:26551218

  16. Kinetic Study of Radiation-Reaction-Limited Particle Acceleration During the Relaxation of Force-Free Equilibria

    NASA Astrophysics Data System (ADS)

    Yuan, Yajie; Nalewajko, Krzysztof; Blandford, Roger D.; East, William E.; Zrake, Jonathan

    2016-01-01

    Many powerful and variable gamma-ray sources, including pulsar wind nebulae, active galactic nuclei and gamma-ray bursts, seem capable of accelerating particles to gamma-ray emitting energies efficiently over short time scales. This might be due to prodigal dissipation in a highly magnetized outflow. In order to understand the generic behavior of relativistic plasma with high magnetization, we consider a class of prototypical force-free equilibria which are shown to be unstable to ideal modes (East et al 2015 PRL 115, 095002). Kinetic simulations are carried out to follow the evolution of the instability and to study the basic mechanisms of particle acceleration, especially in the radiation-reaction-limited regime. We find that the instability naturally produces current layers and these are sites for efficient particle acceleration. Detailed calculations of the gamma ray spectrum, the evolution of the particle distribution function and the dynamical consequences of radiation reaction will be presented.

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

    SciTech Connect

    Lang, M.I.; Convery, M.; 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.

  18. Mass Limited Target Effects on Proton Acceleration with Femtosecond Laser Plasma Interactions

    NASA Astrophysics Data System (ADS)

    Zulick, Calvin; Raymond, A.; McKelvey, A.; Willingale, L.; Chvykov, V.; Maksimchuk, A.; Thomas, A. G. R.; Yanovsky, V.; Krushelnick, K.

    2014-10-01

    Experiments at the HERCULES laser facility have been performed to measure the effect of reduced mass targets on proton acceleration through the use of foil, grid, and wire targets in femtosecond laser plasma interactions. The target thickness was held approximately constant at 12 . 5 ?m, while the lateral extent of the target was varied. The electron current density was measured with an imaging Cu K? crystal. Higher current densities were observed as the target mass was reduced which corresponded to an increase in the temperature of the accelerated proton beam. Additionally, a line focusing feature was observed in the spatial distribution of protons accelerated to from the wire target, believed to be a result of azimuthal magnetic fields generated by electron currents in the wire. Particle-in-cell and Vlasov-Fokker-Plank simulations were performed in order to investigate the focusing magnetic field as well as the complex sheath formation dynamics on the mesh target.

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

    SciTech Connect

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

    2014-06-16

    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.

  20. 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

  1. Laser-Driven Shock Acceleration of Ion Beams from Spherical Mass-Limited Targets

    NASA Astrophysics Data System (ADS)

    Henig, A.; Kiefer, D.; Geissler, M.; Rykovanov, S. G.; Ramis, R.; Hrlein, R.; Osterhoff, J.; Major, Zs.; Veisz, L.; Karsch, S.; Krausz, F.; Habs, D.; Schreiber, J.

    2009-03-01

    We report on experimental studies of ion acceleration from spherical targets of diameter 15?m irradiated by ultraintense (11020W/cm2) pulses from a 20-TW Ti:sapphire laser system. A highly directed proton beam with plateau-shaped spectrum extending to energies up to 8 MeV is observed in the laser propagation direction. This beam arises from acceleration in a converging shock launched by the laser, which is confirmed by 3-dimensional particle-in-cell simulations. The temporal evolution of the shock-front curvature shows excellent agreement with a two-dimensional radiation pressure model.

  2. Effect of Ultrasonic Peening and Accelerated Corrosion Exposure on the Residual Stress Distribution in Welded Marine Steel

    NASA Astrophysics Data System (ADS)

    Ahmad, Bilal; Fitzpatrick, Michael E.

    2015-03-01

    Specimens of DH36 marine steel were prepared with welded attachments. Residual stress measurements were made on the samples as-welded, following an ultrasonic peening treatment, and following accelerated corrosion exposure after ultrasonic peening. Neutron diffraction and the contour method were used for determining the residual stress profiles. The welding introduces tensile near-surface residual stress, approaching the material yield strength, and the ultrasonic peening overlays this with a compressive residual stress. Material removal by corrosion decreases the peak surface compressive stress slightly, by removal of a layer of stressed material, but does not cause significant redistribution of the residual stress profile.

  3. SIMULATIONS OF PARTICLE ACCELERATION BEYOND THE CLASSICAL SYNCHROTRON BURNOFF LIMIT IN MAGNETIC RECONNECTION: AN EXPLANATION OF THE CRAB FLARES

    SciTech Connect

    Cerutti, B.; Werner, G. R.; Uzdensky, D. A.; Begelman, M. C. E-mail: greg.werner@colorado.edu E-mail: mitch@jila.colorado.edu

    2013-06-20

    It is generally accepted that astrophysical sources cannot emit synchrotron radiation above 160 MeV in their rest frame. This limit is given by the balance between the accelerating electric force and the radiation reaction force acting on the electrons. The discovery of synchrotron gamma-ray flares in the Crab Nebula, well above this limit, challenges this classical picture of particle acceleration. To overcome this limit, particles must accelerate in a region of high electric field and low magnetic field. This is possible only with a non-ideal magnetohydrodynamic process, like magnetic reconnection. We present the first numerical evidence of particle acceleration beyond the synchrotron burnoff limit, using a set of two-dimensional particle-in-cell simulations of ultra-relativistic pair plasma reconnection. We use a new code, Zeltron, that includes self-consistently the radiation reaction force in the equation of motion of the particles. We demonstrate that the most energetic particles move back and forth across the reconnection layer, following relativistic Speiser orbits. These particles then radiate >160 MeV synchrotron radiation rapidly, within a fraction of a full gyration, after they exit the layer. Our analysis shows that the high-energy synchrotron flux is highly variable in time because of the strong anisotropy and inhomogeneity of the energetic particles. We discover a robust positive correlation between the flux and the cut-off energy of the emitted radiation, mimicking the effect of relativistic Doppler amplification. A strong guide field quenches the emission of >160 MeV synchrotron radiation. Our results are consistent with the observed properties of the Crab flares, supporting the reconnection scenario.

  4. Simulations of Particle Acceleration beyond the Classical Synchrotron Burnoff Limit in Magnetic Reconnection: An Explanation of the Crab Flares

    NASA Astrophysics Data System (ADS)

    Cerutti, B.; Werner, G. R.; Uzdensky, D. A.; Begelman, M. C.

    2013-06-01

    It is generally accepted that astrophysical sources cannot emit synchrotron radiation above 160 MeV in their rest frame. This limit is given by the balance between the accelerating electric force and the radiation reaction force acting on the electrons. The discovery of synchrotron gamma-ray flares in the Crab Nebula, well above this limit, challenges this classical picture of particle acceleration. To overcome this limit, particles must accelerate in a region of high electric field and low magnetic field. This is possible only with a non-ideal magnetohydrodynamic process, like magnetic reconnection. We present the first numerical evidence of particle acceleration beyond the synchrotron burnoff limit, using a set of two-dimensional particle-in-cell simulations of ultra-relativistic pair plasma reconnection. We use a new code, Zeltron, that includes self-consistently the radiation reaction force in the equation of motion of the particles. We demonstrate that the most energetic particles move back and forth across the reconnection layer, following relativistic Speiser orbits. These particles then radiate >160 MeV synchrotron radiation rapidly, within a fraction of a full gyration, after they exit the layer. Our analysis shows that the high-energy synchrotron flux is highly variable in time because of the strong anisotropy and inhomogeneity of the energetic particles. We discover a robust positive correlation between the flux and the cut-off energy of the emitted radiation, mimicking the effect of relativistic Doppler amplification. A strong guide field quenches the emission of >160 MeV synchrotron radiation. Our results are consistent with the observed properties of the Crab flares, supporting the reconnection scenario.

  5. 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

  6. Pulmonary Evaluation of Permissible Exposure Limit of Syntroleum S-8 Synthetic Jet Fuel in Mice

    PubMed Central

    Wong, Simon S.; Thomas, Alana; Barbaris, Brian; Lantz, R. Clark; Witten, Mark L.

    2009-01-01

    No current studies have systematically examined pulmonary health effects associated with Syntroleum S-8 synthetic jet fuel (S-8). In order to gain an understanding about the threshold concentration in which lung injury is observed, C57BL/6 male mice were nose-only exposed to S-8 for 1 h/day for 7 days at average concentrations of 0 (control), 93, 352, and 616 mg/m3. Evaluation of pulmonary function, airway epithelial barrier integrity, and pathohistology was performed 24 h after the final exposures. Significant decreases were detected in expiratory lung resistance and total lung compliance of the 352 mg/m3 group, for which no clear concentration-dependent alterations could be determined. No significant changes in respiratory permeability were exhibited, indicating that there was no loss of epithelial barrier integrity following S-8 exposure. However, morphological examination and morphometric analysis of distal lung tissue, by using transmission electron microscopy, revealed cellular damage in alveolar type II epithelial cells, with significant increases in volume density of lamellar bodies/vacuoles at 352 and 616 S-8 mg/m3. Moreover, terminal bronchiolar Clara injury, as evidenced by apical membrane blebs, was observed at relatively low concentrations, suggesting if this synthetic jet fuel is utilized, the current permissible exposure limit of 350 mg/m3 for hydrocarbon fuels should cautiously be applied. PMID:19357071

  7. Airborne exposure limits for chemical and biological warfare agents: is everything set and clear?

    PubMed

    Sabelnikov, Alex; Zhukov, Vladimir; Kempf, C Ruth

    2006-08-01

    Emergency response strategies (guidelines) for biological, chemical, nuclear, or radiological terrorist events should be based on scientifically established exposure limits for all the agents or materials involved. In the case of a radiological terrorist event, emergency response guidelines (ERG) have been worked out. In the case of a terrorist event with the use of chemical warfare (CW) agents the situation is not that clear, though the new guidelines and clean-up values are being generated based on re-evaluation of toxicological and risk data. For biological warfare (BW) agents, such guidelines do not yet exist. In this paper the current status of airborne exposure limits (AELs) for chemical and biological warfare (CBW) agents are reviewed. Particular emphasis is put on BW agents that lack such data. An efficient, temporary solution to bridge the gap in experimental infectious data and to set provisional AELs for BW agents is suggested. It is based on mathematically generated risks of infection for BW agents grouped by their alleged ID50 values in three categories: with low, intermediate and high ID50 values. PMID:16854669

  8. The Global Landscape of Occupational Exposure Limits—Implementation of Harmonization Principles to Guide Limit Selection

    PubMed Central

    Deveau, M.; Chen, C-P; Johanson, G.; Krewski, D.; Maier, A.; Niven, K. J.; Ripple, S.; Schulte, P. A.; Silk, J.; Urbanus, J. H.; Zalk, D. M.; Niemeier, R. W.

    2015-01-01

    Occupational exposure limits (OELs) serve as health-based benchmarks against which measured or estimated workplace exposures can be compared. In the years since the introduction of OELs to public health practice, both developed and developing countries have established processes for deriving, setting, and using OELs to protect workers exposed to hazardous chemicals. These processes vary widely, however, and have thus resulted in a confusing international landscape for identifying and applying such limits in workplaces. The occupational hygienist will encounter significant overlap in coverage among organizations for many chemicals, while other important chemicals have OELs developed by few, if any, organizations. Where multiple organizations have published an OEL, the derived value often varies considerably—reflecting differences in both risk policy and risk assessment methodology as well as access to available pertinent data. This article explores the underlying reasons for variability in OELs, and recommends the harmonization of risk-based methods used by OEL-deriving organizations. A framework is also proposed for the identification and systematic evaluation of OEL resources, which occupational hygienists can use to support risk characterization and risk management decisions in situations where multiple potentially relevant OELs exist. PMID:26099071

  9. Uncertainty and variability in human exposure limits - a chemical-specific approach for ciprofloxacin and methotrexate.

    PubMed

    Oldenkamp, Rik; Huijbregts, Mark A J; Ragas, Ad M J

    2016-03-01

    Human exposure limits (HELs) for chemicals with a toxicological threshold are traditionally derived using default assessment factors that account for variations in exposure duration, species sensitivity and individual sensitivity. The present paper elaborates a probabilistic approach for human hazard characterization and the derivation of HELs. It extends the framework for evaluating and expressing uncertainty in hazard characterization recently proposed by WHO-IPCS, i.e. by the incorporation of chemical-specific data on human variability in toxicokinetics. The incorporation of human variability in toxicodynamics was based on the variation between adverse outcome pathways (AOPs). Furthermore, sources of interindividual variability and uncertainty are propagated separately throughout the derivation process. The outcome is a two-dimensional human dose distribution that quantifies the population fraction exceeding a pre-selected critical effect level with an estimate of the associated uncertainty. This enables policy makers to set separate standards for the fraction of the population to be protected and the confidence level of the assessment. The main sources of uncertainty in the human dose distribution can be identified in order to plan new research for reducing uncertainty. Additionally, the approach enables quantification of the relative risk for specific subpopulations. The approach is demonstrated for two pharmaceuticals, i.e. the antibiotic ciprofloxacin and the antineoplastic methotrexate. For both substances, the probabilistic HEL is mainly influenced by uncertainty originating from: (1) the point of departure (PoD), (2) extrapolation from sub-acute to chronic toxicity and (3) interspecies extrapolation. However, when assessing the tails of the two-dimensional human dose distributions, i.e. the section relevant for the derivation of human exposure limits, interindividual variability in toxicodynamics also becomes important. PMID:26648512

  10. 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.

  11. Reach performance while wearing the Space Shuttle launch and entry suit during exposure to launch accelerations

    NASA Technical Reports Server (NTRS)

    Bagian, James P.; Greenisen, Michael C.; Schafer, Lauren E.; Probe, John D.; Krutz, Robert W., Jr.

    1993-01-01

    Crewmen aboard the Space Shuttle are subjected to accelerations during ascent (the powered flight phase of launch) which range up to +3 G(sub x). Despite having 33 missions and nine years experience, not to mention all the time spent in development prior to the first flight, no truly quantitative reach study wearing actual crew equipment, using actual Shuttle seats and restraints has ever been done. What little information exists on reach performance while under acceleration has been derived primarily from subjective comments gathered retrospectively from Shuttle flight crews during their post mission debrief. This lack of reach performance data has resulted in uncertainty regarding emergency procedures that can realistically be performed during and actual Shuttle ascent versus what is practiced in the ground-fixed and motion-based Shuttle Simulators. With the introduction on STS-26 of the current Shuttle escape system, the question of reach performance under launch accelerations was once again raised. The escape system's requirement that each crewman wear a Launch/Entry Suit (LES), parachute harness, and parachute were all anticipated to contribute to a further degradation of reach performance during Shuttle ascent accelerations. In order to answer the reach performance question in a quantitative way, a photogrammetric method was chosen so that the actual reach values and associated envelopes could be captured. This would allow quantitative assessment of potential task performance impact and identify areas where changes to our Shuttle ascent emergency procedures might be required. Also, such a set of reach values would be valid for any similar acceleration profile using the same crew equipment. Potential Space Station applications of this data include predicting reach performance during Assured Crew Return Vehicle (ACRV) operations.

  12. Limitations of predicting in vivo biostability of multiphase polyurethane elastomers using temperature-accelerated degradation testing.

    PubMed

    Padsalgikar, Ajay; Cosgriff-Hernandez, Elizabeth; Gallagher, Genevieve; Touchet, Tyler; Iacob, Ciprian; Mellin, Lisa; Norlin-Weissenrieder, Anna; Runt, James

    2015-01-01

    Polyurethane biostability has been the subject of intense research since the failure of polyether polyurethane pacemaker leads in the 1980s. Accelerated in vitro testing has been used to isolate degradation mechanisms and predict clinical performance of biomaterials. However, validation that in vitro methods reproduce in vivo degradation is critical to the selection of appropriate tests. High temperature has been proposed as a method to accelerate degradation. However, correlation of such data to in vivo performance is poor for polyurethanes due to the impact of temperature on microstructure. In this study, we characterize the lack of correlation between hydrolytic degradation predicted using a high temperature aging model of a polydimethylsiloxane-based polyurethane and its in vivo performance. Most notably, the predicted molecular weight and tensile property changes from the accelerated aging study did not correlate with clinical explants subjected to human biological stresses in real time through 5 years. Further, DMTA, ATR-FTIR, and SAXS experiments on samples aged for 2 weeks in PBS indicated greater phase separation in samples aged at 85C compared to those aged at 37C and unaged controls. These results confirm that microstructural changes occur at high temperatures that do not occur at in vivo temperatures. In addition, water absorption studies demonstrated that water saturation levels increased significantly with temperature. This study highlights that the multiphase morphology of polyurethane precludes the use of temperature accelerated biodegradation for the prediction of clinical performance and provides critical information in designing appropriate in vitro tests for this class of materials. PMID:24810790

  13. 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.

  14. 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.

  15. Development of backsheet tests and measurements to improve correlation of accelerated exposures to fielded modules

    NASA Astrophysics Data System (ADS)

    Felder, Thomas C.; Gambogi, William J.; Kopchick, James G.; Amspacher, Lucas; Peacock, R. Scott; Foltz, Benjamin; Stika, Katherine M.; Bradley, Alexander Z.; Hamzavy, Babak; Yu, Bao-Ling; Garreau-iles, Lucie; Fu, Oakland; Hu, Hongjie; Trout, T. John

    2015-09-01

    Matching accelerated test results to field observations is an important objective in the photovoltaic industry. We continue to develop test methods to strengthen correlations. We have previously reported good correlation of FTIR spectra between accelerated tests and field measurements. The availability of portable FTIR spectrometers has made measurement in the field convenient and reliable. Recently, nano-indentation has shown promise to correlate changes in backsheet mechanical properties. A precisely shaped stylus is pressed into a sample, load vs displacement recorded and mechanical properties of interest calculated in a nondestructive test. This test can be done on full size modules, allowing area variations in mechanical properties to be recorded. Finally, we will discuss optical profilometry. In this technique a white light interferogram of a surface is Fourier transformed to produce a three-dimensional image. Height differences from 1 nm to 5 mm can be detected over an area of a few cm. This technique can be used on minimodules, and is useful to determine crack and defect dimensions. Results will be presented correlating accelerated tests with fielded modules covering spectroscopic, mechanical, and morphological changes.

  16. Flux limit on cosmic ray acceleration by strong spherical pulsar waves

    NASA Technical Reports Server (NTRS)

    Asseo, E.; Kennel, F. C.; Pellat, R.

    1975-01-01

    The study investigates the acceleration of cosmic rays by superrelativistic plasma waves. The pulsar wave field imposed upon the particles is that of a magnetic dipole wave including azimuthal dependence and near field terms. The refractive index of the plasma is assumed to be constant everywhere. Two distinct zones appear: in the near zone spherical effects dominate, particles may be decelerated; in the far zone the results for the motion differ noticeably from the vacuum case. From a WBK-like treatment for a spherical S wave, it is concluded that for a wave solution to be valid even near the light cylinder, the wave can carry a sufficiently small particle flux.

  17. LIMITATIONS ON THE USES OF MULTIMEDIA EXPOSURE MEASUREMENTS FOR MULTIPATHWAY EXPOSURE ASSESSMENT - PART II: EFFECTS OF MISSING DATA AND IMPRECISION

    EPA Science Inventory

    Multimedia data from two probability-based exposure studies were investigated in terms of how missing data and measurement-error imprecision affected estimation of population parameters and associations. Missing data resulted mainly from individuals' refusing to participate in c...

  18. Point: Incident Exposures, Prevalent Exposures, and Causal Inference: Does Limiting Studies to Persons Who Are Followed From First Exposure Onward Damage Epidemiology?

    PubMed Central

    Vandenbroucke, Jan; Pearce, Neil

    2015-01-01

    The idea that epidemiologic studies should start from first exposure onward has been advocated in the past few years. The study of incident exposures is contrasted with studies of prevalent exposures in which follow-up may commence after first exposure. The former approach is seen as a hallmark of a good study and necessary for causal inference. We argue that studying incident exposures may be necessary in some situations, but it is not always necessary and is not the preferred option in many instances. Conducting a study involves decisions as to which person-time experience should be included. Although studies of prevalent exposures involve left truncation (missingness on the left), studies of incident exposures may involve right censoring (missingness on the right) and therefore may not be able to assess the long-term effects of exposure. These considerations have consequences for studies of dynamic (open) populations that involve a mixture of prevalent and incident exposures. We argue that studies with prevalent exposures will remain a necessity for epidemiology. The purpose of this paper is to restore the balance between the emphasis on first exposure cohorts and the richness of epidemiologic information obtained when studying prevalent exposures. PMID:26507305

  19. UVB exposure does not accelerate rates of litter decomposition in a semiarid riparian ecosystem

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Aboveground litter decomposition is controlled mainly by substrate quality and climate factors across terrestrial ecosystems, but photodegradation from exposure to high-intensity ultraviolet-B (UVB) radiation may also be important in arid and semi-arid environments. We investigated the interactive e...

  20. Reduction of Endogenous Melatonin Accelerates Cognitive Decline in Mice in a Simulated Occupational Formaldehyde Exposure Environment.

    PubMed

    Mei, Yufei; Duan, Chunli; Li, Xiaoxiao; Zhao, Yun; Cao, Fenghua; Shang, Shuai; Ding, Shumao; Yue, Xiangpei; Gao, Ge; Yang, Hui; Shen, Luxi; Feng, Xueyan; Jia, Jianping; Tong, Zhiqian; Yang, Xu

    2016-01-01

    Individuals afflicted with occupational formaldehyde (FA) exposure often suffer from abnormal behaviors such as aggression, depression, anxiety, sleep disorders, and in particular, cognitive impairments. Coincidentally, clinical patients with melatonin (MT) deficiency also complain of cognitive problems associated with the above mental disorders. Whether and how FA affects endogenous MT metabolism and induces cognitive decline need to be elucidated. To mimic occupational FA exposure environment, 16 healthy adult male mice were exposed to gaseous FA (3 mg/m³) for 7 consecutive days. Results showed that FA exposure impaired spatial memory associated with hippocampal neuronal death. Biochemical analysis revealed that FA exposure elicited an intensive oxidative stress by reducing systemic glutathione levels, in particular, decreasing brain MT concentrations. Inversely, intraperitoneal injection of MT markedly attenuated FA-induced hippocampal neuronal death, restored brain MT levels, and reversed memory decline. At tissue levels, injection of FA into the hippocampus distinctly reduced brain MT concentrations. Furthermore, at cellular and molecular levels, we found that FA directly inactivated MT in vitro and in vivo. These findings suggest that MT supplementation contributes to the rescue of cognitive decline, and may alleviate mental disorders in the occupational FA-exposed human populations. PMID:26938543

  1. Experiences from Occupational Exposure Limits Set on Aerosols Containing Allergenic Proteins

    PubMed Central

    Nielsen, Gunnar D.

    2012-01-01

    Occupational exposure limits (OELs) together with determined airborne exposures are used in risk assessment based managements of occupational exposures to prevent occupational diseases. In most countries, OELs have only been set for few protein-containing aerosols causing IgE-mediated allergies. They comprise aerosols of flour dust, grain dust, wood dust, natural rubber latex, and the subtilisins, which are proteolytic enzymes. These aerosols show dose-dependent effects and levels have been established, where nearly all workers may be exposed without adverse health effects, which are required for setting OELs. Our aim is to analyse prerequisites for setting OELs for the allergenic protein-containing aerosols. Opposite to the key effect of toxicological reactions, two thresholds, one for the sensitization phase and one for elicitation of IgE-mediated symptoms in sensitized individuals, are used in the OEL settings. For example, this was the case for flour dust, where OELs were based on dust levels due to linearity between flour dust and its allergen levels. The critical effects for flour and grain dust OELs were different, which indicates that conclusion by analogy (read-across) must be scientifically well founded. Except for subtilisins, no OEL have been set for other industrial enzymes, where many of which are high volume chemicals. For several of these, OELs have been proposed in the scientific literature during the last two decades. It is apparent that the scientific methodology is available for setting OELs for proteins and protein-containing aerosols where the critical effect is IgE sensitization and IgE-mediated airway diseases. PMID:22843406

  2. 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

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

    PubMed

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

    2003-08-01

    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. Each automobile was fitted with new replacement asbestos-containing brake shoes and then driven over a predetermined public road course for about 2253 km. Then, each car was separately brought into a repair facility; the brakes removed and replaced with new asbestos-containing shoes. The test conditions, methods, and tools were as commonly used during the 1960s. The mechanic was experienced in brake maintenance, having worked in the automobile repair profession beginning in the 1960s. Effects of three independent variables, e.g., filing, sanding, and arc grinding of the replacement brake shoe elements, were tested. Personal and area air samples were collected and analyzed for the presence of fibers, asbestos fibers, total dust, and respirable dust. The results indicated a presence in the air of only chrysotile asbestos and an absence of other types of asbestos. Airborne chrysotile fiber exposures for each test remained below currently applicable limit of 0.1 fiber/ml (eight-hour time-weighted average). PMID:12878055

  4. Implications of the new radiation exposure limits on Space Station Freedom crews

    NASA Technical Reports Server (NTRS)

    Stanford, M.; Nachtwey, D. S.

    1990-01-01

    Levels of acceptable risk of radiation exposure for SSF crews have been studied. Since the cancer risk per dose equivalent has increased over the last decade, new dose-equivalent limits have been recommended. An astronaut may not receive more than a depth-dose equivalent of 50 rem/year. It is found that a 180-day stay aboard Freedom could result in a worst case depth-dose of 30 rem, and a 180-day mission in a nominally shielded spacecraft in a constant atmospheric density orbit with a varying altitude could result in a depth-dose equivalent of 10 rem. This is twice the annual allowable dose-equivalent for terrestrial radiation workers. It is noted that the present understanding of the biological effectiveness of high-LET radiation is not adequate for accurate health risk assessments and that further research is necessary.

  5. UVB Exposure Does Not Accelerate Rates of Litter Decomposition in a Semiarid Riparian Ecosystem

    NASA Astrophysics Data System (ADS)

    Uselman, S. M.; Snyder, K. A.; Blank, R. R.; Jones, T. J.

    2010-12-01

    Aboveground litter decomposition is controlled mainly by substrate quality and climate factors across terrestrial ecosystems, but photodegradation from exposure to high-intensity ultraviolet-B (UVB) radiation may also be important in arid and semi-arid environments. We investigated the interactive effects of UVB exposure and litter quality on decomposition in a Tamarix-invaded riparian ecosystem during the establishment of an insect biological control agent in northern Nevada. Feeding by the northern tamarisk beetle (Diorhabda carinulata) on Tamarix spp. trees leads to altered leaf litter quality and increased exposure to solar UVB radiation from canopy opening. In addition, we examined the dynamics of litter decomposition of the invasive exotic Lepidium latifolium, because it is well-situated to invade beetle-infested Tamarix sites. Three leaf litter types (natural Tamarix, beetle-affected Tamarix, and L. latifolium) differing in substrate quality were decomposed in litterbags for one year in the field. Litterbags were subjected to one of three treatments: (1) Ambient UVB or (2) Reduced UVB (where UVB was manipulated by using clear plastic films that transmit or block UVB), and (3) No Cover (a control used to test for the effect of using the plastic films, i.e. a cover effect). Results showed a large cover effect on rates of decomposition and nutrient release, and our findings suggested that frequent cycles of freeze-thaw, and possibly rainfall intensity, influenced decomposition at this site. Contrary to our expectations, greater UVB exposure did not result in faster rates of decomposition. Greater UVB exposure resulted in decreased rates of decomposition and P release for the lower quality litter and no change in rates of decomposition and nutrient release for the two higher quality litter types, possibly due to a negative effect of UVB on soil microbes. Among litter types, rates of decomposition and net release of N and P followed this ranking: L. latifolium > beetle-affected Tamarix > natural Tamarix. Altered nutrient dynamics with beetle introduction as well as the rapid decomposition rates exhibited by L. latifolium are consistent with vulnerability to secondary invasion. In this desert ecosystem, decomposition and nutrient release were strongly affected by litter type and much less so by UVB exposure.

  6. Vitamin D intake determines vitamin d status of postmenopausal women, particularly those with limited sun exposure.

    PubMed

    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

    2014-05-01

    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 R(2) = 0.09) explained the most variance in serum 25(OH)D concentrations (total R(2) = 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

  7. 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

  8. 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

  9. Expression of Smad7 in Mouse Eyes Accelerates Healing of Corneal Tissue after Exposure to Alkali

    PubMed Central

    Saika, Shizuya; Ikeda, Kazuo; Yamanaka, Osamu; Miyamoto, Takeshi; Ohnishi, Yoshitaka; Sato, Misako; Muragaki, Yasuteru; Ooshima, Akira; Nakajima, Yuji; Kao, Winston W.-Y.; Flanders, Kathleen C.; Roberts, Anita B.

    2005-01-01

    Damage to the cornea from chemical burns is a serious clinical problem that often leads to permanent visual impairment. Because transforming growth factor (TGF)-? has been implicated in the response to corneal injury, we evaluated the effects of altered TGF-? signaling in a corneal alkali burn model using mice treated topically with an adenovirus (Ad) expressing inhibitory Smad7 and mice with a targeted deletion of the TGF-?/activin signaling mediator Smad3. Expression of exogenous Smad7 in burned corneal tissue resulted in reduced activation of Smad signaling and nuclear factor-?B signaling via RelA/p65. Resurfacing of the burned cornea by conjunctival epithelium and its differentiation to cornea-like epithelium were both accelerated in Smad7-Ad-treated corneas with suppressed stromal ulceration, opacification, and neovascularization 20 days after injury. Introduction of the Smad7 gene suppressed invasion of monocytes/macrophages and expression of monocyte/macrophage chemotactic protein-1, TGF-?1, TGF-?2, vascular endothelial growth factor, matrix metalloproteinase-9, and tissue inhibitors of metalloproteinase-2 and abolished the generation of myofibroblasts. Although acceleration of healing of the burned cornea was also observed in mice lacking Smad3, the effects on epithelial and stromal healing were less pronounced than those in corneas treated with Smad7. Together these data suggest that overexpression of Smad7 may have effects beyond those of simply blocking Smad3/TGF-? signaling and may represent an effective new strategy for treatment of ocular burns. PMID:15855641

  10. Adaption By Low Dose Radiation Exposure: A Look at Scope and Limitations for Radioprotection.

    PubMed

    Mitchel, Ron E J

    2015-01-01

    The procedures and dose limitations used for radiation protection in the nuclear industry are founded on the assumption that risk is directly proportional to dose, without a threshold. Based on this idea that any dose, no matter how small, will increase risk, radiation protection regulations generally attempt to reduce any exposure to "as low as reasonably achievable" (ALARA). We know however, that these regulatory assumptions are inconsistent with the known biological effects of low doses. Low doses induce protective effects, and these adaptive responses are part of a general response to low stress. Adaptive responses have been tightly conserved during evolution, from single celled organisms up to humans, indicating their importance. Here we examine cellular and animal studies that show the influence of radiation induced protective effects on diverse diseases, and examine the radiation dose range that is effective for different tissues in the same animal. The concept of a dose window, with upper and lower effective doses, as well as the effect of multiple stressors and the influence of genetics will also be examined. The effect of the biological variables on low dose responses will be considered from the point of view of the limitations they may impose on any revised radiation protection regulations. PMID:26672725

  11. Estimation of an upper limit on prehistoric peak ground acceleration using the parameters of intact speleothems in Hungarian caves

    NASA Astrophysics Data System (ADS)

    Szeidovitz, Gy?z?; Surnyi, Gergely; Gribovszki, Katalin; Bus, Zoltn; Lel-?ssy, Szabolcs; Varga, Zsolt

    2008-01-01

    The examination of speleothems in the Hajnczy and Baradla caves (northeastern Hungary) allows estimating an upper limit for horizontal peak ground acceleration generated by paleoearthquakes. The density, the Youngs modulus and the tensile failure stress of the samples originating from a broken speleothem have been measured in a laboratory, whereas the natural frequency of intact speleothems was determined by in situ observations. The value of horizontal ground acceleration resulting in failure, the natural frequency and the inner friction coefficient of speleothems were assessed by theoretical calculations. The ages of the samples taken from a stalagmite 5.1 m in height (Baradla cave) have been determined by inductively coupled plasma mass spectrometry analysis and alpha spectrometry. The measured ages fall between 140,000 and 70,000 years; therefore, we assume the speleothem has not been changed since the end of this time interval. According to our modeling results, this speleothem has not been excited by a horizontal acceleration higher than 0.05 g during the last 70,000 years.

  12. 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.

  13. Systems Biology and Biomarkers of Early Effects for Occupational Exposure Limit Setting

    PubMed Central

    DeBord, D. Gayle; Burgoon, Lyle; Edwards, Stephen W.; Haber, Lynne T.; Kanitz, M. Helen; Kuempel, Eileen; Thomas, Russell S.; Yucesoy, Berran

    2015-01-01

    In a recent National Research Council document, new strategies for risk assessment were described to enable more accurate and quicker assessments.( 1 ) This report suggested that evaluating individual responses through increased use of bio-monitoring could improve dose-response estimations. Identi-fication of specific biomarkers may be useful for diagnostics or risk prediction as they have the potential to improve exposure assessments. This paper discusses systems biology, biomarkers of effect, and computational toxicology approaches and their relevance to the occupational exposure limit setting process. The systems biology approach evaluates the integration of biological processes and how disruption of these processes by chemicals or other hazards affects disease outcomes. This type of approach could provide information used in delineating the mode of action of the response or toxicity, and may be useful to define the low adverse and no adverse effect levels. Biomarkers of effect are changes measured in biological systems and are considered to be preclinical in nature. Advances in computational methods and experimental -omics methods that allow the simultaneous measurement of families of macromolecules such as DNA, RNA, and proteins in a single analysis have made these systems approaches feasible for broad application. The utility of the information for risk assessments from -omics approaches has shown promise and can provide information on mode of action and dose-response relationships. As these techniques evolve, estimation of internal dose and response biomarkers will be a critical test of these new technologies for application in risk assessment strategies. While proof of concept studies have been conducted that provide evidence of their value, challenges with standardization and harmonization still need to be overcome before these methods are used routinely. PMID:26132979

  14. Systems Biology and Biomarkers of Early Effects for Occupational Exposure Limit Setting.

    PubMed

    DeBord, D Gayle; Burgoon, Lyle; Edwards, Stephen W; Haber, Lynne T; Kanitz, M Helen; Kuempel, Eileen; Thomas, Russell S; Yucesoy, Berran

    2015-01-01

    In a recent National Research Council document, new strategies for risk assessment were described to enable more accurate and quicker assessments. This report suggested that evaluating individual responses through increased use of bio-monitoring could improve dose-response estimations. Identification of specific biomarkers may be useful for diagnostics or risk prediction as they have the potential to improve exposure assessments. This paper discusses systems biology, biomarkers of effect, and computational toxicology approaches and their relevance to the occupational exposure limit setting process. The systems biology approach evaluates the integration of biological processes and how disruption of these processes by chemicals or other hazards affects disease outcomes. This type of approach could provide information used in delineating the mode of action of the response or toxicity, and may be useful to define the low adverse and no adverse effect levels. Biomarkers of effect are changes measured in biological systems and are considered to be preclinical in nature. Advances in computational methods and experimental -omics methods that allow the simultaneous measurement of families of macromolecules such as DNA, RNA, and proteins in a single analysis have made these systems approaches feasible for broad application. The utility of the information for risk assessments from -omics approaches has shown promise and can provide information on mode of action and dose-response relationships. As these techniques evolve, estimation of internal dose and response biomarkers will be a critical test of these new technologies for application in risk assessment strategies. While proof of concept studies have been conducted that provide evidence of their value, challenges with standardization and harmonization still need to be overcome before these methods are used routinely. PMID:26132979

  15. Secondary Electron Emission in the Limit of Low Energy and its Effect on High Energy Physics Accelerators

    NASA Astrophysics Data System (ADS)

    Andronov, A. N.; Smirnov, A. S.; Kaganovich, I. D.; Startsev, E. A.; Raitses, Y.; Davidson, R. C.; Demidov, V.

    2011-10-01

    Authors of the Letter reported that the secondary electron emission (SEE) coefficient approaches unity in the limit of zero primary electron energy. This occurs due to nearly 100% electron reflection from the surface, for electron energy less than an electron volt. If correct, this finding could have profound implications on electron cloud formation in high-energy accelerators and sheath structure in plasmas, because electrons approaching the wall with energy below an electron volt are reflected from the walls and thus are effectively confined by the walls. In this paper, we summarize comprehensive studies rendering this claim inaccurate; that is most electrons are lost on walls. These studies include theoretical analysis of SEE properties in the limit of low electron energy, analysis of measuring device errors, and experimental observation of the operation of probes collecting electron current. Research supported by the U.S. Department of Energy.

  16. Accelerated soil carbon turnover under tree plantations limits soil carbon storage

    NASA Astrophysics Data System (ADS)

    Chen, Guangshui; Yang, Yusheng; Yang, Zhijie; Xie, Jinsheng; Guo, Jianfen; Gao, Ren; Yin, Yunfeng; Robinson, David

    2016-01-01

    The replacement of native forests by tree plantations is increasingly common globally, especially in tropical and subtropical areas. Improving our understanding of the long-term effects of this replacement on soil organic carbon (SOC) remains paramount for effectively managing ecosystems to mitigate anthropogenic carbon emissions. Meta-analyses imply that native forest replacement usually reduces SOC stocks and may switch the forest from a net sink to a net source of atmospheric carbon. Using a long-term chronosequence during which areas of subtropical native forest were replaced by Chinese fir, we show by direct measurement that plantations have significantly accelerated SOC turnover compared with native forest, an effect that has persisted for almost a century. The immediate stimulation of SOC decomposition was caused by warmer soil before the closure of the plantation’s canopy. Long-term reductions in SOC mean residence times were coupled to litter inputs. Faster SOC decomposition was associated with lower soil microbial carbon use efficiency, which was due to smaller litter inputs and reduced nutrient availabilities. Our results indicate a previously unelucidated control on long-term SOC dynamics in native forests and demonstrate a potential constraint on climate mitigation when such forests are replaced by plantations.

  17. Accelerated soil carbon turnover under tree plantations limits soil carbon storage

    PubMed Central

    Chen, Guangshui; Yang, Yusheng; Yang, Zhijie; Xie, Jinsheng; Guo, Jianfen; Gao, Ren; Yin, Yunfeng; Robinson, David

    2016-01-01

    The replacement of native forests by tree plantations is increasingly common globally, especially in tropical and subtropical areas. Improving our understanding of the long-term effects of this replacement on soil organic carbon (SOC) remains paramount for effectively managing ecosystems to mitigate anthropogenic carbon emissions. Meta-analyses imply that native forest replacement usually reduces SOC stocks and may switch the forest from a net sink to a net source of atmospheric carbon. Using a long-term chronosequence during which areas of subtropical native forest were replaced by Chinese fir, we show by direct measurement that plantations have significantly accelerated SOC turnover compared with native forest, an effect that has persisted for almost a century. The immediate stimulation of SOC decomposition was caused by warmer soil before the closure of the plantation’s canopy. Long-term reductions in SOC mean residence times were coupled to litter inputs. Faster SOC decomposition was associated with lower soil microbial carbon use efficiency, which was due to smaller litter inputs and reduced nutrient availabilities. Our results indicate a previously unelucidated control on long-term SOC dynamics in native forests and demonstrate a potential constraint on climate mitigation when such forests are replaced by plantations. PMID:26805949

  18. Accelerated soil carbon turnover under tree plantations limits soil carbon storage.

    PubMed

    Chen, Guangshui; Yang, Yusheng; Yang, Zhijie; Xie, Jinsheng; Guo, Jianfen; Gao, Ren; Yin, Yunfeng; Robinson, David

    2016-01-01

    The replacement of native forests by tree plantations is increasingly common globally, especially in tropical and subtropical areas. Improving our understanding of the long-term effects of this replacement on soil organic carbon (SOC) remains paramount for effectively managing ecosystems to mitigate anthropogenic carbon emissions. Meta-analyses imply that native forest replacement usually reduces SOC stocks and may switch the forest from a net sink to a net source of atmospheric carbon. Using a long-term chronosequence during which areas of subtropical native forest were replaced by Chinese fir, we show by direct measurement that plantations have significantly accelerated SOC turnover compared with native forest, an effect that has persisted for almost a century. The immediate stimulation of SOC decomposition was caused by warmer soil before the closure of the plantation's canopy. Long-term reductions in SOC mean residence times were coupled to litter inputs. Faster SOC decomposition was associated with lower soil microbial carbon use efficiency, which was due to smaller litter inputs and reduced nutrient availabilities. Our results indicate a previously unelucidated control on long-term SOC dynamics in native forests and demonstrate a potential constraint on climate mitigation when such forests are replaced by plantations. PMID:26805949

  19. Demodulation in tissue, the relevant parameters and the implications for limiting exposure.

    PubMed

    Silny, Jiri

    2007-06-01

    In the biomedical literature there are a number of reports that speculate about possible effects in the body due to the demodulation of electromagnetic fields. However, only few interactions in amplitude-modulated or even pulse-modulated electromagnetic waves are fundamentally plausible and have been demonstrated to occur in humans. The following observations fall into this specific category: thermal effects of amplitude- or pulse-modulated microwaves; demodulation of amplitude- or pulse-modulated electromagnetic waves in cell membranes; and demodulation of amplitude- or pulse-modulated electromagnetic fields in the electronics of implants such as cardiac pacemakers or cardioverter defibrillators. The possible consequences of these effects for the organism, their probability of occurrence in everyday life field conditions, and, consequently, the implications for limiting exposure are very different. Microwave hearing is a harmless effect which is perceived by humans only in strong fields with high peak power densities of more than 100 mW cm(-2). In normal residential or occupational environments the peak power density of even the strongest microwave sources is only around 1 mW cm(-2). Demodulation of pulse-modulated electromagnetic fields in the cell membranes decreases the stimulation threshold of nerves and muscles and can introduce numerous adverse effects ranging from perception of pain to dangerous cardiac fibrillations. The stimulation and demodulation effects are restricted to carrier frequencies up to several MHz. In experiments with 900 and 1,800 MHz packets with lengths of up to 100 ms and applied powers of up to 100 W, neither a direct stimulation of superficial nerves and muscles nor the conditioning of an electrical current stimulus could be confirmed. Pulse-modulated electromagnetic waves are demodulated in the electronic circuits of implants and can inhibit cardiac pacemakers and introduce cardiac arrest in this way. The highest sensitivity results from repetition rates of pulses below 100 Hz. The preceding two implications should be considered in the elaboration of new general guidelines limiting the exposure for healthy as well as for sick persons in the future. PMID:17495662

  20. Accelerator-Based Biological Irradiation Facility Simulating Neutron Exposure from an Improvised Nuclear Device.

    PubMed

    Xu, Yanping; Randers-Pehrson, Gerhard; Turner, Helen C; Marino, Stephen A; Geard, Charles R; Brenner, David J; Garty, Guy

    2015-10-01

    We describe here an accelerator-based neutron irradiation facility, intended to expose blood or small animals to neutron fields mimicking those from an improvised nuclear device at relevant distances from the epicenter. Neutrons are generated by a mixed proton/deuteron beam on a thick beryllium target, generating a broad spectrum of neutron energies that match those estimated for the Hiroshima bomb at 1.5 km from ground zero. This spectrum, dominated by neutron energies between 0.2 and 9 MeV, is significantly different from the standard reactor fission spectrum, as the initial bomb spectrum changes when the neutrons are transported through air. The neutron and gamma dose rates were measured using a custom tissue-equivalent gas ionization chamber and a compensated Geiger-Mueller dosimeter, respectively. Neutron spectra were evaluated by unfolding measurements using a proton-recoil proportional counter and a liquid scintillator detector. As an illustration of the potential use of this facility we present micronucleus yields in single divided, cytokinesis-blocked human peripheral lymphocytes up to 1.5 Gy demonstrating 3- to 5-fold enhancement over equivalent X-ray doses. This facility is currently in routine use, irradiating both mice and human blood samples for evaluation of neutron-specific biodosimetry assays. Future studies will focus on dose reconstruction in realistic mixed neutron/photon fields. PMID:26414507

  1. PREDICTOL: a computer program to determine the thermophysiological duration limited exposures in various climatic conditions.

    PubMed

    Besnard, Yves; Launay, Jean-Claude; Guinet-Lebreton, Anglique; Savourey, Gustave

    2004-12-01

    PREDICTOL is a PC program used to determine the thermophysiological duration limited exposures (DLE) in humans, nude or clothed, submitted to various climatic conditions (hot and cold climates) at rest or during a physical exercise. DLE are determined following different standards of the International Standardization Organization (ISO), especially ISO 7933 for hot environment and ISO-TR 11079 for cold environment. The original aspect of this program is that it can be used whatever the climatic conditions. The program presents two modes: an educational interactive mode and a scenario mode. The educational interactive mode demonstrates the thermophysiological effects, expressed as DLE, of different parameter changes (temperature, humidity, wind speed, metabolic heat production by physical exercise, clothing insulation and water vapor permeability). The scenario mode determines DLE for given various linked sequences as encountered in occupational, military or even recreational activities, each sequence being characterized by its climatic conditions, physical activities performed and by physical clothing properties. DLE given by PREDICTOL are correlated to those obtained in various controlled climatic laboratory conditions (r = 0.86; P < 0.001). PREDICTOL is written in Visual Basic 6.0. A "help menu" is provided to explain the use of the program and give information concerning the equations used to calculate both the thermal balance and DLE. PMID:15501508

  2. 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

  3. The Treponema denticola Major Sheath Protein Is Predominantly Periplasmic and Has Only Limited Surface Exposure

    PubMed Central

    Caimano, Melissa J.; Bourell, Kenneth W.; Bannister, Teresa D.; Cox, David L.; Radolf, Justin D.

    1999-01-01

    The recent discovery that the Treponema pallidum genome encodes 12 orthologs of the Treponema denticola major sheath protein (Msp) prompted us to reexamine the cellular location and topology of the T. denticola polypeptide. Experiments initially were conducted to ascertain whether Msp forms an array on or within the T. denticola outer membrane. Transmission electron microscopy (EM) of negatively stained and ultrathin-sectioned organisms failed to identify a typical surface layer, whereas freeze-fracture EM revealed that the T. denticola outer membrane contains heterogeneous transmembrane proteins but no array. In contrast, a lattice-like structure was observed in vesicles released from mildly sonicated treponemes; combined EM and biochemical analyses demonstrated that this structure was the peptidoglycan sacculus. Immunoelectron microscopy (IEM) subsequently was performed to localize Msp in T. denticola. Examination of negatively stained whole mounts identified substantial amounts of Msp in sonicated organisms. IEM of ultrathin-sectioned, intact treponemes also demonstrated that the preponderance of antigen was unassociated with the outer membrane. Lastly, immunofluorescence analysis of treponemes embedded in agarose gel microdroplets revealed that only minor portions of Msp are surface exposed. Taken as a whole, our findings challenge the widely held belief that Msp forms an array within the T. denticola outer membrane and demonstrate, instead, that it is predominantly periplasmic with only limited surface exposure. These findings also have implications for our evolving understanding of the contribution(s) of Msp/Tpr orthologs to treponemal physiology and disease pathogenesis. PMID:10417176

  4. Exposure to radiation accelerates normal brain aging and produces deficits in spatial learning and memory

    NASA Astrophysics Data System (ADS)

    Shukitt-Hale, B.; Casadesus, G.; Carey, A.; Rabin, B. M.; Joseph, J. A.

    Previous studies have shown that radiation exposure, particularly to particles of high energy and charge (HZE particles), produces deficits in spatial learning and memory. These adverse behavioral effects are similar to those seen in aged animals. It is possible that these shared effects may be produced by the same mechanism; oxidative stress damage to the central nervous system caused by an increased release of reactive oxygen species is likely responsible for the deficits seen in aging and following irradiation. Both aged and irradiated rats display cognitive impairment in tests of spatial learning and memory such as the Morris water maze and the radial arm maze. These rats have decrements in the ability to build spatial representations of the environment and they utilize non-spatial strategies to solve tasks. Furthermore, they show a lack of spatial preference, due to a decline in the ability to process or retain place (position of a goal with reference to a "map" provided by the configuration of numerous cues in the environment) information. These declines in spatial memory occur in measures dependent on both reference and working memory, and in the flexibility to reset mental images. These results show that irradiation with high-energy particles produces age-like decrements in cognitive behavior that may impair the ability of astronauts to perform critical tasks during long-term space travel beyond the magnetosphere. Supported by NASA Grants NAG9-1190 and NAG9-1529

  5. 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...

  6. Extrapolation of frequency-dependent ceiling limit values for occupational exposure to magnetic fields between 0 and 1 Hz.

    PubMed

    Goiceanu, Cristian; Danulescu, Razvan

    2003-06-01

    This paper proposes a method for making a transition between discontinuous magnetic-field limit values set by exposure standards in adjacent frequency ranges. This method is applied to the limit values set by the International Commission on Non-Ionizing Radiation Protection for static and extremely low frequency magnetic fields. In this case, both ceiling and time-weighted average values are provided for static fields, but only ceiling limits are provided for extremely low frequency fields. The proposed method of setting both types of limit values for magnetic fields between 0 and 1 Hz can contribute to achieving exposure standards that have continuity on the entire frequency spectrum. As far as it eliminates discontinuities, it will also help the implementation of regulations by eliminating some uncertainties. Therefore, it could reduce difficulties in checking compliance with standards. PMID:12822587

  7. A Critical Review of Biomarkers Used for Monitoring Human Exposure to Lead: Advantages, Limitations, and Future Needs

    PubMed Central

    Barbosa, Fernando; Tanus-Santos, Jos Eduardo; Gerlach, Raquel Fernanda; Parsons, Patrick J.

    2005-01-01

    Lead concentration in whole blood (BPb) is the primary biomarker used to monitor exposure to this metallic element. The U.S. Centers for Disease Control and Prevention and the World Health Organization define a BPb of 10 ?g/dL (0.48 ?mol/L) as the threshold of concern in young children. However, recent studies have reported the possibility of adverse health effects, including intellectual impairment in young children, at BPb levels < 10 ?g/dL, suggesting that there is no safe level of exposure. It appears impossible to differentiate between low-level chronic Pb exposure and a high-level short Pb exposure based on a single BPb measurement; therefore, serial BPb measurements offer a better estimation of possible health outcomes. The difficulty in assessing the exact nature of Pb exposure is dependent not so much on problems with current analytical methodologies, but rather on the complex toxicokinetics of Pb within various body compartments (i.e., cycling of Pb between bone, blood, and soft tissues). If we are to differentiate more effectively between Pb stored in the body for years and Pb from recent exposure, information on other biomarkers of exposure may be needed. None of the current biomarkers of internal Pb dose have yet been accepted by the scientific community as a reliable substitute for a BPb measurement. This review focuses on the limitations of biomarkers of Pb exposure and the need to improve the accuracy of their measurement. We present here only the traditional analytical protocols in current use, and we attempt to assess the influence of confounding variables on BPb levels. Finally, we discuss the interpretation of BPb data with respect to both external and endogenous Pb exposure, past or recent exposure, as well as the significance of Pb determinations in human specimens including hair, nails, saliva, bone, blood (plasma, whole blood), urine, feces, and exfoliated teeth. PMID:16330345

  8. Protocol for a drugs exposure pregnancy registry for implementation in resource-limited settings

    PubMed Central

    2012-01-01

    Background The absence of robust evidence of safety of medicines in pregnancy, particularly those for major diseases provided by public health programmes in developing countries, has resulted in cautious recommendations on their use. We describe a protocol for a Pregnancy Registry adapted to resource-limited settings aimed at providing evidence on the safety of medicines in pregnancy. Methods/Design Sentinel health facilities are chosen where women come for prenatal care and are likely to come for delivery. Staff capacity is improved to provide better care during the pregnancy, to identify visible birth defects at delivery and refer infants with major anomalies for surgical or clinical evaluation and treatment. Consenting women are enrolled at their first antenatal visit and careful medical, obstetric and drug-exposure histories taken; medical record linkage is encouraged. Enrolled women are followed up prospectively and their histories are updated at each subsequent visit. The enrolled woman is encouraged to deliver at the facility, where she and her baby can be assessed. Discussion In addition to data pooling into a common WHO database, the WHO Pregnancy Registry has three important features: First is the inclusion of pregnant women coming for antenatal care, enabling comparison of birth outcomes of women who have been exposed to a medicine with those who have not. Second is its applicability to resource-poor settings regardless of drug or disease. Third is improvement of reproductive health care during pregnancies and at delivery. Facility delivery enables better health outcomes, timely evaluation and management of the newborn, and the collection of reliable clinical data. The Registry aims to improves maternal and neonatal care and also provide much needed information on the safety of medicines in pregnancy. PMID:22943425

  9. The Role of Home Smoking Bans in Limiting Exposure to Secondhand Tobacco Smoke in Hungary

    ERIC Educational Resources Information Center

    Paulik, Edit; Maroti-Nagy, A.; Nagymajtenyi, 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…

  10. The Role of Home Smoking Bans in Limiting Exposure to Secondhand Tobacco Smoke in Hungary

    ERIC Educational Resources Information Center

    Paulik, Edit; Maroti-Nagy, A.; Nagymajtenyi, 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

  11. 29 CFR Appendix A to Subpart Y of... - Examples of Conditions Which May Restrict or Limit Exposure to Hyperbaric Conditions

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 8 2010-07-01 2010-07-01 false Examples of Conditions Which May Restrict or Limit Exposure to Hyperbaric Conditions A Appendix A to Subpart Y of Part 1926 Labor Regulations Relating to Labor... REGULATIONS FOR CONSTRUCTION Diving Pt. 1926, Subpt. Y, App. A Appendix A to Subpart Y of Part...

  12. 29 CFR Appendix A to Subpart Y of... - Examples of Conditions Which May Restrict or Limit Exposure to Hyperbaric Conditions

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 29 Labor 8 2011-07-01 2011-07-01 false Examples of Conditions Which May Restrict or Limit Exposure to Hyperbaric Conditions A Appendix A to Subpart Y of Part 1926 Labor Regulations Relating to Labor... REGULATIONS FOR CONSTRUCTION Diving Pt. 1926, Subpt. Y, App. A Appendix A to Subpart Y of Part...

  13. Limiter

    DOEpatents

    Cohen, S.A.; Hosea, J.C.; Timberlake, J.R.

    1984-10-19

    A limiter with a specially contoured front face is provided. The front face of the limiter (the plasma-side face) is flat with a central indentation. In addition, the limiter shape is cylindrically symmetric so that the limiter can be rotated for greater heat distribution. This limiter shape accommodates the various power scrape-off distances lambda p, which depend on the parallel velocity, V/sub parallel/, of the impacting particles.

  14. Acute Exposure to Di(2-Ethylhexyl) Phthalate in Adulthood Causes Adverse Reproductive Outcomes Later in Life and Accelerates Reproductive Aging in Female Mice.

    PubMed

    Hannon, Patrick R; Niermann, Sarah; Flaws, Jodi A

    2016-03-01

    Humans are ubiquitously exposed to di(2-ethylhexyl) phthalate (DEHP), which is an environmental toxicant incorporated in consumer products. Studies have shown that DEHP targets the ovary to disrupt essential processes required for reproductive and nonreproductive health. Specifically, 10-day exposure to DEHP accelerates primordial follicle recruitment and disrupts estrous cyclicity in adult mice. However, it is unknown if these effects on folliculogenesis and cyclicity following acute DEHP exposure can have permanent effects on reproductive outcomes. Further, the premature depletion of primordial follicles can cause early reproductive senescence, and it is unknown if acute DEHP exposure accelerates reproductive aging. This study tested the hypothesis that acute DEHP exposure causes infertility, disrupts estrous cyclicity, alters hormone levels, and depletes follicle numbers by inducing atresia later in life, leading to accelerated reproductive aging. Adult CD-1 mice were orally dosed with vehicle or DEHP (20??g/kg/day-500?mg/kg/day) daily for 10 days, and reproductive outcomes were assessed at 6 and 9 months postdosing. Acute DEHP exposure significantly altered estrous cyclicity compared to controls at 6 and 9 months postdosing by increasing the percentage of days the mice were in estrus and metestrus/diestrus, respectively. DEHP also significantly decreased inhibin B levels compared to controls at 9 months postdosing. Further, DEHP significantly increased the BAX/BCL2 ratio in primordial follicles leading to a significant decrease in primordial and total follicle numbers compared to controls at 9 months postdosing. Collectively, the adverse effects present following acute DEHP exposure persist later in life and are consistent with accelerated reproductive aging. PMID:26678702

  15. Accelerated failure time model for case-cohort design with longitudinal covariates subject to measurement error and detection limits.

    PubMed

    Dong, Xinxin; Kong, Lan; Wahed, Abdus S

    2016-04-15

    Biomarkers are often measured over time in epidemiological studies and clinical trials for better understanding of the mechanism of diseases. In large cohort studies, case-cohort sampling provides a cost effective method to collect expensive biomarker data for revealing the relationship between biomarker trajectories and time to event. However, biomarker measurements are often limited by the sensitivity and precision of a given assay, resulting in data that are censored at detection limits and prone to measurement errors. Additionally, the occurrence of an event of interest may preclude biomarkers from being further evaluated. Inappropriate handling of these types of data can lead to biased conclusions. Under a classical case cohort design, we propose a modified likelihood-based approach to accommodate these special features of longitudinal biomarker measurements in the accelerated failure time models. The maximum likelihood estimators based on the full likelihood function are obtained by Gaussian quadrature method. We evaluate the performance of our case-cohort estimator and compare its relative efficiency to the full cohort estimator through simulation studies. The proposed method is further illustrated using the data from a biomarker study of sepsis among patients with community acquired pneumonia. Copyright © 2015 John Wiley & Sons, Ltd. PMID:26530415

  16. A comparison of REACH-derived no-effect levels for workers with EU indicative occupational exposure limit values and national limit values in Finland.

    PubMed

    Tynkkynen, Sallamari; Santonen, Tiina; Stockmann-Juvala, Helene

    2015-05-01

    The purpose of occupational exposure limits values (OELs) is to regulate exposure to chemicals and minimize the risk of health effects at work. National authorities are responsible for the setting and updating of national OELs. In addition, the EU sets indicative occupational exposure limit values (IOELVs), which have to be considered by the Member States. Under the new European legislation on chemicals (REACH), manufacturers and importers are obliged to establish derived no-effect levels (DNELs) for chemicals that are manufactured or imported in quantities >10 tonnes per year. Chemical safety data sheets must report both OELs and the DNEL values, if such have been set. This may cause confusion at workplaces, especially if the values differ from each other. In this study, we explored how EU IOELVs and Finnish national OELs [Haitallisiksi tunnetut pitoisuudet (HTP) values] correlate with worker inhalation DNELs for substances registered under REACH. The long-term DNEL value for workers (inhalation) was identical to the corresponding IOELV for the majority of the substances (64/87 cases). Comparison of DNELs with HTP values revealed that the values were identical or close to each other in 159 cases (49%), whereas the DNEL was considerably higher in 69 cases, and considerably lower in 87 cases. Examples of cases with high differences between Finnish national OELs and DNELs are given. However, as the DNELs were not systematically lower than the OELs, the default assessment factors suggested by REACH technical guidance had obviously not been used in many of the REACH registrations. PMID:25638729

  17. Effect of limited air exposure and comparative performance between thermophilic and mesophilic solid-state anaerobic digestion of switchgrass.

    PubMed

    Sheets, Johnathon P; Ge, Xumeng; Li, Yebo

    2015-03-01

    Switchgrass is an attractive feedstock for biogas production via anaerobic digestion (AD). Many studies have used switchgrass for liquid anaerobic digestion (L-AD), but few have used switchgrass for solid-state anaerobic digestion (SS-AD). Limited air exposure to the reactor headspace has been adopted in commercial scale anaerobic digesters for different applications. However, little research has examined the effect of limited air exposure on biogas production during SS-AD. In this study, the effects of air exposure and total solids (TS) content on SS-AD performance were evaluated under mesophilic (361C) and thermophilic (550.3C) conditions. Limited air exposure did not significantly influence the methane yield during SS-AD. Thermophilic SS-AD had greater methane yields (102-145LCH4kg(-1)VSadded) than mesophilic SS-AD (88-113LCH4kg(-1)VSadded). Both mesophilic SS-AD (73-136GJ) and thermophilic SS-AD (2-95GJ) produced positive net energy based on a theoretical 'garage-type' SS-AD digester operating in a temperate climate. PMID:25618499

  18. Straight Metalworking Fluids and All-Cause and Cardiovascular Mortality Analyzed by Using G-Estimation of an Accelerated Failure Time Model With Quantitative Exposure: Methods and Interpretations.

    PubMed

    Picciotto, Sally; Ljungman, Petter L; Eisen, Ellen A

    2016-04-01

    Straight metalworking fluids have been linked to cardiovascular mortality in analyses using binary exposure metrics, accounting for healthy worker survivor bias by using g-estimation of accelerated failure time models. A cohort of 38,666 Michigan autoworkers was followed (1941-1994) for mortality from all causes and ischemic heart disease. The structural model chosen here, using continuous exposure, assumes that increasing exposure from 0 to 1 mg/m(3) in any single year would decrease survival time by a fixed amount. Under that assumption, banning the fluids would have saved an estimated total of 8,468 (slope-based 95% confidence interval: 2,262, 28,563) person-years of life in this cohort. On average, 3.04 (slope-based 95% confidence interval: 0.02, 25.98) years of life could have been saved for each exposed worker who died from ischemic heart disease. Estimates were sensitive to both model specification for predicting exposure (multinomial or logistic regression) and characterization of exposure as binary or continuous in the structural model. Our results provide evidence supporting the hypothesis of a detrimental relationship between straight metalworking fluids and mortality, particularly from ischemic heart disease, as well as an instructive example of the challenges in obtaining and interpreting results from accelerated failure time models using a continuous exposure in the presence of competing risks. PMID:26968943

  19. Limiter

    DOEpatents

    Cohen, Samuel A. (Hopewell, NJ); Hosea, Joel C. (Princeton, NJ); Timberlake, John R. (Allentown, NJ)

    1986-01-01

    A limiter with a specially contoured front face accommodates the various power scrape-off distances .lambda..sub.p, which depend on the parallel velocity, V.sub..parallel., of the impacting particles. The front face of the limiter (the plasma-side face) is flat with a central indentation. In addition, the limiter shape is cylindrically symmetric so that the limiter can be rotated for greater heat distribution.

  20. 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

  1. A review of studies on maternal occupational exposures and birth defects, and the limitations associated with these studies.

    PubMed

    Shi, L; Chia, S E

    2001-06-01

    The proportion of pregnant women who work during pregnancy is increasing as more women move into previously male-dominated occupations. With this move, occupational exposure to chemical or physical factors during pregnancy could be further increased. In the last decade, there have been many reports on the causes of birth defects. Unfortunately, most reported associations between occupational exposures and adverse reproductive outcomes in epidemiological studies are equivocal and often controversial. Many reported associations are only suggestive. More information is needed before firm conclusions can be drawn. The major reasons for ambiguous findings are due to limitations of study methodology, e.g. inappropriate endpoints, multiple confounders, low study power and inadequate analysis methods. It must also be noted that maternal work, and therefore exposure, may also differ greatly from country to country. PMID:11463868

  2. 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.

  3. 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

  4. 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…

  5. 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.

  6. Measuring exposure to the polyphenol metabolome in observational epidemiologic studies: current tools and applications and their limits123

    PubMed Central

    Zamora-Ros, Raul; Touillaud, Marina; Rothwell, Joseph A; Romieu, Isabelle; Scalbert, Augustin

    2014-01-01

    Much experimental evidence supports a protective role of dietary polyphenols against chronic diseases such as cardiovascular diseases, diabetes, and cancer. However, results from observational epidemiologic studies are still limited and are often inconsistent. This is largely explained by the difficulties encountered in the estimation of exposure to the polyphenol metabolome, which is composed of ∼500 polyphenols distributed across a wide variety of foods and characterized by diverse biological properties. Exposure to the polyphenol metabolome in epidemiologic studies can be assessed by the use of detailed dietary questionnaires or the measurement of biomarkers of polyphenol intake. The questionnaire approach has been greatly facilitated by the use of new databases on polyphenol composition but is limited by bias as a result of self-reporting. The use of polyphenol biomarkers holds much promise for objective estimation of polyphenol exposure in future metabolome-wide association studies. These approaches are reviewed and their advantages and limitations discussed by using examples of epidemiologic studies on polyphenols and cancer. The current improvement in these techniques, along with greater emphasis on the intake of individual polyphenols rather than polyphenols considered collectively, will help unravel the role of these major food bioactive constituents in disease prevention. PMID:24787490

  7. The relationship between anatomically correct electric and magnetic field dosimetry and publishe delectric and magnetic field exposure limits.

    PubMed

    Kavet, Robert; Dovan, Thanh; Reilly, J Patrick

    2012-12-01

    Electric and magnetic field exposure limits published by International Commission for Non-Ionizing Radiation Protection and Institute of Electrical and Electronics Engineers are aimed at protection against adverse electrostimulation, which may occur by direct coupling to excitable tissue and, in the case of electric fields, through indirect means associated with surface charge effects (e.g. hair vibration, skin sensations), spark discharge and contact current. For direct coupling, the basic restriction (BR) specifies the not-to-be-exceeded induced electric field. The key results of anatomically based electric and magnetic field dosimetry studies and the relevant characteristics of excitable tissue were first identified. This permitted us to assess the electric and magnetic field exposure levels that induce dose in tissue equal to the basic restrictions, and the relationships of those exposure levels to the limits now in effect. We identify scenarios in which direct coupling of electric fields to peripheral nerve could be a determining factor for electric field limits. PMID:22619351

  8. Evaluation of exposure in mammography: limitations of average glandular dose and proposal of a new quantity.

    PubMed

    Geeraert, N; Klausz, R; Muller, S; Bloch, I; Bosmans, H

    2015-07-01

    The radiation risk in mammography is traditionally evaluated using the average glandular dose. This quantity for the average breast has proven to be useful for population statistics and to compare exposure techniques and systems. However it is not indicating the individual radiation risk based on the individual glandular amount and distribution. Simulations of exposures were performed for six appropriate virtual phantoms with varying glandular amount and distribution. The individualised average glandular dose (iAGD), i.e. the individual glandular absorbed energy divided by the mass of the gland, and the glandular imparted energy (GIE), i.e. the glandular absorbed energy, were computed. Both quantities were evaluated for their capability to take into account the glandular amount and distribution. As expected, the results have demonstrated that iAGD reflects only the distribution, while GIE reflects both the glandular amount and distribution. Therefore GIE is a good candidate for individual radiation risk assessment. PMID:25897143

  9. Limited effects of ozone exposure during pregnancy on physical and neurobehavioral development of CD-1 mice.

    PubMed

    Bignami, G; Musi, B; Dell'Omo, G; Laviola, G; Alleva, E

    1994-12-01

    Only a few studies have attempted to assess in laboratory rodents the maternal toxicity and behavioral changes in offspring caused by prenatal exposure to ozone (O3). In particular, no data are available concerning the behavioral development of mouse offspring after maternal exposure, despite the fact that increasing use is made of this species in behavioral teratology studies for reasons both of economy and in order to increase the effectiveness of subsequent higher-tier studies (e.g., of treatment-genotype interactions). In the present work, female CD-1 mice were exposed during pregnancy (Days 7-17) to different O3 concentrations (0, 0.4, 0.8, or 1.2 ppm); to avoid confounding by postnatal maternal effects, all litters were assigned shortly after birth to foster dams neither treated nor handled during pregnancy. The dams' food and water intake and body weight gain were depressed in a concentration-dependent fashion. Tolerance to these effects developed during continuing exposure; such tolerance was faster in the case of food than water intake. Several measures of reproductive performance, such as proportion of pregnancies carried to term, litter size, sex ratio, frequency of stillbirth, and neonatal mortality, failed to show differences between control and O3 animals. Postnatal body weight gain was slightly but significantly depressed in the 1.2 ppm offspring. Otherwise, the somatic development of O3 pups was indistinguishable from that of controls, save for a delay in eye opening; this effect, however, failed to show a significant concentration dependence. Negative results were obtained in a wide range of assessments concerning (i) the development of various reflexes and responses ("Fox battery") from birth to Day 18; (ii) ultrasonic emissions on Postnatal Days 3, 7, and 11; and (iii) activity, habituation, response to an unfamiliar object, and hyperactivity produced by a monoaminergic stimulant (d-amphetamine) at 60-61 days. The present data differ from those of a previous study on rats raised by their biological mothers after gestational exposure to O3 (1 and 1.5 ppm), which showed a substantial impairment in somatic and neurobehavioral development (R. Kavlock, E. Meyer, and C. T. Grabowski, 1980, Toxicol. Lett. 5, 3-9). This difference, be it due to species factors, to postnatal maternal effects, or to the time of occurrence of maximal O3 effects (e.g., on food and water intake) after the onset of exposure and before adaptation or tolerance, may provide significant cues for the understanding of O3 effects in pregnant and developing organisms. PMID:7992316

  10. Statistical methodology to evaluate food exposure to a contaminant and influence of sanitary limits: application to Ochratoxin A.

    PubMed

    Tressou, J; Leblanc, J Ch; Feinberg, M; Bertail, P

    2004-12-01

    This paper presents some statistical methodologies to evaluate the food exposure to a contaminant and quantify the outcome of a new maximum limit on a food item. Our application deals with Ochratoxin A (OTA). We focus on the quantitative evaluation of the distribution of exposure based on both consumption data and contamination data. One specific aspect of contamination data is left censorship due to the limits of detection. Three calculation procedures are proposed: [P1] a deterministic method using means of contamination; [P2] a probabilistic method using a parametric adjustment of the distributions of contamination taking into account the left censorship; and [P3] a non-parametric method which consists in randomly selecting the consumption data and the contamination values. Our main result shows that a non-parametric probabilistic approach is well adapted for the purpose of exposure assessment, when large samples are available. In the application to OTA, the probability to exceed a safe level is high, particularly for children. Simulations show that the impact of the existing standards on cereals and the currently proposed standards on wine generally do not significantly reduce the risk to be overexposed to OTA. PMID:15546679

  11. Trioxolane-Mediated Delivery of Mefloquine Limits Brain Exposure in a Mouse Model of Malaria.

    PubMed

    Lauterwasser, Erica M W; Fontaine, Shaun D; Li, Hao; Gut, Jiri; Katneni, Kasiram; Charman, Susan A; Rosenthal, Philip J; Bogyo, Matthew; Renslo, Adam R

    2015-11-12

    Peroxidic antimalarial agents including the sequiterpene artemisinins and the synthetic 1,2,4-trioxolanes function via initial intraparasitic reduction of an endoperoxide bond. By chemically coupling this reduction to release of a tethered drug species it is possible to confer two distinct pharmacological effects in a parasite-selective fashion, both in vitro and in vivo. Here we demonstrate the trioxolane-mediated delivery of the antimalarial agent mefloquine in a mouse malaria model. Selective partitioning of the trioxolane-mefloquine conjugate in parasitized erythrocytes, combined with effective exclusion of the conjugate from brain significantly reduced brain exposure as compared to mice directly administered mefloquine. These studies suggest the potential of trioxolane-mediated drug delivery to mitigate off-target effects of existing drugs, including the adverse neuropsychiatric effects of mefloquine use in therapeutic and chemoprophylactic settings. PMID:26617969

  12. Tinnitus and Other Auditory Problems Occupational Noise Exposure below Risk Limits May Cause Inner Ear Dysfunction

    PubMed Central

    Lindblad, Ann-Cathrine; Rosenhall, Ulf; Olofsson, ke; Hagerman, Bjrn

    2014-01-01

    The aim of the investigation was to study if dysfunctions associated to the cochlea or its regulatory system can be found, and possibly explain hearing problems in subjects with normal or near-normal audiograms. The design was a prospective study of subjects recruited from the general population. The included subjects were persons with auditory problems who had normal, or near-normal, pure tone hearing thresholds, who could be included in one of three subgroups: teachers, Education; people working with music, Music; and people with moderate or negligible noise exposure, Other. A fourth group included people with poorer pure tone hearing thresholds and a history of severe occupational noise, Industry. Ntotal?=?193. The following hearing tests were used: ? pure tone audiometry with Bksy technique, ? transient evoked otoacoustic emissions and distortion product otoacoustic emissions, without and with contralateral noise; ? psychoacoustical modulation transfer function, ? forward masking, ? speech recognition in noise, ? tinnitus matching. A questionnaire about occupations, noise exposure, stress/anxiety, muscular problems, medication, and heredity, was addressed to the participants. Forward masking results were significantly worse for Education and Industry than for the other groups, possibly associated to the inner hair cell area. Forward masking results were significantly correlated to louder matched tinnitus. For many subjects speech recognition in noise, left ear, did not increase in a normal way when the listening level was increased. Subjects hypersensitive to loud sound had significantly better speech recognition in noise at the lower test level than subjects not hypersensitive. Self-reported stress/anxiety was similar for all groups. In conclusion, hearing dysfunctions were found in subjects with tinnitus and other auditory problems, combined with normal or near-normal pure tone thresholds. The teachers, mostly regarded as a group exposed to noise below risk levels, had dysfunctions almost identical to those of the more exposed Industry group. PMID:24827149

  13. Reassessment of data used in setting exposure limits for hot particles

    SciTech Connect

    Baum, J.W.; Kaurin, D.G.

    1991-05-01

    A critical review and a reassessment of data reviewed in NCRP Report 106 on effects of hot particles'' on the skin of pigs, monkeys, and humans were made. Our analysis of the data of Forbes and Mikhail on effects from activated UC{sub 2} particles, ranging in diameter from 144 {mu}m to 328 {mu}m, led to the formulation of a new model for prediction of both the threshold for acute ulceration and for ulcer diameter. A dose of 27 Gy at a depth of 1.33 mm in tissue in this model will result in an acute ulcer with a diameter determined by the radius over which this dose (at 1.33-mm depth) extends. Application of the model to the Forbes-Mikhail data yielded a threshold'' (5% probability) of 6 {times} 10{sup 9} beta particles from a point source on skin of mixed fission product beta particles, or about 10{sup 10} beta particles from Sr--Y-90, since few of the Sr-90 beta particles reach this depth. The data of Hopewell et al. for their 1 mm Sr-Y-90 exposures were also analyzed with the above model and yielded a predicted threshold of 2 {times} 10{sup 10} Sr-Y-90 beta particles for a point source on skin. Dosimetry values were employed in this latter analysis that are 3.3 times higher than previously reported for this source. An alternate interpretation of the Forbes and Mikhail data, derived from linear plots of the data, is that the threshold depends strongly on particle size with the smaller particles yielding a much lower threshold and smaller minimum size ulcer. Additional animal exposures are planned to distinguish between the above explanations. 17 refs., 3 figs., 3 tabs.

  14. A new limit on the time between the nucleosynthesis and the acceleration of cosmic rays in supernova remnants using the Co/Ni ratio

    NASA Technical Reports Server (NTRS)

    Webber, W. R.; Gupta, M.

    1990-01-01

    Using new cross section measurements of Ni into Co, data on the Co/Ni ratio in cosmic rays from the HEAO C spacecraft have been reinterpreted in terms of the time between nucleosynthesis and the acceleration of cosmic rays, delta t. The observed Co/Ni ratio is now consistent with interstellar fragmentation only, leading to a small or zero source abundance. In terms of the decay of e-process nucleosynthesis nuclides into Co after a supernova explosion, this permits an estimate of delta t = 4-30,000 yr for the time between nucleosynthesis and the acceleration of cosmic rays if supernovae are the direct progenitors of cosmic rays. These age limits are used in conjunction with models of the expansion of supernova remnants (SNRs), to estimate that cosmic rays are accelerated when the radius of these remnants is between 0.1 and 25 pc.

  15. A new limit on the time between the nucleosynthesis and the acceleration of cosmic rays in supernova remnants using the Co/Ni ratio

    SciTech Connect

    Webber, W.R.; Gupta, M. )

    1990-01-01

    Using new cross section measurements of Ni into Co, data on the Co/Ni ratio in cosmic rays from the HEAO C spacecraft have been reinterpreted in terms of the time between nucleosynthesis and the acceleration of cosmic rays, delta t. The observed Co/Ni ratio is now consistent with interstellar fragmentation only, leading to a small or zero source abundance. In terms of the decay of e-process nucleosynthesis nuclides into Co after a supernova explosion, this permits an estimate of delta t = 4-30,000 yr for the time between nucleosynthesis and the acceleration of cosmic rays if supernovae are the direct progenitors of cosmic rays. These age limits are used in conjunction with models of the expansion of supernova remnants (SNRs), to estimate that cosmic rays are accelerated when the radius of these remnants is between 0.1 and 25 pc. 19 refs.

  16. Limited exposure of rats to H(2)SO(4) with and without O3.

    PubMed

    Juhos, L T; Evans, M J; Mussenden-Harvey, R; Furiosi, N J; Lapple, C E; Freeman, G

    1978-01-01

    The purpose of this study was to determine the effects of sulfuric acid (H(2)SO(4)) alone and with ozone (O(3)) on rats. To accomplish this, rats were exposed for 8 hours daily to an atmosphere containing either nebulized H(2)SO(4), H(2)SO(4) plus 0.9 ppm O(3), or 0.9 ppm O(3). The atmosphere in the exposure chambers was maintained at a fairly constant temperature and humidity. Nebulized H(2)SO(4) was delivered uniformly to provide a particle size of about 0.3 micron mass median diameter (MMD) and a mass concentration of 2 mg/m(3). In preliminary experiments, animals exposed to 2 mg/m(3) of H(2)SO(4) daily for 82 days showed very slight morphologic injury to the respiratory tract. In contrast, biological effects were readily demonstrable in rats exposed to H(2)SO(4) plus O(3) or to O(3) alone, possibly with some enhancement of effect in animals exposed to the mixture. The effects observed were characteristic of the response to O(3) alone. PMID:659813

  17. Sub-diffraction-limited multilayer coatings for the 0.3-NA Micro-Exposure Tool for extreme ultraviolet lithography

    SciTech Connect

    Soufli, R; Hudyma, R M; Spiller, E; Gullikson, E M; Schmidt, M A; Robinson, J C; Baker, S L; Walton, C C; Taylor, J S

    2007-01-03

    This manuscript discusses the multilayer coating results for the primary and secondary mirrors of the Micro Exposure Tool (MET): a 0.30-numerical aperture (NA) lithographic imaging system with 200 x 600 {micro}m{sup 2} field of view at the wafer plane, operating in the extreme ultraviolet (EUV) wavelength region. Mo/Si multilayers were deposited by DC-magnetron sputtering on large-area, curved MET camera substrates, and a velocity modulation technique was implemented to consistently achieve multilayer thickness profiles with added figure errors below 0.1 nm rms to achieve sub-diffraction-limited performance. This work represents the first experimental demonstration of sub-diffraction-limited multilayer coatings for high-NA EUV imaging systems.

  18. Accelerated Schools.

    ERIC Educational Resources Information Center

    Hopfenberg, Wendy S.; And Others

    This paper describes the Accelerated Schools Project, which was begun at Stanford University in 1986 to improve schools for children caught in at-risk situations. The first sections describe the present deficiencies of schools serving at-risk students and the limitations of general reform proposals for educating at-risk youth. The Accelerated

  19. Limited Internal Radiation Exposure Associated with Resettlements to a Radiation-Contaminated Homeland after the Fukushima Daiichi Nuclear Disaster

    PubMed Central

    Tsubokura, Masaharu; Kato, Shigeaki; Nihei, Masahiko; Sakuma, Yu; Furutani, Tomoyuki; Uehara, Keisuke; Sugimoto, Amina; Nomura, Shuhei; Hayano, Ryugo; Kami, Masahiro; Watanobe, Hajime; Endo, Yukou

    2013-01-01

    Resettlement to their radiation-contaminated hometown could be an option for people displaced at the time of a nuclear disaster; however, little information is available on the safety implications of these resettlement programs. Kawauchi village, located 1230 km southwest of the Fukushima Daiichi nuclear power plant, was one of the 11 municipalities where mandatory evacuation was ordered by the central government. This village was also the first municipality to organize the return of the villagers. To assess the validity of the Kawauchi villagers resettlement program, the levels of internal Cesium (Cs) exposures were comparatively measured in returnees, commuters, and non-returnees among the Kawauchi villagers using a whole body counter. Of 149 individuals, 5 villagers had traceable levels of Cs exposure; the median detected level was 333 Bq/body (range, 3091050 Bq/kg), and 5.3 Bq/kg (range, 5.118.2 Bq/kg). Median annual effective doses of villagers with traceable Cs were 1.1 x 10-2 mSv/y (range, 1.0 x 10-2-4.1 x 10-2 mSv/y). Although returnees had higher chances of consuming locally produced vegetables, Cochran-Mantel-Haenszel test showed that their level of internal radiation exposure was not significantly higher than that in the other 2 groups (p=0.643). The present findings in Kawauchi village imply that it is possible to maintain internal radiation exposure at very low levels even in a highly radiation-contaminated region at the time of a nuclear disaster. Moreover, the risks for internal radiation exposure could be limited with a strict food control intervention after resettlement to the radiation-contaminated village. It is crucial to establish an adequate number of radio-contaminated testing sites within the village, to provide immediate test result feedback to the villagers, and to provide education regarding the importance of re-testing in reducing the risk of high internal radiation exposure. PMID:24312602

  20. Limited internal radiation exposure associated with resettlements to a radiation-contaminated homeland after the Fukushima Daiichi nuclear disaster.

    PubMed

    Tsubokura, Masaharu; Kato, Shigeaki; Nihei, Masahiko; Sakuma, Yu; Furutani, Tomoyuki; Uehara, Keisuke; Sugimoto, Amina; Nomura, Shuhei; Hayano, Ryugo; Kami, Masahiro; Watanobe, Hajime; Endo, Yukou

    2013-01-01

    Resettlement to their radiation-contaminated hometown could be an option for people displaced at the time of a nuclear disaster; however, little information is available on the safety implications of these resettlement programs. Kawauchi village, located 12-30 km southwest of the Fukushima Daiichi nuclear power plant, was one of the 11 municipalities where mandatory evacuation was ordered by the central government. This village was also the first municipality to organize the return of the villagers. To assess the validity of the Kawauchi villagers' resettlement program, the levels of internal Cesium (Cs) exposures were comparatively measured in returnees, commuters, and non-returnees among the Kawauchi villagers using a whole body counter. Of 149 individuals, 5 villagers had traceable levels of Cs exposure; the median detected level was 333 Bq/body (range, 309-1050 Bq/kg), and 5.3 Bq/kg (range, 5.1-18.2 Bq/kg). Median annual effective doses of villagers with traceable Cs were 1.1 x 10(-2) mSv/y (range, 1.0 x 10(-2)-4.1 x 10(-2) mSv/y). Although returnees had higher chances of consuming locally produced vegetables, Cochran-Mantel-Haenszel test showed that their level of internal radiation exposure was not significantly higher than that in the other 2 groups (p=0.643). The present findings in Kawauchi village imply that it is possible to maintain internal radiation exposure at very low levels even in a highly radiation-contaminated region at the time of a nuclear disaster. Moreover, the risks for internal radiation exposure could be limited with a strict food control intervention after resettlement to the radiation-contaminated village. It is crucial to establish an adequate number of radio-contaminated testing sites within the village, to provide immediate test result feedback to the villagers, and to provide education regarding the importance of re-testing in reducing the risk of high internal radiation exposure. PMID:24312602

  1. [Limits of exposure to magnetic fields and national standards for the safety of the patient during magnetic resonance examination].

    PubMed

    Podo, F

    1994-01-01

    This review summarizes experimental bases, limitations and rationale of guide-lines and recommendations adopted by national health authorities for the safety of patients exposed to the magnetic fields utilized during magnetic resonance (MR) examinations: static magnetic field (B0); time-varying magnetic field gradients (dB/dt) and radiofrequency magnetic fields. Although the mechanisms of interaction of these fields with the living matter are today sufficiently understood to identify the main categories of potentially associated health hazards, epidemiological studies and dosimetric concepts are still far from the levels of definition of protection standards adopted in the field of ionizing radiations. The definition of safety thresholds and levels of exposure to magnetic fields during MR examinations has evolved in the last decade and the matter is still under study today. This article summarizes the main steps in this continuous updating process and discusses limitations and criteria, which recently suggested the adoption in some Countries (including Italy) of a two-tier system for the levels of exposure of patients to the magnetic fields generated by clinical MR equipment. PMID:7832402

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

    PubMed

    Johnson, Christine K; Tinker, Martin T; Estes, James A; Conrad, Patricia A; Staedler, Michelle; Miller, Melissa A; Jessup, David A; Mazet, Jonna A K

    2009-02-17

    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. PMID:19164513

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

    PubMed Central

    Johnson, Christine K.; Tinker, Martin T.; Estes, James A.; Conrad, Patricia A.; Staedler, Michelle; Miller, Melissa A.; Jessup, David A.; Mazet, Jonna 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. PMID:19164513

  4. 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.

  5. 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

  6. 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…

  7. Mutagenicity assessment strategy for pharmaceutical intermediates to aid limit setting for occupational exposure.

    PubMed

    Araya, Selene; Lovsin-Barle, Ester; Glowienke, Susanne

    2015-11-01

    Pharmaceutical intermediates (IM) are used in the synthesis of active pharmaceutical ingredients. They are not intended for human administration, yet employees may be exposed to IM during the manufacturing process. In the context of occupational health, hazard assessment of IM is needed to identify potential intrinsic hazards which could cause unwanted adverse effects. In particular, a carcinogenic potential influences the protection strategy in the workplace. DNA reactive substances may, even if present at very low levels, lead to mutations and therefore, potentially cause cancer. The use of in silico methods to predict mutagenicity is increasingly acknowledged and implemented in the recently released ICH M7 guideline for the limitation of DNA reactive impurities. In this study we investigate the possibility to apply (quantitative) structure-activity-relationships ((Q)SARs) during hazard identification to reduce the number of Ames tests needed for a hazard assessment of IM while maintaining high standards of protection of employees. Ames test outcomes for 188 substances used in the pharmaceutical production were compared with their in silico predictions using two different (Q)SAR methodologies (knowledge based and statistical) complemented by expert knowledge. The results of the analysis showed that a negative prediction for mutagenicity provides a high confidence that the IM is not mutagenic in the Ames test with the negative predictive value of 97%. On the other hand the positive predictive value was only 57% and therefore considered too low to reliably consider positive predicted IM to be mutagenic. In order to avoid any unnecessary burden for occupational health purposes caused by falsely positive predicted IM, all positive predicted IM and those with insufficient coverage by the in silico systems are submitted to an Ames test to verify or reject the prediction. It is shown that the described in silico prediction approach ensures appropriate protection strategy of the employees. Resources for performing Ames tests which do not add additional or new information for the purpose of hazard assessment could be reduced. PMID:26454093

  8. 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

  9. Evaluation of real-time techniques to measure hydrogen peroxide in air at the permissible exposure limit.

    PubMed

    Puskar, M A; Plese, M R

    1996-09-01

    The major occupational concern from bio-decontamination of equipment using vapor phase hydrogen peroxide (VHP) generation systems is potential operator exposure outside the protective barrier from possible VHP leaks or accidental releases from the sealed piece of equipment during decontamination. For this reason, different real time monitoring techniques were evaluated to determine their ability to accurately measure VHP at concentrations ranging from 0.5 ppm to 5 ppm. The results of this laboratory evaluation suggest that two of the four methods evaluated (the ion mobility spectrometer [IMS] and Polytron) will approximate the National Institute for Occupational Safety and Health +/- 25% accuracy requirements for measuring the concentration of VHP at and near the Occupational Safety and Health Administration permissible exposure limit of 1.0 ppm. Over the range of 0.5 ppm to 5.1 ppm VHP, the IMS had an approximate pooled method accuracy of +/- 21%, while the Polytron had a pooled method accuracy of +/- 22%. However, both instruments had false readings when exposed to nominal concentrations of methanol, bleach, and sulfur dioxide. The two additional VHP monitoring techniques evaluated (the single point monitor [SPM] and Draeger tube) were unable to accurately measure the concentration of VHP when the relative humidity was below 20%. PMID:8865593

  10. A STUDY ON VISUAL LIMITATION OF AGE, NUMERICAL SIZE, AND EXPOSURE TIME WHILE USERS OPERATE MOBILE DEVICES.

    PubMed

    Yeh, Po-Chan

    2015-12-01

    Technological advances have driven the development of information technology (IT) products and communication using mobile devices has become a part of daily life. When using mobile devices, reading time and font size are important communication elements that significantly affect reading performance. However, studies of reading performance in older samples have mainly used printed material or computer monitors; this study examined the performance of users when reading text messages on the interfaces of mobile devices and described their visual limitations. Sixty-two participants took part in the experiment, which involved displaying different font sizes and exposure times. The younger group read 10-point font accurately, while the older group had much worse accuracy, even at 14 points. The younger group correctly read text messages displayed for 0.4 sec. above 80% of the time, while the older group's accuracy was severely impaired even when text was displayed for 1 sec. PMID:26654989

  11. Both infection with Pneumocystis and virus-like particle exposure prime pulmonary CD11c+ cells, facilitating accelerated immune responses to influenza

    PubMed Central

    Richert, Laura E.; Rynda-Apple, Agnieszka; Harmsen, Ann L.; Han, Soo; Wiley, James A.; Douglas, Trevor; Larson, Kyle; Morton, Rachelle V.; Harmsen, Allen G.

    2014-01-01

    Summary We show that the intranasal delivery of non-replicative virus-like particles (VLPs), which bear structural, but no antigenic similarities to respiratory pathogens, acted to prime the lungs of mice to facilitate heightened and accelerated primary immune responses to high-dose influenza challenge, thus providing a non-pathogenic model of innate imprinting. These responses corresponded closely to those observed following natural infection with the opportunistic fungus, Pneumocystis murina, and were characterized by accelerated antigen processing by dendritic cells (DCs) and alveolar macrophages (AMs), an enhanced influx of cells to the local tracheobronchial lymph node (TBLN), and early upregulation of T cell co-stimulatory/adhesion molecules. CD11c+ cells (DCs and AMs) which had been directly exposed to VLPs or Pneumocystis were necessary in facilitating the observed enhanced clearance of influenza virus. Furthermore, the repopulation of the lung by Ly-6C+ myeloid precursors relied on the expression of CCR2, and in the absence of efficient CCR2-mediated trafficking, resistance to influenza afforded by VLP- or Pneumocystis-exposure was lost. Thus, immune imprinting 72 hours after VLP-, or 2 weeks after Pneumocystis-priming was CCR2-mediated and resulted from the enhanced antigen processing, maturation, and trafficking abilities of DCs and AMs, which caused accelerated influenza-specific primary immune responses, and resulted in superior viral clearance. PMID:24222381

  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 δ-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/μm), 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/μm) where the biological endpoints are majorly dependent on atomic mass and energy of the ion under consideration.

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

    PubMed

    Horneck, G; Schafer, M; Baltschukat, K; Weisbrod, U; Micke, U; Facius, R; Bucker, H

    1989-01-01

    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 delta-ray dose would be effective. Concerning the space experiment, 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/micrometers), 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/micrometers) where the biological endpoints are majorly dependent on atomic mass and energy of the ion under consideration. PMID:11537282

  14. 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.

  15. 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 Womens Health Initiative Observational Study were analyzed (5079 y; n = 3345). Information on diet, lifestyle behaviors, secondhand smoke, use of dietary supplements and medication, chronic diseases, and anthropometry was collected at baseline (19931998) 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, 475500 vs. 300325 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

  16. Chronic ozone exacerbates the reduction in photosynthesis and acceleration of senescence caused by limited N availability in Nicotiana sylvestris

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Elevated ozone (O3) and limiting soil nitrogen (N) availability both negatively affect crop performance. However, little is known about how the combination of elevated O3 and limiting N affect crop growth and metabolism. In this study, we grew tobacco (Nicotiana sylvestris) in ambient and elevated O...

  17. 250 mSv: temporary increase in the emergency exposure dose limit in response to the TEPCO Fukushima Daiichi NPP accident and its decision making process.

    PubMed

    Yasui, Shojiro

    2015-01-01

    The Great East Japan Earthquake on March 11, 2011, led to an accident at the Fukushima Daiichi Nuclear Power Plant of the Tokyo Electric Power Company (TEPCO). In response to this accident, on March 14, 2011, the Ministry of Health, Labour, and Welfare (MHLW) of Japan enforced an ordinance that temporarily increased the radiation exposure dose limit allowed to 250 mSv during the emergency. This article explains the processes of a) temporarily increasing emergency dose limits, b) controlling for the combined emergency and normal exposure doses, and c) reducing the limit back to 100 mSv. Major issues addressed when deliberating the reduction of the emergency limits includes the following: a) political initiative, b) a phased reduction of dose limits, and c) transitional measures for workers who were exposed to more than 100 mSv. This article also identifies key challenges that need further deliberation to be resolved. These include: a) establishing a pre-defined protocol for applying pre-accident emergency dose limits and/or amending post-accident limits; b) designating the conditions in which to apply or amend emergency dose limits; c) selecting methods of radiation control for individuals who are exposed to more than the normal exposure dose limit during emergency work; and d) designating the conditions under which to terminate or reduce emergency dose limits after the accident. PMID:25436995

  18. 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.

  19. 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.

  20. 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.

  1. Exposure to sediments from polluted rivers has limited phenotypic effects on larvae and adults of Chironomus riparius.

    PubMed

    Arambourou, Hlne; Beisel, Jean-Nicolas; Branchu, Philippe; Debat, Vincent

    2014-06-15

    Laboratory studies have sometimes failed to detect a relationship between toxic stress and morphological defects in invertebrates. Several hypotheses have been proposed to account for this lack of effect. (1) It was suggested that only a combination of stressful conditions - rather than a single one - would affect the phenotype. (2) Phenotypic defects should be detected on adult individuals, rather than on juveniles. (3) Phenotypic abnormalities might mostly affect the progeny of the exposed individuals, some contaminants exhibiting trans-generational effects. In the present study, we test those three hypotheses. We first examined the effects of a multiple exposure by using laboratory Chironomus riparius larvae cultured on two sediments sampled in contaminated rivers and those containing a mixture of mineral and organic compounds. On the larvae, we investigated mentum phenotypes: the frequency of phenodeviants, the shape fluctuating asymmetry and the mean shape. To test whether adult's morphology was more sensitive than the larval's, we also measured asymmetry and mean shape of the adult wings. Finally, to test for a trans-generational phenotypic effect, we measured mentum shape variations in the offspring derived from the measured adults. Overall, our results point out a very limited phenotypic response to contaminated sediments, suggesting that a multiple exposure is not necessarily sufficient to generate phenotypic defects. Adult traits were no more affected than larval traits, discarding the hypothesis that adult phenotypes would be more sensitive biomarkers. Finally, no effect was detected on the offspring generation, suggesting that no trans-generational effect occurs. This general lack of effect suggests that the use of phenotypic defects in C. riparius as an indicator of sediment contamination should be considered cautiously. PMID:24691209

  2. Acute soft tissue neck injury from unexpected acceleration.

    PubMed

    Green, Nicholas D

    2003-10-01

    Recent evidence has identified a risk of neck injury resulting from exposure to high sustained G force during operation of fast jet military aircraft. This review considers the risk of acute soft tissue neck injury when exposure to acceleration is unexpected by the individual. In a military jet, this might occur to a back seat occupant such as an instructor or weapons operator/navigator, but unexpected forces may also be encountered by roller coaster riders and human centrifuge users under certain conditions. The mechanisms of injury in this situation are examined, the effect of acceleration axes (Gx, Gy, and Gz) are considered, and relevant experimental data are evaluated. These data are used to determine what influence the unexpected nature of the acceleration exposure has on the risk of neck injury. Injury below previously established 'tolerance' limits is possible, with some individuals being at risk from unexpected acceleration exposure above around +2 to . PMID:14556572

  3. Postnatal exposure to chromium through mothers milk accelerates follicular atresia in F1 offspring through increased oxidative stress and depletion of antioxidant enzymes

    PubMed Central

    Stanley, Jone A.; Sivakumar, Kirthiram K.; Nithy, Thamizh K.; Arosh, Joe A.; Hoyer, Patricia B.; Burghardt, Robert C.; Banu, Sakhila K.

    2013-01-01

    Hexavalent chromium, CrVI, is a heavy metal endocrine disruptor, known as a mutagen, teratogen, and a group A carcinogen. Environmental contamination with CrVI, including drinking water, has been increasing in more than 30 cities in the United States. CrVI is rapidly converted to CrIII intracellularly, and CrIII can cause DNA strand breaks and cancer or apoptosis through different mechanisms. Our previous study demonstrated that lactational exposure to chromium results in a delay or arrest in follicle development and a decrease in steroid hormone levels in F1 female rats, both of which are mitigated (partial inhibition) by vitamin C. The current study tested the hypothesis that lactational exposure to CrIII accelerates follicle atresia in F1 offspring by increasing reactive oxygen species (ROS) and decreasing cellular antioxidants. Results showed that lactational exposure to CrIII dose-dependently increased follicular atresia and decreased steroidogenesis in postnatal day 25, 45, and 65 rats. Vitamin C mitigated or inhibited the effects of CrIII at all doses. CrIII increased hydrogen peroxide and lipid hydroperoxide in plasma and ovary; decreased the antioxidant enzymes (AOXs) GPx1, GR, SOD, and catalase; and increased glutathione S-transferase in plasma and ovary. To understand the effects of CrVI on ROS and AOXs in granulosa (GC) and theca (TC) cell compartments in the ovary, ROS levels and mRNA expression of cytosolic and mitochondrial AOXs, such as SOD1, SOD2, catalase, GLRX1, GSTM1, GSTM2, GSTA4, GR, TXN1, TXN2, TXNRD2, and PRDX3, were studied in GCs and TCs and in a spontaneously immortalized granulosa cell line (SIGC). Overall, CrVI downregulated each of the AOXs; and vitamin C mitigated the effects of CrVI on these enzymes in GCs and SIGCs, but failed to mitigate CrVI effects on GSTM1, GSTM2, TXN1, and TXN2 in TCs. Thus, these data for the first time reveal that lactational exposure to CrIII accelerated follicular atresia and decreased steroidogenesis in F1 female offspring by altering the ratio of ROS and AOXs in the ovary. Vitamin C is able to protect the ovary from CrIII-induced oxidative stress and follicle atresia through protective effects on GCs rather than TCs. PMID:23470461

  4. In utero exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin causes accelerated terminal differentiation in fetal mouse skin.

    PubMed

    Loertscher, Jennifer A; Lin, Tien-Min; Peterson, Richard E; Allen-Hoffmann, B Lynn

    2002-08-01

    2,3,7,8 Tetrachlorodibenzo-p-dioxin (TCDD), a ubiquitous environmental toxin, has been shown to cause a human skin pathology called chloracne. The majority of laboratory mouse strains, with the exception of mice bearing a mutation in thehairless gene, fail to display overt signs of chloracne upon exposure to TCDD. As a result, only minimal data exist on the effects of TCDD in adult haired mice and no data exist on the effects of TCDD in developing mouse skin. Here we report that TCDD affects the temporal expression of protein markers of keratinocyte terminal differentiation during murine skin morphogenesis. Immunohistochemical analysis of E16 mice reveals accelerated expression of the intermediate filament-associated protein filaggrin in response to TCDD. At a later developmental time and after birth, expression of filaggrin and loricrin is indistinguishable between treatment and control groups. At E16 expression of keratins 5, 6, and 10 are unaltered in TCDD-exposed individuals and TUNEL analysis shows no apoptotic cells in the basal and spinous layers of either treatment or control groups. At E16, immunohistochemical analysis of AhR-null mouse skin reveals accelerated filaggrin expression in both vehicle and TCDD exposed animals. We therefore hypothesize that AhR acts as a modulator of late stage keratinocyte terminal differentiation. PMID:12151643

  5. Exposure-Based CBT for Older Adults After Fall Injury: Description of a Manualized, Time-Limited Intervention for Anxiety

    PubMed Central

    Jayasinghe, Nimali; Sparks, Martha A.; Kato, Kaori; Wilbur, Kaitlyn; Ganz, Sandy B.; Chiaramonte, Gabrielle R.; Stevens, Bradford L.; Barie, Philip S.; Lachs, Mark S.; O’Dell, Michael; Evans, Arthur T.; Bruce, Martha L.; Difede, JoAnn

    2014-01-01

    Fall accidents among older adults can be devastating events that, in addition to their physical consequences, lead to disabling anxiety warranting the attention of mental health practitioners. This article presents “Back on My Feet,” an exposure-based cognitive-behavioral therapy (CBT) protocol that is designed for older adults with posttraumatic stress disorder (PTSD), subthreshold PTSD, or fear of falling resulting from a traumatic fall. The protocol can be integrated into care once patients have been discharged from hospital or rehabilitation settings back to the community. Following a brief description of its development, the article presents a detailed account of the protocol, including patient evaluation and the components of the eight home-based sessions. The protocol addresses core symptoms of avoidance, physiological arousal/anxiety, and maladaptive thought patterns. Because older patients face different coping challenges from younger patients (for whom the majority of evidence-based CBT interventions have been developed), the discussion ends with limitations and special considerations for working with older, injured patients. The article offers a blueprint for mental health practitioners to address the needs of patients who may present with fall-related anxiety in primary care and other medical settings. Readers who wish to develop their expertise further can consult the online appendices, which include a clinician manual and patient workbook, as well as guidance on additional resources. PMID:25364226

  6. Comparison of egg excretion and serum pepsinogen levels as measures of nematode worm burdens in calves with limited pasture exposure.

    PubMed

    Murrell, K D; Leighton, E A; Boswell, B A; Gasbarre, L C

    1989-06-01

    Four- to 6-mo-old calves raised on clean pastures were allowed to graze for about 30 days on pastures naturally contaminated with Ostertagia ostertagi, Cooperia spp., Haemonchus placei, and Nematodirus helvetianus. The calves were then housed on concrete for 3 wk before slaughter. At necropsy the eggs per gram of feces (EPG) and the total worm burdens from the abomasum and small intestine were determined. Blood samples were also obtained for serum pepsinogen (PEP) assays. A total of 44 calves was sampled over 27 mo. Adult worm totals were distributed more normally after logarithmic transformation (LOGTOTAL), and EPG and PEP were distributed more normally after square root transformation (SQRT--EPG; SQRT--PEP). Correlation between LOGTOTAL and either SQRT--EPG or SQRT--PEP was about 0.7. These correlations were higher than those obtained with nontransformed data, suggesting that either EPG or PEP are easily measured variables that explain a significant amount of the variation observed in total worm burdens. Polynomial regression models of a cubic order using the SQRT--EPG accounted for 78% of the variation observed in the LOGTOTAL, whereas SQRT--PEP accounted for 58% of the variance. Within the range of worm burdens observed, these results indicate that EPG has value in estimating total worm burdens of naturally infected calves, and that pepsinogen levels are of less value for analysis of total worm burden in calves with a limited previous exposure to trichostrongyle nematodes. PMID:2723922

  7. Examination of virtual phantoms with respect to their possible use in assessing compliance with the electromagnetic field exposure limits specified by Directive 2013/35/EU.

    PubMed

    Zradziński, Patryk

    2015-01-01

    According to Directive 2013/35/EU, any assessment of hazards associated with exposure to electromagnetic fields (EMF) in the workplace needs an evaluation of quantities characterizing biophysical effects caused inside human bodies by exposure. Such quantities (induced electric field or specific energy absorption rate) may be evaluated by computer simulations in virtual models (phantoms), representing interaction between EMF and the worker's body with respect to modelling the EMF source, the structure of the working environment and the human body. The paper describes the effects of the properties of various virtual phantoms used in recently published studies on various aspects of EMF exposure with respect to their possible involvement in assessing occupational electromagnetic hazards as required by Directive 2013/35/ EU. The parameters of phantoms have been discussed with reference to: dimensions, posture, spatial resolution and electric contact with the ground. Such parameters should be considered and specified, and perhaps also standardized, in order to ensure that the numerical simulations yield reliable results in a compliance analysis against exposure limits or in an exposure assessment for EMF-related epidemiological studies. The outcomes of the presented examination of virtual phantoms used in numerical simulations show that they can be effectively used in the assessment of compliance with the exposure limits specified by Directive 2013/35/EU, but various other factors should be also considered, e.g., the relationship between phantom posture and a realistic exposure situation (flexible phantoms use), limited resolution preventing reliable evaluation of physical estimators of exposure, or a non-realistic area of phantom surface in contact with the ground. PMID:26224490

  8. 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.

  9. Exposure to 56Fe irradiation accelerates normal brain aging and produces deficits in spatial learning and memory

    NASA Astrophysics Data System (ADS)

    Shukitt-Hale, Barbara; Casadesus, Gemma; Carey, Amanda N.; Rabin, Bernard M.; Joseph, James A.

    Previous studies have shown that radiation exposure, particularly to particles of high energy and charge (HZE particles) such as 56Fe, produces deficits in spatial learning and memory. These adverse behavioral effects are similar to those seen in aged animals. It is possible that these shared effects may be produced by the same mechanism. For example, an increased release of reactive oxygen species, and the subsequent oxidative stress and inflammatory damage caused to the central nervous system, is likely responsible for the deficits seen in aging and following irradiation. Therefore, dietary antioxidants, such as those found in fruits and vegetables, could be used as countermeasures to prevent the behavioral changes seen in these conditions. Both aged and irradiated rats display cognitive impairment in tests of spatial learning and memory such as the Morris water maze and the radial arm maze. These rats have decrements in the ability to build spatial representations of the environment, and they utilize non-spatial strategies to solve tasks. Furthermore, they show a lack of spatial preference, due to a decline in the ability to process or retain place (position of a goal with reference to a “map” provided by the configuration of numerous cues in the environment) information. These declines in spatial memory occur in measures dependent on both reference and working memory, and in the flexibility to reset mental images. These results show that irradiation with 56Fe high-energy particles produces age-like decrements in cognitive behavior that may impair the ability of astronauts, particularly middle-aged ones, to perform critical tasks during long-term space travel beyond the magnetosphere.

  10. Non-cancer health risk assessment from exposure to cyanide by resident adults from the mining operations of Bogoso Gold Limited in Ghana.

    PubMed

    Obiri, S; Dodoo, D K; Okai-Sam, F; Essumang, D K

    2006-07-01

    Cyanide is a very toxic chemical that is used to extract gold from its ores. Wastewaters from gold mining companies such as Bogoso Gold Limited (BGL) contain cyanide and other potentially toxic chemicals that have adverse effects on human beings and aquatic organisms. This study was conducted to evaluate the human health risk assessment from exposure to free cyanide via oral and dermal contact of surface/underground water by resident adults within the concession of Bogoso Gold Limited. The chronic non-cancer health risk from exposure to cyanide in River Bogo Upstream is 230 and 43 (by Central Tendency Exposure (CTE) parameters respectively). This means that approximately 230 and 43 resident adults are likely to suffer diseases related to cyanide intoxication via oral and dermal contact respectively. For chronic exposure to River Bogo Downstream by resident adults, the non-cancer health risks are: 0.031 and 0.57 via oral and dermal contact for CTE parameters respectively, which also means that, the non-cancer health risks associated with cyanide intoxication is negligible as the hazard index is less than 1.0 via oral and dermal contacts respectively. The results showed that health risk for acute exposure to cyanide by the resident adults is very high. Hence the residents attribute most of the unexplained deaths in the communities to accidental ingestion and dermal contact of cyanide water. PMID:16897533

  11. 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

  12. Long-term perchloroethylene exposure: a limited meta-analysis of neurobehavorial deficits in occupationally and residentially exposed groups

    EPA Science Inventory

    The literature concerning the neurobehavioral and neurophysiological effects of long-term exposure to perchloroethylene (PERC) in humans was meta-analyzed to provide a quantitative review and synthesis. The useable data base from this literature comprised studies reporting effec...

  13. Price To Be Paid for Two-Metal Catalysis: Magnesium Ions That Accelerate Chemistry Unavoidably Limit Product Release from a Protein Kinase

    SciTech Connect

    Jacobsen, Douglas M.; Bao, Zhao-Qin; O'?Brien, Patrick; Brooks, Charles L.; Young, Matthew A.

    2012-08-14

    Incorporation of divalent metal ions into an active site is a fundamental catalytic tool used by diverse enzymes. Divalent cations are used by protein kinases to both stabilize ATP binding and accelerate chemistry. Kinetic analysis establishes that Cyclin-dependent kinase 2 (CDK2) requires simultaneous binding of two Mg2+ ions for catalysis of phosphoryl transfer. This tool, however, comes with a price: the rate-acceleration effects are opposed by an unavoidable rate-limiting consequence of the use of two Mg2+ ions by CDK2. The essential metal ions stabilize ADP product binding and limit the overall rate of the reaction. We demonstrate that product release is rate limiting for activated CDK2 and evaluate the effects of the two catalytically essential Mg2+ ions on the stability of the ADP product within the active site. We present two new crystal structures of CDK2 bound to ADP showing how the phosphate groups can be coordinated by either one or two Mg2+ ions, with the occupancy of one site in a weaker equilibrium. Molecular dynamics simulations indicate that ADP phosphate mobility is more restricted when ADP is coordinated by two Mg2+ ions compared to one. The structural similarity between the rigid ADP2Mg product and the cooperatively assembled transition state provides a mechanistic rational for the rate-limiting ADP release that is observed. We demonstrate that although the simultaneous binding of two Mg2+ ions is essential for efficient phosphoryl transfer, the presence of both Mg2+ ions in the active site also cooperatively increases ADP affinity and opposes its release. Evolution of protein kinases must have involved careful tuning of the affinity for the second Mg2+ ion in order to balance the needs to stabilize the chemical transition state and allow timely product release. The link between Mg2+ site affinity and activity presents a chemical handle that may be used by regulatory factors as well as explain some mutational effects.

  14. Quantification of print, radio and television exposure among previous blood donors in Kenya: an opportunity for encouraging repeat donation in a resource-limited setting?

    PubMed

    Basavaraju, S V; Mwangi, J; Kellogg, T A; Odawo, L; Marum, L H

    2010-10-01

    Blood services in sub-Saharan Africa experience blood shortages and low retention of voluntary, non-remunerated donors. To boost collections by encouraging repeat donations, the Kenya National Blood Transfusion Service is exploring the likelihood of reaching previous donors through targeted print, radio and television advertising. We analysed data from a national AIDS Indicator Survey to determine whether previous donors have significant exposure to media. Respondents reporting history of blood donation had significantly higher exposure to print, radio and television media than those without history of blood donation. Targeted media campaigns encouraging repeat donation are likely to reach previous donors even in resource-limited settings. PMID:20598106

  15. The Biological Effectiveness of Accelerated Particles for the Induction of Chromosome Damage: Track Structure Effects and Cytogenetic Signatures of High-LET Exposure

    NASA Technical Reports Server (NTRS)

    George, K.; Hada, M.; Chappell, L.; Cucinotta, F. A.

    2012-01-01

    Track structure models predict that at a fixed value of LET, particles with lower charge number, Z will have a higher biological effectiveness compared to particles with a higher Z. In this report we investigated how track structure effects induction of chromosomal aberration in human cells. Human lymphocytes were irradiated in vitro with various energies of accelerated iron, silicon, neon, or titanium ions and chromosome damage was assessed in using three color FISH chromosome painting in chemically induced PCC samples collected a first cell division post irradiation. The LET values for these ions ranged from 30 to 195 keV/micrometers. Of the particles studied, Neon ions have the highest biological effectiveness for induction of total chromosome damage, which is consistent with track structure model predictions. For complex-type exchanges 64 MeV/ u Neon and 450 MeV/u Iron were equally effective and induced the most complex damage. In addition we present data on chromosomes exchanges induced by six different energies of protons (5 MeV/u to 2.5 GeV/u). The linear dose response term was similar for all energies of protons suggesting that the effect of the higher LET at low proton energies is balanced by the production of nuclear secondaries from the high energy protons. All energies of protons have a much higher percentage of complex-type chromosome exchanges than gamma rays, signifying a cytogenetic signature for proton exposures.

  16. Low-dose neutron dose response of zebrafish embryos obtained from the Neutron exposure Accelerator System for Biological Effect Experiments (NASBEE) facility

    NASA Astrophysics Data System (ADS)

    Ng, C. Y. P.; Kong, E. Y.; Konishi, T.; Kobayashi, A.; Suya, N.; Cheng, S. H.; Yu, K. N.

    2015-09-01

    The dose response of embryos of the zebrafish, Danio rerio, irradiated at 5 h post fertilization (hpf) by 2-MeV neutrons with ≤100 mGy was determined. The neutron irradiations were made at the Neutron exposure Accelerator System for Biological Effect Experiments (NASBEE) facility in the National Institute of Radiological Sciences (NIRS), Chiba, Japan. A total of 10 neutron doses ranging from 0.6 to 100 mGy were employed (with a gamma-ray contribution of 14% to the total dose), and the biological effects were studied through quantification of apoptosis at 25 hpf. The responses for neutron doses of 10, 20, 25, and 50 mGy approximately fitted on a straight line, while those for neutron doses of 0.6, 1 and 2.5 mGy exhibited neutron hormetic effects. As such, hormetic responses were generically developed by different kinds of ionizing radiations with different linear energy transfer (LET) values. The responses for neutron doses of 70 and 100 mGy were significantly below the lower 95% confidence band of the best-fit line, which strongly suggested the presence of gamma-ray hormesis.

  17. Early Liver and Kidney Dysfunction Associated with Occupational Exposure to Sub-Threshold Limit Value Levels of Benzene, Toluene, and Xylenes in Unleaded Petrol

    PubMed Central

    Neghab, Masoud; Hosseinzadeh, Kiamars; Hassanzadeh, Jafar

    2015-01-01

    Background Unleaded petrol contains significant amounts of monocyclic aromatic hydrocarbons such as benzene, toluene, and xylenes (BTX). Toxic responses following occupational exposure to unleaded petrol have been evaluated only in limited studies. The main purpose of this study was to ascertain whether (or not) exposure to unleaded petrol, under normal working conditions, is associated with any hepatotoxic or nephrotoxic response. Methods This was a cross-sectional study in which 200 employees of Shiraz petrol stations with current exposure to unleaded petrol, as well as 200 unexposed employees, were investigated. Atmospheric concentrations of BTX were measured using standard methods. Additionally, urine and fasting blood samples were taken from individuals for urinalysis and routine biochemical tests of kidney and liver function. Results The geometric means of airborne concentrations of BTX were found to be 0.8 mg m−3, 1.4 mg m−3, and 2.8 mg m−3, respectively. Additionally, means of direct bilirubin, alanine aminotransferase, aspartate aminotransferase, blood urea and plasma creatinine were significantly higher in exposed individuals than in unexposed employees. Conversely, serum albumin, total protein, and serum concentrations of calcium and sodium were significantly lower in petrol station workers than in their unexposed counterparts. Conclusion The average exposure of petrol station workers to BTX did not exceed the current threshold limit values (TLVs) for these chemicals. However, evidence of subtle, subclinical and prepathologic early liver and kidney dysfunction was evident in exposed individuals. PMID:26929843

  18. 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/day750 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

  19. Temporary Blinding Limits versus Maximum Permissible Exposure - A Paradigm Change in Risk Assessment for Visible Optical Radiation

    NASA Astrophysics Data System (ADS)

    Reidenbach, Hans-Dieter

    Safety considerations in the field of laser radiation have traditionally been restricted to maximum permissible exposure levels defined as a function of wavelength and exposure duration. But in Europe according to the European Directive 2006/25/EC on artificial optical radiation the employer has to include in his risk assessment indirect effects from temporary blinding. Whereas sufficient knowledge on various deterministic risks exists, only sparse quantitative data is available for the impairment of visual functions due to temporary blinding from visible optical radiation. The consideration of indirect effects corresponds to a paradigm change in risk assessment when situations have to be treated, where intrabeam viewing of low-power laser radiation is likely or other non-coherent visible radiation might influence certain visual tasks. In order to obtain a sufficient basis for the assessment of certain situations, investigations of the functional relationships between wavelength, exposure time and optical power and the resulting interference on visual functions have been performed and the results are reported. The duration of a visual disturbance is thus predictable. In addition, preliminary information on protective measures is given.

  20. Cytotoxicity testing of materials with limited in vivo exposure is affected by the duration of cell-material contact.

    PubMed

    Ciapetti, G; Granchi, D; Stea, S; Savarino, L; Verri, E; Gori, A; Savioli, F; Montanaro, L

    1998-12-15

    Silicones for dental impression largely are used to record the geometry of hard and soft dental tissues. They are considered to be medical devices, and the assessment of cytotoxicity is a necessary step in the evaluation of their biocompatibility. Extracts of six addition-type and six condensation-type silicones have been tested with L929 cells according to the ISO 10993-Part 5 standard. The cytotoxicity was evaluated by three different methods: neutral red uptake, propidium iodide (PI) staining, and amido black staining. According to the selected specific assay, contact between cells and material extracts was maintained for 24 h in the first series of experiments; then, considering that in vivo application of these materials is restricted to a few minutes, additional experiments were performed after 1 h of cell/extract contact. Analysis of the results showed that the addition-type silicones are nontoxic even when tested after prolonged exposure of the cells to the materials while the condensation-type silicones were cytotoxic at 24 h of incubation. Nevertheless, harm to the patient actually could be negligible, considering its very short time of exposure in vivo. This is supported by our finding that most are not toxic after 1 h. We suggest that the experimental conditions of cytotoxicity testing have to be relevant to the in vivo situation; accordingly, the time of exposure should be designed carefully. PMID:9827670

  1. Recovery of NMDA receptor currents from MK-801 blockade is accelerated by Mg2+ and memantine under conditions of agonist exposure

    PubMed Central

    McKay, Sean; Bengtson, C. Peter; Bading, Hilmar; Wyllie, David J.A.; Hardingham, Giles E.

    2013-01-01

    MK-801 is a use-dependent NMDA receptor open channel blocker with a very slow off-rate. These properties can be exploited to pre-block a population of NMDARs, such as synaptic ones, enabling the selective activation of a different population, such as extrasynaptic NMDARs. However, the usefulness of this approach is dependent on the stability of MK-801 blockade after washout. We have revisited this issue, and confirm that recovery of NMDAR currents from MK-801 blockade is enhanced by channel opening by NMDA, and find that it is further increased when Mg2+ is also present. In the presence of Mg2+, 50% recovery from MK-801 blockade is achieved after 10? of 100?M NMDA, or 30? of 15?M NMDA exposure. In Mg2+-free medium, NMDA-induced MK-801 dissociation was found to be much slower. Memantine, another PCP-site antagonist, could substitute for Mg2+ in accelerating the unblock of MK-801 in the presence of NMDA. This suggests a model whereby, upon dissociation from its binding site in the pore, MK-801 is able to re-bind in a process antagonized by Mg2+ or another PCP-site antagonist. Finally we show that even when all NMDARs are pre-blocked by MK-801, incubation of neurons with 100?M NMDA in the presence of Mg2+ for 2.5h triggers sufficient unblocking to kill >80% of neurons. We conclude that while synaptic MK-801 pre-block protocols are useful for pharmacologically assessing synaptic vs. extrasynaptic contributions to NMDAR currents, or studying short-term effects, it is problematic to use this technique to attempt to study the effects of long-term selective extrasynaptic NMDAR activation. This article is part of the Special Issue entitled Glutamate Receptor-Dependent Synaptic Plasticity. PMID:23402996

  2. 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; Mcnaughton, Michael W

    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.

  3. Acceleration of the Rate-Limiting Step of Thioredoxin Folding by Replacement of its Conserved cis-Proline with (4?S)-Fluoroproline.

    PubMed

    Roderer, Daniel; Glockshuber, Rudi; Rubini, Marina

    2015-10-12

    The incorporation of the non-natural amino acids (4R)- and (4S)-fluoroproline (Flp) has been successfully used to improve protein stability, but little is known about their effect on protein folding kinetics. Here we analyzed the influence of (4R)- and (4S)-Flp on the rate-limiting trans-to-cis isomerization of the Ile75-Pro76 peptide bond in the folding of Escherichia coli thioredoxin (Trx). While (4R)-Flp at position 76 had essentially no effect on the isomerization rate in the context of the intact tertiary structure, (4S)-Flp accelerated the folding reaction ninefold. Similarly, tenfold faster trans-to-cis isomerization of Ile75-(4S)-Flp76 relative to Ile75-Pro76 was observed in the unfolded state of Trx. Our results show that the replacement of cis prolines by non-natural proline analogues can be used for modulating the folding rates of proteins with cis prolyl-peptide bonds in the native state. PMID:26382254

  4. Theoretical assessment of the maximum obtainable power in wireless power transfer constrained by human body exposure limits in a typical room scenario.

    TOXLINE Toxicology Bibliographic Information

    Chen XL; De Santis V; Umenei AE

    2014-07-07

    In this study, the maximum received power obtainable through wireless power transfer (WPT) by a small receiver (Rx) coil from a relatively large transmitter (Tx) coil is numerically estimated in the frequency range from 100 kHz to 10 MHz based on human body exposure limits. Analytical calculations were first conducted to determine the worst-case coupling between a homogeneous cylindrical phantom with a radius of 0.65 m and a Tx coil positioned 0.1 m away with the radius ranging from 0.25 to 2.5 m. Subsequently, three high-resolution anatomical models were employed to compute the peak induced field intensities with respect to various Tx coil locations and dimensions. Based on the computational results, scaling factors which correlate the cylindrical phantom and anatomical model results were derived. Next, the optimal operating frequency, at which the highest transmitter source power can be utilized without exceeding the exposure limits, is found to be around 2 MHz. Finally, a formulation is proposed to estimate the maximum obtainable power of WPT in a typical room scenario while adhering to the human body exposure compliance mandates.

  5. Theoretical assessment of the maximum obtainable power in wireless power transfer constrained by human body exposure limits in a typical room scenario.

    PubMed

    Chen, Xi Lin; De Santis, Valerio; Umenei, Aghuinyue Esai

    2014-07-01

    In this study, the maximum received power obtainable through wireless power transfer (WPT) by a small receiver (Rx) coil from a relatively large transmitter (Tx) coil is numerically estimated in the frequency range from 100 kHz to 10 MHz based on human body exposure limits. Analytical calculations were first conducted to determine the worst-case coupling between a homogeneous cylindrical phantom with a radius of 0.65 m and a Tx coil positioned 0.1 m away with the radius ranging from 0.25 to 2.5 m. Subsequently, three high-resolution anatomical models were employed to compute the peak induced field intensities with respect to various Tx coil locations and dimensions. Based on the computational results, scaling factors which correlate the cylindrical phantom and anatomical model results were derived. Next, the optimal operating frequency, at which the highest transmitter source power can be utilized without exceeding the exposure limits, is found to be around 2 MHz. Finally, a formulation is proposed to estimate the maximum obtainable power of WPT in a typical room scenario while adhering to the human body exposure compliance mandates. PMID:24889372

  6. Theoretical assessment of the maximum obtainable power in wireless power transfer constrained by human body exposure limits in a typical room scenario

    NASA Astrophysics Data System (ADS)

    Chen, Xi Lin; De Santis, Valerio; Esai Umenei, Aghuinyue

    2014-07-01

    In this study, the maximum received power obtainable through wireless power transfer (WPT) by a small receiver (Rx) coil from a relatively large transmitter (Tx) coil is numerically estimated in the frequency range from 100 kHz to 10 MHz based on human body exposure limits. Analytical calculations were first conducted to determine the worst-case coupling between a homogeneous cylindrical phantom with a radius of 0.65 m and a Tx coil positioned 0.1 m away with the radius ranging from 0.25 to 2.5 m. Subsequently, three high-resolution anatomical models were employed to compute the peak induced field intensities with respect to various Tx coil locations and dimensions. Based on the computational results, scaling factors which correlate the cylindrical phantom and anatomical model results were derived. Next, the optimal operating frequency, at which the highest transmitter source power can be utilized without exceeding the exposure limits, is found to be around 2 MHz. Finally, a formulation is proposed to estimate the maximum obtainable power of WPT in a typical room scenario while adhering to the human body exposure compliance mandates.

  7. Playback Experiments for Noise Exposure.

    PubMed

    Holles, Sophie; Simpson, Stephen D; Lecchini, David; Radford, Andrew N

    2016-01-01

    Playbacks are a useful tool for conducting well-controlled and replicated experiments on the effects of anthropogenic noise, particularly for repeated exposures. However, playbacks are unlikely to fully reproduce original sources of anthropogenic noise. Here we examined the sound pressure and particle acceleration of boat noise playbacks in a field experiment and reveal that although there remain recognized limitations, the signal-to-noise ratios of boat playbacks to ambient noise do not exceed those of a real boat. The experimental setup tested is therefore of value for use in experiments on the effects of repeated exposure of aquatic animals to boat noise. PMID:26610992

  8. [Norms and standards for radiofrequency electromagnetic fields in Latin America: guidelines for exposure limits and measurement protocols].

    PubMed

    Skvarca, Jorge; Aguirre, Anbal

    2006-01-01

    New technologies that use electromagnetic fields (EMF) have proved greatly beneficial to humankind. EMF are used in a variety of ways in the transmission of electrical energy and in telecommunications, industry, and medicine. However, some studies have shown that EMF could be detrimental to one's health, having found an association between exposure to EMF on the one hand, and the incidence of some types of cancer as well as behavioral changes on the other. Although so far there is no concrete proof that exposure to low-intensity EMF is hazardous, researchers continue to study the issue in an attempt to reach a consensus opinion and to establish safety standards. While developing and establishing such norms and standards have traditionally been the responsibility of international specialized agencies, national health authorities should take an active part in this process. Currently the Pan American Health Organization is promoting scientific research, often in the form of epidemiologic studies, in order to propose uniform norms and standards. Some Latin American countries, including Argentina, Brazil, Chile, Colombia, Costa Rica, Ecuador, Mexico, Peru, and Venezuela, have already enacted incomplete or partial legislation based on recommended international standards. This article describes the norms established in Latin America and the particular approach taken by each country. PMID:17199914

  9. Limiting human exposures through the ``as low as reasonably achievable`` process at a Department of Energy mixed waste site

    SciTech Connect

    MacDonell, M.; Peterson, J.; Haroun, L.; Blunt, D.; Dunning, D.

    1994-09-01

    Applying a process to reduce human exposures to levels as low as reasonably achievable (ALARA) is a cornerstone of the US Department of Energy`s radiation protection program, and this process is being used to develop cleanup levels for contaminated sites across the country. Under the ALARA process, exposures and risks are reduced as far below protective criteria as can reasonably be achieved--considering technical, economic, and social factors. Risk-based cleanup levels have been developed for radionuclides and chemicals in surface water and soil at the Weldon Spring site in Missouri, following explicit applications of the ALARA process. Among the lessons learned during these applications were the importance of three factors: (1) soliciting early input from the parties involved--because the ALARA process involves a range of technical and nontechnical issues; (2) maintaining site specificity for the ALARA analyses--because contaminant types and distributions will vary, as will local conditions and constraints; and (3) identifying cleanup levels in the planning phase that are distinct from those developed for the field phase--because remedies can be over-designed if the decision levels are the same as the ALARA goals for field work, such that little increased risk reduction is achieved for substantially higher costs.

  10. 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

  11. In vivo comparison of epithelial responses for S-8 versus JP-8 jet fuels below permissible exposure limit.

    PubMed

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

    2008-12-01

    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 53mg/m(3) for 1h/day for 7 days. A pulmonary function test performed 24h 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

  12. Chronic acceleration and brain density

    NASA Technical Reports Server (NTRS)

    Hoffman, L. F.; Smith, A. H.

    1982-01-01

    Tests carried out on rabbits show that the effect of chronic acceleration is not uniform among the various tissues studied. Although body mass is reduced by the treatment, as expected, no change is apparent in brain mass or in the density of cerebrospinal fluid. Acceleration-induced changes are encountered in tissue density, the myocardium exhibiting a transient increase followed by an exponential decrease toward a limit and the brain showing an arithmetic increase in density with continued exposure to 2.5 G. The data are seen as suggesting that a specific brain load is not a regulated phenomenon and that no physiological processes occur to attenuate the increased load imposed by the hyperdynamic environment. An equation is derived indicating that the stimulus potential per unit of brain load increases with body size, even though brain density decreases and cerebrospinal fluid density increases.

  13. 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.

  14. Linear Accelerators

    SciTech Connect

    Sidorin, Anatoly

    2010-01-05

    In linear accelerators the particles are accelerated by either electrostatic fields or oscillating Radio Frequency (RF) fields. Accordingly the linear accelerators are divided in three large groups: electrostatic, induction and RF accelerators. Overview of the different types of accelerators is given. Stability of longitudinal and transverse motion in the RF linear accelerators is briefly discussed. The methods of beam focusing in linacs are described.

  15. Linear Accelerators

    NASA Astrophysics Data System (ADS)

    Sidorin, Anatoly

    2010-01-01

    In linear accelerators the particles are accelerated by either electrostatic fields or oscillating Radio Frequency (RF) fields. Accordingly the linear accelerators are divided in three large groups: electrostatic, induction and RF accelerators. Overview of the different types of accelerators is given. Stability of longitudinal and transverse motion in the RF linear accelerators is briefly discussed. The methods of beam focusing in linacs are described.

  16. 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.

  17. Tolerance of ARPE 19 cells to organophosphorus pesticide chlorpyrifos is limited to concentration and time of exposure.

    PubMed

    Gomathy, Narayanan; Sumantran, Venil N; Shabna, A; Sulochana, K N

    2015-01-01

    Age related macular degeneration is a blinding disease common in elder adults. The prevalence of age related macular degeneration has been found to be 1.8% in the Indian population. Organophosphates are widely used insecticides with well documented neurological effects, and the persistent nature of these compounds in the body results in long term health effects. Farmers exposed to organophosphorus pesticides in USA had an earlier onset of age related macular degeneration when compared to unexposed controls. A recent study found significant levels of an organophosphate, termed chlorpyrifos, in the blood samples of Indian farmers. Therefore, in understanding the link between age related macular degeneration and chlorpyrifos, the need for investigation is important. Our data show that ARPE-19 (retinal pigment epithelial cells) exhibit a cytoprotective response to chlorpyrifos as measured by viability, mitochondrial membrane potential, superoxide dismutase activity, and increased levels of glutathione peroxidase and reduced glutathione, after 24 h exposure to chlorpyrifos. However, this cytoprotective response was absent in ARPE-19 cells exposed to the same range of concentrations of chlorpyrifos for 48 h. These results have physiological significance, since HPLC analysis showed that effects of chlorpyrifos were mediated through its entry into ARPE-19 cells. HPLC analysis also showed that chlorpyrifos remained stable, as we recovered up to 80% of the chlorpyrifos added to 6 different ocular tissues. PMID:25619908

  18. Modeling the effects of a speed limit reduction on traffic-related elemental carbon (EC) concentrations and population exposure to EC

    NASA Astrophysics Data System (ADS)

    Lefebvre, W.; Fierens, F.; Trimpeneers, E.; Janssen, S.; Van de Vel, K.; Deutsch, F.; Viaene, P.; Vankerkom, J.; Dumont, G.; Vanpoucke, C.; Mensink, C.; Peelaerts, W.; Vliegen, J.

    2011-01-01

    Despite the scarce effect of speed limit reduction measures on total mass PM 10 and PM 2.5 concentrations, it is shown that the effect on the probably more hazardous component elemental carbon (EC) is more important which means that, from the viewpoint of health benefit, speed reductions during smog episodes may well be justified. Especially in the very dense highway network in Flanders with a 60% share of diesel cars (the highest in Europe) a speed limit reduction from 120 to 90 km/h during winter smog episodes on selected sections of Flemish highways leads to a significant decrease of the EC concentrations near those highways. Key findings are that the decrease in EC depends on the distance from the highways. In the direct vicinity of the highways, a decrease compared to the base-line scenario where no speed limit changes were implemented of up to 30% of the EC concentrations is modeled. Within a distance of 1500 m of the concerned highway sections there is an average decrease in EC of 0.18 μg m -3 affecting about 1 million people living in these areas. When the speed limit reduction measure is in force, the EC exposure of about 300,000 people decreases by at least 5% and 7500 people experience a decrease of 15% or more.

  19. Phase 2 Study of Accelerated Hypofractionated Thoracic Radiation Therapy and Concurrent Chemotherapy in Patients With Limited-Stage Small-Cell Lung Cancer

    SciTech Connect

    Xia, Bing; Hong, Ling-Zhi; Cai, Xu-Wei; Zhu, Zheng-Fei; Liu, Qi; Zhao, Kuai-Le; Fan, Min; Mao, Jing-Fang; Yang, Huan-Jun; Wu, Kai-Liang; Fu, Xiao-Long

    2015-03-01

    Purpose: To prospectively investigate the efficacy and toxicity of accelerated hypofractionated thoracic radiation therapy (HypoTRT) combined with concurrent chemotherapy in the treatment of limited-stage small-cell lung cancer (LS-SCLC), with the hypothesis that both high radiation dose and short radiation time are important in this setting. Methods and Materials: Patients with previously untreated LS-SCLC, Eastern Cooperative Oncology Group performance status of 0 to 2, and adequate organ function were eligible. HypoTRT of 55 Gy at 2.5 Gy per fraction over 30 days was given on the first day of the second or third cycle of chemotherapy. An etoposide/cisplatin regimen was given to 4 to 6 cycles. Patients who had a good response to initial treatment were offered prophylactic cranial irradiation. The primary endpoint was the 2-year progression-free survival rate. Results: Fifty-nine patients were enrolled from July 2007 through February 2012 (median age, 58 years; 86% male). The 2-year progression-free survival rate was 49.0% (95% confidence interval [CI] 35.3%-62.7%). Median survival time was 28.5 months (95% CI 9.0-48.0 months); the 2-year overall survival rate was 58.2% (95% CI 44.5%-71.9%). The 2-year local control rate was 76.4% (95% CI 63.7%-89.1%). The severe hematologic toxicities (grade 3 or 4) were leukopenia (32%), neutropenia (25%), and thrombocytopenia (15%). Acute esophagitis and pneumonitis of grade ≥3 occurred in 25% and 10% of the patients, respectively. Thirty-eight patients (64%) received prophylactic cranial irradiation. Conclusion: Our study showed that HypoTRT of 55 Gy at 2.5 Gy per fraction daily concurrently with etoposide/cisplatin chemotherapy has favorable survival and acceptable toxicity. This radiation schedule deserves further investigation in LS-SCLC.

  20. Cadmium exposure and sulfate limitation reveal differences in the transcriptional control of three sulfate transporter (Sultr1;2) genes in Brassica juncea

    PubMed Central

    2014-01-01

    Background Cadmium (Cd) exposure and sulfate limitation induce root sulfate uptake to meet the metabolic demand for reduced sulfur. Although these responses are well studied, some aspects are still an object of debate, since little is known about the molecular mechanisms by which changes in sulfate availability and sulfur metabolic demand are perceived and transduced into changes in the expression of the high-affinity sulfate transporters of the roots. The analysis of the natural variation occurring in species with complex and highly redundant genome could provide precious information to better understand the topic, because of the possible retention of mutations in the sulfate transporter genes. Results The analysis of plant sulfur nutritional status and root sulfate uptake performed on plants of Brassica juncea – a naturally occurring allotetraploid species – grown either under Cd exposure or sulfate limitation showed that both these conditions increased root sulfate uptake capacity but they caused quite dissimilar nutritional states, as indicated by changes in the levels of nonprotein thiols, glutathione and sulfate of both roots and shoots. Such behaviors were related to the general accumulation of the transcripts of the transporters involved in root sulfate uptake (BjSultr1;1 and BjSultr1;2). However, a deeper analysis of the expression patterns of three redundant, fully functional, and simultaneously expressed Sultr1;2 forms (BjSultr1;2a, BjSultr1;2b, BjSultr1;2c) revealed that sulfate limitation induced the expression of all the variants, whilst BjSultr1;2b and BjSultr1;2c only seemed to have the capacity to respond to Cd. Conclusions A novel method to estimate the apparent kM for sulfate, avoiding the use of radiotracers, revealed that BjSultr1;1 and BjSultr1;2a/b/c are fully functional high-affinity sulfate transporters. The different behavior of the three BjSultr1;2 variants following Cd exposure or sulfate limitation suggests the existence of at least two distinct signal transduction pathways controlling root sulfate uptake in dissimilar nutritional and metabolic states. PMID:24884748

  1. Multigenerational exposure to ocean acidification during food limitation reveals consequences for copepod scope for growth and vital rates.

    PubMed

    Pedersen, Sindre A; Hkedal, Ole Jacob; Salaberria, Iurgi; Tagliati, Alice; Gustavson, Liv Marie; Jenssen, Bjrn Munro; Olsen, Anders J; Altin, Dag

    2014-10-21

    The copepod Calanus finmarchicus is a key component of northern Atlantic food webs, linking energy-transfer from phytoplankton to higher trophic levels. We examined the effect of different ocean acidification (OA) scenarios (i.e., ambient, 1080, 2080, and 3080 ?atm CO2) over two subsequent generations under limited food availability. Determination of metabolic and feeding rates, and estimations of the scope for growth, suggests that negative effects observed on vital rates (ontogenetic development, somatic growth, fecundity) may be a consequence of energy budget constraints due to higher maintenance costs under high pCO2-environments. A significant delay in development rate among the parental generation animals exposed to 2080 ?atm CO2, but not in the following F1 generation under the same conditions, suggests that C. finmarchicus may have adaptive potential to withstand the direct long-term effects of even the more pessimistic future OA scenarios but underlines the importance of transgenerational experiments. The results also indicate that in a more acidic ocean, increased energy expenditure through rising respiration could lower the energy transfer to higher trophic levels and thus hamper the productivity of the northern Atlantic ecosystem. PMID:25225957

  2. Dietary supplementation with n-3 fatty acids from weaning limits brain biochemistry and behavioural changes elicited by prenatal exposure to maternal inflammation in the mouse model.

    PubMed

    Li, Q; Leung, Y O; Zhou, I; Ho, L C; Kong, W; Basil, P; Wei, R; Lam, S; Zhang, X; Law, A C K; Chua, S E; Sham, P C; Wu, E X; McAlonan, G M

    2015-01-01

    Prenatal exposure to maternal immune activation (MIA) increases the risk of schizophrenia and autism in the offspring. The MIA rodent model provides a valuable tool to directly test the postnatal consequences of exposure to an early inflammatory insult; and examine novel preventative strategies. Here we tested the hypotheses that behavioural differences in the MIA mouse model are accompanied by in vivo and ex vivo alterations in brain biochemistry; and that these can be prevented by a post-weaning diet enriched with n-3 polyunsaturated fatty acid (PUFA). The viral analogue PolyI:C (POL) or saline (SAL) was administered to pregnant mice on gestation day 9. Half the resulting male offspring (POL=21; SAL=17) were weaned onto a conventional lab diet (n-6 PUFA); half were weaned onto n-3 PUFA-enriched diet. In vivo magnetic resonance spectroscopy measures were acquired prior to behavioural tests; glutamic acid decarboxylase 67 (GAD67) and tyrosine hydroxylase protein levels were measured ex vivo. The main findings were: (i) Adult MIA-exposed mice fed a standard diet had greater N-acetylaspartate/creatine (Cr) and lower myo-inositol/Cr levels in the cingulate cortex in vivo. (ii) The extent of these metabolite differences was correlated with impairment in prepulse inhibition. (iii) MIA-exposed mice on the control diet also had higher levels of anxiety and altered levels of GAD67 ex vivo. (iv) An n-3 PUFA diet prevented all the in vivo and ex vivo effects of MIA observed. Thus, n-3 PUFA dietary enrichment from early life may offer a relatively safe and non-toxic approach to limit the otherwise persistent behavioural and biochemical consequences of prenatal exposure to inflammation. This result may have translational importance. PMID:26393487

  3. 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.

  4. 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.

  5. Accelerators (3/5)

    SciTech Connect

    2009-07-07

    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. Accelerators (4/5)

    SciTech Connect

    2009-07-08

    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.

  7. Accelerators (5/5)

    SciTech Connect

    2009-07-09

    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.

  8. Accelerators (5/5)

    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.

  9. An isotope dilution gas chromatography/mass spectrometry method for trace analysis of xylene and its metabolites in tissues following threshold limit value exposures

    SciTech Connect

    Pyon, K.H.; Kracko, D.A.; Strunk, M.R.

    1995-12-01

    The existence of a nose-brain barrier that functions to protect the central nervous system (CNS) from inhaled toxicants has been postulated. Just as a blood-brain barrier protects the CNS from systemic toxicants, the nose-brain barrier may have similar characteristic functions. One component of interest is nasal xenobiotic metabolism and its effect on the transport of pollutants into the CNS at environmentally plausible levels of exposure. Previous results have shown that inhaled xylene are dimethyl phenol (DMP) and methyl benzyl alcohol (MBA), and the nonvolatile metabolites are toluic acid (TA) and methyl hippuric acid (MHA). The nonvolatile metabolites of xylene, along with a small quantity of volatiles, representing either parent xylene or volatile metabolites, are transported via the olfactory epithelium to the glomeruli within the olfactory bulbs of the brain. Further work will be done to establish the linearity for each analyte at the actual highest detection limit of the GC/MS.

  10. 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.

  11. 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.

  12. Examining Geospatial Technology Tools to Compensate for Limited Exposures and Integrate Diverse Map and Data Resources in Geological Studies of the Southern Blue Ridge

    NASA Astrophysics Data System (ADS)

    Collins, N.; Ryan, J. G.

    2010-12-01

    Constraining the tectonic and metamorphic history of rock units in the southern Blue Ridge of western North Carolina is complicated by limited exposures and extensive vegetative cover, as well as burial by human development. Integrating varied data sources for field relations using cyberinformation tools may provide a means around such difficulties. We are examining several different Geographical Information Systems (GIS) tools as a means for effectively integrating available map data, both toward meeting research objectives as well as to facilitate classroom and field instruction. Commercial GIS platforms like ArcGIS and associated software can effectively integrate diverse geoscience information resources within a single platform. The Internet provides free access to databases ranging from geochemical datasets to topographical and structural data. Public domain geochemical databases like EarthChem provide spatially controlled elemental data on rock samples collected by many researchers over extended periods. Once incorporated within the ArcGIS template, this information can then be exported into free geospatial visualization applications such as Goggle Earth, as well as 3D manipulation programs like Fledermaus. Geospatially controlled USGS and NCGS geologic maps and geophysical datasets provide a useful base for examining mafic and ultramafic rock exposures in the Blue Ridge. One can resolve the exposures of specific rock types from these map resources within ArcGIS, as well as fault locations, and magnetics and gravity data. High-resolution DEMs permit data-intensive focusing on areas of interest, and Fledermaus manipulations permit 3D visualization. The output maps and visualizations are of publishable quality, and permit the manipulation of data across a region to infer contact trends and/or chemical or mineralogical, as well as to identify discontinuities that may be geologically relevant. All-in-one GIS applications like GeoMapApp have many of these aspects built in, and allow immediate, global-scale representations. However, these systems include relatively limited capabilities for independent data manipulation, and are constrained by the spatial detail of the integrated databases. Absent the ability to separate out individual rock units from geological maps, the regional study of rock associations via GeoMapApp is necessarily problematic. Also, low-resolution topographic base maps and digital elevation models (DEMs) inhibit exports to three-dimensional manipulation programs, and the exported content can only be minimally manipulated. For multivariate geological data resources such as one encounters in the study of mountain belts, an multi-tool approach combining commercial ArcGIS data management with various visualization tools appears to produce the best results in terms of research study of such datasets, and for the production of effective classroom visualizations.

  13. Rotary acceleration

    NASA Technical Reports Server (NTRS)

    Fraser, T. M.

    1973-01-01

    Rotary acceleration is found to be a manifestation of angular acceleration, and is always present during steady state spinning or tumbling, even when the angular velocity is constant. Subjective reactions and tolerances, performance, physiological effects, and pathological effects are reviewed for rotary acceleration. Thresholds for stimulation perception by angular acceleration in man are presented in tabular form.

  14. Limitations Placed on the Time Coverage, Isoplanatic Patch Size and Exposure Time for Solar Observations Using Image Selection Procedures in the Presence of Telescope Aberrations

    NASA Astrophysics Data System (ADS)

    Beckers, J. M.; Rimmele, T. R.

    1996-12-01

    Image selection, adaptive optics and post-facto image restoration methods are all techniques being used for diffraction limited imaging with ground-based solar and stellar telescopes. Often these techniques are used in a hybrid form like e.g. the application of adaptive optics and/or post-facto image restoration in combination with already good images obtained by image selection in periods of good seeing. Fried (JOSA 56, 1372, 1966), Hecquet and Coupinot (J. Optics/Paris 16, 21, 1985) and Beckers ("Solar and Stellar Granulation", Kluwer, Rutten & Severino Eds, 55, 1988) already discussed the usefulness of image selection, or the "Lucky Observer" mode, for high resolution imaging. All assumed perfect telescope optics. In case of moderate telescope aberrations image selection can still lead to diffraction limited imaging but only when the atmospheric wavefront aberration happens to compensate that of the telescope. In this "Very Lucky Observer" mode the probability of obtaining a good image is reduced over the un-aberrated case, as are the size of the isoplanatic patch and the exposure time. We describe an analysis of these effects for varying telescope aberrations. These result in a strong case for the removal of telescope aberrations either by initial implementation or by the use of slow active optics.

  15. Enhancement of chronic acceleration tolerance by selection

    NASA Technical Reports Server (NTRS)

    Smith, A. H.

    1982-01-01

    A review is presented of experiments concerning the physiological consequences of chronic acceleration and of studies of selection for acceleration tolerance over many generations. It is shown that acceleration selection is effective in improving chronic acceleration tolerance. However, it is determined that the variable selection procedure employed in developing this acceleration-tolerant line limits the confidence in the quantitative evaluation of the procedure.

  16. Acceleration in astrophysics

    SciTech Connect

    Colgate, S.A.

    1993-12-31

    The origin of cosmic rays and applicable laboratory experiments are discussed. Some of the problems of shock acceleration for the production of cosmic rays are discussed in the context of astrophysical conditions. These are: The presumed unique explanation of the power law spectrum is shown instead to be a universal property of all lossy accelerators; the extraordinary isotropy of cosmic rays and the limited diffusion distances implied by supernova induced shock acceleration requires a more frequent and space-filling source than supernovae; the near perfect adiabaticity of strong hydromagnetic turbulence necessary for reflecting the accelerated particles each doubling in energy roughly 10{sup 5} to {sup 6} scatterings with negligible energy loss seems most unlikely; the evidence for acceleration due to quasi-parallel heliosphere shocks is weak. There is small evidence for the expected strong hydromagnetic turbulence, and instead, only a small number of particles accelerate after only a few shock traversals; the acceleration of electrons in the same collisionless shock that accelerates ions is difficult to reconcile with the theoretical picture of strong hydromagnetic turbulence that reflects the ions. The hydromagnetic turbulence will appear adiabatic to the electrons at their much higher Larmor frequency and so the electrons should not be scattered incoherently as they must be for acceleration. Therefore the electrons must be accelerated by a different mechanism. This is unsatisfactory, because wherever electrons are accelerated these sites, observed in radio emission, may accelerate ions more favorably. The acceleration is coherent provided the reconnection is coherent, in which case the total flux, as for example of collimated radio sources, predicts single charge accelerated energies much greater than observed.

  17. Plasma accelerators

    SciTech Connect

    Ruth, R.D.; Chen, P.

    1986-03-01

    In this paper we discuss plasma accelerators which might provide high gradient accelerating fields suitable for TeV linear colliders. In particular we discuss two types of plasma accelerators which have been proposed, the Plasma Beat Wave Accelerator and the Plasma Wake Field Accelerator. We show that the electric fields in the plasma for both schemes are very similar, and thus the dynamics of the driven beams are very similar. The differences appear in the parameters associated with the driving beams. In particular to obtain a given accelerating gradient, the Plasma Wake Field Accelerator has a higher efficiency and a lower total energy for the driving beam. Finally, we show for the Plasma Wake Field Accelerator that one can accelerate high quality low emittance beams and, in principle, obtain efficiencies and energy spreads comparable to those obtained with conventional techniques.

  18. Sequential maintenance treatment with glatiramer acetate after mitoxantrone is safe and can limit exposure to immunosuppression in very active, relapsing remitting multiple sclerosis.

    PubMed

    Ramtahal, Jason; Jacob, Anu; Das, Kumar; Boggild, Mike

    2006-09-01

    Mitoxantrone has been approved by the FDA for worsening relapsing remitting and secondary progressive Multiple Sclerosis. However the benefits of this agent in reducing disease progression and relapse rate cannot be sustained in the long-term, as treatment is limited by the potential for cumulative cardiotoxicity. We report our experience utilising Glatiramer Acetate as maintenance immuno-modulatory treatment following initial immunosuppression with Mitoxantrone in a consecutive series of 27 patients with very active relapsing remitting disease, eight of whom had experienced continuing relapse activity on first-line treatment. Duration of treatment with Mitoxantrone and thereby cumulative dose were reduced as our experience with the combination increased.No unanticipated side effects of combination treatment were encountered over a follow-up period of 66 months. A single patient developed therapy related acute leukaemia (TRAL) 9 months after completion of Mitoxantrone.A sustained 90% reduction in annualised relapse rate (p < 0.001) has been observed. Disability is stable or improved in all patients a mean of 36 (16-66) months from initiation of treatment. Early suppression of relapse activity with Mitoxantrone has been maintained at a mean of 22 months from last dose of this agent. Only two relapses have occurred in the cohort since withdrawal of Mitoxantrone, occurring in the two patients who had previously been treated with Glatiramer Acetate. In 9 of the first 10 patients treated, imaged a mean of 27 months after withdrawal of Mitoxantrone, no enhancing lesions were identified on MRI brain scans. Glatiramer Acetate appears a safe and effective option for continuing disease modification in patients with relapsing remitting multiple sclerosis treated with Mitoxantrone. The treatment protocol utilised in later patients in this series appears to have the potential to limit exposure to this agent. PMID:16990994

  19. 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.

  20. Accelerated atmospheric corrosion testing using a cyclic wet/dry exposure test; Galvanic couples of aluminum with graphite neoprene rubber, galvanized steel, and steel

    SciTech Connect

    Lyon, S.B.; Thompson, G.E.; Johnson, J.E.; Wood, G.C. . Inst. of Science and Technology); Ferguson, J.M. )

    1989-11-01

    Aluminum corrosion is important in overhead electrical conductors constructed from aluminum wire centrally reinforced by galvanized steel strands. Inspection of conductor after long service has implicated rubber bushing material, on the outside, and the galvanized strands, on the inside, as providing potential galvanic sites for the initiation of rapid aluminum corrosion. Therefore, the galvanic corrosion of aluminum in contact with graphite-loaded neoprene rubber, hot-dip galvanized steel and steel was assessed in a cyclic wet/dry exposure test using mixed-salts spray solutions containing appropriate ratios of sulfate and chloride ion. Aluminum was found to corrode at between 3 to 6 times its uncoupled rate when associated with the rubber material. While the eta-phase, relatively pure Zn, galvanized layer remained intact, galvanic corrosion of aluminum was slow. However, on exposure of the zeta-phase, Zn/Fe intermetallic layer, aluminum corroded about 35 times faster than expected in a solution with a high level of Cl{sup -} ion. The importance of these data to conductor lifetime is discussed.

  1. 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.

  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-Romn, Laura; Fernndez Camblor, Carlota; Daz, Carmen; Muoz Bartola, Gema; Carcas-Sansun, 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. Limitations of the American Society of Therapeutic Radiology and Oncology Consensus Panel Guidelines on the Use of Accelerated Partial Breast Irradiation

    SciTech Connect

    Vicini, Frank; Arthur, Douglas; Wazer, David; Chen, Peter; Mitchell, Christina; Wallace, Michelle; Kestin, Larry; Ye, Hong

    2011-03-15

    Purpose: We applied the American Society of Therapeutic Radiology and Oncology (ASTRO) Consensus Panel (CP) guidelines for the use of accelerated partial breast irradiation (APBI) to patients treated with this technique to determine the ability of the guidelines to differentiate patients with significantly different clinical outcomes. Methods and Materials: A total of 199 patients treated with APBI and 199 with whole-breast irradiation (WBI) (matched for tumor size, nodal status, age, margins, receptor status, and tamoxifen use) were stratified into the three ASTRO CP levels of suitability ('suitable,' 'cautionary,' and 'unsuitable') to assess rates of ipsilateral breast tumor recurrence (IBTR), regional nodal failure, distant metastases, disease-free survival, cause-specific survival, and overall survival based on CP category. Median follow-up was 11.1 years. Results: Analysis of the APBI and WBI patient groups, either separately or together (n = 398), did not demonstrate statistically significant differences in 10-year actuarial rates of IBTR when stratified by the three ASTRO groups. Regional nodal failure and distant metastasis were generally progressively worse when comparing the suitable to cautionary to unsuitable CP groups. However, when analyzing multiple clinical, pathologic, or treatment-related variables, only patient age was associated with IBTR using WBI (p = 0.002). Conclusions: The ASTRO CP suitable group predicted for a low risk of IBTR; however, the cautionary and unsuitable groups had an equally low risk of IBTR, supporting the need for continued refinement of patient selection criteria as additional outcome data become available and for the continued accrual of patients to Phase III trials.

  4. Radiation pneumonitis following concurrent accelerated hyperfractionated radiotherapy and chemotherapy for limited-stage small-cell lung cancer: Dose-volume histogram analysis and comparison with conventional chemoradiation

    SciTech Connect

    Tsujino, Kayoko . E-mail: tsuk@mub.biglobe.ne.jp; Hirota, Saeko; Kotani, Yoshikazu; Kado, Tetsuji; Yoden, Eisaku; Fujii, Osamu; Soejima, Toshinori; Adachi, Shuji; Takada, Yoshiki

    2006-03-15

    Purpose: The aim of this study was twofold: to determine whether the dose-volume metrics are valuable in predicting radiation pneumonitis (RP) in small-cell lung cancer (SCLC) patients treated with accelerated hyperfractionated radiotherapy and chemotherapy (AHFRT + CT); and to clarify how AHFRT influences the risk of RP in comparison to conventional once-daily radiotherapy and chemotherapy (QDRT + CT). Methods and Materials: Study subjects were 43 patients with SCLC treated with AHFRT + CT. Radiotherapy was delivered at 1.5 Gy/fraction (fr) twice daily to 45 Gy/30 fr/3 weeks. We analyzed the relation between RP incidence and several dosimetric factors. We also compared this series data with our previously published data from lung cancer patients treated with QDRT + CT. Results: Radiation pneumonitis Grades 1, 2, and 3 were observed in 28 patients, 7 patients, and 1 patient, respectively. Univariate analysis revealed that the percentage of lung volume receiving more than 15 Gy, 20 Gy, and 30 Gy (V15, V20, V30) and normal tissue complication probability were of predictive value for the development of RP. The 12-month cumulative incidences of RP greater than Grade 2 were 0%, 7.1%, 25%, and 42.9% in patients with a V20 of {<=}20%, 21-25%, 26-30%, and {>=}31%, respectively. These incidences were lower than that of our patients treated with QDRT + CT. Conclusions: Dosimetric factors are valuable in predicting RP in SCLC patients treated with AHFRT + CT. Regarding the incidence of RP, AHFRT appears to have some advantage over QDRT.

  5. Loss of c-Met Accelerates Development of Liver Fibrosis in Response to CCl4 Exposure through Deregulation of Multiple Molecular Pathways

    PubMed Central

    Marquardt, Jens U; Seo, Daekwan; Gomez-Quiroz, Luis E; Uchida, Koichi; Gillen, Matthew C; Kitade, Mitsuteru; Kaposi-Novak, Pal; Conner, Elizabeth A; Factor, Valentina M; Thorgeirsson, Snorri S

    2012-01-01

    HGF/c-Met signaling plays a pivotal role in hepatocyte survival and tissue remodeling during liver regeneration. HGF treatment accelerates resolution of fibrosis in experimental animal models. Here, we utilized Metfl/fl;Alb-Cre+/? conditional knockout mice and a carbon tetrachloride(CCl4)-induced liver fibrosis model to formally address the role of c-Met signaling in hepatocytes in the context of chronic tissue injury. Histological changes during injury (4 weeks) and healing phase (4 weeks) were monitored by immunohistochemistry; expression levels of selected key fibrotic molecules were evaluated by western blotting, and time-dependent global transcriptomic changes were examined using a microarray platform. Loss of hepatocyte c-Met signaling altered hepatic microenvironment and aggravated hepatic fibrogenesis. Greater liver damage was associated with decreased hepatocyte proliferation, excessive stellate cell activation and rapid dystrophic calcification of necrotic areas. Global transcriptome analysis revealed a broad impact of c-Met on critical signaling pathways associated with fibrosis. Loss of hepatocyte c-Met caused a strong deregulation of chemotactic and inflammatory signaling (MCP-1, RANTES, Cxcl10) in addition to modulation of genes involved in reorganization of the cytoskeletal network (Actb, Tuba1a, Tuba8), intercellular communications and adhesion (Adam8, Icam1, Itgb2), control of cell proliferation (Ccng2, Csnk2a, Cdc6, cdk10), DNA damage and stress response (Rad9, Rad52, Ercc4, Gsta1 and 2, Jun). Our study demonstrates that deletion of c-Met receptor in hepatocytes results in pronounced changes in hepatic metabolism and microenvironment, and establishes an essential role for c-Met in maintaining the structural integrity and adaptive plasticity of the liver under adverse conditions. PMID:22386877

  6. Uniqueness of current cosmic acceleration

    SciTech Connect

    Linder, Eric V.

    2010-09-15

    One of the strongest arguments against the cosmological constant as an explanation of the current epoch of accelerated cosmic expansion is the existence of an earlier, dynamical acceleration, i.e. inflation. We examine the likelihood that acceleration is an occasional phenomenon, putting stringent limits on the length of any accelerating epoch due to minimally coupled dark energy between recombination and the recent acceleration; such an epoch must last less than 0.05 e-fold (at z>2) or the matter power spectrum is modified by more than 20%.

  7. Accelerated rotation with orbital angular momentum modes

    NASA Astrophysics Data System (ADS)

    Schulze, Christian; Roux, Filippus S.; Dudley, Angela; Rop, Ronald; Duparr, 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.

  8. Biomonitoring - An Exposure Science Tool for Exposure and Risk Assessment

    EPA Science Inventory

    Biomonitoring studies of environmental stressors are useful for confirming exposures, estimating dose levels, and evaluating human health risks. However, the complexities of exposure-biomarker and biomarker-response relationships have limited the use of biomarkers in exposure sc...

  9. 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 Foundations 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

  10. Radical Acceleration

    ERIC Educational Resources Information Center

    Gross, Miraca U. M.; Van Vliet, Helen E.

    2005-01-01

    Research has found that teachers' objections to accelerating gifted students are mainly based on a fear that acceleration will lead to social or emotional damage. Ironically, it is the academic and emotional maturity which characterizes intellectually gifted students, coupled with their high levels of academic achievement, which makes them such

  11. 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 1020 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

  12. 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; Paulus, Rebecca; Ettinger, David S.; Videtic, Gregory M.M.; Bradley, Jeffrey D.; Glisson, Bonnie S.; Sause, William T.; Curran, Walter J.; Choy, Hak

    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).

  13. 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.

  14. Muon acceleration in cosmic-ray sources

    SciTech Connect

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

    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.

  15. 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.

  16. Acceleration in de Sitter spacetimes

    NASA Astrophysics Data System (ADS)

    Cotaescu, Ion I.

    2015-02-01

    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.

  17. 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.

  18. ION ACCELERATOR

    DOEpatents

    Bell, J.S.

    1959-09-15

    An arrangement for the drift tubes in a linear accelerator is described whereby each drift tube acts to shield the particles from the influence of the accelerating field and focuses the particles passing through the tube. In one embodiment the drift tube is splii longitudinally into quadrants supported along the axis of the accelerator by webs from a yoke, the quadrants. webs, and yoke being of magnetic material. A magnetic focusing action is produced by energizing a winding on each web to set up a magnetic field between adjacent quadrants. In the other embodiment the quadrants are electrically insulated from each other and have opposite polarity voltages on adjacent quadrants to provide an electric focusing fleld for the particles, with the quadrants spaced sufficienily close enough to shield the particles within the tube from the accelerating electric field.

  19. IWGT report on quantitative approaches to genotoxicity risk assessment II. Use of point-of-departure (PoD) metrics in defining acceptable exposure limits and assessing human risk.

    PubMed

    MacGregor, James T; Frtschl, Roland; White, Paul A; Crump, Kenny S; Eastmond, David A; Fukushima, Shoji; Gurard, Melanie; Hayashi, Makoto; Soeteman-Hernndez, Lya G; Johnson, George E; Kasamatsu, Toshio; Levy, Dan D; Morita, Takeshi; Mller, Lutz; Schoeny, Rita; Schuler, Maik J; Thybaud, Vronique

    2015-05-01

    This is the second of two reports from the International Workshops on Genotoxicity Testing (IWGT) Working Group on Quantitative Approaches to Genetic Toxicology Risk Assessment (the QWG). The first report summarized the discussions and recommendations of the QWG related to the need for quantitative dose-response analysis of genetic toxicology data, the existence and appropriate evaluation of threshold responses, and methods to analyze exposure-response relationships and derive points of departure (PoDs) from which acceptable exposure levels could be determined. This report summarizes the QWG discussions and recommendations regarding appropriate approaches to evaluate exposure-related risks of genotoxic damage, including extrapolation below identified PoDs and across test systems and species. Recommendations include the selection of appropriate genetic endpoints and target tissues, uncertainty factors and extrapolation methods to be considered, the importance and use of information on mode of action, toxicokinetics, metabolism, and exposure biomarkers when using quantitative exposure-response data to determine acceptable exposure levels in human populations or to assess the risk associated with known or anticipated exposures. The empirical relationship between genetic damage (mutation and chromosomal aberration) and cancer in animal models was also examined. It was concluded that there is a general correlation between cancer induction and mutagenic and/or clastogenic damage for agents thought to act via a genotoxic mechanism, but that the correlation is limited due to an inadequate number of cases in which mutation and cancer can be compared at a sufficient number of doses in the same target tissues of the same species and strain exposed under directly comparable routes and experimental protocols. PMID:25953401

  20. Accelerated molecular dynamics methods

    SciTech Connect

    Perez, Danny

    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.

  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. 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.

  3. 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.

  4. 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.

  5. Diffusive acceleration

    NASA Astrophysics Data System (ADS)

    Scholer, Manfred

    This paper reviews the properties of diffuse energetic ions observed at the quasi-parallel bow shock and at quasi-parallel interplanetary shocks. The first-order Fermi or diffusive acceleration mechanism can consistently explain the many detailed observational facts. In this model, it is assumed that particles are scattered approximately elastically in the solar wind frame, and gain energy by repeated scattering between the converging upstream and downstream flows or between the upstream flow and the shock. An essential feature at both the bow shock and at interplanetary shocks are self-excited low-frequency waves representing the scattering irregularities. The seed particles for the acceleration process at the bow shock are most probably solar wind ions. However, how and with what efficiency a certain fraction of the thermal solar wind population is injected into the acceleration process is at present only poorly understood. Whether the seed particles for the acceleration at interplanetary shocks are solar wind ions or more energetic ions is an open question.

  6. 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…

  7. 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

  8. 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

  9. Compact accelerator

    DOEpatents

    Caporaso, George J. (Livermore, CA); Sampayan, Stephen E. (Manteca, CA); Kirbie, Hugh C. (Los Alamos, NM)

    2007-02-06

    A compact linear accelerator having at least one strip-shaped Blumlein module which guides a propagating wavefront between first and second ends and controls the output pulse at the second end. Each Blumlein module has first, second, and third planar conductor strips, with a first dielectric strip between the first and second conductor strips, and a second dielectric strip between the second and third conductor strips. Additionally, the compact linear accelerator includes a high voltage power supply connected to charge the second conductor strip to a high potential, and a switch for switching the high potential in the second conductor strip to at least one of the first and third conductor strips so as to initiate a propagating reverse polarity wavefront(s) in the corresponding dielectric strip(s).

  10. GRAPE Accelerators

    NASA Astrophysics Data System (ADS)

    Makino, Junichiro

    2011-04-01

    I'll overview the past, present, and future of the GRAPE project, which started as the effort to design and develop specialized hardware for gravitational N-body problem. The current hardware, GRAPE-DR, has an architecture quite different from previous GRAPEs, in the sense that it is a collection of small, but programmable processors, while previous GRAPEs had hardwired pipelines. I'll discuss pros and cons of these two approaches, comparisons with other accelerators and future directions.

  11. BICEP's acceleration

    SciTech Connect

    Contaldi, Carlo R.

    2014-10-01

    The recent Bicep2 [1] 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(?) 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 ?(N) as a function of e-fold N and derived posterior distributions of the primordial power spectrum P(k) and potential V(?). 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?10{sup -3} Mpc {sup -1}. This is in agreement with a previous detection of a suppression in the scalar power [2].

  12. A Meter-Scale Plasma Wakefield Accelerator

    SciTech Connect

    Ischebeck, Rasmus; Berry, Melissa; Blumenfeld, Ian; Decker, Franz-Josef; Hogan, Mark J.; Iverson, Richard; Siemann, Robert H.; Walz, Dieter; Clayton, Christopher E.; Huang, Chengkun; Joshi, Chandrashekhar; Lu, Wei; Marsh, Kenneth A.; Mori, Warren B.; Zhou Miaomiao; Katsouleas, Thomas; Muggli, Patric; Oz, Erdem

    2006-11-27

    Plasma wakefield accelerators (PWFA) have recently shown substantial progress, attaining accelerating fields of more than 30 GV/m. The goal of the present experiment is to show that such accelerating fields can be sustained over the scale of a meter, resulting in a total energy gain comparable to the entire SLAC linear accelerator. We also seek to determine which factors limit the length of the interaction and determine the maximum achievable energy.

  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. Force Limited Vibration Testing

    NASA Technical Reports Server (NTRS)

    Scharton, Terry; Chang, Kurng Y.

    2005-01-01

    This slide presentation reviews the concept and applications of Force Limited Vibration Testing. The goal of vibration testing of aerospace hardware is to identify problems that would result in flight failures. The commonly used aerospace vibration tests uses artificially high shaker forces and responses at the resonance frequencies of the test item. It has become common to limit the acceleration responses in the test to those predicted for the flight. This requires an analysis of the acceleration response, and requires placing accelerometers on the test item. With the advent of piezoelectric gages it has become possible to improve vibration testing. The basic equations have are reviewed. Force limits are analogous and complementary to the acceleration specifications used in conventional vibration testing. Just as the acceleration specification is the frequency spectrum envelope of the in-flight acceleration at the interface between the test item and flight mounting structure, the force limit is the envelope of the in-flight force at the interface . In force limited vibration tests, both the acceleration and force specifications are needed, and the force specification is generally based on and proportional to the acceleration specification. Therefore, force limiting does not compensate for errors in the development of the acceleration specification, e.g., too much conservatism or the lack thereof. These errors will carry over into the force specification. Since in-flight vibratory force data are scarce, force limits are often derived from coupled system analyses and impedance information obtained from measurements or finite element models (FEM). Fortunately, data on the interface forces between systems and components are now available from system acoustic and vibration tests of development test models and from a few flight experiments. Semi-empirical methods of predicting force limits are currently being developed on the basis of the limited flight and system test data. A simple two degree of freedom system is shown and the governing equations for basic force limiting results for this system are reviewed. The design and results of the shuttle vibration forces (SVF) experiments are reviewed. The Advanced Composition Explorer (ACE) also was used to validate force limiting. Test instrumentation and supporting equipment are reviewed including piezo-electric force transducers, signal processing and conditioning systems, test fixtures, and vibration controller systems. Several examples of force limited vibration testing are presented with some results.

  15. 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.

  16. Maximal acceleration and radiative processes

    NASA Astrophysics Data System (ADS)

    Papini, Giorgio

    2015-08-01

    We derive the radiation characteristics of an accelerated, charged particle in a model due to Caianiello in which the proper acceleration of a particle of mass m has the upper limit 𝒜m = 2mc3/?. We find two power laws, one applicable to lower accelerations, the other more suitable for accelerations closer to 𝒜m and to the related physical singularity in the Ricci scalar. Geometrical constraints and power spectra are also discussed. By comparing the power laws due to the maximal acceleration (MA) with that for particles in gravitational fields, we find that the model of Caianiello allows, in principle, the use of charged particles as tools to distinguish inertial from gravitational fields locally.

  17. Typical whole body vibration exposure magnitudes encountered in the open pit mining industry.

    PubMed

    Howard, Bryan; Sesek, Richard; Bloswick, Don

    2009-01-01

    According to recent research, a causal link has been established between occupational exposure to whole body vibration and an increased occurrence of low back pain. To aid in the further development of an in-house health and safety program for a large open pit mining facility interested in reducing back pain among its operators, whole body vibration magnitudes were characterized for a range of jobs. Specifically, thirty-five individual jobs from five different areas across the facility were evaluated for tri-axial acceleration levels during normal operating conditions. Tri-axial acceleration magnitudes were categorized into thirteen job groups. Job groups were ranked according to exposure and compared to the ISO 2631-1 standard for health risk assessment. Three of the thirteen job groups produced tri-axial acceleration magnitudes below the ISO 2631-1 low/moderate health caution limit for a twelve hour exposure. Six of the thirteen job groups produced exposures within the moderate health risk range. Four job groups were found to subject operators to WBV acceleration magnitudes above the moderate/high health caution limit. PMID:20037244

  18. Pulsed electromagnetic gas acceleration

    NASA Technical Reports Server (NTRS)

    Jahn, R. G.; Vonjaskowsky, W. F.; Clark, K. E.

    1974-01-01

    Detailed measurements of the axial velocity profile and electromagnetic structure of a high power, quasi-steady MPD discharge are used to formulate a gasdynamic model of the acceleration process. Conceptually dividing the accelerated plasma into an inner flow and an outer flow, it is found that more than two-thirds of the total power in the plasma is deposited in the inner flow, accelerating it to an exhaust velocity of 12.5 km/sec. The outer flow, which is accelerated to a velocity of only 6.2 km/sec, appears to provide a current conduction path between the inner flow and the anode. Related cathode studies have shown that the critical current for the onset of terminal voltage fluctuations, which was recently shown to be a function of the cathode area, appears to reach an asymptote for cathodes of very large surface area. Detailed floating potential measurements show that the fluctuations are confined to the vicinity of the cathode and hence reflect a cathode emission process rather than a fundamental limit on MPD performance.

  19. Radiation Safety System for SPIDER Neutral Beam Accelerator

    NASA Astrophysics Data System (ADS)

    Sandri, S.; Coniglio, A.; D'Arienzo, M.; Poggi, C.

    2011-12-01

    SPIDER (Source for Production of Ion of Deuterium Extracted from RF Plasma only) and MITICA (Megavolt ITER Injector Concept Advanced) are the ITER neutral beam injector (NBI) testing facilities of the PRIMA (Padova Research Injector Megavolt Accelerated) Center. Both injectors accelerate negative deuterium ions with a maximum energy of 1 MeV for MITICA and 100 keV for SPIDER with a maximum beam current of 40 A for both experiments. The SPIDER facility is classified in Italy as a particle accelerator. At present, the design of the radiation safety system for the facility has been completed and the relevant reports have been presented to the Italian regulatory authorities. Before SPIDER can operate, approval must be obtained from the Italian Regulatory Authority Board (IRAB) following a detailed licensing process. In the present work, the main project information and criteria for the SPIDER injector source are reported together with the analysis of hypothetical accidental situations and safety issues considerations. Neutron and photon nuclear analysis is presented, along with special shielding solutions designed to meet Italian regulatory dose limits. The contribution of activated corrosion products (ACP) to external exposure of workers has also been assessed. Nuclear analysis indicates that the photon contribution to worker external exposure is negligible, and the neutron dose can be considered by far the main radiation protection issue. Our results confirm that the injector has no important radiological impact on the population living around the facility.

  20. Radiation Safety System for SPIDER Neutral Beam Accelerator

    SciTech Connect

    Sandri, S.; Poggi, C.; Coniglio, A.; D'Arienzo, M.

    2011-12-13

    SPIDER (Source for Production of Ion of Deuterium Extracted from RF Plasma only) and MITICA (Megavolt ITER Injector Concept Advanced) are the ITER neutral beam injector (NBI) testing facilities of the PRIMA (Padova Research Injector Megavolt Accelerated) Center. Both injectors accelerate negative deuterium ions with a maximum energy of 1 MeV for MITICA and 100 keV for SPIDER with a maximum beam current of 40 A for both experiments. The SPIDER facility is classified in Italy as a particle accelerator. At present, the design of the radiation safety system for the facility has been completed and the relevant reports have been presented to the Italian regulatory authorities. Before SPIDER can operate, approval must be obtained from the Italian Regulatory Authority Board (IRAB) following a detailed licensing process. In the present work, the main project information and criteria for the SPIDER injector source are reported together with the analysis of hypothetical accidental situations and safety issues considerations. Neutron and photon nuclear analysis is presented, along with special shielding solutions designed to meet Italian regulatory dose limits. The contribution of activated corrosion products (ACP) to external exposure of workers has also been assessed. Nuclear analysis indicates that the photon contribution to worker external exposure is negligible, and the neutron dose can be considered by far the main radiation protection issue. Our results confirm that the injector has no important radiological impact on the population living around the facility.

  1. Persistent metal contamination limits lotic ecosystem heterotrophic metabolism after more than 100 years of exposure: a novel application of the Resazurin Resorufin Smart Tracer.

    PubMed

    Stanaway, Daniel; Haggerty, Roy; Benner, Shawn; Flores, Alejandro; Feris, Kevin

    2012-09-18

    Persistent stress from anthropogenic metal deposition in lotic ecosystems is a global concern. This long-term selective pressure shapes hyporheic microbial assemblages and influences ecosystem functional integrity. We hypothesized that, even after 100 years of adaptation opportunity, ecosystem function remains inhibited by sediment-associated metal stress and that the Resazurin Resorufin Smart Tracer can be used to quantify this impact. The Resazurin Resorufin Smart Tracer system is applied here in a novel capacity as an indicator of ecosystem function by quantifying ecosystem respiration of microbial communities. Hyporheic microbial communities exposed to differing magnitudes of chronic metal stress were compared to pristine reference sites in controlled column experiments. A Markov chain Monte Carlo technique was developed to solve the inverse smart tracer transport equation to derive community respiration data. Results suggest metals inhibit respiration by 13-30% relative to reference sites and this inhibition is directly related to the level of in situ metal stress. We demonstrate the first application of a hydrologic smart tracer as a functional indicator of ecological integrity within anthropogenically influenced flowing water systems and provide data suggesting resilience is limited in hyporheic ecosystems even after more than a century of microbial adaption to chronic pollutants. PMID:22909175

  2. 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.

  3. Suppressing Parasitic Effects in a Long Dielectric Wakefield Accelerator

    SciTech Connect

    Shchegolkov, Dmitry; Simakov, Evgenya Ivanovna; Jing, Chunguang; Li, Chen; Zholents, Alexander A.; Power, John G.

    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.

  4. 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.

  5. Acceleration modules in linear induction accelerators

    NASA Astrophysics Data System (ADS)

    Wang, Shao-Heng; Deng, Jian-Jun

    2014-05-01

    The Linear Induction Accelerator (LIA) is a unique type of accelerator that is capable of accelerating kilo-Ampere charged particle current to tens of MeV energy. The present development of LIA in MHz bursting mode and the successful application into a synchrotron have broadened LIA's usage scope. Although the transformer model is widely used to explain the acceleration mechanism of LIAs, it is not appropriate to consider the induction electric field as the field which accelerates charged particles for many modern LIAs. We have examined the transition of the magnetic cores' functions during the LIA acceleration modules' evolution, distinguished transformer type and transmission line type LIA acceleration modules, and re-considered several related issues based on transmission line type LIA acceleration module. This clarified understanding should help in the further development and design of LIA acceleration modules.

  6. BATSE sky exposure

    SciTech Connect

    Hakkila, Jon; Meegan, Charles A.; Henze, William

    1998-05-16

    Angular sky exposure is presented for a number of published BATSE gamma-ray burst catalogs. A new algorithm was required due to telemetry gaps resulting from onboard tape recorder failures; the new algorithm improves the 1B Catalog exposure calculation. The most influential effects limiting BATSE's exposure are (1) deadtime due to triggering, (2) sky blockage by the Earth, and (3) trigger disabling when the spacecraft is in the SAA and over other specific Earth locations. Exposure has improved during the Compton Gamma-Ray Observatory (CGRO) mission as a result of decreased Solar flares and magnetospheric particle events.

  7. KEKB accelerator control system

    NASA Astrophysics Data System (ADS)

    Akasaka, Nobumasa; Akiyama, Atsuyoshi; Araki, Sakae; Furukawa, Kazuro; Katoh, Tadahiko; Kawamoto, Takashi; Komada, Ichitaka; Kudo, Kikuo; Naito, Takashi; Nakamura, Tatsuro; Odagiri, Jun-ichi; Ohnishi, Yukiyoshi; Sato, Masayuki; Suetake, Masaaki; Takeda, Shigeru; Takeuchi, Yasunori; Yamamoto, Noboru; Yoshioka, Masakazu; Kikutani, Eji

    2003-02-01

    The KEKB accelerator control system including a control computer system, a timing distribution system, and a safety control system are described. KEKB accelerators were installed in the same tunnel where the TRISTAN accelerator was. There were some constraints due to the reused equipment. The control system is based on Experimental Physics and Industrial Control System (EPICS). In order to reduce the cost and labor for constructing the KEKB control system, as many CAMAC modules as possible are used again. The guiding principles of the KEKB control computer system are as follows: use EPICS as the controls environment, provide a two-language system for developing application programs, use VMEbus as frontend computers as a consequence of EPICS, use standard buses, such as CAMAC, GPIB, VXIbus, ARCNET, RS-232 as field buses and use ergonomic equipment for operators and scientists. On the software side, interpretive Python and SAD languages are used for coding application programs. The purpose of the radiation safety system is to protect personnel from radiation hazards. It consists of an access control system and a beam interlock system. The access control system protects people from strong radiation inside the accelerator tunnel due to an intense beam, by controlling access to the beamline area. On the other hand, the beam interlock system prevents people from radiation exposure by interlocking the beam operation. For the convenience of accelerator operation and access control, the region covered by the safety system is divided into three major access control areas: the KEKB area, the PF-AR area, and the beam-transport (BT) area. The KEKB control system required a new timing system to match a low longitudinal acceptance due to a low-alpha machine. This timing system is based on a frequency divider/multiply technique and a digital delay technique. The RF frequency of the KEKB rings and that of the injector Linac are locked with a common divisor frequency. The common divisor frequency determines the injection timing. The RF bucket selection system is also described.

  8. 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

  9. Occupational exposure to crystalline silica and autoimmune disease.

    PubMed

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

    1999-10-01

    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

  10. Beam front accelerators

    SciTech Connect

    Reiser, M.

    1982-01-01

    An intense relativistic electron beam cannot propagate in a metal drift tube when the current exceeds the space charge limit. Very high charge density and electric field gradients (10/sup 2/ to 10/sup 3/ MV/m) develop at the beam front and the electrons are reflected. When a neutral gas or a plasma is present, collective acceleration of positive ions occur, and the resulting charge neutralization enables the beam to propagate. Experimental results, theoretical understanding, and schemes to achieve high ion energies by external control of the beam front velocity will be reviewed.

  11. Effect Of Bed Rest On Tolerance To Acceleration

    NASA Technical Reports Server (NTRS)

    Goldwater, Danielle J.

    1991-01-01

    Report describes experimental comparative study of tolerance of aerobically fit men and sedentary men to +Gz acceleration. Designed to confirm or deny previous observations that long-term aerobic training reduces tolerance to acceleration. Data accumulated in study showed decrease in tolerance to acceleration caused by deconditioning effect of bed rest more pronounced in fit men than in sedentary men. Suggests physically fit people need additional measures to reduce loss of tolerance to acceleration during microgravity exposure.

  12. Electrostatic Plasma Accelerator (EPA)

    NASA Technical Reports Server (NTRS)

    Brophy, John R.; Aston, Graeme

    1995-01-01

    The application of electric propulsion to communications satellites, however, has been limited to the use of hydrazine thrusters with electric heaters for thrust and specific impulse augmentation. These electrothermal thrusters operate at specific impulse levels of approximately 300 s with heater powers of about 500 W. Low power arcjets (1-3 kW) are currently being investigated as a way to increase specific impulse levels to approximately 500 s. Ion propulsion systems can easily produce specific impulses of 3000 s or greater, but have yet to be applied to communications satellites. The reasons most often given for not using ion propulsion systems are their high level of overall complexity, low thrust with long burn times, and the difficulty of integrating the propulsion system into existing commercial spacecraft busses. The Electrostatic Plasma Accelerator (EPA) is a thruster concept which promises specific impulse levels between low power arcjets and those of the ion engine while retaining the relative simplicity of the arcjet. The EPA thruster produces thrust through the electrostatic acceleration of a moderately dense plasma. No accelerating electrodes are used and the specific impulse is a direct function of the applied discharge voltage and the propellant atomic mass.

  13. 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.

  14. The Muon Accelerator Program

    SciTech Connect

    Geer, Steve; 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.

  15. Laboratory Test of Newton's Second Law for Small Accelerations

    SciTech Connect

    Gundlach, J. H.; Schlamminger, S.; Spitzer, C. D.; Choi, K.-Y.; Woodahl, B. A.; Coy, J. J.; Fischbach, E.

    2007-04-13

    We have tested the proportionality of force and acceleration in Newton's second law, F=ma, in the limit of small forces and accelerations. Our tests reach well below the acceleration scales relevant to understanding several current astrophysical puzzles such as the flatness of galactic rotation curves, the Pioneer anomaly, and the Hubble acceleration. We find good agreement with Newton's second law at accelerations as small as 5x10{sup -14} m/s{sup 2}.

  16. Laboratory test of Newton's second law for small accelerations.

    PubMed

    Gundlach, J H; Schlamminger, S; Spitzer, C D; Choi, K-Y; Woodahl, B A; Coy, J J; Fischbach, E

    2007-04-13

    We have tested the proportionality of force and acceleration in Newton's second law, F=ma, in the limit of small forces and accelerations. Our tests reach well below the acceleration scales relevant to understanding several current astrophysical puzzles such as the flatness of galactic rotation curves, the Pioneer anomaly, and the Hubble acceleration. We find good agreement with Newton's second law at accelerations as small as 5 x 10(-14) m/s(2). PMID:17501332

  17. High average power induction accelerators

    SciTech Connect

    Swingle, J.C.

    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)

  18. Accelerator Test of an Imaging Calorimeter

    NASA Technical Reports Server (NTRS)

    Christl, Mark J.; Adams, James H., Jr.; Binns, R. W.; Derrickson, J. H.; Fountain, W. F.; Howell, L. W.; Gregory, J. C.; Hink, P. L.; Israel, M. H.; Kippen, R. M.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    The Imaging Calorimeter for ACCESS (ICA) utilizes a thin sampling calorimeter concept for direct measurements of high-energy cosmic rays. The ICA design uses arrays of small scintillating fibers to measure the energy and trajectory of the produced cascades. A test instrument has been developed to study the performance of this concept at accelerator energies and for comparison with simulations. Two test exposures have been completed using a CERN test beam. Some results from the accelerator tests are presented.

  19. 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.

  20. The physiological basis for spacecraft environmental limits

    NASA Technical Reports Server (NTRS)

    Waligora, J. M. (Compiler)

    1979-01-01

    Limits for operational environments are discussed in terms of acceptable physiological changes. The environmental factors considered are pressure, contaminants, temperature, acceleration, noise, rf radiation, and weightlessness.

  1. Accelerated laboratory weathering of acrylic lens materials

    NASA Astrophysics Data System (ADS)

    Arndt, Thomas; Richter, Steffen; Kogler, Ren; Pasierb, Mike; Walby, Christopher

    2015-09-01

    Flat samples from various poly(methyl methacrylate) (PMMA) formulations were subjected to outdoor weathering in Arizona and Florida, EMMAQUA accelerated outdoor weathering, and two accelerated laboratory weathering procedures at 3 Sun irradiance which, imitate dry (Arizona) and wet (Florida) conditions. The main mode of degradation is yellowing and not the generation of haze for any weathering procedure within the investigated radiant exposure. Higher UV absorber concentrations lead to smaller changes in optical properties and in the resulting relative concentrator photovoltaic (CPV) module efficiencies. Comparison of sample properties after various weathering procedures reveals that the influence of weathering factors other than radiant exposure depends on the sample as well.

  2. Operational Radiation Protection in High-Energy Physics Accelerators: Implementation of ALARA in Design and Operation of Accelerators

    SciTech Connect

    Fasso, A.; Rokni, S.; /SLAC

    2011-06-30

    It used to happen often, to us accelerator radiation protection staff, to be asked by a new radiation worker: ?How much dose am I still allowed?? And we smiled looking at the shocked reaction to our answer: ?You are not allowed any dose?. Nowadays, also thanks to improved training programs, this kind of question has become less frequent, but it is still not always easy to convince workers that staying below the exposure limits is not sufficient. After all, radiation is still the only harmful agent for which this is true: for all other risks in everyday life, from road speed limits to concentration of hazardous chemicals in air and water, compliance to regulations is ensured by keeping below a certain value. It appears that a tendency is starting to develop to extend the radiation approach to other pollutants (1), but it will take some time before the new attitude makes it way into national legislations.

  3. Occupational Diesel Exposure, Duration of Employment, and Lung Cancer

    PubMed Central

    Picciotto, Sally; Costello, Sadie; Eisen, Ellen A.

    2016-01-01

    Background: If less healthy workers terminate employment earlier, thus accumulating less exposure, yet remain at greater risk of the health outcome, estimated health effects of cumulative exposure will be biased downward. If exposure also affects termination of employment, then the bias cannot be addressed using conventional methods. We examined these conditions as a prelude to a reanalysis of lung cancer mortality in the Diesel Exhaust in Miners Study. Methods: We applied an accelerated failure time model to assess the effect of exposures to respirable elemental carbon (a surrogate for diesel) on time to termination of employment among nonmetal miners who ever worked underground (n = 8,307). We then applied the parametric g-formula to assess how possible interventions setting respirable elemental carbon exposure limits would have changed lifetime risk of lung cancer, adjusting for time-varying employment status. Results: Median time to termination was 36% shorter (95% confidence interval = 33%, 39%), per interquartile range width increase in respirable elemental carbon exposure. Lung cancer risk decreased with more stringent interventions, with a risk ratio of 0.8 (95% confidence interval = 0.5, 1.1) comparing a limit of ≤25 µg/m3 respirable elemental carbon to no intervention. The fraction of cases attributable to diesel exposure was 27% in this population. Conclusions: The g-formula controlled for time-varying confounding by employment status, the signature of healthy worker survivor bias, which was also affected by diesel exposure. It also offers an alternative approach to risk assessment for estimating excess cumulative risk, and the impact of interventions based entirely on an observed population. PMID:26426944

  4. 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.

  5. Charged particle acceleration in dense plasma channels

    SciTech Connect

    Dodin, I. Y.; Fisch, N. J.

    2008-10-15

    Reduced nonlinear equations are derived from the oscillation amplitude and the energy of a charged particle accelerated in a plasma channel. The maximum energy gain, as limited by dissipation, is described by three different scalings depending on the channel parameters.

  6. 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.

  7. Laser driven ion accelerator

    DOEpatents

    Tajima, Toshiki

    2006-04-18

    A system and method of accelerating ions in an accelerator to optimize the energy produced by a light source. Several parameters may be controlled in constructing a target used in the accelerator system to adjust performance of the accelerator system. These parameters include the material, thickness, geometry and surface of the target.

  8. Laser driven ion accelerator

    DOEpatents

    Tajima, Toshiki

    2005-06-14

    A system and method of accelerating ions in an accelerator to optimize the energy produced by a light source. Several parameters may be controlled in constructing a target used in the accelerator system to adjust performance of the accelerator system. These parameters include the material, thickness, geometry and surface of the target.

  9. Parasite infection accelerates age polyethism in young honey bees.

    PubMed

    Lecocq, Antoine; Jensen, Annette Bruun; Kryger, Per; Nieh, James C

    2016-01-01

    Honey bees (Apis mellifera) are important pollinators and their health is threatened worldwide by persistent exposure to a wide range of factors including pesticides, poor nutrition, and pathogens. Nosema ceranae is a ubiquitous microsporidian associated with high colony mortality. We used lab micro-colonies of honey bees and video analyses to track the effects of N. ceranae infection and exposure on a range of individual and social behaviours in young adult bees. We provide detailed data showing that N. ceranae infection significantly accelerated the age polyethism of young bees, causing them to exhibit behaviours typical of older bees. Bees with high N. ceranae spore counts had significantly increased walking rates and decreased attraction to queen mandibular pheromone. Infected bees also exhibited higher rates of trophallaxis (food exchange), potentially reflecting parasite manipulation to increase colony infection. However, reduction in queen contacts could help bees limit the spread of infection. Such accelerated age polyethism may provide a form of behavioural immunity, particularly if it is elicited by a wide variety of pathogens. PMID:26912310

  10. Parasite infection accelerates age polyethism in young honey bees

    PubMed Central

    Lecocq, Antoine; Jensen, Annette Bruun; Kryger, Per; Nieh, James C.

    2016-01-01

    Honey bees (Apis mellifera) are important pollinators and their health is threatened worldwide by persistent exposure to a wide range of factors including pesticides, poor nutrition, and pathogens. Nosema ceranae is a ubiquitous microsporidian associated with high colony mortality. We used lab micro-colonies of honey bees and video analyses to track the effects of N. ceranae infection and exposure on a range of individual and social behaviours in young adult bees. We provide detailed data showing that N. ceranae infection significantly accelerated the age polyethism of young bees, causing them to exhibit behaviours typical of older bees. Bees with high N. ceranae spore counts had significantly increased walking rates and decreased attraction to queen mandibular pheromone. Infected bees also exhibited higher rates of trophallaxis (food exchange), potentially reflecting parasite manipulation to increase colony infection. However, reduction in queen contacts could help bees limit the spread of infection. Such accelerated age polyethism may provide a form of behavioural immunity, particularly if it is elicited by a wide variety of pathogens. PMID:26912310

  11. 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; OHara, 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.

  12. 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

  13. Accelerator-driven Transmutation of Waste

    NASA Astrophysics Data System (ADS)

    Venneri, Francesco

    1998-04-01

    Nuclear waste from commercial power plants contains large quantities of plutonium, other fissionable actinides, and long-lived fission products that are potential proliferation concerns and create challenges for the long-term storage. Different strategies for dealing with nuclear waste are being followed by various countries because of their geologic situations and their views on nuclear energy, reprocessing and non-proliferation. The current United States policy is to store unprocessed spent reactor fuel in a geologic repository. Other countries are opting for treatment of nuclear waste, including partial utilization of the fissile material contained in the spent fuel, prior to geologic storage. Long-term uncertainties are hampering the acceptability and eventual licensing of a geologic repository for nuclear spent fuel in the US, and driving up its cost. The greatest concerns are with the potential for radiation release and exposure from the spent fuel for tens of thousands of years and the possible diversion and use of the actinides contained in the waste for weapons construction. Taking advantage of the recent breakthroughs in accelerator technology and of the natural flexibility of subcritical systems, the Accelerator-driven Transmutation of Waste (ATW) concept offers the United States and other countries the possibility to greatly reduce plutonium, higher actinides and environmentally hazardous fission products from the waste stream destined for permanent storage. ATW does not eliminate the need for, but instead enhances the viability of permanent waste repositories. Far from being limited to waste destruction, the ATW concept also brings to the table new technologies that could be relevant for next-generation power producing reactors. In the ATW concept, spent fuel would be shipped to the ATW site where the plutonium, transuranics and selected long-lived fission products would be destroyed by fission or transmutation in their first and only pass through the facility, using an accelerator-driven subcritical burner cooled by liquid lead/bismuth and limited pyrochemical treatment of the spent fuel and residual waste. This approach contrasts with the present-day practices of aqueous reprocessing (Europe and Japan), in which high purity plutonium is produced and used in the fabrication of fresh mixed oxide fuel (MOX) that is shipped off-site for use in light water reactors.

  14. 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.

  15. Superconducting cavities for particle accelerators

    NASA Astrophysics Data System (ADS)

    Padamsee, H.

    1992-02-01

    RF Superconductivity has become an important technology for particle accelerators for high energy physics, nuclear physics, and free electron lasers. More than 100 MVolts of Superconducting RF (SRF) cavities have been installed in accelerators for heavy ions and operated at gradients of 2-3 MV/m in excess of 105 hours. More than 500 MVolts are installed in electron accelerators and operated at gradients of 4-6 MV/m in excess of 104 hours. Encouraged by this success, another 500 meters of SRF cavities are in the production line. New applications for High Energy Physics are forthcoming for high current e+e- colliders in the B-quark energy range (B-factory). For the next linear collider in the TeV energy range, there are many compelling attractions to use SRF, if the gradients can be improved substantially and the costs lowered. Substantial progress has been made in understanding performance limitations and in inventing cures through better cavity geometries, materials, and processes. Techniques are now in hand to reach 15-20 MV/m accelerating. In light of this progress, the potential of high gradient SRF for a TeV Energy Superconducting Linear Accelerator (TESLA) will be explored.

  16. Stealth acceleration and modified gravity

    NASA Astrophysics Data System (ADS)

    Charmousis, Christos; Gregory, Ruth; Padilla, Antonio

    2007-10-01

    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 four-dimensional graviton is only quasi-localized 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-localized we find two main examples of acceleration. In each case, we provide an illustrative model and compare it to ΛCDM.

  17. Induced activation in accelerator components

    NASA Astrophysics Data System (ADS)

    Bungau, Cristian; Bungau, Adriana; Cywinski, Robert; Barlow, Roger; Edgecock, Thomas Robert; Carlsson, Patrick; Danared, Hkan; Mezei, Ferenc; Holm, Anne Ivalu Sander; Mller, Sren Pape; Thomsen, Heine Dlrath

    2014-08-01

    The residual activity induced in particle accelerators is a serious issue from the point of view of radiation safety as the long-lived radionuclides produced by fast or moderated neutrons and impact protons cause problems of radiation exposure for staff involved in the maintenance work and when decommissioning the facility. This paper presents activation studies of the magnets and collimators in the High Energy Beam Transport line of the European Spallation Source due to the backscattered neutrons from the target and also due to the direct proton interactions and their secondaries. An estimate of the radionuclide inventory and induced activation are predicted using the GEANT4 code.

  18. 12 CFR 206.4 - Credit exposure.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 12 Banks and Banking 2 2014-01-01 2014-01-01 false Credit exposure. 206.4 Section 206.4 Banks and... LIABILITIES (REGULATION F) 206.4 Credit exposure. (a) Limits on credit exposure. (1) The policies and... credit exposure to an individual correspondent to not more than 25 percent of the bank's total...

  19. 12 CFR 206.4 - Credit exposure.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 12 Banks and Banking 2 2012-01-01 2012-01-01 false Credit exposure. 206.4 Section 206.4 Banks and... LIABILITIES (REGULATION F) 206.4 Credit exposure. (a) Limits on credit exposure. (1) The policies and... credit exposure to an individual correspondent to not more than 25 percent of the bank's total...

  20. 12 CFR 206.4 - Credit exposure.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 12 Banks and Banking 2 2011-01-01 2011-01-01 false Credit exposure. 206.4 Section 206.4 Banks and... LIABILITIES (REGULATION F) 206.4 Credit exposure. (a) Limits on credit exposure. (1) The policies and... credit exposure to an individual correspondent to not more than 25 percent of the bank's total...

  1. 12 CFR 206.4 - Credit exposure.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 12 Banks and Banking 2 2013-01-01 2013-01-01 false Credit exposure. 206.4 Section 206.4 Banks and... LIABILITIES (REGULATION F) 206.4 Credit exposure. (a) Limits on credit exposure. (1) The policies and... credit exposure to an individual correspondent to not more than 25 percent of the bank's total...

  2. 12 CFR 206.4 - Credit exposure.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 12 Banks and Banking 2 2010-01-01 2010-01-01 false Credit exposure. 206.4 Section 206.4 Banks and... LIABILITIES (REGULATION F) 206.4 Credit exposure. (a) Limits on credit exposure. (1) The policies and... credit exposure to an individual correspondent to not more than 25 percent of the bank's total...

  3. 30 CFR 57.5071 - Exposure monitoring.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... exposure to DPM exceeds the DPM limit specified in 57.5060. (b) The mine operator must provide affected... miner's exposure to diesel particulate matter exceeds the DPM limit specified in 57.5060, the operator... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Exposure monitoring. 57.5071 Section...

  4. The direction of acceleration

    NASA Astrophysics Data System (ADS)

    Wilhelm, Thomas; Burde, Jan-Philipp; Lück, Stephan

    2015-11-01

    Acceleration is a physical quantity that is difficult to understand and hence its complexity is often erroneously simplified. Many students think of acceleration as equivalent to velocity, a ˜ v. For others, acceleration is a scalar quantity, which describes the change in speed Δ|v| or Δ|v|/Δt (as opposed to the change in velocity). The main difficulty with the concept of acceleration therefore lies in developing a correct understanding of its direction. The free iOS app AccelVisu supports students in acquiring a correct conception of acceleration by showing acceleration arrows directly at moving objects.

  5. TURBULENT SHEAR ACCELERATION

    SciTech Connect

    Ohira, Yutaka

    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.

  6. 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.

  7. 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.

  8. 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.

  9. Accelerating electromagnetic magic field from the C-metric

    NASA Astrophysics Data System (ADS)

    Bi?k, Ji?; Kofro?, David

    2009-09-01

    Various aspects of the C-metric representing two rotating charged black holes accelerated in opposite directions are summarized and its limits are considered. A particular attention is paid to the special-relativistic limit in which the electromagnetic field becomes the magic field of two oppositely accelerated rotating charged relativistic discs. When the acceleration vanishes the usual electromagnetic magic field of the Kerr-Newman black hole with gravitational constant set to zero arises. Properties of the accelerated discs and the fields produced are studied and illustrated graphically. The charges at the rim of the accelerated discs move along spiral trajectories with the speed of light. If the magic field has some deeper connection with the field of the Dirac electron, as is sometimes conjectured because of the same gyromagnetic ratio, the accelerating magic field represents the electromagnetic field of a uniformly accelerated spinning electron. It generalizes the classical Borns solution for two uniformly accelerated monopole charges.

  10. 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.

  11. Linear accelerator: A concept

    NASA Technical Reports Server (NTRS)

    Mutzberg, J.

    1972-01-01

    Design is proposed for inexpensive accelerometer which would work by applying pressure to fluid during acceleration. Pressure is used to move shuttle, and shuttle movement is sensed and calibrated to give acceleration readings.

  12. 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.

  13. The Association between Environmental Lead Exposure and Bone Density in Children

    PubMed Central

    Campbell, James R.; Rosier, Randy N.; Novotny, Leonore; Puzas, J. Edward

    2004-01-01

    Osteoporosis is a decrease in bone mineral density (BMD) that predisposes individuals to fractures. Although an elderly affliction, a predisposition may develop during adolescence if a sufficient peak BMD is not achieved. Rat studies have found that lead exposure is associated with decreased BMD. However, human studies are limited. We hypothesized that the BMD of children with high lead exposure would be lower than the BMD of children with low lead exposure. We collected data on 35 subjects; 16 had low cumulative lead exposure (mean, 6.5 ?g/dL), and 19 had high exposure (mean, 23.6 ?g/dL). All were African American; there was no difference between the groups by sex, age, body mass index, socioeconomic status, physical activity, or calcium intake. Significant differences in BMD between low and high cumulative lead exposure were noted in the head (1.589 vs. 1.721 g/cm2), third lumbar vertebra (0.761 vs. 0.819 g/cm2), and fourth lumbar vertebra (0.712 vs. 0.789 g/cm2). Contrary to our hypothesis, subjects with high lead exposure had a significantly higher BMD than did subjects with low lead exposure. This may reflect a true phenomenon because lead exposure has been reported to accelerate bony maturation by inhibiting the effects of parathyroid hormonerelated peptide. Accelerated maturation of bone may ultimately result in a lower peak BMD being achieved in young adulthood, thus predisposing to osteoporosis in later life. Future studies need to investigate this proposed model. PMID:15289167

  14. Using Accelerated Testing to Predict Module Reliability

    SciTech Connect

    Wohlgemuth, J. H.; Kurtz, S.

    2011-01-01

    Long-term reliability is critical to the cost effectiveness and commercial success of photovoltaic (PV) products. Today most PV modules are warranted for 25 years, but there is no accepted test protocol to validate a 25-year lifetime. The qualification tests do an excellent job of identifying design, materials, and process flaws that are likely to lead to premature failure (infant mortality), but they are not designed to test for wear-out mechanisms that limit lifetime. This paper presents a method for evaluating the ability of a new PV module technology to survive long-term exposure to specific stresses. The authors propose the use of baseline technologies with proven long-term field performance as controls in the accelerated stress tests. The performance of new-technology modules can then be evaluated versus that of proven-technology modules. If the new-technology demonstrates equivalent or superior performance to the proven one, there is a high likelihood that they will survive versus the tested stress in the real world.

  15. EXPOSURE ANALYSIS

    EPA Science Inventory

    This proceedings chapter presents the state of the science regarding the evaluation of exposure as it relates to WQC, SQGs, and wildlife criteria (WC). . . . In summary, the exposure workgroup concluded the following: There should be greater use of mechanistic models to predict b...

  16. Far field acceleration

    SciTech Connect

    Fernow, R.C.

    1995-07-01

    Far fields are propagating electromagnetic waves far from their source, boundary surfaces, and free charges. The general principles governing the acceleration of charged particles by far fields are reviewed. A survey of proposed field configurations is given. The two most important schemes, Inverse Cerenkov acceleration and Inverse free electron laser acceleration, are discussed in detail.

  17. 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

  18. 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.

  19. 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 beamone turns on when the other turns off, at different harmonicsso 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.

  20. 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.

  1. Lasers and new methods of particle acceleration

    SciTech Connect

    Parsa, Z.

    1998-02-01

    There has been a great progress in development of high power laser technology. Harnessing their potential for particle accelerators is a challenge and of great interest for development of future high energy colliders. The author discusses some of the advances and new methods of acceleration including plasma-based accelerators. The exponential increase in sophistication and power of all aspects of accelerator development and operation that has been demonstrated has been remarkable. This success has been driven by the inherent interest to gain new and deeper understanding of the universe around us. With the limitations of the conventional technology it may not be possible to meet the requirements of the future accelerators with demands for higher and higher energies and luminosities. It is believed that using the existing technology one can build a linear collider with about 1 TeV center of mass energy. However, it would be very difficult (or impossible) to build linear colliders with energies much above one or two TeV without a new method of acceleration. Laser driven high gradient accelerators are becoming more realistic and is expected to provide an alternative, (more compact, and more economical), to conventional accelerators in the future. The author discusses some of the new methods of particle acceleration, including laser and particle beam driven plasma based accelerators, near and far field accelerators. He also discusses the enhanced IFEL (Inverse Free Electron Laser) and NAIBEA (Nonlinear Amplification of Inverse-Beamstrahlung Electron Acceleration) schemes, laser driven photo-injector and the high energy physics requirements.

  2. Enhancing proton acceleration by using composite targets

    SciTech Connect

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

    2015-07-10

    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.

  3. 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.

  4. Photon acceleration in plasma wake wave

    SciTech Connect

    Bu, Zhigang; Shen, Baifei Yi, Longqing; Zhang, Hao; Huang, Shan; Li, Shun

    2015-04-15

    The photon acceleration effect in a laser wake field is investigated based on photon Hamiltonian dynamics. A test laser pulse is injected into a plasma wave at an incident angle θ{sub i}, which could slow down the photon velocity along the propagating direction of the wake wave so as to increase the acceleration distance for the photons. The photon trapping condition is analyzed in detail, and the maximum frequency shift of the trapped photon is obtained. The acceleration gradient and dephasing length are emphatically studied. The compression of the test laser pulse is examined and used to interpret the acceleration process. The limit of finite transverse width of the wake wave on photon acceleration is also discussed.

  5. Photon acceleration in plasma wake wave

    NASA Astrophysics Data System (ADS)

    Bu, Zhigang; Shen, Baifei; Yi, Longqing; Zhang, Hao; Huang, Shan; Li, Shun

    2015-04-01

    The photon acceleration effect in a laser wake field is investigated based on photon Hamiltonian dynamics. A test laser pulse is injected into a plasma wave at an incident angle θi , which could slow down the photon velocity along the propagating direction of the wake wave so as to increase the acceleration distance for the photons. The photon trapping condition is analyzed in detail, and the maximum frequency shift of the trapped photon is obtained. The acceleration gradient and dephasing length are emphatically studied. The compression of the test laser pulse is examined and used to interpret the acceleration process. The limit of finite transverse width of the wake wave on photon acceleration is also discussed.

  6. Experiment specific processing of residual acceleration data

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    To date, most Spacelab residual acceleration data collection projects have resulted in data bases that are overwhelming to the investigator of low-gravity experiments. This paper introduces a simple passive accelerometer system to measure low-frequency accelerations. Model responses for experiments using actual acceleration data are produced and correlations are made between experiment response and the accelerometer time history in order to test the idea that recorded acceleration data and experimental responses can be usefully correlated. Spacelab 3 accelerometer data are used as input to a variety of experiment models, and sensitivity limits are obtained for particular experiment classes. The modeling results are being used to create experiment-specific residual acceleration data processing schemes for interested investigators.

  7. 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.

  8. Fiber Accelerating Structures

    SciTech Connect

    Hammond, Andrew P.; /Reed Coll. /SLAC

    2010-08-25

    One of the options for future particle accelerators are photonic band gap (PBG) fiber accelerators. PBG fibers are specially designed optical fibers that use lasers to excite an electric field that is used to accelerate electrons. To improve PBG accelerators, the basic parameters of the fiber were tested to maximize defect size and acceleration. Using the program CUDOS, several accelerating modes were found that maximized these parameters for several wavelengths. The design of multiple defects, similar to having closely bound fibers, was studied to find possible coupling or the change of modes. The amount of coupling was found to be dependent on distance separated. For certain distances accelerating coupled modes were found and examined. In addition, several non-periodic fiber structures were examined using CUDOS. The non-periodic fibers produced several interesting results and promised more modes given time to study them in more detail.

  9. Accelerating, hyperaccelerating, and decelerating networks

    NASA Astrophysics Data System (ADS)

    Gagen, M. J.; Mattick, J. S.

    2005-07-01

    Many growing networks possess accelerating statistics where the number of links added with each new node is an increasing function of network size so the total number of links increases faster than linearly with network size. In particular, biological networks can display a quadratic growth in regulator number with genome size even while remaining sparsely connected. These features are mutually incompatible in standard treatments of network theory which typically require that every new network node possesses at least one connection. To model sparsely connected networks, we generalize existing approaches and add each new node with a probabilistic number of links to generate either accelerating, hyperaccelerating, or even decelerating network statistics in different regimes. Under preferential attachment for example, slowly accelerating networks display stationary scale-free statistics relatively independent of network size while more rapidly accelerating networks display a transition from scale-free to exponential statistics with network growth. Such transitions explain, for instance, the evolutionary record of single-celled organisms which display strict size and complexity limits.

  10. Military Exposures

    MedlinePLUS

    ... Enter ZIP code here Enter ZIP code here Military Exposures Veterans may have been exposed to a range of chemical, physical, and environmental hazards during military service. Gulf War Newsletter The winter 2016 issue ...

  11. Inverse free-electron laser accelerator

    SciTech Connect

    Pellegrini, C.; Campisi, R.

    1982-01-01

    We first describe the basic physical properties of an inverse free-electron laser and make an estimate of the order of magnitude of the accelerating field obtainable with such a system; then apply the general ideas to the design of an actual device and through this example we give a more accurate evaluation of the fundamental as well as the technical limitations that this acceleration scheme imposes.

  12. An introduction to acceleration mechanisms

    SciTech Connect

    Palmer, R.B.

    1987-05-01

    This paper discusses the acceleration of charged particles by electromagnetic fields, i.e., by fields that are produced by the motion of other charged particles driven by some power source. The mechanisms that are discussed include: Ponderamotive Forces, Acceleration, Plasma Beat Wave Acceleration, Inverse Free Electron Laser Acceleration, Inverse Cerenkov Acceleration, Gravity Acceleration, 2D Linac Acceleration and Conventional Iris Loaded Linac Structure Acceleration. (LSP)

  13. 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.

  14. Relativistic Shocks: Particle Acceleration and Magnetization

    NASA Astrophysics Data System (ADS)

    Sironi, L.; Keshet, U.; Lemoine, M.

    2015-10-01

    We review the physics of relativistic shocks, which are often invoked as the sources of non-thermal particles in pulsar wind nebulae (PWNe), gamma-ray bursts (GRBs), and active galactic nuclei (AGN) jets, and as possible sources of ultra-high energy cosmic-rays. We focus on particle acceleration and magnetic field generation, and describe the recent progress in the field driven by theory advances and by the rapid development of particle-in-cell (PIC) simulations. In weakly magnetized or quasi parallel-shocks (i.e. where the magnetic field is nearly aligned with the flow), particle acceleration is efficient. The accelerated particles stream ahead of the shock, where they generate strong magnetic waves which in turn scatter the particles back and forth across the shock, mediating their acceleration. In contrast, in strongly magnetized quasi-perpendicular shocks, the efficiencies of both particle acceleration and magnetic field generation are suppressed. Particle acceleration, when efficient, modifies the turbulence around the shock on a long time scale, and the accelerated particles have a characteristic energy spectral index of s_{?}eq2.2 in the ultra-relativistic limit. We discuss how this novel understanding of particle acceleration and magnetic field generation in relativistic shocks can be applied to high-energy astrophysical phenomena, with an emphasis on PWNe and GRB afterglows.

  15. RLA (Recirculating Linear Accelerator) accelerating cavity improvements

    SciTech Connect

    Smith, D.L.; Johnson, W.A.; Turman, B.N.; Bennett, L.F.

    1990-01-01

    In the Recirculating Linear Accelerator, we will inject a 10-kA to 20-kA electron beam, and then focus and guide it with an IFR plasma channel, which is created with a low energy electron beam. The REB will be transported through a closed racetrack or a spiral beam line to be re-accelerated by the ringing waveform of dielectric cavities. By adding more accelerating cavities along the beam line, high energies can be achieved. Experiments are in progress to study IFR beam transport issues. A new injector is needed for beam re- acceleration experiments. We are presently installing this new REB injector which will-provide a higher amplitude ({approximately}4 MV), longer duration ({approximately}40-ns FWHM), more rectangularly shaped({approximately}25-ns full width at 90% peak) waveform and a colder beam than were achievable with the previous 1.5-MV injector. The resultant constant beam energy can be more efficiently matched the guiding IFR plasma channel in the beam line and to the turning section magnetic fields. We are now developing new cavities that produce accelerating voltage pulses with improved waveform flatness, width, and amplitudes that do not suffer unacceptable degradation over the first four ringing periods. This effort requires network solver and electrostatic field stress analysis computer codes, and a scaled test model to compare actual waveforms to those predicted by the simulations. 10 refs., 9 figs.

  16. THE DIELECTRIC WALL ACCELERATOR

    SciTech Connect

    Caporaso, G J; Chen, Y; Sampayan, S E

    2009-08-17

    The Dielectric Wall Accelerator (DWA), a class of induction accelerators, employs a novel insulating beam tube to impress a longitudinal electric field on a bunch of charged particles. The surface flashover characteristics of this tube may permit the attainment of accelerating gradients on the order of 100 MV/m for accelerating pulses on the order of a nanosecond in duration. A virtual traveling wave of excitation along the tube is produced at any desired speed by controlling the timing of pulse generating modules that supply a tangential electric field to the tube wall. Because of the ability to control the speed of this virtual wave, the accelerator is capable of handling any charge to mass ratio particle; hence it can be used for electrons, protons and any ion. The accelerator architectures, key technologies and development challenges will be described.

  17. Acceleration of energetic particles

    NASA Astrophysics Data System (ADS)

    Forman, M. A.; Webb, G. M.

    Acceleration of some particles from the background plasma to highly superthermal energies is a common feature of collisionless shocks in interplanetary space. The complete in situ measurements of bulk flows, thermal plasma, electromagnetic waves and energetic particles available for interplanetary shocks both suggest and test the models of shock acceleration in the solar system and the rest of the universe. This tutorial will review the present state of shock acceleration theory. Scatter-free acceleration by grad B drift in the plasma electric field E = -V x B/c, and diffusive acceleration resulting from scattering by Alfven waves in the plasma on both sides of the shock are discussed. The diffusive theory in simple steady state gives power-law spectra, but also shows the effects of time-dependent shocks and injection rates, escape and other losses, the self-consistent Alfven wave spectra, and plasma flow fields affected by diffusive energetic particle acceleration.

  18. Current limiters

    SciTech Connect

    Loescher, D.H.; Noren, K.

    1996-09-01

    The current that flows between the electrical test equipment and the nuclear explosive must be limited to safe levels during electrical tests conducted on nuclear explosives at the DOE Pantex facility. The safest way to limit the current is to use batteries that can provide only acceptably low current into a short circuit; unfortunately this is not always possible. When it is not possible, current limiters, along with other design features, are used to limit the current. Three types of current limiters, the fuse blower, the resistor limiter, and the MOSFET-pass-transistor limiters, are used extensively in Pantex test equipment. Detailed failure mode and effects analyses were conducted on these limiters. Two other types of limiters were also analyzed. It was found that there is no best type of limiter that should be used in all applications. The fuse blower has advantages when many circuits must be monitored, a low insertion voltage drop is important, and size and weight must be kept low. However, this limiter has many failure modes that can lead to the loss of over current protection. The resistor limiter is simple and inexpensive, but is normally usable only on circuits for which the nominal current is less than a few tens of milliamperes. The MOSFET limiter can be used on high current circuits, but it has a number of single point failure modes that can lead to a loss of protective action. Because bad component placement or poor wire routing can defeat any limiter, placement and routing must be designed carefully and documented thoroughly.

  19. 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.

  20. Airbreathing Acceleration Toward Earth Orbit

    SciTech Connect

    Whitehead, J C

    2007-05-09

    As flight speed increases, aerodynamic drag rises more sharply than the availability of atmospheric oxygen. The ratio of oxygen mass flux to dynamic pressure cannot be improved by changing altitude. The maximum possible speed for airbreathing propulsion is limited by the ratio of air capture area to vehicle drag area, approximately Mach 6 at equal areas. Simulation of vehicle acceleration shows that the use of atmospheric oxygen offers a significant potential for minimizing onboard consumables at low speeds. These fundamental calculations indicate that a practical airbreathing launch vehicle would accelerate to near steady-state speed while consuming only onboard fuel, then transition to rocket propulsion. It is suggested that an aircraft carrying a rocket-propelled vehicle to approximately Mach 5 could be a realistic technical goal toward improving access to orbit.

  1. Ion Acceleration During Magnetic Reconnection

    NASA Astrophysics Data System (ADS)

    Drake, J. F.; Swisdak, M.; Phan, T. D.; Cassak, P. A.; Shay, M. A.; Lepri, S. T.; Quataert, E.; Lin, R. P.; Zurbuchen, T. H.

    2008-12-01

    We explore the mechanism for ion acceleration during magnetic reconnection to understand the energetic particle spectra produced during flares and in the solar wind. Reconnection driven ion acceleration is initiated as particles move from upstream into the Alfvenic exhaust. In the case of a weak guide field, protons and higher mass particles behave like pickup particles in that they abruptly cross a narrow boundary layer and find themselves in a region of Alfvenic outflow. Their motion then mimics that of a classic pickup ion, gaining an Alfvenic ExB flow in the jet and a thermal speed close to the Alfven speed. In the case of a strong guide field particle acceleration is strongly enhanced for ions with high mass-to-charge (m/q) ratio since these particles act as pick-up particles while small m/q particles are adiabatic. Once ions become super-Aflvenic their acceleration is, like electrons, dominated by Fermi reflection during island contraction and their energy increases until it is limited by firehose marginal stability. The ion distribution function for super-Alfvenic ions then takes the form of a v-5 distribution. During reconnection in a multi-island environment, as in flares, strong enhancements in high m/q ions are expected. This picture is consistent with several observations related to flare and local solar wind ion acceleration: (1) the ubiquitous observations of energy proportional to mass; (2) strong enhancements in high m/q ions during impulsive flares; and (3) the temperature increments of solar wind exhausts.

  2. 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.

  3. 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.

  4. The foxhole accelerating structure

    SciTech Connect

    Fernow, R.C.; Claus, J.

    1992-07-17

    This report examines some properties of a new type of open accelerating structure. It consists of a series of rectangular cavities, which we call foxholes, joined by a beam channel. The power for accelerating the particles comes from an external radiation source and enters the cavities through their open upper surfaces. Analytic and computer calculations are presented showing that the foxhole is a suitable structure for accelerating relativistic electrons.

  5. Optically pulsed electron accelerator

    DOEpatents

    Fraser, John S. (Los Alamos, NM); Sheffield, Richard L. (Los Alamos, NM)

    1987-01-01

    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 radio frequency powered accelerator cell which accelerates the electron burst emitted by the photoemissive electron source.

  6. 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.

  7. 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.

  8. 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

  9. FFAGS for rapid acceleration

    SciTech Connect

    Carol J. Johnstone and Shane Koscielniak

    2002-09-30

    When large transverse and longitudinal emittances are to be transported through a circular machine, extremely rapid acceleration holds the advantage that the beam becomes immune to nonlinear resonances because there is insufficient time for amplitudes to build up. Uncooled muon beams exhibit large emittances and require fast acceleration to avoid decay losses and would benefit from this style of acceleration. The approach here employs a fixed-field alternating gradient or FFAG magnet structure and a fixed frequency acceleration system. Acceptance is enhanced by the use only of linear lattice elements, and fixed-frequency rf enables the use of cavities with large shunt resistance and quality factor.

  10. Occupational Exposures and Longitudinal Lung Function Decline

    PubMed Central

    Liao, Shu-Yi; Lin, Xihong; Christiani, David C.

    2015-01-01

    Background Few longitudinal studies have been conducted on occupational exposure and lung function. This study investigated occupational dust exposure effects on lung function and whether genetic variants influence such effects. Methods The study population (1,332 participants) was from the Framingham Heart Study, in which participant lung function measures were available from up to five examinations over nearly 17 years. Occupational dust exposures were classified into more and less likely dust exposure. We used linear mixed effects models for the analysis. Results Participants with more likely dust exposure had a mean 4.5 mL/year excess loss rate of FEV1 over time. However, occupational dust exposures alone or interactions with age or time had no significant effect on FEV1/FVC. No statistically significant effects of genetic modifications in the different subgroups were identified for FEV1 loss. Conclusions Occupational dust exposures may accelerate the rate of FEV1 loss but not FEV1/FVC loss. PMID:25384732

  11. Requirements for Simulating Space Radiation With Particle Accelerators

    NASA Technical Reports Server (NTRS)

    Schimmerling, W.; Wilson, J. W.; Cucinotta, F.; Kim, M-H Y.

    2004-01-01

    Interplanetary space radiation consists of fully ionized nuclei of atomic elements with high energy for which only the few lowest energy ions can be stopped in shielding materials. The health risk from exposure to these ions and their secondary radiations generated in the materials of spacecraft and planetary surface enclosures is a major limiting factor in the management of space radiation risk. Accurate risk prediction depends on a knowledge of basic radiobiological mechanisms and how they are modified in the living tissues of a whole organism. To a large extent, this knowledge is not currently available. It is best developed at ground-based laboratories, using particle accelerator beams to simulate the components of space radiation. Different particles, in different energy regions, are required to study different biological effects, including beams of argon and iron nuclei in the energy range 600 to several thousand MeV/nucleon and carbon beams in the energy range of approximately 100 MeV/nucleon to approximately 1000 MeV/nucleon. Three facilities, one each in the United States, in Germany and in Japan, currently have the partial capability to satisfy these constraints. A facility has been proposed using the Brookhaven National Laboratory Booster Synchrotron in the United States; in conjunction with other on-site accelerators, it will be able to provide the full range of heavy ion beams and energies required. International cooperation in the use of these facilities is essential to the development of a safe international space program.

  12. 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...

  13. Spectral evolution of accelerated particles in supernova remnants

    NASA Astrophysics Data System (ADS)

    Jiang, Z. J.; Zhang, L.; Fang, J.

    2013-08-01

    The spectral evolution of accelerated particles in supernova remnants (SNRs) is studied within the frame of the age-limited acceleration model. Because of possible amplified magnetic field around the shock in SNRs, the Alfvnic effect on the particle distribution accelerated at shock will become important. Based on available evolution models of the amplified magnetic field, the source spectral slope (qtp(t)) in the test particle approximation of shock acceleration evolves with SNR's age and qtp ? 4.2-4.4 depending on assumed values of the maximum energy of the accelerated particles and types of SNRs.

  14. Lifetime Prediction for Degradation of Solar Mirrors using Step-Stress Accelerated Testing (Presentation)

    SciTech Connect

    Lee, J.; Elmore, R.; Kennedy, C.; Gray, M.; Jones, W.

    2011-09-01

    This research is to illustrate the use of statistical inference techniques in order to quantify the uncertainty surrounding reliability estimates in a step-stress accelerated degradation testing (SSADT) scenario. SSADT can be used when a researcher is faced with a resource-constrained environment, e.g., limits on chamber time or on the number of units to test. We apply the SSADT methodology to a degradation experiment involving concentrated solar power (CSP) mirrors and compare the results to a more traditional multiple accelerated testing paradigm. Specifically, our work includes: (1) designing a durability testing plan for solar mirrors (3M's new improved silvered acrylic "Solar Reflector Film (SFM) 1100") through the ultra-accelerated weathering system (UAWS), (2) defining degradation paths of optical performance based on the SSADT model which is accelerated by high UV-radiant exposure, and (3) developing service lifetime prediction models for solar mirrors using advanced statistical inference. We use the method of least squares to estimate the model parameters and this serves as the basis for the statistical inference in SSADT. Several quantities of interest can be estimated from this procedure, e.g., mean-time-to-failure (MTTF) and warranty time. The methods allow for the estimation of quantities that may be of interest to the domain scientists.

  15. 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.

  16. Scaling FFAG accelerator for muon acceleration

    SciTech Connect

    Lagrange, JB.; Planche, T.; Mori, Y.

    2011-10-06

    Recent developments in scaling fixed field alternating gradient (FFAG) accelerators have opened new ways for lattice design, with straight sections, and insertions like dispersion suppressors. Such principles and matching issues are detailed in this paper. An application of these new concepts is presented to overcome problems in the PRISM project.

  17. Accelerators Beyond The Tevatron?

    SciTech Connect

    Lach, Joseph

    2010-07-29

    Following the successful operation of the Fermilab superconducting accelerator three new higher energy accelerators were planned. They were the UNK in the Soviet Union, the LHC in Europe, and the SSC in the United States. All were expected to start producing physics about 1995. They did not. Why?.

  18. Microscale acceleration history discriminators

    DOEpatents

    Polosky, Marc A. (Albuquerque, NM); Plummer, David W. (Albuquerque, NM)

    2002-01-01

    A new class of micromechanical acceleration history discriminators is claimed. These discriminators allow the precise differentiation of a wide range of acceleration-time histories, thereby allowing adaptive events to be triggered in response to the severity (or lack thereof) of an external environment. Such devices have applications in airbag activation, and other safety and surety applications.

  19. 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.

  20. 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.

  1. Accelerators Beyond The Tevatron?

    SciTech Connect

    Lach, Joseph

    2010-07-01

    Following the successful operation of the Fermilab superconducting accelerator three new higher energy accelerators were planned. They were the UNK in the Soviet Union, the LHC in Europe, and the SSC in the United States. All were expected to start producing physics about 1995. They did not. Why?

  2. KEK digital accelerator

    NASA Astrophysics Data System (ADS)

    Iwashita, T.; Adachi, T.; Takayama, K.; Leo, K. W.; Arai, T.; Arakida, Y.; Hashimoto, M.; Kadokura, E.; Kawai, M.; Kawakubo, T.; Kubo, Tomio; Koyama, K.; Nakanishi, H.; Okazaki, K.; Okamura, K.; Someya, H.; Takagi, A.; Tokuchi, A.; Wake, M.

    2011-07-01

    The High Energy Accelerator Research Organization KEK digital accelerator (KEK-DA) is a renovation of the KEK 500 MeV booster proton synchrotron, which was shut down in 2006. The existing 40 MeV drift tube linac and rf cavities have been replaced by an electron cyclotron resonance (ECR) ion source embedded in a 200 kV high-voltage terminal and induction acceleration cells, respectively. A DA is, in principle, capable of accelerating any species of ion in all possible charge states. The KEK-DA is characterized by specific accelerator components such as a permanent magnet X-band ECR ion source, a low-energy transport line, an electrostatic injection kicker, an extraction septum magnet operated in air, combined-function main magnets, and an induction acceleration system. The induction acceleration method, integrating modern pulse power technology and state-of-art digital control, is crucial for the rapid-cycle KEK-DA. The key issues of beam dynamics associated with low-energy injection of heavy ions are beam loss caused by electron capture and stripping as results of the interaction with residual gas molecules and the closed orbit distortion resulting from relatively high remanent fields in the bending magnets. Attractive applications of this accelerator in materials and biological sciences are discussed.

  3. Accelerators, Beams And Physical Review Special Topics - Accelerators And Beams

    SciTech Connect

    Siemann, R.H.; /SLAC

    2011-10-24

    Accelerator science and technology have evolved as accelerators became larger and important to a broad range of science. Physical Review Special Topics - Accelerators and Beams was established to serve the accelerator community as a timely, widely circulated, international journal covering the full breadth of accelerators and beams. The history of the journal and the innovations associated with it are reviewed.

  4. 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

  5. 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.

  6. EXPOSURE ANALYSIS

    EPA Science Inventory

    This proceedings chapter will discuss the state-of-the-science regarding the evaluation of exposure as it relates to water quality criteria (WQC), sediment quality guidelines (SQG), and wildlife criteria (WC). Throughout this discussion, attempts are made to identify the methods ...

  7. Controllable Laser Ion Acceleration

    NASA Astrophysics Data System (ADS)

    Kawata, S.; Kamiyama, D.; Ohtake, Y.; Takano, M.; Barada, D.; Kong, Q.; Wang, P. X.; Gu, Y. J.; Wang, W. M.; Limpouch, J.; Andreev, A.; Bulanov, S. V.; Sheng, Z. M.; Klimo, O.; Psikal, J.; Ma, Y. Y.; Li, X. F.; Yu, Q. S.

    2016-02-01

    In this paper a future laser ion accelerator is discussed to make the laser-based ion accelerator compact and controllable. Especially a collimation device is focused in this paper. The future laser ion accelerator should have an ion source, ion collimators, ion beam bunchers, and ion post acceleration devices [Laser Therapy 22, 103(2013)]: the ion particle energy and the ion energy spectrum are controlled to meet requirements for a future compact laser ion accelerator for ion cancer therapy or for other purposes. The energy efficiency from the laser to ions is improved by using a solid target with a fine sub-wavelength structure or a near-critical density gas plasma. The ion beam collimation is performed by holes behind the solid target or a multi-layered solid target. The control of the ion energy spectrum and the ion particle energy, and the ion beam bunching would be successfully realized by a multistage laser-target interaction.

  8. Psychological effects of thought acceleration.

    PubMed

    Pronin, Emily; Jacobs, Elana; Wegner, Daniel M

    2008-10-01

    Six experiments found that manipulations that increase thought speed also yield positive affect. These experiments varied in both the methods used for accelerating thought (i.e., instructions to brainstorm freely, exposure to multiple ideas, encouragement to plagiarize others' ideas, performance of easy cognitive tasks, narration of a silent video in fast-forward, and experimentally controlled reading speed) and the contents of the thoughts that were induced (from thoughts about money-making schemes to thoughts of five-letter words). The results suggested that effects of thought speed on mood are partially rooted in the subjective experience of thought speed. The results also suggested that these effects can be attributed to the joy-enhancing effects of fast thinking (rather than only to the joy-killing effects of slow thinking). This work is inspired by observations of a link between "racing thoughts" and euphoria in cases of clinical mania, and potential implications of that observed link are discussed. PMID:18837610

  9. Diffusive-Compressive Acceleration of Charged Particles

    NASA Astrophysics Data System (ADS)

    Jokipii, J. R.; Giacalone, J.; Kta, J.

    2001-12-01

    We consider the transport of energetic particles in a medium through which gradual (non-shock) compressions exist and propagate. As is the case with shocks, these compressions can accelerate charged particles. We have previously considered such acceleration in the specific context of CIRs (Giacalone, J., Jokipii, and Kta, Joint SOHO-ACE Symposium Proceedings, in press, 2001). There we suggested that it may explain CIR-related energetic particles observed in the inner Heliosphere, near 1 AU, well inside of the radius where the co-rotating shock has formed. Here we extend this concept to the general problem of acceleration by non-shock compressions, and consider primarily the limit in which the particle motion is diffusive. The relevant dimensionless parameter is the ratio Rc of the characteristic compression length scale L to the diffusive skin depth ? D = ? /U , where U is the velocity and ? is the diffusion coefficient. Clearly, Rc = U L/? . If Rc << 1 , the results reduce to those of diffusive shock acceleration. We present the results from solving the transport equation for a variety of compressive disturbances with various values of Rc, and find significant charged-particle acceleration. We discuss the physics of this acceleration and the dependence on the various parameters. Possible applications of this mechanism to heliospheric and other contexts will be discussed. We sugggest that in some cases this new form of acceleration may help to explain observations.

  10. 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.

  11. Numerical simulation of swash zone fluid accelerations

    NASA Astrophysics Data System (ADS)

    Puleo, Jack A.; Farhadzadeh, Ali; Kobayashi, Nobuhisa

    2007-07-01

    A volume-of-fluid Navier-Stokes solver incorporating a k-ɛ closure model, NumErical Water FLUME (NEWFLUME) (Lin and Xu, 2005) is used to investigate the temporal and spatial structure of accelerations in the swash zone of steep beaches for surging, plunging, and nearly spilling waves. Simulations for idealized swash over planar slopes show that shoreward directed local accelerations exist only for up to 22% of the swash cycle depending on wave type. In general, shoreward directed local accelerations were predicted to occur only near the wave run down limit (Baldock and Holmes, 1997). Similarly, convective accelerations had the largest magnitudes during this time and tended to be either near zero or shoreward directed for the remainder of the swash cycle. This finding is in direct contrast to a modified ballistic theory for swash motion arising as a particular solution to the depth-averaged nonlinear shallow water equations (Peregrine and Williams, 2001) that predicts the convective acceleration maintains the sign of the fluid velocity. Near-bed pressure gradients are found to be poorly correlated to both the depth-averaged and near-bed local acceleration. These numerical findings indicate that local fluid accelerations are not a proxy for pressure gradients in the swash zone for enhanced sediment transporting mechanisms or parameterizations. However, the numerical results require corroboration with highly resolved swash zone data.

  12. Rf cavity primer for cyclic proton accelerators

    SciTech Connect

    Griffin, J.E.

    1988-04-01

    The purpose of this note is to describe the electrical and mechanical properites of particle accelerator rf cavities in a manner which will be useful to physics and engineering graduates entering the accelerator field. The discussion will be limited to proton (or antiproton) synchrotron accelerators or storage rings operating roughly in the range of 20 to 200 MHz. The very high gradient, fixed frequency UHF or microwave devices appropriate for electron machines and the somewhat lower frequency and broader bandwidth devices required for heavy ion accelerators are discussed extensively in other papers in this series. While it is common pratice to employ field calculation programs such as SUPERFISH, URMEL, or MAFIA as design aids in the development of rf cavities, we attempt here to elucidate various of the design parameters commonly dealt with in proton machines through the use of simple standing wave coaxial resonator expressions. In so doing, we treat only standing wave structures. Although low-impedance, moderately broad pass-band travelling wave accelerating systems are used in the CERN SPS, such systems are more commonly found in linacs, and they have not been used widely in large cyclic accelerators. Two appendices providing useful supporting material regarding relativistic particle dynamics and synchrotron motion in cyclic accelerators are added to supplement the text.

  13. Accelerating beams with non-parabolic trajectories

    NASA Astrophysics Data System (ADS)

    Yan, Shaohui; Li, Manman; Yao, Baoli; Lei, Ming; Yu, Xianghua; Qian, Jia; Gao, Peng

    2014-03-01

    We present a family of one-dimensional accelerating beams in the paraxial limit whose trajectory is described, in normalized coordinates (?, s), by a non-parabolic curve ? = ?(s) with ?(s) denoting the transverse shift of beams. When taking different values of the parameters appearing in ?(s), three types of accelerating beams are observed. The first type accelerates initially along X direction and almost stops accelerating after traveling a large distance. The second type is seen to travel along a straight line with an angle with respect to the Z-axis at large distance. The beam of the last type is seen to leave initially upward and cross the Z-axis downward after traveling some distance.

  14. 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.

  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. Muon acceleration in FFAG rings

    NASA Astrophysics Data System (ADS)

    Keil, E.; Sessler, A. M.

    2005-02-01

    Muon acceleration from 6 or 10 to 20 GeV in fixed-field alternating gradient (FFAG) rings is considered. The novel physics issues associated with non-scaling FFAG machines, namely the very acceleration process and the crossing of transverse imperfection resonances are addressed. These FFAG machines are essentially strong-focusing rings with a dispersion small enough to keep muons over the full momentum range inside the same magnet aperture. We consider two cases: (i) A Modified FODO Ring with about a metre long straight sections, enough to house normal-conducting RF cavities at about 200 MHz and (ii) A Doublet Ring with a few metres long straight sections, enough for super-conducting RF cavities also at about 200 MHz. Parameters are derived for the lattice and RF system of an electron model. It accelerates electrons from about 10-20 MeV and allows one to study the critical issues of non-scaling FFAGs. For both a full machine and a model, lattice parameters such as magnet type and dimension, spacing, and number of cells are presented. The consequences of misaligned magnets are studied by simulation. Practical RF system design issues, e.g. RF power, and the limit on the bunch population due to beam loading are estimated.

  17. Limitations and Failures of the Layzer Model

    SciTech Connect

    Mikaelian, K O

    2007-12-21

    We report several limitations and failure modes of the recently expanded Layzer model for hydrodynamic instabilities. The failures occur for large initial amplitudes, for stable accelerations, and for spikes in two-fluid systems.

  18. 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.

  19. Tripartite entanglement of fermionic system in accelerated frames

    SciTech Connect

    Khan, Salman

    2014-09-15

    The dynamics of tripartite entanglement of fermionic system in noninertial frames through linear contraction criterion when one or two observers are accelerated is investigated. In one observer accelerated case the entanglement measurement is not invariant with respect to the partial realignment of different subsystems and for two observers accelerated case it is invariant. It is shown that the acceleration of the frame does not generate entanglement in any bipartite subsystems. Unlike the bipartite states, the genuine tripartite entanglement does not completely vanish in both one observer accelerated and two observers accelerated cases even in the limit of infinite acceleration. The degradation of tripartite entanglement is fast when two observers are accelerated than when one observer is accelerated. It is shown that tripartite entanglement is a better resource for quantum information processing than the bipartite entanglement in noninertial frames. - Highlights: Tripartite entanglement of fermionic system in noninertial frames is studied. Linear contraction criterion for quantifying tripartite entanglement is used. Acceleration does not produce any bipartite entanglement. The invariance of entanglement quantifier depends on accelerated observers. The tripartite entanglement degrades against the acceleration, it never vanishes.

  20. The MESA accelerator

    SciTech Connect

    Aulenbacher, Kurt

    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.

  1. 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.

  2. Acceleration: More than Grade Skipping.

    ERIC Educational Resources Information Center

    Paulus, Pat

    1984-01-01

    The definition of acceleration for gifted students is expanded to include early entrance, partial acceleration, compressing curricula, advanced courses, and mentors and tutors. Popular theories about the social and emotional harm to accelerants is disproved. (Author/CL)

  3. Compact RF ion source for industrial electrostatic ion accelerator.

    PubMed

    Kwon, Hyeok-Jung; Park, Sae-Hoon; Kim, Dae-Il; Cho, Yong-Sub

    2016-02-01

    Korea Multi-purpose Accelerator Complex is developing a single-ended electrostatic ion accelerator to irradiate gaseous ions, such as hydrogen and nitrogen, on materials for industrial applications. ELV type high voltage power supply has been selected. Because of the limited space, electrical power, and robust operation, a 200 MHz RF ion source has been developed. In this paper, the accelerator system, test stand of the ion source, and its test results are described. PMID:26932115

  4. Compact RF ion source for industrial electrostatic ion accelerator

    NASA Astrophysics Data System (ADS)

    Kwon, Hyeok-Jung; Park, Sae-Hoon; Kim, Dae-Il; Cho, Yong-Sub

    2016-02-01

    Korea Multi-purpose Accelerator Complex is developing a single-ended electrostatic ion accelerator to irradiate gaseous ions, such as hydrogen and nitrogen, on materials for industrial applications. ELV type high voltage power supply has been selected. Because of the limited space, electrical power, and robust operation, a 200 MHz RF ion source has been developed. In this paper, the accelerator system, test stand of the ion source, and its test results are described.

  5. A new microwave EB accelerator for radiation processing

    NASA Astrophysics Data System (ADS)

    Cracknell, P. J.

    1995-02-01

    A new high beam power microwave electron linear accelerator, LINTEC 1020, has been built and installed for the AEA, EBIS (Harwell) Limited medical sterilisation irradiation facility. LINTEC microwave electron beam accelerator designs are based upon travelling wave RF structures working at 1300 MHz, with beam powers from 10 to 45 k Watts at 5 to 12 MeV. The accelerator design, installation and operating details are described together with performance characteristics of alternative equipments.

  6. Measuring exposures to glycol ethers.

    PubMed Central

    Clapp, D E; Zaebst, D D; Herrick, R F

    1984-01-01

    In 1981, NIOSH began investigating the potential reproductive health effects resulting from exposures to a class of organic solvents known generically as glycol ethers (GE). This research was begun as a result of the NIOSH criteria document development program which revealed little data available on the health effects of glycol ether exposure. Toxicologic research was begun by NIOSH and other researchers which suggested substantial reproductive effects in animals. These animal data motivated a study of human exposures in the occupational setting. In 1981 and 1982 NIOSH conducted several walk-through surveys which included preliminary measurements of exposures in a variety of industries including painting trades, coal mining, production blending and distribution facilities, aircraft fueling, and communications equipment repair facilities. The human exposure data from these surveys is summarized in this paper with most results well below 1 parts per million (ppm) and only a few values approaching 10 ppm. Blood samples were collected at one site resulting in GE concentrations below the limit of detection. Exposures to airborne glycol ethers, in the industries investigated during the collection of this data, revealed several problems in reliably sampling GE at low concentrations. It became apparent, from the data and observations of work practices, that air monitoring alone provided an inadequate index of GE exposure. Further field studies of exposure to GE are anticipated, pending location of additional groups of exposed workers and development of more reliable methods for characterizing exposure, especially biological monitoring. PMID:6499824

  7. Workers' exposure to isocyanates

    SciTech Connect

    Lesage, J.; Goyer, N.; Desjardins, F.; Vincent, J.Y.; Perrault, G. )

    1992-02-01

    A model of exposure to isocyanates, based on knowledge of industrial processes and starting materials and the results of industrial hygiene surveys, is proposed. This model of exposure suggests the concentration and physical form of airborne isocyanate monomers and oligomers. A new sampling and analytical system was developed that is capable of determining the physical and chemical characteristics of occupational exposure to a variety of aliphatic and aromatic isocyanates as required by the exposure model. The sampling system consisted of a dual-filter 37-mm cassette, in which the first filter captured aerosol phase contaminants and the second captured vapor phase isocyanates through derivatization with 9-(N-methylaminomethyl) anthracene (MAMA). Urea derivative recovery by the sampling system, isocyanate-MAMA reactivity, and linearity of the calibration curve were evaluated in the laboratory. The practicality of the system was evaluated during field trials. Sampling times are reduced to 15 min, and the detection limit for TDI, HDI, and MDI was 1.0 micrograms/m3. A partial validation of the new sampling system was performed for HDI vapor by comparison to a standard method in field trials and for TDI vapor in a controlled test atmosphere. The analytical system may also be used to measure the concentration of oligomeric isocyanates. Airborne concentrations of isocyanates were measured in two foam plants, nine paint shops, and two foundries to verify the usefulness of the model. Exposure in foam plants was predominantly to gaseous monomeric isocyanates. Exposure to oligomer isocyanates was higher than expected in paint shops. Both monomer and oligomer isocyanates were undetectable in foundries.

  8. 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.

  9. 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.

  10. Non-accelerator experiments

    SciTech Connect

    Goldhaber, M.

    1986-01-01

    This report discusses several topics which can be investigated without the use of accelerators. Topics covered are: (1) proton decay, (2) atmospheric neutrinos, (3) neutrino detection, (4) muons from Cygnus X-3, and (5) the double-beta decay.

  11. Wake field acceleration experiments

    SciTech Connect

    Simpson, J.D.

    1988-01-01

    Where and how will wake field acceleration devices find use for other than, possibly, accelerators for high energy physics. I don't know that this can be responsibly answered at this time. What I can do is describe some recent results from an ongoing experimental program at Argonne which support the idea that wake field techniques and devices are potentially important for future accelerators. Perhaps this will spawn expanded interest and even new ideas for the use of this new technology. The Argonne program, and in particular the Advanced Accelerator Test Facility (AATF), has been reported in several fairly recent papers and reports. But because this is a substantially new audience for the subject, I will include a brief review of the program and the facility before describing experiments. 10 refs., 7 figs.

  12. 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)

  13. Principles of Induction Accelerators

    NASA Astrophysics Data System (ADS)

    Briggs*, Richard J.

    The basic concepts involved in induction accelerators are introduced in this chapter. The objective is to provide a foundation for the more detailed coverage of key technology elements and specific applications in the following chapters. A wide variety of induction accelerators are discussed in the following chapters, from the high current linear electron accelerator configurations that have been the main focus of the original developments, to circular configurations like the ion synchrotrons that are the subject of more recent research. The main focus in the present chapter is on the induction module containing the magnetic core that plays the role of a transformer in coupling the pulsed power from the modulator to the charged particle beam. This is the essential common element in all these induction accelerators, and an understanding of the basic processes involved in its operation is the main objective of this chapter. (See [1] for a useful and complementary presentation of the basic principles in induction linacs.)

  14. Learning about Accelerated Learning.

    ERIC Educational Resources Information Center

    Caine, Geoffrey; Caine, Renate Nummela

    1989-01-01

    When accelerated learning programs succeed, they do so in part because they invoke and integrate skills and basic information, theoretical understanding, and natural knowledge. The trainer must blend these elements appropriately. (JOW)

  15. 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.

  16. 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.

  17. 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)

  18. Beam-limiting and radiation-limiting interlocks

    SciTech Connect

    Macek, R.J.

    1996-04-01

    This paper reviews several aspects of beam-limiting and radiation- limiting interlocks used for personnel protection at high-intensity accelerators. It is based heavily on the experience at the Los Alamos Neutron Science Center (LANSCE) where instrumentation-based protection is used extensively. Topics include the need for ``active`` protection systems, system requirements, design criteria, and means of achieving and assessing acceptable reliability. The experience with several specific devices (ion chamber-based beam loss interlock, beam current limiter interlock, and neutron radiation interlock) designed and/or deployed to these requirements and criteria is evaluated.

  19. Design of the Experimental Exposure Conditions to Simulate Ionizing Radiation Effects on Candidate Replacement Materials for the Hubble Space Telescope

    NASA Technical Reports Server (NTRS)

    Smith, L. Montgomery

    1998-01-01

    In this effort, experimental exposure times for monoenergetic electrons and protons were determined to simulate the space radiation environment effects on Teflon components of the Hubble Space Telescope. Although the energy range of the available laboratory particle accelerators was limited, optimal exposure times for 50 keV, 220 keV, 350 keV, and 500 KeV electrons were calculated that produced a dose-versus-depth profile that approximated the full spectrum profile, and were realizable with existing equipment. For the case of proton exposure, the limited energy range of the laboratory accelerator restricted simulation of the dose to a depth of .5 mil. Also, while optimal exposure times were found for 200 keV, 500 keV and 700 keV protons that simulated the full spectrum dose-versus-depth profile to this depth, they were of such short duration that the existing laboratory could not be controlled to within the required accuracy. In addition to the obvious experimental issues, other areas exist in which the analytical work could be advanced. Improved computer codes for the dose prediction- along with improved methodology for data input and output- would accelerate and make more accurate the calculational aspects. This is particularly true in the case of proton fluxes where a paucity of available predictive software appears to exist. The dated nature of many of the existing Monte Carlo particle/radiation transport codes raises the issue as to whether existing codes are sufficient for this type of analysis. Other areas that would result in greater fidelity of laboratory exposure effects to the space environment is the use of a larger number of monoenergetic particle fluxes and improved optimization algorithms to determine the weighting values.

  20. Microgravity Acceleration Measurement System

    NASA Technical Reports Server (NTRS)

    Foster, William

    2009-01-01

    Microgravity Acceleration Measurement System (MAMS) is an ongoing study of the small forces (vibrations and accelerations) on the ISS that result from the operation of hardware, crew activities, as well as dockings and maneuvering. Results will be used to generalize the types of vibrations affecting vibration-sensitive experiments. Investigators seek to better understand the vibration environment on the space station to enable future research.

  1. 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.

  2. 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.

  3. Breakthrough: Fermilab Accelerator Technology

    SciTech Connect

    2012-04-23

    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.

  4. Rolamite acceleration sensor

    DOEpatents

    Abbin, J.P.; Briner, C.F.; Martin, S.B.

    1993-12-21

    A rolamite acceleration sensor is described which has a failsafe feature including a housing, a pair of rollers, a tension band wrapped in an S shaped fashion around the rollers, wherein the band has a force-generation cut out and a failsafe cut out or weak portion. The failsafe cut out or weak portion breaks when the sensor is subjected to an excessive acceleration so that the sensor fails in an open circuit (non-conducting) state permanently. 6 figures.

  5. Rolamite acceleration sensor

    DOEpatents

    Abbin, Joseph P.; Briner, Clifton F.; Martin, Samuel B.

    1993-01-01

    A rolamite acceleration sensor which has a failsafe feature including a housing, a pair of rollers, a tension band wrapped in an S shaped fashion around the rollers, wherein the band has a force-generation cut out and a failsafe cut out or weak portion. The failsafe cut out or weak portion breaks when the sensor is subjected to an excessive acceleration so that the sensor fails in an open circuit (non-conducting) state permanently.

  6. LHCb GPU acceleration project

    NASA Astrophysics Data System (ADS)

    Badalov, A.; Cámpora, D.; Neufeld, N.; Vilasís-Cardona, X.

    2016-01-01

    The LHCb detector is due to be upgraded for processing high-luminosity collisions, which will increase data bandwidth to the event filter farm from 100 GB/s to 4 TB/s, encouraging us to look for new ways of accelerating Online reconstruction. The Coprocessor Manager is a new framework for integrating LHCb's existing computation pipelines with massively parallel algorithms running on GPUs and other accelerators. This paper describes the system and analyzes its performance.

  7. Laser Plasma Accelerators

    NASA Astrophysics Data System (ADS)

    Malka, Victor

    The continuing development of powerful laser systems has permitted to extend the interaction of laser beams with matter far into the relativistic domain, and to demonstrate new approaches for producing energetic particle beams. The extremely large electric fields, with amplitudes exceeding the TV/m level, that are produced in plasma medium are of relevance particle acceleration. Since the value of this longitudinal electric field, 10,000 times larger than those produced in conventional radio-frequency cavities, plasma accelerators appear to be very promising for the development of compact accelerators. The incredible progresses in the understanding of laser plasma interaction physic, allows an excellent control of electron injection and acceleration. Thanks to these recent achievements, laser plasma accelerators deliver today high quality beams of energetic radiation and particles. These beams have a number of interesting properties such as shortness, brightness and spatial quality, and could lend themselves to applications in many fields, including medicine, radio-biology, chemistry, physics and material science,security (material inspection), and of course in accelerator science.

  8. Biomedical accelerator mass spectrometry

    NASA Astrophysics Data System (ADS)

    Freeman, Stewart P. H. T.; Vogel, John S.

    1995-05-01

    Ultrasensitive SIMS with accelerator based spectrometers has recently begun to be applied to biomedical problems. Certain very long-lived radioisotopes of very low natural abundances can be used to trace metabolism at environmental dose levels ( [greater-or-equal, slanted] z mol in mg samples). 14C in particular can be employed to label a myriad of compounds. Competing technologies typically require super environmental doses that can perturb the system under investigation, followed by uncertain extrapolation to the low dose regime. 41Ca and 26Al are also used as elemental tracers. Given the sensitivity of the accelerator method, care must be taken to avoid contamination of the mass spectrometer and the apparatus employed in prior sample handling including chemical separation. This infant field comprises the efforts of a dozen accelerator laboratories. The Center for Accelerator Mass Spectrometry has been particularly active. In addition to collaborating with groups further afield, we are researching the kinematics and binding of genotoxins in-house, and we support innovative uses of our capability in the disciplines of chemistry, pharmacology, nutrition and physiology within the University of California. The field can be expected to grow further given the numerous potential applications and the efforts of several groups and companies to integrate more the accelerator technology into biomedical research programs; the development of miniaturized accelerator systems and ion sources capable of interfacing to conventional HPLC and GMC, etc. apparatus for complementary chemical analysis is anticipated for biomedical laboratories.

  9. APT accelerator technology

    SciTech Connect

    Schneider, J.D.

    1996-09-01

    Proposed accelerator production of tritium (APT) project requires an accelerator providing a cw proton beam of 100 mA at 1300 MeV. Since most of the technical risk of a high-current cw (continuous-wave, 100% DF) accelerator resides in the low-energy section, Los Alamos is building a 20 MeV duplicate of the accelerator front end to confirm design codes, beam performance, and demonstrate operaional reliability. We report on design details of this low-energy demonstration accelerator (LEDA) and discuss the integrated design of the full accelerator for the APT plant. LEDA`s proton injector is under test and has produced more than 130 mA at 75 keV. Fabrication is proceeding on a 6.7-KeV, 8-m long RFQ, and detailed design is underway on coupled-cavity drift-tube linac (CCDTL) structures. Detailed design and technology experiments are underway on medium-beta superconducting cavities to assess feasibility of replacing the conventional (room-temperature copper) high-energy linac with a linac made of niobium superconducting RF cavities.

  10. Short daily exposure to hand-arm vibrations in Swedish car mechanics.

    PubMed

    Barregrd, Lars

    2003-01-01

    The aim of the study was to examine the daily exposure times to hand-arm vibrations in Swedish car mechanics, to test a method for estimating the exposure time without observing the workers for whole days, and to use the results for predicting the prevalence of vibration-induced white fingers (VWF) by the ISO 5349-model. Six garages were surveyed. In each garage, 5-10 car mechanics were observed in random order every 30 seconds throughout working days. The daily exposure time for each mechanic was estimated from the fraction of the observations that the mechanic was exposed. A total of 51 mechanics were observed, most of them on two different working days, yielding estimates for 95 days. The median effective exposure time was 10 minutes per day (95% confidence interval 5-15 minutes, arithmetic mean 14 minutes, maximum 80 minutes), and most of the exposure time was attributable to fastening and loosening nuts. The within-worker and between-worker variability was high (total sigma2 0.99, geometric standard deviation of 2.7). Using the observed exposure time and data on vibration levels of the main tools in Swedish car mechanics (average weighted acceleration level of 3.5 m/s2), the model in ISO-standard 5349 would predict that only three percent of the car mechanics will suffer from VWF after 20 years of exposure. In contrast, a recent survey of VWF showed the prevalence to be 25 percent. The precision of the observation method was estimated and was found to be good for the group daily mean. On the individual level the precision was only acceptable if the daily exposure time was > or = 40 minutes. In conclusion, the daily exposure time was short and the vibration level was limited. Nevertheless, hand-arm vibrations cause VWF in a significant number of car mechanics. The method of observing workers intermittently seemed to work well. PMID:12650547

  11. Accelerated cleanup risk reduction

    SciTech Connect

    Knapp, R.B.; Aines, R.M.; Blake, R.G.; Copeland, A.B.; Newmark, R.L.; Tompson, A.F.B.

    1998-02-01

    There is no proven technology for remediating contaminant plume source regions in a heterogeneous subsurface. This project is an interdisciplinary effort to develop the requisite new technologies so that will be rapidly accepted by the remediation community. Our technology focus is hydrous pyrolysis/oxidation (HPO) which is a novel in situ thermal technique. We have expanded this core technology to leverage the action of steam injection and place an in situ microbial filter downstream to intercept and destroy the accelerated movement of contaminated groundwater. Most contaminant plume source regions, including the chlorinated solvent plume at LLNL, are in subsurface media characterized by a wide range in hydraulic conductivity. At LLNL, the main conduits for contaminant transport are buried stream channels composed of gravels and sands; these have a hydraulic conductivity in the range of 10{sup -1} to 10{sup -2} cm/s. Clay and silt units with a hydraulic conductivity of 10{sup -1} to 10{sup -6} cm/s bound these buried channels; these are barriers to groundwater movement and contain the highest contaminant concentrations in the source region. New remediation technologies are required because the current ones preferentially access the high conductivity units. HPO is an innovative process for the in situ destruction of contaminants in the entire subsurface. It operates by the injection of steam. We have demonstrated in laboratory experiments that many contaminants rapidly oxidize to harmless compounds at temperatures easily achieved by injecting steam, provided sufficient dissolved oxygen is present. One important challenge in a heterogeneous source region is getting heat, contaminants, and an oxidizing agent in the same place at the same time. We have used the NUFT computer program to simulate the cyclic injection of steam into a contaminated aquifer for design of a field demonstration. We used an 8 hour, steam/oxygen injection cycle followed by a 56 hour relaxation period in which the well was `capped`. Our results show the formation of an inclined gas phase during injection and a fast collapse of the steam zone within an hour of terminating steam injection. The majority of destruction occurs during the collapse phase, when contaminant laden water is drawn back towards the well. Little to no noncondensible gasses are created in this process, removing any possibility of sparging processes interfering with contaminant destruction. Our models suggest that the thermal region should be as hot and as large as possible. To have HPO accepted, we need to demonstrate the in situ destruction of contaminants. This requires the ability to inexpensively sample at depth and under high temperatures. We proved the ability to implies monitoring points at depths exceeding 150 feet in highly heterogeneous soils by use of cone penetrometry. In addition, an extractive system has been developed for sampling fluids and measuring their chemistry under the range of extreme conditions expected. We conducted a collaborative field test of HPO at a Superfund site in southern California where the contaminant is mainly creosote and pentachlorophenol. Field results confirm the destruction of contaminants by HPO, validate our field design from simulations, demonstrate that accurate field measurements of the critical fluid parameters can be obtained using existing monitoring wells (and minimal capital cost) and yield reliable cost estimates for future commercial application. We also tested the in situ microbial filter technology as a means to intercept and destroy the accelerated flow of contaminants caused by the injection of steam. A series of laboratory and field tests revealed that the selected bacterial species effectively degrades trichloroethene in LLNL Groundwater and under LLNL site conditions. In addition, it was demonstrated that the bacteria effectively attach to the LLNL subsurface media. An in-well treatability study indicated that the bacteria initially degrade greater than 99% of the contaminant, to concentrations less than regulatory limits. The duration of this in situ performance is not currently known, but should be consistent with previous field tests.

  12. Criminal exposure.

    PubMed

    1999-09-01

    In August, an HIV-positive man plead guilty to sexually assaulting a 14-year-old boy. The sleeping boy awoke to find [name removed] sexually assaulting him, while watching a pornographic video. [Name removed] plead guilty to the assault with intent to rape a child. In addition, [name removed] received three counts of indecent assault and battery on a child, and exposure of pornographic material to a minor. [Name removed] will remain on probation for five years, although the prosecution had recommended sentencing [name removed] to four or five years in prison. The boy continues to be tested for HIV. PMID:11366904

  13. Diffusive Shock Acceleration and Reconnection Acceleration Processes

    NASA Astrophysics Data System (ADS)

    Zank, G. P.; Hunana, P.; Mostafavi, P.; Le Roux, J. A.; Li, Gang; Webb, G. M.; Khabarova, O.; Cummings, A.; Stone, E.; Decker, R.

    2015-12-01

    Shock waves, as shown by simulations and observations, can generate high levels of downstream vortical turbulence, including magnetic islands. We consider a combination of diffusive shock acceleration (DSA) and downstream magnetic-island-reconnection-related processes as an energization mechanism for charged particles. Observations of electron and ion distributions downstream of interplanetary shocks and the heliospheric termination shock (HTS) are frequently inconsistent with the predictions of classical DSA. We utilize a recently developed transport theory for charged particles propagating diffusively in a turbulent region filled with contracting and reconnecting plasmoids and small-scale current sheets. Particle energization associated with the anti-reconnection electric field, a consequence of magnetic island merging, and magnetic island contraction, are considered. For the former only, we find that (i) the spectrum is a hard power law in particle speed, and (ii) the downstream solution is constant. For downstream plasmoid contraction only, (i) the accelerated spectrum is a hard power law in particle speed; (ii) the particle intensity for a given energy peaks downstream of the shock, and the distance to the peak location increases with increasing particle energy, and (iii) the particle intensity amplification for a particular particle energy, f(x,c/{c}0)/f(0,c/{c}0), is not 1, as predicted by DSA, but increases with increasing particle energy. The general solution combines both the reconnection-induced electric field and plasmoid contraction. The observed energetic particle intensity profile observed by Voyager 2 downstream of the HTS appears to support a particle acceleration mechanism that combines both DSA and magnetic-island-reconnection-related processes.

  14. Diagnostics for advanced laser acceleration experiments

    SciTech Connect

    Misuri, Alessio

    2002-06-01

    The first proposal for plasma based accelerators was suggested by 1979 by Tajima and Dawson. Since then there has been a tremendous progress both theoretically and experimentally. The theoretical progress is particularly due to the growing interest in the subject and to the development of more accurate numerical codes for the plasma simulations (especially particle-in-cell codes). The experimental progress follows from the development of multi-terawatt laser systems based on the chirped-pulse amplification technique. These efforts have produced results in several experiments world-wide, with the detection of accelerated electrons of tens of MeV. The peculiarity of these advanced accelerators is their ability to sustain extremely large acceleration gradients. In the conventional radio frequency linear accelerators (RF linacs) the acceleration gradients are limited roughly to 100 MV/m; this is partially due to breakdown which occurs on the walls of the structure. The electrical breakdown is originated by the emission of the electrons from the walls of the cavity. The electrons cause an avalanche breakdown when they reach other metal parts of the RF linacs structure.

  15. A worldly approach to a new accelerator

    SciTech Connect

    Taubes, G.

    1993-02-19

    Particle physicists are learning to their discomfiture that for one country to plan a multibillion-dollar accelerator, then ask other countries to help build it, is a recipe for frustration. That's the lesson emerging from the struggles to build the Superconducting Super Collider (SSC), the mammoth accelerator that is now in limbo as officials wait to see whether Japan and other nations will pitch in. But a group of laboratory directors who are already planning the next-generation accelerator - a large linear collider that will address physics the SSC can't probe - is taking steps to ensure that it will be an international collaboration from day one. The machine would be a linear accelerator tens of kilometers long with an energy limit of 1 TeV, and would collide electrons and positrons. Two international collaborations are studying designs for radiofreqency cavities that would generate powerful accelerating gradients. A third international group is working on learning how to focus electron and positron beams down to 60 nm in diameter. The proposed accelerator would likely cost $2 to $3 billion, and one possible location is the big island of Hawaii.

  16. 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

  17. 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

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

    SciTech Connect

    Hauptman, Jason S.; Barkhoudarian, Garni; Safaee, Michael; Gorgulho, Alessandra; Tenn, Steven; Agazaryan, Nzhde; Selch, Michael; De Salles, Antonio A.F.

    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.

  19. 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.

  20. TRACKING OF ACCELERATION WITH HNJ METHOD.

    SciTech Connect

    RUGGIERO,A.G.

    2007-11-05

    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.