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1

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

PubMed Central

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

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

2015-01-01

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

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

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

2015-04-15

3

Voltage limitations of electrostatic accelerators  

SciTech Connect

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.

Hyder, H.R. (A. W. Wright Nuclear Structure Laboratory, Yale University P.O. Box 208124, New Haven, Connecticut 06520-8124 (United States))

1999-04-01

4

Voltage limitations of electrostatic accelerators  

NASA Astrophysics Data System (ADS)

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.

Hyder, H. R. McK.

1999-04-01

5

Voltage limitations of electrostatic accelerators  

SciTech Connect

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.

Hyder, H. R. McK. [A. W. Wright Nuclear Structure Laboratory, Yale University P.O. Box 208124, New Haven, Connecticut 06520-8124 (United States)

1999-04-26

6

Improving tritium exposure reconstructions using accelerator mass spectrometry  

PubMed Central

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

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

2010-01-01

7

Nonlinear shock acceleration beyond the Bohm limit  

E-print Network

We suggest a physical mechanism whereby the acceleration time of cosmic rays by shock waves can be significantly reduced. This creates the possibility of particle acceleration beyond the knee energy at ~10^15eV. The acceleration results from a nonlinear modification of the flow ahead of the shock supported by particles already accelerated to the knee momentum at p ~ p_*. The particles gain energy by bouncing off converging magnetic irregularities frozen into the flow in the shock precursor and not so much by re-crossing the shock itself. The acceleration rate is thus determined by the gradient of the flow velocity and turns out to be formally independent of the particle mean free path (m.f.p.). The velocity gradient is, in turn, set by the knee-particles at p ~ p_* as having the dominant contribution to the CR pressure. Since it is independent of the m.f.p., the acceleration rate of particles above the knee does not decrease with energy, unlike in the linear acceleration regime. The reason for the knee formation at p ~ p_* is that particles with $p > p_*$ are effectively confined to the shock precursor only while they are within limited domains in the momentum space, while other particles fall into ``loss-islands'', similar to the ``loss-cone'' of magnetic traps. This structure of the momentum space is due to the character of the scattering magnetic irregularities. They are formed by a train of shock waves that naturally emerge from unstably growing and steepening magnetosonic waves or as a result of acoustic instability of the CR precursor. These losses steepen the spectrum above the knee, which also prevents the shock width from increasing with the maximum particle energy.

M. A. Malkov; P. H. Diamond

2005-09-08

8

Timescale Correlation between Marine Atmospheric Exposure and Accelerated Corrosion Testing  

NASA Technical Reports Server (NTRS)

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.

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

2011-01-01

9

47 CFR 1.1310 - Radiofrequency radiation exposure limits.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 false Radiofrequency radiation exposure limits. 1.1310 Section...of 1969 § 1.1310 Radiofrequency radiation exposure limits. The criteria listed...human exposure to radiofrequency (RF) radiation as specified in §...

2011-10-01

10

47 CFR 1.1310 - Radiofrequency radiation exposure limits.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 false Radiofrequency radiation exposure limits. 1.1310 Section...of 1969 § 1.1310 Radiofrequency radiation exposure limits. (a) Specific...human exposure to radiofrequency (RF) radiation as specified in § 1.1307(b)...

2013-10-01

11

47 CFR 1.1310 - Radiofrequency radiation exposure limits.  

Code of Federal Regulations, 2014 CFR

...2014-10-01 false Radiofrequency radiation exposure limits. 1.1310 Section...of 1969 § 1.1310 Radiofrequency radiation exposure limits. (a) Specific...human exposure to radiofrequency (RF) radiation as specified in § 1.1307(b)...

2014-10-01

12

47 CFR 1.1310 - Radiofrequency radiation exposure limits.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 false Radiofrequency radiation exposure limits. 1.1310 Section...of 1969 § 1.1310 Radiofrequency radiation exposure limits. The criteria listed...human exposure to radiofrequency (RF) radiation as specified in §...

2010-10-01

13

47 CFR 1.1310 - Radiofrequency radiation exposure limits.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 false Radiofrequency radiation exposure limits. 1.1310 Section...of 1969 § 1.1310 Radiofrequency radiation exposure limits. The criteria listed...human exposure to radiofrequency (RF) radiation as specified in §...

2012-10-01

14

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

SciTech Connect

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.

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

2010-01-01

15

Gradient limitations in room temperature and superconducting acceleration structures  

Microsoft Academic Search

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

N. A. Solyak

2008-01-01

16

Gradient Limitations in Room Temperature and Superconducting Acceleration Structures  

Microsoft Academic Search

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

N. A. Solyak

2009-01-01

17

Ultra-Accelerated Natural Sunlight Exposure Testing Facilities  

DOEpatents

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.

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

2004-11-23

18

Efficiency limits of diffusive shock acceleration  

E-print Network

It is well accepted today that diffusive acceleration in shocks results to the cosmic ray spectrum formation. This is in principle true for non-relativistic shocks, since there is a detailed theory covering a large range of their properties and the resulting power-law spectrum, which is nevertheless not as efficient to reach the very high energies observed in the cosmic ray spectrum. On the other hand, the cosmic ray maximum energy and the resulting spectra from relativistic shocks, are still under investigation and debate concerning their contribution to the features of the cosmic ray spectrum and the measured, or implied, cosmic ray radiation from candidate astrophysical sources. Here, we discuss the efficiency of the first order Fermi (diffusive) acceleration mechanism up to relativistic shock speeds, presenting Monte Carlo simulations.

A. Meli; A. Mastichiadis

2007-08-10

19

HPLC-Accelerator MS Measurement of Atrazine Metabolites in Human Urine after Dermal Exposure  

E-print Network

HPLC-Accelerator MS Measurement of Atrazine Metabolites in Human Urine after Dermal Exposure Bruce urine after dermal exposure using HPLC to separate and identify metabolites and accelerator mass scintillation counting prior to injection on the HPLC to ensure that

Hammock, Bruce D.

20

Nonlinear dynamics of autonomous vehicles with limits on acceleration  

NASA Astrophysics Data System (ADS)

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

Davis, L. C.

2014-07-01

21

Human exposure limits to hypergolic fuels  

NASA Technical Reports Server (NTRS)

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.

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

1992-01-01

22

Simulation of cardiovascular response to acceleration stress following weightless exposure  

NASA Technical Reports Server (NTRS)

Physiological adjustments taking place during space flight tend to reduce the tolerance of the crew to headward (+Gz) acceleration experienced during the reentry phase of the flight. This reduced tolerance to acceleration stress apparently arises from an adaptation to the microgravity environment of space, including a decrease in the total circulating blood volume. Countermeasures such as anti-g garments have long been known to improve the tolerance to headward g-force, but their effectiveness in space flight has not been fully evaluated. The simulation study presented in this paper is concerned with the response of the cardiovascular system to g-stress following cardiovascular deconditioning, resulting from exposure to weightlessness, or any of its ground-based experimental analogs. The results serve to demonstrate the utility of mathematical modeling and computer simulation for studying the causes of orthostatic intolerance and the remedial measures to lessen it.

Srinivasan, R.; Leonard, J. I.

1983-01-01

23

ELRA: The exposure limiting robotic apparatus  

SciTech Connect

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.

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

1992-09-01

24

[Titanium dioxide nanoparticles: occupational exposure limits].  

PubMed

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

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

2014-01-01

25

Limitation to Communication of Fermionic System in Accelerated Frame  

NASA Astrophysics Data System (ADS)

In this article, we investigate communication between an inertial observer and an accelerated observer, sharing fermionic system, when they use classical and quantum communication using single rail or dual rail encoding. The purpose of this work is to understand the limit to the communication between an inertial observer and an accelerated observer, with single rail or dual rail encoding of fermionic system. We observe that at the infinite acceleration, the coherent information of single(or double) rail quantum channel vanishes, but those of classical ones may have finite values. In addition, we see that even when considering a method beyond the single-mode approximation, for the communication between Alice and Bob, the dual rail entangled state seems to provide better information transfer than the single rail entangled state, when we take a fixed choice of the Unruh mode. Moreover, we find that the single-mode approximation may not be sufficient to analyze communication of fermionic system in an accelerated frame.

Chang, Jinho; Kwon, Younghun

2015-03-01

26

Limitation to Communication of Fermionic System in Accelerated Frame  

NASA Astrophysics Data System (ADS)

In this article, we investigate communication between an inertial observer and an accelerated observer, sharing fermionic system, when they use classical and quantum communication using single rail or dual rail encoding. The purpose of this work is to understand the limit to the communication between an inertial observer and an accelerated observer, with single rail or dual rail encoding of fermionic system. We observe that at the infinite acceleration, the coherent information of single(or double) rail quantum channel vanishes, but those of classical ones may have finite values. In addition, we see that even when considering a method beyond the single-mode approximation, for the communication between Alice and Bob, the dual rail entangled state seems to provide better information transfer than the single rail entangled state, when we take a fixed choice of the Unruh mode. Moreover, we find that the single-mode approximation may not be sufficient to analyze communication of fermionic system in an accelerated frame.

Chang, Jinho; Kwon, Younghun

2014-09-01

27

Linking accelerated laboratory and outdoor exposure results for PV polymeric materials: a mechanistic study of EVA  

NASA Astrophysics Data System (ADS)

Linking accelerated laboratory test to field performance for predicting the service life of polymeric materials are being investigated at NIST using the reliability-based methodology. Based on this methodology, a successful linkage between the laboratory and field exposure data for a model polymeric material has been made. Recently, this methodology, for the first time, was introduced to the lifetime assessment of PV polymeric materials. In this paper, a mechanistic study of the degradation of three unstabilized model ethylene vinyl acetate (EVA) systems---uncured EVA, cured EVA and laminated EVA---was carried out under accelerated laboratory exposure and outdoor exposure. The NIST SPHERE (Simulated Photodegradation via High Energy Radiant Exposure) was used for the accelerated laboratory tests, and the outdoor exposure was conducted in Gaithersburg, Maryland. Simultaneous multiple stresses, including temperature, relative humidity and UV radiation, were applied individually or in combination during SPHERE exposure. The effects of the environmental factors on the main degradation mechanisms of different EVA systems were investigated. The results showed that the UV radiation was the most important factor for the degradation of EVA and a synergistic effect occurred between UV radiation and relative humidity. A slower degradation rate was observed for the laminated system as a result of limited diffusion of O2 and H2O into EVA. It was also found that the substantial chemical changes of the uncured EVA system did not yield yellowing, which was dramatically different from the peroxide cured EVA system. Additionally, the chemical degradation modes of the three EVA systems exposed outdoors appeared to be similar to those exposed to the SPHERE. The implication of this work to the current test standards was discussed.

Gu, Xiaohong; Pang, Yongyan; Lin, Chiao-Chi; Liu, Kaipeng; Nguyen, Tinh; Chin, Jaonnie W.

2013-09-01

28

10 CFR 850.22 - Permissible exposure limit.  

Code of Federal Regulations, 2010 CFR

...Section 850.22 Energy DEPARTMENT OF ENERGY CHRONIC BERYLLIUM DISEASE PREVENTION PROGRAM Specific Program Requirements...assure that no worker is exposed to an airborne concentration of beryllium greater than the permissible exposure limit established in...

2010-01-01

29

Performance Limiting Effects in X-Band Accelerators  

SciTech Connect

Acceleration gradient is a critical parameter for the design of future TeV-scale linear colliders. The major obstacle to higher gradient in room-temperature accelerators is rf breakdown, which is still a very mysterious phenomenon that depends on the geometry and material of the accelerator as well as the input power and operating frequency. Pulsed heating has been associated with breakdown for many years however there have been no experiments that clearly separate field and heating effects on the breakdown rate. Recently, such experiments have been performed at SLAC with both standing-wave and travelling-wave structures. These experiments have demonstrated that pulsed heating is limiting the gradient. Also, a dual-moded cavity has been designed to better distinguish the electric field, magnetic field and pulsed heating effects on breakdown.

Wang Faya; Adolphsen, Chris; Nantista, Christopher [SLAC National Accelerator Laboratory, Menlo Park, CA, 94025 (United States)

2010-11-04

30

Young Children's Limited and Narrow Exposure to Informational Text  

ERIC Educational Resources Information Center

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…

Yopp, Ruth Helen; Yopp, Hallie Kay

2012-01-01

31

Opportunities and limits of AMS with 3-MV tandem accelerators  

NASA Astrophysics Data System (ADS)

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/cm 2) 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. 36Cl 7+ at 28.8 MeV instead of 36Cl 5+ at 18 MeV can be used.

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

2005-10-01

32

Accelerated Fatigue of Dentin with Exposure to Lactic Acid  

PubMed Central

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

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

2013-01-01

33

Lucky Exposures: Diffraction limited astronomical imaging through the atmosphere  

E-print Network

Through selection of short exposure images we achieve diffraction-limited I-band imaging from well-figured ground-based telescopes as large as 2.5 m diameter. The faint limiting magnitude and large isoplanatic patch size for the Lucky Exposures technique at the Nordic Optical Telescope means that 25% of the night sky is within range of a suitable reference star for I-band imaging. Typically the 1%--10% of exposures with the highest Strehl ratios are selected. When these exposures are shifted and added together, field stars in the resulting images have Strehl ratios as high as 0.26 and full width at half maximum flux (FWHM) as small as 90 milliarcseconds. Within the selected exposures the isoplanatic patch is found to be 60 arcseconds in diameter at 810 nm wavelength. Images within globular clusters and of multiple stars from the Nordic Optical Telescope using reference stars as faint as I~16 are presented. A new generation of CCDs (E2V L3Vision CCDs) were used in these observations, allowing extremely low noise high frame-rate imaging with both fine pixel sampling and a relatively wide field of view. The theoretical performance of these CCDs is compared with the experimental results obtained.

Robert N. Tubbs

2003-11-20

34

Allowable exposure limits for carbon dioxide during extravehicular activity  

NASA Technical Reports Server (NTRS)

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.

Seter, Andrew J.

1993-01-01

35

Concepts and limitations of macroparticle accelerators using travelling magnetic waves  

NASA Astrophysics Data System (ADS)

The concept of a traveling magnetic wave accelerator is discussed with reference to the choice of projectile material, the driving acceleration and its magnitude, and options regarding the power supply. It is shown that this accelerator concept has the potential to accelerate small ferromagnetic particles with a linear acceleration of 500 km/sq s or more, or centripetal acceleration of 2000 km/sq s, producing speeds of 50 km/s in linear accelerators of 2.5 km or less long, or circular accelerators of 2.5 km diameter. The projectile mass can be about 100 mg.

Wipf, S. L.

1982-01-01

36

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

PubMed Central

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

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

2001-01-01

37

Effects of Accelerated Exposure Testing (AET) Conditions on Performance Degradation of Solar Cells and Encapsulants  

SciTech Connect

The paper briefly summarizes the results from several accelerated exposure tests (AET) studies. Causes responsible for the photothermal instability of the encapsulated Si solar cells appear to be multiple and complex.

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

2000-01-01

38

Strategies for setting occupational exposure limits for particles.  

PubMed Central

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

Greim, H A; Ziegler-Skylakakis, K

1997-01-01

39

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

PubMed

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

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

2015-04-17

40

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

NASA Technical Reports Server (NTRS)

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.

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

2012-01-01

41

Development of occupational exposure limits for the Hanford tank farms.  

PubMed

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 stored in 177 underground tanks at the Hanford site in southeastern Washington State. Recent attempts to begin the retrieval and treatment of these wastes require moving the waste to more modern tanks and result in potential exposure of the workers to unfamiliar odors emanating from headspace in the tanks. Given the unknown risks involved, workers were placed on supplied air respiratory protection. CH2MHILL, the managers of the 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 (COPCs) and the resultant development of screening values and Acceptable Occupational Exposure Limits (AOELs) for these COPCs. A total of 1826 chemicals were inventoried and evaluated. Over 1500 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 CH2MHILL industrial hygiene department to evaluate these COPCs. PMID:20180654

Still, Kenneth R; Gardner, Donald E; Snyder, Robert; Anderson, Thomas J; Honeyman, James O; Timchalk, Charles

2010-04-01

42

Extensive changes to occupational exposure limits in Korea.  

PubMed

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

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

2010-11-01

43

Airborne isocyanate exposures in the collision repair industry and a comparison to occupational exposure limits.  

PubMed

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/m(3) for HDI polyisocyanate, and (2) the United Kingdom's Health and Safety Executive (UK-HSE) STEL of 70 ?g NCO/m(3) for all isocyanates. Eighty percent of samples containing HDI polyisocyanate exceeded the OR-OSHA STEL while 98% of samples exceeded the UK-HSE STEL. The majority of painters (67%) wore half-face air-purifying respirators while spray painting. Using the OR-OSHA 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

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

2012-01-01

44

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

PubMed Central

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

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

45

EIS studies of coated metals in accelerated exposure  

Microsoft Academic Search

One of the most popular uses of electrochemical impedance spectroscopy (EIS) is the characterization of the protective properties of coatings on corrodible metals. From early studies up to the present time, many EIS studies have been devoted to the study of the changes in the impedance of coated metals as they undergo either natural or artificial exposure to conditions that

Gordon Bierwagen; Dennis Tallman; Junping Li; Lingyun He; Carol Jeffcoate

2003-01-01

46

Concepts and limitations of macroparticle accelerators using travelling magnetic waves  

SciTech Connect

The concept of an accelerator using a travelling magnetic wave acting on magnetized projectiles is discussed. Although superconductors have a high potential as projectile material, their low critical temperature makes them unsuitable. Among ferromagnetic materials dysprosium seems to be superior. For stable suspension and guidance a high conductivity, preferably superconducting, guide sheet is necessary. Magnetic field gradients of 10/sup 9/ A/m/sup 2/ travelling at 10/sup 6/ m/s should be achievable using present state-of-the-art components; resulting accelerations are greater than or equal to 500 km/s/sup 2/. A linear accelerator for final speeds of 50 km/s needs a length of 2.5 km. Guidance forces sufficient to produce acceleration of 2 x 10/sup 6/ m/s/sup 2/ allow circular accelerators of reasonable size to achieve hypervelocities for small (50 to 100 mg) projectiles. An accelerator of 170 m diameter would surpass the best results from light gas guns. Travelling waves suitable for accelerations of the order of 10/sup 4/ m/s/sup 2/ can be produced without switching, by means of flux displacing rotors, easily adapted to circular accelerators.

Wipf, S.L.

1980-01-01

47

Quantify landslide exposure in areas with limited hazard information  

NASA Astrophysics Data System (ADS)

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.

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

2012-04-01

48

An accelerated exposure and testing apparatus for building joint sealants  

NASA Astrophysics Data System (ADS)

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.

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

2013-09-01

49

Preliminary results of accelerated exposure testing of solar cell system components  

NASA Technical Reports Server (NTRS)

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.

Anagnostou, E.; Forestieri, A. F.

1977-01-01

50

Fundamental limitations to information transfer in accelerated frames  

NASA Astrophysics Data System (ADS)

We study communication between an inertial observer and one of two causally disconnected counteraccelerating observers. We will restrict the quantum channel considering inertial-to-accelerated bipartite classical and quantum communication over different sets of Unruh modes (single-rail or dual-rail encoding). We find that the coherent information (and therefore the amount of entanglement that can be generated via state merging protocol) in this strongly restricted channel presents some interesting monogamy properties between the inertial and only one of the accelerated observers if we take a fixed choice of the Unruh mode used in the channel. The optimization of the controllable parameters is also studied and we find that they deviate from the values usually employed in the literature.

Martín-Martínez, Eduardo; Hosler, Dominic; Montero, Miguel

2012-12-01

51

30 CFR 57.5001 - Exposure limits for airborne contaminants.  

Code of Federal Regulations, 2010 CFR

...Quality, Radiation, Physical Agents, and Diesel Particulate Matter Air Quality-Surface and Underground § 57.5001 Exposure...Excursions above the listed thresholds shall not be of a greater magnitude than is characterized as permissible by the Conference....

2010-07-01

52

30 CFR 56.5001 - Exposure limits for airborne contaminants.  

Code of Federal Regulations, 2010 CFR

...personal exposure to asbestos shall not exceed...average full-shift airborne concentration of...exposed at any time to airborne concentrations of asbestos in excess of 1 fiber...Measurement of airborne asbestos fiber...

2010-07-01

53

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

SciTech Connect

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.

Kanunnikov, V.N.

1982-09-01

54

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

Microsoft Academic Search

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

F. J. Pern; S. H. Glick

2000-01-01

55

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

E-print Network

Acceleration of Key Reactions as a Strategy to Elucidate the Rate-Limiting Chemistry Underlying approach for identifying the rate-limiting step in a series of reactions is to evaluate the consequences PURPOSE. A reconstituted system was used to establish a strat- egy to determine the rate

Wensel, Theodore G.

56

Safe human exposure limits for airborne linear siloxanes during spaceflight  

PubMed Central

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

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

2013-01-01

57

Transmaternal bisphenol A exposure accelerates diabetes type 1 development in NOD mice.  

PubMed

Diabetes mellitus type 1 is an autoimmune disease with a genetic predisposition that is triggered by environmental factors during early life. Epidemiological studies show that bisphenol A (BPA), an endocrine disruptor, has been detected in about 90% of all analyzed human urine samples. In this study, BPA was found to increase the severity of insulitis and the incidence of diabetes in female non obese diabetic (NOD) mice offspring after transmaternal exposure through the dams' drinking water (0, 0.1, 1, and 10mg/l). Both the severity of insulitis in the pancreatic islets at 11 weeks of age and the diabetes prevalence at 20 weeks were significantly increased for female offspring in the highest exposure group compared to the control group. Increased numbers of apoptotic cells, a reduction in tissue resident macrophages and an increase in regulatory T cells were observed in islets prior to insulitis development in transmaternally exposed offspring. The detectable apoptotic cells were identified as mostly glucagon producing alpha-cells but also tissue resident macrophages and beta-cells. In the local (pancreatic) lymph node neither regulatory T cell nor NKT cell populations were affected by maternal BPA exposure. Maternal BPA exposure may have induced systemic immune changes in offspring, as evidenced by alterations in LPS- and ConA-induced cytokine secretion in splenocytes. In conclusion, transmaternal BPA exposure, in utero and through lactation, accelerated the spontaneous diabetes development in NOD mice. This acceleration appeared to be related to early life modulatory effects on the immune system, resulting in adverse effects later in life. PMID:24189131

Bodin, Johanna; Bølling, Anette Kocbach; Becher, Rune; Kuper, Frieke; Løvik, Martinus; Nygaard, Unni Cecilie

2014-02-01

58

New limits on magnetic monopoles searches from accelerator and nonaccelerator experiments  

NASA Astrophysics Data System (ADS)

Here, the status of the searches for “classical Dirac” magnetic monopoles (MMs) at accelerators and for GUT MMs in the cosmic radiation is discussed. We present recent analysis for classical Dirac monopoles at accelerators and the lowest flux upper limit for MMs in the mass range 105 1012 GeV obtained with the SLIM experiment at the Chacaltaya high-altitude-laboratory (5290 m a.s.l.).

Cozzi, M.

2007-01-01

59

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

60

Working toward exposure thresholds for blast-induced traumatic brain injury: thoracic and acceleration mechanisms  

E-print Network

Research in blast-induced lung injury resulted in exposure thresholds that are useful in understanding and protecting humans from such injury. Because traumatic brain injury (TBI) due to blast exposure has become a prominent medical and military problem, similar thresholds should be identified that can put available research results in context and guide future research toward protecting warfighters as well as diagnosis and treatment. At least three mechanical mechanisms by which the blast wave may result in brain injury have been proposed - a thoracic mechanism, head acceleration and direct cranial transmission. These mechanisms need not be mutually exclusive. In this study, likely regions of interest for the first two mechanisms based on blast characteristics (positive pulse duration and peak effective overpressure) are developed using available data from blast experiments and related studies, including behind-armor blunt trauma and ballistic pressure wave studies. These related studies are appropriate to in...

Courtney, Michael; 10.1016/j.neuroimage.2010.05.025

2011-01-01

61

30 CFR 57.5060 - Limit on exposure to diesel particulate matter.  

Code of Federal Regulations, 2012 CFR

...2012-07-01 false Limit on exposure to diesel particulate matter. 57.5060 Section 57.5060 Mineral...Radiation, Physical Agents, and Diesel Particulate Matter Diesel Particulate Matter-Underground Only § 57.5060...

2012-07-01

62

30 CFR 57.5060 - Limit on exposure to diesel particulate matter.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Limit on exposure to diesel particulate matter. 57.5060 Section 57.5060 Mineral...Radiation, Physical Agents, and Diesel Particulate Matter Diesel Particulate Matter-Underground Only § 57.5060...

2013-07-01

63

30 CFR 57.5060 - Limit on exposure to diesel particulate matter.  

Code of Federal Regulations, 2014 CFR

...2014-07-01 false Limit on exposure to diesel particulate matter. 57.5060 Section 57.5060 Mineral...Radiation, Physical Agents, and Diesel Particulate Matter Diesel Particulate Matter-Underground Only § 57.5060...

2014-07-01

64

Indirectly sensing accelerator beam currents for limiting maximum beam current magnitude  

DOEpatents

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.

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

1995-01-01

65

Indirectly sensing accelerator beam currents for limiting maximum beam current magnitude  

DOEpatents

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.

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

1995-08-08

66

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

PubMed

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

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

2014-06-01

67

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

NASA Astrophysics Data System (ADS)

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.

Basso, Thomas S.

1999-03-01

68

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

ERIC Educational Resources Information Center

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…

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

2013-01-01

69

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

SciTech Connect

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.

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

2007-01-01

70

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

SciTech Connect

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

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

2010-01-15

71

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

PubMed Central

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 16.5–18.5. 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 21–23 [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

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

2012-01-01

72

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

PubMed

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

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

2014-02-01

73

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

74

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

PubMed

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

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

75

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

PubMed

Both elevated ozone (O(3)) and limiting soil nitrogen (N) availability negatively affect crop performance. However, less is known about how the combination of elevated O(3) and limiting N affect crop growth and metabolism. In this study, we grew tobacco (Nicotiana sylvestris) in ambient and elevated O(3) at two N levels (limiting and sufficient). Results at the whole plant, leaf, and cellular level showed that primary metabolism was reduced by growth in limiting N, and that reduction was exacerbated by exposure to elevated O(3). Limiting N reduced the rates of photosynthetic CO(2) uptake by 40.8% in ambient O(3)-exposed plants, and by 58.6% in elevated O(3)-exposed plants, compared with plants grown with sufficient N. Reductions in photosynthesis compounded to cause large differences in leaf and whole plant parameters including leaf number, leaf area, and leaf and root biomass. These results were consistent with our meta-analysis of all published studies of plant responses to elevated O(3) and N availability. In tobacco, N uptake and allocation was also affected by growth in limiting N and elevated O(3), and there was an O(3)-induced compensatory response that resulted in increased N recycling from senescing leaves. In addition, transcript-based markers were used to track the progress through senescence, and indicated that limiting N and elevated O(3), separately and in combination, caused an acceleration of senescence. These results suggest that reductions in crop productivity in growing regions with poor soil fertility will be exacerbated by rising background O(3). PMID:23625780

Yendrek, Craig R; Leisner, Courtney P; Ainsworth, Elizabeth A

2013-10-01

76

Accelerated exposure tests of encapsulated Si solar cells and encapsulation materials  

SciTech Connect

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.}

Pern, F.J.; Glick, S.H. [Engineering and Reliability Division, National Center for Photovoltaics, National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, Colorado 80401 (United States)

1999-03-01

77

Accelerated Exposure Tests of Encapsulated Si Solar Cells and Encapsulation Materials  

SciTech Connect

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.

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

1998-10-08

78

Accelerated exposure tests of encapsulated Si solar cells and encapsulation materials  

NASA Astrophysics Data System (ADS)

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.

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

1999-03-01

79

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

PubMed Central

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 ( ?² (1) = 4.08, ? = - 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.

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

2014-01-01

80

Long-term changes of response in the inferior colliculus of senescence accelerated mice after early sound exposure.  

PubMed

Early sound exposure could alter auditory sensitivity in young animals. For example, the distribution of frequency tuning at the midbrain inferior colliculus (IC) is altered following early exposure to a tone at a moderate intensity level. Whether such neonatal change is still present in the old animals remains unknown. We studied the long-term effects of early sound exposure using a mutant strain of mice expressing accelerated senescence (SAM). Experimental animals were first exposed to a 9-kHz tone (53 dB sound pressure level (SPL)) for 30 days (10 h/day) after birth. Control animals received no tones. At the age of 15 months, responses of single IC units to sounds were studied electrophysiologically under urethane anesthesia. In the control group, we found an overall reduction in sensitivity to tones particularly at high frequencies, in comparison with normal non-senescent mice. Moreover, neurons exhibited increased spontaneous activities. These signs are consistent with accelerated senescence. Early sound exposure produced two effects in the experimental group. Firstly, IC units showed an apparent 'clustering' of best frequencies towards the frequency of the exposing tone (i.e., 9 kHz). Secondly, there was a further loss in sensitivity to tones particularly at high frequencies. Results suggest that early sound exposure has produced a long-lasting effect on frequency tuning of IC neurons. Acoustic overstimulation early in life may also accelerate the senescence of neurons or structures in the auditory system. PMID:14607316

Chiu, T W; Poon, Paul W F; Chan, W Y; Yew, David T W

2003-12-15

81

Acceleration, beaming, and synchrotron radiation above the 160 MeV limit from relativistic pair reconnection  

NASA Astrophysics Data System (ADS)

Magnetic reconnection converts magnetic field energy into particle kinetic energy, accelerating particles to sufficient energies to emit gamma-ray synchrotron radiation in astrophysical contexts, possibly including pulsar wind nebulae, Gamma-Ray Bursts, and blazar jets. A balance between acceleration (by the electric field E) and synchrotron braking (while orbiting a B-field line) limits particle energy so that synchrotron processes cannot emit photons above about 160 MeV, unless E > B. However, short, intense gamma-ray flares of much higher energies have recently been observed in the Crab nebula. This work demonstrates, using 2D simulations, that reconnection in relativistic electron-positron pair plasmas can accelerate particles in Speiser orbits around the magnetic null (where E > B) such that the particles can emit synchrotron photons above the 160 MeV limit. Furthermore, reconnection bunches particles and focuses them into beams; high-energy synchrotron radiation is also strongly beamed, and the sweeping of the beam across the observer's line of sight can explain the fast time variability of the flares.

Werner, Gregory; Cerutti, Benoit; Uzdensky, Dmitri; Begelman, Mitchell

2013-04-01

82

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

PubMed

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

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

2010-02-01

83

Residual skin damage in rats 1 year after exposure to x rays or accelerated heavy ions  

SciTech Connect

In conjunction with a study on the biological effects of accelerated heavy ions on rat spinal cord, we were able to assess the residual skin damage remaining 1 year postirradiation. In this study, rats were irradiated with 230-kVp fractionated doses of either X rays, carbon ions, or neon ions. Four radiation fractions were given at daily intervals. For the carbon and neon ion exposures, rats were irradiated in both the plateau and spread Bragg peak (4 cm) regions of ionization. Comparing doses that produced complete epilation with a slight suggestion of a residual radiation scar, it was found that the relative biological effectivesness (RBE) values 1 year postirradiation for the four fraction irradiations were: carbon ions (plateau ionization region), 1.06; carbon ions (spread Bragg peak ionization region), 1.88; neon ions (plateau region of ionization), 1.55; and neon ions (spread Bragg peak ionization region), 2.26. RBE values for production of paralysis after spinal cord irradiation (using the same X-ray total dose levels for comparison purposes) were in all cases higher than the RBE values obtained from assessment of residual skin injury.

Leith, J.T. (Brown Univ., Providence, RI); McDonald, M.; Howard, J.

1982-01-01

84

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

PubMed

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

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

85

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

PubMed

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

González-Doncel, Miguel; Torija, Carlos Fernández; Beltrán, Eulalia María; García-Mauriño, José Enrique; Sastre, Salvador; Carbonell, Gregoria

2014-03-01

86

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

Microsoft Academic Search

To investigate further the relationships of asbestos exposure, cigarette smoking, and airflow limitation, we have obtained detailed pulmonary function tests (PFT) in 331 long-term Canadian chrysotile workers, 34 of whom were lifetime nonsmokers. Three disease categories were defined on the bases of standard diagnostic criteria, gallium-67 lung uptake, and the lung pressure-volume curve. Category A was composed of workers without

R. Begin; Robert Boileau; S. Peloquin

1987-01-01

87

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

PubMed

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

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

88

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

SciTech Connect

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.

Brisson, Michael

2013-06-03

89

Benzene Exposure Near the U.S. Permissible Limit Is Associated with Sperm Aneuploidy  

PubMed Central

Background Benzene is a common industrial chemical known to induce leukemia and other blood disorders, as well as aneuploidy, in both human blood cells and sperm at exposures > 10 ppm. Recent reports have identified health effects at exposure levels < 1 ppm, the permissible exposure limit (PEL; 8 hr) set by the U.S. Occupational Safety and Health Administration. Objective We investigated whether occupational exposures to benzene near 1 ppm induce aneuploidy in sperm. Methods We used multicolor fluorescence in situ hybridization to measure the incidence of sperm with numerical abnormalities of chromosomes X, Y, and 21 among 33 benzene-exposed men and 33 unexposed men from Chinese factories. Individual exposures were assessed using personal air monitoring and urinary concentrations of benzene and trans,trans-muconic acid (E,E-MA). Air benzene concentrations were not detectable in unexposed men; in exposed men, concentrations ranged from below the detection limit to 24 ppm (median, 2.9 ppm), with 27% of exposed men (n = 9) having concentrations of ? 1 ppm. Exposed men were categorized into low and high groups based on urinary E,E-MA (median concentrations of 1.9 and 14.4 mg/L, respectively; median air benzene of 1 and 7.7 ppm, respectively), and aneuploidy frequencies were compared with those of unexposed men. Results Sperm aneuploidy increased across low- and high-exposed groups for disomy X [incidence rate ratio (IRR) = 2.0; 95% confidence interval (CI), 1.1–3.4; and IRR = 2.8; 95% CI, 1.5–4.9, respectively], and for overall hyperhaploidy for the three chromosomes investigated (IRR = 1.6; 95% CI, 1.0–2.4; and IRR = 2.3; 95% CI, 1.5–3.6, respectively). We also found elevated disomy X and hyperhaploidy in the nine men exposed to ? 1 ppm benzene compared with unexposed men (IRR = 1.8; 95% CI, 1.1–3.0; and IRR = 2.0; 95% CI, 1.1–3.9, respectively). Conclusions Benzene appeared to increase the frequencies of aneuploid sperm for chromosomes associated with chromosomal abnormality syndromes in human offspring, even in men whose air benzene exposure was at or below the U.S. permissible exposure limit. PMID:20418200

Xing, Caihong; Marchetti, Francesco; Li, Guilan; Weldon, Rosana H.; Kurtovich, Elaine; Young, Suzanne; Schmid, Thomas E.; Zhang, Luoping; Rappaport, Stephen; Waidyanatha, Suramya; Wyrobek, Andrew J.; Eskenazi, Brenda

2010-01-01

90

Limited exposure to ambient ultraviolet radiation and 25-hydroxyvitamin D levels: a systematic review.  

PubMed

Vitamin D can be synthesized following exposure to ultraviolet radiation (UVR), ingested in the diet or provided through oral supplementation. The medical literature frequently states that humans obtain most of their vitamin D from sunshine and that UVR exposure is essential to maintain vitamin D levels. A systematic review was conducted to determine the requirement for UVR in maintaining adequate (> 50 nmol L(-1) ) serum 25-hydroxyvitamin D [25(OH)D] levels. Studies reporting serum 25(OH)D during situations of negligible UVR exposure were sought. Forty-one studies (from a search yielding 42 698 articles) with a total of 4211 healthy adults met the inclusion criteria, providing 56 datasets from different population groups. Over 50% of subjects had > 50 nmol L(-1) 25(OH)D in 10 of 19 datasets reporting winter levels in areas with limited UVR. In addition, > 50% of subjects had adequate 25(OH)D levels in four of 12 datasets from polar regions during periods of negligible UVR, one of nine datasets documenting clothing-related minimal UVR and two of eight datasets detailing employment-related minimal UVR. The data demonstrate that many adults maintain adequate serum vitamin D levels despite negligible UVR exposure for several months. However, we acknowledge that preceding UVR exposure leading to vitamin D storage and delayed release may account for this maintenance of adequate serum vitamin D levels. There remains a need for further research on whether UVR exposure is required for longer-term maintenance of adequate vitamin D levels. PMID:25646772

Rice, S A; Carpenter, M; Fityan, A; Vearncombe, L M; Ardern-Jones, M; Jackson, A A; Cooper, C; Baird, J; Healy, E

2015-03-01

91

Theory of factors limiting high gradient operation of warm accelerating structures  

SciTech Connect

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.

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

2014-07-25

92

[Nanomaterials--proposals of occupational exposure limits in the world and hygiene standards in Poland].  

PubMed

Currently, there are no legally binding workplace exposure limits for substances in the form of nanoobjects. There are different ap proaches to risk assessment and determination of occupational exposure limits. The purpose of this article is to compare exposure levels in the work environment proposed by international organizations and world experts, as well as the assumptions and methods used for their estimation. This paper presents the proposals of the National Institute for Public Health and the Environment in the Netherlands (RIVM), the New Energy and Industrial Technology Development Organization in Japan (NEDO) and the National Institute for Occupational Safety and Health in the USA (NIOSH). The authors also discuss the reports on the levels for carbon nanotubes (Baytubes and Nanocyl) proposed by Pauluhn and Luizi, the derived no-effect levels (DNEL) complying with the REACH Regulation, proposed by experts under the 7th Framework Programme of the European Commission, coordinated by Professor Vicki Stone (ENRHES), and alternative estimation levels for poorly soluble particles by Pauluhn. The issue was also raised whether the method of determining maximum admissible concentrations in the work environment, currently used in Poland, is adequate for nanoobjects. Moreover, the introduction of nanoreference values, as proposed by RIVM, the definition of a new fraction for particles of 1-100 nm, taking into account the surface area and activity of the particles, and an adequate estimation of uncertainty factors seem to be worth considering. Other important, if not key issues are the appropriate measurement (numerical concentration, surface concentration, particle size distribution), as well as the methodology and equipment accessibility to all employers responsible for a reliable risk assessment of exposure to nanoparticles in the work environment. PMID:24645568

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

2013-01-01

93

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

PubMed

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

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

2015-02-17

94

Chronic exposure to sulfide causes accelerated degradation of cytochrome c oxidase in ethylmalonic encephalopathy.  

PubMed

Ethylmalonic encephalopathy (EE) is an autosomal recessive, invariably fatal disorder associated with mutations in ETHE1, a gene encoding a mitochondrial sulfur dioxygenase (SDO). The main consequence of the absence of Ethe1-SDO is the accumulation of sulfide (H(2)S) in critical tissues, including colonic mucosa, liver, muscle, and brain. To make progress in the elucidation of the biochemical mechanisms leading to cytochrome c oxidase (COX) deficiency, we (i) generated tissue-specific conditional Ethe1 knockout mice to clarify the different contributions of endogenous and exogenous H(2)S production, and (ii) studied the development of H(2)S-driven COX deficiency in Ethe1(-/-) mouse tissues and human cells. Ethe1(-/-) conditional animals displayed COX deficiency limited to the specific targeted tissue. The accumulation of H(2)S over time causes progressive COX deficiency in animal tissues and human cells, which is associated with reduced amount of COX holoenzyme, and of several COX subunits, including mitochondrially encoded cytochrome c oxidase 1 (MTCO1), MTCO2, COX4, and COX5A. This reduction is not paralleled by consistent downregulation in expression of the corresponding mRNAs. Tissue-specific ablation of Ethe1 causes COX deficiency in targeted organs, suggesting that failure in neutralizing endogenous, tissue-specific production of H(2)S is sufficient to cause the biochemical defect but neither to determine a clinical impact nor to induce the biomarker profile typical of EE. The mechanism by which H(2)S causes COX deficiency consists of rapid heme a inhibition and accelerated long-term degradation of COX subunits. However, the pleiotropic devastating effects of H(2)S accumulation in EE cannot be fully explained by the sole defect of COX in critical tissues, but are likely consequent to several toxic actions on a number of enzymatic activities in different tissues, including endothelial lining of the small vessels, leading to multiorgan failure. PMID:20812865

Di Meo, Ivano; Fagiolari, Gigliola; Prelle, Alessandro; Viscomi, Carlo; Zeviani, Massimo; Tiranti, Valeria

2011-07-15

95

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

PubMed Central

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

Cohen, B. L.

1981-01-01

96

Electron acceleration with improved Stochastic Differential Equation method: Cutoff shape of electron distribution in test-particle limit  

NASA Astrophysics Data System (ADS)

We develop a method of stochastic differential equation to simulate electron acceleration at astrophysical shocks. Our method is based on Ito's stochastic differential equations coupled with a particle splitting, employing a skew Brownian motion where an asymmetric shock crossing probability is considered. Using this code, we perform simulations of electron acceleration at stationary plane parallel shock with various parameter sets, and studied how the cutoff shape, which is characterized by cutoff shape parameter a, changes with the momentum dependence of the diffusion coefficient ?. In the age-limited cases, we reproduce previous results of other authors, a ? 2 ?. In the cooling-limited cases, the analytical expectation a ? ? + 1 is roughly reproduced although we recognize deviations to some extent. In the case of escape-limited acceleration, numerical result fits analytical stationary solution well, but deviates from the previous asymptotic analytical formula a ? ?.

Yamazaki, Ryo; Yoshida, Tatsuo; Tsuchihashi, Yuka; Nakajima, Ryosuke; Ohira, Yutaka; Yanagita, Shohei

2015-03-01

97

Electron acceleration with improved Stochastic Differential Equation method: cutoff shape of electron distribution in test-particle limit  

E-print Network

We develop a method of stochastic differential equation to simulate electron acceleration at astrophysical shocks. Our method is based on It\\^{o}'s stochastic differential equations coupled with a particle splitting, employing a skew Brownian motion where an asymmetric shock crossing probability is considered. Using this code, we perform simulations of electron acceleration at stationary plane parallel shock with various parameter sets, and studied how the cutoff shape, which is characterized by cutoff shape parameter $a$, changes with the momentum dependence of the diffusion coefficient $\\beta$. In the age-limited cases, we reproduce previous results of other authors, $a\\approx2\\beta$. In the cooling-limited cases, the analytical expectation $a\\approx\\beta+1$ is roughly reproduced although we recognize deviations to some extent. In the case of escape-limited acceleration, numerical result fits analytical stationary solution well, but deviates from the previous asymptotic analytical formula $a\\approx\\beta$.

Yamazaki, Ryo; Tsuchihashi, Yuka; Nakajima, Ryosuke; Ohira, Yutaka; Yanagita, Shohei

2015-01-01

98

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

PubMed

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

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

2012-07-01

99

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

PubMed Central

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

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

2009-01-01

100

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

NASA Astrophysics Data System (ADS)

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.

Ahmad, Bilal; Fitzpatrick, Michael E.

2015-03-01

101

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

SciTech Connect

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

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

1987-01-01

102

Experiences from occupational exposure limits set on aerosols containing allergenic proteins.  

PubMed

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

Nielsen, Gunnar D; Larsen, Søren T; Hansen, Jitka S; Poulsen, Lars K

2012-10-01

103

Experiences from Occupational Exposure Limits Set on Aerosols Containing Allergenic Proteins  

PubMed Central

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

Nielsen, Gunnar D.

2012-01-01

104

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

PubMed

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

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

2014-04-01

105

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...

106

On superconducting niobium accelerating cavities fired under N2-gas exposure  

E-print Network

The dependence of the Q-value on the RF field (Q-slope) is actively studied in various accelerator laboratories. Although remedies against this dependence have been found, the physical cause still remains obscure. A rather straightforward two-fluid model description of the Q-slope in the low and high field domains is presented with emphasis on the recently experimentally identified improvement of the Q-value by so-called "N-doping".

Eichhorn, Ralf; Hoffstaetter, Georg; Liepe, Matthias; Weingarten, Wolfgang

2014-01-01

107

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

NASA Astrophysics Data System (ADS)

Prescribed burning represents a serious threat to the personnel fighting fires because of smoke inhalation. This study aims to increase the knowledge about foresters exposure to the prescribed burning smoke by focusing on exposure to volatile organic compounds (VOCs). We initially assessed the methodology for smoke sampling. Then, we identified potentially dangerous molecules among the VOCs identified at 4 prescribed burning sites located around Corsica. The values measured were very high, exceeding the exposure limits, particularly for benzene, phenol, and furfural, whose concentrations were above short-term exposure limit (STEL) values. In conclusion, obvious but necessary recommendations were made for the protection of the personnel involved in fighting fires on a professional basis.

Barboni, T.; Santoni, P.-A.

2013-11-01

108

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

NASA Astrophysics Data System (ADS)

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.

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

2010-12-01

109

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

SciTech Connect

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.

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

2005-12-15

110

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

PubMed Central

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

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

111

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

Microsoft Academic Search

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

Efstathios Velenis; Panagiotis Tsiotras

2008-01-01

112

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

SciTech Connect

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.

Cerutti, B.; Werner, G. R.; Uzdensky, D. A. [Center for Integrated Plasma Studies, Physics Department, University of Colorado, UCB 390, Boulder, CO 80309-0390 (United States); Begelman, M. C., E-mail: benoit.cerutti@colorado.edu, E-mail: greg.werner@colorado.edu, E-mail: uzdensky@colorado.edu, E-mail: mitch@jila.colorado.edu [JILA, University of Colorado and National Institute of Standards and Technology, UCB 440, Boulder, CO 80309-0440 (United States)

2013-06-20

113

Chronic exposure to bisphenol A can accelerate atherosclerosis in high-fat-fed apolipoprotein E knockout mice.  

PubMed

In epidemiological studies, there is growing concern regarding the association between human exposure to bisphenol A (BPA) and an increased risk for cardiovascular disease. Therefore, we investigated whether BPA accelerates atherosclerosis in mouse model. Apolipoprotein E knockout (ApoE(-/-)) mice were fed a high-fat and high-cholesterol diet with or without 50 ?g/kg body weight/day BPA for 12 weeks. Atherosclerotic lesions of the aorta and aortic sinus were evaluated by Oil red O staining. After the 12-week BPA treatment, BPA significantly increased atherosclerotic lesions in the aortas of ApoE(-/-) mice by 1.7-fold (p = 0.03). Non-high-density lipoprotein (HDL) cholesterol levels in the BPA group were significantly higher compared to those in the control group (1,035 ± 70 vs. 484 ± 48 mg/dL, p = 0.02) although body weight and blood glucose levels were not different between groups. Human umbilical vein endothelial cells (HUVECs) were treated with 0.1-10 nM BPA but BPA did not affect HUVEC proliferation or migration. BPA could accelerate atherosclerosis in ApoE(-/-) mice, which may have resulted from an increase in non-HDL cholesterol levels. PMID:24234673

Kim, Min Joo; Moon, Min Kyong; Kang, Geun Hyung; Lee, Kwan Jae; Choi, Sung Hee; Lim, Soo; Oh, Byung-Chul; Park, Do Joon; Park, Kyong Soo; Jang, Hak Chul; Park, Young Joo

2014-06-01

114

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

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

115

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

SciTech Connect

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.

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

2014-06-16

116

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

PubMed

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

Mossman, Brooke T; Glenn, Robert E

2013-09-01

117

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

PubMed

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

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

2004-12-01

118

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

NASA Astrophysics Data System (ADS)

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.

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

119

Infant Television and Video Exposure Associated With Limited Parent-Child Verbal Interactions in Low Socioeconomic Status Households  

PubMed Central

Objective To assess verbal interactions related to television and other electronic media exposure among mothers and 6 month-old-infants. Design Cross-sectional analysis of 154 mother-infant dyads participating in a long-term study related to early child development. Setting Urban public hospital. Participants Low socioeconomic status mothers of 6-month-old infants. Main Exposure Media exposure and content. Main Outcome Measures Mother-infant verbal interaction associated with media exposure and maternal coviewing. Results Of 154 low socioeconomic status mothers, 149 (96.8%) reported daily media exposure in their infants, with median exposure of 120 (interquartile range, 60-210) minutes in a 24-hour period. Among 426 program exposures, mother-infant interactions were reported during 101 (23.7%). Interactions were reported most frequently with educational young child–oriented media (42.8% of programs), compared with 21.3% of noneducational young child–oriented programs (adjusted odds ratio, 0.4; 95% confidence interval, 0.1-0.98) and 14.7% of school-age/teenage/adult–oriented programs (adjusted odds ratio, 0.2; 95% confidence interval, 0.1-0.3). Among coviewed programs with educational content, mothers reported interactions during 62.7% of exposures. Coviewing was not reported more frequently for educational young child–oriented programs. Conclusions We found limited verbal interactions during television exposure in infancy, with interactions reported for less than one-quarter of exposures. Although interactions were most commonly reported among programs with educational content that had been coviewed, programs with educational content were not more likely to be coviewed than were other programs. Our findings do not support development of infant-directed educational programming in the absence of strategies to increase coviewing and interactions. PMID:18458186

Mendelsohn, Alan L.; Berkule, Samantha B.; Tomopoulos, Suzy; Tamis-LeMonda, Catherine S.; Huberman, Harris S.; Alvir, Jose; Dreyer, Benard P.

2011-01-01

120

Defining Occupational and Consumer Exposure Limits for Nanomaterials - First Experiences from REACH Registrations  

NASA Astrophysics Data System (ADS)

By 1 December 2010 substances manufactured or imported in the EU >= 1000 t (as well as certain other substances) had to be registered under the REACH Regulation 1907/2006. The Joint Research Centre (JRC) in close cooperation with the European Chemicals Agency (ECHA) carried out an analysis and assessment of what type of information on nanomaterials was provided in the received registrations. The aim of the assessment was to develop options for an adaptation of the REACH regulation to ensure proper information generation and reporting and an appropriate risk/safety assessment of nanomaterials (Nano Support project). It should be noted that this analysis and assessment was not a compliance check of the dossiers. From 26000 submitted registration dossiers covering 4700 substances finally 25 dossiers (19 substances) were identified to cover nanomaterials or nanoforms of a substance. It is possible that other dossiers are considered to cover nanomaterials or nanoforms by the registrants, however such dossiers could not be identified to address nanoforms given the information contained in those dossiers. The identified 25 dossiers were subject to a detailed analysis and assessment of information provided for all endpoints including substance identity, physico-chemical properties, human health, environmental fate & behaviour, ecotoxicity, PBT6 assessment, Classification and Labelling as well as the attached Chemical Safety Report documenting the Chemical Risk/Safety Assessment. In order to evaluate how the safety of workers and consumers was ensured, it was appropriate to check how the "Derived No (Minimum) Effect Levels" (DN(M)ELs) were established for substances, covering nanomaterials or nanoforms. DNELs were established mainly for long term inhalation exposure of workers. Half of the assessed dossiers included an oral long term DNEL for the general population. DNELs were usually not specific for nanosized forms and, in the few cases where they were calculated for nanosized materials, they were not derived from hazard data for the nanoform. Different methods for deriving the DNELs were applied and few dossiers derived DNELs by applying the default assessment factors in the REACH guidance. Several DNELs were based on available Occupational Exposure Limits (OELs) for inhalable and respirable dust or the nuisance dust levels, which have not been established for nanosized materials. In general lower (i.e. less strict) assessment factors were applied with different types of justification. All DNELs were expressed in the mass metrics. It is important to note that submission, identification and selection of the dossiers addressed in this study was done before the adoption of the EC recommendation (2011/696/EU) on a definition of nanomaterial and before the publication of the revised ECHA guidance documents that include recommendations for nanomaterials.

Aschberger, K.; Klöslova, Z.; Falck, G.; Christensen, F. M.

2013-04-01

121

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...

122

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

SciTech Connect

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.

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

2007-06-01

123

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

ERIC Educational Resources Information Center

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…

Paulik, Edit; Maroti-Nagy, A.; Nagymajtenyi, L.; Rogers, T.; Easterling, D.

2013-01-01

124

Prenatal Arsenic Exposure Alters Gene Expression in the Adult Liver to a Proinflammatory State Contributing to Accelerated Atherosclerosis  

PubMed Central

The mechanisms by which environmental toxicants alter developmental processes predisposing individuals to adult onset chronic disease are not well-understood. Transplacental arsenic exposure promotes atherogenesis in apolipoprotein E-knockout (ApoE?/?) mice. Because the liver plays a central role in atherosclerosis, diabetes and metabolic syndrome, we hypothesized that accelerated atherosclerosis may be linked to altered hepatic development. This hypothesis was tested in ApoE?/? mice exposed to 49 ppm arsenic in utero from gestational day (GD) 8 to term. GD18 hepatic arsenic was 1.2 µg/g in dams and 350 ng/g in fetuses. The hepatic transcriptome was evaluated by microarray analysis to assess mRNA and microRNA abundance in control and exposed pups at postnatal day (PND) 1 and PND70. Arsenic exposure altered postnatal developmental trajectory of mRNA and microRNA profiles. We identified an arsenic exposure related 51-gene signature at PND1 and PND70 with several hubs of interaction (Hspa8, IgM and Hnf4a). Gene ontology (GO) annotation analyses indicated that pathways for gluconeogenesis and glycolysis were suppressed in exposed pups at PND1, and pathways for protein export, ribosome, antigen processing and presentation, and complement and coagulation cascades were induced by PND70. Promoter analysis of differentially-expressed transcripts identified enriched transcription factor binding sites and clustering to common regulatory sites. SREBP1 binding sites were identified in about 16% of PND70 differentially-expressed genes. Western blot analysis confirmed changes in the liver at PND70 that included increases of heat shock protein 70 (Hspa8) and active SREBP1. Plasma AST and ALT levels were increased at PND70. These results suggest that transplacental arsenic exposure alters developmental programming in fetal liver, leading to an enduring stress and proinflammatory response postnatally that may contribute to early onset of atherosclerosis. Genes containing SREBP1 binding sites also suggest pathways for diabetes mellitus and rheumatoid arthritis, both diseases that contribute to increased cardiovascular disease in humans. PMID:22719926

States, J. Christopher; Singh, Amar V.; Knudsen, Thomas B.; Rouchka, Eric C.; Ngalame, Ntube O.; Arteel, Gavin E.; Piao, Yulan; Ko, Minoru S. H.

2012-01-01

125

Testing the coherence between occupational exposure limits for inhalation and their biological limit values with a generalized PBPK-model: the case of 2-propanol and acetone.  

PubMed

The coherence between occupational exposure limits (OELs) and their corresponding biological limit values (BLVs) was evaluated for 2-propanol and acetone. A generic human PBPK model was used to predict internal concentrations after inhalation exposure at the level of the OEL. The fraction of workers with predicted internal concentrations lower than the BLV, i.e. the 'false negatives', was taken as a measure for incoherence. The impact of variability and uncertainty in input parameters was separated by means of nested Monte Carlo simulation. Depending on the exposure scenario considered, the median fraction of the population for which the limit values were incoherent ranged from 2% to 45%. Parameter importance analysis showed that body weight was the main factor contributing to interindividual variability in blood and urine concentrations and that the metabolic parameters Vmax and Km were the most important sources of uncertainty. This study demonstrates that the OELs and BLVs for 2-propanol and acetone are not fully coherent, i.e. enforcement of BLVs may result in OELs being violated. In order to assess the acceptability of this "incoherence", a maximum population fraction at risk of exceeding the OEL should be specified as well as a minimum level of certainty in predicting this fraction. PMID:24852492

Huizer, Daan; Huijbregts, Mark A J; van Rooij, Joost G M; Ragas, Ad M J

2014-08-01

126

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

PubMed

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 (36±1°C) and thermophilic (55±0.3°C) 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

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

2015-03-01

127

A Comparison of REACH-Derived No-Effect Levels for Workers With EU Indicative Occupational Exposure Limit Values and National Limit Values in Finland.  

PubMed

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

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

2015-05-01

128

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

SciTech Connect

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.

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

2006-02-06

129

Polymer gel dosimetry for neutron beam in the Neutron Exposure Accelerator System for Biological Effect Experiments (NASBEE)  

NASA Astrophysics Data System (ADS)

This study aimed to investigate whether gel dosimetry could be used to measure neutron beams. We irradiated a BANG3-type polymer gel dosimeter using neutron beams in the Neutron exposure Accelerator System for Biological Effect Experiments (NASBEE) at the National Institute of Radiological Sciences (NIRS) in Japan. First, the polymer gels were irradiated from 0 to 7.0 Gy to investigate the dose-R2 responses. Irradiated gels were evaluated using 1.5-T magnetic resonance R2 images. Second, the polymer gels were irradiated to 1.0, 3.0, and 5.0 Gy to acquire a depth-R2 response curve. The dose-R2 response curve was linear up to approximately 7 Gy, with a slope of 1.25 Gy?1·s?1. Additionally, compared with the photon- irradiated gels, the neutron-irradiated gels had lower R2 values. The acquired depth-R2 curves of the central axis from the 3.0- and 5.0-Gy neutron dose-irradiated gels exhibited an initial build-up. Although, a detailed investigation is needed, polymer gel dosimetry is effective for measuring the dose-related R2 linearity and depth-R2 relationships of neutron beams.

Kawamura, H.; Sato, H.; Hamano, T.; Suda, M.; Yoshii, H.

2015-01-01

130

Fundamental and practical limits to image acceleration in parallel magnetic resonance imaging  

E-print Network

Imaging speed in conventional magnetic resonance imaging (MRI) is limited by the performance of magnetic field gradients and the rate of power deposition in tissue. Parallel MRI techniques overcome these constraints by ...

Ohliger, Michael A

2005-01-01

131

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

PubMed

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

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

2015-01-15

132

Limited airway effects in mild asthmatics after exposure to air pollution in a road tunnel.  

PubMed

Ambient air pollution is a contributing factor to respiratory morbidity and mortality and asthmatics are a particularly vulnerable population. The aim of the study was to investigate whether acute exposure to traffic related air pollution in a road tunnel would increase bronchial responsiveness in mild asthmatics, and if this would be accompanied by increased measures of inflammatory markers in the airways assessed by nasal lavage (NAL) and induced sputum. Fourteen mild asthmatics (7 treated with inhaled corticosteroids) were exposed for 2 h in a road tunnel and a control environment, respectively, separated by at least 3 weeks. Symptoms and peak expiratory flow (PEF) were recorded. Seven hours following exposure sessions, subjects underwent measurements of fraction of exhaled nitric oxide (FENO), spirometry, and a bronchial provocation test. NAL, induced sputum and blood samples were collected. The median PM(2.5) and PM(10) levels during the exposure occasions in the road tunnel were 80 (range 41-93) ?g/m(3) and 183 (72-213) ?g/m(3) respectively. Irritative symptoms from the airways increased and PEF decreased after road tunnel exposure. Increased levels of IL-10, IL-12 and TNF-? were observed in NAL fluid from subjects without ongoing inhaled corticosteroid treatment. Forced expiratory volume in 1 s (FEV(1)) and the degree of bronchial responsiveness in asthmatics did not change significantly after tunnel exposure. We conclude that asthmatics exhibit increased symptoms, decreased PEF and signs of inflammatory response in the upper airways, after a 2 h road tunnel exposure. Our findings may further emphasize asthmatics as a vulnerable group to common air pollutants. PMID:20621461

Larsson, Britt-Marie; Grunewald, Johan; Sköld, C Magnus; Lundin, Anders; Sandström, Thomas; Eklund, Anders; Svartengren, Magnus

2010-12-01

133

Accelerated rates of floral evolution at the upper size limit for flowers.  

PubMed

Evolutionary theory explains phenotypic change as the result of natural selection, with constraint limiting the direction, magnitude, and rate of response [1]. Constraint is particularly likely to govern evolutionary change when a trait is at perceived upper or lower limits. Macroevolutionary rates of floral-size change are unknown for any angiosperm family, but it is predicted that rates should be diminished near the upper size limit of flowers, as has been shown for mammal body mass [2]. Our molecular results show that rates of floral-size evolution have been extremely rapid in the endoholoparasite Rafflesia, which contains the world's largest flowers [3]. These data provide the first estimates of macroevolutionary rates of floral-size change and indicate that in this lineage, floral diameter increased by an average of 20 cm (and up to 90 cm)/million years. In contrast to our expectations, it appears that the magnitude and rate of floral-size increase is greater for lineages with larger flowered ancestors. This study suggests that constraints on rates of floral-size evolution may not be limiting in Rafflesia, reinforcing results of artificial- and natural-selection studies in other plants that demonstrated the potential for rapid size changes [4-6]. PMID:18848446

Barkman, Todd J; Bendiksby, Mika; Lim, Seok-Hong; Salleh, Kamarudin Mat; Nais, Jamili; Madulid, Domingo; Schumacher, Trond

2008-10-14

134

Accelerator search for cosmic SIMPs  

NASA Astrophysics Data System (ADS)

We give limits on the contribution to the cosmic dark matter density of neutral, stable, strongly interacting massive particles (SIMPs). The limits are inferred from an accelerator mass spectrometry (AMS) experiment at the Purdue Rare Isotope Measurement Laboratory (PRIME Lab). The experiment accelerated nuclei of both gold and iron. The ``SIMP signal'' would be discovery of nuclei of these elements with anomalous masses. Since no such signal was observed for SIMP masses up to over 1 TeV, cosmic SIMP density limits may be given. Determining the minimum time of exposure to SIMPs trapped in the galaxy is a crucial element in the analysis of each sample.

Teplitz, V.; Javorsek, D.; Fischbach, E.; Mohapatra, R.

2003-07-01

135

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

ERIC Educational Resources Information Center

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…

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

2014-01-01

136

Proposed Occupational Exposure Limits for Select Ethylene Glycol Ethers Using PBPK Models and Monte Carlo Simulations  

Microsoft Academic Search

Methoxyethanol (ethylene glycol monomethyl ether, EGME), ethoxyethanol (ethylene glycol monoethyl ether, EGEE), and ethoxyethyl acetate (ethylene glycol monoethyl ether acetate, EGEEA) are all developmental toxicants in laboratory animals. Due to the imprecise nature of the exposure data in epidemiology studies of these chemicals, we relied on human and animal phar- macokinetic data, as well as animal toxicity data, to derive

L. M. Sweeney; J. F. Holson; M. D. Whorton; K. M. Thompson; M. L. Gargas

137

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

Microsoft Academic Search

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

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

2003-01-01

138

Acute Effects of 10Minute Exposure to Hydrogen Fluoride in Rats and Derivation of a Short-Term Exposure Limit for Humans  

Microsoft Academic Search

A series of acute inhalation exposures of female rats was conducted with hydrogen fluoride (HF) to establish a concentration–response curve for nonlethal exposures. Durations of 2 and 10 min were used to simulate possible short-term exposures. Concentrations of HF ranged from 593 to 8621 ppm for 2-min exposures and from 135 to 1764 ppm for 10-min exposures. Additional exposures were

W. Dalbey; B. Dunn; R. Bannister; W. Daughtrey; C. Kirwin; F. Reitman; A. Steiner; J. Bruce

1998-01-01

139

Setting safe acute exposure limits for halon replacement chemicals using physiologically based pharmacokinetic modeling.  

PubMed

Most proposed replacements for Halon 1301 as a fire suppressant are halogenated hydrocarbons. The acute toxic endpoint of concern for these agents is cardiac sensitization. An approach is described that links the cardiac endpoint as assessed in dogs to a target arterial concentration in humans. Linkage was made using a physiologically based pharmacokinetic (PBPK) model. Monte Carlo simulations, which account for population variability, were used to establish safe exposure times at different exposure concentrations for Halon 1301 (bromotrifluoromethane), CF(3)I (trifluoroiodomethane), HFC-125 (pentafluoroethane), HFC-227ea (1,1,1,2,3,3,3-heptafluoropropane), and HFC-236fa (1,1,1,3,3,3-hexafluoropropane). Application of the modeling technique described here not only makes use of the conservative cardiac sensitization endpoint, but also uses an understanding of the pharmacokinetics of the chemical agents to better establish standards for safe exposure. The combined application of cardiac sensitization data and physiologically based modeling provides a quantitative approach, which can facilitate the selection and effective use of halon replacement candidates. PMID:10880155

Vinegar, A; Jepson, G W; Cisneros, M; Rubenstein, R; Brock, W J

2000-08-01

140

Chimpanzees form long-term memories for food locations after limited exposure.  

PubMed

Remembering the location of fruiting trees for extended periods of time has been hypothesized to play a major role in the evolution of primate cognition. Such ability would be especially useful when paired with a fast learning mechanism capable of consolidating long-term memory after minimal exposure. We investigated whether chimpanzees (Pan troglodytes) can remember different food locations after minimal exposure (i.e., 1-2 trials) both after 24?hr and after 3-month. We released pairs of chimpanzees in their indoor enclosure (the enclosure of group A measured 430?m(2) and group B's measured 175?m(2) ) and tested them for four consecutive days (Baseline, Test, Retest, and Post-test). During the Test and Retest food was hidden in the same location whereas no food was hidden during the Baseline and Post-test days (control trials). Subjects were tested with four different locations and assessed for their retention after 24?hr and 3-month since the initial food discovery. Results revealed that chimpanzees accurately remembered the locations in which they found the food after one or two exposures to them, and both after 24?hr and a 3-month retention interval. PMID:24482025

Mendes, Natacha; Call, Josep

2014-05-01

141

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

PubMed

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

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

2004-12-01

142

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

PubMed

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

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

1994-12-01

143

Early Enriched Environment Exposure Protects Spatial Memory and Accelerates Amyloid Plaque Formation in APPSwe/PS1L166P Mice  

PubMed Central

Enriched environment exposure improves several aspects of cognitive performance in Alzheimer’s disease patients and in animal models and, although the role of amyloid plaques is questionable, several studies also assessed their response to enriched environment, with contrasting results. Here we report that rearing APPSwe/PS1L166P mice in an enriched environment since birth rescued the spatial memory impairment otherwise present at 6 months of age. At the same time, the exposure to the enriched environment caused a transient acceleration of plaque formation, while there was no effect on intracellular staining with the 6E10 antibody, which recognizes ?-amyloid, full length amyloid precursor protein and its C-terminal fragments. The anticipation of plaque formation required exposure during early development, suggesting an action within critical periods for circuits formation. On the other hand, chronic neuronal activity suppression by tetrodotoxin decreased the number of plaques without affecting intracellular amyloid. These results indicate that enriched environment exposure since early life has a protective effect on cognitive deterioration although transiently accelerates amyloid deposition. In addition, the effects of the enriched environment might be due to increased neuronal activity, because plaques were reduced by suppression of electrical signaling by tetrodotoxin. PMID:23894463

Montarolo, Francesca; Parolisi, Roberta; Hoxha, Eriola; Boda, Enrica; Tempia, Filippo

2013-01-01

144

Highly accelerated simulations of glassy dynamics using GPUs: Caveats on limited floating-point precision  

NASA Astrophysics Data System (ADS)

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

Colberg, Peter H.; Höfling, Felix

2011-05-01

145

Exposure limits: the underestimation of absorbed cell phone radiation, especially in children.  

PubMed

The existing cell phone certification process uses a plastic model of the head called the Specific Anthropomorphic Mannequin (SAM), representing the top 10% of U.S. military recruits in 1989 and greatly underestimating the Specific Absorption Rate (SAR) for typical mobile phone users, especially children. A superior computer simulation certification process has been approved by the Federal Communications Commission (FCC) but is not employed to certify cell phones. In the United States, the FCC determines maximum allowed exposures. Many countries, especially European Union members, use the "guidelines" of International Commission on Non-Ionizing Radiation Protection (ICNIRP), a non governmental agency. Radiofrequency (RF) exposure to a head smaller than SAM will absorb a relatively higher SAR. Also, SAM uses a fluid having the average electrical properties of the head that cannot indicate differential absorption of specific brain tissue, nor absorption in children or smaller adults. The SAR for a 10-year old is up to 153% higher than the SAR for the SAM model. When electrical properties are considered, a child's head's absorption can be over two times greater, and absorption of the skull's bone marrow can be ten times greater than adults. Therefore, a new certification process is needed that incorporates different modes of use, head sizes, and tissue properties. Anatomically based models should be employed in revising safety standards for these ubiquitous modern devices and standards should be set by accountable, independent groups. PMID:21999884

Gandhi, Om P; Morgan, L Lloyd; de Salles, Alvaro Augusto; Han, Yueh-Ying; Herberman, Ronald B; Davis, Devra Lee

2012-03-01

146

Limiter  

DOEpatents

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.

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

1984-10-19

147

The limits of predictability of volcanic eruptions from accelerating rates of earthquakes  

NASA Astrophysics Data System (ADS)

Volcanic eruptions are commonly preceded by increased rates of earthquakes. Previous studies argue that in some instances these sequences follow the inverse Omori law (IOL) and that this model could be the basis for forecasting the timing of eruption onset. However, the catalogue of pre-eruptive sequences is small, and the performance of the IOL as a forecasting tool remains largely untested. Here, we use simulations to quantify upper limits to the accuracy and bias of forecast eruption times based on the IOL in the `best-case' scenario that uncertainty only arises from model parameter estimation from single realizations of a stochastic point process. We compare different methods for forecasting based on the IOL, and demonstrate that a maximum-likelihood method yields more accurate and less-biased forecasts than methods currently employed. Even in these idealized conditions, we find that large forecast uncertainty and false alarms are inherent features of the mathematics of the IOL. For example model parameter values and 500-d pre-eruptive sequence durations, at 25 d before the eruption, 10 per cent of the forecasts are more than 8 d early or late if the power-law exponent is known a priori, and more than 18 d early or late if the power-law exponent is unknown. We also evaluate methods for model comparison and estimation of the power-law exponent. These techniques are applied to examples of real pre-eruptive earthquake data sets. We find evidence for systematic deviations from the idealized model, indicating the action of multiple processes and resulting in greater forecast error than in the synthetic examples, especially close to the eruption time.

Bell, Andrew F.; Naylor, Mark; Main, Ian G.

2013-09-01

148

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

PubMed Central

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 Békésy 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

Lindblad, Ann-Cathrine; Rosenhall, Ulf; Olofsson, Åke; Hagerman, Björn

2014-01-01

149

Reassessment of data used in setting exposure limits for hot particles  

SciTech Connect

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.

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

1991-05-01

150

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

SciTech Connect

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.

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

151

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

PubMed

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

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

152

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

PubMed Central

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

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

153

Limiter  

DOEpatents

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.

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

1986-01-01

154

Limits  

NSDL National Science Digital Library

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

2013-06-21

155

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

USGS Publications Warehouse

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.

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

156

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

PubMed Central

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

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

157

Exposure to inflammatory cytokines selectively limits GM-CSF production by induced T regulatory cells  

PubMed Central

Interest in manipulating the immunosuppressive powers of Foxp3-expressing T regulatory cells as an immunotherapy has been tempered by their reported ability to produce proinflammatory cytokines when manipulated in vitro, or in vivo. Understanding processes that can limit this potentially deleterious effect of Treg cells in a therapeutic setting is therefore important. Here, we have studied this using induced (i) Treg cells in which de novo Foxp3 expression is driven by TCR-stimulation in vitro in the presence of TGF-?. We show that iTreg cells can produce significant amounts of three proinflammatory cytokines (IFN-?, GM-CSF and TNF-?) upon secondary TCR stimulation. GM-CSF is a critical T-cell derived cytokine for the induction of EAE in mice. Despite their apparent capacity to produce GM-CSF, myelin autoantigen-responsive iTreg cells were unable to provoke EAE. Instead, they maintained strong suppressive function in vivo, preventing EAE induction by their CD4+Foxp3? counterparts. We identified that although iTreg cells maintained the ability to produce IFN-? and TNF-? in vivo, their ability to produce GM-CSF was selectively degraded upon antigen stimulation under inflammatory conditions. Furthermore, we show that IL-6 and IL-27 individually, or IL-2 and TGF-? in combination, can mediate the selective loss of GM-CSF production by iTreg cells. PMID:25168419

Reynolds, Ben C; Turner, Darryl G; McPherson, Rhoanne C; Prendergast, Catriona T; Phelps, Richard G; Turner, Neil A; O'Connor, Richard A; Anderton, Stephen M

2014-01-01

158

"Nuisance dust": unprotective limits for exposure to coal mine dust in the United States, 1934-1969.  

PubMed

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

Derickson, Alan

2013-02-01

159

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

PubMed Central

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

2013-01-01

160

A Proposal for Calculating Occupational Exposure Limits for Volatile Organic Compounds Acting as Sensory Irritants on the Basis of Their Physicochemical Properties  

Microsoft Academic Search

A common biological effect of exposure to workplace chemicals is sensory irritation. The ACGIH® threshold limit values (TLVs®) are developed based on data derived from industrial settings as well as experimental human and animal studies. Considering the limited amount of human data and the tendency to reduce the volume of animal testing, there is a need for an alternative method

Marek Jakubowski; S?awomir Czerczak

2010-01-01

161

Possibilities and limitations of modeling environmental exposure to engineered nanomaterials by probabilistic material flow analysis.  

PubMed

Information on environmental concentrations is needed to assess the risks that engineered nanomaterials (ENM) may pose to the environment. In this study, predicted environmental concentrations (PEC) were modeled for nano-TiO2, carbon nanotubes (CNT) and nano-Ag for Switzerland. Based on a life-cycle perspective, the model considered as input parameters the production volumes of the ENMs, the manufacturing and consumption quantities of products containing those materials, and the fate and pathways of ENMs in natural and technical environments. Faced with a distinct scarcity of data, we used a probabilistic material flow analysis model, treating all parameters as probability distributions. The modeling included Monte Carlo and Markov Chain Monte Carlo simulations as well as a sensitivity and uncertainty analysis. The PEC values of the ENMs in the different environmental compartments vary widely due to different ENM production volumes and different life cycles of the nanoproducts. The use of ENM in products with high water relevance leads to higher water and sediment concentrations for nano-TiO2 and nano-Ag, compared to CNTs, where smaller amounts of ENM reach the aquatic compartments. This study also presents a sensitivity analysis and a comprehensive discussion of the uncertainties of the simulation results and the limitations of the used approach. To estimate potential risks, the PEC values were compared to the predicted-no-effect concentrations (PNEC) derived from published data. The risk quotients (PEC/PNEC) for nano-TiO2 and nano-Ag were larger than one for treated wastewater and much smaller for all other environmental compartments (e.g., water, sediments, soils). We conclude that probabilistic modeling is very useful for predicting environmental concentrations of ENMs given the current lack of substantiated data. PMID:20821538

Gottschalk, Fadri; Sonderer, Tobias; Scholz, Roland W; Nowack, Bernd

2010-05-01

162

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

USGS Publications Warehouse

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.

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

163

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

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

Yasui, Shojiro

2015-04-01

164

Biological exposure limits estimated from relations between occupational styrene exposure during a workweek and excretion of mandelic and phenylglyoxylic acids in urine  

Microsoft Academic Search

Styrene exposure of 18 workers in fiber-glass reinforced plastic industries was measured for 30-min periods throughout each workday for a week. The styrene uptake was estimated using pulmonary ventilation measurements. All urine voidings were collected separately and the styrene metabolites, mandelic acid (MA) and phenylglyoxylic acid (PGA) were determined. The relationship between both exposure and uptake versus excretion of these

Jan Sollenberg; Rasmus Bjurström; Kent Wrangskog; Olof Vesterberg

1988-01-01

165

Single pre-exposure to a high dose of zymosan enhances lung defense mechanisms and accelerates the pulmonary clearance of a bacterial pathogen in rats.  

PubMed

The present study examines the effects of pre-exposure to zymosan (a 1 --> 3-beta-glucan from baker yeast) on lung defense against bacterial infection. Rats received a single dose of zymosan A (0.6, 1.2, or 2.5 mg/kg body weight [bw]) or vehicle control (saline) via intratracheal instillation 3 days prior to intratracheal inoculation with 5 x 10(5) Listeria monocytogenes. Left lungs were homogenized and cultured to assess bacterial clearance, and bronchoalveolar lavage was performed on the right lungs to monitor lung inflammation and injury. Prior to bacterial infection, zymosan exposure resulted in elevated inflammation and oxidant production in the lungs. Zymosan treatment followed by infection led to an accelerated pulmonary clearance of bacteria when compared to the saline control group in a dose-dependent fashion. In addition, lower levels of injury and inflammation were associated with the enhanced bacteria clearance observed in zymosan-infected rats. Our findings suggest that zymosan exposure may enhance the lung immune response by activating alveolar macrophages prior to infection, and stimulating T cells involved in the adaptive immune response early after infection, thus resulting in a heightened pulmonary immune response. PMID:19005921

Young, Shih-Houng; Antonini, James M; Roberts, Jenny R

2008-11-01

166

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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 pr...

167

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)

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.

Webber, W. R.; Gupta, M.

1990-01-01

168

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

PubMed

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

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

2014-06-15

169

Challenge of ultra-high energies: ultimate limits, possible directions of technology, an approach to collective acceleration  

SciTech Connect

At the request of Panel Chairman Amaldi, the oral version of this rpeort was largely devoted to a recapitulation and critique of the various methods of collective acceleration, including plasma-laser methods, which had been presented at the meeting.

Keefe, D.

1982-11-01

170

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

PubMed

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

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

1989-01-01

171

Accelerator mass spectrometry in biomedical dosimetry: relationship between low-level exposure and covalent binding of heterocyclic amine carcinogens to DNA.  

PubMed Central

Accelerator mass spectrometry (AMS) is used to determine the amount of carcinogen covalently bound to mouse liver DNA (DNA adduct) following very low-level exposure to a 14C-labeled carcinogen. AMS is a highly sensitive method for counting long-lived but rare cosmogenic isotopes. While AMS is a tool of importance in the earth sciences, it has not been applied in biomedical research. The ability of AMS to assay rare isotope concentrations (10Be, 14C, 26Al, 41Ca, and 129I) in microgram amounts suggests that extension to the biomedical sciences is a natural and potentially powerful application of the technology. In this study, the relationship between exposure to low levels of 2-amino-3,8-dimethyl[2-14C]imidazo[4,5-f]quinoxaline and formation of DNA adducts is examined to establish the dynamic range of the technique and the potential sensitivity for biological measurements, as well as to evaluate the relationship between DNA adducts and low-dose carcinogen exposure. Instrument reproducibility in this study is 2%; sensitivity is 1 adduct per 10(11) nucleotides. Formation of adducts is linearly dependent on dose down to an exposure of 500 ng per kg of body weight. With the present measurements, we demonstrate at least 1 order of magnitude improvement over the best adduct detection sensitivity reported to date and 3-5 orders of magnitude improvement over other methods used for adduct measurement. An additional improvement of 2 orders of magnitude in sensitivity is suggested by preliminary experiments to develop bacterial hosts depleted in radiocarbon. Expanded applications involving human subjects, including clinical applications, are now expected because of the great detection sensitivity and small sample size requirements of AMS. PMID:2371271

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

1990-01-01

172

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

NASA Technical Reports Server (NTRS)

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.

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

1987-01-01

173

Postnatal exposure to chromium through mother’s milk accelerates follicular atresia in F1 offspring through increased oxidative stress and depletion of antioxidant enzymes  

PubMed Central

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

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

2013-01-01

174

Accelerated alpha-decay of 232U isotope achieved by exposure of its aqueous solution with gold nanoparticles to laser radiation  

E-print Network

Experimental results are presented on laser-induced accelerated alpha-decay of Uranium-232 nuclei under laser exposure of Au nanoparticles in aqueous solutions of its salt. It is demonstrated that the decrease of alpha-activity strongly depends on the peak intensity of the laser radiation in the liquid and is highest at several terawatt per square centimeter. The decrease of alpha-activity of the exposed solutions is accompanied by the deviation of gamma-activities of daughter nuclides of Uranium-232 from their equilibrium values. Possible mechanisms of the laser influence on the alpha-activity are discussed on the basis of the amplification of the electric field of laser wave on metallic nanoparticles.

A. V. Simakin; G. A. Shafeev

2011-12-29

175

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

PubMed

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

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

2014-11-01

176

Throwing the baby out with the bath water? Occupational hygienists' views on the revised dutch system for occupational exposure limits.  

PubMed

In 2007, the Dutch Working Conditions Act was revised with the goal to decrease the regulatory burden, and to open up for company-specific solutions of establishing a safe and healthy work environment. One tool geared towards company-specific solutions is the compilation of the Arbocatalogs, which are company or sector-level collections of safe working methods and guidelines developed both by employers and employees. The revision also introduced a new occupational exposure limit (OEL) system in the Netherlands. This system encompasses two kinds of OELs: private and public. Private OELs are to be derived by the industry, while public OELs are issued by the Ministry of Social Affairs and Employment. With this change, the majority of the previously set Dutch OELs were removed, as the substances in question now are falling under the private realm. The motivations, expectations, and practical impacts of these revisions have been investigated through interviews with stakeholder organizations and a questionnaire study targeted at occupational hygienists. The questionnaire results show that although the Arbocatalogs seem to be relatively well received, a majority of the Dutch occupational hygienists are still relatively negative to the changes. There is a fear that private OELs will be less scientifically robust than public OELs and that the lack of robustness will have a negative impact on the field of occupational hygiene as a whole. PMID:23253359

Schenk, Linda; Palmen, Nicole Gm

2013-06-01

177

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

Microsoft Academic Search

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)

N. Collins; J. G. Ryan

2010-01-01

178

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

ERIC Educational Resources Information Center

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…

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

2010-01-01

179

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

PubMed

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

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

2015-03-01

180

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...

181

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

SciTech Connect

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.

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

2006-12-01

182

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...

183

Acceleration without Horizons  

E-print Network

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

Doria, Alaric

2015-01-01

184

Acceleration without Horizons  

E-print Network

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

Alaric Doria; Gerardo Munoz

2015-02-18

185

Quantitative property-property relationships for computing occupational exposure limits and vapour hazard ratios of organic solvents.  

PubMed

Vapour Hazard Ratio (VHR) is used in solvent substitution to select the best replacement option regarding overexposure potential of solvents. However, VHR calculations are limited by the availability of Occupational Exposure Limits (OELs). The overall objective of this study was to develop quantitative property-property relationship (QPPR) approaches for computing OELs, in view of supporting the derivation of VHRs for solvents without OELs. QPPRs were developed for estimating OELs using a database of 88 solvents which have health-based Time-Weighted Average (TWA) OELs published by the American Conference of Governmental Industrial Hygienists (ACGIH). Three surrogates of biotic lipid : air partition coefficients [n-octanol : air (K(oa)), olive oil : air (K(oila)) and fat : air (K(fa))] were selected for evaluating the descriptive/predictive relationship with OELs for solvents with local modes of action. For solvents with systemic modes of action, the prediction of OEL needs to consider quantitative differences in toxicokinetics (i.e. kinetic variability factor, KVF) and toxicological potency (i.e. effective internal concentration, EIC). The n-octanol : water (K(ow)), the oil : water (K(oilw)) and the fat : water (K(fw)) partition coefficients were selected for evaluating the relationship with EICs. For local modes of action, K(oa) is the most accurate predictor of OELs [OEL (ppm) = 10(((-0.45 x log K(oa)) + 3.65)); n = 21, r²= 0.71, PRESS/SSY = 0.36, F = 45.5 with p < 0.001] and the mean (±SD) (range) of the recommended to predicted OELs was 1.04 ± 0.61 (0.2-2.5). For systemic modes of action, KVFs and EICs vary in a range from 0.73 to 41.4 µmol L?¹ and 1.20-848 µmol L?¹, respectively. K(ow) is an accurate predictor of calculated EICs [EIC (µmol L?¹) = 10 (((-1.16 x log K(ow)) + 3.65)); n = 27, r²= 0.88, PRESS/SSY = 0.12, F = 181 with p < 0.001] and 50% of the predicted OEL values were within a factor of two of the recommended TWA OELs. Overall, 61% and 87% of the predicted VHRs were within a factor of two and five, respectively, of the calculated VHRs. The QPPR models developed in this study represent potentially useful tools for estimating provisional OELs for solvents lacking such guideline values. These provisional OELs are developed only to support initial estimations of VHR for dealing with the challenge of solvent substitution where relative values rather than absolute values of OEL and vapour pressure guide the hygienist in making pragmatic decisions for managing occupational health hazards. PMID:21120751

Debia, M; Krishnan, K

2010-10-01

186

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)

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.

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

2012-01-01

187

Review of exposure limits and experimental data for corneal and lenticular damage from short pulsed UV and IR laser radiation  

E-print Network

for cornea and lens exposure in the nanosecond to microsecond pulse duration regime in both the ultraviolet UV and infrared spectral ranges. In the UV spectral range, thermal and photochemical damage duration. The thermal UV damage data are compared with levels inferred from CO2 radiation thresholds

188

Exposure to Particulates and Fluorides and Respiratory Health of Workers in an Aluminum Production Potroom with Limited Control Measures  

Microsoft Academic Search

Occupational exposure to air pollutants and health status of potroom workers of an aluminum reduction plant in a developing country were studied and compared with those in developed countries. In this plant, the pots were constructed and installed without recommended gas collecting hoods or segmented side doors, and the workers did not use any respiratory protection. These conditions, combined with

Farhang Akbar-Khanzadeh

1995-01-01

189

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

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.

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

2009-01-01

190

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

E-print Network

trend in the oil and gas (exploration & production) industry is to use compact ­centrifugal forces basedFast Model Based Approximation of the Closed-loop Performance Limits of Gas/Liquid Inline.fuenmayor@shell.com, ruud.henkes@shell.com) Abstract: A current trend in the oil and gas industry is to use compact so

Van den Hof, Paul

191

ACCELERATED EXPOSURE TESTING Accelerated exposure testing has become increasingly  

E-print Network

environments simulation Corrosion evaluation and mitigation technologies Thermal stability testing Thermal and verification Materials research and evaluation Fire performance evaluation Fire testing Electrical

Chapman, Clark R.

192

Health Council of The Netherlands: no need to change from SAR to time-temperature relation in electromagnetic fields exposure limits.  

PubMed

The Health Council of the Netherlands (HCN) and other organisations hold the basic assumption that induced electric current and the generation and absorption of heat in biological material caused by radiofrequency electromagnetic fields are the only causal effects with possible adverse consequences for human health that have been scientifically established to date. Hence, the exposure guidelines for the 10?MHz-10?GHz frequency range are based on avoiding adverse effects of increased temperatures that may occur of the entire human body at a specific absorption rate (SAR) level above 4?W/kg. During the workshop on Thermal Aspects of Radio Frequency Exposure on 11-12 January 2010 in Gaithersburg, Maryland, USA, the question was raised whether there would be a practical advantage in shifting from expressing the exposure limits in SAR to expressing them in terms of a maximum allowable temperature increase. This would mean defining adverse time-temperature thresholds. In this paper, the HCN discusses the need for this, considering six points: consistency, applicability, quantification, causality, comprehensibility and acceptability. The HCN concludes that it seems unlikely that a change of dosimetric quantity will help us forward in the discussion on the scientific controversies regarding the existence or non-existence of non-thermal effects in humans following long duration, low intensity exposure to electromagnetic fields. Therefore, the HCN favours maintaining the current approach of basic restrictions and reference levels being expressed as SAR and in V/m or µT, respectively. PMID:21591902

van Rhoon, Gerard C; Aleman, André; Kelfkens, Gert; Kromhout, Hans; Van Leeuwen, Flora E; Savelkoul, Huub F J; Wadman, Wytse J; Van De Weerdt, Rik D H J; Zwamborn, A Peter M; Van Rongen, Eric

2011-01-01

193

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)

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.

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

2014-07-01

194

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

PubMed Central

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

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

2010-01-01

195

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

SciTech Connect

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.

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

1994-09-01

196

An evaluation of the 3M Organic Vapor Monitor #3500 as a short term exposure limit sampling device for acetone, methyl ethyl ketone, and methyl iso butyl ketone  

E-print Network

AN EVALUATION OF THE 3M ORGANIC VAPOR MONITOR 43500 AS A SHOR'I TERM EXPOSURE LIMIT SAMPLING DEVICE FOR ACETONE, METHYL ETHYL KETONE, AND METHYL ISO BUTYL KETONE A Thesis by LLOYD B. ANDREW III Submitted to the Graduate College of Texas ASM..., METHYL ETHYL KETONE, AND METHYL ISO BUTYL KETONE A Thesis by Lloyd B. Andrew III Approved as to style and content by: (Chai iy' of Co ' i tee) (He of Departme t) e4mY ~. (Member) C~& n (Member) December 1982 ABSTRACT An Evaluation of the 3M...

Andrew, Lloyd B.

1982-01-01

197

Physiological effects of sublethal acid exposure in juvenile rainbow trout on a limited or unlimited ration during a simulated global warming scenario.  

PubMed

Changes in the physiology and cost of living of fish were studied during exposure to simulated global warming and environmental acidification, alone and in combination. Trout were exposed to slightly elevated water temperatures (+2 degrees C), in the presence and absence of sublethal acidity (pH 5.2) in synthetic softwater for 90 d (8 degrees - 12 degrees C). Fish were either fed to satiation (ca. 1%-3% of their wet-body weight daily) or fed 1% of their wet-body weight once every 4 d. Satiation-fed fish exposed to sublethal pH showed no ionoregulatory disturbances but exhibited increased appetites and growth compared to fish in control pH waters. In contrast, fish maintained on a limited ration did not grow and showed typical ionoregulatory responses to acid stress, with lower whole-body Na+ and Cl- concentrations and greater mortality. Detrimental effects were greater in the global warming scenario (+2 degrees C). Overall, a slight temperature increase and sublethal pH increased the cost of living as determined by increased food consumption in satiation-fed fish and greater mortalities in fish maintained on a limited ration. Most important, these findings suggest that fish given sufficient food can compensate for increased energy expenditure or difficulties in maintaining ion balance associated with low pH exposure. PMID:9678497

D'Cruz, L M; Dockray, J J; Morgan, I J; Wood, C M

1998-01-01

198

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

PubMed

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

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

2015-01-01

199

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

PubMed Central

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

2014-01-01

200

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

PubMed

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

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

2014-10-21

201

Laser acceleration with open waveguides  

SciTech Connect

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.

Xie, Ming

1999-03-01

202

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)

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.

Collins, N.; Ryan, J. G.

2010-12-01

203

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)

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.

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

2003-01-01

204

Linear Accelerators  

SciTech Connect

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.

Sidorin, Anatoly [Joint Institute for Nuclear Research, Joliot-Curie 6, Dubna (Russian Federation)

2010-01-05

205

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...

206

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

PubMed Central

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

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

2012-01-01

207

Impact accelerations  

NASA Technical Reports Server (NTRS)

The degree to which impact acceleration is an important factor in space flight environments depends primarily upon the technology of capsule landing deceleration and the weight permissible for the associated hardware: parachutes or deceleration rockets, inflatable air bags, or other impact attenuation systems. The problem most specific to space medicine is the potential change of impact tolerance due to reduced bone mass and muscle strength caused by prolonged weightlessness and physical inactivity. Impact hazards, tolerance limits, and human impact tolerance related to space missions are described.

Vongierke, H. E.; Brinkley, J. W.

1975-01-01

208

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)

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.

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

2008-01-01

209

Accelerators (4/5)  

ScienceCinema

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.

None

2011-10-06

210

Accelerators (3/5)  

ScienceCinema

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.

None

2011-10-06

211

Accelerators (5/5)  

ScienceCinema

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.

None

2011-10-06

212

Can Accelerators Accelerate Learning?  

NASA Astrophysics Data System (ADS)

The 'Young Talented' education program developed by the Brazilian State Funding Agency (FAPERJ) [1] makes it possible for high-schools students from public high schools to perform activities in scientific laboratories. In the Atomic and Molecular Physics Laboratory at Federal University of Rio de Janeiro (UFRJ), the students are confronted with modern research tools like the 1.7 MV ion accelerator. Being a user-friendly machine, the accelerator is easily manageable by the students, who can perform simple hands-on activities, stimulating interest in physics, and getting the students close to modern laboratory techniques.

Santos, A. C. F.; Fonseca, P.; Coelho, L. F. S.

2009-03-01

213

Acceleration in astrophysics  

SciTech Connect

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.

Colgate, S.A.

1993-12-31

214

Vibration safety limits for magnetic resonance elastography  

NASA Astrophysics Data System (ADS)

Magnetic resonance elastography (MRE) has been demonstrated to have potential as a clinical tool for assessing the stiffness of tissue in vivo. An essential step in MRE is the generation of acoustic mechanical waves within a tissue via a coupled mechanical driver. Motivated by an increasing volume of human imaging trials using MRE, the objectives of this study were to audit the vibration amplitude of exposure for our IRB-approved human MRE studies, to compare these values to a conservative regulatory standard for vibrational exposure and to evaluate the applicability and implications of this standard for MRE. MRE displacement data were examined from 29 MRE exams, including the liver, brain, kidney, breast and skeletal muscle. Vibrational acceleration limits from a European Union directive limiting occupational exposure to whole-body and extremity vibrations (EU 2002/44/EC) were adjusted for time and frequency of exposure, converted to maximum displacement values and compared to the measured in vivo displacements. The results indicate that the vibrational amplitudes used in MRE studies are below the EU whole-body vibration limit, and the EU guidelines represent a useful standard that could be readily accepted by Institutional Review Boards to define standards for vibrational exposures for MRE studies in humans.

Ehman, E. C.; Rossman, P. J.; Kruse, S. A.; Sahakian, A. V.; Glaser, K. J.

2008-02-01

215

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

EPA Science Inventory

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

216

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

PubMed Central

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

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

2011-01-01

217

Virtual Accelerator for Accelerator Optics Improvement  

SciTech Connect

Through determination of all quadrupole strengths and sextupole feed-downs by fitting quantities derivable from precision orbit measurement, one can establish a virtual accelerator that matches the real accelerator optics. These quantities (the phase advances, the Green's functions, and the coupling ellipses tilt angles and axis ratios) are obtained by analyzing turn-by-turn Beam Position Monitor (BPM) data with a model-independent analysis (MIA). Instead of trying to identify magnet errors, a limited number of quadrupoles are chosen for optimized strength adjustment to improve the virtual accelerator optics and then applied to the real accelerator accordingly. These processes have been successfully applied to PEP-II rings for beta beating fixes, phase and working tune adjustments, and coupling reduction to improve PEP-II luminosity.

Yan, Y.T.; Cai, Y.; Decker, F-J.; Ecklund, S.; Irwin, J.; Seeman, J.; Sillivan, M.; Turner, J.; Wienands, U.; /SLAC

2005-09-30

218

Limiting worker exposure to highly pathogenic avian influenza a (H5N1): a repeat survey at a rendering plant processing infected poultry carcasses in the UK  

PubMed Central

Background Current occupational and public health guidance does not distinguish between rendering plant workers and cullers/poultry workers in terms of infection risk in their respective roles during highly pathogenic avian influenza poultry outbreaks. We describe an operational approach to human health risk assessment decision making at a large rendering plant processing poultry carcasses stemming from two separate highly pathogenic avian influenza A (H5N1) outbreaks in England during 2007. Methods During the first incident a uniform approach assigned equal exposure risk to all rendering workers in or near the production line. A task based exposure assessment approach was adopted during the second incident based on a hierarchy of occupational activities and potential for infection exposure. Workers assessed as being at risk of infection were offered personal protective equipment; pre-exposure antiviral prophylaxis; seasonal influenza immunisation; hygiene advice; and health monitoring. A repeat survey design was employed to compare the two risk assessment approaches, with allocation of antiviral prophylaxis as the main outcome variable. Results Task based exposure assessment during the second incident reduced the number of workers assessed at risk of infection from 72 to 55 (24% reduction) when compared to the first incident. No cases of influenza like illness were reported in workers during both incidents. Conclusions Task based exposure assessment informs a proportionate public health response in rendering plant workers during highly pathogenic avian influenza H5N1 outbreaks, and reduces reliance on extensive antiviral prophylaxis. PMID:21819563

2011-01-01

219

LONG DAY PHOTOPERIOD THAT ENHANCES PUBERTY DOES NOT LIMIT BODY GROWTH IN HOLSTEIN HEIFERS.  

Technology Transfer Automated Retrieval System (TEKTRAN)

As extended photoperiod accelerates puberty, it may limit mature body size and be detrimental to ultimate milk yield during lactation. We hypothesized that the potential negative effects of rapid growth and puberty through long day photoperiod (LDPP) exposure could be overcome with a greater supply ...

220

Loss of c-Met accelerates development of liver fibrosis in response to CCl(4) exposure through deregulation of multiple molecular pathways.  

PubMed

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 Met(fl/fl);Alb-Cre(+/-) conditional knockout mice and a carbon tetrachloride(CCl(4))-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 (4weeks) and healing phase (4weeks) 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

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

2012-06-01

221

Android Acceleration  

NSDL National Science Digital Library

Students prepare for the associated activity in which they investigate acceleration by collecting acceleration vs. time data using the accelerometer of a sliding Android device. Based on the experimental set-up for the activity, students form hypotheses about the acceleration of the device. Students will investigate how the force on the device changes according to Newton's Second Law. Different types of acceleration, including average, instantaneous and constant acceleration, are introduced. Acceleration and force is described mathematically and in terms of processes and applications.

2014-09-18

222

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

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

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

2013-01-01

223

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

Microsoft Academic Search

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

Andrew Stewart; Elliot P. Douglas

2012-01-01

224

Design and estimation of coded exposure point spread functions.  

PubMed

We address the problem of motion deblurring using coded exposure. This approach allows for accurate estimation of a sharp latent image via well-posed deconvolution and avoids lost image content that cannot be recovered from images acquired with a traditional shutter. Previous work in this area has used either manual user input or alpha matting approaches to estimate the coded exposure Point Spread Function (PSF) from the captured image. In order to automate deblurring and to avoid the limitations of matting approaches, we propose a Fourier-domain statistical approach to coded exposure PSF estimation that allows us to estimate the latent image in cases of constant velocity, constant acceleration, and harmonic motion. We further demonstrate that previously used criteria to choose a coded exposure PSF do not produce one with optimal reconstruction error, and that an additional 30 percent reduction in Root Mean Squared Error (RMSE) of the latent image estimate can be achieved by incorporating natural image statistics. PMID:22585096

McCloskey, Scott; Ding, Yuanyuan; Yu, Jingyi

2012-10-01

225

Future accelerators (?)  

SciTech Connect

I describe the future accelerator facilities that are currently foreseen for electroweak scale physics, neutrino physics, and nuclear structure. I will explore the physics justification for these machines, and suggest how the case for future accelerators can be made.

John Womersley

2003-08-21

226

Electrostatic accelerators  

E-print Network

The principle of electrostatic accelerators is presented. We consider Cockcroft? Walton, Van de Graaff and Tandem Van de Graaff accelerators. We resume high voltage generators such as cascade generators, Van de Graaff band generators, Pelletron generators, Laddertron generators and Dynamitron generators. The speci c features of accelerating tubes, ion optics and methods of voltage stabilization are described. We discuss the characteristic beam properties and the variety of possible beams. We sketch possible applications and the progress in the development of electrostatic accelerators.

Hinterberger, F

2006-01-01

227

Induction linear accelerators  

NASA Astrophysics Data System (ADS)

Among the family of particle accelerators, the Induction Linear Accelerator is the best suited for the acceleration of high current electron beams. Because the electromagnetic radiation used to accelerate the electron beam is not stored in the cavities but is supplied by transmission lines during the beam pulse it is possible to utilize very low Q (typically<10) structures and very large beam pipes. This combination increases the beam breakup limited maximum currents to of order kiloamperes. The micropulse lengths of these machines are measured in 10's of nanoseconds and duty factors as high as 10-4 have been achieved. Until recently the major problem with these machines has been associated with the pulse power drive. Beam currents of kiloamperes and accelerating potentials of megavolts require peak power drives of gigawatts since no energy is stored in the structure. The marriage of liner accelerator technology and nonlinear magnetic compressors has produced some unique capabilities. It now appears possible to produce electron beams with average currents measured in amperes, peak currents in kiloamperes and gradients exceeding 1 MeV/meter, with power efficiencies approaching 50%. The nonlinear magnetic compression technology has replaced the spark gap drivers used on earlier accelerators with state-of-the-art all-solid-state SCR commutated compression chains. The reliability of these machines is now approaching 1010 shot MTBF. In the following paper we will briefly review the historical development of induction linear accelerators and then discuss the design considerations.

Birx, Daniel

1992-03-01

228

Quasi-phase-matched laser wakefield acceleration.  

PubMed

The energy gain in laser wakefield acceleration is ultimately limited by dephasing, occurring when accelerated electrons outrun the accelerating phase of the wakefield. We apply quasi-phase-matching, enabled by axially modulated plasma channels, to overcome this limitation. Theory and simulations are presented showing that weakly relativistic laser intensities can drive significant electron energy gains. PMID:24745430

Yoon, S J; Palastro, J P; Milchberg, H M

2014-04-01

229

Occupational exposure in MRI  

PubMed Central

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

Mcrobbie, D W

2012-01-01

230

Radionuclide production for positron emission tomography: Choosing an appropriate accelerator  

NASA Astrophysics Data System (ADS)

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.

Votaw, John R.; Nickles, R. Jerome

1989-04-01

231

Acceleration in de Sitter spacetimes  

NASA Astrophysics Data System (ADS)

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.

Cotaescu, Ion I.

2015-02-01

232

Occupational exposure to crystalline silica and autoimmune disease.  

PubMed Central

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

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

1999-01-01

233

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

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).

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

2012-07-15

234

Accelerated molecular dynamics methods  

SciTech Connect

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.

Perez, Danny [Los Alamos National Laboratory

2011-01-04

235

Podcast: Acceleration  

NSDL National Science Digital Library

The Podcast: Acceleration is a segment of the Force and Motion Short Course. The podcast is 2 minutes 13 seconds in duration. Presented by science experts and NSTA staff, the NSTA Online Short Courses are professional development opportunities de

2009-07-06

236

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

PubMed

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

Wood, Andrew W

2008-09-01

237

Dose limits for astronauts  

NASA Technical Reports Server (NTRS)

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.

Sinclair, W. K.

2000-01-01

238

Accelerated Degradation of Polymers  

NSDL National Science Digital Library

For this laboratory exercise, you will monitor changes in the visual appearance of the samples, chemical changes and molecular weight changes as a function of exposure condition. Analysis of the neat and degraded systems will be done using visual evaluation, FTIR analysis and GPC analysis. After in-class presentation, completion of hands-on laboratory experiment and review of the information provided, you should be able to: • Confidently discuss the mechanism of breakdown for a polymeric material exposed to various environmental conditions. • Prepare samples and record an accurate account of their preparation for use in an outdoor environment and in an accelerated weathering chamber (Q-sun).

DeRosa, Rebecca L.

2008-09-26

239

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

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

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

2012-09-18

240

Force Limited Vibration Testing  

NASA Technical Reports Server (NTRS)

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.

Scharton, Terry; Chang, Kurng Y.

2005-01-01

241

Plasma accelerator  

DOEpatents

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.

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

2002-01-01

242

Particle acceleration  

NASA Technical Reports Server (NTRS)

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.

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

243

Accelerated Achievement  

ERIC Educational Resources Information Center

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…

Ford, William J.

2010-01-01

244

Shielding design of a treatment room for an accelerator-based epithermal neutron irradiation facility for BNCT  

Microsoft Academic Search

Protecting the facility personnel and the general public from radiation exposure is a primary safety concern of an accelerator-based epithermal neutron irradiation facility. This work makes an attempt at answering the questions {open_quotes}How much?{close_quotes} and {open_quotes}What kind?{close_quotes} of shielding will meet the occupational limits of such a facility. Shielding effectiveness is compared for ordinary and barytes concretes in combination with

Jeffrey F. Evans; Thomas E. Blue

1996-01-01

245

Compact accelerator  

DOEpatents

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).

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

2007-02-06

246

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

NASA Technical Reports Server (NTRS)

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.

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

2002-01-01

247

LANSCE beam current limiter  

SciTech Connect

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

Gallegos, F.R.

1996-06-01

248

LANSCE beam current limiter  

SciTech Connect

The Radiation Security System (RSS) at the Los Alamos Neutron Science Center (LANSCE) provides personnel protection from prompt radiation due to accelerated beam. Active instrumentation, such as the beam current limiter, is a component of the RSS. The current limiter is designed to limit the average current in a beamline below a specific level, thus minimizing the maximum current available for a beam spill accident. The beam current limiter is a self-contained, electrically isolated toroidal beam transformer which continuously monitors beam current. It is designed as fail-safe instrumentation. The design philosophy, hardware design, operation, and limitations of the device are described. {copyright} {ital 1997 American Institute of Physics.}

Gallegos, F.R. [Los Alamos Neutron Scattering Center, AOT Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States of America)

1997-01-01

249

Accelerators and the Accelerator Community  

SciTech Connect

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.

Malamud, Ernest; Sessler, Andrew

2008-06-01

250

Ring accelerators  

SciTech Connect

We present two-dimensional simulations in (r-z) and r-theta) cylinderical geometries of imploding-liner-driven accelerators of rings of charged particles. We address issues of azimuthal and longitudinal stability of the rings. We discuss self-trapping designs in which beam injection and extraction is aided by means of external cusp fields. Our simulations are done with the 2-1/2-D particle-in-cell plasma simulation code CLINER, which combines collisionless, electromagnetic PIC capabilities with a quasi-MHD finite element package.

Gisler, G.; Faehl, R.

1983-01-01

251

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

SciTech Connect

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.

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

2011-06-30

252

Military Exposures  

MedlinePLUS

... Wars & Operations Exposure Categories A-Z Index Agent Orange Agent Orange Home Facts about Herbicides Veterans' Diseases Birth Defects ... Veterans Health Initiative Veterans Health Initiative Home Agent Orange Gulf War Infectious Diseases of Southwest Asia War ...

253

The physiological basis for spacecraft environmental limits  

NASA Technical Reports Server (NTRS)

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.

Waligora, J. M. (compiler)

1979-01-01

254

Oxidised cosmic acceleration  

SciTech Connect

We give detailed proofs of several new no-go theorems for constructing flat four-dimensional accelerating universes from warped dimensional reduction. These new theorems improve upon previous ones by weakening the energy conditions, by including time-dependent compactifications, and by treating accelerated expansion that is not precisely de Sitter. We show that de Sitter expansion violates the higher-dimensional null energy condition (NEC) if the compactification manifold M is one-dimensional, if its intrinsic Ricci scalar R-ring vanishes everywhere, or if R-ring and the warp function satisfy a simple limit condition. If expansion is not de Sitter, we establish threshold equation-of-state parameters w below which accelerated expansion must be transient. Below the threshold w there are bounds on the number of e-foldings of expansion. If M is one-dimensional or R-ring everywhere vanishing, exceeding the bound implies the NEC is violated. If R-ring does not vanish everywhere on M, exceeding the bound implies the strong energy condition (SEC) is violated. Observationally, the w thresholds indicate that experiments with finite resolution in w can cleanly discriminate between different models which satisfy or violate the relevant energy conditions.

Wesley, Daniel H., E-mail: D.H.Wesley@damtp.cam.ac.uk [Centre for Theoretical Cosmology, DAMTP, Cambridge University, Wilberforce Road, Cambridge CB3 0WA (United Kingdom)

2009-01-15

255

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...

256

High average power induction accelerators  

SciTech Connect

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)

Swingle, J.C. (ed.)

1985-10-01

257

Progress on plasma accelerators  

SciTech Connect

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.

Chen, P.

1986-05-01

258

Acceleration technologies for charged particles: an introduction  

Microsoft Academic Search

Particle accelerators have many important uses in scientific experiments, in industry and in medicine. This paper reviews the variety of technologies which are used to accelerate charged particles to high energies. It aims to show how the capabilities and limitations of these technologies are related to underlying physical principles. The paper emphasises the way in which different technologies are used

Richard G. Carter

2011-01-01

259

EXPOSURE ASSESSMENT: INPUT INTO RISK ASSESSMENT  

EPA Science Inventory

The validity of a risk assessment can be no better than that of the exposure assessment upon which it is based. he general paucity of relevant exposure data, combined with the limited appreciation by most risk assessors of the critical dimensions and metrics of exposure, often le...

260

for sequence accelerators  

E-print Network

Wynn's -algorithm for sequence accelerators using high precision arithmetic Rachel Baumann University of Arizona Wynn's -algorithm for sequence accelerators using high precision arithmetic Rachel Baumann University of Arizona April 17, 2012 #12;Wynn's -algorithm for sequence accelerators using high

Zakharov, Vladimir

261

Asbestos Exposure Assessment Database  

NASA Technical Reports Server (NTRS)

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.

Arcot, Divya K.

2010-01-01

262

Chemical Accelerators The phrase "chemical accelerators"  

E-print Network

that there is a wealth of important chemistry occurring only at higher energies (of the order of the strength of chemicalMeetings Chemical Accelerators The phrase "chemical accelerators" is scarcely older than for one or two dozen people grew to include nearly a hundred. Chemical accelerators is a name sug- gested

Zare, Richard N.

263

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 ...

264

Radiative Accelerations in Stellar Evolution  

E-print Network

A brief review of various methods to calculate radiative accelerations for stellar evolution and an analysis of their limitations are followed by applications to Pop I and Pop II stars. Recent applications to Horizontal Branch (HB) star evolution are also described. It is shown that models including atomic diffusion satisfy Schwarzschild's criterion on the interior side of the core boundary on the HB without the introduction of overshooting. Using stellar evolution models starting on the Main Sequence and calculated throughout evolution with atomic diffusion, radiative accelerations are shown to lead to abundance anomalies similar to those observed on the HB of M15.

G. Michaud; J. Richer

2008-01-26

265

Natural sunlight accelerated weathering of photovoltaic modules  

NASA Technical Reports Server (NTRS)

Photovoltaic modules are exposed to the equivalent of ten years of sunlight aging in an accelerated exposure testing and evaluation program, the objective being to determine the long-term durability characteristics of flat plate modules in comparatively short periods of time. The modules are illuminated with concentrated sunlight in a large, sun-tracking, Fresnel-reflecting solar concentrator. The effects of the accelerated exposure are assessed by performing periodic visual inspections and electrical measurements. It is found that field-experienced failure modes are duplicated, that acceleration factors of 6x to 8x are readily attainable, and that the test method is feasible as a predictive tool for photovoltaic module lifetime durability.

Zerlaut, G. A.; Anderson, T. B.; Arnett, J. C.

1981-01-01

266

High Transformer ratios in collinear wakefield accelerators.  

SciTech Connect

Based on our previous experiment that successfully demonstrated wakefield transformer ratio enhancement in a 13.625 GHz dielectric-loaded collinear wakefield accelerator using the ramped bunch train technique, we present here a redesigned experimental scheme for even higher enhancement of the efficiency of this accelerator. Design of a collinear wakefield device with a transformer ratio R2, is presented. Using a ramped bunch train (RBT) rather than a single drive bunch, the enhanced transformer ratio (ETR) technique is able to increase the transformer ratio R above the ordinary limit of 2. To match the wavelength of the fundamental mode of the wakefield with the bunch length (sigmaz=2 mm) of the new Argonne wakefield accelerator (AWA) drive gun (where the experiment will be performed), a 26.625 GHz dielectric based accelerating structure is required. This transformer ratio enhancement technique based on our dielectric-loaded waveguide design will result in a compact, high efficiency accelerating structures for future wakefield accelerators.

Power, J. G.; Conde, M.; Yusof, Z.; Gai, W.; Jing, C.; Kanreykin, A.; Schoessow, P.; High Energy Physics; Euclid Techlabs, LLC

2008-01-01

267

Tritium Exposure Reconstruction Using Tree Rings at Lawrence Berkeley National Laboratory  

NASA Astrophysics Data System (ADS)

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.

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

2002-12-01

268

Induction acceleration scenario from an extremely low energy in the KEK all-ion accelerator  

NASA Astrophysics Data System (ADS)

An all-ion accelerator (AIA)—capable of accelerating all ions of any possible charge state and mass—based on the induction synchrotron concept is under study. This concept was demonstrated in 2006, wherein confinement and acceleration of a proton bunch was independently carried out by the induction cells. In the induction synchrotron based systems, unlike RF synchrotron, the operation frequency of an induction cell is not a limitation, since it generates acceleration voltage by generating trigger signals in synchronization with the bunch signal from the monitors. For the proof of principle experiment of AIA, argon ions is planned to be accelerated in the KEK-PS booster ring (KEK-BR). KEK-BR, operated as a rapid cycle synchrotron at 20 Hz frequency, requires a dynamic acceleration voltage throughout acceleration period. The acceleration voltage pulse provided by the induction cells is fixed in amplitude; therefore a new acceleration scheme using fixed output voltage from the induction acceleration cells is worked out using simulations. This paper discusses the new acceleration scheme for the AIA, its simulation results and a new induction cell giving long acceleration voltage pulse required for AIA. Then various issues are discussed from the practical point of view.

Dixit, Tanuja S.; Iwashita, Taiki; Takayama, Ken

2009-04-01

269

Code Carnivals: resuscitating Code Blue training with accelerated learning.  

PubMed

Nurses in the hospital setting must be knowledgeable about resuscitation procedures and proficient in the delivery of care during an emergency. They must be ready to implement their knowledge and skills at a moment's notice. A common dilemma for many nurses is that cardiopulmonary emergencies (Code Blues) are infrequent occurrences. Therefore, how do nurses remain competent and confident in their implementation of emergency skills while having limited exposure to the equipment and minimal experience in emergency situations? A team of nurse educators at a regional medical center in Washington State applied adult learning theory and accelerated learning techniques to develop and present a series of learning activities to enhance the staff's familiarity with emergency equipment and procedures. The series began with a carnival venue that provided hands-on practice and review of emergency skills and was reinforced with subsequent random unannounced code drills led by both educators and charge nurses. PMID:20000265

Keys, Vicky A; Malone, Peggy; Brim, Carla; Schoonover, Heather; Nordstrom, Cindy; Selzler, Melissa

2009-12-01

270

High-powered pulsed-ion-beam acceleration and transport  

SciTech Connect

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.

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

1981-11-01

271

Beam experiments on the Pulse Line Ion Accelerator  

Microsoft Academic Search

Beam experiments on a new accelerator concept called the Pulse Line Ion Accelerator (PLIA) have demonstrated the ability to accelerate and compress ion bunches. Charging the PLIA to its full potential is limited by a vacuum surface flashover. Discharge issues have been evaluated for possible solutions. A numerical model has been developed to investigate the breakdown phenomena. Experimental results and

J. E. Coleman; A. Friedman; W. L. Waldron; F. M. Bieniosek; R. J. Briggs; D. P. Grote; E. Henestroza; P. K. Roy; P. A. Seidl; S. S. Yu

2007-01-01

272

Personnel Exposure In Interventional Radiology  

NASA Astrophysics Data System (ADS)

The personnel radiation exposure which is possible in interventional radiology is much greater than that in other areas of diagnostic radiology. Following a review of recent film badge records for personnel involved in interventional radiology at our institution, we have examined various methods to reduce head and neck exposures during interventional procedures. Calculations and measurements demonstrate that with even a modest workload ancillary shielding materials are necessary in order to maintain head exposures within regulatory limits. This report presents a newly developed shielding method (surface shield) for use during interventional radiology procedures. The surface shield is inexpensive and reduces head and neck exposure by up to 75% without compromising patient access or radiologist convenience. Due to the special demands of interventional radiology, periodic review of procedures and radiation protection principles with the personnel involved is important in keeping personnel exposure as low as reasonably achievable.

Morin, R. L.; Young, A.; Staiger, J.; Nelson, K.; Cardella, J.

1985-09-01

273

Laser driven ion accelerator  

DOEpatents

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.

Tajima, Toshiki

2005-06-14

274

Induction linear accelerators  

Microsoft Academic Search

Among the family of particle accelerators, the Induction Linear Accelerator is the best suited for the acceleration of high current electron beams. Because the electromagnetic radiation used to accelerate the electron beam is not stored in the cavities but is supplied by transmission lines during the beam pulse it is possible to utilize very low Q (typically<10) structures and very

Daniel Birx

1992-01-01

275

Laser driven ion accelerator  

DOEpatents

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.

Tajima, Toshiki

2006-04-18

276

Induced activation in accelerator components  

NASA Astrophysics Data System (ADS)

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.

Bungau, Cristian; Bungau, Adriana; Cywinski, Robert; Barlow, Roger; Edgecock, Thomas Robert; Carlsson, Patrick; Danared, Hâkan; Mezei, Ferenc; Holm, Anne Ivalu Sander; Møller, Søren Pape; Thomsen, Heine Dølrath

2014-08-01

277

Laser acceleration in novel media  

NASA Astrophysics Data System (ADS)

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.

Tajima, T.

2014-05-01

278

Acceleration of runaway electrons and Joule heating in solar flares  

NASA Technical Reports Server (NTRS)

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.

Holman, G. D.

1984-01-01

279

Acceleration of runaway electrons and Joule heating in solar flares  

NASA Technical Reports Server (NTRS)

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.

Holman, G. D.

1985-01-01

280

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

SciTech Connect

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

Liu, James C

1998-10-12

281

COMPARATIVE STUDIES OF PROTON ACCELERATORS FOR HIGH POWER APPLICATIONS.  

SciTech Connect

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

WENG, W.T.

2006-05-29

282

Using Accelerated Testing to Predict Module Reliability  

SciTech Connect

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.

Wohlgemuth, J. H.; Kurtz, S.

2011-01-01

283

Biological markers of solvent exposure  

SciTech Connect

The important limitation of many epidemiologic studies is the relative inaccuracy of the assessment of the magnitude of exposure. For some solvents, the concentration in biological media is an indication of the internal exposure and is an indirect indication of the health risk, at least for acute effects. For long-term effects, e.g., carcinogenicity, biological monitoring data can also be used as showed with the individual occupational data on the level of trichloroacetic acid (TCA) in urine. Occupational epidemiology can improve the methods for the assessment of the actual total exposure and health risk in environmental epidemiology by providing higher dose cohort data.

Monster, A.C.

1988-03-01

284

Report on accelerated corrosion studies.  

SciTech Connect

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.

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

2011-03-01

285

Domestic asbestos exposure: a review of epidemiologic and exposure data.  

PubMed

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

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

2013-11-01

286

Domestic Asbestos Exposure: A Review of Epidemiologic and Exposure Data  

PubMed Central

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

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

2013-01-01

287

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)

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.

Smith, L. Montgomery

1998-01-01

288

g-LIMIT Status Briefing  

NASA Technical Reports Server (NTRS)

For many microgravity science experiments in the International Space Station, the ambient acceleration environment will be exceed desirable levels. To provide a more quiescent acceleration environment to the microgravity payloads, a vibration isolation system named g-LIMIT (GLovebox Integrated Microgravity Isolation Technology) is being designed. g-LIMIT is a sub-rack level isolation system that can be tailored to a variety of applications. Scheduled for launch on the UF-1 mission, the initial implementation of g-LIMIT will be a Characterization Test in the Microgravity Science Glovebox (MSG). g-LIMIT will be available to glovebox investigators immediately after characterization testing. Standard MSG structural and umbilical interfaces will be used so that the isolation mount is transparent to the user with no additional accommodation requirements. g-LIMIT consists of three integrated isolator modules, each of which is comprised of a dual axis actuator, two axes of acceleration sensing, two axes of position sensing, control electronics, and data transmission capabilities in a minimum-volume package. In addition, this system provides the unique capability for measuring absolute acceleration of the experiment independent of accelerometers as a by-product of the control system and will have the capability of generating pristine accelerations to enhance experiment operations.

Whorton, Mark; Perkins, Brad T.

2000-01-01

289

Human exposure in low Earth orbit  

NASA Technical Reports Server (NTRS)

Human exposure to trapped electrons and protons in low Earth orbit (LEO) is evaluated on a basis of a simple approximation of the human geometry for spherical shell shields of varying thickness. A data base is presented that may be used to make preliminary assessment of the impact of radiation exposure constraints on human performance. Detailed shielding studies should be performed before final design considerations. A sample impact assessment is discussed on the basis of presently accepted allowable exposure limits. A brief discussion is given on the anticipated impact of an ongoing reassessment of allowable exposure limits.

Wilson, J. W.; Cucinotta, F.

1984-01-01

290

Accelerator mass spectrometry of plutonium isotopes  

Microsoft Academic Search

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

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

1996-01-01

291

Acceleration Environment of the International Space Station  

NASA Technical Reports Server (NTRS)

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.

McPherson, Kevin; Kelly, Eric; Keller, Jennifer

2009-01-01

292

Unusual Non-Occupational Exposure to Metals  

PubMed Central

Exposure to metals at workplaces is well known and in many cases occupational studies led to an adoption of limit values. For airborne concentrations of substances as metals refer to the “Maximaleo Arbeitsplatz-Konzentration” (MAK) in Germany or the “Threshold Limit Value” (TLV) in USA. Biological monitoring consists of an assessment of overall exposure to chemicals at the workplace and in the environment. The “Biologischer Arbeitsstoff Toleranzwert” (BAT) in Germany and the “Biological Exposure Index” in the USA serve as reference values. Besides these occupational limit values, reference values exist in Germany for the background exposure of the non occupationally exposed general population. In some cases the reference values are exceeded without any occupational exposure. Several cases of unusual environmental exposure to cobalt, mercury and manganese are reported. In such cases, it is often difficult to evaluate the measured concentration. In Germany, therefore, the “Human-Biomonitoring-Werte” (HBMValues) have been adopted in order to evaluate such high background exposures. The HBM-concept is presented. Environmental exposure to metals is usual within some limits. Reference values are helpful for an assessment. Unusual exposure occurs and the physician should be alert to symptoms of poisoning. PMID:18365042

Wrbitzky, Renate

2003-01-01

293

Accelerated large-scale multiple sequence alignment  

PubMed Central

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

2011-01-01

294

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

SciTech Connect

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.

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

2011-09-01

295

Environmental Exposure Effects on Composite Materials for Commercial Aircraft  

NASA Technical Reports Server (NTRS)

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

Hoffman, D. J.

1980-01-01

296

Acceleration of Gravity 1  

NSDL National Science Digital Library

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

Michael Horton

2009-05-30

297

Linear Accelerator (LINAC)  

MedlinePLUS

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

298

Exposure to Air Pollution Enhances the Generation of Vascular Microparticles  

EPA Science Inventory

Epidemiological studies associate exposure to ambient levels of particulate matter (PM) with cardiovascular morbidity and mortality. The biological mechanisms by which PM exposure induces cardiovascular effects remain to be elucidated. One important limitation is the lack of sens...

299

PERSONAL EXPOSURE TO PARTICLES IN BANSKA BYSTRICA, SLOVAKIA  

EPA Science Inventory

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

300

Requirements for Simulating Space Radiation With Particle Accelerators  

NASA Technical Reports Server (NTRS)

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.

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

2004-01-01

301

Analysis of exposure due to work on activated components  

SciTech Connect

In this brief note the author summarized analysis of the exposure incurred in various maintenance jobs involving activated accelerator and beam line components at Fermilab. A tabulation was made of parameters associated with each job. Included are rather terse descriptions of the various tasks. The author presented various plots of the quantities in the table. All exposure rates are mR/hr while all exposures accumulated are mR. The exposure rates were generally measured at the Fermilab standard one foot distance from the activated component. Accumulated exposures are taken from the self-reading pocket dosimeter records maintained by the radiation control technicians.

Cossairt, J.D.

1987-09-01

302

Environmental tobacco smoke exposure assessment  

SciTech Connect

Environmental tobacco smoke (ETS) is the material released into the environment as tobacco products are smoked. Cigarettes, pipes, and cigars all produce ETS but the term has become all but synonymous with indoor air contamination by cigarette smoking. This is because cigarettes are by far the most commonly consumed tobacco product and because the principal human exposure occurs indoors. Exposure to ETS is variously termed as passive smoking, involuntary smoking, and as exposure to second-hand smoke. Considerable progress has been made toward a better understanding of ETS exposure. Strengths and limitations of various measures of exposure are better understood and much data has been generated on the quantities of many ETS-constituents in many indoor environments. The properties of ETS, methods for its measurement in indoor air, and many results of field studies have recently been reviewed by the author. The recent EPA report includes a major treatment of exposure estimation including air concentrations, questionnaires, and biomarkers. This paper discusses approaches to exposure assessment and summarizes data on indoor air concentrations of ETS-constituents.

Guerin, M.R.

1993-06-01

303

Environmental tobacco smoke exposure assessment  

SciTech Connect

Environmental tobacco smoke (ETS) is the material released into the environment as tobacco products are smoked. Cigarettes, pipes, and cigars all produce ETS but the term has become all but synonymous with indoor air contamination by cigarette smoking. This is because cigarettes are by far the most commonly consumed tobacco product and because the principal human exposure occurs indoors. Exposure to ETS is variously termed as passive smoking, involuntary smoking, and as exposure to second-hand smoke. Considerable progress has been made toward a better understanding of ETS exposure. Strengths and limitations of various measures of exposure are better understood and much data has been generated on the quantities of many ETS-constituents in many indoor environments. The properties of ETS, methods for its measurement in indoor air, and many results of field studies have recently been reviewed by the author. The recent EPA report includes a major treatment of exposure estimation including air concentrations, questionnaires, and biomarkers. This paper discusses approaches to exposure assessment and summarizes data on indoor air concentrations of ETS-constituents.

Guerin, M.R.

1993-01-01

304

Exposure control for HDR video  

NASA Astrophysics Data System (ADS)

This paper proposes an algorithm for determining the exposure times for High Dynamic Range (HDR) video by adapting them to the current lighting. Due to the limited capability of the sensor used, only two exposures per frame can be taken. For each image, the histogram for the exposure time of the other image is estimated. When this histogram is subtracted from the original, the result can be used to adjust the exposure time to the current lighting situation by standard exposure control algorithms. The subtraction removes the dynamic range already covered by the other image, thus the exposure time can be optimized for the residual dynamic range. The algorithm has been compared with state-of-the-art algorithms for HDR imaging. It is proven to have comparable results in mean squared error to a ground truth gained from real-world data. Furthermore this algorithm is capable of running during the capturing process of a video, since it doesn't require additional exposures than those already taken.

Bürker, M.; Rößing, C.; Lensch, H. P. A.

2014-05-01

305

Transresonant Electron Acceleration  

Microsoft Academic Search

ttelliwell and Bell have suggested synchronous acceleration of electrons by electromagnetic waves in the whistler range in the geomagnetic field. The acceleration of trapped electrons by electromagnetic waves is here generalized to include nonsynchronous or transresonant acceleration. It is shown that whistlers will scatter the electron velocity, by an amount inversely proportional to the square root of the time rate

E. N. Parker; Enrico Fermi

1961-01-01

306

Angular Acceleration without Torque?  

ERIC Educational Resources Information Center

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.

Kaufman, Richard D.

2012-01-01

307

Acceleration: It's Elementary  

ERIC Educational Resources Information Center

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…

Willis, Mariam

2012-01-01

308

Force, mass and acceleration  

Microsoft Academic Search

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

Phil Dalrymple; Richard Griffiths

2005-01-01

309

Direction of Acceleration  

NSDL National Science Digital Library

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

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

310

Far field acceleration  

SciTech Connect

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.

Fernow, R.C.

1995-07-01

311

THE EFFECT OF ACCELERATED AGING TESTS ON THE OPTICAL PROPERTIES OF SILICONE AND EVA ENCAPSULANTS  

Microsoft Academic Search

The absorption coefficient of three silicones and EVA is measured before and after exposure to three accelerated aging tests: (i) ~2000 hours under Xe-arc lamp exposure at room temperature, (ii) 1200 hours at 85% relative humidity and 85 °C, and (iii) six months at the focal point of a 30× linear tracker. The first exposure satisfied the IEC's UV conditioning

Keith R. McIntosh; James N. Cotsell; Jeff S. Cumpston; Ann W. Norris; Nick E. Powell; Barry M. Ketola

312

Advanced Accelerator Test Facility (AATF) upgrade plan  

SciTech Connect

We have successfully demonstrated the principles of wake-field acceleration using structures (cavity, dielectric) and plasmas as wake-field devices using the AATF at Argonne National Laboratory. Due to the limited driver electron pulse intensity and relative long pulse length, only modest accelerating gradients were observed. In order to study the wake field effects in much greater detail and demonstrate the feasibility of wake-field accelerator for high energy physics, we are considering construction of a laser photocathode injector on the existing 20 MeV Chem-Linac to produce very intense and short electron pulses. 10 refs., 5 figs.

Gai, W.; Ho, C.; Konecny, R.; Mtingwa, S.; Norem, J.; Rosenzweig, J.; Schoessow, P.; Simpson, J.; Cole, B.; Rosing, M.

1989-01-01

313

Exposure assessment of laboratory students.  

PubMed

The Massachusetts Institute of Technology (MIT) has two kinds of laboratories, teaching for undergraduate students and research laboratories for graduate students and research staff. The objective of this study is to determine chemical exposures during teaching and research activities. There are three hypotheses in this study: (1) Exposures in academic laboratories are well below health standards; (2) Students in undergraduate teaching laboratories have less chemical exposure compared to students in graduate research laboratories; and (3) Students in different disciplines are expected to have different exposures. From September 1996 to December 1996, 132 air samples were collected from both teaching and research laboratories in the departments of Material Sciences and Engineering, Chemical Engineering, and Biology. The most frequently sampled chemicals in these three departments were cobalt, styrene, and formaldehyde, respectively. A total of 23 different agents were measured. In this study, the American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value (TLV)-short-term exposure limit (STEL) is used as the health-effect standard for exposure time less than four hours. The ACGIH TLV-TWA (time-weighted average) is used as the standard for exposure times equal to or greater than four hours. The ratio of measured concentrations to the appropriate ACGIH standard was then calculated. The geometric mean of the ratio for the total samples was 0.34 percent of the standards. There were 70 samples from teaching laboratories (geometric mean = 0.38% of the standards), and 62 samples from research laboratories (geometric mean = 0.08% of the standards). The chemical exposures relative to the standards in teaching laboratories were statistically higher than in research laboratories (p-value < 0.001). Information about personal protective equipment and the use of laboratory chemical hoods was also collected. The differences in use of personal protective equipment (PPE) among these departments was not statistically significant. From the air sampling results, we concluded that (1) Chemical exposures in the academic laboratories in this study were all well below the health standards; (2) Undergraduate students in teaching laboratories had higher chemical exposures than graduate students in research laboratories; (3) Chemical exposures among departments were not significantly different; and (4) Hazard communication, safety training, and laboratory rules enforcement are important for protection and may be the reason that the results from this study indicate that chemical exposures in this academic institution are well below the health standards under normal operations. PMID:10462848

Tan, Y M; DiBerardinis, L; Smith, T

1999-08-01

314

Occupational exposure to formaldehyde in dialysis units  

SciTech Connect

A company in Illinois that operates three dialysis centers became concerned about the occupational exposure of its employees to formaldehyde. The company requested an investigation by the National Institute for Occupational Safety and Health (NIOSH) to determine the extent of employee exposure to formaldehyde. Investigators from NIOSH conducted an initial environmental survey of the facilities in April 1982 and a follow-up environmental survey in June 1982. In the areas used to reprocess dialyzers, they collected air samples to analyze for formaldehyde in the personal breathing zones of workers. The results showed that workers at two of the three facilities involved were exposed to formaldehyde concentrations of 0.50 and 0.57 parts per million (ppm), respectively, as a time-weighted average (TWA). The current Occupational Safety and Health Administration standard establishes a permissible exposure of 3 ppm, 8-hour TWA; NIOSH recommends minimizing workplace exposure levels and limiting exposure levels and limiting exposure to the lowest feasible level.

Not Available

1986-08-08

315

Asbestos exposure and cancerphobia.  

PubMed

In 48 cases of claims of psychic injury due to asbestos exposure, seven were diagnosed as "cancerphobia". Cancerphobia is a concept primarily used in personal injury cases with little support in the medical community. Analysis of standards for phobia indicates that the term is inappropriate for such legal claims. Phobic reactions are avoidant reactions with panic or intense anxiety on exposure to the phobic stimulus. The cases reviewed indicate lack of psychiatric symptomatology, lack of conformance to accepted standards, and insufficient attention to history--medical and otherwise. This clinical review supports the contention of Simon that cancerphobia is not a credible classification. Skepticism is merited where potential damage awards are limited by minimal physical findings with resultant emphasis on claims of illness phobia, an example being exposure to a toxic substance like asbestos, which may be followed, but not necessarily so, by a variety of adverse consequences. Professional persons should be alert to the misuse of medical concepts in such cases. PMID:8006625

Perr, I N

1994-05-01

316

75 FR 25279 - Device Improvements to Reduce the Number of Under-Doses, Over-Doses, and Misaligned Exposures...  

Federal Register 2010, 2011, 2012, 2013, 2014

...Misaligned Exposures From Therapeutic Radiation; Public Meeting; Request for Comments...Misaligned Exposures from Therapeutic Radiation.'' The purpose of this meeting is...manufacturers of linear accelerators, radiation therapy treatment planning...

2010-05-07

317

Constraints on the acceleration of anomalous cosmic rays  

NASA Technical Reports Server (NTRS)

The recent determination of an upper limit of 0.2 pc on the distance to the source of the anomalous cosmic rays, and the implied upper limit on their age imposes a significant observational constraint on possible acceleration mechanisms. Adiabatic cooling in the expanding wind makes the constraints significantly more stringent. In the light of these constraints, the rate of second-order Fermi acceleration is much too low to play a significant role. Diffusive shock acceleration, even at the strong termination shock of the solar wind, is sufficient only if one discards the standard expression for the maximum acceleration rate based on the Bohm limit. Only diffusive acceleration at the quasi-perpendicular solar wind termination shock has a high enough acceleration rate to be the source of the anomalous component.

Jokipii, J. R.

1992-01-01

318

Accelerator Physics Related to Rare Isotope Beams  

NASA Astrophysics Data System (ADS)

Extensive analysis of the existing data and theoretical models has suggested that the highest yield for a wide range of rare isotopes available for experiments can be obtained by using two accelerators: a heavy-ion driver and a post-accelerator for re-acceleration of radioisotopes. The superconducting driver linac provides the primary, 400 kW, stable-ion beams in the energy range from 580 MeV for protons to 200 MeV/u for uranium required to produce the radioisotopes. To overcome intensity limitations from the most advanced ECR ion sources, the driver linac is designed for the simultaneous acceleration of two charge-states of uranium ions in the front-end and 5 charge states of uranium ions after the liquid lithium stripper. The most efficient production mechanisms for slow radioactive ions produce these ions in 1^+ or 2^+ charge states. The post-accelerator must, therefore, be able to accept such low charge-to-mass ratio ions. However, this option results in an expensive post-accelerator. One approach is to increase the charge state of the ions before acceleration via a charge booster stage. The intensity of rare isotope beams can be enhanced by the acceleration of multiple charge state beams.

Ostroumov, Peter

2008-04-01

319

SILICA EXPOSURE IN HAND GRINDING STEEL CASTINGS  

Microsoft Academic Search

Exposure to silica dust was studied in the grinding of castings in a steel foundry that used conventional personal sampling methods and new real-time sampling techniques developed for the identification of high-exposure tasks and tools. Approximately one-third of the personal samples exceeded the National Institute for Occupational Safety and Health recommended exposure limit for crystalline silica, a fraction similar to

Dennis OBrien; Phillip A. Froehlich; Michael G. Gressel; Ronald M. Hall; Nancy J. Clark; Patrick Bost; Thomas Fischbach

1992-01-01

320

Exposure chamber  

DOEpatents

A chamber for exposing animals, plants, or materials to air containing gases or aerosols is so constructed that catch pans for animal excrement, for example, serve to aid the uniform distribution of air throughout the chamber instead of constituting obstacles as has been the case in prior animal exposure chambers. The chamber comprises the usual imperforate top, bottom and side walls. Within the chamber, cages and their associated pans are arranged in two columns. The pans are spaced horizontally from the walls of the chamber in all directions. Corresponding pans of the two columns are also spaced horizontally from each other. Preferably the pans of one column are also spaced vertically from corresponding pans of the other column. Air is introduced into the top of the chamber and withdrawn from the bottom. The general flow of air is therefore vertical. The effect of the horizontal pans is based on the fact that a gas flowing past the edge of a flat plate that is perpendicular to the flow forms a wave on the upstream side of the plate. Air flows downwardly between the chamber walls and the outer edges of the pan. It also flows downwardly between the inner edges of the pans of the two columns. It has been found that when the air carries aerosol particles, these particles are substantially uniformly distributed throughout the chamber.

Moss, Owen R. (Kennewick, WA)

1980-01-01

321

High brightness electron accelerator  

DOEpatents

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.

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

1994-01-01

322

An introduction to acceleration mechanisms  

SciTech Connect

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)

Palmer, R.B.

1987-05-01

323

Accelerated leach test development program  

SciTech Connect

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.

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

1990-11-01

324

The Dose Response Relationship between In Ear Occupational Noise Exposure and Hearing Loss  

PubMed Central

Objectives Current understanding of the dose-response relationship between occupational noise and hearing loss is based on cross-sectional studies prior to the widespread use hearing protection and with limited data regarding noise exposures below 85dBA. We report on the hearing loss experience of a unique cohort of industrial workers with daily monitoring of noise inside of hearing protection devices. Methods At an industrial facility, workers exhibiting accelerated hearing loss were enrolled in a mandatory program to monitor daily noise exposures inside of hearing protection. We compared these noise measurements (as time-weighted LAVG) to interval rates of high frequency hearing loss over a six year period using a mixed effects model, adjusting for potential confounders. Results Workers’ high frequency hearing levels at study inception averaged more than 40 dB hearing threshold level (HTL). Most noise exposures were less than 85dBA (mean LAVG 76 dBA, interquartile range 74 to 80 dBA). We found no statistical relationship between LAvg and high frequency hearing loss (p = 0.53). Using a metric for monthly maximum noise exposure did not improve model fit. Conclusion At-ear noise exposures below 85dBA did not show an association with risk of high frequency hearing loss among workers with substantial past noise exposure and hearing loss at baseline. Therefore, effective noise control to below 85dBA may lead to significant reduction in occupational hearing loss risk in such individuals. Further research is needed on the dose response relationship of noise and hearing loss in individuals with normal hearing and little prior noise exposure. PMID:23825197

Rabinowitz, Peter M.; Galusha, Deron; Dixon-Ernst, Christine; Clougherty, Jane E.; Neitzel, Richard L.

2014-01-01

325

Radiation Contamination Versus Exposure  

MedlinePLUS

RADIATION CONTAMINATION VERSUS EXPOSURE EXTERNAL CONTAMINATION External contamination occurs when radioactive material comes into contact with a ... radioactive materials can accumulate in different body organs. RADIATION EXPOSURE Another word for radiation exposure is irradiation. ...

326

Current limiters  

SciTech Connect

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.

Loescher, D.H. [Sandia National Labs., Albuquerque, NM (United States). Systems Surety Assessment Dept.; Noren, K. [Univ. of Idaho, Moscow, ID (United States). Dept. of Electrical Engineering

1996-09-01

327

Actinides, accelerators and erosion  

NASA Astrophysics Data System (ADS)

Fallout isotopes can be used as artificial tracers of soil erosion and sediment accumulation. The most commonly used isotope to date has been 137Cs. Concentrations of 137Cs are, however, significantly lower in the Southern Hemisphere, and furthermore have now declined to 35% of original values due to radioactive decay. As a consequence the future utility of 137Cs is limited in Australia, with many erosion applications becoming untenable within the next 20 years, and there is a need to replace it with another tracer. Plutonium could fill this role, and has the advantages that there were six times as many atoms of Pu as of 137Cs in fallout, and any loss to decay has been negligible due to the long half-lives of the plutonium isotopes. Uranium-236 is another long-lived fallout isotope with significant potential for exploitation as a tracer of soil and sediment movement. Uranium is expected to be more mobile in soils than plutonium (or caesium), and hence the 236U/Pu ratio will vary with soil depth, and so could provide an independent measure of the amount of soil loss. In this paper we discuss accelerator based ultra-sensitive measurements of plutonium and 236U isotopes and their advantages over 137Cs as tracers of soil erosion and sediment movement.

Tims, S. G.; Fifield, L. K.

2012-10-01

328

Octupole focusing in transport and accelerator systems  

SciTech Connect

The radio-frequency quadrupole (RFQ) linac is capable of accelerating high-current, low-velocity ion beams. In accelerator systems comprising an RFQ and higher velocity accelerating structures, the current bottleneck still typically occurs within the RFQ. This limiting current is quite high in most cases, but linacs with even higher currents may be required in the future. We have begun a study of higher multipole systems to determine their capability or focusing and accelerating very high currents. We have chosen first to examine a radio-frequency octupole (RFQ) transport system, and have developed a smooth-approximation analytical description that includes the conditions for input radial matching of a zero space-charge beam. Further, we have constructed a multiparticle beam-dynamics simulation program that accepts the low-current matched beam and gradually increases the beam current as it is transported. This results in a matched high-current beam, and the procedure can be used to determine the saturation-current limit of a periodic octupole system. As expected, at high currents the beam develops a hollow radial distribution that reduces the space-charge defocusing; initial results show that high currents can be transported. For acceleration, we have formulated the design parameters for a section of RFQ linac, including the potential function, acceleration, and focusing efficiencies, and the geometry of the radially modulated pole tips.

Crandall, K.R.; Pabst, M.; Stokes, R.H.; Wangler, T.P.

1981-01-01

329

Octupole focusing in transport and acceleration systems  

SciTech Connect

The radio-frequency quadrupole (RFQ) linac is capable of accelerating high-current, low-velocity ion beams. In accelerator systems comprising an RFQ and higher velocity accelerating structures, the current bottleneck still typically occurs within the RFQ. This limiting current is quite high in most cases, but linacs with even higher currents may be required in the future. We have begun a study of higher multipole systems to determine their capability for focusing and accelerating very high currents. We have chosen first to examine a radio-frequency octupole (RFO) transport system, and have developed a smooth-approximation analytical description that includes the conditions for input radial matching of a zero space-charge beam. Further, we have constructed a multiparticle beam-dynamics simulation program that accepts the low-current matched beam and gradually increases the beam current as it is transported. This results in a matched high-current beam, and the procedure can be used to determine the saturation-current limit of a periodic octupole system. As expected, at high currents the beam develops a hollow radial distribution that reduces the space-charge defocusing; initial results show that high currents can be transported. For acceleration, we have formulated the design parameters for a section of RFO linac, including the potential function, acceleration, and focusing efficiencies, and the geometry of the radially modulated pole tips.

Crandall, K.R.; Pabst, M.; Stokes, R.H.; Wangler, T.P.

1981-01-01

330

Leaky Fermi accelerators  

E-print Network

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

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

2015-01-01

331

Leaky Fermi accelerators  

E-print Network

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

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

2015-04-03

332

THE DIELECTRIC WALL ACCELERATOR  

SciTech Connect

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.

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

2009-08-17

333

Two-color-laser-driven direct electron acceleration in infinite vacuum  

E-print Network

We propose a direct electron acceleration scheme that uses a two-color pulsed radially polarized laser beam. The two-color scheme achieves electron acceleration exceeding 90% of the theoretical energy gain limit, over twice ...

Wong, Liang Jie

334

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

SciTech Connect

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.

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

2012-06-01

335

Optically pulsed electron accelerator  

DOEpatents

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.

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

1985-05-20

336

Optically pulsed electron accelerator  

DOEpatents

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.

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

1987-01-01

337

Photonic Crystal Laser-Driven Accelerator Structures  

SciTech Connect

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.

Cowan, Benjamin M.

2007-08-22

338

Rf cavity primer for cyclic proton accelerators  

SciTech Connect

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.

Griffin, J.E.

1988-04-01

339

Android Acceleration Application  

NSDL National Science Digital Library

In the first of two sequential lessons, students create mobile apps that collect data from an Android device's accelerometer and then store that data to a database. This lesson provides practice with MIT's App Inventor software and culminates with students writing their own apps for measuring acceleration. In the second lesson, students are given an app for an Android device, which measures acceleration. They investigate acceleration by collecting acceleration vs. time data using the accelerometer of a sliding Android device. Then they use the data to create velocity vs. time graphs and approximate the maximum velocity of the device.

IMPART RET Program, College of Information Science & Technology,

340

Particle acceleration in flares  

NASA Technical Reports Server (NTRS)

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.

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

341

Accelerators and Nobel Laureates  

NSDL National Science Digital Library

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

Kullander, Sven

342

Charged particle accelerator grating  

DOEpatents

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.

Palmer, Robert B. (Shoreham, NY)

1986-01-01

343

Accelerator-based BNCT.  

PubMed

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

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

344

Accelerating Research with  

E-print Network

Accelerating Academic Research with Cloud Computing Published: September 2014 For the latest, maintained, and updated by expert staff. Worries about data loss from disasters (natural disasters, flooding

Bernstein, Phil

345

Radiation Safety Systems for Accelerator Facilities  

SciTech Connect

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

Liu, James C

2001-10-17

346

Radiation Safety Systems for Accelerator Facilities  

SciTech Connect

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

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

2001-10-01

347

Radiation safety systems for accelerator facilities.  

PubMed

The radiation safety system RSS) of an accelerator facility is used to protect people from prompt radiation hazards associated with accelerator operation. The RSS is a fully interlocked, engineered system with a combination of passive and active elements that are reliable, redundant and fail-safe. The RSS consists of the access control system (ACS) and the radiation containment system (RCS). The ACS is to keep people away from the dangerous radiation inside the shielding enclosure. The RCS limits and contains the beam/radiation conditions to protect people from the prompt radiation hazards outside the shielding enclosure in both normal and abnormal operations. The complexity of an RSS depends on the accelerator and its operation. as well as associated hazard conditions. The approaches of RSS among different facilities can be different. This report gives a review of the RSS for accelerator facilities. PMID:11843091

Liu, J C; Bull, J S; Drozdoff, J; May, R; Vylet, V

2001-01-01

348

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

SciTech Connect

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.

Siemann, R.H.; /SLAC

2011-10-24

349

Beam experiments on the Pulse Line Ion Accelerator  

NASA Astrophysics Data System (ADS)

Beam experiments on a new accelerator concept called the Pulse Line Ion Accelerator (PLIA) have demonstrated the ability to accelerate and compress ion bunches. Charging the PLIA to its full potential is limited by a vacuum surface flashover. Discharge issues have been evaluated for possible solutions. A numerical model has been developed to investigate the breakdown phenomena. Experimental results and possible solutions for the elimination of the discharge are described.

Coleman, J. E.; Friedman, A.; Waldron, W. L.; Bieniosek, F. M.; Briggs, R. J.; Grote, D. P.; Henestroza, E.; Roy, P. K.; Seidl, P. A.; Yu, S. S.

2007-07-01

350

Accelerated Hypertension after Venlafaxine Usage  

PubMed Central

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

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

2014-01-01

351

Microscale acceleration history discriminators  

DOEpatents

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.

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

2002-01-01

352

Accelerators Beyond The Tevatron?  

SciTech Connect

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?

Lach, Joseph; /Fermilab

2010-07-01

353

Ion Cyclotron Resonance Accelerator  

Microsoft Academic Search

The Ion Cyclotron Resonance Accelerator (ICRA) is based on the operating principles of cyclotrons and gyrotrons, and should provide beam suitable for the production of radioisotopes for positron emission tomography (PET) or neutrons at a fraction of the cost of present day cyclotrons and linacs. The concept extends cyclotron resonance acceleration to ions by using a superconducting solenoid and a

T. L. Grimm; C. T. Ramsell; R. C. York

1997-01-01

354

KEK digital accelerator  

NASA Astrophysics Data System (ADS)

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.

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

355

Exploring acceleration through vectors  

NSDL National Science Digital Library

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

356

NEW ACCELERATION METHODS  

Microsoft Academic Search

But a glance at the Livingston chart, Fig. 1, of accelerator particle energy as a function of time shows that the energy has steadily, exponentially, increased. Equally significant is the fact that this increase is the envelope of diverse technologies. If one is to stay on, or even near, the Livingston curve in future years then new acceleration techniques need

Sessler

1984-01-01

357

ACCELERATOR RESEARCH STUDIES  

SciTech Connect

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

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

2004-01-23

358

Acceleration in astrophysics  

Microsoft Academic Search

The origin of cosmic rays and applicable laboratory experiments are discussed. The principle problems of shock acceleration for the production of cosmic rays in the context of astrophysical conditions are found to be: (1) The presumed unique explanation of the power law spectrum is shown instead to be expected as a universal property of all accelerators with high loss; (2)

Stirling A Colgate

1994-01-01

359

HUMAN EXPOSURE OF METHYL TERTIARY BUTYL ETHER (MTBE)  

EPA Science Inventory

Data on ambient air quality and microenvironmental exposures (e.g., during refueling, inside cards, in personal garages) are too limited for a quantitative estimate of population exposures to MTBE. t best, they can be used to estimate broad ranges of potential exposures. ecause o...

360

Noise Exposure Estimates of Urban MP3 Player Users  

ERIC Educational Resources Information Center

Purpose: To examine the sound level and duration of use of personal listening devices (PLDs) by 189 college students, ages 18-53 years, as they entered a New York City college campus, to determine whether noise exposure from PLDs was in excess of recommended exposure limits and what factors might influence exposure. Method: Free-field equivalent…

Levey, Sandra; Levey, Tania; Fligor, Brian J.

2011-01-01

361

Prior Trauma Exposure for Youth in Treatment Foster Care  

ERIC Educational Resources Information Center

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

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

2012-01-01

362

Scaling FFAG accelerator for muon acceleration  

SciTech Connect

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.

Lagrange, JB.; Planche, T. [Graduate School of Engineering, Kyoto University Katsura, Nishikyo-ku Kyoto, 615-8530 (Japan); Mori, Y. [Kyoto University Research Reactor Institute, Department of Nuclear Science and Engineering, 2, Asashiro-Nishi, Kumatori-cho, Sennan-gun, Osaka, 590-0494 (Japan)

2011-10-06

363

Secular Acceleration of Barnard's Star  

NASA Astrophysics Data System (ADS)

Barnard's Star should have significant secular acceleration because it lies close to the Sun and has the highest known proper motion along with a large radial velocity. It will pass within about 1.4 pc in another 9,750 years. Secular changes in proper motion and radial velocity are essentially the Coriolis and centrifugal accelerations, respectively, arising from use of a rotating coordinate system defined by the Sun-star radius vector. Although stellar space velocities measured with respect to the Sun are essentially constant, these perspective effects arise with changing distance and viewing angle. Hipparcos-2 plus Nidever et al. (2002) predict a perspective change in the proper motion of 1.285±0.006 mas yr-2 for Barnard's Star. Recent analysis of 900+ photographic plates between 1968 and 1998 with the 26.25-in (0.67-m) McCormick refractor detected a secular acceleration of 1.25±0.04 mas yr-2, which agrees with the predicted value within the measurement errors. Earlier, Benedict et al. (1999) measured its secular acceleration to be 1.2±0.2 mas yr-2 using 3 years of HST FGS observations. Similarly, a perspective change in radial velocity of 4.50±0.01 m s-1 yr-1 can be predicted for Barnard's Star. Kürster et al. (2003) detected variations in their observations of it that are largely attributable to secular acceleration along the line of sight with some contribution from stellar activity. Although secular acceleration effects have been limited for past studies of stellar motions, they can be significant for observations extending over decades or for high-precision measurements required to detect extrasolar planets. Future studies will need to consider this factor for the nearest stars and for those with large proper motions or radial velocities. NSF grant AST 98-20711; Litton Marine Systems; Peninsula Community Foundation Levinson Fund; UVa Governor's Fellowship, Dean's F&A Fellowship, and Graduate School of Arts and Sciences; and, US Naval Observatory supported this research.

Bartlett, Jennifer L.; Ianna, P. A.

2009-01-01

364

An integrated job exposure matrix for electrical exposures of utility workers.  

PubMed

Electric utility workers may be exposed to any combination of magnetic fields, electric fields, nuisance shocks (from spark discharges and continuous currents), imperceptible contact currents, and electrical injuries. Collectively these exposures are referred to as EMF Factors. Previous occupational exposure assessments have mainly characterized the magnetic field, with less attention to the electric field. Nuisance shocks and electrical injuries, though palpable, have received little to no attention. This article presents a prototype job exposure matrix that addresses exposure to all EMF Factors taking into account job category, work environment, and occupied environment. Exposures for all factors were classified into three ordinal levels for 22 job categories. Electric and magnetic field exposures were classified by the geometric mean of daily average of personal exposure measurements. Although relatively sparse, survey data on nuisance shocks were adequate for exposure assignment by job category and indicate that the frequency of these exposures has diminished over time. The least information was available for imperceptible contact currents that are associated with electric field exposures and small contact voltages. Data for electrical injuries by job category were derived from the Electric Power Research Institute Occupational Health Surveillance Database, with exposure assignments based on combined injury rates for flash burn and electric shock/electrocution. The highest exposures for all EMF Factors are essentially limited to four job categories that work on or close to electrical equipment: (1) cable splicers, (2) electricians, (3) line workers, and (4) substation operators. PMID:19452311

Bracken, T Dan; Kavet, Robert; Patterson, Robert M; Fordyce, Tiffani A

2009-08-01

365

New-Style Acceleration Curve of Belt Conveyor  

Microsoft Academic Search

This paper emphasizes on the integrative analysis of existing acceleration curves and reveals their limitations when applied in engineering based on the example of belt conveyor used in East Laneway in Sihe Coal Mine, China. This paper puts forward a new-style acceleration curve which has been verified by experiments that it could decrease vibration enormously and it will produce great

Xiaohan Cheng; Xiao He; Xu Zhang; Guoying Meng

2010-01-01

366

Breaking down the Fermi acceleration with inelastic collisions  

E-print Network

The phenomenon of Fermi acceleration is addressed for a dissipative bouncing ball model with external stochastic perturbation. It is shown that the introduction of energy dissipation (inelastic collisions of the particle with the moving wall) is a sufficient condition to break down the process of Fermi acceleration. The phase transition from bounded to unbounded energy growth in the limit of vanishing dissipation is characterized.

Edson D. Leonel

2009-03-10

367

Neck Forces and Moments and Head Accelerations in Side Impact  

Microsoft Academic Search

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

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

2009-01-01

368

Unavailability of wind turbines due to wind-induced accelerations  

Microsoft Academic Search

The malfunctioning of acceleration-sensitive equipment in wind turbines has the potential to affect their annual failure rates during normal operating conditions. Current protective measures for wind turbines are triggered by wind speed. However, this option neglects the structural response of the wind turbines, and limits the possibility of effectively controlling accelerations at the top of the wind towers. In this

Leonardo Dueñas-Osorio; Biswajit Basu

2008-01-01

369

Genetic susceptibility to occupational exposures  

PubMed Central

Because of their high prevalence in the general population, genetic variants that determine susceptibility to environmental exposures may contribute greatly to the development of occupational diseases in the setting of specific exposures occurring in the workplace. Studies investigating genetic susceptibilities in the workplace may: (1) provide mechanistic insight into the aetiology of disease, in particular the determination of environmentally responsive genes; (2) identify susceptible subpopulations with respect to exposure; and (3) provide valuable input in setting occupational exposure limits by taking genetic susceptibility into account. Polymorphisms in the NAT2 and the HLA-DPB1Glu69 genes provide classic examples of how genetic susceptibility markers have a clear role in identifying disease risk in bladder cancer and chronic beryllium disease, respectively. For diseases with more complex and multifactorial aetiology such as occupational asthma and chronic airways disease, susceptibility studies for selected genetic polymorphisms provide additional insight into the biological mechanisms of disease. Even when polymorphisms for genetic susceptibility have a clear role in identifying disease risk, the value of wide scale genetic screening in occupational settings remains limited due to primarily ethical and social concerns. Thus, large scale genetic screening in the workplace is not currently recommended. PMID:18487431

Christiani, D C; Mehta, A J; Yu, C-L

2013-01-01

370

Genetic susceptibility to occupational exposures.  

PubMed

Because of their high prevalence in the general population, genetic variants that determine susceptibility to environmental exposures may contribute greatly to the development of occupational diseases in the setting of specific exposures occurring in the workplace. Studies investigating genetic susceptibilities in the workplace may: (1) provide mechanistic insight into the aetiology of disease, in particular the determination of environmentally responsive genes; (2) identify susceptible subpopulations with respect to exposure; and (3) provide valuable input in setting occupational exposure limits by taking genetic susceptibility into account. Polymorphisms in the NAT2 and the HLA-DPB1(G)(lu69) genes provide classic examples of how genetic susceptibility markers have a clear role in identifying disease risk in bladder cancer and chronic beryllium disease, respectively. For diseases with more complex and multifactorial aetiology such as occupational asthma and chronic airways disease, susceptibility studies for selected genetic polymorphisms provide additional insight into the biological mechanisms of disease. Even when polymorphisms for genetic susceptibility have a clear role in identifying disease risk, the value of wide scale genetic screening in occupational settings remains limited due to primarily ethical and social concerns. Thus, large scale genetic screening in the workplace is not currently recommended. PMID:18487431

Christiani, D C; Mehta, A J; Yu, C-L

2008-06-01

371

Spacecraft Water Exposure Guidelines (SWEGs)  

NASA Technical Reports Server (NTRS)

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

James, John T.

2008-01-01

372

SHOCK EMERGENCE IN SUPERNOVAE: LIMITING CASES AND ACCURATE APPROXIMATIONS  

SciTech Connect

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

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

2013-08-10

373

DEMONSTRATION OF HUMAN EXPOSURE TOOLS  

EPA Science Inventory

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

374

Use of dielectric material in muon accelerator RF cavities  

E-print Network

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

French, Katheryn Decker

2011-01-01

375

A New Accelerator Structure Concept: The Zipper Structure  

SciTech Connect

I introduce a novel normal-conducting accelerator structure combining standing wave and traveling wave characteristics, with relatively open cells. I describe the concept and geometry, optimize parameters, and discuss the advantages and limitations this new structure presents.

Nantista, C

2009-10-13

376

Large electrostatic accelerators  

SciTech Connect

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.

Jones, C.M.

1984-01-01

377

Space Acceleration Measurement Systems  

NASA Technical Reports Server (NTRS)

The Space Acceleration Measurement Systems (SAMS) Project develops and deploys the measurement systems for the Acceleration Measurement Program (AMP). At this time there are two types of measurement systems available, quasi-steady and vibratory. Orbital Acceleration Research Experiment (OARE) and Microgravity Acceleration Measurement System (MAMS) are the current quasi-steady systems available. OARE has flown numerous times supporting STS missions. MAMS has been delivered to Kennedy Space Center (KSC) for its deployment on the International Space Station (ISS). Vibratory measurements have been made and will be made by the Space Acceleration Measurement System (SAMS-I) Generation I, Space Acceleration Measurement System Generation II (SAMS-II), and Space Acceleration Measurement System Free Flyer or Generation III (SAMS-FF). SAMS-I supported 21 STS missions and has been retired. SAMS-II will be delivered to KSC to support ISS-6A launch (currently April 19, 2001). SAMS-FF has replaced SAMS-I in support of STS missions and has been deployed on sounding rockets, the KC-135 and ground facilities. SAMS-FF hardware shall be deployed on ISS in the future to provide a more compact solution.

Foster, William

2000-01-01

378

Induction of Selected Lipid Metabolic Enzymes and Differentiation-Linked Structural Proteins by Air Exposure in Fetal Rat Skin Explants  

Microsoft Academic Search

The epidermal permeability barrier of premature infants matures rapidly following birth. Previous studies suggest that air exposure could contribute to this acceleration, because: (i) development of a structurally and functionally mature barrier accelerates when fetal rat skin explants are incubated at an air–medium interface, and (ii) occlusion with a water-impermeable membrane prevents this acceleration. To investigate further the effects of

László G Kömüves; Karen Hanley; Yan Jiang; Chika Katagiri; Peter M. Elias; Mary L. Williams; Kenneth R. Feingold

1999-01-01

379

Diagnostics for advanced laser acceleration experiments  

SciTech Connect

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.

Misuri, Alessio

2002-06-01

380

Amps particle accelerator definition study  

NASA Technical Reports Server (NTRS)

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.

Sellen, J. M., Jr.

1975-01-01

381

Entropic Accelerating Universe  

E-print Network

To accommodate the observed accelerated expansion of the universe, one popular idea is to invoke a driving term in the Friedmann-Lemaitre equation of dark energy which must then comprise 70% of the present cosmological energy density. We propose an alternative interpretation which takes into account the entropy and temperature intrinsic to the horizon of the universe due to the information holographically stored there. Dark energy is thereby obviated and the acceleration is due to an entropic force naturally arising from the information storage on the horizon surface screen. We consider an additional quantitative approach inspired by surface terms in general relativity and show that this leads to the entropic accelerating universe.

Damien A. Easson; Paul H. Frampton; George F. Smoot

2010-10-24

382

Entropic accelerating universe  

NASA Astrophysics Data System (ADS)

To accommodate the observed accelerated expansion of the universe, one popular idea is to invoke a driving term in the Friedmann-Lemaître equation of dark energy which must then comprise 70% of the present cosmological energy density. We propose an alternative interpretation which takes into account the entropy and temperature intrinsic to the horizon of the universe due to the information holographically stored there. Dark energy is thereby obviated and the acceleration is due to an entropic force naturally arising from the information storage on the horizon surface screen. We consider an additional quantitative approach inspired by surface terms in general relativity and show that this leads to the entropic accelerating universe.

Easson, Damien A.; Frampton, Paul H.; Smoot, George F.

2011-01-01

383

Accelerator Production of Radionuclides  

NASA Astrophysics Data System (ADS)

While many radioactive isotopes in use today are found in nature, many more are artificially produced by irradiating target materials with nuclear particles. Two different technologies can provide the energetic particles needed: nuclear reactors, which produce a flux of neutrons, and particle accelerators, which produce a flux of charged particles. This chapter will deal with the important aspects of the production of radionuclides with accelerators, along with some details on their applications, commercially-available accelerator systems used for this purpose, and the size of the equipment business.

Schlyer, David J.; Ruth, Thomas J.

2012-06-01

384

The MESA accelerator  

SciTech Connect

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.

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

2013-11-07

385

Schooling Increases Risk Exposure for Fish Navigating Past Artificial Barriers  

PubMed Central

Artificial barriers have become ubiquitous features in freshwater ecosystems and they can significantly impact a region's biodiversity. Assessing the risk faced by fish forced to navigate their way around artificial barriers is largely based on assays of individual swimming behavior. However, social interactions can significantly influence fish movement patterns and alter their risk exposure. Using an experimental flume, we assessed the effects of social interactions on the amount of time required for juvenile palmetto bass (Morone chrysops × M. saxatilis) to navigate downstream past an artificial barrier. Fish were released either individually or in groups into the flume using flow conditions that approached the limit of their expected swimming stamina. We compared fish swimming behaviors under solitary and schooling conditions and measured risk as the time individuals spent exposed to the barrier. Solitary fish generally turned with the current and moved quickly downstream past the barrier, while fish in groups swam against the current and displayed a 23-fold increase in exposure time. Solitary individuals also showed greater signs of skittish behavior than those released in groups, which was reflected by larger changes in their accelerations and turning profiles. While groups displayed fission-fusion dynamics, inter-individual positions were highly structured and remained steady over time. These spatial patterns align with theoretical positions necessary to reduce swimming exertion through either wake capturing or velocity sheltering, but diverge from any potential gains from channeling effects between adjacent neighbors. We conclude that isolated performance trials and projections based on individual behaviors can lead to erroneous predictions of risk exposure along engineered structures. Our results also suggest that risk perception and behavior may be more important than a fish's swimming stamina in artificially modified systems. PMID:25268736

Lemasson, Bertrand H.; Haefner, James W.; Bowen, Mark D.

2014-01-01

386

Schooling increases risk exposure for fish navigating past artificial barriers.  

PubMed

Artificial barriers have become ubiquitous features in freshwater ecosystems and they can significantly impact a region's biodiversity. Assessing the risk faced by fish forced to navigate their way around artificial barriers is largely based on assays of individual swimming behavior. However, social interactions can significantly influence fish movement patterns and alter their risk exposure. Using an experimental flume, we assessed the effects of social interactions on the amount of time required for juvenile palmetto bass (Morone chrysops × M. saxatilis) to navigate downstream past an artificial barrier. Fish were released either individually or in groups into the flume using flow conditions that approached the limit of their expected swimming stamina. We compared fish swimming behaviors under solitary and schooling conditions and measured risk as the time individuals spent exposed to the barrier. Solitary fish generally turned with the current and moved quickly downstream past the barrier, while fish in groups swam against the current and displayed a 23-fold increase in exposure time. Solitary individuals also showed greater signs of skittish behavior than those released in groups, which was reflected by larger changes in their accelerations and turning profiles. While groups displayed fission-fusion dynamics, inter-individual positions were highly structured and remained steady over time. These spatial patterns align with theoretical positions necessary to reduce swimming exertion through either wake capturing or velocity sheltering, but diverge from any potential gains from channeling effects between adjacent neighbors. We conclude that isolated performance trials and projections based on individual behaviors can lead to erroneous predictions of risk exposure along engineered structures. Our results also suggest that risk perception and behavior may be more important than a fish's swimming stamina in artificially modified systems. PMID:25268736

Lemasson, Bertrand H; Haefner, James W; Bowen, Mark D

2014-01-01

387

Head and neck cancer due to heavy metal exposure via tobacco smoking and professional exposure: A review  

SciTech Connect

Chronic exposures to heavy metals via tobacco smoking and professional exposure may increase the risk of head and neck cancer, although the epidemiologic evidence is limited by problems of low study power and inadequate adjustment for tobacco and professional exposure use. Numerous scientific reviews have examined the association of various heavy metals exposure with respiratory cancer as well as other cancer types, but few have been published on head and neck cancer. The purpose of this paper, therefore, is to review the head and neck tract cancer-related data on exposure to heavy metals via smoking and working exposure and to study the major mechanisms underlying some toxic metals carcinogenesis.

Khlifi, Rim, E-mail: rimkhlifi@yahoo.fr; Hamza-Chaffai, Amel

2010-10-15

388

Acceleration Measurements Using Smartphone Sensors: Dealing with the Equivalence Principle  

E-print Network

Acceleration sensors built into smartphones, i-pads or tablets can conveniently be used in the Physics laboratory. By virtue of the equivalence principle, a sensor fixed in a non-inertial reference frame cannot discern between a gravitational field and an accelerated system. Accordingly, acceleration values read by these sensors must be corrected for the gravitational component. A physical pendulum was studied by way of example, and absolute acceleration and rotation angle values were derived from the measurements made by the accelerometer and gyroscope. Results were corroborated by comparison with those obtained by video analysis. The limitations of different smartphone sensors are discussed.

Monteiro, Martín; Martí, Arturo C

2014-01-01

389

LONGITUDINAL REFERENCE PARTICLE MOTION IN NEARLY ISOCHRONOUS FFAG RECIRCULATING ACCELERATORS.  

SciTech Connect

A Fixed Field Alternating Gradient (FFAG) arc can be used to reduce the cost of a recirculating accelerator. Path length variation with energy in such an arc can limit its usefulness, however, due to phase offset at the linac. This paper examines the dynamics of the reference particle in an FFAG recirculating accelerator, and describes the limitations on the design because of path length variation with energy.

BERG,J.S.

2001-07-01

390

Accelerated protocol for measurement of carbonation through a crack surface  

Microsoft Academic Search

This paper introduces a method for accelerating experiments to quantify gaseous carbonation of cementitious materials through a sheltered crack surface. To date the majority of measurements of carbonation have focused upon the determination of the carbonation reaction through an open material face with no restriction to gaseous exposure. Experiments to determine the extent of carbonation through a crack surface can

Laura Sullivan-Green; William Hime; Charles Dowding

2007-01-01

391

TRACKING OF ACCELERATION WITH HNJ METHOD.  

SciTech Connect

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.

RUGGIERO,A.G.

2007-11-05

392

Tracking of Acceleration with HNJ Method  

SciTech Connect

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.

Ruggiero,A.

2008-02-01

393

Stability of non-linear integrable accelerator  

SciTech Connect

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

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

2011-09-01

394

Results from non-accelerator experiments  

SciTech Connect

The diversity of non-accelerator experiments is at first look both dazzling and even daunting. However, nearly all of these experiments strive to attain the same goal, to search for new physics, beyond the current Standard Model. These measurements are also unified in the fact that their results are often dominated by systematic uncertainties. This review necessarily covers only a limited subset of non-accelerator experiments, and will concentrate on the experimental areas where there has been significant recent progress. The topics reviewed include neutrino mazes, double beta decay, solar neutrino, and long-baseline neutrino oscillation measurements.

Wilkerson, J.F.

1992-12-31

395

Results from non-accelerator experiments  

SciTech Connect

The diversity of non-accelerator experiments is at first look both dazzling and even daunting. However, nearly all of these experiments strive to attain the same goal, to search for new physics, beyond the current Standard Model. These measurements are also unified in the fact that their results are often dominated by systematic uncertainties. This review necessarily covers only a limited subset of non-accelerator experiments, and will concentrate on the experimental areas where there has been significant recent progress. The topics reviewed include neutrino mazes, double beta decay, solar neutrino, and long-baseline neutrino oscillation measurements.

Wilkerson, J.F.

1992-01-01

396

TESLA superconducting accelerating structures  

NASA Astrophysics Data System (ADS)

Superconducting standing wave structures have been used for charged particle acceleration for almost 40 years. A brief introduction to this application with examples, test procedures and recently achieved results are discussed in this paper.

Sekutowicz, J.

2007-08-01

397

Learning about Accelerated Learning.  

ERIC Educational Resources Information Center

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)

Caine, Geoffrey; Caine, Renate Nummela

1989-01-01

398

Accelerator on a Chip  

SciTech Connect

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)

England, Joel

2014-06-30

399

Accelerator on a Chip  

ScienceCinema

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)

England, Joel

2014-07-16

400

Non-accelerator experiments  

SciTech Connect

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.

Goldhaber, M.

1986-01-01

401

An active particle accelerator  

SciTech Connect

Although a static charge is difficult to maintain on macroscopic particles, it is straightforward to construct a small object with a regularly oscillating electric dipole moment. For objects of a given size, one may then construct an accelerator by appropriately matching the frequency and separations of an external array of electrodes to this size. Physically feasible size ranges, an accelerator design, and possible applications of such systems are discussed. 8 refs., 9 figs.

Goldman, T.

1991-01-01

402

Breakthrough: Fermilab Accelerator Technology  

SciTech Connect

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.

None

2012-04-23

403

Breakthrough: Fermilab Accelerator Technology  

ScienceCinema

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.

None

2014-08-12

404

Rolamite acceleration sensor  

DOEpatents

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.

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

1993-12-21

405

Uniformly accelerated black holes  

Microsoft Academic Search

The static and stationary C-metric are revisited in a generic framework and\\u000atheir interpretations studied in some detail. Specially those with two event\\u000ahorizons, one for the black hole and another for the acceleration. We found\\u000athat: i) The spacetime of an accelerated static black hole is plagued by either\\u000aconical singularities or lack of smoothness and compactness of the

Patricio S. Letelierand; Samuel R. Oliveira

2001-01-01

406

Rolamite acceleration sensor  

DOEpatents

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.

Abbin, Joseph P. (Albuquerque, NM); Briner, Clifton F. (Albuquerque, NM); Martin, Samuel B. (Albuquerque, NM)

1993-01-01

407

CEBAF accelerator achievements  

SciTech Connect

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.

Y.C. Chao, M. Drury, C. Hovater, A. Hutton, G.A. Krafft, M. Poelker, C. Reece, M. Tiefenback

2011-06-01

408

Laser electron accelerator  

Microsoft Academic Search

An intense electromagnetic pulse can create weak plasma oscillations through the action of the nonlinear ponderomotive force. Electrons trapped in the wake can be accelerated to high energy. Existing glass lasers of power density 10 to the 18th W\\/sq cm shone on plasmas of densities 10 to the 18th\\/cu cm can yield gigaelectronvolts of electron energy per centimeter of acceleration

T. Tajima; J. M. Dawson

1979-01-01

409

Physics of Laser-driven plasma-based acceleration  

SciTech Connect

The physics of plasma-based accelerators driven by short-pulse lasers is reviewed. This includes the laser wake-field accelerator, the plasma beat wave accelerator, the self-modulated laser wake-field accelerator, and plasma waves driven by multiple laser pulses. The properties of linear and nonlinear plasma waves are discussed, as well as electron acceleration in plasma waves. Methods for injecting and trapping plasma electrons in plasma waves are also discussed. Limits to the electron energy gain are summarized, including laser pulse direction, electron dephasing, laser pulse energy depletion, as well as beam loading limitations. The basic physics of laser pulse evolution in underdense plasmas is also reviewed. This includes the propagation, self-focusing, and guiding of laser pulses in uniform plasmas and plasmas with preformed density channels. Instabilities relevant to intense short-pulse laser-plasma interactions, such as Raman, self-modulation, and hose instabilities, are discussed. Recent experimental results are summarized.

Esarey, Eric; Schroeder, Carl B.

2003-06-30

410

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

PubMed

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

Suvorov, P M; Bykova, Iu I

1975-01-01

411

Biological Response to SPE Exposures  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

412

Accelerated cleanup risk reduction  

SciTech Connect

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 limit

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

1998-02-01

413

Direct laser acceleration of electrons in free-space  

E-print Network

Compact laser-driven accelerators are versatile and powerful tools of unarguable relevance on societal grounds for the diverse purposes of science, health, security, and technology because they bring enormous practicality to state-of-the-art achievements of conventional radio-frequency accelerators. Current benchmarking laser-based technologies rely on a medium to assist the light-matter interaction, which impose material limitations or strongly inhomogeneous fields. The advent of few cycle ultra-intense radially polarized lasers has materialized an extensively studied novel accelerator that adopts the simplest form of laser acceleration and is unique in requiring no medium to achieve strong longitudinal energy transfer directly from laser to particle. Here we present the first observation of direct longitudinal laser acceleration of non-relativistic electrons that undergo highly-directional multi-GeV/m accelerating gradients. This demonstration opens a new frontier for direct laser-driven particle accelerati...

Carbajo, Sergio; Wong, Liang Jie; Miller, R J Dwayne; Kärtner, Franz X

2015-01-01

414

A faster scaling in acceleration-sensitive atom interferometers  

E-print Network

Atom interferometers have been used to measure acceleration with at best a $T^2$ scaling in sensitivity as the interferometer time $T$ is increased. This limits the sensitivity to acceleration which is theoretically achievable by these configurations for a given frequency of acceleration. We predict and experimentally measure the acceleration-sensitive phase shift of a large-momentum-transfer atom interferometer based upon Bloch oscillations. Using this novel interferometric scheme we demonstrate an improved scaling of sensitivity which will scale as $T^3$. This enhanced scaling will allow an increase in achievable sensitivity for any given frequency of an oscillatory acceleration signal, which will be of particular use for inertial and navigational sensors, and proposed gravitational wave detectors. A straight forward extension should allow a $T^4$ scaling in acceleration sensitivity.

Gordon D. McDonald; Carlos C. N. Kuhn; Shayne Bennetts; John E. Debs; Kyle S. Hardman; John D. Close; Nicholas P. Robins

2014-03-17

415

A faster scaling in acceleration-sensitive atom interferometers  

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

416

LANSCE Beam Current Limiter (XL)  

SciTech Connect

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

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

1997-01-01

417

Exposure Analysis Modeling System  

EPA Science Inventory

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

418

EPIDEMIOLOGY AND EXPOSURE ASSESSMENT  

EPA Science Inventory

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

419

Particle exposures and infections  

EPA Science Inventory

Particle exposures increase the risk for human infections. Particles can deposit in the nose, pharynx, larynx, trachea, bronchi, and distal lung and, accordingly, the respiratory tract is the system most frequently infected after such exposure; however, meningitis also occurs. Ci...

420

Occupational Noise Exposure  

MedlinePLUS

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

421

CHAPTER ONE: EXPOSURE MEASUREMENTS.  

EPA Science Inventory

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

422

Exposure testing and evaluation of solar-utilization materials  

SciTech Connect

This report discusses studies of material degradation mechanisms and models, development of lifetime prediction models, correlation of outdoor accelerated exposure test results with those of conventional exposures, development of appropriate optical characterization tests and methods, establishment of reasonable criteria for acceptance or rejection of candidate materials, performance of bidirectional optical measurements and analyses of their significance, evaluations of certain individual materials and classes of materials, and general analyses of weather-induced trends in material properties.

Gilligan, J.E.

1980-04-01

423

Shielding at the egress of a 23 mV linear accelerator.  

PubMed Central

Radiation shielding is required in radiotherapy accelerators to limit the dose equivalent rate from x-rays produced at the target in all directions except that of the useful forward directed beam. Calculations were made in terms of weekly workload of 50,000 cGy delivered to the isocenter per 5-day week, treating 25 patients per day at 400 cGy per patient. It is desirable to reduce the total exposure at the maze door below 30 Rem (0.30 Sv)/wk assuming full-time occupancy. The maze was designed to reduce the neutron dose to an acceptable level by slowing the neutrons to thermal velocities and then absorbing them in a low Z material in the egress. PMID:8474134

Trappier, A. S.; Johnson, L. P.

1993-01-01

424

Exposure to Particulate Air Pollution and Cognitive Decline in Older Women  

PubMed Central

Background Chronic exposure to particulate air pollution may accelerate cognitive decline in older adults, although data on this association are limited. Our objective was to examine long-term exposure to particulate matter (PM) air pollution, both coarse ([PM 2.5–10 ?m in diameter [PM2.5-10]) and fine (PM <2.5 ?m in diameter [PM2.5]), in relation to cognitive decline. Methods The study population comprised the Nurses’ Health Study Cognitive Cohort, which included 19 409 US women aged 70 to 81 years. We used geographic information system–based spatiotemporal smoothing models to estimate recent (1 month) and long-term (7–14 years) exposures to PM2.5-10, and PM2.5 preceding base-line cognitive testing (1995–2001) of participants residing in the contiguous United States. We used generalized estimating equation regression to estimate differences in the rate of cognitive decline across levels of PM2.5-10 and PM2.5 exposures. The main outcome measure was cognition, via validated telephone assessments, administered 3 times at approximately 2-year intervals, including tests of general cognition, verbal memory, category fluency, working memory, and attention. Results Higher levels of long-term exposure to both PM2.5-10 and PM2.5 were associated with significantly faster cognitive decline. Two-year decline on a global score was 0.020 (95% CI, ?0.032 to ?0.008) standard units worse per 10 ?g/m3 increment in PM2.5-10 exposure and 0.018 (95% CI, ?0.035 to ?0.002) units worse per 10 ?g/m3 increment in PM2.5 exposure. These differences in cognitive trajectory were similar to those between women in our cohort who were approximately 2 years apart in age, indicating that the effect of a 10-?g/m3 increment in long-term PM exposure is cognitively equivalent to aging by approximately 2 years. Conclusion Long-term exposure to PM2.5-10 and PM2.5 at levels typically experienced by many individuals in the United States is associated with significantly worse cognitive decline in older women. PMID:22332151

Weuve, Jennifer; Puett, Robin C.; Schwartz, Joel; Yanosky, Jeff D.; Laden, Francine; Grodstein, Francine

2013-01-01

425

60 kW Electron Accelerator for a Paint-Curing Facility  

Microsoft Academic Search

Compared with radioactive isotopes, electron accelerators are very powerful sources of radiation. Due to the limited penetration depth of the electrons, these accelerators can only be applied for the radiation processing of surfaces or thin materials. Of special interest is the utilization of low-energy, high-power electron accelerators for the curing of paint coatings on wood, metal, and plastic surfaces. A

G. Reinhold; R. Gleyvod; E. Freiberg

1973-01-01

426

An Examination of the Impact of Accelerating Community College Students' Progression through Developmental Education  

ERIC Educational Resources Information Center

In an effort to improve developmental education students' outcomes, community colleges have been experimenting with acceleration strategies. Models of acceleration allow students to complete their developmental requirements in a shorter amount of time. However, there has been limited empirical research on the effects of accelerating

Hodara, Michelle; Jaggars, Shanna Smith

2014-01-01

427

HUMAN EXPOSURE ACTIVITY PATTERNS  

EPA Science Inventory

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

428

GUIDELINES FOR EXPOSURE ASSESSMENT  

EPA Science Inventory

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

429

DIETARY EXPOSURE MEASUREMENTS  

EPA Science Inventory

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

430

Opioid Antagonist Impedes Exposure.  

ERIC Educational Resources Information Center

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

Merluzzi, Thomas V.; And Others

1991-01-01

431

Optimal Velocity Profile Generation for Given Acceleration Limits: Theoretical Analysis  

E-print Network

]. The path in these references is designed using geometric principles, and an intuitively "optimal" velocity, and fn is the normal (centripetal) force such that the vehicle tracks the prescribed path. Consider now

Tsiotras, Panagiotis

432

TRAIL: a tokamak rail gun limiter  

SciTech Connect

An attractive new limiter concept is investigated. The TRAIL (Tokamak Rail Gun Limiter) system impacts a stream of moderate velocity pellets (100 to 200 m/sec through the plasma edge region to absorb energy and define the plasma boundary. The pellets are recycled, after cooling, to the injector in an E-M mass accelerator. Heat fluxes of approx. 30,000 W/cm/sup 2/ can be readily accommodated by the pellets, with very low recirculating power requirements (approx. 0.1%) for the accelerator. The mass accelerator velocity requirements are well within the present state-of-the-art (several km/sec). Accelerators injecting pellets at approx. 1 km/sec can be used to control local plasma temperature and current profiles and to act as energy absorbers to shut down the plasma without damage to the first wall if a plasma disruption occurs.

Yu, W.S.; Powell, J.R.; Usher, J.L.

1980-01-01

433

US LHC Accelerator Research Program  

E-print Network

US LHC Accelerator Research Program Instrumentation Collaboration Meeting John Marriner May 9, 2003 #12;2/14/03 US LARP Instrumentation Collaboration Mtg 2 US LARP LARP = LHC Accelerator Research Program LARP is an outgrowth of the US LHC Accelerator Project The US LHC Accelerator Project built

Large Hadron Collider Program

434

Plasma-based accelerator structures  

SciTech Connect

Plasma-based accelerators have the ability to sustain extremely large accelerating gradients, with possible high-energy physics applications. This dissertation further develops the theory of plasma-based accelerators by addressing three topics: the performance of a hollow plasma channel as an accelerating structure, the generation of ultrashort electron bunches, and the propagation of laser pulses is underdense plasmas.

Schroeder, Carl B.

1999-12-01

435

Accelerator-based Neutron Sources  

Microsoft Academic Search

Since the earliest experiments defining the properties of the neutron, accelerators have played an important role in providing neutrons for research and applications. For many years, neutrons produced at accelerator facilities have complemented capabilities available from reactor-based sources. Now, with the declining availability of reactor facilities, upgrades of existing accelerator facilities and proposed new, more powerful accelerator-based sources will be

James B. Ball

1997-01-01

436

Exposure to Nanoparticles and Hormesis  

PubMed Central

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

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

2010-01-01

437

Case of accelerated silicosis in a sandblaster  

PubMed Central

Sandblasting is traditionally known as a high-risk profession for potential development of lung silicosis. Reported is a case of a sandblaster with confirmed accelerated silicosis, a condition rather rarely diagnosed in the Czech Republic. Initially, the patient presented with progressive dry cough and exertional dyspnoea. In the early diagnostic process, a possible occupational aetiology was considered given his occupational history and known high-risk exposure to respirable silica particles confirmed by industrial hygiene assessment at the patient’s workplace. The condition was confirmed by clinical, histological and autopsy findings. The patient died during lung transplantation, less than five years from diagnosis. PMID:25567156

HUTYROVÁ, Beáta; SMOLKOVÁ, Petra; NAKLÁDALOVÁ, Marie; TICHÝ, Tomáš; KOLEK, Vít?zslav

2014-01-01