X-ray photoelectron spectroscopy and secondary electron yield analysis of Al and Cu samples exposed to an accelerator environment

NASA Astrophysics Data System (ADS)

Rosenberg, R. A.; McDowell, M. W.; Ma, Q.; Harkay, K. C.

2003-09-01

It is well known that exposure to an accelerator environment can cause ``conditioning'' of the vacuum chamber surfaces. In order to understand the manner in which the surface structure might influence the production of gases and electrons in the accelerator, such surfaces should be studied both before and after exposure to accelerator conditions. Numerous studies have been performed on representative materials prior to being inserted into an accelerator, but very little has been done on materials that have ``lived'' in the accelerator for extended periods. In the present work, we mounted Al and Cu coupons at different positions in a section of the Advanced Photon Source storage ring and removed them following exposures ranging from 6 to 18 months. X-ray photoelectron spectroscopy (XPS) of the surface was performed before and after exposure. Changes were observed that depended on the location and whether the coupon was facing the chamber interior or chamber wall. These results will be presented and compared to XPS and secondary electron yield data obtained from laboratory measurements meant to simulate the accelerator conditions.

Gel nanostructure in alkali-activated binders based on slag and fly ash, and effects of accelerated carbonation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bernal, Susan A., E-mail: s.bernal@sheffield.ac.uk; Department of Materials Science and Engineering, The University of Sheffield, Sheffield S1 3JD; Provis, John L., E-mail: j.provis@sheffield.ac.uk

2013-11-15

Binders formed through alkali-activation of slags and fly ashes, including ‘fly ash geopolymers’, provide appealing properties as binders for low-emissions concrete production. However, the changes in pH and pore solution chemistry induced during accelerated carbonation testing provide unrealistically low predictions of in-service carbonation resistance. The aluminosilicate gel remaining in an alkali-activated slag system after accelerated carbonation is highly polymerised, consistent with a decalcification mechanism, while fly ash-based binders mainly carbonate through precipitation of alkali salts (bicarbonates at elevated CO{sub 2} concentrations, or carbonates under natural exposure) from the pore solution, with little change in the binder gel identifiable by nuclearmore » magnetic resonance spectroscopy. In activated fly ash/slag blends, two distinct gels (C–A–S–H and N–A–S–H) are formed; under accelerated carbonation, the N–A–S–H gel behaves comparably to fly ash-based systems, while the C–A–S–H gel is decalcified similarly to alkali-activated slag. This provides new scope for durability optimisation, and for developing appropriate testing methodologies. -- Highlights: •C-A-S-H gel in alkali-activated slag decalcifies during accelerated carbonation. •Alkali-activated fly ash gel changes much less under CO{sub 2} exposure. •Blended slag-fly ash binder contains two coexisting gel types. •These two gels respond differently to carbonation. •Understanding of carbonation mechanisms is essential in developing test methods.« less

Effects of positive acceleration on the metabolism of endogenous carbon monoxide and serum lipid in atherosclerotic rabbits

PubMed Central

Luo, Huilan; Chen, Yongsheng; Wang, Junhua

2010-01-01

Background: Atherosclerosis (AS) is caused mainly due to the increase in the serum lipid, thrombosis, and injuries of the endothelial cells. During aviation, the incremental load of positive acceleration that leads to dramatic stress reactions and hemodynamic changes may predispose pilots to functional disorders and even pathological changes of organs. However, much less is known on the correlation between aviation and AS pathogenesis. Methods and Results: A total of 32 rabbits were randomly divided into 4 groups with 8 rabbits in each group. The control group was given a high cholesterol diet but no acceleration exposure, whereas the other 3 experimental groups were treated with a high cholesterol diet and acceleration exposure for 4, 8, and 12 weeks, respectively. In each group, samples of celiac vein blood and the aorta were collected after the last exposure for the measurement of endogenous CO and HO-1 activities, as well as the levels of total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C). As compared with the control group, the endocardial CO content and the HO-1 activity in aortic endothelial cells were significantly elevated at the 4th, 8th, and 12th weekend, respectively (P < 0.05 or <0.01). And these measures tended upward as the exposure time was prolonged. Levels of TC and LDL-C in the experimental groups were significantly higher than those in the control group, presenting an upward tendency. Levels of TG were found significantly increased in the 8-week-exposure group, but significantly declined in the 12-week-exposure group (still higher than those in the control group). Levels of the HDL-C were increased in the 4-week-exposure group, declined in the 8-week-exposure group, and once more increased in the 12-week-exposure group, without significant differences with the control group. Conclusions: Positive acceleration exposure may lead to a significant increase of endogenous CO content and HO-1 activity and a metabolic disorder of serum lipid in high-cholesterol diet–fed rabbits, which implicates that the acceleration exposure might accelerate the progression of AS. PMID:20877690

Assessment of human exposure doses received by activation of medical linear accelerator components

NASA Astrophysics Data System (ADS)

Lee, D.-Y.; Kim, J.-H.; Park, E.-T.

2017-08-01

This study analyzes the radiation exposure dose that an operator can receive from radioactive components during maintenance or repair of a linear accelerator. This study further aims to evaluate radiological safety. Simulations are performed on 10 MV and 15 MV photon beams, which are the most frequently used high-energy beams in clinics. The simulation analyzes components in order of activity and the human exposure dose based on the amount of neutrons received. As a result, the neutron dose, radiation dose, and human exposure dose are ranked in order of target, primary collimator, flattening filter, multi-leaf collimator, and secondary collimator, where the minimum dose is 9.34E-07 mSv/h and the maximum is 1.71E-02 mSv/h. When applying the general dose limit (radiation worker 20 mSv/year, pubic 1 mSv/year) in accordance with the Nuclear Safety Act, all components of a linear accelerator are evaluated as below the threshold value. Therefore, the results suggest that there is no serious safety issue for operators in maintaining and repairing a linear accelerator. Nevertheless, if an operator recognizes an exposure from the components of a linear accelerator during operation and considers the operating time and shielding against external exposure, exposure of the operator is expected to be minimized.

Laboratories | NREL

Science.gov Websites

| Z A Accelerated Exposure Testing Laboratory Advanced Optical Materials Laboratory Advanced Thermal Laboratory Structural Testing Laboratory Surface Analysis Laboratory Systems Performance Laboratory T Thermal Storage Materials Laboratory Thermal Storage Process and Components Laboratory Thin-Film Deposition

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

NASA Technical Reports Server (NTRS)

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

2012-01-01

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

ACCELERATED EXTRACTION OF ORGANIC POLLUTANTS USING MICROWAVE ENERGY

EPA Science Inventory

This study is part of an ongoing U.S. Environmental Protection Agency research program, carried out by the National Exposure Research Laboratory, Characterization Research Division-Las Vegas (formerly Environmental Monitoring Systems Laboratory-Las Vegas), addresses new sample pr...

Female puberty acceleration by male odour in mice: neural pathway and behavioural consequences.

PubMed

Jouhanneau, Mélanie; Szymanski, Laura A; Keller, Matthieu

2014-08-01

In female mice, exposure to male chemosignals results in early puberty onset characterized by advanced vaginal opening and higher uterine weight. Evidence suggests that the male chemosignals responsible for acceleration of female puberty are androgen-dependent, but not all of the compounds that contribute to puberty acceleration have been identified. The male chemosignals are primarily detected and processed by the vomeronasal system including the vomeronasal organ, the accessory olfactory bulb and the medial amygdala. By contrast, the mechanism by which this olfactory information is integrated in the hypothalamus is poorly understood. In this context, the recent identification of the neuropeptide kisspeptin as a gatekeeper of puberty onset may provide a good candidate neuropeptide system for the transmission of chemosensory information to the gonadotrope axis.

Diesel engine exhaust accelerates plaque formation in a mouse model of Alzheimer's disease.

PubMed

Hullmann, Maja; Albrecht, Catrin; van Berlo, Damiën; Gerlofs-Nijland, Miriam E; Wahle, Tina; Boots, Agnes W; Krutmann, Jean; Cassee, Flemming R; Bayer, Thomas A; Schins, Roel P F

2017-08-30

Increasing evidence from toxicological and epidemiological studies indicates that the central nervous system is an important target for ambient air pollutants. We have investigated whether long-term inhalation exposure to diesel engine exhaust (DEE), a dominant contributor to particulate air pollution in urban environments, can aggravate Alzheimer's Disease (AD)-like effects in female 5X Familial AD (5XFAD) mice and their wild-type female littermates. Following 3 and 13 weeks exposures to diluted DEE (0.95 mg/m 3 , 6 h/day, 5 days/week) or clean air (controls) behaviour tests were performed and amyloid-β (Aβ) plaque formation, pulmonary histopathology and systemic inflammation were evaluated. In a string suspension task, assessing for grip strength and motor coordination, 13 weeks exposed 5XFAD mice performed significantly less than the 5XFAD controls. Spatial working memory deficits, assessed by Y-maze and X-maze tasks, were not observed in association with the DEE exposures. Brains of the 3 weeks DEE-exposed 5XFAD mice showed significantly higher cortical Aβ plaque load and higher whole brain homogenate Aβ42 levels than the clean air-exposed 5XFAD littermate controls. After the 13 weeks exposures, with increasing age and progression of the AD-phenotype of the 5XFAD mice, DEE-related differences in amyloid pathology were no longer present. Immunohistochemical evaluation of lungs of the mice revealed no obvious genetic background-related differences in tissue structure, and the DEE exposure did not cause histopathological changes in the mice of both backgrounds. Luminex analysis of plasma cytokines demonstrated absence of sustained systemic inflammation upon DEE exposure. Inhalation exposure to DEE causes accelerated plaque formation and motor function impairment in 5XFAD transgenic mice. Our study provides further support that the brain is a relevant target for the effects of inhaled DEE and suggests that long-term exposure to this ubiquitous air pollution mixture may promote the development of Alzheimer's disease.

Vibrotactile perception and effects of short-term exposure to hand-arm vibration.

PubMed

Burström, Lage; Lundström, Ronnie; Hagberg, Mats; Nilsson, Tohr

2009-07-01

This study clarifies whether the established frequency weighting procedure for evaluating exposure to hand-transmitted vibration can effectively evaluate the temporary changes in vibrotactile perception thresholds due to pre-exposure to vibration. In addition, this study investigates the relationship between changes of the vibrotactile perception thresholds and the normalized energy-equivalent frequency-weighted acceleration. The fingers of 10 healthy subjects, five male and five female, were exposed to vibration under 16 conditions with a combination of different frequencies, intensities, and exposure times. The vibration frequencies were 31.5 and 125 Hz and exposure lasted between 2 and 16 min. According to International Organization for Standardization (ISO) 5349-1, the energy-equivalent frequency-weighted acceleration for the experimental time of 16 min is 2.5 or 5.0 m s(-2) root-mean-square, corresponding to a 8-h equivalent acceleration, A(8), of approximately 0.5 and 0.9 m s(-2), respectively. A measure of the vibrotactile perception thresholds was conducted before the different exposures to vibration. Immediately after the vibration exposure, the acute effect was measured continuously on the exposed index finger for the first 75 s, followed by 30 s of measures every minute for a maximum of 10 min. If the subject's thresholds had not recovered, the measures continued for a maximum of 30 min with measurements taken every 5 min. Pre-exposure to vibration significantly influenced vibrotactile thresholds. This study concludes that the influence on the thresholds depends on the frequency of the vibration stimuli. Increased equivalent frequency-weighted acceleration resulted in a significant change in threshold, but the thresholds were unaffected when changes in the vibration magnitude were expressed as the frequency-weighted acceleration or the unweighted acceleration. Moreover, the frequency of the pre-vibration exposure significantly influenced (up to 25 min after exposure) recovery time of the vibrotactile thresholds. This study shows that the frequency weighting procedure in ISO 5349-1 is unable to predict the produced acute changes in the vibrotactile perception. Moreover, the results imply that the calculation of the 'energy-equivalent' frequency-weighted acceleration does not reflect the acute changes of the vibration perception thresholds due to pre-exposure to vibration. Furthermore, when testing for the vibrotactile thresholds, exposure to vibration on the day of a test might influence the results. Until further knowledge is obtained, the previous practice of 3 h avoidance of vibration exposure before assessment is recommended.

A pixel detector system for laser-accelerated ion detection

NASA Astrophysics Data System (ADS)

Reinhardt, S.; Draxinger, W.; Schreiber, J.; Assmann, W.

2013-03-01

Laser ion acceleration is an unique acceleration process that creates ultra-short ion pulses of high intensity ( > 107 ions/cm2/ns), which makes online detection an ambitious task. Non-electronic detectors such as radio-chromic films (RCF), imaging plates (IP) or nuclear track detectors (e.g. CR39) are broadly used at present. Only offline information on ion pulse intensity and position are available by these detectors, as minutes to hours of processing time are required after their exposure. With increasing pulse repetition rate of the laser system, there is a growing need for detection of laser accelerated ions in real-time. Therefore, we have investigated a commercial pixel detector system for online detection of laser-accelerated proton pulses. The CMOS imager RadEye1 was chosen, which is based on a photodiode array, 512 × 1024 pixels with 48 μm pixel pitch, thus offering a large sensitive area of approximately 25 × 50 mm2. First detection tests were accomplished at the conventional electrostatic 14 MV Tandem accelerator in Munich as well as Atlas laser accelerator. Detector response measurements at the conventional accelerator have been accomplished in a proton beam in dc (15 MeV) and pulsed (20 MeV) irradiation mode, the latter providing comparable particle flux as under laser acceleration conditions. Radiation hardness of the device was studied using protons (20 MeV) and C-ions (77 MeV), additionally. The detector system shows a linear response up to a maximum pulse flux of about 107 protons/cm2/ns. Single particle detection is possible in a low flux beam (104 protons/cm2/s) for all investigated energies. The radiation hardness has shown to give reasonable lifetime for an application at the laser accelerator. The results from the irradiation at a conventional accelerator are confirmed by a cross-calibration with CR39 in a laser-accelerated proton beam at the MPQ Atlas Laser in Garching, showing no problems of detector operation in presence of electro-magnetic pulse (EMP). The calibrated detector system was finally used for online detection of laser-accelerated proton and carbon ions at the Astra-Gemini laser.

Ultra-accelerated natural sunlight exposure testing

DOEpatents

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

2000-06-13

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

Ultra-accelerated natural sunlight exposure testing facilities

DOEpatents

Lewandowski, Allan A.; Jorgensen, Gary J.

2003-08-12

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

Dose-response patterns for vibration-induced white finger

PubMed Central

Griffin, M; Bovenzi, M; Nelson, C

2003-01-01

Aims: To investigate alternative relations between cumulative exposures to hand-transmitted vibration (taking account of vibration magnitude, lifetime exposure duration, and frequency of vibration) and the development of white finger (Raynaud's phenomenon). Methods: Three previous studies have been combined to provide a group of 1557 users of powered vibratory tools in seven occupational subgroups: stone grinders, stone carvers, quarry drillers, dockyard caulkers, dockyard boilermakers, dockyard painters, and forest workers. The estimated total operating duration in hours was thus obtained for each subject, for each tool, and for all tools combined. From the vibration magnitudes and exposure durations, seven alternative measurements of cumulative exposure were calculated for each subject, using expressions of the form: dose = ∑amiti, where ai is the acceleration magnitude on tool i, ti is the lifetime exposure duration for tool i, and m = 0, 1, 2, or 4. Results: For all seven alternative dose measures, an increase in dose was associated with a significant increase in the occurrence of vibration-induced white finger, after adjustment for age and smoking. However, dose measures with high powers of acceleration (m > 1) faired less well than measures in which the weighted or unweighted acceleration, and lifetime exposure duration, were given equal weight (m = 1). Dose determined solely by the lifetime exposure duration (without consideration of the vibration magnitude) gave better predictions than measures with m greater than unity. All measures of dose calculated from the unweighted acceleration gave better predictions than the equivalent dose measures using acceleration frequency-weighted according to current standards. Conclusions: Since the total duration of exposure does not discriminate between exposures accumulated over the day and those accumulated over years, a linear relation between vibration magnitude and exposure duration seems appropriate for predicting the occurrence of vibration-induced white finger. Poorer predictions were obtained when the currently recommended frequency weighting was employed than when accelerations at all frequencies were given equal weight. Findings suggest that improvements are possible to both the frequency weighting and the time dependency used to predict the development of vibration-induced white finger in current standards. PMID:12499452

Starvation and imidacloprid exposure influence immune response by Anoplophora glabripennis (Coleoptera: Cerambycidae) to a fungal pathogen

USDA-ARS?s Scientific Manuscript database

In several insect systems, fungal entomopathogens synergize with neonicotinoid insecticides which results in accelerated host death. Using the Asian longhorned beetle, Anoplophora glabripennis (Motschulsky), an invasive woodborer inadvertently introduced into North America and Europe, we investigate...

Radiation exposure and performance of multiple burn LEO-GEO orbit transfer trajectories

NASA Technical Reports Server (NTRS)

Gorland, S. H.

1985-01-01

Many potential strategies exist for the transfer of spacecraft from low Earth orbit (LEO) to geosynchronous (GEO) orbit. One strategy has generally been utilized, that being a single impulsive burn at perigee and a GEO insertion burn at apogee. Multiple burn strategies were discussed for orbit transfer vehicles (OTVs) but the transfer times and radiation exposure, particularly for potentially manned missions, were used as arguments against those options. Quantitative results concerning the trip time and radiation encountered by multiple burn orbit transfer missions in order to establish the feasibility of manned missions, the vulnerability of electronics, and the shielding requirements are presented. The performance of these multiple burn missions is quantified in terms of the payload and propellant variances from the minimum energy mission transfer. The missions analyzed varied from one to eight perigee burns and ranged from a high thrust, 1 g acceleration, cryogenic hydrogen-oxygen chemical prpulsion system to a continuous burn, 0.001 g acceleration, hydrogen fueled resistojet propulsion system with a trip time of 60 days.

Radiation Safety System for SPIDER Neutral Beam Accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sandri, S.; Poggi, C.; Coniglio, A.

2011-12-13

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

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

PubMed

Howard, Bryan; Sesek, Richard; Bloswick, Don

2009-01-01

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

Ultra-Accelerated Natural Sunlight Exposure Testing Facilities

DOEpatents

Lewandowski, Allan A.; Jorgensen, Gary J.

2004-11-23

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

Intelligent transportation systems assessment of ITS deployment : review of metropolitan areas : dscussions of crosscutting issues

DOT National Transportation Integrated Search

2000-08-01

The study on which this report is based sought to compile data on both accelerated and natural exposure of coating and corrosion test panels and then to relate their deterioration to environmental conditions. The report presents data gathered over a ...

Thermoregulation in rats: Effects of varying duration of hypergravic fields

NASA Technical Reports Server (NTRS)

Horowitz, J. M.; Horwitz, B. A.

1980-01-01

The effects of hypergravitational fields on the thermoregulatory system of the rat are examined. The question underlying the investigation was whether the response of the rat to the one hour cold exposure depends only upon the amplitude of the hypergravic field during the period of cold exposure or whether the response is also dependent on the amplitude and duration of the hypergravic field prior to cold exposure. One hour of cold exposure applied over the last hour of either a 1, 4, 7, 13, 19, 25, or 37 hr period of 3G evoked a decrease in core temperature (T sub c) of about 3 C. However, when rats were subjected concurrently to cold and acceleration following 8 days at 3G, they exhibited a smaller fall in T sub c, suggesting partial recovery of the acceleration induced impairment of temperature regulation. In another series of experiments, the gravitational field profile was changed in amplitude in 3 different ways. Despite the different gravitational field profiles used prior to cold, the magnitude of the fall in T sub c over the 1 hr period of cold exposure was the same in all cases. These results suggest that the thermoregulatory impairment has a rapid onset, is a manifestation of an ongoing effect of hypergravity, and is not dependent upon the prior G profile.

The effect of sunshine testing on terrestrial solar cell system components

NASA Technical Reports Server (NTRS)

Forestieri, A. F.; Anagnostou, E.

1975-01-01

Samples of FEP encapsulated silicon solar cells and various potential encapsulation or cover materials were subjected to accelerated and real time testing. By measuring changes in solar cell output or optical transmission as a function of exposure the durability of the samples was evaluated. Results are presented.

Evaluation of surface modification methods to mitigate rusting and pitting in weathering steel bridges : final report.

DOT National Transportation Integrated Search

1986-09-01

Accelerated laboratory atmospheric exposure simulation tests with an acceleration factor of 50 and extending for a maximum of 2200 wet-dry cycles (6-year exposure equivalent) gave corrosion loss data that agreed fairly well with the field data derive...

Head impact exposure measured in a single youth football team during practice drills.

PubMed

Kelley, Mireille E; Kane, Joeline M; Espeland, Mark A; Miller, Logan E; Powers, Alexander K; Stitzel, Joel D; Urban, Jillian E

2017-11-01

OBJECTIVE This study evaluated the frequency, magnitude, and location of head impacts in practice drills within a youth football team to determine how head impact exposure varies among different types of drills. METHODS On-field head impact data were collected from athletes participating in a youth football team for a single season. Each athlete wore a helmet instrumented with a Head Impact Telemetry (HIT) System head acceleration measurement device during all preseason, regular season, and playoff practices. Video was recorded for all practices, and video analysis was performed to verify head impacts and assign each head impact to a specific drill. Eleven drills were identified: dummy/sled tackling, install, special teams, Oklahoma, one-on-one, open-field tackling, passing, position skill work, multiplayer tackle, scrimmage, and tackling drill stations. Generalized linear models were fitted to log-transformed data, and Wald tests were used to assess differences in head accelerations and impact rates. RESULTS A total of 2125 impacts were measured during 30 contact practices in 9 athletes (mean age 11.1 ± 0.6 years, mean mass 44.9 ± 4.1 kg). Open-field tackling had the highest median and 95th percentile linear accelerations (24.7 g and 97.8 g, respectively) and resulted in significantly higher mean head accelerations than several other drills. The multiplayer tackle drill resulted in the highest head impact frequency, with an average of 0.59 impacts per minute per athlete, but the lowest 95th percentile linear accelerations of all drills. The front of the head was the most common impact location for all drills except dummy/sled tackling. CONCLUSIONS Head impact exposure varies significantly in youth football practice drills, with several drills exposing athletes to high-magnitude and/or high-frequency head impacts. These data suggest that further study of practice drills is an important step in developing evidence-based recommendations for modifying or eliminating certain high-intensity drills to reduce head impact exposure and injury risk for all levels of play.

Evaluation of radioactivity in the bodies of mice induced by neutron exposure from an epi-thermal neutron source of an accelerator-based boron neutron capture therapy system

PubMed Central

NAKAMURA, Satoshi; IMAMICHI, Shoji; MASUMOTO, Kazuyoshi; ITO, Masashi; WAKITA, Akihisa; OKAMOTO, Hiroyuki; NISHIOKA, Shie; IIJIMA, Kotaro; KOBAYASHI, Kazuma; ABE, Yoshihisa; IGAKI, Hiroshi; KURITA, Kazuyoshi; NISHIO, Teiji; MASUTANI, Mitsuko; ITAMI, Jun

2017-01-01

This study aimed to evaluate the residual radioactivity in mice induced by neutron irradiation with an accelerator-based boron neutron capture therapy (BNCT) system using a solid Li target. The radionuclides and their activities were evaluated using a high-purity germanium (HP-Ge) detector. The saturated radioactivity of the irradiated mouse was estimated to assess the radiation protection needs for using the accelerator-based BNCT system. 24Na, 38Cl, 80mBr, 82Br, 56Mn, and 42K were identified, and their saturated radioactivities were (1.4 ± 0.1) × 102, (2.2 ± 0.1) × 101, (3.4 ± 0.4) × 102, 2.8 ± 0.1, 8.0 ± 0.1, and (3.8 ± 0.1) × 101 Bq/g/mA, respectively. The 24Na activation rate at a given neutron fluence was found to be consistent with the value reported from nuclear-reactor-based BNCT experiments. The induced activity of each nuclide can be estimated by entering the saturated activity of each nuclide, sample mass, irradiation time, and proton current into the derived activation equation in our accelerator-based BNCT system. PMID:29225308

Evaluation of radioactivity in the bodies of mice induced by neutron exposure from an epi-thermal neutron source of an accelerator-based boron neutron capture therapy system.

PubMed

Nakamura, Satoshi; Imamichi, Shoji; Masumoto, Kazuyoshi; Ito, Masashi; Wakita, Akihisa; Okamoto, Hiroyuki; Nishioka, Shie; Iijima, Kotaro; Kobayashi, Kazuma; Abe, Yoshihisa; Igaki, Hiroshi; Kurita, Kazuyoshi; Nishio, Teiji; Masutani, Mitsuko; Itami, Jun

2017-01-01

This study aimed to evaluate the residual radioactivity in mice induced by neutron irradiation with an accelerator-based boron neutron capture therapy (BNCT) system using a solid Li target. The radionuclides and their activities were evaluated using a high-purity germanium (HP-Ge) detector. The saturated radioactivity of the irradiated mouse was estimated to assess the radiation protection needs for using the accelerator-based BNCT system. 24 Na, 38 Cl, 80m Br, 82 Br, 56 Mn, and 42 K were identified, and their saturated radioactivities were (1.4 ± 0.1) × 10 2 , (2.2 ± 0.1) × 10 1 , (3.4 ± 0.4) × 10 2 , 2.8 ± 0.1, 8.0 ± 0.1, and (3.8 ± 0.1) × 10 1 Bq/g/mA, respectively. The 24 Na activation rate at a given neutron fluence was found to be consistent with the value reported from nuclear-reactor-based BNCT experiments. The induced activity of each nuclide can be estimated by entering the saturated activity of each nuclide, sample mass, irradiation time, and proton current into the derived activation equation in our accelerator-based BNCT system.

Low Earth orbital atomic oxygen environmental simulation facility for space materials evaluation

NASA Technical Reports Server (NTRS)

Stidham, Curtis R.; Banks, Bruce A.; Stueber, Thomas J.; Dever, Joyce A.; Rutledge, Sharon K.; Bruckner, Eric J.

1993-01-01

Simulation of low Earth orbit atomic oxygen for accelerated exposure in ground-based facilities is necessary for the durability evaluation of space power system component materials for Space Station Freedom (SSF) and future missions. A facility developed at the National Aeronautics and Space Administrations's (NASA) Lewis Research Center provides accelerated rates of exposure to a directed or scattered oxygen beam, vacuum ultraviolet (VUV) radiation, and offers in-situ optical characterization. The facility utilizes an electron-cyclotron resonance (ECR) plasma source to generate a low energy oxygen beam. Total hemispherical spectral reflectance of samples can be measured in situ over the wavelength range of 250 to 2500 nm. Deuterium lamps provide VUV radiation intensity levels in the 115 to 200 nm range of three to five equivalent suns. Retarding potential analyses show distributed ion energies below 30 electron volts (eV) for the operating conditions most suited for high flux, low energy testing. Peak ion energies are below the sputter threshold energy (approximately 30 eV) of the protective coatings on polymers that are evaluated in the facility, thus allowing long duration exposure without sputter erosion. Neutral species are expected to be at thermal energies of approximately .04 eV to .1 eV. The maximum effective flux level based on polyimide Kapton mass loss is 4.4 x 10 exp 6 atoms/((sq. cm)*s), thus providing a highly accelerated testing capability.

Acute effects of vibration from a chipping hammer and a grinder on the hand-arm system.

PubMed Central

Kihlberg, S; Attebrant, M; Gemne, G; Kjellberg, A

1995-01-01

OBJECTIVES--The purpose of this study was to compare various effects on the hand-arm system of vibration exposure from a chipping hammer and a grinder with the same frequency weighted acceleration. Grip and push forces were measured and monitored during the exposure. The various effects were: muscle activity (measured with surface electrodes), discomfort ratings for different parts of the hand-arm system (made during and after exposure), and vibration perception threshold (for 10 minutes before and 10 minutes after the exposure). RESULTS--No increase in muscle activity due to exposure to vibration was found in the hand muscle studied. In the forearm, conversely, there was an increase in both muscle studied. For the upper arm the muscle activity only increased when exposed to impact vibration. Subjective ratings in the hand and shift in vibration perception threshold were effected more by the grinder than the hammer exposure. CONCLUSION--These results show that the reaction of the hand-arm system to vibration varies with frequency quantitatively as well as qualitatively. They do not support the notion that one single frequency weighted curve would be valid for the different health effects of hand-arm vibration (vascular, musculoskeletal, neurological, and psychophysiological). PMID:8535492

Working group written presentation: Solar radiation

NASA Technical Reports Server (NTRS)

Slemp, Wayne S.

1989-01-01

The members of the Solar Radiation Working Group arrived at two major solar radiation technology needs: (1) generation of a long term flight data base; and (2) development of a standardized UV testing methodology. The flight data base should include 1 to 5 year exposure of optical filters, windows, thermal control coatings, hardened coatings, polymeric films, and structural composites. The UV flux and wavelength distribution, as well as particulate radiation flux and energy, should be measured during this flight exposure. A standard testing methodology is needed to establish techniques for highly accelerated UV exposure which will correlate well with flight test data. Currently, UV can only be accelerated to about 3 solar constants and can correlate well with flight exposure data. With space missions to 30 years, acceleration rates of 30 to 100X are needed for efficient laboratory testing.

Accelerated testing of an optimized closing system for automotive fuel tank

NASA Astrophysics Data System (ADS)

Gligor, A.; Ilie, S.; Nicolae, V.; Mitran, G.

2015-11-01

Taking into account the legal prescriptions which are in force and the new regulatory requirements that will be mandatory to implement in the near future regarding testing characteristics of automotive fuel tanks, resulted the necessity to develop a new testing methodology which allows to estimate the behaviour of the closing system of automotive fuel tank over a long period of time (10-15 years). Thus, were designed and conducted accelerated tests under extreme assembling and testing conditions (high values for initial tightening torques, extreme values of temperature and pressure). In this paper are presented two of durability tests which were performed on an optimized closing system of fuel tank: (i) the test of exposure to temperature with cyclical variation and (ii) the test of continuous exposure to elevated temperature. In these experimental tests have been used main components of the closing system manufactured of two materials variants, both based on the polyoxymethylene, material that provides higher mechanical stiffness and strength in a wide temperature range, as well as showing increased resistance to the action of chemical agents and fuels. The tested sample included a total of 16 optimized locking systems, 8 of each of 2 versions of material. Over deploying the experiments were determined various parameters such as: the initial tightening torque, the tightening torque at different time points during measurements, the residual tightening torque, defects occurred in the system components (fissures, cracks, ruptures), the sealing conditions of system at the beginning and at the end of test. Based on obtained data were plotted the time evolution diagrams of considered parameter (the residual tightening torque of the system consisting of locking nut and threaded ring), in different temperature conditions, becoming possible to make pertinent assessments on the choice between the two types of materials. By conducting these tests and interpreting the obtained results, it can be created a clear picture of the capacity of closing system of fuel tank to fulfil the functional requirements following the exposure to values of testing parameters significantly above the values that may appear throughout the entire service life of the vehicle. The proposed accelerated testing method shows the main advantage of simulation in a limited time all the situations which may be encountered in a much longer period of time, namely the service life of the vehicle.

Metal-accelerated oxidation in plant cell death

DOE Office of Scientific and Technical Information (OSTI.GOV)

Czuba, M.

1993-05-01

Cadmium and mercury toxicity is further enhanced by external oxidizing conditions O[sub 3] or inherent plant processes. Lepidium sativum L, Lycopersicon esculentum Mill., or Phaseolus vulgaris L, were grown inpeat-lite to maturity under continuous cadmium exposure followed by one oxidant (O[sub 3]-6 hr. 30 pphm) exposure, with or without foliar calcium pretreatments. In comparison, Daucus carota, L and other species grown in a 71-V suspension, with or without 2,4-D were exposed continuously to low levels of methylmercury during exponential growth and analyzed in aggregates of distinct populations. Proteins were extracted and analyzed. Mechanisms of toxicity and eventual cell death aremore » Ca-mediated and involve chloroplast, stomatal-water relations and changes in oxidant-anti-oxidant components in cells. Whether the metal-accelerated oxidative damage proceeds to cell death, depends on the species and its differential biotransformation system and cell association component.« less

The developing immune system - from foetus to toddler.

PubMed

Ygberg, Sofia; Nilsson, Anna

2012-02-01

During foetal development, neonatal period and childhood, the immune system is constantly maturing. In the foetus, infection responsiveness is low and associates with spontaneous abortion. During the neonatal period, the infection response shifts towards a more pro-inflammatory response. The immune system of the newborn acquires adaptive features as a result of exposure to microbes. The development of the human immune system is a continuous process where both accelerated and retarded development is deleterious. © 2011 The Author(s)/Acta Paediatrica © 2011 Foundation Acta Paediatrica.

Issues on human acceleration tolerance after long-duration space flights

NASA Technical Reports Server (NTRS)

Kumar, K. Vasantha; Norfleet, William T.

1992-01-01

This report reviewed the literature on human tolerance to acceleration at 1 G and changes in tolerance after exposure to hypogravic fields. It was found that human tolerance decreased after exposure to hypokinetic and hypogravic fields, but the magnitude of such reduction ranged from 0 to 30 percent for plateau G forces and 30 to 70 percent for time tolerance on sustained G forces. A logistic regression model of the probability of individuals with 25 percent reduction in +Gz tolerance after 1 to 41 days of hypogravic exposures was constructed. The estimated values from the model showed a good correlation with the observed data. A brief review of the need for in-flight centrifuge during long-duration missions was also presented. Review of the available data showed that the use of countermeasures (such as anti-G suits, periodic acceleration, and exercise) reduced the decrement in acceleration tolerance after long-duration space flights. Areas of further research include quantification of the effect of countermeasures on tolerance, and methods to augment tolerance during and after exposures to hypogravic fields. Such data are essential for planning long-duration human missions.

The cardiovascular response to the AGS

NASA Technical Reports Server (NTRS)

Cardus, David; Mctaggart, Wesley G.

1993-01-01

This paper reports the preliminary results of experiments on human subjects conducted to study the cardiovascular response to various g-levels and exposure times using an artificial gravity simulator (AGS). The AGS is a short arm centrifuge consisting of a turntable, a traction system, a platform and four beds. Data collection hardware is part of the communication system. The AGS provides a steep acceleration gradient in subjects in the supine position.

Environmental Exposure and Accelerated Testing of Rubber-to-Metal Vulcanized Bonded Assemblies

DTIC Science & Technology

1974-11-01

by weapon components in the field and to determine the effect of this exposure on the vulcanized bond The purpose is also to duplicate these long term...storage and environmental exposure, and to develop accelerated methods for use in predicting this resistance. BACKGROUND: The most effective method of... the rubber coatings on the M60 machine gun components, the shock isolator and recoil adapter on the CAU 28/A Minigun, rubber pads for all tracked

Resist characteristics with direct-write electron beam and SCALPEL exposure system

NASA Astrophysics Data System (ADS)

Sato, Mitsuru; Omori, Katsumi; Ishikawa, Kiyoshi; Nakayama, Toshimasa; Novembre, Anthony E.; Ocola, Leonidas E.

1999-06-01

High acceleration voltage electron beam exposure is one of the possible candidates for post-optical lithography. The use of electrons, instead of photons, avoids optical related problems such as the standing wave issues. However, resists must conform to certain needs for the SCALPEL system, such as exposure in a vacuum chamber with 100kv electron beams. Taking into account the challenging requirements of high resolution, high sensitivity, low bake dependency and no outgassing, TOK has been able to develop resists to meet most of the SCALPEL system needs. However, due to the nature of chemical amplification and the PEB dependency, as is the case with DUV resist which varies for different features, we must recommend different resist for multiple features such as dense lines, isolated lines and contact holes. TOK has designed an electron beam negative resist, EN-009, which demonstrate 100nm pattern resolution. The dose to print on the SCALPEL system is 5.0(mu) C/cm2. The electron beam positive resist, EP-004M, has been designed for line and space patterns. The dose to print on the SCALPEL system is 8.25(mu) C/cm2. The processing conditions are standard, using 0.26N developer. These are the lowest exposure energies reported to date for similar resolution on this exposure tools.

Hormonal indices of tolerance to +Gz acceleration in female subjects. [personnel selection in Shuttle program

NASA Technical Reports Server (NTRS)

Vernikos-Danellis, J.; Dallman, M. F.; Forsham, P.; Goodwin, A. L.; Leach, C. S.

1978-01-01

As a possible predictive test for screening Space Shuttle passengers, the secretions of the pituitary adrenal system and the adrenal medulla have been studied in conjunction with exposure to gravitational acceleration three times the normal level. The 12 female subjects in the test were divided into ambulatory and bedrest groups. Before bedrest, a high tolerance to centrifugation appeared to be linked to increases in plasma ACTH and cortisol. This relationship did not hold after bedrest. The correlation between tolerance to centrifugation and 24-hour urinary epinephrine-to-norepinephrine ratios was not significant.

Zinc oxide nanoparticles induce migration and adhesion of monocytes to endothelial cells and accelerate foam cell formation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suzuki, Yuka; Tada-Oikawa, Saeko; Ichihara, Gaku

Metal oxide nanoparticles are widely used in industry, cosmetics, and biomedicine. However, the effects of exposure to these nanoparticles on the cardiovascular system remain unknown. The present study investigated the effects of nanosized TiO{sub 2} and ZnO particles on the migration and adhesion of monocytes, which are essential processes in atherosclerogenesis, using an in vitro set-up of human umbilical vein endothelial cells (HUVECs) and human monocytic leukemia cells (THP-1). We also examined the effects of exposure to nanosized metal oxide particles on macrophage cholesterol uptake and foam cell formation. The 16-hour exposure to ZnO particles increased the level of monocytemore » chemotactic protein-1 (MCP-1) and induced the migration of THP-1 monocyte mediated by increased MCP-1. Exposure to ZnO particles also induced adhesion of THP-1 cells to HUVECs. Moreover, exposure to ZnO particles, but not TiO{sub 2} particles, upregulated the expression of membrane scavenger receptors of modified LDL and increased cholesterol uptake in THP-1 monocytes/macrophages. In the present study, we found that exposure to ZnO particles increased macrophage cholesterol uptake, which was mediated by an upregulation of membrane scavenger receptors of modified LDL. These results suggest that nanosized ZnO particles could potentially enhance atherosclerogenesis and accelerate foam cell formation. - Highlights: • Effects of metal oxide nanoparticles on foam cell formation were investigated. • Exposure to ZnO nanoparticles induced migration and adhesion of monocytes. • Exposure to ZnO nanoparticles increased macrophage cholesterol uptake. • Expression of membrane scavenger receptors of modified LDL was also increased. • These effects were not observed after exposure to TiO{sub 2} nanoparticles.« less

Effects of microgravity on vestibular development and function in rats: genetics and environment

NASA Technical Reports Server (NTRS)

Ronca, A. E.; Fritzsch, B.; Alberts, J. R.; Bruce, L. L.

2000-01-01

Our anatomical and behavioral studies of embryonic rats that developed in microgravity suggest that the vestibular sensory system, like the visual system, has genetically mediated processes of development that establish crude connections between the periphery and the brain. Environmental stimuli also regulate connection formation including terminal branch formation and fine-tuning of synaptic contacts. Axons of vestibular sensory neurons from gravistatic as well as linear acceleration receptors reach their targets in both microgravity and normal gravity, suggesting that this is a genetically regulated component of development. However, microgravity exposure delays the development of terminal branches and synapses in gravistatic but not linear acceleration-sensitive neurons and also produces behavioral changes. These latter changes reflect environmentally controlled processes of development.

Neonatal head and torso vibration exposure during inter-hospital transfer

PubMed Central

Blaxter, Laurence; Yeo, Mildrid; McNally, Donal; Crowe, John; Henry, Caroline; Hill, Sarah; Mansfield, Neil; Leslie, Andrew; Sharkey, Don

2017-01-01

Inter-hospital transport of premature infants is increasingly common, given the centralisation of neonatal intensive care. However, it is known to be associated with anomalously increased morbidity, most notably brain injury, and with increased mortality from multifactorial causes. Surprisingly, there have been relatively few previous studies investigating the levels of mechanical shock and vibration hazard present during this vehicular transport pathway. Using a custom inertial datalogger, and analysis software, we quantify vibration and linear head acceleration. Mounting multiple inertial sensing units on the forehead and torso of neonatal patients and a preterm manikin, and on the chassis of transport incubators over the duration of inter-site transfers, we find that the resonant frequency of the mattress and harness system currently used to secure neonates inside incubators is ~9Hz. This couples to vehicle chassis vibration, increasing vibration exposure to the neonate. The vibration exposure per journey (A(8) using the ISO 2631 standard) was at least 20% of the action point value of current European Union regulations over all 12 neonatal transports studied, reaching 70% in two cases. Direct injury risk from linear head acceleration (HIC15) was negligible. Although the overall hazard was similar, vibration isolation differed substantially between sponge and air mattresses, with a manikin. Using a Global Positioning System datalogger alongside inertial sensors, vibration increased with vehicle speed only above 60 km/h. These preliminary findings suggest there is scope to engineer better systems for transferring sick infants, thus potentially improving their outcomes. PMID:28056712

Neonatal head and torso vibration exposure during inter-hospital transfer.

PubMed

Blaxter, Laurence; Yeo, Mildrid; McNally, Donal; Crowe, John; Henry, Caroline; Hill, Sarah; Mansfield, Neil; Leslie, Andrew; Sharkey, Don

2017-02-01

Inter-hospital transport of premature infants is increasingly common, given the centralisation of neonatal intensive care. However, it is known to be associated with anomalously increased morbidity, most notably brain injury, and with increased mortality from multifactorial causes. Surprisingly, there have been relatively few previous studies investigating the levels of mechanical shock and vibration hazard present during this vehicular transport pathway. Using a custom inertial datalogger, and analysis software, we quantify vibration and linear head acceleration. Mounting multiple inertial sensing units on the forehead and torso of neonatal patients and a preterm manikin, and on the chassis of transport incubators over the duration of inter-site transfers, we find that the resonant frequency of the mattress and harness system currently used to secure neonates inside incubators is [Formula: see text]. This couples to vehicle chassis vibration, increasing vibration exposure to the neonate. The vibration exposure per journey (A(8) using the ISO 2631 standard) was at least 20% of the action point value of current European Union regulations over all 12 neonatal transports studied, reaching 70% in two cases. Direct injury risk from linear head acceleration (HIC 15 ) was negligible. Although the overall hazard was similar, vibration isolation differed substantially between sponge and air mattresses, with a manikin. Using a Global Positioning System datalogger alongside inertial sensors, vibration increased with vehicle speed only above 60 km/h. These preliminary findings suggest there is scope to engineer better systems for transferring sick infants, thus potentially improving their outcomes.

Adaptations of the vestibular system to short and long-term exposures to altered gravity

NASA Astrophysics Data System (ADS)

Bruce, L.

Long-term space flight creates unique environmental conditions to which the vestibular system must adapt for optimal survival. We are studying two aspects of this vestibular adaptation: (1) How does long-term exposure to microgravity and hypergravity affect the development of vestibular afferents? (2) How does short- term exposure to extremely rapid changes in gravity, such as those that occur during launch and landing, affect the vestibular system. During space flight the gravistatic receptors in the otolith organs are effectively unloaded. In hypergravity conditions they are overloaded. However, the angular acceleration receptors of the semicircular canals receive relatively normal stimulation in both micro- and hypergravity.Rat embryos exposed to microgravity from gestation day 10 (prior to vestibular function) until gestation day 20 (vestibular system is somewhat functional) showed that afferents from the posterior vertical canal projecting to the medial vestibular nucleus developed similarly in microgravity, hypergravity, and in controls . However, afferents from the saccule showed delayed development in microgravity as compared to development in hypergravity and in controls. Cerebellar plasticity is crucial for modification of sensory-motor control and learning. Thus we explored the possibility that strong vestibular stimuli would modify cerebellar motor control (i.e., eye movement, postural control, gut motility) by altering the morphology of cerebellar Purkinje cells. To study the effects of short-term exposures to strong vestibular stimuli we focused on structural changes in the vestibulo-cerebellum that are caused by strong vestibular stimuli. Adult mice were exposed to various combinations of constant and/or rapidly changing angular and linear accelerations for 8.5 min (the time length of shuttle launch). Our data shows that these stimuli cause intense excitation of cerebellar Purkinje cells, inducing up-regulation of clathrin-mediated endocytosis. Different types of stimulation affect Purkinje cells in particular locations of the vestibulo-cerebellum. This system allows us to study how the vestibular environment can modify cerebellar function, allowing animals to adapt to new environments. Supported by NASA grant NAG2-1353.

Dependence of palmar sweating response and central nervous system activity on the frequency of whole-body vibration.

PubMed

Ando, Hideo; Noguchi, Ryo

2003-06-01

This study was carried out to determine the effects of the frequency of whole-body vibration on palmar sweating response and the activity of the central sympathetic nervous system. Palmar sweating volume was measured on the right palm of six healthy men before and during 3 minutes of exposure to sinusoidal whole-body vibration at three different frequencies (16, 31.5, and 63 Hz). The whole-body vibration had a frequency-weighted, root mean square (rms) acceleration magnitude of 2.0 m/s2. As the index of the activated central sympathetic nervous system, saliva level of 3-methoxy-4-hydroxyphenylglycol (MHPG) was analyzed before and immediately after each vibration exposure. Each vibration frequency induced a palmar sweating response, that of 31.5 Hz being the largest. However, no significant difference was found between the three vibration conditions. Saliva MHPG increased in all the vibration exposures, and the largest change was observed at 31.5 Hz, the difference being significant. Acute exposure to whole-body vibration induced a palmar sweating response and activated the central sympathetic nervous system. The effects on the central nervous system were found to be dependent on the frequency of the vibration.

Atomic oxygen effects on spacecraft materials: The state of the art of our knowledge

NASA Technical Reports Server (NTRS)

Koontz, Steven L.

1989-01-01

In the flight materials exposure data base extensive quantitative data is available from limited exposures in a narrow range of orbital environments. More data is needed in a wider range of environments as well as longer exposure times. Synergistic effects with other environmental factors; polar orbit and higher altitude environments; and real time materials degradation data is needed to understand degradation kinetics and mechanism. Almost no laboratory data exists from high fidelity simulations of the LEO environment. Simulation and test system are under development, and the data base is scanty. Theoretical understanding of hyperthermal atom surface reactions in the LEO environment is not good enough to support development of reliable accelerated test methods. The laser sustained discharge, atom beam sources are the most promising high fidelity simulation-test systems at this time.

Development of the integrated control system for the microwave ion source of the PEFP 100-MeV proton accelerator

NASA Astrophysics Data System (ADS)

Song, Young-Gi; Seol, Kyung-Tae; Jang, Ji-Ho; Kwon, Hyeok-Jung; Cho, Yong-Sub

2012-07-01

The Proton Engineering Frontier Project (PEFP) 20-MeV proton linear accelerator is currently operating at the Korea Atomic Energy Research Institute (KAERI). The ion source of the 100-MeV proton linac needs at least a 100-hour operation time. To meet the goal, we have developed a microwave ion source that uses no filament. For the ion source, a remote control system has been developed by using experimental physics and the industrial control system (EPICS) software framework. The control system consists of a versa module europa (VME) and EPICS-based embedded applications running on a VxWorks real-time operating system. The main purpose of the control system is to control and monitor the operational variables of the components remotely and to protect operators from radiation exposure and the components from critical problems during beam extraction. We successfully performed the operation test of the control system to confirm the degree of safety during the hardware performance.

Ground-based research with heavy ions for space radiation protection

NASA Astrophysics Data System (ADS)

Durante, M.; Kronenberg, A.

Human exposure to ionizing radiation is one of the acknowledged potential showstoppers for long duration manned interplanetary missions. Human exploratory missions cannot be safely performed without a substantial reduction of the uncertainties associated with different space radiation health risks, and the development of effective countermeasures. Most of our knowledge of the biological effects of heavy charged particles comes from accelerator-based experiments. During the 35th COSPAR meeting, recent ground-based experiments with high-energy iron ions were discussed, and these results are briefly summarised in this paper. High-quality accelerator-based research with heavy ions will continue to be the main source of knowledge of space radiation health effects and will lead to reductions of the uncertainties in predictions of human health risks. Efforts in materials science, nutrition and pharmaceutical sciences and their rigorous evaluation with biological model systems in ground-based accelerator experiments will lead to the development of safe and effective countermeasures to permit human exploration of the Solar System.

Sequential accelerated tests: Improving the correlation of accelerated tests to module performance in the field

NASA Astrophysics Data System (ADS)

Felder, Thomas; Gambogi, William; Stika, Katherine; Yu, Bao-Ling; Bradley, Alex; Hu, Hongjie; Garreau-Iles, Lucie; Trout, T. John

2016-09-01

DuPont has been working steadily to develop accelerated backsheet tests that correlate with solar panels observations in the field. This report updates efforts in sequential testing. Single exposure tests are more commonly used and can be completed more quickly, and certain tests provide helpful predictions of certain backsheet failure modes. DuPont recommendations for single exposure tests are based on 25-year exposure levels for UV and humidity/temperature, and form a good basis for sequential test development. We recommend a sequential exposure of damp heat followed by UV then repetitions of thermal cycling and UVA. This sequence preserves 25-year exposure levels for humidity/temperature and UV, and correlates well with a large body of field observations. Measurements can be taken at intervals in the test, although the full test runs 10 months. A second, shorter sequential test based on damp heat and thermal cycling tests mechanical durability and correlates with loss of mechanical properties seen in the field. Ongoing work is directed toward shorter sequential tests that preserve good correlation to field data.

“Triple M” Effect: A Proposed Mechanism to Explain Increased Dental Amalgam Microleakage after Exposure to Radiofrequency Electromagnetic Radiation

PubMed Central

Mortazavi, Gh.; Mortazavi, S.A.R.; Mehdizadeh, A.R.

2018-01-01

A large body of evidence now indicates that the amount of mercury released from dental amalgam fillings can be significantly accelerated by exposure to radiofrequency electromagnetic fields (RF-EMFs) such as common mobile phones and magnetic resonance imaging (MRI). Studies performed on the increased microleakage of dental amalgam restorations after exposure to RF-EMFs have further supported these findings. Although the accelerated microleakage induced by RF-EMFs is clinically significant, the entire mechanisms of this phenomenon are not clearly understood. In this paper, we introduce “Triple M” effect, a new evidence-based theory which can explain the accelerated microleakage of dental amalgam fillings after exposure to different sources of electromagnetic radiation. Based on this theory, there are saliva-filled tiny spaces between amalgam and the tooth. Exposure of the oral cavity to RF-EMFs increases the energy of these small amounts of saliva. Due to the small mass of saliva in these tiny spaces, a small amount of energy will be required for heating. Moreover, reflection of the radiofrequency radiation on the inner walls of the tiny spaces causes interference which in turn produces some “hot spots” in these spaces. Finally, formation of gas bubbles in response to increased temperature and very rapid expansion of these bubbles will accelerate the microleakage of amalgam. Experiments that confirm the validity of this theory are discussed. PMID:29732349

"Triple M" Effect: A Proposed Mechanism to Explain Increased Dental Amalgam Microleakage after Exposure to Radiofrequency Electromagnetic Radiation.

PubMed

Mortazavi, Gh; Mortazavi, S A R; Mehdizadeh, A R

2018-03-01

A large body of evidence now indicates that the amount of mercury released from dental amalgam fillings can be significantly accelerated by exposure to radiofrequency electromagnetic fields (RF-EMFs) such as common mobile phones and magnetic resonance imaging (MRI). Studies performed on the increased microleakage of dental amalgam restorations after exposure to RF-EMFs have further supported these findings. Although the accelerated microleakage induced by RF-EMFs is clinically significant, the entire mechanisms of this phenomenon are not clearly understood. In this paper, we introduce "Triple M" effect, a new evidence-based theory which can explain the accelerated microleakage of dental amalgam fillings after exposure to different sources of electromagnetic radiation. Based on this theory, there are saliva-filled tiny spaces between amalgam and the tooth. Exposure of the oral cavity to RF-EMFs increases the energy of these small amounts of saliva. Due to the small mass of saliva in these tiny spaces, a small amount of energy will be required for heating. Moreover, reflection of the radiofrequency radiation on the inner walls of the tiny spaces causes interference which in turn produces some "hot spots" in these spaces. Finally, formation of gas bubbles in response to increased temperature and very rapid expansion of these bubbles will accelerate the microleakage of amalgam. Experiments that confirm the validity of this theory are discussed.

Tobacco smoke exposure in either the donor or recipient before transplantation accelerates cardiac allograft rejection, vascular inflammation, and graft loss.

PubMed

Khanna, Ashwani K; Xu, Jianping; Uber, Patricia A; Burke, Allen P; Baquet, Claudia; Mehra, Mandeep R

2009-11-03

Tobacco exposure in cardiac transplant recipients, before and after transplantation, may increase the risk of cardiac allograft vasculopathy and allograft loss, but no direct evidence for this phenomenon is forthcoming. In this experimental study, we investigated early consequences of tobacco smoke exposure in cardiac transplant donors and recipients with an emphasis on alloinflammatory mediators of graft outcome. Using heterotopic rat cardiac transplantation, we tested the effects of donor or recipient tobacco smoke exposure in 6 groups of animals (rat heterotopic cardiac transplantation) as follows: tobacco-naïve allogeneic rejecting controls (n=6), tobacco-naïve nonrejecting controls (n=3; killed on day 5 to simulate survival times of tobacco-treated animals), isografts (n=3), both donor and recipient rats exposed to tobacco smoke (n=4), only donor rats exposed to tobacco smoke (n=7), and only recipient rats exposed to tobacco smoke (n=6). Polymerase chain reaction studies of tissue and peripheral (systemic) protein expression were performed to evaluate inflammatory (tumor necrosis factor-alpha, interferon-gamma, interleukin-6) and alloimmune (interleukin-1 receptor 2, programmed cell death-1, and stromal cell-derived factor-1) pathways, as was histological analysis of the cardiac allografts. Our experiments reveal that pretransplantation tobacco exposure in donors and/or recipients results in heightened systemic inflammation and increased oxidative stress, reduces posttransplantation cardiac allograft survival by 33% to 57%, and increases intragraft inflammation (tumor necrosis factor-alpha, interferon-gamma, interleukin-6) and alloimmune activation (CD3, interleukin-1 receptor 2, programmed cell death-1, and stromal cell-derived factor-1) with consequent myocardial and vascular destruction. These sentinel findings confirm that tobacco smoke exposure in either donors or recipients leads to accelerated allograft rejection, vascular inflammation, and graft loss. Molecular pathways that intersect as arbiters in this phenomenon include instigation of alloimmune activation associated with tobacco smoke-induced inflammation.

Neurologic and neuropsychiatric syndrome features of mold and mycotoxin exposure.

PubMed

Empting, L D

2009-01-01

Human exposure to molds, mycotoxins, and water-damaged buildings can cause neurologic and neuropsychiatric signs and symptoms. Many of these clinical features can partly mimic or be similar to classic neurologic disorders including pain syndromes, movement disorders, delirium, dementia, and disorders of balance and coordination. In this article, the author delineates the signs and symptoms of a syndrome precipitated by mold and mycotoxin exposure and contrasts and separates these findings neurodiagnostically from known neurologic diseases. This clinical process is designed to further the scientific exploration of the underlying neuropathophysiologic processes and to promote better understanding of effects of mold/mycotoxin/water-damaged buildings on the human nervous system and diseases of the nervous system. It is clear that mycotoxins can affect sensitive individuals, and possibly accelerate underlying neurologic/pathologic processes, but it is crucial to separate known neurologic and neuropsychiatric disorders from mycotoxin effects in order to study it properly.

Blast-Induced Acceleration in a Shock Tube: Distinguishing Primary and Tertiary Blast Injury

DTIC Science & Technology

2015-10-01

these well-defined exposure conditions, anesthetized rats are used to simultaneously record intracranial pressure (ICP), intravascular pressure , and...blast flow conditions (e.g. peak static and total pressure , positive phase duration, and impulse) and acceleration and displacement of a wide range of...resultant pressure responses in varied compartments in concert with the neuropathological, neurochemical, and neurobehavioral consequences of exposures

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...

An Experimental Study of a Low-Jitter Pulsed Electromagnetic Plasma Accelerator

NASA Technical Reports Server (NTRS)

Thio, Y. C. Francis; Lee, Michael; Eskridge, Richard; Smith, James; Martin, Adam; Rodgers, Stephen L. (Technical Monitor)

2001-01-01

An experimental plasma accelerator for a variety of applications under development at the NASA Marshall Space Flight Center is described. The accelerator is a pulsed plasma thruster and has been tested experimentally and plasma jet velocities of approximately 50 kilometers per second have been obtained. The plasma jet structure has been photographed with 10 ns exposure times to reveal a stable and repeatable plasma structure. Data for velocity profile information has been obtained using light pipes embedded in the gun walls to record the plasma transit at various barrel locations. Preliminary spatially resolved spectral data and magnetic field probe data are also presented. A high speed triggering system has been developed and tested as a means of reducing the gun "jitter". This jitter has been characterized and future work for second generation "ultra-low jitter" gun development is identified.

Critical disease windows shaped by stress exposure alter allocation trade-offs between development and immunity.

PubMed

Kirschman, Lucas J; Crespi, Erica J; Warne, Robin W

2018-01-01

Ubiquitous environmental stressors are often thought to alter animal susceptibility to pathogens and contribute to disease emergence. However, duration of exposure to a stressor is likely critical, because while chronic stress is often immunosuppressive, acute stress can temporarily enhance immune function. Furthermore, host susceptibility to stress and disease often varies with ontogeny; increasing during critical developmental windows. How the duration and timing of exposure to stressors interact to shape critical windows and influence disease processes is not well tested. We used ranavirus and larval amphibians as a model system to investigate how physiological stress and pathogenic infection shape development and disease dynamics in vertebrates. Based on a resource allocation model, we designed experiments to test how exposure to stressors may induce resource trade-offs that shape critical windows and disease processes because the neuroendocrine stress axis coordinates developmental remodelling, immune function and energy allocation in larval amphibians. We used wood frog larvae (Lithobates sylvaticus) to investigate how chronic and acute exposure to corticosterone, the dominant amphibian glucocorticoid hormone, mediates development and immune function via splenocyte immunohistochemistry analysis in association with ranavirus infection. Corticosterone treatments affected immune function, as both chronic and acute exposure suppressed splenocyte proliferation, although viral replication rate increased only in the chronic corticosterone treatment. Time to metamorphosis and survival depended on both corticosterone treatment and infection status. In the control and chronic corticosterone treatments, ranavirus infection decreased survival and delayed metamorphosis, although chronic corticosterone exposure accelerated rate of metamorphosis in uninfected larvae. Acute corticosterone exposure accelerated metamorphosis increased survival in infected larvae. Interactions between stress exposure (via glucocorticoid actions) and infection impose resource trade-offs that shape optimal allocation between development and somatic function. As a result, critical disease windows are likely shaped by stress exposure because any conditions that induce changes in differentiation rates will alter the duration and susceptibility of organisms to stressors or disease. © 2017 The Authors. Journal of Animal Ecology © 2017 British Ecological Society.

NOTE: A method for controlling image acquisition in electronic portal imaging devices

NASA Astrophysics Data System (ADS)

Glendinning, A. G.; Hunt, S. G.; Bonnett, D. E.

2001-02-01

Certain types of camera-based electronic portal imaging devices (EPIDs) which initiate image acquisition based on sensing a change in video level have been observed to trigger unreliably at the beginning of dynamic multileaf collimation sequences. A simple, novel means of controlling image acquisition with an Elekta linear accelerator (Elekta Oncology Systems, Crawley, UK) is proposed which is based on illumination of a photodetector (ORP-12, Silonex Inc., Plattsburgh, NY, USA) by the electron gun of the accelerator. By incorporating a simple trigger circuit it is possible to derive a beam on/off status signal which changes at least 100 ms before any dose is measured by the accelerator. The status signal does not return to the beam-off state until all dose has been delivered and is suitable for accelerator pulse repetition frequencies of 50-400 Hz. The status signal is thus a reliable means of indicating the initiation and termination of radiation exposure, and thus controlling image acquisition of such EPIDs for this application.

Long-term exposure to air pollution is associated with biological aging.

PubMed

Ward-Caviness, Cavin K; Nwanaji-Enwerem, Jamaji C; Wolf, Kathrin; Wahl, Simone; Colicino, Elena; Trevisi, Letizia; Kloog, Itai; Just, Allan C; Vokonas, Pantel; Cyrys, Josef; Gieger, Christian; Schwartz, Joel; Baccarelli, Andrea A; Schneider, Alexandra; Peters, Annette

2016-11-15

Long-term exposure to air pollution is associated with age-related diseases. We explored the association between accelerated biological aging and air pollution, a potential mechanism linking air pollution and health. We estimated long-term exposure to PM10, PM2.5, PM2.5 absorbance/black carbon (BC), and NOx via land-use regression models in individuals from the KORA F4 cohort. Accelerated biological aging was assessed using telomere length (TeloAA) and three epigenetic measures: DNA methylation age acceleration (DNAmAA), extrinsic epigenetic age acceleration (correlated with immune cell counts, EEAA), and intrinsic epigenetic age acceleration (independent of immune cell counts, IEAA). We also investigated sex-specific associations between air pollution and biological aging, given the published association between sex and aging measures. In KORA an interquartile range (0.97 µg/m3) increase in PM2.5 was associated with a 0.33 y increase in EEAA (CI = 0.01, 0.64; P = 0.04). BC and NOx (indicators or traffic exposure) were associated with DNAmAA and IEAA in women, while TeloAA was inversely associated with BC in men. We replicated this inverse BC-TeloAA association in the Normative Aging Study, a male cohort based in the USA. A multiple phenotype analysis in KORA F4 combining all aging measures showed that BC and PM10 were broadly associated with biological aging in men. Thus, we conclude that long-term exposure to air pollution is associated with biological aging measures, potentially in a sex-specific manner. However, many of the associations were relatively weak and further replication of overall and sex-specific associations is warranted.

Long-term exposure to air pollution is associated with biological aging

PubMed Central

Ward-Caviness, Cavin K.; Nwanaji-Enwerem, Jamaji C.; Wolf, Kathrin; Wahl, Simone; Colicino, Elena; Trevisi, Letizia; Kloog, Itai; Just, Allan C.; Vokonas, Pantel; Cyrys, Josef; Gieger, Christian; Schwartz, Joel; Baccarelli, Andrea A.; Schneider, Alexandra; Peters, Annette

2016-01-01

Long-term exposure to air pollution is associated with age-related diseases. We explored the association between accelerated biological aging and air pollution, a potential mechanism linking air pollution and health. We estimated long-term exposure to PM10, PM2.5, PM2.5 absorbance/black carbon (BC), and NOx via land-use regression models in individuals from the KORA F4 cohort. Accelerated biological aging was assessed using telomere length (TeloAA) and three epigenetic measures: DNA methylation age acceleration (DNAmAA), extrinsic epigenetic age acceleration (correlated with immune cell counts, EEAA), and intrinsic epigenetic age acceleration (independent of immune cell counts, IEAA). We also investigated sex-specific associations between air pollution and biological aging, given the published association between sex and aging measures. In KORA an interquartile range (0.97 μg/m3) increase in PM2.5 was associated with a 0.33 y increase in EEAA (CI = 0.01, 0.64; P = 0.04). BC and NOx (indicators or traffic exposure) were associated with DNAmAA and IEAA in women, while TeloAA was inversely associated with BC in men. We replicated this inverse BC-TeloAA association in the Normative Aging Study, a male cohort based in the USA. A multiple phenotype analysis in KORA F4 combining all aging measures showed that BC and PM10 were broadly associated with biological aging in men. Thus, we conclude that long-term exposure to air pollution is associated with biological aging measures, potentially in a sex-specific manner. However, many of the associations were relatively weak and further replication of overall and sex-specific associations is warranted. PMID:27793020

Multi-GPU Accelerated Admittance Method for High-Resolution Human Exposure Evaluation.

PubMed

Xiong, Zubiao; Feng, Shi; Kautz, Richard; Chandra, Sandeep; Altunyurt, Nevin; Chen, Ji

2015-12-01

A multi-graphics processing unit (GPU) accelerated admittance method solver is presented for solving the induced electric field in high-resolution anatomical models of human body when exposed to external low-frequency magnetic fields. In the solver, the anatomical model is discretized as a three-dimensional network of admittances. The conjugate orthogonal conjugate gradient (COCG) iterative algorithm is employed to take advantage of the symmetric property of the complex-valued linear system of equations. Compared against the widely used biconjugate gradient stabilized method, the COCG algorithm can reduce the solving time by 3.5 times and reduce the storage requirement by about 40%. The iterative algorithm is then accelerated further by using multiple NVIDIA GPUs. The computations and data transfers between GPUs are overlapped in time by using asynchronous concurrent execution design. The communication overhead is well hidden so that the acceleration is nearly linear with the number of GPU cards. Numerical examples show that our GPU implementation running on four NVIDIA Tesla K20c cards can reach 90 times faster than the CPU implementation running on eight CPU cores (two Intel Xeon E5-2603 processors). The implemented solver is able to solve large dimensional problems efficiently. A whole adult body discretized in 1-mm resolution can be solved in just several minutes. The high efficiency achieved makes it practical to investigate human exposure involving a large number of cases with a high resolution that meets the requirements of international dosimetry guidelines.

Neural readaptation to earth s gravity following exposure to microgravity

NASA Astrophysics Data System (ADS)

Boyle, R.; Highstein, S.; Mensinger, A.

Vertebrates possess hair cell otolith organs of the inner ear, the utricule and saccule, that transduce inertial force due to head translation and head tilt relative to gravitational vertical, and transform the vector sum of the imposing accelerations into a neural code carried by the afferent nerve fibers. This code is combined in the central vestibular pathways with motion signals obtained from the semicircular canals and other sensory modalities to compute a cent ral representation of the body in space called the gravitoinertial vector. Thus the central nervous system resolves the ambiguity of gravity and self-motion and thereby maintains balance and equilibrium under varying conditions. Exposure to microgravity imposes an extreme condition to which the organism must adapt. Space travelers often experience disorientation during the first few days in microgravity, called Space Adaptation Syndrome. From the earliest manned missions it was evident that adjustments to the microgravity environment in-flight and upon return to Earth's 1g occur. We studied the neural readaptation to Earth's 1g using electrophysiological techniques to measure the response characteristics of utricular nerve afferents in fish upon return from an exposure to microgravity. Following a 9 (STS-95) and 15 (STS-90) day exposure to microgravity aboard two NASA shuttle orbital flights, single afferent recording experiments were conducted in four toadfish, Opsanus tau, to characterize the afferent response properties to gravito inertial accelerations and compare them to- afferent responses of control animals similarly tested. Six recording sessions were made sequentially 10-117 hrs postflight. Afferent responses to translational accelerations and head tilts were detected in the earliest sessions. The most striking result is the occurrence of hypersensitive afferents, having extremely high response sensitivity to minor displacements such as < 0.5 mm displacement at 0.006g, within the first day postflight. After about 30 hrs the afferent response properties of flight and control fish were similar. The reduced gravitational acceleration in orbit apparently resulted in a temporary up-regulation of the sensitivity of utricular afferents. The time course of return to normal afferent sensitivity parallels the decrease in vestibular disorientation in astronauts following return from space. (Supported by NASA, NIH and NASDA)

Observed differences in upper extremity forces, muscle efforts, postures, velocities and accelerations across computer activities in a field study of office workers.

PubMed

Bruno Garza, J L; Eijckelhof, B H W; Johnson, P W; Raina, S M; Rynell, P W; Huysmans, M A; van Dieën, J H; van der Beek, A J; Blatter, B M; Dennerlein, J T

2012-01-01

This study, a part of the PRedicting Occupational biomechanics in OFfice workers (PROOF) study, investigated whether there are differences in field-measured forces, muscle efforts, postures, velocities and accelerations across computer activities. These parameters were measured continuously for 120 office workers performing their own work for two hours each. There were differences in nearly all forces, muscle efforts, postures, velocities and accelerations across keyboard, mouse and idle activities. Keyboard activities showed a 50% increase in the median right trapezius muscle effort when compared to mouse activities. Median shoulder rotation changed from 25 degrees internal rotation during keyboard use to 15 degrees external rotation during mouse use. Only keyboard use was associated with median ulnar deviations greater than 5 degrees. Idle activities led to the greatest variability observed in all muscle efforts and postures measured. In future studies, measurements of computer activities could be used to provide information on the physical exposures experienced during computer use. Practitioner Summary: Computer users may develop musculoskeletal disorders due to their force, muscle effort, posture and wrist velocity and acceleration exposures during computer use. We report that many physical exposures are different across computer activities. This information may be used to estimate physical exposures based on patterns of computer activities over time.

Human habitat positioning system for NASA's space flight environmental simulator

NASA Technical Reports Server (NTRS)

Caldwell, W. F.; Tucker, J.; Keas, P.

1998-01-01

Artificial gravity by centrifugation offers an effective countermeasure to the physiologic deconditioning of chronic exposure to microgravity; however, the system requirements of rotational velocity, radius of rotation, and resultant centrifugal acceleration require thorough investigation to ascertain the ideal human-use centrifuge configuration. NASA's Space Flight Environmental Simulator (SFES), a 16-meter (52-foot) diameter, animal-use centrifuge, was recently modified to accommodate human occupancy. This paper describes the SFES Human Habitat Positioning System, the mechanism that facilitates radius of rotation variability and alignment of the centrifuge occupants with the artificial gravity vector.

+Gz-induced post-cholecystectomy syndrome in rabbit model by using a telemetric method

PubMed Central

Kong, Yalin; Zhao, Gang; Li, Yifeng; Wen, Dongqing; Zhang, Hui; He, Xiaojun; Zhen, Yuying; Zhang, Hongyi

2015-01-01

Aviation-related mechanism may exist in the post-cholecystectomy syndrome (PCS) of aircrew patients. The aim of this study was to test this hypothesis on vivo rabbit model and to explore the mechanism by using a novel telemetric method. We constructed a bile duct-to-intestinal bridge bypass on 30 rabbits, with a telemetry implant attached to the Oddi’s sphincter. Then a telemetric recording system was used to record the biliary pressure fluctuation through the subcutaneous bridge and the changes of electromyography of the Oddi’s sphincter under different +Gz acceleration. Self-control comparison was made before and after cholecystectomy. The fully implantable device was very well accepted by rabbits and the data could reflect the real experimental environment simultaneously. Biliary pressure in common bile duct increased accordingly with +Gz acceleration increased, but bile secretion didn’t change. Although +Gz acceleration could increase the frequency of burst of spike potentials in the Oddi’s sphincter, the frequency didn’t change with the +Gz acceleration increased, and the spike activity didn’t change obviously before cholecystectomy. After cholecystectomy, the biliary pressure in common bile duct remained high in 12 rabbits (40%) under +Gz exposure, and the pressure value didn’t change as the +Gz acceleration increased. The long-time changes in electromyography of the Oddi’s sphincter were observed in the same 12 rabbits, with symptoms of PCS developed in 9 of them. +Gz exposure is an important external factor leading to the biliary physiology disorder, and it may induce PCS in some aircrew patients with individual susceptibility, which means gallbladder maybe a dominant factor in regulating the biliary physiology in theses aircrew patients. PMID:26064268

Effect of vibration duration on human discomfort. [passenger comfort and random vibration

NASA Technical Reports Server (NTRS)

Clevenson, S. A.; Dempsey, T. K.; Leatherwood, J. D.

1978-01-01

The duration effects of random vertical vibration on passenger discomfort were studied in a simulated section of an aircraft cabin configured to seat six persons in tourist-class style. Variables of the study included time of exposure (0.25 min to 60 min) and the rms amplitude of vibration (0.025g to 0.100g). The vibrations had a white noise spectrum with a bandwidth of 10 Hz centered at 5 Hz. Data indicate that the discomfort threshold occurred at an rms vertical acceleration level of 0.027g for all durations of vibration. However, for acceleration levels that exceeded the discomfort threshold, a systematic decrease in discomfort occurred as a function of increasing duration of vibration. For the range of accelerations used, the magnitude of the discomfort decrement was shown to be independent of acceleration level. The results suggest that discomfort from vertical vibration applied in the frequency range at which humans are most sensitive decreases with longer exposure, which is the opposite of the recommendation of the International Standard ISO 2631-1974 (E) Guide for the Evaluation of Human Exposure to Whole-Body Vibration.

Accelerated Aging Test for Plastic Scintillator Gamma Ray Detectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kouzes, Richard T.

Polyvinyl toluene (PVT) and polystyrene (PS), collectively referred to as “plastic scintillator,” are synthetic polymer materials used to detect gamma radiation, and are commonly used in instrumentation. Recent studies have revealed that plastic scintillator undergoes an environmentally related material degradation that adversely affects performance under certain conditions and histories. A significant decrease in gamma ray sensitivity has been seen in some detectors in systems as they age. The degradation of sensitivity of plastic scintillator over time is due to a variety of factors, and the term “aging” is used to encompass all factors. Some plastic scintillator samples show no agingmore » effects (no significant change in sensitivity over more than 10 years), while others show severe aging (significant change in sensitivity in less than 5 years). Aging effects arise from weather (variations in heat and humidity), chemical exposure, mechanical stress, light exposure, and loss of volatile components. The damage produced by these various causes can be cumulative, causing observable damage to increase over time. Damage may be reversible up to some point, but becomes permanent under some conditions. It has been demonstrated that exposure of plastic scintillator in an environmental chamber to 30 days of high temperature and humidity (90% relative humidity and 55°C) followed by a single cycle to cold temperature (-30°C) will produce severe fogging in all PVT samples. This thermal cycle will be referred to as the “Accelerated Aging Test.” This document describes the procedure for performing this Accelerated Aging Test.« less

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

NASA Technical Reports Server (NTRS)

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

2002-01-01

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

Accelerated laboratory weathering of acrylic lens materials

NASA Astrophysics Data System (ADS)

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

2015-09-01

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

Constitutive expression of tdTomato protein as a cytotoxicity and proliferation marker for space radiation biology

NASA Astrophysics Data System (ADS)

Chishti, Arif A.; Hellweg, Christine E.; Berger, Thomas; Baumstark-Khan, Christa; Feles, Sebastian; Kätzel, Thorben; Reitz, Günther

2015-01-01

The radiation risk assessment for long-term space missions requires knowledge on the biological effectiveness of different space radiation components, e.g. heavy ions, on the interaction of radiation and other space environmental factors such as microgravity, and on the physical and biological dose distribution in the human body. Space experiments and ground-based experiments at heavy ion accelerators require fast and reliable test systems with an easy readout for different endpoints. In order to determine the effect of different radiation qualities on cellular proliferation and the biological depth dose distribution after heavy ion exposure, a stable human cell line expressing a novel fluorescent protein was established and characterized. tdTomato, a red fluorescent protein of the new generation with fast maturation and high fluorescence intensity, was selected as reporter of cell proliferation. Human embryonic kidney (HEK/293) cells were stably transfected with a plasmid encoding tdTomato under the control of the constitutively active cytomegalovirus (CMV) promoter (ptdTomato-N1). The stably transfected cell line was named HEK-ptdTomato-N1 8. This cytotoxicity biosensor was tested by ionizing radiation (X-rays and accelerated heavy ions) exposure. As biological endpoints, the proliferation kinetics and the cell density reached 100 h after irradiation reflected by constitutive expression of the tdTomato were investigated. Both were reduced dose-dependently after radiation exposure. Finally, the cell line was used for biological weighting of heavy ions of different linear energy transfer (LET) as space-relevant radiation quality. The relative biological effectiveness of accelerated heavy ions in reducing cellular proliferation peaked at an LET of 91 keV/μm. The results of this study demonstrate that the HEK-ptdTomato-N1 reporter cell line can be used as a fast and reliable biosensor system for detection of cytotoxic damage caused by ionizing radiation.

On the Use of Accelerated Test Methods for Characterization of Advanced Composite Materials

NASA Technical Reports Server (NTRS)

Gates, Thomas S.

2003-01-01

A rational approach to the problem of accelerated testing for material characterization of advanced polymer matrix composites is discussed. The experimental and analytical methods provided should be viewed as a set of tools useful in the screening of material systems for long-term engineering properties in aerospace applications. Consideration is given to long-term exposure in extreme environments that include elevated temperature, reduced temperature, moisture, oxygen, and mechanical load. Analytical formulations useful for predictive models that are based on the principles of time-based superposition are presented. The need for reproducible mechanisms, indicator properties, and real-time data are outlined as well as the methodologies for determining specific aging mechanisms.

Progress In Plasma Accelerator Development for Dynamic Formation of Plasma Liners

NASA Technical Reports Server (NTRS)

Thio, Y. C. Francis; Eskridge, Richard; Martin, Adam; Smith, James; Lee, Michael; Cassibry, Jason T.; Griffin, Steven; Rodgers, Stephen L. (Technical Monitor)

2002-01-01

An experimental plasma accelerator for magnetic target fusion (MTF) applications under development at the NASA Marshall Space Flight Center is described. The accelerator is a coaxial pulsed plasma thruster (Figure 1). It has been tested experimentally and plasma jet velocities of approx.50 km/sec have been obtained. The plasma jet has been photographed with 10-ns exposure times to reveal a stable and repeatable plasma structure (Figure 2). Data for velocity profile information has been obtained using light pipes and magnetic probes embedded in the gun walls to record the plasma and current transit respectively at various barrel locations. Preliminary spatially resolved spectral data and magnetic field probe data are also presented. A high speed triggering system has been developed and tested as a means of reducing the gun "jitter". This jitter is being characterized and future work for second generation "ultra-low jitter" gun development is being identified.

Plasma Accelerator Development for Dynamic Formation of Plasma Liners: A Status Report

NASA Technical Reports Server (NTRS)

Thio, Y. C. Francis; Eskridge, Richard; Martin, Adam; Smith, James; Lee, Michael; Rodgers, Stephen L. (Technical Monitor)

2001-01-01

An experimental plasma accelerator for magnetic target fusion (MTF) applications under development at the NASA Marshall Space Flight Center is described. The accelerator is a pulsed plasma thruster and has been tested experimentally and plasma jet velocities of approximately 50 km/sec have been obtained. The plasma jet structure has been photographed with 10 ns exposure times to reveal a stable and repeatable plasma structure. Data for velocity profile information has been obtained using light pipes embedded in the gun walls to record the plasma transit at various barrel locations. Preliminary spatially resolved spectral data and magnetic field probe data are also presented. A high speed triggering system has been developed and tested as a means of reducing the gun "jitter". This jitter is being characterized and future work for second generation "ultra-low jitter" gun development is being identified.

[Laser exposure and noncoherent infrared therapy in the treatment of mandibular fractures].

PubMed

Deriabin, E I

2001-01-01

The efficiency of laser exposure and noncoherent infrared (IR) therapy in patients with mandibular fractures were compared. Non coherent IR exposure promoted a decrease in the number of inflammatory reactions and accelerated rehabilitation of patients.

Efficacy of visor and helmet for blast protection assessed using a computational head model

NASA Astrophysics Data System (ADS)

Singh, D.; Cronin, D. S.

2017-11-01

Head injury resulting from blast exposure has been identified as a challenge that may be addressed, in part, through improved protective systems. Existing detailed head models validated for blast loading were applied to investigate the influence of helmet visor configuration, liner properties, and shell material stiffness. Response metrics including head acceleration and intracranial pressures (ICPs) generated in brain tissue during primary blast exposure were used to assess and compare helmet configurations. The addition of a visor was found to reduce peak head acceleration and positive ICPs. However, negative ICPs associated with a potential for injury were increased when a visor and a foam liner were present. In general, the foam liner material was found to be more significant in affecting the negative ICP response than positive ICP or acceleration. Shell stiffness was found to have relatively small effects on either metric. A strap suspension system, modeled as an air gap between the head and helmet, was more effective in reducing response metrics compared to a foam liner. In cases with a foam liner, lower-density foam offered a greater reduction of negative ICPs. The models demonstrated the "underwash" effect in cases where no foam liner was present; however, the reflected pressures generated between the helmet and head did not translate to significant ICPs in adjacent tissue, when compared to peak ICPs from initial blast wave interaction. This study demonstrated that the efficacy of head protection can be expressed in terms of load transmission pathways when assessed with a detailed computational model.

High sustained +Gz acceleration: physiological adaptation to high-G tolerance

NASA Technical Reports Server (NTRS)

Convertino, V. A.

1998-01-01

Since the early 1940s, a significant volume of research has been conducted in an effort to describe the impact of acute exposures to high-G acceleration on cardiovascular mechanisms responsible to maintaining cerebral perfusion and conscious in high performance aircraft pilots during aerial combat maneuvers. The value of understanding hemodynamic characteristics that underlie G-induced loss of consciousness has been instrumental in the evolution of optimal technology development (e.g., G-suits, positive pressure breathing, COMBAT EDGE, etc.) and pilot training (e.g., anti-G straining maneuvers). Although the emphasis of research has been placed on the development of protection against acute high +Gz acceleration effects, recent observations suggest that adaptation of cardiovascular mechanism associated with blood pressure regulation may contribute to a protective 'G-training' effect. Regular training at high G enhances G tolerance in humans, rats, guinea pigs, and dogs while prolonged layoff from exposure in high G profiles (G-layoff) can result in reduced G endurance. It seems probable that adaptations in physiological functions following chronically-repeated high G exposure (G training) or G-layoff could have significant impacts on performance during sustained high-G acceleration since protective technology such as G-suits and anit-G straining maneuvers are applied consistently during these periods of training. The purpose of this paper is to present a review of new data from three experiments that support the notion that repeated exposure on a regular basis to high sustained +Gz acceleration induces significant physiological adaptations which are associated with improved blood pressure regulation and subsequent protection of cerebral perfusion during orthostatic challenges.

Plasma vasopressin and renin activity in women exposed to bed rest and +G/z/ acceleration

NASA Technical Reports Server (NTRS)

Keil, L. C.; Ellis, S.

1976-01-01

To study the effect of prolonged recumbency on plasma vasopressin and renin activity, eight women were subjected to 17 days of absolute bed rest. The tolerance to +3G vertical acceleration of the subjects was tested before and after 14 days of bed rest. From day 2 and through day 17 of bed rest, plasma arginine vasopressin (AVP) levels were reduced 33%. Plasma renin activity (PRA) increased 91% above ambulatory control values from days 10 through 15 of bed rest. When compared to precentrifuge values, exposure to vertical acceleration prior to bed rest provoked a 20-fold rise in mean plasma AVP but resulted in only a slight increase in PRA. After bed rest, acceleration increased plasma AVP 7-fold; however, the magnitude of this increase was less than the post +3G acceleration value obtained prior to bed rest. After bed rest, no significant rise was noted in PRA following +3G acceleration. This study demonstrates that prolonged bed rest leads to a significant rise in the PRA of female subjects, while exposure to positive vertical acceleration provokes a marked rise in plasma AVP.

Use of Tritium Accelerator Mass Spectrometry for Tree Ring Analysis

PubMed Central

LOVE, ADAM H.; HUNT, JAMES R.; ROBERTS, MARK L.; SOUTHON, JOHN R.; CHIARAPPA - ZUCCA, MARINA L.; DINGLEY, KAREN H.

2010-01-01

Public concerns over the health effects associated with low-level and long-term exposure to tritium released from industrial point sources have generated the demand for better methods to evaluate historical tritium exposure levels for these communities. The cellulose of trees accurately reflects the tritium concentration in the source water and may contain the only historical record of tritium exposure. The tritium activity in the annual rings of a tree was measured using accelerator mass spectrometry to reconstruct historical annual averages of tritium exposure. Milligram-sized samples of the annual tree rings from a Tamarix located at the Nevada Test Site are used for validation of this methodology. The salt cedar was chosen since it had a single source of tritiated water that was well-characterized as it varied over time. The decay-corrected tritium activity of the water in which the salt cedar grew closely agrees with the organically bound tritium activity in its annual rings. This demonstrates that the milligram-sized samples used in tritium accelerator mass spectrometry are suited for reconstructing anthropogenic tritium levels in the environment. PMID:12144257

Characterization of Frequency-Dependent Responses of the Vascular System to Repetitive Vibration

PubMed Central

Krajnak, Kristine; Miller, G. Roger; Waugh, Stacey; Johnson, Claud; Kashon, Michael L.

2015-01-01

Objective Occupational exposure to hand-transmitted vibration can result in damage to nerves and sensory loss. The goal of this study was to assess the frequency-dependent effects of repeated bouts of vibration on sensory nerve function and associated changes in nerves. Methods The tails of rats were exposed to vibration at 62.5, 125, or 250 Hz (constant acceleration of 49m/s2) for 10 days. The effects on sensory nerve function, nerve morphology, and transcript expression in ventral tail nerves were measured. Results Vibration at all frequencies had effects on nerve function and physiology. However, the effects tended to be more prominent with exposure at 250 Hz. Conclusion Exposure to vibration has detrimental effects on sensory nerve function and physiology. However, many of these changes are more prominent at 250-Hz exposure than at lower frequencies. PMID:22785326

Establishing the Biodynamics Data Resource (BDR): Human Volunteer Impact Acceleration Research Data in the BDR

DTIC Science & Technology

2009-10-01

accelerations (+Z) were applied to HRVs in the supine position to mimic the acceleration of an ejection seat , while runs simulating aircraft crashes were...Naval Biodynamics Laboratory, 1985). The vertical testing provided a more authentic ejection seat simulation than was achievable using axial...impact acceleration exposures with hundreds of human research volunteers. The resulting volumes of kinematic and physiological data serve as a

The use of photostimulable phosphor systems for periodic quality assurance in radiotherapy.

PubMed

Conte, L; Bianchi, C; Cassani, E; Monciardini, M; Mordacchini, C; Novario, R; Strocchi, S; Stucchi, P; Tanzi, F

2008-03-01

The fusion of radiological and optical images can be achieved through charging a photostimulable phosphor plate (PSP) with an exposure to a field of X- or gamma-rays, followed by exposure to an optical image which discharges the plate in relation to the amount of incident light. According to this PSP characteristic, we developed a simple method for periodic quality assurance (QA) of light/radiation field coincidence, distance indicator, field size indicators, crosshair centering, coincidence of radiation and mechanical isocenter for linear accelerators. The geometrical accuracy of radiological units can be subjected to the same QA method. Further, the source position accuracy for an HDR remote afterloader can be checked by taking an autoradiography of the radioactive source and simultaneously an optical image of a reference geometrical system.

Acceleration and holographic studies on different types of dynamization of external fixators of the bones

NASA Astrophysics Data System (ADS)

Podbielska, Halina; Kasprzak, Henryk T.; Voloshin, Arkady S.; Pennig, Dietmar; von Bally, Gert

1992-08-01

The unilateral axially dynamic fixator (Orthofix) was mounted on a sheep tibial shaft. Three fixation modes: static, dynamic controlled, and dynamic free were examined by means of double exposure holographic interferometry. Simultaneously, the acceleration was measured by an accelerometer and displayed on the monitor together with loading characteristics. The first exposure was made before the acting force was applied to the tibia plateau. The second one after the moment when the acceleration wave started to propagate through the specimen. We stated that in the case of dynamization less torsion occurs at the fracture site. So far, we have not been able to determine any correlation between results of holographic and accelerometric measurements.

A Novel Method for Studying the Pharmacokinetics of [14C]Umeclidinium After Application to the Axilla or Palm of Healthy Male Subjects

PubMed Central

Santos, LL; Hughes, SC; Pereira, AI; Young, GC; Hussey, E; Charlton, P; Baptiste‐Brown, S; Stuart, JS; Vincent, V; van Marle, SP; Schmith, VD

2016-01-01

Umeclidinium (UMEC), a long‐acting muscarinic antagonist approved for chronic obstructive pulmonary disease (COPD), was investigated for primary hyperhidrosis as topical therapy. This study evaluated the pharmacokinetics, safety, and tolerability of a single dose of [14C]UMEC applied to either unoccluded axilla (UA), occluded axilla (OA), or occluded palm (OP) of healthy males. After 8 h the formulation was removed. [14C]UMEC plasma concentrations (Cp) were quantified by accelerator mass spectrometry. Occlusion increased systemic exposure by 3.8‐fold. Due to UMEC absorption‐limited pharmacokinetics, Cp data from the OA were combined with intravenous data from a phase I study. The data were described by a two‐compartment population model with sequential zero and first‐order absorption and linear elimination. Simulated systemic exposure following q.d. doses to axilla was similar to the exposure from the inhaled therapy, suggesting that systemic safety following dermal administration can be bridged to the inhaled program, and offering the potential for a reduced number of studies and/or subjects. PMID:27304394

Durability of adhesives in plywood

Treesearch

Robert H. Gillespie; Bryan H. River

1976-01-01

Seven different adhesives were evaluated for durability as plywood adhesives by exposing panels and shear-test specimens to weathering at the Madison exposure site for nearly 8 years. Wet-strength loss and wood-failure changes were measured as a function of exposure time. The method of exposure accelerated the degradation that would have resulted from exposure in most...

Comparative study of neurologic effects of nano-TiO2 versus SiO2 after direct intracerebral exposure in mice

NASA Astrophysics Data System (ADS)

Balvay, A.; Thieriet, N.; Lakhdar, L.; Bencsik, A.

2013-04-01

Titanium and silicon dioxide nanoparticles (TiO2 and SiO2 NPs) are now in daily use in many commercial products of which food, sunscreens, toothpastes or cosmetics. However, their effects on human body, especially on the central nervous system, are still unclear. The aim of this study was to determine whether direct exposition of the brain to TiO2 and SiO2 NPs results in alternations in nervous system function. C57Bl6 mice were exposed to 5 and 10 μg doses of TiO2 and SiO2 NPs through intracerebroventricular administration using a stereotaxic approach. Then the neurologic effects were investigated using motor performance parameters, measured on a rotarod at 20 rpm or at an accelerating rod (from 4 to 40 rpm). Before and after injection, motor activity is registered individually for each mouse exposed, once a week, for 8 weeks. Besides, a group of 3 mice is culled at 1, 2, 3, 4 and 8 weeks after exposure in order to study the time dependant effect on the histopathology of the brain (gliosis, inflammatory process...). Both rotarod tests (accelerating and at 20 rpm) showed that TiO2 and SiO2 NPs exposure could significantly impair the motor performances, even several weeks after initial acute exposure. The first examination of the brain histopathology revealed microglial activation. As it appeared to grow throughout the brain in a time dependant manner this suggests the induction of a long lasting neuroinflammation. These primary findings indicated that exposure to TiO2 and SiO2 NPs could possibly impair the locomotor ability and this deficit may be possibly attributed at least to an inflammatory process maintained till 8 weeks after exposure in the mouse brain. To fully investigate the neurotoxicological consequences of TiO2 and SiO2 NPs exposure, brain contents in these NPs will be also investigated as well as other alterations like neurotransmitter levels. These preliminary data already underline the necessity of more in vivo studies to better characterize TiO2 and SiO2 NPs exposure effects especially on human brain for long-term and low-dose treatment.

Influence of Chronic Exposure to Simulated Shift Work on Disease and Longevity in Disease-Prone Inbred Mice

PubMed Central

Toth, Linda A; Trammell, Rita A; Liberati, Teresa; Verhulst, Steve; Hart, Marcia L; Moskowitz, Jacob E; Franklin, Craig

2017-01-01

Shift work (SW) is viewed as a risk factor for the development of many serious health conditions, yet prospective studies that document such risks are rare. The current study addressed this void by testing the hypothesis that long-term exposure to repeated diurnal phase shifts, mimicking SW, will accelerate disease onset or death in inbred mice with genetic risk of developing cancer, diabetes, or autoimmune disease. The data indicate that 1) life-long exposure to simulated SW accelerates death in female cancer-prone AKR/J mice; 2) a significant proportion of male NON/ShiLtJ mice, which have impaired glucose tolerance but do not normally progress to type 2 diabetes, develop hyperglycemia, consistent with diabetes (that is, blood glucose 250 mg/dL or greater) after exposure to simulated SW for 8 wk; and 3) MRL/MpJ mice, which are prone to develop autoimmune disease, showed sex-related acceleration of disease development when exposed to SW as compared with mice maintained on a stable photocycle. Thus, long-term exposure to diurnal phase shifts that mimic SW reduces health or longevity in a wide variety of disease models. Our approach provides a simple way to assess the effect of chronic diurnal disruption in disease development in at-risk genotypes. PMID:28381312

Modeling of Blood Lead Levels in Astronauts Exposed to Lead from Microgravity-Accelerated Bone Loss

NASA Technical Reports Server (NTRS)

Garcia, H.; James, J.; Tsuji, J.

2014-01-01

Human exposure to lead has been associated with toxicity to multiple organ systems. Studies of various population groups with relatively low blood lead concentrations (<10 µg/dL) have indicated associations of blood lead level with lower cognitive test scores in children, later onset of puberty in girls, and increased blood pressure and cardiovascular mortality rates in adults. Cognitive effects are considered by regulatory agencies to be the most sensitive endpoint at low doses. Although 95% of the body burden of lead is stored in the bones, the adverse effects of lead correlate with the concentration of lead in the blood better than with that in the bones. NASA has found that prolonged exposure to microgravity during spaceflight results in a significant loss of bone minerals, the extent of which varies from individual to individual and from bone to bone, but generally averages about 0.5% per month. During such bone loss, lead that had been stored in bones would be released along with calcium. The effects on the concentration of lead in the blood (PbB) of various concentrations of lead in drinking water (PbW) and of lead released from bones due to accelerated osteoporosis in microgravity, as well as changes in exposure to environmental lead before, during, and after spaceflight were evaluated using a physiologically based pharmacokinetic (PBPK) model that incorporated exposure to environmental lead both on earth and in flight and included temporarily increased rates of osteoporosis during spaceflight.

Dose-response relation between exposure to two types of hand-arm vibration and sensorineural perception of vibration.

PubMed

Virokannas, H

1995-05-01

31 railway workers and 32 lumberjacks were examined to compare the dose-response relation between the exposure to two types of hand-arm vibration and the sensory disturbances in peripheral nerves as evaluated by the vibration perception thresholds (VPTs). Clinical examinations were carried out that included measurements of the VPTs, and electroneuromyography (ENMG), and an inquiry to confirm the use of vibrating tools. Diseases of the central nervous system and neuropathies were checked by inquiry and a clinical examination, diabetes was excluded by a blood sample analysis, and the subjects with carpal tunnel syndrome confirmed with ENMG were excluded from the study. Lifetime use of hand held tamping machines (railway workers) and chain saws (lumberjacks) had a significant correlation with the VPTs at frequencies from 32 to 500 Hz. The increase of the VPTs (250 Hz) in relation to use of vibrating tools was 1.8-fold higher on average in the whole group and 2.3-fold higher in the young (< 45) railway workers who had used hand held tamping machines, than in the corresponding groups of lumberjacks, who had used chain saws, whereas the frequency weighted acceleration of vibration in tamping machines was fourfold. There was a significant dose-response relation between the exposure to hand-arm vibration and the VPTs. The VPTs as a function of the frequency weighted acceleration of vibration and the exposure to vibration gave promising results for assessment of the risk of damage to sensory nerves induced by vibration.

Accelerated hematopoietic recovery with angiotensin-(1-7) after total body radiation.

PubMed

Rodgers, Kathleen E; Espinoza, Theresa; Roda, Norma; Meeks, Christopher J; Hill, Colin; Louie, Stan G; Dizerega, Gere S

2012-06-01

Angiotensin (1-7) [A(1-7)] is a component of the renin angiotensin system (RAS) that stimulates hematopoietic recovery after myelosuppression. In a Phase I/IIa clinical trial, thrombocytopenia after chemotherapy was reduced by A(1-7). In this study, the ability of A(1-7) to improve recovery after total body irradiation (TBI) is shown with specific attention to radiation-induced hematopoietic injury. Mice were exposed to TBI (doses of 2-7 Gray [Gy]) of cesium 137 gamma rays, followed by treatment with A(1-7), typical doses were 100-1000 μg/kg given once or once daily for a specified number of days depending on the study. Animals are injected subcutaneously via the nape of the neck with 0.1 ml drug in saline. The recovery of blood and bone marrow cells was determined. Effects of TBI and A(1-7) on survival and bleeding time was also evaluated. Daily administration of A(1-7) after radiation exposure improved survival (from 60% to 92-97%) and reduced bleeding time at day 30 after TBI. Further, A(1-7) increased early mixed progenitors (3- to 5-fold), megakaryocyte (2- to 3-fold), myeloid (3- to 6-fold) and erythroid (2- to 5-fold) progenitors in the bone marrow and reduced radiation-induced thrombocytopenia (RIT) (up to 2-fold). Reduction in the number of treatments to 3 per week also improved bone marrow recovery and reduced RIT. As emergency responder and healthcare systems in case of nuclear accident or/and terrorist attack may be overwhelmed, the consequence of delayed initiation of treatment was ascertained. Treatment with A(1-7) can be delayed up to 5 days and still be effective in the reduction of RIT or acceleration of bone marrow recovery. The data presented in this paper indicate that A(1-7) reduces the consequences of critical radiation exposure and can be initiated well after initial exposure with maximal effects on early responding hematopoietic progenitors when treatment is initiated 2 days after exposure and 5 days after exposure for the later responding progenitors and reduced thrombocytopenia. There was some effect of A(1-7) even when given days after radiation exposure.

Synthesis of published and unpublished corrosion data from long term tests of fasteners embedded in wood : calculation of corrosion rates and the effect of corrosion on lateral joint strength

Treesearch

Samuel L. Zelinka; Douglas R. Rammer

2011-01-01

In the past 5 years, several accelerated test methods have been developed to measure the corrosion of metals in contact with wood. It is desirable to contrast these accelerated results against those of long term exposure tests. While there have been several published long-term exposure tests performed on metals in treated wood, the data from these studies could not be...

Adaptations of the vestibular system to short and long-term exposures to altered gravity

NASA Astrophysics Data System (ADS)

Bruce, L. L.

2003-10-01

Long-term space flight creates unique environmental conditions to which the vestibular system must adapt for optimal survival of a given organism. The development and maintenance of vestibular connections are controlled by environmental gravitational stimulation as well as genetically controlled molecular interactions. This paper describes the effects of hypergravity on axonal growth and dendritic morphology, respectively. Two aspects of this vestibular adaptation are examined: (1) How does long-term exposure to hypergravity affect the development of vestibular axons? (2) How does short-term exposure to extremely rapid changes in gravity, such as those that occur during shuttle launch and landing, affect dendrites of the vestibulocerebellar system? To study the effects of longterm exposures to altered gravity, embryonic rats that developed in hypergravity were compared to microgravity-exposed and control rats. Examination of the vestibular projections from epithelia devoted to linear and angular acceleration revealed that the terminal fields segregate differently in rat embryos that gestated in each of the gravitational environments.To study the effects of short-term exposures to altered gravity, mice were exposed briefly to strong vestibular stimuli and the vestibulocerebellum was examined for any resulting morphological changes. My data show that these stimuli cause intense vestibular excitation of cerebellar Purkinje cells, which induce up-regulation of clathrin-mediated endocytosis and other morphological changes that are comparable to those seen in long-term depression. This system provides a basis for studying how the vestibular environment can modify cerebellar function, allowing animals to adapt to new environments.

The impact of intratracheally instilled carbon black on the cardiovascular system of rats: elevation of blood homocysteine and hyperactivity of platelets.

PubMed

Kim, Hwa; Oh, Seok-Jeong; Kwak, Hui-Chan; Kim, Jong-Kyu; Lim, Cheol-Hong; Yang, Jeong-Sun; Park, Kwangsik; Kim, Sang-Kyum; Lee, Moo-Yeol

2012-01-01

Carbon black (CB) is an industrial chemical with high potential for human exposure. Although the relationship between exposure to particulate matter (PM) and cardiovascular disease is well documented, the risk of adverse cardiovascular effects attributed to CB particles has not been clearly characterized. This study was performed to (1) investigate the effects of CB on cardiovascular system and (2) identify the target tissue or potential biomarkers. Carbon black with a distinct particle size, N330 (ultrafine particle) and N990 (fine particle), was intratracheally instilled into rats at a doses of 1, 3, or 10 mg/kg. Measurements of thrombotic activity and determination of plasma homocysteine levels, cardiac functionality, and inflammatory responses were conducted at 24-h and 1-wk time points. Exposure to N330 accelerated platelet-dependent blood clotting at 10 mg/kg, the highest exposure tested. Unexpectedly, both N330 and N990 led to prolongation of activated partial thromboplastin time (aPTT), whereas these CB particles failed to affect prothrombin time (PT). N990 produced a significant elevation in the level of plasma homocysteine, a well-established etiological factor in cardiovascular diseases. Both N330 and N990 induced apparent inflammation in the lungs; however, both particles failed to initiate systemic inflammation. Neither CB particle produced observable cardiac symptoms as detected by electrocardiography. Taken together, data show CB exposure enhanced the cardiovascular risk by inducing hyperhomocysteinemia and platelet hyperactivity, although these effects may be variable depending on particle size and exposure duration. Homocysteine may be a potential biomarker for cardiovascular toxicity following CB exposure.

Accelerated weathering of fire-retardant-treated wood for fire testing

Treesearch

Robert H. White

2009-01-01

Fire-retardant-treated products for exterior applications must be subjected to actual or accelerated weathering prior to fire testing. For fire-retardant-treated wood, the two accelerated weathering methods have been Method A and B of ASTM D 2898. The rain test is Method A of ASTM D 2898. Method B includes exposures to ultraviolet (UV) sunlamps in addition to water...

Titanium-Water Thermosyphon Gamma Radiation Exposure and Results

NASA Technical Reports Server (NTRS)

Sanzi, James, L.A; Jaworske, Donald, A.; Goodenow, Debra, A.

2012-01-01

Titanium-water thermosyphons are being considered for use in heat rejection systems for fission power systems. Their proximity to the nuclear reactor will result in some gamma irradiation. Noncondensable gas formation from radiation-induced breakdown of water over time may render portions of the thermosyphon condenser inoperable. A series of developmental thermosyphons were operated at nominal operating temperature under accelerated gamma irradiation, with exposures on the same order of magnitude as that expected in 8 years of heat rejection system operation. Temperature data were obtained during exposure at three locations on each thermosyphon: evaporator, condenser, and condenser end cap. Some noncondensable gas was evident; however, thermosyphon performance was not affected because the noncondensable gas was compressed into the fill tube region at the top of the thermosyphon, away from the heat rejecting fin. The trend appeared to be an increasing amount of noncondensable gas formation with increasing gamma irradiation dose. Hydrogen is thought to be the most likely candidate for the noncondensable gas and hydrogen is known to diffuse through grain boundaries. Post-exposure evaluation of one thermosyphon in a vacuum chamber and at temperature revealed that the noncondensable gas diffused out of the thermosyphon over a relatively short period of time. Further research shows a number of experimental and theoretical examples of radiolysis occurring through gamma radiation alone in pure water.

Accelerator skyshine: Tyger, tyger, burning bright

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stapleton, G.B.; O`Brien, K.; Thomas, R.H.

1992-06-01

Neutron skyshine is, in most cases, the dominant source of radiation exposure to the general public from operation of well-shielded, high-energy accelerators. To estimate this exposure, tabulated solutions of the transport of neutrons through the air are frequently used. In previous works on skyshine, these tabular data have been parameterized into simple empirical equations that are easy and fast to use but are limited to distances greater than a few hundred meters from the accelerator. Our current report has refined this earlier work by including more realistic assumptions of neutron differential energy spectrum and angular distribution. These improved calculations essentiallymore » endorse the earlier parameterizations but make possible reasonably accurate dose estimates much closer to the skyshine source than before.« less

Head impact exposure in youth football.

PubMed

Daniel, Ray W; Rowson, Steven; Duma, Stefan M

2012-04-01

The head impact exposure for athletes involved in football at the college and high school levels has been well documented; however, the head impact exposure of the youth population involved with football has yet to be investigated, despite its dramatically larger population. The objective of this study was to investigate the head impact exposure in youth football. Impacts were monitored using a custom 12 accelerometer array equipped inside the helmets of seven players aged 7-8 years old during each game and practice for an entire season. A total of 748 impacts were collected from the 7 participating players during the season, with an average of 107 impacts per player. Linear accelerations ranged from 10 to 100 g, and the rotational accelerations ranged from 52 to 7694 rad/s(2). The majority of the high level impacts occurred during practices, with 29 of the 38 impacts above 40 g occurring in practices. Although less frequent, youth football can produce high head accelerations in the range of concussion causing impacts measured in adults. In order to minimize these most severe head impacts, youth football practices should be modified to eliminate high impact drills that do not replicate the game situations.

Effects of working memory load and repeated scenario exposure on emergency braking performance.

PubMed

Engström, Johan; Aust, Mikael Ljung; Viström, Matias

2010-10-01

The objective of the present study was to examine the effect of working memory load on drivers' responses to a suddenly braking lead vehicle and whether this effect (if any) is moderated by repeated scenario exposure. Several experimental studies have found delayed braking responses to lead vehicle braking events during concurrent performance of nonvisual, working memory-loading tasks, such as hands-free phone conversation. However, the common use of repeated, and hence somewhat expected, braking events may undermine the generalizability of these results to naturalistic, unexpected, emergency braking scenarios. A critical lead vehicle braking scenario was implemented in a fixed-based simulator.The effects of working memory load and repeated scenario exposure on braking performance were examined. Brake response time was decomposed into accelerator pedal release time and accelerator-to-brake pedal movement time. Accelerator pedal release times were strongly reduced with repeated scenario exposure and were delayed by working memory load with a small but significant amount (178 ms).The two factors did not interact. There were no effects on accelerator-to-brake pedal movement time. The results suggest that effects of working memory load on response performance obtained from repeated critical lead vehicle braking scenarios may be validly generalized to real world unexpected events. The results have important implications for the interpretation of braking performance in experimental settings, in particular in the context of safety-related evaluation of in-vehicle information and communication technologies.

The implementation of physical safety system in bunker of the electron beam accelerator

NASA Astrophysics Data System (ADS)

Ahmad, M. A.; Hashim, S. A.; Ahmad, A.; Leo, K. W.; Chulan, R. M.; Dalim, Y.; Baijan, A. H.; Zain, M. F.; Ros, R. C.

2017-01-01

This paper describes the implementation of physical safety system for the new low energy electron beam (EB) accelerator installed at Block 43T Nuclear Malaysia. The low energy EB is a locally designed and developed with a target energy of 300 keV. The issues on radiation protection have been addressed by the installation of radiation shielding in the form of a bunker and installation radiation monitors. Additional precaution is needed to ensure that personnel are not exposed to radiation and other physical hazards. Unintentional access to the radiation room can cause serious hazard and hence safety features must be installed to prevent such events. In this work we design and built a control and monitoring system for the shielding door. The system provides signals to the EB control panel to allow or prevent operation. The design includes limit switches, key-activated switches and emergency stop button and surveillance camera. Entry procedure is also developed as written record and for information purposes. As a result, through this safety implementation human error will be prevented, increase alertness during operation and minimizing unnecessary radiation exposure.

Skyshine radiation resulting from 6 MV and 10 MV photon beams from a medical accelerator.

PubMed

Elder, Deirdre H; Harmon, Joseph F; Borak, Thomas B

2010-07-01

Skyshine radiation scattered in the atmosphere above a radiation therapy accelerator facility can result in measurable dose rates at locations near the facility on the ground and at roof level. A Reuter Stokes RSS-120 pressurized ion chamber was used to measure exposure rates in the vicinity of a Varian Trilogy Linear Accelerator at the Colorado State University Veterinary Medical Center. The linear accelerator was used to deliver bremsstrahlung photons from 6 MeV and 10 MeV electron beams with several combinations of field sizes and gantry angles. An equation for modeling skyshine radiation in the vicinity of medical accelerators was published by the National Council on Radiation Protection and Measurements in 2005. However, this model did not provide a good fit to the observed dose rates at ground level or on the roof. A more accurate method of estimating skyshine may be to measure the exposure rate of the radiation exiting the roof of the facility and to scale the results using the graphs presented in this paper.

Understanding How Kurtosis Is Transferred from Input Acceleration to Stress Response and Its Influence on Fatigue Llife

NASA Technical Reports Server (NTRS)

Kihm, Frederic; Rizzi, Stephen A.; Ferguson, Neil S.; Halfpenny, Andrew

2013-01-01

High cycle fatigue of metals typically occurs through long term exposure to time varying loads which, although modest in amplitude, give rise to microscopic cracks that can ultimately propagate to failure. The fatigue life of a component is primarily dependent on the stress amplitude response at critical failure locations. For most vibration tests, it is common to assume a Gaussian distribution of both the input acceleration and stress response. In real life, however, it is common to experience non-Gaussian acceleration input, and this can cause the response to be non-Gaussian. Examples of non-Gaussian loads include road irregularities such as potholes in the automotive world or turbulent boundary layer pressure fluctuations for the aerospace sector or more generally wind, wave or high amplitude acoustic loads. The paper first reviews some of the methods used to generate non-Gaussian excitation signals with a given power spectral density and kurtosis. The kurtosis of the response is examined once the signal is passed through a linear time invariant system. Finally an algorithm is presented that determines the output kurtosis based upon the input kurtosis, the input power spectral density and the frequency response function of the system. The algorithm is validated using numerical simulations. Direct applications of these results include improved fatigue life estimations and a method to accelerate shaker tests by generating high kurtosis, non-Gaussian drive signals.

A longitudinal study of vibration white finger, cold response of digital arteries, and measures of daily vibration exposure.

PubMed

Bovenzi, Massimo

2010-03-01

To investigate prospectively the relation between vibration-induced vascular disorders and measures of daily exposure to hand-transmitted vibration (HTV). Two hundred and forty-nine HTV workers and 138 control men of the same companies participated in a 3-year follow-up study. The diagnosis of vibration induced white finger (VWF) in the HTV workers and that of Raynaud's phenomenon in the controls was based on the medical history, the administration of color charts and the results of a cold test with measurement of finger systolic blood pressures. Vibration magnitudes from the tools were measured as r.m.s acceleration, frequency weighted according to international standard ISO 5349-1, and also unweighted over the frequency range 6.3-1,250 Hz. Daily vibration exposure was expressed in terms of daily exposure duration and frequency-weighted or unweighted r.m.s. acceleration normalized to a reference period of 8 h (Aw(8) or Auw(8), respectively). The incidence of VWF varied from 5 to 6% in the HTV workers versus 0-1.5% for Raynaud's phenomenon in the controls. After adjusting for potential confounders, Auw(8) gave better predictions of the incidence of VWF and the cold response of the digital arteries over time than Aw(8) or daily exposure duration. These findings were observed in the entire sample of HTV workers, in those with no VWF at the initial investigation, and in those with normal cold test results at baseline. The findings of this longitudinal study suggest that a measure of daily vibration exposure calculated from unweighted r.m.s. acceleration over the frequency range 6.3-1,250 Hz performs better for the prediction of vascular disorders in users of vibratory tools than a measure derived from r.m.s. acceleration frequency weighted according to ISO 5349-1. This study provides epidemiological evidence that more weight should be given to intermediate and high-frequency vibration for evaluating the severity of hand-transmitted vibration.

a Comparison of Evaluations and Assessments Obtained Using Alternative Standards for Predicting the Hazards of Whole-Body Vibration and Repeated Shocks

NASA Astrophysics Data System (ADS)

Lewis, C. H.; Griffin, M. J.

1998-08-01

There are three current standards that might be used to assess the vibration and shock transmitted by a vehicle seat with respect to possible effects on human health: ISO 2631/1 (1985), BS 6841 (1987) and ISO 2631-1 (1997). Evaluations have been performed on the seat accelerations measured in nine different transport environments (bus, car, mobile crane, fork-lift truck, tank, ambulance, power boat, inflatable boat, mountain bike) in conditions that might be considered severe. For each environment, limiting daily exposure durations were estimated by comparing the frequency weighted root mean square (i.e., r.m.s.) accelerations and the vibration dose values (i.e.,VDV), calculated according to each standard with the relevant exposure limits, action level and health guidance caution zones. Very different estimates of the limiting daily exposure duration can be obtained using the methods described in the three standards. Differences were observed due to variations in the shapes of the frequency weightings, the phase responses of the frequency weighting filters, the method of combining multi-axis vibration, the averaging method, and the assessment method. With the evaluated motions, differences in the shapes of the weighting filters results in up to about 31% difference in r.m.s. acceleration between the “old” and the “new” ISO standard and up to about 14% difference between BS 6841 and the “new” ISO 2631. There were correspondingly greater differences in the estimates of safe daily exposure durations. With three of the more severe motions there was a difference of more than 250% between estimated safe daily exposure durations based on r.m.s. acceleration and those based on fourth power vibration dose values. The vibration dose values provided the more cautious assessments of the limiting daily exposure duration.

Exposure to Carbon Ions Triggers Proinflammatory Signals and Changes in Homeostasis and Epidermal Tissue Organization to a Similar Extent as Photons

PubMed Central

Simoniello, Palma; Wiedemann, Julia; Zink, Joana; Thoennes, Eva; Stange, Maike; Layer, Paul G.; Kovacs, Maximilian; Podda, Maurizio; Durante, Marco; Fournier, Claudia

2016-01-01

The increasing application of charged particles in radiotherapy requires a deeper understanding of early and late side effects occurring in skin, which is exposed in all radiation treatments. We measured cellular and molecular changes related to the early inflammatory response of human skin irradiated with carbon ions, in particular cell death induction and changes in differentiation and proliferation of epidermal cells during the first days after exposure. Model systems for human skin from healthy donors of different complexity, i.e., keratinocytes, coculture of skin cells, 3D skin equivalents, and skin explants, were used to investigate the alterations induced by carbon ions (spread-out Bragg peak, dose-averaged LET 100 keV/μm) in comparison to X-ray and UV-B exposure. After exposure to ionizing radiation, in none of the model systems, apoptosis/necrosis was observed. Carbon ions triggered inflammatory signaling and accelerated differentiation of keratinocytes to a similar extent as X-rays at the same doses. High doses of carbon ions were more effective than X-rays in reducing proliferation and inducing abnormal differentiation. In contrast, changes identified following low-dose exposure (≤0.5 Gy) were induced more effectively after X-ray exposure, i.e., enhanced proliferation and change in the polarity of basal cells. PMID:26779439

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, J.; Elmore, R.; Kennedy, C.

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 "Solarmore » 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.« less

Six-Degree-of-Freedom Sensor Fish Design and Instrumentation

PubMed Central

Deng, Zhiqun; Carlson, Thomas J.; Duncan, Joanne P.; Richmond, Marshall C.

2007-01-01

Fish passing through dams may be injured or killed despite advances in turbine design, project operations and other fish bypass systems. The six-degree-of-freedom (6DOF) Sensor Fish device is an autonomous sensor package that characterizes the physical conditions and physical stresses to which fish are exposed when they pass through complex hydraulic environments. It has been used to identify the locations and operations where conditions are severe enough to injure or kill fish. During the design process, a set of governing equations of motion for the Sensor Fish was derived and simulated to understand the design implications of instrument selection and placement within the body of the device. The Sensor Fish package includes three rotation sensors, three acceleration sensors, a pressure sensor, and a temperature sensor with a sampling frequency of 2,000 Hz. Its housing is constructed of clear polycarbonate plastic. It is 24.5 mm in diameter and 90 mm in length and weighs about 43 g, similar to the size and density of a yearling salmon smolt. The accuracy of the pressure sensor was determined to be within 0.2 psi. In laboratory acceptance tests, the relative errors of both the linear acceleration and angular velocity measurements were determined to be less than 5%. An exposure is defined as a significant event when the acceleration reaches predefined thresholds. Based on the different characteristic of acceleration and rotation velocities, the exposure event is categorized as either a collision between the Sensor Fish and a solid structure or shear caused by turbulence. Since its development in 2005, the 6DOF Sensor Fish has been deployed successfully at many major dams in the United States. PMID:28903301

The Impact of Accelerated Right Prefrontal High-Frequency Repetitive Transcranial Magnetic Stimulation (rTMS) on Cue-Reactivity: An fMRI Study on Craving in Recently Detoxified Alcohol-Dependent Patients

PubMed Central

Herremans, Sarah C.; Van Schuerbeek, Peter; De Raedt, Rudi; Matthys, Frieda; Buyl, Ronald; De Mey, Johan; Baeken, Chris

2015-01-01

In alcohol-dependent patients craving is a difficult-to-treat phenomenon. It has been suggested that high-frequency (HF) repetitive transcranial magnetic stimulation (rTMS) may have beneficial effects. However, exactly how this application exerts its effect on the underlying craving neurocircuit is currently unclear. In an effort to induce alcohol craving and to maximize detection of HF-rTMS effects to cue-induced alcohol craving, patients were exposed to a block and event-related alcohol cue-reactivity paradigm while being scanned with fMRI. Hence, we assessed the effect of right dorsolateral prefrontal cortex (DLPFC) stimulation on cue-induced and general alcohol craving, and the related craving neurocircuit. Twenty-six recently detoxified alcohol-dependent patients were included. First, we evaluated the impact of one sham-controlled stimulation session. Second, we examined the effect of accelerated right DLPFC HF-rTMS treatment: here patients received 15 sessions in an open label accelerated design, spread over 4 consecutive days. General craving significantly decreased after 15 active HF-rTMS sessions. However, cue-induced alcohol craving was not altered. Our brain imaging results did not show that the cue-exposure affected the underlying craving neurocircuit after both one and fifteen active HF-rTMS sessions. Yet, brain activation changes after one and 15 HF-rTMS sessions, respectively, were observed in regions associated with the extended reward system and the default mode network, but only during the presentation of the event-related paradigm. Our findings indicate that accelerated HF-rTMS applied to the right DLPFC does not manifestly affect the craving neurocircuit during an alcohol-related cue-exposure, but instead it may influence the attentional network. PMID:26295336

Free-electron laser emission architecture impact on extreme ultraviolet lithography

NASA Astrophysics Data System (ADS)

Hosler, Erik R.; Wood, Obert R.; Barletta, William A.

2017-10-01

Laser-produced plasma (LPP) EUV sources have demonstrated ˜125 W at customer sites, establishing confidence in EUV lithography (EUVL) as a viable manufacturing technology. However, for extension to the 3-nm technology node and beyond, existing scanner/source technology must enable higher-NA imaging systems (requiring increased resist dose and providing half-field exposures) and/or EUV multipatterning (requiring increased wafer throughput proportional to the number of exposure passes). Both development paths will require a substantial increase in EUV source power to maintain the economic viability of the technology, creating an opportunity for free-electron laser (FEL) EUV sources. FEL-based EUV sources offer an economic, high-power/single-source alternative to LPP EUV sources. Should FELs become the preferred next-generation EUV source, the choice of FEL emission architecture will greatly affect its operational stability and overall capability. A near-term industrialized FEL is expected to utilize one of the following three existing emission architectures: (1) self-amplified spontaneous emission, (2) regenerative amplifier, or (3) self-seeding. Model accelerator parameters are put forward to evaluate the impact of emission architecture on FEL output. Then, variations in the parameter space are applied to assess the potential impact to lithography operations, thereby establishing component sensitivity. The operating range of various accelerator components is discussed based on current accelerator performance demonstrated at various scientific user facilities. Finally, comparison of the performance between the model accelerator parameters and the variation in parameter space provides a means to evaluate the potential emission architectures. A scorecard is presented to facilitate this evaluation and provides a framework for future FEL design and enablement for EUVL applications.

Seismic hazard in the Istanbul metropolitan area: A preliminary re-evaluation

USGS Publications Warehouse

Kalkan, E.; Gulkan, Polat; Ozturk, N.Y.; Celebi, M.

2008-01-01

In 1999, two destructive earthquakes (M7.4 Kocaeli and M7.2 Duzce) occurred in the north west of Turkey and resulted in major stress-drops on the western segment of the North Anatolian Fault system where it continues under the Marmara Sea. These undersea fault segments were recently explored using bathymetric and reflection surveys. These recent findings helped to reshape the seismotectonic environment of the Marmara basin, which is a perplexing tectonic domain. Based on collected new information, seismic hazard of the Marmara region, particularly Istanbul Metropolitan Area and its vicinity, were re-examined using a probabilistic approach. Two seismic source and alternate recurrence models combined with various indigenous and foreign attenuation relationships were adapted within a logic tree formulation to quantify and project the regional exposure on a set of hazard maps. The hazard maps show the peak horizontal ground acceleration and spectral acceleration at 1.0 s. These acceleration levels were computed for 2 and 10 % probabilities of transcendence in 50 years.

Treatment of Diabetic Foot Ulcers through Systemic Effects of Extremely Low Frequency Electromagnetic Fields

NASA Astrophysics Data System (ADS)

Trejo-Núñez, A. D.; Pérez-Chávez, F.; García-Sánchez, C.; Serrano-Luna, G.; Cañendo-Dorantes, L.

2008-08-01

This study was designed to, investigate the healing effects of extremely low frequency electromagnetic fields (ELF-EMF) on diabetic foot ulcers and test two different exposure systems aimed at reducing the ELF-EMF exposure time of patients. In the first system the ELF-EMF were applied to the arm where only 3% of the total blood volume/min circulates at any given time. In the second system the ELF-EMF were applied to the thorax where more than 100% of the total blood volume/minute circulates at any given time. Twenty-six diabetic patients, with superficial neuropathic ulcers unresponsive to medical treatment were included in this preliminary report. In the first group (17 patients), the arm was exposed two hours twice a week to a extremely low frequency electromagnetic field of 0.45-0.9 mTrms, 120 Hz generated inside a solenoid coil of 10.1 cm by 20.5 cm long. In the second group the thorax of 7 patients was exposed 25 minutes twice a week to an electromagnetic field of 0.4-0.85 mTrms, 120 Hz generated in the center of a squared quasi-Helmholtz coil 52 cm by side. One patient was assigned to a placebo configuration of each exposure system with identical appearance as the active equipment but without magnetic field. Patients with deep ulcers, infected ulcers, cancer, or auto-immune disease were excluded. These preliminary results showed that the two exposure systems accelerate the healing process of neuropathic ulcers. Complete healing of the ulcer had a median duration of 90 days in both exposure systems. Therefore thorax exposure where more blood is exposed to ELF-EMF per unit of time was able to reduce 4.8 times the patient treatment time. In those patients assigned to the placebo equipment no healing effects were observed. This study will continue with a parallel, double blind placebo controlled protocol.

Sustained Accelerated Idioventricular Rhythm in a Centrifuge-Simulated Suborbital Spaceflight.

PubMed

Suresh, Rahul; Blue, Rebecca S; Mathers, Charles; Castleberry, Tarah L; Vanderploeg, James M

2017-08-01

Hypergravitational exposures during human centrifugation are known to provoke dysrhythmias, including sinus dysrhythmias/tachycardias, premature atrial/ventricular contractions, and even atrial fibrillations or flutter patterns. However, events are generally short-lived and resolve rapidly after cessation of acceleration. This case report describes a prolonged ectopic ventricular rhythm in response to high G exposure. A previously healthy 30-yr-old man voluntarily participated in centrifuge trials as a part of a larger study, experiencing a total of 7 centrifuge runs over 48 h. Day 1 consisted of two +Gz runs (peak +3.5 Gz, run 2) and two +Gx runs (peak +6.0 Gx, run 4). Day 2 consisted of three runs approximating suborbital spaceflight profiles (combined +Gx and +Gz). Hemodynamic data collected included blood pressure, heart rate, and continuous three-lead electrocardiogram. Following the final acceleration exposure of the last Day 2 run (peak +4.5 Gx and +4.0 Gz combined, resultant +6.0 G), during a period of idle resting centrifuge activity (resultant vector +1.4 G), the subject demonstrated a marked change in his three-lead electrocardiogram from normal sinus rhythm to a wide-complex ectopic ventricular rhythm at a rate of 91-95 bpm, consistent with an accelerated idioventricular rhythm (AIVR). This rhythm was sustained for 2 m, 24 s before reversion to normal sinus. The subject reported no adverse symptoms during this time. While prolonged, the dysrhythmia was asymptomatic and self-limited. AIVR is likely a physiological response to acceleration and can be managed conservatively. Vigilance is needed to ensure that AIVR is correctly distinguished from other, malignant rhythms to avoid inappropriate treatment and negative operational impacts.Suresh R, Blue RS, Mathers C, Castleberry TL, Vanderploeg JM. Sustained accelerated idioventricular rhythm in a centrifuge-simulated suborbital spaceflight. Aerosp Med Hum Perform. 2017; 88(8):789-793.

Depth profiling of mechanical degradation of PV backsheets after UV exposure

NASA Astrophysics Data System (ADS)

Gu, Xiaohong; Krommenhoek, Peter J.; Lin, Chiao-Chi; Yu, Li-Chieh; Nguyen, Tinh; Watson, Stephanie S.

2015-09-01

Polymeric multilayer backsheets protect the photovoltaic modules from damage of moisture and ultraviolet (UV) while providing electrical insulation. Due to the multilayer structures, the properties of the inner layers of the backsheets, including their interfaces, during weathering are not well known. In this study, a commercial type of PPE (polyethylene terephthalate (PET)/PET/ethylene vinyl acetate (EVA)) backsheet films was selected as a model system for a depth profiling study of mechanical properties of a backsheet film during UV exposure. The NIST SPHERE (Simulated Photodegradation via High Energy Radiant Exposure) was used for the accelerated laboratory exposure of the materials with UV at 85°C and two relative humidities (RH) of 5 % (dry) and 60 % (humid). Cryomicrotomy was used to obtain cross-sectional PPE samples. Mechanical depth profiling of the cross-sections of aged and unaged samples was conducted by nanoindentation, and a peak-force based quantitative nanomechanical atomic force microscopy (QNM-AFM) mapping techniquewas used to investigate the microstructure and adhesion properties of the adhesive tie layers. The nanoindentation results show the stiffening of the elastic modulus in the PET outer and pigmented EVA layers. From QNM-AFM, the microstructures and adhesion properties of the adhesive layers between PET outer and core layers and between PET core and EVA inner layers are revealed and found to degrade significantly after aging under humidity environment. The results from mechanical depth profiling of the PPE backsheet are further related to the previous chemical depth profiling of the same material, providing new insights into the effects of accelerated UV and humidity on the degradation of multilayer backsheet.

Dose-response relation between exposure to two types of hand-arm vibration and sensorineural perception of vibration.

PubMed Central

Virokannas, H

1995-01-01

OBJECTIVES--31 railway workers and 32 lumberjacks were examined to compare the dose-response relation between the exposure to two types of hand-arm vibration and the sensory disturbances in peripheral nerves as evaluated by the vibration perception thresholds (VPTs). METHODS--Clinical examinations were carried out that included measurements of the VPTs, and electroneuromyography (ENMG), and an inquiry to confirm the use of vibrating tools. Diseases of the central nervous system and neuropathies were checked by inquiry and a clinical examination, diabetes was excluded by a blood sample analysis, and the subjects with carpal tunnel syndrome confirmed with ENMG were excluded from the study. RESULTS--Lifetime use of hand held tamping machines (railway workers) and chain saws (lumberjacks) had a significant correlation with the VPTs at frequencies from 32 to 500 Hz. The increase of the VPTs (250 Hz) in relation to use of vibrating tools was 1.8-fold higher on average in the whole group and 2.3-fold higher in the young (< 45) railway workers who had used hand held tamping machines, than in the corresponding groups of lumberjacks, who had used chain saws, whereas the frequency weighted acceleration of vibration in tamping machines was fourfold. CONCLUSION--There was a significant dose-response relation between the exposure to hand-arm vibration and the VPTs. The VPTs as a function of the frequency weighted acceleration of vibration and the exposure to vibration gave promising results for assessment of the risk of damage to sensory nerves induced by vibration. PMID:7795756

Improving tritium exposure reconstructions using accelerator mass spectrometry

PubMed Central

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

2010-01-01

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

Predictive models of poly(ethylene-terephthalate) film degradation under multi-factor accelerated weathering exposures

PubMed Central

Ngendahimana, David K.; Fagerholm, Cara L.; Sun, Jiayang; Bruckman, Laura S.

2017-01-01

Accelerated weathering exposures were performed on poly(ethylene-terephthalate) (PET) films. Longitudinal multi-level predictive models as a function of PET grades and exposure types were developed for the change in yellowness index (YI) and haze (%). Exposures with similar change in YI were modeled using a linear fixed-effects modeling approach. Due to the complex nature of haze formation, measurement uncertainty, and the differences in the samples’ responses, the change in haze (%) depended on individual samples’ responses and a linear mixed-effects modeling approach was used. When compared to fixed-effects models, the addition of random effects in the haze formation models significantly increased the variance explained. For both modeling approaches, diagnostic plots confirmed independence and homogeneity with normally distributed residual errors. Predictive R2 values for true prediction error and predictive power of the models demonstrated that the models were not subject to over-fitting. These models enable prediction under pre-defined exposure conditions for a given exposure time (or photo-dosage in case of UV light exposure). PET degradation under cyclic exposures combining UV light and condensing humidity is caused by photolytic and hydrolytic mechanisms causing yellowing and haze formation. Quantitative knowledge of these degradation pathways enable cross-correlation of these lab-based exposures with real-world conditions for service life prediction. PMID:28498875

Measuring Optical Component Radiation Damage

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wenzl, Derek; Tesarek, Richard

2017-08-01

Scintillator based detectors are used to monitor beam losses in the Fermilab accelerator complex. These detectors are approximately 500 times faster than traditional ionization chamber loss monitors and can see beam losses 20 nanoseconds apart. These fast loss monitors are used in areas of the accelerator known to be sources of heavy beam loss and as such, are exposed to high doses of radiation. Over time, radiation exposure reduces the ability of optical components to transmit light by darkening the material. The most dramatic effects are seen in the optical cement and light guide materials comprising the detector. We exploremore » this darkening effect by measuring the transmittance spectra of the detector materials for varying irradiation exposures. Presented here, are the optical transmittance spectra for a variety of radiation exposures and optical materials. The data has revealed an epoxy which withstands exposure far better than traditional optical cements.« less

Recent Improvements of Particle and Heavy Ion Transport code System: PHITS

NASA Astrophysics Data System (ADS)

Sato, Tatsuhiko; Niita, Koji; Iwamoto, Yosuke; Hashimoto, Shintaro; Ogawa, Tatsuhiko; Furuta, Takuya; Abe, Shin-ichiro; Kai, Takeshi; Matsuda, Norihiro; Okumura, Keisuke; Kai, Tetsuya; Iwase, Hiroshi; Sihver, Lembit

2017-09-01

The Particle and Heavy Ion Transport code System, PHITS, has been developed under the collaboration of several research institutes in Japan and Europe. This system can simulate the transport of most particles with energy levels up to 1 TeV (per nucleon for ion) using different nuclear reaction models and data libraries. More than 2,500 registered researchers and technicians have used this system for various applications such as accelerator design, radiation shielding and protection, medical physics, and space- and geo-sciences. This paper summarizes the physics models and functions recently implemented in PHITS, between versions 2.52 and 2.88, especially those related to source generation useful for simulating brachytherapy and internal exposures of radioisotopes.

Space Environmental Effects on Thermal Control Coatings

NASA Technical Reports Server (NTRS)

OBrien, Susan K.; Workman, Gary L.

1997-01-01

The study of long term near ultra-violet (NUV) effects in a vacuum atmosphere, is a crucial element for space applications. NUV radiation causes significant changes in the reflectance of many coatings and types of materials. An ultra high vacuum NUV system was assembled in order to investigate various coatings and materials in this hostile environment. The vacuum is an ion pump that maintains a minimum vacuum in the mid 10(exp -9) range. The system has a base pressure of 10(exp -9) torr and this base pressure is maintained with the ion pump. The NUV exposure was maintained at 2-3 suns which allows accelerated NUV exposure without overheating the samples. The goal of this test was to maintain an intensity of 3.4 x 10(exp -2) Watts/cm(exp 2) which equals 2.9 NUV suns. An NUV sun is defined as 1.16 Watts/cm(exp 2) integrated over wavelength of 200-400 nanometers.

Assessing combined exposures of whole-body vibration and awkward posture--further results from application of a simultaneous field measurement methodology.

PubMed

Raffler, Nastaran; Hermanns, Ingo; Sayn, Detlef; Göres, Benno; Ellegast, Rolf; Rissler, Jörg

2010-01-01

The drivers of ten vehicles (tram, helicopter, saloon car, van, forklift, two mobile excavators, wheel loader, tractor, elevating platform truck) were studied with regard to the combined exposures of whole-body vibration and awkward posture during occupational tasks. Seven degrees of freedom (DOFs), or body angles, were recorded as a function of time by means of the CUELA measuring system (Computer-assisted registration and long-term analysis of musculoskeletal workloads) for the purpose of posture assessment. The vibrational exposure is expressed as the vector sum of the frequency-weighted accelerations in the three Cartesian coordinates; these were recorded simultaneously with the posture measurement. Based upon the percentage of working time spent under different workloads, a scheme is proposed for classification of the two exposures into three categories. In addition, a risk of adverse health effects classified as low, possible or high can be assigned to the combination of the two exposures. With regard to posture, the most severe exposure was measured for the drivers of the wheel loader and for the tractor driver, whereas the lowest exposure was measured for the helicopter pilots and van drivers. With regard to the combination of whole-body and posture exposures, the tractor driver and the elevating platform truck driver exhibited the highest workloads.

Laser-based irradiation apparatus and methods for monitoring the dose-rate response of semiconductor devices

DOEpatents

Horn, Kevin M [Albuquerque, NM

2006-03-28

A scanned, pulsed, focused laser irradiation apparatus can measure and image the photocurrent collection resulting from a dose-rate equivalent exposure to infrared laser light across an entire silicon die. Comparisons of dose-rate response images or time-delay images from before, during, and after accelerated aging of a device, or from periodic sampling of devices from fielded operational systems allows precise identification of those specific age-affected circuit structures within a device that merit further quantitative analysis with targeted materials or electrical testing techniques. Another embodiment of the invention comprises a broad-beam, dose rate-equivalent exposure apparatus. The broad-beam laser irradiation apparatus can determine if aging has affected the device's overall functionality. This embodiment can be combined with the synchronized introduction of external electrical transients into a device under test to simulate the electrical effects of the surrounding circuitry's response to a radiation exposure.

Football Players' Head-Impact Exposure After Limiting of Full-Contact Practices.

PubMed

Broglio, Steven P; Williams, Richelle M; O'Connor, Kathryn L; Goldstick, Jason

2016-07-01

Sporting organizations limit full-contact football practices to reduce concussion risk and based on speculation that repeated head impacts may result in long-term neurodegeneration. To directly compare head-impact exposure in high school football players before and after a statewide restriction on full-contact practices. Cross-sectional study. High school football field. Participants were varsity football athletes from a single high school. Before the rule change, 26 athletes (age = 16.2 ± 0.8 years, height = 179.6 ± 6.4 cm, weight = 81.9 ± 13.1 kg) participated. After the rule change, 24 athletes (age = 15.9 ± 0.8 years, height = 178.3 ± 6.5 cm, weight = 76.2 ± 11.6 kg) participated. Nine athletes participated in both years of the investigation. Head-impact exposure was monitored using the Head Impact Telemetry System while the athletes participated in football games and practices in the seasons before and after the rule change. Head-impact frequency, location, and magnitude (ie, linear acceleration, rotational acceleration, and Head Impact Telemetry severity profile [HITsp], respectively) were measured. A total of 15 398 impacts (592 impacts per player per season) were captured before the rule change and 8269 impacts (345 impacts per player per season) after the change. An average 42% decline in impact exposure occurred across all players, with practice-exposure declines occurring among linemen (46% decline); receivers, cornerbacks, and safeties (41% decline); and tight ends, running backs (including fullbacks), and linebackers (39% decline). Impact magnitudes remained largely unchanged between the years. A rule change limiting full-contact high school football practices appears to have been effective in reducing head-impact exposure across all players, with the largest reduction occurring among linemen. This finding is likely associated with the rule modification, particularly because the coaching staff and offensive scheme remained consistent, yet how this reduction influences concussion risk and long-term cognitive health remains unknown.

In vivo Microscale Measurements of Light and Photosynthesis during Coral Bleaching: Evidence for the Optical Feedback Loop?

PubMed Central

Wangpraseurt, Daniel; Holm, Jacob B.; Larkum, Anthony W. D.; Pernice, Mathieu; Ralph, Peter J.; Suggett, David J.; Kühl, Michael

2017-01-01

Climate change-related coral bleaching, i.e., the visible loss of zooxanthellae from the coral host, is increasing in frequency and extent and presents a major threat to coral reefs globally. Coral bleaching has been proposed to involve accelerating light stress of their microalgal endosymbionts via a positive feedback loop of photodamage, symbiont expulsion and excess in vivo light exposure. To test this hypothesis, we used light and O2 microsensors to characterize in vivo light exposure and photosynthesis of Symbiodinium during a thermal stress experiment. We created tissue areas with different densities of Symbiodinium cells in order to understand the optical properties and light microenvironment of corals during bleaching. Our results showed that in bleached Pocillopora damicornis corals, Symbiodinium light exposure was up to fivefold enhanced relative to healthy corals, and the relationship between symbiont loss and light enhancement was well-described by a power-law function. Cell-specific rates of Symbiodinium gross photosynthesis and light respiration were enhanced in bleached P. damicornis compared to healthy corals, while areal rates of net photosynthesis decreased. Symbiodinium light exposure in Favites sp. revealed the presence of low light microniches in bleached coral tissues, suggesting that light scattering in thick coral tissues can enable photoprotection of cryptic symbionts. Our study provides evidence for the acceleration of in vivo light exposure during coral bleaching but this optical feedback mechanism differs between coral hosts. Enhanced photosynthesis in relation to accelerating light exposure shows that coral microscale optics exerts a key role on coral photophysiology and the subsequent degree of radiative stress during coral bleaching. PMID:28174567

In vivo Microscale Measurements of Light and Photosynthesis during Coral Bleaching: Evidence for the Optical Feedback Loop?

PubMed

Wangpraseurt, Daniel; Holm, Jacob B; Larkum, Anthony W D; Pernice, Mathieu; Ralph, Peter J; Suggett, David J; Kühl, Michael

2017-01-01

Climate change-related coral bleaching, i.e., the visible loss of zooxanthellae from the coral host, is increasing in frequency and extent and presents a major threat to coral reefs globally. Coral bleaching has been proposed to involve accelerating light stress of their microalgal endosymbionts via a positive feedback loop of photodamage, symbiont expulsion and excess in vivo light exposure. To test this hypothesis, we used light and O 2 microsensors to characterize in vivo light exposure and photosynthesis of Symbiodinium during a thermal stress experiment. We created tissue areas with different densities of Symbiodinium cells in order to understand the optical properties and light microenvironment of corals during bleaching. Our results showed that in bleached Pocillopora damicornis corals, Symbiodinium light exposure was up to fivefold enhanced relative to healthy corals, and the relationship between symbiont loss and light enhancement was well-described by a power-law function. Cell-specific rates of Symbiodinium gross photosynthesis and light respiration were enhanced in bleached P. damicornis compared to healthy corals, while areal rates of net photosynthesis decreased. Symbiodinium light exposure in Favites sp. revealed the presence of low light microniches in bleached coral tissues, suggesting that light scattering in thick coral tissues can enable photoprotection of cryptic symbionts. Our study provides evidence for the acceleration of in vivo light exposure during coral bleaching but this optical feedback mechanism differs between coral hosts. Enhanced photosynthesis in relation to accelerating light exposure shows that coral microscale optics exerts a key role on coral photophysiology and the subsequent degree of radiative stress during coral bleaching.

Pediatric respiratory and systemic effects of chronic air pollution exposure: nose, lung, heart, and brain pathology.

PubMed

Calderón-Garcidueñas, Lilian; Franco-Lira, Maricela; Torres-Jardón, Ricardo; Henriquez-Roldán, Carlos; Barragán-Mejía, Gerardo; Valencia-Salazar, Gildardo; González-Maciel, Angelica; Reynoso-Robles, Rafael; Villarreal-Calderón, Rafael; Reed, William

2007-01-01

Exposures to particulate matter and gaseous air pollutants have been associated with respiratory tract inflammation, disruption of the nasal respiratory and olfactory barriers, systemic inflammation, production of mediators of inflammation capable of reaching the brain and systemic circulation of particulate matter. Mexico City (MC) residents are exposed to significant amounts of ozone, particulate matter and associated lipopolysaccharides. MC dogs exhibit brain inflammation and an acceleration of Alzheimer's-like pathology, suggesting that the brain is adversely affected by air pollutants. MC children, adolescents and adults have a significant upregulation of cyclooxygenase-2 (COX2) and interleukin-1beta (IL-1beta) in olfactory bulb and frontal cortex, as well as neuronal and astrocytic accumulation of the 42 amino acid form of beta -amyloid peptide (Abeta 42), including diffuse amyloid plaques in frontal cortex. The pathogenesis of Alzheimer's disease (AD) is characterized by brain inflammation and the accumulation of Abeta 42, which precede the appearance of neuritic plaques and neurofibrillary tangles, the pathological hallmarks of AD. Our findings of nasal barrier disruption, systemic inflammation, and the upregulation of COX2 and IL-1beta expression and Abeta 42 accumulation in brain suggests that sustained exposures to significant concentrations of air pollutants such as particulate matter could be a risk factor for AD and other neurodegenerative diseases.

Photonuclear-based Detection of Nuclear Smuggling in Cargo Containers

NASA Astrophysics Data System (ADS)

Jones, J. L.; Haskell, K. J.; Hoggan, J. M.; Norman, D. R.; Yoon, W. Y.

2003-08-01

The Idaho National Engineering and Environmental Laboratory (INEEL) and the Los Alamos National Laboratory (LANL) have performed experiments in La Honda, California and at the Idaho Accelerator Center in Pocatello, Idaho to assess and develop a photonuclear-based detection system for shielded nuclear materials in cargo containers. The detection system, measuring photonuclear-related neutron emissions, is planned for integration with the ARACOR Eagle Cargo Container Inspection System (Sunnyvale, CA). The Eagle Inspection system uses a nominal 6-MeV electron accelerator and operates with safe radiation exposure limits to both container stowaways and to its operators. The INEEL has fabricated custom-built, helium-3-based, neutron detectors for this inspection application and is performing an experimental application assessment. Because the Eagle Inspection system could not be moved to LANL where special nuclear material was available, the response of the Eagle had to be determined indirectly so as to support the development and testing of the detection system. Experiments in California have successfully matched the delayed neutron emission performance of the ARACOR Eagle with that of the transportable INEEL electron accelerator (i.e., the Varitron) and are reported here. A demonstration test is planned at LANL using the Varitron and shielded special nuclear materials within a cargo container. Detector results are providing very useful information regarding the challenges of delayed neutron counting near the photofission threshold energy of 5.5 - 6.0 MeV, are identifying the possible utilization of prompt neutron emissions to allow enhanced signal-to-noise measurements, and are showing the overall benefits of using higher electron beam energies.

Accelerated Dynamic Corrosion Test Method Development

DTIC Science & Technology

test method has poor correlation to outdoor exposures, particularly for non-chromate primers. As a result, more realistic cyclic environmental...exposures have been developed to more closely resemble actual atmospheric corrosion damage. Several existing tests correlate well with the outdoor performance

Noise and hand-arm vibration exposure in relation to the risk of hearing loss.

PubMed

Pettersson, Hans; Burström, Lage; Hagberg, Mats; Lundström, Ronnie; Nilsson, Tohr

2012-01-01

The aim of this study was to examine the possible association of combined exposure of noise and hand-arm vibration (HAV) and the risk of noise-induced hearing loss. Workers in a heavy engineering industry were part of a dynamic cohort. Of these workers, 189 had HAV exposure, and their age and hearing status were recorded in the same year and were, therefore, included in the analysis. Data on HAV duration and acceleration was gathered through questionnaires, observations, and measurements. All available audiograms were categorized into normal and hearing loss. The first exposure variable included the lifetime HAV exposure. The lifetime HAV exposure was multiplied by the acceleration of HAV for the second and third exposure variable. Logistic regression using the Generalized Estimation Equations method was chosen to analyze the data to account for the repeated measurements. The analysis was performed with both continuous exposure variables and with exposure variables grouped into exposure quartiles with hearing loss as an outcome and age as a covariate. With continuous exposure variables, the odds ratio (OR) with a 95% confidence interval (CI) for hearing loss was equal to or greater than one for all exposure variables. When the exposure variables were grouped into quartiles, the OR with a 95% CI was greater than one at the third and fourth quartile. The results show that working with vibrating machines in an environment with noise exposure increases the risk of hearing loss, supporting an association between exposure to noise and HAV, and the noise-induced hearing loss.

A prospective cohort study of exposure-response relationship for vibration-induced white finger.

PubMed

Bovenzi, M

2010-01-01

To investigate prospectively the relation between vibration-induced white finger (VWF) and measures of cumulative (lifetime) exposure to hand-transmitted vibration (HTV). Two hundred and forty-nine HTV workers and 138 control men of the same companies participated in a 3-year follow-up study. The diagnosis of VWF (Raynaud's phenomenon in the controls) was based on the medical history, the administration of colour charts and the results of a cold test. Tool vibration magnitudes were expressed as root-mean-square (r.m.s.) acceleration, frequency-weighted according to international standard ISO 5349-1 and also unweighted over the frequency range 6.3-1250 Hz. From the vibration magnitudes and exposure durations, alternative measures of cumulative vibration dose were calculated for each HTV worker, according to the expression: dose = Sigmaa(i)(m)t(i), where a(i) is the acceleration magnitude on tool i, t(i) is the lifetime exposure duration (hours) for tool i, and m = 0, 1, 2 or 4. The incidence of VWF varied from 5 to 6% in the HTV workers versus 0 to 1.5% for Raynaud's phenomenon in the controls. After adjusting for potential confounders, measures of cumulative vibration dose derived from total operating hours and high powers of unweighted acceleration (ie, , with m>1) gave better predictions of the occurrence of VWF than dose measures calculated from frequency-weighted acceleration (ie, ). These findings were observed in the entire sample of HTV workers, in those with no VWF at the initial investigation, and in those with normal cold test results at baseline. This prospective cohort study suggests that measures of cumulative vibration doses constructed from unweighted r.m.s. acceleration perform better for the prediction of VWF than dose measures calculated according to the recommendations of current standards. These findings should contribute to the improvement of the ISO frequency weighting for evaluating the severity of hand-transmitted vibration.

Explosive and pyrotechnic aging demonstration

NASA Technical Reports Server (NTRS)

Rouch, L. L., Jr.; Maycock, J. N.

1976-01-01

The survivability was experimentally verified of fine selected explosive and pyrotechnic propellant materials when subjected to sterilization, and prolonged exposure to space environments. This verification included thermal characterization, sterilization heat cycling, sublimation measurements, isothermal decomposition measurements, and accelerated aging at a preselected elevated temperature. Temperatures chosen for sublimation and isothermal decomposition measurements were those in which the decomposition processess occurring would be the same as those taking place in real-time aging. The elevated temperature selected (84 C) for accelerated aging was based upon the parameters calculated from the kinetic data obtained in the isothermal measurement tests and was such that one month of accelerated aging in the laboratory approximated one year of real-time aging at 66 C. Results indicate that HNS-IIA, pure PbN6, KDNBF, and Zr/KC10 are capable of withstanding sterilization. The accelerated aging tests indicated that unsterilized HNS-IIA and Zr/KC104 can withstand the 10 year, elevated temperature exposure, pure PbN6 and KDNBF exhibit small weight losses (less than 2 percent) and B/KC104 exhibits significant changes in its thermal characteristics. Accelerated aging tests after sterilization indicated that only HNS-IIA exhibited high stability.

Titanium-Water Thermosyphon Gamma Radiation Effects and Results

NASA Technical Reports Server (NTRS)

Sanzi, James L.; Jaworske, Donald A.; Goodenow, Debra A.

2012-01-01

Titanium-water thermosyphons are being considered for use in heat rejection systems for fission power systems. Their proximity to the nuclear reactor will result in some exposure to gamma irradiation. Non-condensable gas formation from radiation may breakdown water over time and render a portion of the thermosyphon condenser inoperable. A series of developmental thermosyphons were operated at nominal operating temperature with accelerated gamma irradiation exposures on the same order of magnitude that is expected in eight years of heat rejection system operation. Temperature data were obtained during exposure at three locations on each thermosyphon; evaporator, condenser, and condenser end cap. Some non-condensable gas was evident, however thermosyphon performance was not affected because the non-condensable gas was compressed into the fill tube region at the top of the thermosyphon, away from the heat rejecting fin. The trend appeared to be an increasing amount of non-condensable gas formation with increasing gamma irradiation dose. Hydrogen is thought to be the most likely candidate for the non-condensable gas and hydrogen is known to diffuse through grain boundaries. Post-exposure evaluation of selected thermosyphons at temperature and in a vacuum chamber revealed that the non-condensable gas likely diffused out of the thermosyphons over a relatively short period of time. Further research shows a number of experimental and theoretical examples of radiolysis occurring through gamma radiation alone in pure water.

[The effect of noncoherent infrared radiation on the bone tissue reparation of the mandible in an experiment].

PubMed

Deriabin, E I

1997-01-01

Exposure of rabbits with mandibular bone defects to coherent infrared radiation (IR) at a wavelength of 890 nm decreased the intensity of inflammation by accelerating the repair. The results of exposure of the injured site to noncoherent IR radiation are compatible with those of IR laser exposure.

The internal bond and shear strength of hardwood veneered particleboard composites

Treesearch

P. Chow; J.J. Janowiak; E.W. Price

1986-01-01

The effects of several accelerated aging tests and weather exposures on hardwood reconstituted structural composite panels were evaluated. The results indicated that the internal bond and shear by tension loading strength reductions of the panels were affected by the exposure test method. The ranking of the effects of various exposure tests on strength values in an...

High-Temperature, Dual-Atmosphere Corrosion of Solid-Oxide Fuel Cell Interconnects

NASA Astrophysics Data System (ADS)

Gannon, Paul; Amendola, Roberta

2012-12-01

High-temperature corrosion of ferritic stainless steel (FSS) surfaces can be accelerated and anomalous when it is simultaneously subjected to different gaseous environments, e.g., when separating fuel (hydrogen) and oxidant (air) streams, in comparison with single-atmosphere exposures, e.g., air only. This so-called "dual-atmosphere" exposure is realized in many energy-conversion systems including turbines, boilers, gasifiers, heat exchangers, and particularly in intermediate temperature (600-800°C) planar solid-oxide fuel cell (SOFC) stacks. It is generally accepted that hydrogen transport through the FSS (plate or tube) and its subsequent integration into the growing air-side surface oxide layer can promote accelerated and anomalous corrosion—relative to single-atmosphere exposure—via defect chemistry changes, such as increased cation vacancy concentrations, decreased oxygen activity, and steam formation within the growing surface oxide layers. Establishment of a continuous and dense surface oxide layer on the fuel side of the FSS can inhibit hydrogen transport and the associated effects on the air side. Minor differences in FSS composition, microstructure, and surface conditions can all have dramatic influences on dual-atmosphere corrosion behaviors. This article reviews high-temperature, dual-atmosphere corrosion phenomena and discusses implications for SOFC stacks, related applications, and future research.

Prenatal maternal restraint stress exposure alters the reproductive hormone profile and testis development of the rat male offspring.

PubMed

Pallarés, María Eugenia; Adrover, Ezequiela; Baier, Carlos Javier; Bourguignon, Nadia S; Monteleone, Melisa C; Brocco, Marcela A; González-Calvar, Silvia I; Antonelli, Marta C

2013-07-01

Several studies have demonstrated that the presence of stressors during pregnancy induces adverse effects on the neuroendocrine system of the offspring later in life. In the present work, we investigated the effects of early programming on the male reproductive system, employing a prenatal stress (PS) paradigm. This study found that when pregnant dams were placed in a plastic restrainer three times a day during the last week of pregnancy, the offspring showed reduced anogenital distance and delayed testicular descent. Serum luteinising hormone (LH) and follicle-stimulating hormone (FSH) levels were decreased at postnatal day (PND) 28 and testosterone was decreased at PND 75. Increased testosterone plus dihydrotestosterone (T + DHT) concentrations correlated with increased testicular 5α Reductase-1 (5αR-1) mRNA expression at PND 28. Moreover, PS accelerated spermatogenesis at PND 35 and 60, and increased mean seminiferous tubule diameter in pubertal offspring and reduced Leydig cell number was observed at PND 35 and 60. PS offspring had increased androgen receptor (AR) mRNA level at PND 28, and at PND 35 had increased the numbers of Sertoli cells immunopositive for AR. Overall, the results confirm that stress during gestation can induce long-term effects on the male offspring reproductive system. Of particular interest is the pre-pubertal imbalance of circulating hormones that probably trigger accelerated testicular development, followed by an increase in total androgens and a decrease in testosterone concentration during adulthood. Exposure to an unfavourable intrauterine environment might prepare for harsh external conditions by triggering early puberty, increasing reproductive potential.

Evaluation of selected sidewalk pavement surfaces for vibration experienced by users of manual and powered wheelchairs.

PubMed

Cooper, Rory A; Wolf, Erik; Fitzgerald, Shirley G; Kellerher, Annmarie; Ammer, William; Boninger, Michael L; Cooper, Rosemarie

2004-01-01

Obstacles such as bumps, curb descents, and uneven driving surfaces cause vibrations that affect the wheelchair, and in turn, the wheelchair user. Chronic exposure can cause low-back pain, disk degeneration, and other harmful effects. Little research has been conducted to assess the vibrations experienced by wheelchair users. The purpose of this study was to conduct an evaluation of the vibration exposure during electric-powered wheelchair driving and mechanical energy requirements for manual wheelchair propulsion over selected sidewalk surfaces. The goal was to determine the criteria for a wheelchair-pedestrian access route that does not require excessive propulsive work or expose wheelchair users to potentially harmful vibrations. Ten unimpaired individuals participated in this study. Six sidewalk surfaces were tested. Measured variables included power of the acceleration per octave, mechanical work to propel over surfaces, peak acceleration, and frequency at which peak acceleration occurs. For both the manual and electric-powered wheelchair, at 1 m/s, significant differences were found in peak accelerations between the seat and footrest (P < 0.0001) and between the sidewalk surfaces (P = 0.004). The greatest risk for injury caused by shock and vibration exposure occurs at frequencies near the natural frequency of seated humans (4-15 Hz). The values for work required to propel over the surfaces tested were not statistically significantly different. Besides appearance and construction, the only distinguishing characteristic was surface roughness caused by the joints. When treating the poured concrete sidewalk as the standard, surfaces 2, 3, 5, and 6 compared most favorably in terms of vibration exposure, whereas surface 4 produced mixed results. Surfaces 2, 3, 5, and 6 yielded results that were similar to the poured concrete sidewalk and could be considered acceptable for wheelchair users. In conclusion, surfaces other than the traditional poured concrete can be used for pedestrian access routes without adding vibration exposure or reducing propulsion efficiency.

Three-axial evaluation of whole-body vibration in agricultural telehandlers: The effects of an active cab-suspension system.

PubMed

Caffaro, Federica; Preti, Christian; Micheletti Cremasco, Margherita; Cavallo, Eugenio

2017-10-01

Agricultural and earth-moving machinery operators are particularly exposed to whole-body vibration (WBV), which has severe effects on health and affects comfort and performance. Few studies have investigated vibrational safety and comfort issues in telescopic handlers. These vehicles are widespread in many off-road applications-such as construction, agriculture, and mining-used to handle loads and to lift persons and equipment. This study investigated the effects of an active hydro-pneumatic cab-suspension system fitted to a telehandler on a driver's vibration exposure along the x-, y-, and z-axes, through both objective and subjective assessments. Sixteen healthy professional telehandler drivers took part in the study. Objective measurements were acquired at the operator's seat, and subjective ratings were taken while participants drove the telehandler with either a deactivated or activated suspension system at 12 kph on an ISO 5008 smooth track. The results showed that the activation of the cab-suspension system reduced the root-mean-square acceleration along the x- and z-axes (p =.038 and p =.000, respectively). Moreover, the frequency analysis showed a reduction in the acceleration along the z-axis in the range of 2-25 Hz (p <.05 for all comparisons); in particular, the acceleration was reduced by 50% in the higher frequency range (4-20 Hz). A reduction in the vibration intensity was perceived by the participants along the y- and z-axes (p =.009 and p =.003, respectively). Implications for the future development of suspension systems are discussed.

Dysregulated physiological stress systems and accelerated cellular aging.

PubMed

Révész, Dóra; Verhoeven, Josine E; Milaneschi, Yuri; de Geus, Eco J C N; Wolkowitz, Owen M; Penninx, Brenda W J H

2014-06-01

Exposure to chronic stressors is associated with accelerated biological aging as indicated by reduced leukocyte telomere length (LTL). This impact could be because of chronic overactivation of the body's physiological stress systems. This study examined the associations between LTL and the immune system, hypothalamic-pituitary-adrenal axis and autonomic nervous system. LTL was assessed in 2936 adults from the Netherlands Study of Depression and Anxiety. Inflammation markers (interleukin-6, c-reactive protein, tumor necrosis factor-alpha), hypothalamic-pituitary-adrenal-axis indicators (salivary cortisol awakening curve [area under the curve indicators, with respect to the ground and increase], evening levels, 0.5 mg dexamethasone cortisol suppression ratio), and autonomic nervous system measures (heart rate, respiratory sinus arrhythmia, pre-ejection period) were determined. Linear regression analyses were performed and adjusted for sociodemographic, lifestyle and clinical factors. Shorter LTL was significantly associated with higher c-reactive protein, interleukin-6, area under the curve with respect to increase, and heart rate. A cumulative index score was calculated based on the number of highest tertiles of these 4 stress markers. LTL demonstrated a significant gradient within subjects ranging from having zero (5528 base pairs) to having 4 elevated stress markers (5371 base pairs, p for trend = 0.002), corresponding to a difference of 10 years of accelerated biological aging. Contrary to the expectations, shorter LTL was also associated with longer pre-ejection period, indicating lower sympathetic tone. This large-scale study showed that inflammation, high awakening cortisol response, and increased heart rate are associated with shorter LTL, especially when they are dysregulated cumulatively. Copyright © 2014 Elsevier Inc. All rights reserved.

Environmental Exposure Effects on Composite Materials for Commercial Aircraft

NASA Technical Reports Server (NTRS)

Hoffman, D. J.

1980-01-01

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

A prospective study of decline in lung function in relation to welding emissions.

PubMed

Christensen, Sigve W; Bonde, Jens Peter; Omland, Oyvind

2008-02-26

Numerous cross-sectional studies have reported reduced lung function among welders but limitations of exposure assessment and design preclude causal inference. The aim of this study was to investigate if long-term exposure to welding fume particulates accelerates the age-related decline in lung function. Lung function was measured by spirometry in 1987 and 2004 among 68 steel welders and 32 non-welding production workers. The decline in forced expiratory volume (FEV1) was analysed in relation to cumulated exposure to fume particulates among welders during the follow-up period. Among smokers the decline in FEV1 through follow-up period was in average 150 ml larger among welders than non-welders while the difference was negligible among non-smokers. The results did not reach statistical significance and within welders the decline in lung function was not related to the cumulated welding particulate exposure during follow-up period Long-term exposure to welding emissions may accelerate the age-related decline of lung function but at exposure levels in the range of 1.5 to 6.5 mg/m3 the average annual excess loss of FEV1 is unlikely to exceed 25 ml in smokers and 10 ml in non-smokers.

Accelerator Test of an Imaging Calorimeter

NASA Technical Reports Server (NTRS)

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

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

NASA Technical Reports Server (NTRS)

Smith, L. Montgomery

1998-01-01

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

The effect of a multi-axis suspension on whole body vibration exposures and physical stress in the neck and low back in agricultural tractor applications.

PubMed

Kim, Jeong Ho; Dennerlein, Jack T; Johnson, Peter W

2018-04-01

Whole body vibration (WBV) exposures are often predominant in the fore-aft (x) or lateral (y) axis among off-road agricultural vehicles. However, as the current industry standard seats are designed to reduce mainly vertical (z) axis WBV exposures, they may be less effective in reducing drivers' exposure to multi-axial WBV. Therefore, this laboratory-based study aimed to determine the differences between a single-axial (vertical) and multi-axial (vertical + lateral) suspension seat in reducing WBV exposures, head acceleration, self-reported discomfort, and muscle activity (electromyography) of the major muscle of the low back, neck and shoulders. The results showed that the multi-axial suspension seat had significantly lower WBV exposures compared to the single-axial suspension seats (p' < 0.04). Similarly, the multi-axial suspension seat had lower head acceleration and muscle activity of the neck, shoulder, and low back compared to the single-axial suspension seat; some but not all of the differences were statistically significant. These results indicate that the multi-axial suspension seat may reduce the lateral WBV exposures and associated muscular loading in the neck and low back in agricultural vehicle operators. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effect of gravitational acceleration, hypokinesia and hypodynamia on the structure of the intestinal vascular bed

NASA Technical Reports Server (NTRS)

Nikitin, M. V.

1980-01-01

A series of experiments comparing single and combined effects of hypokinesia and gravitational acceleration on morphology of intestinal blood vessels are discussed. Results indicate that hypokinesia has a whole body nonspecific effect reflected even in an organ whose activity shows little or no change due to hypokinesia. In early hypokinetic stages blood redistribution caused anorexia, intestinal atonia, and secretory disruption. Destructive changes from further exposure include aneurisms, varicoses, extravascular movement of blood elements, and vascular wall muscle fiber degeneration. The effect of acceleration is greatest in the ventrodorsal direction. Changes due to acceleration then hypokinesia are like those due to hypokinesia alone; changes due to acceleration before and after hypokinesia are like those due to acceleration. Adaptation raises acceleration tolerance but the effects do not survive four-week hypokinesia.

R-process Element Cosmic Rays from Neutron Star Mergers

NASA Astrophysics Data System (ADS)

Komiya, Yutaka; Shigeyama, Toshikazu

2017-09-01

Neutron star mergers (NSMs) are one of the most plausible sources of r-process elements in the universe. Therefore, NSMs can also be a major source of ultra-heavy elements in cosmic rays. In this paper, we first estimate the contribution of r-process elements synthesized in NSMs to the ultra-heavy element cosmic rays (UHCRs) by calculating transport equations that take into account energy loss processes and spallations. We show that the flux of UHCRs accelerated by the NSMs themselves fluctuates by many orders of magnitude on a timescale of several million years and can overwhelm UHCRs accelerated by supernova remnants (SNRs) after an NSM takes place within a few kiloparsec from the solar system. Experiments with very long exposure times using meteorites as UHCR detectors can detect this fluctuation. As a consequence, we show that if NSMs are the primary source of UHCRs, future experiments using meteorites may be able to reveal the event history of NSMs in the solar vicinity. We also describe a possible difference in the abundance pattern and energy spectrum of UHCRs between NSM and SNR accelerations.

R -process Element Cosmic Rays from Neutron Star Mergers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Komiya, Yutaka; Shigeyama, Toshikazu

Neutron star mergers (NSMs) are one of the most plausible sources of r -process elements in the universe. Therefore, NSMs can also be a major source of ultra-heavy elements in cosmic rays. In this paper, we first estimate the contribution of r -process elements synthesized in NSMs to the ultra-heavy element cosmic rays (UHCRs) by calculating transport equations that take into account energy loss processes and spallations. We show that the flux of UHCRs accelerated by the NSMs themselves fluctuates by many orders of magnitude on a timescale of several million years and can overwhelm UHCRs accelerated by supernova remnantsmore » (SNRs) after an NSM takes place within a few kiloparsec from the solar system. Experiments with very long exposure times using meteorites as UHCR detectors can detect this fluctuation. As a consequence, we show that if NSMs are the primary source of UHCRs, future experiments using meteorites may be able to reveal the event history of NSMs in the solar vicinity. We also describe a possible difference in the abundance pattern and energy spectrum of UHCRs between NSM and SNR accelerations.« less

Characterization of Vinyl Ester Composites Filled with Carbonized Jatropha seed shell: effect of accelerated weathering

NASA Astrophysics Data System (ADS)

Sri Aprilia, N. A.; Khalil, H. P. S. Abdul; Amin, Amri; Meurah Rosnelly, Cut; Fathanah, Ummi; Mariana

2018-05-01

The effect of accelerated weathering test of carbonized jatropha seed shell filled vinyl ester biocomposites was investigated. In this study, four loading of carbonized jatropha seed shell and one without loading of vinyl ester biocomposites were used. The samples exposure at several circles time in QUV chamber. The durability of vinyl ester biocomposites filled carbonized jatropha seed shell changes in mechanical properties and weight loss during exposure in UV and condensation. The tensile test and flexural indicated decrease with increasing of carbonized jatropha seed shell loading. The SEM fracture surface of biocomposites looks rough and some carbonized out of the matrix.

Vibration responses of two house structures during the Edwards Air Force Base phase of the national sonic boom program

NASA Technical Reports Server (NTRS)

Hubbard, Harvey H.

1990-01-01

The data are reproduced from NSBEO-1-67, which contains some preliminary results of the test program, and from NASA-Langley working papers 259 and 288 which are now out of print. Included are sample acceleration and strain recordings from F-104, B-58, and XB-70 sonic boom exposures, along with tabulations of the maximum acceleration and strain values measured for each one of about 130 flight tests. These data are compared with similar measurements for engine noise exposures of the building during simulated landing approaches and takeoffs of KC-135 aircraft.

Maximizing oyster-reef growth supports green infrastructure with accelerating sea-level rise.

PubMed

Ridge, Justin T; Rodriguez, Antonio B; Joel Fodrie, F; Lindquist, Niels L; Brodeur, Michelle C; Coleman, Sara E; Grabowski, Jonathan H; Theuerkauf, Ethan J

2015-10-07

Within intertidal communities, aerial exposure (emergence during the tidal cycle) generates strong vertical zonation patterns with distinct growth boundaries regulated by physiological and external stressors. Forecasted accelerations in sea-level rise (SLR) will shift the position of these critical boundaries in ways we cannot yet fully predict, but landward migration will be impaired by coastal development, amplifying the importance of foundation species' ability to maintain their position relative to rising sea levels via vertical growth. Here we show the effects of emergence on vertical oyster-reef growth by determining the conditions at which intertidal reefs thrive and the sharp boundaries where reefs fail, which shift with changes in sea level. We found that oyster reef growth is unimodal relative to emergence, with greatest growth rates occurring between 20-40% exposure, and zero-growth boundaries at 10% and 55% exposures. Notably, along the lower growth boundary (10%), increased rates of SLR would outpace reef accretion, thereby reducing the depth range of substrate suitable for reef maintenance and formation, and exacerbating habitat loss along developed shorelines. Our results identify where, within intertidal areas, constructed or natural oyster reefs will persist and function best as green infrastructure to enhance coastal resiliency under conditions of accelerating SLR.

Foam cell formation by particulate matter (PM) exposure: a review.

PubMed

Cao, Yi; Long, Jimin; Ji, Yuejia; Chen, Gui; Shen, Yuexin; Gong, Yu; Li, Juan

2016-11-01

Increasing evidence suggests that exposure of particulate matter (PM) from traffic vehicles, e.g., diesel exhaust particles (DEP), was associated with adverse vascular effects, e.g., acceleration of atherosclerotic plaque progression. By analogy, engineered nanoparticles (NPs) could also induce similar effects. The formation of lipid laden foam cells, derived predominately from macrophages and vascular smooth muscle cells (VSMC), is closely associated with the development of atherosclerosis and adverse vascular effects. We reviewed current studies about particle exposure-induced lipid laden foam cell formation. In vivo studies using animal models have shown that exposure of air pollution by PM promoted lipid accumulation in alveolar macrophages or foam cells in plaques, which was likely associated with pulmonary inflammation or systemic oxidative stress, but not blood lipid profile. In support of these findings, in vitro studies showed that direct exposure of cultured macrophages to DEP or NP exposure, with or without further exposure to external lipids, promoted intracellular lipid accumulation. The mechanisms remained unknown. Although a number studies found increased reactive oxygen species (ROS) or an adaptive response to oxidative stress, the exact role of oxidative stress in mediating particle-induced foam cell formation requires future research. There is currently lack of reports concerning VSMC as a source for foam cells induced by particle exposure. In the future, it is necessary to explore the role of foam cell formation in particle exposure-induced atherosclerosis development. In addition, the formation of VSMC derived foam cells by particle exposure may also need extensive studies.

A new deflection technique applied to an existing scheme of electrostatic accelerator for high energy neutral beam injection in fusion reactor devices

NASA Astrophysics Data System (ADS)

Pilan, N.; Antoni, V.; De Lorenzi, A.; Chitarin, G.; Veltri, P.; Sartori, E.

2016-02-01

A scheme of a neutral beam injector (NBI), based on electrostatic acceleration and magneto-static deflection of negative ions, is proposed and analyzed in terms of feasibility and performance. The scheme is based on the deflection of a high energy (2 MeV) and high current (some tens of amperes) negative ion beam by a large magnetic deflector placed between the Beam Source (BS) and the neutralizer. This scheme has the potential of solving two key issues, which at present limit the applicability of a NBI to a fusion reactor: the maximum achievable acceleration voltage and the direct exposure of the BS to the flux of neutrons and radiation coming from the fusion reactor. In order to solve these two issues, a magnetic deflector is proposed to screen the BS from direct exposure to radiation and neutrons so that the voltage insulation between the electrostatic accelerator and the grounded vessel can be enhanced by using compressed SF6 instead of vacuum so that the negative ions can be accelerated at energies higher than 1 MeV. By solving the beam transport with different magnetic deflector properties, an optimum scheme has been found which is shown to be effective to guarantee both the steering effect and the beam aiming.

A new deflection technique applied to an existing scheme of electrostatic accelerator for high energy neutral beam injection in fusion reactor devices.

PubMed

Pilan, N; Antoni, V; De Lorenzi, A; Chitarin, G; Veltri, P; Sartori, E

2016-02-01

A scheme of a neutral beam injector (NBI), based on electrostatic acceleration and magneto-static deflection of negative ions, is proposed and analyzed in terms of feasibility and performance. The scheme is based on the deflection of a high energy (2 MeV) and high current (some tens of amperes) negative ion beam by a large magnetic deflector placed between the Beam Source (BS) and the neutralizer. This scheme has the potential of solving two key issues, which at present limit the applicability of a NBI to a fusion reactor: the maximum achievable acceleration voltage and the direct exposure of the BS to the flux of neutrons and radiation coming from the fusion reactor. In order to solve these two issues, a magnetic deflector is proposed to screen the BS from direct exposure to radiation and neutrons so that the voltage insulation between the electrostatic accelerator and the grounded vessel can be enhanced by using compressed SF6 instead of vacuum so that the negative ions can be accelerated at energies higher than 1 MeV. By solving the beam transport with different magnetic deflector properties, an optimum scheme has been found which is shown to be effective to guarantee both the steering effect and the beam aiming.

Funduscopic alterations in the rhesus monkey induced by exposure to heavy ions /0+8/ 250 MeV/nucleon

NASA Technical Reports Server (NTRS)

Beckman, F. N.; Bonney, C. H.; Hunter, D. M.

1974-01-01

A heavy-ion, high-energy beam has been extracted from the Lawrence Radiation Laboratory Bevatron, making controlled exposure of biological systems feasible, and a series of experiments have been undertaken to determine the possible deleterious effects of such irradiation upon the primate retina. The left eyes of 54 rhesus monkeys have been exposed to accelerated 0+8 (250 MeV/nucleon). Beam flux ranged from 1.3 x 10 to the 7th particles/ sq cm (171 rads) to 5.9 x 10 to the 8th particles/sq cm (7740 rads). Fundus photography was performed immediately prior to and immediately following exposure, at 24 to 48 hours postexposure and at 1, 2, and 5 weeks postexposure. Punctate hemorrhages of the retina were visible at 1.3 x 10 to the 7th particles/sq cm (171 rads), the lowest exposure level utilized in this study. Acute radiation retinopathy, consisting of geographic retinal hemorrhage and ischemic necrosis of the retina, was not seen until total flux reached 7.7 x 10 to the 7th particles/sq cm (1000 rads).

Decompression Sickness During Simulated Low Pressure Exposure is Increased with Mild Ambulation Exercise

NASA Technical Reports Server (NTRS)

Pollock, N. W.; Natoli, M. J.; Martina, S. D.; Conkin, J.; Wessel, J. H., III; Gernhardt, M. L.

2016-01-01

Musculoskeletal activity accelerates inert gas elimination during oxygen breathing prior to decompression (prebreathe), but may also promote bubble formation (nucleation) and increase the risk of decompression sickness (DCS). The timing, pattern and intensity of musculoskeletal activity are likely critical to the net effect. The NASA Prebreathe Reduction Program (PRP) combined oxygen prebreathe and exercise preceding a 4.3 psia exposure in non-ambulatory subjects (a microgravity analog) to produce two protocols now used by astronauts preparing for extravehicular activity - one employing cycling and non-cycling exercise (CEVIS: 'cycle ergometer vibration isolation system') and one relying on non-cycling exercise only (ISLE: 'in-suit light exercise'). Current efforts investigate whether light exercise normal to 1 G environments increases the risk of DCS over microgravity simulation.

Laser-based irradiation apparatus and method to measure the functional dose-rate response of semiconductor devices

DOEpatents

Horn, Kevin M [Albuquerque, NM

2008-05-20

A broad-beam laser irradiation apparatus can measure the parametric or functional response of a semiconductor device to exposure to dose-rate equivalent infrared laser light. Comparisons of dose-rate response from before, during, and after accelerated aging of a device, or from periodic sampling of devices from fielded operational systems can determine if aging has affected the device's overall functionality. The dependence of these changes on equivalent dose-rate pulse intensity and/or duration can be measured with the apparatus. The synchronized introduction of external electrical transients into the device under test can be used to simulate the electrical effects of the surrounding circuitry's response to a radiation exposure while exposing the device to dose-rate equivalent infrared laser light.

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

USDA-ARS?s Scientific Manuscript database

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...

Precocious puberty secondary to topical testosterone exposure.

PubMed

Franklin, Sherry Lynn; Geffner, Mitchell E

2003-01-01

We report a case of pronounced virilization, including marked penile and pubic hair growth, accelerated height velocity and skeletal maturation, and increased muscle mass in a 2.67 year-old boy resulting from presumed inadvertent, long-term exposure to a topical testosterone cream being used by his father.

Self-Shielding Analysis of the Zap-X System

PubMed Central

Schneider, M. Bret; Adler, John R.

2017-01-01

The Zap-X is a self-contained and first-of-its-kind self-shielded therapeutic radiation device dedicated to brain as well as head and neck stereotactic radiosurgery (SRS). By utilizing an S-band linear accelerator (linac) with a 2.7 megavolt (MV) accelerating potential and incorporating radiation-shielded mechanical structures, the Zap-X does not typically require a radiation bunker, thereby saving SRS facilities considerable cost. At the same time, the self-shielded features of the Zap-X are designed for more consistency of radiation protection, reducing the risk to radiation workers and others potentially exposed from a poorly designed or constructed radiotherapy vault. The hypothesis of the present study is that a radiosurgical system can be self-shielded such that it produces radiation exposure levels deemed safe to the public while operating under a full clinical workload. This study summarizes the Zap-X system shielding and found that the overall system radiation leakage values are reduced by a factor of 50 compared to the occupational radiation limit stipulated by the Nuclear Regulatory Commission (NRC) or agreement states. The goal of self-shielding is achieved under all but the most exceptional conditions for which additional room shielding or a larger restricted area in the vicinity of the Zap-X system would be required. PMID:29441251

Accelerator system and method of accelerating particles

NASA Technical Reports Server (NTRS)

Wirz, Richard E. (Inventor)

2010-01-01

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

Radiolabeled Microsphere Technique in Conscious Subjects during Acceleration Exposures on the USAFSAM Centrifuge.

DTIC Science & Technology

1980-03-01

function even though the pump is pumping air into the blood manifold. R-2 is secured to the plate with two thumb screws, and when the syringes are...the scapula . The animals were allowed 2-4 weeks of surgical recovery before the acceleration studies were performed. Experimental Protocol--On the day

Characterisation of a PdCl 2/SnCl 2 electroless plating catalyst system adsorbed on barium titanate-based electroactive ceramics

NASA Astrophysics Data System (ADS)

Meenan, B. J.; Brown, N. M. D.; Wilson, J. W.

1994-03-01

A PdCl 2/SnCl 2 metallisation catalyst system, of the type used to activate non-conducting surfaces for electroless metal deposition, has been characterised by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The substrate is a barium titanate (BaTiO 3)-based electroactive ceramic of the type used in the fabrication of multilayer ceramic capacitors (MLCC). The treatment of the substrate surface with the PdCl 2/SnCl 2 "sensitiser" solution leads to the adsorption of catalytically inactive compounds of palladium and tin. Subsequent treatment of this surface with an "accelerator" solution removes excess oxides, hydroxides and salts of tin thereby leaving the active catalyst species, Pd xSn y, on the surface. Such sites, on exposure to the appropriete electroless plating bath, are then responsible for the metal deposition. In this study, the chemical state and relative quantities of the various surface species present after each of the processing stages have been determined by XPS. The surface roughness of the substrate results in less of the tin compounds present thereon being removed on washing the catalysed surface in the accelerator solution than normally reported for such systems, thereby affecting the measured Pd: Sn ratio. SEM studies show that the accelerator solution treatment generates crystalline areas, which may be a result of coagulation of the Pd xSn y particles present, in the otherwise amorphous catalyst coating.

Life Stress and Health: A Review of Conceptual Issues and Recent Findings.

PubMed

Slavich, George M

2016-10-01

Life stress is a central construct in many models of human health and disease. The present article reviews research on stress and health, with a focus on (a) how life stress has been conceptualized and measured over time, (b) recent evidence linking stress and disease, and (c) mechanisms that might underlie these effects. Emerging from this body of work is evidence that stress is involved in the development, maintenance, or exacerbation of several mental and physical health conditions, including asthma, rheumatoid arthritis, anxiety disorders, depression, cardiovascular disease, chronic pain, human immunodeficiency virus/AIDS, stroke, and certain types of cancer. Stress has also been implicated in accelerated biological aging and premature mortality. These effects have been studied most commonly using self-report checklist measures of life stress exposure, although interview-based approaches provide a more comprehensive assessment of individuals' exposure to stress. Most recently, online systems like the Stress and Adversity Inventory (STRAIN) have been developed for assessing lifetime stress exposure, and such systems may provide important new information to help advance our understanding of how stressors occurring over the life course get embedded in the brain and body to affect lifespan health.

Report: Progress Made, but Improvements Needed at CTS of Asheville Superfund Site in North Carolina to Advance Cleanup Pace and Reduce Potential Exposure

EPA Pesticide Factsheets

Report #16-P-0296, August 31, 2016. EPA Region 4 can accelerate the cleanup and completeness of work, and improve public communications, to better control human exposure to unsafe industrial contamination at the CTS site.

Lysosomal Changes in Renal Proximal Tubular Epithelial Cells of Male Sprague Dawley Rats Following Decalin Exposure

DTIC Science & Technology

1990-01-01

induced by decalin exposure are processes, accelerated apoptosis has been describedin renal tissue with hydronephrosis (6), during the clearly intact...experimental hydronephrosis in topathology and cell proliferation induced by 2,2.4- the rat. Lab. Invest. 56(3): 273-281. trimethylpentane in the

ACCELERATED SOLVENT EXTRACTION OF ARSENICALS FROM SEAFOOD MATRICES WITH ION CHROMATOGRAPHY AND ICP-MS DETECTION

EPA Science Inventory

The two major sources of arsenic exposure are water and diet. Dietary exposure is considerably more difficult to assess because of the diversity of arsenicals present in dietary matrices coupled with species dependent toxicity of arsenic. Dietary arsenic assessments are further c...

Field evaluation of corrosion inhibitors for concrete. Interim report 1, Evaluation of exposure slabs repaired with corrosion inhibitors.

DOT National Transportation Integrated Search

1998-01-01

One hundred and fifty-six exposure slabs have been constructed with and without a variety of combinations of corrosion inhibiting admixtures and topically applied inhibitors. To accelerate corrosion one hundred and thirty-six of the slabs were constr...

Effects of Moderate Strength Cold Air Exposure on Blood Pressure and Biochemical Indicators among Cardiovascular and Cerebrovascular Patients

PubMed Central

Zhang, Xiakun; Zhang, Shuyu; Wang, Chunling; Wang, Baojian; Guo, Pinwen

2014-01-01

The effects of cold air on cardiovascular and cerebrovascular diseases were investigated in an experimental study examining blood pressure and biochemical indicators. Zhangye, a city in Gansu Province, China, was selected as the experimental site. Health screening and blood tests were conducted, and finally, 30 cardiovascular disease patients and 40 healthy subjects were recruited. The experiment was performed during a cold event during 27–28 April 2013. Blood pressure, catecholamine, angiotensin II (ANG-II), cardiac troponin I (cTnI), muscle myoglobin (Mb) and endothefin-1 (ET-1) levels of the subjects were evaluated 1 day before, during the 2nd day of the cold exposure and 1 day after the cold air exposure. Our results suggest that cold air exposure increases blood pressure in cardiovascular disease patients and healthy subjects via the sympathetic nervous system (SNS) that is activated first and which augments ANG-II levels accelerating the release of the norepinephrine and stimulates the renin-angiotensin system (RAS). The combined effect of these factors leads to a rise in blood pressure. In addition, cold air exposure can cause significant metabolism and secretion of Mb, cTnI and ET-1 in subjects; taking the patient group as an example, ET-1 was 202.7 ng/L during the cold air exposure, increased 58 ng/L compared with before the cold air exposure, Mb and cTnI levels remained relatively high (2,219.5 ng/L and 613.2 ng/L, increased 642.1 ng/L and 306.5 ng/L compared with before the cold air exposure, respectively) 1-day after the cold exposure. This showed that cold air can cause damage to patients’ heart cells, and the damage cannot be rapidly repaired. Some of the responses related to the biochemical markers indicated that cold exposure increased cardiovascular strain and possible myocardial injury. PMID:24583830

Effects of moderate strength cold air exposure on blood pressure and biochemical indicators among cardiovascular and cerebrovascular patients.

PubMed

Zhang, Xiakun; Zhang, Shuyu; Wang, Chunling; Wang, Baojian; Guo, Pinwen

2014-02-27

The effects of cold air on cardiovascular and cerebrovascular diseases were investigated in an experimental study examining blood pressure and biochemical indicators. Zhangye, a city in Gansu Province, China, was selected as the experimental site. Health screening and blood tests were conducted, and finally, 30 cardiovascular disease patients and 40 healthy subjects were recruited. The experiment was performed during a cold event during 27-28 April 2013. Blood pressure, catecholamine, angiotensin II (ANG-II), cardiac troponin I (cTnI), muscle myoglobin (Mb) and endothefin-1 (ET-1) levels of the subjects were evaluated 1 day before, during the 2nd day of the cold exposure and 1 day after the cold air exposure. Our results suggest that cold air exposure increases blood pressure in cardiovascular disease patients and healthy subjects via the sympathetic nervous system (SNS) that is activated first and which augments ANG-II levels accelerating the release of the norepinephrine and stimulates the renin-angiotensin system (RAS). The combined effect of these factors leads to a rise in blood pressure. In addition, cold air exposure can cause significant metabolism and secretion of Mb, cTnI and ET-1 in subjects; taking the patient group as an example, ET-1 was 202.7 ng/L during the cold air exposure, increased 58 ng/L compared with before the cold air exposure, Mb and cTnI levels remained relatively high (2,219.5 ng/L and 613.2 ng/L, increased 642.1 ng/L and 306.5 ng/L compared with before the cold air exposure, respectively) 1-day after the cold exposure. This showed that cold air can cause damage to patients' heart cells, and the damage cannot be rapidly repaired. Some of the responses related to the biochemical markers indicated that cold exposure increased cardiovascular strain and possible myocardial injury.

Vibration responses of test structure no. 1 during the Edwards Air Force Base phase of the national sonic boom program. [F-104, B-58, and XB-70 sonic boom exposures

NASA Technical Reports Server (NTRS)

Findley, D. S.; Huckel, V.; Henderson, H. R.

1975-01-01

In order to evaluate reaction of people to sonic booms of varying overpressures and time durations, a series of closely controlled and systematic flight test studies were conducted in the vicinity of Edwards AFB, California, from June 3 to June 23, 1966. The dynamic responses of several building structures were measured as a part of these studies, and the measurements made in a one-story residence structure (Edwards test structure No. 1) are presented. Sample acceleration and strain recordings are presented from F-104, B-58, and XB-70 sonic-boom exposures, along with tabulations of the maximum acceleration and strain values measured for each one of about 140 flight tests. These data are compared with similar measurements for engine noise exposures of the building during simulated landing approaches and takeoffs of KC-135 aircraft.

Pleiotrophin mediates hematopoietic regeneration via activation of RAS.

PubMed

Himburg, Heather A; Yan, Xiao; Doan, Phuong L; Quarmyne, Mamle; Micewicz, Eva; McBride, William; Chao, Nelson J; Slamon, Dennis J; Chute, John P

2014-11-01

Hematopoietic stem cells (HSCs) are highly susceptible to ionizing radiation-mediated death via induction of ROS, DNA double-strand breaks, and apoptotic pathways. The development of therapeutics capable of mitigating ionizing radiation-induced hematopoietic toxicity could benefit both victims of acute radiation sickness and patients undergoing hematopoietic cell transplantation. Unfortunately, therapies capable of accelerating hematopoietic reconstitution following lethal radiation exposure have remained elusive. Here, we found that systemic administration of pleiotrophin (PTN), a protein that is secreted by BM-derived endothelial cells, substantially increased the survival of mice following radiation exposure and after myeloablative BM transplantation. In both models, PTN increased survival by accelerating the recovery of BM hematopoietic stem and progenitor cells in vivo. PTN treatment promoted HSC regeneration via activation of the RAS pathway in mice that expressed protein tyrosine phosphatase receptor-zeta (PTPRZ), whereas PTN treatment did not induce RAS signaling in PTPRZ-deficient mice, suggesting that PTN-mediated activation of RAS was dependent upon signaling through PTPRZ. PTN strongly inhibited HSC cycling following irradiation, whereas RAS inhibition abrogated PTN-mediated induction of HSC quiescence, blocked PTN-mediated recovery of hematopoietic stem and progenitor cells, and abolished PTN-mediated survival of irradiated mice. These studies demonstrate the therapeutic potential of PTN to improve survival after myeloablation and suggest that PTN-mediated hematopoietic regeneration occurs in a RAS-dependent manner.

Combination effects of airborne particulate matter exposure and high-fat diet on hepatic fibrosis through regulating the ROS-endoplasmic reticulum stress-TGFβ/SMADs axis in mice.

PubMed

Ding, Shibin; Yu, Lanlan; An, Baijie; Zhang, Guofu; Yu, Pengxin; Wang, Zhe

2018-05-01

Hepatic fibrosis, characterized by an excessive accumulation of extracellular matrix, is associated with toxic substance exposure, chronic infections, mechanical injury, airborne fine particulate matter (PM 2.5 ) exposure and metabolic disease. This study aimed to investigate the effect and mechanism of long-term, real-world airborne particulate matter (PM) exposure on hepatic fibrosis and further explored whether combination treatment of PM exposure and high-fat diet (HFD) aggravate the adverse effects in mice. Six-week-old male C57BL/6J mice fed with either a standard chow diet (STD) or an HFD were treated with either filtered air (FA) or PM for 18 weeks. Metabolic parameters, histological examination, gene expression analysis, and Western blot analysis were utilized to measure the effect and mechanism of PM exposure on hepatic fibrosis and to further analyze the synergistic effect of HFD. Subchronic airborne PM exposure induces hepatic fibrosis in mice, and combination treatment of PM exposure and HFD accelerate the adverse effect. Meanwhile, subchronic exposure to real-world PM increased the level of hepatic ROS, and the expression of endoplasmic reticulum (ER) stress markers (GRP78 and CHOP), p-SMAD2 and p-SMAD3, as well as up-regulated TGFβ and collagen 1 in liver tissues. Furthermore, PM exposure and HFD displayed the synergistic effects on these changes in liver. Our findings indicate that airborne PM exposure aggravates HFD -induced hepatic fibrosis. The ROS-ER stress-TGFβ/SMADs regulatory axis mediates the effects of airborne PM exposure on accelerating hepatic fibrosis. Copyright © 2018 Elsevier Ltd. All rights reserved.

Pre-exposure rabies prophylaxis: a systematic review.

PubMed

Kessels, Jocelyn A; Recuenco, Sergio; Navarro-Vela, Ana Maria; Deray, Raffy; Vigilato, Marco; Ertl, Hildegund; Durrheim, David; Rees, Helen; Nel, Louis H; Abela-Ridder, Bernadette; Briggs, Deborah

2017-03-01

To review the safety and immunogenicity of pre-exposure rabies prophylaxis (including accelerated schedules, co-administration with other vaccines and booster doses), its cost-effectiveness and recommendations for use, particularly in high-risk settings. We searched the PubMed, Centre for Agriculture and Biosciences International, Cochrane Library and Web of Science databases for papers on pre-exposure rabies prophylaxis published between 2007 and 29 January 2016. We reviewed field data from pre-exposure prophylaxis campaigns in Peru and the Philippines. Pre-exposure rabies prophylaxis was safe and immunogenic in children and adults, also when co-administered with routine childhood vaccinations and the Japanese encephalitis vaccine. The evidence available indicates that shorter regimens and regimens involving fewer doses are safe and immunogenic and that booster intervals could be extended up to 10 years. The few studies on cost suggest that, at current vaccine and delivery costs, pre-exposure prophylaxis campaigns would not be cost-effective in most situations. Although pre-exposure prophylaxis has been advocated for high-risk populations, only Peru and the Philippines have implemented appropriate national programmes. In the future, accelerated regimens and novel vaccines could simplify delivery and increase affordability. Pre-exposure rabies prophylaxis is safe and immunogenic and should be considered: (i) where access to postexposure prophylaxis is limited or delayed; (ii) where the risk of exposure is high and may go unrecognized; and (iii) where controlling rabies in the animal reservoir is difficult. Pre-exposure prophylaxis should not distract from canine vaccination efforts, provision of postexposure prophylaxis or education to increase rabies awareness in local communities.

Pre-exposure rabies prophylaxis: a systematic review

PubMed Central

Recuenco, Sergio; Navarro-Vela, Ana Maria; Deray, Raffy; Vigilato, Marco; Ertl, Hildegund; Durrheim, David; Rees, Helen; Nel, Louis H; Abela-Ridder, Bernadette; Briggs, Deborah

2017-01-01

Abstract Objective To review the safety and immunogenicity of pre-exposure rabies prophylaxis (including accelerated schedules, co-administration with other vaccines and booster doses), its cost–effectiveness and recommendations for use, particularly in high-risk settings. Methods We searched the PubMed, Centre for Agriculture and Biosciences International, Cochrane Library and Web of Science databases for papers on pre-exposure rabies prophylaxis published between 2007 and 29 January 2016. We reviewed field data from pre-exposure prophylaxis campaigns in Peru and the Philippines. Findings Pre-exposure rabies prophylaxis was safe and immunogenic in children and adults, also when co-administered with routine childhood vaccinations and the Japanese encephalitis vaccine. The evidence available indicates that shorter regimens and regimens involving fewer doses are safe and immunogenic and that booster intervals could be extended up to 10 years. The few studies on cost suggest that, at current vaccine and delivery costs, pre-exposure prophylaxis campaigns would not be cost-effective in most situations. Although pre-exposure prophylaxis has been advocated for high-risk populations, only Peru and the Philippines have implemented appropriate national programmes. In the future, accelerated regimens and novel vaccines could simplify delivery and increase affordability. Conclusion Pre-exposure rabies prophylaxis is safe and immunogenic and should be considered: (i) where access to postexposure prophylaxis is limited or delayed; (ii) where the risk of exposure is high and may go unrecognized; and (iii) where controlling rabies in the animal reservoir is difficult. Pre-exposure prophylaxis should not distract from canine vaccination efforts, provision of postexposure prophylaxis or education to increase rabies awareness in local communities. PMID:28250534

Mesh three-dimensional arm orthosis with built-in ultrasound physiotherapy system

NASA Astrophysics Data System (ADS)

Kashapova, R. M.; Kashapov, R. N.; Kashapova, R. S.

2017-09-01

The possibility of using the built-in ultrasound physiotherapy system of the hand orthosis is explored in the work. The individual mesh orthosis from nylon 12 was manufactured by the 3D prototyping method on the installation of selective laser sintering SLS SPro 60HD. The applied technology of three-dimensional scanning made it possible to obtain a model of the patient’s hand and on the basis of it to build a virtual model of the mesh frame. In the course of the research, the developed system of ultrasound exposure was installed on the orthosis and its tests were carried out. As a result, the acceleration of the healing process and the reduction in the time of wearing orthosis were found.

Football Players' Head-Impact Exposure After Limiting of Full-Contact Practices

PubMed Central

Broglio, Steven P.; Williams, Richelle M.; O'Connor, Kathryn L.; Goldstick, Jason

2016-01-01

Context:  Sporting organizations limit full-contact football practices to reduce concussion risk and based on speculation that repeated head impacts may result in long-term neurodegeneration. Objective:  To directly compare head-impact exposure in high school football players before and after a statewide restriction on full-contact practices. Design:  Cross-sectional study. Setting:  High school football field. Patients or Other Participants:  Participants were varsity football athletes from a single high school. Before the rule change, 26 athletes (age = 16.2 ± 0.8 years, height = 179.6 ± 6.4 cm, weight = 81.9 ± 13.1 kg) participated. After the rule change, 24 athletes (age = 15.9 ± 0.8 years, height = 178.3 ± 6.5 cm, weight = 76.2 ± 11.6 kg) participated. Nine athletes participated in both years of the investigation. Main Outcome Measure(s):  Head-impact exposure was monitored using the Head Impact Telemetry System while the athletes participated in football games and practices in the seasons before and after the rule change. Head-impact frequency, location, and magnitude (ie, linear acceleration, rotational acceleration, and Head Impact Telemetry severity profile [HITsp], respectively) were measured. Results:  A total of 15 398 impacts (592 impacts per player per season) were captured before the rule change and 8269 impacts (345 impacts per player per season) after the change. An average 42% decline in impact exposure occurred across all players, with practice-exposure declines occurring among linemen (46% decline); receivers, cornerbacks, and safeties (41% decline); and tight ends, running backs (including fullbacks), and linebackers (39% decline). Impact magnitudes remained largely unchanged between the years. Conclusions:  A rule change limiting full-contact high school football practices appears to have been effective in reducing head-impact exposure across all players, with the largest reduction occurring among linemen. This finding is likely associated with the rule modification, particularly because the coaching staff and offensive scheme remained consistent, yet how this reduction influences concussion risk and long-term cognitive health remains unknown. PMID:27333460

Chronic exposure to cocaine binging predisposes to an accelerated course of dilated cardiomyopathy in conscious dogs following rapid ventricular pacing.

PubMed

Parikh, Pratik; Nikolaidis, Lazaros A; Stolarski, Carol; Shen, You-Tang; Shannon, Richard P

2005-12-01

Despite extensive study, the extent to which cocaine use predisposes to cardiac injury remains unknown. We hypothesized that chronic cocaine binging would increase susceptibility to a subsequent cardiac insult, even in the absence of demonstrable effects on baseline hemodynamics. We studied progression of dilated cardiomyopathy (DCM) induced by rapid ventricular pacing (240 beats per minute) in five conscious, chronically instrumented dogs, after exposure to repetitive cocaine binging (COC) in the form of four consecutive 1 mg/kg i.v. boluses daily for 8 days, to simulate human cocaine abuse. We compared the results with nine control dogs (CON) undergoing the exact pacing protocol, without prior cocaine exposure. Baseline hemodynamics were not significantly altered by chronic cocaine exposure. Following 2 weeks of pacing, COC dogs exhibited accelerated progression to DCM, depressed plasma nitric oxide levels (CON, 17 +/- 2 microM; COC, 10 +/- 2 microM, p < 0.05), and a significantly greater increase in plasma epinephrine (CON, 33 +/- 6 pg/ml; COC, 104 +/- 24 pg/ml). After only 2 weeks of pacing, COC dogs demonstrated progressive DCM of a magnitude comparable with end-stage pacing-induced DCM. Chronic cocaine binging increases susceptibility to a subsequent myocardial insult and accelerates progression of DCM in conscious dogs following rapid pacing. These data suggest that although chronic cocaine use alone may not affect myocardial function, it predisposes to greater susceptibility to a superimposed insult.

Report on accelerated corrosion studies.

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

2011-03-01

Sandia National Laboratories (SNL) conducted accelerated atmospheric corrosion testing for the U.S. Consumer Product Safety Commission (CPSC) to help further the understanding of the development of corrosion products on conductor materials in household electrical components exposed to environmental conditions representative of homes constructed with problem drywall. The conditions of the accelerated testing were chosen to produce corrosion product growth that would be consistent with long-term exposure to environments containing humidity and parts per billion (ppb) levels of hydrogen sulfide (H{sub 2}S) that are thought to have been the source of corrosion in electrical components from affected homes. This report documentsmore » 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.« less

Head Impact Exposure in Youth Football: High School Ages 14 to 18 Years and Cumulative Impact Analysis

PubMed Central

Urban, Jillian E.; Davenport, Elizabeth M.; Golman, Adam J.; Maldjian, Joseph A.; Whitlow, Christopher T.; Powers, Alexander K.; Stitzel, Joel D.

2015-01-01

Sports-related concussion is the most common athletic head injury with football having the highest rate among high school athletes. Traditionally, research on the biomechanics of football-related head impact has been focused at the collegiate level. Less research has been performed at the high school level, despite the incidence of concussion among high school football players. The objective of this study is to twofold: to quantify the head impact exposure in high school football, and to develop a cumulative impact analysis method. Head impact exposure was measured by instrumenting the helmets of 40 high school football players with helmet mounted accelerometer arrays to measure linear and rotational acceleration. A total of 16,502 head impacts were collected over the course of the season. Biomechanical data were analyzed by team and by player. The median impact for each player ranged from 15.2 to 27.0 g with an average value of 21.7 (±2.4) g. The 95th percentile impact for each player ranged from 38.8 to 72.9 g with an average value of 56.4 (±10.5) g. Next, an impact exposure metric utilizing concussion injury risk curves was created to quantify cumulative exposure for each participating player over the course of the season. Impacts were weighted according to the associated risk due to linear acceleration and rotational acceleration alone, as well as the combined probability (CP) of injury associated with both. These risks were summed over the course of a season to generate risk weighted cumulative exposure. The impact frequency was found to be greater during games compared to practices with an average number of impacts per session of 15.5 and 9.4, respectively. However, the median cumulative risk weighted exposure based on combined probability was found to be greater for practices vs. games. These data will provide a metric that may be used to better understand the cumulative effects of repetitive head impacts, injury mechanisms, and head impact exposure of athletes in football. PMID:23864337

A highly stable monolithic enhancement cavity for second harmonic generation in the ultraviolet

NASA Astrophysics Data System (ADS)

Hannig, S.; Mielke, J.; Fenske, J. A.; Misera, M.; Beev, N.; Ospelkaus, C.; Schmidt, P. O.

2018-01-01

We present a highly stable bow-tie power enhancement cavity for critical second harmonic generation (SHG) into the UV using a Brewster-cut β-BaB2O4 (BBO) nonlinear crystal. The cavity geometry is suitable for all UV wavelengths reachable with BBO and can be modified to accommodate anti-reflection coated crystals, extending its applicability to the entire wavelength range accessible with non-linear frequency conversion. The cavity is length-stabilized using a fast general purpose digital PI controller based on the open source STEMlab 125-14 (formerly Red Pitaya) system acting on a mirror mounted on a fast piezo actuator. We observe 130 h uninterrupted operation without decay in output power at 313 nm. The robustness of the system has been confirmed by exposing it to accelerations of up to 1 g with less than 10% in-lock output power variations. Furthermore, the cavity can withstand 30 min of acceleration exposure at a level of 3 grms without substantial change in the SHG output power, demonstrating that the design is suitable for transportable setups.

Food Irradiation Using Electron Beams and X-Rays

NASA Astrophysics Data System (ADS)

Miller, Bruce

2003-04-01

In this presentation we will discuss the technology of food irradiation using electron accelerators. Food irradiation has generally come to describe the use of ionizing radiation to decrease the population of, or prevent the growth of, undesirable biological organisms in food. The many beneficial applications include insect disinfestation, sprouting inhibition, delayed ripening, and the enhanced safety and sterilization of fresh and frozen meat products, seafood, and eggs. With special regard to food safety, bacteria such as Salmonella enteridis, Listeria monocytogenes, Campylobacter jejuni and Escherichia coli serotype O157:H7 are the primary causes of food poisoning in industrialized countries. Ionizing doses in the range of only 1-5 kilogray (kGy) can virtually eliminate these organisms from food, without affecting the food's sensory and nutritional qualities, and without inducing radioactivity. The key elements of an accelerator-based irradiation facility include the accelerator system, a scanning system, and a material handling system that moves the product through the beam in a precisely controlled manner. Extensive radiation shielding is necessary to reduce the external dose to acceptable levels, and a safety system is necessary to prevent accidental exposure of personnel during accelerator operation. Parameters that affect the dose distribution must be continuously monitored and controlled with process control software. The choice of electron beam vs x-ray depends on the areal density (density times thickness) of the product and the anticipated mass throughput. To eliminate nuclear activation concerns, the maximum kinetic energy of the accelerator is limited by regulation to 10 MeV for electron beams, and 5 MeV for x-rays. From penetration considerations, the largest areal density that can be treated by double-sided electron irradiation at 10 MeV is about 8.8 g/cm2. Products having greater areal densities must be processed using more penetrating x-rays. The mass throughput (dM/dt in kg/s) of an accelerator-based system is proportional to the average beam power (P in kW), and inversely proportional to the minimum required dose (Dm in kGy, with 1 kGy = 1 kJ/kg). The constant of proportionality is the mass throughput efficiency. Throughput efficiencies of 0.4 or better are typical of electron beam installations, but are only 0.025-0.035 for x-ray installations, primarily because of the inefficiency of bremsstrahlung generation at 5 MeV (about 8an axially-coupled, standing-wave, L-band linac with an average power in excess of 100 kW to achieve reasonable throughput rates with x-ray processing. Various design aspects of this new machine will be presented.

Elevated ozone reduces photosynthetic carbon gain by accelerating leaf senescence of inbred and hybrid maize in a genotype-specific manner

USDA-ARS?s Scientific Manuscript database

Exposure to elevated tropospheric ozone concentration ([O3]) accelerates leaf senescence in many C3 crops. However, the effects of elevated [O3] on C4 crops including maize (Zea mays L.) are poorly understood in terms of physiological mechanism and genetic variation in sensitivity. Using Free Air ga...

Magnitude of Head Impact Exposures in Individual Collegiate Football Players

PubMed Central

Wilcox, Bethany J.; Machan, Jason T.; McAllister, Thomas W.; Duhaime, Ann-Christine; Duma, Stefan M.; Rowson, Steven; Beckwith, Jonathan G.; Chu, Jeffrey J.; Greenwald, Richard M.

2013-01-01

The purpose of this study was to quantify the severity of head impacts sustained by individual collegiate football players and to investigate differences between impacts sustained during practice and game sessions, as well as by player position and impact location. Head impacts (N = 184,358) were analyzed for 254 collegiate players at three collegiate institutions. In practice, the 50th and 95th percentile values for individual players were 20.0 g and 49.5 g for peak linear acceleration, 1187 rad/s2 and 3147 rad/s2 for peak rotational acceleration, and 13.4 and 29.9 for HITsp, respectively. Only the 95th percentile HITsp increased significantly in games compared with practices (8.4%, p= .0002). Player position and impact location were the largest factors associated with differences in head impacts. Running backs consistently sustained the greatest impact magnitudes. Peak linear accelerations were greatest for impacts to the top of the helmet, whereas rotational accelerations were greatest for impacts to the front and back. The findings of this study provide essential data for future investigations that aim to establish the correlations between head impact exposure, acute brain injury, and long-term cognitive deficits. PMID:21911854

3D Printed Scintillators For Use in Field Emission Detection and Other Nuclear Physics Experiments

NASA Astrophysics Data System (ADS)

Ficenec, Karen

2015-10-01

In accelerator cavities, field emission electrons - electrons that get stripped away from the cavity walls due to the high electromagnetic field necessary to accelerate the main beam - are partially accelerated and can crash into the cavity walls, adding to the heat-load of the cryogenic system. Because these field electrons emit gamma rays when bent by the electromagnetic field, a scintillator, if made to fit the cavity enclosure, can detect their presence. Eliminating the waste of subtractive manufacturing techniques and allowing for the production of unique, varied shapes, 3D printing of scintillators may allow for an efficient detection system. UV light is used to start a chemical polymerization process that links the monomers of the liquid resin together into larger, intertwined molecules, forming the solid structure. Each shape requires slightly different calibration of its optimal printing parameters, such as slice thickness and exposure time to UV light. Thus far, calibration parameters have been optimized for cylinders of 20 mm diameter, cones of 30 mm diameter and 30 mm height, rectangular prisms 30 by 40 by 10 mm, and square pyramids 20 mm across. Calibration continues on creating holes in the prints (for optical fibers), as well as shapes with overhangs. Scintill This work was supported in part by the National Science Foundation under Grant No. PHY-1405857.

XOR inhibition with febuxostat accelerates pulmonary endothelial barrier recovery and improves survival in lipopolysaccharide-induced murine sepsis.

PubMed

Damarla, Mahendra; Johnston, Laura F; Liu, Gigi; Gao, Li; Wang, Lan; Varela, Lidenys; Kolb, Todd M; Kim, Bo S; Damico, Rachel L; Hassoun, Paul M

2017-08-01

Sepsis is a leading cause of death among patients in the intensive care unit, resulting from multi-organ failure. Activity of xanthine oxidoreductase (XOR), a reactive oxygen species (ROS) producing enzyme, is known to be elevated in nonsurvivors of sepsis compared to survivors. We have previously demonstrated that XOR is critical for ventilator-induced lung injury. Using febuxostat, a novel nonpurine inhibitor of XOR, we sought to determine the role of XOR inhibition in a murine model of sepsis-induced lung injury and mortality. C57BL/6J mice were subjected to intravenous (IV) lipopolysaccharide (LPS) for various time points, and lungs were harvested for analyses. Subsets of mice were treated with febuxostat, pre or post LPS exposure, or vehicle. Separate groups of mice were followed up for mortality after LPS exposure. After 24 hr of IV LPS , mice exhibited an increase in XOR activity in lung tissue and a significant increase in pulmonary endothelial barrier disruption. Pretreatment of animals with febuxostat before exposure to LPS, or treatment 4 h after LPS, resulted in complete abrogation of XOR activity. Inhibition of XOR with febuxostat did not prevent LPS-induced pulmonary vascular permeability at 24 h, however, it accelerated recovery of the pulmonary endothelial barrier integrity in response to LPS exposure. Furthermore, treatment with febuxostat resulted in significant reduction in mortality. Inhibition of XOR with febuxostat accelerates recovery of the pulmonary endothelial barrier and prevents LPS-induced mortality, whether given before or after exposure to LPS. © 2017 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.

Amps particle accelerator definition study

NASA Technical Reports Server (NTRS)

Sellen, J. M., Jr.

1975-01-01

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

New sulfenamide accelerators derived from 'safe' amines for the rubber and tyre industry.

PubMed

Wacker, C D; Spiegelhalder, B; Preussmann, R

1991-01-01

A reduction of the high exposures to N-nitrosamines in the rubber and tyre industry is possible using the concept of 'safe' amines, in which vulcanization accelerators contain amine moieties that are both difficult to nitrosate and, on nitrosation, yield noncarcinogenic N-nitroso compounds. The toxicological and technological properties of more than 50 benzothiazole sulfenamides derived from 'safe' amines have been evaluated. Some of the new compounds show excellent vulcanization properties and seem suitable as replacements for traditional accelerators in this class of compounds.

A new hydrostatic anti-G suit vs. a pneumatic anti-G system: preliminary comparison.

PubMed

Eiken, O; Kölegård, R; Lindborg, B; Aldman, M; Karlmar, K E; Linder, J; Kölegoård, R

2002-07-01

A newly developed hydrostatic anti-G suit is now commercially available. The suit is said to offer a high level of protection against +Gz acceleration. However, past experience shows that it is difficult to produce a hydrostatic suit with effective high-G protection. Careful testing is, therefore, needed to verify its efficacy. The G-protective properties of the hydrostatic anti-G suit (Libelle; L) were compared with those of a pneumatic anti-G ensemble (AGE-39) used in the Swedish JAS 39 Cripen aircraft. Three pilots were studied during vertical (+Gz) acceleration in a centrifuge using the following: 1) the L-suit with varied straining maneuvers; 2) the AGE-39 in combination with full anti-G straining maneuvers (AGSM) throughout each high-G exposure (full maneuver; FM); and 3) the AGE-39 in combination with AGSM during the initial part of each high-G exposure (reduced maneuver; RM). G-intensity tolerance was established during exposures to rapid onset rate (ROR) profiles with G-plateau levels ranging from +6.0 to +9.0 Gz. G-endurance was studied during simulated aerial combat maneuvers (SACM) consisting of 10 cycles of 5.5 to 7.5 G. All three pilots tolerated 9.0 G with the pneumatic system both in the RM and FM conditions; their tolerances averaged 6.3 G (range 6.0 to 7.0 G) for the L suit. Thus, during the ROR exposures only the 6.0 G profile was completed by all subjects in all three conditions. At this G-load both muscle straining (as indicated by electromyographic activity in thigh and abdomen) and heart rate were higher in the L than in the RM condition. Mean arterial pressure at eye level was higher in the FM than in the L and RM conditions. Only one subject was able to complete the SACM profile in the L condition. In the RM condition all subjects completed the SACM profile and in the FM condition two subjects completed the SACM. Whether the AGE-39 was used in combination with maximal AGSM throughout the duration of each high-G exposure or with AGSM only during the initial part of the high-G exposure, G-intensity tolerance was 9.0 G. While wearing the L-suit, G-tolerance was 6.3 G. Thus, under the conditions tested, the G-protection afforded by the L-suit is not adequate for use in a 9-G aircraft.

Combined ultraviolet and water exposure as a preconditioning method in laboratory fungal durability testing

Treesearch

Rebecca E. Ibach; Craig M. Clemons; Nicole M. Stark

2003-01-01

During outdoor exposure, woodfiber-plastic composites (WPC) are subject to biological, moisture, and ultraviolet (UV) degradation. The purpose of laboratory evaluations is to simulate outdoor conditions and accelerate the testing for quicker results. Traditionally, biological, moisture, and W laboratory tests are done separately, and only combined in outdoor field...

Pulmonary responses in current smokers and ex-smokers following a two hour exposure at rest to clean air and fine ambient air particles.

EPA Science Inventory

BACKGROUND: Increased susceptibility of smokers to ambient PM may potentially promote development of COPD and accelerate already present disease. OBJECTIVES: To characterize the acute and subacute lung function response and inflammatory effects of controlled chamber exposure t...

Reducing the radiation dose from inhaled americium-241 using continuously administered DTPA therapy.

PubMed

Guilmette, R A; Muggenburg, B A

1988-02-01

Accelerating the removal of a radionuclide from the body of a contaminated individual is the only available approach to decreasing the radiation dose from such exposures. In this study, continuous infusion of a chelating agent, DTPA, was given to dogs that had inhaled a moderately soluble aerosol, 241 AmO2, not only to accelerate clearance of the radionuclide from the lung but also to prevent its deposition in liver and bone. Treatment was begun with an intravenous injection of CaDTPA 1 h after exposure, and was continued for 64 days after exposure by implanting subcutaneously osmotic pumps containing ZnDTPA at 1 day after exposure. The results showed that the infusion therapy was effective in blocking the translocation of 99.5 per cent of the 241Am that would have been deposited in liver, and 98.3 per cent of the 241Am that would have been deposited in bone. This result was significantly better than the result achieved using repeated intravenous injections of DTPA, the method of treatment in current use for actinide contamination cases.

Cyclic Failure Mechanisms of Thermal and Environmental Barrier Coating Systems Under Thermal Gradient Test Conditions

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Lee, Kang N.; Miller, Robert A.

2002-01-01

Plasma-sprayed ZrO2-8wt%Y2O3 and mullite+BSAS/Si multilayer thermal and environmental barrier coating (TBC-EBC) systems on SiC/SiC ceramic matrix composite (CMC) substrates were thermally cyclic tested under high thermal gradients using a laser high-heat-flux rig in conjunction with furnace exposure in water-vapor environments. Coating sintering and interface damage were assessed by monitoring the real-time thermal conductivity changes during the laser heat-flux tests and by examining the microstructural changes after exposure. Sintering kinetics of the coating systems were also independently characterized using a dilatometer. It was found that the coating failure involved both the time-temperature dependent sintering and the cycle frequency dependent cyclic fatigue processes. The water vapor environments not only facilitated the initial coating conductivity increases due to enhanced sintering and interface reaction, but also promoted later conductivity reductions due to the accelerated coating cracking and delamination. The failure mechanisms of the coating systems are also discussed based on the cyclic test results and are correlated to the sintering and thermal stress behavior under the thermal gradient test conditions.

A new deflection technique applied to an existing scheme of electrostatic accelerator for high energy neutral beam injection in fusion reactor devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pilan, N., E-mail: nicola.pilan@igi.cnr.it; Antoni, V.; De Lorenzi, A.

A scheme of a neutral beam injector (NBI), based on electrostatic acceleration and magneto-static deflection of negative ions, is proposed and analyzed in terms of feasibility and performance. The scheme is based on the deflection of a high energy (2 MeV) and high current (some tens of amperes) negative ion beam by a large magnetic deflector placed between the Beam Source (BS) and the neutralizer. This scheme has the potential of solving two key issues, which at present limit the applicability of a NBI to a fusion reactor: the maximum achievable acceleration voltage and the direct exposure of the BSmore » to the flux of neutrons and radiation coming from the fusion reactor. In order to solve these two issues, a magnetic deflector is proposed to screen the BS from direct exposure to radiation and neutrons so that the voltage insulation between the electrostatic accelerator and the grounded vessel can be enhanced by using compressed SF{sub 6} instead of vacuum so that the negative ions can be accelerated at energies higher than 1 MeV. By solving the beam transport with different magnetic deflector properties, an optimum scheme has been found which is shown to be effective to guarantee both the steering effect and the beam aiming.« less

Altered thermogenesis and impaired bone remodeling in Misty mice

PubMed Central

Motyl, Katherine J; Bishop, Kathleen A; DeMambro, Victoria E; Bornstein, Sheila A; Le, Phuong; Kawai, Masanobu; Lotinun, Sutada; Horowitz, Mark C; Baron, Roland; Bouxsein, Mary L; Rosen, Clifford J

2013-01-01

Fat mass may be modulated by the number of brown-like adipocytes in white adipose tissue (WAT) in humans and rodents. Bone remodeling is dependent on systemic energy metabolism and, with age, bone remodeling becomes uncoupled and brown adipose tissue (BAT) function declines. To test the interaction between BAT and bone, we employed Misty (m/m) mice, which were reported be deficient in BAT. We found that Misty mice have accelerated age-related trabecular bone loss and impaired brown fat function (including reduced temperature, lower expression of Pgc1a and less sympathetic innervation compared to wildtype (+/+)). Despite reduced BAT function, Misty mice had normal core body temperature, suggesting heat is produced from other sources. Indeed, upon acute cold exposure (4°C for 6 hr), inguinal WAT from Misty mice compensated for BAT dysfunction by increasing expression of Acadl, Pgc1a, Dio2 and other thermogenic genes. Interestingly, acute cold exposure also decreased Runx2 and increased Rankl expression in Misty bone, but only Runx2 was decreased in wildtype. Browning of WAT is under the control of the sympathetic nervous system (SNS) and, if present at room temperature, could impact bone metabolism. To test whether SNS activity could be responsible for accelerated trabecular bone loss, we treated wildtype and Misty mice with the β-blocker, propranolol. As predicted, propranolol slowed trabecular BV/TV loss in the distal femur of Misty mice without affecting wildtype. Finally, the Misty mutation (a truncation of DOCK7) also has a significant cell-autonomous role. We found DOCK7 expression in whole bone and osteoblasts. Primary osteoblast differentiation from Misty calvaria was impaired, demonstrating a novel role for DOCK7 in bone remodeling. Despite the multifaceted effects of the Misty mutation, we have shown that impaired brown fat function leads to altered SNS activity and bone loss, and for the first time that cold exposure negatively affects bone remodeling. PMID:23553822

Guidelines for Safe Human Exposure to Impact Acceleration. Update A

DTIC Science & Technology

1989-09-01

and +Y directions were mostly medically insignificant [4]. (4) One subject had pain radiating to his left arm after a +Y expost -re. This condition was... factor . The "Eiband curves" [7] for human wholebody tolerance to impact ac- celeration exposures are based on work with humans and chimpanzees...problems such as severe strains precede head injury, and therefore neck injury is the limiting factor in defining maximum impact exposures. Forces and

Maximizing oyster-reef growth supports green infrastructure with accelerating sea-level rise

PubMed Central

Ridge, Justin T.; Rodriguez, Antonio B.; Joel Fodrie, F.; Lindquist, Niels L.; Brodeur, Michelle C.; Coleman, Sara E.; Grabowski, Jonathan H.; Theuerkauf, Ethan J.

2015-01-01

Within intertidal communities, aerial exposure (emergence during the tidal cycle) generates strong vertical zonation patterns with distinct growth boundaries regulated by physiological and external stressors. Forecasted accelerations in sea-level rise (SLR) will shift the position of these critical boundaries in ways we cannot yet fully predict, but landward migration will be impaired by coastal development, amplifying the importance of foundation species’ ability to maintain their position relative to rising sea levels via vertical growth. Here we show the effects of emergence on vertical oyster-reef growth by determining the conditions at which intertidal reefs thrive and the sharp boundaries where reefs fail, which shift with changes in sea level. We found that oyster reef growth is unimodal relative to emergence, with greatest growth rates occurring between 20–40% exposure, and zero-growth boundaries at 10% and 55% exposures. Notably, along the lower growth boundary (10%), increased rates of SLR would outpace reef accretion, thereby reducing the depth range of substrate suitable for reef maintenance and formation, and exacerbating habitat loss along developed shorelines. Our results identify where, within intertidal areas, constructed or natural oyster reefs will persist and function best as green infrastructure to enhance coastal resiliency under conditions of accelerating SLR. PMID:26442712

Acute exposure of mercury chloride stimulates the tissue regeneration program and reactive oxygen species production in the Drosophila midgut.

PubMed

Chen, Zhi; Wu, Xiaochun; Luo, Hongjie; Zhao, Lingling; Ji, Xin; Qiao, Xianfeng; Jin, Yaping; Liu, Wei

2016-01-01

We used Drosophila as an animal model to study the digestive tract in response to the exposure of inorganic mercury (HgCl2). We found that after oral administration, mercury was mainly sequestered within the midgut. This resulted in increased cell death, which in turn stimulated the tissue regeneration program, including accelerated proliferation and differentiation of the intestinal stem cells (ISCs). We further demonstrated that these injuries correlate closely with the excessive production of the reactive oxygen species (ROS), as vitamin E, an antioxidant reagent, efficiently suppressed the HgCl2-induced phenotypes of midgut and improved the viability. We propose that the Drosophila midgut could serve as a suitable model to study the treatment of acute hydrargyrism on the digestive systems. Copyright © 2015 Elsevier B.V. All rights reserved.

Parasite infection accelerates age polyethism in young honey bees

PubMed Central

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

2016-01-01

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

Parasite infection accelerates age polyethism in young honey bees.

PubMed

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

2016-02-25

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

High-sensitivity x-ray mask damage studies employing holographic gratings and phase-shifting interferometry

NASA Astrophysics Data System (ADS)

Hansen, Matthew E.; Cerrina, Franco

1994-05-01

A high-sensitivity holographic and interferometric metrology developed at the Center for X- ray Lithography (CXrL) has been employed to investigate in-plane distortions (IPD) produced in x-ray mask materials. This metrology has been applied to characterize damage to x-ray mask materials exposed to synchrotron radiation. X-ray mask damage and accelerated mask damage studies on silicon nitride and silicon carbide were conducted on the Aladdin ES-1 and ES-2 beamline exposure stations, respectively. Accumulated in-plane distortions due to x-ray irradiation were extracted from the incremental interferometric phase maps to yield IPD vs. dose curves for silicon nitride mask blanks. Silicon carbide mask blanks were subjected to accelerated mask damage in the high flux 2 mm X 2 mm beam of the ES-2 exposure station. An accelerated damage study of silicon carbide has shown no in-plane distortion for an accumulated dose of 800 kJ/cm2 with a measurement sensitivity of less than 5 nm.

Leukocyte Telomere Length in Major Depression: Correlations with Chronicity, Inflammation and Oxidative Stress - Preliminary Findings

PubMed Central

Wolkowitz, Owen M.; Mellon, Synthia H.; Epel, Elissa S.; Lin, Jue; Dhabhar, Firdaus S.; Su, Yali; Reus, Victor I.; Rosser, Rebecca; Burke, Heather M.; Kupferman, Eve; Compagnone, Mariana; Nelson, J. Craig; Blackburn, Elizabeth H.

2011-01-01

Background Depression is associated with an unusually high rate of aging-related illnesses and early mortality. One aspect of “accelerated aging” in depression may be shortened leukocyte telomeres. When telomeres critically shorten, as often occurs with repeated mitoses or in response to oxidation and inflammation, cells may die. Indeed, leukocyte telomere shortening predicts early mortality and medical illnesses in non-depressed populations. We sought to determine if leukocyte telomeres are shortened in Major Depressive Disorder (MDD), whether this is a function of lifetime depression exposure and whether this is related to putative mediators, oxidation and inflammation. Methodology Leukocyte telomere length was compared between 18 unmedicated MDD subjects and 17 controls and was correlated with lifetime depression chronicity and peripheral markers of oxidation (F2-isoprostane/Vitamin C ratio) and inflammation (IL-6). Analyses were controlled for age and sex. Principal Findings The depressed group, as a whole, did not differ from the controls in telomere length. However, telomere length was significantly inversely correlated with lifetime depression exposure, even after controlling for age (p<0.05). Average telomere length in the depressed subjects who were above the median of lifetime depression exposure (≥9.2 years' cumulative duration) was 281 base pairs shorter than that in controls (p<0.05), corresponding to approximately seven years of “accelerated cell aging.” Telomere length was inversely correlated with oxidative stress in the depressed subjects (p<0.01) and in the controls (p<0.05) and with inflammation in the depressed subjects (p<0.05). Conclusions These preliminary data indicate that accelerated aging at the level of leukocyte telomeres is proportional to lifetime exposure to MDD. This might be related to cumulative exposure to oxidative stress and inflammation in MDD. This suggest that telomere shortening does not antedate depression and is not an intrinsic feature. Rather, telomere shortening may progress in proportion to lifetime depression exposure. PMID:21448457

International Space Station Increment-6/8 Microgravity Environment Summary Report November 2002 to April 2004

NASA Technical Reports Server (NTRS)

Jules, Kenol; Hrovat, Kenneth; Kelly, Eric; Reckart, Timothy

2006-01-01

This summary report presents the analysis results of some of the processed acceleration data measured aboard the International Space Station during the period of November 2002 to April 2004. Two accelerometer systems were used to measure the acceleration levels for the activities that took place during Increment-6/8. However, not all of the activities during that period were analyzed in order to keep the size of the report manageable. The National Aeronautics and Space Administration sponsors the Microgravity Acceleration Measurement System and the Space Acceleration Measurement System to support microgravity science experiments that require microgravity acceleration measurements. On April 19, 2001, both the Microgravity Acceleration Measurement System and the Space Acceleration Measurement System units were launched on STS-100 from the Kennedy Space Center for installation on the International Space Station. The Microgravity Acceleration Measurement System unit was flown to the station in support of science experiments requiring quasi-steady acceleration measurements, while the Space Acceleration Measurement System unit was flown to support experiments requiring vibratory acceleration measurement. Both acceleration systems are also used in support of the vehicle microgravity requirements verification as well as in support of the International Space Station support cadre. The International Space Station Increment-6/8 reduced gravity environment analysis presented in this report uses acceleration data collected by both sets of accelerometer systems: 1. The Microgravity Acceleration Measurement System, which consists of two sensors: the Orbital Acceleration Research Experiment Sensor Subsystem, a low frequency range sensor (up to 1 Hz), is used to characterize the quasi-steady environment for payloads and vehicle, and the High Resolution Accelerometer Package, which is used to characterize the vibratory environment up to 100 Hz. 2. The Space Acceleration Measurement System measures vibratory acceleration data in the range of 0.01 to 400 Hz. This summary report presents analysis of some selected quasi-steady and vibratory activities measured by these accelerometers during Increment-6/8 from November 2002 to April 2004.

International Space Station Increment-2 Microgravity Environment Summary Report

NASA Technical Reports Server (NTRS)

Jules, Kenol; Hrovat, Kenneth; Kelly, Eric; McPherson, Kevin; Reckart, Timothy

2002-01-01

This summary report presents the results of some of the processed acceleration data, collected aboard the International Space Station during the period of May to August 2001, the Increment-2 phase of the station. Two accelerometer systems were used to measure the acceleration levels during activities that took place during the Increment-2 segment. However, not all of the activities were analyzed for this report due to time constraints, lack of precise information regarding some payload operations and other station activities. The National Aeronautics and Space Administration sponsors the Microgravity Acceleration Measurement System and the Space Acceleration Microgravity System to support microgravity science experiments, which require microgravity acceleration measurements. On April 19, 2001, both the Microgravity Acceleration Measurement System and the Space Acceleration Measurement System units were launched on STS-100 from the Kennedy Space Center for installation on the International Space Station. The Microgravity Acceleration Measurement System unit was flown to the station in support of science experiments requiring quasi-steady acceleration measurements, while the Space Acceleration Measurement System unit was flown to support experiments requiring vibratory acceleration measurement. Both acceleration systems are also used in support of vehicle microgravity requirements verification. The International Space Station Increment-2 reduced gravity environment analysis presented in this report uses acceleration data collected by both sets of accelerometer systems: 1) The Microgravity Acceleration Measurement System, which consists of two sensors: the Orbital Acceleration Research Experiment Sensor Subsystem, a low frequency range sensor (up to 1 Hz), is used to characterize the quasi-steady environment for payloads and the vehicle, and the High Resolution Accelerometer Package, which is used to characterize the vibratory environment up to 100 Hz. 2) The Space Acceleration Measurement System, which is a high frequency sensor, measures vibratory acceleration data in the range of 0.01 to 300 Hz. This summary report presents analysis of some selected quasisteady and vibratory activities measured by these accelerometers during Increment-2 from May to August 20, 2001.

International Space Station Increment-3 Microgravity Environment Summary Report

NASA Technical Reports Server (NTRS)

Jules, Kenol; Hrovat, Kenneth; Kelly, Eric; McPherson, Kevin; Reckart, Timothy; Grodsinksy, Carlos

2002-01-01

This summary report presents the results of some of the processed acceleration data measured aboard the International Space Station during the period of August to December 2001. Two accelerometer systems were used to measure the acceleration levels for the activities that took place during Increment-3. However, not all of the activities were analyzed for this report due to time constraint and lack of precise timeline information regarding some payload operations and station activities. The National Aeronautics and Space Administration sponsors the Microgravity Acceleration Measurement System and the Space Acceleration Microgravity System to support microgravity science experiments which require microgravity acceleration measurements. On April 19, 2001, both the Microgravity Acceleration Measurement System and the Space Acceleration Measurement System units were launched on STS-100 from the Kennedy Space Center for installation on the International Space Station. The Microgravity Acceleration Measurement System unit was flown to the station in support of science experiments requiring quasi-steady acceleration measurements, while the Space Acceleration Measurement System unit was flown to support experiments requiring vibratory acceleration measurement. Both acceleration systems are also used in support of the vehicle microgravity requirements verification. The International Space Station Increment-3 reduced gravity environment analysis presented in this report uses acceleration data collected by both sets of accelerometer systems: (1) The Microgravity Acceleration Measurement System, which consists of two sensors: the Orbital Acceleration Research Experiment Sensor Subsystem, a low frequency range sensor (up to 1 Hz), is used to characterize the quasi-steady environment for payloads and vehicle, and the High Resolution Accelerometer Package, which is used to characterize the vibratory environment up to 100 Hz. (2) The Space Acceleration Measurement System, which is a high frequency sensor, measures vibratory acceleration data in the range of 0.01 to 400 Hz. This summary report presents analysis of some selected quasi-steady and vibratory activities measured by these accelerometers during Increment-3 from August to December, 2001.

Development of a composite line source emission model for traffic interrupted microenvironments and its application in particle number emissions at a bus station

NASA Astrophysics Data System (ADS)

Wang, Lina; Jayaratne, Rohan; Heuff, Darlene; Morawska, Lidia

A composite line source emission (CLSE) model was developed to specifically quantify exposure levels and describe the spatial variability of vehicle emissions in traffic interrupted microenvironments. This model took into account the complexity of vehicle movements in the queue, as well as different emission rates relevant to various driving conditions (cruise, decelerate, idle and accelerate), and it utilised multi-representative segments to capture the accurate emission distribution for real vehicle flow. Hence, this model was able to quickly quantify the time spent in each segment within the considered zone, as well as the composition and position of the requisite segments based on the vehicle fleet information, which not only helped to quantify the enhanced emissions at critical locations, but it also helped to define the emission source distribution of the disrupted steady flow for further dispersion modelling. The model then was applied to estimate particle number emissions at a bi-directional bus station used by diesel and compressed natural gas fuelled buses. It was found that the acceleration distance was of critical importance when estimating particle number emission, since the highest emissions occurred in sections where most of the buses were accelerating and no significant increases were observed at locations where they idled. It was also shown that emissions at the front end of the platform were 43 times greater than at the rear of the platform. Although the CLSE model is intended to be applied in traffic management and transport analysis systems for the evaluation of exposure, as well as the simulation of vehicle emissions in traffic interrupted microenvironments, the bus station model can also be used for the input of initial source definitions in future dispersion models.

The Toll-Like Receptor 5 Agonist Entolimod Mitigates Lethal Acute Radiation Syndrome in Non-Human Primates.

PubMed

Krivokrysenko, Vadim I; Toshkov, Ilia A; Gleiberman, Anatoli S; Krasnov, Peter; Shyshynova, Inna; Bespalov, Ivan; Maitra, Ratan K; Narizhneva, Natalya V; Singh, Vijay K; Whitnall, Mark H; Purmal, Andrei A; Shakhov, Alexander N; Gudkov, Andrei V; Feinstein, Elena

2015-01-01

There are currently no approved medical radiation countermeasures (MRC) to reduce the lethality of high-dose total body ionizing irradiation expected in nuclear emergencies. An ideal MRC would be effective even when administered well after radiation exposure and would counteract the effects of irradiation on the hematopoietic system and gastrointestinal tract that contribute to its lethality. Entolimod is a Toll-like receptor 5 agonist with demonstrated radioprotective/mitigative activity in rodents and radioprotective activity in non-human primates. Here, we report data from several exploratory studies conducted in lethally irradiated non-human primates (rhesus macaques) treated with a single intramuscular injection of entolimod (in the absence of intensive individualized supportive care) administered in a mitigative regimen, 1-48 hours after irradiation. Following exposure to LD50-70/40 of radiation, injection of efficacious doses of entolimod administered as late as 25 hours thereafter reduced the risk of mortality 2-3-fold, providing a statistically significant (P<0.01) absolute survival advantage of 40-60% compared to vehicle treatment. Similar magnitude of survival improvement was also achieved with drug delivered 48 hours after irradiation. Improved survival was accompanied by predominantly significant (P<0.05) effects of entolimod administration on accelerated morphological recovery of hematopoietic and immune system organs, decreased severity and duration of thrombocytopenia, anemia and neutropenia, and increased clonogenic potential of the bone marrow compared to control irradiated animals. Entolimod treatment also led to reduced apoptosis and accelerated crypt regeneration in the gastrointestinal tract. Together, these data indicate that entolimod is a highly promising potential life-saving treatment for victims of radiation disasters.

Effect of +Gz Acceleration on the Oxygen Uptake-Excercise Load Relationship during Lower Extremity Ergometer Excercise

NASA Technical Reports Server (NTRS)

Jackson, Catherine G. R.

1996-01-01

Long term spaceflight and habitation of a space station and/or the moon require that astronauts be provided with sufficient environmental and physiological support so that they can not only function in microgravity but be returned to earth safely. As the duration of habitation in microgravity increase the effects of the concomitant deconditioning of body systems becomes a concern for added exercise in space and for reentry to Earth gravity. Many countermeasures have been proposed to maintain proper functioning of the body, but none have proved sufficient, especially when the cost of crew time spent in these activities is considered. The issue of appropriate countermeasures remains unresolved. Spaceflight deconditioning decreases tolerance to +Gz acceleration, head to foot, the direction which is experienced during reentry; the result is that the crew member is more prone to becoming pre-syncopal or syncopal, thus exacerbating the orthostatic intolerance. All ground-based research using microgravity analogues has produced this same lowered G tolerance. When intermittent exposure to +1 to +4 Gz acceleration training was used, some alleviation of orthosatic intolerance and negative physiological effects of deconditioning occurred. Exercise alone was not as effective; but the added G force was. The physiological responses to acceleration added to exercise training have not been clearly shown. We will test the hypothesis that there will be no difference in the exercise oxygen uptake-exercise load relationship with added +Gz acceleration. We wi also compare oxygen uptake during graded exercise-acceleration loads in the human-powered short arm centrifuge with those from normal supine exercise loads. The human-powered short arm centrifuge was built by NASA engineers at Ames Research Center.

The Alcoa ram fastener: A reusable blind rivet

NASA Technical Reports Server (NTRS)

Dewalt, W. J.

1972-01-01

Results of tensile, shear, fatigue and accelerated weathering tests are presented for the ram fastener, a reusable, single unit blind rivet. The effects of variations in hole size, grip length and sheet thickness on strength properties of the fastener were determined. The test results show these fasteners to have strength characteristics suitable for light structural applications. Exposure to accelerated weathering did not impair their performance.

Effects of rehydration on +Gz tolerance after 14-days' bed rest.

NASA Technical Reports Server (NTRS)

Greenleaf, J. E.; Van Beaumont, W.; Bernauer, E. M.; Haines, R. F.; Sandler, H.; Staley, R. W.; Young, H. L.; Yusken, J. W.

1973-01-01

Investigation of the magnitude of reduction in human tolerance to centrifugation following 2 weeks of bed rest with moderate daily exercise. The degree of hypovolemia associated with these exposures is assessed, and the possibility to improve or to return to control levels the tolerance to acceleration forces acting in the head-to-foot direction through rehydration prior to acceleration is explored.

Drosophila melanogaster (fruit fly) locomotion during a sounding rocket flight

NASA Astrophysics Data System (ADS)

Miller, Mark S.; Keller, Tony S.

2008-05-01

The locomotor activity of young Drosophila melanogaster (fruit fly) was studied during a Nike-Orion sounding rocket flight, which included a short-duration microgravity exposure. An infrared monitoring system was used to determine the activity level, instantaneous velocity, and continuous velocity of 240 (120 male, 120 female) fruit flies. Individual flies were placed in chambers that limit their motion to walking. Chambers were oriented both vertically and horizontally with respect to the rocket's longitudinal axis. Significant changes in Drosophila locomotion patterns were observed throughout the sounding rocket flight, including launch, microgravity exposure, payload re-entry, and after ocean impact. During the microgravity portion of the flight (3.8 min), large increases in all locomotion measurements for both sexes were observed, with some measurements doubling compared to pad (1 G) data. Initial effects of microgravity were probably delayed due to large accelerations from the payload despining immediately before entering microgravity. The results indicate that short-duration microgravity exposure has a large effect on locomotor activity for both males and females, at least for a short period of time. The locomotion increases may explain the increased male aging observed during long-duration exposure to microgravity. Studies focusing on long-duration microgravity exposure are needed to confirm these findings, and the relationship of increased aging and locomotion.

A method to quantify hand-transmitted vibration exposure based on the biodynamic stress concept.

PubMed

Dong, R G; Welcome, D E; Wu, J Z

2007-11-01

This study generally hypothesized that the vibration-induced biodynamic stress and number of its cycles in a substructure of the hand-arm system play an important role in the development of vibration-induced disorders in the substructure. As the first step to test this hypothesis, the specific aims of this study were to develop a practical method to quantify the biodynamic stress-cycle measure, to compare it with ISO-weighted and unweighted accelerations, and to assess its potential for applications. A mechanical-equivalent model of the system was established using reported experimental data. The model was used to estimate the average stresses in the fingers and palm. The frequency weightings of the stresses in these substructures were derived using the proposed stress-cycle measure. This study found the frequency dependence of the average stress distributed in the fingers is different from that in the palm. Therefore, this study predicted that the frequency dependencies of finger disorders could also be different from those of the disorders in the palm, wrist, and arms. If vibration-induced white finger (VWF) is correlated better with unweighted acceleration than with ISO-weighted acceleration, the biodynamic stress distributed in the fingers is likely to play a more important role in the development of VWF than is th e biodynamic stressdistributed in the other substructures of the hand-arm system. The results of this study also suggest that the ISO weighting underestimates the high-frequency effect on the finger disorder development but it may provide a reasonable risk assessment of the disorders in the wrist and arm.

Health risks of vibration exposure to wheelchair users in the community

PubMed Central

Garcia-Mendez, Yasmin; Pearlman, Jonathan L.; Boninger, Michael L.; Cooper, Rory A.

2013-01-01

Objective The purpose of this study was to evaluate whole-body vibration (WBV) exposure to wheelchair (WC) users in their communities and to determine the effect of WC frame type (folding, rigid, and suspension) in reducing WBV transmitted to the person. Design An observational case-control study of the WBV exposure levels among WC users. Participants Thirty-seven WC users, with no pressure sores, 18 years old or older and able to perform independent transfers. Main outcome measures WC users were monitored for 2 weeks to collect WBV exposure, as well as activity levels, by using custom vibration and activity data-loggers. Vibration levels were evaluated using ISO 2631-1 methods. Results All WC users who participated in this study were continuously exposed to WBV levels at the seat that were within and above the health caution zone specified by ISO 2631-1 during their day-to-day activities (0.83 ± 0.17 m/second2, weighted root-mean-squared acceleration, for 13.07 ± 3.85 hours duration of exposure). WCs with suspension did not attenuate vibration transmitted to WC users (V = 0.180, F(8, 56) = 0.692, P = 0.697). Conclusions WBV exposure to WC users exceeds international standards. Suspension systems need to be improved to reduce vibrations transmitted to the users. PMID:23820152

Occupational exposure to whole body vibration-train drivers.

PubMed

Birlik, Gülin

2009-01-01

Whole body vibration exposure of the train drivers working for State Railway Lines is assessed by referring to ISO standard 2631 -1 and EU directive 2002/44/EC. The vibration measurements were done in the cabins of suburban and intercity train drivers. Suburban train driver performs his job usually in standing posture. Whereas intercity train driver works generally in seated (bending forward) posture and exposed to longer periods of continuous vibration, compared to suburban train drivers. The mean accelerations, a, along lateral, y, and vertical, z, directions measured on the driver seat (on the cabin floor) of the intercity (suburban) train were 1.4a (y) = 0.55 (0.28) m/s(2) and a (z) = 0.65 (0.23) m/s(2). Daily exposure action values suggested in EU directive are exceeded in case of intercity train drivers and their exposure falls within the health caution zone of ISO 2631-1. Intercity train drivers are therefore under the risk of having spinal disorders. A health surveillance plan requiring every five years the reassessment of the state of the spinal system of train drivers is suggested. As an early preventive measure, extended work day or more than one shift in a day is advised to be discouraged.

Increased lung function decline in blue-collar workers exposed to welding fumes.

PubMed

Thaon, Isabelle; Demange, Valérie; Herin, Fabrice; Touranchet, Annie; Paris, Christophe

2012-07-01

There is no consensus at the present time about the effect of welding on lung function decline. This study compared lung function decline between blue-collar workers exposed and not exposed to welding fumes in a French longitudinal cohort of 21,238 subjects aged 37 to 52 years at inclusion. Medical data, occupation, sector of activity, and spirometry were recorded twice by occupational physicians in 1990 and 1995. A job-exposure matrix was used to identify 503 male blue-collar workers exposed to welding fumes and 709 control subjects and to define the weekly duration of exposure to welding fumes. Baseline lung function parameters were higher in workers exposed to welding fumes than in control subjects. After a 5-year follow-up, welding-fume exposure was associated with a nonsignificant decline in FVC (P = .06) and FEV(1) (P = .07) after adjustment for age, pack-years, BMI, and baseline value of the parameter. A significant accelerated decline in FEV(1) (P = .046) was also observed in never smokers exposed to welding fumes. An “exposure-response” relationship was observed between FEV(1) decline and weekly duration of exposure to welding fumes in nonsmokers but not in smokers. Blue-collar workers exposed to welding fumes showed accelerated decline in lung function, which, in nonsmokers, was related to weekly duration of exposure.

Accelerated weathering of natural fiber-thermoplastic composites : effects of ultraviolet exposure on bending strength and stiffness

Treesearch

Thomas Lundin; Robert H. Falk; Colin Felton

2002-01-01

Mechanical properties of bending stiffness and yield stress were used to evaluate the effects of ultraviolet exposure on natural fiber-thermoplastic composites. Four different specimen formulations were evaluated. Injection molded high density polyethylene (HDPE) served as the polymer base for all formulations. Two lignocellulosic fillers, wood flour and kenaf fiber,...

Exposure assessment in health assessments for hand-arm vibration syndrome.

PubMed

Mason, H J; Poole, K; Young, C

2011-08-01

Assessing past cumulative vibration exposure is part of assessing the risk of hand-arm vibration syndrome (HAVS) in workers exposed to hand-arm vibration and invariably forms part of a medical assessment of such workers. To investigate the strength of relationships between the presence and severity of HAVS and different cumulative exposure metrics obtained from a self-reporting questionnaire. Cumulative exposure metrics were constructed from a tool-based questionnaire applied in a group of HAVS referrals and workplace field studies. These metrics included simple years of vibration exposure, cumulative total hours of all tool use and differing combinations of acceleration magnitudes for specific tools and their daily use, including the current frequency-weighting method contained in ISO 5349-1:2001. Use of simple years of exposure is a weak predictor of HAVS or its increasing severity. The calculation of cumulative hours across all vibrating tools used is a more powerful predictor. More complex calculations based on involving likely acceleration data for specific classes of tools, either frequency weighted or not, did not offer a clear further advantage in this dataset. This may be due to the uncertainty associated with workers' recall of their past tool usage or the variability between tools in the magnitude of their vibration emission. Assessing years of exposure or 'latency' in a worker should be replaced by cumulative hours of tool use. This can be readily obtained using a tool-pictogram-based self-reporting questionnaire and a simple spreadsheet calculation.

Absorbed dose thresholds and absorbed dose rate limitations for studies of electron radiation effects on polyetherimides

NASA Technical Reports Server (NTRS)

Long, Edward R., Jr.; Long, Sheila Ann T.; Gray, Stephanie L.; Collins, William D.

1989-01-01

The threshold values of total absorbed dose for causing changes in tensile properties of a polyetherimide film and the limitations of the absorbed dose rate for accelerated-exposure evaluation of the effects of electron radiation in geosynchronous orbit were studied. Total absorbed doses from 1 kGy to 100 MGy and absorbed dose rates from 0.01 MGy/hr to 100 MGy/hr were investigated, where 1 Gy equals 100 rads. Total doses less than 2.5 MGy did not significantly change the tensile properties of the film whereas doses higher than 2.5 MGy significantly reduced elongation-to-failure. There was no measurable effect of the dose rate on the tensile properties for accelerated electron exposures.

Environmental exposure effects on composite materials for commercial aircraft

NASA Technical Reports Server (NTRS)

Gibbons, M. N.

1982-01-01

The data base for composite materials' properties as they are affected by the environments encountered in operating conditions, both in flight and at ground terminals is expanded. Absorbed moisture degrades the mechanical properties of graphite/epoxy laminates at elevated temperatures. Since airplane components are frequently exposed to atmospheric moisture, rain, and accumulated water, quantitative data are required to evaluate the amount of fluids absorbed under various environmental conditions and the subsequent effects on material properties. In addition, accelerated laboratory test techniques are developed are reliably capable of predicting long term behavior. An accelerated environmental exposure testing procedure is developed, and experimental results are correlated and compared with analytical results to establish the level of confidence for predicting composite material properties.

Vibration Responses of Test Structure No. 2 During the Edward Air Force Base Phase of the National Sonic Boom Program

NASA Technical Reports Server (NTRS)

Findley, D. S.; Huckel, V.; Hubbard, H. H.

1975-01-01

In order to evaluate reaction of people to sonic booms of varying overpressures and time durations, a series of closely controlled and systematic flight tests/studies were conducted from June 3 to June 23, 1966. The dynamic responses of several building structures were measured, with emphasis on a two-story residence structure. Sample acceleration and strain recordings from F-104, B-58, and XB-70 sonic boom exposures are included, along with tabulations of the maximum acceleration and strain values measured for each one of about 140 flight tests. These data are compared with similar measurements for engine noise exposures of the building during simulated landing approaches and takeoffs of KC-135 aircraft.

Effect of space relevant radiation exposure on differentiation and mineralization of murine osteoprogenitor cells

NASA Astrophysics Data System (ADS)

Lau, Patrick; Hu, Yueyuan; Hellweg, Christine; Baumstark-Khan, Christa; Reitz, Guenther

Extended exposure to altered gravity conditions like during long-term space flight results in significant bone loss. Exposure to ionizing radiation for cancer therapy causes bone damage and may increase the risk of fractures. Similarly, besides altered gravity conditions, astronauts on exploratory missions beyond low-Earth orbit will be exposed to high-energy heavy ions in addition to proton and photon radiation, although for prolonged periods and at lower doses and dose rates compared with therapy. Space conditions may place astronauts at a greater risk for mission-critical fractures. Until now, little is known about the effects of space radiation on the skeletal system especially on osteoprogenitor cells. Accelerator facilities are used to simulate parts of the radiation environment in space. Heavy ion accelerators therefore could be used to assess radiation risks for astronauts who will be exposed to higher radiation doses e.g. on a Mars mission. The aim of the present study was to determine the biological effects of spaceflight-relevant radiation exposure on the cellular level using murine osteoprogenitor cell lines compared to nonirradiated controls. To gain a deeper understanding of bone cell differenti-ation and mineralization after exposure to heavy ions, we examined gene expression modulation of bone specific transcription factors, osteoblast specific marker genes as well as genes function as coupling factors that link bone resorption to bone formation. We investigated the transcrip-tional modulation of type I collagen (Col I), osteocalcin (Ocn), Transforming growth factor-β1 (TGF-β1), interleukin-6 (IL-6) and the bone specific transcription factor Runx2 (Cbfa1). To gain deeper insight into potential cellular mechanisms involved in cellular response after ex-posure to heavy ions, we investigated gene expression modulations after exposure to energetic carbon ions (35 MeV/u, 73.2 keV/µm), iron ions (1000 MeV/u, 150 keV/µm) and lead ions (29 MeV/u, 9600 keV/µm) versus low LET X-rays. Exposure to X-irradiation dose-dependently increased the mRNA levels of Runx2 (cbfa1) whereas expression values of OCN and TGF-β1 were elevated at later time points. Exposure to heavy ions provoked a more marked effect on bone specific gene expression within the differentiation process. Collectively, our results indi-cate that heavy ions facilitate differentiation more effectively than X-rays as a major response in the progeny of irradiated osteoprogenitor cells. The data presented allow us to suggest that exposure to ionizing radiation interferes with bone formation at the level of cellular differenti-ation. In this regard, further experiments are needed to investigate gene expression patterns in mammalian cells that respond to differentiation after exposure to ionizing radiation.

Early IGF-1 primes visual cortex maturation and accelerates developmental switch between NKCC1 and KCC2 chloride transporters in enriched animals.

PubMed

Baroncelli, Laura; Cenni, Maria Cristina; Melani, Riccardo; Deidda, Gabriele; Landi, Silvia; Narducci, Roberta; Cancedda, Laura; Maffei, Lamberto; Berardi, Nicoletta

2017-02-01

Environmental enrichment (EE) has a remarkable impact on brain development. Continuous exposure to EE from birth determines a significant acceleration of visual system maturation both at retinal and cortical levels. A pre-weaning enriched experience is sufficient to trigger the accelerated maturation of the visual system, suggesting that factors affected by EE during the first days of life might prime visual circuits towards a faster development. The search for such factors is crucial not only to gain a better understanding of the molecular hierarchy of brain development but also to identify molecular pathways amenable to be targeted to correct atypical brain developmental trajectories. Here, we showed that IGF-1 levels are increased in the visual cortex of EE rats as early as P6 and this is a crucial event for setting in motion the developmental program induced by EE. Early intracerebroventricular (i.c.v.) infusion of IGF-1 in standard rats was sufficient to mimic the action of EE on visual acuity development, whereas blocking IGF-1 signaling by i.c.v. injections of the IGF-1 receptor antagonist JB1 prevented the deployment of EE effects. Early IGF-1 decreased the ratio between the expression of NKCC1 and KCC2 cation/chloride transporters, and the reversal potential for GABA A R-driven Cl - currents (E Cl ) was shifted toward more negative potentials, indicating that IGF-1 is a crucial factor in accelerating the maturation of GABAergic neurotransmission and promoting the developmental switch of GABA polarity from excitation to inhibition. In addition, early IGF-1 promoted a later occurring increase in its own expression, suggesting a priming effect of early IGF-1 in driving post-weaning cortical maturation. Copyright © 2016 Elsevier Ltd. All rights reserved.

Biological responses of human solid tumor cells to X-ray irradiation within a 1.5-Tesla magnetic field generated by a magnetic resonance imaging-linear accelerator.

PubMed

Wang, Li; Hoogcarspel, Stan Jelle; Wen, Zhifei; van Vulpen, Marco; Molkentine, David P; Kok, Jan; Lin, Steven H; Broekhuizen, Roel; Ang, Kie-Kian; Bovenschen, Niels; Raaymakers, Bas W; Frank, Steven J

2016-10-01

Devices that combine magnetic resonance imaging with linear accelerators (MRL) represent a novel tool for MR-guided radiotherapy. However, whether magnetic fields (MFs) generated by these devices affect the radiosensitivity of tumors is unknown. We investigated the influence of a 1.5-T MF on cell viability and radioresponse of human solid tumors. Human head/neck cancer and lung cancer cells were exposed to single or fractionated 6-MV X-ray radiation; effects of the MF on cell viability were determined by cell plating efficiency and on radioresponsiveness by clonogenic cell survival. Doses needed to reduce the fraction of surviving cells to 37% of the initial value (D0s) were calculated for multiple exposures to MF and radiation. Results were analyzed using Student's t-tests. Cell viability was no different after single or multiple exposures to MRL than after exposure to a conventional linear accelerator (Linac, without MR-generated MF) in 12 of 15 experiments (all P > 0.05). Single or multiple exposures to MF had no influence on cell radioresponse (all P > 0.05). Cells treated up to four times with an MRL or a Linac further showed no changes in D0s with MF versus without MF (all P > 0.05). In conclusion, MF within the MRL does not seem to affect in vitro tumor radioresponsiveness as compared with a conventional Linac. Bioelectromagnetics. 37:471-480, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

The Effect of Dose Rate on Composite Durability When Exposed to a Simulated Long-Term Lunar Radiation Environment

NASA Technical Reports Server (NTRS)

Rojdev, Kristina; O'Rourke, Mary Jane; Hill, Charles; Nutt, Steven; Atwell, William

2011-01-01

Human exploration of space beyond low Earth orbit (LEO) requires a safe living and working environment for crew. Composite materials are one type of material being investigated by NASA as a multi-functional structural approach to habitats for long-term use in space or on planetary surfaces with limited magnetic fields and atmosphere. These materials provide high strength with the potential for decreased weight and increased radiation protection of crew and electronics when compared with conventional aluminum structures. However, these materials have not been evaluated in a harsh radiation environment, as would be experienced outside of LEO or on a planetary surface. Thus, NASA has been investigating the durability of select composite materials in a long-term radiation environment. Previously, NASA exposed composite samples to a simulated, accelerated 30-year radiation treatment and tensile stresses similar to those of a habitat pressure vessel. The results showed evidence of potential surface oxidation and enhanced cross-linking of the matrix. As a follow-on study, we performed the same accelerated exposure alongside an exposure with a decreased dose rate. The slower dose ]rate is comparable to a realistic scenario, although still accelerated. Strain measurements were collected during exposure and showed that with a fastdose rate, the strain decreased with time, but with a slow ]dose rate, the strain increased with time. After the radiation exposures, samples were characterized via tensile tests, flexure tests, Fourier Transform Infrared Spectroscopy (FTIR), and Differential Scanning Calorimetry (DSC). The results of these tests will be discussed.

The medical implications of space tourism.

PubMed

Tarzwell, R

2000-06-01

Commercial space travel may soon be a reality. If so, microgravity, high acceleration, and radiation exposure, all known hazards, will be accessible to the general public. Therefore, space tourism has medical implications. Even though the first flights will feature space exposure times of only a few minutes, the potential may someday exist for exposure times long enough to warrant careful consideration of the potential hazards to the space-faring public. The effects of acceleration and microgravity exposure are well known on the corps of astronauts and cosmonauts. The effects of space radiation are partially known on astronauts, but much remains to be discovered. However, there are problems using astronaut data to make inferences about the general public. Astronauts are not necessarily representative of the general public, since they are highly fit, highly screened individuals. Astronaut data can tell us very little about the potential hazards of microgravity in pediatric, obstetric and geriatric populations, all of whom are potential space tourists. Key issues in standard setting will be determining acceptable limits of pre-existing disease and inferring medical standards from mission profiles. It will not be a trivial task drafting minimal medical standards for commercial space travel. It will require the collaboration of space medicine physicians, making the best guesses possible, based on limited amounts of data, with limited applicability. A helpful departure point may be the USAF Class 3 medical standard, applicable to NASA payload specialists. It is time to begin preliminary discussions toward defining those standards. acceleration, aerospace medicine, medical standards, microgravity, radiation, space, space tourism, environmental hazards, environmental medicine.

The radiation field measurement and analysis outside the shielding of A 10 MeV electron irradiation accelerator

NASA Astrophysics Data System (ADS)

Shang, Jing; Li, Juexin; Xu, Bing; Li, Yuxiong

2011-10-01

Electron accelerators are employed widely for diverse purposes in the irradiation-processing industry, from sterilizing medical products to treating gemstones. Because accelerators offer high efficiency, high power, and require little preventative maintenance, they are becoming more and more popular than using the 60Co isotope approach. However, the electron accelerator exposes potential radiation hazards. To protect workers and the public from exposure to radiation, the radiation field around the electronic accelerator must be assessed, especially that outside the shielding. Thus, we measured the radiation dose at different positions outside the shielding of a 10-MeV electron accelerator using a new data-acquisition unit named Mini-DDL (Mini-Digital Data Logging). The measurements accurately reflect the accelerator's radiation status. In this paper, we present our findings, results and compare them with our theoretical calculations. We conclude that the measurements taken outside the irradiation hall are consistent with the findings from our calculations, except in the maze outside the door of the accelerator room. We discuss the reason for this discrepancy.

Assessment of vibration produced by the grinders used in the shipbuilding industry of Korea.

PubMed

Park, Hee-Sok; Yim, Sang-Hyuk

2007-04-01

The objective of this study is to estimate the prevalence of finger blanching among the workers in a shipyard of Korea using the dose-response relationship suggested by ISO 5349. The characteristics of vibration exposure produced by six types of grinders were investigated. Vibration measurement was made under the real work conditions. Exposure time was estimated by questionnaire and direct observation. In addition, cold provocation tests were performed, and the results from the tests were compared with the estimated prevalence. As a result, 4 hour-energy-equivalent frequency-weighted accelerations of the finishing grinding (FG) and the prepainting grinding (PG) jobs were 6.23 m/s(2) and 13.39 m/s(2), respectively. The mean exposure time for holding the grinders was 4.64 h per day. Using the ISO 5349 method, it was predicted that after exposure to vibration for 10.79 yr, about a half of the FG workers could develop finger blanching. For the PG workers, the corresponding predicted latency was 5.02 yr. A discrepancy was found between the results from the ISO relationship and those from the cold provocation tests. A linear regression model was suggested employing vibration acceleration and vibration exposure time as explanatory variables for vascular dysfunction.

The Spallation Neutron Source accelerator system design

NASA Astrophysics Data System (ADS)

Henderson, S.; Abraham, W.; Aleksandrov, A.; Allen, C.; Alonso, J.; Anderson, D.; Arenius, D.; Arthur, T.; Assadi, S.; Ayers, J.; Bach, P.; Badea, V.; Battle, R.; Beebe-Wang, J.; Bergmann, B.; Bernardin, J.; Bhatia, T.; Billen, J.; Birke, T.; Bjorklund, E.; Blaskiewicz, M.; Blind, B.; Blokland, W.; Bookwalter, V.; Borovina, D.; Bowling, S.; Bradley, J.; Brantley, C.; Brennan, J.; Brodowski, J.; Brown, S.; Brown, R.; Bruce, D.; Bultman, N.; Cameron, P.; Campisi, I.; Casagrande, F.; Catalan-Lasheras, N.; Champion, M.; Champion, M.; Chen, Z.; Cheng, D.; Cho, Y.; Christensen, K.; Chu, C.; Cleaves, J.; Connolly, R.; Cote, T.; Cousineau, S.; Crandall, K.; Creel, J.; Crofford, M.; Cull, P.; Cutler, R.; Dabney, R.; Dalesio, L.; Daly, E.; Damm, R.; Danilov, V.; Davino, D.; Davis, K.; Dawson, C.; Day, L.; Deibele, C.; Delayen, J.; DeLong, J.; Demello, A.; DeVan, W.; Digennaro, R.; Dixon, K.; Dodson, G.; Doleans, M.; Doolittle, L.; Doss, J.; Drury, M.; Elliot, T.; Ellis, S.; Error, J.; Fazekas, J.; Fedotov, A.; Feng, P.; Fischer, J.; Fox, W.; Fuja, R.; Funk, W.; Galambos, J.; Ganni, V.; Garnett, R.; Geng, X.; Gentzlinger, R.; Giannella, M.; Gibson, P.; Gillis, R.; Gioia, J.; Gordon, J.; Gough, R.; Greer, J.; Gregory, W.; Gribble, R.; Grice, W.; Gurd, D.; Gurd, P.; Guthrie, A.; Hahn, H.; Hardek, T.; Hardekopf, R.; Harrison, J.; Hatfield, D.; He, P.; Hechler, M.; Heistermann, F.; Helus, S.; Hiatt, T.; Hicks, S.; Hill, J.; Hill, J.; Hoff, L.; Hoff, M.; Hogan, J.; Holding, M.; Holik, P.; Holmes, J.; Holtkamp, N.; Hovater, C.; Howell, M.; Hseuh, H.; Huhn, A.; Hunter, T.; Ilg, T.; Jackson, J.; Jain, A.; Jason, A.; Jeon, D.; Johnson, G.; Jones, A.; Joseph, S.; Justice, A.; Kang, Y.; Kasemir, K.; Keller, R.; Kersevan, R.; Kerstiens, D.; Kesselman, M.; Kim, S.; Kneisel, P.; Kravchuk, L.; Kuneli, T.; Kurennoy, S.; Kustom, R.; Kwon, S.; Ladd, P.; Lambiase, R.; Lee, Y. Y.; Leitner, M.; Leung, K.-N.; Lewis, S.; Liaw, C.; Lionberger, C.; Lo, C. C.; Long, C.; Ludewig, H.; Ludvig, J.; Luft, P.; Lynch, M.; Ma, H.; MacGill, R.; Macha, K.; Madre, B.; Mahler, G.; Mahoney, K.; Maines, J.; Mammosser, J.; Mann, T.; Marneris, I.; Marroquin, P.; Martineau, R.; Matsumoto, K.; McCarthy, M.; McChesney, C.; McGahern, W.; McGehee, P.; Meng, W.; Merz, B.; Meyer, R.; Meyer, R.; Miller, B.; Mitchell, R.; Mize, J.; Monroy, M.; Munro, J.; Murdoch, G.; Musson, J.; Nath, S.; Nelson, R.; Nelson, R.; O`Hara, J.; Olsen, D.; Oren, W.; Oshatz, D.; Owens, T.; Pai, C.; Papaphilippou, I.; Patterson, N.; Patterson, J.; Pearson, C.; Pelaia, T.; Pieck, M.; Piller, C.; Plawski, T.; Plum, M.; Pogge, J.; Power, J.; Powers, T.; Preble, J.; Prokop, M.; Pruyn, J.; Purcell, D.; Rank, J.; Raparia, D.; Ratti, A.; Reass, W.; Reece, K.; Rees, D.; Regan, A.; Regis, M.; Reijonen, J.; Rej, D.; Richards, D.; Richied, D.; Rode, C.; Rodriguez, W.; Rodriguez, M.; Rohlev, A.; Rose, C.; Roseberry, T.; Rowton, L.; Roybal, W.; Rust, K.; Salazer, G.; Sandberg, J.; Saunders, J.; Schenkel, T.; Schneider, W.; Schrage, D.; Schubert, J.; Severino, F.; Shafer, R.; Shea, T.; Shishlo, A.; Shoaee, H.; Sibley, C.; Sims, J.; Smee, S.; Smith, J.; Smith, K.; Spitz, R.; Staples, J.; Stein, P.; Stettler, M.; Stirbet, M.; Stockli, M.; Stone, W.; Stout, D.; Stovall, J.; Strelo, W.; Strong, H.; Sundelin, R.; Syversrud, D.; Szajbler, M.; Takeda, H.; Tallerico, P.; Tang, J.; Tanke, E.; Tepikian, S.; Thomae, R.; Thompson, D.; Thomson, D.; Thuot, M.; Treml, C.; Tsoupas, N.; Tuozzolo, J.; Tuzel, W.; Vassioutchenko, A.; Virostek, S.; Wallig, J.; Wanderer, P.; Wang, Y.; Wang, J. G.; Wangler, T.; Warren, D.; Wei, J.; Weiss, D.; Welton, R.; Weng, J.; Weng, W.-T.; Wezensky, M.; White, M.; Whitlatch, T.; Williams, D.; Williams, E.; Wilson, K.; Wiseman, M.; Wood, R.; Wright, P.; Wu, A.; Ybarrolaza, N.; Young, K.; Young, L.; Yourd, R.; Zachoszcz, A.; Zaltsman, A.; Zhang, S.; Zhang, W.; Zhang, Y.; Zhukov, A.

2014-11-01

The Spallation Neutron Source (SNS) was designed and constructed by a collaboration of six U.S. Department of Energy national laboratories. The SNS accelerator system consists of a 1 GeV linear accelerator and an accumulator ring providing 1.4 MW of proton beam power in microsecond-long beam pulses to a liquid mercury target for neutron production. The accelerator complex consists of a front-end negative hydrogen-ion injector system, an 87 MeV drift tube linear accelerator, a 186 MeV side-coupled linear accelerator, a 1 GeV superconducting linear accelerator, a 248-m circumference accumulator ring and associated beam transport lines. The accelerator complex is supported by ~100 high-power RF power systems, a 2 K cryogenic plant, ~400 DC and pulsed power supply systems, ~400 beam diagnostic devices and a distributed control system handling ~100,000 I/O signals. The beam dynamics design of the SNS accelerator is presented, as is the engineering design of the major accelerator subsystems.

JP-8 jet fuel exposure potentiates tumor development in two experimental model systems.

PubMed

Harris, D T; Sakiestewa, D; Titone, D; He, X; Hyde, J; Witten, M

2007-11-01

The US Air Force has implemented the widespread use of JP-8 jet fuel in its operations, although a thorough understanding of its potential effects upon exposed personnel is unclear. Previous work has reported that JP-8 exposure is immunosuppressive. Exposure of mice to JP-8 for 1 h/day resulted in immediate secretion of two immunosuppressive agents; namely, interleukin-10 (IL-10) and prostaglandin E2 (PGE2). Thus, it was of interest to determine if jet fuel exposure might promote tumor growth and metastasis. The syngeneic B16 tumor model was used for these studies. Animals were injected intravenously with tumor cells, and lung colonies were enumerated. Animals were also examined for metastatic spread of the tumor. Mice were either exposed to 1000 mg/m3 JP-8 (1 h/ day) for 7 days before tumor injection or were exposed to JP-8 at the time of tumor injection. All animals were killed 17 days after tumor injection. In the present study, JP8 exposure potentiated the growth and metastases of B16 tumors in an animal model. Exposure of mice to JP-8 for 1 h/day before tumor induction resulted in an approximately 8.7-fold increase in tumors, whereas those mice exposed to JP8 at the time of tumor induction had a 5.6-fold increase in tumor numbers. Thus, low concentration JP-8 jet fuel exposures have significant immune suppressive effects on the immune system that can result in increased tumor formation and metastases. We have now extended the observations to an experimental subcutaneous tumor model. JP8 exposure at the time of tumor induction in this model did not affect the growth of the tumor. However, JP8-exposed, tumor-bearing animals died at an accelerated rate as compared with air-exposed, tumor-bearing mice.

Metabolic oxygen consumption measurement with a single-cell biosensor after particle microbeam irradiation

PubMed Central

Zhang, Bo; Messerli, Mark; Randers-Pehrson, Gerhard; Hei, Tom K.; Brenner, David J.

2015-01-01

A noninvasive, self-referencing biosensor/probe system has been integrated into the Columbia University Radiological Research Accelerator Facility Microbeam II end station. A single-cell oxygen consumption measurement has been conducted with this type of oxygen probe in 37°C Krebs–Ringer Bicarbonate buffer immediately before and after a single-cell microbeam irradiation. It is the first such measurement made for a microbeam irradiation, and a six fold increment of oxygen flux induced during a 15-s period of time has been observed following radiation exposure. The experimental procedure and the results are discussed. PMID:25335641

Laser driven ion accelerator

DOEpatents

Tajima, Toshiki

2006-04-18

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

A dynamic model of the eye nystagmus response to high magnetic fields.

PubMed

Glover, Paul M; Li, Yan; Antunes, Andre; Mian, Omar S; Day, Brian L

2014-02-07

It was recently shown that high magnetic fields evoke nystagmus in human subjects with functioning vestibular systems. The proposed mechanism involves interaction between ionic currents in the endolymph of the vestibular labyrinth and the static magnetic field. This results in a Lorentz force that causes endolymph flow to deflect the cupulae of the semi-circular canals to evoke a vestibular-ocular reflex (VOR). This should be analogous to stimulation by angular acceleration or caloric irrigation. We made measurements of nystagmus slow-phase velocities in healthy adults experiencing variable magnetic field profiles of up to 7 T while supine on a bed that could be moved smoothly into the bore of an MRI machine. The horizontal slow-phase velocity data were reliably modelled by a linear transfer function incorporating a low-pass term and a high-pass adaptation term. The adaptation time constant was estimated at 39.3 s from long exposure trials. When constrained to this value, the low-pass time constant was estimated at 13.6 ± 3.6 s (to 95% confidence) from both short and long exposure trials. This confidence interval overlaps with values obtained previously using angular acceleration and caloric stimulation. Hence it is compatible with endolymph flow causing a cupular deflection and therefore supports the hypothesis that the Lorentz force is a likely transduction mechanism of the magnetic field-evoked VOR.

Formate generated by cellular oxidation of formaldehyde accelerates the glycolytic flux in cultured astrocytes.

PubMed

Tulpule, Ketki; Dringen, Ralf

2012-04-01

Formaldehyde is a neurotoxic compound that can be endogenously generated in the brain. Because astrocytes play a key role in metabolism and detoxification processes in brain, we have investigated the capacity of these cells to metabolize formaldehyde using primary astrocyte-rich cultures as a model system. Application of formaldehyde to these cultures resulted in the appearance of formate in cells and in a time-, concentration- and temperature-dependent disappearance of formaldehyde from the medium that was accompanied by a matching extracellular accumulation of formate. This formaldehyde-oxidizing capacity of astrocyte cultures is likely to be catalyzed by alcohol dehydrogenase 3 and aldehyde dehydrogenase 2, because the cells of the cultures contain the mRNAs of these formaldehyde-oxidizing enzymes. In addition, exposure to formaldehyde increased both glucose consumption and lactate production by the cells. Both the strong increase in the cellular formate content and the increase in glycolytic flux were only observed after application of formaldehyde to the cells, but not after treatment with exogenous methanol or formate. The accelerated lactate production was not additive to that obtained for azide, a known inhibitor of complex IV of the respiratory chain, and persisted after removal of formaldehyde after a formaldehyde exposure for 1.5 h. These data demonstrate that cultured astrocytes efficiently oxidize formaldehyde to formate, which subsequently enhances glycolytic flux, most likely by inhibition of mitochondrial respiration. Copyright © 2012 Wiley Periodicals, Inc.

Pleiotrophin mediates hematopoietic regeneration via activation of RAS

PubMed Central

Himburg, Heather A.; Yan, Xiao; Doan, Phuong L.; Quarmyne, Mamle; Micewicz, Eva; McBride, William; Chao, Nelson J.; Slamon, Dennis J.; Chute, John P.

2014-01-01

Hematopoietic stem cells (HSCs) are highly susceptible to ionizing radiation–mediated death via induction of ROS, DNA double-strand breaks, and apoptotic pathways. The development of therapeutics capable of mitigating ionizing radiation–induced hematopoietic toxicity could benefit both victims of acute radiation sickness and patients undergoing hematopoietic cell transplantation. Unfortunately, therapies capable of accelerating hematopoietic reconstitution following lethal radiation exposure have remained elusive. Here, we found that systemic administration of pleiotrophin (PTN), a protein that is secreted by BM-derived endothelial cells, substantially increased the survival of mice following radiation exposure and after myeloablative BM transplantation. In both models, PTN increased survival by accelerating the recovery of BM hematopoietic stem and progenitor cells in vivo. PTN treatment promoted HSC regeneration via activation of the RAS pathway in mice that expressed protein tyrosine phosphatase receptor-zeta (PTPRZ), whereas PTN treatment did not induce RAS signaling in PTPRZ-deficient mice, suggesting that PTN-mediated activation of RAS was dependent upon signaling through PTPRZ. PTN strongly inhibited HSC cycling following irradiation, whereas RAS inhibition abrogated PTN-mediated induction of HSC quiescence, blocked PTN-mediated recovery of hematopoietic stem and progenitor cells, and abolished PTN-mediated survival of irradiated mice. These studies demonstrate the therapeutic potential of PTN to improve survival after myeloablation and suggest that PTN-mediated hematopoietic regeneration occurs in a RAS-dependent manner. PMID:25250571

International Space Station Increment-4/5 Microgravity Environment Summary Report

NASA Technical Reports Server (NTRS)

Jules, Kenol; Hrovat, Kenneth; Kelly, Eric; McPherson, Kevin; Reckart, Timothy

2003-01-01

This summary report presents the results of some of the processed acceleration data measured aboard the International Space Station during the period of December 2001 to December 2002. Unlike the past two ISS Increment reports, which were increment specific, this summary report covers two increments: Increments 4 and 5, hereafter referred to as Increment-4/5. Two accelerometer systems were used to measure the acceleration levels for the activities that took place during Increment-4/5. Due to time constraint and lack of precise timeline information regarding some payload operations and station activities, not a11 of the activities were analyzed for this report. The National Aeronautics and Space Administration sponsors the Microgravity Acceleration Measurement System and the Space Acceleration Microgravity System to support microgravity science experiments which require microgravity acceleration measurements. On April 19, 2001, both the Microgravity Acceleration Measurement System and the Space Acceleration Measurement System units were launched on STS-100 from the Kennedy Space Center for installation on the International Space Station. The Microgravity Acceleration Measurement System supports science experiments requiring quasi-steady acceleration measurements, while the Space Acceleration Measurement System unit supports experiments requiring vibratory acceleration measurement. The International Space Station Increment-4/5 reduced gravity environment analysis presented in this report uses acceleration data collected by both sets of accelerometer systems: The Microgravity Acceleration Measurement System, which consists of two sensors: the low-frequency Orbital Acceleration Research Experiment Sensor Subsystem and the higher frequency High Resolution Accelerometer Package. The low frequency sensor measures up to 1 Hz, but is routinely trimmean filtered to yield much lower frequency acceleration data up to 0.01 Hz. This filtered data can be mapped to arbitrary locations for characterizing the quasi-steady environment for payloads and the vehicle. The high frequency sensor is used to characterize the vibratory environment up to 100 Hz at a single measurement location. The Space Acceleration Measurement System, which deploys high frequency sensors, measures vibratory acceleration data in the range of 0.01 to 400 Hz at multiple measurement locations. This summary report presents analysis of some selected quasi-steady and vibratory activities measured by these accelerometers during Increment- 4/5 from December 2001 to December 2002.

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

PubMed

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

2016-02-01

Acceleration (AC) and deceleration (DC) capacities measure heart rate variability during speeding up and slowing down of the heart, respectively. We investigated associations between AC and DC with occupational short-term metal PM2.5 exposures. A panel of 48 male welders had particulate matter less than 2.5 microns in diameter (PM2.5) exposure measurements over 4-6 h repeated over 5 sampling periods between January 2010 and June 2012. We simultaneously obtained continuous recordings of digital ECG using a Holter monitor. We analysed ECG data in the time domain to obtain hourly AC and DC. Linear mixed models were used to assess the associations between hourly PM2.5 exposure and each of hourly AC and DC, controlling for age, smoking status, active smoking, exposure to secondhand smoke, season/time of day when ECG reading was obtained and baseline AC or DC. We also ran lagged exposure response models for each successive hour up to 3 h after onset of exposure. Mean (SD) shift PM2.5 exposure during welding was 0.47 (0.43) mg/m(3). Significant exposure-response associations were found for AC and DC with increased PM2.5 exposure. In our adjusted models without any lag between exposure and response, a 1 mg/m(3) increase of PM2.5 was associated with a decrease of 1.46 (95% CI 1.00 to 1.92) ms in AC and a decrease of 1.00 (95% CI 0.53 to 1.46) ms in DC. The effect of PM2.5 on AC and DC was maximal immediately postexposure and lasted 1 h following exposure. There are short-term effects of metal particulates on AC and DC. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

[State of the reproductive systemin in male rats of 1st generation obtained from irradiated parents and exposed to electromagnetic radiation (897 MHz) during embryogenesis and postnatal development].

PubMed

Vereshchako, G G; Chueshova, N V; Gorokh, G A; Naumov, A D

2014-01-01

The consequences of prolonged exposure to electromagnetic radiation from cellular phone (897 MHz, daily 8 h/day) in male rats of the 1st generation obtained from irradiated parents and subjected to prolonged exposure to electromagnetic radiation of the range of mobile communications during ontogeny and postnatal development were studied. It has been found that irradiation causes a decrease in the number of births of animals, changing the sex ratio towards the increase in the number of males. It had a significant impact on the reproductive system of males, accelerating their sexual development, revealed at the age of two months. Radiation from cell phones led to significant disproportions in the cell number at different stages of spermatogenesis. It increased the number of mature spermatozoa which decreased viability.

Time-temperature-stress capabilities of composite materials for advanced supersonic technology application, phase 1

NASA Technical Reports Server (NTRS)

Kerr, J. R.; Haskins, J. F.

1980-01-01

Implementation of metal and resin matrix composites into supersonic vehicle usage is contingent upon accelerating the demonstration of service capacity and design technology. Because of the added material complexity and lack of extensive service data, laboratory replication of the flight service will provide the most rapid method of documenting the airworthiness of advanced composite systems. A program in progress to determine the time temperature stress capabilities of several high temperature composite materials includes thermal aging, environmental aging, fatigue, creep, fracture, and tensile tests as well as real time flight simulation exposure. The program has two parts. The first includes all the material property determinations and aging and simulation exposures up through 10,000 hours. The second continues these tests up to 50,000 cumulative hours. Results are presented of the 10,000 hour phase, which has now been completed.

Hand-arm vibration in the aetiology of hearing loss in lumberjacks.

PubMed Central

Pyykkö, I; Starck, J; Färkkilä, M; Hoikkala, M; Korhonen, O; Nurminen, M

1981-01-01

A longitudinal study of hearing loss was conducted among a group of lumberjacks in the years 1972 and 1974--8. The number of subjects increased from 72 in 1972 to 203 in 1978. They were classified according to (1) a history of vibration-induced white finger (VWF), (2) age, (3) duration of exposure, an (4) duration of ear muff usage. The hearing level at 4000 Hz was used to indicate the noise-induced permanent threshold shift (NIPTS). The lumberjacks were exposed, at their present pace of work, to noise, Leq values 96-103 dB(A), and to the vibration of a chain saw (linear acceleration 30-70 ms-2). The chain saws of the early 1960s were more hazardous, with the average noise level of 111 dB(A) and a variation acceleration of 60-180 ms-2. When classified on the basis of age, the lumberjacks with VWF had about a 10 dB greater NIPTS than subjects without VWF. NIPTS increased with the duration of exposure to chain saw noise, but with equal noise exposure the NIPTS was about 10 dB greater in lumberjacks with VWF than without VWF. With the same duration of ear protection the lumberjacks with VWF consistently had about a 10 dB greater NIPTS than those without VWF. The differences in NIPTS were statistically significant. The possible reason for more advanced NIPTS in subjects with VWF is that vibration might operate in both of these disorders through a common mechanism--that is, producing a vasoconstriction in both cochlear and digital blood vessels as a result of sympathetic nervous system activity. PMID:7272242

Laser-assisted delivery of synergistic combination chemotherapy in in vivo skin.

PubMed

Wenande, Emily; Tam, Joshua; Bhayana, Brijesh; Schlosser, Steven Kyle; Ishak, Emily; Farinelli, William A; Chlopik, Agata; Hoang, Mai P; Pinkhasov, Omar R; Caravan, Peter; Rox Anderson, R; Haedersdal, Merete

2018-04-10

The effectiveness of topical drugs for treatment of non-melanoma skin cancer is greatly reduced by insufficient penetration to deep skin layers. Ablative fractional lasers (AFLs) are known to enhance topical drug uptake by generating narrow microchannels through the skin, but information on AFL-drug delivery in in vivo conditions is limited. In this study, we examined pharmacokinetics, biodistribution and toxicity of two synergistic chemotherapy agents, cisplatin and 5-fluorouracil (5-FU), following AFL-assisted delivery alone or in combination in in vivo porcine skin. Detected at 0-120 h using mass spectrometry techniques, we demonstrated that fractional CO 2 laser pretreatment (196 microchannels/cm 2 , 852 μm ablation depth) leads to rapid drug uptake in 1500 μm deep skin layers, with a sixfold enhancement in peak cisplatin concentrations versus non-laser-treated controls (5 h, P = 0.005). Similarly, maximum 5-FU deposition was measured within an hour of AFL-delivery, and exceeded peak deposition in non-laser-exposed skin that had undergone topical drug exposure for 5 days. Overall, this accelerated and deeper cutaneous drug uptake resulted in significantly increased inflammatory and histopathological effects. Based on clinical scores and transepidermal water loss measurement, AFL intensified local toxic responses to drugs delivered alone and in combination, while systemic drug exposure remained undetectable. Quantitative histopathologic analyses correspondingly revealed significantly reduced epidermal proliferation and greater cellular apoptosis after AFL-drug delivery; particularly after combined cisplatin + 5-FU exposure. In sum, by overcoming the primary limitation of topical drug penetration and providing accelerated, enhanced and deeper delivery, AFL-assisted combination chemotherapy may represent a promising treatment strategy for non-melanoma skin cancer. Copyright © 2018 Elsevier B.V. All rights reserved.

Hydrocortisone accelerates the decay of iconic memory traces: on the modulation of executive and stimulus-driven constituents of sensory information maintenance.

PubMed

Miller, Robert; Weckesser, Lisa J; Smolka, Michael N; Kirschbaum, Clemens; Plessow, Franziska

2015-03-01

A substantial amount of research documents the impact of glucocorticoids on higher-order cognitive functioning. By contrast, surprisingly little is known about the susceptibility of basic sensory processes to glucocorticoid exposure given that the glucocorticoid receptor density in the human visual cortex exceeds those observed in prefrontal and most hippocampal brain regions. As executive tasks also rely on these sensory processes, the present study investigates the impact of glucocorticoid exposure on different performance parameters characterizing the maintenance and transfer of sensory information from iconic memory (IM; the sensory buffer of the visual system) to working memory (WM). Using a crossover factorial design, we administered one out of three doses of hydrocortisone (0.06, 0.12, or 0.24mg/kg bodyweight) and a placebo to 18 healthy young men. Thereafter participants performed a partial report task, which was used to assess their individual ability to process sensory information. Blood samples were concurrently drawn to determine free and total cortisol concentrations. The compiled pharmacokinetic and psychophysical data demonstrates that free cortisol specifically accelerated the decay of sensory information (r=0.46) without significantly affecting the selective information transfer from IM to WM or the capacity limit of WM. Specifically, nonparametric regression revealed a sigmoid dose-response relationship between free cortisol levels during the testing period and the IM decay rates. Our findings highlight that glucocorticoid exposure may not only impact on the recruitment of top-down control for an active maintenance of sensory information, but alter their passive (stimulus-driven) maintenance thereby changing the availability of information prior to subsequent executive processing. Copyright © 2014 Elsevier Ltd. All rights reserved.

Diet as a factor in behavioral radiation protection following exposure to heavy particles

NASA Technical Reports Server (NTRS)

Rabin, Bernard M.; Shukitt-Hale, Barbara; Joseph, James; Todd, Paul

2005-01-01

Major risks associated with radiation exposures on deep space missions include carcinogenesis due to heavy-particle exposure of cancer-prone tissues and performance decrements due to neurological damage produced by heavy particles. Because exposure to heavy particles can cause oxidative stress, it is possible that antioxidants can be used to mitigate these risks (and possibly some health risks of microgravity). To assess the capacity of antioxidant diets to mitigate the effects of exposure to heavy particles, rats were maintained on antioxidant diets containing 2% blueberry or strawberry extract or a control diet for 8 weeks prior to exposure to 1.5 or 2.0 Gy of accelerated iron particles at Brookhaven National Laboratory. Following irradiation rats were tested on a series of behavioral tasks: amphetamine-induced taste aversion learning, operant responding and spatial learning and memory. The results indicated that the performance of the irradiated rats maintained on the antioxidant diets was, in general, significantly better than that of the control animals, although the effectiveness of the diets ameliorating the radiation-induced deterioration in performance varied as a function of both the specific diet and the specific endpoint. In addition, animals fed antioxidant diets prior to exposure showed reduced heavy particle-induced tumorigenesis one year after exposure compared to the animals fed the control diet. These results suggest that antioxidant diets have the potential to serve as part of a system designed to provide protection to astronauts against the effects of heavy particles on exploratory missions outside the magnetic field of the earth.

Surficial Studies of Mars Using Cosmogenic Nuclides

NASA Technical Reports Server (NTRS)

Nishiizumi, K.

2001-01-01

Cosmogenic nuclides (CNs) are produced by cosmic-ray nuclear interactions with target nuclei in rocks, soils, ice, and the atmosphere. Cosmogenic nuclides have been widely used for investigation of solar system matter for several decades. Stable nuclides, such as He-3, Ne-21, and Ar-38, are built up over time as the surface is exposed to cosmic rays. The concentrations of cosmogenic radionuclides, such as Be-10, Al-26, and C-14 also build up with exposure time but reach saturation values after several half-lives. Especially since the development of accelerator mass spectrometry (AMS), CNs in terrestrial samples have been routinely used for geomorphic studies such as glaciation, surface erosion, and tectonics, and studies of atmospheric and ocean circulation. Cosmogenic nuclides on Mars will be able to answer questions of exposure ages, erosion rates, tectonic events, and deposition rates of sediments and/or volatiles. The concentrations of cosmogenic stable nuclides give the integrated exposure time of the rock/mineral, and the activities of radionuclides give recent records for times back as long as a few half-lives.

A reproducible radiation delivery method for unanesthetized rodents during periods of hind limb unloading

NASA Astrophysics Data System (ADS)

Walb, M. C.; Black, P. J.; Payne, V. S.; Munley, M. T.; Willey, J. S.

2015-07-01

Exposure to the spaceflight environment has long been known to be a health challenge concerning many body systems. Both microgravity and/or ionizing radiation can cause acute and chronic effects in multiple body systems. The hind limb unloaded (HLU) rodent model is a ground-based analogue for microgravity that can be used to simulate and study the combined biologic effects of reduced loading with spaceflight radiation exposure. However, studies delivering radiation to rodents during periods of HLU are rare. Herein we report the development of an irradiation protocol using a clinical linear accelerator that can be used with hind limb unloaded, unanesthetized rodents that is capable of being performed at most academic medical centers. A 30.5 cm × 30.5 cm × 40.6 cm rectangular chamber was constructed out of polymethyl methacrylate (PMMA) sheets (0.64 cm thickness). Five centimeters of water-equivalent material were placed outside of two PMMA inserts on either side of the rodent that permitted the desired radiation dose buildup (electronic equilibrium) and helped to achieve a flatter dose profile. Perforated aluminum strips permitted the suspension dowel to be placed at varying heights depending on the rodent size. Radiation was delivered using a medical linear accelerator at an accelerating potential of 10 MV. A calibrated PTW Farmer ionization chamber, wrapped in appropriately thick tissue-equivalent bolus material to simulate the volume of the rodent, was used to verify a uniform dose distribution at various regions of the chamber. The dosimetry measurements confirmed variances typically within 3%, with maximum variance <10% indicated through optically stimulated luminescent dosimeter (OSLD) measurements, thus delivering reliable spaceflight-relevant total body doses and ensuring a uniform dose regardless of its location within the chamber. Due to the relative abundance of LINACs at academic medical centers and the reliability of their dosimetry properties, this method may find great utility in the implementation of future ground-based studies that examine the combined spaceflight challenges of reduced loading and radiation while using the HLU rodent model.

Reduction in plasma vasopressin levels of dehydrated rats following acute stress

NASA Technical Reports Server (NTRS)

Keil, L. C.; Severs, W. B.

1977-01-01

Results are presented for an investigation directed to substantiate and extend preliminary findings of stress-induced reduction in plasma arginine vasopressin (pAVP). Since normally hydrated rats have very low levels of pAVP, it is difficult to measure reliably any decrease in pAVP that may result from stress. To overcome this problem, the pAVP levels of the tested rats were raised by dehydration prior to application of stress. A radioimmunoassay for pAVP is described and used to determine the levels of vasopressin in the plasma of nondehydrated and dehydrated rats after exposure to ether or acceleration stress. Plasma pAVP is also determined in rats following nicotine administration. It is shown that exposure of nondehydrated rats to ether or acceleration stress does not elicit any significant alterations in circulating pAVP levels while nicotine injections stimulate a marked increase. In particular, ether and acceleration stress produce a rapid reduction in the pAVP level of dehydrated rats, the decrease being observed in both large and small animals. The mechanism for this reduction in pAVP level following stress is yet unknown.

Neutron yield when fast deuterium ions collide with strongly charged tritium-saturated dust particles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Akishev, Yu. S., E-mail: akishev@triniti.ru; Karal’nik, V. B.; Petryakov, A. V.

2017-02-15

The ultrahigh charging of dust particles in a plasma under exposure to an electron beam with an energy up to 25 keV and the formation of a flux of fast ions coming from the plasma and accelerating in the strong field of negatively charged particles are considered. Particles containing tritium or deuterium atoms are considered as targets. The calculated rates of thermonuclear fusion reactions in strongly charged particles under exposure to accelerated plasma ions are presented. The neutron generation rate in reactions with accelerated deuterium and tritium ions has been calculated for these targets. The neutron yield has been calculatedmore » when varying the plasma-forming gas pressure, the plasma density, the target diameter, and the beam electron current density. Deuterium and tritium-containing particles are shown to be the most promising plasmaforming gas–target material pair for the creation of a compact gas-discharge neutron source based on the ultrahigh charging of dust particles by beam electrons with an energy up to 25 keV.« less

Cabin attendants’ exposure to vibration and shocks during landing

NASA Astrophysics Data System (ADS)

Burström, Lage; Lindberg, Lennart; Lindgren, Torsten

2006-12-01

The Scandinavian Airlines System (SAS) has noted that cabin attendants have reported an increase in health problems associated with landing. The European Union reports cover health problems related to neck, shoulder, and lower-back injuries. Moreover, analysis of these reports shows that the problems are often associated with specific airplanes that have a longer tail behind the rear wheels and appear more often in attendants who sit in the back of planes rather then the front. Against this background, this study measures and describes the vibration during landing in specific airplanes to evaluate the health risk for the cabin attendants. Measurements were conducted on regular flights with passengers in the type of airplane, Boeing 737-800, which was related to the highest per cent of reported health problems. All measurements were performed the same day during three landings in one airplane with the same pilots and cabin attendants. The measurements were carried out simultaneously on the cabin crew seats in the back and front of the passenger cabin. Under the cabin crew's seat cushions, a triaxiell seat-accelerometer was placed to measure the vibration in three axes. The signals from the accelerometers were amplified by charge amplifiers and stored on tape. The stored data were analysed with a computer-based analyse system. For the cabin attendants, the dominant direction for the vibration load during landing is the up-and-down direction although some vibration also occurs in the other horizontal directions. The exposure to vibration is higher on the rear crew seat compared to the front seat. For instance, both the vibration dose value (VDV) and the frequency-weighted acceleration in the dominant direction are more then 50% higher on the rear seat. The frequency-weighted acceleration and the VDV measured at the crew seats are below the exposure limits as described by the European vibration directive. The evaluation of the cabin attendants' exposure to multiple shocks during landing shows that the potential of an adverse health effect for the cabin attendants is low in the front of the airplane and increases to moderate in the rear. Although this is a limited study, it could be conclude that there could be a risk for cabin attendants due to the exposure of multiple shocks. Therefore, efforts should be spent to minimize their risk by developing a better seat cushion and back support to lessen the effects of shocks. In addition, attendants should be informed about the most suitable posture to take during landing.

Predictions of cardiovascular responses during STS reentry using mathematical models

NASA Technical Reports Server (NTRS)

Leonard, J. I.; Srinivasan, R.

1985-01-01

The physiological adaptation to weightless exposure includes cardiovascular deconditioning arising in part from a loss of total circulating blood volume and resulting in a reduction of orthostatic tolerance. The crew of the Shuttle orbiter are less tolerant to acceleration forces in the head-to-foot direction during the reentry phase of the flight at a time they must function at a high level of performance. The factors that contribute to orthostatic intolerance during and following reentry and to predict the likelihood of impaired crew performance are evaluated. A computer simulation approach employing a mathematical model of the cardiovascular system is employed. It is shown that depending on the severity of blood volume loss, the reentry acceleration stress may be detrimental to physiologic function and may place the physiologic status of the crew near the borderline of some type of impairment. They are in agreement with conclusions from early ground-based experiments and from observations of early Shuttle flights.

Ocean acidification accelerates reef bioerosion.

PubMed

Wisshak, Max; Schönberg, Christine H L; Form, Armin; Freiwald, André

2012-01-01

In the recent discussion how biotic systems may react to ocean acidification caused by the rapid rise in carbon dioxide partial pressure (pCO(2)) in the marine realm, substantial research is devoted to calcifiers such as stony corals. The antagonistic process - biologically induced carbonate dissolution via bioerosion - has largely been neglected. Unlike skeletal growth, we expect bioerosion by chemical means to be facilitated in a high-CO(2) world. This study focuses on one of the most detrimental bioeroders, the sponge Cliona orientalis, which attacks and kills live corals on Australia's Great Barrier Reef. Experimental exposure to lowered and elevated levels of pCO(2) confirms a significant enforcement of the sponges' bioerosion capacity with increasing pCO(2) under more acidic conditions. Considering the substantial contribution of sponges to carbonate bioerosion, this finding implies that tropical reef ecosystems are facing the combined effects of weakened coral calcification and accelerated bioerosion, resulting in critical pressure on the dynamic balance between biogenic carbonate build-up and degradation.

Accelerated Stress-Corrosion Testing

NASA Technical Reports Server (NTRS)

1986-01-01

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

Reticle writer for next-generation SEMI mask standard: mask handling and exposure

NASA Astrophysics Data System (ADS)

Ehrlich, Christian

1998-12-01

The world semiconductor industry is currently preparing itself for the next evolutionary step in the ongoing development of the integrated circuit, characterized by the 0.18 to 0.15 micrometer technology. The already complex engineering task for the mask tool makers is furthermore complicated by the introduction of the new SEMI reticle standard with a 230 mm by 230 mm large and 9 mm thick quartz glass blank that will have a weight of more than one kilogram. The production of these advanced masks is already identified as a key enabling technology which will stretch the capabilities of the manufacturing process, and its equipment, to the limit. The mask making e-beam system Leica ZBA320, capable of exposing a 230 mm reticle and featuring the variable shaped beam approach with a 20 kV accelerating voltage has been introduced recently. Now the first results of e-beam exposures with this new type of mask writer are presented. Enhancements form the previous generation system include improved deflection systems, stage metrology, pattern data handling, and an address grid down to 10 nanometers. This system's specified performance enables it to produce reticles designed to support semiconductor fabrication utilizing 180 nanometer design rules, and beyond, with high accuracy and productivity.

Current employment status, occupational category, occupational hazard exposure and job stress in relation to telomere length: the Multiethnic Study of Atherosclerosis (MESA).

PubMed

Fujishiro, Kaori; Diez-Roux, Ana V; Landsbergis, Paul A; Jenny, Nancy Swords; Seeman, Teresa

2013-08-01

Telomere length has been proposed as a biomarker of cell senescence, which is associated with a wide array of adverse health outcomes. While work is a major determinant of health, few studies have investigated the association of telomere length with various dimensions of occupation. Accelerated cellular aging could be a common pathway linking occupational exposure to several health outcomes. Leukocyte telomere length was assessed using quantitative PCR in a community-based sample of 981 individuals (age: 45-84 years). Questionnaires were used to collect information on current employment status, current or main occupation before retirement and job strain. The Occupational Resource Network (O*NET) database was linked to the questionnaire data to create five exposure measures: physical activity on the job, physical hazard exposure, interpersonal stressors, job control and job demands. Linear regression was used to estimate associations of occupational characteristics with telomere lengths after adjustment for age, sex, race, socioeconomic position and several behavioural risk factors. There were no mean differences in telomere lengths across current employment status, occupational category, job strain categories or levels of most O*NET exposure measures. There was also no evidence that being in lower status occupational categories or being exposed to higher levels of adverse physical or psychosocial exposures accelerated the association between age and telomere shortening. Cellular aging as reflected by shorter telomeres does not appear to be an important pathway linking occupation to various health outcomes.

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

PubMed Central

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

2015-01-01

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

Piezoelectric wafer active sensors under gamma radiation exposure toward applications for structural health monitoring of nuclear dry cask storage systems

NASA Astrophysics Data System (ADS)

Faisal Haider, Mohammad; Mei, Hanfei; Lin, Bin; Yu, Lingyu; Giurgiutiu, Victor; Lam, Poh-Sang; Verst, Christopher

2018-03-01

Structural health monitoring (SHM) is in urgent need and must be integrated into the nuclear-spent fuel storage systems to guarantee the safe operation. The dry cask storage system (DCSS) is such storage facility, which is licensed for temporary storage for nuclear-spent fuel at the independent spent fuel storage installations (ISFSIs) for certain predetermined period of time. Gamma radiation is one of the major radiation sources near DCSS. Therefore, a detailed experimental investigation was completed on the gamma radiation endurance of piezoelectric wafer active sensors (PWAS) transducers for SHM applications to the DCSS system. The irradiation test was done in a Co-60 gamma irradiator. Lead Zirconate Titanate (PZT) and Gallium Orthophosphate (GaPO4) PWAS transducers were exposed to 40.7 kGy gamma radiation. Total radiation dose was achieved in two different radiation dose rates: (a) slower radiation rate at 0.1 kGy/hr for 20 hours (b) accelerated radiation rate at 1.233 kGy/hr for 32 hours. The total cumulative radiation dose of 40.7 kGy is equivalent to 45 years of operation in DCSS system. Electro-mechanical impedance and admittance (EMIA) signatures and electrical capacitance were measured to evaluate the PWAS performance after each gamma radiation exposure. The change in resonance frequency of PZT-PWAS transducer for both in-plane and thickness mode was observed. The GaPO4-PWAS EMIA spectra do not show a significant shift in resonance frequency after gamma irradiation exposure. Radiation endurance of new high-temperature HPZ-HiT PWAS transducer was also evaluated. The HPZ-HiT transducers were exposed to gamma radiation at 1.233 kGy/hr for 160 hours with 80 hours interval. Therefore, the total accumulated gamma radiation dose is 184 kGy. No significant change in impedance spectra was observed due to gamma radiation exposure.

In vitro oxygen exposure promotes maturation of the oxygen sensitive contraction in pre-term chicken ductus arteriosus.

PubMed

Greyner, Henry; Dzialowski, Edward M

2015-10-01

The ductus arteriosus (DA) are O2-sensitive, embryonic blood vessels that serve as a right-to-left shunt in developing avian embryos. Prior to internal pipping, the chicken DA produces a weak O2-induced contraction. During hatching, the O2-sensitivity of the avian DA vessels increases significantly. To see if we could accelerate the maturation of chicken DA O2-sensitivity, we exposed the vessel in vitro to elevated O2 (25 kPa) for 3-h prior to internal pipping on day 19 of incubation. The DA initially responded to increasing O2 with a weak contraction (0.15±0.04 N/m) that significantly increased in strength (0.63±0.06 N/m) during 3-h 25 kPa O2 exposure. A tonic influence of nitric oxide, not present at low O2, appeared during the 3-h 25 kPa O2 exposure. The long-term O2-induced contraction was mediated by both L-type Ca(2+) channels and internal Ca(2+) stores. The Rho-kinase pathway inhibitors Y-27632 and fasudil produced significant relaxation, suggesting a role for Ca(2+) sensitization in the contractile response to the 3h of elevated O2. While the day 19 DA initially exhibited an immature contractile response to O2, maturation of the pathways regulating O2-induced contraction was accelerated by exposure to 25 kPa O2, producing contractions similar in magnitude to those found during the final stage of hatching. This suggests that maturation of O2-sensitivity may be accelerated in vivo by increasing arterial O2 levels. Copyright © 2015 Elsevier Inc. All rights reserved.

STS-107 Microgravity Environment Summary Report

NASA Technical Reports Server (NTRS)

Jules, Kenol; Hrovat, Kenneth; Kelly, Eric; Reckhart, Timothy

2005-01-01

This summary report presents the results of the processed acceleration data measured aboard the Columbia orbiter during the STS-107 microgravity mission from January 16 to February 1, 2003. Two accelerometer systems were used to measure the acceleration levels due to vehicle and science operations activities that took place during the 16-day mission. Due to lack of precise timeline information regarding some payload's operations, not all of the activities were analyzed for this report. However, a general characterization of the microgravity environment of the Columbia Space Shuttle during the 16-day mission is presented followed by a more specific characterization of the environment for some designated payloads during their operations. Some specific quasi-steady and vibratory microgravity environment characterization analyses were performed for the following payloads: Structure of Flame Balls at Low Lewis-number-2, Laminar Soot Processes-2, Mechanics of Granular Materials-3 and Water Mist Fire-Suppression Experiment. The Physical Science Division of the National Aeronautics and Space Administration sponsors the Orbital Acceleration Research Experiment and the Space Acceleration Measurement System for Free Flyer to support microgravity science experiments, which require microgravity acceleration measurements. On January 16, 2003, both the Orbital Acceleration Research Experiment and the Space Acceleration Measurement System for Free Flyer accelerometer systems were launched on the Columbia Space Transportation System-107 from the Kennedy Space Center. The Orbital Acceleration Research Experiment supported science experiments requiring quasi-steady acceleration measurements, while the Space Acceleration Measurement System for Free Flyer unit supported experiments requiring vibratory acceleration measurement. The Columbia reduced gravity environment analysis presented in this report uses acceleration data collected by these two sets of accelerometer systems: The Orbital Acceleration Research Experiment is a low frequency sensor, which measures acceleration up to 1 Hz, but the 1 Hz acceleration data is trimmean filtered to yield much lower frequency acceleration data up to 0.01 Hz. This filtered data can be mapped to other locations for characterizing the quasi-steady environment for payloads and the vehicle. The Space Acceleration Measurement System for Free Flyer measures vibratory acceleration in the range of 0.01 to 200 Hz at multiple measurement locations. The vibratory acceleration data measured by this system is used to assess the local vibratory environment for payloads as well as to measure the disturbance causes by the vehicle systems, crew exercise devices and payloads operation disturbances. This summary report presents analysis of selected quasi-steady and vibratory activities measured by these two accelerometers during the Columbia 16-day microgravity mission from January 16 to February 1, 2003.

Acceleration of Advanced CN Antidote Agents for Mass Exposure Treatments: DMTS

DTIC Science & Technology

2014-12-01

Intraosseous Injection; Inhalational Delivery 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT 18. NUMBER OF PAGES 19a. NAME OF RESPONSIBLE...exposure models. We have administered antidotes via intramuscular injection, inhalation, and intraosseous routes. These animal models are all available...injection, inhalation, and intraosseous routes. These animal models are all available for ongoing testing of the novel candidate antidotes as was

Review of test methods used to determine the corrosion rate of metals in contact with treated wood

Treesearch

Samuel L. Zelinka; Douglas R. Rammer

2005-01-01

The purpose of this literature review is to give an overview of test methods previously used to evaluate the corrosion of metals in contact with wood. This article reviews the test methods used to evaluate the corrosion of metals in contact with wood by breaking the experiments into three groups: exposure tests, accelerated exposure tests, and electrochemical tests....

A COMPARISON OF EXTRACTION EFFICIENCIES IN SEAFOOD MATRICES USING A SYNTHETIC STOMACH AND AN ACCELERATED SOLVENT EXTRACTION APPROACH WITH IC-ICP-MS DETECTION

EPA Science Inventory

Seafood is one of the largest sources of dietary arsenic exposure. Because most of the arsenic present is non-toxic (such as arsenobetaine [AsB]), the consumption of seafood is thought to result in a low risk or non-toxic exposure. This can be misleading for two reasons. First...

Starvation and Imidacloprid Exposure Influence Immune Response by Anoplophora glabripennis (Coleoptera: Cerambycidae) to a Fungal Pathogen.

PubMed

Fisher, Joanna J; Castrillo, Louela A; Donzelli, Bruno G G; Hajek, Ann E

2017-08-01

In several insect systems, fungal entomopathogens synergize with neonicotinoid insecticides which results in accelerated host death. Using the Asian longhorned beetle, Anoplophora glabripennis (Motschulsky), an invasive woodborer inadvertently introduced into North America and Europe, we investigated potential mechanisms in the synergy between the entomopathogenic fungus Metarhizium brunneum Petch and the insecticide imidacloprid. A potential mechanism underlying this synergy could be imidacloprid's ability to prevent feeding shortly after administration. We investigated whether starvation would have an impact similar to imidacloprid exposure on the mortality of fungal-inoculated beetles. Using real-time PCR to quantify fungal load in inoculated beetles, we determined how starvation and pesticide exposure impacted beetles' ability to tolerate or resist a fungal infection. The effect of starvation and pesticide exposure on the encapsulation and melanization immune responses of the beetles was also quantified. Starvation had a similar impact on the survival of M. brunneum-inoculated beetles compared to imidacloprid exposure. The synergy, however, was not completely due to starvation, as imidacloprid reduced the beetles' melanotic encapsulation response and capsule area, while starvation did not significantly reduce these immune responses. Our results suggest that there are multiple interacting mechanisms involved in the synergy between M. brunneum and imidacloprid. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Integrated Locomotor Function Tests for Countermeasure Evaluation

NASA Technical Reports Server (NTRS)

Bloomberg, J. J.; Mulavara, A. P.; Peters, B. T.; Cohen, H. S.; Landsness, E. C.; Black, F. O.

2005-01-01

Following spaceflight crewmembers experience locomotor dysfunction due to inflight adaptive alterations in sensorimotor function. Countermeasures designed to mitigate these postflight gait alterations need to be assessed with a new generation of tests that evaluate the interaction of various sensorimotor sub-systems central to locomotor control. The goal of the present study was to develop new functional tests of locomotor control that could be used to test the efficacy of countermeasures. These tests were designed to simultaneously examine the function of multiple sensorimotor systems underlying the control of locomotion and be operationally relevant to the astronaut population. Traditionally, gaze stabilization has been studied almost exclusively in seated subjects performing target acquisition tasks requiring only the involvement of coordinated eye-head movements. However, activities like walking involve full-body movement and require coordination between lower limbs and the eye-head-trunk complex to achieve stabilized gaze during locomotion. Therefore the first goal of this study was to determine how the multiple, interdependent, full-body sensorimotor gaze stabilization subsystems are functionally coordinated during locomotion. In an earlier study we investigated how alteration in gaze tasking changes full-body locomotor control strategies. Subjects walked on a treadmill and either focused on a central point target or read numeral characters. We measured: temporal parameters of gait, full body sagittal plane segmental kinematics of the head, trunk, thigh, shank and foot, accelerations along the vertical axis at the head and the shank, and the vertical forces acting on the support surface. In comparison to the point target fixation condition, the results of the number reading task showed that compensatory head pitch movements increased, peak head acceleration was reduced and knee flexion at heel-strike was increased. In a more recent study we investigated the adaptive remodeling of the full-body gaze control systems following exposure to visual-vestibular conflict. Subjects walked on a treadmill before and after a 30- minute exposure to 0.5X minifying during which self-generated sinusoidal vertical head rotations were performed while seated. Following exposure to visual-vestibular conflict subjects showed a restriction in compensatory head movements, increased knee and ankle flexion after heel-strike and a decrease in the rate of body loading during the rapid weight transfer phase after the heel strike event. Taken together, results from both studies provide evidence that the full body contributes to gaze stabilization during locomotion, and that different functional elements are responsive to changes in visual task constraints and are subject to adaptive alterations following exposure to visual-vestibular conflict. This information provides the basis for the design of a new generation of integrative tests that incorporate the evaluation of multiple neural control systems relevant to astronaut operational performance.

Space Age Spuds

NASA Technical Reports Server (NTRS)

2000-01-01

American Ag-Tech International, Ltd. developed a system called Quantum Tubers through the Wisconsin Center for Space Automation and Robotics (a NASA-sponsored Commercial Space Center). Using computerization and technologies originally intended for growing plants in space, the company developed a growth chamber that accelerates plant growth and is free of plant pathogens. The chamber is used to grow minitubers, which serve as nuclear seed stock for potatoes. Using lighting technology, temperature and humidity controls, and automation technology, the minituber can be generated in one closed facility with out much labor handling. This means they can be grown year round in extreme environments. The system eliminates the need for multiple generations of seed and eliminates exposure to pathogens, disease and pests. The Quantum Tubers system can produce 10-20 million tubers throughout the year, about equal to the world's supply of this generation seed stock.

Environmental aging in polycrystalline-Si photovoltaic modules: comparison of chamber-based accelerated degradation studies with field-test data

NASA Astrophysics Data System (ADS)

Lai, T.; Biggie, R.; Brooks, A.; Potter, B. G.; Simmons-Potter, K.

2015-09-01

Lifecycle degradation testing of photovoltaic (PV) modules in accelerated-degradation chambers can enable the prediction both of PV performance lifetimes and of return-on-investment for installations of PV systems. With degradation results strongly dependent on chamber test parameters, the validity of such studies relative to fielded, installed PV systems must be determined. In the present work, accelerated aging of a 250 W polycrystalline silicon module is compared to real-time performance degradation in a similar polycrystalline-silicon, fielded, PV technology that has been operating since October 2013. Investigation of environmental aging effects are performed in a full-scale, industrial-standard environmental chamber equipped with single-sun irradiance capability providing illumination uniformity of 98% over a 2 x 1.6 m area. Time-dependent, photovoltaic performance (J-V) is evaluated over a recurring, compressed night-day cycle providing representative local daily solar insolation for the southwestern United States, followed by dark (night) cycling. This cycle is synchronized with thermal and humidity environmental variations that are designed to mimic, as closely as possible, test-yard conditions specific to a 12 month weather profile for a fielded system in Tucson, AZ. Results confirm the impact of environmental conditions on the module long-term performance. While the effects of temperature de-rating can be clearly seen in the data, removal of these effects enables the clear interpretation of module efficiency degradation with time and environmental exposure. With the temperature-dependent effect removed, the normalized efficiency is computed and compared to performance results from another panel of similar technology that has previously experienced identical climate changes in the test yard. Analysis of relative PV module efficiency degradation for the chamber-tested system shows good comparison to the field-tested system with ~2.5% degradation following an equivalent year of testing.

Exposure to (12)C particles alters the normal dynamics of brain monoamine metabolism and behaviour in rats.

PubMed

Belov, Oleg V; Belokopytova, Ksenia V; Bazyan, Ara S; Kudrin, Vladimir S; Narkevich, Viktor B; Ivanov, Aleksandr A; Severiukhin, Yury S; Timoshenko, Gennady N; Krasavin, Eugene A

2016-09-01

Planning of the deep-space exploration missions raises a number of questions on the radiation protection of astronauts. One of the medical concerns is associated with exposure of a crew to highly energetic particles of galactic cosmic rays. Among many other health disorders, irradiation with these particles has a substantial impact on the central nervous system (CNS). Although radiation damage to CNS has been addressed extensively during the last years, the mechanisms underlying observed impairments remain mostly unknown. The present study reveals neurochemical and behavioural alterations induced in rats by 1Gy of 500MeV/u (12)C particles with a relatively moderate linear energy transfer (10.6keV/μm). It is found that exposure to carbon ions leads to significant modification of the normal monoamine metabolism dynamics as well as the locomotor, exploratory, and anxiety-like behaviours during a two-month period. The obtained results indicate an abnormal redistribution of monoamines and their metabolites in different brain regions after exposure. The most pronounced impairments are detected in the prefrontal cortex, nucleus accumbens, and hypothalamus that illustrate the sensitivity of these brain regions to densely ionizing radiations. It is also shown that exposure to (12)C particles enhances the anxiety in animals and accelerates the age-related reduction in their exploratory capability. The observed monoamine metabolism pattern may indicate the presence of certain compensatory mechanisms being induced in response to irradiation and capable of partial restoration of monoaminergic systems' functions. Overall, these findings support a possibility of CNS damage by space-born particles of a relatively moderate linear energy transfer. Copyright © 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Dual linear accelerator system for use in sterilization of medical disposable supplies

NASA Astrophysics Data System (ADS)

Sadat, Theo

1991-05-01

Accelerators can be used for sterilization or decontamination (medical disposables, food, plastics, hospital waste, etc.). Most of these accelerators are located in an industrial environment and must have a high availability. A dual accelerator system (composed of two accelerators) offers optimal flexibility and reliability. The main advantage of this system is "all-in all-out" because it does not need a turnover of products. Such a dual system, composed of two 10 MeV 20 kW linear accelerators (instead of one 40 kW linac), has been chosen by a Swedish company (Mölnlycke).

Lifetime stress accelerates epigenetic aging in an urban, African American cohort: relevance of glucocorticoid signaling.

PubMed

Zannas, Anthony S; Arloth, Janine; Carrillo-Roa, Tania; Iurato, Stella; Röh, Simone; Ressler, Kerry J; Nemeroff, Charles B; Smith, Alicia K; Bradley, Bekh; Heim, Christine; Menke, Andreas; Lange, Jennifer F; Brückl, Tanja; Ising, Marcus; Wray, Naomi R; Erhardt, Angelika; Binder, Elisabeth B; Mehta, Divya

2015-12-17

Chronic psychological stress is associated with accelerated aging and increased risk for aging-related diseases, but the underlying molecular mechanisms are unclear. We examined the effect of lifetime stressors on a DNA methylation-based age predictor, epigenetic clock. After controlling for blood cell-type composition and lifestyle parameters, cumulative lifetime stress, but not childhood maltreatment or current stress alone, predicted accelerated epigenetic aging in an urban, African American cohort (n = 392). This effect was primarily driven by personal life stressors, was more pronounced with advancing age, and was blunted in individuals with higher childhood abuse exposure. Hypothesizing that these epigenetic effects could be mediated by glucocorticoid signaling, we found that a high number (n = 85) of epigenetic clock CpG sites were located within glucocorticoid response elements. We further examined the functional effects of glucocorticoids on epigenetic clock CpGs in an independent sample with genome-wide DNA methylation (n = 124) and gene expression data (n = 297) before and after exposure to the glucocorticoid receptor agonist dexamethasone. Dexamethasone induced dynamic changes in methylation in 31.2 % (110/353) of these CpGs and transcription in 81.7 % (139/170) of genes neighboring epigenetic clock CpGs. Disease enrichment analysis of these dexamethasone-regulated genes showed enriched association for aging-related diseases, including coronary artery disease, arteriosclerosis, and leukemias. Cumulative lifetime stress may accelerate epigenetic aging, an effect that could be driven by glucocorticoid-induced epigenetic changes. These findings contribute to our understanding of mechanisms linking chronic stress with accelerated aging and heightened disease risk.

Asthma progression to airway remodeling and bone marrow eosinophil responses in genetically distinct strains of mice.

PubMed

Hogan, Mary Beth; Piktel, Debra; Hubbs, Ann F; McPherson, Leslie E; Landreth, Kenneth S

2008-12-01

Patient factors that cause long-term airway remodeling are largely unidentified. This suggests that genetic differences may determine which asthmatic patients develop airway remodeling. A murine model with repeated allergen exposure leading to peribronchial fibrosis in complement factor 5 (C5)-deficient A/J mice has been used to study asthma progression. No studies have addressed the systemic effects of allergen sensitization or chronic allergen exposure on bone marrow eosinophilopoiesis in this mouse strain. To investigate bone marrow eosinophil responses during acute sensitization and chronic allergen exposure using genetically distinct mouse strains differing in persistent airway reactivity and remodeling. The C5-sufficient BALB/c and C5-deficient A/J mice were repetitively exposed to intranasal ovalbumin for 12 weeks. Subsequently, the mice were evaluated for airway eosinophilia, mucus-containing goblet cells, and peribronchial fibrosis. Both strains of mice were also acutely sensitized to ovalbumin. Bone marrow eosinophil progenitor cells and mature eosinophils were enumerated. BALB/c and A/J mice have similar bone marrow responses after acute allergen exposure, with elevations in bone marrow eosinophil progenitor cell and eosinophil numbers. After chronic allergen exposure, only C5-deficient A/J mice that developed peribronchial fibrosis exhibited bone marrow eosinophilia. BALB/c mice lacked peribronchial fibrosis and extinguished accelerated eosinophil production after long-term allergen challenge. Chronic airway remodeling after repeated allergen exposure in genetically different mice correlated with differences in long-term bone marrow eosinophilopoiesis. Preventing asthma from progressing to chronic airway remodeling with fibrosis may involve identifying genetically determined influences on bone marrow responses to chronic allergen exposure.

Science and Technology Review, January-February 1997

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

Table of contents: accelerators at Livermore; the B-Factory and the Big Bang; assessing exposure to radiation; next generation of computer storage; and a powerful new tool to detect clandestine nuclear tests.

Summary of SLAC's SEY Measurement On Flat Accelerator Wall Materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Le Pimpec, F.; /PSI, Villigen /SLAC

The electron cloud effect (ECE) causes beam instabilities in accelerator structures with intense positively charged bunched beams. Reduction of the secondary electron yield (SEY) of the beam pipe inner wall is effective in controlling cloud formation. We summarize SEY results obtained from flat TiN, TiZrV and Al surfaces carried out in a laboratory environment. SEY was measured after thermal conditioning, as well as after low energy, less than 300 eV, particle exposure.

Accelerated Electron-Beam Formation with a High Capture Coefficient in a Parallel Coupled Accelerating Structure

NASA Astrophysics Data System (ADS)

Chernousov, Yu. D.; Shebolaev, I. V.; Ikryanov, I. M.

2018-01-01

An electron beam with a high (close to 100%) coefficient of electron capture into the regime of acceleration has been obtained in a linear electron accelerator based on a parallel coupled slow-wave structure, electron gun with microwave-controlled injection current, and permanent-magnet beam-focusing system. The high capture coefficient was due to the properties of the accelerating structure, beam-focusing system, and electron-injection system. Main characteristics of the proposed systems are presented.

Acceleration Environment of the International Space Station

NASA Technical Reports Server (NTRS)

McPherson, Kevin; Kelly, Eric; Keller, Jennifer

2009-01-01

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

Comparative assessment of chlorine, heat, ozone, and UV light for killing Legionella pneumophila within a model plumbing system.

PubMed Central

Muraca, P; Stout, J E; Yu, V L

1987-01-01

Nosocomial Legionnaires disease can be acquired by exposure to the organism from the hospital water distribution system. As a result, many hospitals have instituted eradication procedures, including hypercholorination and thermal eradication. We compared the efficacy of ozonation, UV light, hyperchlorination, and heat eradication using a model plumbing system constructed of copper piping, brass spigots, Plexiglas reservoir, electric hot water tank, and a pump. Legionella pneumophila was added to the system at 10(7) CFU/ml. Each method was tested under three conditions; (i) nonturbid water at 25 degrees C, (ii) turbid water at 25 degrees C, and (iii) nonturbid water at 43 degrees C. UV light and heat killed L. pneumophila most rapidly and required minimal maintenance. Both UV light and heat (60 degrees C) produced a 5 log kill in less than 1 h. In contrast, both chlorine and ozone required 5 h of exposure to produce a 5 log decrease. Neither turbidity nor the higher temperature of 43 degrees C impaired the efficacy of any of the disinfectant methods. Surprisingly, higher temperature enhanced the disinfecting efficacy of chlorine. However, higher temperature accelerated the decomposition of the chlorine residual such that an additional 120% volume of chlorine was required. All four methods proved efficacious in eradicating L. pneumophila from a model plumbing system. Images PMID:3566272

A systematic FPGA acceleration design for applications based on convolutional neural networks

NASA Astrophysics Data System (ADS)

Dong, Hao; Jiang, Li; Li, Tianjian; Liang, Xiaoyao

2018-04-01

Most FPGA accelerators for convolutional neural network are designed to optimize the inner acceleration and are ignored of the optimization for the data path between the inner accelerator and the outer system. This could lead to poor performance in applications like real time video object detection. We propose a brand new systematic FPFA acceleration design to solve this problem. This design takes the data path optimization between the inner accelerator and the outer system into consideration and optimizes the data path using techniques like hardware format transformation, frame compression. It also takes fixed-point, new pipeline technique to optimize the inner accelerator. All these make the final system's performance very good, reaching about 10 times the performance comparing with the original system.

The effect of track structure on the induction of chromosomal aberrations in murine cells

NASA Technical Reports Server (NTRS)

Durante, M.; Cella, L.; Furusawa, Y.; George, K.; Gialanella, G.; Grossi, G.; Pugliese, M.; Saito, M.; Yang, T. C.

1998-01-01

PURPOSE: To measure chromosome aberrations in C3H 10T1/2 mouse fibroblasts using FISH painting at the first mitosis following exposure to 30 keV/microm hydrogen or neon ions. MATERIALS AND METHODS: Cells in plateau-phase were irradiated with 0.86 MeV protons at the TTT-3 Tandem accelerator in Naples (Italy), or with 400 MeV/n Ne ions at the HIMAC accelerator in Chiba (Japan). Colcemid-blocked cells were harvested at the first mitosis following exposure, and chromosome spreads were hybridized in situ with a fluorescein-labelled composite mouse DNA probe specific for chromosomes 2 and 8. RESULTS: Protons were more efficient than neon ions at the same LET in the induction of chromosome interchanges and breaks. Yields of complex exchanges were similar for both particles at the same dose, but protons produced mostly insertions, while with Ne exposure non-reciprocal exchanges were the most frequent complex-type exchange. CONCLUSIONS: Charged particles with the same LET produce different yields of chromosome aberrations, and some observed differences can be explained based on the available track-structure models.

The effect of track structure on the induction of chromosomal aberrations in murine cells.

PubMed

Durante, M; Cella, L; Furusawa, Y; George, K; Gialanella, G; Grossi, G; Pugliese, M; Saito, M; Yang, T C

1998-03-01

To measure chromosome aberrations in C3H 10T1/2 mouse fibroblasts using FISH painting at the first mitosis following exposure to 30 keV/microm hydrogen or neon ions. Cells in plateau-phase were irradiated with 0.86 MeV protons at the TTT-3 Tandem accelerator in Naples (Italy), or with 400 MeV/n Ne ions at the HIMAC accelerator in Chiba (Japan). Colcemid-blocked cells were harvested at the first mitosis following exposure, and chromosome spreads were hybridized in situ with a fluorescein-labelled composite mouse DNA probe specific for chromosomes 2 and 8. Protons were more efficient than neon ions at the same LET in the induction of chromosome interchanges and breaks. Yields of complex exchanges were similar for both particles at the same dose, but protons produced mostly insertions, while with Ne exposure non-reciprocal exchanges were the most frequent complex-type exchange. Charged particles with the same LET produce different yields of chromosome aberrations, and some observed differences can be explained based on the available track-structure models.

Hypervelocity impact studies using a rotating mirror framing laser shadowgraph camera

NASA Technical Reports Server (NTRS)

Parker, Vance C.; Crews, Jeanne Lee

1988-01-01

The need to study the effects of the impact of micrometeorites and orbital debris on various space-based systems has brought together the technologies of several companies and individuals in order to provide a successful instrumentation package. A light gas gun was employed to accelerate small projectiles to speeds in excess of 7 km/sec. Their impact on various targets is being studied with the help of a specially designed continuous-access rotating-mirror framing camera. The camera provides 80 frames of data at up to 1 x 10 to the 6th frames/sec with exposure times of 20 nsec.

Ultra-low power operation of self-heated, suspended carbon nanotube gas sensors

NASA Astrophysics Data System (ADS)

Chikkadi, Kiran; Muoth, Matthias; Maiwald, Verena; Roman, Cosmin; Hierold, Christofer

2013-11-01

We present a suspended carbon nanotube gas sensor that senses NO2 at ambient temperature and recovers from gas exposure at an extremely low power of 2.9 μW by exploiting the self-heating effect for accelerated gas desorption. The recovery time of 10 min is two orders of magnitude faster than non-heated recovery at ambient temperature. This overcomes an important bottleneck for the practical application of carbon nanotube gas sensors. Furthermore, the method is easy to implement in sensor systems and requires no additional components, paving the way for ultra-low power, compact, and highly sensitive gas sensors.

[Medical big data and precision medicine: prospects of epidemiology].

PubMed

Song, J; Hu, Y H

2016-08-10

Since the development of high-throughput technology, electronic medical record system and big data technology, the value of medical data has caused more attention. On the other hand, the proposal of Precision Medicine Initiative opens up the prospect for medical big data. As a Tool-related Discipline, Epidemiology is, focusing on exploitation the resources of existing big data and promoting the integration of translational research and knowledge to completely unlocking the "black box" of exposure-disease continuum. It also tries to accelerating the realization of the ultimate goal on precision medicine. The overall purpose, however is to translate the evidence from scientific research to improve the health of the people.

Altered thermogenesis and impaired bone remodeling in Misty mice.

PubMed

Motyl, Katherine J; Bishop, Kathleen A; DeMambro, Victoria E; Bornstein, Sheila A; Le, Phuong; Kawai, Masanobu; Lotinun, Sutada; Horowitz, Mark C; Baron, Roland; Bouxsein, Mary L; Rosen, Clifford J

2013-09-01

Fat mass may be modulated by the number of brown-like adipocytes in white adipose tissue (WAT) in humans and rodents. Bone remodeling is dependent on systemic energy metabolism and, with age, bone remodeling becomes uncoupled and brown adipose tissue (BAT) function declines. To test the interaction between BAT and bone, we employed Misty (m/m) mice, which were reported be deficient in BAT. We found that Misty mice have accelerated age-related trabecular bone loss and impaired brown fat function (including reduced temperature, lower expression of Pgc1a, and less sympathetic innervation compared to wild-type (+/ +)). Despite reduced BAT function, Misty mice had normal core body temperature, suggesting heat is produced from other sources. Indeed, upon acute cold exposure (4°C for 6 hours), inguinal WAT from Misty mice compensated for BAT dysfunction by increasing expression of Acadl, Pgc1a, Dio2, and other thermogenic genes. Interestingly, acute cold exposure also decreased Runx2 and increased Rankl expression in Misty bone, but only Runx2 was decreased in wild-type. Browning of WAT is under the control of the sympathetic nervous system (SNS) and, if present at room temperature, could impact bone metabolism. To test whether SNS activity could be responsible for accelerated trabecular bone loss, we treated wild-type and Misty mice with the β-blocker, propranolol. As predicted, propranolol slowed trabecular bone volume/total volume (BV/TV) loss in the distal femur of Misty mice without affecting wild-type. Finally, the Misty mutation (a truncation of DOCK7) also has a significant cell-autonomous role. We found DOCK7 expression in whole bone and osteoblasts. Primary osteoblast differentiation from Misty calvaria was impaired, demonstrating a novel role for DOCK7 in bone remodeling. Despite the multifaceted effects of the Misty mutation, we have shown that impaired brown fat function leads to altered SNS activity and bone loss, and for the first time that cold exposure negatively affects bone remodeling. Copyright © 2013 American Society for Bone and Mineral Research.

Seat Vibration in Military Propeller Aircraft: Characterization, Exposure Assessment, and Mitigation

DTIC Science & Technology

2006-05-01

vibration were fatigue and reduced performance during long missions. assessed in accordance with current international guidelines (ISO 2631 - The incident...Measurements and Flight Configurations ( BPF ) of these aircraft. The health risk and comfort reaction of the vibration exposures were assessed in For...constant bandwidth rms accelerations at the PRF atively level flight at altitudes ranging between 15,000 and BPF of each aircraft were evaluated. For

Status of ion sources at National Institute of Radiological Sciences.

PubMed

Kitagawa, A; Fujita, T; Goto, A; Hattori, T; Hamano, T; Hojo, S; Honma, T; Imaseki, H; Katagiri, K; Muramatsu, M; Sakamoto, Y; Sekiguchi, M; Suda, M; Sugiura, A; Suya, N

2012-02-01

The National Institute of Radiological Sciences (NIRS) maintains various ion accelerators in order to study the effects of radiation of the human body and medical uses of radiation. Two electrostatic tandem accelerators and three cyclotrons delivered by commercial companies have offered various life science tools; these include proton-induced x-ray emission analysis (PIXE), micro beam irradiation, neutron exposure, and radioisotope tracers and probes. A duoplasmatron, a multicusp ion source, a penning ion source (PIG), and an electron cyclotron resonance ion source (ECRIS) are in operation for these purposes. The Heavy-Ion Medical Accelerator in Chiba (HIMAC) is an accelerator complex for heavy-ion radiotherapy, fully developed by NIRS. HIMAC is utilized not only for daily treatment with the carbon beam but also for fundamental experiments. Several ECRISs and a PIG at HIMAC satisfy various research and clinical requirements.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kitagawa, A.; Fujita, T.; Goto, A.

The National Institute of Radiological Sciences (NIRS) maintains various ion accelerators in order to study the effects of radiation of the human body and medical uses of radiation. Two electrostatic tandem accelerators and three cyclotrons delivered by commercial companies have offered various life science tools; these include proton-induced x-ray emission analysis (PIXE), micro beam irradiation, neutron exposure, and radioisotope tracers and probes. A duoplasmatron, a multicusp ion source, a penning ion source (PIG), and an electron cyclotron resonance ion source (ECRIS) are in operation for these purposes. The Heavy-Ion Medical Accelerator in Chiba (HIMAC) is an accelerator complex for heavy-ionmore » radiotherapy, fully developed by NIRS. HIMAC is utilized not only for daily treatment with the carbon beam but also for fundamental experiments. Several ECRISs and a PIG at HIMAC satisfy various research and clinical requirements.« less

Status of ion sources at National Institute of Radiological Sciencesa)

NASA Astrophysics Data System (ADS)

Kitagawa, A.; Fujita, T.; Goto, A.; Hattori, T.; Hamano, T.; Hojo, S.; Honma, T.; Imaseki, H.; Katagiri, K.; Muramatsu, M.; Sakamoto, Y.; Sekiguchi, M.; Suda, M.; Sugiura, A.; Suya, N.

2012-02-01

The National Institute of Radiological Sciences (NIRS) maintains various ion accelerators in order to study the effects of radiation of the human body and medical uses of radiation. Two electrostatic tandem accelerators and three cyclotrons delivered by commercial companies have offered various life science tools; these include proton-induced x-ray emission analysis (PIXE), micro beam irradiation, neutron exposure, and radioisotope tracers and probes. A duoplasmatron, a multicusp ion source, a penning ion source (PIG), and an electron cyclotron resonance ion source (ECRIS) are in operation for these purposes. The Heavy-Ion Medical Accelerator in Chiba (HIMAC) is an accelerator complex for heavy-ion radiotherapy, fully developed by NIRS. HIMAC is utilized not only for daily treatment with the carbon beam but also for fundamental experiments. Several ECRISs and a PIG at HIMAC satisfy various research and clinical requirements.

Summary Report of Mission Acceleration Measurements for MSL-1: STS-83, Launched April 14, 1997; STS-94, Launched July 1, 1997

NASA Technical Reports Server (NTRS)

Moskowitz, Milton E.; Hrovat, Kenneth; Tschen, Peter; McPherson, Kevin; Nati, Maurizio; Reckart, Timothy A.

1998-01-01

The microgravity environment of the Space Shuttle Columbia was measured during the STS-83 and STS-94 flights of the Microgravity Science Laboratory (MSL-1) mission using four different accelerometer systems: the Orbital Acceleration Research Experiment (OARE), the Space Acceleration Measurement System (SAMS), the Microgravity Measurement Assembly (MMA), and the Quasi-Steady Acceleration Measurement (QSAM) system. All four accelerometer systems provided investigators with acceleration measurements downlinked in near-real-time. Data from each system was recorded for post-mission analysis. The OARE measured the Shuttle's acceleration with high resolution in the quasi-steady frequency regime below about 0.1 Hz. The SAMS provided investigators with higher frequency acceleration measurements up to 25 Hz. The QSAM and MMA systems provided investigators with quasi-steady and higher frequency (up to 100 Hz) acceleration measurements, respectively. The microgravity environment related to various Orbiter maneuvers, crew activities, and experiment operations as measured by the OARE and MMA is presented and interpreted in section 8 of this report.

Optimizations of Human Restraint Systems for Short-Period Acceleration

NASA Technical Reports Server (NTRS)

Payne, P. R.

1963-01-01

A restraint system's main function is to restrain its occupant when his vehicle is subjected to acceleration. If the restraint system is rigid and well-fitting (to eliminate slack) then it will transmit the vehicle acceleration to its occupant without modifying it in any way. Few present-day restraint systems are stiff enough to give this one-to-one transmission characteristic, and depending upon their dynamic characteristics and the nature of the vehicle's acceleration-time history, they will either magnify or attenuate the acceleration. Obviously an optimum restraint system will give maximum attenuation of an input acceleration. In the general case of an arbitrary acceleration input, a computer must be used to determine the optimum dynamic characteristics for the restraint system. Analytical solutions can be obtained for certain simple cases, however, and these cases are considered in this paper, after the concept of dynamic models of the human body is introduced. The paper concludes with a description of an analog computer specially developed for the Air Force to handle completely general mechanical restraint optimization programs of this type, where the acceleration input may be any arbitrary function of time.

Some effects of acceleration in man and chimpanzees. [gravitational effects

NASA Technical Reports Server (NTRS)

Wood, E. H.; Sass, D. J.; Ritman, E. L.; Greenleaf, J. F.; Coulam, C. M.; Nathan, D.; Nolan, E. C.

1977-01-01

Early physiologic experiments using dogs and humans in centrifuges are reviewed. Because of the close similarity between the shape and dimensions of the thoraces of chimpanzees and humans, the former were used to obtain roentgenograms and photokymographic recordings of multiple physiologic variables before and during exposure to +5.8 Gy to study the effects of changes in the gravitational-inertial force environment on the cardiovascular and pulmonary systems during long duration space flight. A computer-controlled sciscanning system was used to obtain a two dimensional map of the amount of radiation emanating from the dorsal and ventricle surfaces after insertion of radioactive microspheres in the right ventricle. By using four different batches of microspheres tagged with isotopes of different energies, the spatial distribution of pulmonary blood flow under four conditions was determined.

Modelling the carbonation of cementitious matrixes by means of the unreacted-core model, UR-CORE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Castellote, M.; Andrade, C.

This paper presents a model for the carbonation of cementitious matrixes (UR-CORE). The model is based on the principles of the 'unreacted-core' systems, typical of chemical engineering processes, in which the reacted product remains in the solid as a layer of inert ash, adapted for the specific case of carbonation. Development of the model has been undertaken in three steps: 1) Establishment of the controlling step in the global carbonation rate, by using data of fractional conversion of different phases of the cementitious matrixes, obtained by the authors through neutron diffraction data experiments, and reported in [M. Castellote, C. Andrade,more » X. Turrillas, J. Campo, G. Cuello, Accelerated carbonation of cement pastes in situ monitored by neutron diffraction, Cem. Concr. Res. (2008), doi:10.1016/j.cemconres.2008.07.002]. 2) Then, the model has been adapted and applied to the cementitious materials using different concentrations of CO{sub 2}, with the introduction of the needed assumptions and factors. 3) Finally, the model has been validated with laboratory data at different concentrations (taken from literature) and for long term natural exposure of concretes. As a result, the model seems to be reliable enough to be applied to cementitious materials, being able to extrapolate the results from accelerated tests in any conditions to predict the rate of carbonation in natural exposure, being restricted, at present stage, to conditions with a constant relative humidity.« less

Current employment status, occupational category, occupational hazard exposure, and job stress in relation to telomere length: The Multiethnic Study of Atherosclerosis (MESA)

PubMed Central

Fujishiro, Kaori; Diez-Roux, Ana V; Landsbergis, Paul; Jenny, Nancy Swords; Seeman, Teresa

2014-01-01

Objective Telomere length has been proposed as a biomarker of cell senescence, which is associated with a wide array of adverse health outcomes. While work is a major determinant of health, few studies have investigated the association of telomere length with various dimensions of occupation. Accelerated cellular aging could be a common pathway linking occupational exposure to several health outcomes. Methods Leukocyte telomere length was assessed using quantitative polymerase chain reaction (Q-PCR) in a community-based sample of 981 individuals (age: 45–84 years old). Questionnaires were used to collect information on current employment status, current or main occupation before retirement, and job strain. The O*NET (Occupational Resource Network) database was linked to the questionnaire data to create 5 exposure measures: physical activity on the job, physical hazard exposure, interpersonal stressors, job control, and job demands. Linear regression was used to estimate associations of occupational characteristics with telomere lengths after adjustment for age, sex, race, socioeconomic position, and several behavioral risk factors. Results There were no mean differences in telomere lengths across current employment status, occupational category, job strain categories or levels of most O*NET exposure measures. There was also no evidence that being in lower status occupational categories or being exposed to higher levels of adverse physical or psychosocial exposures accelerated the association between age and telomere shortening. Conclusions Cellular aging as reflected by shorter telomeres does not appear to be an important pathway linking occupation to various health outcomes. PMID:23686115

RFQ design for the RAON accelerator's ISOL system

NASA Astrophysics Data System (ADS)

Choi, Bong Hyuk; Hong, In-Seok

2015-10-01

The heavy-ion accelerator RAON has the advantage of having both an in-flight (IF) and an isotope separator on-line (ISOL) system. Two radio frequency quadrupoles (RFQs) will be installed in the RAON: the main linear accelerator (LINAC) RFQ will be used to accelerate the two-charge state 238U for the IF system, while the post-accelerator RFQ will be used to accelerate low-current isotope beams from the ISOL system. In this paper, the post-accelerator RFQ design for the ISOL system is reported. A beam current of 1 pμA was used, and the input beam and the output beam energies were 5 keV/u and 400 keV/u, respectively. Moreover, the design was optimized by reducing the total length and power, adjusting the beam quality. To quantify the influence of thermal expansion on the frequency, we calculated the frequency difference according to deference between the vane's tip and the body's diameter.

Systems and methods for the magnetic insulation of accelerator electrodes in electrostatic accelerators

DOEpatents

Grisham, Larry R

2013-12-17

The present invention provides systems and methods for the magnetic insulation of accelerator electrodes in electrostatic accelerators. Advantageously, the systems and methods of the present invention improve the practically obtainable performance of these electrostatic accelerators by addressing, among other things, voltage holding problems and conditioning issues. The problems and issues are addressed by flowing electric currents along these accelerator electrodes to produce magnetic fields that envelope the accelerator electrodes and their support structures, so as to prevent very low energy electrons from leaving the surfaces of the accelerator electrodes and subsequently picking up energy from the surrounding electric field. In various applications, this magnetic insulation must only produce modest gains in voltage holding capability to represent a significant achievement.

Advanced Accelerators for Medical Applications

NASA Astrophysics Data System (ADS)

Uesaka, Mitsuru; Koyama, Kazuyoshi

We review advanced accelerators for medical applications with respect to the following key technologies: (i) higher RF electron linear accelerator (hereafter “linac”); (ii) optimization of alignment for the proton linac, cyclotron and synchrotron; (iii) superconducting magnet; (iv) laser technology. Advanced accelerators for medical applications are categorized into two groups. The first group consists of compact medical linacs with high RF, cyclotrons and synchrotrons downsized by optimization of alignment and superconducting magnets. The second group comprises laser-based acceleration systems aimed of medical applications in the future. Laser plasma electron/ion accelerating systems for cancer therapy and laser dielectric accelerating systems for radiation biology are mentioned. Since the second group has important potential for a compact system, the current status of the established energy and intensity and of the required stability are given.

Advanced Accelerators for Medical Applications

NASA Astrophysics Data System (ADS)

Uesaka, Mitsuru; Koyama, Kazuyoshi

We review advanced accelerators for medical applications with respect to the following key technologies: (i) higher RF electron linear accelerator (hereafter "linac"); (ii) optimization of alignment for the proton linac, cyclotron and synchrotron; (iii) superconducting magnet; (iv) laser technology. Advanced accelerators for medical applications are categorized into two groups. The first group consists of compact medical linacs with high RF, cyclotrons and synchrotrons downsized by optimization of alignment and superconducting magnets. The second group comprises laserbased acceleration systems aimed of medical applications in the future. Laser plasma electron/ion accelerating systems for cancer therapy and laser dielectric accelerating systems for radiation biology are mentioned. Since the second group has important potential for a compact system, the current status of the established energy and intensity and of the required stability are given.

Shielding evaluation for IMRT implementation in an existing accelerator vault

PubMed Central

Price, R. A.; Chibani, O.; Ma, C.‐M.

2003-01-01

A formalism is developed for evaluating the shielding in an existing vault to be used for IMRT. Existing exposure rate measurements are utilized as well as a newly developed effective modulation scaling factor. Examples are given for vaults housing 6, 10 and 18 MV linear accelerators. The use of an 18 MV Siemens linear accelerator is evaluated for IMRT delivery with respect to neutron production and the effects on individual patients. A modified modulation scaling factor is developed and the risk of the incurrence of fatal secondary malignancies is estimated. The difference in neutron production between 18 MV Varian and Siemens accelerators is estimated using Monte Carlo results. The neutron production from the Siemens accelerator is found to be approximately 4 times less than that of the Varian accelerator resulting in a risk of fatal secondary malignancy occurrence of approximately 1.6% when using the SMLC delivery technique and our measured modulation scaling factors. This compares with a previously published value of 1.6% for routine 3D CRT delivery on the Varian accelerator. PACS number(s): 87.52.Ga, 87.52.Px, 87.53.Qc, 87.53.Wz PMID:12841794

Environmental Exposure and Accelerated Testing of Rubber-to-Metal Vulcanized-Bonded Assemblies

DTIC Science & Technology

1975-08-01

such bonds are those of rubber coatings on the aluminum M60 machinq gun components, shock isolator and recoil adapter on the GAU 2B/A Minigun, rubber...accelerated humidity test data can be compared to show that both have the same effect on vulcanized bonded assemblies. Butadlene/styrene rubber-to-metal...distribution unlimited. 17. DISTRIBUTION STATEMENT (of the abstract enterd In 8!ock 20. It different frore Rel , V " - ’O" ) " 18. SUPPLEMENTARY NOTES

Time-dependent alterations in growth, photosynthetic pigments and enzymatic defense systems of submerged Ceratophyllum demersum during exposure to the cyanobacterial neurotoxin anatoxin-a.

PubMed

Ha, Mi-Hee; Pflugmacher, Stephan

2013-08-15

Recently, aquatic macrophytes have been considered as promising tools for eco-friendly water management with a low running cost. However, only little information is available thus far regarding the metabolic capacity of macrophytes for coping with cyanobacterial toxins (cyanotoxins) in the aquatic environment. Cyanotoxins have become emerging contaminants of great concern due to the high proliferation of cyanobacteria (cyanobacterial bloom) accelerated by eutrophication and climate change. Anatoxin-a, one of the common and major cyanotoxins, is suggested as a high priority water pollutant for regulatory consideration owing to its notoriously rapid mode of action as a neurotoxin. In this study, the time-course metabolic regulation of the submerged macrophyte Ceratophyllum demersum (C. demersum) was investigated during exposure to anatoxin-a at an environmentally relevant concentration (15 μg/L). Biotransformation and antioxidative systems in C. demersum responded positively to anatoxin-a through the promoted synthesis of most of the involved enzymes within 8h. Maximum enzyme activities were exhibited after 24 or 48 h of exposure to anatoxin-a. However, an apparent decline in enzyme activities was also observed at longer exposure duration (168 and 336 h) in company with high steady-state levels of cell internal H₂O₂, which showed its highest level after 48 h. Meanwhile, irreversible inhibitory influence on chlorophyll content (vitality) was noticed, whereas the ratio of carotenoids to total chlorophyll was increased with the increase in exposure duration. Consequently, the reduction in growth (biomass) of C. demersum was observed in sub-chronic exposure to anatoxin-a (8 weeks). Overall results clearly indicate, on the one hand, that anatoxin-a causes negative allelopathic effects on the macrophyte by inducing oxidative stress. On the other hand, the macrophyte might have interactions with anatoxin-a, based on the prompt reaction of its enzymatic defense systems to the toxin. The result obtained from the present study could contribute to the improvement of basic knowledge about the ecological impact of anatoxin-a and the environmental fate of the toxin in the aquatic environment. Copyright © 2013 Elsevier B.V. All rights reserved.

Correlation between mechanical and chemical degradation after outdoor and accelerated laboratory aging for multilayer photovoltaic backsheets

NASA Astrophysics Data System (ADS)

Lin, Chiao-Chi; Lyu, Yadong; Yu, Li-Chieh; Gu, Xiaohong

2016-09-01

Channel cracking fragmentation testing and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy were utilized to study mechanical and chemical degradation of a multilayered backsheet after outdoor and accelerated laboratory aging. A model sample of commercial PPE backsheet, namely polyethylene terephthalate/polyethylene terephthalate/ethylene vinyl acetate (PET/PET/EVA) was investigated. Outdoor aging was performed in Gaithersburg, Maryland, USA for up to 510 days, and complementary accelerated laboratory aging was conducted on the NIST (National Institute of Standards and Technology) SPHERE (Simulated Photodegradation via High Energy Radiant Exposure). Fracture energy, mode I stress intensity factor and film strength were analyzed using an analytical model based on channel cracking fragmentation testing results. The correlation between mechanical and chemical degradation was discussed for both outdoor and accelerated laboratory aging. The results of this work provide preliminary understanding on failure mechanism of backsheets after weathering, laying the groundwork for linking outdoor and indoor accelerated laboratory testing for multilayer photovoltaic backsheets.

Surface modification: advantages, techniques, and applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Natesan, K.

2000-03-01

Adequate performance of materials at elevated temperatures is a potential problem in many systems within the chemical, petroleum, process, and power-generating industries. Degradation of materials occurs because of interaction between the structural material and the exposure environment. These interactions are generally undesired chemical reactions that can lead to accelerated wastage and alter the functional requirements and/or structural integrity of the materials. Therefore, material selection for high-temperature applications must be based not only on a material strength properties but also on resistance to the complex environments prevalent in the anticipated exposure environment. As plants become larger, the satisfactory performance and reliabilitymore » of components play a greater role in plant availability and economics. However, system designers are becoming increasingly concerned with finding the least expensive material that will satisfactorily perform the design function for the desired service life. This present paper addresses the benefits of surface modification and identified several criteria for selection and application of modified surfaces in the power sector. A brief review is presented on potential methods for modification of surfaces, with the emphasis on coatings. In the final section of the paper, several examples address the requirements of different energy systems and surface modification avenues that have been applied to resolve the issues.« less

Effects of prenatal irradiation with accelerated heavy-ion beams on postnatal development in rats: III. Testicular development and breeding activity

NASA Astrophysics Data System (ADS)

Wang, B.; Murakami, M.; Eguchi-Kasai, K.; Nojima, K.; Shang, Y.; Tanaka, K.; Watanabe, K.; Fujita, K.; Moreno, S. G.; Coffigny, H.; Hayata, I.

With a significant increase in human activities dealing with space missions, potential teratogenic effects on the mammalian reproductive system from prenatal exposure to space radiation have become a hot topic that needs to be addressed. However, even for the ground experiments, such effects from exposure to high LET ionizing radiation are not as well studied as those for low LET ionizing radiations such as X-rays. Using the Heavy-Ion Medical Accelerator in Chiba (HIMAC) and Wistar rats, effects on gonads in prenatal male fetuses, on postnatal testicular development and on breeding activity of male offspring were studied following exposure of the pregnant animals to either accelerated carbon-ion beams with a LET value of about 13 keV/μm or neon-ion beams with a LET value of about 30 keV/μm at a dose range from 0.1 to 2.0 Gy on gestation day 15. The effects of X-rays at 200 kVp estimated for the same biological end points were studied for comparison. A significantly dose-dependent increase of apoptosis in gonocytes appeared 6 h after irradiations with a dose of 0.5 Gy or more. Measured delayed testis descent and malformed testicular seminiferous tubules were observed to be significantly different from the control animals at a dose of 0.5 Gy. These effects are observed to be dose- and LET-dependent. Markedly reduced testicular weight and testicular weight to body weight ratio were scored at postnatal day 30 even in the offspring that were prenatally irradiated with neon-ions at a dose of 0.1 Gy. A dose of 0.5 Gy from neon-ion beams induced a marked decrease in breeding activity in the prenatally irradiated male rats, while for the carbon-ion beams or X-rays, the significantly reduced breeding activity was observed only when the prenatal dose was at 1.0 Gy or more. These findings indicated that prenatal irradiations with heavy-ion beams on gestation day 15 generally induced markedly detrimental effects on prenatal gonads, postnatal testicular development and male breeding activity in rats, which seemed to be a dose and LET-related event.

Accelerator-Reactor Coupling for Energy Production in Advanced Nuclear Fuel Cycles

NASA Astrophysics Data System (ADS)

Heidet, Florent; Brown, Nicholas R.; Haj Tahar, Malek

This article is a review of several accelerator-reactor interface issues and nuclear fuel cycle applications of accelerator-driven subcritical systems. The systems considered here have the primary goal of energy production, but that goal is accomplished via a specific application in various proposed nuclear fuel cycles, such as breed-and-burn of fertile material or burning of transuranic material. Several basic principles are reviewed, starting from the proton beam window including the target, blanket, reactor core, and up to the fuel cycle. We focus on issues of interest, such as the impact of the energy required to run the accelerator and associated systems on the potential electricity delivered to the grid. Accelerator-driven systems feature many of the constraints and issues associated with critical reactors, with the added challenges of subcritical operation and coupling to an accelerator. Reliable accelerator operation and avoidance of beam trips are critically important. One interesting challenge is measurement of blanket subcriticality level during operation. We also review the potential benefits of accelerator-driven systems in various nuclear fuel cycle applications. Ultimately, accelerator-driven subcritical systems with the goal of transmutation of transuranic material have lower 100,000-year radioactivity than a critical fast reactor with recycling of uranium and plutonium.

Cigarette smoking and the pathogenesis of systemic lupus erythematosus.

PubMed

Speyer, Cameron B; Costenbader, Karen H

2018-06-01

Systemic lupus erythematosus (SLE) is a multi-system inflammatory autoimmune disease of incompletely understood etiology. It is thought that environmental exposures 'trigger' or accelerate the disease in genetically-predisposed individuals. Areas covered: Substantial epidemiological evidence exists to support the association between cigarette smoking and the risk of incident SLE. Recent evidence points to current smoking as the specific risk factor, with decreasing risk 5 years after smoking cessation, and the greatest risk for disease characterized by the presence of SLE-specific autoantibodies. Research has begun to search for possible explanations for the temporal nature of the relationship between current smoking and autoantibody positive-SLE. Here we review potential biologic mechanisms linking smoking and SLE risk, including effects upon T and B cells, inflammatory cytokines, oxidative stress, and the formation of short-lived DNA adducts. Expert commentary: The directions for future research in this field include studies of gene-environment interactions, epigenetics, metabolomics and putative biologic mechanisms.

STS-52 deployment of LAGEOS / IRIS spacecraft from OV-102's payload bay (PLB)

NASA Technical Reports Server (NTRS)

1992-01-01

During STS-52 deployment activities, the Italian Research Interim Stage (IRIS), a spinning solid fuel rocket, lifts the Laser Geodynamic Satellite II (LAGEOS II) out of its support cradle and above the thermal shield aboard Columbia, Orbiter Vehicle (OV) 102. The remote manipulator system (RMS) arm, with Material Exposure in Low Earth Orbit (MELEO), is positioned above the port side sill longeron. On the mission-peculiar equipment support structure (MPESS) carriers in the center foreground is the United States (U.S.) Microgravity Payload 1 (USMP-1) with Space Acceleration Measurement System (SAMS), MEPHISTO (its French abbreviation), Lambda Point Experiment (LPE) cryostat assembly (identified by JPL insignia), and LPE vacuum maintenance assembly. Other payload bay (PLB) experiments visible in this image include: (on the starboard wall (left)) the Canadian Experiments 2 (CANEX-2) Space Vision System (SVS) Canadian Target Assembly (CTA) (foreground) and the Attitude Sensor Package (ASP);

Open-field exposure facilitates consummatory extinction.

PubMed

Justel, Nadia; Psyrdellis, Mariana; Pautassi, Ricardo M

2016-12-07

During extinction, the organism learns that a conditioned stimulus or a conditioned response is no longer associated with an unconditioned stimulus, and as a consequence, a decrement in the response is presented. The exposure to novel situations (e.g. exploration of a novel open field) has been used widely to modulate (i.e. either enhance or deteriorate) learning and memory. The aim of the present study was to test whether open-field exposure could modulate consummatory extinction. The results indicated that open-field exposure accelerated the extinction response (i.e. experimental animals provided novelty exposure had lower consummatory behavior than control animals) when applied before - but not after - the first extinction trial, or when applied before the second extinction trial. The results suggest that environmental treatments such as novelty exposure provide a valuable, nonpharmacological alternative to potentially modulate extinction processes.

Experimental Study of Proton Acceleration from Ultra Intense Laser Matter Interactions

NASA Astrophysics Data System (ADS)

Paudel, Yadab Kumar

This dissertation describes proton and ion acceleration measurements from high intensity (˜ 1019 Wcm-2) laser interactions with thin foil targets. Protons and ions accelerated from the back surface of a target driven by a high intensity laser are detected using solid-state nuclear track detector CR39. A simple digital imaging technique, with an adjustable halogen light source shined on CR39 and use of a digital camera with suitable f-number and exposure time, is used to detect particles tracks. This new technique improves the quality 2D image with vivid track patterns in CR39. Our technique allows us to quickly record and sort CR39 pieces for further analysis. This is followed by detailed quantitative information on the protons and ions. Protons and multicharged ions generated from high-intensity laser interactions with thin foil targets have been studied with a 100 TW laser system. Protons/ions with energies up to 10 MeV are accelerated either from the front or the rear surface of the target material. We have observed for the first time a self-radiograph of the target with a glass stalk holding the target itself in the stacked radiochromic films (RCF) placed behind the target. The self-radiography indicates that the fast ions accelerated backward, in a direction opposite to the laser propagation, are turning around in strong magnetic fields. This unique result is a signature of long-living (ns time scale) magnetic fields in the expanding plasma, which are important in energy transport during the intense laser irradiation and have never been considered in the previous studies. The magnetic fields induced by the main pulse near the absorption point expand rapidly with the backward accelerated protons in the pre-formed plasma. The protons are rotated by these magnetic fields and they are recorded in the RCF, making the self-radiography. Angular profiles of protons and multicharged ions accelerated from the target rear surface have been studied with the subpicosecond laser pulse produced by the 100 TW laser system. The protons/ions beam features recorded on CR39 show the hollow beam structure at the center of the beam pattern. This hollow structure in the proton/ion beam pattern associates to the electron transport inside the solid target, which affects the target's rear-surface emission or the electrostatic profile on the target rear-surface. The proton/ion beam filamentation has been seen clearly outside the hollow beam pattern in the CR39 images processed by the new digital imaging technique.

Tilt and Translation Motion Perception during Pitch Tilt with Visual Surround Translation

NASA Technical Reports Server (NTRS)

O'Sullivan, Brita M.; Harm, Deborah L.; Reschke, Millard F.; Wood, Scott J.

2006-01-01

The central nervous system must resolve the ambiguity of inertial motion sensory cues in order to derive an accurate representation of spatial orientation. Previous studies suggest that multisensory integration is critical for discriminating linear accelerations arising from tilt and translation head motion. Visual input is especially important at low frequencies where canal input is declining. The NASA Tilt Translation Device (TTD) was designed to recreate postflight orientation disturbances by exposing subjects to matching tilt self motion with conflicting visual surround translation. Previous studies have demonstrated that brief exposures to pitch tilt with foreaft visual surround translation produced changes in compensatory vertical eye movement responses, postural equilibrium, and motion sickness symptoms. Adaptation appeared greatest with visual scene motion leading (versus lagging) the tilt motion, and the adaptation time constant appeared to be approximately 30 min. The purpose of this study was to compare motion perception when the visual surround translation was inphase versus outofphase with pitch tilt. The inphase stimulus presented visual surround motion one would experience if the linear acceleration was due to foreaft self translation within a stationary surround, while the outofphase stimulus had the visual scene motion leading the tilt by 90 deg as previously used. The tilt stimuli in these conditions were asymmetrical, ranging from an upright orientation to 10 deg pitch back. Another objective of the study was to compare motion perception with the inphase stimulus when the tilts were asymmetrical relative to upright (0 to 10 deg back) versus symmetrical (10 deg forward to 10 deg back). Twelve subjects (6M, 6F, 22-55 yrs) were tested during 3 sessions separated by at least one week. During each of the three sessions (out-of-phase asymmetrical, in-phase asymmetrical, inphase symmetrical), subjects were exposed to visual surround translation synchronized with pitch tilt at 0.1 Hz for a total of 30 min. Tilt and translation motion perception was obtained from verbal reports and a joystick mounted on a linear stage. Horizontal vergence and vertical eye movements were obtained with a binocular video system. Responses were also obtained during darkness before and following 15 min and 30 min of visual surround translation. Each of the three stimulus conditions involving visual surround translation elicited a significantly reduced sense of perceived tilt and strong linear vection (perceived translation) compared to pre-exposure tilt stimuli in darkness. This increase in perceived translation with reduction in tilt perception was also present in darkness following 15 and 30 min exposures, provided the tilt stimuli were not interrupted. Although not significant, there was a trend for the inphase asymmetrical stimulus to elicit a stronger sense of both translation and tilt than the out-of-phase asymmetrical stimulus. Surprisingly, the inphase asymmetrical stimulus also tended to elicit a stronger sense of peak-to-peak translation than the inphase symmetrical stimulus, even though the range of linear acceleration during the symmetrical stimulus was twice that of the asymmetrical stimulus. These results are consistent with the hypothesis that the central nervous system resolves the ambiguity of inertial motion sensory cues by integrating inputs from visual, vestibular, and somatosensory systems.

Space radiation protection: Destination Mars.

PubMed

Durante, Marco

2014-04-01

National space agencies are planning a human mission to Mars in the XXI century. Space radiation is generally acknowledged as a potential showstopper for this mission for two reasons: a) high uncertainty on the risk of radiation-induced morbidity, and b) lack of simple countermeasures to reduce the exposure. The need for radiation exposure mitigation tools in a mission to Mars is supported by the recent measurements of the radiation field on the Mars Science Laboratory. Shielding is the simplest physical countermeasure, but the current materials provide poor reduction of the dose deposited by high-energy cosmic rays. Accelerator-based tests of new materials can be used to assess additional protection in the spacecraft. Active shielding is very promising, but as yet not applicable in practical cases. Several studies are developing technologies based on superconducting magnetic fields in space. Reducing the transit time to Mars is arguably the best solution but novel nuclear thermal-electric propulsion systems also seem to be far from practical realization. It is likely that the first mission to Mars will employ a combination of these options to reduce radiation exposure. Copyright © 2014 The Committee on Space Research (COSPAR). Published by Elsevier Ltd. All rights reserved.

Radiosurgery for cerebral arteriovenous malformation during pregnancy: A case report focusing on fetal exposure to radiation

PubMed Central

Nagayama, Kazuki; Kurita, Hiroki; Tonari, Ayako; Takayama, Makoto; Shiokawa, Yoshiaki

2010-01-01

Introduction: We present the case of a pregnant woman who underwent linear accelerator (LINAC)-based stereotactic radiosurgery (SRS) and we discuss the fetal exposure to radiation. Clinical Presentation: A 20-year-old woman at 18 weeks of gestation presented with right cerebral hemorrhage and underwent urgent evacuation of the hematoma. She recovered well after surgery, but cerebral angiography after the surgery revealed a small deeply seated arteriovenous malformation (AVM) in the right frontal lobe extending to the right basal ganglia. Methods and Results: We examined the diffuse AVM and treated it with LINAC-based SRS at 24 weeks of gestation. Before SRS, the fetus was exposed to a radiation dose of 8.26 mGy, which was estimated by conducting an experiment using an adult RANDO phantom, and a radiophotoluminescent (RPL) glass rod dosimeter (GRD) system. The patient underwent Caesarean delivery at 36 weeks of gestation and gave birth to a healthy baby. Conclusion: The exposure of fetus to radiation during SRS was exceedingly low. SRS can be used as an alternative treatment to microsurgery for resolving small deeply seated AVMs even in pregnant patients. PMID:22028762

Evaluating Weathering of Food Packaging Polyethylene-Nano-clay Composites: Release of Nanoparticles and their Impacts.

PubMed

Han, Changseok; Zhao, Amy; Varughese, Eunice; Sahle-Demessie, E

2018-01-01

Nano-fillers are increasingly incorporated into polymeric materials to improve the mechanical, barrier or other matrix properties of nanocomposites used for consumer and industrial applications. However, over the life cycle, these nanocomposites could degrade due to exposure to environmental conditions, resulting in the release of embedded nanomaterials from the polymer matrix into the environment. This paper presents a rigorous study on the degradation and the release of nanomaterials from food packaging composites. Films of nano-clay-loaded low-density polyethylene (LDPE) composite for food packaging applications were prepared with the spherilene technology and exposed to accelerated weathering of ultraviolet (UV) irradiation or low concentration of ozone at 40 °C. The changes in the structural, surface morphology, chemical and physical properties of the films during accelerated weathering were investigated. Qualitative and quantitative changes in properties of pristine and aged materials and the release of nano-clay proceeded slowly until 130 hr irradiation and then accelerated afterward resulting complete degradation. Although nano-clay increased the stability of LDPE and improved thermal and barrier properties, they accelerated the UV oxidation of LDPE. With increasing exposure to UV, the surface roughness, chemiluminescence index, and carbonyl index of the samples increased while decreasing the intensity of the wide-angle X-ray diffraction pattern. Nano-clay particles with sizes ranging from 2-8 nm were released from UV and ozone weathered composite. The concentrations of released nanoparticles increased with an increase in aging time. Various toxicity tests, including reactive oxygen species generation and cell activity/viability were also performed on the released nano-clay and clay polymer. The released nano-clays basically did not show toxicity. Our combined results demonstrated the degradation properties of nano-clay particle-embedded LDPE composites toxicity of released nano-clay particles to A594 adenocarcinomic human alveolar basal epithelial cells was observed, which will help with future risk based-formulations of exposure.

Effect of 3 Weeks Use of Compression Garments on Stride and Impact Shock during a Fatiguing Run.

PubMed

Lucas-Cuevas, A G; Priego-Quesada, J I; Aparicio, I; Giménez, J V; Llana-Belloch, S; Pérez-Soriano, P

2015-10-01

Excessive and prolonged exposure to impact acceleration during running is associated with increased injury rate. Acute use of compressive garments has been speculated to improve attenuation. However, it is unknown how longer interventions of compressive garments influence attenuation in running. 40 runners trained with compressive and placebo stockings for 3 weeks. Perception of comfort, stride parameters (rate, length) and impact acceleration (head and tibial peak acceleration, magnitude, acceleration rate and attenuation) were measured every 5 min during a fatigue run (30 min at 80% of the individual's maximal aerobic speed). Compressive stockings reduced tibial peak acceleration and magnitude compared to placebo stockings at every minute (p<0.05) except for the initial measurement (p>0.05). Moreover, compressive stockings led to a lower rate of increase in tibial peak acceleration (14%, p<0.005) and magnitude (16%, p<0.001) as a result of the development of fatigue compared to placebo stockings (24% and 26% increase, p=0.014 and p=0.003, respectively). Similar perception of comfort was reported for both garments. Training with compressive stockings for 3 weeks reduced impact acceleration and the rate of increase in acceleration compared to placebo stockings. These findings suggest that compressive stockings may play a protective role by reducing impact accelerations during running. © Georg Thieme Verlag KG Stuttgart · New York.

Accelerated Spirometric Decline in New York City Firefighters With α1-Antitrypsin Deficiency

PubMed Central

Brantly, Mark; Izbicki, Gabriel; Hall, Charles; Shanske, Alan; Chavko, Robert; Santhyadka, Ganesha; Christodoulou, Vasilios; Weiden, Michael D.; Prezant, David J.

2010-01-01

Background: On September 11, 2001, the World Trade Center (WTC) collapse caused massive air pollution, producing variable amounts of lung function reduction in the New York City Fire Department (FDNY) rescue workforce. α1-Antitrypsin (AAT) deficiency is a risk factor for obstructive airway disease. Methods: This prospective, longitudinal cohort study of the first 4 years post-September 11, 2001, investigated the influence of AAT deficiency on adjusted longitudinal spirometric change (FEV1) in 90 FDNY rescue workers with WTC exposure. Workers with protease inhibitor (Pi) Z heterozygosity were considered moderately AAT deficient. PiS homozygosity or PiS heterozygosity without concomitant PiZ heterozygosity was considered mild deficiency, and PiM homozygosity was considered normal. Alternately, workers had low AAT levels if serum AAT was ≤ 20 μmol/L. Results: In addition to normal aging-related decline (37 mL/y), significant FEV1 decline accelerations developed with increasing AAT deficiency severity (110 mL/y for moderate and 32 mL/y for mild) or with low AAT serum levels (49 mL/y). Spirometric rates pre-September 11, 2001, did not show accelerations with AAT deficiency. Among workers with low AAT levels, cough persisted in a significant number of participants at 4 years post-September 11, 2001. Conclusions: FDNY rescue workers with AAT deficiency had significant spirometric decline accelerations and persistent airway symptoms during the first 4 years after WTC exposure, representing a novel gene-by-environment interaction. Clinically meaningful decline acceleration occurred even with the mild serum AAT level reductions associated with PiS heterozygosity (without concomitant PiZ heterozygosity). PMID:20634282

1985 Particle Accelerator Conference: Accelerator Engineering and Technology, 11th, Vancouver, Canada, May 13-16, 1985, Proceedings

NASA Astrophysics Data System (ADS)

Strathdee, A.

1985-10-01

The topics discussed are related to high-energy accelerators and colliders, particle sources and electrostatic accelerators, controls, instrumentation and feedback, beam dynamics, low- and intermediate-energy circular accelerators and rings, RF and other acceleration systems, beam injection, extraction and transport, operations and safety, linear accelerators, applications of accelerators, radiation sources, superconducting supercolliders, new acceleration techniques, superconducting components, cryogenics, and vacuum. Accelerator and storage ring control systems are considered along with linear and nonlinear orbit theory, transverse and longitudinal instabilities and cures, beam cooling, injection and extraction orbit theory, high current dynamics, general beam dynamics, and medical and radioisotope applications. Attention is given to superconducting RF structures, magnet technology, superconducting magnets, and physics opportunities with relativistic heavy ion accelerators.

Study of an External Neutron Source for an Accelerator-Driven System using the PHITS Code

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sugawara, Takanori; Iwasaki, Tomohiko; Chiba, Takashi

A code system for the Accelerator Driven System (ADS) has been under development for analyzing dynamic behaviors of a subcritical core coupled with an accelerator. This code system named DSE (Dynamics calculation code system for a Subcritical system with an External neutron source) consists of an accelerator part and a reactor part. The accelerator part employs a database, which is calculated by using PHITS, for investigating the effect related to the accelerator such as the changes of beam energy, beam diameter, void generation, and target level. This analysis method using the database may introduce some errors into dynamics calculations sincemore » the neutron source data derived from the database has some errors in fitting or interpolating procedures. In this study, the effects of various events are investigated to confirm that the method based on the database is appropriate.« less

Development of accelerated net nitrate uptake. [Zea mays L

DOE Office of Scientific and Technical Information (OSTI.GOV)

MacKown, C.T.; McClure, P.R.

1988-05-01

Upon initial nitrate exposure, net nitrate uptake rates in roots of a wide variety of plants accelerate within 6 to 8 hours to substantially greater rates. Effects of solution nitrate concentrations and short pulses of nitrate ({le}1 hour) upon nitrate-induced acceleration of nitrate uptake in maize (Zea mays L.) were determined. Root cultures of dark-grown seedlings, grown without nitrate, were exposed to 250 micromolar nitrate for 0.25 to 1 hour or to various solution nitrate concentration (10-250 micromolar) for 1 hour before returning them to a nitrate-free solution. Net nitrate uptake rates were assayed at various periods following nitrate exposuremore » and compared to rates of roots grown either in the absence of nitrate (CaSO{sub 4}-grown) or with continuous nitrate for at least 20 hours. Three hours after initial nitrate exposure, nitrate pulse treatments increased nitrate uptake rates three- to four-fold compared to the rates of CaSO{sub 4}-grown roots. When cycloheximide (5 micrograms per milliliter) was included during a 1-hour pulse with 250 micromolar nitrate, development of the accelerated nitrate uptake state was delayed. Otherwise, nitrate uptake rates reached maximum values within 6 hours before declining. Maximum rates, however, were significantly less than those of roots exposed continuously for 20, 32, or 44 hours. Pulsing for only 0.25 hour with 250 micromolar nitrate and for 1 hour with 10 micromolar caused acceleration of nitrate uptake, but the rates attained were either less than or not sustained for a duration comparable to those of roots pulsed for 1 hour with 250 micromolar nitrate. These results indicate that substantial development of nitrate-induced accelerated nitrate uptake state can be achieved by small endogenous accumulations of nitrate, which appear to moderate the activity or level of root nitrate uptake.« less

Physical Simulation of a Prolonged Plasma-Plume Exposure of a Space Debris Object

NASA Astrophysics Data System (ADS)

Shuvalov, V. A.; Gorev, N. B.; Tokmak, N. A.; Kochubei, G. S.

2018-05-01

A methodology has been developed for the physical (laboratory) simulation of the prolonged exposure of a space debris object to high-energy ions of a plasma plume for removing the object into low-Earth orbit with its subsequent burning in the Earth's atmosphere. The methodology is based on the equivalence criteria of two modes of exposure (in the Earth's ionosphere and in the setup) and the procedure for accelerated resource tests in terms of the sputtering of the space debris material and its deceleration by a plasma jet in the Earth's ionosphere.

Collective acceleration of ions in a system with an insulated anode

NASA Astrophysics Data System (ADS)

Bystritskii, V. M.; Didenko, A. N.; Krasik, Ya. E.; Lopatin, V. S.; Podkatov, V. I.

1980-11-01

An investigation was made of the processes of collective acceleration of protons in vacuum in a system with an insulated anode and trans-anode electrodes, which were insulated or grounded, in high-current Tonus and Vera electron accelerators. The influence of external conditions and parameters of the electron beam on the efficiency of acceleration processes was investigated. Experiments were carried out in which protons were accelerated in a system with trans-anode electrodes. A study was made of the influence of a charge prepulse and of the number of trans-anode electrodes on the energy of the accelerated electrons. A system with a single anode produced Np=1014 protons of 2Ee < Ep < 3Ee energy. Suppression of a charge prepulse increased the proton energy to (6 8)Ee and the yield was then 1013. The maximum proton energy of 14Ee was obtained in a system with three trans-anode electrodes. A possible mechanism of proton acceleration was analyzed. The results obtained were compared with those of other investigations. Ways of increasing the efficiency of this acceleration method were considered.

Photon Counting Imaging with an Electron-Bombarded Pixel Image Sensor

PubMed Central

Hirvonen, Liisa M.; Suhling, Klaus

2016-01-01

Electron-bombarded pixel image sensors, where a single photoelectron is accelerated directly into a CCD or CMOS sensor, allow wide-field imaging at extremely low light levels as they are sensitive enough to detect single photons. This technology allows the detection of up to hundreds or thousands of photon events per frame, depending on the sensor size, and photon event centroiding can be employed to recover resolution lost in the detection process. Unlike photon events from electron-multiplying sensors, the photon events from electron-bombarded sensors have a narrow, acceleration-voltage-dependent pulse height distribution. Thus a gain voltage sweep during exposure in an electron-bombarded sensor could allow photon arrival time determination from the pulse height with sub-frame exposure time resolution. We give a brief overview of our work with electron-bombarded pixel image sensor technology and recent developments in this field for single photon counting imaging, and examples of some applications. PMID:27136556

Exposure of the Bone Marrow Microenvironment to Simulated Solar and Galactic Cosmic Radiation Induces Biological Bystander Effects on Human Hematopoiesis

DOE PAGES

Almeida-Porada, Graca; Rodman, Christopher; Kuhlman, Bradford; ...

2018-04-26

The stem cell compartment of the hematopoietic system constitutes one of the most radiosensitive tissues of the body and leukemias represent one of the most frequent radiogenic cancers with short latency periods. As such, leukemias may pose a particular threat to astronauts during prolonged space missions. Control of hematopoiesis is tightly governed by a specialized bone marrow (BM) microenvironment/niche. As such, any environmental insult that damages cells of this niche would be expected to produce pronounced effects on the types and functionality of hematopoietic/immune cells generated. We recently reported that direct exposure of human HSC to simulated SEP and GCRmore » radiation dramatically altered the differentiative potential of these cells, and that simulated GCR exposures can directly induce DNA damage and mutations within human HSC, which led to leukemic transformation when these cells repopulated murine recipients. In the present study, we performed the first in depth examination to define changes that occur in mesenchymal stem cells (MSC) present in the human BM niche following exposure to accelerated protons and iron ions, and assess the impact these changes have upon human hematopoiesis. Here, our data thus provides compelling evidence that simulated SEP/GCR exposures can also contribute to defective hematopoiesis/immunity through so-called “biological bystander effects” by damaging the stromal cells that comprise the human marrow microenvironment, thereby altering their ability to support normal hematopoiesis.« less

Exposure of the Bone Marrow Microenvironment to Simulated Solar and Galactic Cosmic Radiation Induces Biological Bystander Effects on Human Hematopoiesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Almeida-Porada, Graca; Rodman, Christopher; Kuhlman, Bradford

The stem cell compartment of the hematopoietic system constitutes one of the most radiosensitive tissues of the body and leukemias represent one of the most frequent radiogenic cancers with short latency periods. As such, leukemias may pose a particular threat to astronauts during prolonged space missions. Control of hematopoiesis is tightly governed by a specialized bone marrow (BM) microenvironment/niche. As such, any environmental insult that damages cells of this niche would be expected to produce pronounced effects on the types and functionality of hematopoietic/immune cells generated. We recently reported that direct exposure of human HSC to simulated SEP and GCRmore » radiation dramatically altered the differentiative potential of these cells, and that simulated GCR exposures can directly induce DNA damage and mutations within human HSC, which led to leukemic transformation when these cells repopulated murine recipients. In the present study, we performed the first in depth examination to define changes that occur in mesenchymal stem cells (MSC) present in the human BM niche following exposure to accelerated protons and iron ions, and assess the impact these changes have upon human hematopoiesis. Here, our data thus provides compelling evidence that simulated SEP/GCR exposures can also contribute to defective hematopoiesis/immunity through so-called “biological bystander effects” by damaging the stromal cells that comprise the human marrow microenvironment, thereby altering their ability to support normal hematopoiesis.« less

Exposure of the Bone Marrow Microenvironment to Simulated Solar and Galactic Cosmic Radiation Induces Biological Bystander Effects on Human Hematopoiesis.

PubMed

Almeida-Porada, Graça; Rodman, Christopher; Kuhlman, Bradford; Brudvik, Egil; Moon, John; George, Sunil; Guida, Peter; Sajuthi, Satria P; Langefeld, Carl D; Walker, Stephen J; Wilson, Paul F; Porada, Christopher D

2018-04-26

The stem cell compartment of the hematopoietic system constitutes one of the most radiosensitive tissues of the body and leukemias represent one of the most frequent radiogenic cancers with short latency periods. As such, leukemias may pose a particular threat to astronauts during prolonged space missions. Control of hematopoiesis is tightly governed by a specialized bone marrow (BM) microenvironment/niche. As such, any environmental insult that damages cells of this niche would be expected to produce pronounced effects on the types and functionality of hematopoietic/immune cells generated. We recently reported that direct exposure of human hematopoietic stem cells (HSC) to simulated solar energetic particle (SEP) and galactic cosmic ray (GCR) radiation dramatically altered the differentiative potential of these cells, and that simulated GCR exposures can directly induce DNA damage and mutations within human HSC, which led to leukemic transformation when these cells repopulated murine recipients. In this study, we performed the first in-depth examination to define changes that occur in mesenchymal stem cells present in the human BM niche following exposure to accelerated protons and iron ions and assess the impact these changes have upon human hematopoiesis. Our data provide compelling evidence that simulated SEP/GCR exposures can also contribute to defective hematopoiesis/immunity through so-called "biological bystander effects" by damaging the stromal cells that comprise the human marrow microenvironment, thereby altering their ability to support normal hematopoiesis.

Ion extraction capabilities of two-grid accelerator systems. M.S. Thesis

NASA Technical Reports Server (NTRS)

Rovang, D. C.; Wilbur, P. J.

1984-01-01

An experimental investigation into the ion extraction capabilities of two-grid accelerator systems common to electrostatic ion thrusters is described. This work resulted in a large body of experimental data which facilitates the selection of the accelerator system geometries and operating parameters necessary to maximize the extracted ion current. Results suggest that the impingement-limited perveance is not dramatically affected by reductions in screen hole diameter to 0.5 mm. Impingement-limited performance is shown to depend most strongly on grid separation distance, accelerator hole diameter ratio, the discharge-to-total accelerating voltage ratio, and the net-to-total accelerating voltage ratio. Results obtained at small grid separation ratios suggest a new grid operating condition where high beam current per hole levels are achieved at a specified net accelerating voltage. It is shown that this operating condition is realized at an optimum ratio of net-to-total accelerating voltage ratio which is typically quite high. The apparatus developed for this study is also shown to be well suited measuring the electron backstreaming and electrical breakdown characteristics of two-grid accelerator systems.

Laser-wakefield accelerators as hard x-ray sources for 3D medical imaging of human bone

PubMed Central

Cole, J. M.; Wood, J. C.; Lopes, N. C.; Poder, K.; Abel, R. L.; Alatabi, S.; Bryant, J. S. J.; Jin, A.; Kneip, S.; Mecseki, K.; Symes, D. R.; Mangles, S. P. D.; Najmudin, Z.

2015-01-01

A bright μm-sized source of hard synchrotron x-rays (critical energy Ecrit > 30 keV) based on the betatron oscillations of laser wakefield accelerated electrons has been developed. The potential of this source for medical imaging was demonstrated by performing micro-computed tomography of a human femoral trabecular bone sample, allowing full 3D reconstruction to a resolution below 50 μm. The use of a 1 cm long wakefield accelerator means that the length of the beamline (excluding the laser) is dominated by the x-ray imaging distances rather than the electron acceleration distances. The source possesses high peak brightness, which allows each image to be recorded with a single exposure and reduces the time required for a full tomographic scan. These properties make this an interesting laboratory source for many tomographic imaging applications. PMID:26283308

Particulate matter air pollution exposure promotes recruitment of monocytes into atherosclerotic plaques.

PubMed

Yatera, Kazuhiro; Hsieh, Joanne; Hogg, James C; Tranfield, Erin; Suzuki, Hisashi; Shih, Chih-Horng; Behzad, Ali R; Vincent, Renaud; van Eeden, Stephan F

2008-02-01

Epidemiologic studies have shown an association between exposure to ambient particulate air pollution <10 microm in diameter (PM(10)) and increased cardiovascular morbidity and mortality. We previously showed that PM(10) exposure causes progression of atherosclerosis in coronary arteries. We postulate that the recruitment of monocytes from the circulation into atherosclerotic lesions is a key step in this PM(10)-induced acceleration of atherosclerosis. The study objective was to quantify the recruitment of circulating monocytes into vessel walls and the progression of atherosclerotic plaques induced by exposure to PM(10). Female Watanabe heritable hyperlipidemic rabbits, which naturally develop systemic atherosclerosis, were exposed to PM(10) (EHC-93) or vehicle by intratracheal instillation twice a week for 4 wk. Monocytes, labeled with 5-bromo-2'-deoxyuridine (BrdU) in donors, were transfused to recipient rabbits as whole blood, and the recruitment of BrdU-labeled cells into vessel walls and plaques in recipients was measured by quantitative histological methodology. Exposure to PM(10) caused progression of atherosclerotic lesions in thoracic and abdominal aorta. It also decreased circulating monocyte counts, decreased circulating monocytes expressing high levels of CD31 (platelet endothelial cell adhesion molecule-1) and CD49d (very late antigen-4 alpha-chain), and increased expression of CD54 (ICAM-1) and CD106 (VCAM-1) in plaques. Exposure to PM(10) increased the number of BrdU-labeled monocytes adherent to endothelium over plaques and increased the migration of BrdU-labeled monocytes into plaques and smooth muscle underneath plaques. We conclude that exposure to ambient air pollution particles promotes the recruitment of circulating monocytes into atherosclerotic plaques and speculate that this is a critically important step in the PM(10)-induced progression of atherosclerosis.

Novel Regenerative Peptide TP508 Mitigates Radiation-Induced Gastrointestinal Damage By Activating Stem Cells and Preserving Crypt Integrity

PubMed Central

Kantara, Carla; Moya, Stephanie M.; Houchen, Courtney W.; Umar, Shahid; Ullrich, Robert L.; Singh, Pomila; Carney, Darrell H.

2015-01-01

In recent years, increasing threats of radiation exposure and nuclear disasters have become a significant concern for the United States and countries worldwide. Exposure to high doses of radiation triggers a number of potentially lethal effects. Among the most severe is the gastrointestinal (GI) toxicity syndrome caused by the destruction of the intestinal barrier, resulting in bacterial translocation, systemic bacteremia, sepsis and death. The lack of effective radioprotective agents capable of mitigating radiation-induced damage has prompted a search for novel countermeasures that can mitigate the effects of radiation post-exposure, accelerate tissue repair in radiation-exposed individuals, and prevent mortality. We report that a single injection of regenerative peptide TP508 (rusalatide acetate, Chrysalin®) 24h after lethal radiation exposure (9Gy, LD100/15) appears to significantly increase survival and delay mortality by mitigating radiation-induced intestinal and colonic toxicity. TP508 treatment post-exposure prevents the disintegration of gastrointestinal crypts, stimulates the expression of adherens junction protein E-cadherin, activates crypt cell proliferation, and decreases apoptosis. TP508 post-exposure treatment also up-regulates the expression of DCLK1 and LGR5 markers of stem cells that have been shown to be responsible for maintaining and regenerating intestinal crypts. Thus, TP508 appears to mitigate the effects of GI toxicity by activating radioresistant stem cells and increasing the stemness potential of crypts to maintain and restore intestinal integrity. These results suggest that TP508 may be an effective emergency nuclear countermeasure that could be delivered within 24h post-exposure to increase survival and delay mortality, giving victims time to reach clinical sites for advanced medical treatment. PMID:26280221

Microgravity acceleration measurement and environment characterization science (17-IML-1)

NASA Technical Reports Server (NTRS)

1992-01-01

The Space Acceleration Measurement System (SAMS) is a general purpose instrumentation system designed to measure the accelerations onboard the Shuttle Orbiter and Shuttle/Spacelab vehicles. These measurements are used to support microgravity experiments and investigation into the microgravity environment of the vehicle. Acceleration measurements can be made at locations remote from the SAMS main instrumentation unit by the use of up to three remote triaxial sensor heads. The prime objective for SAMS on the International Microgravity Lab (IML-1) mission will be to measure the accelerations experienced by the Fluid Experiment System (FES). The SAMS acceleration measurements for FES will be complemented by low level, low frequency acceleration measurements made by the Orbital Acceleration Research Experiment (OARE) installed on the shuttle. Secondary objectives for SAMS will be to measure accelerations at several specific locations to enable the acceleration transfer function of the Spacelab module to be analyzed. This analysis effort will be in conjunction with similar measurements analyses on other Spacelab missions.

Systems and methods for cylindrical hall thrusters with independently controllable ionization and acceleration stages

DOEpatents

Diamant, Kevin David; Raitses, Yevgeny; Fisch, Nathaniel Joseph

2014-05-13

Systems and methods may be provided for cylindrical Hall thrusters with independently controllable ionization and acceleration stages. The systems and methods may include a cylindrical channel having a center axial direction, a gas inlet for directing ionizable gas to an ionization section of the cylindrical channel, an ionization device that ionizes at least a portion of the ionizable gas within the ionization section to generate ionized gas, and an acceleration device distinct from the ionization device. The acceleration device may provide an axial electric field for an acceleration section of the cylindrical channel to accelerate the ionized gas through the acceleration section, where the axial electric field has an axial direction in relation to the center axial direction. The ionization section and the acceleration section of the cylindrical channel may be substantially non-overlapping.

Principal Investigator Microgravity Services Role in ISS Acceleration Data Distribution

NASA Technical Reports Server (NTRS)

McPherson, Kevin

1999-01-01

Measurement of the microgravity acceleration environment on the International Space Station will be accomplished by two accelerometer systems. The Microgravity Acceleration Measurement System will record 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 will be accomplished by the Space Acceleration Measurement System-II. Due to the dynamic nature of the microgravity environment and its potential to influence sensitive experiments, Principal Investigators require distribution of microgravity acceleration in a timely and straightforward fashion. In addition to this timely distribution of the data, long term access to International Space Station microgravity environment acceleration data is required. The NASA Glenn Research Center's Principal Investigator Microgravity Services project will provide the means for real-time and post experiment distribution of microgravity acceleration data to microgravity science Principal Investigators. Real-time distribution of microgravity environment acceleration data will be accomplished via the World Wide Web. Data packets from the Microgravity Acceleration Measurement System and the Space Acceleration Measurement System-II will be routed from onboard the International Space Station to the NASA Glenn Research Center's Telescience Support Center. Principal Investigator Microgravity Services' ground support equipment located at the Telescience Support Center will be capable of generating a standard suite of acceleration data displays, including various time domain and frequency domain options. These data displays will be updated in real-time and will periodically update images available via the Principal Investigator Microgravity Services web page.

Summary Report of Mission Acceleration Measurements for STS-78. Launched June 20, 1996

NASA Technical Reports Server (NTRS)

Hakimzadeh, Roshanak; Hrovat, Kenneth; McPherson, Kevin M.; Moskowitz, Milton E.; Rogers, Melissa J. B.

1997-01-01

The microgravity environment of the Space Shuttle Columbia was measured during the STS-78 mission using accelerometers from three different instruments: the Orbital Acceleration Research Experiment, the Space Acceleration Measurement System and the Microgravity Measurement Assembly. The quasi-steady environment was also calculated in near real-time during the mission by the Microgravity Analysis Workstation. The Orbital Acceleration Research Experiment provided investigators with real-time quasi-steady acceleration measurements. The Space Acceleration Measurement System recorded higher frequency data on-board for post-mission analysis. The Microgravity Measurement Assembly provided investigators with real-time quasi-steady and higher frequency acceleration measurements. The Microgravity Analysis Workstation provided calculation of the quasi-steady environment. This calculation was presented to the science teams in real-time during the mission. The microgravity environment related to several different Orbiter, crew and experiment operations is presented and interpreted in this report. A radiator deploy, the Flight Control System checkout, and a vernier reaction control system reboost demonstration had minimal effects on the acceleration environment, with excitation of frequencies in the 0.01 to 10 Hz range. Flash Evaporator System venting had no noticeable effect on the environment while supply and waste water dumps caused excursions of 2 x lO(exp -6) to 4 x 10(exp -6) g in the Y(sub b) and Z(sub b) directions. Crew sleep and ergometer exercise periods can be clearly seen in the acceleration data, as expected. Accelerations related to the two Life Science Laboratory Equipment Refrigerator/Freezers were apparent in the data as are accelerations caused by the Johnson Space Center Projects Centrifuge. As on previous microgravity missions, several signals are present in the acceleration data for which a source has not been identified. The causes of these accelerations are under investigation.

Life stress, glucocorticoid signaling, and the aging epigenome: Implications for aging-related diseases.

PubMed

Gassen, Nils C; Chrousos, George P; Binder, Elisabeth B; Zannas, Anthony S

2017-03-01

Life stress has been associated with accelerated cellular aging and increased risk for developing aging-related diseases; however, the underlying molecular mechanisms remain elusive. A highly relevant process that may underlie this association is epigenetic regulation. In this review, we build upon existing evidence to propose a model whereby exposure to life stress, in part via its effects on the hypothalamic-pituitary axis and the glucocorticoid signaling system, may alter the epigenetic landscape across the lifespan and, consequently, influence genomic regulation and function in ways that are conducive to the development of aging-related diseases. This model is supported by recent studies showing that life stressors and stress-related phenotypes can accelerate epigenetic aging, a measure that is based on DNA methylation prediction of chronological age and has been associated with several aging-related disease phenotypes. We discuss the implications of this model for the prevention and treatment of aging-related diseases, as well as the challenges and limitations of this line of research. Copyright © 2016 Elsevier Ltd. All rights reserved.

Priming of microglia in a DNA-repair deficient model of accelerated aging.

PubMed

Raj, Divya D A; Jaarsma, Dick; Holtman, Inge R; Olah, Marta; Ferreira, Filipa M; Schaafsma, Wandert; Brouwer, Nieske; Meijer, Michel M; de Waard, Monique C; van der Pluijm, Ingrid; Brandt, Renata; Kreft, Karim L; Laman, Jon D; de Haan, Gerald; Biber, Knut P H; Hoeijmakers, Jan H J; Eggen, Bart J L; Boddeke, Hendrikus W G M

2014-09-01

Aging is associated with reduced function, degenerative changes, and increased neuroinflammation of the central nervous system (CNS). Increasing evidence suggests that changes in microglia cells contribute to the age-related deterioration of the CNS. The most prominent age-related change of microglia is enhanced sensitivity to inflammatory stimuli, referred to as priming. It is unclear if priming is due to intrinsic microglia ageing or induced by the ageing neural environment. We have studied this in Ercc1 mutant mice, a DNA repair-deficient mouse model that displays features of accelerated aging in multiple tissues including the CNS. In Ercc1 mutant mice, microglia showed hallmark features of priming such as an exaggerated response to peripheral lipopolysaccharide exposure in terms of cytokine expression and phagocytosis. Specific targeting of the Ercc1 deletion to forebrain neurons resulted in a progressive priming response in microglia exemplified by phenotypic alterations. Summarizing, these data show that neuronal genotoxic stress is sufficient to switch microglia from a resting to a primed state. Copyright © 2014 Elsevier Inc. All rights reserved.

The Use of Altered Gravity as a Tool to Understand Neurovestibular Mechanisms in Vertebrates

NASA Technical Reports Server (NTRS)

Boyle, R.; Popova, Y.; Varelas, J.

2017-01-01

Vertebrates sense gravito-inertial acceleration by mechanoreceptors (hair cells) in the otolith structures of the inner ear. These structures consist of ciliated sensory hair cells surmounted by biomineral grains of calcium carbonate (CaCO3) called otoconia that provide mechanical loading of hair cell cilia. Changes in their high density can alter the hair cells sensitivity to acceleration and orientation with respect to gravity. A widely considered mechanism by which the animal responds to a chronic change in amplitude of gravity is a change in weight-lending otoconia. Hair cells are synaptically coupled to the vestibular nerve afferents that convey the signals into the brain. Synapses are modifiable in strength and numbers, and thereby can be an additional target to adjust the sensation as the gravity load changes. Here, we present the results obtained in 2 species exposed both to G and HG. Adult toadfish, Opsanus tau, were exposed to G in 2 short-duration shuttle missions and to 1.4 2.24G [resultant] centrifugation for 1-32 days; re-adaptation was studied following 1-8 days after return to 1G. Results show a biphasic pattern in response to 2.24G: initial hypersensitivity, similar to that observed after G exposure, followed by transition to a significant decrease at 16-32 days. Recovery from HG exposure is 4-8 days. Two major pieces of information are still needed: vertebrate hair cell response to altered gravity and impact of longer duration exposures on sensory plasticity. To address the latter we applied electron microscopic techniques to image otoconia mass obtained from 1) mice subjected to 91-days of weightlessness in the Mouse Drawer System (MDS) flown on International Space Station, 2) mice subjected to 91-days of 1.24G centrifugation on ground, and 3) mice flown on 2 short-duration orbital missions. Images indicate a clear restructuring of individual otoconia, suggesting deposition to the outer shell. Images from their HG counterparts indicate the converse - an ablation of the otoconia mass. For shorter duration exposures to weightlessness on 13-day shuttle missions mice otoconia appear normal. Despite the permanence of 1G in evolution the animal senses exposure to a novel, non-1G, environment and adaptive mechanisms are initiated - in the short term compensation is likely confined to the peripheral sensory receptors, the brain or both. For longer exposures structural modifications of the endorgan may also result.

Failure Engineering Study and Accelerated Stress Test Results for the Mars Global Surveyor Spacecraft's Power Shunt Assemblies

NASA Technical Reports Server (NTRS)

Gibbel, Mark; Larson, Timothy

2000-01-01

An Engineering-of-Failure approach to designing and executing an accelerated product qualification test was performed to support a risk assessment of a "work-around" necessitated by an on-orbit failure of another piece of hardware on the Mars Global Surveyor spacecraft. The proposed work-around involved exceeding the previous qualification experience both in terms of extreme cold exposure level and in terms of demonstrated low cycle fatigue life for the power shunt assemblies. An analysis was performed to identify potential failure sites, modes and associated failure mechanisms consistent with the new use conditions. A test was then designed and executed which accelerated the failure mechanisms identified by analysis. Verification of the resulting failure mechanism concluded the effort.

Plasma development in the accelerator of a 2-kJ focus discharge.

PubMed

Fischer, H; Haering, K H

1979-07-01

Optical image structures from early breakdown ( approximately 200 nsec) to focus formation (~1300 nsec) in 3 Torr hydrogen were studied by means of 2 image converter shutters having 50-nsec and 10-nsec exposure. Space charge limited cathode spots at the outer electrode (OE)-spoke-shaped positive columns across the gap-and an extended electron cloud along the center electrode (CE) determine the current flow during early breakdown. Ionization increases exponentially within the center gap plasma. This is separated from the CE by a pattern of anode drop filaments. Filament structures grow into the z-axis accelerated current sheath, which in addition carries the early spoke pattern. The sheath appears homogeneous after leaving the accelerator exit.

Changes in plasma vasopressin during motion sickness in cats

NASA Technical Reports Server (NTRS)

Fox, Robert; Keil, L.; Daunton, Nancy G.; Thomsen, D.; Dictor, M.; Chee, O.

1991-01-01

Changes in levels of plasma vasopressin (AVP) and cortisol (C) have been shown to be correlated with motion sickness and nausea in man. As part of the research aimed at validation of the cat as an appropriate animal model for motion sickness research, levels of these hormones were investigated in the cat during motion sickness elicited by vertical linear acceleration of approximately 0.6 Hz and 1 +/- 0.6 G. In Study 1, 15 cats previously screened for susceptibility to motion sickness were prepared with indwelling jugular catheters to permit withdrawl of blood with minimal disruption of the stimulus and minimum stress to the animal. AVP and C were measured in blood samples obtained during exposure to vertical linear acceleration and during control sessions in which the animals were placed in the stationary apparatus. 10 min and 1 min prior to duration; 1, 5, 10, and 20 min after start of motion. Total duration of exposure to motion was 20 min. The data indicate that both AVP and C are elevated during exposure to motion if emesis occurs. AVP reaches maximum levels during or about the same time as emesis, while C increases gradually throughout the period of vertical acceleration. In Study 2, four cats were prepared with indwelling catheters and AVP was measured in blood withdrawn during exposure to the vertical linear acceleration. A single pre-motion sample consisting of three samples drawn 5 min prior to motion onset. Two series of samples consisting of three samples drawn at 3-min intervals were obtained during motion. The first series was initiated at emesis, and the second 25 min after emesis. Results show that levels of circulating AVP were elevated (2 to 27 times the control and pre-motion levels) in the samples taken during emesis and decreased, but remained 1 to 6 times above the pre-motion or control levels within 25 min. The results of these two studies indicate that AVP is elevated during motion-produced emesis than is C. These findings are in general agreement with those obtained from humans under motion sickness conditions, and indicate that it is appropriate to continue to use the cat in studies of hormone changes during motion sickness.

BIOCONAID System (Bionic Control of Acceleration Induced Dimming). Final Report.

ERIC Educational Resources Information Center

Rogers, Dana B.; And Others

The system described represents a new technique for enhancing the fidelity of flight simulators during high acceleration maneuvers. This technique forces the simulator pilot into active participation and energy expenditure similar to the aircraft pilot undergoing actual accelerations. The Bionic Control of Acceleration Induced Dimming (BIOCONAID)…

Impact of Biodiesel Impurities on the Performance and Durability of DOC, DPF and SCR Technologies: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Williams, A.; McCormick, R.; Luecke, J.

2011-04-01

An accelerated durability test method determined the potential impact of biodiesel ash impurities, including engine testing with multiple diesel particulate filter substrate types, as well as diesel oxidation catalyst and selective catalyst reduction catalysts. The results showed no significant degradation in the thermo-mechanical properties of a DPF after exposure to 150,000-mile equivalent biodiesel ash and thermal aging. However, exposure to 435,000-mile equivalent aging resulted in a 69% decrease in thermal shock resistance. A decrease in DOC activity was seen after exposure to 150,000-mile equivalent aging, resulting in higher hydrocarbon slip and a reduction in NO2 formation. The SCR catalyst experiencedmore » a slight loss in activity after exposure to 435,000-mile equivalent aging. The SCR catalyst, placed downstream of the DPF and exposed to B20 exhaust suffered a 5% reduction in overall NOx conversion activity over the HDDT test cycle. It is estimated that the additional ash from 150,000 miles of biodiesel use would also result in a moderate increases in exhaust backpressure for a DPF. The results of this study suggest that long-term operation with B20 at the current specification limits for alkali and alkaline earth metal impurities will adversely impact the performance of DOC, DPF and SCR systems.« less

Delayed adverse effects of neonatal exposure to diethylstilbestrol and their dose dependency in female rats.

PubMed

Yoshida, Midori; Takahashi, Miwa; Inoue, Kaoru; Hayashi, Seigo; Maekawa, Akihiko; Nishikawa, Akiyoshi

2011-08-01

Neonatal exposure to estrogenic chemicals causes irreversible complex damage to the hypothalamus-pituitary-gonadal axis and reproductive system in females. Some lesions are noted after maturation as delayed adverse effects. We investigated the characteristics and dose dependence of delayed effects using female rats neonatally exposed to diethylstilbestrol (DES). Female Donryu rats were subcutaneously injected with a single dose of DES of 0 (control), 0.15, 1.5, 15, 150, or 1,500 µg/kg bw after birth. All except the lowest dose had estrogenic activity in a uterotrophic assay. All rats at 1500 µg/kg and some at 150 µg/kg showed abnormal morphologies in the genital tract, indicating they were androgenized before maturation. Although no morphological abnormalities were noted at 15 µg/kg or lower, onset of persistent estrus was significantly accelerated in the 1.5, 15, and 150 µg/kg groups with dose dependency, and the latest onset was from seventeen to twenty-one weeks of age at 1.5 µg/kg. The neonatal exposure to DES increased uterine adenocarcinoma development only at 150 µg/kg, although uterine anomalies were detected at 1,500 µg/kg. These results indicate that neonatal exposure to DES, which exerts estrogenic activity in vivo, induces delayed adverse effects in female rats in a dose-dependent manner. Early onset of persistent estrus appears to be the most sensitive parameter.

BEHAVIOR OF THE SAHARAN SCORPION ANDROCTONUS AMOREUXI (AUD. AND SAV.) AFTER EXPOSURE TO HIGH DOSES OF $gamma$ RADIATION AND AILMENTS FOLLOWING THIS IRRADIATION (in French)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Niaussat, P.; Vachon, M.; Grenot, C.

1963-07-29

The relatively long evolution of radiation sickness in the scorpion Androctonus amoreuxi, after exposure to high gamma doses of 50,000 to 90,000 r confirms the high radioresistivity of this species. Behavior modifications because of shock to sensory and neuromotive centers, an acceleration of the cardiovascular rhythm, and a decrease of the body weight were established. (tr- auth)

On the Health Risk of the Lumbar Spine due to Whole-Body VIBRATION—THEORETICAL Approach, Experimental Data and Evaluation of Whole-Body Vibration

NASA Astrophysics Data System (ADS)

Seidel, H.; Blüthner, R.; Hinz, B.; Schust, M.

1998-08-01

The guidance on the effects of vibration on health in standards for whole-body vibration (WBV) does not provide quantitative relationships between WBV and health risk. The paper aims at the elucidation of exposure-response relationships. An analysis of published data on the static and dynamic strength of vertebrae and bone, loaded with various frequencies under different conditions, provided the basis for a theoretical approach to evaluate repetitive loads on the lumbar spine (“internal loads”). The approach enabled the calculation of “equivalent”—with respect to cumulative fatigue failure—combinations of amplitudes and numbers of internal cyclic stress. In order to discover the relation between external peak accelerations at the seat and internal peak loads, biodynamic data of experiments (36 subjects, three somatotypes, two different postures—relaxed and bent forward; random WBV,aw, r.m.s. 1·4 ms-2, containing high transients) were used as input to a biomechanical model. Internal pressure changes were calculated using individual areas of vertebral endplates. The assessment of WBV was based on the quantitative relations between peak accelerations at the seat and pressures predicted for the disk L5/S1. For identical exposures clearly higher rates of pressure rise in the bent forward compared to the relaxed posture were predicted. The risk assessment for internal forces considered the combined internal static and dynamic loads, in relation to the predicted individual strength, and Miner's hypothesis. For exposure durations between 1 min and 8 h, energy equivalent vibration magnitudes (formula B.1, ISO 2631-1, 1997) and equivalent vibration magnitudes according to formula B.2 (time dependence over-energetic) were compared with equivalent combinations of upward peak accelerations and exposure durations according to predicted cumulative fatigue failures of lumbar vertebrae. Formula B.1 seems to underestimate the health risk caused by high magnitudes, formula B.2 is recommended for the evaluation of such conditions.

Rodent neurotoxicity bioassays for screening contaminated Great Lakes fish

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beattie, M.K.; Hoffman, R.; Gerstenberger, S.

1996-03-01

Standard laboratory rat neurotoxicity protocols were used to study the consequences resulting from the consumption of walleye (Stizostedion vitreum), whitefish (Coregonus clupeaformis), and lake trout (Salvelinus namaycush) from Lake Superior (LS) and the consumption of carp (Cyprinus carpio) from Little Lake Butte des Morte (LLBM) near Oshkosh, Wisconsin, USA. Two 90-d subchronic studies are described, including a 45-d exposure to fish diets using male Sprague-Dawley hooded rats, and a 90-d exposure to fish diets using female rats of the same species. Behavioral alterations were tested using a battery of behavioral tests. In addition, pharmacologic challenges using apomorphine and D-amphetamine weremore » administered to the rats to reveal latent neurotoxic effects. Cumulative fish consumption data were recorded daily, weight gain recorded weekly, and behavior data collected prior to exposure, and on days 7, 14, 55 {+-} 2, 85 {+-} 2. Motor activity data were collected on days 30 {+-} 2, 60 {+-} 2, and 90 {+-} 2 of the feeding protocols. Brain tissue from rodents fed these fish were subsequently analyzed for either mercury (Hg) or polychlorinated biphenyls (PCB). Mercury concentrations were increased in the brains of the walleye-fed rats, and PCB concentrations ranged from 0.5 nl/L to 10 nl/L in the brains of rats fed carp from LLBM, a Lake Michigan tributary. Adult male rats fed LLBM carp for 45 d exhibited the greatest behavior responses to the dopaminergic agonist apomorphine on the accelerating rotarod, although these differences were not significant. The 90-d exposure of LS walleye or Hg-spiked LS walleye resulted in behavior alterations on tactile startle response and second footsplay. D-Amphetamine challenge caused changes in tactile startle response, second footsplay, and accelerating rotarod performance after consuming walleye diets. Rats fed LLBM carp had altered behavioral responses to apomorphine on the accelerating rotarod.« less

Laboratory and field measurements and evaluations of vibration at the handles of riveting hammers

PubMed Central

McDOWELL, THOMAS W.; WARREN, CHRISTOPHER; WELCOME, DANIEL E.; DONG, REN G.

2015-01-01

The use of riveting hammers can expose workers to harmful levels of hand-transmitted vibration (HTV). As a part of efforts to reduce HTV exposures through tool selection, the primary objective of this study was to evaluate the applicability of a standardized laboratory-based riveting hammer assessment protocol for screening riveting hammers. The second objective was to characterize the vibration emissions of reduced vibration riveting hammers and to make approximations of the HTV exposures of workers operating these tools in actual work tasks. Eight pneumatic riveting hammers were selected for the study. They were first assessed in a laboratory using the standardized method for measuring vibration emissions at the tool handle. The tools were then further assessed under actual working conditions during three aircraft sheet metal riveting tasks. Although the average vibration magnitudes of the riveting hammers measured in the laboratory test were considerably different from those measured in the field study, the rank orders of the tools determined via these tests were fairly consistent, especially for the lower vibration tools. This study identified four tools that consistently exhibited lower frequency-weighted and unweighted accelerations in both the laboratory and workplace evaluations. These observations suggest that the standardized riveting hammer test is acceptable for identifying tools that could be expected to exhibit lower vibrations in workplace environments. However, the large differences between the accelerations measured in the laboratory and field suggest that the standardized laboratory-based tool assessment is not suitable for estimating workplace riveting hammer HTV exposures. Based on the frequency-weighted accelerations measured at the tool handles during the three work tasks, the sheet metal mechanics assigned to these tasks at the studied workplace are unlikely to exceed the daily vibration exposure action value (2.5 m s−2) using any of the evaluated riveting hammers. PMID:22539561

Accelerator–Reactor Coupling for Energy Production in Advanced Nuclear Fuel Cycles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heidet, Florent; Brown, Nicholas R.; Haj Tahar, Malek

2015-01-01

This article is a review of several accelerator-reactor interface issues and nuclear fuel cycle applications of accelerator-driven subcritical systems. The systems considered here have the primary goal of energy production, but that goal is accomplished via a specific application in various proposed nuclear fuel cycles, such as breed-and-burn of fertile material or burning of transuranic material. Several basic principles are reviewed, starting from the proton beam window including the target, blanket, reactor core, and up to the fuel cycle. We focused on issues of interest, e.g. the impact of the energy required to run the accelerator and associated systems onmore » the potential electricity delivered to the grid. Accelerator-driven systems feature many of the constraints and issues associated with critical reactors, with the added challenges of subcritical operation and coupling to an accelerator. Reliable accelerator operation and avoidance of beam trips are a critically important. One interesting challenge is measurement of blanket subcriticality level during operation. We also reviewed the potential benefits of accelerator-driven systems in various nuclear fuel cycle applications. Ultimately, accelerator-driven subcritical systems with the goal of transmutation of transuranic material have lower 100,000-year radioactivity versus a critical fast reactor with recycle of uranium and plutonium.« less

High-magnitude head impact exposure in youth football

PubMed Central

Campolettano, Eamon T.; Gellner, Ryan A.; Rowson, Steven

2018-01-01

OBJECTIVE Even in the absence of a clinically diagnosed concussion, research suggests that neurocognitive changes may develop in football players as a result of frequent head impacts that occur during football games and practices. The objectives of this study were to determine the specific situations in which high-magnitude impacts (accelerations exceeding 40g) occur in youth football games and practices and to assess how representative practice activities are of games with regard to high-magnitude head impact exposure. METHODS A total of 45 players (mean age 10.7 ± 1.1 years) on 2 youth teams (Juniors [mean age 9.9 ± 0.6 years; mean body mass 38.9 ± 9.9 kg] and Seniors [mean age 11.9 ± 0.6 years; mean body mass 51.4 ± 11.8 kg]) wore helmets instrumented with accelerometer arrays to record head impact accelerations for all practices and games. Video recordings from practices and games were used to verify all high-magnitude head impacts, identify specific impact characteristics, and determine the amount of time spent in each activity. RESULTS A total of 7590 impacts were recorded, of which 571 resulted in high-magnitude head impact accelerations exceeding 40g (8%). Impacts were characterized based on the position played by the team member who received the impact, the part of the field where the impact occurred, whether the impact occurred during a game or practice play, and the cause of the impact. High-magnitude impacts occurred most frequently in the open field in both games (59.4%) and practices (67.5%). “Back” position players experienced a greater proportion of high-magnitude head impacts than players at other positions. The 2 teams in this study structured their practice sessions similarly with respect to time spent in each drill, but impact rates differed for each drill between the teams. CONCLUSIONS High-magnitude head impact exposure in games and practice drills was quantified and used as the basis for comparison of exposure in the 2 settings. In this cohort, game impact rates exceeded those for practice. Back players, who were often positioned in the open field, were shown to experience elevated levels of head impact exposure relative to players at other positions. The analysis also suggests that practice intensity, which may be influenced by coaching style, may also affect high-magnitude head impact exposure. Future studies should investigate this aspect as a factor affecting head impact exposure. PMID:29037104

High-magnitude head impact exposure in youth football.

PubMed

Campolettano, Eamon T; Gellner, Ryan A; Rowson, Steven

2017-12-01

OBJECTIVE Even in the absence of a clinically diagnosed concussion, research suggests that neurocognitive changes may develop in football players as a result of frequent head impacts that occur during football games and practices. The objectives of this study were to determine the specific situations in which high-magnitude impacts (accelerations exceeding 40 g) occur in youth football games and practices and to assess how representative practice activities are of games with regard to high-magnitude head impact exposure. METHODS A total of 45 players (mean age 10.7 ± 1.1 years) on 2 youth teams (Juniors [mean age 9.9 ± 0.6 years; mean body mass 38.9 ± 9.9 kg] and Seniors [mean age 11.9 ± 0.6 years; mean body mass 51.4 ± 11.8 kg]) wore helmets instrumented with accelerometer arrays to record head impact accelerations for all practices and games. Video recordings from practices and games were used to verify all high-magnitude head impacts, identify specific impact characteristics, and determine the amount of time spent in each activity. RESULTS A total of 7590 impacts were recorded, of which 571 resulted in high-magnitude head impact accelerations exceeding 40 g (8%). Impacts were characterized based on the position played by the team member who received the impact, the part of the field where the impact occurred, whether the impact occurred during a game or practice play, and the cause of the impact. High-magnitude impacts occurred most frequently in the open field in both games (59.4%) and practices (67.5%). "Back" position players experienced a greater proportion of high-magnitude head impacts than players at other positions. The 2 teams in this study structured their practice sessions similarly with respect to time spent in each drill, but impact rates differed for each drill between the teams. CONCLUSIONS High-magnitude head impact exposure in games and practice drills was quantified and used as the basis for comparison of exposure in the 2 settings. In this cohort, game impact rates exceeded those for practice. Back players, who were often positioned in the open field, were shown to experience elevated levels of head impact exposure relative to players at other positions. The analysis also suggests that practice intensity, which may be influenced by coaching style, may also affect high-magnitude head impact exposure. Future studies should investigate this aspect as a factor affecting head impact exposure.

UV exposure in artificial and natural weathering: A comparative study

NASA Astrophysics Data System (ADS)

Heikkilä, A.; Kazadzis, S.; Meinander, O.; Vaskuri, A.; Kärhä, P.; Mylläri, V.; Syrjälä, S.; Koskela, T.

2017-02-01

We report on a study focusing on UV exposure conditions in three different types of chambers used for accelerated ageing of materials. The first chamber is equipped with four 300-W UVA/UVB mercury vapour lamps (Ultra-Vitalux/Osram). The second chamber uses four 40-W UVA fluorescent lamps (QUV-340/Q-Lab). The third chamber is Weather-Ometer Ci3000+ from Atlas with a 4500-W xenon arc lamp. UV irradiance prevailing in each chamber was measured using Bentham DM150 double monochromator spectroradiometer. The results were compared to measurements of solar spectral UV irradiance at Jokioinen, Finland, with a Brewer MkIII double monochromator spectrophotometer. The spectral shapes of the exposing UV radiation in the different chambers were found to notably differ from each other and from the solar UV spectrum. Both spatial inhomogeneities and temporal variability caused by various factors, like the ageing of the lamps, were detected. The effects were found to strongly depend on wavelength of the exposing UV radiation. The findings of this study underline the necessity of careful characterization of the UV exposure conditions provided by the facilities used in accelerated testing of materials.

Plasma volume during stress in man - Osmolality and red cell volume

NASA Technical Reports Server (NTRS)

Greenleaf, J. E.; Convertino, V. A.; Mangseth, G. R.

1979-01-01

The purpose was (1) to test the hypothesis that in man there is a range of plasma osmolality within which the red cell volume (RCV) and mean corpuscular volume (MCV) remain essentially constant and (2) to determine the upper limit of this range. During a variety of stresses - submaximal and maximal exercise, heat and altitude exposure, +Gz acceleration, and tilting - changes in plasma osmolality between -1 and +13 mosmol/kg resulted in essentially no change in the regression of percent change in plasma volume (PV) calculated from a change in hematocrit (Hct) on that calculated from a change in Hct + hemoglobin (Hb), i.e., the RCV and MCV were constant. Factors that do not influence RCV are the level of metabolism, heat exposure at rest, and short-term orthostasis (heat-to-foot acceleration). Factors that may influence RCV are exposure to high altitude and long-term orthostasis (head-up tilting). Factors that definitely influence RCV are prior dehydration and extended periods of stress. Thus, either the Hct or the Hct + Hb equations can be used to calculate percent changes in PV under short-term periods of stress when the change in plasma osmolality is less than 13 mosmol/kg.

On hunger and child mortality in India.

PubMed

Gaiha, Raghav; Kulkarni, Vani S; Pandey, Manoj K; Imai, Katsushi S

2012-01-01

Despite accelerated growth there is pervasive hunger, child undernutrition and mortality in India. Our analysis focuses on their determinants. Raising living standards alone will not reduce hunger and undernutrition. Reduction of rural/urban disparities, income inequality, consumer price stabilization, and mothers’ literacy all have roles of varying importance in different nutrition indicators. Somewhat surprisingly, public distribution system (PDS) do not have a significant effect on any of them. Generally, child undernutrition and mortality rise with poverty. Our analysis confirms that media exposure triggers public action, and helps avert child undernutrition and mortality. Drastic reduction of economic inequality is in fact key to averting child mortality, conditional upon a drastic reordering of social and economic arrangements.

Ion extraction capabilities of two-grid accelerator systems. [for spacecraft propulsion

NASA Technical Reports Server (NTRS)

Rovang, D. C.; Wilbur, P. J.

1984-01-01

An experimental investigation into the ion extraction capabilities of two-grid accelerator systems common to electrostatic ion thrusters is described. A large body of experimental data which facilitates the selection of the accelerator system geometries and operating parameters necessary to maximize the extracted ion current is presented. Results suggest that the impingement-limited perveance is not dramatically affected by reductions in screen hole diameter to 0.5 mm. Impingement-limited performance is shown to depend most strongly on grid separation distance, accelerator hole diameter ratio, the discharge-to-total accelerating voltage ratio, and the net-to-total accelerating voltage ratio. Results obtained at small grid separation ratios suggest a new grid operating condition where high beam current per hole levels are achieved at a specified net accelerating voltage. It is shown that this operating condition is realized at an optimum ratio of net-to-total accelerating voltage ratio which is typically quite high.

Implementation of an IMU Aided Image Stacking Algorithm in a Digital Camera for Unmanned Aerial Vehicles

PubMed Central

Audi, Ahmad; Pierrot-Deseilligny, Marc; Meynard, Christophe

2017-01-01

Images acquired with a long exposure time using a camera embedded on UAVs (Unmanned Aerial Vehicles) exhibit motion blur due to the erratic movements of the UAV. The aim of the present work is to be able to acquire several images with a short exposure time and use an image processing algorithm to produce a stacked image with an equivalent long exposure time. Our method is based on the feature point image registration technique. The algorithm is implemented on the light-weight IGN (Institut national de l’information géographique) camera, which has an IMU (Inertial Measurement Unit) sensor and an SoC (System on Chip)/FPGA (Field-Programmable Gate Array). To obtain the correct parameters for the resampling of the images, the proposed method accurately estimates the geometrical transformation between the first and the N-th images. Feature points are detected in the first image using the FAST (Features from Accelerated Segment Test) detector, then homologous points on other images are obtained by template matching using an initial position benefiting greatly from the presence of the IMU sensor. The SoC/FPGA in the camera is used to speed up some parts of the algorithm in order to achieve real-time performance as our ultimate objective is to exclusively write the resulting image to save bandwidth on the storage device. The paper includes a detailed description of the implemented algorithm, resource usage summary, resulting processing time, resulting images and block diagrams of the described architecture. The resulting stacked image obtained for real surveys does not seem visually impaired. An interesting by-product of this algorithm is the 3D rotation estimated by a photogrammetric method between poses, which can be used to recalibrate in real time the gyrometers of the IMU. Timing results demonstrate that the image resampling part of this algorithm is the most demanding processing task and should also be accelerated in the FPGA in future work. PMID:28718788

Implementation of an IMU Aided Image Stacking Algorithm in a Digital Camera for Unmanned Aerial Vehicles.

PubMed

Audi, Ahmad; Pierrot-Deseilligny, Marc; Meynard, Christophe; Thom, Christian

2017-07-18

Images acquired with a long exposure time using a camera embedded on UAVs (Unmanned Aerial Vehicles) exhibit motion blur due to the erratic movements of the UAV. The aim of the present work is to be able to acquire several images with a short exposure time and use an image processing algorithm to produce a stacked image with an equivalent long exposure time. Our method is based on the feature point image registration technique. The algorithm is implemented on the light-weight IGN (Institut national de l'information géographique) camera, which has an IMU (Inertial Measurement Unit) sensor and an SoC (System on Chip)/FPGA (Field-Programmable Gate Array). To obtain the correct parameters for the resampling of the images, the proposed method accurately estimates the geometrical transformation between the first and the N -th images. Feature points are detected in the first image using the FAST (Features from Accelerated Segment Test) detector, then homologous points on other images are obtained by template matching using an initial position benefiting greatly from the presence of the IMU sensor. The SoC/FPGA in the camera is used to speed up some parts of the algorithm in order to achieve real-time performance as our ultimate objective is to exclusively write the resulting image to save bandwidth on the storage device. The paper includes a detailed description of the implemented algorithm, resource usage summary, resulting processing time, resulting images and block diagrams of the described architecture. The resulting stacked image obtained for real surveys does not seem visually impaired. An interesting by-product of this algorithm is the 3D rotation estimated by a photogrammetric method between poses, which can be used to recalibrate in real time the gyrometers of the IMU. Timing results demonstrate that the image resampling part of this algorithm is the most demanding processing task and should also be accelerated in the FPGA in future work.

Monitor unit settings for intensity modulated beams delivered using a step-and-shoot approach.

PubMed

Sharpe, M B; Miller, B M; Yan, D; Wong, J W

2000-12-01

Two linear accelerators have been commissioned for delivering IMRT treatments using a step-and-shoot approach. To assess beam startup stability for 6 and 18 MV x-ray beams, dose delivered per monitor unit (MU), beam flatness, and beam symmetry were measured as a function of the total number of MU delivered at a clinical dose rate of 400 MU per minute. Relative to a 100 MU exposure, the dose delivered per MU by both linear accelerators was found to be within +/-2% for exposures larger than 4 MU. Beam flatness and symmetry also met accepted quality assurance standards for a minimum exposure of 4 MU. We have found that the performance of the two machines under study is well suited to the delivery of step-and-shoot IMRT. A system of dose calculation has also been commissioned for applying head scatter corrections to fields as small as 1x1 cm2. The accuracy and precision of the relative output calculations in water was validated for small fields and fields offset from the axis of collimator rotation. For both 6 and 18 MV x-ray beams, the dose per MU calculated in a water phantom agrees with measured data to within 1% on average, with a maximum deviation of 2.5%. The largest output factor discrepancies were seen when the actual radiation field size deviated from the set field size. The measured output in water can vary by as much 16% for 1x1 cm2 fields, when the measured field size deviates from the set field size by 2 mm. For a 1 mm deviation, this discrepancy was reduced to 8%. Steps should be taken to ensure collimator precision is tightly controlled when using such small fields. If this is not possible, very small fields should not contribute to a significant portion of the treatment, or uncertainties in the collimator position may effect the accuracy of the dose delivered.

Accelerating locomotor savings in learning: compressing four training days to one.

PubMed

Day, Kevin A; Leech, Kristan A; Roemmich, Ryan T; Bastian, Amy J

2018-06-01

Acquiring new movements requires the capacity of the nervous system to remember previously experienced motor patterns. The phenomenon of faster relearning after initial learning is termed "savings." Here we studied how savings of a novel walking pattern develops over several days of practice and how this process can be accelerated. We introduced participants to a split-belt treadmill adaptation paradigm for 30 min for 5 consecutive days. By training day 5, participants were able to produce near-perfect performance when switching between split and tied-belt environments. We found that this was due to their ability to shift specific elements of their stepping pattern to account for the split treadmill speeds from day to day. We also applied a state-space model to further characterize multiday locomotor savings. We then explored methods of achieving comparable savings with less total training time. We studied people training only on day 1, with either one extended split-belt exposure or alternating four times between split-belt and tied-belt conditions rapidly in succession. Both of these single-day training groups were tested again on day 5. Experiencing four abbreviated exposures on day 1 improved the performance on day 5 compared with one extended exposure on day 1. Moreover, this abbreviated group performed similarly to the group that trained for 4 consecutive days before testing on day 5, despite only having one-quarter of the total training time. These results demonstrate that we can leverage training structure to achieve a high degree of performance while minimizing training sessions. NEW & NOTEWORTHY Learning a new movement requires repetition. Here, we demonstrate how to more efficiently train an adapted walking pattern. By compressing split-belt treadmill training delivered over 4 days to four abbreviated bouts of training delivered on the first day of training, we were able to induce equivalent savings over a 5-day span. These results suggest that we can manipulate the delivery of training to most efficiently drive multiday learning of a novel walking pattern.

Fundamental space radiobiology

NASA Technical Reports Server (NTRS)

Nelson, Gregory A.

2003-01-01

The unique feature of the space radiation environment is the dominance of high-energy charged particles (HZE or high LET radiation) emitted by the Sun and galactic sources, or trapped in the Van Allen radiation belts. These charged particles present a significant hazard to space flight crews, and accelerator-based experiments are underway to quantify the health risks due to unavoidable radiation exposure. There are three principal properties of charged particles that distinguish them from conventional radiation, i.e. gamma rays and x-rays. First, they have a defined range in matter rather than an exponential absorption profile. Second, they undergo nuclear reactions to produce secondary particles. Third, and most important, they deposit their energy along well-defined linear paths or tracks rather than diffuse fields. The structured energy deposition pattern interacts on multiple scales with the biological structures of DNA, cells and tissues to produce correlated patterns of damage that evade repair systems. Traditional concepts of dose and its associated normalization parameter, RBE (relative biological effectiveness), break down under experimental scrutiny, and probabilistic models of risk based on the number of particle traversals per cell may be more appropriate. Unique patterns of DNA damage, gene expression, mobilization of repair proteins, activation of cytokines and remodeling of cellular microenvironment are observed following exposure to high LET radiation. At low levels of exposure the communication of bioactive substances from irradiated to unirradiated "bystander" cells can amplify the damage and cause a significant deviation from linearity in dose vs. response relations. Under some circumstances, there is even a multigenerational delay in the expression of radiation-induced genetic damage (genomic instability) which is not strictly dose dependent. These issues and the experimental evidence derived from ground based experiments at particle accelerators are presented along with speculation about how modified inertial conditions might perturb homeostatic responses to radiation to further complicate risk assessment for space flight.

Acceleration display system for aircraft zero-gravity research

NASA Technical Reports Server (NTRS)

Millis, Marc G.

1987-01-01

The features, design, calibration, and testing of Lewis Research Center's acceleration display system for aircraft zero-gravity research are described. Specific circuit schematics and system specifications are included as well as representative data traces from flown trajectories. Other observations learned from developing and using this system are mentioned where appropriate. The system, now a permanent part of the Lewis Learjet zero-gravity program, provides legible, concise, and necessary guidance information enabling pilots to routinely fly accurate zero-gravity trajectories. Regular use of this system resulted in improvements of the Learjet zero-gravity flight techniques, including a technique to minimize later accelerations. Lewis Gates Learjet trajectory data show that accelerations can be reliably sustained within 0.01 g for 5 consecutive seconds, within 0.02 g for 7 consecutive seconds, and within 0.04 g for up to 20 second. Lewis followed the past practices of acceleration measurement, yet focussed on the acceleration displays. Refinements based on flight experience included evolving the ranges, resolutions, and frequency responses to fit the pilot and the Learjet responses.

Compact all-fiber interferometer system for shock acceleration measurement

NASA Astrophysics Data System (ADS)

Zhao, Jiang; Pi, Shaohua; Hong, Guangwei; Zhao, Dong; Jia, Bo

2013-08-01

Acceleration measurement plays an important role in a variety of fields in science and engineering. In particular, the accurate, continuous and non-contact recording of the shock acceleration profiles of the free target surfaces is considered as a critical technique in shock physics. Various kinds of optical interferometers have been developed to monitor the motion of the surfaces of shocked targets since the 1960s, for instance, the velocity interferometer system for any reflector, the fiber optic accelerometer, the photonic Doppler velocimetry system and the displacement interferometer. However, most of such systems rely on the coherent quasi-monochromatic illumination and discrete optic elements, which are costly in setting-up and maintenance. In 1996, L. Levin et al reported an interferometric fiber-optic Doppler velocimeter with high-dynamic range, in which fiber-coupled components were used to replace the discrete optic elements. However, the fringe visibility of the Levin's system is low because of the coupled components, which greatly limits the reliability and accuracy in the shock measurement. In this paper, a compact all-fiber interferometer system for measuring the shock acceleration is developed and tested. The advantage of the system is that not only removes the non-interfering light and enhances the fringe visibility, but also reduces polarization induced signal fading and the polarization induced phase shift. Moreover, it also does not require a source of long coherence length. The system bases entirely on single-mode fiber optics and mainly consists of a polarization beam splitter, a faraday rotator, a depolarizer and a 3×3 single-mode fiber coupler which work at 1310 nm wavelength. The optical systems of the interferometer are described and the experimental results compared with a shock acceleration calibration system with a pneumatic exciter (PneuShockTM Model 9525C by The Modal Shop) are reported. In the shock acceleration test, the interferometer system measured shock acceleration with peak accelerations of ~100,000 m/s2 and the durations of ~0.2 ms which are conformed to the results of the shock acceleration calibration system. The measured relative error of the acceleration is within 3%.

Acceleration of boundary element method for linear elasticity

NASA Astrophysics Data System (ADS)

Zapletal, Jan; Merta, Michal; Čermák, Martin

2017-07-01

In this work we describe the accelerated assembly of system matrices for the boundary element method using the Intel Xeon Phi coprocessors. We present a model problem, provide a brief overview of its discretization and acceleration of the system matrices assembly using the coprocessors, and test the accelerated version using a numerical benchmark.

SOLVENT-FREE ACCELERATED ORGANIC SYNTHESES USING MICROWAVES

EPA Science Inventory

Abstract: A solvent-free approach for organic synthesis is described which involves microwave (MW) exposure of neat reactants (undiluted) either in presence of a catalyst or catalyzed by the surfaces of inexpensive and recyclable mineral supports such as alumina, silica, clay, or...

DIRECT SYNTHESIS OF TERTIARY AMINES IN WATER USING MICROWAVES

EPA Science Inventory

A direct synthesis of tertiary amines is presented that proceeds expeditiously via N-alkylation of amines using alkyl halides in alkaline aqueous medium. This environmentally benign reaction is accelerated upon exposure to microwave irradiation resulting in shortened reaction tim...

Optimization of salt fog conditions for organic zinc paints : final report.

DOT National Transportation Integrated Search

1981-10-01

Although Louisiana has been testing and using organic zinc coatings since 1963, premature failures have occurred on bridges within the state recently. These failures were not predicted by accelerated testing which included salt fog exposure. the resu...

JAERI R & D on accelerator-based transmutation under OMEGA program

DOE Office of Scientific and Technical Information (OSTI.GOV)

Takizuka, T.; Nishida, T.; Mizumoto, M.

1995-10-01

The overview of the Japanese long-term research and development program on nuclide partitioning and transmutation, called {open_quotes}OMEGA,{close_quotes} is presented. Under this national program, major R&D activities are being carried out at JAERI, PNC, and CRIEPI. Accelerator-based transmutation study at JAERI is focused on a dedicated transmutor with a subcritical actinide-fueled subcritical core coupled with a spallation target driven by a high intensity proton accelerator. Two types of system concept, solid system and molten-salt system, are discussed. The solid system consists of sodium-cooled tungsten target and metallic actinide fuel. The molten-salt system is fueled with molten actinide chloride that acts alsomore » as a target material. The proposed plant transmutes about 250 kg of minor actinide per year, and generates enough electricity to power its own accelerator. JAERI is proposing the development of an intense proton linear accelerator ETA with 1.5 GeV-10 mA beam for engineering tests of accelerator-based transmutation. Recent achievements in the accelerator development are described.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Holley, W.A.

The goals of the NREL PVMaT program are, among others, to reduce module manufacturing costs and improve the quality, and we might add here the reliability, of manufactured PV products. One component critical to the service life of PV modules is the useful life of the EVA resin-based encapsulant which is employed extensively by module manufacturers on a worldwide basis. This pottant has been in commercial use since 1982, and over that time has proven to be a dependable material from the standpoint of production, module fabrication, and end-use. But despite the widespread acceptance of the EVA resin-based A9918 andmore » similar formulations for PV encapsulation, some module producers, end-users, and investigators have reported a yellowing or browning phenomenon with EVA resin-based encapsulants in the field. Wile the incidence of this discoloration/degradation appeared at comparatively few sites at the time that this present program was conceived, it raised serious concern as to the long term reliability of EVA resin-based encapsulation systems. Consequently, under the NREL PVMaT program, Springborn Laboratories proposed a comprehensive study of the EVA aging and discoloration problem and its possible solution(s). During the first year of this program, accelerated U.V. aging methods were surveyed. On careful review of the various types of accelerated U.V. aging equipment available, an Atlas Ci35A Weather-Ometer Xenon Exposure System was selected as appropriate equipment for this work. The following report summarizes how this accelerated aging technique has been used to develop a family of solutions to the discoloration problem, the most significant of which is a series of EVA-based encapsulants which are resistant to discoloration.« less

Chronic Traumatic Encephalopathy in Blast-Exposed Military Veterans and a Blast Neurotrauma Mouse Model

PubMed Central

Goldstein, Lee E.; Fisher, Andrew M.; Tagge, Chad A.; Zhang, Xiao-Lei; Velisek, Libor; Sullivan, John A.; Upreti, Chirag; Kracht, Jonathan M.; Ericsson, Maria; Wojnarowicz, Mark W.; Goletiani, Cezar J.; Maglakelidze, Giorgi M.; Casey, Noel; Moncaster, Juliet A.; Minaeva, Olga; Moir, Robert D.; Nowinski, Christopher J.; Stern, Robert A.; Cantu, Robert C.; Geiling, James; Blusztajn, Jan K.; Wolozin, Benjamin L.; Ikezu, Tsuneya; Stein, Thor D.; Budson, Andrew E.; Kowall, Neil W.; Chargin, David; Sharon, Andre; Saman, Sudad; Hall, Garth F.; Moss, William C.; Cleveland, Robin O.; Tanzi, Rudolph E.; Stanton, Patric K.; McKee, Ann C.

2013-01-01

Blast exposure is associated with traumatic brain injury (TBI), neuropsychiatric symptoms, and long-term cognitive disability. We examined a case series of postmortem brains from U.S. military veterans exposed to blast and/or concussive injury. We found evidence of chronic traumatic encephalopathy (CTE), a tau protein–linked neurodegenerative disease, that was similar to the CTE neuropathology observed in young amateur American football players and a professional wrestler with histories of concussive injuries. We developed a blast neurotrauma mouse model that recapitulated CTE-linked neuropathology in wild-type C57BL/6 mice 2 weeks after exposure to a single blast. Blast-exposed mice demonstrated phosphorylated tauopathy, myelinated axonopathy, microvasculopathy, chronic neuroinflammation, and neurodegeneration in the absence of macroscopic tissue damage or hemorrhage. Blast exposure induced persistent hippocampal-dependent learning and memory deficits that persisted for at least 1 month and correlated with impaired axonal conduction and defective activity-dependent long-term potentiation of synaptic transmission. Intracerebral pressure recordings demonstrated that shock waves traversed the mouse brain with minimal change and without thoracic contributions. Kinematic analysis revealed blast-induced head oscillation at accelerations sufficient to cause brain injury. Head immobilization during blast exposure prevented blast-induced learning and memory deficits. The contribution of blast wind to injurious head acceleration may be a primary injury mechanism leading to blast-related TBI and CTE. These results identify common pathogenic determinants leading to CTE in blast-exposed military veterans and head-injured athletes and additionally provide mechanistic evidence linking blast exposure to persistent impairments in neurophysiological function, learning, and memory. PMID:22593173

Chronic traumatic encephalopathy in blast-exposed military veterans and a blast neurotrauma mouse model.

PubMed

Goldstein, Lee E; Fisher, Andrew M; Tagge, Chad A; Zhang, Xiao-Lei; Velisek, Libor; Sullivan, John A; Upreti, Chirag; Kracht, Jonathan M; Ericsson, Maria; Wojnarowicz, Mark W; Goletiani, Cezar J; Maglakelidze, Giorgi M; Casey, Noel; Moncaster, Juliet A; Minaeva, Olga; Moir, Robert D; Nowinski, Christopher J; Stern, Robert A; Cantu, Robert C; Geiling, James; Blusztajn, Jan K; Wolozin, Benjamin L; Ikezu, Tsuneya; Stein, Thor D; Budson, Andrew E; Kowall, Neil W; Chargin, David; Sharon, Andre; Saman, Sudad; Hall, Garth F; Moss, William C; Cleveland, Robin O; Tanzi, Rudolph E; Stanton, Patric K; McKee, Ann C

2012-05-16

Blast exposure is associated with traumatic brain injury (TBI), neuropsychiatric symptoms, and long-term cognitive disability. We examined a case series of postmortem brains from U.S. military veterans exposed to blast and/or concussive injury. We found evidence of chronic traumatic encephalopathy (CTE), a tau protein-linked neurodegenerative disease, that was similar to the CTE neuropathology observed in young amateur American football players and a professional wrestler with histories of concussive injuries. We developed a blast neurotrauma mouse model that recapitulated CTE-linked neuropathology in wild-type C57BL/6 mice 2 weeks after exposure to a single blast. Blast-exposed mice demonstrated phosphorylated tauopathy, myelinated axonopathy, microvasculopathy, chronic neuroinflammation, and neurodegeneration in the absence of macroscopic tissue damage or hemorrhage. Blast exposure induced persistent hippocampal-dependent learning and memory deficits that persisted for at least 1 month and correlated with impaired axonal conduction and defective activity-dependent long-term potentiation of synaptic transmission. Intracerebral pressure recordings demonstrated that shock waves traversed the mouse brain with minimal change and without thoracic contributions. Kinematic analysis revealed blast-induced head oscillation at accelerations sufficient to cause brain injury. Head immobilization during blast exposure prevented blast-induced learning and memory deficits. The contribution of blast wind to injurious head acceleration may be a primary injury mechanism leading to blast-related TBI and CTE. These results identify common pathogenic determinants leading to CTE in blast-exposed military veterans and head-injured athletes and additionally provide mechanistic evidence linking blast exposure to persistent impairments in neurophysiological function, learning, and memory.

The Future of D-Cycloserine and Other Cognitive Modifiers in Obsessive-Compulsive and Related Disorders

PubMed Central

Sulkowski, Michael L.; Geller, Daniel A.; Lewin, Adam B.; Murphy, Tanya K.; Mittelman, Andrew; Brown, Ashley; Storch, Eric A.

2014-01-01

Variants of exposure therapy are effective for treating obsessive-compulsive and related disorders (OCRDs). However, significant numbers of patients do not respond adequately to exposure therapy resulting in continued distress and functional impairment. Therefore, novel approaches to augmenting exposure therapy are needed to adequately treat non- and partial-responders. Emerging research suggests that interventions that augment learning and memory processes associated with exposure therapy (i.e., extinction training) may display promise in enhancing treatment response in OCRDs. As the most studied example, d-cycloserine (DCS) is a relatively safe cognitive enhancer that appears to accelerate treatment gains associated with exposure therapy. This article reviews research on the use of DCS and other putative cognitive modifiers as they relate to the treatment (or prospective treatment) of obsessive-compulsive disorder and other OCRDs. PMID:25383074

Lifetime predictions for dimmable two-channel drivers for color tuning luminaires

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davis, Lynn; Smith, Aaron; Clark, Terry

Two-channel tunable white lighting (TWL) systems represent the next wave of solid-state lighting (SSL) systems and promise flexibility in light environment while maintaining the high reliability and luminous efficacy expected with SSL devices. TWL systems utilize LED assemblies consisting of two different LED spectra (i.e., often a warm white assembly and a cool white assembly) that are integrated into modules. While these systems provide the ability to adjust the lighting spectrum to match the physiology needs of the task at hand, they also are a potentially more complex lighting system from a performance and reliability perspective. We report an initialmore » study on the reliability performance of such lighting systems including an examination of the lumen maintenance and chromaticity stability of warm white and cool white LED assemblies and the multi-channel driver that provides power to the assemblies. Accelerated stress tests including operational bake tests conducted at 75°C and 95°C were used to age the LED modules, while more aggressive temperature and humidity tests were used for the drivers in this study. Small differences in the performance between the two LED assemblies were found and can be attributed to the different phosphor chemistries. The lumen maintenances of both LED assemblies were excellent. The warm white LED assemblies were found to shift slightly in the green color direction over time while the cool white LED assemblies shifted slightly in the yellow color direction. The net result of these chromaticity shifts is a small, barely perceptible reduction in the tuning range after 6,000 hours of exposure to an accelerating elevated temperature of 75°C.« less

HIMAC RF system with a digital synthesizer

NASA Astrophysics Data System (ADS)

Kanazawa, M.; Sato, K.; Itano, A.; Sudou, M.; Noda, K.; Takada, E.; Kumada, M.; Yamazaki, C.; Yamagishi, T.; Morii, Y.; Toyoda, E.; Tsuzuki, N.; Yagi, T.

2000-04-01

An RF acceleration system, in which digital control with a direct digital synthesizer (DDS) is applied, has been developed for the Heavy Ion Medical Accelerator in Chiba (HIMAC) synchrotron. This digital system allows us to obtain stable operation of the acceleration system over a wide frequency range from 1.04 to 7.9 MHz. In this paper the designed digital RF control system and its performance are described.

Seat vibration in military propeller aircraft: characterization, exposure assessment, and mitigation.

PubMed

Smith, Suzanne D

2006-01-01

There have been increasing reports of annoyance, fatigue, and even neck and back pain during prolonged operation of military propeller aircraft, where persistent multi-axis vibration occurs at higher frequencies beyond human whole-body resonance. This paper characterizes and assesses the higher frequency vibration transmitted to the occupants onboard these aircraft. Multi-axis accelerations were measured at the occupied seating surfaces onboard the WC/C-130J, C-130H3, and E-2C Hawkeye. The effects of the vibration were assessed in accordance with current international guidelines (ISO 2631-1:1997). The relative psychophysical effects of the frequency components and the effects of selected mitigation strategies were also investigated. The accelerations associated with the blade passage frequency measured on the passenger seat pans located on the side of the fuselage near the propeller plane of the C-130J (102 Hz) and C-130H3 (68 Hz) were noteworthy (5.19 +/- 1.72 ms(-2) rms and 7.65 +/- 0.71 ms(-2) rms, respectively, in the lateral direction of the aircraft). The psychophysical results indicated that the higher frequency component would dominate the side passengers' perception of the vibration. Balancing the props significantly reduced the lower frequency propeller rotation vibration (17 Hz), but had little effect on the blade passage frequency vibration. The relationships among the frequency, vibration direction, and seat measurement sites were complex, challenging the development of seating systems and mitigation strategies. Psychophysical metrics could provide a tool for optimizing mitigation strategies, but the current international vibration standard may not provide optimum assessment methods for evaluating higher frequency operational exposures.

Overview of Accelerator Applications in Energy

NASA Astrophysics Data System (ADS)

Garnett, Robert W.; Sheffield, Richard L.

An overview of the application of accelerators and accelerator technology in energy is presented. Applications span a broad range of cost, size, and complexity and include large-scale systems requiring high-power or high-energy accelerators to drive subcritical reactors for energy production or waste transmutation, as well as small-scale industrial systems used to improve oil and gas exploration and production. The enabling accelerator technologies will also be reviewed and future directions discussed.

Developments and applications of accelerator system at the Wakasa Wan Energy Research Center

NASA Astrophysics Data System (ADS)

Hatori, S.; Kurita, T.; Hayashi, Y.; Yamada, M.; Yamada, H.; Mori, J.; Hamachi, H.; Kimura, S.; Shimoda, T.; Hiroto, M.; Hashimoto, T.; Shimada, M.; Yamamoto, H.; Ohtani, N.; Yasuda, K.; Ishigami, R.; Sasase, M.; Ito, Y.; Hatashita, M.; Takagi, K.; Kume, K.; Fukuda, S.; Yokohama, N.; Kagiya, G.; Fukumoto, S.; Kondo, M.

2005-12-01

At the Wakasa Wan Energy Research Center (WERC), an accelerator system with a 5 MV tandem accelerator and a 200 MeV proton synchrotron is used for ion beam analyses and irradiation experiments. The study of cancer therapy with a proton beam is also performed. Therefore, the stable operation and efficient sharing of beam time of the system are required, based on the treatment standard. Recent developments and the operation status of the system put stress on the tandem accelerator operation, magnifying the problems.

Development of Acceleration Sensor and Acceleration Evaluation System for Super-Low-Range Frequencies

NASA Astrophysics Data System (ADS)

Asano, Shogo; Matsumoto, Hideki

2001-05-01

This paper describes the development process for acceleration sensors used on automobiles and an acceleration evaluation system designed specifically for acceleration at super-low-range frequencies. The features of the newly developed sensor are as follows. 1) Original piezo-bimorph design based on a disc-center-fixed structure achieves pyroeffect cancelling and stabilization of sensor characteristics and enables the detection of the acceleration of 0.0009 G at the super-low-range-frequency of 0.03 Hz. 2) The addition of a self-diagnostic function utilizing the characteristics of piezoceramics enables constant monitoring of sensor failure. The frequency range of acceleration for accurate vehicle motion control is considered to be from DC to about 50 Hz. However, the measurement of acceleration in the super-low-range frequency near DC has been difficult because of mechanical and electrical noise interruption. This has delayed the development of the acceleration sensor for automotive use. We have succeeded in the development of an acceleration evaluation system for super-low-range frequencies from 0.015 Hz to 2 Hz with detection of the acceleration range from 0.0002 G (0.2 gal) to 1 G, as well as the development of a piezoelectric-type acceleration sensor for automotive use.

Spinal Disease in Aviators and Its Relationship to G-Exposure, Age, Aircraft Seating Angle, Exercise and Other Lifestyle Factors

DTIC Science & Technology

2000-08-01

34Cervical Spinal Injury all other respects to the HP aviators studied. Methods: from Repeated Exposures to Sustained Acceleration" An anonymous survey...articles have reported anecdotal these groups were matched for all relevant spinal injuries in aviators of high-performance aircraft demographic and...symptoms or disease in the neck or lower back climbing turn and suffered a C5-6 ligamentous injury . were reported in the HP group as compared to the NHP

Primary Blast Traumatic Brain Injury in the Rat: Relating Diffusion Tensor Imaging and Behavior

DTIC Science & Technology

2013-10-14

collegiate football players: the NCAA concussion study. JAMA (2003) 290:2556–63. doi:10.1001/ jama.290.19.2556 6. DePalma RG, Burris DG, Champion HR... concussions in retired pro- fessional football players. Am J Sports Med (2012) 40:2206–12. doi: 10.1177/0363546512456193 10. Verfaellie M, Lafleche G...low-blast exposures and limited excur- sions during high-blast exposures. Angular accelerations were well below the threshold for mild concussion in

The Effect of Chlorides on the Correlation of Accelerated Laboratory Corrosion Tests to Out-Door Exposure Tests for Ceramics-Aluminum Couples

DTIC Science & Technology

2010-02-01

environment *Courtesy : George Hawthorn of Hawaii Corrosion Lab Procedures Outdoor Exposure Kilauea Volcano * Campbell Industrial Park* – Volcanic and marine...Raghu Srinivasan and L.H. Hihara Hawaii Corrosion Laboratory University of Hawaii at Manoa Department of Mechanical Engineering Report Documentation Page...PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) University of Hawaii at Manoa,Department of

Evaluation of the Accelerate Pheno System for Fast Identification and Antimicrobial Susceptibility Testing from Positive Blood Cultures in Bloodstream Infections Caused by Gram-Negative Pathogens.

PubMed

Marschal, Matthias; Bachmaier, Johanna; Autenrieth, Ingo; Oberhettinger, Philipp; Willmann, Matthias; Peter, Silke

2017-07-01

Bloodstream infections (BSI) are an important cause of morbidity and mortality. Increasing rates of antimicrobial-resistant pathogens limit treatment options, prompting an empirical use of broad-range antibiotics. Fast and reliable diagnostic tools are needed to provide adequate therapy in a timely manner and to enable a de-escalation of treatment. The Accelerate Pheno system (Accelerate Diagnostics, USA) is a fully automated test system that performs both identification and antimicrobial susceptibility testing (AST) directly from positive blood cultures within approximately 7 h. In total, 115 episodes of BSI with Gram-negative bacteria were included in our study and compared to conventional culture-based methods. The Accelerate Pheno system correctly identified 88.7% (102 of 115) of all BSI episodes and 97.1% (102 of 105) of isolates that are covered by the system's identification panel. The Accelerate Pheno system generated an AST result for 91.3% (95 of 104) samples in which the Accelerate Pheno system identified a Gram-negative pathogen. The overall category agreement between the Accelerate Pheno system and culture-based AST was 96.4%, the rates for minor discrepancies 1.4%, major discrepancies 2.3%, and very major discrepancies 1.0%. Of note, ceftriaxone, piperacillin-tazobactam, and carbapenem resistance was correctly detected in blood culture specimens with extended-spectrum beta-lactamase-producing Escherichia coli ( n = 7) and multidrug-resistant Pseudomonas aeruginosa ( n = 3) strains. The utilization of the Accelerate Pheno system reduced the time to result for identification by 27.49 h ( P < 0.0001) and for AST by 40.39 h ( P < 0.0001) compared to culture-based methods in our laboratory setting. In conclusion, the Accelerate Pheno system provided fast, reliable results while significantly improving turnaround time in blood culture diagnostics of Gram-negative BSI. Copyright © 2017 American Society for Microbiology.

Frequency weighting derived from power absorption of fingers-hand-arm system under z(h)-axis vibration.

PubMed

Dong, Ren G; Welcome, Daniel E; McDowell, Thomas W; Wu, John Z; Schopper, Aaron W

2006-01-01

The objectives of this study are to derive the frequency weighting from three vibration power absorption (VPA) methods (finger VPA, palm VPA, and total or hand VPA), and to explore whether these energy methods are better than the currently accepted acceleration method. To calculate the VPA weightings, the mechanical impedance of eight subjects exposed to a broadband random vibration spectrum in the z(h)-axis using 18 combinations of hand couplings and applied forces was measured. The VPA weightings were compared with the frequency weighting specified in ISO 5349-1 [2001. Mechanical Vibration--Measurement and Evaluation of Human Exposure to Hand--Transmitted Vibration--Part 1: General Requirements. International Organization for Standardization, Geneva, Switzerland]. This study found that the hand and palm VPA weightings are very similar to the ISO weighting but the finger VPA weighting for the combined grip and push action is much higher than the ISO weighting at frequencies higher than 25 Hz. Therefore, this study predicted that the total power absorption of the entire hand-arm system is likely to be correlated with psychophysical response or subjective sensation. However, if the ISO weighting method cannot yield good predictions of the vibration-induced disorders in the fingers and hand, the hand and palm energy methods are unlikely to yield significantly better predictions. The finger VPA is a vibration measure between unweighted and ISO weighted accelerations. The palm VPA method may have some value for studying the disorders in the wrist-arm system.

Investigation of techniques for accelerating the construction of bridge deck overlays : tech transfer summary.

DOT National Transportation Integrated Search

2016-04-01

Todays environment is increasingly hostile to bridge decks with exposure : to deicing salts and environmental factors such as large temperature swings : and polluting chemicals. Being subjected to the most severe loading of all the : bridge compon...

Cosmic Rays Astrophysics: The Discipline, Its Scope, and Its Applications

NASA Technical Reports Server (NTRS)

Barghouty, A. F.

2009-01-01

This slide presentation gives an overview of the discipline surrounding cosmic ray astrophysics. It includes information on recent assertions surrounding cosmic rays, exposure levels, and a short history with specific information on the origin, acceleration, transport, and modulation of cosmic rays.

Photothermal Stability of an E-Beam Pre-Crosslinked EVA Encapsulant and Its Performance Degradation on a-Si Submodules: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pern, F. J.; Watson, G. L.; Glick, S. H.

2001-10-01

Presented at the 2001 NCPV Program Review Meeting: Study of photothermal stability of special EVA encapsulant by accelerated exposure testing and analysis of causes of performance degradation on a-Si modules.

On-Chip Laser-Power Delivery System for Dielectric Laser Accelerators

NASA Astrophysics Data System (ADS)

Hughes, Tyler W.; Tan, Si; Zhao, Zhexin; Sapra, Neil V.; Leedle, Kenneth J.; Deng, Huiyang; Miao, Yu; Black, Dylan S.; Solgaard, Olav; Harris, James S.; Vuckovic, Jelena; Byer, Robert L.; Fan, Shanhui; England, R. Joel; Lee, Yun Jo; Qi, Minghao

2018-05-01

We propose an on-chip optical-power delivery system for dielectric laser accelerators based on a fractal "tree-network" dielectric waveguide geometry. This system replaces experimentally demanding free-space manipulations of the driving laser beam with chip-integrated techniques based on precise nanofabrication, enabling access to orders-of-magnitude increases in the interaction length and total energy gain for these miniature accelerators. Based on computational modeling, in the relativistic regime, our laser delivery system is estimated to provide 21 keV of energy gain over an acceleration length of 192 μ m with a single laser input, corresponding to a 108-MV/m acceleration gradient. The system may achieve 1 MeV of energy gain over a distance of less than 1 cm by sequentially illuminating 49 identical structures. These findings are verified by detailed numerical simulation and modeling of the subcomponents, and we provide a discussion of the main constraints, challenges, and relevant parameters with regard to on-chip laser coupling for dielectric laser accelerators.

Identification of the key molecules involved in chronic copper exposure-aggravated memory impairment in transgenic mice of Alzheimer's disease using proteomic analysis.

PubMed

Yu, Jun; Luo, Xiaobin; Xu, Hua; Ma, Quan; Yuan, Jianhui; Li, Xuling; Chang, Raymond Chuen-Chung; Qu, Zhongsen; Huang, Xinfeng; Zhuang, Zhixiong; Liu, Jianjun; Yang, Xifei

2015-01-01

Alzheimer's disease (AD) is the most common neurodegenerative disease characterized by a progressive impairment of cognitive functions including spatial learning and memory. Excess copper exposure accelerates the development of AD; however, the potential mechanisms by which copper exacerbates the symptoms of AD remain unknown. In this study, we explored the effects of chronic copper exposure on cognitive function by treating 6 month-old triple AD transgenic (3xTg-AD) mice with 250 ppm copper sulfate in drinking water for 6 months, and identified several potential key molecules involved in the effects of chronic copper exposure on memory by proteomic analysis. The behavioral test showed that chronic copper exposure aggravated memory impairment of 3xTg-AD mice. Two-dimensional fluorescence difference gel electrophoresis (2D-DIGE) coupled with mass spectrometry revealed a total of 44 differentially expressed proteins (18 upregulated and 26 down-regulated) in hippocampus between the wild-type (WT) mice and non-exposed 3xTg-AD mice. A total of 40 differentially expressed proteins were revealed (20 upregulated and 20 down-regulated) in hippocampus between copper exposed and non-exposed 3xTg-AD mice. Among these differentially expressed proteins, complexin-1 and complexin-2, two memory associated proteins, were significantly decreased in hippocampus of 3xTg-AD mice compared with the WT mice. Furthermore, the expression of these two proteins was further down-regulated in 3xTg-AD mice when exposed to copper. The abnormal expression of complexin-1 and complexin-2 identified by proteomic analysis was verified by western blot analysis. Taken together, our data showed that chronic copper exposure accelerated memory impairment and altered the expression of proteins in hippocampus in 3xTg-AD mice. The functional analysis on the differentially expressed proteins suggested that complexin-1 and complexin-2 may be the key molecules involved in chronic copper exposure-aggravated memory impairment in AD.

Evaluation of 10V Chip Polymer Tantalum Capacitors for Space Applications

NASA Technical Reports Server (NTRS)

Teverovsky, Alexander A.

2016-01-01

Due to low ESR and safe failure mode, new technology chip polymer tantalum capacitors (CPTC) have gained popularity in the electronics design community, first in commercial applications, and now in hi-rel and space systems. The major drawbacks of these parts are high leakage currents, degradation under environmental stresses, and a relatively narrow temperature range of operating and storage conditions. Several studies have shown that a certain amount of moisture in polymer cathodes is necessary for a normal operation of the parts. This might limit applications of CPTCs in space systems and requires analysis of long-term exposure to deep vacuum conditions on their performance and reliability. High leakage currents and limited maximum operational temperature complicate accelerated testing that is necessary to assess long-term reliability and require new screening and qualification procedures for quality assurance. A better understanding of behavior of CPTCs as compared to traditional, MnO2, capacitors is necessary to develop adequate approaches for QA system for space applications. A specific of CPTCs is that different materials and processes might be used for low-voltage (10 V and less) and high-voltage (above 10 V) capacitors, so performance and degradation processes in these groups require separate analysis. In this work, that is a part of the NASA Electronic Parts and Packaging (NEPP) program, degradation of AC and DC characteristics under environmental stresses at different temperatures and voltages have been studied in nine lots of commercial and automotive grade capacitors rated to 10 V. Results of analysis of leakage currents, high temperature storage (HTS) up to 5000 hrs in vacuum and air at different temperatures, and Highly Accelerated Life Testing (HALT) in the range from 85 C to 145 C are presented. Temperature and voltage acceleration factors were calculated based on approximation of distributions of degradation rates with a general log-linear Weibull model. Mechanisms of degradation and failures, and requirements for screening and qualification testing are discussed.

Evaluation of accelerated UV and thermal testing for benzene formation in beverages containing benzoate and ascorbic acid.

PubMed

Nyman, Patricia J; Wamer, Wayne G; Begley, Timothy H; Diachenko, Gregory W; Perfetti, Gracia A

2010-04-01

Under certain conditions, benzene can form in beverages containing benzoic and ascorbic acids. The American Beverage Assn. (ABA) has published guidelines to help manufacturers mitigate benzene formation in beverages. These guidelines recommend accelerated testing conditions to test product formulations, because exposure to ultraviolet (UV) light and elevated temperature over the shelf life of the beverage may result in benzene formation in products containing benzoic and ascorbic acids. In this study, the effects of UVA exposure on benzene formation were determined. Benzene formation was examined for samples contained in UV stabilized and non-UV stabilized packaging. Additionally, the usefulness of accelerated thermal testing to simulate end of shelf-life benzene formation was evaluated for samples containing either benzoic or ascorbic acid, or both. The 24 h studies showed that under intense UVA light benzene levels increased by as much as 53% in model solutions stored in non-UV stabilized bottles, whereas the use of UV stabilized polyethylene terephthalate bottles reduced benzene formation by about 13% relative to the non-UV stabilized bottles. Similar trends were observed for the 7 d study. Retail beverages and positive and negative controls were used to study the accelerated thermal testing conditions. The amount of benzene found in the positive controls and cranberry juice suggests that testing at 40 degrees C for 14 d may more reliably simulate end of shelf-life benzene formation in beverages. Except for cranberry juice, retail beverages were not found to contain detectable amounts of benzene (<0.05 ng/g) at the end of their shelf lives.

Reduced cellular redox status induces 4-hydroxynonenal-mediated caspase 3 activation leading to erythrocyte death during chronic arsenic exposure in rats

DOE Office of Scientific and Technical Information (OSTI.GOV)

Biswas, Debabrata; Sen, Gargi; Biswas, Tuli, E-mail: tulibiswas@iicb.res.i

2010-05-01

Chronic exposure to arsenic in rats led to gradual accumulation of the toxicant in erythrocytes causing oxidative stress in these cells. 4-Hydroxynonenal (4-HNE), a major aldehyde product of lipid peroxidation, contributed significantly to the cytopathological events observed during oxidative stress in the erythrocytes of exposed rats. 4-HNE triggered death signal cascade that was initiated with the formation of HNE-protein adducts in cytosol. HNE-protein adduct formation resulted in depletion of cytosolic antioxidants followed by increased generation of ROS. Results showed accumulation of hydrogen peroxide (H{sub 2}O{sub 2}) from the early stages of arsenic exposure, while superoxide (O{sub 2}{sup c}entre dot{sup -})more » and hydroxyl radical ({sup c}entre dotOH) also contributed to the oxidative stress during longer period of exposure. Suppression of antioxidant system coupled with increased generation of ROS eventually led to activation of caspase 3 during arsenic exposure. Attenuation of HNE-mediated activation of caspase 3 in presence of N-acetylcysteine (NAC) indicated the involvement of GSH in the process. Prevention of HNE-mediated degradation of membrane proteins in presence of Z-DEVD-FMK identified caspase 3 as the principal mediator of HNE-induced cellular damage during arsenic exposure. Degradation of band 3 followed by its aggregation on the red cell surface promoted immunologic recognition of redistributed band 3 by autologous IgG with subsequent attachment of C3b. Finally, the formation of C3b-IgG-band 3 immune complex accelerated the elimination of affected cells from circulation and led to the decline of erythrocyte life span during chronic arsenic toxicity.« less

AC magnetic field measurement using a small flip coil system for rapid cycling AC magnets at the China Spallation Neutron Source (CSNS)

NASA Astrophysics Data System (ADS)

Zhou, Jianxin; Kang, Wen; Li, Shuai; Liu, Yudong; Liu, Yiqin; Xu, Shouyan; Guo, Xiaoling; Wu, Xi; Deng, Changdong; Li, Li; Wu, Yuwen; Wang, Sheng

2018-02-01

The China Spallation Neutron Source (CSNS) has two major accelerator systems, a linear accelerator and a rapid cycling synchrotron (RCS). The RCS accelerator is used to accumulate and accelerate protons from the energy of 80 MeV to the design energy of 1.6 GeV at the repetition rate of 25 Hz, and extract the high energy beam to the target. The main magnets of the RCS accelerator are excited by AC current with DC bias. The magnetic field quality is very important for the RCS accelerator operation, since it should guarantee and focus a circulating beam. In order to characterize the AC magnets, a small flip coil measurement system has been developed and one of each type of AC magnets has been studied. The measurement system and selected measurement results are presented in this paper.

Focal spot motion of linear accelerators and its effect on portal image analysis.

PubMed

Sonke, Jan-Jakob; Brand, Bob; van Herk, Marcel

2003-06-01

The focal spot of a linear accelerator is often considered to have a fully stable position. In practice, however, the beam control loop of a linear accelerator needs to stabilize after the beam is turned on. As a result, some motion of the focal spot might occur during the start-up phase of irradiation. When acquiring portal images, this motion will affect the projected position of anatomy and field edges, especially when low exposures are used. In this paper, the motion of the focal spot and the effect of this motion on portal image analysis are quantified. A slightly tilted narrow slit phantom was placed at the isocenter of several linear accelerators and images were acquired (3.5 frames per second) by means of an amorphous silicon flat panel imager positioned approximately 0.7 m below the isocenter. The motion of the focal spot was determined by converting the tilted slit images to subpixel accurate line spread functions. The error in portal image analysis due to focal spot motionwas estimated by a subtraction of the relative displacement of the projected slit from the relative displacement of the field edges. It was found that the motion of the focal spot depends on the control system and design of the accelerator. The shift of the focal spot at the start of irradiation ranges between 0.05-0.7 mm in the gun-target (GT) direction. In the left-right (AB) direction the shift is generally smaller. The resulting error in portal image analysis due to focal spotmotion ranges between 0.05-1.1 mm for a dose corresponding to two monitor units (MUs). For 20 MUs, the effect of the focal spot motion reduces to 0.01-0.3 mm. The error in portal image analysis due to focal spot motion can be reduced by reducing the applied dose rate.

Joint Test Report For Validation of Alternatives to Aliphatic Isocyanate Polyurethanes

NASA Technical Reports Server (NTRS)

Lewis, Pattie

2007-01-01

National Aeronautics and Space Administration (NASA) and Air Force Space Command (AFSPC) have similar missions and therefore similar facilities and structures in similar environments. The standard practice for protecting metallic substrates in atmospheric environments is the application of an applied coating system. The most common topcoats used in coating systems are polyurethanes that contain isocyanates. Isocyanates are classified as potential human carcinogens and are known to cause cancer in animals. The primary objective of this effort was to demonstrate and validate alternatives to aliphatic isocyanate polyurethanes resulting in one or more isocyanate-free coatings qualified for use at AFSPC and NASA installations participating in this project. This joint Test Report (JTR) documents the results of the laboratory and field testing as well as any test modifications made during the execution of the testing. The technical stakeholders agreed upon test procedure modifications documented in this document. This JTR is made available as a reference for future pollution prevention endeavors by other NASA centers, the Department of Defense and commercial users to minimize duplication of effort. All coating system candidates were tested using approved NASA and AFSPC standard coating systems as experimental controls. This study looked at eight alternative coating systems and two control coating systems and was divided into Phase I Screening Tests, Phase II Tests, and Field Testing. The Phase I Screening Tests were preliminary tests performed on all the selected candidate coating systems. Candidate coating systems that did not meet the acceptance criteria of the screening tests were eliminated from further testing. Phase I Screening Tests included: Ease of Application, Surface Appearance, Dry-To-Touch (Sanding), Accelerated Storage Stability, Pot Life (Viscosity), Cure Time (Solvent Rubs), Cleanability, Knife Test, Tensile (pull-off) Adhesion, and X-Cut Adhesion by Wet Tape After a review of the Phase I test results, four of the alternative coating systems showed substandard performance in relation to the Control Systems and were eliminated from the Phase II testing. Due to the interest of stakeholders and time constraints, however, all eight alternatives were subjected to the following Phase II tests, along with field testing at Stennis Space Center (SSC), Mississippi: Hypergol Compatibility, Liquid Oxygen Compatibility, 18-Month Marine Exposure (Gloss Retention, Color Retention, Blistering, Visual Corrosion, Creepage from Scribe, Heat Adhesion), and Field Exposure (6- and 12-month Evaluation for Coating Condition, Color Retention, Gloss Retention). The remaining four alternative coating systems determined to be the best viable alternatives were carried on to Phase II testing that included: Removability, Repairability, Abrasion Resistance, Gravelometer, Fungus Resistance, Accelerated Weathering, Mandrel Bend Flexibility, and Cyclic Corrosion Resistance. Of the systems that continued to Phase II, three (3) alternative coating systems meet the performance requirements as identified by stakeholders. Two (2) other systems, that were not included in Phase II testing, performed well enough on the 18-Month Marine Exposure, the primary requirement for NASA technical standard NASA-STD-5008, Protective Coating of Carbon Steel, Stainless Steel, and Aluminum on Launch Structures, Facilities, and Ground Support Equipment, that they were also considered to be successful candidates. In total, five (5) alternative coating systems were approved for inclusion in the NASA-STD- 5008 Qualified Products List (QPL). The standard is intended to provide a common framework for consistent practices across NASA and is often used by other entities. The standard's QPL does not connote endorsement of the products by NASA, but lists those products that have been tested and meet the requirements as specified.

Basic features of the STS/Spacelab vibration environment

NASA Technical Reports Server (NTRS)

Baugher, Charles R.; Ramachandran, N.

1994-01-01

The Space Shuttle acceleration environment is characterized. The acceleration environment is composed of a residual or quasi-steady component and higher frequency components induced by vehicle structural modes and the operation of onboard machinery. Quasi-steady accelerations are generally due to atmospheric drag, gravity gradient effects, and rotational forces. These accelerations tend to vary with the orbital frequency (approx. 10(exp -4) Hz) and have magnitudes less than or equal to 10(exp -6) g(sub 0) (where 1 g(sub 0) is terrestrial gravity). Higher frequency g-jitter is characterized by oscillatory disturbances in the 1-100 Hz range and transient components. Oscillatory accelerations are related to the response of large flexible structures like antennae, the Spacelab module, and the Orbiter itself, and to the operation of rotating machinery. The Orbiter structural modes in the 1-10 Hz range, are excited by oscillatory and transient disturbances and tend to dominate the energy spectrum of the acceleration environment. A comparison of the acceleration measurements from different Space Shuttle missions reveals the characteristic signature of the structural modes of the Orbiter overlaid with mission specific hardware induced disturbances and their harmonics. Transient accelerations are usually attributed to crew activity and Orbiter thruster operations. During crew sleep periods, the acceleration levels are typically on the order of 10(exp -6) g(sub 0) (1 micro-g). Crew work and exercise tend to raise the accelerations to the 10(exp -3) g(sub 0) (1 milli-g) level. Vernier reaction control system firings tend to cause accelerations of 10(exp -4) g(sub 0), while primary reaction control system and Orbiter maneuvering system firings cause accelerations as large as 10(exp -2) g(sub 0). Vibration isolation techniques (both active and passive systems) used during crew exercise have been shown to significantly reduce the acceleration magnitudes.

The sensitivity of human mesenchymal stem cells to vibration and cold storage conditions representative of cold transportation

PubMed Central

Nikolaev, N. I.; Liu, Y.; Hussein, H.; Williams, D. J.

2012-01-01

In the current study, the mechanical and hypothermic damage induced by vibration and cold storage on human mesenchymal stem cells (hMSCs) stored at 2–8°C was quantified by measuring the total cell number and cell viability after exposure to vibration at 50 Hz (peak acceleration 140 m s−2 and peak displacement 1.4 mm), 25 Hz (peak acceleration 140 m s−2, peak displacement 5.7 mm), 10 Hz (peak acceleration 20 m s−2, peak displacement 5.1 mm) and cold storage for several durations. To quantify the viability of the cells, in addition to the trypan blue exclusion method, the combination of annexin V-FITC and propidium iodide was applied to understand the mode of cell death. Cell granularity and a panel of cell surface markers for stemness, including CD29, CD44, CD105 and CD166, were also evaluated for each condition. It was found that hMSCs were sensitive to vibration at 25 Hz, with moderate effects at 50 Hz and no effects at 10 Hz. Vibration at 25 Hz also increased CD29 and CD44 expression. The study further showed that cold storage alone caused a decrease in cell viability, especially after 48 h, and also increased CD29 and CD44 and attenuated CD105 expressions. Cell death would most likely be the consequence of membrane rupture, owing to necrosis induced by cold storage. The sensitivity of cells to different vibrations within the mechanical system is due to a combined effect of displacement and acceleration, and hMSCs with a longer cold storage duration were more susceptible to vibration damage, indicating a coupling between the effects of vibration and cold storage. PMID:22628214

26 CFR 1.168(a)-1 - Modified accelerated cost recovery system.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 26 Internal Revenue 2 2010-04-01 2010-04-01 false Modified accelerated cost recovery system. 1.168(a)-1 Section 1.168(a)-1 Internal Revenue INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY... Corporations § 1.168(a)-1 Modified accelerated cost recovery system. (a) Section 168 determines the...

26 CFR 1.168(a)-1 - Modified accelerated cost recovery system.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 26 Internal Revenue 2 2011-04-01 2011-04-01 false Modified accelerated cost recovery system. 1.168(a)-1 Section 1.168(a)-1 Internal Revenue INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY... Corporations § 1.168(a)-1 Modified accelerated cost recovery system. (a) Section 168 determines the...

26 CFR 1.168(a)-1 - Modified accelerated cost recovery system.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 26 Internal Revenue 2 2013-04-01 2013-04-01 false Modified accelerated cost recovery system. 1.168(a)-1 Section 1.168(a)-1 Internal Revenue INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY... Corporations § 1.168(a)-1 Modified accelerated cost recovery system. (a) Section 168 determines the...

26 CFR 1.168(a)-1 - Modified accelerated cost recovery system.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 26 Internal Revenue 2 2012-04-01 2012-04-01 false Modified accelerated cost recovery system. 1.168(a)-1 Section 1.168(a)-1 Internal Revenue INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY... Corporations § 1.168(a)-1 Modified accelerated cost recovery system. (a) Section 168 determines the...

26 CFR 1.168(a)-1 - Modified accelerated cost recovery system.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 26 Internal Revenue 2 2014-04-01 2014-04-01 false Modified accelerated cost recovery system. 1.168(a)-1 Section 1.168(a)-1 Internal Revenue INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY... Corporations § 1.168(a)-1 Modified accelerated cost recovery system. (a) Section 168 determines the...

Sea-Level Rise and Land Subsidence in Deltas: Estimating Future Flood Risk Through Integrated Natural and Human System Modeling

NASA Astrophysics Data System (ADS)

Tessler, Z. D.; Vorosmarty, C. J.

2016-12-01

Deltas are highly sensitive to local human activities, land subsidence, regional water management, global sea-level rise, and climate extremes. We present a new delta flood exposure and risk framework for estimating the sensitivity of deltas to relative sea-level rise. We have applied this framework to a set of global environmental, geophysical, and social indicators over 48 major river deltas to quantify how contemporary risks vary across delta systems. The risk modeling framework incorporates upstream sediment flux and coastal land subsidence models, global empirical estimates of contemporary storm surge exposure, and population distribution and growth. Future scenarios are used to test the impacts on coastal flood risk of upstream dam construction, coastal population growth, accelerated sea-level rise, and enhanced storm surge. Results suggest a wide range of outcomes across different delta systems within each scenario. Deltas in highly engineered watersheds (Mississippi, Rhine) exhibit less sensitivity to increased dams due to saturation of sediment retention effects, though planned or under-construction dams are expected to have a substantial impact in the Yangtze, Irrawaddy, and Magdalena deltas. Population growth and sea-level rise are expected to be the dominant drivers of increased human risk in most deltas, with important exceptions in several countries, particularly China, where population are forecast to contract over the next several decades.

History and Technology Developments of Radio Frequency (RF) Systems for Particle Accelerators

NASA Astrophysics Data System (ADS)

Nassiri, A.; Chase, B.; Craievich, P.; Fabris, A.; Frischholz, H.; Jacob, J.; Jensen, E.; Jensen, M.; Kustom, R.; Pasquinelli, R.

2016-04-01

This article attempts to give a historical account and review of technological developments and innovations in radio frequency (RF) systems for particle accelerators. The evolution from electrostatic field to the use of RF voltage suggested by R. Wideröe made it possible to overcome the shortcomings of electrostatic accelerators, which limited the maximum achievable electric field due to voltage breakdown. After an introduction, we will provide reviews of technological developments of RF systems for particle accelerators.

Impact of Biodiesel Impurities on the Performance and Durability of DOC, DPF and SCR Technologies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Williams, A.; McCormick, R.; Luecke, J.

2011-06-01

It is estimated that operating continuously on a B20 fuel containing the current allowable ASTM specification limits for metal impurities in biodiesel could result in a doubling of ash exposure relative to lube-oil derived ash. The purpose of this study was to determine if a fuel containing metals at the ASTM limits could cause adverse impacts on the performance and durability of diesel emission control systems. An accelerated durability test method was developed to determine the potential impact of these biodiesel impurities. The test program included engine testing with multiple DPF substrate types as well as DOC and SCR catalysts.more » The results showed no significant degradation in the thermo-mechanical properties of cordierite, aluminum titanate, or silicon carbide DPFs after exposure to 150,000 mile equivalent biodiesel ash and thermal aging. However, exposure of a cordierite DPF to 435,000 mile equivalent aging resulted in a 69% decrease in the thermal shock resistance parameter. It is estimated that the additional ash from 150,000 miles of biodiesel use would also result in a moderate increases in exhaust backpressure for a DPF. A decrease in DOC activity was seen after exposure to 150,000 mile equivalent aging, resulting in higher HC slip and a reduction in NO{sub 2} formation. The metal-zeolite SCR catalyst experienced a slight loss in activity after exposure to 435,000 mile equivalent aging. This catalyst, placed downstream of the DPF, showed a 5% reduction in overall NOx conversion activity over the HDDT test cycle.« less

Understanding cancer development processes after HZE-particle exposure: roles of ROS, DNA damage repair and inflammation.

PubMed

Sridharan, D M; Asaithamby, A; Bailey, S M; Costes, S V; Doetsch, P W; Dynan, W S; Kronenberg, A; Rithidech, K N; Saha, J; Snijders, A M; Werner, E; Wiese, C; Cucinotta, F A; Pluth, J M

2015-01-01

During space travel astronauts are exposed to a variety of radiations, including galactic cosmic rays composed of high-energy protons and high-energy charged (HZE) nuclei, and solar particle events containing low- to medium-energy protons. Risks from these exposures include carcinogenesis, central nervous system damage and degenerative tissue effects. Currently, career radiation limits are based on estimates of fatal cancer risks calculated using a model that incorporates human epidemiological data from exposed populations, estimates of relative biological effectiveness and dose-response data from relevant mammalian experimental models. A major goal of space radiation risk assessment is to link mechanistic data from biological studies at NASA Space Radiation Laboratory and other particle accelerators with risk models. Early phenotypes of HZE exposure, such as the induction of reactive oxygen species, DNA damage signaling and inflammation, are sensitive to HZE damage complexity. This review summarizes our current understanding of critical areas within the DNA damage and oxidative stress arena and provides insight into their mechanistic interdependence and their usefulness in accurately modeling cancer and other risks in astronauts exposed to space radiation. Our ultimate goals are to examine potential links and crosstalk between early response modules activated by charged particle exposure, to identify critical areas that require further research and to use these data to reduced uncertainties in modeling cancer risk for astronauts. A clearer understanding of the links between early mechanistic aspects of high-LET response and later surrogate cancer end points could reveal key nodes that can be therapeutically targeted to mitigate the health effects from charged particle exposures.

48 CFR 32.009 - Providing accelerated payments to small business subcontractors.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 48 Federal Acquisition Regulations System 1 2014-10-01 2014-10-01 false Providing accelerated payments to small business subcontractors. 32.009 Section 32.009 Federal Acquisition Regulations System... accelerated payments to small business subcontractors. ...

Plug-in module acceleration feedback control for fast steering mirror-based beam stabilization systems

NASA Astrophysics Data System (ADS)

Deng, Chao; Ren, Wei; Mao, Yao; Ren, Ge

2017-08-01

A plug-in module acceleration feedback control (Plug-In AFC) strategy based on the disturbance observer (DOB) principle is proposed for charge-coupled device (CCD)-based fast steering mirror (FSM) stabilization systems. In classical FSM tracking systems, dual-loop control (DLC), including velocity feedback and position feedback, is usually utilized to enhance the closed-loop performance. Due to the mechanical resonance of the system and CCD time delay, the closed-loop bandwidth is severely restricted. To solve this problem, cascade acceleration feedback control (AFC), which is a kind of high-precision robust control method, is introduced to strengthen the disturbance rejection property. However, in practical applications, it is difficult to realize an integral algorithm in an acceleration controller to compensate for the quadratic differential contained in the FSM acceleration model, resulting in a challenging controller design and a limited improvement. To optimize the acceleration feedback framework in the FSM system, different from the cascade AFC, the accelerometers are used to construct DOB to compensate for the platform vibrations directly. The acceleration nested loop can be plugged into the velocity loop without changing the system stability, and the controller design is quite simple. A series of comparative experimental results demonstrate that the disturbance rejection property of the CCD-based FSM can be effectively improved by the proposed approach.

Low-dose megavoltage cone-beam computed tomography for lung tumors using a high-efficiency image receptor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sillanpaa, Jussi; Chang Jenghwa; Mageras, Gikas

2006-09-15

We report on the capabilities of a low-dose megavoltage cone-beam computed tomography (MV CBCT) system. The high-efficiency image receptor consists of a photodiode array coupled to a scintillator composed of individual CsI crystals. The CBCT system uses the 6 MV beam from a linear accelerator. A synchronization circuit allows us to limit the exposure to one beam pulse [0.028 monitor units (MU)] per projection image. 150-500 images (4.2-13.9 MU total) are collected during a one-minute scan and reconstructed using a filtered backprojection algorithm. Anthropomorphic and contrast phantoms are imaged and the contrast-to-noise ratio of the reconstruction is studied as amore » function of the number of projections and the error in the projection angles. The detector dose response is linear (R{sup 2} value 0.9989). A 2% electron density difference is discernible using 460 projection images and a total exposure of 13 MU (corresponding to a maximum absorbed dose of about 12 cGy in a patient). We present first patient images acquired with this system. Tumors in lung are clearly visible and skeletal anatomy is observed in sufficient detail to allow reproducible registration with the planning kV CT images. The MV CBCT system is shown to be capable of obtaining good quality three-dimensional reconstructions at relatively low dose and to be clinically usable for improving the accuracy of radiotherapy patient positioning.« less

Knowledge engineering for PACES, the particle accelerator control expert system

NASA Astrophysics Data System (ADS)

Lind, P. C.; Poehlman, W. F. S.; Stark, J. W.; Cousins, T.

1992-04-01

The KN-3000 used at Defense Research Establishment Ottawa is a Van de Graaff particle accelerator employed primarily to produce monoenergetic neutrons for calibrating radiation detectors. To provide training and assistance for new operators, it was decided to develop an expert system for accelerator operation. Knowledge engineering aspects of the expert system are reviewed. Two important issues are involved: the need to encapsulate expert knowledge into the system in a form that facilitates automatic accelerator operation and to partition the system so that time-consuming inferencing is minimized in favor of faster, more algorithmic control. It is seen that accelerator control will require fast, narrowminded decision making for rapid fine tuning, but slower and broader reasoning for machine startup, shutdown, fault diagnosis, and correction. It is also important to render the knowledge base in a form conducive to operator training. A promising form of the expert system involves a hybrid system in which high level reasoning is performed on the host machine that interacts with the user, while an embedded controller employs neural networks for fast but limited adjustment of accelerator performance. This partitioning of duty facilitates a hierarchical chain of command yielding an effective mixture of speed and reasoning ability.

NOx profile around a signalized intersection of busy roadway

NASA Astrophysics Data System (ADS)

Kim, Kyung Hwan; Lee, Seung-Bok; Woo, Sung Ho; Bae, Gwi-Nam

2014-11-01

The NOx pollution profile around a signalized intersection of a busy roadway was investigated to understand the effect of traffic control on urban air pollution. Traffic flow patterns were classified into three categories of quasi-cruising, a combination of deceleration and acceleration, and a combination of deceleration, idling, and acceleration. The spatial distribution of air pollution levels around an intersection could be represented as a quasi-normal distribution, whose peak height was aggravated by increased emissions due to transient driving patterns. The peak concentration of NOx around the signalized intersection for the deceleration, idling, and acceleration category was five times higher than that for the quasi-cruising category. Severe levels of NOx pollution tailed off approximately 400 m from the center of the intersection. Approximately 200-1000 ppb of additional NOx was observed when traffic was decelerating, idling, and accelerating within the intersection zone, resulting in high exposure levels for pedestrians around the intersection. We propose a fluctuating horizontal distribution of motor vehicle-induced air pollutants as a function of time.

A proposal for antiparallel acceleration of positrons using CEBAF

NASA Astrophysics Data System (ADS)

Tiefenback, M.; Wojtsekhowski, B.

2018-05-01

We present a scheme for positron beam acceleration in CEBAF antiparallel to the normal electron path, requiring no change in polarity of the magnet systems. This feature is essential to the principal benefit: enabling extremely simple configuration changes between conventional (clockwise) e- acceleration and counter clockwise e+ acceleration. Additionally, it appears possible to configure the accelerating cavity phases to support concurrent acceleration of the electron and positron beams. The last mode also may enable use of the higher peak current electron beam for system diagnostics. The inherent penalty of the concurrent mode in acceleration efficiency and increased energy spread may render this a commissioning-only diagnostic option, but the possibility appears worthy of consideration.

Effects on body size and composition of chronic exposure to altered gravity. [centrifuging stress in mammals

NASA Technical Reports Server (NTRS)

Pitts, G. C.

1977-01-01

The effects of chronic centrifugation on body composition and growth of rats, mice, monkeys, and man are studied. The benefits of exercise and restraint during acceleration are investigated. Physiological regulation and energy balance are also discussed.

Stemming the Gap

ERIC Educational Resources Information Center

Kahler, Jim; Valentine, Nancy

2011-01-01

In years past, strong analytical, creative, and communication skills were enough to prepare students for successful careers, but as technological change accelerates, so must innovation in science education. Unfortunately, American students today are lacking exposure to the programs and curriculum that teach these technical skills. Only 32.4% of…

Ambient particulate matter accelerates coagulation via an IL-6-dependent pathway

EPA Science Inventory

The mechanisms by which exposure to particulate matter increases the risk of cardiovascular events are not known. Recent human and animal data suggest that particulate matter may induce alterations in hemostatic factors. In this study we determined the mechanisms by which particu...

Pulmonary Exposure to Combustion Particulate Matter Induces Myocardial Mitochondrial injury and impaired tolerance to ischemia reoxygenation

EPA Science Inventory

Background and aim: Air pollution is associated with increased morbidity and mortality of acute and chronic coronary heart disease. This effect has been attributed to oxidative stress, thrombogenesis, elevation of blood pressure, inflammation and accelerated atherosclerosis. H...

Tertiary Epimutations – A Novel Aspect of Epigenetic Transgenerational Inheritance Promoting Genome Instability

PubMed Central

McCarrey, John R.; Lehle, Jake D.; Raju, Seetha S.; Wang, Yufeng; Nilsson, Eric E.; Skinner, Michael K.

2016-01-01

Exposure to environmental factors can induce the epigenetic transgenerational inheritance of disease. Alterations to the epigenome termed “epimutations” include “primary epimutations” which are epigenetic alterations in the absence of genetic change and “secondary epimutations” which form following an initial genetic change. To determine if secondary epimutations contribute to transgenerational transmission of disease following in utero exposure to the endocrine disruptor vinclozolin, we exposed pregnant female rats carrying the lacI mutation-reporter transgene to vinclozolin and assessed the frequency of mutations in kidney tissue and sperm recovered from F1 and F3 generation progeny. Our results confirm that vinclozolin induces primary epimutations rather than secondary epimutations, but also suggest that some primary epimutations can predispose a subsequent accelerated accumulation of genetic mutations in F3 generation descendants that have the potential to contribute to transgenerational phenotypes. We therefore propose the existence of “tertiary epimutations” which are initial primary epimutations that promote genome instability leading to an accelerated accumulation of genetic mutations. PMID:27992467

Factors and processes causing accelerated decomposition in human cadavers - An overview.

PubMed

Zhou, Chong; Byard, Roger W

2011-01-01

Artefactually enhanced putrefactive and autolytic changes may be misinterpreted as indicating a prolonged postmortem interval and throw doubt on the veracity of witness statements. Review of files from Forensic Science SA and the literature revealed a number of external and internal factors that may be responsible for accelerating these processes. Exogenous factors included exposure to elevated environmental temperatures, both outdoors and indoors, exacerbated by increased humidity or fires. Situations indoor involved exposure to central heating, hot water, saunas and electric blankets. Deaths within motor vehicles were also characterized by enhanced decomposition. Failure to quickly or adequately refrigerate bodies may also lead to early decomposition. Endogenous factors included fever, infections, illicit and prescription drugs, obesity and insulin-dependent diabetes mellitus. When these factors or conditions are identified at autopsy less significance should, therefore, be attached to changes of decomposition as markers of time since death. Copyright © 2010 Elsevier Ltd and Faculty of Forensic and Legal Medicine. All rights reserved.

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

NASA Technical Reports Server (NTRS)

Bagian, James P.; Greenisen, M. C.; Schafer, L. E.; Probe, J. D.; Krutz, Robert W., Jr.

1990-01-01

A crew of four veteran astronaut/pilots were subjected to sustained linear accelerations of up to 3G(x) in order to quantify crew reach performance while wearing the currently used Launch and Entry Suit (LES). Photogrammetric techniques were used to quantify magnitudes of reach in any direction while subjects rode a centrifuge. Subjects exhibited small changes of reach capability in the +x (forward) direction which ranged from an improvement of 2.04 cm to a decrease of 14.4 cm while reach performance in the +z (overhead) direction was improved in three of four subjects, indicating that any task which could be accomplished under exposure to 1G(x) could definitely be done at 3G(x). The data from this experiment demonstrated that Shuttle crews in training can expect to maintain all of the overhead reach capability evident in good simulator runs and suffer only moderate degradation in the forward reach performance during the launch phase of an actual Shuttle mission.

Changes in CR-39 proton sensitivity due to prolonged exposure to high vacuums relevant to the National Ignition Facility and OMEGA.

PubMed

Manuel, M J-E; Rosenberg, M J; Sinenian, N; Rinderknecht, H; Zylstra, A B; Séguin, F H; Frenje, J; Li, C K; Petrasso, R D

2011-09-01

When used at facilities like OMEGA and the NIF, CR-39 is exposed to high vacuum environments before and after irradiation by charged particles and neutrons. Using an electrostatic linear accelerator at MIT, studies have been conducted to investigate the effects of high vacuum exposure on the sensitivity of CR-39 to fusion protons in the ~1-9 MeV energy range. High vacuum conditions, of order 10(-5) Torr, experienced by CR-39 samples at these facilities were emulated. It is shown that vacuum exposure times longer than ~16 h before proton irradiation result in a decrease in proton sensitivity, whereas no effect was observed for up to 67 h of vacuum exposure after proton irradiation. CR-39 sensitivity curves are presented for samples with prolonged exposure to high vacuum before and after proton irradiation. © 2011 American Institute of Physics

Exposure to Carbon Nanotube Material: Assessment of Nanotube Cytotoxicity Using Human Keratinocyte Cells

NASA Technical Reports Server (NTRS)

Shvedova, Anna A.; Castranova, Vincent; Kisin, Elena R.; Schwegler-Berry, Diane; Murray, Ashley R.; Gandelsman, Vadim Z.; Maynard, Andrew; Baron, Paul

2003-01-01

Carbon nanotubes are new members of carbon allotropes similar to fullerenes and graphite. Because of their unique electrical, mechanical, and thermal properties, carbon nanotubes are important for novel applications in the electronics, aerospace, and computer industries. Exposure to graphite and carbon materials has been associated with increased incidence of skin diseases, such as carbon fiber dermatitis, hyperkeratosis, and naevi. We investigated adverse effects of single-wall carbon nanotubes (SWCNT) using a cell culture of immortalized human epidermal keratinocytes (HaCaT). After 18 h of exposure of HaCaT to SWCNT, oxidative stress and cellular toxicity were indicated by formation of free radicals, accumulation of peroxidative products, antioxidant depletion, and loss of cell viability. Exposure to SWCNT also resulted in ultrastructural and morphological changes in cultured skin cells. These data indicate that dermal exposure to unrefined SWCNT may lead to dermal toxicity due to accelerated oxidative stress in the skin of exposed workers.

Mobility of diesel versus non-diesel coal miners: some evidence on the healthy worker effect.

PubMed Central

Ames, R G; Trent, B

1984-01-01

Workers who are particularly susceptible to the effects of their occupational exposure, from the perspective of the healthy worker effect, soon leave the workplace. The result of this mobility, called survival bias, is that cross sectional studies based on the survivors underestimate the true risk of occupational exposures. Two questions are addressed in this empirical study of the "survival bias" component of the "healthy worker" effect. Do miners with respiratory impairment or symptoms disproportionately leave jobs that have a potentially harmful respiratory exposure? And does the presence of an additional potentially harmful respiratory exposure, in this case diesel emissions, accelerate the rate of mobility for miners with respiratory impairment or symptoms? No confirmation was found for the survival effect in a study of 738 diesel and 420 non-diesel US underground coal miners. No additional increment in mobility was associated with exposure to both coal mine dust and diesel emissions. PMID:6722047

Modeling Acceleration of a System of Two Objects Using the Concept of Limits

ERIC Educational Resources Information Center

Sokolowski, Andrzej

2018-01-01

Traditional school laboratory exercises on a system of moving objects connected by strings involve deriving expressions for the system acceleration, a = (?F)/m, and sketching a graph of acceleration vs. force. While being in the form of rational functions, these expressions present great opportunities for broadening the scope of the analysis by…

Repair of DNA damage induced by accelerated heavy ions--a mini review.

PubMed

Okayasu, Ryuichi

2012-03-01

Increasing use of heavy ions for cancer therapy and concerns from exposure to heavy charged particles in space necessitate the study of the basic biological mechanisms associated with exposure to heavy ions. As the most critical damage induced by ionizing radiation is DNA double strand break (DSB), this review focuses on DSBs induced by heavy ions and their repair processes. Compared with X- or gamma-rays, high-linear energy transfer (LET) heavy ion radiation induces more complex DNA damage, categorized into DSBs and non-DSB oxidative clustered DNA lesions (OCDL). This complexity makes the DNA repair process more difficult, partially due to retarded enzymatic activities, leading to increased chromosome aberrations and cell death. In general, the repair process following heavy ion exposure is LET-dependent, but with nonhomologous end joining defective cells, this trend is less emphasized. The variation in cell survival levels throughout the cell cycle is less prominent in cells exposed to high-LET heavy ions when compared with low LET, but this mechanism has not been well understood until recently. Involvement of several DSB repair proteins is suggested to underlie this interesting phenomenon. Recent improvements in radiation-induced foci studies combined with high-LET heavy ion exposure could provide a useful opportunity for more in depth study of DSB repair processes. Accelerated heavy ions have become valuable tools to investigate the molecular mechanisms underlying repair of DNA DSBs, the most crucial form of DNA damage induced by radiation and various chemotherapeutic agents. Copyright © 2011 UICC.

Accelerated habit formation following amphetamine exposure is reversed by D1, but enhanced by D2, receptor antagonists

PubMed Central

Nelson, Andrew J. D.; Killcross, Simon

2013-01-01

Repeated exposure to the psychostimulant amphetamine has been shown to disrupt goal-directed instrumental actions and promote the early and abnormal development of goal-insensitive habitual responding (Nelson and Killcross, 2006). To investigate the neuropharmacological specificity of this effect as well as restore goal-directed responding in animals with pre-training amphetamine exposure, animals were treated with the non-selective dopamine antagonist α-flupenthixol, the selective D1 antagonist SCH 23390 or the selective D2 antagonist eticlopride, prior to instrumental training (three sessions). Subsequently, the reinforcer was paired with LiCL-induced gastric-malaise and animals were given a test of goal-sensitivity both in extinction and reacquisition. The effect of these dopaminergic antagonists on the sensitivity of lever press performance to outcome devaluation was assessed in animals with pre-training exposure to amphetamine (Experiments 1A–C) or in non-sensitized animals (Experiment 2). Both α-flupenthixol and SCH23390 reversed accelerated habit formation following amphetamine sensitization. However, eticlopride appeared to enhance this effect and render instrumental performance compulsive as these animals were unable to inhibit responding both in extinction and reacquisition, even though a consumption test confirmed they had acquired an aversion to the reinforcer. These findings demonstrate that amphetamine induced-disruption of goal-directed behavior is mediated by activity at distinct dopamine receptor subtypes and may represent a putative model of the neurochemical processes involved in the loss of voluntary control over behavior. PMID:23720609

Surface Cracking and Interface Reaction Associated Delamination Failure of Thermal and Environmental Barrier Coatings

NASA Technical Reports Server (NTRS)

Zhu, Dong-Ming; Choi, Sung R.; Eldridge, Jeffrey I.; Lee, Kang N.; Miller, Robert A.

2003-01-01

In this paper, surface cracking and interface reactions of a BSAS coating and a multi-layer ZrO2-8wt%Y2O3 and mullite/BSAS/Si thermal and environmental barrier coating system on SiC/SiC ceramic matrix composites were characterized after long-term combined laser thermal gradient and furnace cyclic tests in a water vapor containing environment. The surface cracking was analyzed based on the coating thermal gradient sintering behavior and thermal expansion mismatch stress characteristics under the thermal cyclic conditions. The interface reactions, which were largely enhanced by the coating surface cracking in the water vapor environment, were investigated in detail, and the reaction phases were identified for the coating system after the long-term exposure. The accelerated coating delamination failure was attributed to the increased delamination driving force under the thermal gradient cyclic loading and the reduced interface adhesion due to the detrimental interface reactions.

Surface Cracking and Interface Reaction Associated Delamination Failure of Thermal and Environmental Barrier Coatings

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Choi, Sung R.; Eldridge, Jeffrey I.; Lee, Kang N.; Miller, Robert A.

2003-01-01

In this paper, surface cracking and interface reactions of a BSAS coating and a multi-layer ZTO2-8wt%Y2O3 and mullite/BSAS/Si thermal and environmental barrier coating system on SiC/SiC ceramic matrix composites were characterized after long-term combined laser thermal gradient and furnace cyclic tests in a water vapor containing environment. The surface cracking was analyzed based on the coating thermal gradient sintering behavior and thermal expansion mismatch stress characteristics under the thermal cyclic conditions. The interface reactions, which were largely enhanced by the coating surface cracking in the water vapor environment, were investigated in detail, and the reaction phases were identified for the coating system after the long- term exposure. The accelerated coating delamination failure was attributed to the increased delamination driving force under the thermal gradient cyclic loading and the reduced interface adhesion due to the detrimental interface reactions.

The Spacelab Instrument Pointing System (IPS) and its first flight

NASA Astrophysics Data System (ADS)

Heusmann, H.; Wolf, P.

1985-11-01

The development of the Instrument Pointing System (IPS) as part of Spacelab's experimental apparatus for open Pallet direct space exposure, and its test flight aboard the Shuttle Orbiter are discussed. The IPS is a three-axis-controlled platform with stellar, sun and earth pointing modes, and a better than 1 arcsec pointing ability. The development of an 'inside-out gimbal' configuration with the platform acting like a joint between the unstable Shuttle and the inertially stabilized payload facilitated close to hemispherical pointing and the adaptability for payloads of almost any size. Gimbal axes torquers counteract Orbiter acceleration due to crew movement and thruster firings, and facilitate target acquisition and precision pointing, by command from a crew-engaged computer preprogrammed for all possible control steps. Carrying an experimental solar-physics payload, the IPS correctly performed all intended functions and withstood launch and orbital loads. Several anomalies were detected and successfully corrected in-flight.

Cherenkov and Scintillation Properties of Cubic Zirconium

NASA Technical Reports Server (NTRS)

Christl, M.J.; Adams, J.H.; Parnell, T.A.; Kuznetsov, E.N.

2008-01-01

Cubic zirconium (CZ) is a high index of refraction (n =2.17) material that we have investigated for Cherenkov counter applications. Laboratory and proton accelerator tests of an 18cc sample of CZ show that the expected fast Cherenkov response is accompanied by a longer scintillation component that can be separated by pulse shaping. This presents the possibility of novel particle spectrometers which exploits both properties of CZ. Other high index materials being examined for Cherenkov applications will be discussed. Results from laboratory tests and an accelerator exposure will be presented and a potential application in solar energetic particle instruments will be discussed

Accelerated laboratory weathering of acrylic lens materials

NASA Astrophysics Data System (ADS)

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

2014-09-01

Flat samples from various PMMA formulations subjected to accelerated laboratory weathering in an "Atlas Xenotest Alpha +" weathering device operating at 3 Sun irradiance remain transparent after 6.48GJ/m2 radiant exposure (300 - 400nm). Transmittance is reduced and yellowness index increases. However, the amount of change depends largely on the PMMA formulation. Higher UV absorber concentrations lead to smaller changes in optical properties. Based on a model of CPV efficiency for a particular power train, relative losses of efficiency are between 1 and 28%. Performance regarding these properties can be linked to the UV absorber type and concentrations used.

Community resilience under multi-hazards: time series measurement and it's strategies for improvement

NASA Astrophysics Data System (ADS)

Tian, Cong-shan; Fang, Yi-ping

2017-04-01

Multi - hazards stress is a big obsession that hampers the social and economic development in disaster - prone areas. There is a need to understand and manage drivers of vulnerability and adaptive capacity to the system of multiple geological hazards. Here we pilot three methods namely the multi - hazards resilience assessment model (new framework), the entropy weight method, and the assess social resilience to flood hazards model to measure the resilience to natural hazards of landslide and debris flow on community scale. Using one typical multi - hazards affected county in southwest China, 32 resilience indicators belonging to antecedent conditions, coping responses, adaptation (including learning), and hazard exposure are selected, and a composite index was calculated under the three methods mentioned above. Results show that the new framework reflected a more detailed fluctuation among the 16 years, despite of the overall similar trend between 2000 and 2015 under the three methods. Medical insurance coverage, unemployment insurance coverage, education degree, and hazard exposure are the main drivers of resilience. The most effective strategies for improving community resilience to multiple hazards are likely to be accelerating the development of education, improving the level of medical security, increasing unemployment insurance, and establishing multi - hazards prevention and mitigation systems.

High efficiency ion beam accelerator system

NASA Technical Reports Server (NTRS)

Aston, G.

1981-01-01

An ion accelerator system that successfully combines geometrical and electrostatic focusing principles is presented. This accelerator system uses thin, concave, multiple-hole, closely spaced graphite screen and focusing grids which are coupled to single slot accelerator and decelerator grids to provide high ion extraction efficiency and good focusing. Tests with the system showed a substantial improvement in ion beam current density and collimation as compared with a Pierce electrode configuration. Durability of the thin graphite screen and focusing grids has been proven, and tests are being performed to determine the minimum screen and focusing grid spacing and thickness required to extract the maximum reliable beam current density. Compared with present neutral beam injector accelerator systems, this one has more efficient ion extraction, easier grid alignment, easier fabrication, a less cumbersome design, and the capacity to be constructed in a modular fashion. Conceptual neutral beam injector designs using this modular approach have electrostatic beam deflection plates downstream of each module.

Design and Construction of Detector and Data Acquisition Elements for Proton Computed Tomography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fermi Research Alliance; Northern Illinois University

2015-07-15

Proton computed tomography (pCT) offers an alternative to x-ray imaging with potential for three-dimensional imaging, reduced radiation exposure, and in-situ imaging. Northern Illinois University (NIU) is developing a second-generation proton computed tomography system with a goal of demonstrating the feasibility of three-dimensional imaging within clinically realistic imaging times. The second-generation pCT system is comprised of a tracking system, a calorimeter, data acquisition, a computing farm, and software algorithms. The proton beam encounters the upstream tracking detectors, the patient or phantom, the downstream tracking detectors, and a calorimeter. The schematic layout of the PCT system is shown. The data acquisition sendsmore » the proton scattering information to an offline computing farm. Major innovations of the second generation pCT project involve an increased data acquisition rate ( MHz range) and development of three-dimensional imaging algorithms. The Fermilab Particle Physics Division and Northern Illinois Center for Accelerator and Detector Development at Northern Illinois University worked together to design and construct the tracking detectors, calorimeter, readout electronics and detector mounting system.« less

CD4 T-Cell Memory Generation and Maintenance

PubMed Central

Gasper, David J.; Tejera, Melba Marie; Suresh, M.

2014-01-01

Immunologic memory is the adaptive immune system's powerful ability to remember a previous antigen encounter and react with accelerated vigor upon antigen re-exposure. It provides durable protection against reinfection with pathogens and is the foundation for vaccine-induced immunity. Unlike the relatively restricted immunologic purview of memory B cells and CD8 T cells, the field of CD4 T-cell memory must account for multiple distinct lineages with diverse effector functions, the issue of lineage commitment and plasticity, and the variable distribution of memory cells within each lineage. Here, we discuss the evidence for lineage-specific CD4 T-cell memory and summarize the known factors contributing to memory-cell generation, plasticity, and long-term maintenance. PMID:24940912

A small amount of tetrachloroethylene ingestion from drinking water accelerates antigen-stimulated allergic responses.

PubMed

Seo, Makoto; Yamagiwa, Takeo; Kobayashi, Ryo; Ikeda, Koji; Satoh, Masahiko; Inagaki, Naoki; Nagai, Hiroichi; Nagase, Hisamitsu

2008-01-01

Previously, we observed that tetrachloroethylene (perchloroethylene, PCE) increased histamine release and inflammatory mediator production from antigen-stimulated mast cells. In this study, we examined the enhancing effect of low concentrations of PCE in drinking water on antigen-stimulated allergic responses. After exposure of Wistar rats to PCE in drinking water for 2 or 4 weeks, we performed a passive cutaneous anaphylaxis (PCA) reaction. PCE exposure for 4 weeks enhanced PCA reaction in a dose-dependent manner. In pathological studies, PCE exposure for 2 weeks exacerbated inflammation characterized by infiltration of lymphocytes and accumulation of mast cells around the vessel. Non-purified mast cells (NPMCs) from rats treated with 1mg/L PCE in drinking water for 2 weeks increased antigen-stimulated histamine release. Furthermore, the leukocytes of rats treated with PCE in drinking water for 4 weeks showed increased interleukin (IL)-4 expression. The mechanism of enhancing the PCA reaction is assumed to be that PCE increases IL-4 production and PCE causes T helper (Th) 1/Th2-type helper T-cell imbalance and increases histamine release from excessively accumulated mast cells. The results suggest that the intake of PCE in drinking water, even at a low concentration, leads to the initiation and acceleration of allergic diseases.

TU-H-BRA-06: Characterization of a Linear Accelerator Operating in a Compact MRIGuided Radiation Therapy System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Green, O; Mutic, S; Li, H

2016-06-15

Purpose: To describe the performance of a linear accelerator operating in a compact MRI-guided radiation therapy system. Methods: A commercial linear accelerator was placed in an MRI unit that is employed in a commercial MR-based image guided radiation therapy (IGRT) system. The linear accelerator components were placed within magnetic field-reducing hardware that provided magnetic fields of less than 40 G for the magnetron, gun driver, and port circulator, with 1 G for the linear accelerator. The system did not employ a flattening filter. The test linear accelerator was an industrial 4 MV model that was employed to test the abilitymore » to run an accelerator in the MR environment. An MR-compatible diode detector array was used to measure the beam profiles with the accelerator outside and inside the MR field and with the gradient coils on and off to examine if there was any effect on the delivered dose distribution. The beam profiles and time characteristics of the beam were measured. Results: The beam profiles exhibited characteristic unflattened Bremsstrahlung features with less than ±1.5% differences in the profile magnitude when the system was outside and inside the magnet and less than 1% differences with the gradient coils on and off. The central axis dose rate fluctuated by less than 1% over a 30 second period when outside and inside the MRI. Conclusion: A linaccompatible MR design has been shown to be effective in not perturbing the operation of a commercial linear accelerator. While the accelerator used in the tests was 4MV, there is nothing fundamentally different with the operation of a 6MV unit, implying that the design will enable operation of the proposed clinical unit. Research funding provided by ViewRay, Inc.« less

EuCARD2: enhanced accelerator research and development in Europe

NASA Astrophysics Data System (ADS)

Romaniuk, Ryszard S.

2013-10-01

Accelerator science and technology is one of a key enablers of the developments in the particle physic, photon physics and also applications in medicine and industry. EuCARD2 is an European research project which will be realized during 2013-2017 inside the EC FP7 framework. The project concerns the development and coordination of European Accelerator Research and Development. The project is particularly important, to a number of domestic laboratories, due to some plans to build large accelerator infrastructure in Poland. Large accelerator infrastructure of fundamental and applied research character stimulates around it the development and industrial applications as well as biomedical of advanced accelerators, material research and engineering, cryo-technology, mechatronics, robotics, and in particular electronics - like networked measurement and control systems, sensors, computer systems, automation and control systems. The paper presents a digest of the European project EuCARD2 which is Enhanced European Coordination for Accelerator Research and Development. The paper presents a digest of the research results and assumptions in the domain of accelerator science and technology in Europe, shown during the final fourth annual meeting of the EuCARD - European Coordination of Accelerator R&D, and the kick-off meeting of the EuCARD2. There are debated a few basic groups of accelerator systems components like: measurement - control networks of large geometrical extent, multichannel systems for large amounts of metrological data acquisition, precision photonic networks of reference time, frequency and phase distribution, high field magnets, superconducting cavities, novel beam collimators, etc. The paper bases on the following materials: Internet and Intranet documents combined with EuCARD2, Description of Work FP7 EuCARD-2 DoW-312453, 2013-02-13, and discussions and preparatory materials worked on by Eucard-2 initiators.

Transfer RNAs Mediate the Rapid Adaptation of Escherichia coli to Oxidative Stress

PubMed Central

Du, Gaofei; Sun, Xuesong; He, Qing-Yu; Zhang, Gong

2015-01-01

Translational systems can respond promptly to sudden environmental changes to provide rapid adaptations to environmental stress. Unlike the well-studied translational responses to oxidative stress in eukaryotic systems, little is known regarding how prokaryotes respond rapidly to oxidative stress in terms of translation. In this study, we measured protein synthesis from the entire Escherichia coli proteome and found that protein synthesis was severely slowed down under oxidative stress. With unchanged translation initiation, this slowdown was caused by decreased translation elongation speed. We further confirmed by tRNA sequencing and qRT-PCR that this deceleration was caused by a global, enzymatic downregulation of almost all tRNA species shortly after exposure to oxidative agents. Elevation in tRNA levels accelerated translation and protected E. coli against oxidative stress caused by hydrogen peroxide and the antibiotic ciprofloxacin. Our results showed that the global regulation of tRNAs mediates the rapid adjustment of the E. coli translation system for prompt adaptation to oxidative stress. PMID:26090660

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khan, Salman, E-mail: sksafi@comsats.edu.pk

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

OARE and SAMS on STS-94/MSL-1

NASA Technical Reports Server (NTRS)

Moskowitz, Milton; Hrovat, Kenneth; McPherson, Kevin; Tschen, Peter; DeLombard, Richard; Nati, Maurizio

1998-01-01

Four microgravity acceleration measurement instruments were included on MSL-1 to measure the accelerations and vibrations to which science experiments were exposed during their operation on the mission. The data were processed and presented to the principal investigators in a variety of formats to aid their assessment of the microgravity environment during their experiment operations. Two accelerometer systems managed by the NASA Lewis Research Center (LeRC) supported the MSL-1 mission: the Orbital Acceleration Research Experiment (OARE), and the Space Acceleration Measurement System (SAMS). In addition, the Microgravity Measurement Assembly (MMA) and the Quasi- Steady Acceleration Measurement (QSAM) system, both sponsored by the Microgravity Research Division, collected acceleration data as a part of the MSL-1 mission. The NIMA was funded and designed by the European Space Agency in the Netherlands (ESA/ESTEC), and the QSAM system was funded and designed by the German Space Agency (DLR). The Principal Investigator Microgravity Services (PIMS) project at the NASA Lewis Research Center (LeRC) supports Principal Investigators (PIs) of the Microgravity science community as they evaluate the effects of acceleration on their experiments. PIMS primary responsibility is to support NASA-sponsored investigators in the area of acceleration data analysis and interpretation. A mission summary report was prepared and published by PIMS in order to furnish interested experiment investigators with a guide for evaluating the acceleration environment during the MSL-1 mission.

XPS Investigation on Changes in UO 2 Speciation following Exposure to Humidity

DOE PAGES

Donald, Scott B.; Davisson, M. Lee; Nelson, Art J.

2016-04-27

High purity UO 2powder samples were subjected to accelerated aging under controlled conditions with relative humidity ranging from 34% to 98%. Characterization of the chemical speciation of the products was accomplished using X-ray photoelectron spectroscopy (XPS). A shift to higher uranium oxidation states was found to be directly correlated to increased relative humidity exposure. In addition, the relative abundance of O 2-, OH -, and H 2O was found to vary with exposure time. Therefore, it is expected that uranium oxide materials exposed to high relative humidity conditions during processing and storage would display a similar increase in average uraniummore » valence.« less

The Glyphosate-Based Herbicide Roundup Does not Elevate Genome-Wide Mutagenesis of Escherichia coli.

PubMed

Tincher, Clayton; Long, Hongan; Behringer, Megan; Walker, Noah; Lynch, Michael

2017-10-05

Mutations induced by pollutants may promote pathogen evolution, for example by accelerating mutations conferring antibiotic resistance. Generally, evaluating the genome-wide mutagenic effects of long-term sublethal pollutant exposure at single-nucleotide resolution is extremely difficult. To overcome this technical barrier, we use the mutation accumulation/whole-genome sequencing (MA/WGS) method as a mutagenicity test, to quantitatively evaluate genome-wide mutagenesis of Escherichia coli after long-term exposure to a wide gradient of the glyphosate-based herbicide (GBH) Roundup Concentrate Plus. The genome-wide mutation rate decreases as GBH concentration increases, suggesting that even long-term GBH exposure does not compromise the genome stability of bacteria. Copyright © 2017 Tincher et al.

Dysrhythmias in Laypersons During Centrifuge-Simulated Suborbital Spaceflight.

PubMed

Suresh, Rahul; Blue, Rebecca S; Mathers, Charles H; Castleberry, Tarah L; Vanderploeg, James M

2017-11-01

There are limited data on cardiac dysrhythmias in laypersons during hypergravity exposure. We report layperson electrocardiograph (ECG) findings and tolerance of dysrhythmias during centrifuge-simulated suborbital spaceflight. Volunteers participated in varied-length centrifuge training programs of 2-7 centrifuge runs over 0.5-2 d, culminating in two simulated suborbital spaceflights of combined +Gz and +Gx (peak +4.0 Gz, +6.0 Gx, duration 5 s). Monitors recorded pre- and post-run mean arterial blood pressure (MAP), 6-s average heart rate (HR) collected at prespecified points during exposures, documented dysrhythmias observed on continuous 3-lead ECG, self-reported symptoms, and objective signs of intolerance on real-time video monitoring. Participating in the study were 148 subjects (43 women). Documented dysrhythmias included sinus pause (N = 5), couplet premature ventricular contractions (N = 4), bigeminy (N = 3), accelerated idioventricular rhythm (N = 1), and relative bradycardia (RB, defined as a transient HR drop of >20 bpm; N = 63). None were associated with subjective symptoms or objective signs of acceleration intolerance. Episodes of RB occurred only during +Gx exposures. Subjects had a higher post-run vs. pre-run MAP after all exposures, but demonstrated no difference in pre- and post-run HR. RB was more common in men, younger individuals, and subjects experiencing more centrifuge runs. Dysrhythmias in laypersons undergoing simulated suborbital spaceflight were well tolerated, though RB was frequently noted during short-duration +Gx exposure. No subjects demonstrated associated symptoms or objective hemodynamic sequelae from these events. Even so, heightened caution remains warranted when monitoring dysrhythmias in laypersons with significant cardiopulmonary disease or taking medications that modulate cardiac conduction.Suresh R, Blue RS, Mathers CH, Castleberry TL, Vanderploeg JM. Dysrhythmias in laypersons during centrifuge-stimulated suborbital spaceflight. Aerosp Med Hum Perform. 2017; 88(11):1008-1015.

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

PubMed Central

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

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

A beamline systems model for Accelerator-Driven Transmutation Technology (ADTT) facilities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Todd, A.M.M.; Paulson, C.C.; Peacock, M.A.

1995-10-01

A beamline systems code, that is being developed for Accelerator-Driven Transmutation Technology (ADTT) facility trade studies, is described. The overall program is a joint Grumman, G.H. Gillespie Associates (GHGA) and Los Alamos National Laboratory effort. The GHGA Accelerator Systems Model (ASM) has been adopted as the framework on which this effort is based. Relevant accelerator and beam transport models from earlier Grumman systems codes are being adapted to this framework. Preliminary physics and engineering models for each ADTT beamline component have been constructed. Examples noted include a Bridge Coupled Drift Tube Linac (BCDTL) and the accelerator thermal system. A decisionmore » has been made to confine the ASM framework principally to beamline modeling, while detailed target/blanket, balance-of-plant and facility costing analysis will be performed externally. An interfacing external balance-of-plant and facility costing model, which will permit the performance of iterative facility trade studies, is under separate development. An ABC (Accelerator Based Conversion) example is used to highlight the present models and capabilities.« less

A beamline systems model for Accelerator-Driven Transmutation Technology (ADTT) facilities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Todd, Alan M. M.; Paulson, C. C.; Peacock, M. A.

1995-09-15

A beamline systems code, that is being developed for Accelerator-Driven Transmutation Technology (ADTT) facility trade studies, is described. The overall program is a joint Grumman, G. H. Gillespie Associates (GHGA) and Los Alamos National Laboratory effort. The GHGA Accelerator Systems Model (ASM) has been adopted as the framework on which this effort is based. Relevant accelerator and beam transport models from earlier Grumman systems codes are being adapted to this framework. Preliminary physics and engineering models for each ADTT beamline component have been constructed. Examples noted include a Bridge Coupled Drift Tube Linac (BCDTL) and the accelerator thermal system. Amore » decision has been made to confine the ASM framework principally to beamline modeling, while detailed target/blanket, balance-of-plant and facility costing analysis will be performed externally. An interfacing external balance-of-plant and facility costing model, which will permit the performance of iterative facility trade studies, is under separate development. An ABC (Accelerator Based Conversion) example is used to highlight the present models and capabilities.« less

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

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

2013-01-01

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

RECOVERY OF VASCULAR FUNCTION AFTER EXPOSURE TO A SINGLE BOUT OF SEGMENTAL VIBRATION

PubMed Central

Krajnak, Kristine; Waugh, Stacey; Miller, G. Roger; Johnson, Claud

2015-01-01

Work rotation schedules may be used to reduce the negative effects of vibration on vascular function. This study determined how long it takes vascular function to recover after a single exposure to vibration in rats (125 Hz, acceleration 5g). The responsiveness of rat-tail arteries to the vasoconstricting factor UK14304, an α2C-adrenoreceptor agonist, and the vasodilating factor acetylcholine (ACh) were measured ex vivo 1, 2, 7, or 9 d after exposure to a single bout of vibration. Vasoconstriction induced by UK14304 returned to control levels after 1 d of recovery. However, re-dilation induced by ACh did not return to baseline until after 9 d of recovery. Exposure to vibration exerted prolonged effects on peripheral vascular function, and altered vascular responses to a subsequent exposure. To optimize the positive results of work rotation schedules, it is suggested that studies assessing recovery of vascular function after exposure to a single bout of vibration be performed in humans. PMID:25072825

Evaluation and modeling of the potential effects of a module manufacturing anomaly

DOE PAGES

Kempe, Michael D.; Jordan, Dirk C.

2017-07-13

Photovoltaic lifetime predictions are in great demand, but are exceedingly difficult to achieve with uncertainties small enough to be useful. During the construction of photovoltaic modules, small unplanned variability in materials or processes can have profound effects on module durability. Thus, continual monitoring of production quality is needed. In the subject production run, module quality, as monitored by damp heat testing, revealed a subset of modules that were prone to higher degradation rates. An assessment of the potential long-term power loss and mitigation strategies was needed. To do this, modules were exposed to variable levels of humidity and temperature withmore » periodic monitoring. The analysis takes into account the kinetics of the degradation and the spatially and temporally varying humidity content within the module during accelerated stress testing. This is an important aspect for extrapolating laboratory results to field exposure because moisture ingress is diffusion limited in most laboratory module tests but not limited in these fielded modules. This analysis predicted that although a solder flux induce degradation mechanism is significant in accelerated stress test, this is probably an artifact of a process with a very large acceleration factor that is not likely to be significant for deployed modules. The degradation mechanism affected a limited area around the tabbing helping to minimize the effect. Furthermore, three years after the system was commissioned, the fielded modules indeed show no significant power loss.« less

Evaluation and modeling of the potential effects of a module manufacturing anomaly

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kempe, Michael D.; Jordan, Dirk C.

Photovoltaic lifetime predictions are in great demand, but are exceedingly difficult to achieve with uncertainties small enough to be useful. During the construction of photovoltaic modules, small unplanned variability in materials or processes can have profound effects on module durability. Thus, continual monitoring of production quality is needed. In the subject production run, module quality, as monitored by damp heat testing, revealed a subset of modules that were prone to higher degradation rates. An assessment of the potential long-term power loss and mitigation strategies was needed. To do this, modules were exposed to variable levels of humidity and temperature withmore » periodic monitoring. The analysis takes into account the kinetics of the degradation and the spatially and temporally varying humidity content within the module during accelerated stress testing. This is an important aspect for extrapolating laboratory results to field exposure because moisture ingress is diffusion limited in most laboratory module tests but not limited in these fielded modules. This analysis predicted that although a solder flux induce degradation mechanism is significant in accelerated stress test, this is probably an artifact of a process with a very large acceleration factor that is not likely to be significant for deployed modules. The degradation mechanism affected a limited area around the tabbing helping to minimize the effect. Furthermore, three years after the system was commissioned, the fielded modules indeed show no significant power loss.« less

THE FAULT DIVERTER-A PROTECTIVE DEVICE FOR HIGH-POWER ELECTRON TUBES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, B.H.

1957-08-01

Fault diverters, or crowbars, have proven to be very effective protection against transient-induced power arcs within accelerator oscillator tubes. This device short circuits the oscillator-plate power supply in the event of an over-current, thus removing the power flow from the fault within a few microseconds. Ignitrons, thyratrons, and triggered spark gaps are used for this purpose. The power supply is protected from the short circuit either by a current-limiting device or a high-speed contactor which removes the system from the power lines within a few milliseconds. The fault diverters, and associated circuitry, used on several of the accelerators in Berkeleymore » and Livermore are described. (auth) l73O Studies of pi -meson and K-meson interactions were continued with counters, emulsions, and the 10-inch liquid hydrogen bubble chanmber. Six emulsion exposures were made for external groups to a pi -meson beam, three to Kmeson beams, two to a neutral-particle beanm, and three to the internal proton beam. An H-D reaction, catalyzed by mu mesons, was observed in the 10-inch liquid hydrogen bubble chamber. Absorption cross-section measurements for antiprotons were continued, using counters. Nineteen target bombardments were made for the chemistry group. A technique of producing two or more secondary-particle beam pulses per acceleration cycle, using different targets, has been successfully tried and used. (For preceding period see UCRL- 36l4.1 (auth)« less

Dehydration Accelerates Respiration in Postharvest Sugarbeet Roots

USDA-ARS?s Scientific Manuscript database

Sugarbeet (Beta vulgaris L.) roots lose water during storage and often become severely dehydrated after prolonged storage and at the outer regions of storage piles which have greater wind and sun exposure. Sucrose loss is known to be elevated in dehydrated roots, although the metabolic processes re...

AN EFFICIENT AQUEOUS N-HETEROCYCLIZATION OF ANILINE DERIVATIVES: MICROWAVE-ASSISTED SYNTHESIS OF N-ARYL AZACYCLOALKANES

EPA Science Inventory

N-aryl azacycloalkanes, an important class of building blocks in natural product and pharmaceuticals, are synthesized via an efficient and simple eco-friendly protocol that involves double N-alkylation of aniline derivatives. The reaction is accelerated by exposure to microwaves ...

Evaluation of several types of curing and protective materials for concrete : interim report part III : performance.

DOT National Transportation Integrated Search

1973-01-01

Various curing and/or protective coatings were evaluated under three conditions: (1) accelerated laboratory freezing and thawing of specimens in 2 percent sodium chloride solution, (2) exposure in an outdoor area of slabs which were subjected to cont...

Evaluation of several types of curing and protective materials for concrete : part IV : final report on performance.

DOT National Transportation Integrated Search

1975-01-01

Various curing and/or protective coatings were evaluated under three conditions: (1) accelerated laboratory freezing and thawing of specimens in 2 percent sodium chloride solution, (2) exposure in an outdoor area of slabs subjected to controlled appl...

[Measurement and analysis of hand-transmitted vibration of vibration tools in workplace for automobile casting and assembly].

PubMed

Xie, X S; Qi, C; Du, X Y; Shi, W W; Zhang, M

2016-02-20

To investigate the features of hand-transmitted vibration of common vibration tools in the workplace for automobile casting and assembly. From September to October, 2014, measurement and spectral analysis were performed for 16 typical hand tools(including percussion drill, pneumatic wrench, grinding machine, internal grinder, and arc welding machine) in 6 workplaces for automobile casting and assembly according to ISO 5349-1-2001 Mechanical vibration-Measurement and evaluation of human exposure to hand-transmitted vibration-part 1: General requirements and ISO 5349-2-2001 Mechanical vibration-Measurement and evaluation of human exposure to hand-transmitted vibration-Part 2: Practical guidance for measurement in the workplace. The vibration acceleration waveforms of shearing machine, arc welding machine, and pneumatic wrench were mainly impact wave and random wave, while those of internal grinder, angle grinder, percussion drill, and grinding machine were mainly long-and short-period waves. The daily exposure duration to vibration of electric wrench, pneumatic wrench, shearing machine, percussion drill, and internal grinder was about 150 minutes, while that of plasma cutting machine, angle grinder, grinding machine, bench grinder, and arc welding machine was about 400 minutes. The range of vibration total value(ahv) was as follows: pneumatic wrench 0.30~11.04 m/s(2), grinding wheel 1.61~8.97 m/s(2), internal grinder 1.46~8.70 m/s(2), percussion drill 11.10~14.50 m/s(2), and arc welding machine 0.21~2.18 m/s(2). The workers engaged in cleaning had the longest daily exposure duration to vibration, and the effective value of 8-hour energy-equivalent frequency-weighted acceleration for them[A(8)] was 8.03 m/s(2), while this value for workers engaged in assembly was 4.78 m/s(2). The frequency spectrogram with an 1/3-time frequency interval showed that grinding machine, angle grinder, and percussion drill had a high vibration acceleration, and the vibration limit curve was recommended for those with a frequency higher than 400 min/d. The workers who are engaged in cleaning, grinding, and a few positions of assembly and use grinding machine, angle grinder, internal grinder, and percussion drill are exposed to vibrations with a high vibration acceleration and at a high position of the frequency spectrum. The hand-transmitted vibration in the positions of cutting, polishing, and cleaning in automobile casting has great harm, and the harm caused by pneumatic wrench in automobile assembly should be taken seriously.

A proposal for antiparallel acceleration of positrons using CEBAF

DOE PAGES

Tiefenback, M.; Wojtsekhowski, B.

2018-05-01

Here, we present a scheme for positron beam acceleration in CEBAF antiparallel to the normal electron path, requiring no change in polarity of the magnet systems. This feature is essential to the principal benefit: enabling extremely simple configuration changes between conventional (clockwise) e - acceleration and counter clockwise e + acceleration. Additionally, it appears possible to configure the accelerating cavity phases to support concurrent acceleration of the electron and positron beams. The last mode also may enable use of the higher peak current electron beam for system diagnostics. The inherent penalty of the concurrent mode in acceleration efficiency and increasedmore » energy spread may render this a commissioning-only diagnostic option, but the possibility appears worthy of consideration.« less

A proposal for antiparallel acceleration of positrons using CEBAF

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tiefenback, M.; Wojtsekhowski, B.

Here, we present a scheme for positron beam acceleration in CEBAF antiparallel to the normal electron path, requiring no change in polarity of the magnet systems. This feature is essential to the principal benefit: enabling extremely simple configuration changes between conventional (clockwise) e - acceleration and counter clockwise e + acceleration. Additionally, it appears possible to configure the accelerating cavity phases to support concurrent acceleration of the electron and positron beams. The last mode also may enable use of the higher peak current electron beam for system diagnostics. The inherent penalty of the concurrent mode in acceleration efficiency and increasedmore » energy spread may render this a commissioning-only diagnostic option, but the possibility appears worthy of consideration.« less

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

PubMed Central

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

2001-01-01

OBJECTIVES—To examine whether underground construction workers exposed to tunnelling pollutants over a follow up period of 8 years have an increased risk of decline in lung function and respiratory symptoms compared with reference subjects working outside the tunnel atmosphere, and relate the findings to job groups and cumulative exposure to dust and gases.
METHODS—96 Tunnel workers and a reference group of 249 other heavy construction workers were examined in 1991 and re-examined in 1999. Exposure measurements were carried out to estimate personal cumulative exposure to total dust, respirable dust, α-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 α-quartz in tunnel workers varied from 1.2-3.6 mg/m3 (respirable dust) and 0.019-0.044 mg/m3 (α-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 α-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 α-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

Status of MAPA (Modular Accelerator Physics Analysis) and the Tech-X Object-Oriented Accelerator Library

NASA Astrophysics Data System (ADS)

Cary, J. R.; Shasharina, S.; Bruhwiler, D. L.

1998-04-01

The MAPA code is a fully interactive accelerator modeling and design tool consisting of a GUI and two object-oriented C++ libraries: a general library suitable for treatment of any dynamical system, and an accelerator library including many element types plus an accelerator class. The accelerator library inherits directly from the system library, which uses hash tables to store any relevant parameters or strings. The GUI can access these hash tables in a general way, allowing the user to invoke a window displaying all relevant parameters for a particular element type or for the accelerator class, with the option to change those parameters. The system library can advance an arbitrary number of dynamical variables through an arbitrary mapping. The accelerator class inherits this capability and overloads the relevant functions to advance the phase space variables of a charged particle through a string of elements. Among other things, the GUI makes phase space plots and finds fixed points of the map. We discuss the object hierarchy of the two libraries and use of the code.

Head Impact Exposure in Youth Football: Comparing Age- and Weight-Based Levels of Play.

PubMed

Kelley, Mireille E; Urban, Jillian E; Miller, Logan E; Jones, Derek A; Espeland, Mark A; Davenport, Elizabeth M; Whitlow, Christopher T; Maldjian, Joseph A; Stitzel, Joel D

2017-06-01

Approximately 5,000,000 athletes play organized football in the United States, and youth athletes constitute the largest proportion with ∼3,500,000 participants. Investigations of head impact exposure (HIE) in youth football have been limited in size and duration. The objective of this study was to evaluate HIE of athletes participating in three age- and weight-based levels of play within a single youth football organization over four seasons. Head impact data were collected using the Head Impact Telemetry (HIT) System. Mixed effects linear models were fitted, and Wald tests were used to assess differences in head accelerations and number of impacts among levels and session type (competitions vs. practices). The three levels studied were levels A (n = 39, age = 10.8 ± 0.7 years, weight = 97.5 ± 11.8 lb), B (n = 48, age = 11.9 ± 0.5 years, weight = 106.1 ± 13.8 lb), and C (n = 32, age = 13.0 ± 0.5 years, weight = 126.5 ± 18.6 lb). A total of 40,538 head impacts were measured. The median/95th percentile linear head acceleration for levels A, B, and C was 19.8/49.4g, 20.6/51.0g, and 22.0/57.9g, respectively. Level C had significantly greater mean linear acceleration than both levels A (p = 0.005) and B (p = 0.02). There were a significantly greater number of impacts per player in a competition than in a practice session for all levels (A, p = 0.0005, B, p = 0.0019, and C, p < 0.0001). Athletes at lower levels experienced a greater percentage of their high magnitude impacts (≥ 80g) in practice, whereas those at the highest level experienced a greater percentage of their high magnitude impacts in competition. These data improve our understanding of HIE within youth football and are an important step in making evidence-based decisions to reduce HIE.

Head Impact Exposure in Youth Football: Comparing Age- and Weight-Based Levels of Play

PubMed Central

Kelley, Mireille E.; Urban, Jillian E.; Miller, Logan E.; Jones, Derek A.; Espeland, Mark A.; Davenport, Elizabeth M.; Whitlow, Christopher T.; Maldjian, Joseph A.

2017-01-01

Abstract Approximately 5,000,000 athletes play organized football in the United States, and youth athletes constitute the largest proportion with ∼3,500,000 participants. Investigations of head impact exposure (HIE) in youth football have been limited in size and duration. The objective of this study was to evaluate HIE of athletes participating in three age- and weight-based levels of play within a single youth football organization over four seasons. Head impact data were collected using the Head Impact Telemetry (HIT) System. Mixed effects linear models were fitted, and Wald tests were used to assess differences in head accelerations and number of impacts among levels and session type (competitions vs. practices). The three levels studied were levels A (n = 39, age = 10.8 ± 0.7 years, weight = 97.5 ± 11.8 lb), B (n = 48, age = 11.9 ± 0.5 years, weight = 106.1 ± 13.8 lb), and C (n = 32, age = 13.0 ± 0.5 years, weight = 126.5 ± 18.6 lb). A total of 40,538 head impacts were measured. The median/95th percentile linear head acceleration for levels A, B, and C was 19.8/49.4g, 20.6/51.0g, and 22.0/57.9g, respectively. Level C had significantly greater mean linear acceleration than both levels A (p = 0.005) and B (p = 0.02). There were a significantly greater number of impacts per player in a competition than in a practice session for all levels (A, p = 0.0005, B, p = 0.0019, and C, p < 0.0001). Athletes at lower levels experienced a greater percentage of their high magnitude impacts (≥ 80g) in practice, whereas those at the highest level experienced a greater percentage of their high magnitude impacts in competition. These data improve our understanding of HIE within youth football and are an important step in making evidence-based decisions to reduce HIE. PMID:28274184

An accelerated exposure and testing apparatus for building joint sealants

NASA Astrophysics Data System (ADS)

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

2013-09-01

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

An accelerated exposure and testing apparatus for building joint sealants.

PubMed

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

2013-09-01

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

Multi-Billion Shot, High-Fluence Exposure of Cr(4+): YAG Passive Q-Switch

NASA Technical Reports Server (NTRS)

Stephen, Mark A.; Dallas, Joseph L.; Afzal, Robert S.

1997-01-01

NASA's Goddard Space Flight Center is developing the Geoscience Laser Altimeter System (GLAS) employing a diode pumped, Q-Switched, ND:YAG laser operating at 40 Hz repetition rate. To meet the five-year mission lifetime goal, a single transmitter would accumulate over 6.3 billion shots. Cr(4+):YAG is a promising candidate material for passively Q-switching the laser. Historically, the performance of saturable absorbers has degraded over long-duration usage. To measure the multi-billion shot performance of Cr(4+):YAG, a passively Q-switched GLAS-like oscillator was tested at an accelerated repetition rate of 500 Hz. The intracavity fluence was calculated to be approximately 2.5 J/cm(exp 2). The laser was monitored autonomously for 165 days. There was no evidence of change in the material optical properties during the 7.2 billion shot test.. All observed changes in laser operation could be attributed to pump laser diode aging. This is the first demonstration of multi-billion shot exposure testing of Cr(4+):YAG in this pulse energy regime

Time-temperature-stress capabilities of composite materials for advanced supersonic technology application

NASA Technical Reports Server (NTRS)

Kerr, James R.; Haskins, James F.

1987-01-01

Advanced composites will play a key role in the development of the technology for the design and fabrication of future supersonic vehicles. However, incorporating the material into vehicle usage is contingent on accelerating the demonstration of service capacity and design technology. Because of the added material complexity and lack of extensive data, laboratory replication of the flight service will provide the most rapid method to document the airworthiness of advanced composite systems. Consequently, a laboratory program was conducted to determine the time-temperature-stress capabilities of several high temperature composites. Tests included were thermal aging, environmental aging, fatigue, creep, fracture, tensile, and real-time flight simulation exposure. The program had two phases. The first included all the material property determinations and aging and simulation exposures up through 10,000 hours. The second continued these tests up to 50,000 cumulative hours. This report presents the results of the Phase 1 baseline and 10,000-hr aging and flight simulation studies, the Phase 2 50,000-hr aging studies, and the Phase 2 flight simulation tests, some of which extended to almost 40,000 hours.

Space Radiation and Manned Mission: Interface Between Physics and Biology

NASA Astrophysics Data System (ADS)

Hei, Tom

2012-07-01

The natural radiation environment in space consists of a mixed field of high energy protons, heavy ions, electrons and alpha particles. Interplanetary travel to the International Space Station and any planned establishment of satellite colonies on other solar system implies radiation exposure to the crew and is a major concern to space agencies. With shielding, the radiation exposure level in manned space missions is likely to be chronic, low dose irradiation. Traditionally, our knowledge of biological effects of cosmic radiation in deep space is almost exclusively derived from ground-based accelerator experiments with heavy ions in animal or in vitro models. Radiobiological effects of low doses of ionizing radiation are subjected to modulations by various parameters including bystander effects, adaptive response, genomic instability and genetic susceptibility of the exposed individuals. Radiation dosimetry and modeling will provide conformational input in areas where data are difficult to acquire experimentally. However, modeling is only as good as the quality of input data. This lecture will discuss the interdependent nature of physics and biology in assessing the radiobiological response to space radiation.

The CSU Accelerator and FEL Facility

NASA Astrophysics Data System (ADS)

Biedron, Sandra; Milton, Stephen; D'Audney, Alex; Edelen, Jonathan; Einstein, Josh; Harris, John; Hall, Chris; Horovitz, Kahren; Martinez, Jorge; Morin, Auralee; Sipahi, Nihan; Sipahi, Taylan; Williams, Joel

2014-03-01

The Colorado State University (CSU) Accelerator Facility will include a 6-MeV L-Band electron linear accelerator (linac) with a free-electron laser (FEL) system capable of producing Terahertz (THz) radiation, a laser laboratory, a microwave test stand, and a magnetic test stand. The photocathode drive linac will be used in conjunction with a hybrid undulator capable of producing THz radiation. Details of the systems used in CSU Accelerator Facility are discussed.

Three-grid accelerator system for an ion propulsion engine

NASA Technical Reports Server (NTRS)

Brophy, John R. (Inventor)

1994-01-01

An apparatus is presented for an ion engine comprising a three-grid accelerator system with the decelerator grid biased negative of the beam plasma. This arrangement substantially reduces the charge-exchange ion current reaching the accelerator grid at high tank pressures, which minimizes erosion of the accelerator grid due to charge exchange ion sputtering, known to be the major accelerator grid wear mechanism. An improved method for life testing ion engines is also provided using the disclosed apparatus. In addition, the invention can also be applied in materials processing.

Spatial distribution of pulmonary blood flow in dogs in increased force environments

NASA Technical Reports Server (NTRS)

Greenleaf, J. F.; Ritman, E. L.; Chevalier, P. A.; Sass, D. J.; Wood, E. H.

1978-01-01

Spatial distribution of pulmonary blood flow during 2- to 3-min exposures to 6-8 Gy acceleration was studied, using radioactive microspheres in dogs, and compared to previously reported 1 Gy control distributions. Isotope distributions were measured by scintiscanning individual 1-cm-thick cross sections of excised, fixed lungs. Results indicate: (1) the fraction of cardiac output traversing left and right lungs did not change systematically with the duration and magnitude of acceleration; but (2) the fraction is strongly affected by the occurrence or absence of fast deep breaths, which cause an increase or decrease, respectively, in blood flow through the dependent lung; and (3) Gy acceleration caused a significant increase in relative pulmonary vascular resistance (PVR) in nondependent and dependent regions of the lung concurrent with a decrease in PVR in the midsagittal region of the thorax.

Accelerator Reactor Coupling for Energy Production in Advanced Nuclear Fuel Cycles

DOE PAGES

Brown, Nicholas R.; Heidet, Florent; Haj Tahar, Malek

2016-01-01

This article is a review of several accelerator–reactor interface issues and nuclear fuel cycle applications of acceleratordriven subcritical systems. The systems considered here have the primary goal of energy production, but that goal is accomplished via a specific application in various proposed nuclear fuel cycles, such as breed-and-burn of fertile material or burning of transuranic material. Several basic principles are reviewed, starting from the proton beam window including the target, blanket, reactor core, and up to the fuel cycle. We focus on issues of interest, such as the impact of the energy required to run the accelerator and associated systemsmore » on the potential electricity delivered to the grid. Accelerator-driven systems feature many of the constraints and issues associated with critical reactors, with the added challenges of subcritical operation and coupling to an accelerator. Reliable accelerator operation and avoidance of beam trips are critically important. One interesting challenge is measurement of blanket subcriticality level during operation. We also review the potential benefits of accelerator-driven systems in various nuclear fuel cycle applications. Ultimately, accelerator-driven subcritical systems with the goal of transmutation of transuranic material have lower 100,000-year radioactivity than a critical fast reactor with recycling of uranium and plutonium.« less

An adaptive cryptographic accelerator for network storage security on dynamically reconfigurable platform

NASA Astrophysics Data System (ADS)

Tang, Li; Liu, Jing-Ning; Feng, Dan; Tong, Wei

2008-12-01

Existing security solutions in network storage environment perform poorly because cryptographic operations (encryption and decryption) implemented in software can dramatically reduce system performance. In this paper we propose a cryptographic hardware accelerator on dynamically reconfigurable platform for the security of high performance network storage system. We employ a dynamic reconfigurable platform based on a FPGA to implement a PowerPCbased embedded system, which executes cryptographic algorithms. To reduce the reconfiguration latency, we apply prefetch scheduling. Moreover, the processing elements could be dynamically configured to support different cryptographic algorithms according to the request received by the accelerator. In the experiment, we have implemented AES (Rijndael) and 3DES cryptographic algorithms in the reconfigurable accelerator. Our proposed reconfigurable cryptographic accelerator could dramatically increase the performance comparing with the traditional software-based network storage systems.

A Summary of the Quasi-Steady Acceleration Environment on-Board STS-94 (MSL-1)

NASA Technical Reports Server (NTRS)

McPherson, Kevin M.; Nati, Maurizio; Touboul, Pierre; Schuette, Andreas; Sablon, Gert

1999-01-01

The continuous free-fall state of a low Earth orbit experienced by NASA's Orbiters results in a unique reduced gravity environment. While microgravity science experiments are conducted in this reduced gravity environment, various accelerometer systems measure and record the microgravity acceleration environment for real-time and post-flight correlation with microgravity science data. This overall microgravity acceleration environment is comprised of quasi-steady, oscillatory, and transient contributions. The First Microgravity Science Laboratory (MSL-1) payload was dedicated to experiments studying various microgravity science disciplines, including combustion, fluid physics, and materials processing. In support of the MSL-1 payload, two systems capable of measuring the quasi-steady acceleration environment were flown: the Orbital Acceleration Research Experiment (OARE) and the Microgravity Measurement Assembly (MMA) system's Accelerometre Spatiale Triaxiale most evident in the quasi-steady acceleration regime. Utilizing such quasi-steady events, a comparison and summary of the quasi-steady acceleration environment for STS-94 will be presented

Variability in hand-arm vibration during grinding operations.

PubMed

Liljelind, Ingrid; Wahlström, Jens; Nilsson, Leif; Toomingas, Allan; Burström, Lage

2011-04-01

Measurements of exposure to vibrations from hand-held tools are often conducted on a single occasion. However, repeated measurements may be crucial for estimating the actual dose with good precision. In addition, knowledge of determinants of exposure could be used to improve working conditions. The aim of this study was to assess hand-arm vibration (HAV) exposure during different grinding operations, in order to obtain estimates of the variance components and to evaluate the effect of work postures. Ten experienced operators used two compressed air-driven angle grinders of the same make in a simulated work task at a workplace. One part of the study consisted of using a grinder while assuming two different working postures: at a standard work bench (low) and on a wall with arms elevated and the work area adjusted to each operator's height (high). The workers repeated the task three times. In another part of the study, investigating the wheel wear, for each grinder, the operators used two new grinding wheels and with each wheel the operator performed two consecutive 1-min grinding tasks. Both grinding tasks were conducted on weld puddles of mild steel on a piece of mild steel. Measurements were taken according to ISO-standard 5349 [the equivalent hand-arm-weighted acceleration (m s(-2)) averaged over 1 min]. Mixed- and random-effects models were used to investigate the influence of the fixed variables and to estimate variance components. The equivalent hand-arm-weighted acceleration assessed when the task was performed on the bench and at the wall was 3.2 and 3.3 m s(-2), respectively. In the mixed-effects model, work posture was not a significant variable. The variables 'operator' and 'grinder' together explained only 12% of the exposure variability and 'grinding wheel' explained 47%; the residual variability of 41% remained unexplained. When the effect of grinding wheel wear was investigated in the random-effects model, 37% of the variability was associated with the wheel while minimal variability was associated with the operator or the grinder and 37% was unexplained. The interaction effect of grinder and operator explained 18% of the variability. In the wheel wear test, the equivalent hand-arm-weighted accelerations for Grinder 1 during the first and second grinding minutes were 3.4 and 2.9 m s(-2), respectively, and for Grinder 2, they were 3.1 and 2.9 m s(-2), respectively. For Grinder 1, the equivalent hand-arm-weighted acceleration during the first grinding minute was significantly higher (P = 0.04) than during the second minute. Work posture during grinding operations does not appear to affect the level of HAV. Grinding wheels explained much of the variability in this study, but almost 40% of the variance remained unexplained. The considerable variability in the equivalent hand-arm-weighted acceleration has an impact on the risk assessment at both the group and the individual level.

Studies on the S-band bunching system with the Hybrid Bunching-accelerating Structure

NASA Astrophysics Data System (ADS)

Pei, Shi-Lun; Gao, Bin

2018-04-01

Generally, a standard bunching system is composed of a standing-wave (SW) pre-buncher (PB), a traveling-wave (TW) buncher (B) and a standard accelerating structure. In the industrial area, the bunching system is usually simplified by eliminating the PB and integrating the B and the standard accelerating structure together to form a β-varied accelerating structure. The beam capturing efficiency for this kind of simplified system is often worse than that for the standard one. The hybrid buncher (HB) has been proved to be a successful attempt to reduce the cost but preserve the beam quality as much as possible. Here we propose to exclusively simplify the standard bunching system by integrating the PB, the B and the standard accelerating structure together to form a Hybrid Bunching-accelerating Structure (HBaS). Compared to the standard bunching system, the one based on the HBaS is more compact, and the cost is lowered to the largest extent. With almost the same beam transportation efficiency (∼70%) from the electron gun to the linac exit, the peak-to-peak (p-to-p) beam energy spread and the 1 σ emittance of the linac with the HBaS are ∼20% and ∼60% bigger than those of the linac based on the split PB/B/standard accelerating structure system. Nonetheless, the proposed HBaS can be widely applied in the industrial linacs to greatly increase the beam capturing efficiency without fairly increasing the construction cost.

Development of a wireless displacement measurement system using acceleration responses.

PubMed

Park, Jong-Woong; Sim, Sung-Han; Jung, Hyung-Jo; Spencer, Billie F

2013-07-01

Displacement measurements are useful information for various engineering applications such as structural health monitoring (SHM), earthquake engineering and system identification. Most existing displacement measurement methods are costly, labor-intensive, and have difficulties particularly when applying to full-scale civil structures because the methods require stationary reference points. Indirect estimation methods converting acceleration to displacement can be a good alternative as acceleration transducers are generally cost-effective, easy to install, and have low noise. However, the application of acceleration-based methods to full-scale civil structures such as long span bridges is challenging due to the need to install cables to connect the sensors to a base station. This article proposes a low-cost wireless displacement measurement system using acceleration. Developed with smart sensors that are low-cost, wireless, and capable of on-board computation, the wireless displacement measurement system has significant potential to impact many applications that need displacement information at multiple locations of a structure. The system implements an FIR-filter type displacement estimation algorithm that can remove low frequency drifts typically caused by numerical integration of discrete acceleration signals. To verify the accuracy and feasibility of the proposed system, laboratory tests are carried out using a shaking table and on a three storey shear building model, experimentally confirming the effectiveness of the proposed system.

Development of a Wireless Displacement Measurement System Using Acceleration Responses

PubMed Central

Park, Jong-Woong; Sim, Sung-Han; Jung, Hyung-Jo; Spencer, Billie F.

2013-01-01

Displacement measurements are useful information for various engineering applications such as structural health monitoring (SHM), earthquake engineering and system identification. Most existing displacement measurement methods are costly, labor-intensive, and have difficulties particularly when applying to full-scale civil structures because the methods require stationary reference points. Indirect estimation methods converting acceleration to displacement can be a good alternative as acceleration transducers are generally cost-effective, easy to install, and have low noise. However, the application of acceleration-based methods to full-scale civil structures such as long span bridges is challenging due to the need to install cables to connect the sensors to a base station. This article proposes a low-cost wireless displacement measurement system using acceleration. Developed with smart sensors that are low-cost, wireless, and capable of on-board computation, the wireless displacement measurement system has significant potential to impact many applications that need displacement information at multiple locations of a structure. The system implements an FIR-filter type displacement estimation algorithm that can remove low frequency drifts typically caused by numerical integration of discrete acceleration signals. To verify the accuracy and feasibility of the proposed system, laboratory tests are carried out using a shaking table and on a three storey shear building model, experimentally confirming the effectiveness of the proposed system. PMID:23881123

Accelerated Testing and Analysis | Photovoltaic Research | NREL

Science.gov Websites

& Engineering pages: Real-Time PV & Solar Resource Testing Systems Engineering Systems PV standards. Each year, NCPV researchers, along with solar companies and other national lab Accelerated Testing and Analysis Accelerated Testing and Analysis PV Research Other Reliability

Tissue Phthalate Levels Correlate With Changes in Immune Gene Expression in a Population of Juvenile Wild Salmon.

PubMed

Martins, Kelly; Hagedorn, Birgit; Ali, Shareen; Kennish, John; Applegate, Ben; Leu, Matthias; Epp, Lidia; Pallister, Chris; Zwollo, Patty

2016-07-01

Phthalates have detrimental effects on health and have been shown to dysregulate the immune system of mammals, birds, and fish. We recently reported that di(2-ethylhexyl) phthalate exposure reduces the abundance and inhibits the proliferation of rainbow trout (Oncorhynchus mykiss) IgM(+) B lymphocytes and expression of secreted immunoglobulin heavy-chain mu transcripts in an in vitro culture system. We proposed that phthalates act as immunomodulators by modifying the normal B cell-activation pathways by accelerating B cell differentiation while suppressing plasmablast expansion, thus resulting in fewer IgM-secreting plasma cells. This hypothesis was tested here in an in vivo field study of juvenile Dolly Varden (Salvelinus malma) from a plastic-polluted lake in the Gulf of Alaska. Fish tissues were analyzed for both phthalate levels using liquid chromatography-coupled tandem mass spectrometry and for changes in immune gene expression using reverse transcriptase-real time polymerase chain reaction. Results showed that fish with higher tissue levels of di(2-ethylhexyl) phthalate, di(n-butyl) phthalate, and/or dimethyl phthalate expressed significantly fewer secreted and membrane-bound immunoglobulin heavy-chain mu and Blimp1 transcripts in their hematopoietic tissue. This suggests that in vivo uptake of phthalates in fish changes the expression of B cell-specific genes. Chronic exposure to phthalates likely dysregulates normal B-lymphoid development and antibody responses in salmonids and may increase susceptibility to infection. Given the conserved nature of B-lineage cells in vertebrate animals, other marine species may be similarly affected by chronic phthalate exposure.

Acrylamide induces accelerated endothelial aging in a human cell model.

PubMed

Sellier, Cyril; Boulanger, Eric; Maladry, François; Tessier, Frédéric J; Lorenzi, Rodrigo; Nevière, Rémi; Desreumaux, Pierre; Beuscart, Jean-Baptiste; Puisieux, François; Grossin, Nicolas

2015-09-01

Acrylamide (AAM) has been recently discovered in food as a Maillard reaction product. AAM and glycidamide (GA), its metabolite, have been described as probably carcinogenic to humans. It is widely established that senescence and carcinogenicity are closely related. In vitro, endothelial aging is characterized by replicative senescence in which primary cells in culture lose their ability to divide. Our objective was to assess the effects of AAM and GA on human endothelial cell senescence. Human umbilical vein endothelial cells (HUVECs) cultured in vitro were used as model. HUVECs were cultured over 3 months with AAM or GA (1, 10 or 100 μM) until growth arrest. To analyze senescence, β-galactosidase activity and telomere length of HUVECs were measured by cytometry and semi-quantitative PCR, respectively. At all tested concentrations, AAM or GA reduced cell population doubling compared to the control condition (p < 0.001). β-galactosidase activity in endothelial cells was increased when exposed to AAM (≥10 μM) or GA (≥1 μM) (p < 0.05). AAM (≥10 μM) or GA (100 μM) accelerated telomere shortening in HUVECs (p < 0.05). In conclusion, in vitro chronic exposure to AAM or GA at low concentrations induces accelerated senescence. This result suggests that an exposure to AAM might contribute to endothelial aging. Copyright © 2015 Elsevier Ltd. All rights reserved.

Elevated ozone reduces photosynthetic carbon gain by accelerating leaf senescence of inbred and hybrid maize in a genotype-specific manner.

PubMed

Yendrek, Craig R; Erice, Gorka; Montes, Christopher M; Tomaz, Tiago; Sorgini, Crystal A; Brown, Patrick J; McIntyre, Lauren M; Leakey, Andrew D B; Ainsworth, Elizabeth A

2017-12-01

Exposure to elevated tropospheric ozone concentration ([O 3 ]) accelerates leaf senescence in many C 3 crops. However, the effects of elevated [O 3 ] on C 4 crops including maize (Zea mays L.) are poorly understood in terms of physiological mechanism and genetic variation in sensitivity. Using free air gas concentration enrichment, we investigated the photosynthetic response of 18 diverse maize inbred and hybrid lines to season-long exposure to elevated [O 3 ] (~100 nl L -1 ) in the field. Gas exchange was measured on the leaf subtending the ear throughout the grain filling period. On average over the lifetime of the leaf, elevated [O 3 ] led to reductions in photosynthetic CO 2 assimilation of both inbred (-22%) and hybrid (-33%) genotypes. There was significant variation among both inbred and hybrid lines in the sensitivity of photosynthesis to elevated [O 3 ], with some lines showing no change in photosynthesis at elevated [O 3 ]. Based on analysis of inbred line B73, the reduced CO 2 assimilation at elevated [O 3 ] was associated with accelerated senescence decreasing photosynthetic capacity and not altered stomatal limitation. These findings across diverse maize genotypes could advance the development of more O 3 tolerant maize and provide experimental data for parameterization and validation of studies modeling how O 3 impacts crop performance. © 2017 John Wiley & Sons Ltd.

Analysis of WBV on standing and seated passengers during off-peak operation in KL monorail

NASA Astrophysics Data System (ADS)

Hasnan, K.; Bakhsh, Q.; Ahmed, A.; Ali, D.; Jamali, A. R.

2018-03-01

In this study, the Whole-Body Vibration (WBV) was analyzed on the standing and seated passenger during off-peak operating hours when train was on the track. The experiments were conducted on two car train at one constant location (bogie-1, which is near to driver’s cabin) during downward direction from KL sentral station towards Titiwangsa station. The aim of this study was to analyze that, in which posture of passenger’s exposures the maximum level of WBV. Since, one passenger was performed the whole journey in standing posture whereas, the other passenger was in seated posture. The result obtained from experiments for the RMS accelerations (Arms), maximum acceleration (Amax) and minimum acceleration (Amin) during the trip. As per standard ISO 2631-1, the daily vibration exposure (A8), Vibration Dose value (VDV) and Crest Factor (CF) of this trip for both standing and sitting orientations were calculated. Results shows that the seated passenger was exposed to longer periods of continuous vibration as compared to the standing passenger. Whereas, the Vibration Dose value (VDV) value was greater than the action value as per ISO 2631-1 and within the limit values. The study concluded that whole body vibration transmitted towards both passengers either standing or seated during their journey. But in overall results comparison of both orientations, the seated passengers gained higher vibration than the standing one.

Ionizing radiation accelerates Drp1-dependent mitochondrial fission, which involves delayed mitochondrial reactive oxygen species production in normal human fibroblast-like cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kobashigawa, Shinko, E-mail: kobashin@nagasaki-u.ac.jp; Suzuki, Keiji; Yamashita, Shunichi

2011-11-04

Highlights: Black-Right-Pointing-Pointer We report first time that ionizing radiation induces mitochondrial dynamic changes. Black-Right-Pointing-Pointer Radiation-induced mitochondrial fission was caused by Drp1 localization. Black-Right-Pointing-Pointer We found that radiation causes delayed ROS from mitochondria. Black-Right-Pointing-Pointer Down regulation of Drp1 rescued mitochondrial dysfunction after radiation exposure. -- Abstract: Ionizing radiation is known to increase intracellular level of reactive oxygen species (ROS) through mitochondrial dysfunction. Although it has been as a basis of radiation-induced genetic instability, the mechanism involving mitochondrial dysfunction remains unclear. Here we studied the dynamics of mitochondrial structure in normal human fibroblast like cells exposed to ionizing radiation. Delayed mitochondrial O{submore » 2}{sup {center_dot}-} production was peaked 3 days after irradiation, which was coupled with accelerated mitochondrial fission. We found that radiation exposure accumulated dynamin-related protein 1 (Drp1) to mitochondria. Knocking down of Drp1 expression prevented radiation induced acceleration of mitochondrial fission. Furthermore, knockdown of Drp1 significantly suppressed delayed production of mitochondrial O{sub 2}{sup {center_dot}-}. Since the loss of mitochondrial membrane potential, which was induced by radiation was prevented in cells knocking down of Drp1 expression, indicating that the excessive mitochondrial fission was involved in delayed mitochondrial dysfunction after irradiation.« less

Physiological Effects of Acceleration Observed During a Centrifuge Study of Pilot Performance

NASA Technical Reports Server (NTRS)

Smedal, Harald A.; Creer, Brent Y.; Wingrove, Rodney C.

1960-01-01

An investigation was conducted by the National Aeronautics and Space Administration, Ames Research Center, and the Naval Air Development Center, Aviation Medical Acceleration Laboratory, to study the effects of acceleration on pilot performance and to obtain some meaningful data for use in establishing tolerance to acceleration levels. The flight simulator used in the study was the Johnsville centrifuge operated as a closed loop system. The pilot was required to perform a control task in various sustained acceleration fields typical of those that Might be encountered by a pilot flying an entry vehicle in which he is seated in a forward-facing position. A special restraint system was developed and designed to increase the pilot's tolerance to these accelerations. The results of this study demonstrated that a well-trained subject, such as a test pilot, can adequately carry out a control task during moderately high accelerations for prolonged periods of time. The maximum levels of acceleration tolerated were approximately 6 times that of gravity for approximately 6 minutes, and varied slightly with the acceleration direction. The tolerance runs were in each case terminated by the subject. In all but two instances, the cause was extreme fatigue. On two occasions the subject terminated the run when he "grayed out." Although there were subjective and objective findings involving the visual and cardiovascular systems, the respiratory system yielded the more critical limiting factors. It would appear that these limiting factors were less severe during the "eyeballs-out" accelerations when compared with the "eyeballs-in" accelerations. These findings are explained on the basis of the influence that the inertial forces of acceleration have on the mechanics of respiration. A condensed version of this report was presented at the Annual Meeting of the Aerospace Medical Association, Miami Beach, May 5-11, 1960, in a paper entitled "Ability of Pilots to Perform a Control Task in Various Sustained Acceleration Fields."

Correlation of Head Impacts to Change in Balance Error Scoring System Scores in Division I Men's Lacrosse Players.

PubMed

Miyashita, Theresa L; Diakogeorgiou, Eleni; Marrie, Kaitlyn

Investigation into the effect of cumulative subconcussive head impacts has yielded various results in the literature, with many supporting a link to neurological deficits. Little research has been conducted on men's lacrosse and associated balance deficits from head impacts. (1) Athletes will commit more errors on the postseason Balance Error Scoring System (BESS) test. (2) There will be a positive correlation to change in BESS scores and head impact exposure data. Prospective longitudinal study. Level 3. Thirty-four Division I men's lacrosse players (age, 19.59 ± 1.42 years) wore helmets instrumented with a sensor to collect head impact exposure data over the course of a competitive season. Players completed a BESS test at the start and end of the competitive season. The number of errors from pre- to postseason increased during the double-leg stance on foam ( P < 0.001), tandem stance on foam ( P = 0.009), total number of errors on a firm surface ( P = 0.042), and total number of errors on a foam surface ( P = 0.007). There were significant correlations only between the total errors on a foam surface and linear acceleration ( P = 0.038, r = 0.36), head injury criteria ( P = 0.024, r = 0.39), and Gadd Severity Index scores ( P = 0.031, r = 0.37). Changes in the total number of errors on a foam surface may be considered a sensitive measure to detect balance deficits associated with cumulative subconcussive head impacts sustained over the course of 1 lacrosse season, as measured by average linear acceleration, head injury criteria, and Gadd Severity Index scores. If there is microtrauma to the vestibular system due to repetitive subconcussive impacts, only an assessment that highly stresses the vestibular system may be able to detect these changes. Cumulative subconcussive impacts may result in neurocognitive dysfunction, including balance deficits, which are associated with an increased risk for injury. The development of a strategy to reduce total number of head impacts may curb the associated sequelae. Incorporation of a modified BESS test, firm surface only, may not be recommended as it may not detect changes due to repetitive impacts over the course of a competitive season.

Dependence on subconcussive impacts of brain metabolism in collision sport athletes: an MR spectroscopic study.

PubMed

Bari, Sumra; Svaldi, Diana O; Jang, Ikbeom; Shenk, Trey E; Poole, Victoria N; Lee, Taylor; Dydak, Ulrike; Rispoli, Joseph V; Nauman, Eric A; Talavage, Thomas M

2018-05-25

Long term neurological impairments due to repetitive head trauma are a growing concern for collision sport athletes. American Football has the highest rate of reported concussions among male high school athletes, a position held by soccer for female high school athletes. Recent research has shown that subconcussive events experienced by collision sport athletes can be a further significant source of accrued damage. Collision sport athletes experience hundreds of subconcussive events in a single season, and these largely go uninvestigated as they produce no overt clinical symptoms. Continued participation by these seemingly uninjured athletes is hypothesized to increase susceptibility to diagnoseable brain injury. This study paired magnetic resonance spectroscopy with head impact monitoring to quantify the relationship between metabolic changes and head acceleration event characteristics in high school-aged male football and female soccer collision sport athletes. During the period of exposure to subconcussive events, asymptomatic male (football) collision sport athletes exhibited statistically significant changes in concentrations of glutamate+glutamine (Glx) and total choline containing compounds (tCho) in dorsolateral prefrontal cortex, and female (soccer) collision sport athletes exhibited changes in glutamate+glutamine (Glx) in primary motor cortex. Neurometabolic alterations observed in football athletes during the second half of the season were found to be significantly associated with the average acceleration per head acceleration events, being best predicted by the accumulation of events exceeding 50 g. These marked deviations in neurometabolism, in the absence of overt symptoms, raise concern about the neural health of adolescent collision-sport athletes and suggest limiting exposure to head acceleration events may help to ameliorate the risk of subsequent cognitive impairment.

Soiling of building envelope surfaces and its effect on solar reflectance – Part II: Development of an accelerated aging method for roofing materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sleiman, Mohamad; Kirchstetter, Thomas W.; Berdahl, Paul

2014-01-09

Highly reflective roofs can decrease the energy required for building air conditioning, help mitigate the urban heat island effect, and slow global warming. However, these benefits are diminished by soiling and weathering processes that reduce the solar reflectance of most roofing materials. Soiling results from the deposition of atmospheric particulate matter and the growth of microorganisms, each of which absorb sunlight. Weathering of materials occurs with exposure to water, sunlight, and high temperatures. This study developed an accelerated aging method that incorporates features of soiling and weathering. The method sprays a calibrated aqueous soiling mixture of dust minerals, black carbon,more » humic acid, and salts onto preconditioned coupons of roofing materials, then subjects the soiled coupons to cycles of ultraviolet radiation, heat and water in a commercial weatherometer. Three soiling mixtures were optimized to reproduce the site-specific solar spectral reflectance features of roofing products exposed for 3 years in a hot and humid climate (Miami, Florida); a hot and dry climate (Phoenix, Arizona); and a polluted atmosphere in a temperate climate (Cleveland, Ohio). A fourth mixture was designed to reproduce the three-site average values of solar reflectance and thermal emittance attained after 3 years of natural exposure, which the Cool Roof Rating Council (CRRC) uses to rate roofing products sold in the US. This accelerated aging method was applied to 25 products₋single ply membranes, factory and field applied coatings, tiles, modified bitumen cap sheets, and asphalt shingles₋and reproduced in 3 days the CRRC's 3-year aged values of solar reflectance. In conclusion, this accelerated aging method can be used to speed the evaluation and rating of new cool roofing materials.« less

Use of active control technology to improve ride qualities of large transport aircraft

NASA Technical Reports Server (NTRS)

Cohen, G. C.; Cotter, C. J.; Taylor, D. L.

1976-01-01

Analyses, construction and flight testing of two systems: Beta-vane and Modal Suppression Augmentation System (MSAS), which were developed to suppress gust induced lateral accelerations of large aircraft, are described. The 747 transport was used as the test vehicle. The purpose of the Beta-vane system is to reduce acceleration levels at the dutch roll frequency whereas the function of the MSAS system is to reduce accelerations due to flexible body motions caused by turbulence. Data from flight test, with both systems engaged shows a 50 to 70 percent reduction in lateral aft body acceleration levels. Furthermore, it is suggested that present day techniques used for developing dynamic equations of motion in the flexible mode region are limited.

A novel electron accelerator for MRI-Linac radiotherapy.

PubMed

Whelan, Brendan; Gierman, Stephen; Holloway, Lois; Schmerge, John; Keall, Paul; Fahrig, Rebecca

2016-03-01

MRI guided radiotherapy is a rapidly growing field; however, current electron accelerators are not designed to operate in the magnetic fringe fields of MRI scanners. As such, current MRI-Linac systems require magnetic shielding, which can degrade MR image quality and limit system flexibility. The purpose of this work was to develop and test a novel medical electron accelerator concept which is inherently robust to operation within magnetic fields for in-line MRI-Linac systems. Computational simulations were utilized to model the accelerator, including the thermionic emission process, the electromagnetic fields within the accelerating structure, and resulting particle trajectories through these fields. The spatial and energy characteristics of the electron beam were quantified at the accelerator target and compared to published data for conventional accelerators. The model was then coupled to the fields from a simulated 1 T superconducting magnet and solved for cathode to isocenter distances between 1.0 and 2.4 m; the impact on the electron beam was quantified. For the zero field solution, the average current at the target was 146.3 mA, with a median energy of 5.8 MeV (interquartile spread of 0.1 MeV), and a spot size diameter of 1.5 mm full-width-tenth-maximum. Such an electron beam is suitable for therapy, comparing favorably to published data for conventional systems. The simulated accelerator showed increased robustness to operation in in-line magnetic fields, with a maximum current loss of 3% compared to 85% for a conventional system in the same magnetic fields. Computational simulations suggest that replacing conventional DC electron sources with a RF based source could be used to develop medical electron accelerators which are robust to operation in in-line magnetic fields. This would enable the development of MRI-Linac systems with no magnetic shielding around the Linac and reduce the requirements for optimization of magnetic fringe field, simplify design of the high-field magnet, and increase system flexibility.

A novel electron accelerator for MRI-Linac radiotherapy

PubMed Central

Whelan, Brendan; Gierman, Stephen; Holloway, Lois; Schmerge, John; Keall, Paul; Fahrig, Rebecca

2016-01-01

Purpose: MRI guided radiotherapy is a rapidly growing field; however, current electron accelerators are not designed to operate in the magnetic fringe fields of MRI scanners. As such, current MRI-Linac systems require magnetic shielding, which can degrade MR image quality and limit system flexibility. The purpose of this work was to develop and test a novel medical electron accelerator concept which is inherently robust to operation within magnetic fields for in-line MRI-Linac systems. Methods: Computational simulations were utilized to model the accelerator, including the thermionic emission process, the electromagnetic fields within the accelerating structure, and resulting particle trajectories through these fields. The spatial and energy characteristics of the electron beam were quantified at the accelerator target and compared to published data for conventional accelerators. The model was then coupled to the fields from a simulated 1 T superconducting magnet and solved for cathode to isocenter distances between 1.0 and 2.4 m; the impact on the electron beam was quantified. Results: For the zero field solution, the average current at the target was 146.3 mA, with a median energy of 5.8 MeV (interquartile spread of 0.1 MeV), and a spot size diameter of 1.5 mm full-width-tenth-maximum. Such an electron beam is suitable for therapy, comparing favorably to published data for conventional systems. The simulated accelerator showed increased robustness to operation in in-line magnetic fields, with a maximum current loss of 3% compared to 85% for a conventional system in the same magnetic fields. Conclusions: Computational simulations suggest that replacing conventional DC electron sources with a RF based source could be used to develop medical electron accelerators which are robust to operation in in-line magnetic fields. This would enable the development of MRI-Linac systems with no magnetic shielding around the Linac and reduce the requirements for optimization of magnetic fringe field, simplify design of the high-field magnet, and increase system flexibility. PMID:26936713

Design of a New Acceleration System for High-Current Pulsed Proton Beams from an ECR Source

NASA Astrophysics Data System (ADS)

Cooper, Andrew L.; Pogrebnyak, Ivan; Surbrook, Jason T.; Kelly, Keegan J.; Carlin, Bret P.; Champagne, Arthur E.; Clegg, Thomas B.

2014-03-01

A primary objective for accelerators at TUNL's Laboratory for Experimental Nuclear Astrophysics (LENA) is to maximize target beam intensity to ensure a high rate of nuclear events during each experiment. Average proton target currents of several mA are needed from LENA's electron cyclotron resonance (ECR) ion source because nuclear cross sections decrease substantially at energies of interest <200 keV. We seek to suppress undesired continuous environmental background by pulsing the beam and detecting events only during beam pulses. To improve beam intensity and transport, we installed a more powerful, stable microwave system for the ECR plasma, and will install a new acceleration system. This system will: reduce defocusing effects of the beam's internal space charge; provide better vacuum with a high gas conductance accelerating column; suppress bremsstrahlung X-rays produced when backstreaming electrons strike internal acceleration tube structures; and provide better heat dissipation by using deionized water to provide the current drain needed to establish the accelerating tube's voltage gradient. Details of beam optical modeling calculations, proposed accelerating tube design, and initial beam pulsing tests will be described. Work supported in part by USDOE Office of HE and Nuclear Physics.

Accelerated Application Development: The ORNL Titan Experience

DOE PAGES

Joubert, Wayne; Archibald, Richard K.; Berrill, Mark A.; ...

2015-05-09

The use of computational accelerators such as NVIDIA GPUs and Intel Xeon Phi processors is now widespread in the high performance computing community, with many applications delivering impressive performance gains. However, programming these systems for high performance, performance portability and software maintainability has been a challenge. In this paper we discuss experiences porting applications to the Titan system. Titan, which began planning in 2009 and was deployed for general use in 2013, was the first multi-petaflop system based on accelerator hardware. To ready applications for accelerated computing, a preparedness effort was undertaken prior to delivery of Titan. In this papermore » we report experiences and lessons learned from this process and describe how users are currently making use of computational accelerators on Titan.« less

Accelerated application development: The ORNL Titan experience

DOE Office of Scientific and Technical Information (OSTI.GOV)

Joubert, Wayne; Archibald, Rick; Berrill, Mark

2015-08-01

The use of computational accelerators such as NVIDIA GPUs and Intel Xeon Phi processors is now widespread in the high performance computing community, with many applications delivering impressive performance gains. However, programming these systems for high performance, performance portability and software maintainability has been a challenge. In this paper we discuss experiences porting applications to the Titan system. Titan, which began planning in 2009 and was deployed for general use in 2013, was the first multi-petaflop system based on accelerator hardware. To ready applications for accelerated computing, a preparedness effort was undertaken prior to delivery of Titan. In this papermore » we report experiences and lessons learned from this process and describe how users are currently making use of computational accelerators on Titan.« less

Laboratory electron exposure of TSS-1 thermal control coating

NASA Technical Reports Server (NTRS)

Vaughn, J. A.; Mccollum, M.; Carruth, M. R., Jr.

1995-01-01

RM400, a conductive thermal control coating, was developed for use on the exterior shell of the tethered satellite. Testing was performed by the Engineering Physics Division to quantify effects of the space environment on this coating and its conductive and optical properties. Included in this testing was exposure of RM400 to electrons with energies ranging from 0.1 to 1 keV, to simulate electrons accelerated from the ambient space plasma when the tethered satellite is fully deployed. During this testing, the coating was found to luminesce, and a prolonged exposure of the coating to high-energy electrons caused the coating to darken. This report describes the tests done to quantify the degradation of the thermal control properties caused by electron exposure and to measure the luminescence as a function of electron energy and current density to the satellite.

Differential effects of zinc exposure on male and female oysters (Crassostrea angulata) as revealed by label-free quantitative proteomics.

PubMed

Luo, Lianzhong; Zhang, Qinghong; Kong, Xue; Huang, Heqing; You, Weiwei; Ke, Caihuan

2017-10-01

Oysters accumulate Zn as an adaptation to Zn exposure; however, it is not known whether male and female oysters respond differently to Zn exposure. Proteomic and real-time polymerase chain reaction analyses were used to investigate differential responses of male and female oysters (Crassostrea angulata) to Zn exposure. After exposure to 50 μg L -1 or 500 μg L -1 Zn for 30 d, gonads of female oysters accumulated more Zn than those of males, and gonadal development was accelerated in females but was abnormal in males. Differentially expressed proteins after exposure to Zn were identified and shown to function in Zn transport, Ca transport, phosphate metabolism, energy metabolism, immune regulation, oxidative stress responses, gene expression regulation, and fat metabolism. Proteins with functions in Zn transportation and storage, and multifunctional proteins, such as hemicentin-1 and histidinol dehydrogenase, were expressed at significantly higher levels in the gonads of female than male oysters after Zn exposure. Environ Toxicol Chem 2017;36:2602-2613. © 2017 SETAC. © 2017 SETAC.

TRICHLOROETHYLENE ACCELERATES AN AUTOIMMUNE RESPONSE IN ASSOCIATION WITH TH1 T-CELL ACTIVATION IN MRL+/+ MICE. (R826409)

EPA Science Inventory

Abstract

Trichloroethylene (1,1,2-trichloroethene) is a major environmental contaminant. There is increasing evidence relating exposure to trichloroethylene with autoimmunity. To investigate potential mechanisms, we treated the autoimmune-prone MRL+/+ mice with trichlo...

Durability of building joint sealants

Treesearch

Christopher C. White; Kar Tean Tan; Donald L. Hunston; R. Sam Williams

2009-01-01

Predicting the service life of building joint sealants exposed to service environments in less than real time has been a need of the sealant community for many decades. Despite extensive research efforts to design laboratory accelerated tests to duplicate the failure modes occurring in field exposures, little success has been achieved using conventional durability...