Science.gov

Sample records for radiation hardness study

  1. Radiation from hard objects

    SciTech Connect

    Canavan, G.H.

    1997-02-01

    The inference of the diameter of hard objects is insensitive to radiation efficiency. Deductions of radiation efficiency from observations are very sensitive - possibly overly so. Inferences of the initial velocity and trajectory vary similarly, and hence are comparably sensitive.

  2. MNOS/SOS radiation hardness performance and reliability study

    NASA Astrophysics Data System (ADS)

    Hampton, F. L.; Cricchi, J. R.

    1982-05-01

    In this investigation the endurance-retention characteristics of fast-write MNOS memory structure, and radiation tolerance of metal-gate dual-dielectric and polysilicon-gate all-oxide devices have been evaluated. Writing and clearing speed have been studied with respect to the NH3:SiH4 ratio (APCVD), and NH3:SiC12H2 ratio (LPCVD). The films deposited with a low NH3:SiC12 ratios could be written and cleared with shorter pulse widths; however, a degradation in retention was observed. An improvement in the endurance retention product of a drain source protected transistor structure has been realized by oxidizing the memory nitride followed by an H2 anneal immediately after deposition. The film was deposited with a LPCVD reactor at 750 deg with a NH3:SiC12H2 ratio of 9:1. Oxidation was performed in steam at 900 C, as was the subsequent H2 anneal. The effect of total dose radiation was found to be more severe for a positive bias. The all oxide polysilicon gate transistor structures were observed to be relatively soft, however results from capacitor structures shows promise in developing a radiation tolerant polysilicon-gate all-oxide gate structure.

  3. Study of radiation hardness of pure CsI crystals for Belle-II calorimeter

    NASA Astrophysics Data System (ADS)

    Boyarintsev, A.; Boyarintseva, Y.; Gektin, A.; Shiran, N.; Shlyakhturov, V.; Taranyuk, V.; Timoshenko, N.; Bobrov, A.; Garmash, A.; Golkovski, M.; Kuzmin, A.; Matvienko, D.; Savrovski, P.; Shebalin, V.; Shwartz, B.; Vinokurova, A.; Vorobyev, V.; Zhilich, V.; Krumshtein, Z. V.; Nozdrin, A. A.; Olshevsky, A. G.

    2016-03-01

    A study of the radiation hardness of pure CsI crystals 30 cm long was performed with a uniformly absorbed dose of up to 14.3 krad. This study was initiated by the proposed upgrade of the end cap calorimeter of the Belle-II detector, using pure CsI crystals. A set of 14 crystals of truncated pyramid shape used in this study was produced at the Institute for Scintillation Materials NAS from 14 different ingots grown with variations of the growing technology. Interrelationship of crystal scintillation characteristics, radiation hardness and the growing technology was observed.

  4. R&D Studies on Radiation Hard Wavelength Shifting Fiber for CMS Hadronic Endcap Calorimeter Upgrade

    NASA Astrophysics Data System (ADS)

    Neuhaus, John

    2009-11-01

    The Hadronic Endcap (HE) calorimeters of the CMS experiment cover the pseudorapidity range of 1.4 to 3 on both sides of the CMS detector, contributing to superior jet and missing transverse energy resolutions. As the integrated luminosity of the LHC increases, the scintillator tiles used in the CMS Hadronic Endcap calorimeter will lose their efficiency. Here, we propose to replace the scintillator tiles in high radiation area with ``radiation hard'' quartz plates. To increase the light collection efficiency, the generated Cerenkov photons are collected by UV absorbing wavelength shifting (WLS) fibers. Our previous study has shown that quartz plates and plastic wavelength shifting fibers can be used as an effective calorimeter. However there is no radiation hard WLS fiber commercially available. Here we summarize the R&D studies on constructing a radiation hard WLS fiber prototype in University of Iowa CMS Laboratories. The results from the tests performed on quartz fibers treated with p-Terphenyl, as well as the Geant4 simulations of this prototype are presented.

  5. Study of runaway electrons using dosimetry of hard x-ray radiations in Damavand tokamak

    SciTech Connect

    Rasouli, C.; Pourshahab, B.; Rasouli, H.; Hosseini Pooya, S. M.; Orouji, T.

    2014-05-15

    In this work several studies have been conducted on hard x-ray emissions of Damavand tokamak based on radiation dosimetry using the Thermoluminescence method. The goal was to understand interactions of runaway electrons with plasma particles, vessel wall, and plasma facing components. Total of 354 GR-200 (LiF:Mg,Cu,P) thermoluminescence dosimeter (TLD) crystals have been placed on 118 points – three TLDs per point – to map hard x-ray radiation doses on the exterior of the vacuum vessel. Results show two distinctive levels of x-ray radiations doses on the exterior of the vessel. The low-dose area on which measured dose is about 0.5 mSv/shot. In the low-dose area there is no particular component inside the vessel. On the contrary, on high-dose area of the vessel, x-ray radiations dose exceeds 30 mSv/shot. The high-dose area coincides with the position of limiters, magnetic probe ducts, and vacuum vessel intersections. Among the high-dose areas, the highest level of dose is measured in the position of the limiter, which could be due to its direct contact with the plasma column and with runaway electrons. Direct collisions of runaway electrons with the vessel wall and plasma facing components make a major contribution for production of hard x-ray photons in Damavand tokamak.

  6. Study of runaway electrons using dosimetry of hard x-ray radiations in Damavand tokamak.

    PubMed

    Rasouli, C; Pourshahab, B; Hosseini Pooya, S M; Orouji, T; Rasouli, H

    2014-05-01

    In this work several studies have been conducted on hard x-ray emissions of Damavand tokamak based on radiation dosimetry using the Thermoluminescence method. The goal was to understand interactions of runaway electrons with plasma particles, vessel wall, and plasma facing components. Total of 354 GR-200 (LiF:Mg,Cu,P) thermoluminescence dosimeter (TLD) crystals have been placed on 118 points--three TLDs per point--to map hard x-ray radiation doses on the exterior of the vacuum vessel. Results show two distinctive levels of x-ray radiations doses on the exterior of the vessel. The low-dose area on which measured dose is about 0.5 mSv/shot. In the low-dose area there is no particular component inside the vessel. On the contrary, on high-dose area of the vessel, x-ray radiations dose exceeds 30 mSv/shot. The high-dose area coincides with the position of limiters, magnetic probe ducts, and vacuum vessel intersections. Among the high-dose areas, the highest level of dose is measured in the position of the limiter, which could be due to its direct contact with the plasma column and with runaway electrons. Direct collisions of runaway electrons with the vessel wall and plasma facing components make a major contribution for production of hard x-ray photons in Damavand tokamak.

  7. Satellite project "CORONAS-PHOTON" for study of solar hard radiation

    NASA Astrophysics Data System (ADS)

    Kotov, Yu.; Cor-Phot Team

    "CORONAS-PHOTON" is the Russian mission for study of the solar hard electromagnetic radiation in the very wide energy range from Extreme UV up to high-energy gamma - radiation. GOAL OF PROJECT: The investigation of energy accumulation and its transformation into energy of accelerated particles processes during solar flares; the study of the acceleration mechanisms, propagation and interaction of fast particles in the solar atmosphere; the study of the solar activity correlation with physical-chemical processes in the Earth upper atmosphere. SCIENTIFIC PAYLOAD CAPABILITY Radiation / Energy region / Detector type: Full solar disk X- radiation / 2keV - 2000MeV / Prop. counter; NaI(Tl); Full solar disk X- and γ-radiation / NaI(Tl)/CsI(Na) phoswich; Full solar disk X- and γ-radiation and solar neutrons / 20 - 300MeV / YalO_3(Ce); CsI(Tl); Hard X-ray polarization in large flares / 20 - 150keV / p-terphenyl scatterer and CsI(Na) absorbers; Full solar disk EUV-radiation monitoring / 6 spectral windows in <10 - 130nm / Filtered photodiodes; Solar images in narrow spectral bands and monochromatic emission lines of hot plasma / Emission of HeII, SiXI, FeXXI, FeXXIII, MgXII ions / Multi-layer and Bregg spherical crystal quartz mirrors with CCDs; Additionally, the temporal and energy spectra of electrons (0.2-14MeV), protons (1-61MeV) and nuclei (Z<26, 2-50MeV/nuclon) at the satellite orbit will be registrated by several instruments. MAIN CHARACTERISTICS OF SPACECRAFT: Spacecraft weight: 1900 kg; Orbit type: Circular; Scientific payload weight: 540 kg; Height: 500 km; Orientation to the Sun [arc min]: better 5; Inclination: 82.5 degree; Instability of orientation [deg/s]: less 0.005; Solar - synchronous orbit is under study. Launching date of "CORONAS-PHOTON" spacecraft is 2006.

  8. Thermopile detector radiation hard readout

    NASA Astrophysics Data System (ADS)

    Gaalema, Stephen; Van Duyne, Stephen; Gates, James L.; Foote, Marc C.

    2010-08-01

    The NASA Jupiter Europa Orbiter (JEO) conceptual payload contains a thermal instrument with six different spectral bands ranging from 8μm to 100μm. The thermal instrument is based on multiple linear arrays of thermopile detectors that are intrinsically radiation hard; however, the thermopile CMOS readout needs to be hardened to tolerate the radiation sources of the JEO mission. Black Forest Engineering is developing a thermopile readout to tolerate the JEO mission radiation sources. The thermal instrument and ROIC process/design techniques are described to meet the JEO mission requirements.

  9. Radiation hard electronics for LHC

    NASA Astrophysics Data System (ADS)

    Raymond, M.; Millmore, M.; Hall, G.; Sachdeva, R.; French, M.; Nygård, E.; Yoshioka, K.

    1995-02-01

    A CMOS front end electronics chain is being developed by the RD20 collaboration for microstrip detector readout at LHC. It is based on a preamplifier and CR-RC filter, analogue pipeline and an analogue signal processor. Amplifiers and transistor test structures have been constructed and evaluated in detail using a Harris 1.2 μm radiation hardened CMOS process. Progress with larger scale elements, including 32 channel front end chips, is described. A radiation hard 128 channel chip, with a 40 MHz analogue multiplexer, is to be submitted for fabrication in July 1994 which will form the basis of the readout of the tracking system of the CMS experiment.

  10. Radiation Hardness Assurance (RHA) Guideline

    NASA Technical Reports Server (NTRS)

    Campola, Michael J.

    2016-01-01

    Radiation Hardness Assurance (RHA) consists of all activities undertaken to ensure that the electronics and materials of a space system perform to their design specifications after exposure to the mission space environment. The subset of interests for NEPP and the REAG, are EEE parts. It is important to register that all of these undertakings are in a feedback loop and require constant iteration and updating throughout the mission life. More detail can be found in the reference materials on applicable test data for usage on parts.

  11. Development of radiation hard scintillators

    SciTech Connect

    Markley, F.; Woods, D.; Pla-Dalmau, A.; Foster, G. ); Blackburn, R. )

    1992-05-01

    Substantial improvements have been made in the radiation hardness of plastic scintillators. Cylinders of scintillating materials 2.2 cm in diameter and 1 cm thick have been exposed to 10 Mrads of gamma rays at a dose rate of 1 Mrad/h in a nitrogen atmosphere. One of the formulations tested showed an immediate decrease in pulse height of only 4% and has remained stable for 12 days while annealing in air. By comparison a commercial PVT scintillator showed an immediate decrease of 58% and after 43 days of annealing in air it improved to a 14% loss. The formulated sample consisted of 70 parts by weight of Dow polystyrene, 30 pbw of pentaphenyltrimethyltrisiloxane (Dow Corning DC 705 oil), 2 pbw of p-terphenyl, 0.2 pbw of tetraphenylbutadiene, and 0.5 pbw of UVASIL299LM from Ferro.

  12. Automated radiation hard ASIC design tool

    NASA Technical Reports Server (NTRS)

    White, Mike; Bartholet, Bill; Baze, Mark

    1993-01-01

    A commercial based, foundry independent, compiler design tool (ChipCrafter) with custom radiation hardened library cells is described. A unique analysis approach allows low hardness risk for Application Specific IC's (ASIC's). Accomplishments, radiation test results, and applications are described.

  13. Radiation hardness studies of n + -in-n planar pixel sensors for the ATLAS upgrades

    NASA Astrophysics Data System (ADS)

    Altenheiner, S.; Goessling, C.; Jentzsch, J.; Klingenberg, R.; Muenstermann, D.; Rummler, A.; Troska, G.; Wittig, T.

    2011-12-01

    The ATLAS experiment at the LHC is planning upgrades of its pixel detector to cope with the luminosity increase foreseen in the coming years within the transition from LHC to Super-LHC (SLHC/HL-LHC). Associated with the increase in instantaneous luminosity is a rise of the target integrated luminosity from 730 to about 3000 fb -1 which directly translates into significantly higher radiation damage. These upgrades consist of the installation of a 4th pixel layer, the insertable b-layer IBL, with a mean sensor radius of only 32 mm from the beam axis, before 2016/17. In addition, the complete pixel detector will be exchanged before 2020/21. Being very close to the beam, the radiation damage of the IBL sensors might be as high as 5×1015 neq cm-2 at their end-of-life. The total fluence of the innermost pixel layer after the SLHC upgrade might even reach 2×1016 neq cm-2. To investigate the radiation hardness and suitability of the current ATLAS pixel sensors for these fluences, n +-in-n silicon pixel sensors from the ATLAS Pixel production have been irradiated by reactor neutrons to the IBL design fluence and been tested with pions at the SPS and with electrons from a 90Sr source in the laboratory. The collected charge after IBL fluences was found to exceed 10 000 electrons per MIP at 1 kV of bias voltage which is in agreement with data collected with strip sensors. After SLHC fluences, still reliable operation of the devices could be observed with a collected charge of more than 5000 electrons per MIP.

  14. Radiation hardness and precision timing study of silicon detectors for the CMS High Granularity Calorimeter (HGC)

    NASA Astrophysics Data System (ADS)

    Currás, Esteban; Fernández, Marcos; Gallrapp, Christian; Gray, Lindsey; Mannelli, Marcello; Meridiani, Paolo; Moll, Michael; Nourbakhsh, Shervin; Scharf, Christian; Silva, Pedro; Steinbrueck, Georg; Fatis, Tommaso Tabarelli de; Vila, Iván

    2017-02-01

    The high luminosity upgraded LHC or Phase-II is expected to increase the instantaneous luminosity by a factor of 10 beyond the LHC's design value, expecting to deliver 250 fb-1 per year for a further 10 years of operation. Under these conditions the performance degradation due to integrated radiation dose will need to be addressed. The CMS collaboration is planning to upgrade the forward calorimeters. The replacement is called the High Granularity Calorimeter (HGC) and it will be realized as a sampling calorimeter with layers of silicon detectors interleaved. The sensors will be realized as pad detectors with sizes of less that ∼1.0 cm2 and an active thickness between 100 and 300 μm depending on the position, respectively, the expected radiation levels. For an integrated luminosity of 3000 fb-1, the electromagnetic calorimetry will sustain integrated doses of 1.5 MGy (150 Mrads) and neutron fluences up to 1016 neq/cm2. A radiation tolerance study after neutron irradiation of 300, 200, and 100 μm n-on-p and p-on-n silicon pads irradiated to fluences up to 1.6×1016 neq/cm2 is presented. The properties of these diodes studied before and after irradiation were leakage current, capacitance, charge collection efficiency, annealing effects and timing capability. The results of these measurements validate these sensors as candidates for the HGC system.

  15. MNOS/SOS radiation hardness performance and reliability study. Interim report Aug 79-Aug 80

    SciTech Connect

    Hampton, F.L.; Cricchi, J.R.

    1982-05-01

    In this investigation the endurance-retention characteristics of fast-write MNOS memory structure, and radiation tolerance of metal-gate dual-dielectric and polysilicon-gate all-oxide devices have been evaluated. Writing and clearing speed have been studied with respect to the NH3:SiH4 ratio (APCVD), and NH3:SiC12H2 ratio (LPCVD). The films deposited with a low NH3:SiC12 ratios could be written and cleared with shorter pulse widths; however, a degradation in retention was observed. An improvement in the endurance retention product of a drain source protected transistor structure has been realized by oxidizing the memory nitride followed by an H2 anneal immediately after deposition. The film was deposited with a LPCVD reactor at 750 deg with a NH3:SiC12H2 ratio of 9:1. Oxidation was performed in steam at 900 C, as was the subsequent H2 anneal. The effect of total dose radiation was found to be more severe for a positive bias. The all oxide polysilicon gate transistor structures were observed to be relatively soft, however results from capacitor structures shows promise in developing a radiation tolerant polysilicon-gate all-oxide gate structure.

  16. Radiation-Hardness Data For Semiconductor Devices

    NASA Technical Reports Server (NTRS)

    Price, W. E.; Nichols, D. K.; Brown, S. F.; Gauthier, M. K.; Martin, K. E.

    1984-01-01

    Document presents data on and analysis of radiation hardness of various semiconductor devices. Data specifies total-dose radiation tolerance of devices. Volume 1 of report covers diodes, bipolar transistors, field effect transistors, silicon controlled rectifiers and optical devices. Volume 2 covers integrated circuits. Volume 3 provides detailed analysis of data in volumes 1 and 2.

  17. Radiation hardness study of Silicon Detectors for the CMS High Granularity Calorimeter (HGCAL)

    NASA Astrophysics Data System (ADS)

    Currás, E.; Mannelli, M.; Moll, M.; Nourbakhsh, S.; Steinbrueck, G.; Vila, I.

    2017-02-01

    The high luminosity LHC (HL-LHC or Phase-II) is expected to increase the instantaneous luminosity of the LHC by a factor of about five, delivering 0~25 fb ‑1 per year between 2025 and 2035. Under these conditions the performance degradation of detectors due to integrated radiation dose/fluence will need to be addressed. The CMS collaboration is planning to upgrade many detector components, including the forward calorimeters. The replacement for the existing endcap preshower, electromagnetic and hadronic calorimeters is called the High Granularity Calorimeter (HGCAL) and it will be realized as a sampling calorimeter, including 40 layers of silicon detectors totalling 600 m2. The sensors will be realized as pad detectors with cell size between 0.5 and 1.0 cm2 and an active thickness between 100 μm and 300 μm depending on their location in the endcaps. The thinner sensors will be used in the highest radiation environment. For an integrated luminosity of 3000 fb ‑1, the electromagnetic calorimeter will have to sustain a maximum integrated dose of 1.5 MGy and neutron fluences of 1.0×1016 neq/cm2. A tolerance study after neutron irradiation of 300 μm, 200 μm, 100 μm and 50 μm n-on-p and p-on-n silicon pads irradiated to fluences up to 1.6×1016 neq/cm2 is presented. The main properties of these diodes have been studied before and after irradiation: leakage current, capacitance, charge collection efficiency with laser and sensitivity to minimum ionizing particles with radioactive source (90Sr). The results show a good performance even after the most extreme irradiation.

  18. Radiation Hardness Assurance for Space Systems

    NASA Technical Reports Server (NTRS)

    Poivey, Christian; Day, John H. (Technical Monitor)

    2002-01-01

    The space radiation environment can lead to extremely harsh operating conditions for on-board electronic box and systems. The characteristics of the radiation environment are highly dependent on the type of mission (date, duration and orbit). Radiation accelerates the aging of the electronic parts and material and can lead to a degradation of electrical performance; it can also create transient phenomena on parts. Such damage at the part level can induce damage or functional failure at electronic box, subsystem, and system levels. A rigorous methodology is needed to ensure that the radiation environment does not compromise the functionality and performance of the electronics during the system life. This methodology is called hardness assurance. It consists of those activities undertaken to ensure that the electronic piece parts placed in the space system perform to their design specifications after exposure to the space environment. It deals with system requirements, environmental definitions, part selection, part testing, shielding and radiation tolerant design. All these elements should play together in order to produce a system tolerant to.the radiation environment. An overview of the different steps of a space system hardness assurance program is given in section 2. In order to define the mission radiation specifications and compare these requirements to radiation test data, a detailed knowledge of the space environment and the corresponding electronic device failure mechanisms is required. The presentation by J. Mazur deals with the Earth space radiation environment as well as the internal environment of a spacecraft. The presentation by J. Schwank deals with ionization effects, and the presentation by T. Weatherford deals with Single particle Event Phenomena (SEP) in semiconductor devices and microcircuits. These three presentations provide more detailed background to complement the sections 3 and 4. Part selection and categorization are discussed in section

  19. Development of radiation hard scintillators

    SciTech Connect

    Markley, F.; Davidson, M.; Keller, J.; Foster, G.; Pla-Dalmau, A.; Harmon, J.; Biagtan, E.; Schueneman, G.; Senchishin, V.; Gustfason, H.; Rivard, M.

    1993-11-01

    The authors have demonstrated that the radiation stability of scintillators made from styrene polymer is very much improved by compounding with pentaphenyltrimethyltrisiloxane (DC 705 vacuum pump oil). The resulting scintillators are softer than desired, so they decided to make the scintillators directly from monomer where the base resin could be easily crosslinked to improve the mechanical properties. They can now demonstrate that scintillators made directly from the monomer, using both styrene and 4-methyl styrene, are also much more radiation resistant when modified with DC705 oil. In fact, they retain from 92% to 95% of their original light output after gamma irradiation to 10 Mrads in nitrogen with air annealing. When these scintillators made directly from monomer are compared with scintillators of the same composition made from polymer the latter have much higher light outputs. They commonly reach 83% while those made form monomer give only 50% to 60% relative to the reference, BC408. When oil modified scintillators using both p-terphenyl and tetraphenylbutadiene are compared with identical scintillators except that they use 3 hydroxy-flavone as the only luminophore the radiation stability is the same. However the 3HF system gives only 30% as much light as BC408 instead of 83% when both are measured with a green extended Phillips XP2081B phototube.

  20. Radiation hardness and timing studies of a monolithic TowerJazz pixel design for the new ATLAS Inner Tracker

    NASA Astrophysics Data System (ADS)

    Riegel, C.; Backhaus, M.; Van Hoorne, J. W.; Kugathasan, T.; Musa, L.; Pernegger, H.; Riedler, P.; Schaefer, D.; Snoeys, W.; Wagner, W.

    2017-01-01

    A part of the upcoming HL-LHC upgrade of the ATLAS Detector is the construction of a new Inner Tracker. This upgrade opens new possibilities, but also presents challenges in terms of occupancy and radiation tolerance. For the pixel detector inside the inner tracker, hybrid modules containing passive silicon sensors and connected readout chips are presently used, but require expensive assembly techniques like fine-pitch bump bonding. Silicon devices fabricated in standard commercial CMOS technologies, which include part or all of the readout chain, are also investigated offering a reduced cost as they are cheaper per unit area than traditional silicon detectors. If they contain the full readout chain, as for a fully monolithic approach, there is no need for the expensive flip-chip assembly, resulting in a further cost reduction and material savings. In the outer pixel layers of the ATLAS Inner Tracker, the pixel sensors must withstand non-ionising energy losses of up to 1015 n/cm2 and offer a timing resolution of 25 ns or less. This paper presents test results obtained on a monolithic test chip, the TowerJazz 180nm Investigator, towards these specifications. The presented program of radiation hardness and timing studies has been launched to investigate this technology's potential for the new ATLAS Inner Tracker.

  1. Study of EUV and x-ray radiation hardness of silicon photodiodes

    NASA Astrophysics Data System (ADS)

    Zabrodsky, Vladimir V.; Aruev, Pavel; Filimonov, Vladimir V.; Sobolev, Nikolay A.; Sherstnev, Evgeniy V.; Belik, Viktor P.; Nikolenko, Anton D.; Ivlyushkin, Denis V.; Pindyurin, Valery F.; Shadrin, Nikita S.; Soldatov, Artem E.; Mashkovtsev, Mikhail R.

    2013-05-01

    This work presents the results of long-term observation of the silicon photodiodes spatial profile response and the silicon photodiodes dark current after their exposure to 10.2 eV quanta and in the spectral range of 150-300 eV. Exposure of the photodiodes to quanta of an energy of 10.2 eV was repeated. Several other photodiodes have been irradiated in the spectral range of 700-1800 eV with a dose of 8 J/cm2. The spatial profile of the irradiated photodiodes was studied with 3.49 eV, 10.2 eV and 100 eV quanta. The effect of the recovery of the response spatial profile has been proved for the p+-n diode. An additional useful method of visualization of irradiated photodiode area is also presented.

  2. Radiation Hardness Assurance (RHA) for Space Systems

    NASA Technical Reports Server (NTRS)

    Poivey, Christian; Buchner, Stephen

    2007-01-01

    This presentation discusses radiation hardness assurance (RHA) for space systems, providing both the programmatic aspects of RHA and the RHA procedure. RHA consists of all activities undertaken to ensure that the electronics and materials of a space system perform to their design specifications after exposure to the space radiation environment. RHA also pertains to environment definition, part selection, part testing, spacecraft layout, radiation tolerant design, and mission/system/subsystems requirements. RHA procedure consists of establishing mission requirements, defining and evaluating the radiation hazard, selecting and categorizing the appropriate parts, and evaluating circuit response to hazard. The RHA approach is based on risk management and is confined only to parts, it includes spacecraft layout, system/subsystem/circuit design, and system requirements and system operations. RHA should be taken into account in the early phases of a program including the proposal and feasibility analysis phases.

  3. Fault-Tolerant, Radiation-Hard DSP

    NASA Technical Reports Server (NTRS)

    Czajkowski, David

    2011-01-01

    Commercial digital signal processors (DSPs) for use in high-speed satellite computers are challenged by the damaging effects of space radiation, mainly single event upsets (SEUs) and single event functional interrupts (SEFIs). Innovations have been developed for mitigating the effects of SEUs and SEFIs, enabling the use of very-highspeed commercial DSPs with improved SEU tolerances. Time-triple modular redundancy (TTMR) is a method of applying traditional triple modular redundancy on a single processor, exploiting the VLIW (very long instruction word) class of parallel processors. TTMR improves SEU rates substantially. SEFIs are solved by a SEFI-hardened core circuit, external to the microprocessor. It monitors the health of the processor, and if a SEFI occurs, forces the processor to return to performance through a series of escalating events. TTMR and hardened-core solutions were developed for both DSPs and reconfigurable field-programmable gate arrays (FPGAs). This includes advancement of TTMR algorithms for DSPs and reconfigurable FPGAs, plus a rad-hard, hardened-core integrated circuit that services both the DSP and FPGA. Additionally, a combined DSP and FPGA board architecture was fully developed into a rad-hard engineering product. This technology enables use of commercial off-the-shelf (COTS) DSPs in computers for satellite and other space applications, allowing rapid deployment at a much lower cost. Traditional rad-hard space computers are very expensive and typically have long lead times. These computers are either based on traditional rad-hard processors, which have extremely low computational performance, or triple modular redundant (TMR) FPGA arrays, which suffer from power and complexity issues. Even more frustrating is that the TMR arrays of FPGAs require a fixed, external rad-hard voting element, thereby causing them to lose much of their reconfiguration capability and in some cases significant speed reduction. The benefits of COTS high

  4. Radiation Hard AlGaN Detectors and Imager

    SciTech Connect

    2012-05-01

    Radiation hardness of AlGaN photodiodes was tested using a 65 MeV proton beam with a total proton fluence of 3x10{sup 12} protons/cm{sup 2}. AlGaN Deep UV Photodiode have extremely high radiation hardness. These new devices have mission critical applications in high energy density physics (HEDP) and space explorations. These new devices satisfy radiation hardness requirements by NIF. NSTec is developing next generation AlGaN optoelectronics and imagers.

  5. Development of a radiation-hard photomultiplier tube

    NASA Technical Reports Server (NTRS)

    Birnbaum, M. M.; Bunker, R. L.; Roderick, J.; Stephenson, K.

    1984-01-01

    In a radiation-hard photomultiplier tube (PMT) such as has been developed for stabilization of the Galileo spacecraft as it goes through the Jovian high energy radiation belts, the primary effects of high energy electron and proton radiation that must be resisted are the production of fluorescence and Cerenkov emission. The present PMT envelope is ceramic rather than glass, and employs a special, electron-focusing design which will collect, accelerate and amplify electrons only from desired photocathode areas. Tests in a Co-60 radiation facility have shown that the radiation-hard PMT produces less than 2.5 percent of the radiation noise of a standard PMT.

  6. Test bench development for the radiation Hard GBTX ASIC

    NASA Astrophysics Data System (ADS)

    Leitao, P.; Feger, S.; Porret, D.; Baron, S.; Wyllie, K.; Barros Marin, M.; Figueiredo, D.; Francisco, R.; Da Silva, J. C.; Grassi, T.; Moreira, P.

    2015-01-01

    This paper presents the development of the GBTX radiation hard ASIC test bench. Developed for the LHC accelerator upgrade programs, the GBTX implements a bidirectional 4.8 Gb/s link between the radiation hard on-detector custom electronics and the off-detector systems. The test bench was used for functional testing of the GBTX and to evaluate its performance in a radiation environment, by conducting Total Ionizing Dose and Single-Event Upsets tests campaigns.

  7. Temperature Insensitive and Radiation Hard Photonics

    DTIC Science & Technology

    2014-03-19

    caused by solar activity follows a cyclic pattern with spurts of activity resulting from sunspots and flares . This pattern has been well studied also...year. One must also consider the effects of periodic solar flares , which would increase the radiation dosage. Worst- case estimates for dosages on...which means that we can examine solar activity from 2003 GSAT-2 data to determine potential maxima. Examination of solar activity for that time period

  8. Statistical Modeling for Radiation Hardness Assurance: Toward Bigger Data

    NASA Technical Reports Server (NTRS)

    Ladbury, R.; Campola, M. J.

    2015-01-01

    New approaches to statistical modeling in radiation hardness assurance are discussed. These approaches yield quantitative bounds on flight-part radiation performance even in the absence of conventional data sources. This allows the analyst to bound radiation risk at all stages and for all decisions in the RHA process. It also allows optimization of RHA procedures for the project's risk tolerance.

  9. Radiation hardness of the storage phosphor europium doped potassium chloride for radiation therapy dosimetry

    SciTech Connect

    Driewer, Joseph P.; Chen, Haijian; Osvet, Andres; Low, Daniel A.; Li, H. Harold

    2011-08-15

    Purpose: An important property of a reusable dosimeter is its radiation hardness, that is, its ability to retain its dosimetric merits after irradiation. The radiation hardness of europium doped potassium chloride (KCl:Eu{sup 2+}), a storage phosphor material recently proposed for radiation therapy dosimetry, is examined in this study. Methods: Pellet-style KCl:Eu{sup 2+} dosimeters, 6 mm in diameter, and 1 mm thick, were fabricated in-house for this study. The pellets were exposed by a 6 MV photon beam or in a high dose rate {sup 137}Cs irradiator. Macroscopic properties, such as radiation sensitivity, dose response linearity, and signal stability, were studied with a laboratory photostimulated luminescence (PSL) readout system. Since phosphor performance is related to the state of the storage centers and the activator, Eu{sup 2+}, in the host lattice, spectroscopic and temporal measurements were carried out in order to explore radiation-induced changes at the microscopic level. Results: KCl:Eu{sup 2+} dosimeters retained approximately 90% of their initial signal strength after a 5000 Gy dose history. Dose response was initially supralinear over the dose range of 100-700 cGy but became linear after 60 Gy. Linearity did not change significantly in the 0-5000 Gy dose history spanned in this study. Annealing high dose history chips resulted in a return of supralinearity and a recovery of sensitivity. There were no significant changes in the PSL stimulation spectra, PSL emission spectra, photoluminescence spectra, or luminescence lifetime, indicating that the PSL signal process remains intact after irradiation but at a reduced efficiency due to reparable radiation-induced perturbations in the crystal lattice. Conclusions: Systematic studies of KCl:Eu{sup 2+} material are important for understanding how the material can be optimized for radiation therapy dosimetry purposes. The data presented here indicate that KCl:Eu{sup 2+} exhibits strong radiation hardness and

  10. Sustainably Sourced, Thermally Resistant, Radiation Hard Biopolymer

    NASA Technical Reports Server (NTRS)

    Pugel, Diane

    2011-01-01

    This material represents a breakthrough in the production, manufacturing, and application of thermal protection system (TPS) materials and radiation shielding, as this represents the first effort to develop a non-metallic, non-ceramic, biomaterial-based, sustainable TPS with the capability to also act as radiation shielding. Until now, the standing philosophy for radiation shielding involved carrying the shielding at liftoff or utilizing onboard water sources. This shielding material could be grown onboard and applied as needed prior to different radiation landscapes (commonly seen during missions involving gravitational assists). The material is a bioplastic material. Bioplastics are any combination of a biopolymer and a plasticizer. In this case, the biopolymer is a starch-based material and a commonly accessible plasticizer. Starch molecules are composed of two major polymers: amylase and amylopectin. The biopolymer phenolic compounds are common to the ablative thermal protection system family of materials. With similar constituents come similar chemical ablation processes, with the potential to have comparable, if not better, ablation characteristics. It can also be used as a flame-resistant barrier for commercial applications in buildings, homes, cars, and heater firewall material. The biopolymer is observed to undergo chemical transformations (oxidative and structural degradation) at radiation doses that are 1,000 times the maximum dose of an unmanned mission (10-25 Mrad), indicating that it would be a viable candidate for robust radiation shielding. As a comparison, the total integrated radiation dose for a three-year manned mission to Mars is 0.1 krad, far below the radiation limit at which starch molecules degrade. For electron radiation, the biopolymer starches show minimal deterioration when exposed to energies greater than 180 keV. This flame-resistant, thermal-insulating material is non-hazardous and may be sustainably sourced. It poses no hazardous

  11. Resonance hard radiation in a gas-loaded FEL

    SciTech Connect

    Gevorgian, L.A.

    1995-12-31

    The process of induced radiation under the condition when the relativistic beam oscillation frequency coincides with the plasma frequency of the FEL filling gas, is investigated. Such a resonance results in a giant enhancement of interaction between electrons and photons providing high gain in the hard FEL frequency region. Meanwhile the spectralwidth of the spontaneous radiation is broadened significantly. A method is proposed for maintaining the synchronism between the electron oscillation frequency and the medium plasma frequency, enabling to transform the electron energy into hard radiation with high efficiency.

  12. Effect of gamma radiation on micromechanical hardness of lead-free solder joint

    SciTech Connect

    Paulus, Wilfred; Rahman, Irman Abdul; Jalar, Azman; Kamil, Insan; Bakar, Maria Abu; Yusoff, Wan Yusmawati Wan

    2015-09-25

    Lead-free solders are important material in nano and microelectronic surface mounting technology for various applications in bio medicine, environmental monitoring, spacecraft and satellite instrumentation. Nevertheless solder joint in radiation environment needs higher reliability and resistance to any damage caused by ionizing radiations. In this study a lead-free 99.0Sn0.3Ag0.7Cu wt.% (SAC) solder joint was developed and subjected to various doses of gamma radiation to investigate the effects of the ionizing radiation to micromechanical hardness of the solder. Averaged hardness of the SAC joint was obtained from nanoindentation test. The results show a relationship between hardness values of indentations and the increment of radiation dose. Highest mean hardness, 0.2290 ± 0.0270 GPa was calculated on solder joint which was exposed to 5 Gray dose of gamma radiation. This value indicates possible radiation hardening effect on irradiated solder. The hardness gradually decreased to 0.1933 ± 0.0210 GPa and 0.1631 ± 0.0173 GPa when exposed to doses 50 and 500 gray respectively. These values are also lower than the hardness of non irradiated sample which was calculated as 0.2084 ± 0.0.3633 GPa indicating possible radiation damage and needs further related atomic dislocation study.

  13. Radiation Hard 0.13 Micron CMOS Library at IHP

    NASA Astrophysics Data System (ADS)

    Jagdhold, U.

    2013-08-01

    To support space applications we have developed an 0.13 micron CMOS library which should be radiation hard up to 200 krad. The article describes the concept to come to a radiation hard digital circuit and was introduces in 2010 [1]. By introducing new radiation hard design rules we will minimize IC-level leakage and single event latch-up (SEL). To reduce single event upset (SEU) we add two p-MOS transistors to all flip flops. For reliability reasons we use double contacts in all library elements. The additional rules and the library elements are integrated in our Cadence mixed signal design kit, “Virtuoso” IC6.1 [2]. A test chip is produced with our in house 0.13 micron BiCMOS technology, see Ref. [3]. As next step we will doing radiation tests according the european space agency (ESA) specifications, see Ref. [4], [5].

  14. Initial Nuclear Radiation Hardness Validation Test

    DTIC Science & Technology

    2008-11-03

    Measurement Accuracy Photocurrent Photocurrent Probes ±5% Gamma Dose **CaF 2 (Mn) TLD ±10% Gamma Radiation Pulse PIN Diode Compton ...1.02 and cGy(tissue)/cGy(CaF2) = 1.13, respectively. Each radiation pulse will be measured using a PIN or Compton diode and digitized on a transient...photocurrents produce secondary effects that include: a. Error generation in logic and analog circuits. b. Secondary photocurrents. TOP 1-2-618 3

  15. RAD hard PROM design study

    NASA Technical Reports Server (NTRS)

    1981-01-01

    The results of a preliminary study on the design of a radiation hardened fusible link programmable read-only memory (PROM) are presented. Various fuse technologies and the effects of radiation on MOS integrated circuits are surveyed. A set of design rules allowing the fabrication of a radiation hardened PROM using a Si-gate CMOS process is defined. A preliminary cell layout was completed and the programming concept defined. A block diagram is used to describe the circuit components required for a 4 K design. A design goal data sheet giving target values for the AC, DC, and radiation parameters of the circuit is presented.

  16. Radiation Hardness Assurance (RHA) for Small Missions

    NASA Technical Reports Server (NTRS)

    Campola, Michael J.

    2016-01-01

    Varied mission life and complexity is growing for small spacecraft. Small missions benefit from detailed hazard definition and evaluation as done in the past. Requirements need to flow from the system down to the parts level and aid system level radiation tolerance. RHA is highlighted with increasing COTS usage.

  17. Radiation hardness of present optical fibres

    NASA Astrophysics Data System (ADS)

    Henschel, Henning

    1994-12-01

    Optical fibers find rapidly growing use also in the nuclear industry. The dependence of their radiation-induced loss on fiber type, wavelength, temperature, light power, dose rate, and radiation type (gamma rays, neutrons) is pointed out and test results of modern (1989 - 1993) single mode (SM), graded index (GI), multimode stepindex (MM SI), and polymer optical fibers (POF) are presented. Continuous 60Co gamma irradiation of the SM fibers with a dose rate of about 1.5 Gy/s up to a final dose of 106 Gy led to radiation-induced losses of only 0.85 to 1.3 dB/10 m at 1300 nm wavelength and temperatures around 30 degree(s)C, whereas the GI fibers had losses of 1.3 to 2 dB/10 m under the same conditions. The lowest radiation-induced loss show MM SI fibers with pure SiO2 core of high OH-content: about 0.15 dB/10 m around 850 nm and about 0.1 dB/10 m around 1060 nm (106 Gy, equals 30 degree(s)C). POF with a core made of polymethyl methacrylate also have loss increases of

  18. Curve Fitting Solar Cell Degradation Due to Hard Particle Radiation

    NASA Technical Reports Server (NTRS)

    Gaddy, Edward M.; Cikoski, Rebecca; Mekadenaumporn, Danchai

    2003-01-01

    This paper investigates the suitability of the equation for accurately defining solar cell parameter degradation as a function of hard particle radiation. The paper also provides methods for determining the constants in the equation and compares results from this equation to those obtained by the more traditionally used.

  19. Hard Scattering Studies at Jlab

    SciTech Connect

    Harutyun Avagyan; Peter Bosted; Volker Burkert; Latifa Elouadrhiri

    2005-09-01

    We present current activities and future prospects for studies of hard scattering processes using the CLAS detector and the CEBAF polarized electron beam. Kinematic dependences of single and double spin asymmetries have been measured in a wide kinematic range at CLAS with a polarized NH{sub 3} and unpolarized liquid hydrogen targets. It has been shown that the data are consistent with factorization and observed target and beam asymmetries are in good agreement with measurements performed at higher energies, suggesting that the high energy-description of the semi-inclusive DIS process can be extended to the moderate energies of JLab measurements.

  20. Development of a radiation-hard CMOS process

    NASA Technical Reports Server (NTRS)

    Power, W. L.

    1983-01-01

    It is recommended that various techniques be investigated which appear to have the potential for improving the radiation hardness of CMOS devices for prolonged space flight mission. The three key recommended processing techniques are: (1) making the gate oxide thin. It has been shown that radiation degradation is proportional to the cube of oxide thickness so that a relatively small reduction in thickness can greatly improve radiation resistance; (2) cleanliness and contamination control; and (3) to investigate different oxide growth (low temperature dry, TCE and HCL). All three produce high quality clean oxides, which are more radiation tolerant. Technique 2 addresses the reduction of metallic contamination. Technique 3 will produce a higher quality oxide by using slow growth rate conditions, and will minimize the effects of any residual sodium contamination through the introduction of hydrogen and chlorine into the oxide during growth.

  1. Solar cell nanotechnology for improved efficiency and radiation hardness

    NASA Astrophysics Data System (ADS)

    Fedoseyev, Alexander I.; Turowski, Marek; Shao, Qinghui; Balandin, Alexander A.

    2006-08-01

    Space electronic equipment, and NASA future exploration missions in particular, require improvements in solar cell efficiency and radiation hardness. Novel nano-engineered materials and quantum-dot array based photovoltaic devices promise to deliver more efficient, lightweight solar cells and arrays which will be of high value to long term space missions. In this paper, we describe issues related to the development of the quantum-dot based solar cells and comprehensive software tools for simulation of the nanostructure-based photovoltaic cells. Some experimental results used for the model validation are also reviewed. The novel modeling and simulation tools for the quantum-dot-based nanostructures help to better understand and predict behavior of the nano-devices and novel materials in space environment, assess technologies, devices, and materials for new electronic systems as well as to better evaluate the performance and radiation response of the devices at an early design stage. The overall objective is to investigate and design new photovoltaic structures based on quantum dots (QDs) with improved efficiency and radiation hardness. The inherently radiation tolerant quantum dots of variable sizes maximize absorption of different light wavelengths, i.e., create a "multicolor" cell, which improves photovoltaic efficiency and diminishes the radiation-induced degradation. The QD models described here are being integrated into the advanced photonic-electronic device simulator NanoTCAD, which can be useful for the optimization of QD superlattices as well as for the development and exploring of new solar cell designs.

  2. Influence of Li-codoping on the radiation hardness of CsBr:Eu{sup 2+}

    SciTech Connect

    Zimmermann, J.; Hesse, S.; Seggern, H. von; Fuchs, M.; Knuepfer, W.

    2007-06-01

    The poor radiation hardness of the otherwise excellent x-ray storage phosphor CsBr:Eu{sup 2+} constitutes a problem for its commercial application in medical diagnostics. X-ray induced vacancy centers such as M-centers enhance the diffusion of Eu{sup 2+} activators resulting in a formation of photostimulated luminescence (PSL) inactive europium clusters or second phases of europium compounds. The present study investigates the influence of Li-codoping on the radiation hardness of CsBr:Eu{sup 2+}. It is reported that the integration of Li{sup +} into the CsBr:Eu{sup 2+} suppresses the generation of M-centers during x-irradiation and thereby partially improves the radiation hardness.

  3. Radiation hardness of three-dimensional polycrystalline diamond detectors

    SciTech Connect

    Lagomarsino, Stefano Sciortino, Silvio; Bellini, Marco; Corsi, Chiara; Cindro, Vladimir; Kanxheri, Keida; Servoli, Leonello; Morozzi, Arianna; Passeri, Daniele; Schmidt, Christian J.

    2015-05-11

    The three-dimensional concept in particle detection is based on the fabrication of columnar electrodes perpendicular to the surface of a solid state radiation sensor. It permits to improve the radiation resistance characteristics of a material by lowering the necessary bias voltage and shortening the charge carrier path inside the material. If applied to a long-recognized exceptionally radiation-hard material like diamond, this concept promises to pave the way to the realization of detectors of unprecedented performances. We fabricated conventional and three-dimensional polycrystalline diamond detectors, and tested them before and after neutron damage up to 1.2 ×10{sup 16 }cm{sup −2}, 1 MeV-equivalent neutron fluence. We found that the signal collected by the three-dimensional detectors is up to three times higher than that of the conventional planar ones, at the highest neutron damage ever experimented.

  4. Radiation-hard electrical coil and method for its fabrication

    DOEpatents

    Grieggs, R.J.; Blake, R.D.; Gac, F.D.

    1982-06-29

    A radiation-hard insulated electrical coil and method for making the same are disclosed. In accordance with the method, a conductor, preferably copper, is wrapped with an aluminum strip and then tightly wound into a coil. The aluminum-wrapped coil is then annealed to relax the conductor in the coiled configuration. The annealed coil is then immersed in an alkaline solution to dissolve the aluminum strip, leaving the bare conductor in a coiled configuration with all of the windings closely packed yet uniformly spaced from one another. The coil is then insulated with a refractory insulating material. In the preferred embodiment, the coil is insulated by coating it with a vitreous enamel and subsequently potting the enamelled coil in a castable ceramic concrete. The resulting coil is substantially insensitive to radiation and may be operated continuously in high radiation environments for long periods of time.

  5. Radiation hardness of 3HF-tile/O2-WLS-fiber calorimeter

    SciTech Connect

    Han, S.W.; Hu, L.D.; Liu, N.Z.

    1993-11-01

    The radiation hardness of a 3HF-tile/O2-WLS-fiber calorimeter with two different tile/fiber patterns has been studied. Two calorimeter modules were irradiated up to 10 Mrad with the BEPC 1.3 GeV electron beam. The radiation damage of these modules is compared with our previous measurements from SCSN81-tile/BCF91A-WLS-fiber modules. The longitudinal damage profiles are fitted as a function of depth.

  6. Radiation Hardness Assurance (RHA): Challenges and New Considerations

    NASA Technical Reports Server (NTRS)

    Campola, Michael J.

    2017-01-01

    Radiation Hardness Assurance (RHA) challenges associated with the use of commercial-off-the-shelf (COTS) components and emerging technologies are cause for risk acceptance in space flight missions. The RHA flow includes environment definition, hazard evaluation, requirements definition, evaluation of design, and design trades to accommodate the risk a project or program takes. The varied missions profiles and environments don't necessarily benefit from the same risk reduction efforts or cost reduction attempts. The level of effort within the RHA flow can be tailored to minimize risk based on the environment or design criticality.

  7. Radiation-hard/high-speed parallel optical links

    NASA Astrophysics Data System (ADS)

    Gan, K. K.; Buchholz, P.; Heidbrink, S.; Kagan, H. P.; Kass, R. D.; Moore, J.; Smith, D. S.; Vogt, M.; Ziolkowski, M.

    2016-09-01

    We have designed and fabricated a compact parallel optical engine for transmitting data at 5 Gb/s. The device consists of a 4-channel ASIC driving a VCSEL (Vertical Cavity Surface Emitting Laser) array in an optical package. The ASIC is designed using only core transistors in a 65 nm CMOS process to enhance the radiation-hardness. The ASIC contains an 8-bit DAC to control the bias and modulation currents of the individual channels in the VCSEL array. The performance of the optical engine up at 5 Gb/s is satisfactory.

  8. Absorption of infrared radiation by human dental hard substances

    NASA Astrophysics Data System (ADS)

    Roth, Klaus K.; Duczynski, Edwin W.; von der Heide, Hans-Joachim; Struve, Bert

    1993-12-01

    Absorption spectra of enamel, dentin, synthetic hydroxyapatite and deionized water were taken in the wavelength band 500 to 3000 nm. It could be shown that infrared radiation is mainly absorbed in the aqueous components of dental hard tissues. Because of their decreased water content extinctions measured are slightly lower than those of deionized water. Furthermore, mineral absorptions could be detected in the range of 2760 to 2840 nm with a maximum at 2800 nm in enamel and a smaller one at 2500 nm in dentin.

  9. A source of hard X-ray radiation based on hybrid X pinches

    NASA Astrophysics Data System (ADS)

    Shelkovenko, T. A.; Pikuz, S. A.; Hoyt, C. L.; Cahill, A. D.; Atoyan, L.; Hammer, D. A.; Tilikin, I. N.; Mingaleev, A. R.; Romanova, V. M.; Agafonov, A. V.

    2016-10-01

    X pinches are well known to produce very small, dense plasma pinches ("hot spots") that emit sub-nanosecond bursts of 1-8 keV radiation. Hard X-ray radiation in the range from 8 to 300 keV or more is also emitted, and only a small portion of which is associated with the X-pinch hot spot. In hybrid X-pinches (HXP), the 10 ns hard X-ray pulse is terminated by fast closure of the gap between the two conical electrodes of the HXP by rapidly expanding electrode plasmas. The temporal, spectral, and spatial properties of this higher energy radiation have been studied. This radiation was used for point-projection imaging with magnification between 1.5 and 6, and spatial resolution of 20-100 μm was demonstrated.

  10. Strategies for Radiation Hardness Testing of Power Semiconductor Devices

    NASA Technical Reports Server (NTRS)

    Soltis, James V. (Technical Monitor); Patton, Martin O.; Harris, Richard D.; Rohal, Robert G.; Blue, Thomas E.; Kauffman, Andrew C.; Frasca, Albert J.

    2005-01-01

    Plans on the drawing board for future space missions call for much larger power systems than have been flown in the past. These systems would employ much higher voltages and currents to enable more powerful electric propulsion engines and other improvements on what will also be much larger spacecraft. Long term human outposts on the moon and planets would also require high voltage, high current and long life power sources. Only hundreds of watts are produced and controlled on a typical robotic exploration spacecraft today. Megawatt systems are required for tomorrow. Semiconductor devices used to control and convert electrical energy in large space power systems will be exposed to electromagnetic and particle radiation of many types, depending on the trajectory and duration of the mission and on the power source. It is necessary to understand the often very different effects of the radiations on the control and conversion systems. Power semiconductor test strategies that we have developed and employed will be presented, along with selected results. The early results that we have obtained in testing large power semiconductor devices give a good indication of the degradation in electrical performance that can be expected in response to a given dose. We are also able to highlight differences in radiation hardness that may be device or material specific.

  11. Medium-induced gluon radiation in hard forward parton scattering in the saturation formalism

    NASA Astrophysics Data System (ADS)

    Munier, Stéphane; Peigné, Stéphane; Petreska, Elena

    2017-01-01

    We derive the medium-induced, fully coherent soft gluon radiation spectrum associated with the hard forward scattering of an energetic parton off a nucleus, in the saturation formalism within the Gaussian approximation for the relevant correlators of Wilson lines and for finite number of colors. The validity range of the result is rigorously specified by keeping track of the order of magnitude of subleading contributions to the spectrum. The connection between the saturation formalism and the opacity expansion used in previous studies of the same observable is made apparent. Our calculation sets the basis for further studies of the interplay between saturation and fully coherent energy loss in hard forward parton scattering.

  12. Impact of Radiation Hardness and Operating Temperatures of Silicon Carbide Electronics on Space Power System Mass

    NASA Technical Reports Server (NTRS)

    Juhasz, Albert J.; Tew, Roy C.; Schwarze, Gene E.

    1998-01-01

    The effect of silicon carbide (SiC) electronics operating temperatures on Power Management and Distribution (PMAD), or Power Conditioning (PC), subsystem radiator size and mass requirements was evaluated for three power output levels (100 kW(e) , 1 MW(e), and 10 MW(e)) for near term technology ( i.e. 1500 K turbine inlet temperature) Closed Cycle Gas Turbine (CCGT) power systems with a High Temperature Gas Reactor (HTGR) heat source. The study was conducted for assumed PC radiator temperatures ranging from 370 to 845 K and for three scenarios of electrical energy to heat conversion levels which needed to be rejected to space by means of the PC radiator. In addition, during part of the study the radiation hardness of the PC electronics was varied at a fixed separation distance to estimate its effect on the mass of the instrument rated reactor shadow shield. With both the PC radiator and the conical shadow shield representing major components of the overall power system the influence of the above on total power system mass was also determined. As expected, results show that the greatest actual mass savings achieved by the use of SiC electronics occur with high capacity power systems. Moreover, raising the PC radiator temperature above 600 K yields only small additional system mass savings. The effect of increased radiation hardness on total system mass is to reduce system mass by virtue of lowering the shield mass.

  13. A comparative study of the radiation hardness of plastic scintillators for the upgrade of the Tile Calorimeter of the ATLAS detector

    NASA Astrophysics Data System (ADS)

    Liao, S.; Erasmus, R.; Jivan, H.; Pelwan, C.; Peters, G.; Sideras-Haddad, E.

    2015-10-01

    The influence of radiation on the light transmittance of plastic scintillators was studied experimentally. The high optical transmittance property of plastic scintillators makes them essential in the effective functioning of the Tile calorimeter of the ATLAS detector at CERN. This significant role played by the scintillators makes this research imperative in the movement towards the upgrade of the tile calorimeter. The radiation damage of polyvinyl toluene (PVT) based plastic scintillators was studied, namely, EJ-200, EJ-208 and EJ-260, all manufactured and provided to us by ELJEN technology. In addition, in order to compare to scintillator brands actually in use at the ATLAS detector currently, two polystyrene (PS) based scintillators and an additional PVT based scintillator were also scrutinized in this study, namely, Dubna, Protvino and Bicron, respectively. All the samples were irradiated using a 6 MeV proton beam at different doses at iThemba LABS Gauteng. The radiation process was planned and mimicked by doing simulations using a SRIM program. In addition, transmission spectra for the irradiated and unirradiated samples of each grade were obtained, observed and analyzed.

  14. Radiation-hard/high-speed array-based optical engine

    NASA Astrophysics Data System (ADS)

    Gan, K. K.; Buchholz, P.; Heidbrink, S.; Kagan, H. P.; Kass, R. D.; Moore, J.; Smith, D. S.; Vogt, M.; Ziolkowski, M.

    2016-12-01

    We have designed and fabricated a compact array-based optical engine for transmitting data at 10 Gb/s. The device consists of a 4-channel ASIC driving a VCSEL (Vertical Cavity Surface Emitting Laser) array in an optical package. The ASIC is designed using only core transistors in a 65 nm CMOS process to enhance the radiation-hardness. The ASIC contains an 8-bit DAC to control the bias and modulation currents of the individual channels in the VCSEL array. The DAC settings are stored in SEU (single event upset) tolerant registers. Several devices were irradiated with 24 GeV/c protons and the performance of the devices is satisfactory after the irradiation.

  15. Extreme Radiation Hardness and Space Qualification of AlGaN Optoelectronic Devices

    SciTech Connect

    Sun, Ke-Xun; Balakrishnan, Kathik; Hultgren, Eric; Goebel, John; Bilenko, Yuri; Yang, Jinwei; Sun, Wenhong; Shatalov, Max; Hu, Xuhong; Gaska, Remis

    2010-09-21

    Unprecedented radiation hardness and environment robustness are required in the new generation of high energy density physics (HEDP) experiments and deep space exploration. National Ignition Facility (NIF) break-even shots will have a neutron yield of 1015 or higher. The Europa Jupiter System Mission (EJSM) mission instruments will be irradiated with a total fluence of 1012 protons/cm2 during the space journey. In addition, large temperature variations and mechanical shocks are expected in these applications under extreme conditions. Hefty radiation and thermal shields are required for Si and GaAs based electronics and optoelectronics devices. However, for direct illumination and imaging applications, shielding is not a viable option. It is an urgent task to search for new semiconductor technologies and to develop radiation hard and environmentally robust optoelectronic devices. We will report on our latest systematic experimental studies on radiation hardness and space qualifications of AlGaN optoelectronic devices: Deep UV Light Emitting Diodes (DUV LEDs) and solarblind UV Photodiodes (PDs). For custom designed AlGaN DUV LEDs with a central emission wavelength of 255 nm, we have demonstrated its extreme radiation hardness up to 2x1012 protons/cm2 with 63.9 MeV proton beams. We have demonstrated an operation lifetime of over 26,000 hours in a nitrogen rich environment, and 23,000 hours of operation in vacuum without significant power drop and spectral shift. The DUV LEDs with multiple packaging styles have passed stringent space qualifications with 14 g random vibrations, and 21 cycles of 100K temperature cycles. The driving voltage, current, emission spectra and optical power (V-I-P) operation characteristics exhibited no significant changes after the space environmental tests. The DUV LEDs will be used for photoelectric charge management in space flights. For custom designed AlGaN UV photodiodes with a central response wavelength of 255 nm, we have demonstrated

  16. Notional Radiation Hardness Assurance (RHA) Planning For NASA Missions: Updated Guidance

    NASA Technical Reports Server (NTRS)

    LaBel, Kenneth A.; Pellish, Jonathan A.

    2014-01-01

    Radiation Hardness Assurance (RHA) is the process of ensuring space system performance in the presence of a space radiation environment. Herein, we present an updated NASA methodology for RHA focusing on content, deliverables and timeframes.

  17. National Radiation Hardness Assurance (RHA) Planning For NASA Missions: Updated Guidance

    NASA Technical Reports Server (NTRS)

    LaBel, Kenneth A.; Pellish, Jonathan Allen

    2014-01-01

    Radiation Hardness Assurance (RHA) is the process of ensuring space system performance in the presence of a space radiation environment. Herein, we present an updated NASA methodology for RHA focusing on content, deliverables and timeframes.

  18. Radiation hard silicon particle detectors for HL-LHC-RD50 status report

    NASA Astrophysics Data System (ADS)

    Terzo, S.

    2017-02-01

    It is foreseen to significantly increase the luminosity of the LHC by upgrading towards the HL-LHC (High Luminosity LHC). The Phase-II-Upgrade scheduled for 2024 will mean unprecedented radiation levels, way beyond the limits of the silicon trackers currently employed. All-silicon central trackers are being studied in ATLAS, CMS and LHCb, with extremely radiation hard silicon sensors to be employed on the innermost layers. Within the RD50 Collaboration, a massive R&D program is underway across experimental boundaries to develop silicon sensors with sufficient radiation tolerance. We will present results of several detector technologies and silicon materials at radiation levels corresponding to HL-LHC fluences. Based on these results, we will give recommendations for the silicon detectors to be used at the different radii of tracking systems in the LHC detector upgrades. In order to complement the measurements, we also perform detailed simulation studies of the sensors.

  19. Fault tolerant, radiation hard, high performance digital signal processor

    NASA Technical Reports Server (NTRS)

    Holmann, Edgar; Linscott, Ivan R.; Maurer, Michael J.; Tyler, G. L.; Libby, Vibeke

    1990-01-01

    An architecture has been developed for a high-performance VLSI digital signal processor that is highly reliable, fault-tolerant, and radiation-hard. The signal processor, part of a spacecraft receiver designed to support uplink radio science experiments at the outer planets, organizes the connections between redundant arithmetic resources, register files, and memory through a shuffle exchange communication network. The configuration of the network and the state of the processor resources are all under microprogram control, which both maps the resources according to algorithmic needs and reconfigures the processing should a failure occur. In addition, the microprogram is reloadable through the uplink to accommodate changes in the science objectives throughout the course of the mission. The processor will be implemented with silicon compiler tools, and its design will be verified through silicon compilation simulation at all levels from the resources to full functionality. By blending reconfiguration with redundancy the processor implementation is fault-tolerant and reliable, and possesses the long expected lifetime needed for a spacecraft mission to the outer planets.

  20. Development of high temperature, radiation hard detectors based on diamond

    NASA Astrophysics Data System (ADS)

    Metcalfe, Alex; Fern, George R.; Hobson, Peter R.; Ireland, Terry; Salimian, Ali; Silver, Jack; Smith, David R.; Lefeuvre, Gwenaelle; Saenger, Richard

    2017-02-01

    Single crystal CVD diamond has many desirable properties compared to current, well developed, detector materials; exceptional radiation, chemical and physical hardness, chemical inertness, low Z (close to human tissue, good for dosimetry), wide bandgap and an intrinsic pathway to fast neutron detection through the 12C(n,α)9Be reaction. However effective exploitation of these properties requires development of a suitable metallisation scheme to give stable contacts for high temperature applications. To best utilise available processing techniques to optimise sensor response through geometry and conversion media configurations, a reliable model is required. This must assess the performance in terms of spectral response and overall efficiency as a function of detector and converter geometry. The same is also required for proper interpretation of experimental data. Sensors have been fabricated with varying metallisation schemes indented to permit high temperature operation; Present test results indicate that viable fabrication schemes for high temperature contacts have been developed and present modelling results, supported by preliminary data from partners indicate simulations provide a useful representation of response.

  1. Radiation hardness of Efratom M-100 rubidium frequency standard

    SciTech Connect

    English, T.C.; Vorwerk, H.; Rudie, N.J.

    1983-02-01

    The effects of nuclear radiation on rubidium gas cell frequency standards and components are presented, including the results of recent tests where a continuously operating rubidium frequency standard (Effratom, Model M-100) was subjected to simultaneous neutron/gamma radiation. At the highest neutron fluence 7.5 10 to the 12th power n/sq cm and total dose 11 krad(Si) tested, the unit operated satisfactorily. The total frequency change over the 2 1/2 hour test period due to all causes, including repeated retraction from and insertion into the reactor, was less than 1 x 10 to the -10th power. The effects of combined neutron/gamma radiation on rubidium frequency standard physics package components were also studied, and the results are presented.

  2. Radiation hardness of Efratom M-100 rubidium frequency standard

    NASA Technical Reports Server (NTRS)

    English, T. C.; Vorwerk, H.; Rudie, N. J.

    1983-01-01

    The effects of nuclear radiation on rubidium gas cell frequency standards and components are presented, including the results of recent tests where a continuously operating rubidium frequency standard (Effratom, Model M-100) was subjected to simultaneous neutron/gamma radiation. At the highest neutron fluence 7.5 10 to the 12th power n/sq cm and total dose 11 krad(Si) tested, the unit operated satisfactorily; the total frequency change over the 2 1/2 hour test period due to all causes, including repeated retraction from and insertion into the reactor, was less than 1 x 10 to the -10th power. The effects of combined neutron/gamma radiation on rubidium frequency standard physics package components were also studied, and the results are presented.

  3. Effect of radiation light characteristics on surface hardness of paint-on resin for shade modification.

    PubMed

    Arikawa, Hiroyuki; Kanie, Takahito; Fujii, Koichi; Ban, Seiji

    2005-12-01

    The purpose of this study was to investigate the effect of radiation light characteristics--of different types of clinical light-curing unit--on polymerization efficiency, as determined by the surface hardness of light-cured paint-on resins. Four shades of paint-on resin for shade modification of restorative resins were used. Materials were cured using one laboratory and three clinical light-curing units with different light sources, namely tungsten-halogen, LED, plasma arc, and xenon flash lamps. Knoop hardness measurements were taken at both the top and bottom surfaces of the specimens to assess the mechanical properties and degree of polymerization. Both LED and plasma arc light units caused significantly poorer surface hardness than the halogen and laboratory xenon lights. In addition, the transparent shade was more sensitive to surface hardness than other chromatic shades. Our results indicated that the polymerization efficiency of paint-on resin was significantly influenced by the radiation light characteristics of clinical light-curing units.

  4. Nonlinear scattering in hard tissue studied with ultrashort laser pulses.

    PubMed

    Eichler, Jürgen; Kim, Beop-Min

    2002-01-01

    The back-scattered spectrum of ultrashort laser pulses (800 nm, 0.2 ps) was studied in human dental and other hard tissues in vitro below the ablation threshold. Frequency doubled radiation (SHG), frequency tripled radiation and two-photon fluorescence were detected. The relative yield for these processes was measured for various pulse energies. The dependence of the SHG signal on probe thickness was determined in forward and back scattering geometry. SHG is sensitive to linear polarization of the incident laser radiation. SHG in human teeth was studied in vitro showing larger signals in dentin than in cementum and enamel. In carious areas no SHG signal could be detected. Possible applications of higher harmonic radiation for diagnostics and microscopy are discussed.

  5. The study of pinch regimes based on radiation-enhanced compression and anomalous resistivity phenomena and their effects on hard x-ray emission in a Mather type dense plasma focus device (SABALAN2)

    SciTech Connect

    Piriaei, D.; Javadi, S.; Ghoranneviss, M.; Mahabadi, T. D.; Saw, S. H.; Lee, S.

    2015-12-15

    In this study, by using argon and nitrogen as the filling gases in a Mather type dense plasma focus device at different values of pressure and charging voltage, two different kinds of pinch regimes were observed for each of the gases. The physics of the pinch regimes could be explained by using the two versions of the Lee's computational model which predicted each of the scenarios and clarified their differences between the two gases according to the radiation-enhanced compression and, additionally, predicted the pinch regimes through the anomalous resistivity effect during the pinch time. This was accomplished through the fitting process (simulation) on the current signal. Moreover, the characteristic amplitude and time scales of the anomalous resistances were obtained. The correlations between the features of the plasma current dip and the emitted hard x-ray pulses were observed. The starting time, intensity, duration, and the multiple or single feature of the emitted hard x-ray strongly correlated to the same respective features of the current dip.

  6. The comparison of radiation hardness of heterojunction SiGe and conventional silicon bipolar transistors

    NASA Astrophysics Data System (ADS)

    Bakerenkov, A. S.; Felitsyn, V. A.; Rodin, A. S.

    2016-10-01

    The results of the X-ray radiation impact on heterojunction SiGe and conventional silicon bipolar transistors are presented. Oxide thickness over the emitter-base junction depletion region determines the radiation hardness of the bipolar transistors. In this article, the estimation of the rate of radiation degradation of electrical parameters for conventional silicon devices and SiGe-transistors is performed.

  7. Effects of He radiation on cavity distribution and hardness of bulk nanolayered Cu-Nb composites

    NASA Astrophysics Data System (ADS)

    Yang, L. X.; Zheng, S. J.; Zhou, Y. T.; Zhang, J.; Wang, Y. Q.; Jiang, C. B.; Mara, N. A.; Beyerlein, I. J.; Ma, X. L.

    2017-04-01

    Interface engineering is an important strategy for developing radiation tolerant materials. In prior work, bulk nanolayered composites fabricated by accumulative roll bonding (ARB) showed outstanding radiation resistance. However, the effects of layer thickness and radiation conditions on damage distributions and their effect on hardness have not been explored. Here, we use transmission electron microscopy (TEM) and nanoindentation to investigate the effects of radiation on the distribution of radiation-induced cavities and post-radiation hardness in ARB nanolayered Cu-Nb composites. We show that whether the cavities cross the interface depends on layer thickness and temperature, and that, remarkably, radiation could generate softening, not always hardening. We posit that the softening mainly results from the recovery of dislocations stored in the crystal after the bulk forming ARB processing due to He radiation and this phenomenon offsets radiation-induced hardening as layers become finer and temperatures rise.

  8. Radiation hardness of n-GaN schottky diodes

    SciTech Connect

    Lebedev, A. A. Belov, S. V.; Mynbaeva, M. G.; Strel’chuk, A. M.; Bogdanova, E. V.; Makarov, Yu. N.; Usikov, A. S.; Kurin, S. Yu.; Barash, I. S.; Roenkov, A. D.; Kozlovski, V. V.

    2015-10-15

    Schottky-barrier diodes with a diameter of ∼10 µm are fabricated on n-GaN epitaxial films grown by hydride vapor-phase epitaxy (HVPE) on sapphire substrates. The changes in the parameters of the diodes under irradiation with 15 MeV protons are studied. The carrier removal rate was found to be 130–145 cm{sup –1}. The linear nature of the dependence N = f(D) (N is the carrier concentration, and D, the irradiation dose) shows that compensation of the material is associated with transitions of electrons from shallow donors to deep acceptor levels which are related to primary radiation defects.

  9. Influence of design variables on radiation hardness of silicon MINP solar cells

    NASA Technical Reports Server (NTRS)

    Anderson, W. A.; Solaun, S.; Rao, B. B.; Banerjee, S.

    1985-01-01

    Metal-insulator-N/P silicon (MINP) solar cells were fabricated using different substrate resistivity values, different N-layer designs, and different I-layer designs. A shallow junction into an 0.3 ohm-cm substrate gave best efficiency whereas a deeper junction into a 1 to 4 ohm-cm substrate gave improved radiation hardness. I-layer design variation did little to influence radiation hardness.

  10. Comparison of the radiation hardness of various VLSI technologies for defense applications

    SciTech Connect

    Gibbon, C.F.

    1985-01-01

    In this review the radiation hardness of various potential very large scale (VLSI) IC technologies is evaluated. IC scaling produces several countervailing trends. Reducing vertical dimensions tends to increase total dose hardness, while reducing lateral feature sizes may increase susceptibility to transient radiation effects. It is concluded that during the next decade at least, silicon complimentary MOS (CMOS), perhaps on an insulating substrate (SOI) will be the technology of choice for VLSI in defense systems.

  11. Improving the radiation hardness of graphene field effect transistors

    NASA Astrophysics Data System (ADS)

    Alexandrou, Konstantinos; Masurkar, Amrita; Edrees, Hassan; Wishart, James F.; Hao, Yufeng; Petrone, Nicholas; Hone, James; Kymissis, Ioannis

    2016-10-01

    Ionizing radiation poses a significant challenge to the operation and reliability of conventional silicon-based devices. Here, we report the effects of gamma radiation on graphene field-effect transistors (GFETs), along with a method to mitigate those effects by developing a radiation-hardened version of our back-gated GFETs. We demonstrate that activated atmospheric oxygen from the gamma ray interaction with air damages the semiconductor device, and damage to the substrate contributes additional threshold voltage instability. Our radiation-hardened devices, which have protection against these two effects, exhibit minimal performance degradation, improved stability, and significantly reduced hysteresis after prolonged gamma radiation exposure. We believe this work provides an insight into graphene's interactions with ionizing radiation that could enable future graphene-based electronic devices to be used for space, military, and other radiation-sensitive applications.

  12. Improving the radiation hardness of graphene field effect transistors

    DOE PAGES

    Alexandrou, Konstantinos; Masurkar, Amrita; Edrees, Hassan; ...

    2016-10-11

    Ionizing radiation poses a significant challenge to the operation and reliability of conventional silicon-based devices. In this paper, we report the effects of gamma radiation on graphene field-effect transistors (GFETs), along with a method to mitigate those effects by developing a radiation-hardened version of our back-gated GFETs. We demonstrate that activated atmospheric oxygen from the gamma ray interaction with air damages the semiconductor device, and damage to the substrate contributes additional threshold voltage instability. Our radiation-hardened devices, which have protection against these two effects, exhibit minimal performance degradation, improved stability, and significantly reduced hysteresis after prolonged gamma radiation exposure. Finally,more » we believe this work provides an insight into graphene's interactions with ionizing radiation that could enable future graphene-based electronic devices to be used for space, military, and other radiation-sensitive applications.« less

  13. Improving the radiation hardness of graphene field effect transistors

    SciTech Connect

    Alexandrou, Konstantinos; Masurkar, Amrita; Edrees, Hassan; Wishart, James F.; Hao, Yufeng; Petrone, Nicholas; Hone, James; Kymissis, Ioannis

    2016-10-11

    Ionizing radiation poses a significant challenge to the operation and reliability of conventional silicon-based devices. In this paper, we report the effects of gamma radiation on graphene field-effect transistors (GFETs), along with a method to mitigate those effects by developing a radiation-hardened version of our back-gated GFETs. We demonstrate that activated atmospheric oxygen from the gamma ray interaction with air damages the semiconductor device, and damage to the substrate contributes additional threshold voltage instability. Our radiation-hardened devices, which have protection against these two effects, exhibit minimal performance degradation, improved stability, and significantly reduced hysteresis after prolonged gamma radiation exposure. Finally, we believe this work provides an insight into graphene's interactions with ionizing radiation that could enable future graphene-based electronic devices to be used for space, military, and other radiation-sensitive applications.

  14. A New Radiation Hard Semiconductor — Semi-Insulating GaN: Photoelectric Properties

    NASA Astrophysics Data System (ADS)

    Vaitkus, J.; Gaubas, E.; Kazukauskas, V.; Blue, A.; Cunningham, W.; Rahman, M.; Smith, K.; Sakai, S.

    2005-06-01

    The anticipated upgrade of the CERN Large Hadron Collider to ten times brighter luminosity poses a severe challenge to semiconductor detectors in the CERN experiments. The suitability of semi-insulating GaN (SI-GaN), proposed as an alternative to silicon for the fabrication of radiation hard detectors, is investigated here in MOCVD GaN layers grown on sapphire. The electrical properties of SI-GaN were studied by dc and microwave techniques, and defect parameters determined by the method of thermally stimulated currents. Variations of charge collection efficiency (CCE) in SI-GaN diodes induced by ionizing radiation of 5.48 MeV alpha particles were revealed. Samples were also irradiated by X-rays, reactor neutrons and high-energy proton fluences of up to 1016 cm-2. The high radiation hardness of SI-GaN was demonstrated by the modest reduction in CCE, from 92% to 77%, in the material irradiated by neutrons (up to a fluence of 1015 cm-2). The CCE was unaffected by an X-rays dose of 600 MRad), but decreased to a few % after proton and neutron fluences of 1016 cm-2. The electrical characteristics vary more significantly, depending on irradiation type and dose. Fast decay components and a significant role of percolation effects are observed in the photoconductivity transients.

  15. Effect Of Clock Mode On Radiation Hardness Of An ADC

    NASA Technical Reports Server (NTRS)

    Lee, Choon I.; Rax, Bernie G.; Johnston, Allan H.

    1995-01-01

    Report discusses techniques for testing and evaluating effects of total dosages of ionizing radiation on performances of high-resolution successive-approximation analog-to-digital converters (ADCs), without having to test each individual bit or transition. Reduces cost of testing by reducing tests to few critical parametric measurements, from which one determines approximate radiation failure levels providing good approximations of responses of converters for purpose of total-dose-radiation evaluations.

  16. Foreign technology assessment: Environmental evaluation of a radiation-hard oscillator/divider

    NASA Astrophysics Data System (ADS)

    Dvorack, M. A.

    1993-03-01

    Salford Electrical Instruments, Ltd., and the General Electric Company's Hirst Research Center, under contract to the United Kingdom's (UK) Ministry of Defence, developed a radiation-hard, leadless chip-carrier-packaged oscillator/divider. Two preproduction clocks brought to Sandia National Laboratories (SNL) by a potential SNL customer underwent mechanical and thermal environmental evaluation. Because of the subsequent failure of one device and the deteriorating condition of another device, the devices were not subjected to radiation tests. The specifics of the environmental evaluation performed on these two clocks and the postmortem analysis of one unit, which ultimately failed, are described. Clock startup time versus temperature studies were also performed and compared to an SNL-designed clock having the same fundamental frequency.

  17. Transition radiation in metal-metal multilayer nanostructures as a medical source of hard x-ray radiation

    SciTech Connect

    Pokrovsky, A. L.; Kaplan, A. E.; Shkolnikov, P. L.

    2006-08-15

    We show that a periodic metal-metal multilayer nanostructure can serve as an efficient source of hard x-ray transition radiation. Our research effort is aimed at developing an x-ray source for medical applications, which is based on using low-energy relativistic electrons. The approach toward choosing radiator-spacer couples for the generation of hard x-ray resonant transition radiation by few-MeV electrons traversing solid multilayer structures for the energies of interest to medicine (30-50 keV) changes dramatically compared with that for soft x-ray radiation. We show that one of the main factors in achieving the required resonant line is the absence of the contrast of the refractive indices between the spacer and the radiator at the far wings of the radiation line; for that purpose, the optimal spacer, as a rule, should have a higher atomic number than the radiator. Having experimental goals in mind, we have considered also the unwanted effects due to bremsstrahlung radiation, absorption and scattering of radiated photons, detector-related issues, and inhibited coherence of transition radiation due to random deviation of spacing between the layers. Choosing as a model example a Mo-Ag radiator-spacer pair of materials, we demonstrate that the x-ray transition radiation line can be well resolved with the use of spatial and frequency filtering.

  18. Radiation hardness improvement of analog front-end microelectronic devices for particle accelerator

    NASA Astrophysics Data System (ADS)

    Miroshnichenko, A. G.; Rodin, A. S.; Bakerenkov, A. S.; Felitsyn, V. A.

    2016-10-01

    Series of schematic techniques for increasing radiation hardness of the current mirrors is developed. These techniques can be used for the design of analog front-end microelectronic devices based on the operational amplifiers. The circuit simulation of radiation degradation of current transmission coefficients was performed for various circuit solutions in LTSpice software.

  19. Design and development of a hard tube flexible radiator system

    NASA Technical Reports Server (NTRS)

    Hixon, C. W.

    1980-01-01

    The construction and operational characteristics of an extended life flexible radiator panel is described. The radiator panel consists of a flexible fin laminate and stainless steel flow tubes designed for a 90 percent probability of surviving 5 years in an Earth orbit micrometeoroid environment. The radiator panel rejects 1.1 kW sub t of heat into an environmental sink temperature of 0 F. Total area is 170 square feet and the panel extends 25 feet in the fully deployed position. When retracted the panel rolls onto a 11.5 inch diameter by 52 inch long storage drum, for a final stored diameter of 22 inches.

  20. Radiation hardness by design for mixed signal infrared readout circuit applications

    NASA Astrophysics Data System (ADS)

    Gaalema, Stephen; Gates, James; Dobyns, David; Pauls, Greg; Wall, Bruce

    2013-09-01

    Readout integrated circuits (ROICs) to support space-based infrared detection applications often have severe radiation tolerance requirements. Radiation hardness-by-design (RHBD) significantly enhances the radiation tolerance of commercially available CMOS and custom radiation hardened fabrication techniques are not required. The combination of application specific design techniques, enclosed gate architecture nFETs and intrinsic thin oxide radiation hardness of 180 nm process node commercial CMOS allows realization of high performance mixed signal circuits. Black Forest Engineering has used RHBD techniques to develop ROICs with integrated A/D conversion that operate over a wide range of temperatures (40K-300K) to support infrared detection. ROIC radiation tolerance capability for 256x256 LWIR area arrays and 1x128 thermopile linear arrays is presented. The use of 130 nm CMOS for future ROIC RHBD applications is discussed.

  1. Test of radiation hardness of CMOS transistors under neutron irradiation

    SciTech Connect

    Sadrozinski, H.F.W.; Rowe, W.A.; Seiden, A.; Spencer, E.; Hoffman, C.M.; Holtkamp, D.; Kinnison, W.W.; Sommer, W.F. Jr.; Ziock, H.J.

    1989-01-01

    We have tested 2 micron CMOS test structures from various foundries in the LAMPF Beam stop for radiation damage under prolongued neutron irradiation. The fluxes employed covered the region expected to be encountered at the SSC and led to fluences of up to 10/sup 14/ neutrons/cm/sup 2/ in about 500 hrs of running. We show that test structures which have been measured to survive ionizing radiation of the order MRad also survive these high neutron fluences. 5 refs., 4 figs.

  2. Radiation Evaluation of an Advanced 64Mb 3.3V DRAM and Insights into the Effects of Scaling on Radiation Hardness

    NASA Technical Reports Server (NTRS)

    Shaw, D. C.; Swift, G. M.; Johnston, A. H.

    1995-01-01

    In this paper, total ionizing dose radiation evaluations of the Micron 64 Mb 3.3 V, fast page mode DRAM and the IBM LUNA-ES 16 Mb DRAM are presented. The effects of scaling on total ionizing dose radiation hardness are studied utilizing test structures and a series of 16 Mb DRAMs with different feature sizes from the same manufacturing line. General agreement was found between the threshold voltage shifts of 16 Mb DRAM test structures and the threshold voltage measured on complete circuits using retention time measurements. Retention time measurement data from early radiation doses are shown that allow internal failure modes to be distinguished.

  3. FPIX2: A radiation-hard pixel readout chip for BTeV

    SciTech Connect

    David C. Christian et al.

    2000-12-11

    A radiation-hard pixel readout chip, FPIX2, is being developed at Fermilab for the recently approved BTeV experiment. Although designed for BTeV, this chip should also be appropriate for use by CDF and DZero. A short review of this development effort is presented. Particular attention is given to the circuit redesign which was made necessary by the decision to implement FPIX2 using a standard deep-submicron CMOS process rather than an explicitly radiation-hard CMOS technology, as originally planned. The results of initial tests of prototype 0.25{micro} CMOS devices are presented, as are plans for the balance of the development effort.

  4. GaN-Based High Temperature and Radiation-Hard Electronics for Harsh Environments

    NASA Technical Reports Server (NTRS)

    Son, Kyung-ah; Liao, Anna; Lung, Gerald; Gallegos, Manuel; Hatakeh, Toshiro; Harris, Richard D.; Scheick, Leif Z.; Smythe, William D.

    2010-01-01

    We develop novel GaN-based high temperature and radiation-hard electronics to realize data acquisition electronics and transmitters suitable for operations in harsh planetary environments. In this paper, we discuss our research on metal-oxide-semiconductor (MOS) transistors that are targeted for 500 (sup o)C operation and >2 Mrad radiation hardness. For the target device performance, we develop Schottky-free AlGaN/GaN MOS transistors, where a gate electrode is processed in a MOS layout using an Al2O3 gate dielectric layer....

  5. Axial ion-electron emission microscopy of IC radiation hardness

    NASA Astrophysics Data System (ADS)

    Doyle, B. L.; Vizkelethy, G.; Walsh, D. S.; Swenson, D.

    2002-05-01

    A new system for performing radiation effects microscopy (REM) has been developed at Sandia National Laboratory in Albuquerque. This system combines two entirely new concepts in accelerator physics and nuclear microscopy. A radio frequency quadrupole (RFQ) linac is used to boost the energy of ions accelerated by a conventional Tandem Van de Graaff-Pelletron to velocities of 1.9 MeV/amu. The electronic stopping power for heavy ions is near a maximum at this velocity, and their range is ˜20 μm in Si. These ions therefore represent the most ionizing form of radiation in nature, and are nearly ideal for performing single event effects testing of integrated circuits. Unfortunately, the energy definition of the RFQ-boosted ions is rather poor (˜ a few %), which makes problematic the focussing of such ions to the submicron spots required for REM. To circumvent this problem, we have invented ion electron emission microscopy (IEEM). One can perform REM with the IEEM system without focussing or scanning the ion beam. This is because the position on the sample where each ion strikes is determined by projecting ion-induced secondary electrons at high magnification onto a single electron position sensitive detector. This position signal is then correlated with each REM event. The IEEM system is now mounted along the beam line in an axial geometry so that the ions pass right through the electron detector (which is annular), and all of the electrostatic lenses used for projection. The beam then strikes the sample at normal incidence which results in maximum ion penetration and removes a parallax problem experienced in an earlier system. Details of both the RFQ-booster and the new axial IEEM system are given together with some of the initial results of performing REM on Sandia-manufactured radiation hardened integrated circuits.

  6. Radiation hard programmable delay line for LHCb calorimeter upgrade

    NASA Astrophysics Data System (ADS)

    Mauricio, J.; Gascón, D.; Vilasís, X.; Picatoste, E.; Machefert, F.; Lefrancois, J.; Duarte, O.; Beigbeder, C.

    2014-01-01

    This paper describes the implementation of a SPI-programmable clock delay chip based on a Delay Locked Loop (DLL) in order to shift the phase of the LHC clock (25 ns) in steps of 1ns, with less than 5 ps jitter and 23 ps of DNL. The delay lines will be integrated into ICECAL, the LHCb calorimeter front-end analog signal processing ASIC in the near future. The stringent noise requirements on the ASIC imply minimizing the noise contribution of digital components. This is accomplished by implementing the DLL in differential mode. To achieve the required radiation tolerance several techniques are applied: double guard rings between PMOS and NMOS transistors as well as glitch suppressors and TMR Registers. This 5.7 mm2 chip has been implemented in CMOS 0.35 μm technology.

  7. Radiation budget study

    NASA Astrophysics Data System (ADS)

    Hartmann, D. L.

    Scientific applications of satellite measurements of the radiative flux density at the top of the atmosphere are discussed in a general review and illustrated with diagrams, maps, and graphs. Topics examined include model development and verification, empirical studies of the global radiation budget, regional energy budgeting, interannual-variability studies, and seasonal and nonseasonal variations in ocean-land radiation budgets. The need for long-term homogeneous series of observations with good spatial and temporal resolution is stressed.

  8. Inclusion of Radiation Environment Variability in Total Dose Hardness Assurance Methodology

    NASA Technical Reports Server (NTRS)

    Xapsos, M. A.; Stauffer, C.; Phan, A.; McClure, S. S.; Ladbury, R. L.; Pellish, J. A.; Campola, M. J.; LaBel, K. A.

    2015-01-01

    Variability of the space radiation environment is investigated with regard to parts categorization for total dose hardness assurance methods. It is shown that it can have a significant impact. A modified approach is developed that uses current environment models more consistently and replaces the design margin concept with one of failure probability.

  9. Magnetic viscosity studies in hard magnetic materials

    SciTech Connect

    Singleton, E.W.; Hadjipanayis, G.C. )

    1990-05-01

    The magnetic viscosity behavior has been studied in several hard magnets with different magnetization reversal mechanisms including barium ferrite powders, Cu-Mn-Al, ferrite magnets, Nd-Fe-B, and SmCo{sub 5}, Sm{sub 2}(Co,Fe,Cu,Zr){sub 17}. The measurements were made with a vibrating sample magnetometer for times up to 60 s and a SQUID magnetometer for longer times in the range of 60--2300 s. For most of the samples the magnetization was found to vary logarithmically with time. The field and temperature dependence of the magnetic viscosity coefficient {ital S} was studied. Here, {ital S} was found to vary with the applied field and it usually peaked around the coercive field {ital H}{sub {ital c}}. The measured values of {ital S}{sub max} at 10 K range from 0.004 to 1.853 emu/g for Cu-Mn-Al and Sm{sub 2}(Co,Fe,Cu,Zr){sub 17}, respectively. The magnetic viscosity coefficient was used together with the magnetic susceptibility to determine the activation volume.

  10. Radiation hardness of Ga0.5In0.5 P/GaAs tandem solar cells

    NASA Technical Reports Server (NTRS)

    Kurtz, Sarah R.; Olson, J. M.; Bertness, K. A.; Friedman, D. J.; Kibbler, A.; Cavicchi, B. T.; Krut, D. D.

    1991-01-01

    The radiation hardness of a two-junction monolithic Ga sub 0.5 In sub 0.5 P/GaAs cell with tunnel junction interconnect was investigated. Related single junction cells were also studied to identify the origins of the radiation losses. The optimal design of the cell is discussed. The air mass efficiency of an optimized tandem cell after irradiation with 10(exp 15) cm (-2) 1 MeV electrons is estimated to be 20 percent using currently available technology.

  11. Creation of a Radiation Hard 0.13 Micron CMOS Library at IHP

    NASA Astrophysics Data System (ADS)

    Jagdhold, U.

    2010-08-01

    To support space applications we will develop an 0.13 micron CMOS library which should be radiation hard up to 200 krad. By introducing new radiation hard design rules we will minimize IC-level leakage and single event latchup (SEL). To reduce single event upset (SEU) we will add two p-MOS transistors to all flip flops. For reliability reasons we will use double contacts in all library elements. The additional rules and the library elements will then be integrated in our Cadence mixed signal designkit, Virtuoso IC6.1 [1]. A test chip will be produced with our in house 0.13 micron BiCMOS technology, see Ref. [2].Thereafter we will doing radiation tests according the ESA specifications, see Ref. [3], [4].

  12. Studies in useful hard x-ray induced chemistry

    NASA Astrophysics Data System (ADS)

    Pravica, Michael; Bai, Ligang; Sneed, Daniel; Park, Changyong

    2013-06-01

    The observed rapid decomposition of potassium chlorate (via 2KClO3 + h ν --> 2KCl +3O2) via synchrotron hard x-ray irradiation (>10 keV) has enabled experiments that are developing novel and useful hard x-ray chemistry. We have observed a number of radiation-induced in situ decomposition reactions in various substances which release O2, H2, N2, NH3, and H2O in a diamond anvil cell (DAC) at ambient and high pressures. These novel acatalytic and isothermal reactions represent a highly controllable, penetrating, and focused method to initiate chemistry (including x-ray induced combustion) in sealed and/or isolated chambers which maintain matter under extreme conditions. During our studies, we have typically observed a slowing of decomposition with pressure including phase dependent decomposition of KClO3. Energy dependent studies have observed an apparent resonance near 15 keV at which the decomposition rate is maximized. This may enable use of much lower flux and portable x-ray sources (e.g. x-ray tubes) in larger scale experiments. These developments support novel means to load DACs and control chemical reactions providing novel routes of synthesis of novel materials under extreme conditions.

  13. Microprocessing of human hard tooth tissues surface by mid-infrared erbium lasers radiation

    NASA Astrophysics Data System (ADS)

    Belikov, Andrey V.; Shatilova, Ksenia V.; Skrypnik, Alexei V.

    2015-03-01

    A new method of hard tooth tissues laser treatment is described. The method consists in formation of regular microdefects on tissue surface by mid-infrared erbium laser radiation with propagation ratio M2<2 (Er-laser microprocessing). Proposed method was used for preparation of hard tooth tissues surface before filling for improvement of bond strength between tissues surface and restorative materials, microleakage reduction between tissues surface and restorative materials, and for caries prevention as a result of increasing microhardness and acid resistance of tooth enamel.

  14. Single-Event Gate Rupture in Power MOSFETs: A New Radiation Hardness Assurance Approach

    NASA Technical Reports Server (NTRS)

    Lauenstein, Jean-Marie

    2011-01-01

    Almost every space mission uses vertical power metal-semiconductor-oxide field-effect transistors (MOSFETs) in its power-supply circuitry. These devices can fail catastrophically due to single-event gate rupture (SEGR) when exposed to energetic heavy ions. To reduce SEGR failure risk, the off-state operating voltages of the devices are derated based upon radiation tests at heavy-ion accelerator facilities. Testing is very expensive. Even so, data from these tests provide only a limited guide to on-orbit performance. In this work, a device simulation-based method is developed to measure the response to strikes from heavy ions unavailable at accelerator facilities but posing potential risk on orbit. This work is the first to show that the present derating factor, which was established from non-radiation reliability concerns, is appropriate to reduce on-orbit SEGR failure risk when applied to data acquired from ions with appropriate penetration range. A second important outcome of this study is the demonstration of the capability and usefulness of this simulation technique for augmenting SEGR data from accelerator beam facilities. The mechanisms of SEGR are two-fold: the gate oxide is weakened by the passage of the ion through it, and the charge ionized along the ion track in the silicon transiently increases the oxide electric field. Most hardness assurance methodologies consider the latter mechanism only. This work demonstrates through experiment and simulation that the gate oxide response should not be neglected. In addition, the premise that the temporary weakening of the oxide due to the ion interaction with it, as opposed to due to the transient oxide field generated from within the silicon, is validated. Based upon these findings, a new approach to radiation hardness assurance for SEGR in power MOSFETs is defined to reduce SEGR risk in space flight projects. Finally, the potential impact of accumulated dose over the course of a space mission on SEGR

  15. Radiation Hard Plastic Scintillators for a New Generation of Particle Detectors

    NASA Astrophysics Data System (ADS)

    Dettmann, M.; Herrig, V.; Maldonis, J.; Neuhaus, J.; Shrestha, D.; Rajbhandari, P.; Thune, Z.; Been, M.; Martinez-Szewczyk, M.; Khristenko, V.; Onel, Y.; Akgun, U.

    2017-03-01

    The radiation hardness of specific scintillating materials used in particle physics experiments is one of the main focuses of research in detector development. This report summarizes the preparation methods, light yield characterization and radiation damage tests of a plastic scintillator with a polysiloxane base and pTP and bis-MSB dopants. The scintillator is shown to be a promising candidate for particle detectors with its intense light output around 400 nm and very little scintillation or transmission loss after proton irradiation of 4 × 105 Gy.

  16. Comparison of proton microbeam and gamma irradiation for the radiation hardness testing of silicon PIN diodes

    NASA Astrophysics Data System (ADS)

    Jakšić, M.; Grilj, V.; Skukan, N.; Majer, M.; Jung, H. K.; Kim, J. Y.; Lee, N. H.

    2013-09-01

    Simple and cost-effective solutions using Si PIN diodes as detectors are presently utilized in various radiation-related applications in which excessive exposure to radiation degrades their charge transport properties. One of the conventional methods for the radiation hardness testing of such devices is time-consuming irradiation with electron beam or gamma-ray irradiation facilities, high-energy proton accelerators, or with neutrons from research reactors. Recently, for the purpose of radiation hardness testing, a much faster nuclear microprobe based approach utilizing proton irradiation has been developed. To compare the two different irradiation techniques, silicon PIN diodes have been irradiated with a Co-60 gamma radiation source and with a 6 MeV proton microbeam. The signal degradation in the silicon PIN diodes for both irradiation conditions has been probed by the IBIC (ion beam induced charge) technique, which can precisely monitor changes in charge collection efficiency. The results presented are reviewed on the basis of displacement damage calculations and NIEL (non-ionizing energy loss) concept.

  17. Observation of hard radiations in a laboratory atmospheric high-voltage discharge

    NASA Astrophysics Data System (ADS)

    Agafonov, A. V.; Bogachenkov, V. A.; Chubenko, A. P.; Oginov, A. V.; Rodionov, A. A.; Rusetskiy, A. S.; Ryabov, V. A.; Shepetov, A. L.; Shpakov, K. V.

    2017-04-01

    The new results concerning neutron emission detection from a laboratory high-voltage discharge in the air are presented. Data were obtained with a combination of plastic scintillation detectors and 3He-filled counters of thermal neutrons. Strong dependence of the hard x-ray and neutron radiation appearance on the field strength near electrodes, which is determined by their form, was found. We have revealed a more sophisticated temporal structure of the neutron bursts observed during electric discharge.

  18. The role of radiation hard solar cells in minimizing the costs of global satellite communication systems

    NASA Technical Reports Server (NTRS)

    Summers, Geoffrey P.; Walters, Robert J.; Messenger, Scott R.; Burke, Edward A.

    1996-01-01

    An analysis embodied in a PC computer program is presented, which quantitatively demonstrates how the availability of radiation hard solar cells can help minimize the cost of a global satellite communications system. An important distinction between the currently proposed systems, such as Iridium, Odyssey and Ellipsat, is the number of satellites employed and their operating altitudes. Analysis of the major costs associated with implementing these systems shows that operation at orbital altitudes within the earth's radiation belts (10(exp 3) to 10(exp 4)km) can reduce the total cost of a system by several hundred percent, so long as radiation hard components including solar cells can be used. A detailed evaluation of the predicted performance of photovoltaic arrays using several different planar solar cell technologies is given, including commercially available Si and GaAs/Ge, and InP/Si which is currently under development. Several examples of applying the program are given, which show that the end of life (EOL) power density of different technologies can vary by a factor of ten for certain missions. Therefore, although a relatively radiation-soft technology can usually provide the required EOL power by simply increasing the size of the array, the impact upon the total system budget could be unacceptable, due to increased launch and hardware costs. In aggregate, these factors can account for more than a 10% increase in the total system cost. Since the estimated total costs of proposed global-coverage systems range from $1B to $9B, the availability of radiation-hard solar cells could make a decisive difference in the selection of a particular constellation architecture.

  19. On the nature of the sources of hard pulse X-ray radiation

    NASA Technical Reports Server (NTRS)

    Shklovskiy, I. S.

    1978-01-01

    Besides the identified sources of cosmic pulse X-ray radiation with globular clusters NGC 6624, NGC 1851 and MXB 1730-335 several new identifications were made. The source in Norma was probably identified with globular cluster NGC 5927, the source in Aquila with globular cluster NGC 6838 (M71), and the source in Puppis with globular cluster NGC 2298. Gamma pulses discovered by the Vela satellites and X-ray pulses thoroughly measured by the SAS-3, Ariel-5, and ANS satellites are thought to be the same phenomenon. The sources of such a radiation must be some kind of peculiarity at the central part of globular clusters; it is most probably a massive black hole. The sources of hard pulse radiation which cannot be identified with globular clusters are considered to be a new kind of galactic object, invisible globular clusters, which are naked nuclei of globular clusters.

  20. Radiation Hardness Tests of SiPMs for the JLab Hall D Barrel Calorimeter

    SciTech Connect

    Yi Qiang, Carl Zorn, Fernando Barbosa, Elton Smith

    2013-01-01

    We report on the measurement of the neutron radiation hardness of silicon photomultipliers (SiPMs) manufactured by Hamamatsu Corporation in Japan and SensL in Ireland. Samples from both companies were irradiated by neutrons created by a 1 GeV electron beam hitting a thin lead target at Jefferson Lab Hall A. More tests regarding the temperature dependence of the neutron radiation damage and self-annealing were performed on Hamamatsu SiPMs using a calibrated Am–Be neutron source from the Jefferson Lab Radiation Control group. As the result of irradiation both dark current and dark rate increase linearly as a function of the 1 MeV equivalent neutron fluence and a temperature dependent self-annealing effect is observed

  1. Hard sphere study of condensation entropy

    NASA Astrophysics Data System (ADS)

    Graziano, Giuseppe

    2008-06-01

    A simple procedure is devised to calculate the Ben-Naim standard condensation entropy by treating neat liquids as hard sphere fluids. The calculated values are close to the experimental ones for nonpolar liquids, but not for polar aprotic ones and for H-bonded liquids. For the latter the calculated entropy values become close to the experimental ones if the molecular van der Waals diameters are used instead of the effective ones. This implies that the magnitude of the orientational entropy loss due to H-bond formation is quantitatively similar to that of the configurational entropy gain for the decrease in excluded volume due to the bunching up effect caused by H-bonds.

  2. Statistical Study of Hard X-ray Footpoint Region

    NASA Astrophysics Data System (ADS)

    Sato, J.

    2003-12-01

    We show statistical characteristics of hard X-ray footpoint sources derived from THE YOHKOH FLARE IMAGE CATALOGUE. We use many hard X-ray images over the whole YOHKOH mission period (1991/08 - 2001/12) and the study is concentrated on following two points. 1) Average height of hard X-ray footpoint sources in the four HXT(Hard X-ray Telescope) energy bands (14-23, 23-33, 33-53, 53-93 keV). 2) Spectral characteristics of hard X-ray footpoint sources. We mainly revealed that A) the hard X-ray emission comes from just above the Hα emitting region and the accelerated electrons loose their energy within 1000 km length leading to the high density around footpoints, and that B) Many hard X-ray footpoint sources show a broken power-law spectrum with very hard spectrum in the low energy range (20-30 keV), suggesting a cut off energy of accelerated electrons is around 20 keV - 30 keV at least.

  3. Aerothermodynamic radiation studies

    NASA Technical Reports Server (NTRS)

    Donohue, K.; Reinecke, W. G.; Rossi, D.; Marinelli, W. J.; Krech, R. H.; Caledonia, G. E.

    1991-01-01

    We have built and made operational a 6 in. electric arc driven shock tube which alloys us to study the non-equilibrium radiation and kinetics of low pressure (0.1 to 1 torr) gases processed by 6 to 12 km/s shock waves. The diagnostic system allows simultaneous monitoring of shock radiation temporal histories by a bank of up to six radiometers, and spectral histories with two optical multi-channel analyzers. A data set of eight shots was assembled, comprising shocks in N2 and air at pressures between 0.1 and 1 torr and velocities of 6 to 12 km/s. Spectrally resolved data was taken in both the non-equilibrium and equilibrium shock regions on all shots. The present data appear to be the first spectrally resolved shock radiation measurements in N2 performed at 12 km/s. The data base was partially analyzed with salient features identified.

  4. The role of radiation hard solar cells in minimizing the costs of global satellite communications systems

    NASA Technical Reports Server (NTRS)

    Summers, Geoffrey P.; Walters, Robert J.; Messenger, Scott R.; Burke, Edward A.

    1995-01-01

    An analysis embodied in a PC computer program is presented which quantitatively demonstrates how the availability of radiation hard solar cells can minimize the cost of a global satellite communication system. The chief distinction between the currently proposed systems, such as Iridium Odyssey and Ellipsat, is the number of satellites employed and their operating altitudes. Analysis of the major costs associated with implementing these systems shows that operation within the earth's radiation belts can reduce the total system cost by as much as a factor of two, so long as radiation hard components including solar cells, can be used. A detailed evaluation of several types of planar solar cells is given, including commercially available Si and GaAs/Ge cells, and InP/Si cells which are under development. The computer program calculates the end of life (EOL) power density of solar arrays taking into account the cell geometry, coverglass thickness, support frame, electrical interconnects, etc. The EOL power density can be determined for any altitude from low earth orbit (LEO) to geosynchronous (GEO) and for equatorial to polar planes of inclination. The mission duration can be varied over the entire range planned for the proposed satellite systems. An algorithm is included in the program for determining the degradation of cell efficiency for different cell technologies due to proton and electron irradiation. The program can be used to determine the optimum configuration for any cell technology for a particular orbit and for a specified mission life. Several examples of applying the program are presented, in which it is shown that the EOL power density of different technologies can vary by an order of magnitude for certain missions. Therefore, although a relatively radiation soft technology can be made to provide the required EOL power by simply increasing the size of the array, the impact on the total system budget could be unacceptable, due to increased launch and

  5. Design of high-efficiency, radiation-hard, GaInP/GaAs solar cells

    NASA Technical Reports Server (NTRS)

    Kurtz, Sarah R.; Bertness, K. A.; Kibbler, A. E.; Kramer, C.; Olson, J. M.

    1994-01-01

    In recently years, Ga(0.5)In((0.5)P/GaAs cells have drawn increased attention both because of their high efficiencies and because they are well suited for space applications. They can be grown and processed as two-junction devices with roughly twice the voltage and half the current of GaAs cells. They have low temperature coefficients, and have good potential for radiation hardness. We have previously reported the effects of electron irradiation on test cells which were not optimally designed for space. From those results we estimated that an optimally designed cell could achieve 20 percent after irradiation with 10(exp 15) cm(exp -2) 1 MeV electrons. Modeling studies predicted that slightly higher efficiencies may be achievable. Record efficiencies for EOL performance of other types of cells are significantly lower. Even the best Si and InP cells have BOL efficiencies lower than the EOL efficiency we report here. Good GaAs cells have an EOL efficiency of 16 percent. The InP/Ga(0.5)In(0.5)As two-junction, two-terminal device has a BOL efficiency as high as 22.2 percent, but radiation results for these cells were limited. In this study we use the previous modeling and irradiation results to design a set of Ga(0.5)In(0.5)P/GaAs cells that will demonstrate the importance of the design parameters and result in high-efficiency devices. We report record AMO efficiencies: a BOL efficiency of 25.7 percent for a device optimized for BOL performance and two of different designs with EOL efficiencies of 19.6 percent (at 10(exp 15) cm(exp -2) 1MeV electrons). We vary the bottom-cell base doping and the top-cell thickness to show the effects of these two important design parameters. We get an unexpected result indicating that the dopant added to the bottom-cell base also increases the degradation of the top cell.

  6. Radiation damage effects in Si materials and detectors and rad-hard Si detectors for SLHC

    NASA Astrophysics Data System (ADS)

    Li, Z.

    2009-03-01

    Silicon sensors, widely used in high energy and nuclear physics experiments, suffer severe radiation damage that leads to degradations in sensor performance. These degradations include significant increases in leakage current, bulk resistivity, space charge concentration, and free carrier trapping. For LHC applications, where the total fluence is in the order of 1 × 1015 neq/cm2 for 10 years, the increase in space charge concentration has been the main problem since it can significantly increase the sensor full depletion voltage, causing either breakdown if operated at high biases or charge collection loss if operated at lower biases than full depletion. For LHC Upgrade, or the SLHC, however, whit an increased total fluence up to 1 × 1016 neq/cm2, the main limiting factor for Si detector operation is the severe trapping of free carriers by radiation-induced defect levels. Several new approaches have been developed to make Si detector more radiation hard/tolerant to such ultra-high radiation, including 3D Si detectors, Current-Injected-Diodes (CID) detectors, and Elevated temperature annealing.

  7. A Hard Look at Independent Study

    ERIC Educational Resources Information Center

    Wilson, Whitelaw

    1976-01-01

    Sparked by James P. Beckford's article, "Administering the Independent Study Program" (Independent School Bulletin, February 1974, p.57), the author supplemented his comments by addressing two major aspects of independent study. The first is the notion that independent study is an educational vehicle or tool and the second is how it fits in with a…

  8. [Studies on bond strength and hardness of base materials].

    PubMed

    Suga, T; Chiba, E; Shinya, A; Yokozuka, S

    1989-04-01

    Since base materials are used in the construction of abutment teeth and the cavity walls of the teeth with healthy pulp, they need considerable bonding and mechanical strength depending on the site of application. In the present study we examined bonding strength, Martens-Mayer hardness and Vickers hardness of base materials in comparison with natural dentin in order to reevaluate them in terms of prosthetic materials and to provide assessment criteria for their application to prosthetic treatment. The results were as follows: 1) The bonding test showed the lowest value (4.6kgf/cm2) in calcium hydroxide FR (HFR) and the highest (47.9kgf/cm2) in HY-Bond polycarboxylate cement (CHC), a type of polycarboxylate cement. 2) In the test of bonding strength with various types of cement, calcium hydroxide preparations and zinc phosphate cement showed low values (4.6-23.5kgf/cm2) while polycarboxylate cement and glass-ionomer cement showed relatively high values (17.8-40.5kgf/cm2). 3) The Martens-Mayer hardness test showed the highest value (10.82 x 10(4] in dentin cement (GDE) and the lowest (1.09 x 10(4] in propack (EPR). 4) The Vickers hardness test showed the highest value (82) in neo-protect cement (ZPR) and the lowest (1) in propack (EPR). 5) In both Martens-Mayer and Vickers hardness tests with various types of cement, zinc phosphate cement and glass- ionomer cement showed high values, while low values were obtained in calcium hydroxide preparations and zinc-oxide eugenol cement. 6) Zinc phosphate cement and glass-ionomer cement showed no statistically significant differences from natural dentin in either Martens-Mayer hardness or Vickers hardness.

  9. Benchmark Study and Characterization of European Rad-Hard Power MOSFEts for Space Applications

    NASA Astrophysics Data System (ADS)

    Becherer, J.; Dittrich, R.; Muschitiello, M.; Constantino, A.

    2014-08-01

    Power Field Effect Transistors are an integral part of the electronic equipment of every space vehicle. In order to survive the harsh conditions of space, the transistors have to fulfill rigorous conditions. A number one in the list of space qualification criteria is the guarantee of radiation hardness. Today several radiation hard Power MOSFETs are available from a variety of companies all over the world. A benchmark study of the available Power MOSFETs for space applications has been compiled in this paper. The newly developed European Superjunction Technologies Power MOSFETs from Infineon show the best performance. Therefore, a total ionizing dose characterization of the 250 V and 150 V European MOSFETs have been performed.

  10. Radiation hard mode-locked laser suitable as a spaceborne frequency comb.

    PubMed

    Buchs, Gilles; Kundermann, Stefan; Portuondo-Campa, Erwin; Lecomte, Steve

    2015-04-20

    We report ground-level gamma and proton radiation tests of a passively mode-locked diode-pumped solid-state laser (DPSSL) with Yb:KYW gain medium. A total gamma dose of 170 krad(H(2)O) applied in 5 days generates minor changes in performances while maintaining solitonic regime. Pre-irradiation specifications are fully recovered over a day to a few weeks timescale. A proton fluence of 9.76·10(10) cm(-2) applied in few minutes shows no alteration of the laser performances. Furthermore, complete stabilization of the laser shows excellent noise properties. From our results, we claim that the investigated femtosecond DPSSL technology can be considered rad-hard and would be suitable for generating frequency combs compatible with long duration space missions.

  11. Decision feedback equalization for radiation hard data link at 5 Gbps

    NASA Astrophysics Data System (ADS)

    Wallängen, V.; Garcia-Sciveres, M.

    2017-01-01

    The increased particle collision rate following the upgrade of the Large Hadron Collider (LHC) to an increased luminosity requires an increased readout data speed, especially for the ATLAS pixel detector, located closest to the particle interaction point. For this reason, during the Phase-II upgrade of the ATLAS experiment the output data speed of the pixel front-end chips will be increased from 160 Mbps to 5 Gbps. The increased radiation levels will require a radiation hard data transmission link to be designed to carry this data from the pixel front-end to the off-detector system where it will undergo optical conversion. We propose a receiver utilizing the concept of Decision Feedback Equalization (DFE) to be used in this link, where the number of filter taps can be determined from simulations using S-parameter data from measurements of various customized cable prototypes under characterization as candidates to function as transmission medium between the on-chip data driver and the receiver of the link. A dedicated framework has been set up in Matlab to analyze the S-parameter characteristics for the various cable prototypes and investigate the possibilities for signal recovery and maintained signal integrity using DFE, as well as pre-emphasis and different encoding schemes. The simulation results indicate that DFE could be an excellent choice for expanding the system bandwidth to reach required data speeds with minimal signal distortion.

  12. Radiation hardness of semiconductor avalanche detectors for calorimeters in future HEP experiments

    NASA Astrophysics Data System (ADS)

    Kushpil, V.; Mikhaylov, V.; Kugler, A.; Kushpil, S.; Ladygin, V. P.; Svoboda, O.; Tlustý, P.

    2016-02-01

    During the last years, semiconductor avalanche detectors are being widely used as the replacement of classical PMTs in calorimeters for many HEP experiments. In this report, basic selection criteria for replacement of PMTs by solid state devices and specific problems in the investigation of detectors radiation hardness are discussed. The design and performance of the hadron calorimeters developed for the future high energy nuclear physics experiments at FAIR, NICA, and CERN are discussed. The Projectile Spectator Detector (PSD) for the CBM experiment at the future FAIR facility, the Forward Calorimeter for the NA61 experiment at CERN and the Multi Purpose Detector at the future NICA facility are reviewed. Moreover, new methods of data analysis and results interpretation for radiation experiments are described. Specific problems of development of detectors control systems and possibilities of reliability improvement of multi-channel detectors systems are shortly overviewed. All experimental material is based on the investigation of SiPM and MPPC at the neutron source in NPI Rez.

  13. High Speed, Radiation Hard CMOS Pixel Sensors for Transmission Electron Microscopy

    NASA Astrophysics Data System (ADS)

    Contarato, Devis; Denes, Peter; Doering, Dionisio; Joseph, John; Krieger, Brad

    CMOS monolithic active pixel sensors are currently being established as the technology of choice for new generation digital imaging systems in Transmission Electron Microscopy (TEM). A careful sensor design that couples μm-level pixel pitches with high frame rate readout and radiation hardness to very high electron doses enables the fabrication of direct electron detectors that are quickly revolutionizing high-resolution TEM imaging in material science and molecular biology. This paper will review the principal characteristics of this novel technology and its advantages over conventional, optically-coupled cameras, and retrace the sensor development driven by the Transmission Electron Aberration corrected Microscope (TEAM) project at the LBNL National Center for Electron Microscopy (NCEM), illustrating in particular the imaging capabilities enabled by single electron detection at high frame rate. Further, the presentation will report on the translation of the TEAM technology to a finer feature size process, resulting in a sensor with higher spatial resolution and superior radiation tolerance currently serving as the baseline for a commercial camera system.

  14. Radiation-hard analog-to-digital converters for space and strategic applications

    NASA Technical Reports Server (NTRS)

    Gauthier, M. K.; Dantas, A. R. V.

    1985-01-01

    During the course of the Jet Propulsion Laboratory's program to study radiation-hardened analog-to-digital converters (ADCs), numerous milestones have been reached in manufacturers' awareness and technology development and transfer, as well as in user awareness of these developments. The testing of ADCs has also continued with twenty different ADCs from seven manufacturers, all tested for total radiation dose and three tested for neutron effects. Results from these tests are reported.

  15. Effects of gamma radiation on hard dental tissues of albino rats using scanning electron microscope - Part 1

    NASA Astrophysics Data System (ADS)

    El-Faramawy, Nabil; Ameen, Reham; El-Haddad, Khaled; Maghraby, Ahmed; El-Zainy, Medhat

    2011-12-01

    In the present study, 40 adult male albino rats were used to study the effect of gamma radiation on the hard dental tissues (enamel surface, dentinal tubules and the cementum surface). The rats were irradiated at 0.2, 0.5, 1.0, 2.0, 4.0 and 6.0 Gy gamma doses. The effects of irradiated hard dental tissues samples were investigated using a scanning electron microscope. For doses up to 0.5 Gy, there was no evidence of the existence of cracks on the enamel surface. With 1 Gy irradiation dose, cracks were clearly observed with localized erosive areas. At 2 Gy irradiation dose, the enamel showed morphological alterations as disturbed prismatic and interprismatic areas. An increase in dentinal tubules diameter and a contemporary inter-tubular dentine volume decrease were observed with higher irradiation dose. Concerning cementum, low doses,<0.5 Gy, showed surface irregularities and with increase in the irradiation dose to≥1 Gy, noticeable surface irregularities and erosive areas with decrease in Sharpey's fiber sites were observed. These observations could shed light on the hazardous effects of irradiation fields to the functioning of the human teeth.

  16. Applications of Robust, Radiation Hard AlGaN Optoelectronic Devices in Space Exploration and High Energy Density Physics

    SciTech Connect

    Sun, K.

    2011-05-04

    This slide show presents: space exploration applications; high energy density physics applications; UV LED and photodiode radiation hardness; UV LED and photodiode space qualification; UV LED AC charge management; and UV LED satellite payload instruments. A UV LED satellite will be launched 2nd half 2012.

  17. Densification of sol-gel silica thin films induced by hard X-rays generated by synchrotron radiation.

    PubMed

    Innocenzi, Plinio; Malfatti, Luca; Kidchob, Tongjit; Costacurta, Stefano; Falcaro, Paolo; Marmiroli, Benedetta; Cacho-Nerin, Fernando; Amenitsch, Heinz

    2011-03-01

    In this article the effects induced by exposure of sol-gel thin films to hard X-rays have been studied. Thin films of silica and hybrid organic-inorganic silica have been prepared via dip-coating and the materials were exposed immediately after preparation to an intense source of light of several keV generated by a synchrotron source. The samples were exposed to increasing doses and the effects of the radiation have been evaluated by Fourier transform infrared spectroscopy, spectroscopic ellipsometry and atomic force microscopy. The X-ray beam induces a significant densification on the silica films without producing any degradation such as cracks, flaws or delamination at the interface. The densification is accompanied by a decrease in thickness and an increase in refractive index both in the pure silica and in the hybrid films. The effect on the hybrid material is to induce densification through reaction of silanol groups but also removal of the organic groups, which are covalently bonded to silicon via Si-C bonds. At the highest exposure dose the removal of the organic groups is complete and the film becomes pure silica. Hard X-rays can be used as an efficient and direct writing tool to pattern coating layers of different types of compositions.

  18. Space radiation studies

    NASA Technical Reports Server (NTRS)

    Gregory, J. C.

    1986-01-01

    Instrument design and data analysis expertise was provided in support of several space radiation monitoring programs. The Verification of Flight Instrumentation (VFI) program at NASA included both the Active Radiation Detector (ARD) and the Nuclear Radiation Monitor (NRM). Design, partial fabrication, calibration and partial data analysis capability to the ARD program was provided, as well as detector head design and fabrication, software development and partial data analysis capability to the NRM program. The ARD flew on Spacelab-1 in 1983, performed flawlessly and was returned to MSFC after flight with unchanged calibration factors. The NRM, flown on Spacelab-2 in 1985, also performed without fault, not only recording the ambient gamma ray background on the Spacelab, but also recording radiation events of astrophysical significance.

  19. R&D of Radiation-Hard Scintillators and WLS Fibers

    NASA Astrophysics Data System (ADS)

    Tiras, Emrah; Wetzel, James; Bilki, Burak; Durgut, Suleyman; Onel, Yasar; Winn, David

    2017-01-01

    Radiation resistant and high light-yield scintillators are in more need than ever at particle physics experiments. In this regard, several polyethylene-based and quartz-based scintillating materials and WLS fibers have been studied. Radiation resistance of plastic scintillators such as PEN, PET, SiX and Eljen samples and WLS fibers has been studied over time after they are exposed to 1.4 and 14 MRad total radiation by 137Cs gamma source. The light-yield and timing measurements of the plastic scintillators as well as coated quartz plates have been studied in beam test at Fermilab Test Beam Facility (FTBF). Here, we discuss the recent developments and the results of beam tests and laboratory measurements.

  20. Radiation-Hard SpaceWire/Gigabit Ethernet-Compatible Transponder

    NASA Technical Reports Server (NTRS)

    Katzman, Vladimir

    2012-01-01

    A radiation-hard transponder was developed utilizing submicron/nanotechnology from IBM. The device consumes low power and has a low fabrication cost. This device utilizes a Plug-and-Play concept, and can be integrated into intra-satellite networks, supporting SpaceWire and Gigabit Ethernet I/O. A space-qualified, 100-pin package also was developed, allowing space-qualified (class K) transponders to be delivered within a six-month time frame. The novel, optical, radiation-tolerant transponder was implemented as a standalone board, containing the transponder ASIC (application specific integrated circuit) and optical module, with an FPGA (field-programmable gate array) friendly parallel interface. It features improved radiation tolerance; high-data-rate, low-power consumption; and advanced functionality. The transponder utilizes a patented current mode logic library of radiation-hardened-by-architecture cells. The transponder was developed, fabricated, and radhard tested up to 1 MRad. It was fabricated using 90-nm CMOS (complementary metal oxide semiconductor) 9 SF process from IBM, and incorporates full BIT circuitry, allowing a loop back test. The low-speed parallel LVCMOS (lowvoltage complementary metal oxide semiconductor) bus is compatible with Actel FPGA. The output LVDS (low-voltage differential signaling) interface operates up to 1.5 Gb/s. Built-in CDR (clock-data recovery) circuitry provides robust synchronization and incorporates two alarm signals such as synch loss and signal loss. The ultra-linear peak detector scheme allows on-line control of the amplitude of the input signal. Power consumption is less than 300 mW. The developed transponder with a 1.25 Gb/s serial data rate incorporates a 10-to-1 serializer with an internal clock multiplication unit and a 10-1 deserializer with internal clock and data recovery block, which can operate with 8B10B encoded signals. Three loop-back test modes are provided to facilitate the built-in-test functionality. The

  1. AlGaN UV LED and Photodiodes Radiation Hardness and Space Qualifications and Their Applications in Space Science and High Energy Density Physics

    SciTech Connect

    Sun, K. X.

    2011-05-31

    This presentation provides an overview of robust, radiation hard AlGaN optoelectronic devices and their applications in space exploration & high energy density physics. Particularly, deep UV LED and deep UV photodiodes are discussed with regard to their applications, radiation hardness and space qualification. AC charge management of UV LED satellite payload instruments, which were to be launched in late 2012, is covered.

  2. Performance prospects for the CMS electromagnetic calorimeter barrel avalanche photodiodes for LHC phase I and phase II: Radiation hardness and longevity

    NASA Astrophysics Data System (ADS)

    Addesa, F.; Cavallari, F.

    2015-07-01

    The electromagnetic calorimeter of the Compact Muon Solenoid (CMS) experiment at the LHC is a hermetic, fine-grained, homogeneous calorimeter, comprising 75,848 lead tungstate scintillating crystals. Avalanche photodiodes produced by Hamamatsu are used as sensors for the electromagnetic barrel calorimeter. These devices were tested for radiation hardness assuming an integrated luminosity of 500 fb-1, which corresponds to a neutron fluence of 2- 4 ×1013 n /cm2, depending on the detector location. Beginning in 2022, a new phase of the LHC is foreseen to exploit the full potential of the accelerator, which will deliver 3000 fb-1 of integrated luminosity. Irradiation studies up to a fluence of 1.5 ×1014 n /cm2 have been performed to qualify the avalanche photodiodes for radiation hardness. We present measurements of gain, quantum efficiency and noise, and discuss the implications for the CMS electromagnetic barrel calorimeter performance.

  3. Pixel frontend electronics in a radiation hard technology for hybrid and monolithic applications

    SciTech Connect

    Pengg, F. |; Campbell, M.; Heijne, E.H.M.; Snoeys, W.

    1996-06-01

    Pixel detector readout cells have been designed in the radiation hard DMILL technology and their characteristics evaluated before and after irradiation to 14Mrad. The test chip consists of two blocks of six readout cells each. Two different charge amplifiers are implemented, one of them using a capacitive feedback loop, the other the fast signal charge transfer to a high impedance integrating node. The measured equivalent noise charge is 110e{sup {minus}}r.m.s. before and 150e{sup {minus}}r.m.s. after irradiation. With a discriminator threshold set to 5000e{sup {minus}}, which reduces for the same bias setting to 400e{sup {minus}} after irradiation, the threshold variation is 300e{sup {minus}}r.m.s. and 250e{sup {minus}}r.m.s. respectively. The time walk is 40ns before and after irradiation. The use of this SOI technology for monolithic integration of electronics and detector in one substrate is under investigation.

  4. Radiation Hard Bandpass Filters for Mid- to Far-IR Planetary Instruments

    NASA Technical Reports Server (NTRS)

    Brown, Ari D.; Aslam, Shahid; Chervenack, James A.; Huang, Wei-Chung; Merrell, Willie C.; Quijada, Manuel; Steptoe-Jackson, Rosalind; Wollack, Edward J.

    2012-01-01

    We present a novel method to fabricate compact metal mesh bandpass filters for use in mid- to far-infrared planetary instruments operating in the 20-600 micron wavelength spectral regime. Our target applications include thermal mapping instruments on ESA's JUICE as well as on a de-scoped JEO. These filters are novel because they are compact, customizable, free-standing copper mesh resonant bandpass filters with micromachined silicon support frames. The filters are well suited for thermal mapping mission to the outer planets and their moons because the filter material is radiation hard. Furthermore, the silicon support frame allows for effective hybridization with sensors made on silicon substrates. Using a Fourier Transform Spectrometer, we have demonstrated high transmittance within the passband as well as good out-of-band rejection [1]. In addition, we have developed a unique method of filter stacking in order to increase the bandwidth and sharpen the roll-off of the filters. This method allows one to reliably control the spacing between filters to within 2 microns. Furthermore, our method allows for reliable control over the relative position and orienta-tion between the shared faces of the filters.

  5. Low-mass, intrinsically-hard high temperature radiator. Final report, Phase I

    SciTech Connect

    1990-07-15

    This paper reports on the investigation of layered ceramic/metal composites in the design of low-mass hardened radiators for space heat rejection systems. The investigation is part of the Strategic Defence Initiative. This effort evaluated the use of layered composites as a material to form thin-walled, vacuum leaktight heat pipes. The heat pipes would be incorporated into a large heat pipe radiator for waste heat rejection from a space nuclear power source. Composite materials evaluations were performed on combinations of refractory metals and ceramic powders. Fabrication experiments were performed to demonstrate weldability. Two titanium/titanium diboride composite tubes were successfully fabricated into potassium heat pipes and operated at temperatures in excess of 700C. Testing and analysis for composite tubes are described in the report. The study has verified the feasibility of using layered composites for forming thin-walled, light weight heat pipe tubes for use in hardened space radiators.

  6. TOPEX orbital radiation study

    NASA Technical Reports Server (NTRS)

    Stassinopoulos, E. G.; Barth, J. M.

    1984-01-01

    The space radiation environment of the TOPEX spacecraft is investigated. A single trajectory was considered. The external (surface incident) charged particle radiation, predicted for the satellite, is determined by orbital flux integration for the specified trajectory. The latest standard models of the environment are used in the calculations. The evaluation is performed for solar maximum conditions. The spacecraft exposure to cosmic rays of galactic origin is evaluated over its flight path through the magnetosphere in terms of geomagnetic shielding effects, both for surface incident heavy ions and for particles emerging behind different material thickness. Limited shielding and dose evaluations are performed for simple infinite slab and spherical geometries. Results, given in graphical and tabular form, are analyzed, explained, and discussed. Conclusions are presented and commented on.

  7. LDEF satellite radiation study

    NASA Technical Reports Server (NTRS)

    Armstrong, T. W.; Colborn, B. L.

    1994-01-01

    Some early results are summarized from a program under way to utilize LDEF satellite data for evaluating and improving current models of the space radiation environment in low earth orbit. Reported here are predictions and comparisons with some of the LDEF dose and induced radioactivity data, which are used to check the accuracy of current models describing the magnitude and directionality of the trapped proton environment. Preliminary findings are that the environment models underestimate both dose and activation from trapped protons by a factor of about two, and the observed anisotropy is higher than predicted.

  8. Initial Hardness Response and Hardness Profiles in the Study of Woodward-Hoffmann Rules for Electrocyclizations.

    PubMed

    De Proft, F; Chattaraj, P K; Ayers, P W; Torrent-Sucarrat, M; Elango, M; Subramanian, V; Giri, S; Geerlings, P

    2008-04-01

    The fundamental principles of pericyclic reactions are governed by the Woodward-Hoffmann rules, which state that these reactions can only take place if the symmetries of the reactants' molecular orbitals and the products' molecular orbitals are the same. As such, these rules rely on the nodal structure of either the wave function or the frontier molecular orbitals, so it is unclear how these rules can be recovered in the density functional reactivity theory (or "conceptual DFT"), where the basic quantity is the strictly positive electron density. A third, nonsymmetry based approach to predict the outcome of pericyclic reactions is due to Zimmerman which uses the concept of the aromatic transition states: allowed reactions possess aromatic transition states, while forbidden reactions possess antiaromatic transition states. Based on our recent work on cycloadditions, we investigate the initial response of the chemical hardness, a central DFT based reactivity index, along the reaction profiles of a series of electrocyclizations. For a number of cases, we also compute complete initial reaction coordinate (IRC) paths and hardness profiles. We find that the hardness response is always higher for the allowed modes than for the forbidden modes. This suggests that the initial hardness response along the IRC is the key for casting the Woodward-Hoffmann rules into conceptual DFT.

  9. Study of hot hardness characteristics of tool steels

    NASA Technical Reports Server (NTRS)

    Chevalier, J. L.; Dietrich, M. W.; Zaretsky, E. V.

    1972-01-01

    Hardness measurements of tool steel materials in electric furnace at elevated temperatures and low oxygen environment are discussed. Development of equation to predict short term hardness as function of intial room temperature hardness of steel is reported. Types of steel involved in the process are identified.

  10. Space radiation studies

    NASA Technical Reports Server (NTRS)

    1989-01-01

    Two Active Radiation Dosimeters (ARD's) flown on Spacelab 1, performed without fault and were returned to Space Science Laboratory, MSFC for recalibration. During the flight, performance was monitored at the Huntsville Operations Center (HOSC). Despite some problems with the Shuttle data system handling the verification flight instrumentation (VFI), it was established that the ARD's were operating normally. Postflight calibrations of both units determined that sensitivities were essentially unchanged from preflight values. Flight tapes were received for approx. 60 percent of the flight and it appears that this is the total available. The data was analyzed in collaboration with Space Science Laboratory, MSFC. Also, the Nuclear Radiation Monitor (NRM) was assembled and tested at MSFC. Support was rendered in the areas of materials control and parts were supplied for the supplementary heaters, dome gas-venting device and photomultiplier tube housing. Performance characteristics of some flight-space photomultipliers were measured. The NRM was flown on a balloon-borne test flight and subsequently performed without fault on Spacelab-2. This data was analyzed and published.

  11. Hard tooth tissue removal by short and long Er:YAG or Er,Cr:YSGG mid-infrared laser radiation

    NASA Astrophysics Data System (ADS)

    Jelínková, H.; Dostálová, T.; Remeš, M.; Šulc, J.; Němec, M.; Fibrich, M.

    2017-02-01

    Hard dental tissue removal by laser radiation is an alternative treatment to conventional dental-drilling procedures. The advantages of this therapy are fast and localized treatment of hard dental tissue and painlessness. The most effective systems for those purposes are Er-lasers generating radiation at wavelengths of around 3 μm. The aim of this study was qualitative and quantitative examination of human dentin and ivory tissue removal by pulsed free-running (FR) and Q-switched (QSW) Er:YAG and Er,Cr:YSGG laser radiations. From the obtained results it follows that generally Er:YAG laser has lower threshold for the tissue removal in both FR and QSW regimes. Furthermore, the FR Er:YAG and Er,Cr:YSGG radiation can be effective for both dentin and ivory ablation and can prepare smooth cavities without side effects. The QSW regime is useful preferably for precise ablation of a starting tooth defect and for the part of the tooth very close to the gum. This regime is excellent for micro-preparation or for tooth treatment of children.

  12. Radiation Hard Silicon Particle Detectors for Phase-II LHC Trackers

    NASA Astrophysics Data System (ADS)

    Oblakowska-Mucha, A.

    2017-02-01

    The major LHC upgrade is planned after ten years of accelerator operation. It is foreseen to significantly increase the luminosity of the current machine up to 1035 cm‑2s‑1 and operate as the upcoming High Luminosity LHC (HL-LHC) . The major detectors upgrade, called the Phase-II Upgrade, is also planned, a main reason being the aging processes caused by severe particle radiation. Within the RD50 Collaboration, a large Research and Development program has been underway to develop silicon sensors with sufficient radiation tolerance for HL-LHC trackers. In this summary, several results obtained during the testing of the devices after irradiation to HL-LHC levels are presented. Among the studied structures, one can find advanced sensors types like 3D silicon detectors, High-Voltage CMOS technologies, or sensors with intrinsic gain (LGAD). Based on these results, the RD50 Collaboration gives recommendation for the silicon detectors to be used in the detector upgrade.

  13. The radiation hardness and temperature stability of Planar Light-wave Circuit splitters for the High Luminosity LHC

    NASA Astrophysics Data System (ADS)

    Ryder, N. C.; Hamilton, P.; Huffman, B. T.; Teng, P. K.; Weidberg, A. R.; Issever, C.

    2011-10-01

    High Luminosity LHC (HL-LHC) Inner Tracker designs may include the sharing of Timing, Trigger and Control (TTC) signals between several tracker modules. This is possible because the highest frequency signals are common to all modules. Such designs are an attractive option because they reduce the number of optical links required and hence the cost. These designs will require optical signal splitters that are radiation hard up to high doses and capable of operating in cold temperatures. Optical splitters are available as either fused-fibre splitters or Planar Light-wave Circuit (PLC) splitters. PLC splitters are preferable because they are smaller than fused-fibre splitters. A selection of PLC splitters from different manufacturers and of two different technologies (silica and glass based) have been tested for radiation hardness up to a dose of 500 kGy(Si) and for temperature stability. All the tested splitters displayed small increases in insertion losses ( < 0.1 dB) in reducing the operating temperature from 25°C to -25°C. The silica based splitters from all manufacturers did not exhibit significant radiation induced insertion losses, despite the high dose they were exposed to. The glass based sample, however, had a per channel radiation induced insertion loss of up to 1.16 dB. Whilst the silica based splitters can be considered as qualified for HL-LHC use with regards to radiation hardness, the glass technology would require further testing at a lower, more realistic, dose to also be considered as a potential component for HL-LHC upgrade designs.

  14. Radiation damage studies for the SDC electromagnetic calorimeter

    NASA Astrophysics Data System (ADS)

    Fazely, A. R.; Gunasingha, R.; Imlay, R. L.; Khosravi, E. S.; Lim, Jit-Ning; Lyndon, C.; McMills, G.; McNeil, R. R.; Metcalf, W. J.; Courtney, J. C.; Tashakkori, R.; Vegara, B. J.

    1993-01-01

    We report the results from a year long study aimed at radiation resistance and optical performance of scintillator tile with green wave shifter fiber readout. A careful investigation of several rad-hard plastic scintillators from Bicron and Kuraray, studies indicate that for a specific rad-hard Bicron scintillator, it is possible to build a tile/fiber EM calorimeter that can operate in the design luminosity of SSC. This calorimeter with excellent optical response would only have a light loss of about 5% after being exposed to 1 Mrad.

  15. Radiation hardness measurements of new permanent magnet materials for high-intensity linac applications

    SciTech Connect

    Barlow, D.B.; Kraus, R.H.; Borden, M.J.

    1998-12-31

    This is the final report of a two-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The radiation resistance of samples of high-strength samarium cobalt permanent-magnet material has been studied. Samples of commercially available material were obtained from four different manufacturers. The remanent field of the samples was measured before and after the samples were irradiated with neutrons produced at the beam stop of the Los Alamos Neutron Science Center (LANSCE) proton accelerator.

  16. RADECS Short Course Section 4 Radiation Hardness Assurance (RHA) for Space Systems

    NASA Technical Reports Server (NTRS)

    Poivey, Christian

    2003-01-01

    Contents include the following: Introduction. Programmatic aspects of RHA. RHA componens: requirements and specifications; mission radiation environment; and parts selection and radiation tolerance. Analysis at the function/subsystem/system level: TID/DD; SEE. Conclusion.

  17. High-resolution single-shot spectral monitoring of hard x-ray free-electron laser radiation

    SciTech Connect

    Makita, M.; Karvinen, P.; Zhu, D.; Juranic, P. N.; Grünert, J.; Cartier, S.; Jungmann-Smith, J. H.; Lemke, H. T.; Mozzanica, A.; Nelson, S.; Patthey, L.; Sikorski, M.; Song, S.; Feng, Y.; David, C.

    2015-10-16

    We have developed an on-line spectrometer for hard x-ray free-electron laser (XFEL) radiation based on a nanostructured diamond diffraction grating and a bent crystal analyzer. Our method provides high spectral resolution, interferes negligibly with the XFEL beam, and can withstand the intense hard x-ray pulses at high repetition rates of >100 Hz. The spectrometer is capable of providing shot-to-shot spectral information for the normalization of data obtained in scientific experiments and optimization of the accelerator operation parameters. We have demonstrated these capabilities of the setup at the Linac Coherent Light Source, in self-amplified spontaneous emission mode at full energy of >1 mJ with a 120 Hz repetition rate, obtaining a resolving power of Ε/δΕ > 3 × 104. In conclusion, the device was also used to monitor the effects of pulse duration down to 8 fs by analysis of the spectral spike width.

  18. Effects of quenching, irradiation, and annealing processes on the radiation hardness of silica fiber cladding materials (I)

    NASA Astrophysics Data System (ADS)

    Wen, Jianxiang; Gong, Renxiang; Xiao, Zhongyin; Luo, Wenyun; Wu, Wenkai; Luo, Yanhua; Peng, Gang-ding; Pang, Fufei; Chen, Zhenyi; Wang, Tingyun

    2016-07-01

    Silica optical fiber cladding materials were experimentally treated by a series of processes. The treatments involved quenching, irradiation, followed by annealing and subsequent re-irradiation, and they were conducted in order to improve the radiation hardness. The microstructural properties of the treated materials were subsequently investigated. Following the treatment of the optical fiber cladding materials, the results from the electron spin resonance (ESR) analysis demonstrated that there was a significant decrease in the radiation-induced defect structures. The ESR signals became significantly weaker when the samples were annealed at 1000 °C in combination with re-irradiation. In addition, the microstructure changes within the silica optical fiber cladding material were also analyzed using Raman spectroscopy. The experimental results demonstrate that the Sisbnd Osbnd Si bending vibrations at ω3 = 800-820 cm-1 and ω4 = 1000-1200 cm-1 (with longitudinal optical (LO) and transverse optical (TO) splitting bands) were relatively unaffected by the quenching, irradiation, and annealing treatments. In particular, the annealing process resulted in the disappearance of the defect centers; however, the LO and TO modes at the ω3 and ω4 bands were relatively unchanged. With the additional support of the ESR test results, we can conclude that the combined treatment processes can significantly enhance the radiation hardness properties of the optical fiber cladding materials.

  19. Tests of the radiation hardness of VLSI Integrated Circuits and Silicon Strip Detectors for the SSC (Superconducting Super Collider) under neutron, proton, and gamma irradiation

    SciTech Connect

    Ziock, H.J.; Milner, C.; Sommer, W.F. ); Carteglia, N.; DeWitt, J.; Dorfan, D.; Hubbard, B.; Leslie, J.; O'Shaughnessy, K.F.; Pitzl, D.; Rowe, W.A.; Sadrozinski, H.F.W.; Seiden, A.; Spencer, E. . Inst. for Particle Physics); Ellison, J.A. ); Ferguson, P. ); Giubellino

    1990-01-01

    As part of a program to develop a silicon strip central tracking detector system for the Superconducting Super Collider (SSC) we are studying the effects of radiation damage in silicon detectors and their associated front-end readout electronics. We report on the results of neutron and proton irradiations at the Los Alamos National Laboratory (LANL) and {gamma}-ray irradiations at UC Santa Cruz (UCSC). Individual components on single-sided AC-coupled silicon strip detectors and on test structures were tested. Circuits fabricated in a radiation hard CMOS process and individual transistors fabricated using dielectric isolation bipolar technology were also studied. Results indicate that a silicon strip tracking detector system should have a lifetime of at least one decade at the SSC. 17 refs., 17 figs.

  20. Investigation of avalanche photodiodes radiation hardness for baryonic matter studies

    NASA Astrophysics Data System (ADS)

    Kushpil, V.; Mikhaylov, V.; Ladygin, V. P.; Kugler, A.; Kushpil, S.; Svoboda, O.; Tlustý, P.

    2016-01-01

    Modern avalanche photodiodes (APDs) with high gain are good device candidates for light readout from detectors applied in relativistic heavy ion collisions experiments. The results of the investigations of the APDs properties from Zecotek, Ketek and Hamamatsu manufacturers after irradiation using secondary neutrons from cyclotron facility U120M at NPI of ASCR in Řež are presented. The results of the investigations can be used for the design of the detectors for the experiments at NICA and FAIR.

  1. Quantitative analysis of flare accelerated electrons through their hard X-ray and microwave radiation

    NASA Technical Reports Server (NTRS)

    Klein, K. L.; Trottet, G.

    1985-01-01

    Hard X-ray and microwave modelling that takes into account the temporal evolution of the electron spectrum as well as the inhomogeneity of the magnetic field and the ambient medium in the radio source is presented. This method is illustrated for the June 29 1980 10:41 UT event. The implication on the process of acceleration/injection is discussed.

  2. Radiation hardness assessment of the charge-integrating hybrid pixel detector JUNGFRAU 1.0 for photon science

    SciTech Connect

    Jungmann-Smith, J. H. Bergamaschi, A.; Brückner, M.; Dinapoli, R.; Greiffenberg, D.; Jaggi, A.; Maliakal, D.; Mayilyan, D.; Mezza, D.; Mozzanica, A.; Ramilli, M.; Ruder, Ch.; Schädler, L.; Schmitt, B.; Shi, X.; Tinti, G.; Cartier, S.; Medjoubi, K.

    2015-12-15

    JUNGFRAU (adJUstiNg Gain detector FoR the Aramis User station) is a two-dimensional hybrid pixel detector for photon science applications in free electron lasers, particularly SwissFEL, and synchrotron light sources. JUNGFRAU is an automatic gain switching, charge-integrating detector which covers a dynamic range of more than 10{sup 4} photons of an energy of 12 keV with a good linearity, uniformity of response, and spatial resolving power. The JUNGFRAU 1.0 application-specific integrated circuit (ASIC) features a 256 × 256 pixel matrix of 75 × 75 μm{sup 2} pixels and is bump-bonded to a 320 μm thick Si sensor. Modules of 2 × 4 chips cover an area of about 4 × 8 cm{sup 2}. Readout rates in excess of 2 kHz enable linear count rate capabilities of 20 MHz (at 12 keV) and 50 MHz (at 5 keV). The tolerance of JUNGFRAU to radiation is a key issue to guarantee several years of operation at free electron lasers and synchrotrons. The radiation hardness of JUNGFRAU 1.0 is tested with synchrotron radiation up to 10 MGy of delivered dose. The effect of radiation-induced changes on the noise, baseline, gain, and gain switching is evaluated post-irradiation for both the ASIC and the hybridized assembly. The bare JUNGFRAU 1.0 chip can withstand doses as high as 10 MGy with minor changes to its noise and a reduction in the preamplifier gain. The hybridized assembly, in particular the sensor, is affected by the photon irradiation which mainly shows as an increase in the leakage current. Self-healing of the system is investigated during a period of 11 weeks after the delivery of the radiation dose. Annealing radiation-induced changes by bake-out at 100 °C is investigated. It is concluded that the JUNGFRAU 1.0 pixel is sufficiently radiation-hard for its envisioned applications at SwissFEL and synchrotron beam lines.

  3. Radiation hardness assessment of the charge-integrating hybrid pixel detector JUNGFRAU 1.0 for photon science

    NASA Astrophysics Data System (ADS)

    Jungmann-Smith, J. H.; Bergamaschi, A.; Brückner, M.; Cartier, S.; Dinapoli, R.; Greiffenberg, D.; Jaggi, A.; Maliakal, D.; Mayilyan, D.; Medjoubi, K.; Mezza, D.; Mozzanica, A.; Ramilli, M.; Ruder, Ch.; Schädler, L.; Schmitt, B.; Shi, X.; Tinti, G.

    2015-12-01

    JUNGFRAU (adJUstiNg Gain detector FoR the Aramis User station) is a two-dimensional hybrid pixel detector for photon science applications in free electron lasers, particularly SwissFEL, and synchrotron light sources. JUNGFRAU is an automatic gain switching, charge-integrating detector which covers a dynamic range of more than 104 photons of an energy of 12 keV with a good linearity, uniformity of response, and spatial resolving power. The JUNGFRAU 1.0 application-specific integrated circuit (ASIC) features a 256 × 256 pixel matrix of 75 × 75 μm2 pixels and is bump-bonded to a 320 μm thick Si sensor. Modules of 2 × 4 chips cover an area of about 4 × 8 cm2. Readout rates in excess of 2 kHz enable linear count rate capabilities of 20 MHz (at 12 keV) and 50 MHz (at 5 keV). The tolerance of JUNGFRAU to radiation is a key issue to guarantee several years of operation at free electron lasers and synchrotrons. The radiation hardness of JUNGFRAU 1.0 is tested with synchrotron radiation up to 10 MGy of delivered dose. The effect of radiation-induced changes on the noise, baseline, gain, and gain switching is evaluated post-irradiation for both the ASIC and the hybridized assembly. The bare JUNGFRAU 1.0 chip can withstand doses as high as 10 MGy with minor changes to its noise and a reduction in the preamplifier gain. The hybridized assembly, in particular the sensor, is affected by the photon irradiation which mainly shows as an increase in the leakage current. Self-healing of the system is investigated during a period of 11 weeks after the delivery of the radiation dose. Annealing radiation-induced changes by bake-out at 100 °C is investigated. It is concluded that the JUNGFRAU 1.0 pixel is sufficiently radiation-hard for its envisioned applications at SwissFEL and synchrotron beam lines.

  4. Radiation hardness assessment of the charge-integrating hybrid pixel detector JUNGFRAU 1.0 for photon science.

    PubMed

    Jungmann-Smith, J H; Bergamaschi, A; Brückner, M; Cartier, S; Dinapoli, R; Greiffenberg, D; Jaggi, A; Maliakal, D; Mayilyan, D; Medjoubi, K; Mezza, D; Mozzanica, A; Ramilli, M; Ruder, Ch; Schädler, L; Schmitt, B; Shi, X; Tinti, G

    2015-12-01

    JUNGFRAU (adJUstiNg Gain detector FoR the Aramis User station) is a two-dimensional hybrid pixel detector for photon science applications in free electron lasers, particularly SwissFEL, and synchrotron light sources. JUNGFRAU is an automatic gain switching, charge-integrating detector which covers a dynamic range of more than 10(4) photons of an energy of 12 keV with a good linearity, uniformity of response, and spatial resolving power. The JUNGFRAU 1.0 application-specific integrated circuit (ASIC) features a 256 × 256 pixel matrix of 75 × 75 μm(2) pixels and is bump-bonded to a 320 μm thick Si sensor. Modules of 2 × 4 chips cover an area of about 4 × 8 cm(2). Readout rates in excess of 2 kHz enable linear count rate capabilities of 20 MHz (at 12 keV) and 50 MHz (at 5 keV). The tolerance of JUNGFRAU to radiation is a key issue to guarantee several years of operation at free electron lasers and synchrotrons. The radiation hardness of JUNGFRAU 1.0 is tested with synchrotron radiation up to 10 MGy of delivered dose. The effect of radiation-induced changes on the noise, baseline, gain, and gain switching is evaluated post-irradiation for both the ASIC and the hybridized assembly. The bare JUNGFRAU 1.0 chip can withstand doses as high as 10 MGy with minor changes to its noise and a reduction in the preamplifier gain. The hybridized assembly, in particular the sensor, is affected by the photon irradiation which mainly shows as an increase in the leakage current. Self-healing of the system is investigated during a period of 11 weeks after the delivery of the radiation dose. Annealing radiation-induced changes by bake-out at 100 °C is investigated. It is concluded that the JUNGFRAU 1.0 pixel is sufficiently radiation-hard for its envisioned applications at SwissFEL and synchrotron beam lines.

  5. Studying Polymer Transport on Soft and Hard Surfaces

    NASA Astrophysics Data System (ADS)

    Kumar, Sanat

    2007-03-01

    We have employed experiments and simulations to understand the factors controlling the transport of polymers on surfaces. From an experimental viewpoint we have focused on the transport of DNA (single stranded) on lipid bilayers. We show that this behavior is slaved to the mobility of the lipids. More surprisingly, it appears that the transport of molecules adsorbed on surfaces follows the same dependence on lipid mobility as for molecules incorporated into the lipid layer. The ability to control this surface diffusion through the introduction of posts or varying the strength of adsorption (by the use of an AC field normal to the surfaces) will also be studied. Theoretically we have used molecular dynamics simulations of a polymer chain of length N dissolved in explicit solvent and adsorbed as a pancake at the solid-liquid interface to discriminate between respective influences on surface diffusion of hydrodynamics and adsorption energetics. Only for analytically-smooth surfaces do we observe a strong influence of hydrodynamics; the polymer lateral diffusion constant, D, scales as D 1/N^3/4, more weakly than for implicit solvent. For atomistic surface corrugation with uniform surface chemical makeup, D 1/N instead. This suggests that while we can understand the results for diffusion on lipid surfaces, more recent experimental observations of stronger N dependence for diffusion on hard solid surfaces originate not in hydrodynamic interactions but in spatially patchy energetic interactions.

  6. A Radiation Hard Multi-Channel Digitizer ASIC for Operation in the Harsh Jovian Environment

    NASA Technical Reports Server (NTRS)

    Aslam, Shahid; Aslam, S.; Akturk, A.; Quilligan, G.

    2011-01-01

    In 1995, the Galileo spacecraft arrived at Jupiter to conduct follow-up experiments on pathfinder Pioneer and key Voyager discoveries especially at Io, Europa, Ganymede and Callisto. These new observations helped expand our scientific knowledge of the prominent Galilean satellites; studies revealed diversity with respect to their geology, internal structure, evolution and degree of past and present activity. Jupiter's diverse Galilean satellites, of which three are believed to harbor internal oceans, are central to understanding the habitability of icy worlds. Galileo provided for the first time compelling evidence of a near-surface global ocean on Europa. Furthermore, by understanding the Jupiter system and unraveling the history of its evolution from initial formation to the emergence of possible habitats and life, gives insight into how giant planets and their satellite systems form and evolve. Most important, new light is shed on the potential for the emergence and existence of life in icy satellite oceans. In 2009, NASA released a detailed Jupiter Europa Mission Study (EJSM) that proposed an ambitious Flagship Mission to understand more fully the satellites Europa and Ganymede within the context of the Jovian system. Key to EJSM is the NASA led Jupiter Europa Orbiter (JEO) and the ESA led Jupiter Ganymede Orbiter (JGO). JEO and JGO would execute a choreographed exploration of the Jovian system before settling into orbit around Europa and Ganymede, respectively. The National Academies Planetary Decadal Survey, 2011 has listed the NASA-led JEO as the second highest priority mission for the decade 2013-2022, and if chosen it would be launched in 2020 with arrival at Jupiter in 2025. If the JEO mission is not chosen it is anticipated that there will be opportunities in future decadal cycles. Jupiter Orbit Insertion (JOI) begins a 30-month Jovian system tour followed by nine months of science mapping after Europa Orbit Insertion (EOI) in July 2028. The orbiter will

  7. Radiation Hardness Assurance Issues Associated with COTS in JPL Flight Systems: The Challenge of Europa

    NASA Technical Reports Server (NTRS)

    Barnes, C.; Johnston, A.

    1999-01-01

    With the decreasing availability of radiation hardened electronics and the new NASA paradigm of faster, more aggressive and less expensive space missions, there has been an increasing emphasis on using high performance commercial microelectronic parts and circuits in NASA spacecraft.

  8. RADIATION HARDNESS / TOLERANCE OF SI SENSORS / DETECTORS FOR NUCLEAR AND HIGH ENERGY PHYSICS EXPERIMENTS.

    SciTech Connect

    LI,Z.

    2002-09-09

    Silicon sensors, widely used in high energy and nuclear physics experiments, suffer severe radiation damage that leads to degradations in sensor performance. These degradations include significant increases in leakage current, bulk resistivity, and space charge concentration. The increase in space charge concentration is particularly damaging since it can significantly increase the sensor full depletion voltage, causing either breakdown if operated at high biases or charge collection loss if operated at lower biases than full depletion. Several strategies can be used to make Si detectors more radiation had tolerant to particle radiations. In this paper, the main radiation induced degradations in Si detectors will be reviewed. The details and specifics of the new engineering strategies: material/impurity/defect engineering (MIDE); device structure engineering (DSE); and device operational mode engineering (DOME) will be given.

  9. A Radiation-Hard Silicon Drift Detector Array for Extraterrestrial Element Mapping

    NASA Technical Reports Server (NTRS)

    Gaskin, Jessica; Chen, Wei; De Geronimo, Gianluigi; Keister, Jeff; Li, Shaouri; Li, Zhen; Siddons, David P.; Smith, Graham

    2011-01-01

    Measurement of x-rays from the surface of objects can tell us about the chemical composition Absorption of radiation causes characteristic fluorescence from material being irradiated. By measuring the spectrum of the radiation and identifying lines in the spectrum, the emitting element (s) can be identified. This technique works for any object that has no absorbing atmosphere and significant surface irradiation : Our Moon, the icy moons of Jupiter, the moons of Mars, the planet Mercury, Asteroids and Comets

  10. Radiation hardness of plastic scintillators for the Tile Calorimeter of the ATLAS detector

    NASA Astrophysics Data System (ADS)

    Jivan, H.; Mellado, B.; Sideras-Haddad, E.; Erasmus, R.; Liao, S.; Madhuku, M.; Peters, G.; Solvyanov, O.

    2015-06-01

    The radiation damage in polyvinyl toluene based plastic scintillator EJ200 obtained from ELJEN technology was investigated. This forms part of a comparative study conducted to aid in the upgrade of the Tile Calorimeter of the ATLAS detector during which the Gap scintillators will be replaced. Samples subjected to 6 MeV proton irradiation using the tandem accelerator of iThemba LABS, were irradiated with doses of approximately 0.8 MGy, 8 MGy, 25 MGy and 80 MGy. The optical properties were investigated using transmission spectroscopy whilst structural damage was assessed using Raman spectroscopy. Findings indicate that for the dose of 0.8 MGy, no structural damage occurs but a breakdown in the light transfer between base and fluor dopants is observed. For doses of 8 MGy to 80 MGy, structural damage leads to hydrogen loss in the benzene ring of the PVT base which forms free radicals. This results in an additional absorptive component causing increased transmission loss as dose is increased.

  11. Radiation hardness of plastic scintillators for the Tile Calorimeter of the ATLAS detector

    NASA Astrophysics Data System (ADS)

    Jivan, H.; Sideras-Haddad, E.; Erasmus, R.; Liao, S.; Madhuku, M.; Peters, G.; Sekonya, K.; Solvyanov, O.

    2015-10-01

    The radiation damage in polyvinyl toluene based plastic scintillator EJ200 obtained from ELJEN technology was investigated. This forms part of a comparative study conducted to aid in the upgrade of the Tile Calorimeter of the ATLAS detector during which the Gap scintillators will be replaced. Samples subjected to 6 MeV proton irradiation using the tandem accelerator of iThemba LABS, were irradiated with doses of approximately 0.8 MGy, 8 MGy, 25 MGy and 80 MGy. The optical properties were investigated using transmission spectroscopy and light yield analysis whilst structural damage was assessed using Raman spectroscopy. Findings indicate that for the dose of 0.8 MGy, no structural damage occurs and light loss can be attributed to a breakdown in the light transfer between base and fluor dopants. For doses of 8 MGy to 80 MGy, structural damage leads to possible hydrogen loss in the benzene ring of the PVT base which forms free radicals. This results in an additional absorptive component causing increased transmission loss and light yield loss with increasing dose.

  12. Improvement of the radiation hardness of a directly converting high resolution intra-oral X-ray imaging sensor

    NASA Astrophysics Data System (ADS)

    Spartiotis, Konstantinos; Pyyhtiä, Jouni; Schulman, Tom

    2003-11-01

    The radiation tolerance of a directly converting digital intra-oral X-ray imaging sensor reported in Spartiotis et al. [Nucl. Instr. and Meth. A 501 (2003) 594] has been tested using a typical dental X-ray beam spectrum. Radiation induced degradation in the performance of the sensor which consists of CMOS signal readout circuits bump bonded to a high resistivity silicon pixel detector was observed already before a dose (in air) of 1 krad. Both increase in the leakage current of the pixel detector manufactured by Sintef, Norway and signal leakage to ground from the gate of the pixel input MOSFETs of the readout circuit were observed and measured. The sensitive part of the CMOS circuit was identified as the protection diode of the gate of the input MOSFET. After removing the gate protection diode no signal leakage was observed up to a dose of 5 krad (air) which approximately corresponds to 125.000 typical dental X-ray exposures. The radiation hardness of the silicon pixel detector was improved by using a modified oxidation process supplied by Colibrys, Switzerland. The improved pixel detectors showed no increase in the leakage current at dental doses.

  13. A study of sound balances for the hard of hearing

    NASA Astrophysics Data System (ADS)

    Mathers, C. D.

    Over a period of years, complaints have been received from television viewers, especially those who are hard of hearing, that background sound (e.g., audience laughter, crowd noise, mood music) is often transmitted at too high a level with respect to speech, so that information essential to the understanding of the program is lost. To consider possible solutions to the problem, a working party was set up representing both broadcasters and organizations for the hard of hearing. At early meetings, it was resolved that a series of subjective tests should be carried out to determine what reduction of background levels would be needed to provide a significant improvement in the intelligibility of television speech for viewers with hearing difficulties. The preparation of test tapes and the analysis of results are given.

  14. Radiation Hardness Tests of a Scintillation Detector with Wavelength Shifting Fiber Readout

    SciTech Connect

    Alfaro, R.; Sandoval, A.; Cruz, E.; Martinez, M. I.; Paic, G.; Montano, L. M.

    2006-09-25

    We have performed radiation tolerance tests on the BCF-99-29MC wavelength shifting fibers and the BC404 plastic scintillator from Bicron as well as on silicon rubber optical couplers. We used the 60Co gamma source at the Instituto de Ciencias Nucleares facility to irradiate 30-cm fiber samples with doses from 50 Krad to 1 Mrad. We also irradiated a 10x10 cm2 scintillator detector with the WLS fibers embedded on it with a 200 krad dose and the optical conectors between the scintillator and the PMT with doses from 100 to 300 krad. We measured the radiation damage on the materials by comparing the pre- and post-irradiation optical transparency as a function of time.

  15. Radiation-hard ceramic Resistive Plate Chambers for forward TOF and T0 systems

    NASA Astrophysics Data System (ADS)

    Akindinov, A.; Dreyer, J.; Fan, X.; Kämpfer, B.; Kiselev, S.; Kotte, R.; Garcia, A. Laso; Malkevich, D.; Naumann, L.; Nedosekin, A.; Plotnikov, V.; Stach, D.; Sultanov, R.; Voloshin, K.

    2017-02-01

    Resistive Plate Chambers with ceramic electrodes are the main candidates for a use in precise multi-channel timing systems operating in high-radiation conditions. We report the latest R&D results on these detectors aimed to meet the requirements of the forward T0 counter at the CBM experiment. RPC design, gas mixture, limits on the bulk resistivity of ceramic electrodes, efficiency, time resolution, counting rate capabilities and ageing test results are presented.

  16. Radiation hardness test of the Philips Digital Photon Counter with proton beam

    NASA Astrophysics Data System (ADS)

    Barnyakov, M. Yu.; Frach, T.; Kononov, S. A.; Kuyanov, I. A.; Prisekin, V. G.

    2016-07-01

    The Philips Digital Photon Counter (DPC) is a silicon photomultiplier combining Geiger-mode avalanche photodiodes (G-APD) and dedicated readout electronics in the same chip. The DPC is a promising photon sensor for future RICH detectors. A known issue of G-APD is its sensitivity to radiation damage. Two DPC sensors were tested using 800 MeV/c protons. An increase of dark counting rate with proton fluence up to 4 ·1011cm-2 has been measured.

  17. Low-mass, intrinsically-hard high-temperature radiator. Final report, Phase I

    SciTech Connect

    1990-06-15

    Thermacore, Inc. of Lancaster, Pennsylvania has completed a Phase I SBIR program to investigate the use of layered ceramic/metal composites in the design of low-mass hardened radiators for space heat rejection systems. The program is being monitored by the Los Alamos National Laboratory (LANL) for the Strategic Defense Initiative Organization (SDIO). This effort evaluated the use of layered composites as a material to form thin-walled, vacuum leaktight heat pipes. The heat pipes would be incorporated into a large heat pipe radiator for waste heat rejection from a space nuclear power source. This approach forms an attractive alternative to metal or silicon-carbon fiber reinforced metal heat pipes by offering a combination of low mass and improved fabricability. Titanium has been shown to have a yield strength too low at 875{degrees}K to be a useful radiator material. A silicon carbide fiber reinforced titanium material appears to have sufficient strength at 875{degrees}K. but cannot be welded due to the continuous fibers, and the preferred heat pipe working fluid (potassium) has been demonstrated to be incompatible with silicon carbide at 875{degrees}K. Moreover, titanium does not appear to be acceptable for radiators subjected to anticipated laser threats. As part of this effort, Thermacore performed composite material evaluations on combinations of refractory metals and ceramic powders. Layered composite tube samples with wall thicknesses as thin as 0.012 inches were developed. Fabrication experiments were performed that demonstrated the weldability of layered composites. Two titanium/titanium diboride composite tubes were successfully fabricated into potassium heat pipes and operated at temperatures in excess of 700{degrees}C. A hybrid composite tube was also fabricated into a potassium heat pipe. The tube was composed of alternating layers of niobium-1% zirconium foil and layers of a mixture of titanium powder and titanium diboride powder.

  18. Hardness Changes of Tissue Conditioners in Various Storage Media: An in Vitro Study.

    PubMed

    Ntounis, Athanasios; Kamposiora, Phophi; Papavasiliou, George; Divaris, Kimon; Zinelis, Spiros

    2015-03-01

    The aim of the present study was to evaluate the effects of storage media on the longitudinal hardness changes of tissue conditioning materials. Four tissue-conditioning materials were used for fabrication of 80 disc-shaped specimens and divided in four groups, stored in four storage media. The specimens underwent artificial ageing corresponding to 30 nights of extra-oral storage. Hardness measurements were obtained at nine intervals between 8 and 240 hours after specimen fabrication. To test the effects of storage media on hardness we employed multivariate modelling (Bonferroni correction; α = 0.05). The materials exhibited varying hardness changes, most pronounced when stored in ambient air.

  19. High-resolution single-shot spectral monitoring of hard x-ray free-electron laser radiation

    DOE PAGES

    Makita, M.; Karvinen, P.; Zhu, D.; ...

    2015-10-16

    We have developed an on-line spectrometer for hard x-ray free-electron laser (XFEL) radiation based on a nanostructured diamond diffraction grating and a bent crystal analyzer. Our method provides high spectral resolution, interferes negligibly with the XFEL beam, and can withstand the intense hard x-ray pulses at high repetition rates of >100 Hz. The spectrometer is capable of providing shot-to-shot spectral information for the normalization of data obtained in scientific experiments and optimization of the accelerator operation parameters. We have demonstrated these capabilities of the setup at the Linac Coherent Light Source, in self-amplified spontaneous emission mode at full energy ofmore » >1 mJ with a 120 Hz repetition rate, obtaining a resolving power of Ε/δΕ > 3 × 104. In conclusion, the device was also used to monitor the effects of pulse duration down to 8 fs by analysis of the spectral spike width.« less

  20. A confident source of hard X-rays: radiation from a tokamak applicable for runaway electrons diagnosis.

    PubMed

    Kafi, M; Salar Elahi, A; Ghoranneviss, M; Ghanbari, M R; Salem, M K

    2016-09-01

    In a tokamak with a toroidal electric field, electrons that exceed the critical velocity are freely accelerated and can reach very high energies. These so-called `runaway electrons' can cause severe damage to the vacuum vessel and are a dangerous source of hard X-rays. Here the effect of toroidal electric and magnetic field changes on the characteristics of runaway electrons is reported. A possible technique for runaways diagnosis is the detection of hard X-ray radiation; for this purpose, a scintillator (NaI) was used. Because of the high loop voltage at the beginning of a plasma, this investigation was carried out on toroidal electric field changes in the first 5 ms interval from the beginning of the plasma. In addition, the toroidal magnetic field was monitored for the whole discharge time. The results indicate that with increasing toroidal electric field the mean energy of runaway electrons rises, and also an increase in the toroidal magnetic field can result in a decrease in intensity of magnetohydrodynamic oscillations which means that for both conditions more of these high-energy electrons will be generated.

  1. Liquid belt radiator design study

    NASA Technical Reports Server (NTRS)

    Teagan, W. P.; Fitzgerald, K. F.

    1986-01-01

    The Liquid Belt Radiator (LBR) is an advanced concept developed to meet the needs of anticipated future space missions. A previous study documented the advantages of this concept as a lightweight, easily deployable alternative to present day space heat rejection systems. The technical efforts associated with this study concentrate on refining the concept of the LBR as well as examining the issues of belt dynamics and potential application of the LBR to intermediate and high temperature heat rejection applications. A low temperature point design developed in previous work is updated assuming the use of diffusion pump oil, Santovac-6, as the heat transfer media. Additional analytical and design effort is directed toward determining the impact of interface heat exchanger, fluid bath sealing, and belt drive mechanism designs on system performance and mass. The updated design supports the earlier result by indicating a significant reduction in system specific system mass as compared to heat pipe or pumped fluid radiator concepts currently under consideration (1.3 kg/sq m versus 5 kg/sq m).

  2. Metric Analysis of the Hard Palate in Children with Down Syndrome--A Comparative Study

    ERIC Educational Resources Information Center

    Bhagyalakshmi, Gopalan; Renukarya, Annappa Jai; Rajangam, Sayee

    2007-01-01

    The hard palate is viewed as playing an important role in the passive articulation of speech. Its probable role in the defective articulation of speech in individuals with Down syndrome has been examined in the present study. In individuals with Down syndrome, the hard palate is highly arched, constricted, and narrow and stair type with malformed…

  3. Radiation damage studies for the D0 silicon detector

    SciTech Connect

    Lehner, F.; /Zurich U.

    2004-01-01

    We report on irradiation studies performed on spare production silicon detector modules for the current D0 silicon detector. The lifetime expectations due to radiation damage effects of the existing silicon detector are reviewed. A new upgrade project was started with the goal of a complete replacement of the existing silicon detector. In that context, several investigations on the radiation hardness of new prototype silicon microstrip detectors were carried out. The irradiation on different detector types was performed with 10 MeV protons up to fluences of 10{sup 14} p/cm{sup 2} at the J.R. Mcdonald Laboratory at Kansas State University. The flux calibration was carefully checked using different normalization techniques. As a result, we observe roughly 40-50% less radiation damage in silicon for 10 MeV p exposure than it is expected by the predicted NIEL scaling.

  4. Product assurance technology for procuring reliable, radiation-hard, custom LSI/VLSI electronics

    NASA Technical Reports Server (NTRS)

    Buehler, M. G.; Allen, R. A.; Blaes, B. R.; Hicks, K. A.; Jennings, G. A.; Lin, Y.-S.; Pina, C. A.; Sayah, H. R.; Zamani, N.

    1989-01-01

    Advanced measurement methods using microelectronic test chips are described. These chips are intended to be used in acquiring the data needed to qualify Application Specific Integrated Circuits (ASIC's) for space use. Efforts were focused on developing the technology for obtaining custom IC's from CMOS/bulk silicon foundries. A series of test chips were developed: a parametric test strip, a fault chip, a set of reliability chips, and the CRRES (Combined Release and Radiation Effects Satellite) chip, a test circuit for monitoring space radiation effects. The technical accomplishments of the effort include: (1) development of a fault chip that contains a set of test structures used to evaluate the density of various process-induced defects; (2) development of new test structures and testing techniques for measuring gate-oxide capacitance, gate-overlap capacitance, and propagation delay; (3) development of a set of reliability chips that are used to evaluate failure mechanisms in CMOS/bulk: interconnect and contact electromigration and time-dependent dielectric breakdown; (4) development of MOSFET parameter extraction procedures for evaluating subthreshold characteristics; (5) evaluation of test chips and test strips on the second CRRES wafer run; (6) two dedicated fabrication runs for the CRRES chip flight parts; and (7) publication of two papers: one on the split-cross bridge resistor and another on asymmetrical SRAM (static random access memory) cells for single-event upset analysis.

  5. Depletion layer recombination effects on the radiation damage hardness of gallium arsenide cells

    NASA Technical Reports Server (NTRS)

    Garlick, G. F. J.

    1985-01-01

    The significant effect of junction depletion layer recombination on the efficiency of windowed GaAs cells was demonstrated. The effect becomes more pronounced as radiation damage occurs. The depletion is considered for 1 MeV electron fluences up to 10 to the 16th power e/sq m. The cell modeling separates damage in emitter and base or buffer layers using different damage coefficients is reported. The lower coefficient for the emitter predicts less loss of performance at fluences greater than 10 to the 15th power e/sq cm. A method for obtaining information on junction recombination effects as damage proceeds is described; this enables a more complete diagnosis of damage to be made.

  6. Design of Si-photonic structures to evaluate their radiation hardness dependence on design parameters

    NASA Astrophysics Data System (ADS)

    Zeiler, M.; Detraz, S.; Olantera, L.; Pezzullo, G.; Seif El Nasr-Storey, S.; Sigaud, C.; Soos, C.; Troska, J.; Vasey, F.

    2016-01-01

    Particle detectors for future experiments at the HL-LHC will require new optical data transmitters that can provide high data rates and be resistant against high levels of radiation. Furthermore, new design paths for future optical readout systems for HL-LHC could be opened if there was a possibility to integrate the optical components with their driving electronics and possibly also the silicon particle sensors themselves. All these functionalities could potentially be combined in the silicon photonics technology which currently receives a lot of attention for conventional optical link systems. Silicon photonic test chips were designed in order to assess the suitability of this technology for deployment in high-energy physics experiments. The chips contain custom-designed Mach-Zehnder modulators, pre-designed ``building-block'' modulators, photodiodes and various other passive test structures. The simulation and design flow of the custom designed Mach-Zehnder modulators and some first measurement results of the chips are presented.

  7. A study of the surface hardness and dimensional stability of several intermaxillary registration materials.

    PubMed

    Chai, J; Tan, E; Pang, I C

    1994-01-01

    This study compared the surface hardness, the effect of time on surface hardness, and the dimensional stability of various intermaxillary relationship registration materials. The Shore hardness values of one zinc oxide-eugenol material, one polyether, and seven poly(vinyl siloxane) materials were obtained at 30 minutes and 24 hours after the start of mixing. The dimensional stability of one polyether and seven poly(vinyl siloxane) materials was measured using a standard mold as described in American Dental Association (ADA) Specification No. 19. All materials exhibited relatively high surface hardness despite some statistical differences among them. Four materials possessed higher surface hardness at 24 hours than at 30 minutes. Although the polyether showed significantly lower dimensional stability than the other materials, all materials satisfied the minimum requirement for Type I elastomeric impression material.

  8. Spaceflight Ka-Band High-Rate Radiation-Hard Modulator

    NASA Technical Reports Server (NTRS)

    Jaso, Jeffery M.

    2011-01-01

    A document discusses the creation of a Ka-band modulator developed specifically for the NASA/GSFC Solar Dynamics Observatory (SDO). This flight design consists of a high-bandwidth, Quadriphase Shift Keying (QPSK) vector modulator with radiation-hardened, high-rate driver circuitry that receives I and Q channel data. The radiationhard design enables SDO fs Ka-band communications downlink system to transmit 130 Mbps (300 Msps after data encoding) of science instrument data to the ground system continuously throughout the mission fs minimum life of five years. The low error vector magnitude (EVM) of the modulator lowers the implementation loss of the transmitter in which it is used, thereby increasing the overall communication system link margin. The modulator comprises a component within the SDO transmitter, and meets the following specifications over a 0 to 40 C operational temperature range: QPSK/OQPSK modulator, 300-Msps symbol rate, 26.5-GHz center frequency, error vector magnitude less than or equal to 10 percent rms, and compliance with the NTIA (National Telecommunications and Information Administration) spectral mask.

  9. Data Fitting to Study Ablated Hard Dental Tissues by Nanosecond Laser Irradiation

    PubMed Central

    Abdel-Daiem, A. M.; Ansari, M. Shahnawaze; Babkair, Saeed S.; Salah, Numan A.; Al-Mujtaba, A.

    2016-01-01

    Laser ablation of dental hard tissues is one of the most important laser applications in dentistry. Many works have reported the interaction of laser radiations with tooth material to optimize laser parameters such as wavelength, energy density, etc. This work has focused on determining the relationship between energy density and ablation thresholds using pulsed, 5 nanosecond, neodymium-doped yttrium aluminum garnet; Nd:Y3Al5O12 (Nd:YAG) laser at 1064 nanometer. For enamel and dentin tissues, the ablations have been performed using laser-induced breakdown spectroscopy (LIBS) technique. The ablation thresholds and relationship between energy densities and peak areas of calcium lines, which appeared in LIBS, were determined using data fitting. Furthermore, the morphological changes were studied using Scanning Electron Microscope (SEM). Moreover, the chemical stability of the tooth material after ablation has been studied using Energy-Dispersive X-Ray Spectroscopy (EDX). The differences between carbon atomic % of non-irradiated and irradiated samples were tested using statistical t-test. Results revealed that the best fitting between energy densities and peak areas of calcium lines were exponential and linear for enamel and dentin, respectively. In addition, the ablation threshold of Nd:YAG lasers in enamel was higher than that of dentin. The morphology of the surrounded ablated region of enamel showed thermal damages. For enamel, the EDX quantitative analysis showed that the atomic % of carbon increased significantly when laser energy density increased. PMID:27228169

  10. Radiation effects on microstructure and hardness of a titanium aluminide alloy irradiated by helium ions at room and elevated temperatures

    NASA Astrophysics Data System (ADS)

    Wei, Tao; Zhu, Hanliang; Ionescu, Mihail; Dayal, Pranesh; Davis, Joel; Carr, David; Harrison, Robert; Edwards, Lyndon

    2015-04-01

    A 45XD TiAl alloy possessing a lamellar microstructure was irradiated using 5 MeV helium ions to a fluence of 5 × 1021 ion m-2 (5000 appm) with a dose of about 1 dpa (displacements per atom). A uniform helium ion stopping damage region about 17 μm deep from the target surface was achieved by applying an energy degrading wheel. Radiation damage defects including helium-vacancy clusters and small helium bubbles were found in the microstructure of the samples irradiated at room temperature. With increasing irradiation temperature to 300 °C and 500 °C helium bubbles were clearly observed in both the α2 and γ phases of the irradiated microstructure. By means of nanoindentation significant irradiation hardening was measured. For the samples irradiated at room temperature the hardness increased from 5.6 GPa to 8.5 GPa and the irradiation-hardening effect reduced to approximately 8.0 GPa for the samples irradiated at 300 °C and 500 °C.

  11. Radiation hardness of AlxGa1-xN photodetectors exposed to Extreme UltraViolet (EUV) light beam

    NASA Astrophysics Data System (ADS)

    Malinowski, Pawel E.; John, Joachim; Barkusky, Frank; Duboz, Jean Yves; Lorenz, Anne; Cheng, Kai; Derluyn, Joff; Germain, Marianne; De Moor, Piet; Minoglou, Kyriaki; Bayer, Armin; Mann, Klaus; Hochedez, Jean-Francois; Giordanengo, Boris; Borghs, Gustaaf; Mertens, Robert

    2009-05-01

    We report on the results of fabrication and optoelectrical characterization of Gallium Nitride (GaN) based Extreme UltraViolet (EUV) photodetectors. Our devices were Schottky photodiodes with a finger-shaped rectifying contact, allowing better penetration of light into the active region. GaN layers were epitaxially grown on Silicon (111) by Metal- Organic-Chemical Vapor Deposition (MOCVD). Spectral responsivity measurements in the Near UltraViolet (NUV) wavelength range (200-400 nm) were performed to verify the solar blindness of the photodetectors. After that the devices were exposed to the EUV focused beam of 13.5 nm wavelength using table-top EUV setup. Radiation hardness was tested up to a dose of 3.3Â.1019 photons/cm2. Stability of the quantum efficiency was compared to the one measured in the same way for a commercially available silicon based photodiode. Superior behavior of GaN devices was observed at the wavelength of 13.5 nm.

  12. Proposal to produce novel, transparent radiation hard low refractive index polymers. Final report, 1 October-31 December 1993

    SciTech Connect

    Schuman, P.D.; Harmon, J.

    1994-02-09

    Low and high molecular weight polymers of heptafluorobutyl methacrylate, HFBM, were prepared for commercial evaluation by Bicron, an optical fiber manufacturer. Polymers were evaluated as low refractive index fiber cladding materials. Test results of Low MW polymer solutions gave excellent results. Higher MW polymers were prepared for cladding by melt co-extrusion. Corning Glass Corp, also expressed an interest in these cladding materials. These results appear to be sufficiently unique that a search has been initiated to determine patentability of the soluble fluorocarbon acrylate, methacrylate and copolymer compositions for cladding use. This research resulted in identifying a radiation hard, low refractive index polymer, poly(heptafluorobutyl methacrylate), P(HFBM) as the best candidate for a novel cladding material. P(HFBM) has a refractive index of 1.387. When used to clad a styrene core, the theoretical light propagation efficiency is 50% greater than that of styrene fiber core clad with PMMA, a common commercial cladding material. These polymers will be the only commercial fluorocarbon acrylic cladding polymers available to U.S. manufacturers. Japanese optical fiber manufacturers produce fluorocarbon clad fibers but their polymers are not available to U.S. manufacturers. These polymers can fill an urgent need in the optical fiber market.

  13. A Theoretical Study of the Brinell Hardness Test

    NASA Astrophysics Data System (ADS)

    Hill, R.; Storakers, B.; Zdunek, A. B.

    1989-06-01

    Brinell tests have long been the preferred method of assaying the hardness of metals during forming operations. The general significance of the test has been codified in empirical laws, especially those of Meyer, O'Neill and Tabor. On the other hand, the indentation of elastoplastic media by a ball has never been thoroughly analysed in the context of modern mechanics of continua; this is the objective here. The actual boundary-value problem is non-steady but can be made steady in terms of reduced variables when the material response is suitably modelled. Namely, the strain should be infinitesimal and expressible as the tensor gradient of a potential function of the stress deviator; the function must be homogeneous of degree n + 1 (>=slant 2), but is otherwise arbitrary. Meyer's law is then derivable rigorously ahead of a detailed solution. Moreover the predicted index is (2n + 1)/n, substantiating O'Neill's rule for materials whose strain under uniaxial tension varies as some nth power of the stress. It is predicted also that the piling-up or sinking-in around the indenter is correlated with n in the manner observed. These immediate implications of the model amount to a priori evidence of its overall ability to simulate elastoplastic response of the kind induced in Brinell tests. Evidence a posteriori was supplied by finite element computations for a standard potential whose level surfaces are of Mises type. Mixed nine-node quadrilateral elements were adopted; these are known to promote optimal convergence and are well suited to handling incompressibility. A carefully graded mesh provided about 24 000 degrees of freedom. Computations were performed for n = 1, 2, 4 and 10, covering the practical range. The results include (i) distributions of the contact pressure and the radial and circumferential in-surface stresses; (ii) profiles of the deformed surface; and (iii) contours of representative strain in the main body of material. Excellent agreement was obtained with

  14. Radiation hardness of 30 cm long CsI(Tl) crystals

    NASA Astrophysics Data System (ADS)

    Longo, S.; Roney, J. M.

    2016-08-01

    Measurements of the degradation in performance of 30 cm long CsI(Tl) scintillation crystals exposed to 1 MeV photon doses of 2, 10, 35, 100 and 1000 Gy are presented. The light yield, light yield longitudinal non-uniformity, scintillation decay times, energy resolution and timing resolution of a set of spare crystals from the BABAR and Belle experiments are studied as a function of these doses. In addition, a model that describes the plateau observed in the light output loss as a function of dose in terms of increase in concentrations of absorption centres with irradiation is presented.

  15. Hardness in rare earth diboride systems: Ab initio full-potential study

    NASA Astrophysics Data System (ADS)

    Zaoui, A.; Abderrahmane, S. Ait; Djermouni, M.; Kacimi, S.; Zazoua, F.; Boukortt, A.; Bejar, M.; Dhahri, E.

    2017-01-01

    We study in this paper the macroscopic hardness of TiB2 and TmB2 compounds and their corresponding ternary alloys Tm1-xTixB2 by calculating the mechanical properties and electronic structure of these systems. The mechanical results show that TiB2 compound is found ultra-hard compared with TmB2 and the covalent Bsbnd B bonds have an enormous impact on the macroscopic hardness of these systems. These results are in excellent agreement with experiment. In addition, a large charge density was observed in the TiB2 compound comparing to that of TmB2 and of the considered alloys. For short interatomic distances Bsbnd B, the hardness in Tm1-xTixB2 alloys is important.

  16. [The study on the influence of bovine enamel hardness measurement methods on the result evaluation].

    PubMed

    Zhang, Dianyun; Lin, Hong; Zheng, Rui; Han, Jianmin; Zheng, Gang

    2013-02-01

    The variation in hardness of enamel is a frequently used method to evaluate the influence of whiting materials on the enamel. The purpose of this study is to improve the veracity on the evaluation tests caused by the tooth itself with point selection method. Three kinds of testing point selection methods on enamel were carried out, i. e. random selection, grid measurement and symmetrical measurement, respectively. The selected points were used to measure the micro hardness by Vickers. The influence of the variation of tooth structure itself on the hardness measurements results can be reduced by using testing point selection methods of symmetry, and thus, the accuracy of the test method used in the evaluation of the influence of dental materials on tooth hardness will be guaranteed.

  17. Radiator Study for Stationary Lunar Landers

    NASA Technical Reports Server (NTRS)

    OConnor, Brian; Abel, Elisabeth

    2010-01-01

    This paper provides an overview of a study to identify, select and evaluate potential heat rejection radiators for application to small, low power, stationary lunar landers. While this study supported risk mitigation activities related to the International Lunar Network project, the radiator concepts and performance assessments are applicable to a wide range of lunar lander applications. The radiator concepts identified and evaluated in this study were aimed at providing reliable heat rejection for landers that might be subjected to hot lunar noon conditions at the equator. As a part of the study, a literature search of lunar radiators was performed from which many radiator designs were developed. These designs were compared in a trade study and two of the most promising were used to develop six concepts. These six radiator concepts went through a more detailed thermal analysis using Thermal Desktop. The analysis considered heat rejection capability, and sensitivity to many factors such as dust deposition, latitude, life, and topographical features like landing on a hill, on a rock, or in a hole/crater. From the result of the analysis, two radiator concepts were selected for recommendation: a flat horizontal plate with a dust cover and a stacked vertical radiator with parabolic reflectors and a one degree tilting mechanism.

  18. Beta Backscatter Measures the Hardness of Rubber

    NASA Technical Reports Server (NTRS)

    Morrissey, E. T.; Roje, F. N.

    1986-01-01

    Nondestructive testing method determines hardness, on Shore scale, of room-temperature-vulcanizing silicone rubber. Measures backscattered beta particles; backscattered radiation count directly proportional to Shore hardness. Test set calibrated with specimen, Shore hardness known from mechanical durometer test. Specimen of unknown hardness tested, and radiation count recorded. Count compared with known sample to find Shore hardness of unknown.

  19. Silicon PM Radiation Hardness

    SciTech Connect

    Rohlf, James

    2016-08-25

    Detailed measurements have been made of 9 mm2 SiPMs from Hamamatsu (MPPC) and Zecotek (MAPD) after room temperature annealing after exposure to fluences of 1012 to 1013 cm-2. The data was used to complete the final ADR report.

  20. Radiation hard vacuum switch

    DOEpatents

    Boettcher, Gordon E.

    1990-03-06

    A vacuum switch with an isolated trigger probe which is not directly connected to the switching electrodes. The vacuum switch within the plasmatron is triggered by plasma expansion initiated by the trigger probe which travels through an opening to reach the vacuum switch elements. The plasma arc created is directed by the opening to the space between the anode and cathode of the vacuum switch to cause conduction.

  1. Radiation hard vacuum switch

    DOEpatents

    Boettcher, Gordon E.

    1990-01-01

    A vacuum switch with an isolated trigger probe which is not directly connected to the switching electrodes. The vacuum switch within the plasmatron is triggered by plasma expansion initiated by the trigger probe which travels through an opening to reach the vacuum switch elements. The plasma arc created is directed by the opening to the space between the anode and cathode of the vacuum switch to cause conduction.

  2. Hard Biscuits: Motivation to Learn in Secondary School Social Studies.

    ERIC Educational Resources Information Center

    Allen, Rodney F.

    1995-01-01

    Maintains that much of the high school curriculum, particularly in social studies, contains innumerable facts that have no use except to pass school tests. Reviews research on effective instruction as applied to social studies. Includes 17 characteristics of highly engaging social studies teaching and learning. (ACM)

  3. Computational studies of radiation characteristics for U-238 gamma and neutron protection

    SciTech Connect

    Babicheva, T.S.; Vatulin, V.V.; Zhitnik, A.K.

    1993-12-31

    This paper is devoted to predicting the radiation security and nuclear safety of the ZhT-80 container design used to transport 18 WWER-1000 fuel assemblies and is promising in terms of increasing specific loading based on U-238 and hard neutron protection consisting of boron filled organic materials. Studies were carried out using the Monte Carlo Method.

  4. Microstructural and Hardness Studies of Cu-10wt.%Sn Alloy Under Different Aging Conditions

    NASA Astrophysics Data System (ADS)

    Bashir, Farooq; Butt, Muhammad Zakria; Saleemi, Farhat

    2008-02-01

    Microstructure of Cu-10wt.%Sn alloy, prepared by powder metallurgy technique and sintered at 900 °C for 120 min in hydrogen atmosphere, was studied by optical microscopy and XRD technique as a function of aging time. Isothermal aging of the alloy specimens was performed at 250 °C for a period of 30, 60, 120, 300, and 1440 min after solution treatment at 500 °C for 60 min. Rockwell hardness of aged specimens was also measured at room temperature as a function of aging time. It was observed that microstructure of the as-sintered specimens consists of the grains of alpha Cu-Sn solid solution. Moreover, solution treatment of the alloy specimens followed by quenching in water increased the hardness of the as-sintered alloy specimens from 35.5 to 59.8 HRF due to the residual stresses generated by fast cooling. Aging at 250 °C for 30, 60, and 120 min was found to cause a decrease in hardness from 59.8 to 45.1 HRF, whereas the specimens aged for 300 and 1440 min show an increase in hardness from 45.1 to 75.7 HRF. The values of porosity calculated from XRD patterns of the alloy specimens referred to show that porosity varies with aging time in a manner opposite to that of hardness, e.g., porosity is maximum for 120 min aging time where hardness is minimum.

  5. Surface properties of hard protective coatings studied by optical techniques

    NASA Astrophysics Data System (ADS)

    Jaglarz, Janusz; Wolska, N.; Mitura, K.; Duraj, R.; Marszalek, K. W.; El Kouari, Y.

    2016-06-01

    The paper describes optical study of SiC, C and NiC layers deposited on Si substrates by double beam ion sputtering (DBIS) method. The following optical methods: ellipsometry, bidirectional reflection distribution function (BRDF) and total integrated scattering (TIS) studies have been applied. The obtained results allowed us to determine the refractive indices, extinction coefficients and the roughness parameters of DBIS films. Also surface profiles of optical constants determined from scanning ellipsometric measurements have been presented. The power spectral density functions (PSD) of surface roughness for studied samples have been determined. The influence of the deposition technology on film topography has been discussed.

  6. In Study Abroad, Men Are Hard to Find

    ERIC Educational Resources Information Center

    Fischer, Karin

    2012-01-01

    In the 2009-2010 academic year, women accounted for nearly two-thirds of the 270,600 American students going overseas. Indeed, the proportion of men studying overseas has remained the same--or flatlined, to put it less charitably--for more than two decades. Sending a broader cross-section of majors abroad has not made a dent in the gender gap…

  7. A study on hardness behavior of geopolymer paste in different condition

    NASA Astrophysics Data System (ADS)

    Zainal, Farah Farhana; Hussin, Kamarudin; Rahmat, Azmi; Abdullah, Mohd Mustafa Al Bakri; Shamsudin, Shaiful Rizam

    2016-07-01

    This study has been conducted to understand the hardness behavior of geopolymer paste in different conditions; with and without being immersed in water. Geopolymer paste has been used nowadays as an alternative way to reduce global warming pollution by carbon dioxide (CO2) released to the air caused from the production of Ordinary Portland Cement (OPC). Geopolymer has many advantages such as high compressive strength, lower water absorption and lower porosity. Geopolymer paste in this study was made from a mixture of fly ash and alkaline activators. The alkaline activators that have been used were sodium hydroxide (NaOH) solution and sodium silicate (Na2SiO3) solution. Then the mixture was allowed to harden for 24hrs at ambient temperature and then placed in the oven for 24hrs with 60°C for the curing process. The hardness testing was conducted after a few months when the samples already achieved the optimum design. The samples were divided to two conditions; without immersion which was placed at ambient temperature (S1) and immersed in water for one week (S2). The samples then are divided into two at the center and testing was conducted into 4 parts which are part 1, part 2, part 3 and part 4. Various methods of non-destructively testing concrete and mortar have been in use for many years such as Vickers hardness test, Rockwell hardness test, Brinell hardness test and many more. The Rockwell hardness test method as defined in ASTM E-18 is the most commonly used hardness test method which is also used in this study. From the results, S1 has higher hardness value than S2 for all parts with the maximum value of S1 is 118.6 and the minimum value is 71.8. The maximum value of S2 is 114.4 and the minimum value is 0. The central part of the geopolymer paste also showed greater hardness values than the edge area of the samples.

  8. A study to evaluate cephalometric hard tissue profile of Tamil population for orthognathic surgery

    PubMed Central

    Nachiappan, S.; Tharanikumar, S.; Chandran, Ajay; Anusudha, P.; Nandini, G. D.; Balasubramaniam, Murali

    2015-01-01

    The primary aim of this study is to compare, the cephalometric hard tissue profile values and analysis between Tamil and Caucasian population. The study also aims to create a better understanding in the facial proportions of Tamil Nadu population and to have better diagnosis and treatment planning for orthognathic surgery for Tamil population in Tamil Nadu. PMID:26538943

  9. A study to evaluate cephalometric hard tissue profile of Tamil population for orthognathic surgery.

    PubMed

    Nachiappan, S; Tharanikumar, S; Chandran, Ajay; Anusudha, P; Nandini, G D; Balasubramaniam, Murali

    2015-08-01

    The primary aim of this study is to compare, the cephalometric hard tissue profile values and analysis between Tamil and Caucasian population. The study also aims to create a better understanding in the facial proportions of Tamil Nadu population and to have better diagnosis and treatment planning for orthognathic surgery for Tamil population in Tamil Nadu.

  10. Investigation on the long-term radiation hardness of low resistivity starting silicon materials for RT silicon detectors in high energy physics

    SciTech Connect

    Li, Z.

    1994-02-01

    Relatively low resistivity (200 to 1000 {Omega}-cm) starting silicon materials have been studied in the search of room temperature neutron radiation-hard silicon detectors. It has been found that, moderate resistivity (300-700 {Omega}-cm) silicon detectors, after being irradiated to 5.0 {times} 10{sup 13} to 2.0 {times} 10{sup 14} n/cm{sup 2}, are extremely stable in terms of the detector full depletion voltage (V{sub d}) or the net effective concentration of ionized space charges (N{sub eff} ---- there is little ``reverse annealing`` of N{sub eff} at RT and elevated temperatures as compared with large reverse annealing observed for high resistivity silicon detectors. Detectors with starting resistivity of 300-700 {Omega}-cm have been found to be stable, during the equivalent of one year RT anneal that would reach the saturation of the first stage of reverse anneal, within then N{sub eff} window of {vert_bar}N{sub eff}{vert_bar}{le} 2.5 {times} 10{sup 12} cm{sup {minus}3} (V{sub d} = 180 V for d = 300 {mu}m) in a working range of 5.0 {times} 10{sup 13} to 1.5 {times} 10{sup 14} n/cm{sup 2}, or a net neutron radiation tolerance of 1.0 {times} 10{sup 14} n/cm{sup 2}. The observed effects are in very good agreement with an early proposed model, which predicted among others, that there might be an off set between the reverse annealing effect and the partial annealing of the P-V centers that leads to the partial recovery of the shallow impurity donors.

  11. Examining metacognition in hearing and deaf/hard of hearing students: a comparative study.

    PubMed

    al-Hilawani, Y A

    2001-03-01

    The metacognitive performance of 87 hearing and 20 deaf/hard of hearing students was examined. The hearing students consisted of 42 males (mean age 15.6 years) and 45 females (mean age 15.4 years). The deaf/hard of hearing students consisted of 13 males (mean age 16.9 years) and 7 females (mean age 15.9 years). Metacognition was conceptualized in terms of choosing the best response to problematic situations drawing upon problem-solving and logical reasoning skills. In the test, pictures represented various daily life interactions. There was no significant difference between hearing and deaf/hard of hearing students in metacognitive performance, nor was there a gender-based significant difference among the deaf/hard of hearing students. However, hearing female students scored significantly higher on the metacognitive test than hearing male students. Further analysis of the study findings possibly would show students' overall performance on the metacognitive test to be independent of grade point average. Analysis did show, however, a significant negative correlation between test performance and grades in Arabic among deaf/hard of hearing students.

  12. Comparative study of microwave radiation-induced magnetoresistive oscillations induced by circularly- and linearly- polarized photo-excitation

    PubMed Central

    Ye, Tianyu; Liu, Han-Chun; Wang, Zhuo; Wegscheider, W.; Mani, Ramesh G.

    2015-01-01

    A comparative study of the radiation-induced magnetoresistance oscillations in the high mobility GaAs/AlGaAs heterostructure two dimensional electron system (2DES) under linearly- and circularly- polarized microwave excitation indicates a profound difference in the response observed upon rotating the microwave launcher for the two cases, although circularly polarized microwave radiation induced magnetoresistance oscillations observed at low magnetic fields are similar to the oscillations observed with linearly polarized radiation. For the linearly polarized radiation, the magnetoresistive response is a strong sinusoidal function of the launcher rotation (or linear polarization) angle, θ. For circularly polarized radiation, the oscillatory magnetoresistive response is hardly sensitive to θ. PMID:26450679

  13. Comparative study of microwave radiation-induced magnetoresistive oscillations induced by circularly- and linearly- polarized photo-excitation

    SciTech Connect

    Ye, Tianyu; Liu, Han -Chun; Wang, Zhuo; Wegscheider, W.; Mani, Ramesh G.

    2015-10-09

    A comparative study of the radiation-induced magnetoresistance oscillations in the high mobility GaAs/AlGaAs heterostructure two dimensional electron system (2DES) under linearly- and circularly- polarized microwave excitation indicates a profound difference in the response observed upon rotating the microwave launcher for the two cases, although circularly polarized microwave radiation induced magnetoresistance oscillations observed at low magnetic fields are similar to the oscillations observed with linearly polarized radiation. For the linearly polarized radiation, the magnetoresistive response is a strong sinusoidal function of the launcher rotation (or linear polarization) angle, θ. As a result, for circularly polarized radiation, the oscillatory magnetoresistive response is hardly sensitive to θ.

  14. Radiative Studies of Planetary Atmospheres

    NASA Technical Reports Server (NTRS)

    Conrath, Barney J.

    2005-01-01

    Retrieval algorithms and associated software for application to CIRS infrared spectral data have been developed and coded. A general forward radiative transfer code has been written that runs efficiently on a Macintosh, even at high spectral resolution (0.5 per centimeter). It makes use of the correlated-k approach for representation of the gaseous absorption and can include those gases listed in the HITRAN and GEISA atlases, along with collision-induced absorption. Cloud effects are included as spectrally dependent absorbers. Provision has been made for future extension to include particle scattering in an n-stream approximation. The primary purpose of the code is to produce synthetic data and to serve as the forward calculating element in gas and cloud retrieval programs developed for the Mac as well as other platforms. Initial development of algorithms and production software suitable for application to CIRS data to be obtained from Jupiter, Saturn and Titan has been completed, and production versions of the software for application to the spectral data are in place. This includes temperature, gaseous constituent, and cloud opacity retrieval, algorithms that can be applied to both nadir and limb data. This work has been done as a cooperative effort between Conrath and Matcheva (Cornell), Achterberg (GSFWSSAI), and Flasar (GSFC).

  15. Carpet vs. Hard Surface Floors: Studies Compare Health Effects of Each.

    ERIC Educational Resources Information Center

    Schmidt, Edward A.

    1994-01-01

    This article, third in a three-part series of articles that discuss indoor air quality (IAQ) issues affecting schools, looks at studies that compare the health effect of carpet and hard surface floors. Concludes that carpet is appropriate for use in schools when it is properly maintained. (MLF)

  16. Hard X-ray imaging facility for space shuttle: A scientific and conceptual engineering study

    NASA Technical Reports Server (NTRS)

    Peterson, L. E.; Hudson, H. S.; Hurford, G.; Schneible, D.

    1976-01-01

    A shuttle-accommodated instrument for imaging hard X-rays in the study of nonthermal particles and high temperature particles in various solar and cosmic phenomena was defined and its feasibility demonstrated. The imaging system configuration is described as well as the electronics, aspect systems, mechanical and thermal properties and the ground support equipment.

  17. A pixel unit-cell targeting 16 ns resolution and radiation hardness in a column read-out particle vertex detector

    SciTech Connect

    Wright, M.; Millaud, J.; Nygren, D.

    1992-10-01

    A pixel unit cell (PUC) circuit architecture, optimized for a column read out architecture, is reported. Each PUC contains an integrator, active filter, comparator, and optional analog store. The time-over-threshold (TOT) discriminator allows an all-digital interface to the array periphery readout while passing an analog measure of collected charge. Use of (existing) radiation hard processes, to build a detector bump-bonded to a pixel readout array, is targeted. Here, emphasis is on a qualitative explanation of how the unique circuit implementation benefits operation for Super Collider (SSC) detector application.

  18. Digital radiology using active matrix readout of amorphous selenium: radiation hardness of cadmium selenide thin film transistors.

    PubMed

    Zhao, W; Waechter, D; Rowlands, J A

    1998-04-01

    A flat-panel x-ray imaging detector using active matrix readout of amorphous selenium (a-Se) is being investigated for digital radiography and fluoroscopy. The active matrix consists of a two-dimensional array of thin film transistors (TFTs). Radiation penetrating through the a-Se layer will interact with the TFTs and it is important to ensure that radiation induced changes will not affect the operation of the x-ray imaging detector. The methodology of the present work is to investigate the effects of radiation on the characteristic curves of the TFTs using individual TFT samples made with cadmium selenide (CdSe) semiconductor. Four characteristic parameters, i.e., threshold voltage, subthreshold swing, field effect mobility, and leakage current, were examined. This choice of parameters was based on the well established radiation damage mechanisms for crystalline silicon metal-oxide-semiconductor field-effect transistors (MOSFETs), which have a similar principle of operation as CdSe TFTs. It was found that radiation had no measurable effect on the leakage current and the field effect mobility. However, radiation shifted the threshold voltage and increased the subthreshold swing. But even the estimated lifetime dose (50 Gy) of a diagnostic radiation detector will not affect the normal operation of an active matrix x-ray detector made with CdSe TFTs. The mechanisms of the effects of radiation will be discussed and compared with those for MOSFETs and hydrogenated amorphous silicon (a-Si:H) TFTs.

  19. Overlay metrology for dark hard mask process: simulation and experiment study

    NASA Astrophysics Data System (ADS)

    Shin, Jangho; Chalykh, Roman; Kang, Hyunjae; Kim, SeongSue; Lee, SukJoo; Cho, Han-Ku

    2007-03-01

    Simulation and experimental study results are reported to solve align/overlay problem in dark hard mask process in lithography. For simulation part, an in-house simulator, which is based on rigorous coupled wave analysis and Fourier optics method of high NA imaging, is used. According to the simulation and experiment study, image quality of alignment and overlay marks can be optimized by choosing hard mask and sub-film thickness carefully for a given process condition. In addition, it is important to keep the specification of film thickness uniformity within a certain limit. Simulation results are confirmed by experiment using the state of art memory process in Samsung semiconductor R&D facility.

  20. Molecular electronics studies by synchrotron radiation

    SciTech Connect

    Wee, Andrew T. S.; Chen Wei; Chi Dongchen; Chen Shi; Wang Li; Gao Xingyu

    2009-01-29

    In molecular electronics research, the molecule-metal interfacial properties crucially control the electronic properties of the devices fabricated. We use synchrotron radiation techniques of PES and NEXAFS, complemented by STM, to study the molecular orientation and interfacial charge transfer processes of model molecule-metal systems.

  1. STUDIES OF RADIATIVE PENGUIN DECAYS AT BABAR

    SciTech Connect

    Jessop, C

    2003-10-27

    The electromagnetic radiative ''penguin'' decays b {yields} s{gamma}, b {yields} d{gamma} are sensitive to physics beyond the Standard Model. The authors present recent studies made with the BABAR detector at the PEP-II asymmetric e{sup +}e{sup -} storage ring.

  2. X-ray emission from cataclysmic variables with accretion disks. I - Hard X-rays. II - EUV/soft X-ray radiation

    NASA Technical Reports Server (NTRS)

    Patterson, J.; Raymond, J. C.

    1985-01-01

    Theoretical models explaining the hard-X-ray, soft-X-ray, and EUV emission of accretion-disk cataclysmic variables in terms of the disk boundary layer (DBL) are developed on the basis of a survey of the published observational data. The data are compared with model predictions in graphs for systems with high or low (greater than or less than 10-Pg/s) accretion rates. Good agreement is obtained both at low accretion rates, where an optically thin rarefied hot (Te = 10 to the 8th K) DBL radiates most of its energy as hard X-rays, and at high accretion rates, where an optically thick 100,000-K DBL radiates most of its energy in the EUV and as soft X-rays. Detailed analysis of the old nova V603 Aql suggests that previous models predicting more detections of soft-X-ray/EUV emissions from thick-DBL objects (Ferland et al., 1982) used inappropriate dwarf masses, interstellar column densities, or classical-nova space densities.

  3. A new technique to prepare hard fruits and seeds for anatomical studies1

    PubMed Central

    Benedict, John C.

    2015-01-01

    Premise of the study: A novel preparation technique was developed to examine fruits and seeds of plants with exceptionally hard or brittle tissues that are very difficult to prepare using standard histological techniques. Methods and Results: The method introduced here was modified from a technique employed on fossil material and has been adapted for use on fruits and seeds of extant plants. A variety of fruits and seeds have been prepared with great success, and the technique will be useful for any excessively hard fruits or seeds that are not able to be prepared using traditional embedding or sectioning methods. Conclusions: When compared to existing techniques for obtaining anatomical features of fruits and seeds, the protocol described here has the potential to create high-quality thin sections of materials that are not able to be sectioned using traditional histological techniques, which can be produced quickly and without the need for harmful chemicals. PMID:26504684

  4. Hard X-Ray, Soft X-Ray, and EUV Studies of Solar Eruptions

    NASA Technical Reports Server (NTRS)

    Sterling, Alphonse C.; Wagner, William (Technical Monitor)

    2003-01-01

    Document study the hard X-ray (HXR), soft X-ray (SXR) ,EUV, and magnetic nature of solar eruptions, with the objective of elucidating the physics of the eruption process. In particular, it was examine the viability of two specific eruption mechanisms, detailed in our proposal. These mechanisms are the "breakout model", and the "tether cutting model". During the second year, it was a significant progress in the goals to Data Sets Utilized. In the publications during this second year of the grant period, the data was used from the E W Imaging Telescope (EIT) and the Michelson Doppler Imager (MDI) instruments on SOHO, and from the Soft X-ray Telescope (SXT), Hard X-ray Telescope (HXT), and the Bragg Crystal Spectrometer (BCS) on Yooh.

  5. Magneto-optical studies of flux penetration in super-hard Nb wire

    NASA Astrophysics Data System (ADS)

    Young, D. P.; Moldovan, M.; Adams, P. W.; Prozorov, R.

    2005-05-01

    We present a study of the magnetic response of type-II superconductivity in the extreme pinning limit, where screening currents within an order of magnitude of the Ginzburg-Landau depairing critical current density develop upon the application of a magnetic field. We show that this 'super-hard' limit is realized in highly disordered, cold drawn, Nb wire whose magnetization response is characterized by a cascade of Meissner-like phases, each terminated by a catastrophic collapse of the magnetization. Direct magneto-optic measurements of the flux penetration depth in the virgin magnetization branch are in excellent agreement with the exponential model in which Jc(B) = Jcoexp(-B/B0), where Jco~5 × 106 A cm-2 for Nb. The implications for the fundamental limiting hardness of a superconductor are discussed.

  6. Machine learning from hard x-ray surveys: applications to magnetic cataclysmic variable studies

    NASA Astrophysics Data System (ADS)

    Scaringi, Simone

    2009-11-01

    Within this thesis are discussed two main topics of contemporary astrophysics. The first is that of machine learning algorithms for astronomy whilst the second is that of magnetic cataclysmic variables (mCVs). To begin, an overview is given of ISINA: INTEGRAL Scouce Identifiction Network Algorithm. This machine learning algorithm, using random forests, is applied to the IBIS/ISGRI data set in order to ease the production of unbiased future soft gamma-ray source catalogues. The feature extraction process on an initial candidate list is described together with feature merging. Three trainng and testing sets are created in order to deal with the diverse time-scales encountered when dealing with the gamma-ray sky: one dealing with faint persistent source recognition, one dealing with strong persistent sources and a final one dealing with transients. For the latter, a new transient detection technique is introduced and described: the transient matrix. Finally the performance of the network is assessed and discussed using the testing set and some illustrative source examples. ISINA is also compared to the more conventional approach of visual inspection. Next mCVs are discussed, and in particular the properties arising from a hard X-ray selected sample which has proven remarkably efficient in detecting intermediate polars and asynchronous polars, two of the rarest type of cataclysmic variables (CVs). This thesis focuses particularly on the link between hard X-ray properties and spin/orbital periods. To this end, a new sample of these objects is constructed by cross-corelating candidate sources detected in INTEGRAL/IBIS observations against catalogues of known CVs. Also included in the analysis are hard X-ray Observations from Swift/BAT and SUZAKU/HXD in order to make the study more complete. It is found that most hard X-ray detected mCVs have Pspin/Porb<0.1 above the period gap. In this respect, attention is given to the very low number of detected systems in any ban

  7. Computer monitoring of the thermal effects induced by Er:YAG laser radiation during preparation of the hard tooth tissue

    NASA Astrophysics Data System (ADS)

    Dostalova, Tatjana; Krejsa, Otakar; Jelinkova, Helena; Hamal, Karel; Prochazka, Ivan; Bakule, Pavel

    1993-12-01

    We are presenting the results of the thermal changes of enamel, dentin and pulp temperature monitoring in extracted human teeth subjected to a pulsed Er:YAG laser radiation. We made a series of experiments irradiating the tooth using the pulsed Er:YAG laser and monitoring simultaneously the temperature of various parts of the tooth. The temperature was measured by the bead thermistor either in contact with the tooth surface or built in the pulp chamber. In the former experiments it was demonstrated, that the uncooled preparation can cause irreversible changes of the pulp. In the second part of the experiments the teeth have been cooled by flowing water. During the laser preparation of the enamel and the dentin the temperature did not increase more than 2 degree(s)C. In the moment of dentin perforation and hence laser irradiation of the pulp, the pulp temperature increased rapidly. The opening of the pulp coincides with the rapid temperature increase. These studies verified the feasibility of the pulsed Erbium:YAG laser use in stomatology.

  8. Selecting Optimal Random Forest Predictive Models: A Case Study on Predicting the Spatial Distribution of Seabed Hardness.

    PubMed

    Li, Jin; Tran, Maggie; Siwabessy, Justy

    2016-01-01

    Spatially continuous predictions of seabed hardness are important baseline environmental information for sustainable management of Australia's marine jurisdiction. Seabed hardness is often inferred from multibeam backscatter data with unknown accuracy and can be inferred from underwater video footage at limited locations. In this study, we classified the seabed into four classes based on two new seabed hardness classification schemes (i.e., hard90 and hard70). We developed optimal predictive models to predict seabed hardness using random forest (RF) based on the point data of hardness classes and spatially continuous multibeam data. Five feature selection (FS) methods that are variable importance (VI), averaged variable importance (AVI), knowledge informed AVI (KIAVI), Boruta and regularized RF (RRF) were tested based on predictive accuracy. Effects of highly correlated, important and unimportant predictors on the accuracy of RF predictive models were examined. Finally, spatial predictions generated using the most accurate models were visually examined and analysed. This study confirmed that: 1) hard90 and hard70 are effective seabed hardness classification schemes; 2) seabed hardness of four classes can be predicted with a high degree of accuracy; 3) the typical approach used to pre-select predictive variables by excluding highly correlated variables needs to be re-examined; 4) the identification of the important and unimportant predictors provides useful guidelines for further improving predictive models; 5) FS methods select the most accurate predictive model(s) instead of the most parsimonious ones, and AVI and Boruta are recommended for future studies; and 6) RF is an effective modelling method with high predictive accuracy for multi-level categorical data and can be applied to 'small p and large n' problems in environmental sciences. Additionally, automated computational programs for AVI need to be developed to increase its computational efficiency and

  9. Selecting Optimal Random Forest Predictive Models: A Case Study on Predicting the Spatial Distribution of Seabed Hardness

    PubMed Central

    Li, Jin; Tran, Maggie; Siwabessy, Justy

    2016-01-01

    Spatially continuous predictions of seabed hardness are important baseline environmental information for sustainable management of Australia’s marine jurisdiction. Seabed hardness is often inferred from multibeam backscatter data with unknown accuracy and can be inferred from underwater video footage at limited locations. In this study, we classified the seabed into four classes based on two new seabed hardness classification schemes (i.e., hard90 and hard70). We developed optimal predictive models to predict seabed hardness using random forest (RF) based on the point data of hardness classes and spatially continuous multibeam data. Five feature selection (FS) methods that are variable importance (VI), averaged variable importance (AVI), knowledge informed AVI (KIAVI), Boruta and regularized RF (RRF) were tested based on predictive accuracy. Effects of highly correlated, important and unimportant predictors on the accuracy of RF predictive models were examined. Finally, spatial predictions generated using the most accurate models were visually examined and analysed. This study confirmed that: 1) hard90 and hard70 are effective seabed hardness classification schemes; 2) seabed hardness of four classes can be predicted with a high degree of accuracy; 3) the typical approach used to pre-select predictive variables by excluding highly correlated variables needs to be re-examined; 4) the identification of the important and unimportant predictors provides useful guidelines for further improving predictive models; 5) FS methods select the most accurate predictive model(s) instead of the most parsimonious ones, and AVI and Boruta are recommended for future studies; and 6) RF is an effective modelling method with high predictive accuracy for multi-level categorical data and can be applied to ‘small p and large n’ problems in environmental sciences. Additionally, automated computational programs for AVI need to be developed to increase its computational efficiency and

  10. Rad-Hard Silicon Detectors

    NASA Astrophysics Data System (ADS)

    Giorgi, Marco

    2005-06-01

    For the next generation of High Energy Physics (HEP) Experiments silicon microstrip detectors working in harsh radiation environments with excellent performances are necessary. The irradiation causes bulk and surface damages that modify the electrical properties of the detector. Solutions like AC coupled strips, overhanging metal contact, <100> crystal lattice orientation, low resistivity n-bulk and Oxygenated substrate are studied for rad-hard detectors. The paper presents an outlook of these technologies.

  11. An Exploratory Study of Psychosocial Risk Behaviors of Adolescents Who Are Deaf or Hard of Hearing: Comparisons and Recommendations

    ERIC Educational Resources Information Center

    Coll, Kenneth M.; Cutler, Martin M.; Thobro, Patti; Haas, Robin; Powell, Stephanie

    2009-01-01

    The study compared psychosocial risk behaviors of adolescents who were deaf or hard of hearing with those of their hearing peers in a residential treatment facility. Statistically significant differences emerged between groups. The adolescents who were deaf or hard of hearing demonstrated clinically higher scores than those of their hearing peers…

  12. The study of ionizing radiation effects on polypropylene and rice husk ash composite

    NASA Astrophysics Data System (ADS)

    Alfaro, E. F.; Dias, D. B.; Silva, L. G. A.

    2013-03-01

    The aim of this work was to study the ionizing radiation effects on polypropylene/20% of rice husk ash composites. The composites were irradiated by electron beam at different doses and the mechanical and thermal properties were evaluated using tensile strength, Izod impact, hardness, softening temperature, differential scanning calorimetry (DSC) and thermogravimetry (TG). The results showed that the properties decreased by increasing irradiation dose due to chain scission.

  13. WIYN Open Cluster Study. XLVIII. The Hard-binary Population of NGC 188

    NASA Astrophysics Data System (ADS)

    Geller, Aaron M.; Mathieu, Robert D.

    2012-08-01

    We present an in-depth study of the hard-binary population of the old (7 Gyr) open cluster NGC 188. Utilizing 85 spectroscopic binary orbits out of a complete sample of 129 detected binary members, we study the cluster binary frequency and the distributions of binary orbital elements among the main-sequence (MS), giant, and blue straggler (BS) populations. The results are derived from our ongoing radial velocity survey of the cluster, which spans in magnitude from the brightest stars in the cluster to V = 16.5 (about 1.1-0.9 M ⊙), and extends to a projected radius of 17 pc (~13 core radii). Our detectable binaries have periods ranging from a few days to of order 104 days, and thus are hard binaries that dynamically power the cluster. The MS solar-type hard binaries in NGC 188 are nearly indistinguishable from similar binaries in the Galactic field. We observe a global solar-type MS hard-binary frequency in NGC 188 of 23% ± 2%, which when corrected for incompleteness results in a frequency of 29% ± 3% for binaries with periods less than 104 days. For MS hard binaries in the cluster, we observe a log-period distribution that rises toward our detection limit, a roughly Gaussian eccentricity distribution centered on e = 0.35 (for binaries with periods longer than the circularization period), and a secondary-mass distribution that rises toward lower-mass companions. Importantly, the NGC 188 BS binaries show significantly different characteristics than the solar-type MS binaries in NGC 188. We observe a BS hard-binary frequency of 76% ± 19%, three times that of the MS. The excess of this binary frequency over the normal MS binary frequency is valid at the >99% confidence level. Furthermore, the BS binary eccentricity-log-period distribution is distinct from that of the MS at the 99% confidence level, with the majority of the BS binaries having periods of order 1000 days and lower eccentricities. The secondary-mass distribution for these long-period BS binaries is

  14. Hard X-ray Spectroscopic, Microwave and H-alpha Linear Polarization Studies with Hard X-Ray Observations from HESSI

    NASA Technical Reports Server (NTRS)

    Kiplinger, Alan L.

    2005-01-01

    The Principal Investigator (P.I.) has been pursuing a three year grant under NASA's Sun-Earth Connection Guest Investigator Program in support of the Ramaty High Energy Solar Spectroscopic Imager (RHESSI). An objective of these efforts is to combine X-ray and other data on solar flares, coronal mass ejections and interplanetary particle events in order to obtain a more comprehensive recognition of signatures, and understanding of interplanetary proton events. Thus, part of these efforts are to investigate if signatures seen in hard X-rays and microwaves can lead to better predictions of interplanetary proton events that can be dangerous to astronauts and spacecraft. The original proposal was written in May, 2000 and it discusses a three-pronged approach for data comparisons with three new types of instrumentation observing at X-ray, microwave and optical wavelengths. The major impetus behind this work and the proposal is that the P.I. discovered a strong correlation between a particular type of hard X-ray signature seen in spectral evolutions and interplanetary proton events (Kiplinger, 1995). The basic signature is that hard X-ray flux peaks either exhibit spectra that soften on their decays (Le. show fewer and fewer high energy X-rays with time) or they harden during decays (i.e. high energy X-rays decay significantly slower that lower energy X-rays). This signature is called progressive hardening. Studies were conducted over an eight-year period of data from the Hard X-Ray Burst Spectrometer (HXRBS) of the Solar maximum mission. Out of the 750 well observed flares studied, 41 flares had major associated proton events. Of these, 29 events were predicted on the basis of progressive hardening for a hit rate of 71%. The 152 largest flares had a hit rate of 82%.

  15. Hard, soft, and sticky spheres for dynamical studies of disordered colloidal packings

    NASA Astrophysics Data System (ADS)

    Gratale, Matthew Daniel

    This thesis describes experiments which explore the role of interparticle interactions as a means to alter, and control, the properties of dense colloidal packings. The first set of experiments studied phonon modes in two-dimensional colloidal crystals composed of soft microgel particles with hard polystyrene particle dopants distributed randomly on the triangular lattice. By mixing hard and soft spheres we obtain close-packed lattices of spheres with random bond strength disorder, textit{i.e.,} the effective springs coupling nearest-neighbors are either very stiff, very soft, or of intermediate stiffness. Video microscopy, particle tracking, and covariance matrix techniques are employed to derive the phonon modes of the corresponding ``shadow'' crystals, thereby enabling us to study how bond strength disorder affects vibrational properties. Hard and soft particles participate equally in low frequency phonon modes, and the samples exhibit Debye-like density of states behavior characteristic of crystals at low frequency. For mid- and high-frequency phonons, the relative participation of hard versus soft particles in each mode is found to vary systematically with dopant concentration. The second set of experiments investigated depletion interaction potentials between micron-size colloidal particles induced by nanometer-scale micelles composed of the surfactant hexaethylene glycol monododecyl ether (C12E6). The strength and range of the depletion interaction is revealed to arise from variations in shape anisotropy of the rod-like surfactant micelles. This shape anisotropy increases with increasing sample temperature. By fitting the colloidal interaction potentials to theoretical models, we extract the rod-like micelle length and shape anisotropy as a function of temperature. This work introduces micelle shape anisotropy as a means to control interparticle interactions in colloidal suspensions, and shows how interparticle depletion potentials of micron-scale objects

  16. A study of the pair and triplet structures of the quantum hard-sphere Yukawa fluid.

    PubMed

    Sesé, Luis M

    2009-02-21

    The pair and triplet structures of the quantum hard-sphere Yukawa fluid, evaluated for equilateral and isosceles correlations in both the r and the k spaces for a range of conditions and with a particular focus on a region where the onset of increasing number fluctuations takes place (for densities 0.4studied. Complementary results report an assessment of the performances of the Kirkwood superposition and the Jackson-Feenberg convolution. Comparisons with results also obtained in this work for the bare quantum and the classical hard-sphere fluids are made, allowing one to draw conclusions on the interplay between the inclusion of Yukawa attractions and the quantum diffraction effects in hard-sphere fluids.

  17. Study of Flux Ratio of C60 to Ar Cluster Ion for Hard DLC Film deposition

    NASA Astrophysics Data System (ADS)

    Miyauchi, K.; Kitagawa, T.; Toyoda, N.; Kanda, K.; Matsui, S.; Yamada, I.

    2003-08-01

    To study the influence of the flux ratio of C60 molecule to Ar cluster ion on DLC film characteristics, DLC films deposited under various flux ratios were characterized with Raman spectrometry and Near Edge X-ray Absorption Fine Structure (NEXAFS). From results of these measurements, hard DLC films were deposited when the flux ratio of C60 to Ar cluster ion was between 0.7 and 4. Furthermore the DLC film with constant sp2 content was obtained in the range of the ratio from 0.7 to 4, which contents are lower values than that of conventional films such as RF plasma. DLC films deposited under the ratio from 1 to 4 had hardness from 40 to 45GPa. It was shown that DLC films with stable properties of low sp2 content and high hardness were formed even when the fluxes were varied from 1 to 4 during deposition. It was indicated that this process was useful in the view of industrial application.

  18. Hard x-ray scanning microscopy with coherent radiation: Beyond the resolution of conventional x-ray microscopes

    SciTech Connect

    Schropp, A.; Hoppe, R.; Patommel, J.; Samberg, D.; Seiboth, F.; Stephan, S.; Schroer, C. G.; Wellenreuther, G.; Falkenberg, G.

    2012-06-18

    We demonstrate x-ray scanning coherent diffraction microscopy (ptychography) with 10 nm spatial resolution, clearly exceeding the resolution limits of conventional hard x-ray microscopy. The spatial resolution in a ptychogram is shown to depend on the shape (structure factor) of a feature and can vary for different features in the object. In addition, the resolution and contrast are shown to increase with increasing coherent fluence. For an optimal ptychographic x-ray microscope, this implies a source with highest possible brilliance and an x-ray optic with a large numerical aperture to generate the optimal probe beam.

  19. PROSPECT OF STUDYING HARD X- AND GAMMA-RAYS FROM TYPE Ia SUPERNOVAE

    SciTech Connect

    Maeda, K.; Nomoto, K.; Terada, Y.; Kasen, D.; Roepke, F. K.; Seitenzahl, I. R.; Bamba, A.; Diehl, R.; Kromer, M.; Hillebrandt, W.; Yamaguchi, H.; Tamagawa, T.

    2012-11-20

    We perform multi-dimensional, time-dependent radiation transfer simulations for hard X-ray and {gamma}-ray emissions, following radioactive decays of {sup 56}Ni and {sup 56}Co, for two-dimensional delayed-detonation models of Type Ia supernovae (SNe Ia). The synthetic spectra and light curves are compared with the sensitivities of current and future observatories for an exposure time of 10{sup 6} s. The non-detection of the {gamma}-ray signal from SN 2011fe at 6.4 Mpc by SPI on board INTEGRAL places an upper limit on the mass of {sup 56}Ni of {approx}< 1.0 M {sub Sun }, independently from observations in any other wavelengths. Signals from the newly formed radioactive species have not yet been convincingly measured from any SN Ia, but future X-ray and {gamma}-ray missions are expected to deepen the observable horizon to provide high energy emission data for a significant SN Ia sample. We predict that the hard X-ray detectors on board NuStar (launched in 2012) or ASTRO-H (scheduled for launch in 2014) will reach to SNe Ia at {approx}15 Mpc, i.e., one SN every few years. Furthermore, according to the present results, the soft {gamma}-ray detector on board ASTRO-H will be able to detect the 158 keV line emission up to {approx}25 Mpc, i.e., a few SNe Ia per year. Proposed next-generation {gamma}-ray missions, e.g., GRIPS, could reach to SNe Ia at {approx}20-35 Mpc by MeV observations. Those would provide new diagnostics and strong constraints on explosion models, detecting rather directly the main energy source of supernova light.

  20. Study of factors determining the radiation sensitivity of quartz crystal oscillators (A0189)

    NASA Technical Reports Server (NTRS)

    Venables, J. D.; Ahearn, J. S.

    1984-01-01

    The correlation between defect cluster concentrations observed for different grades of quartz examined by transmission electron microscopy (TEM) and the electrical stability of quartz resonators exposed to complex radiation in an orbital LDEF was determined. It is demonstrated that the technique TEM provides a powerful method for studying the effect of radiation on crystalline quartz. Two factors suggest that the observed clusters may be responsible for the radiation-induced frequency drift and acoustic absorption effects associated with irradiated quartz resonators: (1) the clusters are expected to be very effective in modifying the piezoelectric properties of quartz because of the large strain fields associated with them; (2) both phenomena appear to be sensitive to the impurity concentration. It is suggested that TEM can be used to classify grades of quartz according to their suitability for use in radiation-hard resonators. This technique may identify the impurities that are responsible and thereby effect an improvement in the stability of quartz oscillators.

  1. Study of chemical and radiation induced carcinogenesis

    SciTech Connect

    Chmura, A.

    1995-11-01

    The study of chemical and radiation induced carcinogenesis has up to now based many of its results on the detection of genetic aberrations using the fluorescent in situ hybridization (FISH) technique. FISH is time consuming and this tends to hinder its use for looking at large numbers of samples. We are currently developing new technological advances which will increase the speed, clarity and functionality of the FISH technique. These advances include multi-labeled probes, amplification techniques, and separation techniques.

  2. Studies of semi-inclusive and hard exclusive processes at Jlab

    SciTech Connect

    Harutyun Avagyan

    2008-06-19

    The main goal of experiments proposed for the {\\tt CLAS12} detector in conjunction with the 12-GeV CEBAF accelerator is the study of the nucleon through hard exclusive, semi-inclusive, and inclusive processes. This will provide new insights into nucleon dynamics at the elementary quark and gluon level. In this contribution we provide an overview of ongoing studies of the structure of nucleon in terms of quark and gluon degrees of freedom and future physics program planned with CLAS and {\\tt CLAS12}.

  3. Radiation studies for the MOMENT target station

    NASA Astrophysics Data System (ADS)

    Xu, Qing-Nian; Tong, Jian-Fei; Vassilopoulos, Nikolaos; Cao, Jun; He, Miao; Hou, Zhi-Long; Jing, Han-Tao; Liu, Huai-Min; Lü, Xiao-Rui; Tang, Jing-Yu; Yuan, Ye; Zhao, Guang; Zheng, Yang-Heng

    2016-12-01

    The discovery of the neutrino mixing angle θ13 opens new opportunities for the discovery of leptonic CP violation at high intensity neutrino beams. MOMENT, a future neutrino facility with a high-power proton beam of 15 MW from a continuous-wave linac, is focused on that discovery. The high power of the proton beam causes extreme radiation conditions for the facility and especially for the target station, where the pion capture system of five superconducting solenoids is located. In this paper initial studies are performed for the effects of the radiation on the solenoid structure and the area surrounding it. A concept cooling system is also proposed. Supported by National Natural Science Foundation of China (11425524, 11527811, 11575226) and Strategic Priority Research Program of the Chinese Academy of Sciences (XDA10010100)

  4. The study of laser induced fluorescence of tooth hard tissues with aluminum phthalocyanine nanoparticles

    NASA Astrophysics Data System (ADS)

    Farrakhova, D. S.; Kuznetsova, J. O.; Loschenov, V. B.

    2016-08-01

    This work is about the possibility of fluorescence diagnosis application with the use of aluminum phthalocyanine nanoparticles (nAlPc) in order to detect enamel microdamage. For the investigation, five human teeth samples of various age groups were removed for various reasons. The autofluorescence spectrums of these samples hard tissues and fluorescence spectrums of nAlPc mixed with enamel powder were obtained during the experiment. The research shows that sample pathogenic microflora causes nAlPc fluorescence. This fact will allow detecting enamel microdamage in future studies.

  5. Analysis of dental hard tissues exposed to high temperatures for forensic applications: An in vitro study

    PubMed Central

    Shekhawat, Kuldeep Singh; Chauhan, Arunima

    2016-01-01

    Aim: The aim of this study was to observe and record the macroscopic, radiographic, and microscopic findings obtained after subjecting the teeth to high temperatures. Materials and Methods: An in vitro study was conducted to observe macroscopic, radiographic, and microscopic changes in dental hard tissues in 60 unrestored non carious extracted human teeth. The teeth were grouped based on age: Below 30 years, 30–40 years, and above 40 years The teeth from each age group were further divided into five subgroups, and each subgroup was subjected to a particular temperature: 200°C, 400°C, 600°C, 800°C, and 1000°C. [C = Celsius]. Results: Various degrees of changes in relation to temperature were observed macroscopically, radiographically, and microscopically. The histological examination was limited for teeth exposed to 200°C. Conclusion: This investigation was carried out to study the gross changes, radiographic changes and histological changes in dental hard tissues exposed to high temperatures, which is an important part of forensic science. The aforementioned alterations caused by heat may provide useful information about temperature ranges and duration of exposure to high temperatures. PMID:27555725

  6. Thermal Radiometer Signal Processing Using Radiation Hard CMOS Application Specific Integrated Circuits for Use in Harsh Planetary Environments

    NASA Technical Reports Server (NTRS)

    Quilligan, G.; DuMonthier, J.; Aslam, S.; Lakew, B.; Kleyner, I.; Katz, R.

    2015-01-01

    Thermal radiometers such as proposed for the Europa Clipper flyby mission require low noise signal processing for thermal imaging with immunity to Total Ionizing Dose (TID) and Single Event Latchup (SEL). Described is a second generation Multi- Channel Digitizer (MCD2G) Application Specific Integrated Circuit (ASIC) that accurately digitizes up to 40 thermopile pixels with greater than 50 Mrad (Si) immunity TID and 174 MeV-sq cm/mg SEL. The MCD2G ASIC uses Radiation Hardened By Design (RHBD) techniques with a 180 nm CMOS process node.

  7. Bread-Board Testing of the Radiation Hard Electron Monitor (RADEM) being developed for the ESA JUICE Mission

    NASA Astrophysics Data System (ADS)

    Mrigakshi, Alankrita; Hajdas, Wojtek; Marcinkowski, Radoslaw; Xiao, Hualin; Goncalves, Patricia; Pinto, Marco; Pinto, Costa; Marques, Arlindo; Meier, Dirk

    2016-04-01

    The RADEM instrument will serve as the radiation monitor for the JUICE spacecraft. It will characterize the highly dynamic radiation environment of the Jovian system by measuring the energy spectra of energetic electrons and protons up to 40 MeV and 250 MeV, respectively. It will also determine the directionality of 0.3-10 MeV electrons. Further goals include the detection of heavy ions, and the determination of the corresponding LET spectra and dose rates. Here, the tests of the Electron and Proton Telescopes, and the Directionality Detector of the RADEM Bread-Board model are described. The objective of these tests is to validate RADEM design and physical concept applied therein. The tests were performed at various irradiation facilities at the Paul Scherrer Institute (PSI) where energy ranges relevant for space applications can be covered (electrons: ≤100 MeV and protons: ≤230 MeV). The measured values are also compared with GEANT4 Monte-Carlo Simulation results.

  8. METEOSAT studies of clouds and radiation budget

    NASA Technical Reports Server (NTRS)

    Saunders, R. W.

    1982-01-01

    Radiation budget studies of the atmosphere/surface system from Meteosat, cloud parameter determination from space, and sea surface temperature measurements from TIROS N data are all described. This work was carried out on the interactive planetary image processing system (IPIPS), which allows interactive manipulationion of the image data in addition to the conventional computational tasks. The current hardware configuration of IPIPS is shown. The I(2)S is the principal interactive display allowing interaction via a trackball, four buttons under program control, or a touch tablet. Simple image processing operations such as contrast enhancing, pseudocoloring, histogram equalization, and multispectral combinations, can all be executed at the push of a button.

  9. Study of the radiative pion decay

    SciTech Connect

    Chen, Chuan-Hung; Geng, Chao-Qiang; Lih, Chong-Chung

    2011-04-01

    We study the radiative pion decay of {pi}{sup +}{yields}e{sup +}{nu}{sub e}{gamma} in the light-front quark model. We also summarize the result in the chiral perturbation theory. The vector and axial-vector hadronic form factors (F{sub V,A}) for the {pi}{yields}{gamma} transition are evaluated in the whole allowed momentum transfer. In terms of these momentum dependent form factors, we calculate the decay branching ratio and compare our results with the experimental data and other theoretical predictions in the literature. We also constrain the possible size of the tensor interaction in the light-front quark model.

  10. Development of a compact radiation-hardened low-noise front-end readout ASIC for CZT-based hard X-ray imager

    NASA Astrophysics Data System (ADS)

    Gao, W.; Gan, B.; Li, X.; Wei, T.; Gao, D.; Hu, Y.

    2015-04-01

    In this paper, we present the development and performances of a radiation-hardened front-end readout application-specific integrated circuit (ASIC) dedicated to CZT detectors for a hard X-ray imager in space applications. The readout channel consists of a charge sensitive amplifier (CSA), a CR-RC shaper, a fast shaper, a discriminator and a driving buffer. With the additional digital filtering, the readout channel can achieve very low noise performances and low power dissipation. An eight-channel prototype ASIC is designed and fabricated in 0.35 μm CMOS process. The energy range of the detected X-rays is evaluated as 1.45 keV to 281 keV. The gain is larger than 100 mV/fC. The equivalent noise charge (ENC) of the ASIC is 53 e- at zero farad plus 10 e- per picofarad. The power dissipation is less than 4.4 mW/channel. Through the measurement with a CZT detector, the energy resolution is less than 3.45 keV (FWHM) under the irradiation of the radioactive source 241Am. The radiation effect experiments indicate that the proposed ASIC can resist the total ionization dose (TID) irradiation of higher than 200 krad (Si).

  11. A system-level model for high-speed, radiation-hard optical links in HEP experiments based on silicon Mach-Zehnder modulators

    NASA Astrophysics Data System (ADS)

    Zeiler, M.; Detraz, S.; Olantera, L.; Sigaud, C.; Soos, C.; Troska, J.; Vasey, F.

    2016-12-01

    Silicon Mach-Zehnder modulators have been shown to be relatively insensitive to displacement damage beyond a 1-MeV-equivalent neutron fluence of 3ṡ1016n/cm2. Recent investigations on optimized device designs have also led to a high resistance against total ionizing dose levels of above 1 MGy. Such devices could potentially replace electrical and/or optical links close to the particle interaction points in future high energy physics experiments. Since they require an external continuous-wave light source, radiation-hard optical links based on silicon Mach-Zehnder modulators need to have a different system design when compared to existing directly modulated laser-based optical links. 10 Gb/s eye diagrams of irradiated Mach-Zehnder modulators were measured. The outcomes demonstrate the suitability for using these components in harsh radiation environments. A proposal for the implementation of silicon Mach-Zehnder modulators in CERN's particle detectors was developed and a model to calculate the system performance is presented. The optical power budget and the electrical power dissipation of the proposed link is compared to that of the upcoming Versatile Link system that will be installed in 2018.

  12. Adaptive radiations: From field to genomic studies

    PubMed Central

    Hodges, Scott A.; Derieg, Nathan J.

    2009-01-01

    Adaptive radiations were central to Darwin's formation of his theory of natural selection, and today they are still the centerpiece for many studies of adaptation and speciation. Here, we review the advantages of adaptive radiations, especially recent ones, for detecting evolutionary trends and the genetic dissection of adaptive traits. We focus on Aquilegia as a primary example of these advantages and highlight progress in understanding the genetic basis of flower color. Phylogenetic analysis of Aquilegia indicates that flower color transitions proceed by changes in the types of anthocyanin pigments produced or their complete loss. Biochemical, crossing, and gene expression studies have provided a wealth of information about the genetic basis of these transitions in Aquilegia. To obtain both enzymatic and regulatory candidate genes for the entire flavonoid pathway, which produces anthocyanins, we used a combination of sequence searches of the Aquilegia Gene Index, phylogenetic analyses, and the isolation of novel sequences by using degenerate PCR and RACE. In total we identified 34 genes that are likely involved in the flavonoid pathway. A number of these genes appear to be single copy in Aquilegia and thus variation in their expression may have been key for floral color evolution. Future studies will be able to use these sequences along with next-generation sequencing technologies to follow expression and sequence variation at the population level. The genetic dissection of other adaptive traits in Aquilegia should also be possible soon as genomic resources such as whole-genome sequencing become available. PMID:19528644

  13. Physics of Hard Sphere Experiment: Scattering, Rheology and Microscopy Study of Colloidal Particles

    NASA Technical Reports Server (NTRS)

    Cheng, Z.-D.; Zhu, J.; Phan, S.-E.; Russel, W. B.; Chaikin, P. M.; Meyer, W. V.

    2002-01-01

    The Physics of Hard Sphere Experiment has two incarnations: the first as a scattering and rheology experiment on STS-83 and STS-94 and the second as a microscopy experiment to be performed in the future on LMM on the space station. Here we describe some of the quantitative and qualitative results from previous flights on the dynamics of crystallization in microgravity and especially the observed interaction of growing crystallites in the coexistance regime. To clarify rheological measurements we also present ground based experiments on the low shear rate viscosity and diffusion coefficient of several hard sphere experiments at high volume fraction. We also show how these experiments will be performed with confocal microscopy and laser tweezers in our lab and as preparation for the phAse II experiments on LMM. One of the main aims of the microscopy study will be the control of colloidal samples using an array of applied fields with an eye toward colloidal architectures. Temperature gradients, electric field gradients, laser tweezers and a variety of switchable imposed surface patterns are used toward this control.

  14. Multiperiodicity in quasi-periodic pulsations of flare hard X-rays: a case study

    NASA Astrophysics Data System (ADS)

    Tomczak, M.; Szaforz, Ż.

    We present a case study of the solar flare (SOL2001-10-02T17:31) that showed quasi-periodic pulsations (QPPs) in hard X-rays with two simultaneously excited periods, P_1 = 26-31 s and P_2 = 110 s. Complete evolution of the flare recorded by the Yohkoh telescopes, together with the patrol SOHO/EIT images, allowed us to identify magnetic structures responsible for particular periods and to propose an overall scenario which is consistent with the available observations. Namely, we suggest that emerging magnetic flux initiated the reconnection with legs of a large arcade of coronal loops that had been present in an active region for several days. The reconnection excited MHD oscillations in both magnetic structures simultaneously: period P_1 was generated in the emerging loop and in a loop being a result of the reconnection; period P_2 occurred in the arcade. Both resonators produced photons of different spectra. We anticipate that multiperiodicity in hard X-rays can be a common feature of flare hybrids, i.e. the events, in which magnetic structures of different sizes interact.

  15. Can joint sound assess soft and hard endpoints of the Lachman test?: A preliminary study.

    PubMed

    Hattori, Koji; Ogawa, Munehiro; Tanaka, Kazunori; Matsuya, Ayako; Uematsu, Kota; Tanaka, Yasuhito

    2016-05-12

    The Lachman test is considered to be a reliable physical examination for anterior cruciate ligament (ACL) injury. Patients with a damaged ACL demonstrate a soft endpoint feeling. However, examiners judge the soft and hard endpoints subjectively. The purpose of our study was to confirm objective performance of the Lachman test using joint auscultation. Human and porcine knee joints were examined. Knee joint sound during the Lachman test (Lachman sound) was analyzed by fast Fourier transformation. As quantitative indices of Lachman sound, the peak sound as the maximum relative amplitude (acoustic pressure) and its frequency were used. The mean Lachman peak sound for healthy volunteer knees was 86.9 ± 12.9 Hz in frequency and -40 ± 2.5 dB in acoustic pressure. The mean Lachman peak sound for intact porcine knees was 84.1 ± 9.4 Hz and -40.5 ± 1.7 dB. Porcine knees with ACL deficiency had a soft endpoint feeling during the Lachman test. The Lachman peak sounds of porcine knees with ACL deficiency were dispersed into four distinct groups, with center frequencies of around 40, 160, 450, and 1600. The Lachman peak sound was capable of assessing soft and hard endpoints of the Lachman test objectively.

  16. Submicrometre beams from a hard X-ray waveguide at a third-generation synchrotron radiation source.

    PubMed

    Cedola, A; Lagomarsino, S; Di Fonzo, S; Jark, W; Riekel, C; Deschamps, P

    1998-01-01

    The use of an X-ray waveguide for scattering experiments at an undulator of a third-generation synchrotron radiation source is discussed. The performance with a perfect crystal monochromator, multilayer monochromator and focusing mirror is explored. A maximum flux of 8 x 109 photons s(-1) at lambda = 0.083 nm was obtained for a 0.15 (V) x 600 (H) micron(2) beam at the exit of the waveguide with a multilayer monochromator. The combination of an Si (111) monochromator and ellipsoidal mirror resulted in a flux of approximately 10(9) photons s(-1) but with a horizontal compression of the beam to approximately 30 micron. The use of the waveguide in diffraction experiments is addressed.

  17. Radiation Resistance Study of Semi-Insulating GaAs-Based Radiation Detectors to Extremely High Gamma Doses

    NASA Astrophysics Data System (ADS)

    Ly Anh, T.; Perd'ochová, A.; Nečas, V.; Pavlicová, V.

    2006-01-01

    In our previous paper [V. Nečas et al.: Nucl. Inst. and Meth. A 458 (2001) 348-351] we reported on the study on radiation stability of semi-insulating (SI) LEG GaAs detectors to doses of photons from 60Co up to 19.2 kGy. Later we presented a study, which covered radiation hardness to the same doses on the base of detector material itself, where strong dependence has been proved [T. Ly Anh et al., Proceedings of the XII th International Conference on Semiconducting and Insulating Materials (SIMC-XII-2002). Smolenice Castle, Slovakia (2002) 292-295 (0-7803-7418-5)]. In this paper we present both the key electrical and detection characteristics of SI GaAs radiation detectors prepared using substrates from four various supplies and two different types of contacts, which were exposed to several gamma doses from 60Co up to the integral dose of about 1 MGy. The obtained results show that SI LEG GaAs detectors provide good spectroscopic performances and even their slight improvement after low to middle gamma irradiation doses (3 -10 kGy) was observed. Further dose exposure caused the degradation of detection properties with an extreme and following improvement depending on detector material properties. SI GaAs detector still retains its working capabilities even after very high doses applied, up to 1 MGy.

  18. Experimental Study on the Relationship between Hardness and Principal Strain in Tube Hydroforming Process

    NASA Astrophysics Data System (ADS)

    Wang, G. D.; Chan, L. C.

    2009-11-01

    In order to find a feasible method to evaluate the deformation of tubes during the Tube Hydroforming (THF) process, the hardness and the strain in two selected deformation areas of hydro formed copper tubes (C11000) were measured and tested, and an instinct relationship was found between the hardness and the principal strains of the tubes. The major strain of the surface of tubes had the strongest linear relationship with hardness. A regression formula was used to describe the relationship between hardness and the sensitive strain which is defined in the present work as a dependent variable of major strain and thickness strain.

  19. Developments for radiation hard silicon detectors by defect engineering—results by the CERN RD48 (ROSE) Collaboration

    NASA Astrophysics Data System (ADS)

    Lindström, G.; Ahmed, M.; Albergo, S.; Allport, P.; Anderson, D.; Andricek, L.; Angarano, M. M.; Augelli, V.; Bacchetta, N.; Bartalini, P.; Bates, R.; Biggeri, U.; Bilei, G. M.; Bisello, D.; Boemi, D.; Borchi, E.; Botila, T.; Brodbeck, T. J.; Bruzzi, M.; Budzynski, T.; Burger, P.; Campabadal, F.; Casse, G.; Catacchini, E.; Chilingarov, A.; Ciampolini, P.; Cindro, V.; Costa, M. J.; Creanza, D.; Clauws, P.; Da Via, C.; Davies, G.; De Boer, W.; Dell'Orso, R.; De Palma, M.; Dezillie, B.; Eremin, V.; Evrard, O.; Fallica, G.; Fanourakis, G.; Feick, H.; Focardi, E.; Fonseca, L.; Fretwurst, E.; Fuster, J.; Gabathuler, K.; Glaser, M.; Grabiec, P.; Grigoriev, E.; Hall, G.; Hanlon, M.; Hauler, F.; Heising, S.; Holmes-Siedle, A.; Horisberger, R.; Hughes, G.; Huhtinen, M.; Ilyashenko, I.; Ivanov, A.; Jones, B. K.; Jungermann, L.; Kaminsky, A.; Kohout, Z.; Kramberger, G.; Kuhnke, M.; Kwan, S.; Lemeilleur, F.; Leroy, C.; Letheren, M.; Li, Z.; Ligonzo, T.; Linhart, V.; Litovchenko, P.; Loukas, D.; Lozano, M.; Luczynski, Z.; Lutz, G.; MacEvoy, B.; Manolopoulos, S.; Markou, A.; Martinez, C.; Messineo, A.; Miku, M.; Moll, M.; Nossarzewska, E.; Ottaviani, G.; Oshea, V.; Parrini, G.; Passeri, D.; Petre, D.; Pickford, A.; Pintilie, I.; Pintilie, L.; Pospisil, S.; Potenza, R.; Radicci, V.; Raine, C.; Rafi, J. M.; Ratoff, P. N.; Richter, R. H.; Riedler, P.; Roe, S.; Roy, P.; Ruzin, A.; Ryazanov, A. I.; Santocchia, A.; Schiavulli, L.; Sicho, P.; Siotis, I.; Sloan, T.; Slysz, W.; Smith, K.; Solanky, M.; Sopko, B.; Stolze, K.; Sundby Avset, B.; Svensson, B.; Tivarus, C.; Tonelli, G.; Tricomi, A.; Tzamarias, S.; Valvo, G.; Vasilescu, A.; Vayaki, A.; Verbitskaya, E.; Verdini, P.; Vrba, V.; Watts, S.; Weber, E. R.; Wegrzecki, M.; Wegrzecka, I.; Weilhammer, P.; Wheadon, R.; Wilburn, C.; Wilhelm, I.; Wunstorf, R.; Wüstenfeld, J.; Wyss, J.; Zankel, K.; Zabierowski, P.; Zontar, D.

    2001-06-01

    This report summarises the final results obtained by the RD48 collaboration. The emphasis is on the more practical aspects directly relevant for LHC applications. The report is based on the comprehensive survey given in the 1999 status report (RD48 3rd Status Report, CERN/LHCC 2000-009, December 1999), a recent conference report (Lindström et al. (RD48), and some latest experimental results. Additional data have been reported in the last ROSE workshop (5th ROSE workshop, CERN, CERN/LEB 2000-005). A compilation of all RD48 internal reports and a full publication list can be found on the RD48 homepage (http://cern.ch/RD48/). The success of the oxygen enrichment of FZ-silicon as a highly powerful defect engineering technique and its optimisation with various commercial manufacturers are reported. The focus is on the changes of the effective doping concentration (depletion voltage). The RD48 model for the dependence of radiation effects on fluence, temperature and operational time is verified; projections to operational scenarios for main LHC experiments demonstrate vital benefits. Progress in the microscopic understanding of damage effects as well as the application of defect kinetics models and device modelling for the prediction of the macroscopic behaviour has also been achieved but will not be covered in detail.

  20. Constant-pitch microprism-array optical device for beam condensers in hard x-ray synchrotron radiation beamlines

    NASA Astrophysics Data System (ADS)

    Kagoshima, Y.; Takano, H.; Takeda, S.

    2013-06-01

    A constant-pitch microprism-array optical device has been developed. It is a modified version of the previously reported quasi-Fresnel lens [Kagoshima et al., Appl. Phys. Lett. 101, 163102 (2012)]. The modification eases the fabrication of the lens, although it degrades some of the focusing performance. It consists of twenty 50-μm-wide right-angle microprisms, whose slope angles gradually increase to 67.8° at the outer side. By inclining the array, the aspect ratio of the microprisms becomes large enough for X-ray use. The effective slope angle can be enlarged to 86.4° at an inclination angle of 80.5°. A 10-keV synchrotron beam with a size of 680 μm (V) × 660 μm (H) was two-dimensionally condensed to 130 μm (V) × 380 μm (H) with a photon flux density gain of ˜3. We also show that the microprism array is suitable for practical use below the critical radiation dose rate.

  1. Theoretical and computer simulation study of phase coexistence of nonadditive hard-disk mixtures.

    PubMed

    Fiumara, Giacomo; Pandaram, Owen D; Pellicane, Giuseppe; Saija, Franz

    2014-12-07

    We have studied the equation of state (EOS) and the equilibrium behavior of a two-component mixture of equal-sized, nonadditive hard disks with an interspecies collision diameter that is larger than that of each component. For this purpose, we have calculated the fifth virial coefficient by evaluating numerically the irreducible cluster integrals by a Monte Carlo method. This information is used to calculate both the virial equation of state and an equation of state based on a resummation of the virial expansion. Then, the fluid-fluid phase coexistence boundaries are determined by integrating the EOS so as to obtain the free energy of the system. Canonical and Gibbs ensemble Monte Carlo simulations over a wide range of nonadditivity are also performed in order to provide a benchmark to the theoretical predictions.

  2. Radiation in the workplace-a review of studies of the risks of occupational exposure to ionising radiation.

    PubMed

    Wakeford, Richard

    2009-06-01

    Many individuals are, or have been, exposed to ionising radiation in the course of their work and the epidemiological study of occupationally irradiated groups offers an important opportunity to complement the estimates of risks to health resulting from exposure to radiation that are obtained from other populations, such as the Japanese survivors of the atomic bombings of Hiroshima and Nagasaki in 1945. Moreover, workplace exposure to radiation usually involves irradiation conditions that are of direct relevance to the principal concern of radiological protection: protracted exposure to low level radiation. Further, some workers have been exposed to radioactive material that has been inadvertently taken into the body, and the study of these groups leads to risk estimates derived directly from the experience of those irradiated by these 'internal emitters', intakes of alpha-particle-emitters being of particular interest. Workforces that have been the subject of epidemiological study include medical staff, aircrews, radium dial luminisers, underground hard-rock miners, Chernobyl clean-up workers, nuclear weapons test participants and nuclear industry workers. The first solid epidemiological evidence of the stochastic effects of irradiation came from a study of occupational exposure to medical x-rays that was reported in 1944, which demonstrated a large excess risk of leukaemia among US radiologists; but the general lack of dose records for early medical staff who tended to experience the highest exposures hampers the derivation of risks per unit dose received by medical workers. The instrument dial luminisers who inadvertently ingested large amounts of radium-based paint and underground hard-rock miners who inhaled large quantities of radon and its decay products suffered markedly raised excess risks of, respectively, bone and lung cancers; the miner studies have provided standard risk estimates for radon-induced lung cancer. The large numbers of nuclear industry

  3. Parametric Study of Variable Emissivity Radiator Surfaces

    NASA Technical Reports Server (NTRS)

    Grob, Lisa M.; Swanson, Theodore D.

    2000-01-01

    The goal of spacecraft thermal design is to accommodate a high function satellite in a low weight and real estate package. The extreme environments that the satellite is exposed during its orbit are handled using passive and active control techniques. Heritage passive heat rejection designs are sized for the hot conditions and augmented for the cold end with heaters. The active heat rejection designs to date are heavy, expensive and/or complex. Incorporating an active radiator into the design that is lighter, cheaper and more simplistic will allow designers to meet the previously stated goal of thermal spacecraft design Varying the radiator's surface properties without changing the radiating area (as with VCHP), or changing the radiators' views (traditional louvers) is the objective of the variable emissivity (vary-e) radiator technologies. A parametric evaluation of the thermal performance of three such technologies is documented in this paper. Comparisons of the Micro-Electromechanical Systems (MEMS), Electrochromics, and Electrophoretics radiators to conventional radiators, both passive and active are quantified herein. With some noted limitations, the vary-e radiator surfaces provide significant advantages over traditional radiators and a promising alternative design technique for future spacecraft thermal systems.

  4. Comparative study of microwave radiation-induced magnetoresistive oscillations induced by circularly- and linearly- polarized photo-excitation

    DOE PAGES

    Ye, Tianyu; Liu, Han -Chun; Wang, Zhuo; ...

    2015-10-09

    A comparative study of the radiation-induced magnetoresistance oscillations in the high mobility GaAs/AlGaAs heterostructure two dimensional electron system (2DES) under linearly- and circularly- polarized microwave excitation indicates a profound difference in the response observed upon rotating the microwave launcher for the two cases, although circularly polarized microwave radiation induced magnetoresistance oscillations observed at low magnetic fields are similar to the oscillations observed with linearly polarized radiation. For the linearly polarized radiation, the magnetoresistive response is a strong sinusoidal function of the launcher rotation (or linear polarization) angle, θ. As a result, for circularly polarized radiation, the oscillatory magnetoresistive response ismore » hardly sensitive to θ.« less

  5. Low-dose radiation epidemiology studies: status and issues.

    PubMed

    Shore, Roy E

    2009-11-01

    Although the Japanese atomic bomb study and radiotherapy studies have clearly documented cancer risks from high-dose radiation exposures, radiation risk assessment groups have long recognized that protracted or low exposures to low-linear energy transfer radiations are key radiation protection concerns because these are far more common than high-exposure scenarios. Epidemiologic studies of human populations with low-dose or low dose-rate exposures are one approach to addressing those concerns. A number of large studies of radiation workers (Chernobyl clean-up workers, U.S. and Chinese radiological technologists, and the 15-country worker study) or of persons exposed to environmental radiation at moderate to low levels (residents near Techa River, Semipalatinsk, Chernobyl, or nuclear facilities) have been conducted. A variety of studies of medical radiation exposures (multiple-fluoroscopy, diagnostic (131)I, scatter radiation doses from radiotherapy, etc.) also are of interest. Key results from these studies are summarized and compared with risk estimates from the Japanese atomic bomb study. Ideally, one would like the low-dose and low dose-rate studies to guide radiation risk estimation regarding the shape of the dose-response curve, DDREF (dose and dose-rate effectiveness factor), and risk at low doses. However, the degree to which low-dose studies can do so is subject to various limitations, especially those pertaining to dosimetric uncertainties and limited statistical power. The identification of individuals who are particularly susceptible to radiation cancer induction also is of high interest in terms of occupational and medical radiation protection. Several examples of studies of radiation-related cancer susceptibility are discussed, but none thus far have clearly identified radiation-susceptible genotypes.

  6. Deep Space Test Bed for Radiation Studies

    NASA Technical Reports Server (NTRS)

    Adams, James H.; Adcock, Leonard; Apple, Jeffery; Christl, Mark; Cleveand, William; Cox, Mark; Dietz, Kurt; Ferguson, Cynthia; Fountain, Walt; Ghita, Bogdan

    2006-01-01

    The Deep Space Test-Bed (DSTB) Facility is designed to investigate the effects of galactic cosmic rays on crews and systems during missions to the Moon or Mars. To gain access to the interplanetary ionizing radiation environment the DSTB uses high-altitude polar balloon flights. The DSTB provides a platform for measurements to validate the radiation transport codes that are used by NASA to calculate the radiation environment within crewed space systems. It is also designed to support other Exploration related investigations such as measuring the shielding effectiveness of candidate spacecraft and habitat materials, testing new radiation monitoring instrumentation and flight avionics and investigating the biological effects of deep space radiation. We describe the work completed thus far in the development of the DSTB and its current status.

  7. Development and Study of Hard-Facing Materials on the Base of Heat-Resisting High-Hardness Steels for Plasma-Jet Hard- Facing in Shielding-Doping Nitrogen Atmosphere

    NASA Astrophysics Data System (ADS)

    Malushin, N. N.; Kovalev, A. P.; Valuev, D. V.; Shats, E. A.; Borovikov, I. F.

    2016-08-01

    The authors develop hard-facing materials on the base of heat-resisting highhardness steels for plasma-jet hard-facing in nitrogen atmosphere for manufacturing parts of mining and metallurgic equipment which significantly simplify the production process and effect a saving when producing bimetallic parts and tools.

  8. Uranium hohlraum with an ultrathin uranium-nitride coating layer for low hard x-ray emission and high radiation temperature

    NASA Astrophysics Data System (ADS)

    Guo, Liang; Ding, Yongkun; Xing, Pifeng; Li, Sanwei; Kuang, Longyu; Li, Zhichao; Yi, Taimin; Ren, Guoli; Wu, Zeqing; Jing, Longfei; Zhang, Wenhai; Zhan, Xiayu; Yang, Dong; Jiang, Baibin; Yang, Jiamin; Liu, Shenye; Jiang, Shaoen; Li, Yongsheng; Liu, Jie; Huo, Wenyi; Lan, Ke

    2015-11-01

    An ultrathin layer of uranium nitrides (UN) has been coated on the inner surface of depleted uranium hohlraum (DUH), which has been proven by our experiment to prevent the oxidization of uranium (U) effectively. Comparative experiments between the novel depleted uranium hohlraum and pure golden (Au) hohlraum are implemented on an SGIII-prototype laser facility. Under a laser intensity of 6 × 1014 W cm-2, we observe that the hard x-ray (hν \\gt 1.8 keV) fraction of the uranium hohlraum decreases by 61% and the peak intensity of the total x-ray flux (0.1 keV˜5.0 keV) increases by 5%. Radiation hydrodynamic code LARED is used to interpret the above observations. Our result for the first time indicates the advantages of the UN-coated DUH in generating a uniform x-ray source with a quasi-Planckian spectrum, which should have important applications in high energy density physics.

  9. Strategy on removing oxygen impurity for crystal growth of one candidate Tl6SeI4 for room-temperature hard radiation detector(Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Lin, Wenwen; Liu, Zhifu; Churilov, Alexei V.; He, Yihui; Kim, Hadong; Cirignano, Leonard J.; Malliakas, Christos D.; Li, Hao; Stoumpos, Constantinos C.; Chung, Duck Young; Wessels, Bruce W.; Kanatzidis, Mercouri G.

    2016-09-01

    Thallium based chalcogenide and halide semiconductors such as Tl4HgI6, TlGaSe2, Tl6SeI4 and Tl6SI4 are promising materials for room-temperature hard radiation detection. They feature appropriate band gaps, high mass densities and facile growth technology. However, these materials are being plagued by the Tl oxides impurity from Tl precursor or Tl containing binary precursors, which leads to problems including tube breakage, parasitic nucleation and detector performance deterioration. In this work, we present a facile way to chemically reduce Tl oxidations, and then eliminate oxygen impurity by adding high-purity graphite powder during synthesis and crystal growth. We also further investigated the reactivity between Tl oxides and graphite. The detector performance of Tl6SeI4 crystal was dramatically improved after lowering/removing the oxygen impurities. This result not only indicates the significance of removing oxygen impurity for improving detector performance. Our results suggest that the chemical reduction method we developed by adding carbon powder during synthesis is highly effective in substantially reducing oxygen impurities from Tl containing materials.

  10. LDQ10: a compact ultra low-power radiation-hard 4 × 10 Gb/s driver array

    NASA Astrophysics Data System (ADS)

    Zeng, Z.; Zhang, T.; Wang, G.; Gui, P.; Kulis, S.; Moreira, P.

    2017-02-01

    A High-speed and low-power VCSEL driver is an important component of the Versatile Link for the high-luminosity LHC (HL-LHC) experiments. A compact low-power radiation-hard 4 × 10 Gb/s VCSEL driver array (LDQ10) has been developed in 65 nm CMOS technology. Each channel in LDQ10 can provide a modulation current up to 8 mA and bias current up to 12 mA. Edge pre-emphasis is employed to compensate for the bandwidth limitations due to parasitic and the turn-on delay of VCSEL devices. LDQ10 occupies a chip area of 1900 μm × 1700 μm and consumes 130 mW power for typical current settings. The modulation amplitude degrades less than 5% after 300 Mrad total ionizing dose. LDQ10 can be directly wire-bonded to the VCSEL array and it is a suitable candidate for the Versatile Link.

  11. Study retention as bias reduction in a hard-to-reach population

    PubMed Central

    Western, Bruce; Braga, Anthony; Hureau, David; Sirois, Catherine

    2016-01-01

    Collecting data from hard-to-reach populations is a key challenge for research on poverty and other forms of extreme disadvantage. With data from the Boston Reentry Study (BRS), we document the extreme marginality of released prisoners and the related difficulties of study retention and analysis. Analysis of the BRS data yields three findings. First, released prisoners show high levels of “contact insecurity,” correlated with social insecurity, in which residential addresses and contact information change frequently. Second, strategies for data collection are available to sustain very high rates of study participation. Third, survey nonresponse in highly marginal populations is strongly nonignorable, closely related to social and economic vulnerability. The BRS response rate of 94% over a 1-y follow-up period allows analysis of hypothetically high nonresponse rates. In this setting, nonresponse attenuates regression estimates in analyses of housing insecurity, drug use, and unemployment. These results suggest that in the analysis of very poor and disadvantaged populations, methods that maximize study participation reduce bias and yield data that can usefully supplement large-scale household or administrative data collections. PMID:27162332

  12. Predicted levels of human radiation tolerance extrapolated from clinical studies of radiation effects

    NASA Technical Reports Server (NTRS)

    Lushbaugh, C. C.

    1972-01-01

    Results of clinical studies of radiation effects on man are used to evaluate space radiation hazards encountered during manned space travel. Considered are effects of photons as well as of mixed fission neutrons and gamma irradiations in establishing body radiosensitivity and tolerance levels. Upper and lower dose-response-time relations for acute radiation syndromes in patients indicate that man is more than sufficiently radioresistant to make the risks of an early radiation effect during one short space mission intangibly small in relation to the other nonradiation risks involved.

  13. Association of limited joint mobility and increased plantar hardness in diabetic foot ulceration in north Asian Indian: a preliminary study.

    PubMed

    Periyasamy, R; Anand, Sneh; Ammini, A C

    2012-04-01

    The aim of this article is to investigate the association of limited joint mobility and foot sole hardness in north Asian Indian type 2 diabetic patients. Limited joint mobility and hardness of the foot sole were measured for 39 subjects attending the AIIMS Endocrinology & Metabolism Clinic. The total subject divided into three groups: 13 control subjects (nondiabetic), 13 diabetic patients without neuropathy and 13 diabetic neuropathy patients. Neuropathy status was assessed using 10 gm Semen's Weinstein monofilament. Joint mobility parameters, such as ankle dorsiflexion/plantar flexion and metatarsophalangeal-1 dorsiflexion/plantar flexion, are measured using a goniometer. Foot sole hardness was measured using a durometer or shore meter. We found that diabetic patients with a neuropathic foot had significantly reduced joint mobility and increased foot sole hardness, placing them at risk for subsequent ulceration. Metatarsophalangeal-1 dorsiflexion/plantar flexion of both feet of diabetic patients had significant correlation (at p < 0.05, p < 0.001, p < 0.001 level) over age and body mass index. Also ankle plantar flexion/dorsiflexion and metatarsophalangeal-1 dorsiflexion/plantar flexion has a significant correlations (at p < 0.01, p < 0.05, p < 0.001, p < 0.001 level) with foot sole hardness in both feet of diabetic neuropathy subjects. Also linear regression analysis showed that duration of diabetes was significantly associated with the joint mobility parameters. In this study we conclude that joint mobility had reduced further if neuropathy and increased foot sole hardness coexisted owing to high plantar pressures. Hence, both limited joint mobility and increased foot sole hardness appears to be important determinants of foot sole ulceration in diabetic neuropathic subject.

  14. Studies of isothermal crystallisation kinetics of sunflower hard stearin-based confectionery fats.

    PubMed

    Bootello, Miguel A; Hartel, Richard W; Levin, Madeline; Martínez-Blanes, Jose M; Real, Concepción; Garcés, Rafael; Martínez-Force, Enrique; Salas, Joaquín J

    2013-08-15

    The crystallisation and polymorphic properties of three sunflower hard stearins (SHSs) and cocoa butter equivalents (CBEs) formulated by blending SHSs and palm mid fraction (PMF) were studied and compared with those from cocoa butter (CB), to explore their possibilities as confectionery fats. The isothermal crystallisation kinetics of these fats were examined by pNMR and DSC at three different temperatures. All samples studied displayed a two-step crystallisation profile that could be fitted to an exponential-Gompertz equation. Stop-and-return DSC studies showed that SHSs and CBEs exhibited different crystallisation mechanisms according to their triacylglycerol composition, with a quick formation of metastable crystals, followed by a polymorphic transition to the more stable β or β' forms. X-ray diffraction (XRD) was used to investigate the polymorphic forms of tempered SHSs and CBEs in the long term. In all cases the resulting fats displayed short spacing patterns associated with β polymorphism. These formulations based on SHSs and PMF met all the requirements to be considered as CBEs; therefore they could be used as an alternative to traditional confectionery fats.

  15. Determinants of Wealth Fluctuation: Changes in Hard-To-Measure Economic Variables in a Panel Study

    PubMed Central

    Pfeffer, Fabian T.; Griffin, Jamie

    2017-01-01

    Measuring fluctuation in families’ economic conditions is the raison d’être of household panel studies. Accordingly, a particularly challenging critique is that extreme fluctuation in measured economic characteristics might indicate compounding measurement error rather than actual changes in families’ economic wellbeing. In this article, we address this claim by moving beyond the assumption that particularly large fluctuation in economic conditions might be too large to be realistic. Instead, we examine predictors of large fluctuation, capturing sources related to actual socio-economic changes as well as potential sources of measurement error. Using the Panel Study of Income Dynamics, we study between-wave changes in a dimension of economic wellbeing that is especially hard to measure, namely, net worth as an indicator of total family wealth. Our results demonstrate that even very large between-wave changes in net worth can be attributed to actual socio-economic and demographic processes. We do, however, also identify a potential source of measurement error that contributes to large wealth fluctuation, namely, the treatment of incomplete information, presenting a pervasive challenge for any longitudinal survey that includes questions on economic assets. Our results point to ways for improving wealth variables both in the data collection process (e.g., by measuring active savings) and in data processing (e.g., by improving imputation algorithms). PMID:28316752

  16. Sensitivity study of ignition capsule implosion performance on the hard x-ray spectral distribution of hohlraum

    SciTech Connect

    Gu Jianfa; Zou Shiyang; Li Yongsheng; Dai Zhensheng; Ye Wenhua

    2012-12-15

    The paper investigates theoretically the sensitivities of ignition capsule implosion performance on the hard x-ray spectral distribution of hohlraum. In the simulation, the hohlraum radiation is represented by a Planckian spectrum for the main drive plus a gaussian bump centered at energy E{sub c} for preheating x-rays. Simulation results show that with the increasing of center energy E{sub c}, the Atwood number at the fuel-ablator interface increases rapidly due to the preheating and expanding of the inner undoped CH layer. The growing of Atwood number indicates the hydrodynamic instability (HI) growth and mixing at this interface. On the other hand, the increasing of E{sub c} results in a large density gradient scale length of ablation front and stabilizes the HI growth at ablation front. The changes of the hard x-ray spectrum have significant influences on other important implosion parameters including the ablator mass remaining, shock timing, implosion velocity, and yield as well. High-precision results on the hard x-ray spectral distribution of hohlraum are thus critical for optimizing the ignition capsule design to limit the HI growth.

  17. Recent studies on UV radiation in Brazil

    NASA Astrophysics Data System (ADS)

    Correa, M. P.; Ceballos, J. C.; Moregula, A.; Okuno, E.; Fausto, A.; Mol, A.; Santos, J. C.

    2009-04-01

    This presentation shows a summary of UV index measurements performed in the last years in Southeastern (SE) and Northeastern (NE) Brazilian regions. Brazil has an area of 8.5 million km2 distributed between latitudes 5˚ N and 35˚ S and longitudes 5˚ W and 75˚ W. SE is the most important economic pole of South America and the NE coast is an important tourist region. This large area has a great diversity of climatic, atmospheric and geographical conditions in addition to very diverse social and cultural habits. Non-melanoma skin cancer (NMSC) is an epidemiological health problem with more than 120,000 new cases each year. The most of these cases are found in the South and Southeast regions, with about 70 new NMSC per 100,000 inhabitants. Solar Light UV501 biometers are installed in the SE cities of São Paulo (23.6˚ S, 46.7˚ W, 865 m ASL), Itajubá/Minas Gerais (22.4˚ S; 45.5˚ W, 846 m ASL) and the NE city of Ilhéus/Bahia (14.8˚ S; 39.3˚ W; 54 m ASL). First measurements began in 2005 in São Paulo city, while Itajubá and Ilhéus have regular measurements from the beginning of 2008. Other studies related to the UV radiation modeling and interactions with atmosphere components, as ozone, aerosols and clouds, have also been performed. For example: a) UVI modelling calculations performed by a multiple-scattering spectral models; b) studies on the aerosol radiative properties based on satellite (MODIS/Terra-Aqua) and ground-based (Aeronet) observation; c) ozone content variability from satellite (OMI/Aura) and ground-based (Microtops ozonometer) measurements; d) behavioral profile of the population, as regarding habits of solar exposure and sun protection measures. Results show that more than 75% of the measurements conducted in the summer (outside noon) can be classified as upper than high UVI according to World Health Organization (WHO) recommended categories: Low (UVI < 2), Medium (3 ? UVI < 6), High (6 ? UVI < 8), Very High (8 ? UVI

  18. Studies of radiative transfer in planetary atmospheres

    NASA Technical Reports Server (NTRS)

    Irvine, W. M.; Schloerb, F. P.

    1986-01-01

    Schloerb and Claussen continued their analysis of the very high quality data set obtained on the 18 centimeter OH line from the Comet P/Halley with the NRAO 43 meter antenna. The high spectral resolution (0.22 km/sec) and high signal-to-noise of the OH spectra make them ideal for the study of kinematics in the coma. Synthetic profiles were initiated for comparison with the data. A vectorial model was developed using the Monte Carlo techniques originated by Combi and Delsemme. Analysis of the millimeter wavelength observations of HCN emission from P/Halley obtained throughout much of the recent apparition were continued using the University of Massachusetts 14 millimeter-wavelength (FCRAO) antenna. A detailed analysis of the HCN lineshpaes was performed over the last six months. The excitation of HCN in the coma was studied to obtain a detailed match to the observed spectra. The passive millimeter wave radiometer was used to probe the physical and chemical nature of comets from spacecraft. Work was continued on an improved theory of radiative transfer for rough and porous surfaces, such as the regoliths of satellites, asteroids, and comets.

  19. Molecular photoemission studies using synchrotron radiation

    SciTech Connect

    Truesdale, C.M.

    1983-04-01

    The angular distributions of photoelectrons and Auger electrons were measured by electron spectroscopy using synchrotron radiation. The experimental results are compared with theoretical calculations to interpret the electronic behavior of photoionization for molecular systems.

  20. Study on planarization machining of sapphire wafer with soft-hard mixed abrasive through mechanical chemical polishing

    NASA Astrophysics Data System (ADS)

    Xu, Yongchao; Lu, Jing; Xu, Xipeng

    2016-12-01

    This study investigated the material removal mechanism of sapphire wafer with soft-hard mixed abrasives through mechanical chemical polishing (MCP). The polishing film, which contains diamond as hard abrasives and high reactivity silica as soft abrasives, is prepared through sol-gel technology. Silica abrasives with regular spherical shape and high reactivity are prepared through hydrolysis-precipitation. Diamond grits with three different particle sizes are used as abrasives. Results show that the rate of material removal of mixed abrasives during MCP is more than 52.6% of that of single hard abrasives and the decrease in surface roughness is more than 21.6% of that of single hard abrasives. These results demonstrate that the ideal planarization of sapphire wafer with high removal rate and good surface quality can be achieved when the effect of mechanical removal of hard abrasives and the chemical corrosion effect of soft abrasives are in dynamic equilibrium. A model that describes the material removal mechanism of sapphire with mixed abrasives during MCP is proposed. The results of thermodynamic calculation and polishing residue analysis are used to demonstrate the rationality of the model.

  1. Hardness Analysis and Empirical Studies of the Relations among Robustness, Topology and Flow in Dynamic Networks.

    PubMed

    Zhou, Xing; Peng, Wei; Xu, Zhen; Yang, Bo

    2015-01-01

    Network robustness is the ability of a network to maintain performance after disruption, thus it is an important index for network designers to refer to. Every actual network has its own topology structure, flow magnitude (scale) and flow distribution. How the robustness relates to these factors still remains unresolved. To analyze the relations, we first established a robustness problem model, studied the hardness of a special case of the model, and generated a lot of representative network instances. We conducted experiments on these instances, deleting 5% to 50% edges on each instance and found that the robustness of a network has an approximate linearity to its structural entropy and flow entropy, when the correlation coefficient between the structure and flow is fixed. We also found that robustness is unlikely to have a relation to the flow scale and edge scale in our model. The empirical studies thus can provide a way of quickly estimating the robustness of real-world networks by using the regression coefficients we obtained during the experiments. We conducted computation on a real-world dataset and got favorable results, which exhibited the effectiveness of the estimation.

  2. Reactive ZnO/Ti/ZnO interfaces studied by hard x-ray photoelectron spectroscopy

    SciTech Connect

    Knut, Ronny Lindblad, Rebecka; Rensmo, Håkan; Karis, Olof; Grachev, Sergey; Faou, Jean-Yvon; Søndergård, Elin

    2014-01-28

    The chemistry and intermixing at buried interfaces in sputter deposited ZnO/Ti/ZnO thin layers were studied by hard x-ray photoelectron spectroscopy. The long mean free path of the photoelectrons allowed for detailed studies of the oxidation state, band bending effects, and intrinsic doping of the buried interfaces. Oxidation of the Ti layer was observed when ZnO was deposited on top. When Ti is deposited onto ZnO, Zn Auger peaks acquire a metallic character indicating a strong reduction of ZnO at the interface. Annealing of the stack at 200 °C results in further reduction of ZnO and oxidation of Ti. Above 300 °C, oxygen transport from the bulk of the ZnO layer takes place, leading to re-oxidation of ZnO at the interface and further oxidation of Ti layer. Heating above 500 °C leads to an intermixing of the layers and the formation of a Zn{sub x}TiO{sub y} compound.

  3. Bubble generation and venous air filtration by hard-shell venous reservoirs: a comparative study.

    PubMed

    Mitchell, S J; Willcox, T; Gorman, D F

    1997-09-01

    We have previously shown significant bubble formation in Medtronic Maxima hard-shell venous reservoirs (HSVRs). In the present study, we not only investigated the mechanism of this bubble formation, but also the extent of bubble clearance by membrane oxygenators and arterial line filters. In addition, we also compared the performance of five HSVRs with respect to bubble formation and venous air filtration. Salvaged clinical CPB circuits containing different HSVRs were studied by downstream Doppler monitoring under fixed flow-decreasing volume, fixed volume-increasing flow, and entrained venous air conditions. Bubbles formed in the Medtronic Maxima top entry HSVR at volumes below 800 ml and flows above 3.5 l min-1, and were incompletely removed by a membrane oxygenator and arterial line filter. Decreased bubbling was seen when the reservoir atmosphere was flushed with CO2, suggesting that these bubbles formed in a fountain at the venous inflow. The Medtronic Maxima Forte HSVR formed significantly fewer bubbles at low volumes, and filtered venous air effectively. Negligible bubble formation occurred in the Sorin, Terumo, or Baxter reservoirs. The minimum recommended operating volume for the Medtronic Maxima top entry reservoir should be reset at 600 ml and this device should always be used with an arterial filter. Bubble formation is substantially reduced in the new Medtronic Maxima Forte HSVR and this device is a good filter for venous air.

  4. RADIATION PROTECTION IN AN INTERVENTIONAL LABORATORY: A COMPARATIVE STUDY OF AUSTRALIAN AND SAUDI ARABIAN HOSPITALS.

    PubMed

    Alahmari, Mohammed Ali S; Sun, Zhonghua; Bartlett, Andrew

    2016-12-01

    This study aimed to investigate whether the use of protection devices and attitudes of interventional professionals (including radiologists, cardiologists, vascular surgeons, medical imaging technicians and nurses) towards radiation protection will differ between Saudi Arabian and Australian hospitals. Hard copies of an anonymous survey were distributed to 10 and 6 clinical departments in the Eastern province of Saudi Arabia and metropolitan hospitals in Western Australia, respectively. The overall response rate was 43 % comprising 110 Australian participants and 63 % comprising 147 Saudi participants. Analysis showed that Australian respondents differed significantly from Saudi respondents with respect to their usages of leaded glasses (p < 0.001), ceiling-suspended lead screen (p < 0.001) and lead drape suspended from the table (p < 0.001). This study indicates that the trained interventional professionals in Australia tend to adhere to benefit from having an array of tools for personal radiation protection than the corresponding group in Saudi Arabia.

  5. Pre-flight performance and radiation hardness of the Tokyo Tech pico-satellite Cute-1.7

    NASA Astrophysics Data System (ADS)

    Kotoku, J.; Kataoka, J.; Kuramoto, Y.; Tsubuku, Y.; Yatsu, Y.; Sato, R.; Ikagawa, T.; Saito, T.; Kawai, N.; Konoue, K.; Miyashita, N.; Iai, M.; Omagari, K.; Kashiwa, M.; Yabe, H.; Imai, K.; Miyamoto; Fujiwara, K.; Masumoto, S.; Usuda, T.; Iljic, T.; Konda, A.; Sugita, S.; Yamanaka, T.; Matsuura, D.; Sagami, T.; Kajiwara, S.; Funaki, Y.; Matsunaga, S.; Shima, T.; Kishimoto, S.

    2006-09-01

    The Cute-1.7 was launched successfully in February 2006 as a piggyback satellite of the Astro-F mission. The Cute-1.7 dimensions are 10×10×20cm box with a total mass of 3.6 kg. It is the second pico-satellite to have been developed completely by students of the Tokyo Institute of Technology (Tokyo Tech.) after the successful launch of the CUTE-I in June 2003. The goals of the Cute-1.7 mission are two-fold: (1) to validate high-performance, commercially available products for the first time in space. We particularly use personal digital assistants (PDAs) as a main computer in orbit (2) to demonstrate new potential uses for small satellites in various space studies, as proposed by the “satellite-core” concept. For the Cute-1.7 mission, we will carry avalanche photo diodes (APDs) as a high-count particle monitor in low-Earth orbit. Here we present details of various ground tests and pre-flight performance of the Cute-1.7 immediately before the launch. Results of the Cute-1.7 mission will provide quick feedback for space applications of APDs in Japan's future X-ray astronomy mission NeXT.

  6. Compressibility and hardness of Co-based bulk metallic glass: A combined experimental and density functional theory study

    SciTech Connect

    Wang Jianfeng; Li Ran; Xu Tao; Li Yan; Liu Zengqian; Huang Lu; Hua Nengbin; Zhang Tao; Xiao Ruijuan; Li Gong; Li Yanchun

    2011-10-10

    An incompressible Co{sub 54}Ta{sub 11}B{sub 35} bulk metallic glass (BMG) was investigated using in situ high-pressure synchrotron diffraction and nanoindendation. The elastic constants were deduced from the experiments based on the isotropic model. The Vickers hardness was measured to be 17.1 GPa. The elastic moduli and hardness are the highest values known in BMGs. The theoretically calculated elastic properties by density-functional study were well consistent with experimental measurements. The analysis of charge density and bonding character indicates the covalent character of Co-B and B-B bonds, underlying the unusually high elastic modulus and hardness in this material.

  7. Method for Developing Descriptions of Hard-to-Price Products: Results of the Telecommunications Product Study

    SciTech Connect

    Conrad, F.; Tonn, B.

    1999-05-01

    This report presents the results of a study to test a new method for developing descriptions of hard-to-price products. The Bureau of Labor Statistics (BLS) is responsible for collecting data to estimate price indices such as the Consumers Price Index (BLS) is responsible for collecting data to estimate price indices such as the Consumers Price Index (CPI). BLS accomplishes this task by sending field staff to places of business to price actual products. The field staff are given product checklists to help them determine whether products found today are comparable to products priced the previous month. Prices for non-comparable products are not included in the current month's price index calculations. A serious problem facing BLS is developing product checklists for dynamic product areas, new industries, and the service sector. It is difficult to keep checklists up-to-date and quite often simply to develop checklists for service industry products. Some people estimates that upwards of 50 % of US economic activity is not accounted for in the CPI

  8. Novel use of the CO2 laser on dental hard tissues: an SEM study

    NASA Astrophysics Data System (ADS)

    Wigdor, Harvey A.; Gilbert, Jeremy L.; Chomsky, Doron; Raif, Joshua

    1997-05-01

    There is great interest in dentistry to find a replacement for the dental drill which is a great source fear in dental patients. Lasers have been considered a potential replacement. Hard tissue use of lasers on dental tissues has been slow in development has had very limited acceptance by the dental community. The ultimate goal is to develop a laser which can remove both healthy and diseased dental hard tissues and dental materials. The CO2 laser surgical applications on sot tissues has been reported by many authors. It is hard tissue applications have had very few published reports. The thermal effects of this laser on hard tissues precluded its use on hard tissues. A new CO2 laser has been developed to reduce the thermal effects on dentin and enamel. Powers of 3-5 watts were used to ablate the buccal surface of extracted human molar teeth. These teeth were gold coated and evaluated under scanning electron microscopy. The results show some melting of the dentin and enamel, however patent dentinal tubules are evident and there appears to be a non-thermal cutting of the enamel at the boarder of the cut surface. In conclusion these very preliminary results appear to show that this new CO2 laser can cut dentin and enamel efficiently and with very little thermal effect as seen under SEM.

  9. Hearing Dogs: A Longitudinal Study of Social and Psychological Effects on Deaf and Hard-of-Hearing Recipients

    ERIC Educational Resources Information Center

    Guest, Claire M.; Collis, Glyn M.; McNicholas, June

    2006-01-01

    The organization Hearing Dogs for Deaf People provides assistance dogs that alert their deaf or hard-of-hearing recipients to key sounds, thus increasing their independence and also providing companionship. Fifty-one recipients took part in a longitudinal study to monitor the dogs' working performance over time and to examine the social and…

  10. Radiation Hard Sensors for Surveillance.

    DTIC Science & Technology

    1988-03-11

    Dark Matter ", Proc. Workshop, Ringberg Castle, Tegerusee May 12-13, 1987 ed. K. Pretzl D.et al., Springer Verlay 1987 D. Perret-Gallix ,ibid 4) A...Low Temperature Detectors for *-., Neutrino/ Dark Matter ", Ringberg Castle, Tegernsee, May 1987. In the following this paper is quoted as UBC, 1987...advantage of the SQUID sensitivity. Multichannel readout capability is presently being buil.I. 30 DISIAIIBUIIU’..AVAILANI..TY Of AeStRAC? 3

  11. A radiation hard vacuum switch

    DOEpatents

    Boettcher, G.E.

    1988-07-19

    A vacuum switch with an isolated trigger probe which is not directly connected to the switching electrodes. The vacuum switch within the plasmatron is triggered by plasma expansion initiated by the trigger probe which travels through an opening to reach the vacuum switch elements. The plasma arc created is directed by the opening to the space between the anode and cathode of the vacuum switch to cause conduction. 3 figs.

  12. Silver-Teflon contamination UV radiation study

    NASA Technical Reports Server (NTRS)

    Muscari, J. A.

    1978-01-01

    Silver-Teflon (Ag/FEP) is planned to be used as the thermal control material covering the radiator surfaces on the shuttle orbiter payload bay doors. These radiators require the use of materials that have a very low solar absorptance and a high emittance for heat rejection. However, operationally, materials used on these critical radiator surfaces, such as silver-Teflon, will be exposed to a variety of conditions which include both the natural as well as the induced environments from the Shuttle Orbiter. A complete test facility was assembled, and detailed test procedures and a test matrix were developed. Measurements of low solar absorptance were taken before and after contamination, at intervals during irradiation, and after sample cleaning to fulfill all the requirements.

  13. A study of Monte Carlo radiative transfer through fractal clouds

    SciTech Connect

    Gautier, C.; Lavallec, D.; O`Hirok, W.; Ricchiazzi, P.

    1996-04-01

    An understanding of radiation transport (RT) through clouds is fundamental to studies of the earth`s radiation budget and climate dynamics. The transmission through horizontally homogeneous clouds has been studied thoroughly using accurate, discreet ordinates radiative transfer models. However, the applicability of these results to general problems of global radiation budget is limited by the plane parallel assumption and the fact that real clouds fields show variability, both vertically and horizontally, on all size scales. To understand how radiation interacts with realistic clouds, we have used a Monte Carlo radiative transfer model to compute the details of the photon-cloud interaction on synthetic cloud fields. Synthetic cloud fields, generated by a cascade model, reproduce the scaling behavior, as well as the cloud variability observed and estimated from cloud satellite data.

  14. Study on electroplating technology of diamond tools for machining hard and brittle materials

    NASA Astrophysics Data System (ADS)

    Cui, Ying; Chen, Jian Hua; Sun, Li Peng; Wang, Yue

    2016-10-01

    With the development of the high speed cutting, the ultra-precision machining and ultrasonic vibration technique in processing hard and brittle material , the requirement of cutting tools is becoming higher and higher. As electroplated diamond tools have distinct advantages, such as high adaptability, high durability, long service life and good dimensional stability, the cutting tools are effective and extensive used in grinding hard and brittle materials. In this paper, the coating structure of electroplating diamond tool is described. The electroplating process flow is presented, and the influence of pretreatment on the machining quality is analyzed. Through the experimental research and summary, the reasonable formula of the electrolyte, the electroplating technologic parameters and the suitable sanding method were determined. Meanwhile, the drilling experiment on glass-ceramic shows that the electroplating process can effectively improve the cutting performance of diamond tools. It has laid a good foundation for further improving the quality and efficiency of the machining of hard and brittle materials.

  15. Atomic photoelectron-spectroscopy studies using synchrotron radiation

    SciTech Connect

    Kobrin, P.H.

    1983-02-01

    Photoelectron spectroscopy combined with tunable synchrotron radiation has been used to study the photoionization process in several atomic systems. The time structure of the synchrotron radiation source at the Stanford Synchrotron Radiation Laboratory (SSRL) was used to record time-of-flight (TOF) photoelectron spectra of gaseous Cd, Hg, Ne, Ar, Ba, and Mn. The use of two TOF analyzers made possible the measurement of photoelectron angular distributions as well as branching ratios and partial cross sections.

  16. Radiation hardness studies of AMS HV-CMOS 350 nm prototype chip HVStripV1

    NASA Astrophysics Data System (ADS)

    Kanisauskas, K.; Affolder, A.; Arndt, K.; Bates, R.; Benoit, M.; Di Bello, F.; Blue, A.; Bortoletto, D.; Buckland, M.; Buttar, C.; Caragiulo, P.; Das, D.; Dopke, J.; Dragone, A.; Ehrler, F.; Fadeyev, V.; Galloway, Z.; Grabas, H.; Gregor, I. M.; Grenier, P.; Grillo, A.; Hiti, B.; Hoeferkamp, M.; Hommels, L. B. A.; Huffman, B. T.; John, J.; Kenney, C.; Kramberger, J.; Liang, Z.; Mandic, I.; Maneuski, D.; Martinez-Mckinney, F.; MacMahon, S.; Meng, L.; Mikuž, M.; Muenstermann, D.; Nickerson, R.; Peric, I.; Phillips, P.; Plackett, R.; Rubbo, F.; Segal, J.; Seidel, S.; Seiden, A.; Shipsey, I.; Song, W.; Staniztki, M.; Su, D.; Tamma, C.; Turchetta, R.; Vigani, L.; Volk, J.; Wang, R.; Warren, M.; Wilson, F.; Worm, S.; Xiu, Q.; Zhang, J.; Zhu, H.

    2017-02-01

    CMOS active pixel sensors are being investigated for their potential use in the ATLAS inner tracker upgrade at the HL-LHC. The new inner tracker will have to handle a significant increase in luminosity while maintaining a sufficient signal-to-noise ratio and pulse shaping times. This paper focuses on the prototype chip "HVStripV1" (manufactured in the AMS HV-CMOS 350nm process) characterization before and after irradiation up to fluence levels expected for the strip region in the HL-LHC environment. The results indicate an increase of depletion region after irradiation for the same bias voltage by a factor of ≈2.4 and ≈2.8 for two active pixels on the test chip. There was also a notable increase in noise levels from 85 e‑ to 386 e‑ and from 75 e‑ to 277 e‑ for the corresponding pixels.

  17. Study of Radiation Hardness of Lattice Matched AlInN/GaN HEMT Heterostructures

    DTIC Science & Technology

    2016-10-01

    of wide bandgap high power, high frequency electronics, as well as fundamental materials science of these materials. The technical approach consists...along the center vertical z-axis (i.e. growth direction ) of the volume shown in Figure 11(a). By looking at the very center of the material we can...function of depth in the growth direction , where the individual layers in the AlInN/GaN heterostructure can be identified. Iso-concentration surfaces

  18. Assuring the quality of results of test hardness IRHD: IPT's case study

    NASA Astrophysics Data System (ADS)

    Yojo, T.; Miranda, M. J. A. C.; Oliveira, C. B.; Matteucci, C.

    2015-10-01

    This paper presents the experience of the Laboratory Trees, Woods and Furniture - LAMM in calibrating the durometer IRHD and assuring the quality of its test results, since there are no Certified Reference Material and laboratory in the Brazilian Calibration Network that can calibrate the equipment. To solve this problem, the IRHD hardness (N method) was quantified in three ways: a) by measuring the modulus of elasticity of the material, b) by measuring the depth the sphere entered the material and c) the durometer's direct reading. With the IRHD hardness measured by accepted international standards techniques, it was possible to evaluate the accuracy of the test results that assured the calibration of the equipment.

  19. Memory deficits and industrial toxicant exposure: a comparative study of hard metal, solvent and asbestos workers.

    PubMed

    Jordan, C M; Whitman, R D; Harbut, M

    1997-06-01

    Memory functioning was examined in ex-factory workers with hard metal disease, resulting from exposure to alloys utilizing cobalt. Since these workers are also exposed to organic solvents and may suffer from chronic hypoxia as a result of their pulmonary disorder, solvent and asbestos workers, as well as an unexposed matched sample, served as controls. Results demonstrated deficits in the allocation of attentional resources and in short-term verbal memory. A pattern of findings across several tests suggested that repetition or delay is important for adequate memory performance in individuals exposed to hard metal, implicating a deficit in encoding or slowed consolidation.

  20. Treatment of radiation enteritis: a comparison study

    SciTech Connect

    Loiudice, T.A.; Lang, J.A.

    1983-08-01

    Twenty-four patients with severe radiation injury to the small bowel seen over a 4-year period were randomized to four treatment groups: 1) methylprednisolone 80 mg intravenously plus Vivonex-HN, 2 L/day po, 2) methylprednisolone 80 mg intravenously plus total parenteral nutrition, 2.5 L/day, 3) total parenteral nutrition, 2.5 L/day, and 4) Vivonex-HN, 2 L/day po. Patients received nothing by mouth except water in groups II and III, and only Vivonex-HN in groups I and IV. Patients were treated for 8-wk periods. Improvement was gauged by overall nutritional assessment measurements, nitrogen balance data and by radiological and clinical parameters. No significant difference between groups I, II, III, and IV could be found for age, sex, mean radiation dosage, time of onset after radiation therapy, or initial nutritional assessment data. Differences statistically could be found between groups II and III and I and IV regarding nutritional assessment data, nitrogen balance, radiographic and clinical parameters after therapy, with marked improvement noted in groups II and III. We conclude that a treatment regimen consisting of total parenteral nutrition and bowel rest is beneficial in the treatment of radiation enteritis. Methylprednisolone appears to enhance this effect and indeed, may be responsible for a longer lasting response.

  1. Space radiation studies. [Spacelab 2 Payload

    NASA Technical Reports Server (NTRS)

    1985-01-01

    The overall data flow diagram for the nuclear radiation monitor to fly on Spacelab 2 was revised. The use of structured techniques for the software design appears to be working well. An example of the PASCAL pseudocode written to develop and document the software design is included.

  2. Radiation environment study of near space in China area

    NASA Astrophysics Data System (ADS)

    Fan, Dongdong; Chen, Xingfeng; Li, Zhengqiang; Mei, Xiaodong

    2015-10-01

    Aerospace activity becomes research hotspot for worldwide aviation big countries. Solar radiation study is the prerequisite for aerospace activity to carry out, but lack of observation in near space layer becomes the barrier. Based on reanalysis data, input key parameters are determined and simulation experiments are tried separately to simulate downward solar radiation and ultraviolet radiation transfer process of near space in China area. Results show that atmospheric influence on the solar radiation and ultraviolet radiation transfer process has regional characteristic. As key factors such as ozone are affected by atmospheric action both on its density, horizontal and vertical distribution, meteorological data of stratosphere needs to been considered and near space in China area is divided by its activity feature. Simulated results show that solar and ultraviolet radiation is time, latitude and ozone density-variant and has complicated variation characteristics.

  3. Moisture influence on near-infrared prediction of wheat hardness

    NASA Astrophysics Data System (ADS)

    Windham, William R.; Gaines, Charles S.; Leffler, Richard G.

    1991-02-01

    Recently near infrared (NTR) reflectance instrumentation has been used to provide an empirical measure of wheat hardness. This hardness scale is based on the radiation scattering properties of meal particles at 1680 and 2230 nm. Hard wheats have a larger mean particles size (PS) after grinding than soft wheats. However wheat kernel moisture content can influence mean PS after grinding. The objective of this study was to determine the sensitivity of MR wheat hardness measurements to moisture content and to make the hardness score independent of moisture by correcting hardness measurements for the actual moisture content of measured samples. Forty wheat cultivars composed of hard red winter hard red spring soft red winter and soft white winter were used. Wheat kernel subsamples were stored at 20 40 60 and 80 relative humidity (RH). After equilibration samples were ground and the meal analyzed for hardness score (HS) and moisture. HS were 48 50 54 and 65 for 20 40 60 and 80 RH respectively. Differences in HS within each wheat class were the result of a moisture induced change in the PS of the meal. An algorithm was developed to correct HS to 11 moisture. This correction provides HS that are nearly independent of moisture content. 1.

  4. Simbol-X Hard X-ray Focusing Mirrors: Results Obtained During the Phase A Study

    NASA Astrophysics Data System (ADS)

    Tagliaferri, G.; Basso, S.; Borghi, G.; Burkert, W.; Citterio, O.; Civitani, M.; Conconi, P.; Cotroneo, V.; Freyberg, M.; Garoli, D.; Gorenstein, P.; Hartner, G.; Mattarello, V.; Orlandi, A.; Pareschi, G.; Romaine, S.; Spiga, D.; Valsecchi, G.; Vernani, D.

    2009-05-01

    Simbol-X will push grazing incidence imaging up to 80 keV, providing a strong improvement both in sensitivity and angular resolution compared to all instruments that have operated so far above 10 keV. The superb hard X-ray imaging capability will be guaranteed by a mirror module of 100 electroformed Nickel shells with a multilayer reflecting coating. Here we will describe the technogical development and solutions adopted for the fabrication of the mirror module, that must guarantee an Half Energy Width (HEW) better than 20 arcsec from 0.5 up to 30 keV and a goal of 40 arcsec at 60 keV. During the phase A, terminated at the end of 2008, we have developed three engineering models with two, two and three shells, respectively. The most critical aspects in the development of the Simbol-X mirrors are i) the production of the 100 mandrels with very good surface quality within the timeline of the mission, ii) the replication of shells that must be very thin (a factor of 2 thinner than those of XMM-Newton) and still have very good image quality up to 80 keV, iii) the development of an integration process that allows us to integrate these very thin mirrors maintaining their intrinsic good image quality. The Phase A study has shown that we can fabricate the mandrels with the needed quality and that we have developed a valid integration process. The shells that we have produced so far have a quite good image quality, e.g. HEW <~30 arcsec at 30 keV, and effective area. However, we still need to make some improvements to reach the requirements. We will briefly present these results and discuss the possible improvements that we will investigate during phase B.

  5. Simbol-X Hard X-ray Focusing Mirrors: Results Obtained During the Phase A Study

    SciTech Connect

    Tagliaferri, G.; Basso, S.; Civitani, M.; Conconi, P.; Cotroneo, V.; Pareschi, G.; Spiga, D.; Borghi, G.; Garoli, D.; Mattarello, V.; Orlandi, A.; Valsecchi, G.; Vernani, D.; Burkert, W.; Freyberg, M.; Hartner, G.; Citterio, O.; Gorenstein, P.; Romaine, S.

    2009-05-11

    Simbol-X will push grazing incidence imaging up to 80 keV, providing a strong improvement both in sensitivity and angular resolution compared to all instruments that have operated so far above 10 keV. The superb hard X-ray imaging capability will be guaranteed by a mirror module of 100 electroformed Nickel shells with a multilayer reflecting coating. Here we will describe the technogical development and solutions adopted for the fabrication of the mirror module, that must guarantee an Half Energy Width (HEW) better than 20 arcsec from 0.5 up to 30 keV and a goal of 40 arcsec at 60 keV. During the phase A, terminated at the end of 2008, we have developed three engineering models with two, two and three shells, respectively. The most critical aspects in the development of the Simbol-X mirrors are i) the production of the 100 mandrels with very good surface quality within the timeline of the mission, ii) the replication of shells that must be very thin (a factor of 2 thinner than those of XMM-Newton) and still have very good image quality up to 80 keV, iii) the development of an integration process that allows us to integrate these very thin mirrors maintaining their intrinsic good image quality. The Phase A study has shown that we can fabricate the mandrels with the needed quality and that we have developed a valid integration process. The shells that we have produced so far have a quite good image quality, e.g. HEW < or approx. 30 arcsec at 30 keV, and effective area. However, we still need to make some improvements to reach the requirements. We will briefly present these results and discuss the possible improvements that we will investigate during phase B.

  6. A REVIEW OF EPIDEMIOOGICAL STUDIES ON DRINKING WATER HARDNESS AND CARDIOVASCULAR DISEASES

    EPA Science Inventory

    Major risk factors do not entirely explain the worldwide variability of morbidity and mortality due to

    cardiovascular disease. Several environmental factors, including the hardness of drinking water may

    affect cardiovascular disease risks. We conducted a qualitative...

  7. Study of runaway electrons with Hard X-ray spectrometry of tokamak plasmas

    SciTech Connect

    Shevelev, A.; Chugunov, I.; Khilkevitch, E.; Gin, D.; Doinikov, D.; Naidenov, V.; Kiptily, V.; Collaboration: EFDA-JET Contributors

    2014-08-21

    Hard-X-ray spectrometry is a tool widely used for diagnostic of runaway electrons in existing tokamaks. In future machines, ITER and DEMO, HXR spectrometry will be useful providing information on runaway electron energy, runaway beam current and its profile during disruption.

  8. Epidemiological studies on radiation carcinogenesis in human populations following acute exposure: nuclear explosions and medical radiation

    SciTech Connect

    Fabrikant, J.I.

    1982-08-01

    The present review provides an understanding of our current knowledge of the carcinogenic effect of low-dose radiation in man, and surveys the epidemiological studies of human populations exposed to nuclear explosions and medical radiation. Discussion centers on the contributions of quantitative epidemiology to present knowledge, the reliability of the dose-incidence data, and those relevant epidemiological studies that provide the most useful information for risk estimation of cancer-induction in man. Reference is made to dose-incidence relationships from laboratory animal experiments where they may obtain for problems and difficulties in extrapolation from data obtained at high doses to low doses, and from animal data to the human situation. The paper describes the methods of application of such epidemiological data for estimation of excess risk of radiation-induced cancer in exposed human populations, and discusses the strengths and limitations of epidemiology in guiding radiation protection philosophy and public health policy.

  9. Ultrastructural study of thyroid capillaries after IR laser radiation

    NASA Astrophysics Data System (ADS)

    Vidal, Lourdes; Perez de Vargas, I.; Carrillo, F.; Parrado, C.; Pelaez, A.

    1994-02-01

    Laser radiation causes microscopical changes in the follicular cells relative to dose intensity. So, we have observed focal degenerative phenomena, at maximal doses, and activation of cellular function similar to the ones observed after stimulation with TSH, at minimal doses. In order to evaluate the evolution of these changes we have planned an ultrastructural study of rats thyroid capillaries treated with IR laser radiation.

  10. Film type SO-168 radiation study

    NASA Technical Reports Server (NTRS)

    Pierce, W. N.

    1972-01-01

    Investigations were performed to determine optimum exposure and processing procedures necessary to partially offset the effect of radiation to which film type SO-168 will be exposed during the Skylab Mission. This task became necessary when it was determined that original predictions of 2 to 3 RADS of radiation to which the film will be exposed were too low, and that levels as high as 3.5 to 4.0 RADS may be incurred, thus reducing image quality below an acceptable level. Tests results show that forced processing of type SO-168 film tended to reduce the density range to an unusable level, and that processing to a lower ASA value would provide greater image quality for the user.

  11. Epidemiological studies on radiation carcinogenesis in human populations following acute exposure: nuclear explosions and medical radiation

    SciTech Connect

    Fabrikant, J.I.

    1981-05-01

    The current knowledge of the carcinogenic effect of radiation in man is considered. The discussion is restricted to dose-incidence data in humans, particularly to certain of those epidemiological studies of human populations that are used most frequently for risk estimation for low-dose radiation carcinogenesis in man. Emphasis is placed solely on those surveys concerned with nuclear explosions and medical exposures. (ACR)

  12. Radiation Protection Studies for LCLS Tune Up Dump

    SciTech Connect

    Santana-Leitner, M.; Fass, A.; Mao, S.; Nuhn, H.D.; Roesler, S.; Rokni, S.; Vollaire, J.; /SLAC

    2010-04-29

    The Linac Coherent Light Source (LCLS) at the Stanford Linear Accelerator Center is a pioneer fourth generation hard x-ray free electron laser that shall start to deliver laser pulses in 2009. Among other components of LCLS that present radiation protection concerns, the tune up dump (tdund) is of special interest because it also constitutes an issue for machine protection, as it is placed close to radiation sensitive components, like electronic devices and permanent magnets in the undulators. This paper first introduces the stopper of tdund looking at the heat load, and then it describes the shielding around the dump necessary to maintain the prompt and residual dose within design values. Next, preliminary comparisons of the magnetization loss in a dedicated on-site magnet irradiation experiment with FLUKA simulations serve to characterize the magnetic response to radiation of magnets like those of LCLS. The previous knowledge, together with the limit for the allowed demagnetization, are used to estimate the lifetime of the undulator. Further simulations provide guidelines on which lifetime can be expected for an electronic device placed at a given distance of tdund.

  13. Cleaner Technology in the Hard Disk Drive Manufacturing Industry: A Case Study

    NASA Astrophysics Data System (ADS)

    Moolla, Premchai; Chompu-inwai, Rungchat

    2010-10-01

    The objectives of this research are to improve raw material and energy consumption efficiency, as well as reduce defects and the use of chemicals in the arm coil assembly process of hard disk drive manufacturing in the case study company by applying the Cleaner Technology concepts. The four main sequential steps used in this research were: (1) pre-assessment, (2) assessment, (3) feasibility study, and (4) implementation. In the first step, raw data, such as process flows, raw material usage and defects data were collected. In the second step, the loss during production and causes of loss were analyzed. Opportunities to reduce raw material, chemical and energy wastage could then be recommended. The next step was to evaluate the feasibility and potential benefits of a particular Cleaner Technology opportunity. Finally, in the last step, after a thorough evaluation and implementation of the opportunities to apply Cleaner Technology, the results showed that arm coil defects could be reduced by improving the production process using the ECRS technique. ECRS stands for Eliminate, Combine, Rearrange and Simplify. This improvement reduced arm coil defect rates from 0.48% to 0.15%, thus saving approximately 139,638 Thai Baht per month. In addition, production stoppage decision made by workers was used to increase employee involvement in defect detection. Allowing workers to participate in such a decision was an effective way to reduce defect rate and could motivate workers to produce a better quality job. This resulted in arm coil defects reducing from 0.41% to 0.025%, with about 74,562 Thai Baht per month saving. Additionally, an increase in the efficiency of electricity consumption occurred, by increasing the speed of the infrared oven conveyor belt, improving average productivity from 533 pieces/hour to 560 pieces/hour, without adversely affecting product costs and quality, thus producing products of up to the value of 206,242 Thai Baht per month. Furthermore, the new

  14. Frequency-independent radiation modes of interior sound radiation: An analytical study

    NASA Astrophysics Data System (ADS)

    Hesse, C.; Vivar Perez, J. M.; Sinapius, M.

    2017-03-01

    Global active control methods of sound radiation into acoustic cavities necessitate the formulation of the interior sound field in terms of the surrounding structural velocity. This paper proposes an efficient approach to do this by presenting an analytical method to describe the radiation modes of interior sound radiation. The method requires no knowledge of the structural modal properties, which are often difficult to obtain in control applications. The procedure is exemplified for two generic systems of fluid-structure interaction, namely a rectangular plate coupled to a cuboid cavity and a hollow cylinder with the fluid in its enclosed cavity. The radiation modes are described as a subset of the acoustic eigenvectors on the structural-acoustic interface. For the two studied systems, they are therefore independent of frequency.

  15. A Study of Surface Temperatures, Clouds and Net Radiation

    NASA Technical Reports Server (NTRS)

    Dhuria, Harbans

    1996-01-01

    This study focused on the seasonal relationships and interactions of climate parameters such as the surface temperatures, net radiation, long wave flux, short wave flux, and clouds on a global basis. Five years of observations (December 1984 to November 1989) from the Earth Radiation Budget Experiment (ERBE) and the International Satellite Cloud Climatology Program (ISCCP) were used to study both seasonal variations and interannual variations by use of a basic radiation budget equation. In addition, the study was extended to include an analysis of the cloud forcing due El-Nino's impact on the ERBE parameters.

  16. STATISTICAL STUDY of HARD X-RAY SPECTRAL CHARACTERISTICS OF SOLAR FLARES

    NASA Astrophysics Data System (ADS)

    Alaoui, M.; Krucker, S.; Saint-Hilaire, P.; Lin, R. P.

    2009-12-01

    We investigate the spectral characteristics of 75 solar flares at the hard X-ray peak time observed by RHESSI (Ramaty High Energy Solar Spectroscopic Imager) in the energy range 12-150keV. At energies above 40keV, the Hard X-ray emission is mostly produced by bremsstrahlung of suprathermal electrons as they interact with the ambient plasma in the chromosphere. The observed photon spectra therefore provide diagnostics of electron acceleration processes in Solar flares. We will present statistical results of spectral fitting using two models: a broken power law plus a thermal component which is a direct fit of the photon spectrum and a thick target model plus a thermal component which is a fit of the photon spectra with assumptions on the electrons emitting bremsstrahlung in the thick target approximation.

  17. Study of radiation effects on the cell structure and evaluation of the dose delivered by x-ray and {alpha}-particles microscopy

    SciTech Connect

    Kosior, Ewelina; Cloetens, Peter; Deves, Guillaume; Ortega, Richard; Bohic, Sylvain

    2012-12-24

    Hard X-ray fluorescence microscopy and magnified phase contrast imaging are combined to study radiation effects on cells. Experiments were performed on freeze-dried cells at the nano-imaging station ID22NI of the European synchrotron radiation facility. Quantitative phase contrast imaging provides maps of the projected mass and is used to evaluate the structural changes due to irradiation during X-ray fluorescence experiments. Complementary to phase contrast imaging, scanning transmission ion microscopy is performed and doses of all the experiments are compared. We demonstrate the sensitivity of the proposed approach to study radiation-induced damage at the sub-cellular level.

  18. Radiation resistance studies of amorphous silicon films

    NASA Technical Reports Server (NTRS)

    Woodyard, James R.; Payson, J. Scott

    1989-01-01

    Hydrogenated amorphous silicon thin films were irradiated with 2.00 MeV helium ions using fluences ranging from 1E11 to 1E15 cm(-2). The films were characterized using photothermal deflection spectroscopy and photoconductivity measurements. The investigations show that the radiation introduces sub-band-gap states 1.35 eV below the conduction band and the states increase supralinearly with fluence. Photoconductivity measurements suggest the density of states above the Fermi energy is not changing drastically with fluence.

  19. Study on micro-hardness of electroless composite plating of Ni-P with SiC Nano-particles

    NASA Astrophysics Data System (ADS)

    Sun, Yong; Zhang, Zhaoguo; Li, Jiamin; Xu, Donghui

    2007-07-01

    In this paper, a Ni-P electroless composite coating containing nano SiC particles was produced. The wearability of the composite coating was studied. Temperature, PH of the plating liquid and the concentration of SiC nanoparticles in the plating liquid were taken as parameters and the experiment with three factors and five levels was designed through the method of quadratic orthogonal rotation combination. SiC nanoparticles were dispersed by ultrasonic. The influence of the testing parameters on the hardness of the coating was studied intensively. The optimal parameters were obtained when the temperature is 86+/-1°C, PH is 6+/-0.5 and the concentration of SiC nanoparticles is 6g/L. The maximal hardness of the coating is over 1700HV after heat treatment.

  20. [The study of transpiration influence on plant infrared radiation character].

    PubMed

    Ling, Jun; Zhang, Shuan-Qin; Pan, Jia-Liang; Lian, Chang-Chun; Yang, Hui

    2012-07-01

    Studying vegetation infrared radiation character is the base of developing infrared camouflage and concealment technology of ground military target. Accurate fusion of target and background can be achieved by simulating formation mechanism of vegetation infrared radiation character. Leaf transpiration is characteristic physiological mechanism of vegetation and one of the main factors that influence its infrared radiation character. In the present paper, physical model of leaf energy balance is set up. Based on this model the influence of plant transpiration on leaf temperature is analyzed and calculated. The daily periodic variation of transpiration, leaf temperature and infrared radiation character of typical plants such as camphor tree and holly is actually measured with porometer and infrared thermal imaging system. By contrasting plant leaf with dryness leaf, experimental data indicates that plant transpiration can regulate leaf energy balance effectively and control leaf temperature in a reasonable range and suppress deep range variation of leaf infrared radiation character.

  1. Determination of the total nitrogen content of hard, semihard, and processed cheese by the Kjeldahl method: collaborative study.

    PubMed

    Lynch, Joanna M; Barbano, David M; Fleming, J Richard

    2002-01-01

    The objective of this collaborative study was to determine interlaboratory performance statistics for a modified and optimized version of AOAC Method 920.123 for the determination of the total nitrogen content of hard, semihard, and processed cheese by Kjeldahl analysis. Details included addressing the issues of material homogeneity, test portion size (1 g), quantitative transfer (weighing on to filter paper), ensuring system suitability (nitrogen recoveries), and using AOAC Method 991.20 as the basis for nitrogen analysis. Fifteen laboratories tested 18 pairs of blind duplicate cheese materials with a crude protein content between 18 and 36%. Materials represented hard, semihard, and processed commercial cheeses with a wide range of composition. Statistical performance parameters expressed as crude protein (nitrogen x 6.38), g/100 g, with invalid and outlier data removed were mean = 26.461, repeatability standard deviation (Sr) 0.111, reproducibility standard deviation (S(R)) = 0.153, repeatability relative standard deviation (RSDr) = 0.42%, reproducibility relative standard deviation (RSDR) = 0.58%, repeatability (r) = 0.312, and reproducibility (R) = 0.428. The interlaboratory study results were acceptable and comparable to those for the milk Kjeldahl nitrogen method on a relative nitrogen basis. The Study Directors recommend that this modified method for the determination of total nitrogen in hard, semihard, and processed cheese by Kjeldahl analysis be adopted First Action as an improved method to replace Method 920.123.

  2. A spin dependent recombination study of radiation induced defects at and near the Si/SiO sub 2 interface

    SciTech Connect

    Jupina, M.A.; Lenahan, P.M. )

    1989-12-01

    A new electron spin resonance technique, spin dependent recombination (SDR) permits extremely rapid, high signal to noise ratio electron spin resonance (ESR) measurements of electrically active radiation damage centers in (relatively) hard MOS transistors in integrated circuits. Using SDR the authors observe the radiation induced buildup of Pbo and E' centers at relatively low concentration in individual MOSFETs in integrated circuits with (100) silicon surface orientation. Earlier ESR studies of extremely large ({approximately}1 cm{sup 2}) capacitor structures have identified Pb and E' centers as the dominant radiation induced defects in MOS devices. The authors discuss how their results extend and confirm these earlier results and at least qualitatively answer objections to the earlier work related to the relevance of large capacitor studies to transistors in an integrated circuit.

  3. Gallium arsenide solar cell radiation damage study

    NASA Technical Reports Server (NTRS)

    Maurer, R. H.; Herbert, G. A.; Kinnison, J. D.; Meulenberg, A.

    1989-01-01

    A thorough analysis has been made of electron- and proton- damaged GaAs solar cells suitable for use in space. It is found that, although some electrical parametric data and spectral response data are quite similar, the type of damage due to the two types of radiation is different. An I-V analysis model shows that electrons damage the bulk of the cell and its currents relatively more, while protons damage the junction of the cell and its voltages more. It is suggested that multiple defects due to protons in a strong field region such as a p/n junction cause the greater degradation in cell voltage, whereas the individual point defects in the quasi-neutral minority-carrier-diffusion regions due to electrons cause the greater degradation in cell current and spectral response.

  4. [Radiation Environment Study of Near Space in China Area].

    PubMed

    Mei, Xiao-dong; Sun, Ji-lin; Li, Zheng-qiang; Chen, Xing-feng; Xing, Jin; Xu, Hua; Qie, Li-li; Lü, Yang; Li, Yang; Liu, Li

    2016-03-01

    Aerospace activity in near space (20-50 km) has become a research hotspot for aviation big countries worldwide. Solar radiation study, as the prerequisite to carry out aerospace activity, is facing the barrier of lacking of observation in near space layer. Ozone is the most important factor that affects radiation value in this layer. Based on ECMWF reanalysis data, this input key parameter and its horizontal, vertical and temporal characteristics are analyzedwith results showing obvious regional features in temporal-spatial distribution and varieties. With meteorological data and surface parameters, near space over China is divided into 5 parts. Key factors' value is confirmed over each division. With SBDART radiation transfer model, solar radiation and ultraviolet radiation simulation in near space are conducted separately. Results show that it is influenced by latitude, total ozone and its vertical distribution, radiation varies under complex rules. The average year and monthly solar radiation strengthens changes with latitude reduction, while annual range changes reversely. Air absorbing is related to latitude and land-sea contrast and shows different values and seasonal variations. The ultraviolet radiation over South China Sea reaches its maximum value and minimum annual range, as well as minimum monthly range with value strengthening in summer and weakening in winter. In other areas radiation increases in summer while weakens in winter, monthly range shows double peaks with higher value in spring and autumn, lower in summer and winter. Air absorption in ultraviolet radiation is influenced by multiple factors, vertical varieties over areas besides South China Sea enhance in summer time. The vertical changes of monthly ranges affected by air absorption show consistence in higher and lower layer in June and July, while in other months ranges are bigger in higher layer.

  5. In situ studies of nucleation and assembly at soft-hard interfaces

    SciTech Connect

    Dutta, Pulak

    2013-04-01

    The overall goal of this project was the exploration of new ways to make organic and hybrid (organic-inorganic) materials for energy-related applications. Towards this end, our research focused on the structure and behavior of molecular monolayers at interfaces (including floating monolayers, transferred Langmuir-Blodgett monolayers, and self-assembled monolayers), as well as the biomimetic nucleation of inorganic crystals at soft-hard interfaces. The project resulted in a number of 'firsts' and other notable achievements, which are described in the report.

  6. A study of starting time in great hard X-ray flares

    NASA Technical Reports Server (NTRS)

    Klein, K. L.; Pick, M.; Magun, A.

    1986-01-01

    An analysis of the starting time in ten great hard X-ray bursts observed with the X-Ray Burst Spectrometer (HXRBS) is presented. It is shown that the impulsive phase of nine of them is composed of a preflash phase, during which the burst is observed up to an energy limit ranging from some tens of keV to 200 keV, followed ten to some tens of seconds afterwards by a flash phase, where the count rate rises simultaneously in all detector channels. For two events strong gamma-ray line emission is observed and is shown to start close to the onset of the flash phase.

  7. Experimental and simulation studies of hard contact in force reflecting teleoperation

    NASA Technical Reports Server (NTRS)

    Hannaford, Blake; Anderson, Robert

    1988-01-01

    Experiments and simulations of a single-axis force-reflecting teleoperation system have been conducted to investigate the problem of contacting a hard environment and maintaining a controlled force in teleoperation in which position is fed forward from the hand controller (master) to the manipulator (slave), and force is fed back to the human operator through motors in the master. The simulations, using an electrical circuit model, reproduce the behavior of the real system, including effects of human operator biomechanics. It is shown that human operator properties, which vary as a result of different types of grasp of the handle, affect the stability of the system in the hard-contact task. The effect of a heavier grasp on the handle is equivalent to increased hand-controller velocity damping in terms of the systems stability in the contact task, but control system damping sufficient to guarantee stable contact results in perceptible sluggishness of the control handle's response in free motion. These results suggest that human operator biomechanics must be taken into account to guarantee stable and ergonomic performance of advanced teleoperators.

  8. Comparative study of the shell development of hard- and soft-shelled turtles.

    PubMed

    Nagashima, Hiroshi; Shibata, Masahiro; Taniguchi, Mari; Ueno, Shintaro; Kamezaki, Naoki; Sato, Noboru

    2014-07-01

    The turtle shell provides a fascinating model for the investigation of the evolutionary modifications of developmental mechanisms. Different conclusions have been put forth for its development, and it is suggested that one of the causes of the disagreement could be the differences in the species of the turtles used - the differences between hard-shelled turtles and soft-shelled turtles. To elucidate the cause of the difference, we compared the turtle shell development in the two groups of turtle. In the dorsal shell development, these two turtle groups shared the gene expression profile that is required for formation, and shared similar spatial organization of the anatomical elements during development. Thus, both turtles formed the dorsal shell through a folding of the lateral body wall, and the Wnt signaling pathway appears to have been involved in the development. The ventral portion of the shell, on the other hand, contains massive dermal bones. Although expression of HNK-1 epitope has suggested that the trunk neural crest contributed to the dermal bones in the hard-shelled turtles, it was not expressed in the initial anlage of the skeletons in either of the types of turtle. Hence, no evidence was found that would support a neural crest origin.

  9. Metallography studies and hardness measurements on ferritic/martensitic steels irradiated in STIP

    NASA Astrophysics Data System (ADS)

    Zhang, H.; Long, B.; Dai, Y.

    2008-06-01

    In this work metallography investigations and microhardness measurements have been performed on 15 ferritic/martensitic (FM) steels and 6 weld metals irradiated in the SINQ Target Irradiation Program (STIP). The results demonstrate that all the steels have quite similar martensite lath structures. However, the sizes of the prior austenite grain (PAG) of these steels are quite different and vary from 10 to 86 μm. The microstructure in the fusion zones (FZ) of electron-beam welds (EBWs) of 5 steels (T91, EM10, MANET-II, F82H and Optifer-IX) is similar in respect to the martensite lath structure and PAG size. The FZ of the inert-gas-tungsten weld (TIGW) of the T91 steel shows a duplex structure of large ferrite gains and martensite laths. The microhardness measurements indicate that the normalized and tempered FM steels have rather close hardness values. The unusual high hardness values of the EBW and TIGW of the T91 steel were detected, which suggests that these materials are without proper tempering or post-welding heat treatment.

  10. Nuclear-chemical methods in a hard tooth tissue abrasion study

    NASA Astrophysics Data System (ADS)

    Gosman, A.; Spěváček, V.; Koníček, J.; Vopálka, D.; Houŝová, D.; Doležalová, L.

    1999-01-01

    The advanced method consists in implantation—labelling of the thin surface layers of the solid objects, e.g. hard tooth tissue, by atoms of suitable natural or artificial radionuclides. Nuclides from the uranium series were implanted into the surface by using nuclear recoil effect at alpha decay of 226Ra to 222Rn, alpha decay of 222Rn to RaA, alpha decay of RaA to RaB (beta-emitter) and further alpha or beta emitters. With regard to chosen alpha detection and to the half—lives of the radionuclides, there was actually measured the activity of 222Rn, RaA and RaC’ in the thin surface layer. This was followed by the laboratory simulation of the abrasion in the system of “toothbrush—various suspensions of the tooth-pastes—hard tooth tissue (or material standard—ivory)” in specially designed device—the dentoabrasionmeter. The activities of the tissue surface measured before and after abrasion were used for calculations of the relative drop of the surface activity. On this basis the influence of various tooth-pastes containing various abrasive substances was determined.

  11. Freezable Radiator Model Correlation Improvements and Fluids Study

    NASA Technical Reports Server (NTRS)

    Lillibridge, Sean; Navarro, Moses

    2011-01-01

    Freezable radiators offer an attractive solution to the issue of thermal control system scalability. As thermal environments change, a freezable radiator will effectively scale the total heat rejection it is capable of as a function of the thermal environment and flow rate through the radiator. Scalable thermal control systems are a critical technology for spacecraft that will endure missions with widely varying thermal requirements. These changing requirements are a result of the space craft s surroundings and because of different thermal rejection requirements during different mission phases. However, freezing and thawing (recovering) a radiator is a process that has historically proven very difficult to predict through modeling, resulting in highly inaccurate predictions of recovery time. To attempt to improve this, tests were conducted in 2009 to determine whether the behavior of a simple stagnating radiator could be predicted or emulated in a Thermal Desktop(trademark) numerical model. A 50-50 mixture of DowFrost HD and water was used as the working fluid. Efforts to scale this model to a full scale design, as well as efforts to characterize various thermal control fluids at low temperatures are also discussed. Previous testing and modeling efforts showed that freezable radiators could be operated as intended, and be fairly, if not perfectly predicted by numerical models. This paper documents the improvements made to the numerical model, and outcomes of fluid studies that were determined necessary to go forward with further radiator testing.

  12. Megacity Radiative Forcing: A Mexico City Case Study

    NASA Astrophysics Data System (ADS)

    Dubey, M.; Olsen, S.; Mazzoleni, C.; Chylek, P.; Zhang, Y.; Randerson, J. T.; Horowitz, L.

    2007-05-01

    We assess the radiative forcing of the largest megacity in North America, Mexico City. While particular aspects of the regional environmental impacts of cities on their surroundings have been thoroughly investigated, e.g., air quality and acid rain, relatively little effort has been focused on the net radiative impact of a megacity on global climate. The range of radiative impacts from a megacity covers many spatial and temporal scales from short-term regional-scale effects due to aerosols and relatively short-lived gases (ozone) to long-term global-scale impacts due to longer-lived trace gases (e.g., carbon dioxide, methane). In this study we combine chemistry-transport model simulations from the Model for Ozone And Related Chemical Tracers (MOZART-2) with in situ and satellite observations from the Aerosol Robotic Network (AERONET) and the Moderate Resolution Imaging Spectroradiometer (MODIS) to calculate the global radiative forcing of megacity emissions. We also explore the radiative impact of various emission control strategies that focus on improving regional air quality. Our results suggest that the warming by greenhouse gases like carbon dioxide and ozone can be moderated or exacerbated by aerosols depending on their optical properties. As the size and number of megacities increase and clean air regulations are implemented, metrics such as the net radiative forcing may become increasingly important in comparing the impact of urban centers and assessing the trade-offs between improving local air quality and minimizing global radiative impacts.

  13. A systematic review of analytical observational studies investigating the association between cardiovascular disease and drinking water hardness.

    PubMed

    Catling, Louise A; Abubakar, Ibrahim; Lake, Iain R; Swift, Louise; Hunter, Paul R

    2008-12-01

    The aim of this study is to systematically review and critically assess analytical observational epidemiology studies investigating the association between levels of drinking water hardness and cardiovascular disease. We searched electronic databases and used standardised forms to extract data and assess study quality. Of 2,906 papers identified, 14 met the inclusion criteria (nine case control and five cohort studies). Of the nine case control studies, seven examined both drinking water magnesium and calcium and risk of death from cardiovascular disease. A pooled odds ratio showed a statistically significant inverse association between magnesium and cardiovascular mortality (OR 0.75 (95%CI 0.68, 0.82), p < 0.001). Only two studies reported a statistically significant effect for calcium. Substantial heterogeneity between studies made calculation of a summary estimate for drinking water calcium inappropriate. Of three cohort studies reviewed, two were of good quality. A weak suggestion that soft water was harmful in females and possibly associated with a slightly greater risk of sudden death was reported, but there was no association between water hardness and mortality from stroke or cardiovascular disease. This study found significant evidence of an inverse association between magnesium levels in drinking water and cardiovascular mortality following a meta-analysis of case control studies. Evidence for calcium remains unclear.

  14. Studies Concerned with Basic Radiation Protection Criteria and Studies Concerned with Guidance and Information.

    DTIC Science & Technology

    2014-09-26

    has been completed and is ready to enter the review stage. Task Group 2 Uranium Mining and Milling - Radiation Safety Programs - A draft report is in...8217RD-fl158 319 STUDIES CONCERNED WITH BASIC RADIATION PROTECTION i/i I CRITERIA AND STUDIES CO..(U) N T ONAL COUNCIL ON I RADIATION PROTECTION AND...NATIONAL BUREAU Of STANDARDS 1963 A ’--- ( National Council on Radiation Protection and Measurements 7910 WOODMONT AVENUE, SUITE 1016, BETHESDA

  15. [Update in radiation-induced neoplasms: genetic studies].

    PubMed

    Chauveinc, Laurent; Lefevre, Sandrine; Malfoy, Bernard; Dutrillaux, Bernard

    2002-02-01

    Radiation induced tumors are a possible (very) late complications of radiotherapy. The evaluation of the risks of radiation-induced tumors has been presented in different epidemiological studies, with the evaluation of the relative risk for different tissues. But, the genetic studies are rare, and no global theory exists. Two cytogenetic profiles are described, one with translocations and one with genetic material losses, evoking two different genetic evolutions. Two questions are stated. What are the radiation-induced genetic mechanisms? Is it possible to differentiate the radiation-induced and spontaneous tumors with genetic approaches? With 37 cytogenetic cases, 12 analyzed in our laboratory, the radiation-induced tumors were characterized by genetic material losses. An anti-oncogenic evolution is probable. A new molecularly study confirm these results. Only thyroid tumors do not have this evolution. For tumors with simple karyotype, like meningioma, radiation-induced tumors seem to be more complex than spontaneous tumors. But for the others, the differentiation is impossible to be done with cytogenetic. The mechanism of the chromosomic material losses in unknown, but some hypothesis are discussed.

  16. Comparative study of mechanical properties of dental restorative materials and dental hard tissues in compressive loads

    PubMed Central

    Lee, Jong Yeop

    2014-01-01

    There are two objectives. One is to show the differences in the mechanical properties of various dental restorative materials compared to those of enamel and dentin. The other is to ascertain which dental restorative materials are more suitable for clinical treatments. Amalgam, dental ceramic, gold alloy, dental resin, zirconia, and titanium alloy were processed as dental restorative material specimens. The specimens (width, height, and length of 1.2, 1.2, and 3.0 mm, respectively) were compressed at a constant loading speed of 0.1 mm/min. The maximum stress (115.0 ± 40.6, 55.0 ± 24.8, 291.2 ± 45.3, 274.6 ± 52.2, 2206.0 ± 522.9, and 953.4 ± 132.1 MPa), maximum strain (7.8% ± 0.5%, 4.0% ± 0.1%, 12.7% ± 0.8%, 32.8% ± 0.5%, 63.5% ± 14.0%, and 45.3% ± 7.4%), and elastic modulus (1437.5 ± 507.2, 1548.4 ± 583.5, 2323.4 ± 322.4, 833.1 ± 92.4, 3895.2 ± 202.9, and 2222.7 ± 277.6 MPa) were evident for amalgam, dental ceramic, gold alloy, dental resin, zirconia, and titanium alloy, respectively. The reference hardness value of amalgam, dental ceramic, gold alloy, dental resin, zirconia, and titanium alloy was 90, 420, 130–135, 86.6–124.2, 1250, and 349, respectively. Since enamel grinds food, its abrasion resistance is important. Therefore, hardness value should be prioritized for enamel. Since dentin absorbs bite forces, mechanical properties should be prioritized for dentin. The results suggest that gold alloy simultaneously has a hardness value lower than enamel (74.8 ± 18.1), which is important in the wear of the opposing natural teeth, and higher maximum stress, maximum strain, and elastic modulus than dentin (193.7 ± 30.6 MPa, 11.9% ± 0.1%, 1653.7 ± 277.9 MPa, respectively), which are important considering the rigidity to absorb bite forces. PMID:25352921

  17. American Society for Radiation Oncology (ASTRO) 2012 Workforce Study: The Radiation Oncologists' and Residents' Perspectives

    SciTech Connect

    Pohar, Surjeet; Fung, Claire Y.; Hopkins, Shane; Miller, Robert; Azawi, Samar; Olsen, Christine

    2013-12-01

    Purpose: The American Society for Radiation Oncology (ASTRO) conducted the 2012 Radiation Oncology Workforce Survey to obtain an up-to-date picture of the workforce, assess its needs and concerns, and identify quality and safety improvement opportunities. The results pertaining to radiation oncologists (ROs) and residents (RORs) are presented here. Methods: The ASTRO Workforce Subcommittee, in collaboration with allied radiation oncology professional societies, conducted a survey study in early 2012. An online survey questionnaire was sent to all segments of the radiation oncology workforce. Respondents who were actively working were included in the analysis. This manuscript describes the data for ROs and RORs. Results: A total of 3618 ROs and 568 RORs were surveyed. The response rate for both groups was 29%, with 1047 RO and 165 ROR responses. Among ROs, the 2 most common racial groups were white (80%) and Asian (15%), and the male-to-female ratio was 2.85 (74% male). The median age of ROs was 51. ROs averaged 253.4 new patient consults in a year and 22.9 on-treatment patients. More than 86% of ROs reported being satisfied or very satisfied overall with their career. Close to half of ROs reported having burnout feelings. There was a trend toward more frequent burnout feelings with increasing numbers of new patient consults. ROs' top concerns were related to documentation, reimbursement, and patients' health insurance coverage. Ninety-five percent of ROs felt confident when implementing new technology. Fifty-one percent of ROs thought that the supply of ROs was balanced with demand, and 33% perceived an oversupply. Conclusions: This study provides a current snapshot of the 2012 radiation oncology physician workforce. There was a predominance of whites and men. Job satisfaction level was high. However a substantial fraction of ROs reported burnout feelings. Perceptions about supply and demand balance were mixed. ROs top concerns reflect areas of attention for the

  18. Preliminary design study of underground pumped hydro and compressed-air energy storage in hard rock. Volume 1: Executive summary

    NASA Astrophysics Data System (ADS)

    1981-05-01

    A preliminary design study of water compensated Compressed Air Energy Storage (CAES) and Underground Pumped Hydroelectric (UPH) plants for siting in geological conditions suitable for hard rock excavations was performed. The study was divided into five primary tasks as follows: establishment of design criteria and analysis of impact on power system; selection of site and establishment of site characteristics; formulation of design approaches; assessment of environmental and safety aspects; and preparation of preliminary design of plant. The salient aspects considered and the conclusions reached during the consideration of the five primary tasks for both CAES and UPH are presented.

  19. Studies on the multistage nature of radiation carcinogenesis

    SciTech Connect

    Fry, R.J.M.; Ley, R.D.; Grube, D.; Staffeldt, E.

    1980-01-01

    With low dose levels of ionizing or ultraviolet radiation, the number of initiation events exceeds the number of tumors that grow to a detectable size. Ionizing radiation, which is a complete carcinogen, appears to be a more effective initiator than an enhancer or promoter. However, the initiation and promotion aspects of ionizing radiation have been studied in very few organ systems. In the case of UVR, with or without photosensitizers such as psoralens, the requirement of a relatively large number of exposures for carcinogenesis suggests that the expression of the initiated cells as frank tumors requires a number of events spread out over the time of the development of the tumor. Both ionizing and ultraviolet radiation are, perhaps, underutilized as tools for probing the mechanism of both initiation and promotion.

  20. A study of distortion and surface hardness of improved artificial stone casts.

    PubMed

    Kaiser, D A; Nicholls, J I

    1976-10-01

    1. The single-pour technique is as accurate as the double-pour technique except for point 6 (palatal point). Here the double-pour technique has greater accuracy. Impression material thickness over point 6 was approximately 15 mm. 2. The double-pour technique produced specimens which had superficial hardness values significantly higher than those of casts produced by the single-pour technique. 3. Specimens made with slurry water showed no greater distortion than specimens from other techniques. Surfaces of the specimens made with slurry water were significantly harder than those of specimens made with distilled water. Both types of specimens were made with the single-pour technique. 4. No significant difference in distortion was found in specimens produced with varying thickness of irreversible hydrocolloid impression material over the occlusal pins.

  1. Why Do Some Find it Hard to Disagree? An fMRI Study

    PubMed Central

    Domínguez D, Juan F.; Taing, Sreyneth A.; Molenberghs, Pascal

    2016-01-01

    People often find it hard to disagree with others, but how this disposition varies across individuals or how it is influenced by social factors like other people's level of expertise remains little understood. Using functional magnetic resonance imaging (fMRI), we found that activity across a network of brain areas [comprising posterior medial frontal cortex (pMFC), anterior insula (AI), inferior frontal gyrus (IFG), lateral orbitofrontal cortex, and angular gyrus] was modulated by individual differences in the frequency with which participants actively disagreed with statements made by others. Specifically, participants who disagreed less frequently exhibited greater brain activation in these areas when they actually disagreed. Given the role of this network in cognitive dissonance, our results suggest that some participants had more trouble disagreeing due to a heightened cognitive dissonance response. Contrary to expectation, the level of expertise (high or low) had no effect on behavior or brain activity. PMID:26858629

  2. Numerical investigation to study effect of radiation on thermal performance of radiator for onan cooling configuration of transformer

    NASA Astrophysics Data System (ADS)

    Chandak, V.; Paramane, S. B.; Veken, W. V. d.; Codde, J.

    2015-09-01

    In the present work, flow and temperature distribution in the radiator fins of a power transformer is studied numerically with conjugate heat transfer using commercial CFD software to study the effect of radiation on heat dissipation. The approach considered here is a complete 3D geometry of the radiator fins with average height of the flute geometry of the fins for meshing and computational time reduction. Simulations are performed for ONAN (Oil Natural Air Natural) case for one radiator configuration. The simulations also study the effect of radiation and its impact on the overall heat dissipation. These results would give a holistic picture of heat transfer phenomenon to the designers.

  3. Loads on Sprayed Waterproof Tunnel Linings in Jointed Hard Rock: A Study Based on Norwegian Cases

    NASA Astrophysics Data System (ADS)

    Holter, Karl Gunnar

    2014-05-01

    A composite tunnel lining system based on a sprayed waterproofing membrane combined with sprayed concrete is currently being considered for future Norwegian rail and road tunnels. Possible loading of the tunnel linings caused by water pressure is being investigated. This tunnel lining system consists of a waterproof membrane which, during application on the sprayed concrete lining, bonds mechanically to the sprayed concrete on either side. Hence, a continuous, sealing, and non-draining structure from the rock mass to the interior tunnel surface is formed in the walls and crown. Experiences from some successful recent projects with this lining system in Europe are reviewed. However, these experiences are not directly comparable to the Scandinavian hard rock tunnel lining approach, which utilizes a relatively thin sprayed and irregular concrete layer for permanent lining. When considering the sprayed membrane and sprayed concrete composite lining concept, introducing a partially sealing and undrained element in the lining, the experiences with the traditionally used lining systems in Norway need to be reconsidered and fully understood. A review of several hard rock tunnels with adverse conditions, in which the tunnel lining has been subject to load monitoring, shows that only very small loads in the tunnel linings occur. Recent investigations with in situ water pressure testing, including two sites with the composite sprayed membrane in a partially drained waterproof tunnel lining, are discussed. In a case with a cavern located in a hydraulically saturated rock mass subjected to approximately 8 bar hydrostatic pressure, a negative pressure gradient towards the tunnel lining has been measured. The investigation results from the Norwegian test sites indicate that no significant loading of the tunnel lining takes place in a hydraulically saturated rock when applying this composite waterproof tunnel lining in parts of the tunnel perimeter.

  4. Studies of high temperature superconductors as radiation detectors

    NASA Astrophysics Data System (ADS)

    Qiu, A.; Bhattarai, A. R.; Dahlberg, E. D.; Khan, M. Asif; Moloni, K.; van Hove, James M.

    1992-12-01

    Both DyBaCuO (DBCO) and YBaCuO (YBCO) films deposited on a variety of substrates have been investigated for their applicability as detectors of high frequency radiation. Both 10 GHz and infrared radiation (IR) were used as the high frequency radiation source. The measurements consisted of monitoring the temperature dependent resistance of superconducting films both in the presence and absence of radiation. This investigation shows that because the superconducting transition temperature is sensitive to the magnitude of the current in the film, the temperature dependence of the bolometric response is slightly tunable. In addition, effects of radiation on the current voltage characteristics below T superconducting were studied. This study found that films in this regime could also serve as radiation detectors. The substrates used included MgO, SiO, LaAlO(subscript 3), and SrTiO(subscript 3). The results obtained were independent of the substrate except for the width of the resistive transition. Disorder in the films as characterized by the resistive transition, affected the microwave more than the IR response.

  5. Radiation

    NASA Video Gallery

    Outside the protective cocoon of Earth's atmosphere, the universe is full of harmful radiation. Astronauts who live and work in space are exposed not only to ultraviolet rays but also to space radi...

  6. A simple solar radiation index for wildlife habitat studies

    USGS Publications Warehouse

    Keating, Kim A.; Gogan, Peter J.; Vore, John N.; Irby, Lynn R.

    2007-01-01

    Solar radiation is a potentially important covariate in many wildlife habitat studies, but it is typically addressed only indirectly, using problematic surrogates like aspect or hillshade. We devised a simple solar radiation index (SRI) that combines readily available information about aspect, slope, and latitude. Our SRI is proportional to the amount of extraterrestrial solar radiation theoretically striking an arbitrarily oriented surface during the hour surrounding solar noon on the equinox. Because it derives from first geometric principles and is linearly distributed, SRI offers clear advantages over aspect-based surrogates. The SRI also is superior to hillshade, which we found to be sometimes imprecise and ill-behaved. To illustrate application of our SRI, we assessed niche separation among 3 ungulate species along a single environmental axis, solar radiation, on the northern Yellowstone winter range. We detected no difference between the niches occupied by bighorn sheep (Ovis canadensis) and elk (Cervus elaphus; P = 0.104), but found that mule deer (Odocoileus hemionus) tended to use areas receiving more solar radiation than either of the other species (P < 0.001). Overall, our SRI provides a useful metric that can reduce noise, improve interpretability, and increase parsimony in wildlife habitat models containing a solar radiation component.

  7. Study Regarding Electromagnetic Radiation Exposure Generated By Mobile Phone

    SciTech Connect

    Marica, Lucia; Moraru, Luminita

    2011-12-26

    Number of mobile phone users reached to 5 billion subscribers in 2010 [ABI Research, 2010]. A large number of studies illustrated the public concern about adverse effects of mobile phone radiation and possible health hazards. Position of mobile phone use in close proximity to the head leads the main radiation between the hand and the head. Many investigations studying the possible effects of mobile phone exposure, founded no measurable effects of short-term mobile phone radiation, and there was no evidence for the ability to perceive mobile phone EMF in the general population. In this study, field radiation measurements were performed on different brand and different models of mobile phones in active mode, using an EMF RF Radiation Field Strength Power Meter 1 MHz-8 GHz. The study was effectuated on both the 2G and 3G generations phones connected to the providers operating in the frequency range 450 MHz-1800 MHz. There were recorded values in outgoing call and SMS mode, incoming call and SMS mode. Results were compared with ICNIRP guidelines for exposure to general public.

  8. Study Regarding Electromagnetic Radiation Exposure Generated By Mobile Phone

    NASA Astrophysics Data System (ADS)

    Marica, Lucia; Moraru, Luminita

    2011-12-01

    Number of mobile phone users reached to 5 billion subscribers in 2010 [ABI Research, 2010]. A large number of studies illustrated the public concern about adverse effects of mobile phone radiation and possible health hazards. Position of mobile phone use in close proximity to the head leads the main radiation between the hand and the head. Many investigations studying the possible effects of mobile phone exposure, founded no measurable effects of short-term mobile phone radiation, and there was no evidence for the ability to perceive mobile phone EMF in the general population. In this study, field radiation measurements were performed on different brand and different models of mobile phones in active mode, using an EMF RF Radiation Field Strength Power Meter 1 MHz-8 GHz. The study was effectuated on both the 2G and 3G generations phones connected to the providers operating in the frequency range 450 MHz-1800 MHz. There were recorded values in outgoing call and SMS mode, incoming call and SMS mode. Results were compared with ICNIRP guidelines for exposure to general public.

  9. Radiation Studies with Argentine Ion Exchange Material

    SciTech Connect

    Crawford, C.L.

    2002-06-28

    A recent technology exchange between Argentina Nuclear Energy Commission (CNEA) and the US Department of Energy involved vitrification studies of ion exchange resins. Details of the spent ion exchange resins currently stored at two Argentine nuclear power plants, Atucha I and Embalse, have been presented in earlier reports. The present study examines irradiation of simulant samples of ion exchange resins.

  10. Atomic Force Microscopy Study of an Ideally Hard Contact: The Diamond{bold (}111{bold )}/Tungsten Carbide Interface

    SciTech Connect

    Enachescu, M.; van den Oetelaar, R.J.; Carpick, R.W.; Ogletree, D.F.; Flipse, C.F.; Salmeron, M.

    1998-08-01

    A comprehensive nanotribological study of a hydrogen-terminated diamond(111)/tungsten carbide interface has been performed using ultrahigh vacuum atomic force microscopy. Both contact conductance, which is proportional to contact area, and friction have been measured as a function of applied load. We demonstrate for the first time that the load dependence of the contact area in UHV for this extremely hard single asperity contact is described by the Derjaguin-M{umlt u}ller-Toporov continuum mechanics model. Furthermore, the frictional force is found to be directly proportional to the contact area. {copyright} {ital 1998} {ital The American Physical Society}

  11. STUDYING THE POLARIZATION OF HARD X-RAY SOLAR FLARES WITH THE GAMMA RAY POLARIMETER EXPERIMENT (GRAPE)

    NASA Astrophysics Data System (ADS)

    Ertley, Camden

    2014-01-01

    The degree of linear polarization of hard X-rays (50-500 keV) can provide a better understanding of the particle acceleration mechanisms and the emission of radiation during solar flares. Difficulties in measuring the linear polarization has limited the ability of past experiments to place constraints on solar flare models. The Gamma RAy Polarimeter Experiment (GRAPE) is a balloon-borne Compton polarimeter designed to measure polarization in the 50 - 500 keV energy range. This energy range minimizes the thermal contamination that can potentially affect measurements at lower energies. This research focuses on the analysis of data acquired during the first high altitude balloon flight of the GRAPE payload in 2011. During this 26 hour balloon flight two M-class flares were observed. The analysis effort includes the development of a Monte Carlo simulation of the full instrument payload with the GEANT4 toolkit. The simulations were used in understanding the background environment, creating a response matrix for the deconvolution of the energy loss spectra, and determining the modulation factor for a 100% linearly polarized source. We report on the results from the polarization analysis of the solar flare data. The polarization and spectral data can be used to further our understanding of particle acceleration in the context of current solar flare models.

  12. Simulation and experimental study of aspect ratio limitation in Fresnel zone plates for hard-x-ray optics.

    PubMed

    Liu, Jianpeng; Shao, Jinhai; Zhang, Sichao; Ma, Yaqi; Taksatorn, Nit; Mao, Chengwen; Chen, Yifang; Deng, Biao; Xiao, Tiqiao

    2015-11-10

    For acquiring high-contrast and high-brightness images in hard-x-ray optics, Fresnel zone plates with high aspect ratios (zone height/zone width) have been constantly pursued. However, knowledge of aspect ratio limits remains limited. This work explores the achievable aspect ratio limit in polymethyl methacrylate (PMMA) by electron-beam lithography (EBL) under 100 keV, and investigates the lithographic factors for this limitation. Both Monte Carlo simulation and EBL on thick PMMA are applied to investigate the profile evolution with exposure doses over 100 nm wide dense zones. A high-resolution scanning electron microscope at low acceleration mode for charging free is applied to characterize the resultant zone profiles. It was discovered for what we believe is the first time that the primary electron-beam spreading in PMMA and the proximity effect due to extra exposure from neighboring areas could be the major causes of limiting the aspect ratio. Using the optimized lithography condition, a 100 nm zone plate with aspect ratio of 15/1 was fabricated and its focusing property was characterized at the Shanghai Synchrotron Radiation Facility. The aspect ratio limit found in this work should be extremely useful for guiding further technical development in nanofabrication of high-quality Fresnel zone plates.

  13. Nurses and ionizing radiation: A study of two institutions

    SciTech Connect

    Miracle, V.A.; Wigginton, M.A.

    1990-05-01

    The results of this study revealed that the nurses studied were exposed to ionizing radiation at levels defined as safe. However, since the actual exposure level that increases health risks is unknown, it is recommended that critical care nurses take as many precautions as possible to minimize exposure that, over the long run, could have deleterious effects.

  14. A Two-Year Study of Hard-Core Unemployed Clerical Workers: Effects of Scholastic Achievement, Clerical Skill, and Self-Esteem on Job Success

    ERIC Educational Resources Information Center

    Beatty, Richard W.

    1975-01-01

    This study was designed to longitudinally assess the predictive validity and the nature of the relationships of scholastic achievement, clerical skill, and social self-esteem with the job success of hard-core unemployed clerical workers. (Author/RK)

  15. Hard x-ray tomographic studies of the destruction of an energetic electron ring

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Gekelman, W.; Pribyl, P.

    2013-05-01

    A tomography system was designed and built at the Large Plasma Device to measure the spatial distribution of hard x-ray (100 KeV-3 MeV) emissivity. The x-rays were generated when a hot electron ring was significantly disrupted by a shear Alfvén wave. The plasma is pulsed at 1 Hz (1 shot/s). A lead shielded scintillator detector with an acceptance angle defined by a lead pinhole is mounted on a rotary gimbal and used to detect the x-rays. The system measures one chord per plasma shot using only one detector. A data plane usually consists of several hundred chords. A novel Dot by Dot Reconstruction (DDR) method is introduced to calculate the emissivity profile from the line integrated data. In the experiments, there are often physical obstructions, which make measurements at certain angles impossible. The DDR method works well even in this situation. The method was tested with simulated data, and was found to be more effective than previously published methods for the specific geometry of this experiment. The reconstructed x-ray emissivity from experimental data by this method is shown.

  16. Experimental study of hard-X ray emission from laboratory sparks

    NASA Astrophysics Data System (ADS)

    Marisaldi, Martino; Rizzi, Rolando; Levi, Giuseppe; Malgesini, Roberto; Villa, Andrea; Mazza, Paolo; Labanti, Claudio; Fuschino, Fabio; Campana, Riccardo; Bianchini, David; Brancaccio, Rossella; Montanari, Alessandro; Patrizii, Laura

    2014-05-01

    We present the characterization of hard-X rays produced by meter-long laboratory sparks carried out at the high-voltage laboratory of RSE, Milano, Italy. Sparks are known to emit X-rays when positive and negative streamers connect, before breakdown. Numerical simulations suggest that X-rays are produced by Bremsstrahlung in air by electrons accelerated to the runaway regime in the high electric field at the streamers tip. Positive meter-long discharges are produced by a Marx generator loaded by a meter-long air gap formed by a spherical anode and a conical-shaped cathode. Maximum voltage at breakdown is about 1 MV. We investigate the production of X-rays by means of an array of scintillation detectors deployed around the cathode. Each detector is a 2'' NaI(Tl) scintillating crystal coupled to a photomultiplier tube (PMT). Each detector is battery-powered and enclosed in a metallic housing for EM shielding. Analog signal output is trasmitted to a shielded control room by means of optical fibre tranceivers, and then collected by a fast digitizer. We present the experimental setup and first results concerning detection efficiency, energy spectra, and geometrical distribution of the emission.

  17. Variational Monte Carlo study of soliton excitations in hard-sphere Bose gases

    NASA Astrophysics Data System (ADS)

    Rota, R.; Giorgini, S.

    2015-10-01

    By using a full many-body approach, we calculate the excitation energy, the effective mass, and the density profile of soliton states in a three-dimensional Bose gas of hard spheres at zero temperature. The many-body wave function used to describe the soliton contains a one-body term, derived from the solution of the Gross-Pitaevskii equation, and a two-body Jastrow term, which accounts for the repulsive correlations between atoms. We optimize the parameters in the many-body wave function via a variational Monte Carlo procedure, calculating the grand-canonical energy and the canonical momentum of the system in a moving reference frame where the soliton is stationary. As the density of the gas is increased, significant deviations from the mean-field predictions are found for the excitation energy and the density profile of both dark and gray solitons. In particular, the soliton effective mass m* and the mass m Δ N of missing particles in the region of the density depression are smaller than the result from the Gross-Pitaevskii equation, their ratio, however, being well reproduced by this theory up to large values of the gas parameter. We also calculate the profile of the condensate density around the soliton notch, finding good agreement with the prediction of the local-density approximation.

  18. Study warns of radiation risk in medical imaging

    NASA Astrophysics Data System (ADS)

    Gwynne, Peter

    2009-10-01

    A study of a million US patients suggests that some who undergo medical imaging could be exposed to more ionizing radiation than those who work with radioactive materials in nuclear power plants. The study, reported in The New England Journal of Medicine (361 849), implies that current exposure to radiation from conventional X-ray equipment as well as computed tomography (CT) and positron-emission tomography (PET) scanners could lead to tens of thousands of extra cases of cancer in the US alone.

  19. Evaluating scintillator performance in time-resolved hard X-ray studies at synchrotron light sources

    PubMed Central

    Rutherford, Michael E.; Chapman, David J.; White, Thomas G.; Drakopoulos, Michael; Rack, Alexander; Eakins, Daniel E.

    2016-01-01

    The short pulse duration, small effective source size and high flux of synchrotron radiation is ideally suited for probing a wide range of transient deformation processes in materials under extreme conditions. In this paper, the challenges of high-resolution time-resolved indirect X-ray detection are reviewed in the context of dynamic synchrotron experiments. In particular, the discussion is targeted at two-dimensional integrating detector methods, such as those focused on dynamic radiography and diffraction experiments. The response of a scintillator to periodic synchrotron X-ray excitation is modelled and validated against experimental data collected at the Diamond Light Source (DLS) and European Synchrotron Radiation Facility (ESRF). An upper bound on the dynamic range accessible in a time-resolved experiment for a given bunch separation is calculated for a range of scintillators. New bunch structures are suggested for DLS and ESRF using the highest-performing commercially available crystal LYSO:Ce, allowing time-resolved experiments with an interframe time of 189 ns and a maximum dynamic range of 98 (6.6 bits). PMID:27140147

  20. Evaluating scintillator performance in time-resolved hard X-ray studies at synchrotron light sources.

    PubMed

    Rutherford, Michael E; Chapman, David J; White, Thomas G; Drakopoulos, Michael; Rack, Alexander; Eakins, Daniel E

    2016-05-01

    The short pulse duration, small effective source size and high flux of synchrotron radiation is ideally suited for probing a wide range of transient deformation processes in materials under extreme conditions. In this paper, the challenges of high-resolution time-resolved indirect X-ray detection are reviewed in the context of dynamic synchrotron experiments. In particular, the discussion is targeted at two-dimensional integrating detector methods, such as those focused on dynamic radiography and diffraction experiments. The response of a scintillator to periodic synchrotron X-ray excitation is modelled and validated against experimental data collected at the Diamond Light Source (DLS) and European Synchrotron Radiation Facility (ESRF). An upper bound on the dynamic range accessible in a time-resolved experiment for a given bunch separation is calculated for a range of scintillators. New bunch structures are suggested for DLS and ESRF using the highest-performing commercially available crystal LYSO:Ce, allowing time-resolved experiments with an interframe time of 189 ns and a maximum dynamic range of 98 (6.6 bits).

  1. Biological studies with continuous-wave radiofrequency (28 MHz) radiation

    SciTech Connect

    Wright, N.A.; Borland, R.G.; Cookson, J.H.; Coward, R.F.; Davies, J.A.; Nicholson, A.N.; Christie, J.L.; Flanagan, N.G.; Goodridge, V.D.

    1984-03-01

    Effects of high-frequency (28 MHz) continous-wave radiation have been studied in the rat and monkey. No histopathological or hematological changes could be attributed to the radiation. In the monkey there was an increase in urinary calcium concentration which was most likely due to restricted movement. In the rat there was reduced uptake of iodine by the thyroid, lower levels of plasma thyroid-stimulating hormone, and reduced ratio of protein bound to nonprotein bound iodine. Food consumption was also decreased. The changes are likely to have arisen as a compensatory response to an induced heat load. A nonthermal effect of continuous-wave high-frequency radiation has not been shown in this study. The effects were likely to be associated with either physiological compensation for induced heating or restriction of movement.

  2. High Resolution Cloud Microphysics and Radiation Studies

    DTIC Science & Technology

    2011-06-16

    characteristics of mid level altocumulus clouds and upper level visible and subvisual cirrus clouds The MPL lidar provided information about the temporal...balloon, lidar, and radar study of cirrus and altocumulus clouds to further investigate the presence of multi- cloud and nearly cloud -free layers...data set of the clouds and thermodynanuc structure to build a mesoscale and LF.S test-bed for cirrus and altocumulus cloud layers. The project was

  3. Additive Manufacturing Materials Study for Gaseous Radiation Detection

    SciTech Connect

    Steer, C.A.; Durose, A.; Boakes, J.

    2015-07-01

    Additive manufacturing (AM) techniques may lead to improvements in many areas of radiation detector construction; notably the rapid manufacturing time allows for a reduced time between prototype iterations. The additive nature of the technique results in a granular microstructure which may be permeable to ingress by atmospheric gases and make it unsuitable for gaseous radiation detector development. In this study we consider the application of AM to the construction of enclosures and frames for wire-based gaseous radiation tracking detectors. We have focussed on oxygen impurity ingress as a measure of the permeability of the enclosure, and the gas charging and discharging curves of several simplistic enclosure shapes are reported. A prototype wire-frame is also presented to examine structural strength and positional accuracy of an AM produced frame. We lastly discuss the implications of this study for AM based radiation detection technology as a diagnostic tool for incident response scenarios, such as the interrogation of a suspect radiation-emitting package. (authors)

  4. Design and experimental study of a secondary hohlraum radiation source with laser focal spots blocked

    SciTech Connect

    Song, Tianming Zhu, Tuo; Yang, Jiamin; Huang, Chengwu; Wang, Feng; Peng, Xiaoshi; Xu, Tao; Li, Zhichao; Zhang, Huan

    2016-01-15

    A design of secondary hohlraum radiation source with laser focal spots blocked is introduced. The hard x-ray radiation such as the gold M-band emission and hot electrons from the coronal plasma were designed to be shielded using a cylindrical shield. Three-dimensional view factor analysis was carried out to optimize the shield structure to achieve higher radiation temperature. An experiment was performed at Shenguang III prototype laser facility to verify the design. Velocity Interferometer System for Any Reflector was used to measure the shock wave speed in a three-stepped Al sample driven by this radiation source and the peak radiation temperature of the radiation source was estimated to be about 90 eV.

  5. Design and experimental study of a secondary hohlraum radiation source with laser focal spots blocked

    NASA Astrophysics Data System (ADS)

    Song, Tianming; Zhu, Tuo; Yang, Jiamin; Huang, Chengwu; Wang, Feng; Peng, Xiaoshi; Xu, Tao; Li, Zhichao; Zhang, Huan

    2016-01-01

    A design of secondary hohlraum radiation source with laser focal spots blocked is introduced. The hard x-ray radiation such as the gold M-band emission and hot electrons from the coronal plasma were designed to be shielded using a cylindrical shield. Three-dimensional view factor analysis was carried out to optimize the shield structure to achieve higher radiation temperature. An experiment was performed at Shenguang III prototype laser facility to verify the design. Velocity Interferometer System for Any Reflector was used to measure the shock wave speed in a three-stepped Al sample driven by this radiation source and the peak radiation temperature of the radiation source was estimated to be about 90 eV.

  6. SP-100 radiator design trade study

    NASA Technical Reports Server (NTRS)

    Ewell, Richard

    1992-01-01

    A design trade study of the SP-100 heat rejection subsystem (HRSS) was made. A system code was used to evaluate the sensitivity of the HRSS mass and performance to changes. Variations in heat pipe diameter and cross-section, fin length and thickness, armor thickness, and overall configuration and materials were evaluated. The analysis indicates that the minimum system mass occurs for the case with many small diameter heat pipes, with ducting that maximizes the fraction of the heat pipe evaporator perimeter in contact with it.

  7. Using Synchrotron Radiation to Study Polymer Processing

    NASA Astrophysics Data System (ADS)

    Ryan, Anthony J.

    1998-03-01

    The growth of polymer crystals is well established in the literature and there are reliable theories to predict their kinetics, understanding of the initiation, or nucleation, step remains a mystery. Understanding this step should provide us with insights to the final morphology, and is thus essential to a complete understanding of polymer crystallisation. To probe nucleation behavior, slow, isothermal crystallisations with long induction times were studied by simultaneous, time-resolved SAXS and WAXS. These experiments show clear development of small angle scattering, due to the density fluctuations, with a characteristic length scale of 100 Angstroms, prior to the presence of crystals identified by wide-angle scattering. Once wide-angle diffraction from crystals (atomic order on the 1 Angstrom scale) was observed the kinetics reverted to those of nucleation and growth. This type of behaviour has also been observed in PET and PEEK. X-ray studies during tape extrusion also show SAXS patterns developing before the WAXS patterns. New experimental results for crystallisation of polymers in elongational and shear flow, as well as the quiescent state, will be presented along with a new model for nucleation in polymer crystallisation.

  8. A Study on Effect of Graphite Particles on Tensile, Hardness and Machinability of Aluminium 8011 Matrix Material

    NASA Astrophysics Data System (ADS)

    Latha Shankar, B.; Anil, K. C.; Karabasappagol, Prasann J.

    2016-09-01

    Industrial application point of view, metal matrix composites in general and Aluminium alloy matrix composites in particular are ideal candidates because of their favourable engineering properties. Being lightweight Aluminium matrix composites are widely used in aircraft, defence and automotive industries. In this work Aluminium 8011 metal matrix was reinforced with fine Graphite particles of 50 μm. developed by two-step Stir casting method. Graphite weight %was varied in the range 2, 4, 6 and 8%. Uniform dispersion of graphite particle is examined under optical microscope. Tensile test coupons were prepared as per standard to determine % of elongation and tensile strength for various % of graphite particle. Hardness of developed composite for various % of graphite particle and Machinability parameters were also studied for effect on surface finish. It was observed that with increase of weight percentage of Graphite particles up to 8% in Aluminium 8011 alloy matrix there was increase in tensile strength, decrease in % of elongation with increase in hardness. Machinability study revealed that, there was decrease in surface roughness with increase in Graphite content.

  9. Promoting healthy diets and active lives to hard-to-reach groups: market research study.

    PubMed

    White, S L; Maloney, S K

    1990-01-01

    Continued progress over the next decade in reducing premature morbidity and mortality from chronic disease will require that health communication efforts target a significant proportion of the American public that has not been influenced by the health promotion efforts of the 1980s. Focus groups conducted with members of the hard-to-reach American public showed that while being healthy seemed to be important to participants, and they were generally aware of what to do to stay healthy, they had a different operational definition of health than that used in health promotion programs. Participants seemed to believe that better health behaviors would build their resistance to acute illnesses, that is, keep them healthy, but that chronic diseases, such as cancer and diabetes, were due to fate and heredity and beyond their individual control. The focus group results show that participants had not made the link between chronic disease prevention and the importance of diet, exercise, and weight control. Although most of them seemed to express a genuine interest in "doing better," they were not able to supply more than superficial examples of how such changes might be made. Surprisingly, there were more similarities than differences in participants' attitudes and beliefs, with the similarities cutting across boundaries of race-ethnicity, age, and sex. Interest in changing behaviors was only slightly more pronounced among female rather than male, and older rather than younger, participants. However, there was not much evidence from the participants that they were actively seeking health information or trying to reconcile conflicting knowledge and beliefs.

  10. An XMM-Newton study of the hard X-ray sky

    NASA Astrophysics Data System (ADS)

    Piconcelli, E.; Cappi, M.; Bassani, L.; Di Cocco, G.; Dadina, M.

    2003-12-01

    We report on the spectral properties of a sample of 90 hard X-ray selected serendipitous sources detected in 12 XMM-Newton observations with 1 <≈F2-10simlt 80 x 10-14 erg cm-2 s-1. Approximately 40% of the sources are optically identified with 0.1 <~ z<~ 2 and most of them are classified as broad line AGNs. A simple model consisting of power law modified by Galactic absorption offers an acceptable fit to ~ 65% of the source spectra. This fit yields an average photon index of <Γ> ≈ 1.55 over the whole sample. We also find that the mean slope of the QSOs in our sample turns out to remain nearly constant (<Γ> (≈ 1.8-1.9) between 0 <~ z<~ 2, with no hints of particular trends emerging along z. An additional cold absorption component with 1021 ˜< NH˜< 1023 cm-2 is required in ~ 30% of the sources. Considering only subsamples that are complete in flux, we find that the observed fraction of absorbed sources (i.e. with NH˜> 1022 cm-2) is ~ 30%, with little evolution in the range 2 <≈ F2-10˜< 80 x 10-14 erg cm-2 s-1. Interestingly, this value is a factor ~ 2 lower than predicted by the synthesis models of the CXB. This finding, detected for the first time in this survey, therefore suggests that most of the heavily obscured objects which make up the bulk of the CXB will be found at lower fluxes (F2-10< 10-14 erg cm-2 s-1). This mismatch together with other recent observational evidences which contrast with CXB model predictions suggest that one (or more) of the assumptions usually included in these models need to be revised.

  11. Spectro-Timing Study of GX 339-4 in a Hard Intermediate State

    NASA Astrophysics Data System (ADS)

    Fürst, F.; Grinberg, V.; Tomsick, J. A.; Bachetti, M.; Boggs, S. E.; Brightman, M.; Christensen, F. E.; Craig, W. W.; Gandhi, P.; Grefenstette, B.; Hailey, C. J.; Harrison, F. A.; Madsen, K. K.; Parker, M. L.; Pottschmidt, K.; Stern, D.; Walton, D. J.; Wilms, J.; Zhang, W. W.

    2016-09-01

    We present an analysis of Nuclear Spectroscopic Telescope Array observations of a hard intermediate state of the transient black hole GX 339-4 taken in 2015 January. With the source softening significantly over the course of the 1.3 day long observation we split the data into 21 sub-sets and find that the spectrum of all of them can be well described by a power-law continuum with an additional relativistically blurred reflection component. The photon index increases from ˜1.69 to ˜1.77 over the course of the observation. The accretion disk is truncated at around nine gravitational radii in all spectra. We also perform timing analysis on the same 21 individual data sets, and find a strong type-C quasi-periodic oscillation (QPO), which increases in frequency from ˜0.68 to ˜1.05 Hz with time. The frequency change is well correlated with the softening of the spectrum. We discuss possible scenarios for the production of the QPO and calculate predicted inner radii in the relativistic precession model as well as the global disk mode oscillations model. We find discrepancies with respect to the observed values in both models unless we allow for a black hole mass of ˜100 {M}⊙ , which is highly unlikely. We discuss possible systematic uncertainties, in particular with the measurement of the inner accretion disk radius in the relativistic reflection model. We conclude that the combination of observed QPO frequencies and inner accretion disk radii, as obtained from spectral fitting, is difficult to reconcile with current models.

  12. Radiation resistance studies of amorphous silicon films

    NASA Technical Reports Server (NTRS)

    Payson, J. Scott; Woodyard, James R.

    1988-01-01

    A study of hydrogenated amorphous silicon thin films irradiated with 2.00 MeV helium ions using fluences ranging from 1E11 to 1E15/sq cm is presented. The films were characterized using photothermal deflection spectroscopy, transmission and reflection spectroscopy, and photoconductivity and annealing measurements. Large changes were observed in the subband-gap optical absorption for energies between 0.9 and 1.7 eV. The steady-state photoconductivity showed decreases of almost five orders of magnitude for a fluence of 1E15/sq cm, but the slope of the intensity dependence of the photoconductivity remained almost constant for all fluences. Substantial annealing occurs even at room temperature, and for temperatures greater than 448 K the damage is completely annealed. The data are analyzed to describe the defects and the density of states function.

  13. Cloud and Radiation Studies during SAFARI 2000

    NASA Technical Reports Server (NTRS)

    Platnick, Steven; King, M. D.; Hobbs, P. V.; Osborne, S.; Piketh, S.; Bruintjes, R.; Lau, William K. M. (Technical Monitor)

    2001-01-01

    Though the emphasis of the Southern Africa Regional Science Initiative 2000 (SAFARI-2000) dry season campaign was largely on emission sources and transport, the assemblage of aircraft (including the high altitude NASA ER-2 remote sensing platform and the University of Washington CV-580, UK MRF C130, and South African Weather Bureau JRA in situ aircrafts) provided a unique opportunity for cloud studies. Therefore, as part of the SAFARI initiative, investigations were undertaken to assess regional aerosol-cloud interactions and cloud remote sensing algorithms. In particular, the latter part of the experiment concentrated on marine boundary layer stratocumulus clouds off the southwest coast of Africa. Associated with cold water upwelling along the Benguela current, the Namibian stratocumulus regime has received limited attention but appears to be unique for several reasons. During the dry season, outflow of continental fires and industrial pollution over this area can be extreme. From below, upwelling provides a rich nutrient source for phytoplankton (a source of atmospheric sulphur through DMS production as well as from decay processes). The impact of these natural and anthropogenic sources on the microphysical and optical properties of the stratocumulus is unknown. Continental and Indian Ocean cloud systems of opportunity were also studied during the campaign. Aircraft flights were coordinated with NASA Terra Satellite overpasses for synergy with the Moderate Resolution Imaging Spectroradiometer (MODIS) and other Terra instruments. An operational MODIS algorithm for the retrieval of cloud optical and physical properties (including optical thickness, effective particle radius, and water path) has been developed. Pixel-level MODIS retrievals (11 km spatial resolution at nadir) and gridded statistics of clouds in th SAFARI region will be presented. In addition, the MODIS Airborne Simulator flown on the ER-2 provided high spatial resolution retrievals (50 m at nadir

  14. Imaging Primary Lung Cancers in Mice to Study Radiation Biology

    SciTech Connect

    Kirsch, David G.; Grimm, Jan; Guimaraes, Alexander R.; Wojtkiewicz, Gregory R.; Perez, Bradford A.; Santiago, Philip M.; Anthony, Nikolas K.; Forbes, Thomas; Doppke, Karen

    2010-03-15

    Purpose: To image a genetically engineered mouse model of non-small-cell lung cancer with micro-computed tomography (micro-CT) to measure tumor response to radiation therapy. Methods and Materials: The Cre-loxP system was used to generate primary lung cancers in mice with mutation in K-ras alone or in combination with p53 mutation. Mice were serially imaged by micro-CT, and tumor volumes were determined. A comparison of tumor volume by micro-CT and tumor histology was performed. Tumor response to radiation therapy (15.5 Gy) was assessed with micro-CT. Results: The tumor volume measured with free-breathing micro-CT scans was greater than the volume calculated by histology. Nevertheless, this imaging approach demonstrated that lung cancers with mutant p53 grew more rapidly than lung tumors with wild-type p53 and also showed that radiation therapy increased the doubling time of p53 mutant lung cancers fivefold. Conclusions: Micro-CT is an effective tool to noninvasively measure the growth of primary lung cancers in genetically engineered mice and assess tumor response to radiation therapy. This imaging approach will be useful to study the radiation biology of lung cancer.

  15. Study of electromagnetic radiation pollution in an Indian city.

    PubMed

    Dhami, A K

    2012-11-01

    Electromagnetic radiation emitted by cell phone towers is a form of environmental pollution and is a new health hazard, especially to children and patients. The present studies were taken to estimate the microwave/RF pollution by measuring radiation power densities near schools and hospitals of Chandigarh city in India. The cell phone radiations were measured using a handheld portable power density meter TES 593 and specific absorption rates were estimated from the measured values. These values of electromagnetic radiation in the environment were compared with the levels at which biological system of humans and animals starts getting affected. The values were also compared with the international exposure limits set by the International Commission on Non-Ionizing Radiation Protection (ICNIRP). The highest measured power density was 11.48 mW/m(2) which is 1,148% of the biological limit. The results indicated that the exposure levels in the city were below the ICNIRP limit, but much above the biological limit.

  16. Design of laboratory experiments to study radiation-driven implosions

    NASA Astrophysics Data System (ADS)

    Keiter, P. A.; Trantham, M.; Malamud, G.; Klein, S. R.; Davis, J.; VanDervort, R.; Shvarts, D.; Drake, R. P.; Stone, J. M.; Fraenkel, M.; Frank, Y.; Raicher, E.

    2017-03-01

    The interstellar medium is heterogeneous with dense clouds amid an ambient medium. Radiation from young OB stars asymmetrically irradiate the dense clouds. Bertoldi (1989) developed analytic formulae to describe possible outcomes of these clouds when irradiated by hot, young stars. One of the critical parameters that determines the cloud's fate is the number of photon mean free paths in the cloud. For the extreme cases where the cloud size is either much greater than or much less than one mean free path, the radiation transport should be well understood. However, as one transitions between these limits, the radiation transport is much more complex and is a challenge to solve with many of the current radiation transport models implemented in codes. We present the design of laboratory experiments that use a thermal source of x-rays to asymmetrically irradiate a low-density plastic foam sphere. The experiment will vary the density and hence the number of mean free paths of the sphere to study the radiation transport in different regimes. We have developed dimensionless parameters to relate the laboratory experiment to the astrophysical system and we show that we can perform the experiment in the same transport regime.

  17. Comparison of radiation dose to operator between transradial and transfemoral coronary angiography with optimised radiation protection: a phantom study.

    PubMed

    Liu, Huiliang; Jin, Zhigeng; Jing, Limin

    2014-03-01

    A growing concern in applying radial access in cardiac catheterisation is the increased operator radiation exposure. This study used an anthropomorphic phantom to simulate transradial and transfemoral coronary angiography with optimised radiation protection conditions. Operator radiation exposure was measured with thermoluminescent dosemeters at predefined locations. Compared with the femoral route, the radial route was associated with a dose decrease of 15 % at the operator's chest level with optimised radiation shielding. However, radiation exposure to the operator's hand remained significantly higher when applying radial access even with collective protective equipment used (by a factor of 2). Furthermore, the efficiency of operator radiation protection was found to be dependent on the tube incidence. Awareness should be raised about the significant increase of radiation exposure to operators' hands in transradial coronary angiography. Protection to reduce the dose level to the hands is necessary and should be further improved.

  18. Computation of noise radiation from turbofans: A parametric study

    NASA Astrophysics Data System (ADS)

    Nallasamy, M.

    1995-07-01

    This report presents the results of a parametric study of the turbofan far-field noise radiation using a finite element technique. Several turbofan noise radiation characteristics of both the inlet and the aft ducts have been examined through the finite element solutions. The predicted far-field principal lobe angle variations with duct Mach number and cut-off ratio compare very well with the available analytical results. The solutions also show that the far-field lobe angle is only a function of cut-off ratio, and nearly independent of the mode number. These results indicate that the finite element codes are well suited for the prediction of noise radiation characteristics of a turbofan. The effects of variations in the aft duct geometry are examined. The ability of the codes to handle ducts with acoustic treatments is also demonstrated.

  19. Computation of noise radiation from turbofans: A parametric study

    NASA Technical Reports Server (NTRS)

    Nallasamy, M.

    1995-01-01

    This report presents the results of a parametric study of the turbofan far-field noise radiation using a finite element technique. Several turbofan noise radiation characteristics of both the inlet and the aft ducts have been examined through the finite element solutions. The predicted far-field principal lobe angle variations with duct Mach number and cut-off ratio compare very well with the available analytical results. The solutions also show that the far-field lobe angle is only a function of cut-off ratio, and nearly independent of the mode number. These results indicate that the finite element codes are well suited for the prediction of noise radiation characteristics of a turbofan. The effects of variations in the aft duct geometry are examined. The ability of the codes to handle ducts with acoustic treatments is also demonstrated.

  20. Study of radiation effects on mammalian cells in vitro

    NASA Technical Reports Server (NTRS)

    Sinclair, W. K.

    1968-01-01

    Radiation effect on single cells and cell populations of Chinese hamster lung tissue is studied in vitro. The rate and position as the cell progresses through the generation cycle shows division delay, changes in some biochemical processes in the cell, chromosomal changes, colony size changes, and loss of reproductive capacity.

  1. Experimental Study on Thermal Conductivity and Hardness of Cu and Ni Nanoparticle Packed Bed for Thermoelectric Application

    NASA Astrophysics Data System (ADS)

    Lin, Zi-Zhen; Huang, Cong-Liang; Zhen, Wen-Kai; Feng, Yan-Hui; Zhang, Xin-Xin; Wang, Ge

    2017-03-01

    The hot-wire method is applied in this paper to probe the thermal conductivity (TC) of Cu and Ni nanoparticle packed beds (NPBs). A different decrease tendency of TC versus porosity than that currently known is discovered. The relationship between the porosity and nanostructure is investigated to explain this unusual phenomenon. It is found that the porosity dominates the TC of the NPB in large porosities, while the TC depends on the contact area between nanoparticles in small porosities. Meanwhile, the Vickers hardness (HV) of NPBs is also measured. It turns out that the enlarged contact area between nanoparticles is responsible for the rapid increase of HV in large porosity, and the saturated nanoparticle deformation is responsible for the small increase of HV in low porosity. With both TC and HV considered, it can be pointed out that a structure of NPB with a porosity of 0.25 is preferable as a thermoelectric material because of the low TC and the higher hardness. Although Cu and Ni are not good thermoelectric materials, this study is supposed to provide an effective way to optimize thermoelectric figure of merit (ZT) and HV of nanoporous materials prepared by the cold-pressing method.

  2. Refined Synthesis and Crystal Growth of Pb{sub 2}P{sub 2}Se{sub 6} for Hard Radiation Detectors.

    SciTech Connect

    Wang, Peng L.; Kostina, Svetlana S.; Meng, Fang; Kontsevoi, Oleg Y.; Liu, Zhifu; Chen, Pice; Peters, John A.; Hanson, Micah; He, Yihui; Chung, Duck Young; Freeman, Arthur J.; Wessels, Bruce W.; Kanatzidis, Mercouri G.

    2016-09-01

    The refined synthesis and optimized crystal growth of high quality Pb2P2Se6 single crystals are reported. Improved experimental procedures were implemented to reduce the oxygen contamination and improve the stoichiometry of the single crystal samples. The impact of oxygen contamination and the nature of the stoichiometry deviation in the Pb2P2Se6 system were studied by first-principles density functional theory (DFT) electronic structure calculations as well as experimental methods. The DFT calculations indicated that the presence of interstitial oxygen atoms (O-int) leads to the formation of a deep level located near the middle of the gap, as well as a shallow acceptor level near the valence band maximum. In addition, total energy calculations of the heat of formation of Pb2P2Se6 suggest that the region of thermodynamic stability is sufficiently wide. By refining the preparative procedures, high quality Pb2P2Se6 single crystal samples were reproducibly obtained. These Pb2P2Se6 single crystals exhibited excellent optical transparency, electrical resistivity in the range of 10(11) Omega.cm, and a significant increase in photoconductivity. Infrared photoluminescence of the Pb2P2Se6 single crystals was observed over the temperature range of 15-75 K. Detectors fabricated from boules yielded a clear spectroscopic response to both Ag K alpha X-ray and Co-57 gamma-ray radiation. The electron and hole mobility lifetime product (mu tau) of the current Pb2P2Se6 detectors were estimated to be 3.1 x 10(-4) and 4.8 X 10(-5) cm(2)/V, respectively.

  3. Megacity Radiative Forcing: A Mexico City Case Study

    NASA Astrophysics Data System (ADS)

    Olsen, S. C.; Dubey, M. K.; Chylek, P.; Mazzoleni, C.; Zhang, Y.; Randerson, J. T.; Horowitz, L.

    2006-12-01

    We assess the radiative forcing budget of the largest megacity in North America, Mexico City. While particular aspects of the regional environmental impacts of cities on their surroundings have been thoroughly investigated, e.g., air quality and acid rain, relatively little effort has been focused on the net radiative impact of a megacity on global climate. The range of radiative impacts from a megacity covers many spatial and temporal scales from short-term regional-scale effects due to aerosols and relatively short-lived gases (O3) to long-term global-scale impacts due to long-lived trace gases (e.g., CH4, CO2). In this study we use both bottom-up and top-down approaches to evaluate these radiative forcings. From the bottom up we utilize emission inventories and the Model for Ozone And Related Chemical Tracers (MOZART-2) chemistry-aerosol model. From the top down we use observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument, the Aerosol Robotic Network (AERONET), and in situ aerosol single scattering albedo measurements collected during the Megacity Initiative-Local and Global Research Observations (MILAGRO) campaign. We also explore the radiative impact of various emission control strategies that focus on improving urban air quality. We show that the warming by greenhouse gases like CO2 and ozone can be moderated or exacerbated by aerosols depending on their optical properties. As the size and number of megacities increase and clean air regulations are implemented, metrics such as the net radiative forcing may become increasingly important in comparing the impact of urban centers and assessing pollution abatement policies.

  4. THE EFFECT OF CORONAL RADIATION ON A RESIDUAL INNER DISK IN THE LOW/HARD SPECTRAL STATE OF BLACK HOLE X-RAY BINARY SYSTEMS

    SciTech Connect

    Liu, B. F.; Taam, Ronald E. E-mail: r-taam@northwestern.edu

    2011-01-01

    Thermal conduction between a cool accretion disk and a hot inner corona can result in either evaporation of the disk or condensation of the hot corona. At low mass accretion rates, evaporation dominates and can completely remove the inner disk. At higher mass accretion rates, condensation becomes more efficient in the very inner regions, so that part of the mass accretes via a weak (initially formed) inner disk which is separated from the outer disk by a fully evaporated region at mid radii. At still higher mass accretion rates, condensation dominates everywhere, so there is a continuous cool disk extending to the innermost stable circular orbit. We extend these calculations by including the effect of irradiation by the hot corona on the disk structure. The flux which is not reflected is reprocessed in the disk, adding to the intrinsic thermal emission from gravitational energy release. This increases the seed photons for Compton cooling of the hot corona, enhancing condensation of the hot flow, and reinforcing the residual inner disk rather than evaporating it. Our calculations confirm that a residual inner disk can coexist with a hard, coronally dominated spectrum over the range of 0.006< m-dot <0.016 (for {alpha} = 0.2). This provides an explanation for the weak thermal component seen recently in the low/hard state of black hole X-ray binary systems.

  5. Studying Radiation Damage in Structural Materials by Using Ion Accelerators

    NASA Astrophysics Data System (ADS)

    Hosemann, Peter

    2011-02-01

    Radiation damage in structural materials is of major concern and a limiting factor for a wide range of engineering and scientific applications, including nuclear power production, medical applications, or components for scientific radiation sources. The usefulness of these applications is largely limited by the damage a material can sustain in the extreme environments of radiation, temperature, stress, and fatigue, over long periods of time. Although a wide range of materials has been extensively studied in nuclear reactors and neutron spallation sources since the beginning of the nuclear age, ion beam irradiations using particle accelerators are a more cost-effective alternative to study radiation damage in materials in a rather short period of time, allowing researchers to gain fundamental insights into the damage processes and to estimate the property changes due to irradiation. However, the comparison of results gained from ion beam irradiation, large-scale neutron irradiation, and a variety of experimental setups is not straightforward, and several effects have to be taken into account. It is the intention of this article to introduce the reader to the basic phenomena taking place and to point out the differences between classic reactor irradiations and ion irradiations. It will also provide an assessment of how accelerator-based ion beam irradiation is used today to gain insight into the damage in structural materials for large-scale engineering applications.

  6. Study of scattered radiation during fluoroscopy in hip surgery*

    PubMed Central

    Lesyuk, Oksana; Sousa, Patrick Emmanuel; Rodrigues, Sónia Isabel do Espirito Santo; Abrantes, António Fernando; de Almeida, Rui Pedro Pereira; Pinheiro, João Pedro; Azevedo, Kevin Barros; Ribeiro, Luís Pedro Vieira

    2016-01-01

    Objective To measure the scattered radiation dose at different positions simulating hip surgery. Materials and Methods We simulated fluoroscopy-assisted hip surgery in order to study the distribution of scattered radiation in the operating room. To simulate the patient, we used a anthropomorphic whole-body phantom, and we used an X-ray-specific detector to quantify the radiation. Radiographs were obtained with a mobile C-arm X-ray system in continuous scan mode, with the tube at 0º (configuration 1) or 90º (configuration 2). The operating parameters employed (voltage, current, and exposure time) were determined by a statistical analysis based on the observation of orthopedic surgical procedures involving the hip. Results For all measurements, higher exposures were observed in configuration 2. In the measurements obtained as a function of height, the maximum dose rates observed were 1.167 (± 0.023) µSv/s and 2.278 (± 0.023) µSv/s in configurations 1 and 2, respectively, corresponding to the chest level of health care professionals within the operating room. Proximal to the patient, the maximum values were recorded in the position occupied by the surgeon. Conclusion We can conclude that, in the scenario under study, health care professionals workers are exposed to low levels of radiation, and that those levels can be reduced through the use of personal protective equipment. PMID:27777477

  7. Ultra-low power high temperature and radiation hard complementary metal-oxide-semiconductor (CMOS) silicon-on-insulator (SOI) voltage reference.

    PubMed

    Boufouss, El Hafed; Francis, Laurent A; Kilchytska, Valeriya; Gérard, Pierre; Simon, Pascal; Flandre, Denis

    2013-12-13

    This paper presents an ultra-low power CMOS voltage reference circuit which is robust under biomedical extreme conditions, such as high temperature and high total ionized dose (TID) radiation. To achieve such performances, the voltage reference is designed in a suitable 130 nm Silicon-on-Insulator (SOI) industrial technology and is optimized to work in the subthreshold regime of the transistors. The design simulations have been performed over the temperature range of -40-200 °C and for different process corners. Robustness to radiation was simulated using custom model parameters including TID effects, such as mobilities and threshold voltages degradation. The proposed circuit has been tested up to high total radiation dose, i.e., 1 Mrad (Si) performed at three different temperatures (room temperature, 100 °C and 200 °C). The maximum drift of the reference voltage V(REF) depends on the considered temperature and on radiation dose; however, it remains lower than 10% of the mean value of 1.5 V. The typical power dissipation at 2.5 V supply voltage is about 20 μW at room temperature and only 75 μW at a high temperature of 200 °C. To understand the effects caused by the combination of high total ionizing dose and temperature on such voltage reference, the threshold voltages of the used SOI MOSFETs were extracted under different conditions. The evolution of V(REF) and power consumption with temperature and radiation dose can then be explained in terms of the different balance between fixed oxide charge and interface states build-up. The total occupied area including pad-ring is less than 0.09 mm2.

  8. Ultra-Low Power High Temperature and Radiation Hard Complementary Metal-Oxide-Semiconductor (CMOS) Silicon-on-Insulator (SOI) Voltage Reference

    PubMed Central

    Boufouss, El Hafed; Francis, Laurent A.; Kilchytska, Valeriya; Gérard, Pierre; Simon, Pascal; Flandre, Denis

    2013-01-01

    This paper presents an ultra-low power CMOS voltage reference circuit which is robust under biomedical extreme conditions, such as high temperature and high total ionized dose (TID) radiation. To achieve such performances, the voltage reference is designed in a suitable 130 nm Silicon-on-Insulator (SOI) industrial technology and is optimized to work in the subthreshold regime of the transistors. The design simulations have been performed over the temperature range of −40–200 °C and for different process corners. Robustness to radiation was simulated using custom model parameters including TID effects, such as mobilities and threshold voltages degradation. The proposed circuit has been tested up to high total radiation dose, i.e., 1 Mrad (Si) performed at three different temperatures (room temperature, 100 °C and 200 °C). The maximum drift of the reference voltage VREF depends on the considered temperature and on radiation dose; however, it remains lower than 10% of the mean value of 1.5 V. The typical power dissipation at 2.5 V supply voltage is about 20 μW at room temperature and only 75 μW at a high temperature of 200 °C. To understand the effects caused by the combination of high total ionizing dose and temperature on such voltage reference, the threshold voltages of the used SOI MOSFETs were extracted under different conditions. The evolution of VREF and power consumption with temperature and radiation dose can then be explained in terms of the different balance between fixed oxide charge and interface states build-up. The total occupied area including pad-ring is less than 0.09 mm2. PMID:24351635

  9. Study of the Radiative Properties of Inhomogeneous Stratocumulus Clouds

    NASA Technical Reports Server (NTRS)

    Batey, Michael

    1996-01-01

    Clouds play an important role in the radiation budget of the atmosphere. A good understanding of how clouds interact with solar radiation is necessary when considering their effects in both general circulation models and climate models. This study examined the radiative properties of clouds in both an inhomogeneous cloud system, and a simplified cloud system through the use of a Monte Carlo model. The purpose was to become more familiar with the radiative properties of clouds, especially absorption, and to investigate the excess absorption of solar radiation from observations over that calculated from theory. The first cloud system indicated that the absorptance actually decreased as the cloud's inhomogeneity increased, and that cloud forcing does not indicate any changes. The simplified cloud system looked at two different cases of absorption of solar radiation in the cloud. The absorptances calculated from the Monte Carlo is compared to a correction method for calculating absorptances and found that the method can over or underestimate absorptances at cloud edges. Also the cloud edge effects due to solar radiation points to a possibility of overestimating the retrieved optical depth at the edge, and indicates a possible way to correct for it. The effective cloud fraction (Ne) for a long time has been calculated from a cloud's reflectance. From the reflectance it has been observed that the N, for most cloud geometries is greater than the actual cloud fraction (Nc) making a cloud appear wider than it is optically. Recent studies we have performed used a Monte Carlo model to calculate the N, of a cloud using not only the reflectance but also the absorptance. The derived Ne's from the absorptance in some of the Monte Carlo runs did not give the same results as derived from the reflectance. This study also examined the inhomogeneity of clouds to find a relationship between larger and smaller scales, or wavelengths, of the cloud. Both Fourier transforms and wavelet

  10. A study on leakage radiation dose at ELV-4 electron accelerator bunker

    NASA Astrophysics Data System (ADS)

    Chulan, Mohd Rizal Md; Yahaya, Redzuwan; Ghazali, Abu BakarMhd

    2014-09-01

    Shielding is an important aspect in the safety of an accelerator and the most important aspects of a bunker shielding is the door. The bunker's door should be designed properly to minimize the leakage radiation and shall not exceed the permitted limit of 2.5μSv/hr. In determining the leakage radiation dose that passed through the door and gaps between the door and the wall, 2-dimensional manual calculations are often used. This method is hard to perform because visual 2-dimensional is limited and is also very difficult in the real situation. Therefore estimation values are normally performed. In doing so, the construction cost would be higher because of overestimate or underestimate which require costly modification to the bunker. Therefore in this study, two methods are introduced to overcome the problem such as simulation using MCNPX Version 2.6.0 software and manual calculation using 3-dimensional model from Autodesk Inventor 2010 software. The values from the two methods were eventually compared to the real values from direct measurements using Ludlum Model 3 with Model 44-9 probe survey meter.

  11. A study on leakage radiation dose at ELV-4 electron accelerator bunker

    SciTech Connect

    Chulan, Mohd Rizal Md E-mail: redzuwan@ukm.my; Yahaya, Redzuwan E-mail: redzuwan@ukm.my; Ghazali, Abu BakarMhd

    2014-09-03

    Shielding is an important aspect in the safety of an accelerator and the most important aspects of a bunker shielding is the door. The bunker’s door should be designed properly to minimize the leakage radiation and shall not exceed the permitted limit of 2.5μSv/hr. In determining the leakage radiation dose that passed through the door and gaps between the door and the wall, 2-dimensional manual calculations are often used. This method is hard to perform because visual 2-dimensional is limited and is also very difficult in the real situation. Therefore estimation values are normally performed. In doing so, the construction cost would be higher because of overestimate or underestimate which require costly modification to the bunker. Therefore in this study, two methods are introduced to overcome the problem such as simulation using MCNPX Version 2.6.0 software and manual calculation using 3-dimensional model from Autodesk Inventor 2010 software. The values from the two methods were eventually compared to the real values from direct measurements using Ludlum Model 3 with Model 44-9 probe survey meter.

  12. Development of an impulsive noise source to study the acoustic reflection characteristics of hard-walled wind tunnels

    NASA Technical Reports Server (NTRS)

    Salikuddin, M.; Burrin, R. H.; Ahuja, K. K.; Bartel, H. W.

    1986-01-01

    Two impulsive sound sources, one using multiple acoustic drivers and the other using a spark discharge were developed to study the acoustic reflection characteristics of hard-walled wind tunnels, and the results of laboratory tests are presented. The analysis indicates that though the intensity of the pulse generated by the spark source was higher than that obtained from the acoustic source, the number of averages needed for a particular test may require an unacceptibly long tunnel-run time due to the low spark generation repeat rate because of capacitor charging time. The additional hardware problems associated with the longevity of electrodes and electrode holders in sustaining the impact of repetitive spark discharges, show the multidriver acoustic source to be more suitable for this application.

  13. Radiation dose study in nuclear medicine using GATE

    NASA Astrophysics Data System (ADS)

    Aguwa, Kasarachi

    Dose as a result of radiation exposure is the notion generally used to disclose the imparted energy in a volume of tissue to a potential biological effect. The basic unit defined by the international system of units (SI system) is the radiation absorbed dose, which is expressed as the mean imparted energy in a mass element of the tissue known as "gray" (Gy) or J/kg. The procedure for ascertaining the absorbed dose is complicated since it involves the radiation transport of numerous types of charged particles and coupled photon interactions. The most precise method is to perform a full 3D Monte Carlo simulation of the radiation transport. There are various Monte Carlo toolkits that have tool compartments for dose calculations and measurements. The dose studies in this thesis were performed using the GEANT4 Application for Emission Tomography (GATE) software (Jan et al., 2011) GATE simulation toolkit has been used extensively in the medical imaging community, due to the fact that it uses the full capabilities of GEANT4. It also utilizes an easy to-learn GATE macro language, which is more accessible than learning the GEANT4/C++ programming language. This work combines GATE with digital phantoms generated using the NCAT (NURBS-based cardiac-torso phantom) toolkit (Segars et al., 2004) to allow efficient and effective estimation of 3D radiation dose maps. The GATE simulation tool has developed into a beneficial tool for Monte Carlo simulations involving both radiotherapy and imaging experiments. This work will present an overview of absorbed dose of common radionuclides used in nuclear medicine and serve as a guide to a user who is setting up a GATE simulation for a PET and SPECT study.

  14. Radiation exposure of fertile women in medical research studies

    SciTech Connect

    Vetter, R.J.

    1988-08-01

    Fertile women may be exposed to ionizing radiation as human subjects in medical research studies. If the woman is pregnant, such exposures may result in risk to an embryo/fetus. Fertile women may be screened for pregnancy before exposure to ionizing radiation by interview, general examination, or pregnancy test. Use of the sensitive serum pregnancy test has become common because it offers concrete evidence that the woman is not pregnant (more specifically, that an embryo is not implanted). Evidence suggests that risk to the embryo from radiation exposure before organogenesis is extremely low or nonexistent. Further, demonstrated effects on organogenesis are rare or inconclusive at fetal doses below 50 mSv (5 rem). Therefore, there may be some level of radiation exposure below which risk to the fetus may be considered essentially zero, and a serum pregnancy test is unnecessary. This paper reviews the fetal risks and suggests that consideration be given to establishing a limit to the fetus of 0.5 mSv (50 mrem), below which pregnancy screening need not include the use of a serum pregnancy test.

  15. Study of surface properties of ATLAS12 strip sensors and their radiation resistance

    NASA Astrophysics Data System (ADS)

    Mikestikova, M.; Allport, P. P.; Baca, M.; Broughton, J.; Chisholm, A.; Nikolopoulos, K.; Pyatt, S.; Thomas, J. P.; Wilson, J. A.; Kierstead, J.; Kuczewski, P.; Lynn, D.; Hommels, L. B. A.; Ullan, M.; Bloch, I.; Gregor, I. M.; Tackmann, K.; Hauser, M.; Jakobs, K.; Kuehn, S.; Mahboubi, K.; Mori, R.; Parzefall, U.; Clark, A.; Ferrere, D.; Sevilla, S. Gonzalez; Ashby, J.; Blue, A.; Bates, R.; Buttar, C.; Doherty, F.; McMullen, T.; McEwan, F.; O'Shea, V.; Kamada, S.; Yamamura, K.; Ikegami, Y.; Nakamura, K.; Takubo, Y.; Unno, Y.; Takashima, R.; Chilingarov, A.; Fox, H.; Affolder, A. A.; Casse, G.; Dervan, P.; Forshaw, D.; Greenall, A.; Wonsak, S.; Wormald, M.; Cindro, V.; Kramberger, G.; Mandić, I.; Mikuž, M.; Gorelov, I.; Hoeferkamp, M.; Palni, P.; Seidel, S.; Taylor, A.; Toms, K.; Wang, R.; Hessey, N. P.; Valencic, N.; Hanagaki, K.; Dolezal, Z.; Kodys, P.; Bohm, J.; Stastny, J.; Bevan, A.; Beck, G.; Milke, C.; Domingo, M.; Fadeyev, V.; Galloway, Z.; Hibbard-Lubow, D.; Liang, Z.; Sadrozinski, H. F.-W.; Seiden, A.; To, K.; French, R.; Hodgson, P.; Marin-Reyes, H.; Parker, K.; Jinnouchi, O.; Hara, K.; Sato, K.; Hagihara, M.; Iwabuchi, S.; Bernabeu, J.; Civera, J. V.; Garcia, C.; Lacasta, C.; Marti i Garcia, S.; Rodriguez, D.; Santoyo, D.; Solaz, C.; Soldevila, U.

    2016-09-01

    A radiation hard n+-in-p micro-strip sensor for the use in the Upgrade of the strip tracker of the ATLAS experiment at the High Luminosity Large Hadron Collider (HL-LHC) has been developed by the "ATLAS ITk Strip Sensor collaboration" and produced by Hamamatsu Photonics. Surface properties of different types of end-cap and barrel miniature sensors of the latest sensor design ATLAS12 have been studied before and after irradiation. The tested barrel sensors vary in "punch-through protection" (PTP) structure, and the end-cap sensors, whose stereo-strips differ in fan geometry, in strip pitch and in edge strip ganging options. Sensors have been irradiated with proton fluences of up to 1×1016 neq/cm2, by reactor neutron fluence of 1×1015 neq/cm2 and by gamma rays from 60Co up to dose of 1 MGy. The main goal of the present study is to characterize the leakage current for micro-discharge breakdown voltage estimation, the inter-strip resistance and capacitance, the bias resistance and the effectiveness of PTP structures as a function of bias voltage and fluence. It has been verified that the ATLAS12 sensors have high breakdown voltage well above the operational voltage which implies that different geometries of sensors do not influence their stability. The inter-strip isolation is a strong function of irradiation fluence, however the sensor performance is acceptable in the expected range for HL-LHC. New gated PTP structure exhibits low PTP onset voltage and sharp cut-off of effective resistance even at the highest tested radiation fluence. The inter-strip capacitance complies with the technical specification required before irradiation and no radiation-induced degradation was observed. A summary of ATLAS12 sensors tests is presented including a comparison of results from different irradiation sites. The measured characteristics are compared with the previous prototype of the sensor design, ATLAS07.

  16. A Comparative Clinical Study of the Effect of Denture Cleansing on the Surface Roughness and Hardness of Two Denture Base Materials

    PubMed Central

    Moussa, Amani Ramadan; Dehis, Wessam Mohamed; Elboraey, Asmaa Nabil; ElGabry, Hisham Samir

    2016-01-01

    AIM: This study aimed to verify the influence of oral environment and denture cleansers on the surface roughness and hardness of two different denture base materials. METHODS: A total of sixteen identical removable disc specimens (RDS) were processed. Eight RDS were made from heat-cured acrylic resin (AR) and the other eight were fabricated from thermoplastic injection moulded resin (TR). Surface roughness and hardness of DRS were measured using ultrasonic profilometry and Universal testing machine respectively. Then the four RDS (two AR and two of TR) were fixed to each maxillary denture, after three months RDS were retrieved. Surface roughness and hardness of RDS have measured again. RESULTS: The surface roughness measurements revealed no significant difference (p >0.05) for both disc groups at baseline. However, both groups showed a significant increase in the surface roughness after three months with higher mean value for (TR) group. On the other hand, the (AR) group showed higher hardness mean value than (TR) group at baseline with no significant decrease in the hardness values (p >0.05) following three months follow-up period. CONCLUSIONS: Denture cleansers have an effect on the denture’s surface roughness and hardness concurrently with an oral condition which will consequently influence the complete dentures’ lifetime and patients’ satisfaction. PMID:27703578

  17. An Exploratory Study of Characteristics Associated with Postsecondary Educational Attainment in Students Who Are Deaf or Hard of Hearing

    ERIC Educational Resources Information Center

    Hebert, Amy M.

    2012-01-01

    It is well documented that attrition in the postsecondary settings for students who are deaf or hard of hearing is greatly due to their academic and communication skills, as well as pre-entry attributes. However there is little evidence that indicates why students who are deaf or hard of hearing are successful in the postsecondary setting. This…

  18. Seismo-acoustic imaging of marine hard substrate habitats: a case study from the German Bight (SE North Sea)

    NASA Astrophysics Data System (ADS)

    Papenmeier, Svenja; Hass, H. Christian

    2016-04-01

    The detection of hard substrate habitats in sublittoral environments is a considerable challenge in spite of modern high resolution hydroacoustic techniques. In offshore areas those habitats are mainly represented by either cobbles and boulders (stones) often located in wide areas of soft sediments or by glacial relict sediments (heterogeneous mixture of medium sand to gravel size with cobbles and boulders). Sediment classification and object detection is commonly done on the basis of hydroacoustic backscatter intensities recorded with e.g. sidescan sonar (SSS) and multibeam echo sounder (MBES). Single objects lying on the sediment such as stones can generally be recognized by the acoustic shadow behind the object. However, objects close to the sonar's nadir may remain undetected because their shadows are below the data resolution. Further limitation in the detection of objects is caused by sessile communities that thrive on the objects. The bio-cover tends to absorb most of the acoustic signal. Automated identification based on the backscatter signal is often not satisfactory, especially when stones are present in a setting with glacial deposits. Areas characterized by glacial relict sediments are hardly differentiable in their backscatter characteristics from rippled coarse sand and fine gravel (rippled coarse sediments) without an intensive ground-truthing program. From the ecological point of view the relict and rippled coarse sediments are completely different habitats and need to be distinguished. The case study represents a seismo-acoustic approach in which SSS and nonlinear sediment echo sounder (SES) data are combined to enable a reliable and reproducible differentiation between relict sediments (with stones and coarse gravels) and rippled coarse sediments. Elevated objects produce hyperbola signatures at the sediment surface in the echo data which can be used to complement the SSS data. The nonlinear acoustic propagation of the SES sound pulses produces a

  19. Advances in Radiation Mutagenesis through Studies on Drosophila

    DOE R&D Accomplishments Database

    Muller, H. J.

    1958-06-01

    mutation occurred in peri- fertilization stages. All loci studied mutated from one to nine times. Loci mutating oftener spontaneously also gave more radiation mutation, in other studies, Spectra of individual loci prove similar for spontaneous and induced mutation. Studies on back-mutation also showed similarity of spontaneous and radiation mutations. The doubling dose for back-mutations of forked induced in spermatozoa was several hundred roentgens, gonia at diverse loci. Recent analyses of human mutational load lead to mutation-rate estimated like those earlier based on extrapolations from Drosophila, thus supporting the significance for man of the present studies. (auth)

  20. Radiation energy budget studies using collocated AVHRR and ERBE observations

    SciTech Connect

    Ackerman, S.A.; Inoue, Toshiro

    1994-03-01

    Changes in the energy balance at the top of the atmosphere are specified as a function of atmospheric and surface properties using observations from the Advanced Very High Resolution Radiometer (AVHRR) and the Earth Radiation Budget Experiment (ERBE) scanner. By collocating the observations from the two instruments, flown on NOAA-9, the authors take advantage of the remote-sensing capabilities of each instrument. The AVHRR spectral channels were selected based on regions that are strongly transparent to clear sky conditions and are therefore useful for characterizing both surface and cloud-top conditions. The ERBE instruments make broadband observations that are important for climate studies. The approach of collocating these observations in time and space is used to study the radiative energy budget of three geographic regions: oceanic, savanna, and desert. 25 refs., 8 figs.

  1. A new radiometer for earth radiation budget studies

    SciTech Connect

    Weber, P.G.

    1992-01-01

    A critical need for the US Global Change Research Program is to provide continuous, well-calibrated radiometric data for radiation balance studies. This paper describes a new, compact, relatively light-weight, adaptable radiometer which will provide both spectrally integrated measurements and data in selected spectral bands. The radiometer design is suitable for use on (small) satellites, aircraft, or Unmanned Aerospace Vehicles (UAVs). Some considerations for the implementation of this radiometer on a small satellite are given. 17 refs.

  2. CARES: Carbonaceous Aerosol and Radiative Effects Study Science Plan

    SciTech Connect

    Zaveri, RA; Shaw, WJ; Cziczo, DJ

    2010-05-27

    Carbonaceous aerosol components, which include black carbon (BC), urban primary organic aerosols (POA), biomass burning aerosols, and secondary organic aerosols (SOA) from both urban and biogenic precursors, have been previously shown to play a major role in the direct and indirect radiative forcing of climate. The primary objective of the CARES 2010 intensive field study is to investigate the evolution of carbonaceous aerosols of different types and their effects on optical and cloud formation properties.

  3. A new radiometer for earth radiation budget studies

    SciTech Connect

    Weber, P.G.

    1992-05-01

    A critical need for the US Global Change Research Program is to provide continuous, well-calibrated radiometric data for radiation balance studies. This paper describes a new, compact, relatively light-weight, adaptable radiometer which will provide both spectrally integrated measurements and data in selected spectral bands. The radiometer design is suitable for use on (small) satellites, aircraft, or Unmanned Aerospace Vehicles (UAVs). Some considerations for the implementation of this radiometer on a small satellite are given. 17 refs.

  4. A first-principles approach to total-dose hardness assurance

    SciTech Connect

    Fleetwood, D.M.

    1995-11-01

    A first-principles approach to radiation hardness assurance was described that provides the technical background to the present US and European total-dose radiation hardness assurance test methods for MOS technologies, TM 1019.4 and BS 22900. These test methods could not have been developed otherwise, as their existence depends not on a wealth of empirical comparisons of IC data from ground and space testing, but on a fundamental understanding of MOS defect growth and annealing processes. Rebound testing should become less of a problem for advanced MOS small-signal electronics technologies for systems with total dose requirements below 50--100 krad(SiO{sub 2}) because of trends toward much thinner gate oxides. For older technologies with thicker gate oxides and for power devices, rebound testing is unavoidable without detailed characterization studies to assess the impact of interface traps on devices response in space. The QML approach is promising for future hardened technologies. A sufficient understanding of process effects on radiation hardness has been developed that should be able to reduce testing costs in the future for hardened parts. Finally, it is hoped that the above discussions have demonstrated that the foundation for cost-effective hardness assurance tests is laid with studies of the basic mechanisms of radiation effects. Without a diligent assessment of new radiation effects mechanisms in future technologies, one cannot be assured that the present generation of radiation test standards will continue to apply.

  5. Good Help Is Hard to Find: A Study in Retention and Motivation

    ERIC Educational Resources Information Center

    Norman, Scott W.

    2010-01-01

    This case study confronts the issues of staff motivation and teacher retention that face administrators in low-paying and/or low-performing small school settings when teacher pay is low and morale is lower, especially in communities having a lower economic base. It will present not only opportunities to try to keep good teachers but also…

  6. AN 11-YEAR FIELD STUDY WITH PASTEURIA PENETRANS: LESSONS LEARNED THE HARD WAY.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Beginning in 1998, a bioassay using second-stage juveniles (J2) from a greenhouse (GH) population of the root-knot nematode Meloidogyne arenaria (Ma) was used to monitor endospore densities of the bacterium Pasteuria penetrans, which was parasitizing Ma in a long-term rotation study (begun in 1991)....

  7. P-stop isolation study of irradiated n-in-p type silicon strip sensors for harsh radiation environments

    NASA Astrophysics Data System (ADS)

    Printz, Martin

    2016-09-01

    In order to determine the most radiation hard silicon sensors for the CMS Experiment after the Phase II Upgrade in 2023 a comprehensive study of silicon sensors after a fluence of up to 1.5 ×1015neq /cm2 corresponding to 3000fb-1 after the HL-LHC era has been carried out. The results led to the decision that the future Outer Tracker (20 cm < R < 110 cm) of CMS will consist of n-in-p type sensors. This technology is more radiation hard but also the manufacturing is more challenging compared to p-in-n type sensors due to additional process steps in order to suppress the accumulation of electrons between the readout strips. One possible isolation technique of adjacent strips is the p-stop structure which is a p-type material implantation with a certain pattern for each individual strip. However, electrical breakdown and charge collection studies indicate that the process parameters of the p-stop structure have to be carefully calibrated in order to achieve a sufficient strip isolation but simultaneously high breakdown voltages. Therefore a study of the isolation characteristics with four different silicon sensor manufacturers has been executed in order to determine the most suitable p-stop parameters for the harsh radiation environment during HL-LHC. Several p-stop doping concentrations, doping depths and different p-stop pattern have been realized and experiments before and after irradiation with protons and neutrons have been performed and compared to T-CAD simulation studies with Synopsys Sentaurus. The measurements combine the electrical characteristics measured with a semi-automatic probestation with Sr90 signal measurements and analogue readout. Furthermore, some samples have been investigated with the help of a cosmic telescope with high resolution allowing charge collection studies of MIPs penetrating the sensor between two strips.

  8. A Study of Radiative Bottomonium Transitions using Converted Photons

    SciTech Connect

    Lees, J.P.; Poireau, V.; Prencipe, E.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Martinelli, M.; Milanes, D.A.; Palano, A.; Pappagallo, M.; Eigen, G.; Stugu, B.; Sun, L.; Brown, D.N.; Kerth, L.T.; Kolomensky, Yu.G.; Lynch, G.; Koch, H.; Schroeder, T.; Asgeirsson, D.J.; Hearty, C.; /British Columbia U. /Brunel U. /Novosibirsk, IYF /UC, Irvine /UC, Riverside /UC, Santa Barbara /UC, Santa Cruz /Caltech /Cincinnati U. /Colorado U. /Colorado State U. /Dortmund U. /Dresden, Tech. U. /Ecole Polytechnique /Edinburgh U. /INFN, Ferrara /INFN, Ferrara /Ferrara U. /INFN, Ferrara /Frascati /INFN, Genoa /Genoa U. /INFN, Genoa /INFN, Genoa /Genoa U. /INFN, Genoa /Indian Inst. Tech., Guwahati /Harvard U. /Harvey Mudd Coll. /Heidelberg U. /Humboldt U., Berlin /Imperial Coll., London /Iowa State U. /Iowa State U. /Johns Hopkins U. /Paris U., VI-VII /LLNL, Livermore /Liverpool U. /Queen Mary, U. of London /Royal Holloway, U. of London /Royal Holloway, U. of London /Louisville U. /Mainz U., Inst. Kernphys. /Manchester U. /Maryland U. /Massachusetts U., Amherst /MIT /McGill U. /INFN, Milan /Milan U. /INFN, Milan /INFN, Milan /Milan U. /Mississippi U. /Montreal U. /INFN, Naples /Naples U. /NIKHEF, Amsterdam /NIKHEF, Amsterdam /Notre Dame U. /Ohio State U. /Oregon U. /INFN, Padua /Padua U. /INFN, Padua /INFN, Padua /Padua U. /Paris U., VI-VII /INFN, Perugia /Perugia U. /INFN, Pisa /Pisa U. /INFN, Pisa /Pisa, Scuola Normale Superiore /INFN, Pisa /Pisa U. /INFN, Pisa /INFN, Pisa /Pisa U. /INFN, Pisa /Princeton U. /INFN, Rome /INFN, Rome /Rome U. /INFN, Rome /INFN, Rome /Rome U. /INFN, Rome /Rostock U. /Rutherford /DAPNIA, Saclay /SLAC /South Carolina U. /Southern Methodist U. /Stanford U., Phys. Dept. /SUNY, Albany /Tel Aviv U. /Tennessee U. /Texas Nuclear Corp., Austin /Texas U., Dallas /INFN, Turin /Turin U. /INFN, Trieste /Trieste U. /Valencia U. /Victoria U. /Warwick U. /Wisconsin U., Madison

    2011-08-15

    The authors use (111 {+-} 1) million {Upsilon}(3S) and (89 {+-} 1) million {Upsilon}(2S) events recorded by the BABAR detector at the PEP-II B-factory at SLAC to perform a study of radiative transitions betwen bottomonium states using photons that have been converted to e{sup +}e{sup -} pairs by the detector material. They observe {Upsilon}(3S) {yields} {gamma}{chi}{sub b0,2}(1P) decay, make precise measurements of the branching fractions for {chi}{sub b1,2}(1P, 2P) {yields} {gamma}{Upsilon}(1S) and {chi}{sub b1,2}(2P) {yields} {gamma}{Upsilon}(2S) decays, and search for radiative decay to the {eta}{sub b}(1S) and {eta}{sub b}(2S) states.

  9. A study of the acoustical radiation force considering attenuation

    NASA Astrophysics Data System (ADS)

    Wu, RongRong; Liu, XiaoZhou; Gong, XiuFen

    2013-07-01

    Acoustical tweezer is a primary application of the radiation force of a sound field. When an ultrasound focused beam passes through a micro-particle, like a cell or living biological specimens, the particle will be manipulated accurately without physical contact and invasion, due to the three-dimensional acoustical trapping force. Based on the Ray acoustics approach in the Mie regime, this work discusses the effects on the particle caused by Gaussian focused ultrasound, studies the acoustical trapping force of spherical Mie particles by ultrasound in any position, and analyzes the numerical calculation on the two-dimensional acoustical radiation force. This article also analyzes the conditions for the acoustical trapping phenomenon, and discusses the impact of the initial position and size of the particle on the magnitude of the acoustical radiation force. Furthermore, this paper considers the ultrasonic attenuation in a particle in the case of two-dimension, studies the attenuation's effects on the acoustical trapping force, and amends the calculation to the ordinary case with attenuation.

  10. Magnetospheric Line Radiation: A systematic study using DEMETER spacecraft

    NASA Astrophysics Data System (ADS)

    Nemec, F.; Santolik, O.; Parrot, M.; Berthelier, J.-J.

    We present results of a systematic survey of Magnetospheric Line Radiation MLR observed since the beginning of the DEMETER mission DEMETER is a French micro-satellite launched in June 2004 altitude of orbit about 700 km designed to study electromagnetic phenomena connected with seismic or man-made activity An automatic identification procedure of possible MLR events has been developed and used in order to obtain a statistically significant data set We show that there are two principally different classes of events 1 events with the spacing of 50 100 or 60 120 Hz so-called Power Line Harmonic Radiation PLHR 2 events with other spacing While the first class of events originates from power systems on the Earth s surface and the frequency spacing well corresponds to the fundamental frequency of the radiating power system the second class is most probably generated in a completely natural way All the events are thoroughly analyzed using both statistical tens of cases have been found and case-study approach especially for low frequencies when all the six components of electromagnetic field are measured

  11. A hard X-ray study of a manganese-terpyridine catalyst in a chromium-based Metal Organic Framework

    SciTech Connect

    Ramsey, Alexandra V.

    2015-08-28

    Hydrogen produced from water splitting is a promising source of clean energy. However, a robust catalyst is necessary to carry out the water oxidation step of water splitting. In this study, the catalyst studied was [(terpy)Mn(μ-O)2Mn(terpy)]3+ (MnTD) synthesized in the Metal Organic Framework (MOF) MIL-101(Cr), and the method used for analysis was hard X-ray powder diffraction. The diffraction data was used to detect the presence of MOF in different catalytic stages, and lattice parameters were assigned to the samples containing MOF. Fourier maps were constructed with GSAS II to determine the contents of the MOF as preliminary studies suggested that MnTD may not be present. Results showed that MOF is present before catalysis occurs but disappears by the time 45 minutes of catalysis has ensued. Changes in the MOF’s lattice parameters and location of electron density in the Fourier maps suggest attractions between the MOF and catalyst that may lead to MOF degradation. Fourier maps also revealed limited, if any, amounts of MnTD, even before catalysis occurred. Molecular manganese oxide may be the source of the high rate of water oxidation catalysis in the studied system.

  12. Chemometric Study of Trace Elements in Hard Coals of the Upper Silesian Coal Basin, Poland

    PubMed Central

    Rompalski, Przemysław; Cybulski, Krzysztof; Chećko, Jarosław

    2014-01-01

    The objective of the study was the analysis of trace elements contents in coals of the Upper Silesian Coal Basin (USCB), which may pose a potential threat to the environment when emitted from coal processing systems. Productive carbon overburden in central and southern zones of the USCB is composed mostly of insulating tertiary formations of a thickness from a few m to 1,100 m, and is represented by Miocene and Pliocene formations. In the data study the geological conditions of the coal seams of particular zones of the USCB were taken into account and the hierarchical clustering analysis was applied, which enabled the exploration of the dissimilarities between coal samples of various zones of the USCB in terms of basic physical and chemical parameters and trace elements contents. Coals of the northern and eastern zones of the USCB are characterized by high average Hg and low average Ba, Cr, and Ni contents, whereas coals of southern and western zones are unique due to high average concentrations of Ba, Co, Cu, Ni, and V. Coals of the central part of the USCB are characterized by the highest average concentration of Mn and the lowest average concentrations of As, Cd, Pb, V, and Zn. PMID:24967424

  13. Bidirectional Reflectance Functions for Application to Earth Radiation Budget Studies

    NASA Technical Reports Server (NTRS)

    Manalo-Smith, N.; Tiwari, S. N.; Smith, G. L.

    1997-01-01

    Reflected solar radiative fluxes emerging for the Earth's top of the atmosphere are inferred from satellite broadband radiance measurements by applying bidirectional reflectance functions (BDRFs) to account for the anisotropy of the radiation field. BDRF's are dependent upon the viewing geometry (i.e. solar zenith angle, view zenith angle, and relative azimuth angle), the amount and type of cloud cover, the condition of the intervening atmosphere, and the reflectance characteristics of the underlying surface. A set of operational Earth Radiation Budget Experiment (ERBE) BDRFs is available which was developed from the Nimbus 7 ERB (Earth Radiation Budget) scanner data for a three-angle grid system, An improved set of bidirectional reflectance is required for mission planning and data analysis of future earth radiation budget instruments, such as the Clouds and Earth's Radiant Energy System (CERES), and for the enhancement of existing radiation budget data products. This study presents an analytic expression for BDRFs formulated by applying a fit to the ERBE operational model tabulations. A set of model coefficients applicable to any viewing condition is computed for an overcast and a clear sky scene over four geographical surface types: ocean, land, snow, and desert, and partly cloudy scenes over ocean and land. The models are smooth in terms of the directional angles and adhere to the principle of reciprocity, i.e., they are invariant with respect to the interchange of the incoming and outgoing directional angles. The analytic BDRFs and the radiance standard deviations are compared with the operational ERBE models and validated with ERBE data. The clear ocean model is validated with Dlhopolsky's clear ocean model. Dlhopolsky developed a BDRF of higher angular resolution for clear sky ocean from ERBE radiances. Additionally, the effectiveness of the models accounting for anisotropy for various viewing directions is tested with the ERBE along tract data. An area

  14. Experimental study on hard x-rays emitted from metre-scale negative discharges in air

    NASA Astrophysics Data System (ADS)

    Kochkin, P. O.; van Deursen, A. P. J.; Ebert, U.

    2015-01-01

    We investigate the development of metre long negative discharges and focus on their x-ray emissions. We describe appearance, timing and spatial distribution of the x-rays. They appear in bursts of nanosecond duration mostly in the cathode area. The spectrum can be characterized by an exponential function with 200 keV characteristic photon energy. With nanosecond-fast photography we took detailed images of the pre-breakdown phenomena during the time when x-rays were registered. We found bipolar discharge structures, also called ‘pilot systems’, in the vicinity of the cathode. As in our previous study of x-rays from positive discharges, we correlate the x-ray emission with encounters between positive and negative streamers. We suggest that a similar process is responsible for x-rays generated by lightning leaders.

  15. A study of microindentation hardness tests by mechanism-based strain gradient plasticity

    SciTech Connect

    Huang, Y.; Xue, Z.; Gao, H.; Nix, W. D.; Xia, Z. C.

    2000-08-01

    We recently proposed a theory of mechanism-based strain gradient (MSG) plasticity to account for the size dependence of plastic deformation at micron- and submicron-length scales. The MSG plasticity theory connects micron-scale plasticity to dislocation theories via a multiscale, hierarchical framework linking Taylor's dislocation hardening model to strain gradient plasticity. Here we show that the theory of MSG plasticity, when used to study micro-indentation, indeed reproduces the linear dependence observed in experiments, thus providing an important self-consistent check of the theory. The effects of pileup, sink-in, and the radius of indenter tip have been taken into account in the indentation model. In accomplishing this objective, we have generalized the MSG plasticity theory to include the elastic deformation in the hierarchical framework. (c) 2000 Materials Research Society.

  16. Retaining traditionally hard to reach participants: Lessons learned from three childhood obesity studies.

    PubMed

    Buscemi, Joanna; Blumstein, Lara; Kong, Angela; Stolley, Melinda R; Schiffer, Linda; Odoms-Young, Angela; Bittner, Cheryl; Fitzgibbon, Marian L

    2015-05-01

    Retaining underserved populations, particularly low-income and/or minority participants in research trials, presents a unique set of challenges. In this paper, we describe the initial retention strategies and enhanced the retention strategies over time across three childhood obesity prevention trials. Hip-Hop to Health Jr. (HH) was a randomized controlled trial (RCT) testing a preschool-based obesity prevention intervention among predominately African-American children. Retention was 89% at 14-weeks, 71% at 1-year, and 73% at 2-year follow-up. Primary retention strategies for HH included: 1) collaboration with a community-based organization to enhance program credibility; 2) continuity of data collection locations; 3) collecting detailed contact information and provision of monetary compensation; and 4) developing a detailed tracking/search protocol. In a follow-up trial, Hip-Hop to Health Jr. Obesity Prevention Effectiveness Trial (HH Effectiveness), 95% of participants completed assessment at 14 weeks and 88% completed assessment at 1 year. For this trial, we emphasized staffing continuity in order to enhance participant relationship building and required data collection staff to have relevant community service experience. In a third study, we assessed dietary quality among participants in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) across three time points following the WIC food package shift instituted nationally in 2009. Retention rates were 91% at 12 months and 89% at 18 months. For our WIC\\ study, we augmented retention by developing a home data collection protocol and increased focus on staff diversity training. We conclude with a summary of key strategies and suggestions for future research.

  17. More Older Women Hitting the Bottle Hard

    MedlinePlus

    ... medlineplus.gov/news/fullstory_164321.html More Older Women Hitting the Bottle Hard Study found dramatic jump ... March 28, 2017 (HealthDay News) -- More older American women than ever are drinking -- and drinking hard, a ...

  18. Kinetics of hardness evolution during annealing of gamma-irradiated polycarbonate

    SciTech Connect

    Yeh, S. H.; Chen, P. Y.; Lee, Sanboh; Harmon, Julie

    2012-12-01

    This study focuses on the evolution in microhardness values that accompany isothermal annealing in gamma-irradiated polycarbonate (PC). Hardness increases with increasing annealing time, temperature, and gamma radiation dose. A model composed of a mixture of first and zero order structure relaxation is proposed to interpret the hardness data. The rate constant data fit the Arrhenius equation, and the corresponding activation energy decreases with increasing dose. The extent of structural relaxation that controls the hardness in post-annealed PC increases with increasing annealing temperature and dose. The model demonstrates that hardness evolution in PC is an endothermic process. By contrast, when the model is applied to irradiated poly(methyl methacrylate) and hydroxyethyl methacrylate copolymer, hardness evolution is an exothermic process.

  19. Computational Studies of Hard Disks: Contact Percolation, Fragility, Frictional Families and Basin Volumes

    NASA Astrophysics Data System (ADS)

    Shen, Tianqi

    This thesis presents four computational and theoretical studies of the structural, mechanical, and vibrational properties of purely repulsive disks, dimer-, and ellipse-shaped particles with and without friction. The first study investigated the formation of interparticle contact networks below jamming onset at packing fraction φJ, where the pressure of the system becomes nonzero. We generated ensembles of static packings of frictionless disks over a range of packing fraction. We find that the network of interparticle contacts forms a system spanning cluster at a critical packing fraction φP < φJ. The contact percolation transition also signals the onset of cooperative non-affine particle motion and non-trivial response to applied stress. For the second project, we performed molecular dynamics simulations of dense liquids composed of bidisperse dimer- and ellipse-shaped particles over a wide range of temperature and packing fraction. We measured structural relaxation times for the translational and rotational degrees of freedom. We find that the slow dynamics for dense liquids composed of dimer- and ellipse-shaped particles are qualitatively the same, despite the fact that zero-temperature static packings of dimers are isostatic, while static packings of ellipses are hypostatic. We also show that the fragility of the structural relaxation time decreases with increasing aspect ratio for both dimer- and ellipse-shaped particles. For the third project, we developed a novel method to calculate and predict the average contact number as a function of the static friction coefficient for disk packings. We employed a novel numerical method that allowed us to enumerate sets of packings with m = N0c -- Nc missing contacts relative to the isostatic value N0c We show that the probability Pm(micro) to obtain a static packing with m missing contacts at micro can be expressed as a power series in micro. Using Pm(micro), we find that the average contact number versus micro

  20. Energetic electrons, hard x-ray emission and MHD activity studies in the IR-T1 tokamak.

    PubMed

    Agah, K Mikaili; Ghoranneviss, M; Elahi, A Salar

    2015-01-01

    Determinations of plasma parameters as well as the Magnetohydrodynamics (MHD) activity, energetic electrons energy and energy confinement time are essential for future fusion reactors experiments and optimized operation. Also some of the plasma information can be deduced from these parameters, such as plasma equilibrium, stability, and MHD instabilities. In this contribution we investigated the relation between energetic electrons, hard x-ray emission and MHD activity in the IR-T1 Tokamak. For this purpose we used the magnetic diagnostics and a hard x-ray spectroscopy in IR-T1 tokamak. A hard x-ray emission is produced by collision of the runaway electrons with the plasma particles or limiters. The mean energy was calculated from the slope of the energy spectrum of hard x-ray photons.

  1. Frequent hard physical activity lowered serum beta-carotene level in a population study of a rural city of Japan.

    PubMed

    Takatsuka, N; Kawakami, N; Ohwaki, A; Ito, Y; Matsushita, Y; Ido, M; Shimizu, H

    1995-07-01

    To determine the effect of physical activity on serum beta-carotene, we analyzed data about life styles including 3-day food records and blood samples collected from 57 men and 74 women in a rural city of Japan. Physical activity was asked as mean frequency of hard physical activities per week last year. A declining trend in serum beta-carotene was observed with increasing frequency of hard physical activities in men. In multiple regression analyses, the frequency of hard physical activities showed a negative partial correlation coefficient (r = -0.38, p = 0.007) with serum beta-carotene in men when controlled by age, BMI (body mass index), dietary factors (carotene intake, alcohol consumption and vitamin supplements use), smoking status, serum total cholesterol and serum triglycerides. These results suggest that frequent hard physical activity decreases serum beta-carotene especially in men.

  2. Hearing dogs: a longitudinal study of social and psychological effects on deaf and hard-of-hearing recipients.

    PubMed

    Guest, Claire M; Collis, Glyn M; McNicholas, June

    2006-01-01

    The organization Hearing Dogs for Deaf People provides assistance dogs that alert their deaf or hard-of-hearing recipients to key sounds, thus increasing their independence and also providing companionship. Fifty-one recipients took part in a longitudinal study to monitor the dogs' working performance over time and to examine the social and psychological effects of having a Hearing Dog. The Profile of Mood State (POMS) questionnaire and the General Health Questionnaire (GHQ) were used together with a Hearing Dog Questionnaire (HDQ) specifically developed for this study. There were a number of significant differences in measures of well-being between the period prior to placing the Hearing Dog and the period after placement, but there were no comparable differences during the year-long waiting period prior to placement of the dog. Recipients reported significant reductions in hearing-related problems such as response to environmental sounds; significant reductions in measures of tension, anxiety, and depression; and significant improvements in social involvement and independence. The longitudinal nature of this study supports evidence that these improvements persist for some time after the placement of a dog, with significant differences being reported, in many cases, up to 18 months after acquiring a dog.

  3. Effects of nicotine-containing chewing gum on oral soft and hard tissues: A clinical study.

    PubMed

    Christen, A G; Beiswanger, B B; Mallatt, M E; Tomich, C E; Drook, C A; McDonald, J L; Olson, B L; Stookey, G K

    1985-01-01

    A double-blind clinical trial was conducted to determine whether the use of a chewing gum containing 2.0 mg nicotine (as an adjunct to a stop-smoking program) had any effects upon oral health. A total of 193 adults who smoked cigarettes volunteered with informed consent, were given routine dental prophylaxes, and were examined for the presence of plaque, stained pellicle, gingivitis, calculus, and general oral pathosis. The subjects were then randomly assigned to use either a nicotine-containing or a placebo chewing gum. After 15 weeks the subjects were recalled and re-examined. Smoking cessation was determined through questionnaire and analysis of the carbon monoxide content of alveolar air. At the completion of the study, 79 subjects had used the placebo gum and 78 had used the nicotine gum. Data analysis indicated that the nicotine chewing gum had no significant influence on any of the oral health parameters graded, as compared to the placebo gum. The continuation of smoking, however, was associated with significant increases in gingivitis and calculus rates.

  4. QMC and phonon study of super-hard cubic boron carbon nitride

    NASA Astrophysics Data System (ADS)

    Atambo, Michael O.; Makau, N. W.; Amolo, G. O.; Maezono, Ryo

    2015-10-01

    In this study, we have applied phonon and quantum Monte Carlo (QMC) calculations to c-BC2N, which is derived from c-BN by the introduction of carbon, in search of cheaper as well as harder materials that have advantages over the traditionally known hardest material, diamond. There have been theoretical density functional theory (DFT) results of the bulk modulus, which indicate that c-BC2N has a higher bulk modulus than c-BN. However, varied findings of experimental data for the properties of c-BC2N reported by various groups appear to indicate a wide range of values. We found lattice structure instability at the high pressure region of c-BC2N which has been used for theoretical estimations of bulk modulus. We also examined the widely varying predictions depending on the functionals used in previous DFT works, using QMC with a more accurate treatment of the electronic interactions. Taking the instabilities into account, the QMC energy-volume fitting is still found to support that c-BC2N has a higher bulk modulus than c-BN, but with smaller difference than the prediction of the previous theoretical works. We also find substantial reductions in the bulk modulus due to zero point vibrational effects.

  5. a Study of Head-Disk Interaction Detection in the Hard-Disk Drives

    NASA Astrophysics Data System (ADS)

    Segu, Dawit Zenebe; Khan, Polina V.; Hwang, Pyung

    2015-09-01

    The reliability and performance of precision mechanical components that experience sliding under contact depend heavily on the friction and wear characteristics at the sliding interface. In order to improve the reliability of the sliding interface, there is a need to predict, measure and monitor any physical interactions at the head-disk interface (HDI). In the present work, the basic tribological characteristics of HDI were analyzed. The HDI during start-stop and constant speed operation using acoustic emission (AE) were studied. The Fast Fourier Transform (FFT) analysis of the AE signal was used to understand the interaction between the AE signal and the state of contact. In addition, we developed laser textured (LT) disk and the contact start-stop (CSS) tests were performed to investigate the effect of dimples on the stiction performance of the HDI. Furthermore, numerical analysis between the slider and disk surface pressure were performed using the boundary coordinate system and divergence formulation for the nonlinear Reynold's equation solution.

  6. NIST/ISAC standardization study: variability in assignment of intensity values to fluorescence standard beads and in cross calibration of standard beads to hard dyed beads.

    PubMed

    Hoffman, Robert A; Wang, Lili; Bigos, Martin; Nolan, John P

    2012-09-01

    Results from a standardization study cosponsored by the International Society for Advancement of Cytometry (ISAC) and the US National Institute of Standards and Technology (NIST) are reported. The study evaluated the variability of assigning intensity values to fluorophore standard beads by bead manufacturers and the variability of cross calibrating the standard beads to stained polymer beads (hard-dyed beads) using different flow cytometers. Hard dyed beads are generally not spectrally matched to the fluorophores used to stain cells, and spectral response varies among flow cytometers. Thus if hard dyed beads are used as fluorescence calibrators, one expects calibration for specific fluorophores (e.g., FITC or PE) to vary among different instruments. Using standard beads surface-stained with specific fluorophores (FITC, PE, APC, and Pacific Blue™), the study compared the measured intensity of fluorophore standard beads to that of hard dyed beads through cross calibration on 133 different flow cytometers. Using robust CV as a measure of variability, the variation of cross calibrated values was typically 20% or more for a particular hard dyed bead in a specific detection channel. The variation across different instrument models was often greater than the variation within a particular instrument model. As a separate part of the study, NIST and four bead manufacturers used a NIST supplied protocol and calibrated fluorophore solution standards to assign intensity values to the fluorophore beads. Values assigned to the reference beads by different groups varied by orders of magnitude in most cases, reflecting differences in instrumentation used to perform the calibration. The study concluded that the use of any spectrally unmatched hard dyed bead as a general fluorescence calibrator must be verified and characterized for every particular instrument model. Close interaction between bead manufacturers and NIST is recommended to have reliable and uniformly assigned

  7. Appraisal of selected epidemiologic issues from studies of lung cancer among uranium and hard rock miners

    SciTech Connect

    Petersen, G R; Sever, L E

    1982-04-01

    An extensive body of published information about lung cancer among uranium miners was reviewed and diverse information, useful in identifying important issues but not in resolving them was found. Measuring exposure and response; thresholds of exposure; latency or the period from first mining experience to death; effort to predict excess risk of death, using a model; effects of smoking and radon daughter exposure on the histology of lung tumors; and the interplay of factors on the overall risk of death were all examined. The general concept of thresholds; that is, an exposure level below which risk does not increase was considered. The conclusion is that it should be possible to detect and estimate an epidemiologic threshold when the cohorts have been followed to the death of all members. Issues concerning latency in the studies of uranium miners published to date were examined. It is believed that the induction-latent period for lung cancer among uranium miners may be: as little as 10 to more than 40 years; dependent on age at which exposure begins; exposure rate; and ethnicity or smoking habits. Although suggested as factual, their existence is uncertain. An effect due to the exposure rate may exist although it has not been factual, their existence is uncertain. An effect due to the exposure rate may exist although it has not been confirmed. The median induction-latent period appears to be in excess of the 15 years frequently cited for US uranium miner. A distinct pattern of shorter induction-latent periods with increasing age at first mining exposure is reported. The evidence for and against an unusual histologic pattern of lung cancers among uranium miners was examined. The ratio of epidermoid to small cell types was close to 1:2; the ratio in the general population is nearer 2:1. The histologic pattern warrants closer attention of pathologists and epidemiologists. (ERB) (ERB)

  8. Raman study of radiation-damaged zircon under hydrostatic compression

    NASA Astrophysics Data System (ADS)

    Nasdala, Lutz; Miletich, Ronald; Ruschel, Katja; Váczi, Tamás

    2008-12-01

    Pressure-induced changes of Raman band parameters of four natural, gem-quality zircon samples with different degrees of self-irradiation damage, and synthetic ZrSiO4 without radiation damage, have been studied under hydrostatic compression in a diamond anvil cell up to ~10 GPa. Radiation-damaged zircon shows similar up-shifts of internal SiO4 stretching modes at elevated pressures as non-damaged ZrSiO4. Only minor changes of band-widths were observed in all cases. This makes it possible to estimate the degree of radiation damage from the width of the ν3(SiO4) band of zircon inclusions in situ, almost independent from potential “fossilized pressures” or compressive strain acting on the inclusions. An application is the non-destructive analysis of gemstones such as corundum or spinel: broadened Raman bands are a reliable indicator of self-irradiation damage in zircon inclusions, whose presence allows one to exclude artificial color enhancement by high-temperature treatment of the specimen.

  9. Millimeter wave radiative transfer studies for precipitation measurements

    NASA Technical Reports Server (NTRS)

    Vivekanandan, J.; Evans, Frank

    1989-01-01

    Scattering calculations using the discrete dipole approximation and vector radiative transfer calculations were performed to model multiparameter radar return and passive microwave emission for a simple model of a winter storm. The issue of dendrite riming was addressed by computing scattering properties of thin ice disks with varying bulk density. It was shown that C-band multiparameter radar contains information about particle density and the number concentration of the ice particles. The radiative transfer modeling indicated that polarized multifrequency passive microwave emission may be used to infer some properties of ice hydrometers. Detailed radar modeling and vector radiative transfer modeling is in progress to enhance the understanding of simultaneous radar and radiometer measurements, as in the case of the proposed TRMM field program. A one-dimensional cloud model will be used to simulate the storm structure in detail and study the microphysics, such as size and density. Multifrequency polarized radiometer measurements from the SSMI satellite instrument will be analyzed in relation to dual-frequency and dual-polarization radar measurements.

  10. A study on characteristics of EM radiation from stripline structure

    NASA Astrophysics Data System (ADS)

    Kayano, Yoshiki; Inoue, Hiroshi

    2011-10-01

    In recent years, effective methods for predicting and suppressing electromagnetic interference over a broad band are required. In this paper, we focus on the prediction of electromagnetic (EM) radiation from a stripline structure with a ground thin wire by an equivalent circuit model. First, frequency responses of common-mode (CM) current on the printed circuit board and EM radiation are studied with finite difference time domain modeling. Secondly, an equivalent circuit model for predicting CM current is proposed. The equivalent circuit model for prediction is based on the concepts of CM antenna impedance, distributed constant circuit, and electric coupling between the power plane and the thin ground wire. Good agreement between the predicted and full-wave analysis results indicates the validity of the proposed equivalent circuit model. The frequency response of EM radiation from the stripline structure can be identified using our proposed model. In addition, the equivalent circuit model provides enough flexibility for different geometric parameters and can be used to develop physical insights and design guidelines.

  11. Carbon nanotubes buckypaper radiation studies for medical physics applications.

    PubMed

    Alanazi, Abdulaziz; Alkhorayef, Mohammed; Alzimami, Khalid; Jurewicz, Izabela; Abuhadi, Nouf; Dalton, Alan; Bradley, D A

    2016-11-01

    Graphite ion chambers and semiconductor diode detectors have been used to make measurements in phantoms but these active devices represent a clear disadvantage when considered for in vivo dosimetry. In such circumstance, dosimeters with atomic number similar to human tissue are needed. Carbon nanotubes have properties that potentially meet the demand, requiring low voltage in active devices and an atomic number similar to adipose tissue. In this study, single-wall carbon nanotubes (SWCNTs) buckypaper has been used to measure the beta particle dose deposited from a strontium-90 source, the medium displaying thermoluminescence at potentially useful sensitivity. As an example, the samples show a clear response for a dose of 2Gy. This finding suggests that carbon nanotubes can be used as a passive dosimeter specifically for the high levels of radiation exposures used in radiation therapy. Furthermore, the finding points towards further potential applications such as for space radiation measurements, not least because the medium satisfies a demand for light but strong materials of minimal capacitance.

  12. Rad-Hard/HI-REL FPGA

    NASA Technical Reports Server (NTRS)

    Wang, Jih-Jong; Cronquist, Brian E.; McGowan, John E.; Katz, Richard B.

    1997-01-01

    The goals for a radiation hardened (RAD-HARD) and high reliability (HI-REL) field programmable gate array (FPGA) are described. The first qualified manufacturer list (QML) radiation hardened RH1280 and RH1020 were developed. The total radiation dose and single event effects observed on the antifuse FPGA RH1280 are reported on. Tradeoffs and the limitations in the single event upset hardening are discussed.

  13. BioSentinel: Biosensors for Deep-Space Radiation Study

    NASA Technical Reports Server (NTRS)

    Lokugamage, Melissa P.; Santa Maria, Sergio R.; Marina, Diana B.; Bhattacharya, Sharmila

    2016-01-01

    The BioSentinel mission will be deployed on NASA's Exploration Mission 1 (EM-1) in 2018. We will use the budding yeast, Saccharomyces cerevisiae, as a biosensor to study the effect of deep-space radiation on living cells. The BioSentinel mission will be the first investigation of a biological response to space radiation outside Low Earth Orbit (LEO) in over 40 years. Radiation can cause damage such as double stand breaks (DSBs) on DNA. The yeast cell was chosen for this mission because it is genetically controllable, shares homology with human cells in its DNA repair pathways, and can be stored in a desiccated state for long durations. Three yeast strains will be stored dry in multiple microfluidic cards: a wild type control strain, a mutant defective strain that cannot repair DSBs, and a biosensor strain that can only grow if it gets DSB-and-repair events occurring near a specific gene. Growth and metabolic activity of each strain will be measured by a 3-color LED optical detection system. Parallel experiments will be done on the International Space Station and on Earth so that we can compare the results to that of deep space. One of our main objectives is to characterize the microfluidic card activation sequence before the mission. To increase the sensitivity of yeast cells as biosensors, desiccated yeast in each card will be resuspended in a rehydration buffer. After several weeks, the rehydration buffer will be exchanged with a growth medium in order to measure yeast growth and metabolic activity. We are currently working on a time-course experiment to better understand the effects of the rehydration buffer on the response to ionizing radiation. We will resuspend the dried yeast in our rehydration medium over a period of time; then each week, we will measure the viability and ionizing radiation sensitivity of different yeast strains taken from this rehydration buffer. The data obtained in this study will be useful in finalizing the card activation sequence for

  14. Free energies, vacancy concentrations, and density distribution anisotropies in hard-sphere crystals: A combined density functional and simulation study

    NASA Astrophysics Data System (ADS)

    Oettel, M.; Görig, S.; Härtel, A.; Löwen, H.; Radu, M.; Schilling, T.

    2010-11-01

    We perform a comparative study of the free energies and the density distributions in hard-sphere crystals using Monte Carlo simulations and density functional theory (employing Fundamental Measure functionals). Using a recently introduced technique [T. Schilling and F. Schmid, J. Chem. Phys. 131, 231102 (2009)10.1063/1.3274951] we obtain crystal free energies to a high precision. The free energies from fundamental measure theory are in good agreement with the simulation results and demonstrate the applicability of these functionals to the treatment of other problems involving crystallization. The agreement between fundamental measure theory and simulations on the level of the free energies is also reflected in the density distributions around single lattice sites. Overall, the peak widths and anisotropy signs for different lattice directions agree, however, it is found that fundamental measure theory gives slightly narrower peaks with more anisotropy than seen in the simulations. Among the three types of fundamental measure functionals studied, only the White Bear II functional [H. Hansen-Goos and R. Roth, J. Phys.: Condens. Matter 18, 8413 (2006)10.1088/0953-8984/18/37/002] exhibits sensible results for the equilibrium vacancy concentration and a physical behavior of the chemical potential in crystals constrained by a fixed vacancy concentration.

  15. Radiative Energy Budget Studies Using Observations from the Earth Radiation Budget Experiment (ERBE)

    NASA Technical Reports Server (NTRS)

    Ackerman, Steven A.; Frey, R.; Shie, M.; Olson, R.; Collimore, C.; Friedman, M.

    1997-01-01

    Our research activities under this NASA grant have focused on two broad topics associated with the Earth Radiation Budget Experiment (ERBE): (1) the role of clouds and the surface in modifying the radiative balance; and (2) the spatial and temporal variability of the earth's radiation budget. Each of these broad topics is discussed separately in the text that follows. The major points of the thesis are summarized in section 3 of this report. Other dissertation focuses on deriving the radiation budget over the TOGA COARE region.

  16. A Study of Selected Properties and Applications of AlMgB14 and Related Composites: Ultra-Hard Materials

    SciTech Connect

    Lewis, Theron L.

    2001-01-01

    This research presents a study of the hardness, electrical, and thermal properties AlMgB14 containing Al2MgO4 spinel. This research also investigated how much Al2MgO4 spinel consistently forms with AlMgB14, if AlMgB14 materials can be produced by hot isostatic pressing (HIP), what effects TiC and TiB2 have on this composite material, and the importance of mechanical alloying. Included also is a study of the variation in hardness measurements and how they relate to SI units. Heretofore, all ultra-hard materials (hardness > 40 GPA) have been found to be cubic in structure, electrical insulators, and expensive; the behavior of AlMgB14, which in certain specimens and compositions can have hardness values greater than 40 GPa, is therefore quite unusual since it is non-cubic, conductive, and moderate in cost. This offers an opportunity to investigate the relationship between hardness, thermal, and electrical properties from a new perspective. The main purpose of this project was to characterize the different properties of the AlMgB14 materials and to demonstrate that this material can be made in bulk. The technologies used for this study include microhardness measurement techniques, scanning electron microscopy, energy dispersive spectroscopy, x-ray diffraction spectroscopy, x-ray diffraction spectroscopy at different temperatures, optical microscopy, thermomechanical analysis, differential thermal analysis, 4-point probe resistivity, density techniques, Seebeck Effect, and Hall Effect. This research may lead to use of this material for applications where high abrasion resistance along with electrical conduction is needed. Also this research gave more information about a material that could have a great impact on industrial applications.

  17. A Next-Generation Hard X-Ray Nanoprobe Beamline for In Situ Studies of Energy Materials and Devices

    NASA Astrophysics Data System (ADS)

    Maser, Jörg; Lai, Barry; Buonassisi, Tonio; Cai, Zhonghou; Chen, Si; Finney, Lydia; Gleber, Sophie-Charlotte; Jacobsen, Chris; Preissner, Curt; Roehrig, Chris; Rose, Volker; Shu, Deming; Vine, David; Vogt, Stefan

    2014-01-01

    The Advanced Photon Source is developing a suite of new X-ray beamlines to study materials and devices across many length scales and under real conditions. One of the flagship beamlines of the APS upgrade is the In Situ Nanoprobe (ISN) beamline, which will provide in situ and operando characterization of advanced energy materials and devices under varying temperatures, gas ambients, and applied fields, at previously unavailable spatial resolution and throughput. Examples of materials systems include inorganic and organic photovoltaic systems, advanced battery systems, fuel cell components, nanoelectronic devices, advanced building materials and other scientifically and technologically relevant systems. To characterize these systems at very high spatial resolution and trace sensitivity, the ISN will use both nanofocusing mirrors and diffractive optics to achieve spots sizes as small as 20 nm. Nanofocusing mirrors in Kirkpatrick-Baez geometry will provide several orders of magnitude increase in photon flux at a spatial resolution of 50 nm. Diffractive optics such as zone plates and/or multilayer Laue lenses will provide a highest spatial resolution of 20 nm. Coherent diffraction methods will be used to study even small specimen features with sub-10 nm relevant length scale. A high-throughput data acquisition system will be employed to significantly increase operations efficiency and usability of the instrument. The ISN will provide full spectroscopy capabilities to study the chemical state of most materials in the periodic table, and enable X-ray fluorescence tomography. In situ electrical characterization will enable operando studies of energy and electronic devices such as photovoltaic systems and batteries. We describe the optical concept for the ISN beamline, the technical design, and the approach for enabling a broad variety of in situ studies. We furthermore discuss the application of hard X-ray microscopy to study defects in multi-crystalline solar cells, one

  18. A Next-Generation Hard X-Ray Nanoprobe Beamline for In Situ Studies of Energy Materials and Devices

    SciTech Connect

    Maser, Jong; Lai, Barry; Buonassisi, Toni; Cai, Zhonghou; Chen, Si; Finney, Lydia; Gleber, Sophie-Charlotte; Jacobsen, Chris; Preissner, Curt; Chris Roehrig; Rose, Volker; Shu, Deming; Vine, David; Vogt, Stefan

    2013-08-20

    The Advanced Photon Source is developing a suite of new X-ray beamlines to study materials and devices across many length scales and under real conditions. One of the flagship beamlines of the APS upgrade is the In Situ Nanoprobe (ISN) beamline, which will provide in situ and operando characterization of advanced energy materials and devices under varying temperatures, gas ambients, and applied fields, at previously unavailable spatial resolution and throughput. Examples of materials systems include inorganic and organic photovoltaic systems, advanced battery systems, fuel cell components, nanoelectronic devices, advanced building materials and other scientifically and technologically relevant systems. To characterize these systems at very high spatial resolution and trace sensitivity, the ISN will use both nanofocusing mirrors and diffractive optics to achieve spots sizes as small as 20 nm. Nanofocusing mirrors in Kirkpatrick–Baez geometry will provide several orders of magnitude increase in photon flux at a spatial resolution of 50 nm. Diffractive optics such as zone plates and/or multilayer Laue lenses will provide a highest spatial resolution of 20 nm. Coherent diffraction methods will be used to study even small specimen features with sub-10 nm relevant length scale. A high-throughput data acquisition system will be employed to significantly increase operations efficiency and usability of the instrument. The ISN will provide full spectroscopy capabilities to study the chemical state of most materials in the periodic table, and enable X-ray fluorescence tomography. In situ electrical characterization will enable operando studies of energy and electronic devices such as photovoltaic systems and batteries. We also describe the optical concept for the ISN beamline, the technical design, and the approach for enabling a broad variety of in situ studies. Furthermore, we discuss the application of hard X-ray microscopy to study defects in multi-crystalline solar

  19. Tensile and shear bond strength of hard and soft denture relining materials to the conventional heat cured acrylic denture base resin: An In-vitro study

    PubMed Central

    Lau, Mayank; Amarnath, G S; Muddugangadhar, B C; Swetha, M U; Das, Kopal Anshuraj Ashok Kumar

    2014-01-01

    significantly lower than denture hard reliners. How to cite the article: Lau M, Amarnath GS, Muddugangadhar BC, Swetha MU, Das KA. Tensile and shear bond strength of hard and soft denture relining materials to the conventional heat cured acrylic denture base resin: An In-vitro study. J Int Oral Health 2014;6(2):55-61. PMID:24876703

  20. Monte Carlo dose enhancement studies in microbeam radiation therapy

    SciTech Connect

    Martinez-Rovira, I.; Prezado, Y.

    2011-07-15

    Purpose: A radical radiation therapy treatment for gliomas requires extremely high absorbed doses resulting in subsequent deleterious side effects in healthy tissue. Microbeam radiation therapy (MRT) is an innovative technique based on the fact that normal tissue can withstand high radiation doses in small volumes without any significant damage. The synchrotron-generated x-ray beam is collimated and delivered to an array of narrow micrometer-sized planar rectangular fields. Several preclinical experiments performed at the Brookhaven National Laboratory (BNL) and at the European Synchrotron Radiation Facility (ESRF) confirmed that MRT yields a higher therapeutic index than nonsegmented beams of the same characteristics. This index can be greatly improved by loading the tumor with high atomic number (Z) contrast agents. The aim of this work is to find the high-Z element that provides optimum dose enhancement. Methods: Monte Carlo simulations (PENELOPE/penEasy) were performed to assess the peak and valley doses as well as their ratio (PVDR) in healthy tissue and in the tumor, loaded with different contrast agents. The optimization criteria used were maximization of the ratio between the PVDR values in healthy tissue respect to the PVDR in the tumor and minimization of bone and brain valley doses. Results: Dose enhancement factors, PVDR, and valley doses were calculated for different high-Z elements. A significant decrease of PVDR values in the tumor, accompanied by a gain in the valley doses, was found in the presence of high-Z elements. This enables the deposited dose in the healthy tissue to be reduced. The optimum high-Z element depends on the irradiation configuration. As a general trend, the best outcome is provided by the highest Z contrast agents considered, i.e., gold and thallium. However, lanthanides (especially Lu) and hafnium also offer a satisfactory performance. Conclusions: The remarkable therapeutic index in microbeam radiation therapy can be further

  1. Study of deuteron spectra under radiation belt with PAMELA instrument

    NASA Astrophysics Data System (ADS)

    Koldobskiy, S. A.; Adriani, O.; Barbarino, G. C.; Bazilevskaya, G. A.; Bellotti, R.; Boezio, M.; Bogomolov, E. A.; Bongi, M.; Bonvicini, V.; Bottai, S.; Bruno, A.; Cafagna, F.; Campana, D.; Carlson, P.; Casolino, M.; Castellini, G.; De Donato, C.; De Santis, C.; De Simone, N.; Di Felice, V.; Formato, V.; Galper, A. M.; Karelin, A. V.; Koldashov, S. V.; Krutkov, S. Y.; Kvashnin, A. A.; Kvashnin, A. N.; Leonov, A. A.; Malakhov, V. V.; Marcelli, L.; Martucci, M.; Mayorov, A. G.; Menn, W.; Merge', M.; Mikhailov, V. V.; Mocchiutti, E.; Monaco, A.; Mori, N.; Munini, R.; Osteria, G.; Palma, F.; Panico, B.; Papini, P.; Pearce, M.; Picozza, P.; Ricci, M.; Ricciarini, S. B.; Sarkar, R.; Scotti, V.; Simon, M.; Sparvoli, R.; Spillantini, P.; Stozhkov, Y. I.; Vacchi, A.; Vannuccini, E.; Vasilyev, G. I.; Voronov, S. A.; Yurkin, Y. T.; Zampa, G.; Zampa, N.

    2015-08-01

    This paper presents the results of measurements of proton and deuteron fluxes of albedo radiation in the Earth vicinity, obtained in the PAMELA experiment. PAMELA is an international experiment meant to study cosmic rays. PAMELA is carried out on board the satellite Resurs-DK1. High-precision equipment of the experiment allows registration and identification of cosmic ray particles of different varieties in a wide energy range. The albedo deuteron spectrum and albedo deuteron-to-proton fluxes ratio in the energy range 70 - 600 MeV/nucleon at altitude of 350 - 600 km for different geomagnetic latitudes is presented.

  2. When the truth is not too hard to handle: an event-related potential study on the pragmatics of negation.

    PubMed

    Nieuwland, Mante S; Kuperberg, Gina R

    2008-12-01

    Our brains rapidly map incoming language onto what we hold to be true. Yet there are claims that such integration and verification processes are delayed in sentences containing negation words like not. However, studies have often confounded whether a statement is true and whether it is a natural thing to say during normal communication. In an event-related potential (ERP) experiment, we aimed to disentangle effects of truth value and pragmatic licensing on the comprehension of affirmative and negated real-world statements. As in affirmative sentences, false words elicited a larger N400 ERP than did true words in pragmatically licensed negated sentences (e.g., "In moderation, drinking red wine isn't bad/good..."), whereas true and false words elicited similar responses in unlicensed negated sentences (e.g., "A baby bunny's fur isn't very hard/soft..."). These results suggest that negation poses no principled obstacle for readers to immediately relate incoming words to what they hold to be true.

  3. Upstream ion events with hard energy spectra: Lessons for their origin from a comparative statistical study (ACE/Geotail)

    NASA Astrophysics Data System (ADS)

    Maragkakis, M. G.; Anagnostopoulos, G. C.; Vassiliadis, E. S.

    2013-09-01

    In this paper we present statistical results from a comparison of ion events observed almost simultaneously by the Geotail spacecraft near the Earth's bow shock and by ACE moving around the libration point L1 (∼220 km). The main result of this study is that important features of the ACE ion events, as for instance, the ion flux, the ion energy spectral slope, and the particle composition, change drastically through propagation from the magnetosphere to the L1 point. Among other results we found that the ACE events show (1) a strong spectral hardening compared to the spectral index γGeotail value observed just outside the magnetosphere. It is a decreased value by an average factor<γGeotail/γACE>≈3, and (2) a percentage as low as ∼22% of the Geotail electron events which is accompanied by the presence of electrons at the position of ACE. We infer that a short duration ion event with a hard “solar” type energy spectrum, which is non-accompanied by energetic electrons, can originate from the Earth's magnetosphere, and that therefore, these results should be taken into account in space weather prediction research. More detailed information on the varying features of traveling ions and electrons from the bow shock to far distances are important with respect to the problem of their origin and are also presented and discussed in the paper.

  4. Exact diagonalization study of a half-filled extended hard-core boson model in one dimension

    NASA Astrophysics Data System (ADS)

    Kim, Sung Moon; Choi, Hwan Bin; Lee, Yong Woo; Lee, Ji-Woo

    2015-09-01

    We study a model for interacting spinless bosons in one dimension. The bosons are under a hard-core condition, which does not allow two or more bosons in the same site. However, nearestneighbor interactions between bosons ( V) and hoppings to the nearest empty site ( t) are allowed. As V increases from a large negative value, the system undergoes a quantum phase transition from a phase-separation (PS) phase to a superfluid (SF) phase because the hopping term overcomes the attractive energy. When V becomes positive and is increased more, the superfluid phase becomes a charge-density-wave (CDW) phase because the repulsive energy blocks the movements of bosons. Via exact diagonalizations, we calculated the ground-state energies, the correlation energies, and the kinetic energies to obtain signatures of the quantum phase transitions. We adopted a fast stateseeking algorithm that enabled us to calculate the ground states and the ground-state energies up to L = 32 more efficiently. Some results are compared with those of quantum Monte Carlo simulations by using stochastic series expansion for the Heisenberg point, and the momentum distribution functions for the three phases are discussed.

  5. Ultra-long Duration Balloon Mission Concept Study: EXIST-LITE Hard X-ray Imaging Survey

    NASA Technical Reports Server (NTRS)

    2003-01-01

    We carried out a mission concept Study for an ultra-long duration balloon (ULDB) mission to conduct a high-sensitivity hard x-ray (approx. 20-600 keV) imaging sky survey. The EXIST-LITE concept has been developed, and critical detector technologies for realistic fabrication of very large area Cd-Zn-Te imaging detector arrays are now much better understood. A ULDB mission such as EXIST-LITE is now even more attractive as a testbed for the full Energetic X-ray Imaging Survey Telescope (EXIST) mission, recommended by the Decadal Survey, and now included in the NASA Roadmap and Strategic Plan as one of the 'Einstein Probes'. In this (overdue!) Final Report we provide a brief update for the science opportunities possible with a ULDB mission such as EXIST-LITE and relate these to upcoming missions (INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) and Swift) as well as the ultimate very high sensitivity sky survey mission EXIST. We then review the progress made over this investigation in Detector/Telescope design concept, Gondola and Mission design concept, and Data Handling/Analysis.

  6. STUDIES IN WORKMEN'S COMPENSATION AND RADIATION INJURY. VOLUME III, A REPORT ON IONIZING RADIATION RECORD KEEPING.

    ERIC Educational Resources Information Center

    Atomic Energy Commission, Washington, DC.

    THE SUCCESSFUL OPERATION OF THE PERMISSIBLE LEVEL CONCEPT OF RADIATION CONTROL NECESSARILY ENTAILS A COMPREHENSIVE SYSTEM UNDER WHICH EXPOSURE MUST BE RECORDED AND EMPLOYEES NOTIFIED OF THEIR EXPOSURE HISTORY. IN AN INVESTIGATION OF RECORD KEEPING NECESSARY TO PROCESS RADIATION CLAIMS, QUESTIONNAIRES OR LETTERS WERE RECEIVED FROM 45 STATE AGENCIES…

  7. Influence of alkalinity, hardness and dissolved solids on drinking water taste: A case study of consumer satisfaction.

    PubMed

    Lou, Jie-Chung; Lee, Wei-Li; Han, Jia-Yun

    2007-01-01

    Two surveys of consumer satisfaction with drinking water conducted by Taiwan Water Supply Corp. are presented in this study. The study results show that although a lot of money was invested to modify traditional treatment processes, over 60% of local residents still avoided drinking tap water. Over half of the respondents felt that sample TT (from the traditional treatment process) was not a good drinking water, whether in the first or second survey, whereas almost 60% of respondents felt that samples PA, PB, CCL and CT (from advanced treatment processes) were good to drink. For all drinking water samples, respondent satisfaction with a sample primarily depended on it having no unpleasant flavors. Taiwan Environmental Protection Administration plans to revise the drinking water quality standards for TH and TDS in the near future. The new standards require a lower TH concentration (from currently 400mg/L (as CaCO(3)) to 150mg/L (as CaCO(3))), and a lower TDS maximum admissible concentration from the current guideline of 600 to 250mg/L. Therefore, this study also evaluated the impacts on drinking water tastes caused by variations in TH and TDS concentrations, and assessed the need to issue more strict drinking water quality standards for TH and TDS. The research results showed that most respondents could not tell the difference in water taste among water samples with different TDS, TH and alkalinity. Furthermore, hardness was found to be inversely associated with cardiovascular diseases and cancers, and complying with more strict standards would lead most water facilities to invest billions of dollars to upgrade their treatment processes. Consequently, in terms of drinking water tastes alone, this study suggested that Taiwan Environmental Protection Administration should conduct more thorough reviews of the scientific literature that provides the rationale for setting standards and reconsider if it is necessary to revise drinking water quality standards for TH and

  8. A solar radiation model for use in climate studies

    NASA Technical Reports Server (NTRS)

    Chou, Ming-Dah

    1992-01-01

    A solar radiation routine is developed for use in climate studies that includes absorption and scattering due to ozone, water vapor, oxygen, carbon dioxide, clouds, and aerosols. Rayleigh scattering is also included. Broadband parameterization is used to compute the absorption by water vapor in a clear atmosphere, and the k-distribution method is applied to compute fluxes in a scattering atmosphere. The reflectivity and transmissivity of a scattering layer are computed analytically using the delta-four-stream discrete-ordinate approximation. The two-stream adding method is then applied to compute fluxes for a composite of clear and scattering layers. Compared to the results of high spectral resolution and detailed multiple-scattering calculations, fluxes and heating rate are accurately computed to within a few percent. The high accuracy of the flux and heating-rate calculations is achieved with a reasonable amount of computing time. With the UV and visible region grouped into four bands, this solar radiation routine is useful not only for climate studies but also for studies on photolysis in the upper atmosphere and photosynthesis in the biosphere.

  9. Perceptions of Itinerant Deaf Educators and General Educators: A Case Study of Teacher Insights on the Deaf and Hard-of-Hearing Push-In Service Model

    ERIC Educational Resources Information Center

    Rabinsky, Rebecca J.

    2012-01-01

    This dissertation examined the perceptions of three itinerant deaf educators and three general educators at the elementary level on the deaf and hard-of-hearing (D/HH) push-in service model in one American southwestern, PK-12 public school district. Open-ended research questions guided the study on educator perceptions of the model in general and…

  10. Comprehension of Written Grammar Test: Reliability and Known-Groups Validity Study with Hearing and Deaf and Hard-of-Hearing Students

    ERIC Educational Resources Information Center

    Cannon, Joanna E.; Hubley, Anita M.; Millhoff, Courtney; Mazlouman, Shahla

    2016-01-01

    The aim of the current study was to gather validation evidence for the "Comprehension of Written Grammar" (CWG; Easterbrooks, 2010) receptive test of 26 grammatical structures of English print for use with children who are deaf and hard of hearing (DHH). Reliability and validity data were collected for 98 participants (49 DHH and 49…

  11. OCT visualization of acute radiation mucositis: pilot study

    NASA Astrophysics Data System (ADS)

    Gladkova, Natalia; Maslennikova, Anna; Terentieva, Anna; Fomina, Yulia; Khomutinnikova, Nina; Balalaeva, Irina; Vyseltseva, Yulia; Larin, Roman; Kornoukhova, Natalia; Shakhov, Andrey; Shakhova, Natalia; Gelikonov, Grigory; Kamensky, Vladislav; Feldchtein, Felix

    2005-08-01

    We present pilot results in optical coherence tomography (OCT) visualization of normal mucosa radiation damage. 15 patients undergoing radiation treatment of head and neck cancer were enrolled. OCT was used to monitor the mucositis development during and after treatment. OCT can see stages of radiation mucositis development, including hidden ones, before any clinical manifestations.

  12. Biodiversity of green algae covering artificial hard substrate surfaces in a suburban environment: a case study using molecular approaches.

    PubMed

    Hallmann, Christine; Hoppert, Michael; Mudimu, Opayi; Friedl, Thomas

    2016-10-01

    In Middle European suburban environments green algae often cover open surfaces of artificial hard substrates. Microscopy reveals the Apatococcus/Desmococcus morphotype predominant over smaller coccoid forms. Adverse conditions such as limited water availability connected with high PAR and UV irradiance may narrow the algal diversity to a few specialists in these subaerial habitats. We used rRNA gene cloning/sequencing from both DNA extracts of the biofilms without culturing as well as cultures, for the unambiguous determination of the algal composition and to assess the algal diversity more comprehensively. The culture independent approach revealed mainly just two genera (Apatococcus, Trebouxia) for all study sites and five molecular operational taxonomic units (OTUs) for a particular study site, which based on microscopic observation was the one with the highest morphological diversity. The culture approach, however, revealed seven additional OTUs from five genera (Chloroidium, Coccomyxa, Coenochloris, Pabia, Klebsormidium) and an unidentified trebouxiophyte lineage for that same site; only two OTUs were shared by both approaches. Two OTUs or species were recovered for which references have been isolated only from Antarctica so far. However, the internal transcribed spacer (ITS) sequence differences among them supported they are representing distinct populations of the same species. Within Apatococcus five clearly distinct groups of ITS sequences, each putatively representing a distinct species, were recovered with three or four such ITS types co-occurring at the same study site. Except for the streptophyte Klebsormidium only members of Trebouxiophyceae were detected suggesting these algae may be particularly well-adapted to subaerial habitats.

  13. The peri-implant hard and soft tissues at different implant systems. A comparative study in the dog.

    PubMed

    Abrahamsson, I; Berglundh, T; Wennström, J; Lindhe, J

    1996-09-01

    The aim of this study of the present experiment was to study the marginal periimplant tissues at intentionally non-submerged (1-stage implants) and initially submerged and subsequently exposed implants (2-stage implants). 5 beagle dogs, about 1-year-old, were used, 3 months after the extraction of the mandibular premolars, fixtures of the Astra Tech Implants Dental System, the Brånemark System and the Bonefit--ITI system were installed. In each mandibular quadrant, 1 fixture of each implant system was installed in a randomised order. The installation procedure followed the recommendations given in the manuals for each system. Thus, following installation, the bone crest coincided with the fixture margin of the Astra Tech Implants Dental System and the Brånemark System, whereas the border between the plasma sprayed and the machined surface of the Bonefit-ITI implant system was positioned at the level of the bone crest. Following a healing period of 3 months, abutment connection was carried out in the 2-stage systems (the Astra Tech Implants Dental System and the Brånemark system). A 6-month period of plaque control was initiated. The animals were sacrificed and biopsies representing each important region dissected. The tissue samples were prepared for light microscopy and exposed to histometric and morphometric measurements. The mucosal barrier which formed to the titanium surface following 1-stage and 2-stage implant installations comprised an epithelial and a connective tissue component, which for that 3 systems studied, had similar dimensions and composition. The amount of lamellar bone contained in the periimplant region close to the fixture part of the 3-implant systems was almost identical. It is suggested that correctly performed implant installation may ensure proper conditions for both and hard tissue healing, and that the geometry of the titanium implant seems to be of limited importance.

  14. Theoretical cloud radiation studies in support of the Atmospheric Radiation Measurement Program. Final report, October 1990--October 1993

    SciTech Connect

    Wiscombe, W.J.; Cahalan, R.F.; Davis, A.B.; Marshak, A.L.; Ridgway, W.L.

    1994-01-01

    The ARM research project has as its ultimate goal the improvement of theoretical understanding of radiation processes in real clouds. The strategy is to use remote and in situ cloud observations to inform fractal models that elegantly capture the enormous spatial heterogeneity of real clouds. The project was motivated by the great importance assigned to the cloud-radiation problem in understanding climate, and by the recognition that GCM predictions of grid-box-average liquid/ice water are insufficient to assign cloud radiative properties. The project was designed to have the following logical progression: analyze cloud observations, using statistical methods developed in turbulence theory, non-linear dynamics, and the study of multifractals; based on these analyses, develop models, mainly with a multi-fractal origin, for the spatial distribution of cloud water; and study the radiative properties of these model clouds using the Monte Carlo method.

  15. Ionizing radiation-induced mutagenesis: radiation studies in Neurospora predictive for results in mammalian cells

    NASA Technical Reports Server (NTRS)

    Evans, H. H.; DeMarini, D. M.

    1999-01-01

    Ionizing radiation was the first mutagen discovered and was used to develop the first mutagenicity assay. In the ensuing 70+ years, ionizing radiation became a fundamental tool in understanding mutagenesis and is still a subject of intensive research. Frederick de Serres et al. developed and used the Neurospora crassa ad-3 system initially to explore the mutagenic effects of ionizing radiation. Using this system, de Serres et al. demonstrated the dependence of the frequency and spectra of mutations induced by ionizing radiation on the dose, dose rate, radiation quality, repair capabilities of the cells, and the target gene employed. This work in Neurospora predicted the subsequent observations of the mutagenic effects of ionizing radiation in mammalian cells. Modeled originally on the mouse specific-locus system developed by William L. Russell, the N. crassa ad-3 system developed by de Serres has itself served as a model for interpreting the results in subsequent systems in mammalian cells. This review describes the primary findings on the nature of ionizing radiation-induced mutagenesis in the N. crassa ad-3 system and the parallel observations made years later in mammalian cells.

  16. Interpenetrating polymer networks based on a thermoplastic elastomer, using radiation techniques

    NASA Astrophysics Data System (ADS)

    Shirodkar, Bhavna D.; Burford, Robert P.

    2001-07-01

    Styrene-butadiene-styrene thermoplastic elastomers can be transformed into Interpenetrating polymer networks using γ-radiation crosslinking. Trimethylol propanetriacrylate was used as the radiation crosslinker for styrene. The study shows that the hardness of the sample increased with radiation dose while the tensile strength remained constant.

  17. Evaluation of Norfolk Harbor Deepening Project (A Study on Its Possible Impact on Oysters, Hard Clams and Oyster Drills).

    DTIC Science & Technology

    1984-06-20

    Virginia 23062 DTIC 20 June 1984 ELECTE ~L&JMAR 12 i9BB IA B! ,", Contract No. DACW65-84-M-0056 -Ap’oved to: publicO t01b0 I D)WtbuZidon Unlimited .~Norfolk...impact on the transport of the larval oysters and hard clams during their planktonic stage. Oysters and hard clams are widely tolerant to high salinity...planktonic for about 2 weeks and during this period are transported by currents. This latter aspect will be covered later in our discussion on oysters. ~i

  18. Excited state property of hardly photodissociable heme-CO adduct studied by time-dependent density functional theory.

    PubMed

    Ohta, Takehiro; Pal, Biswajit; Kitagawa, Teizo

    2005-11-10

    While most of CO-bound hemes are easily photodissociated with a quantum yield of nearly unity, we occasionally encounter a CO-heme which appears hardly photodissociable under the ordinary measurement conditions of resonance Raman spectra using CW laser excitation and a spinning cell. This study aims to understand such hemes theoretically, that is, the excited-state properties of the five-coordinate heme-CO adduct (5cH) as well as the 6c heme-CO adduct (6cH) with a weak axial ligand. Using a hybrid density functional theory, we scrutinized the properties of the ground and excited spin states of the computational models of a 5cH and a water-ligated 6cH (6cH-H(2)O) and compared these properties with those of a photodissociable imidazole-ligated 6cH (6cH-Im). Jahn-Teller softening for the Fe-C-O bending potential in the a(1)-e excited state was suggested. The excited-state properties of 6cH-Im and 5cH were further studied with time-dependent DFT theory. The reaction products of 6cH-Im and 5cH were assumed to be quintet and triplet states, respectively. According to the time-dependent DFT calculations, the Q excited state of 6cH-Im, which is initially a pure pi-pi state, crosses the Fe-CO dissociative state (2A') without large elongation of the Fe-CO bond. In contrast, the Q state of the 5cH does not cross the Fe-CO dissociative state but results in the formation of the excited spin state with a bent Fe-C-O. Consequently, photoisomerization from linear to bent Fe-C-O in the 5cH is a likely mechanism for apparent nonphotodissociation.

  19. New BNL 3D-Trench Electrode Si Detectors for Radiation Hard Detectors for sLHC and for X-ray Applications

    SciTech Connect

    Li Z.

    2011-05-11

    A new international-patent-pending (PCT/US2010/52887) detector type, named here as 3D-Trench electrode Si detectors, is proposed in this work. In this new 3D electrode configuration, one or both types of electrodes are etched as trenches deep into the Si (fully penetrating with SOI or supporting wafer, or non-fully penetrating into 50-90% of the thickness), instead of columns as in the conventional ('standard') 3D electrode Si detectors. With trench etched electrodes, the electric field in the new 3D electrode detectors are well defined without low or zero field regions. Except near both surfaces of the detector, the electric field in the concentric type 3D-Trench electrode Si detectors is nearly radial with little or no angular dependence in the circular and hexangular (concentric-type) pixel cell geometries. In the case of parallel plate 3D trench pixels, the field is nearly linear (like the planar 2D electrode detectors), with simple and well-defined boundary conditions. Since each pixel cell in a 3D-Trench electrode detector is isolated from others by highly doped trenches, it is an electrically independent cell. Therefore, an alternative name 'Independent Coaxial Detector Array', or ICDA, is assigned to an array of 3D-Trench electrode detectors. The electric field in the detector can be reduced by a factor of nearly 10 with an optimal 3D-Trench configuration where the junction is on the surrounding trench side. The full depletion voltage in this optimal configuration can be up to 7 times less than that of a conventional 3D detector, and even a factor of two less than that of a 2D planar detector with a thickness the same as the electrode spacing in the 3D-Trench electrode detector. In the case of non-fully penetrating trench electrodes, the processing is true one-sided with backside being unprocessed. The charge loss due to the dead space associated with the trenches is insignificant as compared to that due to radiation-induced trapping in sLHC environment

  20. Hard Physical Work Intensifies the Occupational Consequence of Physician-Diagnosed Back Disorder: Prospective Cohort Study with Register Follow-Up among 10,000 Workers

    PubMed Central

    2017-01-01

    While musculoskeletal pain is common in the population, less is known about its labor market consequences in relation to physical activity at work. This study investigates whether hard physical work aggravates the consequences of back disorder. Using Cox regression analyses, we estimated the joint association of physical activity at work and physician-diagnosed back disorder in 2010 with the risk of register-based long-term sickness absence (LTSA) of at least 6 consecutive weeks during 2011-2012 among 9,544 employees from the general working population (Danish Work Environment Cohort Study). Control variables were age, gender, psychosocial work environment, smoking, leisure physical activity, BMI, depression, and mental health. At baseline, 19.4% experienced high low-back pain intensity (≥5, 0–9 scale) and 15.2% had diagnosed back disorder. While high pain intensity was a general predictor for LTSA, physician-diagnosed back disorder was a stronger predictor among those with hard physical work (HR 2.23; 95% CI 1.68–2.96) compared with light work (HR 1.40; 95% CI 1.09–1.80). Similarly, physician-diagnosed back disorder with simultaneous high pain intensity predicted LTSA to a greater extent among those with hard physical work. In conclusion, the occupational consequence of physician-diagnosed back disorder on LTSA is greater among employees with hard physical work. PMID:28255304

  1. Gamma response study of radiation sensitive MOSFETs for their use as gamma radiation sensor

    NASA Astrophysics Data System (ADS)

    Srivastava, Saurabh; Aggarwal, Bharti; Singh, Arvind; Kumar, A. Vinod; Topkar, Anita

    2016-05-01

    Continuous monitoring of gamma dose is important in various fields like radiation therapy, space-related research, nuclear energy programs and high energy physics experiment facilities. The present work is focused on utilization of radiation-sensitive Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) to monitor gamma radiation doses. Static characterization of these detectors was performed to check their expected current-voltage relationship. Threshold voltage and transconductance per unit gate to source voltage (K factor) were calculated from the experimental data. The detector was exposed to gamma radiation in both, with and without gate bias voltage conditions, and change in threshold voltage was monitored at different gamma doses. The experimental data was fitted to obtain equation for dependence of threshold voltage on gamma dose. More than ten times increase in sensitivity was observed in biased condition (+3 V) compared to the unbiased case.

  2. Incorporation of multiple cloud layers for ultraviolet radiation modeling studies

    NASA Technical Reports Server (NTRS)

    Charache, Darryl H.; Abreu, Vincent J.; Kuhn, William R.; Skinner, Wilbert R.

    1994-01-01

    Cloud data sets compiled from surface observations were used to develop an algorithm for incorporating multiple cloud layers into a multiple-scattering radiative transfer model. Aerosol extinction and ozone data sets were also incorporated to estimate the seasonally averaged ultraviolet (UV) flux reaching the surface of the Earth in the Detroit, Michigan, region for the years 1979-1991, corresponding to Total Ozone Mapping Spectrometer (TOMS) version 6 ozone observations. The calculated UV spectrum was convolved with an erythema action spectrum to estimate the effective biological exposure for erythema. Calculations show that decreasing the total column density of ozone by 1% leads to an increase in erythemal exposure by approximately 1.1-1.3%, in good agreement with previous studies. A comparison of the UV radiation budget at the surface between a single cloud layer method and a multiple cloud layer method presented here is discussed, along with limitations of each technique. With improved parameterization of cloud properties, and as knowledge of biological effects of UV exposure increase, inclusion of multiple cloud layers may be important in accurately determining the biologically effective UV budget at the surface of the Earth.

  3. Radiative snowflake divertor studies in DIII-D

    NASA Astrophysics Data System (ADS)

    Soukhanovskii, V. A.; Allen, S. L.; Fenstermacher, M. E.; Hill, D. N.; Lasnier, C. J.; Makowski, M. A.; McLean, A. G.; Meyer, W. H.; Kolemen, E.; Groebner, R. J.; Hyatt, A. W.; Leonard, A. W.; Osborne, T. H.; Petrie, T. W.

    2015-08-01

    Recent DIII-D experiments assessed the snowflake divertor (SF) configuration in a radiative regime in H-mode discharges with D2 seeding. The SF configuration was maintained for many energy confinement times (2-3 s) in H-mode discharges (Ip = 1.2 MA, PNBI = 4- 5 MW, and B × ∇B down (favorable direction toward the divertor)), and found to be compatible with high performance operation (H98y2 ⩾ 1). The two studied SF configurations, the SF-plus and the SF-minus, have a small finite distance between the primary X-point and the secondary Bp null located in the private flux region or the common flux region, respectively. In H-mode discharges with the SF configurations (cf. H-mode discharges with the standard divertor with similar conditions) the stored energy lost per the edge localized mode (ELM) was reduced, and significant divertor heat flux reduction between and during ELMs was observed over a range of collisionalities, from lower density conditions toward a higher density H-modes with the radiative SF divertor.

  4. Radiation Damage Studies for Silicon Sensors for the XFEL

    NASA Astrophysics Data System (ADS)

    Perrey, H.

    2012-12-01

    For the study of radiation damage of silicon sensors by 12 keV X-rays for doses up to 1 GGy an irradiation facility has been set up at HASYLAB at DESY. Test structures (gate-controlled diodes) have been irradiated and the properties of the Si-SiO2 interface under high irradiation have been studied using I/V, C/V, and TDRC measurements. In addition to a strong increase of the interface current and a large shift of the flat-band voltage, strong hysteresis effects have been found. The data can be qualitatively described by a model which includes interface traps, fixed and mobile oxide charges. It is found that above doses of several MGy the density of interface traps decreases, whereas the density of fixed and mobile oxide charges appears to saturate. The origin of these effects is not understood so far.

  5. Radiation Damage Studies for Silicon Sensors for the XFEL

    NASA Astrophysics Data System (ADS)

    Perrey, H.

    For the study of radiation damage of silicon sensors by 12 keV X-rays for doses up to 1 GGy an irradiation facility has been set up at HASYLAB at DESY. Test structures (gate-controlled diodes) have been irradiated and the properties of the Si-SiO2 interface under high irradiation have been studied using I/V, C/V, and TDRC measurements. In addition to a strong increase of the interface current and a large shift of the flat-band voltage, strong hysteresis effects have been found. The data can be qualitatively described by a model which includes interface traps, fixed and mobile oxide charges. It is found that above doses of several MGy the density of interface traps decreases, whereas the density of fixed and mobile oxide charges appears to saturate. The origin of these effects is not understood so far.

  6. Atomic physics with hard X-rays from high brilliance synchrotron light sources

    SciTech Connect

    Southworth, S.; Gemmell, D.

    1996-08-01

    A century after the discovery of x rays, the experimental capability for studying atomic structure and dynamics with hard, bright synchrotron radiation is increasing remarkably. Tempting opportunities arise for experiments on many-body effects, aspects of fundamental photon-atom interaction processes, and relativistic and quantum-electrodynamic phenomena. Some of these possibilities are surveyed in general terms.

  7. Study of the Correlations and the MAXI Hardness Ratio between the Anomalous and Normal Low States of LMC X-3

    NASA Astrophysics Data System (ADS)

    Torpin, Trevor; Boyd, Patricia T.; Smale, Alan P.

    2015-01-01

    The bright, unusual black-hole X-ray binary LMC X-3 has been monitored virtually continuously by the Japanese MAXI X-ray All-Sky Monitor aboard the International Space Station (Matsuoka, et al., PASJ, 2009) from August 2009 to the present. Comparison with RXTE PCA and ASM light curves during the ~2.33-year period of overlap demonstrate that despite slight differences in energy-band boundaries both the ASM and MAXI faithfully reproduce characteristics of the high-amplitude, nonperiodic long-term variability, on the order of 100-300 days, clearly seen in the more sensitive PCA monitoring. The mechanism for this variability at a timescale many times longer than the 1.7-day orbital period is still unknown. Models to explain the long-term variability invoke mechanisms such as changes in mass transfer rate, and/or a precessing warped accretion disk. Observations of LMC X-3 have not definitely determined whether wind accretion or Roche-love overflow is the driver of the long-term variability. Recent MAXI monitoring of LMC X-3 includes excellent coverage of a rare anomalous low state (ALS) where the X-ray source cannot be distinguished from the background, as well as several normal low states, in which the source count rate passes smoothly through a low, yet detectable value. Pointed Swift XRT and UVOT observations also sample this ALS and one normal low state well. We combine these data sets to study the correlations between the wavelength regimes observed during the ALS versus the normal low. We also examine the behavior of the X-ray hardness ratios using XRT and MAXI monitoring data during the ALS versus the normal low state.

  8. Respondent-Driven Sampling with Hard-to-Reach Emerging Adults: An Introduction and Case Study with Rural African Americans

    ERIC Educational Resources Information Center

    Kogan, Steven M.; Wejnert, Cyprian; Chen, Yi-fu; Brody, Gene H.; Slater, LaTrina M.

    2011-01-01

    Obtaining representative samples from populations of emerging adults who do not attend college is challenging for researchers. This article introduces respondent-driven sampling (RDS), a method for obtaining representative samples of hard-to-reach but socially interconnected populations. RDS combines a prescribed method for chain referral with a…

  9. Supporting Students Who Are Deaf or Hard of Hearing in General Education Classrooms: A Washington State Case Study

    ERIC Educational Resources Information Center

    Berndsen, Maura; Luckner, John

    2012-01-01

    The majority of students who are deaf or hard of hearing currently receive educational services in general education settings. Trends that have led to this shift in placement as well as potential benefits and barriers are presented. A unique partnership between the Washington State Center for Childhood Deafness and Hearing Loss (formerly the…

  10. A Hypothesis and Pilot Study of Age-Related Sensory Innervation of the Hard Palate: Sensory Disorder After Nasopalatine Nerve Division

    PubMed Central

    Liu, Jiyuan; Li, Xiufen; Ma, Liyuan; Pan, Jian; Tang, Xiufa; Wu, Yunlong; Hua, Chengge

    2017-01-01

    Background The nasopalatine nerve may be injured during extraction of teeth embedded in the anterior hard palate. The neural recovery process and its impact on sensation in the anterior hard palatal region are controversial. In our clinical practice, we noticed a distinct recovery process in children compared with adolescents or adults after surgery. We hypothesized that the sensory innervations of the anterior palate might shift during later childhood and pre-adolescence, which is due to the development of the nasopalatine nerve along with the maxillary growth and permanent teeth eruption. Material/Method Forty patients (20 females and 20 males, mean age 11.8±2.2) with impacted supernumerary teeth in anterior palatine area were included into our study, and were divided into 3 groups according to their age. A 24-week follow-up was conducted and the sensation in the anterior hard palate region was examined at every check point. All the data were collected and analyzed by Kaplan-Meier analysis. Results Fourteen children did not complain of any numbness immediately after anesthetization, and other children with sensory disorders had shorter healing periods compared to adolescent/adult patients. Conclusions The results indicated that the dominant nerve of the anterior hard palate region was dramatically changed from the greater palatine nerve to the nasopalatine nerve, which is important in deciding when to operate and in selection of anesthesia method. PMID:28132066

  11. Quality of life themes in Canadian adults and street youth who are homeless or hard-to-house: A multi-site focus group study

    PubMed Central

    2012-01-01

    Background The aim of this study was to identify what is most important to the quality of life (QoL) of those who experience homelessness by directly soliciting the views of homeless and hard-to-house Canadians themselves. These individuals live within a unique social context that differs considerably from that of the general population. To understand the life areas that are most important to them, it is critical to have direct input from target populations of homeless and hard-to-house persons. Methods Focus groups were conducted with 140 individuals aged 15 to 73 years who were homeless or hard-to-house to explore the circumstances in which they were living and to capture what they find to be important and relevant domains of QoL. Participants were recruited in Toronto, Ottawa, Montreal, and Vancouver. Content analysis was used to analyze the data. Results Six major content themes emerged: Health/health care; Living conditions; Financial situation; Employment situation; Relationships; and Recreational and leisure activities. These themes were linked to broader concepts that included having choices, stability, respect, and the same rights as other members of society. Conclusions These findings not only aid our understanding of QoL in this group, but may be used to develop measures that capture QoL in this population and help programs and policies become more effective in improving the life situation for persons who are homeless and hard-to-house. Quality of life themes in Canadian adults and street youth who are homeless or hard-to-house: A multi-site focus group study. PMID:22894551

  12. Potassium Rankine cycle vapor chamber (heat pipe) radiator study

    NASA Technical Reports Server (NTRS)

    Gerrels, E. E.; Killen, R. E.

    1971-01-01

    A structurally integrated vapor chamber fin (heat pipe) radiator is defined and evaluated as a potential candidate for rejecting waste heat from the potassium Rankine cycle powerplant. Several vapor chamber fin geometries, using stainless steel construction, are evaluated and an optimum is selected. A comparison is made with an operationally equivalent conduction fin radiator. Both radiators employ NaK-78 in the primary coolant loop. In addition, the Vapor Chamber Fin (VCF) radiator utilizes sodium in the vapor chambers. Preliminary designs are developed for the conduction fin and VCF concepts. Performance tests on a single vapor chamber were conducted to verify the VCF design. A comparison shows the conduction fin radiator easier to fabricate, but heavier in weight, particularly as meteoroid protection requirements become more stringent. While the analysis was performed assuming the potassium Rankine cycle powerplant, the results are equally applicable to any system radiating heat to space in the 900 to 1400 F temperature range.

  13. 38 CFR 1.17 - Evaluation of studies relating to health effects of radiation exposure.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... health effects of radiation exposure. (a) From time to time, the Secretary shall publish evaluations of... studies affecting epidemiological assessments including case series, correlational studies and...

  14. The studies and legislation on radiation disinfestation, Taiwan

    NASA Astrophysics Data System (ADS)

    Fu, Ying-Kai; Chang, Ming-Shia; Hu, Tsan

    The studies of radiation disinfestation at the Institute of Nuclear Energy Research cover four harmful cereal insects, tobacco beetles, and dry beam insects etc. The four most harmful insects of stored rice in Taiwan are Sitophilus zeamais Mostschulsky. Rhyzopertha dominica F. Tribolitum custaneum Herbst, and Sitotroga cerealella Oliver. Adults, eggs or larvae of these insect pests were irradiated by 60Co gamma rays. The results show that 400 Gy of gamma irradiation could completely control these four species of pests in stored rice. Tobacco beetle ( Lasioderma serricorne F.) is the most serious pest of stored tobaccos in Taiwan. The aim of this study is to use 60Co gamma ray irradiation to control tabacco beetles of stored tobaccos. The results are (1) the sterility dose of adults irradiated by 60Co gamma rays is 96 Gy, with an immediate lethal dose of 5 kGy and a total death 18 days post-irradiation at 2 kGy; (2) the immediate lethal dose of larvae is 4 kGy, with a nonemerging dose of 2 kGy; (3) adults could not emerge from the pupae irradiated by 60Co gamma rays at 2 kGy; (4) larvae could not be hatched from the oval stage irradiated by 250 Gy. In conclusion, 60Co gamma ray irradiation of 2 kGy could be applied to stored tobaccos to control tobacco beetles with total disinfestation of larvae and adults and complete nonappearence of F 1 generation 18 days post-irradiation. The cowpea weevil ( Callosobruchus chinensis L.) was one of the most serious pests of stored dry beans in Taiwan. It caused damage during larval stage. Treatment of gamma irradiation with 10 Gy to eggs of the cowpea weevil prevented their hatching; a dose of 20 Gy applied to larvae prevented their development. The sterility dosage aginst the pupae and adult were 20 and 50 Gy, respectively. It is concluded that a 50 Gy gamma irradiation could be applied to stored dry beans to control the cowpea weevils. The food irradiation legislation has been approved by the Department of Health, Taiwan, R

  15. Study of radiation induced cancers in a breast screening programme.

    PubMed

    León, A; Verdú, G; Cuevas, M D; Salas, M D; Villaescusa, J I; Bueno, F

    2001-01-01

    It is demonstrated that screening mammography programmes reduce breast cancer mortality considerably. Nevertheless, radiology techniques have an intrinsic risk, the most important being the late somatic effect of the induction of cancer. This study was carried out in order to evaluate the risk to the population produced by the Comunidad Valenciana Breast Screening Programme. All the calculations are carried out for two risk models, UNSCEAR 94 and NRPB 93. On the one hand, screening series detriments are investigated as a function of doses delivered and other parameters related to population structure and X ray equipment. On the other hand the radiation induced cancer probability for a woman who starts at 45 years and remains in the programme until 65 years old is calculated as a function of mammography units' doses and average compression breast thickness. Finally, risk comparison between a screening programme starting at 45 years old and another one starting at 50 years old is made.

  16. Study of radiatively sustained cesium plasmas for solar energy conversion

    NASA Technical Reports Server (NTRS)

    Palmer, A. J.; Dunning, G. J.

    1980-01-01

    The results of a study aimed at developing a high temperature solar electric converter are reported. The converter concept is based on the use of an alkali plasma to serve as both an efficient high temperature collector of solar radiation as well as the working fluid for a high temperature working cycle. The working cycle is a simple magnetohydrodynamic (MHD) Rankine cycle employing a solid electrode Faraday MHD channel. Research milestones include the construction of a theoretical model for coupling sunlight in a cesium plasma and the experimental demonstration of cesium plasma heating with a solar simulator in excellent agreement with the theory. Analysis of a solar MHD working cycle in which excimer laser power rather than electric power is extracted is also presented. The analysis predicts a positive gain coefficient on the cesium-xenon excimer laser transition.

  17. Hard alpha-keratin degradation inside a tissue under high flux X-ray synchrotron micro-beam: a multi-scale time-resolved study.

    PubMed

    Leccia, Emilie; Gourrier, Aurélien; Doucet, Jean; Briki, Fatma

    2010-04-01

    X-rays interact strongly with biological organisms. Synchrotron radiation sources deliver very intense X-ray photon fluxes within micro- or submicro cross-section beams, resulting in doses larger than the MGy. The relevance of synchrotron radiation analyses of biological materials is therefore questionable since such doses, million times higher than the ones used in radiotherapy, can cause huge damages in tissues, with regard to not only DNA, but also proteic and lipid organizations. Very few data concerning the effect of very high X-ray doses in tissues are available in the literature. We present here an analysis of the structural phenomena which occur when the model tissue of human hair is irradiated by a synchrotron X-ray micro-beam. The choice of hair is supported by its hierarchical and partially ordered keratin structure which can be analysed inside the tissue by X-ray diffraction. To assess the damages caused by hard X-ray micro-beams (1 microm(2) cross-section), short exposure time scattering SAXS/WAXS patterns have been recorded at beamline ID13 (ESRF) after various irradiation times. Various modifications of the scattering patterns are observed, they provide fine insight of the radiation damages at various hierarchical levels and also unexpectedly provide information about the stability of the various hierarchical structural levels. It appears that the molecular level, i.e. the alpha helices which are stabilized by hydrogen bonds and the alpha-helical coiled coils which are stabilized by hydrophobic interactions, is more sensitive to radiation than the supramolecular architecture of the keratin filament and the filament packing within the keratin associated proteins matrix, which is stabilized by disulphide bonds.

  18. Imperfection and radiation damage in protein crystals studied with coherent radiation

    PubMed Central

    Nave, Colin; Sutton, Geoff; Evans, Gwyndaf; Owen, Robin; Rau, Christoph; Robinson, Ian; Stuart, David Ian

    2016-01-01

    Fringes and speckles occur within diffraction spots when a crystal is illuminated with coherent radiation during X-ray diffraction. The additional information in these features provides insight into the imperfections in the crystal at the sub-micrometre scale. In addition, these features can provide more accurate intensity measurements (e.g. by model-based profile fitting), detwinning (by distinguishing the various components), phasing (by exploiting sampling of the molecular transform) and refinement (by distinguishing regions with different unit-cell parameters). In order to exploit these potential benefits, the features due to coherent diffraction have to be recorded and any change due to radiation damage properly modelled. Initial results from recording coherent diffraction at cryotemperatures from polyhedrin crystals of approximately 2 µm in size are described. These measurements allowed information about the type of crystal imperfections to be obtained at the sub-micrometre level, together with the changes due to radiation damage. PMID:26698068

  19. Early predictors of autism in young children who are deaf or hard of hearing: three longitudinal case studies.

    PubMed

    Kellogg, Elizabeth Cameron; Thrasher, Amy; Yoshinaga-Itano, Christine

    2014-11-01

    Early assessment data (starting at 9 months) for three children who were deaf or hard of hearing and later diagnosed with autism spectrum disorder (ASD) were analyzed. The results from the MacArthur-Bates Communicative Development Inventories (CDI) Words and Gestures and the Child Development Inventory were used to develop three profiles of children who were deaf or hard of hearing and had ASD. One child lacked expected skills and language at ages 9 and 14 months. Another child lost skills and language after 17 months. The third child had results usually within or above the average range until 3 years of age. However, his age quotient decreased for MacArthur-Bates CDI: Words and Gestures Words Expressed and the Child Development Inventory: Social to significantly below the normal range. Although it can be difficult to diagnose the co-occurrence of ASD and deafness, there were early warning signs for these children.

  20. Use of COTS microelectronics in radiation environments

    SciTech Connect

    Winokur, P.S.; Lum, G.K.; Shaneyfelt, M.R.; Sexton, F.W.; Hash, G.L.; Scott, L.

    1999-12-01

    This paper addresses key issues for the cost-effective use of COTS (Commercially available Off The Shelf) microelectronics in radiation environments that enable circuit or system designers to manage risks and ensure mission success. They review several factors and tradeoffs affecting the successful application of COTS parts including (1) hardness assurance and qualification issues, (2) system hardening techniques, and (3) life-cycle costs. The paper also describes several experimental studies that address trends in total-dose, transient, and single-event radiation hardness as COTS technology scales to smaller feature sizes. As an example, the level at which dose-rate upset occurs in Samsung SRAMs increases from 1.4 x 10{sup 8} rad(Si)/s for a 256K SRAM to 7.7 x 10{sup 9} rad(Si)/s for a 4M SRAM, indicating unintentional hardening improvements in the design of process of a commercial technology. Additional experiments were performed to quantify variations in radiation hardness for COTS parts. In one study, only small (10--15%) variations were found in the dose-rate upset and latchup thresholds for Samsung 4M SRAMs from three different date codes. In another study, irradiations of 4M SRAMs from Samsung, Hitachi, and Toshiba indicate large differences in total-dose radiation hardness. The paper attempts to carefully define terms and clear up misunderstandings about the definitions of COTS and radiation-hardened (RH) technology.

  1. The Molecular Architecture for the Intermediate Filaments of Hard α -Keratin Based on the Superlattice Data Obtained from a Study of Mammals Using Synchrotron Fibre Diffraction

    DOE PAGES

    James, Veronica

    2011-01-01

    High- and low-angle X-ray diffraction studies of hard α -keratin have been studied, and various models have been proposed over the last 70 years. Most of these studies have been confined to one or two forms of alpha keratin. This high- and low-angle synchrotron fibre diffraction study extends the study to cover all available data for all known forms of hard α -keratin including hairs, fingernails, hooves, horn, and quills from mammals, marsupials, and a monotreme, and it confirms that the model proposed is universally acceptable for all mammals. A complete Bragg analysis of the meridional diffraction patterns, includingmore » multiple-time exposures to verify any weak reflections, verified the existence of a superlattice consisting of two infinite lattices and three finite lattices. An analysis of the equatorial patterns establishes the radii of the oligomeric levels of dimers, tetramers, and intermediate filaments (IFs) together with the centre to centre distance for the IFs, thus confirming the proposed helices within helices molecular architecture for hard α -keratin. The results verify that the structure proposed by Feughelman and James meets the criteria for a valid α -keratin structure.« less

  2. The Molecular Architecture for the Intermediate Filaments of Hard [alpha]-Keratin Based on the Superlattice Data Obtained from a Study ofMammals Using Synchrotron Fibre Diffraction

    SciTech Connect

    James, Veronica

    2014-09-24

    High- and low-angle X-ray diffraction studies of hard {alpha}-keratin have been studied, and various models have been proposed over the last 70 years. Most of these studies have been confined to one or two forms of alpha keratin. This high- and low-angle synchrotron fibre diffraction study extends the study to cover all available data for all known forms of hard {alpha}-keratin including hairs, fingernails, hooves, horn, and quills from mammals, marsupials, and a monotreme, and it confirms that the model proposed is universally acceptable for all mammals. A complete Bragg analysis of the meridional diffraction patterns, including multiple-time exposures to verify any weak reflections, verified the existence of a superlattice consisting of two infinite lattices and three finite lattices. An analysis of the equatorial patterns establishes the radii of the oligomeric levels of dimers, tetramers, and intermediate filaments (IFs) together with the centre to centre distance for the IFs, thus confirming the proposed helices within helices molecular architecture for hard {alpha}-keratin. The results verify that the structure proposed by Feughelman and James meets the criteria for a valid {alpha}-keratin structure.

  3. Fundamental measure density functional theory studies on the freezing of binary hard-sphere and Lennard-Jones mixtures

    SciTech Connect

    Warshavsky, Vadim B.; Song, Xueyu

    2008-07-18

    Free energies and correlation functions of liquid and solid hard-sphere (HS) mixtures are calculated using the fundamental measure density functional theory. Using the thermodynamic perturbation theory the free energies of solid and liquid Lennard-Jones (LJ) mixtures are obtained from correlation functions of HS systems within a single theoretical approach. The resulting azeotrope- and spindle-type solid-liquid phase diagrams of HS and LJ binary mixtures are in good agreement with the corresponding ones from computer simulations.

  4. Gamma-ray, neutron, and hard X-ray studies and requirements for a high-energy solar physics facility

    NASA Technical Reports Server (NTRS)

    Ramaty, R.; Dennis, B. R.; Emslie, A. G.

    1988-01-01

    The requirements for future high-resolution spatial, spectral, and temporal observation of hard X-rays, gamma rays and neutrons from solar flares are discussed in the context of current high-energy flare observations. There is much promise from these observations for achieving a deep understanding of processes of energy release, particle acceleration and particle transport in a complicated environment such as the turbulent and highly magnetized atmosphere of the active sun.

  5. A study on directions of significant efficiency increase of rock fracture by tools equipped with super hard inserts from composite

    NASA Astrophysics Data System (ADS)

    Dvornikov, L. T.; Klishin, V. I.; Nikitenko, S. M.; Korneyev, V. A.; Korneyev, P. A.

    2016-10-01

    In the paper the directions of a significant increase in effectiveness of mine rocks destruction by tools equipped with super hard inserts from composite materials are reviewed and justified. Designs of mining drill bits with the cutting insert in the form of elliptical Cassinian oval and the asymmetric ring cleaves are suggested. Versions of laboratory stand constructions are developed in order to determine the power consumption of rock destruction.

  6. Statistical Studies on Sequential Probability Ratio Test for Radiation Detection

    SciTech Connect

    Warnick Kernan, Ding Yuan, et al.

    2007-07-01

    A Sequential Probability Ratio Test (SPRT) algorithm helps to increase the reliability and speed of radiation detection. This algorithm is further improved to reduce spatial gap and false alarm. SPRT, using Last-in-First-Elected-Last-Out (LIFELO) technique, reduces the error between the radiation measured and resultant alarm. Statistical analysis determines the reduction of spatial error and false alarm.

  7. Positron-annihilation study of radiation defects in sodium azide

    SciTech Connect

    Etin, G.I.; Ryabykh, S.M.

    1987-07-01

    Annihilation-photon angular correlation has been used to examine radiation defects in sodium azide capable of trapping positrons. The calculated and measured characteristics have been determined for various defects, including micropores filled by radiolytic nitrogen. The positron annihilation rates have been determined for the regions around radiation defects.

  8. Post-radiation cranial malignant fibrous histiocytoma studied by CT.

    PubMed

    Romero, F J; Ortega, A; Ibarra, B; Piqueras, J; Rovira, M

    1989-01-01

    A 37-year-old woman presented with a proven case of malignant fibrous histiocytoma of the skull. This is thought to be a rare complication of post-radiation to a chromophobe adenoma which was treated by radiotherapy nine years previously. The radiation dose given to the sella region after the removal of the chromophobe adenoma was 4500 cGy.

  9. Laboratory studies on the tribology of hard bearing hip prostheses: ceramic on ceramic and metal on metal.

    PubMed

    Vassiliou, K; Scholes, S C; Unsworth, A

    2007-01-01

    Total hip replacements offer relief to a great many patients every year around the world. With an expected service life of around 25 years on most devices, and with younger and younger patients undergoing this surgery, it is of great importance to understand the mechanisms of their function. Tribological testing of both conventional and hard bearing joint combinations have been conducted in many centres throughout the world, and, after being initially abandoned owing to premature failures, hard bearing combinations have been revisited as viable options for joint replacements. Improved design, manufacturing procedures, and material compositions have led to improved performance over first-generation designs in both metal-on-metal and ceramic-on-ceramic hip prostheses. This paper offers a review of the work conducted in an attempt to highlight the most important factors affecting joint performance and tribology of hard bearing combinations. The tribological performance of these joints is superior to that of conventional metal- or ceramic-on-polymer designs.

  10. XAFS studies of radiation damage in nuclear materials

    NASA Astrophysics Data System (ADS)

    Olive, Daniel Thomas

    The growing demand for nuclear energy places a high importance on the development of new materials capable of withstanding higher temperatures and harsher irradiation conditions than those used in existing reactors. By supporting the development of next generation reactors it also becomes possible to close the nuclear fuel cycle, greatly reducing the amount of waste sent for disposal in deep geologic repositories, where its interaction with the environment is also a matter of interest. In this thesis, X-ray absorption fine structure (XAFS) spectroscopy is used to investigate the local atomic structure of systems of interest to nuclear energy. First, two XAFS studies on environmental materials are presented. Granular activated carbon (GAC) was treated with iron to improve its water remediation properties, specifically with respect to arsenic. XAFS was used to determine the nature of iron coating on the GAC surface, and the method of arsenic bonding to the treated surface. Next, a neodymium precipitate from solubility studies carried out for the Waste Isolation Pilot Plant (WIPP) was analyzed. Neodymium was used as an analog for plutonium in brine solutions. XAFS fitting indicated that the neodymium substituted for calcium in a gypsum lattice, providing information useful for future geochemical modeling. XAFS was also used to study radiation damage in materials. A candidate material for advanced reactor structural materials, modified 9Cr--1Mo, was irradiated to 1, 4, and 10 displacements per atom (dpa). XAFS analyses were performed on the Fe, Mo, and Nb K-edges. Irradiation caused a reduction in coordination for all three elements, but the exact behavior was element specific. Damage around Fe atoms was linear with dose, while damage around Mo atoms saturated at or before 1 dpa. XAFS was shown to provide a useful atomic level description of radiation damage for a complex alloy system. Finally, zirconium carbide and zirconium nitride, candidate materials for advanced

  11. Ionising radiation and risk of death from leukaemia and lymphoma in radiation-monitored workers (INWORKS): an international cohort study

    PubMed Central

    Leuraud, Klervi; Richardson, David B; Cardis, Elisabeth; Daniels, Robert D; Gillies, Michael; O'Hagan, Jacqueline A; Hamra, Ghassan B; Haylock, Richard; Laurier, Dominique; Moissonnier, Monika; Schubauer-Berigan, Mary K; Thierry-Chef, Isabelle; Kesminiene, Ausrele

    2015-01-01

    Summary Background There is much uncertainty about the risks of leukaemia and lymphoma after repeated or protracted low-dose radiation exposure typical of occupational, environmental, and diagnostic medical settings. We quantified associations between protracted low-dose radiation exposures and leukaemia, lymphoma, and multiple myeloma mortality among radiation-monitored adults employed in France, the UK, and the USA. Methods We assembled a cohort of 308 297 radiation-monitored workers employed for at least 1 year by the Atomic Energy Commission, AREVA Nuclear Cycle, or the National Electricity Company in France, the Departments of Energy and Defence in the USA, and nuclear industry employers included in the National Registry for Radiation Workers in the UK. The cohort was followed up for a total of 8·22 million person-years. We ascertained deaths caused by leukaemia, lymphoma, and multiple myeloma. We used Poisson regression to quantify associations between estimated red bone marrow absorbed dose and leukaemia and lymphoma mortality. Findings Doses were accrued at very low rates (mean 1·1 mGy per year, SD 2·6). The excess relative risk of leukaemia mortality (excluding chronic lymphocytic leukaemia) was 2·96 per Gy (90% CI 1·17–5·21; lagged 2 years), most notably because of an association between radiation dose and mortality from chronic myeloid leukaemia (excess relative risk per Gy 10·45, 90% CI 4·48–19·65). Interpretation This study provides strong evidence of positive associations between protracted low-dose radiation exposure and leukaemia. Funding Centers for Disease Control and Prevention, Ministry of Health, Labour and Welfare of Japan, Institut de Radioprotection et de Sûreté Nucléaire, AREVA, Electricité de France, National Institute for Occupational Safety and Health, US Department of Energy, US Department of Health and Human Services, University of North Carolina, Public Health England. PMID:26436129

  12. Pediatric Computed Tomography. Radiation Dose in Abdominal Studies

    SciTech Connect

    Lopez, X.; Ruiz-Trejo, C.; Buenfil, A. E.; Gamboa-deBuen, I.; Dies, P

    2008-08-11

    Computed tomography is one of the most popular medical imaging modalities used in the last years. However, because is one of the techniques that delivered a considerable radiation dose, precautions should be taken into account. Pediatric patients are more radiosensitive than adults, and the probability that no desirable biological effects can occur is greater. To this, also it adds the probability that they will need more radiological studies in the future. The work consisted in determining the received dose by the pediatric patients undergoing abdominal studies in a multislice computed tomograph, according to the dosimetric quantities established by a Code of Practice published by the International Atomic Energy Agency; using a ionization chamber and a phantom that simulates the abdomen of a pediatric patient. The weighted air kerma index (C{sub w}) was 14.3{+-}0.4 mGy, this value is lower than the published by the American College of Radiology, 25 mGy. The multiple scan average dose (MSAD), which is a quantity established by the NOM-229-SSA1-2002 was determined, finding a value of 14.2{+-}0.1 mGy, it is also below the value established, 25 mGy for an adult study.

  13. Dually diagnosed: a retrospective study of the process of diagnosing autism spectrum disorders in children who are deaf and hard of hearing.

    PubMed

    Szarkowski, Amy; Flynn, Suzanne; Clark, Terrell

    2014-11-01

    Utilizing a retrospective chart review of 30 children who have been dually diagnosed with hearing loss and autism spectrum disorders (ASDs), this study explores the process of arriving at the diagnosis of ASD in this population. Factors of interest include the age of ASD diagnosis in children who are deaf and hard of hearing, the types of professionals involved in making the diagnosis, and the measures used for assessment. Complications in the diagnostic process are highlighted.

  14. Hardness of irradiated poly(methyl methacrylate) at elevated temperatures

    SciTech Connect

    Lu, K.-P.; Lee, Sanboh; Cheng, Cheu Pyeng

    2001-08-15

    The decrease in hardness induced by gamma irradiation in poly(methyl methacrylate) (PMMA) has been investigated. The hardness is assumed to decrease linearly with the concentration of radiation-induced defects. Annealing at high temperatures induces defect annihilation as tracked by an increase in hardness. The annihilation follows first-order kinetics during isothermal annealing. The dependence of hardness on the reciprocal of the time constant satisfies the Arrhenius equation, and the corresponding activation energy of the kinetic process decreases with increasing dose. The hardness of postannealed PMMA decreases linearly with increasing dose. {copyright} 2001 American Institute of Physics.

  15. H-alpha and hard X-ray development in two-ribbon flares

    NASA Technical Reports Server (NTRS)

    Dwivedi, B. N.; Hudson, H. S.; Kane, S. R.; Svestka, Z.

    1984-01-01

    Morphological features of two-ribbon flares have been studied, using simultaneous ISEE-3 hard X-ray records and high-resolution Big Bear H-alpha movies for more than 20 events. Long-lasting and complex hard X-ray bursts are almost invariably found associated with flares of the two-ribbon type. At least three events are found, namely March 31, 1979, April 10, 1980, and July 1, 1980, where the occurrence of individual spikes in hard X-ray radiation coincides with suddenly enhanced H-alpha emission covering the sunspot penumbra. There definitely exist important (greater than or equal to 1 B) two-ribbon flares without significant hard X-ray emission.

  16. Studies on High Energy Radiation Mechanisms and Gamma-Ray Burst Prompt Emissions

    NASA Astrophysics Data System (ADS)

    Zhang, B.

    2014-07-01

    Gamma-Ray Bursts (GRBs) are the most violent high-energy explosion in the universe. They are randomly happened, pulse-like phenomena with short durations. Since its discovery in 1960's by Vela satellite, GRBs have become a hot topic for astrophysical research. In 1997 the BeppoSAX satellite discovered afterglows of GRBs, and then helped to measure GRB redshifts. Thus it was found that GRBs are the events occurred at cosmological distances. Now it is widely accepted that the long bursts with durations longer than 2 s are from the collapsing massive stars, while the short bursts with durations less than 2 s are results of the merging compact binaries. By studying GRBs, the physical processes in ultrarelativistic and very high energy conditions can be investigated, and the researches on other fields, including constraining the cosmological models, can also get helped. The goal of this thesis is to present some discussions on possible radiation mechanisms and prompt light curves of GRBs. Since radiation mechanisms and prompt emissions are related to GRB central engines directly, studying these topics can help us to get a better understanding of some properties of the central engine. In Chapter 1, we review the discovery and observations of GRBs, presenting major achievements from major GRB-monitoring satellites including Compton Gamma-ray Observatory, BeppoSAX satellite, Swift satellite, as well as the latest Fermi Gamma-ray Space Telescope. The multi-wavelength properties of prompt emission as well as afterglows of GRBs are also summarized in Chapter 1. In Chapter 2 the current GRB standard model is presented. According to standard model, a fireball is ejected by the central engine. The internal shock is produced by collisions between various shells with different velocities inside the fireball. The directional kinetic energy of the fireball is then converted to internal energy, and finally the non-thermal radiation (the prompt emission) is produced by internal shocks

  17. Coastal-inland solar radiation difference study. Final report

    SciTech Connect

    Bach, W.D. Jr.; Vukovich, F.M.

    1980-04-01

    The purpose of this study was to quantify the characteristics of solar insolation in the coastal zone and to determine the effect of the sea breeze circulation on the global insolation. In order to satisfy these objectives, a six station sampling network was established in the coastal plain of southeastern North Carolina, where previous evidence has indicated that the sea breeze circulation is almost a daily occurrence from late May through October. Three sites (Sloop Point, Onslow Beach, and Cape Fear Technical Institute (CFTI)) were located near the coast (coastal sites) to assess the insolation at the coast. A site (Clinton) was located in an area seldom affected by the sea breeze (about 100 km from the coast). Two additional sites, Wallace and Ellis Airport, located between the coastal sites and the control site, were to be used to assess the transient impact of the sea breeze upon the insolation. Pyranometers were located at each site to measure the global insolation. Direct normal insolation measured by a pyrheliometer and ultraviolet radiation measured by uv radiometers were observed at the Sloop Point and Clinton sites only. Data were collected during the calendar year 1978. The results of the study indicated that the global insolation had greater variability over the network during the summer season (June, July, and August). During the summer, there was a systematicdiurnal variation of the difference in global insolation between the inland and the coastal sites.

  18. Solid State Studies of the Radiation Histosy of Lunar Samples

    NASA Technical Reports Server (NTRS)

    Crozaz, G.; Haack, U.; Hair, M.; Hoyt, H.; Kardos, J.; Maurette, M.; Miyajima, M.; Seitz, M.; Sun, S.; Walker, R.; Wittels, M.; Woolum, D.

    1970-01-01

    Particle track densities up to greater than 3 x 10(exp 9) per square centimeter have been measured in different samples. Rocks 17, 47, 57, and 58 have VH (Z greater than 22) galactic cosmic ray ages of 11, 14, 28, and 13 x 10(exp 6) years, respectively. Rock 57 has a calculated erosion rate of approximately less than 10(exp -7) centimeter per year. Near-surface track versus depth data in rock 17 can be fit with solar flare particles that have a differential energy spectrum alpha E(exp -s); lunar samples can be used to study the history of solar activity. The uranium in the crystalline rocks occurs principally in small regions less than 10 to approximately equal to 100 micrometers in size. The (low) thermoluminescence of the fines increases with depth in core 10004. With one possible exception, x-ray studies have not shown pronounced radiation damage effects. The total energy release upon heating is small up to 900 C and occurs in three broad regions.

  19. Power line harmonic radiation: A systematic study using DEMETER spacecraft

    NASA Astrophysics Data System (ADS)

    Němec, F.; Santolík, O.; Parrot, M.; Berthelier, J. J.

    We present results of a systematic survey of Power line harmonic radiation (PLHR) observed by the DEMETER spacecraft. DEMETER is a French micro-satellite launched in June, 2004 with an altitude of orbit of about 700 km. It is designed specifically to study electromagnetic effects connected with seismic and man-made activity. All available high-resolution burst-mode electromagnetic data measured since the beginning of the mission till July 2006 (altogether about 1650 h of data) have been analyzed using an automatic identification procedure. This procedure was specially developed to search for emissions of PLHR type. It is running in DEMETER control center in Orléans, France. 49 PLHR events with frequency spacing of 50/100 or 60/120 Hz have been found, allowing us to perform a statistical study of properties of PLHR. It is shown that for all the events, the observed frequency spacing corresponds well to the power system frequency at anticipated source locations. Moreover, the frequency of the observed lines often (80%) corresponds to the exact harmonics of the power system base frequency. Finally, the most intense events are observed at lower frequencies and no weak events are observed under geomagnetically disturbed conditions.

  20. Studying Simple Molecular Ionization using Radiation Emission Spectroscopy

    NASA Astrophysics Data System (ADS)

    Proctor, Christopher; Lemmer, Kristina; Western Michigan University Aerospace LaboratoryPlasma Experiments Team

    2015-11-01

    This study focuses on radiation emission from the formation of simple molecular plasma using a DC glow discharge. The purpose is to measure the emission from argon and molecular nitrogen gas as a function of time with an optical emission spectroscopy system operating in kinetic mode as the gases go from their neutral state to ionized state. The end goal of the research is to develop a diagnostic tool that will be used to study the formation of plasma discharges from complex molecules. The kinetic mode of the CCD camera allows for fast data acquisition so that the species present and their relative concentrations as a function of time can be measured as the plasma is forming. The primary difficulty in the development of this diagnostic tool is designing a device and data analysis technique to allow for kinetic mode operation of the CCD camera. Experimental devices have been designed and built to enable the CCD to operate in kinetic mode, including a fiber optic adapter, camera mount, and twin razor blade system. The twin blades allow for the reduction of exposed pixels on the CCD camera and thereby allow the camera to store data on rows of pixels, rather than imaging the entire camera, allowing for faster data transfer. PhD in Aerospace Engineering.

  1. Studies of Coherent Synchrotron Radiation with the Discontinuous Galerkin Method

    NASA Astrophysics Data System (ADS)

    Bizzozero, David A.

    In this thesis, we present methods for integrating Maxwell's equations in Frenet-Serret coordinates in several settings using discontinuous Galerkin (DG) finite element method codes in 1D, 2D, and 3D. We apply these routines to the study of coherent synchrotron radiation, an important topic in accelerator physics. We build upon the published computational work of T. Agoh and D. Zhou in solving Maxwell's equations in the frequency-domain using a paraxial approximation which reduces Maxwell's equations to a Schrodinger-like system. We also evolve Maxwell's equations in the time-domain using a Fourier series decomposition with 2D DG motivated by an experiment performed at the Canadian Light Source. A comparison between theory and experiment has been published (Phys. Rev. Lett. 114, 204801 (2015)). Lastly, we devise a novel approach to integrating Maxwell's equations with 3D DG using a Galilean transformation and demonstrate proof-of-concept. In the above studies, we examine the accuracy, efficiency, and convergence of DG.

  2. Hard Metal Disease

    PubMed Central

    Bech, A. O.; Kipling, M. D.; Heather, J. C.

    1962-01-01

    In Great Britain there have been no published reports of respiratory disease occurring amongst workers in the hard metal (tungsten carbide) industry. In this paper the clinical and radiological findings in six cases and the pathological findings in one are described. In two cases physiological studies indicated mild alveolar diffusion defects. Histological examination in a fatal case revealed diffuse pulmonary interstitial fibrosis with marked peribronchial and perivascular fibrosis and bronchial epithelial hyperplasia and metaplasia. Radiological surveys revealed the sporadic occurrence and low incidence of the disease. The alterations in respiratory mechanics which occurred in two workers following a day's exposure to dust are described. Airborne dust concentrations are given. The industrial process is outlined and the literature is reviewed. The toxicity of the metals is discussed, and our findings are compared with those reported from Europe and the United States. We are of the opinion that the changes which we would describe as hard metal disease are caused by the inhalation of dust at work and that the component responsible may be cobalt. Images PMID:13970036

  3. Statistical Modeling for Radiation Hardness Assurance

    NASA Technical Reports Server (NTRS)

    Ladbury, Raymond L.

    2014-01-01

    We cover the models and statistics associated with single event effects (and total ionizing dose), why we need them, and how to use them: What models are used, what errors exist in real test data, and what the model allows us to say about the DUT will be discussed. In addition, how to use other sources of data such as historical, heritage, and similar part and how to apply experience, physics, and expert opinion to the analysis will be covered. Also included will be concepts of Bayesian statistics, data fitting, and bounding rates.

  4. Studies Related to Crystal Growth Using Synchrotron Radiation Diffraction.

    NASA Astrophysics Data System (ADS)

    Rule, Robert J.

    1990-01-01

    Available from UMI in association with The British Library. Small crystals of ammonium dihydrogenphosphate (ADP), sodium chlorate and sucrose, generated by secondary nucleation in aqueous solution, have been grown under constant conditions of supersaturation. A wide dispersion of growth rates was observed for each material using optical microscopy. A number of individual crystals of known growth rate were successfully retrieved from solution for each system. An assessment of the mosaic spread of each crystal was made using synchrotron radiation Laue diffraction on station 9.7 at Daresbury laboratory. All of the crystals produced diffraction patterns comprising small, sharp spots, indicative of low mosaic spread (<0.5 ^circ), contrary to published work. No correlation was found between growth rate and mosaic spread for these simple, small-molecule materials. An explanation of the previously reported discrepancies has been provided. The susceptibility of these compounds to radiation damage has been systematically investigated; ADP proved highly robust whilst sucrose and sodium chlorate showed significant sensitivity to irradiation. The role of mosaic spread in the growth of more complex systems is discussed with specific reference to two materials possessing channel structures: chenodeoxycholic acid and SAPO-5. In each case, the directions of slow growth have been related to high mosaic spread. An order of magnitude calculation of the rate of absorption of energy has been made for a variety of materials in the SRS white beam. The associated theoretical heating capability of the beam has also been estimated. A crystal melting experiment using crystals of 2 bromobenzophenone has indicated that the heating rate under standard experimental conditions is of the order of 1-2^circ C per sec., substantially less than anticipated. A pilot study of the combined use of SR Laue diffraction and high resolution powder diffraction for microcrystal structure determination has been

  5. Second Solid Cancers After Radiation Therapy: A Systematic Review of the Epidemiologic Studies of the Radiation Dose-Response Relationship

    SciTech Connect

    Berrington de Gonzalez, Amy; Gilbert, Ethel; Curtis, Rochelle; Inskip, Peter; Kleinerman, Ruth; Morton, Lindsay; Rajaraman, Preetha; Little, Mark P.

    2013-06-01

    Rapid innovations in radiation therapy techniques have resulted in an urgent need for risk projection models for second cancer risks from high-dose radiation exposure, because direct observation of the late effects of newer treatments will require patient follow-up for a decade or more. However, the patterns of cancer risk after fractionated high-dose radiation are much less well understood than those after lower-dose exposures (0.1-5 Gy). In particular, there is uncertainty about the shape of the dose-response curve at high doses and about the magnitude of the second cancer risk per unit dose. We reviewed the available evidence from epidemiologic studies of second solid cancers in organs that received high-dose exposure (>5 Gy) from radiation therapy where dose-response curves were estimated from individual organ-specific doses. We included 28 eligible studies with 3434 second cancer patients across 11 second solid cancers. Overall, there was little evidence that the dose-response curve was nonlinear in the direction of a downturn in risk, even at organ doses of ≥60 Gy. Thyroid cancer was the only exception, with evidence of a downturn after 20 Gy. Generally the excess relative risk per Gray, taking account of age and sex, was 5 to 10 times lower than the risk from acute exposures of <2 Gy among the Japanese atomic bomb survivors. However, the magnitude of the reduction in risk varied according to the second cancer. The results of our review provide insights into radiation carcinogenesis from fractionated high-dose exposures and are generally consistent with current theoretical models. The results can be used to refine the development of second solid cancer risk projection models for novel radiation therapy techniques.

  6. A study of regional aerosol radiative properties and effects on ultraviolet-B radiation

    NASA Astrophysics Data System (ADS)

    Wenny, B. N.; Schafer, J. S.; Deluisi, J. J.; Saxena, V. K.; Barnard, W. F.; Petropavlovskikh, I. V.; Vergamini, A. J.

    1998-07-01

    A field experiment was conducted in western North Carolina to investigate the relationship between aerosol optical properties and atmospheric transmission. Two research measurement sites in close horizontal proximity but at different altitudes were established to measure the transmission of UV radiation through a slab of atmosphere. An identical set of radiation sensing instruments, including a broadband UV-B radiometer, a direct Sun pyrheliometer, a shadowband radiometer, and a spectral photometer, was placed at both sites, a mountaintop site (Mount Gibbes 35.78°N, 82.29°W, 2004 m elevation) and a valley site (Black Mountain, North Carolina 35.66°N, 82.38°N, 951 m elevation). Aerosol size distribution sampling equipment was located at the valley site. Broadband solar pseudo-optical depth and aerosol optical depths at 415 nm, 500 nm, and 673 nm were measured for the lowest 1-km layer of the troposphere. The measurements exhibited variations based on an air mass source region as determined by back trajectory analysis. Broadband UV-B transmission through the layer also displayed variations relating to air mass source region. Spectral UV transmission revealed a dependence upon wavelength, with decreased transmission in the UV-B region (300-320 nm) versus UV-A region (320-363.5 nm). UV-B transmission was found to be negatively correlated with aerosol optical depth. Empirical relations were developed to allow prediction of solar noon UV-B transmission if aerosol optical depth at two visible wavelengths (415 and 500 nm) is known. A new method was developed for determining aerosol optical properties from the radiation and aerosol size distribution measurements. The aerosol albedo of single scatter was found to range from 0.75 to 0.93 and the asymmetry factor ranged from 0.63 to 0.76 at 312 nm, which is close to the peak response of human skin to UV radiation.

  7. Study of UV radiation dose received by the Spanish population.

    PubMed

    Gurrea, Gonzalo; Cañada, Javier

    2007-01-01

    Excess exposure to UV radiation can affect our health by causing sunburn, skin cancer, etc. It is therefore useful to determine the UV dosage received by people as a way of protecting them from the possible negative effects that this kind of radiation can cause. In this work, the personal outdoor percentage, which shows the time spent in outdoor activities, as well as personal UV doses, has been calculated by means of global UV radiation on a horizontal plane. A database of average daily UVB radiation on the horizontal plane given by the National Institute of Meteorology has been used. In this work we evaluate the standard erythema dose of the Spanish population throughout the year.

  8. Comparative study of finite temperature demagnetization in Nd2Fe14B and SmCo5 based hard-soft composites

    NASA Astrophysics Data System (ADS)

    Belemuk, A. M.; Chui, S. T.

    2011-10-01

    We study with finite temperature Monte Carlo simulation under periodic boundary conditions the demagnetization behavior of exchanged-coupled hard/soft magnets composed of hard cube inclusions (Nd2 Fe14B, or SmCo5) in a soft (FeCo) matrix. The easy axis of the hard and soft phases are parallel to the applied field. We study the effect of finite temperature and the soft phase content on the coercivity, the remanence, and the energy product of the composites. We find that because of the difference in magnetization between the two phases, to lower the dipolar energy the magnetization of the two phases is not completely parallel to each other. This results in a much smaller increase of the remnant magnetization with increasing the soft magnet content than anticipated, especially at higher temperatures. This, together with the lower coercivity of Nd2 Fe14B, greatly affects the energy product in Nd2 Fe14B/FeCo in comparison with SmCo5/FeCo. We underline the essential difference in the induction dependence on the applied field in these compounds.

  9. Ultraviolet radiation and the eye: an epidemiologic study.

    PubMed Central

    Taylor, H R

    1989-01-01

    Circumstantial evidence from biochemical, animal, and epidemiologic studies suggests an association between exposure to UV-B radiation (290 nm to 320 nm) and cataract. Such an association had not been proven because it had not been possible to quantify ocular UV-B exposure of individuals or to reliably grade the type and severity of cataract in field studies. We undertook an epidemiologic survey of cataract among 838 watermen who work on the Chesapeake Bay. Their individual ocular UV-B exposure was quantified for each year of life over the age of 16, on the basis of a detailed occupational history combined with laboratory and field measurements of ocular UV-B exposure. Cataracts were graded by both type and severity through clinical and photographic means. SMD changes were ascertained by fundal photography. A general medical history was taken to discover potentially confounding factors. This study showed that people with cortical lens opacities had a 21% higher UV-B exposure at each year of life than people without these opacities. A doubling in lifetime UV-B exposure led to a 60% increase in the risk of cortical cataract, and those with a high annual UV-B exposure increased their risk of cortical cataract over threefold. Corneal changes, namely pterygium and CDK, were also strongly associated with high UV-B exposure. No association was found between nuclear lens opacities or macular degeneration and UV-B exposure. This study also indicated several simple, practical measures, such as wearing spectacles or a hat, that effectively protect the eye from UV-B exposure. Thus it is easily within the power of individuals to protect their eyes from excessive UV-B exposure and reduce their risk of cortical cataract. A program of public education in this area could be a cost-effective means of reducing this important disease. PMID:2562534

  10. A study of solar radiation pressure acting on GPS satellites

    NASA Astrophysics Data System (ADS)

    Froideval, Laurent Olivier

    An increasing number of GPS applications require a high level of accuracy. To reduce the error contributed by the GPS ephemerides, an accurate modeling of the forces acting on GPS satellites is necessary. These forces can be categorized into gravitational and non-gravitational forces. The non-gravitational forces are a significant contribution to the total force on a GPS satellite but they are still not fully understood whereas the gravitational forces are well modeled. This study focuses on two non-gravitational forces: Solar Radiation Pressure (SRP) and the y-bias force. Different SRP models are available in the University of Texas Multi-Satellite Orbit Determination Program (MSODP). The recently developed University College London model was implemented for the purpose of this study. Several techniques to compute parameters associated with SRP models and the y-bias force during an orbit prediction were examined. Using the International GNSS Service (IGS) precise ephemerides as a reference, five different models were compared in the study. Satellite Laser Ranging (SLR) residuals were also studied to validate the approach. Results showed that the analytical UCL model performed as well as a purely empirical model such as the Extended CODE model. This is important since analytical models attempt to represent the physical phenomena and thus might be better suited to separate SRP from other forces. The y-bias force was then shown to have a once per revolution effect. The time evolution of the y-bias was found to be dependent on the SRP model used, the satellite Block type, the orbital plane, and the attitude of the satellite which suggests that estimates of y-bias contain errors from other sources, particularly the SRP models. The dependency of the y-bias evolution on the orbital plane suggests that the orientation of the plane towards the Sun is important.

  11. Study of two-photon corrections in the pp{yields}e{sup +}e{sup -} process: Hard rescattering mechanism

    SciTech Connect

    Guttmann, Julia; Vanderhaeghen, Marc; Kivel, Nikolai

    2011-05-01

    We investigate the two-photon corrections to the process pp{yields}e{sup +}e{sup -} at large momentum transfer, aimed to access the timelike nucleon form factors. We estimate the two-photon corrections using a hard rescattering mechanism, which has already been used to calculate the corresponding corrections to elastic electron-proton scattering. Using different nucleon distribution amplitudes, we find that the two-photon corrections to the pp{yields}e{sup +}e{sup -} cross sections in the momentum transfer range 5-30 GeV{sup 2} is below the 1% level.

  12. Origin of resistivity change in NiO thin films studied by hard x-ray photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Calka, P.; Martinez, E.; Lafond, D.; Minoret, S.; Tirano, S.; Detlefs, B.; Roy, J.; Zegenhagen, J.; Guedj, C.

    2011-06-01

    We investigated origins of the resistivity change during the forming of NiO based resistive random access memories in a nondestructive way using hard x-ray photoelectron spectroscopy. Energy shifts and bandgap states observed after switching suggest that oxygen vacancies are created in the low resistive state. As a result conduction may occur via defects such as electrons traps and metallic nickel impurities. Migration of oxygen atoms seems to be the driving mechanism. This provides concrete evidence of the major role played by oxygen defects in decreasing resistivity. This is a key point since oxygen vacancies are particularly unstable and thus difficult to identify by physico-chemical analyses.

  13. Ordering of hard particles between hard walls

    NASA Astrophysics Data System (ADS)

    Chrzanowska, A.; Teixeira, P. I. C.; Ehrentraut, H.; Cleaver, D. J.

    2001-05-01

    The structure of a fluid of hard Gaussian overlap particles of elongation κ = 5, confined between two hard walls, has been calculated from density-functional theory and Monte Carlo simulations. By using the exact expression for the excluded volume kernel (Velasco E and Mederos L 1998 J. Chem. Phys. 109 2361) and solving the appropriate Euler-Lagrange equation entirely numerically, we have been able to extend our theoretical predictions into the nematic phase, which had up till now remained relatively unexplored due to the high computational cost. Simulation reveals a rich adsorption behaviour with increasing bulk density, which is described semi-quantitatively by the theory without any adjustable parameters.

  14. Review of radiation damage studies on DNW CMOS MAPS

    NASA Astrophysics Data System (ADS)

    Traversi, G.; Gaioni, L.; Manazza, A.; Manghisoni, M.; Ratti, L.; Re, V.; Zucca, S.; Bettarini, S.; Rizzo, G.; Morsani, F.; Bosisio, L.; Rashevskaya, I.; Cindro, V.

    2013-12-01

    Monolithic active pixel sensors fabricated in a bulk CMOS technology with no epitaxial layer and standard resistivity (10 Ω cm) substrate, featuring a deep N-well as the collecting electrode (DNW MAPS), have been exposed to γ-rays, up to a final dose of 10 Mrad (SiO2), and to neutrons from a nuclear reactor, up to a total 1 MeV neutron equivalent fluence of about 3.7 ·1013cm-2. The irradiation campaign was aimed at studying the effects of radiation on the most significant parameters of the front-end electronics and on the charge collection properties of the sensors. Device characterization has been carried out before and after irradiations. The DNW MAPS irradiated with 60Co γ-rays were also subjected to high temperature annealing (100 °C for 168 h). Measurements have been performed through a number of different techniques, including electrical characterization of the front-end electronics and of DNW diodes, laser stimulation of the sensors and tests with 55Fe and 90Sr radioactive sources. This paper reviews the measurement results, their relation with the damage mechanisms underlying performance degradation and provides a new comparison between DNW devices and MAPS fabricated in a CMOS process with high resistivity (1 kΩ cm) epitaxial layer.

  15. Longitudinal bunch dynamics study with coherent synchrotron radiation

    NASA Astrophysics Data System (ADS)

    Billinghurst, B. E.; Bergstrom, J. C.; Baribeau, C.; Batten, T.; May, T. E.; Vogt, J. M.; Wurtz, W. A.

    2016-02-01

    An electron bunch circulating in a storage ring constitutes a dynamical system with both longitudinal and transverse degrees of freedom. Through a self-interaction with the wakefields created by the bunch, certain of these degrees may get excited, defining a set of eigenmodes analogous to a spectroscopic series. The present study focuses on the longitudinal modes of a single bunch. The excitation of a mode appears as an amplitude modulation at the mode frequency of the coherent synchrotron radiation (CSR) emitted by the bunch. The modulations are superimposed on a much larger continuum from CSR emission in the continuous mode. A given eigenmode is classified by the integer m which is the ratio of the mode frequency to the synchrotron frequency. The present measurements extend up to m =8 and focus on the region near the instability thresholds. At threshold the modes are excited sequentially, resembling a staircase when the mode frequencies are plotted as a function of bunch length or synchrotron frequency. Adjacent modes are observed to coexist at the boundaries between the modes. An energy-independent correlation is observed between the threshold current for an instability and the corresponding zero-current bunch length. Measurements were made at five beam energies between 1.0 and 2.9 GeV at the Canadian Light Source. The CSR was measured in the time domain using an unbiased Schottky diode spanning 50-75 GHz.

  16. OSL studies of alkali fluoroperovskite single crystals for radiation dosimetry

    NASA Astrophysics Data System (ADS)

    Daniel, D. Joseph; Raja, A.; Madhusoodanan, U.; Annalakshmi, O.; Ramasamy, P.

    2016-08-01

    This paper presents a preliminary investigation of the optically stimulated luminescence (OSL) of alkali fluoroperovskite single crystals for radiation dosimetry. The perovskite-like KMgF3, NaMgF3 and LiBaF3 polycrystalline compounds doped with rare earths (Eu2+ and Ce3+) were synthesized by standard solid state reaction technique. Phase purity of the synthesized compounds was analyzed by powder X-ray diffraction technique. Single crystals of these compounds have been grown from melt by using vertical Bridgman-Stockbarger method. The Linearly Modulated OSL and Continuous Wave OSL measurements were performed in these alkali fluorides using blue light stimulation. Thermal bleaching experiments have shown that OSL signals originate from traps which are unstable near 200 °C, thus proving the suitability of the signals for dosimetric purposes. Optical bleaching measurements were also performed for these fluoride samples. OSL dose response was studied as a function of dose which was found to increase with beta dose.

  17. Radiative Beta Decay for Studies of CP Violation

    NASA Astrophysics Data System (ADS)

    Gardner, Susan; He, Daheng

    2013-10-01

    A triple-product correlation in the radiative β decay rate of neutrons or of nuclei, characterized by the kinematical variable, where, e.g., n (p) --> p (p') +e- (le) + νe (lν) + γ (k) , can be generated by the pseudo-Chern-Simons term found by Harvey, Hill, and Hill as a consequence of the baryon vector current anomaly and SU(2)L ×U(1)Y gauge invariance at low energies. The correlation probes the imaginary part of its coupling constant, so that its observation at anticipated levels of sensitivity would reflect the presence of sources of CP violation beyond the standard model. We compute the size of the asymmetry in n --> pe-νe γ decay in chiral effective theory, compare it with the computed background from standard-model final-state interactions, and consider the new physics scenarios which would be limited by its experimental study. Work supported in part by the U.S. Department of Energy Office of Nuclear Physics under contract no. DE-FG02-96ER40989.

  18. Positron annihilation lifetime study of radiation-damaged natural zircons

    NASA Astrophysics Data System (ADS)

    Roberts, J.; Gaugliardo, P.; Farnan, I.; Zhang, M.; Vance, E. R.; Davis, J.; Karatchevtseva, I.; Knott, R. B.; Mudie, S.; Buckman, S. J.; Sullivan, J. P.

    2016-04-01

    Zircons are a well-known candidate waste form for actinides and their radiation damage behaviour has been widely studied by a range of techniques. In this study, well-characterised natural single crystal zircons have been studied using Positron Annihilation Lifetime Spectroscopy (PALS). In some, but not all, of the crystals that had incurred at least half of the alpha-event damage of ∼1019 α/g required to render them structurally amorphous, PALS spectra displayed long lifetimes corresponding to voids of ∼0.5 nm in diameter. The long lifetimes corresponded to expectations from published Small-Angle X-ray Scattering data on similar samples. However, the non-observation by PALS of such voids in some of the heavily damaged samples may reflect large size variations among the voids such that no singular size can be distinguished or. Characterisation of a range of samples was also performed using scanning electron microscopy, optical absorption spectroscopy, Raman scattering and X-ray scattering/diffraction, with the degree of alpha damage being inferred mainly from the Raman technique and X-ray diffraction. The observed void diameters and intensities of the long lifetime components were changed somewhat by annealing at 700 °C; annealing at 1200 °C removed the voids entirely. The voids themselves may derive from He gas bubbles or voids created by the inclusion of small quantities of organic and hydrous matter, notwithstanding the observation that no voidage was evidenced by PALS in two samples containing hydrous and organic matter.

  19. Assessment and Implications of Scattered Microbeam and Broadbeam Synchrotron Radiation for Bystander Effect Studies.

    PubMed

    Lobachevsky, Pavel; Ivashkevich, Alesia; Forrester, Helen B; Stevenson, Andrew W; Hall, Chris J; Sprung, Carl N; Martin, Olga A

    2015-12-01

    Synchrotron radiation is an excellent tool for investigating bystander effects in cell and animal models because of the well-defined and controllable configuration of the beam. Although synchrotron radiation has many advantages for such studies compared to conventional radiation, the contribution of dose exposure from scattered radiation nevertheless remains a source of concern. Therefore, the influence of scattered radiation on the detection of bystander effects induced by synchrotron radiation in biological in vitro models was evaluated. Radiochromic XRQA2 film-based dosimetry was employed to measure the absorbed dose of scattered radiation in cultured cells at various distances from a field exposed to microbeam radiotherapy and broadbeam X-ray radiation. The level of scattered radiation was dependent on the distance, dose in the target zone and beam mode. The number of γ-H2AX foci in cells positioned at the same target distances was measured and used as a biodosimeter to evaluate the absorbed dose. A correlation of absorbed dose values measured by the physical and biological methods was identified. The γ-H2AX assay successfully quantitated the scattered radiation in the range starting from 10 mGy and its contribution to the observed radiation-induced bystander effect.

  20. Comparative evaluation of surface hardness and depth of cure of silorane and methacrylate-based posterior composite resins: An in vitro study

    PubMed Central

    Agrawal, Abhishek; Manwar, Narendra U; Hegde, Shubha G; Chandak, Manoj; Ikhar, Anuja; Patel, Aditya

    2015-01-01

    Aim: This in vitro study was carried out to compare the effect of LED light curing system on polymerization and hardness of silorane-based and methacrylate-based posterior composite resin. Materials and Methods: A total of 40 samples, 20 of silorane-based composite Filtek P-90 and 20 of methacrylate-based composite Heliomolar HB measuring 2 mm thickness and 8 mm diameter were prepared using Teflon molds and cured using LED curing light. The samples were polished and tested in Knoop hardness tester using a 50-gram load and dwell time of 15 seconds on top and bottom surfaces. The percentage depth of cure was calculated, and statistical analysis was performed using two-way ANOVA test and Student t- test. Results: Higher statistically significant values were seen for both the top and bottom surface hardness in silorane-based resins than methacrylate-based resins on LED light curing. Conclusion: Greater depth of cure was achieved in silorane-based posterior composite than in methacrylate-based posterior composite resins with a statistically significant difference. PMID:25829693