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Sample records for high damage threshold

  1. High-Damage-Threshold Pinhole for Glass Fusion Laser Applications

    International Nuclear Information System (INIS)

    Kumit, N.A.; Letzring, S.A.; Johnson, R.P.

    1998-01-01

    We are investigating methods to fabricate high-damage-threshold spatial-filter pinholes that might not be susceptible to plasma closure for relatively high energies and long pulses. These are based on the observation that grazing-incidence reflection from glass can withstand in excess of 5 kJ/cm 2 (normal to the beam) without plasma formation. The high damage threshold results from both the cos q spreading of the energy across the surface and the reflection of a large fraction of the energy from the surface, thereby greatly reducing the field strength within the medium

  2. Damage thresholds of thin film materials and high reflectors at 248 nm

    International Nuclear Information System (INIS)

    Rainer, F.; Lowdermilk, W.H.; Milam, D.; Carniglia, C.K.; Hart, T.T.; Lichtenstein, T.L.

    1982-01-01

    Twenty-ns, 248-nm KrF laser pulses were used to measure laser damage thresholds for halfwave-thick layers of 15 oxide and fluoride coating materials, and for high reflectance coatings made with 13 combinations of these materials. The damage thresholds of the reflectors and single-layer films were compared to measurements of several properties of the halfwave-thick films to determine whether measurements of these properties of single-layer films to determine whether measurements of these properties of single-layer films were useful for identifying materials for fabrication of damage resistant coatings

  3. Robust optimization of the laser induced damage threshold of dielectric mirrors for high power lasers.

    Science.gov (United States)

    Chorel, Marine; Lanternier, Thomas; Lavastre, Éric; Bonod, Nicolas; Bousquet, Bruno; Néauport, Jérôme

    2018-04-30

    We report on a numerical optimization of the laser induced damage threshold of multi-dielectric high reflection mirrors in the sub-picosecond regime. We highlight the interplay between the electric field distribution, refractive index and intrinsic laser induced damage threshold of the materials on the overall laser induced damage threshold (LIDT) of the multilayer. We describe an optimization method of the multilayer that minimizes the field enhancement in high refractive index materials while preserving a near perfect reflectivity. This method yields a significant improvement of the damage resistance since a maximum increase of 40% can be achieved on the overall LIDT of the multilayer.

  4. High-damage-threshold static laser beam shaping using optically patterned liquid-crystal devices.

    Science.gov (United States)

    Dorrer, C; Wei, S K-H; Leung, P; Vargas, M; Wegman, K; Boulé, J; Zhao, Z; Marshall, K L; Chen, S H

    2011-10-15

    Beam shaping of coherent laser beams is demonstrated using liquid crystal (LC) cells with optically patterned pixels. The twist angle of a nematic LC is locally set to either 0 or 90° by an alignment layer prepared via exposure to polarized UV light. The two distinct pixel types induce either no polarization rotation or a 90° polarization rotation, respectively, on a linearly polarized optical field. An LC device placed between polarizers functions as a binary transmission beam shaper with a highly improved damage threshold compared to metal beam shapers. Using a coumarin-based photoalignment layer, various devices have been fabricated and tested, with a measured single-shot nanosecond damage threshold higher than 30 J/cm2.

  5. Laser-damage thresholds of thin-film optical coatings at 248 nm

    International Nuclear Information System (INIS)

    Milam, D.; Rainer, F.; Lowdermilk, W.H.

    1981-01-01

    We have measured the laser-induced damage thresholds for 248 nm wavelength light of over 100 optical coatings from commercial vendors and research institutions. All samples were irradiated once per damage site with temporally multi-lobed, 20-ns pulses generated by a KrF laser. The survey included high, partial, and dichroic reflectors, anti-reflective coatings, and single layer films. The samples were supplied by ten vendors. The majority of samples tested were high reflectors and antireflective coatings. The highest damage thresholds were 8.5 to 9.4 J/cm 2 , respectively. Although these represent extremes of what has been tested so far, several vendors have produced coatings of both types with thresholds which consistently exceed 6 J/cm 2 . Repeated irradiations of some sites were made on a few samples. These yielded no degradation in threshold, but in fact some improvement in damage resistance. These same samples also exhibited no change in threshold after being retested seven months later

  6. Design and fabrication of a high-damage threshold infrared Smattt interferometer

    International Nuclear Information System (INIS)

    Hammond, R.B.; Gibbs, A.J.

    1981-01-01

    It has been shown that a Smartt interferometer may be used as a very precise alignment tool for infrared lasers. This interferometer may also be used effectively to investigate the phase front of a laser pulse. To use this tool for applications to high-power, fast-pulse laser systems such as Helios and Antares; however, it has been necessary to fabricate a structure with the unique optical characteristics of the Smartt interferometer combined with a very high optical-damage threshold. We have been successful in this effort by utilizing the high technology, process control, and unique properties of semiconductor-grade, single-crystal Si

  7. Development of high damage threshold optics for petawatt-class short-pulse lasers

    International Nuclear Information System (INIS)

    Stuart, B.C.; Perry, M.D.; Boyd, R.D.

    1995-01-01

    The authors report laser-induced damage threshold measurements on pure and multilayer dielectrics and gold-coated optics at 1053 and 526 nm for pulse durations, τ, ranging from 140 fs to 1 ns. Damage thresholds of gold coatings are limited to 500 mJ/cm 2 in the subpicosecond range for 1053-nm pulses. In dielectrics, qualitative differences in the morphology of damage and a departure from the diffusion-dominated τ1/2 scaling indicate that damage results from plasma formation and ablation for τ≤10 ps and from conventional melting and boiling for τ>50 ps. A theoretical model based on electron production via multiphoton ionization, Joule heating, and collisional (avalanche) ionization is in quantitative agreement with both the pulsewidth and wavelength scaling of experimental results

  8. Improvement of the damage threshold of high reflectivity multidielectric coatings 1.06 μM

    International Nuclear Information System (INIS)

    Geenen, B.; Malherbes, A.; Guerain, J.; Boisgard, D.

    1985-01-01

    Development of new high power laser for laser-matter interaction in C.E.A. Limeil requires the realization of H.R. coatings with damage thresholds above 8 J/cm/sup 2/. MATRA's laboratory ''couches minces optiques'' (thin optical layers) production commercial mirrors was around 3.5 J/cm/sup 2/ in 1982. In order to obtain better results the authors decided to improve the control of evaporation parameters such as: vacuum and regulation of oxygen pressure by means of a mass spectrometer; better measurements of evaporation temperature and regulation of evaporation rate; measurement and control of substrate temperature by pyrometric observation; and to automatize the process. These different measurements and controls enable them to establish new processing operations giving better evaporation conditions. The result was an increase of damage threshold from 3.5 J/cm/sup 2/ to 8 J/cm/sup 2/

  9. Laser-induced damage thresholds of gold, silver and their alloys in air and water

    Energy Technology Data Exchange (ETDEWEB)

    Starinskiy, Sergey V.; Shukhov, Yuri G.; Bulgakov, Alexander V., E-mail: bulgakov@itp.nsc.ru

    2017-02-28

    Highlights: • Laser damage thresholds of Ag, Au and Ag-Au alloys in air and water are measured. • Alloy thresholds are lower than those of Ag and Au due to low thermal conductivity. • Laser damage thresholds in water are ∼1.5 times higher than those in air. • Light scattering mechanisms responsible for high thresholds in water are suggested. • Light scattering mechanisms are supported by optical reflectance measurements. - Abstract: The nanosecond-laser-induced damage thresholds of gold, silver and gold-silver alloys of various compositions in air and water have been measured for single-shot irradiation conditions. The experimental results are analyzed theoretically by solving the heat flow equation for the samples irradiated in air and in water taking into account vapor nucleation at the solid-water interface. The damage thresholds of Au-Ag alloys are systematically lower than those for pure metals, both in air and water that is explained by lower thermal conductivities of the alloys. The thresholds measured in air agree well with the calculated melting thresholds for all samples. The damage thresholds in water are found to be considerably higher, by a factor of ∼1.5, than the corresponding thresholds in air. This cannot be explained, in the framework of the used model, neither by the conductive heat transfer to water nor by the vapor pressure effect. Possible reasons for the high damage thresholds in water such as scattering of the incident laser light by the vapor-liquid interface and the critical opalescence in the superheated water are suggested. Optical pump-probe measurements have been performed to study the reflectance dynamics of the surface irradiated in air and water. Comparison of the transient reflectance signal with the calculated nucleation dynamics provides evidence that the both suggested scattering mechanisms are likely to occur during metal ablation in water.

  10. Large-aperture, high-damage-threshold optics for beamlet

    International Nuclear Information System (INIS)

    Campbell, J.H.; Atherton, L.J.; DeYoreo, J.J.; Kozlowski, M.R.; Maney, R.T.; Montesanti, R.C.; Sheehan, L.M.; Barker, C.E.

    1995-01-01

    Beamlet serves as a test bed for the proposed NIF laser design and components. Therefore, its optics are similar in size and quality to those proposed for the NIF. In general, the optics in the main laser cavity and transport section of Beamlet are larger and have higher damage thresholds than the optics manufactured for any of our previous laser systems. In addition, the quality of the Beamlet optical materials is higher, leading to better wavefront quality, higher optical transmission, and lower-intensity modulation of the output laser beam than, for example, that typically achieved on Nova. In this article, we discuss the properties and characteristics of the large-aperture optics used on Beamlet

  11. Database of average-power damage thresholds at 1064 nm

    International Nuclear Information System (INIS)

    Rainer, F.; Hildum, E.A.; Milam, D.

    1987-01-01

    We have completed a database of average-power, laser-induced, damage thresholds at 1064 nm on a variety of materials. Measurements were made with a newly constructed laser to provide design input for moderate and high average-power laser projects. The measurements were conducted with 16-ns pulses at pulse-repetition frequencies ranging from 6 to 120 Hz. Samples were typically irradiated for time ranging from a fraction of a second up to 5 minutes (36,000 shots). We tested seven categories of samples which included antireflective coatings, high reflectors, polarizers, single and multiple layers of the same material, bare and overcoated metal surfaces, bare polished surfaces, and bulk materials. The measured damage threshold ranged from 2 for some metals to > 46 J/cm 2 for a bare polished glass substrate. 4 refs., 7 figs., 1 tab

  12. Infrared laser damage thresholds in corneal tissue phantoms using femtosecond laser pulses

    Science.gov (United States)

    Boretsky, Adam R.; Clary, Joseph E.; Noojin, Gary D.; Rockwell, Benjamin A.

    2018-02-01

    Ultrafast lasers have become a fixture in many biomedical, industrial, telecommunications, and defense applications in recent years. These sources are capable of generating extremely high peak power that can cause laser-induced tissue breakdown through the formation of a plasma upon exposure. Despite the increasing prevalence of such lasers, current safety standards (ANSI Z136.1-2014) do not include maximum permissible exposure (MPE) values for the cornea with pulse durations less than one nanosecond. This study was designed to measure damage thresholds in corneal tissue phantoms in the near-infrared and mid-infrared to identify the wavelength dependence of laser damage thresholds from 1200-2500 nm. A high-energy regenerative amplifier and optical parametric amplifier outputting 100 femtosecond pulses with pulse energies up to 2 mJ were used to perform exposures and determine damage thresholds in transparent collagen gel tissue phantoms. Three-dimensional imaging, primarily optical coherence tomography, was used to evaluate tissue phantoms following exposure to determine ablation characteristics at the surface and within the bulk material. The determination of laser damage thresholds in the near-IR and mid-IR for ultrafast lasers will help to guide safety standards and establish the appropriate MPE levels for exposure sensitive ocular tissue such as the cornea. These data will help promote the safe use of ultrafast lasers for a wide range of applications.

  13. Cleaning Process Versus Laser-Damage Threshold of Coated Optical Components

    International Nuclear Information System (INIS)

    Rigatti, A.L.

    2005-01-01

    The cleaning of optical surfaces is important in the manufacture of high-laser-damage-threshold coatings, which are a key component on peak-power laser systems such as OMEGA located at the Laboratory for Laser Energetics (LLE). Since cleaning adds time, labor, and ultimately cost to the final coated component, this experiment was designed to determine the impact of different cleaning protocols on the measured laser-damage performance

  14. Acoustic emission sensor radiation damage threshold experiment

    International Nuclear Information System (INIS)

    Beeson, K.M.; Pepper, C.E.

    1994-01-01

    Determination of the threshold for damage to acoustic emission sensors exposed to radiation is important in their application to leak detection in radioactive waste transport and storage. Proper response to system leaks is necessary to ensure the safe operation of these systems. A radiation impaired sensor could provide ''false negative or false positive'' indication of acoustic signals from leaks within the system. Research was carried out in the Radiochemical Technology Division at Oak Ridge National Laboratory to determine the beta/gamma radiation damage threshold for acoustic emission sensor systems. The individual system consisted of an acoustic sensor mounted with a two part epoxy onto a stainless steel waveguide. The systems were placed in an irradiation fixture and exposed to a Cobalt-60 source. After each irradiation, the sensors were recalibrated by Physical Acoustics Corporation. The results were compared to the initial calibrations performed prior to irradiation and a control group, not exposed to radiation, was used to validate the results. This experiment determines the radiation damage threshold of each acoustic sensor system and verifies its life expectancy, usefulness and reliability for many applications in radioactive environments

  15. Computer simulation of threshold radiation damage in rutile, TiO2

    International Nuclear Information System (INIS)

    Richardson, D.D.

    1983-01-01

    Computer simulation methods have been used to study threshold radiation damage structures in rutile. It was found Ti ions have threshold energies much larger than O ions. Basal plane displacements for oxygen were shown to be complex, and focuson behaviour was only found at energies several times the threshold energy. Oxygen ions do not have simple interstitials or vacancies, but rather a three-ion crowdion and divacancy-interstitial combination were found, respectively. Threshold energies were found to be highly dependent on crystallographic direction, being as low as 10 eV in one instance, but often much higher. Oxygen ions were seen to defocus along the c-axis. (author)

  16. Influence of microstructure on laser damage threshold of IBS coatings

    International Nuclear Information System (INIS)

    Stolz, C.J.; Genin, F.Y.; Kozlowski, M.R.; Long, D.; Lalazari, R.; Wu, Z.L.; Kuo, P.K.

    1996-01-01

    Ion-beam sputtering (IBS) coatings were developed for the laser gyro industry to meet significantly different requirements than those of fusion lasers. Laser gyro mirrors are small ( 26 J/cm 2 at 1,064 nm with 3-ns pulses). As part of the National Ignition Facility (NIF) coating development effort, IBS coatings are being studied to explore the possible benefits of this technology to NIF optics. As an initial step to achieving the NIF size and damage threshold requirements, the coating process is being scaled to uniformly coat a 20 x 40 cm 2 area with reduced spectral, reflected wavefront, and laser damage threshold requirements. Here, multilayer coatings deposited by ion-beam sputtering with amorphous layers were found to have lower damage thresholds at 1,064 nm than similar coatings with crystalline layers. Interestingly, at higher fluences the damage was less severe for the amorphous coatings. The magnitude of the difference in damage thresholds between the two different microstructures was strongly influenced by the size of the tested area. To better understand the microstructure effects, single layers of HfO 2 with different microstructures were studied using transmission electron microscopy, ellipsometry, and a photothermal deflection technique. Since the laser damage initiated at defects, the influence of thermal diffusivity on thermal gradients in nodular defects is also presented

  17. High-threshold motor unit firing reflects force recovery following a bout of damaging eccentric exercise.

    Science.gov (United States)

    Macgregor, Lewis J; Hunter, Angus M

    2018-01-01

    Exercise-induced muscle damage (EIMD) is associated with impaired muscle function and reduced neuromuscular recruitment. However, motor unit firing behaviour throughout the recovery period is unclear. EIMD impairment of maximal voluntary force (MVC) will, in part, be caused by reduced high-threshold motor unit firing, which will subsequently increase to recover MVC. Fourteen healthy active males completed a bout of eccentric exercise on the knee extensors, with measurements of MVC, rate of torque development and surface electromyography performed pre-exercise and 2, 3, 7 and 14 days post-exercise, on both damaged and control limb. EIMD was associated with decreased MVC (235.2 ± 49.3 Nm vs. 161.3 ± 52.5 Nm; p exercise. Mean motor unit firing rate was reduced (16.4 ± 2.2 Hz vs. 12.6 ± 1.7 Hz; p motor units only, 48h post-exercise, and common drive was elevated (0.36 ± 0.027 vs. 0.56 ± 0.032; pexercise. The firing rate of high-threshold motor units was reduced in parallel with impaired muscle function, whilst early recruited motor units remained unaltered. Common drive of motor units increased in offset to the firing rate impairment. These alterations correlated with the recovery of force decrement, but not of pain elevation. This study provides fresh insight into the central mechanisms associated with EIMD recovery, relative to muscle function. These findings may in turn lead to development of novel management and preventative procedures.

  18. Laser-induced damage thresholds of gold, silver and their alloys in air and water

    Science.gov (United States)

    Starinskiy, Sergey V.; Shukhov, Yuri G.; Bulgakov, Alexander V.

    2017-02-01

    The nanosecond-laser-induced damage thresholds of gold, silver and gold-silver alloys of various compositions in air and water have been measured for single-shot irradiation conditions. The experimental results are analyzed theoretically by solving the heat flow equation for the samples irradiated in air and in water taking into account vapor nucleation at the solid-water interface. The damage thresholds of Au-Ag alloys are systematically lower than those for pure metals, both in air and water that is explained by lower thermal conductivities of the alloys. The thresholds measured in air agree well with the calculated melting thresholds for all samples. The damage thresholds in water are found to be considerably higher, by a factor of ∼1.5, than the corresponding thresholds in air. This cannot be explained, in the framework of the used model, neither by the conductive heat transfer to water nor by the vapor pressure effect. Possible reasons for the high damage thresholds in water such as scattering of the incident laser light by the vapor-liquid interface and the critical opalescence in the superheated water are suggested. Optical pump-probe measurements have been performed to study the reflectance dynamics of the surface irradiated in air and water. Comparison of the transient reflectance signal with the calculated nucleation dynamics provides evidence that the both suggested scattering mechanisms are likely to occur during metal ablation in water.

  19. Femtosecond laser damage threshold and nonlinear characterization in bulk transparent SiC materials

    International Nuclear Information System (INIS)

    DesAutels, G. Logan; Finet, Marc; Ristich, Scott; Whitaker, Matt; Brewer, Chris; Juhl, Shane; Walker, Mark; Powers, Peter

    2008-01-01

    Semi-insulating and conducting SiC crystalline transparent substrates were studied after being processed by femtosecond (fs) laser radiation (780 nm at 160 fs). Z-scan and damage threshold experiments were performed on both SiC bulk materials to determine each sample's nonlinear and threshold parameters. 'Damage' in this text refers to an index of refraction modification as observed visually under an optical microscope. In addition, a study was performed to understand the damage threshold as a function of numerical aperture. Presented here for the first time, to the best of our knowledge, are the damage threshold, nonlinear index of refraction, and nonlinear absorption measured values

  20. Synthesis and stabilization of oxide-based colloidal suspensions in organic media: application in the preparation of hybrids organic-inorganic materials for very high laser damage threshold coatings

    International Nuclear Information System (INIS)

    Marchet, N.

    2008-02-01

    Multilayer coatings are widely used in optic and particular in the field of high power laser on the components of laser chains. The development of a highly reflective coating with a laser damage resistance requires the fine-tuning of a multilayer stack constituted by a succession alternated by materials with low and high refractive index. In order to limit the number of layers in the stack, refractive indexes must be optimized. To do it, an original approach consists in synthesizing new organic-inorganic hybrid materials satisfying the criteria of laser damage resistance and optimized refractive index. These hybrid materials are constituted by nano-particles of metal oxides synthesized by sol-gel process and dispersed in an organic polymer with high laser damage threshold. Nevertheless, this composite system requires returning both compatible phases between them by chemical grafting of alc-oxy-silanes or carboxylic acids. We showed that it was so possible to disperse in a homogeneous way these functionalized nano-particles in non-polar, aprotic solvent containing solubilized organic polymers, to obtain time-stable nano-composite solutions. From these organic-inorganic hybrid solutions, thin films with optical quality and high laser damage threshold were obtained. These promising results have permitted to realize highly reflective stacks, constituted by 7 pairs with optical properties in agreement with the theoretical models and high laser damage threshold. (author)

  1. Efficient Phase Locking of Fiber Amplifiers Using a Low-Cost and High-Damage-Threshold Phase Control System

    International Nuclear Information System (INIS)

    Pu, Zhou; Yan-Xing, Ma; Xiao-Lin, Wang; Hao-Tong, Ma; Xiao-Jun, Xu; Ze-Jin, Liu

    2010-01-01

    We propose a low-cost and high-damage-threshold phase control system that employs a piezoelectric ceramic transducer modulator controlled by a stochastic parallel gradient descent algorithm. Efficient phase locking of two fiber amplifiers is demonstrated. Experimental results show that energy encircled in the target pinhole is increased by a factor of 1.76 and the visibility of the fringe pattern is as high as 90% when the system is in close-loop. The phase control system has potential in phase locking of large-number and high-power fiber laser endeavors. (fundamental areas of phenomenology (including applications))

  2. Modelling single shot damage thresholds of multilayer optics for high-intensity short-wavelength radiation sources

    NARCIS (Netherlands)

    Loch, R.A.; Sobierajski, R.; Louis, Eric; Bosgra, J.; Bosgra, J.; Bijkerk, Frederik

    2012-01-01

    The single shot damage thresholds of multilayer optics for highintensity short-wavelength radiation sources are theoretically investigated, using a model developed on the basis of experimental data obtained at the FLASH and LCLS free electron lasers. We compare the radiation hardness of commonly

  3. Experimental Determination of Damage Threshold Characteristics of IR Compatible Optical Materials

    International Nuclear Information System (INIS)

    Soong, Ken

    2011-01-01

    The accelerating gradient in a laser-driven dielectric accelerating structure is often limited by the laser damage threshold of the structure. For a given laser-driven dielectric accelerator design, we can maximize the accelerating gradient by choosing the best combination of the accelerator's constituent material and operating wavelength. We present here a model of the damage mechanism from ultrafast infrared pulses and compare that model with experimental measurements of the damage threshold of bulk silicon. Additionally, we present experimental measurements of a variety of candidate materials, thin films, and nanofabricated accelerating structures.

  4. Long-range pulselength scaling of 351nm laser damage thresholds

    Science.gov (United States)

    Foltyn, S. R.; Jolin, L. J.

    1986-12-01

    In a series of experiments incorporating 351nm pulselength of 9, 26, 54, and 625ns, it was found that laser damage thresholds increased as (pulselength)/sup x/, and that the exponent averaged 0.36 and ranged, for different samples, from 0.23 to 0.48. Similar results were obtained when only catastrophic damage was considered. Samples included Al2O3/SiO2 in both AR and HR multilayers, HR's of Sc2O3/SiO2 and HfO2/SiO2, and Al-on-pyrex mirror; 9ns thresholds were between 0.2 to 5.6 J/sq cm. When these data were compared with a wide range of other results - for wavelengths from 0.25 to 10.6 microns and pulselengths down to 4ps - a remarkably consistent picture emerged. Damage thresholds, on average, increase approximately as the cube-root of pulselength from picoseconds to nearly a microsecond, and do so regardless of wavelength or material under test.

  5. Infrared skin damage thresholds from 1319-nm continuous-wave laser exposures

    Science.gov (United States)

    Oliver, Jeffrey W.; Vincelette, Rebecca; Noojin, Gary D.; Clark, Clifton D.; Harbert, Corey A.; Schuster, Kurt J.; Shingledecker, Aurora D.; Kumru, Semih S.; Maughan, Justin; Kitzis, Naomi; Buffington, Gavin D.; Stolarski, David J.; Thomas, Robert J.

    2013-12-01

    A series of experiments were conducted in vivo using Yucatan miniature pigs (Sus scrofa domestica) to determine thermal damage thresholds to the skin from 1319-nm continuous-wave Nd:YAG laser irradiation. Experiments employed exposure durations of 0.25, 1.0, 2.5, and 10 s and beam diameters of ˜0.6 and 1 cm. Thermal imagery data provided a time-dependent surface temperature response from the laser. A damage endpoint of fifty percent probability of a minimally visible effect was used to determine threshold for damage at 1 and 24 h postexposure. Predicted thermal response and damage thresholds are compared with a numerical model of optical-thermal interaction. Resultant trends with respect to exposure duration and beam diameter are compared with current standardized exposure limits for laser safety. Mathematical modeling agreed well with experimental data, predicting that though laser safety standards are sufficient for exposures <10 s, they may become less safe for very long exposures.

  6. Preparation of high laser-induced damage threshold Ta{sub 2}O{sub 5} films

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Cheng, E-mail: xucheng@cumt.edu.cn [School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou 221116 (China); Yi, Peng; Fan, Heliang; Qi, Jianwei; Yang, Shuai; Qiang, Yinghuai; Liu, Jiongtian [School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou 221116 (China); Li, Dawei [Key Laboratory of High Power Laser Materials, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China)

    2014-08-01

    High laser-induced damage threshold (LIDT) Ta{sub 2}O{sub 5} films were prepared by the sol–gel method using TaCl{sub 5} as a new precursor. The optical properties, surface morphologies, chemical composition, absorption and LIDT of the films were investigated. The results showed that the transparent and homogenous Ta{sub 2}O{sub 5} films had small surface roughness, low absorption and high LIDT even with large number of layers. The maximum LIDT at 1064 nm and 12 ns of the films was 24.8 J/cm{sup 2}. The ion chromatograph and Fourier transform infrared spectrum were used to reveal the functions of the addition of H{sub 2}O{sub 2} in the sol formation. It was shown that H{sub 2}O{sub 2} had two important functions, which were the decrease of Cl element content and the rapid generation of tantalum oxide. The high LIDT achieved was mainly due to the nearly free of defects in the films.

  7. Damage threshold in adult rabbit eyes after scleral cross-linking by riboflavin/blue light application.

    Science.gov (United States)

    Iseli, Hans Peter; Körber, Nicole; Karl, Anett; Koch, Christian; Schuldt, Carsten; Penk, Anja; Liu, Qing; Huster, Daniel; Käs, Josef; Reichenbach, Andreas; Wiedemann, Peter; Francke, Mike

    2015-10-01

    Several scleral cross-linking (SXL) methods were suggested to increase the biomechanical stiffness of scleral tissue and therefore, to inhibit axial eye elongation in progressive myopia. In addition to scleral cross-linking and biomechanical effects caused by riboflavin and light irradiation such a treatment might induce tissue damage, dependent on the light intensity used. Therefore, we characterized the damage threshold and mechanical stiffening effect in rabbit eyes after application of riboflavin combined with various blue light intensities. Adult pigmented and albino rabbits were treated with riboflavin (0.5 %) and varying blue light (450 ± 50 nm) dosages from 18 to 780 J/cm(2) (15 to 650 mW/cm(2) for 20 min). Scleral, choroidal and retinal tissue alterations were detected by means of light microscopy, electron microscopy and immunohistochemistry. Biomechanical changes were measured by shear rheology. Blue light dosages of 480 J/cm(2) (400 mW/cm(2)) and beyond induced pathological changes in ocular tissues; the damage threshold was defined by the light intensities which induced cellular degeneration and/or massive collagen structure changes. At such high dosages, we observed alterations of the collagen structure in scleral tissue, as well as pigment aggregation, internal hemorrhages, and collapsed blood vessels. Additionally, photoreceptor degenerations associated with microglia activation and macroglia cell reactivity in the retina were detected. These pathological alterations were locally restricted to the treated areas. Pigmentation of rabbit eyes did not change the damage threshold after a treatment with riboflavin and blue light but seems to influence the vulnerability for blue light irradiations. Increased biomechanical stiffness of scleral tissue could be achieved with blue light intensities below the characterized damage threshold. We conclude that riboflavin and blue light application increased the biomechanical stiffness of scleral tissue at

  8. Porcine skin damage thresholds for pulsed nanosecond-scale laser exposure at 1064-nm

    Science.gov (United States)

    DeLisi, Michael P.; Peterson, Amanda M.; Noojin, Gary D.; Shingledecker, Aurora D.; Tijerina, Amanda J.; Boretsky, Adam R.; Schmidt, Morgan S.; Kumru, Semih S.; Thomas, Robert J.

    2018-02-01

    Pulsed high-energy lasers operating in the near-infrared (NIR) band are increasingly being used in medical, industrial, and military applications, but there are little available experimental data to characterize their hazardous effects on skin tissue. The current American National Standard for the Safe Use of Lasers (ANSI Z136.1-2014) defines the maximum permissible exposure (MPE) on the skin as either a single-pulse or total exposure time limit. This study determined the minimum visible lesion (MVL) damage thresholds in Yucatan miniature pig skin for the single-pulse case and several multiple-pulse cases over a wide range of pulse repetition frequencies (PRFs) (10, 125, 2,000, and 10,000 Hz) utilizing nanosecond-scale pulses (10 or 60 ns). The thresholds are expressed in terms of the median effective dose (ED50) based on varying individual pulse energy with other laser parameters held constant. The results confirm a decrease in MVL threshold as PRF increases for exposures with a constant number of pulses, while also noting a PRF-dependent change in the threshold as a function of the number of pulses. Furthermore, this study highlights a change in damage mechanism to the skin from melanin-mediated photomechanical events at high irradiance levels and few numbers of pulses to bulk tissue photothermal additivity at lower irradiance levels and greater numbers of pulses. The observed trends exceeded the existing exposure limits by an average factor of 9.1 in the photothermally-damaged cases and 3.6 in the photomechanicallydamaged cases.

  9. Damage threshold of lithium niobate crystal under single and multiple femtosecond laser pulses: theoretical and experimental study

    International Nuclear Information System (INIS)

    Meng, Qinglong; Zhang, Bin; Zhong, Sencheng; Zhu, Liguo

    2016-01-01

    The damage threshold of lithium niobate crystal under single and multiple femtosecond laser pulses has been studied theoretically and experimentally. Firstly, the model for the damage threshold prediction of crystal materials based on the improved rate equation has been proposed. Then, the experimental measure method of the damage threshold of crystal materials has been given in detail. On the basis, the variation of the damage threshold of lithium niobate crystal with the pulse duration has also been analyzed quantitatively. Finally, the damage threshold of lithium niobate crystal under multiple laser pulses has been measured and compared to the theoretical results. The results show that the transmittance of lithium niobate crystal is almost a constant when the laser pulse fluence is relative low, whereas it decreases linearly with the increase in the laser pulse fluence below the damage threshold. The damage threshold of lithium niobate crystal increases with the increase in the duration of the femtosecond laser pulse. And the damage threshold of lithium niobate crystal under multiple laser pulses is obviously lower than that irradiated by a single laser pulse. The theoretical data fall in good agreement with the experimental results. (orig.)

  10. Correlating optical damage threshold with intrinsic defect populations in fused silica as a function of heat treatment temperature

    Energy Technology Data Exchange (ETDEWEB)

    Shen, N. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Matthews, M. J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Elhadj, S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Miller, P. E. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Nelson, A. J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Hamilton, J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2013-04-03

    Here, chemical vapor deposition (CVD) is used for the production of fused silica optics in high-power laser applications. However, relatively little is known about the ultraviolet laser damage threshold of CVD films and how they relate to intrinsic defects produced during deposition. We present here a study relating structural and electronic defects in CVD films to 355 nm pulsed-laser damage threshold as a function of post-deposition annealing temperature (THT). Plasma-enhanced CVD based on SiH4/N2O under oxygen-rich conditions was used to deposit 1.5, 3.1 and 6.4 µm thick films on etched SiO2 substrates. Rapid annealing was performed using a scanned CO2 laser beam up to THT ~ 2100 K. The films were then characterized using x-ray photoemission spectroscopy, Fourier transform infrared spectroscopy (FTIR) and photoluminescence spectroscopy. A gradual transition in the damage threshold of annealed films was observed for THT values up to 1600 K, correlating with a decrease in non-bridging silanol and oxygen deficient centres. An additional sharp transition in damage threshold also occurs at ~1850 K indicating substrate annealing. Based on our results, a mechanism for damage-related defect annealing is proposed, and the potential of using high-THT CVD SiO2 to mitigate optical damage is also discussed.

  11. Reduction of damage threshold in dielectric materials induced by negatively chirped laser pulses

    International Nuclear Information System (INIS)

    Louzon, E.; Henis, Z.; Pecker, S.; Ehrlich, Y.; Fisher, D.; Fraenkel, M.; Zigler, A.

    2005-01-01

    The threshold fluence for laser induced damage in wide band gap dielectric materials, fused silica and MgF 2 , is observed to be lower by up to 20% for negatively (down) chirped pulses than for positively (up) chirped, at pulse durations ranging from 60 fs to 1 ps. This behavior of the threshold fluence for damage on the chirp direction was not observed in semiconductors (silicon and GaAs). Based on a model including electron generation in the conduction band and Joule heating, it is suggested that the decrease in the damage threshold for negatively chirped pulse is related to the dominant role of multiphoton ionization in wide gap materials

  12. Design of a high pulse repitition frequency carbon dioxide laser for processing high damage threshold materials

    Science.gov (United States)

    Chatwin, Christopher R.; McDonald, Donald W.; Scott, Brian F.

    1989-07-01

    The absence of an applications led design philosophy has compromised both the development of laser source technology and its effective implementation into manufacturing technology in particular. For example, CO2 lasers are still incapable of processing classes of refractory and non-ferrous metals. Whilst the scope of this paper is restricted to high power CO2 lasers; the design methodology reported herein is applicable to source technology in general, which when exploited, will effect an expansion of applications. The CO2 laser operational envelope should not only be expanded to incorporate high damage threshold materials but also offer a greater degree of controllability. By a combination of modelling and experimentation the requisite beam characteristics, at the workpiece, were determined then utilised to design the Laser Manufacturing System. The design of sub-system elements was achieved by a combination of experimentation and simulation which benefited from a comprehensive set of software tools. By linking these tools the physical processes in the laser - electron processes in the plasma, the history of photons in the resonator, etc. - can be related, in a detailed model, to the heating mechanisms in the workpiece.

  13. Effects of deposition rates on laser damage threshold of TiO2/SiO2 high reflectors

    International Nuclear Information System (INIS)

    Yao Jianke; Xu Cheng; Ma Jianyong; Fang Ming; Fan Zhengxiu; Jin Yunxia; Zhao Yuanan; He Hongbo; Shao Jianda

    2009-01-01

    TiO 2 single layers and TiO 2 /SiO 2 high reflectors (HR) are prepared by electron beam evaporation at different TiO 2 deposition rates. It is found that the changes of properties of TiO 2 films with the increase of rate, such as the increase of refractive index and extinction coefficient and the decrease of physical thickness, lead to the spectrum shift and reflectivity bandwidth broadening of HR together with the increase of absorption and decrease of laser-induced damage threshold. The damages are found of different morphologies: a shallow pit to a seriously delaminated and deep crater, and the different amorphous-to-anatase-to-rutile phase transition processes detected by Raman study. The frequency shift of Raman vibration mode correlates with the strain in film. Energy dispersive X-ray analysis reveals that impurities and non-stoichiometric defects are two absorption initiations resulting to the laser-induced transformation.

  14. Neodymium: YAG laser damage threshold. A comparison of injection-molded and lathe-cut polymethylmethacrylate intraocular lenses.

    Science.gov (United States)

    Wilson, S E; Brubaker, R F

    1987-01-01

    The possibility that injection-molded intraocular lenses (IOLs) with imperfections called iridescent clefts could have a decreased threshold to neodymium: YAG (Nd:YAG) laser-induced damage was investigated. Thresholds for Nd:YAG laser-induced damage were determined for injection-molded and lathe-cut polymethylmethacrylate lenses. When aimed at a membrane in contact with a posterior convex surface, the average thresholds were 0.96 +/- 0.18 mJ (Standard deviation [SD]) and 1.80 +/- 0.55 mJ, respectively. The difference was significant at P = 0.001. When injection-molding polymethylmethacrylate was used to make lathe-cut IOLs, very few iridescent clefts were present, and the threshold to Nd:YAG laser-induced damage was 0.94 +/- 0.25 mJ. Iridescent clefts are therefore produced during the injection-molding process but they do not lower the threshold to Nd:YAG laser-induced damage. Rather, the reduced threshold in injection-molded lenses is most probably a result of the polymethylmethacrylate used in their manufacture. Clinically, iridescent clefts in a lens suggest that it has been manufactured by an injection-molding process and that Nd:YAG laser posterior capsulotomy must be performed at the lowest possible energy level to avoid damage.

  15. Wavelength dependence of femtosecond laser-induced damage threshold of optical materials

    Energy Technology Data Exchange (ETDEWEB)

    Gallais, L., E-mail: laurent.gallais@fresnel.fr; Douti, D.-B.; Commandré, M. [Aix-Marseille Université, CNRS, Centrale Marseille, Institut Fresnel UMR 7249, 13013 Marseille (France); Batavičiūtė, G.; Pupka, E.; Ščiuka, M.; Smalakys, L.; Sirutkaitis, V.; Melninkaitis, A. [Laser Research Center, Vilnius University, Saulétekio aléja 10, LT-10223 Vilnius (Lithuania)

    2015-06-14

    An experimental and numerical study of the laser-induced damage of the surface of optical material in the femtosecond regime is presented. The objective of this work is to investigate the different processes involved as a function of the ratio of photon to bandgap energies and compare the results to models based on nonlinear ionization processes. Experimentally, the laser-induced damage threshold of optical materials has been studied in a range of wavelengths from 1030 nm (1.2 eV) to 310 nm (4 eV) with pulse durations of 100 fs with the use of an optical parametric amplifier system. Semi-conductors and dielectrics materials, in bulk or thin film forms, in a range of bandgap from 1 to 10 eV have been tested in order to investigate the scaling of the femtosecond laser damage threshold with the bandgap and photon energy. A model based on the Keldysh photo-ionization theory and the description of impact ionization by a multiple-rate-equation system is used to explain the dependence of laser-breakdown with the photon energy. The calculated damage fluence threshold is found to be consistent with experimental results. From these results, the relative importance of the ionization processes can be derived depending on material properties and irradiation conditions. Moreover, the observed damage morphologies can be described within the framework of the model by taking into account the dynamics of energy deposition with one dimensional propagation simulations in the excited material and thermodynamical considerations.

  16. Analysis of high resolution scatter images from laser damage experiments performed on KDP

    International Nuclear Information System (INIS)

    Runkel, M.; Woods, B.; Yan, M.

    1996-01-01

    Interest in producing high damage threshold KH 2 PO 4 (KDP) and (D x H 1-x ) 2 PO 4 (KD*P, DKDP) for optical switching and frequency conversion applications is being driven by the system requirements for the National Ignition Facility (NIF) at Lawrence Livermore National Lab (LLNL). Historically, the path to achieving higher damage thresholds has been to improve the purity of crystal growth solutions. Application of advanced filtration technology has increased the damage threshold, but gives little insight into the actual mechanisms of laser damage. We have developed a laser scatter diagnostic to better study bulk defects and laser damage mechanisms in KDP and KD*P crystals. This diagnostic consists of a cavity doubled, kilohertz class, Nd:YLF laser (527 nm) and high dynamic range CCD camera which allows imaging of bulk scatter signals. With it, we have performed damage tests at 355 nm on four different open-quotes vintagesclose quotes of KDP crystals, concentrating on crystals produced via fast growth methods. We compare the diagnostic's resolution to LLNL's standard damage detection method of 100X darkfield microscopy and discuss its impact on damage threshold determination. We have observed the disappearance of scatter sites upon exposure to subthreshold irradiation. In contrast, we have seen scatterers appear where none previously existed. This includes isolated, large (high signal) sites as well as multiple small scatter sites which appear at fluences above 7 J/cm 2 (fine tracking). However, we have not observed a strong correlation of preexisting scatter sites and laser damage sites. We speculate on the connection between the laser-induced disappearance of scatter sites and the observed increase in damage threshold with laser conditioning

  17. Calculation of femtosecond pulse laser induced damage threshold for broadband antireflective microstructure arrays.

    Science.gov (United States)

    Jing, Xufeng; Shao, Jianda; Zhang, Junchao; Jin, Yunxia; He, Hongbo; Fan, Zhengxiu

    2009-12-21

    In order to more exactly predict femtosecond pulse laser induced damage threshold, an accurate theoretical model taking into account photoionization, avalanche ionization and decay of electrons is proposed by comparing respectively several combined ionization models with the published experimental measurements. In addition, the transmittance property and the near-field distribution of the 'moth eye' broadband antireflective microstructure directly patterned into the substrate material as a function of the surface structure period and groove depth are performed by a rigorous Fourier model method. It is found that the near-field distribution is strongly dependent on the periodicity of surface structure for TE polarization, but for TM wave it is insensitive to the period. What's more, the femtosecond pulse laser damage threshold of the surface microstructure on the pulse duration taking into account the local maximum electric field enhancement was calculated using the proposed relatively accurate theoretical ionization model. For the longer incident wavelength of 1064 nm, the weak linear damage threshold on the pulse duration is shown, but there is a surprising oscillation peak of breakdown threshold as a function of the pulse duration for the shorter incident wavelength of 532 nm.

  18. Review of ultraviolet damage threshold measurements at Lawrence Livermore National Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Lowdermilk, W.H.; Milam, D.

    1984-01-01

    The results of damage threshold measurements made at LLNL using ultraviolet wavelength laser pulses are reviewed. Measurements were made with pulses from a krypton fluoride laser with wavelength of 248 nm and pulse duration of 20 ns and with Nd-glass laser pulses converted to the third harmonic wavelength of 355 nm with duration of 0.6 ns. Measurements are presented for transparent window materials, crystals and harmonic generation, single layer dielectric films of oxide and fluoride materials and multilayer high reflectivity and antireflective coatings.

  19. Review of ultraviolet damage threshold measurements at Lawrence Livermore National Laboratory

    International Nuclear Information System (INIS)

    Lowdermilk, W.H.; Milam, D.

    1984-01-01

    The results of damage threshold measurements made at LLNL using ultraviolet wavelength laser pulses are reviewed. Measurements were made with pulses from a krypton fluoride laser with wavelength of 248 nm and pulse duration of 20 ns and with Nd-glass laser pulses converted to the third harmonic wavelength of 355 nm with duration of 0.6 ns. Measurements are presented for transparent window materials, crystals and harmonic generation, single layer dielectric films of oxide and fluoride materials and multilayer high reflectivity and antireflective coatings

  20. Multiple pulse nanosecond laser induced damage threshold on hybrid mirrors

    Science.gov (United States)

    Vanda, Jan; Muresan, Mihai-George; Bilek, Vojtech; Sebek, Matej; Hanus, Martin; Lucianetti, Antonio; Rostohar, Danijela; Mocek, Tomas; Škoda, Václav

    2017-11-01

    So-called hybrid mirrors, consisting of broadband metallic surface coated with dielectric reflector designed for specific wavelength, becoming more important with progressing development of broadband mid-IR sources realized using parametric down conversion system. Multiple pulse nanosecond laser induced damage on such mirrors was tested by method s-on-1, where s stands for various numbers of pulses. We show difference in damage threshold between common protected silver mirrors and hybrid silver mirrors prepared by PVD technique and their variants prepared by IAD. Keywords: LIDT,

  1. The Laser Damage Threshold for Materials and the Relation Between Solid-Melt and Melt-Vapor Interface Velocities

    International Nuclear Information System (INIS)

    Khalil, Osama Mostafa

    2010-01-01

    Numerous experiments have demonstrated and analytic theories have predicted that there is a threshold for pulsed laser ablation of a wide range of materials. Optical surface damage threshold is a very complex and important application of high-power lasers. Optical damage may also be considered to be the initial phase of laser ablation. In this work it was determined the time required and the threshold energy of a layer of thickness to heat up. We used the Finite Difference method to simulate the process of laser-target interaction in three cases. Namely, the case before melting begins using a continuous wave (c.w) laser source and a pulsed laser source, the case after the first change of state (from solid to melt), and the case after the second change of state (from melt to vapor). And also study the relation between the solid-melt and melt-vapor interface velocities to have a commonsense of the laser ablation process.

  2. High-threshold motor unit firing reflects force recovery following a bout of damaging eccentric exercise

    Science.gov (United States)

    Macgregor, Lewis J.

    2018-01-01

    Exercise-induced muscle damage (EIMD) is associated with impaired muscle function and reduced neuromuscular recruitment. However, motor unit firing behaviour throughout the recovery period is unclear. EIMD impairment of maximal voluntary force (MVC) will, in part, be caused by reduced high-threshold motor unit firing, which will subsequently increase to recover MVC. Fourteen healthy active males completed a bout of eccentric exercise on the knee extensors, with measurements of MVC, rate of torque development and surface electromyography performed pre-exercise and 2, 3, 7 and 14 days post-exercise, on both damaged and control limb. EIMD was associated with decreased MVC (235.2 ± 49.3 Nm vs. 161.3 ± 52.5 Nm; p motor unit firing rate was reduced (16.4 ± 2.2 Hz vs. 12.6 ± 1.7 Hz; p motor units only, 48h post-exercise, and common drive was elevated (0.36 ± 0.027 vs. 0.56 ± 0.032; pmotor units was reduced in parallel with impaired muscle function, whilst early recruited motor units remained unaltered. Common drive of motor units increased in offset to the firing rate impairment. These alterations correlated with the recovery of force decrement, but not of pain elevation. This study provides fresh insight into the central mechanisms associated with EIMD recovery, relative to muscle function. These findings may in turn lead to development of novel management and preventative procedures. PMID:29630622

  3. Development of damage functions for high-rise building components

    International Nuclear Information System (INIS)

    Kustu, O.; Miller, D.D.; Brokken, S.T.

    1982-10-01

    The component approach for predicting the effects that ground motion from underground nuclear explosions will have on structures involves predicting the damage to each structural and nonstructural component of a building on the basis of the expected local deformation that most affects the damage to the component. This study was conducted to provide the basic data necessary to evaluate the component approach. Available published laboratory test data for various high-rise building components were collected. These data were analyzed statistically to determine damage threshold values and their variabilities, which in turn were used to derive component damage functions. The portion of construction costs attributable to various building components was determined statistically. This information was needed because component damage functions define damage as a percentage of the replacement values of the component, and, in order to calculate the overall building damage factor, the relative cost of each component must be estimated. The feasibility of the component approach to damage prediction is demonstrated. It is recommended that further experimental research directed towards developing an adequate data base of component damage thresholds for all significant building components should be encouraged. Parallel to this effort, detailed damage data from specific buildings damaged in earthquakes should be collected to verify the theoretical procedure

  4. Damage Mechanisms In Polymers Upon NIR Femtosecond Pulse Laser Irradiation: Sub-Threshold Processes And Their Implications For Laser Safety Applications

    International Nuclear Information System (INIS)

    Bonse, Joern; Krueger, Joerg; Solis, Javier; Spielmann, Christian; Lippert, Thomas

    2010-01-01

    This contribution investigates laser-induced damage of thin film and bulk polymer samples, with the focus on physical processes occurring close to the damage threshold. In-situ real-time reflectivity (RTR) measurements with picosecond (ps) and nanosecond (ns) temporal resolution were performed on thin polymer films on a timescale up to a few microseconds (μs). A model for polymer thin film damage is presented, indicating that irreversible chemical modification processes take place already below the fluence threshold for macroscopic damage. On dye-doped bulk polymer filters (as used for laser goggles), transmission studies using fs-and ps-laser pulses reveal the optical saturation behavior of the material and its relation to the threshold of permanent damage. Implications of the sub-threshold processes for laser safety applications will be discussed for thin film and bulk polymer damage.

  5. Enhancement of laser induced damage threshold of fused silica by acid etching combined with UV laser conditioning

    International Nuclear Information System (INIS)

    Chen Meng; Xiang Xia; Jiang Yong; Zu Xiaotao; Yuan Xiaodong; Zheng Wanguo; Wang Haijun; Li Xibin; Lu Haibing; Jiang Xiaodong; Wang Chengcheng

    2010-01-01

    Acid etching combined with UV laser conditioning is developed to enhance the laser induced damage threshold (LIDT) of fused silica. Firstly, the fused silica is etched for 1 ∼ 100 min with a buffered 1% HF solution. After acid etching, its transmittance, surface roughness and LIDT are measured. The results reveal that the fused silica has the highest LIDT and transmittance after etching for 10 min. Then UV laser (355 nm) conditioning is adopted to process the 10-min-etched fused silica. When the laser fluence is below 60% of fused silica's zero probability damage threshold, the LIDT increases gradually with the increase of laser conditioning fluence. However, the LIDT rapidly decreases to be lower than the threshold of the 10-min-etched fused silica when the conditioning fluence is up to 80% of the threshold. Proper acid etching and laser conditioning parameters will effectively enhance the laser damage resistance of fused silica. (authors)

  6. Laser-induced damage threshold tests of ultrafast multilayer dielectric coatings in various environmental conditions relevant for operation of ELI beamlines laser systems

    Science.gov (United States)

    Ďurák, Michal; Velpula, Praveen Kumar; Kramer, Daniel; Cupal, Josef; Medřík, Tomáš; Hřebíček, Jan; Golasowski, Jiří; Peceli, Davorin; Kozlová, Michaela; Rus, Bedřich

    2017-01-01

    Increasing the laser-induced damage resistance of optical components is one of the major challenges in the development of Peta-watt (PW) class laser systems. The extreme light infrastructure (ELI) beamlines project will provide ultrafast laser systems with peak powers up to 10 PW available every minute and PW class beams at 10 Hz complemented by a 5-TW, 1-kHz beamline. Sustainable performance of PW class laser systems relies on the durability of the employed optical components. As part of an effort to evaluate the damage resistance of components utilized in ELI beamlines systems, damage thresholds of several optical multilayer dielectric coatings were measured with different laser parameters and in different environments. Three coatings were tested with 10 Hz and 1 kHz pulse repetition rates, and the effect of a cleaning treatment on their damage resistance was examined. To explore the damage threshold behavior at different vacuum levels, one coating was subject to tests at various residual gas pressures. No change of damage threshold in a high vacuum with respect to ambient pressure was recorded. The effect of the cleaning treatment was found to be inconsistent, suggesting that development of the optimal cleaning treatment for a given coating requires consideration of its specific properties.

  7. Investigation of damage threshold to TiO2 coatings at different laser wavelength and pulse duration

    International Nuclear Information System (INIS)

    Yao Jianke; Fan Zhengxiu; Jin Yunxia; Zhao Yuanan; He Hongbo; Shao Jianda

    2008-01-01

    Laser-induced damages to TiO 2 single layers and TiO 2 /SiO 2 high reflectors at laser wavelength of 1064 nm, 800 nm, 532 nm, and pulse width of 12 ns, 220 ps, 50 fs, 8 ns are investigated. All films are prepared by electron beam evaporation. The relations among microstructure, chemical composition, optical properties and laser-induced damage threshold (LIDT), have been researched. The dependence of damage mechanism on laser wavelength and pulse width is discussed. It is found that from 1064 nm to 532 nm, LIDT is mainly absorption related, which is determined by film's extinction coefficient and stoichiometric defects. The rapid decrease of LIDT at 800 nm is due to the pulse width factor. TiO 2 coatings are mainly thermally by damaged at long pulse (τ ≥ 220 ps). The damage shows ablation feature at 50 fs

  8. Program requirements to determine and relate fuel damage and failure thresholds to anticipated conditions in pressurized water reactors

    International Nuclear Information System (INIS)

    Loyd, R.F.; Croucher, D.W.

    1980-03-01

    Anticipated transients, licensing criteria, and damage mechanisms for PWR fuel rods are reviewed. Potential mechanistic fuel rod damage limits for PWRs are discussed. An expermental program to be conducted out-of-pile and in the Engineering Test Reactor (ETR) to generate a safety data base to define mechanistic fuel damage and failure thresholds and to relate these thresholds to the thermal-hydraulic and power conditions in a PWR is proposed. The requirements for performing the tests are outlined. Analytical support requirements are defined

  9. Very high laser-damage threshold of polymer-derived Si(B)CN-carbon nanotube composite coatings.

    Science.gov (United States)

    Bhandavat, R; Feldman, A; Cromer, C; Lehman, J; Singh, G

    2013-04-10

    We study the laser irradiance behavior and resulting structural evolution of polymer-derived silicon-boron-carbonitride (Si(B)CN) functionalized multiwall carbon nanotube (MWCNT) composite spray coatings on copper substrate. We report a damage threshold value of 15 kWcm(-2) and an optical absorbance of 0.97 after irradiation. This is an order of magnitude improvement over MWCNT (1.4 kWcm(-2), 0.76), SWCNT (0.8 kWcm(-2), 0.65) and carbon paint (0.1 kWcm(-2), 0.87) coatings previously tested at 10.6 μm (2.5 kW CO2 laser) exposure. Electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy suggests partial oxidation of Si(B)CN forming a stable protective SiO2 phase upon irradiation.

  10. Modeling of damage generation mechanisms in silicon at energies below the displacement threshold

    International Nuclear Information System (INIS)

    Santos, Ivan; Marques, Luis A.; Pelaz, Lourdes

    2006-01-01

    We have used molecular dynamics simulation techniques to study the generation of damage in Si within the low-energy deposition regime. We have demonstrated that energy transfers below the displacement threshold can produce a significant amount of damage, usually neglected in traditional radiation damage calculations. The formation of amorphous pockets agrees with the thermal spike concept of local melting. However, we have found that the order-disorder transition is not instantaneous, but it requires some time to reach the appropriate kinetic-potential energy redistribution for melting. The competition between the rate of this energy redistribution and the energy diffusion to the surrounding atoms determines the amount of damage generated by a given deposited energy. Our findings explain the diverse damage morphology produced by ions of different masses

  11. Increasing the laser-induced damage threshold of single-crystal ZnGeP{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Zawilski, Kevin T; Setzler, Scott D; Schunemann, Peter G; Pollak, Thomas M [BAE Systems, Advanced Systems and Technology, P.O. Box 868, MER15-1813, Nashua, New Hampshire 03061-0868 (United States)

    2006-11-15

    The laser-induced damage threshold (LIDT) of single-crystal zinc germanium phosphide (ZGP), ZnGeP{sub 2}, was increased to 2 J/cm{sup 2} at 2.05 {mu}m and a 10 kHz pulse rate frequency (double the previously measured value of 1 J/cm{sup 2}). This increased LIDT was achieved by improving the polishing of ZGP optical parametric oscillator crystals. Two different polishing techniques were evaluated. Surfaces were characterized using scanning white-light interferometry to determine rms surface roughness and sample flatness. The photon backscatter technique was used to determine the degree of surface and subsurface damage in the sample induced through the fabrication process. The effect of subsurface damage in the samples was studied by removing different amounts of material during polishing for otherwise identical samples. Statistical LIDT was measured using a high-average-power, repetitively Q-switched Tm,Ho:YLF 2.05 {mu}m pump laser. On average, lower surface roughness and photon backscatter measurements were a good indicator of ZGP samples exhibiting higher LIDT. The removal of more material during polishing significantly improved the LIDT of otherwise identical samples, indicating the importance of subsurface damage defects in the LIDT of ZGP.

  12. Tornado risk analysis at Savannah River Plant using windspeed damage thresholds and single building strike frequencies

    International Nuclear Information System (INIS)

    Taylor, D.H.; McDonald, J.R.; Twisdale, L.A.

    1985-01-01

    Tornado risk analysis at the Savannah River Plant has taken a two pronged approach: (1) developing a catalogue of damage thresholds as a function of windspeed for processing buildings and other representative site structures; (2) developing a method of estimating, for each building, the probability of a tornado exceeding each damage threshold. Wind resistance of building construction at SRP varies widely depending on the function of the structure. It was recognized that all tornadoes do not necessarily seriously damage buildings, but the damage thresholds were unknown. In order to evaluate the safety of existing structures and properly design new structures, an analysis of tornado resistance was conducted by J.R. McDonald on each process building at SRP and other buildings by type. Damage estimates were catalogued for each Fujita class windspeed interval and windspeeds were catalogued as a function of increased levels of damage. Tornado single point and structure specific strike probabilities for the SRP site were determined by L.A. Twisdale using the TORRISK computer code. To calculate the structure specific strike probability, a correction factor is determined from a set of curves using building area and aspect ratio (length/width relative to north) as parameters. The structure specific probability is then the product of the correction factor and the point probability. The correction factor increases as a function of building size and windspeed. For large buildings (10 5 ft 2 ) and very intense storms (250 mph), the correction factor is equal to or greater than 4. The cumulative probability of a tornado striking any building type (process, personnel, etc.) was also calculated

  13. On the threshold conditions for electron beam damage of asbestos amosite fibers in the transmission electron microscope (TEM).

    Science.gov (United States)

    Martin, Joannie; Beauparlant, Martin; Sauvé, Sébastien; L'Espérance, Gilles

    2016-12-01

    Asbestos amosite fibers were investigated to evaluate the damage caused by a transmission electron microscope (TEM) electron beam. Since elemental x-ray intensity ratios obtained by energy dispersive x-ray spectroscopy (EDS) are commonly used for asbestos identification, the impact of beam damage on these ratios was evaluated. It was determined that the magnesium/silicon ratio best represented the damage caused to the fiber. Various tests showed that most fibers have a current density threshold above which the chemical composition of the fiber is modified. The value of this threshold current density varied depending on the fiber, regardless of fiber diameter, and in some cases could not be determined. The existence of a threshold electron dose was also demonstrated. This value was dependent on the current density used and can be increased by providing a recovery period between exposures to the electron beam. This study also established that the electron beam current is directly related to the damage rate above a current density of 165 A/cm 2 . The large number of different results obtained suggest, that in order to ensure that the amosite fibers are not damaged, analysis should be conducted below a current density of 100 A/cm 2 .

  14. A historical perspective on fifteen years of laser damage thresholds at LLNL

    International Nuclear Information System (INIS)

    Rainer, F.; De Marco, F.P.; Staggs, M.C.; Kozlowski, M.R.; Atherton, L.J.; Sheehan, L.M.

    1993-01-01

    We have completed a fifteen year, referenced and documented compilation of more than 15,000 measurements of laser-induced damage thresholds (LIDT) conducted at the Lawrence Livermore National Laboratory (LLNL). These measurements cover the spectrum from 248 to 1064 nm with pulse durations ranging from < 1 ns to 65 ns and at pulse-repetition frequencies (PRF) from single shots to 6.3 kHz. We emphasize the changes in LIDTs during the past two years since we last summarized our database. We relate these results to earlier data concentrating on improvements in processing methods, materials, and conditioning techniques. In particular, we highlight the current status of anti-reflective (AR) coatings, high reflectors (HR), polarizers, and frequency-conversion crystals used primarily at 355 nm and 1064 nm

  15. Damage threshold from large retinal spot size repetitive-pulse laser exposures.

    Science.gov (United States)

    Lund, Brian J; Lund, David J; Edsall, Peter R

    2014-10-01

    The retinal damage thresholds for large spot size, multiple-pulse exposures to a Q-switched, frequency doubled Nd:YAG laser (532 nm wavelength, 7 ns pulses) have been measured for 100 μm and 500 μm retinal irradiance diameters. The ED50, expressed as energy per pulse, varies only weakly with the number of pulses, n, for these extended spot sizes. The previously reported threshold for a multiple-pulse exposure for a 900 μm retinal spot size also shows the same weak dependence on the number of pulses. The multiple-pulse ED50 for an extended spot-size exposure does not follow the n dependence exhibited by small spot size exposures produced by a collimated beam. Curves derived by using probability-summation models provide a better fit to the data.

  16. Determination of ultra-short laser induced damage threshold of KH2PO4 crystal: Numerical calculation and experimental verification

    Directory of Open Access Journals (Sweden)

    Jian Cheng

    2016-03-01

    Full Text Available Rapid growth and ultra-precision machining of large-size KDP (KH2PO4 crystals with high laser damage resistance are tough challenges in the development of large laser systems. It is of high interest and practical significance to have theoretical models for scientists and manufacturers to determine the laser-induced damage threshold (LIDT of actually prepared KDP optics. Here, we numerically and experimentally investigate the laser-induced damage on KDP crystals in ultra-short pulse laser regime. On basis of the rate equation for free electron generation, a model dedicated to predicting the LIDT is developed by considering the synergistic effect of photoionization, impact ionization and decay of electrons. Laser damage tests are performed to measure the single-pulse LIDT with several testing protocols. The testing results combined with previously reported experimental data agree well with those calculated by the model. By taking the light intensification into consideration, the model is successfully applied to quantitatively evaluate the effect of surface flaws inevitably introduced in the preparation processes on the laser damage resistance of KDP crystals. This work can not only contribute to further understanding of the laser damage mechanisms of optical materials, but also provide available models for evaluating the laser damage resistance of exquisitely prepared optical components used in high power laser systems.

  17. Determination of the threshold-energy surface for copper using in-situ electrical-resistivity measurements in the high-voltage electron microscope

    International Nuclear Information System (INIS)

    King, W.E.; Merkle, K.L.; Meshii, M.

    1981-01-01

    A detailed study of the anisotropy of the threshold energy for Frenkel-pair production in copper was carried out experimentally, using in-situ electrical-resistivity measurements in the high-voltage electron microscope. These electrical-resistivity measurements, which are sensitive to small changes in point-defect concentration, were used to determine the damage or defect production rate. Damage-rate measurements in copper single crystals were carried out for approx.40 incident electron-beam directions and six electron energies from 0.4 to 1.1 MeV. The total cross section for Frenkel-pair production is proportional to the measured damage rate and can be theoretically calculated if the form of the threshold-energy surface is known. Trial threshold-energy surfaces were systematically altered until a ''best fit'' of the calculated to the measured total cross sections for Frenkel-pair production was obtained. The average threshold energy of this surface is 28.5 eV. The minimum threshold energy is 18 +- 2 eV and is located near . A ring of very high threshold energy (>50 eV) surrounds the direction. A damage function for single-defect production was derived from this surface and was applied to defect-production calculations at higher recoil energies. This function rises rather sharply from a value of zero at 17 eV to 0.8 at 42 eV. It has the value of 0.5 at 24.5 eV. Above 30 eV the slope of the curve begins to decrease, reflecting the presence of the high-energy regions of the threshold-energy surface. Both topographical and quantitative comparisons of the present surface with those in the literature were presented. Based on a chi 2 goodness-of-fit test, the present surface was found to predict the experimentally observed total cross sections for Frenkel-pair production significantly better than the other available surfaces. Also, the goodness of fit varied substantially less with energy and direction for the present surface

  18. On the threshold of damage formation in aluminum oxide via electronic excitations

    International Nuclear Information System (INIS)

    Skuratov, V.A.; O’Connell, J.; Kirilkin, N.S.; Neethling, J.

    2014-01-01

    This work is aimed to determine the threshold of dense ionization induced damage formation and their morphology in sapphire single crystals irradiated with 1.2 MeV/amu Xe ions. Cross-sectional TEM examination of r-oriented Al 2 O 3 specimens irradiated to fluences of 2 × 10 12 and 2 × 10 13 cm −2 has revealed discontinuous ion tracks visible from the irradiated surface up to a depth of 7.6 ± 0.1 μm. According to the SRIM code calculation, the threshold electronic stopping power for track formation in Al 2 O 3 is within the range 9.8 ÷ 10.5 keV/nm. This value agrees with those predicted by both inelastic and analytical thermal spike models

  19. Anisotropy of hardness and laser damage threshold of unidirectional organic NLO crystal in relation to the internal structure

    International Nuclear Information System (INIS)

    Natarajan, V.; Arivanandhan, M.; Sankaranarayanan, K.; Hayakawa, Y.

    2011-01-01

    Highlights: · Growth rate of the unidirectional organic crystals were measured and the variation in the growth rate was explained based on the attachment energy model. · Anisotropic behaviors of hardness and laser damage threshold of the unidirectional materials were analyzed. · The obtained results were explained based on the crystal structure of the material. - Abstract: Unidirectional benzophenone crystals were grown along , and directions by uniaxially solution crystallization method at ambient temperature. The growth rate of the grown crystals was varied with orientation. The optical absorption coefficients of benzophenone were measured as a function of wavelength. The optical absorption study reveals that the benzophenone crystal has very low absorption in the wavelength range of interest. Moreover, the laser damage threshold and micro hardness for , and oriented unidirectional benzophenone crystals were measured using a Q-switched Nd:YAG laser operating at 1064 nm radiation and Vicker's micro hardness tester, respectively. The laser damage threshold is larger for the and oriented crystals compared to oriented crystal at 1064 nm wavelength. The result is consistent with the hardness variation observed for the three different crystallographic directions of benzophenone crystal. The relation between the laser damage profile and mechanical hardness anisotropy is discussed based on the crystal structure of benzophenone.

  20. On the threshold of damage formation in aluminum oxide via electronic excitations

    Energy Technology Data Exchange (ETDEWEB)

    Skuratov, V.A., E-mail: skuratov@jinr.ru [Joint Institute for Nuclear Research, Dubna (Russian Federation); O’Connell, J. [Centre for HRTEM, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa); Kirilkin, N.S. [Joint Institute for Nuclear Research, Dubna (Russian Federation); Neethling, J. [Centre for HRTEM, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa)

    2014-05-01

    This work is aimed to determine the threshold of dense ionization induced damage formation and their morphology in sapphire single crystals irradiated with 1.2 MeV/amu Xe ions. Cross-sectional TEM examination of r-oriented Al{sub 2}O{sub 3} specimens irradiated to fluences of 2 × 10{sup 12} and 2 × 10{sup 13} cm{sup −2} has revealed discontinuous ion tracks visible from the irradiated surface up to a depth of 7.6 ± 0.1 μm. According to the SRIM code calculation, the threshold electronic stopping power for track formation in Al{sub 2}O{sub 3} is within the range 9.8 ÷ 10.5 keV/nm. This value agrees with those predicted by both inelastic and analytical thermal spike models.

  1. Eccentric muscle damage has variable effects on motor unit recruitment thresholds and discharge patterns in elbow flexor muscles.

    Science.gov (United States)

    Dartnall, Tamara J; Rogasch, Nigel C; Nordstrom, Michael A; Semmler, John G

    2009-07-01

    The purpose of this study was to determine the effect of eccentric muscle damage on recruitment threshold force and repetitive discharge properties of low-threshold motor units. Ten subjects performed four tasks involving isometric contraction of elbow flexors while electromyographic (EMG) data were recorded from human biceps brachii and brachialis muscles. Tasks were 1) maximum voluntary contraction (MVC); 2) constant-force contraction at various submaximal targets; 3) motor unit recruitment threshold task; and 4) minimum motor unit discharge rate task. These tasks were performed on three separate days before, immediately after, and 24 h after eccentric exercise of elbow flexor muscles. MVC force declined (42%) immediately after exercise and remained depressed (29%) 24 h later, indicative of muscle damage. Mean motor unit recruitment threshold for biceps brachii was 8.4+/-4.2% MVC, (n=34) before eccentric exercise, and was reduced by 41% (5.0+/-3.0% MVC, n=34) immediately after and by 39% (5.2+/-2.5% MVC, n=34) 24 h after exercise. No significant changes in motor unit recruitment threshold were observed in the brachialis muscle. However, for the minimum tonic discharge rate task, motor units in both muscles discharged 11% faster (10.8+/-2.0 vs. 9.7+/-1.7 Hz) immediately after (n=29) exercise compared with that before (n=32). The minimum discharge rate variability was greater in brachialis muscle immediately after exercise (13.8+/-3.1%) compared with that before (11.9+/-3.1%) and 24 h after exercise (11.7+/-2.4%). No significant changes in minimum discharge rate variability were observed in the biceps brachii motor units after exercise. These results indicate that muscle damage from eccentric exercise alters motor unit recruitment thresholds for >or=24 h, but the effect is not the same in the different elbow flexor muscles.

  2. Influence of post-deposition treatment by UV light and oxygen (ozone) on 350 nm damage thresholds of SiO2 films deposited from sols

    International Nuclear Information System (INIS)

    Thomas, I.; Wilder, J.; Lee, A.; George, D.

    1988-01-01

    Certain multilayer porous silica AR coatings on fused silica substrates prepared by the sol-gel process have been found to have a much lower laser damage threshold than single layer coatings prepared by the same method. Treatment with UV light in the presence of oxygen (which gives ozone) at low temperature was found to restore damage thresholds to the levels found in single layers. Damage thresholds were measured at 350 nm with a 25 ns pulse for 1000 shots at 25 Hz. The effect of exposure time and other factors such as replacement of oxygen with nitrogen and vacuum are described

  3. Simulation and experimental study of high power microwave damage effect on AlGaAs/InGaAs pseudomorphic high electron mobility transistor

    International Nuclear Information System (INIS)

    Yu Xin-Hai; Chai Chang-Chun; Liu Yang; Yang Yin-Tang; Xi Xiao-Wen

    2015-01-01

    The high power microwave (HPM) damage effect on the AlGaAs/InGaAs pseudomorphic high electron mobility transistor (pHEMT) is studied by simulation and experiments. Simulated results suggest that the HPM damage to pHEMT is due to device burn-out caused by the emerging current path and strong electric field beneath the gate. Besides, the results demonstrate that the damage power threshold decreases but the energy threshold slightly increases with the increase of pulse-width, indicating that HPM with longer pulse-width requires lower power density but more energy to cause the damage to pHEMT. The empirical formulas are proposed to describe the pulse-width dependence. Then the experimental data validate the pulse-width dependence and verify that the proposed formula P = 55τ −0.06 is capable of quickly and accurately estimating the HPM damage susceptibility of pHEMT. Finally the interior observation of damaged samples by scanning electron microscopy (SEM) illustrates that the failure mechanism of the HPM damage to pHEMT is indeed device burn-out and the location beneath the gate near the source side is most susceptible to burn-out, which is in accordance with the simulated results. (paper)

  4. Determination of ultra-short laser induced damage threshold of KH{sub 2}PO{sub 4} crystal: Numerical calculation and experimental verification

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Jian [Center for Precision Engineering, School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001 (China); Department of Physics, The Ohio State University, 191 W. Woodruff Ave, Columbus, OH 43210 (United States); Chen, Mingjun, E-mail: chenmj@hit.edu.cn, E-mail: chowdhury.24@osu.edu; Wang, Jinghe; Xiao, Yong [Center for Precision Engineering, School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001 (China); Kafka, Kyle; Austin, Drake; Chowdhury, Enam, E-mail: chenmj@hit.edu.cn, E-mail: chowdhury.24@osu.edu [Department of Physics, The Ohio State University, 191 W. Woodruff Ave, Columbus, OH 43210 (United States)

    2016-03-15

    Rapid growth and ultra-precision machining of large-size KDP (KH{sub 2}PO{sub 4}) crystals with high laser damage resistance are tough challenges in the development of large laser systems. It is of high interest and practical significance to have theoretical models for scientists and manufacturers to determine the laser-induced damage threshold (LIDT) of actually prepared KDP optics. Here, we numerically and experimentally investigate the laser-induced damage on KDP crystals in ultra-short pulse laser regime. On basis of the rate equation for free electron generation, a model dedicated to predicting the LIDT is developed by considering the synergistic effect of photoionization, impact ionization and decay of electrons. Laser damage tests are performed to measure the single-pulse LIDT with several testing protocols. The testing results combined with previously reported experimental data agree well with those calculated by the model. By taking the light intensification into consideration, the model is successfully applied to quantitatively evaluate the effect of surface flaws inevitably introduced in the preparation processes on the laser damage resistance of KDP crystals. This work can not only contribute to further understanding of the laser damage mechanisms of optical materials, but also provide available models for evaluating the laser damage resistance of exquisitely prepared optical components used in high power laser systems.

  5. Investigation of damage in KDP using scattering techniques

    International Nuclear Information System (INIS)

    Woods, B.; Runkel, M.; Yan, M.; Staggs, M.; Zaitseva, N.; Kozlowski, M.; De Yoreo, J.

    1997-01-01

    Interest in producing high damage threshold KH 2 PO 4 (KDP) and (D x H 1-x ) 2 PO 4 (DKDP)(also called KD*P) for frequency conversion and optical switching applications is driven by the requirements of the National Ignition Facility (NIF). Presently only the best crystals meet the NIF system requirements at the third harmonic (351 nm) and only after a laser conditioning process. Neither the mechanism for damage in bulk KDP nor the mechanism for conditioning is understood. As part of a development effort to increase the damage thresholds of KDP and DKDP, we have been developing techniques to pinpoint the locations where damage will initiate in the bulk material. After we find these locations we will use other measurement techniques to determine how these locations differ from the other surrounding material and why they cause damage. This will allow crystal growers to focus their efforts to improve damage thresholds. Historically damage thresholds have increased it is believed as a consequence of increased purity of the growth solution and through the use of constant filtration during the growth process. As a result we believe that damage is caused by defects in the crystals and have conducted a series of experiments using light scatter to locate these defects and to determine when and where damage occurs. In this paper we present results which show a low correlation between light scatter from bulk defects in KDP and the initiation sites for damage. We have also studied the effects of thermal conditioning on light scatter, strain induced birefringence and damage threshold. We have seen evidence that regions of high strain also exhibit lower damage threshold than the surrounding lower strain material. When thermally conditioned, these crystals show a decrease in some of the strong linear scattering features and a decrease in the strain birefringence while the damage threshold in these regions increased to that of the surrounding bulk material

  6. Analysis of the damage threshold of the GaAs pseudomorphic high electron mobility transistor induced by the electromagnetic pulse

    International Nuclear Information System (INIS)

    Xi Xiao-Wen; Chai Chang-Chun; Liu Yang; Yang Yin-Tang; Fan Qing-Yang; Shi Chun-Lei

    2016-01-01

    An electromagnetic pulse (EMP)-induced damage model based on the internal damage mechanism of the GaAs pseudomorphic high electron mobility transistor (PHEMT) is established in this paper. With this model, the relationships among the damage power, damage energy, pulse width and signal amplitude are investigated. Simulation results show that the pulse width index from the damage power formula obtained here is higher than that from the empirical formula due to the hotspot transferring in the damage process of the device. It is observed that the damage energy is not a constant, which decreases with the signal amplitude increasing, and then changes little when the signal amplitude reaches up to a certain level. (paper)

  7. Development and validation of rheumatoid arthritis magnetic resonance imaging inflammation thresholds associated with lack of damage progression

    DEFF Research Database (Denmark)

    Baker, Joshua F.; Østergaard, Mikkel; Emery, Paul

    2017-01-01

    Objective To determine thresholds for rheumatoid arthritis (RA) magnetic resonance imaging scores (RAMRIS) associated with a low risk of structural damage progression. Methods MRI of the dominant hand was performed and RAMRIS scores determined at weeks 0, 24, and 52. X-rays were performed and van...

  8. Influence of Different Substrates on Laser Induced Damage Thresholds at 1064 nm of Ta2O5 Films

    International Nuclear Information System (INIS)

    Cheng, Xu; Jian-Yong, Ma; Yun-Xia, Jin; Hong-Bo, He; Jian-Da, Shao; Zheng-Xiu, Fan

    2008-01-01

    Ta 2 O 5 films are prepared on Si, BK7, fused silica, antireflection (AR) and high reflector (HR) substrates by electron beam evaporation method, respectively. Both the optical property and laser induced damage thresholds (LIDTs) at 1064 nm of Ta 2 O 5 films on different substrates are investigated before and after annealing at 673K for 12 h. It is shown that annealing increases the refractive index and decreases the extinction index, and improves the O/Ta ratio of the Ta 2 O 5 films from 2.42 to 2.50. Moreover, the results show that the LIDTs of the Ta 2 O 5 films are mainly correlated with three parameters: substrate property, substoichiometry defect in the films and impurity defect at the interface between the substrate and the films. Details of the laser induced damage models in different cases are discussed

  9. Radiation damage by high-energy electrons in GaAs: DLTS investigation

    International Nuclear Information System (INIS)

    Lehmann, B.

    1991-10-01

    An isothermal variation of the DLTS technique is developed and applied to the study of displacement damage in GaAs, through the determination of threshold energies and displacement cross sections. Its results correspond to those of an LED based method. A pronounced anisotropy is found for the threshold energy. A linearly increasing displacement probability function is shown to properly model the displacement cross section in direction, as compared with the direction which requires only a single step function. Differences in the damage between these two directions are as large as a factor of two. (orig.) [de

  10. Accelerated Threshold Fatigue Crack Growth Effect-Powder Metallurgy Aluminum Alloy

    Science.gov (United States)

    Piascik, R. S.; Newman, J. A.

    2002-01-01

    Fatigue crack growth (FCG) research conducted in the near threshold regime has identified a room temperature creep crack growth damage mechanism for a fine grain powder metallurgy (PM) aluminum alloy (8009). At very low (Delta) K, an abrupt acceleration in room temperature FCG rate occurs at high stress ratio (R = K(sub min)/K(sub max)). The near threshold accelerated FCG rates are exacerbated by increased levels of K(sub max) (K(sub max) = 0.4 K(sub IC)). Detailed fractographic analysis correlates accelerated FCG with the formation of crack-tip process zone micro-void damage. Experimental results show that the near threshold and K(sub max) influenced accelerated crack growth is time and temperature dependent.

  11. Effect of temperature on surface error and laser damage threshold for self-healing BK7 glass.

    Science.gov (United States)

    Wang, Chu; Wang, Hongxiang; Shen, Lu; Hou, Jing; Xu, Qiao; Wang, Jian; Chen, Xianhua; Liu, Zhichao

    2018-03-20

    Cracks caused during the lapping and polishing process can decrease the laser-induced damage threshold (LIDT) of the BK7 glass optical elements, which would shorten the lifetime and limit the output power of the high-energy laser system. When BK7 glass is heated under appropriate conditions, the surface cracks can exhibit a self-healing phenomenon. In this paper, based on thermodynamics and viscous fluid mechanics theory, the mechanisms of crack self-healing are explained. The heat-healing experiment was carried out, and the effect of water was analyzed. The multi-spatial-frequency analysis was used to investigate the effect of temperature on surface error for self-healing BK7 glass, and the lapped BK7 glass specimens before and after heat healing were detected by an interferometer and atomic force microscopy. The low-spatial-frequency error was analyzed by peak to valley and root mean square, the mid-spatial-frequency error was analyzed by power spectral density, and the high-spatial-frequency error was analyzed by surface roughness. The results showed that the optimal heating temperature for BK7 was 450°C, and when the heating temperature was higher than the glass transition temperature (555°C), the surface quality decreased a lot. The laser damage test was performed, and the specimen heated at 450°C showed an improvement in LIDT.

  12. Synchronization of low- and high-threshold motor units.

    Science.gov (United States)

    Defreitas, Jason M; Beck, Travis W; Ye, Xin; Stock, Matt S

    2014-04-01

    We examined the degree of synchronization for both low- and high-threshold motor unit (MU) pairs at high force levels. MU spike trains were recorded from the quadriceps during high-force isometric leg extensions. Short-term synchronization (between -6 and 6 ms) was calculated for every unique MU pair for each contraction. At high force levels, earlier recruited motor unit pairs (low-threshold) demonstrated relatively low levels of short-term synchronization (approximately 7.3% extra firings than would have been expected by chance). However, the magnitude of synchronization increased significantly and linearly with mean recruitment threshold (reaching 22.1% extra firings for motor unit pairs recruited above 70% MVC). Three potential mechanisms that could explain the observed differences in synchronization across motor unit types are proposed and discussed. Copyright © 2013 Wiley Periodicals, Inc.

  13. Threshold Assessment of Gear Diagnostic Tools on Flight and Test Rig Data

    Science.gov (United States)

    Dempsey, Paula J.; Mosher, Marianne; Huff, Edward M.

    2003-01-01

    A method for defining thresholds for vibration-based algorithms that provides the minimum number of false alarms while maintaining sensitivity to gear damage was developed. This analysis focused on two vibration based gear damage detection algorithms, FM4 and MSA. This method was developed using vibration data collected during surface fatigue tests performed in a spur gearbox rig. The thresholds were defined based on damage progression during tests with damage. The thresholds false alarm rates were then evaluated on spur gear tests without damage. Next, the same thresholds were applied to flight data from an OH-58 helicopter transmission. Results showed that thresholds defined in test rigs can be used to define thresholds in flight to correctly classify the transmission operation as normal.

  14. Quantification of high-power ultrasound induced damage on potato starch granules using light microscopy.

    Science.gov (United States)

    Zuo, Yue Yue J; Hébraud, Pascal; Hemar, Yacine; Ashokkumar, Muthupandian

    2012-05-01

    A simple light microscopic technique was developed in order to quantify the damage inflicted by high-power low-frequency ultrasound (0-160 W, 20 kHz) treatment on potato starch granules in aqueous dispersions. The surface properties of the starch granules were modified using ethanol and SDS washing methods, which are known to displace proteins and lipids from the surface of the starch granules. The study showed that in the case of normal and ethanol-washed potato starch dispersions, two linear regions were observed. The number of defects first increased linearly with an increase in ultrasound power up to a threshold level. This was then followed by another linear dependence of the number of defects on the ultrasound power. The power threshold where the change-over occurred was higher for the ethanol-washed potato dispersions compared to non-washed potato dispersions. In the case of SDS-washed potato starch, although the increase in defects was linear with the ultrasound power, the power threshold for a second linear region was not observed. These results are discussed in terms of the different possible mechanisms of cavitation induced-damage (hydrodynamic shear stresses and micro-jetting) and by taking into account the hydrophobicity of the starch granule surface. Copyright © 2011 Elsevier B.V. All rights reserved.

  15. High-order above-threshold dissociation of molecules

    Science.gov (United States)

    Lu, Peifen; Wang, Junping; Li, Hui; Lin, Kang; Gong, Xiaochun; Song, Qiying; Ji, Qinying; Zhang, Wenbin; Ma, Junyang; Li, Hanxiao; Zeng, Heping; He, Feng; Wu, Jian

    2018-03-01

    Electrons bound to atoms or molecules can simultaneously absorb multiple photons via the above-threshold ionization featured with discrete peaks in the photoelectron spectrum on account of the quantized nature of the light energy. Analogously, the above-threshold dissociation of molecules has been proposed to address the multiple-photon energy deposition in the nuclei of molecules. In this case, nuclear energy spectra consisting of photon-energy spaced peaks exceeding the binding energy of the molecular bond are predicted. Although the observation of such phenomena is difficult, this scenario is nevertheless logical and is based on the fundamental laws. Here, we report conclusive experimental observation of high-order above-threshold dissociation of H2 in strong laser fields where the tunneling-ionized electron transfers the absorbed multiphoton energy, which is above the ionization threshold to the nuclei via the field-driven inelastic rescattering. Our results provide an unambiguous evidence that the electron and nuclei of a molecule as a whole absorb multiple photons, and thus above-threshold ionization and above-threshold dissociation must appear simultaneously, which is the cornerstone of the nowadays strong-field molecular physics.

  16. Re-examination of the threshold energy surface in copper

    International Nuclear Information System (INIS)

    King, W.E.; Benedek, R.; Merkle, K.L.; Meshii, M.

    1981-01-01

    Radiation-induced defect production in copper has been studied using in-situ electrical resistivity damage-rate measurements in the HVEM and molecular dynamics simulations. Analysis of the results yields a threshold energy surface characterized by two isolated pockets of low threshold energy centered at and surrounded by regions of much higher threshold energy; the corresponding damage function exhibits a plateau at 0.65 Frenkel pairs. A Frenkel pair resistivity of (2.75/sub -0.2/ + 0 6 ) x 10 - 4 Ω-cm is proposed. A model damage function is constructed and compared to results from ion irradiation damage-rate measurements. 7 figures

  17. Lifetime laser damage performance of β-Ga2O3 for high power applications

    Directory of Open Access Journals (Sweden)

    Jae-Hyuck Yoo

    2018-03-01

    Full Text Available Gallium oxide (Ga2O3 is an emerging wide bandgap semiconductor with potential applications in power electronics and high power optical systems where gallium nitride and silicon carbide have already demonstrated unique advantages compared to gallium arsenide and silicon-based devices. Establishing the stability and breakdown conditions of these next-generation materials is critical to assessing their potential performance in devices subjected to large electric fields. Here, using systematic laser damage performance tests, we establish that β-Ga2O3 has the highest lifetime optical damage performance of any conductive material measured to date, above 10 J/cm2 (1.4 GW/cm2. This has direct implications for its use as an active component in high power laser systems and may give insight into its utility for high-power switching applications. Both heteroepitaxial and bulk β-Ga2O3 samples were benchmarked against a heteroepitaxial gallium nitride sample, revealing an order of magnitude higher optical lifetime damage threshold for β-Ga2O3. Photoluminescence and Raman spectroscopy results suggest that the exceptional damage performance of β-Ga2O3 is due to lower absorptive defect concentrations and reduced epitaxial stress.

  18. Lifetime laser damage performance of β -Ga2O3 for high power applications

    Science.gov (United States)

    Yoo, Jae-Hyuck; Rafique, Subrina; Lange, Andrew; Zhao, Hongping; Elhadj, Selim

    2018-03-01

    Gallium oxide (Ga2O3) is an emerging wide bandgap semiconductor with potential applications in power electronics and high power optical systems where gallium nitride and silicon carbide have already demonstrated unique advantages compared to gallium arsenide and silicon-based devices. Establishing the stability and breakdown conditions of these next-generation materials is critical to assessing their potential performance in devices subjected to large electric fields. Here, using systematic laser damage performance tests, we establish that β-Ga2O3 has the highest lifetime optical damage performance of any conductive material measured to date, above 10 J/cm2 (1.4 GW/cm2). This has direct implications for its use as an active component in high power laser systems and may give insight into its utility for high-power switching applications. Both heteroepitaxial and bulk β-Ga2O3 samples were benchmarked against a heteroepitaxial gallium nitride sample, revealing an order of magnitude higher optical lifetime damage threshold for β-Ga2O3. Photoluminescence and Raman spectroscopy results suggest that the exceptional damage performance of β-Ga2O3 is due to lower absorptive defect concentrations and reduced epitaxial stress.

  19. Measurements of the dependence of damage thresholds on laser wavelength, pulse duration and film thickness

    International Nuclear Information System (INIS)

    Rainer, F.; Vercimak, C.L.; Carniglia, C.K.; Milam, D.; Hart, T.T.

    1985-01-01

    Results of three experiments are described. The authors used 351-nm and 355-nm pulses with durations of 0.6, 1, 5 and 9 ns to measure thresholds for a variety of antireflectance and high reflectance coatings. The functional form t/sup m/, with t the pulse duration, was used to scale fluence thresholds measured at 0.6 ns to those measured at 9.0 ns. Values of the coefficient m ranged from 0.10 to 0.51. The average value was 0.30. In the second experiment, they measured thresholds at 1064 nm, 527 nm and 355 nm for single-frequency high reflectance ZrO/sub 2//SiO/sub 2/ coatings. Coatings for all three frequencies were deposited simultaneously by use of masks in the coating chamber. Thresholds varied from 2-4 J/cm/sup 2/ at 355 nm to 7-10 J/cm/sup 2/ at 1064 nm. The third experiment measured thresholds at 355 nm for antireflection coatings made with layer thicknesses varying from greater than one wavelength to less than a quarterwavelength. A significant variation of threshold with coating thickness was not observed, but the median thresholds increased slightly as coating thickness increased

  20. Outstanding laser damage threshold in Li2MnGeS4 and tunable optical nonlinearity in diamond-like semiconductors.

    Science.gov (United States)

    Brant, Jacilynn A; Clark, Daniel J; Kim, Yong Soo; Jang, Joon I; Weiland, Ashley; Aitken, Jennifer A

    2015-03-16

    The new Li2MnGeS4 and Li2CoSnS4 compounds result from employing a rational and simple design strategy that guides the discovery of diamond-like semiconductors (DLSs) with wide regions of optical transparency, high laser damage threshold, and efficient second-order optical nonlinearity. Single-crystal X-ray diffraction was used to solve and refine the crystal structures of Li2MnGeS4 and Li2CoSnS4, which crystallize in the noncentrosymmetric space groups Pna21 and Pn, respectively. Synchrotron X-ray powder diffraction (SXRPD) was used to assess the phase purity, and diffuse reflectance UV-vis-NIR spectroscopy was used to estimate the bandgaps of Li2MnGeS4 (Eg = 3.069(3) eV) and Li2CoSnS4 (Eg = 2.421(3) eV). In comparison with Li2FeGeS4, Li2FeSnS4, and Li2CoSnS4 DLSs, Li2MnGeS4 exhibits the widest region of optical transparency (0.60-25 μm) and phase matchability (≥1.6 μm). All four of the DLSs exhibit second-harmonic generation and are compared with the benchmark NLO material, AgGaSe2. Most remarkably, Li2MnGeS4 does not undergo two- or three-photon absorption upon exposure to a fundamental Nd:YAG beam (λ = 1.064 μm) and exhibits a laser damage threshold > 16 GW/cm(2).

  1. Accelerated Near-Threshold Fatigue Crack Growth Behavior of an Aluminum Powder Metallurgy Alloy

    Science.gov (United States)

    Piascik, Robert S.; Newman, John A.

    2002-01-01

    Fatigue crack growth (FCG) research conducted in the near threshold regime has identified a room temperature creep crack growth damage mechanism for a fine grain powder metallurgy (PM) aluminum alloy (8009). At very low DK, an abrupt acceleration in room temperature FCG rate occurs at high stress ratio (R = Kmin/Kmax). The near threshold accelerated FCG rates are exacerbated by increased levels of Kmax (Kmax less than 0.4 KIC). Detailed fractographic analysis correlates accelerated FCG with the formation of crack-tip process zone micro-void damage. Experimental results show that the near threshold and Kmax influenced accelerated crack growth is time and temperature dependent.

  2. Image thresholding in the high resolution target movement monitor

    Science.gov (United States)

    Moss, Randy H.; Watkins, Steve E.; Jones, Tristan H.; Apel, Derek B.; Bairineni, Deepti

    2009-03-01

    Image thresholding in the High Resolution Target Movement Monitor (HRTMM) is examined. The HRTMM was developed at the Missouri University of Science and Technology to detect and measure wall movements in underground mines to help reduce fatality and injury rates. The system detects the movement of a target with sub-millimeter accuracy based on the images of one or more laser dots projected on the target and viewed by a high-resolution camera. The relative position of the centroid of the laser dot (determined by software using thresholding concepts) in the images is the key factor in detecting the target movement. Prior versions of the HRTMM set the image threshold based on a manual, visual examination of the images. This work systematically examines the effect of varying threshold on the calculated centroid position and describes an algorithm for determining a threshold setting. First, the thresholding effects on the centroid position are determined for a stationary target. Plots of the centroid positions as a function of varying thresholds are obtained to identify clusters of thresholds for which the centroid position does not change for stationary targets. Second, the target is moved away from the camera in sub-millimeter increments and several images are obtained at each position and analyzed as a function of centroid position, target movement and varying threshold values. With this approach, the HRTMM can accommodate images in batch mode without the need for manual intervention. The capability for the HRTMM to provide automated, continuous monitoring of wall movement is enhanced.

  3. High-frequency (8 to 16 kHz) reference thresholds and intrasubject threshold variability relative to ototoxicity criteria using a Sennheiser HDA 200 earphone.

    Science.gov (United States)

    Frank, T

    2001-04-01

    The first purpose of this study was to determine high-frequency (8 to 16 kHz) thresholds for standardizing reference equivalent threshold sound pressure levels (RETSPLs) for a Sennheiser HDA 200 earphone. The second and perhaps more important purpose of this study was to determine whether repeated high-frequency thresholds using a Sennheiser HDA 200 earphone had a lower intrasubject threshold variability than the ASHA 1994 significant threshold shift criteria for ototoxicity. High-frequency thresholds (8 to 16 kHz) were obtained for 100 (50 male, 50 female) normally hearing (0.25 to 8 kHz) young adults (mean age of 21.2 yr) in four separate test sessions using a Sennheiser HDA 200 earphone. The mean and median high-frequency thresholds were similar for each test session and increased as frequency increased. At each frequency, the high-frequency thresholds were not significantly (p > 0.05) different for gender, test ear, or test session. The median thresholds at each frequency were similar to the 1998 interim ISO RETSPLs; however, large standard deviations and wide threshold distributions indicated very high intersubject threshold variability, especially at 14 and 16 kHz. Threshold repeatability was determined by finding the threshold differences between each possible test session comparison (N = 6). About 98% of all of the threshold differences were within a clinically acceptable range of +/-10 dB from 8 to 14 kHz. The threshold differences between each subject's second, third, and fourth minus their first test session were also found to determine whether intrasubject threshold variability was less than the ASHA 1994 criteria for determining a significant threshold shift due to ototoxicity. The results indicated a false-positive rate of 0% for a threshold shift > or = 20 dB at any frequency and a false-positive rate of 2% for a threshold shift >10 dB at two consecutive frequencies. This study verified that the output of high-frequency audiometers at 0 dB HL using

  4. Large area damage testing of optics

    International Nuclear Information System (INIS)

    Sheehan, L.; Kozlowski, M.; Stolz, C.

    1996-01-01

    The damage threshold specifications for the National Ignition Facility will include a mixture of standard small-area tests and new large-area tests. During our studies of laser damage and conditioning processes of various materials we have found that some damage morphologies are fairly small and this damage does not grow with further illumination. This type of damage might not be detrimental to the laser performance. We should therefore assume that some damage can be allowed on the optics, but decide on a maximum damage allowance of damage. A new specification of damage threshold termed open-quotes functional damage thresholdclose quotes was derived. Further correlation of damage size and type to system performance must be determined in order to use this measurement, but it is clear that it will be a large factor in the optics performance specifications. Large-area tests have verified that small-area testing is not always sufficient when the optic in question has defect-initiated damage. This was evident for example on sputtered polarizer and mirror coatings where the defect density was low enough that the features could be missed by standard small- area testing. For some materials, the scale-length at which damage non-uniformities occur will effect the comparison of small-area and large-area tests. An example of this was the sub-aperture tests on KD*P crystals on the Beamlet test station. The tests verified the large-area damage threshold to be similar to that found when testing a small-area. Implying that for this KD*P material, the dominate damage mechanism is of sufficiently small scale-length that small-area testing is capable of determining the threshold. The Beamlet test station experiments also demonstrated the use of on-line laser conditioning to increase the crystals damage threshold

  5. Fractional sunburn threshold UVR doses generate equivalent vitamin D and DNA damage in skin types I-VI, but with epidermal DNA damage gradient correlated to skin darkness.

    Science.gov (United States)

    Shih, Barbara B; Farrar, Mark D; Cooke, Marcus S; Osman, Joanne; Langton, Abigail K; Kift, Richard; Webb, Ann R; Berry, Jacqueline L; Watson, Rachel E B; Vail, Andy; de Gruijl, Frank R; Rhodes, Lesley E

    2018-05-03

    Public health guidance recommends limiting sun-exposure to sub-sunburn levels, but it's unknown whether these can gain vitamin D (for musculoskeletal health) whilst avoiding epidermal DNA damage (initiates skin cancer). Well-characterised healthy humans of all skin types (I-VI; lightest to darkest skin) were exposed to a low dose-series of solar simulated UVR of 20-80% their individual sunburn threshold dose (minimal erythemal dose, MED). Significant UVR dose-responses were seen for serum 25(OH)D and whole epidermal CPD, with as little as 0.2 MED concurrently producing 25(OH)D and CPD. Notably, fractional MEDs generated equivalent levels of whole epidermal CPD and 25(OH)D across all skin types. Crucially, we demonstrated an epidermal gradient of CPD formation strongly correlated with skin darkness (r=0.74; Pskin types, ranging from darkest skin, where high CPD levels occurred superficially with none in the germinative basal layer, through to lightest skin where CPD were induced evenly across the epidermal depth. Darker skin people can be encouraged to utilise sub-sunburn UVR-exposure to enhance their vitamin D. In lighter skin people, basal cell damage occurs concurrent with vitamin D synthesis at exquisitely low UVR levels, providing an explanation for their high skin cancer incidence; greater caution is required. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

  6. Growth, structural, optical, thermal and laser damage threshold studies of an organic single crystal: 1,3,5 – triphenylbenzene (TPB)

    International Nuclear Information System (INIS)

    Raja, R. Subramaniyan; Babu, G. Anandha; Ramasamy, P.

    2016-01-01

    Good quality single crystals of pure hydrocarbon 1,3,5-Triphenylbenzene (TPB) have been successfully grown using toluene as a solvent using controlled slow cooling solution growth technique. TPB crystallizes in orthorhombic structure with the space group Pna2 1 . The structural perfection of the grown crystal has been analysed by high resolution X-ray diffraction measurements. The range and percentage of the optical transmission are ascertained by recording the UV-vis spectrum. Thermo gravimetric analysis (TGA) and differential thermal analysis (DTA) were used to study its thermal properties. Powder second harmonic generation studies were carried out to explore its NLO properties. Laser damage threshold value has been determined using Nd:YAG laser operating at 1064 nm.

  7. Status of SiO2/TiO2 HR coating damage

    International Nuclear Information System (INIS)

    Lowermilk, W.H.

    1979-01-01

    The data, observations, and conclusions from a number of experiments on high-reflector (HR) coating damage which were done in FY 1979 are summarized. Damage threshold measurements for the experiments described are presented

  8. Theoretical research of multi-pulses laser induced damage in dielectrics

    International Nuclear Information System (INIS)

    Luo Jin; Liu Zhichao; Chen Songlin; Ma Ping

    2013-01-01

    The pulse width is different, the mechanism of the laser-matter interaction is different. Damage results from plasma formation and ablation forτ≤10 ps and from heat depositing and conventional melting for τ>100 ps. Two theoretical models of transparent dielectrics irradiated by multi-pulses laser are respectively developed based on the above-mentioned different mechanism. One is the dielectric breakdown model based on electron density evolution equation for femtosecond multi-pluses laser, the other is the dielectric heat-damage model based on Fourier's heat exchange equation for nanosecond multi-pluses laser. Using these models, the effects of laser parameters and material parameters on the laser-induced damage threshold of dielectrics are analyzed. The analysis results show that different parameters have different influence on the damage threshold. The effect of parameters on the multi -pulses damage threshold is not entirely the same to the single-pulse damage threshold. The multi-pulses damage mechanism of dielectrics is discussed in detail, considering the effect of different parameters. The discussion provides more information for understanding its damage process and more knowledge to improve its damage thresholds. And the relationship between damage threshold and pulse number is illustrated, it is in good agreement with experimental results. The illustration can help us to predict the multi-pulses damage threshold and the lifetime of optical components. (authors)

  9. Ultrasonic detection of spall damage nucleation under low-velocity repeated impact

    Directory of Open Access Journals (Sweden)

    Watanabe T.

    2012-08-01

    Full Text Available Repeated plate impact testing with impact stress well below the threshold spall-stress (2.6 GPa on medium carbon steel was carried out to the identical target plate by impacting the flyer plate. Occurrence of spall damage under low-velocity repeated impact was evaluated nondestructively with a low frequency scanning acoustic microscope. We observed the spall damage distribution by the B- and C-scan images. In order to initiate the spall damage (voids in a ductile material or cracks in a brittle one the particular value of threshold spall-stress should be exceeded what already belongs to a commonly accepted knowledge. Generally, the spall damage development is dependent on the amplitude and the duration of the stress pulse. If the stress is high and duration is long enough to create tensile failure of material, the voids or cracks nucleate along the spall plane, and consequently, they form macrocracks. Therefore, the spall damage does not create when the first impact stress is less than the threshold spall-stress. However, after the fifth low-velocity repeated impact test, the generation of the spall damage was detected, even if the impact stress (1.1–1.7 GPa was lower than the threshold spall-stress (2.6 GPa.

  10. Effect of Li and NH4 doping on the crystal perfection, second harmonic generation efficiency and laser damage threshold of potassium pentaborate crystals

    Science.gov (United States)

    Vigneshwaran, A. N.; Kalainathan, S.; Raja, C. Ramachandra

    2018-03-01

    Potassium pentaborate (KB5) is an excellent nonlinear optical material especially in the UV region. In this work, Li and NH4 doped KB5 crystals were grown using slow evaporation solution growth method. The incorporation of dopant has been confirmed and analysed by Energy dispersive X-ray analysis (EDAX), Inductively coupled plasma (ICP) analysis and Raman spectroscopy. The crystalline perfection of pure and doped KB5 crystals was studied by High resolution X-ray diffraction (HRXRD) analysis. Structural grain boundaries were observed in doped crystals. Second harmonic generation was confirmed for pure and doped crystals and output values revealed the enhancement of SHG efficiency in doped crystals. Resistance against laser damage was carried out using 1064 nm Nd-YAG laser of pulse width 10 ns. The laser damage threshold value is increased in Li doped crystal and decreased in NH4 doped crystal when compared to pure KB5 crystal.

  11. Low cycle fatigue: high cycle fatigue damage accumulation in a 304L austenitic stainless steel

    International Nuclear Information System (INIS)

    Lehericy, Y.

    2007-05-01

    The aim of this study was to evaluate the consequences of a Low Cycle Fatigue pre-damage on the subsequent fatigue limit of a 304L stainless steel. The effects of hardening and severe roughness (grinding) have also been investigated. In a first set of tests, the evolution of the surface damage induced by the different LCF pre-cycling was characterized. This has permitted to identify mechanisms and kinetics of damage in the plastic domain for different surface conditions. Then, pre-damaged samples were tested in the High Cycle Fatigue domain in order to establish the fatigue limits associated with each level of pre-damage. Results evidence that, in the case of polished samples, an important number of cycles is required to initiate surface cracks ant then to affect the fatigue limit of the material but, in the case of ground samples, a few number of cycles is sufficient to initiate cracks and to critically decrease the fatigue limit. The fatigue limit of pre-damaged samples can be estimated using the stress intensity factor threshold. Moreover, this detrimental effect of severe surface conditions is enhanced when fatigue tests are performed under a positive mean stress (author)

  12. A high sensitivity process variation sensor utilizing sub-threshold operation

    OpenAIRE

    Meterelliyoz, Mesut; Song, Peilin; Stellari, Franco; Kulkarni, Jaydeep P.; Roy, Kaushik

    2008-01-01

    In this paper, we propose a novel low-power, bias-free, high-sensitivity process variation sensor for monitoring random variations in the threshold voltage. The proposed sensor design utilizes the exponential current-voltage relationship of sub-threshold operation thereby improving the sensitivity by 2.3X compared to the above-threshold operation. A test-chip containing 128 PMOS and 128 NMOS devices has been fabri...

  13. Modeling laser damage to the retina

    Science.gov (United States)

    Clark, Clifton D.

    This dissertation presents recent progress in several areas related to modeling laser damage to the retina. In Chapter 3, we consider the consequences of using the Arrhenius damage model to predict the damage thresholds of multiple pulse, or repetitive pulse, exposures. We have identified a few fundamental trends associated with the multiple pulse damage predictions made by the Arrhenius model. These trends differ from what would be expected by non-thermal mechanisms, and could prove useful in differentiating thermal and non-thermal damage. Chapter 4 presents a new rate equation damage model hypothesized to describe photochemical damage. The model adds a temperature dependent term to the simple rate equation implied by the principle of reciprocity that is characteristic of photochemical damage thresholds. A recent damage threshold study, conducted in-vitro, has revealed a very sharp transition between thermal and photochemical damage threshold trends. For the wavelength used in the experiment (413 nm), thermal damage thresholds were observed at exposure levels that were twice the expected photochemical damage threshold, based on the traditional understanding of photochemical damage. Our model accounts for this observed trend by introducing a temperature dependent quenching, or repair, rate to the photochemical damage rate. For long exposures that give a very small temperature rise, the model reduces to the principle of reciprocity. Near the transition region between thermal and photochemical damage, the model allows the damage threshold to be set by thermal mechanisms, even at exposure above the reciprocity exposure. In Chapter 5, we describe a retina damage model that includes thermal lensing in the eye by coupling beam propagation and heat transfer models together. Thermal lensing has recently been suggested as a contributing factor to the large increase in measured retinal damage thresholds in the near infrared. The transmission of the vitreous decreases

  14. A study of the high-frequency hearing thresholds of dentistry professionals

    Directory of Open Access Journals (Sweden)

    Lopes, Andréa Cintra

    2012-01-01

    Full Text Available Introduction: In the dentistry practice, dentists are exposed to harmful effects caused by several factors, such as the noise produced by their work instruments. In 1959, the American Dental Association recommended periodical hearing assessments and the use of ear protectors. Aquiring more information regarding dentists', dental nurses', and prosthodontists' hearing abilities is necessary to propose prevention measures and early treatment strategies. Objective: To investigate the auditory thresholds of dentists, dental nurses, and prosthodontists. Method: In this clinical and experimental study, 44 dentists (Group I; GI, 36 dental nurses (Group II; GII, and 28 prosthodontists (Group III; GIII were included, , with a total of 108 professionals. The procedures that were performed included a specific interview, ear canal inspection, conventional and high-frequency threshold audiometry, a speech reception threshold test, and an acoustic impedance test. Results: In the 3 groups that were tested, the comparison between the mean hearing thresholds provided evidence of worsened hearing ability relative to the increase in frequency. For the tritonal mean at 500 to 2,000 Hz and 3,000 to 6,000 Hz, GIII presented the worst thresholds. For the mean of the high frequencies (9,000 and 16,000 Hz, GII presented the worst thresholds. Conclusion: The conventional hearing threshold evaluation did not demonstrate alterations in the 3 groups that were tested; however, the complementary tests such as high-frequency audiometry provided greater efficacy in the early detection of hearing problems, since this population's hearing loss impaired hearing ability at frequencies that are not tested by the conventional tests. Therefore, we emphasize the need of utilizing high-frequency threshold audiometry in the hearing assessment routine in combination with other audiological tests.

  15. Laser-induced damage to thin film dielectric coatings

    International Nuclear Information System (INIS)

    Walker, T.W.

    1980-01-01

    The laser-induced damage thresholds of dielectric thin film coatings have been found to be more than an order of magnitude lower than the bulk material damage thresholds. Prior damage studies have been inconclusive in determining the damage mechanism which is operative in thin films. A program was conducted in which thin film damage thresholds were measured as a function of laser wavelength (1.06 μm, 0.53 μm, 0.35 μm and 0.26 μm), laser pulse length (5 and 15 nanoseconds), film materials and film thickness. The large matrix of data was compared to predictions given by avalanche ionization, multiphoton ionization and impurity theories of laser damage. When Mie absorption cross-sections and the exact thermal equations were included into the impurity theory excellent agreement with the data was found. The avalanche and multiphoton damage theories could not account for most parametric variations in the data. For example, the damage thresholds for most films increased as the film thickness decreased and only the impurity theory could account for this behavior. Other observed changes in damage threshold with changes in laser wavelength, pulse length and film material could only be adequately explained by the impurity theory. The conclusion which results from this study is that laser damage in thin film coatings results from absorbing impurities included during the deposition process

  16. High-light damage in air-dry thalli of the old forest lichen Lobaria pulmonaria - interactions of irradiance, exposure duration and high temperature

    International Nuclear Information System (INIS)

    Gauslaa, Y.; Solhaug, K.A.

    1999-01-01

    High-light damage in air-dry thalli of Lobaria pulmonaria were measured in the laboratory as reductions in maximal PSII efficiency (FV/FM) after a 48 h recovery in a hydrated state at low light to account for permanent damage. Thalli treated with the lowest light dose (90 mol photons m −2 ) recovered normal FV/FM-values with increasing irradiances (400–700 nm) up to 1000 µmol photons m −2 s −1 . Doubling this dose lowered the threshold level for damage from 1000 to 320 µmol photons m −2 s −1 , and reduced FV/FM at 1000 µmol photons m −2 s −1 by more than 50%. A second doubling of the dose to 360 mol photons m −2 caused damage at 200 µmol photons m −2 s −1 , and a nearly complete cessation of PSII efficiency occurred at 1000 µmol photons m −2 s −1 . No reciprocity of irradiance and duration of illumination for PSII function was found. The measured time-dependent decrease in FV/FM was remarkably similar for the naturally coupled, but artificially separated, light and temperature factors. Therefore, the damage of high light on desiccated L. pulmonaria seemed to be an additive effect of high irradiance and high temperatures. Air-dry thalli were highly heat susceptible, being affected already at temperatures around 40 °C. Logging operations in forests are likely to raise the solar radiation at remaining lichen sites to destructive levels. (author)

  17. Simulation of electron displacement damage in a high voltage electron microscope

    International Nuclear Information System (INIS)

    Ono, Susumu; Kanaya, Koichi

    1979-01-01

    By applying the fundamental theory of the neutron cooling to the conservation law of energy and momentum, the threshold energies of incident electrons for displacing atoms are calculated and illustrated periodically for the atomic number. And the observable damage due to the secondary action of displaced atoms in the practical use of a high voltage electron microscope is described for several materials and accelerating voltages. The trajectories of incident electrons and displaced atoms in several materials are simulated by a Monte-Carlo method, using rigorous formulas of electron scattering events, i.e. elastic and inelastic scattering cross-sections, ionization loss and plasmon excitation. The simulation results are substantially agreement with experiments. (author)

  18. Optical Thin Film Coating Having High Damage Resistance in Near-Stoichiometric MgO-Doped LiTaO3

    Science.gov (United States)

    Tateno, Ryo; Kashiwagi, Kunihiro

    2008-08-01

    Currently, High power and compact red, green, and blue (RGB) lasers are being considered for use in large screen laser televisions and reception-lobby projectors. Among these three laser sources, green semiconductor lasers are expensive and exhibit inferior performance in terms of the semiconductor material used, making it difficult to achieve a high output. In this study, we examined the use of our coating on MgO-doped LiTaO3, using a mirror coated with a multilayer film. Over a substrate, a Ta2O5 film was used to coat a high-refractive-index film layer, and a SiO2 film was used to coat a low-refractive-index film layer. To improve reflectivity, we designed the peak of the electric field intensity to be in the film layer with the low refractive index. As a result, the film endurance of 100 J/cm2 was obtained by one-on-one testing. With the nonlinear crystal material, the mirror without our coating exhibited a damage threshold of 33 J/cm2; however, after coating, this mirror demonstrated a higher damage threshold of 47 J/cm2. Thus, the film we fabricated using this technique is useful for improving the strength and durability of laser mirrors.

  19. First-principles and classical molecular dynamics study of threshold displacement energy in beryllium

    Energy Technology Data Exchange (ETDEWEB)

    Vladimirov, P.V. [Institute for Applied Materials – Applied Materials Physics, Karlsruhe Institute of Technology, P.O. Box 3640, 76021 Karlsruhe (Germany); Borodin, V.A., E-mail: Borodin_VA@nrcki.ru [National Research Center “Kurchatov Institute”, 123182 Moscow (Russian Federation); NRNU MEPhI, 115409 Moscow (Russian Federation)

    2017-02-15

    Highlights: • Beryllium is a functional material of future fusion reactors. • The threshold displacement energy by fast particles is studied. • Classical and first principles simulations are used. - Abstract: Beryllium selected as a neutron multiplier material for the tritium breeding blanket of fusion reactor should withstand high doses of fast neutron irradiation. The damage produced by irradiation is usually evaluated assuming that the number of atomic displacements to the threshold displacement energy, E{sub d}, which is considered as an intrinsic material parameter. In this work the value of E{sub d} for hcp beryllium is estimated simultaneously from classical and first-principles molecular dynamics simulations. Quite similar quantitative pictures of defect production are observed in both simulation types, though the predicted displacement threshold values seem to be approximately two times higher in the first-principles approach. We expect that, after more detailed first-principles investigations, this approach can be used for scaling the damage prediction predictions by classical molecular dynamics, opening a way for more consistent calculations of displacement damage in materials.

  20. Applications of molecules as high-resolution, high-sensitivity threshold electron detectors

    International Nuclear Information System (INIS)

    Chutjian, A.

    1991-01-01

    The goal of the work under the contract entitled ''Applications of Molecules as High-Resolution, High-Sensitivity Threshold Electron Detectors'' (DoE IAA No. DE-AI01-83ER13093 Mod. A006) was to explore the electron attachment properties of a variety of molecules at electron energies not accessible by other experimental techniques. As a result of this work, not only was a large body of basic data measured on attachment cross sections and rate constants; but also extensive theoretical calculations were carried out to verify the underlying phenomenon of s-wave attachment. Important outgrowths of this week were also realized in other areas of research. The basic data have applications in fields such as combustion, soot reduction, rocket-exhaust modification, threshold photoelectron spectroscopy, and trace species detection

  1. Synthesis, growth and characterization of o-phenylinediaminium benzilate: An SHG material with high laser damage threshold for NLO applications

    Science.gov (United States)

    Rajkumar, M.; Chandramohan, A.

    2017-02-01

    An organic molecular charge transfer complex salt, o-phenylenediaminium benzilate was synthesized and single crystals grown by slow solvent evaporation solution growth technique in methanol at ambient temperature. The grown crystal was subjected to Single crystal XRD analysis to establish the molecular structure. The molecular structure was further confirmed by 1H and 13C NMR spectral studies. The formation of the charge transfer complex salt was confirmed by UV-VIS spectroscopic technique. To identify the optical transmittance window and lower wavelength cut-off, the crystal was subjected to UV-Vis-NIR transmission spectral studies. The presence of various functional groups in the salt crystal was confirmed by FT-IR spectroscopic technique. Photoluminescence study was carried out to explore its efficiency towards device fabrications. The TG and DTA thermal analyses were simultaneously carried out to establish the thermal stability of the crystal. The dielectric studies of the grown crystal were executed at different temperatures as a function of frequency to investigate its electrical properties. The SHG efficiency of the crystal was determined using the modified Kurtz and Perry powder technique and its value was found to be 1.98 times that of the KDP crystal. Laser damage threshold value was measured using Nd:YAG laser. The mechanical stability of the title crystal was established employing Vickers micro hardness tester.

  2. Downregulation of Wip1 phosphatase modulates the cellular threshold of DNA damage signaling in mitosis

    Science.gov (United States)

    Macurek, Libor; Benada, Jan; Müllers, Erik; Halim, Vincentius A.; Krejčíková, Kateřina; Burdová, Kamila; Pecháčková, Sona; Hodný, Zdeněk; Lindqvist, Arne; Medema, René H.; Bartek, Jiri

    2013-01-01

    Cells are constantly challenged by DNA damage and protect their genome integrity by activation of an evolutionary conserved DNA damage response pathway (DDR). A central core of DDR is composed of a spatiotemporally ordered net of post-translational modifications, among which protein phosphorylation plays a major role. Activation of checkpoint kinases ATM/ATR and Chk1/2 leads to a temporal arrest in cell cycle progression (checkpoint) and allows time for DNA repair. Following DNA repair, cells re-enter the cell cycle by checkpoint recovery. Wip1 phosphatase (also called PPM1D) dephosphorylates multiple proteins involved in DDR and is essential for timely termination of the DDR. Here we have investigated how Wip1 is regulated in the context of the cell cycle. We found that Wip1 activity is downregulated by several mechanisms during mitosis. Wip1 protein abundance increases from G1 phase to G2 and declines in mitosis. Decreased abundance of Wip1 during mitosis is caused by proteasomal degradation. In addition, Wip1 is phosphorylated at multiple residues during mitosis, and this leads to inhibition of its enzymatic activity. Importantly, ectopic expression of Wip1 reduced γH2AX staining in mitotic cells and decreased the number of 53BP1 nuclear bodies in G1 cells. We propose that the combined decrease and inhibition of Wip1 in mitosis decreases the threshold necessary for DDR activation and enables cells to react adequately even to modest levels of DNA damage encountered during unperturbed mitotic progression. PMID:23255129

  3. Azygos Vein Lead Implantation For High Defibrillation Thresholds In Implantable Cardioverter Defibrillator Placement

    Directory of Open Access Journals (Sweden)

    Naga VA Kommuri

    2010-01-01

    Full Text Available Evaluation of defibrillation threshold is a standard of care during implantation of implantable cardioverter defibrillator. High defibrillation thresholds are often encountered and pose a challenge to electrophysiologists to improve the defibrillation threshold. We describe a case series where defibrillation thresholds were improved after implanting a defibrillation lead in the azygos vein.

  4. Improved laser damage threshold performance of calcium fluoride optical surfaces via Accelerated Neutral Atom Beam (ANAB) processing

    Science.gov (United States)

    Kirkpatrick, S.; Walsh, M.; Svrluga, R.; Thomas, M.

    2015-11-01

    Optics are not keeping up with the pace of laser advancements. The laser industry is rapidly increasing its power capabilities and reducing wavelengths which have exposed the optics as a weak link in lifetime failures for these advanced systems. Nanometer sized surface defects (scratches, pits, bumps and residual particles) on the surface of optics are a significant limiting factor to high end performance. Angstrom level smoothing of materials such as calcium fluoride, spinel, magnesium fluoride, zinc sulfide, LBO and others presents a unique challenge for traditional polishing techniques. Exogenesis Corporation, using its new and proprietary Accelerated Neutral Atom Beam (ANAB) technology, is able to remove nano-scale surface damage and particle contamination leaving many material surfaces with roughness typically around one Angstrom. This surface defect mitigation via ANAB processing can be shown to increase performance properties of high intensity optical materials. This paper describes the ANAB technology and summarizes smoothing results for calcium fluoride laser windows. It further correlates laser damage threshold improvements with the smoothing produced by ANAB surface treatment. All ANAB processing was performed at Exogenesis Corporation using an nAccel100TM Accelerated Particle Beam processing tool. All surface measurement data for the paper was produced via AFM analysis on a Park Model XE70 AFM, and all laser damage testing was performed at Spica Technologies, Inc. Exogenesis Corporation's ANAB processing technology is a new and unique surface modification technique that has demonstrated to be highly effective at correcting nano-scale surface defects. ANAB is a non-contact vacuum process comprised of an intense beam of accelerated, electrically neutral gas atoms with average energies of a few tens of electron volts. The ANAB process does not apply mechanical forces associated with traditional polishing techniques. ANAB efficiently removes surface

  5. Threshold effect under nonlinear limitation of the intensity of high-power light

    International Nuclear Information System (INIS)

    Tereshchenko, S A; Podgaetskii, V M; Gerasimenko, A Yu; Savel'ev, M S

    2015-01-01

    A model is proposed to describe the properties of limiters of high-power laser radiation, which takes into account the threshold character of nonlinear interaction of radiation with the working medium of the limiter. The generally accepted non-threshold model is a particular case of the threshold model if the threshold radiation intensity is zero. Experimental z-scan data are used to determine the nonlinear optical characteristics of media with carbon nanotubes, polymethine and pyran dyes, zinc selenide, porphyrin-graphene and fullerene-graphene. A threshold effect of nonlinear interaction between laser radiation and some of investigated working media of limiters is revealed. It is shown that the threshold model more adequately describes experimental z-scan data. (nonlinear optical phenomena)

  6. Music students: conventional hearing thresholds and at high frequencies

    Directory of Open Access Journals (Sweden)

    Débora Lüders

    2014-07-01

    Full Text Available INTRODUCTION: Research has shown that hearing loss in musicians may cause difficulty in timbre recognition and tuning of instruments. AIM: To analyze the hearing thresholds from 250 Hz to 16,000 Hz in a group of music students and compare them to a non-musician group in order to determine whether high-frequency audiometry is a useful tool in the early detection of hearing impairment. METHODS: Study design was a retrospective observational cohort. Conventional and high-frequency audiometry was performed in 42 music students (Madsen Itera II audiometer and TDH39P headphones for conventional audiometry, and HDA 200 headphones for high-frequency audiometry. RESULTS: Of the 42 students, 38.1% were female students and 61.9% were male students, with a mean age of 26 years. At conventional audiometry, 92.85% had hearing thresholds within normal limits; but even within the normal limits, the worst results were observed in the left ear for all frequencies, except for 4000 Hz; compared to the non-musician group, the worst results occurred at 500 Hz in the left ear, and at 250 Hz, 6000 Hz, 9000 Hz, 10,000 Hz, and 11,200 Hz in both the ears. CONCLUSION: The periodic evaluation of high-frequency thresholds may be useful in the early detection of hearing loss in musicians.

  7. Influence of resonator length on catastrophic optical damage in high-power AlGaInP broad-area lasers

    Science.gov (United States)

    Bou Sanayeh, Marwan

    2017-05-01

    The increasing importance of extracting high optical power out of semiconductor lasers motivated several studies in catastrophic optical damage (COD) level improvement. In this study, the influence of the resonator length in high-power broad-area (BA) AlGaInP lasers on COD is presented. For the analyses, several 638 nm AlGaInP 60 μm BA lasers from the same wafer were used. Resonator lengths of 900, 1200, 1500, and 1800 μm were compared. In order to independently examine the effect of the resonator length on the maximum power reached by the lasers before COD (PCOD), the lasers used are uncoated and unmounted, and PCOD under pulsed mode was determined. It was found that higher output powers and eventually higher PCOD can be achieved using longer resonators; however, it was also found that this is mainly useful when working at high output powers far away from the laser threshold, since the threshold current and slope efficiency worsen when the resonator length increases.

  8. Supra-threshold epidermis injury from near-infrared laser radiation prior to ablation onset

    Science.gov (United States)

    DeLisi, Michael P.; Peterson, Amanda M.; Lile, Lily A.; Noojin, Gary D.; Shingledecker, Aurora D.; Stolarski, David J.; Zohner, Justin J.; Kumru, Semih S.; Thomas, Robert J.

    2017-02-01

    With continued advancement of solid-state laser technology, high-energy lasers operating in the near-infrared (NIR) band are being applied in an increasing number of manufacturing techniques and medical treatments. Safety-related investigations of potentially harmful laser interaction with skin are commonplace, consisting of establishing the maximum permissible exposure (MPE) thresholds under various conditions, often utilizing the minimally-visible lesion (MVL) metric as an indication of damage. Likewise, characterization of ablation onset and velocity is of interest for therapeutic and surgical use, and concerns exceptionally high irradiance levels. However, skin injury response between these two exposure ranges is not well understood. This study utilized a 1070-nm Yb-doped, diode-pumped fiber laser to explore the response of excised porcine skin tissue to high-energy exposures within the supra-threshold injury region without inducing ablation. Concurrent high-speed videography was employed to assess the effect on the epidermis, with a dichotomous response determination given for three progressive damage event categories: observable permanent distortion on the surface, formation of an epidermal bubble due to bounded intra-cutaneous water vaporization, and rupture of said bubble during laser exposure. ED50 values were calculated for these categories under various pulse configurations and beam diameters, and logistic regression models predicted injury events with approximately 90% accuracy. The distinction of skin response into categories of increasing degrees of damage expands the current understanding of high-energy laser safety while also underlining the unique biophysical effects during induced water phase change in tissue. These observations could prove useful in augmenting biothermomechanical models of laser exposure in the supra-threshold region.

  9. Effects of high repetition rate and beam size on hard tissue damage due to subpicosecond laser pulses

    International Nuclear Information System (INIS)

    Kim, Beop-Min; Feit, Michael D.; Rubenchik, Alexander M.; Joslin, Elizabeth J.; Eichler, Juergen; Stoller, Patrick C.; Da Silva, Luiz B.

    2000-01-01

    We report the effects of the repetition rate and the beam size on the threshold for ultrashort laser pulse induced damage in dentin. The observed results are explained as cumulative thermal effects. Our model is consistent with the experimental results and explains the dependence of the threshold on repetition rate, beam size, and exposure time. (c) 2000 American Institute of Physics

  10. Characterisation of radiation damage in perovskite using high angular resolution electron channeling x-ray spectroscopy (HARECXS)

    International Nuclear Information System (INIS)

    Smith, K.L.; Zaluzec, N.J.

    2002-01-01

    Full text: Predicting and/or modelling the occurrence of radiation damage induced defects and their effects on physical properties (eg. amorphisation induced swelling, electrical conductivity., optical response etc.) in ceramic phases requires knowledge of the displacement energies, E d , of cations and anions in those phases. In this study, High Angular Resolution Electron Channelling X-ray Spectroscopy (HARECXS) spectra were collected from perovskite (CaTiO 3 ) samples that had been exposed to high-energy electrons or high-energy heavy ions. Calculations based on experimental data were then used to indicate the E d of the cations in perovskite. The HARECXS measurements were conducted on a Philips EM 420T AEM (LaB6 source, operated at 120 kV) fitted with an EDAX ultra thin window Si(Li) detector. The specimen was first manually oriented to an appropriate zone axis. Then control of the relative orientation of the incident probe was accomplished via direct computer control of the beam tilt coils, Typical acquisition times for a complete two-dimensional scan were 18-24 hours, while one dimensional scans ranged from 1-5 hours. Our experiments established that: a) HARECXS can detect radiation damage in perovskite caused by either high energy heavy ions or high energy electrons, b) the HARECXS signature of perovskite shows a systematic change with ion dose, c) HARECXS detects damage in perovskite that has been irradiated with 900kV electrons and does not detect damage in perovskite that has been irradiated with 620kV electrons, indicating the existance of an electron irradiation damage threshold. Calculations based on the latter results indicate that the displacement energy, E d of calcium and titanium in perovskite lie between 50 and 85eV. Copyright (2002) Australian Society for Electron Microscopy Inc

  11. A New Integrated Threshold Selection Methodology for Spatial Forecast Verification of Extreme Events

    Science.gov (United States)

    Kholodovsky, V.

    2017-12-01

    Extreme weather and climate events such as heavy precipitation, heat waves and strong winds can cause extensive damage to the society in terms of human lives and financial losses. As climate changes, it is important to understand how extreme weather events may change as a result. Climate and statistical models are often independently used to model those phenomena. To better assess performance of the climate models, a variety of spatial forecast verification methods have been developed. However, spatial verification metrics that are widely used in comparing mean states, in most cases, do not have an adequate theoretical justification to benchmark extreme weather events. We proposed a new integrated threshold selection methodology for spatial forecast verification of extreme events that couples existing pattern recognition indices with high threshold choices. This integrated approach has three main steps: 1) dimension reduction; 2) geometric domain mapping; and 3) thresholds clustering. We apply this approach to an observed precipitation dataset over CONUS. The results are evaluated by displaying threshold distribution seasonally, monthly and annually. The method offers user the flexibility of selecting a high threshold that is linked to desired geometrical properties. The proposed high threshold methodology could either complement existing spatial verification methods, where threshold selection is arbitrary, or be directly applicable in extreme value theory.

  12. A study on reactor core failure thresholds to safety operation of LMFBR

    International Nuclear Information System (INIS)

    Kazuo, Haga; Hiroshi, Endo; Tomoko, Ishizu; Yoshihisa, Shindo

    2006-01-01

    Japan Nuclear Safety Organization (JNES) has been developing the methodology and computer codes for applying level-1 PSA to LMFBR. Many of our efforts have been directed to the judging conditions of reactor core damage and the time allowed to initiate the accident management. Several candidates of the reactor core failure threshold were examined to a typical proto-type LMFBR with MOX fuel based on the plant thermal-hydraulic analyses to the actual progressions leading to the core damage. The results of the present study showed that the judging condition of coolant-boundary integrity failure, 750 degree-C of the boundary temperature, is enough as the threshold of core damage to PLOHS (protected loss-of-heat sink). High-temperature fuel cladding creep failure will not take place before the coolant-boundary reaches the judging temperature and sodium boiling will not occur due to the system pressure rise. In cases of ATWS (anticipated transient without scrum) the accident progression is so fast and the reactor core damage will be inevitable even a realistic negative reactivity insertion due to the temperature rise is considered. Only in the case of ULOHS (unprotected loss-of-heat sink) a relatively long time of 11 min will be allowed till the shut-down of the reactor before the core damage. (authors)

  13. Music students: conventional hearing thresholds and at high frequencies.

    Science.gov (United States)

    Lüders, Débora; Gonçalves, Cláudia Giglio de Oliveira; Lacerda, Adriana Bender de Moreira; Ribas, Ângela; Conto, Juliana de

    2014-01-01

    Research has shown that hearing loss in musicians may cause difficulty in timbre recognition and tuning of instruments. To analyze the hearing thresholds from 250 Hz to 16,000 Hz in a group of music students and compare them to a non-musician group in order to determine whether high-frequency audiometry is a useful tool in the early detection of hearing impairment. Study design was a retrospective observational cohort. Conventional and high-frequency audiometry was performed in 42 music students (Madsen Itera II audiometer and TDH39P headphones for conventional audiometry, and HDA 200 headphones for high-frequency audiometry). Of the 42 students, 38.1% were female students and 61.9% were male students, with a mean age of 26 years. At conventional audiometry, 92.85% had hearing thresholds within normal limits; but even within the normal limits, the worst results were observed in the left ear for all frequencies, except for 4000 Hz; compared to the non-musician group, the worst results occurred at 500 Hz in the left ear, and at 250 Hz, 6000 Hz, 9000 Hz, 10,000 Hz, and 11,200 Hz in both the ears. The periodic evaluation of high-frequency thresholds may be useful in the early detection of hearing loss in musicians. Copyright © 2014 Associação Brasileira de Otorrinolaringologia e Cirurgia Cérvico-Facial. Published by Elsevier Editora Ltda. All rights reserved.

  14. Damage Analysis and Evaluation of High Strength Concrete Frame Based on Deformation-Energy Damage Model

    Directory of Open Access Journals (Sweden)

    Huang-bin Lin

    2015-01-01

    Full Text Available A new method of characterizing the damage of high strength concrete structures is presented, which is based on the deformation energy double parameters damage model and incorporates both of the main forms of damage by earthquakes: first time damage beyond destruction and energy consumption. Firstly, test data of high strength reinforced concrete (RC columns were evaluated. Then, the relationship between stiffness degradation, strength degradation, and ductility performance was obtained. And an expression for damage in terms of model parameters was determined, as well as the critical input data for the restoring force model to be used in analytical damage evaluation. Experimentally, the unloading stiffness was found to be related to the cycle number. Then, a correction for this changing was applied to better describe the unloading phenomenon and compensate for the shortcomings of structure elastic-plastic time history analysis. The above algorithm was embedded into an IDARC program. Finally, a case study of high strength RC multistory frames was presented. Under various seismic wave inputs, the structural damages were predicted. The damage model and correction algorithm of stiffness unloading were proved to be suitable and applicable in engineering design and damage evaluation of a high strength concrete structure.

  15. Threshold values characterizing iodine-induced SCC of zircaloys

    International Nuclear Information System (INIS)

    Une, K.

    1984-01-01

    Threshold values of stress, stress intensity factor, strain, strain rate and iodine concentration for SCC of unirradiated and irradiated Zircaloys are reviewed. The ratio of σsub(th)/σsub(y) adequately represents the effects of cold work and irradiation damage on the SCC susceptibility, where threshold stress σsub(th) is defined as the minimum stress to cause SCC to failure after -6 and 10 -3 min -1 . A comparison of SCC data between constant strain rate and constant stress tests is presented in order to examine the validity of a cumulative-damage concept under SCC conditions. (author)

  16. Doubler system quench detection threshold

    International Nuclear Information System (INIS)

    Kuepke, K.; Kuchnir, M.; Martin, P.

    1983-01-01

    The experimental study leading to the determination of the sensitivity needed for protecting the Fermilab Doubler from damage during quenches is presented. The quench voltage thresholds involved were obtained from measurements made on Doubler cable of resistance x temperature and voltage x time during quenches under several currents and from data collected during operation of the Doubler Quench Protection System as implemented in the B-12 string of 20 magnets. At 4kA, a quench voltage threshold in excess of 5.OV will limit the peak Doubler cable temperature to 452K for quenches originating in the magnet coils whereas a threshold of 0.5V is required for quenches originating outside of coils

  17. Some considerations regarding the creep crack growth threshold

    International Nuclear Information System (INIS)

    Thouless, M.D.; Evans, A.G.

    1984-01-01

    The preceding analysis reveals that the existence of a threshold determined by the sintering stress does not influence the post threshold crack velocity. Considerations of the sintering stress can thus be conveniently excluded from analysis of the post threshold crack velocity. The presence of a crack growth threshold has been predicted, based on the existence of cavity nucleation controlled crack growth. A preliminary analysis of cavity nucleation rates within the damage zone reveals that this threshold is relatively abrupt, in accord with experimental observations. Consequently, at stress intensities below K /SUB th/ growth becomes nucleation limited and crack blunting occurs in preference to crack growth

  18. Relaxed damage threshold intensity conditions and nonlinear increase in the conversion efficiency of an optical parametric oscillator using a bi-directional pump geometry.

    Science.gov (United States)

    Norris, G; McConnell, G

    2010-03-01

    A novel bi-directional pump geometry that nonlinearly increases the nonlinear optical conversion efficiency of a synchronously pumped optical parametric oscillator (OPO) is reported. This bi-directional pumping method synchronizes the circulating signal pulse with two counter-propagating pump pulses within a linear OPO resonator. Through this pump scheme, an increase in nonlinear optical conversion efficiency of 22% was achieved at the signal wavelength, corresponding to a 95% overall increase in average power. Given an almost unchanged measured pulse duration of 260 fs under optimal performance conditions, this related to a signal wavelength peak power output of 18.8 kW, compared with 10 kW using the traditional single-pass geometry. In this study, a total effective peak intensity pump-field of 7.11 GW/cm(2) (corresponding to 3.55 GW/cm(2) from each pump beam) was applied to a 3 mm long periodically poled lithium niobate crystal, which had a damage threshold intensity of 4 GW/cm(2), without impairing crystal integrity. We therefore prove the application of this novel pump geometry provides opportunities for power-scaling of synchronously pumped OPO systems together with enhanced nonlinear conversion efficiency through relaxed damage threshold intensity conditions.

  19. Effects of microwave pulse-width damage on a bipolar transistor

    International Nuclear Information System (INIS)

    Ma Zhen-Yang; Chai Chang-Chun; Ren Xing-Rong; Yang Yin-Tang; Chen Bin; Zhao Ying-Bo

    2012-01-01

    This paper presents a theoretical study of the pulse-width effects on the damage process of a typical bipolar transistor caused by high power microwaves (HPMs) through the injection approach. The dependences of the microwave damage power, P, and the absorbed energy, E, required to cause the device failure on the pulse width τ are obtained in the nanosecond region by utilizing the curve fitting method. A comparison of the microwave pulse damage data and the existing dc pulse damage data for the same transistor is carried out. By means of a two-dimensional simulator, ISE-TCAD, the internal damage processes of the device caused by microwave voltage signals and dc pulse voltage signals are analyzed comparatively. The simulation results suggest that the temperature-rising positions of the device induced by the microwaves in the negative and positive half periods are different, while only one hot spot exists under the injection of dc pulses. The results demonstrate that the microwave damage power threshold and the absorbed energy must exceed the dc pulse power threshold and the absorbed energy, respectively. The dc pulse damage data may be useful as a lower bound for microwave pulse damage data. (interdisciplinary physics and related areas of science and technology)

  20. Method to reduce damage to backing plate

    Science.gov (United States)

    Perry, Michael D.; Banks, Paul S.; Stuart, Brent C.

    2001-01-01

    The present invention is a method for penetrating a workpiece using an ultra-short pulse laser beam without causing damage to subsequent surfaces facing the laser. Several embodiments are shown which place holes in fuel injectors without damaging the back surface of the sack in which the fuel is ejected. In one embodiment, pulses from an ultra short pulse laser remove about 10 nm to 1000 nm of material per pulse. In one embodiment, a plasma source is attached to the fuel injector and initiated by common methods such as microwave energy. In another embodiment of the invention, the sack void is filled with a solid. In one other embodiment, a high viscosity liquid is placed within the sack. In general, high-viscosity liquids preferably used in this invention should have a high damage threshold and have a diffusing property.

  1. Fabrication of Pt nanowires with a diffraction-unlimited feature size by high-threshold lithography

    International Nuclear Information System (INIS)

    Li, Li; Zhang, Ziang; Yu, Miao; Song, Zhengxun; Weng, Zhankun; Wang, Zuobin; Li, Wenjun; Wang, Dapeng; Zhao, Le; Peng, Kuiqing

    2015-01-01

    Although the nanoscale world can already be observed at a diffraction-unlimited resolution using far-field optical microscopy, to make the step from microscopy to lithography still requires a suitable photoresist material system. In this letter, we consider the threshold to be a region with a width characterized by the extreme feature size obtained using a Gaussian beam spot. By narrowing such a region through improvement of the threshold sensitization to intensity in a high-threshold material system, the minimal feature size becomes smaller. By using platinum as the negative photoresist, we demonstrate that high-threshold lithography can be used to fabricate nanowire arrays with a scalable resolution along the axial direction of the linewidth from the micro- to the nanoscale using a nanosecond-pulsed laser source with a wavelength λ 0  = 1064 nm. The minimal feature size is only several nanometers (sub λ 0 /100). Compared with conventional polymer resist lithography, the advantages of high-threshold lithography are sharper pinpoints of laser intensity triggering the threshold response and also higher robustness allowing for large area exposure by a less-expensive nanosecond-pulsed laser

  2. Gain optimization in fiber optical parametric amplifiers by combining standard and high-SBS threshold highly nonlinear fibers

    DEFF Research Database (Denmark)

    Da Ros, Francesco; Rottwitt, Karsten; Peucheret, Christophe

    2012-01-01

    Combining Al-doped and Ge-doped HNLFs as gain media in FOPAs is proposed and optimized, resulting in efficient SBS mitigation while circumventing the additional loss of the high SBS threshold Al-doped fiber.......Combining Al-doped and Ge-doped HNLFs as gain media in FOPAs is proposed and optimized, resulting in efficient SBS mitigation while circumventing the additional loss of the high SBS threshold Al-doped fiber....

  3. Synthesis and physicochemical properties of bis(L-asparaginato) zinc(II): A promising new semiorganic crystal with high laser damage threshold for shorter wavelength generation

    Science.gov (United States)

    Subhashini, R.; Arjunan, S.

    2018-05-01

    An exceedingly apparent nonlinear semiorganic optical crystals of bis(L-asparaginato)zinc(II) [BLAZ], was synthesized by a traditional slow evaporation solution growth technique. The cell parameters were estimated from single crystal X-ray diffraction analysis. Spectroscopic study substantiates the presence of functional groups. The UV spectrum shows the sustenance of wide transparency window and several optical constants, such as extinction coefficient (K), refractive index, optical conductivity and electric susceptibility with real and imaginary parts of dielectric constant were calculated using the transmittance data. The fluorescence emission spectrum of the crystal pronounces red emission. The laser induced surface damage threshold of the crystal was measured using Nd:YAG laser. The output intensity of second harmonic generation was estimated using the Kurtz and Perry powder method. The hardness stability was investigated by Vickers microhardness test. The decomposition and thermal stability of the compound were scrutinized by TGA-DSC studies. Dielectric studies were carried out to anatomize the electrical properties of the crystal. SEM analysis reveals the existence of minute crystallites on the growth surface.

  4. Temporary threshold shifts from exposures to equal equivalent continuous A-weighted sound pressure level

    DEFF Research Database (Denmark)

    Ordoñez, Rodrigo Pizarro; Hammershøi, Dorte

    2014-01-01

    the assumptions made using the A-weighting curve for the assessment of hearing damage. By modifying exposure ratings to compensate for the build-up of energy at mid and high-frequencies (above 1 kHz) due to the presence of the listener in the sound field and for the levels below an effect threshold that does...... not induce changes in hearing (equivalent quiet levels), ratings of the sound exposure that reflect the observed temporary changes in auditory function can be obtained.......According to existing methods for the assessment of hearing damage, signals with the same A-weighted equivalent level should pose the same hazard to the auditory system. As a measure of hazard, it is assumed that Temporary Thresholds Shifts (TTS) reflect the onset of alterations to the hearing...

  5. High pain sensitivity is distinct from high susceptibility to non-painful sensory input at threshold level.

    Science.gov (United States)

    Hummel, Thomas; Springborn, Maria; Croy, Ilona; Kaiser, Jochen; Lötsch, Jörn

    2011-04-01

    Individuals may differ considerably in their sensitivity towards various painful stimuli supporting the notion of a person as stoical or complaining about pain. Molecular and functional imaging research provides support that this may extend also to other sensory qualities. Whether a person can be characterized as possessing a generally high or low sensory acuity is unknown. This was therefore assessed with thresholds to painful and non-painful stimuli, with a focus on chemical stimuli that besides pain may evoke clearly non-painful sensations such as taste or smell. In 36 healthy men and 78 women (ages 18 to 52 years), pain thresholds to chemo-somatosensory (intranasal gaseous CO(2)) and electrical stimuli (cutaneous stimulation) were significantly correlated (ρ(2)=0.2268, psensory qualities, i.e., for the rose-like odor phenyl ethyl alcohol and gustatory thresholds for sour (citric acid) and salty (NaCl). Similarly, pain clusters showed no differences in thresholds to other stimuli. Moreover, no clustering was obtained for thresholds to both painful and non-painful stimuli together. Thus, individuals could not be characterized as highly sensitive (or insensitive) to all chemical stimuli no matter of evoking pain. This suggests that pain is primarily a singular sensory perception distinct from others such as olfaction or taste. Copyright © 2011 Elsevier B.V. All rights reserved.

  6. Evaluating the thermal damage resistance of graphene/carbon nanotube hybrid composite coatings

    Science.gov (United States)

    David, L.; Feldman, A.; Mansfield, E.; Lehman, J.; Singh, G.

    2014-03-01

    We study laser irradiation behavior of multiwalled carbon nanotubes (MWCNT) and chemically modified graphene (rGO)-composite spray coatings for use as a thermal absorber material for high-power laser calorimeters. Spray coatings on aluminum test coupon were exposed to increasing laser irradiance for extended exposure times to quantify their damage threshold and optical absorbance. The coatings, prepared at varying mass % of MWCNTs in rGO, demonstrated significantly higher damage threshold values at 2.5 kW laser power at 10.6 μm wavelength than carbon paint or MWCNTs alone. Electron microscopy and Raman spectroscopy of irradiated specimens show that the coating prepared at 50% CNT loading endure at least 2 kW.cm-2 for 10 seconds without significant damage. The improved damage resistance is attributed to the unique structure of the composite in which the MWCNTs act as an efficient absorber of laser light while the much larger rGO sheets surrounding them, dissipate the heat over a wider area.

  7. Laser induced damage threshold on metallic surfaces during laser cleaning

    CSIR Research Space (South Africa)

    Labuschagne, K

    2005-07-01

    Full Text Available laser paint removal. Laser induced damage on 316L stainless steel was studied, with the target subjected to single and multiple pulse irradiations using a Q-switched Nd:YAG, with fluences between 0.15 and 11.8 J/cm2. Several different damage morphologies...

  8. Motor unit activity after eccentric exercise and muscle damage in humans.

    Science.gov (United States)

    Semmler, J G

    2014-04-01

    It is well known that unaccustomed eccentric exercise leads to muscle damage and soreness, which can produce long-lasting effects on muscle function. How this muscle damage influences muscle activation is poorly understood. The purpose of this brief review is to highlight the effect of eccentric exercise on the activation of muscle by the nervous system, by examining the change in motor unit activity obtained from surface electromyography (EMG) and intramuscular recordings. Previous research shows that eccentric exercise produces unusual changes in the EMG–force relation that influences motor performance during isometric, shortening and lengthening muscle contractions and during fatiguing tasks. When examining the effect of eccentric exercise at the single motor unit level, there are substantial changes in recruitment thresholds, discharge rates, motor unit conduction velocities and synchronization, which can last for up to 1 week after eccentric exercise. Examining the time course of these changes suggests that the increased submaximal EMG after eccentric exercise most likely occurs through a decrease in motor unit conduction velocity and an increase in motor unit activity related to antagonist muscle coactivation and low-frequency fatigue. Furthermore, there is a commonly held view that eccentric exercise produces preferential damage to high-threshold motor units, but the evidence for this in humans is limited. Further research is needed to establish whether there is preferential damage to high-threshold motor units after eccentric exercise in humans, preferably by linking changes in motor unit activity with estimates of motor unit size using selective intramuscular recording techniques.

  9. High-Density Plasma-Induced Etch Damage of GaN

    International Nuclear Information System (INIS)

    Baca, A.G.; Han, J.; Lester, L.F.; Pearton, S.J.; Ren, F.; Shul, R.J.; Willison, C.G.; Zhang, L.; Zolper, J.C.

    1999-01-01

    Anisotropic, smooth etching of the group-III nitrides has been reported at relatively high rates in high-density plasma etch systems. However, such etch results are often obtained under high de-bias and/or high plasma flux conditions where plasma induced damage can be significant. Despite the fact that the group-III nitrides have higher bonding energies than more conventional III-V compounds, plasma-induced etch damage is still a concern. Attempts to minimize such damage by reducing the ion energy or increasing the chemical activity in the plasma often result in a loss of etch rate or anisotropy which significantly limits critical dimensions and reduces the utility of the process for device applications requiring vertical etch profiles. It is therefore necessary to develop plasma etch processes which couple anisotropy for critical dimension and sidewall profile control and high etch rates with low-damage for optimum device performance. In this study we report changes in sheet resistance and contact resistance for n- and p-type GaN samples exposed to an Ar inductively coupled plasma (ICP). In general, plasma-induced damage was more sensitive to ion bombardment energies as compared to plasma flux. In addition, p-GaN was typically more sensitive to plasma-induced damage as compared to n-GaN

  10. Laser damage to production- and research-grade KDP crystals

    International Nuclear Information System (INIS)

    Rainer, F.; Atherton, L.J.; DeYoreo, J.J.

    1992-10-01

    We present the results of laser damage measurements conducted on potassium dihydrogen phosphate (KDP) and deuterated potassium dihydrogen phosphate (KD*P) crystals that were grown recently for both production and research applications by several sources. We have measured extrinsic damage thresholds that cover wavelengths from 1064 nm to 266 nm at pulse durations in the 3- to 10-ns regime. Many of the samples were extracted from boules grown specifically to yield large-area crystals, up to 32-cm square, for laser fusion applications. These crystals were the result of efforts, both by the Lawrence Livermore National Laboratory (LLNL) and commercial crystal-growth companies, to yield high-threshold KDP. In particular we have established that such crystals can reliably survive fluences exceeding 15 j/cm 2 at 355 nm and 20 j/cm 2 at 1064 nm when irradiated with 3-ns pulses. We present details of how bulk and surface damage to these crystals scale with pulse duration and wavelength as well as of morphological effects due to laser conditioning

  11. Unidirectional threshold switching in Ag/Si-based electrochemical metallization cells for high-density bipolar RRAM applications

    Science.gov (United States)

    Wang, Chao; Song, Bing; Li, Qingjiang; Zeng, Zhongming

    2018-03-01

    We herein present a novel unidirectional threshold selector for cross-point bipolar RRAM array. The proposed Ag/amorphous Si based threshold selector showed excellent threshold characteristics in positive field, such as high selectivity ( 105), steep slope (type RRAM. By integrating a bipolar RRAM device with the selector, experiments showed that the undesired sneak was significantly suppressed, indicating its potentiality for high-density integrated nonvolatile memory applications.

  12. Picosecond laser damage of fused silica at 355 nm

    International Nuclear Information System (INIS)

    Meng Xiangjie; Liu Hongjie; Wang Fang; Zhang Zhen; An Xinyou; Huang Jin; Jiang Xiaodong; Wu Weidong; Ren Weiyi

    2013-01-01

    This paper studies the initiated damage threshold, the damage morphology and the subsequent damage growth on fused silica's input-surface and exit-surface under picosecond laser irradiation at 355 nm. Defects induced fluorescence on surface of the optical component is observed. The results demonstrate a significant dependence of the initiated damage on pulse duration and surface defects, and that of the damage growth on self-focusing, sub-surface defects. The damage-threshold is 3.98 J/cm 2 of input surface and 2.91 J/cm 2 of exit surface. The damage morphologies are quite different between input surface and exit surface. Slow growth behavior appears for the diameter of exit-surface and linear growth one for the depth of exit-surface in the lateral side of damage site with the increase of shot number. Defects have changed obviously compared with nanosecond laser damage in the damage area. Several main reasons such as electric intensification and self-focusing for the observed initiated damage and damage growth behavior are discussed. (authors)

  13. Applications of high order harmonic radiation to UVX-solids interaction: high excitation density in electronic relaxation dynamics and surface damaging

    International Nuclear Information System (INIS)

    De Grazia, M.

    2007-12-01

    The new sources of radiation in the extreme-UV (X-UV: 10-100 nm), which deliver spatially coherent, ultra-short and intense pulses, allow studying high flux processes and ultra-fast dynamics in various domains. The thesis work presents two applications of the high-order laser harmonics (HH) to solid state physics. In Part I, we describe the optimization of the harmonic for studies of X-UV/solids interaction. In Part II, we investigate effects of high excitation density in the dynamics of electron relaxation in dielectric scintillator crystals - tungstates and fluorides, using time-resolved luminescence spectroscopy. Quenching of luminescence at short time gives evidence of the competition between radiative and non-radiative recombination of self-trapped excitons (STE). The non-radiative channel is identified to mutual interaction of STE at high excitation density. In Part III, we study the X-UV induced damage mechanism in various materials, either conductor (amorphous carbon) or insulators (organic polymers, e.g., PMMA). In PMMA-Plexiglas, in the desorption regime (0.2 mJ/cm 2 , i.e., below damage threshold), the surface modifications reflect X-UV induced photochemical processes that are tentatively identified, as a function of dose: at low dose, polymer chain scission followed by the blow-up of the volatile, low-molecular fragments leads to crater formation; at high dose, cross-linking in the near-surface layer of remaining material leads to surface hardening. These promising results have great perspectives considering the performances already attained and planned in the next future in the development of the harmonic sources. (author)

  14. Crack Growth Behavior in the Threshold Region for High Cycle Fatigue Loading

    Science.gov (United States)

    Forman, R. G.; Zanganeh, M.

    2014-01-01

    This paper describes the results of a research program conducted to improve the understanding of fatigue crack growth rate behavior in the threshold growth rate region and to answer a question on the validity of threshold region test data. The validity question relates to the view held by some experimentalists that using the ASTM load shedding test method does not produce valid threshold test results and material properties. The question involves the fanning behavior observed in threshold region of da/dN plots for some materials in which the low R-ratio data fans out from the high R-ratio data. This fanning behavior or elevation of threshold values in the low R-ratio tests is generally assumed to be caused by an increase in crack closure in the low R-ratio tests. Also, the increase in crack closure is assumed by some experimentalists to result from using the ASTM load shedding test procedure. The belief is that this procedure induces load history effects which cause remote closure from plasticity and/or roughness changes in the surface morphology. However, experimental studies performed by the authors have shown that the increase in crack closure is a result of extensive crack tip bifurcations that can occur in some materials, particularly in aluminum alloys, when the crack tip cyclic yield zone size becomes less than the grain size of the alloy. This behavior is related to the high stacking fault energy (SFE) property of aluminum alloys which results in easier slip characteristics. Therefore, the fanning behavior which occurs in aluminum alloys is a function of intrinsic dislocation property of the alloy, and therefore, the fanned data does represent the true threshold properties of the material. However, for the corrosion sensitive steel alloys tested in laboratory air, the occurrence of fanning results from fretting corrosion at the crack tips, and these results should not be considered to be representative of valid threshold properties because the fanning is

  15. White Light Generation and Anisotropic Damage in Gold Films near Percolation Threshold

    DEFF Research Database (Denmark)

    Novikov, Sergey M.; Frydendahl, Christian; Beermann, Jonas

    2017-01-01

    in vanishingly small gaps between gold islands in thin films near the electrically determined percolation threshold. Optical explorations using two-photon luminescence (TPL) and near-field microscopies reveals supercubic TPL power dependencies with white-light spectra, establishing unequivocally...... that the strongest TPL signals are generated close to the percolation threshold films, and occurrence of extremely confined (similar to 30 nm) and strongly enhanced (similar to 100 times) fields at the illumination wavelength. For linearly polarized and sufficiently powerful light, we observe pronounced optical...

  16. High-power optical coatings for a mega-joule class ICF laser

    International Nuclear Information System (INIS)

    Kozlowski, M.R.; Thomas, I.M.; Campbell, J.H.; Rainer, F.

    1992-11-01

    As a consequence of advancements in Inertial Confinement Fusion research, LLNL is developing plans for a new 1.5 to 2 mega-joule solid-state Nd:glass laser designed to achieve fusion ignition. The new design is possible in part due to advances in optical coatings suitable for high power laser systems. High damage threshold mirrors and polarizers are comprised of electron beam deposited dielectric multilayers. Subthreshold illumination, or laser conditioning, of the multilayer coatings results in an increase in the damage thresholds by factors of 2 to 3 at 1.06μm, thus meeting the fluence requirements of the advanced architecture. For anti-reflective coatings, protective organic coatings for non-linear crystals and phase plates for beam smoothing, sol-gel films provide high damage thresholds coatings at low cost

  17. High temperature damage of a re-sulfurized stainless steel

    International Nuclear Information System (INIS)

    Tinet, Hougo

    2002-01-01

    After having evoked the industrial problem raised by high-temperature damage in the 303 stainless steel, and outlined that the experimental study of high-temperature damage implies the study of the sane (or non damaged) material, the study of micro-voids germination, growth and coalescence, and the study of the material failure process, the author of this research thesis reports a bibliographical study on the behaviour of sane re-sulfurized stainless steel and different damage models. He presents experimental techniques (thermal-mechanical compression and tensile tests, image analysis in optical microscopy) which have been used in this work, and describes and comments results obtained on axisymmetric samples for micro-void germination, growth and coalescence in case of a damage under low and medium stress triaxiality. The last part addresses the study of the damage of strongly notched samples (stress triaxialities close to those existing at the crack bottom) [fr

  18. Seismic damage assessment for high-rise buildings

    Science.gov (United States)

    Scholl, Roger E.

    1980-01-01

    The problem considered in this project, conducted by URS/John A. Blume & Associates, Engineers (URS/Blume), for the U.S. Geological Survey, is the identification, evaluation, and correlation of ground-motion and structural parameters in order to improve procedures for predicting dollar losses for high-rise structures damaged by earthquakes. Ground-motion data bases, analytical techniques, and known motion-damage relationships already developed for high-rise buildings and for other classes of structures will be refined and extended so that reliable quantitative seismic risk evaluations can be made.

  19. Extended high-frequency thresholds in college students: effects of music player use and other recreational noise.

    Science.gov (United States)

    Le Prell, Colleen G; Spankovich, Christopher; Lobariñas, Edward; Griffiths, Scott K

    2013-09-01

    Human hearing is sensitive to sounds from as low as 20 Hz to as high as 20,000 Hz in normal ears. However, clinical tests of human hearing rarely include extended high-frequency (EHF) threshold assessments, at frequencies extending beyond 8000 Hz. EHF thresholds have been suggested for use monitoring the earliest effects of noise on the inner ear, although the clinical usefulness of EHF threshold testing is not well established for this purpose. The primary objective of this study was to determine if EHF thresholds in healthy, young adult college students vary as a function of recreational noise exposure. A retrospective analysis of a laboratory database was conducted; all participants with both EHF threshold testing and noise history data were included. The potential for "preclinical" EHF deficits was assessed based on the measured thresholds, with the noise surveys used to estimate recreational noise exposure. EHF thresholds measured during participation in other ongoing studies were available from 87 participants (34 male and 53 female); all participants had hearing within normal clinical limits (≤25 HL) at conventional frequencies (0.25-8 kHz). EHF thresholds closely matched standard reference thresholds [ANSI S3.6 (1996) Annex C]. There were statistically reliable threshold differences in participants who used music players, with 3-6 dB worse thresholds at the highest test frequencies (10-16 kHz) in participants who reported long-term use of music player devices (>5 yr), or higher listening levels during music player use. It should be possible to detect small changes in high-frequency hearing for patients or participants who undergo repeated testing at periodic intervals. However, the increased population-level variability in thresholds at the highest frequencies will make it difficult to identify the presence of small but potentially important deficits in otherwise normal-hearing individuals who do not have previously established baseline data. American

  20. Improving the bulk laser-damage resistance of KDP by baking and pulsed-laser irradiation

    International Nuclear Information System (INIS)

    Swain, J.E.; Stokowski, S.E.; Milam, D.; Rainer, F.

    1981-01-01

    Isolated bulk damage centers are produced when KDP crystals are irradiated by 1-ns 1064-nm pulses. We have tested about 100 samples and find the median threshold to be 7 J/cm 2 when the samples are irradiated only once at each test volume (1-on-1 tests). The median threshold increased to 11 J/cm 2 when the test volumes were first subjected to subthreshold laser irradiation (n-on-1 tests). We baked several crystals at temperatures from 110 to 165 0 C and remeasured their thresholds. Baking increased thresholds in some crystals, but did not change thresholds of others. The median threshold of baked crystals ranged from 8 to 10 J/cm 2 depending on the baking temperature. In crystals that had been baked, subthreshold irradiation produced a large change in the bulk damage threshold, and reduced the volume density of damage centers relative to the density observed in unbaked crystals. The data are summarized in the table

  1. Fission neutron damage rates and efficiencies in several metals

    International Nuclear Information System (INIS)

    Klabunde, C.E.; Coltman, R.R. Jr.

    1981-11-01

    Initial rates of resistivity-measured low-temperature damage production by fission-spectrum fast neutrons have been determined for 14 metals in the same very well characterized irradiation facility. Six of these metals were fcc, 5 bcc, and 3 hcp. Most were of quite high purity. Observed damage rates, after correction for all known extraneous resistivity-producing effects, were compared with rates predicted by the damage calculation code RECOIL, using parameters chosen from the literature. These parameters, effective displacement threshold energy, E/sub d/, and Frenkel-pair resistivity, rho/sub F/, were in many cases only best estimates, the further refinement of which may be aided by the present results. Damage efficiencies (measured/predicted rates) follow the same trends by crystal classes as seen in other fast-neutron studies

  2. Pulsed laser damage to optical fibers

    International Nuclear Information System (INIS)

    Allison, S.W.; Gillies, G.T.; Magnuson, D.W.; Pagano, T.S.

    1985-01-01

    This paper describes some observations of pulsed laser damage to optical fibers with emphasis on a damage mode characterized as a linear fracture along the outer core of a fiber. Damage threshold data are presented which illustrate the effects of the focusing lens, end-surface preparation, and type of fiber. An explanation based on fiber-beam misalignment is given and is illustrated by a simple experiment and ray trace

  3. High LET radiation and mechanism of DNA damage repair

    International Nuclear Information System (INIS)

    Furusawa, Yoshiya

    2004-01-01

    Clarifying the mechanism of repair from radiation damage gives most important information on radiation effects on cells. Approximately 10% of biological experiments groups in Heavy Ion Medical Accelerator in Chiba (HIMAC) cooperative research group has performed the subject. They gave a lot of new findings on the mechanism, and solved some open questions. The reason to show the peak of relative biological effectiveness RBE at around 100-200 keV/μm causes miss-repair of DNA damage. Sub-lethal damage generated by high linear energy transfer (LET) radiation can be repaired fully. Potentially lethal damages by high-LET radiation also repaired, but the efficiency decreased with the LET, and so on. (author)

  4. 1.06 μm 150 psec laser damage study of diamond turned, diamond turned/polished and polished metal mirrors

    International Nuclear Information System (INIS)

    Saito, T.T.; Milam, D.; Baker, P.; Murphy, G.

    1975-01-01

    Using a well characterized 1.06 μm 150 ps glass laser pulse the damage characteristics for diamond turned, diamond turned/ polished, and polished copper and silver mirrors less than 5 cm diameter were studied. Although most samples were tested with a normal angle of incidence, some were tested at 45 0 with different linear polarization showing an increase in damage threshold for S polarization. Different damage mechanisms observed will be discussed. Laser damage is related to residual surface influences of the fabrication process. First attempts to polish diamond turned surfaces resulted in a significant decrease in laser damage threshold. The importance of including the heat of fusion in the one dimensional heat analysis of the theoretical damage threshold and how close the samples came to the theoretical damage threshold is discussed. (auth)

  5. Corneal Damage from Infrared Radiation

    National Research Council Canada - National Science Library

    McCally, Russell

    2000-01-01

    ...) laser radiation at 10.6 (micrometer) and Tm: YAG laser radiation at 2.02 (micrometer). Retinal damage from sources with rectangular irradiance distributions was also modeled. Thresholds for CO(2...

  6. Four-harmonic database of laser-damage testing

    International Nuclear Information System (INIS)

    Rainer, F.; Atherton, L.J.; Campbell, J.H.; DeMarco, F.P.; Kozlowski, M.R.; Morgan, A.J.; Staggs, M.C.

    1991-01-01

    In the past two years we have made a sixfold expansion of our laser-damage database. Our primary emphasis has been with the fundamental 1064-nm irradiation generated by Nd:YAG. Because of the increasing need for high-threshold optics designed to operate in the UV, we include data covering the harmonics at 532, 355 and 266 nm. This is further supplemented with results of excimer-laser damage testing at 351 and 248 nm. The presented summaries cover over either years of complete data plus selected results spanning over a fourteen-year history of damage testing at LLNL using thirteen different laser systems. Besides the range of wavelengths, our parameter space covers pulse durations from < 1 ns to 84 ns, repetition rates from single shots to 6000 Hz, and irradiation modes from single shots to a variety of multiple-shot laser-conditioning techniques

  7. Damage detection in high-rise buildings using damage-induced rotations

    International Nuclear Information System (INIS)

    Sung, Seung Hun; Jung, Ho Youn; Lee, Jung Hoon; Jung, Hyung Jo

    2016-01-01

    In this paper, a new damage-detection method based on structural vibration is proposed. The essence of the proposed method is the detection of abrupt changes in rotation. Damage-induced rotation (DIR), which is determined from the modal flexibility of the structure, initially occurs only at a specific damaged location. Therefore, damage can be localized by evaluating abrupt changes in rotation. We conducted numerical simulations of two damage scenarios using a 10-story cantilever-type building model. Measurement noise was also considered in the simulation. We compared the sensitivity of the proposed method to localize damage to that of two conventional modal-flexibility-based damage-detection methods, i.e., uniform load surface (ULS) and ULS curvature. The proposed method was able to localize damage in both damage scenarios for cantilever structures, but the conventional methods could not

  8. Damage detection in high-rise buildings using damage-induced rotations

    International Nuclear Information System (INIS)

    Sung, Seung Hoon; Jung, Ho Youn; Lee, Jung Hoon; Jung, Hyung Jo

    2014-01-01

    In this paper, a new damage-detection method based on structural vibration is proposed. The essence of the proposed method is the detection of abrupt changes in rotation. Damage-induced rotation (DIR), which is determined from the modal flexibility of the structure, initially occurs only at a specific damaged location. Therefore, damage can be localized by evaluating abrupt changes in rotation. We conducted numerical simulations of two damage scenarios using a 10-story cantilever-type building model. Measurement noise was also considered in the simulation. We compared the sensitivity of the proposed method to localize damage to that of two conventional modal-flexibility-based damage-detection methods, i.e., uniform load surface (ULS) and ULS curvature. The proposed method was able to localize damage in both damage scenarios for cantilever structures, but the conventional methods could not.

  9. Genotoxic thresholds, DNA repair, and susceptibility in human populations

    International Nuclear Information System (INIS)

    Jenkins, Gareth J.S.; Zair, Zoulikha; Johnson, George E.; Doak, Shareen H.

    2010-01-01

    It has been long assumed that DNA damage is induced in a linear manner with respect to the dose of a direct acting genotoxin. Thus, it is implied that direct acting genotoxic agents induce DNA damage at even the lowest of concentrations and that no 'safe' dose range exists. The linear (non-threshold) paradigm has led to the one-hit model being developed. This 'one hit' scenario can be interpreted such that a single DNA damaging event in a cell has the capability to induce a single point mutation in that cell which could (if positioned in a key growth controlling gene) lead to increased proliferation, leading ultimately to the formation of a tumour. There are many groups (including our own) who, for a decade or more, have argued, that low dose exposures to direct acting genotoxins may be tolerated by cells through homeostatic mechanisms such as DNA repair. This argument stems from the existence of evolutionary adaptive mechanisms that allow organisms to adapt to low levels of exogenous sources of genotoxins. We have been particularly interested in the genotoxic effects of known mutagens at low dose exposures in human cells and have identified for the first time, in vitro genotoxic thresholds for several mutagenic alkylating agents (Doak et al., 2007). Our working hypothesis is that DNA repair is primarily responsible for these thresholded effects at low doses by removing low levels of DNA damage but becoming saturated at higher doses. We are currently assessing the roles of base excision repair (BER) and methylguanine-DNA methyltransferase (MGMT) for roles in the identified thresholds (Doak et al., 2008). This research area is currently important as it assesses whether 'safe' exposure levels to mutagenic chemicals can exist and allows risk assessment using appropriate safety factors to define such exposure levels. Given human variation, the mechanistic basis for genotoxic thresholds (e.g. DNA repair) has to be well defined in order that susceptible individuals are

  10. Precipitation thresholds for triggering floods in Corgo hydrographic basin (Northern Portugal)

    Science.gov (United States)

    Santos, Monica; Fragoso, Marcelo

    2016-04-01

    The precipitation is a major cause of natural hazards and is therefore related to the flood events (Borga et al., 2011; Gaál et al., 2014; Wilhelmi & Morss, 2013). The severity of a precipitation event and their potential damage is dependent on the total amount of rain but also on the intensity and duration event (Gaál et al., 2014). In this work, it was established thresholds based on critical combinations: amount / duration of flood events with daily rainfall data for Corgo hydrographic basin, in northern Portugal. In Corgo basin are recorded 31 floods events between 1865 and 2011 (Santos et al., 2015; Zêzere et al., 2014). We determined the minimum, maximum and pre-warning thresholds that define the boundaries so that an event may occur. Additionally, we applied these thresholds to different flood events occurred in the past in the study basin. The results show that the ratio between the flood events and precipitation events that occur above the minimum threshold has relatively low probability of a flood happen. These results may be related to the reduced number of floods events (only those that caused damage reported by the media and produced some type of damage). The maximum threshold is not useful for floods forecasting, since the majority of true positives are below this limit. The retrospective analysis of the thresholds defined suggests that the minimum and pre warning thresholds are well adjusted. The application of rainfall thresholds contribute to minimize possible situations of pre-crisis or immediate crisis, reducing the consequences and the resources involved in emergency response of flood events. References Borga, M., Anagnostou, E. N., Blöschl, G., & Creutin, J. D. (2011). Flash flood forecasting, warning and risk management: the HYDRATE project. Environmental Science & Policy, 14(7), 834-844. doi: 10.1016/j.envsci.2011.05.017 Gaál, L., Molnar, P., & Szolgay, J. (2014). Selection of intense rainfall events based on intensity thresholds and

  11. Laser-induced damage investigation at 1064 nmin KTiOPO4 crystals and its analogy with RbTiOPO4

    International Nuclear Information System (INIS)

    Hildenbrand, A.; Wagner, F. R.; Akhouayri, H.; Natoli, J.-Y.; Commandre, M.; Theodore, F.; Albrecht, H.

    2009-01-01

    Bulk laser-induced damage at 1064 nm has been investigated in KTiOPO4 (KTP) and RbTiOPO4 (RTP) crystals with a nanosecond pulsed Nd:YAG laser. Both crystals belong to the same family. Throughout this study, their comparison shows a very similar laser-damage behavior. The evolution of the damage resistance under a high number of shots per site (10,000 shots) reveals a fatigue effect of KTP and RTP crystals. In addition, S-on-1 damage probability curves have been measured in both crystals for all combinations of polarization and propagation direction aligned with the principal axes of the crystals. The results show an influence of the polarization on the laser-induced damage threshold (LIDT), with a significantly higher threshold along the z axis, whereas no effect of the propagation direction has been observed. This LIDT anisotropy is discussed with regard to the crystallographic structure.

  12. Radiogenic damage to the sense of taste

    International Nuclear Information System (INIS)

    Schulz-Freywald, G.

    1975-01-01

    In order to determine radiogenic impairment of taste and the natural laws it obeys, gustometric investigations were carried out on 11 patients under radiation treatment. From the investigations it could be seen that the first measurable impairment is present after about 2,000 rad and the climax of the sensory radiation injury occurs after 4,000 rad. The individual taste qualities are damaged in the sequence bitter, sweet, salty and sour. Then the taste surprisingly improves somewhat although irradiation continues. Our observation that the interval between sensation threshold and recognition threshold during radiotherapy grows indicating an apparently stronger damage to the recognition threshold and only later goes back to the standard, is also new and has so far no explanation. It was seen in all posttherapeutical taste tests that the taste function was only fully normalized with a few patients, while in most cases a more or less large function defect remained. This result contradicts the general opinion that there is a complete restitution at the latest 3 months after terminating the irradiation. The present result is fully confirmed by the post-investigation of 55 patients whose irradiation went back up to 13 years. A significant, remaining reduction of the average taste function can also be found here. As the extent of the remaining taste impairment is measurable but very small, it is hardly ever noticed by the patients. Similar to in the course investigations, one could see here, too, that the sensation thresholds on the long run are less damaged than the recognition thresholds. (orig./MG) [de

  13. Thresholds for Coral Bleaching: Are Synergistic Factors and Shifting Thresholds Changing the Landscape for Management? (Invited)

    Science.gov (United States)

    Eakin, C.; Donner, S. D.; Logan, C. A.; Gledhill, D. K.; Liu, G.; Heron, S. F.; Christensen, T.; Rauenzahn, J.; Morgan, J.; Parker, B. A.; Hoegh-Guldberg, O.; Skirving, W. J.; Strong, A. E.

    2010-12-01

    As carbon dioxide rises in the atmosphere, climate change and ocean acidification are modifying important physical and chemical parameters in the oceans with resulting impacts on coral reef ecosystems. Rising CO2 is warming the world’s oceans and causing corals to bleach, with both alarming frequency and severity. The frequent return of stressful temperatures has already resulted in major damage to many of the world’s coral reefs and is expected to continue in the foreseeable future. Warmer oceans also have contributed to a rise in coral infectious diseases. Both bleaching and infectious disease can result in coral mortality and threaten one of the most diverse ecosystems on Earth and the important ecosystem services they provide. Additionally, ocean acidification from rising CO2 is reducing the availability of carbonate ions needed by corals to build their skeletons and perhaps depressing the threshold for bleaching. While thresholds vary among species and locations, it is clear that corals around the world are already experiencing anomalous temperatures that are too high, too often, and that warming is exceeding the rate at which corals can adapt. This is despite a complex adaptive capacity that involves both the coral host and the zooxanthellae, including changes in the relative abundance of the latter in their coral hosts. The safe upper limit for atmospheric CO2 is probably somewhere below 350ppm, a level we passed decades ago, and for temperature is a sustained global temperature increase of less than 1.5°C above pre-industrial levels. How much can corals acclimate and/or adapt to the unprecedented fast changing environmental conditions? Any change in the threshold for coral bleaching as the result of acclimation and/or adaption may help corals to survive in the future but adaptation to one stress may be maladaptive to another. There also is evidence that ocean acidification and nutrient enrichment modify this threshold. What do shifting thresholds mean

  14. A threshold-voltage model for small-scaled GaAs nMOSFET with stacked high-k gate dielectric

    International Nuclear Information System (INIS)

    Liu Chaowen; Xu Jingping; Liu Lu; Lu Hanhan; Huang Yuan

    2016-01-01

    A threshold-voltage model for a stacked high-k gate dielectric GaAs MOSFET is established by solving a two-dimensional Poisson's equation in channel and considering the short-channel, DIBL and quantum effects. The simulated results are in good agreement with the Silvaco TCAD data, confirming the correctness and validity of the model. Using the model, impacts of structural and physical parameters of the stack high-k gate dielectric on the threshold-voltage shift and the temperature characteristics of the threshold voltage are investigated. The results show that the stacked gate dielectric structure can effectively suppress the fringing-field and DIBL effects and improve the threshold and temperature characteristics, and on the other hand, the influence of temperature on the threshold voltage is overestimated if the quantum effect is ignored. (paper)

  15. Evaluating the Thermal Damage Resistance of Reduced Graphene Oxide/Carbon Nanotube Hybrid Coatings

    Science.gov (United States)

    David, Lamuel; Feldman, Ari; Mansfield, Elisabeth; Lehman, John; Singh, Gurpreet; National Institute of Standards and Technology Collaboration

    2014-03-01

    Carbon nanotubes and graphene are known to exhibit some exceptional thermal (K ~ 2000 to 4400 W.m-1K-1 at 300K) and optical properties. Here, we demonstrate preparation and testing of multiwalled carbon nanotubes and chemically modified graphene-composite spray coatings for use on thermal detectors for high-power lasers. The synthesized nanocomposite material was tested by preparing spray coatings on aluminum test coupons used as a representation of the thermal detector's surface. These coatings were then exposed to increasing laser powers and extended exposure times to quantify their damage threshold and optical absorbance. The graphene/carbon nanotube (prepared at varying mass% of graphene in CNTs) coatings demonstrated significantly higher damage threshold values at 2.5 kW laser power (10.6 μm wavelength) than carbon paint or MWCNTs alone. Electron microscopy and Raman spectroscopy of irradiated specimens showed that the composite coating endured high laser-power densities (up to 2 kW.cm-2) without significant visual damage. This research is based on work supported by the National Science Foundation (Chemical, Bioengineering, Environmental, and Transport Systems Division), under grant no. 1335862 to G. Singh.

  16. Rainfall thresholds for the triggering of landslides in Slovenia

    Science.gov (United States)

    Peternel, Tina; Jemec Auflič, Mateja; Rosi, Ascanio; Segoni, Samuele; Komac, Marko; Casagli, Nicola

    2017-04-01

    Both at the worldwide level and in Slovenia, precipitation and related phenomena represent one of the most important triggering factors for the occurrence of slope mass movements. In the past decade, extreme rainfall events with a very high amount of precipitation occurs in a relatively short rainfall period have become increasingly important and more frequent, that causing numerous undesirable consequences. Intense rainstorms cause flash floods and mostly trigger shallow landslides and soil slips. On the other hand, the damage of long lasting rainstorms depends on the region's adaptation and its capacity to store or infiltrate excessive water from the rain. The amount and, consequently, the intensity of daily precipitation that can cause floods in the eastern part of Slovenia is a rather common event for the north-western part of the country. Likewise, the effect of rainfall is very dependent on the prior soil moisture, periods of full soil saturation and the creation of drifts in groundwater levels due to the slow melting of snow, growing period, etc. Landslides could be identified and to some extent also prevent with better knowledge of the relation between landslides and rainfall. In this paper the definition of rainfall thresholds for rainfall-induced landslides in Slovenia is presented. The thresholds have been calculated by collecting approximately 900 landslide data and the relative rainfall amounts, which have been collected from 41 rain gauges all over the country. The thresholds have been defined by the (1) use of an existing procedure, characterized by a high degree of objectiveness and (2) software that was developed for a test site with very different geological and climatic characteristics (Tuscany, central Italy). Firstly, a single national threshold has been defined, later the country was divided into four zones, on the basis of major the river basins and a single threshold has been calculated for each of them. Validation of the calculated

  17. A threshold-voltage model for small-scaled GaAs nMOSFET with stacked high-k gate dielectric

    Science.gov (United States)

    Chaowen, Liu; Jingping, Xu; Lu, Liu; Hanhan, Lu; Yuan, Huang

    2016-02-01

    A threshold-voltage model for a stacked high-k gate dielectric GaAs MOSFET is established by solving a two-dimensional Poisson's equation in channel and considering the short-channel, DIBL and quantum effects. The simulated results are in good agreement with the Silvaco TCAD data, confirming the correctness and validity of the model. Using the model, impacts of structural and physical parameters of the stack high-k gate dielectric on the threshold-voltage shift and the temperature characteristics of the threshold voltage are investigated. The results show that the stacked gate dielectric structure can effectively suppress the fringing-field and DIBL effects and improve the threshold and temperature characteristics, and on the other hand, the influence of temperature on the threshold voltage is overestimated if the quantum effect is ignored. Project supported by the National Natural Science Foundation of China (No. 61176100).

  18. Laser-induced damage study of polymer PMMA

    International Nuclear Information System (INIS)

    Mansour, N.

    2001-01-01

    This article presents the results of bulk laser-induced damage measurements in polymer PMMA at 532 nm and 1064 nm for nanosecond laser pulses. The damage thresholds were measured for focused spot sizes ranging over two orders of magnitude. In this work, self-focusing effects were verified to be absent by measurements of breakdown thresholds using both linearly and circularly polarized light. At both 1064 nm and 532 nm, the dependence of the breakdown field, E B , on the spot size, ω, was empirically determined to be E B = C/√ω, where C depends on the wavelength. The extracted value for C(λ) at 1064 nm is larger by a factor of 5 than at 532 nm. Possible reasons for this strong dispersion and mechanism for laser-induced damage in polymer materials will be discussed

  19. Growth of Laser Initiated Damage in Fused Silica at 527 nm

    International Nuclear Information System (INIS)

    Norton, M A; Donohue, E E; Hollingsworth, W G; McElroy, J N; Hackel, R P

    2003-01-01

    The effective lifetime of optics is limited by both laser-induced damage and the subsequent growth of laser initiated damage sites. We have measured the growth rate of laser-induced damage in fused silica in both air and vacuum at 527 nm. For damage on the exit surface, the data shows exponential growth in the lateral size of the damage site with shot number. The exponential growth coefficient depends linearly on the laser fluence. The behavior at the fluence threshold for growth is contrasted to that observed at 351 nm. The growth rate was not significantly affected by either the wavelength of the initiating fluence or the presence of 10 torr of air as compared to vacuum. When the damage is located on the input surface, it has both a higher threshold for growth and does not grow exponentially

  20. Vendor-based laser damage metrology equipment supporting the National Ignition Facility

    International Nuclear Information System (INIS)

    Campbell, J. H; Jennings, R. T.; Kimmons, J. F.; Kozlowski, M. R.; Mouser, R. P.; Schwatz, S.; Stolz, C. J.; Weinzapfel, C. L.

    1998-01-01

    A sizable laser damage metrology effort is required as part of optics production and installation for the 192 beam National Ignition Facility (NIF) laser. The large quantities, high damage thresholds, and large apertures of polished and coated optics necessitates vendor-based metrology equipment to assure component quality during production. This equipment must be optimized to provide the required information as rapidly as possible with limited operator experience. The damage metrology tools include: (1) platinum inclusion damage test systems for laser amplifier slabs, (2) laser conditioning stations for mirrors and polarizers, and (3) mapping and damage testing stations for UV transmissive optics. Each system includes a commercial Nd:YAG laser, a translation stage for the optics, and diagnostics to evaluate damage. The scanning parameters, optical layout, and diagnostics vary with the test fluences required and the damage morphologies expected. This paper describes the technical objectives and milestones involved in fulfilling these metrology requirements

  1. Modeling of beam-induced damage of the LHC tertiary collimators

    Directory of Open Access Journals (Sweden)

    E. Quaranta

    2017-09-01

    Full Text Available Modern hadron machines with high beam intensity may suffer from material damage in the case of large beam losses and even beam-intercepting devices, such as collimators, can be harmed. A systematic method to evaluate thresholds of damage owing to the impact of high energy particles is therefore crucial for safe operation and for predicting possible limitations in the overall machine performance. For this, a three-step simulation approach is presented, based on tracking simulations followed by calculations of energy deposited in the impacted material and hydrodynamic simulations to predict the thermomechanical effect of the impact. This approach is applied to metallic collimators at the CERN Large Hadron Collider (LHC, which in standard operation intercept halo protons, but risk to be damaged in the case of extraction kicker malfunction. In particular, tertiary collimators protect the aperture bottlenecks, their settings constrain the reach in β^{*} and hence the achievable luminosity at the LHC experiments. Our calculated damage levels provide a very important input on how close to the beam these collimators can be operated without risk of damage. The results of this approach have been used already to push further the performance of the present machine. The risk of damage is even higher in the upgraded high-luminosity LHC with higher beam intensity, for which we quantify existing margins before equipment damage for the proposed baseline settings.

  2. Modeling of beam-induced damage of the LHC tertiary collimators

    Science.gov (United States)

    Quaranta, E.; Bertarelli, A.; Bruce, R.; Carra, F.; Cerutti, F.; Lechner, A.; Redaelli, S.; Skordis, E.; Gradassi, P.

    2017-09-01

    Modern hadron machines with high beam intensity may suffer from material damage in the case of large beam losses and even beam-intercepting devices, such as collimators, can be harmed. A systematic method to evaluate thresholds of damage owing to the impact of high energy particles is therefore crucial for safe operation and for predicting possible limitations in the overall machine performance. For this, a three-step simulation approach is presented, based on tracking simulations followed by calculations of energy deposited in the impacted material and hydrodynamic simulations to predict the thermomechanical effect of the impact. This approach is applied to metallic collimators at the CERN Large Hadron Collider (LHC), which in standard operation intercept halo protons, but risk to be damaged in the case of extraction kicker malfunction. In particular, tertiary collimators protect the aperture bottlenecks, their settings constrain the reach in β* and hence the achievable luminosity at the LHC experiments. Our calculated damage levels provide a very important input on how close to the beam these collimators can be operated without risk of damage. The results of this approach have been used already to push further the performance of the present machine. The risk of damage is even higher in the upgraded high-luminosity LHC with higher beam intensity, for which we quantify existing margins before equipment damage for the proposed baseline settings.

  3. High damage tolerance of electrochemically lithiated silicon

    Science.gov (United States)

    Wang, Xueju; Fan, Feifei; Wang, Jiangwei; Wang, Haoran; Tao, Siyu; Yang, Avery; Liu, Yang; Beng Chew, Huck; Mao, Scott X.; Zhu, Ting; Xia, Shuman

    2015-01-01

    Mechanical degradation and resultant capacity fade in high-capacity electrode materials critically hinder their use in high-performance rechargeable batteries. Despite tremendous efforts devoted to the study of the electro–chemo–mechanical behaviours of high-capacity electrode materials, their fracture properties and mechanisms remain largely unknown. Here we report a nanomechanical study on the damage tolerance of electrochemically lithiated silicon. Our in situ transmission electron microscopy experiments reveal a striking contrast of brittle fracture in pristine silicon versus ductile tensile deformation in fully lithiated silicon. Quantitative fracture toughness measurements by nanoindentation show a rapid brittle-to-ductile transition of fracture as the lithium-to-silicon molar ratio is increased to above 1.5. Molecular dynamics simulations elucidate the mechanistic underpinnings of the brittle-to-ductile transition governed by atomic bonding and lithiation-induced toughening. Our results reveal the high damage tolerance in amorphous lithium-rich silicon alloys and have important implications for the development of durable rechargeable batteries. PMID:26400671

  4. Cranial nerve threshold for thermal injury induced by MRI-guided high-intensity focused ultrasound (MRgHIFU): preliminary results on an optic nerve model.

    Science.gov (United States)

    Harnof, Sagi; Zibly, Zion; Cohen, Zvi; Shaw, Andrew; Schlaff, Cody; Kassel, Neal F

    2013-04-01

    Future clinical applications of magnetic resonance imaging-guided high-intensity focused ultrasound (MRgHIFU) are moving toward the management of different intracranial pathologies. We sought to validate the production, safety, and efficacy of thermal injury to cranial nerves generated by MRgHIFU. In this study, five female domestic pigs underwent a standard bifrontal craniectomy under general anesthesia. Treatment was then given using an MRgHIFU system to induce hyperthermic ablative sonication (6 to 10 s; 50 to 2000 J.) Histological analyses were done to confirm nerve damage; temperature measured on the optic nerve was approximately 53.4°C (range: 39°C to 70°C.) Histology demonstrated a clear definition between a necrotic, transitional zone, and normal tissue. MRgHIFU induces targeted thermal injury to nervous tissue within a specific threshold of 50°C to 60°C with the tissue near the sonication center yielding the greatest effect; adjacent tissue showed minimal changes. Additional studies utilizing this technology are required to further establish accurate threshold parameters for optic nerve thermo-ablation.

  5. Laser-Induced Damage with Femtosecond Pulses

    Science.gov (United States)

    Kafka, Kyle R. P.

    The strong electric fields of focused femtosecond laser pulses lead to non-equilibrium dynamics in materials, which, beyond a threshold intensity, causes laser-induced damage (LID). Such a strongly non-linear and non-perturbative process renders important LID observables like fluence and intensity thresholds and damage morphology (crater) extremely difficult to predict quantitatively. However, femtosecond LID carries a high degree of precision, which has been exploited in various micro/nano-machining and surface engineering applications, such as human eye surgery and super-hydrophobic surfaces. This dissertation presents an array of experimental studies which have measured the damage behavior of various materials under femtosecond irradiation. Precision experiments were performed to produce extreme spatio-temporal confinement of the femtosecond laser-solid damage interaction on monocrystalline Cu, which made possible the first successful direct-benchmarking of LID simulation with realistic damage craters. A technique was developed to produce laser-induced periodic surface structures (LIPSS) in a single pulse (typically a multi-pulse phenomenon), and was used to perform a pump-probe study which revealed asynchronous LIPSS formation on copper. Combined with 1-D calculations, this new experimental result suggests more drastic electron heating than expected. Few-cycle pulses were used to study the LID performance and morphology of commercial ultra-broadband optics, which had not been systematically studied before. With extensive surface analysis, various morphologies were observed, including LIPSS, swelling (blisters), simple craters, and even ring-shaped structures, which varied depending on the coating design, number of pulses, and air/vacuum test environment. Mechanisms leading to these morphologies are discussed, many of which are ultrafast in nature. The applied damage behavior of multi-layer dielectric mirrors was measured and compared between long pulse (150 ps

  6. Radiation damage in flash memory cells

    International Nuclear Information System (INIS)

    Claeys, C.; Ohyama, H.; Simoen, E.; Nakabayashi, M.; Kobayashi, K.

    2002-01-01

    Results are presented of a study on the effects of total ionization dose and displacement damage, induced by high-energy electrons, protons and alphas, on the performance degradation of flash memory cells integrated in a microcomputer. A conventional stacked-gate n-channel flash memory cell using a 0.8 μm n-polysilicon gate technology is employed. Irradiations by 1-MeV electrons and 20-MeV protons and alpha particles were done at room temperature. The impact of the fluence on the input characteristics, threshold voltage shift and drain and gate leakage was investigated. The threshold voltage change for proton and alpha irradiations is about three orders of magnitude larger than that for electrons. The performance degradation is mainly caused by the total ionization dose (TID) damage in the tunnel oxide and in the interpoly dielectric layer and by the creation of interface traps at the Si-SiO 2 interface. The impact of the irradiation temperature on the device degradation was studied for electrons and gammas, pointing out that irradiation at room temperature is mostly the worst case. Finally, attention is given to the impact of isochronal and isothermal annealing on the recovery of the degradation introduced after room temperature proton and electron irradiation

  7. Damage Threshold of In Vivo Rabbit Cornea by 2 micron Laser Irradiation

    National Research Council Canada - National Science Library

    Chen, Bo; Oliver, Jeffery; Dutta, Soumak; Rylander, III, Grady H; Thomsen, Sharon L; Welch, Ashley J

    2007-01-01

    To support refinement of the Maximum Permissible Exposure (MPE) safety limits, a series of experiments were conducted in vivo on Dutch Belted rabbit corneas to determine corneal minimum visible lesion thresholds...

  8. Damage resistance of AR-coated germanium surfaces for nanosecond CO2 laser pulses

    International Nuclear Information System (INIS)

    Newnam, B.E.; Gill, D.H.

    1977-01-01

    An evaluation of the state-of-the-art of AR coatings on gallium-doped germanium, used as a saturable absorber at 10.6 μm, has been conducted. Both 1-on-1 and N-on-1 laser damage thresholds were measured with 1.2 ns pulses on bare and coated surfaces. Only front surface damage was observed. With few exceptions, the thresholds for coated surfaces were centered at 0.49 +- 0.3 J/cm 2 . Bare Ge had a threshold ranging from 0.65 to 0.70 J/cm 2 . No significant differences due to substrate polish, crystallinity or doping level were evident and multiple-shot conditioning resulted in the same threshold as for single shot tests. From an analysis of standing-wave electric fields, damage for AR-coated Ge appeared to be limited by the surface properties of Ge. Measurements at both 1.2 and 70 ns indicated that the threshold (J/cm 2 ) of both coated and uncoated Ge increases as the square root of the pulse-width

  9. Measurement of radiation damage on an optical reflector

    International Nuclear Information System (INIS)

    Peng, K.C.; Sahu, S.K.; Huang, H.C.; Ueno, K.; Chang, Y.H.; Wang, C.H.; Hou, W.S.

    1997-01-01

    We measured the radiation damage on an optical white fluorocarbon reflector called Goretex, which is to be used for aerogel threshold counters and crystal calorimeters of the BELLE detector of the KEK B-factory. Reflectance of the Goretex surface was monitored to see any effect of the radiation damage. Maximum equivalent dose was 8.6 Mrad. No radiation damage is observed within measurement errors. (orig.)

  10. Hydrometeorological threshold conditions for debris flow initiation in Norway

    Directory of Open Access Journals (Sweden)

    N. K. Meyer

    2012-10-01

    Full Text Available Debris flows, triggered by extreme precipitation events and rapid snow melt, cause considerable damage to the Norwegian infrastructure every year. To define intensity-duration (ID thresholds for debris flow initiation critical water supply conditions arising from intensive rainfall or snow melt were assessed on the basis of daily hydro-meteorological information for 502 documented debris flow events. Two threshold types were computed: one based on absolute ID relationships and one using ID relationships normalized by the local precipitation day normal (PDN. For each threshold type, minimum, medium and maximum threshold values were defined by fitting power law curves along the 10th, 50th and 90th percentiles of the data population. Depending on the duration of the event, the absolute threshold intensities needed for debris flow initiation vary between 15 and 107 mm day−1. Since the PDN changes locally, the normalized thresholds show spatial variations. Depending on location, duration and threshold level, the normalized threshold intensities vary between 6 and 250 mm day−1. The thresholds obtained were used for a frequency analysis of over-threshold events giving an estimation of the exceedance probability and thus potential for debris flow events in different parts of Norway. The absolute thresholds are most often exceeded along the west coast, while the normalized thresholds are most frequently exceeded on the west-facing slopes of the Norwegian mountain ranges. The minimum thresholds derived in this study are in the range of other thresholds obtained for regions with a climate comparable to Norway. Statistics reveal that the normalized threshold is more reliable than the absolute threshold as the former shows no spatial clustering of debris flows related to water supply events captured by the threshold.

  11. Radiation damage

    CERN Document Server

    Heijne, Erik H M; CERN. Geneva

    1998-01-01

    a) Radiation damage in organic materials. This series of lectures will give an overview of radiation effects on materials and components frequently used in accelerator engineering and experiments. Basic degradation phenomena will be presented for organic materials with comprehensive damage threshold doses for commonly used rubbers, thermoplastics, thermosets and composite materials. Some indications will be given for glass, scintillators and optical fibres. b) Radiation effects in semiconductor materials and devices. The major part of the time will be devoted to treat radiation effects in semiconductor sensors and the associated electronics, in particular displacement damage, interface and single event phenomena. Evaluation methods and practical aspects will be shown. Strategies will be developed for the survival of the materials under the expected environmental conditions of the LHC machine and detectors. I will describe profound revolution in our understanding of black holes and their relation to quantum me...

  12. Short-pulse CO2-laser damage studies of NaCl and KCl windows

    International Nuclear Information System (INIS)

    Newnam, B.E.; Nowak, A.V.; Gill, D.H.

    1979-01-01

    The damage resistance of bare surfaces and the bulk interior of NaCl and KCl windows was measured with a short-pulse CO 2 laser at 10.6 μm. Parametric studies with 1.7-ns pulses indicated that adsorbed water was probably the limiting agent on surface thresholds in agreement with previous studies at long pulsewidths. Rear-surface thresholds up to 7 J/cm 2 were measured for polished NaCl windows, whereas KCl surfaces damaged at approximately 60% of this level. The breakdown electric-field thresholds of exit surfaces were only 50% of the value of the bulk materials. The pulsewidth dependence of surface damage from 1 to 65 ns, in terms of incident laser fluence, increased as t/sup 1/3/

  13. Pulsed total dose damage effect experimental study on EPROM

    International Nuclear Information System (INIS)

    Luo Yinhong; Yao Zhibin; Zhang Fengqi; Guo Hongxia; Zhang Keying; Wang Yuanming; He Baoping

    2011-01-01

    Nowadays, memory radiation effect study mainly focus on functionality measurement. Measurable parameters is few in china. According to the present situation, threshold voltage testing method was presented on floating gate EPROM memory. Experimental study of pulsed total dose effect on EPROM threshold voltage was carried out. Damage mechanism was analysed The experiment results showed that memory cell threshold voltage negative shift was caused by pulsed total dose, memory cell threshold voltage shift is basically coincident under steady bias supply and no bias supply. (authors)

  14. Multiscale Modeling of Dewetting Damage in Highly Filled Particulate Composites

    Science.gov (United States)

    Geubelle, P. H.; Inglis, H. M.; Kramer, J. D.; Patel, J. J.; Kumar, N. C.; Tan, H.

    2008-02-01

    Particle debonding or dewetting constitutes one of the key damage processes in highly filled particulate composites such as solid propellant and other energetic materials. To analyze this failure process, we have developed a multiscale finite element framework that combines, at the microscale, a nonlinear description of the binder response with a cohesive model of the damage process taking place in a representative periodic unit cell (PUC). To relate micro-scale damage to the macroscopic constitutive response of the material, we employ the mathematical theory of homogenization (MTH). After a description of the numerical scheme, we present the results of the damage response of a highly filled particulate composite subjected to a uniaxial macroscopic strain, and show the direct correlation between the complex damage processes taking place in the PUC and the nonlinear macroscopic constitutive response. We also present a detailed study of the PUC size and a comparison between the finite element MTH-based study and a micromechanics model of the dewetting process.

  15. Measurement and interpretation of threshold stress intensity factors for steels in high-pressure hydrogen gas.

    Energy Technology Data Exchange (ETDEWEB)

    Dadfarnia, Mohsen (University of Illinois at Urbana-Champaign, Urbana, IL); Nibur, Kevin A.; San Marchi, Christopher W.; Sofronis, Petros (University of Illinois at Urbana-Champaign, Urbana, IL); Somerday, Brian P.; Foulk, James W., III; Hayden, Gary A. (CP Industries, McKeesport, PA)

    2010-07-01

    Threshold stress intensity factors were measured in high-pressure hydrogen gas for a variety of low alloy ferritic steels using both constant crack opening displacement and rising crack opening displacement procedures. The sustained load cracking procedures are generally consistent with those in ASME Article KD-10 of Section VIII Division 3 of the Boiler and Pressure Vessel Code, which was recently published to guide design of high-pressure hydrogen vessels. Three definitions of threshold were established for the two test methods: K{sub THi}* is the maximum applied stress intensity factor for which no crack extension was observed under constant displacement; K{sub THa} is the stress intensity factor at the arrest position for a crack that extended under constant displacement; and K{sub JH} is the stress intensity factor at the onset of crack extension under rising displacement. The apparent crack initiation threshold under constant displacement, K{sub THi}*, and the crack arrest threshold, K{sub THa}, were both found to be non-conservative due to the hydrogen exposure and crack-tip deformation histories associated with typical procedures for sustained-load cracking tests under constant displacement. In contrast, K{sub JH}, which is measured under concurrent rising displacement and hydrogen gas exposure, provides a more conservative hydrogen-assisted fracture threshold that is relevant to structural components in which sub-critical crack extension is driven by internal hydrogen gas pressure.

  16. 75 FR 75911 - Adjustment of Monetary Threshold for Reporting Rail Equipment Accidents/Incidents for Calendar...

    Science.gov (United States)

    2010-12-07

    ..., Notice No. 3] RIN 2130-ZA04 Adjustment of Monetary Threshold for Reporting Rail Equipment Accidents... (DOT). ACTION: Final rule. SUMMARY: This rule increases the rail equipment accident/incident reporting threshold from $9,200 to $9,400 for certain railroad accidents/incidents involving property damage that...

  17. Follow-up of hearing thresholds among forge hammering workers

    Energy Technology Data Exchange (ETDEWEB)

    Kamal, A.A.; Mikael, R.A.; Faris, R. (Ain Shams Univ., Abbasia, Cairo (Egypt))

    1989-01-01

    Hearing threshold was reexamined in a group of forge hammering workers investigated 8 years ago with consideration of the age effect and of auditory symptoms. Workers were exposed to impact noise that ranged from 112 to 139 dB(A)--at an irregular rate of 20 to 50 drop/minute--and a continuous background noise that ranged from 90 to 94 dB(A). Similar to what was observed 8 years ago, the present permanent threshold shift (PTS) showed a maximum notch at the frequency of 6 kHz and considerable elevations at the frequencies of 0.25-1 kHz. The age-corrected PTS and the postexposure hearing threshold were significantly higher than the corresponding previous values at the frequencies 0.25, 0.5, 1, and 8 kHz only. The rise was more evident at the low than at the high frequencies. Temporary threshold shift (TTS) values were significantly less than those 8 years ago. Contrary to the previous TTS, the present TTS were higher at low than at high frequencies. Although progression of PTS at the frequencies 0.25 and 0.5 kHz was continuous throughout the observed durations of exposure, progression at higher frequencies occurred essentially in the first 10 to 15 years of exposure. Thereafter, it followed a much slower rate. Tinnitus was significantly associated with difficulty in hearing the human voice and with elevation of PTS at all the tested frequencies, while acoustic after-image was significantly associated with increment of PTS at the frequencies 0.25-2 kHz. No relation between PTS and smoking was found. PTS at low frequencies may provide an indication of progression of hearing damage when the sensitivity at 6 and 4 kHz diminishes after prolonged years of exposure. Tinnitus and acoustic after-image are related to the auditory effect of forge hammering noise.

  18. Threshold voltage control in TmSiO/HfO2 high-k/metal gate MOSFETs

    Science.gov (United States)

    Dentoni Litta, E.; Hellström, P.-E.; Östling, M.

    2015-06-01

    High-k interfacial layers have been proposed as a way to extend the scalability of Hf-based high-k/metal gate CMOS technology, which is currently limited by strong degradations in threshold voltage control, channel mobility and device reliability when the chemical oxide (SiOx) interfacial layer is scaled below 0.4 nm. We have previously demonstrated that thulium silicate (TmSiO) is a promising candidate as a high-k interfacial layer, providing competitive advantages in terms of EOT scalability and channel mobility. In this work, the effect of the TmSiO interfacial layer on threshold voltage control is evaluated, showing that the TmSiO/HfO2 dielectric stack is compatible with threshold voltage control techniques commonly used with SiOx/HfO2 stacks. Specifically, we show that the flatband voltage can be set in the range -1 V to +0.5 V by the choice of gate metal and that the effective workfunction of the stack is properly controlled by the metal workfunction in a gate-last process flow. Compatibility with a gate-first approach is also demonstrated, showing that integration of La2O3 and Al2O3 capping layers can induce a flatband voltage shift of at least 150 mV. Finally, the effect of the annealing conditions on flatband voltage is investigated, finding that the duration of the final forming gas anneal can be used as a further process knob to tune the threshold voltage. The evaluation performed on MOS capacitors is confirmed by the fabrication of TmSiO/HfO2/TiN MOSFETs achieving near-symmetric threshold voltages at sub-nm EOT.

  19. Precipitation Thresholds for Triggering Floods in the Corgo Basin, Portugal

    Directory of Open Access Journals (Sweden)

    Mónica Santos

    2016-08-01

    Full Text Available Thresholds based on critical combinations of amount/duration of precipitation and flood events were estimated for the Corgo hydrographic basin, in northern Portugal. Thirty-one flood events in the Corgo basin were identified between 1865 and 2011 from a database of hydrometeorological disasters in Portugal. The minimum, maximum, and pre-warning thresholds that define the boundaries for flood occurrence were determined. The results show that the ratio between the total number of floods and precipitation events exceeding the minimum threshold denotes a relatively low probability of successful forecasting. This result may be due to the reduced number of flooding events in the floods database, which only include floods that caused damage as reported by the media. The estimated maximum threshold is not adequate for use in floods, since the majority of true positives are below this limit. However, and more interestingly, the retrospective verification of the estimated thresholds suggests that the minimum and pre-warning thresholds are well adjusted. Therefore, the application of these precipitation thresholds may contribute to minimize possible situations of pre-crisis or immediate crisis by reducing the flood consequences and the resources involved in emergency response to flood events.

  20. An assessment of threshold shifts in nonprofessional pop/rock musicians using conventional and extended high-frequency audiometry.

    Science.gov (United States)

    Schmuziger, Nicolas; Patscheke, Jochen; Probst, Rudolf

    2007-09-01

    The clinical value of extended high-frequency audiometry for the detection of noise-induced hearing loss has not been established conclusively. The purpose of this study was to assess the relative temporary threshold shift (TTS) in two frequency regions (conventional versus extended high frequency). In this exploratory study, pure-tone thresholds from 0.5 to 14 kHz were measured in both ears of 16 nonprofessional pop/rock musicians (mean age, 35 yr; range, 27 to 49 yr), before and after a 90-minute rehearsal session. All had experienced repeated exposures to intense sound levels during at least 5 yr of their musical careers. After the rehearsal, median threshold levels were found to be significantly poorer for frequencies from 0.5 to 8 kHz (Wilcoxon signed rank test, p high-frequency range from 9 to 14 kHz. Decreases in the median threshold values measured before the rehearsal were present across the conventional frequency range, most notably at 6 kHz, but were not observed in the extended high-frequency range. On the basis of these results, extended high-frequency audiometry does not seem advantageous as a means of the early detection of noise-induced hearing loss.

  1. Setting limits: Using air pollution thresholds to protect and restore US ecosystems

    Science.gov (United States)

    Fenn, Mark E.; Lambert, Kathleen F.; Blett, Tamara F.; Burns, Douglas A.; Pardo, Linda H.; Lovett, Gary M.; Haeuber, Richard A.; Evers, David C.; Driscoll, Charles T.; Jeffries, Dean S.

    2011-01-01

    More than four decades of research provide unequivocal evidence that sulfur, nitrogen, and mercury pollution have altered, and will continue to alter, our nation's lands and waters. The emission and deposition of air pollutants harm native plants and animals, degrade water quality, affect forest productivity, and are damaging to human health. Many air quality policies limit emissions at the source but these control measures do not always consider ecosystem impacts. Air pollution thresholds at which ecological effects are observed, such as critical loads, are effective tools for assessing the impacts of air pollution on essential ecosystem services and for informing public policy. U.S. ecosystems can be more effectively protected and restored by using a combination of emissions-based approaches and science-based thresholds of ecosystem damage.

  2. Derivation of critical rainfall thresholds for landslide in Sicily

    Science.gov (United States)

    Caracciolo, Domenico; Arnone, Elisa; Noto, Leonardo V.

    2015-04-01

    Rainfall is the primary trigger of shallow landslides that can cause fatalities, damage to properties and economic losses in many areas of the world. For this reason, determining the rainfall amount/intensity responsible for landslide occurrence is important, and may contribute to mitigate the related risk and save lives. Efforts have been made in different countries to investigate triggering conditions in order to define landslide-triggering rainfall thresholds. The rainfall thresholds are generally described by a functional relationship of power in terms of cumulated or intensity event rainfall-duration, whose parameters are estimated empirically from the analysis of historical rainfall events that triggered landslides. The aim of this paper is the derivation of critical rainfall thresholds for landslide occurrence in Sicily, southern Italy, by focusing particularly on the role of the antecedent wet conditions. The creation of the appropriate landslide-rainfall database likely represents one of main efforts in this type of analysis. For this work, historical landslide events occurred in Sicily from 1919 to 2001 were selected from the archive of the Sistema Informativo sulle Catastrofi Idrogeologiche, developed under the project Aree Vulnerabili Italiane. The corresponding triggering precipitations were screened from the raingauges network in Sicily, maintained by the Osservatorio delle Acque - Agenzia Regionale per i Rifiuti e le Acque. In particular, a detailed analysis was carried out to identify and reconstruct the hourly rainfall events that caused the selected landslides. A bootstrapping statistical technique has been used to determine the uncertainties associated with the threshold parameters. The rainfall thresholds at different exceedance probability levels, from 1% to 10%, were defined in terms of cumulated event rainfall, E, and rainfall duration, D. The role of rainfall prior to the damaging events was taken into account by including in the analysis

  3. Detection of impact damage on thermal protection systems using thin-film piezoelectric sensors for integrated structural health monitoring

    Science.gov (United States)

    Na, Jeong K.; Kuhr, Samuel J.; Jata, Kumar V.

    2008-03-01

    Thermal Protection Systems (TPS) can be subjected to impact damage during flight and/or during ground maintenance and/or repair. AFRL/RXLP is developing a reliable and robust on-board sensing/monitoring capability for next generation thermal protection systems to detect and assess impact damage. This study was focused on two classes of metallic thermal protection tiles to determine threshold for impact damage and develop sensing capability of the impacts. Sensors made of PVDF piezoelectric film were employed and tested to evaluate the detectability of impact signals and assess the onset or threshold of impact damage. Testing was performed over a range of impact energy levels, where the sensors were adhered to the back of the specimens. The PVDF signal levels were analyzed and compared to assess damage, where digital microscopy, visual inspection, and white light interferometry were used for damage verification. Based on the impact test results, an assessment of the impact damage thresholds for each type of metallic TPS system was made.

  4. Micro-damage propagation in ultra-high vacuum seals

    CERN Document Server

    Lutkiewicz, P; Garion, C

    2010-01-01

    The paper addresses a fundamental problem of tightness of ultra-high vacuum systems (UHV) at cryogenic temperatures in the light of continuum damage mechanics (CDM). The problem of indentation of a rigid punch into an elastic-plastic half-space is investigated based on rate independent plasticity with mixed kinematic and isotropic hardening. The micro-damage fields are modeled by using an anisotropic approach with a kinetic law of damage evolution suitable for ductile materials and cryogenic temperatures. The model has been experimentally validated and the results are used to predict the onset of macro-cracking (loss of tightness) and the corresponding load (contact pressure). The algorithm is applied in the design of UHV systems for particle accelerators. (C) 2009 Published by Elsevier Ltd.

  5. Damage resistant optics for a mega-joule solid-state laser

    International Nuclear Information System (INIS)

    Campbell, J.H.; Rainer, F.; Kozlowski, M.; Wolfe, C.R.; Thomas, I.; Milanovich, F.

    1990-01-01

    Research on Inertial Confinement Fusion (ICF) has progressed rapidly in the past several years. As a consequence, LLNL is developing plans to upgrade the current 120 kJ solid state (Nd +3 -phosphate glass) Nova laser to a 1.5 to 2 megajoule system with the goal of achieving fusion ignition. The design of the planned Nova Upgrade is briefly discussed. Because of recent improvements in the damage resistance of optical materials it is now technically and economically feasible to build a megajoule-class solid state laser. Specifically, the damage threshold of Nd +3 -doped phosphate laser glass, multilayer dielectric coatings, and non-linear optical crystals (e.g., KDP) have been dramatically improved. These materials now meet the fluence requirements for a 1.5--2 MJ Nd 3+ -glass laser operating at 1054 and 351 nm and at a pulse length of 3 ns. The recent improvements in damage thresholds are reviewed; threshold data at both 1064 and 355 nm and the measured pulse length scaling are presented. 20 refs., 9 figs., 2 tabs

  6. Use of non-quarter-wave designs to increase the damage resistance of reflectors at 532 and 1064 nanometers

    International Nuclear Information System (INIS)

    Gill, D.H.; Newnam, B.E.; McLeod, J.

    1977-01-01

    The damage resistance of multilayer dielectric laser reflectors has been increased by using non-quarter-wave thicknesses for the top few layers. These designs minimize the standing-wave electric field in the high-index layers, which are generally the weaker layers. Algebraic equations have been derived for optimum film thicknesses and for the resulting peak electric fields. Five sets of reflectors for 532 and 1064 nm were fabricated according to these designs by two vendors using two different material combinations. Each set contained one reflector of standard all-quarter-wave design and three reflectors each with a different number of modified layers. The damage thresholds of the modified designs were found to be higher than the all-quarter-wave designs, in some cases by a factor greater than 2. The damage thresholds have been analyzed and explained in terms of standing-wave electric field patterns

  7. Impact of gain saturation on the mode instability threshold in high-power fiber amplifiers

    DEFF Research Database (Denmark)

    Hansen, Kristian Rymann; Lægsgaard, Jesper

    2014-01-01

    We present a coupled-mode model of transverse mode instability in high-power fiber amplifiers, which takes the effect of gain saturation into account. The model provides simple semi-analytical formulas for the mode instability threshold, which are valid also for highly saturated amplifiers...

  8. Damage performance of TiO2/SiO2 thin film components induced by a long-pulsed laser

    International Nuclear Information System (INIS)

    Wang Bin; Dai Gang; Zhang Hongchao; Ni Xiaowu; Shen Zhonghua; Lu Jian

    2011-01-01

    In order to study the long-pulsed laser induced damage performance of optical thin films, damage experiments of TiO 2 /SiO 2 films irradiated by a laser with 1 ms pulse duration and 1064 nm wavelength are performed. In the experiments, the damage threshold of the thin films is measured. The damages are observed to occur in isolated spots, which enlighten the inducement of the defects and impurities originated in the films. The threshold goes down when the laser spot size decreases. But there exists a minimum threshold, which cannot be further reduced by decreasing the laser spot size. Optical microscopy reveals a cone-shaped cavity in the film substrate. Changes of the damaged sizes in film components with laser fluence are also investigated. The results show that the damage efficiency increases with the laser fluence before the shielding effects start to act.

  9. Thresholding magnetic resonance images of human brain

    Institute of Scientific and Technical Information of China (English)

    Qing-mao HU; Wieslaw L NOWINSKI

    2005-01-01

    In this paper, methods are proposed and validated to determine low and high thresholds to segment out gray matter and white matter for MR images of different pulse sequences of human brain. First, a two-dimensional reference image is determined to represent the intensity characteristics of the original three-dimensional data. Then a region of interest of the reference image is determined where brain tissues are present. The non-supervised fuzzy c-means clustering is employed to determine: the threshold for obtaining head mask, the low threshold for T2-weighted and PD-weighted images, and the high threshold for T1-weighted, SPGR and FLAIR images. Supervised range-constrained thresholding is employed to determine the low threshold for T1-weighted, SPGR and FLAIR images. Thresholding based on pairs of boundary pixels is proposed to determine the high threshold for T2- and PD-weighted images. Quantification against public data sets with various noise and inhomogeneity levels shows that the proposed methods can yield segmentation robust to noise and intensity inhomogeneity. Qualitatively the proposed methods work well with real clinical data.

  10. Temporal scaling law and intrinsic characteristic of laser induced damage on the dielectric coating

    Science.gov (United States)

    Zhou, Li; Jiang, Youen; Wang, Chao; Wei, Hui; Zhang, Peng; Fan, Wei; Li, Xuechun

    2018-01-01

    High power laser is essential for optical manipulation and fabrication. When the laser travels through optics and to the target finally, irreversible damage on the dielectric coating is always accompanied without knowing the law and principle of laser induced damage. Here, an experimental study of laser induced damage threshold (LIDT) Fth of the dielectric coating under different pulse duration t is implemented. We observe that the temporal scaling law of square pulse for high-reflectivity (HR) coating and anti-reflectivity (AR) coating are Fth = 9.53t0.47 and Fth = 6.43t0.28 at 1064 nm, respectively. Moreover, the intrinsic LIDT of HR coating is 62.7 J/cm2 where the coating is just 100% damaged by gradually increasing the fluence densities of a 5ns-duration pulse, which is much higher than the actual LIDT of 18.6 J/cm2. Thus, a more robust and reliable high power laser system will be a reality, even working at very high fluence, if measures are taken to improve the actual LIDT to a considerable level near the intrinsic value.

  11. Monitoring Moisture Damage Propagation in GFRP Composites Using Carbon Nanoparticles

    Directory of Open Access Journals (Sweden)

    Ahmed Al-Sabagh

    2017-03-01

    Full Text Available Glass fiber reinforced polymer (GFRP composites are widely used in infrastructure applications including water structures due to their relatively high durability, high strength to weight ratio, and non-corrosiveness. Here we demonstrate the potential use of carbon nanoparticles dispersed during GFRP composite fabrication to reduce water absorption of GFRP and to enable monitoring of moisture damage propagation in GFRP composites. GFRP coupons incorporating 2.0 wt % carbon nanofibers (CNFs and 2.0 wt % multi-wall carbon nanotubes (MWCNTs were fabricated in order to study the effect of moisture damage on mechanical properties of GFRP. Water absorption tests were carried out by immersing the GFRP coupons in a seawater bath at two temperatures for a time period of three months. Effects of water immersion on the mechanical properties and glass transition temperature of GFRP were investigated. Furthermore, moisture damage in GFRP was monitored by measuring the electrical conductivity of the GFRP coupons. It was shown that carbon nanoparticles can provide a means of self-sensing that enables the monitoring of moisture damage in GFRP. Despite the success of the proposed technique, it might not be able to efficiently describe moisture damage propagation in GFRP beyond a specific threshold because of the relatively high electrical conductivity of seawater. Microstructural investigations using Fourier Transform Infrared (FTIR explained the significance of seawater immersion time and temperature on the different levels of moisture damage in GFRP.

  12. Time-over-threshold readout to enhance the high flux capabilities of single-photon-counting detectors

    International Nuclear Information System (INIS)

    Bergamaschi, Anna; Dinapoli, Roberto; Greiffenberg, Dominic; Henrich, Beat; Johnson, Ian; Mozzanica, Aldo; Radicci, Valeria; Schmitt, Bernd; Shi, Xintian; Stoppani, Laura

    2011-01-01

    The MYTHEN photon-counting ASIC operated in time-over-threshold mode shows an innovative approach towards the development of a detector operating with very high photon intensities while maintaining the single-photon sensitivity for synchrotron radiation experiments. The MYTHEN single-photon-counting (SPC) detector has been characterized using the time-over-threshold (ToT) readout method, i.e. measuring the time that the signal produced by the detected X-rays remains above the comparator threshold. In the following it is shown that the ToT readout preserves the sensitivity, dynamic range and capability of background suppression of the SPC mode, while enhancing the count-rate capability, which is the main limitation of state-of-the-art SPC systems

  13. Time-over-threshold readout to enhance the high flux capabilities of single-photon-counting detectors

    Energy Technology Data Exchange (ETDEWEB)

    Bergamaschi, Anna, E-mail: anna.bergamaschi@psi.ch; Dinapoli, Roberto; Greiffenberg, Dominic; Henrich, Beat; Johnson, Ian; Mozzanica, Aldo; Radicci, Valeria; Schmitt, Bernd; Shi, Xintian; Stoppani, Laura [Paul Scherrer Institut, CH-5232 Villigen (Switzerland)

    2011-11-01

    The MYTHEN photon-counting ASIC operated in time-over-threshold mode shows an innovative approach towards the development of a detector operating with very high photon intensities while maintaining the single-photon sensitivity for synchrotron radiation experiments. The MYTHEN single-photon-counting (SPC) detector has been characterized using the time-over-threshold (ToT) readout method, i.e. measuring the time that the signal produced by the detected X-rays remains above the comparator threshold. In the following it is shown that the ToT readout preserves the sensitivity, dynamic range and capability of background suppression of the SPC mode, while enhancing the count-rate capability, which is the main limitation of state-of-the-art SPC systems.

  14. [FRAX® thresholds to identify people with high or low risk of osteoporotic fracture in Spanish female population].

    Science.gov (United States)

    Azagra, Rafael; Roca, Genís; Martín-Sánchez, Juan Carlos; Casado, Enrique; Encabo, Gloria; Zwart, Marta; Aguyé, Amada; Díez-Pérez, Adolf

    2015-01-06

    To detect FRAX(®) threshold levels that identify groups of the population that are at high/low risk of osteoporotic fracture in the Spanish female population using a cost-effective assessment. This is a cohort study. Eight hundred and sixteen women 40-90 years old selected from the FRIDEX cohort with densitometry and risk factors for fracture at baseline who received no treatment for osteoporosis during the 10 year follow-up period and were stratified into 3 groups/levels of fracture risk (low20%) according to the real fracture incidence. The thresholds of FRAX(®) baseline for major osteoporotic fracture were: low riskX-ray absorptiometry (DXA-scan) for FRAX(®)≥ 5 (Intermediate and high risk) to reclassify by FRAX(®) with DXA-scan at high/low risk. These thresholds select 17.5% of women for DXA-scan and 10% for treatment. With these thresholds of FRAX(®), compared with the strategy of opportunistic case finding isolated risk factors, would improve the predictive parameters and reduce 82.5% the DXA-scan, 35.4% osteoporosis prescriptions and 28.7% cost to detect the same number of women who suffer fractures. The use of FRAX ® thresholds identified as high/low risk of osteoporotic fracture in this calibration (FRIDEX model) improve predictive parameters in Spanish women and in a more cost-effective than the traditional model based on the T-score ≤ -2.5 of DXA scan. Copyright © 2013 Elsevier España, S.L.U. All rights reserved.

  15. Effect of low dose pre-irradiation on DNA damage and genetic material damage caused by high dosage of cyclophosphamide

    International Nuclear Information System (INIS)

    Yu Hongsheng; Zhu Jingjuan; Shang Qingjun; Wang Zhuomin; Cui Fuxian

    2007-01-01

    Objective: To study the effect of low dose γ-rays pre-irradiation on the induction of DNA damage and genetic material damage in peripheral lymphocytes by high dosage of cyclophosphamide (CTX). Methods: Male Kunming strain mice were randomly divided into five groups: control group, sham-irradiated group, low dose irradiated group(LDR group), cyclophosphamide chemotherapy group(CTX group) and low dose irradiation combined with chemotherapy group(LDR + CTX group). After being feeded for one week, all the mice were implanted subcutaneously with S180 cells in the left groin (control group excluded). On days 8 and 11, groups of LDR and LDR + CTX were administered with 75 mGy of whole-body irradiation, 30 h later groups CTX and LDR + CTX were injected intraperitoneally 3.0 mg cyclophosphamide. All the mice were sacrificed on day 13. DNA damage of the peripheral lymphocytes was analyzed using single cell gel electrophoresis (SCGE). Genetic material damage was analyzed using micronucleus frequency(MNF) of polychromatoerythrocytes(PCE) in bone marrow. Results: (1) Compared with control group and sham-irradiated group, the DNA damage of peripheral lymphocytes in CTX group were increased significantly (P 0.05). Conclusions: (1) High- dosage of CTX chemotherapy can cause DNA damage in peripheral lymphocytes. 75 mGy y-irradiation before chemotherapy may have certain protective effect on DNA damage. (2) CTX has potent mutagenic effect, giving remarkable rise to MNF of PCE. 75 mGy γ-ray pre-irradiation has not obvious protection against genetic toxicity of high-dose CTX chemotherapy. (authors)

  16. Checking the foundation: recent radiobiology and the linear no-threshold theory.

    Science.gov (United States)

    Ulsh, Brant A

    2010-12-01

    The linear no-threshold (LNT) theory has been adopted as the foundation of radiation protection standards and risk estimation for several decades. The "microdosimetric argument" has been offered in support of the LNT theory. This argument postulates that energy is deposited in critical cellular targets by radiation in a linear fashion across all doses down to zero, and that this in turn implies a linear relationship between dose and biological effect across all doses. This paper examines whether the microdosimetric argument holds at the lowest levels of biological organization following low dose, low dose-rate exposures to ionizing radiation. The assumptions of the microdosimetric argument are evaluated in light of recent radiobiological studies on radiation damage in biological molecules and cellular and tissue level responses to radiation damage. There is strong evidence that radiation initially deposits energy in biological molecules (e.g., DNA) in a linear fashion, and that this energy deposition results in various forms of prompt DNA damage that may be produced in a pattern that is distinct from endogenous (e.g., oxidative) damage. However, a large and rapidly growing body of radiobiological evidence indicates that cell and tissue level responses to this damage, particularly at low doses and/or dose-rates, are nonlinear and may exhibit thresholds. To the extent that responses observed at lower levels of biological organization in vitro are predictive of carcinogenesis observed in vivo, this evidence directly contradicts the assumptions upon which the microdosimetric argument is based.

  17. Threshold-voltage modulated phase change heterojunction for application of high density memory

    International Nuclear Information System (INIS)

    Yan, Baihan; Tong, Hao; Qian, Hang; Miao, Xiangshui

    2015-01-01

    Phase change random access memory is one of the most important candidates for the next generation non-volatile memory technology. However, the ability to reduce its memory size is compromised by the fundamental limitations inherent in the CMOS technology. While 0T1R configuration without any additional access transistor shows great advantages in improving the storage density, the leakage current and small operation window limit its application in large-scale arrays. In this work, phase change heterojunction based on GeTe and n-Si is fabricated to address those problems. The relationship between threshold voltage and doping concentration is investigated, and energy band diagrams and X-ray photoelectron spectroscopy measurements are provided to explain the results. The threshold voltage is modulated to provide a large operational window based on this relationship. The switching performance of the heterojunction is also tested, showing a good reverse characteristic, which could effectively decrease the leakage current. Furthermore, a reliable read-write-erase function is achieved during the tests. Phase change heterojunction is proposed for high-density memory, showing some notable advantages, such as modulated threshold voltage, large operational window, and low leakage current

  18. Threshold-voltage modulated phase change heterojunction for application of high density memory

    Science.gov (United States)

    Yan, Baihan; Tong, Hao; Qian, Hang; Miao, Xiangshui

    2015-09-01

    Phase change random access memory is one of the most important candidates for the next generation non-volatile memory technology. However, the ability to reduce its memory size is compromised by the fundamental limitations inherent in the CMOS technology. While 0T1R configuration without any additional access transistor shows great advantages in improving the storage density, the leakage current and small operation window limit its application in large-scale arrays. In this work, phase change heterojunction based on GeTe and n-Si is fabricated to address those problems. The relationship between threshold voltage and doping concentration is investigated, and energy band diagrams and X-ray photoelectron spectroscopy measurements are provided to explain the results. The threshold voltage is modulated to provide a large operational window based on this relationship. The switching performance of the heterojunction is also tested, showing a good reverse characteristic, which could effectively decrease the leakage current. Furthermore, a reliable read-write-erase function is achieved during the tests. Phase change heterojunction is proposed for high-density memory, showing some notable advantages, such as modulated threshold voltage, large operational window, and low leakage current.

  19. Comparison on taste threshold between adult male white cigarette and clove cigarette smokers using Murphy clinical test method

    OpenAIRE

    Ronald Reyses Tapilatu; Edeh Rolleta Haroen; Rosiliwati Wihardja

    2008-01-01

    The habit of smoking white cigarettes and clove cigarettes may affect the gustatory function, that is, it will cause damage to taste buds, resulting in an increase in gustatory threshold. This research used the descriptive comparative method and had the purpose of obtaining an illustration of gustatory threshold and compare gustatory threshold in white cigarette smokers and clove cigarette smokers in young, male adults. For gustatory threshold evaluation, the Murphy method was used to obtain ...

  20. Full-length high-temperature severe fuel damage test No. 2

    International Nuclear Information System (INIS)

    Hesson, G.M.; Lombardo, N.J.; Pilger, J.P.; Rausch, W.N.; King, L.L.; Hurley, D.E.; Parchen, L.J.; Panisko, F.E.

    1993-09-01

    Hazardous conditions associated with performing the Full-Length High- Temperature (FLHT). Severe Fuel Damage Test No. 2 experiment have been analyzed. Major hazards that could cause harm or damage are (1) radioactive fission products, (2) radiation fields, (3) reactivity changes, (4) hydrogen generation, (5) materials at high temperature, (6) steam explosion, and (7) steam pressure pulse. As a result of this analysis, it is concluded that with proper precautions the FLHT- 2 test can be safely conducted

  1. Near threshold fatigue testing

    Science.gov (United States)

    Freeman, D. C.; Strum, M. J.

    1993-01-01

    Measurement of the near-threshold fatigue crack growth rate (FCGR) behavior provides a basis for the design and evaluation of components subjected to high cycle fatigue. Typically, the near-threshold fatigue regime describes crack growth rates below approximately 10(exp -5) mm/cycle (4 x 10(exp -7) inch/cycle). One such evaluation was recently performed for the binary alloy U-6Nb. The procedures developed for this evaluation are described in detail to provide a general test method for near-threshold FCGR testing. In particular, techniques for high-resolution measurements of crack length performed in-situ through a direct current, potential drop (DCPD) apparatus, and a method which eliminates crack closure effects through the use of loading cycles with constant maximum stress intensity are described.

  2. A model for damage load and its implications for the evolution of bacterial aging.

    Directory of Open Access Journals (Sweden)

    Lin Chao

    2010-08-01

    Full Text Available Deleterious mutations appearing in a population increase in frequency until stopped by natural selection. The ensuing equilibrium creates a stable frequency of deleterious mutations or the mutational load. Here I develop the comparable concept of a damage load, which is caused by harmful non-heritable changes to the phenotype. A damage load also ensues when the increase of damage is opposed by selection. The presence of a damage load favors the evolution of asymmetrical transmission of damage by a mother to her daughters. The asymmetry is beneficial because it increases fitness variance, but it also leads to aging or senescence. A mathematical model based on microbes reveals that a cell lineage dividing symmetrically is immortal if lifetime damage rates do not exceed a threshold. The evolution of asymmetry allows the lineage to persist above the threshold, but the lineage becomes mortal. In microbes with low genomic mutation rates, it is likely that the damage load is much greater than the mutational load. In metazoans with higher genomic mutation rates, the damage and the mutational load could be of the same magnitude. A fit of the model to experimental data shows that Escherichia coli cells experience a damage rate that is below the threshold and are immortal under the conditions examined. The model estimates the asymmetry level of E. coli to be low but sufficient for persisting at higher damage rates. The model also predicts that increasing asymmetry results in diminishing fitness returns, which may explain why the bacterium has not evolved higher asymmetry.

  3. Chemical Etching, AFM, Laser Damage Threshold, and Nonlinear Optical Studies of Potential Nonlinear Optical Crystal: Bis (L-Glutamine Potassium Nitrate

    Directory of Open Access Journals (Sweden)

    Redrothu Hanumantharao

    2013-01-01

    Full Text Available A novel semiorganic nonlinear optical crystal bis (L-glutamine potassium nitrate (BGPN grown by slow evaporation technique at ambient temperature. The grown crystal surface has been analyzed by chemical etching and atomic force microscopy (AFM studies. Amplitude parameters like area roughness, roughness average, valley height, valley depth, peak height, and peak valley height were measured successfully from AFM studies. Etching studies were carried out by various solvents like water, methanol and ethanol. The etching study indicates the occurrence of different types of etch pit patterns like striations and steplike pattern. The laser damage threshold energy has been measured by irradiating laser beam using a Q-switched Nd: YAG laser (1064 nm. Second harmonic generation (SHG studies have been performed by famous Kurtz powder technique with reference to standard potassium dihydrogen phosphate single crystals (KDP. It is found from this technique that SHG efficiency of BGPN is in comparison to that of standard KDP crystals.

  4. On the implications of thresholds for economic science and environmental policy

    NARCIS (Netherlands)

    Aalbers, R.F.T.

    1999-01-01

    This dissertation analyses the implications for economic analyses of the occurrence of thresholds in environmental damage functions. This research question is analysed for the case of global warming from three different perspectives. The first perspective is that of certainty of information. Using

  5. Bottom Raking Damage to High-Speed Craft

    DEFF Research Database (Denmark)

    Simonsen, Bo Cerup

    1998-01-01

    This paper presents a comparative study of the raking damage to high speed craft (HSC) and conventional ships. The analysis is based on a detailed theoretical model for the raking resistance of an assembled ship bottom structure and on the idea that the impact conditions for various ship types have...

  6. Amorphization threshold in Si-implanted strained SiGe alloy layers

    International Nuclear Information System (INIS)

    Simpson, T.W.; Love, D.; Endisch, E.; Goldberg, R.D.; Mitchell, I.V.; Haynes, T.E.; Baribeau, J.M.

    1994-12-01

    The authors have examined the damage produced by Si-ion implantation into strained Si 1-x Ge x epilayers. Damage accumulation in the implanted layers was monitored in situ by time-resolved reflectivity and measured by ion channeling techniques to determine the amorphization threshold in strained Si 1-x Ge x (x = 0.16 and 0.29) over the temperature range 30--110 C. The results are compared with previously reported measurements on unstrained Si 1-x Ge x , and with the simple model used to describe those results. They report here data which lend support to this model and which indicate that pre-existing strain does not enhance damage accumulation in the alloy layer

  7. A Modified Fatigue Damage Model for High-Cycle Fatigue Life Prediction

    Directory of Open Access Journals (Sweden)

    Meng Wang

    2016-01-01

    Full Text Available Based on the assumption of quasibrittle failure under high-cycle fatigue for the metal material, the damage constitutive equation and the modified damage evolution equation are obtained with continuum damage mechanics. Then, finite element method (FEM is used to describe the failure process of metal material. The increment of specimen’s life and damage state can be researched using damage mechanics-FEM. Finally, the lifetime of the specimen is got at the given stress level. The damage mechanics-FEM is inserted into ABAQUS with subroutine USDFLD and the Python language is used to simulate the fatigue process of titanium alloy specimens. The simulation results have a good agreement with the testing results under constant amplitude loading, which proves the accuracy of the method.

  8. Setting limits: Using air pollution thresholds to protect and restore U.S. ecosystems

    Science.gov (United States)

    Fenn, M.E.; Lambert, K.F.; Blett, T.F.; Burns, Douglas A.; Pardo, L.H.; Lovett, Gary M.; Haeuber, R. A.; Evers, D.C.; Driscoll, C.T.; Jeffries, D.S.

    2011-01-01

    states and on many tribal lands. High concentrations of mercury in wildlife are also widespread and have multiple adverse effects. ??? Air quality programs, such as those stemming from the 1990 Clean Air Act Amendments, have helped decrease air pollution even as population and energy demand have increased. Yet, they do not adequately protect ecosystems from long-term damage. Moreover they do not address ammonia emissions. ??? A stronger ecosystem basis for air pollutant policies could be established through adoption of science-based thresholds. Existing monitoring programs track vital information needed to measure the response to policies, and could be expanded to include appropriate chemical and biological indicators for terrestrial and aquatic ecosystems and establishment of a national ecosystem monitoring network for mercury. The development and use of air pollution thresholds for ecosystem protection and management is increasing in the United States, yet threshold approaches remain underutilized. Ecological thresholds for air pollution, such as critical loads for nitrogen and sulfur deposition, are not currently included in the formal regulatory process for emissions controls in the United States, although they are now considered in local management decisions by the National Park Service and U.S. Forest Service. Ecological thresholds offer a scientifically sound approach to protecting and restoring U.S. ecosystems and an important tool for natural resource management and policy. ?? The Ecological Society of America.

  9. A high-energy, low-threshold tunable intracavity terahertz-wave parametric oscillator with surface-emitted configuration

    International Nuclear Information System (INIS)

    Wang, Y Y; Xu, D G; Jiang, H; Zhong, K; Yao, J Q

    2013-01-01

    A high-energy, low-threshold THz-wave output has been experimentally demonstrated with an intracavity terahertz-wave parametric oscillator based on a surface-emitted configuration, which was pumped by a diode-side-pumped Q-switched Nd:YAG laser. Different beam sizes and repetition rates of the pump light have been investigated for high-energy and high-efficiency THz-wave generation. The maximum THz-wave output energy of 283 nJ/pulse was obtained at 1.54 THz under an intracavity 1064 nm pump energy of 59 mJ. The conversion efficiency was 4.8 × 10 −6 , corresponding to a photon conversion efficiency of 0.088%. The pump threshold was 12.9 mJ/pulse. A continuously tunable range from 0.75 to 2.75 THz was realized. (paper)

  10. Fluence thresholds for grazing incidence hard x-ray mirrors

    Czech Academy of Sciences Publication Activity Database

    Aquila, A.; Sobierajski, R.; Ozkan, C.; Hájková, Věra; Burian, Tomáš; Chalupský, Jaromír; Juha, Libor; Störmer, M.; Bajt, S.; Klepka, M.T.; Dlužewski, P.; Morawiec, K.; Ohashi, H.; Koyama, T.; Tono, K.; Inubushi, Y.; Yabashi, M.; Sinn, H.; Tschentscher, T.; Mancuso, A.P.; Gaudin, J.

    2015-01-01

    Roč. 106, č. 24 (2015), "241905-1"-"241905-5" ISSN 0003-6951 R&D Projects: GA ČR(CZ) GA14-29772S Grant - others:AVČR(CZ) M100101221 Institutional support: RVO:68378271 Keywords : XFEL * Free Electron Laser * damage threshold * X-ray optics Subject RIV: BH - Optics , Masers, Lasers Impact factor: 3.142, year: 2015

  11. Comparison of Two Models for Damage Accumulation in Simulations of System Performance

    Energy Technology Data Exchange (ETDEWEB)

    Youngblood, R. [Idaho National Laboratory, Idaho Falls, ID (United States); Mandelli, D. [Idaho National Laboratory, Idaho Falls, ID (United States)

    2015-11-01

    A comprehensive simulation study of system performance needs to address variations in component behavior, variations in phenomenology, and the coupling between phenomenology and component failure. This paper discusses two models of this: 1. damage accumulation is modeled as a random walk process in each time history, with component failure occurring when damage accumulation reaches a specified threshold; or 2. damage accumulation is modeled mechanistically within each time history, but failure occurs when damage reaches a time-history-specific threshold, sampled at time zero from each component’s distribution of damage tolerance. A limiting case of the latter is classical discrete-event simulation, with component failure times sampled a priori from failure time distributions; but in such models, the failure times are not typically adjusted for operating conditions varying within a time history. Nowadays, as discussed below, it is practical to account for this. The paper compares the interpretations and computational aspects of the two models mentioned above.

  12. Influence of standing-wave electric field pattern on the laser damage resistance of HfO sub 2 thin films

    CERN Document Server

    Protopapa, M L; De Tomasi, F; Di Giulio, M; Perrone, M R; Scaglione, S

    2002-01-01

    The standing-wave electric field pattern that forms inside an optical coating as a consequence of laser irradiation is one of the factors influencing the coating laser-induced damage threshold. The influence of the standing-wave electric field profile on the damage resistance to ultraviolet radiation of hafnium dioxide (HfO sub 2) thin films was investigated in this work. To this end, HfO sub 2 thin films of different thicknesses deposited by the electron beam evaporation technique at the same deposition conditions were analyzed. Laser damage thresholds of the samples were measured at 308 nm (XeCl laser) by the photoacoustic beam deflection technique and microscopic inspections. The dependence of the laser damage threshold on the standing-wave electric field pattern was analyzed.

  13. The Caenorhabditis elegans interneuron ALA is (also) a high-threshold mechanosensor

    OpenAIRE

    Sanders, Jarred; Nagy, Stanislav; Fetterman, Graham; Wright, Charles; Treinin, Millet; Biron, David

    2013-01-01

    Background To survive dynamic environments, it is essential for all animals to appropriately modulate their behavior in response to various stimulus intensities. For instance, the nematode Caenorhabditis elegans suppresses the rate of egg-laying in response to intense mechanical stimuli, in a manner dependent on the mechanosensory neurons FLP and PVD. We have found that the unilaterally placed single interneuron ALA acted as a high-threshold mechanosensor, and that it was required for this pr...

  14. Ultraviolet damage resistance of laser coatings

    International Nuclear Information System (INIS)

    Newnam, B.E.; Gill, D.H.

    1978-01-01

    The damage resistance of several thin-film materials used in ultraviolet laser optics was measured at 266 and 355 nm. The coatings included single, quarterwave (QW) layers of NaF, LaF 3 , MgF 2 , ThO 2 , Al 2 O 3 , HfO 2 , ZrO 2 , Y 2 O 3 and SiO 2 , plus multilayer reflectors composed of some of these materials. The substrates were uv-grade fused silica. Single-shot thresholds were obtained with 22 ns and 27 ns (FWHM) pulses at 266 and 355 nm, respectively. One of the samples had previously been tested using 20-ps pulses, providing a pulsewidth comparison. At 266 nm the coating with the highest damage threshold was a QW layer of NaF at 10.8 J/cm 2 (450 MW/cm 2 ), whereas for a maximum reflector of Al 2 O 3 /NaF the value was 3.6 J/cm 2 (154 MW/cm 2 ), and the threshold of the maximum reflector was 12.2 J/cm 2 (470 MW/cm 2 ). The results were analyzed to determine correlations with standing-wave electric fields and linear and two-photon absorption. Scaling relationships for wavelength, refractive index and atomic density, and pulsewidth were found

  15. Vacuum ultra-violet damage and damage mitigation for plasma processing of highly porous organosilicate glass dielectrics

    Energy Technology Data Exchange (ETDEWEB)

    Marneffe, J.-F. de, E-mail: marneffe@imec.be; Lukaszewicz, M.; Porter, S. B.; Vajda, F.; Rutigliani, V.; Verdonck, P.; Baklanov, M. R. [IMEC v.z.w., 3001 Leuven (Belgium); Zhang, L.; Heyne, M.; El Otell, Z.; Krishtab, M. [IMEC v.z.w., 3001 Leuven (Belgium); Department of Chemistry, KULeuven, 3001 Leuven (Belgium); Goodyear, A.; Cooke, M. [Oxford Instruments Plasma Technology, BS49 4AP Bristol (United Kingdom)

    2015-10-07

    Porous organosilicate glass thin films, with k-value 2.0, were exposed to 147 nm vacuum ultra-violet (VUV) photons emitted in a Xenon capacitive coupled plasma discharge. Strong methyl bond depletion was observed, concomitant with a significant increase of the bulk dielectric constant. This indicates that, besides reactive radical diffusion, photons emitted during plasma processing do impede dielectric properties and therefore need to be tackled appropriately during patterning and integration. The detrimental effect of VUV irradiation can be partly suppressed by stuffing the low-k porous matrix with proper sacrificial polymers showing high VUV absorption together with good thermal and VUV stability. In addition, the choice of an appropriate hard-mask, showing high VUV absorption, can minimize VUV damage. Particular processing conditions allow to minimize the fluence of photons to the substrate and lead to negligible VUV damage. For patterned structures, in order to reduce VUV damage in the bulk and on feature sidewalls, the combination of both pore stuffing/material densification and absorbing hard-mask is recommended, and/or the use of low VUV-emitting plasma discharge.

  16. A pilot study on the determination of performance indicator threshold values for domestic nuclear power plants using risk-informed approach

    International Nuclear Information System (INIS)

    Kang, D. I.; Kim, K. Y.; Park, J. H.; Hwang, M. J.; Ha, J. J.; Sung, K. Y.

    2004-01-01

    In this paper, a pilot study on the determination of the performance indicator (PI) threshold values of the unplanned reactor scram and the unavailability of safety systems for domestic nuclear power plants (NPPs) has been performed using risk-informed approach. The crtiteria of core damage frequency changes (ΔCDF) in the RG 1.174, which has been used for the risk-informed decisionmaking, were adopted as the basic criteria for the dermination of the PI threshold values. The PI threshold values of the unplanned reactor scram (URS) were determined on the assumptions that the the initiating event frequencies are changed and their conditional core damage probabilities are constant. The PI threshold values of the safety system unavailabilities were determined using the Fussel-Vesely importance, CDF, and ΔCDF. The study results for two domestic NPPs show that the PI threshold values of the URS are greatly dependent on the methodology of initiating event analysis and those of safety system unavailabilities currently used are somewhat conservatively set up

  17. Comparing the ISO-recommended and the cumulative data-reduction algorithms in S-on-1 laser damage test by a reverse approach method

    Science.gov (United States)

    Zorila, Alexandru; Stratan, Aurel; Nemes, George

    2018-01-01

    We compare the ISO-recommended (the standard) data-reduction algorithm used to determine the surface laser-induced damage threshold of optical materials by the S-on-1 test with two newly suggested algorithms, both named "cumulative" algorithms/methods, a regular one and a limit-case one, intended to perform in some respects better than the standard one. To avoid additional errors due to real experiments, a simulated test is performed, named the reverse approach. This approach simulates the real damage experiments, by generating artificial test-data of damaged and non-damaged sites, based on an assumed, known damage threshold fluence of the target and on a given probability distribution function to induce the damage. In this work, a database of 12 sets of test-data containing both damaged and non-damaged sites was generated by using four different reverse techniques and by assuming three specific damage probability distribution functions. The same value for the threshold fluence was assumed, and a Gaussian fluence distribution on each irradiated site was considered, as usual for the S-on-1 test. Each of the test-data was independently processed by the standard and by the two cumulative data-reduction algorithms, the resulting fitted probability distributions were compared with the initially assumed probability distribution functions, and the quantities used to compare these algorithms were determined. These quantities characterize the accuracy and the precision in determining the damage threshold and the goodness of fit of the damage probability curves. The results indicate that the accuracy in determining the absolute damage threshold is best for the ISO-recommended method, the precision is best for the limit-case of the cumulative method, and the goodness of fit estimator (adjusted R-squared) is almost the same for all three algorithms.

  18. Analysis of the relationships between oxidative stress, DNA damage and sperm vitality in a patient population: development of diagnostic criteria.

    Science.gov (United States)

    Aitken, R John; De Iuliis, Geoffry N; Finnie, Jane M; Hedges, Andrew; McLachlan, Robert I

    2010-10-01

    DNA damage in human spermatozoa is known to be associated with a variety of adverse clinical outcomes affecting both reproductive efficiency and the health and wellbeing of the offspring. However, the origin of this damage, its biochemical nature and strategies for its amelioration, still await resolution. Using novel methods to simultaneously assess DNA fragmentation (modified TUNEL assay), DNA-base adduct formation (8-hydroxy-2'-deoxyguanosine [8OHdG]) and cell vitality, spermatozoa from a cohort of 50 assisted conception patients were examined and compared with a group of donors. Receiver operating characteristic (ROC) curve analysis was then used to examine the frequency distribution of the data and to determine optimized thresholds for identifying patients exhibiting abnormally high levels of DNA damage. 8OHdG formation and DNA fragmentation were highly correlated with each other and frequently associated with cell death. Percoll centrifugation improved sperm quality but, unexpectedly, increased 8OHdG formation in live cells, as did sperm fractionation using Puresperm gradients. ROC analysis indicated that the frequency distribution of 8OHdG and DNA fragmentation data were significantly different between patients and donors (P live cells. However, the development of novel methods and optimized thresholds for diagnosing oxidative DNA damage in human spermatozoa should assist in the clinical management of this pathology.

  19. Updated Simulation Studies of Damage Limit of LHC Tertiary Collimators

    CERN Document Server

    AUTHOR|(CDS)2085459; Bertarelli, Alessandro; Bruce, Roderik; Carra, Federico; Cerutti, Francesco; Gradassi, Paolo; Lechner, Anton; Redaelli, Stefano; Skordis, Eleftherios

    2015-01-01

    The tertiary collimators (TCTs) in the LHC, installed in front of the experiments, in standard operation intercept fractions of 10−3 halo particles. However, they risk to be hit by high-intensity primary beams in case of asynchronous beam dump. TCT damage thresholds were initially inferred from results of destructive tests on a TCT jaw, supported by numerical simulations, assuming simplified impact scenarios with one single bunch hitting the jaw with a given impact parameter. In this paper, more realistic failure conditions, including a train of bunches and taking into account the full collimation hierarchy, are used to derive updated damage limits. The results are used to update the margins in the collimation hierarchy and could thus potentially have an influence on the LHC performance.

  20. Heat-Related Deaths in Hot Cities: Estimates of Human Tolerance to High Temperature Thresholds

    Directory of Open Access Journals (Sweden)

    Sharon L. Harlan

    2014-03-01

    Full Text Available In this study we characterized the relationship between temperature and mortality in central Arizona desert cities that have an extremely hot climate. Relationships between daily maximum apparent temperature (ATmax and mortality for eight condition-specific causes and all-cause deaths were modeled for all residents and separately for males and females ages <65 and ≥65 during the months May–October for years 2000–2008. The most robust relationship was between ATmax on day of death and mortality from direct exposure to high environmental heat. For this condition-specific cause of death, the heat thresholds in all gender and age groups (ATmax = 90–97 °F; 32.2‒36.1 °C were below local median seasonal temperatures in the study period (ATmax = 99.5 °F; 37.5 °C. Heat threshold was defined as ATmax at which the mortality ratio begins an exponential upward trend. Thresholds were identified in younger and older females for cardiac disease/stroke mortality (ATmax = 106 and 108 °F; 41.1 and 42.2 °C with a one-day lag. Thresholds were also identified for mortality from respiratory diseases in older people (ATmax = 109 °F; 42.8 °C and for all-cause mortality in females (ATmax = 107 °F; 41.7 °C and males <65 years (ATmax = 102 °F; 38.9 °C. Heat-related mortality in a region that has already made some adaptations to predictable periods of extremely high temperatures suggests that more extensive and targeted heat-adaptation plans for climate change are needed in cities worldwide.

  1. The Effect of High-Frequency Stimulation on Sensory Thresholds in Chronic Pain Patients.

    Science.gov (United States)

    Youn, Youngwon; Smith, Heather; Morris, Brian; Argoff, Charles; Pilitsis, Julie G

    2015-01-01

    High-frequency stimulation (HFS) has recently gained attention as an alternative to parameters used in traditional spinal cord stimulation (SCS). Because HFS is paresthesia free, the gate theory of pain control as a basis of SCS has been called into question. The mechanism of action of HFS remains unclear. We compare the effects of HFS and traditional SCS on quantitative sensory testing parameters to provide insight into how HFS modulates the nervous system. Using quantitative sensory testing, we measured thermal detection and pain thresholds and mechanical detection and pressure pain thresholds, as well as vibratory detection, in 20 SCS patients off stimulation (OFF), on traditional stimulation (ON) and on HFS in a randomized order. HFS significantly increased the mechanical detection threshold compared to OFF stimulation (p < 0.001) and traditional SCS (p = 0.01). Pressure pain detection and vibratory detection thresholds also significantly increased with HFS compared to ON states (p = 0.04 and p = 0.01, respectively). In addition, HFS significantly decreased 10- and 40-gram pinprick detection compared to OFF states (both p = 0.01). No significant differences between OFF, ON and HFS states were seen in thermal and thermal pain detection. HFS is a new means of modulating chronic pain. The mechanism by which HFS works seems to differ from that of traditional SCS, offering a new platform for innovative advancements in treatment and a greater potential to treat patients by customizing waveforms. © 2015 S. Karger AG, Basel.

  2. Novel high-fidelity realistic explosion damage simulation for urban environments

    Science.gov (United States)

    Liu, Xiaoqing; Yadegar, Jacob; Zhu, Youding; Raju, Chaitanya; Bhagavathula, Jaya

    2010-04-01

    Realistic building damage simulation has a significant impact in modern modeling and simulation systems especially in diverse panoply of military and civil applications where these simulation systems are widely used for personnel training, critical mission planning, disaster management, etc. Realistic building damage simulation should incorporate accurate physics-based explosion models, rubble generation, rubble flyout, and interactions between flying rubble and their surrounding entities. However, none of the existing building damage simulation systems sufficiently faithfully realize the criteria of realism required for effective military applications. In this paper, we present a novel physics-based high-fidelity and runtime efficient explosion simulation system to realistically simulate destruction to buildings. In the proposed system, a family of novel blast models is applied to accurately and realistically simulate explosions based on static and/or dynamic detonation conditions. The system also takes account of rubble pile formation and applies a generic and scalable multi-component based object representation to describe scene entities and highly scalable agent-subsumption architecture and scheduler to schedule clusters of sequential and parallel events. The proposed system utilizes a highly efficient and scalable tetrahedral decomposition approach to realistically simulate rubble formation. Experimental results demonstrate that the proposed system has the capability to realistically simulate rubble generation, rubble flyout and their primary and secondary impacts on surrounding objects including buildings, constructions, vehicles and pedestrians in clusters of sequential and parallel damage events.

  3. Healing of damaged metal by a pulsed high-energy electromagnetic field

    Science.gov (United States)

    Kukudzhanov, K. V.; Levitin, A. L.

    2018-04-01

    The processes of defect (intergranular micro-cracks) transformation are investigated for metal samples in a high-energy short-pulsed electromagnetic field. This investigation is based on a numerical coupled model of the impact of high-energy electromagnetic field on the pre-damaged thermal elastic-plastic material with defects. The model takes into account the melting and evaporation of the metal and the dependence of its physical and mechanical properties on the temperature. The system of equations is solved numerically by finite element method with an adaptive mesh using the arbitrary Euler–Lagrange method. The calculations show that the welding of the crack and the healing of micro-defects under treatment by short pulses of the current takes place. For the macroscopic description of the healing process, the healing and damage parameters of the material are introduced. The healing of micro-cracks improves the material healing parameter and reduces its damage. The micro-crack shapes practically do not affect the time-dependence of the healing and damage under the treatment by the current pulses. These changes are affected only by the value of the initial damage of the material and the initial length of the micro-crack. The time-dependence of the healing and the damage is practically the same for all different shapes of micro-defects, provided that the initial lengths of micro-cracks and the initial damages are the same for these different shapes of defects.

  4. Speech-in-Noise Tests and Supra-threshold Auditory Evoked Potentials as Metrics for Noise Damage and Clinical Trial Outcome Measures.

    Science.gov (United States)

    Le Prell, Colleen G; Brungart, Douglas S

    2016-09-01

    In humans, the accepted clinical standards for detecting hearing loss are the behavioral audiogram, based on the absolute detection threshold of pure-tones, and the threshold auditory brainstem response (ABR). The audiogram and the threshold ABR are reliable and sensitive measures of hearing thresholds in human listeners. However, recent results from noise-exposed animals demonstrate that noise exposure can cause substantial neurodegeneration in the peripheral auditory system without degrading pure-tone audiometric thresholds. It has been suggested that clinical measures of auditory performance conducted with stimuli presented above the detection threshold may be more sensitive than the behavioral audiogram in detecting early-stage noise-induced hearing loss in listeners with audiometric thresholds within normal limits. Supra-threshold speech-in-noise testing and supra-threshold ABR responses are reviewed here, given that they may be useful supplements to the behavioral audiogram for assessment of possible neurodegeneration in noise-exposed listeners. Supra-threshold tests may be useful for assessing the effects of noise on the human inner ear, and the effectiveness of interventions designed to prevent noise trauma. The current state of the science does not necessarily allow us to define a single set of best practice protocols. Nonetheless, we encourage investigators to incorporate these metrics into test batteries when feasible, with an effort to standardize procedures to the greatest extent possible as new reports emerge.

  5. Bulk and surface laser damage of silica by picosecond and nanosecond pulses at 1064 nm

    International Nuclear Information System (INIS)

    Smith, Arlee V.; Do, Binh T.

    2008-01-01

    We measured bulk and surface dielectric breakdown thresholds of pure silica for 14 ps and 8 ns pulses of 1064 nm light. The thresholds are sharp and reproducible. For the 8 ns pulses the bulk threshold irradiance is 4.75 ± 0.25 kW/μm 2 . The threshold is approximately three times higher for 14 ps pulses. For 8 ns pulses the input surface damage threshold can be made equal to the bulk threshold by applying an alumina or silica surface polish

  6. Using self-organizing maps to determine observation threshold limit predictions in highly variant data

    Science.gov (United States)

    Paganoni, C.A.; Chang, K.C.; Robblee, M.B.

    2006-01-01

    A significant data quality challenge for highly variant systems surrounds the limited ability to quantify operationally reasonable limits on the data elements being collected and provide reasonable threshold predictions. In many instances, the number of influences that drive a resulting value or operational range is too large to enable physical sampling for each influencer, or is too complicated to accurately model in an explicit simulation. An alternative method to determine reasonable observation thresholds is to employ an automation algorithm that would emulate a human analyst visually inspecting data for limits. Using the visualization technique of self-organizing maps (SOM) on data having poorly understood relationships, a methodology for determining threshold limits was developed. To illustrate this approach, analysis of environmental influences that drive the abundance of a target indicator species (the pink shrimp, Farfantepenaeus duorarum) provided a real example of applicability. The relationship between salinity and temperature and abundance of F. duorarum is well documented, but the effect of changes in water quality upstream on pink shrimp abundance is not well understood. The highly variant nature surrounding catch of a specific number of organisms in the wild, and the data available from up-stream hydrology measures for salinity and temperature, made this an ideal candidate for the approach to provide a determination about the influence of changes in hydrology on populations of organisms.

  7. Effects of foreign object damage from small hard particles on the high-cycle fatigue life of titanium-(6)aluminum-(4)vanadium

    Science.gov (United States)

    Hamrick, Joseph L., II

    Thin rectangular samples of Ti-6Al-4V were damaged by four methods to represent foreign object damage found in turbine engine blades: (1) impact with 2 mm. and 5 mm diameter glass spheres at 305 m/s, (2) impact with 2 mm and 4 mm diameter steel spheres at 305 m/s, (3) quasi-static displacement controlled indentation using steel chisels with 1 mm, 2 nun and 5 mm diameter tips and (4) shearing notches with a 2 mm. diameter chisel point under a quasi-static loading condition. Finite element analysis was used to study the relationship between the stress state created by the plastic damage and the fatigue strength. A new method of quantifying the amount of plastic damage from multiple methods was developed. The fatigue strength required for crack initiation at 10E7 cycles was found to be a function of the total depth from the edge of the undeformed specimen up to the end of the plastically deformed zone. For damage depths less than 1750 mum, the reduction in fatigue strength is proportional to the depth of total damage. For depths > 1750 mum, there appears to be a threshold value of fatigue strength.

  8. Evaluation of supra-threshold hearing following an event of recreational acoustic exposure

    DEFF Research Database (Denmark)

    Smits, Bertrand; Holtegaard, Pernille; Jeong, Cheol-Ho

    2018-01-01

    Studies with small rodents have exhibited physiological evidence of noise-induced cochlear synaptopathy prior to outer-hair-cell loss following noise-induced large temporary threshold shifts (TTS). The auditory system may thus not fully recover after a TTS. If this noise-induced damage also occurs...

  9. Heat-related deaths in hot cities: estimates of human tolerance to high temperature thresholds.

    Science.gov (United States)

    Harlan, Sharon L; Chowell, Gerardo; Yang, Shuo; Petitti, Diana B; Morales Butler, Emmanuel J; Ruddell, Benjamin L; Ruddell, Darren M

    2014-03-20

    In this study we characterized the relationship between temperature and mortality in central Arizona desert cities that have an extremely hot climate. Relationships between daily maximum apparent temperature (ATmax) and mortality for eight condition-specific causes and all-cause deaths were modeled for all residents and separately for males and females ages heat. For this condition-specific cause of death, the heat thresholds in all gender and age groups (ATmax = 90-97 °F; 32.2-36.1 °C) were below local median seasonal temperatures in the study period (ATmax = 99.5 °F; 37.5 °C). Heat threshold was defined as ATmax at which the mortality ratio begins an exponential upward trend. Thresholds were identified in younger and older females for cardiac disease/stroke mortality (ATmax = 106 and 108 °F; 41.1 and 42.2 °C) with a one-day lag. Thresholds were also identified for mortality from respiratory diseases in older people (ATmax = 109 °F; 42.8 °C) and for all-cause mortality in females (ATmax = 107 °F; 41.7 °C) and males Heat-related mortality in a region that has already made some adaptations to predictable periods of extremely high temperatures suggests that more extensive and targeted heat-adaptation plans for climate change are needed in cities worldwide.

  10. Continuum damage growth analysis using element free Galerkin ...

    Indian Academy of Sciences (India)

    and two-dimensional problems are presented to illustrate the effectiveness of the proposed method ... will enhance the computational cost required. .... where εpD is the damage threshold in pure tension, m is the correction parameter, σu is the.

  11. Laser-induced damage thresholds of bulk and coating optical materials at 1030  nm, 500  fs.

    Science.gov (United States)

    Gallais, Laurent; Commandré, Mireille

    2014-02-01

    We report on extensive femtosecond laser damage threshold measurements of optical materials in both bulk and thin-film form. This study, which is based on published and new data, involved simple oxide and fluoride films, composite films made from a mixture of two dielectric materials, metallic films, and the surfaces of various bulk materials: oxides, fluorides, semiconductors, and ionic crystals. The samples were tested in comparable conditions at 1030 nm, 375 to 600 fs, under single-pulse irradiation. A large number of different samples prepared by different deposition techniques have been tested, involving classical materials used in the fabrication of optical thin film components (Ag, AlF3, Al2O3, HfO2, MgF2, Nb2O5, Pt, Sc2O3, SiO2, Ta2O5, Y2O3, and ZrO2) and their combination with codeposition processes. Their behaviors are compared with the surfaces of bulk materials (Al2O3, BaF2, CaF2, Ge, KBr, LiF, MgF2, NaCl, Quartz, Si, ZnS, ZnSe, and different silica glasses). Tabulated values of results are presented and discussed.

  12. The ship edge feature detection based on high and low threshold for remote sensing image

    Science.gov (United States)

    Li, Xuan; Li, Shengyang

    2018-05-01

    In this paper, a method based on high and low threshold is proposed to detect the ship edge feature due to the low accuracy rate caused by the noise. Analyze the relationship between human vision system and the target features, and to determine the ship target by detecting the edge feature. Firstly, using the second-order differential method to enhance the quality of image; Secondly, to improvement the edge operator, we introduction of high and low threshold contrast to enhancement image edge and non-edge points, and the edge as the foreground image, non-edge as a background image using image segmentation to achieve edge detection, and remove the false edges; Finally, the edge features are described based on the result of edge features detection, and determine the ship target. The experimental results show that the proposed method can effectively reduce the number of false edges in edge detection, and has the high accuracy of remote sensing ship edge detection.

  13. Monitoring of corrosion damage using high-frequency guided ultrasonic waves

    Science.gov (United States)

    Chew, D.; Fromme, P.

    2015-03-01

    Due to adverse environmental conditions corrosion can develop during the life cycle of industrial structures, e.g., offshore oil platforms, ships, and desalination plants. Both pitting corrosion and generalized corrosion leading to wall thickness loss can cause the degradation of the integrity and load bearing capacity of the structure. Structural health monitoring of corrosion damage in difficult to access areas can in principle be achieved using high frequency guided waves propagating along the structure from accessible areas. Using standard ultrasonic transducers with single sided access to the structure, high frequency guided wave modes were generated that penetrate through the complete thickness of the structure. Wall thickness reduction was induced using accelerated corrosion in a salt water bath. The corrosion damage was monitored based on the effect on the wave propagation and interference of the different modes. The change in the wave interference was quantified based on an analysis in the frequency domain (Fourier transform) and was found to match well with theoretical predictions for the wall thickness loss. High frequency guided waves have the potential for corrosion damage monitoring at critical and difficult to access locations from a stand-off distance.

  14. The relationship between high-frequency pure-tone hearing loss, hearing in noise test (HINT) thresholds, and the articulation index.

    Science.gov (United States)

    Vermiglio, Andrew J; Soli, Sigfrid D; Freed, Daniel J; Fisher, Laurel M

    2012-01-01

    Speech recognition in noise testing has been conducted at least since the 1940s (Dickson et al, 1946). The ability to recognize speech in noise is a distinct function of the auditory system (Plomp, 1978). According to Kochkin (2002), difficulty recognizing speech in noise is the primary complaint of hearing aid users. However, speech recognition in noise testing has not found widespread use in the field of audiology (Mueller, 2003; Strom, 2003; Tannenbaum and Rosenfeld, 1996). The audiogram has been used as the "gold standard" for hearing ability. However, the audiogram is a poor indicator of speech recognition in noise ability. This study investigates the relationship between pure-tone thresholds, the articulation index, and the ability to recognize speech in quiet and in noise. Pure-tone thresholds were measured for audiometric frequencies 250-6000 Hz. Pure-tone threshold groups were created. These included a normal threshold group and slight, mild, severe, and profound high-frequency pure-tone threshold groups. Speech recognition thresholds in quiet and in noise were obtained using the Hearing in Noise Test (HINT) (Nilsson et al, 1994; Vermiglio, 2008). The articulation index was determined by using Pavlovic's method with pure-tone thresholds (Pavlovic, 1989, 1991). Two hundred seventy-eight participants were tested. All participants were native speakers of American English. Sixty-three of the original participants were removed in order to create groups of participants with normal low-frequency pure-tone thresholds and relatively symmetrical high-frequency pure-tone threshold groups. The final set of 215 participants had a mean age of 33 yr with a range of 17-59 yr. Pure-tone threshold data were collected using the Hughson-Weslake procedure. Speech recognition data were collected using a Windows-based HINT software system. Statistical analyses were conducted using descriptive, correlational, and multivariate analysis of covariance (MANCOVA) statistics. The

  15. Challenges in devising economic spray thresholds for a major pest of Australian canola, the redlegged earth mite (Halotydeus destructor).

    Science.gov (United States)

    Arthur, Aston L; Hoffmann, Ary A; Umina, Paul A

    2015-10-01

    A key component for spray decision-making in IPM programmes is the establishment of economic injury levels (EILs) and economic thresholds (ETs). We aimed to establish an EIL for the redlegged earth mite (Halotydeus destructor Tucker) on canola. Complex interactions between mite numbers, feeding damage and plant recovery were found, highlighting the challenges in linking H. destructor numbers to yield. A guide of 10 mites plant(-1) was established at the first-true-leaf stage; however, simple relationships were not evident at other crop development stages, making it difficult to establish reliable EILs based on mite number. Yield was, however, strongly associated with plant damage and plant densities, reflecting the impact of mite feeding damage and indicating a plant-based alternative for establishing thresholds for H. destructor. Drawing on data from multiple field trials, we show that plant densities below 30-40 plants m(-2) could be used as a proxy for mite damage when reliable estimates of mite densities are not possible. This plant-based threshold provides a practical tool that avoids the difficulties of accurately estimating mite densities. The approach may be applicable to other situations where production conditions are unpredictable and interactions between pests and plant hosts are complex. © 2015 Society of Chemical Industry.

  16. White matter damage impairs access to consciousness in multiple sclerosis.

    Science.gov (United States)

    Reuter, Françoise; Del Cul, Antoine; Malikova, Irina; Naccache, Lionel; Confort-Gouny, Sylviane; Cohen, Laurent; Cherif, André Ali; Cozzone, Patrick J; Pelletier, Jean; Ranjeva, Jean-Philippe; Dehaene, Stanislas; Audoin, Bertrand

    2009-01-15

    Global neuronal workspace theory predicts that damage to long-distance white matter (WM) tracts should impair access to consciousness during the perception of brief stimuli. To address this issue, we studied visual backward masking in 18 patients at the very first clinical stage of multiple sclerosis (MS), a neurological disease characterized by extensive WM damage, and in 18 matched healthy subjects. In our masking paradigm, the visibility of a digit stimulus increases non-linearly as a function of the interval duration between this target and a subsequent mask. In order to characterize quantitatively, for each subject, the transition between non-conscious and conscious perception of the stimulus, we used non-linear regression to fit a sigmoid curve to objective performance and subjective visibility reports as a function of target-mask delay. The delay corresponding to the inflexion point of the sigmoid, where visibility suddenly increases, was termed the "non-linear transition threshold" and used as a summary measure of masking efficiency. Objective and subjective non-linear transition thresholds were highly correlated across subjects in both groups, and were higher in patients compared to controls. In patients, variations in the non-linear transition threshold were inversely correlated to the Magnetization transfer ratio (MTR) values inside the right dorsolateral prefrontal WM, the right occipito-frontal fasciculus and the left cerebellum. This study provides clinical evidence of a relationship between impairments of conscious access and integrity of large WM bundles, particularly involving prefrontal cortex, as predicted by global neuronal workspace theory.

  17. Testing electrode suitability for field stimulation of high-threshold biological preparations

    Directory of Open Access Journals (Sweden)

    Hugo Fernando Maia Milan

    Full Text Available IntroductionA problem posed by electrical field (E stimulation of biological preparations with high excitation threshold is that the E intensity required for excitation is likely to induce water electrolysis at the electrode surface, which can alter the extracellular medium and cause deleterious effects on the cells. In this study, different electrode materials and geometries were tested aiming at identifying electrode configurations that could transduce the E intensity required for exciting ventricular cardiomyocytes isolated from neonatal rats (threshold E ~30 V/cm without causing water electrolysis.MethodsWire and plate electrodes made of platinum, stainless steel and nickel/chrome alloy were used. The effect of blasting the electrode surface with sand and NaHCO3 solution was also tested. Electrodes were inserted into a cell perfusion chamber containing the saline solution routinely used for physiological experiments. During E application for 5 min, the electrode surface and its surroundings were examined at high magnification for the presence of microbubbles, which indicates the occurrence of water electrolysis. The greatest E intensity applied that failed to generate microbubbles (En was estimated.ResultsWhile nickel/chrome and stainless steel electrodes resulted in low En values, the best performance was observed for sandblasted platinum wire (2 mm diameter and plate (25 mm x 5 mm; 0.1 mm thickness electrodes, for which Enwas ≥40 V/cm.ConclusionThese electrode configurations are suitable for effective and safe stimulation of isolated neonatal cardiomyocytes.

  18. The Caenorhabditis elegans interneuron ALA is (also) a high-threshold mechanosensor.

    Science.gov (United States)

    Sanders, Jarred; Nagy, Stanislav; Fetterman, Graham; Wright, Charles; Treinin, Millet; Biron, David

    2013-12-17

    To survive dynamic environments, it is essential for all animals to appropriately modulate their behavior in response to various stimulus intensities. For instance, the nematode Caenorhabditis elegans suppresses the rate of egg-laying in response to intense mechanical stimuli, in a manner dependent on the mechanosensory neurons FLP and PVD. We have found that the unilaterally placed single interneuron ALA acted as a high-threshold mechanosensor, and that it was required for this protective behavioral response. ALA was required for the inhibition of egg-laying in response to a strong (picking-like) mechanical stimulus, characteristic of routine handling of the animals. Moreover, ALA did not respond physiologically to less intense touch stimuli, but exhibited distinct physiological responses to anterior and posterior picking-like touch, suggesting that it could distinguish between spatially separated stimuli. These responses required neither neurotransmitter nor neuropeptide release from potential upstream neurons. In contrast, the long, bilaterally symmetric processes of ALA itself were required for producing its physiological responses; when they were severed, responses to stimuli administered between the cut and the cell body were unaffected, while responses to stimuli administered posterior to the cut were abolished. C. elegans neurons are typically classified into three major groups: sensory neurons with specialized sensory dendrites, interneurons, and motoneurons with neuromuscular junctions. Our findings suggest that ALA can autonomously sense intense touch and is thus a dual-function neuron, i.e., an interneuron as well as a novel high-threshold mechanosensor.

  19. Aging, Loss-of-Coolant Accident (LOCA), and high potential testing of damaged cables

    International Nuclear Information System (INIS)

    Vigil, R.A.; Jacobus, M.J.

    1994-04-01

    Experiments were conducted to assess the effects of high potential testing of cables and to assess the survivability of aged and damaged cables under Loss-of-Coolant Accident (LOCA) conditions. High potential testing at 240 Vdc/mil on undamaged cables suggested that no damage was incurred on the selected virgin cables. During aging and LOCA testing, Okonite ethylene propylene rubber (EPR) cables with a bonded jacket experienced unexpected failures. The failures appear to be primarily related to the level of thermal aging and the presence of a bonded jacket that ages more rapidly than the insulation. For Brand Rex crosslinked polyolefin (XLPO) cables, the results suggest that 7 mils of insulation remaining should give the cables a high probability of surviving accident exposure following aging. The voltage necessary to detect when 7 mils of insulation remain on unaged Brand Rex cables is approximately 35 kVdc. This voltage level would almost certainly be unacceptable to a utility for use as a damage assessment tool. However, additional tests indicated that a 35 kvdc voltage application would not damage virgin Brand Rex cables when tested in water. Although two damaged Rockbestos silicone rubber cables also failed during the accident test, no correlation between failures and level of damage was apparent

  20. Laser damage studies on MgF2 thin films

    International Nuclear Information System (INIS)

    Protopapa, Maria Lucia; De Tomasi, Ferdinando; Perrone, Maria Rita; Piegari, Angela; Masetti, Enrico; Ristau, Detlev; Quesnel, Etienne; Duparre, Angela

    2001-01-01

    The results of laser damage studies performed at 248 nm (KrF excimer laser) on MgF 2 thin films deposited by different techniques (electron-beam evaporation, thermal boat evaporation, and ion-beam sputtering) on fused silica and CaF 2 substrates are presented. We find that the films deposited on CaF 2 substrates by the electron-beam evaporation technique present the highest damage threshold fluence (9 J/cm2). The photoacoustic (PA) beam deflection technique was employed, in addition to microscopical inspection, to determine laser damage fluences. We confirm, by scanning electron microscopy analysis of the damaged spots, the capability of the PA technique to provide information on the mechanisms leading to damage. The dependence of both laser damage fluence and damage morphology on the film deposition technique, as well as on the film substrate, is discussed

  1. Relationship Between Unusual High-Temperature Fatigue Crack Growth Threshold Behavior in Superalloys and Sudden Failure Mode Transitions

    Science.gov (United States)

    Telesman, J.; Smith, T. M.; Gabb, T. P.; Ring, A. J.

    2017-01-01

    An investigation of high temperature cyclic fatigue crack growth (FCG) threshold behavior of two advanced nickel disk alloys was conducted. The focus of the study was the unusual crossover effect in the near-threshold region of these type of alloys where conditions which produce higher crack growth rates in the Paris regime, produce higher resistance to crack growth in the near threshold regime. It was shown that this crossover effect is associated with a sudden change in the fatigue failure mode from a predominant transgranular mode in the Paris regime to fully intergranular mode in the threshold fatigue crack growth region. This type of a sudden change in the fracture mechanisms has not been previously reported and is surprising considering that intergranular failure is typically associated with faster crack growth rates and not the slow FCG rates of the near-threshold regime. By characterizing this behavior as a function of test temperature, environment and cyclic frequency, it was determined that both the crossover effect and the onset of intergranular failure are caused by environmentally driven mechanisms which have not as yet been fully identified. A plausible explanation for the observed behavior is proposed.

  2. High-resolution tide projections reveal extinction threshold in response to sea-level rise.

    Science.gov (United States)

    Field, Christopher R; Bayard, Trina S; Gjerdrum, Carina; Hill, Jason M; Meiman, Susan; Elphick, Chris S

    2017-05-01

    Sea-level rise will affect coastal species worldwide, but models that aim to predict these effects are typically based on simple measures of sea level that do not capture its inherent complexity, especially variation over timescales shorter than 1 year. Coastal species might be most affected, however, by floods that exceed a critical threshold. The frequency and duration of such floods may be more important to population dynamics than mean measures of sea level. In particular, the potential for changes in the frequency and duration of flooding events to result in nonlinear population responses or biological thresholds merits further research, but may require that models incorporate greater resolution in sea level than is typically used. We created population simulations for a threatened songbird, the saltmarsh sparrow (Ammodramus caudacutus), in a region where sea level is predictable with high accuracy and precision. We show that incorporating the timing of semidiurnal high tide events throughout the breeding season, including how this timing is affected by mean sea-level rise, predicts a reproductive threshold that is likely to cause a rapid demographic shift. This shift is likely to threaten the persistence of saltmarsh sparrows beyond 2060 and could cause extinction as soon as 2035. Neither extinction date nor the population trajectory was sensitive to the emissions scenarios underlying sea-level projections, as most of the population decline occurred before scenarios diverge. Our results suggest that the variation and complexity of climate-driven variables could be important for understanding the potential responses of coastal species to sea-level rise, especially for species that rely on coastal areas for reproduction. © 2016 John Wiley & Sons Ltd.

  3. A Time-Domain Structural Damage Detection Method Based on Improved Multiparticle Swarm Coevolution Optimization Algorithm

    Directory of Open Access Journals (Sweden)

    Shao-Fei Jiang

    2014-01-01

    Full Text Available Optimization techniques have been applied to structural health monitoring and damage detection of civil infrastructures for two decades. The standard particle swarm optimization (PSO is easy to fall into the local optimum and such deficiency also exists in the multiparticle swarm coevolution optimization (MPSCO. This paper presents an improved MPSCO algorithm (IMPSCO firstly and then integrates it with Newmark’s algorithm to localize and quantify the structural damage by using the damage threshold proposed. To validate the proposed method, a numerical simulation and an experimental study of a seven-story steel frame were employed finally, and a comparison was made between the proposed method and the genetic algorithm (GA. The results show threefold: (1 the proposed method not only is capable of localization and quantification of damage, but also has good noise-tolerance; (2 the damage location can be accurately detected using the damage threshold proposed in this paper; and (3 compared with the GA, the IMPSCO algorithm is more efficient and accurate for damage detection problems in general. This implies that the proposed method is applicable and effective in the community of damage detection and structural health monitoring.

  4. Enhanced thermomechanical stability on laser-induced damage by functionally graded layers in quasi-rugate filters

    Science.gov (United States)

    Pu, Yunti; Ma, Ping; Lv, Liang; Zhang, Mingxiao; Lu, Zhongwen; Qiao, Zhao; Qiu, Fuming

    2018-05-01

    Ta2O5-SiO2 quasi-rugate filters with a reasonable optimization of rugate notch filter design were prepared by ion-beam sputtering. The optical properties and laser-induced damage threshold are studied. Compared with the spectrum of HL-stacks, the spectrum of quasi-rugate filters have weaker second harmonic peaks and narrower stopbands. According to the effect of functionally graded layers (FGLs), 1-on-1 and S-on-1 Laser induced damage threshold (LIDT) of quasi-rugate filters are about 22% and 50% higher than those of HL stacks, respectively. Through the analysis of the damage morphologies, laser-induced damage of films under nanosecond multi-pulse are dominated by a combination of thermal shock stress and thermomechanical instability due to nodules. Compared with catastrophic damages, the damage sits of quasi-rugate filters are developed in a moderate way. The damage growth behavior of defect-induced damage sites have been effectively restrained by the structure of FGLs. Generally, FGLs are used to reduce thermal stress by the similar thermal-expansion coefficients of neighboring layers and solve the problems such as instability and cracking raised by the interface discontinuity of nodular boundaries, respectively.

  5. NRC Information Notice No. 92-01: Cable damage caused by inadequate cable installation procedures and controls

    International Nuclear Information System (INIS)

    Rossi, C.E.

    1993-01-01

    In June 1989, the Tennessee Valley Authority (TVA) removed the cables from a conduit in the reactor protection system of the Watts Bar Nuclear Plant, Unit 2, to inspect for damage. TVA selected this conduit in response to an employee's concern that a welding arc that struck the conduit in response to an employee's concern that a welding arc that struck the conduit during construction may have damaged cables in the conduit. When the cables were removed, TVA found significant damage in the insulation of some cables. This damage was not attributed to heat generated by the alleged welding arc. The damage was principally attributed to the pulling stresses exerted during the initial installation of the cables. Some of the cables had insulation removed down to the conductors. To assess the extent of cable damage and determine the scope of its investigation, TVA removed more cables from conduits that constituted the most difficult pulls (worst case) and found varying degrees of damage that it attributed to pulling stresses. To fill a conduit at Watts Bar, personnel used pull cords to pull more cables through the conduits over the top of existing cables. This practice is called ''pull-by.'' This practice can cause damage to the existing cables from the sawing action of the pull cords and the friction of cables as they are pulled over existing cables. TVA instituted programs to assess the adequacy of cable installation at all its nuclear facilities and take appropriate corrective actions. At Watts Bar, TVA replaced cables in conduits which exceeded a calculated threshold value of side wall bearing pressure (SWBP) and performed a high-potential (hi-pot) tests on a number of other cables in conduits with SWBP below the calculated threshold value

  6. Ab initio and Molecular Dynamic models of displacement damage in crystalline and turbostratic graphite

    Science.gov (United States)

    McKenna, Alice

    One of the functions of graphite is as a moderator in several nuclear reactor designs, including the Advanced Gas-cooled Reactor (AGR). In the reactor graphite is used to thermalise the neutrons produced in the fission reaction thus allowing a self-sustained reaction to occur. The graphite blocks, acting as the moderator, are constantly irradiated and consequently suffer damage. This thesis examines the types of damage caused using molecular dynamic (MD) simulations and ab intio calculations. Neutron damage starts with a primary knock-on atom (PKA), which is travelling so fast that it creates damage through electronic and thermal excitation (this is addressed with thermal spike simulations). When the PKA has lost energy the subsequent cascade is based on ballistic atomic displacement. These two types of simulations were performed on single crystal graphite and other carbon structures such as diamond and amorphous carbon as a comparison. The thermal spike in single crystal graphite produced results which varied from no defects to a small number of permanent defects in the structure. It is only at the high energy range that more damage is seen but these energies are less likely to occur in the nuclear reactor. The thermal spike does not create damage but it is possible that it can heal damaged sections of the graphite, which can be demonstrated with the motion of the defects when a thermal spike is applied. The cascade simulations create more damage than the thermal spike even though less energy is applied to the system. A new damage function is found with a threshold region that varies with the square root of energy in excess of the energy threshold. This is further broken down in to contributions from primary and subsequent knock-on atoms. The threshold displacement energy (TDE) is found to be Ed=25eV at 300K. In both these types of simulation graphite acts very differently to the other carbon structures. There are two types of polycrystalline graphite structures

  7. Application of a handheld Pressure Application Measurement device for the characterisation of mechanical nociceptive thresholds in intact pig tails

    DEFF Research Database (Denmark)

    Di Giminiani, Pierpaolo; Sandercock, Dale A.; Malcolm, Emma M.

    2016-01-01

    The assessment of nociceptive thresholds is employed in animals and humans to evaluate changes in sensitivity potentially arising from tissue damage. Its application on the intact pig tail might represent a suitable method to assess changes in nociceptive thresholds arising from tail injury...... to the body was observed (P knowledge, no other...... nociceptive threshold in pig tails. This methodological approach is possibly suitable for assessing changes in tail stump MNTs after tail injury caused by tail docking and biting....

  8. Techniques for preventing damage to high power laser components

    International Nuclear Information System (INIS)

    Stowers, I.F.; Patton, H.G.; Jones, W.A.; Wentworth, D.E.

    1977-09-01

    Techniques for preventing damage to components of the LASL Shiva high power laser system were briefly presented. Optical element damage in the disk amplifier from the combined fluence of the primary laser beam and the Xenon flash lamps that pump the cavity was discussed. Assembly and cleaning techniques were described which have improved optical element life by minimizing particulate and optically absorbing film contamination on assembled amplifier structures. A Class-100 vertical flaw clean room used for assembly and inspection of laser components was also described. The life of a disk amplifier was extended from less than 50 shots to 500 shots through application of these assembly and cleaning techniques

  9. Systematic variation of threshold reaction rates in EBR-II

    International Nuclear Information System (INIS)

    Lippincott, E.P.; Combs, B.L.; Davis, A.I.

    1976-01-01

    Characterization of neutron flux, fluence, and spectra in fast reactor irradiation environments is presently being carried out at HEDL utilizing the multiple foil technique. These fluences and spectra are then used to correlate damage effects data to produce damage functions or equations to predict materials effects under future irradiation conditions. The neutron flux and spectrum, then, act as a transfer function to relate present observations to future effects in the same or different environments and thus consistent fluence evaluations are of utmost importance. As part of a continuing program to establish the data base to meet consistency requirements, a systematic correlation of data from a recent dosimetry test in EBR-II is being made. The paper presents preliminary results of some of these correlations involving threshold reactions

  10. Lowered threshold energy for femtosecond laser induced optical breakdown in a water based eye model by aberration correction with adaptive optics.

    Science.gov (United States)

    Hansen, Anja; Géneaux, Romain; Günther, Axel; Krüger, Alexander; Ripken, Tammo

    2013-06-01

    In femtosecond laser ophthalmic surgery tissue dissection is achieved by photodisruption based on laser induced optical breakdown. In order to minimize collateral damage to the eye laser surgery systems should be optimized towards the lowest possible energy threshold for photodisruption. However, optical aberrations of the eye and the laser system distort the irradiance distribution from an ideal profile which causes a rise in breakdown threshold energy even if great care is taken to minimize the aberrations of the system during design and alignment. In this study we used a water chamber with an achromatic focusing lens and a scattering sample as eye model and determined breakdown threshold in single pulse plasma transmission loss measurements. Due to aberrations, the precise lower limit for breakdown threshold irradiance in water is still unknown. Here we show that the threshold energy can be substantially reduced when using adaptive optics to improve the irradiance distribution by spatial beam shaping. We found that for initial aberrations with a root-mean-square wave front error of only one third of the wavelength the threshold energy can still be reduced by a factor of three if the aberrations are corrected to the diffraction limit by adaptive optics. The transmitted pulse energy is reduced by 17% at twice the threshold. Furthermore, the gas bubble motions after breakdown for pulse trains at 5 kilohertz repetition rate show a more transverse direction in the corrected case compared to the more spherical distribution without correction. Our results demonstrate how both applied and transmitted pulse energy could be reduced during ophthalmic surgery when correcting for aberrations. As a consequence, the risk of retinal damage by transmitted energy and the extent of collateral damage to the focal volume could be minimized accordingly when using adaptive optics in fs-laser surgery.

  11. TID and Displacement Damage Effects in Vertical and Lateral Power MOSFETs for Integrated DC-DC Converters

    CERN Document Server

    Faccio, F; Michelis, S; Faccio, Federico; Fuentes, C; Allongue, B; Sorge, R; Orlandi, S

    2010-01-01

    TID and displacement damage effects are studied for vertical and lateral power MOSFETs in five different technologies in view of the development of radiation-tolerant fully integrated DC-DC converters. Investigation is pushed to the very high level of radiation expected for an upgrade to the LHC experiments. TID induces threshold voltage shifts and, in n-channel transistors, source-drain leakage currents. Wide variability in the magnitude of these effects is observed. Displacement damage increases the on-resistance of both vertical and lateral high-voltage transistors. In the latter case, degradation at high particle fluence might lead to a distortion of the output characteristics curve. HBD techniques to limit or eliminate the radiation-induced leakage currents are successfully applied to these high-voltage transistors, but have to be used carefully to avoid consequences on the breakdown voltage.

  12. Experimental research for γ-ray interference threshold effect of high electromagnetic pulse sensor

    International Nuclear Information System (INIS)

    Meng Cui; Chen Xiangyue; Nie Xin; Xiang Hui; Guo Xiaoqiang; Mao Congguang; Cheng Jianping; Ni Jianping

    2007-01-01

    The high electromagnetic pulse (EMP) sensor using optical-fiber to transmit signal can restrain electromagnetic interference. The Compton electrons scattered by γ-ray irradiated from nuclear explosion or nuclear explosion simulator can generate high EMP, γ-ray can penetrate the shielding box and irradiate the integrated circuit directly. The γ-ray irradiation effect includes interference, latch up and burn out, these will make the measurement result unbelievable. In this paper, the experimental method researching the γ-ray irradiation effect of high electromagnetic pulse sensor on Qiangguang-I accelerator is introduced. The γ-ray dose rate interference threshold is 2 x 10 6 Gy/s. (authors)

  13. A numerical study of threshold states

    International Nuclear Information System (INIS)

    Ata, M.S.; Grama, C.; Grama, N.; Hategan, C.

    1979-01-01

    There are some experimental evidences of charged particle threshold states. On the statistical background of levels, some simple structures were observed in excitation spectrum. They occur near the coulombian threshold and have a large reduced width for the decay in the threshold channel. These states were identified as charged cluster threshold states. Such threshold states were observed in sup(15,16,17,18)O, sup(18,19)F, sup(19,20)Ne, sup(24)Mg, sup(32)S. The types of clusters involved were d, t, 3 He, α and even 12 C. They were observed in heavy-ions transfer reactions in the residual nucleus as strong excited levels. The charged particle threshold states occur as simple structures at high excitation energy. They could be interesting both from nuclear structure as well as nuclear reaction mechanism point of view. They could be excited as simple structures both in compound and residual nucleus. (author)

  14. Laser-induced damage of materials in bulk, thin-film, and liquid forms

    International Nuclear Information System (INIS)

    Natoli, Jean-Yves; Gallais, Laurent; Akhouayri, Hassan; Amra, Claude

    2002-01-01

    Accurate threshold curves of laser-induced damage (7-ns single shot at 1.064 μm) are measured in bulk and at the surfaces of optical components such as substrates, thin films, multilayers, and liquids. The shapes and the slopes of the curves are related to the spot size and to the densities of the nanodefects that are responsible for damage. First, these densities are reported for bulk substrates. In surfaces and films the recorded extrinsic and intrinsic threshold curves permit the discrimination of the effects of microdefects and nanodefects. In all cases the density of nanocenters is extracted by means of a phenomenological approach. Then we test liquids and mixtures of liquids with controlled defect densities. The results emphasize the agreement between measurement and prediction and demonstrate the validity of the presence of different kinds of nanocenter as the precursors of laser damage

  15. Damage production by fast electrons in dilute alloys of vanadium, niobium and molybdenum

    International Nuclear Information System (INIS)

    Jung, P.

    1975-01-01

    Vanadium, niobium and molybdenum samples containing about 300 ppm of zirconium were irradiated at helium temperature with electrons of energies between 0,6 and 3.1 MeV. The measured damage rates were analysed in terms of minimum threshold energy, damage function and resistivity per unit concentration of Frenkel pairs. For the minimum threshold energy T(Sub)d, values of 25+-2 eV (V) 28+-2 e V(Nb) and 34+-2 e V(Mo) were obtained. Pronounced differences between the displacement functions of molybdenum and that of niobium and vanadium are found which are explained by different stability of the defects during the irradiation at helium temperature

  16. Landslide triggering thresholds for Switzerland based on a new gridded precipitation dataset

    Science.gov (United States)

    Leonarduzzi, Elena; Molnar, Peter; McArdell, Brian W.

    2017-04-01

    In Switzerland floods are responsible for most of the damage caused by rainfall-triggered natural hazards (89%), followed by landslides (6%, ca. 520 M Euros) as reported in Hilker et al. (2009) for the period 1972-2007. The prediction of landslide occurrence is particularly challenging because of their wide distribution in space and the complex interdependence of predisposing and triggering factors. The overall goal of our research is to develop an Early Warning System for landsliding in Switzerland based on hydrological modelling and rainfall forecasts. In order to achieve this, we first analyzed rainfall triggering thresholds for landslides from a new gridded daily precipitation dataset (RhiresD, MeteoSwiss) for Switzerland combined with landslide events recorded in the Swiss Damage Database (Hilker et al.,2009). The high-resolution gridded precipitation dataset allows us to collocate rainfall and landslides accurately in space, which is an advantage over many previous studies. Each of the 2272 landslides in the database in the period 1972-2012 was assigned to the corresponding 2x2 km precipitation cell. For each of these cells, precipitation events were defined as series of consecutive rainy days and the following event parameters were computed: duration (day), maximum and mean daily intensity (mm/day), total rainfall depth (mm) and maximum daily intensity divided by Mean Daily Precipitation (MDP). The events were classified as triggering or non-triggering depending on whether a landslide was recorded in the cell during the event. This classification of observations was compared to predictions based on a threshold for each of the parameters. The predictive power of each parameter and the best threshold value were quantified by ROC analysis and statistics such as AUC and the True Skill Statistic (TSS). Event parameters based on rainfall intensity were found to have similarly high predictive power (TSS=0.54-0.59, AUC=0.85-0.86), while rainfall duration had a

  17. In which metals are high electronic excitations able to create damage?

    International Nuclear Information System (INIS)

    Legrand, P.; Dunlop, A.; Lesueur, D.; Lorenzelli, N.; Morillo, J.; Bouffard, S.

    1992-01-01

    Since a few years a certain number of results have shown that high energy deposition through electronic excitation can lead to damage creation in metallic targets. In order to test which is the right parameter favouring damage creation (high d-electrons density favouring electron-phonon coupling, various electrical conductivities, existence of different displacive phase transformations . . .) chosen metallic targets (Zr, Co, Ti, Ag, Pd, Pt, W, Ni) were irradiated on the french accelerator GANIL in Caen, at cryogenic temperatures with GeV-ions (Pb, O). In situ electrical resistance variation measurements at low temperature were achieved, followed by isochronal annealing of defects and post-X-ray observations at room temperature. This study shows that a very strong enhancement of the damage production occurs only in Zr, Ti and Co which present different allotropic phases and in particular a displacive transformation associated with soft modes in the phonon spectrum. The structure of stage I recovery of all the samples depends on the electronic stopping power

  18. High Resolution SAR Imaging Employing Geometric Features for Extracting Seismic Damage of Buildings

    Science.gov (United States)

    Cui, L. P.; Wang, X. P.; Dou, A. X.; Ding, X.

    2018-04-01

    Synthetic Aperture Radar (SAR) image is relatively easy to acquire but difficult for interpretation. This paper probes how to identify seismic damage of building using geometric features of SAR. The SAR imaging geometric features of buildings, such as the high intensity layover, bright line induced by double bounce backscattering and dark shadow is analysed, and show obvious differences texture features of homogeneity, similarity and entropy in combinatorial imaging geometric regions between the un-collapsed and collapsed buildings in airborne SAR images acquired in Yushu city damaged by 2010 Ms7.1 Yushu, Qinghai, China earthquake, which implicates a potential capability to discriminate collapsed and un-collapsed buildings from SAR image. Study also shows that the proportion of highlight (layover & bright line) area (HA) is related to the seismic damage degree, thus a SAR image damage index (SARDI), which related to the ratio of HA to the building occupation are of building in a street block (SA), is proposed. While HA is identified through feature extraction with high-pass and low-pass filtering of SAR image in frequency domain. A partial region with 58 natural street blocks in the Yushu City are selected as study area. Then according to the above method, HA is extracted, SARDI is then calculated and further classified into 3 classes. The results show effective through validation check with seismic damage classes interpreted artificially from post-earthquake airborne high resolution optical image, which shows total classification accuracy 89.3 %, Kappa coefficient 0.79 and identical to the practical seismic damage distribution. The results are also compared and discussed with the building damage identified from SAR image available by other authors.

  19. Analysis of Ricefield Land Damage in Denpasar City, Bali, Indonesia

    Science.gov (United States)

    Suyarto, R.; Wiyanti; Dibia, I. N.

    2018-02-01

    Soil as a natural resource, living area, environmental media, and factors of production including biomass production that supports human life and other living beings must be preserved, on the other hand, uncontrolled biomass production activities can cause soil damage, ultimately can threaten the survival of humans and other living things. Therefore, in order to control soil damage, first must inventories the soil condition data and its damage which then visualised in soil damage potential and soil damage status. The activities of the study are the preparation of a map of the initial soil conditions and the delineation of potentially land degradation distribution. Mapping results are used as work maps for verification on the field to take soil samples and create soil damage status. In general, Denpasar City have soil damage potential at very low, low until medium rate. Soil damage status in Denpasar City generally is low damage of bulk volume, total porosity, soil permeability and electrolyte conductivity which beyond limitation thresholds.

  20. Two scale damage model and related numerical issues for thermo-mechanical high cycle fatigue

    International Nuclear Information System (INIS)

    Desmorat, R.; Kane, A.; Seyedi, M.; Sermage, J.P.

    2007-01-01

    On the idea that fatigue damage is localized at the microscopic scale, a scale smaller than the mesoscopic one of the Representative Volume Element (RVE), a three-dimensional two scale damage model has been proposed for High Cycle Fatigue applications. It is extended here to aniso-thermal cases and then to thermo-mechanical fatigue. The modeling consists in the micro-mechanics analysis of a weak micro-inclusion subjected to plasticity and damage embedded in an elastic meso-element (the RVE of continuum mechanics). The consideration of plasticity coupled with damage equations at micro-scale, altogether with Eshelby-Kroner localization law, allows to compute the value of microscopic damage up to failure for any kind of loading, 1D or 3D, cyclic or random, isothermal or aniso-thermal, mechanical, thermal or thermo-mechanical. A robust numerical scheme is proposed in order to make the computations fast. A post-processor for damage and fatigue (DAMAGE-2005) has been developed. It applies to complex thermo-mechanical loadings. Examples of the representation by the two scale damage model of physical phenomena related to High Cycle Fatigue are given such as the mean stress effect, the non-linear accumulation of damage. Examples of thermal and thermo-mechanical fatigue as well as complex applications on real size testing structure subjected to thermo-mechanical fatigue are detailed. (authors)

  1. Acoustic Emission and Damage Characteristics of Granite Subjected to High Temperature

    Directory of Open Access Journals (Sweden)

    X. L. Xu

    2018-01-01

    Full Text Available Acoustic emission (AE signals can be detected from rocks under the effect of temperature and loading, which can be used to reflect rock damage evolution process and predict rock fracture. In this paper, uniaxial compression tests of granite at high temperatures from 25°C to 1000°C were carried out, and AE signals were monitored simultaneously. The results indicated that AE ring count rate shows the law of “interval burst” and “relatively calm,” which can be explained from the energy point of view. From 25°C to 1000°C, the rock failure mode changes from single splitting failure to multisplitting failure, and then to incomplete shear failure, ideal shear failure, and double shear failure, until complete integral failure. Thermal damage (DT defined by the elastic modulus shows logistic increase with the rise of temperature. Mechanical damage (DM derived by the AE ring count rate can be divided into initial stage, stable stage, accelerated stage, and destructive stage. Total damage (D increases with the rise of strain, which is corresponding to the stress-strain curve at various temperatures. Using AE data, we can further analyze the mechanism of deformation and fracture of rock, which helps to gather useful data for predicting rock stability at high temperatures.

  2. Early-state damage detection, characterization, and evolution using high-resolution computed tomography

    Science.gov (United States)

    Grandin, Robert John

    Safely using materials in high performance applications requires adequately understanding the mechanisms which control the nucleation and evolution of damage. Most of a material's operational life is spent in a state with noncritical damage, and, for example in metals only a small portion of its life falls within the classical Paris Law regime of crack growth. Developing proper structural health and prognosis models requires understanding the behavior of damage in these early stages within the material's life, and this early-stage damage occurs on length scales at which the material may be considered "granular'' in the sense that the discrete regions which comprise the whole are large enough to require special consideration. Material performance depends upon the characteristics of the granules themselves as well as the interfaces between granules. As a result, properly studying early-stage damage in complex, granular materials requires a means to characterize changes in the granules and interfaces. The granular-scale can range from tenths of microns in ceramics, to single microns in fiber-reinforced composites, to tens of millimeters in concrete. The difficulty of direct-study is often overcome by exhaustive testing of macro-scale damage caused by gross material loads and abuse. Such testing, for example optical or electron microscopy, destructive and further, is costly when used to study the evolution of damage within a material and often limits the study to a few snapshots. New developments in high-resolution computed tomography (HRCT) provide the necessary spatial resolution to directly image the granule length-scale of many materials. Successful application of HRCT with fiber-reinforced composites, however, requires extending the HRCT performance beyond current limits. This dissertation will discuss improvements made in the field of CT reconstruction which enable resolutions to be pushed to the point of being able to image the fiber-scale damage structures and

  3. Grinding damage assessment on four high-strength ceramics.

    Science.gov (United States)

    Canneto, Jean-Jacques; Cattani-Lorente, Maria; Durual, Stéphane; Wiskott, Anselm H W; Scherrer, Susanne S

    2016-02-01

    The purpose of this study was to assess surface and subsurface damage on 4 CAD-CAM high-strength ceramics after grinding with diamond disks of 75 μm, 54 μm and 18 μm and to estimate strength losses based on damage crack sizes. The materials tested were: 3Y-TZP (Lava), dense Al2O3 (In-Ceram AL), alumina glass-infiltrated (In-Ceram ALUMINA) and alumina-zirconia glass-infiltrated (In-Ceram ZIRCONIA). Rectangular specimens with 2 mirror polished orthogonal sides were bonded pairwise together prior to degrading the top polished surface with diamond disks of either 75 μm, 54 μm or 18 μm. The induced chip damage was evaluated on the bonded interface using SEM for chip depth measurements. Fracture mechanics were used to estimate fracture stresses based on average and maximum chip depths considering these as critical flaws subjected to tension and to calculate possible losses in strength compared to manufacturer's data. 3Y-TZP was hardly affected by grinding chip damage viewed on the bonded interface. Average chip depths were of 12.7±5.2 μm when grinding with 75 μm diamond inducing an estimated loss of 12% in strength compared to manufacturer's reported flexural strength values of 1100 MPa. Dense alumina showed elongated chip cracks and was suffering damage of an average chip depth of 48.2±16.3 μm after 75 μm grinding, representing an estimated loss in strength of 49%. Grinding with 54 μm was creating chips of 32.2±9.1 μm in average, representing a loss in strength of 23%. Alumina glass-infiltrated ceramic was exposed to chipping after 75 μm (mean chip size=62.4±19.3 μm) and 54 μm grinding (mean chip size=42.8±16.6 μm), with respectively 38% and 25% estimated loss in strength. Alumina-zirconia glass-infiltrated ceramic was mainly affected by 75 μm grinding damage with a chip average size of 56.8±15.1 μm, representing an estimated loss in strength of 34%. All four ceramics were not exposed to critical chipping at 18 μm diamond grinding. Reshaping a

  4. Dose-rate-dependent damage of cerium dioxide in the scanning transmission electron microscope.

    Science.gov (United States)

    Johnston-Peck, Aaron C; DuChene, Joseph S; Roberts, Alan D; Wei, Wei David; Herzing, Andrew A

    2016-11-01

    Beam damage caused by energetic electrons in the transmission electron microscope is a fundamental constraint limiting the collection of artifact-free information. Through understanding the influence of the electron beam, experimental routines may be adjusted to improve the data collection process. Investigations of CeO 2 indicate that there is not a critical dose required for the accumulation of electron beam damage. Instead, measurements using annular dark field scanning transmission electron microscopy and electron energy loss spectroscopy demonstrate that the onset of measurable damage occurs when a critical dose rate is exceeded. The mechanism behind this phenomenon is that oxygen vacancies created by exposure to a 300keV electron beam are actively annihilated as the sample re-oxidizes in the microscope environment. As a result, only when the rate of vacancy creation exceeds the recovery rate will beam damage begin to accumulate. This observation suggests that dose-intensive experiments can be accomplished without disrupting the native structure of the sample when executed using dose rates below the appropriate threshold. Furthermore, the presence of an encapsulating carbonaceous layer inhibits processes that cause beam damage, markedly increasing the dose rate threshold for the accumulation of damage. Published by Elsevier B.V.

  5. A new qualitative acoustic emission parameter based on Shannon's entropy for damage monitoring

    Science.gov (United States)

    Chai, Mengyu; Zhang, Zaoxiao; Duan, Quan

    2018-02-01

    An important objective of acoustic emission (AE) non-destructive monitoring is to accurately identify approaching critical damage and to avoid premature failure by means of the evolutions of AE parameters. One major drawback of most parameters such as count and rise time is that they are strongly dependent on the threshold and other settings employed in AE data acquisition system. This may hinder the correct reflection of original waveform generated from AE sources and consequently bring difficulty for the accurate identification of the critical damage and early failure. In this investigation, a new qualitative AE parameter based on Shannon's entropy, i.e. AE entropy is proposed for damage monitoring. Since it derives from the uncertainty of amplitude distribution of each AE waveform, it is independent of the threshold and other time-driven parameters and can characterize the original micro-structural deformations. Fatigue crack growth test on CrMoV steel and three point bending test on a ductile material are conducted to validate the feasibility and effectiveness of the proposed parameter. The results show that the new parameter, compared to AE amplitude, is more effective in discriminating the different damage stages and identifying the critical damage.

  6. Extreme implanting in Si: A study of ion-induced damage at high temperature and high dose

    International Nuclear Information System (INIS)

    Holland, O.W.

    1994-01-01

    Ion-solid interactions near room temperature and below have been well studied in single-crystal Si. While this has led to a better understanding of the mechanisms responsible for nucleation and growth of lattice damage during irradiation, these studies have not, in general, been extended to high temperatures (e.g., >200 degrees C). This is the case despite the commercialization of ion beam technologies which utilize high-temperature processing, such as separation by implantation of oxygen (SIMOX). In this process, a silicon-on-insulator (SOI) material is produced by implanting a high dose of oxygen ions into a Si wafer to form a buried, stoichiometric oxide layer. Results will be presented of a study of damage accumulation during high-dose implantation of Si at elevated temperatures. In particular, O + -ions were used because of the potential impact of the results on the SIMOX technology. It will be shown that the nature of the damage accumulation at elevated temperatures is quite distinctive and portends the presence of a new mechanism, one which is only dominant under the extreme conditions encountered during ion beam synthesis (i.e., high temperature and high dose). This mechanism is discussed and shown to be quite general and not dependent on the chemical identity of the ions. Also, techniques for suppressing this mechanism by open-quotes defect engineeringclose quotes are discussed. Such techniques are technologically relevant because they offer the possibility of reducing the defect density of the SOI produced by SIMOX

  7. Near-threshold fatigue crack behaviour in EUROFER 97 at different temperatures

    Science.gov (United States)

    Aktaa, J.; Lerch, M.

    2006-07-01

    The fatigue crack behaviour in EUROFER 97 was investigated at room temperature (RT), 300, 500 and 550 °C for the assessment of cracks in first wall structures built from EUROFER 97 of future fusion reactors. For this purpose, fatigue crack growth tests were performed using CT specimens with two R-ratios, R = 0.1 and R = 0.5 ( R is the load ratio with R = Fmin/ Fmax where Fmin and Fmax are the minimum and maximum applied loads within a cycle, respectively). Hence, fatigue crack threshold, fatigue crack growth behaviour in the near-threshold range and their dependences on temperature and R-ratio were determined and described using an analytical formula. The fatigue crack threshold showed a monotonous dependence on temperature which is for R = 0.5 insignificantly small. The fatigue crack growth behaviour exhibited for R = 0.1 a non-monotonous dependence on temperature which is explained by the decrease of yield stress and the increase of creep damage with increasing temperature.

  8. Measurements and modeling for examination of magnitudes and thresholds and transitions of cellular radio-protective mechanisms

    International Nuclear Information System (INIS)

    Leonard, B.

    2007-01-01

    factor of 10 excess dose to connective tissue and organs. Finally, a method for measuring the changes in endogenic cell capabilities to carry-out increased radio-protective processes i.e. separate decreased direct damage (greater ROS scavenging) and the increased repair rates (increased damage recognition, increased damage site location, increased repair mobilization and finally increased repair of the actual damage). This method shows for low LET IDRE no decreased direct damage occurs and significant increased repair occurs. After the 'triggered' threshold and transition of IDRE protection against cell killing, a larger fraction of cell damage produces viable mutations. This suggests that the cells bio-chemically conclude it is senseless to provide protection against potentially mutations in the low dose rate region if all the cells are being killed. Conclusions: The BE does not cause the underground miners high Radon IDRE. Single Specific Energy nucleus hits at very low dose rates activate adaptive response protection of spontaneous neoplastic transformations from mammography X-rays. A dose and dose-rate coupling is modeled. A correlation between the 'triggering' of the transition of the radio-protection for the Hyper-radiosensitivity and dose induced radio-resistance effect (HRS/IRR) and the low LET 'inverse' dose-rate effect (IDRE) as if they are from same radioprotective mechanisms. Possible excess connective tissue and organs damage occurs from low LET IDRE in LDR Brachytherapy treatments with permanent implants.

  9. Radiation damage in molybdenum and tungsten in high neutron fluxes

    International Nuclear Information System (INIS)

    Veljkovic, S.; Milasin, N.

    1964-01-01

    The effects of radiation on molybdenum and tungsten in high neutron fluxes are presented. The changes induced, particularly defects with a high migration activation energy, are analyzed. The correlation of these changes with the basic concepts of radiation damage in solids is considered. An attempt is made to relate the defects studied with the changes in macroscopic properties (author)

  10. Radiation damage in molybdenum and tungsten in high neutron fluxes

    Energy Technology Data Exchange (ETDEWEB)

    Veljkovic, S; Milasin, N [Institute of Nuclear Sciences Boris Kidric, Department of Reactor Materials, Vinca, Beograd (Serbia and Montenegro)

    1964-04-15

    The effects of radiation on molybdenum and tungsten in high neutron fluxes are presented. The changes induced, particularly defects with a high migration activation energy, are analyzed. The correlation of these changes with the basic concepts of radiation damage in solids is considered. An attempt is made to relate the defects studied with the changes in macroscopic properties (author)

  11. Stochastic Threshold Exponential (TE) Model for Hematopoietic Tissue Reconstitution Deficit after Radiation Damage.

    Science.gov (United States)

    Scott, B R; Potter, C A

    2014-07-01

    Whole-body exposure to large radiation doses can cause severe loss of hematopoietic tissue cells and threaten life if the lost cells are not replaced in a timely manner through natural repopulation (a homeostatic mechanism). Repopulation to the baseline level N 0 is called reconstitution and a reconstitution deficit (repopulation shortfall) can occur in a dose-related and organ-specific manner. Scott et al. (2013) previously introduced a deterministic version of a threshold exponential (TE) model of tissue-reconstitution deficit at a given follow-up time that was applied to bone marrow and spleen cellularity (number of constituent cells) data obtained 6 weeks after whole-body gamma-ray exposure of female C.B-17 mice. In this paper a more realistic, stochastic version of the TE model is provided that allows radiation response to vary between different individuals. The Stochastic TE model is applied to post gamma-ray-exposure cellularity data previously reported and also to more limited X-ray cellularity data for whole-body irradiated female C.B-17 mice. Results indicate that the population average threshold for a tissue reconstitution deficit appears to be similar for bone marrow and spleen and for 320-kV-spectrum X-rays and Cs-137 gamma rays. This means that 320-kV spectrum X-rays could successfully be used in conducting such studies.

  12. Preservation of auditory brainstem response thresholds after cochleostomy and titanium microactuator implantation in the lateral wall of cat scala tympani.

    Science.gov (United States)

    Lesinski, S George; Prewitt, Jessica; Bray, Victor; Aravamudhan, Radhika; Bermeo Blanco, Oscar A; Farmer-Fedor, Brenda L; Ward, Jonette A

    2014-04-01

    The safety of implanting a titanium microactuator into the lateral wall of cat scala tympani was assessed by comparing preoperative and postoperative auditory brainstem response (ABR) thresholds for 1 to 3 months. The safety of directly stimulating cochlear perilymph with an implantable hearing system requires maintaining preoperative hearing levels. This cat study is an essential step in the development of the next generation of fully implantable hearing devices for humans. Following GLP surgical standards, a 1-mm cochleostomy was drilled into the lateral wall of the scala tympani, and a nonfunctioning titanium anchor/microactuator assembly was inserted in 8 cats. The scala media was damaged in the 1 cat. ABR thresholds with click and 4- and 8-kHz stimuli were measured preoperatively and compared with postoperative thresholds at 1, 2, and 3 months. Nonimplanted ear thresholds were also measured to establish statistical significance for threshold shifts (>28.4 dB). Two audiologists independently interpreted thresholds. Postoperatively, 7 cats implanted in the scala tympani demonstrated no significant ABR threshold shift for click stimulus; one shifted ABR thresholds to 4- and 8-kHz stimuli. The eighth cat, with surgical damage to the scala media, maintained stable click threshold but had a significant shift to 4- and 8-kHz stimuli. This cat study provides no evidence of worsening hearing thresholds after fenestration of the scala tympani and insertion of a titanium anchor/microactuator, provided there is no surgical trauma to the scala media and the implanted device is securely anchored in the cochleostomy. These 2 issues have been resolved in the development of a fully implantable hearing system for humans. The long-term hearing stability (combined with histologic studies) reaffirm that the microactuator is well tolerated by the cat cochlea.

  13. Limits for Beam Induced Damage: Reckless or too Cautious?

    CERN Document Server

    Bertarelli, A; Carra, F; Cerutti, F; Dallocchio, A; Mariani, N; Peroni, L; Scapin, M

    2011-01-01

    Accidental events implying direct beam impacts on collimators are of the utmost importance as they may lead to serious limitations of the overall LHC Performance. In order to assess damage threshold of components impacted by high energy density beams, entailing changes of phase and extreme pressures, state-of-the-art numerical simulation methods are required. In this paper, a review of the different dynamic response regimes induced by particle beams is given along with an indication of the most suited tools to treat each regime. Particular attention is paid to the most critical case, that of shock waves, for which standard Finite Element codes are totally unfit. A novel category of numerical tools, named Hydrocodes, has been adapted and used to analyse the consequences of an asynchronous beam abort on Phase 1 Tertiary Collimators (TCT). A number of simulations has been carried out with varying beam energy, number of bunches and bunch sizes allowing to identify different damage levels for the TCT up to catastr...

  14. Damage Mechanisms and Mechanical Properties of High-Strength Multiphase Steels

    Directory of Open Access Journals (Sweden)

    Sebastian Heibel

    2018-05-01

    Full Text Available The usage of high-strength steels for structural components and reinforcement parts is inevitable for modern car-body manufacture in reaching lightweight design as well as increasing passive safety. Depending on their microstructure these steels show differing damage mechanisms and various mechanical properties which cannot be classified comprehensively via classical uniaxial tensile testing. In this research, damage initiation, evolution and final material failure are characterized for commercially produced complex-phase (CP and dual-phase (DP steels in a strength range between 600 and 1000 MPa. Based on these investigations CP steels with their homogeneous microstructure are characterized as damage tolerant and hence less edge-crack sensitive than DP steels. As final fracture occurs after a combination of ductile damage evolution and local shear band localization in ferrite grains at a characteristic thickness strain, this strain measure is introduced as a new parameter for local formability. In terms of global formability DP steels display advantages because of their microstructural composition of soft ferrite matrix including hard martensite particles. Combining true uniform elongation as a measure for global formability with the true thickness strain at fracture for local formability the mechanical material response can be assessed on basis of uniaxial tensile testing incorporating all microstructural characteristics on a macroscopic scale. Based on these findings a new classification scheme for the recently developed high-strength multiphase steels with significantly better formability resulting of complex underlying microstructures is introduced. The scheme overcomes the steel designations using microstructural concepts, which provide no information about design and production properties.

  15. Threshold quantum cryptography

    International Nuclear Information System (INIS)

    Tokunaga, Yuuki; Okamoto, Tatsuaki; Imoto, Nobuyuki

    2005-01-01

    We present the concept of threshold collaborative unitary transformation or threshold quantum cryptography, which is a kind of quantum version of threshold cryptography. Threshold quantum cryptography states that classical shared secrets are distributed to several parties and a subset of them, whose number is greater than a threshold, collaborates to compute a quantum cryptographic function, while keeping each share secretly inside each party. The shared secrets are reusable if no cheating is detected. As a concrete example of this concept, we show a distributed protocol (with threshold) of conjugate coding

  16. HEDL empirical correlation of fuel pin top failure thresholds, status 1976

    International Nuclear Information System (INIS)

    Baars, R.E.

    1976-01-01

    The Damage Parameter (DP) empirical correlation of fuel pin cladding failure thresholds for TOP events has been revised and recorrelated to the results of twelve TREAT tests. The revised correlation, called the Failure Potential (FP) correlation, predicts failure times for the tests in the data base with an average error of 35 ms for $3/s tests and of 150 ms for 50 cents/s tests

  17. The development of an economic threshold for Nasonovia ribisnigri (Hemiptera: Aphididae) on lettuce in central Spain.

    Science.gov (United States)

    Morales, Ignacio; Diaz, Beatriz María; Hermoso de Mendoza, Alfonso; Nebreda, Miguel; Fereres, Alberto

    2013-04-01

    This study reports economic thresholds for the lettuce aphid Nasonovia ribisnigri (Mosley), based exclusively on cosmetic damage, that is, presence or absence of aphids at harvest time. Field trials were conducted in La Poveda Experimental Farm, Madrid (Spain) during autumn (2004 and 2005) and spring (2005 and 2006). Plants were arranged in plots and just before the formation of lettuce hearts they were infested with different densities of N. ribisnigri. Two days later, half of each plot was treated with tau-fluvalinate (Klartan24AF) and the other half remained as an untreated control. Economic thresholds were obtained from nonlinear regressions calculated between the percentage of commercial plants at the end of the crop cycle for both, treated and untreated semiplots, and the different initial densities of N. ribisnigri per plant. Two criteria were used to consider a commercial lettuce plant: a conservative estimate (0 aphids/plant) and a lax one (aphids/plant). Thus, an economic threshold was established for each season and criterium. The economic thresholds that were obtained with the most and least conservative criteria were in spring 0.06 and 0.12 aphids per plant, and in autumn 0.07 and 0.13 aphids per plant, respectively. These results show that to avoid cosmetic damage, insecticide sprays are required when a very low aphid density is detected in lettuce seedlings soon after transplant.

  18. Robust Adaptive Thresholder For Document Scanning Applications

    Science.gov (United States)

    Hsing, To R.

    1982-12-01

    In document scanning applications, thresholding is used to obtain binary data from a scanner. However, due to: (1) a wide range of different color backgrounds; (2) density variations of printed text information; and (3) the shading effect caused by the optical systems, the use of adaptive thresholding to enhance the useful information is highly desired. This paper describes a new robust adaptive thresholder for obtaining valid binary images. It is basically a memory type algorithm which can dynamically update the black and white reference level to optimize a local adaptive threshold function. The results of high image quality from different types of simulate test patterns can be obtained by this algorithm. The software algorithm is described and experiment results are present to describe the procedures. Results also show that the techniques described here can be used for real-time signal processing in the varied applications.

  19. Comparison on taste threshold between adult male white cigarette and clove cigarette smokers using Murphy clinical test method

    Directory of Open Access Journals (Sweden)

    Ronald Reyses Tapilatu

    2008-03-01

    Full Text Available The habit of smoking white cigarettes and clove cigarettes may affect the gustatory function, that is, it will cause damage to taste buds, resulting in an increase in gustatory threshold. This research used the descriptive comparative method and had the purpose of obtaining an illustration of gustatory threshold and compare gustatory threshold in white cigarette smokers and clove cigarette smokers in young, male adults. For gustatory threshold evaluation, the Murphy method was used to obtain a value for perception threshold and taste identification threshold using sucrose solution of 0.0006 M-0.06 M concentration. Research results indicate that the perception threshold and identification threshold of young, male adult smokers are 0.0119 M and 0.0292 M. Young, male adult clove cigarette smokers have a perception threshold and identification threshold of 0.0151 M and 0.0348 M. The conclusion of this research is that the perception threshold of young, male adult white cigarette smokers and clove cigarette smokers are the same, whereas the identification threshold of young, male adult white cigarette smokers and clove cigarette smokers are different, that is, the identification threshold of clove cigarette smokers is higher than that of white cigarette smokers.

  20. A comprehensive analysis of earthquake damage patterns using high dimensional model representation feature selection

    Science.gov (United States)

    Taşkin Kaya, Gülşen

    2013-10-01

    Recently, earthquake damage assessment using satellite images has been a very popular ongoing research direction. Especially with the availability of very high resolution (VHR) satellite images, a quite detailed damage map based on building scale has been produced, and various studies have also been conducted in the literature. As the spatial resolution of satellite images increases, distinguishability of damage patterns becomes more cruel especially in case of using only the spectral information during classification. In order to overcome this difficulty, textural information needs to be involved to the classification to improve the visual quality and reliability of damage map. There are many kinds of textural information which can be derived from VHR satellite images depending on the algorithm used. However, extraction of textural information and evaluation of them have been generally a time consuming process especially for the large areas affected from the earthquake due to the size of VHR image. Therefore, in order to provide a quick damage map, the most useful features describing damage patterns needs to be known in advance as well as the redundant features. In this study, a very high resolution satellite image after Iran, Bam earthquake was used to identify the earthquake damage. Not only the spectral information, textural information was also used during the classification. For textural information, second order Haralick features were extracted from the panchromatic image for the area of interest using gray level co-occurrence matrix with different size of windows and directions. In addition to using spatial features in classification, the most useful features representing the damage characteristic were selected with a novel feature selection method based on high dimensional model representation (HDMR) giving sensitivity of each feature during classification. The method called HDMR was recently proposed as an efficient tool to capture the input

  1. High and Low LET Radiation Differentially Induce Normal Tissue Damage Signals

    International Nuclear Information System (INIS)

    Niemantsverdriet, Maarten; Goethem, Marc-Jan van; Bron, Reinier; Hogewerf, Wytse; Brandenburg, Sytze; Langendijk, Johannes A.; Luijk, Peter van; Coppes, Robert P.

    2012-01-01

    Purpose: Radiotherapy using high linear energy transfer (LET) radiation is aimed at efficiently killing tumor cells while minimizing dose (biological effective) to normal tissues to prevent toxicity. It is well established that high LET radiation results in lower cell survival per absorbed dose than low LET radiation. However, whether various mechanisms involved in the development of normal tissue damage may be regulated differentially is not known. Therefore the aim of this study was to investigate whether two actions related to normal tissue toxicity, p53-induced apoptosis and expression of the profibrotic gene PAI-1 (plasminogen activator inhibitor 1), are differentially induced by high and low LET radiation. Methods and Materials: Cells were irradiated with high LET carbon ions or low LET photons. Cell survival assays were performed, profibrotic PAI-1 expression was monitored by quantitative polymerase chain reaction, and apoptosis was assayed by annexin V staining. Activation of p53 by phosphorylation at serine 315 and serine 37 was monitored by Western blotting. Transfections of plasmids expressing p53 mutated at serines 315 and 37 were used to test the requirement of these residues for apoptosis and expression of PAI-1. Results: As expected, cell survival was lower and induction of apoptosis was higher in high -LET irradiated cells. Interestingly, induction of the profibrotic PAI-1 gene was similar with high and low LET radiation. In agreement with this finding, phosphorylation of p53 at serine 315 involved in PAI-1 expression was similar with high and low LET radiation, whereas phosphorylation of p53 at serine 37, involved in apoptosis induction, was much higher after high LET irradiation. Conclusions: Our results indicate that diverse mechanisms involved in the development of normal tissue damage may be differentially affected by high and low LET radiation. This may have consequences for the development and manifestation of normal tissue damage.

  2. Correlation of damage threshold and surface geometry of nodular defects in HR coatings as determined by in-situ atomic force microscopy

    International Nuclear Information System (INIS)

    Staggs, M.C.; Kozlowski, M.R.; Siekhaus, W.J.; Balooch, M.

    1992-10-01

    Atomic force microscopy (AFM) was used to determine in-situ the correlation between the surface dimensions of defects in dielectric multilayer optical coatings and their susceptibility to damage by pulsed laser illumination. The primary surface defects studied were μm-scale domes associated with the classic nodule defect. The optical film studied was a highly reflective dielectric multilayer consisting of pairs of alternating HfO 2 and SiO 2 layers of quarter wave thickness at 1.06 μm. Nodule defect height and width dimensions were measured prior to laser illumination on two different samples. Correlation between these dimensions supported a simple model for the defect geometry. Defects with high nodule heights (> 0.6 μm) were found to be most susceptible to laser damage over a range of fluences between 0-35 J/cm 2 (1.06 μm, 10 ns, and 1/e 2 diam. of 1.3 mm). Crater defects, formed by nodules ejected from the coating prior to illumination, were also studied. None of the crater defects damaged when illuminated over the same range of fluences that the nodule defects were subjected to

  3. Laser damage testing at LLL: an overview and an update

    International Nuclear Information System (INIS)

    Milam, D.; Lowdermilk, W.H.; Wirtenson, G.R.

    1978-01-01

    Damage thresholds for single layers of common coating materials such as MgF 2 , SiO 2 , ThF 4 , Al 2 O 3 , ZrO 2 , and TiO 2 are given. Laser-induced damage of coated and uncoated optically polished surfaces has been studied at LLL for laser pulsewidths between 0.17 ns and 3 ns. Two 1064 nm Nd lasers generated this range of pulsewidths. This report contains a review of the results

  4. Modeling of DNA damage-cluster, cell-cycle and repair pathway dependent radiosensitivity after low- and high-LET irradiation

    International Nuclear Information System (INIS)

    Guenther, Paul

    2017-01-01

    This work focuses on modeling of the effects of ionizing radiation on cells, primarily on, the influence of the DNA repair pathway availability and the radiation quality on the cell-survival probability. The availability of DNA repair pathways depends on the replication state and defects of the DNA repair pathways. The radiation quality manifests itself in the microscopic ionization pattern. The Giant LOop Binary LEsion (GLOBLE) model and the Local Effect Model (LEM) describe the cell-survival after photon and ion irradiation, respectively. Both models assume that cell survival can be modeled based on the spatial distribution of Double-Strand Breaks (DSB) of the DNA (damage pattern), within a higher order chromatin structure. Single DSB are referred to as isolated DSB (iDSB) and two or more DSB in close proximity (within 540 nm) are called complex DSB (cDSB). In order to predict the cell-survival, the GLOBLE-Model considers different iDSB repair-pathways and their availability. One central assumption of the LEM is that the same damage patterns imply same effects, regardless of the radiation quality. In order to predict the damage pattern the microscopic local dose distribution of ions, described by the amorphous track structure, is evaluated. The cell survival after ion irradiation is predicted from a comparison with corresponding damage patterns after photon irradiation. The cell-survival curves after high dose photon irradiation cannot be predicted from the Linear Quadratic (LQ) Model due to their transition towards a linear dose dependence. This work uses the GLOBLE-Model to introduce a novel mechanistic approach, which allows the threshold dose to be predicted for the transition from a linear quadratic dose dependence, of survival curves at low doses, to a linear dose dependence at high doses. Furthermore, a method is presented, which allows LEM to predict the survival of synchronous cells after ion irradiation based on the cell survival after photon

  5. Study of the Hearing Threshold of Dance Teachers

    Directory of Open Access Journals (Sweden)

    Nehring, Cristiane

    2015-03-01

    Full Text Available Introduction High sound pressure levels can cause hearing loss, beginning at high frequencies. Objective To analyze the hearing thresholds of dance teachers. Methods This study had a cross-sectional, observational, prospective, and descriptive design. Conventional and high-frequency hearing evaluations were performed with dance teachers and subjects in the control group. Results In all, 64 individuals were assessed, 32 in the research group and 32 in the control group. Results showed that individuals in the research group had hearing loss at frequencies between 4 and 8 kHz, but no significant difference was found between groups. Frequency analysis showed that individuals in the control group had higher thresholds than individuals in the research group at the frequency of 0.25 kHz. In the control group, men showed higher thresholds than women at the frequency of 9 kHz. Conclusion A low prevalence of hearing loss was found, with no difference between teachers and subjects from the control group. No difference was found for hearing thresholds at high frequencies between groups. Results have been partially affected by sex.

  6. Rainfall thresholds for the possible occurrence of landslides in Italy

    Directory of Open Access Journals (Sweden)

    M. T. Brunetti

    2010-03-01

    Full Text Available In Italy, rainfall is the primary trigger of landslides that frequently cause fatalities and large economic damage. Using a variety of information sources, we have compiled a catalogue listing 753 rainfall events that have resulted in landslides in Italy. For each event in the catalogue, the exact or approximate location of the landslide and the time or period of initiation of the slope failure is known, together with information on the rainfall duration D, and the rainfall mean intensity I, that have resulted in the slope failure. The catalogue represents the single largest collection of information on rainfall-induced landslides in Italy, and was exploited to determine the minimum rainfall conditions necessary for landslide occurrence in Italy, and in the Abruzzo Region, central Italy. For the purpose, new national rainfall thresholds for Italy and new regional rainfall thresholds for the Abruzzo Region were established, using two independent statistical methods, including a Bayesian inference method and a new Frequentist approach. The two methods proved complementary, with the Bayesian method more suited to analyze small data sets, and the Frequentist method performing better when applied to large data sets. The new regional thresholds for the Abruzzo Region are lower than the new national thresholds for Italy, and lower than the regional thresholds proposed in the literature for the Piedmont and Lombardy Regions in northern Italy, and for the Campania Region in southern Italy. This is important, because it shows that landslides in Italy can be triggered by less severe rainfall conditions than previously recognized. The Frequentist method experimented in this work allows for the definition of multiple minimum rainfall thresholds, each based on a different exceedance probability level. This makes the thresholds suited for the design of probabilistic schemes for the prediction of rainfall-induced landslides. A scheme based on four

  7. Damage and fracture in large aperture, fused silica, vacuum spatial filter lenses

    International Nuclear Information System (INIS)

    Campbell, J.H.; Edwards, G.J.; Marion, J.E.

    1995-01-01

    Optical damage that results in large scale fracture has been observed in the large, high-fluence, fused-silica, spatial filter lenses on the Nova and Beamlet lasers. In nearly all cases damage occurs on the vacuum side of the lenses and because the vacuum side of the lens is under tensile stress this damage can lead to catastrophic crack growth if the flaw (damage) size exceeds the critical flaw size for SiO 2 . The damaged 52 cm Nova lenses fracture into two and sometimes three large pieces. Although under full vacuum load at the time they fracture, the Nova lenses do not implode. Rather the authors have observed that the pieces lock together and air slowly leaks into the vacuum spatial filter housing through the lens cracks. The Beamlet lenses have a larger aspect ratio and peak tensile stress than Nova. The peak tensile stress at the center of the output surface of the Beamlet lens is 1,490 psi versus 810 psi for Nova. During a recent Beamlet high energy shot, a damage spot on the lens grew to the critical flaw size and the lens imploded. Post shot data indicate the lens probably fractured into 5 to 7 pieces, however, unlike Nova, these pieces did not lock together. Analysis shows that the likely source of damage is contamination from pinhole blow-off or out-gassing of volatile materials within the spatial filter. Contamination degrades the antireflection properties of the sol-gel coating and reduces its damage threshold. By changing the design of the Beamlet lens it may be possible to insure that it fails safe by locking up in much that same manner as the Nova lens

  8. Condition-Based Maintenance Strategy for Production Systems Generating Environmental Damage

    Directory of Open Access Journals (Sweden)

    L. Tlili

    2015-01-01

    Full Text Available We consider production systems which generate damage to environment as they get older and degrade. The system is submitted to inspections to assess the generated environmental damage. The inspections can be periodic or nonperiodic. In case an inspection reveals that the environmental degradation level has exceeded the critical level U, the system is considered in an advanced deterioration state and will have generated significant environmental damage. A corrective maintenance action is then performed to renew the system and clean the environment and a penalty has to be paid. In order to prevent such an undesirable situation, a lower threshold level L is considered to trigger a preventive maintenance action to bring back the system to a state as good as new at a lower cost and without paying the penalty. Two inspection policies are considered (periodic and nonperiodic. For each one of them, a mathematical model and a numerical procedure are developed to determine simultaneously the preventive maintenance (PM threshold L∗ and the inspection sequence which minimize the average long-run cost per time unit. Numerical calculations are performed to illustrate the proposed maintenance policies and highlight their main characteristics with respect to relevant input parameters.

  9. High index of refraction films for dielectric mirrors prepared by metal-organic chemical vapor deposition

    International Nuclear Information System (INIS)

    Brusasco, R.M.

    1989-01-01

    A wide variety of metal oxides with high index of refraction can be prepared by Metal-Organic Chemical Vapor Deposition. We present some recent optical and laser damage results on oxide films prepared by MOCVD which could be used in a multilayer structure for highly reflecting (HR) dielectric mirror applications. The method of preparation affects both optical properties and laser damage threshold. 10 refs., 8 figs., 4 tabs

  10. Ductile failure analysis of high strength steel in hot forming based on micromechanical damage model

    OpenAIRE

    Ying Liang; Liu Wenquan; Wang Dantong; Hu Ping

    2016-01-01

    The damage evolution of high strength steel at elevated temperature is investigated by using the Gurson-Tvergaard-Needleman (GTN) model. A hybrid method integrated thermal tensile test and numerical technique is employed to identify the damage parameters. The analysis results show that the damage parameters are different at different temperature as the variation of tested material microstructure. Furthermore, the calibrated damage parameters are implemented to simulate a bugling forming at el...

  11. Ambient high temperature and mortality in Jinan, China: A study of heat thresholds and vulnerable populations.

    Science.gov (United States)

    Li, Jing; Xu, Xin; Yang, Jun; Liu, Zhidong; Xu, Lei; Gao, Jinghong; Liu, Xiaobo; Wu, Haixia; Wang, Jun; Yu, Jieqiong; Jiang, Baofa; Liu, Qiyong

    2017-07-01

    Understanding the health consequences of continuously rising temperatures-as is projected for China-is important in terms of developing heat-health adaptation and intervention programs. This study aimed to examine the association between mortality and daily maximum (T max ), mean (T mean ), and minimum (T min ) temperatures in warmer months; to explore threshold temperatures; and to identify optimal heat indicators and vulnerable populations. Daily data on temperature and mortality were obtained for the period 2007-2013. Heat thresholds for condition-specific mortality were estimated using an observed/expected analysis. We used a generalised additive model with a quasi-Poisson distribution to examine the association between mortality and T max /T min /T mean values higher than the threshold values, after adjustment for covariates. T max /T mean /T min thresholds were 32/28/24°C for non-accidental deaths; 32/28/24°C for cardiovascular deaths; 35/31/26°C for respiratory deaths; and 34/31/28°C for diabetes-related deaths. For each 1°C increase in T max /T mean /T min above the threshold, the mortality risk of non-accidental-, cardiovascular-, respiratory, and diabetes-related death increased by 2.8/5.3/4.8%, 4.1/7.2/6.6%, 6.6/25.3/14.7%, and 13.3/30.5/47.6%, respectively. Thresholds for mortality differed according to health condition when stratified by sex, age, and education level. For non-accidental deaths, effects were significant in individuals aged ≥65 years (relative risk=1.038, 95% confidence interval: 1.026-1.050), but not for those ≤64 years. For most outcomes, women and people ≥65 years were more vulnerable. High temperature significantly increases the risk of mortality in the population of Jinan, China. Climate change with rising temperatures may bring about the situation worse. Public health programs should be improved and implemented to prevent and reduce health risks during hot days, especially for the identified vulnerable groups. Copyright

  12. Non-damaging laser therapy of the macula: Titration algorithm and tissue response

    Science.gov (United States)

    Palanker, Daniel; Lavinsky, Daniel; Dalal, Roopa; Huie, Philip

    2014-02-01

    Retinal photocoagulation typically results in permanent scarring and scotomata, which limit its applicability to the macula, preclude treatments in the fovea, and restrict the retreatments. Non-damaging approaches to laser therapy have been tested in the past, but the lack of reliable titration and slow treatment paradigms limited their clinical use. We developed and tested a titration algorithm for sub-visible and non-damaging treatments of the retina with pulses sufficiently short to be used with pattern laser scanning. The algorithm based on Arrhenius model of tissue damage optimizes the power and duration for every energy level, relative to the threshold of lesion visibility established during titration (and defined as 100%). Experiments with pigmented rabbits established that lesions in the 50-75% energy range were invisible ophthalmoscopically, but detectable with Fluorescein Angiography and OCT, while at 30% energy there was only very minor damage to the RPE, which recovered within a few days. Patients with Diabetic Macular Edema (DME) and Central Serous Retinopathy (CSR) have been treated over the edematous areas at 30% energy, using 200μm spots with 0.25 diameter spacing. No signs of laser damage have been detected with any imaging modality. In CSR patients, subretinal fluid resolved within 45 days. In DME patients the edema decreased by approximately 150μm over 60 days. After 3-4 months some patients presented with recurrence of edema, and they responded well to retreatment with the same parameters, without any clinically visible damage. This pilot data indicates a possibility of effective and repeatable macular laser therapy below the tissue damage threshold.

  13. Low cycle fatigue: high cycle fatigue damage accumulation in a 304L austenitic stainless steel; Endommagement et cumul de dommage en fatigue dans le domaine de l'endurance limitee d'un acier inoxydable austenitique 304L

    Energy Technology Data Exchange (ETDEWEB)

    Lehericy, Y

    2007-05-15

    The aim of this study was to evaluate the consequences of a Low Cycle Fatigue pre-damage on the subsequent fatigue limit of a 304L stainless steel. The effects of hardening and severe roughness (grinding) have also been investigated. In a first set of tests, the evolution of the surface damage induced by the different LCF pre-cycling was characterized. This has permitted to identify mechanisms and kinetics of damage in the plastic domain for different surface conditions. Then, pre-damaged samples were tested in the High Cycle Fatigue domain in order to establish the fatigue limits associated with each level of pre-damage. Results evidence that, in the case of polished samples, an important number of cycles is required to initiate surface cracks ant then to affect the fatigue limit of the material but, in the case of ground samples, a few number of cycles is sufficient to initiate cracks and to critically decrease the fatigue limit. The fatigue limit of pre-damaged samples can be estimated using the stress intensity factor threshold. Moreover, this detrimental effect of severe surface conditions is enhanced when fatigue tests are performed under a positive mean stress (author)

  14. The Chromatin Scaffold Protein SAFB1 Renders Chromatin Permissive for DNA Damage Signaling

    DEFF Research Database (Denmark)

    Altmeyer, Matthias; Toledo Lazaro, Luis Ignacio; Gudjonsson, Thorkell

    2013-01-01

    Although the general relevance of chromatin modifications for genotoxic stress signaling, cell-cycle checkpoint activation, and DNA repair is well established, how these modifications reach initial thresholds in order to trigger robust responses remains largely unexplored. Here, we identify...... the chromatin-associated scaffold attachment factor SAFB1 as a component of the DNA damage response and show that SAFB1 cooperates with histone acetylation to allow for efficient γH2AX spreading and genotoxic stress signaling. SAFB1 undergoes a highly dynamic exchange at damaged chromatin in a poly......(ADP-ribose)-polymerase 1- and poly(ADP-ribose)-dependent manner and is required for unperturbed cell-cycle checkpoint activation and guarding cells against replicative stress. Altogether, our data reveal that transient recruitment of an architectural chromatin component is required in order to overcome physiological...

  15. Dose rate effects during damage accumulation in silicon

    Energy Technology Data Exchange (ETDEWEB)

    Caturla, M.J.; Diaz de la Rubia, T.

    1997-01-01

    We combine molecular dynamics and Monte Carlo simulations to study damage accumulation and dose rate effects during irradiation of Silicon. We obtain the initial stage of the damage produced by heavy and light ions using classical molecular dynamics simulations. While heavy ions like As or Pt induce amorphization by single ion impact, light ions like B only produce point defects or small clusters of defects. The amorphous pockets generated by heavy ions are stable below room temperature and recrystallize at temperatures below the threshold for recrystallization of a planar amorphous-crystalline interface. The damage accumulation during light ion irradiation is simulated using a Monte Carlo model for defect diffusion. In this approach, we study the damage in the lattice as a function of dose and dose rate. A strong reduction in the total number of defects left in the lattice is observed for lower dose rates.

  16. Dose rate effects during damage accumulation in silicon

    International Nuclear Information System (INIS)

    Caturla, M.J.; Diaz de la Rubia, T.

    1997-01-01

    The authors combine molecular dynamics and Monte Carlo simulations to study damage accumulation and dose rate effects during irradiation of silicon. They obtain the initial stage of the damage produced by heavy and light ions using classical molecular dynamics simulations. While heavy ions like As or Pt induce amorphization by single ion impact, light ions like B only produce point defects or small clusters of defects. The amorphous pockets generated by heavy ions are stable below room temperature and recrystallize at temperatures below the threshold for recrystallization of a planar amorphous-crystalline interface. The damage accumulation during light ion irradiation is simulated using a Monte Carlo model for defect diffusion. In this approach, the authors study the damage in the lattice as a function of dose and dose rate. A strong reduction in the total number of defects left in the lattice is observed for lower dose rates

  17. Ductile failure analysis of high strength steel in hot forming based on micromechanical damage model

    Directory of Open Access Journals (Sweden)

    Ying Liang

    2016-01-01

    Full Text Available The damage evolution of high strength steel at elevated temperature is investigated by using the Gurson-Tvergaard-Needleman (GTN model. A hybrid method integrated thermal tensile test and numerical technique is employed to identify the damage parameters. The analysis results show that the damage parameters are different at different temperature as the variation of tested material microstructure. Furthermore, the calibrated damage parameters are implemented to simulate a bugling forming at elevated temperature. The experimental results show the availability of GTN damage model in analyzing sheet formability in hot forming.

  18. High-Temperature Performance and Multiscale Damage Mechanisms of Hollow Cellulose Fiber-Reinforced Concrete

    Directory of Open Access Journals (Sweden)

    Liping Guo

    2016-01-01

    Full Text Available Spalling resistance properties and their damage mechanisms under high temperatures are studied in hollow cellulose fiber-reinforced concrete (CFRC used in tunnel structures. Measurements of mass loss, relative dynamic elastic modulus, compressive strength, and splitting tensile strength of CFRC held under high temperatures (300, 600, 800, and 1050°C for periods of 2.5, 4, and 5.5 h were carried out. The damage mechanism was analyzed using scanning electron microscopy, mercury intrusion porosimetry, thermal analysis, and X-ray diffraction phase analysis. The results demonstrate that cellulose fiber can reduce the performance loss of concrete at high temperatures; the effect of holding time on the performance is more noticeable below 600°C. After exposure to high temperatures, the performance of ordinary concrete deteriorates faster and spalls at 700–800°C; in contrast, cellulose fiber melts at a higher temperature, leaving a series of channels in the matrix that facilitate the release of the steam pressure inside the CFRC. Hollow cellulose fibers can thereby slow the damage caused by internal stress and improve the spalling resistance of concrete under high temperatures.

  19. High energy proton simulation of 14-MeV neutron damage in Al2O3

    International Nuclear Information System (INIS)

    Muir, D.W.; Bunch, J.M.

    1975-01-01

    High-energy protons are a potentially useful tool for simulating the radiation damage produced by 14-MeV neutrons in CTR materials. A comparison is given of calculations and measurements of the relative damage effectiveness of these two types of radiation in single-crystal Al 2 O 3 . The experiments make use of the prominent absorption band at 206 nm as an index to lattice damage, on the assumption that peak absorption is proportional to the concentration of lattice vacancies. The induced absorption is measured for incident proton energies ranging from 5 to 15 MeV and for 14-MeV neutrons. Recoil-energy spectra are calculated for elastic and inelastic scattering using published angular distributions. Recoil-energy spectra also are calculated for the secondary alpha particles and 12 C nuclei produced by (p,p'α) reactions on 16 O. The recoil spectra are converted to damage-energy spectra and then integrated to yield the damage-energy cross section at each proton energy and for 14 MeV neutrons. A comparison of the calculations with experimental results suggests that damage energy, at least at high energies, is a reasonable criterion for estimating this type of radiation damage. (auth)

  20. Threshold photoelectron spectroscopy of acetaldehyde and acrolein

    International Nuclear Information System (INIS)

    Yencha, Andrew J.; Siggel-King, Michele R.F.; King, George C.; Malins, Andrew E.R.; Eypper, Marie

    2013-01-01

    Highlights: •High-resolution threshold photoelectron spectrum of acetaldehyde. •High-resolution threshold photoelectron spectrum of acrolein. •High-resolution total photoion yield spectrum of acetaldehyde. •High-resolution total photoion yield spectrum of acrolein. •Determination of vertical ionization potentials in acetaldehyde and acrolein. -- Abstract: High-resolution (6 meV and 12 meV) threshold photoelectron (TPE) spectra of acetaldehyde and acrolein (2-propenal) have been recorded over the valence binding energy region 10–20 eV, employing synchrotron radiation and a penetrating-field electron spectrometer. These TPE spectra are presented here for the first time. All of the band structures observed in the TPE spectra replicate those found in their conventional HeI photoelectron (PE) spectra. However, the relative band intensities are found to be dramatically different in the two types of spectra that are attributed to the different dominant operative formation mechanisms. In addition, some band shapes and their vertical ionization potentials are found to differ in the two types of spectra that are associated with the autoionization of Rydberg states in the two molecules

  1. Accumulated surface damage on ZnS crystals produced by closely spaced pairs of picosecond laser pulses

    International Nuclear Information System (INIS)

    Chase, L.L.; Lee, H.W.H.

    1988-12-01

    Excitation of a transparent ZnS crystal by repetitive picosecond dye laser pulses causes an accumulated surface modification leading to optical damage. The onset of the damage is detected by an abrupt increase in the emission of neutral Zn (and possibly S 2 ) from the surface. Comparison of the neutral emission thresholds with pulse-pair and single-pulse excitation shows that linear absorption is the dominant laser-surface interaction. In general, this measurement technique shows considerable promise for investigating the possible influence of nonlinear absorption or excitation processes on damage mechanisms. The data suggest that heating of small absorbing regions produces the surface modification that leads to the observed surface ablation. The nature of the damage observed at fluences above the threshold suggests that it is caused by heating of a relatively large (/approximately/10 - 100 μm) surface region that has been modified by the accumulation pulses. 3 refs., 5 figs

  2. Particle damage sources for fused silica optics and their mitigation on high energy laser systems.

    Science.gov (United States)

    Bude, J; Carr, C W; Miller, P E; Parham, T; Whitman, P; Monticelli, M; Raman, R; Cross, D; Welday, B; Ravizza, F; Suratwala, T; Davis, J; Fischer, M; Hawley, R; Lee, H; Matthews, M; Norton, M; Nostrand, M; VanBlarcom, D; Sommer, S

    2017-05-15

    High energy laser systems are ultimately limited by laser-induced damage to their critical components. This is especially true of damage to critical fused silica optics, which grows rapidly upon exposure to additional laser pulses. Much progress has been made in eliminating damage precursors in as-processed fused silica optics (the advanced mitigation process, AMP3), and very high damage resistance has been demonstrated in laboratory studies. However, the full potential of these improvements has not yet been realized in actual laser systems. In this work, we explore the importance of additional damage sources-in particular, particle contamination-for fused silica optics fielded in a high-performance laser environment, the National Ignition Facility (NIF) laser system. We demonstrate that the most dangerous sources of particle contamination in a system-level environment are laser-driven particle sources. In the specific case of the NIF laser, we have identified the two important particle sources which account for nearly all the damage observed on AMP3 optics during full laser operation and present mitigations for these particle sources. Finally, with the elimination of these laser-driven particle sources, we demonstrate essentially damage free operation of AMP3 fused silica for ten large optics (a total of 12,000 cm 2 of beam area) for shots from 8.6 J/cm 2 to 9.5 J/cm 2 of 351 nm light (3 ns Gaussian pulse shapes). Potentially many other pulsed high energy laser systems have similar particle sources, and given the insight provided by this study, their identification and elimination should be possible. The mitigations demonstrated here are currently being employed for all large UV silica optics on the National Ignition Facility.

  3. Study on Relaxation Damage Properties of High Viscosity Asphalt Sand under Uniaxial Compression

    Directory of Open Access Journals (Sweden)

    Yazhen Sun

    2018-01-01

    Full Text Available Laboratory investigations of relaxation damage properties of high viscosity asphalt sand (HVAS by uniaxial compression tests and modified generalized Maxwell model (GMM to simulate viscoelastic characteristics coupling damage were carried out. A series of uniaxial compression relaxation tests were performed on HVAS specimens at different temperatures, loading rates, and constant levels of input strain. The results of the tests show that the peak point of relaxation modulus is highly influenced by the loading rate in the first half of an L-shaped curve, while the relaxation modulus is almost constant in the second half of the curve. It is suggested that for the HVAS relaxation tests, the temperature should be no less than −15°C. The GMM is used to determine the viscoelastic responses, the Weibull distribution function is used to characterize the damage of the HVAS and its evolution, and the modified GMM is a coupling of the two models. In this paper, the modified GMM is implemented through a secondary development with the USDFLD subroutine to analyze the relaxation damage process and improve the linear viscoelastic model in ABAQUS. Results show that the numerical method of coupling damage provides a better approximation of the test curve over almost the whole range. The results also show that the USDFLD subroutine can effectively predict the relaxation damage process of HVAS and can provide a theoretical support for crack control of asphalt pavements.

  4. Magnetic Flux Leakage Sensing and Artificial Neural Network Pattern Recognition-Based Automated Damage Detection and Quantification for Wire Rope Non-Destructive Evaluation.

    Science.gov (United States)

    Kim, Ju-Won; Park, Seunghee

    2018-01-02

    In this study, a magnetic flux leakage (MFL) method, known to be a suitable non-destructive evaluation (NDE) method for continuum ferromagnetic structures, was used to detect local damage when inspecting steel wire ropes. To demonstrate the proposed damage detection method through experiments, a multi-channel MFL sensor head was fabricated using a Hall sensor array and magnetic yokes to adapt to the wire rope. To prepare the damaged wire-rope specimens, several different amounts of artificial damages were inflicted on wire ropes. The MFL sensor head was used to scan the damaged specimens to measure the magnetic flux signals. After obtaining the signals, a series of signal processing steps, including the enveloping process based on the Hilbert transform (HT), was performed to better recognize the MFL signals by reducing the unexpected noise. The enveloped signals were then analyzed for objective damage detection by comparing them with a threshold that was established based on the generalized extreme value (GEV) distribution. The detected MFL signals that exceed the threshold were analyzed quantitatively by extracting the magnetic features from the MFL signals. To improve the quantitative analysis, damage indexes based on the relationship between the enveloped MFL signal and the threshold value were also utilized, along with a general damage index for the MFL method. The detected MFL signals for each damage type were quantified by using the proposed damage indexes and the general damage indexes for the MFL method. Finally, an artificial neural network (ANN) based multi-stage pattern recognition method using extracted multi-scale damage indexes was implemented to automatically estimate the severity of the damage. To analyze the reliability of the MFL-based automated wire rope NDE method, the accuracy and reliability were evaluated by comparing the repeatedly estimated damage size and the actual damage size.

  5. Ultrafuzziness Optimization Based on Type II Fuzzy Sets for Image Thresholding

    Directory of Open Access Journals (Sweden)

    Hudan Studiawan

    2010-11-01

    Full Text Available Image thresholding is one of the processing techniques to provide high quality preprocessed image. Image vagueness and bad illumination are common obstacles yielding in a poor image thresholding output. By assuming image as fuzzy sets, several different fuzzy thresholding techniques have been proposed to remove these obstacles during threshold selection. In this paper, we proposed an algorithm for thresholding image using ultrafuzziness optimization to decrease uncertainty in fuzzy system by common fuzzy sets like type II fuzzy sets. Optimization was conducted by involving ultrafuzziness measurement for background and object fuzzy sets separately. Experimental results demonstrated that the proposed image thresholding method had good performances for images with high vagueness, low level contrast, and grayscale ambiguity.

  6. Methodology for determining void swelling at very high damage under ion irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Getto, E., E-mail: embecket@umich.edu [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI 48109 (United States); Sun, K. [Department of Materials Science Engineering, University of Michigan, Ann Arbor, MI 48109 (United States); Taller, S.; Monterrosa, A.M.; Jiao, Z. [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI 48109 (United States); Was, G.S. [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI 48109 (United States); Department of Materials Science Engineering, University of Michigan, Ann Arbor, MI 48109 (United States)

    2016-08-15

    At very high damage levels in ion irradiated samples, the decrease in effective density of the irradiated material due to void swelling can lead to errors in quantifying swelling. HT9 was pre-implanted with 10 appm He and subjected to a raster-scanned beam with a damage rate of ∼1 × 10{sup −3} dpa/s at 460{sup o}C. Voids were characterized from 0 to 1300 nm. Fixed damage rate and fixed depth methods were developed to account for damage-dependent porosity increase and resulting dependence on depth. The fixed depth method was more appropriate as it limits undue effects from the injected interstitial while maintaining a usable void distribution. By keeping the depth fixed and accounting for the change in damage rate due to reduced density, the steady state swelling rate was 10% higher than calculation of swelling from raw data. This method is easily translatable to other materials, ion types and energies and limits the impact of the injected interstitial.

  7. Converting Hangar High Expansion Foam Systems to Prevent Cockpit Damage: Full-Scale Validation Tests

    Science.gov (United States)

    2017-09-01

    AFCEC-CO-TY-TR-2018-0001 CONVERTING HANGAR HIGH EXPANSION FOAM SYSTEMS TO PREVENT COCKPIT DAMAGE: FULL-SCALE VALIDATION TESTS Gerard G...manufacturer, or otherwise does not constitute or imply its endorsement, recommendation , or approval by the United States Air Force. The views and...09-2017 Final Test Report May 2017 Converting Hangar High Expansion Foam Systems to Prevent Cockpit Damage: Full-Scale Validation Tests N00173-15-D

  8. Increased effects of machining damage in beryllium observed at high strain rates

    International Nuclear Information System (INIS)

    Beitscher, S.; Brewer, A.W.; Corle, R.R.

    1980-01-01

    Tensile tests at both low and high strain rates, and also impact shear tests, were performed on a weldable grade powder-source beryllium. Impact energies increased by a factor of 2 to 3 from the as-machined level after etching or annealing. Similar increases in the ductility from machining damage removal were observed from the tensile data at the higher strain rate (10 s -1 ) while an insignificant increase in elongation was measured at the lower strain rate (10 -4 s -1 ). High strain-rate tests appear to be more sensitive and reliable for evaluating machining practice and damage removal methods for beryllium components subjected to sudden loads. 2 tables

  9. Persistent DNA damage after high dose in vivo gamma exposure of minipig skin.

    Directory of Open Access Journals (Sweden)

    Emad A Ahmed

    Full Text Available Exposure to high doses of ionizing radiation (IR can lead to localized radiation injury of the skin and exposed cells suffer dsDNA breaks that may elicit cell death or stochastic changes. Little is known about the DNA damage response after high-dose exposure of the skin. Here, we investigate the cellular and DNA damage response in acutely irradiated minipig skin.IR-induced DNA damage, repair and cellular survival were studied in 15 cm(2 of minipig skin exposed in vivo to ~50 Co-60 γ rays. Skin biopsies of control and 4 h up to 96 days post exposure were investigated for radiation-induced foci (RIF formation using γ-H2AX, 53BP1, and active ATM-p immunofluorescence. High-dose IR induced massive γ-H2AX phosphorylation and high 53BP1 RIF numbers 4 h, 20 h after IR. As time progressed RIF numbers dropped to a low of 3-fold elevated at all subsequent time points. Replicating basal cells (Ki67+ were reduced 3 days post IR followed by increased proliferation and recovery of epidermal cellularity after 28 days.Acute high dose irradiation of minipig epidermis impaired stem cell replication and induced elevated apoptosis from 3 days onward. DNA repair cleared the high numbers of DBSs in skin cells, while RIFs that persisted in <1% cells marked complex and potentially lethal DNA damage up to several weeks after exposure. An elevated frequency of keratinocytes with persistent RIFs may thus serve as indicator of previous acute radiation exposure, which may be useful in the follow up of nuclear or radiological accident scenarios.

  10. Near-threshold fatigue crack behaviour in EUROFER 97 at different temperatures

    International Nuclear Information System (INIS)

    Aktaa, J.; Lerch, M.

    2006-01-01

    The fatigue crack behaviour in EUROFER 97 was investigated at room temperature (RT), 300, 500 and 550 deg. C for the assessment of cracks in first wall structures built from EUROFER 97 of future fusion reactors. For this purpose, fatigue crack growth tests were performed using CT specimens with two R-ratios, R = 0.1 and R = 0.5 (R is the load ratio with R = F min /F max where F min and F max are the minimum and maximum applied loads within a cycle, respectively). Hence, fatigue crack threshold, fatigue crack growth behaviour in the near-threshold range and their dependences on temperature and R-ratio were determined and described using an analytical formula. The fatigue crack threshold showed a monotonous dependence on temperature which is for R = 0.5 insignificantly small. The fatigue crack growth behaviour exhibited for R = 0.1 a non-monotonous dependence on temperature which is explained by the decrease of yield stress and the increase of creep damage with increasing temperature

  11. Rainfall threshold definition using an entropy decision approach and radar data

    Directory of Open Access Journals (Sweden)

    V. Montesarchio

    2011-07-01

    Full Text Available Flash flood events are floods characterised by a very rapid response of basins to storms, often resulting in loss of life and property damage. Due to the specific space-time scale of this type of flood, the lead time available for triggering civil protection measures is typically short. Rainfall threshold values specify the amount of precipitation for a given duration that generates a critical discharge in a given river cross section. If the threshold values are exceeded, it can produce a critical situation in river sites exposed to alluvial risk. It is therefore possible to directly compare the observed or forecasted precipitation with critical reference values, without running online real-time forecasting systems. The focus of this study is the Mignone River basin, located in Central Italy. The critical rainfall threshold values are evaluated by minimising a utility function based on the informative entropy concept and by using a simulation approach based on radar data. The study concludes with a system performance analysis, in terms of correctly issued warnings, false alarms and missed alarms.

  12. Research of the mode instability threshold in high power double cladding Yb-doped fiber amplifiers

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yanshan; Ma, Yi; Sun, Yinhong; Peng, Wanjing; Tang, Chun [Institute of Applied Electronics, CAEP, Mianyang, Sichuan (China); The Key Laboratory of Science and Technology on High Energy Laser, CAEP, Mianyang, Sichuan (China); Liu, Qinyong; Ke, Weiwei [Institute of Applied Physics and Computational Mathematics, CAEP, Beijing (China); Wang, Xiaojun [Institute of Applied Physics and Computational Mathematics, CAEP, Beijing (China); Technical Institute of Physics and Chemistry, CAS, Beijing (China)

    2017-08-15

    We experimentally investigate the behavior of the mode instability (MI) threshold in the double cladding Yb-doped fiber amplifier when the amplifier is pumped by broad linewidth laser diodes and narrow linewidth laser diodes respectively. It is found that the MI threshold increases by 26% when the amplifier is pumped by the broad linewidth laser diodes. Experiment results show that the MI threshold is affected by the local heat load rather than the average or the total heat load. The calculation shows that the local heat deposit actually plays the key role to stimulate the MI behaviour. At the MI threshold position in the fiber, the local heat deposit also changes dramatically. The effect of the thermal conductivity on the MI threshold is also studied. Our investigation shows that the MI threshold increases from 1269 W to 1950 W when the thermal conductivity of the fiber amplifier is increased from 0.3 W/(m . K) to 5 W/(m . K). Through optimizing the pump linewidth and the cooling efficiency of the gain fiber, the MI threshold is doubled in our experiment. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. Research of the mode instability threshold in high power double cladding Yb-doped fiber amplifiers

    International Nuclear Information System (INIS)

    Wang, Yanshan; Ma, Yi; Sun, Yinhong; Peng, Wanjing; Tang, Chun; Liu, Qinyong; Ke, Weiwei; Wang, Xiaojun

    2017-01-01

    We experimentally investigate the behavior of the mode instability (MI) threshold in the double cladding Yb-doped fiber amplifier when the amplifier is pumped by broad linewidth laser diodes and narrow linewidth laser diodes respectively. It is found that the MI threshold increases by 26% when the amplifier is pumped by the broad linewidth laser diodes. Experiment results show that the MI threshold is affected by the local heat load rather than the average or the total heat load. The calculation shows that the local heat deposit actually plays the key role to stimulate the MI behaviour. At the MI threshold position in the fiber, the local heat deposit also changes dramatically. The effect of the thermal conductivity on the MI threshold is also studied. Our investigation shows that the MI threshold increases from 1269 W to 1950 W when the thermal conductivity of the fiber amplifier is increased from 0.3 W/(m . K) to 5 W/(m . K). Through optimizing the pump linewidth and the cooling efficiency of the gain fiber, the MI threshold is doubled in our experiment. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. Using a cover layer to improve the damage resistance of gold-coated gratings induced by a picosecond pulsed laser

    Science.gov (United States)

    Xia, Zhilin; Wu, Yihan; Kong, Fanyu; Jin, Yunxia

    2018-04-01

    The chirped pulse amplification (CPA) technology is the main approach to achieve high-intensity short-pulse laser. Diffraction gratings are good candidates for stretching and compressing laser pulses in CPA. In this paper, a kind of gold-coated grating has been prepared and its laser damage experiment has been performed. The results reflect that the gratings laser damage was dominated by thermal ablation due to gold films or inclusions absorption and involved the deformation or eruption of the gold film. Based on these damage phenomena, a method of using a cover layer to prevent gold films from deforming and erupting has been adopted to improve the gold-coated gratings laser damage threshold. Since the addition of a cover layer changes the gratings diffraction efficiency, the gratings structure has been re-optimized. Furthermore, according to the calculated thermal stress distributions in gratings with optimized structures, the cover layer was demonstrated to be helpful for improving the gratings laser damage resistance if it is thick enough.

  15. Automatic Detection of Storm Damages Using High-Altitude Photogrammetric Imaging

    Science.gov (United States)

    Litkey, P.; Nurminen, K.; Honkavaara, E.

    2013-05-01

    The risks of storms that cause damage in forests are increasing due to climate change. Quickly detecting fallen trees, assessing the amount of fallen trees and efficiently collecting them are of great importance for economic and environmental reasons. Visually detecting and delineating storm damage is a laborious and error-prone process; thus, it is important to develop cost-efficient and highly automated methods. Objective of our research project is to investigate and develop a reliable and efficient method for automatic storm damage detection, which is based on airborne imagery that is collected after a storm. The requirements for the method are the before-storm and after-storm surface models. A difference surface is calculated using two DSMs and the locations where significant changes have appeared are automatically detected. In our previous research we used four-year old airborne laser scanning surface model as the before-storm surface. The after-storm DSM was provided from the photogrammetric images using the Next Generation Automatic Terrain Extraction (NGATE) algorithm of Socet Set software. We obtained 100% accuracy in detection of major storm damages. In this investigation we will further evaluate the sensitivity of the storm-damage detection process. We will investigate the potential of national airborne photography, that is collected at no-leaf season, to automatically produce a before-storm DSM using image matching. We will also compare impact of the terrain extraction algorithm to the results. Our results will also promote the potential of national open source data sets in the management of natural disasters.

  16. CARA Risk Assessment Thresholds

    Science.gov (United States)

    Hejduk, M. D.

    2016-01-01

    Warning remediation threshold (Red threshold): Pc level at which warnings are issued, and active remediation considered and usually executed. Analysis threshold (Green to Yellow threshold): Pc level at which analysis of event is indicated, including seeking additional information if warranted. Post-remediation threshold: Pc level to which remediation maneuvers are sized in order to achieve event remediation and obviate any need for immediate follow-up maneuvers. Maneuver screening threshold: Pc compliance level for routine maneuver screenings (more demanding than regular Red threshold due to additional maneuver uncertainty).

  17. High dose radiation damage in nuclear energy structural materials investigated by heavy ion irradiation simulation

    International Nuclear Information System (INIS)

    Zheng Yongnan; Xu Yongjun; Yuan Daqing

    2014-01-01

    Structural materials in ITER, ADS and fast reactor suffer high dose irradiations of neutrons and/or protons, that leads to severe displacement damage up to lOO dpa per year. Investigation of radiation damage induced by such a high dose irradiation has attracted great attention along with the development of nuclear energy facilities of new generation. However, it is deeply hampered for the lacking of high dose neutron and proton sources. Irradiation simulation of heavy ions produced by accelerators opens up an effective way for laboratory investigation of high dose irradiation induced radiation damage encountered in the ITER, ADS, etc. Radiation damage is caused mainly by atomic displacement in materials. The displacement rate of heavy ions is about lO 3 ∼10 7 orders higher than those of neutrons and protons. High displacement rate of heavy ions significantly reduces the irradiation time. The heavy ion irradiation simulation technique (HIIS) technique has been developed at China Institute of Atomic Energy and a series of the HIIS experiments have been performed to investigate radiation damage in stainless steels, tungsten and tantalum at irradiation temperatures from room temperature to 800 ℃ and in the irradiation dose region up to 100 dpa. The experimental results show that he radiation swelling peak for the modified stainless steel appears in the temperature region around 580 ℃ and the radiation damage is more sensitive to the temperature, the size of the radiation induced vacancy cluster or void increase with the increasing of the irradiation dose, and among the three materials the home-made modified stainless steel has the best radiation resistant property. (authors)

  18. Detection of Fatigue Damage by Using High Frequency Nonlinear Laser Ultrasonic Signals

    International Nuclear Information System (INIS)

    Park, Seung Kyu; Park, Nak Kyu; Baik, Sung Hoon; Cheong, Yong Moo; Cha, Byung Heon

    2012-01-01

    The detection of fatigue damage for the components of a nuclear power plant is one of key techniques to prevent a catastrophic accident and the subsequent severe losses. Specifically, it is preferred to detect at an early stage of the fatigue damage. If the fatigue damage that is in danger of growing into a fracture is accurately detected, an appropriate treatment could be carried out to improve the condition. Although most engineers and designers take precautions against fatigue, some breakdowns of nuclear power plant components still occur due to fatigue damage. It is considered that ultrasound testing technique is the most promising method to detect the fatigue damage in many nondestructive testing methods. Laser ultrasound has attracted attention as a noncontact testing technique. Especially, laser ultrasonic signal has wide band frequency spectrum which can provide more accurate information for a testing material. The conventional linear ultrasonic technique is sensitive to gross defects or opened cracks whereas it is less sensitive to evenly distributed micro-cracks or degradation. An alternative technique to overcome this limitation is nonlinear ultrasound. The principal difference between linear and nonlinear technique is that in the latter the existence and characteristics of defects are often related to an acoustic signal whose frequency differs from that of the input signal. This is related to the radiation and propagation of finite amplitude, especially high power, ultrasound and its interaction with discontinuities, such as cracks, interfaces and voids. Since material failure or degradation is usually preceded by some kind of nonlinear mechanical behavior before significant plastic deformation or material damage occurs. The presence of nonlinear terms in the wave equation causes intense acoustic waves to generate new waves at frequencies which are multiples of the initial sound wave frequency. The nonlinear effect can exert a strong effect on the

  19. LONG-TERM SD-OCT/SLO IMAGING OF NEURORETINA AND RETINAL PIGMENT EPITHELIUM AFTER SUB-THRESHOLD INFRARED LASER TREATMENT OF DRUSEN

    Science.gov (United States)

    MOJANA, FRANCESCA; BRAR, MANPREET; CHENG, LINGYUN; BARTSCH, DIRK-UWE G.; FREEMAN, WILLIAM R.

    2012-01-01

    PURPOSE To determine the long-term effect of sub-threshold diode laser treatment for drusen in patients with non-exudative age-related macular degeneration (AMD) with spectral domain optical coherence tomography combined with simultaneous scanning laser ophthalmoscope (SD-OCT/SLO). METHODS 8 eyes of 4 consecutive AMD patients with bilateral drusen previously treated with sub-threshold diode laser were imaged with SD-OCT/SLO. Abnormalities in the outer retina layers reflectivity as seen with SD-OCT/SLO were retrospectively analyzed and compared with color fundus pictures and autofluorescence images (AF) acquired immediately before and after the laser treatment. RESULTS A focal discrete disruptions in the reflectivity of the outer retinal layers was noted in 29% of the laser lesions. The junction in between the inner and outer segment of the photoreceptor was more frequently affected, with associated focal damage of the outer nuclear layer. Defects of the RPE were occasionally detected. These changes did not correspond to threshold burns on color fundus photography, but corresponded to focal areas of increased AF in the majority of the cases. CONCLUSIONS Sub-threshold diode laser treatment causes long-term disruption of the retinal photoreceptor layer as analyzed by SD-OCT/SLO. The concept that sub-threshold laser treatment can achieve a selected RPE effect without damage to rods and cones may be flawed. PMID:21157398

  20. Initiation and propagation of damage in actively cooled CFC armoured high heat flux components in fusion machines

    International Nuclear Information System (INIS)

    Chevet, G.; Schlosser, J.; Martin, E.; Herb, V.; Camus, G.; Escourbiac, F.

    2009-01-01

    Plasma facing components (PFCs) in magnetic confinement controlled fusion machines are armoured with carbon fibre composite (CFC) bonded to a copper alloy heat sink. The manufacturing process induces high level of residual stresses due to the thermal expansion mismatch between CFC and copper and PFCs have to withstand strong stress ranges during operation. To study the initiation and propagation of damage in the CFC part, the ONERA damage model is used to describe the behaviour of the N11 material. The finite element simulations show that the damage is located near the interface and develops during the manufacturing of the PFCs as a consequence of the high amplitude of shear stresses. Under high heat flux, stresses decrease and the damage does not evolve. Further studies will take into account the damageable behaviour of the composite/copper interface, which will lead to geometrical optimisations and better knowledge of the link between damage and conductivity.

  1. Recent Advancements in DNA Damage-Transcription Crosstalk and High-Resolution Mapping of DNA Breaks.

    Science.gov (United States)

    Vitelli, Valerio; Galbiati, Alessandro; Iannelli, Fabio; Pessina, Fabio; Sharma, Sheetal; d'Adda di Fagagna, Fabrizio

    2017-08-31

    Until recently, DNA damage arising from physiological DNA metabolism was considered a detrimental by-product for cells. However, an increasing amount of evidence has shown that DNA damage could have a positive role in transcription activation. In particular, DNA damage has been detected in transcriptional elements following different stimuli. These physiological DNA breaks are thought to be instrumental for the correct expression of genomic loci through different mechanisms. In this regard, although a plethora of methods are available to precisely map transcribed regions and transcription start sites, commonly used techniques for mapping DNA breaks lack sufficient resolution and sensitivity to draw a robust correlation between DNA damage generation and transcription. Recently, however, several methods have been developed to map DNA damage at single-nucleotide resolution, thus providing a new set of tools to correlate DNA damage and transcription. Here, we review how DNA damage can positively regulate transcription initiation, the current techniques for mapping DNA breaks at high resolution, and how these techniques can benefit future studies of DNA damage and transcription.

  2. Bulk damage and absorption in fused silica due to high-power laser applications

    Science.gov (United States)

    Nürnberg, F.; Kühn, B.; Langner, A.; Altwein, M.; Schötz, G.; Takke, R.; Thomas, S.; Vydra, J.

    2015-11-01

    Laser fusion projects are heading for IR optics with high broadband transmission, high shock and temperature resistance, long laser durability, and best purity. For this application, fused silica is an excellent choice. The energy density threshold on IR laser optics is mainly influenced by the purity and homogeneity of the fused silica. The absorption behavior regarding the hydroxyl content was studied for various synthetic fused silica grades. The main absorption influenced by OH vibrational excitation leads to different IR attenuations for OH-rich and low-OH fused silica. Industrial laser systems aim for the maximum energy extraction possible. Heraeus Quarzglas developed an Yb-doped fused silica fiber to support this growing market. But the performance of laser welding and cutting systems is fundamentally limited by beam quality and stability of focus. Since absorption in the optical components of optical systems has a detrimental effect on the laser focus shift, the beam energy loss and the resulting heating has to be minimized both in the bulk materials and at the coated surfaces. In collaboration with a laser research institute, an optical finisher and end users, photo thermal absorption measurements on coated samples of different fused silica grades were performed to investigate the influence of basic material properties on the absorption level. High purity, synthetic fused silica is as well the material of choice for optical components designed for DUV applications (wavelength range 160 nm - 260 nm). For higher light intensities, e.g. provided by Excimer lasers, UV photons may generate defect centers that effect the optical properties during usage, resulting in an aging of the optical components (UV radiation damage). Powerful Excimer lasers require optical materials that can withstand photon energy close to the band gap and the high intensity of the short pulse length. The UV transmission loss is restricted to the DUV wavelength range below 300 nm and

  3. Single-longitudinal mode distributed-feedback fiber laser with low-threshold and high-efficiency

    Science.gov (United States)

    Jiang, Man; Zhou, Pu; Gu, Xijia

    2018-01-01

    Single-frequency fiber laser has attracted a lot of interest in recent years due to its numerous application potentials in telecommunications, LIDAR, high resolution sensing, atom frequency standard, etc. Phosphate glass fiber is one of the candidates for building compact high gain fiber lasers because of its capability of high-concentration of rare-earth ions doping in fiber core. Nevertheless, it is challenging for the integration of UV-written intra-core fiber Bragg gratings into the fiber laser cavity due to the low photosensitivity of phosphate glass fiber. The research presented in this paper will focus on demonstration of UV-written Bragg gratings in phosphate glass fiber and its application in direct-written short monolithic single-frequency fiber lasers. Strong π-phase shift Bragg grating structure is direct-inscribed into the Er/Yb co-doped gain fiber using an excimer laser, and a 5-cm-long phase mask is used to inscribe a laser cavity into the Er/Yb co-doped phosphate glass fibers. The phase mask is a uniform mask with a 50 μm gap in the middle. The fiber laser device emits output power of 10.44 mW with a slope efficiency of 21.5% and the threshold power is about 42.8 mW. Single-longitudinal mode operation is validated by radio frequency spectrum measurement. Moreover, the output spectrum at the highest power shows an excellent optical signal to noise ratio of about 70 dB. These results, to the best of our knowledge, show the lowest power threshold and highest efficiency among the reports that using the same structure to achieve single-longitudinal mode laser output.

  4. Reduced firing rates of high threshold motor units in response to eccentric overload.

    Science.gov (United States)

    Balshaw, Tom G; Pahar, Madhu; Chesham, Ross; Macgregor, Lewis J; Hunter, Angus M

    2017-01-01

    Acute responses of motor units were investigated during submaximal voluntary isometric tasks following eccentric overload (EO) and constant load (CL) knee extension resistance exercise. Ten healthy resistance-trained participants performed four experimental test sessions separated by 5 days over a 20 day period. Two sessions involved constant load and the other two used eccentric overload. EO and CL used both sessions for different target knee eccentric extension phases; one at 2 sec and the other at 4 sec. Maximal voluntary contractions (MVC) and isometric trapezoid efforts for 10 sec at 70% MVC were completed before and after each intervention and decomposed electromyography was used to measure motor unit firing rate. The firing rate of later recruited, high-threshold motor units declined following the 2-sec EO but was maintained following 2sec CL (P motor units were maintained for both loading types following 4-sec extension phases. MVC and rate of force development where maintained following both EO and CL and 2 and 4 sec phases. This study demonstrates a slower firing rate of high-threshold motor units following fast eccentric overload while MVC was maintained. This suggests that there was a neuromuscular stimulus without cost to the force-generating capacity of the knee extensors. © 2017 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.

  5. An application of impediography to the high sensitivity and high resolution identification of structural damage

    International Nuclear Information System (INIS)

    Zhao, L; Yang, J; Semperlotti, F; Wang, K W

    2015-01-01

    In this study we explore the use of impediographic techniques to perform damage detection in plate-like metal structures. Impediography relies on the piezo-resistive coupling of the host structure to reconstruct high sensitivity and high resolution maps of the internal electrical conductivity. By exploiting localized strain perturbations generated via focused acoustic waves, the piezo-resistive coupling allows extracting a set of linearly independent boundary voltage data that drastically reduces the ill-conditioning of the inverse problem, therefore increasing the performance. The localized perturbation is achieved by leveraging the concept of frequency selective structure (FSS), that is a dynamically tailored structural element enabling the required acoustic focusing via vibration localization. Based on the FSS approach, the impediographic technique is numerically tested to investigate the performance of the combined approach for structural damage detection. The effects of practical implementation issues, such as limited perturbations and limited boundary data, are also explored. (paper)

  6. Brain parenchymal damage in neuromyelitis optica spectrum disorder - A multimodal MRI study

    Energy Technology Data Exchange (ETDEWEB)

    Pache, F.; Paul, F. [Max Delbrueck Center for Molecular Medicine and Charite Universitaetsmedizin Berlin, NeuroCure Clinical Research Center and Experimental and Clinical Research Center, Berlin (Germany); Charite Universitaetsmedizin Berlin, Department of Neurology, Berlin (Germany); Zimmermann, H.; Lacheta, A.; Papazoglou, S.; Kuchling, J.; Wuerfel, J.; Brandt, A.U. [Max Delbrueck Center for Molecular Medicine and Charite Universitaetsmedizin Berlin, NeuroCure Clinical Research Center and Experimental and Clinical Research Center, Berlin (Germany); Finke, C. [Charite Universitaetsmedizin Berlin, Department of Neurology, Berlin (Germany); Humboldt-Universitaet zu Berlin, Berlin School of Mind and Brain, Berlin (Germany); Hamm, B. [Charite Universitaetsmedizin Berlin, Department of Radiology, Berlin (Germany); Ruprecht, K. [Charite Universitaetsmedizin Berlin, Department of Neurology, Berlin (Germany); Scheel, M. [Max Delbrueck Center for Molecular Medicine and Charite Universitaetsmedizin Berlin, NeuroCure Clinical Research Center and Experimental and Clinical Research Center, Berlin (Germany); Charite Universitaetsmedizin Berlin, Department of Radiology, Berlin (Germany)

    2016-12-15

    To investigate different brain regions for grey (GM) and white matter (WM) damage in a well-defined cohort of neuromyelitis optica spectrum disorder (NMOSD) patients and compare advanced MRI techniques (VBM, Subcortical and cortical analyses (Freesurfer), and DTI) for their ability to detect damage in NMOSD. We analyzed 21 NMOSD patients and 21 age and gender matched control subjects. VBM (GW/WM) and DTI whole brain (TBSS) analyses were performed at different statistical thresholds to reflect different statistical approaches in previous studies. In an automated atlas-based approach, Freesurfer and DTI results were compared between NMOSD and controls. DTI TBSS and DTI atlas based analysis demonstrated microstructural impairment only within the optic radiation or in regions associated with the optic radiation (posterior thalamic radiation p < 0.001, 6.9 % reduction of fractional anisotropy). VBM demonstrated widespread brain GM and WM reduction, but only at exploratory statistical thresholds, with no differences remaining after correction for multiple comparisons. Freesurfer analysis demonstrated no group differences. NMOSD specific parenchymal brain damage is predominantly located in the optic radiation, likely due to a secondary degeneration caused by ON. In comparison, DTI appears to be the most reliable and sensitive technique for brain damage detection in NMOSD. (orig.)

  7. Brain parenchymal damage in neuromyelitis optica spectrum disorder - A multimodal MRI study

    International Nuclear Information System (INIS)

    Pache, F.; Paul, F.; Zimmermann, H.; Lacheta, A.; Papazoglou, S.; Kuchling, J.; Wuerfel, J.; Brandt, A.U.; Finke, C.; Hamm, B.; Ruprecht, K.; Scheel, M.

    2016-01-01

    To investigate different brain regions for grey (GM) and white matter (WM) damage in a well-defined cohort of neuromyelitis optica spectrum disorder (NMOSD) patients and compare advanced MRI techniques (VBM, Subcortical and cortical analyses (Freesurfer), and DTI) for their ability to detect damage in NMOSD. We analyzed 21 NMOSD patients and 21 age and gender matched control subjects. VBM (GW/WM) and DTI whole brain (TBSS) analyses were performed at different statistical thresholds to reflect different statistical approaches in previous studies. In an automated atlas-based approach, Freesurfer and DTI results were compared between NMOSD and controls. DTI TBSS and DTI atlas based analysis demonstrated microstructural impairment only within the optic radiation or in regions associated with the optic radiation (posterior thalamic radiation p < 0.001, 6.9 % reduction of fractional anisotropy). VBM demonstrated widespread brain GM and WM reduction, but only at exploratory statistical thresholds, with no differences remaining after correction for multiple comparisons. Freesurfer analysis demonstrated no group differences. NMOSD specific parenchymal brain damage is predominantly located in the optic radiation, likely due to a secondary degeneration caused by ON. In comparison, DTI appears to be the most reliable and sensitive technique for brain damage detection in NMOSD. (orig.)

  8. A Violation of the Conditional Independence Assumption in the Two-High-Threshold Model of Recognition Memory

    Science.gov (United States)

    Chen, Tina; Starns, Jeffrey J.; Rotello, Caren M.

    2015-01-01

    The 2-high-threshold (2HT) model of recognition memory assumes that test items result in distinct internal states: they are either detected or not, and the probability of responding at a particular confidence level that an item is "old" or "new" depends on the state-response mapping parameters. The mapping parameters are…

  9. Review of BLM thresholds at tertiary LHC collimators

    CERN Document Server

    AUTHOR|(CDS)2257482; Zanetti, Marco

    The Large Hadron Collider is designed to accelerate protons at the unprecedented energy of 7 TeV. With a total stored energy of 360 MJ, even tiny losses can cause machine downtime or induce damage to sensitive accelerator components. The Beam Loss Monitors (BLMs) are an important component of the complex LHC protection system. They consist of a series of ionisation chambers located all around the ring to detect secondary particle showers induced by beam losses. The monitors are assigned thresholds such that if the radiation generated by the loss is too high, the BLM triggers a beam dump, preventing the loss to grow excessively. BLM signals are recorded for different integration windows, in order to detect losses on very different time scales, ranging from the extremely short ones (taking place over half a turn) to those very close to steady state (i.e. lasting for more than a minute). The LHC is equipped with a complex collimation system, to provide the machine with passive protection in case of transient los...

  10. Single-shot and single-spot measurement of laser ablation threshold for carbon nanotubes

    International Nuclear Information System (INIS)

    Lednev, Vasily N; Pershin, Sergey M; Bunkin, Alexey F; Obraztsova, Elena D; Kudryashov, Sergey I

    2013-01-01

    A simple and convenient procedure for single-shot, single-spot ablation threshold measurement is developed. It is based on the employment of cylindrical lens to obtain an elliptical Gaussian laser spot. The ablated spot chords that are parallel to the minor axis are measured across the spot major axis, which is proportional to the fluence cross-section, thus providing wide range dependence of damaged spot size versus fluence in one spot measurement. For both conventional and newly developed procedures the ablation threshold for typical Nd:YAG laser parameters (1064 nm, 10 ns) is measured as 50 ± 5 mJ cm -2 , which is one order of magnitude lower than that for bulk graphite.

  11. Molecular dynamics study on threshold displacement energies in Fe-Cr alloys

    Science.gov (United States)

    Fu, Jiawei; Ding, Wenyi; Zheng, Mingjie; Mao, Xiaodong

    2018-03-01

    The threshold displacement energies (Ed) of Fe and Cr atoms in Fe-Cr alloys with Cr contents ranging from 0% to 21% have been obtained with molecular dynamics (MD) method. The values of Ed have been calculated along the three high-symmetry crystallographic directions [0 0 1], [0 1 1] and [1 1 1], a slightly 2° tilt from these directions, and a high-index crystallographic directions [1 3 5]. The results showed that [0 1 1] crystallographic direction had the highest Ed among the three high-symmetry directions in each Cr content alloy. Fe-9Cr had higher weighted average Ed than the other Cr content alloys for both Fe and Cr PKA due to its statistically high Ed along the [0 1 1] crystallographic direction up to 44.3 eV. And the statistical analysis on the primary damage configuration demonstrated that 〈1 1 0〉Fe-Fe dumbbells were the dominant defect structures after relaxation. These data can enrich the database of Ed in Fe-Cr alloys and have potential applications in guiding the optimization design of radiation-resistant RAFM steels.

  12. Physical Interpretation of Laboratory Friction Laws in the Context of Damage Physics

    Science.gov (United States)

    Rundle, J. B.; Tiampo, K. F.; Martins, J. S.; Klein, W.

    2002-12-01

    Frictional on sliding surfaces is ultimately related to processes of surface damage, and can be understood in the context of the physics of dynamical threshold systems. Threshold systems are known to be some of the most important nonlinear, self-organizing systems in nature, including networks of earthquake faults, neural networks, superconductors and semiconductors, and the World Wide Web, as well as political, social, and ecological systems. All of these systems have dynamics that are strongly correlated in space and time, and all typically display a multiplicity of spatial and temporal scales. Here we discuss the physics of self-organization and damage in earthquake threshold systems at the "microscopic" laboratory scale, in which consideration of results from simulations leads to dynamical equations that can be used to derive results obtained from sliding friction experiments, specifically, the empirical "rate-and-state" friction equations of Ruina. Paradoxically, in all of these dissipative systems, long-range interactions induce the existence of locally ergodic dynamics, even though the dissipation of energy is involved. The existence of dissipative effects leads to the appearance of a "leaky threshold" dynamics, equivalent to a new scaling field that controls the size of nucleation events relative to the size of the background fluctuations. The corresponding appearance of a mean field spinodal leads to a general coarse-grained equation, which expresses the balance between rate of stress supplied, and rate of stress dissipated in the processes leading to surface damage. We can use ideas from thermodynamics and kinetics of phase transitions to develop the exact form of the rate-and-state equations, giving clear physical meaning to all terms and variables. Ultimately, the self-organizing dynamics arise from the appearance of an energy landscape in these systems, which in turn arises from the strong correlations and mean field nature of the physics.

  13. Comparison of retina damage thresholds simulating the femtosecond-laser in situ keratomileusis (fs-LASIK) process with two laser systems in the CW- and fs-regime

    Science.gov (United States)

    Sander, M.; Minet, O.; Zabarylo, U.; Müller, M.; Tetz, M. R.

    2012-04-01

    The femtosecond-laser in situ keratomileusis procedure affords the opportunity to correct ametropia by cutting transparent corneal tissue with ultra-short laser pulses. Thereby the tissue cut is generated by a laser-induced optical breakdown in the cornea with ultra-short laser pulses in the near-infrared range. Compared to standard procedures such as photorefractive keratectomy and laser in-situ keratomileusis with the excimer laser, where the risk potential for the eye is low due to the complete absorption of ultraviolet irradiation from corneal tissue, only a certain amount of the pulse energy is deposited in the cornea during the fs-LASIK process. The remaining energy propagates through the eye and interacts with the retina and the strong absorbing tissue layers behind. The objective of the presented study was to determine and compare the retina damage thresholds during the fs-LASIK process simulated with two various laser systems in the CW- and fs-regime.

  14. Rainfall thresholds and susceptibility mapping for shallow landslides and debris flows in Scotland

    Science.gov (United States)

    Postance, Benjamin; Hillier, John; Dijkstra, Tom; Dixon, Neil

    2017-04-01

    Shallow translational slides and debris flows (hereafter 'landslides') pose a significant threat to life and cause significant annual economic impacts (e.g. by damage and disruption of infrastructure). The focus of this research is on the definition of objective rainfall thresholds using a weather radar system and landslide susceptibility mapping. In the study area Scotland, an inventory of 75 known landslides was used for the period 2003 to 2016. First, the effect of using different rain records (i.e. time series length) on two threshold selection techniques in receiver operating characteristic (ROC) analysis was evaluated. The results show that thresholds selected by 'Threat Score' (minimising false alarms) are sensitive to rain record length and which is not routinely considered, whereas thresholds selected using 'Optimal Point' (minimising failed alarms) are not; therefore these may be suited to establishing lower limit thresholds and be of interest to those developing early warning systems. Robust thresholds are found for combinations of normalised rain duration and accumulation at 1 and 12 day's antecedence respectively; these are normalised using the rainy-day normal and an equivalent measure for rain intensity. This research indicates that, in Scotland, rain accumulation provides a better indicator than rain intensity and that landslides may be generated by threshold conditions lower than previously thought. Second, a landslide susceptibility map is constructed using a cross-validated logistic regression model. A novel element of the approach is that landslide susceptibility is calculated for individual hillslope sections. The developed thresholds and susceptibility map are combined to assess potential hazards and impacts posed to the national highway network in Scotland.

  15. Effects of ionizing radiation on laser-induced damage in SiO/sub 2/

    Energy Technology Data Exchange (ETDEWEB)

    Soileau, M J; Mansour, N; Canto, E; Griscom, D L

    1988-05-01

    The effects of radiation damage on bulk laser-induced damage in SiO/sub 2/ were investigated. Samples studied included Spectrasil A, B, and WF (water free). Measurements of laser-induced breakdown were conducted with 532 and 1064 nm laser pulses of approximately 20 ns duration. Reductions of up to 40% in the laser-induced breakdown threshold were observed at 532 nm for samples exposed to 10/sup 8/ rad of ..gamma..-radiation. The decrease in breakdown threshold for irradiated SiO/sub 2/ samples at 532 nm was found to be proportional to the linear absorption of the specimen at 266 nm. These results are in good agreement with a proposed model which suggests that two-photon absorption initiated avalanche process is responsible for laser-induced breakdown for these materials.

  16. Hearing thresholds at high frequency in patients with cystic fibrosis: a systematic review

    Directory of Open Access Journals (Sweden)

    Debora T.M. Caumo

    Full Text Available Abstract Introduction: High-frequency audiometry may contribute to the early detection of hearing loss caused by ototoxic medications. Many ototoxic drugs are widely used in the treatment of patients with cystic fibrosis. Early detection of hearing loss should allow known harmful drugs to be identified before the damage affects speech frequencies. The damage caused by ototoxicity is irreversible, resulting in important social and psychological consequences. In children, hearing loss, even when restricted to high frequencies, can affect the development of language. Objective: To investigate the efficacy and effectiveness of hearing monitoring through high-frequency audiometry in pediatric patients with cystic fibrosis. Methods: Electronic databases PubMed, MedLine, Web of Science and LILACS were searched, from January to November 2015. The selected studies included those in which high-frequency audiometry was performed in patients with cystic fibrosis, undergoing treatment with ototoxic drugs and published in Portuguese, English and Spanish. The GRADE system was chosen for the evaluation of the methodological quality of the articles. Results: During the search process carried out from January 2015 to November 2015, 512 publications were identified, of which 250 were found in PubMed, 118 in MedLine, 142 in Web of Science and 2 in LILACS. Of these, nine articles were selected. Conclusion: The incidence of hearing loss was identified at high frequencies in cystic fibrosis patients without hearing complaints. It is assumed that high-frequency audiometry can be an early diagnostic method to be recommended for hearing investigation of patients at risk of ototoxicity.

  17. Theory of threshold phenomena

    International Nuclear Information System (INIS)

    Hategan, Cornel

    2002-01-01

    Theory of Threshold Phenomena in Quantum Scattering is developed in terms of Reduced Scattering Matrix. Relationships of different types of threshold anomalies both to nuclear reaction mechanisms and to nuclear reaction models are established. Magnitude of threshold effect is related to spectroscopic factor of zero-energy neutron state. The Theory of Threshold Phenomena, based on Reduced Scattering Matrix, does establish relationships between different types of threshold effects and nuclear reaction mechanisms: the cusp and non-resonant potential scattering, s-wave threshold anomaly and compound nucleus resonant scattering, p-wave anomaly and quasi-resonant scattering. A threshold anomaly related to resonant or quasi resonant scattering is enhanced provided the neutron threshold state has large spectroscopic amplitude. The Theory contains, as limit cases, Cusp Theories and also results of different nuclear reactions models as Charge Exchange, Weak Coupling, Bohr and Hauser-Feshbach models. (author)

  18. Determination of displacement threshold energies in pure Ti and in γ-TiAl alloys by electron irradiation

    International Nuclear Information System (INIS)

    Sattonnay, G.; Dimitrov, O.

    1999-01-01

    Resistivity damage rates, determined during low-temperature electron irradiations in the energy range 0.3-2.5 MeV, were used for evaluating displacement threshold energies of titanium in high purity hcp titanium, and of titanium and aluminium in γ-TiAl intermetallic compounds. These parameters were deduced from a comparison of experimental displacement cross-section variations as a function of electron energy, with theoretical curves based on a displacement model for diatomic materials. The displacement energy of titanium in hcp titanium appears to depend on the electron energy. A threshold value of 21±1 eV was obtained in the range 0.3-0.5 MeV, and a larger value of 30±2 eV is determined in the range 0.5-2.5 MeV. In γ-TiAl, aluminium atoms are displaced first, with a threshold displacement energy (34±2 eV) larger than the one of titanium atoms, and much higher than the value in pure aluminium. The displacement energy of Ti atoms is 28±2 eV, close to the one obtained in pure titanium under similar conditions. These results were used for re-evaluating the Frenkel-pair resistivity of the stoichiometric TiAl compound. (orig.)

  19. Actual implications of industrial smoke damage to forests

    Energy Technology Data Exchange (ETDEWEB)

    Zieger, E

    1955-01-01

    General problems of smoke-induced damages, diagnosis, and control methods are reviewed. Damages caused by etching of leaves and needles are mostly of an acute and local character. Damages due to disturbed assimilation, caused primarily by sulfur dioxide, are of the greatest importance economically. Sulfur dioxide is less harmful in winter and during night hours. Acids and sulfur dioxide both turn the soil acid, and affect the edaphon. Such damages are primarily of chronic character. Different diagnostic methods such as plant, soil, and air analyses should be combined to obtain reliable results. Due to the complexity of the processes involved in smoke damages, biological tests are best in diagnosis. The sunlight test exploits the fact that branches cut from smoke-damaged trees lose their needles more readily than such from intact trees. Haertels turbidity test is based on the increased wax secretion by smoke-damaged needles. The appraisal of damages is made by evaluation of the economic losses after the limitation of the smoke-affected area. The possible control measures in forestry are the breeding of smoke-resistant species and liming, while the pollution control techniques presently available in industry are unsatisfactory, the major problems being caused by sulfur dioxide. Standardization of thresholds and maximum allowable concentrations, as well as cooperation of forestry and industries are imperative. 12 references.

  20. Foton Crosses the High Threshold of Overseas Market--the First 40 Van Arrives at Russia

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    @@ On January 14, 2006, after half year's planning, 40 Foton View Van start the expedition from the headquarter square of Foton Motor.It is believed that it is another achievement of Foton Motor's overseas "strategic market" export. The export is a landmark for Foton Motor. Iran, Russia and India are defined as the 3 major overseas strategic markets for the export thresholds are very high and hard to operate.

  1. Effects of programming threshold and maplaw settings on acoustic thresholds and speech discrimination with the MED-EL COMBI 40+ cochlear implant.

    Science.gov (United States)

    Boyd, Paul J

    2006-12-01

    The principal task in the programming of a cochlear implant (CI) speech processor is the setting of the electrical dynamic range (output) for each electrode, to ensure that a comfortable loudness percept is obtained for a range of input levels. This typically involves separate psychophysical measurement of electrical threshold ([theta] e) and upper tolerance levels using short current bursts generated by the fitting software. Anecdotal clinical experience and some experimental studies suggest that the measurement of [theta]e is relatively unimportant and that the setting of upper tolerance limits is more critical for processor programming. The present study aims to test this hypothesis and examines in detail how acoustic thresholds and speech recognition are affected by setting of the lower limit of the output ("Programming threshold" or "PT") to understand better the influence of this parameter and how it interacts with certain other programming parameters. Test programs (maps) were generated with PT set to artificially high and low values and tested on users of the MED-EL COMBI 40+ CI system. Acoustic thresholds and speech recognition scores (sentence tests) were measured for each of the test maps. Acoustic thresholds were also measured using maps with a range of output compression functions ("maplaws"). In addition, subjective reports were recorded regarding the presence of "background threshold stimulation" which is occasionally reported by CI users if PT is set to relatively high values when using the CIS strategy. Manipulation of PT was found to have very little effect. Setting PT to minimum produced a mean 5 dB (S.D. = 6.25) increase in acoustic thresholds, relative to thresholds with PT set normally, and had no statistically significant effect on speech recognition scores on a sentence test. On the other hand, maplaw setting was found to have a significant effect on acoustic thresholds (raised as maplaw is made more linear), which provides some theoretical

  2. Development of hybrid organic-inorganic optical coatings to prevent laser damage

    International Nuclear Information System (INIS)

    Compoint, Francois

    2015-01-01

    The optical devices (lents, mirrors, portholes...) that are set on the chains of the Laser Megajoule (LMJ) may be damaged by the high energy laser beam especially around the UV wavelength of 351 nm. The damages are micronic craters on the rear of the optics that grows exponentially after each laser shots. The study aims at developing some optical thin coatings on the rear of the optical substrates to prevent the growth of the damage by amortizing the laser shock wave, self-healing the craters that has appeared, or repairing the laser hole after the damage occurs. The thin coatings have been prepared by a sol-gel method by using silica precursor and a polydimethylsiloxane (PDMS) elastomer. The two species reacted together to get a hybrid organic-inorganic Ormosil (organically modified silica) material, by creating a silica network linked to the PDMS species with covalent and hydrogen bounds. The thin layers are obtained from the sol-gel solution by using a dip and spin coating method. The coatings have an excellent optical transmission around the UV (351 nm) wavelength. They also have some self-healing properties by using mechanical (viscoelastic) mechanism and chemical reversible hydrogen bounds action in the materials. The silica-PDMS coatings prove to be resistant to the laser beam at 351 nm, despite some optimizations that still need to be done to reach the sought laser damage threshold. (author) [fr

  3. High-damage-resistant tungsten disulfide saturable absorber mirror for passively Q-switched fiber laser.

    Science.gov (United States)

    Chen, Hao; Chen, YuShan; Yin, Jinde; Zhang, Xuejun; Guo, Tuan; Yan, Peiguang

    2016-07-25

    In this paper, we demonstrate a high-damage-resistant tungsten disulfide saturable absorber mirror (WS2-SAM) fabricated by magnetron sputtering technique. The WS2-SAM has an all-fiber-integrated configuration and high-damage-resistant merit because the WS2 layer is protected by gold film so as to avoid being oxidized and destroyed at high pump power. Employing the WS2-SAM in an Erbium-doped fiber laser (EDFL) with linear cavity, the stable Q-switching operation is achieved at central wavelength of 1560 nm, with the repetition rates ranging from 29.5 kHz to 367.8 kHz and the pulse duration ranging from 1.269 μs to 154.9 ns. For the condition of the maximum pump power of 600 mW, the WS2-SAM still works stably with an output power of 25.2 mW, pulse energy of 68.5 nJ, and signal-noise-ratio of 42 dB. The proposed WS2-SAM configuration provides a promising solution for advanced pulsed fiber lasers with the characteristics of high damage resistance, high output energy, and wide tunable frequency.

  4. Demonstration of a 100-mJ OPO/OPA for future lidar applications and laser-induced damage threshold testing of optical components for MERLIN

    Science.gov (United States)

    Elsen, Florian; Livrozet, Marie; Strotkamp, Michael; Wüppen, Jochen; Jungbluth, Bernd; Kasemann, Raphael; Löhring, Jens; Meissner, Ansgar; Meyer, Rudolf; Hoffmann, Hans-Dieter; Poprawe, Reinhart

    2018-02-01

    In the field of atmospheric research, lidar is a powerful technology that can measure gas or aerosol concentrations, wind speed, or temperature profiles remotely. To conduct such measurements globally, spaceborne systems are advantageous. Pulse energies in the 100-mJ range are required to achieve highly accurate, longitudinal resolved measurements. Measuring concentrations of specific gases, such as CH4 or CO2, requires output wavelengths in the IR-B, which can be addressed by optical-parametric frequency conversion. An OPO/OPA frequency conversion setup was designed and built as a demonstration module to address the 1.6-μm range. The pump laser is an Nd:YAG-MOPA system, consisting of a stable oscillator and two subsequent Innoslab-based amplifier stages that deliver up to 500 mJ of output pulse energy at 100 Hz repetition frequency. The OPO is inherited from the OPO design for the CH4 lidar instrument on the French-German climate satellite methane remote-sensing lidar mission (MERLIN). To address the 100-mJ regime, the OPO output beam is amplified in a subsequent multistage OPA. With potassium titanyl phosphate as nonlinear medium, the OPO/OPA delivered more than 100 mJ of output energy at 1645 nm from 450 mJ of the pump energy and a pump pulse duration of 30 ns. This corresponds to a quantum conversion efficiency of about 25%. In addition to demonstrating optical performance for future lidar systems, this laser will be part of a laser-induced damage thresholds test facility, which will be used to qualify optical components especially for the MERLIN.

  5. Particles near threshold

    International Nuclear Information System (INIS)

    Bhattacharya, T.; Willenbrock, S.

    1993-01-01

    We propose returning to the definition of the width of a particle in terms of the pole in the particle's propagator. Away from thresholds, this definition of width is equivalent to the standard perturbative definition, up to next-to-leading order; however, near a threshold, the two definitions differ significantly. The width as defined by the pole position provides more information in the threshold region than the standard perturbative definition and, in contrast with the perturbative definition, does not vanish when a two-particle s-wave threshold is approached from below

  6. Flux threshold measurements of He-ion beam induced nanofuzz formation on hot tungsten surfaces

    International Nuclear Information System (INIS)

    Meyer, F W; Hijazi, H; Bannister, M E; Unocic, K A; Garrison, L M; Parish, C M

    2016-01-01

    We report measurements of the energy dependence of flux thresholds and incubation fluences for He-ion induced nano-fuzz formation on hot tungsten surfaces at UHV conditions over a wide energy range using real-time sample imaging of tungsten target emissivity change to monitor the spatial extent of nano-fuzz growth, corroborated by ex situ SEM and FIB/SEM analysis, in conjunction with accurate ion-flux profile measurements. The measurements were carried out at the multicharged ion research facility (MIRF) at energies from 218 eV to 8.5 keV, using a high-flux deceleration module and beam flux monitor for optimizing the decel optics on the low energy MIRF beamline. The measurements suggest that nano-fuzz formation proceeds only if a critical rate of change of trapped He density in the W target is exceeded. To understand the energy dependence of the observed flux thresholds, the energy dependence of three contributing factors: ion reflection, ion range and target damage creation, were determined using the SRIM simulation code. The observed energy dependence can be well reproduced by the combined energy dependences of these three factors. The incubation fluences deduced from first visual appearance of surface emissivity change were (2–4) × 10 23 m −2 at 218 eV, and roughly a factor of 10 less at the higher energies, which were all at or above the displacement energy threshold. The role of trapping at C impurity sites is discussed. (paper)

  7. A threshold for dissipative fission

    International Nuclear Information System (INIS)

    Thoennessen, M.; Bertsch, G.F.

    1993-01-01

    The empirical domain of validity of statistical theory is examined as applied to fission data on pre-fission data on pre-fission neutron, charged particle, and γ-ray multiplicities. Systematics are found of the threshold excitation energy for the appearance of nonstatistical fission. From the data on systems with not too high fissility, the relevant phenomenological parameter is the ratio of the threshold temperature T thresh to the (temperature-dependent) fission barrier height E Bar (T). The statistical model reproduces the data for T thresh /E Bar (T) thresh /E Bar (T) independent of mass and fissility of the systems

  8. Threshold current for fireball generation

    Science.gov (United States)

    Dijkhuis, Geert C.

    1982-05-01

    Fireball generation from a high-intensity circuit breaker arc is interpreted here as a quantum-mechanical phenomenon caused by severe cooling of electrode material evaporating from contact surfaces. According to the proposed mechanism, quantum effects appear in the arc plasma when the radius of one magnetic flux quantum inside solid electrode material has shrunk to one London penetration length. A formula derived for the threshold discharge current preceding fireball generation is found compatible with data reported by Silberg. This formula predicts linear scaling of the threshold current with the circuit breaker's electrode radius and concentration of conduction electrons.

  9. Median filters as a tool to determine dark noise thresholds in high resolution smartphone image sensors for scientific imaging

    Science.gov (United States)

    Igoe, Damien P.; Parisi, Alfio V.; Amar, Abdurazaq; Rummenie, Katherine J.

    2018-01-01

    An evaluation of the use of median filters in the reduction of dark noise in smartphone high resolution image sensors is presented. The Sony Xperia Z1 employed has a maximum image sensor resolution of 20.7 Mpixels, with each pixel having a side length of just over 1 μm. Due to the large number of photosites, this provides an image sensor with very high sensitivity but also makes them prone to noise effects such as hot-pixels. Similar to earlier research with older models of smartphone, no appreciable temperature effects were observed in the overall average pixel values for images taken in ambient temperatures between 5 °C and 25 °C. In this research, hot-pixels are defined as pixels with intensities above a specific threshold. The threshold is determined using the distribution of pixel values of a set of images with uniform statistical properties associated with the application of median-filters of increasing size. An image with uniform statistics was employed as a training set from 124 dark images, and the threshold was determined to be 9 digital numbers (DN). The threshold remained constant for multiple resolutions and did not appreciably change even after a year of extensive field use and exposure to solar ultraviolet radiation. Although the temperature effects' uniformity masked an increase in hot-pixel occurrences, the total number of occurrences represented less than 0.1% of the total image. Hot-pixels were removed by applying a median filter, with an optimum filter size of 7 × 7; similar trends were observed for four additional smartphone image sensors used for validation. Hot-pixels were also reduced by decreasing image resolution. The method outlined in this research provides a methodology to characterise the dark noise behavior of high resolution image sensors for use in scientific investigations, especially as pixel sizes decrease.

  10. Structural influences on the laser damage resistance of optical oxide coatings for use at 1064 nm

    Energy Technology Data Exchange (ETDEWEB)

    Hacker, E; Lauth, H; Meyer, J; Weissbrodt, P [Zeiss Jena GmbH, Jena (Germany, F.R.); Wolf, R; Zscherpe, G [Ingenieurhochschule Mittweida (Germany, F.R.); Heyer, H [Sektion Physik, Friedrich-Schiller-Univ. Jena (Germany, F.R.)

    1990-11-01

    Optical coatings of titania (TiO{sub 2}) and tantala (Ta{sub 2}O{sub 5}) prepared by reactive r.f. diode and d.c. plasmatron sputtering were investigated for the influence of structural properties on the 1064 nm laser damage resistance. Using various methods of characterizing the compositional, crystallographic, microstructural and optical properties, it was found that the damage thresholds are directly related to the content of oxygen in the films in excess of the stoichiometric values, whereas grain sizes and refractive indices show no systematic influences valid for both oxide materials. The highest oxygen-to-metal atomic ratios and thus the highest damage threshold were achieved by the use of r.f diode sputtering. X-ray photospectroscopy investigations of tantala coatings with different oxygen-to-tantalum atomic ratios up to 2.75 revealed for both constituents of the oxide only binding energies representative for tantalum pentoxide. (orig.).

  11. Tunneling-induced shift of the cutoff law for high-order above-threshold ionization

    International Nuclear Information System (INIS)

    Lai, X. Y.; Quan, W.; Liu, X.

    2011-01-01

    We investigate the cutoff law for high-order above-threshold ionization (HATI) within a semiclassical framework. By explicitly adopting the tunneling effect and considering the initial position shift of the tunneled electron from the origin in the model, the cutoff energy position in HATI spectrum exhibits a well-defined upshift from the simple-man model prediction. The comparison between numerical results from our improved semiclassical model and the quantum-orbit theory shows a good agreement for small values of the Keldysh parameter γ, implying the important role of the inherent quantum tunneling effect in HATI dynamics.

  12. Use of high voltage electron microscope to simulate radiation damage by neutrons

    International Nuclear Information System (INIS)

    Mayer, R.M.

    1976-01-01

    The use of the high voltage electron microscope to simulate radiation damage by neutrons is briefly reviewed. This information is important in explaining how alloying affects void formation during neutron irradiation

  13. High-Threshold Low-Overhead Fault-Tolerant Classical Computation and the Replacement of Measurements with Unitary Quantum Gates.

    Science.gov (United States)

    Cruikshank, Benjamin; Jacobs, Kurt

    2017-07-21

    von Neumann's classic "multiplexing" method is unique in achieving high-threshold fault-tolerant classical computation (FTCC), but has several significant barriers to implementation: (i) the extremely complex circuits required by randomized connections, (ii) the difficulty of calculating its performance in practical regimes of both code size and logical error rate, and (iii) the (perceived) need for large code sizes. Here we present numerical results indicating that the third assertion is false, and introduce a novel scheme that eliminates the two remaining problems while retaining a threshold very close to von Neumann's ideal of 1/6. We present a simple, highly ordered wiring structure that vastly reduces the circuit complexity, demonstrates that randomization is unnecessary, and provides a feasible method to calculate the performance. This in turn allows us to show that the scheme requires only moderate code sizes, vastly outperforms concatenation schemes, and under a standard error model a unitary implementation realizes universal FTCC with an accuracy threshold of p<5.5%, in which p is the error probability for 3-qubit gates. FTCC is a key component in realizing measurement-free protocols for quantum information processing. In view of this, we use our scheme to show that all-unitary quantum circuits can reproduce any measurement-based feedback process in which the asymptotic error probabilities for the measurement and feedback are (32/63)p≈0.51p and 1.51p, respectively.

  14. Subsurface damage mechanism of high speed grinding process in single crystal silicon revealed by atomistic simulations

    International Nuclear Information System (INIS)

    Li, Jia; Fang, Qihong; Zhang, Liangchi; Liu, Youwen

    2015-01-01

    Highlights: • Molecular dynamic model of nanoscale high speed grinding of silicon workpiece has been established. • The effect of grinding speed on subsurface damage and grinding surface integrity by analyzing the chip, dislocation movement, and phase transformation during high speed grinding process are thoroughly investigated. • Subsurface damage is studied by the evolution of surface area at first time for more obvious observation on transition from ductile to brittle. • The hydrostatic stress and von Mises stress by the established analytical model are studied subsurface damage mechanism during nanoscale grinding. - Abstract: Three-dimensional molecular dynamics (MD) simulations are performed to investigate the nanoscale grinding process of single crystal silicon using diamond tool. The effect of grinding speed on subsurface damage and grinding surface integrity by analyzing the chip, dislocation movement, and phase transformation are studied. We also establish an analytical model to calculate several important stress fields including hydrostatic stress and von Mises stress for studying subsurface damage mechanism, and obtain the dislocation density on the grinding subsurface. The results show that a higher grinding velocity in machining brittle material silicon causes a larger chip and a higher temperature, and reduces subsurface damage. However, when grinding velocity is above 180 m s −1 , subsurface damage thickness slightly increases because a higher grinding speed leads to the increase in grinding force and temperature, which accelerate dislocation nucleation and motion. Subsurface damage is studied by the evolution of surface area at first time for more obvious observation on transition from ductile to brittle, that provides valuable reference for machining nanometer devices. The von Mises stress and the hydrostatic stress play an important role in the grinding process, and explain the subsurface damage though dislocation mechanism under high

  15. Use of enzymes to minimize the rheological dough problems caused by high levels of damaged starch in starch-gluten systems.

    Science.gov (United States)

    Barrera, Gabriela N; León, Alberto E; Ribotta, Pablo D

    2016-05-01

    During wheat milling, starch granules can experience mechanical damage, producing damaged starch. High levels of damaged starch modify the physicochemical properties of wheat flour, negatively affecting the dough behavior as well as the flour quality and cookie and bread making quality. The aim of this work was to evaluate the effect of α-amylase, maltogenic amylase and amyloglucosidase on dough rheology in order to propose alternatives to reduce the issues related to high levels of damaged starch. The dough with a high level of damaged starch became more viscous and resistant to deformations as well as less elastic and extensible. The soluble fraction of the doughs influenced the rheological behavior of the systems. The α-amylase and amyloglucosidase reduced the negative effects of high damaged starch contents, improving the dough rheological properties modified by damaged starch. The rheological behavior of dough with the higher damaged-starch content was related to a more open gluten network arrangement as a result of the large size of the swollen damaged starch granules. We can conclude that the dough rheological properties of systems with high damaged starch content changed positively as a result of enzyme action, particularly α-amylase and amyloglucosidase additions, allowing the use of these amylases and mixtures of them as corrective additives. Little information was reported about amyloglucosidase activity alone or combined with α-amylase. The combinations of these two enzymes are promising to minimize the negative effects caused by high levels of damaged starch on product quality. More research needs to be done on bread quality combining these two enzymes. © 2015 Society of Chemical Industry. © 2015 Society of Chemical Industry.

  16. Foton Crosses the High Threshold of Overseas Market--the First 40 Van Arrives at Russia

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

      On January 14, 2006, after half year's planning, 40 Foton View Van start the expedition from the headquarter square of Foton Motor.It is believed that it is another achievement of Foton Motor's overseas "strategic market" export. The export is a landmark for Foton Motor. Iran, Russia and India are defined as the 3 major overseas strategic markets for the export thresholds are very high and hard to operate.……

  17. QRS Detection Based on Improved Adaptive Threshold

    Directory of Open Access Journals (Sweden)

    Xuanyu Lu

    2018-01-01

    Full Text Available Cardiovascular disease is the first cause of death around the world. In accomplishing quick and accurate diagnosis, automatic electrocardiogram (ECG analysis algorithm plays an important role, whose first step is QRS detection. The threshold algorithm of QRS complex detection is known for its high-speed computation and minimized memory storage. In this mobile era, threshold algorithm can be easily transported into portable, wearable, and wireless ECG systems. However, the detection rate of the threshold algorithm still calls for improvement. An improved adaptive threshold algorithm for QRS detection is reported in this paper. The main steps of this algorithm are preprocessing, peak finding, and adaptive threshold QRS detecting. The detection rate is 99.41%, the sensitivity (Se is 99.72%, and the specificity (Sp is 99.69% on the MIT-BIH Arrhythmia database. A comparison is also made with two other algorithms, to prove our superiority. The suspicious abnormal area is shown at the end of the algorithm and RR-Lorenz plot drawn for doctors and cardiologists to use as aid for diagnosis.

  18. Organic nonlinear crystals and high power frequency conversion

    International Nuclear Information System (INIS)

    Velsko, S.P.; Davis, L.; Wang, F.; Monaco, S.; Eimerl, D.

    1987-01-01

    The authors are searching for new second and third harmonic generators among the salts of organic acids and bases. They discuss the relevant properties of crystals from this group of compounds, including their nonlinear and phasematching characteristics, linear absorption, damage threshold and crystal growth. In addition, they summarize what is known concerning other nonlinear optical properties of these crystals, such as two-photon absorption, nonlinear refractive index, and stimulated Raman thresholds. A preliminary assessment is made of the potential of these materials for use in future high power, large aperture lasers such as those used for inertial confinement fusion experiments

  19. Combined effects of displacement damage and high gas content in aluminum

    International Nuclear Information System (INIS)

    Farrell, K.; Houston, J.T.

    1976-01-01

    A solid solution alloy of 2300 at. ppM of 6 Li isotope in aluminum was neutron irradiated at about 0.36 T/sub m/ in high, fast and thermal fluxes producing a damage level of 2 to 3 dpa and simultaneously inducing a gas content of about 2200 at. ppM each of helium and tritium from burnup of 6 Li. The gases significantly increased the nucleation of structural defects but did not change the degree of swelling; cavity concentrations were increased approximately 1000-fold, cavity sizes were decreased approximately 10-fold and there was approximately 10-fold increase in the concentrations of dislocations. Also, large cavities were developed on grain boundaries. The cavities were consistent with their being gas-filled bubbles. The refinement of damage structure by the gases caused a considerable increase in radiation hardening. Bend tests at 77 and 296 0 K revealed severe embrittlement and intergranular fracture. Comparison with data from material irradiated to produce comparable gas levels but relatively little displacement damage indicates that premature intergranular failure is much enhanced by the presence of a defect-hardened matrix. Postirradiation annealing tests showed the cavity and dislocation structures to have high resistance to annealing. Annealing also encouraged the development of a secondary population of large cavities believed to be associated with migration and precipitation of tritium

  20. Combined effects of displacement damage and high gas content in aluminum

    International Nuclear Information System (INIS)

    Farrell, K.; Houston, J.T.

    1976-05-01

    A solid solution alloy of 2300 appm of 6 Li isotope in aluminum was neutron irradiated at about 0.36 T/sub m/ in high, fast and thermal fluxes producing a damage level of 2 to 3 dpa and simultaneously inducing a gas content of about 2200 appm each of helium and tritium from burnup of 6 Li. The gases significantly increased the nucleation of structural defects but did not change the degree of swelling; cavity concentrations were increased approximately 1000-fold, cavity sizes were decreased approximately 10-fold and there was approximately 10-fold increase in the concentrations of dislocations. Also, large cavities were developed on grain boundaries. The cavities were consistent with their being gas-filled bubbles. The refinement of damage structure by the gases caused a considerable increase in radiation hardening. Bend tests at 77 and 296 K revealed severe embrittlement and intergranular fracture. Comparison with data from material irradiated to produce comparable gas levels but relatively little displacement damage indicates that premature intergranular failure is much enhanced by the presence of a defect-hardened matrix. Postirradiation annealing tests showed the cavity and dislocation structures to have high resistance to annealing. Annealing also encouraged the development of a secondary population of large cavities believed to be associated with migration and precipitation of tritium

  1. How much can disaster and climate science contribute to loss and damage mechanisms in international climate policy?

    Science.gov (United States)

    Huggel, Christian; Allen, Simon; Eicken, Hajo; Hansen, Gerrit; Stone, Dáithí

    2015-04-01

    As the 5th Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) recently has shown, there is increasing evidence of observed impacts of climate change on natural and human systems. Some of these impacts are negative and result in damage and loss of lives and assets. In international climate policy negotiations under the UNFCCC the discussions on loss and damage have gained significant traction during the past negotiation rounds. At COP 19 the Warsaw International Mechanism for Loss and Damage (WIM) was created as an institutional arrangement to address this issue. Thereby, loss and damage (L&D) are typically defined as the residual damage and loss that occur beyond mitigation and adaptation efforts. This implies that effective mitigation and adaptation policy can substantially reduce L&D. While there is wide agreement that knowledge and understanding needs to be strengthened on how L&D due to climate change affects countries, in particular highly vulnerable countries and populations, there is still substantial disagreement on several aspects. In fact, after COP20 in Lima a number of options are on the table, including whether L&D should be located under the adaptation framework or form a separate institutional arrangement, or whether a compensation regime should be established to support developing countries. Similarly, the scientific framework for a clear L&D concept, its application in real-world cases, and implications for international climate policy, in particular with respect to questions of responsibility, liability, compensation and financing, is still evolving. Earlier proposals, for instance, have included a threshold concept, with payments released upon crossing of certain thresholds of climate (related) parameters, similar to insurance procedures. The threshold would be defined as a departure of the parameter from baseline conditions, for instance a rainfall event that is more intense than a certain baseline based threshold. Further

  2. Thermotactile perception thresholds measurement conditions.

    Science.gov (United States)

    Maeda, Setsuo; Sakakibara, Hisataka

    2002-10-01

    The purpose of this paper is to investigate the effects of posture, push force and rate of temperature change on thermotactile thresholds and to clarify suitable measuring conditions for Japanese people. Thermotactile (warm and cold) thresholds on the right middle finger were measured with an HVLab thermal aesthesiometer. Subjects were eight healthy male Japanese students. The effects of posture in measurement were examined in the posture of a straight hand and forearm placed on a support, the same posture without a support, and the fingers and hand flexed at the wrist with the elbow placed on a desk. The finger push force applied to the applicator of the thermal aesthesiometer was controlled at a 0.5, 1.0, 2.0 and 3.0 N. The applicator temperature was changed to 0.5, 1.0, 1.5, 2.0 and 2.5 degrees C/s. After each measurement, subjects were asked about comfort under the measuring conditions. Three series of experiments were conducted on different days to evaluate repeatability. Repeated measures ANOVA showed that warm thresholds were affected by the push force and the rate of temperature change and that cold thresholds were influenced by posture and push force. The comfort assessment indicated that the measurement posture of a straight hand and forearm laid on a support was the most comfortable for the subjects. Relatively high repeatability was obtained under measurement conditions of a 1 degrees C/s temperature change rate and a 0.5 N push force. Measurement posture, push force and rate of temperature change can affect the thermal threshold. Judging from the repeatability, a push force of 0.5 N and a temperature change of 1.0 degrees C/s in the posture with the straight hand and forearm laid on a support are recommended for warm and cold threshold measurements.

  3. DOE approach to threshold quantities

    International Nuclear Information System (INIS)

    Wickham, L.E.; Kluk, A.F.; Department of Energy, Washington, DC)

    1985-01-01

    The Department of Energy (DOE) is developing the concept of threshold quantities for use in determining which waste materials must be handled as radioactive waste and which may be disposed of as nonradioactive waste at its sites. Waste above this concentration level would be managed as radioactive or mixed waste (if hazardous chemicals are present); waste below this level would be handled as sanitary waste. Ideally, the threshold must be set high enough to significantly reduce the amount of waste requiring special handling. It must also be low enough so that waste at the threshold quantity poses a very small health risk and multiple exposures to such waste would still constitute a small health risk. It should also be practical to segregate waste above or below the threshold quantity using available instrumentation. Guidance is being prepared to aid DOE sites in establishing threshold quantity values based on pathways analysis using site-specific parameters (waste stream characteristics, maximum exposed individual, population considerations, and site specific parameters such as rainfall, etc.). A guidance dose of between 0.001 to 1.0 mSv/y (0.1 to 100 mrem/y) was recommended with 0.3 mSv/y (30 mrem/y) selected as the guidance dose upon which to base calculations. Several tasks were identified, beginning with the selection of a suitable pathway model for relating dose to the concentration of radioactivity in the waste. Threshold concentrations corresponding to the guidance dose were determined for waste disposal sites at a selected humid and arid site. Finally, cost-benefit considerations at the example sites were addressed. The results of the various tasks are summarized and the relationship of this effort with related developments at other agencies discussed

  4. Impact Damage Evaluation Method of Friction Disc Based on High-Speed Photography and Tooth-Root Stress Coupling

    International Nuclear Information System (INIS)

    Yin, L; Shao, Y M; Liu, J; Zheng, H L

    2015-01-01

    The stability of friction disc could be seriously affected by the tooth surface damage due to poor working conditions of the wet multi-disc brake in heavy trucks. There are few current works focused on the damage of the friction disc caused by torsion-vibration impacts. Hence, it is necessary to investigate its damage mechanisms and evaluation methods. In this paper, a damage mechanism description and evaluation method of a friction disc based on the high-speed photography and tooth-root stress coupling is proposed. According to the HighSpeed Photography, the collision process between the friction disc and hub is recorded, which can be used to determine the contact position and deformation. Combined with the strain-stress data obtained by the strain gauge at the place of the tooth-root, the impact force and property are studied. In order to obtain the evaluation method, the damage surface morphology data of the friction disc extracted by 3D Super Depth Digital Microscope (VH-Z100R) is compared with the impact force and property. The quantitative relationships between the amount of deformation and collision number are obtained using a fitting analysis method. The experimental results show that the damage of the friction disc can be evaluated by the proposed impact damage evaluation method based on the high-speed photography and tooth-root stress coupling. (paper)

  5. Assessment of damage domains of the High-Temperature Engineering Test Reactor (HTTR)

    International Nuclear Information System (INIS)

    Flores, Alain; Izquierdo, José María; Tuček, Kamil; Gallego, Eduardo

    2014-01-01

    Highlights: • We developed an adequate model for the identification of damage domains of the HTTR. • We analysed an anticipated operational transient, using the HTTR5+/GASTEMP code. • We simulated several transients of the same sequence. • We identified the corresponding damage domains using two methods. • We calculated exceedance frequency using the two methods. - Abstract: This paper presents an assessment analysis of damage domains of the 30 MW th prototype High-Temperature Engineering Test Reactor (HTTR) operated by the Japan Atomic Energy Agency (JAEA). For this purpose, an in-house deterministic risk assessment computational tool was developed based on the Theory of Stimulated Dynamics (TSD). To illustrate the methodology and applicability of the developed modelling approach, assessment results of a control rod (CR) withdrawal accident during subcritical conditions are presented and compared with those obtained by the JAEA

  6. Carbon-carbon composite and copper-composite bond damages for high flux component controlled fusion

    International Nuclear Information System (INIS)

    Chevet, G.

    2010-01-01

    Plasma facing components constitute the first wall in contact with plasma in fusion machines such as Tore Supra and ITER. These components have to sustain high heat flux and consequently elevated temperatures. They are made up of an armour material, the carbon-carbon composite, a heat sink structure material, the copper chromium zirconium, and a material, the OFHC copper, which is used as a compliant layer between the carbon-carbon composite and the copper chromium zirconium. Using different materials leads to the apparition of strong residual stresses during manufacturing, because of the thermal expansion mismatch between the materials, and compromises the lasting operation of fusion machines as damage which appeared during manufacturing may propagate. The objective of this study is to understand the damage mechanisms of the carbon-carbon composite and the composite-copper bond under solicitations that plasma facing components may suffer during their life. The mechanical behaviours of carbon-carbon composite and composite-copper bond were studied in order to define the most suitable models to describe these behaviours. With these models, thermomechanical calculations were performed on plasma facing components with the finite element code Cast3M. The manufacturing of the components induces high stresses which damage the carbon-carbon composite and the composite-copper bond. The damage propagates during the cooling down to room temperature and not under heat flux. Alternative geometries for the plasma facing components were studied to reduce damage. The relation between the damage of the carbon-carbon composite and its thermal conductivity was also demonstrated. (author) [fr

  7. Music effect on pain threshold evaluated with current perception threshold

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    AIM: Music relieves anxiety and psychotic tension. This effect of music is applied to surgical operation in the hospital and dental office. It is still unclear whether this music effect is only limited to the psychological aspect but not to the physical aspect or whether its music effect is influenced by the mood or emotion of audience. To elucidate these issues, we evaluated the music effect on pain threshold by current perception threshold (CPT) and profile of mood states (POMC) test. METHODS: Healthy 30 subjects (12 men, 18 women, 25-49 years old, mean age 34.9) were tested. (1)After POMC test, all subjects were evaluated pain threshold with CPT by Neurometer (Radionics, USA) under 6 conditions, silence, listening to the slow tempo classic music, nursery music, hard rock music, classic paino music and relaxation music with 30 seconds interval. (2)After Stroop color word test as the stresser, pain threshold was evaluated with CPT under 2 conditions, silence and listening to the slow tempo classic music. RESULTS: Under litening to the music, CPT sores increased, especially 2 000 Hz level related with compression, warm and pain sensation. Type of music, preference of music and stress also affected CPT score. CONCLUSION: The present study demonstrated that the concentration on the music raise the pain threshold and that stress and mood influence the music effect on pain threshold.

  8. 64 x 64 thresholding photodetector array for optical pattern recognition

    Science.gov (United States)

    Langenbacher, Harry; Chao, Tien-Hsin; Shaw, Timothy; Yu, Jeffrey W.

    1993-10-01

    A high performance 32 X 32 peak detector array is introduced. This detector consists of a 32 X 32 array of thresholding photo-transistor cells, manufactured with a standard MOSIS digital 2-micron CMOS process. A built-in thresholding function that is able to perform 1024 thresholding operations in parallel strongly distinguishes this chip from available CCD detectors. This high speed detector offers responses from one to 10 milliseconds that is much higher than the commercially available CCD detectors operating at a TV frame rate. The parallel multiple peaks thresholding detection capability makes it particularly suitable for optical correlator and optoelectronically implemented neural networks. The principle of operation, circuit design and the performance characteristics are described. Experimental demonstration of correlation peak detection is also provided. Recently, we have also designed and built an advanced version of a 64 X 64 thresholding photodetector array chip. Experimental investigation of using this chip for pattern recognition is ongoing.

  9. Low and high frequency tonal threshold audiometry: comparing hearing thresholds between smokers and non-smokers Da audiometria tonal limiar em baixa e alta frequência: comparação dos limiares auditivos entre tabagistas e não-tabagistas

    Directory of Open Access Journals (Sweden)

    Daniela Cecílio Capra Marques de Oliveira

    2009-10-01

    Full Text Available Cigarette smoking can cause many potentially fatal diseases and worsen others. Numerous studies have shown the relationship between smoking and hearing loss. However, the increase in auditory threshold in high frequency arising from smoking has been very little described. AIM: to compare low and high frequency auditory thresholds among a group of smoking and non-smoking male individuals between 18 and 40 years. STUDY DESIGN: Cross-sectional. MATERIALS AND METHODS: by means of low and high frequency tonal threshold audiometry we studied 30 male individuals between 18 and 40 years and 30 non-smokers of matching age and gender. RESULTS: auditory thresholds were different between smokers and non-smokers, being worse in the former. Although within normal ranges, auditory thresholds in low frequencies were higher among smokers. In high frequencies we noticed a marked increase in auditory thresholds among smokers. CONCLUSION: we found statistically significant difference in auditory thresholds in low and high frequencies, among young male individuals, smokers and non-smokers, being worse in the former.O uso do cigarro pode levar a diversas doenças potencialmente fatais e contribuir para o agravo de outras condições patológicas. Inúmeros estudos mostram a relação entre tabagismo e perda auditiva, entretanto, o aumento dos limiares auditivos em alta frequência decorrente do tabagismo é pouco descrito. OBJETIVO: Comparar os limiares auditivos em baixas e altas frequências, entre um grupo de indivíduos não-tabagistas e tabagistas, do sexo masculino com idades entre 18 e 40 anos. FORMA DE ESTUDO: Tipo transversal. MATERIAL E MÉTODO: Foram estudados, através de audiometria tonal limiar em baixas e altas frequências, 30 indivíduos tabagistas do sexo masculino com idades entre 18 e 40 anos e 30 indivíduos não-tabagistas do mesmo sexo e da mesma faixa etária. RESULTADOS: Os limiares auditivos foram diferentes entre os indivíduos do grupo n

  10. Structurally integrated fiber optic damage assessment system for composite materials.

    Science.gov (United States)

    Measures, R M; Glossop, N D; Lymer, J; Leblanc, M; West, J; Dubois, S; Tsaw, W; Tennyson, R C

    1989-07-01

    Progress toward the development of a fiber optic damage assessment system for composite materials is reported. This system, based on the fracture of embedded optical fibers, has been characterized with respect to the orientation and location of the optical fibers in the composite. Together with a special treatment, these parameters have been tailored to yield a system capable of detecting the threshold of damage for various impacted Kevlar/epoxy panels. The technique has been extended to measure the growth of a damage region which could arise from either impact, manufacturing flaws, or static overloading. The mechanism of optical fiber fracture has also been investigated. In addition, the influence of embedded optical fibers on the tensile and compressive strength of the composite material has been studied. Image enhanced backlighting has been shown to be a powerful and convenient method of assessing internal damage to translucent composite materials.

  11. Surface damage characterization of FBK devices for High Luminosity LHC (HL-LHC) operations

    Science.gov (United States)

    Moscatelli, F.; Passeri, D.; Morozzi, A.; Dalla Betta, G.-F.; Mattiazzo, S.; Bomben, M.; Bilei, G. M.

    2017-12-01

    The very high fluences (e.g. up to 2×1016 1 MeV neq/cm2) and total ionising doses (TID) of the order of 1 Grad, expected at the High Luminosity LHC (HL-LHC), impose new challenges for the design of effective, radiation resistant detectors. Ionising energy loss is the dominant effect for what concerns SiO2 and SiO2/Si interface radiation damage. In particular, surface damage can create a positive charge layer near the SiO2/Si interface and interface traps along the SiO2/Si interface, which strongly influence the breakdown voltage, the inter-electrode isolation and capacitance, and might also impact the charge collection properties of silicon sensors. To better understand in a comprehensive framework the complex and articulated phenomena related to surface damage at these very high doses, measurements on test structures have been carried out in this work (e.g. C-V and I-V). In particular, we have studied the properties of the SiO2 layer and of the SiO2/Si interface, using MOS capacitors, gated diodes (GD) and MOSFETs manufactured by FBK on high-resistivity n-type and p-type silicon, before and after irradiation with X-rays in the range from 50 krad(SiO2) to 20 Mrad(SiO2). Relevant parameters have been determined for all the tested devices, converging in the oxide charge density NOX, the surface generation velocity s0 and the integrated interface-trap density NIT dose-dependent values. These parameters have been extracted to both characterize the technology as a function of the dose and to be used in TCAD simulations for the surface damage effect modeling and the analysis and optimization of different classes of detectors for the next HEP experiments.

  12. A comparison of ionizing radiation damage in CMOS devices from 60Co gamma rays, electrons and protons

    International Nuclear Information System (INIS)

    He Baoping; Yao Zhibin; Zhang Fengqi

    2009-01-01

    Radiation hardened CC4007RH and non-radiation hardened CC4011 devices were irradiated using 60 Co gamma rays, 1 MeV electrons and 1-9 MeV protons to compare the ionizing radiation damage of the gamma rays with the charged particles. For all devices examined, with experimental uncertainty, the radiation induced threshold voltage shifts (ΔV th ) generated by 60 Co gamma rays are equal to that of 1 MeV electron and 1-7 MeV proton radiation under 0 gate bias condition. Under 5 V gate bias condition, the distinction of threshold voltage shifts (ΔV th ) generated by 60 Co gamma rays and 1 MeV electrons irradiation are not large, and the radiation damage for protons below 9 MeV is always less than that of 60 Co gamma rays. The lower energy the proton has, the less serious the radiation damage becomes. (authors)

  13. Freezing cytorrhysis and critical temperature thresholds for photosystem II in the peat moss Sphagnum capillifolium.

    Science.gov (United States)

    Buchner, Othmar; Neuner, Gilbert

    2010-07-01

    Leaflets of Sphagnum capillifolium were exposed to temperatures from -5 degrees C to +60 degrees C under controlled conditions while mounted on a microscope stage. The resultant cytological response to these temperature treatments was successfully monitored using a light and fluorescence microscope. In addition to the observable cytological changes during freezing cytorrhysis and heat exposure on the leaflets, the concomitant critical temperature thresholds for inactivation of photosystem II (PS II) were studied using a micro fibre optic and a chlorophyll fluorometer mounted to the microscope stage. Chlorophyllous cells of S. capillifolium showed extended freezing cytorrhysis immediately after ice nucleation at -1.1 degrees C in the water in which the leaflets were submersed during the measurement. The occurrence of freezing cytorrhysis, which was visually manifested by cell shrinkage, was highly dynamic and was completed within 2 s. A total reduction of the mean projected diameter of the chloroplast containing area during freezing cytorrhysis from 8.9 to 3.8 microm indicates a cell volume reduction of approximately -82%. Simultaneous measurement of chlorophyll fluorescence of PS II was possible even through the frozen water in which the leaf samples were submersed. Freezing cytorrhysis was accompanied by a sudden rise of basic chlorophyll fluorescence. The critical freezing temperature threshold of PS II was identical to the ice nucleation temperature (-1.1 degrees C). This is significantly above the temperature threshold at which frost damage to S. capillifolium leaflets occurs (-16.1 degrees C; LT(50)) which is higher than observed in most higher plants from the European Alps during summer. High temperature thresholds of PS II were 44.5 degrees C which is significantly below the heat tolerance of chlorophyllous cells (49.9 degrees C; LT(50)). It is demonstrated that light and fluorescence microscopic techniques combined with simultaneous chlorophyll fluorescence

  14. Increase the threshold voltage of high voltage GaN transistors by low temperature atomic hydrogen treatment

    Energy Technology Data Exchange (ETDEWEB)

    Erofeev, E. V., E-mail: erofeev@micran.ru [Tomsk State University of Control Systems and Radioelectronics, Research Institute of Electrical-Communication Systems (Russian Federation); Fedin, I. V.; Kutkov, I. V. [Research and Production Company “Micran” (Russian Federation); Yuryev, Yu. N. [National Research Tomsk Polytechnic University, Institute of Physics and Technology (Russian Federation)

    2017-02-15

    High-electron-mobility transistors (HEMTs) based on AlGaN/GaN epitaxial heterostructures are a promising element base for the fabrication of high voltage electronic devices of the next generation. This is caused by both the high mobility of charge carriers in the transistor channel and the high electric strength of the material, which makes it possible to attain high breakdown voltages. For use in high-power switches, normally off-mode GaN transistors operating under enhancement conditions are required. To fabricate normally off GaN transistors, one most frequently uses a subgate region based on magnesium-doped p-GaN. However, optimization of the p-GaN epitaxial-layer thickness and the doping level makes it possible to attain a threshold voltage of GaN transistors close to V{sub th} = +2 V. In this study, it is shown that the use of low temperature treatment in an atomic hydrogen flow for the p-GaN-based subgate region before the deposition of gate-metallization layers makes it possible to increase the transistor threshold voltage to V{sub th} = +3.5 V. The effects under observation can be caused by the formation of a dipole layer on the p-GaN surface induced by the effect of atomic hydrogen. The heat treatment of hydrogen-treated GaN transistors in a nitrogen environment at a temperature of T = 250°C for 12 h reveals no degradation of the transistor’s electrical parameters, which can be caused by the formation of a thermally stable dipole layer at the metal/p-GaN interface as a result of hydrogenation.

  15. Increase the threshold voltage of high voltage GaN transistors by low temperature atomic hydrogen treatment

    International Nuclear Information System (INIS)

    Erofeev, E. V.; Fedin, I. V.; Kutkov, I. V.; Yuryev, Yu. N.

    2017-01-01

    High-electron-mobility transistors (HEMTs) based on AlGaN/GaN epitaxial heterostructures are a promising element base for the fabrication of high voltage electronic devices of the next generation. This is caused by both the high mobility of charge carriers in the transistor channel and the high electric strength of the material, which makes it possible to attain high breakdown voltages. For use in high-power switches, normally off-mode GaN transistors operating under enhancement conditions are required. To fabricate normally off GaN transistors, one most frequently uses a subgate region based on magnesium-doped p-GaN. However, optimization of the p-GaN epitaxial-layer thickness and the doping level makes it possible to attain a threshold voltage of GaN transistors close to V_t_h = +2 V. In this study, it is shown that the use of low temperature treatment in an atomic hydrogen flow for the p-GaN-based subgate region before the deposition of gate-metallization layers makes it possible to increase the transistor threshold voltage to V_t_h = +3.5 V. The effects under observation can be caused by the formation of a dipole layer on the p-GaN surface induced by the effect of atomic hydrogen. The heat treatment of hydrogen-treated GaN transistors in a nitrogen environment at a temperature of T = 250°C for 12 h reveals no degradation of the transistor’s electrical parameters, which can be caused by the formation of a thermally stable dipole layer at the metal/p-GaN interface as a result of hydrogenation.

  16. Prediction of microstructure and ductile damage of a high-speed railway axle steel during cross wedge rolling

    OpenAIRE

    Huo, Y; Lin, J; Bai, Q; Wang, B; Tang, X; Ji, H

    2016-01-01

    Microstructure and ductile damage have a significant influence on the deformation behavior of high-speed railway axles during hot cross wedge rolling (CWR) and its final performance. In this study, based on the continuum damage mechanics, a multiaxial constitutive model coupling microstructure and ductile damage was established to predict the evolution of microstructure and ductile damage of 25CrMo4 during hot CWR processes. Material constants within the multiaxial constitutive model were det...

  17. 10-Year prospective study of noise exposure and hearing damage among construction workers.

    Science.gov (United States)

    Seixas, Noah S; Neitzel, Rick; Stover, Bert; Sheppard, Lianne; Feeney, Patrick; Mills, David; Kujawa, Sharon

    2012-09-01

    To characterise the effects of noise exposure, including intermittent and peaky exposure, on hearing damage as assessed by standard pure-tone thresholds and otoacoustic emissions, a longitudinal study was conducted on newly hired construction apprentices and controls over a 10-year period. Among the 456 subjects recruited at baseline, 316 had at least two (mean 4.6) examinations and were included in this analysis. Annual examinations included hearing threshold levels (HTLs) for air conducted pure tones and distortion product otoacoustic emission (DPOAE) amplitudes. Task-based occupational noise exposure levels and recreational exposures were estimated. Linear mixed models were fit for HTLs and DPOAEs at 3, 4 and 6 kHz in relation to time since baseline and average noise level since baseline, while controlling for hearing level at baseline and other risk factors. Estimated L(EQ) noise exposures were 87±3.6 dBA among the construction workers. Linear mixed modelling demonstrated significant exposure-related elevations in HTL of about 2-3 dB over a projected 10-year period at 3, 4 or 6 kHz for a 10 dB increase in exposure. The DPOAE models (using L1=40) predicted about 1 dB decrease in emission amplitude over 10 years for a 10 dB increase in exposure. The study provides evidence of noise-induced damage at an average exposure level around the 85 dBA level. The predicted change in HTLs was somewhat higher than would be predicted by standard hearing loss models, after accounting for hearing loss at baseline. Limited evidence for an enhanced effect of high peak component noise was observed, and DPOAEs, although similarly affected, showed no advantage over standard hearing threshold evaluation in detecting effects of noise on the ear and hearing.

  18. 10-Year prospective study of noise exposure and hearing damage among construction workers

    Science.gov (United States)

    Seixas, Noah S; Neitzel, Rick; Stover, Bert; Sheppard, Lianne; Feeney, Patrick; Mills, David; Kujawa, Sharon

    2015-01-01

    Objectives To characterise the effects of noise exposure, including intermittent and peaky exposure, on hearing damage as assessed by standard pure-tone thresholds and otoacoustic emissions, a longitudinal study was conducted on newly hired construction apprentices and controls over a 10-year period. Methods Among the 456 subjects recruited at baseline, 316 had at least two (mean 4.6) examinations and were included in this analysis. Annual examinations included hearing threshold levels (HTLs) for air conducted pure tones and distortion product otoacoustic emission (DPOAE) amplitudes. Task-based occupational noise exposure levels and recreational exposures were estimated. Linear mixed models were fit for HTLs and DPOAEs at 3, 4 and 6 kHz in relation to time since baseline and average noise level since baseline, while controlling for hearing level at baseline and other risk factors. Results Estimated LEQ noise exposures were 87±3.6 dBA among the construction workers. Linear mixed modelling demonstrated significant exposure-related elevations in HTL of about 2–3 dB over a projected 10-year period at 3, 4 or 6 kHz for a 10 dB increase in exposure. The DPOAE models (using L1=40) predicted about 1 dB decrease in emission amplitude over 10 years for a 10 dB increase in exposure. Conclusions The study provides evidence of noise-induced damage at an average exposure level around the 85 dBA level. The predicted change in HTLs was somewhat higher than would be predicted by standard hearing loss models, after accounting for hearing loss at baseline. Limited evidence for an enhanced effect of high peak component noise was observed, and DPOAEs, although similarly affected, showed no advantage over standard hearing threshold evaluation in detecting effects of noise on the ear and hearing. PMID:22693267

  19. Spot-shadowing optimization to mitigate damage growth in a high-energy-laser amplifier chain.

    Science.gov (United States)

    Bahk, Seung-Whan; Zuegel, Jonathan D; Fienup, James R; Widmayer, C Clay; Heebner, John

    2008-12-10

    A spot-shadowing technique to mitigate damage growth in a high-energy laser is studied. Its goal is to minimize the energy loss and undesirable hot spots in intermediate planes of the laser. A nonlinear optimization algorithm solves for the complex fields required to mitigate damage growth in the National Ignition Facility amplifier chain. The method is generally applicable to any large fusion laser.

  20. Perspective: Uses and misuses of thresholds in diagnostic decision making.

    Science.gov (United States)

    Warner, Jeremy L; Najarian, Robert M; Tierney, Lawrence M

    2010-03-01

    The concept of thresholds plays a vital role in decisions involving the initiation, continuation, and completion of diagnostic testing. Much research has focused on the development of explicit thresholds, in the form of practice guidelines and decision analyses. However, these tools are used infrequently; most medical decisions are made at the bedside, using implicit thresholds. Study of these thresholds can lead to a deeper understanding of clinical decision making. The authors examine some factors constituting individual clinicians' implicit thresholds. They propose a model for static thresholds using the concept of situational gravity to explain why some thresholds are high, and some low. Next, they consider the hypothetical effects of incorrect placement of thresholds (miscalibration) and changes to thresholds during diagnosis (manipulation). They demonstrate these concepts using common clinical scenarios. Through analysis of miscalibration of thresholds, the authors demonstrate some common maladaptive clinical behaviors, which are nevertheless internally consistent. They then explain how manipulation of thresholds gives rise to common cognitive heuristics including premature closure and anchoring. They also discuss the case where no threshold has been exceeded despite exhaustive collection of data, which commonly leads to application of the availability or representativeness heuristics. Awareness of implicit thresholds allows for a more effective understanding of the processes of medical decision making and, possibly, to the avoidance of detrimental heuristics and their associated medical errors. Research toward accurately defining these thresholds for individual physicians and toward determining their dynamic properties during the diagnostic process may yield valuable insights.

  1. Development of martensitic steels for high neutron damage applications

    International Nuclear Information System (INIS)

    Gelles, D.S.

    1998-01-01

    Martensitic stainless steels have been developed for both in-core applications in advanced liquid metal fast breeder reactors (LMFBR) and for first wall and structural materials applications for commercial fusion reactors. It can now be shown that these steels can be expected to maintain properties to levels as high as 175 or 200 dpa, respectively. The 12Cr-1Mo-0.5W-0.2C alloy HT-9 has been extensively tested for LMFBR applications and shown to resist radiation damage, providing a creep and swelling resistant alternative to austenitic steels. Degradation of fracture toughness and Charpy impact properties have been observed, but properties are sufficient to provide reliable service. In comparison, alloys with lower chromium contents are found to decarburize in contact with liquid sodium and are therefore not recommended. Tungsten stabilized martensitic stainless steels have appropriate properties for fusion applications. Radioactivity levels are being less than 500 years after service, radiation damage resistance is excellent, including impact properties, and swelling is modest. This report describes the history of the development effort. (author)

  2. Development of martensitic steels for high neutron damage applications

    Science.gov (United States)

    Gelles, D. S.

    1996-12-01

    Martensitic stainless steels have been developed for both in-core applications in advanced liquid metal fast breeder reactors (LMFBR) and for first wall and structural materials applications for commercial fusion reactors. It can now be shown that these steels can be expected to maintain properties to levels as high as 175 or 200 dpa, respectively. The 12Cr1Mo0.5W0.2C alloy HT-9 has been extensively tested for LMFBR applications and shown to resist radiation damage, providing a creep and swelling resistant alternative to austenitic steels. Degradation of fracture toughness and Charpy impact properties have been observed, but properties are sufficient to provide reliable service. In comparison, alloys with lower chromium contents are found to decarburize in contact with liquid sodium and are therefore not recommended. Tungsten stabilized martensitic stainless steels have appropriate properties for fusion applications. Radioactivity levels are benign less than 500 years after service, radiation damage resistance is excellent, including impact properties, and swelling is modest. This report describes the history of the development effort.

  3. Deuteron threshold electrodisintegration at high momentum transfer

    International Nuclear Information System (INIS)

    Schmitt, W.M.; Turchinetz, W.; Williamson, C.F.

    1997-01-01

    Absolute differential cross sections for the threshold electrodisintegration of the deuteron with good resolution were measured at a laboratory scattering angle of 160 degree for five values of Q 2 ranging from 8.66 to 42.4 fm -2 . Comparisons of the data averaged over E np from 0--3 MeV and 0--10 MeV are made with nonrelativistic meson-exchange calculations. These calculations are sensitive to the nucleon electromagnetic form factors, nucleon-nucleon potential, and relativistic effects. The data are also compared with a hybrid quark-hadron model calculation that describes the deuteron as a six-quark cluster for the short range part of the interaction. Some of these calculations can describe the data reasonably well over certain ranges of Q 2 ; however, none of these calculations can accurately describe the data over the entire measured Q 2 range

  4. Characterization of optical and microstructure properties of ultraviolet Sc2O3 thin films and their damage mechanism at high laser power

    International Nuclear Information System (INIS)

    Liu Guanghui; Xue Chunrong; Jin Yunxia; Zhang Weili; Fang Ming; He Hongbo; Fan Zhengxiu

    2010-01-01

    The electron beam evaporation deposition method was employed to prepare scandium oxide (Sc 2 O 3 ) films with substrate temperatures varying from 50 to 350 degree C. A spectrophotometer, a glancing incidence X-ray diffraction spectrometer and a WYKO optical profilograph were employed to investigate the optical, microstructure properties and surface roughness of the Sc 2 O 3 films. The refractive index and the extinction coefficient were calculated from the transmittance and reflectance spectra with the help of the Essential Macleod. The laser induced damage threshold (LIDT) of the Sc 2 O 3 films was characterized by a pulsed Nd: YAG laser system at 355 nm with a pulse duration of 8 ns. A maximum value of 2.6 J/cm 2 was derived, and the LIDT results were found to vary in the opposite direction to the extinction coefficient, surface root mean square roughness and optical loss of the Sc 2 O 3 films. An optical microscope and a scanning electron microscope were used to characterize the damage morphology of the samples, and the development of damage with increasing laser energy density was recorded and discussed. The relationship between the LIDT and the deposition parameters of the Sc 2 O 3 thin films was analyzed, and the damage mechanism of the films under 355 nm laser irradiation was discussed. (authors)

  5. A plasma microlens for ultrashort high power lasers

    Science.gov (United States)

    Katzir, Yiftach; Eisenmann, Shmuel; Ferber, Yair; Zigler, Arie; Hubbard, Richard F.

    2009-07-01

    We present a technique for generation of miniature plasma lens system that can be used for focusing and collimating a high intensity femtosecond laser pulse. The plasma lens was created by a nanosecond laser, which ablated a capillary entrance. The spatial configuration of the ablated plasma focused a high intensity femtosecond laser pulse. This configuration offers versatility in the plasma lens small f-number for extremely tight focusing of high power lasers with no damage threshold restrictions of regular optical components.

  6. A plasma microlens for ultrashort high power lasers

    International Nuclear Information System (INIS)

    Katzir, Yiftach; Eisenmann, Shmuel; Ferber, Yair; Zigler, Arie; Hubbard, Richard F.

    2009-01-01

    We present a technique for generation of miniature plasma lens system that can be used for focusing and collimating a high intensity femtosecond laser pulse. The plasma lens was created by a nanosecond laser, which ablated a capillary entrance. The spatial configuration of the ablated plasma focused a high intensity femtosecond laser pulse. This configuration offers versatility in the plasma lens small f-number for extremely tight focusing of high power lasers with no damage threshold restrictions of regular optical components.

  7. A comparison of two different approaches for mapping potential ozone damage to vegetation. A model study

    International Nuclear Information System (INIS)

    Simpson, D.; Ashmore, M.R.; Emberson, L.; Tuovinen, J.-P.

    2007-01-01

    Two very different types of approaches are currently in use today for indicating risk of ozone damage to vegetation in Europe. One approach is the so-called AOTX (accumulated exposure over threshold of X ppb) index, which is based upon ozone concentrations only. The second type of approach entails an estimate of the amount of ozone entering via the stomates of vegetation, the AFstY approach (accumulated stomatal flux over threshold of Y nmol m -2 s -1 ). The EMEP chemical transport model is used to map these different indicators of ozone damage across Europe, for two illustrative vegetation types, wheat and beech forests. The results show that exceedences of critical levels for either type of indicator are widespread, but that the indicators give very different spatial patterns across Europe. Model simulations for year 2020 scenarios suggest reductions in risks of vegetation damage whichever indicator is used, but suggest that AOT40 is much more sensitive to emission control than AFstY values. - Model calculations of AOT40 and AFstY show very different spatial variations in the risks of ozone damage to vegetation

  8. Threshold pump power of a solar-pumped dye laser

    Science.gov (United States)

    Lee, Ja H.; Kim, Kyung C.; Kim, Kyong H.

    1988-01-01

    Threshold solar power for dye laser pumping has been determined by measuring the gain of a rhodamine 6G dye laser amplifier at various solar-simulated irradiances on an amplifier cell. The measured threshold was 20,000 solar constants (2.7 kW/sq cm) for the dye volume of 2 x 5 x 40 cu mm and the optimum dye concentration of 0.001 M. The threshold is about one-third of that achievable with a high-intensity solar concentrator.

  9. Probability of growth of small damage sites on the exit surface of fused silica optics.

    Science.gov (United States)

    Negres, Raluca A; Abdulla, Ghaleb M; Cross, David A; Liao, Zhi M; Carr, Christopher W

    2012-06-04

    Growth of laser damage on fused silica optical components depends on several key parameters including laser fluence, wavelength, pulse duration, and site size. Here we investigate the growth behavior of small damage sites on the exit surface of SiO₂ optics under exposure to tightly controlled laser pulses. Results demonstrate that the onset of damage growth is not governed by a threshold, but is probabilistic in nature and depends both on the current size of a damage site and the laser fluence to which it is exposed. We also develop models for use in growth prediction. In addition, we show that laser exposure history also influences the behavior of individual sites.

  10. On the implications of thresholds for economic science and environmental policy

    Energy Technology Data Exchange (ETDEWEB)

    Aalbers, R.

    1999-05-11

    This thesis consists of four chapters on the topic of thresholds. Chapter 2 deals with the issue of a truly catastrophic threshold. Society has perfect information on both the location and the impact of crossing the threshold. The assumption is made that crossing the threshold will result in the destruction of all human utility on earth (which is not the same as the destruction of all human life on earth). On the basis of a simple neoclassical growth model the question is posed under what conditions society would like to cross the threshold, and hence, initiate a catastrophe. The trade-off for society is to have a relatively low consumption level for an infinite period of time, or to have a relatively high consumption level for a short period of time. Perhaps surprisingly, it turns out that the doomsday scenario may be optimal (in the sense of maximizing human utility). Chapter 3 extends the analysis of the second chapter by allowing society to spend resources either on consumption or on abatement. In chapter 4 the assumption of certainty of information about both the location and the impact of a threshold is relaxed. Instead it is assumed that a society has information - in the form of a probability density function - about both the location of the threshold and its impact. What then is the optimal strategy for that society? In addition, it will be analysed how society`s optimal strategy changes, if the uncertainty increases. We will see that if uncertainty about the impact of the threshold increases, society`s strategy will become more prudent. Moreover, it is argued that any form of cost-benefit analysis must - whenever thresholds cannot be excluded a priori from the analysis - necessarily be based on arbitrary, in the sense of non-empirically verifiable, assumptions about the shape of the damage function. Finally, the author examines the case in which society has not enough - quantitative or qualitative - information in order to obtain, or estimate, a

  11. Laser-induced damage in dielectrics with nanosecond to subpicosecond pulses. I. Experimental. Part 1

    International Nuclear Information System (INIS)

    Stuart, B.C.; Herman, S.; Perry, M.D.

    1994-12-01

    The authors report extensive laser-induced damage threshold measurements on pure and multilayer dielectrics at 1053 and 526 mm for pulse durations, τ, ranging from 140 fs to 1 ns. Qualitative differences in the morphology of damage and a departure from the diffusion-dominated τ 1/2 scaling indicate that damage results from plasma formation and ablation for τ≤10 ps and from conventional melting and boiling for τ>50 ps. A theoretical model based on electron production via multiphoton ionization, Joule heating, and collisional (avalanche) ionization is in good agreement with both the pulsewidth and wavelength scaling of experimental results

  12. Comparison of skin barrier function and sensory nerve electric current perception threshold between IgE-high extrinsic and IgE-normal intrinsic types of atopic dermatitis.

    Science.gov (United States)

    Mori, T; Ishida, K; Mukumoto, S; Yamada, Y; Imokawa, G; Kabashima, K; Kobayashi, M; Bito, T; Nakamura, M; Ogasawara, K; Tokura, Y

    2010-01-01

    Background Two types of atopic dermatitis (AD) have been proposed, with different pathophysiological mechanisms underlying this seemingly heterogeneous disorder. The extrinsic type shows high IgE levels presumably as a consequence of skin barrier damage and feasible allergen permeation, whereas the intrinsic type exhibits normal IgE levels and is not mediated by allergen-specific IgE. Objectives To investigate the relationship between pruritus perception threshold and skin barrier function of patients with AD in a comparison between the extrinsic and intrinsic types. Methods Enrolled in this study were 32 patients with extrinsic AD, 17 with intrinsic AD and 24 healthy individuals. The barrier function of the stratum corneum was assessed by skin surface hydration and transepidermal water loss (TEWL), and pruritus perception was evaluated by the electric current perception threshold (CPT) of sensory nerves upon neuroselective transcutaneous electric stimulation. Results Skin surface hydration was significantly lower and TEWL was significantly higher in extrinsic AD than intrinsic AD or normal controls. Although there was no statistically significant difference in CPT among extrinsic AD, intrinsic AD and normal controls, CPT was significantly correlated with skin surface hydration and inversely with TEWL in intrinsic AD and normal controls, but not extrinsic AD. Finally, CPT was correlated with the visual analogue scale of itch in the nonlesional skin of patients with extrinsic but not intrinsic AD. Conclusions Patients with extrinsic AD have an impaired barrier, which increases the pre-existing pruritus but rather decreases sensitivity to external stimuli. In contrast, patients with intrinsic AD retain a normal barrier function and sensory reactivity to external pruritic stimuli.

  13. 1.3μm low threshold distributed feedback lasers for high bit-rate applications

    International Nuclear Information System (INIS)

    Artigue, C.; Louis, Y.; Padioleau, C.; Poingt, F.; Sigogne, D.; Starck, C.; Benoit, J.

    1985-01-01

    A low threshold current (≅ 30 mA) 1.3μm (InGaAsP) second order DFB laser with a ridge structure made by liquid phase epitaxy is reported. The low threshold results from: optimized heterostructure and grating profile, good tuning of the DFB wavelength with the peak gain wavelength, and the proper LPE regrowth conditions on the grating

  14. Vibratory perception threshold in young and middle-aged patients at high risk of knee osteoarthritis compared to controls

    DEFF Research Database (Denmark)

    Thorlund, Jonas Bloch; Shakoor, Najia; Ageberg, Eva

    2012-01-01

    Vibratory perception threshold (VPT) is impaired in patients with knee osteoarthritis (OA). It is, however, not known if sensory deficits precede or follow as a consequence of OA. The aim of this study was to investigate VPT in 2 independent groups of patients with high risk of future OA (young a...

  15. Modeling DPOAE input/output function compression: comparisons with hearing thresholds.

    Science.gov (United States)

    Bhagat, Shaum P

    2014-09-01

    Basilar membrane input/output (I/O) functions in mammalian animal models are characterized by linear and compressed segments when measured near the location corresponding to the characteristic frequency. A method of studying basilar membrane compression indirectly in humans involves measuring distortion-product otoacoustic emission (DPOAE) I/O functions. Previous research has linked compression estimates from behavioral growth-of-masking functions to hearing thresholds. The aim of this study was to compare compression estimates from DPOAE I/O functions and hearing thresholds at 1 and 2 kHz. A prospective correlational research design was performed. The relationship between DPOAE I/O function compression estimates and hearing thresholds was evaluated with Pearson product-moment correlations. Normal-hearing adults (n = 16) aged 22-42 yr were recruited. DPOAE I/O functions (L₂ = 45-70 dB SPL) and two-interval forced-choice hearing thresholds were measured in normal-hearing adults. A three-segment linear regression model applied to DPOAE I/O functions supplied estimates of compression thresholds, defined as breakpoints between linear and compressed segments and the slopes of the compressed segments. Pearson product-moment correlations between DPOAE compression estimates and hearing thresholds were evaluated. A high correlation between DPOAE compression thresholds and hearing thresholds was observed at 2 kHz, but not at 1 kHz. Compression slopes also correlated highly with hearing thresholds only at 2 kHz. The derivation of cochlear compression estimates from DPOAE I/O functions provides a means to characterize basilar membrane mechanics in humans and elucidates the role of compression in tone detection in the 1-2 kHz frequency range. American Academy of Audiology.

  16. Ultracompact low-threshold organic laser.

    Science.gov (United States)

    Deotare, Parag B; Mahony, Thomas S; Bulović, Vladimir

    2014-11-25

    We report an ultracompact low-threshold laser with an Alq3:DCM host:guest molecular organic thin film gain layer. The device uses a photonic crystal nanobeam cavity which provides a high quality factor to mode volume (Q/V) ratio and increased spontaneous emission factor along with a small footprint. Lasing is observed with a threshold of 4.2 μJ/cm(2) when pumped by femtosecond pulses of λ = 400 nm wavelength light. We also model the dynamics of the laser and show good agreement with the experimental data. The inherent waveguide geometry of the structure enables easy on-chip integration with potential applications in biochemical sensing, inertial sensors, and data communication.

  17. Growth, structural, physical and computational perspectives of trans-4-hydroxy-l-proline: a promising organic nonlinear optical material with large laser-induced damage threshold

    Science.gov (United States)

    Thirumurugan, Ramaiah; Anitha, Kandasamy

    2017-05-01

    In this work, a systematic study of an organic nonlinear optical (NLO) material, trans-4-hydroxy-l-proline (THP), C5H9NO3 is reported. An optical quality single crystals of THP have been successfully grown by using slow evaporation solution growth technique (SEST). The single crystal x-ray diffraction (SXRD) analysis reveals that grown crystal belongs to the orthorhombic system with non-centrosymmetric space group (NCS), P212121. Powder x-ray diffraction (PXRD) analysis shows relatively a good crystalline nature. The molecular structure of THP was recognized by NMR (1H and 13C) studies and its vibrational modes were confirmed by FTIR and FT-Raman vibrational studies. UV-Vis-NIR spectrum of grown crystal shows high optical transparency in the visible and near-IR region with low near-UV cut-off wavelength at 218 nm. Photoluminescence study confirms ultraviolet wavelength emission of THP crystal. The second harmonic generation (SHG) efficiency of grown crystal is 1.6 times greater with respect to standard potassium dihydrogen phosphate (KDP). Nonlinear refractive index (n 2) and nonlinear absorption coefficient (β) were determined using the Z-scan technique. The title compound owns high thermal stability of 294 °C and specific heat capacity (C P) of 1.21 J g-1 K-1 at 300 K and 11.33 J g-1 K-1 at 539 K (melting point). The laser-induced damage threshold (LDT) value of grown crystal was measured as 7.25 GW cm-2. The crystal growth mechanism and defects of grown crystal were studied by chemical etching technique. Mechanical strength was extensively studied by Vickers microhardness test and crystal void percentage analysis. Moreover, density functional theory (DFT) studies were carried out to probe the Mulliken charge distribution, frontier molecular orbitals (FMOs) and first order hyperpolarizability (β) of the optimized molecular structure to get a better insight of the molecular properties. These characterization results endorse that grown THP crystal as a

  18. The study of past damaging hydrogeological events for damage susceptibility zonation

    Directory of Open Access Journals (Sweden)

    O. Petrucci

    2008-08-01

    Full Text Available Damaging Hydrogeological Events are defined as periods during which phenomena, such as landslides, floods and secondary floods, cause damage to people and the environment.

    A Damaging Hydrogeological Event which heavily damaged Calabria (Southern Italy between December 1972, and January 1973, has been used to test a procedure to be utilised in the zonation of a province according to damage susceptibility during DHEs. In particular, we analyzed the province of Catanzaro (2391 km2, an administrative district composed of 80 municipalities, with about 370 000 inhabitants.

    Damage, defined in relation to the reimbursement requests sent to the Department of Public Works, has been quantified using a procedure based on a Local Damage Index. The latter, representing classified losses, has been obtained by multiplying the value of the damaged element and the percentage of damage affecting it.

    Rainfall has been described by the Maximum Return Period of cumulative rainfall, for both short (1, 3, 5, 7, 10 consecutive days and long duration (30, 60, 90, 180 consecutive days, recorded during the event.

    Damage index and population density, presumed to represent the location of vulnerable elements, have been referred to Thiessen polygons associated to rain gauges working at the time of the event.

    The procedure allowed us to carry out a preliminary classification of the polygons composing the province according to their susceptibility to damage during DHEs. In high susceptibility polygons, severe damage occurs during rainfall characterised by low return periods; in medium susceptibility polygons maximum return period rainfall and induced damage show equal levels of exceptionality; in low susceptibility polygons, high return period rainfall induces a low level of damage.

    The east and west sectors of the province show the highest susceptibility, while polygons of the N-NE sector show the lowest

  19. Organic nonlinear crystals and high power frequency conversion

    International Nuclear Information System (INIS)

    Velsko, S.P.; Davis, L.; Wang, F.; Monaco, S.; Eimerl, D.

    1987-12-01

    We are searching for a new second- and third-harmonic generators among the salts of chiral organic acids and bases. We discuss the relevant properties of crystals from this group of compounds, including their nonlinear and phasematching characteristics, linear absorption, damage threshold and crystal growth. In addition, we summarize what is known concerning other nonlinear optical properties of these crystals, such as two-photon absorption, nonlinear refractive index, and stimulated Raman thresholds. A preliminary assessment is made of the potential of these materials for use in future high power, large aperture lasers such as those used for inertial confinement fusion experiments. 14 refs., 1 fig., 3 tabs

  20. A threshold auto-adjustment algorithm of feature points extraction based on grid

    Science.gov (United States)

    Yao, Zili; Li, Jun; Dong, Gaojie

    2018-02-01

    When dealing with high-resolution digital images, detection of feature points is usually the very first important step. Valid feature points depend on the threshold. If the threshold is too low, plenty of feature points will be detected, and they may be aggregated in the rich texture regions, which consequently not only affects the speed of feature description, but also aggravates the burden of following processing; if the threshold is set high, the feature points in poor texture area will lack. To solve these problems, this paper proposes a threshold auto-adjustment method of feature extraction based on grid. By dividing the image into numbers of grid, threshold is set in every local grid for extracting the feature points. When the number of feature points does not meet the threshold requirement, the threshold will be adjusted automatically to change the final number of feature points The experimental results show that feature points produced by our method is more uniform and representative, which avoids the aggregation of feature points and greatly reduces the complexity of following work.

  1. Deuteron threshold electrodisintegration at high momentum transfer

    International Nuclear Information System (INIS)

    Schmitt, W.M.; Turchinetz, W.; Williamson, C.F.; Yates, T.C.; Zumbro, J.D.; Lee, K.S.; Baghaei, H.; Churchwell, S.; Hicks, R.S.; Miskimen, R.; Peterson, G.A.; Wang, K.; Bosted, P.E.; Spengos, M.; Frois, B.; Martino, J.; Platchkov, S.; Hotta, A.

    1997-01-01

    Absolute differential cross sections for the threshold electrodisintegration of the deuteron with good resolution were measured at a laboratory scattering angle of 160 degree for five values of Q 2 ranging from 8.66 to 42.4fm -2 . Comparisons of the data averaged over E np from 0 to 3 MeV and from 0 to 10 MeV are made with nonrelativistic meson exchange calculations. These calculations are sensitive to the nucleon electromagnetic form factors, nucleon-nucleon potential, and relativistic effects. The data are also compared with a hybrid quark-hadron model calculation that describes the deuteron as a six-quark cluster for the short range part of the interaction. Some of these calculations can describe the data reasonably well over certain ranges of Q 2 ; however, none of these calculations can accurately describe the data over the entire measured Q 2 range. copyright 1997 The American Physical Society

  2. Post-processing of fused silica and its effects on damage resistance to nanosecond pulsed UV lasers.

    Science.gov (United States)

    Ye, Hui; Li, Yaguo; Zhang, Qinghua; Wang, Wei; Yuan, Zhigang; Wang, Jian; Xu, Qiao

    2016-04-10

    HF-based (hydrofluoric acid) chemical etching has been a widely accepted technique to improve the laser damage performance of fused silica optics and ensure high-power UV laser systems at designed fluence. Etching processes such as acid concentration, composition, material removal amount, and etching state (etching with additional acoustic power or not) may have a great impact on the laser-induced damage threshold (LIDT) of treated sample surfaces. In order to find out the effects of these factors, we utilized the Taguchi method to determine the etching conditions that are helpful in raising the LIDT. Our results show that the most influential factors are concentration of etchants and the material etched away from the viewpoint of damage performance of fused silica optics. In addition, the additional acoustic power (∼0.6  W·cm-2) may not benefit the etching rate and damage performance of fused silica. Moreover, the post-cleaning procedure of etched samples is also important in damage performances of fused silica optics. Different post-cleaning procedures were, thus, experiments on samples treated under the same etching conditions. It is found that the "spraying + rinsing + spraying" cleaning process is favorable to the removal of etching-induced deposits. Residuals on the etched surface are harmful to surface roughness and optical transmission as well as laser damage performance.

  3. Health effects of radiation damage

    International Nuclear Information System (INIS)

    Gasimova, K; Azizova, F; Mehdieva, K.

    2012-01-01

    Full text : A summary of the nature of radiactive contamination would be incomplete without some mention of the human health effects relatied to radioactivity and radioactive materials. Several excellent reviews at the variety of levels of detail have been written and should be consulted by the reader. Internal exposures of alpha and beta particles are important for ingested and inhaled radionuclides. Dosimetry models are used to estimate the dose from internally deposited radioactive particles. As mentioned above weighting parameters that take into account the radiation type, the biological half-life and the tissue or organ at risk are used to convert the physically absorbed dose in units of gray (or red) to the biologically significant committed equivalent dose and effective dose, measured in units of Sv (or rem). There is considerable controversy over the shape of the dose-response curve at the chronic low dose levels important for enviromental contamination. Proposed models include linear models, non-linear models and threshold models. Because risks at low dose must be extrapolated from available date at high doses, the shape of the dose-response curve has important implications for the environmental regulations used to protect the general public. The health effect of radiation damage depends on a combination of events of on the cellular, tissue and systemic levels. These lead to mutations and cellular of the irradiated parent cell. The dose level at which significant damage occurs depends on the cell type. Cells that reproduce rapidily, such as those found in bone marrow or the gastrointestinal tract, will be more sensitive to radiation than those that are longer lived, such as striated muscle or nerve cells. The effects of high radiation doses on an organ depends on the various cell types it contains

  4. Pain thresholds, supra-threshold pain and lidocaine sensitivity in patients with erythromelalgia, including the I848Tmutation in NaV 1.7.

    Science.gov (United States)

    Helås, T; Sagafos, D; Kleggetveit, I P; Quiding, H; Jönsson, B; Segerdahl, M; Zhang, Z; Salter, H; Schmelz, M; Jørum, E

    2017-09-01

    Nociceptive thresholds and supra-threshold pain ratings as well as their reduction upon local injection with lidocaine were compared between healthy subjects and patients with erythromelalgia (EM). Lidocaine (0.25, 0.50, 1.0 or 10 mg/mL) or placebo (saline) was injected intradermally in non-painful areas of the lower arm, in a randomized, double-blind manner, to test the effect on dynamic and static mechanical sensitivity, mechanical pain sensitivity, thermal thresholds and supra-threshold heat pain sensitivity. Heat pain thresholds and pain ratings to supra-threshold heat stimulation did not differ between EM-patients (n = 27) and controls (n = 25), neither did the dose-response curves for lidocaine. Only the subgroup of EM-patients with mutations in sodium channel subunits Na V 1.7, 1.8 or 1.9 (n = 8) had increased lidocaine sensitivity for supra-threshold heat stimuli, contrasting lower sensitivity to strong mechanical stimuli. This pattern was particularly clear in the two patients carrying the Na V 1.7 I848T mutations in whom lidocaine's hyperalgesic effect on mechanical pain sensitivity contrasted more effective heat analgesia. Heat pain thresholds are not sensitized in EM patients, even in those with gain-of-function mutations in Na V 1.7. Differential lidocaine sensitivity was overt only for noxious stimuli in the supra-threshold range suggesting that sensitized supra-threshold encoding is important for the clinical pain phenotype in EM in addition to lower activation threshold. Intracutaneous lidocaine dose-dependently blocked nociceptive sensations, but we did not identify EM patients with particular high lidocaine sensitivity that could have provided valuable therapeutic guidance. Acute pain thresholds and supra-threshold heat pain in controls and patients with erythromelalgia do not differ and have the same lidocaine sensitivity. Acute heat pain thresholds even in EM patients with the Na V 1.7 I848T mutation are normal and only nociceptor

  5. Investigating coseismic fracture damage using a new high speed triaxial apparatus

    Science.gov (United States)

    Mitchell, T. M.; Aben, F. M.; Pricci, R.; Brantut, N.; Rockwell, T. K.; Boon, S.

    2017-12-01

    The occurence of pulverized rocks, a type of intensely damaged fault rock which has undergone minimal shear strain, has been linked to damage induced by transient high strain-rate stress perturbations during earthquake rupture. Damage induced by such transient stresses, whether compressional or tensional, likely constitute heterogeneous modulations of the remote stresses that will impart significant changes on the strength, elastic and fluid flow properties of a fault zone immediately after rupture propagation, at the early stage of fault slip. While the physical mechanisms for pulverized rock generation are still not yet fully understood, it is likely that they are in some way related to a combination of the dynamic compressive and tensional stresses imparted on the rock surrounding a fault at the tip of a propagating earthquake rupture. Typical triaxial rock deformation apparatuses are limited by their loading systems to strain rates on the order of 10-4 s-1, which in terms of the seismic cycle, is only applicable to processes operating within the inter-seismic period. In order to achieve strain rates in excess of 100 s-1 under confined conditions with pore fluids (currently unachievable with conventional deformation apparatus such as split bar Hopkinson), we have designed, manufactured and constructed a new high strain rate triaxial rock deformation apparatus, with a unique innovative hydraulic loading system that allows samples to be deformed in compression and tension at strain rates from 10-7 up to 200 s-1 . We present preliminary data demonstrating the unique capability of this apparatus to produce co-seismic experimental conditions not previously acheived.

  6. Thresholds for pulse wave velocity, urine albumin creatinine ratio and left ventricular mass index using SCORE, Framingham and ESH/ESC risk charts

    DEFF Research Database (Denmark)

    Sehestedt, Thomas Berend; Jeppesen, Jørgen; Hansen, Tine Willum

    2012-01-01

    Markers of subclinical target organ damage (TOD) increase cardiovascular (CV) risk prediction beyond traditional risk factors. We wanted to establish thresholds for three markers of TOD based on absolute CV risk in different risk chart categories....

  7. Single-shot and single-spot measurement of laser ablation threshold for carbon nanotubes

    OpenAIRE

    Lednev, Vasily N.; Pershin, Sergey M.; Obraztsova, Elena D.; Kudryashov, Sergey I.; Bunkin, Alexey F.

    2013-01-01

    A simple and convenient procedure for single-shot, single-spot ablation threshold measurement has been developed. It is based on the employment of cylindrical lens to obtain elliptical Gaussian laser spot. The ablated spot chords which are parallel to the minor axis were measured across the spot major axis which is proportional to the fluence cross-section thus providing wide range dependence of damaged spot size versus fluence in one spot measurement. For both conventional and new-developed ...

  8. Monitoring of corrosion damage using high-frequency guided ultrasonic waves

    OpenAIRE

    Chew, D.; Fromme, P.

    2014-01-01

    Due to adverse environmental conditions corrosion can develop during the life cycle of industrial structures, e.g., offshore oil platforms, ships, and desalination plants. Both pitting corrosion and generalized corrosion leading to wall thickness loss can cause the degradation of the integrity and load bearing capacity of the structure. Structural health monitoring of corrosion damage in difficult to access areas can in principle be achieved using high frequency guided waves propagating along...

  9. Threshold Signature Schemes Application

    Directory of Open Access Journals (Sweden)

    Anastasiya Victorovna Beresneva

    2015-10-01

    Full Text Available This work is devoted to an investigation of threshold signature schemes. The systematization of the threshold signature schemes was done, cryptographic constructions based on interpolation Lagrange polynomial, elliptic curves and bilinear pairings were examined. Different methods of generation and verification of threshold signatures were explored, the availability of practical usage of threshold schemes in mobile agents, Internet banking and e-currency was shown. The topics of further investigation were given and it could reduce a level of counterfeit electronic documents signed by a group of users.

  10. Damage characterization of E-glass and C-glass fibre polymer composites after high velocity impact

    Science.gov (United States)

    Razali, N.; Sultan, M. T. H.; Cardona, F.; Jawaid, M.

    2017-12-01

    The purpose of this work is to identify impact damage on glass fibre reinforced polymer composite structures after high velocity impact. In this research, Type C-glass (600 g/m2) and Type E-glass (600 g/m2) were used to fabricate Glass Fibre-Reinforced Polymer composites (GFRP) plates. The panels were fabricated using a vacuum bagging and hot bounder method. Single stage gas gun (SSGG) was used to do the testing and data acquisition system was used to collect the damage data. Different types of bullets and different pressure levels were used for the experiment. The obtained results showed that the C-glass type of GFRP experienced more damage in comparison to E-glass type of materials based on the amount of energy absorbed on impact and the size of the damage area. All specimens underwent a partial fibre breakage but the laminates were not fully penetrated by the bullets. This indicated that both types of materials have high impact resistance even though the applied pressures of the gas gun were on the high range. We concluded that within the material specifications of the laminates including the type of glass fibre reinforcement and the thickness of the panels, those composite materials are safe to be applied in structural and body armour applications as an alternative to more expensive materials such as Kevlar and type S-glass fibre based panels.

  11. Thresholds in radiobiology

    International Nuclear Information System (INIS)

    Katz, R.; Hofmann, W.

    1982-01-01

    Interpretations of biological radiation effects frequently use the word 'threshold'. The meaning of this word is explored together with its relationship to the fundamental character of radiation effects and to the question of perception. It is emphasised that although the existence of either a dose or an LET threshold can never be settled by experimental radiobiological investigations, it may be argued on fundamental statistical grounds that for all statistical processes, and especially where the number of observed events is small, the concept of a threshold is logically invalid. (U.K.)

  12. Automatic recognition of damaged town buildings caused by earthquake using remote sensing information: Taking the 2001 Bhuj, India, earthquake and the 1976 Tangshan, China, earthquake as examples

    Science.gov (United States)

    Liu, Jia-Hang; Shan, Xin-Jian; Yin, Jing-Yuan

    2004-11-01

    In the high-resolution images, the undamaged buildings generally show a natural textural feature, while the damaged or semi-damaged buildings always exhibit some low-grayscale blocks because of their coarsely damaged sections. If we use a proper threshold to classify the grayscale of image, some independent holes will appear in the damaged regions. By using such statistical information as the number of holes in every region, or the ratio between the area of holes and that of the region, etc, the damaged buildings can be separated from the undamaged, thus automatic detection of damaged buildings can be realized. Based on these characteristics, a new method to automatically detect the damage buildings by using regional structure and statistical information of texture is presented in the paper. In order to test its validity, 1-m-resolution iKonos merged image of the 2001 Bhuj earthquake and grayscale aerial photos of the 1976 Tangshan earthquake are selected as two examples to automatically detect the damaged buildings. Satisfied results are obtained.

  13. Thermal damage study of beryllium windows used as vacuum barriers in synchrotron radiation beamlines

    International Nuclear Information System (INIS)

    Holdener, F.R.; Johnson, G.L.; Karpenko, V.P.; Wiggins, R.K.; Cerino, J.A.; Dormiani, M.T.; Youngman, B.P.; Hoyt, E.W.

    1987-01-01

    An experimental study to investigate thermal-induced damage to SSRL-designed beryllium foil windows was performed at LLNL's Laser Welding Research Facility. The primary goal of this study was to determine the threshold at which thermal-stress-induced damage occurs in these commonly used vacuum barriers. An Nd:Yag pulsed laser with cylindrical optics and a carefully designed test cell provided a test environment that closely resembles the actual beamline conditions at SSRL. Tests performed on two beryllium window geometries, with different vertical aperture dimensions but equal foil thicknesses of 0.254 mm, resulted in two focused total-power thresholds at which incipient damage was determined. For a beam spot size similar to that of the Beamline-X Wiggler Line, onset of surface damage for a 5-mm by 25-mm aperture window was observed at 170 W after 174,000 laser pulses (1.2-ms pulse at 100 pps). A second window with double the vertical aperture dimension (10 mm by 25 mm) was observed to have surface cracking after 180,000 laser pulses with 85 W impinging its front surface. It failed after approximately 1,000,000 pulses. Another window of the same type (10 mm by 25 mm) received 2,160,000 laser pulses at 74.4 W, and subsequent metallographic sectioning revealed no signs of through-thickness damage. Comparison of windows with equal foil thicknesses and aperture dimensions has effectively identified the heat flux limit for incipient failure. The data show that halving the aperture's vertical dimension allows doubling the total incident power for equivalent onsets of thermal-induced damage

  14. Simulation of Anisotropic Rock Damage for Geologic Fracturing

    Science.gov (United States)

    Busetti, S.; Xu, H.; Arson, C. F.

    2014-12-01

    A continuum damage model for differential stress-induced anisotropic crack formation and stiffness degradation is used to study geologic fracturing in rocks. The finite element-based model solves for deformation in the quasi-linear elastic domain and determines the six component damage tensor at each deformation increment. The model permits an isotropic or anisotropic intact or pre-damaged reference state, and the elasticity tensor evolves depending on the stress path. The damage variable, similar to Oda's fabric tensor, grows when the surface energy dissipated by three-dimensional opened cracks exceeds a threshold defined at the appropriate scale of the representative elementary volume (REV). At the laboratory or wellbore scale (1000m) scales the damaged REV reflects early natural fracturing (background or tectonic fracturing) or shear strain localization (fault process zone, fault-tip damage, etc.). The numerical model was recently benchmarked against triaxial stress-strain data from laboratory rock mechanics tests. However, the utility of the model to predict geologic fabric such as natural fracturing in hydrocarbon reservoirs was not fully explored. To test the ability of the model to predict geological fracturing, finite element simulations (Abaqus) of common geologic scenarios with known fracture patterns (borehole pressurization, folding, faulting) are simulated and the modeled damage tensor is compared against physical fracture observations. Simulated damage anisotropy is similar to that derived using fractured rock-mass upscaling techniques for pre-determined fracture patterns. This suggests that if model parameters are constrained with local data (e.g., lab, wellbore, or reservoir domain), forward modeling could be used to predict mechanical fabric at the relevant REV scale. This reference fabric also can be used as the starting material property to pre-condition subsequent deformation or fluid flow. Continuing efforts are to expand the present damage

  15. THRESHOLD PARAMETER OF THE EXPECTED LOSSES

    Directory of Open Access Journals (Sweden)

    Josip Arnerić

    2012-12-01

    Full Text Available The objective of extreme value analysis is to quantify the probabilistic behavior of unusually large losses using only extreme values above some high threshold rather than using all of the data which gives better fit to tail distribution in comparison to traditional methods with assumption of normality. In our case we estimate market risk using daily returns of the CROBEX index at the Zagreb Stock Exchange. Therefore, it’s necessary to define the excess distribution above some threshold, i.e. Generalized Pareto Distribution (GPD is used as much more reliable than the normal distribution due to the fact that gives the accent on the extreme values. Parameters of GPD distribution will be estimated using maximum likelihood method (MLE. The contribution of this paper is to specify threshold which is large enough so that GPD approximation valid but low enough so that a sufficient number of observations are available for a precise fit.

  16. High-Intensity Exercise Induced Oxidative Stress and Skeletal Muscle Damage in Postpubertal Boys and Girls: A Comparative Study.

    Science.gov (United States)

    Pal, Sangita; Chaki, Biswajit; Chattopadhyay, Sreya; Bandyopadhyay, Amit

    2018-04-01

    Pal, S, Chaki, B, Chattopadhyay, S, and Bandyopadhyay, A. High-intensity exercise induced oxidative stress and skeletal muscle damage in post-pubertal boys and girls: a comparative study. J Strength Cond Res 32(4): 1045-1052, 2018-The purpose of this study was to examine the sex variation in high-intensity exercise induced oxidative stress and muscle damage among 44 sedentary postpubertal boys and girls through estimation of postexercise release pattern of muscle damage markers like creatine kinase, lactate dehydrogenase (LDH), alanine aminotransferase (ALT), aspartate aminotransferase (AST) and oxidative stress markers like extent of lipid peroxidation (thiobarbituric acid-reactive substances) and catalase activity. Muscle damage markers like creatine kinase, LDH, ALT, and AST were measured before, immediately after, and 24 and 48 hours after high-intensity incremental treadmill running. Oxidative stress markers like thiobarbituric acid-reactive substances and catalase activity were estimated before and immediately after the exercise. Lipid peroxidation and serum catalase activity increased significantly in both groups after exercise (p exercise level at 24 and 48 hours after exercise in both the sexes, (p exercise, the pattern of postexercise release of these markers were found to be similar in both the groups. Accordingly, it has been concluded from the present investigation that high-intensity exercise induces significant oxidative stress and increases indices of skeletal muscle damage in both postpubertal girls and boys. However, postpubertal girls are relatively better protected from oxidative stress and muscle damage as compared to the boys of similar age and physical activity level. It is further evident that sex difference may not be apparent for all the biomarkers of muscle damage in this age group.

  17. Relationships between browsing damage and the species dominance by the highly food-attractive and less food-attractive trees

    Directory of Open Access Journals (Sweden)

    Petr Čermák

    2011-01-01

    Full Text Available The paper analyses data on the browsing damage to Acer pseudoplatanus, Carpinus betulus, Fraxinus excelsior, Quercus spp., Tilia cordata and Fagus sylvatica. Field research was carried out in the period 2007–2010 and analysed data came from 33 transects at 10 localities with the various abundance of game in the CR (everywhere Capreolus capreolus, on several plots also Cervus elaphus, Ovis musimon or Dama dama. Trees were monitored up to a height of 150 cm in natural regeneration under stands and in plantations and the occurrence was noted of new browsing damage. Differences between the percentage of damaged individuals of the given species of a food-attractive species (A. p., C. b., F. e. and the percentage of damaged individuals of all tree species on a transect as well as the proportion of these parameters correlate negatively with the given species dominance and thus, they appear to be suitable parameters for the analysis of relationships between the damage intensity and dominance. The higher the percentage proportions of highly food-attractive species and the lower the percentage of less-attractive species, the lower the relative intensity of damage to highly food-attractive species. At the same time, the higher the percentage proportion of highly food-attractive species and the lower the percentage of less-attractive species then the lower a difference between damage to less food-attractive species and all species.

  18. Dynamical fusion thresholds in macroscopic and microscopic theories

    International Nuclear Information System (INIS)

    Davies, K.T.R.; Sierk, A.J.; Nix, J.R.

    1983-01-01

    Macroscopic and microscopic results demonstrating the existence of dynamical fusion thresholds are presented. For macroscopic theories, it is shown that the extra-push dynamics is sensitive to some details of the models used, e.g. the shape parametrization and the type of viscosity. The dependence of the effect upon the charge and angular momentum of the system is also studied. Calculated macroscopic results for mass-symmetric systems are compared to experimental mass-asymmetric results by use of a tentative scaling procedure, which takes into account both the entrance-channel and the saddle-point regions of configuration space. Two types of dynamical fusion thresholds occur in TDHF studies: (1) the microscopic analogue of the macroscopic extra push threshold, and (2) the relatively high energy at which the TDHF angular momentum window opens. Both of these microscopic thresholds are found to be very sensitive to the choice of the effective two-body interaction

  19. The organ specificity in pathological damage of chronic intermittent hypoxia: an experimental study on rat with high-fat diet.

    Science.gov (United States)

    Wang, Hui; Tian, Jian-li; Feng, Shu-zhi; Sun, Ning; Chen, Bao-yuan; Zhang, Yun

    2013-09-01

    It is known today that sleep apnea hypopnea syndrome and its characteristic chronic intermittent hypoxia can cause damages to multiple organs, including the cardiovascular system, urinary system, and liver. It is still unclear, however, whether the damage caused by sleep apnea hypopnea syndrome and the severity of the damage are organ-specific. This research observed the pathological effects of chronic intermittent hypoxia on rat's thoracic aorta, myocardium, liver, and kidney, under the condition of lipid metabolism disturbance, through establishing the rat model of chronic intermittent hypoxia with high-fat diet by imitating the features of human sleep apnea hypopnea syndrome. In this model, 24 male Wistar rats were randomly divided into three groups: a control group fed by regular diet, a high-fat group fed by high-fat diet, and a high-fat plus intermittent hypoxia group fed by high-fat diet and treated with intermittent hypoxia 7 h a day. At the end of the ninth week, the pathological changes of rat's organs, including the thoracic aorta, myocardium, liver, and kidney are observed (under both optical microscopy and transmission electron microscopy). As the result of the experiment shows, while there was no abnormal effect observed on any organs of the control group, slight pathological changes were found in the organs of the high-fat group. For the high-fat plus intermittent hypoxia group, however, remarkably severer damages were found on all the organs. It also showed that the severity of the damage varies by organ in the high-fat plus intermittent hypoxia group, with the thoracic aorta being the worst, followed by the liver and myocardium, and the kidney being the slightest. Chronic intermittent hypoxia can lead to multiple-organ damage to rat with high-fat diet. Different organs appear to have different sensitivity to chronic intermittent hypoxia.

  20. Polarized training has greater impact on key endurance variables than threshold, high intensity or high volume training

    Directory of Open Access Journals (Sweden)

    Thomas eStöggl

    2014-02-01

    Full Text Available Endurance athletes integrate four conditioning concepts in their training programs: high-volume training (HVT, ‘threshold-training’ (THR, high-intensity interval training (HIIT and a combination of these aforementioned concepts known as polarized training (POL. The purpose of this study was to explore which of these four training concepts provides the greatest response on key components of endurance performance in well-trained endurance athletes. Methods: Forty eight runners, cyclists, triathletes and cross-country skiers (peak oxygen uptake: (VO2peak: 62.6±7.1 mL∙min-1∙kg-1 were randomly assigned to one of four groups performing over nine weeks. An incremental test, work economy and a VO2peak tests were performed. Training intensity was heart rate controlled. Results: POL demonstrated the greatest increase in VO2peak (+6.8 ml∙min∙kg-1 or 11.7%, P0.05. Conclusion: POL resulted in the greatest improvements in most key variables of endurance performance in well-trained endurance athletes. THR or HVT did not lead to further improvements in performance related variables.

  1. A prediction and damage assessment model for snowmelt flood events in middle and high latitudes Region

    Science.gov (United States)

    Qiao, C.; Huang, Q.; Chen, T.; Zhang, X.

    2017-12-01

    In the context of global warming, the snowmelt flood events in the mountainous area of the middle and high latitudes are increasingly frequent and create severe casualties and property damages. Carrying out the prediction and risk assessment of the snowmelt flood is of great importance in the water resources management, the flood warning and prevention. Based on the remote sensing and GIS techniques, the relationships of the variables influencing the snowmelt flood such as the snow area, the snow depth, the air temperature, the precipitation, the land topography and land covers are analyzed and a prediction and damage assessment model for snowmelt floods is developed. This model analyzes and predicts the flood submerging area, flood depth, flood grade, and the damages of different underlying surfaces in the study area in a given time period based on the estimation of snowmelt amount, the snowmelt runoff, the direction and velocity of the flood. Then it was used to predict a snowmelt flood event in the Ertis River Basin in northern Xinjiang, China, during March and June, 2005 and to assess its damages including the damages of roads, transmission lines, settlements caused by the floods and the possible landslides using the hydrological and meteorological data, snow parameter data, DEM data and land use data. A comparison was made between the prediction results from this model and observation data including the flood measurement and its disaster loss data, which suggests that this model performs well in predicting the strength and impact area of snowmelt flood and its damage assessment. This model will be helpful for the prediction and damage assessment of snowmelt flood events in the mountainous area in the middle and high latitudes in spring, which has great social and economic significance because it provides a relatively reliable method for snowmelt flood prediction and reduces the possible damages caused by snowmelt floods.

  2. A survey of high explosive-induced damage and spall in selected metals using proton radiography

    International Nuclear Information System (INIS)

    Holtkamp, D.B.; Clark, D.A.; Ferm, E.N.; Gallegos, R.A.; Hammon, D.; Hemsing, W.F.; Hogan, G.E.; Holmes, V.H.; King, N.S.P.; Lopez, R.P.; Merrill, F.E.; Morris, C.L.; Morley, K.B.; Murray, M.M.; Pazuchanics, P.D.; Prestridge, K.P.; Quintana, J.P.; Saunders, A.; Shinas, M.A.; Stacy, H.L.

    2004-01-01

    Multiple spall and damage layers can be created in metal when the free surface reflects a Taylor wave generated by high explosives. These phenomena have been explored in different thicknesses of several metals (tantalum, copper, 6061 T6-aluminum, and tin) using high-energy proton radiography. Multiple images (up to 21) can be produced of the dynamic evolution of damaged material on the microsecond time scale with a <50 ns 'shutter' time. Movies and multiframe still images of areal and (Abel inverted) volume densities are presented. An example of material that is likely melted on release (tin) is also presented

  3. High-speed, low-damage grinding of advanced ceramics Phase 1. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Kovach, J.A. [Eaton Corp., Willoughby Hills, OH (United States). Mfg. Technologies Center; Malkin, S. [Univ. of Massachusetts (United States)

    1995-03-01

    In manufacture of structural ceramic components, grinding costs can comprise up to 80% of the entire manufacturing cost. Most of these costs arise from the conventional multi-step grinding process with numerous grinding wheels and additional capital equipment, perishable dressing tools, and labor. In an attempt to reduce structural ceramic grinding costs, a feasibility investigation was undertaken to develop a single step, roughing-finishing process suitable for producing high-quality silicon nitride ceramic parts at high material removal rates at lower cost than traditional, multi-stage grinding. This feasibility study employed combined use of laboratory grinding tests, mathematical grinding models, and characterization of resultant material surface condition. More specifically, this Phase 1 final report provides a technical overview of High-Speed, Low-Damage (HSLD) ceramic grinding and the conditions necessary to achieve the small grain depths of cut necessary for low damage grinding while operating at relatively high material removal rates. Particular issues addressed include determining effects of wheel speed and material removal rate on resulting mode of material removal (ductile or brittle fracture), limiting grinding forces, calculation of approximate grinding zone temperatures developed during HSLD grinding, and developing the experimental systems necessary for determining HSLD grinding energy partition relationships. In addition, practical considerations for production utilization of the HSLD process are also discussed.

  4. Shifts in the relationship between motor unit recruitment thresholds versus derecruitment thresholds during fatigue.

    Science.gov (United States)

    Stock, Matt S; Mota, Jacob A

    2017-12-01

    Muscle fatigue is associated with diminished twitch force amplitude. We examined changes in the motor unit recruitment versus derecruitment threshold relationship during fatigue. Nine men (mean age = 26 years) performed repeated isometric contractions at 50% maximal voluntary contraction (MVC) knee extensor force until exhaustion. Surface electromyographic signals were detected from the vastus lateralis, and were decomposed into their constituent motor unit action potential trains. Motor unit recruitment and derecruitment thresholds and firing rates at recruitment and derecruitment were evaluated at the beginning, middle, and end of the protocol. On average, 15 motor units were studied per contraction. For the initial contraction, three subjects showed greater recruitment thresholds than derecruitment thresholds for all motor units. Five subjects showed greater recruitment thresholds than derecruitment thresholds for only low-threshold motor units at the beginning, with a mean cross-over of 31.6% MVC. As the muscle fatigued, many motor units were derecruited at progressively higher forces. In turn, decreased slopes and increased y-intercepts were observed. These shifts were complemented by increased firing rates at derecruitment relative to recruitment. As the vastus lateralis fatigued, the central nervous system's compensatory adjustments resulted in a shift of the regression line of the recruitment versus derecruitment threshold relationship. Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.

  5. Modeling of material properties of piezoelectric ceramics taking into account damage development under static compression

    International Nuclear Information System (INIS)

    Mizuno, M; Nishikata, T; Okayasu, M

    2013-01-01

    We have carried out static compression tests in the poling direction for PZT ceramics and evaluated the material properties by measuring the resonance and anti-resonance frequencies and electrostatic capacity at regular intervals. Then the variation in the material properties up to fracture was clarified. Also, the development of internal damage was also clarified quantitatively by evaluating a damage variable on the basis of the continuum damage mechanics. The damage variable was calculated from the ratio of the elastic coefficient to its initial value. In the present paper, the development of internal damage was formulated as an evolution equation of the damage variable. In the formulation, a threshold stress leading to the onset of damage was considered. Moreover, the variation in material properties was related to the damage variable and formulated as material functions of the damage variable. The development of internal damage and the variation in material properties were simulated by the equations proposed in the present paper and the validity of the equations was verified by comparing the predictions with experimental results. (paper)

  6. The threshold photoelectron spectrum of mercury

    International Nuclear Information System (INIS)

    Rojas, H; Dawber, G; Gulley, N; King, G C; Bowring, N; Ward, R

    2013-01-01

    The threshold photoelectron spectrum of mercury has been recorded over the energy range (10–40 eV) which covers the region from the lowest state of the singly charged ion, 5d 10 6s( 2 S 1/2 ), to the double charged ionic state, 5d 9 ( 2 D 3/2 )6s( 1 D 2 ). Synchrotron radiation has been used in conjunction with the penetrating-field threshold-electron technique to obtain the spectrum with high resolution. The spectrum shows many more features than observed in previous photoemission measurements with many of these assigned to satellite states converging to the double ionization limit. (paper)

  7. Effect of Tritium on Cracking Threshold in 7075 Aluminum

    Energy Technology Data Exchange (ETDEWEB)

    Duncan, A. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Morgan, M. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2017-02-28

    The effect of long-term exposure to tritium gas on the cracking threshold (KTH) of 7075 Aluminum Alloy was investigated. The alloy is the material of construction for a cell used to contain tritium in an accelerator at Jefferson Laboratory designed for inelastic scattering experiments on nucleons. The primary safety concerns for the Jefferson Laboratory tritium cell is a tritium leak due to mechanical failure of windows from hydrogen isotope embrittlement, radiation damage, or loss of target integrity from accidental excessive beam heating due to failure of the raster or grossly mis-steered beam. Experiments were conducted to investigate the potential for embrittlement of the 7075 Aluminum alloy from tritium gas.

  8. Analysis of dynamic accumulative damage about the lining structure of high speed railway’s tunnel based on ultrasonic testing technology

    Science.gov (United States)

    Wang, Xiang-qiu; Zhang, Huojun; Xie, Wen-xi

    2017-08-01

    Based on the similar material model test of full tunnel, the theory of elastic wave propagation and the testing technology of intelligent ultrasonic wave had been used to research the dynamic accumulative damage characteristics of tunnel’s lining structure under the dynamic loads of high speed train. For the more, the dynamic damage variable of lining structure of high speed railway’s tunnel was obtained. The results shown that the dynamic cumulative damage of lining structure increases nonlinearly with the times of cumulative vibration, the weakest part of dynamic cumulative damage is the arch foot of tunnel. Much more attention should be paid to the design and operation management of high speed railway’s tunnel.

  9. Laser Induced Damage of Potassium Dihydrogen Phosphate (KDP Optical Crystal Machined by Water Dissolution Ultra-Precision Polishing Method

    Directory of Open Access Journals (Sweden)

    Yuchuan Chen

    2018-03-01

    Full Text Available Laser induced damage threshold (LIDT is an important optical indicator for nonlinear Potassium Dihydrogen Phosphate (KDP crystal used in high power laser systems. In this study, KDP optical crystals are initially machined with single point diamond turning (SPDT, followed by water dissolution ultra-precision polishing (WDUP and then tested with 355 nm nanosecond pulsed-lasers. Power spectral density (PSD analysis shows that WDUP process eliminates the laser-detrimental spatial frequencies band of micro-waviness on SPDT machined surface and consequently decreases its modulation effect on the laser beams. The laser test results show that LIDT of WDUP machined crystal improves and its stability has a significant increase by 72.1% compared with that of SPDT. Moreover, a subsequent ultrasonic assisted solvent cleaning process is suggested to have a positive effect on the laser performance of machined KDP crystal. Damage crater investigation indicates that the damage morphologies exhibit highly thermal explosion features of melted cores and brittle fractures of periphery material, which can be described with the classic thermal explosion model. The comparison result demonstrates that damage mechanisms for SPDT and WDUP machined crystal are the same and WDUP process reveals the real bulk laser resistance of KDP optical crystal by removing the micro-waviness and subsurface damage on SPDT machined surface. This improvement of WDUP method makes the LIDT more accurate and will be beneficial to the laser performance of KDP crystal.

  10. Threshold factorization redux

    Science.gov (United States)

    Chay, Junegone; Kim, Chul

    2018-05-01

    We reanalyze the factorization theorems for the Drell-Yan process and for deep inelastic scattering near threshold, as constructed in the framework of the soft-collinear effective theory (SCET), from a new, consistent perspective. In order to formulate the factorization near threshold in SCET, we should include an additional degree of freedom with small energy, collinear to the beam direction. The corresponding collinear-soft mode is included to describe the parton distribution function (PDF) near threshold. The soft function is modified by subtracting the contribution of the collinear-soft modes in order to avoid double counting on the overlap region. As a result, the proper soft function becomes infrared finite, and all the factorized parts are free of rapidity divergence. Furthermore, the separation of the relevant scales in each factorized part becomes manifest. We apply the same idea to the dihadron production in e+e- annihilation near threshold, and show that the resultant soft function is also free of infrared and rapidity divergences.

  11. Casualties and threshold effects

    International Nuclear Information System (INIS)

    Mays, C.W.; National Cancer Inst., Bethesda

    1988-01-01

    Radiation effects like cancer are denoted as casualties. Other radiation effects occur almost in everyone when the radiation dose is sufficiently high. One then speaks of radiation effects with a threshold dose. In this article the author puts his doubt about this classification of radiation effects. He argues that some effects of exposure to radiation do not fit in this classification. (H.W.). 19 refs.; 2 figs.; 1 tab

  12. Comparison between intensity- duration thresholds and cumulative rainfall thresholds for the forecasting of landslide

    Science.gov (United States)

    Lagomarsino, Daniela; Rosi, Ascanio; Rossi, Guglielmo; Segoni, Samuele; Catani, Filippo

    2014-05-01

    This work makes a quantitative comparison between the results of landslide forecasting obtained using two different rainfall threshold models, one using intensity-duration thresholds and the other based on cumulative rainfall thresholds in an area of northern Tuscany of 116 km2. The first methodology identifies rainfall intensity-duration thresholds by means a software called MaCumBA (Massive CUMulative Brisk Analyzer) that analyzes rain-gauge records, extracts the intensities (I) and durations (D) of the rainstorms associated with the initiation of landslides, plots these values on a diagram, and identifies thresholds that define the lower bounds of the I-D values. A back analysis using data from past events can be used to identify the threshold conditions associated with the least amount of false alarms. The second method (SIGMA) is based on the hypothesis that anomalous or extreme values of rainfall are responsible for landslide triggering: the statistical distribution of the rainfall series is analyzed, and multiples of the standard deviation (σ) are used as thresholds to discriminate between ordinary and extraordinary rainfall events. The name of the model, SIGMA, reflects the central role of the standard deviations in the proposed methodology. The definition of intensity-duration rainfall thresholds requires the combined use of rainfall measurements and an inventory of dated landslides, whereas SIGMA model can be implemented using only rainfall data. These two methodologies were applied in an area of 116 km2 where a database of 1200 landslides was available for the period 2000-2012. The results obtained are compared and discussed. Although several examples of visual comparisons between different intensity-duration rainfall thresholds are reported in the international literature, a quantitative comparison between thresholds obtained in the same area using different techniques and approaches is a relatively undebated research topic.

  13. An analysis of the development of high temperature cavitation damage

    International Nuclear Information System (INIS)

    Tinivella, R.

    1986-07-01

    The objective of the paper is the investigation of creep cavitation damage in copper. Radii distribution curves obtained from small angle neutron scattering experiments conducted on crept specimens were analyzed and compared with calculated curves. The latter were derived from cavity nucleation- and growth models. From the comparison the appropriateness of particular models can be infered. Valuable information is obtained about the nucleation behaviour. In crept and fatigued specimens, already after very short loading times, cavities appear with remarkable different radii, an observation which is contradictory to the concept of a critical radius. The analysis of the nucleation behavior emphasizes the influence of the stress dependence of the nucleation rate upon the stress dependence of damage and hence upon the stress dependence of the lifetime. In most of damage theories the latter is attributed to the stress dependency of cavity growth. A strong argument is derived in this paper in favour of the idea that both the mechanisms - growth and nucleation - contribute to the stress dependence of the lifetime. The damage development in Cu (as well as in alpha-Fe, AISI 304 and AISI 347) is compared with the prediction of the phenomenological A-model which assumes that the damage rate is proportional to the damage itself. The experiments show, that the damage increases in time slower (Cu, alpha-Fe, AISI 304) or faster (AISI 347) than predicted by the model. In copper the damage rate turns out to be constant independent of time. Accordingly the A-model is modified and the respective consequences are briefly discussed. (orig./GSCH) [de

  14. Handling of BLM abort thresholds in the LHC

    CERN Document Server

    Nebot Del Busto, E; Holzer, EB; Zamantzas, C; Kruk, G; Nordt, A; Sapinski, M; Nemcic, M; Orecka, A; Jackson, S; Roderick, C; Skaugen, A

    2011-01-01

    The Beam Loss Monitoring system (BLM) for the LHC consists of about 3600 Ionization Chambers (IC) located around the ring. Its main purpose is to request a beam abort when the measured losses exceed a certain threshold. The BLM detectors integrate the measured signals in 12 different time intervals (running from 40us to 83.8s) enabling for a different set of abort thresholds depending on the duration of the beam loss. Furthermore, 32 energy levels running from 450GeV to 7TeV account for the fact that the energy density of a particle shower increases with the energy of the primary particle, i.e. the beam energy. Thus, a set of ! 3600 × 12 × 32 = 1.3 · 106 thresholds must be handled. These thresholds are highly critical for the safety of the machine and depend to a large part on human judgment, which cannot be replaced by automatic test procedures. The BLM team has defined well established procedures to compute, set and check new BLM thresholds, in order to avoid and/or find non-conformities due to manipulat...

  15. Oxidative DNA damage and repair in skeletal muscle of humans exposed to high-altitude hypoxia

    International Nuclear Information System (INIS)

    Lundby, Carsten; Pilegaard, Henriette; Hall, Gerrit van; Sander, Mikael; Calbet, Jose; Loft, Steffen; Moeller, Peter

    2003-01-01

    Recent research suggests that high-altitude hypoxia may serve as a model for prolonged oxidative stress in healthy humans. In this study, we investigated the consequences of prolonged high-altitude hypoxia on the basal level of oxidative damage to nuclear DNA in muscle cells, a major oxygen-consuming tissue. Muscle biopsies from seven healthy humans were obtained at sea level and after 2 and 8 weeks of hypoxia at 4100 m.a.s.l. We found increased levels of strand breaks and endonuclease III-sensitive sites after 2 weeks of hypoxia, whereas oxidative DNA damage detected by formamidopyrimidine DNA glycosylase (FPG) protein was unaltered. The expression of 8-oxoguanine DNA glycosylase 1 (OGG1), determined by quantitative RT-PCR of mRNA levels did not significantly change during high-altitude hypoxia, although the data could not exclude a minor upregulation. The expression of heme oxygenase-1 (HO-1) was unaltered by prolonged hypoxia, in accordance with the notion that HO-1 is an acute stress response protein. In conclusion, our data indicate high-altitude hypoxia may serve as a good model for oxidative stress and that antioxidant genes are not upregulated in muscle tissue by prolonged hypoxia despite increased generation of oxidative DNA damage

  16. The Efficiency of Damage Production in Silicon Carbide

    International Nuclear Information System (INIS)

    Weber, William J.; Gao, Fei; Devanathan, Ram; Jiang, Weilin

    2004-01-01

    Molecular dynamics simulations are used to study the statistics of damage production in 3C-SiC due to C, Si and Au primary knock-on atoms (PKAs) over energies from 0.25 to 50 keV. In order to account for the different displacement energies on the Si and C sublattices and accurately assess the damage efficiency, a modified version of the SRIM (Stopping and Range of Ions in Matter) code, with the electronic stopping turned off to duplicate the molecular dynamics conditions, was used to calculate the statistics of damage production for the same PKAs over the energy range from 0.1 to 400 keV under the binary collision approximation using threshold displacement energies of 20 and 35 eV for C and Si, respectively. Using the modified SRIM predictions as a reference, the efficiencies of total damage production are determined for C, Si and Au PKAs as functions of energy. The efficiency for production of C displacements is similar for all PKAs; however, C PKAs have a much lower efficiency for producing stable Si displacements than Si and Au PKAs, which leads to a much higher ratio of C to Si displacements for C PKAs. These results are consistent with the experimental damage production behavior observed in SiC irradiated with C, Si and Au ions at 150 K

  17. The efficiency of damage production in silicon carbide

    International Nuclear Information System (INIS)

    Weber, W.J.; Gao, F.; Devanathan, R.; Jiang, W.

    2004-01-01

    Molecular dynamics (MD) simulations are used to study the statistics of damage production in 3C-SiC due to C, Si and Au primary knock-on atoms (PKAs) over energies from 0.25 to 50 keV. In order to account for the different displacement energies on the Si and C sublattices and accurately assess the damage efficiency, a modified version of the SRIM (stopping and range of ions in matter) code, with the electronic stopping turned off to duplicate the MD conditions, was used to calculate the statistics of damage production for the same PKAs over the energy range from 0.1 to 400 keV under the binary collision approximation using threshold displacement energies of 20 and 35 eV for C and Si, respectively. Using the modified SRIM predictions as a reference, the efficiencies of total damage production are determined for C, Si and Au PKAs as functions of energy. The efficiency for production of C displacements is similar for all PKAs; however, C PKAs have a much lower efficiency for producing stable Si displacements than Si and Au PKAs, which leads to a much higher ratio of C to Si displacements for C PKAs. These results are consistent with the experimental damage production behavior observed in SiC irradiated with C, Si and Au ions at 150 K

  18. A novel theory of radiation damage at high doses

    International Nuclear Information System (INIS)

    Seeger, A.; Stuttgart Univ.

    1989-01-01

    Deviations of radiation damage (in the case of metals usually monitored by the residual electrical resistivity) from proportionality with the irradiation dose have so far been analysed almost exclusively in terms of extensions of models originally developed for small doses. The present theory considers the opposite limit i.e. the quasi-saturated state. It is argued that at high doses the Lueck-Sizmann effect may result in a self-organization of clusters of vacancies and self-interstitials, forming a heterogeneous froth. Possible structures of this froth and its effect on the electrical resistivity of metals are discussed. The model is shown to account for the dependence of the ''saturation resistivity'' on the nature of the irradiation as well as for several other hitherto poorly explained observations. Among them are the electrical-resistivity variation induced by high-dose irradiation with heavy ions, the amorphization of certain alloys by high-dose electron irradiation, and the occurrence of ordered arrays of stacking-fault tetrahedra after in-situ irradiations in high-voltage electron microscopes. (author)

  19. Detection thresholds of macaque otolith afferents.

    Science.gov (United States)

    Yu, Xiong-Jie; Dickman, J David; Angelaki, Dora E

    2012-06-13

    The vestibular system is our sixth sense and is important for spatial perception functions, yet the sensory detection and discrimination properties of vestibular neurons remain relatively unexplored. Here we have used signal detection theory to measure detection thresholds of otolith afferents using 1 Hz linear accelerations delivered along three cardinal axes. Direction detection thresholds were measured by comparing mean firing rates centered on response peak and trough (full-cycle thresholds) or by comparing peak/trough firing rates with spontaneous activity (half-cycle thresholds). Thresholds were similar for utricular and saccular afferents, as well as for lateral, fore/aft, and vertical motion directions. When computed along the preferred direction, full-cycle direction detection thresholds were 7.54 and 3.01 cm/s(2) for regular and irregular firing otolith afferents, respectively. Half-cycle thresholds were approximately double, with excitatory thresholds being half as large as inhibitory thresholds. The variability in threshold among afferents was directly related to neuronal gain and did not depend on spike count variance. The exact threshold values depended on both the time window used for spike count analysis and the filtering method used to calculate mean firing rate, although differences between regular and irregular afferent thresholds were independent of analysis parameters. The fact that minimum thresholds measured in macaque otolith afferents are of the same order of magnitude as human behavioral thresholds suggests that the vestibular periphery might determine the limit on our ability to detect or discriminate small differences in head movement, with little noise added during downstream processing.

  20. Regional rainfall thresholds for landslide occurrence using a centenary database

    Science.gov (United States)

    Vaz, Teresa; Luís Zêzere, José; Pereira, Susana; Cruz Oliveira, Sérgio; Quaresma, Ivânia

    2017-04-01

    Rainfall is one of the most important triggering factors for landslides occurrence worldwide. The relation between rainfall and landslide occurrence is complex and some approaches have been focus on the rainfall thresholds identification, i.e., rainfall critical values that when exceeded can initiate landslide activity. In line with these approaches, this work proposes and validates rainfall thresholds for the Lisbon region (Portugal), using a centenary landslide database associated with a centenary daily rainfall database. The main objectives of the work are the following: i) to compute antecedent rainfall thresholds using linear and potential regression; ii) to define lower limit and upper limit rainfall thresholds; iii) to estimate the probability of critical rainfall conditions associated with landslide events; and iv) to assess the thresholds performance using receiver operating characteristic (ROC) metrics. In this study we consider the DISASTER database, which lists landslides that caused fatalities, injuries, missing people, evacuated and homeless people occurred in Portugal from 1865 to 2010. The DISASTER database was carried out exploring several Portuguese daily and weekly newspapers. Using the same newspaper sources, the DISASTER database was recently updated to include also the landslides that did not caused any human damage, which were also considered for this study. The daily rainfall data were collected at the Lisboa-Geofísico meteorological station. This station was selected considering the quality and completeness of the rainfall data, with records that started in 1864. The methodology adopted included the computation, for each landslide event, of the cumulative antecedent rainfall for different durations (1 to 90 consecutive days). In a second step, for each combination of rainfall quantity-duration, the return period was estimated using the Gumbel probability distribution. The pair (quantity-duration) with the highest return period was

  1. Damage parameters for non-metals in a high energy neutron environment

    International Nuclear Information System (INIS)

    Dell, G.F.; Berry, H.C.; Lazareth, O.W.; Goland, A.N.

    1980-01-01

    Simulation of radiation damage induced in monatomic and binary non-metals by FMIT and fusion neutrons is described. Damage produced by elastic scattering of recoil atoms and by ionization-assisted processes has been evaluated using the damage program DON. Displacement damage from gamma rays has been evaluated by using the technique of Oen and Holmes. A comparison of damage for an anticipated FMIT radiation environment generated by a coupled n-γ transport calculations and a fusion spectrum is made. Gamma-induced displacement damage is sufficiently small that it is dominated by neutron-induced recoil processes. Ionization-assisted displacements may be important depending upon the ionization cross section of the particular non-metal under consideration

  2. Effect of tensile stress on cavitation damage formation in mercury

    Energy Technology Data Exchange (ETDEWEB)

    Naoe, Takashi, E-mail: naoe.takashi@jaea.go.j [J-PARC Center, Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan); Kogawa, Hiroyuki [J-PARC Center, Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan); Yamaguchi, Yoshihito [Nuclear Safety Research Center, Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan); Futakawa, Masatoshi [J-PARC Center, Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan)

    2010-03-15

    Cavitation erosion or so called pitting damage was investigated under tensile stress conditions in mercury. In MW-class liquid metal spallation targets, pitting damage is a critical issue to satisfy required power and/or lifetime of the target vessel. Cavitation occurs by negative pressure which is induced through pressure wave propagation due to proton beam injection. Pitting damage is formed by microjet and/or shock wave during cavitation bubble collapse. A mercury target vessel suffers tensile stress due to thermal stress or welding. In order to investigate the effect of tensile stress on pitting damage formation, cavitation erosion tests were performed using stress imposed specimens in mercury. An ultrasonic vibratory horn and electro-Magnetic IMpact Testing Machine (MIMTM) were used to vary the cavitation intensity. In the incubation period of pitting damage, damaged area was slightly increased with increasing imposed tensile stress. In the steady state period, a mean depth of erosion was increased by the tensile stress. Additionally, in order to quantitatively evaluate the effect of tensile stress, an indentation test with Vickers indenter was carried out to quasi-statically simulate the impact load. From the measurement of the diagonal length of the indent aspect ratio and hardness, it is recognized that the threshold of the deformation, i.e. pitting damage formation, was decreased by the tensile stress.

  3. Damage of plasmid DNA by high energy ions

    International Nuclear Information System (INIS)

    Michaelidesova, A.; Pachnerova Brabcova, K.; Davidkova, M.

    2018-01-01

    The aim of the study was to determine the degree of direct DNA damage by high-energy ions, which are one of the components of cosmic rays, and therefore the knowledge of the biological effects of these ions is key to long-term space missions with human crew. The pBR322 plasmid containing 4361 base pairs was used in this study. The aqueous solution of plasmid pBR322 was transferred on ice to Japan to the Heavy Ion Medical Accelerator in Chiba, the Research Center for Charged Particle Therapy. Just before the experiment, the droplets of solution of known concentration were applied to the slides and the water was allowed to evaporate to produce dry DNA samples. Half of the slides were irradiated with 290 MeV/u of carbon ions and a dose rate of 20 Gy/min. The other half of the slides were irradiated with helium nuclei of 150 MeV/hr and a dose rate of 12.6 Gy/min. Both sets of slides were irradiated with doses of 0-1,400 Gy with a 200 Gy step. After irradiation, the samples were re-dissolved in distilled water, frozen and transported on ice to the Czech Republic for processing. Samples were analyzed by agarose gel electrophoresis. The plasmid was evaluated separately to determine the degree of radiation induced lesions and further to incubation with enzymes recognizing basal damage. (authors)

  4. Assessment of Mechanical Properties and Damage of High Performance Concrete Subjected to Magnesium Sulfate Environment

    Directory of Open Access Journals (Sweden)

    Sheng Cang

    2017-01-01

    Full Text Available Sulfate attack is one of the most important problems affecting concrete structures, especially magnesium sulfate attack. This paper presents an investigation on the mechanical properties and damage evolution of high performance concrete (HPC with different contents of fly ash exposure to magnesium sulfate environment. The microstructure, porosity, mass loss, dimensional variation, compressive strength, and splitting tensile strength of HPC were investigated at various erosion times up to 392 days. The ultrasonic pulse velocity (UPV propagation in HPC at different erosion time was determined by using ultrasonic testing technique. A relationship between damage and UPV of HPC was derived according to damage mechanics, and a correlation between the damage of HPC and erosion time was obtained eventually. The results indicated that (1 the average increasing amplitude of porosity for HPCs was 34.01% before and after exposure to magnesium sulfate solution; (2 the damage evolution of HPCs under sulfate attack could be described by an exponential fitting; (3 HPC containing 20% fly ash had the strongest resistance to magnesium sulfate attack.

  5. Threshold guidance update

    International Nuclear Information System (INIS)

    Wickham, L.E.

    1986-01-01

    The Department of Energy (DOE) is developing the concept of threshold quantities for use in determining which waste materials must be handled as radioactive waste and which may be disposed of as nonradioactive waste at its sites. Waste above this concentration level would be managed as radioactive or mixed waste (if hazardous chemicals are present); waste below this level would be handled as sanitary waste. Last years' activities (1984) included the development of a threshold guidance dose, the development of threshold concentrations corresponding to the guidance dose, the development of supporting documentation, review by a technical peer review committee, and review by the DOE community. As a result of the comments, areas have been identified for more extensive analysis, including an alternative basis for selection of the guidance dose and the development of quality assurance guidelines. Development of quality assurance guidelines will provide a reasonable basis for determining that a given waste stream qualifies as a threshold waste stream and can then be the basis for a more extensive cost-benefit analysis. The threshold guidance and supporting documentation will be revised, based on the comments received. The revised documents will be provided to DOE by early November. DOE-HQ has indicated that the revised documents will be available for review by DOE field offices and their contractors

  6. Ascending-ramp biphasic waveform has a lower defibrillation threshold and releases less troponin I than a truncated exponential biphasic waveform.

    Science.gov (United States)

    Huang, Jian; Walcott, Gregory P; Ruse, Richard B; Bohanan, Scott J; Killingsworth, Cheryl R; Ideker, Raymond E

    2012-09-11

    We tested the hypothesis that the shape of the shock waveform affects not only the defibrillation threshold but also the amount of cardiac damage. Defibrillation thresholds were determined for 11 waveforms-3 ascending-ramp waveforms, 3 descending-ramp waveforms, 3 rectilinear first-phase biphasic waveforms, a Gurvich waveform, and a truncated exponential biphasic waveform-in 6 pigs with electrodes in the right ventricular apex and superior vena cava. The ascending, descending, and rectilinear waveforms had 4-, 8-, and 16-millisecond first phases and a 3.5-millisecond rectilinear second phase that was half the voltage of the first phase. The exponential biphasic waveform had a 60% first-phase and a 50% second-phase tilt. In a second study, we attempted to defibrillate after 10 seconds of ventricular fibrillation with a single ≈30-J shock (6 pigs successfully defibrillated with 8-millisecond ascending, 8-millisecond rectilinear, and truncated exponential biphasic waveforms). Troponin I blood levels were determined before and 2 to 10 hours after the shock. The lowest-energy defibrillation threshold was for the 8-milliseconds ascending ramp (14.6±7.3 J [mean±SD]), which was significantly less than for the truncated exponential (19.6±6.3 J). Six hours after shock, troponin I was significantly less for the ascending-ramp waveform (0.80±0.54 ng/mL) than for the truncated exponential (1.92±0.47 ng/mL) or the rectilinear waveform (1.17±0.45 ng/mL). The ascending ramp has a significantly lower defibrillation threshold and at ≈30 J causes 58% less troponin I release than the truncated exponential biphasic shock. Therefore, the shock waveform affects both the defibrillation threshold and the amount of cardiac damage.

  7. Exploring ultrashort high-energy electron-induced damage in human carcinoma cells

    International Nuclear Information System (INIS)

    Rigaud, O.; Fortunel, N.O.; Vaigot, P.; Cadio, E.; Martin, M.T.; Lundh, O.; Faure, J.; Rechatin, C.; Malka, V.; Gauduel, Y.A.

    2010-01-01

    In conventional cancer therapy or fundamental radiobiology research, the accumulated knowledge on the complex responses of healthy or diseased cells to ionizing radiation is generally obtained with low-dose rates. Under these radiation conditions, the time spent for energy deposition is very long compared with the dynamics of early molecular and cellular responses. The use of ultrashort pulsed radiation would offer new perspectives for exploring the 'black box' aspects of long irradiation profiles and favouring the selective control of early damage in living targets. Several attempts were previously performed using nanosecond or picosecond pulsed irradiations on various mammalian cells and radiosensitive mutants at high dose rate. The effects of single or multi-pulsed radiations on cell populations were generally analyzed in the framework of dose survival curves or characterized by 2D imaging of γ-H2AX foci and no increase in cytotoxicity was shown compared with a delivery at a conventional dose rate. Moreover, when multi-shot irradiations were performed, the overall time needed to obtain an integrated dose of several Grays again overlapped with the multi-scale dynamics of bio-molecular damage-repair sequences and cell signalling steps. Ideally, a single-shot irradiation delivering a well-defined energy profile, via a very short temporal window, would permit the approach of a real-time investigation of early radiation induced molecular damage within the confined spaces of cell compartments. Owing to the potential applications of intense ultrashort laser for radiation therapy, the model of the A431 carcinoma cell line was chosen. An ultrafast single-shot irradiation strategy was carried out with these radio-resistant human skin carcinoma cells, using the capacity of an innovating laser-plasma accelerator to generate quasi mono-energetic femtosecond electron bunches in the MeV domain and to deliver a very high dose rate of 10 13 Gy s -1 per pulse. The alkaline comet

  8. High performance Si nanowire field-effect-transistors based on a CMOS inverter with tunable threshold voltage.

    Science.gov (United States)

    Van, Ngoc Huynh; Lee, Jae-Hyun; Sohn, Jung Inn; Cha, Seung Nam; Whang, Dongmok; Kim, Jong Min; Kang, Dae Joon

    2014-05-21

    We successfully fabricated nanowire-based complementary metal-oxide semiconductor (NWCMOS) inverter devices by utilizing n- and p-type Si nanowire field-effect-transistors (NWFETs) via a low-temperature fabrication processing technique. We demonstrate that NWCMOS inverter devices can be operated at less than 1 V, a significantly lower voltage than that of typical thin-film based complementary metal-oxide semiconductor (CMOS) inverter devices. This low-voltage operation was accomplished by controlling the threshold voltage of the n-type Si NWFETs through effective management of the nanowire (NW) doping concentration, while realizing high voltage gain (>10) and ultra-low static power dissipation (≤3 pW) for high-performance digital inverter devices. This result offers a viable means of fabricating high-performance, low-operation voltage, and high-density digital logic circuits using a low-temperature fabrication processing technique suitable for next-generation flexible electronics.

  9. Annealing simulation of cascade damage using MARLOWE-DAIQUIRI codes

    International Nuclear Information System (INIS)

    Muroga, Takeo

    1984-01-01

    The localization effect of the defects generated by the cascade damage on the properties of solids was studied by using a computer code. The code is based on the two-body collision approximation method and the Monte Carlo method. The MARLOWE and DAIQUIRI codes were partly improved to fit the present calculation of the annealing of cascade damage. The purpose of this study is to investigate the behavior of defects under the simulated reactive and irradiation condition. Calculation was made for alpha iron (BCC), and the threshold energy was set at 40 eV. The temperature dependence of annealing and the growth of a cluster were studied. The overlapping effect of cascade was studied. At first, the extreme case of overlapping was studied, then the practical cases were estimated by interpolation. The state of overlapping of cascade corresponded to the irradiation speed. The interaction between cascade and dislocations was studied, and the calculation of the annealing of primary knock-out atoms (PKA) in alpha iron was performed. At low temperature, the effect of dislocations was large, but the growth of vacancy was not seen. At high temperature, the effect of dislocations was small. The evaluation of the simulation of various ion irradiation and the growth efficiency of defects were performed. (Kato, T.)

  10. High-intensity interval training and β-hydroxy-β-methylbutyric free acid improves aerobic power and metabolic thresholds

    OpenAIRE

    Robinson, Edward H; Stout, Jeffrey R; Miramonti, Amelia A; Fukuda, David H; Wang, Ran; Townsend, Jeremy R; Mangine, Gerald T; Fragala, Maren S; Hoffman, Jay R

    2014-01-01

    Background Previous research combining Calcium β-hydroxy-β-methylbutyrate (CaHMB) and running high-intensity interval training (HIIT) have shown positive effects on aerobic performance measures. The purpose of this study was to examine the effect of β-hydroxy-β-methylbutyric free acid (HMBFA) and cycle ergometry HIIT on maximal oxygen consumption (VO2peak), ventilatory threshold (VT), respiratory compensation point (RCP) and time to exhaustion (Tmax) in college-aged men and women. Methods Thi...

  11. Threshold burnup for recrystallization and model for rim porosity in the high burnup UO2 fuel

    International Nuclear Information System (INIS)

    Lee, Byung Ho; Koo, Yang Hyun; Sohn, Dong Seong

    1998-01-01

    Applicability of the threshold burnup for rim formation was investigated as a function of temperature by Rest's model. The threshold burnup was the lowest in the intermediate temperature region, while on the other temperature regions the threshold burnup is higher. The rim porosity was predicted by the van der Waals equation based of the rim pore radius of 0.75μm and the overpressurization model on rim pores. The calculated centerline temperature is in good agreement with the measured temperature. However, more efforts seem to be necessary for the mechanistic model of the rim effect including rim growth with the fuel burnup

  12. Experimental study of EUV mirror radiation damage resistance under long-term free-electron laser exposures below the single-shot damage threshold

    Czech Academy of Sciences Publication Activity Database

    Makhotkin, I.A.; Sobierajski, R.; Chalupský, J.; Tiedtke, K.; de Vries, G.; Stoermer, M.; Scholze, F.; Siewert, F.; van de Kruijs, R.W.E.; Louis, E.; Jacyna, I.; Jurek, M.; Klinger, D.; Nittler, L.; Syryanyy, Y.; Juha, Libor; Hájková, V.; Vozda, V.; Burian, Tomáš; Saksl, K.; Faatz, B.; Keitel, B.; Ploenjes, E.; Schreiber, S.; Toleikis, S.; Loch, R.; Hermann, M.; Strobel, S.; Nienhuys, H.-K.; Gwalt, G.; Mey, T.; Enkisch, H.

    2018-01-01

    Roč. 25, č. 1 (2018), s. 77-84 ISSN 0909-0495. [Workshop on FEL Photon Diagnostics, Instrumentation and Beamline Design (PhotonDiag2017). Stanford, 01.05.2017-03.05.2017] R&D Projects: GA ČR(CZ) GA14-29772S; GA MŠk LG15013 Institutional support: RVO:61389021 Keywords : free-electron laser induced damage * EUV optics * thin films * FELs Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics)

  13. Carbon deposition thresholds on nickel-based solid oxide fuel cell anodes I. Fuel utilization

    Science.gov (United States)

    Kuhn, J.; Kesler, O.

    2015-03-01

    In the first of a two part publication, the effect of fuel utilization (Uf) on carbon deposition rates in solid oxide fuel cell nickel-based anodes was studied. Representative 5-component CH4 reformate compositions (CH4, H2, CO, H2O, & CO2) were selected graphically by plotting the solutions to a system of mass-balance constraint equations. The centroid of the solution space was chosen to represent a typical anode gas mixture for each nominal Uf value. Selected 5-component and 3-component gas mixtures were then delivered to anode-supported cells for 10 h, followed by determination of the resulting deposited carbon mass. The empirical carbon deposition thresholds were affected by atomic carbon (C), hydrogen (H), and oxygen (O) fractions of the delivered gas mixtures and temperature. It was also found that CH4-rich gas mixtures caused irreversible damage, whereas atomically equivalent CO-rich compositions did not. The coking threshold predicted by thermodynamic equilibrium calculations employing graphite for the solid carbon phase agreed well with empirical thresholds at 700 °C (Uf ≈ 32%); however, at 600 °C, poor agreement was observed with the empirical threshold of ∼36%. Finally, cell operating temperatures correlated well with the difference in enthalpy between the supplied anode gas mixtures and their resulting thermodynamic equilibrium gas mixtures.

  14. The assessment of bond strength between heat damaged concrete and high strength fibre reinforced concrete

    Science.gov (United States)

    Zahid, M. Z. A. Mohd; Muhamad, K.

    2017-09-01

    The aim of this study is to assess the bond strength between heat damaged concrete and high strength fibre reinforced concrete (HPFRC). Firstly, this paper presents the various steps taken to prepare the HPFRC with self-compacting property. The minimum targeted slump flow is 600 mm and minimum targeted compressive strength is 80 MPa. The key mix variables considered are such as type of superplasticizer, water cement ratio and silica fume content. Then, the bond strength between the heat damaged concrete with HPFRC was examined. The experimental parameters are heating temperature, surface treatment technique and curing method and the results show that, all experimental parameters are significantly affected the bond strength between heat damaged concrete and HPFRC.

  15. Auditory-nerve single-neuron thresholds to electrical stimulation from scala tympani electrodes.

    Science.gov (United States)

    Parkins, C W; Colombo, J

    1987-12-31

    Single auditory-nerve neuron thresholds were studied in sensory-deafened squirrel monkeys to determine the effects of electrical stimulus shape and frequency on single-neuron thresholds. Frequency was separated into its components, pulse width and pulse rate, which were analyzed separately. Square and sinusoidal pulse shapes were compared. There were no or questionably significant threshold differences in charge per phase between sinusoidal and square pulses of the same pulse width. There was a small (less than 0.5 dB) but significant threshold advantage for 200 microseconds/phase pulses delivered at low pulse rates (156 pps) compared to higher pulse rates (625 pps and 2500 pps). Pulse width was demonstrated to be the prime determinant of single-neuron threshold, resulting in strength-duration curves similar to other mammalian myelinated neurons, but with longer chronaxies. The most efficient electrical stimulus pulse width to use for cochlear implant stimulation was determined to be 100 microseconds/phase. This pulse width delivers the lowest charge/phase at threshold. The single-neuron strength-duration curves were compared to strength-duration curves of a computer model based on the specific anatomy of auditory-nerve neurons. The membrane capacitance and resulting chronaxie of the model can be varied by altering the length of the unmyelinated termination of the neuron, representing the unmyelinated portion of the neuron between the habenula perforata and the hair cell. This unmyelinated segment of the auditory-nerve neuron may be subject to aminoglycoside damage. Simulating a 10 micron unmyelinated termination for this model neuron produces a strength-duration curve that closely fits the single-neuron data obtained from aminoglycoside deafened animals. Both the model and the single-neuron strength-duration curves differ significantly from behavioral threshold data obtained from monkeys and humans with cochlear implants. This discrepancy can best be explained by

  16. Hearing Threshold Level Inworkers of Meybod Tile Factory

    Directory of Open Access Journals (Sweden)

    F Nourani

    2008-04-01

    Full Text Available Introduction: Occupational exposure to excessive noise is commonly encountered in a large number of industries in Iran. This study evaluated the hearing threshold and hearing loss in Meybod tile factory workers. Methods: This cross-sectional study included 371 tile factoryworkers during summer and autumn of 2005. Current noise exposure was estimated using sound level meter .A specially formatted questionnaire was used. Totoscophc examination and conductive air audiometery were used to assess the hearing loss in each subject .Finally data was analyzed using SPSS version 11.5. Results: Occupational noise increased mean of hearing threshold at all frequencies which was significant at 3, 4 KHz in both ears (p<0.05.Prevalence of hearing impairment at high and low frequencies were 39.2% and 46.5%.Prevalence of occupational NIHL was 12.9% and the odds of NIHL significantly increased with noise exposure of more than 10 years. The hearing threshold was worse in both ears of workers with tinnitus. Conclusion: High prevalence of hearing loss and NIHL emphasizes on the necessity of hearing conservational programs in tile factory workers.

  17. Radiation damage in a high Ni weld

    International Nuclear Information System (INIS)

    Brumovsky, M.; Kytka, M.; Kopriva, R.

    2015-01-01

    WWER-1000 RPV weld metals are characterized by a high content of nickel, mostly about 1.7 mass % with content of manganese around 0.8 mass % with a very low copper content - about 0.05 mass %. In such material some late blooming phase effect should be observed during irradiation. Such typical weld material was irradiated in the experimental reactor LVR-15 in N RI Rez at the irradiation temperature 290 C degrees and at five neutron fluences from 1.5 to 9.5 *10 23 m -2 (E>1 MeV). Charpy V-notch impact tests, static fracture toughness tests, tensile and hardness measurement were performed to obtain effect of neutron fluence on radiation hardening as well as embrittlement. Neutron fluence dependences of all these property changes have monotonic character but with a high neutron embrittlement exponent around 0.8. Scanning electron microscope of fracture surfaces showed no or very small portion of intercrystalline fracture. Transmission electron microscopy was performed on specimens from all neutron fluences. Only low density of black-dot damage has been observed. It is assumed that most of defect are dislocation loops. The late blooming phase which may be observed from results of mechanical properties are probably below the resolution of the used JEM-2010, i.e. 1.5 nm. (authors)

  18. High-fidelity Modeling of Local Effects of Damage for Derated Offshore Wind Turbines

    Science.gov (United States)

    Richards, Phillip W.; Griffith, D. Todd; Hodges, Dewey H.

    2014-06-01

    Offshore wind power production is an attractive clean energy option, but the difficulty of access can lead to expensive and rare opportunities for maintenance. As part of the Structural Health and Prognostics Management (SHPM) project at Sandia National Laboratories, smart loads management (controls) are investigated for their potential to increase the fatigue life of offshore wind turbine rotor blades. Derating refers to altering the rotor angular speed and blade pitch to limit power production and loads on the rotor blades. High- fidelity analysis techniques like 3D finite element modeling (FEM) should be used alongside beam models of wind turbine blades to characterize these control strategies in terms of their effect to mitigate fatigue damage and extend life of turbine blades. This study will consider a commonly encountered damage type for wind turbine blades, the trailing edge disbond, and show how FEM can be used to quantify the effect of operations and control strategies designed to extend the fatigue life of damaged blades. The Virtual Crack Closure Technique (VCCT) will be used to post-process the displacement and stress results to provide estimates of damage severity/criticality and provide a means to estimate the fatigue life under a given operations and control strategy.

  19. High-fidelity Modeling of Local Effects of Damage for Derated Offshore Wind Turbines

    International Nuclear Information System (INIS)

    Richards, Phillip W; Griffith, D Todd; Hodges, Dewey H

    2014-01-01

    Offshore wind power production is an attractive clean energy option, but the difficulty of access can lead to expensive and rare opportunities for maintenance. As part of the Structural Health and Prognostics Management (SHPM) project at Sandia National Laboratories, smart loads management (controls) are investigated for their potential to increase the fatigue life of offshore wind turbine rotor blades. Derating refers to altering the rotor angular speed and blade pitch to limit power production and loads on the rotor blades. High- fidelity analysis techniques like 3D finite element modeling (FEM) should be used alongside beam models of wind turbine blades to characterize these control strategies in terms of their effect to mitigate fatigue damage and extend life of turbine blades. This study will consider a commonly encountered damage type for wind turbine blades, the trailing edge disbond, and show how FEM can be used to quantify the effect of operations and control strategies designed to extend the fatigue life of damaged blades. The Virtual Crack Closure Technique (VCCT) will be used to post-process the displacement and stress results to provide estimates of damage severity/criticality and provide a means to estimate the fatigue life under a given operations and control strategy

  20. Prediction of temperature and damage in an irradiated human eye-Utilization of a detailed computer model which includes a vectorial blood stream in the choroid.

    Science.gov (United States)

    Heussner, Nico; Holl, Lukas; Nowak, Timo; Beuth, Thorsten; Spitzer, Martin S; Stork, Wilhelm

    2014-08-01

    The work presented here describes the development and use of a three-dimensional thermo-dynamic model of the human eye for the prediction of temperatures and damage thresholds under irradiation. This model takes into account the blood flow by the implementation of a vectorial blood stream in the choroid and also uses the actual physiological extensions and tissue parameters of the eye. Furthermore it considers evaporation, radiation and convection at the cornea as well as the eye lid. The predicted temperatures were successfully validated against existing eye models in terms of corneal and global thermal behaviour. The model׳s predictions were additionally checked for consistency with in-vivo temperature measurements of the cornea, the irradiated retina and its damage thresholds. These thresholds were calculated from the retinal temperatures using the Arrhenius integral. Hence the model can be used to predict the temperature increase and irradiation hazard within the human eye as long as the absorption values and the Arrhenius coefficients are known and the damage mechanism is in the thermal regime. Copyright © 2014 Elsevier Ltd. All rights reserved.

  1. Calculation of abort thresholds for the Beam Loss Monitoring System of the Large Hadron Collider at CERN

    CERN Document Server

    Nemcic, Martin; Dehning, Bernd

    The Beam Loss Monitoring (BLM) System is one of the most critical machine protection systems for the Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN), Switzerland. Its main purpose is to protect the superconducting magnets from quenches and other equipment from damage by requesting a beam abort when the measured losses exceed any of the predefined threshold levels. The system consist of circa 4000 ionization chambers which are installed around the 27 kilometres ring (LHC). This study aims to choose a technical platform and produce a system that addresses all of the limitations with the current system that is used for the calculation of the LHC BLM abort threshold values. To achieve this, a comparison and benchmarking of the Java and .NET technical platforms is performed in order to establish the most suitable solution. To establish which technical platform is a successful replacement of the current abort threshold calculator, comparable prototype systems in Java and .NET we...

  2. The numerical high cycle fatigue damage model of fillet weld joint under weld-induced residual stresses

    Science.gov (United States)

    Nguyen Van Do, Vuong

    2018-04-01

    In this study, a development of nonlinear continuum damage mechanics (CDM) model for multiaxial high cycle fatigue is proposed in which the cyclic plasticity constitutive model has been incorporated in the finite element (FE) framework. T-joint FE simulation of fillet welding is implemented to characterize sequentially coupled three-dimensional (3-D) of thermo-mechanical FE formulation and simulate the welding residual stresses. The high cycle fatigue damage model is then taken account into the fillet weld joints under the various cyclic fatigue load types to calculate the fatigue life considering the residual stresses. The fatigue crack initiation and the propagation in the present model estimated for the total fatigue is compared with the experimental results. The FE results illustrated that the proposed high cycle fatigue damage model in this study could become a powerful tool to effectively predict the fatigue life of the welds. Parametric studies in this work are also demonstrated that the welding residual stresses cannot be ignored in the computation of the fatigue life of welded structures.

  3. Predicting visual acuity from detection thresholds.

    Science.gov (United States)

    Newacheck, J S; Haegerstrom-Portnoy, G; Adams, A J

    1990-03-01

    Visual performance based exclusively on high luminance and high contrast letter acuity measures often fails to predict individual performance at low contrast and low luminance. Here we measured visual acuity over a wide range of contrasts and luminances (low mesopic to photopic) for 17 young normal observers. Acuity vs. contrast functions appear to fit a single template which can be displaced laterally along the log contrast axis. The magnitude of this lateral displacement for different luminances was well predicted by the contrast threshold difference for a 4 min arc spot. The acuity vs. contrast template, taken from the mean of all 17 subjects, was used in conjunction with individual spot contrast threshold measures to predict an individual's visual acuity over a wide range of luminance and contrast levels. The accuracy of the visual acuity predictions from this simple procedure closely approximates test-retest accuracy for both positive (projected Landolt rings) and negative contrast (Bailey-Lovie charts).

  4. Radiation damage in silicon exposed to high-energy protons

    International Nuclear Information System (INIS)

    Davies, Gordon; Hayama, Shusaku; Murin, Leonid; Krause-Rehberg, Reinhard; Bondarenko, Vladimir; Sengupta, Asmita; Davia, Cinzia; Karpenko, Anna

    2006-01-01

    Photoluminescence, infrared absorption, positron annihilation, and deep-level transient spectroscopy (DLTS) have been used to investigate the radiation damage produced by 24 GeV/c protons in crystalline silicon. The irradiation doses and the concentrations of carbon and oxygen in the samples have been chosen to monitor the mobility of the damage products. Single vacancies (and self-interstitials) are introduced at the rate of ∼1 cm -1 , and divacancies at 0.5 cm -1 . Stable di-interstitials are formed when two self-interstitials are displaced in one damage event, and they are mobile at room temperature. In the initial stages of annealing the evolution of the point defects can be understood mainly in terms of trapping at the impurities. However, the positron signal shows that about two orders of magnitude more vacancies are produced by the protons than are detected in the point defects. Damage clusters exist, and are largely removed by annealing at 700 to 800 K, when there is an associated loss of broad band emission between 850 and 1000 meV. The well-known W center is generated by restructuring within clusters, with a range of activation energies of about 1.3 to 1.6 eV, reflecting the disordered nature of the clusters. Comparison of the formation of the X centers in oxygenated and oxygen-lean samples suggests that the J defect may be interstitial related rather than vacancy related. To a large extent, the damage and annealing behavior may be factorized into point defects (monitored by sharp-line optical spectra and DLTS) and cluster defects (monitored by positron annihilation and broadband luminescence). Taking this view to the limit, the generation rates for the point defects are as predicted by simply taking the damage generated by the Coulomb interaction of the protons and Si nuclei

  5. Evidence for thermally assisted threshold switching behavior in nanoscale phase-change memory cells

    International Nuclear Information System (INIS)

    Le Gallo, Manuel; Athmanathan, Aravinthan; Krebs, Daniel; Sebastian, Abu

    2016-01-01

    In spite of decades of research, the details of electrical transport in phase-change materials are still debated. In particular, the so-called threshold switching phenomenon that allows the current density to increase steeply when a sufficiently high voltage is applied is still not well understood, even though there is wide consensus that threshold switching is solely of electronic origin. However, the high thermal efficiency and fast thermal dynamics associated with nanoscale phase-change memory (PCM) devices motivate us to reassess a thermally assisted threshold switching mechanism, at least in these devices. The time/temperature dependence of the threshold switching voltage and current in doped Ge 2 Sb 2 Te 5 nanoscale PCM cells was measured over 6 decades in time at temperatures ranging from 40 °C to 160 °C. We observe a nearly constant threshold switching power across this wide range of operating conditions. We also measured the transient dynamics associated with threshold switching as a function of the applied voltage. By using a field- and temperature-dependent description of the electrical transport combined with a thermal feedback, quantitative agreement with experimental data of the threshold switching dynamics was obtained using realistic physical parameters

  6. High-sensitivity C-reactive protein predicts target organ damage in Chinese patients with metabolic syndrome

    DEFF Research Database (Denmark)

    Zhao, Zhigang; Nie, Hai; He, Hongbo

    2007-01-01

    with metabolic syndrome. A total of 1082 consecutive patients of Chinese origin were screened for the presence of metabolic syndrome according to the National Cholesterol Education Program's Adult Treatment Panel III. High-sensitivity C-reactive protein and target organ damage, including cardiac hypertrophy......Observational studies established high-sensitivity C-reactive protein as a risk factor for cardiovascular events in the general population. The goal of this study was to determine the relationship between target organ damage and high-sensitivity C-reactive protein in a cohort of Chinese patients......, carotid intima-media thickness, and renal impairment, were investigated. The median (25th and 75th percentiles) of high-sensitivity C-reactive protein in 619 patients with metabolic syndrome was 2.42 mg/L (0.75 and 3.66 mg/L) compared with 1.13 mg/L (0.51 and 2.46 mg/L) among 463 control subjects (P

  7. Determination of ablation threshold for composite resins and amalgam irradiated with femtosecond laser pulses

    International Nuclear Information System (INIS)

    Freitas, A Z; Samad, R E; Zezell, D M; Vieira Jr, N D; Freschi, L R; Gouw-Soares, S C

    2010-01-01

    The use of laser for caries removal and cavity preparation is already a reality in the dental clinic. The objective of the present study was to consider the viability of ultrashort laser pulses for restorative material selective removal, by determining the ablation threshold fluence for composite resins and amalgam irradiated with femtosecond laser pulses. Lasers pulses centered at 830 nm with 50 fs of duration and 1 kHz of repetition rate, with energies in the range of 300 to 770 μJ were used to irradiate the samples. The samples were irradiated using two different geometrical methods for ablation threshold fluence determinations and the volume ablation was measured by optical coherence tomography. The shape of the ablated surfaces were analyzed by optical microscopy and scanning electron microscopy. The determined ablation threshold fluence is 0.35 J/cm 2 for the composite resins Z-100 and Z-350, and 0.25 J/cm 2 for the amalgam. These values are half of the value for enamel in this temporal regime. Thermal damages were not observed in the samples. Using the OCT technique (optical coherence tomography) was possible to determine the ablated volume and the total mass removed

  8. Effects of field high temperature on grain yield and quality of a subtropical type japonica rice—Pon-Lai rice

    Directory of Open Access Journals (Sweden)

    Yi-Chien Wu

    2016-01-01

    Full Text Available Typical japonica type rice is sensitive to high temperature. Pon-Lai rice is a special japonica type with adaptation to the subtropical climate in Taiwan. Facing climate change, rising temperatures would damage the yield and quality of rice production. This research was conducted using Pon-Lai rice in the field of a subtropical climate. We conducted 2 experiments, including a year-round experiment and collection of samples from different districts for building different temperature conditions. We analyzed the correlation between rising temperature and rice yield or quality. In our results, the critical period of temperature effect is 0–15 days after heading (H15. The threshold of high temperature damage in yield and appearance quality was 25–27 °C. Grain weight decreased about 2–6%, while the temperature of H15 was raised 1 °C above the thresholds. Perfect grain ratio and chalky grain ratio decreased and increased, respectively, while the temperature of H15 was raised above the thresholds. However, the high temperature in H15 affected the physicochemical characteristics. In addition, we found positive correlation between grain length to width ratio and perfect grain ratio. Grain length to width ratio could be an index of temperature effects for grain quality. In our study, when the temperature was below 30 °C, a rising temperature of H15 could damage rice yield and appearance quality, and change grain shape. Our results could provide reference for dealing with the warming future in other temperate rice-cultivated countries.

  9. An examination of neuromuscular and metabolic fatigue thresholds

    International Nuclear Information System (INIS)

    Bergstrom, Haley C; Housh, Terry J; Cochrane, Kristen C; Jenkins, Nathaniel D M; Lewis, Robert W Jr; Traylor, Daniel A; Schmidt, Richard J; Johnson, Glen O; Cramer, Joel T; Zuniga, Jorge M

    2013-01-01

    This study examined the relationships among the physical working capacity at the fatigue threshold (PWC FT ), the power outputs associated with the gas exchange threshold (PGET) and the respiratory compensation point (PRCP), and critical power (CP) to identify possible physiological mechanisms underlying the onset of neuromuscular fatigue. Ten participants (mean ± SD age: 20 ± 1 years) performed a maximal incremental cycle ergometer test to determine the PWC FT , PGET, and PRCP. CP was determined from the 3 min all-out test. The PWC FT (197 ± 55 W), PRCP (212 ± 50 W), and CP (208 ± 63 W) were significantly greater than the PGET (168 ± 40 W), but there were no significant differences among the PWC FT , PRCP, and CP. All thresholds were significantly inter-4 (r = 0.794–0.958). The 17% greater estimates for the PWC FT than PGET were likely related to differences in the physiological mechanisms that underlie these fatigue thresholds, while the non-significant difference and high correlation between the PWC FT and the PRCP suggested that hyperkalemia may underlie both thresholds. Furthermore, it is possible that the 5% lower estimate of the PWC FT than CP could more accurately reflect the demarcation of the heavy from severe exercise intensity domains. (paper)

  10. Input-output relation and energy efficiency in the neuron with different spike threshold dynamics.

    Science.gov (United States)

    Yi, Guo-Sheng; Wang, Jiang; Tsang, Kai-Ming; Wei, Xi-Le; Deng, Bin

    2015-01-01

    Neuron encodes and transmits information through generating sequences of output spikes, which is a high energy-consuming process. The spike is initiated when membrane depolarization reaches a threshold voltage. In many neurons, threshold is dynamic and depends on the rate of membrane depolarization (dV/dt) preceding a spike. Identifying the metabolic energy involved in neural coding and their relationship to threshold dynamic is critical to understanding neuronal function and evolution. Here, we use a modified Morris-Lecar model to investigate neuronal input-output property and energy efficiency associated with different spike threshold dynamics. We find that the neurons with dynamic threshold sensitive to dV/dt generate discontinuous frequency-current curve and type II phase response curve (PRC) through Hopf bifurcation, and weak noise could prohibit spiking when bifurcation just occurs. The threshold that is insensitive to dV/dt, instead, results in a continuous frequency-current curve, a type I PRC and a saddle-node on invariant circle bifurcation, and simultaneously weak noise cannot inhibit spiking. It is also shown that the bifurcation, frequency-current curve and PRC type associated with different threshold dynamics arise from the distinct subthreshold interactions of membrane currents. Further, we observe that the energy consumption of the neuron is related to its firing characteristics. The depolarization of spike threshold improves neuronal energy efficiency by reducing the overlap of Na(+) and K(+) currents during an action potential. The high energy efficiency is achieved at more depolarized spike threshold and high stimulus current. These results provide a fundamental biophysical connection that links spike threshold dynamics, input-output relation, energetics and spike initiation, which could contribute to uncover neural encoding mechanism.

  11. Relation of radiation damage of metallic solids to electronic structure. Pt. 5

    International Nuclear Information System (INIS)

    Shalaev, A.M.; Adamenko, A.A.

    1977-01-01

    The problem of relating a damage in metal solids to the parameters of radiation fluxes and the physical nature of a target is considered. Basing upon experimental and theoretical investigations into the processes of interaction of particle fluxes with solids, the following conclusions have been reached. Threshold energy of ion displacement in the crystal lattice of a metal solid is dependent on the energy of a bombarding particle, which is due to ionization and electroexcitation stimulated by energy transfer from a fast particle to a system of collectivized electrons. The rate of metal solid damage by radiation depends on the state of the crystal lattice, in particular on its defectness. Variations of local electron density in the vicinity of a defect are related with changing thermodynamic characteristics of radiation-induced defect formation. A type of atomic bond in a solid affects the rate of radiation damage. The greatest damage occurs in materials with a covalent bond

  12. Intermediate structure and threshold phenomena

    International Nuclear Information System (INIS)

    Hategan, Cornel

    2004-01-01

    The Intermediate Structure, evidenced through microstructures of the neutron strength function, is reflected in open reaction channels as fluctuations in excitation function of nuclear threshold effects. The intermediate state supporting both neutron strength function and nuclear threshold effect is a micro-giant neutron threshold state. (author)

  13. Hidrogenionic potential (pH of the attractant, trap density and control threshold for Ceratitis capitata (DIPTERA: TEPHRITIDAE on Hamlin oranges in São Paulo central region, Brazil

    Directory of Open Access Journals (Sweden)

    Paulo Eduardo Branco Paiva

    2013-06-01

    Full Text Available This study evaluated the effect of initial pH values of 4.5, 6.5 and 8.5 of the attractant (protein bait Milhocina® and borax (sodium borate in the field, on the capture of fruit flies in McPhail traps, using 1, 2, 4 and 8 traps per hectare, in order to estimate control thresholds in a Hamlin orange grove in the central region of the state of São Paulo. The most abundant fruit fly species was Ceratitis capitata, comprising almost 99% of the fruit flies captured, of which 80% were females. The largest captures of C. capitata were found in traps baited with Milhocina® and borax at pH 8.5. Captures per trap for the four densities were similar, indicating that the population can be estimated with one trap per hectare in areas with high populations. It was found positive relationships between captures of C. capitata and the number of Hamlin oranges damaged, 2 and 3 weeks after capture. It was obtained equations that correlate captures and damage levels which can be used to estimate control thresholds. The average loss caused in Hamlin orange fruits by C. capitata was 2.5 tons per hectare or 7.5% of production.

  14. Proceedings of damage and oxidation protection in high temperature composites

    International Nuclear Information System (INIS)

    Haritos, G.K.; Ochoa, O.O.

    1991-01-01

    This book contains proceedings of Damage and Oxidation Protection in High Temperature Composites. Topics covered include: current issues in the development of new materials and structural concepts for the aerospace structures of the future; transportation vehicles of the future; materials and structural concepts; fundamental understanding and quantitative descriptions of the physical processes and mechanisms controlling the behavior of emerging materials and structures; and the critical need for advances in our understanding of how the interaction of service loads and environment influences the lifecycle of emerging structures and materials

  15. Fatigue crack growth thresholds measurements in structural materials

    International Nuclear Information System (INIS)

    Lindstroem, R.; Lidar, P.; Rosborg, B.

    1999-05-01

    Fatigue crack growth thresholds and da/dN-data at low Δk I -values ( 1/2 ) have been determined for type 304 stainless steel, nickel-base weld metal Alloy 182, nickel-base metal Alloy 600, and low-alloy steel in air at ambient temperature and in high-temperature water and steam. The stainless alloys have been tested in water with 0.2 ppm O 2 at 288 deg C and the low-alloy steel in steam at 286 deg C. The fatigue crack growth threshold was defined as the ΔK I -value resulting in a crack growth rate of 10 -7 mm per cycle. The measured fatigue crack growth thresholds (at frequencies from 0.5 to 20 Hz) are quite similar independent of the material and the environment. A relatively inexpensive and time-saving method for measuring fatigue crack growth thresholds, and fatigue crack growth rates at low ΔK I -values, has been used in the tests. The method is a ΔK I -decreasing test with constant K I Max

  16. Nuclear threshold effects and neutron strength function

    International Nuclear Information System (INIS)

    Hategan, Cornel; Comisel, Horia

    2003-01-01

    One proves that a Nuclear Threshold Effect is dependent, via Neutron Strength Function, on Spectroscopy of Ancestral Neutron Threshold State. The magnitude of the Nuclear Threshold Effect is proportional to the Neutron Strength Function. Evidence for relation of Nuclear Threshold Effects to Neutron Strength Functions is obtained from Isotopic Threshold Effect and Deuteron Stripping Threshold Anomaly. The empirical and computational analysis of the Isotopic Threshold Effect and of the Deuteron Stripping Threshold Anomaly demonstrate their close relationship to Neutron Strength Functions. It was established that the Nuclear Threshold Effects depend, in addition to genuine Nuclear Reaction Mechanisms, on Spectroscopy of (Ancestral) Neutron Threshold State. The magnitude of the effect is proportional to the Neutron Strength Function, in their dependence on mass number. This result constitutes also a proof that the origins of these threshold effects are Neutron Single Particle States at zero energy. (author)

  17. Determining cardiac vagal threshold from short term heart rate complexity

    Directory of Open Access Journals (Sweden)

    Hamdan Rami Abou

    2016-09-01

    Full Text Available Evaluating individual aerobic exercise capacity is fundamental in sports and exercise medicine but associated with organizational and instrumental effort. Here, we extract an index related to common performance markers, the aerobic and anaerobic thresholds enabling the estimation of exercise capacity from a conventional sports watch supporting beatwise heart rate tracking. Therefore, cardiac vagal threshold (CVT was determined in 19 male subjects performing an incremental maximum exercise test. CVT varied around the anaerobic threshold AnT with mean deviation of 7.9 ± 17.7 W. A high correspondence of the two thresholds was indicated by Bland-Altman plots with limits of agreement −27.5 W and 43.4 W. Additionally, CVT was strongly correlated AnT (rp = 0.86, p < 0.001 and reproduced this marker well (rc = 0.81. We conclude, that cardiac vagal threshold derived from compression entropy time course can be useful to assess physical fitness in an uncomplicated way.

  18. Ultralow-threshold electrically pumped quantum-dot photonic-crystal nanocavity laser

    Science.gov (United States)

    Ellis, Bryan; Mayer, Marie A.; Shambat, Gary; Sarmiento, Tomas; Harris, James; Haller, Eugene E.; Vučković, Jelena

    2011-05-01

    Efficient, low-threshold and compact semiconductor laser sources are under investigation for many applications in high-speed communications, information processing and optical interconnects. The best edge-emitting and vertical-cavity surface-emitting lasers have thresholds on the order of 100 µA (refs 1,2), but dissipate too much power to be practical for many applications, particularly optical interconnects. Optically pumped photonic-crystal nanocavity lasers represent the state of the art in low-threshold lasers; however, to be practical, techniques to electrically pump these structures must be developed. Here, we demonstrate a quantum-dot photonic-crystal nanocavity laser in gallium arsenide pumped by a lateral p-i-n junction formed by ion implantation. Continuous-wave lasing is observed at temperatures up to 150 K. Thresholds of only 181 nA at 50 K and 287 nA at 150 K are observed--the lowest thresholds ever observed in any type of electrically pumped laser.

  19. Improved assay for thymine base damage in E. coli using high performance liquid chromatography

    International Nuclear Information System (INIS)

    Claycamp, H.G.

    1985-01-01

    A simple high performance liquid chromatography (HPLC) technique has been established for the simultaneous assay of thymine and thymidine radiation damage products. The HPLC procedure uses an isocratic mobile phase of 4% acetonitrile in 0.2 M ammonium dihydrogen phosphate (pH 5.0), a reversed-phase octadecylsilicate (5 micro-spherical packing) 0.45 x 25 cm column, and a variable wavelength UV detector. This procedure affords much better resolution than other published procedures that use 10 micron columns or separate assays for bases and nucleosides. For example, irradiation of 5 x 10 -3 M thymidine solutions have been performed to calibrate the system for base damage assays in E. coli. This yields up to 15 resolvable residues within 20 minutes. Sensitivity of the system (at 2210 nm) for 5,6- dihydrothymine (DHT) is about 10 -10 moles. Preliminary results show that this translates to about 0.4 DHT residues per 10 6 daltons of E. coli DNA. This is comparable to the sensitivities of monoclonal assays to thymine damage products that have recently been reported by others. Since it is feasible that the sensitivity of this system can be improved by 2-3 times, this HPLC technique should provide a simple and rapid means of detecting E. coli base damage release and base damage in nucleoside hydrolysates of DNA

  20. Measurement of 54Fe(n,2n)53Fe cross section near threshold

    International Nuclear Information System (INIS)

    Smither, R.K.; Greenwood, L.R.

    1984-01-01

    A series of experiments were performed at the Princeton Plasma Physics Laboratory to measure the cross section of the 54 Fe(n,2n) 53 Fe reaction near threshold. Measurements were made at 6 different neutron energies and cover the 1 MeV energy range from threshold (13.64 MeV) to 14.64 MeV. The 54 Fe(n,2n) cross section was measured relative to the 27 Al(n,p) 27 Mg cross section to an accuracy of a few percent. These accurate cross-section measurements will be useful in calculating damage caused by 14 MeV D-T plasma neutrons in Fe and calculating the production of the long-lived 53 Mn nuclei that account for much of the buildup of long-lived radioactivity in steel structures and other ferrous materials used in the construction of fusion reactors. They will also play an important part in a new method for measuring the plasma ion temperature of a D-T plasma

  1. Higher defibrillation threshold in methamphetamine cardiomyopathy patients with implantable cardioverter-defibrillator

    Directory of Open Access Journals (Sweden)

    Rakesh Malhotra

    2017-11-01

    Full Text Available Introduction: Identification of patients with an increased risk of high defibrillation thresholds (DFTs is important in planning implantable cardioverter-defibrillator (ICD procedures. Clinical observations have suggested that patients with methamphetamine cardiomyopathy (MACMP have significantly elevated defibrillation thresholds. We hypothesized that MACMP patients would have higher DFT thresholds than controls and would require procedural changes during ICD implantation to accommodate higher thresholds. Methods: We identified consecutive patients with MACMP undergoing ICD implantation at the academic center from 2003 to 2007. We then compared DFTs against age-and sex-matched controls. Results: The MACMP (n = 10 group showed significantly increased DFT thresholds (23.7 ± 6.7 J compared with age and sex-matched controls (14.5 ± 4.6 J, p < 0.005. Additionally, patients with MACMP had evidence of more severe congestive heart failure, with increased B-type natrieutic protein (BNP levels (1173 ± 784 vs 260 ± 349, p = 0.02 and decreased left ventricular ejection fraction (LVEF (17.8 ± 9.4 vs 35.9 ± 15.2, p = 0.02. MACMP patients required high output devices than controls (50% versus 0%, p = 0.03. Differences between groups remained significant despite adjusting for LVEF. Conclusions: Planning for ICD implantation should take into consideration a history of methamphetamine abuse, mandating DFT testing and empiric consideration of high output devices for such patients. Keywords: Methamphetamine cardiomyopathy, Implantable cardioverter-defibrillatior, Defibrillation threshold testing, B-type natriuretic peptide, Ejection fraction

  2. Protective Effects of α-Tocopherol on ABR Threshold Shift in Rabbits Exposed to Noise and Carbon Monoxide.

    Science.gov (United States)

    Motallebi Kashani, Masoud; Mortazavi, Seyyed Bagher; Khavanin, Ali; Allameh, Abdolamir; Mirzaee, Ramezan; Akbari, Mehdi

    2011-01-01

    Noise induced hearin gloss (NIHL) is one of the most important occupational disease world wide. NIHL has been found potentiate by simultaneous carbon monoxide (CO) exposure. Free radicals have been implicated in cochlear damage resulted from the exposure to noise and due to the CO hypoxia. This study examined whether α-tocopherol administration , as a free radical scavenger, causes the attenuation of auditory brainstem response (ABR) threshold shifts resulting from noise exposure and noise plus CO exposure. Forty-two rabbits were divided in to seven groups including control, noise + saline, noise + CO + saline, noise + α-tocopherol, noise + CO + α-tocopherol , CO + α-tocopherol and α-tocopherol alone. ABR was assessed before exposure, 1 hand 14 days post exposure. The administration of 50 mg/Kg of α-tocopherol prior, following and post exposure to noise or noise plus CO recovered permanent ABR threshold shift at 1 and KHz almost to the baseline and provided significant attenuation in permanent ABR threshold shift at 4 and 8 KHz in subject swhich were exposed to noise but it did not block the potentiating of threshold elevation by CO exposure (extra threshold loss by combined exposure) at 4 and 8 KHz. α Tocopherol provides protective effect against the hearing loss resulting from noise exposure and simultaneous exposure to noise plus CO.

  3. Radiation Damage Observations in the ATLAS Pixel Detector Using the High Voltage Delivery System

    CERN Document Server

    Toms, K

    2011-01-01

    We describe the implementation of radiation damage monitoring using leakage current measurement of the silicon pixel sensors provided by the circuits of the ATLAS Pixel Detector high voltage delivery (HVPP4) system. The dependence of the leakage current upon the integrated luminosity for several temperature scenarios is presented. Based on the analysis we have determined the sensitivity specifications for a Current Measurement System. The status of the system and the first measurement of the radiation damage corresponding to 2--4 fb$^{-1}$ of integrated luminosity are presented, as well as the comparison with the theoretical model.

  4. Experimental study of EUV mirror radiation damage resistance under long-term free-electron laser exposures below the single-shot damage threshold

    Czech Academy of Sciences Publication Activity Database

    Makhotkin, I.; Sobierajski, R.; Chalupský, Jaromír; Tiedtke, K.; de Vries, G.; Stoermer, M.; Scholze, F.; Siewert, F.; van de Kruijs, R.W.E.; Milov, I.; Louis, E.; Jacyna, I.; Jurek, M.; Klinger, D.; Nittler, L.; Syryanyy, Y.; Juha, Libor; Hájková, Věra; Vozda, Vojtěch; Burian, Tomáš; Saksl, Karel; Faatz, B.; Keitel, B.; Ploenjes, E.; Schreiber, S.; Toleikis, S.; Loch, R.A.; Hermann, M.; Strobel, S.; Nienhuys, H.-K.; Gwalt, G.; Mey, T.; Enkisch, H.

    2018-01-01

    Roč. 25, č. 1 (2018), s. 77-84 ISSN 1600-5775. [Workshop on FEL Photon Diagnostics, Instrumentation and Beamline Design (PhotonDiag2017). Stanford, 01.05.2017-03.05.2017] R&D Projects: GA MŠk LG15013; GA ČR(CZ) GA17-05167s; GA ČR(CZ) GA14-29772S Institutional support: RVO:68378271 Keywords : free-electron laser induced damage * EUV optics * thin films * FELs Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 3.011, year: 2016

  5. Oxidatively damaged DNA in animals exposed to particles

    DEFF Research Database (Denmark)

    Møller, Peter; Danielsen, Pernille Høgh; Jantzen, Kim

    2013-01-01

    on optimal methods. The majority of studies have used single intracavitary administration or inhalation with dose rates exceeding the pulmonary overload threshold, resulting in cytotoxicity and inflammation. It is unclear whether this is relevant for the much lower human exposure levels. Still...... not be equivocally determined. Roles of cytotoxicity or inflammation for oxidatively induced DNA damage could not be documented or refuted. Studies on exposure to particles in the gastrointestinal tract showed consistently increased levels of 8-oxo-7,8-dihydroguanine in the liver. Collectively, there is evidence...

  6. A New Wavelet Threshold Function and Denoising Application

    Directory of Open Access Journals (Sweden)

    Lu Jing-yi

    2016-01-01

    Full Text Available In order to improve the effects of denoising, this paper introduces the basic principles of wavelet threshold denoising and traditional structures threshold functions. Meanwhile, it proposes wavelet threshold function and fixed threshold formula which are both improved here. First, this paper studies the problems existing in the traditional wavelet threshold functions and introduces the adjustment factors to construct the new threshold function basis on soft threshold function. Then, it studies the fixed threshold and introduces the logarithmic function of layer number of wavelet decomposition to design the new fixed threshold formula. Finally, this paper uses hard threshold, soft threshold, Garrote threshold, and improved threshold function to denoise different signals. And the paper also calculates signal-to-noise (SNR and mean square errors (MSE of the hard threshold functions, soft thresholding functions, Garrote threshold functions, and the improved threshold function after denoising. Theoretical analysis and experimental results showed that the proposed approach could improve soft threshold functions with constant deviation and hard threshold with discontinuous function problems. The proposed approach could improve the different decomposition scales that adopt the same threshold value to deal with the noise problems, also effectively filter the noise in the signals, and improve the SNR and reduce the MSE of output signals.

  7. High-energy-neutron damage in Nb3Sn: changes in critical properties, and damage-energy analysis

    International Nuclear Information System (INIS)

    Snead, C.L. Jr.; Parkin, D.M.; Guinan, M.W.

    1981-01-01

    Filamentary wires of Nb 3 Sn have been irradiated with fission-reactor, 14.8-MeV, and d-Be neutrons and the changes in critical properties measured. The changes observed scale reasonably well with the calculated damage energies for the irradiations. A critical dose for operation of these conductors in fusion-magnet applications is determined to be 0.19 eV/atom damage energy or 0.0019 dpa

  8. Color-discrimination threshold determination using pseudoisochromatic test plates

    Directory of Open Access Journals (Sweden)

    Kaiva eJurasevska

    2014-11-01

    Full Text Available We produced a set of pseudoisochromatic plates for determining individual color-difference thresholds to assess test performance and test properties, and analyzed the results. We report a high test validity and classification ability for the deficiency type and severity level (comparable to that of the fourth edition of the Hardy–Rand–Rittler (HRR test. We discuss changes of the acceptable chromatic shifts from the protan and deutan confusion lines along the CIE xy diagram, and the high correlation of individual color-difference thresholds and the red–green discrimination index. Color vision was tested using an Oculus HMC anomaloscope, a Farnsworth D15, and an HRR test on 273 schoolchildren, and 57 other subjects with previously diagnosed red–green color-vision deficiency.

  9. A large multi-cell threshold gas Cerenkov counter

    International Nuclear Information System (INIS)

    Declais, Y.; Aubert, J.J.; Bassompierre, G.; Payre, P.; Thenard, J.M.; Urban, L.

    1980-08-01

    A large multi-cell threshold gas Cerenkov counter consisting of 78 cells has been built for use in a high energy muon scattering experiment at CERN (European Muon Collaboration). It is used with neon, nitrogen or a mixture of those two gases, allowing the pion threshold to be varied between 6 and 20 GeV/c. The sensitive region of the counter has a length of 4.0 m and entrance and exit windows of 1.1 x 2.4 m 2 and 2.4 x 5.0 m 2 , respectively

  10. Oxidative DNA damage and repair in skeletal muscle of humans exposed to high-altitude hypoxia

    DEFF Research Database (Denmark)

    Lundby, Carsten; Pilegaard, Henriette; van Hall, Gerrit

    2003-01-01

    Recent research suggests that high-altitude hypoxia may serve as a model for prolonged oxidative stress in healthy humans. In this study, we investigated the consequences of prolonged high-altitude hypoxia on the basal level of oxidative damage to nuclear DNA in muscle cells, a major oxygen-consuming...

  11. Comparisons between detection threshold and loudness perception for individual cochlear implant channels

    Science.gov (United States)

    Bierer, Julie Arenberg; Nye, Amberly D

    2014-01-01

    Objective The objective of the present study, performed in cochlear implant listeners, was to examine how the level of current required to detect single-channel electrical pulse trains relates to loudness perception on the same channel. The working hypothesis was that channels with relatively high thresholds, when measured with a focused current pattern, interface poorly to the auditory nerve. For such channels a smaller dynamic range between perceptual threshold and the most comfortable loudness would result, in part, from a greater sensitivity to changes in electrical field spread compared to low-threshold channels. The narrower range of comfortable listening levels may have important implications for speech perception. Design Data were collected from eight, adult cochlear implant listeners implanted with the HiRes90k cochlear implant (Advanced Bionics Corp.). The partial tripolar (pTP) electrode configuration, consisting of one intracochlear active electrode, two flanking electrodes carrying a fraction (σ) of the return current, and an extracochlear ground, was used for stimulation. Single-channel detection thresholds and most comfortable listening levels were acquired using the most focused pTP configuration possible (σ ≥ 0.8) to identify three channels for further testing – those with the highest, median, and lowest thresholds – for each subject. Threshold, equal-loudness contours (at 50% of the monopolar dynamic range), and loudness growth functions were measured for each of these three test channels using various partial tripolar fractions. Results For all test channels, thresholds increased as the electrode configuration became more focused. The rate of increase with the focusing parameter σ was greatest for the high-threshold channel compared to the median- and low-threshold channels. The 50% equal-loudness contours exhibited similar rates of increase in level across test channels and subjects. Additionally, test channels with the highest

  12. Threshold Learning Dynamics in Social Networks

    Science.gov (United States)

    González-Avella, Juan Carlos; Eguíluz, Victor M.; Marsili, Matteo; Vega-Redondo, Fernado; San Miguel, Maxi

    2011-01-01

    Social learning is defined as the ability of a population to aggregate information, a process which must crucially depend on the mechanisms of social interaction. Consumers choosing which product to buy, or voters deciding which option to take with respect to an important issue, typically confront external signals to the information gathered from their contacts. Economic models typically predict that correct social learning occurs in large populations unless some individuals display unbounded influence. We challenge this conclusion by showing that an intuitive threshold process of individual adjustment does not always lead to such social learning. We find, specifically, that three generic regimes exist separated by sharp discontinuous transitions. And only in one of them, where the threshold is within a suitable intermediate range, the population learns the correct information. In the other two, where the threshold is either too high or too low, the system either freezes or enters into persistent flux, respectively. These regimes are generally observed in different social networks (both complex or regular), but limited interaction is found to promote correct learning by enlarging the parameter region where it occurs. PMID:21637714

  13. Experiments in high voltage electron microscopy. Progress report, October 31, 1975--August 1976

    International Nuclear Information System (INIS)

    Mitchell, T.E.; Das, G.; Barnard, R.; Ro, D.

    1976-08-01

    High voltage electron microscopy (HVEM) is being used to study the effects of irradiation on a variety of materials. The vacancies and interstitials produced by displacement can agglomerate to form dislocation loops and voids, annihilate at sinks, or enhance various diffusion processes such as precipitation and recrystallization. Threshold displacement energies, E/sub d/, have been determined for a number of fcc, bcc, and hcp metals. Directions for minimum E/sub d/ have been correlated with the crystal structure and the magnitude of E/sub d/ has been related to the sublimation energy. The effects of electron irradiation on precipitation in Al--Cu, Al--Si and Ni--Al alloys have been investigated. Precipitation respectively of theta', Si and γ' is enhanced and growth rates are being related quantitatively to theories of radiation-enhanced diffusion. Results on radiation damage in oxides (quartz, alumina, and magnesia) have also been obtained. Displacement damage gives rise to dislocation loop nucleation and growth in all cases, including multi-layer loops in Al 2 O 3 . In SiO 2 , ionization damage also occurs, which destroys the crystallinity. Threshold displacement and temperature effects have also been investigated

  14. Exposure to elevated sea-surface temperatures below the bleaching threshold impairs coral recovery and regeneration following injury.

    Science.gov (United States)

    Bonesso, Joshua Louis; Leggat, William; Ainsworth, Tracy Danielle

    2017-01-01

    Elevated sea surface temperatures (SSTs) are linked to an increase in the frequency and severity of bleaching events due to temperatures exceeding corals' upper thermal limits. The temperatures at which a breakdown of the coral- Symbiodinium endosymbiosis (coral bleaching) occurs are referred to as the upper thermal limits for the coral species. This breakdown of the endosymbiosis results in a reduction of corals' nutritional uptake, growth, and tissue integrity. Periods of elevated sea surface temperature, thermal stress and coral bleaching are also linked to increased disease susceptibility and an increased frequency of storms which cause injury and physical damage to corals. Herein we aimed to determine the capacity of corals to regenerate and recover from injuries (removal of apical tips) sustained during periods of elevated sea surface temperatures which result in coral stress responses, but which do not result in coral bleaching (i.e., sub-bleaching thermal stress events). In this study, exposure of the species Acropora aspera to an elevated SST of 32 °C (2 °C below the bleaching threshold, 34 °C) was found to result in reduced fluorescence of green fluorescent protein (GFP), reduced skeletal calcification and a lack of branch regrowth at the site of injury, compared to corals maintained under ambient SST conditions (26 °C). Corals maintained under normal, ambient, sea surface temperatures expressed high GFP fluorescence at the injury site, underwent a rapid regeneration of the coral branch apical tip within 12 days of sustaining injury, and showed extensive regrowth of the coral skeleton. Taken together, our results have demonstrated that periods of sustained increased sea surface temperatures, below the corals' bleaching threshold but above long-term summertime averages, impair coral recovery from damage, regardless of the onset or occurrence of coral bleaching.

  15. Calculating the dim light melatonin onset: the impact of threshold and sampling rate.

    Science.gov (United States)

    Molina, Thomas A; Burgess, Helen J

    2011-10-01

    The dim light melatonin onset (DLMO) is the most reliable circadian phase marker in humans, but the cost of assaying samples is relatively high. Therefore, the authors examined differences between DLMOs calculated from hourly versus half-hourly sampling and differences between DLMOs calculated with two recommended thresholds (a fixed threshold of 3 pg/mL and a variable "3k" threshold equal to the mean plus two standard deviations of the first three low daytime points). The authors calculated these DLMOs from salivary dim light melatonin profiles collected from 122 individuals (64 women) at baseline. DLMOs derived from hourly sampling occurred on average only 6-8 min earlier than the DLMOs derived from half-hourly saliva sampling, and they were highly correlated with each other (r ≥ 0.89, p 30 min from the DLMO derived from half-hourly sampling. The 3 pg/mL threshold produced significantly less variable DLMOs than the 3k threshold. However, the 3k threshold was significantly lower than the 3 pg/mL threshold (p < .001). The DLMOs calculated with the 3k method were significantly earlier (by 22-24 min) than the DLMOs calculated with the 3 pg/mL threshold, regardless of sampling rate. These results suggest that in large research studies and clinical settings, the more affordable and practical option of hourly sampling is adequate for a reasonable estimate of circadian phase. Although the 3 pg/mL fixed threshold is less variable than the 3k threshold, it produces estimates of the DLMO that are further from the initial rise of melatonin.

  16. Hexavalent chrome: threshold concept for carcinogenicity.

    Science.gov (United States)

    Jones, R E

    1990-03-01

    Certain hexavalent chromium (Cr6+) compounds when administered via inhalation at high doses have the potential to induce lung tumors in humans and experimental animals. Trivalent chromium (Cr3+) is an essential human and animal nutrient at levels of 50 to 200 micrograms/day. Recent data have shown that the human body is able to reduce Cr6+ to Cr3+. This reduction occurs in bodily fluids such as gastric juice, epithelial lining fluid of the respiratory tract, blood, and other fluids. Secondary reduction occurs at the cellular level by the cytosol, mitochondria, and microsomes. Thus, at low levels of exposure hexavalent chromium ions are reduced before the 6+ ions can interact with DNA unless the dose is sufficient to overwhelm the body's reduction capacity. This paper summarizes the available data concerning the reducing ability of the body and formulates the steps in the mechanism of cancer induction. These steps include: (1) only certain Cr6+ compounds have the capacity to interact with cellular components; (2) Cr6+ is reduced by body fluids and excess Cr6+ enters the cell (Cr3+ is poorly absorbed across membranes); (3) cellular organelles and the cytoplasm reduce Cr6+ to Cr3+; (4) excess Cr6+ can enter the nucleus; (5) Cr6+ reduction through 5+ and 4+ to 3+ has a potential to interact with the DNA molecule; and (6) if unrepaired, this DNA damage can lead to cancer induction. On the basis of current evidence Cr6+ has a threshold for carcinogenic potential in humans that is greater than the current TLV.

  17. Large Covariance Estimation by Thresholding Principal Orthogonal Complements.

    Science.gov (United States)

    Fan, Jianqing; Liao, Yuan; Mincheva, Martina

    2013-09-01

    This paper deals with the estimation of a high-dimensional covariance with a conditional sparsity structure and fast-diverging eigenvalues. By assuming sparse error covariance matrix in an approximate factor model, we allow for the presence of some cross-sectional correlation even after taking out common but unobservable factors. We introduce the Principal Orthogonal complEment Thresholding (POET) method to explore such an approximate factor structure with sparsity. The POET estimator includes the sample covariance matrix, the factor-based covariance matrix (Fan, Fan, and Lv, 2008), the thresholding estimator (Bickel and Levina, 2008) and the adaptive thresholding estimator (Cai and Liu, 2011) as specific examples. We provide mathematical insights when the factor analysis is approximately the same as the principal component analysis for high-dimensional data. The rates of convergence of the sparse residual covariance matrix and the conditional sparse covariance matrix are studied under various norms. It is shown that the impact of estimating the unknown factors vanishes as the dimensionality increases. The uniform rates of convergence for the unobserved factors and their factor loadings are derived. The asymptotic results are also verified by extensive simulation studies. Finally, a real data application on portfolio allocation is presented.

  18. An experimental test of the linear no-threshold theory of radiation carcinogenesis

    International Nuclear Information System (INIS)

    Cohen, B.L.

    1990-01-01

    There is a substantial body of quantitative information on radiation-induced cancer at high dose, but there are no data at low dose. The usual method for estimating effects of low-level radiation is to assume a linear no-threshold dependence. if this linear no-threshold assumption were not used, essentially all fears about radiation would disappear. Since these fears are costing tens of billions of dollars, it is most important that the linear no-threshold theory be tested at low dose. An opportunity for possibly testing the linear no-threshold concept is now available at low dose due to radon in homes. The purpose of this paper is to attempt to use this data to test the linear no-threshold theory

  19. Cumulative Damage in Strength-Dominated Collisions of Rocky Asteroids: Rubble Piles and Brick Piles

    Science.gov (United States)

    Housen, Kevin

    2009-01-01

    Laboratory impact experiments were performed to investigate the conditions that produce large-scale damage in rock targets. Aluminum cylinders (6.3 mm diameter) impacted basalt cylinders (69 mm diameter) at speeds ranging from 0.7 to 2.0 km/s. Diagnostics included measurements of the largest fragment mass, velocities of the largest remnant and large fragments ejected from the periphery of the target, and X-ray computed tomography imaging to inspect some of the impacted targets for internal damage. Significant damage to the target occurred when the kinetic energy per unit target mass exceeded roughly 1/4 of the energy required for catastrophic shattering (where the target is reduced to one-half its original mass). Scaling laws based on a rate-dependent strength were developed that provide a basis for extrapolating the results to larger strength-dominated collisions. The threshold specific energy for widespread damage was found to scale with event size in the same manner as that for catastrophic shattering. Therefore, the factor of four difference between the two thresholds observed in the lab also applies to larger collisions. The scaling laws showed that for a sequence of collisions that are similar in that they produce the same ratio of largest fragment mass to original target mass, the fragment velocities decrease with increasing event size. As a result, rocky asteroids a couple hundred meters in diameter should retain their large ejecta fragments in a jumbled rubble-pile state. For somewhat larger bodies, the ejection velocities are sufficiently low that large fragments are essentially retained in place, possibly forming ordered "brick-pile" structures.

  20. Radiation damages in superconducting materials

    International Nuclear Information System (INIS)

    Heinz, W.; Seibt, E.

    1978-01-01

    Radiation damage investigations of technical superconductors are reported and discussed with respect to their main properties like critical current jsub(c), transition temperature Tsub(c), upper critical field Bsub(c2), pinning and annealing behaviour. Ordered A15 type alloys (like Nb 3 Sn and V 3 Ga) show significant reductions of all critical parameters above a threshold of about 2x10 21 m -2 with 50 MeV deuterons corresponding to 2x10 22 neutrons/m 2 (Esub(n)>0.1 MeV). Pure metals and disordered B1 type alloys (like Nb or NbTi) show only a small linear decrease in critical parameters (except Bsub(c2) of niobium). Experimental results are compared with theoretical calculations. (author)