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Sample records for radiation defect responsible

  1. Alteration of cellular radiation response as a consequence of defective DNA mismatch repair

    International Nuclear Information System (INIS)

    Weese, Theodore L. de; Bucci, Jennifer M.; Larrier, Nicole A.; Cutler, Richard G.; Riele, Hein te; Nelson, William G.

    1997-01-01

    Purpose/Objective: A number of genes have been implicated in the response of mammalian cells to ionizing radiation. Among these include the genes P53 and P21. Disruption of these genes can alter the predicted cellular behavior following radiation-induced DNA damage. Similarly, cells defective in mismatch repair are known to be tolerant to the lethal effects of alkylating agents. We hypothesized that mammalian cells which are defective in mismatch repair and tolerant to alkylating DNA damage might also be tolerant to the effects of oxidative DNA damage inflicted by ionizing radiation. Materials and Methods: Mouse embryonic stem cells homozygous for disrupted Msh2 alleles (Msh2-/-), heterozygous for a disrupted Msh2 allele (Msh2+/-) or intact cells (Msh2+/+) were exposed to both acute dose (1 Gy/min) and low dose rate (LDR) radiation (0.004 Gy/min) and cell survival was determined by clonogenic assay. Apoptosis induced by LDR was assessed by a terminal transferase assay. Immunoblot analysis was performed in order to evaluate induction of the polypeptides p53 and p21. Another measure of radiation damage tolerance may be accumulation of oxidative DNA species. Therefore, we monitored levels of 8-hydroxyguanine (8-OHG) and 8-hydroxyadenine (8-OHA) by gas chromatography - mass spectrometry with selected ion monitoring (GC-MS/SIM). Results: Cells containing either one or two disrupted Msh2 alleles (Msh2+/-, Msh2-/-) were found to be less sensitive to LDR than cells containing a complete complement of Msh2 alleles (Msh2+/+). Interestingly, all three cell lines had a nearly identical radiosensitivity to acute dose ionizing radiation despite differences in mismatch repair capacity. Apoptosis after LDR also varied between cells, with the Msh2+/+ cells exhibiting higher levels of apoptosis as compared to either the Msh2+/- or Msh2-/- cell lines. In addition, GC-MS/SIM revealed the Msh2+/- and Msh2-/- cell lines to have an approximately ten fold greater accumulation of the

  2. Cell lines derived from a Medaka radiation-sensitive mutant have defects in DNA double-strand break responses

    International Nuclear Information System (INIS)

    Hidaka, Masayuki; Oda, Shoji; Mitani, Hiroshi; Kuwahara, Yoshikazu; Fukumoto, Manabu

    2010-01-01

    It was reported that the radiation-sensitive Medaka mutant 'ric1' has a defect in the repair of DNA double-strand breaks (DSBs) induced by γ-rays during early embryogenesis. To study the cellular response of a ric1 mutant to ionizing radiation (IR), we established the mutant embryonic cell lines RIC1-e9, RIC1-e42, RIC1-e43. Following exposure to γ-irradiation, the DSBs in wild-type cells were repaired within 1 h, while those in RIC1 cells were not rejoined even after 2 h. Cell death was induced in the wild-type cells with cell fragmentation, but only a small proportion of the RIC1 cells underwent cell death, and without cell fragmentation. Although both wild-type and RIC1 cells showed mitotic inhibition immediately after γ-irradiation, cell division was much slower to resume in the wild-type cells (20 h versus 12 h). In both wild-type and RIC1 cells, Ser139 phosphorylated H2AX (γH2AX) foci were formed after γ-irradiation, however, the γH2AX foci disappeared more quickly in the RIC1 cell lines. These results suggest that the instability of γH2AX foci in RIC1 cells cause an aberration of the DNA damage response. As RIC1 cultured cells showed similar defective DNA repair as ric1 embryos and RIC1 cells revealed defective cell death and cell cycle checkpoint, they are useful for investigating DNA damage responses in vitro. (author)

  3. Modelling ionising radiation induced defect generation in bipolar oxides with gated diodes

    International Nuclear Information System (INIS)

    Barnaby, H.J.; Cirba, C.; Schrimpf, R.D.; Kosier, St.; Fouillat, P.; Montagner, X.

    1999-01-01

    Radiation-induced oxide defects that degrade electrical characteristics of bipolar junction transistor (BJTs) can be measured with the use of gated diodes. The buildup of defects and their effect on device radiation response are modeled with computer simulation. (authors)

  4. Impurity-related point defects and gamma-radiation response of massive quartz from the Borborema pegmatite province, in Brazil

    International Nuclear Information System (INIS)

    Miranda, Milena Ribas de; Gonzaga, Raysa Sthefany Gomes; Guzzo, Pedro Luiz; Barreto, Sandra de Brito; Melgarejo, Joan Carles

    2012-01-01

    This work has investigated the changes induced by γ-radiation on impurity-related point defects in massive rose quartz from one deposit located at The Borborema Pegmatite Province (Northeast Region, in Brazil). Samples extracted from rose and colorless (milky) quartz blocks were irradiated with doses of 60 Co, from 0.5 to 96 kGy. Point defects related to Al, Ge, Li and OH were measured by optical, infrared, and electron paramagnetic resonance spectroscopy, prior and after irradiation. The contents of Al, Li, Ge, Fe, Ti and other impurities were measured by inductively-coupled plasma mass spectrometry in quartz fragments exhibiting rose, pale-rose, and milky colorations. It was found that [AlO 4 ] 0 , [AlO 4 /H] 0 and [GeO 4 /Li] 0 were generated by the dissociation of [AlO 4 /Li] 0 and [Li-OH] centers with doses as lower as 0.5 kGy. Above 8 kGy, the electron paramagnetic resonance signal related to [GeO 4 /Li] 0 decreases due to the intense mobility of Li species throughout the quartz lattice, giving rise to E' 1 centers perturbed by Ge. The increase in [AlO 4 ] 0 content with γ doses and the consequent rise in the intensity of smoky color were similar for both rose and colorless quartz. Scanning electron microscopy carried out in insoluble residues obtained after chemical dissolution of each type of quartz revealed the presence of nanometric fibers only in rose specimens. These results suggested that the cause of rose color in massive quartz from Borborema Pegmatite Province is probably related to the presence of dumortierite inclusions. (author)

  5. Creation of radiation defects in KCl crystals

    International Nuclear Information System (INIS)

    Lushchik, A.Ch.; Pung, L.A.; Khaldre, Yu.Yu.; Kolk, Yu.V.

    1981-01-01

    Optical and EPR methods were used to study the creation of anion and cation Frenkel defects in KCl crystals irradiated by X-ray and VUV-radiation. The decay of excitons with the creation of charged Frenkel defects (α and I centres) was detected and investigated at 4.2 K. The decay of excitons as well as the recombination of electrons with self-trapped holes leads to the creation of neutral Frenkel defects (F and H centres). The creation of Cl 3 - and Vsub(F) centres (cation vacancy is a component of these centres) by X-irradiation at 80 K proves the possibility of cation defects creation in KCl [ru

  6. Photometric estimation of defect size in radiation direction

    International Nuclear Information System (INIS)

    Zuev, V.M.

    1993-01-01

    Factors, affecting accuracy of photometric estimation of defect size in radiation transmission direction, are analyzed. Experimentally obtained dependences of contrast of defect image on its size in radiation transmission direction are presented. Practical recommendations on improving accuracy of photometric estimation of defect size in radiation transmission direction, are developed

  7. Influence of radiation induced defect clusters on silicon particle detectors

    Energy Technology Data Exchange (ETDEWEB)

    Junkes, Alexandra

    2011-10-15

    The Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN) addresses some of today's most fundamental questions of particle physics, like the existence of the Higgs boson and supersymmetry. Two large general-purpose experiments (ATLAS, CMS) are installed to detect the products of high energy protonproton and nucleon-nucleon collisions. Silicon detectors are largely employed in the innermost region, the tracking area of the experiments. The proven technology and large scale availability make them the favorite choice. Within the framework of the LHC upgrade to the high-luminosity LHC, the luminosity will be increased to L=10{sup 35} cm{sup -2}s{sup -1}. In particular the pixel sensors in the innermost layers of the silicon trackers will be exposed to an extremely intense radiation field of mainly hadronic particles with fluences of up to {phi}{sub eq}=10{sup 16} cm{sup -2}. The radiation induced bulk damage in silicon sensors will lead to a severe degradation of the performance during their operational time. This work focusses on the improvement of the radiation tolerance of silicon materials (Float Zone, Magnetic Czochralski, epitaxial silicon) based on the evaluation of radiation induced defects in the silicon lattice using the Deep Level Transient Spectroscopy and the Thermally Stimulated Current methods. It reveals the outstanding role of extended defects (clusters) on the degradation of sensor properties after hadron irradiation in contrast to previous works that treated effects as caused by point defects. It has been found that two cluster related defects are responsible for the main generation of leakage current, the E5 defects with a level in the band gap at E{sub C}-0.460 eV and E205a at E{sub C}-0.395 eV where E{sub C} is the energy of the edge of the conduction band. The E5 defect can be assigned to the tri-vacancy (V{sub 3}) defect. Furthermore, isochronal annealing experiments have shown that the V{sub 3} defect

  8. Influence of radiation induced defect clusters on silicon particle detectors

    International Nuclear Information System (INIS)

    Junkes, Alexandra

    2011-10-01

    The Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN) addresses some of today's most fundamental questions of particle physics, like the existence of the Higgs boson and supersymmetry. Two large general-purpose experiments (ATLAS, CMS) are installed to detect the products of high energy protonproton and nucleon-nucleon collisions. Silicon detectors are largely employed in the innermost region, the tracking area of the experiments. The proven technology and large scale availability make them the favorite choice. Within the framework of the LHC upgrade to the high-luminosity LHC, the luminosity will be increased to L=10 35 cm -2 s -1 . In particular the pixel sensors in the innermost layers of the silicon trackers will be exposed to an extremely intense radiation field of mainly hadronic particles with fluences of up to Φ eq =10 16 cm -2 . The radiation induced bulk damage in silicon sensors will lead to a severe degradation of the performance during their operational time. This work focusses on the improvement of the radiation tolerance of silicon materials (Float Zone, Magnetic Czochralski, epitaxial silicon) based on the evaluation of radiation induced defects in the silicon lattice using the Deep Level Transient Spectroscopy and the Thermally Stimulated Current methods. It reveals the outstanding role of extended defects (clusters) on the degradation of sensor properties after hadron irradiation in contrast to previous works that treated effects as caused by point defects. It has been found that two cluster related defects are responsible for the main generation of leakage current, the E5 defects with a level in the band gap at E C -0.460 eV and E205a at E C -0.395 eV where E C is the energy of the edge of the conduction band. The E5 defect can be assigned to the tri-vacancy (V 3 ) defect. Furthermore, isochronal annealing experiments have shown that the V 3 defect exhibits a bistability, as does the leakage current. In oxygen

  9. Defect in radiation signal transduction in ataxia-telangiectasia

    International Nuclear Information System (INIS)

    Lavin, M.F.

    1994-01-01

    Exposure of mammalian cells to ionizing radiation causes a delay in progression through the cycle at several checkpoints. Cells from patients with ataxia-telangiectasia (A-T) ignore these checkpoint controls postirradiation. The tumour suppressor gene product p53 plays a key role at the G 1 /S checkpoint preventing the progression of cells into S phase. The induction of p53 by radiation is reduced and/or delayed in A-T cells, which appears to account for the failure of delay at the G 1 /S checkpoint. We have investigated further this defect in radiation signal transduction in A-T. While the p53 response was defective after radiation, agents that interfered with cell cycle progression such as mimosine, aphidicolin and deprivation of serum led to a normal p53 response in A-T cells. None of these agents caused breaks in DNA, as determined by pulse-field gel electrophoresis, in order to elicit the response. Since this pathway is mediated by protein kinases, we investigated the activity of several of these enzymes in control and A-T cells. Ca +2 -dependent and -independent protein kinase C activities were increased by radiation to the same extent in the two cell types, a variety of serine/threonine protein kinase activities were approximately the same and anti-tyrosine antibodies failed to reveal any differences in protein phosphorylation between A-T and control cells. (author)

  10. Radiation defects in lithium fluoride induced by heavy ions

    Energy Technology Data Exchange (ETDEWEB)

    Trautmann, C.; Schwartz, K.; Steckenreiter, T. [Gesellschaft fuer Schwerionenforschung mbH, Darmstadt (Germany); Costantini, J.M. [CEA Centre d`Etudes de Bruyeres-le-Chatel, 91 (France). DPTA/SPMC; Toulemonde, M. [Centre Interdisciplinaire de Recherches avec les Ions Lourds (CIRIL), 14 - Caen (France)

    1998-07-01

    Single crystals of lithium fluoride were irradiated with various species of heavy ions in the energy regime between 1 and 30 MeV/u. The induced radiation damage was studied with techniques such as optical absorption spectroscopy, small-angle x-ray scattering, chemical etching and profilometry, complemented by annealing experiments. Clear evidence is given for a complex track structure and defect morphology. Single defects such as F-centers are produced in a large halo of several tens of nanometers around the ion trajectory. The defect creation in this zone is similar to that under conventional radiation. For heavy ions above a critical energy loss of 10 keV/nm, new effects occur within a very small core region of 2-4 nm in diameter. The damage in this zone is responsible for chemical etching and for a characteristic anisotropic x-ray scattering. It is assumed that in this core, complex defect aggregates (e.g., cluster of color centers, molecular anions and vacancies) are created. Their formation is only slightly influenced by the irradiation temperature and takes place even at 15 K where diffusion processes of primary defects are frozen. Furthermore, irradiation with heavy ions leads to pronounced swelling effects which can be related to an intermediate zone of around 10 nm around the ion path. (orig.) 40 refs.

  11. An investigation of the role of defect levels on the radiation response of synthetic diamond crystals when used as sensors for the detection of mammography X-rays.

    Science.gov (United States)

    Ade, Nicholas

    2017-09-01

    This study evaluates the role of defects on the performances of synthetic diamond sensors on exposure to mammography X-rays. Through systematic investigations, the main cause of instability of response of examined sensors necessitating pre-irradiation was isolated and ascribed to the presence of ambient light which has the effect of emptying shallow trapping levels. The changes in response between measurements in light and dark conditions varied from 2.8 ± 1.2% to 63.0 ± 0.3%. Sensitivities between 0.4 and 6.7nCGy -1 mm -3 determined for the sensors varied with defect levels. The study indicates that differences in crystal quality due to the presence and influence of defects would cause a discrepancy in the dosimetric performances of various diamond detectors. Once a sensor plate is selected (based on the influence of defect levels) and coupled to the probe housing with the response of the diamond sensor stabilised and appropriately shielded from ambient light, daily priming is not needed. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Direct Observation of Radiation Defects: Experiment and Interpretation

    International Nuclear Information System (INIS)

    Dudarev, S.L.

    2012-01-01

    Electron microscopy is arguably the only available experimental method suitable for the direct visualization of nano-scale defect structures formed under irradiation. Images of dislocation loops and point-defect clusters in crystals are usually produced using diffraction contrast methods. For relatively large defects, a combination of dynamical imaging and image contrast simulations is required for determining the nature of visible radiation defects. At the same time, density functional theory (DFT) models developed over the last decade have provided unique information about the structure of nano-scale defects produced by irradiation, including the defects that are so small that they cannot be observed in an electron microscope, and about the pathways of migration and interaction between radiation defects. DFT models, involving no experimental input parameters and being as quantitatively accurate and informative as the most advanced experimental techniques for the direct observation of defects, have created a new paradigm for the scientific investigation of radiation damage phenomena. In particular, DFT models offer new insight into the origin of temperature-dependent response of materials to irradiation, a problem of pivotal significance for applications. By combining information derived from the first-principles models for radiation defects with information derived from small-scale experimental observations it may be possible to acquire quantitative knowledge about how materials respond to irradiation and, using this knowledge, develop materials suitable for advanced applications in fission and fusion. It now appears possible to pose the question about the development of integrated fusion power plant models, combining neutron transport calculations and microscopic models for microstructural evolution of materials, for example models for ab initio prediction of helium embrittlement. Such models, based on scientific principles and quantitative data, and developed

  13. Influence of radiation defects on tritium release parameters from Li2O

    International Nuclear Information System (INIS)

    Grishmanov, V.; Tanaka, S.; Yoneoka, T.

    1998-01-01

    The study of the influence of radiation defects on tritium release behavior from polycrystalline Li 2 O was performed by simultaneous measurements of the luminescence emission and tritium release. It was found that the radiation defects in Li 2 O introduced by electron irradiation cause the retention of tritium. It is thought that the tritium recovery is affected by the formation of a Li-T bond, which is tolerant of high temperatures. The retardation of tritium decreases with increasing absorbed dose in the dose range from 50 to 140 MGy. The aggregation of radiation defects at high irradiation doses is considered to be responsible for the decrease of the interaction of tritium with radiation defects. The mechanism of the interaction of radiation defects with tritium is discussed. (orig.)

  14. Regularities of radiation defects build up on oxide materials surface

    International Nuclear Information System (INIS)

    Bitenbaev, M.I.; Polyakov, A.I.; Tuseev, T.

    2005-01-01

    Analysis of experimental data by radiation defects study on different oxide elements (silicon, beryllium, aluminium, rare earth elements) irradiated by the photo-, gamma-, neutron-, alpha- radiation, protons and helium ions show, that gas adsorption process on the surface centers and radiation defects build up in metal oxide correlated between themselves. These processes were described by the equivalent kinetic equations for analysis of radiation defects build up in the different metal oxides. It was revealed in the result of the analysis: number of radiation defects are droningly increasing up to limit value with the treatment temperature growth. Constant of radicals death at ionizing radiation increases as well. Amount of surface defects in different oxides defining absorbing activity of these materials looks as: silicon oxide→beryllium oxide→aluminium oxide. So it was found, that most optimal material for absorbing system preparation is silicon oxide by it power intensity and berylium oxide by it adsorption efficiency

  15. On kinetics of paramagnetic radiation defects accumulation in beryllium ceramics

    International Nuclear Information System (INIS)

    Polyakov, A.I.; Ryabikin, Yu.A.; Zashkvara, O.V.; Bitenbaev, M.I.; Petykhov, Yu.V.

    1999-01-01

    Results of paramagnetic radiation defects concentration dependence study in beryllium ceramics from gamma-irradiation dose ( 60 Co) within interval 0-100 Mrem are cited. Obtained dose dependence has form of accumulation curve with saturation typical of for majority of solids (crystals, different polymers, organic substances and others) , in which under irradiation occur not only formation of paramagnetic radiation defects, but its destruction due to recombination and interaction with radiation fields. Analysis of accumulation curve by the method of distant asymptotics allows to determine that observed in gamma-irradiated beryllium ceramics double line of electron spin resonance is forming of two types of paramagnetic radiation defects. It was defined, that sum paramagnetic characteristics of beryllium ceramics within 1-100 Mrad gamma- irradiation dose field change insignificantly and define from first type of paramagnetic radiation defects

  16. Investigation of radiation defects in solids using the EXAFS method

    International Nuclear Information System (INIS)

    Eritsyan, G.N.

    1983-01-01

    The exafs method is proposed as a more informative, universal one to investigate the radiation defects in solids. The successful results as obtained by the author using the synchrotron radiation source are reported for the first time. The measurements were carried out in GaAsP crystals irradiated with 50 MeV electrons

  17. Electron-spin-resonance study of radiation-induced paramagnetic defects in oxides grown on (100) silicon substrates

    International Nuclear Information System (INIS)

    Kim, Y.Y.; Lenahan, P.M.

    1988-01-01

    We have used electron-spin resonance to investigate radiation-induced point defects in Si/SiO 2 structures with (100) silicon substrates. We find that the radiation-induced point defects are quite similar to defects generated in Si/SiO 2 structures grown on (111) silicon substrates. In both cases, an oxygen-deficient silicon center, the E' defect, appears to be responsible for trapped positive charge. In both cases trivalent silicon (P/sub b/ centers) defects are primarily responsible for radiation-induced interface states. In earlier electron-spin-resonance studies of unirradiated (100) substrate capacitors two types of P/sub b/ centers were observed; in oxides prepared in three different ways only one of these centers, the P/sub b/ 0 defect, is generated in large numbers by ionizing radiation

  18. Radiation damage in silicon. Defect analysis and detector properties

    International Nuclear Information System (INIS)

    Hoenniger, F.

    2008-01-01

    Silicon microstrip and pixel detectors are vital sensor-components as particle tracking detectors for present as well as future high-energy physics (HEP) experiments. All experiments at the large Hadron Collider (LHC) are equipped with such detectors. Also for experiments after the upgrade of the LHC (the so-called Super-LHC), with its ten times higher luminosity, or the planned International Linear Collider (ILC) silicon tracking detectors are forseen. Close to the interaction region these detectors have to face harsh radiation fields with intensities above the presently tolerable level. defect engineering of the used material, e. g. oxygen enrichment of high resistivity float zone silicon and growing of thin low resistivityepitaxial layers on Czochralski silicon substrates has been established to improve the radiation hardness of silicon sensors. This thesis focuses mainly on the investigation of radiation induced defects and their differences observed in various kinds of epitaxial silicon material. Comparisons with other materials like float zone or Czochralski silicon are added. Deep Level Transient Spectroscopy (DLTS) and Thermally Stimulated Current (TSC) measurements have been performed after γ-, electron-, proton- and neutron-irradiation. The differenced in the formation of vacancy and interstitial related defects as well as so-called clustered regions were investigated for various types of irradiation. In addition to the well known defects VO i , C i O i , C i C s , VP or V 2 several other defect complexes have been found and investigated. Also the material dependence of the defect introduction rates and the defect annealing behavior has been studied by isothermal and isochronal annealing experiments. Especially the IO 2 defect which is an indicator for the oxygen-dimer content of the material has been investigated in detail. On the basis of radiation induced defects like the bistable donor (BD) defect and a deep acceptor, a model has been introduced to

  19. Radiation damage in silicon. Defect analysis and detector properties

    Energy Technology Data Exchange (ETDEWEB)

    Hoenniger, F.

    2008-01-15

    Silicon microstrip and pixel detectors are vital sensor-components as particle tracking detectors for present as well as future high-energy physics (HEP) experiments. All experiments at the large Hadron Collider (LHC) are equipped with such detectors. Also for experiments after the upgrade of the LHC (the so-called Super-LHC), with its ten times higher luminosity, or the planned International Linear Collider (ILC) silicon tracking detectors are forseen. Close to the interaction region these detectors have to face harsh radiation fields with intensities above the presently tolerable level. defect engineering of the used material, e. g. oxygen enrichment of high resistivity float zone silicon and growing of thin low resistivityepitaxial layers on Czochralski silicon substrates has been established to improve the radiation hardness of silicon sensors. This thesis focuses mainly on the investigation of radiation induced defects and their differences observed in various kinds of epitaxial silicon material. Comparisons with other materials like float zone or Czochralski silicon are added. Deep Level Transient Spectroscopy (DLTS) and Thermally Stimulated Current (TSC) measurements have been performed after {gamma}-, electron-, proton- and neutron-irradiation. The differenced in the formation of vacancy and interstitial related defects as well as so-called clustered regions were investigated for various types of irradiation. In addition to the well known defects VO{sub i}, C{sub i}O{sub i}, C{sub i}C{sub s}, VP or V{sub 2} several other defect complexes have been found and investigated. Also the material dependence of the defect introduction rates and the defect annealing behavior has been studied by isothermal and isochronal annealing experiments. Especially the IO{sub 2} defect which is an indicator for the oxygen-dimer content of the material has been investigated in detail. On the basis of radiation induced defects like the bistable donor (BD) defect and a deep

  20. Radiation response of tumours

    International Nuclear Information System (INIS)

    Twentyman, P.R.

    1988-01-01

    In this chapter knowledge regarding cellular radiation response and the factors which modify it is related to the volume changes and probability of control of irradiated solid tumors. After a discussion of the different cell populations present within solid tumors the cell population kinetics of the neoplastic cells are considered in more detail. The influence of factors related to the three-dimensional geometry of the tumor, particularly hypoxia, are considered, and also the role of the tumor vasculature in radiation response. Repair of sublethal damage (SLD) and potentially lethal damage (PLD) is dealt with and finally the relationship between the various end-points of tumor radioresponsiveness is discussed

  1. Vacancy defects in electron-irradiated ZnO studied by Doppler broadening of annihilation radiation

    Science.gov (United States)

    Chen, Z. Q.; Betsuyaku, K.; Kawasuso, A.

    2008-03-01

    Vacancy defects in ZnO induced by electron irradiation were characterized by the Doppler broadening of annihilation radiation measurements together with the local density approximation calculations. Zinc vacancies (VZn) are responsible for positron trapping in the as-irradiated state. These are annealed out below 200°C . The further annealing at 400°C results in the formation of secondary defects attributed to the complexes composed of zinc vacancies and zinc antisites (VZn-ZnO) .

  2. The formation of radiation defects in monohydrate of lithium sulfate

    International Nuclear Information System (INIS)

    Bahytzhan, A.B.; Zhussupov, A.A.; Kim, L.M.

    2005-01-01

    Full text: The crystals of lithium sulfate are monohydrate. At heating it pass waterless form. This crystals are represented the convenient for study of the crystal water influence on the radiation-induced processes. After irradiation in Li 2 SO 4 · H 2 O it was established the radicals SO 3 - and SO 4 - by the EPR method. The similar radiation induced centres are characteristic for the all sulphates. We established that at after irradiation by X-rays monohydrate sulphate lithium have not the absorption bands in a range 200-800 nm. It complicates study of the given systems. The dominant peak of recombination luminescence (TL) has a maximum in area 100 K. On its high-temperature wing there is 'shoulder' showing of more high-temperature and weak luminescence. At higher temperatures some very weak of TL peaks are observed. The dehydration of the samples does not essential influence for this weak TL. Because we have concentrated the basic attention only on low temperature peaks of recombination luminescence. The TL peak of a luminescence with a maximum at 100 K as a result of thermo treatment has disappeared. Dominant emission became the TL peak with a maximum at 130 K. It is necessary to note, that after dehydration the radiative sensitivity of sulphate lithium sharply has increased. Our rough estimation for this change give value almost two orders. In monohydrate the maximum of TL peak is observed at 130 K radiation by UV. This peak can be divided into two peaks with maximums at 100 K and 130 K. At an irradiation dehydrated samples by ultraviolet light the TL peaks are not observed. The given results allow connecting a luminescence at 100 K with disintegration of defects in the subsystem of crystal water. The products radiolysis of water molecules essential influence on recombination processes in sulphate subsystem. The one hand they suppress them, with another - there is a new channel of disintegration complex anions. It is established that photoconductivity of the

  3. The fractal character of radiation defects aggregation in crystals

    International Nuclear Information System (INIS)

    Akylbekov, A.; Akimbekov, E.; Baktybekov, K.; Vasil'eva, I.

    2002-01-01

    In processes of self-organization, which characterize open systems, the source of ordering is a non-equilibrium. One of the samples of ordering system is radiation-stimulated aggregation of defects in solids. In real work the analysis of criterions of ordering defects structures in solid, which is continuously irradiate at low temperature is presented. The method of cellular automata used in simulation of irradiation. It allowed us to imitate processes of defects formation and recombination. The simulation realized on the surfaces up to 1000x1000 units with initial concentration of defects C n (the power of dose) 0.1-1 %. The number of iterations N (duration of irradiation) mounted to 10 6 cycles. The single centers, which are the sources of formation aggregates, survive in the result of probabilistic nature of formation and recombination genetic pairs of defects and with strictly fixed radius of recombination (the minimum inter anionic distance). For determination the character of same type defects distribution the potential of their interaction depending of defects type and reciprocal distance is calculated. For more detailed study of processes, proceeding in cells with certain sizes of aggregates, the time dependence of potential interaction is constructed. It is shown, that on primary stage the potential is negative, then it increase and approach the saturation in positive area. The minimum of interaction potential corresponds to state of physical chaos in system. Its increasing occurs with formation of same type defects aggregates. Further transition to saturation and 'undulating' character of curves explains by formation and destruction aggregates. The data indicated that - these processes occur simultaneously in cells with different sizes. It allows us to assume that the radiation defects aggregation have a fractal nature

  4. Simulation of radiation-induced defects

    CERN Document Server

    Peltola, Timo

    2015-09-14

    Mainly due to their outstanding performance the position sensitive silicon detectors are widely used in the tracking systems of High Energy Physics experiments such as the ALICE, ATLAS, CMS and LHCb at LHC, the world's largest particle physics accelerator at CERN, Geneva. The foreseen upgrade of the LHC to its high luminosity (HL) phase (HL-LHC scheduled for 2023), will enable the use of maximal physics potential of the facility. After 10 years of operation the expected fluence will expose the tracking systems at HL-LHC to a radiation environment that is beyond the capacity of the present system design. Thus, for the required upgrade of the all-silicon central trackers extensive measurements and simulation studies for silicon sensors of different designs and materials with sufficient radiation tolerance have been initiated within the RD50 Collaboration. Supplementing measurements, simulations are in vital role for e.g. device structure optimization or predicting the electric fields and trapping in the silicon...

  5. Adaptive repair induced by small doses of γ radiation in repair-defective human cells

    International Nuclear Information System (INIS)

    Zasukhina, G.D.; L'vova, G.N.; Vasil'eva, I.M.; Sinel'shchikova, T.A.; Semyachkina, A.N.

    1993-01-01

    Adaptive repair induced by small doses of gamma radiation was studied in repair-defective xeroderma pigmentosum, gout, and homocystinuria cells. The adaptation of cells induced by small doses of radiation was estimated after subsequent exposure to gamma radiation, 4-nitroquinoline-1-oxide, and N-methyl-N-nitro-N-nitrosoguanidine by three methods: (1) by the reduction in DNA breaks; (2) by induction of resistant DNA synthesis; and (3) by increased reactivation of vaccinia virus. The three cell types in response to the three different mutagens revealed differences in the mechanism of cell defense in excision repair, in the adaptive response, and in Weigl reactivation

  6. Evolution of Radiation Induced Defects in SiC: A Multiscale Simulation Approach

    Science.gov (United States)

    Jiang, Hao

    temperatures beyond that. Even though clusters cannot diffuse by thermal vibrations, we found they can migrate at room temperature under the influence of electron radiation. This is the first direct observation of radiation-induced diffusion of defect clusters in bulk materials. We show that the underlying mechanism of this athermal diffusion is elastic collision between incoming electrons and cluster atoms. Our findings suggest that defect clusters may be mobile under certain irradiation conditions, changing current understanding of cluster annealing process in irradiated SiC. With the knowledge of cluster diffusion in SiC demonstrated in this thesis, we now become able to predict cluster evolution in SiC with good agreement with experimental measurements. This ability can enable us to estimate changes in many properties of irradiated SiC relevant for its applications in reactors. Internal interfaces such as grain boundaries can behave as sinks to radiation induced defects. The ability of GBs to absorb, transport, and annihilate radiation-induced defects (sink strength) is important to understand radiation response of polycrystalline materials and to better design interfaces for improved resistance to radiation damage. Nowadays, it is established GBs' sink strength is not a static property but rather evolves with many factors, including radiation environments, grain size, and GB microstructure. In this thesis, I investigated the response of small-angle tilt and twist GBs to point defects fluxes in SiC. First of all, I found the pipe diffusion of interstitials in tilt GBs is slower than bulk diffusion. This is because the increased interatomic distance at dislocation cores raises the migration barrier of interstitial dumbbells. Furthermore, I show that both the annihilation of interstitials at jogs and jog nucleation from clusters are diffusion-controlled and can occur under off-stoichiometric interstitial fluxes. Finally, a dislocation line model is developed to predict the

  7. Hydrogen interaction with radiation defects in p-type silicon

    CERN Document Server

    Feklisova, O V; Yakimov, E B; Weber, J

    2001-01-01

    Hydrogen interaction with radiation defects in p-type silicon has been investigated by deep-level non-stationary spectroscopy. Hydrogen is introduced into the high-energy electron-irradiated crystals under chemical etching in acid solutions at room temperature followed by the reverse-bias annealing at 380 K. It is observed that passivation of the irradiation-induced defects is accompanied by formation of novel electrically active defects with hydrogen-related profiles. Effect of hydrogen on the electrical activity of the C sub s C sub i complexes is shown for the first time. Based on the spatial distribution and passivation kinetics, possible nature of the novel complexes is analyzed. The radii for hydrogen capture by vacancies, K-centers, C sub s C sub i centers and the novel complexes are determined

  8. EPR of radiation defects in lithium-oxyfluoride glass ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Fedotovs, A; Rogulis, U; Sarakovskis, A; Dimitrocenko, L, E-mail: andris-f@navigator.l [Institute of Solid State Physics, University of Latvia, Kengaraga st. 8, LV-1063, Riga (Latvia)

    2010-11-01

    We studied oxyfluoride composites based on lithium silicate glasses with yttrium fluorides and rare-earth dopants. The electron paramagnetic resonance (EPR) has been used to obtain information about radiation induced defects in these materials. Spectra have been measured before and after X-ray irradiation at room temperature and at liquid nitrogen temperature. Fluoride crystallites within samples were created by means of thermal treatment at specific temperatures. EPR spectra of radiation induced defects in oxyfluoride glass ceramics, in which crystallites have not been yet created, show no explicit hfs interaction of fluorine nuclei. However, in glass ceramics, which already contains fluoride crystallites, the hfs characteristic to fluorine nuclei appears in the EPR spectra. EPR hyperfine structure could be explained within a model of an F-type centre in YF{sub 3} crystalline phase.

  9. EPR of radiation defects in lithium-oxyfluoride glass ceramics

    Science.gov (United States)

    Fedotovs, A.; Rogulis, U.; Sarakovskis, A.; Dimitrocenko, L.

    2010-11-01

    We studied oxyfluoride composites based on lithium silicate glasses with yttrium fluorides and rare-earth dopants. The electron paramagnetic resonance (EPR) has been used to obtain information about radiation induced defects in these materials. Spectra have been measured before and after X-ray irradiation at room temperature and at liquid nitrogen temperature. Fluoride crystallites within samples were created by means of thermal treatment at specific temperatures. EPR spectra of radiation induced defects in oxyfluoride glass ceramics, in which crystallites have not been yet created, show no explicit hfs interaction of fluorine nuclei. However, in glass ceramics, which already contains fluoride crystallites, the hfs characteristic to fluorine nuclei appears in the EPR spectra. EPR hyperfine structure could be explained within a model of an F-type centre in YF3 crystalline phase.

  10. Structural defects in monocrystalline silicon: from radiation ones to growing and technological

    International Nuclear Information System (INIS)

    Gerasimenko, N.N.; Pavlyuchenko, M.N.; Dzhamanbalin, K.K.

    2001-01-01

    The systematical review of properties and conditions of radiation structures in monocrystalline silicon including own defects (elementary and complex, disordered fields) as well as defect-impurity formations is presented. The most typical examples of principle effects influence of known defects on radiation-induced processes (phase transformations, diffusion and heteration and others are considered. Experimental facts and models of silicon radiation amorphization have been analyzed in comparison of state of the radiation amorphization radiation problem of metals and alloys. The up-to-date status of the problem of the radiation defects physics are discussed, including end-of-range -, n+-, rod-like- defects. The phenomenon self-organization in crystals with defects has been considered. The examples of directed using radiation defects merged in independent trend - defects engineering - are given

  11. Positron Annihilation Study of Radiation Defects in Zinc Oxide

    OpenAIRE

    Tomiyama, Noriyuki; Takenaka, Minoru; Kuramoto, Eiichi

    1992-01-01

    Positron annihilation studies have been carried out to clarify the radiation induced defects in ZnO single crystals. Vapor-grown ZnO crystals were irradiated at 77 K with 28 MeV electrons. Before irradiation as-grown specimens showed the mean positron lifetime in the range of 160-195 ps. Electron irradiation increased the mean positron lifetime up to 205-210 ps.This long-lifetime disappeared until 473 K during successive isochronal annealing steps. The radiation-induced coloration was anneale...

  12. Features of accumulation of radiation defects in metal with impurity

    International Nuclear Information System (INIS)

    Iskakov, B.M.

    2002-01-01

    The processes of accumulation and annealing of radiation defects in solids are being studied for the last fifty years quite intensively. Many regularities of these processes are fixed, but there are more unsolved problems. The computer simulation is one of the effective tools in finding the mechanisms of accumulation and annealing of radiation defects in solids. The numerical solution of the system of the differential equations by means of computers describing kinetics of accumulation of radiation point defects in metals with impurity, has allowed to receive a number of new outcomes. It was revealed, that a determinative factor influential in concentration of point defects (vacancies and interstitial atoms), formed during an exposure of metal, is the correlation a speed of Frenkel twins recombination, the capture of defects by impurity atoms and absorption of defects by other drainage, for example by dislocations. If the speed of capture of interstitial atoms by impurity atoms for two - three order is lower than the recombination speed of Frenkel twins and on two - three order exceeds the speed of capture of vacancies by impurity atoms, the concentration of interstitial atoms within the first seconds of an exposure passes through a maximum, then quickly decreases in some times and after that starts slowly to grow. The change of concentration of interstitial atoms in an initial period of an exposure does not influence on the change of a vacancy concentration. Within the whole period of an exposure, during which the concentration of interstitial atoms achieves a maximum and then is reduced, the vacancy concentration is steadily enlarged. However subsequent sluggish rise of concentration of interstitial atoms during an exposure is followed by the decrease of the vacancy concentration. The most remarkable feature of the kinetics of accumulation of interstitial atoms in metals with impurity is the presence of two extremum on curve dependence of interstitial atoms on a

  13. Radiation induced defect flux behaviors at zirconium based component

    International Nuclear Information System (INIS)

    Choi, Sang Il; Kim, Ji Hyun; Kwon, Jun Hyun; Lee, Gyeong Geun

    2013-01-01

    In commercial reactor core, structure materials are located in high temperature and high pressure environment. Therefore, main concern of structure materials is corrosion and mechanical properties change than radiation effects on materials. However, radiation effects on materials become more important phenomena because research reactor condition is different from commercial reactor. The temperature is lower than 100 .deg. C and radiation dose is much higher than that of commercial reactor. Among the radiation effect on zirconium based metal, radiation induced growth (RIG), known as volume conservative distortion, is one of the most important phenomena. Recently, theoretical RIG modeling based on radiation damage theory (RDT) and balance equation are developed. However, these growth modeling have limited framework of single crystal and high temperature. To model theoretical RIG in research reactor, qualitative mechanism must be set up. Therefore, this paper intent is establishing defect flux mechanism of zirconium base metal in research reactor for RIG modeling. After than theoretical RIG work will be expanded to research reactor condition

  14. Molecular dynamics simulation on the formation and annihilation behaviors of radiation defects in Li2O

    International Nuclear Information System (INIS)

    Takuji Oda; Satoru Tanaka; Yasuhisa Oya

    2006-01-01

    The influence of radiation defects is one of the main factors that determine tritium release behavior from blanket breeding materials in fusion reactors. Classical molecular dynamics simulation (MD) is a powerful technique to investigate the radiation damage processes, because it can provide atomic-scale information on the defects. In this study, we conducted radiation simulation for Li 2 O using MD and analyzed formation and annihilation behaviors of radiation defects, as a fundamental research for radiation response of Li-containing oxides. Buckingham type two-body potential model was used. In order to remove the unphysical impulsive force at short inter-ionic distances in Buckingham model, each potential function was connected to that of the ZBL potential models at around 0.8 A. NEV ensemble was employed with the initial simulation temperature of 0 K. 10 x 10 x 10 supercell consisting of 4000 Li 2 O was used as a unit cell under 3D periodic boundary conditions. Radiation simulation was initiated by introducing an energy of a certain direction to an ion, as a displacement energy. The lowest displacement energy by which a defect was created and survived beyond 5 ps was regarded as the threshold energy. 42 and 21 displacement directions were surveyed for Li and O, respectively, based on the symmetry of the Li 2 O crystal. In both Li and O defect formations, [100] displacement shows significantly lower threshold energy than [111] displacement. Li defects were easily created than O defects almost in all directions. In fact, the average threshold energy except [111] displacement, which possesses extremely high threshold energy, was 21 eV for Li and 49 eV for O. In some cases, no defect could survive beyond 5 ps even by higher displacement energies than the threshold energy, due to the self-annealing effect. The self-annealing completed basically within 1 ps after introduction of displacement energy. At around this time, velocity distribution of all ions in the system

  15. Interaction of alpha radiation with thermally-induced defects in silicon

    International Nuclear Information System (INIS)

    Ali, Akbar; Majid, Abdul

    2008-01-01

    The interaction of radiation-induced defects created by energetic alpha particles and thermally-induced defects in silicon has been studied using a Deep Level Transient Spectroscopy (DLTS) technique. Two thermally-induced defects at energy positions E c -0.48 eV and E c -0.25 eV and three radiation-induced defects E2, E3 and E5 have been observed. The concentration of both of the thermally-induced defects has been observed to increase on irradiation. It has been noted that production rates of the radiation-induced defects are suppressed in the presence of thermally-induced defects. A significant difference in annealing characteristics of thermally-induced defects in the presence of radiation-induced defects has been observed compared to the characteristics measured in pre-irradiated samples

  16. Polymers under ionizing radiation: the study of energy transfers to radiation induced defects

    International Nuclear Information System (INIS)

    Ventura, A.

    2013-01-01

    Radiation-induced defects created in polymers submitted to ionizing radiations, under inert atmosphere, present the same trend as a function of the dose. When the absorbed dose increases, their concentrations increase then level off. This behavior can be assigned to energy transfers from the polymer to the previously created macromolecular defects; the latter acting as energy sinks. During this thesis, we aimed to specify the influence of a given defect, namely the trans-vinylene, in the behavior of polyethylene under ionizing radiations. For this purpose, we proposed a new methodology based on the specific insertion, at various concentrations, of trans-vinylene groups in the polyethylene backbone through chemical synthesis. This enables to get rid of the variety of created defects on one hand and on the simultaneity of their creation on the other hand. Modified polyethylenes, containing solely trans-vinylene as odd groups, were irradiated under inert atmosphere, using either low LET beams (gamma, beta) or high LET beams (swift heavy ions). During irradiations, both macromolecular defects and H 2 emission were quantified. According to experimental results, among all defects, the influence of the trans-vinylene on the behavior of polyethylene is predominant. (author) [fr

  17. Laser radiation effect on radiation-induced defects in heavy ion tracks in dielectrics

    International Nuclear Information System (INIS)

    Egorov, A.N.; Zhiryakov, B.M.; Kushin, V.V.; Lyapidevskij, V.K.; Khokhlov, N.B.

    1988-01-01

    Possibility of laser radiation resonance effect on radiation-induced defects in heavy ion tracks in dielectric materials is investigated. Absorption spectra in infrared, visible and ultraviolet ranges for cellulose nitrate samples irradiated by 6 MeV/nucleon 58 Ni ions and reactor gamma radiation are measured. Absorption spectra for irradiated and reference samples are presented. Two absorption bands λ 1 =0.33 μm (E 1 =3.9 eV) and λ 2 =0.72 μm (E 2 =1.7 eV) are detected. Etching rate decrease in a track under laser radiation effect is noticed. 3 refs.; 1 fig

  18. Radiation induced segregation and point defects in binary copper alloys

    International Nuclear Information System (INIS)

    Monteiro, W.A.

    1984-01-01

    Considerable progress, both theoretical and experimental, has been made in establishing and understanding the influence of factors such as temperature, time, displacement rate dependence and the effect of initial solute misfit on radiation induced solute diffusion and segregation. During irradiation, the composition of the alloy changes locally, due to defect flux driven non-equilibrium segregation near sinks such as voids, external surfaces and grain boundaries. This change in composition could influence properties and phenomena such as ductility, corrosion resistance, stress corrosion cracking, sputtering and blistering of materials used in thermo-nuclear reactors. In this work, the effect of 1 MeV electron irradiation on the initiation and development of segregation and defect diffusion in binary copper alloys has been studied in situ, with the aid of a high voltage electron microscope. The binary copper alloys had Be, Pt and Sn as alloying elements which had atomic radii less than, similar and greater than that of copper, respectively. It has been observed that in a wide irradiation temperature range, stabilization and growth of dislocation loops took place in Cu-Sn and Cu-Pt alloys. Whereas in the Cu-Be alloy, radiation induced precipitates formed and transformed to the stable γ phase. (Author) [pt

  19. Metastable defect response in CZTSSe from admittance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Koeper, Mark J.; Hages, Charles J.; Li, Jian V.; Levi, Dean; Agrawal, Rakesh

    2017-10-02

    Admittance spectroscopy is a useful tool used to study defects in semiconductor materials. However, metastable defect responses in non-ideal semiconductors can greatly impact the measurement and therefore the interpretation of results. Here, admittance spectroscopy was performed on Cu2ZnSn(S,Se)4 where metastable defect response is illustrated due to the trapping of injected carriers into a deep defect state. To investigate the metastable response, admittance measurements were performed under electrically and optically relaxed conditions in comparison to a device following a low level carrier-injection pretreatment. The relaxed measurement demonstrates a single capacitance signature while two capacitance signatures are observed for the device measured following carrier-injection. The deeper level signature, typically reported for kesterites, is activated by charge trapping following carrier injection. Both signatures are attributed to bulk level defects. The significant metastable response observed on kesterites due to charge trapping obscures accurate interpretation of defect levels from admittance spectroscopy and indicates that great care must be taken when performing and interpreting this measurement on non-ideal devices.

  20. Electric field deformation in diamond sensors induced by radiation defects

    Energy Technology Data Exchange (ETDEWEB)

    Kassel, Florian; Boer, Wim de; Boegelspacher, Felix; Dierlamm, Alexander; Mueller, Thomas; Steck, Pia [Institut fuer Experimentelle Kernphysik (IEKP), Karlsruher Institut fuer Technologie (KIT) (Germany); Dabrowski, Anne; Guthoff, Moritz [CERN (Switzerland)

    2016-07-01

    The BCML system is a beam monitoring device in the CMS experiment at the LHC. As detectors 32 poly-crystalline CVD diamond sensors are positioned in a ring around the beam pipe at a distance of ±1.8 m and ±14.4 m from the interaction point. The radiation hardness of the diamond sensors in terms of measured signal during operation was significantly lower than expected from laboratory measurements. At high particle rates, such as those occurring during the operation of the LHC, a significant fraction of the defects act as traps for charge carriers. This space charge modifies the electrical field in the sensor bulk leading to a reduction of the charge collection efficiency (CCE). A diamond irradiation campaign was started to investigate the rate dependent electrical field deformation with respect to the radiation damage. Besides the electrical field measurements via the Transient Current Technique, the CCE was measured. The experimental results were used to create an effective trap model that takes the radiation damage into account. Using this trap model the rate dependent electrical field deformation and the CCE were simulated with the software ''SILVACO TCAD''. This talk compares the experimental measurement results with the simulations.

  1. Radiation induced defects and thermoluminescence mechanism in aluminum oxide

    Energy Technology Data Exchange (ETDEWEB)

    Atobe, K.; Kobayashi, T.; Awata, T. [Naruto Univ. of Education, Tokushima (Japan); Okada, M. [Kyoto Univ., Kumatori, Osaka (Japan). Research Reactor Inst; Nakagawa, M. [Kagawa Univ., Faculty of Education, Takamatsu, Kagawa (Japan)

    2001-01-01

    The thermoluminescence of the irradiated aluminum oxides were measured to study the radiation induced defects and their behaviors. Neutron and {gamma}-ray irradiation were performed for a shingle crystal of the high purity aluminum oxide. The thermoluminescence glow curve and its activation energy were measured. The spectroscopy measurement on the thermoluminescence and the absorption are also carried out. The observed 430 and 340 nm peaks are discussed relating to the F{sup +} and F centers, respectively. Activation state of the F center transits to 3P state through 1P state by emitting phonons. Trapped electron on 3P state emits phonon of 2.9 eV (430 nm) during transition to the ground state. The above reaction can be written by the equation. F{sup +} + e {yields} (F){sup *} {yields} F + h{nu}(2.9 eV, 470 nm). (Katsuta, H.)

  2. Radiation effects and defects in lithium borate crystals

    Science.gov (United States)

    Ogorodnikov, Igor N.; Poryvay, Nikita E.; Pustovarov, Vladimir A.

    2010-11-01

    The paper presents the results of a study of the formation and decay of lattice defects in wide band-gap optical crystals of LiB3O5 (LBO), Li2B4O7 (LTB) and Li6Gd(BO3)3 (LGBO) with a sublattice of mobile lithium cations. By means of thermoluminescence techniques, and luminescent and absorption optical spectroscopy with a nanosecond time resolution under excitation with an electron beam, it was revealed that the optical absorption in these crystals in the visible and ultraviolet spectral ranges is produced by optical hole-transitions from the local defect level to the valence band states. The valence band density of the states determines mainly the optical absorption spectral profile, and the relaxation kinetics is rated by the interdefect non-radiative tunnel recombination between the trapped-hole center and the Li0 trapped-electron centers. At 290 K, the Li0 centers are subject to thermally stimulated migration. Based on experimental results, the overall picture of thermally stimulated recombination processes with the participation of shallow traps was established for these crystals.

  3. Radiation effects and defects in lithium borate crystals

    Energy Technology Data Exchange (ETDEWEB)

    Ogorodnikov, Igor N; Poryvay, Nikita E; Pustovarov, Vladimir A, E-mail: igor.ogorodnikov@bk.ru [Ural Federal University, Mira Street, 19, Ekaterinburg 620002 (Russian Federation)

    2010-11-15

    The paper presents the results of a study of the formation and decay of lattice defects in wide band-gap optical crystals of LiB{sub 3}O{sub 5} (LBO), Li{sub 2}B{sub 4}O{sub 7} (LTB) and Li{sub 6}Gd(BO{sub 3}){sub 3} (LGBO) with a sublattice of mobile lithium cations. By means of thermoluminescence techniques, and luminescent and absorption optical spectroscopy with a nanosecond time resolution under excitation with an electron beam, it was revealed that the optical absorption in these crystals in the visible and ultraviolet spectral ranges is produced by optical hole-transitions from the local defect level to the valence band states. The valence band density of the states determines mainly the optical absorption spectral profile, and the relaxation kinetics is rated by the interdefect non-radiative tunnel recombination between the trapped-hole center and the Li{sup 0} trapped-electron centers. At 290 K, the Li{sup 0} centers are subject to thermally stimulated migration. Based on experimental results, the overall picture of thermally stimulated recombination processes with the participation of shallow traps was established for these crystals.

  4. Study of defects in radiation tolerant semiconductor SiC

    Energy Technology Data Exchange (ETDEWEB)

    Itoh, Hisayoshi; Kawasuso, Atsuo; Ohshima, Takeshi; Yoshikawa, Masahito; Nashiyama, Isamu [Japan Atomic Energy Research Inst., Takasaki, Gunma (Japan). Takasaki Radiation Chemistry Research Establishment; Okumura, Hajime; Yoshida, Sadafumi

    1997-03-01

    Electron spin resonance (ESR) was used to study defects introduced in n-type 6H-SiC by 3 MeV electron irradiation. Two ESR signals labeled A and B related to radiation induced defects were observed. An ESR signal B can be explained by a fine interaction with an effective spin S=1. The g and D tensors of the signal B were found to be axially symmetric along the c-axis. The principal values of the g were obtained to be g parallel = 2.003 and g perpendicular = 2.008, and the absolute value of the D was 3.96x10{sup -2} cm{sup -1} at 100 K for this signal. It was also found that the value |D| decreased with increasing temperature. Isochronal annealing showed that the A and B centers have annealing stages of {approx_equal}200degC and {approx_equal}800degC, respectively. Tentative structural models are discussed for these ESR centers. (author)

  5. Luminescence Properties of Surface Radiation-Induced Defects in Lithium Fluoride

    Science.gov (United States)

    Voitovich, A. P.; Kalinov, V. S.; Martynovich, E. F.; Novikov, A. N.; Runets, L. P.; Stupak, A. P.

    2013-11-01

    Luminescence and luminescence excitation spectra are recorded for surface radiation-induced defects in lithium fluoride at temperatures of 77 and 293 K. The presence of three bands with relatively small intensity differences is a distinctive feature of the excitation spectrum. These bands are found to belong to the same type of defects. The positions of the peaks and the widths of the absorption and luminescence bands for these defects are determined. The luminescence decay time is measured. All the measured characteristics of these surface defects differ from those of previously known defects induced by radiation in the bulk of the crystals. It is found that the luminescence of surface defects in an ensemble of nanocrystals with different orientations is not polarized. The number of anion vacancies in the surface defects is estimated using the polarization measurements. It is shown that radiative scattering distorts the intensity ratios of the luminescence excitation bands located in different spectral regions.

  6. Low-temperature annealing of radiation defects in electron-irradiated gallium phosphide

    International Nuclear Information System (INIS)

    Kolb, A.A.; Megela, I.G.; Buturlakin, A.P.; Goyer, D.B.

    1990-01-01

    The isochronal annealing of radiation defects in high-energy electron irradiated n-GaP monocrystals within the 77 to 300 K range has been investigated by optical and electrical techniques. The changes in conductance and charge carrier mobility as functions of annealing temperature as well as the variation of optical absorption spectra of GaP under irradiation and annealing provide evidence that most of radiation defects are likely secondary complexes of defects

  7. Diffusion and aggregation of subsurface radiation defects in lithium fluoride nanocrystals

    Science.gov (United States)

    Voitovich, A. P.; Kalinov, V. S.; Martynovich, E. F.; Stupak, A. P.; Runets, L. P.

    2015-09-01

    Lithium fluoride nanocrystals were irradiated by gamma rays at a temperature below the temperature corresponding to the mobility of anion vacancies. The kinetics of the aggregation of radiation-induced defects in subsurface layers of nanocrystals during annealing after irradiation was elucidated. The processes that could be used to determine the activation energy of the diffusion of anion vacancies were revealed. The value of this energy in subsurface layers was obtained. For subsurface layers, the concentrations ratio of vacancies and defects consisting of one vacancy and two electrons was found. The factors responsible for the differences in the values of the activation energies and concentration ratios in subsurface layers and in the bulk of the crystals were discussed.

  8. Radiation-induced segregation: A microchemical gauge to quantify fundamental defect parameters

    International Nuclear Information System (INIS)

    Simonen, E.P.; Bruemmer, S.M.

    1994-12-01

    Defect Kinetic are evaluated for austenitic stainless alloys by comparing model predictions to measured responses for radiation-induced grain boundary segregation. Heavy-ions, neutrons and proton irradiations having substantial statistical bases are examined. The combined modeling and measurement approach is shown to be useful for quantifying fundamental defect parameters. The mechanism evaluation indicates vacancy, migration energies of 1.15 eV or less and a vacancy formation energy at grain boundaries of 1.5 eV. Damage efficiencies of about 0.03 were established for heavy-ions and for light-water reactor neutrons. Inferred proton damage efficiencies were about 0.15. Segregation measured in an advanced gas-cooled reactor component was much greater than expected using the above parameters

  9. The investigation of radiation induced defects in MgO

    International Nuclear Information System (INIS)

    Puetz, M.

    1990-05-01

    In this paper Frenkel defects were induced in MgO by 3 MeV electrons at low temperature. These defects were investigated by measurements of the optical absorption, by investigating the lattice parameters and Huang diffuse scattering. (WL)

  10. Influence of oxygen impurity atoms on defect clusters and radiation hardening in neutron-irradiated vanadium

    International Nuclear Information System (INIS)

    Bajaj, R.; Wechsler, M.S.

    1975-01-01

    Single crystal TEM samples and polycrystalline tensile samples of vanadium containing 60-640 wt ppm oxygen were irradiated at about 100 0 C to about 1.3 x 10 19 neutrons/cm 2 (E greater than 1 MeV) and post-irradiation annealed up to 800 0 C. The defect cluster density increased and the average size decreased with increasing oxygen concentration. Higher oxygen concentrations caused the radiation hardening and radiation-anneal hardening to increase. The observations are consistent with the nucleation of defect clusters by small oxygen or oxygen-point defect complexes and the trapping of oxygen at defect clusters upon post-irradiation annealing

  11. Impurity-related point defects and gamma-radiation response of massive quartz from the Borborema pegmatite province, in Brazil; Estudo da suscetibilidade ao escurecimento por radiacao gama de quartzo roseo-leitoso da provincia pegmatitica da Borborema

    Energy Technology Data Exchange (ETDEWEB)

    Miranda, Milena Ribas de [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Programa de Pos-Graduacao em Engenharia Mineral; Gonzaga, Raysa Sthefany Gomes; Guzzo, Pedro Luiz [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Dept. de Engenharia de Minas; Barreto, Sandra de Brito [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Dept. de Geologia; Melgarejo, Joan Carles, E-mail: milaribas@hotmail.com, E-mail: raysagonzaga@hotmail.com, E-mail: pguzzo@ufpe.br, E-mail: sandrabrito@smart.net.br, E-mail: joan.carles.melgarejo.draper@ub.edu [Universidade de Barcelona, Barcelona (Spain). Dept. de Cristalografia, Mineralogia e Depositos Minerais

    2012-06-15

    This work has investigated the changes induced by {gamma}-radiation on impurity-related point defects in massive rose quartz from one deposit located at The Borborema Pegmatite Province (Northeast Region, in Brazil). Samples extracted from rose and colorless (milky) quartz blocks were irradiated with doses of {sup 60}Co, from 0.5 to 96 kGy. Point defects related to Al, Ge, Li and OH were measured by optical, infrared, and electron paramagnetic resonance spectroscopy, prior and after irradiation. The contents of Al, Li, Ge, Fe, Ti and other impurities were measured by inductively-coupled plasma mass spectrometry in quartz fragments exhibiting rose, pale-rose, and milky colorations. It was found that [AlO{sub 4}]{sup 0}, [AlO{sub 4}/H]{sup 0} and [GeO{sub 4}/Li]{sup 0} were generated by the dissociation of [AlO{sub 4}/Li]{sup 0} and [Li-OH] centers with doses as lower as 0.5 kGy. Above 8 kGy, the electron paramagnetic resonance signal related to [GeO{sub 4}/Li]{sup 0} decreases due to the intense mobility of Li species throughout the quartz lattice, giving rise to E'{sub 1} centers perturbed by Ge. The increase in [AlO{sub 4}]{sup 0} content with {gamma} doses and the consequent rise in the intensity of smoky color were similar for both rose and colorless quartz. Scanning electron microscopy carried out in insoluble residues obtained after chemical dissolution of each type of quartz revealed the presence of nanometric fibers only in rose specimens. These results suggested that the cause of rose color in massive quartz from Borborema Pegmatite Province is probably related to the presence of dumortierite inclusions. (author)

  12. The semiconductor doping with radiation defects via proton and alpha-particle irradiation. Review

    CERN Document Server

    Kozlov, V A

    2001-01-01

    Paper presents an analytical review devoted to semiconductor doping with radiation defects resulted from irradiation by light ions, in particular, by protons and alpha-particles. One studies formation of radiation defects in silicon, gallium arsenide and indium phosphide under light ion irradiation. One analyzes effect of proton and alpha-particle irradiation on electric conductivity of the above-listed semiconducting materials. Semiconductor doping with radiation defects under light ion irradiation enables to control their electrophysical properties and to design high-speed opto-, micro- and nanoelectronic devices on their basis

  13. Effect of radiation-induced substrate defects on microstrip gas chamber gain behaviour

    International Nuclear Information System (INIS)

    Pallares, A.; Brom, J.M.; Bergdolt, A.M.; Coffin, J.; Eberle, H.; Sigward, M.H.; Fontaine, J.C.; Barthe, S.; Schunck, J.P.

    1998-01-01

    The aim of this work was to quantify the influence of radiation-induced substrate defects on microstrip gas chamber (MSGC) gain behaviour. The first part of this paper focuses on radiation effects on a typical MSGC substrate: Desag D263 glass. Defect generation was studied for Desag D263 with pure silica (Suprasil 1) as a reference. We studied the evolution of defect concentration with respect to accumulated doses up to 480 kGy. Annealing studies of defects in Desag D263 were also performed. In the second part, the radiation sensitivity of Desag D263 glass has been linked to the behaviour of the detector under irradiation. Comparative gain measurements were taken before and after substrate irradiation at 10 and 80 kGy the minimal dose received during LHC operation and the dose for which defect density is maximum (respectively). (orig.)

  14. Effect of radiation-induced substrate defects on microstrip gas chamber gain behaviour

    Energy Technology Data Exchange (ETDEWEB)

    Pallares, A.; Brom, J.M.; Bergdolt, A.M.; Coffin, J.; Eberle, H.; Sigward, M.H. [Institute de Recherches Subatomiques, 67 - Strasbourg (France); Fontaine, J.C. [Universite de Haute Alsace, GRPHE, 61 rue Albert Camus, 68093 Mulhouse Cedex (France); Barthe, S.; Schunck, J.P. [Laboratoire PHASE (UPR 292 du CNRS), 23 rue du Loess, BP 28, 67037 Strasbourg Cedex 2 (France)

    1998-08-01

    The aim of this work was to quantify the influence of radiation-induced substrate defects on microstrip gas chamber (MSGC) gain behaviour. The first part of this paper focuses on radiation effects on a typical MSGC substrate: Desag D263 glass. Defect generation was studied for Desag D263 with pure silica (Suprasil 1) as a reference. We studied the evolution of defect concentration with respect to accumulated doses up to 480 kGy. Annealing studies of defects in Desag D263 were also performed. In the second part, the radiation sensitivity of Desag D263 glass has been linked to the behaviour of the detector under irradiation. Comparative gain measurements were taken before and after substrate irradiation at 10 and 80 kGy the minimal dose received during LHC operation and the dose for which defect density is maximum (respectively). (orig.) 26 refs.

  15. Chromosomal Aberrations in DNA Repair Defective Cell Lines: Comparisons of Dose Rate and Radiation Quality

    Science.gov (United States)

    George, K. A.; Hada, M.; Patel, Z.; Huff, J.; Pluth, J. M.; Cucinotta, F. A.

    2009-01-01

    Chromosome aberration yields were assessed in DNA double-strand break repair (DSB) deficient cells after acute doses of gamma-rays or high-LET iron nuclei, or low dose-rate (0.018 Gy/hr) gamma-rays. We studied several cell lines including fibroblasts deficient in ATM (product of the gene that is mutated in ataxia telangiectasia patients) or NBS (product of the gene mutated in the Nijmegen breakage syndrome), and gliomablastoma cells that are proficient or lacking in DNA-dependent protein kinase, DNA-PK activity. Chromosomes were analyzed using the fluorescence in-situ hybridization (FISH) chromosome painting method in cells at the first division post-irradiation and chromosome aberrations were identified as either simple exchanges (translocations and dicentrics) or complex exchanges (involving >2 breaks in 2 or more chromosomes). Gamma radiation induced higher yields of both simple and complex exchanges in the DSB repair defective cells than in the normal cells. The quadratic dose-response terms for both chromosome exchange types were significantly higher for the ATM and NBS defective lines than for normal fibroblasts. However, the linear dose-response term was significantly higher only for simple exchanges in the NBS cells. Large increases in the quadratic dose response terms indicate the important roles of ATM and NBS in chromatin modifications that facilitate correct DSB repair and minimize aberration formation. Differences in the response of AT and NBS deficient cells at lower doses suggests important questions about the applicability of observations of radiation sensitivity at high dose to low dose exposures. For all iron nuclei irradiated cells, regression models preferred purely linear and quadratic dose responses for simple and complex exchanges, respectively. All the DNA repair defective cell lines had lower Relative biological effectiveness (RBE) values than normal cells, the lowest being for the DNA-PK-deficient cells, which was near unity. To further

  16. Toward a comprehensive theory of radiation-induced swelling and creep - the point defect concentrations

    International Nuclear Information System (INIS)

    Mansur, L.K.; Yoo, M.H.

    1979-01-01

    The theory of void swelling and irradiation creep is now fairly comprehensive. A unifying concept on which most of this understanding rests is that of the rate theory point defect concentrations. Several basic aspects of this unifying conept are reviewed. These relate to local fluctuations in point defect concentrations produced by cascades, the effects of thermal and radiation-produced divacancies, and the effects of point defect trapping

  17. Investigation of radiation defects in InSb formed by charged high energy nuclear particles

    International Nuclear Information System (INIS)

    Vikhlij, G.A.; Karpenko, A.Ya.; Litovchenko, P.G.; Tarabrova, L.I.; Groza, A.A.

    1990-01-01

    A possibility of creation of high concentrations of radiation defects in the bulk of InSb samples by 47 MeV protons and 80 MeV alpha particles is considered. Dose dependences of electroconductivity, optical absorption spectra as well as temperature and field relations of galvanomagnetic properties of samples with defects are investigated. Annealing stages and electrical properties of defects annealed at these stages are determined. 17 refs.; 7 figs

  18. Stabilization of primary mobile radiation defects in MgF{sub 2} crystals

    Energy Technology Data Exchange (ETDEWEB)

    Lisitsyn, V.M. [National Research Tomsk Polytechnic University, pr. Lenina 30, Tomsk 634050 (Russian Federation); Lisitsyna, L.A. [State University of Architecture and Building, pl. Solyanaya 2, Tomsk 634003 (Russian Federation); Popov, A.I., E-mail: popov@ill.fr [Institute of Solid State Physics, University of Latvia, 8 Kengaraga Str., LV-1063 Riga (Latvia); Kotomin, E.A. [Institute of Solid State Physics, University of Latvia, 8 Kengaraga Str., LV-1063 Riga (Latvia); Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart (Germany); Abuova, F.U.; Akilbekov, A. [L.N. Gumilyov Eurasian National University, 3 Munaitpasova Str., Astana (Kazakhstan); Maier, J. [Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart (Germany)

    2016-05-01

    Non-radiative decay of the electronic excitations (excitons) into point defects (F–H pairs of Frenkel defects) is main radiation damage mechanism in many ionic (halide) solids. Typical time scale of the relaxation of the electronic excitation into a primary, short-lived defect pair is about 1–50 ps with the quantum yield up to 0.2–0.8. However, only a small fraction of these primary defects are spatially separated and survive after transformation into stable, long-lived defects. The survival probability (or stable defect accumulation efficiency) can differ by orders of magnitude, dependent on the material type; e.g. ∼10% in alkali halides with f.c.c. or b.c.c. structure, 0.1% in rutile MgF{sub 2} and <0.001% in fluorides MeF{sub 2} (Me: Ca, Sr, Ba). The key factor determining accumulation of stable radiation defects is stabilization of primary defects, first of all, highly mobile hole H centers, through their transformation into more complex immobile defects. In this talk, we present the results of theoretical calculations of the migration energies of the F and H centers in poorely studied MgF{sub 2} crystals with a focus on the H center stabilization in the form of the interstitial F{sub 2} molecules which is supported by presented experimental data.

  19. Radiation defects in lithium salts of normal oxyacids of the sixth B subgroup elements. [Gamma radiation

    Energy Technology Data Exchange (ETDEWEB)

    Kurilenko, L.N.; Saunin, E.I.; Gromov, V.V.

    1984-05-01

    EPR and thermoluminescence methods are used to investigate radiation defects in the series of compounds Li/sub 2/ElO/sub 4/(El=W, Mo, Cr) belonging to the structural type of phenacite. The example of polycrystalline Li/sub 2/WO/sub 4/ of hexagonal modification is used to show that three-axis anisotropic signal (g/sub 1/=1.997, g/sub 2/=2.007, g/sub 3/=2.023) observed after effect of ..gamma..-quanta and completely disappearing at 570 K is conditioned by preliminary localization of the hole on oxygen of octahedral mononuclear groupings of admixture cubic phases, i.e. defects of WO/sub 6//sup 5 -/ type. Li/sub 2/WO/sub 4/ of cubic modification is the main impurity. Thermal stability of WO/sub 6//sup 5 -/ defects is much higher than stability of proper tetrahedral hole centres. Mo admixture does not make a noticeable contribution to the stabilization of high-temperature hole centres in Li/sub 2/WO/sub 4/ simultaneously changing localization conditions for electrons and holes in the range of low temperatures. It is shown that Li/sub 2/MoO/sub 4/ and Li/sub 2/CrO/sub 4/ radiolysis occurs analogously to Li/sub 2/WO/sub 4/ radiolysis, but stabilization conditions of defects observed are different. It is found that thermal stability of hole paramagnetic centres of the ElO/sub 6//sup 5 -/ type correlates with ..delta..H/sub 298//sup 0/ values formation heat of compounds studied, and energy characteristics of electron paramagnetic centres of the ElO/sub 4//sup 3 -/ type change according to the values of ionization potential of El/sup 5 +/ ions.

  20. Radiation-induced segregation on defect clusters in single-phase concentrated solid-solution alloys

    International Nuclear Information System (INIS)

    Lu, Chenyang; Yang, Taini; Jin, Ke; Gao, Ning; Xiu, Pengyuan; Zhang, Yanwen; Gao, Fei; Bei, Hongbin; Weber, William J.; Sun, Kai; Dong, Yan; Wang, Lumin

    2017-01-01

    A group of single-phase concentrated solid-solution alloys (SP-CSAs), including NiFe, NiCoFe, NiCoFeCr, as well as a high entropy alloy NiCoFeCrMn, was irradiated with 3 MeV Ni"2"+ ions at 773 K to a fluence of 5 × 10"1"6 ions/cm"2 for the study of radiation response with increasing compositional complexity. Advanced transmission electron microscopy (TEM) with electron energy loss spectroscopy (EELS) was used to characterize the dislocation loop distribution and radiation-induced segregation (RIS) on defect clusters in the SP-CSAs. The results show that a higher fraction of faulted loops exists in the more compositionally complex alloys, which indicate that increasing compositional complexity can extend the incubation period and delay loop growth. The RIS behaviors of each element in the SP-CSAs were observed as follows: Ni and Co tend to enrich, but Cr, Fe and Mn prefer to deplete near the defect clusters. RIS level can be significantly suppressed by increasing compositional complexity due to the sluggish atom diffusion. According to molecular static (MS) simulations, “disk” like segregations may form near the faulted dislocation loops in the SP-CSAs. Segregated elements tend to distribute around the whole faulted loop as a disk rather than only around the edge of the loop.

  1. Radiation Response of Rhombohedral Oxides

    International Nuclear Information System (INIS)

    Devanathan, R.; Weber, W.J.; Mitchell, J.N.; Sickafus, K.E.; Nastasi, M.

    1997-05-01

    The radiation response of three rhombohedral oxides, namely, sapphire (α-Al 2 O 3 ), ilmenite (FeTiO 3 ), and geikielite (MgTiO 3 ), has been examined by irradiating electron transparent samples with 1 MeV Kr(+) and 1.5 MeV Xe(+)ions. The microstructural changes during irradiation were observed in situ in a high-voltage electron microscope using electron diffraction and microscopy. The irradiation conditions were designed to minimize beam heating and chemical effects due to the implanted ion. Of the three oxides studied, ilmenite is the most susceptible to radiation-induced amorphization while sapphire is the least susceptible. In all three materials, the critical temperature for amorphization was below 300 K indicating good room temperature resistance to amorphization by energetic beams

  2. Temperature dependence of radiation induced defect creation in a-SiO2

    International Nuclear Information System (INIS)

    Devine, R.A.B.; Grouillet, A.; Berlivet, J.Y.

    1988-01-01

    The efficiency of oxygen vacancy defect creation in samples of amorphous SiO 2 subjected to ultraviolet laser or ionizing particle radiation (energetic H + ions) has been measured as a function of sample temperature during irradiation. For the case of laser radiation (E photon ≅ 5 eV) we find that vacancy centers are only created when the irradiation temperature is above 150 K. The efficiency of peroxy radical defect creation observed after post irradiation annealing is consistent with the behaviour of the oxygen vacancy creation efficiency. In samples with energetic protons, the opposite behaviour is observed and one finds that defect creation is enhanced as the implantation temperature is lowered. Possible physical mechanisms controlling the defect creation efficiency as a function of sample temperature and radiation are discussed. (orig.)

  3. Radiation damage and defect behavior in ion-implanted, lithium counterdoped silicon solar cells

    Science.gov (United States)

    Weinberg, I.; Mehta, S.; Swartz, C. K.

    1984-01-01

    Boron doped silicon n+p solar cells were counterdoped with lithium by ion implantation and the resuitant n+p cells irradiated by 1 MeV electrons. The function of fluence and a Deep Level Transient Spectroscopy (DLTS) was studied to correlate defect behavior with cell performance. It was found that the lithium counterdoped cells exhibited significantly increased radiation resistance when compared to boron doped control cells. It is concluded that the annealing behavior is controlled by dissociation and recombination of defects. The DLTS studies show that counterdoping with lithium eliminates at least three deep level defects and results in three new defects. It is speculated that the increased radiation resistance of the counterdoped cells is due primarily to the interaction of lithium with oxygen, single vacanies and divacancies and that the lithium-oxygen interaction is the most effective in contributing to the increased radiation resistance.

  4. Radiation protection - radiographer's role and responsibilities

    International Nuclear Information System (INIS)

    Popli, P.K.

    2002-01-01

    Ever since discovery of x-rays, radiographers has been the prime user of radiation. With the passage of time, the harmful effects of radiation were detected. Some of radiographers, radiologists and public were affected by radiation, but today with enough knowledge of radiation, the prime responsibility of radiation protection lies with the radiographers only. The radiologist and physicist are also associated with radiation protection to some extent

  5. Atypical radiation response of SCID cells

    Science.gov (United States)

    Chawapun, Nisa

    Murine SCID (severe combined immune deficiency) cells are well known for their defect in DNA double-strand break repair and in variable(diversity)joining [V(D)J] recombination due to a mutation in a catalytic subunit of DNA-dependent protein kinase (DNA-PKcs). As a consequence, scid cells are hypersensitive to ionizing radiation. The present study showed that asynchronous populations of scid cells were about two-fold more sensitive than Balb/c with respect to cell killing and the defect in scid cells was corrected by complementation with human chromosome 8. Analysis of the survival of synchronized populations as a function of the cell cycle revealed that while scid cells were hypersensitive in all cell cycle phases compared to wild-type cells, this hypersensitivity is even more pronounced in G1 phase. The hypersensitivity reduced as the cells progressed into S phase suggested that homologous recombination repair plays a role. The results imply that there are at least two pathways for the repair of DSB DNA, consistent with a model previously proposed by others. The scid cells were also more sensitive to UVC light (254 nm) killing as compared to wild type cells by clonogenic survival. Using a host cell reactivation (HCR) assay to study the nucleotide excision repair (NER) which is the major repair pathway for UV-photoproducts, the results showed that NER in scid cells was not as efficient as CB- 17. This suggests that DNA-PK is involved in NER as well as non-homologous end-joining (NHEJ) DSB repair which is responsible for ionizing radiation sensitivity in scid cells. Repair in scid cells was not totally absent as shown by low dose rate sparing of cell killing after exposure to 137Cs γ-rays at dose rate of 0.6 cGy/h, 1.36 cGy/h, 6 cGy/h as compared to high dose rate at 171 cGy/min, although this phenomenon could be explained partly by proliferation. However, for radiation induced transformation, no significant dose rate effect was seen. A plot of transformation

  6. Radiation defects in electron-irradiated InP crystals

    International Nuclear Information System (INIS)

    Brailovskii, E.Yu.; Karapetyan, F.K.; Megela, I.G.; Tartachnik, V.P.

    1982-01-01

    The results are presented of formation and annealing of defects in InP crystals at 1 to 50 MeV electron irradiation. The recovery of electrical properties in the range of 77 to 970 K during annealing processes is studied. Five low temperature annealing states in n-InP and the reverse annealing in p-InP are observed at 77 to 300 K. Four annealing stages at temperatures higher than 300 K are present. When the electron energy is increased more complicated thermostable defects are formed, and at 50 MeV electron energy besides of the point defect clusters are formed, which anneal at temperatures of 800 to 970 K. It is shown that the peculiarities of the Hall mobility at irradiation and annealing are caused by the scattering centres E/sub c/ - 0.2 eV. The 'limiting' position of the Fermi level in electron irradiated InP crystals is discussed. (author)

  7. Low-dose ionizing radiation alleviates Aβ42-induced defective phenotypes in Drosophila Alzheimer's disease models

    International Nuclear Information System (INIS)

    Hwang, SooJin; Jeong, Hae Min; Nam, Seon Young

    2017-01-01

    Alzheimer's disease (AD) is the most common neurodegenerative disease that is characterized by amyloid plaques, progressive neuronal loss, and gradual deterioration of memory. Amyloid imaging using positron emission tomography (PET) radiotracers have been developed and approved for clinical use in the evaluation of suspected neurodegenerative disease, including AD. Particularly, previous studies involving low-dose ionizing radiation on Aβ 42-treated mouse hippocampal neurons have suggested a potential role for low-dose ionizing radiation in the treatment of AD. However, associated in vivo studies involving the therapy effects of low-dose ionizing radiation on AD are still insufficient. As a powerful cell biological system, Drosophila AD models have been generated and established a useful model organism for study on the etiology of human AD. In this study, we investigated the hormesis effects of low-dose ionizing radiation on Drosophila AD models. Our results suggest that low-dose ionizing radiation have the beneficial effects on not only the Aβ42-induced developmental defective phenotypes but also motor defects in Drosophila AD models. These results might be due to a regulation of apoptosis, and provide insight into the hormesis effects of low-dose ionizing radiation. Our results suggest that low-dose ionizing radiation have the beneficial effects on not only the Aβ42-induced developmental defective phenotypes but also motor defects in Drosophila AD models. These results might be due to a regulation of apoptosis, and provide insight into the hormesis effects of low-dose ionizing radiation.

  8. Radiation response and chromatin dynamics

    International Nuclear Information System (INIS)

    Ikura, Tsuyoshi

    2009-01-01

    Described is a recent progress in studies of chromatin structural alterations induced by DNA damage by radiation. DNA in eukaryotes exists in the chromatin structure and different mechanisms of response to damage and repair of DNA from those in prokaryotes have been recognized. Chromatin is composed from its unit structure of mono-nucleosome, which is formed from DNA and an octamer of core histones of H2A, H2B, H3 and H4. When DNA is damaged, histone structural alterations are required for repair factors and checkpoint proteins to access the damaged site. At the actual genome damage, chemical modification of histone to work as a code occurs dependently on the damage where chromatin remodeling factors and histone chaperone participate for structural alteration and remodeling. As well, the exchange of histone variants and fluidization of histones are recently reported. Known chemical modification involves phosphorylation, acetylation and ubiquitination of H2AX (a variant of H2A), and acetylation and methylation of H3. Each complex of TIP60, NuA4 and INO80 is known to be included in the regulation of chromatin with damaged/repaired DNA for remodeling, but little is known about recruitment of the factors concerned at the damage site. Regulatory mechanisms in above chromatin dynamics with consideration of quality and timing of radiation should be further elucidated for understanding the precise response to DNA damage. (K.T.)

  9. Defect complexes and thermoluminescence in lithium fluoride. [X radiation

    Energy Technology Data Exchange (ETDEWEB)

    McKeever, S.W.S. (Oklahoma State Univ., Stillwater (USA). Dept. of Physics)

    1984-01-01

    X-ray induced luminescence measurements indicate that the emission wavelength is dependent upon the aggregation state of Mg within the LiF lattice. This suggests a close association between Mg and Ti within a defect complex. Pulse annealing measurements indicate that peak 5 may be due to the dissociation of trimers, followed by charge release.

  10. Radiation defects in electron-irradiated InP crystals

    Energy Technology Data Exchange (ETDEWEB)

    Brailovskii, E.Yu.; Karapetyan, F.K.; Megela, I.G.; Tartachnik, V.P. (AN Ukrainskoj SSR, Kiev. Inst. Yadernykh Issledovanij)

    1982-06-16

    The results are presented of formation and annealing of defects in InP crystals at 1 to 50 MeV electron irradiation. The recovery of electrical properties in the range of 77 to 970 K during annealing processes is studied. Five low temperature annealing states in n-InP and the reverse annealing in p-InP are observed at 77 to 300 K. Four annealing stages at temperatures higher than 300 K are present. When the electron energy is increased more complicated thermostable defects are formed, and at 50 MeV electron energy besides of the point defect clusters are formed, which anneal at temperatures of 800 to 970 K. It is shown that the peculiarities of the Hall mobility at irradiation and annealing are caused by the scattering centres E/sub c/ - 0.2 eV. The 'limiting' position of the Fermi level in electron irradiated InP crystals is discussed.

  11. The radiation response of human dermal fibroblasts

    Science.gov (United States)

    Mitchell, Stephen Andrew

    A clinically reliable predictive assay based on normal-tissue radiosensitivity may lead to improved tumour control through individualised dose prescriptions. In-vitro fibroblast radiosensitivity has been shown, in several studies, to correlate with late radiation morbidity. The aim of this study was to investigate some of the cellular mechanisms underlying the normal-tissue response. In this study, seventeen primary fibroblast strains were established by enzymatic disaggregation of skin biopsies obtained from patients. These comprised seven who experienced acute tissue reactions to radiotherapy, four patients with a normal response and six non-cancer volunteers. An AT cell line was included as a positive control for radiosensitivity. In-vitro radiosensitivity was measured using a clonogenic assay at both high (HDR: 1.6 Gymin-1) and low dose rate (LDR: 0.01 Gymin-1). The radiation parameter HDR SF2 was the most sensitive in discriminating the seven sensitive patients from the remaining ten normal patients (range 0.11-0.19 sensitive patients compared with 0.17-0.34 control patients: puse of an internal control or LDR radiation protocol increased this discrimination. Pulsed-field gel electrophoresis (PFGE) was used to measure the level of initial and residual double-strand breaks following irradiation. No correlation was found between HDR SF2 and initial DNA damage. However, a strong correlation was found between clonogenic survival and both residual DNA damage (measured over 10-70 Gy, allowing 4 h repair, correlation coefficient: 0.90, <0.0001) and the ratio of residual/initial DNA damage, with the sensitive cell lines generally showing a higher level of residual DNA damage. Cell-cycle delays were found in all 18 cell strains in response to 2 Gy irradiation, but were not found to discriminate between sensitive and normal patients. Associated studies found no mutations of the ATM gene in the five radiosensitive patients studied. However, a coding sequence alteration

  12. Peculiarities of radiation defect formation and annealing in n-Si due to their interaction with each other and defect clusters

    International Nuclear Information System (INIS)

    Lugakov, P.F.; Lukyanitsa, V.V.

    1984-01-01

    Rearrangement processes proceeding during annealing (T/sub a/ = 50 to 500 0 C) of radiation defects in 60 Co γ-irradiated (T/sub irr/ 0 C) n-Si crystals (rho = 100 to 600 Ωcm) grown by the vacuum float-zone technique are studied. The temperature dependences of the Hall coefficient are measured. The results obtained are interpreted taking into account the interaction during annealing of vacancy-type defects (E-centres, divacancies) with each other and interstitial radiation defects (C/sub i/-C/sub s/ complexes, interstitial carbon C/sub i/). Phosphorus-two vacancies complexes, stable to T/sub a/ >= 500 0 C, are shown to be formed as a result of rearrangements and interaction of E-centres between themselves. The character of interaction of vacancy defects with interstitial ones is found to change significantly in the presence of defect clusters in the bulk of the crystal which are formed under heat treatment (T = 800 0 C, two hours) of the samples preliminary irradiated with fast neutrons (flux PHI/sub n/ = 1x10 14 to 1x10 16 cm -2 ). The peculiarities of radiation defects annealing observed in this case are explained taking into account the influence of defect clusters on the migration processes of mobile defects. Nature of radiation defects being formed at various stages of annealing is discussed. (author)

  13. Medical response to effects of ionising radiation

    International Nuclear Information System (INIS)

    Crosbie, W.A.; Gittus, J.H.

    1989-01-01

    The proceedings of a conference on 'Medical Response to Effects of Ionising Radiation' in 1989 in the form of nineteen papers published as a book. Topics discussed include radiation accidents at nuclear facilities, the medical management of radiation casualties, the responsibilities, plans and resources for coping with a nuclear accident and finally the long term effects of radiation, including leukaemia epidemiology studies. All papers were selected and indexed separately. (UK)

  14. Radiation-induced defects in As-Sb-S glass

    International Nuclear Information System (INIS)

    Balitska, V; Shpotyuk, Ya; Filipecki, J; Shpotyuk, O

    2010-01-01

    Defect-related instability was studied in γ-irradiated (As 2 S 3 ) 1-x (Sb 2 S 3 ) x glasses (x = 0, 0.1, 0.2 and 0.3) using positron annihilation lifetime spectroscopy treated within high-measurement statistics. The observed decrease in average positron lifetime in the studied glasses is explained as a renovation of destroyed covalent chemical bonds after irradiation. This process is governed by monomolecular relaxation kinetics, being described in the framework of universal configuration-coordinate model.

  15. Radiation-induced defects in As-Sb-S glass

    Energy Technology Data Exchange (ETDEWEB)

    Balitska, V; Shpotyuk, Ya; Filipecki, J; Shpotyuk, O, E-mail: shpotyuk@novas.lviv.ua

    2010-11-15

    Defect-related instability was studied in {gamma}-irradiated (As{sub 2}S{sub 3}){sub 1-x}(Sb{sub 2}S{sub 3}){sub x} glasses (x = 0, 0.1, 0.2 and 0.3) using positron annihilation lifetime spectroscopy treated within high-measurement statistics. The observed decrease in average positron lifetime in the studied glasses is explained as a renovation of destroyed covalent chemical bonds after irradiation. This process is governed by monomolecular relaxation kinetics, being described in the framework of universal configuration-coordinate model.

  16. Measurement of the energy stored in alkalihalogenids by radiation defects

    International Nuclear Information System (INIS)

    Schrey, P.

    1976-01-01

    The energy stored in alkali-halogen crystals after X-ray irradiation is studied at 11 K. Using a heat flux calorimeter designed especially for this experiment, single crystals are irradiated and the energy release is recorded as the temperature is increased proportional to time from 10 K to 50 K. The energy release spectra are compared with relevant optical measurements and thus a relation between energy release and tempering of point defects is established. The energy release peaks can be assigned definitly to tempering stages of the Frenkel pairs. For explanation a simple model is proposed. (orig./HPOE) [de

  17. Radiation defects produced by neutron irradiation in germanium single crystals

    International Nuclear Information System (INIS)

    Fukuoka, Noboru; Honda, Makoto; Atobe, Kozo; Yamaji, Hiromichi; Ide, Mutsutoshi; Okada, Moritami.

    1992-01-01

    The nature of defects produced in germanium single crystals by neutron irradiation at 25 K was studied by measuring the electrical resistivity. It was found that two levels located at E c -0.06 eV and E c -0.13 eV were introduced in an arsenic-doped sample. Electron traps at E c -0.10eV were observed in an indium-doped sample. The change in electrical resistivity during irradiation was also studied. (author)

  18. Doping of semiconductors using radiation defects produced by irradiation with protons and alpha particles

    International Nuclear Information System (INIS)

    Kozlov, V.A.; Kozlovski, V.V.

    2001-01-01

    One of the modern methods for modifying semiconductors using beams of protons and alpha particles is analyzed; this modification is accomplished by the controlled introduction of radiation defects into the semiconductor. It is shown that doping semiconductors with radiation defects produced by irradiation with light ions opens up fresh opportunities for controlling the properties of semiconducting materials and for the development of new devices designed for optoelectronics, microelectronics, and nanoelectronics based on these materials; these devices differ favorably from those obtained by conventional doping methods, i.e., by diffusion, epitaxy, and ion implantation

  19. Programmed cellular response to ionizing radiation damage

    International Nuclear Information System (INIS)

    Crompton, N.E.A.

    1998-01-01

    Three forms of radiation response were investigated to evaluate the hypothesis that cellular radiation response is the result of active molecular signaling and not simply a passive physicochemical process. The decision whether or not a cell should respond to radiation-induced damage either by induction of rescue systems, e.g. mobilization of repair proteins, or induction of suicide mechanisms, e.g. programmed cell death, appears to be the expression of intricate cellular biochemistry. A cell must recognize damage in its genetic material and then activate the appropriate responses. Cell type is important; the response of a fibroblast to radiation damage is both quantitatively and qualitatively different form that of a lymphocyte. The programmed component of radiation response is significant in radiation oncology and predicted to create unique opportunities for enhanced treatment success. (orig.)

  20. Correlation between nuclear response and defects in CZT

    International Nuclear Information System (INIS)

    Hermon, H.; Schieber, M.; James, R. B.; Lee, E.; Cross, E.; Goorsky, M.; Lam, T.; Schlesinger, T. E.; Greaves, M.

    1999-01-01

    Vertical high pressure Bridgman (VHPB) was considered until now to be the most successful crystal growth method to produce Cd 1-x Zn x Te (CZT), (0.04 1-x Zn x Te crystals produced by IMARAD Co. have also been successfully fabricated into nuclear spectroscopic radiation detectors. In view of the database of many years' study of the electrical properties of VHPB CZT grown and obtained from various sources, the authors also studied the HB CZT crystals in order to compare the defects present in both different kinds of crystals grown by different methods. The VHB-grown samples were examined using thermoelectric emission spectroscopy (TEES), X- and gamma ray spectroscopy and laser induced transient charge technique (TCT). The surface and the bulk crystalline homogeneity were mapped using triaxial double crystal x-ray diffraction (TADXRD) and infrared transmission spectroscopy (IR). They have found a correlation between crystallinity, IR transmission microstructure and trapping times. Spectrometer grade VHPB CZT crystals exhibit trapping times of 20 (micro)s for electrons and 7 (micro)s for holes, however, regions, which were opaque to IR transmission, had trapping times shorter by one order of magnitude. The trapping times of HB CZT for electrons, were 10--15 (micro)s. A similar trend has been observed on VHPB CZT crystals with poor crystallinity. The HB CZT crystals that they measured in this study had a crystallinity that was inferior to that of the best spectroscopic grade VHPB crystals

  1. Edge dislocations as sinks for sub-nanometric radiation induced defects in α-iron

    Science.gov (United States)

    Anento, N.; Malerba, L.; Serra, A.

    2018-01-01

    The role of edge dislocations as sinks for small radiation induced defects in bcc-Fe is investigated by means of atomistic computer simulation. In this work we investigate by Molecular Statics (T = 0K) the interaction between an immobile dislocation line and defect clusters of small sizes invisible experimentally. The study highlights in particular the anisotropy of the interaction and distinguishes between absorbed and trapped defects. When the considered defect intersects the dislocation glide plane and the distance from the dislocation line to the defect is on the range between 2 nm and 4 nm, either total or partial absorption of the cluster takes place leading to the formation of jogs. Residual defects produced during partial absorption pin the dislocation. By the calculation of stress-strain curves we have assessed the strength of those residues as obstacles for the motion of the dislocation, which is reflected on the unpinning stresses and the binding energies obtained. When the defect is outside this range, but on planes close to the dislocation glide plane, instead of absorption we have observed a capture process. Finally, with a view to introducing explicitly in kinetic Monte Carlo models a sink with the shape of a dislocation line, we have summarized our findings on a table presenting the most relevant parameters, which define the interaction of the dislocation with the defects considered.

  2. Radiation defects in SrB4O7:Eu2+ crystals

    International Nuclear Information System (INIS)

    Yavetskiy, R.P.; Dolzhenkova, E.F.; Tolmachev, A.V.; Parkhomenko, S.V.; Baumer, V.N.; Prosvirnin, A.L.

    2007-01-01

    Radiation-induced defects in SrB 4 O 7 :Eu 2+ (0.033 at.%) single crystal irradiated with γ and X-ray quanta has been studied. The induced optical absorption in the 400-700 nm region has been ascribed to F + centers. The Eu 2+ ions have been shown to act simultaneously as traps and as radiative recombination centers of charge carriers. Basing on the thermally stimulated luminescence (TSL), optical absorption and photoluminescence studies of SrB 4 O 7 :Eu 2+ crystals, a TSL mechanism has been proposed associated with the decay of F + centers being in non-equivalent crystallographic positions followed by radiative recombination of charge carriers on europium ions. Various positions of localization of the radiation-induced defects in the SrB 4 O 7 crystal structure have been discussed

  3. Regularities of radiation defects build up on oxide materials surface; Zakonomernosti nakopleniya radiatsionnykh defektov na poverkhnosti oksidnykh materialov

    Energy Technology Data Exchange (ETDEWEB)

    Bitenbaev, M I; Polyakov, A I [Fiziko-Tekhnicheskij Inst., Almaty (Kazakhstan); Tuseev, T [Inst. Yadernoj Fiziki, Almaty (Kazakhstan)

    2005-07-01

    Analysis of experimental data by radiation defects study on different oxide elements (silicon, beryllium, aluminium, rare earth elements) irradiated by the photo-, gamma-, neutron-, alpha- radiation, protons and helium ions show, that gas adsorption process on the surface centers and radiation defects build up in metal oxide correlated between themselves. These processes were described by the equivalent kinetic equations for analysis of radiation defects build up in the different metal oxides. It was revealed in the result of the analysis: number of radiation defects are droningly increasing up to limit value with the treatment temperature growth. Constant of radicals death at ionizing radiation increases as well. Amount of surface defects in different oxides defining absorbing activity of these materials looks as: silicon oxide{yields}beryllium oxide{yields}aluminium oxide. So it was found, that most optimal material for absorbing system preparation is silicon oxide by it power intensity and berylium oxide by it adsorption efficiency.

  4. Electron paramagnetic resonance study on the ionizing radiation induced defects of the tooth enamel hydroxyapatite

    International Nuclear Information System (INIS)

    Oliveira, Liana Macedo de

    1995-01-01

    Hydroxyapatite is the main constituent of calcified tissues. Defects induced by ionizing radiations in this biomineral can present high stability and then, these are used as biological markers in radiological accidents, irradiated food identifying and geological and archaeological dating. In this work, paramagnetic centers induced on the enamel of the teeth by environmental ionizing radiation, are investigated by electron paramagnetic resonance (EPR). Decay thermal kinetic presents high complexity and shows the formation of different electron ligation energy centers and structures

  5. Current Evidence for Developmental, Structural, and Functional Brain Defects following Prenatal Radiation Exposure

    Directory of Open Access Journals (Sweden)

    Tine Verreet

    2016-01-01

    Full Text Available Ionizing radiation is omnipresent. We are continuously exposed to natural (e.g., radon and cosmic and man-made radiation sources, including those from industry but especially from the medical sector. The increasing use of medical radiation modalities, in particular those employing low-dose radiation such as CT scans, raises concerns regarding the effects of cumulative exposure doses and the inappropriate utilization of these imaging techniques. One of the major goals in the radioprotection field is to better understand the potential health risk posed to the unborn child after radiation exposure to the pregnant mother, of which the first convincing evidence came from epidemiological studies on in utero exposed atomic bomb survivors. In the following years, animal models have proven to be an essential tool to further characterize brain developmental defects and consequent functional deficits. However, the identification of a possible dose threshold is far from complete and a sound link between early defects and persistent anomalies has not yet been established. This review provides an overview of the current knowledge on brain developmental and persistent defects resulting from in utero radiation exposure and addresses the many questions that still remain to be answered.

  6. Radiation-induced defect production in MgF2-Co crystals

    International Nuclear Information System (INIS)

    Nuritdinov, I.; Turdanov, K.; Mirinoyatova, N.M.; Rejterov, V.M.

    1996-01-01

    Impact of Co-admixture on structural radiation defects formation in the MgF 2 crystals is studied. It is found that the Co admixture facilitates the probability of generating the F- and m-type centers of radiation defects as well as creation of the F- and M-centers, perturbed by admixtures. The availability of structural defects leads in its turn to the admixture ions perturbation. It is reflected in the removal of prohibition on spin-prohibited transitions of the Co 2 + ions. It is assumed that creation of the M-centers is the main cause for removal of the prohibition on the spin-prohibited transitions. 8 refs., 4 figs

  7. TEM study of radiation induced defects in baffle-former-barrel assembly from decommissioned NPP Greifswald

    International Nuclear Information System (INIS)

    Srba, O.; Michalicka, J.; Keilova, E.; Kocik, K.

    2013-06-01

    A complex transmission electron microscopy (TEM) study of reactor vessel internal (RVI) materials from the baffle-former-barrel assembly from NPP Greifswald (VVER 440), Unit 1 decommissioned after 15 service cycles has been undertaken. All parts of the baffle-former-barrel assembly are made from Ti-stabilized austenitic stainless steel 08Ch18N10T. The materials were exposed to different dose of neutron radiation (2.4 - 11.4 dpa) at temperatures 267 - 398 deg. C depending on position in the core. Three types of radiation induced defects were identified and quantified, namely: dislocations, cavities (voids) and fine-scaled precipitated particles of Ni-Si rich phases. Black-dot type defects were observed too. Operation conditions are around ≅ 300 deg. C that is why we have observed defect typical for both low and high regions of irradiation temperatures. (authors)

  8. Annealing of radiation-induced defects in silicon in a simplified phenomenological model

    International Nuclear Information System (INIS)

    Lazanu, S.; Lazanu, I.

    2001-01-01

    The concentration of primary radiation-induced defects has been previously estimated considering both the explicit mechanisms of the primary interaction between the incoming particle and the nuclei of the semiconductor lattice, and the recoil energy partition between ionisation and displacements, in the frame of the Lindhard theory. The primary displacement defects are vacancies and interstitials that are essentially unstable in silicon. They interact via migration, recombination, annihilation or produce other defects. In the present work, the time evolution of the concentration of defects induced by pions in medium and high resistivity silicon for detectors is modelled, after irradiation. In some approximations, the differential equations representing the time evolution processes could be decoupled. The theoretical equations so obtained are solved analytically in some particular cases, with one free parameter, for a wide range of particle fluences and/or for a wide energy range of incident particles, for different temperatures; the corresponding stationary solutions are also presented

  9. Characterization of defects and microstructures by neutrons and synchrotron radiations topography

    International Nuclear Information System (INIS)

    Baruchel, J.

    1993-01-01

    Neutrons and synchrotron radiation topography are complementary for defects study, for domains or phases coexistence in magnetic or high absorbing crystals, or crystals not supporting intense X irradiation. Applications to CuGe, NiAl, CuAl, FeSi binary alloys are shortly presented. (A.B.). 8 refs, 1 fig

  10. Formation and properties of radiation-induced defects and radiolysis products in lithium orthosilicate

    Energy Technology Data Exchange (ETDEWEB)

    Tiliks, J.E.; Kizane, G.K.; Supe, A.A.; Abramenkovs, A.A.; Tiliks, J.J. (Latvian Univ., Riga (Latvia)); Vasiljev, V.G. (Acad. A.A. Bochvar Inst. of Inorganic Materials, Moscow (USSR))

    1991-12-01

    Formation and properties of radiation-induced defects and radiolysis products in polycrystalline powders and ceramic pellets of Li{sub 4}SiO{sub 4} were studied under the effect of various types of ionizing irradiation ({gamma} quants, accelerated electrons, reactor irradiation), humidity, temperature, impurities in the samples, etc. The content of radiation defects and radiolysis products poorly depends on irradiation type, dose rate, admixture elements. The concentration of defects highly depends on the temperature of irradiation, humidity, granural size. Empirical dependence of radiolysis degree {alpha} on the dose was found: {alpha}=5x10{sup -2}xD{sup 0.5} for {gamma} and electron irradiation (T{sub rad}=300-350 K) and {alpha}=5x10{sup -3}xD{sup 0.5} for reactor radiation (T{sub rad}=700-800 K); {alpha} - matrix dissociation degree (in %); D - dose (in MGy). Colloidal lithium and silicon, lithium and silicon oxides, and O{sub 2} are the final products of radiolysis. Radiation-induced defects change tritium thermo-extraction parameters, deteriorate mechanical, thermo-physical and electric properties of ceramics. (orig.).

  11. Radiation-induced defect-formation in lithium hydride and deuteride monocrystals. [Electron and X-ray irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Pustovarov, V.A.; Betenekova, T.A.; Zav' yalov, N.A.; Cholakh, S.O. (Ural' skij Politekhnicheskij Inst., Sverdlovsk (USSR))

    1983-08-01

    Methods of stationary and pulse absorption spectroscopy were used to investigate into processes of formation and decay of radiation defects in cubic LiH and LiD crystals. F- and V-centers form at low temperatures during crystal irradiation by photons, creating excitons selectively, accelerator electrons, X-ray radiation. Analysis of possible mechanisms of defect formation shows that radiation defect formation in LiH is based on radiationless exciton decay. It is shown that efficiency of F- and V-centers generation in pure and impure crystals in 80-298 K range is the same. Exciton decay with formation of Frenkel radiation defects in pure LiH and LiD crystals takes place, probably, in regular crystal lattice points. Process of radiation defect formation as a result of near activator exciton decay takes place in impure LiH-Na, LiD-Na crystals.

  12. Radiation induced deep level defects in bipolar junction transistors under various bias conditions

    International Nuclear Information System (INIS)

    Liu, Chaoming; Yang, Jianqun; Li, Xingji; Ma, Guoliang; Xiao, Liyi; Bollmann, Joachim

    2015-01-01

    Bipolar junction transistor (BJT) is sensitive to ionization and displacement radiation effects in space. In this paper, 35 MeV Si ions were used as irradiation source to research the radiation damage on NPN and PNP bipolar transistors. The changing of electrical parameters of transistors was in situ measured with increasing irradiation fluence of 35 MeV Si ions. Using deep level transient spectroscopy (DLTS), defects in the bipolar junction transistors under various bias conditions are measured after irradiation. Based on the in situ electrical measurement and DLTS spectra, it is clearly that the bias conditions can affect the concentration of deep level defects, and the radiation damage induced by heavy ions.

  13. Radiation-induced defects formation in Bi-containing vitreous chalcogenides

    International Nuclear Information System (INIS)

    Shpotyuk, O.; Vakiv, M.; Balitska, V.; Kovalskiy, A.

    1997-01-01

    Processes of formation and annihilation of coordination defects in As 2 Se 3 Bi y and (As 2 Se 3 )(Bi 2 Se 3 ) y amorphous chalcogenide semiconductors induced by influence of Co 60 gamma-irradiation are investigated by photoelectric spectroscopy method. It is obtained that radiation-induced changes of photoelectrical properties on bioconcentration of As 2 Se 3 Bi y glasses are characterized by anomalous concentration dependence. The nature of this effect is associated with diamagnetic coordination defects formation. (author). 19 refs, 3 figs

  14. Radiation-induced defects formation in Bi-containing vitreous chalcogenides

    Energy Technology Data Exchange (ETDEWEB)

    Shpotyuk, O.; Vakiv, M.; Balitska, V.; Kovalskiy, A. [Institute of Materials, Lvov (Ukraine)

    1997-12-01

    Processes of formation and annihilation of coordination defects in As{sub 2}Se{sub 3}Bi{sub y} and (As{sub 2}Se{sub 3})(Bi{sub 2}Se{sub 3}){sub y} amorphous chalcogenide semiconductors induced by influence of Co{sup 60} gamma-irradiation are investigated by photoelectric spectroscopy method. It is obtained that radiation-induced changes of photoelectrical properties on bioconcentration of As{sub 2}Se{sub 3}Bi{sub y} glasses are characterized by anomalous concentration dependence. The nature of this effect is associated with diamagnetic coordination defects formation. (author). 19 refs, 3 figs.

  15. Nature of oxygen donors and radiation defects in oxygen-doped germanium

    International Nuclear Information System (INIS)

    Fukuoka, Noboru; Atobe, Kozo; Honda, Makoto; Matsuda, Koji.

    1991-01-01

    The nature of oxygen donors and radiation defects in oxygen-doped germanium were studied through measurements of the infrared absorption spectrum, deep level transient spectroscopy spectrum and carrier concentration. It is revealed that a new donor is not formed in oxygen-doped germanium. An A-center (interstitial oxygen-vacancy pair) forms a complex with a thermal donor in its annealing stage at 60degC-140degC. The introduction rate of defects by 1.5 MeV electron irradiation was enhanced in thermal-donor-doped samples. (author)

  16. Use of EMW radiation in the building industry at defects in buildings

    Directory of Open Access Journals (Sweden)

    Sobotka Jindřich

    2017-01-01

    Full Text Available This paper discusses theory and application of microwave radiation and experimental optimization of microwave radiation to eliminate moisture content in wood elements. It will be appreciated that the rising moisture leaking into the structure, resulting in defects and structures of the buildings themselves. Owing to its properties, microwave radiation has been used in the construction industry in modern times, in particular to dry wet masonry of buildings. Effects of electromagnetic radiation on building structures lead to relatively sharp decreases in moisture content from damp building structures or elements. The influence of electromagnetic radiation on building structures lead to oscillation of water molecules contained in the material, which cause a phase transformation of water into vapour. Consequently, the vapour evaporates from the moist material, thereby drying the element exposed to radiation. The article describes experiments carried out at the Faculty of Civil Engineering of the Faculty of Technology in Brno that demonstrate successful decrease of water content in building materials using microwave radiation. First, the understanding of microwave radiation will be discussed. Following an analysis of research results an optimum intensity of microwave radiation sources as well as the necessary length of the irradiation of microwave radiation have been determined with respect to the particular type of building material and the success rate of elimination of moisture.

  17. The responsibility of the radiation protection expert

    International Nuclear Information System (INIS)

    Varescon, M.

    2008-01-01

    After having recalled the two main different types of responsibility in the French law system (civil liability and criminal responsibility), and how criminal law has been gradually introduced in companies, the author analyzes and describes how the radiation protection expert's responsibility is tightly related to that of his employer, and how both can be committed on a disciplinary and criminal level

  18. Radiation defect distribution in silicon irradiated with 600 keV electrons

    International Nuclear Information System (INIS)

    Hazdra, P.; Dorschner, H.

    2003-01-01

    Low-doped n-type float zone silicon was irradiated with 600 keV electrons to fluences from 2x10 13 to 1x10 15 cm -2 . Radiation defects, their introduction rates and full-depth profiles were measured by two complementary methods - the capacitance deep level spectroscopy and the high-voltage current transient spectroscopy. Results show that, in the vicinity of the anode junction, the profile of vacancy-related defect centers is strongly influenced by electric field and an excessive generation of vacancies. In the bulk, the slope of the profile can be derived from the distribution of absorbed dose taking into the account the threshold energy necessary for Frenkel pair formation and the dependency of the defect introduction rate on electron energy

  19. On kinetics of paramagnetic radiation defects accumulation in beryllium ceramics; O kinetike nakopleniya paramagnitnykh radiatsionnykh defektov v berillievykh keramikakh

    Energy Technology Data Exchange (ETDEWEB)

    Polyakov, A I; Ryabikin, Yu A; Zashkvara, O V; Bitenbaev, M I; Petykhov, Yu V [Fiziko-Tekhnicheskij Inst., Almaty (Kazakhstan); Inst. Atomnoj Ehnergii, Kurchatov (Kazakhstan)

    1999-07-01

    Results of paramagnetic radiation defects concentration dependence study in beryllium ceramics from gamma-irradiation dose ({sup 60}Co) within interval 0-100 Mrem are cited. Obtained dose dependence has form of accumulation curve with saturation typical of for majority of solids (crystals, different polymers, organic substances and others) , in which under irradiation occur not only formation of paramagnetic radiation defects, but its destruction due to recombination and interaction with radiation fields. Analysis of accumulation curve by the method of distant asymptotics allows to determine that observed in gamma-irradiated beryllium ceramics double line of electron spin resonance is forming of two types of paramagnetic radiation defects. It was defined, that sum paramagnetic characteristics of beryllium ceramics within 1-100 Mrad gamma- irradiation dose field change insignificantly and define from first type of paramagnetic radiation defects.

  20. Recombination of charge carriers on radiation-induced defects in silicon doped by transition metals impurities

    CERN Document Server

    Kazakevich, L A

    2003-01-01

    It has been studied the peculiarities of recombination of nonequilibrium charge carriers on radiation-induced defects in received according to Czochralski method p-silicon (p approx 3 - 20 Ohm centre dot cm), doped by one of the impurities of transition metals of the IV-th group of periodic table (titanium, zirconium, hafnium). Experimental results are obtained out of the analysis of temperature and injection dependence of the life time of charge carriers. The results are explained taking into consideration the influences of elastic stress fields created by the aggregates of transition metals atoms on space distribution over the crystal of oxygen and carbon background impurities as well as on the migration of movable radiation-induced defects during irradiation. (authors).

  1. Study of radiation defects in semiconductors by means of positron annihilation

    International Nuclear Information System (INIS)

    Krause-Rehberg, R.; Bondarenko, V.; Redmann, F.

    2003-01-01

    In a nuclear environment, a strong degradation of important properties is observed for many materials which are otherwise very reliable. This is especially valid for silicon, the most important semiconductor. In the presented paper, two examples for the study of lattice defects in silicon by means of positron annihilation will be given. Firstly, the degradation of silicon detectors used for the particle detection in high-luminosity collider experiments starts to limit the lifetime of the whole experiment. An annealing experiment on n-irradiated Si will be presented. Beside the destructive effect of high-radiation conditions, such radiation-induced defects can have a beneficial result. This will be demonstrated for the creation of new gettering zones by high-energy self-implantation of silicon. (author)

  2. Peculiarities of approximation for reactor neutron energy spectra during computerized simulation of radiation defects

    International Nuclear Information System (INIS)

    Kupchishin, A.A.; Kupchishin, A.I.; Stusik, G.; Omarbekova, Zh.

    2001-01-01

    Peculiarities of approximation for reactor neutron energy spectra during radiation defects computerized simulation were discussed. Approximation of neutron spectra N(E) was carried out by N(E)=α·exp(-β·E)·sh(γ·E) formula (1), where α, β, γ - approximation coefficients. In the capacity of operating reactor data experimental data on 235 U and 239 Pu were applied. The algorithm was designed, and acting soft ware for spectra parameters calculation was developed. The following values of approximation parameters were obtained: α=80.8; β=0.935;γ=2.04 (for uranium and plutonium these coefficients are less distinguishing). Then with use of formula 1 and α, β, γ coefficients the approximation curves were constructed. These curves satisfactorily describe existing experimental data and allowing to use its for radiation defects simulation in the reactor materials

  3. Deterministic Role of Collision Cascade Density in Radiation Defect Dynamics in Si

    Science.gov (United States)

    Wallace, J. B.; Aji, L. B. Bayu; Shao, L.; Kucheyev, S. O.

    2018-05-01

    The formation of stable radiation damage in solids often proceeds via complex dynamic annealing (DA) processes, involving point defect migration and interaction. The dependence of DA on irradiation conditions remains poorly understood even for Si. Here, we use a pulsed ion beam method to study defect interaction dynamics in Si bombarded in the temperature range from ˜-30 ° C to 210 °C with ions in a wide range of masses, from Ne to Xe, creating collision cascades with different densities. We demonstrate that the complexity of the influence of irradiation conditions on defect dynamics can be reduced to a deterministic effect of a single parameter, the average cascade density, calculated by taking into account the fractal nature of collision cascades. For each ion species, the DA rate exhibits two well-defined Arrhenius regions where different DA mechanisms dominate. These two regions intersect at a critical temperature, which depends linearly on the cascade density. The low-temperature DA regime is characterized by an activation energy of ˜0.1 eV , independent of the cascade density. The high-temperature regime, however, exhibits a change in the dominant DA process for cascade densities above ˜0.04 at.%, evidenced by an increase in the activation energy. These results clearly demonstrate a crucial role of the collision cascade density and can be used to predict radiation defect dynamics in Si.

  4. The radiative heating response to climate change

    Science.gov (United States)

    Maycock, Amanda

    2016-04-01

    The structure and magnitude of radiative heating rates in the atmosphere can change markedly in response to climate forcings; diagnosing the causes of these changes can aid in understanding parts of the large-scale circulation response to climate change. This study separates the relative drivers of projected changes in longwave and shortwave radiative heating rates over the 21st century into contributions from radiatively active gases, such as carbon dioxide, ozone and water vapour, and from changes in atmospheric and surface temperatures. Results are shown using novel radiative diagnostics applied to timeslice experiments from the UM-UKCA chemistry-climate model; these online estimates are compared to offline radiative transfer calculations. Line-by-line calculations showing spectrally-resolved changes in heating rates due to different gases will also be presented.

  5. Characterization of radiation-induced defects in ZnO probed by positron annihilation spectroscopy

    International Nuclear Information System (INIS)

    Brunner, S.; Puff, W.; Balogh, A.G.; Mascher, P.

    2001-01-01

    In this study we discuss the microstructural changes after electron and proton irradiation and the thermal evolution of the radiation induced defects during isochronal annealing of single crystals irradiated either with 3 MeV protons or with 1 or 2 MeV electrons, respectively. The investigations were performed with positron lifetime and Doppler-broadening measurements. The differently grown ZnO single crystals show positron bulk lifetimes in the range of 159-173 ps. (orig.)

  6. Radiation-induced defects in chalcogenide glasses characterized by combined optical spectroscopy, XPS and PALS methods

    International Nuclear Information System (INIS)

    Shpotyuk, O.; Kovalskiy, A.; Jain, H.; Golovchak, R.; Zurawska, A.

    2007-01-01

    Temperature-dependent optical absorption spectroscopy, high-resolution X-ray photoelectron spectroscopy and positron annihilation lifetimes spectroscopy are utilized to understand radiation-induced changes in Ge-Sb-S chalcogenide glasses. Theoretically predicted topological scheme of γ-induced coordination defect formation in stoichiometric Ge 23.5 Sb 11.8 S 64.7 glass composition is supported by these measurements. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  7. Simulation of the accumulation kinetics for radiation point defects in a metals with impurity

    International Nuclear Information System (INIS)

    Iskakov, B.M.; Nurova, A.B.

    2001-01-01

    In the work a kinetics of vacancies (V) and interstitial atoms (IA) accumulation for cases when the V and IA are recombining with each other, absorbing by drain and capturing by impurity atoms has been simulated. The differential equations system numerical solution was carried out by the Runge-Kutta method. The dynamical equilibrium time achievement for the point radiation defects accumulation process in the metal with impurity is considered

  8. Characterization of radiation-induced defects in ZnO probed by positron annihilation spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Brunner, S.; Puff, W. [Technische Univ. Graz (Austria). Inst. fuer Technische Physik; Balogh, A.G. [Technische Hochschule Darmstadt (Germany). FB Materialwissenschaft; Mascher, P. [McMaster Univ., Hamilton, ON (Canada). Dept. of Engineering Physics

    2001-07-01

    In this study we discuss the microstructural changes after electron and proton irradiation and the thermal evolution of the radiation induced defects during isochronal annealing of single crystals irradiated either with 3 MeV protons or with 1 or 2 MeV electrons, respectively. The investigations were performed with positron lifetime and Doppler-broadening measurements. The differently grown ZnO single crystals show positron bulk lifetimes in the range of 159-173 ps. (orig.)

  9. Radiofrequency electromagnetic radiation from cell phone causes defective testicular function in male Wistar rats.

    Science.gov (United States)

    Oyewopo, A O; Olaniyi, S K; Oyewopo, C I; Jimoh, A T

    2017-12-01

    Cell phones have become an integral part of everyday life. As cell phone usage has become more widespread, concerns have increased regarding the harmful effects of radiofrequency electromagnetic radiation from these devices. The current study was undertaken to investigate the effects of the emitted radiation by cell phones on testicular histomorphometry and biochemical analyses. Adult male Wistar rats weighing 180-200 g were randomly allotted to control, group A (switched off mode exposure), group B (1-hr exposure), group C (2-hr exposure) and group D (3-hr exposure). The animals were exposed to radiofrequency electromagnetic radiation of cell phone for a period of 28 days. Histomorphometry, biochemical and histological investigations were carried out. The histomorphometric parameters showed no significant change (p electromagnetic radiation of cell phone leads to defective testicular function that is associated with increased oxidative stress and decreased gonadotropic hormonal profile. © 2017 Blackwell Verlag GmbH.

  10. Development of defects in the structure of PIN dosimetry diodes exposed to gamma radiation

    Energy Technology Data Exchange (ETDEWEB)

    Sopko, V. [Hospital Na Bulovce, Department of Radiological Physics, Budinova 2, CZ-18081 Prague 8 (Czech Republic); Institute of Experimental and Applied Physics, Czech Technical University in Prague, Horska 3a/22, CZ 12800 Prague 2 (Czech Republic); Sopko, B., E-mail: bruno.sopko@cern.ch [Department of Physics, Faculty of Mechanical Engineering, Czech Technical University in Prague, Technicka 4, CZ 16000 Prague 6 (Czech Republic); Faculty of Production Technology and Management, J. E. Purkyně Univerzity in Ústí nad Labem, Na Okraji 1001, 400 01 Ústí nad Labem (Czech Republic); Chren, D. [Department of Physics, Faculty of Mechanical Engineering, Czech Technical University in Prague, Technicka 4, CZ 16000 Prague 6 (Czech Republic); Dammer, J. [Hospital Na Bulovce, Department of Radiological Physics, Budinova 2, CZ-18081 Prague 8 (Czech Republic); Institute of Experimental and Applied Physics, Czech Technical University in Prague, Horska 3a/22, CZ 12800 Prague 2 (Czech Republic); Charles University in Prague, First Faculty of Medicine, Salmovská 1,CZ-12000 Prague 2 (Czech Republic)

    2013-12-01

    Studies of radiation induced defects continue to be relevant as they find an ever greater application due to the increasing radiation doses to which semiconductor detectors are exposed. Efforts of figuring out the changes due to high radiation doses provide the fundamental motivation for this type of experiments. The PIN diode is described, and a developmental disorder caused thereto by 60Co source gamma quanta ranging from 100 kGy to 1 MGy. The calibration curve shows the effect of disturbances on the volt-ampere characteristics as a function of the dose of gamma radiation. The results are compared with earlier published data. Highlights: •We have studied Si PIN diode dosimeters irradiated by gamma. •We measured DLTS spectra and calculated energy traps caused by gamma irradiation. •Increasing dose caused creation of new traps and disappearance of others.

  11. Synergistic effects of interstitial impurities and radiation defects on mechanical characteristics of ferritic steels

    International Nuclear Information System (INIS)

    Charit, I.; Seok, C.S.; Murty, K.L.

    2007-01-01

    Ferritic steels are generally used in pressure vessels and various reactor support structures in light water reactors. They are known to exhibit radiation embrittlement in terms of decreased toughness and increased ductile-brittle transition temperature as a result of exposure to neutron radiation. The superimposed effects of strain aging due to interstitial impurity atoms on radiation embrittlement were considered first by Wechsler, Hall and others. Here we summarize some of our efforts on the investigation of synergistic effects between interstitial impurity atoms (IIAs) and radiation-induced point defects, which result in interesting effects at appropriate temperature and strain rate conditions. Two materials, a mild steel and a pressure vessel steel (A516 Gr.70), are evaluated using tensile and three-point bend tests

  12. Radiation defect formation in two-barrier structures based on silicon

    International Nuclear Information System (INIS)

    Madatov, R.S.; Abbasov, F.P.; Mustafayev, Yu.M.

    2013-01-01

    It was developed a silicon-based photodetector with high integral sensitivity in low-wave spectrum. It was investigated the effect of gamma radiation on the mechanism of current transport in the structure of Schottky barrier type and in transitions. It is shown that the double-barrier structures can improve the photovoltaic parameters of conventional detectors. For the first time it was obtained and studied the characteristics of two-barrier structures created on the same plane. The advantages over conventional structures are shown. The annealing point is changing the structure of radiation defects and leads to their disappearance

  13. Sigmoidal response model for radiation risk

    International Nuclear Information System (INIS)

    Kondo, Sohei

    1995-01-01

    From epidemiologic studies, we find no measurable increase in the incidences of birth defects and cancer after low-level exposure to radiation. Based on modern understanding of the molecular basis of teratogenesis and cancer, I attempt to explain thresholds observed in atomic bomb survivors, radium painters, uranium workers and patients injected with Thorotrast. Teratogenic injury induced by doses below threshold will be completely eliminated as a result of altruistic death (apoptosis) of injured cells. Various lines of evidence obtained show that oncomutations produced in cancerous cells after exposure to radiation are of spontaneous origin and that ionizing radiation acts not as an oncomutation inducer but as a tumor promoter by induction of chronic wound-healing activity. The tissue damage induced by radiation has to be repaired by cell growth and this creates opportunity for clonal expansion of a spontaneously occurring preneoplastic cell. If the wound-healing error model is correct, there must be a threshold dose range of radiation giving no increase in cancer risk. (author)

  14. Study of interaction among silicon, lithium, oxygen and radiation-induced defects for radiation-hardened solar cells

    Science.gov (United States)

    Berman, P. A.

    1973-01-01

    In order to improve reliability and the useful lifetime of solar cell arrays for space use, a program was undertaken to develop radiation-hardened lithium-doped silicon solar cells. These cells were shown to be significantly more resistant to degradation by ionized particles than the presently used n-p nonlithium-doped silicon solar cells. The results of various analyses performed to develop a more complete understanding of the physics of the interaction among lithium, silicon, oxygen, and radiation-induced defects are presented. A discussion is given of those portions of the previous model of radiation damage annealing which were found to be in error and those portions which were upheld by these extensive investigations.

  15. Medical response to radiation emergencies in Argentina

    International Nuclear Information System (INIS)

    Gisone, Pablo A.; Perez, Maria del R.; Dubner, Diana L.; Michelin, Severino C.; Vazquez, M.; Demayo, O.

    2006-01-01

    Although radiation accidents are not frequent, the increasing use of radioisotopes in medicine and industry increases the likelihood of such accidental situations. Additionally, risks posed by the malevolent use of radiation sources have been highlighted during the last few years. In this context, the enhancement of national capabilities for medical assistance of victims in radiation emergencies becomes relevant. This communication describes the organization of medical response to radiation emergencies existing in Argentina. A three-level system for medical response has been developed: pre-hospital response given on-site by local emergency services, assistance provided by emergency departments of local general hospitals and central reference hospitals for treatment of acute radiation syndrome, cutaneous radiation syndrome and internal contamination. An education and training program is regularly executed at the three levels, including theoretical background as well as practical training. Guidelines and protocols for medical handling of victims have been elaborated and implemented. Research and development of new strategies for diagnosis and treatment of radiation injuries are promoted by ARN in close collaboration with physicians belonging to reference hospitals. (author)

  16. Process of defect formation in alkaline halogenides contaminated with Eu2+ induced by non ionizing radiation

    International Nuclear Information System (INIS)

    Pedroza M, M.; Melendrez, R.; Barboza F, M.; Castaneda, B.

    2004-01-01

    The creation of defects in polluted alkaline halogenides with divalent impurities exposed to ionizing radiation is explained by means of the creation of auto trapped excitons (STE), which can be formed by means of the excitement of the halogen ion or through the trapping of electrons in centers V K taken place during the process of ionization of the halogen ion. The luminescent recombination of the exciton auto trapped produces a characteristic exciton luminescence and the recombination non radiative causes the formation of the Frenkel type defects, even of centers F - H. Experimentally has been demonstrated that the same type of glasses, exposed to radiation non ionizing of the type UV of around 230 nm, they produce defects similar Frenkel. The situation is interesting all time that photons of 230 nm (5.3 eV) they cannot create excitons directly since they are in an energy level of approximately 2.4 inferior eV to the necessary energy for the production of the same ones. In order to investigating the type of process of creation of defects with UV light energy below the energy of the band prohibited in polluted alkaline halogenides with Eu 2+ , mainly looking for experimental information that allows to explain the creation of defects taken place by the radiation non ionizing, one carries out the present work. It was found that, independently of the energy of the radiation used for the excitement, the emission comes from the transition 4f 6 5d(t 2g )-4f 7 ( 8 S 7/2 ) of the ion Eu 2+ characterized by a wide band centered in 420 nm and an additional component in 460 nm of possibly intrinsic origin. It was determined that so much the F centers and F z participate in the thermoluminescent processes and of optically stimulated luminescence, achieving to identify those peaks of Tl strictly associated to the F centers (peak in 470 K for the KCl: Eu 2+ ) and F z (peak in 370 K). Also, by means of a process of selective photo stimulation evidence was obtained that the F

  17. Study of grown-in and radiation-induced defects in indium phosphide

    International Nuclear Information System (INIS)

    Shaban, E.H.

    1986-01-01

    This research is focused on (1) conducting detailed theoretical and experimental study of grown-in and radiation-induced defects in liquid encapsulated Czohralski (LEC) grown, Zn-doped P-type indium phosphide (InP), (2) identifying the physical origin of the defects detected using Deep Level Transient Spectroscopy (DLTS) method, and (3) and developing a second-order model to interpret the presence of nonexponential capacitance transients in DLTS method. Analysis of grown-in and radiation-induced defects in P-type InP is undertaken. The main research results are summarized as follows: (1) DLTS analysis of grown-in defects in liquid LEC-grown, Zn-doped, P-type InP is made in this study. A single-hole trap of E/sub v/ + 0.52 eV is detected with a trap density of 1.8 x 10 15 cm -3 . The physical origin of this hole trap is attributed to a phosphorus vacancy or phosphorus interstitial-related defect. (2) One-MeV electron-irradiated P-type InP introduced two new hole traps, namely E/sub v/ + 0.34 and E/sub v/ + 0.58 eV with introduction rates (dN/sub T/d phi) of 0.4 and 1.2 per electron-cm, respectively. (3) A theoretical model is developed to interpret nonexponential capacitance transients in a deep-level transient spectroscopy method when the capture process competes with the dominant thermal-emission process

  18. Adriamycin resistance and radiation response

    International Nuclear Information System (INIS)

    Belli, J.A.; Harris, J.R.

    1979-01-01

    Mammalian cells (V79) in culture developed resistance to Adriamycin during continuous exposure to low levels of drug. This resistance was accompanied by change in x-ray survival properties which, in turn, depended upon the isolation of subpopulations from resistant sub lines. These changes in x-ray survival properties were characterized by reduced D/sub Q/ values and a decrease in the D/sub O/. However, these changes were not observed together in the same cell sub line. Adriamycin-resistant cells did not appear to be radiation damage repair deficient. Other phenotypic changes (cell morphology, DNA content and chromosome number) suggested mutational events coincident with the development of Adriamycin resistance

  19. Investigation of γ-radiation defect formation at the Si-SiO2 interface

    International Nuclear Information System (INIS)

    Zaynabidinov, S.; Yulchiev, Sh.; Aliev, R.

    2004-01-01

    Full text: In work the results of an experimental research of process radiating defects formation on border are submitted undressed Si-SiO 2 at γ-radiation of the silicon MOS structures. As against similar researches the basic attention is given on the analysis of generation-recombination characteristics of structures, that allowed to establish character of the defects formation both on border undressed Si-SiO 2 , and in about border of Si. In experiments the structures received by thermal oxidation at T=1000 deg. C in environment of dry oxygen n-Si substrates with specific resistance ρ=0.3 Ω·cm are used. The thickness of oxygen layer made ∼0.1 μm. The test MOS-structures with an aluminium electrode and area ∼0.01 cm 2 irradiated with γ-quanta from the 60 Co source by a dose of 10 6 rad. The choice of a dose of an radiation is caused by that at such dose the essential increase of concentration of superficial defects is observed, and at the same time there are no significant changes of parameters of a substrate because of formation of point defects in volume of silicon. The generation characteristics of structures such, as speed of superficial generation s and time of life τ g of carriers of a charge in about surface before and after an radiation defined by a method isothermal relaxation of nonequilibrium high-frequency capacity. The relaxation of nonequilibrium capacity registered at submission on translating structure in a condition of deeper inversion. Such mode of measurement allows to neglect the contribution which is brought in recharged of superficial condition in superficial generation currents. Are received relaxation dependence of structures before and after an radiation, and also spectra of distribution of density of superficial condition on width of the forbidden zone Si dN ss /dE. The increase at 12-15 of time of concentration of superficial condition with E=E c -(0.18±0.03) eV in the irradiated structures is established. Such condition is

  20. Radiation-induced gene responses

    International Nuclear Information System (INIS)

    Woloschak, G.E.; Paunesku, T.; Shearin-Jones, P.; Oryhon, J.

    1996-01-01

    In the process of identifying genes that are differentially regulated in cells exposed to ultraviolet radiation (UV), we identified a transcript that was repressed following the exposure of cells to a combination of UV and salicylate, a known inhibitor of NF-kappaB. Sequencing this band determined that it has identify to lactate dehydrogenase, and Northern blots confirmed the initial expression pattern. Analysis of the sequence of the LDH 5' region established the presence of NF-kappaB, Sp1, and two Ap-2 elements; two partial AP- 1; one partial RE, and two halves of E-UV elements were also found. Electromobility shift assays were then performed for the AP-1, NF- kappaB, and E-UV elements. These experiments revealed that binding to NF-kappaB was induced by UV but repressed with salicylic acid; UV did not affect AP-1 binding, but salicylic acid inhibited it alone or following UV exposure; and E-UV binding was repressed by UV, and salicylic acid had little effect. Since the binding of no single element correlated with the expression pattern of LDH, it is likely that multiple elements govern UV/salicylate-mediated expression

  1. Influence of rare earth elements on radiation defect formation in silicon

    International Nuclear Information System (INIS)

    Nazyrov, D.E.

    2006-01-01

    Full text: It is known that efficiency of form and kinetics annealing of radiation defects influence greatly presence of initial in controlling electrically active or inactive impurities, their concentration and position in a lattice of a semiconductor. From this point of view of impurities of group of rare earths elements (REE) are of great interest, they interact with primary radiation defects creating electrically passive complexes such as . Thus they increase radiation stability of silicon. The purpose of the given work was the investigation of effect of irradiation by γ-quanta 60 Co properties of silicon doped REE-by samarium, gadolinium and erbium. The doping of silicon was carried out by growth process. Concentration of REE - samarium, gadolinium and erbium in silicon according to neutron-activation analysis equaled 10 14 /5·10 18 cm 2 . Silicon doped by phosphorus - 15/50 Ωcm were used as control samples. The results of investigations were obtained from DLTS (deep level transient spectroscopy) measurements, Hall effect and electrical measurements on definition of a resistivity, lifetime of minority carriers of a charge and optically active of concentrations of oxygen and carbon. The optical recharge by the infrared light emitting diode (P=10 mV, λ=0,95 μm) was used for investigation of deep levels (DL) situated in lower half of band gap. In control samples irradiated by the γ-quanta 60 Co with a dose 10 16 / 5·10 18 cm -2 formation DL was found in band, the parameters of which are well-known: A-, E-centers etc. Depending on a dose of an effect of irradiate in an energy spectrum of radiation defects in Si of essential changes, except for concentration is not observed. The deep levels concentration the E c -0,17 eV and E c -0,4 eV in Si is essentially reduced with respect control samples. The comparison the dose of associations of observable levels in irradiated n-Si with similar associations in control samples shows, that a velocity of introduction

  2. Large-Scale Molecular Simulations on the Mechanical Response and Failure Behavior of a defective Graphene: Cases of 5-8-5 Defects

    Science.gov (United States)

    Wang, Shuaiwei; Yang, Baocheng; Yuan, Jinyun; Si, Yubing; Chen, Houyang

    2015-10-01

    Understanding the effect of defects on mechanical responses and failure behaviors of a graphene membrane is important for its applications. As examples, in this paper, a family of graphene with various 5-8-5 defects are designed and their mechanical responses are investigated by employing molecular dynamics simulations. The dependence of fracture strength and strain as well as Young’s moduli on the nearest neighbor distance and defect types is examined. By introducing the 5-8-5 defects into graphene, the fracture strength and strain become smaller. However, the Young’s moduli of DL (Linear arrangement of repeat unit 5-8-5 defect along zigzag-direction of graphene), DS (a Slope angle between repeat unit 5-8-5 defect and zigzag direction of graphene) and DZ (Zigzag-like 5-8-5 defects) defects in the zigzag direction become larger than those in the pristine graphene in the same direction. A maximum increase of 11.8% of Young’s modulus is obtained. Furthermore, the brittle cracking mechanism is proposed for the graphene with 5-8-5 defects. The present work may provide insights in controlling the mechanical properties by preparing defects in the graphene, and give a full picture for the applications of graphene with defects in flexible electronics and nanodevices.

  3. Health status of grandchildren of subjects occupationally exposed to chronic radiation. Communication 4. Congenital developmental defects

    International Nuclear Information System (INIS)

    Petrushkina, N.P.; Musatkova, O.B.

    1996-01-01

    The purpose of this study was to analyze the incidence and structure of cogenital developmental defects in the grandchildren of subjects occupationally exposed to chronic external gamma-irradiation. For 830 children only grandfather was exposed, for 259 only grandmother, and for 468 grandfather and grandmother. The mean equivalent doses for gonads by the moment of conception of future parents of the cohort examined ranged from 17.3 to 145.3 sSv. The incidence and structure of congenital developmental defects in 1557 grandchildren of occupationally exposed subjects differed from that in controls. Multifactorial analysis failed to establish the effect of grandparents' and parents' exposure on the development of diseases in the progeny. Factors other than radiation proved to be significant. 13 refs.; 1 tab

  4. Influence of radiation defects on electrical losses in silicon diodes irradiated with electrons

    International Nuclear Information System (INIS)

    Poklonski, N. A.; Gorbachuk, N. I.; Shpakovski, S. V.; Lastovskii, S. B.; Wieck, A.

    2010-01-01

    Silicon diodes with a p + -n junction irradiated with 3.5-MeV electrons (the fluence ranged from 10 15 to 4 x 10 16 cm -2 ) have been studied. It is established that the dependence of the tangent of the angle of electrical losses tanδ on the frequency f of alternating current in the range f = 10 2 -10 6 Hz is a nonmonotonic function with two extrema: a minimum and a maximum. Transformation of the dependences tanδ(f) as the electron fluence and annealing temperature are increased is caused by a variation in the resistance of n-Si (the base region of the diodes) as a result of accumulation (as the fluence is increased) or disappearance and reconfiguration (in the course of annealing) of radiation defects. The role of time lag of the defect recharging in the formation of tanδ(f) is insignificant.

  5. Electron radiation defects in TaCsub(1-x) and TiCsub(0.97)

    International Nuclear Information System (INIS)

    Morillo, J.; Novion, C.H. de; Dural, J.

    1981-08-01

    The electrical resistivity changes of TaCsub(0.99) and TaCsub(0.80) have been measured at 21 K during irradiation with electrons of incident energies ranging from 2.5 to 0.25 MeV: a non-zero production rate is observed, even at the lowest energies. The recovery of defects was followed up to 400 K for TaCsub(0.99) and TiCsub(0.97) irradiated with 2.25 MeV electrons and up to 160 K for TaCsub(0.80) irradiated with 0.75 MeV electrons. The results are compared to fast neutron radiation damage data. For TiCsub(0.97) and TaCsub(0.99), the contributions of the different defects to the production rates and recovery spectra are tentatively separated, and a rough estimate of Frenkel pair resistivities is given

  6. Study of a radiation point defects ensemble in thin GaAs layers implanted by Be+ and Se+ ions

    International Nuclear Information System (INIS)

    Shcherbachev, K.D.; Bublik, V.T.; Kuripyatnik, A.V.; Yurchuk, S.Yu.

    2001-01-01

    The behaviour of a radiation point defects ensemble in SI-GaAs(100) wafers implanted by Be + (a dose of 1x10 14 at/cm 2 , an energy of 50 and 150 keV) and Se + (a dose of 5x10 14 at/cm 2 , an energy of 150, 180 and 240 keV) ions are studied by a triple-crystal diffractometry method. The strain profile and a number of residual radiation point defects are shown to be determined by defects annihilation, their sink to the surface and rechanneling during the implantation [ru

  7. Study on radiation-responsive epigenomes

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jin Hong; Chung, Byung Yeop; Lee, Seung Sik; Moon, Yu Ran; Lee, Min Hee; Kim, Ji Hong [KAERI, Daejeon (Korea, Republic of)

    2011-01-15

    The purpose of this project is development of world-class headspring techniques of biological science for application of plant genomes/epigenomes through study on radiation- responsive epigenomes and improvement of the national competitiveness in the field of fundamental technology for biological science and industry. Research scope includes 1) Investigation of radiation-responsive epigenomes and elucidation of their relation with phenotypes, 2) Elucidation of interaction and transcription control of epigenomes and epigenetic regulators using ionizing radiation (IR), 3) Investigation of epigenome-mediated traits in plant development, differentiation and antioxidant defense using IR, and 4) Development of application techniques of radiation-responsive epigenomes for eco-monitoring and molecular breeding. Main results are as follow: Setup of conditions for chromatin immunoprecipitation in irradiated plants: investigation of aberrations in DNA methylation after treatment with different IR: elucidation of responses of epigenetic regulators to gamma rays (GR): investigation of aberrations in GR-responsive epigenetic regulators at different developmental stages: elucidation of interactive aberrations of epigenomes and epigenetic regulators after treatment of GR: comparison of functional genomes after treatment of GR or H{sub 2}O{sub 2}: elucidation of relation of epigenomes with GR-induced delay in senescence: elucidation of relation of epigenomes with GR-induced aberrations in pigment metabolism: comparison of antioxidant defense in epigenetic mutants: investigation of senescence-associated changes in epigenomes: investigation of senescence-associated changes in epigenetic regulators: comparison of aberrations in epigenomes at different dose of GR for mutation.

  8. Study on radiation-responsive epigenomes

    International Nuclear Information System (INIS)

    Kim, Jin Hong; Chung, Byung Yeop; Lee, Seung Sik; Moon, Yu Ran; Lee, Min Hee; Kim, Ji Hong

    2011-01-01

    The purpose of this project is development of world-class headspring techniques of biological science for application of plant genomes/epigenomes through study on radiation- responsive epigenomes and improvement of the national competitiveness in the field of fundamental technology for biological science and industry. Research scope includes 1) Investigation of radiation-responsive epigenomes and elucidation of their relation with phenotypes, 2) Elucidation of interaction and transcription control of epigenomes and epigenetic regulators using ionizing radiation (IR), 3) Investigation of epigenome-mediated traits in plant development, differentiation and antioxidant defense using IR, and 4) Development of application techniques of radiation-responsive epigenomes for eco-monitoring and molecular breeding. Main results are as follow: Setup of conditions for chromatin immunoprecipitation in irradiated plants: investigation of aberrations in DNA methylation after treatment with different IR: elucidation of responses of epigenetic regulators to gamma rays (GR): investigation of aberrations in GR-responsive epigenetic regulators at different developmental stages: elucidation of interactive aberrations of epigenomes and epigenetic regulators after treatment of GR: comparison of functional genomes after treatment of GR or H 2 O 2 : elucidation of relation of epigenomes with GR-induced delay in senescence: elucidation of relation of epigenomes with GR-induced aberrations in pigment metabolism: comparison of antioxidant defense in epigenetic mutants: investigation of senescence-associated changes in epigenomes: investigation of senescence-associated changes in epigenetic regulators: comparison of aberrations in epigenomes at different dose of GR for mutation

  9. Fanconi anemia: a disorder defective in the DNA damage response.

    Science.gov (United States)

    Kitao, Hiroyuki; Takata, Minoru

    2011-04-01

    Fanconi anemia (FA) is a cancer predisposition disorder characterized by progressive bone marrow failure, congenital developmental defects, chromosomal abnormalities, and cellular hypersensitivity to DNA interstrand crosslink (ICL) agents. So far mutations in 14 FANC genes were identified in FA or FA-like patients. These gene products constitute a common ubiquitin-phosphorylation network called the "FA pathway" and cooperate with other proteins involved in DNA repair and cell cycle control to repair ICL lesions and to maintain genome stability. In this review, we summarize recent exciting discoveries that have expanded our view of the molecular mechanisms operating in DNA repair and DNA damage signaling.

  10. Corrective measures and actions in response to defects

    International Nuclear Information System (INIS)

    1981-01-01

    This guideline presents a number of corrective measures which can be taken when the derived limits in the Code or the relevant action levels are exceeded. Appropriate actions to be taken for external β and γ radiation, airborne contamination, surface contamination and uranium or thorium concentrate spillage are specified

  11. Study on radiation-responsive epigenomes

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jin Hong; Lee, Seung Sik; Bae, Hyung Woo; Kim, Ji Hong; Kim, Ji Eun; Cho, Eun Ju; Lee, Min Hee; Moon, Yu Ran [KAERI, Daejeon (Korea, Republic of)

    2012-01-15

    The purpose of this project is development of world-class headspring techniques of biological science for application of plant genomes/epigenomes through study on radiation- responsive epigenomes and improvement of the national competitiveness in the field of fundamental technology for biological science and industry. Research scope includes 1) Investigation of radiation-responsive epigenomes and elucidation of their relation with phenotypes, 2) Elucidation of interaction and transcription control of epigenomes and epigenetic regulators using IR, 3) Investigation of epigenome-mediated traits in plant development, differentiation and antioxidant defense using IR, and 4) Development of application techniques of radiation-responsive epigenomes for eco-monitoring and molecular breeding. Main results are as follow: practical application of ChIP in GR-treated Arabidopsis using anti-histone antibodies: mapping of DNA methylomes associated with GR-responsive transcriptomes: setup of methylated DNA quantification using HPLC: elucidation of aberrations in epigenetic regulation induced by low-dose GR using gamma phytotron: comparison of gene expression of histone-modifying enzymes after treatment of GR: elucidation of transcriptomes and physiological alterations associated with delayed senescence of drd1-6 mutant: comparison of gene expression of DNA methylation-related enzymes in GR-treated rice callus and Arabidopsis: investigation of germination capacity, low-temperature, salinity and drought stress-resistance in drd1-6 epigenetic mutant: investigation of aberrations in DNA methylation depending on dose rates of gamma radiation

  12. Study on radiation-responsive epigenomes

    International Nuclear Information System (INIS)

    Kim, Jin Hong; Lee, Seung Sik; Bae, Hyung Woo; Kim, Ji Hong; Kim, Ji Eun; Cho, Eun Ju; Lee, Min Hee; Moon, Yu Ran

    2012-01-01

    The purpose of this project is development of world-class headspring techniques of biological science for application of plant genomes/epigenomes through study on radiation- responsive epigenomes and improvement of the national competitiveness in the field of fundamental technology for biological science and industry. Research scope includes 1) Investigation of radiation-responsive epigenomes and elucidation of their relation with phenotypes, 2) Elucidation of interaction and transcription control of epigenomes and epigenetic regulators using IR, 3) Investigation of epigenome-mediated traits in plant development, differentiation and antioxidant defense using IR, and 4) Development of application techniques of radiation-responsive epigenomes for eco-monitoring and molecular breeding. Main results are as follow: practical application of ChIP in GR-treated Arabidopsis using anti-histone antibodies: mapping of DNA methylomes associated with GR-responsive transcriptomes: setup of methylated DNA quantification using HPLC: elucidation of aberrations in epigenetic regulation induced by low-dose GR using gamma phytotron: comparison of gene expression of histone-modifying enzymes after treatment of GR: elucidation of transcriptomes and physiological alterations associated with delayed senescence of drd1-6 mutant: comparison of gene expression of DNA methylation-related enzymes in GR-treated rice callus and Arabidopsis: investigation of germination capacity, low-temperature, salinity and drought stress-resistance in drd1-6 epigenetic mutant: investigation of aberrations in DNA methylation depending on dose rates of gamma radiation

  13. Initial Human Response to Nuclear Radiation

    Science.gov (United States)

    1982-04-01

    symptomatic response to radiation. In the second phase, the models will be used to infer performance effects. DNA staff members Cyrus Knowles and David ...P. Setty ATTN: K. Schwartz ATTN: J. NcGahan Kamn Tempo System Planning Corp ATTN: R. Miller ATTN: J. JonesATTN: G. Perks Kamen Tempo AiT: S. Shrier

  14. Microstructural evolution of radiation induced defects in ZnO during isochronal annealing

    International Nuclear Information System (INIS)

    Brunner, S.; Puff, W.; Balogh, A.G.

    1999-01-01

    In this study the authors discuss the microstructural changes after electron and proton irradiation and the thermal evolution of the radiation induced defects during isochronal annealing. The nominally undoped samples were irradiated either with 3 MeV protons to a fluence of 1.2 x 10 18 p/cm 2 or with 1 MeV electrons to a fluence of 1 x 10 18 e/cm 2 . The investigation was performed with positron lifetime and Doppler-Broadening measurements. The measurements were done at room temperature and in some cases down to 10 K to investigate the thermal dependence of the trapping characteristics of the positrons

  15. Electric field effects on radiation defects annealing in p-InP

    International Nuclear Information System (INIS)

    Sibille, A.

    1983-01-01

    Annealing experiments have been performed on electron irradiated Schottky diodes on p-InP. They show a strong influence of the applied reverse bias during annealing on the recovery of the free holes concentration, as well as on the disappearance of the dominant radiation induced hole traps detected by deep level transient spectroscopy (DLTS). Compensating defects are observed to drift under the action of the electric field and accumulate at the edge of the depleted zone, while the main hole traps created by the irradiation anneal faster when empty of holes or subjected to an electric field. (author)

  16. Radiation-induced defects in chalcogenide glasses characterized by combined optical spectroscopy, XPS and PALS methods

    Energy Technology Data Exchange (ETDEWEB)

    Shpotyuk, O. [Institute of Physics of Jan Dlugosz University, 13/15 al. Armii Krajowej, Czestochowa 42201 (Poland); Lehigh University, 5 East Packer Avenue, Bethlehem, PA 18015-3195 (United States); Lviv Institute of Materials of SRC ' ' Carat' ' , 202, Stryjska str., 79031 Lviv (Ukraine); Kovalskiy, A.; Jain, H. [Lehigh University, 5 East Packer Avenue, Bethlehem, PA 18015-3195 (United States); Golovchak, R. [Lehigh University, 5 East Packer Avenue, Bethlehem, PA 18015-3195 (United States); Lviv Institute of Materials of SRC ' ' Carat' ' , 202, Stryjska str., 79031 Lviv (Ukraine); Zurawska, A. [Opole University of Technology, 75, Ozimska str., Opole 45370 (Poland)

    2007-03-15

    Temperature-dependent optical absorption spectroscopy, high-resolution X-ray photoelectron spectroscopy and positron annihilation lifetimes spectroscopy are utilized to understand radiation-induced changes in Ge-Sb-S chalcogenide glasses. Theoretically predicted topological scheme of {gamma}-induced coordination defect formation in stoichiometric Ge{sub 23.5}Sb{sub 11.8}S{sub 64.7} glass composition is supported by these measurements. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  17. Complex of GRAD programs for analytical calculation of radiation defects generation in solids

    International Nuclear Information System (INIS)

    Suvorov, A.L.; Zabolotnyj, V.T.; Babaev, V.P.

    1989-01-01

    Complex of programms for analytical calculation of generation of radiation defects (GRAD) in solids, and also of their recombination during cascade area relaxation and postradiation annealing, of mass removing by atomic collisions in volume (mixing) and through the surface (sputtering), of structure - phase state and property changes is suggested. The complex volume is less than 10 KBytes and it may be realized by computer of any type. Satisfactional agreement with more wide range of experimental data in comparison with tradition models is obtained. 27 refs.; 2 figs

  18. Responsibility structure in medical radiation applications

    International Nuclear Information System (INIS)

    Beekman, Z.M.

    1989-01-01

    The author discusses the various aspects of the responsibilities of physicians and clinical physicists with regard to radiation protection in medical applications of ionizing radiation. It becomes still clearer that the physician, who carries out the examination or the treatment, also has to bear the responsibility. this holds for the indication assessment as well as for optimization of the quality of the examination or treatment versus radiation burden of the patient, radiologic worker and thirds. Further it is clear that the physician in these will have to delegate specific tasks and responsibilities, whether or not in the elongated-arm construction. The clinical physicist is responsible in particular for the applications of the physical methods and watches the quality of the apparatus and methods used. As such he also is responsible for the technical workers, who take care of the preventive and corrective maintenance. The principal responsibility of the clinical physicist however lies in the field of standardization and calibration of medical-physical instruments. Besides this investigation into and development of new techniques, methods and apparatus come up, while also education and training of various profession groups involved need attention. (author). 6 refs.; 1 tab

  19. Incidence of neural tube defects in the natural radiation coastal areas of Kerala

    International Nuclear Information System (INIS)

    Jaikrishan, G.; Sudheer, K.R.; Andrews, V.J.; Koya, P.K.M.; Cheriyan, V.D.; Seshadri, M.

    2010-01-01

    All consecutive births in selected government hospitals in and around the high level natural background radiation areas (HLNRA) of Kerala were monitored for congenital malformations observable at birth since 1995. The HLNR area, a coastal strip of land about 55 km in length and 0.5 km in breadth from Purakkad in the north in Alleppey district to Sakthikulangara in the south of Quilon district, stands out among the most prominent background radiation areas of the world. Natural deposit of monazite sand, containing Thorium (8-10%), Uranium (0.3%) and corresponding decay products, is the source of elevated background radiation, ranging from < 1 to 45 mGy/year. Wide variation in dose, due to the patchy and non-uniform distribution of Monazite sand, enables in built controls. High population density, limited migration, ethnic diversity, good literacy, health awareness, institutionalized births and acceptance of small family norm are some of the key features of the population. Areas with a mean radiation dose of more than 1.5 mGy/year were treated as HLNR areas and areas with a dose level of 1.5 mGy/year or less were treated as normal level radiation (NLNR) areas. The study carried out since 1995 does not seem to implicate HLNR in the incidence of neural tube defects among newborns

  20. Low-dose ionizing radiation alleviates Aβ42-induced defective phenotypes in Drosophila Alzheimer's disease models

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, SooJin; Jeong, Hae Min; Nam, Seon Young [Low-dose Radiation Research Team, Radiation Health Institute, Korea Hydro & Nuclear Power Co. Ltd., Daejeon (Korea, Republic of)

    2017-04-15

    Alzheimer's disease (AD) is the most common neurodegenerative disease that is characterized by amyloid plaques, progressive neuronal loss, and gradual deterioration of memory. Amyloid imaging using positron emission tomography (PET) radiotracers have been developed and approved for clinical use in the evaluation of suspected neurodegenerative disease, including AD. Particularly, previous studies involving low-dose ionizing radiation on Aβ 42-treated mouse hippocampal neurons have suggested a potential role for low-dose ionizing radiation in the treatment of AD. However, associated in vivo studies involving the therapy effects of low-dose ionizing radiation on AD are still insufficient. As a powerful cell biological system, Drosophila AD models have been generated and established a useful model organism for study on the etiology of human AD. In this study, we investigated the hormesis effects of low-dose ionizing radiation on Drosophila AD models. Our results suggest that low-dose ionizing radiation have the beneficial effects on not only the Aβ42-induced developmental defective phenotypes but also motor defects in Drosophila AD models. These results might be due to a regulation of apoptosis, and provide insight into the hormesis effects of low-dose ionizing radiation. Our results suggest that low-dose ionizing radiation have the beneficial effects on not only the Aβ42-induced developmental defective phenotypes but also motor defects in Drosophila AD models. These results might be due to a regulation of apoptosis, and provide insight into the hormesis effects of low-dose ionizing radiation.

  1. Radiation, Inflammation, and Immune Responses in Cancer

    Energy Technology Data Exchange (ETDEWEB)

    Multhoff, Gabriele [Department of Radiation Oncology, Klinikum rechts der Isar, Technische Universität München, Munich (Germany); Helmholtz Zentrum München, Clinical Cooperation Group Innate Immunity in Tumor Biology, Munich (Germany); Radons, Jürgen, E-mail: raj10062@web.de [multimmune GmbH, Munich (Germany)

    2012-06-04

    Chronic inflammation has emerged as one of the hallmarks of cancer. Inflammation also plays a pivotal role in modulating radiation responsiveness of tumors. As discussed in this review, ionizing radiation (IR) leads to activation of several transcription factors modulating the expression of numerous mediators in tumor cells and cells of the microenvironment promoting cancer development. Novel therapeutic approaches thus aim to interfere with the activity or expression of these factors, either in single-agent or combinatorial treatment or as supplements of the existing therapeutic concepts. Among them, NF-κB, STAT-3, and HIF-1 play a crucial role in radiation-induced inflammatory responses embedded in a complex inflammatory network. A great variety of classical or novel drugs including nutraceuticals such as plant phytochemicals have the capacity to interfere with the inflammatory network in cancer and are considered as putative radiosensitizers. Thus, targeting the inflammatory signaling pathways induced by IR offers the opportunity to improve the clinical outcome of radiation therapy by enhancing radiosensitivity and decreasing putative metabolic effects. Since inflammation and sex steroids also impact tumorigenesis, a therapeutic approach targeting glucocorticoid receptors and radiation-induced production of tumorigenic factors might be effective in sensitizing certain tumors to IR.

  2. Radiation, Inflammation, and Immune Responses in Cancer

    International Nuclear Information System (INIS)

    Multhoff, Gabriele; Radons, Jürgen

    2012-01-01

    Chronic inflammation has emerged as one of the hallmarks of cancer. Inflammation also plays a pivotal role in modulating radiation responsiveness of tumors. As discussed in this review, ionizing radiation (IR) leads to activation of several transcription factors modulating the expression of numerous mediators in tumor cells and cells of the microenvironment promoting cancer development. Novel therapeutic approaches thus aim to interfere with the activity or expression of these factors, either in single-agent or combinatorial treatment or as supplements of the existing therapeutic concepts. Among them, NF-κB, STAT-3, and HIF-1 play a crucial role in radiation-induced inflammatory responses embedded in a complex inflammatory network. A great variety of classical or novel drugs including nutraceuticals such as plant phytochemicals have the capacity to interfere with the inflammatory network in cancer and are considered as putative radiosensitizers. Thus, targeting the inflammatory signaling pathways induced by IR offers the opportunity to improve the clinical outcome of radiation therapy by enhancing radiosensitivity and decreasing putative metabolic effects. Since inflammation and sex steroids also impact tumorigenesis, a therapeutic approach targeting glucocorticoid receptors and radiation-induced production of tumorigenic factors might be effective in sensitizing certain tumors to IR.

  3. Interaction between radiation-induced defects and lithium impurity atoms in germanium

    International Nuclear Information System (INIS)

    Vasil'eva, E.D.; Daluda, Yu.N.; Emtsev, V.V.; Kervalishvili, P.D.; Mashovets, T.V.

    1981-01-01

    The effect of gamma radiation on germanium doped with lithium in the course of extraction from a melt was studied. 60 Co γ-ray irradiation with the 6.2x10 12 cm -2 x1 -1 intensity was performed at 300 K. The temperature dependences of conductivity and Hall effect was studied in the 4.2-300 K range. It was shown that using this alloying technique lithium atoms in germanium were in a ''free'' state. It was found that on irradiation the lithium atom concentration decreases as a result of production of electrically inactive complexes with participation of lithium atoms. Besides this principal process secondary ones are observed: production of radiation donor-defects with the ionization energy Esub(c) of 80 MeV and compensating acceptors

  4. Influence of pretreatment temperature cycling on the radiating defect formation in silicon doped by samarium

    International Nuclear Information System (INIS)

    Abdurakhmanov, K.P.; Nazyrov, D.E.

    2006-01-01

    Full text: The raise of thermal and radiation stability as it is known, is one of actual problems of physics semiconductors. Recently it is established, that the rare-earth elements (REE) raise a stability of silicon to exterior action. In this connection the investigation of silicon doped REE by samarium and influence on its properties of heat treatments and radiation exposure is important. In sectional operation the outcomes of investigations of influence of samarium on thermal (600 degree C are reduced; 600 deg. + 900 deg. C; 900 deg. C; 900 deg. C + 600 deg. C; 1100 deg. C; 600 deg. C + 900 deg. C + 1100 deg. C; 900 deg. C + 600 deg. C + 1100 deg. C) thermal defect formation and radiation defect formation (exposure of γ-quanta 60 Co) both in beforehand wrought, and in thermally unfinished samples. After each cycle of heat treatments samples cool fast (throwing off in oil) or slowly (together with the furnace). Doping n-silicon REE by gadolinium and samarium was carried out during cultivation. The concentration of gadolinium and samarium in silicon, on sectional of a neutron-activation analysis was equaled 10 14 - 10 18 cm -3 . As control is model monocrystal silicon such as KEP-15/50. Para-meters of deep levels originating in control and doped REE samples, both past heat treatment or temperature cycling, and irradiated by the γ-quanta are defined by methods of a capacity spectroscopy: DLTS and IRC. The obtained outcomes have shown, that in irradiated with the γ-quanta 60 Co deep levels samples are formed with energies: E C -0,17 eV, E C -0,32 eV, EC-0,41 eV. Thus the parameters of deep levels vary depending on requirements of prestress heat treatment. For example heat treatment at 600 deg. C essentially increments a velocity of introduction of and centre (deep level of E C -0,17 eV), in comparison with a velocity of introduction of this level in samples with prestress heat treatment at 900 deg. C. In samples n-Si doped by samarium effectiveness of formation

  5. Annealing study on radiation-induced defects in 6H-SiC

    International Nuclear Information System (INIS)

    Pinheiro, M.V.B.; Lingner, T.; Caudepon, F.; Greulich-Weber, S.; Spaeth, J.M.

    2004-01-01

    We present the results of a systematic isochronal annealing investigation of vacancy-related defects in electron-irradiated n-type 6H-SiC:N. A series of 10 samples cut from a commercial wafer and annealed up to 1200 C after electron-irradiation (1.5 x 10 18 cm -3 ) was characterized with photoluminescence (PL), Magnetic circular dichroism of the absorption (MCDA) and conventional electron paramagnetic resonance (EPR). Apart from less stable triplet-related defects which vanished between 150 C and 300 C, the thermal behavior of three radiation-induced defects was studied: the silicon vacancy (V Si ), the carbon-antisite-carbon-vacancy pair (C Si -V C ) and the D1 center. Their annealing behavior showed that the destruction of the isolated V Si between 750 C and 900 C is followed by the formation of thermally more stable C Si -V C pairs, a result that has been theoretically predicted recently. By further heating the samples the C Si -V C pairs are annealed out between 900 C and 1050 C and were followed by an increase in the D1 center concentration. (orig.)

  6. Defects of a mammography quality control phantom visualized by synchrotron radiation imaging

    International Nuclear Information System (INIS)

    Imamura, Keiko; Fukuda, Mamoru; Ehara, Norishige; Miyamoto, Keiko; Kanemaki, Yoshihide; Ogata, Haruki; Nakajima, Yasuo

    2002-01-01

    Synchrotron radiation (SR) imaging of an RMI 156 mammography quality control phantom, serial number 156-15330, revealed some defects which degraded the visibility of calcification specks. SR imaging was performed at SPring-8, in Harima, Japan by using a monochromatic energy of 20 keV with a field-of-view of 24 X 24 mm. Different kinds of images were obtained by changing sample-to-detector distances; absorption images and refraction-enhanced images. Specks were embedded in a wax matrix and were imaged as black in an absorption image. In a refraction-enhanced image, they were imaged as a black region with white margins. Foreign objects with opposite contrast were detected near, or overlapped with, some specks. As they were depicted as white in the absorption image and as white with a black margin in the refraction-enhanced image, it seemed that they had low X-ray attenuation and a low refraction index compared with the surrounding wax. They might presumable be air bubbles. Visibility of specks in an absorption image was seriously interfered with when those object(s) overlapped with specks. This kind of defect may cause a difficulty in meeting quality assurance specifications when a facility inadvertently purchases defective phantoms. (author)

  7. Radiation response of the central nervous system

    International Nuclear Information System (INIS)

    Schultheiss, T.E.; Kun, L.E.; Ang, K.K.; Stephens, L.C.

    1995-01-01

    This report reviews the anatomical, pathophysiological, and clinical aspects of radiation injury to the central nervous system (CNS). Despite the lack of pathognomonic characteristics for CNS radiation lesions, demyelination and malacia are consistently the dominant morphological features of radiation myelopathy. In addition, cerebral atrophy is commonly observed in patients with neurological deficits related to chemotherapy and radiation, and neurocognitive deficits are associated with diffuse white matter changes. Clinical and experimental dose-response information have been evaluated and summarized into specific recommendations for the spinal cord and brain. The common spinal cord dose limit of 45 Gy in 22 to 25 fractions is conservative and can be relaxed if respecting this limit materially reduces the probability of tumor control. It is suggested that the 5% incidence of radiation myelopathy probably lies between 57 and 61 Gy to the spinal cord in the absence of dose modifying chemotherapy. A clinically detectable length effect for the spinal cord has not been observed. The effects of chemotherapy and altered fractionation are also discussed. Brain necrosis in adults is rarely noted below 60 Gy in conventional fractionation, with imaging and clinical changes being observed generally only above 50 Gy. However, neurocognitive effects are observed at lower doses, especially in children. A more pronounced volume effect is believed to exist in the brain than in the spinal cord. Tumor progression may be hard to distinguish from radiation and chemotherapy effects. Diffuse white matter injury can be attributed to radiation and associated with neurological deficits, but leukoencephalopathy is rarely observed in the absence of chemotherapy. Subjective, objective, management, and analytic (SOMA) parameters related to radiation spinal cord and brain injury have been developed and presented on ordinal scales

  8. Radiation response of the central nervous system

    International Nuclear Information System (INIS)

    Schultheiss, T.E.; Kun, L.E.; Stephens, L.C.

    1995-01-01

    This report reviews the anatomical, pathophysiological, and clinical aspects of radiation injury to the central nervous system (CNS). Despite the lack of pathoGyomonic characteristics for CNS radiation lesions, demyelination and malacia are consistently the dominant morphological features of radiation myelopathy. In addition, cerebral atrophy is commonly observed in patients with neurological deficits related to chemotherapy and radiation, and neurocognitive deficits are associated with diffuse white matter changes. Clinical and experimental dose-response information have been evaluated and summarized into specific recommendations for the spinal cord and brain. The common spinal cord dose limit of 45 Gn in 22 to 25 fractions is conservative and can be relaxed if respecting this limit materially reduces the probability of tumor control. It is suggested that the 5% incidence of radiation myelopathy probably lies between 57 and 61 Gy to the spinal cord in the absence of dose modifying chemotherapy. A clinically detectable length effect for the spinal cord has not been observed. The effects of chemotherapy and altered fractionation are also discussed. Brain necrosis in adults is rarely noted below 60 Gy in conventional fractionation, with imaging and clinical changes being observed generally only above 50 Gy. However, neurocognitive effects are observed at lower doses, especially in children. A more pronounced volume effect is believed to exist in the brain than in the spinal cord. Tumor progression may be hard to distinguish from radiation and chemotherapy effects. Diffuse white matter injury can be attributed to radiation and associated with neurological deficits, but leukoencephalopathy is rarely observed in the absence of chemotherapy. Subjective, objective, management, and analytic (SOMA) parameters related to radiation spinal cord and brain injury have been developed and presented on ordinal scales. 140 refs., 3 figs., 6 tabs

  9. Investigation of anisotropy in EPR spectra of radiation defects in irradiated beryllium ceramics

    International Nuclear Information System (INIS)

    Polyakov, A.I.; Ryabikin, Yu.A.; Zashkvara, O. V.; Bitenbaev, M.I.; Petukhov, Yu. V.

    2004-01-01

    Full text: In this work results of analysis of anisotropy and hyperfine structure in EPR spectra of paramagnetic defects in irradiated samples of beryllium ceramics are presented. To explain peculiarities in a shape and parameters of the EPR spectrum hyperfine structure in beryllium ceramics, we have analyzed several versions of model representations for the radiation-induced paramagnetic defects uniformly distributed in a sample as well as for cluster defects which hyperfine structure is determined by interactions between electrons and nuclei of impurity atoms (S=1/2) and which are characterized by anisotropy in the g factors. Calculations of a shape of the uniformly widened EPR spectra are carried out by the model of random interactions between electron spins. The EPR spectra, widened at the expense of anisotropy in the g factors, are calculated by the following equation: g(Δ)=[2(ω-ω 0 )+α] -1/2 , where ω 0 =γH 0 , α is the quantify proportional to the anisotropy shift. To describe wings of spectral lines, where the equation doesn't work, we use the Gaussian function. To determine the frequency of precession of electron spins packages with local concentration N loc , the following expression is used: ω=ω 0 +1/2α(3cos 2 θ-1), where θ is an angle between the symmetry axis and the direction of the external magnetic field. It is shown that the best agreement between the calculated and experimental EPR spectra is observed with the following computational model: paramagnetic radiation defects are distributed uniformly over a ceramics sample, and the g factors of its EPR spectra have the anisotropy typical for dipole-dipole interaction in powder samples. By results of the data we obtained, it's clear that in future we'll need in more detailed information than that published in scientific journals about formation of the paramagnetic defect EPR spectra structure in beryllium oxides and ceramics at the expense of resonance line hyperfine splitting on atoms of

  10. Investigation of anisotropy in EPR spectra of radiation defects in irradiated beryllium ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Polyakov, A I; Ryabikin, Yu A; Zashkvara, O V; Bitenbaev, M I; Petukhov, Yu V [Inst. of Physics and Technology, Almaty (Kazakhstan)

    2004-07-01

    Full text: In this work results of analysis of anisotropy and hyperfine structure in EPR spectra of paramagnetic defects in irradiated samples of beryllium ceramics are presented. To explain peculiarities in a shape and parameters of the EPR spectrum hyperfine structure in beryllium ceramics, we have analyzed several versions of model representations for the radiation-induced paramagnetic defects uniformly distributed in a sample as well as for cluster defects which hyperfine structure is determined by interactions between electrons and nuclei of impurity atoms (S=1/2) and which are characterized by anisotropy in the g factors. Calculations of a shape of the uniformly widened EPR spectra are carried out by the model of random interactions between electron spins. The EPR spectra, widened at the expense of anisotropy in the g factors, are calculated by the following equation: g({delta})=[2({omega}-{omega}{sub 0})+{alpha}]{sup -1/2}, where {omega}{sub 0}={gamma}H{sub 0}, {alpha} is the quantify proportional to the anisotropy shift. To describe wings of spectral lines, where the equation doesn't work, we use the Gaussian function. To determine the frequency of precession of electron spins packages with local concentration N{sub loc}, the following expression is used: {omega}={omega}{sub 0}+1/2{alpha}(3cos{sup 2}{theta}-1), where {theta} is an angle between the symmetry axis and the direction of the external magnetic field. It is shown that the best agreement between the calculated and experimental EPR spectra is observed with the following computational model: paramagnetic radiation defects are distributed uniformly over a ceramics sample, and the g factors of its EPR spectra have the anisotropy typical for dipole-dipole interaction in powder samples. By results of the data we obtained, it's clear that in future we'll need in more detailed information than that published in scientific journals about formation of the paramagnetic defect EPR spectra structure in

  11. Natural products as radiation response modifiers

    International Nuclear Information System (INIS)

    Colin Seymour; Carmel Mothersill

    2007-01-01

    Complete text of publication follows. Protection of cells and organisms against low doses of radiation is a complex issue which must be considered at the level of cells, tissues and organisms. 'Protection' at one level, for example, prevention of cell death, may be adverse at another level, if it allows a damaged cell to survive and form a malignant tumour. Conversely, death of a cell carrying damage can be protective for the organism if it eliminates a damaged cell. Thus, it is important to understand the mechanisms involved in protection against radiation damage at several hierarchical levels. The use of natural products as radiation response modifiers is very attractive. Many of these compounds are readily available and their function and pharmacology is well understood. Some derive from venoms or natural defenses and are currently used in medicine, others include vitamins, antioxidants or cofactors, which are tried and tested nutritional supplements. Radiation effects may be targeted or untargeted. Radiation may interact directly within a cell causing a direct DNA lesion or it may elicit a bystander response from the irradiated cell. A bystander effect is produced when the irradiated cell apparently exhibits no damage from the radiation, but passes on a biochemical signal which induces neighbouring cells to apoptose or undergo a number of other responses usually associated with irradiation such as mutation induction, transformation, induction of ROS responses etc.. Effects induced in progeny of non-targeted cells in receipt of bystander signals include genetic instability, mini and microsatellite mutations and carcinogenesis. A key characteristic of these non targeted effects is that they occur at very low acute doses (of the order of 5mGy) and saturate so that effective prevention requires an agent which can effectively shut off the mechanism. While the mechanism is not fully known, it is thought to involve signals from irradiated cells communicating via

  12. Effect of radiation doses rate on SOS response induction in irradiated Escherichia coli Cells

    International Nuclear Information System (INIS)

    Cuetara Lugo, Elizabeth B.; Fuentes Lorenzo, Jorge L.; Almeida Varela, Eliseo; Prieto Miranda, Enrique F.; Sanchez Lamar, Angel; Llagostera Casal, Montserrat

    2005-01-01

    The present work is aimed to study the effect of radiation dose rate on the induction of SOS response in Escherichia coli cells. We measured the induction of sul A reporter gene in PQ-37 (SOS Chromotest) cells. Lead devises were built with different diameter and these were used for diminishing the dose rate of PX- -30M irradiator. Our results show that radiation doses rate significantly modifies the induction of SOS response. Induction factor increases proportionally to doses rate in Escherichia coli cells defective to nucleotide excision repair (uvrA), but not in wild type cells. We conclude that the dose rate affects the level of induction of SOS response

  13. Non-stoichiometry defects and radiation hardness of lead tungstate crystals PbWO sub 4

    CERN Document Server

    Devitsin, E G; Potashov, S Yu; Terkulov, A R; Nefedov, V A; Polyansky, E V; Zadneprovski, B I; Kjellberg, P; Korbel, V

    2002-01-01

    It has been stated many times that the formation of radiation infringements in PbWO sub 4 is to a big extent stipulated by the non-stoichiometry defects of the crystals, arising in the process of their growth and annealing. To refine the idea of characteristics of the non-stoichiometry defects and their effect on the radiation hardness of PbWO sub 4 , the current study is aimed at the melt composition infringements during its evaporation and at optical transmission of crystals obtained in these conditions after their irradiation ( sup 1 sup 3 sup 7 Cs source). In the optical transmission measurements along with traditional techniques a method 'in situ' was used, which provided the measurements in fixed points of the spectrum (380, 470 and 535 nm) directly in the process of the irradiation. X-ray phase and fluorescence analysis of condensation products of vapours over PbWO sub 4 melt has found PbWO sub 4 phase in their content as well as compounds rich in lead PbO, Pb sub 2 WO sub 5 with overall ratio Pb/W (3....

  14. Non-stoichiometry Defects and Radiation Hardness of Lead Tungstate Crystals PbWO4

    CERN Document Server

    Devitsin, E G; Kozlov, V A; Nefedov, L; Polyansky, E V; Potashov, S Yu; Terkulov, A R; Zadneprovski, B I

    2001-01-01

    It has been stated many times that the formation of radiation infringements in PbWO4 is to big extent stipulated by non-stoichiometry defects of the crystals, arising in the process of their growth and annealing. To refine the idea of characteristics of non-stoichiometry defects and their effect on the radiation hardness of PbWO4 the current study is aimed at the melt composition infringements during its evaporation and at optical transmission of crystals obtained in these conditions after their irradiation (137Cs source). In the optical transmission measurements along with traditional techniques a method "in situ" was used, which provided the measurements in fixed points of the spectrum (380, 470 and 535 nm) directly in the process of the irradiation. X-ray phase and fluorescence analysis of condensation products of vapours over PbWO4 melt has found PbWO4 phase in their content as well as compounds rich in lead, PbO, Pb2WO5, with overall ratio Pb/W = 3.2. Correspondingly the lack of lead and variations in th...

  15. Tritium release kinetics of Li{sub 2}O with radiation defects

    Energy Technology Data Exchange (ETDEWEB)

    Grishmanov, V; Tanaka, Satoru [Tokyo Univ. (Japan). Faculty of Engineering

    1998-03-01

    The study of an influence of radiation defects on tritium release behavior from polycrystalline Li{sub 2}O was performed by the in-pile and out-of-pile tritium release experiments. The samples were pre-irradiated by accelerated electrons to various absorbed doses up to 140 MGy and then exposed to the fluence of 10{sup 17} thermal neutrons/m{sup 2}. The radiation defects introduced by electron irradiation in Li{sub 2}O cause the retention of tritium. The linear temperature increase of the electron-irradiated samples disclosed two tritium release peaks: first starts at {approx}600 K with the maximum at {approx}800 K and second appears at {approx}950 K with the maximum at {approx}1200 K. It is thought that the tritium release at high temperatures (> 950 K) is due to the thermal decomposition of LiT. In order to further investigated the formation of lithium hydrides, the diffuse-reflectance Fourier transform infrared (FTIR) absorption spectroscopy was applied. The Li{sub 2}O powder was irradiated by electron accelerator under D{sub 2} containing atmosphere (N{sub 2} + 10% D{sub 2}). An absorption band specific to the Li{sub 2}O was observed at 668 cm{sup -1} and attributed to the Li-D stretching vibration. (author)

  16. Description of radiation damage in diamond sensors using an effective defect model

    Energy Technology Data Exchange (ETDEWEB)

    Kassel, Florian [Institute for Experimental Nuclear Physics (IEKP), KIT, Karlsruhe (Germany); CERN, Meyrin (Switzerland); Guthoff, Moritz; Dabrowski, Anne [CERN, Meyrin (Switzerland); Boer, Wim de [Institute for Experimental Nuclear Physics (IEKP), KIT, Karlsruhe (Germany)

    2017-11-15

    The Beam Condition Monitoring Leakage (BCML) system is a beam monitoring device in the CMS experiment at the LHC consisting of 32 poly-crystalline (pCVD) diamond sensors. The BCML sensors, located in rings around the beam, are exposed to high particle rates originating from the colliding beams. These particles cause lattice defects, which act as traps for the ionized charge carrier leading to a reduced charge collection efficiency (CCE). The radiation induced CCE degradation was, however, much more severe than expected from low rate laboratory measurements. Measurement and simulations presented in this paper show that this discrepancy is related to the rate of incident particles. At high particle rates, the trapping rate of the ionization is strongly increased compared to the detrapping rate leading to an increased build-up of space charge. This space charge locally reduces the internal electric field increasing the trapping rate and hence reducing the CCE even further. In order to connect these macroscopic measurements with the microscopic defects acting as traps for the ionization charge, the TCAD simulation program SILVACO was used. It allows to introduce the defects as effective donor and acceptor levels, and can calculate the electric field from Transient Current Technique (TCT) signals and CCE as a function of the effective trap properties, like density, energy level, and trapping cross section. After each irradiation step, these properties were fitted to the data on the electric field from the TCT signals and CCE. Two effective acceptor and donor levels were needed to fit the data after each step. It turned out that the energy levels and cross sections could be kept constant and the trap density was proportional to the cumulative fluence of the irradiation steps. The highly non-linear rate dependent diamond polarization and the resulting signal loss can be simulated using this effective defect model and is in agreement with the measurement results

  17. Description of radiation damage in diamond sensors using an effective defect model

    International Nuclear Information System (INIS)

    Kassel, Florian; Guthoff, Moritz; Dabrowski, Anne; Boer, Wim de

    2017-01-01

    The Beam Condition Monitoring Leakage (BCML) system is a beam monitoring device in the CMS experiment at the LHC consisting of 32 poly-crystalline (pCVD) diamond sensors. The BCML sensors, located in rings around the beam, are exposed to high particle rates originating from the colliding beams. These particles cause lattice defects, which act as traps for the ionized charge carrier leading to a reduced charge collection efficiency (CCE). The radiation induced CCE degradation was, however, much more severe than expected from low rate laboratory measurements. Measurement and simulations presented in this paper show that this discrepancy is related to the rate of incident particles. At high particle rates, the trapping rate of the ionization is strongly increased compared to the detrapping rate leading to an increased build-up of space charge. This space charge locally reduces the internal electric field increasing the trapping rate and hence reducing the CCE even further. In order to connect these macroscopic measurements with the microscopic defects acting as traps for the ionization charge, the TCAD simulation program SILVACO was used. It allows to introduce the defects as effective donor and acceptor levels, and can calculate the electric field from Transient Current Technique (TCT) signals and CCE as a function of the effective trap properties, like density, energy level, and trapping cross section. After each irradiation step, these properties were fitted to the data on the electric field from the TCT signals and CCE. Two effective acceptor and donor levels were needed to fit the data after each step. It turned out that the energy levels and cross sections could be kept constant and the trap density was proportional to the cumulative fluence of the irradiation steps. The highly non-linear rate dependent diamond polarization and the resulting signal loss can be simulated using this effective defect model and is in agreement with the measurement results

  18. Effect of potential barrier growth of auto-localized excitons decay on radiation defects in AHC at low lattice symmetry

    International Nuclear Information System (INIS)

    Shunkeev, K.; Sagimbaeva, Sh.; Shunkeev, S.

    2007-01-01

    Effect of auto-localized excitons (ALE) luminescence strengthening is conditioned by two mechanisms: either decrease of potential barrier divided of quasi-free states and auto-localized states or decrease of emission-less channel effectiveness of exciton decay on primary radiation defects. In considered range (80 K) all excitons are only in auto-localized state. Therefore a realization of the first mechanism is improbable, For instant, in KI crystal at 80-100 K luminescence of free exciton is completely putting out, and ALE luminescence has maximal intensity. It is known that in the temperature range when ALE luminescence putting out is beginning an effectiveness of radiation defects is beginning to grow. This effect is related with predominating at that time emission-less exciton decay on radiation defects (F-H pairs). Experimentally by luminescence spectroscopy method activation energy of temperature putting out of ALE in AHC under uniaxial deformation. It is revealed, that increase of activation energy value has observed in a number of crystals: KBr→NaCl→KI→Na Br→CsBr→RbI. It is concluded, that effect of ALE intensity building-up and decrease of effectiveness of radiation defect formation are interpreted by growth of potential barrier of ALE decay into radiation defects under low symmetry of AHC lattice of low-temperature uniaxial deformation

  19. Irregular radiation response of a chondrosarcoma

    International Nuclear Information System (INIS)

    Marsden, J.J.; Kember, N.F.; Shaw, J.E.H.

    1980-01-01

    The DC II mouse chondrosarcoma was shown to be a potentially valuable radiobiological tumour system since it recovered from radiation injury by regrowth from clones that could be counted in histological sections. Unfortunately, the normal growth of this tumour following s.c. implantation in the thigh was irregular both in the time before growth became evident and in the rate of growth. The response to radiation was also unreliable since tumours irradiated with the same dose (e.g. 30 Gy) showed a range of responses from shrinkage to no detectable change in growth rate. The delay in normal growth can be attributed largely to delays in vascularization while changes in growth rate may be explained by differences in tumour architecture. Radiation response may depend on variations in hypoxic fraction and in relative cellularity. Tumours having the same external dimensions may differ by a factor of 80 in the numbers of tumour cells they contain. This chondrosarcoma may prove a closer model to some human tumours than many transplantable tumours that display regular growth patterns. (author)

  20. Study on radiation-responsive epigenomes

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Seung Sik; Lee, Seung Sik; Chung, Byung Yeoup; and others

    2013-01-15

    The purpose of this project is development of world-class head spring techniques of biological science for application of plant genomes/epigenomes through study on radiation-responsive epigenomes and improvement of the national competitiveness in the field of fundamental technology for biological science and industry. Research scope includes 1) Investigation of radiation-responsive epigenomes and elucidation of their relation with phenotypes, 2) Elucidation of interaction and transcription control of epigenomes and epigenetic regulators using IR, 3) Investigation of epigenome-mediated traits in plant development, differentiation and antioxidant defense using IR, and 4) Development of application techniques of radiation-responsive epigenomes for eco-monitoring and molecular breeding. Main results are as follow: investigation of the expression level of histone-modifying enzymes by IR; elucidation of the structural and functional changes of chaperone protein by IR; development of transgenic plant (DRD1-6); investigation of transcription control of epigenetic regulators by IR; investigation of relevance between DNA methylation and miRNA; comparison of gene expression in wild type and cmt mutant from Arabidopsis using gene chip; investigation control of epigenetic regulators in drd1-6 mutant by drought stress; development of transgenic plant using epigenetic regulators.

  1. Nonlinear response matrix methods for radiative transfer

    International Nuclear Information System (INIS)

    Miller, W.F. Jr.; Lewis, E.E.

    1987-01-01

    A nonlinear response matrix formalism is presented for the solution of time-dependent radiative transfer problems. The essential feature of the method is that within each computational cell the temperature is calculated in response to the incoming photons from all frequency groups. Thus the updating of the temperature distribution is placed within the iterative solution of the spaceangle transport problem, instead of being placed outside of it. The method is formulated for both grey and multifrequency problems and applied in slab geometry. The method is compared to the more conventional source iteration technique. 7 refs., 1 fig., 4 tabs

  2. Quartz gauge response in ion radiation

    International Nuclear Information System (INIS)

    Taylor, P.E.; Gilbert, P.H.; Kernthaler, C.; Anderson, M.U.

    1995-01-01

    This paper describes recent work to make high quality quartz gauge (temporal and spatial) shock wave measurements in a pulsed ion beam environment. Intense ion beam radiation, nominally 1 MeV protons, was deposited into material samples instrumented with shunted quartz gauges adjacent to the ion deposition zone. Fluence levels were chosen to excite three fundamentally different material response modes (1) strong vapor, (2) combined vapor and melt phase and (3) thermoelastic material response. A unique quartz gauge design was utilized that employed printed circuit board (PCB) technology to facilitate electrical shielding, ruggedness, and fabrication at sign e meeting the essential one dimensional requirements of the characterized Sandia shunted quartz gauge. Shock loading and unloading experiments were conducted to evaluate the piezoelectric response of the coupled quartz gauge/PCB transducer. High fidelity shock wave profiles were recorded at the three ion fluence levels providing dynamic material response data for vapor, melt and solid material phases

  3. Radiation response of Philippine natural rubber latex

    International Nuclear Information System (INIS)

    Dela Rosa, A.M.; Abad, L.V.; Ana-Relleve, L.S.; Tranquilan-Aranilla, C.; Pascual, C.L.

    1998-01-01

    Our earlier work has shown that the natural rubber latex (NRL) produced and processed in the Philippines is suited for radiation vulcanization. The cast films from NRL with 50% TSC exhibited maximum tensile strengths of 25-32 MPa at 15 kGy, which is the vulcanization dose or Dv. In the manufacture of dipped NRL products, certain specifications such as %TSC, protein content and tensile properties, must be met to ensure an acceptable product. For radiation vulcanization of natural rubber latex (RVNRL) to be accepted as an alternative process, it must also meet the requirements. Thus, this paper presents additional data on the radiation response of local NRL at different total solids contents (TSC), leachable proteins from NRL films as a function of dose, and the thermal activities of irradiated natural rubber latex (INRL). Different formulations of NRL showed varying tolerances to nBA. Data showed that as %TSC increases, the maximum concentration of nBA that can be added without affecting the stability of the latex decreases. The Dv increases as the %TSC increases and the nBA content decreases. This difference in response may be attributed to a lower concentration of nBA in formulations with higher %TSC. These data indicate that the parameters in the radiation treatment will be dictated by the intended applications of INRL. The thermogravimetric data showed greater stability of INRL to thermal oxidation relative to the unirradiated NRL, which correlates directly with the tensile properties of the INRL. A radiation dose of 10 kGy increased the amount of proteins leached from cast latex films. The amount of extractable proteins did not increase significantly at higher doses. The SDS PAGE analysis of the extractable proteins from unirradiated latex film showed distinct bands. An additional band at 60 Kda appeared at 10 kGy. All these bands became diffuse at higher doses, indicating the radiolysis of the proteins

  4. Defects in codoped NiO with gigantic dielectric response

    Science.gov (United States)

    Wu, Ping; Ligatchev, Valeri; Yu, Zhi Gen; Zheng, Jianwei; Sullivan, Michael B.; Zeng, Yingzhi

    2009-06-01

    We combine first-principles, statistical, and phenomenological methods to investigate the electronic and dielectric properties of NiO and clarify the nature of the gigantic dielectric response in codoped NiO. Unlike previous models which are dependent on grain-boundary effects, our model based on small polaron hopping in homogeneous material predicts the dielectric permittivity (104-5) for heavily Li- and MD -codoped NiO (MD=Ti,Al,Si) . Furthermore, we reproduce the experimental trends in dielectric properties as a function of the dopants nature and their concentrations, as well as the reported activation energies for the relaxation in Li- and Ti-codoped NiO (0.308 eV or 0.153 eV depending on the Fermi-level position). In this study, we demonstrate that small polaron hopping on dopant levels is the dominant mechanism for the gigantic dielectric response in these codoped NiO.

  5. WORTMANNIN affect cellular response by radiation

    International Nuclear Information System (INIS)

    Li Yu; Li Bailong

    2010-01-01

    Objective: To observe radiation Response of cells by WORTMANNIN (WT), which is inhibitor for Phosphatidylinositol-3 Kinase (PI-3K). Methods: LP3 cells are prepared with different concentration of WT for 1 hour and receive different dose γ irradiation. To continue the cell for clone culture, and get the production of dose-survival curve. 1800 pulsed-field gel electrophoresis is used to detect DNA double-strand breaks after the 20 Gy γ irradiation. Continue to use the mobility shift assays (Electrophoresis Mobility Shift Assay, EMSA) to observe NF-kB transcription factor of the corresponding changes. Result: WT can be found to increase the radiation sensitivity of SP3 cells, the best sensitizer concentration in 20 μmol /L or more, obvious sensitizing effect within 6 h time; the electrophoresis experiments showed that after irradiation with time, by 50 μmol /L WT group DNA the gel is higher than that of the simple exposure group; transcription factor NF-kB binding activity in the 6 hours after exposure experiences a low-rise and then the process of rising with its the peak of the change reaching after about 3 hours after irradiation. Conclusion: It suggests the existence of PI-3K-mediated radiation sensitizer pathways. Ionizing radiation may activate NF-kB, which caused some DNA damage repair and other defense mechanisms and cell-related gene activity in order to reduce radiation damage. WT may block this process through the early stages of radiation-sensitizing effect. (authors)

  6. Optical spectroscopy and microscopy of radiation-induced light-emitting point defects in lithium fluoride crystals and films

    Science.gov (United States)

    Montereali, R. M.; Bonfigli, F.; Menchini, F.; Vincenti, M. A.

    2012-08-01

    Broad-band light-emitting radiation-induced F2 and F3+ electronic point defects, which are stable and laser-active at room temperature in lithium fluoride crystals and films, are used in dosimeters, tuneable color-center lasers, broad-band miniaturized light sources and novel radiation imaging detectors. A brief review of their photoemission properties is presented, and their behavior at liquid nitrogen temperatures is discussed. Some experimental data from optical spectroscopy and fluorescence microscopy of these radiation-induced point defects in LiF crystals and thin films are used to obtain information about the coloration curves, the efficiency of point defect formation, the effects of photo-bleaching processes, etc. Control of the local formation, stabilization, and transformation of radiation-induced light-emitting defect centers is crucial for the development of optically active micro-components and nanostructures. Some of the advantages of low temperature measurements for novel confocal laser scanning fluorescence microscopy techniques, widely used for spatial mapping of these point defects through the optical reading of their visible photoluminescence, are highlighted.

  7. Radiation-Induced Defects in Kaolinite as Tracers of Past Occurrence of Radionuclides in a Natural Analogue of High Level Nuclear Waste Repository

    Science.gov (United States)

    Allard, T.; Fourdrin, C.; Calas, G.

    2007-05-01

    Understanding the processes controlling migrations of radioelements at the Earth's surface is an important issue for the long-term safety assessment of high level nuclear waste repositories (HLNWR). Evidence of past occurrence and transfer of radionuclides can be found using radiation-induced defects in minerals. Clay minerals are particularly relevant because of their widespread occurrence at the Earth's surface and their finely divided nature which provides high contact area with radioactive fluids. Owing to its sensitivity to radiations, kaolinite can be used as natural, in situ dosimeter. Kaolinite is known to contain radiation-induced defects which are detected by Electron Paramagnetic Resonance. They are differentiated by their nature, their production kinetics and their thermal stability. One of these defects is stable at the scale of geological periods and provides a record of past radionuclide occurrence. Based on artificial irradiations, a methodology has been subsequently proposed to determine paleodose cumulated by kaolinite since its formation. The paleodose can be used to derive equivalent radioelement concentrations, provided that the age of kaolinite formation can be constrained. This allows quantitative reconstruction of past transfers of radioelements in natural systems. An example is given for the Nopal I U-deposit (Chihuahua, Mexico), hosted in hydrothermally altered volcanic tufs and considered as analogue of the Yucca Mountain site. The paleodoses experienced by kaolinites were determined from the concentration of defects and dosimetry parameters of experimental irradiations. Using few geochemical assumption, a equivalent U-content responsible for defects in kaolinite was calculated from the paleodose, a dose rate balance and model ages of kaolinites constrained by tectonic phases. In a former study, the ages were assumptions derived from regional tectonic events. In thepresent study, ages of mineralization events are measured from U

  8. Study on radiation-induced defects in germanium monocrystals by the X-ray diffusive scattering method

    International Nuclear Information System (INIS)

    Malinenko, I.A.; Perelygina, E.A.; Chudinova, S.A.; Shivrin, O.N.

    1979-01-01

    The method of X-ray diffusion scattering was used to study the defective structure of germanium monocrystals exposed to 750 keV proton irradiation with 3.8x10 16 -4.6x10 17 cm -2 doses and subjected to the subsequent annealing at temperatures up to 450 deg C. Detected in the crystals were the complex radiation induced structure characterized with oriented vacancy complexes and results from the both effects: irradiation and annealing. Radiation defect sizes in the section (hhO) have been determined. With increasing the annealing temperature the structure reconstruction resulting in the complex dissociation is observed

  9. Study by electrical resistivity measurements of the radiation induced defects in gold-copper alloys

    International Nuclear Information System (INIS)

    Alamo, A.

    1983-09-01

    Point defect production rate in Cu 3 Au and CuAu ordered and disordered alloys was studied by electrical resistivity measurements, as function of electron energy ranging from 0.4 to 2.5 MeV. The irradiations were performed at 20 K. The production curves are analysed using a displacement model for diatomic materials and the following values are found for the average displacement threshold energies: Esub(d)sup(Cu) approximately 22 eV and Esub(d)sup(Au) approximately 18 eV, for both alloys. Elementary defect migration was examined during isochronal annealing performed after irradiations. A simple type of self-interstitial seems to migrate in the ordered alloys: probably a split-interstitial of Cu-Cu type. Interstitial migration seems to be very difficult and complex in the disordered alloys. Vacancy mobility was detected after recovery at temperature above 300 K and was responsible of an increase of long range order. Fast neutron irradiations at 20 K produce disordering in the initially ordered alloys. Ratios of 38 and 18 antistructure defects per atomic displacement are estimated for Cu 3 Au and CuAu respectively [fr

  10. Annealing of radiation-induced defects in vanadium and vanadium-titanium alloys

    International Nuclear Information System (INIS)

    Leguey, T.

    1996-01-01

    The annealing of defects induced by electron irradiation up to a dose of 6.10 21 m -2 at T<293 K has been investigated in single-crystals of pure vanadium and in vanadium-titanium alloys with compositions 0.3, 1 and 5 at.% Ti using positron annihilation spectroscopy. The recovery of the positron annihilation parameters in V single-crystals indicates that the defect annealing takes place in the temperature range 410-470 K without formation of microvoids for the present irradiation conditions. For the alloys the recovery onset is shifted to 460 K, the width of the annealing stage is gradually broadened with increasing Ti content, and microvoids are formed for annealing temperatures at the end of the recovery stage. The results show that the vacancy release from vacancy-interstitial impurity pairs and subsequent recombination with interstitial loops is the mechanism of the recovery in pure V. For V-Ti alloys, vacancy-Ti-interstitial impurity complexes and vacancy-Ti pairs appear to be the defects responsible for the positron trapping. The broadening of the recovery stage with increasing Ti content indicates that solute Ti is a very effective trap for vacancies in V. (orig.)

  11. Peculiarities of the point radiation defects accumulation in the fine- and ultra-disperse metallic media

    International Nuclear Information System (INIS)

    Aliev, B.A.; Zajkin, Yu.A.; Potapov, A.S.

    2004-01-01

    Fine-dispersive powders are a samples of solid systems. In which under irradiation the particle surface layers defect structure changes and has mostly an effect on structural transformations. Theoretical calculations and experimental data show, that the increased interstitials atoms concentration near particles surface during irradiation by either electrons or gamma quanta with energy about 1 MeV give rise to intensive pores healing. At the same time as the dense surface layer formation the pores healing leads to the brachiate borders system formation. The borders serve as pathways for accelerated diffusion. Sintering process and a metal recrystallization are stimulating as well. Both processes lead to the ordered super-structure formation which contributes the additional contribution in an improvement of the mechanical properties of a metal. A liner sizes of the ordered net depend on both the powder sizes and the irradiation conditions. The especial interest present a conditions for such superstructure formation (when the particle sizes are becoming so small (∼1 μm), that effect has being resulted on a defect-formation in the whole volume of a powder particle). In the considered case the point radiation defects accumulation kinetics in the metallic particle is analyzed on the ground of the equation system for atomic concentrations both interstitial atoms and vacancies. The numerical solution of this equation system shows, that particles sizes decline leads to considerable micro-pores healing increase and improvement of conditions for net strengthening. In dependence on irradiation conditions (temperature, dose and dose rate) the forming super-structure could have micro- and nano-sizes

  12. Computer simulation of the interaction between an extended dislocation and radiation defects in the fcc lattice

    International Nuclear Information System (INIS)

    Kuramoto, E.; Nakamura, Y.; Tsutsumi, T.

    1993-01-01

    The interaction between an extended dislocation and a radiation-induced defect, especially, a self-interstitial atom (SIA), has been investigated in the model fcc lattice by computer simulation technique. An SIA was absorbed into the core of one of the two partial dislocations of the extended screw dislocation as a crowdion which extends along the dislocation line. Under the applied shear stress this crowdion acted as a pinning point, resulting in irradiation hardening. On the other hand, an SIA was absorbed at the jog site of the extended edge dislocation (at one of the two jog sites on two partial dislocations) and after some relaxation the total jog was shifted to one atomic distance through the spreading out of the strain due to an SIA from one partial side to the other side. (orig.)

  13. Radiation defects in Te-implanted germanium. Electron microscopy and computer simulation studies

    International Nuclear Information System (INIS)

    Kalitzova, M.G.; Karpuzov, D.S.; Pashov, N.K.

    1985-01-01

    Direct observation of radiation damage induced by heavy ion implantation in crystalline germanium by means of high-resolution electron microscopy is reported. The dark-field lattice imaging mode is used, under conditions suitable for object-like imaging. Conventional TEM is used for estimating the efficiency of creating visibly damaged regions. Heavy ion damage clusters with three types of inner structure are observed: with near-perfect crystalline cores, and with metastable and stable amorphous cores. The MARLOWE computer code is used to simulate the atomic collision cascades and to obtain the lateral spread distributions of point defects created. A comparison of high-resolution electron microscopy (HREM) with computer simulation results shows encouraging agreement for the average cluster dimensions and for the lateral spread of vacancies and interstitials. (author)

  14. Overexposure of patients due to malfunctions or defects in radiation equipment

    International Nuclear Information System (INIS)

    Gill, J.R.

    1992-01-01

    Some 38 incidents involving patient overexposure due to malfunctions or defects in radiation equipment were notified to HSE between 1986 and 1990. Of these cases, 30 involved diagnostic X ray equipment, while the remainder involved nuclear medicine or radiotherapy equipment. Those cases involving X ray equipment are examined in detail and grouped into six categories. The numbers of patients affected varied. In one case an estimated 350 patients were affected: in another, 240; while 13 cases affected only a single patient. A very rough estimate of the collective effective dose equivalent in the 30 cases comes to 5 man sieverts. It is concluded that improvements are needed in fault finding procedures, and guidance is needed on consistent methods of dose estimation and reporting. Improvements for the longer term include the selection of reliable components during manufacture; application of HSE guidance in software design for programmable electronic systems; and equipment design to incorporate fault detection and inhibition of operation to prevent excessive exposures

  15. Positron annihilation study of radiation defects in α-Al2O3

    International Nuclear Information System (INIS)

    Kuramoto, Eiichi; Aono, Yasuhisa; Takenaka, Minoru

    1989-01-01

    Positron annihilation studies have been performed for the radiation-induced defects in α-Al 2 O 3 specimens. Before irradiation polycrystals of α-Al 2 O 3 showed positron annihilation lifetime about 125 psec. But this value was increased by 60 MeV O 6+ ion irradiation to about 155 psec. This is considered to be corresponding to positron lifetime at O-vacancy sites. But, this lifetime disappeared gradually in the period of several months probably because of recombination of vacancies and interstitial atoms at room temperature. On the other hand, it was found that in single crystals positron lifetime before irradiation is between these two values. This is probably due to lack of oxygen atoms in single crystals in the fabrication process and it already has O-vacancies in the matrix before irradiation. (author)

  16. Enhanced diffusion of solute metals forming complexes with radiation defects in silica

    International Nuclear Information System (INIS)

    Pivin, J.C.; Garrido, E.; Rizza, G.; Thome, L.

    1998-01-01

    The mixing kinetics of Cu, Ag, W, Pt, and Au single layers embedded in silica when irradiated with heavy ions at temperatures (T) of 110 and 300 K was investigated by means of in situ RBS analyses in alternation with irradiations. The spreading of peaks related to the metallic species is generally anisotropic and obeys either a quadratic or a linear dependence on the ion dose according to the increasing T. The quadratic law is attributed to a control of the diffusion by the coupling of the large impurity atoms M with matrix defects, and a classical regime of radiation enhanced diffusion is observed when this coupling is made easier (higher T or mass of M). Other factors such as internal stresses affect the rates of M dissolution and diffusion. (orig.)

  17. Effect of homologous impurities on primary radiation defect accumulation in alkali halides

    International Nuclear Information System (INIS)

    Chernov, S.A.; Gavrilov, V.V.

    1981-01-01

    To clarify the mechanism of the effect of anion and cation homologous impurities on the primary radiation-induced defect accumulation, the transient absorption of H and F centers was studied in KCl and KBr crystals. Pulse electron accelerator technique was used. Pure and doped crystals were investigated. It was obtained that the cation homologue Na in the concentration range from 0 to 0.5 m. % in 10 -8 -10 -6 s post-irradiation time has no effect on the defect accumulation efficiency at low temperature and increases the latter at high temperature. At large post-irradiation time and at high temperatures the rise of efficiency at low Na concentration and decrease of it at high Na concentrations were observed. The conclusion was made that Na does not affect the generation process. The anion homologous impurities (I and Br) lead to a significant increase of the accumulation efficiency due to the formation of more stable F-H pair at self-trapped exciton decay on anion impurities compared with that formed in perfect lattice. Some assumptions are advanced to explain the effect [ru

  18. Intrinsic and extrinsic contributors to defective CD8+ T cell responses with aging.

    Science.gov (United States)

    Jergović, Mladen; Smithey, Megan J; Nikolich-Žugich, Janko

    2018-05-01

    Aging has a profound effect on the immune system, and both innate and adaptive arms of the immune system show functional decline with age. In response to infection with intracellular microorganisms, old animals mobilize decreased numbers of antigen-specific CD8+ T cells with reduced production of effector molecules and impaired cytolytic activity. However, the CD8+ T cell-intrinsic contribution to, and molecular mechanisms behind, these defects remain unclear. In this review we will discuss the mechanistic contributions of age related changes in the CD8+ T cell pool and the relative roles of intrinsic functional defects in aged CD8+ T cells vs. defects in the aged environment initiating the CD8+ T cell response. Copyright © 2018 Elsevier Inc. All rights reserved.

  19. The Dose Response Relationship for Radiation Carcinogenesis

    Science.gov (United States)

    Hall, Eric

    2008-03-01

    Recent surveys show that the collective population radiation dose from medical procedures in the U.S. has increased by 750% in the past two decades. It would be impossible to imagine the practice of medicine today without diagnostic and therapeutic radiology, but nevertheless the widespread and rapidly increasing use of a modality which is a known human carcinogen is a cause for concern. To assess the magnitude of the problem it is necessary to establish the shape of the dose response relationship for radiation carcinogenesis. Information on radiation carcinogenesis comes from the A-bomb survivors, from occupationally exposed individuals and from radiotherapy patients. The A-bomb survivor data indicates a linear relationship between dose and the risk of solid cancers up to a dose of about 2.5 Sv. The lowest dose at which there is a significant excess cancer risk is debatable, but it would appear to be between 40 and 100 mSv. Data from the occupation exposure of nuclear workers shows an excess cancer risk at an average dose of 19.4 mSv. At the other end of the dose scale, data on second cancers in radiotherapy patients indicates that cancer risk does not continue to rise as a linear function of dose, but tends towards a plateau of 40 to 60 Gy, delivered in a fractionated regime. These data can be used to estimate the impact of diagnostic radiology at the low dose end of the dose response relationship, and the impact of new radiotherapy modalities at the high end of the dose response relationship. In the case of diagnostic radiology about 90% of the collective population dose comes from procedures (principally CT scans) which involve doses at which there is credible evidence of an excess cancer incidence. While the risk to the individual is small and justified in a symptomatic patient, the same is not true of some screening procedures is asymptomatic individuals, and in any case the huge number of procedures must add up to a potential public health problem. In the

  20. Magnetic responsive hydroxyapatite composite scaffolds construction for bone defect reparation

    Directory of Open Access Journals (Sweden)

    Zeng XB

    2012-07-01

    Full Text Available Xiao Bo Zeng, Hao Hu, Li Qin Xie, Fang Lan, Wen Jiang, Yao Wu, Zhong Wei GuNational Engineering Research Center for Biomaterials, Sichuan University, Chengdu, Sichuan, People's Republic of ChinaIntroduction: In recent years, interest in magnetic biomimetic scaffolds for tissue engineering has increased considerably. A type of magnetic scaffold composed of magnetic nanoparticles (MNPs and hydroxyapatite (HA for bone repair has been developed by our research group.Aim and methods: In this study, to investigate the influence of the MNP content (in the scaffolds on the cell behaviors and the interactions between the magnetic scaffold and the exterior magnetic field, a series of MNP-HA magnetic scaffolds with different MNP contents (from 0.2% to 2% were fabricated by immersing HA scaffold into MNP colloid. ROS 17/2.8 and MC3T3-E1 cells were cultured on the scaffolds in vitro, with and without an exterior magnetic field, respectively. The cell adhesion, proliferation and differentiation were evaluated via scanning electron microscopy; confocal laser scanning microscopy; and 3-(4,5-Dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide (MTT, alkaline phosphatase, and bone gla protein activity tests.Results: The results demonstrated the positive influence of the magnetic scaffolds on cell adhesion, proliferation, and differentiation. Further, a higher amount of MNPs on the magnetic scaffolds led to more significant stimulation.Conclusion: The magnetic scaffold can respond to the exterior magnetic field and engender some synergistic effect to intensify the stimulating effect of a magnetic field to the proliferation and differentiation of cells.Keywords: magnetic therapy, magnetic nanoparticles, bone repair, magnetic responsive

  1. Radiation damage and defect behavior in proton irradiated lithium-counterdoped n/sup +/p silicon solar cells

    International Nuclear Information System (INIS)

    Stupica, J.; Goradia, C.; Swartz, C.K.; Weinberg, I.

    1987-01-01

    Two lithium-counterdoped n/sup +/p silicon solar cells with different lithium concentrations were irradiated by 10 MeV protons. Cell performance was measured as a function of fluence, and it was found that the cell with the highest concentration of lithium had the higher radiation resistance. Deep level defects were studied using deep level transient spectroscopy which yielded two defects that were lithium related. Relating the defect energy levels obtained from this study under 10 MeV protons, with an earlier work using 1 MeV electron irradiations shows no correlation of the defect energy levels. There is one marked comparison though. The absence of the boron interstitial-oxygen interstitial defect. This consistency strengthens the belief that lithium interacts with oxygen to prevent the formation of the boron interstitial-oxygen interstitial defect. The present results indicate that, in general, addition of lithium in small amounts to the p-base of a boron doped silicon solar cell such that the base remains p-type, tends to increase the radiation resistance of the cell

  2. Reconstruction of road defects and road roughness classification using vehicle responses with artificial neural networks simulation

    CSIR Research Space (South Africa)

    Ngwangwa, HM

    2010-04-01

    Full Text Available -1 Journal of Terramechanics Volume 47, Issue 2, April 2010, Pages 97-111 Reconstruction of road defects and road roughness classification using vehicle responses with artificial neural networks simulation H.M. Ngwangwaa, P.S. Heynsa, , , F...

  3. Radiation defect production in quartz crystals with various structure perfectness degree; Radiatsionnoe defektoobrazovanie v kristallakh kvartsa s razlichnoj stepen`yu sovershenstva struktury

    Energy Technology Data Exchange (ETDEWEB)

    Khushvakov, O B

    1992-01-01

    Radiation defects production processes in pure and doped quartz crystals with various structure defectness, caused by preliminary irradiation with neutrons, protons, deuterons and {alpha}-particles, during various electron excitation densities were investigated. The distribution of colour centres along the thickness of irradiated quartz crystals was measured. It was supposed that colour centres are produced on account of inelastic energy losses as the result of collective decay of two or more interacting excitons. It was shown that in quartz crystals under the actions of protons with overthreshold energy 18 MeV and electrons with subthreshold energy 100 keV the same structure defects are formed. It was established that radiation defect production process has two stages. The first stage reveals radiation defects produced by preliminary irradiation. The second one reveals additional intrinsic defects formed under the action of gamma-rays and electrons. The probability dependence of defect production on neutron fluence and masses of incident particles was studied. It was supposed that the creation of additional defects in preliminary irradiated crystals is due to non-radiative decay of electron excitations near radiation-induced defects. It was shown that increase of impurity concentration leads to rate growth of accumulation of radiation induced defects. (A.A.D.) 15 refs. 4 figs.

  4. Effect of stacking fault energy on the neutron radiation induced defect accumulation in stainless steels

    International Nuclear Information System (INIS)

    Li Xiaoqiang; Al Mazouzi Abderrahim

    2009-01-01

    Current knowledge highlights the radiation induced segregation (RIS) and the radiation hardening as the two main effects on irradiation assisted stress corrosion cracking (IASCC). Stacking fault energy is considered as a key parameter of materials, which can influence IASCC of stainless steels in nuclear light water reactor (LWR), because it plays an important role in every process of plastic deformation, work hardening and creep behaviour. The study of the impact of SFE variations on the plastic deformation and SCC behaviour of irradiated and unirradiated austenitic steels will contribute to the understanding of IASCC mechanism. The objectives of this work, as a task within the FP6-European Project PERFECT, are to investigate the influence of the SFE on IASCC susceptibility of stainless steels, to correlation n-irradiation induced defect production, accumulation and mechanical deformation behaviour with SFE by using the state of the art experimental tools such as transmission electron microscope (TEM), positron annihilation spectroscopy (PAS), slow strain rate tests (SSRT) in simulated LWR conditions

  5. Recombination of radiation defects in solid methane: neutron sources and cryo-volcanism on celestial bodies

    Science.gov (United States)

    Kirichek, O.; Savchenko, E. V.; Lawson, C. R.; Khyzhniy, I. V.; Jenkins, D. M.; Uyutnov, S. A.; Bludov, M. A.; Haynes, D. J.

    2018-03-01

    Physicochemical properties of solid methane exposed to ionizing radiation have attracted significant interest in recent years. Here we present new trends in the study of radiation effects in solid methane. We particularly focus on relaxation phenomena in solid methane pre-irradiated by energetic neutrons and electron beam. We compare experimental results obtained in the temperature range from 10K to 100K with a model based on the assumption that radiolysis defect recombinations happen in two stages, at two different temperatures. In the case of slow heating up of the solid methane sample, irradiated at 10K, the first wave of recombination occurs around 20K with a further second wave taking place between 50 and 60K. We also discuss the role of the recombination mechanisms in “burp” phenomenon discovered by J. Carpenter in the late 1980s. An understanding of these mechanisms is vital for the designing and operation of solid methane moderators used in advanced neutron sources and could also be a possible explanation for the driving forces behind cryo-volcanism on celestial bodies.

  6. Modeling of excimer laser radiation induced defect generation in fluoride phosphate glasses

    International Nuclear Information System (INIS)

    Natura, U.; Ehrt, D.

    2001-01-01

    Fluoride phosphate (FP) glasses with low phosphate content are high-transparent in the deep ultraviolet (UV) range and attractive candidates for UV-optics. Their optical properties are complementary to fluoride crystals. The anomalous partial dispersion makes them desirable for optical lens designs to reduce the secondary spectrum. Their UV transmission is limited by trace impurities introduced by raw materials and decreases when exposed to UV-radiation (lamps, lasers). The experiments of the paper published previously in this journal were used in order to separate radiation induced absorption bands in the fluoride phosphate glass FP10. In this paper the generation mechanism of the phosphorus-oxygen related hole center POHC 2 is investigated in detail in glasses of various compositions (various phosphate and impurity contents) in order to predict the transmission loss in case of long-time irradiation. Experiments were carried out using ArF- and KrF-excimer lasers (ns-pulses). POHC 2 generation strongly depends on the phosphate content and on the content of Pb 2+ . A model was developed on these terms. Rate equations are formulated, incorporating the influence of the Pb 2+ -content on the defect generation, a two-step creation term including an energy transfer process and a one-photon bleaching term. This results in a set of coupled nonlinear differential equations. Absorption coefficients and lifetimes of the excited states were calculated as well. Experimental results compared well with the numerical analysis of the theoretical rate equations

  7. Systematic Analysis of the DNA Damage Response Network in Telomere Defective Budding Yeast

    Directory of Open Access Journals (Sweden)

    Eva-Maria Holstein

    2017-07-01

    Full Text Available Functional telomeres are critically important to eukaryotic genetic stability. Scores of proteins and pathways are known to affect telomere function. Here, we report a series of related genome-wide genetic interaction screens performed on budding yeast cells with acute or chronic telomere defects. Genetic interactions were examined in cells defective in Cdc13 and Stn1, affecting two components of CST, a single stranded DNA (ssDNA binding complex that binds telomeric DNA. For comparison, genetic interactions were also examined in cells with defects in Rfa3, affecting the major ssDNA binding protein, RPA, which has overlapping functions with CST at telomeres. In more complex experiments, genetic interactions were measured in cells lacking EXO1 or RAD9, affecting different aspects of the DNA damage response, and containing a cdc13-1 induced telomere defect. Comparing fitness profiles across these data sets helps build a picture of the specific responses to different types of dysfunctional telomeres. The experiments show that each context reveals different genetic interactions, consistent with the idea that each genetic defect causes distinct molecular defects. To help others engage with the large volumes of data, the data are made available via two interactive web-based tools: Profilyzer and DIXY. One particularly striking genetic interaction observed was that the chk1∆ mutation improved fitness of cdc13-1 exo1∆ cells more than other checkpoint mutations (ddc1∆, rad9∆, rad17∆, and rad24∆, whereas, in cdc13-1 cells, the effects of all checkpoint mutations were similar. We show that this can be explained by Chk1 stimulating resection—a new function for Chk1 in the eukaryotic DNA damage response network.

  8. AFM studies of a new type of radiation defect on mica surfaces caused by highly charged ion impact

    International Nuclear Information System (INIS)

    Ruehlicke, C.; Briere, M.A.; Schneider, D.

    1994-01-01

    Radiation induced defects on mica caused by the impact of slow very highly charged ions (SVHCI) have been investigated with an atomic force microscope (AFM). Freshly cleaved surfaces of different types of muscovite were irradiated with SVHCI extracted from the LLNL electron beam ion trap (EBIT) at velocities of ca. 2 keV/amu. Atomic force microscopy of the surface reveals the formation of blisterlike defects associated with single ion impact. The determined defect volume which appears to increase linearly with the incident charge state and exhibits a threshold incident charge state has been determined using the AFM. These results indicate that target atoms are subjected to mutual electrostatic repulsion due to ionization through potential electron emission upon approach of the ion. If the repulsion leads to permanent atomic displacement, surface defects are formed

  9. Reconstruction of mandibular defects after radiation, using a free, living bone, graft transferred by microvascular anastomoses. An experimental study

    International Nuclear Information System (INIS)

    Ostrup, L.T.; Fredrickson, J.M.

    1975-01-01

    The replacement of a mandibular defect by a free, composite rib graft, transferred by microvascular anastomoses of the posterior intercostal vessels to donor vessels in the neck was described previously. We now present data which demonstrate that successful results can be achieved even after radical mandibular radiation. This technique, done in dogs, has obvious implications in the management of oral cancer in man

  10. Study of defects and radiation damage in solids by field-ion and atom-probe microscopy

    International Nuclear Information System (INIS)

    Seidman, D.N.

    1979-06-01

    A brief review is presented of: the basic physical principles of the field-ion and atom-probe microscopes; the many applications of these instruments to the study of defects and radiation damage in solids; and the application of the atom-probe field-ion microscope to the study of the behavior of implanted 3 He and 4 He in tungsten

  11. Effect of gamma radiation on resting B lymphocytes. II. Functional characterization of the antigen-presentation defect

    International Nuclear Information System (INIS)

    Ashwell, J.D.; Jenkins, M.K.; Schwartz, R.H.

    1988-01-01

    The effect of radiation on three discrete Ag-presentation functions in resting B cells was examined: 1) Ag uptake and processing, 2) expression of processed Ag in the context of functional class II molecules, and 3) provision of necessary co-stimulatory, or second, signals. Analysis of radiation's effect on B cell presentation of intact vs fragmented Ag or its effect on presentation by Ag-pulsed B cells indicated that damage to Ag uptake and processing could not account for the bulk of the radiation-induced Ag-presentation defect. Experiments with phosphatidylinositol hydrolysis as an indirect measure of TCR occupancy suggested that irradiation caused a fairly rapid (within 1 to 2 h) decrease in the ability of the B cell APC to display a stimulatory combination of Ag and class II molecule. Ag dose-response analyses demonstrated that when presenting a fragment of the Ag pigeon cytochrome c to a T cell clone, 3000 rad-treated B cell APC were able to stimulate approximately 50% as much phosphatidylinositol turnover as unirradiated B cells. It was also found that, in contrast to their inability to initiate T cell proliferation, and similarly to chemically cross-linked splenocytes, heavily irradiated resting B cells plus Ag induced a state of Ag hyporesponsiveness in T cell clones. This effect on T cells had the same Ag- and MHC-specificity as did receptor occupancy required for proliferation, indicating that heavily irradiated resting B cells bear functional class II molecules. Co-culture of T cells with allogeneic B cells and syngeneic heavily irradiated B cells or chemically cross-linked splenic APC plus Ag resulted in T cell proliferation and interfered with the induction of the hyporesponsive state. This co-stimulatory function was radiosensitive in resting allogeneic B cells

  12. Point Defect Properties of Cd(Zn)Te and TlBr for Room-Temperature Gamma Radiation Detectors

    Science.gov (United States)

    Lordi, Vincenzo

    2013-03-01

    The effects of various crystal defects in CdTe, Cd1-xZnxTe (CZT), and TlBr are critical for their performance as room-temperature gamma radiation detectors. We use predictive first principles theoretical methods to provide fundamental, atomic scale understanding of the defect properties of these materials to enable design of optimal growth and processing conditions, such as doping, annealing, and stoichiometry. Several recent cases will be reviewed, including (i) accurate calculations of the thermodynamic and electronic properties of native point defects and point defect complexes in CdTe and CZT; (ii) the effects of Zn alloying on the native point defect properties of CZT; (iii) point defect diffusion and binding related to Te clustering in Cd(Zn)Te; (iv) the profound effect of native point defects--principally vacancies--on the intrinsic material properties of TlBr, particularly electronic and ionic conductivity; (v) tailored doping of TlBr to independently control the electronic and ionic conductivity; and (vi) the effects of metal impurities on the electronic properties and device performance of TlBr detectors. Prepared by LLNL under Contract DE-AC52-07NA27344 with support from the National Nuclear Security Administration Office of Nonproliferation and Verification Research and Development NA-22.

  13. Lung Cancer Cell Line Screen Links Fanconi Anemia/BRCA Pathway Defects to Increased Relative Biological Effectiveness of Proton Radiation

    International Nuclear Information System (INIS)

    Liu, Qi; Ghosh, Priyanjali; Magpayo, Nicole; Testa, Mauro; Tang, Shikui; Gheorghiu, Liliana; Biggs, Peter; Paganetti, Harald; Efstathiou, Jason A.; Lu, Hsiao-Ming; Held, Kathryn D.; Willers, Henning

    2015-01-01

    Purpose: Growing knowledge of genomic heterogeneity in cancer, especially when it results in altered DNA damage responses, requires re-examination of the generic relative biological effectiveness (RBE) of 1.1 of protons. Methods and Materials: For determination of cellular radiosensitivity, we irradiated 17 lung cancer cell lines at the mid-spread-out Bragg peak of a clinical proton beam (linear energy transfer, 2.5 keV/μm). For comparison, 250-kVp X rays and 137 Cs γ-rays were used. To estimate the RBE of protons relative to 60 Co (Co60eq), we assigned an RBE(Co60Eq) of 1.1 to X rays to correct the physical dose measured. Standard DNA repair foci assays were used to monitor damage responses. FANCD2 was depleted using RNA interference. Results: Five lung cancer cell lines (29.4%) exhibited reduced clonogenic survival after proton irradiation compared with X-irradiation with the same physical doses. This was confirmed in a 3-dimensional sphere assay. Corresponding proton RBE(Co60Eq) estimates were statistically significantly different from 1.1 (P≤.05): 1.31 to 1.77 (for a survival fraction of 0.5). In 3 of these lines, increased RBE was correlated with alterations in the Fanconi anemia (FA)/BRCA pathway of DNA repair. In Calu-6 cells, the data pointed toward an FA pathway defect, leading to a previously unreported persistence of proton-induced RAD51 foci. The FA/BRCA-defective cells displayed a 25% increase in the size of subnuclear 53BP1 foci 18 hours after proton irradiation. Conclusions: Our cell line screen has revealed variations in proton RBE that are partly due to FA/BRCA pathway defects, suggesting that the use of a generic RBE for cancers should be revisited. We propose that functional biomarkers, such as size of residual 53BP1 foci, may be used to identify cancers with increased sensitivity to proton radiation

  14. Lung Cancer Cell Line Screen Links Fanconi Anemia/BRCA Pathway Defects to Increased Relative Biological Effectiveness of Proton Radiation

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Qi; Ghosh, Priyanjali; Magpayo, Nicole [Laboratory of Cellular and Molecular Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts (United States); Testa, Mauro; Tang, Shikui [Division of Radiation Physics, Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts (United States); Gheorghiu, Liliana [Laboratory of Cellular and Molecular Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts (United States); Biggs, Peter; Paganetti, Harald [Division of Radiation Physics, Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts (United States); Efstathiou, Jason A. [Laboratory of Cellular and Molecular Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts (United States); Lu, Hsiao-Ming [Division of Radiation Physics, Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts (United States); Held, Kathryn D. [Laboratory of Cellular and Molecular Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts (United States); Willers, Henning, E-mail: hwillers@mgh.harvard.edu [Laboratory of Cellular and Molecular Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts (United States)

    2015-04-01

    Purpose: Growing knowledge of genomic heterogeneity in cancer, especially when it results in altered DNA damage responses, requires re-examination of the generic relative biological effectiveness (RBE) of 1.1 of protons. Methods and Materials: For determination of cellular radiosensitivity, we irradiated 17 lung cancer cell lines at the mid-spread-out Bragg peak of a clinical proton beam (linear energy transfer, 2.5 keV/μm). For comparison, 250-kVp X rays and {sup 137}Cs γ-rays were used. To estimate the RBE of protons relative to {sup 60}Co (Co60eq), we assigned an RBE(Co60Eq) of 1.1 to X rays to correct the physical dose measured. Standard DNA repair foci assays were used to monitor damage responses. FANCD2 was depleted using RNA interference. Results: Five lung cancer cell lines (29.4%) exhibited reduced clonogenic survival after proton irradiation compared with X-irradiation with the same physical doses. This was confirmed in a 3-dimensional sphere assay. Corresponding proton RBE(Co60Eq) estimates were statistically significantly different from 1.1 (P≤.05): 1.31 to 1.77 (for a survival fraction of 0.5). In 3 of these lines, increased RBE was correlated with alterations in the Fanconi anemia (FA)/BRCA pathway of DNA repair. In Calu-6 cells, the data pointed toward an FA pathway defect, leading to a previously unreported persistence of proton-induced RAD51 foci. The FA/BRCA-defective cells displayed a 25% increase in the size of subnuclear 53BP1 foci 18 hours after proton irradiation. Conclusions: Our cell line screen has revealed variations in proton RBE that are partly due to FA/BRCA pathway defects, suggesting that the use of a generic RBE for cancers should be revisited. We propose that functional biomarkers, such as size of residual 53BP1 foci, may be used to identify cancers with increased sensitivity to proton radiation.

  15. Radiation response issues for infrared detectors

    Science.gov (United States)

    Kalma, Arne H.

    1990-01-01

    Researchers describe the most important radiation response issues for infrared detectors. In general, the two key degradation mechanisms in infrared detectors are the noise produced by exposure to a flux of ionizing particles (e.g.; trapped electronics and protons, debris gammas and electrons, radioactive decay of neutron-activated materials) and permanent damage produced by exposure to total dose. Total-dose-induced damage is most often the result of charge trapping in insulators or at interfaces. Exposure to short pulses of ionization (e.g.; prompt x rays or gammas, delayed gammas) will cause detector upset. However, this upset is not important to a sensor unless the recovery time is too long. A few detector technologies are vulnerable to neutron-induced displacement damage, but fortunately most are not. Researchers compare the responses of the new technologies with those of the mainstream technologies of PV HgCdTe and IBC Si:As. One important reason for this comparison is to note where some of the newer technologies have the potential to provide significantly improved radiation hardness compared with that of the mainstream technologies, and thus to provide greater motivation for the pursuit of these technologies.

  16. Adaptive response to high LET radiations

    International Nuclear Information System (INIS)

    Dam, Annamaria; Bogdandi, E. Noemi; Polonyi, Istvan; Sardy, M. Marta; Balashazy, Imre; Palfalvy, Jozsef

    2001-01-01

    The biological consequences of exposure to ionizing radiation include gene mutation, chromosome aberrations, cellular transformation and cell death. These effects are attributed to the DNA damaging effects of the irradiation resulting in irreversible changes during DNA replication or during the processing of the DNA damage by enzymatic repair processes. These repair processes could initiate some adaptive mechanisms in the cell, which could lead to radioadaptive response (RAR). Adaptive responses have typically been detected by exposing cells to a low radiation dose (1-50 mGy) and then challenging the cells with a higher dose of radiation (2-4 Gy) and comparing the outcome to that seen with the challenge dose only. For adaptive response to be seen the challenge dose must be delivered within 24 hour of the inducing dose. Radio-adaptation is extensively studied for low LET radiation. Nevertheless, few data are available for high LET radiation at very low doses and dose rate. Our study was aimed to investigate the radioadaptive response to low-dose neutron irradiation by detection of the genotoxic damage i.e.: hprt-mutant colonies induced. Altered protein synthesis was also studied to identify stress proteins may responsible for radio-adaptation. New alpha particle irradiator system was also built up to study the biological effects of low dose alpha irradiation. The experiments were carried out on monolayers of human melanoma and CHO (Chines Hamster Ovary) cells irradiated by neutrons produced in the biological irradiation channel of the Research Reactor of Budapest Neutron Center. Cells were exposed to 0.5-50 mGy neutron doses with dose rates of 1.59-10 mGy/min. The challenge doses of 2-4 Gy gamma rays were administrated within 1-48 hours after priming treatment. The induced mutants at hprt locus were selected by adding 6-thioguanine and allow to grow for 10 days for expression of the phenotype. The protein synthesis was studied by PAGE, the molecular mass of specific

  17. Radiation emergency response in Illinois, Alabama, and Texas

    International Nuclear Information System (INIS)

    Larsen, D.K.; Chester, R.O.

    1978-03-01

    The objective of this study was to examine state radiation emergency response and to locate any areas of emergency planning in need of improvement. This report briefly presents a summary of laws and defining documents governing radiation emergency response, describes the existing and projected need for such response, and presents the authors' analyses of the evolution of state response plans and their application to radiation incidents. Three states' programs are discussed in detail: Illinois, Alabama, and Texas. These states were selected because they have quite different emergency-response programs. Therefore, these state programs provide a wide variety of approaches to state radiation emergency response

  18. The influence of radiation-induced defects on thermoluminescence and optically stimulated luminescence of α-Al_2O_3:C

    International Nuclear Information System (INIS)

    Nyirenda, A.N.; Chithambo, M.L.

    2017-01-01

    It is known that when α-Al_2O_3:C is exposed to excessive amounts of ionising radiation, defects are induced within its matrix. We report the influence of radiation-induced defects on the thermoluminescence (TL) and optically stimulated luminescence (OSL) measured from α-Al_2O_3:C after irradiation to 1000 Gy. These radiation-induced defects are thermally unstable in the region 450–650 °C and result in TL peaks in this range when the TL is measured at 1 °C/s. Heating a sample to 700 °C obliterates the radiation-induced defects, that is, the TL peaks corresponding to the radiation induced defects are no longer observed in the subsequent TL measurements when moderate irradiation doses below 10 Gy are used. The charge traps associated with these radiation-induced defects are more stable than the dosimetric trap when the sample is exposed to either sunlight or 470-nm blue light from LEDs. TL glow curves measured following the defect-inducing irradiation produce a dosimetric peak that is broader and positioned at a higher temperature than observed in glow curves obtained before the heavy irradiation. In addition, sample sensitization/desensitization occurs due to the presence of these radiation-induced defects. Furthermore, both the activation energy and the kinetic order of the dosimetric peak evaluated when the radiation-induced defects are present in the sample are significantly lower in value than those obtained when these defects are absent. The radiation-induced defects also affect the shape and total light sum of the OSL signal as well as the position and width of the resultant residual phototransferred thermoluminescence main peak.

  19. The influence of radiation-induced defects on thermoluminescence and optically stimulated luminescence of α-Al{sub 2}O{sub 3}:C

    Energy Technology Data Exchange (ETDEWEB)

    Nyirenda, A.N., E-mail: anyirenda@gmail.com; Chithambo, M.L.

    2017-04-15

    It is known that when α-Al{sub 2}O{sub 3}:C is exposed to excessive amounts of ionising radiation, defects are induced within its matrix. We report the influence of radiation-induced defects on the thermoluminescence (TL) and optically stimulated luminescence (OSL) measured from α-Al{sub 2}O{sub 3}:C after irradiation to 1000 Gy. These radiation-induced defects are thermally unstable in the region 450–650 °C and result in TL peaks in this range when the TL is measured at 1 °C/s. Heating a sample to 700 °C obliterates the radiation-induced defects, that is, the TL peaks corresponding to the radiation induced defects are no longer observed in the subsequent TL measurements when moderate irradiation doses below 10 Gy are used. The charge traps associated with these radiation-induced defects are more stable than the dosimetric trap when the sample is exposed to either sunlight or 470-nm blue light from LEDs. TL glow curves measured following the defect-inducing irradiation produce a dosimetric peak that is broader and positioned at a higher temperature than observed in glow curves obtained before the heavy irradiation. In addition, sample sensitization/desensitization occurs due to the presence of these radiation-induced defects. Furthermore, both the activation energy and the kinetic order of the dosimetric peak evaluated when the radiation-induced defects are present in the sample are significantly lower in value than those obtained when these defects are absent. The radiation-induced defects also affect the shape and total light sum of the OSL signal as well as the position and width of the resultant residual phototransferred thermoluminescence main peak.

  20. A century of quantitating radiation response

    International Nuclear Information System (INIS)

    Withers, H.R.; Geffen, D.

    2003-01-01

    As their name indicates, X rays were a surprise serendipitous discovery about which nothing was known a little over a century ago. Not surprisingly, characterizing of dose responses evolved slowly, reflecting difficulties in quantifying both physical dose and biological responses. It was about 35 years after Roentgen's discovery before an international standard (the R) was accepted for measuring dose and named after him. Within 10 years of that there was pressure to change from measuring ionization of air to absorbed dose in tissue but another 20 years and a second World War before the rad was adopted. Thirty years later the rad was dropped in favor of SI units to describe the same thing and named the Gray after the main proponent of the concept of the rad. Early on, radiochemical dosimetry was introduced in the form of color changes in proprietary pastilles. Biological function was also used as a dosimeter in the early times, examples being erythema of the skin, inhibition of growth of bean roots, or the suppression of hatching of eggs from fruit flies or worms. Other biological responses were measured (eg destruction of fertility by irradiating testes), but were not used as dosimeters. Dose survival curves based on clonal regrowth by survivors were first described for bacteria about 30 years before Puck's first description of mammalian ceFll radiosensitivity, using Chinese hamster cells. Functional changes in irradiated normal tissues after a multifraction course of radiation therapy can provide a very precise estimate of cell survival per single dose fraction but conversely, it requires very precise measurement of survival from a single dose fraction to be able to predict the ultimate response to a series of doses, a level of precision never likely to be achieved for clinical application. It seems that there is not a wide spread in radiosensitivities of normal tissues within the population. Progress is slow in predicting which tumors will respond poorly to

  1. Defective B cell response to T-dependent immunization in lupus-prone mice

    Science.gov (United States)

    Niu, Haitao; Sobel, Eric S.; Morel, Laurence

    2009-01-01

    Lupus anti-nuclear Abs show the characteristics of Ag-driven T cell-dependent (TD) humoral responses. If autoAgs elicit the same response as exogenous Ags, lupus should enhance humoral responses to immunization. Blunted responses to various immunizations have, however, been reported in a significant portion of lupus patients. In this study, we show that lupus-prone B6.Sle1.Sle2.Sle3 (B6.TC) mice produce significantly less Ab in response to TD immunization than congenic controls, while producing significantly more total Ig. This blunted Ab response to TD Ag could be reconstituted with B6.TC B and CD4+ T cells. Multiple defects were found in the B6.TC response to NP-KLH as compared to total Ig, including a smaller percentage of B cells participating to the NP-response, a reduced entry into germinal centers, and highly defective production of NP-specific long-lived plasma cells in the bone marrow. B6.TC plasma cells expressed reduced levels of FcγRIIb, which suggests that reduced apoptosis in resident plasma cells prevents the establishment of newly-formed NP-specific plasma cells in bone marrow niches. Overall, these results show that lupus-prone mice responded differently to auto- and exogenous antigens and suggest that low FcγRIIb, hypergammaglobulinemia and high autoantibody production would be predictive of a poor response to immunization in lupus patients. PMID:18924209

  2. Radiation damage and defect behavior in proton irradiated lithium-counterdoped n+p silicon solar cells

    Science.gov (United States)

    Stupica, John; Goradia, Chandra; Swartz, Clifford K.; Weinberg, Irving

    1987-01-01

    Two lithium-counterdoped n+p silicon solar cells with different lithium concentrations were irradiated by 10-MeV protons. Cell performance was measured as a function of fluence, and it was found that the cell with the highest concentration of lithium had the highest radiation resistance. Deep level transient spectroscopy which showed two deep level defects that were lithium related. Relating the defect energy levels obtained from this study with those from earlier work using 1-MeV electron irradiation shows no correlation of the defect energy levels. There is one marked similarity: the absence of the boron-interstitial-oxygen-interstitial defect. This consistency strengthens the belief that lithium interacts with oxygen to prevent the formation of the boron interstitial-oxygen interstitial defect. The results indicate that, in general, addition of lithium in small amounts to the p-base of a boron doped silicon solar cell such that the base remains p-type, tends to increase the radiation resistance of the cell.

  3. Photoionization spectroscopy of deep defects responsible for current collapse in nitride-based field effect transistors

    International Nuclear Information System (INIS)

    Klein, P B; Binari, S C

    2003-01-01

    This review is concerned with the characterization and identification of the deep centres that cause current collapse in nitride-based field effect transistors. Photoionization spectroscopy is an optical technique that has been developed to probe the characteristics of these defects. Measured spectral dependences provide information on trap depth, lattice coupling and on the location of the defects in the device structure. The spectrum of an individual trap may also be regarded as a 'fingerprint' of the defect, allowing the trap to be followed in response to the variation of external parameters. The basis for these measurements is derived through a modelling procedure that accounts quantitatively for the light-induced drain current increase in the collapsed device. Applying the model to fit the measured variation of drain current increase with light illumination provides an estimate of the concentrations and photoionization cross-sections of the deep defects. The results of photoionization studies of GaN metal-semiconductor field effect transistors and AlGaN/GaN high electron mobility transistors (HEMTs) grown by metal-organic chemical vapour deposition (MOCVD) are presented and the conclusions regarding the nature of the deep traps responsible are discussed. Finally, recent photoionization studies of current collapse induced by short-term (several hours) bias stress in AlGaN/GaN HEMTs are described and analysed for devices grown by both MOCVD and molecular beam epitaxy. (topical review)

  4. Medical Response in Radiation Emergency in Argentina

    International Nuclear Information System (INIS)

    Vazquez, M.A.; Tadic, M.M.

    2011-01-01

    According to the Nuclear Federal Law No. 24804, the Nuclear Regulatory Authority (ARN) is empowered to regulate and control the nuclear activity with regard to radiological and nuclear safety, physical protection and nuclear non-proliferation issues. ARN has a system for intervention in radiological -and nuclear emergencies with a primary intervention group, which is on duty in weekly shifts all year round. This paper aims at describing the system as implemented at present. The Emergency Medical System has been developed into three levels: Level I: local emergency services. This level includes triage (conventional and radiological), first-aid care, and first management of contaminated victims Level II: emergency departments of local general hospitals that are in charge of performing a second triage by a biomedical approach, the treatment of conventional and/or radiocombined injuries and completing decontamination as necessary. In this way the initial triage is completed by a physical examination, timing and severity of prodromal signs and symptoms, sequential blood counts and serum enzymatic levels that allow a first-stage dosimetric approach at this level. Victims requiring higher complexity assistance shall be transferred to third-level hospitals. Level III: three central reference hospitals (Hospital Naval 'Pedro Mallo', Hospital de Quemados from Gobierno Autonomo de la Ciudad de Buenos Aires and Hospital Britanico de Ciudad de Buenos Aires) capable of providing healthcare for diagnosis and treatment of acute radiation syndrome, cutaneous radiation syndrome and internal contamination constitute this level. An educational program for medical and paramedical responders is regularly carried out at the three levels, including theoretical background as well as practical training. Guidelines and protocols for medical handling of victims have been drawn up. Research and development of new strategies for first medical response, diagnosis and treatment of radiation

  5. Medical response in radiation emergency in Argentina

    International Nuclear Information System (INIS)

    Vazquez, Marina A.; Tadic, Maria M.

    2008-01-01

    According to the Nuclear Federal Law Nr. 24804, the Nuclear Regulatory Authority (ARN) is empowered to regulate and control the nuclear activity with regard to radiological and nuclear safety, physical protection and nuclear non-proliferation issues. ARN has a system for intervention in radiological -and nuclear emergencies with a primary intervention group, which is on duty in weekly shifts all year round. This paper aims at describing the system as implemented at present. The Emergency Medical System has been developed into three levels: Level I: local emergency services. This level includes triage (conventional and radiological), first-aid care, and first management of contaminated victims. Level II: Emergency departments of local general hospitals that are in charge of performing a second triage by a biomedical approach, the treatment of conventional and/or radio-combined injuries and completing decontamination as necessary. In this way the initial triage is completed by a physical examination, timing and severity of prodromal signs and symptoms, sequential blood counts and serum enzymatic levels that allow a first-stage dosimetric approach at this level. Victims requiring higher complexity assistance shall be transferred to third-level hospitals. Level III: three central reference hospitals (Hospital Naval 'Pedro Mallo', Hospital de Quemados from Gobierno Autonomo de la Ciudad de Buenos Aires and Hospital Britanico de Ciudad de Buenos Aires) capable of providing health care for diagnosis and treatment of acute radiation syndrome, cutaneous radiation syndrome and internal contamination constitute this level. An educational program for medical and paramedical responders is regularly carried out at the three levels, including theoretical background as well as practical training. Guidelines and protocols for medical handling of victims have been drawn up. Research and development of new strategies for first medical response, diagnosis and treatment of radiation

  6. Direct analysis of quantal radiation response data

    International Nuclear Information System (INIS)

    Thames, H.D. Jr.; Rozell, M.E.; Tucker, S.L.; Ang, K.K.; Travis, E.L.; Fisher, D.R.

    1986-01-01

    A direct analysis is proposed for quantal (all-or-nothing) responses to fractionated radiation and endpoint-dilution assays of cell survival. As opposed to two-step methods such as the reciprocal-dose technique, in which ED 50 values are first estimated for different fractionation schemes and then fit (as reciprocals) against dose per fraction, all raw data are included in a single maximum-likelihood treatment. The method accommodates variations such as short-interval fractionation regimens designed to determine tissue repair kinetics, tissue response to continuous exposures, and data obtained using endpoint-dilution assays of cell survival after fractionated doses. Monte-Carlo techniques were used to compare the direct and reciprocal-dose methods for analysis of small-scale and large-scale studies of response to fractionated doses. Both methods tended toward biased estimates in the analysis of small-scale (3 fraction numbers) studies. The α/β ratios showed less scatter when estimated by the direct method. The 95% confidence intervals determined by the direct method were more appropriate than those determined by reciprocal-dose analysis, for which 18% (small-scale study) or 8% (large-scale study) of the confidence intervals did not include the 'true' value of α/β. (author)

  7. Production and recombination of radiation defects in argon and krypton crystals

    International Nuclear Information System (INIS)

    Giersberg, E.J.

    1981-01-01

    Relative changes in the lattice constants of argon and krypton crystals have been measured by X-ray diffraction. As a result X-ray irradiation is found to produce stable defects. The recombination behaviour of these defects can be determined by isochronous and isothermal annealing. The creation of primary defects can be explained by exciton excitation and double-ionisation. (orig.) [de

  8. Radioadaptive response and radiation-induced teratogenesis in the late period of organogenesis in mice. Involvement of p53-dependent apoptosis

    International Nuclear Information System (INIS)

    Wang, Bing; Ohyama, Harumi; Nose, Masako; Yukawa, Osami; Yamada, Takeshi; Hayata, Isamu

    2003-01-01

    In the past 5 years, a series of study was done at our institute to investigate radiation effects on the embryogenesis in mice with an emphasis on mechanisms involved in the radiation-induced adaptive response and the role of radiation-induced apoptosis played in teratogenesis in the late period of organogenesis. Using the limb bud system, we first found that radiation-induced apoptosis is involved in malformations, namely, radiation-induced apoptosis in the predigital regions of embryonic limb buds is responsible for digital defects in ICR mice. Examination of embryonic C57BL/6J mice with different p53 status led to further finding that susceptibility to the radiation-induced apoptosis and digital defects depends on both the p53 status and the radiation dose. p53 wild-type mice appeared to be the most sensitive, while p53 knockout mice were the most resistant. These results indicate that p53-dependent apoptosis mediates radiation-induced digital defects. The existence of a radioadaptive response in fetuses, i.e., the priming dose significantly decreases the apoptosis induction, prenatal death, and digital defects in the living fetuses induced by the challenging dose, was found first in ICR strain mice and later confirmed again in C57BL/6J mice. p53 heterozygous embryos did not show the radioadaptive response, indicating the involvement of p53 in the radioadaptive response. (author)

  9. Microstrip linear phase low pass filter based on defected ground structures for partial response modulation

    DEFF Research Database (Denmark)

    Cimoli, Bruno; Johansen, Tom Keinicke; Olmos, Juan Jose Vegas

    2018-01-01

    We report a high performance linear phase low pass filter (LPF) designed for partial response (PR) modulations. For the implementation, we adopted microstrip technology and a variant of the standard stepped‐impedance technique. Defected ground structures (DGS) are used for increasing the characte......We report a high performance linear phase low pass filter (LPF) designed for partial response (PR) modulations. For the implementation, we adopted microstrip technology and a variant of the standard stepped‐impedance technique. Defected ground structures (DGS) are used for increasing...... the characteristic impedance of transmission lines. Experimental results prove that the proposed filter can successfully modulate a non‐return‐to‐zero (NRZ) signal into a five levels PR one....

  10. Radiation defects in GaP and solid solution of GaAssub(1-x)Psub(x)

    International Nuclear Information System (INIS)

    Brailovsky, E.Y.; Grigoryan, N.E.; Marchouk, N.D.; Pambuhchyan, N.H.; Tartachnik, V.P.

    1979-01-01

    The introduction and annealing behaviour of radiation defects in GaP and GaAssub(1-x)Psub(x) at 1 to 50 MeV electron irradiation was investigated by the Hall effect, thermal stimulated current (TSC) and optical absorption. The recovery of electrical properties of irradiated GaAssub(1-x)Psub(x) was dependent on x. From TSC measurement it has been shown that the predominant radiation defects in GaP are electron traps Esub(c) - (1.2 +- 0.1)eV and hole traps Esub(v) + (1.5 +- 0.15)eV which are the cause of n and p decreasing in GaP crystals. The formation of density state 'tails' during irradiation was investigated. (author)

  11. Study of correlation between the structural defects and inhomogeneities of CDTE based radiation detectors used for medical imaging

    International Nuclear Information System (INIS)

    Buis, Camille

    2013-01-01

    In the present Ph.D. thesis, we investigate microstructural defects in a chlorine-doped cadmium telluride crystal (CdTe:Cl), to understand the relationship between defects and performance of CdTe-based radiation detectors. Characterization tools, such as diffraction topography and chemical etching, are used for bulk and surface investigations of the distribution of dislocations. Dislocations are arranged into walls. Most of them appear to cross the whole thickness of the sample. Very good correlation is observed between areas with variations of dark-current and photo-current, and positions of the dislocation walls revealed at the surface of the sample. Then spectroscopic analysis of these defects was performed at low temperatures. It highlighted that dislocation walls induce non-radiative recombination, but it didn't show any Y luminescence usually attributed to dislocations in the literature. Ion Beam Induced Current (IBIC) measurements were used to evaluate the influence of dislocation walls on charge carrier transport properties. This experiment shows that they reduce the mobility-lifetime product of the charge carriers. A very clear correlation was, in fact, established between the distribution of the dislocation network and the linear defects revealed by their lower CIE on the device. (author) [fr

  12. On correction of model of stabilization of distribution of concentration of radiation defects in a multilayer structure with account experiment data

    Science.gov (United States)

    Pankratov, E. L.

    2018-05-01

    We introduce a model of redistribution of point radiation defects, their interaction between themselves and redistribution of their simplest complexes (divacancies and diinterstitials) in a multilayer structure. The model gives a possibility to describe qualitatively nonmonotonicity of distributions of concentrations of radiation defects on interfaces between layers of the multilayer structure. The nonmonotonicity was recently found experimentally. To take into account the nonmonotonicity we modify recently used in literature model for analysis of distribution of concentration of radiation defects. To analyze the model we used an approach of solution of boundary problems, which could be used without crosslinking of solutions on interfaces between layers of the considered multilayer structures.

  13. Responses of populations of small mammals to ionizing radiation

    International Nuclear Information System (INIS)

    Kitchings, J.T.

    1978-01-01

    Studies on the responses of small mammals to ionizing radiation have, over the past 30 years, documented numerous effects on direct mortality, reproduction, the hemopoietic systems, and radionuclide metabolism. Three general findings have resulted from past efforts: (1) ionizing radiation is a factor in environmental stress, (2) the response of wild small mammals to ionizing radiation is a mosaic of varying radiosensitivities interacting with environmental variables, and (3) one of the most sensitive organismal processes to radiation is reproduction. While an excellent understanding of the biological effects resulting from high or intermediate-level radiation exposures has been developed, this is not the case for effects of low-level doses

  14. Destruction-polymerization transformations as a source of radiation-induced extended defects in chalcogenide glassy semiconductors

    International Nuclear Information System (INIS)

    Shpotyuk, Oleh; Filipecki, Jacek; Shpotyuk, Mykhaylo

    2013-01-01

    Long-wave shift of the optical transmission spectrum in the region of fundamental optical absorption edge is registered for As 2 S 3 chalcogenide glassy semiconductors after γ-irradiation. This effect is explained in the frameworks of the destruction-polymerization transformations concept by accepting the switching of the heteropolar As-S covalent bonds into homopolar As-As ones. It is assumed that (As 4 + ; S 1 - ) defect pairs are created under such switching. Formula to calculate content of the induced defects in chalcogenide glassy semiconductors is proposed. It is assumed that defects concentration depends on energy of broken covalent bond, bond-switching energy balance, correlation energy, optical band-gap and energy of excitation light. It is shown that theoretically calculated maximally possible content of radiation-induced defects in As 2 S 3 is about 1.6% while concentration of native defects is negligible. (copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  15. Complex control of ATM in response to radiation damage to DNA

    International Nuclear Information System (INIS)

    Lavin, M.F.; Beamish, H.; Chen, P.; Keating, K.; Scott, S.; Spring, K.; Kozlov, S.; Walters, D.

    2000-01-01

    Full text: The human genetic disorder ataxia-telangiectasia is characterized by neurodegeneration, immunodeficiency, extreme sensitivity to ionizing radiation, abnormalities in cell cycle checkpoints and a predisposition to develop leukemias and lymphomas. It appears likely that the basis of the hypersensitivity to ionizing radiation is due to defective sensing of double strand breaks in DNA and as a consequence a failure to repair all of these breaks. After exposure of cells to radiation the kinase activity of pre-existing ATM protein is rapidly activated leading to the radiation-induced phosphoylation of a number of important substrates including p53, c-Abl, BRCA1, NBS1 and chk2. Defective phosphorylation of BRCA1 and NBS1 is associated with increased sensitivity to ionizing radiation. We have also demonstrated that a reduction in the amount of ATM protein using antisense ATM cDNA transfection prior to exposure to radiation also sensitizes cells. This was further confirmed by treating human lymphoblastoid cells with EGF prior to radiation exposure. Furthermore radiation reverses the downregulation of ATM by EGF over a 3 hour period. Under these conditions cells are still sensitized to radiation since the restoration of ATM kinase activity is slower than that arising from activation of existing protein. Alterations in the amount of ATM protein are also observed in response to mitogenic agents. Thus it is evident that ATM protein and kinase activity are regulated in a complex fashion and this appears to vary in different tissues. The implications for altering ATM for therapeutic benefit will be discussed

  16. Abnormal photothermal effect of laser radiation on highly defect oxide bronze nanoparticles under the sub-threshold excitation of absorption

    Science.gov (United States)

    Gulyaev, P.; Kotvanova, M.; Omelchenko, A.

    2017-05-01

    The mechanism of abnormal photo-thermal effect of laser radiation on nanoparticles of oxide bronzes has been proposed in this paper. The basic features of the observed effect are: a) sub-threshold absorption of laser radiation by the excitation of donor-like levels formed in the energy gap due to superficial defects of the oxide bronze nano-crystals; b) an interband radiationless transition of energy of excitation on deep triplet levels and c) consequent recombination occurring at the plasmon absorption. K or Na atoms thermally intercalated to the octahedral crystal structure of TiO2 in the wave SHS combustion generate acceptor levels in the gap. The prepared oxide bronzes of the non-stoichiometric composition NaxTiO2 and KxTiO2 were examined by high resolution TEM, and then grinded in a planetary mill with powerful dispersion energy density up to 4000 J/g. This made it possible to obtain nanoparticles about 50 nm with high surface defect density (1017-1019 cm-2 at a depth of 10 nm). High photo-thermal effect of laser radiation on the defect nanocrystals observed after its impregnation into cartilaginous tissue exceeds 7 times in comparison with the intact ones.

  17. Design of radiation dose tumor response assays

    International Nuclear Information System (INIS)

    Suit, H.D.; Hwang, T.; Hsieh, C.; Thames, H.

    1985-01-01

    The efficient utilization of animals in a radiation dose response assay for tumor control requires a definition of the goal, e.g., TCD50 or slope. A series of computer modelled ''experiments'' have been performed for each of a number of allocations of dose levels (DL) and number of animals/DL. The authors stipulated that the assumed TCD50 was .85 of true value; assumed slope was correct. They stipulated a binominal distribution of observed tumor control results at each dose level. A pilot assay used 6 tumors at 7 DL (from TCD1-TCD97). The second assay used 30 tumors assigned to 2,3,5 or 9 DL and to selected tumor control probabilities (TCP derived from the pilot run. Results from 100 test runs were combined with the pilot run for each of the combination of DL and TCP values. Logit regression lines were fitted through these ''data'' and the 95% CL around the TCD50 and the TCD37 values and the variances of the slopes were computed. These experiments were repeated using the method suggested by Porter (1980). Results show that a different strategy is needed depending upon the goal, viz. TCD50 or TCD37 vs slope. The differences between the two approaches are discussed

  18. Antibody responses in allogeneic radiation chimeras

    International Nuclear Information System (INIS)

    Coico, R.F.

    1982-01-01

    The construction of long-lived allogeneic radiation chimeras, free of graft-versus-host disease, has been achieved using serologic elimination of Thy 1 + cells from donor bone marrow. Humoral immune function was not restored in these animals as evidenced by lack of primary antibody responses to a T cell-dependent antigen, namely, sheep erythrocytes (SRBC) both in vivo and in vitro. No evidence for a suppressor cell-mediated mechanism was found. Using separated chimera spleen cell populations and specific helper cell soluble mediators, the functional capabilities of chimera B cells, T cells, and macrophages were assessed. These findings suggested that the failure of chimeras to produce antibody is not the result of impaired B cell, T cell, or macrophage function, but rather, that it is due to ineffective cellular interactions. Physiologic cellular interactions depend upon the sharing of major histocompatibility complex (MHC) determinants between interacting cells. However, the self-recognition repertoire of developing T cells may be influenced by the environment which these cells differentiate such that they learn to recognize host MHC determinants as self. These findings support the interpretation that the immunologic hyporeactivity of allogeneic bone marrow chimeras reflects the role of the host environment in restricting the interactive capabilities of donor-derived cells

  19. Ionizing radiation induced biological response and its public health implication

    International Nuclear Information System (INIS)

    Koeteles, Gy.

    1994-01-01

    Several sources of ionizing radiation exist in natural and artificial environment of humanity. An overview of their biological effects and the biological response of man is present. Emphasize is given to the differences caused by high and low doses. The interrelation of radiology, radiation hygiene and public health is pointed out. Especially, the physical and biological effects of radiation on cells and their responses are discussed in more detail. (R.P.)

  20. Modification of Acute Radiation Response in Different Demographic Age Groups

    Science.gov (United States)

    2017-10-25

    greater radiosensitivity. Other studies provided further mechanistic insight into the observed age effect of radiation responses. For example ...DISTRIBUTION A. Approved for public release; distribution is unlimited. October 2017 HDTRA1-14-0003; 0005 Prepared by: Applied ... Research Associates, Inc. 801 N. Quincy Street Suite 700 Arlington, VA 22203 Modification of Acute Radiation Response in Different Demographic Age

  1. Echo detected EPR as a tool for detecting radiation-induced defect signals in pottery

    International Nuclear Information System (INIS)

    Zoleo, Alfonso; Bortolussi, Claudia; Brustolon, Marina

    2011-01-01

    Archaeological fragments of pottery have been investigated by using CW-EPR and Echo Detected EPR (EDEPR). EDEPR allows to remove the CW-EPR dominant Fe(III) background spectrum, hiding much weaker signals potentially useful for dating purpose. EDEPR spectra attributed to a methyl radical and to feldspar defects have been recorded at room and low temperature for an Iron Age cooking ware (700 B.C.). A study on the dependence of EDEPR intensity over absorbed dose on a series of γ-irradiated brick samples (estimated age of 562 ± 140 B.C.) has confirmed the potential efficacy of the proposed method for spotting defect signals out of the strong iron background. - Highlights: → Fe(III) CW-EPR signals cover CW-EPR-detectable defects in ceramics. → Echo detected EPR gets rid of Fe(III) signals, disclosing defect signals. → Echo detected EPR detects defect signals even at relatively low doses.

  2. Impact of time to maternal interview on interview responses in the National Birth Defects Prevention Study.

    Science.gov (United States)

    Tinker, Sarah C; Gibbs, Cassandra; Strickland, Matthew J; Devine, Owen J; Crider, Krista S; Werler, Martha M; Anderka, Marlene T; Reefhuis, Jennita

    2013-06-01

    Prenatal exposures often are assessed using retrospective interviews. Time from exposure to interview may influence data accuracy. We investigated the association of time to interview (TTI) with aspects of interview responses in the National Birth Defects Prevention Study, a population-based case-control study of birth defects in 10 US states. Mothers completed a computer-assisted telephone interview 1.5-24 months after their estimated date of delivery. Proxy metrics for interview quality were whether certain exposures were reported, whether the start month of reported medication use or illness was reported, or whether responses were missing. Interaction by case status was assessed. Interviews were completed with 30,542 mothers (22,366 cases and 8,176 controls) who gave birth between 1997 and 2007. Mothers of cases were interviewed later than were mothers of controls (11.7 months vs. 9.5 months, respectively). In adjusted analyses, having a TTI that was greater than 6 months was associated with only a few aspects of interview responses (e.g., start month of pseudoephedrine use). Interaction by case-control status was observed for some exposures; mothers of controls had a greater reduction in interview quality with increased TTI in these instances (e.g., report of morning sickness, start month of acetaminophen use and ibuprofen use). The results suggest that TTI might impact interview responses; however, the impact may be minimal and specific to the type of exposure.

  3. Physiological responses of plants to ionizing radiation

    International Nuclear Information System (INIS)

    Gaur, B.K.

    1985-01-01

    Based on the parallelism between the effects of radiation and 2, 4-dinitrophenol on oxygen uptake, oxidative phosphorylation, mitochondrial swelling and contraction and ATPase activity, it is inferred that radiation acts as an uncoupling agent, probably through stimulated hydrolysis of the non-phosphorylated high energy intermediate I-X

  4. Semiconductors Under Ion Radiation: Ultrafast Electron-Ion Dynamics in Perfect Crystals and the Effect of Defects

    Science.gov (United States)

    Lee, Cheng-Wei; Schleife, André

    Stability and safety issues have been challenging difficulties for materials and devices under radiation such as solar panels in outer space. On the other hand, radiation can be utilized to modify materials and increase their performance via focused-ion beam patterning at nano-scale. In order to grasp the underlying processes, further understanding of the radiation-material and radiation-defect interactions is required and inevitably involves the electron-ion dynamics that was traditionally hard to capture. By applying Ehrenfest dynamics based on time-dependent density functional theory, we have been able to perform real-time simulation of electron-ion dynamics in MgO and InP/GaP. By simulating a high-energy proton penetrating the material, the energy gain of electronic system can be interpreted as electronic stopping power and the result is compared to existing data. We also study electronic stopping in the vicinity of defects: for both oxygen vacancy in MgO and interface of InP/GaP superlattice, electronic stopping shows strong dependence on the velocity of the proton. To study the energy transfer from electronic system to lattice, simulations of about 100 femto-seconds are performed and we analyze the difference between Ehrenfest and Born-Oppenheimer molecular dynamics.

  5. Influence of surface defects in ZnO thin films on its biosensing response characteristic

    Energy Technology Data Exchange (ETDEWEB)

    Saha, Shibu; Gupta, Vinay [Department of Physics and Astrophysics, University of Delhi, Delhi-110007 (India)

    2011-09-15

    Highly c-axis oriented zinc oxide (ZnO) thin films deposited by rf magnetron sputtering under varying processing pressure (20-50 mT) in a reactive gas mixture of argon and oxygen were studied for biosensing application. The as-deposited ZnO thin films were in a state of compressive stress having defects related to interstitial Zn and antisite oxygen. Glucose oxidase has been chosen as the model enzyme in the present study and was immobilized on the surface of ZnO thin films deposited on indium tin oxide coated Corning Glass substrate. The studies reveal a correlation between the biosensing characteristic and the presence of defects in the ZnO films. The ZnO films deposited under high pressure (50 mT) are found to be more sensitive for biosensing application due to availability of more surface area for effective immobilization of biomolecules and exhibits a suitable microenvironment with good electron transfer characteristic. The obtained results highlight the importance of desired microstate besides availability of suitable native defects in the ZnO thin film for exhibiting enhanced biosensing response.

  6. Influence of surface defects in ZnO thin films on its biosensing response characteristic

    International Nuclear Information System (INIS)

    Saha, Shibu; Gupta, Vinay

    2011-01-01

    Highly c-axis oriented zinc oxide (ZnO) thin films deposited by rf magnetron sputtering under varying processing pressure (20-50 mT) in a reactive gas mixture of argon and oxygen were studied for biosensing application. The as-deposited ZnO thin films were in a state of compressive stress having defects related to interstitial Zn and antisite oxygen. Glucose oxidase has been chosen as the model enzyme in the present study and was immobilized on the surface of ZnO thin films deposited on indium tin oxide coated Corning Glass substrate. The studies reveal a correlation between the biosensing characteristic and the presence of defects in the ZnO films. The ZnO films deposited under high pressure (50 mT) are found to be more sensitive for biosensing application due to availability of more surface area for effective immobilization of biomolecules and exhibits a suitable microenvironment with good electron transfer characteristic. The obtained results highlight the importance of desired microstate besides availability of suitable native defects in the ZnO thin film for exhibiting enhanced biosensing response.

  7. Survival and SOS response induction in ultraviolet B irradiated Escherichia coli cells with defective repair mechanisms.

    Science.gov (United States)

    Prada Medina, Cesar Augusto; Aristizabal Tessmer, Elke Tatjana; Quintero Ruiz, Nathalia; Serment-Guerrero, Jorge; Fuentes, Jorge Luis

    2016-06-01

    Purpose In this paper, the contribution of different genes involved in DNA repair for both survival and SOS induction in Escherichia coli mutants exposed to ultraviolet B radiation (UVB, [wavelength range 280-315 nm]) was evaluated. Materials and methods E. coli strains defective in uvrA, oxyR, recO, recN, recJ, exoX, recB, recD or xonA genes were used to determine cell survival. All strains also had the genetic sulA::lacZ fusion, which allowed for the quantification of SOS induction through the SOS Chromotest. Results Five gene products were particularly important for survival, as follows: UvrA > RecB > RecO > RecJ > XonA. Strains defective in uvrA and recJ genes showed elevated SOS induction compared with the wild type, which remained stable for up to 240 min after UVB-irradiation. In addition, E. coli strains carrying the recO or recN mutation showed no SOS induction. Conclusions The nucleotide excision and DNA recombination pathways were equally used to repair UVB-induced DNA damage in E. coli cells. The sulA gene was not turned off in strains defective in UvrA and RecJ. RecO protein was essential for processing DNA damage prior to SOS induction. In this study, the roles of DNA repair proteins and their contributions to the mechanisms that induce SOS genes in E. coli are proposed.

  8. Early transcriptional responses of internalization defective Brucella abortus mutants in professional phagocytes, RAW 264.7.

    Science.gov (United States)

    Cha, Seung Bin; Lee, Won Jung; Shin, Min Kyoung; Jung, Myung Hwan; Shin, Seung Won; Yoo, An Na; Kim, Jong Wan; Yoo, Han Sang

    2013-06-27

    Brucella abortus is an intracellular zoonotic pathogen which causes undulant fever, endocarditis, arthritis and osteomyelitis in human and abortion and infertility in cattle. This bacterium is able to invade and replicate in host macrophage instead of getting removed by this defense mechanism. Therefore, understanding the interaction between virulence of the bacteria and the host cell is important to control brucellosis. Previously, we generated internalization defective mutants and analyzed the envelope proteins. The present study was undertaken to evaluate the changes in early transcriptional responses between wild type and internalization defective mutants infected mouse macrophage, RAW 264.7. Both of the wild type and mutant infected macrophages showed increased expression levels in proinflammatory cytokines, chemokines, apoptosis and G-protein coupled receptors (Gpr84, Gpr109a and Adora2b) while the genes related with small GTPase which mediate intracellular trafficking was decreased. Moreover, cytohesin 1 interacting protein (Cytip) and genes related to ubiquitination (Arrdc3 and Fbxo21) were down-regulated, suggesting the survival strategy of this bacterium. However, we could not detect any significant changes in the mutant infected groups compared to the wild type infected group. In summary, it was very difficult to clarify the alterations in host cellular transcription in response to infection with internalization defective mutants. However, we found several novel gene changes related to the GPCR system, ubiquitin-proteosome system, and growth arrest and DNA damages in response to B. abortus infection. These findings may contribute to a better understanding of the molecular mechanisms underlying host-pathogen interactions and need to be studied further.

  9. Proceedings of the TMS symposium on radiation facilities and defect studies

    International Nuclear Information System (INIS)

    Snead, C.L. Jr.

    1992-01-01

    Intent of the symposium is to highlight the various means of producing and characterizing irradition-induced defects in materials of interest in nuclear applications. Viewgraphs are presented for 18 papers. Separate abstracts were prepared for the data base

  10. The detection of radiation defects by means of the Kossel effect investigated in proton-irradiated GaP

    International Nuclear Information System (INIS)

    Ullrich, H.J.; Rolle, S.; Geist, V.; Stephan, D.

    1984-01-01

    The line intensity of Ga-K/sub α/- and P-K/sub α/-Kossel reflections from GaP irradiated by 0.3 to 1.3 MeV protons in a wide dose range (10 14 to 5 x 10 17 cm -2 ) has been investigated. The excitation of the characteristic X-rays inside the crystal lattice has been performed either by 40 keV electrons or 1.3 MeV protons. It is established that, in contrast to the P-K/sub α/-lines, certain Ga-K/sub α/-reflections respond very sensitively to radiation defects, manifest as increase or decrease in line intensity. The reason is probably a modification of extinction effects caused by lattice defects. The different behaviour of these phenomena is discussed and an explanation proposed. The lattice disorder is determined by channeling backscattering measurements. (author)

  11. Study of defects, radiation damage and implanted gases in solids by field-ion and atom-probe microscopy

    International Nuclear Information System (INIS)

    Seidman, D.N.; Amano, J.; Wagner, A.

    1980-10-01

    The ability of the field-ion microscope to image individual atoms has been applied, at Cornell University, to the study of fundamental properties of point defects in irradiated or quenched metals. The capability of the atom probe field-ion microscope to determine the chemistry - that is, the mass-to-charge ratio - of a single ion has been used to investigate the behavior of different implanted species in metals. A brief review is presented of: (1) the basic physical principles of the field-ion and atom-probe microscopes; (2) the many applications of these instruments to the study of defects and radiation damage in solids; and (3) the application of the atom-probe field-ion microscope to the study of the behavior of implanted 3 He and 4 He atoms in tungsten. The paper is heavily referenced so that the reader can pursue his specific research interests in detail

  12. Use of Isobestic and Isoemission Points in Absorption and Luminescence Spectra for Study of the Transformation of Radiation Defects in Lithium Fluoride

    Science.gov (United States)

    Voitovich, A. P.; Kalinov, V. S.; Stupak, A. P.; Runets, L. P.

    2015-03-01

    Isobestic and isoemission points are recorded in the combined absorption and luminescence spectra of two types of radiation defects involved in complex processes consisting of several simultaneous parallel and sequential reactions. These points are observed if a constant sum of two terms, each formed by the product of the concentration of the corresponding defect and a characteristic integral coefficient associated with it, is conserved. The complicated processes involved in the transformation of radiation defects in lithium fluoride are studied using these points. It is found that the ratio of the changes in the concentrations of one of the components and the reaction product remains constant in the course of several simultaneous reactions.

  13. Chinese experience on medical response to radiation emergencies

    International Nuclear Information System (INIS)

    Liu, Ying; Qin, Bin; Lei, Cuiping; Chen, Huifang; Han, Yuhong

    2008-01-01

    Full text: Chinese Center for Medical Response to Radiation Emergency (CCMRRE) was established in 1992, based on the National Institute for Radiological Protection, China CDC (NIRP, China CDC). CCMRRE is a liaison of WHO/REMPAN and functions as a national and professional institute for medical preparedness and response to emergencies involving radioactive material. CCMRRE participates in drafting National Medical Assistant Program for Radiation Emergency and relevant technical documents, develops preventive measures and technique means of medical preparedness and response to radiation emergency. CCMRRE is responsible for medical response to radiological or nuclear accident on national level. CCMRRE holds training courses, organizes drills and provides technical support to local medical organizations in practicing medical preparedness and response to radiation emergency. CCMRRE collects, analyzes and exchanges information on medical response to radiological and nuclear emergency and establishes relevant database. CCMRRE also guides and participates in radiation pollution monitoring on accident sites. In the past ten years, we accumulate much knowledge and experience on medical response to radiation emergencies. In this context, we will discuss Xinzhou Accident, which took place in 1992 and involved in three deaths, and Ha'erbin Accident that took place in 2005 and involved one death. A father and two brothers in Xinzhou Accident died of over-exposed to 60 Co source and misdiagnosis and improper treatment, which indicates that most general practitioners are uncertain about the health consequences of exposure to ionizing radiation and the medical management of exposed patients. When Ha'erbin Accident happened in 2005, the local hospital gave the right diagnosis and treatment based on the clinic symptoms and signs, which prevent more people suffering from over-expose to 192 Ir source. The distinct changes comes from the education and training to primary doctors related

  14. Tissue response after radiation exposure. Intestine

    International Nuclear Information System (INIS)

    Otsuka, Kensuke; Tomita, Masanori; Yamauchi, Motohiro; Iwasaki, Toshiyasu

    2014-01-01

    Gastrointestinal syndrome followed by 'gut death' is due to intestinal disorders. This syndrome is induced by high-dose (>10 Gy) of ionizing radiation. Recovery from the gastrointestinal syndrome would depend on the number of survived clonogens and regeneration capability of crypts. These tissue alterations can be observed by high-dose radiation, however, cellular dynamics in crypts can be affected by low-dose radiation. For example, Potten et al. found that low-dose radiation induce apoptosis of intestinal stem cells, which produce all differentiated function cells. Recently, intestinal stem cells are characterized by molecular markers such as Lgr5. Since intestinal adenomas can be induced by deletion of Apc gene in Lgr5 + stem cells, it is widely recognized that Lgr5 + stem cells are the cell-of-origin of cancer. Duodenal Lgr5 + stem cells are known as radioresistant cells, however, we found that ionizing radiation significantly induces the turnover of colonic Lgr5 + stem cells. Combined with the knowledge of other radioresistant markers, stem-cell dynamics in tissue after irradiation are becoming clear. The present review introduces the history of gastrointestinal syndrome and intestinal stem cells, and discusses those future perspectives. (author)

  15. Biological Bases for Radiation Adaptive Responses in the Lung

    Energy Technology Data Exchange (ETDEWEB)

    Scott, Bobby R. [Lovelace Biomedical and Environmental Research Inst., Albuquerque, NM (United States); Lin, Yong [Lovelace Biomedical and Environmental Research Inst., Albuquerque, NM (United States); Wilder, Julie [Lovelace Biomedical and Environmental Research Inst., Albuquerque, NM (United States); Belinsky, Steven [Lovelace Biomedical and Environmental Research Inst., Albuquerque, NM (United States)

    2015-03-01

    Our main research objective was to determine the biological bases for low-dose, radiation-induced adaptive responses in the lung, and use the knowledge gained to produce an improved risk model for radiation-induced lung cancer that accounts for activated natural protection, genetic influences, and the role of epigenetic regulation (epiregulation). Currently, low-dose radiation risk assessment is based on the linear-no-threshold hypothesis, which now is known to be unsupported by a large volume of data.

  16. MOSFET and MOS capacitor responses to ionizing radiation

    Science.gov (United States)

    Benedetto, J. M.; Boesch, H. E., Jr.

    1984-01-01

    The ionizing radiation responses of metal oxide semiconductor (MOS) field-effect transistors (FETs) and MOS capacitors are compared. It is shown that the radiation-induced threshold voltage shift correlates closely with the shift in the MOS capacitor inversion voltage. The radiation-induced interface-state density of the MOSFETs and MOS capacitors was determined by several techniques. It is shown that the presence of 'slow' states can interfere with the interface-state measurements.

  17. Study of radiation detectors response in standard X, gamma and beta radiation standard beams

    International Nuclear Information System (INIS)

    Nonato, Fernanda Beatrice Conceicao

    2010-01-01

    The response of 76 Geiger-Mueller detectors, 4 semiconductor detectors and 34 ionization chambers were studied. Many of them were calibrated with gamma radiation beams ( 37 Cs and 60 Co), and some of them were tested in beta radiation ( 90 Sr+ 9' 0Y e 204 Tl) and X radiation (N-60, N-80, N-100, N-150) beams. For all three types of radiation, the calibration factors of the instruments were obtained, and the energy and angular dependences were studied. For beta and gamma radiation, the angular dependence was studied for incident radiation angles of 0 deg and +- 45 deg. The curves of the response of the instruments were obtained over an angle interval of 0 deg to +- 90 deg, for gamma, beta and X radiations. The calibration factors obtained for beta radiation were compared to those obtained for gamma radiation. For gamma radiation, 24 of the 66 tested Geiger-Mueller detectors presented results for the energy dependence according to international recommendation of ISO 4037-2 and 56 were in accordance with the Brazilian ABNT 10011 recommendation. The ionization chambers and semiconductors were in accordance to national and international recommendations. All instruments showed angular dependence less than 40%. For beta radiation, the instruments showed unsatisfactory results for the energy dependence and angular dependence. For X radiation, the ionization chambers presented results for energy dependence according to the national recommendation, and the angular dependence was less than 40%. (author)

  18. Formation of radiation-induced point defects in silicon doped thin films upon ion implantation and activating annealing

    International Nuclear Information System (INIS)

    Bublik, V.T.; Shcherbachev, K.D.; Komarnitskaya, E.A.; Parkhomenko, Yu.N.; Vygovskaya, E.A.; Evgen'ev, S.B.

    1999-01-01

    The formation and relaxation processes for radiation-induced defects in the implantation of 50 keV Si + ions into gallium arsenide and subsequent 10-min annealing in arsine at 850 deg. C have been studied by the triple-crystal X-ray diffractometry and secondary-ion mass spectroscopy techniques. It is shown that the existence of the vacancy-enriched layer stimulating diffusion of introduced dopants into the substrate surface can significantly affect the distribution profile of the dopant in the course of preparation of thin implanted layers

  19. Calculation of the Doppler broadening of the electron-positron annihilation radiation in defect-free bulk materials

    International Nuclear Information System (INIS)

    Ghosh, V. J.; Alatalo, M.; Asoka-Kumar, P.; Nielsen, B.; Lynn, K. G.; Kruseman, A. C.; Mijnarends, P. E.

    2000-01-01

    Results of a calculation of the Doppler broadening of the positron-electron annihilation radiation and positron lifetimes in a large number of elemental defect-free materials are presented. A simple scheme based on the method of superimposed atoms is used for these calculations. Calculated values of the Doppler broadening are compared with experimental data for a number of elemental materials, and qualitative agreement is obtained. These results provide a database which can be used for characterizing materials and identifying impurity-vacancy complexes. (c) 2000 The American Physical Society

  20. Study of defects and radiation damage in solids by field-ion and atom-probe microscopy

    International Nuclear Information System (INIS)

    Seidman, D.N.

    1982-01-01

    An attempt is made to introduce the reader to the basic physical ideas involved in the field-ion and atom-probe field-ion microscope techniques, and to the applications of these techniques to the study of defects and radiation damage in solids. The final section discusses, in precise form, the application of the atom-probe field-ion microscope to the study of the behavior of implanted 3 He and 4 He atoms in tungsten. The paper is heavily referenced so that the reader can pursue his specific research interest in detail

  1. Mouse genetic approaches applied to the normal tissue radiation response

    International Nuclear Information System (INIS)

    Haston, Christina K.

    2012-01-01

    The varying responses of inbred mouse models to radiation exposure present a unique opportunity to dissect the genetic basis of radiation sensitivity and tissue injury. Such studies are complementary to human association studies as they permit both the analysis of clinical features of disease, and of specific variants associated with its presentation, in a controlled environment. Herein I review how animal models are studied to identify specific genetic variants influencing predisposition to radiation-induced traits. Among these radiation-induced responses are documented strain differences in repair of DNA damage and in extent of tissue injury (in the lung, skin, and intestine) which form the base for genetic investigations. For example, radiation-induced DNA damage is consistently greater in tissues from BALB/cJ mice, than the levels in C57BL/6J mice, suggesting there may be an inherent DNA damage level per strain. Regarding tissue injury, strain specific inflammatory and fibrotic phenotypes have been documented for principally, C57BL/6 C3H and A/J mice but a correlation among responses such that knowledge of the radiation injury in one tissue informs of the response in another is not evident. Strategies to identify genetic differences contributing to a trait based on inbred strain differences, which include linkage analysis and the evaluation of recombinant congenic (RC) strains, are presented, with a focus on the lung response to irradiation which is the only radiation-induced tissue injury mapped to date. Such approaches are needed to reveal genetic differences in susceptibility to radiation injury, and also to provide a context for the effects of specific genetic variation uncovered in anticipated clinical association studies. In summary, mouse models can be studied to uncover heritable variation predisposing to specific radiation responses, and such variations may point to pathways of importance to phenotype development in the clinic.

  2. Mechanism for radiative recombination and defect properties of GaP/GaNP core/shell nanowires

    International Nuclear Information System (INIS)

    Dobrovolsky, A.; Stehr, J. E.; Chen, S. L.; Chen, W. M.; Buyanova, I. A.; Kuang, Y. J.; Sukrittanon, S.; Tu, C. W.

    2012-01-01

    Recombination processes in GaP/GaNP core/shell nanowires (NWs) grown on a Si substrate by molecular beam epitaxy are examined using a variety of optical characterization techniques, including cw- and time-resolved photoluminescence and optically detected magnetic resonance (ODMR). Superior optical quality of the structures is demonstrated based on the observation of intense emission from a single NW at room temperature. This emission is shown to originate from radiative transitions within N-related localized states. From ODMR, growth of GaP/GaNP NWs is also found to facilitate formation of complex defects containing a P atom at its core that act as centers of competing non-radiative recombination.

  3. 3D-imaging of selective laser melting defects in a Co–Cr–Mo alloy by synchrotron radiation micro-CT

    International Nuclear Information System (INIS)

    Zhou, Xin; Wang, Dianzheng; Liu, Xihe; Zhang, DanDan; Qu, Shilian; Ma, Jing; London, Gary; Shen, Zhijian; Liu, Wei

    2015-01-01

    Microstructure defects set the mechanical property limits for solid Co–Cr–Mo alloy prepared by selective laser melting (SLM). Previous studies were mainly based on 2D SEM images and thus not able to provide information of the 3D morphologies of the complex defects. In this paper, the remaining porosities in Co–Cr–Mo alloy parts prepared by selective laser melting were presented in relation to the laser processing parameters. In order to understand the defect forming mechanism, accurate 3D images of defects inside SLM fabricated Co–Cr–Mo samples were provided by synchrotron radiation micro-CT imaging of 300 μm thick slices cut from a 10 mm cube. With 3D reconstructed images distinctive morphologies of SLM defects spanning across the consolidated powder layers were generated. The faults can be classified as single layer or multi-layers defects. The accidental single layer defects form as gaps between adjacent laser melt tracks or melt track discontinuousness caused by inherent fluid instability under various disturbances. The first formed single layer defect generates often a multi-layer defect spanning for 2–3 subsequent powder layers. By stabilizing the melt pool flow and by reducing the surface roughness through adjusting processing parameters it appears possible to reduce the defect concentrations

  4. Unravelling radiation response: from public health to personalized radiotherapy

    International Nuclear Information System (INIS)

    Manna, Soumen Kanti

    2017-01-01

    Understanding the mechanism underlying response to ionizing radiation exposure is at the heart of radiation biology and its applications. This presentation will showcase how the mass spectrometry-based global profiling helped to identify not only potential age-independent biomarkers of ionizing radiation exposure in mice but also a hitherto unexplored link between DNA repair and polyamine metabolism at an organismal level. It will then provide a glimpse of how a combination of metabolomics and molecular biological tools combined to elucidate the metabolic reprogramming underlying therapeutic resistance of cancer cells. It will then elaborate how an integrated -omics approach could be adopted to understand the heterogeneity in the effects ionizing radiation in the context of development and health. Finally, it will present a framework on how clinicians, epidemiologists and basic researchers can come together to usher in a new era of personalized radiation therapy as well as to develop a paradigm of personalized counter measures against radiation exposure. (author)

  5. Responsibility, coresponsibility and responsibility to the future in radiation protection and the question of final disposal

    International Nuclear Information System (INIS)

    Gellermann, R.

    2005-01-01

    Based on philosophical terms and concepts the responsibility, coresponsibility and responsibility to the future of people working in radiation protection are discussed and some resultant conclusions concerning finals disposal are derived. (orig.)

  6. Corroborating tomographic defect metrics with mechanical response in an additively manufactured precipitation-hardened stainless steel

    Science.gov (United States)

    Madison, Jonathan D.; Underwood, Olivia D.; Swiler, Laura P.; Boyce, Brad L.; Jared, Bradley H.; Rodelas, Jeff M.; Salzbrenner, Bradley C.

    2018-04-01

    The intrinsic relation between structure and performance is a foundational tenant of most all materials science investigations. While the specific form of this relation is dictated by material system, processing route and performance metric of interest, it is widely agreed that appropriate characterization of a material allows for greater accuracy in understanding and/or predicting material response. However, in the context of additive manufacturing, prior models and expectations of material performance must be revisited as performance often diverges from traditional values, even among well explored material systems. This work utilizes micro-computed tomography to quantify porosity and lack of fusion defects in an additively manufactured stainless steel and relates these metrics to performance across a statistically significant population using high-throughput mechanical testing. The degree to which performance in additively manufactured stainless steel can and cannot be correlated to detectable porosity will be presented and suggestions for performing similar experiments will be provided.

  7. Emergency response and radiation monitoring systems in Russian regions

    International Nuclear Information System (INIS)

    Arutyunyan, R.; Osipiyants, I.; Kiselev, V.; Ogar, K; Gavrilov, S.

    2008-01-01

    Full text: Preparedness of the emergency response system to elimination of radiation incidents and accidents is one of the most important elements of ensuring safe operation of nuclear power facilities. Routine activities on prevention of emergency situations along with adequate, efficient and opportune response actions are the key factors reducing the risks of adverse effects on population and environment. Both high engineering level and multiformity of the nuclear branch facilities make special demands on establishment of response system activities to eventual emergency situations. First and foremost, while resolving sophisticated engineering and scientific problems emerging during the emergency response process, one needs a powerful scientific and technical support system.The emergency response system established in the past decade in Russian nuclear branch provides a high efficiency of response activities due to the use of scientific and engineering potential and experience of the involved institutions. In Russia the responsibility for population protection is imposed on regional authority. So regional emergence response system should include up-to-date tools of radiation monitoring and infrastructure. That's why new activities on development of radiation monitoring and emergency response system were started in the regions of Russia. The main directions of these activities are: 1) Modernization of the existing and setting-up new facility and territorial automatic radiation monitoring systems, including mobile radiation surveillance kits; 2) Establishment of the Regional Crisis Centres and Crisis Centres of nuclear and radiation hazardous facilities; 3) Setting up communication systems for transfer, acquisition, processing, storage and presentation of data for participants of emergency response at the facility, regional and federal levels; 4) Development of software and hardware systems for expert support of decision-making on protection of personnel, population

  8. Medical response to effects of ionising radiation

    International Nuclear Information System (INIS)

    Terrell, J.D.

    1989-01-01

    This paper will first of all deal with a scenario in which a radiation hazard arises within the DPH's Health District and, building on this, will go on to consider a modified role for the Community Physician where a hazard arises outside his District but poses some threat to it. The submissions made on the role of the Community Physician as Director of Public Health of a District Health Authority are based on experience of exercises conducted over recent years in relation to a possible incident at Sellafield in West Cumbria. (author)

  9. Vanguards of paradigm shift in radiation biology. Radiation-induced adaptive and bystander responses

    International Nuclear Information System (INIS)

    Matsumoto, Hideki; Hamada, Nobuyuki; Kobayashi, Yasuhiko; Takahashi, Akihisa; Ohnishi, Takeo

    2007-01-01

    The risks of exposure to low dose ionizing radiation (below 100 mSv) are estimated by extrapolating from data obtained after exposure to high dose radiation, using a linear no-threshold model (LNT model). However, the validity of using this dose-response model is controversial because evidence accumulated over the past decade has indicated that living organisms, including humans, respond differently to low dose/low dose-rate radiation than they do to high dose/high dose-rate radiation. In other words, there are accumulated findings which cannot be explained by the classical ''target theory'' of radiation biology. The radioadaptive response, radiation-induced bystander effects, low-dose radio-hypersensitivity, and genomic instability are specifically observed in response to low dose/low dose-rate radiation, and the mechanisms underlying these responses often involve biochemical/molecular signals that respond to targeted and non-targeted events. Recently, correlations between the radioadaptive and bystander responses have been increasingly reported. The present review focuses on the latter two phenomena by summarizing observations supporting their existence, and discussing the linkage between them from the aspect of production of reactive oxygen and nitrogen species. (author)

  10. Biological response of cancer cells to radiation treatment

    Directory of Open Access Journals (Sweden)

    Rajamanickam eBaskar

    2014-11-01

    Full Text Available Cancer is a class of diseases characterized by uncontrolled cell growth and has the ability to spread or metastasize throughout the body. In recent years, remarkable progress has been made towards the understanding of proposed hallmarks of cancer development, care and treatment modalities. Radiation therapy or radiotherapy is an important and integral component of cancer management, mostly conferring a survival benefit. Radiation therapy destroys cancer by depositing high-energy radiation on the cancer tissues. Over the years, radiation therapy has been driven by constant technological advances and approximately 50% of all patients with localized malignant tumors are treated with radiation at some point in the course of their disease. In radiation oncology, research and development in the last three decades has led to considerable improvement in our understanding of the differential responses of normal and cancer cells. The biological effectiveness of radiation depends on the linear energy transfer (LET, total dose, number of fractions and radiosensitivity of the targeted cells or tissues. Radiation can either directly or indirectly (by producing free radicals damages the genome of the cell. This has been challenged in recent years by a newly identified phenomenon known as radiation induced bystander effect (RIBE. In RIBE, the non-irradiated cells adjacent to or located far from the irradiated cells/tissues demonstrate similar responses to that of the directly irradiated cells. Understanding the cancer cell responses during the fractions or after the course of irradiation will lead to improvements in therapeutic efficacy and potentially, benefitting a significant proportion of cancer patients. In this review, the clinical implications of radiation induced direct and bystander effects on the cancer cell are discussed.

  11. The octadecanoid signalling pathway in plants mediates a response to ultraviolet radiation

    International Nuclear Information System (INIS)

    Conconi, A.; Smerdon, M.J.; Howe, G.A.; Ryan, C.A.

    1996-01-01

    Many plant genes that respond to environmental and developmental changes are regulated by jasmonic acid, which is derived from linolenic acid via the octadecanoid pathway. Linolenic acid is an important fatty-acid constituent of membranes in most plant species and its intracellular levels increase in response to certain signals. Here we report that irradiation of tomato leaves with ultraviolet light induces the expression of several plant defensive genes that are normally activated through the octadecanoid pathway after wounding. The response to ultraviolet light is blocked by an inhibitor of the octadecanoid pathway and it does not occur in a tomato mutant defective in this pathway. The ultraviolet irradiation maximally induces the defence genes at levels where cyclobutane pyrimidine dimer formation, an indicator of DNA damage, is less than 0.2 dimers per gene. Our evidence indicates that this plant defence response to certain wavelengths of ultraviolet radiation requires the activation of the octadecanoid defence signalling pathway. (author)

  12. Electron radiation damage of metals and nature of point defects by high voltage electron microscopy

    International Nuclear Information System (INIS)

    Kiritani, M.

    1975-01-01

    The formation of point defect clusters by electron irradiation in a variety of metals (Al, Au, Cu, Fe, Ni, Mo, Pt, W) in a wide range of temperatures 10 to 1000 0 K are observed. A unified explanation is given for their nucleation and growth from the viewpoint of the migration and interaction of point defects. The effect of free surfaces and other permanent sinks are examined. Analysis of the systematic variation of the nucleation of interstitial clustered defects lead to confirm the free migration of interstitials with fairly small activation energies. Their apparent values obtained from the impurity sensitive nucleation at medium temperatures are 0.08 (Al), 0.19 (Au), 0.26 (Fe), 0.18 (Mo) and 0.21 eV (W), and their values obtained from low temperature irradiation are 0.03 (Al), 0.04 (Au) and 0.05 eV (Mo). The trapping of interstitials by foreign atoms and heterogeneous effects on nucleation of interstitial clusters are discussed

  13. Radiation in response to food preservation

    International Nuclear Information System (INIS)

    Bharti, Navaldey; Ram, R.B.; Gautam, Shreesh Kumar; Kumar, Vikas; Singh, Abhishek

    2012-01-01

    Preservation of food items is a pre-requisite for food security. The seasonal nature of production, perishable nature of food materials (fruits, vegetables and other value added products) and the rising gap between demand and supply have posed great challenges to conventional techniques of food preservation and thereby to food security. Food irradiation, one of the beneficial applications of atomic energy, is an important innovation in food preservation, since the development of canning in the 19th century. It provides an effective alternative to fumigants, which are being phased out owing to their adverse effects on the environment and human health. Moreover, exposure of food material to radiation has strong advantages over conventional methods of preservation such as cold storage, fumigation, salting and drying because it does not lead to loss of taste, texture, flavour, odour etc. or overall quality attributes. Generally, two types of radiations are used i.e., ionizing and non-ionizing. Since radiation does not generate heat, it is termed 'cold sterilization'. Gamma rays, E-beam and X-rays are used for irradiation. Irradiation under approved conditions has been demonstrated to have no dangerous effects on food, either chemical or microbial in nature and does not cause any significant loss of macronutrients. Proteins, fats and carbohydrates undergo little change in nutritional value during irradiation even with doses over 10 kGy, though there may be sensory changes. Similarly, the essential amino acids, essential fatty acids, minerals and trace elements are also unaffected. There can be a decrease in certain vitamins (particularly thiamin) but these are of the same order of magnitude as occurs in other manufacturing processes such as drying/dehydration or canning (thermal sterilization). So, there is urgent need to exploit the benefits of irradiation involve standardization, communication and education. The potential benefits of irradiation technology have been

  14. Radiation response of perfused tracheal sections

    International Nuclear Information System (INIS)

    Ford, J.R.; Maslowski, A.J.; Braby, L.A.

    2003-01-01

    Full text: A model of respiratory tissue using a perfusion culture system is being developed. We are using this system to quantify the effects of normal tissue architecture and the interaction of epithelial cells with other cell types on radiation-induced bystander effects. Tracheal tissue taken from young adult male Fischer 344 rats is imbedded in a growth factor enriched agarose matrix. The chamber is designed to allow growth medium to periodically wash the epithelial surface of the tracheal lumen while maintaining the air-interface that is necessary for the normal differentiation of the epithelium. In preliminary experiments with rat trachea we have shown that a differentiated epithelial lining can be maintained for several days. Cells can be obtained for a number of different cell culture assays for endpoints such as survival and preneoplastic transformation after irradiation

  15. Genetic and epigenetic features in radiation sensitivity. Part I: Cell signalling in radiation response

    International Nuclear Information System (INIS)

    Bourguignon, Michel H.; Gisone, Pablo A.; Perez, Maria R.; Michelin, Severino; Dubner, Diana; Giorgio, Marina di; Carosella, Edgardo D.

    2005-01-01

    Recent progress especially in the field of gene identification and expression has attracted greater attention to genetic and epigenetic susceptibility to cancer, possibly enhanced by ionising radiation. It has been proposed that the occurrence and severity of the adverse reactions to radiation therapy are also influenced by such genetic susceptibility. This issue is especially important for radiation therapists since hypersensitive patients may suffer from adverse effects in normal tissues following standard radiation therapy, while normally sensitive patients could receive higher doses of radiation offering a better likelihood of cure for malignant tumours. This paper, the first of two parts, reviews the main mechanisms involved in cell response to ionising radiation. DNA repair machinery and cell signalling pathways are considered and their role in radiosensitivity is analysed. The implication of non-targeted and delayed effects in radiosensitivity is also discussed. (orig.)

  16. Tumor radiation responses and tumor oxygenation in aging mice

    International Nuclear Information System (INIS)

    Rockwell, S.

    1989-01-01

    EMT6 mouse mammary tumors transplanted into aging mice are less sensitive to radiation than tumors growing in young adult animals. The experiments reported here compare the radiation dose-response curves defining the survivals of tumor cells in aging mice and in young adult mice. Cell survival curves were assessed in normal air-breathing mice and in mice asphyxiated with N 2 to produce uniform hypoxia throughout the tumors. Analyses of survival curves revealed that 41% of viable malignant cells were severely hypoxic in tumors in aging mice, while only 19% of the tumor cells in young adult animals were radiobiologically hypoxic. This did not appear to reflect anaemia in the old animals. Treatment of aging animals with a perfluorochemical emulsion plus carbogen (95% O 2 /5% CO 2 ) increased radiation response of the tumors, apparently by improving tumor oxygenation and decreasing the number of severely hypoxic, radiation resistant cells in the tumors. (author)

  17. Anomalous response of superconducting titanium nitride resonators to terahertz radiation

    International Nuclear Information System (INIS)

    Bueno, J.; Baselmans, J. J. A; Coumou, P. C. J. J.; Zheng, G.; Visser, P. J. de; Klapwijk, T. M.; Driessen, E. F. C.; Doyle, S.

    2014-01-01

    We present an experimental study of kinetic inductance detectors (KIDs) fabricated of atomic layer deposited TiN films and characterized at radiation frequencies of 350 GHz. The responsivity to radiation is measured and found to increase with the increase in radiation powers, opposite to what is expected from theory and observed for hybrid niobium titanium nitride/aluminium (NbTiN/Al) and all-aluminium (all-Al) KIDs. The noise is found to be independent of the level of the radiation power. The noise equivalent power improves with higher radiation powers, also opposite to what is observed and well understood for hybrid NbTiN/Al and all-Al KIDs. We suggest that an inhomogeneous state of these disordered superconductors should be used to explain these observations

  18. Anomalous response of superconducting titanium nitride resonators to terahertz radiation

    Energy Technology Data Exchange (ETDEWEB)

    Bueno, J., E-mail: j.bueno@sron.nl; Baselmans, J. J. A [SRON, Netherlands Institute of Space Research, Utrecht (Netherlands); Coumou, P. C. J. J.; Zheng, G. [Kavli Institute of Nanoscience, Delft University of Technology, Delft (Netherlands); Visser, P. J. de [SRON, Netherlands Institute of Space Research, Utrecht (Netherlands); Kavli Institute of Nanoscience, Delft University of Technology, Delft (Netherlands); Klapwijk, T. M. [Kavli Institute of Nanoscience, Delft University of Technology, Delft (Netherlands); Physics Department, Moscow State Pedagogical University, 119991 Moscow (Russian Federation); Driessen, E. F. C. [Université Grenoble Alpes, INAC-SPSMS, F-38000 Grenoble (France); CEA, INAC-SPSMS, F-38000 Grenoble (France); Doyle, S. [Cardiff University, School of Physics and Astronomy, Queens Buildings, Cardiff CF24 3AA (United Kingdom)

    2014-11-10

    We present an experimental study of kinetic inductance detectors (KIDs) fabricated of atomic layer deposited TiN films and characterized at radiation frequencies of 350 GHz. The responsivity to radiation is measured and found to increase with the increase in radiation powers, opposite to what is expected from theory and observed for hybrid niobium titanium nitride/aluminium (NbTiN/Al) and all-aluminium (all-Al) KIDs. The noise is found to be independent of the level of the radiation power. The noise equivalent power improves with higher radiation powers, also opposite to what is observed and well understood for hybrid NbTiN/Al and all-Al KIDs. We suggest that an inhomogeneous state of these disordered superconductors should be used to explain these observations.

  19. Verifying a nuclear weapon`s response to radiation environments

    Energy Technology Data Exchange (ETDEWEB)

    Dean, F.F.; Barrett, W.H.

    1998-05-01

    The process described in the paper is being applied as part of the design verification of a replacement component designed for a nuclear weapon currently in the active stockpile. This process is an adaptation of the process successfully used in nuclear weapon development programs. The verification process concentrates on evaluating system response to radiation environments, verifying system performance during and after exposure to radiation environments, and assessing system survivability.

  20. Extended abstracts: Microbeam Probes of Cellular Radiation Response [final report

    International Nuclear Information System (INIS)

    Brenner, David J.

    2000-01-01

    In July 1999, we organized the 4th International Workshop: Microbeam Probes of Cellular Radiation Response, held in Killiney Bay, Dublin, Ireland, on July 17-18. Roughly 75 scientists (about equal numbers of physicists and biologists) attended the workshop, the fourth in a bi-annual series. Extended abstracts from the meeting were published in the Radiation Research journal, vol. 153, iss. 2, pp. 220-238 (February 2000)(attached). All the objectives in the proposal were met

  1. Radiation-induced defects in Czochralski-grown silicon containing carbon and germanium

    International Nuclear Information System (INIS)

    Londos, C A; Andrianakis, A; Emtsev, V V; Ohyama, H

    2009-01-01

    Formation processes of vacancy-oxygen (VO) and carbon interstitial-oxygen interstitial (C i O i ) complexes in electron-irradiated Czochralski-grown Si crystals (Cz–Si), also doped with Ge, are investigated. IR spectroscopy measurements are employed to monitor the production of these defects. In Cz–Si with carbon concentrations [C s ] up to 1 × 10 17 cm −3 and Ge concentrations [Ge] up to 1 × 10 20 cm −3 the production rate of VO defects as well as the rate of oxygen loss show a slight growth of about 10% with the increasing Ge concentration. At high concentrations of carbon [C s ] around 2 × 10 17 cm −3 the production rate of VO defects is getting larger by ∼40% in Cz–Si:Ge at Ge concentrations around 1 × 10 19 cm −3 and then at [Ge] ≈ 2 × 10 20 cm −3 this enlargement drops to ∼13%, thus approaching the values characteristic of lesser concentrations of carbon. A similar behavior against Ge concentration displays the production rate of C i O i complexes. The same trend is also observed for the rate of carbon loss, whereas the trend for the rate of oxygen loss is opposite. The behavior of Ge atoms is different at low and high concentrations of this isoelectronic impurity in Cz–Si. At low concentrations most isolated Ge atoms serve as temporary traps for vacancies preventing them from indirect annihilation with self-interstitials. At high concentrations Ge atoms are prone to form clusters. The latter ones are traps for vacancies and self-interstitials due to the strain fields, increasing the importance of indirect annihilation of intrinsic point defects. Such a model allows one to give a plausible explanation for the obtained results. A new band at 994 cm −1 seen only in irradiated Ge-doped Cz–Si is also studied. Interestingly, its annealing behavior was found to be very similar to that of VO complexes

  2. Evaluation of defects induced by neutron radiation in reactor pressure vessels steels

    International Nuclear Information System (INIS)

    Lopez Jimenez, J.

    1978-01-01

    We have developed a method for calculating the production of neutron induced defects (depleted zone and crowdions) in ferritic pressure vessel steels for different neutron spectra. They have been analysed both the recoil primary atoms produced by elastic and inelastic collisions with fast neutrons and the ones produced by gamma-ray emission by thermal neutron absorption. Theoretical modelling of increasing in the ductile-brittle transition temperature of ferritic steels has been correlated with experimental data at irradiation temperature up to 400 degree centigree (Author) 15 refs

  3. Radiation-Induced Bystander Response: Mechanism and Clinical Implications

    Science.gov (United States)

    Suzuki, Keiji; Yamashita, Shunichi

    2014-01-01

    Significance: Absorption of energy from ionizing radiation (IR) to the genetic material in the cell gives rise to damage to DNA in a dose-dependent manner. There are two types of DNA damage; by a high dose (causing acute or deterministic effects) and by a low dose (related to chronic or stochastic effects), both of which induce different health effects. Among radiation effects, acute cutaneous radiation syndrome results from cell killing as a consequence of high-dose exposure. Recent advances: Recent advances in radiation biology and oncology have demonstrated that bystander effects, which are emerged in cells that have never been exposed, but neighboring irradiated cells, are also involved in radiation effects. Bystander effects are now recognized as an indispensable component of tissue response related to deleterious effects of IR. Critical issues: Evidence has indicated that nonapoptotic premature senescence is commonly observed in various tissues and organs. Senesced cells were found to secrete various proteins, including cytokines, chemokines, and growth factors, most of which are equivalent to those identified as bystander factors. Secreted factors could trigger cell proliferation, angiogenesis, cell migration, inflammatory response, etc., which provide a tissue microenvironment assisting tissue repair and remodeling. Future directions: Understandings of the mechanisms and physiological relevance of radiation-induced bystander effects are quite essential for the beneficial control of wound healing and care. Further studies should extend our knowledge of the mechanisms of bystander effects and mode of cell death in response to IR. PMID:24761341

  4. Transient radiation responses of optical fibers: influence of MCVD process parameters

    International Nuclear Information System (INIS)

    Girard, Sylvain; Alessi, Antonino; Boukenter, Aziz; Ouerdane, Y.; Marcandella, Claude; Richard, Nicolas; Paillet, Philippe; Gaillardin, Marc; Raine, Melanie

    2012-01-01

    A dedicated set of fibers elaborated via the Modified Chemical Vapor Deposition (MCVD) technique is used to study the influence of composition and drawing parameters on their responses to an X-ray pulse representative of the radiation environments associated with Megajoule class lasers. These canonical fibers were designed to highlight the impact of these parameters on the amplitude and kinetics of the transient pulsed X-ray Radiation Induced Attenuation (RIA) at room temperature. From pre-forms differing by their core composition, three optical fibers were elaborated by varying the tension and speed during the drawing process. No or only slight RIA change results from the tested variations in drawing process parameters of Ge-doped, F-doped, and pure-silica-core fibers. This study reveals that the drawing process is not the main parameter to be optimized in order to enhance the radiation tolerance of MCVD specialty optical fibers for the LMJ harsh environment. From the hardness assurance point of view, a specialty fiber sufficiently tolerant to this environment should be robust against changes in the drawing process. The origins of the RIA observed in the different fibers are discussed on the basis of spectral decomposition of their measured RIA spectra, using sets of defects from the literature and related to the different core dopants. This analysis highlights the limits of the well-known defect set to reproduce the RIA above 1 for Ge-doped fibers whereas self-trapped holes and chlorine-related species seem responsible for the transient responses of pure-silica-core and F-doped fibers. (authors)

  5. Mechanisms of radiation-induced gene responses

    International Nuclear Information System (INIS)

    Woloschak, G.E.; Paunesku, T.

    1996-01-01

    In the process of identifying genes differentially expressed in cells exposed ultraviolet radiation, we have identified a transcript having a 26-bp region that is highly conserved in a variety of species including Bacillus circulans, yeast, pumpkin, Drosophila, mouse, and man. When the 5' region (flanking region or UTR) of a gene, the sequence is predominantly in +/+ orientation with respect to the coding DNA strand; while in the coding region and the 3' region (UTR), the sequence is most frequently in the +/-orientation with respect to the coding DNA strand. In two genes, the element is split into two parts; however, in most cases, it is found only once but with a minimum of 11 consecutive nucleotides precisely depicting the original sequence. The element is found in a large number of different genes with diverse functions (from human ras p21 to B. circulans chitonase). Gel shift assays demonstrated the presence of a protein in HeLa cell extracts that binds to the sense and antisense single-stranded consensus oligomers, as well as to the double- stranded oligonucleotide. When double-stranded oligomer was used, the size shift demonstrated as additional protein-oligomer complex larger than the one bound to either sense or antisense single-stranded consensus oligomers alone. It is speculated either that this element binds to protein(s) important in maintaining DNA is a single-stranded orientation for transcription or, alternatively that this element is important in the transcription-coupled DNA repair process

  6. Development of a radiation-responsive gene expression system

    International Nuclear Information System (INIS)

    Ogawa, Ryohei; Morii, Akihiro; Watanabe, Akihiko

    2013-01-01

    We have obtained a promoter enhancing expression of a gene of our interest connected downstream after activation in response to radiation stimulation and it could be used in radiogenetic therapy, a combination between radiotherapy and gene therapy. The promoter has been chosen out of a library of DNA fragments constructed by connecting the TATA box to randomly combined binding sequences of transcription factors that are activated in response to radiation. Although it was shown that the promoter activation was cell type specific, it turned out that radiation responsive promoters could be obtained for a different type of cells by using another set of transcription factor binding sequences, suggesting that the method would be feasible to obtain promoters functioning in any type of cells. Radiation reactivity of obtained promoters could be improved by techniques such as random introduction of point mutations. The improved promoters significantly enhanced expression of the luciferase gene connected downstream in response to radiation even in vivo, in addition, a gene cassette composed of one such promoter and the fcy::fur gene was confirmed useful for suicide gene therapy as shown in vitro simulation experiment, suggesting possible clinical application. (author)

  7. Summary Report of the Technical Meeting on Primary Radiation Damage: From Nuclear Reaction to Point Defects

    International Nuclear Information System (INIS)

    Stoller, R. E.; Nordlund, K.; Simakov, S.P.

    2012-11-01

    The Meeting was convened to bring together the experts from both the nuclear data and materials research communities because of their common objective of accurately characterizing irradiation environments and resulting material damage. The meeting demonstrated that significant uncertainties remain regarding both the status of nuclear data and the use of these data by the materials modeling community to determine the primary damage state obtained in irradiated materials. At the conclusion of the meeting, the participants agreed that there is clear motivation to initiate a CRP that engages participants from the nuclear data and materials research communities. The overall objective of this CRP would be to determine the best possible parameter (or a few parameters) for correlating damage from irradiation facilities with very different particle types and energy spectra, including fission and fusion reactors, charged particle accelerators, and spallation irradiation facilities. Regarding progress achieved during the last decade in the atomistic simulation of primary defects in crystalline materials, one of the essential and quantitative outcomes from the CRP is expected to be cross sections for point defects left after recoil cascade quenching. (author)

  8. arXiv Description of radiation damage in diamond sensors using an effective defect model

    CERN Document Server

    Kassel, Florian; Dabrowski, Anne; De Boer, Wim

    The BCML system is a beam monitoring device in the CMS experiment at the LHC. As detectors poly-crystalline diamond sensors are used. Here high particle rates occur from the colliding beams scattering particles outside the beam pipe. These particles cause defects, which act as traps for the ionization, thus reducing the CCE. However, the loss in CCE was much more severe than expected. The reason why in real experiments the CCE is so much worse than in laboratory experiments is related to the rate of incident particles. At high particle rates the trapping rate of the ionization is so high compared with the detrapping rate, that space charge builds up. This space charge reduces locally the internal electric field, which in turn increases the trapping rate and hence reduces the CCE even further. In order to connect these macroscopic measurements with the microscopic defects acting as traps for the ionization charge the TCAD simulation program SILVACO was used. Two effective acceptor and donor levels were needed ...

  9. Radiation Dose-Response Relationships and Risk Assessment

    International Nuclear Information System (INIS)

    Strom, Daniel J.

    2005-01-01

    The notion of a dose-response relationship was probably invented shortly after the discovery of poisons, the invention of alcoholic beverages, and the bringing of fire into a confined space in the forgotten depths of ancient prehistory. The amount of poison or medicine ingested can easily be observed to affect the behavior, health, or sickness outcome. Threshold effects, such as death, could be easily understood for intoxicants, medicine, and poisons. As Paracelsus (1493-1541), the 'father' of modern toxicology said, 'It is the dose that makes the poison.' Perhaps less obvious is the fact that implicit in such dose-response relationships is also the notion of dose rate. Usually, the dose is administered fairly acutely, in a single injection, pill, or swallow; a few puffs on a pipe; or a meal of eating or drinking. The same amount of intoxicants, medicine, or poisons administered over a week or month might have little or no observable effect. Thus, before the discovery of ionizing radiation in the late 19th century, toxicology ('the science of poisons') and pharmacology had deeply ingrained notions of dose-response relationships. This chapter demonstrates that the notion of a dose-response relationship for ionizing radiation is hopelessly simplistic from a scientific standpoint. While useful from a policy or regulatory standpoint, dose-response relationships cannot possibly convey enough information to describe the problem from a quantitative view of radiation biology, nor can they address societal values. Three sections of this chapter address the concepts, observations, and theories that contribute to the scientific input to the practice of managing risks from exposure to ionizing radiation. The presentation begins with irradiation regimes, followed by responses to high and low doses of ionizing radiation, and a discussion of how all of this can inform radiation risk management. The knowledge that is really needed for prediction of individual risk is presented

  10. Clinical implications of heterogeneity of tumor response to radiation therapy

    International Nuclear Information System (INIS)

    Suit, H.; Skates, S.; Taghian, A.; Okunieff, P.; Efird, J.T.

    1992-01-01

    Heterogeneity of response of tumor tissue to radiation clearly exists. Major parameters include histopathologic type, size (number of tumor rescue units (TRUs)), hemoglobin concentration, cell proliferation kinetics and immune rejection reaction by host. Further, normal and presumably tumor tissue response is altered in certain genetic diseases, e.g. ataxia telangiectasia. Any assessment of response of tumor tissue to a new treatment method or the testing of a new clinical response predictor is optimally based upon a narrow strata, viz., uniform with respect to known parameters of response, e.g. size, histological type. Even among tumors of such a clinical defined narrow strata, there will be residual heterogeneity with respect to inherent cellular radiation sensitivity, distributions of pO 2 , (SH), cell proliferation, etc. (author). 39 refs., 7 figs., 3 tabs

  11. First principles calculation of point defects and mobility degradation in bulk AlSb for radiation detection application

    International Nuclear Information System (INIS)

    Lordi, V; Aberg, D; Erhart, P; Wu, K J

    2007-01-01

    The development of high resolution, room temperature semiconductor radiation detectors requires the introduction of materials with increased carrier mobility-lifetime (μτ) product, while having a band gap in the 1.4-2.2 eV range. AlSb is a promising material for this application. However, systematic improvements in the material quality are necessary to achieve an adequate μτ product. We are using a combination of simulation and experiment to develop a fundamental understanding of the factors which affect detector material quality. First principles calculations are used to study the microscopic mechanisms of mobility degradation from point defects and to calculate the intrinsic limit of mobility from phonon scattering. We use density functional theory (DFT) to calculate the formation energies of native and impurity point defects, to determine their equilibrium concentrations as a function of temperature and charge state. Perturbation theory via the Born approximation is coupled with Boltzmann transport theory to calculate the contribution toward mobility degradation of each type of point defect, using DFT-computed carrier scattering rates. A comparison is made to measured carrier concentrations and mobilities from AlSb crystals grown in our lab. We find our predictions in good quantitative agreement with experiment, allowing optimized annealing conditions to be deduced. A major result is the determination of oxygen impurity as a severe mobility killer, despite the ability of oxygen to compensation dope AlSb and reduce the net carrier concentration. In this case, increased resistivity is not a good indicator of improved material performance, due to the concomitant sharp reduction in μτ

  12. Modulation of radiation response by histone deacetylase inhibition

    International Nuclear Information System (INIS)

    Chinnaiyan, Prakash; Vallabhaneni, Geetha; Armstrong, Eric M.S.; Huang, Shyh-Min; Harari, Paul M.

    2005-01-01

    Purpose: Histone deacetylase (HDAC) inhibitors, which modulate chromatin structure and gene expression, represent a class of anticancer agents that hold particular potential as radiation sensitizers. In this study, we examine the capacity of the HDAC inhibitor suberoylanilide hydroxamic acid (SAHA) to modulate radiation response in human tumor cell lines and explore potential mechanisms underlying these interactions. Methods and materials: Cell proliferation: Exponentially growing tumor cells were incubated in medium containing 0-10 μM of SAHA for 72 h. Cells were fixed/stained with crystal violet to estimate cell viability. Apoptosis: Caspase activity was analyzed by fluorescence spectroscopy using a fluorescein labeled pan-caspase inhibitor. Cells were harvested after 48 h of exposure to SAHA (1.0 μM), radiation (6 Gy), or the combination. Whole cell lysates were evaluated for poly(ADP-ribose) polymerase (PARP) cleavage by western blot analysis. Radiation survival: Cells were exposed to varying doses of radiation ± 3 days pretreatment with SAHA (0.75-1.0 μM). After incubation intervals of 14-21 days, colonies were stained with crystal violet and manually counted. Immunocytochemistry: Cells were grown and treated in chamber slides. At specified times after treatment with SAHA, cells were fixed in paraformaldehyde, permeabilized in methanol, and probed with primary and secondary antibody solutions. Slides were analyzed using an epifluorescent microscope. Results: SAHA induced a dose-dependent inhibition of proliferation in human prostate (DU145) and glioma (U373vIII) cancer cell lines. Exposure to SAHA enhanced radiation-induced apoptosis as measured by caspase activity (p < 0.05) and PARP cleavage. The impact of SAHA on radiation response was further characterized using clonogenic survival analysis, which demonstrated that treatment with SAHA reduced tumor survival after radiation exposure. We identified several oncoproteins and DNA damage repair proteins

  13. Generation and alteration of the defects induced by particle irradiation and electromagnetic radiation in alkali halogen compounds

    International Nuclear Information System (INIS)

    Nistor, L.C.

    1979-01-01

    Interactions between electron beams, CO 2 - laser radiation and alkali halogen compound have led to interesting results: 1. The development of two types of F-centre respectively in normal lattice or near the dislocations. 2. The beginning of metal colloids development process at low temperature when a thermal treatment is applied. 3. An experimental confirmation of the Pooley-Hersh model for crystal defects has been brought up. 4. The surface penetration is an explosive process. 5. Surface polygonizations were also investigated. A model has been proposed to describe the destructive channels development within alkali halogen crystals with molecular anions impurities of less than 10 ppm. KCl monocrystals of advanced purity level was prepared for building up passive optical components of strong CO 2 lasers. (author)

  14. Electronic relaxations of radiative defects of the anion sublattice in cesium bromide crystals and exoemission of electrons

    CERN Document Server

    Galyij, P V

    2002-01-01

    The paper presents the results of investigations of thermostimulated exoelectron emission (TSEE) from CsBr crystal, excited by moderate doses (D <= 10 sup 4 Gy) of ultraviolet (h nu <= 7 eV) that selectively creates anion excitons and radiative defects in the anion sublattice. Having used the previously established connection between thermoactivated processes such as thermostimulated exoemission, electroconductivity, and luminescence in the irradiated crystal lattice, the concentrations of exoemission-active centers (EAC) and kinetics parameters of TSEE are calculated. The EAC concentration calculated on a base of the bulk, thermoactivated-recombinational, and band-gap Auger-like exoemission mechanisms, are in satisfactory agreement with the concentration of electron color centers in the irradiated crystals.

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

    International Nuclear Information System (INIS)

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

    2001-01-01

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

  16. Overview of radiation damage in silicon detectors - models and defect engineering

    International Nuclear Information System (INIS)

    Watts, S.J.

    1997-01-01

    This paper reviews recent work in the area of radiation damage in silicon detectors. It is not intended as a comprehensive review, but provides a snapshot guide to current ideas and indicates how the subject is expected to develop in the immediate future. (orig.)

  17. Investigation of single defects created in crystals by laser emission and hard radiation

    International Nuclear Information System (INIS)

    Martynovich, E F; Dresvyanskiy, V P; Boychenko, S V; Rakevich, A L; Zilov, S A; Bagayev, S N

    2017-01-01

    The possibility of identifying radiation-created quantum systems via the characteristics of quantum trajectories of luminescence intensity measured on individual centers by confocal scanning fluorescence microscopy with the time-correlated single photon counting has been studied. Calculations of the quantum trajectories have been carried out by the density matrix method. Experimental studies have been carried out using a confocal microscope. (paper)

  18. Method for Vibration Response Simulation and Sensor Placement Optimization of a Machine Tool Spindle System with a Bearing Defect

    Science.gov (United States)

    Cao, Hongrui; Niu, Linkai; He, Zhengjia

    2012-01-01

    Bearing defects are one of the most important mechanical sources for vibration and noise generation in machine tool spindles. In this study, an integrated finite element (FE) model is proposed to predict the vibration responses of a spindle bearing system with localized bearing defects and then the sensor placement for better detection of bearing faults is optimized. A nonlinear bearing model is developed based on Jones' bearing theory, while the drawbar, shaft and housing are modeled as Timoshenko's beam. The bearing model is then integrated into the FE model of drawbar/shaft/housing by assembling equations of motion. The Newmark time integration method is used to solve the vibration responses numerically. The FE model of the spindle-bearing system was verified by conducting dynamic tests. Then, the localized bearing defects were modeled and vibration responses generated by the outer ring defect were simulated as an illustration. The optimization scheme of the sensor placement was carried out on the test spindle. The results proved that, the optimal sensor placement depends on the vibration modes under different boundary conditions and the transfer path between the excitation and the response. PMID:23012514

  19. Epidermal stem cells response to radiative genotoxic stress

    International Nuclear Information System (INIS)

    Marie, Melanie

    2013-01-01

    Human skin is the first organ exposed to various environmental stresses, which requires the development by skin stem cells of specific mechanisms to protect themselves and to ensure tissue homeostasis. As stem cells are responsible for the maintenance of epidermis during individual lifetime, the preservation of genomic integrity in these cells is essential. My PhD aimed at exploring the mechanisms set up by epidermal stem cells in order to protect themselves from two genotoxic stresses, ionizing radiation (Gamma Rays) and ultraviolet radiation (UVB). To begin my PhD, I have taken part of the demonstration of protective mechanisms used by keratinocyte stem cells after ionizing radiation. It has been shown that these cells are able to rapidly repair most types of radiation-induced DNA damage. Furthermore, we demonstrated that this repair is activated by the fibroblast growth factor 2 (FGF2). In order to know if this protective mechanism is also operating in cutaneous carcinoma stem cells, we investigated the response to gamma Rays of carcinoma stem cells isolated from a human carcinoma cell line. As in normal keratinocyte stem cells, we demonstrated that cancer stem cells could rapidly repair radio-induced DNA damage. Furthermore, fibroblast growth factor 2 also mediates this repair, notably thanks to its nuclear isoforms. The second project of my PhD was to study human epidermal stem cells and progenitors responses to UVB radiation. Once cytometry and irradiation conditions were set up, the toxicity of UVB radiation has been evaluate in the primary cell model. We then characterized UVB photons effects on cell viability, proliferation and repair of DNA damage. This study allowed us to bring out that responses of stem cells and their progeny to UVB are different, notably at the level of part of their repair activity of DNA damage. Moreover, progenitors and stem cells transcriptomic responses after UVB irradiation have been study in order to analyze the global

  20. Global DNA methylation responses to low dose radiation exposure

    International Nuclear Information System (INIS)

    Newman, M.R.; Ormsby, R.J.; Blyth, B.J.; Sykes, P.J.; Bezak, E.

    2011-01-01

    Full text: High radiation doses cause breaks in the DNA which are considered the critical lesions in initiation of radiation-induced cancer. However, at very low radiation doses relevant for the general public, the induction of such breaks will be rare, and other changes to the DNA such as DNA methylation which affects gene expression may playa role in radiation responses. We are studying global DNA methylation after low dose radiation exposure to determine if low dose radiation has short- and/or long-term effects on chromatin structure. We developed a sensitive high resolution melt assay to measure the levels of DNA methylation across the mouse genome by analysing a stretch of DNA sequence within Long Interspersed Nuclear Elements-I (LINE I) that comprise a very large proportion of the mouse and human genomes. Our initial results suggest no significant short-term or longterm) changes in global NA methylation after low dose whole-body X-radiation of 10 J1Gyor 10 mGy, with a significant transient increase in NA methylation observed I day after a high dose of I Gy. If the low radiation doses tested are inducing changes in bal DNA methylation, these would appear to be smaller than the variation observed between the sexes and following the general stress of the sham-irradiation procedure itself. This research was funded by the Low Dose Radiation Research Program, Biological and Environmental Research, US DOE, Grant DE-FG02-05ER64104 and MN is the recipient of the FMCF/BHP Dose Radiation Research Scholarship.

  1. Tissue specific mutagenic and carcinogenic responses in NER defective mouse models.

    NARCIS (Netherlands)

    Wijnhoven, Susan W P; Hoogervorst, Esther M; Waard, Harm de; Horst, Gijsbertus T J van der; Steeg, Harry van

    2007-01-01

    Several mouse models with defects in genes encoding components of the nucleotide excision repair (NER) pathway have been developed. In NER two different sub-pathways are known, i.e. transcription-coupled repair (TC-NER) and global-genome repair (GG-NER). A defect in one particular NER protein can

  2. Canine tumor and normal tissue response to heat and radiation

    International Nuclear Information System (INIS)

    Gillette, E.L.; McChesney, S.L.

    1985-01-01

    Oral squamous cell carcinomas of dogs were treated with either irradiation alone or combined with hyperthermia. Tumor control was assessed as no evidence of disease one year following treatment. Dogs were randomized to variable radiation doses which were given in ten fractions three times a week for three weeks. Heat was given three hours after the first and third radiation dose each week for seven treatments. The attempt was made to achieve a minimum tumor temperature of 42 0 C for thirty minutes with a maximum normal tissue temperature of 40 0 C. It was usually possible to selectively heat tumors. The TCD 50 for irradiation alone was about 400 rads greater than for heat plus irradiation. The dose response curve for heat plus radiation was much steeper than for radiation alone indicating less heterogeneity of tumor response. That also implies a much greater effectiveness of radiation combined with heat at higher tumor control probabilities. Early necrosis caused by heating healed with conservative management. No increase in late radiation necrosis was observed

  3. Trapping of hydrogen isotopes in radiation defects formed in tungsten by neutron and ion irradiations

    Energy Technology Data Exchange (ETDEWEB)

    Hatano, Y., E-mail: hatano@ctg.u-toyama.ac.jp [Hydrogen Isotope Research Center, University of Toyama, Toyama 930-8555 (Japan); Shimada, M. [Fusion Safety Program, Idaho National Laboratory, Idaho Falls, ID 83415 (United States); Alimov, V.Kh.; Shi, J.; Hara, M.; Nozaki, T. [Hydrogen Isotope Research Center, University of Toyama, Toyama 930-8555 (Japan); Oya, Y.; Kobayashi, M.; Okuno, K. [Faculty of Science, Shizuoka University, Shizuoka 422-8529 (Japan); Oda, T. [Department of Nuclear Engineering and Management, The University of Tokyo, Tokyo 113-8656 (Japan); Cao, G. [Department of Engineering Physics, The University of Wisconsin, Madison, WI 53706 (United States); Yoshida, N.; Futagami, N. [Research Institute for Applied Mechanics, Kyushu University, Kasuga 816-8580 (Japan); Sugiyama, K.; Roth, J.; Tyburska-Püschel, B.; Dorner, J. [Max-Planck-Institut für Plasmaphysik, EURATOM Association, D-85748 Garching (Germany); Takagi, I. [Department of Nuclear Engineering, Kyoto University, Kyoto 606-8501 (Japan); Hatakeyama, M.; Kurishita, H. [Institute for Materials Research, Tohoku University, Oarai 311-1313 (Japan); and others

    2013-07-15

    Retention of D in neutron-irradiated W and desorption were examined after plasma exposure at 773 K. Deuterium was accumulated at a relatively high concentration up to a large depth of 50–100 μm due to the trapping effects of defects uniformly induced in the bulk. A significant D release in a vacuum continued to temperatures ⩾1173 K because of the small effective diffusion coefficient and the long diffusion distance. Exposure of ion-irradiated W to D{sub 2} gas showed a clear correlation between concentrations of trapped and solute D as determined by the trapping–detrapping equilibrium. These observations indicated that the accumulation of tritium in high concentrations is possible even at high temperatures if the concentration of solute tritium is high, and baking at moderate temperatures is ineffective for removal of tritium deeply penetrating into the bulk. Nevertheless, clear enhancement of D release was observed under the presence of solute H.

  4. Allograft pretreatment for the repair of sciatic nerve defects: green tea polyphenols versus radiation

    Directory of Open Access Journals (Sweden)

    Sheng-hu Zhou

    2015-01-01

    Full Text Available Pretreatment of nerve allografts by exposure to irradiation or green tea polyphenols can eliminate neuroimmunogenicity, inhibit early immunological rejection, encourage nerve regeneration and functional recovery, improve tissue preservation, and minimize postoperative infection. In the present study, we investigate which intervention achieves better results. We produced a 1.0 cm sciatic nerve defect in rats, and divided the rats into four treatment groups: autograft, fresh nerve allograft, green tea polyphenol-pretreated (1 mg/mL, 4°C nerve allograft, and irradiation-pretreated nerve allograft (26.39 Gy/min for 12 hours; total 19 kGy. The animals were observed, and sciatic nerve electrophysiology, histology, and transmission electron microscopy were carried out at 6 and 12 weeks after grafting. The circumference and structure of the transplanted nerve in rats that received autografts or green tea polyphenol-pretreated nerve allografts were similar to those of the host sciatic nerve. Compared with the groups that received fresh or irradiation-pretreated nerve allografts, motor nerve conduction velocity in the autograft and fresh nerve allograft groups was greater, more neurites grew into the allografts, Schwann cell proliferation was evident, and a large number of new blood vessels was observed; in addition, massive myelinated nerve fibers formed, and abundant microfilaments and microtubules were present in the axoplasm. Our findings indicate that nerve allografts pretreated by green tea polyphenols are equivalent to transplanting autologous nerves in the repair of sciatic nerve defects, and promote nerve regeneration. Pretreatment using green tea polyphenols is better than pretreatment with irradiation

  5. Response of radiation monitors for ambient dose equivalent, H*(10)

    International Nuclear Information System (INIS)

    Grecco, Claudio Henrique dos Santos

    2001-01-01

    Radiation monitors are used all over the world to evaluate if places with presence of ionising radiation present safe conditions for people. Radiation monitors should be tested according to international or national standards in order to be qualified for use. This work describes a methodology and procedures to evaluate the energy and angular responses of any radiation monitor for ambient dose equivalent, H*(10), according to the recommendations of ISO and IEC standards. The methodology and the procedures were applied to the Monitor Inteligente de Radiacao MIR 7026, developed by the Instituto em Engenharia Nuclear (IEN), to evaluate and to adjust its response for H*(10), characterizing it as an ambient dose equivalent meter. The tests were performed at the Laboratorio Nacional de Metrologia das Radiacoes Ionizantes (LNMRI), at Instituto de Radioprotecao e Dosimetria (IRD), and results showed that the Monitor Inteligente de Radiacao MIR 7026 can be used as an EI*(10) meter, in accordance to the IEC 60846 standard requirements. The overall estimated uncertainty for the determination of the MIR 7026 response, in all radiation qualities used in this work, was 4,5 % to a 95 % confidence limit. (author)

  6. Response dependence of a ring ionization chamber response on the size of the X radiation field

    International Nuclear Information System (INIS)

    Yoshizumi, Maira T.; Caldas, Linda V.E.

    2009-01-01

    A ring monitor ionization chamber was developed at the IPEN-Sao Paulo, Brazil, fixed on a system of collimators which determine the dimension of the radiation field size. This work verified that the ring chamber response depends on the exponential form with the size of de radiation field

  7. Respiratory activity as a determinant of radiation survival response

    Energy Technology Data Exchange (ETDEWEB)

    Bruce, A K; Berner, J D [State Univ. of New York, Buffalo (USA). Dept. of Biology

    1976-09-01

    Respiration is depressed in irradiated bacteria reaching a minimum level in most strains at 1-3 h after exposure when incubated in growth medium. Since a delay in response is observed, direct action on respiratory enzymes is unlikely. The dosage response of respiration varies widely in the strains studied. All strains exhibit two-component dosage-response curves. The facts suggest that respiration is a major factor in influencing cell survival and may be the principal mechanism through which chemical agents modify radiation response.

  8. Response of nuclear emulsions to ionizing radiations

    International Nuclear Information System (INIS)

    Katz, R.; Pinkerton, F.E.

    1975-01-01

    Heavy ion tracks in Ilford K-2 emulsion are simulated with a computer program which makes use of the delta-ray theory of track structure, and the special assumption that the response of this emulsion to gamma-rays is 8-or-more hit. The Ilford K-series of nuclear emulsions is produced from a parent stock called K.0 emulsion, sensitized to become K.1 to K.5, and desensitized to become K-1 to K-3. Our simulations demonstrate that the emulsions K.5 through K.0 to K-1 are 1-or-more hit detectors, while K-2 is an 8-or-more hit detector. We have no data for K-3 emulsion. It would appear that emulsions of intermediate hittedness might be produced by an intermediate desensitization, to mimic or match the RBE-LET variations of biological cells, perhaps to produce a ''rem-dosimeter''. In the K-2 emulsion no developable gains are produced by stopping H, He, and Li ions. The emulsion has ''threshold-like'' properties, resembling etchable track detectors. It should prove useful in the measurement of high LET dose in a strong low LET background, as for pions or neutrons. Since it can be expected to accumulate and repair ''sub-lethal damage'', to display the ion-kill and gamma-kill inactivation modes, the grain-count and track width regimes, it may serve to model biological effects. (auth)

  9. Response of high Tc superconducting Josephson junction to nuclear radiation

    International Nuclear Information System (INIS)

    Ding Honglin; Zhang Wanchang; Zhang Xiufeng

    1992-10-01

    The development of nuclear radiation detectors and research on high T c superconducting nuclear radiation detectors are introduced. The emphases are the principle of using thin-film and thick-film Josephson junctions (bridge junction) based on high T c YBCO superconductors to detect nuclear radiation, the fabrication of thin film and thick-film Josephson junction, and response of junction to low energy gamma-rays of 59.5 keV emitted from 241 Am and beta-rays of 546 keV. The results show that a detector for measuring nuclear radiation spectrum made of high T c superconducting thin-film or thick-film, especially, thick-film Josephson junction, certainly can be developed

  10. Response of Soft Continuous Structures and Topological Defects to a Temperature Gradient.

    Science.gov (United States)

    Kurita, Rei; Mitsui, Shun; Tanaka, Hajime

    2017-09-08

    Thermophoresis, which is mass transport induced by a temperature gradient, has recently attracted considerable attention as a new way to transport materials. So far the study has been focused on the transport of discrete structures such as colloidal particles, proteins, and polymers in solutions. However, the response of soft continuous structures such as membranes and gels to a temperature gradient has been largely unexplored. Here we study the behavior of a lamellar phase made of stacked surfactant bilayer membranes under a temperature gradient. We find the migration of membranes towards a low-temperature region, causing the increase in the degree of membrane undulation fluctuations towards that direction. This is contrary to our intuition that the fluctuations are weaker at a lower temperature. We show that this can be explained by temperature-gradient-induced migration of membranes under the topological constraint coming from the connectivity of each membrane. We also reveal that the pattern of an edge dislocation array formed in a wedge-shaped cell can be controlled by a temperature gradient. These findings suggest that application of a temperature gradient provides a novel way to control the organization of soft continuous structures such as membranes, gels, and foams, in a manner essentially different from the other types of fields, and to manipulate topological defects.

  11. Lipopolysaccharides with acylation defects potentiate TLR4 signaling and shape T cell responses.

    Directory of Open Access Journals (Sweden)

    Anna Martirosyan

    Full Text Available Lipopolysaccharides or endotoxins are components of Gram-negative enterobacteria that cause septic shock in mammals. However, a LPS carrying hexa-acyl lipid A moieties is highly endotoxic compared to a tetra-acyl LPS and the latter has been considered as an antagonist of hexa-acyl LPS-mediated TLR4 signaling. We investigated the relationship between the structure and the function of bacterial LPS in the context of human and mouse dendritic cell activation. Strikingly, LPS with acylation defects were capable of triggering a strong and early TLR4-dependent DC activation, which in turn led to the activation of the proteasome machinery dampening the pro-inflammatory cytokine secretion. Upon activation with tetra-acyl LPS both mouse and human dendritic cells triggered CD4(+ T and CD8(+ T cell responses and, importantly, human myeloid dendritic cells favored the induction of regulatory T cells. Altogether, our data suggest that LPS acylation controlled by pathogenic bacteria might be an important strategy to subvert adaptive immunity.

  12. Symmetry, strain, defects, and the nonlinear optical response of crystalline BaTiO3/silicon

    Science.gov (United States)

    Kormondy, Kristy; Abel, Stefan; Popoff, Youri; Sousa, Marilyne; Caimi, Daniele; Siegwart, Heinz; Marchiori, Chiara; Rossell, Marta; Demkov, Alex; Fompeyrine, Jean

    Recent progress has been made towards exploiting the linear electro-optic or Pockels effect in ferroelectric BaTiO3 (BTO) for novel integrated silicon photonics devices. In such structures, the crystalline symmetry and domain structure of BTO determine which electro-optic tensor elements are accessible under application of an external electric field. For epitaxial thin films of BTO on Si (001), the role of defects in strain relaxation can lead to very different crystalline symmetry even for films of identical thickness. Indeed, through geometric phase analysis of high-resolution scanning transmission electron microscopy images, we map changes of the in-plane and out-of-plane lattice parameters across two 80-nm-thick BTO films. A corresponding 20% difference in the effective electro-optic response was measured by analyzing induced rotation of the polarization of a laser beam (λ = 1550 nm) transmitted through lithographically defined electrodes. Understanding, controlling, and modelling the role of BTO symmetry in nonlinear optics is of fundamental importance for the development of a hybrid BTO/Si photonics platform.. Work supported by the NSF (IRES-1358111), AFOSR (FA9550-12-10494), and European Commission (FP7-ICT-2013-11-619456-SITOGA).

  13. Study of the response of radiation protection monitors in terms of H*(10) in X radiation

    International Nuclear Information System (INIS)

    Nonato, Fernanda B.C.; Carvalho, Valdir S.; Vivolo, Vitor; Caldas, Linda V.E.

    2009-01-01

    The ambient dose equivalent, H * (10), is an operational quantity recommended by the International Commission of radiation Units and Measurements Report 39 for measurements in area monitoring. However, most of the monitoring instruments used in radiation protection in Brazil still use the old quantities exposure rate and absorbed dose rate. Therefore, it is necessary to study how to change the operational quantity to H * (10). In this work, the response of radiation protection monitoring detectors was studied in terms of H * (10) for different energies using standard X-rays (narrow beams) at the Calibration Laboratory of IPEN. (author)

  14. Caffeine ameliorates radiation-induced skin reactions in mice but does not influence tumour radiation response

    Energy Technology Data Exchange (ETDEWEB)

    Hebbar, S.A.; Mitra, A.K.; George, K.C.; Verma, N.C. [Radiation Biology Division, Bhabha Atomic Research Centre, Trombay, Mumbai (India)]. E-mail: ncverma@apsara.barc.ernet.in

    2002-03-01

    Intramuscular administration of caffeine at a dose of 80 mg kg{sup -1} body weight to the gastrocnemius muscles of Swiss mice 5 min prior to local irradiation (35 Gy) of the leg delayed the progression of radiation-induced skin reactions in such animals. While 90% epilation with reddening of the skin was noted in animals treated with radiation alone, animals pretreated with caffeine suffered only partial hair loss with slight reddening of the skin on the 16th and 20th days post-irradiation. Beyond the 28th day, damage scores in irradiated feet for both the groups were similar (score 3) and remained unchanged until the 32nd day and then decreased and disappeared completely in both treatment groups by the 40th day after irradiation. In addition, the effect of caffeine on the radiation response of a mouse fibrosarcoma was investigated. Results showed that intratumoral administration of caffeine at a dose of 80 mg kg{sup -1} body weight 5 min prior to local exposure of tumours to 10 Gy of {sup 60}Co {gamma}-rays did not influence the response of tumours to radiation. The present study thus showed that although caffeine ameliorated radiation-induced skin reactions in the mouse leg, it did not affect the tumour radiation response, indicating its potential application in cancer radiotherapy. (author)

  15. Cellular Response to Ionizing Radiation: A MicroRNA Story

    Science.gov (United States)

    Halimi, Mohammad; Asghari, S. Mohsen; Sariri, Reyhaneh; Moslemi, Dariush; Parsian, Hadi

    2012-01-01

    MicroRNAs (miRNAs) represent a class of small non-coding RNA molecules that regulate gene expression at the post-transcriptional level. They play a crucial role in diverse cellular pathways. Ionizing radiation (IR) is one of the most important treatment protocols for patients that suffer from cancer and affects directly or indirectly cellular integration. Recently it has been discovered that microRNA-mediated gene regulation interferes with radio-related pathways in ionizing radiation. Here, we review the recent discoveries about miRNAs in cellular response to IR. Thoroughly understanding the mechanism of miRNAs in radiation response, it will be possible to design new strategies for improving radiotherapy efficiency and ultimately cancer treatment. PMID:24551775

  16. Radiation response of high speed CMOS integrated circuits

    International Nuclear Information System (INIS)

    Yue, H.; Davison, D.; Jennings, R.F.; Lothongkam, P.; Rinerson, D.; Wyland, D.

    1987-01-01

    This paper studies the total dose and dose rate radiation response of the FCT family of high speed CMOS integrated circuits. Data taken on the devices is used to establish the dominant failure modes, and this data is further analyzed using one-sided tolerance factors for normal distribution statistical analysis

  17. Minimally Invasive Radiation Biodosimetry and Evaluation of Organ Responses

    Science.gov (United States)

    2016-10-01

    and time. The levels of circulating miR-150 was found reduced in a dose and time dependent manner , while that of miRNA-574 was found increasing after...radiation in dose and time dependent manner . Additional putative biomarkers exhibiting dose-time response have been identified, which need

  18. Radiation-induced augmentation of the immune response

    International Nuclear Information System (INIS)

    Anderson, R.E.; Lefkovits, I.; Troup, G.M.

    1980-01-01

    Radiation-induced augmentation of the immune response has been shown to occur both in vivo and in vitro. Evidence is presented to implicate injury to an extremely radiosensitive T cell in the expression of this phenomenon. Experiments are outlined which could be employed to support or reflect this hypothesis

  19. Evaluation of normal tissue responses to high-LET radiations

    International Nuclear Information System (INIS)

    Halnan, K.E.

    1979-01-01

    Clinical results presented have been analysed to evaluate normal tissue responses to high-LET radiations. Damage to brain, spinal cord, gut, skin, connective tissue and bone has occurred. A high RBE is probable for brain and possible for spinal cord and gut but other reasons for damage are also discussed. A net gain seems likely. Random controlled trials are advocated. (author)

  20. Optical properties of Ni2+ and radiation defects in MgF sub 2 and MnF sub 2

    Science.gov (United States)

    Feuerhelm, L. N.

    1980-03-01

    The radiation defects in pure MgF2 were made by observating the polarized absorption, luminescence, and excitation spectra in electron-irradiated MgF2. Additionally, studies of the absorption, emission, excitation, and temperature dependence of the lifetimes of transitions in nickel-doped MgF2 and MnF2 were accomplished, as well as the observation of radiation effects on these crystals. The absorption band at about 320 nm in irradiated MgF2 is identified to be due to the F2(D2b) center, and to have an emission at about 450 nm. Analysis of the temperature dependence of this band indicates a dominant phonon mode of 255 cm(-1) for the excited state. The F2(C1) center is identified with an absorption of about 360 nm and an emission of 410 nm. An absorption peak at 300 nm, for which no corresponding emission was found, is tentatively identified to be the F3-center, and to have a dominant phonon mode of 255 cm(-1). The temperature dependence of the lifetimes of transitions in nickel-doped MgF2 is analyzed by the quantum mechanical single configuration coordinate model of Struck and Fonger, and a complete configuration coordinate model is made for this crystal. Similar studies are made in MnF2:Ni.

  1. Response of induced bone defects in horses to collagen matrix containing the human parathyroid hormone gene.

    Science.gov (United States)

    Backstrom, Kristin C; Bertone, Alicia L; Wisner, Erik R; Weisbrode, Stephen E

    2004-09-01

    To determine whether human parathyroid hormone (hPTH) gene in collagen matrix could safely promote bone formation in diaphyseal or subchondral bones of horses. 8 clinically normal adult horses. Amount, rate, and quality of bone healing for 13 weeks were determined by use of radiography, quantitative computed tomography, and histomorphometric analysis. Diaphyseal cortex and subchondral bone defects of metacarpi were filled with hPTH(1-34) gene-activated matrix (GAM) or remained untreated. Joints were assessed on the basis of circumference, synovial fluid analysis, pain on flexion, lameness, and gross and histologic examination. Bone volume index was greater for cortical defects treated with hPTH(1-34) GAM, compared with untreated defects. Bone production in cortical defects treated with hPTH(1-34) GAM positively correlated with native bone formation in untreated defects. In contrast, less bone was detected in hPTH(1-34) GAM-treated subchondral bone defects, compared with untreated defects, and histology confirmed poorer healing and residual collagen sponge. Use of hPTH(1-34) GAM induced greater total bone, specifically periosteal bone, after 13 weeks of healing in cortical defects of horses. The hPTH(1-34) GAM impeded healing of subchondral bone but was biocompatible with joint tissues. Promotion of periosteal bone formation may be beneficial for healing of cortical fractures in horses, but the delay in onset of bone formation may negate benefits. The hPTH(1-34) GAM used in this study should not be placed in articular subchondral bone defects, but contact with articular surfaces is unlikely to cause short-term adverse effects.

  2. A comparative study of low energy radiation responses of SiC, TiC and ZrC

    International Nuclear Information System (INIS)

    Jiang, M.; Xiao, H.Y.; Zhang, H.B.; Peng, S.M.; Xu, C.H.; Liu, Z.J.; Zu, X.T.

    2016-01-01

    In this study, an ab initio molecular dynamics method is employed to compare the responses of SiC, TiC and ZrC to low energy irradiation. It reveals that C displacements are dominant in the cascade events of the three carbides. The associated defects in SiC are mainly Frenkel pairs and antisite defects, whereas damage end states in TiC and ZrC generally consist of Frenkel pairs and very few antisite defects are created. It is proposed that the susceptibility to antisite formation in SiC contributes to its crystalline-to-amorphous transformation under irradiation that is observed experimentally. The stronger radiation tolerance of TiC and ZrC than SiC can be originated from their different electronic structures, i.e., the and bonds are a mixture of covalent, metallic, and ionic character, whereas the bond is mainly covalent. The presented results provide underlying mechanisms for defect generation in SiC, TiC and ZrC, and advance the fundamental understanding of the radiation resistances of carbide materials.

  3. Formation of radiation-induced defects and their influence on tritium extraction from lithium silicates in out-of-pile experiments

    International Nuclear Information System (INIS)

    Abramenkovs, A.A.; Tiliks, J.E.

    1991-01-01

    Formation and properties of radiation-induced defects and radiolysis products in lithium silicates irradiated in nuclear reactor till absorbed doses 1000 MGy were studied. Radiation-induced defects (RD) and radiolysis products (RP) were qualitatively and quantitatively determinated by methods of chemical scavengers (MHS), electron-spin resonance (ESR) and optical spectroscopy. Colloidal silicon and lithium, lithium and silicon oxides, oxygen, silicon and lithium peroxides are the final products of the lithium silicates radiolysis at absorbed energy doses D abs = 1000 MGy. The concentration of radiation defects and products of radiolysis strongly depend on the temperature of irradiation, humidity, granural size. The thermostimulated extraction of tritiated water (95-98% of the released tritium is in chemical form of water) from lithium silicates ceramics proceeds according to two independent mechanisms: a) chemidesorption of surface localized tritiated water (the first order chemical reaction); b) formation of the tritium water molecules limited by triton diffusion to the near-surface layer of grains. It has been found that the concentration of radiation-induced defects considerably affects the tritium localization and releasing processes from lithium silicates. (orig.)

  4. Computer stimulation of radiation-induced defects in metals irradiated with heavy ions

    International Nuclear Information System (INIS)

    Kupchishin, A.A.; Kupchishin, A.I.; Shmygaleva, T.A.

    2004-01-01

    Full text: In the work for account of defect concentration at ion irradiation the formula is proposed with use the modified cascade-probability function. It is necessary to find a real domain of result for account of cascade-probability functions (CPF) subject to losses of energy for ions depend upon a number of interactions. CPF first grows, achieving a maximum, then one decreases in the found region. The regularities of behavior of result region at change of a charge of flying particles are the following: 1. The increase of a charge z of a flying particle results in a displacement of result determination region to the left and narrowing it; 2. At the large value z, the maximum value of CPF displaces to the left as respects of h/λ already at small depths, and at the large depths the result is in a narrow region (less than 1 %, silver, gold); 3. The narrowest region of result arises at a large charge of flying particle and a target with small charge on the end of run and amounts to 100-th shares of percents

  5. Identification of explosives and drugs and inspection of material defects with THz radiation

    Science.gov (United States)

    Zhang, Cunlin; Mu, Kaijun; Jiang, Xue; Jiao, Yueying; Zhang, Liangliang; Zhou, Qingli; Zhang, Yan; Shen, Jingling; Zhao, Guoshong; Zhang, X.-C.

    2008-03-01

    We report the sensing of explosive materials and illicit drugs by using terahertz time-domain spectroscopy (THz-TDS) and imaging. Several explosive materials, such as γ-HNIW, RDX, 2,4-DNT, TNT, Nitro-aniline, and illicit drugs, such as methamphetamine (MA) etc were researched here. Non-destructive testing, as one of the major applications of THz imaging, can be applied to an area of critical need: the testing of aerospace materials. Composite materials such as carbon fiber are widely used in this industry. The nature of their use requires technologies that are able to differentiate between safe and unsafe materials, due to either manufacturing tolerance or damage acquired while in use. In this paper, we discuss the applicability of terahertz (THz) imaging systems to this purpose, focusing on graphite fiber composite materials, carbon silicon composite materials and so on. We applied THz imaging technology to evaluate the fire damage to a variety of carbon fiber composite samples. Major carbon fiber materials have polarization-dependent reflectivity in THz frequency range, and we show how the polarization dependence changes versus the burned damage level. Additionally, time domain information acquired through a THz time-domain spectroscopy (TDS) system provides further information with which to characterize the damage. We also detect fuel tank insulation foam panel defects with pulse and continuous-wave (CW) terahertz system.

  6. Dose rate effect on the yield of radiation induced response with thermal fading

    International Nuclear Information System (INIS)

    Chernov, V.; Rogalev, B.; Barboza-Flores, M.

    2005-01-01

    A model describing the dependences of the accumulation of thermally unstable radiation induced defects on the dose and dose rate is proposed. The model directly takes into account the track nature of the ionizing radiation represented as accumulation processes of defects in tracks averaged over a crystal volume considering various degrees of overlapping in space and time. The accumulation of the defects in the tracks is phenomenologically described. General expressions are obtained that allows radiation yield simulation of defects involving known creation and transformation processes. The cases considered, of linear accumulation (constant increment of the defects in tracks) and accumulation with saturation (complete saturation of the defects in one track), lead to a set of linear dose dependences with saturation, which are routinely used in luminescence and ESR dating. The accumulation, with increase of sensitivity in regions overlapped by two or more tracks, gave a set of dose dependences, from linear-sublinear-linear-saturation, distinctive of quartz up to linear-supralinear-linear-saturation. It is shown that the effect of the dose rate on dose dependences is determined by a dimensionless parameter a=Pτ/D0, where P is the dose rate, τ is the defect lifetime and D0 is the track dose. At a-bar 1 the dose rate influences basically the accumulation of thermally unstable defects. In the reverse case the dose dependences did not seems to be influenced by the dose rate

  7. Enhanced tumor responses through therapies combining CCNU, MISO and radiation

    International Nuclear Information System (INIS)

    Siemann, D.W.; Hill, S.A.

    1984-01-01

    Studies were performed to determine whether the radiation sensitizer misonidazole (MISO) could enhance the tumor control probability in a treatment strategy combining radiation and the nitrosourea 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU). In initial experiments KHT sarcoma-bearing mice were injected with 1.0 mg/g of MISO simultaneously with a 20 mg/kg dose of CCNU 30-40 min prior to irradiation (1500 rad). With this treatment protocol approximately 60% of the mice were found to be tumor-free 100 days post treatment. By comparison all 2 agent combinations led to 0% cures. To evaluate the relative importance of chemopotentiation versus radiosensitization in the 3 agent protocol, tumors were treated with MISO plus one anti-tumor agent (either radiation of CCNU) and then at times ranging from 0 to 24 hr later exposed to the other agent. When the time between treatments was 0 to 6 hr, a 60 to 80% tumor control rate was achieved for both MISO plus radiation followed by CCNU and MISO plus CCNU followed by radiation. However if the time interval was increased to 18 or 24 hr, the cure rate in the former treatment regimen dropped to 10% while that of the latter remained high at 40%. The data therefore indicate that (1) improved tumor responses may be achieved when MISO is added to a radiation-chemotherapy combination and (2) MISO may be more effective in such a protocol when utilized as a chemopotentiator

  8. Preferential repair of ionizing radiation-induced damage in the transcribed strand of an active human gene is defective in Cockayne syndrome

    International Nuclear Information System (INIS)

    Leadon, S.A.; Copper, P.K.

    1993-01-01

    Cells from patients with Cockayne syndrome (CS), which are sensitive to killing by UV although overall damage removal appears normal, are specifically defective in repair of UV damage in actively transcribe genes. Because several CS strains display cross-sensitivity to killing by ionizing radiation, the authors examined whether ionizing radiation-induced damage in active genes is preferentially repaired by normal cells and whether the radiosensitivity of CS cells can be explained by a defect in this process. They found that ionizing radiation-induced damage was repaired more rapidly in the transcriptionally active metallothionein IIA (MTIIA) gene than in the inactive MTIIB gene or in the genome overall in normal cells as a result of faster repair on the transcribed strand of MTIIA. Cells of the radiosensitive CS strain CS1AN are completely defective in this strand-selective repair of ionizing radiation-induced damage, although their overall repair rate appears normal. CS3BE cells, which are intermediate in radiosensitivity, do exhibit more rapid repair of the transcribed strand but at a reduced rate compared to normal cells. Xeroderma pigmentosum complementation group A cells, which are hypersensitive to UV light because of a defect in the nucleotide excision repair pathway but do not show increased sensitivity to ionizing radiation, preferentially repair ionizing radiation-induced damage on the transcribed strand of MTIIA. Thus, the ability to rapidly repair ionizing radiation-induced damage in actively transcribing genes correlates with cell survival. The results extend the generality of preferential repair in active genes to include damage other than bulky lesions

  9. Response to defects in multipartite and bipartite entanglement of isotropic quantum spin networks

    Science.gov (United States)

    Roy, Sudipto Singha; Dhar, Himadri Shekhar; Rakshit, Debraj; SenDe, Aditi; Sen, Ujjwal

    2018-05-01

    Quantum networks are an integral component in performing efficient computation and communication tasks that are not accessible using classical systems. A key aspect in designing an effective and scalable quantum network is generating entanglement between its nodes, which is robust against defects in the network. We consider an isotropic quantum network of spin-1/2 particles with a finite fraction of defects, where the corresponding wave function of the network is rotationally invariant under the action of local unitaries. By using quantum information-theoretic concepts like strong subadditivity of von Neumann entropy and approximate quantum telecloning, we prove analytically that in the presence of defects, caused by loss of a finite fraction of spins, the network, composed of a fixed numbers of lattice sites, sustains genuine multisite entanglement and at the same time may exhibit finite moderate-range bipartite entanglement, in contrast to the network with no defects.

  10. Radiation response of skin in young and old rats

    Energy Technology Data Exchange (ETDEWEB)

    Hamlet, R.; Hopewell, J.W. (Churchill Hospital, Oxford (UK))

    1982-11-01

    The results of this investigation clearly demonstrate the different radiation skin response in rats of differing ages. The reasons for these differences cannot be clarified until cell kinetic studies have been completed. These results obtained for rodent skin would appear to be in disagreement with the available data for human skin (Rubin and Casarett 1968) where no marked age-related changes were reported. Also, in pig skin studies (Hopewell and Young 1982) there was no evidence of an age effect in the dermal vascular response in 3-12-month-old animals. This may be related to the different tissue being investigated or it may reflect important species differences. Whatever the reasons behind these observations, the different skin response to radiation in rats of 7, 14 and 52 weeks of age has clearly been demonstrated and should be borne in mind when extrapolating data with rodent skin to the clinical situation.

  11. The radiation response of skin in young and old rats

    International Nuclear Information System (INIS)

    Hamlet, R.; Hopewell, J.W.

    1982-01-01

    The results of this investigation clearly demonstrate the different radiation skin response in rats of differing ages. The reasons for these differences cannot be clarified until cell kinetic studies have been completed. These results obtained for rodent skin would appear to be in disagreement with the available data for human skin (Rubin and Casarett 1968) where no marked age-related changes were reported. Also, in pig skin studies (Hopewell and Young 1982) there was no evidence of an age effect in the dermal vascular response in 3-12-month-old animals. This may be related to the different tissue being investigated or it may reflect important species differences. Whatever the reasons behind these observations, the different skin response to radiation in rats of 7, 14 and 52 weeks of age has clearly been demonstrated and should be borne in mind when extrapolating data with rodent skin to the clinical situation. (author)

  12. Optical Properties of Nickel(ii) and Radiation Defects in Magnesium-Fluoride and Manganese-Fluoride

    Science.gov (United States)

    Feuerhelm, Leonard Norman

    1980-12-01

    Scope and Method of Study. A study has been made of the radiation defects in pure MgF(,2) by observating the polarized absorption, luminescence, and excitation spectra in electron-irradiated MgF(,2). Additionally, studies of the absorption, emission, excitation, and temperature dependence of the lifetimes of transitions in nickel-doped MgF(,2) and MnF(,2) have been accomplished, as well as the observation of radiation effects on these crystals. Findings and Conclusions. The absorption band at about 320 nm in irradiated MgF(,2) is identified to be due to the F(,2)(D(,2h)) center, and to have an emission at about 450 nm. Analysis of the temperature dependence of this band indicates a dominant phonon mode of 255 cm(' -1) for the excited state. The F(,2)(C(,1)) center is identified with an absorption of about 360 nm and an emission of 410 nm. An absorption peak at 300 nm, for which no corresponding emission has been found, is tentatively identified to be the F(,3)-center, and to have a dominant phonon mode of 255 cm('-1). The temperature dependence of the lifetimes of transitions in nickel-doped MgF(,2) have been analyzed by the quantum mechanical single configuration coordinate model of Struck and Fonger, and a complete configuration coordinate model has been made for this crystal. Similar studies have been made in MnF(,2):Ni, but energy transfer between Mn('2+) ions and Ni('2+) ions prevents completion of the complete model. Energy transfer in this crystal was studied, with the finding that a gain of about 2 in luminescence output was possible for excitation in the visible region (400-600 nm) as compared with MgF(,2):Ni. The effects of radiation upon the Ni('2+) transitions in these crystals were studied with the finding that no observable change occurred in the Ni('2+) transitions with radiation, although other radiation effects were noted in the crystal.

  13. AMPK regulates metabolism and survival in response to ionizing radiation

    International Nuclear Information System (INIS)

    Zannella, Vanessa E.; Cojocari, Dan; Hilgendorf, Susan; Vellanki, Ravi N.; Chung, Stephen; Wouters, Bradly G.; Koritzinsky, Marianne

    2011-01-01

    Background and purpose: AMPK is a metabolic sensor and an upstream inhibitor of mTOR activity. AMPK is phosphorylated by ionizing radiation (IR) in an ATM dependent manner, but the cellular consequences of this phosphorylation event have remained unclear. The objective of this study was to assess whether AMPK plays a functional role in regulating cellular responses to IR. Methods: The importance of AMPK expression for radiation responses was investigated using both MEFs (mouse embryo fibroblasts) double knockout for AMPK α1/α2 subunits and human colorectal carcinoma cells (HCT 116) with AMPK α1/α2 shRNA mediated knockdown. Results: We demonstrate here that IR results in phosphorylation of both AMPK and its substrate, ACC. IR moderately stimulated mTOR activity, and this was substantially exacerbated in the absence of AMPK. AMPK was required for IR induced expression of the mTOR inhibitor REDD1, indicating that AMPK restrains mTOR activity through multiple mechanisms. Likewise, cellular metabolism was deregulated following irradiation in the absence of AMPK, as evidenced by a substantial increase in oxygen consumption rates and lactate production. AMPK deficient cells showed impairment of the G1/S cell cycle checkpoint, and were unable to support long-term proliferation during starvation following radiation. Lastly, we show that AMPK proficiency is important for clonogenic survival after radiation during starvation. Conclusions: These data reveal novel functional roles for AMPK in regulating mTOR signaling, cell cycle, survival and metabolic responses to IR.

  14. Obligations and responsibilities in radiation protection in the medical field

    International Nuclear Information System (INIS)

    2011-01-01

    This document briefly presents the various obligations and responsibilities of the various actors involved in or concerned by radiation protection in the medical field: the hospital administration (with respect to workers and patients), the physician (authorization and declaration, justification, optimization), the medical electro-radiology operator, the person with expertise in medical radio-physics (PSRPM), the radio-pharmacist (he is required in nuclear medicine with internal use of pharmaceutical product), the personnel with expertise in radiation protection (PCR), and other health professionals

  15. Radionuclide analysis of right and left ventricular response to exercise in patients with atrial and ventricular septal defects

    International Nuclear Information System (INIS)

    Peter, C.A.; Bowyer, K.; Jones, R.H.

    1983-01-01

    In patients with ventricular or atrial septal defect, the ventricle which is chronically volume overloaded might not appropriately respond to increased demand for an augmentation in output and thereby might limit total cardiac function. In this study we simultaneously measured right and left ventricular response to exercise in 10 normal individuals, 10 patients with ventricular septal defect (VSD), and 10 patients with atrial septal defect (ASD). The normal subjects increased both right and left ventricular ejection fraction, end-diastolic volume, and stroke volume to achieve a higher cardiac output during exercise. Patients with VSD failed to increase right ventricular ejection fraction, but increased right ventricular end-diastolic volume and stroke volume. Left ventricular end-diastolic volume did not increase in these patients but ejection fraction, stroke volume, and forward left ventricular output achieved during exercise were comparable to the response observed in healthy subjects. In the patients with ASD, no rest-to-exercise change occurred in either right ventricular ejection fraction, end-diastolic volume, or stroke volume. In addition, left ventricular end-diastolic volume failed to increase, and despite an increase in ejection fraction, left ventricular stroke volume remained unchanged from rest to exercise. Therefore, cardiac output was augmented only by the heart rate increase in these patients. Right ventricular function appeared to be the major determinant of total cardiac output during exercise in patients with cardiac septal defects and left-to-right shunt

  16. Radiation and desiccation response motif mediates radiation induced gene expression in D. radiodurans

    International Nuclear Information System (INIS)

    Anaganti, Narasimha; Basu, Bhakti; Apte, Shree Kumar

    2015-01-01

    Deinococcus radiodurans is an extremophile that withstands lethal doses of several DNA damaging agents such as gamma irradiation, UV rays, desiccation and chemical mutagens. The organism responds to DNA damage by inducing expression of several DNA repair genes. At least 25 radiation inducible gene promoters harbour a 17 bp palindromic sequence known as radiation and desiccation response motif (RDRM) implicated in gamma radiation inducible gene expression. However, mechanistic details of gamma radiation-responsive up-regulation in gene expression remain enigmatic. The promoters of highly radiation induced genes ddrB (DR0070), gyrB (DR0906), gyrA (DR1913), a hypothetical gene (DR1143) and recA (DR2338) from D. radiodurans were cloned in a green fluorescence protein (GFP)-based promoter probe shuttle vector pKG and their promoter activity was assessed in both E. coli as well as in D. radiodurans. The gyrA, gyrB and DR1143 gene promoters were active in E. coli although ddrB and recA promoters showed very weak activity. In D. radiodurans, all the five promoters were induced several fold following 6 kGy gamma irradiation. Highest induction was observed for ddrB promoter (25 fold), followed by DR1143 promoter (15 fold). The induction in the activity of gyrB, gyrA and recA promoters was 5, 3 and 2 fold, respectively. To assess the role of RDRM, the 17 bp palindromic sequence was deleted from these promoters. The promoters devoid of RDRM sequence displayed increase in the basal expression activity, but the radiation-responsive induction in promoter activity was completely lost. The substitution of two conserved bases of RDRM sequence yielded decreased radiation induction of PDR0070 promoter. Deletion of 5 bases from 5'-end of PDR0070 RDRM increased basal promoter activity, but radiation induction was completely abolished. Replacement of RDRM with non specific sequence of PDR0070 resulted in loss of basal expression and radiation induction. The results demonstrate that

  17. The Effect of Grain Size on the Radiation Response of Silicon Carbide and its Dependence on Irradiation Species and Temperature

    Science.gov (United States)

    Jamison, Laura

    In recent years the push for green energy sources has intensified, and as part of that effort accident tolerant and more efficient nuclear reactors have been designed. These reactors demand exceptional material performance, as they call for higher temperatures and doses. Silicon carbide (SiC) is a strong candidate material for many of these designs due to its low neutron cross-section, chemical stability, and high temperature resistance. The possibility of improving the radiation resistance of SiC by reducing the grain size (thus increasing the sink density) is explored in this work. In-situ electron irradiation and Kr ion irradiation was utilized to explore the radiation resistance of nanocrystalline SiC (nc-SiC), SiC nanopowders, and microcrystalline SiC. Electron irradiation simplifies the experimental results, as only isolated Frenkel pairs are produced so any observed differences are simply due to point defect interactions with the original microstructure. Kr ion irradiation simulates neutron damage, as large radiation cascades with a high concentration of point defects are produced. Kr irradiation studies found that radiation resistance decreased with particle size reduction and grain refinement (comparing nc-SiC and microcrystalline SiC). This suggests that an interface-dependent amorphization mechanism is active in SiC, suggested to be interstitial starvation. However, under electron irradiation it was found that nc-SiC had improved radiation resistance compared to single crystal SiC. This was found to be due to several factors including increased sink density and strength and the presence of stacking faults. The stacking faults were found to improve radiation response by lowering critical energy barriers. The change in radiation response between the electron and Kr ion irradiations is hypothesized to be due to either the change in ion type (potential change in amorphization mechanism) or a change in temperature (at the higher temperatures of the Kr ion

  18. T lymphocytes and normal tissue responses to radiation

    International Nuclear Information System (INIS)

    Schaue, Dörthe; McBride, William H.

    2012-01-01

    There is compelling evidence that lymphocytes are a recurring feature in radiation damaged normal tissues, but assessing their functional significance has proven difficult. Contradictory roles have been postulated in both tissue pathogenesis and protection, although these are not necessarily mutually exclusive as the immune system can display what may seem to be opposing faces at any one time. While the exact role of T lymphocytes in irradiated normal tissue responses may still be obscure, their accumulation after tissue damage suggests they may be critical targets for radiotherapeutic intervention and worthy of further study. This is accentuated by recent findings that pathologically damaged “self,” such as occurs after exposure to ionizing radiation, can generate danger signals with the ability to activate pathways similar to those that activate adoptive immunity to pathogens. In addition, the demonstration of T cell subsets with their recognition radars tuned to “self” moieties has revolutionized our ideas on how all immune responses are controlled and regulated. New concepts of autoimmunity have resulted based on the dissociation of immune functions between different subsets of immune cells. It is becoming axiomatic that the immune system has the power to regulate radiation-induced tissue damage, from failure of regeneration to fibrosis, to acute and chronic late effects, and even to carcinogenesis. Our understanding of the interplay between T lymphocytes and radiation-damaged tissue may still be rudimentary but this is a good time to re-examine their potential roles, their radiobiological and microenvironmental influences, and the possibilities for therapeutic manipulation. This review will discuss the yin and yang of T cell responses within the context of radiation exposures, how they might drive or protect against normal tissue side effects and what we may be able do about it.

  19. A Computational Model of Cellular Response to Modulated Radiation Fields

    Energy Technology Data Exchange (ETDEWEB)

    McMahon, Stephen J., E-mail: stephen.mcmahon@qub.ac.uk [Centre for Cancer Research and Cell Biology, Queen' s University Belfast, Belfast, Northern Ireland (United Kingdom); Butterworth, Karl T. [Centre for Cancer Research and Cell Biology, Queen' s University Belfast, Belfast, Northern Ireland (United Kingdom); McGarry, Conor K. [Centre for Cancer Research and Cell Biology, Queen' s University Belfast, Belfast, Northern Ireland (United Kingdom); Radiotherapy Physics, Northern Ireland Cancer Centre, Belfast Health and Social Care Trust, Northern Ireland (United Kingdom); Trainor, Colman [Centre for Cancer Research and Cell Biology, Queen' s University Belfast, Belfast, Northern Ireland (United Kingdom); O' Sullivan, Joe M. [Centre for Cancer Research and Cell Biology, Queen' s University Belfast, Belfast, Northern Ireland (United Kingdom); Clinical Oncology, Northern Ireland Cancer Centre, Belfast Health and Social Care Trust, Belfast, Northern Ireland (United Kingdom); Hounsell, Alan R. [Centre for Cancer Research and Cell Biology, Queen' s University Belfast, Belfast, Northern Ireland (United Kingdom); Radiotherapy Physics, Northern Ireland Cancer Centre, Belfast Health and Social Care Trust, Northern Ireland (United Kingdom); Prise, Kevin M. [Centre for Cancer Research and Cell Biology, Queen' s University Belfast, Belfast, Northern Ireland (United Kingdom)

    2012-09-01

    Purpose: To develop a model to describe the response of cell populations to spatially modulated radiation exposures of relevance to advanced radiotherapies. Materials and Methods: A Monte Carlo model of cellular radiation response was developed. This model incorporated damage from both direct radiation and intercellular communication including bystander signaling. The predictions of this model were compared to previously measured survival curves for a normal human fibroblast line (AGO1522) and prostate tumor cells (DU145) exposed to spatially modulated fields. Results: The model was found to be able to accurately reproduce cell survival both in populations which were directly exposed to radiation and those which were outside the primary treatment field. The model predicts that the bystander effect makes a significant contribution to cell killing even in uniformly irradiated cells. The bystander effect contribution varies strongly with dose, falling from a high of 80% at low doses to 25% and 50% at 4 Gy for AGO1522 and DU145 cells, respectively. This was verified using the inducible nitric oxide synthase inhibitor aminoguanidine to inhibit the bystander effect in cells exposed to different doses, which showed significantly larger reductions in cell killing at lower doses. Conclusions: The model presented in this work accurately reproduces cell survival following modulated radiation exposures, both in and out of the primary treatment field, by incorporating a bystander component. In addition, the model suggests that the bystander effect is responsible for a significant portion of cell killing in uniformly irradiated cells, 50% and 70% at doses of 2 Gy in AGO1522 and DU145 cells, respectively. This description is a significant departure from accepted radiobiological models and may have a significant impact on optimization of treatment planning approaches if proven to be applicable in vivo.

  20. A Computational Model of Cellular Response to Modulated Radiation Fields

    International Nuclear Information System (INIS)

    McMahon, Stephen J.; Butterworth, Karl T.; McGarry, Conor K.; Trainor, Colman; O’Sullivan, Joe M.; Hounsell, Alan R.; Prise, Kevin M.

    2012-01-01

    Purpose: To develop a model to describe the response of cell populations to spatially modulated radiation exposures of relevance to advanced radiotherapies. Materials and Methods: A Monte Carlo model of cellular radiation response was developed. This model incorporated damage from both direct radiation and intercellular communication including bystander signaling. The predictions of this model were compared to previously measured survival curves for a normal human fibroblast line (AGO1522) and prostate tumor cells (DU145) exposed to spatially modulated fields. Results: The model was found to be able to accurately reproduce cell survival both in populations which were directly exposed to radiation and those which were outside the primary treatment field. The model predicts that the bystander effect makes a significant contribution to cell killing even in uniformly irradiated cells. The bystander effect contribution varies strongly with dose, falling from a high of 80% at low doses to 25% and 50% at 4 Gy for AGO1522 and DU145 cells, respectively. This was verified using the inducible nitric oxide synthase inhibitor aminoguanidine to inhibit the bystander effect in cells exposed to different doses, which showed significantly larger reductions in cell killing at lower doses. Conclusions: The model presented in this work accurately reproduces cell survival following modulated radiation exposures, both in and out of the primary treatment field, by incorporating a bystander component. In addition, the model suggests that the bystander effect is responsible for a significant portion of cell killing in uniformly irradiated cells, 50% and 70% at doses of 2 Gy in AGO1522 and DU145 cells, respectively. This description is a significant departure from accepted radiobiological models and may have a significant impact on optimization of treatment planning approaches if proven to be applicable in vivo.

  1. Reevaluating the worst-case radiation response of MOS transistors

    Science.gov (United States)

    Fleetwood, D. M.

    Predicting worst-case response of a semiconductor device to ionizing radiation is a formidable challenge. As processes change and MOS gate insulators become thinner in advanced VLSI and VHSIC technologies, failure mechanisms must be constantly re-examined. Results are presented of a recent study in which more than 100 MOS transistors were monitored for up to 300 days after Co-60 exposure. Based on these results, a reevaluation of worst-case n-channel transistor response (most positive threshold voltage shift) in low-dose-rate and postirradiation environments is required in many cases. It is shown for Sandia hardened n-channel transistors with a 32 nm gate oxide, that switching from zero-volt bias, held during the entire radiation period, to positive bias during anneal clearly leads to a more positive threshold voltage shift (and thus the slowest circuit response) after Co-60 exposure than the standard case of maintaining positive bias during irradiation and anneal. It is concluded that irradiating these kinds of transistors with zero-volt bias, and annealing with positive bias, leads to worst-case postirradiation response. For commercial devices (with few interface states at doses of interest), on the other hand, device response only improves postirradiation, and worst-case response (in terms of device leakage) is for devices irradiated under positive bias and annealed with zero-volts bias.

  2. Genistein-induced alterations of radiation-responsive gene expression

    Energy Technology Data Exchange (ETDEWEB)

    Grace, M.B. [Armed Forces Radiobiology Research Institute, 8901 Wisconsin Avenue, Bethesda, MD 20889-5603 (United States)], E-mail: grace@afrri.usuhs.mil; Blakely, W.F.; Landauer, M.R. [Armed Forces Radiobiology Research Institute, 8901 Wisconsin Avenue, Bethesda, MD 20889-5603 (United States)

    2007-07-15

    In order to clarify the molecular mechanism of radioprotection and understand biological dosimetry in the presence of medical countermeasure-radioprotectants, their effects on ionizing radiation (IR)-responsive molecular biomarkers must be examined. We used genistein in a radiation model system and measured gene expression by multiplex QRT-PCR assay in drug-treated healthy human blood cultures. Genistein has been demonstrated to be a radiosensitizer of malignant cells and a radioprotector against IR-induced lethality in a mouse model. Whole-blood cultures were supplemented with 50, 100, and 200{mu}M concentrations of genistein, 16 h prior to receiving a 2-Gy ({sup 60}Co-{gamma} rays, 10 cGy/min) dose of IR. Total RNA was isolated from whole blood 24 h postirradiation for assessments. Combination treatments of genistein and IR resulted in no significant genistein effects on ddb2 and bax downstream transcripts to p53, or proliferating cell-nuclear antigen, pcna, necessary for DNA synthesis and cell-cycle progression. Use of these radiation-responsive targets would be recommended for dose-assessment applications. We also observed decreased expression of pro-survival transcript, bcl-2. Genistein and IR-increased expression of cdkn1a and gadd45a, showing that genistein also stimulates p53 transcriptional activity. These results confirm published molecular signatures for genistein in numerous in vitro models. Evaluation of gene biomarkers may be further exploited for devising novel radiation countermeasure and/or therapeutic strategies.

  3. Heritability of Radiation Response in Lung Cancer Families

    Directory of Open Access Journals (Sweden)

    H.-Erich Wichmann

    2012-03-01

    Full Text Available Radiation sensitivity is assumed to be a cancer susceptibility factor due to impaired DNA damage signalling and repair. Relevant genetic factors may also determine the observed familial aggregation of early onset lung cancer. We investigated the heritability of radiation sensitivity in families of 177 Caucasian cases of early onset lung cancer. In total 798 individuals were characterized for their radiation-induced DNA damage response. DNA damage analysis was performed by alkaline comet assay before and after in vitro irradiation of isolated lymphocytes. The cells were exposed to a dose of 4 Gy and allowed to repair induced DNA-damage up to 60 minutes. The primary outcome parameter Olive Tail Moment was the basis for heritability estimates. Heritability was highest for basal damage (without irradiation 70% (95%-CI: 51%–88% and initial damage (directly after irradiation 65% (95%-CI: 47%–83% and decreased to 20%–48% for the residual damage after different repair times. Hence our study supports the hypothesis that genomic instability represented by the basal DNA damage as well as radiation induced and repaired damage is highly heritable. Genes influencing genome instability and DNA repair are therefore of major interest for the etiology of lung cancer in the young. The comet assay represents a proper tool to investigate heritability of the radiation sensitive phenotype. Our results are in good agreement with other mutagen sensitivity assays.

  4. Intraspecific responses of 188 rice cultivars to enhanced UVB radiation

    International Nuclear Information System (INIS)

    Dai, Q.; Peng, A.; Chavez, A.Q.; Vergara, B.S.

    1994-01-01

    Phytotron studies were conducted to determine the intraspecific variation in sensitivity of rice (Oryza sativa L.) to enhanced UVB and to test the hypothesis that rice cultivars originating from regions with higher ambient UVB radiation are more tolerant to enhanced UVB. Out of the 188 rice cultivars (from various rice growing regions and ecosystems) tested, 143 had significantly reduced plant height, 52 had smaller leaf area, 61 had lower plant dry weight and 41 had less tiller number under elevated UVB radiation (13.0 kJ m −2 day −1 ) for 3 weeks. Six cultivars showed significant positive growth response to enhanced UVB radiation, although the mechanism is not clear at present. These six cultivars were from the summer rice crop of Bangladesh and from high elevation rice areas where prevailing UVB radiation is most likely to be greater. However, there was no correlation between the dry matter changes under enhanced UVB and the ambient UVB level at the origin of the cultivar across the 188 cultivars tested. Therefore, cultivars originating from regions with higher ambient UVB are not necessarily more tolerant to enhanced UVB radiation. (author)

  5. Modeling of the response under radiation of electronic dosemeters

    International Nuclear Information System (INIS)

    Menard, S.

    2003-01-01

    The simulation with with calculation codes the interactions and the transport of primary and secondary radiations in the detectors allows to reduce the number of developed prototypes and the number of experiments under radiation. The simulation makes possible the determination of the response of the instrument for exposure configurations more extended that these ones of references radiations produced in laboratories. The M.C.N.P.X. allows to transport, over the photons, electrons and neutrons, the charged particles heavier than the electrons and to simulate the radiation - matter interactions for a certain number of particles. The present paper aims to present the interest of the use of the M.C.N.P.X. code in the study, research and evaluation phases of the instrumentation necessary to the dosimetry monitoring. To do that the presentation gives the results of the modeling of a prototype of a equivalent tissue proportional counter (C.P.E.T.) and of the C.R.A.M.A.L. ( radiation protection apparatus marketed by the Eurisys Mesures society). (N.C.)

  6. Calculating the Responses of Self-Powered Radiation Detectors.

    Science.gov (United States)

    Thornton, D. A.

    Available from UMI in association with The British Library. The aim of this research is to review and develop the theoretical understanding of the responses of Self -Powered Radiation Detectors (SPDs) in Pressurized Water Reactors (PWRs). Two very different models are considered. A simple analytic model of the responses of SPDs to neutrons and gamma radiation is presented. It is a development of the work of several previous authors and has been incorporated into a computer program (called GENSPD), the predictions of which have been compared with experimental and theoretical results reported in the literature. Generally, the comparisons show reasonable consistency; where there is poor agreement explanations have been sought and presented. Two major limitations of analytic models have been identified; neglect of current generation in insulators and over-simplified electron transport treatments. Both of these are developed in the current work. A second model based on the Explicit Representation of Radiation Sources and Transport (ERRST) is presented and evaluated for several SPDs in a PWR at beginning of life. The model incorporates simulation of the production and subsequent transport of neutrons, gamma rays and electrons, both internal and external to the detector. Neutron fluxes and fuel power ratings have been evaluated with core physics calculations. Neutron interaction rates in assembly and detector materials have been evaluated in lattice calculations employing deterministic transport and diffusion methods. The transport of the reactor gamma radiation has been calculated with Monte Carlo, adjusted diffusion and point-kernel methods. The electron flux associated with the reactor gamma field as well as the internal charge deposition effects of the transport of photons and electrons have been calculated with coupled Monte Carlo calculations of photon and electron transport. The predicted response of a SPD is evaluated as the sum of contributions from individual

  7. Selection and Characterization of Palmitic Acid Responsive Patients with an OXPHOS Complex I Defect

    Directory of Open Access Journals (Sweden)

    Tom E. J. Theunissen

    2017-10-01

    Full Text Available Mitochondrial disorders are genetically and clinically heterogeneous, mainly affecting high energy-demanding organs due to impaired oxidative phosphorylation (OXPHOS. Currently, effective treatments for OXPHOS defects, with complex I deficiency being the most prevalent, are not available. Yet, clinical practice has shown that some complex I deficient patients benefit from a high-fat or ketogenic diet, but it is unclear how these therapeutic diets influence mitochondrial function and more importantly, which complex I patients could benefit from such treatment. Dietary studies in a complex I deficient patient with exercise intolerance showed increased muscle endurance on a high-fat diet compared to a high-carbohydrate diet. We performed whole-exome sequencing to characterize the genetic defect. A pathogenic homozygous p.G212V missense mutation was identified in the TMEM126B gene, encoding an early assembly factor of complex I. A complementation study in fibroblasts confirmed that the p.G212V mutation caused the complex I deficiency. The mechanism turned out to be an incomplete assembly of the peripheral arm of complex I, leading to a decrease in the amount of mature complex I. The patient clinically improved on a high-fat diet, which was supported by the 25% increase in maximal OXPHOS capacity in TMEM126B defective fibroblast by the saturated fatty acid palmitic acid, whereas oleic acid did not have any effect in those fibroblasts. Fibroblasts of other patients with a characterized complex I gene defect were tested in the same way. Patient fibroblasts with complex I defects in NDUFS7 and NDUFAF5 responded to palmitic acid, whereas ACAD9, NDUFA12, and NDUFV2 defects were non-responding. Although the data are too limited to draw a definite conclusion on the mechanism, there is a tendency that protein defects involved in early assembly complexes, improve with palmitic acid, whereas proteins defects involved in late assembly, do not. Our data show at

  8. Production and stability of radiation-induced defects in MgAl2O4 under electronic excitation

    International Nuclear Information System (INIS)

    Yasuda, K.; Yamamoto, T.; Seki, S.; Shiiyama, K.; Matsumura, S.

    2008-01-01

    This paper investigates the formation process of radiation-induced defects in magnesium aluminate spinel and their stability using transmission electron microscopy, with emphasis on the effects of electronic excitation. Small interstitial-type dislocation loops disappeared under electron-induced electronic excitation. The elimination rate of the loops was found to be one order higher than for α-alumina. The disappearance of dislocation loops by a dissociation mechanism into isolated interstitials is discussed through analysis of the growth-and-shrink process of the loops. HARECXS analysis on cross section specimens irradiated with 350 MeV Au ions has shown the progress of cation disordering along ion tracks to be a function of electronic stopping power, (dE/dx) e . Cations were found to exchange their sites toward a random configuration. Such disordering appears from (dE/dx) e = 10 keV/nm, and increases in size with increasing (dE/dx) e to reach nearly 10 nm in diameter at 30 keV/nm, under an assumption of a fully disordered configuration

  9. Calculations of radiation defect formation cross sections in reactor materials in (n,p) and (n,α) reactions

    International Nuclear Information System (INIS)

    Kupchishin, A.A.; Kupchishin, A.I.; Omarbekova, Zh.

    2001-01-01

    In the work an experimental data analysis by integral σ(E 1 ) and differential [dσ(E 1 ,E 2 )]/dE 2 neutron interaction cross sections with reactor materials with the secondary protons and alpha particles generation as well as with the primarily knock-on atoms production in such reactions are carried out. It is shown, that in the (n,p) and (n',α) reactions the recoil nuclei receive essential energy portion and they are the patriarchs for atom-atom cascades in the substance. Nuclear reactions with formation of the secondary α-particles and and recoil nuclei are considered. It is shown, that these reactions are effectively proceeding within neutrons energy range 0.3-15 MeV. The nuclear reactions kinematics of above mentioned processes is studied. Energy conservation law for these reaction is applied. Deferential cross section conservation and transformation law for radiation defect formation in the (n,α) reaction are considered as well

  10. Optical studies of defects produced by radiation in LiF:Mg

    International Nuclear Information System (INIS)

    Ranieri, Izilda Marcia

    1979-01-01

    Lithium fluoride crystals doped with magnesium were grown from the melt by the Czochralski's method. Using the fact that the presence of Mg enhances the production of F and M color centers, the relative concentration of Mg was determined by a method devised in this work, This method utilizes the optical density of color centers in irradiated samples where the dose rate is proportional to the rate of formation of these centers. The dynamical equilibrium between F and M centers was studies after X-Rays radiation damage. Thermal treatments at 1000 K and quenches to 77 K, previously to the irradiation, showed that one can dissociate impurity aggregates formed when the crystal was grown. This dissociation implies in a decrease of the formation rate of F and M centers. It was found that isolated Mg impurities trap F centers to form Z centers. In the aggregate form, Mg impurities trap interstitial ions that are produced by the irradiation and that are the anti-centers of the F center. By this mechanism F and its anti-centers are thermally stabilized. It was observed that stoking the crystals at room temperature and well protected from the light show an increase in the M center production with a corresponding decrease in the F center production. This is because periods such as 20 hours are enough to perturb the thermodynamical equilibrium between F and M centers obtained just after the irradiation. To determine the stability of these color centers under light of different wavelengths, optical exposures were used. It was found that M center band is stable under its own wavelength's irradiation at room temperature and does not show dichroism. It was determined that the rate of formation of F and M centers at 343 and 403 K, follows the same behavior at room temperature. An Arrhenius study was made to determine the activation energies of these processes and produced 0,12 eV and 0,24 eV for the F and M centers respectively. Studies of fluorescence were also made after X and t

  11. Study on the radiation-induced biological responses based on the analysis of metabolites

    Energy Technology Data Exchange (ETDEWEB)

    Jo, Sungkee; Jung, Uhee; Park, Haeran; Roh, Changhyun; Shin, Heejune; Ryu, Dongkyoung

    2013-01-15

    1. Objectives □ Establishment of basis of biological radiation response study by metabolite analysis 2. Project results □ Establishment of analytical basis of radiation-responsive metabolites in biological samples - Large scale collection of tissue samples from irradiated animal for radiation metabolomics research - Establishment of mass spectromety (GC MS, LC MS-MS) analysis methods of biological samples - 3 Standard Operation Protocols (SOP) for ultra high resolution mass spectrometry (FT-ICR MS, Q-TOF MS) analysis of metabolites from biological samples - Establishment of database for radiation metabolites □ Basic research on radiation-responsive metabolites and the interpretation of their functions - Validation of spermidine as a candidate biomarker of acute radiation response in mouse blood - Verification of 5 radiation-responsive steroid hormones and alteration of their metabolic enzyme activities in mouse blood - Verification of 13 radiation-responsive amino acids (related to oxidative stress, neurotransmission, energy metabolism) in regional mouse brain -Verification of 10 radiation-responsive amino acids (related to oxidative stress, neurotransmission, energy metabolism) in regional mouse brain - Verification of 74 radiation-responsive metabolites in whole rat brain by ultra high resolution FT-ICR MS and Q-TOF MS analysis 3. Expected benefits and plan of application □ Establishment of research basis of radiation metabolomics in Korea □ Provision of core technology in radiation bioscience and safety field by application of radiation metabolomics results to the technology development in radiation biodosimetry, and radiation response evaluation and modulation.

  12. Study on the radiation-induced biological responses based on the analysis of metabolites

    International Nuclear Information System (INIS)

    Jo, Sungkee; Jung, Uhee; Park, Haeran; Roh, Changhyun; Shin, Heejune; Ryu, Dongkyoung

    2013-01-01

    1. Objectives □ Establishment of basis of biological radiation response study by metabolite analysis 2. Project results □ Establishment of analytical basis of radiation-responsive metabolites in biological samples - Large scale collection of tissue samples from irradiated animal for radiation metabolomics research - Establishment of mass spectromety (GC MS, LC MS-MS) analysis methods of biological samples - 3 Standard Operation Protocols (SOP) for ultra high resolution mass spectrometry (FT-ICR MS, Q-TOF MS) analysis of metabolites from biological samples - Establishment of database for radiation metabolites □ Basic research on radiation-responsive metabolites and the interpretation of their functions - Validation of spermidine as a candidate biomarker of acute radiation response in mouse blood - Verification of 5 radiation-responsive steroid hormones and alteration of their metabolic enzyme activities in mouse blood - Verification of 13 radiation-responsive amino acids (related to oxidative stress, neurotransmission, energy metabolism) in regional mouse brain -Verification of 10 radiation-responsive amino acids (related to oxidative stress, neurotransmission, energy metabolism) in regional mouse brain - Verification of 74 radiation-responsive metabolites in whole rat brain by ultra high resolution FT-ICR MS and Q-TOF MS analysis 3. Expected benefits and plan of application □ Establishment of research basis of radiation metabolomics in Korea □ Provision of core technology in radiation bioscience and safety field by application of radiation metabolomics results to the technology development in radiation biodosimetry, and radiation response evaluation and modulation

  13. Fundamental radiation effects in αAg-Zn alloys: Zener relaxation, study of the mobility of point defects and the evolution of their populations in a particle flux

    International Nuclear Information System (INIS)

    Halbwachs, Michel.

    1977-01-01

    After a recall on the physical effects of radiations, a model used to describe the defect populations produced in a fast particle flux is presented. The experimental devices used and the measurements carried out on a solid solution of αAg-Zn are described. The results obtained in an electron flux are compared with the forecastings of the theoretical models. The mobility and the apparent recombination radius of vacancies and autointerstitials, the absorption efficiency of dislocations in regard to point defects and the participation of autointerstitials to short-range order are studied. A similar study carried out under neutron irradiation is reported. The influence of neutron doses and temperature on atomic mobility is investigated. An experiment carried out under gamma photon irradiation enables a comparison to be made between the creation of defects by gamma photons and electrons [fr

  14. Integration of radiation monitoring for nuclear emergency response teams

    Energy Technology Data Exchange (ETDEWEB)

    Olsen, J T; Thompson, N Y [Royal Military Coll. of Canada, Kingston, ON (Canada)

    1994-12-31

    The Canadian Forces have established Nuclear Emergency Response Teams to cope with potential radiation accidents. Previously, only gamma and high-energy beta radiation could be detected. Recently, new radiation sampling, detecting, and analytical equipment has been bought, including air samplers, beta counters, high-purity germanium gamma detectors, and multi-channel analyzers together with Gamma Vision Software to analyze gamma spectra. The purpose of the present study is to propose a way to use the new equipment, to analyze the results from the gamma and beta detectors, and to integrate the results into a format for decision making. Integration is achieved through the creation of a computer program, Radiation Integration Program (RIP). This program analyzes gross beta counts, and uses them to estimate danger to the thyroid. As well the results from Gamma Vision are converted from Bq to dose rate for several parts of the body. Overall gamma results affecting the thyroid are compared to the beta results to verify the initial estimations.

  15. Radiation effects on tumor-specific DTH response, 2

    International Nuclear Information System (INIS)

    Nobusawa, Hiroshi; Hachisu, Reiko.

    1991-01-01

    Tumor-specific immunity was induced in C3H mice by immunizing with syngeneic MH134 hepatoma cells. Radiation sensitivity of anti-tumor activity of immunized spleen cells were examined and compared with the radiation sensitivity of the delayed-type hypersensitivity (DTH)-response. The spleen cells were irradiated in vitro, then mixed with the tumor cells. DTH-response intensity was determined from the footpad increment twenty-four hours after inoculation of tumor cells with immunized spleen cells. Anti-tumor activity of the spleen cells, based on growth inhibition of tumor cells, was measured by a cytostatic test in vivo with diffusion chambers. Tumor-specific DTH response was suppressed dose-dependently in the range of 12-24 Gy irradiation. No suppression was observed below 12 Gy. Without irradiation, growth of tumor cells was inhibited by immunized spleen cells more effectively than by normal spleen cells. Anti-tumor activity of immunized and normal spleen cells was diminished by irradiation doses of 20 Gy and 10 Gy, respectively. Comparing our report with others that analyzed the type of anti-tumor effector cells induced in this experimental system, we concluded that tumor-specific anti-tumor activity (tumor growth inhibition in vivo) that was radiosensitive at 10-20 Gy depended on a DTH-response. (author)

  16. Biological responses to low dose rate gamma radiation

    International Nuclear Information System (INIS)

    Magae, Junji; Ogata, Hiromitsu

    2003-01-01

    Linear non-threshold (LNT) theory is a basic theory for radioprotection. While LNT dose not consider irradiation time or dose-rate, biological responses to radiation are complex processes dependent on irradiation time as well as total dose. Moreover, experimental and epidemiological studies that can evaluate LNT at low dose/low dose-rate are not sufficiently accumulated. Here we analyzed quantitative relationship among dose, dose-rate and irradiation time using chromosomal breakage and proliferation inhibition of human cells as indicators of biological responses. We also acquired quantitative data at low doses that can evaluate adaptability of LNT with statistically sufficient accuracy. Our results demonstrate that biological responses at low dose-rate are remarkably affected by exposure time, and they are dependent on dose-rate rather than total dose in long-term irradiation. We also found that change of biological responses at low dose was not linearly correlated to dose. These results suggest that it is necessary for us to create a new model which sufficiently includes dose-rate effect and correctly fits of actual experimental and epidemiological results to evaluate risk of radiation at low dose/low dose-rate. (author)

  17. Dose-response relationship of cadmium or radiation-induced embryotoxicity in mouse whole embryo culture

    International Nuclear Information System (INIS)

    Nakashima, Kiyohito; Kawamata, Akitoshi; Matsuoka, Masato; Wakisaka, Takashi; Fujiki, Yoshishige

    1988-01-01

    Mouse embryos of B6C3F 1 strain were exposed in vitro to 1.2 to 2.2 μM cadmium chloride (Cd) or to 100 to 320 R x-rays, and the effects of the exposure on development were examined after 39 h of culture. Development of embryos was assessed from lethality, formation of the neural tube defect, diameter and protein of yolk sac, crown-rump and head lengths, embryonic protein, and number of somites. Incidence of the neural tube defect increased from 3.4 to 100% by 1.2 to 2.0 μM Cd, while embryo deaths increased from 13.8 to 93.3% by 2.0 to 2.2 μM Cd. Embryonic protein was significantly reduced at the teratogenic range, but the number of somites was only affected by 1.6 to 2.0 μM Cd. X-irradiation at 100 to 320 R induced the neural tube defect in 2.9 to 72.7% of the embryos. An embryolethal effect was observed only at the 320 R dose. Crown-rump and head lengths and embryonic protein were significantly affected at the teratogenic range, but the diameter and protein of yolk sac and number of somites were hardly affected. Cadmium- or radiation-induced response data of both teratogenicity and endpoints indicating inhibition of embryonic development were acceptably fitted to a linear log-probit regression. These regressions suggest that as an estimation of interference in development of embryos, embryonic protein and head length are sensitive endpoints while the number of somites is an insensitive criterion. (author)

  18. Birth defects in Norway by levels of external and food-based exposure to radiation from Chernobyl

    International Nuclear Information System (INIS)

    Lie, R.T.; Irgens, L.M.; Skjaerven, R.; Reitan, J.B.; Strand, P.; Strand, T.

    1992-01-01

    In Norway, external doses of radiation resulting from fallout from the Chernobyl nuclear accident were estimated from detailed measurements, including soil deposition patterns. Internal doses were estimated from measurements of radioactive cesium in meat and milk supplies. The doses were calculated as average monthly doses for each of 454 municipalities during 36 consecutive months after the accident in spring 1986. Prospectively collected data on all newborns listed in the Medical Birth Registry of Norway who were conceived in the period May 1983-April 1989 were used to assess possible dose-response relations between estimated external and food-based exposures and congenital malformations and some other conditions. A positive association was observed between total radiation dose (external plus food-based) and hydrocephaly, while a negative association was observed for Down's syndrome. However, an important conclusion of the study was that no associations were found for conditions previously reported to be associated with radiation, i.e., small head circumference, congenital cataracts, anencephaly, spina bifida, and low birth weight. Potential sources of bias, including exposure misclassification and incomplete ascertainment of cases, are discussed

  19. Modifiers of radiation response in tumor therapy: strategies and expectations

    International Nuclear Information System (INIS)

    Elkind, M.M.

    1982-01-01

    The administration of two (or more) cytotoxic agents to widen the differential between the responses of tumor and normal tissues depends upon the biological properties of the agents in the cells and tissues, their interactive potential, and the strategy employed in their administration. Assuming that one agent is ionizing radiation, and considering response modification in broad terms, the qualitative features of various strategies are developed for physical as well as chemical modifies. The heterogeneity of human tumor cells and the compensatory mechanisms of normal tissues following injury are identified as topical areas requiring sustained research effort. Finally, estimates are developed for the degree of improvement required from a response modifier to effect significant improvements in tumor cure rates

  20. Modifiers of radiation response in tumor therapy: strategies and expectations

    International Nuclear Information System (INIS)

    Elkind, M.M.

    1982-01-01

    The administration of two (or more) cytotoxic agents to widen the differential between the responses of tumor and normal tissues depends upon the biological properties of the agents in the cells and tissues, their interactive potential, and the strategy employed in their administration. Assuming that one agent is ionizing radiation, and considering response modification in broad terms, the qualitative features of various strategies are developed for physical as well as chemical modifiers. The heterogeneity of human tumor cells and the compensatory mechanisms of normal tissues following injury are identified as topical areas requiring sustained research effort. Finally, estimates are developed for the degree of improvement from a response modifier to effect significant improvements in tumor cure rates

  1. Qualification criteria for persons responsible for radiation protection

    International Nuclear Information System (INIS)

    Wehner, G

    1980-01-01

    A survey of the qualification criteria included in the German atomic law (Atomic Energy Act, Radiological Protection Ordinance and X-ray Protection Ordinance) for persons responsible for radiation protection is given. Especially the various activities for which a health physics officer is required, the range of qualification in each case and the way the qualification has to be proved, are pointed out. Also the different guides that are issued to complete the legal requirements are mentioned. The definitions of the term qualification for health physics given in the different guides are cited and it is shown, that the qualification of a healt physics officer has to be based on the three criteria (I) vocational training. (II) professional experience and (III) the necessary knowledge in radiation protection. (orig./HP) [de

  2. Dose response curves for effects of low-level radiation

    International Nuclear Information System (INIS)

    Myers, D.K.

    1980-01-01

    The linear dose-response model used by international committees to assess the genetic and carcinogenic hazards of low-level radiation appears to be the most reasonable interpretation of the available scientific data that are relevant to this topic. There are, of course, reasons to believe that this model may overestimate radiation hazards in certain instances, a fact acknowledged in recent reports of these committees. The linear model is now also being utilized to estimate the potential carcinogenic hazards of other agents such as asbestos and polycyclic aromatic hydrocarbons. This model implies that there is no safe dose for any of these agents and that potential health hazards will increase in direct proportion to total accumulated dose. The practical implication is the recommendation that all exposures should be kept 'as low as reasonably achievable, economic and social factors being taken into account'. (auth)

  3. Criminal Responsibility on the Use of Ionizing Radiations in Medicine

    International Nuclear Information System (INIS)

    El-Baroodi, M.

    2003-01-01

    The present work has been undertaken to study the existing Egyptian Laws which regulate the applications of ionizing radiations in medicine and the criminal responsibility related to the violations of these regulations by the medical staff and hospital's administrative body. The study involves the nature of physicians relationship and attitudes towards their patients on applying the recent techniques in nuclear medicine and the requirements imposed by law concerning the habilitation of the medical staff, and their licensing. It assumed that the physicians should apply the most recent scientific knowledge and medical practices in nuclear medicine. One of the requirements of the law is that the physician should inform the patient about his medical problem and seek his consent about the radiation treatment necessary for him

  4. The feasibility of 10 keV X-ray as radiation source in total dose response radiation test

    International Nuclear Information System (INIS)

    Li Ruoyu; Li Bin; Luo Hongwei; Shi Qian

    2005-01-01

    The standard radiation source utilized in traditional total dose response radiation test is 60 Co, which is environment-threatening. X-rays, as a new radiation source, has the advantages such as safety, precise control of dose rate, strong intensity, possibility of wafer-level test or even on-line test, which greatly reduce cost for package, test and transportation. This paper discussed the feasibility of X-rays replacing 60 Co as the radiation source, based on the radiation mechanism and the effects of radiation on gate oxide. (authors)

  5. Effect of thermal treatment on the density of radiation-induced defects in dielectrics and on the semiconductor surface of silicon MDS structures

    International Nuclear Information System (INIS)

    Daliev, Kh.S.; Lebedev, A.A.; Ehkke, V.; 3425000DD)

    1987-01-01

    Isochronous annealing of radiation defects formed under MIS structure irradiation by γ-quanta at the presence of shift stress on a metal electrode is studied. Complex measurements of non-stationary capacitance spectroscopy and volt-farad characteristics (VFC) have shown that a built-in charge and volumetric states (VS) of the dielectric are annealed at 250 deg C, fast surface states (SS) - at 350 deg C, and the characteristic radiation defect in the Si-SiO 2 transition layer is completely annealed only at 400 deg C. Additional VS and SS occurring in the structures at positive shift on the metal electrode under radiation are annealed at 120 deg C, the kinetics of defect annealing at higher temperatures is independent from shift polarity. SS density calculated by VFC is determined in reality by recharging not only SS but some VS of the dielectric in the range of width of the order of 3.5 nm from the surface of the semiconductor

  6. Dependence of radiation damage accumulation in iron on underlying models of displacement cascades and subsequent defect migration

    International Nuclear Information System (INIS)

    Souidi, A.; Becquart, C.S.; Domain, C.; Terentyev, D.; Malerba, L.; Calder, A.F.; Bacon, D.J.; Stoller, R.E.; Osetsky, Yu. N.; Hou, M.

    2006-01-01

    Groups of displacement cascades calculated independently with different simulation models and computer codes are compared on a statistical basis. The parameters used for this comparison are the number of Frenkel pairs (FP) produced, the percentages of vacancies and self-interstitial atoms (SIAs) in clusters, the spatial extent and the aspect ratio of the vacancies and the SIAs formed in each cascade. One group of cascades was generated in the binary collision approximation (BCA) and all others by full molecular dynamics (MD). The MD results differ primarily due to the empirical interatomic potentials used and, to some extent, in code strategies. Cascades were generated in simulation boxes at different initial equilibrium temperatures. Only modest differences in the predicted numbers of FP are observed, but the other cascade parameters may differ by more than 100%. The consequences of these differences on long-term cluster growth in a radiation environment are examined by means of object kinetic Monte Carlo (OKMC) simulations. These were repeated with three different parameterizations of SIA and SIA cluster mobility. The differences encompassed low to high mobility, one- and three-dimensional migration of clusters, and complete immobility of large clusters. The OKMC evolution was followed until 0.1 dpa was reached. With the range of OKMC parameters used, cluster populations after 0.1 dpa differ by orders of magnitude. Using the groups of cascades from different sources induced no difference larger than a factor of 2 in the OKMC results. No correlation could be identified between the cascade parameters considered and the number densities of vacancies and SIAs predicted by OKMC to cluster in the long term. However, use of random point defect distributions instead of those obtained for displacement cascades as input for the OKMC modeling led to significantly different results. It is therefore suggested that although the displacement cascade characteristics considered

  7. The radiation response of cells recovering after chronic hypoxia

    International Nuclear Information System (INIS)

    Kwok, T.T.; Sutherland, R.M.

    1989-01-01

    Experiments were performed to study the influence of hypoxic pretreatment on the radiation response of A431 human squamous carcinoma cells. Reaeration for 10 min after chronic hypoxia (greater than 2 h) was found to enhance the radiosensitivity of A431 cells, and the maximal effect was seen for those cells reaerated after 12 h of hypoxia. The radiosensitivity enhancement for reaerated cells after 12 h of hypoxia was maximized by 5 min after the return to aerobic conditions and reached the control level by 12 h of reaeration. This enhanced radiosensitive state was characterized by a reduced shoulder region and increased slope of the radiation dose-response curve for cells in both the exponential and plateau phases of growth. There was a slight increase in the number of G1 and decrease in the number of S and G2 + M cells for both exponential- and plateau-phase cultures following 12 h hypoxic treatment. Although growth inhibition induced by 12 h of hypoxia was seen for cells in the exponential phase, there was no cell number change in the plateau-phase culture after hypoxia. Plating efficiency (PE) of cells in both growth phases was reduced by 30% after hypoxia. Furthermore, in the exponential-phase culture, the extent of reduction in PE after hypoxia was similar among cells in different phases of the cell cycle. Although S-phase cells in exponentially growing cultures were relatively more resistant to radiation than G1 and G2 + M cells, the cell age-response pattern was the same whether the cells had been aerobic or hypoxic before reaeration and irradiation. Furthermore, the enhancement ratio associated with reaeration after 12 h of hypoxia for these three subpopulations of cells was 1.3. Our results indicate that the increase in radiosensitivity due to reaeration after chronic hypoxia is unlikely to be related to the changes of cell cycle stage and growth phase during hypoxic treatment

  8. Theoretic simulation for CMOS device on total dose radiation response

    International Nuclear Information System (INIS)

    He Baoping; Zhou Heqin; Guo Hongxia; He Chaohui; Zhou Hui; Luo Yinhong; Zhang Fengqi

    2006-01-01

    Total dose effect is simulated for C4007B, CC4007RH and CC4011 devices at different absorbed dose rate by using linear system theory. When irradiation response and dose are linear, total dose radiation and post-irradiation annealing at room temperature are determined for one random by choosing absorbed dose rate, and total dose effect at other absorbed dose rate can be predicted by using linear system theory. The simulating results agree with the experimental results at different absorbed dose rate. (authors)

  9. Kinetic Modeling of the Lif:Mg,Ti TL System including Defect Creation: Implications to, and Development of Track Structure Theory Calculations of Heavy Charged Particle Radiation Effects

    International Nuclear Information System (INIS)

    Eliyahu, Ian

    2015-01-01

    differ somewhat from the vacancies originally present in un-irradiated samples due to differences in their immediate environment. The kinetic model accurately simulates the experimentally observed F center dose response over the entire investigated dose range of 10 Gy -105 Gy under the following conditions: (i) The concentration of vacancies initially present is unexpectedly high at ~ 1023 m-3, possibly due to the highly doped, noncrystalline and hot-pressed nature of the LiF:Mg,Ti samples. (ii) The transition probability, An4o, for electron capture into the initially-present vacancies is ~ 40 times greater than An4, the transition probability for the viii radiation-created vacancies. These two factors marginalize the effect of the created vacancies at low dose resulting in a linear dose response. 3. Track structure theory: The third focus of investigation concerned the ability of TST to accurately calculate HCP induced OA Relative HCP OA efficiencies. Values of ηTST based on LID dose response, were compared with experimentally measured relative efficiencies, ηm, at no-track-overlap fluence levels of 1010-1011 cm-2 for protons and He particles. The F band values of ηm/ηTST are 2.0 and 2.6 for the He ions and protons respectively. The deviation from unity is explained as due to the neglect of enhanced vacancy/F center creation in the conventional TST calculations which ignore defect creation. It is demonstrated that kinetic analysis simulating LID dose response with enhanced vacancy creation, and incorporated into the TST calculation, can lead to values of ηm=ηTST for the F band. At the other extreme, for the 4.0 eV band, the values of ηm/ηTST are much less than unity, equal to 0.18 for the protons and < 0.12 for the He ions. These very low values suggest that the 4.0 eV trapping structure is being either destroyed or de-populated (perhaps by local heating/thermal spike/Coulomb explosion) during the HCP slowing down. Processes which do not occur (or are greatly

  10. Determinates of tumor response to radiation: Tumor cells, tumor stroma and permanent local control

    International Nuclear Information System (INIS)

    Li, Wende; Huang, Peigen; Chen, David J.; Gerweck, Leo E.

    2014-01-01

    Background and purpose: The causes of tumor response variation to radiation remain obscure, thus hampering the development of predictive assays and strategies to decrease resistance. The present study evaluates the impact of host tumor stromal elements and the in vivo environment on tumor cell kill, and relationship between tumor cell radiosensitivity and the tumor control dose. Material and methods: Five endpoints were evaluated and compared in a radiosensitive DNA double-strand break repair-defective (DNA-PKcs −/− ) tumor line, and its DNA-PKcs repair competent transfected counterpart. In vitro colony formation assays were performed on in vitro cultured cells, on cells obtained directly from tumors, and on cells irradiated in situ. Permanent local control was assessed by the TCD 50 assay. Vascular effects were evaluated by functional vascular density assays. Results: The fraction of repair competent and repair deficient tumor cells surviving radiation did not substantially differ whether irradiated in vitro, i.e., in the absence of host stromal elements and factors, from the fraction of cells killed following in vivo irradiation. Additionally, the altered tumor cell sensitivity resulted in a proportional change in the dose required to achieve permanent local control. The estimated number of tumor cells per tumor, their cloning efficiency and radiosensitivity, all assessed by in vitro assays, were used to predict successfully, the measured tumor control doses. Conclusion: The number of clonogens per tumor and their radiosensitivity govern the permanent local control dose

  11. The responsible radiation protection supervisor: Who actually is he? Legal entities under public law and their legal responsibilities pursuant to radiation protection laws

    International Nuclear Information System (INIS)

    Brinkmann, M.

    1998-01-01

    All radiation protection relevant activities subject to licencing or notifying include observation of legally allocated responsibilities. Responsible radiation protection supervisor is the licence owner in person. If the holder is a legal entity, that entity is responsible as such. The executives of the entity exercise the functions of a responsible radiation protection officer, or may delegate them to an authorized deputy. In this case, the yardstick of a possible liability may be changed. The liability of the responsible persons is determined by the general legal regulations. (orig.) [de

  12. Responses of diode detectors to radiation beams from teletherapy machines

    International Nuclear Information System (INIS)

    Malinda, Lora; Nasukha

    2003-01-01

    Responses of diode detectors to radiation beams from teletherapy machines. It has been carried out responses to two sets of diode detector by using the beams of teletherapy Co-60 and medical linear accelerator. Each set of consist of 8 diode detectors was irradiated by using gamma beams from teletherapy Co-60 machines and 6 MV and 10 MV foron beams from medical linear accelerator and 6.9.12.16. and 20 MeV electron beams from medical linear accelerator. The detectors were positioned on the phantom circularly and radially and electronic equilibrium condition for all type and energy beams. It was found that every detectors had own individual response and it is not to be uniformity, since the fluctuation in between 16.6 % to 30.9 %. All detectors responses are linear to gamma and foron beams, and also for energy above 6 MeV for electron beams. Nonlinearity response occurs for 6 MeV electron beam, it is probably from the assumption of electronic equilibrium

  13. Retinoblastoma pathway defects show differential ability to activate the constitutive DNA damage response in human tumorigenesis

    DEFF Research Database (Denmark)

    Tort, F.; Bartkova, J.; Sehested, M.

    2006-01-01

    culture models with differential defects of retinoblastoma pathway components, as overexpression of cyclin D1 or lack of p16(Ink4a), either alone or combined, did not elicit detectable DDR. In contrast, inactivation of pRb, the key component of the pathway, activated the DDR in cultured human or mouse...... with their hierarchical positions along the retinoblastoma pathway. Our data provide new insights into oncogene-evoked DDR in human tumorigenesis, with potential implications for individualized management of tumors with elevated cyclin D1 versus cyclin E, due to their distinct clinical variables and biological behavior....

  14. Adaptive response induced by occupational exposures to ionizing radiation

    International Nuclear Information System (INIS)

    Barquinero, J.F.; Caballin, M.R.; Barrios, L.; Murtra, P.; Egozcue, J.; Miro, R.; Ribas, M.

    1997-01-01

    We have found a significant decreased sensitivity to the cytogenetic effects of ionizing radiation (IR) and bleomycin (BLM) in lymphocytes from individuals occupationally exposed to IR when compared with a control population. These results suggest that occupational exposures to IR can induce adaptive response that can be detected by a subsequent treatment by IR or by BLM. However, no correlation between the results obtained with both treatments was observed. A great heterogeneity in the frequencies of chromatid aberrations induced by BLM was observed. The study of the influence of different harvesting times showed that there was no correlation with the frequencies of chromatid breaks. Our results indicate that the use of BLM to detect adaptive response has several difficulties at the individual level. (author)

  15. New aspects on the contribution of primary defects in silicon due to long-time degradation of detectors operating in high fields of radiation

    International Nuclear Information System (INIS)

    Lazanu, Sorina; Lazanu, Ionel

    2006-01-01

    Full text: Silicon detectors will represent an important option for the next generation of experiments in high energy physics, for astroparticle and nuclear experiments, where the requirements to operate long time in high radiation environments will represent a major problem. After the long-time operation in high radiation fields, the bulk displacement damage produces the following effects at the device level: increase of the leakage current, decrease of the satisfactory Signal/Noise ratio, increase of the effective carrier concentration, and thus of the depletion voltage, decrease of the charge collection efficiency up to unacceptable levels. In this contribution we investigate the new perspective in understanding the fundamental phenomena in silicon and implications for the degradation of the characteristics of detectors given by the consideration of the existence of the new primary defect: fourfold coordinated defect, Si FFCD , with a lower value of the formation energy by comparison with the 'classically' known vacancies and interstitials. Predicted by Goedecker and co-workers, its characteristics were indirectly determined by Lazanu and Lazanu. The correlation between the rate of generation of primary defects, material composition and observable effects is investigated considering different growth technologies and resistivities (up to tens of kΩcm) as time and fluence dependencies. This allows to estimate the expected behaviour of the materials and detectors in concrete environments at the next generations of high energy physics experiments as SLHC or VLHC for example. This new defect could represent the elementary block for new extended defects and in principle it could generate local amorphization of the semiconductor. Its existence and characteristics in other semiconductors is also investigated. (author)

  16. Radiation-induced adaptive response and intracellular signal transduction pathways

    International Nuclear Information System (INIS)

    Tachibana, Akira

    2009-01-01

    As an essential biological function, cells can sense the radiation even at low dose and respond to it, and which is one of bases of the radiation-induced adaptive response (AR) where effects caused by high dose radiation are reduced by prior exposure to low dose radiation (LDR). Here described are studies of AR in well established m5S cells on the intracellular signal transduction that involves sensing of LDR and transmitting of its signal within the cell network. The first signal for AR yielded by LDR on the cell membrane is exactly unknown though hydrogen peroxide and phorbol ester (PMA) can reportedly cause AR. As PMA activates protein kinase C (PKC) and its inhibitors suppress AR, participation of PKC in AR has been suggested and supported by studies showing PKCα activation by LDR. In addition, p38 mitogen-activated protein kinase (MAPK) is shown to participate in AR by those facts that the enzyme is activated by LDR, a p38 MAPK inhibitor suppresses AR, and PKC inhibitors suppress the enzyme activation, which also suggesting that the signaling from PKC to p38 MAPK can become operative by LDR. However, the possible reverse signaling is also suggested, and thus the activation of positive feedback mechanism is postulated in PKC/p38 MAPK/phospholipase δ1/ PKC pathway. Cells introduced with siRNA against Prkca gene (coding PKCs) produce reduced amount of the enzyme, particularly, of PKCα. In those cells, AR by 5 Gy X-ray is not observed and thereby PKCα is involved in AR. The signaling in AR is only partly elucidated at present as above, and more detailed studies including identification of more PKC subtypes and signaling to DNA repair system are considered necessary. (K.T.)

  17. Molecular events basic to cellular radiation response. Progress report

    International Nuclear Information System (INIS)

    Kolodny, G.M.

    1974-01-01

    Work during the past year has been focused on three areas related to the cellular effects of radiation. Radiation effects on RNA and the regulation of gene expression and amino acid-nucleic acid interactions were studied. Studies on the radiation response of RNA in growing and confluent cells were continued. We have derived radiation survival curves and demonstrated repair of potentially lethal damage in 3T3 cells. Studies of giant cell formation and turnover of ribosomal RNA in irradiated cells has demonstrated differences in growing and confluent cells. We have sought evidence consistent with our hypothesis for regulation of eukaryotic gene expression with segments of RNA reutilized to prime new RNA synthesis. Data derived from the turnover of ribosomal RNA and the methylation pattern of ribosomal RNA during turnover are consistent with the possibility that a segment of 18s ribosomal RNA is being conserved during new RNA synthesis. We were unable to show reutilization of the 5' trinucleotide of 18s and 28s ribosomal RNA but did find a ribonuclease resistant oligonucleotide in 18s RNA which appeared to be reutilized. In studies of amino acid nucleic-acid interactions using nuclear magnetic resonance spectroscopy we have been able to successfully synthesize an amidate and begin an examination of the intramolecular interactions. We have also studied intermolecular interactions betweentryptophan and nucleoside monophosphates and found upfield shifts which provide evidence for preferential stacking of the 6-membered ring of tryptophan with adenine and evidence for specific geometry of interactions of tryptophan with cytosine. (U.S.)

  18. Solar ultraviolet radiation response of EBT2 Gafchromic, radiochromic film

    International Nuclear Information System (INIS)

    Butson, Ethan T; Yu, Peter K N; Butson, Martin J

    2013-01-01

    Measurement of solar ultraviolet (UV) radiation is an important aspect of dosimetry for the improved knowledge of UV exposure and its associated health related issues. EBT2 Gafchromic film has been designed by its manufacturers as an improved tool for ionizing radiation dosimetry. The film is stated as exhibiting a significant reduction in UV response. However, results have shown that when exposed to UV from the ‘bottom side’ i.e. from the thick laminate side, the film exhibits a sensitivity to solar UV radiation which is both measurable and accurate for UV dosimetry. Films were irradiated in this position to known solar UV exposures and results are quantified showing a reproducibility of measurement to within ±7% (1 SD) when compared to calibrated UV meters. With an exposure of 20 J cm −2 broad spectrum solar UV, the films net OD change was found to be 0.248 OD ± 0.021 OD when analysing the results using the red channel region of an Epson V700 desktop scanner. This was compared to 0.0294 OD ± 0.0053 OD change with exposure to the same UV exposure from the top side. This means that solar UV dosimetry can be performed using EBT2 Gafchromic film utilizing the underside of the film for dosimetry. The main advantages of this film type for measurement of UV exposure is the visible colour change and thus easy analysis using a desktop scanner as well as its uniformity in response and its robust physical strength for use in outside exposure situations. (note)

  19. Antioxidant Responses Induced by UVB Radiation in Deschampsia antarctica Desv.

    Directory of Open Access Journals (Sweden)

    Hans Köhler

    2017-05-01

    Full Text Available Deschampsia antarctica Desv. is one of two vascular plants that live in the Maritime Antarctic Territory and is exposed to high levels of ultraviolet-B (UVB radiation. In this work, antioxidant physiology of D. antarctica was studied in response to UVB induced oxidative changes. Samples were collected from Antarctica and maintained in vitro culture during 2 years. Plants were sub-cultured in a hydroponic system and exposed to 21.4 kJ m-2 day-1, emulating summer Antarctic conditions. Results showed rapid and significant increases in reactive oxygen species (ROS at 3 h, which rapidly decreased. No dramatic changes were observed in photosynthetic efficiency, chlorophyll content, and level of thiobarbituric acid reactive species (MDA. The enzymatic (superoxide dismutase, SOD and total peroxidases, POD and non-enzymatic antioxidant activity (total phenolic increased significantly in response to UVB treatment. These findings suggest that tolerance of D. antarctica to UVB radiation could be attributed to its ability to activate both enzymatic and non-enzymatic antioxidant systems.

  20. Current trends in gamma radiation detection for radiological emergency response

    Science.gov (United States)

    Mukhopadhyay, Sanjoy; Guss, Paul; Maurer, Richard

    2011-09-01

    Passive and active detection of gamma rays from shielded radioactive materials, including special nuclear materials, is an important task for any radiological emergency response organization. This article reports on the current trends and status of gamma radiation detection objectives and measurement techniques as applied to nonproliferation and radiological emergencies. In recent years, since the establishment of the Domestic Nuclear Detection Office by the Department of Homeland Security, a tremendous amount of progress has been made in detection materials (scintillators, semiconductors), imaging techniques (Compton imaging, use of active masking and hybrid imaging), data acquisition systems with digital signal processing, field programmable gate arrays and embedded isotopic analysis software (viz. gamma detector response and analysis software [GADRAS]1), fast template matching, and data fusion (merging radiological data with geo-referenced maps, digital imagery to provide better situational awareness). In this stride to progress, a significant amount of inter-disciplinary research and development has taken place-techniques and spin-offs from medical science (such as x-ray radiography and tomography), materials engineering (systematic planned studies on scintillators to optimize several qualities of a good scintillator, nanoparticle applications, quantum dots, and photonic crystals, just to name a few). No trend analysis of radiation detection systems would be complete without mentioning the unprecedented strategic position taken by the National Nuclear Security Administration (NNSA) to deter, detect, and interdict illicit trafficking in nuclear and other radioactive materials across international borders and through the global maritime transportation-the so-called second line of defense.

  1. Characterization of a smartphone camera's response to ultraviolet A radiation.

    Science.gov (United States)

    Igoe, Damien; Parisi, Alfio; Carter, Brad

    2013-01-01

    As part of a wider study into the use of smartphones as solar ultraviolet radiation monitors, this article characterizes the ultraviolet A (UVA; 320-400 nm) response of a consumer complementary metal oxide semiconductor (CMOS)-based smartphone image sensor in a controlled laboratory environment. The CMOS image sensor in the camera possesses inherent sensitivity to UVA, and despite the attenuation due to the lens and neutral density and wavelength-specific bandpass filters, the measured relative UVA irradiances relative to the incident irradiances range from 0.0065% at 380 nm to 0.0051% at 340 nm. In addition, the sensor demonstrates a predictable response to low-intensity discrete UVA stimuli that can be modelled using the ratio of recorded digital values to the incident UVA irradiance for a given automatic exposure time, and resulting in measurement errors that are typically less than 5%. Our results support the idea that smartphones can be used for scientific monitoring of UVA radiation. © 2012 Wiley Periodicals, Inc. Photochemistry and Photobiology © 2012 The American Society of Photobiology.

  2. Is There a Dose-Response Relationship for Heart Disease With Low-Dose Radiation Therapy?

    Energy Technology Data Exchange (ETDEWEB)

    Chung, Eugene [Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan (United States); Corbett, James R. [Division of Nuclear Medicine, Department of Radiology, University of Michigan, Ann Arbor, Michigan (United States); Moran, Jean M. [Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan (United States); Griffith, Kent A. [Department of Biostatistics, University of Michigan, Ann Arbor, Michigan (United States); Marsh, Robin B.; Feng, Mary; Jagsi, Reshma; Kessler, Marc L. [Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan (United States); Ficaro, Edward C. [Division of Nuclear Medicine, Department of Radiology, University of Michigan, Ann Arbor, Michigan (United States); Pierce, Lori J., E-mail: ljpierce@umich.edu [Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan (United States)

    2013-03-15

    Purpose: To quantify cardiac radiation therapy (RT) exposure using sensitive measures of cardiac dysfunction; and to correlate dysfunction with heart doses, in the setting of adjuvant RT for left-sided breast cancer. Methods and Materials: On a randomized trial, 32 women with node-positive left-sided breast cancer underwent pre-RT stress single photon emission computed tomography (SPECT-CT) myocardial perfusion scans. Patients received RT to the breast/chest wall and regional lymph nodes to doses of 50 to 52.2 Gy. Repeat SPECT-CT scans were performed 1 year after RT. Perfusion defects (PD), summed stress defects scores (SSS), and ejection fractions (EF) were evaluated. Doses to the heart and coronary arteries were quantified. Results: The mean difference in pre- and post-RT PD was −0.38% ± 3.20% (P=.68), with no clinically significant defects. To assess for subclinical effects, PD were also examined using a 1.5-SD below the normal mean threshold, with a mean difference of 2.53% ± 12.57% (P=.38). The mean differences in SSS and EF before and after RT were 0.78% ± 2.50% (P=.08) and 1.75% ± 7.29% (P=.39), respectively. The average heart Dmean and D95 were 2.82 Gy (range, 1.11-6.06 Gy) and 0.90 Gy (range, 0.13-2.17 Gy), respectively. The average Dmean and D95 to the left anterior descending artery were 7.22 Gy (range, 2.58-18.05 Gy) and 3.22 Gy (range, 1.23-6.86 Gy), respectively. No correlations were found between cardiac doses and changes in PD, SSS, and EF. Conclusions: Using sensitive measures of cardiac function, no clinically significant defects were found after RT, with the average heart Dmean <5 Gy. Although a dose response may exist for measures of cardiac dysfunction at higher doses, no correlation was found in the present study for low doses delivered to cardiac structures and perfusion, SSS, or EF.

  3. [Radiation-induced bystander effect: the important part of ionizing radiation response. Potential clinical implications].

    Science.gov (United States)

    Wideł, Maria; Przybyszewski, Waldemar; Rzeszowska-Wolny, Joanna

    2009-08-18

    It has long been a central radiobiological dogma that the damaging effects of ionizing radiation, such as cell death, cytogenetic changes, apoptosis, mutagenesis, and carcinogenesis, are the results of the direct ionization of cell structures, particularly DNA, or indirect damage via water radiolysis products. However, several years ago attention turned to a third mechanism of radiation, termed the "bystander effect" or "radiation-induced bystander effect" (RIBE). This is induced by agents and signals emitted by directly irradiated cells and manifests as a lowering of survival, cytogenetic damage, apoptosis enhancement, and biochemical changes in neighboring non-irradiated cells. The bystander effect is mainly observed in in vitro experiments using very low doses of alpha particles (range; mGy, cGy), but also after conventional irradiation (X-rays, gamma rays) at low as well as conventional doses. The mechanisms responsible for the bystander effect are complex and still poorly understood. It is believed that molecular signals released from irradiated cells induce different signaling ways in non-irradiated neighboring cells, leading to the observed events. The molecular signals may be transmitted through gap junction intercellular communication and through a medium transfer mechanism. The nature of these transmitted factors are diverse, and still not definitely established. It seems that RIBE may have important clinical implications for health risk associated with radiation exposure. Potentially, this effect may have important implications in the creation of whole-body or localized side effects in tissues beyond the irradiation field and also in low-dose radiological and radioisotope diagnostics. Factors emitted by irradiated cells may result in the risk of genetic instability, mutations, and second primary cancer induction. They might also have their own part in inducing and extending post-radiation side effects in normal tissue. The bystander effect may be a

  4. Radiation-induced bystander effect: The important part of ionizing radiation response. Potential clinical implications

    Directory of Open Access Journals (Sweden)

    Maria Wideł

    2009-08-01

    Full Text Available It has long been a central radiobiological dogma that the damaging effects of ionizing radiation, such as cell death, cytogenetic changes, apoptosis, mutagenesis, and carcinogenesis, are the results of the direct ionization of cell structures, particularly DNA, or indirect damage via water radiolysis products. However, several years ago attention turned to a third mechanism of radiation, termed the “bystander effect” or “radiation-induced bystander effect” (RIBE. This is induced by agents and signals emitted by directly irradiated cells and manifests as a lowering of survival, cytogenetic damage, apoptosis enhancement, and biochemical changes in neighboring non-irradiated cells. The bystander effect is mainly observed in in vitro experiments using very low doses of alpha particles (range; mGy, cGy, but also after conventional irradiation (X-rays, gamma rays at low as well as conventional doses. The mechanisms responsible for the bystander effect are complex and still poorly understood. It is believed that molecular signals released from irradiated cells induce different signaling ways in non-irradiated neighboring cells, leading to the observed events. The molecular signals may be transmitted through gap junction intercellular communication and through a medium transfer mechanism. The nature of these transmitted factors are diverse, and still not defi nitely established. It seems that RIBE may have important clinical implications for health risk associated with radiation exposure. Potentially, this effectmay have important implications in the creation of whole-body or localized side effects in tissues beyond the irradiation fi eld and also in low-dose radiological and radioisotope diagnostics. Factors emitted by irradiated cells may result in the risk of genetic instability, mutations, and second primary cancer induction. They might also have their own part in inducing and extending post-radiation side effects in normal tissue. The

  5. A method to adjust radiation dose-response relationships for clinical risk factors

    DEFF Research Database (Denmark)

    Appelt, Ane Lindegaard; Vogelius, Ivan R

    2012-01-01

    Several clinical risk factors for radiation induced toxicity have been identified in the literature. Here, we present a method to quantify the effect of clinical risk factors on radiation dose-response curves and apply the method to adjust the dose-response for radiation pneumonitis for patients...

  6. Right ventricular pressure response to exercise in adults with isolated ventricular septal defect closed in early childhood.

    Science.gov (United States)

    Moller, Thomas; Lindberg, Harald; Lund, May Brit; Holmstrom, Henrik; Dohlen, Gaute; Thaulow, Erik

    2018-06-01

    We previously demonstrated an abnormally high right ventricular systolic pressure response to exercise in 50% of adolescents operated on for isolated ventricular septal defect. The present study investigated the prevalence of abnormal right ventricular systolic pressure response in 20 adult (age 30-45 years) patients who underwent surgery for early ventricular septal defect closure and its association with impaired ventricular function, pulmonary function, or exercise capacity. The patients underwent cardiopulmonary tests, including exercise stress echocardiography. Five of 19 patients (26%) presented an abnormal right ventricular systolic pressure response to exercise ⩾ 52 mmHg. Right ventricular systolic function was mixed, with normal tricuspid annular plane systolic excursion and fractional area change, but abnormal tricuspid annular systolic motion velocity (median 6.7 cm/second) and isovolumetric acceleration (median 0.8 m/second2). Left ventricular systolic and diastolic function was normal at rest as measured by the peak systolic velocity of the lateral wall and isovolumic acceleration, early diastolic velocity, and ratio of early diastolic flow to tissue velocity, except for ejection fraction (median 53%). The myocardial performance index was abnormal for both the left and right ventricle. Peak oxygen uptake was normal (mean z score -0.4, 95% CI -2.8-0.3). There was no association between an abnormal right ventricular systolic pressure response during exercise and right or left ventricular function, pulmonary function, or exercise capacity. Abnormal right ventricular pressure response is not more frequent in adult patients compared with adolescents. This does not support the theory of progressive pulmonary vascular disease following closure of left-to-right shunts.

  7. Synthetic Defects for Vibrothermography

    Science.gov (United States)

    Renshaw, Jeremy; Holland, Stephen D.; Thompson, R. Bruce; Eisenmann, David J.

    2010-02-01

    Synthetic defects are an important tool used for characterizing the performance of nondestructive evaluation techniques. Viscous material-filled synthetic defects were developed for use in vibrothermography (also known as sonic IR) as a tool to improve inspection accuracy and reliability. This paper describes how the heat-generation response of these VMF synthetic defects is similar to the response of real defects. It also shows how VMF defects can be applied to improve inspection accuracy for complex industrial parts and presents a study of their application in an aircraft engine stator vane.

  8. Loss of CHD1 causes DNA repair defects and enhances prostate cancer therapeutic responsiveness

    DEFF Research Database (Denmark)

    Kari, Vijayalakshmi; Mansour, Wael Yassin; Raul, Sanjay Kumar

    2016-01-01

    The CHD1 gene, encoding the chromo-domain helicase DNA-binding protein-1, is one of the most frequently deleted genes in prostate cancer. Here, we examined the role of CHD1 in DNA double-strand break (DSB) repair in prostate cancer cells. We show that CHD1 is required for the recruitment of Ct......-homologous end joining. Together, we provide evidence for a previously unknown role of CHD1 in DNA DSB repair via HR and show that CHD1 depletion sensitizes cells to PARP inhibitors, which has potential therapeutic relevance. Our findings suggest that CHD1 deletion, like BRCA1/2 mutation in ovarian cancer, may...... serve as a marker for prostate cancer patient stratification and the utilization of targeted therapies such as PARP inhibitors, which specifically target tumors with HR defects....

  9. Experimental and numerical response of rigid slender blocks with geometrical defects under seismic excitation

    Directory of Open Access Journals (Sweden)

    Mathey Charlie

    2015-01-01

    Full Text Available The present work investigates on the influence of small geometrical defects on the behavior of slender rigid blocks. A comprehensive experimental campaign was carried out on one of the shake tables of CEA/Saclay in France. The tested model was a massive steel block with standard manufacturing quality. Release, free oscillations tests as well as shake table tests revealed a non-negligible out-of-plane motion even in the case of apparently plane initial conditions or excitations. This motion exhibits a highly reproducible part for a short duration that was used to calibrate a numerical geometrically asymmetrical model. The stability of this model when subjected to 2 000 artificial seismic horizontal bidirectional signals was compared to the stability of a symmetrical one. This study showed that the geometrical imperfections slightly increase the rocking and overturning probabilities under bidirectional seismic excitations in a narrow range of peak ground acceleration.

  10. Cytogenetic dose-response and adaptive response in cells of ungulate species exposed to ionizing radiation

    International Nuclear Information System (INIS)

    Ulsh, B.A.; Miller, S.M.; Mallory, F.F.; Mitchel, R.E.J.; Morrison, D.P.; Boreham, D.R.

    2004-01-01

    In the studies reported here, the micronucleus assay, a common cytogenetic technique, was used to examine the dose-responses in fibroblasts from three ungulate species (white-tailed deer, woodland caribou, and Indian muntjac) exposed to high doses of ionizing radiation (1-4 Gy of 60 Co gamma radiation). This assay was also used to examine the effects of exposure to low doses (1-100 mGy) typical of what these species experience in a year from natural and anthropogenic environmental sources. An adaptive response, defined as the induction of resistance to a stressor by a prior exposure to a small 'adapting' stress, was observed after exposure to low doses. This work indicates that very small doses are protective for the endpoint examined. The same level of protection was seen at all adapting doses, including 1 radiation track per cell, the lowest possible cellular dose. These results are consistent with other studies in a wide variety of organisms that demonstrate a protective effect of low doses at both cellular and whole-organism levels. This implies that environmental regulations predicated on the idea that even the smallest dose of radiation carries a quantifiable risk of direct adverse consequences to the exposed organism require further examination. Cytogenetic assays provide affordable and feasible biological effects-based alternatives that are more biologically relevant than traditional contaminant concentration-based radioecological risk assessment

  11. New strategies to interfere with radiation response: bio-modulation of radiation therapy

    International Nuclear Information System (INIS)

    Deutsch, E.; Kaliski, A.; Maggiorella, L.; Bourhis, J.

    2005-01-01

    The development of several new anti cancer agents has been made possible because of recent significant achievements in our global understanding of cancer biology. These new 'targeted' agents selectively inhibit targets necessary for tumor cell growth and viability with little toxicity to normal cells compared to conventional cytotoxic agents. So far, the efficacy of many of these new promising agents when used alone treatment remains limited, it is likely that the optimal use of these agents could be obtained in combination with conventional agents such as radiation therapy. The potential benefit of these targeted therapies combined with irradiation seems important. They might offer the advantage of increasing the tumor response to radiation with no or little increase in normal tissue damage. Therefore, these new types of chemo-radiation approaches might respect the normal tissue versus tumor cell 'therapeutic ratio'. These approaches can be sub divided in three sub groups: 1) Therapeutics targeting selectively one tumor related biochemical activity such as EGFR inhibitors. These approaches are efficient but one mutation of the target might render them inefficient. 2) Therapeutics directed against a widely expressed target. This is the case for anti insulin Growth Factor-1 (IGFIR) interventions: IGFIR inhibition seems to specifically alter tumor cell viability with a minimal effect on normal cells viability. 3) Strategies which are not targeted against the tumor but the microenvironment, especially angiogenesis. This type of approaches seems to be applicable independently of tumor intrinsic biologic related factors. (author)

  12. Contrasting Responses of Marine and Freshwater Photosynthetic Organisms to UVB Radiation: A Meta-Analysis

    KAUST Repository

    Jin, Peng; Duarte, Carlos M.; Agusti, Susana

    2017-01-01

    artificial lamps. We found that marine photosynthetic organisms tend to be more sensitive than freshwater photosynthetic organisms to UVB radiation; responses to either decreased or increased UVB radiation vary among taxa; the mortality rate is the most

  13. The radiation response of mesoporous nanocrystalline zirconia thin films

    Energy Technology Data Exchange (ETDEWEB)

    Manzini, Ayelén M.; Alurralde, Martin A. [Comisión Nacional de Energía Atómica, Centro Atómico Constituyentes, Av. General Paz 1499, 1650 San Martin, Provincia de Buenos Aires (Argentina); Giménez, Gustavo [Instituto Nacional de Tecnología Industrial - CMNB, Av. General Paz 5445, 1650 San Martín, Provincia de Buenos Aires (Argentina); Luca, Vittorio, E-mail: vluca@cnea.gov.ar [Comisión Nacional de Energía Atómica, Centro Atómico Constituyentes, Av. General Paz 1499, 1650 San Martin, Provincia de Buenos Aires (Argentina)

    2016-12-15

    The next generation of nuclear systems will require materials capable of withstanding hostile chemical, physical and radiation environments over long time-frames. Aside from its chemical and physical stability, crystalline zirconia is one of the most radiation tolerant materials known. Here we report the first ever study of the radiation response of nanocrystalline and mesoporous zirconia and Ce{sup 3+}-stabilized nanocrystalline zirconia (Ce{sub 0.1}Zr{sub 0.9}O{sub 2}) thin films supported on silicon wafers. Zirconia films prepared using the block copolymer Brij-58 as the template had a thickness of around 60–80 nm. In the absence of a stabilizing trivalent cation they consisted of monoclinic and tetragonal zirconia nanocrystals with diameters in the range 8–10 nm. Films stabilized with Ce{sup 3+} contained only the tetragonal phase. The thin films were irradiated with iodine ions of energies of 70 MeV and 132 keV at low fluences (10{sup 13} - 10{sup 14} cm{sup −2}) corresponding to doses of 0.002 and 1.73 dpa respectively, and at 180 keV and high fluences (2 × 10{sup 16} cm{sup −2}) corresponding to 82.4 dpa. The influence of heavy ion irradiation on the nanocrystalline structure was monitored through Rietveld analysis of grazing incidence X-ray diffraction (GIXRD) patterns recorded at angles close to the critical angle to ensure minimum contribution to the diffraction pattern from the substrate. Irradiation of the mesoporous nanocrystalline zirconia thin films with 70 MeV iodine ions, for which electronic energy loss is dominant, resulted in slight changes in phase composition and virtually no change in crystallographic parameters as determined by Rietveld analysis. Iodine ion bombardment in the nuclear energy loss regime (132–180 keV) at low fluences did not provoke significant changes in phase composition or crystallographic parameters. However, at 180 keV and high fluences the monoclinic phase was totally eliminated from the GIXRD

  14. Enhancement of radiation response in human hepatocarcinoma cells by Metformin

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Eun Ho; Kim, Won Woo; Kim, Joon; Jung, Won Gyun [Division of heavy ion clinical research, Korea University, Seoul (Korea, Republic of); Jeong, Jae Hoon; Jeong, Youn Kyoung; Kim, Mi Sook [Korea Institute of Radiological and Medical Sciences, Seoul (Korea, Republic of)

    2012-11-15

    Metformin (1, 1-dimethylbiguanide hydrochloride), the most widely used drug to treat type 2 diabetic patients under benefit good tolerability profile and low cost, has sparked keen interest as potential anticancer agent. Preclinical studies showed that the primary mechanism of action of metformin is through its ability to activate AMP-activated protein kinase (AMPK). Metformin inhibits complex 1 in the mitochondrial electron transport chain, leading to an increase in the AMP-to-ATP ratio, then, phospholylated AMPK increase energy generation or suppress energy consumption and then, inhibits cell growth. However, important caveat in direct action theory of metformin is that millimorlar range, effective dose for inhibition tumor cell growth in vitro, cannot be achieved in patients. This is probably because metformin enter cells through the organic cation transporters OCT1 and OCT2, which is lowly expressed in human cells except liver and adipose cells. dependent pathway rather than through direct effects of the tumor cells. We analyzed combination effect of metformin and radiation focusing to HCC cell lines, which theoretically express high organic cation transporters, producing high centration of metformin in tumor cells. The purpose of this study is to investigate whether metformin had anti-tumor effects when combined with radiation as radiosensitizer in HCC. The results showed that metformin increased radiosensitizing efficacy in HCC cells , as well as in Huh7 xenograft mouse models. Interestingly, metformin effectively sensitizes IR-induced apoptosis in HCC through upregulation of cleaved PARP and caspase3 and increase synergically on DNA damage response with combined treatment.HCC, suggesting potential usefulness of combined therapy of metformin together with radiation for HCC cancer therapy.

  15. Enhancement of radiation response in human hepatocarcinoma cells by Metformin

    International Nuclear Information System (INIS)

    Kim, Eun Ho; Kim, Won Woo; Kim, Joon; Jung, Won Gyun; Jeong, Jae Hoon; Jeong, Youn Kyoung; Kim, Mi Sook

    2012-01-01

    Metformin (1, 1-dimethylbiguanide hydrochloride), the most widely used drug to treat type 2 diabetic patients under benefit good tolerability profile and low cost, has sparked keen interest as potential anticancer agent. Preclinical studies showed that the primary mechanism of action of metformin is through its ability to activate AMP-activated protein kinase (AMPK). Metformin inhibits complex 1 in the mitochondrial electron transport chain, leading to an increase in the AMP-to-ATP ratio, then, phospholylated AMPK increase energy generation or suppress energy consumption and then, inhibits cell growth. However, important caveat in direct action theory of metformin is that millimorlar range, effective dose for inhibition tumor cell growth in vitro, cannot be achieved in patients. This is probably because metformin enter cells through the organic cation transporters OCT1 and OCT2, which is lowly expressed in human cells except liver and adipose cells. dependent pathway rather than through direct effects of the tumor cells. We analyzed combination effect of metformin and radiation focusing to HCC cell lines, which theoretically express high organic cation transporters, producing high centration of metformin in tumor cells. The purpose of this study is to investigate whether metformin had anti-tumor effects when combined with radiation as radiosensitizer in HCC. The results showed that metformin increased radiosensitizing efficacy in HCC cells , as well as in Huh7 xenograft mouse models. Interestingly, metformin effectively sensitizes IR-induced apoptosis in HCC through upregulation of cleaved PARP and caspase3 and increase synergically on DNA damage response with combined treatment.HCC, suggesting potential usefulness of combined therapy of metformin together with radiation for HCC cancer therapy

  16. Regulation of protein translation initiation in response to ionizing radiation

    International Nuclear Information System (INIS)

    Trivigno, Donatella; Bornes, Laura; Huber, Stephan M; Rudner, Justine

    2013-01-01

    Proliferating tumor cells require continuous protein synthesis. De novo synthesis of most proteins is regulated through cap-dependent translation. Cellular stress such as ionizing radiation (IR) blocks cap-dependent translation resulting in shut-down of global protein translation which saves resources and energy needed for the stress response. At the same time, levels of proteins required for stress response are maintained or even increased. The study aimed to analyze the regulation of signaling pathways controlling protein translation in response to IR and the impact on Mcl-1, an anti-apoptotic and radioprotective protein, which levels rapidly decline upon IR. Protein levels and processing were analyzed by Western blot. The assembly of the translational pre-initiation complex was examined by Immunoprecipitation and pull-down experiments with 7-methyl GTP agarose. To analyze IR-induced cell death, dissipation of the mitochondrial membrane potential and DNA fragmentation were determined by flow cytometry. Protein levels of the different initiation factors were down-regulated using RNA interference approach. IR induced caspase-dependent cleavage of the translational initiation factors eIF4G1, eIF3A, and eIF4B resulting in disassembly of the cap-dependent initiation complex. In addition, DAP5-dependent initiation complex that regulates IRES-dependent translation was disassembled in response to IR. Moreover, IR resulted in dephosphorylation of 4EBP1, an inhibitor of cap-dependent translation upstream of caspase activation. However, knock-down of eIF4G1, eIF4B, DAP5, or 4EBP1 did not affect IR-induced decline of the anti-apoptotic protein Mcl-1. Our data shows that cap-dependent translation is regulated at several levels in response to IR. However, the experiments indicate that IR-induced Mcl-1 decline is not a consequence of translational inhibition in Jurkat cells

  17. Regulation of protein translation initiation in response to ionizing radiation

    Directory of Open Access Journals (Sweden)

    Trivigno Donatella

    2013-02-01

    Full Text Available Abstract Background Proliferating tumor cells require continuous protein synthesis. De novo synthesis of most proteins is regulated through cap-dependent translation. Cellular stress such as ionizing radiation (IR blocks cap-dependent translation resulting in shut-down of global protein translation which saves resources and energy needed for the stress response. At the same time, levels of proteins required for stress response are maintained or even increased. The study aimed to analyze the regulation of signaling pathways controlling protein translation in response to IR and the impact on Mcl-1, an anti-apoptotic and radioprotective protein, which levels rapidly decline upon IR. Methods Protein levels and processing were analyzed by Western blot. The assembly of the translational pre-initiation complex was examined by Immunoprecipitation and pull-down experiments with 7-methyl GTP agarose. To analyze IR-induced cell death, dissipation of the mitochondrial membrane potential and DNA fragmentation were determined by flow cytometry. Protein levels of the different initiation factors were down-regulated using RNA interference approach. Results IR induced caspase-dependent cleavage of the translational initiation factors eIF4G1, eIF3A, and eIF4B resulting in disassembly of the cap-dependent initiation complex. In addition, DAP5-dependent initiation complex that regulates IRES-dependent translation was disassembled in response to IR. Moreover, IR resulted in dephosphorylation of 4EBP1, an inhibitor of cap-dependent translation upstream of caspase activation. However, knock-down of eIF4G1, eIF4B, DAP5, or 4EBP1 did not affect IR-induced decline of the anti-apoptotic protein Mcl-1. Conclusion Our data shows that cap-dependent translation is regulated at several levels in response to IR. However, the experiments indicate that IR-induced Mcl-1 decline is not a consequence of translational inhibition in Jurkat cells.

  18. Response of air stagnation frequency to anthropogenically enhanced radiative forcing

    International Nuclear Information System (INIS)

    Horton, Daniel E; Diffenbaugh, Noah S; Harshvardhan

    2012-01-01

    Stagnant atmospheric conditions can lead to hazardous air quality by allowing ozone and particulate matter to accumulate and persist in the near-surface environment. By changing atmospheric circulation and precipitation patterns, global warming could alter the meteorological factors that regulate air stagnation frequency. We analyze the response of the National Climatic Data Center (NCDC) air stagnation index (ASI) to anthropogenically enhanced radiative forcing using global climate model projections of late-21st century climate change (SRESA1B scenario). Our results indicate that the atmospheric conditions over the highly populated, highly industrialized regions of the eastern United States, Mediterranean Europe, and eastern China are particularly sensitive to global warming, with the occurrence of stagnant conditions projected to increase by 12–25% relative to late-20th century stagnation frequencies (3–18 + days yr −1 ). Changes in the position/strength of the polar jet, in the occurrence of light surface winds, and in the number of precipitation-free days all contribute to more frequent late-21st century air mass stagnation over these high-population regions. In addition, we find substantial inter-model spread in the simulated response of stagnation conditions over some regions using either native or bias corrected global climate model simulations, suggesting that changes in the atmospheric circulation and/or the distribution of precipitation represent important sources of uncertainty in the response of air quality to global warming. (letter)

  19. Optical response of thin amorphous films to infrared radiation

    Science.gov (United States)

    Orosco, J.; Coimbra, C. F. M.

    2018-03-01

    We briefly review the electrical-optical response of materials to radiative forcing within the formalism of the Kramers-Kronig relations. A commensurate set of criteria is described that must be met by any frequency-domain model representing the time-domain response of a real (i.e., physically possible) material. The criteria are applied to the Brendel-Bormann (BB) oscillator, a model that was originally introduced for its fidelity at reproducing the non-Lorentzian peak broadening experimentally observed in the infrared absorption by thin amorphous films but has since been used for many other common materials. We show that the BB model fails to satisfy the established physical criteria. Taking an alternative approach to the model derivation, a physically consistent model is proposed. This model provides the appropriate line-shape broadening for modeling the infrared optical response of thin amorphous films while adhering strictly to the Kramers-Kronig criteria. Experimental data for amorphous alumina (Al2O3 ) and amorphous quartz silica (SiO2) are used to obtain model parametrizations for both the noncausal BB model and the proposed causal model. The proposed model satisfies consistency criteria required by the underlying physics and reproduces the experimental data with better fidelity (and often with fewer parameters) than previously proposed permittivity models.

  20. Response of pig skin to fractionated radiation doses

    International Nuclear Information System (INIS)

    Wiernik, G.; Hopewell, J.W.; Patterson, T.J.S.; Young, C.M.A.; Foster, J.L.

    1977-01-01

    The individual components of a fractionated course of irradiation treatment have been considered separately. Methods of accurate measurement of individual parameters has brought to light different interpretations of the observations. Reasons are given for the necessity of having a radiobiological model which has a direct relevance to the clinical situation. Results are reported for fractionated regimes of irradiation in which the dose has been varied above and below normal tissue tolerance which has been equated with clinical skin necrosis. The components of the acute skin reaction, erythema, pigmentation and desquamation have been analysed separately and their contribution as a method of measurement assessed. Initially, the range of numerical scores attributed to erythema did not reach the scores attributed to necrosis but we now believe that radiation damage expressed as erythema can move directly into necrosis without passing through desquamation. Desquamation, on the other hand, only became a useful parameter at higher dose levels; it has also been shown to be a component associated with skin breakdown. Pigmentation showed no dose response at the dose levels employed in our experiments and it is our belief that this is due to this system being fully saturated under these circumstances. Measurement of the late radiation reaction in the skin has been considered in detail and our results have been expressed by comparing the relative lengths of irradiated and control fields in the same pig. From these findings iso-effect graphs have been constructed and time and fractionation factors have been derived. (author)

  1. Effect of radiation induced defects and incompatibility elastic stresses on the diffusion of ion implantated boron in silicon at the pulse annealing

    International Nuclear Information System (INIS)

    Stel'makh, V.F.; Suprun-Belevich, Yu.R.; Chelyadinskij, A.R.

    1987-01-01

    For determination of radiation defects effect on diffusion of the implanted boron in silicon at the pulse annealing, silicon crystals, implanted with boron, preliminary irradiated by silicon ions of different flows for checked defects implantation, were investigated. Silicon crystals additionally implanted by Ge + ions were investigated to research the effect of the incompatibility elastic stresses, emerging in implanted structures due to lattice periods noncoincidence in matrix and alloyed layers, on implanted boron diffusion. It is shown, that abnormally high values of boron diffusion coefficients in silicon at the pulse annealing are explained by silicon interstitial atom participation in redistribution of diffusing boron atoms by two diffusion channels - interstitial and vacation - and by incompatibility elastic stresses effect on diffusion

  2. Role of 3d-ions for radiation defect production in MgO and MgAl2O4

    International Nuclear Information System (INIS)

    Mironova, N.A.; Grinvald, G.A.; Skvortsova, V.N.

    1985-01-01

    Optical properties of MgO and MgAl 2 O 4 crystals containing chromium and manganese impurity ions were studied by exposure to but all types of radiation. Complicated defects of the ''impurity-intrinsic matrix defect'' type were preferably considered. It has been shown that different symmetry center forming chromium ions in MgO:Crsup(3+) change their valency with various efficiency being exposed to external action. Besides, the compensating vacancy does not participate in the hole center formation. For MgOxAl 2 O 3 single crystals the presence of octahedrally coordinated manganese ions suppresses the hole center creation by gamma-irradiation. Studying luminescence spectra of Crsup(3+) ions in MgAl 2 O 4 it has been states that neutron irradiation increases the degree of inversion for the magnesium-aluminium spinel

  3. Oligodendroglial response to ionizing radiation: Dose and dose-rate response

    International Nuclear Information System (INIS)

    Levy, R.P.

    1991-12-01

    An in vitro system using neuroglia from neonatal rat brain was developed to examine the morphologic, immunocytochemical and biochemical response of oligodendroglia to ionizing radiation. Following acute γ-irradiation at day-in-culture (DIC) 8, oligodendrocyte counts at DIC 14 were 55% to 65% of control values after 2 Gy, and 29% to 36% after 5 Gy. Counts increased to near-normal levels at DIC 21 in the 2 Gy group and to 75% of normal in the 5 Gy group. Myelin basic protein levels (MBP) at DIC 14 were 60% of control values after 2 Gy, and 40% after 5 Gy. At DIC 21, MBP after 2 Gy was 45% greater than that observed at DIC 14, but MBP, as a fraction of age-matched control values, dropped from 60% to 50%. Following 5 Gy, absolute MBP changed little between DIC 14 and DIC 21, but decreased from 40% to 25% of control cultures. The response to split-dose irradiation indicated that nearly all sublethal damage in the oligodendrocyte population (and its precursors) was repaired within 3 h to 4 h. A new compartmental cell model for radiation response in vitro of the oligodendrocyte population is proposed and examined in relation to the potential reaction to radiation injury in the brain

  4. Oligodendroglial response to ionizing radiation: Dose and dose-rate response

    Energy Technology Data Exchange (ETDEWEB)

    Levy, Richard P. [Univ. of California, Berkeley, CA (United States)

    1991-12-01

    An in vitro system using neuroglia from neonatal rat brain was developed to examine the morphologic, immunocytochemical and biochemical response of oligodendroglia to ionizing radiation. Following acute γ-irradiation at day-in-culture (DIC) 8, oligodendrocyte counts at DIC 14 were 55% to 65% of control values after 2 Gy, and 29% to 36% after 5 Gy. Counts increased to near-normal levels at DIC 21 in the 2 Gy group and to 75% of normal in the 5 Gy group. Myelin basic protein levels (MBP) at DIC 14 were 60% of control values after 2 Gy, and 40% after 5 Gy. At DIC 21, MBP after 2 Gy was 45% greater than that observed at DIC 14, but MBP, as a fraction of age-matched control values, dropped from 60% to 50%. Following 5 Gy, absolute MBP changed little between DIC 14 and DIC 21, but decreased from 40% to 25% of control cultures. The response to split-dose irradiation indicated that nearly all sublethal damage in the oligodendrocyte population (and its precursors) was repaired within 3 h to 4 h. A new compartmental cell model for radiation response in vitro of the oligodendrocyte population is proposed and examined in relation to the potential reaction to radiation injury in the brain.

  5. Oligodendroglial response to ionizing radiation: Dose and dose-rate response

    Energy Technology Data Exchange (ETDEWEB)

    Levy, R.P.

    1991-12-01

    An in vitro system using neuroglia from neonatal rat brain was developed to examine the morphologic, immunocytochemical and biochemical response of oligodendroglia to ionizing radiation. Following acute {gamma}-irradiation at day-in-culture (DIC) 8, oligodendrocyte counts at DIC 14 were 55% to 65% of control values after 2 Gy, and 29% to 36% after 5 Gy. Counts increased to near-normal levels at DIC 21 in the 2 Gy group and to 75% of normal in the 5 Gy group. Myelin basic protein levels (MBP) at DIC 14 were 60% of control values after 2 Gy, and 40% after 5 Gy. At DIC 21, MBP after 2 Gy was 45% greater than that observed at DIC 14, but MBP, as a fraction of age-matched control values, dropped from 60% to 50%. Following 5 Gy, absolute MBP changed little between DIC 14 and DIC 21, but decreased from 40% to 25% of control cultures. The response to split-dose irradiation indicated that nearly all sublethal damage in the oligodendrocyte population (and its precursors) was repaired within 3 h to 4 h. A new compartmental cell model for radiation response in vitro of the oligodendrocyte population is proposed and examined in relation to the potential reaction to radiation injury in the brain.

  6. Recurrent Vulvovaginal Candidiasis: Could It Be Related to Cell-Mediated Immunity Defect in Response to Candida Antigen?

    Directory of Open Access Journals (Sweden)

    Zahra Talaei

    2017-09-01

    Full Text Available Background Recurrent vulvovaginal candidiasis (RVVC is a common cause of morbidity affecting millions of women worldwide. Patients with RVVC are thought to have an underlying immunologic defect. This study has been established to evaluate cell-mediated immunity defect in response to candida antigen in RVVC cases. Materials and Methods Our cross-sectional study was performed in 3 groups of RVVC patients (cases, healthy individuals (control I and known cases of chronic mucocutaneous candidiasis (CMC (control II. Patients who met the inclusion criteria of RVVC were selected consecutively and were allocated in the case group. Peripheral blood mononuclear cells were isolated and labeled with CFSE and proliferation rate was measured in exposure to candida antigen via flow cytometry. Results T lymphocyte proliferation in response to candida was significantly lower in RVVC cases (n=24 and CMC patients (n=7 compared to healthy individuals (n=20, P0.05. Family history of primary immunodeficiency diseases (PID differed significantly among groups (P=0.01, RVVC patients has family history of PID more than control I (29.2 vs. 0%, P=0.008 but not statistically different from CMC patients (29.2 vs. 42.9%, P>0.05. Prevalence of atopy was greater in RVVC cases compared to healthy individuals (41.3 vs. 15%, P=0.054. Lymphoproliferative activity and vaginal symptoms were significantly different among RVVC cases with and without allergy (P=0.01, P=0.02. Conclusion Our findings revealed that T cells do not actively proliferate in response to Candida antigen in some RVVC cases. So it is concluded that patients with cell-mediated immunity defect are more susceptible to recurrent fungal infections of vulva and vagina. Nonetheless, some other cases of RVVC showed normal function of T cells. Further evaluations showed that these patients suffer from atopy. It is hypothesized that higher frequency of VVC in patients with history of atopy might be due to allergic response

  7. Approach of combined cancer gene therapy and radiation: response of promoters to ionizing radiation

    International Nuclear Information System (INIS)

    Anstett, A.

    2005-09-01

    Gene therapy is an emerging cancer treatment modality. We are interested in developing a radiation-inducible gene therapy system to sensitize the tumor vasculature to the effects of ionizing radiation (IR) treatment. An expression system based on irradiation-inducible promoters will drive the expression of anti-tumor genes in the tumor vasculature. Solid tumors are dependent on angio genesis, a process in which new blood vessels are formed from the pre-existing vasculature. Vascular endothelial cells are un transformed and genetically stable, thus avoiding the problem of resistance to the treatments. Vascular endothelial cells may therefore represent a suitable target for this therapeutic gene therapy strategy.The identification of IR-inducible promoters native to endothelial cells was performed by gene expression profiling using cDNA micro array technology. We describe the genes modified by clinically relevant doses of IR. The extension to high doses aimed at studying the effects of total radiation delivery to the tumor. The radio-inductiveness of the genes selected for promoter study was confirmed by RT-PCR. Analysis of the activity of promoters in response to IR was also assessed in a reporter plasmid. We found that authentic promoters cloned onto a plasmid are not suitable for cancer gene therapy due to their low induction after IR. In contrast, synthetic promoters containing repeated sequence-specific binding sites for IR-activated transcription factors such as NF-κB are potential candidates for gene therapy. The activity of five tandemly repeated TGGGGACTTTCCGC elements for NF-κB binding in a luciferase reporter was increased in a dose-dependent manner. Interestingly, the response to fractionated low doses was improved in comparison to the total single dose. Thus, we put present evidence that a synthetic promoter for NF-κB specific binding may have application in the radio-therapeutic treatment of cancer. (author)

  8. Radiation response of haematopoietic cell lines of human origin

    International Nuclear Information System (INIS)

    Lehnert, S.; Rybka, W.B.; Suissa, S.; Giambattisto, D.

    1986-01-01

    Six human haematopoietic cell lines, five of leukaemic origin, including cells with myeloid, lymphoid and undifferentiated phenotype have been studied with respect to radiation response. The intrinsic radio-sensitivity of the cells varied widely, the D 0 s ranging from 0.53 to 1.39 Gy. Five of the cell lines showed some capacity to accumulate sublethal damage; in three of these, enhanced survival was demonstrated in split-dose experiments. One cell line (HL-60) was anomalous in that although little accumulation of sublethal damage was demonstrable, survival was enhanced by fractionation of the dose. Five of the six cell lines studied were of leukaemic origin. The results support the belief that, in contrast to the almost constant radiosensitivity of normal haematopoietic cell progenitors, leukaemic cell progenitors may show a wide range of radiosensitivities. (author)

  9. UV radiation in marine ectotherms: Molecular effects and responses

    International Nuclear Information System (INIS)

    Dahms, Hans-U.; Lee, Jae-Seong

    2010-01-01

    This review summarizes current knowledge on ultraviolet radiation (UVR)-induced cellular and molecular damage in marine ectotherms (invertebrates and fish). UVR impairs sperm motility, reduces fertilization, and causes embryo malformation that in turn affects recruitment and therefore the sustainability of natural populations. The direct molecular effects of UVR are mediated by absorption of certain wavelengths by specific macromolecules and the dissipation of the absorbed energy via photochemical reactions. Most organisms have defense mechanisms that either prevent UVR-induced damage, or mechanisms that repair the damage. Photoprotective pigments, antioxidant defense compounds, and cell cycle development genes are some of the molecules involved in UVR defense. Photoenzymatic repair and nucleotide excision repair are the two primary DNA repair systems in marine ectotherms. We anticipate that toxicogenomic studies will gain importance in UVR research because they can elucidate the primary processes involved in UVR damage and the cellular response to this damage.

  10. Rapid enzymatic response to compensate UV radiation in copepods.

    Directory of Open Access Journals (Sweden)

    María Sol Souza

    Full Text Available Ultraviolet radiation (UVR causes physical damage to DNA, carboxylation of proteins and peroxidation of lipids in copepod crustaceans, ubiquitous and abundant secondary producers in most aquatic ecosystems. Copepod adaptations for long duration exposures include changes in behaviour, changes in pigmentation and ultimately changes in morphology. Adaptations to short-term exposures are little studied. Here we show that short-duration exposure to UVR causes the freshwater calanoid copepod, Eudiaptomus gracilis, to rapidly activate production of enzymes that prevent widespread collateral peroxidation (glutathione S-transferase, GST, that regulate apoptosis cell death (Caspase-3, Casp-3, and that facilitate neurotransmissions (cholinesterase-ChE. None of these enzyme systems is alone sufficient, but they act in concert to reduce the stress level of the organism. The interplay among enzymatic responses provides useful information on how organisms respond to environmental stressors acting on short time scales.

  11. Neuropharmacologic responses of animals to extreme effects: exposure to radiation

    International Nuclear Information System (INIS)

    Mikhajlichenko, P.P.; Tikhonchuk, V.S.; Ushakov, I.B.

    1990-01-01

    The functional state of neurochemical structures of male mice was investigated after their gamma-irradiation with 137 Cs (1.9 Gy/min) at a dose of 100 Gy. The animals were treated with the following drugs that produce selective effects on specific receptors: galanthamine, amizyl, arpenal, phenamine, phentolamine and obsidan, haloperidol, apomorphine, phenazepam, phenibut and strychnin. The results point to the development of heterologous desensibilization of receptors at early post-irradiation periods. The high effectiveness of agonists and antagonists of CNS transmitters in the nonirradiated animals and their low effectiveness in the irradiated animals and their low effectiveness in the irradiated animals may be considered as an indicator of post-radiation injury of specific receptors. These neuropharmacological interactions may obviously be modified in response to the combined effects of space flight factors

  12. Detection of defect states responsible for leakage current in ultrathin tantalum pentoxide (Ta2O5) films by zero-bias thermally stimulated current spectroscopy

    International Nuclear Information System (INIS)

    Lau, W.S.; Zhong, L.; Lee, A.; See, C.H.; Han, T.; Sandler, N.P.; Chong, T.C.

    1997-01-01

    Defect states responsible for leakage current in ultrathin (physical thickness 2 O 5 ) films were measured with a novel zero-bias thermally stimulated current technique. It was found that defect states A, whose activation energy was estimated to be about 0.2 eV, can be more efficiently suppressed by using N 2 O rapid thermal annealing (RTA) instead of using O 2 RTA for postdeposition annealing. The leakage current was also smaller for samples with N 2 O RTA than those with O 2 RTA for postdeposition annealing. Hence, defect states A are quite likely to be important in causing leakage current. copyright 1997 American Institute of Physics

  13. Radiative Forcing from Emissivity Response in Polar Regions

    Science.gov (United States)

    Kuo, C.; Feldman, D.; Huang, X.; Flanner, M.; Chen, X.; Yang, P.; Kuo, C.

    2016-12-01

    A detailed assessment of the radiative balance and its controlling factors in polar regions is a critical prerequisite for understanding and predicting the polar amplification of climate change. Accordingly, we investigate the role of infrared surface emissivity in polar regions as a potential feedback mechanism following Feldman et al, 2014. In this work, we investigate the climatic response of the Community Earth System Model (CESM) with spectral emissivity values that are implemented in a physically consistent manner for non-vegetated surfaces. In a control model run where 1850 CO2 volume mixing ratio (vmr) is fixed, the updated spectral emissivity values are imposed for modified surface boundary conditions in the atmospheric model component. Climatic stability in the emergent globally averaged surface temperature is observed on decadal scales for an unforced (control) run. Analytic kernels representing the change in top of the atmosphere OLR given changes in emissivity are calculated on-line during the model runs, incorporating spatially and temporally varied humidity profiles impactful to transmission. Globally averaged kernels of the sensitivity of OLR to surface emissivity calculated for control and ramped CO2 runs exhibit temporal evolution with statistically significant differences in shape. Additionally, kernel and spectrally-averaged emissivity differences between monthly-averaged maps of control and ramped runs demonstrate a seasonal cycle. Similar to the treatment of cryosphere radiative forcing in Flanner et al, 2011, we define emissivity response as the product of the emissivity kernel and the change in month-to-month emissivity. At the end of 20th century, the 10-year emissivity forcing averaged at latitudes > 60°, is found to be negative (positive) in January (July), due to increasing (decreasing) sea-ice. These findings indicate that differences in surface emissivity between frozen and unfrozen surfaces decrease wintertime and increase summertime

  14. Stochastic biological response to radiation. Comprehensive analysis of gene expression

    International Nuclear Information System (INIS)

    Inoue, Tohru; Hirabayashi, Yoko

    2012-01-01

    Authors explain that the radiation effect on biological system is stochastic along the law of physics, differing from chemical effect, using instances of Cs-137 gamma-ray (GR) and benzene (BZ) exposures to mice and of resultant comprehensive analyses of gene expression. Single GR irradiation is done with Gamma Cell 40 (CSR) to C57BL/6 or C3H/He mouse at 0, 0.6 and 3 Gy. BE is given orally at 150 mg/kg/day for 5 days x 2 weeks. Bone marrow cells are sampled 1 month after the exposure. Comprehensive gene expression is analyzed by Gene Chip Mouse Genome 430 2.0 Array (Affymetrix) and data are processed by programs like case normalization, statistics, network generation, functional analysis etc. GR irradiation brings about changes of gene expression, which are classifiable in common genes variable commonly on the dose change and stochastic genes variable stochastically within each dose: e.g., with Welch-t-test, significant differences are between 0/3 Gy (dose-specific difference, 455 pbs (probe set), in stochastic 2113 pbs), 0/0.6 Gy (267 in 1284 pbs) and 0.6/3 Gy (532 pbs); and with one-way analysis of variation (ANOVA) and hierarchial/dendrographic analyses, 520 pbs are shown to involve the dose-dependent 226 and dose-specific 294 pbs. It is also shown that at 3 Gy, expression of common genes are rather suppressed, including those related to the proliferation/apoptosis of B/T cells, and of stochastic genes, related to cell division/signaling. Ven diagram of the common genes of above 520 pbs, stochastic 2113 pbs at 3 Gy and 1284 pbs at 0.6 Gy shows the overlapping genes 29, 2 and 4, respectively, indicating only 35 pbs are overlapping in total. Network analysis of changes by GR shows the rather high expression of genes around hub of cAMP response element binding protein (CREB) at 0.6 Gy, and rather variable expression around CREB hub/suppressed expression of kinesin hub at 3 Gy; in the network by BZ exposure, unchanged or low expression around p53 hub and suppression

  15. Long-term anisotropic mechanical response of surgical meshes used to repair abdominal wall defects.

    Science.gov (United States)

    Hernández-Gascón, B; Peña, E; Pascual, G; Rodríguez, M; Bellón, J M; Calvo, B

    2012-01-01

    Routine hernia repair surgery involves the implant of synthetic mesh. However, this type of procedure may give rise to pain and bowel incarceration and strangulation, causing considerable patient disability. The purpose of this study was to compare the long-term behaviour of three commercial meshes used to repair the partially herniated abdomen in New Zealand White rabbits: the heavyweight (HW) mesh, Surgipro(®) and lightweight (LW) mesh, Optilene(®), both made of polypropylene (PP), and a mediumweight (MW) mesh, Infinit(®), made of polytetrafluoroethylene (PTFE). The implanted meshes were mechanical and histological assessed at 14, 90 and 180 days post-implant. This behaviour was compared to the anisotropic mechanical behaviour of the unrepaired abdominal wall in control non-operated rabbits. Both uniaxial mechanical tests conducted in craneo-caudal and perpendicular directions and histological findings revealed substantial collagen growth over the repaired hernial defects causing stiffness in the repair zone, and thus a change in the original properties of the meshes. The mechanical behaviour of the healthy tissue in the craneo-caudal direction was not reproduced by any of the implanted meshes after 14 days or 90 days of implant, whereas in the perpendicular direction, SUR and OPT achieved similar behaviour. From a mechanical standpoint, the anisotropic PP-lightweight meshes may be considered a good choice in the long run, which correlates with the structure of the regenerated tissue. Copyright © 2011 Elsevier Ltd. All rights reserved.

  16. Annealing of the Sb-vacancy and a closely related radiation induced defect in n-type germanium

    Science.gov (United States)

    Barnard, Abraham W.; Auret, F. D.; Meyer, W. E.

    2018-04-01

    Deep level transient spectroscopy was used to study the defects induced by alpha-particle irradiation from an Am241 source in antimony doped n-type germanium. Previous investigations of the well know Sb-vacancy defect have led to the discovery of a second defect with very similar emission properties, referred to as the E‧. Although both defects have similar emission rates, they have very different annealing properties. In this study we further investigated these properties of the E‧ in Sb doped samples irradiated at 270 K with alpha particles from an Am241 source. Laplace deep level transient spectroscopy was used to determine the concentration of each defect. An isothermal annealing study of the E‧ was carried out in the temperature range 300 K to 325 K in 5 K increments, while the Sb-vacancy was annealed out completely at 410 K onwards, long after the E‧ was completely annealed out. The annealing activation energy was determined through isothermal annealing profiles for both the Sb-Vacancy and the E‧ as 1.05 eV and 0.73 eV respectively with a prefactor of 2.05 × 109 s-1 and 2.7 × 108 s-1.

  17. Insight into the effect of screw dislocations and oxygen vacancy defects on the optical nonlinear refraction response in chemically grown ZnO/Al2O3 films

    Science.gov (United States)

    Agrawal, Arpana; Saroj, Rajendra K.; Dar, Tanveer A.; Baraskar, Priyanka; Sen, Pratima; Dhar, Subhabrata

    2017-11-01

    We report the effect of screw dislocations and oxygen vacancy defects on the optical nonlinear refraction response of ZnO films grown on a sapphire substrate at various oxygen flow rates using the chemical vapor deposition technique. The nonlinear refraction response was investigated in the off-resonant regime using a CW He-Ne laser source to examine the role of the intermediate bandgap states. It has been observed that the structural defects strongly influence the optical nonlinearity in the off-resonant regime. Nonlinearity has been found to improve as the oxygen flow rate is lowered from 2 sccm to 0.3 sccm. From photoluminescence studies, we observe that the enhanced defect density of the electronic defect levels due to the increased concentration of structural defects (with the decrease in the oxygen flow rate) is responsible for this improved optical nonlinearity along with the thermal effect. This suggests that defect engineering is an effective way to tailor the nonlinearity of ZnO films and their utility for optoelectronic device applications.

  18. Defective pulmonary innate immune responses post-stem cell transplantation; review and results from one model system

    Directory of Open Access Journals (Sweden)

    Racquel eDomingo-Gonzalez

    2013-05-01

    Full Text Available Infectious pulmonary complications limit the success of hematopoietic stem cell transplantation (HSCT as a therapy for malignant and nonmalignant disorders. Susceptibility to pathogens in both autologous and allogeneic HSCT recipients persists despite successful immune reconstitution. As studying the causal effects of these immune defects in the human population can be limiting, a bone marrow transplant (BMT mouse model can be used to understand the defect in mounting a productive innate immune response post-transplantation. When syngeneic BMT is performed, this system allows the study of BMT-induced alterations in innate immune cell function that are independent of the confounding effects of immunosuppressive therapy and graft-versus-host disease. Studies from several laboratories, including our own show that pulmonary susceptibility to bacterial infections post-BMT are largely due to alterations in the lung alveolar macrophages. Changes in these cells post-BMT include cytokine and eicosanoid dysregulations, scavenger receptor alterations, changes in micro RNA profiles, and alterations in intracellular signaling molecules that limit bacterial phagocytosis and killing. The changes that occur highlight mechanisms that promote susceptibility to infections commonly afflicting HSCT recipients and provide insight into therapeutic targets that may improve patient outcomes post-HSCT.

  19. Defects in dilute nitrides

    International Nuclear Information System (INIS)

    Chen, W.M.; Buyanova, I.A.; Tu, C.W.; Yonezu, H.

    2005-01-01

    We provide a brief review our recent results from optically detected magnetic resonance studies of grown-in non-radiative defects in dilute nitrides, i.e. Ga(In)NAs and Ga(Al,In)NP. Defect complexes involving intrinsic defects such as As Ga antisites and Ga i self interstitials were positively identified.Effects of growth conditions, chemical compositions and post-growth treatments on formation of the defects are closely examined. These grown-in defects are shown to play an important role in non-radiative carrier recombination and thus in degrading optical quality of the alloys, harmful to performance of potential optoelectronic and photonic devices based on these dilute nitrides. (author)

  20. Radiation adaptive response for the growth of cultured glial cells

    International Nuclear Information System (INIS)

    Suzuki, S.; Miura, Y.; Kano, M.; Toda, T.; Urano, S.

    2003-01-01

    Full text: To examine the molecular mechanism of radiation adaptive response (RAR) for the growth of cultured glial cells and to investigate the influence of aging on the response, glial cells were cultured from young and aged rats (1 month and 24 months old). RAR for the growth of glial cells conditioned with a low dose of X-rays and subsequently exposed to a high dose of X-rays was examined for cell number and BrdU incorporation. Involvement of the subcellular signaling pathway factors in RAR was investigated using their inhibitors, activators and mutated glial cells. RAR was observed in cells cultured from young rats, but was not in cells from aged rats. The inhibitors of protein kinase C (PKC) and DNA-dependent protein kinase (DNA-PK) or phosphatidylinositol 3-kinase (PI3K) suppressed RAR. The activators of PKC instead of low dose irradiation also caused RAR. Moreover, glial cells cultured from severe combined immunodeficiency (scid) mice (CB-17 scid) and ataxia-telangiectasia (AT) cells from AT patients showed no RAR. These results indicated that PKC, ATM, DNAPK and/or PI3K were involved in RAR for growth and BrdU incorporation of cultured glial cells and RAR decreased with aging. Proteomics data of glial cells exposed to severe stress of H 2 O 2 or X-rays also will be presented in the conference since little or no difference has not been observed with slight stress yet

  1. The Radiation Dose-Response of the Human Spinal Cord

    International Nuclear Information System (INIS)

    Schultheiss, Timothy E.

    2008-01-01

    Purpose: To characterize the radiation dose-response of the human spinal cord. Methods and Materials: Because no single institution has sufficient data to establish a dose-response function for the human spinal cord, published reports were combined. Requisite data were dose and fractionation, number of patients at risk, number of myelopathy cases, and survival experience of the population. Eight data points for cervical myelopathy were obtained from five reports. Using maximum likelihood estimation correcting for the survival experience of the population, estimates were obtained for the median tolerance dose, slope parameter, and α/β ratio in a logistic dose-response function. An adequate fit to thoracic data was not possible. Hyperbaric oxygen treatments involving the cervical cord were also analyzed. Results: The estimate of the median tolerance dose (cervical cord) was 69.4 Gy (95% confidence interval, 66.4-72.6). The α/β = 0.87 Gy. At 45 Gy, the (extrapolated) probability of myelopathy is 0.03%; and at 50 Gy, 0.2%. The dose for a 5% myelopathy rate is 59.3 Gy. Graphical analysis indicates that the sensitivity of the thoracic cord is less than that of the cervical cord. There appears to be a sensitizing effect from hyperbaric oxygen treatment. Conclusions: The estimate of α/β is smaller than usually quoted, but values this small were found in some studies. Using α/β = 0.87 Gy, one would expect a considerable advantage by decreasing the dose/fraction to less than 2 Gy. These results were obtained from only single fractions/day and should not be applied uncritically to hyperfractionation

  2. The inflammatory response plays a major role in the acute radiation syndrome induced by fission radiation

    International Nuclear Information System (INIS)

    Agay, D.; Chancerelle, Y.; Hirodin, F.; Mathieu, J.; Multon, E.; Van Uye, A.; Mestries, J.C.

    1997-01-01

    At high dose rates, both gamma and neutron irradiation induce an acute inflammatory syndrome with huge intercellular communication disorders. This inflammatory syndrome evolves in two phases, separated by a latency phase. During the prodromal phase, the molecular and cellular lesions induced by free radicals trigger an initial response which associates cellular repair and multicellular interactions involving both humoral and nervous communications. A large part of perturbations constitute a non specific inflammatory syndrome and clinically silent coagulation disorders which are linked by common intercellular mediators. All these perturbations are rapidly reversible and there is no correlation between the radiation dose and the severity of the response. During the manifest-illness phase, both inflammatory and coagulation disorders resume, slightly preceding the clinical symptoms. Biochemical symptoms are moderate in the animals which will survive, but they escape regulatory mechanisms in those which will die, giving rise to a vicious circle. These biochemical disorders are largely responsible for the death. With lower dose rates, it cannot be excluded that great cellular communication disorders take place at the tissue level, with limited blood modifications. This aspect should be taken into account for the optimization of cytokine therapies. (authors)

  3. Radiation-induced adaptive response in the intact mouse

    International Nuclear Information System (INIS)

    Yonezawa, Morio

    2009-01-01

    The author and coworkers have revealed that radiation adaptive response (AR) is seen also in the bone marrow of the intact mouse, of which details are described here. First, SPF ICR mice were pre-irradiated (PI) with 0-0.1 Gy of X-ray and after 2 months, subsequently irradiated (SI) with 7.75 Gy. Survival rates at 30 days after SI were about 14% in mice with PI 0-0.025 Gy whereas 40% or more in animals with PI 0.05-0.1 Gy: bone marrow death was found significantly suppressed in this effective PI dose range. The death 2 weeks after SI was found also inhibited at PI 0.3-0.5 Gy. Second, PI doses and interval between PI and SI for acquiring the radio-resistance (RR) were studied and third, the PI 0.3-0.5 Gy with SI 8.0 Gy at 9-17 days later revealed that regional PI of the head (central nervous system) was found unnecessary for RR and of abdomen (systems of hemopoiesis, immunity and digestion), essential. Fourth, strain difference of RR was shown by the fact that RR was observed only in C57BL mouse as well, but neither in BALB/c nor C3H strain. Next, at 12 days after SI 4.25-6.75 Gy (PI 0.5 Gy at 14 days before), mouse spleen cells were subjected to colony formation analysis by counting the endogenous hemopoietic stem cells, which revealed that those cells were increased to about 5 times by PI. Suppression of SI-induced hemorrhage was found in mice with PI by the decreased fecal hemoglobin content. Finally, AR was similarly studied in p53 +/+ and its knockout C57BL mice and was not found in the latter animal, indicating the participation of p53 in AR of the intact mouse. Elucidation of AR mechanisms in the intact animal seems to require somewhat different aspect from that in cells. The results were controvertible to the general concept that radiation risk is proportional to cumulative dose, suggesting that low dose radiation differs from high dose one in biological effect. (K.T.)

  4. Theory of differential and integral scattering of laser radiation by a dielectric surface taking a defect layer into account

    NARCIS (Netherlands)

    Azarova, VV; Dmitriev, VG; Lokhov, YN; Malitskii, KN

    The differential and integral light scattering by dielectric surfaces is studied theoretically taking a thin nearsurface defect layer into account. The expressions for the intensities of differential and total integral scattering are found by the Green function method. Conditions are found under

  5. System of medical response to radiation emergency after a terror attack in China

    International Nuclear Information System (INIS)

    Liu, Y.; Wang, Z.

    2005-01-01

    Full text: Nuclear or radiological accident is an unintended or unexpected event occurring with a radiation source or during a practice involving ionizing radiation, which may result in significant human exposure and/or material damage. Recent events involving terrorist activities have focused attention on the radiological threats. The full spectrum of radiological threats from terrorist spans the deliberate dispersal of radioactive material to the detonation of a nuclear weapon. While the most likely threat is the dispersal of radioactive materials, the use of a crude nuclear weapon against a major city cannot be dismissed. Radiological incident response requires functions similar to non-radiological incident response. Radiation emergency system in China has been established for radiological emergency preparedness and response. National coordination committee of radiation emergency has been setup in 1994, which consist of 17 ministries. The ministry is responsible for the medical assistance for radiation emergency. Chinese Center for Medical Response to Radiation Emergency (CCMRRE) was established in 1992, based on the National Institute for Radiological Protection, China CDC (NIRP, China CDC). The CCMRRE has been as one liaison institutes of WHO/REMPAN and functions as a national and professional institute for medical assistance in radiation accidents and terrorist events involving radioactive material. Under Provincial Committee of Radiation Emergency, there are local organizations of medical assistance in radiation emergency. The organizations carry out the first aid, regional clinic treatment, radiation protection and radiation monitory in nuclear accidents and radiological accidents. (author)

  6. Study of radiation defects by in-situ measurements of the Hall effect in narrow-gap semiconductors

    International Nuclear Information System (INIS)

    Favre, J.

    1990-01-01

    Semiconducting compounds of II-VI, III-V and IV-VI groups were irradiated in liquid hydrogen by high energy (0.7 to 2.7 MeV) electrons. The Hall coefficient and resistivity variations were measured in situ during irradiation. The doping by irradiation induced defects is of p-type in III-V group compounds, while n-type doping occurs in II-VI and IV-VI group materials. A semiconductor to insulator or reverse transition was observed under irradiation when the chemical potential crossed the band edges. In IV-VI group compounds the two successive transitions take place in initially p-type samples. A metastable behaviour, characteristic to strong compensation, appears in the vicinity of those semiconductor - insulator transitions in IV-VI compounds. The slope of free carrier concentration vs. fluence variation was analyzed. It was compared to defect creation rates, calculated in the framework of a cascade model. The charge state of created defects was deduced in this way. - In IV-VI group compounds, the presence of localized levels degenerated with the conduction band and, in PbTe, of additional defect associated levels in the forbidden gap, was demonstrated. Those results are consistent with the saturation of electron concentration increase at high fluence as well as with the analysis of annealing experiments. - In Hg 1-x Cd x Te compounds, the analysis of electron concentration versus fluence increase indicates that only mercury Frenkel pairs are electrically active. The variation with cadmium content of the defect associated level energy was deduced from the saturation values of the electron concentration [fr

  7. Experimental response function of NaI(Tl) scintillation detector for gamma photons and tomographic measurements for defect detection

    International Nuclear Information System (INIS)

    Sharma, Amandeep; Singh, Karamjit; Singh, Bhajan; Sandhu, B.S.

    2011-01-01

    The response function of gamma detector is an important factor for spectrum analysis because some photons and secondary electrons may escape the detector volume before fully depositing their energy, of course destroys the ideal delta function response. An inverse matrix approach, for unfolding of observed pulse-height distribution to a true photon spectrum, is used for construction of experimental response function by formulating a 40 x 40 matrix with bin mesh (E 1/2 ) of 0.025 (MeV) 1/2 for the present measurements. A tomographic scanner system, operating in a non-destructive and non-invasive way, is also presented for inspection of density variation in any object. The incoherent scattered intensity of 662 keV gamma photons, obtained by unfolding (deconvolution) the experimental pulse-height distribution of NaI(Tl) scintillation detector, provides the desired information. The method is quite sensitive, for showing inclusion of medium Z (atomic number) material (iron) in low Z material (aluminium) and detecting a void of ∼2 mm in size for iron block, to investigate the inhomogeneities in the object. Also, the grey scale images (using 'MATLAB') are shown to visualise the presence of defects/inclusion in metal samples.

  8. Radiation Dose-Response Model for Locally Advanced Rectal Cancer After Preoperative Chemoradiation Therapy

    DEFF Research Database (Denmark)

    Appelt, A. L.; Ploen, J.; Vogelius, I. R.

    2013-01-01

    estimated radiation dose-response curves for various grades of tumor regression after preoperative CRT. Methods and Materials: A total of 222 patients, treated with consistent chemotherapy and radiation therapy techniques, were considered for the analysis. Radiation therapy consisted of a combination...... of external-beam radiation therapy and brachytherapy. Response at the time of operation was evaluated from the histopathologic specimen and graded on a 5-point scale (TRG1-5). The probability of achieving complete, major, and partial response was analyzed by ordinal logistic regression, and the effect...... of including clinical parameters in the model was examined. The radiation dose-response relationship for a specific grade of histopathologic tumor regression was parameterized in terms of the dose required for 50% response, D-50,D-i, and the normalized dose-response gradient, gamma(50,i). Results: A highly...

  9. Study by electronic structure calculations of the radiation damage in the UO2 nuclear fuel: behaviour of the point defects and fission gases

    International Nuclear Information System (INIS)

    Vathonne, Emerson

    2014-01-01

    Uranium dioxide (UO 2 ) is worldwide the most widely used fuel in nuclear plants in the world and in particular in pressurized water reactors (PWR). In-pile the fission of uranium nuclei creates fission products and point defects in the fuel. The understanding of the evolution of these radiation damages requires a multi-scale modelling approach of the nuclear fuel, from the scale of the pellet to the atomic scale. We used an electronic structure calculation method based on the density functional theory (DFT) to model radiation damage in UO 2 at the atomic scale. A Hubbard-type Coulomb interaction term is added to the standard DFT formalism to take into account the strong correlations of the 5f electrons in UO 2 . This method is used to study point defects with various charge states and the incorporation and diffusion of krypton in uranium dioxide. This study allowed us to obtain essential data for higher scale models but also to interpret experimental results. In parallel of this study, three ways to improve the state of the art of electronic structure calculations of UO 2 have been explored: the consideration of the spin-orbit coupling neglected in current point defect calculations, the application of functionals allowing one to take into account the non-local interactions such as van der Waals interactions important for rare gases and the use of the Dynamical Mean Field Theory combined to the DFT method in order to take into account the dynamical effects in the 5f electron correlations. (author) [fr

  10. Radiation response of spermatogonial stem cells in the mouse

    International Nuclear Information System (INIS)

    Bootsma, A.L.

    1978-01-01

    Spermatogonial stem cells are able to repopulate the testis by forming clones that elongate along the walls of the seminiferous tubules depleted of spermatogenetic cells as a result of an irradiation. The surviving number of stem cells after irradiation was estimated by determining the fraction of repopulated tubules in cross-sections of the testis 11 weeks after irradiation. This fraction, called the 'repopulation index', is assumed to be directly proportional to the number of surviving stem cells. The response of spermatogonial stem cells in the CBA mouse to 1-MeV fission neutrons was investigated. Radioresistant, colony forming stem cells in the mouse testis move into a much more radiosensitive phase of their cell cycle shortly after irradiation. This is demonstrated in publication II in experiments in which total doses of 300 rad of neutrons and 1200 rad of X-rays were split into two equal fractions. The radiation response of spermatogonial stem cells in the mouse which survived various doses of fission neutrons 24 hours before was studied in publication III. Twenty four hours after a dose of 150 rad of fission neutrons all first-dose survivors have moved from a radioresistant (D 0 89+-4 rad in this study) towards a radiosensitive phase of their cell cycle. Spermatogonial stem cells which survive a neutron dose of 150 rad all belong to a radioresistant stem cell population in the seminiferous epithelium. The data in publication IV show that during the first 26 days after a dose of 150 rad of neutrons the stem cell population first increases and then slowly decreases its radiosensitivity, to stay fixed at a relatively high level. (Auth.)

  11. Features of transformation of impurity-defect complexes in СdTe:Сl under the influence of microwave radiation

    Directory of Open Access Journals (Sweden)

    Budzulyak S. I.

    2014-08-01

    Full Text Available High-resistance cadmium telluride single crystals are promising material for production of ionizing radiation detectors. To increase crystal resistance, they are doped with chlorine. The detector quality depends on uniformity of chlorine impurity distribution over crystal. It is known that low-dose microwave irradiation can homogenize impurity distribution in a specimen. In the present work, we made an attempt to improve the detector material quality by using such post-technological treatment, as well as to study state variation for impurity-defect complexes. To this end, the effect of microwave irradiation on transformation of impurity-defect complexes in CdTe:Cl single crystals was investigated using low-temperature photoluminescence. It is shown that activation of ClTe donor centers by microwave irradiation for 10 s and presence of VCd acceptor centers in the specimens under investigation effectively facilitate formation of (VNd–ClTe defect centers at which excitons are bound. Detailed investigations of the band form for donor-acceptor pairs (DAPs in CdTe:Cl single crystals made it possible to determine the Huang—Rhys factor (that characterizes electron-phonon interaction in CdTe:Cl DAPs as a function of microwave treatment duration. It is shown for single crystals with NCl = 5·1017 cm–3 and 5·1019 cm–3 that the Huang—Rhys factor grows with microwave irradiation dose. This is related to both homogenization of donor and acceptor centers distribution and increase of donor—acceptor spacing. It is shown that microwave irradiation of CdTe:Cl single crystals results in concentration reduction for separate cadmium vacancies VCd because of formation of (VNd—ClTe defect centers at which excitons are bound.

  12. Radiation response of SiC-based fibers

    Energy Technology Data Exchange (ETDEWEB)

    Youngblood, G.E.; Jones, R.H. [Battelle Pacific Northwest Labs., Richland, WA (United States); Kohyama, A. [Inst. of Advanced Energy, Kyoto Univ. (Japan); Snead, L.L. [Oak Ridge National Lab., TN (United States)

    1998-10-01

    Loss of strength in irradiated fiber-reinforced SiC/SiC composite generally is related to degradation in the reinforcing fiber. To assess fiber degradation, the density and length changes were determined for four types of SiC-based fibers (Tyranno, Nicalon CG, Hi Nicalon and Dow X) after high temperature (up to 1000 C) and high dose (up to 80 dpa-SiC) irradiations. For the fibers with nonstoichiometric compositions (the first three types in the list), the fiber densities increased from 6% to 12%. In contrast, a slight decrease in density (<1%) was observed for the Dow X fiber with a quasi-stoichiometric composition. Fiber length changes (0-5.6% shrinkage) suggested small mass losses (1-6%) had occurred for irradiated uncoated fibers. In contrast, excessive linear shrinkage of the pyrocarbon-coated Nicalon CG and Tyranno fibers (7-9% and 16-32%, respectively) indicated that much larger mass losses (11-84%) had occurred for these coated fibers. Crystallization and crystal growth were observed to have taken place at fiber surfaces by SEM and in the bulk by XRD, moreso for irradiated Nicalon CG than for Hi Nicalon fiber. The radiation response of the quasi-stoichiometric Dow X fiber was the most promising. Further testing of this type fiber is recommended. (orig.) 11 refs.

  13. Adaptive response induced by occupational exposures to ionizing radiation

    International Nuclear Information System (INIS)

    Barquinero, J.F.; Caballin, M.R.; Barrios, L.; Egozcue, J.; Miro, R.; Ribas, M.

    1997-01-01

    We have found a significant decreased sensitivity to the cytogenetic effects of both ionizing radiation (IR) (2 Gy of γ rays) and bleomycin (BLM, 0,03 U/ml), in lymphocytes from individuals occupationally exposed to IR when compared with controls. These results suggest that occupational exposures to IR can induce adaptive response that can be detected by a subsequent treatment either by IR or by BLM. When a comparison is made between the cytogenetic effects of both treatments, no correlation was observed at the individual level. On the other hand, the individual frequencies of chromosome aberrations induced by a challenge dose of IR were negatively correlated with the occupationally received doses during the last three years. This correlation was not observed after the challenge treatment of BLM. Moreover, the individual frequencies of chromosome aberrations induced by IR treatment were homogeneous. This is not the case of the individual frequencies of chromatid aberrations induced by BLM, where a great heterogeneity was observed. (authors)

  14. Response of a forest ecotone to ionizing radiation

    International Nuclear Information System (INIS)

    Murphy, P.G.; Sharitz, R.R.; Murphy, A.J.

    1977-01-01

    Compositional and structural characteristics of a forest ecotone in northern Wisconsin, including aspen and maple-birch forest types and the intervening midecotone, were studied before and after irradiation. Irradiation occurred during the summer of 1972. By the summer of 1973, the density of viable tree seedlings at 10 m from the radiation source was substantially reduced in all three areas relative to the preirradiation densities of 1971. As of 1975, reestablishment of tree seedlings had been prevented by the vigorous development of ground vegetation at 10 m. At 20 m, the density of seedlings in the three areas increased during the period between 1971 and 1973 in response to the partially opened canopy. The overall density of seedlings of Populus tremuloides and Acer rubrum increased markedly in the three areas, and P. tremuloides invaded some areas in which it had not been found before irradiation. By 1974 many of the seedlings at 20 m had reached the sapling size class. Viable trees greater than 2.5 cm dbh were eliminated at 10 m in all three areas by June 1974 and were reduced in density at 20 m. Leaf-litter production was reduced by up to 92 percent at 10 m and 62 percent at 20 m during the period between 1971 and 1973 in the irradiated areas. The reduction was greatest in the aspen area. Leaf-litter reduction in the midecotone and maple-birch areas was less severe, averaging 50 percent at 10 m and 24 percent at 20 m

  15. Chromatin modifications and the DNA damage response to ionizing radiation

    International Nuclear Information System (INIS)

    Kumar, Rakesh; Horikoshi, Nobuo; Singh, Mayank; Gupta, Arun; Misra, Hari S.; Albuquerque, Kevin; Hunt, Clayton R.; Pandita, Tej K.

    2013-01-01

    In order to survive, cells have evolved highly effective repair mechanisms to deal with the potentially lethal DNA damage produced by exposure to endogenous as well as exogenous agents. Ionizing radiation exposure induces highly lethal DNA damage, especially DNA double-strand breaks (DSBs), that is sensed by the cellular machinery and then subsequently repaired by either of two different DSB repair mechanisms: (1) non-homologous end joining, which re-ligates the broken ends of the DNA and (2) homologous recombination, that employs an undamaged identical DNA sequence as a template, to maintain the fidelity of DNA repair. Repair of DSBs must occur within the natural context of the cellular DNA which, along with specific proteins, is organized to form chromatin, the overall structure of which can impede DNA damage site access by repair proteins. The chromatin complex is a dynamic structure and is known to change as required for ongoing cellular processes such as gene transcription or DNA replication. Similarly, during the process of DNA damage sensing and repair, chromatin needs to undergo several changes in order to facilitate accessibility of the repair machinery. Cells utilize several factors to modify the chromatin in order to locally open up the structure to reveal the underlying DNA sequence but post-translational modification of the histone components is one of the primary mechanisms. In this review, we will summarize chromatin modifications by the respective chromatin modifying factors that occur during the DNA damage response.

  16. Defective awakening response to nocturnal hypoglycemia in patients with type 1 diabetes mellitus.

    Directory of Open Access Journals (Sweden)

    Bernd Schultes

    2007-02-01

    Full Text Available BACKGROUND: Nocturnal hypoglycemia frequently occurs in patients with type 1 diabetes mellitus (T1DM. It can be fatal and is believed to promote the development of the hypoglycemia-unawareness syndrome. Whether hypoglycemia normally provokes awakening from sleep in individuals who do not have diabetes, and whether this awakening response is impaired in T1DM patients, is unknown. METHODS AND FINDINGS: We tested two groups of 16 T1DM patients and 16 healthy control participants, respectively, with comparable distributions of gender, age, and body mass index. In one night, a linear fall in plasma glucose to nadir levels of 2.2 mmol/l was induced by infusing insulin over a 1-h period starting as soon as polysomnographic recordings indicated that stage 2 sleep had been reached. In another night (control, euglycemia was maintained. Only one of the 16 T1DM patients, as compared to ten healthy control participants, awakened upon hypoglycemia (p = 0.001. In the control nights, none of the study participants in either of the two groups awakened during the corresponding time. Awakening during hypoglycemia was associated with increased hormonal counterregulation. In all the study participants (from both groups who woke up, and in five of the study participants who did not awaken (three T1DM patients and two healthy control participants, plasma epinephrine concentration increased with hypoglycemia by at least 100% (p < 0.001. A temporal pattern was revealed such that increases in epinephrine in all participants who awakened started always before polysomnographic signs of wakefulness (mean +/- standard error of the mean: 7.5 +/- 1.6 min. CONCLUSIONS: A fall in plasma glucose to 2.2 mmol/l provokes an awakening response in most healthy control participants, but this response is impaired in T1DM patients. The counterregulatory increase in plasma epinephrine that we observed to precede awakening suggests that awakening forms part of a central nervous system

  17. Frustrated magnetic response of a superconducting Nb film with a square lattice of columnar defects

    Energy Technology Data Exchange (ETDEWEB)

    Zadorosny, R; Ortiz, W A [Grupo de Supercondutividade e Magnetismo, Departamento de Fisica, Universidade Federal de Sao Carlos, Sao Carlos, SP (Brazil); Lepienski, C M [Universidade Federal do Parana, Departamento de Fisica, Curitiba, PR (Brazil); Patino, E; Blamire, M G [Department of Materials Science, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom)], E-mail: rafazad@df.ufscar.br

    2008-02-01

    The magnetic response of a superconducting system presenting a frustrated state is investigated. The system is a superconducting film with mechanically pierced columns, cooled in a field which is then removed. Frustration originates from the competition between return flux of a dipole - created by flux trapped in the empty columns - and flux exclusion by the surrounding superconductor in the Meissner state. The system resolves the incompatibility among conflicting constraints, leading to frustration, by eliminating return flux, which is possibly assimilated by nearby columns, as manifested by a sudden reduction of the magnetic moment on the decreasing field branch of the hysteresis loop.

  18. Frustrated magnetic response of a superconducting Nb film with a square lattice of columnar defects

    International Nuclear Information System (INIS)

    Zadorosny, R; Ortiz, W A; Lepienski, C M; Patino, E; Blamire, M G

    2008-01-01

    The magnetic response of a superconducting system presenting a frustrated state is investigated. The system is a superconducting film with mechanically pierced columns, cooled in a field which is then removed. Frustration originates from the competition between return flux of a dipole - created by flux trapped in the empty columns - and flux exclusion by the surrounding superconductor in the Meissner state. The system resolves the incompatibility among conflicting constraints, leading to frustration, by eliminating return flux, which is possibly assimilated by nearby columns, as manifested by a sudden reduction of the magnetic moment on the decreasing field branch of the hysteresis loop

  19. Deficient innate immunity, thymopoiesis, and gene expression response to radiation in survivors of childhood acute lymphoblastic leukemia.

    Science.gov (United States)

    Leung, Wing; Neale, Geoffrey; Behm, Fred; Iyengar, Rekha; Finkelstein, David; Kastan, Michael B; Pui, Ching-Hon

    2010-06-01

    Survivors of childhood acute lymphoblastic leukemia (ALL) are at an increased risk of developing secondary malignant neoplasms. Radiation and chemotherapy can cause mutations and cytogenetic abnormalities and induce genomic instability. Host immunity and appropriate DNA damage responses are critical inhibitors of carcinogenesis. Therefore, we sought to determine the long-term effects of ALL treatment on immune function and response to DNA damage. Comparative studies on 14 survivors in first complete remission and 16 siblings were conducted. In comparison to siblings on the cells that were involved in adaptive immunity, the patients had either higher numbers (CD19+ B cells and CD4+CD25+ T regulatory cells) or similar numbers (alphabetaT cells and CD45RO+/RA- memory T cells) in the blood. In contrast, patients had lower numbers of all lymphocyte subsets involved in innate immunity (gammadeltaT cells and all NK subsets, including KIR2DL1+ cells, KIR2DL2/L3+ cells, and CD16+ cells), and lower natural cytotoxicity against K562 leukemia cells. Thymopoiesis was lower in patients, as demonstrated by less CD45RO-/RA+ naïve T cell and less SjTREC levels in the blood, whereas the Vbeta spectratype complexity score was similar. Array of gene expression response to low-dose radiation showed that about 70% of the probesets had a reduced response in patients. One of these genes, SCHIP-1, was also among the top-ranked single nucleotide polymorphisms (SNPs) during the whole-genome scanning by SNP microarray analysis. ALL survivors were deficient in innate immunity, thymopoiesis, and DNA damage responses to radiation. These defects may contribute to their increased likelihood of second malignancy. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

  20. Ultraviolet radiation response of two heterotropy Antarctic marine bacterial

    International Nuclear Information System (INIS)

    Hernandez, Edgardo A.; Ferreyra, Gustavo A.; Mac Cormack, Walter P.

    2004-01-01

    Two Antarctic marine bacterial strains, were exposed to different irradiance of ultraviolet (UV) solar radiation using several experimental protocols and interferential filters. Results showed that both, UV-A and UV-B radiation produce deleterious effects on two tested bacterial strains. The mortality values under UVB treatments were higher than those observed under UVA treatments. UVvi strain proved to be more resistant to UV radiation than the UVps strain. (author) [es

  1. Epigenetic cell response to an influence of ionizing radiation

    International Nuclear Information System (INIS)

    Mikheev, A.N.; Gushcha, N.I.; Malinovskij, Yu.Yu.

    1999-01-01

    Importance of radiation modification of epigenetic activity in the general mechanism of radiobiological reactions is proved. Inheritable epigenetic changes induced by irradiation are one of the basic reasons of formation of the remote radiation pathology. It is noted that epigenetic inheritable changes of cells have the determined character distinguishing them mutation changes, being individual and not directed. It is underlined the ability of ionizing radiation to modify level of spontaneous genetic instability inherited in a number of cell generations on epigenetic mechanism [ru

  2. Radiation-Induced Bystander Response: Mechanism and Clinical Implications

    OpenAIRE

    Suzuki, Keiji; Yamashita, Shunichi

    2014-01-01

    Significance: Absorption of energy from ionizing radiation (IR) to the genetic material in the cell gives rise to damage to DNA in a dose-dependent manner. There are two types of DNA damage; by a high dose (causing acute or deterministic effects) and by a low dose (related to chronic or stochastic effects), both of which induce different health effects. Among radiation effects, acute cutaneous radiation syndrome results from cell killing as a consequence of high-dose exposure.

  3. Defective thymine dimer excision in radiation-sensitive mutants rad10 and rad16 of Saccharomyces cerevisiae

    Energy Technology Data Exchange (ETDEWEB)

    Prakash, L [Rochester Univ., N.Y. (USA). School of Medicine and Dentistry

    1977-04-01

    Two rad mutants of yeast, rad10 and rad16, are shown to be defective in the removal of UV-induced pyrimidine dimers since DNAs obtained from irradiated cells following a post-irradiation incubation in the dark still retain UV-endonuclease-sensitive sites. Both rad10 and rad16 mutants are in the same pathway of excision-repair as the rad1, rad2, rad3, and rad4 mutants.

  4. Birth Defects

    Science.gov (United States)

    A birth defect is a problem that happens while a baby is developing in the mother's body. Most birth defects happen during the first 3 months of ... in the United States is born with a birth defect. A birth defect may affect how the ...

  5. Response of hematopoietic stem cells to ionizing radiation

    International Nuclear Information System (INIS)

    Simonnet, A.

    2008-12-01

    Hematopoietic stem cells (HSCs) maintain blood and immune system throughout life and restore them after hematological injuries. Exposure of an organism to ionizing radiation (IR) causes rapid and acute myelosuppression and challenges the replenishment capacity of HSCs. Yet, the precise damages that are generated remain largely unexplored. To better understand these effects, phenotypic and functional changes in the stem/progenitor compartments of sublethally irradiated mice were monitored over a ten week period after radiation exposure. We report that shortly after sublethal IR-exposure, HSCs, defined by their repopulating ability, still segregate in the Hoechst dye excluding side population (SP); yet, their Sca-1 (S) and c-Kit (K) expression levels are increased and severely reduced, respectively, with a concurrent increase in the proportion of SP SK cells positive for established indicators of HSC presence: CD150 + and CD105 + . A great proportion of HSCs quickly but transiently enter the cell cycle to replenish the bone marrow of myelo-ablated mice. Ten weeks after, whereas bone marrow cellularity has recovered and hematopoietic homeostasis is restored, major phenotypic modifications can be observed within the Lin -/low Sca-1 + c-Kit + (LSK) stem/progenitor compartment: CD150 + /Flk2 - and CD150 - /Flk2 + LSK cell frequencies are increased and dramatically reduced, respectively. CD150 + LSK cells also show impaired reconstitution capacity, accrued number of γ-H2AX foci and increased tendency to apoptosis. This demonstrates that the LSK compartment is not properly restored 10 weeks after sublethal exposure, and that long-term IR-induced injury to the bone marrow proceeds, at least partially, through direct damage to the stem cell pool. Thrombopoietin (TPO) has been shown to promote the survival of lethally irradiated mice when administrated quickly after exposure. We investigated the mechanisms underlying this effect, and found in a competitive transplant

  6. Scleroderma dermal microvascular endothelial cells exhibit defective response to pro-angiogenic chemokines

    Science.gov (United States)

    Rabquer, Bradley J.; Ohara, Ray A.; Stinson, William A.; Campbell, Phillip L.; Amin, M. Asif; Balogh, Beatrix; Zakhem, George; Renauer, Paul A.; Lozier, Ann; Arasu, Eshwar; Haines, G. Kenneth; Kahaleh, Bashar; Schiopu, Elena; Khanna, Dinesh; Koch, Alisa E.

    2016-01-01

    Objectives. Angiogenesis plays a critical role in SSc (scleroderma). The aim of this study was to examine the expression of growth-regulated protein-γ (Gro-γ/CXCL3), granulocyte chemotactic protein 2 (GCP-2/CXCL6) and their receptor CXCR2 in endothelial cells (ECs) isolated from SSc skin and determine whether these cells mount an angiogenic response towards pro-angiogenic chemokines. The downstream signalling pathways as well as the pro-angiogenic transcription factor inhibitor of DNA-binding protein 1 (Id-1) were also examined. Methods. Skin biopsies were obtained from patients with dcSSc. ECs were isolated via magnetic positive selection. Angiogenesis was measured by EC chemotaxis assay. Results. Gro-γ/CXCL3 and GCP-2/CXCL6 were minimally expressed in both skin types but elevated in SSc serum. Pro-angiogenic chemokine mRNA was greater in SSc ECs than in normal ECs. SSc ECs did not migrate to vascular endothelial growth factor (VEGF), Gro-γ/CXCL3, GCP-2/CXCL6 or CXCL16. The signalling pathways stimulated by these chemokines were also dysregulated. Id-1 mRNA in SSc ECs was lower compared with normal ECs, and overexpression of Id-1 in SSc ECs increased their ability to migrate towards VEGF and CXCL16. Conclusion. Our results show that SSc ECs are unable to respond to pro-angiogenic chemokines despite their increased expression in serum and ECs. This might be due to the differences in the signalling pathways activated by these chemokines in normal vs SSc ECs. In addition, the lower expression of Id-1 also decreases the angiogenic response. The inability of pro-angiogenic chemokines to promote EC migration provides an additional mechanism for the impaired angiogenesis that characterizes SSc. PMID:26705326

  7. SU-E-J-274: Responses of Medulloblastoma Cells to Radiation Dosimetric Parameters in Intensity-Modulated Radiation Therapy

    International Nuclear Information System (INIS)

    Park, J; Park, J; Rogalla, S; Contag, C; Woo, D; Lee, D; Park, H; Suh, T

    2015-01-01

    Purpose: To evaluate radiation responses of the medulloblastoma cell line Daoy in intensity-modulated radiation therapy (IMRT), quantitative variations to variable radiation dosimetic parameters were tracked by bioluminescent images (BLIs). Methods: The luciferase and green fluorescent protein positive Daoy cells were cultured on dishes. The medulloblastoma cells irradiated to different dose rate, interval of fractionated doses, field margin and misalignment, and dose uniformity in IMRT were monitored using bioluminescent images. The cultured cells were placed into a dedicated acrylic phantom to deliver intensity-modulated fluences and calculate accurate predicted dose distribution. The radiation with dose rate from 0.5 Gy/min to 15 Gy/min was irradiated by adjusting monitor unit per minute and source-to-surface distances. The intervals of fractionated dose delivery were changed considering the repair time of double strand breaks (DSB) revealed by straining of gamma-H2AX.The effect of non-uniform doses on the cells were visualized by registering dose distributions and BLIs. The viability according to dosimetric parameters was correlated with bioluminescent intensities for cross-check of radiation responses. Results: The DSB and cell responses due to the first fractionated dose delivery significantly affected final tumor control rather than other parameters. The missing tumor volumes due to the smaller field margin than the tumor periphery or field misalignment caused relapse of cell responses on BLIs. The dose rate and gradient had effect on initial responses but could not bring out the distinguishable killing effect on cancer cells. Conclusion: Visualized and quantified bioluminescent images were useful to correlate the dose distributions with spatial radiation effects on cells. This would derive the effective combination of dose delivery parameters and fractionation. Radiation responses in particular IMRT configuration could be reflected to image based-dose re-optimization

  8. Epididymis response partly compensates for spermatozoa oxidative defects in snGPx4 and GPx5 double mutant mice.

    Directory of Open Access Journals (Sweden)

    Anaïs Noblanc

    Full Text Available We report here that spermatozoa of mice lacking both the sperm nucleus glutathione peroxidase 4 (snGPx4 and the epididymal glutathione peroxidase 5 (GPx5 activities display sperm nucleus structural abnormalities including delayed and defective nuclear compaction, nuclear instability and DNA damage. We show that to counteract the GPx activity losses, the epididymis of the double KO animals mounted an antioxydant response resulting in a strong increase in the global H(2O(2-scavenger activity especially in the cauda epididymis. Quantitative RT-PCR data show that together with the up-regulation of epididymal scavengers (of the thioredoxin/peroxiredoxin system as well as glutathione-S-transferases the epididymis of double mutant animals increased the expression of several disulfide isomerases in an attempt to recover normal disulfide-bridging activity. Despite these compensatory mechanisms cauda-stored spermatozoa of double mutant animals show high levels of DNA oxidation, increased fragmentation and greater susceptibility to nuclear decondensation. Nevertheless, the enzymatic epididymal salvage response is sufficient to maintain full fertility of double KO males whatever their age, crossed with young WT female mice.

  9. Radiation response of two Harris semiconductor radiation hardened 1k CMOS RAMs

    International Nuclear Information System (INIS)

    Abare, W.E.; Huffman, D.D.; Moffett, G.E.

    1982-01-01

    This paper describes the testing of two types 1K CMOS static RAMs in various transient and steady state ionizing radiation environments. Type HM 6551R (256x4 bits) and type HM 6508R (1024x1 bit) RAMs were evaluated. The RAMs are radiation hardened versions of Harris' commercial RAMs. A brief description of the radiation hardened process is presented

  10. Effect of random inhomogeneities in the spatial distribution of radiation-induced defect clusters on carrier transport through the thin base of a heterojunction bipolar transistor upon neutron irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Puzanov, A. S.; Obolenskiy, S. V., E-mail: obolensk@rf.unn.ru; Kozlov, V. A. [Lobachevsky State University of Nizhny Novgorod (NNSU) (Russian Federation)

    2016-12-15

    We analyze the electron transport through the thin base of a GaAs heterojunction bipolar transistor with regard to fluctuations in the spatial distribution of defect clusters induced by irradiation with a fissionspectrum fast neutron flux. We theoretically demonstrate that the homogeneous filling of the working region with radiation-induced defect clusters causes minimum degradation of the dc gain of the heterojunction bipolar transistor.

  11. The response of thrombosis in the portal vein or hepatic vein in hepatocellular carcinoma to radiation therapy

    Energy Technology Data Exchange (ETDEWEB)

    Bae, Bong Kyung; Kim, Jae Chul [Dept. of Radiation Oncology, Kyungpook National University School of Medicine, Daegu (Korea, Republic of)

    2016-09-15

    The purpose of current study is to evaluate the response of the patients with portal vein thrombosis (PVT) or hepatic vein thrombosis (HVT) in hepatocellular carcinoma (HCC) treated with three-dimensional conformal radiation therapy (3D-CRT). In addition, survival of patients and potential prognostic factors of the survival was evaluated. Forty-seven patients with PVT or HVT in HCC, referred to our department for radiotherapy, were retrospectively reviewed. For 3D-CRT plans, a gross tumor volume (GTV) was defined as a hypodense filling defect area in the portal vein (PV) or hepatic vein (HV). Survival of patients, and response to radiation therapy (RT) were analyzed. Potential prognostic factors for survival and response to RT were evaluated. The median survival time of 47 patients was 8 months, with 1-year survival rate of 15% and response rate of 40%. Changes in Child-Pugh score, response to RT, Eastern cooperative oncology group performance status (ECOG PS), hepatitis C antibody (HCVAb) positivity, and additional post RT treatment were statistically significant prognostic factors for survival in univariate analysis (p = 0.000, p = 0.018, p = 0.000, p = 0.013, and p = 0.047, respectively). Of these factors, changes in Child-Pugh score, and response to RT were significant for patients' prognosis in multivariate analysis (p = 0.001 and p = 0.035, respectively). RT could constitute a reasonable treatment option for patients with PVT or HVT in HCC with acceptable toxicity. Changes in Child-Pugh score, and response to RT were statistically significant factors of survival of patients.

  12. Estimating the risks of cancer mortality and genetic defects resulting from exposures to low levels of ionizing radiation

    International Nuclear Information System (INIS)

    Buhl, T.E.; Hansen, W.R.

    1984-05-01

    Estimators for calculating the risk of cancer and genetic disorders induced by exposure to ionizing radiation have been recommended by the US National Academy of Sciences Committee on the Biological Effects of Ionizing Radiations, the UN Scientific Committee on the Effects of Atomic Radiation, and the International Committee on Radiological Protection. These groups have also considered the risks of somatic effects other than cancer. The US National Council on Radiation Protection and Measurements has discussed risk estimate procedures for radiation-induced health effects. The recommendations of these national and international advisory committees are summarized and compared in this report. Based on this review, two procedures for risk estimation are presented for use in radiological assessments performed by the US Department of Energy under the National Environmental Policy Act of 1969 (NEPA). In the first procedure, age- and sex-averaged risk estimators calculated with US average demographic statistics would be used with estimates of radiation dose to calculate the projected risk of cancer and genetic disorders that would result from the operation being reviewed under NEPA. If more site-specific risk estimators are needed, and the demographic information is available, a second procedure is described that would involve direct calculation of the risk estimators using recommended risk-rate factors. The computer program REPCAL has been written to perform this calculation and is described in this report. 25 references, 16 tables

  13. Estimating the risks of cancer mortality and genetic defects resulting from exposures to low levels of ionizing radiation

    Energy Technology Data Exchange (ETDEWEB)

    Buhl, T.E.; Hansen, W.R.

    1984-05-01

    Estimators for calculating the risk of cancer and genetic disorders induced by exposure to ionizing radiation have been recommended by the US National Academy of Sciences Committee on the Biological Effects of Ionizing Radiations, the UN Scientific Committee on the Effects of Atomic Radiation, and the International Committee on Radiological Protection. These groups have also considered the risks of somatic effects other than cancer. The US National Council on Radiation Protection and Measurements has discussed risk estimate procedures for radiation-induced health effects. The recommendations of these national and international advisory committees are summarized and compared in this report. Based on this review, two procedures for risk estimation are presented for use in radiological assessments performed by the US Department of Energy under the National Environmental Policy Act of 1969 (NEPA). In the first procedure, age- and sex-averaged risk estimators calculated with US average demographic statistics would be used with estimates of radiation dose to calculate the projected risk of cancer and genetic disorders that would result from the operation being reviewed under NEPA. If more site-specific risk estimators are needed, and the demographic information is available, a second procedure is described that would involve direct calculation of the risk estimators using recommended risk-rate factors. The computer program REPCAL has been written to perform this calculation and is described in this report. 25 references, 16 tables.

  14. Ionizing radiation causes the stress response in Drosophila melanogaster

    International Nuclear Information System (INIS)

    Gruntenko, N.E.; Zakharenko, L.P.; Raushenbakh, I.Yu.

    1998-01-01

    Potentiality of the stress-reaction arising in Drosophila melanogaster under gamma-irradiation of the source with 137 Cs (irradiation dose is 10 Gy , radiation dose rate amounts 180 c Gy/min) is studied. It is shown that radiation induces the stress-reaction in Drosophila resulting in alterations in energetic metabolism (biogenic amines metabolic system) and in reproductive function [ru

  15. Responses to the low-level-radiation controversy

    International Nuclear Information System (INIS)

    Bond, V.P.

    1981-01-01

    Some data sets dealing with the hazards of low-level radiation are discussed. It is concluded that none of these reports, individually or collectively, changes appreciably or even significantly the evaluations of possible low-level radiation effects that have been made by several authoritative national and international groups

  16. Problems of medical personnel deontology during radiation emergency response

    International Nuclear Information System (INIS)

    Poplavskij, K.K.; Popov, A.O.

    1990-01-01

    Problems of deontology in the process of liquidation of radiation accident consequences are considered in the article. It is noted, that shortages of ethical nature in the activities of physicians are related to insufficient qualification of medical personnel in the area of radiation medicine. Problems of medical personnel participation in the large scale propaganda activities among various groups of population are considered. 5 refs

  17. Radiation-induced adaptive response in human lymphoblast

    International Nuclear Information System (INIS)

    Yatagai, Fumio; Sugasawa, Kaoru

    2009-01-01

    Described are the genetic analysis of variant strains obtained by the optimal condition for radiation-induced adaptive response (AR), and molecular elucidation of the suppression of concomitant mutation. The TK6 cells (heterozygous thymidine kinase, +/-) were used for detection of mutation by loss of heterozygosity (LOH). The optimal conditions for reducing the mutation by subsequent irradiation (SI) to its rate of about 60% (vs control 100%, no PI) were found to be 5 cGy of pre-irradiation (PI) of X-ray and 2 Gy of SI with the interval of 6 hr, where mutated cells were of non-LOH type in around 25% and homo-LOH type by homologous recombination (HR) in 60%. By cDNA sequencing, the former cells having changed bases were found to be in variant strain ratio of 1/8 vs control 7/18, suggesting that the mutation was decreased mainly by suppression of base change. Expression of XPC protein, an important component for recognition of the base damage in global genome nucleotide excision repair, was studied by Western blotting as the possible mechanism of suppressing the mutation, which revealed different time dynamics of the protein in cells with PI+SI and SI alone (control). To see the effect of PI on the double strand break (DSB) repair, cells with PI were infected with restriction enzyme I-SceI vector to yield DSB instead of SI, which revealed more efficient repair (70% increase) by HR than control, without significant difference in non-homologous end-joining repair. Micro-array analysis to study the gene expression in the present experimental conditions for AR is in progress. The TK6 cells used here were thought useful for additional studies of the mechanism of AR as mutation by direct or indirect irradiation can be tested. (K.T.)

  18. Elastic and failure response of imperfect three-dimensional metallic lattices: the role of geometric defects induced by Selective Laser Melting

    Science.gov (United States)

    Liu, Lu; Kamm, Paul; García-Moreno, Francisco; Banhart, John; Pasini, Damiano

    2017-10-01

    This paper examines three-dimensional metallic lattices with regular octet and rhombicuboctahedron units fabricated with geometric imperfections via Selective Laser Sintering. We use X-ray computed tomography to capture morphology, location, and distribution of process-induced defects with the aim of studying their role in the elastic response, damage initiation, and failure evolution under quasi-static compression. Testing results from in-situ compression tomography show that each lattice exhibits a distinct failure mechanism that is governed not only by cell topology but also by geometric defects induced by additive manufacturing. Extracted from X-ray tomography images, the statistical distributions of three sets of defects, namely strut waviness, strut thickness variation, and strut oversizing, are used to develop numerical models of statistically representative lattices with imperfect geometry. Elastic and failure responses are predicted within 10% agreement from the experimental data. In addition, a computational study is presented to shed light into the relationship between the amplitude of selected defects and the reduction of elastic properties compared to their nominal values. The evolution of failure mechanisms is also explained with respect to strut oversizing, a parameter that can critically cause failure mode transitions that are not visible in defect-free lattices.

  19. Apoptosis-related molecules and radiation response in human oral cancers

    International Nuclear Information System (INIS)

    Teni, Tanuja; Mallick, Sanchita; Palve, Vinayak; Yasser, Mohd; Pawar, Sagar; Kannan, Sadhana; Agarwal, Jai Prakash; Kane, Shubhada

    2013-01-01

    The ability of the tumor cells to respond to radiotherapy depends upon their intrinsic radiosensitivity, which may be partly governed by molecules of the intrinsic cell death pathway. To identify the defects in this pathway in oral cancers, transcript expression analysis of the pathway members was done using the Ribonuclease protection assay in oral cell lines and tumors. The intrinsic apoptosis pathway was found to be deregulated in oral cell lines and majority of oral tumors with altered expression of Mcl-l, bclxl, survivin, p53 and p16 mRNA. To identify factors associated with radiosensitivity, differential gene expression profiles of radiation-treated versus untreated oral cell lines of differing radiosensitivities was carried out. To assess the predictive value of above altered molecules in radiotherapy outcome in oral cancer patients, pretreated biopsies from thirty nine oral cancer patients were examined for the expression of the apoptotic markers using immunohistochemistry and their expression was correlated with the clinico pathological parameters. High expression of Mcl-1 (p = 0.05) and PCNA (p = 0.007) was seen to be associated with poor disease free survival. High expression of Bcl-xL was associated with poor response to radiotherapy treatment. PCNA (p=0.04) and Mcl-1 (p=0.05) emerged as independent prognostic markers for predicting disease free survival in oral cancers treated with primary radiotherapy. A predominant overexpression of anti-apoptotic Mcl-1L over pro-apoptotic Mcl-1S isoform was observed in the oral cancer cell lines and oral tumors. An inverse correlation was observed between Mcl-1L expression and apoptosis induction in AW8507 cell line post-radiation treatment supporting its pro-survival role. A rapid and short induction of Mcl-1L versus sustained induction of Mcl-1L was observed in the relatively more radiosensitive FBM versus AW8507 respectively. siRNA treatment in combination with IR demonstrated significant induction of apoptosis

  20. Dual responsive promoters to target therapeutic gene expression to radiation-resistant hypoxic tumor cells

    International Nuclear Information System (INIS)

    Chadderton, Naomi; Cowen, Rachel L.; Sheppard, Freda C.D.; Robinson, Suzanne; Greco, Olga; Scott, Simon D.; Stratford, Ian J.; Patterson, Adam V.; Williams, Kaye J.

    2005-01-01

    Purpose: Tumor hypoxia is unequivocally linked to poor radiotherapy outcome. This study aimed to identify enhancer sequences that respond maximally to a combination of radiation and hypoxia for use in genetic radiotherapy approaches. Methods and materials: The influence of radiation (5 Gy) and hypoxia (1% O 2 ) on reporter-gene expression driven by hypoxia (HRE) and radiation (Egr-1) responsive elements was evaluated in tumor cells grown as monolayers or multicellular spheroids. Hypoxia-inducible factor-1α (HIF-1α) and HIF-2α protein expression was monitored in parallel. Results: Of the sequences tested, an HRE from the phosphoglycerate kinase-1 gene (PGK-18[5+]) was maximally induced in response to hypoxia plus radiation in all 5 cell lines tested. The additional radiation treatment afforded a significant increase in the induction of PGK-18[5+] compared with hypoxia alone in 3 cell lines. HIF-1α/2α were induced by radiation but combined hypoxia/radiation treatment did not yield a further increase. The dual responsive nature of HREs was maintained when spheroids were irradiated after delivery of HRE constructs in a replication-deficient adenovirus. Conclusions: Hypoxia-responsive enhancer element sequences are dually responsive to combined radiation and hypoxic treatment. Their use in genetic radiotherapy in vivo could maximize expression in the most radio-resistant population at the time of radiation and also exploit microenvironmental changes after radiotherapy to yield additional switch-on

  1. Deletion of Nhlh2 results in a defective torpor response and reduced Beta adrenergic receptor expression in adipose tissue.

    Directory of Open Access Journals (Sweden)

    Umesh D Wankhade

    2010-08-01

    Full Text Available Mice with a targeted deletion of the basic helix-loop-helix transcription factor, Nescient Helix-Loop-Helix 2 (Nhlh2, display adult-onset obesity with significant increases in their fat depots, abnormal responses to cold exposure, and reduced spontaneous physical activity levels. These phenotypes, accompanied by the hypothalamic expression of Nhlh2, make the Nhlh2 knockout (N2KO mouse a useful model to study the role of central nervous system (CNS control on peripheral tissue such as adipose tissue.Differences in body temperature and serum analysis of leptin were performed in fasted and ad lib fed wild-type (WT and N2KO mice. Histological analysis of white (WAT and brown adipose tissue (BAT was performed. Gene and protein level expression of inflammatory and metabolic markers were compared between the two genotypes.We report significant differences in serum leptin levels and body temperature in N2KO mice compared with WT mice exposed to a 24-hour fast, suggestive of a defect in both white (WAT and brown adipose tissue (BAT function. As compared to WT mice, N2KO mice showed increased serum IL-6 protein and WAT IL-6 mRNA levels. This was accompanied by slight elevations of mRNA for several macrophage markers, including expression of macrophage specific protein F4/80 in adipose, suggestive of macrophage infiltration of WAT in the mutant animals. The mRNAs for beta3-adrenergic receptors (beta3-AR, beta2-AR and uncoupling proteins were significantly reduced in WAT and BAT from N2KO mice compared with WT mice.These studies implicate Nhlh2 in the central control of WAT and BAT function, with lack of Nhlh2 leading to adipose inflammation and altered gene expression, impaired leptin response to fasting, all suggestive of a deficient torpor response in mutant animals.

  2. The comparison of gamma-radiation and electrical stress influences on oxide and interface defects in power VDMOSFET

    Directory of Open Access Journals (Sweden)

    Đorić-Veljković Snežana M.

    2013-01-01

    Full Text Available The behaviour of oxide and interface defects in n-channel power vertical double-diffused metal-oxide-semiconductor field-effect transistors, firstly degraded by the gamma-irradiation and electric field and subsequently recovered and annealed, is presented. By analyzing the transfer characteristic shifts, the changes of threshold voltage and underlying changes of gate oxide and interface trap densities during the stress (recovery, annealing of investigated devices, it is shown that these two types of stress influence differently on the gate oxide and the SiO2-Si interface. [Projekat Ministarstva nauke Republike Srbije, br. OI171026

  3. Preoperative Single-Fraction Partial Breast Radiation Therapy: A Novel Phase 1, Dose-Escalation Protocol With Radiation Response Biomarkers

    International Nuclear Information System (INIS)

    Horton, Janet K.; Blitzblau, Rachel C.; Yoo, Sua; Geradts, Joseph; Chang, Zheng; Baker, Jay A.; Georgiade, Gregory S.; Chen, Wei; Siamakpour-Reihani, Sharareh; Wang, Chunhao; Broadwater, Gloria; Groth, Jeff; Palta, Manisha; Dewhirst, Mark; Barry, William T.; Duffy, Eileen A.

    2015-01-01

    Purpose: Women with biologically favorable early-stage breast cancer are increasingly treated with accelerated partial breast radiation (PBI). However, treatment-related morbidities have been linked to the large postoperative treatment volumes required for external beam PBI. Relative to external beam delivery, alternative PBI techniques require equipment that is not universally available. To address these issues, we designed a phase 1 trial utilizing widely available technology to 1) evaluate the safety of a single radiation treatment delivered preoperatively to the small-volume, intact breast tumor and 2) identify imaging and genomic markers of radiation response. Methods and Materials: Women aged ≥55 years with clinically node-negative, estrogen receptor–positive, and/or progesterone receptor–positive HER2−, T1 invasive carcinomas, or low- to intermediate-grade in situ disease ≤2 cm were enrolled (n=32). Intensity modulated radiation therapy was used to deliver 15 Gy (n=8), 18 Gy (n=8), or 21 Gy (n=16) to the tumor with a 1.5-cm margin. Lumpectomy was performed within 10 days. Paired pre- and postradiation magnetic resonance images and patient tumor samples were analyzed. Results: No dose-limiting toxicity was observed. At a median follow-up of 23 months, there have been no recurrences. Physician-rated cosmetic outcomes were good/excellent, and chronic toxicities were grade 1 to 2 (fibrosis, hyperpigmentation) in patients receiving preoperative radiation only. Evidence of dose-dependent changes in vascular permeability, cell density, and expression of genes regulating immunity and cell death were seen in response to radiation. Conclusions: Preoperative single-dose radiation therapy to intact breast tumors is well tolerated. Radiation response is marked by early indicators of cell death in this biologically favorable patient cohort. This study represents a first step toward a novel partial breast radiation approach. Preoperative radiation should

  4. Preoperative Single-Fraction Partial Breast Radiation Therapy: A Novel Phase 1, Dose-Escalation Protocol With Radiation Response Biomarkers

    Energy Technology Data Exchange (ETDEWEB)

    Horton, Janet K., E-mail: janet.horton@duke.edu [Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina (United States); Blitzblau, Rachel C.; Yoo, Sua [Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina (United States); Geradts, Joseph [Department of Pathology, Duke University Medical Center, Durham, North Carolina (United States); Chang, Zheng [Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina (United States); Baker, Jay A. [Department of Radiology, Duke University Medical Center, Durham, North Carolina (United States); Georgiade, Gregory S. [Department of Surgery, Duke University Medical Center, Durham, North Carolina (United States); Chen, Wei [Department of Bioinformatics: Duke Cancer Institute, Duke University Medical Center, Durham, North Carolina (United States); Siamakpour-Reihani, Sharareh; Wang, Chunhao [Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina (United States); Broadwater, Gloria [Department of Biostatistics: Duke Cancer Institute, Duke University Medical Center, Durham, North Carolina (United States); Groth, Jeff [Department of Pathology, Duke University Medical Center, Durham, North Carolina (United States); Palta, Manisha; Dewhirst, Mark [Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina (United States); Barry, William T. [Department of Biostatistics and Bioinformatics, Duke University Medical Center, Durham, North Carolina (United States); Biostatistics and Computational Biology, Dana-Farber Cancer Institute, Boston, Massachusetts (United States); Duffy, Eileen A. [Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina (United States); and others

    2015-07-15

    Purpose: Women with biologically favorable early-stage breast cancer are increasingly treated with accelerated partial breast radiation (PBI). However, treatment-related morbidities have been linked to the large postoperative treatment volumes required for external beam PBI. Relative to external beam delivery, alternative PBI techniques require equipment that is not universally available. To address these issues, we designed a phase 1 trial utilizing widely available technology to 1) evaluate the safety of a single radiation treatment delivered preoperatively to the small-volume, intact breast tumor and 2) identify imaging and genomic markers of radiation response. Methods and Materials: Women aged ≥55 years with clinically node-negative, estrogen receptor–positive, and/or progesterone receptor–positive HER2−, T1 invasive carcinomas, or low- to intermediate-grade in situ disease ≤2 cm were enrolled (n=32). Intensity modulated radiation therapy was used to deliver 15 Gy (n=8), 18 Gy (n=8), or 21 Gy (n=16) to the tumor with a 1.5-cm margin. Lumpectomy was performed within 10 days. Paired pre- and postradiation magnetic resonance images and patient tumor samples were analyzed. Results: No dose-limiting toxicity was observed. At a median follow-up of 23 months, there have been no recurrences. Physician-rated cosmetic outcomes were good/excellent, and chronic toxicities were grade 1 to 2 (fibrosis, hyperpigmentation) in patients receiving preoperative radiation only. Evidence of dose-dependent changes in vascular permeability, cell density, and expression of genes regulating immunity and cell death were seen in response to radiation. Conclusions: Preoperative single-dose radiation therapy to intact breast tumors is well tolerated. Radiation response is marked by early indicators of cell death in this biologically favorable patient cohort. This study represents a first step toward a novel partial breast radiation approach. Preoperative radiation should

  5. Mutations in the Caenorhabditis elegans orthologs of human genes required for mitochondrial tRNA modification cause similar electron transport chain defects but different nuclear responses.

    Science.gov (United States)

    Navarro-González, Carmen; Moukadiri, Ismaïl; Villarroya, Magda; López-Pascual, Ernesto; Tuck, Simon; Armengod, M-Eugenia

    2017-07-01

    Several oxidative phosphorylation (OXPHOS) diseases are caused by defects in the post-transcriptional modification of mitochondrial tRNAs (mt-tRNAs). Mutations in MTO1 or GTPBP3 impair the modification of the wobble uridine at position 5 of the pyrimidine ring and cause heart failure. Mutations in TRMU affect modification at position 2 and cause liver disease. Presently, the molecular basis of the diseases and why mutations in the different genes lead to such different clinical symptoms is poorly understood. Here we use Caenorhabditis elegans as a model organism to investigate how defects in the TRMU, GTPBP3 and MTO1 orthologues (designated as mttu-1, mtcu-1, and mtcu-2, respectively) exert their effects. We found that whereas the inactivation of each C. elegans gene is associated with a mild OXPHOS dysfunction, mutations in mtcu-1 or mtcu-2 cause changes in the expression of metabolic and mitochondrial stress response genes that are quite different from those caused by mttu-1 mutations. Our data suggest that retrograde signaling promotes defect-specific metabolic reprogramming, which is able to rescue the OXPHOS dysfunction in the single mutants by stimulating the oxidative tricarboxylic acid cycle flux through complex II. This adaptive response, however, appears to be associated with a biological cost since the single mutant worms exhibit thermosensitivity and decreased fertility and, in the case of mttu-1, longer reproductive cycle. Notably, mttu-1 worms also exhibit increased lifespan. We further show that mtcu-1; mttu-1 and mtcu-2; mttu-1 double mutants display severe growth defects and sterility. The animal models presented here support the idea that the pathological states in humans may initially develop not as a direct consequence of a bioenergetic defect, but from the cell's maladaptive response to the hypomodification status of mt-tRNAs. Our work highlights the important association of the defect-specific metabolic rewiring with the pathological phenotype

  6. Evolution of the radiation-induced defect structure in 316 type stainless steel after post-irradiation annealing

    Energy Technology Data Exchange (ETDEWEB)

    Van Renterghem, W., E-mail: wvrenter@sckcen.be; Konstantinović, M.J., E-mail: mkonstan@sckcen.be; Vankeerberghen, M., E-mail: mvankeer@sckcen.be

    2014-09-15

    Highlights: • TEM study of irradiated CW316 steel after post-irradiation annealing. • Frank loops were removed after annealing at 550 °C, by unfaulting and growing. • The cavity density decreases after annealing at 550 °C, but not completely removed. • Frank loop and cavity removal is controlled by the annealing temperature. • The dissolution of γ' precipitates is controlled by the iron diffusion length. - Abstract: The thermal stability of Frank loops, black dots, cavities and γ′ precipitates in an irradiated 316 stainless steel was studied by transmission electron microscopy. The samples were retrieved from a thimble tube irradiated at around 320 °C up to 80 dpa in a commercial nuclear power reactor, and thermally annealed, varying both annealing temperature and time. With increasing annealing temperature the density of all defects gradually decreased, resulting in the complete removal of Frank loops at 550 °C. In contrast to other defects, the density of the γ′ precipitates sharply decreased with increasing annealing time, which indicates that the dissolution of the γ′ precipitates is governed by the iron diffusion length.

  7. Defects in semiconductors

    CERN Document Server

    Romano, Lucia; Jagadish, Chennupati

    2015-01-01

    This volume, number 91 in the Semiconductor and Semimetals series, focuses on defects in semiconductors. Defects in semiconductors help to explain several phenomena, from diffusion to getter, and to draw theories on materials' behavior in response to electrical or mechanical fields. The volume includes chapters focusing specifically on electron and proton irradiation of silicon, point defects in zinc oxide and gallium nitride, ion implantation defects and shallow junctions in silicon and germanium, and much more. It will help support students and scientists in their experimental and theoret

  8. Response of hematopoietic stem cells to ionizing radiation; Reponse des cellules souches hematopoitiques aux radiations ionisantes

    Energy Technology Data Exchange (ETDEWEB)

    Simonnet, A

    2008-12-15

    Hematopoietic stem cells (HSCs) maintain blood and immune system throughout life and restore them after hematological injuries. Exposure of an organism to ionizing radiation (IR) causes rapid and acute myelosuppression and challenges the replenishment capacity of HSCs. Yet, the precise damages that are generated remain largely unexplored. To better understand these effects, phenotypic and functional changes in the stem/progenitor compartments of sublethally irradiated mice were monitored over a ten week period after radiation exposure. We report that shortly after sublethal IR-exposure, HSCs, defined by their repopulating ability, still segregate in the Hoechst dye excluding side population (SP); yet, their Sca-1 (S) and c-Kit (K) expression levels are increased and severely reduced, respectively, with a concurrent increase in the proportion of SP{sup SK} cells positive for established indicators of HSC presence: CD150{sup +} and CD105{sup +}. A great proportion of HSCs quickly but transiently enter the cell cycle to replenish the bone marrow of myelo-ablated mice. Ten weeks after, whereas bone marrow cellularity has recovered and hematopoietic homeostasis is restored, major phenotypic modifications can be observed within the Lin{sup -/low} Sca-1{sup +} c-Kit{sup +} (LSK) stem/progenitor compartment: CD150{sup +}/Flk2{sup -} and CD150{sup -}/Flk2{sup +} LSK cell frequencies are increased and dramatically reduced, respectively. CD150{sup +} LSK cells also show impaired reconstitution capacity, accrued number of {gamma}-H2AX foci and increased tendency to apoptosis. This demonstrates that the LSK compartment is not properly restored 10 weeks after sublethal exposure, and that long-term IR-induced injury to the bone marrow proceeds, at least partially, through direct damage to the stem cell pool. Thrombopoietin (TPO) has been shown to promote the survival of lethally irradiated mice when administrated quickly after exposure. We investigated the mechanisms underlying

  9. Clinical application of radiation sterilized demineralized freeze dried bone allograft (DFDBA) and DFDBA combined with bovine periosteum membrane in periodontal defects

    International Nuclear Information System (INIS)

    Tantin R Dwijartini; Paramita Pandansari; Basril Abbas; Nazly Hilmy

    2008-01-01

    Full text: The objective of this report is to evaluate the effects of Radiation Sterilized Demineralized Freeze Dried Bone Allograft (DFDBA) and DFDBA combined with Bovine Periosteum Membrane (BPM) as well as BPM only in some cases of Periodontal Defects. BPM was used as a guided tissue regeneration. This study was carried out to 26 patients as follows : 10 cases for periodontal pocket using only DFDBA and DFDBA combined with BPM for 16 cases which consist of 10 cases of post extraction socket, 5 cases of gingival recession and one case of maxillary bone defect. DFDBA and periosteum membrane used were produced by BATAN Research Tissue Bank. Flap operation was done for all of the treatments, and followed by filling with DFDBA and/or DFDBA combined with periosteum membrane or BPM only. Evaluations were done up to 6 months. Parameters observed were the improvement of bone level, clinical attachment level, pocket depth and gingival margin location as well as increasing the thickness of maxillary bone. All of those evaluations were done by clinical observation and x-ray examination. Results obtained show that the improvement of clinical attachment level, reduces the pocket depth and increases bone density happened in all cases observed. It was also shows that BPM can be used as a guided tissue regeneration. No rejection could be observed in all of those cases. This study clearly indicated that DFDBA had an inductive effect on the formation of new bone and connective tissue. It can be concluded that DFDBA and Bovine Periosteum Membrane are promising to be used in treatment of the case of Periodontal Defects. (Author)

  10. Contrasting Responses of Marine and Freshwater Photosynthetic Organisms to UVB Radiation: A Meta-Analysis

    KAUST Repository

    Jin, Peng

    2017-03-14

    Ultraviolet-B (UVB) radiation is a global stressor that has profound impacts on freshwater and marine ecosystems. However, an analysis of the patterns of sensitivity to UVB radiation across aquatic photosynthetic organisms has not yet been published. Here, we performed a meta-analysis on results reported in 214 studies compiled from the published literature to quantify and compare the magnitude of responses of aquatic photosynthetic organisms to changes in UVB radiation. The meta-analysis was conducted on observations of marine (n = 893) and freshwater macroalgae (n = 126) and of marine (n = 1,087) and freshwater (n = 2,889) microalgae (total n = 4,995). Most of these studies (85%) analyzed the performance of organisms exposed to natural solar radiation when UVB was partially or totally reduced compared with the organismal performance under the full solar radiation spectrum, whereas the remaining 15% of the studies examined the responses of organisms to elevated UVB radiation mostly using artificial lamps. We found that marine photosynthetic organisms tend to be more sensitive than freshwater photosynthetic organisms to UVB radiation; responses to either decreased or increased UVB radiation vary among taxa; the mortality rate is the most sensitive of the trait responses to elevated UVB radiation, followed by changes in cellular and molecular traits; the sensitivity of microalgae to UVB radiation is dependent on size, with small-celled microalgae more sensitive than large-celled microalgae to UVB radiation. Thick macroalgae morphotypes were the less sensitive to UVB, but this effect could not be separated from phylogenetic differences. The high sensitivity of marine species, particularly the smallest photosynthetic organisms, to increased UVB radiation suggests that the oligotrophic ocean, a habitat comprising 70% of the world\\'s oceans with high UVB penetration and dominated by picoautotrophs, is extremely vulnerable to changes in UVB radiation.

  11. Faculty of Radiation Oncology 2014 Workforce Census: a comparison of New Zealand and Australian responses.

    Science.gov (United States)

    James, Melissa; Munro, Philip M; Leung, John

    2015-04-17

    This paper outlines the key results of the Royal Australian and New Zealand College of Radiologists (RANZCR) Faculty of Radiation Oncology (FRO) 2014 workforce census, and compares the results of New Zealand and Australian responses in order to identify similarities and differences in workforce characteristics. The workforce census was conducted online in mid-2014. The census was distributed to all radiation oncologists (Fellows, life members, educational affiliates, retired) and radiation oncology trainees on the RANZCR membership database. Six weekly reminders were sent to non-respondents and all responses were aggregated for analysis. This paper addresses only consultant radiation oncologist responses. The combined response rate for New Zealand radiation oncologists was 85.7% (compared with 76% from Australian respondents). The census found that the demographic characteristics of New Zealand and Australian radiation oncologists are similar. Points of difference include (i) the role of educational affiliates in New Zealand, (ii) New Zealand radiation oncologists reporting higher hours spent at work, (iii) New Zealand radiation oncologists spending a higher proportion of time on clinical duties, (iv) A lower proportion of New Zealand radiation oncologists with higher degrees, and (v) private/ public workplace mix. A comparison by country would suggest that there are many similarities, but also some important differences that may affect workforce issues in New Zealand. Separate datasets are useful for RANZCR to better inform members, governments and other key stakeholders in each country. Separate datasets also provide a basis for comparison with future surveys to facilitate the monitoring of trends.

  12. Understanding the role of p53 in adaptive response to radiation-induced germline mutations

    International Nuclear Information System (INIS)

    Langlois, N.L.; Quinn, J.S.; Somers, C.M.; Boreham, D.R.; Mitchel, R.E.J.

    2003-01-01

    Full text: Radiation-induced adaptive response is now a widely studied area of radiation biology. Studies have demonstrated reduced levels of radiation-induced biological damage when an 'adaptive dose' is given before a higher 'challenge dose' compared to when the challenge dose is given alone. It has been shown in some systems to be a result of inducible cellular repair systems. The adaptive response has been clearly demonstrated in many model systems, however its impact on heritable effects in the mammalian germline has never been studied. Expanded Simple Tandem Repeat (ESTR) loci have been used as markers demonstrating that induced heritable mutations in mice follow a dose-response relationship. Recent data in our laboratory show preliminary evidence of radiation-induced adaptive response suppressing germline mutations at ESTR loci in wild type mice. The frequency of heritable mutations was significantly reduced when a priming dose of 0.1 Gy was given 24 hours prior to a 1 Gy acute challenging dose. We are now conducting a follow-up study to attempt to understand the mechanism of this adaptive response. P53 is known to play a significant role in governing apoptosis, DNA repair and cancer induction. In order to determine what function p53 has in the adaptive response for heritable mutations, we have mated radiation treated Trp53+/- male mice (C57Bl) to untreated, normal females (C57Bl). Using DNA fingerprinting, we are investigating the rate of inherited radiation-induced mutations on pre- and post-meiotic radiation-treated gametocytes by examining mutation frequencies in offspring DNA. If p53 is integral in the mechanism of adaptive response, we should not see an adaptive response in radiation-induced heritable mutations in these mice. This research is significant in that it will provide insight to understanding the mechanism behind radiation-induced adaptive response in the mammalian germline

  13. Radiation response of cubic mesoporous silicate and borosilicate thin films

    Science.gov (United States)

    Manzini, Ayelén; Alurralde, Martín; Luca, Vittorio

    2018-01-01

    The radiation response has been studied of cubic mesoporous silicate and borosilicate thin films having different boron contents prepared using the block copolymer template Brij 58 and the dip coating technique. The degree of pore ordering of the films was analysed using low-angle X-ray diffraction and film thickness measured by X-ray reflectivity. For films calcined at 350 °C, the incorporation of boron resulted in a reproducible oscillatory variation in the d-spacing and intensity of the primary reflection as a function of boron content. A clear peak was observed in the d-spacing at 5-10 mol% boron incorporation. For borosilicate films of a given composition an overall suppression of d-spacing was observed as a function of aging time relative to films that did not contain boron. This was ascribed to a slow condensation process. The films were irradiated in pile with neutrons and with iodine ions at energies of 180 keV and 70 MeV. Neutron irradiation of the silicate thin films for periods up to 30 days and aged for 400 days resulted in little reduction in either d-spacing or intensity of the primary low-angle X-ray reflection indicating that the films retained their mesopore ordering. In contrast borosilicate films for which the B (n, α) reaction was expected to result in enhanced displacement damage showed much larger variations in X-ray parameters. For these films short irradiation times resulted in a reduction of the d-spacing and intensity of the primary reflections considerably beyond that observed through aging. It is concluded that prolonged neutron irradiation and internal α irradiation have only a small, although measurable, impact on mesoporous borosilicate thin films increasing the degree of condensation and increasing unit cell contraction. When these borosilicate films were irradiated with iodine ions, more profound changes occurred. The pore ordering of the films was significantly degraded when low energy ions were used. In some cases the degree

  14. Space radiation-induced bystander effect: kinetics of biologic responses, mechanisms, and significance of secondary radiations

    International Nuclear Information System (INIS)

    Gonon, Geraldine

    2011-01-01

    Widespread evidence indicates that exposure of cell cultures to a particles results in significant biological changes in both the irradiated and non-irradiated bystander cells in the population. The induction of non-targeted biological responses in cell cultures exposed to low fluences of high charge (Z) and high energy (E) particles is relevant to estimates of the health risks of space radiation and to radiotherapy. Here, we investigated the mechanisms underlying the induction of stressful effects in confluent normal human fibroblast cultures exposed to low fluences of 1000 MeV/u iron ions (linear energy transfer (LET) 151 keV/μm), 600 MeV/u silicon ions (LET 50 keV/μm) or 290 MeV/u carbon ions (LET 13 keV/μm). We compared the results with those obtained in cell cultures exposed, in parallel, to low fluences of 0.92 MeV/u a particles (LET 109 keV/μm). Induction of DNA damage, changes in gene expression, protein carbonylation and lipid peroxidation during 24 h after exposure of confluent cultures to mean doses as low as 0.2 cGy of iron or silicon ions strongly supported the propagation of stressful effects from irradiated to bystander cells. At a mean dose of 0.2 cGy, only 1 and 3 % of the cells would be targeted through the nucleus by an iron or silicon ion, respectively. Within 24 h post-irradiation, immunoblot analyses revealed significant increases in the levels of phospho-TP53 (serine 15), p21Waf1 (also known as CDKN1A), HDM2, phospho-ERK1/2, protein carbonylation and lipid peroxidation. The magnitude of the responses suggested participation of non-targeted cells in the response. Furthermore, when the irradiated cell populations were subcultured in fresh medium shortly after irradiation, greater than expected increases in the levels of these markers were also observed during 24 h. Together, the results imply a rapidly propagated and persistent bystander effect. In situ analyses in confluent cultures showed 53BP1 foci formation, a marker of DNA damage, in

  15. Molecular dynamics study on the interaction of a dislocation and radiation induced defect clusters in Fcc crystals

    International Nuclear Information System (INIS)

    Hideo, Kaburaki; Tomoko, Kadoyoshi; Futoshi, Shimizu; Hajime; Kimizuka; Shiro, Jitsukawa

    2003-01-01

    Irradiation of high-energy neutrons and charged particles into solids is known to cause a significant change in mechanical properties, in particular, hardening of metals. Hardening of solids arises as a result of interactions of dislocations with irradiation induced defect clusters. Molecular dynamics method combined with the visualization method has been used to elucidate these complex pinning structures in details. In particular, we have successfully observed the transient process for the formation of a super-jog from an edge dislocation and interstitial and vacancy clusters under irradiation cascade conditions. Parallel molecular dynamics programs, called as Parallel Molecular Dynamics Stencil (PMDS), have been developed in order to perform these large scale simulations for materials simulations. The contents of the program and its parallel performance are also reported. (authors)

  16. Health effects of low-dose radiation: Molecular, cellular, and biosystem response

    International Nuclear Information System (INIS)

    Pollycove, M.; Paperiello, C.J.

    1997-01-01

    Since the fifties, the prime concern of radiation protection has been protecting DNA from damage. UNSCEAR initiated a focus on biosystem response to damage with its 1994 report, ''Adaptive Responses to Radiation of Cells and Organisms''. The DNA damage-control biosystem is physiologically operative on both metabolic and radiation induced damage, both effected predominantly by free radicals. These adaptive responses are suppressed by high-dose and stimulated by low dose radiation. Increased biosystem efficiently reduces the number of mutations that accumulate during a lifetime and decrease DNA damage-control with resultant aging and malignancy. Several statistically significant epidemiologic studies have shown risk decrements of cancer mortality and mortality from all causes in populations exposed to low-dose radiation. Further biologic and epidemiologic research is needed to establish a valid threshold below which risk decrements occur. (author)

  17. Parallel Study of HEND, RAD, and DAN Instrument Response to Martian Radiation and Surface Conditions

    Science.gov (United States)

    Martiniez Sierra, Luz Maria; Jun, Insoo; Litvak, Maxim; Sanin, Anton; Mitrofanov, Igor; Zeitlin, Cary

    2015-01-01

    Nuclear detection methods are being used to understand the radiation environment at Mars. JPL (Jet Propulsion Laboratory) assets on Mars include: Orbiter -2001 Mars Odyssey [High Energy Neutron Detector (HEND)]; Mars Science Laboratory Rover -Curiosity [(Radiation Assessment Detector (RAD); Dynamic Albedo Neutron (DAN))]. Spacecraft have instruments able to detect ionizing and non-ionizing radiation. Instrument response on orbit and on the surface of Mars to space weather and local conditions [is discussed] - Data available at NASA-PDS (Planetary Data System).

  18. Gustatory tissue injury in man: radiation dose response relationships and mechanisms of taste loss

    International Nuclear Information System (INIS)

    Mossman, K.L.

    1986-01-01

    In this report dose response data for gustatory tissue damage in patients given total radiation doses ranging from 3000 to 6000 cGy are presented. In order to evaluate direct radiation injury to gustatory tissues as a mechanism of taste loss, measurements of damage to specific taste structures in bovine and murine systems following radiation exposure in the clinical range are correlated to taste impairment observed in radiotherapy patients. (author)

  19. Defect modelling

    International Nuclear Information System (INIS)

    Norgett, M.J.

    1980-01-01

    Calculations, drawing principally on developments at AERE Harwell, of the relaxation about lattice defects are reviewed with emphasis on the techniques required for such calculations. The principles of defect modelling are outlined and various programs developed for defect simulations are discussed. Particular calculations for metals, ionic crystals and oxides, are considered. (UK)

  20. Contribution of radiation-induced, nitric oxide-mediated bystander effect to radiation-induced adaptive response.

    Science.gov (United States)

    Matsumoto, H.; Ohnishi, T.

    There has been a recent upsurge of interest in radiation-induced adaptive response and bystander effect which are specific modes in stress response to low-dose low-dose rate radiation Recently we found that the accumulation of inducible nitric oxide NO synthase iNOS in wt p53 cells was induced by chronic irradiation with gamma rays followed by acute irradiation with X-rays but not by each one resulting in an increase in nitrite concentrations of medium It is suggested that the accumulation of iNOS may be due to the depression of acute irradiation-induced p53 functions by pre-chronic irradiation In addition we found that the radiosensitivity of wt p53 cells against acute irradiation with X-rays was reduced after chronic irradiation with gamma rays This reduction of radiosensitivity of wt p53 cells was nearly completely suppressed by the addition of NO scavenger carboxy-PTIO to the medium This reduction of radiosensitivity of wt p53 cells is just radiation-induced adaptive response suggesting that NO-mediated bystander effect may considerably contribute to adaptive response induced by radiation

  1. Plant's adaptive response under UV-B-radiation influence

    International Nuclear Information System (INIS)

    Danil'chenko, O.A.; Grodzinskij, D.M.

    2002-01-01

    Reduction of ozone layer, owing to anthropogenic contamination of an atmosphere results in increase of intensity of UV-radiation and shift of its spectrum in the short-wave side that causes strengthening of various biological effects of irradiation. Consequences of these processes may include increase of injuring of plants and decrease of productivity of agricultural crops to increased UV levels. The important significance in the plant's adaptation to different unfavorable factors has the plant's radioadaptive answer. It has been shown that radioadaptation of plants occurred not only after irradiation with g-radiation in low doses but after UV-rays action . Reaction of radioadaptation it seems to be nonspecific phenomenon in relation to type radiations

  2. Macrophage biology plays a central role during ionizing radiation-elicited tumor response

    Directory of Open Access Journals (Sweden)

    Qiuji Wu

    2017-08-01

    Full Text Available Radiation therapy is one of the major therapeutic modalities for most solid tumors. The anti-tumor effect of radiation therapy consists of the direct tumor cell killing, as well as the modulation of tumor microenvironment and the activation of immune response against tumors. Radiation therapy has been shown to promote immunogenic cells death, activate dendritic cells and enhance tumor antigen presentation and anti-tumor T cell activation. Radiation therapy also programs innate immune cells such as macrophages that leads to either radiosensitization or radioresistance, according to different tumors and different radiation regimen studied. The mechanisms underlying radiation-induced macrophage activation remain largely elusive. Various molecular players such as NF-κB, MAPKs, p53, reactive oxygen species, inflammasomes have been involved in these processes. The skewing to a pro-inflammatory phenotype thus results in the activation of anti-tumor immune response and enhanced radiotherapy effect. Therefore, a comprehensive understanding of the mechanism of radiation-induced macrophage activation and its role in tumor response to radiation therapy is crucial for the development of new therapeutic strategies to enhance radiation therapy efficacy.

  3. The radiologist's responsibilities for the radiation protection of patients

    International Nuclear Information System (INIS)

    Etard, C.

    2010-01-01

    The obligations of the radiologist for the radiation protection of patients include a review of the appropriateness of the examination and optimization of the protocol. Both internal and external quality assurance programs are mandatory. The specific tasks and their frequency are defined by the AFSSAPS. The radiology report of procedures performed over radiosensitive regions must include the delivered dose. The imaging technique must be optimized based on published guidelines or law for the most frequent examinations. All radiologists should be familiar with radiation protection. Incidents should be reported to the Nuclear Safety Authority. (author)

  4. Electrical Characterization of Defects Created by γ-Radiation in HfO2-Based MIS Structures for RRAM Applications

    Science.gov (United States)

    García, H.; González, M. B.; Mallol, M. M.; Castán, H.; Dueñas, S.; Campabadal, F.; Acero, M. C.; Sambuco Salomone, L.; Faigón, A.

    2018-04-01

    The γ-radiation effects on the electrical characteristics of metal-insulator-semiconductor capacitors based on HfO2, and on the resistive switching characteristics of the structures have been studied. The HfO2 was grown directly on silicon substrates by atomic layer deposition. Some of the capacitors were submitted to a γ ray irradiation using three different doses (16 kGy, 96 kGy and 386 kGy). We studied the electrical characteristics in the pristine state of the capacitors. The radiation increased the interfacial state densities at the insulator/semiconductor interface, and the slow traps inside the insulator near the interface. However, the leakage current is not increased by the irradiation, and the conduction mechanism is Poole-Frenkel for all the samples. The switching characteristics were also studied, and no significant differences were obtained in the performance of the devices after having been irradiated, indicating that the fabricated capacitors present good radiation hardness for its use as a RS element.

  5. Oligodendroglial response to ionizing radiation: Dose and dose-rate response

    International Nuclear Information System (INIS)

    Levy, R.P.

    1991-01-01

    An in vitro system using neuroglia from neonatal rat brain was developed to examining the morphologic, immunocytochemical and biochemical response of oligodendroglia to ionizing radiation. Following acute γ-radiation at day-in-culture (DIC) 8, oligodendrocyte counts at DIC 14 were 55% to 65% of control values after 2 Gy, and 29% to 36% after 5 Gy. Counts increased to near-normal levels at DIC 21 in the 2 Gy group and to 75% of normal in the 5 Gy group. Myelin basic protein levels (MBP) at DIC 14 were 60% of control values after 2 Gy, and 40% after 5 Gy. At DIC 21, MBP after 2 Gy was 45% greater than that observed at DIC 14, but MBP, as a fraction of age-matched control values, dropped from 60% to 50%. Following 5 Gy, absolute MBP changed little between DIC 14 and DIC 21, but decreased from 40% to 25% of control cultures. It was concluded that oligodendrocytes in irradiated cultures had significantly lower functional capacity than did unirradiated controls. The response to split-dose irradiation indicated that nearly all sublethal damage in the oligodendrocyte population (and its precursors) was repaired within 3 h to 4 h. At DIC 14, the group irradiated in a single fraction had significantly lower oligodendrocyte counts than any group given split doses; all irradiated cultures had marked depression of MBP synthesis, but to significant differences referable to time interval between doses. At DIC 21, cultures irradiated at intervals of 0 h to 2 h had similar oligodendrocyte counts to one another, but these counts were significantly lower than in cultures irradiated at intervals of 4 h to 6 h; MBP levels remained depressed at DIC 21 for all irradiated cultures. The oligodendrocyte response to dose rate (0.03 to 1.97 Gy/min) was evaluated at DIC 14 and DIC 21. Exposure at 0.03 Gy/min suppressed oligodendrocyte counts at DIC 21 less than did higher dose rates in 5-Gy irradiated cultures

  6. Role for c-Abl and p73 in the radiation response of male germ cells

    NARCIS (Netherlands)

    Hamer, G.; Gademan, I. S.; Kal, H. B.; de rooij, D. G.

    2001-01-01

    p53 plays a central role in the induction of apoptosis of spermatogonia in response to ionizing radiation. In p53(-/-) testes, however, spermatogonial apoptosis still can be induced by ionizing radiation, so p53 independent apoptotic pathways must exist in spermatogonia. Here we show that the p53

  7. Evaluation of detector responses to natural environmental and fall-out gamma radiation

    International Nuclear Information System (INIS)

    Arvela, H.

    1988-01-01

    Instrument responses to the thorium, uranium and potassium components of the natural environmental as well as the fall-out radiation field were evaluated. The responses to the 137 Cs fall-out radiation field differ by less than 6% from the response at 0.662 MeV, except for that of the NaI scintillator. Differences of more than 30% were found in the responses of two energy compensated instruments to normal natural background radiation and to radiation from fresh fall-out. The best estimate of the terrestrial component of the dose rate measured was obtained by carrying out the following corrections of the measured readings: cosmic ray contribution and internal background subtraction with response correction, including 137 Cs calibration correction. After the Chernobyl accident the dose rate levels due to 137 Cs and 134 Cs fall-out were comparable to the natural background gamma radiation. The responses calculated as well as the results from measurements of the low level environmental exposure levels caused by the Chernobyl fall-out, confirmed the need to take into account the instrument response to natural as well as fall-out radiation fields. (author)

  8. Gene expression profiling of PBL in response to ionising radiation and modeled microgravity

    Data.gov (United States)

    National Aeronautics and Space Administration — BACKGROUND: Ionizing radiation (IR) can be extremely harmful for human cells since an improper DNA-damage response (DDR) to IR can contribute to carcinogenesis...

  9. Identification of miRNAs involved in cell response to ionising radiation and modeled microgravity

    Data.gov (United States)

    National Aeronautics and Space Administration — BACKGROUND: Ionizing radiation (IR) can be extremely harmful for human cells since an improper DNA-damage response (DDR) to IR can contribute to carcinogenesis...

  10. Response of asymmetric carbon nanotube network devices to sub-terahertz and terahertz radiation

    International Nuclear Information System (INIS)

    Gayduchenko, I.; Kardakova, A.; Voronov, B.; Finkel, M.; Fedorov, G.; Jiménez, D.; Morozov, S.; Presniakov, M.; Goltsman, G.

    2015-01-01

    Demand for efficient terahertz radiation detectors resulted in intensive study of the asymmetric carbon nanostructures as a possible solution for that problem. It was maintained that photothermoelectric effect under certain conditions results in strong response of such devices to terahertz radiation even at room temperature. In this work, we investigate different mechanisms underlying the response of asymmetric carbon nanotube (CNT) based devices to sub-terahertz and terahertz radiation. Our structures are formed with CNT networks instead of individual CNTs so that effects probed are more generic and not caused by peculiarities of an individual nanoscale object. We conclude that the DC voltage response observed in our structures is not only thermal in origin. So called diode-type response caused by asymmetry of the device IV characteristic turns out to be dominant at room temperature. Quantitative analysis provides further routes for the optimization of the device configuration, which may result in appearance of novel terahertz radiation detectors

  11. The effects of emitter-tied field plates on lateral PNP ionizing radiation response

    International Nuclear Information System (INIS)

    Barnaby, H.J.; Schrimpf, R.D.; Cirba, C.R.; Pease, R.L.; Fleetwood, D.M.; Kosier, S.L.

    1998-03-01

    Radiation response comparisons of lateral PNP bipolar technologies reveal that device hardening may be achieved by extending the emitter contact over the active base. The emitter-tied field plate suppresses recombination of carriers with interface traps

  12. Deconvolving the temporal response of photoelectric x-ray detectors for the diagnosis of pulsed radiations

    International Nuclear Information System (INIS)

    Zou, Shiyang; Song, Peng; Pei, Wenbing; Guo, Liang

    2013-01-01

    Based on the conjugate gradient method, a simple algorithm is presented for deconvolving the temporal response of photoelectric x-ray detectors (XRDs) to reconstruct the resolved time-dependent x-ray fluxes. With this algorithm, we have studied the impact of temporal response of XRD on the radiation diagnosis of hohlraum heated by a short intense laser pulse. It is found that the limiting temporal response of XRD not only postpones the rising edge and peak position of x-ray pulses but also smoothes the possible fluctuations of radiation fluxes. Without a proper consideration of the temporal response of XRD, the measured radiation flux can be largely misinterpreted for radiation pulses of a hohlraum heated by short or shaped laser pulses

  13. Acetylation dynamics of human nuclear proteins during the ionizing radiation-induced DNA damage response

    DEFF Research Database (Denmark)

    Bennetzen, Martin; Andersen, J.S.; Lasen, D.H.

    2013-01-01

    Genotoxic insults, such as ionizing radiation (IR), cause DNA damage that evokes a multifaceted cellular DNA damage response (DDR). DNA damage signaling events that control protein activity, subcellular localization, DNA binding, protein-protein interactions, etc. rely heavily on time...

  14. Radiation response of vitamin A in aqueous dispersions

    International Nuclear Information System (INIS)

    Bhushan, B.; Kumta, U.S.

    1977-01-01

    The radiation destruction of vitamin A acetate was monitored in isooctane, coconut oil, and aqueous dispersions. The G(-vit. A), i.e., the number of vitamin A molecules destroyed per 100 eV of energy absorbed in lipid solvents and aqueous preparations, increased with the concentrations of vitamin A used. In the freely dissolved state, as in isooctane or coconut oil, the extent of destruction of vitamin A was more or less identical. However, a marked reduction in the radiation destruction of vitamin A was observed in aqueous dispersions at all concentrations except at 1 x 10 -4 M. Incorporation of sugars, starch, and egg albumin in aqueous preparations offered considerable protection to vitamin A from radiation damage which could be discerned even at the lowest concentration (1 x 10 -4 M). The protective influence of aqueous dispersion as noted for vitamin A was also observed for β-carotene, vitamin A alcohol, and ubiquinone-30. The significance of the above findings in radiation processing of foods has been discussed

  15. Study of the circadian rhythm in radiation response

    Science.gov (United States)

    Gamma-Radiation is often used for the treatment of solid tumors. It induces DNA double-stranded breaks that lead to cell cycle arrest or apoptosis of tumor cells. However, such treatment could also damage normal host tissues that need cell proliferation for function. We have reported previously that...

  16. Molecular mechanisms of responses to radiation through protein kinase C

    International Nuclear Information System (INIS)

    Nakajima, Tetsuo

    2005-01-01

    Described are the activation and cascade of the protein kinase C (PKC) which mediating the control of radiation-induced apoptosis. PKC is a family of c-, n- and a-subtypes and plays a major role in responding to the radiation exposure for DNA repair, cell cycle arrest and apoptosis. The author has conducted studies of mouse thymic lymphoma cells which have a property to respond even to low dose radiation, and has showed that, in the highly radiosensitive cell strain, 3SBH5 where apoptosis occurs in 50 and 90% post 0.5 and 2 Gy exposure, respectively, cPKC works as a surviving signal without intracellular movement after irradiation. In contrast, PKC has been alternatively shown to participate in apoptosis induction, showing that different enzyme species in the subtypes work specifically depending on passing time. Comparison with the radio-resistant cell strain, XR223, has revealed that the difference in the localization controls of PKCδ in the cell determines the radiosensitivity, however, the control mechanism is found to be separate from Atm pathway by which PKCδ is usually regulated. Recent studies have revealed that PKC performs the intracellular cross-talk in various phosphorylation cascades. Studies of PKC can be toward their uses for radiation effect assessment, radiotherapy and medicare for urgent exposure. (S.I.)

  17. Physiological responses of Escherichia coli to far-ultraviolet radiation

    International Nuclear Information System (INIS)

    Swenson, P.A.

    1976-01-01

    The following topics are reviewed: photochemical damage to DNA; measurement of cell survival; DNA repair processes and genetics of radiation sensitivity; degradation of DNA and RNA; biochemical and physiological consequences; reactivation of bacteriophage in Escherichia coli cells; filament formation; influence of growth phase on survival after uv irradiation; and post-uv-irradiation treatment

  18. Chromatin decondensed by acetylation shows an elevated radiation response

    International Nuclear Information System (INIS)

    Nackerdien, Z.; Michie, J.; Boehm, L.

    1989-01-01

    V-79 Chinese hamster lung fibroblasts exposed to 5 mM n-sodium butyrate were irradiated with 60Co gamma rays and cell survival was determined by the cell colony assay. In a separate set of experiments the acetylated chromatin obtained from these cells was irradiated and the change of molecular weight of the DNA was evaluated by alkaline sucrose density centrifugation. At a survival level of 10(-2) to 10(-4) cells exposed to butyrate were found to be 1.3-1.4 times more radiosensitive than control cells. Exposure of isolated chromatin to 100 Gy of 60Co gamma irradiation generated 0.9 +/- 0.03 single-strand breaks (ssb) per 10 Gy per 10(8) Da and 2.0 +/- 0.3 ssb/10 Gy/10(8) Da for control and acetylated chromatin, respectively. The elevated radiation sensitivity of chromatin relaxed by acetylation is in good agreement with previous results on chromatin expanded by histone H1 depletion. Packing and accessibility of DNA in chromatin appear to be major factors which influence the radiation sensitivity. The intrinsic radiation sensitivity of chromatin in various packing states is discussed in light of the variation of radiation sensitivity of whole cells in the cell cycle which incorporates repair

  19. Radiation hardening: study of production velocity and post-irradiation recovery of defect clusters produced by neutron irradiation at 77 K

    International Nuclear Information System (INIS)

    Gonzalez, Hector C.; Miralles, Monica T.

    1999-01-01

    This work includes three basic studies using radiation hardening of Cu single crystals irradiated at 77 K in the RA-1-reactor of CNEA: 1) The initial of a production curve of defect clusters originated during radiation until 5.2 x 10 20 n m 2 . The shape of the curve is compared with those obtained from measurement of resistivity increased (Δρ) with neutronic doses (φt) and the acceptance of the linear dependency of Δρ with Frenkel Pairs concentration (PFs); 2) The isochronal hardening recovery in the temperature interval of stage V (T > 450 K). The existence of the sub-stages Vb (∼ 550 K) and Vc (∼ 587 K), determined for the first time from hardening measurements, are shown and compared with results obtained by other techniques; 3) Isothermal recoveries performed in the temperature interval of the sub-stage Vc to determine phenomenologically the apparent activation energy of the sub-stage. The value obtained was in agreement with the energy for Cu vacancies auto diffusion. (author)

  20. Gamma response study of radiation sensitive MOSFETs for their use as gamma radiation sensor

    Energy Technology Data Exchange (ETDEWEB)

    Srivastava, Saurabh; Kumar, A. Vinod [Radiation Safety Systems Division, Bhabha Atomic Research Centre, Mumbai (India); Aggarwal, Bharti; Singh, Arvind; Topkar, Anita, E-mail: anita@barc.gov.in [Electronics Division, Bhabha Atomic Research Centre, Mumbai (India)

    2016-05-23

    Continuous monitoring of gamma dose is important in various fields like radiation therapy, space-related research, nuclear energy programs and high energy physics experiment facilities. The present work is focused on utilization of radiation-sensitive Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) to monitor gamma radiation doses. Static characterization of these detectors was performed to check their expected current-voltage relationship. Threshold voltage and transconductance per unit gate to source voltage (K factor) were calculated from the experimental data. The detector was exposed to gamma radiation in both, with and without gate bias voltage conditions, and change in threshold voltage was monitored at different gamma doses. The experimental data was fitted to obtain equation for dependence of threshold voltage on gamma dose. More than ten times increase in sensitivity was observed in biased condition (+3 V) compared to the unbiased case.

  1. Influence of some exo nucleases in response to the induced genetic damage in Escherichia coli by alpha radiation

    International Nuclear Information System (INIS)

    Aguilar M, M.

    2005-01-01

    Within the strategies with those that E. coli counts to overcome to the genetic damage there is the SOS response, a group of genes that participate in repair and/or tolerance that it confers to the bacteria major opportunities of surviving. These genes are repressed and its only are expressed when it happens genetic damage. So that this system is activated it is necessary that DNA of a band exists and in this sense the double ruptures (RDB) its are not able to induce this response unless there is a previous processing. In stumps with defects in certain genes that have to do with repair of RDB (as recO, recJ and xonA) the activity of SOS is smaller than in a wild stump what suggests that these participate in the previous processes to the activation of the response. The ionizing radiation produce among other many lesions, RDB in greater or smaller proportion, depending on the ionization capacity. A parameter to evaluate this capacity is the lineal energy transfer (LET), defined as the average energy given by unit of distance travelled. In general the LET of the corpuscular radiations is a lot but high that of the electromagnetic one, for what produces bigger quantity of ionizations inside a restricted zone and it increases by this way the probability that RDB has been generated. This work has for object to infer the participation of xonA and recJ in this response and to evaluate the damage produced by ionizing radiation of different LET (alpha particles of different energies) in a stump with all the functional repair mechanisms. Its were considered two parameters: the survival and the activity of SOS evaluated by means of the chromo test. The results indicate that the activity of these exo nucleases is necessary for the repair of RDB as well as for the processing of lesions foresaw to the activation of SOS. As for the treatment with alphas of different energies is observed that so much the survival like the activity of SOS vary as the LET of the radiation changes

  2. Second Solid Cancers After Radiation Therapy: A Systematic Review of the Epidemiologic Studies of the Radiation Dose-Response Relationship

    Energy Technology Data Exchange (ETDEWEB)

    Berrington de Gonzalez, Amy, E-mail: berringtona@mail.nih.gov [Radiation Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Bethesda, Maryland (United States); Gilbert, Ethel; Curtis, Rochelle; Inskip, Peter; Kleinerman, Ruth; Morton, Lindsay; Rajaraman, Preetha; Little, Mark P. [Radiation Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Bethesda, Maryland (United States)

    2013-06-01

    Rapid innovations in radiation therapy techniques have resulted in an urgent need for risk projection models for second cancer risks from high-dose radiation exposure, because direct observation of the late effects of newer treatments will require patient follow-up for a decade or more. However, the patterns of cancer risk after fractionated high-dose radiation are much less well understood than those after lower-dose exposures (0.1-5 Gy). In particular, there is uncertainty about the shape of the dose-response curve at high doses and about the magnitude of the second cancer risk per unit dose. We reviewed the available evidence from epidemiologic studies of second solid cancers in organs that received high-dose exposure (>5 Gy) from radiation therapy where dose-response curves were estimated from individual organ-specific doses. We included 28 eligible studies with 3434 second cancer patients across 11 second solid cancers. Overall, there was little evidence that the dose-response curve was nonlinear in the direction of a downturn in risk, even at organ doses of ≥60 Gy. Thyroid cancer was the only exception, with evidence of a downturn after 20 Gy. Generally the excess relative risk per Gray, taking account of age and sex, was 5 to 10 times lower than the risk from acute exposures of <2 Gy among the Japanese atomic bomb survivors. However, the magnitude of the reduction in risk varied according to the second cancer. The results of our review provide insights into radiation carcinogenesis from fractionated high-dose exposures and are generally consistent with current theoretical models. The results can be used to refine the development of second solid cancer risk projection models for novel radiation therapy techniques.

  3. Formation and accumulation of radiation-induced defects and radiolysis products in modified lithium orthosilicate pebbles with additions of titanium dioxide

    Science.gov (United States)

    Zarins, Arturs; Valtenbergs, Oskars; Kizane, Gunta; Supe, Arnis; Knitter, Regina; Kolb, Matthias H. H.; Leys, Oliver; Baumane, Larisa; Conka, Davis

    2016-03-01

    Lithium orthosilicate (Li4SiO4) pebbles with 2.5 wt.% excess of silicon dioxide (SiO2) are the European Union's designated reference tritium breeding ceramics for the Helium Cooled Pebble Bed (HCPB) Test Blanket Module (TBM). However, the latest irradiation experiments showed that the reference Li4SiO4 pebbles may crack and form fragments under operation conditions as expected in the HCPB TBM. Therefore, it has been suggested to change the chemical composition of the reference Li4SiO4 pebbles and to add titanium dioxide (TiO2), to obtain lithium metatitanate (Li2TiO3) as a second phase. The aim of this research was to investigate the formation and accumulation of radiation-induced defects (RD) and radiolysis products (RP) in the modified Li4SiO4 pebbles with different contents of TiO2 for the first time, in order to estimate and compare radiation stability. The reference and the modified Li4SiO4 pebbles were irradiated with accelerated electrons (E = 5 MeV) up to 5000 MGy absorbed dose at 300-990 K in a dry argon atmosphere. By using electron spin resonance (ESR) spectroscopy it was determined that in the modified Li4SiO4 pebbles, several paramagnetic RD and RP are formed and accumulated, like, E' centres (SiO33-/TiO33-), HC2 centres (SiO43-/TiO3-) etc. On the basis of the obtained results, it is concluded that the modified Li4SiO4 pebbles with TiO2 additions have comparable radiation stability with the reference pebbles.

  4. Growth and applicability of radiation-responsive silica nanowires

    Science.gov (United States)

    Bettge, Martin

    manganese oxide (LiMn2O4), for use as positive materials, retain their unique texture after 30 cycles, as verified by scanning and transmission electron microscopy. Some accelerated capacity fade is however observed and attributed to chemical dissolution of the oxide material. Frequency-dependent impedances of textured oxide films are lower than those for planar films. These findings suggest that thin film texturing can indeed enhance some of the material's electrochemical performance characteristics and can be applied to a wide range of materials through use of appropriate nanostructured templates. In summary, this dissertation outlines physical and chemical factors leading to the formation of free-standing and uniquely stranded nanowires. It also provides an outlook on how ion-induced nanowire bending and alignment could be exploited. Key technological advantages of the developed process are refractory nanowire growth at low substrate temperatures and the ability to form radiation-responsive nanowire arrays without the use of lithography or templates.

  5. Transgene Expression and Host Cell Responses to Replication-Defective, Single-Cycle, and Replication-Competent Adenovirus Vectors

    Directory of Open Access Journals (Sweden)

    Catherine M. Crosby

    2017-02-01

    Full Text Available Most adenovirus (Ad vectors are E1 gene deleted replication defective (RD-Ad vectors that deliver one transgene to the cell and all expression is based on that one gene. In contrast, E1-intact replication-competent Ad (RC-Ad vectors replicate their DNA and their transgenes up to 10,000-fold, amplifying transgene expression markedly higher than RD-Ad vectors. While RC-Ad are more potent, they run the real risk of causing adenovirus infections in vector recipients and those that administer them. To gain the benefits of transgene amplification, but avoid the risk of Ad infections, we developed “single cycle” Ad (SC-Ad vectors. SC-Ads amplif