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Sample records for methyl viologen mv

  1. Radiochromic film containing methyl viologen for radiation dosimetry

    DEFF Research Database (Denmark)

    Lavalle, M.; Corda, U.; Fuochi, P.G.

    2007-01-01

    Poly(vinyl alcohol) (PVA) films containing methyl viologen (MV2+) that colours blue upon exposure to ionizing radiation were investigated as possible dosimeters for use in radiation processing applications. In order to find the most suitable composition of the PVA-MV2+ film, different......, humidity and temperature on the response of the PVA-MV2+ dosimeter film have been studied under laboratory conditions. We conclude that the PVA film containing MV2+ is a promising tool for the absorbed dose measurements in several industrial applications of ionizing radiations. (C) 2007 Elsevier Ltd. All...

  2. Hydrogen-Atom Attack on Methyl Viologen in Aqueous Solution Studied by Pulse Radiolysis

    DEFF Research Database (Denmark)

    Solar, S.; Solar, W.; Getoff, N.

    1984-01-01

    Using hydrogen at high pressures of up to 150 bar (0.12 mol dm–3 H2) as an OH scavenger in aqueous MV2+ solutions (pH 1) it is possible to differentiate between two kinds of transient formed simultaneously by H-atom attack on methyl viologen. One of them is assigned to an H adduct on the N atom, ...

  3. Temperature effect on the photoinduced reduction of methyl viologen with several sensitizers and the evolution of hydrogen from water

    Energy Technology Data Exchange (ETDEWEB)

    Nenadovic, M.T.; Micic, O.I.; Rajh, T.; Savic, D.

    1983-01-01

    Irradiation by visible light of an aqueous solution containing a photosensitizer, methyl viologen (MV/sup 2 +/) and ethylenediaminetetraacetic acid leads to the formation of the reduced form of methyl viologen (MV/sup +/). The quantum yield for the formation of MV/sup +/ depends strongly on the time during which the formation is observed owing to the reaction of MV/sup +/ with oxidative products and its reduction to MV/sup 0/. Proflavin, acridine yellow and ruthenium(II)tris(2,2-bipyridyl) were used as photosensitizers and showed the same ability to promote hydrogen evolution. When CdS was used as a sensitizer a factor of 10 less hydrogen was obtained than when the dyes were used. The redox catalysts platinum, Pt-TiO/sub 2/-RuO/sub 2/ and Pt-CdS in colloidal systems showed approximately the same activity towards the reduction of water. The reduction of MV/sup 2 +/ and the evolution of hydrogen were enhanced at higher temperatures (70/sup 0/C). The optimum conditions for water reduction on redox catalysts in colloidal system under continuous illumination are analysed.

  4. Effects of Exogenous Melatonin on Methyl Viologen-Mediated Oxidative Stress in Apple Leaf

    Directory of Open Access Journals (Sweden)

    Zhiwei Wei

    2018-01-01

    Full Text Available Oxidative stress is a major source of damage of plants exposed to adverse environments. We examined the effect of exogenous melatonin (MT in limiting of oxidative stress caused by methyl viologen (MV; paraquatin in apple leaves (Malus domestica Borkh.. When detached leaves were pre-treated with melatonin, their level of stress tolerance increased. Under MV treatment, melatonin effectively alleviated the decrease in chlorophyll concentrations and maximum potential Photosystem II efficiency while also mitigating membrane damage and lipid peroxidation when compared with control leaves that were sprayed only with water prior to the stress experiment. The melatonin-treated leaves also showed higher activities and transcripts of antioxidant enzymes superoxide dismutase, peroxidase, and catalase. In addition, the expression of genes for those enzymes was upregulated. Melatonin-synthesis genes MdTDC1, MdT5H4, MdAANAT2, and MdASMT1 were also upregulated under oxidative stress in leaves but that expression was suppressed in response to 1 mM melatonin pretreatment during the MV treatments. Therefore, we conclude that exogenous melatonin mitigates the detrimental effects of oxidative stress, perhaps by slowing the decline in chlorophyll concentrations, moderating membrane damage and lipid peroxidation, increasing the activities of antioxidant enzymes, and changing the expression of genes for melatonin synthesis.

  5. A One-compartment direct glucose alkaline fuel cell with methyl viologen as electron mediator

    International Nuclear Information System (INIS)

    Liu, Xianhua; Hao, Miaoqing; Feng, Mengnan; Zhang, Lin; Zhao, Yong; Du, Xiwen; Wang, Guangyi

    2013-01-01

    Highlights: ► A glucose–air alkaline fuel cell without using noble metal catalysts has been developed. ► The rudimentary fuel cell generates a maximum power density of 0.62 mW m −2 . ► The high performance is attributed to the use of MV and nickel foam. ► Main oxidation products are small organic acids indicating deep oxidation of glucose. - Abstract: Glucose is abundant, renewable, non-toxic and convenient as a fuel for fuel cells, but current technologies are unavailable for us to directly oxidize it to obtain energy. Fuel cells using enzymes and micro-organisms as catalysts are limited by their extremely low power output and rather short durability. Fuel cells using precious metal catalyst are expensive for large-scale use. In this work, a one-compartment direct glucose alkaline fuel cell has been developed that use methyl viologen (MV) as electron mediator and nickel foam as the anode. The rudimentary fuel cell generates a maximum power density of 0.62 mW cm −2 , while the maximum current density is 5.03 mA cm −2 . Electro-catalytic activities of MV and the nickel foam in alkaline conditions were studied by cyclic voltammetry. It is indicated that the high performance of the fuel cell is attributed to the combined use of MV and nickel foam. 13 C-NMR and HPLC were used to analyze oxidation products of glucose. The result shows that the principal oxidation products are short-chain organic acids indicating deep oxidation of glucose is achieved

  6. Differential Antioxidant Responses and Perturbed Porphyrin Biosynthesis after Exposure to Oxyfluorfen and Methyl Viologen in Oryza sativa

    Directory of Open Access Journals (Sweden)

    Nhi-Thi Pham

    2015-07-01

    Full Text Available We compared antioxidant responses and regulation of porphyrin metabolism in rice plants treated with oxyfluorfen (OF or methyl viologen (MV. Plants treated with MV exhibited not only greater increases in conductivity and malondialdehyde but also a greater decline in Fv/Fm, compared to plants treated with OF. MV-treated plants had greater increases in activities of superoxide dismutase (SOD and catalase (CAT as well as transcript levels of SODA and CATA than OF-treated plants after 28 h of the treatments, whereas increases in ascorbate peroxidase (APX activity and transcript levels of APXA and APXB were greater in OF-treated plants. Both OF- and MV-treated plants resulted in not only down-regulation of most genes involved in porphyrin biosynthesis but also disappearance of Mg-porphyrins during the late stage of photooxidative stress. By contrast, up-regulation of heme oxygenase 2 (HO2 is possibly part of an efficient antioxidant response to compensate photooxidative damage in both treatments. Our data show that down-regulated biosynthesis and degradation dynamics of porphyrin intermediates have important roles in photoprotection of plants from perturbed porphyrin biosynthesis and photosynthetic electron transport. This study suggests that porphyrin scavenging as well as strong antioxidative activities are required for mitigating reactive oxygen species (ROS production under photooxidative stress caused by OF and MV.

  7. Differential Antioxidant Responses and Perturbed Porphyrin Biosynthesis after Exposure to Oxyfluorfen and Methyl Viologen in Oryza sativa.

    Science.gov (United States)

    Pham, Nhi-Thi; Kim, Jin-Gil; Jung, Sunyo

    2015-07-21

    We compared antioxidant responses and regulation of porphyrin metabolism in rice plants treated with oxyfluorfen (OF) or methyl viologen (MV). Plants treated with MV exhibited not only greater increases in conductivity and malondialdehyde but also a greater decline in Fv/Fm, compared to plants treated with OF. MV-treated plants had greater increases in activities of superoxide dismutase (SOD) and catalase (CAT) as well as transcript levels of SODA and CATA than OF-treated plants after 28 h of the treatments, whereas increases in ascorbate peroxidase (APX) activity and transcript levels of APXA and APXB were greater in OF-treated plants. Both OF- and MV-treated plants resulted in not only down-regulation of most genes involved in porphyrin biosynthesis but also disappearance of Mg-porphyrins during the late stage of photooxidative stress. By contrast, up-regulation of heme oxygenase 2 (HO2) is possibly part of an efficient antioxidant response to compensate photooxidative damage in both treatments. Our data show that down-regulated biosynthesis and degradation dynamics of porphyrin intermediates have important roles in photoprotection of plants from perturbed porphyrin biosynthesis and photosynthetic electron transport. This study suggests that porphyrin scavenging as well as strong antioxidative activities are required for mitigating reactive oxygen species (ROS) production under photooxidative stress caused by OF and MV.

  8. A high sensitive ion pairing probe (the interaction of pyrenetetrasulphonate and methyl viologen): Salt and temperature dependences and applications

    Energy Technology Data Exchange (ETDEWEB)

    Santana, Jeferson [Departamento de Bioquímica e Departamento de Química, Instituto de Química, Universidade de São Paulo, SP (Brazil); Perez, Katia R. [Departamento de Biofísica, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo-SP (Brazil); Pisco, Thiago B.; Pavanelli, David D.; Briotto Filho, Décio; Rezende, Daisy [Departamento de Bioquímica e Departamento de Química, Instituto de Química, Universidade de São Paulo, SP (Brazil); Rezende Triboni, Eduardo [Universidade Nove de Julho, São Paulo, São Paulo-SP (Brazil); Chagas Alves Lima, Francisco das [Coordenação de Química, Universidade Estadual do Piauí, Teresina-PI (Brazil); Lopes Magalhães, Janildo [Departamento de Química, Centro de Ciências da Natureza, Universidade Federal do Piauí, Centro de Ciências da Natureza, Teresina, PI (Brazil); Midea Cuccovia, Iolanda [Departamento de Bioquímica e Departamento de Química, Instituto de Química, Universidade de São Paulo, SP (Brazil); and others

    2014-07-01

    The interaction between pyrenetetrasulphonate (PTS) and methyl viologen (MV{sup 2+}) leads to a 1:1 charge transfer complex (CTC) in the concentration range below mmol L{sup −1} of the ligands. Quantum mechanical calculations show the 1:1 complex having the planar moiety of PTS and the charges of the sulfonate groups stabilized by the twisted rings of the positively charged MV{sup 2+} species. The peculiar nature of PTS includes high fluorescence quantum yield (∼1), clear specular UV–vis spectra and fluorescence emission images, as well similar S{sub 2}←S{sub 0} and S{sub 3}←S{sub 0} transitions as those of S{sub 1}←S{sub 0,} all of them exhibiting well resolved vibrational structure. MV{sup 2+} has well known electron-accepting properties that favor the complexation. These features were studied as a function of salt concentration and temperature dependences allowing a detailed comprehension of static and dynamic association processes. Quantum mechanical calculations show the 1:1 stabilization of PTS/MV{sup 2+}. In addition the effect of urea on the CTC equilibrium is presented, as expected the additive acts towards the non-complexed species (solvated free ions). The fluorescence quenching of MV{sup 2+}over PTS highlights is one of the applications of this effect for giant vesicles characterization. - Highlights: • We determined the details of PTS/MV{sup 2+} 1:1 complex formation. • Ground and excited states formation is operative. • Ion pairing effects due to urea effect are shown. • Vesicle formation is illustrated by the pair.

  9. A high constitutive catalase activity confers resistance to methyl viologen-promoted oxidative stress in a mutant of the cyanobacterium Nostoc punctiforme ATCC 29133.

    Science.gov (United States)

    Moirangthem, Lakshmipyari Devi; Bhattacharya, Sudeshna; Stensjö, Karin; Lindblad, Peter; Bhattacharya, Jyotirmoy

    2014-04-01

    A spontaneous methyl viologen (MV)-resistant mutant of the nitrogen-fixing cyanobacterium Nostoc punctiforme ATCC 29133 was isolated and the major enzymatic antioxidants involved in combating MV-induced oxidative stress were evaluated. The mutant displayed a high constitutive catalase activity as a consequence of which, the intracellular level of reactive oxygen species in the mutant was lower than the wild type (N. punctiforme) in the presence of MV. The superoxide dismutase (SOD) activity that consisted of a SodA (manganese-SOD) and a SodB (iron-SOD) was not suppressed in the mutant following MV treatment. The mutant was, however, characterised by a lower peroxidase activity compared with its wild type, and its improved tolerance to externally added H₂O₂ could only be attributed to enhanced catalase activity. Furthermore, MV-induced toxic effects on the wild type such as (1) loss of photosynthetic performance assessed as maximal quantum yield of photosystem II, (2) nitrogenase inactivation, and (3) filament fragmentation and cell lysis were not observed in the mutant. These findings highlight the importance of catalase in preventing MV-promoted oxidative damage and cell death in the cyanobacterium N. punctiforme. Such oxidative stress resistant mutants of cyanobacteria are likely to be a better source of biofertilisers, as they can grow and fix nitrogen in an unhindered manner in agricultural fields that are often contaminated with the herbicide MV, also commonly known as paraquat.

  10. A Rice CPYC-Type Glutaredoxin OsGRX20 in Protection against Bacterial Blight, Methyl Viologen and Salt Stresses

    Directory of Open Access Journals (Sweden)

    Xi Ning

    2018-02-01

    Full Text Available Glutaredoxins (GRXs belong to the antioxidants involved in the cellular stress responses. In spite of the identification 48 GRX genes in rice genomes, the biological functions of most of them remain unknown. Especially, the biological roles of members of GRX family in disease resistance are still lacking. Our proteomic analysis found that OsGRX20 increased by 2.7-fold after infection by bacterial blight. In this study, we isolated and characterized the full-length nucleotide sequences of the rice OsGRX20 gene, which encodes a GRX family protein with CPFC active site of CPYC-type class. OsGRX20 protein was localized in nucleus and cytosol, and its transcripts were expressed predominantly in leaves. Several stress- and hormone-related motifs putatively acting as regulatory elements were found in the OsGRX20 promoter. Real-time quantitative PCR analysis indicated that OsGRX20 was expressed at a significantly higher level in leaves of a resistant or tolerant rice genotype, Yongjing 50A, than in a sensitive genotype, Xiushui 11, exposed to bacterial blight, methyl viologen, heat, and cold. Its expression could be induced by salt, PEG-6000, 2,4-D, salicylic acid, jasmonic acid, and abscisic acid treatments in Yongjing 50A. Overexpression of OsGRX20 in rice Xiushui 11 significantly enhanced its resistance to bacterial blight attack, and tolerance to methyl viologen and salt stresses. In contrast, interference of OsGRX20 in Yongjing 50A led to increased susceptibility to bacterial blight, methyl viologen and salt stresses. OsGRX20 restrained accumulation of superoxide radicals in aerial tissue during methyl viologen treatment. Consistently, alterations in OsGRX20 expression affect the ascorbate/dehydroascorbate ratio and the abundance of transcripts encoding four reactive oxygen species scavenging enzymes after methyl viologen-induced stress. Our results demonstrate that OsGRX20 functioned as a positive regulator in rice tolerance to multiple stresses

  11. Photoinduced electron transfer between anionic fluorophores and methyl viologen in homogeneous and microheterogeneous media

    Energy Technology Data Exchange (ETDEWEB)

    Burai, Tarak Nath; Panda, Debashis; Iyer, E Siva Subramaniam [Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400 076 (India); Datta, Anindya, E-mail: anindya@chem.iitb.ac.in [Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400 076 (India)

    2012-11-15

    The rate and extent of photoinduced electron transfer change significantly as a result of confinement in nanovolumes. Study of such processes is an active area of research in physical chemistry. The effect is most interesting when the molecules that participate in PET are charged. In the present article, the modulation of PET has been studied for two anionic fluorophores: Lucifer Yellow CH and chlorin p{sub 6} with Methylviologen dication. PET, manifested in the quenching of fluorescence of the fluorophores, has been modulated by incorporating the molecules in organized assemblies like micelles, reverse micelles and supramolecular hosts. The dynamics of the process has been monitored in the femtosecond to nanosecond timescale. The modulation of the electron transfer has been found to be occurring mainly due to the disruption of contact ion pairs formed between the fluorophores and the quencher. - Highlights: Black-Right-Pointing-Pointer Modulation of PET of biologically active fluorophores and Methyl viologen. Black-Right-Pointing-Pointer Static and Dynamic Quenching present. Black-Right-Pointing-Pointer PET enhanced upon encapsulation, studied through Fluorescence upconversion experiments. Black-Right-Pointing-Pointer Rotational anisotropy has significant contribution in quenching.

  12. Photoinduced electron transfer between anionic fluorophores and methyl viologen in homogeneous and microheterogeneous media

    International Nuclear Information System (INIS)

    Burai, Tarak Nath; Panda, Debashis; Iyer, E Siva Subramaniam; Datta, Anindya

    2012-01-01

    The rate and extent of photoinduced electron transfer change significantly as a result of confinement in nanovolumes. Study of such processes is an active area of research in physical chemistry. The effect is most interesting when the molecules that participate in PET are charged. In the present article, the modulation of PET has been studied for two anionic fluorophores: Lucifer Yellow CH and chlorin p 6 with Methylviologen dication. PET, manifested in the quenching of fluorescence of the fluorophores, has been modulated by incorporating the molecules in organized assemblies like micelles, reverse micelles and supramolecular hosts. The dynamics of the process has been monitored in the femtosecond to nanosecond timescale. The modulation of the electron transfer has been found to be occurring mainly due to the disruption of contact ion pairs formed between the fluorophores and the quencher. - Highlights: ► Modulation of PET of biologically active fluorophores and Methyl viologen. ► Static and Dynamic Quenching present. ► PET enhanced upon encapsulation, studied through Fluorescence upconversion experiments. ► Rotational anisotropy has significant contribution in quenching.

  13. Molecular Cloning and Biochemical Characterization of the Iron Superoxide Dismutase from the Cyanobacterium Nostoc punctiforme ATCC 29133 and Its Response to Methyl Viologen-Induced Oxidative Stress.

    Science.gov (United States)

    Moirangthem, Lakshmipyari Devi; Ibrahim, Kalibulla Syed; Vanlalsangi, Rebecca; Stensjö, Karin; Lindblad, Peter; Bhattacharya, Jyotirmoy

    2015-12-01

    Superoxide dismutase (SOD) detoxifies cell-toxic superoxide radicals and constitutes an important component of antioxidant machinery in aerobic organisms, including cyanobacteria. The iron-containing SOD (SodB) is one of the most abundant soluble proteins in the cytosol of the nitrogen-fixing cyanobacterium Nostoc punctiforme ATCC 29133, and therefore, we investigated its biochemical properties and response to oxidative stress. The putative SodB-encoding open reading frame Npun_R6491 was cloned and overexpressed in Escherichia coli as a C-terminally hexahistidine-tagged protein. The purified recombinant protein had a SodB specific activity of 2560 ± 48 U/mg protein at pH 7.8 and was highly thermostable. The presence of a characteristic iron absorption peak at 350 nm, and its sensitivity to H2O2 and azide, confirmed that the SodB is an iron-containing SOD. Transcript level of SodB in nitrogen-fixing cultures of N. punctiforme decreased considerably (threefold) after exposure to an oxidative stress-generating herbicide methyl viologen for 4 h. Furthermore, in-gel SOD activity analysis of such cultures grown at increasing concentrations of methyl viologen also showed a loss of SodB activity. These results suggest that SodB is not the primary scavenger of superoxide radicals induced by methyl viologen in N. punctiforme.

  14. Reactivity of OH and O– with aqueous methyl viologen studied by pulse radiolysis

    DEFF Research Database (Denmark)

    Solar, Sonja; Solar, Wolfgang; Getoff, Nikola

    1985-01-01

    The behaviour of aqueous MV2+ towards oxidizing radicals (OH and O–) has been investigated in the pH range from 6 to 14 by means of pulse radiolysis. A semi-linear optimization method was applied for resolving the complex reaction mechanism. In the pH range from 6 to 8 the rate constant for attac...

  15. An Investigation of Methyl Viologen Functionalized Reduced Graphene Oxide: Chitosan as a Support for Pt Nanoparticles Towards Ethanol Electrooxidation

    Science.gov (United States)

    Ekrami-Kakhki, Mehri-Saddat; Farzaneh, Nahid; Abbasi, Sedigheh; Beitollahi, Hadi; Ekrami-Kakhki, Seyed Ali

    2018-05-01

    In this research, graphene oxide was prepared by a modified Hummers' method, and then functionalized with 1, 1'-dimethyl-4, 4'-bipyridinium dichloride (MV), and chitosan (CH) to get a MV-RGO-CH support. Pt nanoparticles were prepared on this support to get Pt/MV-RGO-CH catalyst. The morphology and microstructure of Pt/MV-RGO-CH catalyst were characterized with transmission electron microscopy image and X-ray diffraction analysis. The electrocatalytic activity of the prepared catalyst towards ethanol oxidation was investigated by carbon monoxide stripping voltammetry, cyclic voltammetry, and electrochemical impedance spectroscopy techniques. The effects of some experimental parameters such as scan rate, ethanol concentration, and temperature were investigated for ethanol electrooxidation at Pt/MV-RGO-CH catalyst. Durability of the catalyst was also investigated. The electrocatalytic performance of Pt/MV-RGO-CH catalyst for ethanol oxidation was compared with those of Pt/CH and Pt/MV-RGO catalysts. The higher electrocatalytic performance of Pt/MV-RGO-CH than Pt/CH and Pt/MV-RGO catalysts towards ethanol electrooxidation indicated that Pt/MV-RGO-CH could be a promising catalyst for application in direct ethanol fuel cells.

  16. CaMV-35S promoter sequence-specific DNA methylation in lettuce.

    Science.gov (United States)

    Okumura, Azusa; Shimada, Asahi; Yamasaki, Satoshi; Horino, Takuya; Iwata, Yuji; Koizumi, Nozomu; Nishihara, Masahiro; Mishiba, Kei-ichiro

    2016-01-01

    We found 35S promoter sequence-specific DNA methylation in lettuce. Additionally, transgenic lettuce plants having a modified 35S promoter lost methylation, suggesting the modified sequence is subjected to the methylation machinery. We previously reported that cauliflower mosaic virus 35S promoter-specific DNA methylation in transgenic gentian (Gentiana triflora × G. scabra) plants occurs irrespective of the copy number and the genomic location of T-DNA, and causes strong gene silencing. To confirm whether 35S-specific methylation can occur in other plant species, transgenic lettuce (Lactuca sativa L.) plants with a single copy of the 35S promoter-driven sGFP gene were produced and analyzed. Among 10 lines of transgenic plants, 3, 4, and 3 lines showed strong, weak, and no expression of sGFP mRNA, respectively. Bisulfite genomic sequencing of the 35S promoter region showed hypermethylation at CpG and CpWpG (where W is A or T) sites in 9 of 10 lines. Gentian-type de novo methylation pattern, consisting of methylated cytosines at CpHpH (where H is A, C, or T) sites, was also observed in the transgenic lettuce lines, suggesting that lettuce and gentian share similar methylation machinery. Four of five transgenic lettuce lines having a single copy of a modified 35S promoter, which was modified in the proposed core target of de novo methylation in gentian, exhibited 35S hypomethylation, indicating that the modified sequence may be the target of the 35S-specific methylation machinery.

  17. Overexpression of Iron Superoxide Dismutase in Transformed Poplar Modifies the Regulation of Photosynthesis at Low CO2 Partial Pressures or Following Exposure to the Prooxidant Herbicide Methyl Viologen1

    Science.gov (United States)

    Arisi, Ana-Carolina M.; Cornic, Gabriel; Jouanin, Lise; Foyer, Christine H.

    1998-01-01

    Chloroplast-targeted overexpression of an Fe superoxide dismutase (SOD) from Arabidopsis thaliana resulted in substantially increased foliar SOD activities. Ascorbate peroxidase, glutathione reductase, and monodehydroascorbate reductase activities were similar in the leaves from all of the lines, but dehydroascorbate reductase activity was increased in the leaves of the FeSOD transformants relative to untransformed controls. Foliar H2O2, ascorbate, and glutathione contents were comparable in all lines of plants. Irradiance-dependent changes in net CO2 assimilation and chlorophyll a fluorescence quenching parameters were similar in all lines both in air (21% O2) and at low (1%) O2. CO2-response curves for photosynthesis showed similar net CO2-exchange characteristics in all lines. In contrast, values of photochemical quenching declined in leaves from untransformed controls at intercellular CO2 (Ci) values below 200 μL L−1 but remained constant with decreasing Ci in leaves of FeSOD transformants. When the O2 concentration was decreased from 21 to 1%, the effect of FeSOD overexpression on photochemical quenching at limiting Ci was abolished. At high light (1000 μmol m−2 s−1) a progressive decrease in the ratio of variable (Fv) to maximal (Fm) fluorescence was observed with decreasing temperature. At 6oC the high-light-induced decrease in the Fv/Fm ratio was partially prevented by low O2 but values were comparable in all lines. Methyl viologen caused decreased Fv/Fm ratios, but this was less marked in the FeSOD transformants than in the untransformed controls. These observations suggest that the rate of superoxide dismutation limits flux through the Mehler-peroxidase cycle in certain conditions. PMID:9625709

  18. Electrochromic mirror using viologen-anchored nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Han Na [Electronics and Telecommunications Research Institute, Nature-mimic I/O interface Research Section, 218 Gajeong-roYuseong-gu, Daejeon 305-700 (Korea, Republic of); University of Science and Technology, Advanced Device Technology, 217 Gajeong-roYuseong-gu, Daejeon 305-350 (Korea, Republic of); Cho, Seong M.; Ah, Chil Seong; Song, Juhee; Ryu, Hojun; Kim, Yong Hae [Electronics and Telecommunications Research Institute, Nature-mimic I/O interface Research Section, 218 Gajeong-roYuseong-gu, Daejeon 305-700 (Korea, Republic of); Kim, Tae-Youb, E-mail: youby@etri.re.kr [Electronics and Telecommunications Research Institute, Nature-mimic I/O interface Research Section, 218 Gajeong-roYuseong-gu, Daejeon 305-700 (Korea, Republic of); University of Science and Technology, Advanced Device Technology, 217 Gajeong-roYuseong-gu, Daejeon 305-350 (Korea, Republic of)

    2016-10-15

    Highlights: • Three types of ECM device were fabricated using viologen-anchored ECDs. • The devices were investigated according to their optical structures. • The anti-reflection material affects the reflectance and the coloration efficiency. • The device design of ECMs is a crucial factor for clear reflected images. - Abstract: Electrochromic mirrors (ECMs) that are used in automobile mirrors need to have high reflectance, a high contrast ratio, and a clear image. In particular, it is critical that distortions of clear images are minimized for safety. Therefore, an ECM is fabricated using viologen-anchored nanoparticles and a magnesium fluoride (MgF{sub 2}) layer with an anti-reflection function. The ECM has approximately 30.42% in the reflectance dynamic range and 125 cm{sup 2}/C high coloration efficiency.

  19. Photoreduction of viologen with (Zn-TPPS/sub 3/)/sup 3 -/. Triethanolamine- viologen system in the presence of micelles

    Energy Technology Data Exchange (ETDEWEB)

    Kita, Tatsuya; Okura, Ichiro

    1988-04-10

    Photoreduction of viologen was made in the presence of various surfactant micelles by irradading a trinary system of triethanol-amine, zinc meso-tetraphenylporphyrintrisulfonate ; (Zn-TPPS/sub 3/)/sup 3 -/, and viologen with the visible light. Although the rate of photoreduction of viologen was remarkably increased in the presence of either cationic or anionic micelles, it is not noticeably increased in the presence of neutral ones. The elementary reactions were measured by the laser flashing method. The elementary reactions were measured by the laser flashing method. The result indicates that the presence of ionic micelles retards both the quenching reaction of photoexcited (Zn-TPPS/sub 3/)/sup 3 -/ by viologen and the recombination reaction of the oxidative (Zn-TPPS/sub 3/)/sup 3 -/ with the reductive viologen and that the rate of reduction of viologen is much increased by the retardation of the recombination reaction. (6 figs, 1 tab, 16 refs)

  20. Interaction between viologen-phosphorus dendrimers and α-synuclein

    International Nuclear Information System (INIS)

    Milowska, Katarzyna; Grochowina, Justyna; Katir, Nadia; El Kadib, Abdelkrim; Majoral, Jean-Pierre; Bryszewska, Maria; Gabryelak, Teresa

    2013-01-01

    In this study the interaction between viologen-phosphorus dendrimers and α-synuclein (ASN) was examined. Polycationic viologen-phosphorus dendrimers (two positive charges per viologen unit) are novel compounds with relatively unknown properties. The influence of these viologen dendrimers on ASN was tested using fluorimetric and circular dichroism methods. ASN contains four tyrosine residues; therefore, the influence of dendrimers on protein molecular conformation by measuring the changes in the ASN fluorescence in the presence of dendrimers was evaluated. The interaction of dendrimers with free L-tyrosine was also monitored. Results show that viologen-phosphorus dendrimers interact with ASN; they quenched the fluorescence of ASN as well as free tyrosine by dynamic and static ways. However, the quenching was not accompanied by modifications in the ASN secondary structure. - Highlights: ► Interaction between viologen-phosphorus dendrimers and α-synuclein (ASN) was investigated. ► Viologen-phosphorus dendrimers can quench the fluorescence of tyrosine in ASN. ► Dendrimers caused red-shift in maximum of fluorescence. ► Viologen-phosphorus dendrimers did not change the secondary structure of ASN.

  1. Interaction between viologen-phosphorus dendrimers and {alpha}-synuclein

    Energy Technology Data Exchange (ETDEWEB)

    Milowska, Katarzyna, E-mail: milowska@biol.uni.lodz.pl [Department of General Biophysics, Faculty of Biology and Environmental Protection, University of Lodz, Pomorska 141/143, 90-236 Lodz (Poland); Grochowina, Justyna [Department of General Biophysics, Faculty of Biology and Environmental Protection, University of Lodz, Pomorska 141/143, 90-236 Lodz (Poland); Katir, Nadia [Laboratoire de Chimie de Coordination CNRS, 205 route de Narbonne, 31077 Toulouse (France); El Kadib, Abdelkrim [Institute of Nanomaterials and Nanotechnology (INANOTECH)-MAScIR (Moroccan Foundation for Advanced Science, Innovation and Research), ENSET, Avenue de I' Armee Royale, Madinat El Irfane, 10100 Rabat (Morocco); Majoral, Jean-Pierre [Laboratoire de Chimie de Coordination CNRS, 205 route de Narbonne, 31077 Toulouse (France); Bryszewska, Maria; Gabryelak, Teresa [Department of General Biophysics, Faculty of Biology and Environmental Protection, University of Lodz, Pomorska 141/143, 90-236 Lodz (Poland)

    2013-02-15

    In this study the interaction between viologen-phosphorus dendrimers and {alpha}-synuclein (ASN) was examined. Polycationic viologen-phosphorus dendrimers (two positive charges per viologen unit) are novel compounds with relatively unknown properties. The influence of these viologen dendrimers on ASN was tested using fluorimetric and circular dichroism methods. ASN contains four tyrosine residues; therefore, the influence of dendrimers on protein molecular conformation by measuring the changes in the ASN fluorescence in the presence of dendrimers was evaluated. The interaction of dendrimers with free L-tyrosine was also monitored. Results show that viologen-phosphorus dendrimers interact with ASN; they quenched the fluorescence of ASN as well as free tyrosine by dynamic and static ways. However, the quenching was not accompanied by modifications in the ASN secondary structure. - Highlights: Black-Right-Pointing-Pointer Interaction between viologen-phosphorus dendrimers and {alpha}-synuclein (ASN) was investigated. Black-Right-Pointing-Pointer Viologen-phosphorus dendrimers can quench the fluorescence of tyrosine in ASN. Black-Right-Pointing-Pointer Dendrimers caused red-shift in maximum of fluorescence. Black-Right-Pointing-Pointer Viologen-phosphorus dendrimers did not change the secondary structure of ASN.

  2. Synthesis and Characterization of Ru(II) Tris(1,1O-phenanthroline)-Electron Acceptor Dyads Incorporating the 4-benzoyl-N-methylpyridinium Cation or N-Benzyl-N'-methyl-viologen. Improving the Dynamic Range, Sensitivity and Response Time of Sol-Gel Based Optical Oxygen Sensors

    Science.gov (United States)

    Leventis, Nicholas; Rawashdeh, Abdel-Monen M.; Elder, Ian A.; Yang, Jinhua; Dass, Amala; Sotiriou-Leventis, Chariklia

    2004-01-01

    The title compounds (1 and 2, above) were synthesized by Sonogashira coupling reactions of appropriate Ru(1I) complexes with the electron a cceptors. Characterization was conducted in solution and in frozen ma trices. Finally, the title compounds were evaluated as dopants of sol-gel materials. It was found that the intramolecular quenching efficie ncy of 4-benzoyl-Nmethylpyridinium cation in solution depends on the solvent: photoluminescence is quenched completely in CH,CN, but not i n methanol or ethanol. On the other hand, intramolecular emission que nching by 4-benzyl-N-methyl viologen is complete in all solvents. The difference between the two quenchers is traced electrochemically to t he solvation of the 4-benzoyl-Nmethylpyridiniums by alcohol. In froze n matrices or adsorbed on the surfaces of silica aerogel, both Ru(I1) complex/electron acceptor dyads of this study are photoluminescent, and the absence of quenching has been traced to the environmental rigi dity. When doped aerogels are cooled at 77 K, the emission intensity increases by approximately 4x, and the spectra shift to the blue, analogous to what is observed with Ru(I1) complexes in solutions undergoi ng fluid-to-rigid transition. However, in contrast to frozen solution s, the luminescent moieties in the bulk of aerogels kept at low tempe ratures are still accessible to gas-phase quenchers diffusing through the mesopores, leading to more sensitive platforms for sensors than o ther room-temperature configurations. Thus the photoluminescence of o ur Ru(I1) complex dyads adsorbed on aerogel is quenchable by O2 both at room temperature and at 77 K. Furthermore, it was also found that O 2 modulates the photoluminescence of aerogels doped with 4-benzoyl -N -methylpyridinium-based dyads over a wider dynamic range compared wi th aerogels doped with either our vislogen-based dyads or with Ru(I1) tris(1,lO-phenanthroline) itself.

  3. Biological properties of new viologen-phosphorus dendrimers.

    Science.gov (United States)

    Ciepluch, Karol; Katir, Nadia; El Kadib, Abdelkrim; Felczak, Aleksandra; Zawadzka, Katarzyna; Weber, Monika; Klajnert, Barbara; Lisowska, Katarzyna; Caminade, Anne-Marie; Bousmina, Mostapha; Bryszewska, Maria; Majoral, Jean Pierre

    2012-03-05

    Some biological properties of eight dendrimers incorporating both phosphorus linkages and viologen units within their cascade structure or at the periphery were investigated for the first time. In particular cytotoxicity, hemotoxicity, and antimicrobial and antifungal activity of these new macromolecules were examined. Even if for example all these species exhibited good antimicrobial properties, it was demonstrated that their behavior strongly depends on several parameters as their size and molecular weight, the number of viologen units and the nature of the terminal groups.

  4. Pulse Radiolysis of Methyl Viologen in Aqueous Solutions

    DEFF Research Database (Denmark)

    Solar, S.; Solar, W.; Getoff, N.

    1982-01-01

    dm3 mol–1 s–1, absorbs at 310 nm (ε310= 900 m2 mol–1) and 470 nm (ε470= 630 m2 mol–1) and decays by conversion into MV˙+H+ in a first-order process with k= 6 × 103 s–1. For the equilibrium MV˙+H+ MV˙++ H+ pK= 2.9 ± 0.1 was determined. The presented data explain, at least partly, the instability...

  5. Search for a one-electron reduction of the cation radical of an "extended viologen," p-phenylene-bis-4,4´(1-aryl-2,6-diphenylpyridinium)

    Czech Academy of Sciences Publication Activity Database

    Pospíšil, Lubomír; Fiedler, Jan; Hromadová, Magdaléna; Gál, Miroslav; Valášek, M.; Pecka, J.; Michl, J.

    2006-01-01

    Roč. 153, č. 11 (2006), E179-E183 ISSN 0013-4651 R&D Projects: GA AV ČR IAA400400505; GA AV ČR KJB400400603; GA MŠk LC510; GA MŠk OC 140 Grant - others:U.S. National Science Foundation(US) CHE-0446688; US National Science Foundation(US) OISE 0532040 Institutional research plan: CEZ:AV0Z40400503 Keywords : aromatic poly(pyridinium salt)s * methyl viologen * aqueous-solution * heptyl viologen Subject RIV: CG - Electrochemistry Impact factor: 2.387, year: 2006

  6. Viologen-Phosphorus Dendrimers Inhibit α-Synuclein Fibrillation.

    Science.gov (United States)

    Milowska, Katarzyna; Grochowina, Justyna; Katir, Nadia; El Kadib, Abdelkrim; Majoral, Jean-Pierre; Bryszewska, Maria; Gabryelak, Teresa

    2013-03-04

    Inhibition of α-synuclein (ASN) fibril formation is a potential therapeutic strategy in Parkinson's disease and other synucleinopathies. The aim of this study was to examine the role of viologen-phosphorus dendrimers in the α-synuclein fibrillation process and to assess the structural changes in α-synuclein under the influence of dendrimers. ASN interactions with phosphonate and pegylated surface-reactive viologen-phosphorus dendrimers were examined by measuring the zeta potential, which allowed determining the number of dendrimer molecules that bind to the ASN molecule. The fibrillation kinetics and the structural changes were examined using ThT fluorescence and CD spectroscopy. Depending on the concentration of the used dendrimer and the nature of the reactive groups located on the surface, ASN fibrillation kinetics can be significantly reduced, and even, in the specific case of phosphonate dendrimers, the fibrillation can be totally inhibited at low concentrations. The presented results indicate that viologen-phosphorus dendrimers are able to inhibit ASN fibril formation and may be used as fibrillar regulating agents in neurodegenerative disorders.

  7. Porphyrinic supramolecular daisy chains incorporating pillar[5]arene-viologen host-guest interactions

    KAUST Repository

    Fathalla, Maher; Strutt, Nathan; Srinivasan, Sampath; Katsiev, Khabiboulakh; Hartlieb, Karel J.; Bakr, Osman; Stoddart, J. Fraser

    2015-01-01

    A porphyrin functionalised with pillar[5]arene and a viologen at its 5- and 15-meso positions assembles in a head-to-tail manner, producing linear supramolecular daisy chains in dichloromethane. At high concentrations, it forms an organogel which has been investigated by electron microscopy and rheological measurements, paving the way for the preparation of other functional supramolecular assemblies which harness viologen"⊂" pillararene host-guest interactions.

  8. Porphyrinic supramolecular daisy chains incorporating pillar[5]arene-viologen host-guest interactions

    KAUST Repository

    Fathalla, Maher

    2015-05-18

    A porphyrin functionalised with pillar[5]arene and a viologen at its 5- and 15-meso positions assembles in a head-to-tail manner, producing linear supramolecular daisy chains in dichloromethane. At high concentrations, it forms an organogel which has been investigated by electron microscopy and rheological measurements, paving the way for the preparation of other functional supramolecular assemblies which harness viologen"⊂" pillararene host-guest interactions.

  9. Photo-physical and structural interactions between viologen phosphorus-based dendrimers and human serum albumin

    International Nuclear Information System (INIS)

    Ciepluch, Karol; Katir, Nadia; El Kadib, Abdelkrim; Weber, Monika; Caminade, Anne-Marie; Bousmina, Mostapha; Pierre Majoral, Jean; Bryszewska, Maria

    2012-01-01

    This work deals with photo-physical and structural interactions between viologen phosphorus dendrimers and human serum albumin (HSA). Viologens are derivatives of 4,4′-bipyridinium salts. Aiming to rationalize the parameters governing such interactions eight types of these polycationic dendrimers in which the generation, the number of charges, the nature of the core and of the terminal groups vary from one to another, were designed and used. The influence of viologen-based dendrimers' on human serum albumin has been investigated. The photo-physical interactions of the two systems have been monitored by fluorescence quenching of free L-tryptophan and of HSA tryptophan residue. Additionally, using circular dichroism (CD) the effect of dendrimers on the secondary structure of albumin was measured. The obtained results show that viologen dendrimers interact with human serum albumin quenching its fluorescence either by collisional (dynamic) way or by forming complexes in a ground state (static quenching). In some cases the quenching is accompanied by changes of the secondary structure of HSA. - Highlights: ► Photo-physical interactions between viologen phosphorus dendrimers and human serum albumin (HSA) were investigated. ► The viologen dendrimers can quench the fluorescence of tryptophan in HSA. ► CD spectra to explain the changes in secondary structure of albumin after exposition of dendrimers.

  10. Photo-physical and structural interactions between viologen phosphorus-based dendrimers and human serum albumin

    Energy Technology Data Exchange (ETDEWEB)

    Ciepluch, Karol, E-mail: ciepluch@biol.uni.lodz.pl [Department of General Biophysics, University of Lodz, 141/143 Pomorska St., 90-236 Lodz (Poland); Katir, Nadia [Laboratoire de Chimie de Coordination du CNRS (LCC), 205 route de Narbonne, F-31077 Toulouse cedex 4 (France); Institute of Nanomaterials and Nanotechnology (INANOTECH)-MAScIR (Moroccan Foundation for Advanced Science, Innovation and Research), ENSET, Avenue de l' Armee Royale, Madinat El Irfane, 10100 Rabat (Morocco); El Kadib, Abdelkrim [Institute of Nanomaterials and Nanotechnology (INANOTECH)-MAScIR (Moroccan Foundation for Advanced Science, Innovation and Research), ENSET, Avenue de l' Armee Royale, Madinat El Irfane, 10100 Rabat (Morocco); Weber, Monika [Department of General Biophysics, University of Lodz, 141/143 Pomorska St., 90-236 Lodz (Poland); Caminade, Anne-Marie [Laboratoire de Chimie de Coordination du CNRS (LCC), 205 route de Narbonne, F-31077 Toulouse cedex 4 (France); Bousmina, Mostapha [Hassan II Academy of Sciences and Technology, Avenue MVI, Km4, 10220 Rabat (Morocco); Pierre Majoral, Jean [Laboratoire de Chimie de Coordination du CNRS (LCC), 205 route de Narbonne, F-31077 Toulouse cedex 4 (France); Hassan II Academy of Sciences and Technology, Avenue MVI, Km4, 10220 Rabat (Morocco); Bryszewska, Maria [Department of General Biophysics, University of Lodz, 141/143 Pomorska St., 90-236 Lodz (Poland)

    2012-06-15

    This work deals with photo-physical and structural interactions between viologen phosphorus dendrimers and human serum albumin (HSA). Viologens are derivatives of 4,4 Prime -bipyridinium salts. Aiming to rationalize the parameters governing such interactions eight types of these polycationic dendrimers in which the generation, the number of charges, the nature of the core and of the terminal groups vary from one to another, were designed and used. The influence of viologen-based dendrimers' on human serum albumin has been investigated. The photo-physical interactions of the two systems have been monitored by fluorescence quenching of free L-tryptophan and of HSA tryptophan residue. Additionally, using circular dichroism (CD) the effect of dendrimers on the secondary structure of albumin was measured. The obtained results show that viologen dendrimers interact with human serum albumin quenching its fluorescence either by collisional (dynamic) way or by forming complexes in a ground state (static quenching). In some cases the quenching is accompanied by changes of the secondary structure of HSA. - Highlights: Black-Right-Pointing-Pointer Photo-physical interactions between viologen phosphorus dendrimers and human serum albumin (HSA) were investigated. Black-Right-Pointing-Pointer The viologen dendrimers can quench the fluorescence of tryptophan in HSA. Black-Right-Pointing-Pointer CD spectra to explain the changes in secondary structure of albumin after exposition of dendrimers.

  11. Photoinduced Charge Shifts and Electron Transfer in Viologen-Tetraphenylborate Complexes: Push-Pull Character of the Exciplex.

    Science.gov (United States)

    Santos, Willy G; Budkina, Darya S; Deflon, Victor M; Tarnovsky, Alexander N; Cardoso, Daniel R; Forbes, Malcolm D E

    2017-06-14

    Viologen-tetraarylborate ion-pair complexes were prepared and investigated by steady-state and time-resolved spectroscopic techniques such as fluorescence and femtosecond transient absorption. The results highlight a charge transfer transition that leads to changes in the viologen structure in the excited singlet state. Femtosecond transient absorption reveals the formation of excited-state absorption and stimulated emission bands assigned to the planar (k obs < 10 12 s -1 ) and twisted (k obs ∼ 10 10 s -1 ) structures between two pyridinium groups in the viologen ion. An efficient photoinduced electron transfer from the tetraphenylborate anionic moiety to the viologen dication was observed less than 1 μs after excitation. This is a consequence of the push-pull character of the electron donor twisted viologen structure, which helps formation of the borate triplet state. The borate triplet state is deactivated further via a second electron transfer process, generating viologen cation radical (V •+ ).

  12. A new repeatable, optical writing and electrical erasing device based on photochromism and electrochromism of viologen

    International Nuclear Information System (INIS)

    Gao, Li-ping; Wei, Jian; Wang, Yue-chuan; Ding, Guo-jing; Yang, Yu-lin

    2012-01-01

    New optical writing and electrical erasing devices have been successfully fabricated that exploit the photochromism and electrochromism of viologen. In a preliminary study, both the structures of viologen and device were investigated in detail by UV–vis spectra in order to confirm their effects on the optical writing and electrical erasing performances of corresponding devices. For sandwiched, single and complementary devices based on benzyl viologen (BV 2+ ), only optical writing can be performed, not electrical erasing operations, which indicated these devices cannot realize optical information rewriting. For single and complementary devices based on styrene-functional viologen (V BV 2+ ) and acrylic-functional viologen (ACV 2+ ), optical writing and electrical erasing operations can be reversibly performed and optical information rewriting realized. It is clear that single devices based on V BV 2+ and ACV 2+ possess better performance accompanied with contrast without significant degradation and bleaching times and without significant deterioration over 10 repeated writing/erasing cycles. Furthermore, we put forward possible mechanisms for sandwiched, single and complementary devices based on V BV 2+ and ACV 2+ for the optical writing and electrical erasing operations. This study provides a new strategy to design optical writing and electrical erasing devices to realize optical information rewriting. (paper)

  13. Organic layers at metal/electrolyte interfaces: molecular structure and reactivity of viologen monolayers

    International Nuclear Information System (INIS)

    Breuer, Stephan; Pham, Duc T; Huemann, Sascha; Gentz, Knud; Zoerlein, Caroline; Wandelt, Klaus; Broekmann, Peter; Hunger, Ralf

    2008-01-01

    The adsorption of viologens (1,1'-disubstituted-4,4'-bipyridinium molecules) on a chloride-modified copper electrode has been studied using a combination of cyclic voltammetry (CV), in-situ scanning tunneling microscopy (STM) and ex-situ photoemission spectroscopy (XPS). Two prototypes of viologens could be identified with respect to their redox behavior upon adsorption, namely those which retain (non-reactive adsorption) and those which change their redox state (reactive adsorption) upon interaction with the chloride-modified copper surface at given potential. The first class of viologens represented by 1,1'-dibenzyl-4,4'-bipyridinium molecules (dibenzyl-viologens, abbreviated as DBV) can be adsorbed and stabilized on this electrode surface in their di-cationic state at potentials more positive than the reduction potential of the solution species. XPS N1s core level shifts verify that the adsorbed DBV molecules on the electrode are in their oxidized di-cationic state. Electrostatic attraction between the partially solvated viologen di-cations and the anionic chloride layer is discussed as the main driving force for the DBV stabilization on the electrode surface. Analysis of the N1s and O1s core level shifts points to a non-reactive DBV adsorption leaving the DBV ads 2+ solvation shell partly intact. The laterally ordered DBV ads 2+ monolayer turns out to be hydrophilic with at least four water molecules per viologen present within this cationic organic film. The analysis of the Cl2p core level reveals that no further chloride species are present at the surface besides those which are specifically adsorbed, i.e. which are in direct contact with the metallic copper surface underneath the organic layer. The reduction of these adsorbed DBV ads 2+ surface species takes place only in the same potential regime where the solvated DBV aq 2+ bulk solution species react and is accompanied by a pronounced structural change from the di-cationic 'cavitand'-structure to a

  14. Reversible polycolour change of viologens from violet through transparent to white

    International Nuclear Information System (INIS)

    Hoshino, Katsuyoshi; Oikawa, Yosuke; Sakabe, Ichiro; Komatsu, Toshiki

    2009-01-01

    The electrochromic properties of 1,1'-dibenzyl-4,4'-bipyridinium and 1,1'-diheptyl-4,4'-bipyridinium were investigated in the presence of MBr (M = Li + , Na + , and K + ). The cyclic voltammograms of these viologens showed a white-coloured state in addition to the usual violet one-electron reduction state and the colourless divalent state. Chemical analyses (FT-IR and XPS spectra) of the white film and some control experiments with different supporting electrolytes, MX (X = Cl - and I - ), revealed that the viologens formed water-insoluble ion pairs with tribromide generated by the electrooxidation of monobromide to produce a white film. The film was reversibly decolourized electrochemically to the initial transparent state, providing the polyelectrochromism using the simple viologen/MBr systems. The colouration efficiencies for the violet and the white-coloured states were 170 cm 2 /C and 104 cm 2 /C, respectively.

  15. Effect of viologen-phosphorus dendrimers on acetylcholinesterase and butyrylcholinesterase activities.

    Science.gov (United States)

    Ciepluch, Karol; Weber, Monika; Katir, Nadia; Caminade, Anne-Marie; El Kadib, Abdelkrim; Klajnert, Barbara; Majoral, Jean Pierre; Bryszewska, Maria

    2013-03-01

    The inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) is the first step in checking whether new compounds can be considered as drugs for treating neurodegenerative diseases. The effect of viologen-phosphorus dendrimers on AChE and BChE activities was studied. The results show that the effects on the cholinesterase activities depend on dendrimer type and size. Viologen dendrimers can interact with the enzymes in two ways: they can bind either to a peripheral site of the enzyme or to amino acids located near the active site, inhibiting catalysis by both cholinesterases. All tested non-toxic viologen-phosphorus dendrimers inhibited the activities of both cholinesterases, showing their potential as new drugs for treating neurodegenerative diseases. Copyright © 2012 Elsevier B.V. All rights reserved.

  16. MV controlled spark gap

    International Nuclear Information System (INIS)

    Evdokimovich, V.M.; Evlampiev, S.B.; Korshunov, G.S.; Nikolaev, V.A.; Sviridov, Yu.F.; Khmyrov, V.V.

    1980-01-01

    A megavolt gas-filled trigatron gap with a sectional gas-discharge chamber having a more than three-fold range of operating voltages is described. The discharge chamber consists of ten sections, each 70 mm thick, made of organic glass. The sections are separated one from another by aluminium gradient rings to which ohmic voltage divider is connected. Insulational sections and gradient rings are braced between themselves by means of metal flanges through gaskets made of oil-resistant rubber with the help of fiberglass-laminate pins. The gap has two electrodes 110 mm in diameter. The trigatron ignition assembly uses a dielectric bushing projecting over the main electrode plane. Use has been made of a gas mixture containing 10% of SF 6 and 90% of air making possible to ensure stable gap operation without readjusting in the voltage range from 0.4 to 1.35 MV. The operation time lag in this range is equal to 10 μs at a spread of [ru

  17. Complexation between Methyl Viologen (Paraquat) Bis(Hexafluorophosphate) and Dibenzo[24]Crown-8 Revisited

    DEFF Research Database (Denmark)

    Gasa, Travis B.; Spruell, Jason M.; Dichtel, William R.

    2009-01-01

    Paraquat bis(hexafluorophosphate) undergoes stepwise dissociation in acetone. All three species - the neutral molecule, and the mono- and dications - are represented significantly under the experimental conditions typically used in host-guest binding studies. Paraquat forms at least four host...... toward dibenzo[24]crown-8. Thus, the relative abundance of neutral, singly, and doubly charged pseudorotaxanes is identical to the relative abundance of neutral, singly, and doubly charged paraquat unbound with respect to the crown ether in acetone. In the specific case of paraquat/dibenzo[24]crown-8...

  18. An aqueous all-organic redox-flow battery employing a (2,2,6,6-tetramethylpiperidin-1-yl)oxyl-containing polymer as catholyte and dimethyl viologen dichloride as anolyte

    Science.gov (United States)

    Hagemann, Tino; Winsberg, Jan; Grube, Mandy; Nischang, Ivo; Janoschka, Tobias; Martin, Norbert; Hager, Martin D.; Schubert, Ulrich S.

    2018-02-01

    Herein we present a new redox-flow battery (RFB) that employs a (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) containing copolymer (P1) as catholyte and the viologen derivative N,N‧-dimethyl-4,4‧-bipyridinium dichloride (MV) as anolyte in an aqueous sodium chloride solution. This is the first time that a combination of an organic polymer and a low-molar-mass organic redox-active material is presented. The electrochemical behavior of the utilized charge-storage materials were investigated by cyclic voltammetry (CV) and feature reversible redox-reactions at E½ = 0.7 V (TEMPO/TEMPO+) and E½ = -0.6 V vs. AgCl/Ag (MV++/MV+•), which lead to a promising cell voltage of 1.3 V in the subsequent battery application. Studies were performed to determine the most suitable anion-exchange membrane (AEM), the ideal conducting salt concentration and the optimal flow rate. The resulting battery reveals a stable charge/discharge performance over 100 consecutive cycles with coulombic efficiencies of up to 95%, a high energy efficiency of 85% and an overall energy density of the electrolyte system of 3.8 W h L-1.

  19. Structural and spectroscopic properties of the second generation phosphorus-viologen "molecular asterisk".

    Science.gov (United States)

    Furer, V L; Vandukov, A E; Katir, N; Majoral, J P; El Kadib, A; Caminade, A M; Bousmina, M; Kovalenko, V I

    2013-11-01

    The FTIR and FT Raman spectra of the second generation phosphorus-viologen "molecular asterisk" G2 built from cyclotriphosphazene core with 12 viologen units and 6 terminal phosphonate groups have been recorded and analyzed. The experimental X-ray data of 1,1-bis(4-formylbenzyl)-4,4'-bipyridinium bis(hexaflurophosphate) was used in molecular modeling studies. The optimization of isolated 1,1-bis(4-formylbenzyl)-4,4'-bipyridinium (BFBP) molecule without counter ions PF6(-) does not lead to significant changes of dihedral angles, thus the molecular conformation does not depend on interactions with the counter ions. The structural optimization and normal mode analysis were performed for G2 on the basis of the density functional theory (DFT). The calculated geometrical parameters and harmonic vibrational frequencies are predicted in a good agreement with the experimental data. It was found that G2 has a kind of "egg timer" structure with planar OC6H4CHNN(CH3) fragments and slightly non-planar cyclotriphosphazene core. The experimental IR and Raman spectra of G2 were interpreted by means of potential energy distribution. Copyright © 2013 Elsevier B.V. All rights reserved.

  20. An Aqueous Redox-Flow Battery with High Capacity and Power: The TEMPTMA/MV System.

    Science.gov (United States)

    Janoschka, Tobias; Martin, Norbert; Hager, Martin D; Schubert, Ulrich S

    2016-11-07

    Redox-flow batteries (RFB) can easily store large amounts of electric energy and thereby mitigate the fluctuating output of renewable power plants. They are widely discussed as energy-storage solutions for wind and solar farms to improve the stability of the electrical grid. Most common RFB concepts are based on strongly acidic metal-salt solutions or poorly performing organics. Herein we present a battery which employs the highly soluble N,N,N-2,2,6,6-heptamethylpiperidinyl oxy-4-ammonium chloride (TEMPTMA) and the viologen derivative N,N'-dimethyl-4,4-bipyridinium dichloride (MV) in a simple and safe aqueous solution as redox-active materials. The resulting battery using these electrolyte solutions has capacities of 54 Ah L -1 , giving a total energy density of 38 Wh L -1 at a cell voltage of 1.4 V. With peak current densities of up to 200 mA cm -2 the TEMPTMA/MV system is a suitable candidate for compact high-capacity and high-power applications. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Surfactant 1-Hexadecyl-3-methylimidazolium Chloride Can Convert One-Dimensional Viologen Bromoplumbate into Zero-Dimensional.

    Science.gov (United States)

    Liu, Guangfeng; Liu, Jie; Nie, Lina; Ban, Rui; Armatas, Gerasimos S; Tao, Xutang; Zhang, Qichun

    2017-05-15

    A zero-dimensional N,N'-dibutyl-4,4'-dipyridinium bromoplumbate, [BV] 6 [Pb 9 Br 30 ], with unusual discrete [Pb 9 Br 30 ] 12- anionic clusters was prepared via a facile surfactant-mediated solvothermal process. This bromoplumbate exhibits a narrower optical band gap relative to the congeneric one-dimensional viologen bromoplumbates.

  2. Synthesis of 3-(4,5-dihydroimidazol-1-YL)propyltriethoxysilane bound Ru(II) complex bearing viologen segment

    International Nuclear Information System (INIS)

    Gurbuz, N.; Seckin, T.; Ozdemir, I.; Cetinkaya, B.

    2005-01-01

    The nanostructured metallopolymers consisting of the partially quaternized 3-(4,5-dihydroimidazol-1-yl)propyl having the viologen group linked covalently through the alkyl spacer its Ru(II) complex have been prepared by sol-gel method. Structural elucidation was done with Fourier transform infrared spectroscopy, ultraviolet spectroscopy, and differential thermal analysis (DTA) [ru

  3. Charge-Transfer Supra-Amphiphiles Built by Water-Soluble Tetrathiafulvalenes and Viologen-Containing Amphiphiles: Supramolecular Nanoassemblies with Modifiable Dimensions.

    Science.gov (United States)

    Lv, Zhong-Peng; Chen, Bin; Wang, Hai-Ying; Wu, Yue; Zuo, Jing-Lin

    2015-08-05

    In this study, multidimensional nanoassemblies with various morphologies such as nanosheets, nanorods, and nanofibers are developed via charge-transfer interaction and supra-amphiphile self-assembling in aqueous phase. The charge-transfer interactions between tetrathiafulvalene derivatives (TTFs) and methyl viologen derivatives (MVs) have been confirmed by the characteristic charger-transfer absorption. (1) H NMR and electrospray ionizsation mass spectrometry (ESI-MS) analyses also indicate supra-amphiphiles are formed by the combination of TTFs and MVs head group through charge-transfer interaction and Coulombic force. X-ray single crystal structural studies, transmission electron microscopy (TEM), and scanning electron microscopy (SEM) reveal that both linkage pattern of TTFs in hydrophilic part and alkane chain structure in hydrophobic part have significant influence on nanoassemblies morphology and microstructure. Moreover, gold nanoparticles (AuNPs) are introduced in the above supramolecular nanoassemblies to construct a supra-amphiphile-driven organic-AuNPs assembly system. AuNPs could be assembled into 1D-3D structures by adding different amount of MVs. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. JAERI 20 MV tandem accelerator

    International Nuclear Information System (INIS)

    Tsukada, Kineo; Harada, Kichinosuke

    1977-01-01

    Accelerators have been developed as the experimental apparatuses for the studies on nuclei and elementary particles. One direction of the development is the acceleration of protons and electrons to more and more high energy, and another direction is the acceleration of heavy ions up to uranium to several MeV up to several hundreds MeV. However recently, accelerators are used as the useful tools for the studies in wider fields. There are electrostatic acceleration and high frequency acceleration in ion acceleration, and at present, super-large accelerators are high frequency acceleration type. In Japan Atomic Energy Research Institute, it was decided in 1975 to construct an electrostatic accelerator of tandem type in order to accelerate heavy ions. In case of the electrostatic acceleration, the construction is relatively simple, the acceleration of heavy ions is easy, the property of the ion beam is very good, and the energy is stable. Especially, the tandem type is convenient for obtaining high energy. The tandem accelerator of 20 MV terminal voltage was ordered from the National Electrostatics Corp., USA, and is expected to be completed in 1978. The significance of heavy ion acceleration in the development and research of atomic energy, tandem van de Graaff accelerators, the JAERI 20MV tandem accelerator, and the research project with this accelerator are described. (Kako, I.)

  5. PTMC in post-MV repair status

    Directory of Open Access Journals (Sweden)

    Lachikarathman Devegowda

    2016-09-01

    Full Text Available MV repair in the rheumatic population is feasible with acceptable long-term results.1 Incidence of mitral stenosis (MS following mitral valve (MV repair for severe rheumatic mitral regurgitation (MR and usefulness of percutaneous transluminal mitral valvuloplasty (PTMC in these patients is not described in literature. We report a case of successful PTMC in severe MS following MV repair for severe rheumatic MR.

  6. Turn-on fluorescence probes based on pyranine/viologen charge-transfer complexes for the determination of nucleotides

    Energy Technology Data Exchange (ETDEWEB)

    Schäferling, Michael, E-mail: Michael.schaeferling@utu.fi; Lang, Thomas; Schnettelker, Annette

    2014-10-15

    The formation of ground state charge-transfer complexes between pyranine (8-hydroxypyrene-1,3,6-trisulfonic acid) and viologen (paraquat) derivatives is utilized for the design of novel fluoroionophores for the determination of phosphate species, particularly of nucleotides. The strong quenching of the pyranine fluorescence by viologen-type charge transfer acceptors can be countermanded if these are functionalized with triethylammonium groups that serve as recognition elements for phosphate anions. We report on the fluorogenic responses of these water-soluble molecular probes in presence of different phosphates. Absorbance measurements give additional information on the charge transfer complex formation and the interaction with nucleotides. The experimental data show that these aggregates form attractive, simple and versatile fluorescence turn-on probes for nucleoside triphosphates. The reversibility of the fluorescence response is demonstrated by means of an enzymatic model assay using ATPase for the decomposition of adenosine triphosphate. - Highlights: • Pyranine/viologen charge-transfer complexes as molecular probe for ATP recognition. • Fluorescence turn on mechanism. • Selective compared to other nucleotides and phosphate anions. • Fast and reversible response applicable to monitor enzymatic reactions.

  7. Magnetic Field Effects on Photoelectrochemical Reactions of Porphyrin-Viologen Linked Compounds in an Ionic Liquid

    Science.gov (United States)

    Tahara, Hironobu; Yonemura, Hiroaki; Harada, Satoko; Yamada, Sunao

    2011-08-01

    Magnetic field effects (MFEs) on photoelectrochemical reactions of three porphyrin-viologen linked compounds with various methylene groups [ZnP(n)V (n=4,6,8)] were examined in 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) as an ionic liquid using a two-electrode cell. Stable anodic photocurrents are produced by irradiating ZnP(n)V (n=4,6,8) in [BMIM][BF4] with visible light, and the MFEs on photocurrents were clearly observed in ZnP(n)V (n=4,6,8). The MFEs on photocurrents increase with magnetic field for lower magnetic fields (B ≤200 mT) and are constant for higher magnetic fields (B > 200 mT). The magnitude of the MFEs in ZnP(n)V (n=6,8) are larger than that in ZnP(4)V. The MFEs can be explained by radical pair mechanism. The magnitude of the MFEs is larger than those in electrodes modified with ZnP(n)V (n=4,6,8) as Langmuir-Blodgett films. The results are most likely attributable to the properties of [BMIM][BF4] and the mechanism of photoelectrochemical reaction.

  8. Promising Low-Toxicity of Viologen-Phosphorus Dendrimers against Embryonic Mouse Hippocampal Cells

    Directory of Open Access Journals (Sweden)

    Jean-Pierre Majoral

    2013-09-01

    Full Text Available A new class of viologen-phosphorus dendrimers (VPDs has been recently shown to possess the ability to inhibit neurodegenerative processes in vitro. Nevertheless, in the Central Nervous Systems domain, there is little information on their impact on cell functions, especially on neuronal cells. In this work, we examined the influence of two VPD (VPD1 and VPD3 of zero generation (G0 on murine hippocampal cell line (named mHippoE-18. Extended analyses of cell responses to these nanomolecules comprised cytotoxicity test, reactive oxygen species (ROS generation studies, mitochondrial membrane potential (ΔΨm assay, cell death detection, cell morphology assessment, cell cycle studies, as well as measurements of catalase (CAT activity and glutathione (GSH level. The results indicate that VPD1 is more toxic than VPD3. However, these two tested dendrimers did not cause a strong cellular response, and induced a low level of apoptosis. Interestingly, VPD1 and VPD3 treatment led to a small decline in ROS level compared to untreated cells, which correlated with slightly increased catalase activity. This result indicates that the VPDs can indirectly lower the level of ROS in cells. Summarising, low-cytotoxicity on mHippoE-18 cells together with their ability to quench ROS, make the VPDs very promising nanodevices for future applications in the biomedical field as nanocarriers and/or drugs per se.

  9. Reaction of N,N’-dimethylformamide and divalent viologen molecule to generate an organic dopant for molybdenum disulfide

    Directory of Open Access Journals (Sweden)

    A. Fukui

    2018-05-01

    Full Text Available Tuning the carrier concentration is essential for semiconducting materials to apply optoelectronic devices. Molybdenum disulfide (MoS2 is a semiconducting material composed of atomically thin (∼0.7 nm thickness layers. To dope thin MoS2, instead of using conventional atom/ion injection processes, a surface charge transfer method was successfully applied. In this study, we report a simple preparation method of a molecular dopant applicable to the doping process. The method follows a previous report for producing a molecular dopant, benzyl viologen (BV which shows electron doping to MoS2. To prepare dopant BV molecules, a reduction process with a commercially available divalent BV by sodium borohydride (NaBH4 is required; however, the reaction requires a large consumption of NaBH4. NaBH4 drastically reacts with the solvent water itself. We found a reaction process of BV in an organic solvent, N,N’-dimethylformamide (DMF, by adding a small amount of water dissolving the divalent BV. The reaction is mild (at room temperature and is autonomous once DMF comes into contact with the divalent BV aqueous solution. The reaction can be monitored with a UV-Vis spectrometer, and kinetic analysis indicates two reaction steps between divalent/monovalent/neutral viologen isomers. The product was soluble in toluene and did not dissolve in water, indicating it is similar to the reported dopant BV. The synthesized molecule was found to act as a dopant for MoS2 by applying a metal-oxide-semiconductor field-effect-transistor (MOSFET structure. The process is a general method and applicable to other viologen-related dopants to tune the electronic structure of 2D materials to facilitate generating atomically thin devices.

  10. Reaction of N,N'-dimethylformamide and divalent viologen molecule to generate an organic dopant for molybdenum disulfide

    Science.gov (United States)

    Fukui, A.; Miura, K.; Ichimiya, H.; Tsurusaki, A.; Kariya, K.; Yoshimura, T.; Ashida, A.; Fujimura, N.; Kiriya, D.

    2018-05-01

    Tuning the carrier concentration is essential for semiconducting materials to apply optoelectronic devices. Molybdenum disulfide (MoS2) is a semiconducting material composed of atomically thin (˜0.7 nm thickness) layers. To dope thin MoS2, instead of using conventional atom/ion injection processes, a surface charge transfer method was successfully applied. In this study, we report a simple preparation method of a molecular dopant applicable to the doping process. The method follows a previous report for producing a molecular dopant, benzyl viologen (BV) which shows electron doping to MoS2. To prepare dopant BV molecules, a reduction process with a commercially available divalent BV by sodium borohydride (NaBH4) is required; however, the reaction requires a large consumption of NaBH4. NaBH4 drastically reacts with the solvent water itself. We found a reaction process of BV in an organic solvent, N,N'-dimethylformamide (DMF), by adding a small amount of water dissolving the divalent BV. The reaction is mild (at room temperature) and is autonomous once DMF comes into contact with the divalent BV aqueous solution. The reaction can be monitored with a UV-Vis spectrometer, and kinetic analysis indicates two reaction steps between divalent/monovalent/neutral viologen isomers. The product was soluble in toluene and did not dissolve in water, indicating it is similar to the reported dopant BV. The synthesized molecule was found to act as a dopant for MoS2 by applying a metal-oxide-semiconductor field-effect-transistor (MOSFET) structure. The process is a general method and applicable to other viologen-related dopants to tune the electronic structure of 2D materials to facilitate generating atomically thin devices.

  11. A π-Conjugation Extended Viologen as a Two-Electron Storage Anolyte for Total Organic Aqueous Redox Flow Batteries.

    Science.gov (United States)

    Luo, Jian; Hu, Bo; Debruler, Camden; Liu, Tianbiao Leo

    2018-01-02

    Extending the conjugation of viologen by a planar thiazolo[5,4-d]thiazole (TTz) framework and functionalizing the pyridinium with hydrophilic ammonium groups yielded a highly water-soluble π-conjugation extended viologen, 4,4'-(thiazolo[5,4-d]thiazole-2,5-diyl)bis(1-(3-(trimethylammonio)propyl)pyridin-1-ium) tetrachloride, [(NPr) 2 TTz]Cl 4  , as a novel two-electron storage anolyte for aqueous organic redox flow battery (AORFB) applications. Its physical and electrochemical properties were systematically investigated. Paired with 4-trimethylammonium-TEMPO (N Me -TEMPO) as catholyte, [(NPr) 2 TTz]Cl 4 enables a 1.44 V AORFB with a theoretical energy density of 53.7 Wh L -1 . A demonstrated [(NPr) 2 TTz]Cl 4 /N Me -TEMPO AORFB delivered an energy efficiency of 70 % and 99.97 % capacity retention per cycle. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. A study of ion exchange at the poly(butyl viologen)-electrolyte interface by SECM

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, Chih-Yu.; Vasantha, V.S. [Department of Chemical Engineering, National Taiwan University, Taipei 10617 (China); Ho, Kuo-Chuan [Department of Chemical Engineering, National Taiwan University, Taipei 10617 (China); Institute of Polymer Science and Engineering, National Taiwan University, Taipei 10617 (China)

    2008-09-01

    In this work, the ion exchange characteristics of poly(butyl viologen) (PBV) thin films on a platinum electrode has been investigated by cyclic voltammetric (CV) scans. Since ferrocyanide anions (Fe(CN){sub 6}{sup 4-}) were added during the polymerization of the PBV thin-film for its stability, Fe(CN){sub 6}{sup 4-} could form charge transfer complex with monomer and co-deposited with polymer. Scanning electrochemical microscopy (SECM) was used to probe the released Fe(CN){sub 6}{sup 4-} ions from PBV film with Os(bpy){sub 3}Cl{sub 2} as a mediator for the approaching process in 0.5 M KCl medium. Mass changes during the redox process of the film were also monitored in-situ by electrochemical quartz crystal microbalance (EQCM). The ion exchange and transport behavior was observed during CV cycling of the film of the SECM and EQCM. The insertion and extraction of anions were found to be potential-dependence. Moreover, the decrease in tip current of released Fe(CN){sub 6}{sup 4-} with increasing cycle number accounted for the ion exchange between Fe(CN){sub 6}{sup 4-} and Cl{sup -} in the KCl electrolyte. However, the Fe(CN){sub 6}{sup 4-}/Fe(CN){sub 6}{sup 3-} redox couple was found to be highly stable between 0.0 and 0.5 V (vs. Ag/AgCl/saturated KCl) in the phosphate buffer solution. Therefore, the electrochemical property of Fe(CN){sub 6}{sup 4-}/Fe(CN){sub 6}{sup 3-} redox couple was studied at different scan rates using CV technique. The peak currents were directly proportional to the scan rate as predicted for a surface confined diffusionless system. The surface coverage ({gamma}) and the concentration of Fe(CN){sub 6}{sup 4-} were determined to be 1.88 x 10{sup -8} mol/cm{sup 2} and 0.641 mol/dm{sup 3}, respectively. By neglecting cations incorporation during redox reaction of the PBV film and also based on the results obtained from energy-dispersive X-ray spectroscopy for the films of as-deposited, reduced and oxidized states, an ion exchange mechanism was

  13. 25 MV tandem accelerator at Oak Ridge

    International Nuclear Information System (INIS)

    Jones, C.M.

    1980-01-01

    A new heavy-ion accelerator facility is under construction at the Oak Ridge National Laboratory. A brief description of the scope and status of this project is presented with emphasis on the first operational experience with the 25 MV tandem accelerator

  14. Conditional probability on MV-algebras

    Czech Academy of Sciences Publication Activity Database

    Kroupa, Tomáš

    2005-01-01

    Roč. 149, č. 2 (2005), s. 369-381 ISSN 0165-0114 R&D Projects: GA AV ČR IAA2075302 Institutional research plan: CEZ:AV0Z10750506 Keywords : conditional probability * tribe * MV-algebra Subject RIV: BA - General Mathematics Impact factor: 1.039, year: 2005

  15. Heavy ion fusion 2 MV injector

    International Nuclear Information System (INIS)

    Yu, S.; Eylon, S.; Henestroza, E.

    1995-04-01

    A heavy-ion-fusion driver-scale injector has been constructed and operated at Lawrence Berkeley Laboratory. The injector has produced 2.3 MV and 950 mA of K + , 15% above original design goals in energy and current. Normalized edge emittance of less than 1 π mm-mr was measured over a broad range of parameters. The head-to-tail energy flatness is less than ± 0.2% over the 1 micros pulse

  16. Enhanced photocurrent in RuL2(NCS)2/di-(3-aminopropyl)-viologen/SnO2/ITO system

    International Nuclear Information System (INIS)

    Lee, Wonjoo; Kwak, Chang Gon; Mane, R.S.; Min, Sun Ki; Cai, Gangri; Ganesh, T.; Koo, Gumae; Chang, Jinho; Cho, Byung Won; Kim, Sei-Ki; Han, Sung-Hwan

    2008-01-01

    A Ru(2,2'-bipyridine-4,4'-dicarboxylic acid) 2 (NCS) 2 [RuL 2 (NCS) 2 ]/di-(3-aminopropyl)-viologen (DAPV)/tin oxide (SnO 2 ) system was prepared and applied to extensive photocurrent generation with its maximum surface area. The SnO 2 thin films on tin-doped indium oxide (ITO) were prepared using the chemical bath deposition method. Then, RuL 2 (NCS) 2 /DAPV on SnO 2 /ITO was easily prepared using self-assembled monolayers (SAMs). The photocurrent measurement of the system showed an excellent photocurrent of 20 nA cm -2 under the air mass 1.5 conditions (100 mW cm -2 ), which was increased by a factor of four compared to ones without SnO 2 layers

  17. 3 MV, Tandetron accelerator at CCCM

    International Nuclear Information System (INIS)

    Raju, V.S.

    2003-01-01

    Surface analysis requires compositional characterisation of thin films such as stoichiometries and the depth distributions of the constituents present in 100 A to a few tens of microns. Complimented by Ultra Trace laboratory and Bulk laboratory of the Centre, for cross validation with other state of art specialized analytical techniques in specific times, this laboratory has been providing the services to different end users around the country. The surface laboratory has three major facilities viz. a 3MV Tandem accelerator dedicated for Ion Beam Analysis, an Analytical Electron Microscope and an indigenously built X-Ray Photoelectron Spectroscopy system

  18. Evaluation of IMRT plans for prostate treatment using energies of 6 MV and 15 MV

    International Nuclear Information System (INIS)

    Guimaraes, Lucas Francisco C.; Silva, Murilo C. da; Silveira, Paula J.; Flosi, Adriana A.; Boccaletti, Karina W.

    2013-01-01

    This study aims to evaluate and compare radiotherapy plans with intensity-modulated radiation therapy (IMRT) for prostate cancer treatments optimized for photon energies of 6 MV and 15 MV. We retrospectively evaluated 29 patients with prostate cancer, planned with IMRT technique with prescribed dose of 78 Gy. The initial plan was done for the two photon energies, keeping the same optimization parameters and comparing maximum, minimum and modal PTV doses, conformity and homogeneity indexes, dose gradients, isodoses volumes of 30, 40, 50, 60, and 70 Gy, and the total number of monitor units. It was found that the plans are equivalent regarding higher isodose volumes, conformity and homogeneity indexes, maximum, minimum and modal PTV doses. However, for 6 MV plans there was a considerable increase in both number of monitor units and volume lower isodose volumes, especially the 30 Gy. (author)

  19. Fabrication, electrochemical and catalytic properties of the nanocomposites composed of phosphomolybdic acid and viologen-functionalized multi-walled carbon nanotubes

    Science.gov (United States)

    Liu, Jiang; Wang, Jing; Chen, Meng; Qian, Dong-Jin

    2017-08-01

    Electroactive nanocomposites composed of phosphomolybdic acid (PMA) and viologen-functionalized carbon nanotubes were synthesized and used as heterogeneous catalysts for the electrocatalytic reduction of bromate. Viologen (V) was first covalently anchored on the surface of multi-walled carbon nanotubes (MWNTs) to produce positively charged MWNT-V polyelectrolyte, which was then combined with PMA through electrostatic interaction to form MWNT-V@PMA nanocomposites. Thermogravimetric analysis revealed that the organic species in the MWNT-V polyelectrolyte was about 30% in weight. Composition, structure, and morphology of the nanocomposites were investigated by using UV-vis, infrared, Raman and X-ray photoelectron spectroscopy as well as field emission transition electron microscope. The thickness of organic substituents, viologen, and PMA in the nanocomposites was approximately 10 nm covered on the surface of MWNTs. Cyclic voltammogram measurements for the casting films of MWNT-V@PMA nanocomposites revealed four couples of redox waves with cathodic potentials at about -0.56, -0.19, 0.02, 0.21 V, and anodic ones at about -0.46, -0.11, 0.12, 0.31 V (vs Ag/AgCl), respectively, among which the first one corresponded to the electron transfer process of viologens and others to that of the PMA adsorbed. Finally, the MWNT-V@PMA modified electrodes were used as heterogeneous catalysts for the electrocatalytic bromate reduction, which revealed an almost linear correction between the current density and the bromate concentrations in the concentration range from 1 to 15 mmol/l. [Figure not available: see fulltext.

  20. 1 MV low-induction pulse generator

    International Nuclear Information System (INIS)

    Koba, G.I.; Koba, Yu.V.; Slivkov, I.N.; Sukhov, A.D.; Tarumov, Eh.Z.

    1980-01-01

    A high-voltage pulse generator is described. The generator Uses the Arkadiev-Marx circuit at 1 MV voltage and 12 kJ energy; the inductance of the discharge circuit is 1.3 μN. Low inductance of the generator has been obtained due to the use of low-inductance capacitors and employment of bifilar buses with oil barrier insulation. To provide reliable generator triggering, an ignition circuit has been developed with a resistive coupling between generator steps, based on controlled three-electrode sparkgaps with a distorted field. The generator switching time is slightly dependent on pressure and constitutes 200-300 ns. The generator efficiency is 83%

  1. The 16-MV pelletron accelerator at NSC

    International Nuclear Information System (INIS)

    Narayanan, M.M.; Chopra, S.; Kanjilal, D.

    1994-01-01

    A 15-UD 16-MV Pelletron accelerator was commissioned at Nuclear Science Centre (NSC) in July 1991. It is a large tandem Van de Graaff type electrostatic accelerator capable of accelerating almost any ion beam from hydrogen to uranium to energies from a few tens of MeV (Million electron Volts) to hundreds of MeV. The availability of the various beams having widely variable energy, good energy resolution and excellent quality makes this accelerator an extremely versatile machine. This gives rise to the possibilities of basic and applied research in various disciplines of science. The principle of operation of a tandem accelerator and the salient features of the accelerator system at NSC are described. (author). 2 refs., 4 figs

  2. A 3 MV pelletron at Fudan University

    International Nuclear Information System (INIS)

    Sun Chuanchen; Lu Chengrong; Fe Zhiyu; Yuan Daosheng

    1989-01-01

    A 3 MV Pelletron tandem, model 9SDH-2, the fourth machine manufactured by NEC was installed and has been operating at Fudan University since 1987. The operating experiences obtained during the past year are described. Three beam lines have been established: one is for Auger-ESCA and RBS in an ultrahigh-vacuum chamber in which Al(100) clean surfaces have been studied; the second beam line is used as a microbeam analysis system using a 2 μm proton beam for resonant prefitting studies. The third is a general purpose beam line, for studies of the effect of nuclear resonance on K X-ray yield. At present, the third beam line is also used for ion beam analysis studies of 8.8 MeV He 2+ non-Rutherford scattering on high T c superconductors. (orig.)

  3. Electro neutrons around a 12 MV Linac

    International Nuclear Information System (INIS)

    Vega C, H. R.; Perez L, L. H.

    2012-10-01

    Neutron contamination around Linacs for radiotherapy is a source of undesirable doses for the patient. The main source of these neutrons is the photonuclear reactions occurring in the Linac head and the patient body. Electrons also produce neutrons through (e, en) reactions. This reaction is known as electro disintegration and is carried out by the electron scattering that produce a virtual photon that is absorbed by the scattering nucleus producing the reaction e + A → (A-1) + n + e'. In this work the electron-neutron spectrum to 100 cm from the isocenter of a 12 MV Linac has been measured using a passive Bonner spheres spectrometer in a novel procedure named Planetary mode. (Author)

  4. Comparative study of 6 MV and 15 MV treatment plans for large chest wall irradiation

    International Nuclear Information System (INIS)

    Prasana Sarathy, N.; Kothanda Raman, S.; Sen, Dibyendu; Pal, Bipasha

    2007-01-01

    Conventionally, opposed tangential fields are used for the treatment of chest wall irradiation. If the chest wall is treated in the linac, 4 or 6 MV photons will be the energy of choice. It is a welI-established rule that for chest wall separations up to 22 cm, one can use mid-energies, with acceptable volume of hot spots. For larger patient sizes (22 cm and above), mid-energy beams produce hot spots over large volumes. The purpose of this work is to compare plans made with 6 and 15 MV photons, for patients with large chest wall separations. The obvious disadvantage in using high-energy photons for chest wall irradiation is inadequate dose to the skin. But this can be compensated by using a bolus of suitable thickness

  5. Shielding provision in an old 6MV bunker for a new 18MV linac

    International Nuclear Information System (INIS)

    Howlett, S.J.; Ebert, M.A.; Kenny, W.

    2004-01-01

    Full text: In October 2003 the Newcastle Mater Hospital commenced clinical use of a new Varian 21EX which replaced it's 14 year old Varian Clinac l800. The 1800 had only been enabled for 6MV X-ray beam for most of its clinical use but was enabled for 18MV for a period in 2000. This was to make up for the loss of an 18MV beam from another Clinac 1800 which was being replaced in a bunker designed for that higher energy. The new 21EX would provide both 6MV and 18MV beams for routine clinical use. The original bunker had been designed for the lower energy and hence additional shielding was required to meet radiation dose limits recommended in ICRP 60 and adopted in ARPANSA RPS6. A general radiation survey was conducted around the bunker area when the 18MV beam was available on the older linear accelerator. This rather unique situation provided data which would normally be impossible to obtain. Photon activation in the neutron door was a source of increased dose levels in the control area. Commercial design was contracted for the additional barrier calculations and supply. Additional shielding was required on one primary barrier and the neutron door. Post installation surveys were conducted and the R and V system was used for usage figures. Using dose constraints for public and occupational exposure, various survey points were measured around the bunker. This data was assessed in terms of calculated requirements, actual requirements and the ALARA principle for radiation shielding design. Review of staff dose histories was also performed. The final survey calculations showed the additional shielding more than adequate for the usage of 18MV and 6MV photon beams. The availability of the R and V data gives supporting evidence for design of barriers to be adjusted on usage values as has been reported in an earlier work at this centre. The issue of occupancy arises in this work as dose histories indicate. Typically barrier design is always conservative and survey results on

  6. On MV-algebras of non-linear functions

    Directory of Open Access Journals (Sweden)

    Antonio Di Nola

    2017-01-01

    Full Text Available In this paper, the main results are:a study of the finitely generated MV-algebras of continuous functions from the n-th power of the unit real interval I to I;a study of Hopfian MV-algebras; anda category-theoretic study of the map sending an MV-algebra as above to the range of its generators (up to a suitable form of homeomorphism.

  7. On MV-algebras of non-linear functions

    Directory of Open Access Journals (Sweden)

    Antonio Di Nola

    2017-01-01

    Full Text Available In this paper, the main results are: a study of the finitely generated MV-algebras of continuous functions from the n-th power of the unit real interval I to I; a study of Hopfian MV-algebras; and a category-theoretic study of the map sending an MV-algebra as above to the range of its generators (up to a suitable form of homeomorphism.

  8. ORNL 25 MV tandem accelerator control system

    International Nuclear Information System (INIS)

    Juras, R.C.; Biggerstaff, J.A.; Hoglund, D.E.

    1985-01-01

    The CAMAC-based control system for the 25 MV tandem electrostatic accelerator of the Holifield Heavy Ion Research Facility at Oak Ridge National Laboratory (ORNL) was specified by ORNL and built by the National Electrostatics Corporation. Two Perkin-Elmer 32-bit minicomputers are used in the system, a message switching computer and a supervisory computer. The message switching computer transmits and receives control information on six serial highways. This computer shares memory with the supervisory computer. Operator consoles are located on a serial highway; control is by means of a console CRT, trackball, and assignable shaft encoders and meters. Two identical consoles operate simultaneously: one is located in the tandem control room; the other is located in the cyclotron control room to facilitate operation during injection of tandem beams into the cyclotron or when beam lines under control of the cyclotron control system are used. The supervisory computer is used for accelerator parameter setup calculations, actual accelerator setup for new beams based on scaled, recorded parameters from previously run beams, and various other functions. Nearly seven years of control system operation and improvements will be discussed

  9. A simple self-breaking 2 MV gas switch

    Energy Technology Data Exchange (ETDEWEB)

    Di Capua, M.S.; Freytag, E.K.; Dixon, W.R.; Hawley, R.A.

    1987-06-29

    We describe a simple self-breaking 2 MV gas master switch for the LLNL 2 MV general purpose relativistic electron beam (REB) accelerator. The switch cavity has been hollowed out in a 17.8 cm-thick acrylic slab. The switch gap is 3.55 cm. At 2 MV the maximum field at the cathode is 740 kV cm/sup -1/ and the maximum envelope field is 172 kV cm/sup -1/. The maximum measured switching voltage is 1.90 +- 0.1 MV (10 bar abs). The minimum switching voltage is 1.1 MV (4.3 bar abs). The operating characteristics break away from the 89 kV/(cm atm) dc breakdown strength of SF/sub 6/ at 5 bar abs. Careful electrical and mechanical design as well as strict quality control during assembly and operation have resulted in reliable and reproducible operation.

  10. Dosimetric Comparison in Breast Radiotherapy of 4 MV and 6 MV on Physical Chest Simulator

    Energy Technology Data Exchange (ETDEWEB)

    Donato da Silva, Sabrina; Passos Ribeiro Campos, Tarcisio [Nuclear Engineering Department, Federal University of Minas Gerais, Belo Horizonte (Brazil); Batista Nogueira, Luciana [Anatomy and Imaging Department, Federal University of Minas Gerais, Belo Horizonte (Brazil); Lima Souza Castro, Andre [Nuclear Engineering Department, Federal University of Minas Gerais, Belo Horizonte (Brazil); Institute of Radiation San Francisco, Belo Horizonte (Brazil); Alves de oliveira, Marcio; Galvao Dias, Humberto [Cancer Hospital in Uberlandia, Uberlandia (Brazil)

    2015-07-01

    According to the World Health Organization (2014) breast cancer is the main cause of death by cancer in women worldwide. The biggest challenge of radiotherapy in the treatment of cancer is to deposit the entire prescribed dose homogeneously in the breast, sparing the surrounding tissue. In this context, this paper aimed at evaluating and comparing internal dose distribution in the mammary gland based on experimental procedures submitted to two distinct energy spectra produced in breast cancer radiotherapy. The methodology consisted of reproducing opposite parallel fields used in the treatment of breast tumors in a chest phantom. This simulator with synthetic breast, composed of equivalent tissue material (TE), was previously developed by the NRI Research Group (UFMG). The computer tomography (CT) scan of the simulator was obtained antecedently. The radiotherapy planning systems (TPS) in the chest phantom were performed in the ECLIPSE system from Varian Medical Systems and CAT 3D system from MEVIS. The irradiations were reproduced in the Varian linear accelerator, model SL- 20 Precise, 6 MV energy and Varian linear accelerator, 4 MV Clinac 6x SN11 model. Calibrations of the absorbed dose versus optical density from radiochromic films were generated in order to obtain experimental dosimetric distribution at the films positioned within the glandular and skin equivalent tissues of the chest phantom. The spatial dose distribution showed equivalence with the TPS on measurement data performed in the 6 MV spectrum. The average dose found in radiochromic films placed on the skin ranged from 49 to 79%, and from 39 to 49% in the mammary areola, for the prescribed dose. Dosimetric comparisons between the spectra of 4 and 6 MV, keeping the constant geometry of the fields applied in the same phantom, will be presented showing their equivalence in breast radiotherapy, as well as the variations will be discussed. To sum up, the dose distribution has reached the value expected in

  11. The reduction of nitrate, nitrite and hydroxylamine to ammonia by enzymes from Cucurbita pepo L. in the presence of reduced benzyl viologen as electron donor

    Science.gov (United States)

    Cresswell, C. F.; Hageman, R. H.; Hewitt, E. J.; Hucklesby, D. P.

    1965-01-01

    1. Enzyme systems from Cucurbita pepo have been shown to catalyse the reduction of nitrite and hydroxylamine to ammonia in yields about 90–100%. 2. Reduced benzyl viologen serves as an efficient electron donor for both systems. Activity of the nitrite-reductase system is directly related to degree of dye reduction when expressed in terms of the function for oxidation–reduction potentials, but appears to decrease to negligible activity below about 9% dye reduction. 3. NADH and NADPH alone produce negligible nitrite loss, but NADPH can be linked to an endogenous diaphorase system to reduce nitrite to ammonia in the presence of catalytic amounts of benzyl viologen. 4. The NADH– or NADPH–nitrate-reductase system that is also present can accept electrons from reduced benzyl viologen, but shows relationships opposite to that for the nitrite-reductase system with regard to effect of degree of dye reduction on activity. The product of nitrate reduction may be nitrite alone, or nitrite and ammonia, or ammonia alone, according only to the degree of dye reduction. 5. The relative activities of nitrite-reductase and hydroxylamine-reductase systems show different relationships with degree of dye reduction and may become reversed in magnitude when effects of degree of dye reduction are tested over a suitable range. 6. Nitrite severely inhibits the rate of reduction of hydroxylamine without affecting the yield of ammonia as a percentage of total substrate loss, but hydroxylamine has a negligible effect on the activity of the nitrite-reductase system. 7. The apparent Km for nitrite (1 μm) is substantially less than that for hydroxylamine, for which variable values between 0·05 and 0·9mm (mean 0·51 mm) have been observed. 8. The apparent Km values for reduced benzyl viologen differ for the nitrite-reductase and hydroxylamine-reductase systems: 60 and 7·5 μm respectively. 9. It is concluded that free hydroxylamine may not be an intermediate in the reduction of nitrite

  12. Intense Chiroptical Switching in a Dicationic Helicene-Like Derivative: Exploration of a Viologen-Type Redox Manifold of a Non-Racemic Helquat

    Czech Academy of Sciences Publication Activity Database

    Pospíšil, Lubomír; Bednárová, Lucie; Štěpánek, Petr; Slavíček, P.; Vávra, Jan; Hromadová, Magdaléna; Dlouhá, Helena; Tarábek, Ján; Teplý, Filip

    2014-01-01

    Roč. 136, č. 31 (2014), s. 10826-10829 ISSN 0002-7863 R&D Projects: GA ČR GA13-19213S Grant - others:GA ČR(CZ) GA13-34168S; GA MŠk(CZ) ED3.2.00/08.0144 Institutional support: RVO:61388963 ; RVO:61388955 Keywords : helicenoids * helquats * helical cations * ECD spectra * redox switching * chiroptical properties * helicene-viologen hybrids Subject RIV: CC - Organic Chemistry Impact factor: 12.113, year: 2014

  13. A Note on the M/V "Louisa" Case

    DEFF Research Database (Denmark)

    Tanaka, Yoshifumi

    2014-01-01

    In the M/V “Louisa” case of 28 May 2013, the International Tribunal for the Law of the Sea held that it had no jurisdiction, even though it had established prima facie jurisdiction at the provisional measures stage. The M/V “Louisa” case thus gives rise to questions regarding the relationship...... between prima facie jurisdiction and jurisdiction on the merits. Moreover, the M/V “Louisa” Judgment also sheds some light on the applicability of the doctrine of abuse of rights provided in Article 300 of the UN Convention on the Law of the Sea....

  14. Assessment of Automated Measurement and Verification (M&V) Methods

    Energy Technology Data Exchange (ETDEWEB)

    Granderson, Jessica [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Touzani, Samir [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Custodio, Claudine [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Sohn, Michael [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Fernandes, Samuel [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Jump, David [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2015-07-01

    This report documents the application of a general statistical methodology to assess the accuracy of baseline energy models, focusing on its application to Measurement and Verification (M&V) of whole-building energy savings.

  15. Accelerator mass spectrometry at the Rossendorf 5 MV tandem accelerator

    International Nuclear Information System (INIS)

    Friedrich, M.; Buerger, W.; Curian, H.; Hartmann, B.; Hentschel, E.; Matthes, H.; Probst, W.; Seidel, M.; Turuc, S.; Hebert, D.; Rothe, T.; Stolz, W.

    1992-01-01

    The Rossendorf electrostatic accelerators (5 MV tandem accelerator and single ended 2 MV van de Graaff accelerator) are already used for ion beam analysis. The existing methods (RBS, PIXE, ERDA, NRA, nuclear microprobe and external beam) will be completed by introduction of Accelerator Mass Spectrometry (AMS). A short description of the Rossendorf AMS system is given and first experimental results are presented. (R.P.) 4 refs.; 6 figs

  16. DNA methylation

    DEFF Research Database (Denmark)

    Williams, Kristine; Christensen, Jesper; Helin, Kristian

    2012-01-01

    DNA methylation is involved in key cellular processes, including X-chromosome inactivation, imprinting and transcriptional silencing of specific genes and repetitive elements. DNA methylation patterns are frequently perturbed in human diseases such as imprinting disorders and cancer. The recent...... discovery that the three members of the TET protein family can convert 5-methylcytosine (5mC) into 5-hydroxymethylcytosine (5hmC) has provided a potential mechanism leading to DNA demethylation. Moreover, the demonstration that TET2 is frequently mutated in haematopoietic tumours suggests that the TET...... proteins are important regulators of cellular identity. Here, we review the current knowledge regarding the function of the TET proteins, and discuss various mechanisms by which they contribute to transcriptional control. We propose that the TET proteins have an important role in regulating DNA methylation...

  17. Dosimetric properties of germanium doped calcium borate glass subjected to 6 MV and 10 MV X-ray irradiations

    Science.gov (United States)

    Tengku Kamarul Bahri, T. N. H.; Wagiran, H.; Hussin, R.; Saeed, M. A.; Hossain, I.; Ali, H.

    2014-10-01

    Germanium doped calcium borate glasses are investigated in term of thermoluminescence properties to seek their possibility to use as glass radiation dosimeter. The samples were exposed to 6 MV, and 10 MV photon beams in a dose range of 0.5-4.0 Gy. There is a single and broad thermoluminescence glow curve that exhibits its maximum intensity at about 300 °C. Linear dose response behavior has been found in this dose range for the both photon energies. Effective atomic number, TL sensitivity, and reproducibility have also been studied. It is found that the sensitivity of germanium doped sample at 6 MV is only 1.28% and it is superior to the sensitivity at 10 MV. The reproducibility of germanium doped sample is good with a percentage of relative error less than 10%. The results indicate that this glass has a potential to be used as a radiation dosimetry, especially for application in radiotherapy.

  18. Dosimetric properties of germanium doped calcium borate glass subjected to 6 MV and 10 MV X-ray irradiations

    Energy Technology Data Exchange (ETDEWEB)

    Tengku Kamarul Bahri, T.N.H., E-mail: tnhidayah2@gmail.com [Department of Physics, Faculty of Science, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru (Malaysia); Wagiran, H.; Hussin, R.; Saeed, M.A. [Department of Physics, Faculty of Science, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru (Malaysia); Hossain, I. [Department of Physics, College of Science and Arts, King Abdul Aziz University, 21911 Rabigh (Saudi Arabia); Ali, H. [Department of Radiotherapy and Oncology, Hospital Sultan Ismail, 81100 Johor Bahru (Malaysia)

    2014-10-01

    Highlights: •The TL properties of 29.9CaO–70B{sub 2}O{sub 3}: 0.1GeO{sub 2} glass has been investigated. •We exposed glass samples to 6 MV and 10 MV in a dose range of 0.5–4.0 Gy. •This glass has a potential material to be used for application in radiotherapy. -- Abstract: Germanium doped calcium borate glasses are investigated in term of thermoluminescence properties to seek their possibility to use as glass radiation dosimeter. The samples were exposed to 6 MV, and 10 MV photon beams in a dose range of 0.5–4.0 Gy. There is a single and broad thermoluminescence glow curve that exhibits its maximum intensity at about 300 °C. Linear dose response behavior has been found in this dose range for the both photon energies. Effective atomic number, TL sensitivity, and reproducibility have also been studied. It is found that the sensitivity of germanium doped sample at 6 MV is only 1.28% and it is superior to the sensitivity at 10 MV. The reproducibility of germanium doped sample is good with a percentage of relative error less than 10%. The results indicate that this glass has a potential to be used as a radiation dosimetry, especially for application in radiotherapy.

  19. Dosimetric properties of germanium doped calcium borate glass subjected to 6 MV and 10 MV X-ray irradiations

    International Nuclear Information System (INIS)

    Tengku Kamarul Bahri, T.N.H.; Wagiran, H.; Hussin, R.; Saeed, M.A.; Hossain, I.; Ali, H.

    2014-01-01

    Highlights: •The TL properties of 29.9CaO–70B 2 O 3 : 0.1GeO 2 glass has been investigated. •We exposed glass samples to 6 MV and 10 MV in a dose range of 0.5–4.0 Gy. •This glass has a potential material to be used for application in radiotherapy. -- Abstract: Germanium doped calcium borate glasses are investigated in term of thermoluminescence properties to seek their possibility to use as glass radiation dosimeter. The samples were exposed to 6 MV, and 10 MV photon beams in a dose range of 0.5–4.0 Gy. There is a single and broad thermoluminescence glow curve that exhibits its maximum intensity at about 300 °C. Linear dose response behavior has been found in this dose range for the both photon energies. Effective atomic number, TL sensitivity, and reproducibility have also been studied. It is found that the sensitivity of germanium doped sample at 6 MV is only 1.28% and it is superior to the sensitivity at 10 MV. The reproducibility of germanium doped sample is good with a percentage of relative error less than 10%. The results indicate that this glass has a potential to be used as a radiation dosimetry, especially for application in radiotherapy

  20. SU-D-BRA-07: Applications of Combined KV/MV CBCT Imaging with a High-DQE MV Detector

    International Nuclear Information System (INIS)

    Bazalova-Carter, M; Newson, M; Wang, A; Star-Lack, J; Wu, M; Xing, L; Fahrig, R; Ansbacher, W

    2016-01-01

    Purpose: To investigate whether a high detection quantum efficiency (DQE) MV detector makes combined kV/MV CBCT clinically practical. Methods: Combined kV/MV CBCT was studied for scan time reduction (STR) and metal artifact reduction (MAR). 6MV CBCT data (dose rate = 0.017 MU/degree) were collected using 1) a novel focused pixelated cadmium tungstate (CWO) scintillator (15mm thickness, DQE(0) = 22%, 0.784mm pixel pitch) coupled to a flat panel imager, and 2) a commercial portal imager with a 133mg/cm"2 gadolinium oxysulfide (GOS) screen (DQE(0) = 1.2%). The 100kVp data were acquired using a commercial imager employing a columnar cesium iodide scintillator (DQE(0) = 70%) with a dose rate of 0.0016 cGy/degree. For STR, MV and kV projections spanning 105° were combined to constitute a complete CBCT scan. Total dose was ∼2cGy and acquisition time was 18s. For MAR, only the metalcorrupted pixels in the kV projections were replaced with MV data resulting in a total dose of less than 1cGy for a 360° scan. Image quality was assessed using an 18-cm diameter electron density phantom with nine tissue inserts, some of which were replaced with steel rods for MAR studies. Results: The CWO contrast-to-noise ratio (CNR) was ∼4.0x higher than the GOS CNR and was ∼4.8x lower than the kV CNR when normalized for dose. When CWO MV data were combined with kV data for STR, all contrast inserts were visible, but only two were detectable in the composite kV/GOS image. Metal artifacts were greatly reduced using the kV/MV MAR technique with all contrast inserts clearly visible in the composite kV/CWO image but only two inserts visible in the composite kV/GOS image. Conclusion: We have demonstrated that a high DQE MV detector significantly improves kV/MV CBCT image quality thus enabling scan time reduction and metal artifact reduction without a severe dose penalty. AW and JS-L are employees of Varian, RF is an employee of Siemens.

  1. Evaluation of IMRT plans for prostate treatment using energies of 6 MV and 15 MV; Avaliacao de planejamentos de IMRT para tratamento de prostata utilizando energias de 6 MV e 15 MV

    Energy Technology Data Exchange (ETDEWEB)

    Guimaraes, Lucas Francisco C.; Silva, Murilo C. da; Silveira, Paula J.; Flosi, Adriana A.; Boccaletti, Karina W., E-mail: mcollete@gmail.com [A. C. Camargo Cancer Center, Sao Paulo, SP (Brazil). Servico de Radioterapia

    2013-08-15

    This study aims to evaluate and compare radiotherapy plans with intensity-modulated radiation therapy (IMRT) for prostate cancer treatments optimized for photon energies of 6 MV and 15 MV. We retrospectively evaluated 29 patients with prostate cancer, planned with IMRT technique with prescribed dose of 78 Gy. The initial plan was done for the two photon energies, keeping the same optimization parameters and comparing maximum, minimum and modal PTV doses, conformity and homogeneity indexes, dose gradients, isodoses volumes of 30, 40, 50, 60, and 70 Gy, and the total number of monitor units. It was found that the plans are equivalent regarding higher isodose volumes, conformity and homogeneity indexes, maximum, minimum and modal PTV doses. However, for 6 MV plans there was a considerable increase in both number of monitor units and volume lower isodose volumes, especially the 30 Gy. (author)

  2. MECHANICAL CAVITY DESIGN FOR 100MV UPGRADE CRYOMODULE

    International Nuclear Information System (INIS)

    K.M. Wilson; G. Ciovati; E. F. Daly; J. Henry; R. Hicks; J. Hogan; D. Machie; P. Kneisel; C. Reece; J. Sekutowicz; T. Whitlatch

    2003-01-01

    To achieve up to 6 GeV, each cryomodule in the CEBAF accelerator currently provides about 30 MV of acceleration. To raise the accelerator energy to 12 GeV, ten additional cryomodules capable of providing over 100 MV of acceleration are required. A prototype of the 100 MV cryomodule has been designed, is presently under construction, and will be completed in 2004. This prototype cryomodule comprises two new cavity designs, four cavities of the low loss design and four cavities of the high gradient design. Although the cavity shapes were designed for their RF properties, the mechanical implications must be considered. In addition to the new cavity shapes, changes have also been made to the cavity end dish assemblies, weld joints, and stiffening rings. This paper will present the results of the stress and vibration analyses used for designing the cryomodule

  3. {sup 36}Cl exposure dating with a 3-MV tandem

    Energy Technology Data Exchange (ETDEWEB)

    Steier, Peter, E-mail: peter.steier@univie.ac.a [VERA Laboratory, Fakultaet fuer Physik - Isotopenforschung, Universitaet Wien, Waehringer Strasse 17, A-1090 Wien (Austria); HPK H 31, Institut fuer Teilchenphysik, ETH Zuerich, Schafmattstr. 20 CH-8093 Zuerich (Switzerland); Forstner, Oliver; Golser, Robin; Kutschera, Walter; Martschini, Martin [VERA Laboratory, Fakultaet fuer Physik - Isotopenforschung, Universitaet Wien, Waehringer Strasse 17, A-1090 Wien (Austria); HPK H 31, Institut fuer Teilchenphysik, ETH Zuerich, Schafmattstr. 20 CH-8093 Zuerich (Switzerland); Merchel, Silke [CEREGE, CNRS-IRD-Universite Aix-Marseille, Europole Mediterraneen de L' Arbois, 13545 Aix-en-Provence (France); Forschungszentrum Dresden-Rossendorf, D-01314 Dresden (Germany); HPK H 31, Institut fuer Teilchenphysik, ETH Zuerich, Schafmattstr. 20 CH-8093 Zuerich (Switzerland); Orlowski, Tobias; Priller, Alfred [VERA Laboratory, Fakultaet fuer Physik - Isotopenforschung, Universitaet Wien, Waehringer Strasse 17, A-1090 Wien (Austria); HPK H 31, Institut fuer Teilchenphysik, ETH Zuerich, Schafmattstr. 20 CH-8093 Zuerich (Switzerland); Vockenhuber, Christof [Forschungszentrum Dresden-Rossendorf, D-01314 Dresden (Germany); HPK H 31, Institut fuer Teilchenphysik, ETH Zuerich, Schafmattstr. 20 CH-8093 Zuerich (Switzerland); Wallner, Anton [VERA Laboratory, Fakultaet fuer Physik - Isotopenforschung, Universitaet Wien, Waehringer Strasse 17, A-1090 Wien (Austria); HPK H 31, Institut fuer Teilchenphysik, ETH Zuerich, Schafmattstr. 20 CH-8093 Zuerich (Switzerland)

    2010-04-15

    {sup 36}Cl AMS measurements at natural isotopic concentrations have yet been performed only at tandem accelerators with 5 MV terminal voltage or beyond. We have developed a method to detect {sup 36}Cl at natural terrestrial isotopic concentrations with a 3-MV system, operated above specifications at 3.5 MV. An effective separation was obtained with an optimized split-anode ionization chamber design (adopted from the ETH/PSI Zurich AMS group), providing a suppression factor of up to 30,000 for the interfering isobar {sup 36}S. Despite the good separation, a relatively high sulfur output from the ion source ({sup 36}S{sup -}/{sup 35}Cl{sup -} approx 4 x 10{sup -10} for samples prepared from chemically pure reagents), and a possibly cross contamination resulted in a background corresponding to {sup 36}Cl/Cl approx 3 x 10{sup -14}. The method was applied to samples containing between 10{sup 5} and 10{sup 6} atoms {sup 36}Cl/g rock from sites in Italy and Iran, which were already investigated by other laboratories for surface exposure dating. The {sup 36}Cl/Cl ratios in the range from 2 x 10{sup -13} to 5 x 10{sup -12} show a generally good agreement with the previous results. These first measurements demonstrate that also 3-MV tandems, constituting the majority of dedicated AMS facilities, are capable of {sup 36}Cl exposure dating, which is presently the domain of larger facilities.

  4. Three level MV converter using series connected IGBT's

    DEFF Research Database (Denmark)

    Munk-Nielsen, Stig; Vaerens, M.C.P.; Sundvall, J.

    2009-01-01

    A simple method of serial connecting IGBT's is applied and standard low voltage IGBT modules are used in the MV test inverter to evaluate the method. The dc link voltage is 2.4 kV and the RMS output line to line voltage is 1.7kV. The method works and test experiences are presented in paper....

  5. Technical aspects of 3MV particle accelerator at GGV Bilaspur

    International Nuclear Information System (INIS)

    Mallik, C.

    2013-01-01

    The accelerator at GGV, Bilaspur is a 3 MV pelletron operating is Tandem mode. The talk will describe the technical aspects of the accelerator. It will also discuss the beam aspects of the pelletron and the feasibility options with the accelerator. (author)

  6. A comparison of two photon planning algorithms for 8 MV and 25 MV X-ray beams in lung

    International Nuclear Information System (INIS)

    Kan, M.W.K.; Young, E.C.M.; Yu, P.K.N.

    1995-01-01

    The results of a comparison of two photon planning algorithms, the Clarkson Scatter Integration algorithm and the Equivalent Tissue-air Ratio algorithm are reported, using a simple lung phantom for 8 MV and 25 MV X-ray beams of field sizes 5 cm x 5 cm and 10 cm x 10 cm. Central axis depth-dose distributions were measured with a thimble chamber or a Markus parallel-plate chamber. Dose profile distributions were measured with TLD rods and films. Measured dose distributions were then compared to predicted dose distributions. Both algorithms overestimate the dose at mid-lung as they do not account for the effect of electronic disequilibrium. The Clarkson algorithm consistently shows less accurate results in comparison with the ETAR algorithm. There is additional error in the case of the Clarkson algorithm because of the assumption of a unit density medium in calculating scatter, which gives an overestimate in the effective scatter-air ratios in lung. For a 5 cm x 5 cm field, the error of dose prediction for 25 MV x-ray beam at mid-lung is 15.8 % and 12.8 % for Clarkson and ETAR algorithm respectively. At 8 MV the error is 9.3 % and 5.1 % respectively. In addition, both algorithms underestimate the penumbral width at mid-lung as they do not account for the penumbral flaring effect in low density medium. 25 refs., 2 tabs., 5 figs

  7. Chalcopyrite Dissolution at 650 mV and 750 mV in the Presence of Pyrite

    Directory of Open Access Journals (Sweden)

    Yubiao Li

    2015-08-01

    Full Text Available The dissolution of chalcopyrite in association with pyrite in mine waste results in the severe environmental issue of acid and metalliferous drainage (AMD. To better understand chalcopyrite dissolution, and the impact of chalcopyrite’s galvanic interaction with pyrite, chalcopyrite dissolution has been examined at 75 °C, pH 1.0, in the presence of quartz (as an inert mineral and pyrite. The presence of pyrite increased the chalcopyrite dissolution rate by more than five times at Eh of 650 mV (SHE (Cu recovery 2.5 cf. 12% over 132 days due to galvanic interaction between chalcopyrite and pyrite. Dissolution of Cu and Fe was stoichiometric and no pyrite dissolved. Although the chalcopyrite dissolution rate at 750 mV (SHE was approximately four-fold greater (Cu recovery of 45% within 132 days as compared to at 650 mV in the presence of pyrite, the galvanic interaction between chalcopyrite and pyrite was negligible. Approximately all of the sulfur from the leached chalcopyrite was converted to S0 at 750 mV, regardless of the presence of pyrite. At this Eh approximately 60% of the sulfur associated with pyrite dissolution was oxidised to S0 and the remaining 40% was released in soluble forms, e.g., SO42−.

  8. Untitled

    Indian Academy of Sciences (India)

    Iot A a. (1) pH - 108. ------ -----. -200 -800 -400 O - 1200 -800 - 400 0. mV NHE mv NHE. Figure 3. CV of 1 and 2 at pH = 108. The voltammograms of compound 1 and 2 are more complex than, for example, those of methyl viologen. Shoulders, appearing in the CV's of 1 and 2, indicate competing reactions. Rapid reversible or ...

  9. 36Cl AMS measurement with 3 MV tandem accelerator

    International Nuclear Information System (INIS)

    Wang Huijuan; Guan Yongjing; Zhang Wei; Jiang Shan; He Ming

    2012-01-01

    Developing the 36 Cl and other medium heavy isotopes measurement at 3 MV AMS facilities is one of the vital trends in AMS measurement. To further increase suppression factor of 36 S, the energy loss straggling and angular straggling of 36 C1 and 36 S ions in various counter gases (Pl0, isobutane and propane) were investigated. Some water samples were measured with the energy of 32 MeV, the results are in good agreement with the result by ion energy of 72 MeV. The results indicate that the detection limit of 36 C1 with 3 MV AMS facility is approximately 36 Cl/Cl ≈ l0 -14 , and the uncertainty is 30% for the sample with isotopic ration 36 Cl/Cl ≈ lO -13 . (authors)

  10. Core of Coalition Games on MV-algebras

    Czech Academy of Sciences Publication Activity Database

    Kroupa, Tomáš

    2011-01-01

    Roč. 21, č. 3 (2011), s. 479-492 ISSN 0955-792X R&D Projects: GA MŠk 1M0572; GA ČR GA102/08/0567 Institutional research plan: CEZ:AV0Z10750506 Keywords : coalition game * core * MV-algebra Subject RIV: BA - General Mathematics Impact factor: 0.611, year: 2011 http://library.utia.cas.cz/separaty/2011/MTR/kroupa-0359839.pdf

  11. The Strasbourg project: A vivitron of 35 MV

    International Nuclear Information System (INIS)

    Letournel, M.

    1984-01-01

    Alternative configurations are described for the Vivitron, a 35 MV tandem accelerator of novel design. The general features of the machine and its associated electrostatic field are described. The machine is designed to minimise energy dissipation within the accelerator column in the event of electrical breakdown. This is discussed. Insulator and conductor design is described and details are given of the CN Van de Graaff which has been adapted as a test machine for Vivitron components. (orig.)

  12. 36Cl-AMS measurements with 3-MV tandem accelerator

    International Nuclear Information System (INIS)

    Wang Huijuan; Guan Yongjing; Zhang Wei; Jiang Shan; Ming He

    2013-01-01

    36 C- is one of the most interesting nuclides in accelerator mass spectrometry (AMS) measurements. The application of 36 Cl has been widely applied in various fields. All most all of 36 Cl AMS measurements at natural isotopic concentrations have yet been performed at tandem accelerator with 5 MV or higher terminal voltage. The measure improvement of 36 Cl and other medium heavy isotopes performed at 3 MV in AMS facilities is one of the hottest topics in AMS measurements. In order to increase the suppression factor of 36 S, the energy loss straggling and angular straggling of 36 Cl and 36 S ions in various counter gases (P10, isobutane and propane) were investigated. Some groundwater samples were measured with energy of 32 MeV, and the results were in good agreement with the result obtained with ion energy of 72 MeV. The results indicate that the approximate detection limit of 36 Cl in 3 MV AMS facility is 36 Cl/Cl=1 × 10 -14 , and the uncertainty is 30% when the sample with isotopic ration 36 Cl/Cl≈10 -13 . (authors)

  13. Reliability 'H' scheme of HV/MV substations

    Directory of Open Access Journals (Sweden)

    Perić Dragoslav M.

    2015-01-01

    Full Text Available Substations (HV/MV connect transmission and distribution systems with consumers of electric energy. The selective search method was used for calculation of substation reliability, where all arrangement elements were grouped into blocks. Subject of the analysis was H-arrangements comprising air-insulated switchgears on the high voltage side of HV/MV substations with different number of feeder and transformer bays and diverse scope of the installed switching equipment. Failure rate and duration were used as main HV/MV substation equipment reliability indices. A large number of arrangements were classified into groups, and within a group the arrangements were ranked with the use of multiple criteria. It is shown that the reliability of the electricity transit depends on the equipment of field for the transit of electricity, which favors poorly equipped field. On the other hand, the reliability of transformation of the full power depends mostly on the equipment in coupling field. It is essential that in the coupling field, there are at least two disconnectors. Installation of the switch in the coupling field is meaningful only with appropriate protection, because it further improves reliability. Conclusions are drawn for phased construction and expansion of the single pole diagram with an additional field for the transmission line.

  14. Visualization of atomic distances at the 1MV electron microscope: first results obtained on the Grenoble 1MV microscope

    International Nuclear Information System (INIS)

    Bourret, A.

    1975-01-01

    Practical and theoretical conditions for obtaining high resolution lattice images are presented. The use of a high voltage electron microscope is particularly powerful to visualize distances smaller than 3A. A 2A resolution test on (200) gold planes has been carried out on the Grenoble 1MV microscope. It would be possible at this level to study the crystalline defects such as dislocations or grain boundaries [fr

  15. The roles of anion and solvent transport during the redox switching process at a poly(butyl viologen) film studied by an EQCM

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, Chih-Yu.; Liao, Chun-Hao [Department of Chemical Engineering, National Taiwan University, Taipei 10617 (China); Ho, Kuo-Chuan [Department of Chemical Engineering, National Taiwan University, Taipei 10617 (China); Institute of Polymer Science and Engineering, National Taiwan University, Taipei 10617 (China)

    2008-02-15

    In this study, three electrolytes (KCl, LiCl, and KNO{sub 3}, each at 0.5 M in aqueous solution) were chosen to study the ion and solvent effect on the redox performance of poly(butyl viologen) (PBV) thin-films between its di-cation and radical-cation state, which is referred as its first redox couple. Before considering the role of ionic transport on the redox process, the exchange between ferrocyanide and anion should be completed. Since the deposition solution of PBV contains potassium ferrocyanide, the residual ferrocyanides inside the films would be exchanged by smaller anions from the bulk solution during the redox reaction of PBV. From cyclic voltammetry (CV) and electrochemical quartz crystal microbalance (EQCM) results, the exchange was almost complete around 50 cycles when scanning the potential within its first redox range. After completion of the exchange process, the transfer would reach a steady state. At 50 cycles, the EQCM results suggested that the transport involves anions and water only for both being extracted upon reduction and being inserted upon oxidation. Therefore, we could obtain the molar fluxes of Cl{sup -}, NO{sub 3}{sup -}, and water. Besides, the average numbers of accompanying water were calculated to be about 24.8 per Cl{sup -} and 14.2 per NO{sub 3}{sup -} upon redox switching process. The instantaneous water to anion molar ratios at any potential were also obtained for Cl{sup -} and NO{sub 3}{sup -}. (author)

  16. The new 6 MV AMS-facility DREAMS at Dresden

    International Nuclear Information System (INIS)

    Akhmadaliev, Shavkat; Heller, René; Hanf, Daniel; Rugel, Georg; Merchel, Silke

    2013-01-01

    Highlights: ► New 6 MV tandem accelerator in operation in Germany for AMS, IBA and HE-implantation. ► DREsden AMS (DREAMS) primarily used for radionuclides 10 Be, 26 Al, 36 Cl, 41 Ca and 129 I. ► Quality assurance by traceable calibration materials and interlaboratory comparisons. High accuracy data for future DREAMS users. ► Energy calibration of accelerator by 1 H( 15 N,γα) 12 C yield correction factor of 1.019. - Abstract: A new 6 MV electrostatic tandem accelerator has been put into operation at Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The system is equipped for accelerator mass spectrometry and opens a new research field at HZDR and the Helmholtz Association. It will be also used for ion beam analysis as well as for material modification via high-energy ion implantation. The research activity at the DREsden Accelerator Mass Spectrometry facility (DREAMS) based on a 6 MV Tandetron is primarily dedicated to the long-lived radioisotopes of 10 Be, 26 Al, 36 Cl, 41 Ca, and 129 I. DREAMS background levels have been found to be at 4.5 × 10 −16 for 10 Be/ 9 Be, 8 × 10 −16 for 26 Al/ 27 Al, 3 × 10 −15 for 36 Cl/ 35 Cl and 8 × 10 −15 for 41 Ca/ 40 Ca, respectively. The observed background of 2 × 10 −13 for 129 I/ 127 I originates from intrinsic 129 I from AgI produced from commercial KI. The introduction of quality assurance approaches for AMS, such as the use of traceable calibration materials and taking part in interlaboratory comparisons, guarantees high accuracy data for future DREAMS users. During first experiments an energy calibration of the accelerator has been carried out using the nuclear reaction 1 H( 15 N,γα) 12 C yielding an energy correction factor of 1.019.

  17. Spectral reconstruction for a 6 MV linear accelerator

    International Nuclear Information System (INIS)

    Hernandez-Bojorquez, M.; Martinez-Davalos, A.; Larraga, J. M.

    2004-01-01

    In this work we present the first results of an x-ray spectral reconstruction for a 6 MV Varian LINAC. The shape of the spectrum will be used in Monte Carlo treatment planning in order to improve the quality and accuracy of the calculated dose distributions. We based our simulation method on the formalism proposed by Francois et al. In this method the spectrum is reconstructed from transmission measurements under narrow beam geometry for multiple attenuator thicknesses. These data allowed us to reconstruct the x-ray spectrum through direct solution of matrix systems using spectral algebra formalism

  18. Technical specification for a 25 MV tandem electrostatic accelerator

    International Nuclear Information System (INIS)

    Jones, C.M.; Biggerstaff, J.A.; Blair, J.K.; Ball, J.B.; Larson, J.D.; Martin, J.A.; McConnell, J.W.; Milner, W.T.; Murray, J.A.; Ziegler, N.F.

    1975-08-01

    Specifications are given for an accelerator system to consist of a 25 MV tandem electrostatic accelerator and specified ancillary equipment, including an injector, a beam transport system, a vacuum system, a control system, and a system for storage of the insulating gas and transport of the gas to and from the accelerator. The insulating gas shall be SF 6 . The tandem electrostatic accelerator shall be vertical in orientation and of folded construction, and shall be installed in a new structure adjacent to the Oak Ridge Isochronous Cyclotron. (auth)

  19. Development of the 2-MV Injector for HIF

    Energy Technology Data Exchange (ETDEWEB)

    Bieniosek, F.M. E-mail: fmbieniosek@lbl.gov; Kwan, J.W.; Henestroza, E.; Kim, C

    2001-05-21

    The 2-MV Injector consists of a 17-cm-diameter surface ionization source, an extraction diode, and an electrostatic quadrupole (ESQ) accelerator, with maximum current of 0.8 A of potassium beam at 2 MeV. Previous performance of the Injector produced a beam with adequate current and emittance but with a hollow profile at the end of the ESQ section. We have examined the profile of the beam as it leaves the diode. The measured nonuniform beam density distribution qualitatively agrees with EGUN simulation. Implications for emittance growth in the post acceleration and transport phase will be investigated.

  20. Development of the 2-MV Injector for HIF

    Science.gov (United States)

    Bieniosek, F. M.; Kwan, J. W.; Henestroza, E.; Kim, C.

    2001-05-01

    The 2-MV Injector consists of a 17-cm-diameter surface ionization source, an extraction diode, and an electrostatic quadrupole (ESQ) accelerator, with maximum current of 0.8 A of potassium beam at 2 MeV. Previous performance of the Injector produced a beam with adequate current and emittance but with a hollow profile at the end of the ESQ section. We have examined the profile of the beam as it leaves the diode. The measured nonuniform beam density distribution qualitatively agrees with EGUN simulation. Implications for emittance growth in the post acceleration and transport phase will be investigated.

  1. Development of the 2-MV Injector for HIF

    International Nuclear Information System (INIS)

    Bieniosek, F.M.; Kwan, J.W.; Henestroza, E.; Kim, C.

    2001-01-01

    The 2-MV Injector consists of a 17-cm-diameter surface ionization source, an extraction diode, and an electrostatic quadrupole (ESQ) accelerator, with maximum current of 0.8 A of potassium beam at 2 MeV. Previous performance of the Injector produced a beam with adequate current and emittance but with a hollow profile at the end of the ESQ section. We have examined the profile of the beam as it leaves the diode. The measured nonuniform beam density distribution qualitatively agrees with EGUN simulation. Implications for emittance growth in the post acceleration and transport phase will be investigated

  2. Development of the 2-MV injector for HIF

    International Nuclear Information System (INIS)

    Bieniosek, F.M.; Kwan, J.W.; Henestroza, E.; Kim, C.

    2000-01-01

    The 2-MV Injector consists of a 17-cm-diameter surface ionization source, an extraction diode, and an electrostatic quadrupole (ESQ) accelerator, with maximum current of 0.8 A of potassium beam at 2 MeV. Previous performance of the Injector produced a beam with adequate current and emittance but with a hollow profile at the end of the ESQ section. We have examined the profile of the beam as it leaves the diode. The measured nonuniform beam density distribution qualitatively agrees with EGUN simulation. Implications for emittance growth in the post acceleration and transport phase will be investigated

  3. Design of a treatment room for an 18 MV Linac

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez A, L.; Contreras S, H.; Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Calle Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico); Perez L, L. H., E-mail: dameluis@hotmail.co [Instituto Zacatecano del Tumor, Apdo. Postal 294, 98000 Zacatecas (Mexico)

    2010-10-15

    In this work it has been calculated the treatment room for an 18 MV Linac. The walls thickness, the door and the maze were designed according to the NCRP Report 151 recommendations. The results of this work are contrasted with the Monte Carlo calculations performed with the MCNP5 code where dose equivalent due to neutrons and neutron spectra are estimated at different points inside and outside of the radiotherapy room, verify the shielding thickness obtained are enough to reduce the dose level allowed by the Mexican regulation. (Author)

  4. The NSC 16 MV tandem accelerator control system

    International Nuclear Information System (INIS)

    Ajith Kumar, B.P.; Kannaiyan, J.; Sugathan, P.; Bhowmik, R.K.

    1994-01-01

    The computerized control system for the 16 MV Pelletron accelerator at the Nuclear Science Centre runs on a PC-AT 386 computer. Devices in the accelerator are interfaced to the computer by using a CAMAC Serial Highway. The software, written in C, is Database oriented and supports many features useful for the accelerator operation. The control console consists of an EGA monitor, keyboard, assignable control knobs and meters, a diagrammatic display showing the overall status of the machine and a similar panel for showing the status of radiation safety interlocks. The system has been operational for the past three years and is discussed below. (orig.)

  5. MV-22 Squadron Organization: A Different Way to Support

    Science.gov (United States)

    2017-06-09

    to analyze the current organizational make up of a MV-22 squadron in order to determine if a change in size and composition would result in an...never been used by the military. Increased speed, range, and the ability to take-off and land like a helicopter , laid the foundation for a platform that...Tilt- rotor technology is a significant leap forward for employment of forces. This is an asset unlike the USMC has ever had before. For the USMC most

  6. Dissociation dynamics of methylal

    Energy Technology Data Exchange (ETDEWEB)

    Beaud, P; Frey, H -M; Gerber, T; Mischler, B; Radi, P P; Tzannis, A -P [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1999-08-01

    The dissociation of methylal is investigated using mass spectrometry, combined with a pyrolytic radical source and femtosecond pump probe experiments. Based on preliminary results two reaction paths of methylal dissociation are proposed and discussed. (author) 4 fig., 3 refs.

  7. A piecewise-focused high DQE detector for MV imaging.

    Science.gov (United States)

    Star-Lack, Josh; Shedlock, Daniel; Swahn, Dennis; Humber, Dave; Wang, Adam; Hirsh, Hayley; Zentai, George; Sawkey, Daren; Kruger, Isaac; Sun, Mingshan; Abel, Eric; Virshup, Gary; Shin, Mihye; Fahrig, Rebecca

    2015-09-01

    Electronic portal imagers (EPIDs) with high detective quantum efficiencies (DQEs) are sought to facilitate the use of the megavoltage (MV) radiotherapy treatment beam for image guidance. Potential advantages include high quality (treatment) beam's eye view imaging, and improved cone-beam computed tomography (CBCT) generating images with more accurate electron density maps with immunity to metal artifacts. One approach to increasing detector sensitivity is to couple a thick pixelated scintillator array to an active matrix flat panel imager (AMFPI) incorporating amorphous silicon thin film electronics. Cadmium tungstate (CWO) has many desirable scintillation properties including good light output, a high index of refraction, high optical transparency, and reasonable cost. However, due to the 0 1 0 cleave plane inherent in its crystalline structure, the difficulty of cutting and polishing CWO has, in part, limited its study relative to other scintillators such as cesium iodide and bismuth germanate (BGO). The goal of this work was to build and test a focused large-area pixelated "strip" CWO detector. A 361 × 52 mm scintillator assembly that contained a total of 28 072 pixels was constructed. The assembly comprised seven subarrays, each 15 mm thick. Six of the subarrays were fabricated from CWO with a pixel pitch of 0.784 mm, while one array was constructed from BGO for comparison. Focusing was achieved by coupling the arrays to the Varian AS1000 AMFPI through a piecewise linear arc-shaped fiber optic plate. Simulation and experimental studies of modulation transfer function (MTF) and DQE were undertaken using a 6 MV beam, and comparisons were made between the performance of the pixelated strip assembly and the most common EPID configuration comprising a 1 mm-thick copper build-up plate attached to a 133 mg/cm(2) gadolinium oxysulfide scintillator screen (Cu-GOS). Projection radiographs and CBCT images of phantoms were acquired. The work also introduces the use of a

  8. Energy calibration of the 3 MV tandem accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Bunnak, S; Mizuhashi, K; Tajima, S

    1996-12-01

    By this study, a graphite calorimeter has been developed to measure the average ion energy from electrostatic ion accelerator (3 MV Tandem Ion Accelerator of the Takasaki Ion Accelerators for Advanced Radiation Application). A graphite calorimeter was designed for measuring the ion beam energy in wide ion energy ranges (from 3 MeV to 10 MeV). By a couple of this study, the {sup 1} H({sup 15} N, {alpha} {gamma}) {sup 12} C resonant nuclear reactions (resonant energy 6.385 MeV and 13.355 MeV) has been applied for measuring the absolute ion beam energy serve as a comparative method. The obtained results were compared in terms of resolution and accuracy. Close agreement was found for both methods, the deviation was observed within {+-} 3%

  9. Neutron H*(10) estimation and measurements around 18MV linac.

    Science.gov (United States)

    Cerón Ramírez, Pablo Víctor; Díaz Góngora, José Antonio Irán; Paredes Gutiérrez, Lydia Concepción; Rivera Montalvo, Teodoro; Vega Carrillo, Héctor René

    2016-11-01

    Thermoluminescent dosimetry, analytical techniques and Monte Carlo calculations were used to estimate the dose of neutron radiation in a treatment room with a linear electron accelerator of 18MV. Measurements were carried out through neutron ambient dose monitors which include pairs of thermoluminescent dosimeters TLD 600 ( 6 LiF: Mg, Ti) and TLD 700 ( 7 LiF: Mg, Ti), which were placed inside a paraffin spheres. The measurements has allowed to use NCRP 151 equations, these expressions are useful to find relevant dosimetric quantities. In addition, photoneutrons produced by linac head were calculated through MCNPX code taking into account the geometry and composition of the linac head principal parts. Copyright © 2016 Elsevier Ltd. All rights reserved.

  10. Experimental vapor pressures (from 1 Pa to 100 kPa) of six saturated Fatty Acid Methyl Esters (FAMEs): Methyl hexanoate, methyl octanoate, methyl decanoate, methyl dodecanoate, methyl tetradecanoate and methyl hexadecanoate

    International Nuclear Information System (INIS)

    Sahraoui, Lakhdar; Khimeche, Kamel; Dahmani, Abdallah; Mokbel, Ilham; Jose, Jacques

    2016-01-01

    Highlight: • Vapor-liquid equilibria, Enthalpy of Vaporization, saturated Fatty Acid Methyl Ester. - Abstract: Vapor pressures of six saturated Fatty Acid Methyl Esters (FAMEs), methyl hexanoate (or methyl caproate), methyl octanoate (or methyl caprylate), Methyl decanoate (or methyl caprate), methyl dodecanoate (or methyl laurate), methyl tetradecanoate (or methyl myristate), and methyl hexadecanoate (or methyl palmitate) were measured from 1 Pa to 100 kPa and at temperature range between 262 and 453 K using a static apparatus. The experimental data (P-T) were compared with the available literature data.

  11. 6 MV Folded Tandem Ion Accelerator facility at BARC

    International Nuclear Information System (INIS)

    Gupta, S.K.

    2010-01-01

    The 6 MV Folded Tandem Ion Accelerator (FOTIA) facility is operational round the clock and accelerated beams of both light and heavy ions are being used extensively by various divisions of BARC, Universities, lIT Bombay and other R and D labs across the country. The FOTIA is an upgraded version of the old 5.5 MV single stage Van-de-Graaff accelerator (1962-1992). Since its commissioning in the year 2000, the poor beam transmission through the 180 deg folding magnet was a matter of concern. A systematic study for beam transmission through the accelerator was carried out and progressive modifications in folding magnet chamber, foil stripper holder and improvement in average vacuum level through the accelerator have resulted in large improvement of beam transmission leading to up to 2.0 micro-amp analyzed proton beams on target. Now the utilization of the beams from the accelerator has increased many folds for basic and applied research in the fields of atomic and nuclear physics, material science and radiation biology etc. Few new beam lines after the indigenously developed 5-port switching magnet are added and the experimental setup for PIXE, PIGE, External PIXE, 4 neutron detector, Proton Induced Positron Annihilation Spectroscopy (PIPAS) setup and the general purpose scattering chamber etc have been commissioned in the beam hall. The same team has developed a Low Energy Accelerator Facility (LEAF) which delivers negative ions of light and heavy ions for application in implantation, irradiation damage studies in semiconductor devices and testing of new beam line components being developed for Low Energy High Intensity Proton Accelerator (LEHIPA) programme at BARC. The LEAF has been developed as stand alone facility and can deliver beam quickly with minimum intervention of the operator. Few more features are being planned to deliver uniform scanned beams on large targets. (author)

  12. Transient Beam Dynamics in the LBL 2 MV Injector

    International Nuclear Information System (INIS)

    Henestroza, E; Grote, D

    1999-01-01

    A driver-scale injector for the Heavy Ion Fusion Accelerator project has been built at LBL. This machine has exceeded the design goals of high voltage (> 2 MV), high current (> 0.8 A of K + ) and low normalized emittance (< 1 π mm-mr). The injector consists of a 750 keV gun pre-injector followed by an electrostatic quadrupole accelerator (ESQ) which provides strong (alternating gradient) focusing for the space-charge dominated beam, and simultaneously accelerates the ions to 2 MeV. A matching section is being built to match the beam to the electrostatic accelerator ELISE. The gun preinjector, designed to hold up to 1 MV with minimal breakdown risks, consists of a hot aluminosilicate source with a large curved emitting surface surrounded by a thick ''extraction electrode''. During beam turn-on the voltage at the source is biased from a negative potential, enough to reverse the electric field on the emitting surface and avoid emission, to a positive potential to start extracting the beam; it stays constant for about 1 (micro)s, and is reversed to turn-off the emission. Since the Marx voltage applied on the accelerating quadrupoles and the main pre-injector gap is a long, constant pulse (several (micro)s), the transient behavior is dominated by the extraction pulser voltage time profile. The transient longitudinal dynamics of the beam in the injector was simulated by running the Particle in Cell codes GYMNOS and WARP3d in a time dependent mode. The generalization and its implementation in WAIW3d of a method proposed by Lampel and Tiefenback to eliminate transient oscillations in a one-dimensional planar diode will be presented

  13. Portal film charts for a 6 MV linear accelerator

    International Nuclear Information System (INIS)

    Faermann, S.; Regev, E.; Leser, Y.

    1990-01-01

    Localization errors frequently arise in the portal film technique due to over-or underdevelop films, for high energy radiotherapy machines. To guarantee the accuracy and reproducibility of the localization film technique portal film charts were introduced into the routine planning for the Mevatron 6MV linear accelerator of the Beilinson Radiotherapy Dept. Maintaining reproducible film processor conditions, two films were used: medical X-ray film Curix RPI Agfa and localization film X-OMAT TL Kodak, combined with front and rear copper screens of 0.5 mm thickness each. The sensitometric curves for each film-screen combination were obtained (optical density as function of cassette dose). The least square fitted O.D. curve was used to obtain the cassette dose which produces an O.D. of 1.6. A theoretical equation for the calculation of the dose at the cassette positions, beyond a water phantom, as function of field size, SSD, patient thickness and patient to cassette separation, was experimentally checked with a 0.6 cc Farmer ionization chamber coupled to a 2570 Farmer dosimeter. As a result portal film charts (expressed in MU) were constructed as a function of FS, air-gap and patient-thickness, and the best partition dose for the double-exposure technique was also established. The patients dose in the double exposure technique was compared to that delivered in diagnostic radiology procedures. (author)

  14. Preliminary design of a 10 MV ion accelerator

    International Nuclear Information System (INIS)

    Fessenden, T.J.; Celata, C.M.; Faltens, A.

    1986-06-01

    At the low energy end of an induction linac HIF driver the beam current is limited by our ability to control space charge by a focusing system. As a consequence, HIF induction accelerator designs feature simultaneous acceleration of many beams in parallel within a single accelerator structure. As the speed of the beams increase, the focusing system changes from electrostatic to magnetic quadrupoles with a corresponding increase in the maximum allowable current. At that point the beams are merged thereby decreasing the cost of the subsequent accelerator structure. The LBL group is developing an experiment to study the physics of merging and of focusing ion beams. In the design, parallel beams of ions (C + , Al + , or Al ++ ) are accelerated to several MV and merged transversely. The merged beams are then further accelerated and the growth in transverse and longitudinal emittance is determined for comparison with theory. The apparatus will then be used to study the problems associated with focusing ion beams to a small spot. Details of the accelerator design and considerations of the physics of combining beams are presented

  15. Integrating techniques for neutron dosimetry in Linac 18 MV

    International Nuclear Information System (INIS)

    Ceron R, P. V.; Diaz G, J. A. I.; Rivera M, T.; Paredes G, L. C.; Vega C, H. R.

    2015-10-01

    In this paper thermoluminescent dosimetry, analytical techniques and Monte Carlo calculations were used to estimate the neutron dose equivalent in a radiotherapy room with a linear electron accelerator of 18 MV. The equivalent dose was measured at isocenter to 1.42 m of target and at the entrance of the labyrinth of the room of a Novalis Tx. The neutron detectors were constructed with pairs of thermoluminescent dosimeters TLD 600 ( 6 LiF: Mg, Ti) and TLD 700 ( 7 LiF: Mg, Ti) which are placed inside a paraffin sphere of 20 cm in diameter. These measurements enabled the calculation of equivalent dose in the gate and the source term, using the relationships contained in the NCRP-151. Through the models carried out with the code MCNPX the absorbed dose distribution with regard to depth in a paraffin phantom are included and the neutron spectrum produced by the head, taking into account the geometry and component materials. The results are in the order of neutron milli sievert by gray of X-rays (mSv/Gy x) which are in the same order as those found in other reports for different accelerators. (Author)

  16. Phantom dosimetry at 15 MV conformal radiation therapy

    International Nuclear Information System (INIS)

    Thompson, Larissa; Campos, Tarcisio P.R.; Dias, Humberto G.

    2013-01-01

    The main goal of this work was to evaluate the spatial dose distribution into a tumor simulator inside a head phantom exposed to a 15MV 3D conformal radiation therapy in order to validate internal doses. A head and neck phantom developed by the Ionizing Radiation Research Group (NRI) was used on the experiments. Therapy Radiation planning (TPS) was performed based on those CT images, satisfying a 200 cGy prescribed dose split in three irradiation fields. The TPS assumed 97% of prescribed dose cover the prescribed treatment volume (PTV). Radiochromic films in a solid water phantom provided dose response as a function of optical density. Spatial dosimetric distribution was generated by radiochromic film samples inserted into tumor simulator and brain. The spatial dose profiles held 70 to 120% of the prescribed dose. In spite of the stratified profile, as opposed to the smooth dose profile from TPS, the tumor internal doses were within a 5% deviation from 214.4 cGy evaluated by TPS. 83.2% of the points with a gamma value of less than 1 (3%/3mm) for TPS and experimental values, respectively. At the tumor, a few dark spots in the film caused the appearance of outlier points in 13-15% of dose deviation percentage. As final conclusion, such dosimeter choice and the physical anthropomorphic and anthropometric phantom provided an efficient method for validating radiotherapy protocols. (author)

  17. Phantom dosimetry at 15 MV conformal radiation therapy

    International Nuclear Information System (INIS)

    Thompson, Larissa; Campos, Tarcisio P.R.

    2015-01-01

    The main goal of this work was to evaluate the spatial dose distribution into a tumor simulator inside a head phantom exposed to a 15MV 3D conformal radiation therapy in order to validate internal doses. A head and neck phantom developed by the Ionizing Radiation Research Group (NRI) was used on the experiments. Therapy Radiation planning (TPS) was performed based on those CT images, satisfying a 200 cGy prescribed dose split in three irradiation fields. The TPS assumed 97% of prescribed dose cover the prescribed treatment volume (PTV). Radiochromic films in a solid water phantom provided dose response as a function of optical density. Spatial dosimetric distribution was generated by radiochromic film samples inserted into tumor simulator and brain. The spatial dose profiles held 70 to 120% of the prescribed dose. In spite of the stratified profile, as opposed to the smooth dose profile from TPS, the tumor internal doses were within a 5% deviation from 214.4 cGy evaluated by TPS. 83.2% of the points with a gamma value of less than 1 (3%/3mm) for TPS and experimental values, respectively. At the tumor, a few dark spots in the film caused the appearance of outlier points in 13-15% of dose deviation percentage. As final conclusion, such dosimeter choice and the physical anthropomorphic and anthropometric phantom provided an efficient method for validating radiotherapy protocols. (author)

  18. Radiological safety around a Linac of 18 MV

    International Nuclear Information System (INIS)

    Ceron R, P.; Rivera M, T.; Paredes G, L.; Azorin N, J.; Sanchez, A.; Vega C, H. R.

    2014-10-01

    There are now several neutron detection systems, such as proportional counters based on BF 3 , He 3 and Bonner sphere spectrometers. However, the cost and complexity of the implementation of such systems makes them inaccessible for dosimetry purposes in radiotherapy rooms (Rt) and other facilities with this type of radiation fields. For these reasons the use of a neutron detection system is proposed composed by a paraffin moderator media forming an array 4π (spheres) and several pairs of thermoluminescent dosimeters TLD 600/TLD 700 inside, in order to make useful measurements for radiation protection around high-energy lineal accelerators (Linacs). In the first part of this work the system response when irradiated with a source of Pu Be and their corresponding calibration factor is displayed. In the second part are presented the ambient dose equivalent (H(10)) due to neutrons at various points of a living of Rt with a Linac of 18 MV, which are in the order mSv/Gy by X-ray treatment. The measurements made are similar to those taken in the memories of the accelerator and in previous work for this type of facility. (Author)

  19. Radiological safety around a Linac of 18 MV; Seguridad radiologica alrededor de un LINAC de 18 MV

    Energy Technology Data Exchange (ETDEWEB)

    Ceron R, P.; Rivera M, T. [IPN, Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Calz. Legaria No. 694, Col. Irrigacion, 11500 Mexico D. F. (Mexico); Paredes G, L. [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico); Azorin N, J. [Universidad Autonoma Metropolitana, Unidad Iztapalapa, San Rafael Atlixco No. 186, Col. Vicentina, 09340 Mexico D. F. (Mexico); Sanchez, A. [IPN, Escuela Superior de Fisica y Matematicas, Av. IPN s/n, Edif. 9, Col. San Pedro Zacatenco, 07738 Mexico D. F. (Mexico); Vega C, H. R., E-mail: victceronr@hotmail.com [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 09868 Zacatecas (Mexico)

    2014-10-15

    There are now several neutron detection systems, such as proportional counters based on BF{sub 3}, He{sub 3} and Bonner sphere spectrometers. However, the cost and complexity of the implementation of such systems makes them inaccessible for dosimetry purposes in radiotherapy rooms (Rt) and other facilities with this type of radiation fields. For these reasons the use of a neutron detection system is proposed composed by a paraffin moderator media forming an array 4π (spheres) and several pairs of thermoluminescent dosimeters TLD 600/TLD 700 inside, in order to make useful measurements for radiation protection around high-energy lineal accelerators (Linacs). In the first part of this work the system response when irradiated with a source of Pu Be and their corresponding calibration factor is displayed. In the second part are presented the ambient dose equivalent (H(10)) due to neutrons at various points of a living of Rt with a Linac of 18 MV, which are in the order mSv/Gy by X-ray treatment. The measurements made are similar to those taken in the memories of the accelerator and in previous work for this type of facility. (Author)

  20. Design and characteristics of a 4 MV total body irradiator

    International Nuclear Information System (INIS)

    Lutz, W.R.; Chin, L.M.

    1988-01-01

    A facility for total body X-ray irradiation (TBI) has been built using two 4 MV linear accelerators, one mounted under the ceiling, the other in a floor-pit. The distance between the two sources is 410 cm to produce a field size of 200 cm x 75 cm in the midplane. This field covers the patient, lying supine on a stretcher halfway between the sources. Components from commercially available accelerators were used. Special beam hardening and flattening filters were built to achieve acceptable dose profiles in the large field. The primary collimator was modified to produce a 235 cm x 92 cm field at 205 cm from the source, while movable focused collimators were designed to define fields up to 220 cm x 80 cm. Because of the wide beams, large rectangular parallel-plate ionization chambers were built to serve as beam monitors. The dose rate at 205 cm distance from the sources can be set between 5 and 80 cGy/min, each machine contributing half. The dosimetric characteristics are practically the same for both units. The per cent depth dose for the TBI beams is 76% at a source-surface distance of 195 cm. The half value layer decreases by 12% from the centre to near the edge of the beam. Owing to the large field size, the surface dose for the TBI beams is about 80% of the dose at 1 cm depth. The dose delivery has been verified to be within 2% of the calculated value at the reference point in a homogeneous water humanoid phantom. Measurements indicate that lung doses can be predicted by the ratio-of-TMR (tissue-to-maximum ratio) method with acceptable accuracy. Lead sheets are used as attenuators to prevent excessive lung doses. (author). 7 refs, 7 figs

  1. Photons and photoneutrons spectra of a Linac of 15 MV

    International Nuclear Information System (INIS)

    Benites R, J. L.; Carrillo C, A.; Vega C, H. R.; Velazquez F, J. B.

    2011-10-01

    Using the Monte Carlo code MCNP-5, the photons and photoneutrons spectra generated in the head stock of the lineal accelerator (Linac) Varian of 15 MV of the Cancerology State of Nayarit were determined. For the calculations a heterogeneous head stock was modeled, more compatible with the work conditions. In the center of the head stock a tungsten target was located on a copper support, followed by the flattened filter. The photons and photoneutrons spectra were obtained accelerating electrons and making them collide against the target to produce photons by Bremsstrahlung, these photons were transported inside the head stock and the photons and photoneutrons spectra were calculated in a punctual detector located under the flattened filter and in the isocenter. The spectra were evaluated in punctual detectors that were located in the plane from the isocenter to the long of the X and Y axes each 20 cm, in an equidistant way, up to 2 m, so much in the longitudinal and transversal axes. In the calculations were used histories 5E(6) with the purpose of obtaining smaller uncertainties to 1%. It was found that the photons spectrum in the punctual detector inside the head stock presents a pick of 1.25 MeV in the energy interval of 0.5 and 1.5 MeV, later suffers a filtration and diminishes in asymptote form. This spectrum modifies when the beam reaches the isocenter, diminishing the low energy photons. Inside the head stock the photoneutrons spectrum shows a structure with two picks, one before 1 MeV and other after 1 MeV; this is for effect of the collimators geometry and the distance. Finally an increment of the total neutrons flow to 60 cm of distance of the isocenter on the Y axis was observed, due to the design geometry of the modeling heterogeneous head stock. (Author)

  2. Whole-genome methylation caller designed for methyl- DNA ...

    African Journals Online (AJOL)

    etchie

    2013-02-20

    Feb 20, 2013 ... Our method uses a single-CpG-resolution, whole-genome methylation ... Key words: Methyl-DNA immunoprecipitation, next-generation sequencing, ...... methylation is prevalent in embryonic stem cells andmaybe mediated.

  3. Comparison of Head Scatter Factor for 6MV and 10MV flattened (FB) and Unflattened (FFF) Photon Beam using indigenously Designed Columnar Mini Phantom.

    Science.gov (United States)

    Ashokkumar, Sigamani; Nambi Raj, N Arunai; Sinha, Sujit Nath; Yadav, Girigesh; Thiyagarajan, Rajesh; Raman, Kothanda; Mishra, Manindra Bhushan

    2014-07-01

    To measure and compare the head scatter factor for flattened (FB) and unflattened (FFF) of 6MV and 10MV photon beam using indigenously designed mini phantom. A columnar mini phantom was designed as recommended by AAPM Task Group 74 with low and high atomic number materials at 10 cm (mini phantom) and at approximately twice the depth of maximum dose water equivalent thickness (brass build-up cap). Scatter in the accelerator (Sc) values of 6MV-FFF photon beams are lesser than that of the 6MV-FB photon beams (0.66-2.8%; Clinac iX, 2300CD) and (0.47-1.74%; True beam) for field sizes ranging from 10 × 10 cm(2) to 40 × 40 cm(2). Sc values of 10MV-FFF photon beams are lesser (0.61-2.19%; True beam) than that of the 10MV-FB photons beams for field sizes ranging from 10 × 10 cm(2) to 40 × 40 cm(2). The SSD had no influence on head scatter for both flattened and unflattened beams and irrespective of head design of the different linear accelerators. The presence of field shaping device influences the Sc values. The collimator exchange effect reveals that the opening of the upper jaw increases Sc irrespective of FB or FFF photon beams and different linear accelerators, and it is less significant in FFF beams. Sc values of 6MV-FB square field were in good agreement with that of AAPM, TG-74 published data for Varian (Clinac iX, 2300CD) accelerator. Our results confirm that the removal of flattening filter decreases in the head scatter factor compared to flattened beam. This could reduce the out-of-field dose in advanced treatment delivery techniques.

  4. Irradiation with x-rays of the energy 18 MV induces radioactivity in transfusion blood: Proposal of a safe method using 6 MV.

    Science.gov (United States)

    Frentzel, Katharina; Badakhshi, Harun

    2016-12-01

    To prevent a fatal transfusion-associated graft-versus-host disease, it is recommended to irradiate transfusion blood and blood components with ionizing radiation. Using x-rays from a linear accelerator of the radiotherapy department is an accepted alternative to gamma irradiation devices of the blood bank and to the orthovoltage units that are replacing the gamma irradiators today. However, the use of high energy x-rays may carry a potential risk of induced radioactivity. The objective of this study was to investigate the effect of two different energy levels, 6 and 18 MV, which are executed in routine clinical settings. The research question was if induced radioactivity occurs at one of these standard energy levels. The authors aimed to give a proposal for a blood irradiation procedure that certainly avoids induced radioactivity. For this study, the authors developed a blood bag phantom, irradiated it with x-ray energies of 6 and 18 MV, and measured the induced radioactivity in a well counter. Thereafter, the same irradiation and measuring procedure was performed with a unit of packed red blood cells. A feasible clinical procedure was developed using 6 MV and an acrylic box. With the irradiation planning system XiO, the authors generated an irradiation protocol for the linear accelerator Siemens ONCOR Anvant-Garde. Both measurement setups showed that there was induced radioactivity for 18 MV but not for 6 MV. The induced radioactivity for 18 MV was up to 190 times the background. This is significant and of clinical relevance especially since there are newborn and fetal blood recipients for whom every radiation exposure has to be strictly avoided. The irradiation of blood with x-rays from a linear accelerator of the radiotherapy department is safe and feasible, but by the current state of scientific knowledge, the authors recommend to use an x-ray energy of 6 MV or less to avoid induced radioactivity in transfusion blood.

  5. Clostridium beijerinckii mutant obtained atmospheric pressure glow discharge generates enhanced electricity in a microbial fuel cell.

    Science.gov (United States)

    Liu, Jun; Guo, Ting; Wang, Dong; Ying, Hanjie

    2015-01-01

    A Clostridium beijerinckii mutant M13 was derived from C. beijerinckii NCIMB 8052 by atmospheric pressure glow discharge. C. beijerinckii M13 generated a maximum output power density of 79.2 mW m(-2) and a maximum output voltage of 230 mV in a microbial fuel cell containing 1 g glucose l(-1) as carbon source and 0.15 g methyl viologen l(-1) as an electron carrier.

  6. Determination of one-electron reduction potentials of some radiosensitive compounds by pulse radiolysis

    International Nuclear Information System (INIS)

    Zuo Zhihua; Yao Side; Li Hucheng; Lin Nianyun; Jin Yizun

    1994-01-01

    One-electron reduction potential (E 7 1 ) is one of the important parameters of radiosensitive compound with high electron affinity. In this work one-electron reduction potentials of some radiosensitizers, such as Miso, 911, CMNa, SMU-1, SMU-2, SMD, SNN, S 3 and BSO, were determined pulse radiolytically by using anthraquinone-2-sulfate (AQS), duroquinone (DQ) and methyl viologen (MV 2+ ) as references

  7. Methylation pathways in schizophrenia

    International Nuclear Information System (INIS)

    Sargent, T.W. III.

    1982-01-01

    Research on the biochemical causes of human psychosis concentrates on investigating whether schizophremia is linked to abnormalities in the metabolism of methyl carbon groups in the body. The metabolism of C-14 labeled methyl groups in methionine is studied in animals, normal subjects and patient volunteers

  8. Adsorption of methyl violet from aqueous solution using gum xanthan/Fe3O4 based nanocomposite hydrogel

    CSIR Research Space (South Africa)

    Mittal, H

    2016-08-01

    Full Text Available This research paper reports the utilization of gum xanthan-grafted-polyacrylic acid and Fe(sub3)O(sub4) magnetic nanoparticles based nanocomposite hydrogel (NCH) for the highly effective adsorption of methyl violet (MV) from aqueous solution...

  9. Methyl-Analyzer--whole genome DNA methylation profiling.

    Science.gov (United States)

    Xin, Yurong; Ge, Yongchao; Haghighi, Fatemeh G

    2011-08-15

    Methyl-Analyzer is a python package that analyzes genome-wide DNA methylation data produced by the Methyl-MAPS (methylation mapping analysis by paired-end sequencing) method. Methyl-MAPS is an enzymatic-based method that uses both methylation-sensitive and -dependent enzymes covering >80% of CpG dinucleotides within mammalian genomes. It combines enzymatic-based approaches with high-throughput next-generation sequencing technology to provide whole genome DNA methylation profiles. Methyl-Analyzer processes and integrates sequencing reads from methylated and unmethylated compartments and estimates CpG methylation probabilities at single base resolution. Methyl-Analyzer is available at http://github.com/epigenomics/methylmaps. Sample dataset is available for download at http://epigenomicspub.columbia.edu/methylanalyzer_data.html. fgh3@columbia.edu Supplementary data are available at Bioinformatics online.

  10. Achievement of 35 MV/m in the superconducting nine-cell cavities for TESLA

    International Nuclear Information System (INIS)

    Lilje, L.; Kostin, D.; Matheisen, A.; Moeller, W.D.; Proch, D.; Reschke, D.; Simrock, S.; Twarowski, K.; Kako, E.; Saito, K.; Schmueser, P.; Suzuki, T.

    2004-01-01

    The tera electronvolt superconducting linear accelerator TESLA is the only linear electron-positron collider project based on superconductor technology for particle acceleration. In the first stage with 500 GeV center-of-mass energy an accelerating field of 23.4 MV/m is needed in the superconducting niobium cavities which are operated at a temperature of 2 K and a quality factor Q 0 of 10 10 . This performance has been reliably achieved in the cavities of the TESLA test facility (TTF) accelerator. The upgrade of TESLA to 800 GeV requires accelerating gradients of 35 MV/m. Using an improved cavity treatment by electrolytic polishing it has been possible to raise the gradient to 35 - 43 MV/m in single cell resonators. Here we report on the successful transfer of the electropolishing technique to multi-cell cavities. Presently four nine-cell cavities have achieved 35 MV/m at Q 0 ≥ 5 x 10 9 , and a fifth cavity could be excited to 39 MV/m. In two high-power tests it could be verified that EP-cavities preserve their excellent performance after welding into the helium cryostat and assembly of the high-power coupler. One cavity has been operated for 1100 hours at the TESLA-800 gradient of 35 MV/m and 57 hours at 36 MV/m without loss in performance. (orig.)

  11. Chlorine measurements at the 5MV French AMS national facility ASTER: Associated external uncertainties and comparability with the 6MV DREAMS facility

    Science.gov (United States)

    Braucher, R.; Keddadouche, K.; Aumaître, G.; Bourlès, D. L.; Arnold, M.; Pivot, S.; Baroni, M.; Scharf, A.; Rugel, G.; Bard, E.

    2018-04-01

    After 6 years of 36Cl routine operation, more than 6000 unknown samples have been measured at the 5MV French accelerator mass spectrometry (AMS) national facility ASTER (CEREGE, Aix en Provence). This paper presents the long term behavior of ASTER through the analysis of the measurements of the most used chlorine standards and reference materials, KNSTD1600, SM-Cl-12 and SM-CL-13 over a 46 months' time period. Comparison of measured chlorine concentrations (both 35Cl and 36Cl) from ice samples on two AMS facilities operating at 5MV (ASTER) and 6MV (DREAMS, Helmholtz-Zentrum Dresden-Rossendorf) and normalizing to two different reference materials agree within uncertainties making both reference materials (SM-Cl-12 and KNSTD1600) suitable for 36Cl measurement at ASTER.

  12. SU-E-T-611: Photon and Neutron Peripheral Dose Ratio for Low (6 MV) and High (15 MV) Energy for Treatment Selection

    Energy Technology Data Exchange (ETDEWEB)

    Irazola, L; Sanchez-Doblado, F [Departamento de Fisiologia Medica y Biofisica, Universidad de Seville (Spain); Servicio de Radiofisica, Hospital Universitario Virgen Macarena, Seville (Spain); Terron, J; Ortiz-Seidel, M [Servicio de Radiofisica, Hospital Universitario Virgen Macarena, Seville (Spain); Departamento de Fisiologia Medica y Biofisica, Universidad de Seville (Spain); Sanchez-Nieto, B [Instituto de Fisica, Pontificia Universidad Catolica de Chile, Santiago (Chile)

    2015-06-15

    Purpose: Differences between radiotherapy techniques and energies, can offer improvements in tumor coverage and organs at risk preservation. However, a more complete decision should include peripheral doses delivered to the patient. The purpose of this work is the balance of photon and neutron peripheral doses for a prostate case solved with 6 different treatment modalities. Methods: Inverse and Forward IMRT and 3D-CRT in 6 and 15 MV for a Siemens Primus linac, using the same CT data set and contours. The methodology described in [1], was used with the TNRD thermal neutron detector [2] for neutron peripheral dose estimation at 7 relevant organs (colon, esophagus, stomach, liver, lung, thyroid and skin). Photon doses were estimated for these organs by terms of the algorithm proposed in [3]. Plans were optimized with the same restrictions and limited to 30 segments in the Inverse case. Results: A similar photon peripheral dose was found comparing 6 and 15 MV cases with slightly higher values of (1.9 ± 1.6) % in mean, for the 6 MV cases. Neutron presence when using 15 MV, represents an increase in peripheral dose of (18 ± 17) % in average. Due to the higher number of MU used in Inverse IMRT, an increasing of (22 ± 3) % in neutron dose is found related to Forward and 3D-CRT plans. This corresponds to photon doses within 44 and 255 mSv along the organs, for a dose prescription of 68 Gy at the isocenter. Conclusion: Neutron and photon peripheral doses for a prostate treatment planified in 6 different techniques have been analyzed. 6 MV plans are slightly more demanding in terms of photon peripheral doses. Inverse technique in 15 MV has Result to be the most demanding one in terms of total peripheral doses, including neutrons and photons.

  13. The comparison of Co-60 and 4MV photons matching dosimetry during half-beam technique

    International Nuclear Information System (INIS)

    Cakir, Aydin; Bilge, Hatice; Dadasbilge, Alpar; Kuecuecuek, Halil; Okutan, Murat; Merdan Fayda, Emre

    2005-01-01

    In this phantom study, we tried to compare matching dosimetry differences between half-blocking of Co-60 and asymmetric collimation of the 4MV photons during craniospinal irradiation. The dose distributions are compared and discussed. Firstly, some gaps with different sizes are left between cranial and spinal field borders. Secondly, the fields are overlapped in the same sizes. We irradiate the films located in water-equivalent solid phantoms with Co-60 and 4MV photon beams. This study indicates that the field placement errors in +/- 1mm are acceptable for both Co-60 and 4MV photon energies during craniospinal irradiation with half-beam block technique. Within these limits the dose variations are specified in +/- 5%. However, the setup errors that are more than 1mm are unacceptable for both asymmetric collimation of 4MV photon and half-blocking of Co-60

  14. M&V Guidelines: Measurement and Verification for Performance-Based Contracts Version 4.0

    Energy Technology Data Exchange (ETDEWEB)

    None

    2015-11-02

    Document outlines the Federal Energy Management Program's standard procedures and guidelines for measurement and verification (M&V) for federal energy managers, procurement officials, and energy service providers.

  15. WE-G-18A-02: Calibration-Free Combined KV/MV Short Scan CBCT

    Energy Technology Data Exchange (ETDEWEB)

    Wu, M; Loo, B; Bazalova, M; Fahrig, R [Stanford University, Stanford, CA (United States); Star-Lack, J [Varian Medical Systems, Palo Alto, CA (United States)

    2014-06-15

    Purpose: To combine orthogonal kilo-voltage (kV) and Mega-voltage (MV) projection data for short scan cone-beam CT to reduce imaging time on current radiation treatment systems, using a calibration-free gain correction method. Methods: Combining two orthogonal projection data sets for kV and MV imaging hardware can reduce the scan angle to as small as 110° (90°+fan) such that the total scan time is ∼18 seconds, or within a breath hold. To obtain an accurate reconstruction, the MV projection data is first linearly corrected using linear regression using the redundant data from the start and end of the sinogram, and then the combined data is reconstructed using the FDK method. To correct for the different changes of attenuation coefficients in kV/MV between soft tissue and bone, the forward projection of the segmented bone and soft tissue from the first reconstruction in the redundant region are added to the linear regression model. The MV data is corrected again using the additional information from the segmented image, and combined with kV for a second FDK reconstruction. We simulated polychromatic 120 kVp (conventional a-Si EPID with CsI) and 2.5 MVp (prototype high-DQE MV detector) projection data with Poisson noise using the XCAT phantom. The gain correction and combined kV/MV short scan reconstructions were tested with head and thorax cases, and simple contrast-to-noise ratio measurements were made in a low-contrast pattern in the head. Results: The FDK reconstruction using the proposed gain correction method can effectively reduce artifacts caused by the differences of attenuation coefficients in the kV/MV data. The CNRs of the short scans for kV, MV, and kV/MV are 5.0, 2.6 and 3.4 respectively. The proposed gain correction method also works with truncated projections. Conclusion: A novel gain correction and reconstruction method was developed to generate short scan CBCT from orthogonal kV/MV projections. This work is supported by NIH Grant 5R01CA138426-05.

  16. Spark-protected ion-source control and monitoring system at 1.5 MV

    International Nuclear Information System (INIS)

    Bogaty, J.M.; Zolecki, R.

    1981-01-01

    The Heavy Ion Fusion Program at Argonne National Laboratory utilizes a 1.5-MV Xe ion preaccelerator. Reliable beam transport requires accurate measurements and precise control of various ion-source parameters. This paper discusses the use of a multiplexed fiberoptic data-transmission system and low-cost digital stepper motors for control functions. Techniques are discussed which allow TTL and CMOS semiconductor curcuits to survive the destructive sparks which can occur in the 1.5-MV preaccelerator

  17. Validation of calculated tissue maximum ratio obtained from measured percentage depth dose (PPD) data for high energy photon beam ( 6 MV and 15 MV)

    International Nuclear Information System (INIS)

    Osei, J.E.

    2014-07-01

    During external beam radiotherapy treatments, high doses are delivered to the cancerous cell. Accuracy and precision of dose delivery are primary requirements for effective and efficiency in treatment. This leads to the consideration of treatment parameters such as percentage depth dose (PDD), tissue air ratio (TAR) and tissue phantom ratio (TPR), which show the dose distribution in the patient. Nevertheless, tissue air ratio (TAR) for treatment time calculation, calls for the need to measure in-air-dose rate. For lower energies, measurement is not a problem but for higher energies, in-air measurement is not attainable due to the large build-up material required for the measurement. Tissue maximum ratio (TMR) is the quantity required to replace tissue air ratio (TAR) for high energy photon beam. It is known that tissue maximum ratio (TMR) is an important dosimetric function in radiotherapy treatment. As the calculation methods used to determine tissue maximum ratio (TMR) from percentage depth dose (PDD) were derived by considering the differences between TMR and PDD such as geometry and field size, where phantom scatter or peak scatter factors are used to correct dosimetric variation due to field size difference. The purpose of this study is to examine the accuracy of calculated tissue maximum ratio (TMR) data with measured TMR values for 6 MV and 15 MV photon beam at Sweden Ghana Medical Centre. With the help of the Blue motorize water phantom and the Omni pro-Accept software, Pdd values from which TMRs are calculated were measured at 100 cm source-to-surface distance (SSD) for various square field sizes from 5x5 cm to 40x40 cm and depth of 1.5 cm to 25 cm for 6 MV and 15 MV x-ray beam. With the same field sizes, depths and energies, the TMR values were measured. The validity of the calculated data was determined by making a comparison with values measured experimentally at some selected field sizes and depths. The results show that; the reference depth of maximum

  18. Design of a -1 MV dc UHV power supply for ITER NBI

    Science.gov (United States)

    Watanabe, K.; Yamamoto, M.; Takemoto, J.; Yamashita, Y.; Dairaku, M.; Kashiwagi, M.; Taniguchi, M.; Tobari, H.; Umeda, N.; Sakamoto, K.; Inoue, T.

    2009-05-01

    Procurement of a dc -1 MV power supply system for the ITER neutral beam injector (NBI) is shared by Japan and the EU. The Japan Atomic Energy Agency as the Japan Domestic Agency (JADA) for ITER contributes to the procurement of dc -1 MV ultra-high voltage (UHV) components such as a dc -1 MV generator, a transmission line and a -1 MV insulating transformer for the ITER NBI power supply. The inverter frequency of 150 Hz in the -1 MV power supply and major circuit parameters have been proposed and adopted in the ITER NBI. The dc UHV insulation has been carefully designed since dc long pulse insulation is quite different from conventional ac insulation or dc short pulse systems. A multi-layer insulation structure of the transformer for a long pulse up to 3600 s has been designed with electric field simulation. Based on the simulation the overall dimensions of the dc UHV components have been finalized. A surge energy suppression system is also essential to protect the accelerator from electric breakdowns. The JADA contributes to provide an effective surge suppression system composed of core snubbers and resistors. Input energy into the accelerator from the power supply can be reduced to about 20 J, which satisfies the design criteria of 50 J in total in the case of breakdown at -1 MV.

  19. Validation of the Spanish Addiction Severity Index Multimedia Version (S-ASI-MV).

    Science.gov (United States)

    Butler, Stephen F; Redondo, José Pedro; Fernandez, Kathrine C; Villapiano, Albert

    2009-01-01

    This study aimed to develop and test the reliability and validity of a Spanish adaptation of the ASI-MV, a computer administered version of the Addiction Severity Index, called the S-ASI-MV. Participants were 185 native Spanish-speaking adult clients from substance abuse treatment facilities serving Spanish-speaking clients in Florida, New Mexico, California, and Puerto Rico. Participants were administered the S-ASI-MV as well as Spanish versions of the general health subscale of the SF-36, the work and family unit subscales of the Social Adjustment Scale Self-Report, the Michigan Alcohol Screening Test, the alcohol and drug subscales of the Personality Assessment Inventory, and the Hopkins Symptom Checklist-90. Three-to-five-day test-retest reliability was examined along with criterion validity, convergent/discriminant validity, and factorial validity. Measurement invariance between the English and Spanish versions of the ASI-MV was also examined. The S-ASI-MV demonstrated good test-retest reliability (ICCs for composite scores between .59 and .93), criterion validity (rs for composite scores between .66 and .87), and convergent/discriminant validity. Factorial validity and measurement invariance were demonstrated. These results compared favorably with those reported for the original interviewer version of the ASI and the English version of the ASI-MV.

  20. Influence of Routine MV CBCT Usage on Dose Distribution in Pelvic Radiotherapy

    International Nuclear Information System (INIS)

    Faj, D.; Kasabasic, M.; Ivkovic, A.; Tomas, I.; Jurkovic, S.

    2013-01-01

    The pelvic radiotherapy is a standard treatment for patients with cervical, uterine and rectal carcinomas. During radiation treatment open tabletop device or bellyboard is used to reduce the side effects of healthy surrounding tissue. Patients are continually adjusting to the bellyboard during the treatment which causes geometrical and dosage uncertainties and influences the results of the treatment. Therefore, to reduce these uncertainties, megavoltage cone-beam computed tomography (MV CBCT) system is used. The objective of this research was to evaluate the image acquisition dose delivered to patients from MV CBCT. MV CBCT imaging was simulated on 15 patients using 3D treatment planning software XiO (CMS Inc., St. Louis, MO). The influence of the routine MV CBCT usage on treatment plan was investigated by analyzing the changes in dose volume histograms, mean values and maximum doses in the planning volumes. Simulations have shown that daily usage of MV CBCT causes differences in the dose volume histograms. Moreover, for every patient mean value exceeded prescribed tolerance (±1% of the prescribed dose) and maximum value exceeded recommended maximum of 107% of the prescribed dose. The results have shown that MV CBCT dose to the patient should be a part of the RT plan.(author)

  1. A comparison of kV and MV imaging in head and neck image guided radiotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Devereux, B. [Radiation Oncology Queensland, 280 North St, Toowoomba 4350 (Australia)], E-mail: beth.devereux@roq.net.au; Frantzis, J.; Sisson, T.; Jones, M.; Martin, J.; Middleton, M. [Radiation Oncology Queensland, 280 North St, Toowoomba 4350 (Australia)

    2010-02-15

    Purpose: To compare and assess kV and MV imaging modalities and their role in image guided radiotherapy (IGRT) for head and neck cancer patients. Method: Twelve patients receiving radical radiotherapy to the head and neck were analysed in this study. Six patients undertook MV daily online intervention and a further six patients undertook kV daily online intervention. Pre-intervention field placement data were collected from three separate observers' image match analysis for each patient. The radiotherapy collective involved in the daily online image match analysis formed the fourth observer in the study. The primary end point was to establish the difference in inter- and intra-observer variance between kV and MV imaging modalities. Results: The range of the standard deviations of systematic set-up error for MV imaging calculated was 1.47-2.33 mm (MV) and 1.61-1.64 mm (kV) for the right-left (RL), 2.10-2.17 mm (MV) and 1.53-1.84 mm (kV) for the cranio-caudal (CC) and 1.43-1.63 mm (MV) and 1.02-1.11 mm (kV) for the anterior-posterior (AP). The mean inter-observer variance was 0.21 mm (MV) and 0.41 mm (kV) for the RL, 0.53 mm (MV) and 0.55 mm (kV) for the CC and 0.23 mm (MV) and 0.16 mm (kV) for the AP direction. Intra-observer mean variance was in the order of 0.60 mm (MV) and 0.16 mm (kV) for the RL, 1.41 mm (MV) and 0.05 mm (kV) for the CC and 1.41 mm (MV) and 0.08 mm (kV) for the AP. Discussion: The data in this study suggest both inter- and intra-observer consistency across kV and MV imaging modalities were comparable. However, it is felt that the improved clarity and quality of kV imaging allows all observers to analyse images in a consistent manner, identifying and acting on potential field placement moves. Conclusion: The introduction of kV imaging has maintained the high levels of inter- and intra-observer consistency achieved with MV imaging. This in turn further enables positive verification outcomes and supports the implementation of potential

  2. Geometric validation of MV topograms for patient localization on TomoTherapy

    International Nuclear Information System (INIS)

    Blanco Kiely, Janid P; White, Benjamin M; Low, Daniel A; Qi, Sharon X

    2016-01-01

    Our goal was to geometrically validate the use of mega-voltage orthogonal scout images (MV topograms) as a fast and low-dose alternative to mega-voltage computed tomography (MVCT) for daily patient localization on the TomoTherapy system. To achieve this, anthropomorphic head and pelvis phantoms were imaged on a 16-slice kilo-voltage computed tomography (kVCT) scanner to synthesize kilo-voltage digitally reconstructed topograms (kV-DRT) in the Tomotherapy detector geometry. MV topograms were generated for couch speeds of 1–4 cm s −1 in 1 cm s −1 increments with static gantry angles in the anterior-posterior and left-lateral directions. Phantoms were rigidly translated in the anterior-posterior (AP), superior-inferior (SI), and lateral (LAT) directions to simulate potential setup errors. Image quality improvement was demonstrated by estimating the noise level in the unenhanced and enhanced MV topograms using a principle component analysis-based noise level estimation algorithm. Average noise levels for the head phantom were reduced by 2.53 HU (AP) and 0.18 HU (LAT). The pelvis phantom exhibited average noise level reduction of 1.98 HU (AP) and 0.48 HU (LAT). Mattes Mutual Information rigid registration was used to register enhanced MV topograms with corresponding kV-DRT. Registration results were compared to the known rigid displacements, which assessed the MV topogram localization’s sensitivity to daily positioning errors. Reduced noise levels in the MV topograms enhanced the registration results so that registration errors were  <1 mm. The unenhanced head MV topograms had discrepancies  <2.1 mm and the pelvis topograms had discrepancies  <2.7 mm. Result were found to be consistent regardless of couch speed. In total, 64.7% of the head phantom MV topograms and 60.0% of the pelvis phantom MV topograms exactly measured the phantom offsets. These consistencies demonstrated the potential for daily patient positioning using MV topogram pairs

  3. Combined kV and MV imaging for real-time tracking of implanted fiducial markers

    International Nuclear Information System (INIS)

    Wiersma, R. D.; Mao Weihua; Xing, L.

    2008-01-01

    In the presence of intrafraction organ motion, target localization uncertainty can greatly hamper the advantage of highly conformal dose techniques such as intensity modulated radiation therapy (IMRT). To minimize the adverse dosimetric effect caused by tumor motion, a real-time knowledge of the tumor position is required throughout the beam delivery process. The recent integration of onboard kV diagnostic imaging together with MV electronic portal imaging devices on linear accelerators can allow for real-time three-dimensional (3D) tumor position monitoring during a treatment delivery. The aim of this study is to demonstrate a near real-time 3D internal fiducial tracking system based on the combined use of kV and MV imaging. A commercially available radiotherapy system equipped with both kV and MV imaging systems was used in this work. A hardware video frame grabber was used to capture both kV and MV video streams simultaneously through independent video channels at 30 frames per second. The fiducial locations were extracted from the kV and MV images using a software tool. The geometric tracking capabilities of the system were evaluated using a pelvic phantom with embedded fiducials placed on a moveable stage. The maximum tracking speed of the kV/MV system is approximately 9 Hz, which is primarily limited by the frame rate of the MV imager. The geometric accuracy of the system is found to be on the order of less than 1 mm in all three spatial dimensions. The technique requires minimal hardware modification and is potentially useful for image-guided radiation therapy systems

  4. Two dissimilar approaches to dynamical systems on hyper MV -algebras and their information entropy

    Science.gov (United States)

    Mehrpooya, Adel; Ebrahimi, Mohammad; Davvaz, Bijan

    2017-09-01

    Measuring the flow of information that is related to the evolution of a system which is modeled by applying a mathematical structure is of capital significance for science and usually for mathematics itself. Regarding this fact, a major issue in concern with hyperstructures is their dynamics and the complexity of the varied possible dynamics that exist over them. Notably, the dynamics and uncertainty of hyper MV -algebras which are hyperstructures and extensions of a central tool in infinite-valued Lukasiewicz propositional calculus that models many valued logics are of primary concern. Tackling this problem, in this paper we focus on the subject of dynamical systems on hyper MV -algebras and their entropy. In this respect, we adopt two varied approaches. One is the set-based approach in which hyper MV -algebra dynamical systems are developed by employing set functions and set partitions. By the other method that is based on points and point partitions, we establish the concept of hyper injective dynamical systems on hyper MV -algebras. Next, we study the notion of entropy for both kinds of systems. Furthermore, we consider essential ergodic characteristics of those systems and their entropy. In particular, we introduce the concept of isomorphic hyper injective and hyper MV -algebra dynamical systems, and we demonstrate that isomorphic systems have the same entropy. We present a couple of theorems in order to help calculate entropy. In particular, we prove a contemporary version of addition and Kolmogorov-Sinai Theorems. Furthermore, we provide a comparison between the indispensable properties of hyper injective and semi-independent dynamical systems. Specifically, we present and prove theorems that draw comparisons between the entropies of such systems. Lastly, we discuss some possible relationships between the theories of hyper MV -algebra and MV -algebra dynamical systems.

  5. Identification of Differentially Methylated Sites with Weak Methylation Effects

    Directory of Open Access Journals (Sweden)

    Hong Tran

    2018-02-01

    Full Text Available Deoxyribonucleic acid (DNA methylation is an epigenetic alteration crucial for regulating stress responses. Identifying large-scale DNA methylation at single nucleotide resolution is made possible by whole genome bisulfite sequencing. An essential task following the generation of bisulfite sequencing data is to detect differentially methylated cytosines (DMCs among treatments. Most statistical methods for DMC detection do not consider the dependency of methylation patterns across the genome, thus possibly inflating type I error. Furthermore, small sample sizes and weak methylation effects among different phenotype categories make it difficult for these statistical methods to accurately detect DMCs. To address these issues, the wavelet-based functional mixed model (WFMM was introduced to detect DMCs. To further examine the performance of WFMM in detecting weak differential methylation events, we used both simulated and empirical data and compare WFMM performance to a popular DMC detection tool methylKit. Analyses of simulated data that replicated the effects of the herbicide glyphosate on DNA methylation in Arabidopsis thaliana show that WFMM results in higher sensitivity and specificity in detecting DMCs compared to methylKit, especially when the methylation differences among phenotype groups are small. Moreover, the performance of WFMM is robust with respect to small sample sizes, making it particularly attractive considering the current high costs of bisulfite sequencing. Analysis of empirical Arabidopsis thaliana data under varying glyphosate dosages, and the analysis of monozygotic (MZ twins who have different pain sensitivities—both datasets have weak methylation effects of <1%—show that WFMM can identify more relevant DMCs related to the phenotype of interest than methylKit. Differentially methylated regions (DMRs are genomic regions with different DNA methylation status across biological samples. DMRs and DMCs are essentially the same

  6. DNA methylation in obesity

    Directory of Open Access Journals (Sweden)

    Małgorzata Pokrywka

    2014-11-01

    Full Text Available The number of overweight and obese people is increasing at an alarming rate, especially in the developed and developing countries. Obesity is a major risk factor for diabetes, cardiovascular disease, and cancer, and in consequence for premature death. The development of obesity results from the interplay of both genetic and environmental factors, which include sedentary life style and abnormal eating habits. In the past few years a number of events accompanying obesity, affecting expression of genes which are not directly connected with the DNA base sequence (e.g. epigenetic changes, have been described. Epigenetic processes include DNA methylation, histone modifications such as acetylation, methylation, phosphorylation, ubiquitination, and sumoylation, as well as non-coding micro-RNA (miRNA synthesis. In this review, the known changes in the profile of DNA methylation as a factor affecting obesity and its complications are described.

  7. Generation of virtual monochromatic CBCT from dual kV/MV beam projections

    International Nuclear Information System (INIS)

    Li, Hao; Liu, Bo; Yin, Fang-Fang

    2013-01-01

    Purpose: To develop a novel on-board imaging technique which allows generation of virtual monochromatic (VM) cone-beam CT (CBCT) with a selected energy from combined kilovoltage (kV)/megavoltage (MV) beam projections. Methods: With the current orthogonal kV/MV imaging hardware equipped in modern linear accelerators, both MV projections (from gantry angle of 0°–100°) and kV projections (90°–200°) were acquired as gantry rotated a total of 110°. A selected range of overlap projections between 90° to 100° were then decomposed into two material projections using experimentally determined parameters from orthogonally stacked aluminum and acrylic step-wedges. Given attenuation coefficients of aluminum and acrylic at a predetermined energy, one set of VM projections could be synthesized from two corresponding sets of decomposed projections. Two linear functions were generated using projection information at overlap angles to convert kV and MV projections at nonoverlap angles to approximate VM projections for CBCT reconstruction. The contrast-to-noise ratios (CNRs) were calculated for different inserts in VM CBCTs of a CatPhan phantom with various selected energies and compared with those in kV and MV CBCTs. The effect of overlap projection number on CNR was evaluated. Additionally, the effect of beam orientation was studied by scanning the CatPhan sandwiched with two 5 cm solid-water phantoms on both lateral sides and an electronic density phantom with two metal bolt inserts. Results: Proper selection of VM energy [30 and 40 keV for low-density polyethylene (LDPE), polymethylpentene, 2 MeV for Delrin] provided comparable or even better CNR results as compared with kV or MV CBCT. An increased number of overlap kV and MV projection demonstrated only marginal improvements of CNR for different inserts (with the exception of LDPE) and therefore one projection overlap was found to be sufficient for the CatPhan study. It was also evident that the optimal CBCT image

  8. An Analysis of Possibilities How the Collision Between M/V ‘Baltic Ace’ and M/V ‘Corvus J’ Could Have Been Avoided

    Directory of Open Access Journals (Sweden)

    Kulbiej Eric

    2016-12-01

    Full Text Available The report presents the simulation results of collision between m/v ‘Baltic Ace’ and m/v ‘Corvus J’. The analysis was performed by means of navigation decision support system (NDSS in collision situations. This system (NAVDEC works out anti-collision manoeuvre using AIS (Automatic Identification System and ARPA (Automatic Radar Plotting Aids data. Then they are processed by specialized computing algorithms and presented to the operator on a display in the alphanumeric and graphic forms. The data on the specific navigational situation from the report of Bahamas Maritime Authority was used for the generation of signals transmitted to NDSS as a sequence of NMEA strings.

  9. Hyaluronan synthase 3 (HAS3) overexpression downregulates MV3 melanoma cell proliferation, migration and adhesion

    International Nuclear Information System (INIS)

    Takabe, Piia; Bart, Geneviève; Ropponen, Antti; Rilla, Kirsi; Tammi, Markku; Tammi, Raija; Pasonen-Seppänen, Sanna

    2015-01-01

    Malignant skin melanoma is one of the most deadly human cancers. Extracellular matrix (ECM) influences the growth of malignant tumors by modulating tumor cells adhesion and migration. Hyaluronan is an essential component of the ECM, and its amount is altered in many tumors, suggesting an important role for hyaluronan in tumorigenesis. Nonetheless its role in melanomagenesis is not understood. In this study we produced a MV3 melanoma cell line with inducible expression of the hyaluronan synthase 3 (HAS3) and studied its effect on the behavior of the melanoma cells. HAS3 overexpression expanded the cell surface hyaluronan coat and decreased melanoma cell adhesion, migration and proliferation by cell cycle arrest at G1/G0. Melanoma cell migration was restored by removal of cell surface hyaluronan by Streptomyces hyaluronidase and by receptor blocking with hyaluronan oligosaccharides, while the effect on cell proliferation was receptor independent. Overexpression of HAS3 decreased ERK1/2 phosphorylation suggesting that inhibition of MAP-kinase signaling was responsible for these suppressive effects on the malignant phenotype of MV3 melanoma cells. - Highlights: • Inducible HAS3-MV3 melanoma cell line was generated using Lentiviral transduction. • HAS3 overexpression inhibits MV3 cell migration via hyaluronan–receptor interaction. • HAS3 overexpression decreases MV3 melanoma cell proliferation and adhesion. • ERK1/2 phosphorylation is downregulated by 50% in HAS3 overexpressing cells. • The results suggest that hyaluronan has anti-cancer like effects in melanoma

  10. Modification of 300kV RF Ion Source for 1-MV Electrostatic Accelerator at KOMAC

    International Nuclear Information System (INIS)

    Kim, Dae-Il; Kwon, Hyeok-Jung; Park, Sae-Hoon; Cho, Yong-Sub

    2015-01-01

    The specifications of the 1-MV electrostatic accelerator are shown as below. High voltage power supply is electron transformer rectifier (ELV) type which was developed in Nuclear Physics Institute (Novosibirsk) for industrial electron accelerators. And accelerator column consists of alumina and metal electrode rings were 0.5m-long brazed structure which can be installed horizontally. In case of ion source for 1-MV electrostatic accelerator, it is chosen a thonemann type rf ion source and 300-kV test-stand was made up to confirm the stable operating conditions. High voltage power supply is fabricated by domestic company, and its operation has been confirming at KOMAC site. Equally, the ion source of 300-kV test-stand should be modified to install into the high voltage power supply. In this paper, modification of ion source of 300-kV test-stand for 1-MV electrostatic accelerator is presented and its processes are considered. 300-kV RF ion source and power supply are testing for the 1-MV electrostatic accelerator and trying for combination between them. The 1-MV electrostatic accelerator will be fabricated with domestic companies and tested in the beam application research building at KOMAC

  11. Modification of 300kV RF Ion Source for 1-MV Electrostatic Accelerator at KOMAC

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Dae-Il; Kwon, Hyeok-Jung; Park, Sae-Hoon; Cho, Yong-Sub [KOMAC, Gyeongju (Korea, Republic of)

    2015-05-15

    The specifications of the 1-MV electrostatic accelerator are shown as below. High voltage power supply is electron transformer rectifier (ELV) type which was developed in Nuclear Physics Institute (Novosibirsk) for industrial electron accelerators. And accelerator column consists of alumina and metal electrode rings were 0.5m-long brazed structure which can be installed horizontally. In case of ion source for 1-MV electrostatic accelerator, it is chosen a thonemann type rf ion source and 300-kV test-stand was made up to confirm the stable operating conditions. High voltage power supply is fabricated by domestic company, and its operation has been confirming at KOMAC site. Equally, the ion source of 300-kV test-stand should be modified to install into the high voltage power supply. In this paper, modification of ion source of 300-kV test-stand for 1-MV electrostatic accelerator is presented and its processes are considered. 300-kV RF ion source and power supply are testing for the 1-MV electrostatic accelerator and trying for combination between them. The 1-MV electrostatic accelerator will be fabricated with domestic companies and tested in the beam application research building at KOMAC.

  12. Dual-energy (MV/kV) CT with probabilistic attenuation mapping for IGRT applications

    Science.gov (United States)

    Pearson, Erik; Pan, Xiaochuan; Pelizzari, Charles

    2015-03-01

    Imaging plays an important role in the delivery of external beam radiation therapy. It is used to confirm the setup of the patient and to ensure accurate targeting and delivery of the therapeutic radiation dose. Most modern linear accelerators come equipped with a flat panel detector opposite the MV source as well as an independent kV imaging system, typically mounted perpendicular to the MV beam. kV imaging provides superior soft tissue contrast and is typically lower dose to the patient than MV imaging, however it can suffer from artifacts caused by metallic objects such as implants and immobilization devices. In addition to being less artifact prone, MV imaging also provides a direct measure of the attenuation for the MV beam which is useful for computing the therapeutic dose distributions. Furthermore either system requires a large angular coverage, which is slow for large linear accelerators. We present a method for reconstructing tomographic images from data acquired at multiple x-ray beam energies using a statistical model of inherent physical properties of the imaged object. This approach can produce image quality superior to traditional techniques in the case of limited measurement data (angular sampling range, sampling density or truncated projections) and/or conditions in which the lower energy image would typically suffer from corrupting artifacts such as the presence of metals in the object. Both simulation and real data results are shown.

  13. Hyaluronan synthase 3 (HAS3) overexpression downregulates MV3 melanoma cell proliferation, migration and adhesion

    Energy Technology Data Exchange (ETDEWEB)

    Takabe, Piia, E-mail: piia.takabe@uef.fi [University of Eastern Finland, Institute of Biomedicine, 70211 Kuopio (Finland); Bart, Geneviève [University of Eastern Finland, Institute of Biomedicine, 70211 Kuopio (Finland); Ropponen, Antti [University of Eastern Finland, Institute of Clinical Medicine, 70211 Kuopio (Finland); Rilla, Kirsi; Tammi, Markku; Tammi, Raija; Pasonen-Seppänen, Sanna [University of Eastern Finland, Institute of Biomedicine, 70211 Kuopio (Finland)

    2015-09-10

    Malignant skin melanoma is one of the most deadly human cancers. Extracellular matrix (ECM) influences the growth of malignant tumors by modulating tumor cells adhesion and migration. Hyaluronan is an essential component of the ECM, and its amount is altered in many tumors, suggesting an important role for hyaluronan in tumorigenesis. Nonetheless its role in melanomagenesis is not understood. In this study we produced a MV3 melanoma cell line with inducible expression of the hyaluronan synthase 3 (HAS3) and studied its effect on the behavior of the melanoma cells. HAS3 overexpression expanded the cell surface hyaluronan coat and decreased melanoma cell adhesion, migration and proliferation by cell cycle arrest at G1/G0. Melanoma cell migration was restored by removal of cell surface hyaluronan by Streptomyces hyaluronidase and by receptor blocking with hyaluronan oligosaccharides, while the effect on cell proliferation was receptor independent. Overexpression of HAS3 decreased ERK1/2 phosphorylation suggesting that inhibition of MAP-kinase signaling was responsible for these suppressive effects on the malignant phenotype of MV3 melanoma cells. - Highlights: • Inducible HAS3-MV3 melanoma cell line was generated using Lentiviral transduction. • HAS3 overexpression inhibits MV3 cell migration via hyaluronan–receptor interaction. • HAS3 overexpression decreases MV3 melanoma cell proliferation and adhesion. • ERK1/2 phosphorylation is downregulated by 50% in HAS3 overexpressing cells. • The results suggest that hyaluronan has anti-cancer like effects in melanoma.

  14. Dose-volume histogram comparison between static 5-field IMRT with 18-MV X-rays and helical tomotherapy with 6-MV X-rays.

    Science.gov (United States)

    Hayashi, Akihiro; Shibamoto, Yuta; Hattori, Yukiko; Tamura, Takeshi; Iwabuchi, Michio; Otsuka, Shinya; Sugie, Chikao; Yanagi, Takeshi

    2015-03-01

    We treated prostate cancer patients with static 5-field intensity-modulated radiation therapy (IMRT) using linac 18-MV X-rays or tomotherapy with 6-MV X-rays. As X-ray energies differ, we hypothesized that 18-MV photon IMRT may be better for large patients and tomotherapy may be more suitable for small patients. Thus, we compared dose-volume parameters for the planning target volume (PTV) and organs at risk (OARs) in 59 patients with T1-3 N0M0 prostate cancer who had been treated using 5-field IMRT. For these same patients, tomotherapy plans were also prepared for comparison. In addition, plans of 18 patients who were actually treated with tomotherapy were analyzed. The evaluated parameters were homogeneity indicies and a conformity index for the PTVs, and D2 (dose received by 2% of the PTV in Gy), D98, Dmean and V10-70 Gy (%) for OARs. To evaluate differences by body size, patients with a known body mass index were grouped by that index ( 25 kg/m(2)). For the PTV, all parameters were higher in the tomotherapy plans compared with the 5-field IMRT plans. For the rectum, V10 Gy and V60 Gy were higher, whereas V20 Gy and V30 Gy were lower in the tomotherapy plans. For the bladder, all parameters were higher in the tomotherapy plans. However, both plans were considered clinically acceptable. Similar trends were observed in 18 patients treated with tomotherapy. Obvious trends were not observed for body size. Tomotherapy provides equivalent dose distributions for PTVs and OARs compared with 18-MV 5-field IMRT. Tomotherapy could be used as a substitute for high-energy photon IMRT for prostate cancer regardless of body size. © The Author 2015. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.

  15. Radiation transmission of heavyweight and normal-weight concretes containing colemanite for 6 MV and 18 MV X-rays using linear accelerator

    International Nuclear Information System (INIS)

    Demir, F.; Budak, G.; Sahin, R.; Karabulut, A.; Oltulu, M.; Serifoglu, K.; Un, A.

    2010-01-01

    Accurate measurements have been made to determine radiation transmission of concretes produced with barite, colemanite and normal aggregate by using beam transmission method for 6 and 18 MV X-rays with a linear accelerator (LINAC). Linear attenuation coefficients of thirteen heavy- and four normal-weight concretes were calculated. It was determined that linear attenuation coefficient (μ, cm -1 ) decreased with colemanite concentration and increased with barite concentration in both types of the concretes.

  16. Rate dependence of electron transfer on donor-acceptor separation and on free enthalpy change. The Ru(bpy)32+/viologen2+ system

    International Nuclear Information System (INIS)

    Rau, H.; Frank, R.; Greiner, G.

    1986-01-01

    By attachment of hydrocarbon chains of different lengths to the bipyridyl ligands in Ru(bpy) 3 2+ we have adjusted the donor-acceptor separation in the electron-transfer system Ru[(C/sub n/H/sub 2n+1/) 2 bpyl 3 2+ /methylviolgen. Two electron-transfer reactions with different ΔG are investigated in fluid solution: the quenching of the excited complexes by methylviologen (MV 2+ ) which is exergonic with -0.4 eV and the thermal back electron transfer which is exergonic with -1.7 eV. We observe an exponential decrease of the quenching rate on distance. The back electron transfer is independent of donor-acceptor separation; electron transfer is found to take place at distances of 1.5 nm and more. The results are discussed in terms of a hypothesis on the interdependence of transfer distance and free enthalpy change and compared with current theories. In the framework of the simple classical Marcus model, the Marcus equation relating transfer rate and free enthalpy change is transposed into the Rehm-Weller equation by simple mathematical manipulations and the implications of this are discussed

  17. Performance Results for Building the 1 MV Electrostatic Accelerator at KOMAC

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Dae-Il; Kwon, Hyeok-Jung; Park, Sae-Hoon; Cho, Yong-Sub [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-10-15

    1 MV electrostatic accelerator of KOrea Multi-purpose Accelerator Complex (KOMAC) is being developed to satisfy the needs from the users, especially for the applications with a MeV range ion beam implantation. Table 1 shows specifications of the 1MV electrostatic accelerator. The accelerator consists of ion source, beam transport system and target chamber. The ion source and accelerating column are installed inside the pressure vessel of high voltage power supply. The layout of the system is shown in Fig. 1. A 1 MV electrostatic accelerator is being developed at KOMAC. The high voltage power supply is already developed. The 200 MHz RF ion source is now being tested in the 300 kV test-stand. In the test results, it is necessary to improve increasing RF power absorption into the plasma in order to supply 1 mA beam. For this goal, we need more reliable the matching circuit and should be modified the matching components.

  18. Basic Design Study on 1-MV Electrostatic Accelerator for ion irradiation

    International Nuclear Information System (INIS)

    Cho, Yongsub; Kim, Kyeryung; Lee, Chanyoung

    2014-01-01

    The KOMAC (KOrea Multi-purpose Accelerator Complex) has electrostatic ion accelerators whose terminal voltages are less than 100kV. To extend ion beam irradiations with higher energy ions for industrial purposes, an electrostatic accelerator of 1-MV terminal voltage should have been studied. For industrial applications, the most important features of the accelerator are high current and high reliability for high irradiation dose and high through-put with high current and long irradiation time. The basic study on 1-MV electrostatic ion accelerator for industrial applications has been done. The key components are a high voltage power supply, an ion source, and an accelerating column. The feasibility study for fabrication is being performed. Especially the R and D for ion source is required. The 1-MV ion accelerator will be constructed with domestic companies and installed in the beam application research building, which is under construction in the site of KOMAC at Gyeongju

  19. Dose corrections for field obliquity for 45-MV x-ray therapy

    International Nuclear Information System (INIS)

    McGinley, P.H.; Clanton, A.; Downes, B.; Nuskind, J.

    1983-01-01

    The degree of dose perturbation produced by a 25.7-cm-diam circular water phantom was determined for a 45-MV x-ray beam by direct measurement. Data obtained in a circular and a cubical water phantom was utilized to test three accepted techniques (isodose shift, TAR method, and effective SSD method) for the correction of isodose levels to account for patient curvature. In general, the effective SSD method yielded the most accurate results for all depth including the buildup region. An isodose shift factor of 0.8 was found for the 45-MV x-ray beam. Key words: curvature corrections, 45-MV x ray, isodose shift, TAR, effective SSD method

  20. Development of a 1.0 MV 100 Hz compact tesla transformer with PFL

    International Nuclear Information System (INIS)

    Kang Qiang; Chang Anbi; Li Mingjia; Meng Fanbao; Su Youbin

    2006-01-01

    The theory and characteristic of a compact Tesla transformer are introduced, and an unitized configuration design is performed for 1.0 MV, 100 Hz Tesla transformer and 40 Ω, 40 ns pulse forming line (PFL). Two coaxial open cores in Tesla transformer serve as the inner and outer conductors of PFL, and a traditional PFL is combined with the Tesla transformer, then the pulse generator can be smaller, more efficient, and more stable. The designed compact Tesla transformer employed in electron beams accelerator CHP01 can charge PFL of 600 pF for 1.3 MV voltage at a single shot, and keep 1.15 MV at 100 Hz repeated rates. Furthermore, a continuance run in 5 seconds is achieved by Tesla transformer under voltage and frequency ratings. (authors)

  1. Methylated β-Cyclodextrins

    DEFF Research Database (Denmark)

    Schönbeck, Jens Christian Sidney; Westh, Peter; Madsen, Jens Christian

    2011-01-01

    The complexation of 6 bile salts with various methylated β-cyclodextrins was studied to elucidate how the degree and pattern of substitution affects the binding. The structures of the CDs were determined by mass spectrometry and NMR techniques, and the structures of the inclusion complexes were...

  2. Geometric validation of MV topograms for patient localization on TomoTherapy

    Science.gov (United States)

    Blanco Kiely, Janid P.; White, Benjamin M.; Low, Daniel A.; Qi, Sharon X.

    2016-01-01

    Our goal was to geometrically validate the use of mega-voltage orthogonal scout images (MV topograms) as a fast and low-dose alternative to mega-voltage computed tomography (MVCT) for daily patient localization on the TomoTherapy system. To achieve this, anthropomorphic head and pelvis phantoms were imaged on a 16-slice kilo-voltage computed tomography (kVCT) scanner to synthesize kilo-voltage digitally reconstructed topograms (kV-DRT) in the Tomotherapy detector geometry. MV topograms were generated for couch speeds of 1-4 cm s-1 in 1 cm s-1 increments with static gantry angles in the anterior-posterior and left-lateral directions. Phantoms were rigidly translated in the anterior-posterior (AP), superior-inferior (SI), and lateral (LAT) directions to simulate potential setup errors. Image quality improvement was demonstrated by estimating the noise level in the unenhanced and enhanced MV topograms using a principle component analysis-based noise level estimation algorithm. Average noise levels for the head phantom were reduced by 2.53 HU (AP) and 0.18 HU (LAT). The pelvis phantom exhibited average noise level reduction of 1.98 HU (AP) and 0.48 HU (LAT). Mattes Mutual Information rigid registration was used to register enhanced MV topograms with corresponding kV-DRT. Registration results were compared to the known rigid displacements, which assessed the MV topogram localization’s sensitivity to daily positioning errors. Reduced noise levels in the MV topograms enhanced the registration results so that registration errors were  pairs in the context bony-anatomy based procedures such as total marrow irradiation, total body irradiation, and cranial spinal irradiation.

  3. Guidelines for plant operation with MH-MV10 opening time fluctuations

    International Nuclear Information System (INIS)

    Saqib, N.

    1992-02-01

    In this report high opening time problems for MH-MV10 and such behavior leading to a sound policy and action to be taken has been described. An upper limit on acceptable opening time can be had by determining the time it would take for MH-pimps to gas lock if recirculation is not esteblished. Comparing the different methods it seems that conservative MOAT (maximum allowable opening time) would be 221 seconds. This allows for maximum observed drift in MH-MV10-XT1/XT2. Some recommendations for high opening time has been also given. (A.B.)

  4. SIRIUS – A new 6 MV accelerator system for IBA and AMS at ANSTO

    Energy Technology Data Exchange (ETDEWEB)

    Pastuovic, Zeljko, E-mail: zkp@ansto.gov.au; Button, David; Cohen, David; Fink, David; Garton, David; Hotchkis, Michael; Ionescu, Mihail; Long, Shane; Levchenko, Vladimir; Mann, Michael; Siegele, Rainer; Smith, Andrew; Wilcken, Klaus

    2016-03-15

    The Centre for Accelerator Science (CAS) facility at ANSTO has been expanded with a new 6 MV tandem accelerator system supplied by the National Electrostatic Corporation (NEC). The beamlines, end-stations and data acquisition software for the accelerator mass spectrometry (AMS) were custom built by NEC for rare isotope mass spectrometry, while the beamlines with end-stations for the ion beam analysis (IBA) are largely custom designed at ANSTO. An overview of the 6 MV system and its performance during testing and commissioning phase is given with emphasis on the IBA end-stations and their applications for materials modification and characterisation.

  5. SIRIUS - A new 6 MV accelerator system for IBA and AMS at ANSTO

    Science.gov (United States)

    Pastuovic, Zeljko; Button, David; Cohen, David; Fink, David; Garton, David; Hotchkis, Michael; Ionescu, Mihail; Long, Shane; Levchenko, Vladimir; Mann, Michael; Siegele, Rainer; Smith, Andrew; Wilcken, Klaus

    2016-03-01

    The Centre for Accelerator Science (CAS) facility at ANSTO has been expanded with a new 6 MV tandem accelerator system supplied by the National Electrostatic Corporation (NEC). The beamlines, end-stations and data acquisition software for the accelerator mass spectrometry (AMS) were custom built by NEC for rare isotope mass spectrometry, while the beamlines with end-stations for the ion beam analysis (IBA) are largely custom designed at ANSTO. An overview of the 6 MV system and its performance during testing and commissioning phase is given with emphasis on the IBA end-stations and their applications for materials modification and characterisation.

  6. Emission lines in the hydrogen-deficient variable MV Sagittarii near maximum light

    International Nuclear Information System (INIS)

    Herbig, G.H.

    1975-01-01

    The H-deficient R CrB type variable MV Sgr near maximum light shows a rich emission spectrum in the 5800--8600 A region. Most of these lines are due to Fe ii, but Si ii, N i, O i, and Hα also are present. Such a spectrum has not been observed in any other R CrB star, but there is some resemblance to v Sgr. The emission lines in MV Sgr probably originate in an extended region of low temperature, which may also be responsible for the infrared excess observed by Feast and Glass

  7. Protein methylation in pea chloroplasts

    International Nuclear Information System (INIS)

    Niemi, K.J.; Adler, J.; Selman, B.R.

    1990-01-01

    The methylation of chloroplast proteins has been investigated by incubating intact pea (Pisum sativum) chloroplasts with [ 3 H-methyl]-S-adenosylmethionine. Incubation in the light increases the amount of methylation in both the thylakoid and stromal fractions. Numerous thylakoid proteins serve as substrates for the methyltransfer reactions. Three of these thylakoid proteins are methylated to a significantly greater extent in the light than in the dark. The primary stromal polypeptide methylated is the large subunit of ribulose bisphosphate carboxylase/oxygenase. One other stromal polypeptide is also methylated much more in the light than in the dark. Two distinct types of protein methylation occur. One methylinkage is stable to basic conditions whereas a second type is base labile. The base-stable linkage is indicative of N-methylation of amino acid residues while base-lability is suggestive of carboxymethylation of amino acid residues. Labeling in the light increases the percentage of methylation that is base labile in the thylakoid fraction while no difference is observed in the amount of base-labile methylations in light-labeled and dark-labeled stromal proteins. Also suggestive of carboxymethylation is the detection of volatile [ 3 H]methyl radioactivity which increases during the labeling period and is greater in chloroplasts labeled in the light as opposed to being labeled in the dark; this implies in vivo turnover of the [ 3 H]methyl group

  8. Methylation of food commodities during fumigation with methyl bromide

    International Nuclear Information System (INIS)

    Starratt, A.N.; Bond, E.J.

    1990-01-01

    Sites of methylation in several commodities (wheat, oatmeal, peanuts, almonds, apples, oranges, maize, alfalfa and potatoes) during fumigation with 14 C-methyl bromide were studied. Differences were observed in levels of the major volatiles: methanol, dimethyl sulphide and methyl mercaptan, products of O- and S-methylation, resulting from treatment of the fumigated materials with 1N sodium hydroxide. In studies of maize and wheat, histidine was the amino acid which underwent the highest level of N-methylation. (author). 24 refs, 3 tabs

  9. Treatment of early and moderately advanced vocal cord carcinoma with 6-MV X-rays

    International Nuclear Information System (INIS)

    Parsons, James T.; Greene, Bruce D.; Speer, Tod W.; Kirkpatrick, Steven A.; Barhorst, D. Brad; Yanckowitz, Tina

    2001-01-01

    Purpose: Whereas there are many reports regarding treatment of early vocal cord cancer with cobalt 60 or 2-4-MV X-rays, there are still few reports on the results of treatment with 6-MV X-rays. Theoretically, 6-MV X-rays result in greater underdosage of tumor at the air-tissue interface and at the anterior commissure. This paper analyzes the results of irradiation of early and moderately advanced squamous cell carcinoma of the true vocal cord treated exclusively with 6-MV X-rays in a community hospital. The literature pertinent to the issue is reviewed. Methods and Materials: Eighty-three patients with Tis, T1, T2, or T3 squamous cell carcinoma of the true vocal cord were treated with curative intent at Bethesda Memorial Hospital in Boynton Beach, Florida between April 1986 and April 1998. The dose schedules most commonly used were 63 Gy in 28 fractions (2.25 Gy per fraction once a day) for T1 tumors or 74.40 Gy in 62 fractions (1.2 Gy per fraction twice a day) for T2 and T3 tumors. All patients have minimum 2-year follow-up; 63 (76%) have 5-year minimum follow-up. Results: Local control was achieved in 6 of 6 Tis, 53 of 54 (98%) T1, 8 of 8 T2, and 6 of 6 T3 lesions. No complications were encountered. Conclusions: A recent literature review indicates that the treatment of early vocal cord cancer with 6-MV X-rays remains controversial. The dose schedules used in the present paper produced a high rate of local control, a finding that is consistent with reports of other investigators who used dose schedules similar to those used in the present series. However, several other investigators have reported significantly lower rates of local control for T1 or T2 glottic cancer treated with 6-MV X-rays when compared to results obtained with cobalt 60 or 4 MV at their own institution. The latter institutions used lower total doses and/or lower dose per fraction than those institutions reporting high rates of local control with 6 MV. Data from the literature, as well as our

  10. Synthesis of [Ru3(μ3-NPh)(Br)(CO)9]- on self-assembled monolayers of di(3-aminopropyl)viologen/ITO surfaces and its application to photoelectrochemical cells

    International Nuclear Information System (INIS)

    Lee, Deok Yeon; Lee, Mi-Sun; Lim, Iseul; Kang, Soon Hyung; Nah, Yoon-Chae; Lee, Wonjoo; Han, Sung-Hwan

    2011-01-01

    Triruthenium carbonyl clusters {[Ru 3 (Br)(CO) 11 ] - (denoted as Ru-1), [Ru 3 (μ 2 -Br)(CO) 10 ] - (denoted as Ru-2), and [Ru 3 (μ 3 -NPh)(Br)(CO) 9 ] - (denoted as Ru-3)} were synthesized on di(3-aminopropyl)viologen (DAPV)/indium tin oxide (ITO) using a surface reaction in a ruthenium (III) carbonyl [Ru 3 (CO) 12 ] solution, and were applied to photoelectrochemical cells (PECs) at the molecular level. The formation of DAPV on ITO was realized in the form of self-assembled monolayers. Ru 3 (CO) 12 then easily reacted with the Br - of DAPV, and a mixture of Ru-1 and Ru-2 was formed on DAPV/ITO. Furthermore, Ru-3 was successfully anchored on DAPV/ITO by adding nitrosobenzene in order to react with Ru-2 on DAPV/ITO. The photocurrents of (Ru-1 and Ru-2)/DAPV/ITO and Ru-3/DAPV/ITO in PECs at the molecular level were 6.3 nA cm -2 and 8.6 nA cm -2 , respectively. The quantum yield of Ru-3/DAPV/ITO was ∼0.8%. Time-resolved photoluminescence spectroscopy and emission spectroscopy were recorded to bring out the photoinduced charge transfer process from ruthenium clusters to DAPV.

  11. TEMPO/viologen electrochemical heterojunction for diffusion-controlled redox mediation: a highly rectifying bilayer-sandwiched device based on cross-reaction at the interface between dissimilar redox polymers.

    Science.gov (United States)

    Tokue, Hiroshi; Oyaizu, Kenichi; Sukegawa, Takashi; Nishide, Hiroyuki

    2014-03-26

    A couple of totally reversible redox-active molecules, which are different in redox potentials, 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) and viologen (V(2+)), were employed to give rise to a rectified redox conduction effect. Single-layer and bilayer devices were fabricated using polymers containing these sites as pendant groups per repeating unit. The devices were obtained by sandwiching the redox polymer layer(s) with indium tin oxide (ITO)/glass and Pt foil electrodes. Electrochemical measurements of the single-layer device composed of polynorbornene-bearing TEMPO (PTNB) exhibited a diffusion-limited current-voltage response based on the TEMPO(+)/TEMPO exchange reaction, which was almost equivalent to a redox gradient through the PTNB layer depending upon the thickness. The bilayer device gave rise to the current rectification because of the thermodynamically favored cross-reaction between TEMPO(+) and V(+) at the polymer/polymer interface. A current-voltage response obtained for the bilayer device demonstrated a two-step diffusion-limited current behavior as a result of the concurrent V(2+)/V(+) and V(+)/V(0) exchange reactions according to the voltage and suggested that the charge transport process through the device was most likely to be rate-determined by a redox gradient in the polymer layer. Current collection experiments revealed a charge transport balance throughout the device, as a result of the electrochemical stability and robustness of the polymers in both redox states.

  12. Forventninger om nye standarder m.v. i 2012-2014

    DEFF Research Database (Denmark)

    Kiertzner, Lars

    2012-01-01

    Denne artikel præsenterer kortfattet IAASB' s igangværende og forventet kommende projekter inden for de næste par år. Emnets relevans er indlysende, idet IAASB er den direkte pipeline til kommende ændringer af standarder m.v. for danske godkendte revisorer. Kilderne til fremstillingen er dels...

  13. The Investigation of Nova-like Variable MV Lyr during the 1999 ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    The Investigation of Nova-like Variable MV Lyr during the 1999–2001. Years. N. A. Katysheva & S. Yu. Shugarov. 1. , E. P. Pavlenko. 2. & P. V. Abolmasov. 3. 1Sternberg Astronomical Institute, Moscow, Russia. 2Crimean Astrophysical Observatory, p. Nauchny, Crimea. 3Physical Department, Moscow State University, ...

  14. Characterization of the Photon Energy Spectrum of a 6 MV Linac

    International Nuclear Information System (INIS)

    Hernandez Bojorquez, M.; Larraga, J. M.; Garcia, A.; Celis, M. A.; Martinez-Davalos, A.; Rodriguez-Villafuerte, M.

    2006-01-01

    In this work we study the influence of the purity of the materials used in experimental transmission measurements to obtain data to reconstruct the photon energy spectrum of a 6 MV Linac. We also evaluate the contribution to PDDs due to electron contamination in the reconstructed spectrum

  15. Changes in forecasting of HV/MV transformer loading due to distributed generation

    NARCIS (Netherlands)

    Berende, M.J.C.; Ruiter, de A.; Morren, J.

    2013-01-01

    This paper describes how Enexis, one of the largest distribution network operators in the Netherlands, has adapted its load forecasting method for HV/MV-transformers to incorporate the influence of distributed generation. This new method involves the making of separate forecasts for demand and

  16. Current distribution in LV networks during 1-phase MV short-circuit

    NARCIS (Netherlands)

    Waes, van J.B.M.; Provoost, F.; Merwe, van der J.; Cobben, J.F.G.; Deursen, van A.P.J.; van Riet, M.J.M.; Laan, van der P.C.T.

    2000-01-01

    This paper describes the consequences of a fault in a medium voltage network on the grounding systems at the LV-side. To study the current distribution and to verify the models, we deliberately introduced one phase to ground faults in the 10 kV floating MV network. The selected site was the end of a

  17. Monitoring programme for the MV2, Part IV : Archeological and palaeontological finds

    NARCIS (Netherlands)

    Borst, W.; Weerts, H.; Vellinga, T.; Otte, A.

    2014-01-01

    This is the fourth and last of a series of articles describing the extensive monitoring related to the construction of Maasvlakte 2, Port of Rotterdam, the Netherlands. As far back as the 1990s during the first studies by the Main Port Rotterdam (PMR) project organisation for Maasvlakte 2 (MV2),

  18. 2 MV injector as the Elise front-end and as an experimental facility

    International Nuclear Information System (INIS)

    Yu, S.S.; Eylon, S.; Henestroza, E.; Peters, C.; Reginato, L.; Tauschwitz, A.; Grote, D.; Deadrick, F.

    1996-01-01

    We report on progress in the preparation of the 2 MV injector at LBNL as the front end of Elise and as a multipurpose experimental facility for heavy ion fusion beam dynamics studies. Recent advances in the performance and understanding of the injector are described, and some of the ongoing experimental activities are summarized. (orig.)

  19. High quality beams of MV/cm THz pulses generated from DSTMS

    DEFF Research Database (Denmark)

    Pedersen, Pernille Klarskov; Jepsen, Peter Uhd

    2015-01-01

    A beam characterization of a THz beam generated from the organic crystal DSTMS is presented. The simple, collinear phase-matching geometry for this crystal results in an M2 factor below 1.5, resulting in a focused field strength of more than 4 MV/cm....

  20. The MV formalism for IBL$_infty$- and BV$_infty$-algebras

    Czech Academy of Sciences Publication Activity Database

    Markl, Martin; Voronov, A.A.

    2017-01-01

    Roč. 107, č. 8 (2017), s. 1515-1543 ISSN 0377-9017 Institutional support: RVO:67985840 Keywords : MV-algebra * IBL$_infty$-algebra * master equation Subject RIV: BA - General Mathematics OBOR OECD: Applied mathematics Impact factor: 1.671, year: 2016 https://link.springer.com/article/10.1007/s11005-017-0954-y

  1. Monitoring of Dips in the MV Network for Regulation- A Case Study

    NARCIS (Netherlands)

    Weldemariam, L.E.; Cuk, V.; Cobben, J.F.G.; Kling, W.L.

    2014-01-01

    Abstract— Voltage dips constitute to a noticeable part of power quality (PQ) problems but causing major financial losses to industrial and commercial customers. This work involves comparative studies to choose the most appropriate location of monitoring dips for regulation. In this paper, a Dutch MV

  2. Transient phenomena analysis of a DC-1 MV power supply for the ITER NBI

    International Nuclear Information System (INIS)

    Yamamoto, Masanori; Watanabe, Kazuhiro; Yamanaka, Haruhiko; Takemoto, Jumpei; Inoue, Takashi; Yamashita, Yasuo

    2010-08-01

    A power supply for the ITER Neutral Beam Injector (NBI) is a DC ultra-high voltage (UHV) power supply to accelerate negative ion beams of 40 A up to an energy of 1 MeV. Japan Atomic Energy Agency as the Japan Domestic Agency for ITER contributes procurement of dc -1 MV main components such as step-up -1 MV transformers rectifiers, a high voltage deck 2, a -1 MV insulating transformer, a transmission line, a surge reduction system and equipments for site test. Design of the surge suppression in the NBI power supply is one of the key issues to obtain the stable injector performance. This report describes the design study using EMTDC code on the surge suppression by optimizing the core snubber and additional elements in the -1 MV power supply. The results show that the input energy from the stray capacitance to the accelerator at the breakdown can be reduced to about 25 J that is smaller than design criteria for ITER. (author)

  3. Influence of the corn resistance gene Mv on the fitness of Peregrinus maidis (Hemiptera: Delphacidae) and on the transmission of maize mosaic virus (Rhabdoviridae: Nucleorhabdovirus).

    Science.gov (United States)

    Higashi, C H V; Brewbaker, J L; Bressan, A

    2013-08-01

    Crops that are resistant to pests and pathogens are cost-effective for the management of pests and diseases. A corn (Zea mays L.) breeding program conducted in Hawaii has identified a source of heritable resistance to maize mosaic virus (MMV) (Rhabdoviridae: Nucleorhabdovirus). This resistance is controlled by the gene Mv, which has been shown to have a codominant action. To date, no studies have examined whether the resistance associated with this gene affects only MMV or whether it also affects the insect vector, the corn planthopper Peregrinus maidis (Ashmead) (Hemiptera: Delphacidae). Here, we examined the life history of the corn planthopper and its ability to transmit MMV on near isogenic lines that were homozygous dominant (Mv/Mv), homozygous recessive (mv/mv), or heterozygous (Mv/mv) for the gene. A field trial was also conducted to study the colonization of the corn plants with different genotypes by the planthopper. Although field observations revealed slightly lower densities ofplanthoppers on corn with the genotype Mv/Mv than on the inbreds with the genotype mv/mv and their hybrids with the genotype Mv/mv, laboratory assays showed no effects of the gene on planthopper development, longevity, or fecundity. In the field, the corn lines Mv/Mv had a lower incidence of MMV-infected plants. However, in the greenhouse, the transmission of MMV to corn seedlings did not differ across the near isogenic lines, although the corn lines Mv/Mv showed a delayed onset of symptoms compared with the corn lines mv/mv and Mv/mv. The acquisition of MMV by corn planthoppers on the corn genotypes Mv/Mv and Mv/mv averaged 0.2, whereas the acquisition on the corn genotypes mv/mv averaged > 0.3. Our results show that the Mv gene does not influence the fitness of the planthopper vector, suggesting that it may confer resistance by other means, possibly by limiting virus replication or movement within the host plant.

  4. Constituent Components of Out-of-Field Scatter Dose for 18-MV Intensity Modulated Radiation Therapy Versus 3-Dimensional Conformal Radiation Therapy: A Comparison With 6-MV and Implications for Carcinogenesis

    International Nuclear Information System (INIS)

    Ruben, Jeremy D.; Smith, Ryan; Lancaster, Craig M.; Haynes, Matthew; Jones, Phillip; Panettieri, Vanessa

    2014-01-01

    Purpose: To characterize and compare the components of out-of-field dose for 18-MV intensity modulated radiation therapy (IMRT) versus 3-dimensional conformal radiation therapy (3D-CRT) and their 6-MV counterparts and consider implications for second cancer induction. Methods and Materials: Comparable plans for each technique/energy were delivered to a water phantom with a sloping wall; under full scatter conditions; with field edge abutting but outside the bath to prevent internal/phantom scatter; and with shielding below the linear accelerator head to attenuate head leakage. Neutron measurements were obtained from published studies. Results: Eighteen-megavolt IMRT produces 1.7 times more out-of-field scatter than 18-MV 3D-CRT. In absolute terms, however, differences are just approximately 0.1% of central axis dose. Eighteen-megavolt IMRT reduces internal/patient scatter by 13%, but collimator scatter (C) is 2.6 times greater than 18-MV 3D-CRT. Head leakage (L) is minimal. Increased out-of-field photon scatter from 18-MV IMRT carries out-of-field second cancer risks of approximately 0.2% over and above the 0.4% from 18-MV 3D-CRT. Greater photoneutron dose from 18-MV IMRT may result in further maximal, absolute increased risk to peripheral tissue of approximately 1.2% over 18-MV 3D-CRT. Out-of-field photon scatter remains comparable for the same modality irrespective of beam energy. Machine scatter (C+L) from 18 versus 6 MV is 1.2 times higher for IMRT and 1.8 times for 3D-CRT. It is 4 times higher for 6-MV IMRT versus 3D-CRT. Reduction in internal scatter with 18 MV versus 6 MV is 27% for 3D-CRT and 29% for IMRT. Compared with 6-MV 3D-CRT, 18-MV IMRT increases out-of-field second cancer risk by 0.2% from photons and adds 0.28-2.2% from neutrons. Conclusions: Out-of-field photon dose seems to be independent of beam energy for both techniques. Eighteen-megavolt IMRT increases out-of-field scatter 1.7-fold over 3D-CRT because of greater collimator scatter despite

  5. Real-time automatic fiducial marker tracking in low contrast cine-MV images

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Wei-Yang; Lin, Shu-Fang; Yang, Sheng-Chang; Liou, Shu-Cheng; Nath, Ravinder; Liu Wu [Department of Computer Science and Information Engineering, National Chung Cheng University, Taiwan, 62102 (China); Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, Connecticut 06510-3220 (United States)

    2013-01-15

    Purpose: To develop a real-time automatic method for tracking implanted radiographic markers in low-contrast cine-MV patient images used in image-guided radiation therapy (IGRT). Methods: Intrafraction motion tracking using radiotherapy beam-line MV images have gained some attention recently in IGRT because no additional imaging dose is introduced. However, MV images have much lower contrast than kV images, therefore a robust and automatic algorithm for marker detection in MV images is a prerequisite. Previous marker detection methods are all based on template matching or its derivatives. Template matching needs to match object shape that changes significantly for different implantation and projection angle. While these methods require a large number of templates to cover various situations, they are often forced to use a smaller number of templates to reduce the computation load because their methods all require exhaustive search in the region of interest. The authors solve this problem by synergetic use of modern but well-tested computer vision and artificial intelligence techniques; specifically the authors detect implanted markers utilizing discriminant analysis for initialization and use mean-shift feature space analysis for sequential tracking. This novel approach avoids exhaustive search by exploiting the temporal correlation between consecutive frames and makes it possible to perform more sophisticated detection at the beginning to improve the accuracy, followed by ultrafast sequential tracking after the initialization. The method was evaluated and validated using 1149 cine-MV images from two prostate IGRT patients and compared with manual marker detection results from six researchers. The average of the manual detection results is considered as the ground truth for comparisons. Results: The average root-mean-square errors of our real-time automatic tracking method from the ground truth are 1.9 and 2.1 pixels for the two patients (0.26 mm/pixel). The

  6. Real-time automatic fiducial marker tracking in low contrast cine-MV images

    International Nuclear Information System (INIS)

    Lin, Wei-Yang; Lin, Shu-Fang; Yang, Sheng-Chang; Liou, Shu-Cheng; Nath, Ravinder; Liu Wu

    2013-01-01

    Purpose: To develop a real-time automatic method for tracking implanted radiographic markers in low-contrast cine-MV patient images used in image-guided radiation therapy (IGRT). Methods: Intrafraction motion tracking using radiotherapy beam-line MV images have gained some attention recently in IGRT because no additional imaging dose is introduced. However, MV images have much lower contrast than kV images, therefore a robust and automatic algorithm for marker detection in MV images is a prerequisite. Previous marker detection methods are all based on template matching or its derivatives. Template matching needs to match object shape that changes significantly for different implantation and projection angle. While these methods require a large number of templates to cover various situations, they are often forced to use a smaller number of templates to reduce the computation load because their methods all require exhaustive search in the region of interest. The authors solve this problem by synergetic use of modern but well-tested computer vision and artificial intelligence techniques; specifically the authors detect implanted markers utilizing discriminant analysis for initialization and use mean-shift feature space analysis for sequential tracking. This novel approach avoids exhaustive search by exploiting the temporal correlation between consecutive frames and makes it possible to perform more sophisticated detection at the beginning to improve the accuracy, followed by ultrafast sequential tracking after the initialization. The method was evaluated and validated using 1149 cine-MV images from two prostate IGRT patients and compared with manual marker detection results from six researchers. The average of the manual detection results is considered as the ground truth for comparisons. Results: The average root-mean-square errors of our real-time automatic tracking method from the ground truth are 1.9 and 2.1 pixels for the two patients (0.26 mm/pixel). The

  7. Methylation in hepatocellular carcinoma

    Directory of Open Access Journals (Sweden)

    Regina M. Santella

    2007-02-01

    Full Text Available

    The development of HCC is a complex, multistep, multistage process. The molecular pathogenesis of HCC appears to involve multiple genetic aberrations in the molecular control of hepatocyte proliferation, differentiation and death and the maintenance of genomic integrity. This process is influenced by the cumulative activation and inactivation of oncogenes, tumor suppressor genes and other genes. p53, a tumor suppressor gene, is the most frequently mutated gene in human cancers. There is also a striking sequence specific binding and induction of mutations by AFB1 at codon 249 of p53 in HCC.

    Epigenetic alterations are also involved in cancer development and progression. Methylation of promoter CpG islands is associated with inhibition of transcriptional initiation and permanent silencing of downstream genes.

    It is now known that most important tumor suppressor genes are inactivated, not only by mutations and deletions but also by promoter methylation. Several studies indicated that p16, p15, RASSF1A, MGMT, and GSTP1 promoter hypermethylation are prevalent in HCC. In addition, geographic variation in the methylation status of tumor DNA indicates that environmental factors may influence the frequent and concordant degree of hypermethylation in multiple genes in HCC and that epigeneticenvironmental interactions may be involved in hepatocarcinogenesis. We have found significant relationships between promoter methylation and AFB1-DNA adducts confirming the impact of environmental exposures on gene methylation.

    DNA isolated from serum or plasma of cancer patients frequently contains the same genetic and

  8. Analysis of the electrochemistry of hemes with Ems spanning 800 mV

    Science.gov (United States)

    Zheng, Zhong; Gunner, M. R.

    2009-01-01

    The free energy of heme reduction in different proteins is found to vary over more than 18 kcal/mol. It is a challenge to determine how proteins manage to achieve this enormous range of Ems with a single type of redox cofactor. Proteins containing 141 unique hemes of a-, b-, and c-type, with bis-His, His-Met, and aquo-His ligation were calculated using Multi-Conformation Continuum Electrostatics (MCCE). The experimental Ems range over 800 mV from −350 mV in cytochrome c3 to 450 mV in cytochrome c peroxidase (vs. SHE). The quantitative analysis of the factors that modulate heme electrochemistry includes the interactions of the heme with its ligands, the solvent, the protein backbone, and sidechains. MCCE calculated Ems are in good agreement with measured values. Using no free parameters the slope of the line comparing calculated and experimental Ems is 0.73 (R2 = 0.90), showing the method accounts for 73% of the observed Em range. Adding a +160 mV correction to the His-Met c-type hemes yields a slope of 0.97 (R2 = 0.93). With the correction 65% of the hemes have an absolute error smaller than 60 mV and 92% are within 120 mV. The overview of heme proteins with known structures and Ems shows both the lowest and highest potential hemes are c-type, whereas the b-type hemes are found in the middle Em range. In solution, bis-His ligation lowers the Em by ≈205 mV relative to hemes with His-Met ligands. The bis-His, aquo-His, and His-Met ligated b-type hemes all cluster about Ems which are ≈200 mV more positive in protein than in water. In contrast, the low potential bis-His c-type hemes are shifted little from in solution, whereas the high potential His-Met c-type hemes are raised by ≈300 mV from solution. The analysis shows that no single type of interaction can be identified as the most important in setting heme electrochemistry in proteins. For example, the loss of solvation (reaction field) energy, which raises the Em, has been suggested to be a major factor in

  9. 75 FR 44720 - Safety Zone; Live-Fire Gun Exercise, M/V Del Monte, James River, VA

    Science.gov (United States)

    2010-07-29

    ... DEPARTMENT OF HOMELAND SECURITY Coast Guard 33 CFR Part 165 [Docket No. USCG-2010-0585] RIN 1625-AA00 Safety Zone; Live-Fire Gun Exercise, M/V Del Monte, James River, VA AGENCY: Coast Guard, DHS... follows: Sec. 165.T05-0585 Safety Zone; Live-Fire Gun Exercise, M/V Del Monte, James River, VA (a...

  10. DNA methylation and memory formation.

    Science.gov (United States)

    Day, Jeremy J; Sweatt, J David

    2010-11-01

    Memory formation and storage require long-lasting changes in memory-related neuronal circuits. Recent evidence indicates that DNA methylation may serve as a contributing mechanism in memory formation and storage. These emerging findings suggest a role for an epigenetic mechanism in learning and long-term memory maintenance and raise apparent conundrums and questions. For example, it is unclear how DNA methylation might be reversed during the formation of a memory, how changes in DNA methylation alter neuronal function to promote memory formation, and how DNA methylation patterns differ between neuronal structures to enable both consolidation and storage of memories. Here we evaluate the existing evidence supporting a role for DNA methylation in memory, discuss how DNA methylation may affect genetic and neuronal function to contribute to behavior, propose several future directions for the emerging subfield of neuroepigenetics, and begin to address some of the broader implications of this work.

  11. Dosimetric Comparison of 6 MV and 15 MV Single Arc Rapidarc to Helical TomoTherapy for the Treatment of Pancreatic Cancer

    International Nuclear Information System (INIS)

    Cai Jing; Yue Jinbo; McLawhorn, Robert; Yang Wensha; Wijesooriya, Krishni; Dunlap, Neal E.; Sheng Ke; Yin Fangfang; Benedict, Stanley H.

    2011-01-01

    We conducted a planning study to compare Varian's RapidArc (RA) and helical TomoTherapy (HT) for the treatment of pancreatic cancer. Three intensity-modulated radiotherapy (IMRT) plans were generated for 8 patients with pancreatic cancer: one using HT with 6-MV beam (Plan HT6 ), one using single-arc RA with 6-MV beam (Plan RA6 ), and one using single-arc RA with 15-MV beam (Plan RA15 ). Dosimetric indices including high/low conformality index (CI 100% /CI 50% ), heterogeneity index (HI), monitor units (MUs), and doses to organs at risk (OARs) were compared. The mean CI 100% was statistically equivalent with respect to the 2 treatment techniques, as well as beam energy (0.99, 1.01, and 1.02 for Plan HT6 , Plan RA6 , and Plan RA156, respectively). The CI 50% and HI were improved in both RA plans over the HT plan. The RA plans significantly reduced MU (MU RA6 = 697, MU RA15 = 548) compared with HT (MU HT6 = 6177, p = 0.008 in both cases). The mean maximum cord dose was decreased from 29.6 Gy in Plan H T6 to 21.6 Gy (p = 0.05) in Plan RA6 and 21.7 Gy (p = 0.04) in Plan RA15 . The mean bowel dose decreased from 17.2 Gy in Plan HT6 to 15.2 Gy (p = 0.03) in Plan RA6 and 15.0 Gy (p = 0.03) Plan RA15 . The mean liver dose decreased from 8.4 Gy in Plan HT6 to 6.3 Gy (p = 0.04) in Plan RA6 and 6.2 Gy in Plan RA15 . Variations of the mean dose to the duodenum, kidneys, and stomach were statistically insignificant. RA and HT can both deliver conformal dose distributions to target volumes while limiting the dose to surrounding OARs in the treatment of pancreatic cancer. Dosimetric advantages might be gained by using RA over HT by reducing the dose to OARs and total MUs used for treatment.

  12. Voltage regulation and power losses reduction in a wind farm integrated MV distribution network

    Science.gov (United States)

    Fandi, Ghaeth; Igbinovia, Famous Omar; Tlusty, Josef; Mahmoud, Rateb

    2018-01-01

    A medium-voltage (MV) wind production system is proposed in this paper. The system applies a medium-voltage permanent magnet synchronous generator (PMSG) as well as MV interconnection and distribution networks. The simulation scheme of an existing commercial electric-power system (Case A) and a proposed wind farm with a gearless PMSG insulated gate bipolar transistor (IGBT) power electronics converter scheme (Case B) is compared. The analyses carried out in MATLAB/Simulink environment shows an enhanced voltage profile and reduced power losses, thus, efficiency in installed IGBT power electronics devices in the wind farm. The resulting wind energy transformation scheme is a simple and controllable medium voltage application since it is not restrained by the IGBT power electronics voltage source converter (VSC) arrangement. Active and reactive power control is made possible with the aid of the gearless PMSG IGBT power converters.

  13. Impact ionization dynamics in silicon by MV/cm THz fields

    DEFF Research Database (Denmark)

    Tarekegne, Abebe Tilahun; Hirori, Hideki; Tanaka, Koichiro

    2017-01-01

    We investigate the dynamics of the impact ionization (IMI) process in silicon in extremely high fields in the MV/cm range and at low initial carrier concentrations; conditions that are not accessible with conventional transport measurements. We use ultrafast measurements with high-intensity terah......We investigate the dynamics of the impact ionization (IMI) process in silicon in extremely high fields in the MV/cm range and at low initial carrier concentrations; conditions that are not accessible with conventional transport measurements. We use ultrafast measurements with high......-intensity terahertz pulses to show that IMI is significantly more efficient at lower than at higher initial carrier densities. Specifically, in the case of silicon with an intrinsic carrier concentration (∼1010 cm−3), the carrier multiplication process can generate more than 108 electrons from just a single free...

  14. Fabrication Technologies of the High Gradient Accelerator Structures at 100MV/m Range

    CERN Document Server

    Wang, Juwen; Van Pelt, John; Yoneda, Charles; Gudkov, D; Riddone, Germana; Higo, Toshiyasu; Takatomi, Toshikazu

    2010-01-01

    A CERN-SLAC-KEK collaboration on high gradient X-band structure research has been established in order to demonstrate the feasibility of the CLIC baseline design for the main linac stably operating at more than 100 MV/m loaded accelerating gradient. Several prototype CLIC structures were successfully fabricated and high power tested. They operated at 105 MV/m with a breakdown rate that meets the CLIC linear collider specifications of <5×10-7/pulse/m. This paper summarizes the fabrication technologies including the mechanical design, precision machining, chemical cleaning, diffusion bonding as well as vacuum baking and all related assembly technologies. Also, the tolerances control, tuning and RF characterization will be discussed

  15. Extension of the Commonwealth standard of absorbed dose from cobalt-60 energy to 25 MV

    International Nuclear Information System (INIS)

    Sherlock, S.L.

    1986-01-01

    With the introduction of high energy linear accelerators in hospitals, there is a need for direct measurement of absorbed dose for energies to 25 MV for photons and 20 MeV electrons. The present Australian standard for absorbed dose at cobalt-60 energy is a graphite micro-calorimeter maintained at the AAEC Lucas Heights Research Laboratories. A thorough theoretical analysis of calorimeter operation suggests that computer control and monitoring techniques are appropriate. Solution of Newton's law of cooling for a four-body calorimeter allows development of a computer simulation model. Different temperature control algorithms may then be run and assessed using this model. In particular, the application of a simple differencer is examined. Successful implementation of the calorimeter for energies up to 25 MV could lead to the introduction of an Australian absorbed dose protocol based on calorimetry, therby reducing the uncertainties associated with exposure-based protocols

  16. Rod-pinch diode operation at 2 to 4 MV for high resolution pulsed radiography

    International Nuclear Information System (INIS)

    Young, F.C.; Commisso, R.J.; Allen, R.J.; Mosher, D.; Swanekamp, S.B.; Cooperstein, G.; Bayol, F.; Charre, P.; Garrigues, A.; Gonzales, C.; Pompier, F.; Vezinet, R.

    2002-01-01

    The rod-pinch diode is operated successfully at peak voltages of 2.4-4.4 MV for peak electrical currents of 55-135 kA delivered to the diode. At 4 MV, tungsten anode rods of 1 or 2 mm diam produce on-axis doses at 1 m of 16 rad(Si) or 20 rad(Si), respectively. The on-axis source diameter based on the full width at half-maximum (FWHM) of the line-spread function (LSF) is 0.9±0.1 mm for a 1 mm diam rod and 1.4±0.1 mm for a 2 mm diam rod, independent of voltage. The LANL source diameter, determined from the modulation transfer function of the LSF, is nearly twice the FWHM. The measured rod-pinch current is reproduced with a diode model that includes ions and accounts for anode and cathode plasma expansion

  17. A 320 mV, 6 kb subthreshold 10T SRAM employing voltage lowering techniques

    International Nuclear Information System (INIS)

    Cai Jiangzheng; Zhang Sumin; Yuan Jia; Shang Xinchao; Chen Liming; Hei Yong

    2015-01-01

    This paper presents a 6 kb SRAM that uses a novel 10T cell to achieve a minimum operating voltage of 320 mV in a 130 nm CMOS process. A number of low power circuit techniques are included to enable the proposed SRAM to operate in the subthreshold region. The reverse short channel effect and the reverse narrow channel effect are utilized to improve the performance of the SRAM. A novel subthreshold pulse generation circuit produces an ideal pulse to make read operation stable. A floating write bit-line effectively reduces the standby leakage consumption. Finally, a short read bit-line makes the read operation fast and energy-saving. Measurements indicate that these techniques are effective, the SRAM can operate at 800 kHz and consume 1.94 μW at its lowest voltage (320 mV). (paper)

  18. Transport of dc and bunched beams through a 25 MV folded tandem accelerator

    International Nuclear Information System (INIS)

    Milner, W.T.; Alton, G.D.; Hensley, D.C.; Jones, C.M.; King, R.F.; Larson, J.D.; Moak, C.D.; Sayer, R.O.

    1975-01-01

    Studies of beam transport through the planned ORNL 25 MV folded tandem accelerator demonstrate efficient utilization of phase-space acceptance and the feasibility of injecting bunched beams from the tandem accelerator into the Oak Ridge Isochronous Cyclotron (ORIC). Use of a 180 0 bending magnet in the terminal provides outstanding charge state selection and permits better control of the high-energy beam transport than has previously been possible in conventional tandem accelerators. Time spreads introduced in bunched beams by the 180 0 magnet are kept within a 6 0 RF acceptance window at ORIC provided the beam has a crossover in the center of the 180 0 magnet. Ion masses from 12 to 240 amu, preinjection energies from 150 to 500 keV and terminal voltages from 7.5 to 25 MV were studied for dc beams and beams bunched by various modulation techniques. (U.S.)

  19. Shot reproducibility of the self-magnetic-pinch diode at 4.5 MV

    OpenAIRE

    Nichelle Bennett; M. Dale Crain; Darryl W. Droemer; Raymond E. Gignac; Greg Lare; Isidro Molina; Robert Obregon; Chase C. Smith; Frank L. Wilkins; Dale R. Welch; Steve Cordova; Manuel L. Gallegos; Mark D. Johnston; Mark L. Kiefer; Joshua J. Leckbee

    2014-01-01

    In experiments conducted at Sandia National Laboratories’ RITS-6 accelerator, the self-magnetic-pinch diode exhibits significant shot-to-shot variability. Specifically, for identical hardware operated at the same voltage, some shots exhibit a catastrophic drop in diode impedance. A study is underway to identify sources of shot-to-shot variations which correlate with diode impedance collapse. The scope of this report is limited to data collected at 4.5-MV peak voltage and sources of variabilit...

  20. The erect of earth fault protection practices on the frequency of outages in MV lines

    Energy Technology Data Exchange (ETDEWEB)

    Lakervi, E.; Nikander, A. [Tampere Univ. of Technology (Finland)

    1996-12-31

    In this presentation different methods to improve extinction of the earth fault arc in the medium voltage network and reducing the short interruptions to customers are discussed. First the disadvantages of the rapid autoreclosing functions to customers are studied. Then the influence of the star point impedance to the number of short interruptions is discussed. Finally, the feasibility of utilizing shunt circuit-breakers in the Finnish MV networks to extinguish the arc, is studied

  1. Radiation-Induced Bystander Effects in A549 Cells Exposed to 6 MV X-rays.

    Science.gov (United States)

    Yang, Shuning; Xu, Jing; Shao, Weixian; Geng, Chong; Li, Jia; Guo, Feng; Miao, Hui; Shen, Wenbin; Ye, Tao; Liu, Yazhou; Xu, Haiting; Zhang, Xuguang

    2015-07-01

    The aim of the study is to explore the bystander effects in A549 cells that have been exposed to 6MV X-ray. Control group, irradiated group, irradiated conditioned medium (ICM)-received group, and fresh medium group were designed in this study. A549 cells in the logarithmic growth phase were irradiated with 6MV X-ray at 0, 0.5, 1, 1.5, and 2. In ICM-received group, post-irradiation A549 cells were cultured for 3 h and were transferred into non-irradiated A549 cells for further cultivation. Clone forming test was applied to detect the survival fraction of cells. Annexin V-FITC/PI double-staining assay was used to detect the apoptosis of A549 cells 24, 48, 72, and 96 h after 2-Gy 6MV X-ray irradiation, and the curves of apoptosis were drawn. The changes in the cell cycles 4, 48, 72, and 96 h after 2-Gy 6MV X-ray irradiation were detected using PI staining flow cytometry. With the increase of irradiation dose, the survival fraction of A549 cells after the application of 0.5 Gy irradiation was decreasing continuously. In comparison to the control group, the apoptosis rate of the ICM-received group was increased in a time-dependent pattern, with the highest apoptosis rate observed at 72 h (p X-ray irradiation can induce bystander effect on A549 cells, which reaches a peak at 72 h.

  2. Relative dosimetry of photon beam of 6 MV with a liquid ionization chamber

    International Nuclear Information System (INIS)

    Benitez Villegas, E. M.; Casado Villalon, F. J.; Martin-Cueto, J. A.; Caudepon Moreno, F.; Garcia Pareja, S.; Galan Montenegro, P.

    2011-01-01

    The increasing use of reduced size fields in the special techniques of treatment generates regions with high dose gradients. It therefore requires the use of detectors that present high spatial resolution. The aim of this study is to compare the dosimetric measurements obtained with a liquid ionization chamber PTW MicroLion recently acquired with other commonly used detectors for a photon beam of 6 MV linear electron accelerator Varian 600DBX.

  3. Improved field abutment-wedge design for 6-MV x-rays

    International Nuclear Information System (INIS)

    Nyerick, C.E.; Steadham, R.E.

    1989-01-01

    This paper presents an improved abutment wedge for matching large photon fields. The wedge is used with a 6-MV Linac accelerator and generates a 5-cm pseudopenumbra at the 50% relative dose juncture. The features allow treatment of fields up to 40 cm long in any fractional step of increment, simultaneous generation of two wide penumbrae or one wide and one sharp penumbra, and attachment of the device downstream of standard beam-shaping accessories in any 90 degrees angular orientation

  4. A 2 MV heavy ion Van de Graaff implanter for research and development

    International Nuclear Information System (INIS)

    Hemment, P.L.F.; Sealy, B.J.; Stephens, K.G.; Mynard, J.E.; Jeynes, C.; Browton, M.D.; Wilson, R.J.; Ma, M.X.; Cansell, A.; Mous, D.J.W.; Koudijs, R.

    1993-01-01

    A high energy heavy ion implantation system is described which is based upon a 2 MV High Voltage Engineering Europa Van de Graaff accelerator, which incorporates an ion source rapid exchange mechanism. The design and performance are described with particular reference to the system mass resolution, beam transport and performance of a sputter ion source. The system is used to provide a wide ranging implantation service and also supports material science studies, some of which are described briefly. (orig.)

  5. Definition of MV Load Diagrams via Weighted Evidence Accumulation Clustering using Subsampling

    OpenAIRE

    Duarte, Jorge; Fred, Ana; Rodrigues, Fátima; Duarte, João; Ramos, Sérgio; Vale, Zita

    2007-01-01

    A definition of medium voltage (MV) load diagrams was made, based on the data base knowledge discovery process. Clustering techniques were used as support for the agents of the electric power retail markets to obtain specific knowledge of their customers’ consumption habits. Each customer class resulting from the clustering operation is represented by its load diagram. The Two-step clustering algorithm and the WEACS approach based on evidence accumulation (EAC) were applied to an electricity ...

  6. From carbon to actinides: A new universal 1MV accelerator mass spectrometer at ANSTO

    Energy Technology Data Exchange (ETDEWEB)

    Wilcken, K.M., E-mail: klaus.wilcken@ansto.gov.au [Australian Nuclear Science & Technology Organisation, Sydney, New South Wales (Australia); Hotchkis, M.; Levchenko, V.; Fink, D. [Australian Nuclear Science & Technology Organisation, Sydney, New South Wales (Australia); Hauser, T.; Kitchen, R. [National Electrostatics Corporation, 7540 Graber Road, Middleton, WI 53562-0310 (United States)

    2015-10-15

    A new 1 MV NEC pelletron AMS system at ANSTO is presented. The spectrometer comprises large radius magnets for actinide measurements. A novel feature of the system is fast switching between isotopes both at low and high energy sections allowing measurements of up to 8 isotopes within a single sequence. Technical details and layout of the spectrometer is presented. Performance data for {sup 14}C, {sup 10}Be, {sup 26}Al and actinides demonstrate the system is ready for routine AMS measurements.

  7. Status of the 15 UD MV Pelletron accelerator at Nuclear Science Centre

    International Nuclear Information System (INIS)

    Chopra, S.

    1997-01-01

    Nuclear Science Centre has 15 UD Pelletron accelerator. This accelerator is equipped with compressed geometry tubes to go up to terminal potential of 16 MV. The 15 UD accelerator has been operational more than five years and in these years there had been certain upgradations and different problems occurred during operation of the accelerator and maintenance of column, rotating shafts, charging system and other associated systems. (author). 2 refs

  8. From carbon to actinides: A new universal 1MV accelerator mass spectrometer at ANSTO

    Science.gov (United States)

    Wilcken, K. M.; Hotchkis, M.; Levchenko, V.; Fink, D.; Hauser, T.; Kitchen, R.

    2015-10-01

    A new 1 MV NEC pelletron AMS system at ANSTO is presented. The spectrometer comprises large radius magnets for actinide measurements. A novel feature of the system is fast switching between isotopes both at low and high energy sections allowing measurements of up to 8 isotopes within a single sequence. Technical details and layout of the spectrometer is presented. Performance data for 14C, 10Be, 26Al and actinides demonstrate the system is ready for routine AMS measurements.

  9. Structural Shielding Design of a 6 MV Flattening Filter Free Linear Accelerator: Indian Scenario

    OpenAIRE

    Mishra, Bibekananda; Selvam, T. Palani; Sharma, P. K. Dash

    2017-01-01

    Detailed structural shielding of primary and secondary barriers for a 6 MV medical linear accelerator (LINAC) operated with flattening filter (FF) and flattening filter free (FFF) modes are calculated. The calculations have been carried out by two methods, one using the approach given in National Council on Radiation Protection (NCRP) Report No. 151 and the other based on the monitor units (MUs) delivered in clinical practice. Radiation survey of the installations was also carried out. NCRP a...

  10. Simulation Of Substation HV/MV In DIGSILENT Power Factory Software

    International Nuclear Information System (INIS)

    Mladenovski, Ljubisha; Dimova, Iskra; Iliev, Atanas; Fushtikj, Vangel

    2003-01-01

    This paper presents a method for creating a model for substation high voltage/middle voltage (HV/MV) that supplies consumers at middle voltage side and capacitor battery that regulates the voltage at the middle voltage busbar. The results from the analyses are presented and discussed. The models of the transformer and the capacitor battery were made at the University of Rostock, Germany, in DYSIMAC (DYnaniic SImulation of the MACedonian power plants in a new technological and market environment) project. (Author)

  11. The erect of earth fault protection practices on the frequency of outages in MV lines

    Energy Technology Data Exchange (ETDEWEB)

    Lakervi, E; Nikander, A [Tampere Univ. of Technology (Finland)

    1997-12-31

    In this presentation different methods to improve extinction of the earth fault arc in the medium voltage network and reducing the short interruptions to customers are discussed. First the disadvantages of the rapid autoreclosing functions to customers are studied. Then the influence of the star point impedance to the number of short interruptions is discussed. Finally, the feasibility of utilizing shunt circuit-breakers in the Finnish MV networks to extinguish the arc, is studied

  12. Whole-genome methylation caller designed for methyl- DNA ...

    African Journals Online (AJOL)

    etchie

    2013-02-20

    Feb 20, 2013 ... Key words: Methyl-DNA immunoprecipitation, next-generation sequencing, Hidden ... its response to environmental cues. .... have a great potential to become the most cost-effective ... hg18 reference genome (set to 0 if not present in retrieved reads). ..... DNA methylation patterns and epigenetic memory.

  13. The new 6 MV multi-nuclide AMS facility at the University of Tsukuba

    International Nuclear Information System (INIS)

    Sasa, Kimikazu; Takahashi, Tsutomu; Matsumura, Masumi; Matsunaka, Tetsuya; Satou, Yukihiko; Izumi, Daiki; Sueki, Keisuke

    2015-01-01

    The former accelerator mass spectrometry (AMS) system installed on the 12UD Pelletron tandem accelerator at the University of Tsukuba was completely destroyed by the Great East Japan Earthquake on 11 March 2011. A replacement has been designed and constructed at the university as part of the post-quake reconstruction project. It consists of a 6 MV Pelletron tandem accelerator, two multiple cathode AMS ion sources (MC-SNICSs), and a rare-particle detection system. The 6 MV Pelletron tandem accelerator will be applied not only to AMS, but also to areas such as nanotechnology, ion beam analysis, heavy ion irradiation, and nuclear physics. The rare-particle detection system will be capable of measuring environmental levels of long-lived radioisotopes of "1"0Be, "1"4C, "2"6Al, "3"6Cl, "4"1Ca, and "1"2"9I. It is also expected to measure other radioisotopes such as "3"2Si and "9"0Sr. The 6 MV Pelletron tandem accelerator was installed in the spring of 2014 at the University of Tsukuba. Routine beam delivery and AMS experiments will start in 2015.

  14. Poisson simulation for high voltage terminal of test stand for 1MV electrostatic accelerator

    International Nuclear Information System (INIS)

    Park, Sae-Hoon; Kim, Jeong-Tae; Kwon, Hyeok-Jung; Cho, Yong-Sub; Kim, Yu-Seok

    2014-01-01

    KOMAC provide ion beam to user which energy range need to expand to MeV range and develop 1 MV electrostatic accelerator. The specifications of the electrostatic accelerator are 1MV acceleration voltage, 10 mA peak current and variable gas ion. We are developing test stand before set up 1 MV electrostatic accelerator. The test stand voltage is 300 kV and operating time is 8 hours. The test stand is consist of 300 kV high voltage terminal, DC-AC-DC inverter, power supply device inside terminal, 200MHz RF power, 5 kV extraction power supply, 300 kV accelerating tube and vacuum system.. The beam measurement system and beam dump will be installed next to accelerating tube. Poisson code simulation results of the high voltage terminal are presented in this paper. Poisson code has been used to calculate the electric field for high voltage terminal. The results of simulation were verified with reasonable results. The poisson code structure could be apply to the high voltage terminal of the test stand

  15. The new 6 MV multi-nuclide AMS facility at the University of Tsukuba

    Energy Technology Data Exchange (ETDEWEB)

    Sasa, Kimikazu, E-mail: ksasa@tac.tsukuba.ac.jp; Takahashi, Tsutomu; Matsumura, Masumi; Matsunaka, Tetsuya; Satou, Yukihiko; Izumi, Daiki; Sueki, Keisuke

    2015-10-15

    The former accelerator mass spectrometry (AMS) system installed on the 12UD Pelletron tandem accelerator at the University of Tsukuba was completely destroyed by the Great East Japan Earthquake on 11 March 2011. A replacement has been designed and constructed at the university as part of the post-quake reconstruction project. It consists of a 6 MV Pelletron tandem accelerator, two multiple cathode AMS ion sources (MC-SNICSs), and a rare-particle detection system. The 6 MV Pelletron tandem accelerator will be applied not only to AMS, but also to areas such as nanotechnology, ion beam analysis, heavy ion irradiation, and nuclear physics. The rare-particle detection system will be capable of measuring environmental levels of long-lived radioisotopes of {sup 10}Be, {sup 14}C, {sup 26}Al, {sup 36}Cl, {sup 41}Ca, and {sup 129}I. It is also expected to measure other radioisotopes such as {sup 32}Si and {sup 90}Sr. The 6 MV Pelletron tandem accelerator was installed in the spring of 2014 at the University of Tsukuba. Routine beam delivery and AMS experiments will start in 2015.

  16. The new 6 MV multi-nuclide AMS facility at the University of Tsukuba

    Science.gov (United States)

    Sasa, Kimikazu; Takahashi, Tsutomu; Matsumura, Masumi; Matsunaka, Tetsuya; Satou, Yukihiko; Izumi, Daiki; Sueki, Keisuke

    2015-10-01

    The former accelerator mass spectrometry (AMS) system installed on the 12UD Pelletron tandem accelerator at the University of Tsukuba was completely destroyed by the Great East Japan Earthquake on 11 March 2011. A replacement has been designed and constructed at the university as part of the post-quake reconstruction project. It consists of a 6 MV Pelletron tandem accelerator, two multiple cathode AMS ion sources (MC-SNICSs), and a rare-particle detection system. The 6 MV Pelletron tandem accelerator will be applied not only to AMS, but also to areas such as nanotechnology, ion beam analysis, heavy ion irradiation, and nuclear physics. The rare-particle detection system will be capable of measuring environmental levels of long-lived radioisotopes of 10Be, 14C, 26Al, 36Cl, 41Ca, and 129I. It is also expected to measure other radioisotopes such as 32Si and 90Sr. The 6 MV Pelletron tandem accelerator was installed in the spring of 2014 at the University of Tsukuba. Routine beam delivery and AMS experiments will start in 2015.

  17. Poisson simulation for high voltage terminal of test stand for 1MV electrostatic accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sae-Hoon; Kim, Jeong-Tae; Kwon, Hyeok-Jung; Cho, Yong-Sub [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Kim, Yu-Seok [Dongguk Univ.., Gyeongju (Korea, Republic of)

    2014-10-15

    KOMAC provide ion beam to user which energy range need to expand to MeV range and develop 1 MV electrostatic accelerator. The specifications of the electrostatic accelerator are 1MV acceleration voltage, 10 mA peak current and variable gas ion. We are developing test stand before set up 1 MV electrostatic accelerator. The test stand voltage is 300 kV and operating time is 8 hours. The test stand is consist of 300 kV high voltage terminal, DC-AC-DC inverter, power supply device inside terminal, 200MHz RF power, 5 kV extraction power supply, 300 kV accelerating tube and vacuum system.. The beam measurement system and beam dump will be installed next to accelerating tube. Poisson code simulation results of the high voltage terminal are presented in this paper. Poisson code has been used to calculate the electric field for high voltage terminal. The results of simulation were verified with reasonable results. The poisson code structure could be apply to the high voltage terminal of the test stand.

  18. Characterization of Ge-doped optical fibres for MV radiotherapy dosimetry

    International Nuclear Information System (INIS)

    Noor, Noramaliza M.; Hussein, M.; Kadni, T.; Bradley, D.A.; Nisbet, A.

    2014-01-01

    Ge-doped optical fibres offer promising thermoluminescence (TL) properties together with small physical size and modest cost. Their use as dosimeters for postal radiotherapy dose audits of megavoltage photon beams has been investigated. Key dosimetric characteristics including reproducibility, linearity, dose rate, temperature and angular dependence have been established. A methodology of measuring absorbed dose under reference conditions was developed. The Ge-doped optical fibres offer linearity between TL yield and dose, with a reproducibility of better than 5%, following repeated measurements (n=5) for doses from 5 cGy to 1000 cGy. The fibres also offer dose rate, angular and temperature independence, while an energy-dependent response of 7% was found over the energy range 6 MV to 15 MV (TPR 20,10 of 0.660, 0.723 and 0.774 for 6, 10 and 15 MV respectively). The audit methodology has been developed with an expanded uncertainty of 4.22% at 95% confidence interval for the photon beams studied. - Highlights: • We investigate dosimetric characteristics of commercial Ge-doped optical fibres. • We develop audit methodology for measuring absorbed dose under reference conditions. • Ge-doped optical fibres offer promising thermoluminescence (TL) properties. • Audit methodology has been developed with an expanded uncertainty of 4.22%

  19. Ambient neutron dose equivalent outside concrete vault rooms for 15 and 18 MV radiotherapy accelerators

    International Nuclear Information System (INIS)

    Martinez-ovalle, S. A.; Barquero, R.; Gomez-ros, J. M.; Lallena, A. M.

    2012-01-01

    In this work, the ambient dose equivalent, H*(10), due to neutrons outside three bunkers that house a 15- and a 18-MV Varian Clinac 2100C/D and a 15-MV Elekta Inor clinical linacs, has been calculated. The Monte Carlo code MCNPX (v. 2.5) has been used to simulate the neutron production and transport. The complete geometries including linacs and full installations have been built up according to the specifications of the manufacturers and the planes provided by the corresponding medical physical services of the hospitals where the three linacs operate. Two of these installations, those lodging the Varian linacs, have an entrance door to the bunker while the other one does not, although it has a maze with two bends. Various treatment orientations were simulated in order to establish plausible annual equivalent doses. Specifically anterior-posterior, posterior-anterior, left lateral, right lateral orientations and an additional one with the gantry rotated 30 deg. have been studied. Significant dose rates have been found only behind the walls and the door of the bunker, near the entrance and the console, with a maximum of 12 μSv h -1 . Dose rates per year have been calculated assuming a conservative workload for the three facilities. The higher dose rates in the corresponding control areas were 799 μSv y -1 , in the case of the facility which operates the 15-MV Clinac, 159 μSv y -1 , for that with the 15-MV Elekta, and 21 μSv y -1 for the facility housing the 18-MV Varian. A comparison with measurements performed in similar installations has been carried out and a reasonable agreement has been found. The results obtained indicate that the neutron contamination does not increase the doses above the legal limits and does not produce a significant enhancement of the dose equivalent calculated. When doses are below the detection limits provided by the measuring devices available today, MCNPX simulation provides an useful method to evaluate neutron dose equivalents

  20. Phytoextraction potential of water fern (Azolla pinnata) in the removal of a hazardous dye, methyl violet 2B: Artificial neural network modelling.

    Science.gov (United States)

    Kooh, Muhammad Raziq Rahimi; Lim, Linda B L; Lim, Lee-Hoon; Malik, Owais Ahmed

    2018-04-16

    This study investigated the potential of Azolla pinnata (AP) in the removal of toxic methyl violet 2B (MV) dye wastewater using the phytoextraction approach with the inclusion of an Artificial Neural Network (ANN) modelling. Parameters examined included the effects of dye concentration, pH and plant dosage. The highest removal efficiency was 93% which was achieved at a plant dosage of 0.8 g (dye volume = 200 mL, initial pH = 6.0, initial dye concentration = 10 mg L -1 ). A significant decrease in relative frond number (RFN), a growth rate estimator, observed at a dye concentration of 20 mg L -1 MV indicated some toxicity, which coincided with the plant pigments studies where the chlorophyll a content was lower than the control. There were little differences in the plant pigment contents between the control and those in the presence of dye (5 to 15 mg L -1 ) indicating the tolerance of AP to MV at lower concentrations. A three-layer ANN model was optimized (6 neurons in the hidden layer) and successfully predicted the phytoextraction of MV (R = 0.9989, RMSE = 0.0098). In conclusion, AP proved to be a suitable plant that could be used for the phytoextraction of MV while the ANN modelling has shown to be a reliable method for the modelling of phytoextraction of MV using AP.

  1. Accuracy of automated measurement and verification (M&V) techniques for energy savings in commercial buildings

    International Nuclear Information System (INIS)

    Granderson, Jessica; Touzani, Samir; Custodio, Claudine; Sohn, Michael D.; Jump, David; Fernandes, Samuel

    2016-01-01

    Highlights: • A testing procedure and metrics to asses the performance of whole-building M&V methods is presented. • The accuracy of ten baseline models is evaluated on measured data from 537 commercial buildings. • The impact of reducing the training period from 12-months to shorter time horizon is examined. - Abstract: Trustworthy savings calculations are critical to convincing investors in energy efficiency projects of the benefit and cost-effectiveness of such investments and their ability to replace or defer supply-side capital investments. However, today’s methods for measurement and verification (M&V) of energy savings constitute a significant portion of the total costs of efficiency projects. They also require time-consuming manual data acquisition and often do not deliver results until years after the program period has ended. The rising availability of “smart” meters, combined with new analytical approaches to quantifying savings, has opened the door to conducting M&V more quickly and at lower cost, with comparable or improved accuracy. These meter- and software-based approaches, increasingly referred to as “M&V 2.0”, are the subject of surging industry interest, particularly in the context of utility energy efficiency programs. Program administrators, evaluators, and regulators are asking how M&V 2.0 compares with more traditional methods, how proprietary software can be transparently performance tested, how these techniques can be integrated into the next generation of whole-building focused efficiency programs. This paper expands recent analyses of public-domain whole-building M&V methods, focusing on more novel M&V 2.0 modeling approaches that are used in commercial technologies, as well as approaches that are documented in the literature, and/or developed by the academic building research community. We present a testing procedure and metrics to assess the performance of whole-building M&V methods. We then illustrate the test procedure

  2. DNA methylation in metabolic disorders

    DEFF Research Database (Denmark)

    Barres, Romain; Zierath, Juleen R

    2011-01-01

    DNA methylation is a major epigenetic modification that controls gene expression in physiologic and pathologic states. Metabolic diseases such as diabetes and obesity are associated with profound alterations in gene expression that are caused by genetic and environmental factors. Recent reports...... have provided evidence that environmental factors at all ages could modify DNA methylation in somatic tissues, which suggests that DNA methylation is a more dynamic process than previously appreciated. Because of the importance of lifestyle factors in metabolic disorders, DNA methylation provides...... a mechanism by which environmental factors, including diet and exercise, can modify genetic predisposition to disease. This article considers the current evidence that defines a role for DNA methylation in metabolic disorders....

  3. FEM design and simulation of a short, 10 MV, S-band Linac with Monte Carlo dose simulations

    International Nuclear Information System (INIS)

    Baillie, Devin; Aubin, J. St.; Steciw, S.; Fallone, B. G.

    2015-01-01

    Purpose: Current commercial 10 MV Linac waveguides are 1.5 m. The authors’ current 6 MV linear accelerator–magnetic resonance imager (Linac–MR) system fits in typical radiotherapy vaults. To allow 10 MV treatments with the Linac–MR and still fit within typical vaults, the authors design a 10 MV Linac with an accelerator waveguide of the same length (27.5 cm) as current 6 MV Linacs. Methods: The first design stage is to design a cavity such that a specific experimental measurement for breakdown is applicable to the cavity. This is accomplished through the use of finite element method (FEM) simulations to match published shunt impedance, Q factor, and ratio of peak to mean-axial electric field strength from an electric breakdown study. A full waveguide is then designed and tuned in FEM simulations based on this cavity design. Electron trajectories are computed through the resulting radio frequency fields, and the waveguide geometry is modified by shifting the first coupling cavity in order to optimize the electron beam properties until the energy spread and mean energy closely match values published for an emulated 10 MV Linac. Finally, Monte Carlo dose simulations are used to compare the resulting photon beam depth dose profile and penumbra with that produced by the emulated 10 MV Linac. Results: The shunt impedance, Q factor, and ratio of peak to mean-axial electric field strength are all matched to within 0.1%. A first coupling cavity shift of 1.45 mm produces an energy spectrum width of 0.347 MeV, very close to the published value for the emulated 10 MV of 0.315 MeV, and a mean energy of 10.53 MeV, nearly identical to the published 10.5 MeV for the emulated 10 MV Linac. The depth dose profile produced by their new Linac is within 1% of that produced by the emulated 10 MV spectrum for all depths greater than 1.5 cm. The penumbra produced is 11% narrower, as measured from 80% to 20% of the central axis dose. Conclusions: The authors have successfully

  4. Um estudo psicossocial dos significados e sentidos expressos nas músicas de MV Bill A psychosocial study of the meanings expressed in the songs of MV Bill

    Directory of Open Access Journals (Sweden)

    Jaison Hinkel

    2009-08-01

    Full Text Available Este artigo tem por propósito estudar os significados e sentidos expressos nas letras das músicas de MV Bill, um dos ícones do rap nacional, com o intuito de possibilitar a compreensão da sua tendência afetivo-volitiva. Com base na Psicologia Sócio-Histórica, a pesquisa se caracteriza como um estudo de caso e utiliza como método a análise de conteúdo de quatro músicas: "Soldado do Morro", "Só Deus pode me julgar", "EMIVI" e "Atitude Errada". Os significados e sentidos das canções estudadas denunciam as dimensões objetiva, ética e subjetiva da dialética exclusão/inclusão social, bem como a proposta de enfrentamento desta condição. Assim, podem-se considerar tais músicas como indicadores de uma práxis ético-política que propõe ações coletivas com o objetivo de superar a situação de padecimento humano e utiliza a arte como expressão afetiva de potência de vida e criação, em prol da cidadania.The purpose of this article is the analysis of meanings expressed in the song of MV Bill, one of the icons of the Brazilian rap, aiming at the comprehension of its affectionate-volitive tendency. The investigation is characterized as a case study and applies content analysis to four songs: "Soldado do Morro", "Só Deus pode me julgar", "EMIVI", and "Atitude Errada". The meanings and senses of the songs studied identify three dimensions of the dialectics social exclusion/enclosure (objective, ethical and subjective, as well as the clashing of this condition. It seems reasonable to consider such songs as indicators of an ethical-political practice that proposes collective actions with the objective of overcoming the situation of human suffering and utilizes art as affectionate expression of power of life and creation, in behalf of the citizenship.

  5. High Performance Multi-GPU SpMV for Multi-component PDE-Based Applications

    KAUST Repository

    Abdelfattah, Ahmad

    2015-07-25

    Leveraging optimization techniques (e.g., register blocking and double buffering) introduced in the context of KBLAS, a Level 2 BLAS high performance library on GPUs, the authors implement dense matrix-vector multiplications within a sparse-block structure. While these optimizations are important for high performance dense kernel executions, they are even more critical when dealing with sparse linear algebra operations. The most time-consuming phase of many multicomponent applications, such as models of reacting flows or petroleum reservoirs, is the solution at each implicit time step of large, sparse spatially structured or unstructured linear systems. The standard method is a preconditioned Krylov solver. The Sparse Matrix-Vector multiplication (SpMV) is, in turn, one of the most time-consuming operations in such solvers. Because there is no data reuse of the elements of the matrix within a single SpMV, kernel performance is limited by the speed at which data can be transferred from memory to registers, making the bus bandwidth the major bottleneck. On the other hand, in case of a multi-species model, the resulting Jacobian has a dense block structure. For contemporary petroleum reservoir simulations, the block size typically ranges from three to a few dozen among different models, and still larger blocks are relevant within adaptively model-refined regions of the domain, though generally the size of the blocks, related to the number of conserved species, is constant over large regions within a given model. This structure can be exploited beyond the convenience of a block compressed row data format, because it offers opportunities to hide the data motion with useful computations. The new SpMV kernel outperforms existing state-of-the-art implementations on single and multi-GPUs using matrices with dense block structure representative of porous media applications with both structured and unstructured multi-component grids.

  6. Scattered fractions of dose from 18 and 25 MV X-ray radiotherapy linear accelerators

    International Nuclear Information System (INIS)

    Shobe, J.; Rodgers, J.E.; Taylor, P.L.; Jackson, J.; Popescu, G.

    1996-01-01

    Over the years, measurements have been made at a few energies to estimate the scattered fraction of dose from the patient in medical radiotherapy operations. This information has been a useful aid in the determination of shielding requirements for these facilities. With these measurements, known characteriztics of photons, and various other known parameters, Monte Carlo codes are being used to calculate the scattered fractions and hence the shielding requirements for the photons of other energies commonly used in radiotherapeutic applications. The National Institute of Standards and Technology (NIST) acquired a Sagittaire medical linear accelerator (linac) which was previously located at the Yale-New Haven Hospital. This linac provides an X-ray beam of 25 MV photons and electron beams with energies up to 32 MeV. The housing on the gantry was permanently removed from the accelerator during installation. A Varian Clinac 1800 linear accelerator was used to produce the 18 MV photons at the Frederick Memorial Hospital Regional Cancer Therapy Center in Frederick, MD. This paper represents a study of the photon dose scattered from a patient in typical radiation treatment situations as it relates to the dose delivered at the isocenter in water. The results of these measurements will be compared to Monte Carlo calculations. Photon spectral measurements were not made at this time. Neutron spectral measurements were made on this Sagittaire machine in its previous location and that work was not repeated here, although a brief study of the neutron component of the 18 and 25 MV linacs was performed utilizing thermoluminescent dosimetry (TLD) to determine the isotropy of the neutron dose. (author)

  7. ANALISA KINERJA KEMUDI KAPAL “MV SIRENA“ PADA PELAYARAN PERCOBAAN KAPAL BARU

    Directory of Open Access Journals (Sweden)

    Budi Utomo

    2012-02-01

    Full Text Available Every ship building to the after constructed should be done sea trial, it is intended to find out all machinery andequipment in the ship to run well and deserve to normal weather conditions in accordance with the plan. Themain purpose of this study is to know the performance of steering ship MV. SIRENA in sea trial on new ship,because in the operation of a vessel, the steering has a very important role is to ship control or shipmanouvering. After doing sea trial produced several motion graphics board. To ship left spinning PS tacticaldiameter DT = 114,4120 meter and advance = 157,3716 meter, while rotating to the right to ship SB tacticaldiameter DT = 120,9048 meter and advance = 161,9024 meter. There is a difference of 120,9048 – 114,4120 =6,4928 meter in tactical diameter for PS, and 161, 9024 - 157, 3716 = 4,5308 meter in advance, which meansthat the ship sailed round the larger right and left to right, this is due to spin the propeller rotation is right theship sailed toward him continue in the direction of nuts bolts, steering performance of the experimental results ofthe MV. SIRENA after the sea trial, then matched with the demand for ship owners and ship classificationagency, the steering performance of the new ship MV SIRENA can run well which means it can be accepte,because The resulting DT = 6,4928 meter still within the recommended limit is within their rules that is DT =3,45 - 7,50 meter.

  8. Methylation-Specific PCR Unraveled

    Directory of Open Access Journals (Sweden)

    Sarah Derks

    2004-01-01

    Full Text Available Methylation‐specific PCR (MSP is a simple, quick and cost‐effective method to analyze the DNA methylation status of virtually any group of CpG sites within a CpG island. The technique comprises two parts: (1 sodium bisulfite conversion of unmethylated cytosine's to uracil under conditions whereby methylated cytosines remains unchanged and (2 detection of the bisulfite induced sequence differences by PCR using specific primer sets for both unmethylated and methylated DNA. This review discusses the critical parameters of MSP and presents an overview of the available MSP variants and the (clinical applications.

  9. Metal artifact correction for x-ray computed tomography using kV and selective MV imaging

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Meng, E-mail: mengwu@stanford.edu [Department of Electrical Engineering, Stanford University, Stanford, California 94305 (United States); Keil, Andreas [microDimensions GmbH, Munich 81379 (Germany); Constantin, Dragos; Star-Lack, Josh [Varian Medical Systems, Inc., Palo Alto, California 94304 (United States); Zhu, Lei [Nuclear and Radiological Engineering and Medical Physics Programs, The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Fahrig, Rebecca [Department of Radiology, Stanford University, Stanford, California 94305 (United States)

    2014-12-15

    Purpose: The overall goal of this work is to improve the computed tomography (CT) image quality for patients with metal implants or fillings by completing the missing kilovoltage (kV) projection data with selectively acquired megavoltage (MV) data that do not suffer from photon starvation. When both of these imaging systems, which are available on current radiotherapy devices, are used, metal streak artifacts are avoided, and the soft-tissue contrast is restored, even for regions in which the kV data cannot contribute any information. Methods: Three image-reconstruction methods, including two filtered back-projection (FBP)-based analytic methods and one iterative method, for combining kV and MV projection data from the two on-board imaging systems of a radiotherapy device are presented in this work. The analytic reconstruction methods modify the MV data based on the information in the projection or image domains and then patch the data onto the kV projections for a FBP reconstruction. In the iterative reconstruction, the authors used dual-energy (DE) penalized weighted least-squares (PWLS) methods to simultaneously combine the kV/MV data and perform the reconstruction. Results: The authors compared kV/MV reconstructions to kV-only reconstructions using a dental phantom with fillings and a hip-implant numerical phantom. Simulation results indicated that dual-energy sinogram patch FBP and the modified dual-energy PWLS method can successfully suppress metal streak artifacts and restore information lost due to photon starvation in the kV projections. The root-mean-square errors of soft-tissue patterns obtained using combined kV/MV data are 10–15 Hounsfield units smaller than those of the kV-only images, and the structural similarity index measure also indicates a 5%–10% improvement in the image quality. The added dose from the MV scan is much less than the dose from the kV scan if a high efficiency MV detector is assumed. Conclusions: The authors have shown that it

  10. Metal artifact correction for x-ray computed tomography using kV and selective MV imaging

    International Nuclear Information System (INIS)

    Wu, Meng; Keil, Andreas; Constantin, Dragos; Star-Lack, Josh; Zhu, Lei; Fahrig, Rebecca

    2014-01-01

    Purpose: The overall goal of this work is to improve the computed tomography (CT) image quality for patients with metal implants or fillings by completing the missing kilovoltage (kV) projection data with selectively acquired megavoltage (MV) data that do not suffer from photon starvation. When both of these imaging systems, which are available on current radiotherapy devices, are used, metal streak artifacts are avoided, and the soft-tissue contrast is restored, even for regions in which the kV data cannot contribute any information. Methods: Three image-reconstruction methods, including two filtered back-projection (FBP)-based analytic methods and one iterative method, for combining kV and MV projection data from the two on-board imaging systems of a radiotherapy device are presented in this work. The analytic reconstruction methods modify the MV data based on the information in the projection or image domains and then patch the data onto the kV projections for a FBP reconstruction. In the iterative reconstruction, the authors used dual-energy (DE) penalized weighted least-squares (PWLS) methods to simultaneously combine the kV/MV data and perform the reconstruction. Results: The authors compared kV/MV reconstructions to kV-only reconstructions using a dental phantom with fillings and a hip-implant numerical phantom. Simulation results indicated that dual-energy sinogram patch FBP and the modified dual-energy PWLS method can successfully suppress metal streak artifacts and restore information lost due to photon starvation in the kV projections. The root-mean-square errors of soft-tissue patterns obtained using combined kV/MV data are 10–15 Hounsfield units smaller than those of the kV-only images, and the structural similarity index measure also indicates a 5%–10% improvement in the image quality. The added dose from the MV scan is much less than the dose from the kV scan if a high efficiency MV detector is assumed. Conclusions: The authors have shown that it

  11. Metal artifact correction for x-ray computed tomography using kV and selective MV imaging.

    Science.gov (United States)

    Wu, Meng; Keil, Andreas; Constantin, Dragos; Star-Lack, Josh; Zhu, Lei; Fahrig, Rebecca

    2014-12-01

    The overall goal of this work is to improve the computed tomography (CT) image quality for patients with metal implants or fillings by completing the missing kilovoltage (kV) projection data with selectively acquired megavoltage (MV) data that do not suffer from photon starvation. When both of these imaging systems, which are available on current radiotherapy devices, are used, metal streak artifacts are avoided, and the soft-tissue contrast is restored, even for regions in which the kV data cannot contribute any information. Three image-reconstruction methods, including two filtered back-projection (FBP)-based analytic methods and one iterative method, for combining kV and MV projection data from the two on-board imaging systems of a radiotherapy device are presented in this work. The analytic reconstruction methods modify the MV data based on the information in the projection or image domains and then patch the data onto the kV projections for a FBP reconstruction. In the iterative reconstruction, the authors used dual-energy (DE) penalized weighted least-squares (PWLS) methods to simultaneously combine the kV/MV data and perform the reconstruction. The authors compared kV/MV reconstructions to kV-only reconstructions using a dental phantom with fillings and a hip-implant numerical phantom. Simulation results indicated that dual-energy sinogram patch FBP and the modified dual-energy PWLS method can successfully suppress metal streak artifacts and restore information lost due to photon starvation in the kV projections. The root-mean-square errors of soft-tissue patterns obtained using combined kV/MV data are 10-15 Hounsfield units smaller than those of the kV-only images, and the structural similarity index measure also indicates a 5%-10% improvement in the image quality. The added dose from the MV scan is much less than the dose from the kV scan if a high efficiency MV detector is assumed. The authors have shown that it is possible to improve the image quality of

  12. Coupled operation of the Oak Ridge isochronous cyclotron and the 25 MV tandem

    Energy Technology Data Exchange (ETDEWEB)

    Lord, R.S.; Ball, J.B.; Beckers, R.M.; Cleary, T.P.; Hudson, E.D.; Ludemann, C.A.; Martin, J.A.; Milner, W.T.; Mosko, S.W.; Ziegler, N.F.

    1981-01-01

    Coupled operation of the 25 MV tandem and the Oak Ridge Isochronous Cyclotron (ORIC) was achieved on January 27, 1981. A beam of 38 MeV /sup 16/O/sup 2 +/ was injected into ORIC, stripped to 8/sup +/ and accelerated to 324 MeV. Shortly afterwards, the energy was increased to the maximum design value of 25 MeV/amu (400 MeV). A spectrum taken of the scattering of this beam from a thin /sup 208/Pb target in the broad range spectrograh exhibited a resolution of 115 keV (FWHM). Performance of the system was in close agreement with that predicted from calculations.

  13. Coupled operation of the Oak Ridge isochronous cyclotron and the 25 MV tandem

    International Nuclear Information System (INIS)

    Lord, R.S.; Ball, J.B.; Beckers, R.M.; Cleary, T.P.; Hudson, E.D.; Ludemann, C.A.; Martin, J.A.; Milner, W.T.; Mosko, S.W.; Ziegler, N.F.

    1981-01-01

    Coupled operation of the 25 MV tandem and the Oak Ridge Isochronous Cyclotron (ORIC) was achieved on January 27, 1981. A beam of 38 MeV 16 O 2+ was injected into ORIC, stripped to 8 + and accelerated to 324 MeV. Shortly afterwards, the energy was increased to the maximum design value of 25 MeV/amu (400 MeV). A spectrum taken of the scattering of this beam from a thin 208 Pb target in the broad range spectrograh exhibited a resolution of 115 keV (FWHM). Performance of the system was in close agreement with that predicted from calculations

  14. Dosimetric characteristics of a 6 MV photon beam from a linear accelerator with asymmetric collimator jaws

    International Nuclear Information System (INIS)

    Palta, J.R.; Ayyangar, K.M.; Suntharalingam, N.

    1988-01-01

    Dosimetric measurements have been made of a 6 MV photon beam from a linear accelerator equipped with asymmetric jaws. The field size factors for asymmetrically set fields are compared to those for symmetrically set fields. The change of beam quality has been measured as a function of off-axis position of the asymmetric fields to assess its effect on depth dose. Additional measurements include beam penumbra and shape of isodose curves for open and wedge fields as the field opening is moved asymmetrically from the central ray

  15. Expansion of the data acquisition system for the 20 MV tandem accelerator

    International Nuclear Information System (INIS)

    Tomita, Yoshiaki

    1981-02-01

    This report describes an expansion of the program of the data acquisition system for the 20 MV tandem accelerator. By the present expansion it became possible to change the accuisition mode or to use non-standard CAMAC modules with partial modification of the program according to well defined prescriptions. The modification can be made by writing microprograms for the MBD or appending subroutines for the reduced spectra in the LIST mode data acquisition. The new program can handle up to 32 ADC's in the standard LIST mode data acquisition. The present expansion aimed to increase the flexibility in data acquisition. It can also be applied to control experimental devices. (author)

  16. A new accelerator tube and column for a horizontal 8 MV tandem

    International Nuclear Information System (INIS)

    Sundquist, M.L.; Rathmell, R.D.; Raatz, J.E.

    1990-01-01

    A horizontal 8 MV tandem is being installed in an existing tank at Kyoto University in Japan. This NEC Model 8UDH is the largest horizontal Pelletron constructed to date. The terminal is charged by two Pelletron chains. The acceleration tube is a metal and ceramic construction made into tube sections with a length of 30 cm each. This tube design adds 27% more live ceramic than in the standard NEC tube design, which had heated apertures in 5 cm long shorted regions every 20 cm. The column structure and tube design are reviewed. (orig.)

  17. Nuclear safeguards research with the LASL 3. 75-MV Van de Graaff accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Krick, M.S.; Evans, A.E.

    1976-01-01

    The continued use of the Los Alamos Scientific Laboratory (LASL) 3.75-MV Van de Graaff accelerator for the nondestructive assay of nuclear material in support of nuclear safeguards is reviewed. A brief description of the accelerator facility and the small-sample assay station (SSAS) is provided. Factors affecting high-accuracy assay of small samples are outlined. Examples are provided for the assay of uranium--thorium mixtures, low-level uranium samples, and high-temperature gas-cooled reactor (HTGR) fuel rods. Research on delayed-neutron energy spectra, radiation damage to /sup 3/He proportional counters, and /sup 4/He gas scintillators is summarized.

  18. Oak Ridge isochronous cyclotron as an energy booster for a 25 MV tandem

    International Nuclear Information System (INIS)

    Lord, R.S.; Hudson, E.D.; McNeilly, G.S.

    1975-01-01

    The maximum heavy-ion energy available at Oak Ridge will be substantially increased by using ORIC as an energy booster for the 25 MV ''folded'' tandem now being acquired. Beams of ions with mass up to A = 160, with energy sufficient to overcome the Coulomb barrier on lead, will be produced. The beams will enter the cyclotron through the dee stem and will be directed by a magnet through the fringe and main fields to a stripping foil which lies on the appropriate orbit for acceleration. General orbit and beam transport codes were used to aid in the design of the injection system. (U.S.)

  19. Development of isodose curves for A 6 mv x-ray beam

    International Nuclear Information System (INIS)

    Hidaytalla, Lamya Abbas

    1994-08-01

    In this thesis radiation distribution of 6 Mv x-ray beam in a water phantom is developed. The method is based on a simple empirical equation and the assumption that the x-ray source is a point source. This leads to a simple equation for the calculation and plotting of the isodose curves. the charts obtained for two fields, 6*6 and 12*12 cm 2 show good agreement with the previous data used in the isotope and radiation centre, Khartoum hospital. It is suggested that further development should be carried out by writing a computer program for all the fields. (Author)

  20. Vivitron - A 35 MV Van de Graaff tandem. Design, performance, charge transport system

    International Nuclear Information System (INIS)

    Letournel, M.; Helleboid, J.M.; Bertein, H.

    1985-01-01

    This paper describes a new configuration for an electrostatic tandem accelerator. The project of the Strasbourg Nuclear Center is a 35 MV Van de Graaff tandem, in fact a new design in that field. The general features of the machine and its associated electrostatic field are described. The machine is designed to minimise energy dissipation within the accelerator column in the event of electrical breakdown. This is discussed as also insulator and conductor designs. Charge transport system is a particular field. The choice of a belt system and its design result from specific studies carried out at the C.R.N. with reference to the electrostatics of solid and gaseous insulations [fr

  1. Small-Field Dosimetry in A 6 MV Photon Beam Using Alanine and Liquid Ionisation Chamber

    DEFF Research Database (Denmark)

    Zimmermann, S.; Riis, H. L.; Hjelm-Hansen, M.

    2012-01-01

    Purpose/Objective: Dosimetry of small field sizes in MV photon beams is an increasingly important subject, and a generally accepted guideline for clinical measurements is still lacking. The present comparative study was carried out to further investigate the use of alanine and the PTW microLion...... of each field and depth. This dose maximum was measured for each field using a Scanditronix Wellhöfer photon field diode. The same measurements were carried out using a liquid ionchamber, PTW microLion, irradiated by 500 MU. The output of the accelerator was controlled by a PTW semiflex ion chamber...

  2. Design and testing of the 2 MV heavy ion injector for the Fusion Energy Research Program

    International Nuclear Information System (INIS)

    Abraham, W.; Benjegerdes, R.; Reginato, L.; Stoker, J.; Hipple, R.; Peters, C.; Pruyn, J.; Vanecek, D.; Yu, S.

    1995-04-01

    The Fusion Energy Research Group at the Lawrence Berkeley Laboratory has constructed and tested a pulsed 2 MV injector that produces a driver size beam of potassium ions. This paper describes the engineering aspects of this development which were generated in a closely coupled effort with the physics staff. Details of the ion source and beam transport physics are covered in another paper at this conference. This paper discusses the design details of the pulse generator, the ion source, the extractor, the diode column, and the electrostatic quadrupole column. Included will be the test results and operating experience of the complete injector

  3. 2. 5 MV Van de Graaff accelerator (VdG) and associated experimental equipments

    Energy Technology Data Exchange (ETDEWEB)

    Hasai, Hiromi; Iwatani, Kazuo; Shizuma, Kiyoshi; Nishiyama, Fumitaka

    1984-12-01

    A 2.5 MV VdG accelerator was recently installed in Saijo new campus, Higashi-Hiroshima and started into operation. This paper reports specifications of the accelerator and associated experimental equipments. Available ion beams are hydrogen, helium, nitrogen and, in addition, electrons by means of quick-conversion kit. A switching magnet, a beam transport tube with two beam slits and a vacuum chamber are connected to the accelerator. This VdG accelerator will be used not only for nuclear physics but also for researches of atomic, solid-state physics and microanalysis of elements of enviromental samples. (author).

  4. Design and simulation of a short, variable-energy 4 to 10 MV S-band linear accelerator waveguide.

    Science.gov (United States)

    Baillie, Devin; Fallone, B Gino; Steciw, Stephen

    2017-06-01

    To modify a previously designed, short, 10 MV linac waveguide, so that it can produce any energy from 4 to 10 MV. The modified waveguide is designed to be a drop-in replacement for the 6 MV waveguide used in the author's current linear accelerator-magnetic resonance imager (Linac-MR). Using our group's previously designed short 10 MV linac as a starting point, the port was moved to the fourth cavity, the shift to the first coupling cavity was removed and a tuning cylinder added to the first coupling cavity. Each cavity was retuned using finite element method (FEM) simulations to resonate at the desired frequency. FEM simulations were used to determine the RF field distributions for various tuning cylinder depths, and electron trajectories were computed using a particle-in-cell model to determine the required RF power level and tuning cylinder depth to produce electron energy distributions for 4, 6, 8, and 10 MV photon beams. Monte Carlo simulations were then used to compare the depth dose profiles with those produced by published electron beam characteristics for Varian linacs. For each desired photon energy, the electron beam energy was within 0.5% of the target mean energy, the depth of maximum dose was within 1.5 mm of that produced by the Varian linac, and the ratio of dose at 10 cm depth to 20 cm depth was within 1%. A new 27.5 cm linear accelerator waveguide design capable of producing any photon energy between 4 and 10 MV has been simulated, however coupling port design and the implications of increased electron beam current at 10 MV remain to be investigated. For the specific cases of 4, 6, and 10 MV, this linac produces depth dose profiles similar to those produced by published spectra for Varian linacs. © 2017 American Association of Physicists in Medicine.

  5. Using of beam spoilers in linear accelerators with photons of 10 MV; Empleo de degradadores del haz en aceleradores lineales con fotones de 10 MV

    Energy Technology Data Exchange (ETDEWEB)

    Sansogne, R.; Palacios, V.; Arbiser, S. [Vidt Centro Medico- CETRO. Vidt 1924- (1428) Buenos Aires (Argentina)

    1998-12-31

    This work come along of the necessity to utilize an unique High-Energy Electron Linear Accelerator (10 MV) for radiant treatments which require higher doses in the surface levels of tissue. It is analyzed the interposition of acrylic degraders (spoilers) in the beam, especially for opposed and parallel fields in the cases of head and neck. It was analyzed the possible combinations of the following parameters: 1) Field sizes defined at isocenter (100 cm) 6 x 6 cm{sup 2}, 8 x 8 cm{sup 2} and 10 x 10 cm{sup 2} ; 2) Surface-spoiler distance (DSS) of 4, 7 and 10 cm; 3) Spoilers with different thickness 1.1 and 1.5 cm. It was observed a displacement of the maximum dose toward the surface, and an increase in the percentile doses in the build-up zone when the spoiler is nearing and/or increasing its thickness. It is verified that the use of spoilers, support the symmetry and plane of the beam inside of the clinically acceptable margins. When the results obtained are analyzed then it is proposed as a calculation method to incorporate an attenuation factor. (Author)

  6. H(10) due to radiation scattered in a 6 MV Linac for tomotherapy; H*(10) debida a la radiacion dispersada en un LINAC de 6 MV para tomoterapia

    Energy Technology Data Exchange (ETDEWEB)

    Vega C, H. R.; Esparza H, A. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98060 Zacatecas, Zac. (Mexico); Garcia R, M. G. [Instituto Tecnologico y de Estudios Superiores de Monterrey, Campus Zacatecas, Calz. Pedro Coronel 16, Dependencias Federales, 98600 Guadalupe, Zacatecas (Mexico); Reyes R, E. [Universidad de Guanajuato, Campus Leon, Division de Ciencias e Ingenierias, Loma del Bosque 103, Col. Lomas del Campestre, 37150 Leon, Guanajuato (Mexico); Hernandez A, L. [Consejo Nacional de Ciencia y Tecnologia, CIBNOR, Mar Bermejo 195, Col. Playa Palo de Santa Rita, 23090 La Paz, Baja California Sur (Mexico); Rivera, T., E-mail: fermineutron@yahoo.com [IPN, Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Calz. Legaria 694, Col. Irrigacion, 11500 Ciudad de Mexico (Mexico)

    2017-10-15

    In order to determine the environmental equivalent dose (H(10)), due to the radiation that is dispersed over the body of a patient, 100 thermoluminescent dosimeters (TLD) around 6 MV TomoLINAC were used. The characteristics of the tomotherapy have the disadvantage that the shielding of the bunker increases considerably and for its design validated parameters are used for the conventional Linacs. In order to determine H(10) due to scattered radiation, measurements were made in the vicinity of the isocenter, while the 6 MeV photon beam was applied on a phantom. Also, TLDs were placed on the walls of the bunker that remained for 7 days, where approximately 50 patients were treated per day. At points close to the isocenter, the H(10) has an angular distribution caused by the phantom shape. In the bunker walls the highest H(10) was observed in the primary barriers. In the labyrinth, the impact of the scattered radiation was observed when measuring a greater value of the environmental equivalent dose in the wall furthest from the isocenter compared to the point located closest to it. (Author)

  7. 15. dialogue on waste management MV. Current developments in waste and resources economics. Proceedings; 15. Dialog Abfallwirtschaft MV. Aktuelle Entwicklungen in der Abfall und Ressourcenwirtschaft. Tagungsband

    Energy Technology Data Exchange (ETDEWEB)

    Nelles, Michael (ed.)

    2012-07-01

    Within the 15th dialogue on waste management MV at the University of Rostock (Rostock, Federal Republic of Germany) at 13th June, 2012, the following lectures were held: (1) 20 Years GAA - 20 years of successful work (Hartwig Roessler); (2) Acquisition and evaluation of waste management data in Mecklenburg-Western Pommerania - A basis for planning for strategies according to Cycle and Waste Management Act KrWG (Helmut Kietzmann); (3) Demographic change in Mecklenburg-Western Pommerania - Implications for the waste management (Matthias Leuchter); (4) The HPWM project (Jan Marquardt); (5) Consequences of the modified legal and regulatory situation for the operation of refuse-fuelled power stations (Kurt Wengenroth); (6) Foodstuffs in the waste - Analysis and mitigation proposals (Jakob Barabosz); (7) Disposal of electric and electronic equipment as well as manufacturer responsibility (Vera Susanne Rotter); (8) Advanced waste management concepts in developing countries - foundable? Realizable? Sustainable? (Wolfgang Pfaff-Simoneit); (9) Further development of the mechanical-biological waste treatment (Stephan Schuett); (10) Airjet-pipecleaner - the automatic cleaning facility for ventilation nozzles (Armin Seidel); (11) Exploitation of reusable materials from bottom ash (Dirk Bludau); (12) Is the thermal treatment suitable for the utilization of glass-fibre reinforced plastics wastes? (Karl-Heinz Plepla); (13) Recyclability of bioplastics(An-Sophie Kitzler); (14) Development of process-oriented quality inspections for the near private collection of refuse and recyclable material (Nico Schulte).

  8. Integrating techniques for neutron dosimetry in Linac 18 MV; Integrando tecnicas para dosimetria de neutrones en un Linac de 18 MV

    Energy Technology Data Exchange (ETDEWEB)

    Ceron R, P. V.; Diaz G, J. A. I.; Rivera M, T. [IPN, Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Av. Legaria 694, 11500 Mexico D. F. (Mexico); Paredes G, L. C. [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico); Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas, Zac. (Mexico)

    2015-10-15

    In this paper thermoluminescent dosimetry, analytical techniques and Monte Carlo calculations were used to estimate the neutron dose equivalent in a radiotherapy room with a linear electron accelerator of 18 MV. The equivalent dose was measured at isocenter to 1.42 m of target and at the entrance of the labyrinth of the room of a Novalis Tx. The neutron detectors were constructed with pairs of thermoluminescent dosimeters TLD 600 ({sup 6}LiF: Mg, Ti) and TLD 700 ({sup 7}LiF: Mg, Ti) which are placed inside a paraffin sphere of 20 cm in diameter. These measurements enabled the calculation of equivalent dose in the gate and the source term, using the relationships contained in the NCRP-151. Through the models carried out with the code MCNPX the absorbed dose distribution with regard to depth in a paraffin phantom are included and the neutron spectrum produced by the head, taking into account the geometry and component materials. The results are in the order of neutron milli sievert by gray of X-rays (mSv/Gy x) which are in the same order as those found in other reports for different accelerators. (Author)

  9. Simulation and Analysis of Small Break LOCA for AP1000 Using RELAP5-MV and Its Comparison with NOTRUMP Code

    Directory of Open Access Journals (Sweden)

    Eltayeb Yousif

    2017-01-01

    Full Text Available Many reactor safety simulation codes for nuclear power plants (NPPs have been developed. However, it is very important to evaluate these codes by testing different accident scenarios in actual plant conditions. In reactor analysis, small break loss of coolant accident (SBLOCA is an important safety issue. RELAP5-MV Visualized Modularization software is recognized as one of the best estimate transient simulation programs of light water reactors (LWR. RELAP5-MV has new options for improved modeling methods and interactive graphics display. Though the same models incorporated in RELAP5/MOD 4.0 are in RELAP5-MV, the significant difference of the latter is the interface for preparing the input deck. In this paper, RELAP5-MV is applied for the transient analysis of the primary system variation of thermal hydraulics parameters in primary loop under SBLOCA in AP1000 NPP. The upper limit of SBLOCA (10 inches is simulated in the cold leg of the reactor and the calculations performed up to a transient time of 450,000.0 s. The results obtained from RELAP5-MV are in good agreement with those of NOTRUMP code obtained by Westinghouse when compared under the same conditions. It can be easily inferred that RELAP5-MV, in a similar manner to RELAP5/MOD4.0, is suitable for simulating a SBLOCA scenario.

  10. Naturally occurring methyl salicylate glycosides.

    Science.gov (United States)

    Mao, Ping; Liu, Zizhen; Xie, Meng; Jiang, Rui; Liu, Weirui; Wang, Xiaohong; Meng, Shen; She, Gaimei

    2014-01-01

    As an important part of non steroids anti-inflammation drug (NSAIDs), salicylate has developed from natural substance salicylic acid to natrium salicylicum, to aspirin. Now, methyl salicylate glycoside, a new derivative of salicylic acid, is modified with a -COOH group integrated one methyl radical into formic ether, and a -OH linked with a monosaccharide, a disaccharide or a trisaccharide unit by glycosidic linkage. It has the similar pharmacological activities, anti-inflammatory, analgesic, antipyretic and antithrombotic as the previous salicylates' without resulting in serious side effects, particularly the gastrointestinal toxicity. Owing to the superiority of those significant bioactivities, methyl salicylate glycosides have became a hot research area in NSAIDs for several years. This paper compiles all 9 naturally occurring methyl salicylate glycosides, their distribution of the resource and pharmacological mechanism, which could contribute to the new drug discovery.

  11. Process for the production of methyl methacrylate

    NARCIS (Netherlands)

    Eastham, G.R.; Johnson, D.W.; Straathof, A.J.J.; Fraaije, Marco; Winter, Remko

    2015-01-01

    A process of producing methyl methacrylate or derivatives thereof is described. The process includes the steps of; (i) converting 2-butanone to methyl propionate using a Baeyer-Villiger monooxygenase, and (ii) treating the methyl propionate produced to obtain methyl methacrylate or derivatives

  12. Dosimetric properties of dysprosium doped lithium borate glass irradiated by 6 MV photons

    International Nuclear Information System (INIS)

    Ab Rasid, A.; Wagiran, H.; Hashim, S.; Ibrahim, Z.; Ali, H.

    2015-01-01

    Undoped and dysprosium doped lithium borate glass system with empirical formula (70–x) B 2 O 3 –30 Li 2 O–(x) Dy 2 O 3 (x=0.1, 0.3, 0.5, 0.7, 1.0 mol%) were prepared using the melt-quenching technique. The dosimetric measurements were performed by irradiating the samples to 6 MV photon beam using linear accelerator (LINAC) over a dose range of 0.5–5.0 Gy. The glass series of dysprosium doped lithium borate glass produced the best thermoluminescence (TL) glow curve with the highest intensity peak from sample with 1.0 mol% Dy 2 O 3 concentration. Minimum detectable dose was detected at 2.24 mGy, good linearity of regression coefficient, high reproducibility and high sensitivity compared to the undoped glass are from 1.0 mol% dysprosium doped lithium borate glass. The results indicated that the series of dysprosium doped lithium glasses have a great potential to be considered as a thermoluminescence dosimetry (TLD). - Highlights: • TL response of undoped and dysprosium doped lithium borate glass subjected to 6 MV photons irradiation at low dose range. • TL linear response of dysprosium doped lithium borate glass. • The sensitivity of dysprosium doped lithium borate glass is approximately 93 times higher than undoped glass

  13. Neutron contamination of Varian Clinac iX 10 MV photon beam using Monte Carlo simulation

    International Nuclear Information System (INIS)

    Yani, S; Haryanto, F; Arif, I; Tursinah, R; Rhani, M F; Soh, R C X

    2016-01-01

    High energy medical accelerators are commonly used in radiotherapy to increase the effectiveness of treatments. As we know neutrons can be emitted from a medical accelerator if there is an incident of X-ray that hits any of its materials. This issue becomes a point of view of many researchers. The neutron contamination has caused many problems such as image resolution and radiation protection for patients and radio oncologists. This study concerns the simulation of neutron contamination emitted from Varian Clinac iX 10 MV using Monte Carlo code system. As neutron production process is very complex, Monte Carlo simulation with MCNPX code system was carried out to study this contamination. The design of this medical accelerator was modelled based on the actual materials and geometry. The maximum energy of photons and neutron in the scoring plane was 10.5 and 2.239 MeV, respectively. The number and energy of the particles produced depend on the depth and distance from beam axis. From these results, it is pointed out that the neutron produced by linac 10 MV photon beam in a typical treatment is not negligible. (paper)

  14. Experimental Comparison of 2-3MV X-Ray Sources for Flash Radiography

    International Nuclear Information System (INIS)

    MENGE, PETER RICHARD; JOHNSON, DAVID LEE; MAENCHEN, JOHN E.; OLSON, CRAIG L.; ROVANG, DEAN C.; DROEMER, D.; HUNT, E.; OLIVER, BRYAN VELTEN; ROSE, DAVID VINCENT; WELCH, DALE ROBERT

    2002-01-01

    High-brightness flash x-ray sources are needed for penetrating dynamic radiography for a variety of applications. Various bremsstrahlung source experiments have been conducted on the TriMeV accelerator (3MV, 60 Ω 20 ns) to determine the best diode and focusing configuration in the 2-3 MV range. Three classes of candidate diodes were examined: gas cell focusing, magnetically immersed, and rod pinch. The best result for the gas cell diode was 6 rad at 1 meter from the source with a 5 mm diameter x-ray spot. Using a 0.5 mm diameter cathode immersed in a 17 T solenoidal magnetic field, the best shot produced 4.1 rad with a 2.9 mm spot. The rod pinch diode demonstrated very reproducible radiographic spots between 0.75 and 0.8 mm in diameter, producing 1.2 rad. This represents a factor of eight improvement in the TriMeV flash radiographic capability above the original gas cell diode to a figure of merit (dose/spot diameter) > 1.8 rad/mm. These results clearly show the rod pinch diode to be the choice x-ray source for flash radiography at 2-3 M V

  15. Design study of a 1 MV, 4 A, D- test bed in european community

    International Nuclear Information System (INIS)

    Pamela, J.; Hemsworth, R.; Jacquot, C.; Holmes, A.J.T.

    1991-01-01

    The design study of a 1 MV, 4 A, D - , > 30 seconds, test bed is being conducted by the EURATOM-CEA association (Cadarache) with support from the EURATOM-UKAEA association (Culham) and from FOM-Amsterdam. A proposal for the construction of this test bed at Cadarache will be made by the middle of next year. The options chosen for the beamline are derived from the conceptual design originally proposed one year ago by A.Holmes et al. for the ITER neutral beam systems: pure volume negative ion production, electrostatic multi-stage accelerator, vertically subdivided beamline, electrostatic deflection of the ions at the neutralizer exit, HV vacuum insulation with voltage grading screens. This design has been reviewed in detail and in particular three basic topics have been carefully examined: beam acceleration, gas flow and beam transmission. This review resulted in various changes with respect to the original design, the major change being the decision to put the ion source at high voltage. In parallel to this test bed design study, the conceptual study of a 1 MV, 15 A power supply and of its protection system is conducted by european industrial companies under the supervision of Cadarache

  16. Measurement of MV CT dose index for Hi-ART helical tomotherapy unit

    International Nuclear Information System (INIS)

    Wang Yunlai; Liao Xiongfei

    2010-01-01

    Objective: To evaluate the patient dose from Hi-ART MV helical CT imaging in image-guided radiotherapy. Methods: Weighted CT dose index (CTDI W ) was measured with PTW TM30009 CT ion chamber in head and body phantoms, respectively,for slice thicknesses of 2, 4, 6 mm with scanned range of 5 cm and 15 cm. Dose length products (DLP) were subsequently calculated. The CTDI W and DLP were compared with XVI kV CBCT and ACQSim simulator CT for routine clinical protocols. Results: An inverse relationship between CTDI and the slice thickness was found. The dose distribution was inhomogeneous owing to the attenuation of the couch. CTDI and DLP had close relationship with the slice thickness and the scanned range. Patient dose from MVCT was lower than XVI CBCT for head, but larger for body scan. Conclusions: CTDI W can be used to assess the patient dose in MV helical CT due to its simplicity for measurement and reproducibility. Regular measurement should be performed in QA and QC program. Appropriate slice thickness and scan range should be chosen to reduce the patient dose. (authors)

  17. Activation products in a treatment room of a 15 MV linear accelerator for medical use

    International Nuclear Information System (INIS)

    De Leon M, H. A.; Soto B, T. G.; Rivera P, E.; Hernandez D, V. M.; Vega C, H. R.

    2012-10-01

    Linacs working above 8 MV produce an undesirable neutron field mainly through (γ, n) nuclear reactions. Due to room-return effect inside the vault there is a thermal neutron flux that is constant regarded the distance to the isocenter. When thermal neutrons collide with the bunker walls and the Linac head some radioisotopes are induced in the concrete, wedges and collimators due to neutron and photon activation. The aim of this work is to study the induced radioisotopes in concrete samples and a wedge, which emits gamma-ray during its decay, the presence of this protons will represent a radiological risk for the patient. Induced radioisotopes were studied with a 15 MV Linac, and a gamma-ray spectrometer with a Nal(Tl) scintillator where 846.8, 1368.6 and 1778.8 keV gamma-rays were observed, these photons are produced during the decay of 54 Mn, 24 Na and 28 Al respectively, being in agreement with radionuclides reported in the literature. (Author)

  18. Scatter fractions from linear accelerators with x-ray energies from 6 to 24 MV.

    Science.gov (United States)

    Taylor, P L; Rodgers, J E; Shobe, J

    1999-08-01

    Computation of shielding requirements for a linear accelerator must take into account the amount of radiation scattered from the patient to areas outside the primary beam. Currently, the most frequently used data are from NCRP 49 that only includes data for x-ray energies up to 6 MV and angles from 30 degrees to 135 degrees. In this work we have determined by Monte Carlo simulation the scattered fractions of dose for a wide range of energies and angles of clinical significance including 6, 10, 18, and 24 MV and scattering angles from 10 degrees to 150 degrees. Calculations were made for a 400 cm2 circular field size impinging onto a spherical phantom. Scattered fractions of dose were determined at 1 m from the phantom. Angles from 10 degrees to 30 degrees are of concern for higher energies where the scatter is primarily in the forward direction. An error in scatter fraction may result in too little secondary shielding near the junction with the primary barrier. The Monte Carlo code ITS (Version 3.0) developed at Sandia National Laboratory and NIST was used to simulate scatter from the patient to the barrier. Of significance was the variation of calculated scattered dose with depth of measurement within the barrier indicating that accurate values may be difficult to obtain. Mean energies of scatter x-ray spectra are presented.

  19. Beam Characterization of 10-MV Photon Beam from Medical Linear Accelerator without Flattening Filter.

    Science.gov (United States)

    Shimozato, Tomohiro; Aoyama, Yuichi; Matsunaga, Takuma; Tabushi, Katsuyoshi

    2017-01-01

    This work investigated the dosimetric properties of a 10-MV photon beam emitted from a medical linear accelerator (linac) with no flattening filter (FF). The aim of this study is to analyze the radiation fluence and energy emitted from the flattening filter free (FFF) linac using Monte Carlo (MC) simulations. The FFF linac was created by removing the FF from a linac in clinical use. Measurements of the depth dose (DD) and the off-axis profile were performed using a three-dimensional water phantom with an ionization chamber. A MC simulation for a 10-MV photon beam from this FFF linac was performed using the BEAMnrc code. The off-axis profiles for the FFF linac exhibited a chevron-like distribution, and the dose outside the irradiation field was found to be lower for the FFF linac than for a linac with an FF (FF linac). The DD curves for the FFF linac included many contaminant electrons in the build-up region. Therefore, for clinical use, a metal filter is additionally required to reduce the effects of the electron contamination. The mean energy of the FFF linac was found to be lower than that of the FF linac owing to the absence of beam hardening caused by the FF.

  20. A dynamic material discrimination algorithm for dual MV energy X-ray digital radiography

    International Nuclear Information System (INIS)

    Li, Liang; Li, Ruizhe; Zhang, Siyuan; Zhao, Tiao; Chen, Zhiqiang

    2016-01-01

    Dual-energy X-ray radiography has become a well-established technique in medical, industrial, and security applications, because of its material or tissue discrimination capability. The main difficulty of this technique is dealing with the materials overlapping problem. When there are two or more materials along the X-ray beam path, its material discrimination performance will be affected. In order to solve this problem, a new dynamic material discrimination algorithm is proposed for dual-energy X-ray digital radiography, which can also be extended to multi-energy X-ray situations. The algorithm has three steps: α-curve-based pre-classification, decomposition of overlapped materials, and the final material recognition. The key of the algorithm is to establish a dual-energy radiograph database of both pure basis materials and pair combinations of them. After the pre-classification results, original dual-energy projections of overlapped materials can be dynamically decomposed into two sets of dual-energy radiographs of each pure material by the algorithm. Thus, more accurate discrimination results can be provided even with the existence of the overlapping problem. Both numerical and experimental results that prove the validity and effectiveness of the algorithm are presented. - Highlights: • A material discrimination algorithm for dual MV energy X-ray digital radiography is proposed. • To solve the materials overlapping problem of the current dual energy algorithm. • The experimental results with the 4/7 MV container inspection system are shown.

  1. Photons and photoneutrons spectra of a Linac of 15 MV; Espectros de fotones y fotoneutrones de un LINAC de 15 MV

    Energy Technology Data Exchange (ETDEWEB)

    Benites R, J. L.; Carrillo C, A. [Centro Estatal de Cancerologia de Nayarit, Av. Enfermeria, Fracc. Fray Junipero Serra, 63000 Tepic, Nayarit (Mexico); Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Calle Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico); Velazquez F, J. B., E-mail: jlbenitesr@prodigy.net.mx [Universidad Autonoma de Nayarit, Posgrado CBAP, Carretera Tepic Compostela Km. 9, Xalisco, Nayarit (Mexico)

    2011-10-15

    Using the Monte Carlo code MCNP-5, the photons and photoneutrons spectra generated in the head stock of the lineal accelerator (Linac) Varian of 15 MV of the Cancerology State of Nayarit were determined. For the calculations a heterogeneous head stock was modeled, more compatible with the work conditions. In the center of the head stock a tungsten target was located on a copper support, followed by the flattened filter. The photons and photoneutrons spectra were obtained accelerating electrons and making them collide against the target to produce photons by Bremsstrahlung, these photons were transported inside the head stock and the photons and photoneutrons spectra were calculated in a punctual detector located under the flattened filter and in the isocenter. The spectra were evaluated in punctual detectors that were located in the plane from the isocenter to the long of the X and Y axes each 20 cm, in an equidistant way, up to 2 m, so much in the longitudinal and transversal axes. In the calculations were used histories 5E(6) with the purpose of obtaining smaller uncertainties to 1%. It was found that the photons spectrum in the punctual detector inside the head stock presents a pick of 1.25 MeV in the energy interval of 0.5 and 1.5 MeV, later suffers a filtration and diminishes in asymptote form. This spectrum modifies when the beam reaches the isocenter, diminishing the low energy photons. Inside the head stock the photoneutrons spectrum shows a structure with two picks, one before 1 MeV and other after 1 MeV; this is for effect of the collimators geometry and the distance. Finally an increment of the total neutrons flow to 60 cm of distance of the isocenter on the Y axis was observed, due to the design geometry of the modeling heterogeneous head stock. (Author)

  2. WE-DE-BRA-05: Monte Carlo Simulation of a Novel Multi-Layer MV Imager

    Energy Technology Data Exchange (ETDEWEB)

    Myronakis, M; Rottmann, J; Berbeco, R [Brigham and Women’s Hospital, Boston, MA (United States); Hu, Y [Dana Farber Cancer Institute, Boston, MA (United States); Wang, A; Shedlock, D; Star-Lack, J [Varian Medical Systems, Palo Alto, CA (United States); Morf, D [Varian Medical Systems, Dattwil, Aargau (Switzerland)

    2016-06-15

    Purpose: To develop and validate a Monte Carlo (MC) model of a novel multi-layer imager (MLI) for megavolt (MV) energy beams. The MC model will enable performance optimization of the MLI design for clinical applications including patient setup verification, tumor tracking and MVCBCT. Methods: The MLI is composed of four layers of converter, scintillator and light detector, each layer similar to the current clinical AS1200 detector (Varian Medical Systems, Inc). The MLI model was constructed using the Geant4 Application for Tomographic Emission (GATE v7.1) and includes interactions for x-ray photons, charged particles and optical photons. Computational experiments were performed to assess Modulation Transfer Function (MTF), Detective Quantum Efficiency (DQE) and Noise Power Spectrum normalized by photon fluence and average detector signal (qNNPS). Results were compared with experimental measurements. The current work incorporates, in one model, the complete chain of events occurring in the imager; i.e. starting from x-ray interaction to charged particle transport and energy deposition to subsequent generation, interactions and detection of optical photons. Results: There is good agreement between measured and simulated MTF, qNNPS and DQE values. Normalized root mean squared error (NRMSE) between measured and simulated values over all four layers was 2.18%, 2.43% and 6.05% for MTF, qNNPS and DQE respectively. The relative difference between simulated and measured values for qNNPS(0) was 1.68% and 1.57% for DQE(0). Current results were obtained using a 6MV Varian Truebeam™ spectrum. Conclusion: A comprehensive Monte Carlo model of the MLI prototype was developed to allow optimization of detector components. The model was assessed in terms of imaging performance using standard metrics (i.e. MTF, qNNPS, DQE). Good agreement was found between simulated and measured values. The model will be used to assess alternative detector constructions to facilitate advanced

  3. Comprehensive automation and monitoring of MV grids as the key element of improvement of energy supply reliability and continuity

    Directory of Open Access Journals (Sweden)

    Stanisław Kubacki

    2012-03-01

    Full Text Available The paper presents the issue of comprehensive automation and monitoring of medium voltage (MV grids as a key element of the Smart Grid concept. The existing condition of MV grid control and monitoring is discussed, and the concept of a solution which will provide the possibility of remote automatic grid reconfiguration and ensure full grid observability from the dispatching system level is introduced. Automation of MV grid switching is discussed in detail to isolate a faulty line section and supply electricity at the time of the failure to the largest possible number of recipients. An example of such automation controls’ operation is also presented. The paper’s second part presents the key role of the quick fault location function and the possibility of the MV grid’s remote reconfiguration for improving power supply reliability (SAIDI and SAIFI indices. It is also shown how an increase in the number of points fitted with faulted circuit indicators with the option of remote control of switches from the dispatch system in MV grids may affect reduction of SAIDI and SAIFI indices across ENERGA-OPERATOR SA divisions.

  4. Design and experimental research on a self-magnetic pinch diode under MV

    Science.gov (United States)

    Pengfei, ZHANG; Yang, HU; Jiang, SUN; Yan, SONG; Jianfeng, SUN; Zhiming, YAO; Peitian, CONG; Mengtong, QIU; Aici, QIU

    2018-01-01

    A self-magnetic pinch diode (SMPD) integrating an anode foil-reinforced electron beam pinch focus and a small high-dose x-ray spot output was designed and optimized. An x-ray focal spot measuring system was developed in accordance with the principle of pinhole imaging. The designed SMPD and the corresponding measuring system were tested under ∼MV, with 1.75 × 2 mm2 oval x-ray spots (AWE defined) and forward directed dose 1.6 rad at 1 m. Results confirmed that the anode foil can significantly strengthen the electron beam pinch focus, and the focal spot measuring system can collect clear focal spot images. This finding indicated that the principle and method are feasible.

  5. Volume dose ratios relevant for alanine dosimetry in small, 6 MV photon beams

    DEFF Research Database (Denmark)

    Cronholm, Rickard O.; Andersen, Claus Erik; Behrens, Claus F.

    2012-01-01

    therapy). To this end, we here present the results of a Monte Carlo simulation study with DOSRZnrc that investigated the influence of field and detector size for small 6 MV photon beams. The study focusses on doses averaged over the volume of the detector rather than point doses.The ratio of volume...... averaged doses to water (D¯W) and alanine (D¯det) was found to be approximately 1.025 for most situations studied, and a constant ratio is likely to be representative for many applications in radiation therapy. However, D¯W/D¯det was found to be as low as 0.9908 ± 0.0037 in situations where one might...... expect significant deviations from charged particle equilibrium (i.e. at shallow depths and when the field size was smaller than the range of the secondary electrons). These effects therefore need consideration when finite-size alanine dosimeters are used under such conditions....

  6. Measurement and diagnosis system for 1.2 MV repetitive pulsed power source

    International Nuclear Information System (INIS)

    Li Yawei; Deng Jianjun; Xie Min; Feng Zongming; Liu Yuntao; Ma Chenggang

    2010-01-01

    In order to analyze the discharge performance and improve the design of the power system, a set of measurement and diagnosis system for the 1.2 MV repetitive pulsed power source, which supplies the drive power for a high power microwave source, has been designed by studying the high-voltage, high-current testing technology, data acquisition, signal processing, fault diagnosis, virtual instruments and electromagnetic compatibility technology, etc. A resistive-capacitive divider and a Rogowski coil are adopted in measurement; ADLINK corporation's PXI chips are used in data acquisition; data transmission system, condition monitoring and data analysis are developed by LabVIEW. This system can realize on-line monitoring and data analysis for the repetitive pulsed power source. (authors)

  7. Active and reactive power support of MV distribution systems using battery energy storage

    DEFF Research Database (Denmark)

    Wang, Jiawei; Hashemi Toghroljerdi, Seyedmostafa; You, Shi

    2017-01-01

    shaving and voltage support service from the perspective of Distribution System Operators (DSOs). An active power support algorithm is implemented and the effects of various load profiles as well as different Photovoltaic (PV) penetration scenarios on the operation of BESS and the optimal BESS converter......Adoption of Battery Energy Storage Systems (BESSs) for provision of grid services is increasing. This paper investigates the applications of BESS for the grid upgrade deferral and voltage support of Medium Voltage (MV) distribution systems. A BESS is modelled in Matlab/Simulink to perform peak load...... size for peak load shaving are investigated. The BESS annual lifetime degradation is also estimated using a rainflow counting algorithm. A reactive power support algorithm embedded with Q-U droop control is proposed in order to reduce the voltage drop in a part of 10 kV distribution network of Nordhavn...

  8. Effect of dental metal in 10 MV X-ray beam therapy

    International Nuclear Information System (INIS)

    Mimura, Seiichi; Mikami, Yasutaka; Inamura, Keiji; Tahara, Seiji; Nagaya, Isao; Egusa, Tomomi; Nakagiri, Yoshitada; Sugita, Katsuhiko.

    1991-01-01

    We have often encountered patients with dental metal when employing the 10 MV X-ray beam therapy for head and neck tumors, and felt it important to investigate the effect of dental metal in relation to dose distribution. The absorbed dose rose abruptly in the vicinity of the metal reaching an interface value equal to 150% of the dose within the acrylic phantom. These results showed that an overdose occurred about 5 mm from the metal. We also learned that the overdose can be avoided by using a 5-mm thick tissue equivalent material. Six patients with dental metal were treated after first covering their metal with a 5-mm thick mouthpiece. No radiation stomatitis caused by the metal was observed in any of these cases. (author)

  9. Pulse radiolysis with (sub) nanosecond time resolution using a 3 MV electron accelerator

    International Nuclear Information System (INIS)

    Luthjens, L.H.

    1986-01-01

    In this thesis the development of equipment for pulse radiolysis is described and the application of the technique to time-resolved measurements of the fluorescence emission of excited states formed after irradiation of some alkanes is dealt with. A review is given of the development of the pulsed 3MV Van de Graaf electron accelerator for the generation of subnanosecond electron beam pulses and of the development of the equipment for optical detection as accomplished by the author. The initial stage of a further development for shorter pulses and higher time resolution is briefly discussed. A collection of papers on the development of apparatus and a collection of papers dealing with the results obtained from measurements of the fluorescence of excited states, formed by the recombination of electrons and ions in irradiated alkanes such as cyclohexane and the decalines, are included. (Auth.)

  10. Development of isodose curves for A 6 mv x-ray beam

    Energy Technology Data Exchange (ETDEWEB)

    Hidaytalla, Lamya Abbas [Department of Physics, Faculty of Science, University of Khartoum, Khartoum (Sudan)

    1994-08-01

    In this thesis radiation distribution of 6 Mv x-ray beam in a water phantom is developed. The method is based on a simple empirical equation and the assumption that the x-ray source is a point source. This leads to a simple equation for the calculation and plotting of the isodose curves. the charts obtained for two fields, 6*6 and 12*12 cm{sup 2} show good agreement with the previous data used in the isotope and radiation centre, Khartoum hospital. It is suggested that further development should be carried out by writing a computer program for all the fields. (Author) 14 refs. , 9 tabs. , 34 figs. Also available from the Department of Physics, Faculty of Science, University of Khartoum, Khartoum (SD)

  11. Anode sputtering characteristics of the Berkeley 2.5 MV source

    International Nuclear Information System (INIS)

    Gavin, B.

    1975-10-01

    An investigation was made of a number of parameters affecting the performance of the SuperHILAC 2.5 MV Adam injector source. The description will emphasize anode sputtered materials, and will discuss in some detail calcium and gold ion production. Parameters varied include electrode geometry, support gas type and electrode bias, to optimize beam intensity and electrode consumption. A factor of three improvement with high n + gold ions appears evident with a new displaced electrode geometry. The source is operated in cold mode, is pulsed and operates usually at less than 0.6 amperes average current. Under these conditions source life has been measured to be sixteen hours at 25 percent duty factor when generating calcium ions with neon support gas

  12. Photonuclear processes in the treatment room and patient during radiation therapy with 50 MV photons

    Energy Technology Data Exchange (ETDEWEB)

    Gudowska, Irena [Karolinska Inst., Stockholm (Sweden). Dept. of Radiation Physics

    1997-10-01

    The objectives of this project were to determine the level of photoneutron radiation around the MM50 Racetrack Microtron at Karolinska Hospital, operating in different modes and to evaluate the photonuclear absorbed dose to the treated volume during therapy with a 50 MV photon beam. The photoneutron radiation has been studied both using a {sup 235}U fission chamber and by computer simulation. The estimated neutron equivalent dose due to accelerator produced neutrons delivered to the tissues inside and outside the treatment volume do not exceed the recommended values. However, there is a potential risk that the sensitive tissues (lens of the eye and gonads), outside the treatment volume, can receive a dose of about 300-500 mSv per photon treatment course of 60 Gy with a slight increase for secondary malignancies. 47 refs, 15 figs, 6 tabs.

  13. Design and experimental research on a self-magnetic pinch diode under MV

    Institute of Scientific and Technical Information of China (English)

    Pengfei ZHANG; Yang HU; Jiang SUN; Yan SONG; Jianfeng SUN; Zhiming YAO; Peitian CONG; Mengtong QIU; Aici QIU

    2018-01-01

    A self-magnetic pinch diode (SMPD) integrating an anode foil-reinforced electron beam pinch focus and a small high-dose x-ray spot output was designed and optimized.An x-ray focal spot measuring system was developed in accordance with the principle of pinhole imaging.The designed SMPD and the corresponding measuring system were tested under ~MV,with 1.75 × 2 mm2 oval x-ray spots (AWE defined) and forward directed dose 1.6 rad at 1 m.Results confirmed that the anode foil can significantly strengthen the electron beam pinch focus,and the focal spot measuring system can collect clear focal spot images.This finding indicated that the principle and method are feasible.

  14. Performance tests of a 1.6-MV Van de Graaff accelerator of tandem type, 1

    International Nuclear Information System (INIS)

    Yano, Syukuro; Nakajima, Tadashi; Kitamura, Akira

    1981-01-01

    Experimental studies on the performance of a 1.6-MV Van de Graaff accelerator of tandem type, Model 5SDH of NEC, are reported. Two kinds of performance test were conducted. First, it was successfully demonstrated that the beam currents observed at two positions, 1m and 7m apart from a switching magnet in the +15 0 beam line, exceed the values accepted for our test according to the specifications of NEC. Second, it turned out that the beam transmission could be kept maximum by selecting the optimum number of live sections in the lower energy accelerator tube depending on terminal voltage. Moreover, the plot of optimum insulating SF 6 gas pressure against terminal voltage prepared by us is found very useful for efficient operation of the 5SDH accelerator. (author)

  15. High-voltage terminal test of a test stand for a 1-MV electrostatic accelerator

    Science.gov (United States)

    Park, Sae-Hoon; Kim, Yu-Seok

    2015-10-01

    The Korea Multipurpose Accelerator Complex has been developing a 300-kV test stand for a 1-MV electrostatic accelerator ion source. The ion source and accelerating tube will be installed in a high-pressure vessel. The ion source in the high-pressure vessel is required to have a high reliability. The test stand has been proposed and developed to confirm the stable operating conditions of the ion source. The ion source will be tested at the test stand to verify the long-time operating conditions. The test stand comprises a 300-kV high-voltage terminal, a battery for the ion-source power, a 60-Hz inverter, 200-MHz radio-frequency power supply, a 5-kV extraction power supply, a 300-kV accelerating tube, and a vacuum system. The results of the 300-kV high-voltage terminal tests are presented in this paper.

  16. Optimization of the Compensation of a Meshed MV Network by a Modified Genetic Algorithm

    DEFF Research Database (Denmark)

    Nielsen, Hans; Paar, M.; Toman, P.

    2007-01-01

    The article discusses the utilization of a modified genetic algorithm (GA) for the optimization of the shunt compensation in meshed and radial MV distribution networks. The algorithm looks for minimum costs of the network power losses and minimum capital and operating costs of applied capacitors......, all of this under limitations specified by a multicriteria penalization function. The parallel evolution branches in the GA are used for the purpose of the optimization accelaration. The application of this GA has been implemented in Matlab. The evaluation part of the GA implementation is based...... on the steady-state analysis using a linear one-line diagram model of a power network. The results of steady-state solutions are compared with the results from the DIgSILENT PowerFactory program. Its practical applicability is demonstrated on examples of 22 kV and meshed overhead distribution networks....

  17. Dielectric-breakdown tests of water at 6 MV

    Directory of Open Access Journals (Sweden)

    W. A. Stygar

    2009-01-01

    Full Text Available We have conducted dielectric-breakdown tests on water subject to a single unipolar pulse. The peak voltages used for the tests range from 5.8 to 6.8 MV; the effective pulse widths range from 0.60 to 1.1  μs; and the effective areas tested range from 1.8×10^{5} to 3.6×10^{6}  cm^{2}. The tests were conducted on water-insulated coaxial capacitors. The two electrodes of each capacitor have outer and inner radii of 99 and 56 cm, respectively. Results of the tests are consistent with predictions of the water-dielectric-breakdown relation developed in [Phys. Rev. ST Accel. Beams 9, 070401 (2006PRABFM1098-440210.1103/PhysRevSTAB.9.070401].

  18. Managing high penetration of renewable energy in MV grid by electric vehicle storage

    DEFF Research Database (Denmark)

    Kordheili, Reza Ahmadi; Bak-Jensen, Birgitte; Pillai, Jayakrishnan Radhakrishna

    2015-01-01

    This paper proposes an intelligent algorithm for dealing with high penetration of renewable energy sources (RESs) in the medium voltage by intelligently managing electric vehicles (EVs), as one of the grid flexible loads. The MV grid used in this work is a CIGRE benchmark grid. Different...... residential and industrial loads are considered in this grid. The connection of medium voltage wind turbines to the grid is investigated. The solar panels in this study are residential panels. Also, EVs are located among the buses with residential demand. The study is done for different winter and summer...... scenarios, considering typical load profiles in Denmark. Different scenarios have been studied with different penetration level of RESs in the grid. The results show the capability of the proposed algorithm to reduce voltage deviations among the grid buses, as well as to increase the RES penetration...

  19. Photonuclear processes in the treatment room and patient during radiation therapy with 50 MV photons

    International Nuclear Information System (INIS)

    Gudowska, Irena

    1997-01-01

    The objectives of this project were to determine the level of photoneutron radiation around the MM50 Racetrack Microtron at Karolinska Hospital, operating in different modes and to evaluate the photonuclear absorbed dose to the treated volume during therapy with a 50 MV photon beam. The photoneutron radiation has been studied both using a 235 U fission chamber and by computer simulation. The estimated neutron equivalent dose due to accelerator produced neutrons delivered to the tissues inside and outside the treatment volume do not exceed the recommended values. However, there is a potential risk that the sensitive tissues (lens of the eye and gonads), outside the treatment volume, can receive a dose of about 300-500 mSv per photon treatment course of 60 Gy with a slight increase for secondary malignancies. 47 refs, 15 figs, 6 tabs

  20. Experimental dosimetric evaluation in pelvis phantom, subjected to prostate radiation therapy protocol at 15 MV Linac

    Energy Technology Data Exchange (ETDEWEB)

    Matos, Andrea Silva Dias de; Campos, Tarcisio P.R., E-mail: campos@nuclear.ufmg.b [Universidade Federal de Minas Gerais (DEN/UFMG), Belo Horizonte, MG (Brazil). Dept. de Engenharia Nuclear; Dias, Humberto Galvao [Centro de Radioterapia Hospital Luxemburgo, Belo Horizonte, MG (Brazil)

    2011-07-01

    Among the existing malignant neoplasia, the prostate cancer is most common among male population. Due to its high incidence and morbidity, there is a need for investment in advanced technology for better treatment associated with research and social mobilization to prevent the disease. As an efficient method of treatment for such tumor, radiation teletherapy brings favorable results for the patient, particularly when the cancer is diagnosed early. There are, however, the needs to assess the absorbed doses that reach the prostate in the radiation protocols in order to certify the treatment efficacy. The present research goal is to obtain the profile of absorbed dose distributed in a synthetic prostate on male pelvis phantom following a standard radiation therapy protocol. The methodology makes use of a NRI made phantom and a 15MV Linac accelerator. This phantom has anthropomorphic and anthropometric features containing the major internal organs, including bone, prostate, intestine, and bladder. The exposition was made in a 15 MV linear accelerator taken the isocenter in four fields as a 'BOX' of opposing beams. The dosimetry was prepared using GafChromic EBT type 2 radiochromic film and calibration in a solid water phantom. The radiochromic films were digitized on the Microtek Scan Maker 6900XL model scanner operating in the transmission mode and optical density readings based on RGB mode in the computer program Imagedig. The absorbance readings were performed in the spectrophotometer SP-220 mark BIOSPECTRO obtaining calibration curves generated by the collected data. The results reproduce the dose distribution generated in two orthogonal radiochromic films positioned onto the synthetic prostate. Discussions regarding the characteristics of the phantom and methods of irradiation in relation to the achieved dose profile will be addressed. (author)

  1. Transient beam dynamics in the Lawrence Berkeley Laboratory 2 MV injector

    International Nuclear Information System (INIS)

    Henestroza, E.

    1996-01-01

    A driver-scale injector for the heavy ion fusion accelerator project has been built at LBL. This machine has exceeded the design goals of high voltage (above 2 MV), high current (more than 0.8 A of K + ) and low normalized emittance (less than 1 π mm mrad). The injector consists of a 750 keV gun pre-injector followed by an electrostatic quadrupole accelerator which provides strong (alternating gradient) focusing for the space-charge-dominated beam, and simultaneously accelerates the ions to 2 MeV. A matching section is being built to match the beam to the electrostatic accelerator ELISE. The gun pre-injector, designed to hold up to 1 MV with minimal breakdown risks, consists of a hot alumino-silicate source with a large curved emitting surface surrounded by a thick ''extraction electrode''. During beam turn-on the voltage at the source is biased from a negative potential, enough to reverse the electric field on the emitting surface and to avoid emission, to a positive potential to start extracting the beam; it stays constant for about 1 μs, and is reversed to turn off the emission. Since the Marx voltage applied on the accelerating quadrupoles and the main pre-injector gap is a long, constant pulse (several microseconds), the transient behavior is dominated by the extraction pulser voltage time profile. The transient longitudinal dynamics of the beam in the injector was simulated by running the particle-in-cell codes GYMNOS and WARP3D in a time-dependent mode. The generalization and its implementation is WARP3D of a method proposed by Lampel and Tiefenback to eliminate transient oscillations in a one-dimensional planar diode will be presented. (orig.)

  2. Experimental dosimetric evaluation in pelvis phantom, subjected to prostate radiation therapy protocol at 15 MV Linac

    International Nuclear Information System (INIS)

    Matos, Andrea Silva Dias de; Campos, Tarcisio P.R.

    2011-01-01

    Among the existing malignant neoplasia, the prostate cancer is most common among male population. Due to its high incidence and morbidity, there is a need for investment in advanced technology for better treatment associated with research and social mobilization to prevent the disease. As an efficient method of treatment for such tumor, radiation teletherapy brings favorable results for the patient, particularly when the cancer is diagnosed early. There are, however, the needs to assess the absorbed doses that reach the prostate in the radiation protocols in order to certify the treatment efficacy. The present research goal is to obtain the profile of absorbed dose distributed in a synthetic prostate on male pelvis phantom following a standard radiation therapy protocol. The methodology makes use of a NRI made phantom and a 15MV Linac accelerator. This phantom has anthropomorphic and anthropometric features containing the major internal organs, including bone, prostate, intestine, and bladder. The exposition was made in a 15 MV linear accelerator taken the isocenter in four fields as a 'BOX' of opposing beams. The dosimetry was prepared using GafChromic EBT type 2 radiochromic film and calibration in a solid water phantom. The radiochromic films were digitized on the Microtek Scan Maker 6900XL model scanner operating in the transmission mode and optical density readings based on RGB mode in the computer program Imagedig. The absorbance readings were performed in the spectrophotometer SP-220 mark BIOSPECTRO obtaining calibration curves generated by the collected data. The results reproduce the dose distribution generated in two orthogonal radiochromic films positioned onto the synthetic prostate. Discussions regarding the characteristics of the phantom and methods of irradiation in relation to the achieved dose profile will be addressed. (author)

  3. Ultrafast static and diffusion-controlled electron transfer at Ag 29 nanocluster/molecular acceptor interfaces

    KAUST Repository

    Aly, Shawkat Mohammede; AbdulHalim, Lina G.; Besong, Tabot M.D.; Soldan, Giada; Bakr, Osman; Mohammed, Omar F.

    2015-01-01

    Efficient absorption of visible light and a long-lived excited state lifetime of silver nanoclusters (Ag29 NCs) are integral properties for these new clusters to serve as light-harvesting materials. Upon optical excitation, electron injection at Ag29 NC/methyl viologen (MV2+) interfaces is very efficient and ultrafast. Interestingly, our femto- and nanosecond time-resolved results demonstrate clearly that both dynamic and static electron transfer mechanisms are involved in photoluminescence quenching of Ag29 NCs. © 2016 The Royal Society of Chemistry.

  4. Ultrafast static and diffusion-controlled electron transfer at Ag 29 nanocluster/molecular acceptor interfaces

    KAUST Repository

    Aly, Shawkat Mohammede

    2015-10-29

    Efficient absorption of visible light and a long-lived excited state lifetime of silver nanoclusters (Ag29 NCs) are integral properties for these new clusters to serve as light-harvesting materials. Upon optical excitation, electron injection at Ag29 NC/methyl viologen (MV2+) interfaces is very efficient and ultrafast. Interestingly, our femto- and nanosecond time-resolved results demonstrate clearly that both dynamic and static electron transfer mechanisms are involved in photoluminescence quenching of Ag29 NCs. © 2016 The Royal Society of Chemistry.

  5. Investigation of the accuracy of MV radiation isocentre calculations in the Elekta cone-beam CT software XVI

    DEFF Research Database (Denmark)

    Zimmermann, S. J.; Rowshanfarzad, P.; Ebert, M. A.

    2015-01-01

    ) and the radiation field centre (RFC) is calculated. A software package was developed for accurate calculation of the linac isocentre position. This requires precise determination of the position of the ball bearing and the RFC. Results: Data were acquired for 6 MV, 18 MV and flattening filter free (FFF) 6 MV FFF...... radiation isocentre prior to routine use of the cone-beam CT system. The isocentre determination method used in the XVI software is not available to users. The aim of this work is to perform an independent evaluation of the Elekta XVI 4.5 software for isocentre verification with focus on the robustness...... iView GT software. Two images were acquired at each cardinal gantry angle (-180o, -90o , 0o, 90o) at two opposing collimator angles. The images were exported to the conebeam CT software XVI 4.5 where the difference between the ball bearing position in the XYZ-room coordinates (IEC61217...

  6. A fiducial detection algorithm for real-time image guided IMRT based on simultaneous MV and kV imaging.

    Science.gov (United States)

    Mao, Weihua; Riaz, Nadeem; Lee, Louis; Wiersma, Rodney; Xing, Lei

    2008-08-01

    The advantage of highly conformal dose techniques such as 3DCRT and IMRT is limited by intrafraction organ motion. A new approach to gain near real-time 3D positions of internally implanted fiducial markers is to analyze simultaneous onboard kV beam and treatment MV beam images (from fluoroscopic or electronic portal image devices). Before we can use this real-time image guidance for clinical 3DCRT and IMRT treatments, four outstanding issues need to be addressed. (1) How will fiducial motion blur the image and hinder tracking fiducials? kV and MV images are acquired while the tumor is moving at various speeds. We find that a fiducial can be successfully detected at a maximum linear speed of 1.6 cm/s. (2) How does MV beam scattering affect kV imaging? We investigate this by varying MV field size and kV source to imager distance, and find that common treatment MV beams do not hinder fiducial detection in simultaneous kV images. (3) How can one detect fiducials on images from 3DCRT and IMRT treatment beams when the MV fields are modified by a multileaf collimator (MLC)? The presented analysis is capable of segmenting a MV field from the blocking MLC and detecting visible fiducials. This enables the calculation of nearly real-time 3D positions of markers during a real treatment. (4) Is the analysis fast enough to track fiducials in nearly real time? Multiple methods are adopted to predict marker positions and reduce search regions. The average detection time per frame for three markers in a 1024 x 768 image was reduced to 0.1 s or less. Solving these four issues paves the way to tracking moving fiducial markers throughout a 3DCRT or IMRT treatment. Altogether, these four studies demonstrate that our algorithm can track fiducials in real time, on degraded kV images (MV scatter), in rapidly moving tumors (fiducial blurring), and even provide useful information in the case when some fiducials are blocked from view by the MLC. This technique can provide a gating signal or

  7. Investigation of the accuracy of MV radiation isocentre calculations in the Elekta cone-beam CT software XVI

    DEFF Research Database (Denmark)

    Lynggaard Riis, Hans; Moltke, Lars N; Zimmermann, S. J.

    2016-01-01

    Accurate determination of the megavoltage (MV) radiation isocentre of a linear accelerator (linac) is an important task in radiotherapy. The localization of the MV radiation isocentre is crucial for correct calibration of the in-room lasers and the cone-beam CT scanner used for patient positioning...... orientation or the phantom asymmetry in the longitudinal direction do not appear to cause the discrepancy. The main cause of the differences could not be clearly identified. However, it is our opinion that the commercial software delivered by the linac manufacturer should be improved to reach better stability...

  8. Environmental protection congress M-V. Use of regenerative energy sources and hydrogen technology 2010. Proceedings; Klimaschutzkongress M-V. Nutzung regenerativer Energiequellen und Wasserstofftechnik 2010. Tagungsband

    Energy Technology Data Exchange (ETDEWEB)

    Luschtinetz, Thomas; Lehmann, Jochen (eds.)

    2010-07-01

    Within the Environmental Protection Congress M-V from 4th to 6th November, 2010, in Stralsund (Federal Republic of Germany) the following lectures were held: (1) Conception for climate production in Stralsund (Matthias Ahlhaus); (2) Regenerative energies in the power land North Rhine Westfalia (Frank-Michael Baumann); (3) Heat storages - Supporting pillars of the comprehensive utilization of regenerative ideas (Juergen Buehl); (4) Logistics analysis of rice straw for power exploitations and potential green house gas mitigations - An example in Thailand (Mitra Kami Delivand); (5) The Heatpipe-Reformer registered - Development, start-up and testing (Andreas Dengel); (6) The ecological cost of the use of biomass of plants for energy production (Bohdan Deptula); (7) Hydrogen as fuel and energy storage: Strategy and implementation in NIP (Oliver Ehret); (8) The ORGA test: Development of a testing procedure for a practical evaluation of the fermenter biology and NaWaRo biogas plants (Nils Engler); (9) Large scale integration of offshore wind power through wind farm clusters (Alejandro J. Gesino); (10) NANOSITR - Healt, coldness and electricity from one biomass vessel (Bodo Gross); (11) OPTISTRAHL - A two-stage washer unit for biogas (Bodo Gross); (12) Innovation development for renewable energies (Bernward Janzing); (12) Strategic action options for energy supply utilities at renewable energies (Patrick Kemnitz); (13) Hydrogen - An option for a sustainable storage of wind power (Martin Kleimaier); (14) Small parabolic trough power plants - Actual technology and outlook (Joachim Krueger); (15) A photocatalytic generation of hydrogen: Efficient iron-based water reduction catalysts (Sebastian Losse); (16) Environmental assessment of municipal solid waste management in Sri Lanka and India in a life cycle perspective (Samanthi Nirmala M. Menikpura); (17) High temperature low sag conductors in power system with wind power farms (Olgierd Malyszka); (18) Wind

  9. Histone Lysine Methylation and Neurodevelopmental Disorders

    Directory of Open Access Journals (Sweden)

    Jeong-Hoon Kim

    2017-06-01

    Full Text Available Methylation of several lysine residues of histones is a crucial mechanism for relatively long-term regulation of genomic activity. Recent molecular biological studies have demonstrated that the function of histone methylation is more diverse and complex than previously thought. Moreover, studies using newly available genomics techniques, such as exome sequencing, have identified an increasing number of histone lysine methylation-related genes as intellectual disability-associated genes, which highlights the importance of accurate control of histone methylation during neurogenesis. However, given the functional diversity and complexity of histone methylation within the cell, the study of the molecular basis of histone methylation-related neurodevelopmental disorders is currently still in its infancy. Here, we review the latest studies that revealed the pathological implications of alterations in histone methylation status in the context of various neurodevelopmental disorders and propose possible therapeutic application of epigenetic compounds regulating histone methylation status for the treatment of these diseases.

  10. miRNAting control of DNA methylation

    Indian Academy of Sciences (India)

    miRNAting control of DNA methylation. ASHWANI ... function and biological process ... Enrichment analysis of the genes methylated by DRM2 for molecular function and biological ... 39(3), June 2014, 365–380, © Indian Academy of Sciences.

  11. Bacterial production of methyl ketones

    Energy Technology Data Exchange (ETDEWEB)

    Beller, Harry R.; Goh, Ee-Been

    2017-01-31

    The present invention relates to methods and compositions for increasing production of methyl ketones in a genetically modified host cell that overproduces .beta.-ketoacyl-CoAs through a re-engineered .beta.-oxidation pathway and overexpresses FadM.

  12. Electronic transport in methylated fragments of DNA

    International Nuclear Information System (INIS)

    Almeida, M. L. de; Oliveira, J. I. N.; Lima Neto, J. X.; Gomes, C. E. M.; Fulco, U. L.; Albuquerque, E. L.; Freire, V. N.; Caetano, E. W. S.; Moura, F. A. B. F. de; Lyra, M. L.

    2015-01-01

    We investigate the electronic transport properties of methylated deoxyribonucleic-acid (DNA) strands, a biological system in which methyl groups are added to DNA (a major epigenetic modification in gene expression), sandwiched between two metallic platinum electrodes. Our theoretical simulations apply an effective Hamiltonian based on a tight-binding model to obtain current-voltage curves related to the non-methylated/methylated DNA strands. The results suggest potential applications in the development of novel biosensors for molecular diagnostics

  13. Electronic transport in methylated fragments of DNA

    Energy Technology Data Exchange (ETDEWEB)

    Almeida, M. L. de; Oliveira, J. I. N.; Lima Neto, J. X.; Gomes, C. E. M.; Fulco, U. L., E-mail: umbertofulco@gmail.com; Albuquerque, E. L. [Departamento de Biofísica e Farmacologia, Universidade Federal do Rio Grande do Norte, 59072-970 Natal-RN (Brazil); Freire, V. N. [Departamento de Física, Universidade Federal do Ceará, 60455-760 Fortaleza, CE (Brazil); Caetano, E. W. S. [Instituto Federal de Educação, Ciência e Tecnologia do Ceará, 60040-531 Fortaleza, CE (Brazil); Moura, F. A. B. F. de; Lyra, M. L. [Instituto de Física, Universidade Federal de Alagoas, 57072-900 Maceió-AL (Brazil)

    2015-11-16

    We investigate the electronic transport properties of methylated deoxyribonucleic-acid (DNA) strands, a biological system in which methyl groups are added to DNA (a major epigenetic modification in gene expression), sandwiched between two metallic platinum electrodes. Our theoretical simulations apply an effective Hamiltonian based on a tight-binding model to obtain current-voltage curves related to the non-methylated/methylated DNA strands. The results suggest potential applications in the development of novel biosensors for molecular diagnostics.

  14. TU-E-BRA-05: Reverse Geometry Imaging with MV Detector for Improved Image Resolution.

    Science.gov (United States)

    Ganguly, A; Abel, E; Sun, M; Fahrig, R; Virshup, G; Star-Lack, J

    2012-06-01

    Thick pixilated scintillators can offer significant improvements in quantum efficiency over phosphor screen megavoltage (MV) detectors. However spatial resolution can be compromised due to the spreading of light across pixels within septa. Of particular interest are the lower energy x-ray photons and associated light photons that produce higher image contrast but are stopped near the scintillator entrance surface. They suffer the most scattering in the scintillator prior to detection in the photodiodes. Reversing the detector geometry, so that the incident x-ray beam passes through the photodiode array into the scintillator, allows the light to scatter less prior to detection. This also reduces the Swank noise since now higher and lower energy x-ray photons tend to produce similar electronic signals. In this work, we present simulations and measurements of detector MTF for the conventional/forward and reverse geometries to demonstrate this phenomenon. A tabletop system consisting of a Varian CX1 1MeV linear accelerator and a modified Varian Paxscan4030 with the readout electronics moved away from the incident the beam was used. A special holder was used to press a 2.5W×5.0L×2.0Hcm 3 pixellated Cesium Iodide (CsI:Tl) scintillator array on to the detector glass. The CsI array had a pitch of 0.784mm with plastic septa between pixels and the photodiode array pitch was 0.192 mm. The MTF in the forward and reverse geometries was measured using a 0.5mm thick Tantalum slanted edge. Geant4-based Monte Carlo simulations were performed for comparison. The measured and simulated MTFs matched to within 3.4(±3.7)% in the forward and 4.4(±1.5)% in reverse geometries. The reverse geometry MTF was higher than the forward geometry MTF at all spatial frequencies and doubled to .25 at 0.3lp/mm. A novel method of improving the image resolution at MV energies was demonstrated. The improvements should be more pronounced with increased scintillator thickness. Funding support provided

  15. Improved 36Cl performance at the ASTER HVE 5 MV accelerator mass spectrometer national facility

    International Nuclear Information System (INIS)

    Finkel, R.; Arnold, M.; Aumaître, G.; Benedetti, L.; Bourlès, D.; Keddadouche, K.; Merchel, S.

    2013-01-01

    The HVE 5 MV ASTER AMS national facility at CEREGE was accepted in 2007. Since then we have continued to optimize performance for 36 Cl. Cl-36 analyses use AgCl, a Cs negative ion sputter source, Ar stripping to +5 in the terminal of the Tandetron™ accelerator at 5 MV and a silicon nitride post-acceleration stripper foil to enhance suppression of 36 S relative to 36 Cl. The major challenges to obtaining the desired performance for Earth science applications are ion source memory, mass fractionation effects, 36 S isobar suppression and sensitivity. Redesign of the SO110 ion source by HVE to change the size of the aperture and the shape of cathode significantly reduced ion source memory to less than ∼0.1%, a level that can be compensated for by matching standards to samples. We observe small systematic drifts in 35 Cl/ 37 Cl ratios over time, the source of which is not yet determined. Measurement of standards indicates that this effect limits the precision of 35 Cl/ 37 Cl ratio determination to about 2%. 36 S is suppressed in several ways. First, the sample chemistry has been designed to reduce S to low levels. Second, cathodes are constructed of low-S nickel, enabling direct target loading without the use of AgBr pre-packing. Third, a post-acceleration Si 3 N 4 stripper foil differentially absorbs energy from 36 Cl and 36 S. A subsequent electrostatic deflector is then able to suppress 36 S by a factor of ∼240 relative to 36 Cl. Differential energy loss in the detector further suppresses 36 S by about 10 −4 , for an overall suppression factor of 4 × 10 −7 . 36 S count rates are typically equivalent to a background 36 Cl/Cl of ∼10 −15 . At typical 35 Cl currents of ∼20 μA Cl 5+ samples with 36 Cl/ 35 Cl of 6 × 10 −14 can be measured to ±5% statistical uncertainty with 1 h of analysis time. Typical machine blanks have 36 Cl/Cl ∼2 × 10 −15 .

  16. Calibration of a MOSFET detection system for 6-MV in vivo dosimetry

    International Nuclear Information System (INIS)

    Scalchi, Paolo; Francescon, P.

    1998-01-01

    Purpose: Metal oxide semiconductor field-effect transistor (MOSFET) detectors were calibrated to perform in vivo dosimetry during 6-MV treatments, both in normal setup and total body irradiation (TBI) conditions. Methods and Materials: MOSFET water-equivalent depth, dependence of the calibration factors (CFs) on the field sizes, MOSFET orientation, bias supply, accumulated dose, incidence angle, temperature, and spoiler-skin distance in TBI setup were investigated. MOSFET reproducibility was verified. The correlation between the water-equivalent midplane depth and the ratio of the exit MOSFET readout divided by the entrance MOSFET readout was studied. MOSFET midplane dosimetry in TBI setup was compared with thermoluminescent dosimetry in an anthropomorphic phantom. By using ionization chamber measurements, the TBI midplane dosimetry was also verified in the presence of cork as a lung substitute. Results: The water-equivalent depth of the MOSFET is about 0.8 mm or 1.8 mm, depending on which sensor side faces the beam. The field size also affects this quantity; Monte Carlo simulations allow driving this behavior by changes in the contaminating electron mean energy. The CFs vary linearly as a function of the square field side, for fields ranging from 5 x 5 to 30 x 30 cm 2 . In TBI setup, varying the spoiler-skin distance between 5 mm and 10 cm affects the CFs within 5%. The MOSFET reproducibility is about 3% (2 SD) for the doses normally delivered to the patients. The effect of the accumulated dose on the sensor response is negligible. For beam incidence ranging from 0 deg. to 90 deg. , the MOSFET response varies within 7%. No monotonic correlation between the sensor response and the temperature is apparent. Good correlation between the water-equivalent midplane depth and the ratio of the exit MOSFET readout divided by the entrance MOSFET readout was found (the correlation coefficient is about 1). The MOSFET midplane dosimetry relevant to the anthropomorphic phantom

  17. Beam pulsing in the 2.5 MV - VdG accelerator

    International Nuclear Information System (INIS)

    Kirsch, Robert; Tromeur, William; Champelovier, Yves; Miguet, Michel

    2003-01-01

    This is a technical report describing the work of beam pulsing of the 2.5 MV Van de Graaff. The objective is to supply the 2.5 MV VdG with gold clusters (Au n ) events by events (ion by ion), with a time synchronization signal with a precision of a coupled of nano seconds. The technical specifications are as follows: deflection plates in the present installation: l - length of plates = 245 mm; d - plates' separation = 16 mm; Lp - plate separation / D2 = 1812 mm (center of horizontal deflection) and 1547 mm center of vertical deflection; Lc - distance between collimator = 2020 mm; D1, D2 φ of collimators = 50 to 100 μm; Acceptance with 50 and 100 μm = ± 2.5 x 10 -2 mrad (= 3/1000 angle). The time of presence inside collimator equals the time necessary for passing from + Vc to - Vc, where Vc is the voltage necessary to deflect the beam from + 2.5 x 10 -2 to - 2.5 x 10 -2 mrad. The contents of the report is the following: I. Geometry of pulsing system. 1. Method; 2. Obtaining short times of beam presence; 3. Amplitude of ion deflection; 4. Au n cluster velocities; II. Control electronics and high voltages; 5. Defining the guiding module of the low voltage section; 6. Further details in Annex II under the definition of high voltage supply; 7. Definition of high voltage supply. For details see Annex III under III PVX - 4130 modulator for high voltage pulsed commutation. III. PVX - 4130 modulator for high voltage pulsed switching; 8. Limitations; 9. Dynamical characteristics; 10. Connection circuitry and operation; 11. Measurements; 12. Power for high voltage supplies; 13. Power requirement for pulsation; IV. Electromagnetic spurious effects; 14. Evidencing; 15. Suppression; Annex I - PVX-4130 modulator; 16. Measurements; 17. PVX-4130 documentation; Annex II - IPNL control and switching module; 18.I. Technical specifications; 19. II. Conception; 20. III. Adjustments; 21. IV. Layout; 22. V. Results; Annex III - High voltage supply; 23. Technical specifications for

  18. Methylation sensitive amplified polymorphism (MSAP) reveals that ...

    African Journals Online (AJOL)

    ajl yemi

    2011-12-19

    Dec 19, 2011 ... Key words: Salt stress, alkali stress, Gossypium hirsutum L., DNA methylation, methylation sensitive amplified polymorphism (MSAP). INTRODUCTION. DNA methylation is one of the key epigenetic mecha- nisms among eukaryotes that can modulate gene expression without the changes of DNA sequence.

  19. miRNAting control of DNA methylation

    Indian Academy of Sciences (India)

    DNA methylation is a type of epigenetic modification where a methyl group is added to the cytosine or adenine residue of a given DNA sequence. It has been observed that DNA methylation is achieved by some collaborative agglomeration of certain proteins and non-coding RNAs. The assembly of IDN2 and its ...

  20. Using ferrite to improve directional sensing for pulse travelling in MV power cables with two inductive sensors

    NARCIS (Netherlands)

    Li, Y.; Wouters, P.A.A.F.; Wagenaars, P.; Wielen, van der P.C.J.M.; Steennis, E.F.

    2013-01-01

    Inductive sensors are widely used for detection of high frequency signal, e.g. from partial discharge (PD) activity. A single inductive sensor, installed in a ring main unit (RMU) in a medium-voltage (MV) system, is not able to judge the direction of the signal origin. A method to determine its

  1. Terahertz field enhancement to the MV/cm regime in a tapered parallel plate waveguide

    DEFF Research Database (Denmark)

    Iwaszczuk, Krzysztof; Andryieuski, Andrei; Lavrinenko, Andrei

    2012-01-01

    measurement of the field strength at the output of the waveguide. Field enhancement factors greater than 20 are demonstrated and record-high field strengths of > 1.4 MV/cm are reached. We find an excellent agreement between the two independent methods of field measurement and a numerical 3D full...

  2. Development of 66 kV/6.9 kV 2 MV A prototype HTS power transformer

    International Nuclear Information System (INIS)

    Bohno, T.; Tomioka, A.; Imaizumi, M.; Sanuki, Y.; Yamamoto, T.; Yasukawa, Y.; Ono, H.; Yagi, Y.; Iwadate, K.

    2005-01-01

    We have developed the technology of the producing a HTS magnet for the power transformer. Three subjects have been mainly studied, high voltage technologies, large current and low AC loss technologies and sub-cooling system technologies to establish the technology of 66 kV/6.9 kV 10 MV A class HTS power transformer. In order to verify the validity of elemental technologies, such as high voltage technologies, large current and low AC loss technologies and sub-cooling system technologies, single-phase 2 MV A class 66 kV/6.9 kV prototype HTS transformer was manufactured and tested. In the load loss (AC loss) measurement, it was obtained that the measured value of 633 W was almost corresponding to the calculated value of 576 W at the rated operation of 2 MV A. Moreover, the breakdown was not found all voltage withstand test. These test results indicate that elemental technologies were established for the development of 66 kV/6.9 kV 10 MV A class HTS power transformer

  3. Investigation of beam transmission in A 9SDH-2 3.0 MV NEC pelletron tandem accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Deoli, Naresh T.; Kummari, Venkata C.; Pacheco, Jose L.; Duggan, Jerome L.; Glass, Gary A.; McDaniel, Floyd D.; Reinert, Tilo; Rout, Bibhudutta; Weathers, Duncan L. [Ion Beam Modification And Analysis Laboratory, Department of Physics, University of North Texas, Denton, Texas 76203 (United States)

    2013-04-19

    Electrostatic tandem accelerators are widely used to accelerate ions for experiments in materials science such as high energy ion implantation, materials modification, and analyses. Many applications require high beam current as well as high beam brightness at the target; thus, maximizing the beam transmission through such electrostatic accelerators becomes important. The Ion Beam Modification and Analysis Laboratory (IBMAL) at University of North Texas is equipped with four accelerators, one of which is a 9SDH-2 3.0 MV National Electrostatic Corporation (NEC) Pelletron Registered-Sign tandem accelerator. The tandem accelerator is equipped with three ion sources: one radio frequency-He ion source (Alphatross) and two ion sources of Cs-sputter type, the SNICS II (Source of Negative Ions by Cesium Sputtering) and a Cs-sputter source for trace-element accelerator based mass spectrometry. This work presents a detailed study of the beam transmission of hydrogen, silicon, and silver ions through the accelerator using the SNICS ion source with injection energies ranging from 20 keV to 70 keV. The beam transmission is quantified for three different terminal voltages: 1.5 MV, 2.0 MV and 2.5 MV. For a given terminal voltage, it has been found that beam transmission is strongly dependent on the ion source injector potential. Details of experiments and data analysis are presented.

  4. Variations in 6MV x-ray radiotherapy build-up dose with treatment distance

    International Nuclear Information System (INIS)

    Butson, M.J.; Illawarra Cancer Care Centre, Wollongong, NSW; Cheung, T.; Yu, P.K.N.

    2003-01-01

    Dose in the build up region for high energy x-rays produced by a medical linear accelerator is affected by the x-ray source to patient surface distance (SSD). The use of isocentric treatments whereby the tumour is positions 100cm from the source means that depending of the depth of the tumour and the size of the patient, the SSD can vary from distances of 80cm to 100cm. To achieve larger field sizes, the SSD can also be extended out to 120cm at times. Results have shown that open fields are not significantly affected by SSD changes with deviations in percentage dose being less than 4% of maximum dose for SSD's from 80cm to 120cm SSD. With the introduction of beam modifying devices such as Perspex blocking trays, the effects are significant with a deviation of up to 22% measured at 6MV energy with a 6mm Perspex tray for SSD's from 80cm to 120cm. These variations are largest at the skin surface and reduce with depth. The use of a multi leaf collimator for blocking removes extra skin dose caused by the Perspex block trays with decreasing SSD. Copyright (2003) Australasian College of Physical Scientists and Engineers in Medicine

  5. Analytical calculation of central-axis dosimetric data for a dedicated 6-MV radiosurgery linear accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Yang, James N.; Pino, Ramiro [Department of Radiation Physics, Unit 94, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030 (United States); Department of Radiology, Baylor College of Medicine and Methodist Hospital, Houston, Texas 77030 (United States)

    2008-10-15

    Narrow beams are extensively used in stereotactic radiosurgery. The accuracy of treatment planning dose calculation depends largely on how well the dosimetric data are measured during the machine commissioning. Narrow beams are characterized by the lack of lateral electronic equilibrium. The lateral electronic disequilibrium in the radiation field and detector's finite size are likely to compromise the accuracy in dose measurements in these beams. This may have a profound impact on outcome in patients who undergo stereotactic radiosurgery. To confirm the measured commissioning data for a dedicated 6-MV linear accelerator-based radiosurgery system, we developed an analytical model to calculate the narrow photon beam central-axis dose. This model is an extension of a previously reported method of Nizin and Mooij for the calculation of the absorbed dose under lateral electronic disequilibrium conditions at depth of d{sub max} or greater. The scatter factor and tissue-maximum ratio were calculated for narrow beams using the parametrized model and compared to carefully measured results for the same beams. For narrow beam radii ranging from 0.2 to 1.5 cm, the differences between the analytical and measured scatter factors were no greater than 1.4%. In addition, the differences between the analytical and measured tissue-maximum ratios were within 3.3% for regions greater than the maximum dose depth. The estimated error of this analytical calculation was less than 2%, which is sufficient to validate measurement results.

  6. Shot reproducibility of the self-magnetic-pinch diode at 4.5 MV

    Directory of Open Access Journals (Sweden)

    Nichelle Bennett

    2014-05-01

    Full Text Available In experiments conducted at Sandia National Laboratories’ RITS-6 accelerator, the self-magnetic-pinch diode exhibits significant shot-to-shot variability. Specifically, for identical hardware operated at the same voltage, some shots exhibit a catastrophic drop in diode impedance. A study is underway to identify sources of shot-to-shot variations which correlate with diode impedance collapse. The scope of this report is limited to data collected at 4.5-MV peak voltage and sources of variability which occur away from the diode, such as sheath electron emission and trajectories, variations in pulsed power, load and transmission line alignment, and different field shapers. We find no changes in the transmission line hardware, alignment, or hardware preparation methods which correlate with impedance collapse. However, in classifying good versus poor shots, we find that there is not a continuous spectrum of diode impedance behavior but that the good and poor shots can be grouped into two distinct impedance profiles. In poor shots, the sheath current in the load region falls from 16%–30% of the total current to less than 10%. This result will form the basis of a follow-up study focusing on the variability resulting from diode physics.

  7. Dosimetric characterization of the 18-MV photon beam from the Siemens Mevatron 77 linear accelerator

    International Nuclear Information System (INIS)

    Palta, J.R.; Meyer, J.A.; Hogstrom, K.R.

    1984-01-01

    A comprehensive set of dosimetric measurements has been made on the Mevatron 77.80.67 18-MV photon beam. Percentage depth dose, dose in the buildup region, field size dependence of output, transmission through lead, tray attenuation, and isodose curves for the open and wedged fields were measured using an ionization chamber in water and polystyrene phantoms. These dosimetric measurements sufficiently characterized the beam to permit clinical use. The depth dose at 10-cm depth for a 10 x 10 cm 2 field at 100-cm source-to-skin distance (SSD) is 80.9%, which meets design specifications. Central axis depth-dose data were fitted to within 0.5% by a set of polynomial equations utilizing a two-dimensional linear regression analysis. Tissue--maximum ratios calculated from depth-dose data agree with measured data to within 2%. Output differences as large as 2.5% were measured for rectangular fields depending on which collimator jaws defined the long dimension of the field. The field size dependence of output was fit to within +- 0.1% by a linear regression. The half-value thickness of the beam was measured to be 13 mm of lead

  8. Effect of transverse magnetic fields on a simulated in-line 6 MV linac

    International Nuclear Information System (INIS)

    St Aubin, J; Fallone, B G; Steciw, S

    2010-01-01

    The effects of a transverse magnetic field on an in-line side-coupled 6 MV linear accelerator are given. The results are directly applicable to a linac-MR system used for real-time image guided adaptive radiotherapy. Our previously designed end-to-end linac simulation incorporated the results from the axisymmetric 2D electron gun program EGN2w. However, since the magnetic fields being investigated are non-axisymmetric in nature for the work presented here, the electron gun simulation was performed using OPERA-3d/SCALA. The simulation results from OPERA-3d/SCALA showed excellent agreement with previous results. Upon the addition of external magnetic fields to our fully 3D linac simulation, it was found that a transverse magnetic field of 6 G resulted in a 45 ± 1% beam loss, and by 14 G, no electrons were incident on the target. Transverse magnetic fields on the linac simulation produced a highly asymmetric focal spot at the target, which translated into a 13% profile asymmetry at 6 G. Upon translating the focal spot with respect to the target coordinates, profile symmetry was regained at the expense of a lateral shift in the dose profiles. It was found that all points in the penumbra failed a 1%/1 mm acceptance criterion for fields between 4 and 6 G. However, it was also found that the lateral profile shifts were corrected by adjusting the jaw positions asymmetrically.

  9. Acceleration of cluster and molecular ions by TIARA 3 MV tandem accelerator

    CERN Document Server

    Saitoh, Y; Tajima, S

    2000-01-01

    We succeeded in accelerating molecular and cluster ions (B sub 2 sub - sub 4 , C sub 2 sub - sub 1 sub 0 , O sub 2 , Al sub 2 sub - sub 4 , Si sub 2 sub - sub 4 , Cu sub 2 sub - sub 3 , Au sub 2 sub - sub 3 , LiF, and AlO) to MeV energies with high-intensity beam currents by means of a 3 MV tandem accelerator in the TIARA facility. These cluster ions were generated by a cesium sputter-type negative ion source. We tested three types of carbon sputter cathodes in which graphite powder was compressed with different pressures. The pressure difference affected the generating ratio of clusters generated to single atom ions extracted from the source and it appeared that the high-density cathode was suitable. We also investigated the optimum gas pressure for charge exchange in the tandem high-voltage terminal. Clusters of larger size tend to require lower pressure than do smaller ones. In addition, we were able to obtain doubly charged AlO molecular ions. (authors)

  10. Effect of transverse magnetic fields on a simulated in-line 6 MV linac

    Science.gov (United States)

    St. Aubin, J.; Steciw, S.; Fallone, B. G.

    2010-08-01

    The effects of a transverse magnetic field on an in-line side-coupled 6 MV linear accelerator are given. The results are directly applicable to a linac-MR system used for real-time image guided adaptive radiotherapy. Our previously designed end-to-end linac simulation incorporated the results from the axisymmetric 2D electron gun program EGN2w. However, since the magnetic fields being investigated are non-axisymmetric in nature for the work presented here, the electron gun simulation was performed using OPERA-3d/SCALA. The simulation results from OPERA-3d/SCALA showed excellent agreement with previous results. Upon the addition of external magnetic fields to our fully 3D linac simulation, it was found that a transverse magnetic field of 6 G resulted in a 45 ± 1% beam loss, and by 14 G, no electrons were incident on the target. Transverse magnetic fields on the linac simulation produced a highly asymmetric focal spot at the target, which translated into a 13% profile asymmetry at 6 G. Upon translating the focal spot with respect to the target coordinates, profile symmetry was regained at the expense of a lateral shift in the dose profiles. It was found that all points in the penumbra failed a 1%/1 mm acceptance criterion for fields between 4 and 6 G. However, it was also found that the lateral profile shifts were corrected by adjusting the jaw positions asymmetrically.

  11. Dosimetric properties of dysprosium doped lithium borate glass irradiated by 6 MV photons

    Science.gov (United States)

    Ab Rasid, A.; Wagiran, H.; Hashim, S.; Ibrahim, Z.; Ali, H.

    2015-07-01

    Undoped and dysprosium doped lithium borate glass system with empirical formula (70-x) B2O3-30 Li2O-(x) Dy2O3 (x=0.1, 0.3, 0.5, 0.7, 1.0 mol%) were prepared using the melt-quenching technique. The dosimetric measurements were performed by irradiating the samples to 6 MV photon beam using linear accelerator (LINAC) over a dose range of 0.5-5.0 Gy. The glass series of dysprosium doped lithium borate glass produced the best thermoluminescence (TL) glow curve with the highest intensity peak from sample with 1.0 mol% Dy2O3 concentration. Minimum detectable dose was detected at 2.24 mGy, good linearity of regression coefficient, high reproducibility and high sensitivity compared to the undoped glass are from 1.0 mol% dysprosium doped lithium borate glass. The results indicated that the series of dysprosium doped lithium glasses have a great potential to be considered as a thermoluminescence dosimetry (TLD).

  12. Virtual instrument automation of ion channeling setup for 1.7 MV tandetron accelerator

    International Nuclear Information System (INIS)

    Suresh, K.; Sundaravel, B.; Panigrahi, B.K.; Nair, K.G.M.; Viswanathan, B.

    2004-01-01

    A virtual instrument based automated ion channeling experimental setup has been developed and implemented in a 1.7 MV tandetron accelerator. Automation of the PC based setup is done using a windows based virtual instrument software allowing the setup to be easily ported between different computer operating systems. The virtual instrument software has been chosen to achieve quick and easy development of versatile, multi-purpose user friendly graphical interface for carrying out channeling experiments. The software has been modular designed to provide independent control of the stepper motors for fixing the sample at any user defined orientation, running and on-line display of azimuthal and tilt angular scans, auto storage of the angular scan data. Using this automated setup, the crystallographic axis of the sample can be aligned with the incident ion beam rapidly minimizing the beam damages to the sample. A standard single crystalline GaAs(100) has been characterized with this set up using 2 MeV He ++ ion beam. The crystalline quality (χ min ) and channeling half angle (ψ 1sol2 ) are measured to be 3.7% and 0.48 deg., respectively, which are close to the theoretical values. Salient features, working principles and design details of the automated setup are discussed in this paper

  13. Investigations of shot reproducibility for the SMP diode at 4.5 MV.

    Energy Technology Data Exchange (ETDEWEB)

    Bennett, Nichelle [National Security Technologies, LLC, Las Vegas, NV (United States); Crain, Marlon D. [National Security Technologies, LLC, Las Vegas, NV (United States); Droemer, Darryl W. [National Security Technologies, LLC, Las Vegas, NV (United States); Gignac, Raymond Edward [National Security Technologies, LLC, Las Vegas, NV (United States); Lare, Gregory A. [National Security Technologies, LLC, Las Vegas, NV (United States); Molina, Isidro [National Security Technologies, LLC, Las Vegas, NV (United States); Obregon, Rafael [National Security Technologies, LLC, Las Vegas, NV (United States); Smith, Chase C. [National Security Technologies, LLC, Las Vegas, NV (United States); Wilkins, Frank Lee [National Security Technologies, LLC, Las Vegas, NV (United States); Welch, Dale Robert [Voss Scientific, LLC, Albuquerque, NM (United States); Cordova, Steve Ray; Gallegos, M.; Johnston, Mark D.; Kiefer, Mark Linden; Leckbee, Joshua J.; Nielsen, Daniel Scott; Oliver, Bryan Velten; Renk, Timothy Jerome; Romero, Tobias; Webb, Timothy Jay; Ziska, Derek Raymond

    2013-11-01

    In experiments conducted on the RITS-6 accelerator, the SMP diode exhibits sig- ni cant shot-to-shot variability. Speci cally, for identical hardware operated at the same voltage, some shots exhibit a catastrophic drop in diode impedance. A study is underway to identify sources of shot-to-shot variations which correlate with diode impedance collapse. To remove knob emission as a source, only data from a shot series conducted with a 4.5-MV peak voltage are considered. The scope of this report is limited to sources of variability which occur away from the diode, such as power ow emission and trajectory changes, variations in pulsed power, dustbin and transmission line alignment, and di erent knob shapes. We nd no changes in the transmission line hardware, alignment, or hardware preparation methods which correlate with impedance collapse. However, in classifying good versus poor shots, we nd that there is not a continuous spectrum of diode impedance behavior but that the good and poor shots can be grouped into two distinct impedance pro les. This result forms the basis of a follow-on study focusing on the variability resulting from diode physics. 3

  14. Optimization of a rod pinch diode radiography source at 2.3 MV

    International Nuclear Information System (INIS)

    Menge, P.R.; Johnson, D.L.; Maenchen, J.E.; Rovang, D.C.; Oliver, B.V.; Rose, D.V.; Welch, D.R.

    2003-01-01

    Rod pinch diodes have shown considerable capability as high-brightness flash x-ray sources for penetrating dynamic radiography. The rod pinch diode uses a small diameter (0.4-2 mm) anode rod extended through a cathode aperture. When properly configured, the electron beam born off of the aperture edge can self-insulate and pinch onto the tip of the rod creating an intense, small x-ray source. Sandia's SABRE accelerator (2.3 MV, 40 Ω, 70 ns) has been utilized to optimize the source experimentally by maximizing the figure of merit (dose/spot diameter2) and minimizing the diode impedance droop. Many diode parameters have been examined including rod diameter, rod length, rod material, cathode aperture diameter, cathode thickness, power flow gap, vacuum quality, and severity of rod-cathode misalignment. The configuration producing the greatest figure of merit uses a 0.5 mm diameter gold rod, a 6 mm rod extension beyond the cathode aperture (diameter=8 mm), and a 10 cm power flow gap to produce up to 3.5 rad (filtered dose) at 1 m from a 0.85 mm x-ray on-axis spot (1.02 mm at 3 deg. off axis). The resultant survey of parameter space has elucidated several physics issues that are discussed

  15. Using of beam spoilers in linear accelerators with photons of 10 MV

    International Nuclear Information System (INIS)

    Sansogne, R.; Palacios, V.; Arbiser, S.

    1998-01-01

    This work come along of the necessity to utilize an unique High-Energy Electron Linear Accelerator (10 MV) for radiant treatments which require higher doses in the surface levels of tissue. It is analyzed the interposition of acrylic degraders (spoilers) in the beam, especially for opposed and parallel fields in the cases of head and neck. It was analyzed the possible combinations of the following parameters: 1) Field sizes defined at isocenter (100 cm) 6 x 6 cm 2 , 8 x 8 cm 2 and 10 x 10 cm 2 ; 2) Surface-spoiler distance (DSS) of 4, 7 and 10 cm; 3) Spoilers with different thickness 1.1 and 1.5 cm. It was observed a displacement of the maximum dose toward the surface, and an increase in the percentile doses in the build-up zone when the spoiler is nearing and/or increasing its thickness. It is verified that the use of spoilers, support the symmetry and plane of the beam inside of the clinically acceptable margins. When the results obtained are analyzed then it is proposed as a calculation method to incorporate an attenuation factor. (Author)

  16. A dose-response curve for biodosimetry from a 6 MV electron linear accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Lemos-Pinto, M.M.P.; Cadena, M.; Santos, N.; Fernandes, T.S.; Borges, E.; Amaral, A., E-mail: marcelazoo@yahoo.com.br [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Departamento de Energia Nuclear

    2015-10-15

    Biological dosimetry (biodosimetry) is based on the investigation of radiation-induced biological effects (biomarkers), mainly dicentric chromosomes, in order to correlate them with radiation dose. To interpret the dicentric score in terms of absorbed dose, a calibration curve is needed. Each curve should be constructed with respect to basic physical parameters, such as the type of ionizing radiation characterized by low or high linear energy transfer (LET) and dose rate. This study was designed to obtain dose calibration curves by scoring of dicentric chromosomes in peripheral blood lymphocytes irradiated in vitro with a 6 MV electron linear accelerator (Mevatron M, Siemens, USA). Two software programs, CABAS (Chromosomal Aberration Calculation Software) and Dose Estimate, were used to generate the curve. The two software programs are discussed; the results obtained were compared with each other and with other published low LET radiation curves. Both software programs resulted in identical linear and quadratic terms for the curve presented here, which was in good agreement with published curves for similar radiation quality and dose rates. (author)

  17. A study on tissue compensator thickness ratio and an application for 4MV X-rays

    International Nuclear Information System (INIS)

    Kim, Young Bum; Kwon, Young Ho; Jung, Hee Young; Kim, You Hyun

    1996-01-01

    A radiation beam incident on irregular or sloping surface produces an inhomogeneity of absorbed dose. The use of a tissue compensator can partially correct this dose inhomogeneity. The tissue compensator should be made based on experimentally measured thickness ratio. The thickness ratio depends on beam energy, distance from the tissue compensator to the surface of patient, field size, treatment depth, tissue deficit and other factors. In this study, the thickness ratio was measured for various field size of 5cm x 5cm, 10cm x 10cm, 15cm x 15cm, 20 x 20cm for 4MV X-ray beams. The distance to the compensator from the X-ray target was fixed, 49cm, and measurement depth was 3, 5, 7, 9 cm. For each measurement depth, the tissue deficit was changed from 0 to(measurement depth-1)cm by 1cm increment. As a result, thickness ratio was decreased according to field size and tissue deficit was increased. Use of a representative thickness ratio for tissue compensator, there was 10% difference of absorbed dose but use of a experimentally measured thickness ratio for tissue compensator, there was 2% difference of absorbed dose. Therefore, it can be concluded that the tissue compensator made by experimentally measured thickness ratio can produce good distribution with acceptable inhomogeneity and such tissue compensator can be effectively applied to clinical radiotherapy.

  18. Dosimetry of a Small-Animal Irradiation Model using a 6 MV Linear Accelerator

    International Nuclear Information System (INIS)

    Fitch, F. Moran; Martinez-Davalos, A.; Garcia-Garduno, O. A.

    2010-01-01

    A custom made rat-like phantom was used to measure dose distributions using a 6 MV linear accelerator. The phantom has air cavities that simulate the lungs and cylindrical inserts that simulate the backbone. The calculated dose distributions were obtained with the BrainScan v.5.31 TPS software. For the irradiation two cases were considered: (a) near the region where the phantom has two air cavities that simulate the lungs, and (b) with an entirely uniform phantom. The treatment plan consisted of two circular cone arcs that imparted a 500 cGy dose to a simulated lesion in the backbone. We measured dose distributions using EBT2 GafChromic film and an Epson Perfection V750 scanner working in transmission mode. Vertical and horizontal profiles, isodose curves from 50 to 450 cGy, dose and distance to agreement (DTA) histograms and Gamma index were obtained to compare the dose distributions using DoseLab v4.11. As a result, these calculations show very good agreement between calculated and measured dose distribution in both cases. With a 2% 2 mm criteria 100% of the points pass the Gamma test for the uniform case, while 98.9% of the points do it for the lungs case.

  19. The M/V Selendang Ayu commercial fisheries work group process

    International Nuclear Information System (INIS)

    DeCola, E.; Robertson, T.; Pearson, L.; Dietrick, L.; Folley, G.

    2006-01-01

    The process used to form and operate the Selendang Ayu Fisheries Work Group was discussed. The M/V Selendang Ayu ran aground and broke apart near Unalaska Island, Alaska in December 2004, causing immediate concern to nearby commercial fisheries and seafood processors. The work group, which was formed less than 2 weeks after the initial spill, was modeled after other Alaska work groups and consisted of experts in environmental health, fisheries biology and oceanography. Its task was to facilitate communication between fishery managers and spill responders to identify risk-reducing measures and to minimize impacts to fisheries in Alaska. In support of Alaska's zero tolerance policy toward any contamination of food processed in Alaska, the working group conducted water quality sampling in and around Unalaska Island from December 2004 though March 2005. Information was gathered regarding fishery opening and closing dates, geographic extent of fisheries, gear and vessel types, seawater circulation systems, fish processing operations, vessel transit routes and other considerations related to the potential exposure of vessels, gear or seafood to oil. This paper described the different pathways that commercial fish species may be exposed to spilled oil, along with the major fish species at risk. One small fishery closure was enacted. The working group was successful in ensuring that major commercial fisheries for snow crab, pollock, halibut and other species were successfully conducted during the spill, with all loads undergoing mandatory seafood inspections. Seafood products were not contaminated and market prices remained stable. 15 refs., 6 tabs., 4 figs

  20. Plutonium measurements on the 1 MV AMS system at the Centro Nacional de Aceleradores (CNA)

    International Nuclear Information System (INIS)

    Chamizo, Elena; Enamorado, Santiago Miguel; Garcia-Leon, Manuel; Suter, Martin; Wacker, Lukas

    2008-01-01

    Plutonium isotopes have been recently added to the list of radionuclides that can be measured with the new generation of compact AMS facilities. In this paper we present first experimental results concerning the development of the plutonium AMS technique at 680 kV on the 1 MV AMS system at the Centro Nacional de Aceleradores (CNA) in Sevilla, Spain. This is the first compact AMS machine designed and manufactured by High Voltage Engineering Europa. As we demonstrate, the obtained backgrounds for 239,240 Pu, of about 10 6 atoms, and the 239 Pu/ 238 U mass suppression factor, in the range of 10 -9 , compare to the ones achieved on other AMS facilities. With the measurement of reference materials provided by the International Atomic Energy Agency (IAEA-375, IAEA-Soil-6, IAEA-381) and samples already studied on the 600 kV compact ETH/PSI AMS system at Zuerich, we show that the CNA system can be perfectly used for the routine measurement of plutonium isotopes at environmental levels.

  1. Beam Extraction for 1-MV Electrostatic Accelerator at the 300 kV Test Stand

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sae-Hoon; Kim, Yu-Seok [Dongguk University, Seoul (Korea, Republic of); Kwon, Hyeok-Jung; Cho, Yong-Sub [KOMAC, Gyeongju (Korea, Republic of)

    2015-05-15

    The Korea Multipurpose Accelerator Complex (KOMAC) has been developing a 300-kV test stand for a 1-MV electrostatic accelerator ion source. The ion source in the high-pressure vessel is required to have a high reliability. The test stand has been proposed and developed to confirm the stable operating conditions of the ion source. The ion source will be tested at the test stand to verify the long-time operating conditions. The test stand comprises a 300-kV high-voltage terminal, a battery for the ion-source power, a 60-Hz inverter, 200-MHz RF power, a 5-kV extraction power supply, a 300-kV accelerating tube, and a vacuum system. A beam extraction experiment for the test stand was performed, and the beam current was measured using a faraday cup in the chamber. A beam extraction results for the RF ion source will be presented. Beam extraction from the RF ion source of the test stand is verified by measuring the beam current with a faraday cup in the chamber. Thus far NI Labview, PLC and faraday cup have been used to measure the beam current. The OPC server is useful for monitoring the PLC values. The average beam current of (a), (b) and (c) shown in figure 2 are 110.241µA, 105.8597µA and 103.5278µA respectively.

  2. H(10) due to radiation scattered in a 6 MV Linac for tomotherapy

    International Nuclear Information System (INIS)

    Vega C, H. R.; Esparza H, A.; Garcia R, M. G.; Reyes R, E.; Hernandez A, L.; Rivera, T.

    2017-10-01

    In order to determine the environmental equivalent dose (H(10)), due to the radiation that is dispersed over the body of a patient, 100 thermoluminescent dosimeters (TLD) around 6 MV TomoLINAC were used. The characteristics of the tomotherapy have the disadvantage that the shielding of the bunker increases considerably and for its design validated parameters are used for the conventional Linacs. In order to determine H(10) due to scattered radiation, measurements were made in the vicinity of the isocenter, while the 6 MeV photon beam was applied on a phantom. Also, TLDs were placed on the walls of the bunker that remained for 7 days, where approximately 50 patients were treated per day. At points close to the isocenter, the H(10) has an angular distribution caused by the phantom shape. In the bunker walls the highest H(10) was observed in the primary barriers. In the labyrinth, the impact of the scattered radiation was observed when measuring a greater value of the environmental equivalent dose in the wall furthest from the isocenter compared to the point located closest to it. (Author)

  3. Structural shielding design of a 6 MV flattening filter free linear accelerator: Indian scenario

    Directory of Open Access Journals (Sweden)

    Bibekananda Mishra

    2017-01-01

    Full Text Available Detailed structural shielding of primary and secondary barriers for a 6 MV medical linear accelerator (LINAC operated with flattening filter (FF and flattening filter free (FFF modes are calculated. The calculations have been carried out by two methods, one using the approach given in National Council on Radiation Protection (NCRP Report No. 151 and the other based on the monitor units (MUs delivered in clinical practice. Radiation survey of the installations was also carried out. NCRP approach suggests that the primary and secondary barrier thicknesses are higher by 24% and 26%. respectively, for a LINAC operated in FF mode to that of a LINAC operated in both FF and FFF modes with an assumption that only 20% of the workload is shared in FFF mode. Primary and secondary barrier thicknesses calculated from MUs delivered on clinical practice method also show the same trend and are higher by 20% and 19%, respectively, for a LINAC operated in FF mode to that of a LINAC operated in both FF and FFF modes. Overall, the barrier thickness for a LINAC operated in FF mode is higher about 20% to that of a LINAC operated in both FF and FFF modes.

  4. Structural Shielding Design of a 6 MV Flattening Filter Free Linear Accelerator: Indian Scenario.

    Science.gov (United States)

    Mishra, Bibekananda; Selvam, T Palani; Sharma, P K Dash

    2017-01-01

    Detailed structural shielding of primary and secondary barriers for a 6 MV medical linear accelerator (LINAC) operated with flattening filter (FF) and flattening filter free (FFF) modes are calculated. The calculations have been carried out by two methods, one using the approach given in National Council on Radiation Protection (NCRP) Report No. 151 and the other based on the monitor units (MUs) delivered in clinical practice. Radiation survey of the installations was also carried out. NCRP approach suggests that the primary and secondary barrier thicknesses are higher by 24% and 26%. respectively, for a LINAC operated in FF mode to that of a LINAC operated in both FF and FFF modes with an assumption that only 20% of the workload is shared in FFF mode. Primary and secondary barrier thicknesses calculated from MUs delivered on clinical practice method also show the same trend and are higher by 20% and 19%, respectively, for a LINAC operated in FF mode to that of a LINAC operated in both FF and FFF modes. Overall, the barrier thickness for a LINAC operated in FF mode is higher about 20% to that of a LINAC operated in both FF and FFF modes.

  5. Variation in Depth Dose Data between Open and Wedge Fields for 6 MV X-Rays

    International Nuclear Information System (INIS)

    U, Hong; Ryu, M. S. Samuel; Park, In Kyu

    1989-01-01

    Central axis depth dose data for 6 MV X-rays, including tissue maximum ratios, were measured for wedge fields according to Tatcher equation. In wedge fields, the differences in magnitude which increased with depth, field size, and wedge thickness increased when compared with the corresponding open field data. However, phantom scatter correction factors for wedge fields differed less that 1% from the corresponding open field factors. The differences in central axis percent depth dose between two types of fields indicated beam hardening by the wedge filter. The deviation of percent depth doses and scatter correction factors between the effective wedge field and the nominal wedge field at same angle was negligible. The differences were less than 3.26% between the nominal or effective wedge fields and the open fields for percent depth doses to the depth 7cm in 6cm x 6cm field. For larger (10cm x 10cm) field size, however, the deviation of percent depth doses between the nominal or effective wedge fields and the open fields were greater-dosimetric errors were 3.56% at depth 7cm and nearly 5.30% at 12cm. We suggest that the percent depth doses of individual wedge and wedge transmission factors should be considered for the dose calculation or monitor setting in the treatment of deep seated tumor

  6. Verification of Radiation Isocenter on Linac Beam 6 MV using Computed Radiography

    Science.gov (United States)

    Irsal, Muhammad; Hidayanto, Eko; Sutanto, Heri

    2017-06-01

    Radiation isocenter is more important part of quality assurance for the linear accelerator (Linac) due to radiation isocenter is a main location in irradiation radiotherapy, isocenter can shift when the gantry and collimator rotation. In general, the radiation isocenter verification using a special film. This research was conducted radiation isocenter verification using computed radiography with digital image processing techniques. Image acquisition was done using the modalities of Linac 6 MV with star shot method is star-shaped beam due to rotation of the collimator, gantry and couch. Then do the delineation on each beam to determine the centroid and beam diameter. By the results of verification of radiation isocenter performed on collimator and the couch, it shows that the size diameter for rotational collimator is 0.632 mm and 0.458 mm for the couch. Based on AAPM report 40 about the size of the Linac radiation isocenter diameter used in this study is still in good condition and worth to be operated because the value of the radiation isocenter diameter is below 2 mm.

  7. The effect of earth fault protection practices on the frequency of outages in MV lines

    Energy Technology Data Exchange (ETDEWEB)

    Nikander, A; Lakervi, E [Tampere Univ. of Technology (Finland)

    1998-08-01

    In this presentation methods to improve extinction of the earth fault arc in the medium voltage network and reducing the short interruptions to customers are discussed. Earth fault distance estimation with permanent faults and determination of the key parameters of the compensated system are also studied. The three essential targets of this study are the following: An economic principle to improve fault arc extinction without a reclosing function is introduced. This novel compensation and protection practice is tested in one rural distribution network The selective functioning of the active current based earth fault protection was ensured by simulations and field tests. The influence of the star point impedance to the number of short interruptions is discussed. The determination of the key parameters of a compensated distribution system by utilizing the simulated and measured data is introduced. The earth fault distance estimation by rearranging the affected feeder into a closed ring over an adjacent feeder, is studied. This method was also tested in one rural distribution network. In the latter part of the chapter different methods to improve extinction of the earth fault arc in the medium voltage network and reducing the short interruptions to customers are discussed. The disadvantages of the rapid autoreclosing functions to customers are studied. Then the influence of star point impedance on the number of short interruptions is discussed. Finally, the feasibility of utilizing shunt circuit-breakers in the Finnish MV networks to extinguish the arc, is studied

  8. Detailed design of the RF source for the 1 MV neutral beam test facility

    International Nuclear Information System (INIS)

    Marcuzzi, D.; Palma, M. Dalla; Pavei, M.; Heinemann, B.; Kraus, W.; Riedl, R.

    2009-01-01

    In the framework of the EU activities for the development of the Neutral Beam Injector for ITER, the detailed design of the Radio Frequency (RF) driven negative ion source to be installed in the 1 MV ITER Neutral Beam Test Facility (NBTF) has been carried out. Results coming from ongoing R and D on IPP test beds [A. Staebler et al., Development of a RF-Driven Ion Source for the ITER NBI System, this conference] and the design of the new ELISE facility [B. Heinemann et al., Design of the Half-Size ITER Neutral Beam Source Test Facility ELISE, this conference] brought several modifications to the solution based on the previous design. An assessment was carried out regarding the Back-Streaming positive Ions (BSI+) that impinge on the back plates of the ion source and cause high and localized heat loads. This led to the redesign of most heated components to increase cooling, and to different choices for the plasma facing materials to reduce the effects of sputtering. The design of the electric circuit, gas supply and the other auxiliary systems has been optimized. Integration with other components of the beam source has been revised, with regards to the interfaces with the supporting structure, the plasma grid and the flexible connections. In the paper the design will be presented in detail, as well as the results of the analyses performed for the thermo-mechanical verification of the components.

  9. The Study of Tissue Dose Perturbation by Air Cavity with 6MV Photon Beam

    International Nuclear Information System (INIS)

    Shin, Byung Chul; Yoo, Myung Jin; Moon, Chang Woo; Jeung, Tae Sig; Yum, Ha Yong

    1995-01-01

    Purpose : To determine the perturbation effect in the tissue downstream from surface layers of lesions located in the air/tumor-tissue interface of larynx using 6MV photon beam. Materials and Methods : Thermoluminescent dosimeters(TLDs). Were embedded at 3 measurement locations in slab no.7 of a humanoid phantom and exposed to forward and backward direction using various field sizes(4 X 4cm 2 - 15 X 15 cm 2 ). Results : At the air/tissue interface, forward dose perturbation factor(FDPF) is about 1.085 with 4 X 4 cm 2 , 1.05 with 7 X 7 cm 2 , 1.048 with 10 X 10 cm 2 , and 1.041 with 15 X 15 cm 2 . Backscatter dose perturbation factor(BDPF) is about 0.99 with 4 X 4 cm 2 , 0.981 with 7 X 7 cm 2 , 0.956 with 10 X 10 cm 2 and 0.97 with 15 X 15 cm 2 . Conclusion : FDPF is greater as field size is smaller. And FDPF is smaller as the distance is further from the air/tissue interface

  10. Technique and dosimetry for total body irradiation with an 8-MV linear accelerator

    International Nuclear Information System (INIS)

    Svahn-Tapper, G.; Nilsson, P.; Jonsson, C.; Alvegard, T.A.

    1987-01-01

    The aim of the study was to develop a method for calculation of the absorbed dose at an arbitrary point in the patient (adults and children). The method should be accurate but simple to use in clinical routine and it should as far as possible follow the recommendations by ICRU for conventional radiotherapy. An 8-MV linear accelerator is used with a diamond-shaped field and an isocentric technique at a focus-axis distance of 430 cm. The dose rate in an arbitrary point in the patient is calculated from the absorbed dose rate in dose maximum for a phantom size of 30 x 30 x 30 cm 3 in the TBI field, an inverse square law factor, the tissue-maximum ratio, an equivalent field size correction factor determined from the patient contour using the Clarkson method, a factor correcting for lack of backscattering material, an off-axis output correction factor, and a factor that corrects for off-axis variations in effective photon beam energy and for oblique beam penetration of the patient. A personal computer is used for the dose calculations. The formula was tested with TLD measurements in a RT Humanoid (adult) phantom and in a Pedo-RT Humanoid (child) phantom. In vivo dose measurements are also presented

  11. The insulation structure of the 1 MV transmission line for the ITER neutral beam injector

    International Nuclear Information System (INIS)

    De Lorenzi, A.; Grando, L.; Gobbo, R.; Pesavento, G.; Bettini, P.; Specogna, R.; Trevisan, F.

    2007-01-01

    The paper describes the studies and the tests for the development of the insulation structure of the 1 MV-50 A gas insulated (SF 6 ) line of the ITER NBI in the SinGap configuration characterized by two kinds of spacers: at least a couple of disk-shaped spacers, designed to be gas tight, and a larger number (several tens) of inner conductor post spacers. To this aim a test campaign has been carried out to assess the capability of standard epoxy spacers to withstand a high dc voltage with frequent short circuits, simulating the operational condition for the ITER NBI. Two computational tools, the first for the epoxy spacer shape optimization under electrostatic distribution and the other for the nonlinear time variant evolution of the electric field and surface charge, have been developed specifically for designing epoxy spacer under dc voltage stress. The results on the optimization of the disk spacer and on the electric field-surface charge time evolution of the post spacer are reported and discussed. The effects of the SF 6 radiation induced conductivity on the post spacer are also reported

  12. The insulation structure of the 1 MV transmission line for the ITER neutral beam injector

    Energy Technology Data Exchange (ETDEWEB)

    De Lorenzi, A. [Consorzio RFX, Associazione Euratom-Enea sulla Fusione, Corso Stati Uniti 4, I-35127 Padova (Italy)], E-mail: antonio.delorenzi@igi.cnr.it; Grando, L. [Consorzio RFX, Associazione Euratom-Enea sulla Fusione, Corso Stati Uniti 4, I-35127 Padova (Italy); Gobbo, R.; Pesavento, G. [DIE, Universita di Padova, Via Gradenigo 6A, I-35100 Padova (Italy); Bettini, P.; Specogna, R.; Trevisan, F. [DIEGM, Universita di Udine, Via delle Scienze 208, I-33100 Udine (Italy)

    2007-10-15

    The paper describes the studies and the tests for the development of the insulation structure of the 1 MV-50 A gas insulated (SF{sub 6}) line of the ITER NBI in the SinGap configuration characterized by two kinds of spacers: at least a couple of disk-shaped spacers, designed to be gas tight, and a larger number (several tens) of inner conductor post spacers. To this aim a test campaign has been carried out to assess the capability of standard epoxy spacers to withstand a high dc voltage with frequent short circuits, simulating the operational condition for the ITER NBI. Two computational tools, the first for the epoxy spacer shape optimization under electrostatic distribution and the other for the nonlinear time variant evolution of the electric field and surface charge, have been developed specifically for designing epoxy spacer under dc voltage stress. The results on the optimization of the disk spacer and on the electric field-surface charge time evolution of the post spacer are reported and discussed. The effects of the SF{sub 6} radiation induced conductivity on the post spacer are also reported.

  13. Development of a remote control console for the HHIRF 25-MV tandem accelerator

    International Nuclear Information System (INIS)

    Hasanul Basher, A.M.

    1991-09-01

    The CAMAC-based control system for the 25-MV Tandem Accelerator at HHIRF uses two Perkin-Elmer, 32-bit minicomputers: a message-switching computer and a supervisory computer. Two operator consoles are located on one of the six serial highways. Operator control is provided by means of a console CRT, trackball, assignable shaft encoders and meters. The message-switching computer transmits and receives control information on the serial highways. At present, the CRT pages with updated parameters can be displayed and parameters can be controlled only from the two existing consoles, one in the Tandem control room and the other in the ORIC control room. It has become necessary to expand the control capability to several other locations in the building. With the expansion of control and monitoring capability of accelerator parameters to other locations, the operators will be able to control and observe the result of the control action at the same time. Since the new control console will be PC-based, the existing page format will be changed. The PC will be communicating with the Perkin-Elmer through RS-232 and a communication software package. Hardware configuration has been established, a communication software program that reads the pages from the shared memory has been developed. In this paper, we present the implementation strategy, works completed, existing and new page format, future action plans, explanation of pages and use of related global variables, a sample session, and flowcharts

  14. A dose-response curve for biodosimetry from a 6 MV electron linear accelerator.

    Science.gov (United States)

    Lemos-Pinto, M M P; Cadena, M; Santos, N; Fernandes, T S; Borges, E; Amaral, A

    2015-10-01

    Biological dosimetry (biodosimetry) is based on the investigation of radiation-induced biological effects (biomarkers), mainly dicentric chromosomes, in order to correlate them with radiation dose. To interpret the dicentric score in terms of absorbed dose, a calibration curve is needed. Each curve should be constructed with respect to basic physical parameters, such as the type of ionizing radiation characterized by low or high linear energy transfer (LET) and dose rate. This study was designed to obtain dose calibration curves by scoring of dicentric chromosomes in peripheral blood lymphocytes irradiated in vitro with a 6 MV electron linear accelerator (Mevatron M, Siemens, USA). Two software programs, CABAS (Chromosomal Aberration Calculation Software) and Dose Estimate, were used to generate the curve. The two software programs are discussed; the results obtained were compared with each other and with other published low LET radiation curves. Both software programs resulted in identical linear and quadratic terms for the curve presented here, which was in good agreement with published curves for similar radiation quality and dose rates.

  15. Verification of Radiation Isocenter on Linac Beam 6 MV using Computed Radiography

    International Nuclear Information System (INIS)

    Irsal, Muhammad; Hidayanto, Eko; Sutanto, Heri

    2017-01-01

    Radiation isocenter is more important part of quality assurance for the linear accelerator (Linac) due to radiation isocenter is a main location in irradiation radiotherapy, isocenter can shift when the gantry and collimator rotation. In general, the radiation isocenter verification using a special film. This research was conducted radiation isocenter verification using computed radiography with digital image processing techniques. Image acquisition was done using the modalities of Linac 6 MV with star shot method is star-shaped beam due to rotation of the collimator, gantry and couch. Then do the delineation on each beam to determine the centroid and beam diameter. By the results of verification of radiation isocenter performed on collimator and the couch, it shows that the size diameter for rotational collimator is 0.632 mm and 0.458 mm for the couch. Based on AAPM report 40 about the size of the Linac radiation isocenter diameter used in this study is still in good condition and worth to be operated because the value of the radiation isocenter diameter is below 2 mm. (paper)

  16. A new ion beam facility based on a 3 MV Tandetron™ at IFIN-HH, Romania

    Science.gov (United States)

    Burducea, I.; Straticiuc, M.; Ghiță, D. G.; Moșu, D. V.; Călinescu, C. I.; Podaru, N. C.; Mous, D. J. W.; Ursu, I.; Zamfir, N. V.

    2015-09-01

    A 3 MV Tandetron™ accelerator system has been installed and commissioned at the "Horia Hulubei" National Institute for Physics and Nuclear Engineering - IFIN-HH, Măgurele, Romania. The main purpose of this machine is to strengthen applied nuclear physics research ongoing in our institute for more than four decades. The accelerator system was developed by High Voltage Engineering Europa B.V. (HVE) and comprises three high energy beam lines. The first beam line is dedicated to ion beam analysis (IBA) techniques: Rutherford Backscattering Spectrometry - RBS, Nuclear Reaction Analysis - NRA, Particle Induced X-ray and γ-ray Emission - PIXE and PIGE and micro-beam experiments - μ-PIXE. The second beam line is dedicated to high energy ion implantation experiments and the third beam line was designed mainly for nuclear cross-sections measurements used in nuclear astrophysics. A unique feature, the first time in operation at an accelerator facility is the Na charge exchange canal (CEC), which is used to obtain high intensity beams of He- of at least 3 μA. The results of the acceptance tests demonstrate the huge potential of this new facility in various fields, from IBA to radiation hardness studies and from medical or environmental applications to astrophysics. The main features of the accelerator are presented in this paper.

  17. Sources of electron contamination for the Clinac-35 25-MV photon beam

    International Nuclear Information System (INIS)

    Petti, P.L.; Goodman, M.S.; Sisterson, J.M.; Biggs, P.J.; Gabriel, T.A.; Mohan, R.

    1983-01-01

    A detailed Monte Carlo approach has been employed to investigate the sources of electron contamination for the 25-MV photon beam generated by Varian's Clinac-35. Three sources of contamination were examined: (a) the flattening filter and beam monitor chamber, (b) the fixed primary collimators downstream from the monitor chamber and the adjustable photon jaws, and (c) the air volume separating the treatment head from the observation point. Five source-to-surface distances (SSDs) were considered for a single field size, 28 cm in diameter at 80 cm SSD. It was found that for small SSDs (80-100 cm), the dominant sources of electron contamination were the flattening filter and the beam monitor chamber which accounted for 70% of the unwanted electrons. Thirteen percent of the remaining electrons originated in the downstream primary collimators and the photon jaws, and 17% were produced in air. At larger SSDs, the fraction of unwanted electrons originating in air increased. At 400 cm SSD, 61% of the contaminating electrons present in the beam were produced in air, 34% originated in the flattening filter and beam monitor chamber, and 5% were due to interactions in the fixed collimators downstream from the monitor chamber and the adjustable photon jaws. These calculated results are substantiated by recent experiments

  18. Identification of endometrial cancer methylation features using combined methylation analysis methods.

    Directory of Open Access Journals (Sweden)

    Michael P Trimarchi

    Full Text Available DNA methylation is a stable epigenetic mark that is frequently altered in tumors. DNA methylation features are attractive biomarkers for disease states given the stability of DNA methylation in living cells and in biologic specimens typically available for analysis. Widespread accumulation of methylation in regulatory elements in some cancers (specifically the CpG island methylator phenotype, CIMP can play an important role in tumorigenesis. High resolution assessment of CIMP for the entire genome, however, remains cost prohibitive and requires quantities of DNA not available for many tissue samples of interest. Genome-wide scans of methylation have been undertaken for large numbers of tumors, and higher resolution analyses for a limited number of cancer specimens. Methods for analyzing such large datasets and integrating findings from different studies continue to evolve. An approach for comparison of findings from a genome-wide assessment of the methylated component of tumor DNA and more widely applied methylation scans was developed.Methylomes for 76 primary endometrial cancer and 12 normal endometrial samples were generated using methylated fragment capture and second generation sequencing, MethylCap-seq. Publically available Infinium HumanMethylation 450 data from The Cancer Genome Atlas (TCGA were compared to MethylCap-seq data.Analysis of methylation in promoter CpG islands (CGIs identified a subset of tumors with a methylator phenotype. We used a two-stage approach to develop a 13-region methylation signature associated with a "hypermethylator state." High level methylation for the 13-region methylation signatures was associated with mismatch repair deficiency, high mutation rate, and low somatic copy number alteration in the TCGA test set. In addition, the signature devised showed good agreement with previously described methylation clusters devised by TCGA.We identified a methylation signature for a "hypermethylator phenotype" in

  19. A performance comparison of flat-panel imager-based MV and kV cone-beam CT

    International Nuclear Information System (INIS)

    Groh, B.A.; Siewerdsen, J.H.; Drake, D.G.; Wong, J.W.; Jaffray, D.A.

    2002-01-01

    The use of cone-beam computed tomography (CBCT) has been proposed for guiding the delivery of radiation therapy, and investigators have examined the use of both kilovoltage (kV) and megavoltage (MV) x-ray beams in the development of such CBCT systems. In this paper, the inherent contrast and signal-to-noise ratio (SNR) performance for a variety of existing and hypothetical detectors for CBCT are investigated analytically as a function of imaging dose and object size. Theoretical predictions are compared to the results of experimental investigations employing large-area flat-panel imagers (FPIs) at kV and MV energies. Measurements were performed on two different FPI-based CBCT systems: a bench-top prototype incorporating an FPI and kV x-ray source (100 kVp x rays), and a system incorporating an FPI mounted on the gantry of a medical linear accelerator (6 MV x rays). The SNR in volume reconstructions was measured as a function of dose and found to agree reasonably with theoretical predictions. These results confirm the theoretically predicted advantages of employing kV energy x rays in imaging soft-tissue structures found in the human body. While MV CBCT may provide a valuable means of correcting 3D setup errors and may offer an advantage in terms of simplicity of mechanical integration with a linear accelerator (e.g., implementation in place of a portal imager), kV CBCT offers significant performance advantages in terms of image contrast and SNR per unit dose for visualization of soft-tissue structures. The relatively poor SNR performance at MV energies is primarily a result of the low x-ray quantum efficiencies (∼a few percent or less) that are currently achieved with FPIs at high energies. Furthermore, kV CBCT with an FPI offers the potential of combined volumetric and radiographic/fluoroscopic imaging using the same device

  20. MethylMix 2.0: an R package for identifying DNA methylation genes.

    Science.gov (United States)

    Cedoz, Pierre-Louis; Prunello, Marcos; Brennan, Kevin; Gevaert, Olivier

    2018-04-14

    DNA methylation is an important mechanism regulating gene transcription, and its role in carcinogenesis has been extensively studied. Hyper and hypomethylation of genes is a major mechanism of gene expression deregulation in a wide range of diseases. At the same time, high-throughput DNA methylation assays have been developed generating vast amounts of genome wide DNA methylation measurements. We developed MethylMix, an algorithm implemented in R to identify disease specific hyper and hypomethylated genes. Here we present a new version of MethylMix that automates the construction of DNA-methylation and gene expression datasets from The Cancer Genome Atlas (TCGA). More precisely, MethylMix 2.0 incorporates two major updates: the automated downloading of DNA methylation and gene expression datasets from TCGA and the automated preprocessing of such datasets: value imputation, batch correction and CpG sites clustering within each gene. The resulting datasets can subsequently be analyzed with MethylMix to identify transcriptionally predictive methylation states. We show that the Differential Methylation Values created by MethylMix can be used for cancer subtyping. olivier.gevaert@stanford.edu. https://bioconductor.org/packages/release/bioc/manuals/MethylMix/man/MethylMix.pdf. MethylMix 2.0 was implemented as an R package and is available in bioconductor.

  1. Avocado and olive oil methyl esters

    International Nuclear Information System (INIS)

    Knothe, Gerhard

    2013-01-01

    Biodiesel, the mono-alkyl esters of vegetable oils, animal fats or other triacylglycerol-containing materials and an alternative to conventional petroleum-based diesel fuel, has been derived from a variety of feedstocks. Numerous feedstocks have been investigated as potential biodiesel sources, including commodity oils, however, the methyl esters of avocado and olive oil would likely be suitable as biodiesel fuel. In order to expand the database and comprehensive evaluation of the properties of vegetable oil esters, in this work the fuel-related properties of avocado and olive oil methyl esters, which exhibit similar fatty acid profiles including high oleic acid content, are determined. The cetane numbers of avocado oil methyl esters and olive oil methyl esters are relatively high, determined as 59.2 and 62.5, respectively, due to their elevated content of methyl oleate. Other properties are well within the ranges specified in biodiesel standards. The cloud points of both esters are slightly above 0 °C due to their content of saturated esters, especially methyl palmitate. Overall, avocado and olive oil yield methyl esters with fuel properties comparable to methyl esters from other commodity vegetable oils. The 1 H and 13 C NMR spectra of avocado and olive oil methyl esters are reported. -- Highlights: • Methyl esters of avocado and olive oil meet biodiesel fuel standards. • Provides comparison for methyl esters of other vegetable oils with high oleic content. • Discusses and compares present results with prior literature

  2. Methylated genes as new cancer biomarkers.

    LENUS (Irish Health Repository)

    Duffy, M J

    2012-02-01

    Aberrant hypermethylation of promoter regions in specific genes is a key event in the formation and progression of cancer. In at least some situations, these aberrant alterations occur early in the formation of malignancy and appear to be tumour specific. Multiple reports have suggested that measurement of the methylation status of the promoter regions of specific genes can aid early detection of cancer, determine prognosis and predict therapy responses. Promising DNA methylation biomarkers include the use of methylated GSTP1 for aiding the early diagnosis of prostate cancer, methylated PITX2 for predicting outcome in lymph node-negative breast cancer patients and methylated MGMT in predicting benefit from alkylating agents in patients with glioblastomas. However, prior to clinical utilisation, these findings require validation in prospective clinical studies. Furthermore, assays for measuring gene methylation need to be standardised, simplified and evaluated in external quality assurance programmes. It is concluded that methylated genes have the potential to provide a new generation of cancer biomarkers.

  3. Methyl mercury in terrestrial compartments

    International Nuclear Information System (INIS)

    Stoeppler, M.; Burow, M.; Padberg, S.; May, K.

    1993-09-01

    On the basis of the analytical methodology available at present the state of the art for the determination of total mercury and of various organometallic compounds of mercury in air, precipitation, limnic systems, soils, plants and biota is reviewed. This is followed by the presentation and discussion of examples for the data obtained hitherto for trace and ultratrace levels of total mercury and mainly methyl mercury in terrestrial and limnic environments as well as in biota. The data discussed stem predominantly from the past decade in which, due to significant methodological progress, many new aspects were elucidated. They include the most important results in this area achieved by the Research Centre (KFA) Juelich within the project 'Origin and Fate of Methyl Mercury' (contracts EV4V-0138-D and STEP-CT90-0057) supported by the Commission of the European Communities, Brussels. (orig.) [de

  4. Thermophysical study of methyl levulinate

    International Nuclear Information System (INIS)

    Lomba, Laura; Lafuente, Carlos; García-Mardones, Mónica; Gascón, Ignacio; Giner, Beatriz

    2013-01-01

    Highlights: • We have carried out a thermophysical characterization of methyl levulinate. • The study has been performed over a temperature range from (278.15 to 328.15) K. • pρT behavior has been studied over a temperature range from (333.15 to 453.15) K. • TRIDEN equation has been used to correlate pρT data. • Results have been compared with of ethyl and butyl levulinate and levulinic acid. -- Abstract: Several thermophysical properties (density, speed of sound, refractive index, surface tension, static permittivity and dynamic viscosity) of methyl levulinate have been measured under atmospheric pressure at temperatures from (278.15 to 338.15) K, while the vapor pressure was determined over a temperature range from (333.15 to 453.15) K. Furthermore, pρT behavior has been also investigated using a high-pressure, high-temperature vibrating tube densimeter over a temperature range from (283.15 to 338.15) K and a pressure range from (0.1 to 60.0) MPa. All these values obtained for methyl levulinate have been compared with other members of the levulinate family and also with levulinic acid

  5. Regime of preventing, detecting and responding to unauthorized actions in Mecklenburg-Vorpommern (M-V)

    International Nuclear Information System (INIS)

    Gomoll, L.; Gegusch, M.

    2001-01-01

    Full text: In the Federal Republic of Germany (FRG) the ensuring of safety for the population is at first the task of the countries. It also imposes to minimize the radiation risk to the public. Mecklenburg-Vorpommern is a country in northeast of the FRG with coast length of 1470 km and 78 km boundary of European Community. M-V is a sparsely populated area with nearly 2 million people in 23,500 km 2 . Concurrent with law ordinances and regulations by the Federal Government in M-V a system for preventing, detecting and responding to unauthorized actions with radioactive materials is prescribed by ordinance. This regime of preventing, detecting and responding to unlawful uses of radioactive material exists independent of the national system for the accountability, control and security of the materials. 1. Responsibility - The authorities of defence - police and fire service - have to secure the place where the radioactive material is found or laid down together with a bomb. The authorities for atomic supervision are responsible for the clearing and elimination of the radioactive material, to combat illicit situation. 2. To be reachable - In cases of finding, recognizing or blackmailing of/in connection with radioactive material, the information arrives on civil way the police centre in the Internal Ministry. There upon the working staff of defence and the staff of atomic supervision/measurement group being on standby duty on call are mobilized. 3. Equipment - The policemen and firemen have dosimeter for self-safety. The measurement group of the atomic supervision uses instruments and analyser for all different radiation situations. In this kind also there is worth mentioning the connection with remote handling systems of the defuser of munitions. Last kind can be important in cases of blackmailing. 4. Whereabouts of unauthorized material - Unauthorized radioactive material with unknown owners must be storied under separate conditions. Confiscated material, which isn

  6. Monte Carlo simulation of Varian Linac for 6 MV photon beam with BEAMnrc code

    Science.gov (United States)

    Mohammed, Maged; El Bardouni, T.; Chakir, E.; Boukhal, H.; Saeed, M.; Ahmed, Abdul-Aziz

    2018-03-01

    The purpose of this study is to investigate the effects of the initial electron beam parameters on the absorbed dose distribution calculated with EGSnrc Monte Carlo code, for 6 MV photon beam. A proposed methodology for benchmarking the BEAMnrc model of Varian Linac has been used. Also, a new photon cross section data based on ENDF/B-VII release 8 evaluation has been employed. The parameters tested include mean energy, radial intensity distribution and angular spread of the initial electron beam. Mean energy and angular spread were tested for a square irradiation field 10 × 10 cm2, whereas beam width of the electron beam was studied for 10 × 10 cm2 at different depths and 30 × 30 cm2 at depth of 10 cm. The results obtained are compared with measurement data to select the optimal electron beam parameters. The differences between MC calculation and measurements data are analyzed using gamma index criteria which fixed within 1% -1 mm accuracy. The obtained results indicated that the depth-dose and dose-profile curves were considerably influenced by the mean energy of the electron beam. The depth-dose curves were unaffected by the beam width of the electron beam, for both irradiation fields. On the contrary, lateral dose-profile curves were affected by the beam width of initial electron beam. Both dose-profile and depth-dose curves were unaffected to the angular spread of the electron beam. A deep depth of 10 × 10 cm2 is very accurate to tune the beam width. Mean energy and beam width must be tuned precisely, to get the MC does distribution with acceptable accuracy.

  7. Comparison of the radiochromic EBT2 responses for 4MV LINACs in calibration processes

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Sabrina D.; Castro, André L.S.; Mendes, Thais M.; Campos, Tarcisio P.R. [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Dept. de Energia Nuclear; Nogueira, Luciana B., E-mail: sadonatosilva@hotmail.com, E-mail: radioterapia.andre@gmail.com, E-mail: thaismelomendes@yahoo.com.br, E-mail: tprcampos@yahoo.com.br, E-mail: Lucibn19@yahoo.com.br [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Departamento de Anatomia e Imagem

    2017-07-01

    Background: Actually, cancer has gained a larger dimension and become a global public health problem. Radiotherapy (RT) is a neoplasia treatment and RT linear accelerators must undergo a strict dose quality control. Pure liquid water or solid water phantoms can be used with this intuit. In recent years, radiochromic films with equivalent tissue composition have been widely used as dosimeters in the medical field. Objective: the proposal was to analyze two distinct radiochromic film responses in water and solid water phantoms, in a distinct LINAC spectra of 4MV beam. Methods: Solid water phantom and EBT2 Radiochromic films were set. Films were exposed to a set of absorbed doses established by distinct monitor units (MU) specified in each RT-center. Mathematical relations between the degree of red-intensity from digitized films and the absorbed dose for both spectra were established. The coefficients of the polynomial function of the calibration curve were determined from the Origin software. The uncertainty of both processes was analyzed. The efficiency of the two calibration processes was set up. Results: The adjustment of the calibration curve provided the coefficients of the second-order equation that relates the dose absorbed with the optical density of the film. The uncertainty regarding the calibration performed in water and solid water and the dose-error accuracy are in agreement with the literature. Conclusion: Both water or solid water were effective in calibration and can be used in routines of quality-control measurements. The results show that EBT2-radiochromic films is suitable to for dose-calibration in RT. (author)

  8. Radiation processing of food products with 5 MV Bremsstrahlung x-rays

    International Nuclear Information System (INIS)

    Petwal, V.C.; Soni, H.C.

    2004-01-01

    Foods and agricultural products are treated with ionizing radiation to accomplish many different goals. The desired goals may be the reduction of pathogenic bacteria, other microorganisms and parasites that cause food borne diseases; or inactivation of food spoilage organisms, including bacteria, molds, and yeasts; or lengthening the shelf-life of fresh fruits and vegetables by decreasing the normal biological changes associated with growth and maturation processes, such as ripening or sprouting. It has become more important due to mounting concern over food born diseases, and growing international trade in food products that must meet stiff import standards of quality and quarantine. A 10 MeV 10 kW LINAC based multi-product EB radiation processing facility is being established at CAT to meet the processing requirement of various food, agricultural and medical products. The facility will be operated in two modes: (a) Electron: 10 MeV, 10 kW (b) Photon: 5 MeV, 10 kW Treatment with electron beam provides the highest processing rate and lowest unit cost. But the electrons have relatively short range in the solid product, hence the maximum product areal density (density times depth) that can be processed using direct 10 MeV electron beam is limited to about 8.5 gm/cm 2 (double sided irradiation). On the other hand x-rays are more penetrating, hence can be used to process the products having larger areal densities e.g. onions and potatoes packed in gunny bags. In order to address various issues related to food irradiation using 5 MV X-ray beam, a mathematical model is developed on the basis of the analytical calculations and experimental data presented by R.B.Miller, 2003, and J. Meissner et.al, 2000. (author)

  9. Accelerated radiation damage test facility using a 5 MV tandem ion accelerator

    International Nuclear Information System (INIS)

    Wady, P.T.; Draude, A.; Shubeita, S.M.; Smith, A.D.; Mason, N.; Pimblott, S.M.; Jimenez-Melero, E.

    2016-01-01

    We have developed a new irradiation facility that allows to perform accelerated damage tests of nuclear reactor materials at temperatures up to 400 °C using the intense proton (<100 μA) and heavy ion (≈10 μA) beams produced by a 5 MV tandem ion accelerator. The dedicated beam line for radiation damage studies comprises: (1) beam diagnosis and focusing optical components, (2) a scanning and slit system that allows uniform irradiation of a sample area of 0.5–6 cm"2, and (3) a sample stage designed to be able to monitor in-situ the sample temperature, current deposited on the sample, and the gamma spectrum of potential radio-active nuclides produced during the sample irradiation. The beam line capabilities have been tested by irradiating a 20Cr–25Ni–Nb stabilised stainless steel with a 3 MeV proton beam to a dose level of 3 dpa. The irradiation temperature was 356 °C, with a maximum range in temperature values of ±6 °C within the first 24 h of continuous irradiation. The sample stage is connected to ground through an electrometer to measure accurately the charge deposited on the sample. The charge can be integrated in hardware during irradiation, and this methodology removes uncertainties due to fluctuations in beam current. The measured gamma spectrum allowed the identification of the main radioactive nuclides produced during the proton bombardment from the lifetimes and gamma emissions. This dedicated radiation damage beam line is hosted by the Dalton Cumbrian Facility of the University of Manchester.

  10. A neutron survey of a 25 MV x-ray clinical linac treatment room

    International Nuclear Information System (INIS)

    Price, Kenneth W.; Holeman, George R.; Nath, Ravinder

    1978-01-01

    Neutron production in high energy x-ray radiotherapy machines results in unnecessary dose to patients and has been of recent interest to private and Federal agencies. An activation technique has been used to measure fast and thermal neutron fluxes in the high energy x-ray beam, and at radial distances of 1 and 2 meters from the beam axis of the 25 MV Sagittaire Linear Accelerator located at the Yale-New Haven Hospital's Cancer Therapy Center. Phosphorous pentoxide activation detectors were used to monitor the thermal flux and the fast neutron flux above 0.7 MeV neutron energy. Unlike other techniques for measuring neutrons, this detector has been shown to be insensitive to high energy photon interference at the photon dose rates present in the beam. Neutron spectra at various distances from the accelerator target were computed for the treatment room geometry using the Morse Monte Carlo Code (R.C. McCall, SLAC, Personal Communication). Normalization of these spectra provided the means by which the activation products measured in the phosphorous were converted to fast neutron fluxes. Dose equivalent conversion factors were applied to each energy of the calculated neutron spectra and integrated, resulting in fast neutron flux to dose equivalent conversion factors at various locations in the treatment room. Fast neutron dose equivalent was found to maximize in the photon beam, (0.005 - .007 neutron Rem/photon Rad) and decrease with distance thereafter. Thermal neutron dose equivalent was found to be essentially constant through- out the treatment room (∼ 3.35x10 -5 neutron Rem/ photon Rad). (author)

  11. Physics considerations in MV-CBCT multi-layer imager design.

    Science.gov (United States)

    Hu, Yue-Houng; Fueglistaller, Rony; Myronakis, Marios E; Rottmann, Joerg; Wang, Adam; Shedlock, Daniel; Morf, Daniel; Baturin, Paul; Huber, Pascal; Star-Lack, Josh M; Berbeco, Ross I

    2018-05-30

    Megavoltage (MV) cone-beam computed tomography (CBCT) using an electronic portal imaging (EPID) offers advantageous features, including 3D mapping, treatment beam registration, high-z artifact suppression, and direct radiation dose calculation. Adoption has been slowed by image quality limitations and concerns about imaging dose. Developments in imager design, including pixelated scintillators, structured phosphors, inexpensive scintillation materials, and multi-layer imager (MLI) architecture have been explored to improve EPID image quality and reduce imaging dose. The present study employs a hybrid Monte Carlo and linear systems model to determine the effect of detector design elements, such as multi-layer architecture and scintillation materials. We follow metrics of image quality including modulation transfer function (MTF) and noise power spectrum (NPS) from projection images to 3D reconstructions to in-plane slices and apply a task based figure-of-merit, the ideal observer signal-to-noise ratio (d') to determine the effect of detector design on object detectability. Generally, detectability was limited by detector noise performance. Deploying an MLI imager with a single scintillation material for all layers yields improvement in noise performance and d' linear with the number of layers. In general, improving x-ray absorption using thicker scintillators results in improved DQE(0). However, if light yield is low, performance will be affected by electronic noise at relatively high doses, resulting in rapid image quality degradation. Maximizing image quality in a heterogenous MLI detector (i.e. multiple different scintillation materials) is most affected by limiting imager noise. However, while a second-order effect, maximizing total spatial resolution of the MLI detector is a balance between the intensity contribution of each layer against its individual MTF. So, while a thinner scintillator may yield a maximal individual-layer MTF, its quantum efficiency will

  12. Neutron spectra and H*(10) around and 18 MV Linac by Ann's

    Energy Technology Data Exchange (ETDEWEB)

    Banuelos F, A.; Valero L, C.; Borja H, C. G.; Hernandez D, V. M.; Vega C, H. R., E-mail: alanb535@hotmail.com [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Calle Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico)

    2011-10-15

    Neutron spectra and ambient dose equivalent H*(10) were calculated for a radiotherapy room in 16 point-like detectors, 15 located inside the vault room and 1 located outside the bunker. The calculation was carried out using Monte Carlo Methods with the MCNP5 code for a generic radiotherapy room model operating with a 18 MV Linac, obtaining 16 neutron spectra with 47 energy bins, the H*(10) values were calculated from the neutron spectra by the use of the fluence-dose conversion factors. An artificial neural network were designed and trained to determine the neutron H*(10) in 15 different locations inside the vault room from the H*(10) dose calculated for the detector located outside the room, using the calculated dose values as training set, using the scaled conjugated gradient training algorithm. The mean squared error set for the network training was 1E(-14), adjusting the data in 99.992 %. In the treatment hall, as the distance respect to the isocenter is increased, the amount of neutrons and the H*(10) are reduced, neutrons in the high-energy region are shifted to lower region peaking around 0.1 MeV, however the epithermal and thermal neutrons remain constant due to the room-return effect. In the maze the spectra are dominated by epithermal and thermal neutrons that contributes to produce activation and the production of prompt gamma-rays. The results shows the using this artificial intelligence technic as a useful tool for the neutron spectrometry and dosimetry by the simplification on the neutronic fields characterization inside radiotherapy rooms avoiding the use of traditional spectrometric systems. And once the H*(10) doses have been calculated, to take the appropriated actions to reduce or prevent the patient and working staff exposure to this undesirable neutron radiation. (Author)

  13. 3 MV hypervelocity dust accelerator at the Colorado Center for Lunar Dust and Atmospheric Studies.

    Science.gov (United States)

    Shu, Anthony; Collette, Andrew; Drake, Keith; Grün, Eberhard; Horányi, Mihály; Kempf, Sascha; Mocker, Anna; Munsat, Tobin; Northway, Paige; Srama, Ralf; Sternovsky, Zoltán; Thomas, Evan

    2012-07-01

    A hypervelocity dust accelerator for studying micrometeorite impacts has been constructed at the Colorado Center for Lunar Dust and Atmospheric Studies (CCLDAS) at the University of Colorado. Based on the Max-Planck-Institüt für Kernphysik (MPI-K) accelerator, this accelerator is capable of emitting single particles of a specific mass and velocity selected by the user. The accelerator consists of a 3 MV Pelletron generator with a dust source, four image charge pickup detectors, and two interchangeable target chambers: a large high-vacuum test bed and an ultra-high vacuum impact study chamber. The large test bed is a 1.2 m diameter, 1.5 m long cylindrical vacuum chamber capable of pressures as low as 10(-7) torr while the ultra-high vacuum chamber is a 0.75 m diameter, 1.1 m long chamber capable of pressures as low as 10(-10) torr. Using iron dust of up to 2 microns in diameter, final velocities have been measured up to 52 km/s. The spread of the dust particles and the effect of electrostatic focusing have been measured using a long exposure CCD and a quartz target. Furthermore, a new technique of particle selection is being developed using real time digital filtering techniques. Signals are digitized and then cross-correlated with a shaped filter, resulting in a suppressed noise floor. Improvements over the MPI-K design, which include a higher operating voltage and digital filtering for detection, increase the available parameter space of dust emitted by the accelerator. The CCLDAS dust facility is a user facility open to the scientific community to assist with instrument calibrations and experiments.

  14. 3 MV hypervelocity dust accelerator at the Colorado Center for Lunar Dust and Atmospheric Studies

    Energy Technology Data Exchange (ETDEWEB)

    Shu, Anthony; Horanyi, Mihaly; Kempf, Sascha; Thomas, Evan [Colorado Center for Lunar Dust and Atmospheric Studies, Boulder, Colorado 80303 (United States); Department of Physics, University of Colorado, Boulder, Colorado 80309 (United States); Laboratory for Atmospheric and Space Physics, 1234 Innovation Drive, Boulder, Colorado 80303 (United States); Collette, Andrew; Drake, Keith; Northway, Paige [Colorado Center for Lunar Dust and Atmospheric Studies, Boulder, Colorado 80303 (United States); Laboratory for Atmospheric and Space Physics, 1234 Innovation Drive, Boulder, Colorado 80303 (United States); Gruen, Eberhard [Colorado Center for Lunar Dust and Atmospheric Studies, Boulder, Colorado 80303 (United States); MPI fuer Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany); Mocker, Anna [Colorado Center for Lunar Dust and Atmospheric Studies, Boulder, Colorado 80303 (United States); MPI fuer Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany); IRS, Universitaet Stuttgart, Pfaffenwaldring 31, D-70569 Stuttgart (Germany); Munsat, Tobin [Colorado Center for Lunar Dust and Atmospheric Studies, Boulder, Colorado 80303 (United States); Department of Physics, University of Colorado, Boulder, Colorado 80309 (United States); Srama, Ralf [MPI fuer Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany); IRS, Universitaet Stuttgart, Pfaffenwaldring 31, D-70569 Stuttgart (Germany); and others

    2012-07-15

    A hypervelocity dust accelerator for studying micrometeorite impacts has been constructed at the Colorado Center for Lunar Dust and Atmospheric Studies (CCLDAS) at the University of Colorado. Based on the Max-Planck-Instituet fuer Kernphysik (MPI-K) accelerator, this accelerator is capable of emitting single particles of a specific mass and velocity selected by the user. The accelerator consists of a 3 MV Pelletron generator with a dust source, four image charge pickup detectors, and two interchangeable target chambers: a large high-vacuum test bed and an ultra-high vacuum impact study chamber. The large test bed is a 1.2 m diameter, 1.5 m long cylindrical vacuum chamber capable of pressures as low as 10{sup -7} torr while the ultra-high vacuum chamber is a 0.75 m diameter, 1.1 m long chamber capable of pressures as low as 10{sup -10} torr. Using iron dust of up to 2 microns in diameter, final velocities have been measured up to 52 km/s. The spread of the dust particles and the effect of electrostatic focusing have been measured using a long exposure CCD and a quartz target. Furthermore, a new technique of particle selection is being developed using real time digital filtering techniques. Signals are digitized and then cross-correlated with a shaped filter, resulting in a suppressed noise floor. Improvements over the MPI-K design, which include a higher operating voltage and digital filtering for detection, increase the available parameter space of dust emitted by the accelerator. The CCLDAS dust facility is a user facility open to the scientific community to assist with instrument calibrations and experiments.

  15. AMS of 36Cl with the VERA 3 MV tandem accelerator

    International Nuclear Information System (INIS)

    Martschini, Martin; Andersson, Pontus; Forstner, Oliver; Golser, Robin; Hanstorp, Dag; Lindahl, Anton O.; Kutschera, Walter; Pavetich, Stefan; Priller, Alfred; Rohlén, Johan; Steier, Peter; Suter, Martin; Wallner, Anton

    2013-01-01

    Recent progress with compact ionization chambers has opened new possibilities for isobar suppression in accelerator mass spectrometry (AMS). Separation of 36 Cl (t 1/2 = 0.30 Ma) at natural isotopic levels from its stable isobar 36 S became feasible at particle energies of 24 MeV, which are also accessible for medium-sized tandem accelerators with 3 MV terminal voltage like VERA (Vienna Environmental Research Accelerator). Investigations with an ionization chamber revealed how physics favors isobar separation even at energies below the maximum of the Bragg curve. The strong energy focusing effect at high energy losses reduces energy straggling significantly and isobar separation steadily increases up to almost full energy loss. With an optimized detection setup, sulfur suppression factors of 2 × 10 4 have been achieved. Refraining from the additional use of degrader foils has the benefit of high transmission to the detector (∼16%), but requires a low sulfur output from the ion source. Therefore several backing materials have been screened for sulfur content. The dependence of the sulfur output on the AgCl sample size has been investigated as well. Precision and accuracy have been thoroughly assessed over the last two years. Since drifts in the spectra are efficiently corrected by monitoring the position of the 36 S peak, the reproducibility for high ratio samples ( 36 Cl/Cl > 10 −12 ) is better than 2%. Our blank value of 36 Cl/Cl ≈ (5 ± 5) × 10 −16 is competitive to other labs. 36 Cl has become a routine AMS-isotope at VERA. Recently we also explored novel techniques for additional sulfur suppression already in the ion source. While results with a small gas reaction cell in front of the sputter target were discouraging, a decrease in the sulfur/chlorine ratio by one order of magnitude was achieved by directing 300 mW continuous wave laser beam at 445 nm towards the cathode in the ion source.

  16. Neutron spectra and H*(10) around and 18 MV Linac by Ann's

    International Nuclear Information System (INIS)

    Banuelos F, A.; Valero L, C.; Borja H, C. G.; Hernandez D, V. M.; Vega C, H. R.

    2011-10-01

    Neutron spectra and ambient dose equivalent H*(10) were calculated for a radiotherapy room in 16 point-like detectors, 15 located inside the vault room and 1 located outside the bunker. The calculation was carried out using Monte Carlo Methods with the MCNP5 code for a generic radiotherapy room model operating with a 18 MV Linac, obtaining 16 neutron spectra with 47 energy bins, the H*(10) values were calculated from the neutron spectra by the use of the fluence-dose conversion factors. An artificial neural network were designed and trained to determine the neutron H*(10) in 15 different locations inside the vault room from the H*(10) dose calculated for the detector located outside the room, using the calculated dose values as training set, using the scaled conjugated gradient training algorithm. The mean squared error set for the network training was 1E(-14), adjusting the data in 99.992 %. In the treatment hall, as the distance respect to the isocenter is increased, the amount of neutrons and the H*(10) are reduced, neutrons in the high-energy region are shifted to lower region peaking around 0.1 MeV, however the epithermal and thermal neutrons remain constant due to the room-return effect. In the maze the spectra are dominated by epithermal and thermal neutrons that contributes to produce activation and the production of prompt gamma-rays. The results shows the using this artificial intelligence technic as a useful tool for the neutron spectrometry and dosimetry by the simplification on the neutronic fields characterization inside radiotherapy rooms avoiding the use of traditional spectrometric systems. And once the H*(10) doses have been calculated, to take the appropriated actions to reduce or prevent the patient and working staff exposure to this undesirable neutron radiation. (Author)

  17. The characterization of unflattened photon beams from a 6 MV linear accelerator

    International Nuclear Information System (INIS)

    Cashmore, Jason

    2008-01-01

    Commissioning data have been measured for an Elekta Precise linear accelerator running at 6 MV without a flattening filter with the aim of studying the effects of flattening filter removal on machine operation and beam characterization. Modern radiotherapy practice now routinely relies on the use of fluence modifying techniques such as IMRT, i.e. the active production of non-flat beams. For these techniques the flattening filter should not be necessary. It is also possible that the increased intensity around the central axis associated with unflattened beams may be useful for conventional treatment planning by acting as a field-in-field or integrated boost technique. For this reason open and wedged field data are presented. Whilst problems exist in running the machine filter free clinically, this paper shows that in many ways the beam is actually more stable, exhibiting almost half the variation in field symmetry for changes in steering and bending currents. Dosimetric benefits are reported here which include a reduction in head scatter by approx. 70%, decreased penumbra (0.5 mm), lower dose outside of the field edge (11%) and a doubling in dose rate (2.3 times for open and 1.9 times for wedged fields). Measurements also show that reduced scatter also reduces leakage radiation by approx. 60%, significantly lowering whole body doses. The greatest benefit of filter-free use is perceived to be for IMRT where increased dose rate combined with reduced head scatter and leakage radiation should lead to improved dose calculation, giving simpler, faster and more accurate dose delivery with reduced dose to normal tissues

  18. Influence of a transverse magnetic field on the dose deposited by a 6 MV linear accelerator

    Directory of Open Access Journals (Sweden)

    Richter Sebastian

    2017-09-01

    Full Text Available An integrated system of a linear accelerator and a magnetic resonance imaging (MRI device may provide real-time imaging during radiotherapy treatments. This work investigated changes affecting the dose deposition caused by a magnetic field (B-field transverse to the beam direction by means of Monte Carlo simulations. Two different phantoms were used: A water phantom (Ph1 and a water-air phantom (Ph2 with a 4-2-4 cm water-air-water cross section. Dose depositions were scored for B-field values of 0 T, 0.35 T, 0.5 T, 1.5 T, 3 T and 5 T. Beams were based on a precalculated photon spectrum taken from an earlier simulated Elekta 6 MV FFF accelerator. All lateral profiles in Ph1 showed a Lorentz force driven shift w.r.t. the B-field strength, presenting a steeper penumbra in the shift's direction. Depositions were shifted up to 0.3 cm for 5 T, showing a constant central axis plateau-dose or an increase by 2.3 % for small fields. Depth-dose curves in Ph1 showed a shift of the dose maximum towards the beam entrance direction for increasing B-field of up to 1.1 cm; the maximum dose was increased by 6.9 %. In Ph2, an asymmetric dose increase by up to 36.9 % was observed for 1.5 T at the water-air boundary, resulting from the electron return effect (ERE. In our scenario, B-field dependent dose shifts and local build-ups were observed, which consequently affect the resulting dose distribution and need to be considered in magnetic resonance guided radiotherapy treatment planning.

  19. SU-F-T-490: Separating Effects Influencing Detector Response in Small MV Photon Fields

    Energy Technology Data Exchange (ETDEWEB)

    Wegener, S; Sauer, O [University of Wuerzburg, Wuerzburg (Germany)

    2016-06-15

    Purpose: Different detector properties influence their responses especially in field sizes below the lateral electron range. Due to the finite active volume, the detector density and electron perturbation at other structural parts, the response factor is in general field size dependent. We aimed to visualize and separate the main effects contributing to detector behavior for a variety of detector types. This was achieved in an experimental setup, shielding the field center. Thus, effects caused by scattered radiation could be examined separately. Methods: Signal ratios for field sizes down to 8 mm (SSD 90 cm, water depth 10 cm) of a 6MV beam from a Siemens Primus LINAC were recorded with several detectors: PTW microDiamond and PinPoint ionization chamber, shielded diodes (PTW P-60008, IBA PFD and SNC Edge) and unshielded diodes (PTW E-60012 and IBA SFD). Measurements were carried out in open fields and with an aluminum pole of 4 mm diameter as a central block. The geometric volume effect was calculated from profiles obtained with Gafchromic EBT3 film, evaluated using FilmQA Pro software (Ashland, USA). Results: Volume corrections were 1.7% at maximum. After correction, in small open fields, unshielded diodes showed a lower response than the diamond, i.e. diamond detector over-response seems to be higher than that for unshielded diodes. Beneath the block, this behavior was amplified by a factor of 2. For the shielded diodes, the overresponse for small open fields could be confirmed. However their lateral response behavior was strongly type dependent, e.g. the signal ratio dropped from 1.02 to 0.98 for the P-60008 diode. Conclusion: The lateral detector response was experimentally examined. Detector volume and density alone do not fully account for the field size dependence of detector response. Detector construction details play a major role, especially for shielded diodes.

  20. Radiobiological Characterization of Two Photon-Beam Energies 6 and 15 MV used in Radiotherapy From Linear Accelerator

    International Nuclear Information System (INIS)

    Eltayeb, A.E.H.

    2009-02-01

    The main objective of this study is to perform radiobiological characterization of two different photon beam energies, 6 MV and 15 MV, from linear accelerator used in radiotherapy, with special regard to late effects of radiation. Two end-points, namely cell survival and micronucleus induction were used for the characterization. Chinese hamster V 79 lung fibroblast cell line to prepare cell culture and to perform the innervate experiments. chromosomes number was counted and found to be 22 chromosomes per cell, this result is in complete agreement with expected 11 pairs of chromosomes representing the genome of this species. Cells were kept in confluent growth for two days and then exposed to two photon beam energies, 6 and 15 MV respectively. Different dose rates were used for the two beam energies, 0.25, 0.5, 1.0, 2.0, 4.0, 7.0 Gy. Cells were counted immediately after irradiation and re seeded, the seeded number of cells was calculated to the dose rate used. Another set of unirradiated cells treated the same as the experimental set was used as a control group. The plating efficiency (PE) was calculated for the control group, then cells were incubated at 37 o C for 6 days to construct the survival curve, five samples were counted per dose and the mean was calculated. The two survival curves are similar for photon beam energies (6 and 15 MV) and the surviving fraction was decreased with dose rate. The two curves showed similar values of α and β parameters, this result is expected for the same radiation type (X-ray). For the micronuclei assay three samples for each dose were seeded and incubated at 37 o C for 24 hours then Cytochalasin-B was added to block cells in cytokinesis phase of the mitosis. The micronuclei number was counted and plotted with dose. A significant positive correlation was found between dose and micronuclei frequency (P=0.00), moreover, the micronuclei frequency is relatively higher with 15 MV compared with 6 MV energy. This indicates the

  1. A Measurement and Analysis of Buildup Region Dose for Open Field Photon Beams (Cobalt-60 through 24 MV)

    International Nuclear Information System (INIS)

    McCullough, Edwin C.

    2015-01-01

    The central axis depth dose in the build-up region (surface to d_m_a_x) of single open field photon beams (cobalt-60 through 24 MV) has been measured utilizing parallel plate and extrapolation chamber methodology. These data were used to derive, for a prescription dose of 100 cGy, values of surface dose, the maximum value of dose along the central axis (D_m_a_x) and the depth (nearest the surface) at which 90% of the prescription dose occurs (d_9_0). For both single and parallel opposed pair (POP) open field configurations, data are presented at field sizes of 5 × 5, 15 × 15 and 25 × 25 cm"2 for prescription depths of 10, 15 and 20 cm (midplane for POP). For the treatment machines, field sizes, and prescription depths studied, it is possible to conclude that: for single open field irradiation, surface dose values (as a percentage of the prescription dose) can be either low (<10%) or comparable to the prescription dose itself; for POP open fields, surface dose values are relatively independent of photon energy and midplane depth, and range between 30% and 70% of prescription dose, being principally dependent on field size; the depth of the initial 90 cGy point for a prescription dose of 100 cGy, d_9_0, was larger for POP fields. For either single or POP open field treatments, d_9_0 was always less than 22 mm, while for 6 MV or less, values of d_9_0 were less than 4 mm; D_m_a_x values can be very large (e.g., above 300 cGy) for certain treatment situations and are reduced significantly for POP treatments; for open field POP treatments, the percent reduction in D_m_a_x with each increment in beam energy above 10 MV is reduced over that seen at 10 MV or less and, possibly, this further reduction may be clinically insignificant; for open field POP treatments, changes in surface dose, d_9_0 and D_m_a_x with beam energy above 10 MV do not suggest, with regard to these specific build-up curve parameters, any obvious advantage for treatment with beam energies greater

  2. Relative dosimetry of photon beam of 6 MV with a liquid ionization chamber; Dosimetria relativa de un haz de fotones de 6 MV con una camara de ionizacion liquida

    Energy Technology Data Exchange (ETDEWEB)

    Benitez Villegas, E. M.; Casado Villalon, F. J.; Martin-Cueto, J. A.; Caudepon Moreno, F.; Garcia Pareja, S.; Galan Montenegro, P.

    2011-07-01

    The increasing use of reduced size fields in the special techniques of treatment generates regions with high dose gradients. It therefore requires the use of detectors that present high spatial resolution. The aim of this study is to compare the dosimetric measurements obtained with a liquid ionization chamber PTW MicroLion recently acquired with other commonly used detectors for a photon beam of 6 MV linear electron accelerator Varian 600DBX.

  3. Evolution of DNA Methylation across Insects.

    Science.gov (United States)

    Bewick, Adam J; Vogel, Kevin J; Moore, Allen J; Schmitz, Robert J

    2017-03-01

    DNA methylation contributes to gene and transcriptional regulation in eukaryotes, and therefore has been hypothesized to facilitate the evolution of plastic traits such as sociality in insects. However, DNA methylation is sparsely studied in insects. Therefore, we documented patterns of DNA methylation across a wide diversity of insects. We predicted that underlying enzymatic machinery is concordant with patterns of DNA methylation. Finally, given the suggestion that DNA methylation facilitated social evolution in Hymenoptera, we tested the hypothesis that the DNA methylation system will be associated with presence/absence of sociality among other insect orders. We found DNA methylation to be widespread, detected in all orders examined except Diptera (flies). Whole genome bisulfite sequencing showed that orders differed in levels of DNA methylation. Hymenopteran (ants, bees, wasps and sawflies) had some of the lowest levels, including several potential losses. Blattodea (cockroaches and termites) show all possible patterns, including a potential loss of DNA methylation in a eusocial species whereas solitary species had the highest levels. Species with DNA methylation do not always possess the typical enzymatic machinery. We identified a gene duplication event in the maintenance DNA methyltransferase 1 (DNMT1) that is shared by some Hymenoptera, and paralogs have experienced divergent, nonneutral evolution. This diversity and nonneutral evolution of underlying machinery suggests alternative DNA methylation pathways may exist. Phylogenetically corrected comparisons revealed no evidence that supports evolutionary association between sociality and DNA methylation. Future functional studies will be required to advance our understanding of DNA methylation in insects. © The Author 2016. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

  4. Systemic effects of chronically administered methyl prednisolonate and methyl 17-deoxyprednisolonate.

    Science.gov (United States)

    Olejniczak, E; Lee, H J

    1984-06-01

    The systemic activities of methyl prednisolonate and methyl 17-deoxyprednisolonate (1) were studied in rats. Methyl 17-deoxyprednisolonate produced significant changes in the amount of sodium ion (decreased) and potassium ion (increased) in urine; however, methyl prednisolonate had no effect on electrolyte balance. Both methyl prednisolonate and methyl 17-deoxyprednisolonate had no effect on liver glycogen content, plasma corticosterone level and relative adrenal weight. In contrast, the parent compound prednisolone caused a significant decrease in liver glycogen content, plasma corticosterone level and relative adrenal weight.

  5. SU-E-I-72: First Experimental Study of On-Board CBCT Imaging Using 2.5MV Beam On a Radiotherapy Linac

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Q [Department of Radiation Oncology, Stanford University, Stanford, CA (United States); Institute of Image Processing and Pattern Recognition, Xi' an Jiaotong University, Xi' an (China); Li, R; Yang, Y; Xing, L [Department of Radiation Oncology, Stanford University, Stanford, CA (United States)

    2014-06-01

    Purpose: Varian TrueBeam version 2.0 comes with a new inline 2.5MV beam modality for image guided patient setup. In this work we develop an iterative volumetric image reconstruction technique specific to the beam and investigate the possibility of obtaining metal artifact free CBCT images using the new imaging modality. Methods: An iterative reconstruction algorithm with a sparse representation constraint based on dictionary learning is developed, in which both sparse projection and low dose rate (10 MU/min) are considered. Two CBCT experiments were conducted using the newly available 2.5MV beam on a Varian TrueBeam linac. First, a Rando anthropomorphic head phantom with and without a copper bar inserted in the center was scanned using both 2.5MV and kV (100kVp) beams. In a second experiment, an MRI phantom with many coils was scanned using 2.5MV, 6MV, and kV (100kVp) beams. Imaging dose and the resultant image quality is studied. Results: Qualitative assessment suggests that there were no visually detectable metal artifacts in MV CBCT images, compared with significant metal artifacts in kV CBCT images, especially in the MRI phantom. For a region near the metal object in the head phantom, the 2.5MV CBCT gave a more accurate quantification of the electron density compared with kV CBCT, with a ∼50% reduction in mean HU error. As expected, the contrast between bone and soft-tissue in 2.5MV CBCT decreased compared with kV CBCT. Conclusion: On-board CBCT imaging with the new 2.5MV beam can effectively reduce metal artifacts, although with a reduced softtissue contrast. Combination of kV and MV scanning may lead to metal artifact free CBCT images with uncompromised soft-tissue contrast.

  6. Relative measurements of fast neutron contamination in 18-MV photon beams from two linear accelerators and a betatron

    International Nuclear Information System (INIS)

    Gur, D.; Bukovitz, A.G.; Rosen, J.C.; Holmes, B.G.

    1979-01-01

    Fast neutron contamination in photon beams in the 20 MV range have been reported in recent years. In order to determine if the variations were due mainly to differences in measurement procedures, or inherent in the design of the accelerators, three different 18-MV (BJR) photon beams were compared using identical analytical techniques. The units studied were a Philips SL/75-20 and a Siemens Mevatron-20 linear accelerators and a Schimadzu betatron. Gamma spectroscopy of an activated aluminum foil was the method used. By comparing the relative amounts of neutron contamination, errors associated with absolute measurements such as detector efficiency and differences in activation foils were eliminated. Fast neutron contaminations per rad of x rays in a ratio of 6.7:3.7:1 were found for the Philips, Schimadzu and Siemens accelerators, respectively

  7. A 200 mV low leakage current subthreshold SRAM bitcell in a 130 nm CMOS process

    International Nuclear Information System (INIS)

    Bai Na; Lü Baitao

    2012-01-01

    A low leakage current subthreshold SRAM in 130 nm CMOS technology is proposed for ultra low voltage (200 mV) applications. Almost all of the previous subthreshold works ignore the leakage current in both active and standby modes. To minimize leakage, a self-adaptive leakage cut off scheme is adopted in the proposed design without any extra dynamic energy dissipation or performance penalty. Combined with buffering circuit and reconfigurable operation, the proposed design ensures both read and standby stability without deteriorating writability in the subthreshold region. Compared to the referenced subthreshold SRAM bitcell, the proposed bitcell shows: (1) a better critical state noise margin, and (2) smaller leakage current in both active and standby modes. Measurement results show that the proposed SRAM functions well at a 200 mV supply voltage with 0.13 μW power consumption at 138 kHz frequency. (semiconductor integrated circuits)

  8. Injector for CESAR (2 MeV electron storage ring): 2-beam, 2 MV van de Graaff generator.

    CERN Multimedia

    CERN PhotoLab

    1963-01-01

    The van de Graaff generator in its tank. For voltage-holding, the tank was filled with pressurized extra-dry nitrogen. 2 beams emanated from 2 separate electron-guns. The left beam, for injection into the CESAR ring, was pulsed at 50 Hz, with currents of up to 1 A for 400 ns. The right beam was sent to a spectrometer line. Its pulselength was also 400 ns, but the pulse current was 12 microA, at a rate variable from 50 kHz to 1 MHz. This allowed stabilization of the top-terminal voltage to an unprecedented stability of +- 100 V, i.e. 6E-5. Although built for a nominal voltage of 2 MV, the operational voltage was limited to 1.75 MV in order to minimize voltage break-down events.

  9. Absorbed dose beam quality factors for cylindrical ion chambers: Experimental determination at 6 and 15 MV photon beams

    Energy Technology Data Exchange (ETDEWEB)

    Caporali, C; Guerra, A S; Laitano, R F; Pimpinella, M [ENEA-Casaccia, Inst. Nazionale di Meterologia delle Radiazioni Ionizzanti, Rome (Italy). Dipt. Ambiente

    1996-08-01

    Ion chambers calibrated in terms of absorbed dose to water need an additional factor conventionally designed by k{sub Q} in order to determine the absorbed dose. The quantity k{sub Q} depends on beam quality and chamber characteristics. Rogers and Andreo provided calculations of the k{sub Q} factors for most commercially available ionization chambers for clinical dosimetry. Experimental determinations of the k{sub Q} factors for a number of cylindrical ion chambers have been made and are compared with the calculated values so far published. Measurements were made at 6 MV and 15 MV clinical photon beams at a point in water phantom where the ion chambers and a Fricke dosimeter were alternatively irradiated. The uncertainty on the experimental k{sub Q} factors resulted about {+-} 0.6%. The theoretical and experimental k{sub Q} values are in fairly good agreement. (author). 12 refs, 3 tabs.

  10. 1.3 MV voltage pulse shaping for 13 Ohm load by means of the VMG-160 magnetocumulative generator

    International Nuclear Information System (INIS)

    Kravchenko, A.S.; Boriskin, A.S.; Vilkov, Yu.V.; Selemir, V.D.; Dimant, E.M.; Yuryzhev, A.S.; Zenkov, D.I.; Tkachuk, A.A.; Kirshanova, E.N.; Kozlov, M.B.

    2000-01-01

    The device on the basis of a magnetocumulative generator with a transformer output making it possible to form powerful (≥ 100 GW) pulses with current rise time of approximately 1 μs on the load of about 10 Ohm is described. The results of testing the generator on the load in form of a liquid resistor are presented. The voltage pulse of 13 MV is obtained on the resistive load of 13 Ohm as a result of the superconductors electrical explosion. The results of the numerical modeling indicated the possibility of forming the voltage pulses ≥ 1MV with the current rise time of approximately 100 ns on the resistance of 13 Ohm [ru

  11. Effects of propylene, methyl methacrylate and isopropanol poisoning on spatial performance of a proton exchange membrane fuel cell

    Science.gov (United States)

    Reshetenko, Tatyana V.; St-Pierre, Jean

    2018-02-01

    This paper studies the effects of propylene, methyl methacrylate (MMA) and isopropanol (IPA) in air on the spatial performance of proton exchange membrane fuel cells (PEMFCs). The introduction of 100 ppm C3H6 into the oxidant stream resulted in a performance decrease of 130 mV at 1.0 A cm-2, whereas 20 ppm MMA caused a voltage loss of 80 mV. A moderate performance decline of 60 mV was detected in the presence of 5.3ṡ103 ppm IPA in air. Spatial electrochemical impedance spectroscopy (EIS) data showed an increase in charge and mass transfer resistances under exposure to C3H6 and MMA, although IPA did not affect the impedance. The observed PEMFC performances, local current redistributions and EIS data can be explained by the adsorption of contaminants on the Pt surface, their subsequent transformations, and their impacts on the electrochemical surface area and oxygen reduction mechanism. It was assumed that the studied contaminants were oxidized mainly to CO2 via electrochemical and chemical pathways under the operating conditions and at the cathode potential. Self-recovery of PEMFC performance was observed for each contaminant after halting its introduction into the air. Possible contaminant oxidation/reduction mechanisms and their correlations with spatial performance and EIS are presented and discussed.

  12. A 4 MV flattening filter-free beam: commissioning and application to conformal therapy and volumetric modulated arc therapy

    International Nuclear Information System (INIS)

    Stevens, S W; Rosser, K E; Bedford, J L

    2011-01-01

    Recent studies have indicated that radiotherapy treatments undertaken on a flattening filter-free (FFF) linear accelerator have a number of advantages over treatments undertaken on a conventional linear accelerator. In addition, 4 MV photon beams may give improved isodose coverage for some treatment volumes at air/tissue interfaces, compared to when utilizing the clinical standard of 6 MV photons. In order to investigate these benefits, FFF beams were established on an Elekta Beam Modulator linear accelerator for 4 MV photons. Commissioning beam data were obtained for open and wedged fields. The measured data were then imported into a treatment planning system and a beam model was commissioned. The beam model was optimized to improve dose calculations at shallow, clinically relevant depths. Following verification, the beam model was utilized in a treatment planning study, including volumetric modulated arc therapy, for a selection of lung, breast/chest wall and larynx patients. Increased dose rates of around 800 MU min -1 were recorded for open fields (relative to 320 MU min -1 for filtered open fields) and reduced head scatter was inferred from output factor measurements. Good agreement between planned and delivered dose was observed in verification of treatment plans. The planning study indicated that with a FFF beam, equivalent (and in some cases improved) isodose profiles could be achieved for small lung and larynx treatment volumes relative to 4 MV filtered treatments. Furthermore, FFF treatments with wedges could be replicated using open fields together with an 'effective wedge' technique and isocentre shift. Clinical feasibility of a FFF beam was therefore demonstrated, with beam modelling, treatment planning and verification being successfully accomplished.

  13. First Demonstration of Combined kV/MV Image-Guided Real-Time Dynamic Multileaf-Collimator Target Tracking

    International Nuclear Information System (INIS)

    Cho, Byungchul; Poulsen, Per R.; Sloutsky, Alex; Sawant, Amit; Keall, Paul J.

    2009-01-01

    Purpose: For intrafraction motion management, a real-time tracking system was developed by combining fiducial marker-based tracking via simultaneous kilovoltage (kV) and megavoltage (MV) imaging and a dynamic multileaf collimator (DMLC) beam-tracking system. Methods and Materials: The integrated tracking system employed a Varian Trilogy system equipped with kV/MV imaging systems and a Millennium 120-leaf MLC. A gold marker in elliptical motion (2-cm superior-inferior, 1-cm left-right, 10 cycles/min) was simultaneously imaged by the kV and MV imagers at 6.7 Hz and segmented in real time. With these two-dimensional projections, the tracking software triangulated the three-dimensional marker position and repositioned the MLC leaves to follow the motion. Phantom studies were performed to evaluate time delay from image acquisition to MLC adjustment, tracking error, and dosimetric impact of target motion with and without tracking. Results: The time delay of the integrated tracking system was ∼450 ms. The tracking error using a prediction algorithm was 0.9 ± 0.5 mm for the elliptical motion. The dose distribution with tracking showed better target coverage and less dose to surrounding region over no tracking. The failure rate of the gamma test (3%/3-mm criteria) was 22.5% without tracking but was reduced to 0.2% with tracking. Conclusion: For the first time, a complete tracking system combining kV/MV image-guided target tracking and DMLC beam tracking was demonstrated. The average geometric error was less than 1 mm, and the dosimetric error was negligible. This system is a promising method for intrafraction motion management.

  14. The development of a cryopump for stripper gas pumping in a 30 MV tandem Van de Graaff

    International Nuclear Information System (INIS)

    Halliday, B.S.

    1980-04-01

    The development of a cryopump is described for a 30 MV tandem Van de Graaf accelerator to control the vacuum pressure in the beam tube at the centre terminal when a gas stripper is in use. The system has been fully assembled and has been mechanically tested, the cryo pumps have been cooled to 18 0 K and the insulation tested electrically to +- 20 kV between the pump elements and the biased stripper canal. (UK)

  15. SU-E-T-163: Thin-Film Organic Photocell (OPV) Properties in MV and KV Beams for Dosimetry Applications.

    Science.gov (United States)

    Ng, S K; Hesser, J; Zhang, H; Gowrisanker, S; Yakushevich, S; Shulhevich, Y; Abkai, C; Wack, L; Zygmanski, P

    2012-06-01

    To characterize dosimetric properties of low-cost thin film organic-based photovoltaic (OPV) cells to kV and MV x-ray beams for their usage as large area dosimeter for QA and patient safety monitoring device. A series of thin film OPV cells of various areas and thicknesses were irradiated with MV beams to evaluate the stability and reproducibility of their response, linearity and sensitivity to absorbed dose. The OPV response to x-rays of various linac energies were also characterized. Furthermore the practical (clinical) sensitivity of the cells was determined using IMRT sweeping gap test generated with various gap sizes. To evaluate their potential usage in the development of low cost kV imaging device, the OPV cells were irradiated with kV beam (60-120 kVp) from a fluoroscopy unit. Photocell response to the absorbed dose was characterized as a function of the organic thin film thickness and size, beam energy and exposure for kV beams as well. In addition, photocell response was determined with and without thin plastic scintillator. Response of the OPV cells to the absorbed dose from kV and MV beams are stable and reproducible. The photocell response was linearly proportional to the size and about slightly decreasing with the thickness of the organic thin film, which agrees with the general performance of the photocells in visible light. The photocell response increases as a linear function of absorbed dose and x-ray energy. The sweeping gap tests performed showed that OPV cells have sufficient practical sensitivity to measured MV x-ray delivery with gap size as small as 1 mm. With proper calibration, the OPV cells could be used for online radiation dose measurement for quality assurance and patient safety purposes. Their response to kV beam show promising potential in development of low cost kV radiation detection devices. © 2012 American Association of Physicists in Medicine.

  16. CARACTERIZACIÓN MOLECULAR PARCIAL DEL VIRUS DEL MOTEADO DEL CLAVEL (CarMV PRESENTE EN LA SABANA DE BOGOTÁ

    Directory of Open Access Journals (Sweden)

    Ana Yervid Rodríguez

    2000-12-01

    Full Text Available En el presente trabajo se realizó un estudio del virus moteado del clavel (CarMV, en el cual se analizaron con la prueba de ELISA muestras de clavel de diferentes variedades de la Sabana de Bogotá. Esta prueba indicó que el82% de las muestras analizadas eran positivas para el CarMV. El CarMV presente en las muestras positivas fue inoculado mecánicamente en plantas de clavel certificadas libres de virus. La partícula viral se purificó utilizando centrifugación en gradientes y colchones de sacarosa. La proteína de la cápside fue analizada por electroforesis SDS-PAGE, encontrándose una banda de proteína de masa molecular relativa aproximada de 38kDa. El tejido infectado con el CarMV se sometió a un proceso de extracción de RNA de doble cadena (dsRNA encontrándose de 3 a5 componentes electroforéticos cuyos tamaños fluctuaron aproximadamente entre 8.0 y 0.9 kpb. Este patrón de dsRNA pennitió diferenciar al menos 3 aislamientos virales. El análisis electroforético en geles de agarosa del RNA genómico de varios aislamientos virales, mostró una banda de peso molecular aproximado de 4.0 kb. El análisis del RNA genómico digerido con RNAsa TI pennitió diferenciar 2 grupos de patrones electroforéticos de los aislamientosestudiados.

  17. Methylation patterns in marginal zone lymphoma.

    Science.gov (United States)

    Arribas, Alberto J; Bertoni, Francesco

    Promoter DNA methylation is a major regulator of gene expression and transcription. The identification of methylation changes is important for understanding disease pathogenesis, for identifying prognostic markers and can drive novel therapeutic approaches. In this review we summarize the current knowledge regarding DNA methylation in MALT lymphoma, splenic marginal zone lymphoma, nodal marginal zone lymphoma. Despite important differences in the study design for different publications and the existence of a sole large and genome-wide methylation study for splenic marginal zone lymphoma, it is clear that DNA methylation plays an important role in marginal zone lymphomas, in which it contributes to the inactivation of tumor suppressors but also to the expression of genes sustaining tumor cell survival and proliferation. Existing preclinical data provide the rationale to target the methylation machinery in these disorders. Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. Wp specific methylation of highly proliferated LCLs

    International Nuclear Information System (INIS)

    Park, Jung-Hoon; Jeon, Jae-Pil; Shim, Sung-Mi; Nam, Hye-Young; Kim, Joon-Woo; Han, Bok-Ghee; Lee, Suman

    2007-01-01

    The epigenetic regulation of viral genes may be important for the life cycle of EBV. We determined the methylation status of three viral promoters (Wp, Cp, Qp) from EBV B-lymphoblastoid cell lines (LCLs) by pyrosequencing. Our pyrosequencing data showed that the CpG region of Wp was methylated, but the others were not. Interestingly, Wp methylation was increased with proliferation of LCLs. Wp methylation was as high as 74.9% in late-passage LCLs, but 25.6% in early-passage LCLs. From two Burkitt's lymphoma cell lines, Wp specific hypermethylation was also found (>80%). Interestingly, the expression of EBNA2 gene which located directly next to Wp was associated with its methylation. Our data suggested that Wp specific methylation may be important for the indicator of the proliferation status of LCLs, and the epigenetic viral gene regulation of EBNA2 gene by Wp should be further defined possibly with other biological processes

  19. 6 MV dosimetric characterization of the 160 MLC, the new Siemens multileaf collimator

    International Nuclear Information System (INIS)

    Tacke, Martin B.; Nill, Simeon; Haering, Peter; Oelfke, Uwe

    2008-01-01

    New technical developments constantly aim at improving the outcome of radiation therapy. With the use of a computer-controlled multileaf collimator (MLC), the quality of the treatment and the efficiency in patient throughput is significantly increased. New MLC designs aim to further enhance the advantages. In this article, we present the first detailed experimental investigation of the new 160 MLC TM , Siemens Medical Solutions. The assessment included the experimental investigation of typical MLC characteristics such as leakage, tongue-and-groove effect, penumbra, leaf speed, and leaf positioning accuracy with a 6 MV treatment beam. The leakage is remarkably low with an average of 0.37% due to a new design principle of slightly tilted leaves instead of the common tongue-and-groove design. But due to the tilt, the triangular tongue-and-groove effect occurs. Its magnitude of approximately 19% is similar to the dose defect measured for MLCs with the common tongue-and-groove design. The average longitudinal penumbra measured at depth d max =15 mm with standard 100x100 mm 2 fields is 4.1±0.5 mm for the central range and increases to 4.9±1.3 mm for the entire field range of 400x400 mm 2 . The increase is partly due to the single-focusing design and the large distance between the MLC and the isocenter enabling a large patient clearance. Regarding the leaf speed, different velocity tests were performed. The positions of the moving leaves were continuously recorded with the kilovoltage-imaging panel. The maximum leaf velocities measured were 42.9±0.6 mm/s. In addition, several typical intensity-modulated radiation therapy treatments were performed and the delivery times compared to the Siemens OPTIFOCUS MLC. An average decrease of 11% in delivery time was observed. The experimental results presented in this article indicate that the dosimetric characteristics of the 160 MLC are capable of improving the quality of dose delivery with respect to precision and dose

  20. A 2 MV Van de Graaff accelerator as a tool for planetary and impact physics research

    International Nuclear Information System (INIS)

    Mocker, Anna; Bugiel, Sebastian; Srama, Ralf; Auer, Siegfried; Baust, Guenter; Matt, Guenter; Otto, Katharina; Colette, Andrew; Drake, Keith; Kempf, Sascha; Munsat, Tobin; Shu, Anthony; Sternovsky, Zoltan; Fiege, Katherina; Postberg, Frank; Gruen, Eberhard; Heckmann, Frieder; Helfert, Stefan; Hillier, Jonathan; Mellert, Tobias

    2011-01-01

    Investigating the dynamical and physical properties of cosmic dust can reveal a great deal of information about both the dust and its many sources. Over recent years, several spacecraft (e.g., Cassini, Stardust, Galileo, and Ulysses) have successfully characterised interstellar, interplanetary, and circumplanetary dust using a variety of techniques, including in situ analyses and sample return. Charge, mass, and velocity measurements of the dust are performed either directly (induced charge signals) or indirectly (mass and velocity from impact ionisation signals or crater morphology) and constrain the dynamical parameters of the dust grains. Dust compositional information may be obtained via either time-of-flight mass spectrometry of the impact plasma or direct sample return. The accurate and reliable interpretation of collected spacecraft data requires a comprehensive programme of terrestrial instrument calibration. This process involves accelerating suitable solar system analogue dust particles to hypervelocity speeds in the laboratory, an activity performed at the Max Planck Institut fuer Kernphysik in Heidelberg, Germany. Here, a 2 MV Van de Graaff accelerator electrostatically accelerates charged micron and submicron-sized dust particles to speeds up to 80 km s -1 . Recent advances in dust production and processing have allowed solar system analogue dust particles (silicates and other minerals) to be coated with a thin conductive shell, enabling them to be charged and accelerated. Refinements and upgrades to the beam line instrumentation and electronics now allow for the reliable selection of particles at velocities of 1-80 km s -1 and with diameters of between 0.05 μm and 5 μm. This ability to select particles for subsequent impact studies based on their charges, masses, or velocities is provided by a particle selection unit (PSU). The PSU contains a field programmable gate array, capable of monitoring in real time the particles' speeds and charges, and is

  1. Initial experience with megavoltage (MV) CT guidance for daily prostate alignments

    International Nuclear Information System (INIS)

    Langen, Katja M.; Zhang Yashan; Andrews, Rhonda D.; Hurley, Monica E.; Meeks, Sanford L.; Poole, Darrell O.; Willoughby, Twyla R.; Kupelian, Patrick A.

    2005-01-01

    Purpose: The on-board megavoltage (MV) computed tomography (CT) capabilities of a TomoTherapy Hi*ART unit were used to obtain daily MVCT images of prostate cancer patients. For patient alignment the daily MVCT image needs to be registered with the planning CT image to calculate couch shifts. Three manual techniques of registering the MVCT images with the planning kilovoltage (kV) CT images were evaluated. The techniques are based on visual alignment of (1) fiducial prostate markers (2) CT anatomy, and (3) kVCT contours. Methods and Materials: One hundred and twelve alignments from 3 patients were available for analysis. The radiation therapists visually registered the MVCT images with the planning kVCT images based on fiducial markers for actual patient alignment. Retrospectively, the therapists registered each image set using anatomy and contour-based techniques. In addition to the therapists, a physician retrospectively registered each image set based on each of the three techniques. For each MVCT to kVCT image pair a reference alignment was computed from the center-of-mass (COM) of the three fiducial markers. All registration results were compared with these reference alignments. The physician's image registrations were compared with the radiation therapists' registrations to assess the user variability of the different techniques. Results: The marker-based registration results agree best with the reference alignments, while the contour-based registrations show the least degree of agreement. Using anatomy and contour-based registrations, the radiation therapist's alignments differed by ≥ 3 mm from the reference alignments in 24%, 33%, and 3% and 55%, 48%, and 21% of all registrations in the anterior-posterior, superior-inferior, and lateral directions, respectively. The respective values for the marker-based alignments were 3%, 6%, and 3%. The physician's registrations showed the same general trend. The marker-based registrations showed the least amount of

  2. Tracking tumor boundary in MV-EPID images without implanted markers: A feasibility study

    International Nuclear Information System (INIS)

    Zhang, Xiaoyong; Homma, Noriyasu; Ichiji, Kei; Takai, Yoshihiro; Yoshizawa, Makoto

    2015-01-01

    Purpose: To develop a markerless tracking algorithm to track the tumor boundary in megavoltage (MV)-electronic portal imaging device (EPID) images for image-guided radiation therapy. Methods: A level set method (LSM)-based algorithm is developed to track tumor boundary in EPID image sequences. Given an EPID image sequence, an initial curve is manually specified in the first frame. Driven by a region-scalable energy fitting function, the initial curve automatically evolves toward the tumor boundary and stops on the desired boundary while the energy function reaches its minimum. For the subsequent frames, the tracking algorithm updates the initial curve by using the tracking result in the previous frame and reuses the LSM to detect the tumor boundary in the subsequent frame so that the tracking processing can be continued without user intervention. The tracking algorithm is tested on three image datasets, including a 4-D phantom EPID image sequence, four digitally deformable phantom image sequences with different noise levels, and four clinical EPID image sequences acquired in lung cancer treatment. The tracking accuracy is evaluated based on two metrics: centroid localization error (CLE) and volume overlap index (VOI) between the tracking result and the ground truth. Results: For the 4-D phantom image sequence, the CLE is 0.23 ± 0.20 mm, and VOI is 95.6% ± 0.2%. For the digital phantom image sequences, the total CLE and VOI are 0.11 ± 0.08 mm and 96.7% ± 0.7%, respectively. In addition, for the clinical EPID image sequences, the proposed algorithm achieves 0.32 ± 0.77 mm in the CLE and 72.1% ± 5.5% in the VOI. These results demonstrate the effectiveness of the authors’ proposed method both in tumor localization and boundary tracking in EPID images. In addition, compared with two existing tracking algorithms, the proposed method achieves a higher accuracy in tumor localization. Conclusions: In this paper, the authors presented a feasibility study of tracking

  3. Evaluation of build-up dose from 6 MV X-rays under pelvic and abdominal patient immobilisation devices

    Energy Technology Data Exchange (ETDEWEB)

    Cheung Tsang; Butson, M.J.Martin J. E-mail: mbutson@usa.netmbutson@guessmail.com; Yu, P.K.N

    2002-06-01

    The use of pelvic and abdominal immobilisation devices in radiotherapy is required for accurate positioning and repositioning of patients during their fractionated treatment delivered normally over a period of 5-6 weeks. 6 MV X-rays produced by a medical linear accelerator have a skin sparing effect whereby the skin dose delivered is considerably less than that received by the tumour. The treatment through a vacuum compressed immobilisation device (Vacbag) however increases the dose delivered to the skin by interactions of the X-rays within the Vacbag material. For example, the basal layer doses increased from 16% for an open field to 52% of maximum with a bag thickness of 2.5 cm for a 10 cmx10 cm field at 6 MV X-ray energy. At the same field size the dermal skin layer (1 mm depth) doses increased from 44% (no bag) to 60% for a bag thickness of 2.5 cm at 6 MV X-rays. The Vacbag should be placed outside the treatment field whenever possible to keep skin dose to a minimum level.

  4. Evaluation of build-up dose from 6 MV X-rays under pelvic and abdominal patient immobilisation devices

    International Nuclear Information System (INIS)

    Cheung Tsang; Butson, M.J.Martin J.; Yu, P.K.N.

    2002-01-01

    The use of pelvic and abdominal immobilisation devices in radiotherapy is required for accurate positioning and repositioning of patients during their fractionated treatment delivered normally over a period of 5-6 weeks. 6 MV X-rays produced by a medical linear accelerator have a skin sparing effect whereby the skin dose delivered is considerably less than that received by the tumour. The treatment through a vacuum compressed immobilisation device (Vacbag) however increases the dose delivered to the skin by interactions of the X-rays within the Vacbag material. For example, the basal layer doses increased from 16% for an open field to 52% of maximum with a bag thickness of 2.5 cm for a 10 cmx10 cm field at 6 MV X-ray energy. At the same field size the dermal skin layer (1 mm depth) doses increased from 44% (no bag) to 60% for a bag thickness of 2.5 cm at 6 MV X-rays. The Vacbag should be placed outside the treatment field whenever possible to keep skin dose to a minimum level

  5. Design of a high average-power FEL driven by an existing 20 MV electrostatic-accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Kimel, I.; Elias, L.R. [Univ. of Central Florida, Orlando, FL (United States)

    1995-12-31

    There are some important applications where high average-power radiation is required. Two examples are industrial machining and space power-beaming. Unfortunately, up to date no FEL has been able to show more than 10 Watts of average power. To remedy this situation we started a program geared towards the development of high average-power FELs. As a first step we are building in our CREOL laboratory, a compact FEL which will generate close to 1 kW in CW operation. As the next step we are also engaged in the design of a much higher average-power system based on a 20 MV electrostatic accelerator. This FEL will be capable of operating CW with a power output of 60 kW. The idea is to perform a high power demonstration using the existing 20 MV electrostatic accelerator at the Tandar facility in Buenos Aires. This machine has been dedicated to accelerate heavy ions for experiments and applications in nuclear and atomic physics. The necessary adaptations required to utilize the machine to accelerate electrons will be described. An important aspect of the design of the 20 MV system, is the electron beam optics through almost 30 meters of accelerating and decelerating tubes as well as the undulator. Of equal importance is a careful design of the long resonator with mirrors able to withstand high power loading with proper heat dissipation features.

  6. Design of a 7-MV Linear Transformer Driver (LTD) for down-hole flash x-ray radiography

    International Nuclear Information System (INIS)

    Cordova, Steve Ray; Welch, Dale Robert; Oliver, Bryan Velten; Rose, David Vincent; Johnson, David Lee; Bruner, Nichelle Lee; Leckbee, Joshua J.

    2008-01-01

    Pulsed power driven flash x-ray radiography is a valuable diagnostic for subcritical experiments at the Nevada Test Site. The existing dual-axis Cygnus system produces images using a 2.25 MV electron beam diode to produce intense x-rays from a small source. Future hydrodynamic experiments will likely use objects with higher areal mass, requiring increased x-ray dose and higher voltages while maintaining small source spot size. A linear transformer driver (LTD) is a compact pulsed power technology with applications ranging from pulsed power flash x-ray radiography to high current Z-pinch accelerators. This report describes the design of a 7-MV dual-axis system that occupies the same lab space as the Cygnus accelerators. The work builds on a design proposed in a previous report [1]. This new design provides increased diode voltage from a lower impedance accelerator to improve coupling to low impedance diodes such as the self magnetic pinch (SMP) diode. The design also improves the predicted reliability by operating at a lower charge voltage and removing components that have proven vulnerable to failure. Simulations of the new design and experimental results of the 1-MV prototype are presented

  7. PIC simulation of the vacuum power flow for a 5 terawatt, 5 MV, 1 MA pulsed power system

    Science.gov (United States)

    Liu, Laqun; Zou, Wenkang; Liu, Dagang; Guo, Fan; Wang, Huihui; Chen, Lin

    2018-03-01

    In this paper, a 5 Terawatt, 5 MV, 1 MA pulsed power system based on vacuum magnetic insulation is simulated by the particle-in-cell (PIC) simulation method. The system consists of 50 100-kV linear transformer drive (LTD) cavities in series, using magnetically insulated induction voltage adder (MIVA) technology for pulsed power addition and transmission. The pulsed power formation and the vacuum power flow are simulated when the system works in self-limited flow and load-limited flow. When the pulsed power system isn't connected to the load, the downstream magnetically insulated transmission line (MITL) works in the self-limited flow, the maximum of output current is 1.14 MA and the amplitude of voltage is 4.63 MV. The ratio of the electron current to the total current is 67.5%, when the output current reached the peak value. When the impedance of the load is 3.0 Ω, the downstream MITL works in the self-limited flow, the maximums of output current and the amplitude of voltage are 1.28 MA and 3.96 MV, and the ratio of the electron current to the total current is 11.7% when the output current reached the peak value. In addition, when the switches are triggered in synchronism with the passage of the pulse power flow, it effectively reduces the rise time of the pulse current.

  8. Structure, bioactivity, and synthesis of methylated flavonoids.

    Science.gov (United States)

    Wen, Lingrong; Jiang, Yueming; Yang, Jiali; Zhao, Yupeng; Tian, Miaomiao; Yang, Bao

    2017-06-01

    Methylated flavonoids are an important type of natural flavonoid derivative with potentially multiple health benefits; among other things, they have improved bioavailability compared with flavonoid precursors. Flavonoids have been documented to have broad bioactivities, such as anticancer, immunomodulation, and antioxidant activities, that can be elevated, to a certain extent, by methylation. Understanding the structure, bioactivity, and bioavailability of methylated flavonoids, therefore, is an interesting topic with broad potential applications. Though methylated flavonoids are widely present in plants, their levels are usually low. Because developing efficient techniques to produce these chemicals would likely be beneficial, we provide an overview of their chemical and biological synthesis. © 2017 New York Academy of Sciences.

  9. Colorectal Cancer "Methylator Phenotype": Fact or Artifact?

    Directory of Open Access Journals (Sweden)

    Charles Anacleto

    2005-04-01

    Full Text Available It has been proposed that human colorectal tumors can be classified into two groups: one in which methylation is rare, and another with methylation of several loci associated with a "CpG island methylated phenotype (CIMP," characterized by preferential proximal location in the colon, but otherwise poorly defined. There is considerable overlap between this putative methylator phenotype and the well-known mutator phenotype associated with microsatellite instability (MSI. We have examined hypermethylation of the promoter region of five genes (DAPK, MGMT, hMLH1, p16INK4a, and p14ARF in 106 primary colorectal cancers. A graph depicting the frequency of methylated loci in the series of tumors showed a continuous, monotonically decreasing distribution quite different from the previously claimed discontinuity. We observed a significant association between the presence of three or more methylated loci and the proximal location of the tumors. However, if we remove from analysis the tumors with hMLH1 methylation or those with MSI, the significance vanishes, suggesting that the association between multiple methylations and proximal location was indirect due to the correlation with MSI. Thus, our data do not support the independent existence of the so-called methylator phenotype and suggest that it rather may represent a statistical artifact caused by confounding of associations.

  10. Methylation diet and methyl group genetics in risk for adenomatous polyp occurrence

    Directory of Open Access Journals (Sweden)

    Mark Lucock

    2015-06-01

    Conclusion: A methylation diet influences methyl group synthesis in the regulation of blood homocysteine level, and is modulated by genetic interactions. Methylation-related nutrients also interact with key genes to modify risk of AP, a precursor of colorectal cancer. Independent of diet, two methylation-related genes (A2756G-MS and A66G-MSR were directly associated with AP occurrence.

  11. Electrochemical Studies on Uranyl Chloride Complexes in 1-Butyl-3-methyl-imidazolium Based Ionic liquids

    Energy Technology Data Exchange (ETDEWEB)

    Yasuhisa Ikeda; Katsuyuki Hiroe; Nobutaka Ohta; Masanobu Nogami; Atsushi Shirai [Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology 2-12-1-N1-34 Ookayama, Meguro-ku, Tokyo 152-8550 (Japan); Noriko Asanuma [Department of Energy Science and Engineering, Tokai University 1117 Kitakaname, Hiratsuka-shi, Kanagawa 259-1292 (Japan)

    2008-07-01

    Sample solutions were prepared by dissolving UO{sub 2}Cl{sub 2}-nH{sub 2}O or Cs{sub 2}UO{sub 2}Cl{sub 4} into 1-butyl-3-methyl-imidazolium chloride (BMICl). Their UV-visible absorption spectra showed that uranyl species in BMICl exist as [UO{sub 2}Cl{sub 4}]{sup 2-}. Cyclic voltammograms were measured using a glassy carbon working electrode, a platinum wire counter electrode, and an Ag/AgCl reference electrode with a liquid junction filled with BMIBF{sub 4} at 80 {+-} 1 deg. C in glove box under an Ar atmosphere. Peaks of one redox couple were observed at around -0.73 V and -0.65 V on both systems. Potential differences between two peaks ({delta}E{sub p}) at scan rates in the range of 10 to 50 mV/s are 70 - 80 mV, which are almost consistent with theoretical {delta}E{sub p} value (67 mV) for the reversible one electron transfer reaction at 80 deg. C. From these results, it is concluded that [UO{sub 2}Cl{sub 4}]{sup 2-} in BMICl is reduced quasi-reversibly to [UO{sub 2}Cl{sub 4}]{sup 3-}. (authors)

  12. Andrographolide Suppresses MV4-11 Cell Proliferation through the Inhibition of FLT3 Signaling, Fatty Acid Synthesis and Cellular Iron Uptake

    Directory of Open Access Journals (Sweden)

    Xiao Chen

    2017-08-01

    Full Text Available Background: Andrographolide (ADR, the main active component of Andrographis paniculata, displays anticancer activity in various cancer cell lines, among which leukemia cell lines exhibit the highest sensitivity to ADR. In particular, ADR was also reported to have reduced drug resistance in multidrug resistant cell lines. However, the mechanism of action (MOA of ADR’s anticancer and anti-drug-resistance activities remain elusive. Methods: In this study, we used the MV4-11 cell line, a FLT3 positive acute myeloid leukemia (AML cell line that displays multidrug resistance, as our experimental system. We first evaluated the effect of ADR on MV4-11 cell proliferation. Then, a quantitative proteomics approach was applied to identify differentially expressed proteins in ADR-treated MV4-11 cells. Finally, cellular processes and signal pathways affected by ADR in MV4-11 cell were predicted with proteomic analysis and validated with in vitro assays. Results: ADR inhibits MV4-11 cell proliferation in a dose- and time-dependent manner. With a proteomic approach, we discovered that ADR inhibited fatty acid synthesis, cellular iron uptake and FLT3 signaling pathway in MV4-11 cells. Conclusions: ADR inhibits MV4-11 cell proliferation through inhibition of fatty acid synthesis, iron uptake and protein synthesis. Furthermore, ADR reduces drug resistance by blocking FLT3 signaling.

  13. A genome-wide methylation study on obesity Differential variability and differential methylation

    NARCIS (Netherlands)

    Xu, Xiaojing; Su, Shaoyong; Barnes, Vernon A.; De Miguel, Carmen; Pollock, Jennifer; Ownby, Dennis; Shi, Huidong; Zhu, Haidong; Snieder, Harold; Wang, Xiaoling

    2013-01-01

    Besides differential methylation, DNA methylation variation has recently been proposed and demonstrated to be a potential contributing factor to cancer risk. Here we aim to examine whether differential variability in methylation is also an important feature of obesity, a typical non-malignant common

  14. 21 CFR 177.2000 - Vinylidene chloride/methyl acrylate/methyl methacrylate polymers.

    Science.gov (United States)

    2010-04-01

    ... methacrylate polymers. 177.2000 Section 177.2000 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF...: POLYMERS Substances for Use as Basic Components of Single and Repeated Use Food Contact Surfaces § 177.2000 Vinylidene chloride/methyl acrylate/methyl methacrylate polymers. The vinylidene chloride/methyl acrylate...

  15. Aberrant TET1 Methylation Closely Associated with CpG Island Methylator Phenotype in Colorectal Cancer.

    Science.gov (United States)

    Ichimura, Norihisa; Shinjo, Keiko; An, Byonggu; Shimizu, Yasuhiro; Yamao, Kenji; Ohka, Fumiharu; Katsushima, Keisuke; Hatanaka, Akira; Tojo, Masayuki; Yamamoto, Eiichiro; Suzuki, Hiromu; Ueda, Minoru; Kondo, Yutaka

    2015-08-01

    Inactivation of methylcytosine dioxygenase, ten-eleven translocation (TET) is known to be associated with aberrant DNA methylation in cancers. Tumors with a CpG island methylator phenotype (CIMP), a distinct subgroup with extensive DNA methylation, show characteristic features in the case of colorectal cancer. The relationship between TET inactivation and CIMP in colorectal cancers is not well understood. The expression level of TET family genes was compared between CIMP-positive (CIMP-P) and CIMP-negative (CIMP-N) colorectal cancers. Furthermore, DNA methylation profiling, including assessment of the TET1 gene, was assessed in colorectal cancers, as well as colon polyps. The TET1 was silenced by DNA methylation in a subset of colorectal cancers as well as cell lines, expression of which was reactivated by demethylating agent. TET1 methylation was more frequent in CIMP-P (23/55, 42%) than CIMP-N (2/113, 2%, P CIMP-P, 16/40, 40%; CIMP-N, 2/24, 8%; P = 0.002), suggesting that TET1 methylation is an early event in CIMP tumorigenesis. TET1 methylation was significantly associated with BRAF mutation but not with hMLH1 methylation in the CIMP-P colorectal cancers. Colorectal cancers with TET1 methylation have a significantly greater number of DNA methylated genes and less pathological metastasis compared to those without TET1 methylation (P = 0.007 and 0.045, respectively). Our data suggest that TET1 methylation may contribute to the establishment of a unique pathway in respect to CIMP-mediated tumorigenesis, which may be incidental to hMLH1 methylation. In addition, our findings provide evidence that TET1 methylation may be a good biomarker for the prediction of metastasis in colorectal cancer. ©2015 American Association for Cancer Research.

  16. The Synthesis of Methyl Salicylate: Amine Diazotization.

    Science.gov (United States)

    Zanger, Murray; McKee, James R.

    1988-01-01

    Notes that this experiment takes safety and noncarcinogenic reactants into account. Demonstrates the use of diazonium salts for the replacement of an aromatic amine group by a phenolic hydroxyl. Involves two pleasant-smelling organic compounds, methyl anthranilate (grape) and methyl salicylate (oil of wintergreen). (MVL)

  17. Evidence Suggesting Absence of Mitochondrial DNA Methylation

    DEFF Research Database (Denmark)

    Mechta, Mie; Ingerslev, Lars R; Fabre, Odile

    2017-01-01

    , 16S, ND5 and CYTB, suggesting that mtDNA supercoiled structure blocks the access to bisulfite conversion. Here, we identified an artifact of mtDNA bisulfite sequencing that can lead to an overestimation of mtDNA methylation levels. Our study supports that cytosine methylation is virtually absent...

  18. DNA Methylation Modulates Nociceptive Sensitization after Incision.

    Directory of Open Access Journals (Sweden)

    Yuan Sun

    Full Text Available DNA methylation is a key epigenetic mechanism controlling DNA accessibility and gene expression. Blockade of DNA methylation can significantly affect pain behaviors implicated in neuropathic and inflammatory pain. However, the role of DNA methylation with regard to postoperative pain has not yet been explored. In this study we sought to investigate the role of DNA methylation in modulating incisional pain and identify possible targets under DNA methylation and contributing to incisional pain. DNA methyltranferase (DNMT inhibitor 5-Aza-2'-deoxycytidine significantly reduced incision-induced mechanical allodynia and thermal sensitivity. Aza-2'-deoxycytidine also reduced hindpaw swelling after incision, suggesting an anti-inflammatory effect. Global DNA methylation and DNMT3b expression were increased in skin after incision, but none of DNMT1, DNMT3a or DNMT3b was altered in spinal cord or DRG. The expression of proopiomelanocortin Pomc encoding β-endorphin and Oprm1 encoding the mu-opioid receptor were upregulated peripherally after incision; moreover, Oprm1 expression was further increased under DNMT inhibitor treatment. Finally, local peripheral injection of the opioid receptor antagonist naloxone significantly exacerbated incision-induced mechanical hypersensitivity. These results suggest that DNA methylation is functionally relevant to incisional nociceptive sensitization, and that mu-opioid receptor signaling might be one methylation regulated pathway controlling sensitization after incision.

  19. Methyl 3-(Quinolin-2-ylindolizine-1-carboxylate

    Directory of Open Access Journals (Sweden)

    Roumaissa Belguedj

    2015-12-01

    Full Text Available A novel compound, methyl 3-(quinolin-2-ylindolizine-1-carboxylate (2 has been synthesized by cycloaddition reaction of 1-(quinolin-2-ylmethylpyridinium ylide (1 with methyl propiolate in presence of sodium hydride in THF. The structure of this compound was established by IR, 1H-NMR, 13C-NMR and MS data

  20. Adenine N6-methylation in diverse fungi

    NARCIS (Netherlands)

    Seidl, Michael F.

    2017-01-01

    A DNA modification - methylation of cytosines and adenines - has important roles in diverse processes such as regulation of gene expression and genome stability, yet until recently adenine methylation had been considered to be only a hallmark of prokaryotes. A new study identifies abundant

  1. Spectra and absorbed dose by photo-neutrons in a solid water mannequin exposed to a Linac of 15 MV; Espectros y dosis absorbida por fotoneutrones en un maniqui de agua solida expuesta a una Linac de 15 MV

    Energy Technology Data Exchange (ETDEWEB)

    Benites R, J. [Centro Estatal de Cancerologia de Nayarit, Servicio de Seguridad Radiologica, Calz. de la Cruz 118 Sur, 63000 Tepic, Nayarit (Mexico); Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Apdo. Postal 336, 98000 Zacatecas (Mexico); Velazquez F, J., E-mail: jlbenitesr@prodigy.net.mx [Universidad Autonoma de Nayarit, Posgrado en Ciencias Biologico Agropecuarias, Carretera Tepic-Compostela Km 9, 63780 Jalisco-Nayarit (Mexico)

    2012-10-15

    Using Monte Carlo methods was modeled a solid water mannequin; according to the ICRU 44 (1989), Tissue substitutes in radiation dosimetry and measurements, of the International Commission on Radiation Units and Measurements; Report 44. This material Wt 1 is made of H (8.1%), C (67.2%), N (2.4%), O (19.9%), Cl (0.1%), Ca (2.3%) and its density is of 1.02 gr/cm{sup 3}. The mannequin was put instead of the patient, inside the treatment room and the spectra and absorbed dose were determined by photo-neutrons exposed to a Linac of 15 MV. (Author)

  2. Testing MV-4 hydraulic supports on shearer faces with gradients of over 40 degrees. Ensayode pilas hidraulicas tipo MV-4 para talleres con buzamiento mayor de 40 degree con Rozadora

    Energy Technology Data Exchange (ETDEWEB)

    Garcia Villa, M

    1990-10-01

    The Minas de Figaredo company forms part of the INI coal-mining group which is located in the Central Asturias coalfield. Production has recently increased by 56% as a result of coal face mechanisation. A vertical powered support, known as the MV-4, has been supplied by EMCOR and tested in steeply-dipping seams on face no. 28. This type of support was chosen not only to improve safety during both support setting and coal cutting but also to increase unit production and underground productivity. 6 figs., 2 tabs.

  3. Experimental apparatus with {sup 3}He detectors for photoneutron measurements greater than 8 MV; Aparato experimental de detector {sup 3}He, para medida fotonêutrons em acelerador com energia acima 8 MV

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Marcelo Vilela da; Fontes, Gladson Silva; Cardoso, Domingos D’Oliveira, E-mail: marcelovilelasilva@gmail.com [Instituto Militar de Engenharia (IME), Rio de Janeiro, RJ (Brazil)

    2017-07-01

    Particle technology has a profound impact on society. Its applications are well established mainly in the treatment of cancer and other diseases. The objective of this work was to develop an experimental apparatus with {sup 3}He detectors for photoneutron measurements greater than 8 MV. The apparatus allowed to obtain a multi energetic neutron measurements with detector and changing the different thicknesses of shields and for different dose rates. Additionally, an analytical model was developed, based on the approximation of the diffusion, for two groups of energy. The results indicated an increasing and linear behavior in the detector response. (author)

  4. Effects of cytosine methylation on transcription factor binding sites

    KAUST Repository

    Medvedeva, Yulia A; Khamis, Abdullah M.; Kulakovskiy, Ivan V; Ba Alawi, Wail; Bhuyan, Md Shariful I; Kawaji, Hideya; Lassmann, Timo; Harbers, Matthias; Forrest, Alistair RR; Bajic, Vladimir B.

    2014-01-01

    Background: DNA methylation in promoters is closely linked to downstream gene repression. However, whether DNA methylation is a cause or a consequence of gene repression remains an open question. If it is a cause, then DNA methylation may affect

  5. DMPD: TLR ignores methylated RNA? [Dynamic Macrophage Pathway CSML Database

    Lifescience Database Archive (English)

    Full Text Available 16111629 TLR ignores methylated RNA? Ishii KJ, Akira S. Immunity. 2005 Aug;23(2):11...1-3. (.png) (.svg) (.html) (.csml) Show TLR ignores methylated RNA? PubmedID 16111629 Title TLR ignores methylated

  6. Modeling spatiotemporal dynamics of DNA methylation

    DEFF Research Database (Denmark)

    Lövkvist, Cecilia Elisabet

    into how epigenetic marks are distributed in the human genome. In the first part of the thesis, we investigate DNA methylation and maintenance of methylation patterns throughout cell division. We argue that collaborative models, those where the methylation of CpG sites depends on the methylation status...... into the game more explicitly in another type of model that speaks out the duality of the two aspects. Using statistical analysis of experimental data, this thesis further explores a link between DNA methylation and nucleosome occupancy. By comparing the patterns on promoters to regions with similar Cp...... division. The patterns of epigentic marks depend on enzymes that ensure their maintenance and introduction. Using theoretical models, this thesis proposes new mechanisms for how enzymes operate to maintain patterns of epigenetic marks. Through analysis of experimental data this work gives new insight...

  7. Protein methylation reactions in intact pea chloroplasts

    International Nuclear Information System (INIS)

    Niemi, K.J.

    1989-01-01

    Post-translational protein methylation was investigated in Pisum sativum chloroplasts. Intact pea chloroplasts were incubated with ( 3 H-methyl)-S-adenosylmethionine under various conditions. The chloroplasts were then separated into stromal and thylakoid fractions and analyzed for radioactivity transferred to protein. Light enhanced the magnitude of labeling in both fractions. One thylakoid polypeptide with an apparent molecular mass of 43 kDa was labeled only in the light. Several other thylakoid and stromal proteins were labeled in both light and dark-labeling conditions. Both base-labile methylation, carboxy-methylesters and base-stable groups, N-methylations were found. Further characterization of the methyl-transfer reactions will be presented

  8. Radiation effects on DNA methylation in mice

    International Nuclear Information System (INIS)

    Komura, J.; Kurishita, A.; Miyamura, Y.; Ono, T.; Tawa, R.; Sakurai, H.

    1992-01-01

    Effects of ionizing radiation on DNA methylation in liver, brain and spleen were examined by high performance liquid chromatography (HPLC). The total methylated cytosine level in the genome was reduced within 8 hours after 3.8 Gy of irradiation in liver of adult mice. But no appreciable effect was observed in brain and spleen. When mice were irradiated at newborn, liver DNA revealed no change in methylated cytosine level. Even though slight effects of radiation were detected in he methylation of the c-myc and c-fos genes, they were only temporary and no long-term effects were observed. These data suggest that the effect of radiation on DNA methylation in vivo is not prevailing a DNA damage, but rather influenced much through biological parameters. (author)

  9. Methylation analysis of polysaccharides: Technical advice.

    Science.gov (United States)

    Sims, Ian M; Carnachan, Susan M; Bell, Tracey J; Hinkley, Simon F R

    2018-05-15

    Glycosyl linkage (methylation) analysis is used widely for the structural determination of oligo- and poly-saccharides. The procedure involves derivatisation of the individual component sugars of a polysaccharide to partially methylated alditol acetates which are analysed and quantified by gas chromatography-mass spectrometry. The linkage positions for each component sugar can be determined by correctly identifying the partially methylated alditol acetates. Although the methods are well established, there are many technical aspects to this procedure and both careful attention to detail and considerable experience are required to achieve a successful methylation analysis and to correctly interpret the data generated. The aim of this article is to provide the technical details and critical procedural steps necessary for a successful methylation analysis and to assist researchers (a) with interpreting data correctly and (b) in providing the comprehensive data required for reviewers to fully assess the work. Copyright © 2018 Elsevier Ltd. All rights reserved.

  10. DNA sequence explains seemingly disordered methylation levels in partially methylated domains of Mammalian genomes.

    Directory of Open Access Journals (Sweden)

    Dimos Gaidatzis

    2014-02-01

    Full Text Available For the most part metazoan genomes are highly methylated and harbor only small regions with low or absent methylation. In contrast, partially methylated domains (PMDs, recently discovered in a variety of cell lines and tissues, do not fit this paradigm as they show partial methylation for large portions (20%-40% of the genome. While in PMDs methylation levels are reduced on average, we found that at single CpG resolution, they show extensive variability along the genome outside of CpG islands and DNase I hypersensitive sites (DHS. Methylation levels range from 0% to 100% in a roughly uniform fashion with only little similarity between neighboring CpGs. A comparison of various PMD-containing methylomes showed that these seemingly disordered states of methylation are strongly conserved across cell types for virtually every PMD. Comparative sequence analysis suggests that DNA sequence is a major determinant of these methylation states. This is further substantiated by a purely sequence based model which can predict 31% (R(2 of the variation in methylation. The model revealed CpG density as the main driving feature promoting methylation, opposite to what has been shown for CpG islands, followed by various dinucleotides immediately flanking the CpG and a minor contribution from sequence preferences reflecting nucleosome positioning. Taken together we provide a reinterpretation for the nucleotide-specific methylation levels observed in PMDs, demonstrate their conservation across tissues and suggest that they are mainly determined by specific DNA sequence features.

  11. Detection of DNA methylation changes in micropropagated banana plants using methylation-sensitive amplification polymorphism (MSAP).

    Science.gov (United States)

    Peraza-Echeverria, S; Herrera-Valencia, V A.; Kay, A -J.

    2001-07-01

    The extent of DNA methylation polymorphisms was evaluated in micropropagated banana (Musa AAA cv. 'Grand Naine') derived from either the vegetative apex of the sucker or the floral apex of the male inflorescence using the methylation-sensitive amplification polymorphism (MSAP) technique. In all, 465 fragments, each representing a recognition site cleaved by either or both of the isoschizomers were amplified using eight combinations of primers. A total of 107 sites (23%) were found to be methylated at cytosine in the genome of micropropagated banana plants. In plants micropropagated from the male inflorescence explant 14 (3%) DNA methylation events were polymorphic, while plants micropropagated from the sucker explant produced 8 (1.7%) polymorphisms. No DNA methylation polymorphisms were detected in conventionally propagated banana plants. These results demonstrated the usefulness of MSAP to detect DNA methylation events in micropropagated banana plants and indicate that DNA methylation polymorphisms are associated with micropropagation.

  12. The origin and fate of 4-methyl steroid hydrocarbons. I. Diagenesis of 4-methyl sterenes

    Science.gov (United States)

    Wolff, George A.; Lamb, Neil A.; Maxwell, James R.

    1986-03-01

    Treatment of 4-methylcholest-4-ene under mild acid conditions at low temperatures gives chemical evidence for certain features seen in the distributions of sedimentary 4-methyl steroid hydrocarbons, and further indicates that many low temperature diagenetic reactions of steroids are explicable in terms of acid catalysed rearrangements. Specifically, the results provide: (i) Indirect evidence that the 4-ene skeleton is a key intermediate in the dehydration of 4-methyl stanols in sediments. (ii) An explanation for the distribution of 4-methyl sterenes and A-nor sterenes in the lacustrine Messel shale (Eocene). (iii) An explanation for the presence of 4β-methyl steranes in relatively immature sedimentary rocks, despite the precursor stanols having the 4α-methyl configuration. With increasing maturity in the Paris Basin shales (Lower Toarcian), the less stable 4β-methyl steranes decrease gradually in abundance relative to their 4α-methyl counterparts, at a rate fairly similar to the change in pristane stereochemistry.

  13. Dosimetric comparative analysis between 10 MV Megavoltage unidirectional beam and boron neutron capture therapy for brain tumors treatment

    International Nuclear Information System (INIS)

    Brandao, Samia F.; Campos, Tarcisio P.R.

    2011-01-01

    This paper present a comparative dosimetric analysis between boron neutron capture therapy and 10 MV megavoltage employed in brain tumor treatments, limited to a unidirectional beam. A computational phantom of a human head was developed to be used in computational simulations of the two protocols, conducted in MCNP5 code. This phantom represents several head's structures, mainly, the central nervous system and a tumor that represents a Glioblastoma Multiform - one of the most malignant and aggressive brain tumors. Absorbed and biological weighted dose rates and neutron fluency in the computational phantom were evaluated from the MCNP5 code. The biologically weighted dose rate to 10 MV megavoltage beam presented no specificity in deposited dose in tumor. The average total biologically weighted dose rate in tumor was 9.93E-04 RBE.Gy.h"-"1/Mp.s"-"1 while in healthy tissue it was 8.67E-04 RBE.Gy.h"-"1/Mp.s"-1. On the BNCT simulations the boron concentration was particularly relevant since the largest dose deposition happened in borate tissues. The average total biologically weighted dose rate in tumor was 3.66E-02 RBE.Gy.h"-"1/Mp.s"-"1 while in healthy tissue it was 1.39E-03 RBE.Gy.h"-"1/Mp.s"-"1. In comparison to the 10 MV megavoltage beam, BNCT showed clearly a largest dose deposition in the tumor, on average, 37 times larger than in the megavoltage beam, while in healthy tissue that average was only 1,6 time larger in BNCT. (author)

  14. 6.1-MV, 0.79-MA laser-triggered gas switch for multimodule, multiterawatt pulsed-power accelerators

    Directory of Open Access Journals (Sweden)

    K. R. LeChien

    2010-03-01

    Full Text Available A 6.1-MV, 0.79-MA laser-triggered gas switch (LTGS is used to synchronize the 36 modules of the Z machine at Sandia National Laboratories. Each module includes one switch, which serves as the last command-fired switch of the module, and hence is used to determine the time at which each module electrically closes relative to the other modules. The switch is ∼81-cm in length, ∼45-cm in diameter, and is immersed in mineral oil. The outer switch envelope consists of six corrugated monomer-cast acrylic insulators and five contoured stainless-steel rings. The trigger electrodes are fabricated from copper-infused tungsten. The switch is pressurized with several atmospheres of sulfur hexafluoride (SF_{6}, which is turbulently purged within 2 seconds after every shot. Each switch is powered from a 6-MV, 0.78-MJ Marx generator which pulse charges a 24-nF intermediate-store water capacitor in 1.4-μs. Closure of the switch allows power to flow into pulse-forming transmission lines. The power pulse is subsequently compressed by water switches, which results in a total accelerator output power in excess of 70-TW. A previous version of the LTGS performed exceptionally at a 5.4-MV, 0.7-MA level on an engineering test module used for switch development. It exhibited a 1-σ jitter of ∼5  ns, a prefire and flashover rate less than 0.1%, and a lifetime in excess of 150 shots. When installed on the Z accelerator, however, the switch exhibited a prefire probability of ∼3%, a flashover probability of ∼7%, and a 15-ns jitter. The difference in performance is attributed to several factors such as higher total charge transfer, exposure to more debris, and more stressful dynamic mechanical loading upon machine discharge. Under these conditions, the replacement lifetime was less than ten shots. Since refurbishment of Z in October 2007, there have been three LTGS design iterations to improve the performance at 6.1-MV. The most recent design exhibits a

  15. A new AMS facility based on a Cockcroft-Walton type 1 MV tandetron at IFIN-HH Magurele, Romania

    Science.gov (United States)

    Stan-Sion, C.; Enachescu, M.; Ghita, D. G.; Calinescu, C. I.; Petre, A.; Mosu, D. V.; Klein, M.

    2014-01-01

    A 1 MV AMS machine was recently installed in the National Institute for Physics and Nuclear Engineering IFIN-HH, Bucharest Romania. It is the second AMS facility at IFIN-HH having the goal not only to continue but mainly to enlarge the research area of this highly sensitive analyzing method. The multi-element AMS was developed by HVEE to measure 14C, 10Be, and 26Al, and 129I. The results of an acceptance test are presented and demonstrate that this machine is capable of routine 14C age dating and of measurements of other radioisotopes in terms of accuracy and precision as well as a low background level.

  16. Spectra and absorbed dose by photo-neutrons in a solid water mannequin exposed to a Linac of 15 MV

    International Nuclear Information System (INIS)

    Benites R, J.; Vega C, H. R.; Velazquez F, J.

    2012-10-01

    Using Monte Carlo methods was modeled a solid water mannequin; according to the ICRU 44 (1989), Tissue substitutes in radiation dosimetry and measurements, of the International Commission on Radiation Units and Measurements; Report 44. This material Wt 1 is made of H (8.1%), C (67.2%), N (2.4%), O (19.9%), Cl (0.1%), Ca (2.3%) and its density is of 1.02 gr/cm 3 . The mannequin was put instead of the patient, inside the treatment room and the spectra and absorbed dose were determined by photo-neutrons exposed to a Linac of 15 MV. (Author)

  17. Note: Establishing α-particle radiation damage experiments using the Dalton Cumbrian Facility's 5 MV tandem pelletron

    Science.gov (United States)

    Bower, W. R.; Smith, A. D.; Pattrick, R. A. D.; Pimblott, S. M.

    2015-04-01

    Evaluating the radiation stability of mineral phases is a vital research challenge when assessing the performance of the materials employed in a Geological Disposal Facility for radioactive waste. This report outlines the setup and methodology for efficiently allowing the determination of the dose dependence of damage to a mineral from a single ion irradiated sample. The technique has been deployed using the Dalton Cumbrian Facility's 5 MV tandem pelletron to irradiate a suite of minerals with a controlled α-particle (4He2+) beam. Such minerals are proxies for near-field clay based buffer material surrounding radioactive canisters, as well as the sorbent components of the host rock.

  18. Variations in depth-dose data between open and wedge fields for 4-MV x-rays

    International Nuclear Information System (INIS)

    Sewchand, W.; Khan, F.M.; Williamson, J.

    1978-01-01

    Central-axis depth-dose data for 4-MV x rays, including tissue-maximum ratios, were measured for wedge fields. Comparison with corresponding open-field data revealed differences in magnitude which increased with depth, field size, and wedge thickness. However, phantom scatter correction factors for the wedge fields differed less than 1% from corresponding open-field factors. The differences in central-axis percent depth doses between the two types of fields indicate beam hardening by the wedge filter. This study also implies that the derivation of tissue-maximum ratios from central-axis percent depth is as valid for wedge as for open fields

  19. Energy calibration of a 5. 5 MV Van de Graaff accelerator using a time-of-flight technique

    Energy Technology Data Exchange (ETDEWEB)

    Andrade, E.; Feregrino, M.; Zavala, E.P.; Pineda, J.C.; Jimenez, R.; Jaidar, A. (Universidad Nacional Autonoma de Mexico, Mexico City. Inst. de Fisica (Mexico))

    1990-02-01

    Energy calibration of the analysing magnet for the University of Mexico 5.5 MV Van de Graaff accelerator has been carried out using a time-of-flight method. The pulsed and bunched beam produced by the accelerator was used to deduce the energy E of the beam particles from the transit time between a coaxial pickup and a charged particle detector separated by 1.5 m. The measured FWHM energy resolution of this system was about 20 keV. (orig.).

  20. Energy calibration of a 5.5 MV Van de Graaff accelerator using a time-of-flight technique

    Science.gov (United States)

    Andrade, E.; Feregrino, M.; Zavala, E. P.; Pineda, J. C.; Jiménez, R.; Jaidar, A.

    1990-02-01

    Energy calibration of the analysing magnet for the University of México 5.5 MV Van de Graaff accelerator has been carried out using a time-of-flight method. The pulsed and bunched beam produced by the accelerator was used to deduce the energy E of the beam particles from the transit time between a coaxial pickup and a charged particle detector separated by 1.5 m. The measured FWHM energy resolution of this system was about 20 keV.

  1. Age-related variability of some characters of karyotype instability in the mouse line CC57W/Mv

    International Nuclear Information System (INIS)

    Glazko, T.T.; Safonova, N.A.; Kovaleva, O.A.; Stolina, M.P.; Solomko, A.P.; Malyuta, S.S.; Glazko, V.I.; AN Ukrainskoj SSR, Kiev

    1995-01-01

    The investigations of relations between cytogenetical variability in cells of bone marrow of the mouse line CC57W/Mv and factors of age and radioactivity pollution (the specific vivarium in the 30-km Chernobyl zone) were carried out. The karyotype instability on some characters were similarly between young mice in the Chernobyl zone and old mice under control conditions. The old Chernobyl mice differentiated from old control ones by a low frequency of some cytogenetic anomalies and higher values of the mitotic index. The contribution of the intensity of cell division into observed variabilities of cytogenetic character between different mouse groups was discussed

  2. Simulation-assisted technology assessment of an industrial X-ray source concept up to 1 MV

    International Nuclear Information System (INIS)

    Schultheis, Lothar

    2009-01-01

    A novel concept for a new generation of industrial X-ray sources up to 1MV is presented. A ceramic DC acceleration tube is directly connected to the high-voltage cascade within an SF6 pressure tank. Monte-Carlo simulations for specific applications reveal the relevant performance figures which are compared with measurements of a prototype. Design parameters and their mutual dependencies as well as technological performance limits can be investigated enabling efficient design optimizations. Thus, development projects can be advanced faster and much more focused. (orig.)

  3. 77 FR 4897 - Safety Zone; M/V Del Monte Live-Fire Gun Exercise, James River, Isle of Wight, VA

    Science.gov (United States)

    2012-02-01

    ...-AA00 Safety Zone; M/V Del Monte Live-Fire Gun Exercise, James River, Isle of Wight, VA AGENCY: Coast... provide for the safety of life on navigable waters during the live-fire gun exercises on the M/V Del Monte... associated with the live-fire gun exercise. DATES: This rule is effective in the CFR on February 1, 2012...

  4. 76 FR 31848 - Safety Zone; M/V Del Monte Live-Fire Gun Exercise, James River, Isle of Wight, Virginia

    Science.gov (United States)

    2011-06-02

    ...-AA00 Safety Zone; M/V Del Monte Live-Fire Gun Exercise, James River, Isle of Wight, Virginia AGENCY... provide for the safety of life on navigable waters during the live-fire gun exercises on the M/V Del Monte... associated with the live-fire gun exercise. DATES: This rule will be effective from 11 a.m. June 6, 2011...

  5. Will the Measurement Robots Take Our Jobs? An Update on the State of Automated M&V for Energy Efficiency Programs

    Energy Technology Data Exchange (ETDEWEB)

    Granderson, Jessica [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Touzani, Samir [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Taylor, Cody [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Fernandes, Samuel [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2017-07-28

    Trustworthy savings calculations are critical to convincing regulators of both the cost-effectiveness of energy efficiency program investments and their ability to defer supply-side capital investments. Today’s methods for measurement and verification (M&V) of energy savings constitute a significant portion of the total costs of energy efficiency programs. They also require time-consuming data acquisition. A spectrum of savings calculation approaches is used, with some relying more heavily on measured data and others relying more heavily on estimated, modeled, or stipulated data. The rising availability of “smart” meters and devices that report near-real time data, combined with new analytical approaches to quantifying savings, offers potential to conduct M&V more quickly and at lower cost, with comparable or improved accuracy. Commercial energy management and information systems (EMIS) technologies are beginning to offer M&V capabilities, and program administrators want to understand how they might assist programs in quickly and accurately measuring energy savings. This paper presents the results of recent testing of the ability to use automation to streamline some parts of M&V. Here in this paper, we detail metrics to assess the performance of these new M&V approaches, and a framework to compute the metrics. We also discuss the accuracy, cost, and time trade-offs between more traditional M&V, and these emerging streamlined methods that use high-resolution energy data and automated computational intelligence. Finally we discuss the potential evolution of M&V and early results of pilots currently underway to incorporate M&V automation into ratepayer-funded programs and professional implementation and evaluation practice.

  6. An autopsied case of MV2K + C-type sporadic Creutzfeldt-Jakob disease presenting with widespread cerebral cortical involvement and Kuru plaques.

    Science.gov (United States)

    Iwasaki, Yasushi; Saito, Yufuko; Aiba, Ikuko; Kobayashi, Atsushi; Mimuro, Maya; Kitamoto, Tetsuyuki; Yoshida, Mari

    2017-06-01

    MV2-type sporadic Creutzfeldt-Jakob disease (sCJD), which was previously called "Kuru-plaque variant", was gradually revealed to have a wide spectrum and has been classified into three pathological subtypes: MV2K, MV2C and MV2K + C. We herein describe the detailed clinical findings and neuropathologic observations from an autopsied MV2K + C-type Japanese sCJD case with widespread cerebral cortical pathology and Kuru plaques. In the early stages of the disease, the patient exhibited gait disturbance with ataxia and dysarthria as well as gradual appearance of cognitive dysfunction. Diffusion-weighted images (DWI) on MRI revealed extensive cerebral cortical hyperintensity. Pathologic investigation revealed extensive spongiform change in the cerebral cortex, particularly in the deeper layers. Vacuole size varied, and some were confluent. Prion protein (PrP) immunostaining revealed extensive PrP deposition in the cerebral cortex, basal ganglia, thalamus, cerebellum, brainstem and spinal cord. In the cerebral cortex, synaptic-type, Kuru plaque-like, and coarse plaque-type PrP depositions were mainly observed, along with some perivacuolar-type PrP depositions. Kuru plaques and coarse plaque-type PrP depositions also were observed in the cerebellar cortex. PrP gene analysis revealed no mutations, and polymorphic codon 129 exhibited Met/Val heterozygosity. Western blot analysis revealed a mixture of intermediate-type PrP Sc and type 2 PrP Sc . Based on previous reports regarding MV2-type sCJD and the clinicopathologic findings of the present case, we speculated that it may be possible to clinically distinguish each MV2 subtype. Clinical presentation of the MV2K + C subtype includes predominant cerebral cortical involvement signs with ataxia and DWI hyperintensity of the cerebral cortex on MRI. © 2016 Japanese Society of Neuropathology.

  7. Calorimetric determination of kQ factors for NE 2561 and NE 2571 ionization chambers in 5 cm x 5 cm and 10 cm x 10 cm radiotherapy beams of 8 MV and 16 MV photons.

    Science.gov (United States)

    Krauss, Achim; Kapsch, Ralf-Peter

    2007-10-21

    The relative uncertainty of the ionometric determination of the absorbed dose to water, D(w), in the reference dosimetry of high-energy photon beams is in the order of 1.5% and is dominated by the uncertainty of the calculated chamber- and energy-dependent correction factors k(Q). In the present investigation, k(Q) values were determined experimentally in 5 cm x 5 cm and 10 cm x 10 cm radiotherapy beams of 8 MV and 16 MV bremsstrahlung by means of a water calorimeter operated at 4 degrees C. Ionization chambers of the types NE 2561 and NE 2571 were calibrated directly in the water phantom of the calorimeter. The measurements were carried out at the linear accelerator of the Physikalisch-Technische Bundesanstalt. It is shown that the k(Q) factor of a single ionization chamber can be measured with a standard uncertainty of less than 0.3%. No significant variations of k(Q) were found for the different lateral sizes of the radiation fields used in this investigation.

  8. Gold work function reduction by 2.2 eV with an air-stable molecular donor layer

    Energy Technology Data Exchange (ETDEWEB)

    Broeker, Benjamin; Blum, Ralf-Peter; Frisch, Johannes; Rabe, Juergen P.; Koch, Norbert [Institut fuer Physik, Humboldt-Universitaet zu Berlin (Germany); Vollmer, Antje [Berliner Elektronenspeicherring-Gesellschaft fuer Synchrotronstrahlung mbH, Berlin (Germany); Hofmann, Oliver T.; Zojer, Egbert [Institut of Solid State Physics, Graz University of Technology (Austria); Rieger, Ralph; Muellen, Klaus [Max Planck Institut fuer Polymerforschung, Mainz (Germany)

    2009-07-01

    Ultraviolet photoelectron spectroscopy was used to investigate neutral methyl viologen (1,1'-dimethyl-1H,1'H-[4,4']bipyridinylidene, MV0) deposited on Au(111) surfaces. As a result of molecule-to-metal electron transfer, the work function of Au(111) was decreased from 5.5 eV to 3.3 eV. The energy levels of electron transport layers deposited on top of modified Au surfaces were shifted to higher binding energy compared to layers on pristine Au, and the electron injection barrier was reduced by 0.8 eV for tris(8-hydroxyquinoline)aluminum (Alq3) and by 0.7 eV for C60. The air-stable donor MV0 can thus be used to facilitate electron injection into organic semiconductors even from high work function metals.

  9. Efficient photocatalytic hydrogen production from water over Pt-Eosin Y catalyst: A systemic study of reaction parameters

    Science.gov (United States)

    Wang, Li; Zhao, Hui; Chen, Yong; Sun, Ruimin; Han, Bing

    2016-07-01

    A high efficient homogeneous system for hydrogen production from water consisting of Eosin Y as a photosensitizer, methyl viologen (MV2+) as an electron transfer mediator, triethanolamine (TEOA) as a sacrificial electron donor and colloid Pt as a catalyst, has been systemicly studied. The initial system pH and the concentration of Eosin Y have remarkable effects on the rate of hydrogen evolution. The optimal pH and concentration of Eosin Y are 9 and 7.2×10-5 M. Triethanolamine (TEOA) as an electron donor, can reductively quench the oxidized Eosin Y and the quenching is well modeled by the Stern-Volmer equation. The optimal concentration of TEOA and the concentration of MV2+ are 0.3 M and 3.1×10-4 M, respectively. In addition, the role of colloid Pt has been investigated.

  10. Effect of exogenous electron shuttles on growth and fermentative metabolism in Clostridium sp. BC1

    Energy Technology Data Exchange (ETDEWEB)

    Yarlagadda V. N.; Francis A.; Gupta, A.; Dodge, C. J.

    2012-03-01

    In this study, the influence exogenous electron shuttles on the growth and glucose fermentative metabolism of Clostridium sp. BC1 was investigated. Bicarbonate addition to mineral salts (MS) medium accelerated growth and glucose fermentation which shifted acidogenesis (acetic- and butyric-acids) towards solventogenesis (ethanol and butanol). Addition of ferrihydrite, anthraquinone disulfonate, and nicotinamide adenine dinucleotide in bicarbonate to growing culture showed no significant influence on fermentative metabolism. In contrast, methyl viologen (MV) enhanced ethanol- and butanol-production by 28- and 12-fold, respectively with concomitant decrease in hydrogen, acetic- and butyric-acids compared to MS medium. The results show that MV addition affects hydrogenase activity with a significant reduction in hydrogen production and a shift in the direction of electron flow towards enhanced production of ethanol and butanol.

  11. Global DNA methylation analysis using methyl-sensitive amplification polymorphism (MSAP).

    Science.gov (United States)

    Yaish, Mahmoud W; Peng, Mingsheng; Rothstein, Steven J

    2014-01-01

    DNA methylation is a crucial epigenetic process which helps control gene transcription activity in eukaryotes. Information regarding the methylation status of a regulatory sequence of a particular gene provides important knowledge of this transcriptional control. DNA methylation can be detected using several methods, including sodium bisulfite sequencing and restriction digestion using methylation-sensitive endonucleases. Methyl-Sensitive Amplification Polymorphism (MSAP) is a technique used to study the global DNA methylation status of an organism and hence to distinguish between two individuals based on the DNA methylation status determined by the differential digestion pattern. Therefore, this technique is a useful method for DNA methylation mapping and positional cloning of differentially methylated genes. In this technique, genomic DNA is first digested with a methylation-sensitive restriction enzyme such as HpaII, and then the DNA fragments are ligated to adaptors in order to facilitate their amplification. Digestion using a methylation-insensitive isoschizomer of HpaII, MspI is used in a parallel digestion reaction as a loading control in the experiment. Subsequently, these fragments are selectively amplified by fluorescently labeled primers. PCR products from different individuals are compared, and once an interesting polymorphic locus is recognized, the desired DNA fragment can be isolated from a denaturing polyacrylamide gel, sequenced and identified based on DNA sequence similarity to other sequences available in the database. We will use analysis of met1, ddm1, and atmbd9 mutants and wild-type plants treated with a cytidine analogue, 5-azaC, or zebularine to demonstrate how to assess the genetic modulation of DNA methylation in Arabidopsis. It should be noted that despite the fact that MSAP is a reliable technique used to fish for polymorphic methylated loci, its power is limited to the restriction recognition sites of the enzymes used in the genomic

  12. DNA methylation analysis reveals distinct methylation signatures in pediatric germ cell tumors

    International Nuclear Information System (INIS)

    Amatruda, James F; Frazier, A Lindsay; Poynter, Jenny N; Ross, Julie A; Christensen, Brock; Fustino, Nicholas J; Chen, Kenneth S; Hooten, Anthony J; Nelson, Heather; Kuriger, Jacquelyn K; Rakheja, Dinesh

    2013-01-01

    Aberrant DNA methylation is a prominent feature of many cancers, and may be especially relevant in germ cell tumors (GCTs) due to the extensive epigenetic reprogramming that occurs in the germ line during normal development. We used the Illumina GoldenGate Cancer Methylation Panel to compare DNA methylation in the three main histologic subtypes of pediatric GCTs (germinoma, teratoma and yolk sac tumor (YST); N = 51) and used recursively partitioned mixture models (RPMM) to test associations between methylation pattern and tumor and demographic characteristics. We identified genes and pathways that were differentially methylated using generalized linear models and Ingenuity Pathway Analysis. We also measured global DNA methylation at LINE1 elements and evaluated methylation at selected imprinted loci using pyrosequencing. Methylation patterns differed by tumor histology, with 18/19 YSTs forming a distinct methylation class. Four pathways showed significant enrichment for YSTs, including a human embryonic stem cell pluripotency pathway. We identified 190 CpG loci with significant methylation differences in mature and immature teratomas (q < 0.05), including a number of CpGs in stem cell and pluripotency-related pathways. Both YST and germinoma showed significantly lower methylation at LINE1 elements compared with normal adjacent tissue while there was no difference between teratoma (mature and immature) and normal tissue. DNA methylation at imprinted loci differed significantly by tumor histology and location. Understanding methylation patterns may identify the developmental stage at which the GCT arose and the at-risk period when environmental exposures could be most harmful. Further, identification of relevant genetic pathways could lead to the development of new targets for therapy

  13. PCR Primer Specific CaMV 35S Promoter to Detect Transgenic Soybean in Indonesia Commercial Soy Bean and Tempeh

    Directory of Open Access Journals (Sweden)

    Tri Joko Raharjo

    2017-11-01

    Full Text Available In the framework of the supervision and enforcement of the regulation regarding the content of soybean transgenic in food and processed foods such as tempeh, a reliable testing method is indispensable. Performance specific primer PCR amplification with promoter of CaMV 35S tested to detect the presence of GMOs. The parameters tested were specificity, precision and cut off detection using CRM transgenic soybean. The method is reliable to detect transgenic soybean specifically and has the annealing temperature at 59 °C during the 30 cycle standard PCR condition. The method did not show any false positive and false negative results meaning good precision. The cut off the methods is up to 2 copies total DNA of soybean or less than 104 copies of the CaMV 35S promoter. Observation to the commercial soybeans and tempeh found that most of the commercially available soybean in Indonesia are transgenic (8 of 10 sample while all tested tempeh sample were detected have been fermented from transgenic soybeans.

  14. The effect of energy spectrum change on DNA damage in and out of field in 10-MV clinical photon beams.

    Science.gov (United States)

    Ezzati, A O; Xiao, Y; Sohrabpour, M; Studenski, M T

    2015-01-01

    The aim of this study was to quantify the DNA damage induced in a clinical megavoltage photon beam at various depths in and out of the field. MCNPX was used to simulate 10 × 10 and 20 × 20 cm(2) 10-MV photon beams from a clinical linear accelerator. Photon and electron spectra were collected in a water phantom at depths of 2.5, 12.5 and 22.5 cm on the central axis and at off-axis points out to 10 cm. These spectra were used as an input to a validated microdosimetric Monte Carlo code, MCDS, to calculate the RBE of induced DSB in DNA at points in and out of the primary radiation field at three depths. There was an observable difference in the energy spectra for photons and electrons for points in the primary radiation field and those points out of field. In the out-of-field region, the mean energy for the photon and electron spectra decreased by a factor of about six and three from the in-field mean energy, respectively. Despite the differences in spectra and mean energy, the change in RBE was photon and electron spectra, these changes do not correlate with a change in RBE in a clinical MV photon beam as the electron spectra are dominated by electrons with energies >20 keV.

  15. Injector for CESAR (2 MeV electron storage ring): 2-beam, 2 MV van de Graaff generator; tank removed.

    CERN Multimedia

    CERN PhotoLab

    1968-01-01

    The van de Graaff generator in its tank. For voltage-holding, the tank was filled with pressurized extra-dry nitrogen. 2 beams emanated from 2 separate electron-guns. The left beam, for injection into the CESAR ring, was pulsed at 50 Hz, with currents of up to 1 A for 400 ns. The right beam was sent to a spectrometer line. Its pulselength was also 400 ns, but the pulse current was 12 microA, at a rate variable from 50 kHz to 1 MHz. This allowed stabilization of the top-terminal voltage to an unprecedented stability of +- 100 V, i.e. 6E-5. Although built for a nominal voltage of 2 MV, the operational voltage was limited to 1.75 MV in order to minimize voltage break-down events. CESAR was terminated at the end of 1967 and dismantled in 1968. R.Nettleton (left) and H.Burridge (right) are preparing the van de Graaff for shipment to the University of Swansea.

  16. A computer adaptive testing version of the Addiction Severity Index-Multimedia Version (ASI-MV): The Addiction Severity CAT.

    Science.gov (United States)

    Butler, Stephen F; Black, Ryan A; McCaffrey, Stacey A; Ainscough, Jessica; Doucette, Ann M

    2017-05-01

    The purpose of this study was to develop and validate a computer adaptive testing (CAT) version of the Addiction Severity Index-Multimedia Version (ASI-MV), the Addiction Severity CAT. This goal was accomplished in 4 steps. First, new candidate items for Addiction Severity CAT domains were evaluated after brainstorming sessions with experts in substance abuse treatment. Next, this new item bank was psychometrically evaluated on a large nonclinical (n = 4,419) and substance abuse treatment (n = 845) sample. Based on these results, final items were selected and calibrated for the creation of the Addiction Severity CAT algorithms. Once the algorithms were developed for the entire assessment, a fully functioning prototype of an Addiction Severity CAT was created. CAT simulations were conducted, and optimal termination criteria were selected for the Addiction Severity CAT algorithms. Finally, construct validity of the CAT algorithms was evaluated by examining convergent and discriminant validity and sensitivity to change. The Addiction Severity CAT was determined to be valid, sensitive to change, and reliable. Further, the Addiction Severity CAT's time of completion was found to be significantly less than the average time of completion for the ASI-MV composite scores. This study represents the initial validation of an Addiction Severity CAT based on item response theory, and further exploration of the Addiction Severity CAT is needed. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

  17. Evaluation of secondary electron filter for removing contaminant electrons from high-energy 6 MV x-ray beam

    International Nuclear Information System (INIS)

    Kumagai, Kozo

    1988-01-01

    When using high energy X-rays, the dose increases at the skin surface and build-up region of beam contamination of secondary electrons coming out from the inner surface of the lineac head. At our radiotherapy department, many cases of external otitis from severe skin reactions, particularly resulting from whole brain irradiation of primary and metastatic brain tumors with a 6 MV X-ray lineac, have been encountered. An investigation was made of the physical aspects of a 6 MV X-ray beam using three electron filters, lead lucite, lead glass and lucite to remove secondary electrons. Transparent materials for filters should be preferable for locating the light field. The following results were obtained: 1) For removing secondary electrons, a lead lucite filter was found best. 2) The lead lucite filter proved most effective for removing secondary electrons from the area of treatment. It reduced the dose of irradiation to the skin surface and build-up region, and furthermore improved the depth dose relative to that without filters. 3) From a clinical standpoint, skin reactions such as external otitis remarkably decreased using a lead lucite filter. 4) It thus appears necessary to use a high energy X-ray with newly designed filters to reduce beam contamination of secondary electrons. (author)

  18. Characteristics of a symmetrical Cockcroft-Walton power supply of 50 Hz 1.2 MV/50 mA

    Energy Technology Data Exchange (ETDEWEB)

    He Zifeng; Zhang Jinling; Liu Yonghao; Zhang Yutian; Zhang Yin [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China)

    2011-05-15

    A 1.2 MV/50 mA symmetrical Cockcroft-Walton (SCW) power supply of over 83% power efficiency, driven by 50 Hz frequency, was developed for an industrial electron beam irradiator. It is constructed by capacitors of 45 nF and 28.13 nF in the coupling column and capacitors of 18.75 nF in the smoothing column. Working status of the rectifier in high power output condition was analyzed, and the conduction angle of the rectifier was calculated. The power factor (PF) of the SCW circuit has been studied, and the equivalent condensance of the circuit has been derived. Measurements were done for the PF compensation. The surge impact during the short circuit transient process was considered in choosing the protection resistance. Test results showed that design specifications of the power supply were achieved, with the non-load voltage being up to 1.32 MV and the ratio of ripple voltage to output voltage as 9.4%.

  19. Use of a 3-MV proton accelerator for study of noble gases, including laser ionization of excited states

    International Nuclear Information System (INIS)

    Hurst, G.S.; Judish, J.P.; Nayfeh, M.H.; Parks, J.E.; Payne, M.G.; Wagner, E.B.

    1974-01-01

    The use of a pulsed 3-MV accelerator to study energy pathways in the noble gases is described. The objectives of pathways research are to obtain (1) information on the spectrum of excited states produced by a charged particle in a noble gas, (2) the rate of decay of the various states through various channels as a function of gas pressure, and (3) the modification of the decay channels due to the introduction of foreign species. A new energy pathways model is presented for helium as a general illustration. A method for the study of excited states, using a laser ionization technique is reported. Use is made of a laser which is tuned to a resonance transition between the desired excited state and some higher excited state. Photons in the same pulse photoionize the higher excited state; thus the ionization current vs photon wavelength has a resonance structure. Absolute yields of selected excited states can be obtained whenever the photon fluence per pulse is large enough to saturate the ionization current. A general summary is given of experimental facilities which include a 3-MV Van de Graaff accelerator, electronics for measuring radiation lifetimes, vacuum ultraviolet spectrometers, and a pulsed laser facility for direct study of excited states. Finally, the relevance of pathways research to (1) the interaction of radiation with matter, (2) the development of gas lasers, and (3) methods of ultrasensitive elemental analysis is pointed out

  20. Integrin Activation Contributes to Lower Cisplatin Sensitivity in MV3 Melanoma Cells by Inducing the Wnt Signalling Pathway

    Directory of Open Access Journals (Sweden)

    Maria B. R. Piva

    2017-09-01

    Full Text Available Background: integrins have been associated with the development of chemotherapy resistant tumour cells, mostly those of hematopoietic origin, by mediating the binding to the extracellular matrix. The relevance for solid tumour cells and the underlying mechanisms remain elusive. Methods: using MTT assays, we detected the loss in cisplatin sensitivity of human MV3 melanoma cells upon integrin activation. Underlying cellular pathways were evaluated by flow cytometry. A crosstalk between integrin activation and the canonical wnt signalling pathway was tested by measuring β-catenin activity. Results: MV3 cells display a higher resistance against cisplatin cytotoxicity when cellular integrins were activated by manganese or collagen. Proteome profiler array showed a deregulation of the integrin expression pattern by cisplatin. Integrin activation by manganese induces the phosphorylation of PI3K/AKT. The inhibition of PI3K using BEZ235 strongly increases cell sensitivity to cisplatin, blocking manganese and collagen effects. PI3K/AKT activates wnt signalling by blocking Gsk3-β, which was confirmed by β-catenin up-regulation and nuclear localization. Integrins did not affect E-cadherin expression levels, thus endothelial to mesenchymal transition (EMT can be excluded. Conclusion: This is the first report on an integrin/wnt signalling activation axis addressing the consequences for chemotherapy sensitiveness of melanoma cells, which thus offers novel therapeutic targets for approaches to interfere with chemoresistance.

  1. Plasmid integration in a wide range of bacteria mediated by the integrase of Lactobacillus delbrueckii bacteriophage mv4.

    Science.gov (United States)

    Auvray, F; Coddeville, M; Ritzenthaler, P; Dupont, L

    1997-01-01

    Bacteriophage mv4 is a temperate phage infecting Lactobacillus delbrueckii subsp. bulgaricus. During lysogenization, the phage integrates its genome into the host chromosome at the 3' end of a tRNA(Ser) gene through a site-specific recombination process (L. Dupont et al., J. Bacteriol., 177:586-595, 1995). A nonreplicative vector (pMC1) based on the mv4 integrative elements (attP site and integrase-coding int gene) is able to integrate into the chromosome of a wide range of bacterial hosts, including Lactobacillus plantarum, Lactobacillus casei (two strains), Lactococcus lactis subsp. cremoris, Enterococcus faecalis, and Streptococcus pneumoniae. Integrative recombination of pMC1 into the chromosomes of all of these species is dependent on the int gene product and occurs specifically at the pMC1 attP site. The isolation and sequencing of pMC1 integration sites from these bacteria showed that in lactobacilli, pMC1 integrated into the conserved tRNA(Ser) gene. In the other bacterial species where this tRNA gene is less or not conserved; secondary integration sites either in potential protein-coding regions or in intergenic DNA were used. A consensus sequence was deduced from the analysis of the different integration sites. The comparison of these sequences demonstrated the flexibility of the integrase for the bacterial integration site and suggested the importance of the trinucleotide CCT at the 5' end of the core in the strand exchange reaction. PMID:9068626

  2. Apoptosis induction in MV4-11 and K562 human leukemic cells by Pereskia sacharosa (Cactaceae) leaf crude extract.

    Science.gov (United States)

    Asmaa, Mat Jusoh Siti; Al-Jamal, Hamid Ali Nagi; Ang, Cheng Yong; Asan, Jamaruddin Mat; Seeni, Azman; Johan, Muhammad Farid

    2014-01-01

    Pereskia sacharosa is a genus of cacti widely used in folk medicine for cancer-related treatment. Anti-proliferative effects have been studied in recent years against colon, breast, cervical and lung cancer cell lines, with promising results. We here extended study of anti-proliferative effects to a blood malignancy, leukemia. Two leukemic cell lines, MV4-11 (acute myeloid leukemia) and K562 (chronic myeloid leukemia), were studied. IC50 concentrations were determined and apoptosis and cell cycle regulation were studied by flow cytometric analysis. The expression of apoptosis and cell-cycle related regulatory proteins was assessed by Western blotting. P sacharosa inhibited growth of MV4-11 and K562 cells in a dose-dependent manner. The mode of cell death was via induction of intrinsic apoptotic pathways and cell cycle arrest. There was profound up-regulation of cytochrome c, caspases, p21 and p53 expression and repression of Akt and Bcl-2 expression in treated cells. These results suggest that P sacharosa induces leukemic cell death via apoptosis induction and changes in cell cycle checkpoint, thus deserves further study for anti-leukemic potential.

  3. Investigation of the HU-density conversion method and comparison of dose distribution for dose calculation on MV cone beam CT images

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Min Joo; Lee, Seu Ran; Suh, Tae Suk [Dept. of Biomedical Engineering, The Catholic University of Korea, Bucheon (Korea, Republic of)

    2011-11-15

    Modern radiation therapy techniques, such as Image-guided radiation therapy (IGRT), Adaptive radiation therapy (ART) has become a routine clinical practice on linear accelerators for the increase the tumor dose conformity and improvement of normal tissue sparing at the same time. For these highly developed techniques, megavoltage cone beam computed tomography (MVCBCT) system produce volumetric images at just one rotation of the x-ray beam source and detector on the bottom of conventional linear accelerator for real-time application of patient condition into treatment planning. MV CBCT image scan be directly registered to a reference CT data set which is usually kilo-voltage fan-beam computed tomography (kVFBCT) on treatment planning system and the registered image scan be used to adjust patient set-up error. However, to use MV CBCT images in radiotherapy, reliable electron density (ED) distribution are required. Patients scattering, beam hardening and softening effect caused by different energy application between kVCT, MV CBCT can cause cupping artifacts in MV CBCT images and distortion of Houns field Unit (HU) to ED conversion. The goal of this study, for reliable application of MV CBCT images into dose calculation, MV CBCT images was modified to correct distortion of HU to ED using the relationship of HU and ED from kV FBCT and MV CBCT images. The HU-density conversion was performed on MV CBCT image set using Dose difference map was showing in Figure 1. Finally, percentage differences above 3% were reduced depending on applying density calibration method. As a result, total error co uld be reduced to under 3%. The present study demonstrates that dose calculation accuracy using MV CBCT image set can be improved my applying HU-density conversion method. The dose calculation and comparison of dose distribution from MV CBCT image set with/without HU-density conversion method was performed. An advantage of this study compared to other approaches is that HU

  4. The Status and Promise of Advanced M&V: An Overview of “M&V 2.0” Methods, Tools, and Applications

    Energy Technology Data Exchange (ETDEWEB)

    Franconi, Ellen [Rocky Mountain Inst., Boulder, CO (United States); Gee, Matt [Univ. of Chicago, IL (United States); Goldberg, Miriam [DNV GL, Oslo (Norway); Granderson, Jessica [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Guiterman, Tim [EnergySavvy, Seattle, WA (United States); Li, Michael [U.S. Department of Energy (DOE), Baltimore, MD (United States); Smith, Brian Arthur [Pacific Gas and Electric, San Francisco, CA (United States)

    2017-04-11

    Advanced measurement and verification (M&V) of energy efficiency savings, often referred to as M&V 2.0 or advanced M&V, is currently an object of much industry attention. Thus far, however, there has been a lack of clarity about what techniques M&V 2.0 includes, how those techniques differ from traditional approaches, what the key considerations are for their use, and what value propositions M&V 2.0 presents to different stakeholders. The objective of this paper is to provide background information and frame key discussion points related to advanced M&V. The paper identifies the benefits, methods, and requirements of advanced M&V and outlines key technical issues for applying these methods. It presents an overview of the distinguishing elements of M&V 2.0 tools and of how the industry is addressing needs for tool testing, consistency, and standardization, and it identifies opportunities for collaboration. In this paper, we consider two key features of M&V 2.0: (1) automated analytics that can provide ongoing, near-real-time savings estimates, and (2) increased data granularity in terms of frequency, volume, or end-use detail. Greater data granularity for large numbers of customers, such as that derived from comprehensive implementation of advanced metering infrastructure (AMI) systems, leads to very large data volumes. This drives interest in automated processing systems. It is worth noting, however, that automated processing can provide value even when applied to less granular data, such as monthly consumption data series. Likewise, more granular data, such as interval or end-use data, delivers value with or without automated processing, provided the processing is manageable. But it is the combination of greater data detail with automated processing that offers the greatest opportunity for value. Using M&V methods that capture load shapes together with automated processing1 can determine savings in near-real time to provide stakeholders with more timely and

  5. Towards clinical implementation of ultrafast combined kV-MV CBCT for IGRT of lung cancer. Evaluation of registration accuracy based on phantom study

    Energy Technology Data Exchange (ETDEWEB)

    Arns, Anna; Blessing, Manuel; Fleckenstein, Jens; Stsepankou, Dzmitry; Boda-Heggemann, Judit; Simeonova-Chergou, Anna; Hesser, Juergen; Lohr, Frank; Wenz, Frederik; Wertz, Hansjoerg [University Medical Center Mannheim, University of Heidelberg, Department of Radiation Oncology, Mannheim (Germany)

    2016-05-15

    Combined kV-MV cone-beam CT (CBCT) is a promising approach to accelerate imaging for patients with lung tumors treated with deep inspiration breath-hold. During a single breath-hold (15 s), a 3D kV-MV CBCT can be acquired, thus minimizing motion artifacts and increasing patient comfort. Prior to clinical implementation, positioning accuracy was evaluated and compared to clinically established imaging techniques. An inhomogeneous thorax phantom with four tumor-mimicking inlays was imaged in 10 predefined positions and registered to a planning CT. Novel kV-MV CBCT imaging (90 arc) was compared to clinically established kV-chest CBCT (360 ) as well as nonclinical kV-CBCT and low-dose MV-CBCT (each 180 ). Manual registration, automatic registration provided by the manufacturer and an additional in-house developed manufacturer-independent framework based on the MATLAB registration toolkit were applied. Systematic setup error was reduced to 0.05 mm by high-precision phantom positioning with optical tracking. Stochastic mean displacement errors were 0.5 ± 0.3 mm in right-left, 0.4 ± 0.4 mm in anteroposterior and 0.0 ± 0.4 mm in craniocaudal directions for kV-MV CBCT with manual registration (maximum errors of no more than 1.4 mm). Clinical kV-chest CBCT resulted in mean errors of 0.2 mm (other modalities: 0.4-0.8 mm). Similar results were achieved with both automatic registration methods. The comparison study of repositioning accuracy between novel kV-MV CBCT and clinically established volume imaging demonstrated that registration accuracy is maintained below 1 mm. Since imaging time is reduced to one breath-hold, kV-MV CBCT is ideal for image guidance, e.g., in lung stereotactic ablative radiotherapy. (orig.) [German] Kombiniertes kV-MV-Cone-Beam-CT (CBCT) ist ein vielversprechender Ansatz zur Beschleunigung der Bildgebung bei Patienten mit Lungentumoren, die mit wiederholter Atemanhaltetechnik in tiefer Inspiration behandelt werden. Waehrend einer einzigen

  6. Evaluating genome-wide DNA methylation changes in mice by Methylation Specific Digital Karyotyping

    Directory of Open Access Journals (Sweden)

    Maruoka Shuichiro

    2008-12-01

    Full Text Available Abstract Background The study of genome-wide DNA methylation changes has become more accessible with the development of various array-based technologies though when studying species other than human the choice of applications are limited and not always within reach. In this study, we adapted and tested the applicability of Methylation Specific Digital Karyotyping (MSDK, a non-array based method, for the prospective analysis of epigenetic changes after perinatal nutritional modifications in a mouse model of allergic airway disease. MSDK is a sequenced based method that allows a comprehensive and unbiased methylation profiling. The method generates 21 base pairs long sequence tags derived from specific locations in the genome. The resulting tag frequencies determine in a quantitative manner the methylation level of the corresponding loci. Results Genomic DNA from whole lung was isolated and subjected to MSDK analysis using the methylation-sensitive enzyme Not I as the mapping enzyme and Nla III as the fragmenting enzyme. In a pair wise comparison of the generated mouse MSDK libraries we identified 158 loci that are significantly differentially methylated (P-value = 0.05 after perinatal dietary changes in our mouse model. Quantitative methylation specific PCR and sequence analysis of bisulfate modified genomic DNA confirmed changes in methylation at specific loci. Differences in genomic MSDK tag counts for a selected set of genes, correlated well with changes in transcription levels as measured by real-time PCR. Furthermore serial analysis of gene expression profiling demonstrated a dramatic difference in expressed transcripts in mice exposed to perinatal nutritional changes. Conclusion The genome-wide methylation survey applied in this study allowed for an unbiased methylation profiling revealing subtle changes in DNA methylation in mice maternally exposed to dietary changes in methyl-donor content. The MSDK method is applicable for mouse models

  7. Homogalacturonan methyl-esterification and plant development.

    Science.gov (United States)

    Wolf, Sebastian; Mouille, Grégory; Pelloux, Jérome

    2009-09-01

    The ability of a plant cell to expand is largely defined by the physical constraints imposed by its cell wall. Accordingly, cell wall properties have to be regulated during development. The pectic polysaccharide homogalacturonan is a major component of the plant primary walls. Biosynthesis and in muro modification of homogalacturonan have recently emerged as key determinants of plant development, controlling cell adhesion, organ development, and phyllotactic patterning. This review will focus on recent findings regarding impact of homogalacturonan content and methyl-esterification status of this polymer on plant life. De-methyl-esterification of homogalacturonan occurs through the action of the ubiquitous enzyme 'pectin methyl-esterase'. We here describe various strategies developed by the plant to finely tune the methyl-esterification status of homogalacturonan along key events of the plant lifecycle.

  8. Annotating the genome by DNA methylation.

    Science.gov (United States)

    Cedar, Howard; Razin, Aharon

    2017-01-01

    DNA methylation plays a prominent role in setting up and stabilizing the molecular design of gene regulation and by understanding this process one gains profound insight into the underlying biology of mammals. In this article, we trace the discoveries that provided the foundations of this field, starting with the mapping of methyl groups in the genome and the experiments that helped clarify how methylation patterns are maintained through cell division. We then address the basic relationship between methyl groups and gene repression, as well as the molecular rules involved in controlling this process during development in vivo. Finally, we describe ongoing work aimed at defining the role of this modification in disease and deciphering how it may serve as a mechanism for sensing the environment.

  9. Methylation of hemoglobin to enhance flocculant performance

    Science.gov (United States)

    An inexpensive bioflocculant, bovine hemoglobin (Hb), has been covalently modified through methylation of the side chain carboxyl groups of aspartic and glutamic acid residues to improve its flocculation activity. Potentiometric titration of the recovered products showed approximately 28% degree of ...

  10. MSeqDR mvTool: A mitochondrial DNA Web and API resource for comprehensive variant annotation, universal nomenclature collation, and reference genome conversion.

    Science.gov (United States)

    Shen, Lishuang; Attimonelli, Marcella; Bai, Renkui; Lott, Marie T; Wallace, Douglas C; Falk, Marni J; Gai, Xiaowu

    2018-06-01

    Accurate mitochondrial DNA (mtDNA) variant annotation is essential for the clinical diagnosis of diverse human diseases. Substantial challenges to this process include the inconsistency in mtDNA nomenclatures, the existence of multiple reference genomes, and a lack of reference population frequency data. Clinicians need a simple bioinformatics tool that is user-friendly, and bioinformaticians need a powerful informatics resource for programmatic usage. Here, we report the development and functionality of the MSeqDR mtDNA Variant Tool set (mvTool), a one-stop mtDNA variant annotation and analysis Web service. mvTool is built upon the MSeqDR infrastructure (https://mseqdr.org), with contributions of expert curated data from MITOMAP (https://www.mitomap.org) and HmtDB (https://www.hmtdb.uniba.it/hmdb). mvTool supports all mtDNA nomenclatures, converts variants to standard rCRS- and HGVS-based nomenclatures, and annotates novel mtDNA variants. Besides generic annotations from dbNSFP and Variant Effect Predictor (VEP), mvTool provides allele frequencies in more than 47,000 germline mitogenomes, and disease and pathogenicity classifications from MSeqDR, Mitomap, HmtDB and ClinVar (Landrum et al., 2013). mvTools also provides mtDNA somatic variants annotations. "mvTool API" is implemented for programmatic access using inputs in VCF, HGVS, or classical mtDNA variant nomenclatures. The results are reported as hyperlinked html tables, JSON, Excel, and VCF formats. MSeqDR mvTool is freely accessible at https://mseqdr.org/mvtool.php. © 2018 Wiley Periodicals, Inc.

  11. Analysis of DNA methylation in Arabidopsis thaliana based on methylation-sensitive AFLP markers.

    Science.gov (United States)

    Cervera, M T; Ruiz-García, L; Martínez-Zapater, J M

    2002-12-01

    AFLP analysis using restriction enzyme isoschizomers that differ in their sensitivity to methylation of their recognition sites has been used to analyse the methylation state of anonymous CCGG sequences in Arabidopsis thaliana. The technique was modified to improve the quality of fingerprints and to visualise larger numbers of scorable fragments. Sequencing of amplified fragments indicated that detection was generally associated with non-methylation of the cytosine to which the isoschizomer is sensitive. Comparison of EcoRI/ HpaII and EcoRI/ MspI patterns in different ecotypes revealed that 35-43% of CCGG sites were differentially digested by the isoschizomers. Interestingly, the pattern of digestion among different plants belonging to the same ecotype is highly conserved, with the rate of intra-ecotype methylation-sensitive polymorphisms being less than 1%. However, pairwise comparisons of methylation patterns between samples belonging to different ecotypes revealed differences in up to 34% of the methylation-sensitive polymorphisms. The lack of correlation between inter-ecotype similarity matrices based on methylation-insensitive or methylation-sensitive polymorphisms suggests that whatever the mechanisms regulating methylation may be, they are not related to nucleotide sequence variation.

  12. Recognition of methylated DNA through methyl-CpG binding domain proteins

    DEFF Research Database (Denmark)

    Zou, Xueqing; Ma, Wen; Solov'yov, Ilia

    2012-01-01

    DNA methylation is a key regulatory control route in epigenetics, involving gene silencing and chromosome inactivation. It has been recognized that methyl-CpG binding domain (MBD) proteins play an important role in interpreting the genetic information encoded by methylated DNA (mDNA). Although...... the function of MBD proteins has attracted considerable attention and is well characterized, the mechanism underlying mDNA recognition by MBD proteins is still poorly understood. In this article, we demonstrate that the methyl-CpG dinucleotides are recognized at the MBD-mDNA interface by two MBD arginines...

  13. Maternal intake of methyl-group donors affects DNA methylation of metabolic genes in infants.

    Science.gov (United States)

    Pauwels, Sara; Ghosh, Manosij; Duca, Radu Corneliu; Bekaert, Bram; Freson, Kathleen; Huybrechts, Inge; Langie, Sabine A S; Koppen, Gudrun; Devlieger, Roland; Godderis, Lode

    2017-01-01

    Maternal nutrition during pregnancy and infant nutrition in the early postnatal period (lactation) are critically involved in the development and health of the newborn infant. The Maternal Nutrition and Offspring's Epigenome (MANOE) study was set up to assess the effect of maternal methyl-group donor intake (choline, betaine, folate, methionine) on infant DNA methylation. Maternal intake of dietary methyl-group donors was assessed using a food-frequency questionnaire (FFQ). Before and during pregnancy, we evaluated maternal methyl-group donor intake through diet and supplementation (folic acid) in relation to gene-specific ( IGF2 DMR, DNMT1 , LEP , RXRA ) buccal epithelial cell DNA methylation in 6 months old infants ( n  = 114) via pyrosequencing. In the early postnatal period, we determined the effect of maternal choline intake during lactation (in mothers who breast-fed for at least 3 months) on gene-specific buccal DNA methylation ( n  = 65). Maternal dietary and supplemental intake of methyl-group donors (folate, betaine, folic acid), only in the periconception period, was associated with buccal cell DNA methylation in genes related to growth ( IGF2 DMR), metabolism ( RXRA ), and appetite control ( LEP ). A negative association was found between maternal folate and folic acid intake before pregnancy and infant LEP (slope = -1.233, 95% CI -2.342; -0.125, p  = 0.0298) and IGF2 DMR methylation (slope = -0.706, 95% CI -1.242; -0.107, p  = 0.0101), respectively. Positive associations were observed for maternal betaine (slope = 0.875, 95% CI 0.118; 1.633, p  = 0.0241) and folate (slope = 0.685, 95% CI 0.245; 1.125, p  = 0.0027) intake before pregnancy and RXRA methylation. Buccal DNMT1 methylation in the infant was negatively associated with maternal methyl-group donor intake in the first and second trimester of pregnancy and negatively in the third trimester. We found no clear association between maternal choline intake

  14. Methyl Iodide Decomposition at BWR Conditions

    International Nuclear Information System (INIS)

    Pop, Mike; Bell, Merl

    2012-09-01

    Based on favourable results from short-term testing of methanol addition to an operating BWR plant, AREVA has performed numerous studies in support of necessary Engineering and Plant Safety Evaluations prior to extended injection of methanol. The current paper presents data from a study intended to provide further understanding of the decomposition of methyl iodide as it affects the assessment of methyl iodide formation with the application of methanol at BWR Plants. This paper describes the results of the decomposition testing under UV-C light at laboratory conditions and its effect on the subject methyl iodide production evaluation. The study as to the formation and decomposition of methyl iodide as it is effected by methanol addition is one phase of a larger AREVA effort to provide a generic plant Safety Evaluation prior to long-term methanol injection to an operating BWR. Other testing phases have investigated the compatibility of methanol with fuel construction materials, plant structural materials, plant consumable materials (i.e. elastomers and coatings), and ion exchange resins. Methyl iodide is known to be very unstable, typically preserved with copper metal or other stabilizing materials when produced and stored. It is even more unstable when exposed to light, heat, radiation, and water. Additionally, it is known that methyl iodide will decompose radiolytically, and that this effect may be simulated using ultra-violet radiation (UV-C) [2]. In the tests described in this paper, the use of a UV-C light source provides activation energy for the formation of methyl iodide. Thus is similar to the effect expected from Cherenkov radiation present in a reactor core after shutdown. Based on the testing described in this paper, it is concluded that injection of methanol at concentrations below 2.5 ppm in BWR applications to mitigate IGSCC of internals is inconsequential to the accident conditions postulated in the FSAR as they are related to methyl iodide formation

  15. Whole genome DNA methylation: beyond genes silencing

    OpenAIRE

    Tirado-Magallanes, Roberto; Rebbani, Khadija; Lim, Ricky; Pradhan, Sriharsa; Benoukraf, Touati

    2016-01-01

    The combination of DNA bisulfite treatment with high-throughput sequencing technologies has enabled investigation of genome-wide DNA methylation at near base pair level resolution, far beyond that of the kilobase-long canonical CpG islands that initially revealed the biological relevance of this covalent DNA modification. The latest high-resolution studies have revealed a role for very punctual DNA methylation in chromatin plasticity, gene regulation and splicing. Here, we aim to outline the ...

  16. Study of air cavities influence in head and neck radiotherapy with 10 MV photon beam; Estudo da influencia de cavidades de ar em radioterapia de cabeca e pescoco com feixe de fotons de 10 MV

    Energy Technology Data Exchange (ETDEWEB)

    Souza, C.N. de

    1989-03-01

    This is a study about dose distribution in the larynx region under irradiation with a 10 MV photon beam. This localization presents air cavities, that can compromise the dose at air-tissue interfaces by electronic equilibrium loss and backscattering lack. For this study, a parallel ionization chamber was used in the air cavities simulated with a perspex phantom. The influence of the air cavities in the proximal, distal and lateral interfaces was analysed. The results showed a expressive loss of dose at the air-tissue interface. For typical irradiation field and anatomic cavity, under dose values of 4% in the proximal interface, 11% in the distal interface and 7% in the lateral interface were found. Irradiation field larger than 6 X 6 cm{sup 2} were optimal in reducing the total effect of under dosing at the interface. (author). 39 refs, 23 figs, 12 tabs.

  17. DNA methylation abnormalities in congenital heart disease.

    Science.gov (United States)

    Serra-Juhé, Clara; Cuscó, Ivon; Homs, Aïda; Flores, Raquel; Torán, Núria; Pérez-Jurado, Luis A

    2015-01-01

    Congenital heart defects represent the most common malformation at birth, occurring also in ∼50% of individuals with Down syndrome. Congenital heart defects are thought to have multifactorial etiology, but the main causes are largely unknown. We have explored the global methylation profile of fetal heart DNA in comparison to blood DNA from control subjects: an absolute correlation with the type of tissue was detected. Pathway analysis revealed a significant enrichment of differential methylation at genes related to muscle contraction and cardiomyopathies in the developing heart DNA. We have also searched for abnormal methylation profiles on developing heart-tissue DNA of syndromic and non-syndromic congenital heart defects. On average, 3 regions with aberrant methylation were detected per sample and 18 regions were found differentially methylated between groups. Several epimutations were detected in candidate genes involved in growth regulation, apoptosis and folate pathway. A likely pathogenic hypermethylation of several intragenic sites at the MSX1 gene, involved in outflow tract morphogenesis, was found in a fetus with isolated heart malformation. In addition, hypermethylation of the GATA4 gene was present in fetuses with Down syndrome with or without congenital heart defects, as well as in fetuses with isolated heart malformations. Expression deregulation of the abnormally methylated genes was detected. Our data indicate that epigenetic alterations of relevant genes are present in developing heart DNA in fetuses with both isolated and syndromic heart malformations. These epimutations likely contribute to the pathogenesis of the malformation by cis-acting effects on gene expression.

  18. Methylated spirit burns: an ongoing problem.

    Science.gov (United States)

    Jansbeken, J R H; Vloemans, A F P M; Tempelman, F R H; Breederveld, R S

    2012-09-01

    Despite many educational campaigns we still see burns caused by methylated spirit every year. We undertook a retrospective study to analyse the impact of this problem. We retrospectively collected data of all patients with burns caused by methylated spirit over twelve years from 1996 to 2008. Our main endpoints were: incidence, age, mechanism of injury, total body surface area (TBSA) burned, burn depth, need for surgery and length of hospital stay. Ninety-seven patients with methylated spirit burns were included. During the study period there was no decrease in the number of patients annually admitted to the burn unit with methylated spirit burns. 28% of the patients (n=27) were younger than eighteen years old, 15% (n=15) were ten years old or younger. The most common cause of burns was carelessness in activities involving barbecues, campfires and fondues. Mean TBSA burned was 16% (SD 12.4). 70% (n=68) had full thickness burns. 66% (n=64) needed grafting. Mean length of hospital stay was 23 days (SD 24.7). The use of methylated spirit is an ongoing problem, which continues to cause severe burns in adults and children. Therefore methylated spirit should be banned in households. We suggest sale only in specialised shops, clear labelling and mandatory warnings. Copyright © 2012 Elsevier Ltd and ISBI. All rights reserved.

  19. DNA Methylation Biomarkers: Cancer and Beyond

    Directory of Open Access Journals (Sweden)

    Thomas Mikeska

    2014-09-01

    Full Text Available Biomarkers are naturally-occurring characteristics by which a particular pathological process or disease can be identified or monitored. They can reflect past environmental exposures, predict disease onset or course, or determine a patient’s response to therapy. Epigenetic changes are such characteristics, with most epigenetic biomarkers discovered to date based on the epigenetic mark of DNA methylation. Many tissue types are suitable for the discovery of DNA methylation biomarkers including cell-based samples such as blood and tumor material and cell-free DNA samples such as plasma. DNA methylation biomarkers with diagnostic, prognostic and predictive power are already in clinical trials or in a clinical setting for cancer. Outside cancer, strong evidence that complex disease originates in early life is opening up exciting new avenues for the detection of DNA methylation biomarkers for adverse early life environment and for estimation of future disease risk. However, there are a number of limitations to overcome before such biomarkers reach the clinic. Nevertheless, DNA methylation biomarkers have great potential to contribute to personalized medicine throughout life. We review the current state of play for DNA methylation biomarkers, discuss the barriers that must be crossed on the way to implementation in a clinical setting, and predict their future use for human disease.

  20. SU-E-J-27: Shifting Multiple EPID Imager Layers to Improve Image Quality and Resolution in MV CBCT

    Energy Technology Data Exchange (ETDEWEB)

    Chen, H; Rottmann, J; Yip, S; Berbeco, R [Brigham and Women’s Hospital, Boston, Massachusetts (United States); Morf, D; Fueglistaller, R; Star-Lack, J; Zentai, G [Varian Medical Systems, Palo Alto, CA (United States)

    2015-06-15

    Purpose: Vertical stacking of four conventional EPID layers can improve DQE for MV-CBCT applications. We hypothesize that shifting each layer laterally by half a pixel relative to the layer above, will improve the contrast-to-noise ratio (CNR) and image resolution. Methods: For CNR assessment, a 20 cm diameter digital phantom with 8 inserts is created. The attenuation coefficient of the phantom is similar to lung at the average energy of a 6 MV photon beam. The inserts have attenuations 1, 2…8 times of lung. One of the inserts is close to soft tissue, resembling the case of a tumor in lung. For resolution assessment, a digital phantom featuring a bar pattern is created. The phantom has an attenuation coefficient similar to soft tissue and the bars have an attenuation coefficient of calcium sulfate. A 2 MeV photon beam is attenuated through these phantoms and hits each of the four stacked detector layers. Each successive layer is shifted by half a pixel in the x only, y only, and x and y (combined) directions, respectively. Blurring and statistical noise are added to the projections. Projections from one, two, three and four layers are used for reconstruction. CNR and image resolution are evaluated and compared. Results: When projections from multiple layers are combined for reconstruction, CNR increases with the number of layers involved. CNR in reconstructions from two, three and four layers are 1.4, 1.7 and 1.99 times that from one layer. The resolution from the shifted four layer detector is also improved from a single layer. In a comparison between one layer versus four layers in this preliminary study, the resolution from four shifted layers is at least 20% better. Conclusion: Layer-shifting in a stacked EPID imager design enhances resolution as well as CNR for half scan MV-CBCT. The project described was supported, in part, by a grant from Varian Medical Systems, Inc., and Award No. R01CA188446-01 from the National Cancer Institute. The content is solely

  1. Improvement of Radiation Safety in Radiotherapy Facilities: Catering for Neutrons Outside Short Mazes in 10MV Linear Accelerators

    International Nuclear Information System (INIS)

    Severa, R.

    2016-01-01

    It has been demonstrated that neutron leakage cannot be neglected at 10MV when direct access doors are used or when short mazes, typically less than 7 metres in length, are employed. The majority of radiotherapy facilities in Africa have Co-60 machines installed that are now being replaced by linear accelerators. The in-coming linear accelerators are being installed in the same bunkers that were designed for Co-60 energy ranges albeit with some shielding modifications. The modifications do not alter the length of the maze and where the maze length is less than 7 metres, neutron leakage will occur in 10MV linear accelerators. There is lack of capacity within the regulatory bodies in Africa to handle this changeover from a technical and equipment perspective. The justification of medical exposures ensures that the benefits to the patients substantially outweigh any risks that the patient may incur. As such, the justification process needs to be implemented through the effective use of evidence-based referral guidelines and clinical audits. In the case of most African countries, medical diagnostic exposures of patients are not underpinned by an effective justification system. This, coupled with the scenario where physicians own outpatient diagnostic centres to which they refer patients (self-referral) increases the conflict of physicians due to dual roles as professionals and businessmen, further compromising on patient protection. Nuclear security is the responsibility of the Member State and requires that a number of key stakeholders work closely together. In the case of research reactors and nuclear power plants, this cooperation is evident and functional. However, this does not extend to the use of high-activity radioactive sources in medicine (category 1&2) where in most cases the regulators seem to be the only authority having oversight on the security of these sources without the benefit of direct input and collaboration of other key security stakeholders. This

  2. Experimental measurement of radiological penumbra associated with intermediate energy x-rays (1 MV) and small radiosurgery field sizes

    International Nuclear Information System (INIS)

    Keller, Brian M.; Beachey, David J.; Pignol, Jean-Philippe

    2007-01-01

    Stereotactic radiosurgery is used to treat intracranial lesions with a high degree of accuracy. At the present time, x-ray energies at or above Co-60 gamma rays are used. Previous Monte Carlo simulations have demonstrated that intermediate energy x-ray photons or IEPs (defined to be photons in the energy range of 0.2-1.2 MeV), combined with small field sizes, produce a reduced radiological penumbra leading to a sharper dose gradient, improved dose homogeneity and sparing of critical anatomy adjacent to the target volume. This hypothesis is based on the fact that, for small x-ray fields, a dose outside the treatment volume is dictated mainly by the range of electrons set into motion by x-ray photons. The purpose of this work is: (1) to produce intermediate energy x rays using a detuned medical linear accelerator (2) to characterize the energy of this beam (3) to measure the radiological penumbra for IEPs and small fields to compare with that produced by 6 MV x rays or Co-60, and (4) to compare these experimental measurements with Monte Carlo computer simulations. The maximum photon energy of our IEP x-ray spectrum was measured to be 1.2 MeV. Gafchromic EBT films (ISP Technologies, Wayne, NJ) were irradiated and read using a novel digital microscopy imaging system with high spatial resolution. Under identical irradiation conditions the measured radiological penumbra widths (80%-20% distance), for field sizes ranging from 0.3x0.3 to 4.0x4.0 cm 2 , varied from 0.3-0.77 mm (1.2 MV) and from 1.1-2.1 mm (6 MV). Even more dramatic were the differences found when comparing the 90%-10% or the 95%-5% widths, which are in fact more significant in radiotherapy. Monte Carlo simulations agreed well with the experimental findings. The reduction in radiological penumbra could be substantial for specific clinical situations such as in the treatment of an ocular melanoma abutting the macula or for the treatment of functional disorders such as trigeminal neuralgia (a nonlethal

  3. Study and optimization of negative polarity rod pinch diode as flash radiography source at 4.5 MV

    International Nuclear Information System (INIS)

    Etchessahar, Bertrand; Bicrel, Béatrice; Cassany, Bruno; Desanlis, Thierry; Voisin, Luc; Hébert, David; Bernigaud, Virgile; Magnin, Laurent; Nicolas, Rémi; Poulet, Frédéric; Tailleur, Yaël; Caron, Michel; Cartier, Frédéric; Cartier, Stéphanie; Hourdin, Laurent; Rosol, Rodolphe; Toury, Martial; Delbos, Christophe; Garrigues, Alain; Soleilhavoup, Isabelle

    2012-01-01

    The negative polarity rod pinch diode (NPRPD) is a potential millimeter spot size radiography source for high voltage generators (4 to 8 MV) [Cooperstein et al., “Considerations of rod-pinch diode operation in negative polarity for radiography,” in Proceedings of the 14th IEEE Pulsed Power Conference, 2003, pp. 975–978]. The NPRPD consists of a small diameter (few mm) cylindrical anode extending from the front end of the vacuum cell through a thin annular cathode, held by a central conductor. The polarity has been inverted when compared to the original rod pinch diode [Cooperstein et al., “Theoretical modeling and experimental characterization of a rod-pinch diode,” Phys. Plasmas 8(10), 4618–4636 (2001)] in order to take advantage from the maximal x-ray emission toward the anode holder at such a voltage [Swanekamp et al., “Evaluation of self-magnetically pinched diodes up to 10 MV as high resolution flash X-ray sources,” IEEE Trans. Plasma Sci. 32(5), 2004–2016 (2004). We have studied this diode at 4.5 MV, driven by the ASTERIX generator [Raboisson et al., “ASTERIX, a high intensity X-ray generator,” in Proceedings of the 7th IEEE Pulsed Power Conference, 1989, pp. 567–570.]. This generator, made up of a capacitor bank and a Blumlein line, was initially designed to test the behavior of electronic devices under irradiation. In our experiments, the vacuum diode has been modified in order to set up flash a radiographic diode [Etchessahar et al., “Negative polarity rod pinch diode experiments on the ASTERIX generator,” in Conference Records–Abstracts, 37th IEEE International Conference on Plasma Science, 2010]. The experiments and numerical simulations presented here allowed the observation and analysis of various physical phenomena associated with the diode operation. Also, the influence of several experimental parameters, such as cathode and anode diameters, materials and surface states, was examined. In order to achieve the most

  4. Study and optimization of negative polarity rod pinch diode as flash radiography source at 4.5 MV

    Energy Technology Data Exchange (ETDEWEB)

    Etchessahar, Bertrand; Bicrel, Beatrice; Cassany, Bruno; Desanlis, Thierry; Voisin, Luc; Hebert, David [CEA, DAM, CESTA, F-33114 Le Barp (France); Bernigaud, Virgile; Magnin, Laurent; Nicolas, Remi; Poulet, Frederic; Tailleur, Yaeel [CEA, DAM, VALDUC, F-21120 Is sur Tille (France); Caron, Michel; Cartier, Frederic; Cartier, Stephanie; Hourdin, Laurent; Rosol, Rodolphe; Toury, Martial; Delbos, Christophe; Garrigues, Alain; Soleilhavoup, Isabelle [CEA, DAM, GRAMAT, F-46500 Gramat (France); and others

    2012-09-15

    The negative polarity rod pinch diode (NPRPD) is a potential millimeter spot size radiography source for high voltage generators (4 to 8 MV) [Cooperstein et al., 'Considerations of rod-pinch diode operation in negative polarity for radiography,' in Proceedings of the 14th IEEE Pulsed Power Conference, 2003, pp. 975-978]. The NPRPD consists of a small diameter (few mm) cylindrical anode extending from the front end of the vacuum cell through a thin annular cathode, held by a central conductor. The polarity has been inverted when compared to the original rod pinch diode [Cooperstein et al., 'Theoretical modeling and experimental characterization of a rod-pinch diode,' Phys. Plasmas 8(10), 4618-4636 (2001)] in order to take advantage from the maximal x-ray emission toward the anode holder at such a voltage [Swanekamp et al., 'Evaluation of self-magnetically pinched diodes up to 10 MV as high resolution flash X-ray sources,' IEEE Trans. Plasma Sci. 32(5), 2004-2016 (2004). We have studied this diode at 4.5 MV, driven by the ASTERIX generator [Raboisson et al., 'ASTERIX, a high intensity X-ray generator,' in Proceedings of the 7th IEEE Pulsed Power Conference, 1989, pp. 567-570.]. This generator, made up of a capacitor bank and a Blumlein line, was initially designed to test the behavior of electronic devices under irradiation. In our experiments, the vacuum diode has been modified in order to set up flash a radiographic diode [Etchessahar et al., 'Negative polarity rod pinch diode experiments on the ASTERIX generator,' in Conference Records-Abstracts, 37th IEEE International Conference on Plasma Science, 2010]. The experiments and numerical simulations presented here allowed the observation and analysis of various physical phenomena associated with the diode operation. Also, the influence of several experimental parameters, such as cathode and anode diameters, materials and surface states, was examined. In order to

  5. WE-AB-303-06: Combining DAO with MV + KV Optimization to Improve Skin Dose Sparing with Real-Time Fluoroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Grelewicz, Z; Wiersma, R [The University of Chicago, Chicago, IL (United States)

    2015-06-15

    Purpose: Real-time fluoroscopy may allow for improved patient positioning and tumor tracking, particularly in the treatment of lung tumors. In order to mitigate the effects of the imaging dose, previous studies have demonstrated the effect of including both imaging dose and imaging constraints into the inverse treatment planning object function. That method of combined MV+kV optimization may Result in plans with treatment beams chosen to allow for more gentle imaging beam-on times. Direct-aperture optimization (DAO) is also known to produce treatment plans with fluence maps more conducive to lower beam-on times. Therefore, in this work we demonstrate the feasibility of a combination of DAO and MV+kV optimization for further optimized real-time kV imaging. Methods: Therapeutic and imaging beams were modeled in the EGSnrc Monte Carlo environment, and applied to a patient model for a previously treated lung patient to provide dose influence matrices from DOSXYZnrc. An MV + kV IMRT DAO treatment planning system was developed to compare DAO treatment plans with and without MV+kV optimization. The objective function was optimized using simulated annealing. In order to allow for comparisons between different cases of the stochastically optimized plans, the optimization was repeated twenty times. Results: Across twenty optimizations, combined MV+kV IMRT resulted in an average of 12.8% reduction in peak skin dose. Both non-optimized and MV+kV optimized imaging beams delivered, on average, mean dose of approximately 1 cGy per fraction to the target, with peak doses to target of approximately 6 cGy per fraction. Conclusion: When using DAO, MV+kV optimization is shown to Result in improvements to plan quality in terms of skin dose, when compared to the case of MV optimization with non-optimized kV imaging. The combination of DAO and MV+kV optimization may allow for real-time imaging without excessive imaging dose. Financial support for the work has been provided in part by NIH

  6. The motley family of polar compounds (MV)[M(X{sub 5-x}X Prime {sub x})] based on anionic chains of trans-connected M{sup (III)}(X,X Prime ){sub 6} octahedra (M=Bi, Sb; X, X Prime =Cl, Br, I) and methylviologen (MV) dications

    Energy Technology Data Exchange (ETDEWEB)

    Leblanc, Nicolas [Laboratoire MOLTECH-Anjou, UMR-CNRS 6200, Universite d' Angers 2 Bd Lavoisier, 49045 Angers (France); Mercier, Nicolas, E-mail: nicolas.mercier@univ-angers.fr [Laboratoire MOLTECH-Anjou, UMR-CNRS 6200, Universite d' Angers 2 Bd Lavoisier, 49045 Angers (France); Allain, Magali; Toma, Oksana [Laboratoire MOLTECH-Anjou, UMR-CNRS 6200, Universite d' Angers 2 Bd Lavoisier, 49045 Angers (France); Auban-Senzier, Pascale; Pasquier, Claude [Laboratoire de Physique des Solides, UMR-CNRS 8502, Bat. 510,Universite Paris Sud, 91405 Orsay (France)

    2012-11-15

    The search for hybrid organic-inorganic materials remains a great challenge in the field of ferroelectrics. Following the discovery of the room temperature ferroelectric material (MV)[BiI{sub 3}Cl{sub 2}] (MV{sup 2+}: methylviologen) exhibiting the highest polarization value in the field of hybrid ferroelectrics, we report here nine new hybrids with the general formulation (MV)[M{sup (III)}X{sub 5-x}X Prime {sub x}] (M=Bi, Sb; X, X Prime =Cl, Br, I): (MV)[BiCl{sub 3.3}Br{sub 1.7}] (1), (MV)[BiCl{sub 1.3}Br{sub 3.7}] (2), (MV)[BiBr{sub 3.2}I{sub 1.8}] (3), (MV)[SbCl{sub 5}] (4), (MV)[SbBr{sub 5}] (5), (MV)[SbCl{sub 3.8}Br{sub 1.2}] (6), (MV)[SbCl{sub 2.4}Br{sub 2.6}] (7), (MV)[SbI{sub 3}Cl{sub 2}] (8) and (MV)[SbBr{sub 3.8}I{sub 1.2}] (9). Depending on the presence of polar chains or not, and on the coupling of polar chains, two types of centrosymmetrical structures [C1] and [C2] and two types of polar structures [P1] and [P2] are defined. (2) undergoes a paraelectric-to-relaxor ferroelectric transition around 100-150 K depending of the frequency showing that the Curie temperature, T{sub C}, of (MV)[BiBr{sub 5}] (243 K) can be modulated by the substitution of Br by Cl. The most interesting family is the [P2] type because the syn coupling of polar chains is in favor of high polarization values, as in (MV)[BiI{sub 3}Cl{sub 2}]. Five of the nine new hybrids, (4), (6-9), which have the [P2] type structure are potential ferroelectrics. - Graphical abstract: The methylviologen haloantimonate (MV)[SbX{sub 5-x}X Prime {sub x}] families (X, X Prime =Cl, Br, I) - [P1] and [P2] are the two kinds of polar structures - and view of the (MV)[SbBr{sub 3.8}I{sub 1.2}] hybrid based on chiral polar chains which are in syn coupling. Highlights: Black-Right-Pointing-Pointer Nine hybrids based on methylviologen and halometalate chains have been discovered. Black-Right-Pointing-Pointer The polar nature of chains is due to the ns{sup 2} stereoactivity of Sb{sup (III)} or Bi{sup (III

  7. A 290 mV Sub-V(T) ASIC for Real-Time Atrial Fibrillation Detection.

    Science.gov (United States)

    Andersson, Oskar; Chon, Ki H; Sornmo, Leif; Rodrigues, Joachim Neves

    2015-06-01

    A real-time detector for episodes of atrial fibrillation is fabricated as an application specific integrated circuit (ASIC). The basis for detection is a set of three parameters for characterizing the RR interval series, i.e., turning point ratio, root mean square of successive differences, and Shannon entropy. The developed hardware architecture targets ultra-low voltage operation, suitable for implantable loop recorders with ultra-low energy requirements. Algorithmic and architectural optimizations are performed to minimize area and energy dissipation, with a total area footprint reduction of 44%. The design is fabricated in 65-nm CMOS low-leakage high-threshold technology. Measurements with aggressively scaled supply voltage (VDD) in the subthreshold (sub-VT) region show energy savings of up to 41 X when operating at 1 kHz with a VDD of 300 mV compared to a nominal VDD of 1.2 V.

  8. Utilisation of symmetrical components in a communication-based protection for loop MV feeders with variable short-circuit power

    DEFF Research Database (Denmark)

    Ciontea, Catalin-Iosif; Bak, Claus Leth; Blaabjerg, Frede

    2018-01-01

    -circuit power is presented. It relies on utilisation of symmetrical components of the short-circuit currents and on communication between the protection relays. The proposed method addresses the Single Phase to Ground (SPG) faults occurring in directly grounded distribution networks, with focus on closed......Variability of the available short-circuit power also implies variation of the fault level, which can potentially cause several protection problems in the electric networks. In this paper, a novel protection method that is insensitive to the fault level changes caused by variable short......-loop Medium Voltage (MV) feeders. Case studies are presented, which demonstrate that the proposed protection scheme is capable of effectively detecting the SPG faults in closed-loop feeders with variable short-circuit power....

  9. Comparison of detector systems for the separation of {sup 36}Cl and {sup 36}S with a 3-MV tandem

    Energy Technology Data Exchange (ETDEWEB)

    Orlowski, Tobias, E-mail: a0447924@unet.univie.ac.a [VERA Laboratory, Fakultaet fuer Physik, Universitaet Wien, Waehringer Str. 17, Wien 1090 (Austria); Forstner, Oliver; Golser, Robin; Kutschera, Walter [VERA Laboratory, Fakultaet fuer Physik, Universitaet Wien, Waehringer Str. 17, Wien 1090 (Austria); Merchel, Silke [CEREGE, CNRS-IRD-Universite Aix-Marseille, Europole Mediterraneen de L' Arbois, BP 80, Aix-en-Provence 13545 (France); Forschungszentrum Dresden-Rossendorf, D-01314 Dresden (Germany); Martschini, Martin; Priller, Alfred; Steier, Peter [VERA Laboratory, Fakultaet fuer Physik, Universitaet Wien, Waehringer Str. 17, Wien 1090 (Austria); Vockenhuber, Christof [HPK H 31, Institut fuer Teilchenphysik, ETH Zuerich, Schafmattstr. 20 CH-8093 Zuerich (Switzerland); Wallner, Anton [VERA Laboratory, Fakultaet fuer Physik, Universitaet Wien, Waehringer Str. 17, Wien 1090 (Austria)

    2010-04-15

    The possibility of detecting {sup 36}Cl for geological exposure dating has been explored for several years at VERA (the Vienna Environmental Research Accelerator). First results on real samples were obtained with an ionization chamber (developed at the ETH/PSI, Zuerich, Switzerland) with two anodes. To improve the suppression of {sup 36}S, we equipped the ionization chamber with an exit window and added a Time-of-Flight (TOF) system with a double-sided silicon strip detector (50 x 50 mm{sup 2}) as stop detector. We optimized the TOF setup by using silicon nitride foils to reduce scattering tails in the energy spectra. At 3 MV terminal voltage, corresponding to a particle energy of 24 MeV of {sup 36}Cl{sup 7+}, we achieved a {sup 36}S{sup 7+}-suppression of 21,500 (50% {sup 36}Cl-detector-efficiency).

  10. Investigating the performances of a 1 MV high pulsed power linear transformer driver: from beam dynamics to x radiation

    Science.gov (United States)

    Maisonny, R.; Ribière, M.; Toury, M.; Plewa, J. M.; Caron, M.; Auriel, G.; d'Almeida, T.

    2016-12-01

    The performance of a 1 MV pulsed high-power linear transformer driver accelerator were extensively investigated based on a numerical approach which utilizes both electromagnetic and Monte Carlo simulations. Particle-in-cell calculations were employed to examine the beam dynamics throughout the magnetically insulated transmission line which governs the coupling between the generator and the electron diode. Based on the information provided by the study of the beam dynamics, and using Monte Carlo methods, the main properties of the resulting x radiation were predicted. Good agreement was found between these simulations and experimental results. This work provides a detailed understanding of mechanisms affecting the performances of this type of high current, high-voltage pulsed accelerator, which are very promising for a growing number of applications.

  11. Fast and slow neutrons in an 18-MV photon beam from a Philips SL/75-20 linear accelerator

    International Nuclear Information System (INIS)

    Gur, D.; Rosen, J.C.; Bukovitz, A.G.; Gill, A.W.

    1978-01-01

    Fast- and slow-neutron contamination in an 18-MV photon beam from a Philips SL/75-20 linear accelerator has been measured. Aluminum and indium foils were activated to determine fast- and slow-neutron fluence, which were largely independent of field sizes. Measured fast-neutron fluences were typically 13.9 x 10 4 and 4.4 x 10 4 neutrons/cm 2 /rad of x ray inside and 5 cm outside the field, respectively. Slow-neutron fluences, 1.3 x 10 4 neutrons/cm 2 /rad of x ray, remained relatively constant inside and outside the field. The reported results are about three times higher than neutron fluences recently reported with a betatron operated at the same energy

  12. Evaluation of a 50-MV photon therapy beam from a racetrack microtron using MCNP4B Monte Carlo code

    International Nuclear Information System (INIS)

    Gudowska, I.; Svensson, R.

    2001-01-01

    High energy photon therapy beam from the 50 MV racetrack microtron has been evaluated using the Monte Carlo code MCNP4B. The spatial and energy distribution of photons, radial and depth dose distributions in the phantom are calculated for the stationary and scanned photon beams from different targets. The calculated dose distributions are compared to the experimental data using a silicon diode detector. Measured and calculated depth-dose distributions are in fairly good agreement, within 2-3% for the positions in the range 2-30 cm in the phantom, whereas the larger discrepancies up to 10% are observed in the dose build-up region. For the stationary beams the differences in the calculated and measured radial dose distributions are about 2-10%. (orig.)

  13. Beam property measurement of a 300-kV ion source test stand for a 1-MV electrostatic accelerator

    Science.gov (United States)

    Park, Sae-Hoon; Kim, Dae-Il; Kim, Yu-Seok

    2016-09-01

    The KOMAC (Korea Multi-purpose Accelerator Complex) has been developing a 300-kV ion source test stand for a 1-MV electrostatic accelerator for industrial purposes. A RF ion source was operated at 200 MHz with its matching circuit. The beam profile and emittance were measured behind an accelerating column to confirm the beam property from the RF ion source. The beam profile was measured at the end of the accelerating tube and at the beam dump by using a beam profile monitor (BPM) and wire scanner. An Allison-type emittance scanner was installed behind the beam profile monitor (BPM) to measure the beam density in phase space. The measurement results for the beam profile and emittance are presented in this paper.

  14. Ion Beam Facilities at the National Centre for Accelerator based Research using a 3 MV Pelletron Accelerator

    Science.gov (United States)

    Trivedi, T.; Patel, Shiv P.; Chandra, P.; Bajpai, P. K.

    A 3.0 MV (Pelletron 9 SDH 4, NEC, USA) low energy ion accelerator has been recently installed as the National Centre for Accelerator based Research (NCAR) at the Department of Pure & Applied Physics, Guru Ghasidas Vishwavidyalaya, Bilaspur, India. The facility is aimed to carried out interdisciplinary researches using ion beams with high current TORVIS (for H, He ions) and SNICS (for heavy ions) ion sources. The facility includes two dedicated beam lines, one for ion beam analysis (IBA) and other for ion implantation/ irradiation corresponding to switching magnet at +20 and -10 degree, respectively. Ions with 60 kV energy are injected into the accelerator tank where after stripping positively charged ions are accelerated up to 29 MeV for Au. The installed ion beam analysis techniques include RBS, PIXE, ERDA and channelling.

  15. Note: Establishing α-particle radiation damage experiments using the Dalton Cumbrian Facility’s 5 MV tandem pelletron

    Energy Technology Data Exchange (ETDEWEB)

    Bower, W. R. [Research Centre for Radwaste Disposal, University of Manchester, Oxford Road, Manchester M13 9PL (United Kingdom); Dalton Cumbrian Facility, Westlakes Science and Technology Park, University of Manchester, Cumbria CA24 3HA (United Kingdom); Smith, A. D.; Pimblott, S. M. [Dalton Cumbrian Facility, Westlakes Science and Technology Park, University of Manchester, Cumbria CA24 3HA (United Kingdom); Pattrick, R. A. D. [Research Centre for Radwaste Disposal, University of Manchester, Oxford Road, Manchester M13 9PL (United Kingdom)

    2015-04-15

    Evaluating the radiation stability of mineral phases is a vital research challenge when assessing the performance of the materials employed in a Geological Disposal Facility for radioactive waste. This report outlines the setup and methodology for efficiently allowing the determination of the dose dependence of damage to a mineral from a single ion irradiated sample. The technique has been deployed using the Dalton Cumbrian Facility’s 5 MV tandem pelletron to irradiate a suite of minerals with a controlled α-particle ({sup 4}He{sup 2+}) beam. Such minerals are proxies for near-field clay based buffer material surrounding radioactive canisters, as well as the sorbent components of the host rock.

  16. The 1 MV multi-element AMS system for biomedical applications at the Netherlands Organization for Applied Scientific Research (TNO)

    Energy Technology Data Exchange (ETDEWEB)

    Klein, Matthias, E-mail: mklein@highvolteng.com [High Voltage Engineering Europa B.V., P.O. Box 99, 3800 AB Amersfoort (Netherlands); Vaes, W.H.J.; Fabriek, B.; Sandman, H. [TNO, P.O. Box 360, 3700 AJ Zeist (Netherlands); Mous, D.J.W.; Gottdang, A. [High Voltage Engineering Europa B.V., P.O. Box 99, 3800 AB Amersfoort (Netherlands)

    2013-01-15

    The Netherlands Organization for Applied Scientific Research (TNO) has installed a compact 1 MV multi-element AMS system manufactured by High Voltage Engineering Europa B.V., The Netherlands. TNO performs clinical research programs for pharmaceutical and innovative foods industry to obtain early pharmacokinetic data and to provide anti-osteoporotic efficacy data of new treatments. The AMS system will analyze carbon, iodine and calcium samples for this purpose. The first measurements on blank samples indicate background levels in the low 10{sup -12} for calcium and iodine, making the system well suited for these biomedical applications. Carbon blanks have been measured at low 10{sup -16}. For unattended, around-the-clock analysis, the system features the 200 sample version of the SO110 hybrid ion source and user friendly control software.

  17. Comparison of detector systems for the separation of 36Cl and 36S with a 3-MV tandem

    International Nuclear Information System (INIS)

    Orlowski, Tobias; Forstner, Oliver; Golser, Robin; Kutschera, Walter; Merchel, Silke; Martschini, Martin; Priller, Alfred; Steier, Peter; Vockenhuber, Christof; Wallner, Anton

    2010-01-01

    The possibility of detecting 36 Cl for geological exposure dating has been explored for several years at VERA (the Vienna Environmental Research Accelerator). First results on real samples were obtained with an ionization chamber (developed at the ETH/PSI, Zuerich, Switzerland) with two anodes. To improve the suppression of 36 S, we equipped the ionization chamber with an exit window and added a Time-of-Flight (TOF) system with a double-sided silicon strip detector (50 x 50 mm 2 ) as stop detector. We optimized the TOF setup by using silicon nitride foils to reduce scattering tails in the energy spectra. At 3 MV terminal voltage, corresponding to a particle energy of 24 MeV of 36 Cl 7+ , we achieved a 36 S 7+ -suppression of 21,500 (50% 36 Cl-detector-efficiency).

  18. Pareto front analysis of 6 and 15 MV dynamic IMRT for lung cancer using pencil beam, AAA and Monte Carlo

    DEFF Research Database (Denmark)

    Ottosson, R O; Hauer, Anna Karlsson; Behrens, C.F.

    2010-01-01

    to normal tissue sparing weighted. All optimized treatment plans were calculated using three different calculation algorithms (PBC, AAA and MC). In order to study the influence of motion, two virtual lung phantoms were created. The idea was to mimic two different situations: one where the GTV is located...... centrally in the PTV and another where the GTV was close to the edge of the PTV. PBC is in poor agreement with MC and AAA for all cases and treatment plans. AAA overestimates the dose, compared to MC. This effect is more pronounced for 15 than 6MV. AAA and MC both predict similar perturbations in dose...... distributions when moving the GTV to the edge of the PTV. PBC, however, predicts results contradicting those of AAA and MC. This study shows that PB-based dose calculation algorithms are clinically insufficient for patient geometries involving large density inhomogeneities. AAA is in much better agreement...

  19. Evaluation of the usefulness of a MOSFET detector in an anthropomorphic phantom for 6-MV photon beam.

    Science.gov (United States)

    Kohno, Ryosuke; Hirano, Eriko; Kitou, Satoshi; Goka, Tomonori; Matsubara, Kana; Kameoka, Satoru; Matsuura, Taeko; Ariji, Takaki; Nishio, Teiji; Kawashima, Mitsuhiko; Ogino, Takashi

    2010-07-01

    In order to evaluate the usefulness of a metal oxide-silicon field-effect transistor (MOSFET) detector as a in vivo dosimeter, we performed in vivo dosimetry using the MOSFET detector with an anthropomorphic phantom. We used the RANDO phantom as an anthropomorphic phantom, and dose measurements were carried out in the abdominal, thoracic, and head and neck regions for simple square field sizes of 10 x 10, 5 x 5, and 3 x 3 cm(2) with a 6-MV photon beam. The dose measured by the MOSFET detector was verified by the dose calculations of the superposition (SP) algorithm in the XiO radiotherapy treatment-planning system. In most cases, the measured doses agreed with the results of the SP algorithm within +/-3%. Our results demonstrated the utility of the MOSFET detector for in vivo dosimetry even in the presence of clinical tissue inhomogeneities.

  20. Application of MV/LV Transformers with OLTC for Increasing the PV Hosting Capacity Of LV Grids

    DEFF Research Database (Denmark)

    Hashemi Toghroljerdi, Seyedmostafa; Heckmann, Wolfram; Geibel, Dominik

    2015-01-01

    The increased use of grid connected photovoltaic (PV) systems in low voltage (LV) grids also raises concern regarding the effects of these new generation units on the grid operation. Overvoltage in LV grids during high PV generation periods is one of the well-known effects caused by PV systems......) and the reactive power absorption by PV inverters, are investigated using field test results and simulations performed on the mentioned LV grid. The results show that the application of OLTC can effectively increase the PV hosting capacity of the grid......., which potentially can decrease the PV hosting capacity of electric grids. This paper presents the applications of medium voltage to low voltage (MV/LV) transformers with on-load tap changers (OLTCs) to prevent overvoltage in high PV penetration conditions. Autonomous methods for controlling...

  1. Measurement of trigger and cascade section runtimes in 6 MV switches using fiber coupled photodetectors

    Directory of Open Access Journals (Sweden)

    Jens Schwarz

    2012-07-01

    Full Text Available Since October 2007 Sandia National Laboratories has operated the refurbished Z machine at an improved load current of 26 MA yielding 400 TW of x-ray power. The current pulse shape to the load is controlled by 36 independently timed laser triggered gas switches. As part of the refurbishment effort, a fiber coupled laser spark detector system has been installed which is able to detect the laser generated plasma in situ inside the trigger section of the high voltage switch. In this paper we describe how this detection system can be used to characterize the discharge dynamics of these 5.9 MV, 820 kA switches.

  2. Two-dimensional modelling of internal arc effects in an enclosed MV cell provided with a protection porous filter

    International Nuclear Information System (INIS)

    Rochette, D; Clain, S; Andre, P; Bussiere, W; Gentils, F

    2007-01-01

    Medium voltage (MV) cells have to respect standards (for example IEC ones (IEC TC 17C 2003 IEC 62271-200 High Voltage Switchgear and Controlgear-Part 200 1st edn)) that define security levels against internal arc faults such as an accidental electrical arc occurring in the apparatus. New protection filters based on porous materials are developed to provide better energy absorption properties and a higher protection level for people. To study the filter behaviour during a major electrical accident, a two-dimensional model is proposed. The main point is the use of a dedicated numerical scheme for a non-conservative hyperbolic problem. We present a numerical simulation of the process during the first 0.2 s when the safety valve bursts and we compare the numerical results with tests carried out in a high power test laboratory on real electrical apparatus

  3. Two-dimensional modelling of internal arc effects in an enclosed MV cell provided with a protection porous filter

    Science.gov (United States)

    Rochette, D.; Clain, S.; André, P.; Bussière, W.; Gentils, F.

    2007-05-01

    Medium voltage (MV) cells have to respect standards (for example IEC ones (IEC TC 17C 2003 IEC 62271-200 High Voltage Switchgear and Controlgear—Part 200 1st edn)) that define security levels against internal arc faults such as an accidental electrical arc occurring in the apparatus. New protection filters based on porous materials are developed to provide better energy absorption properties and a higher protection level for people. To study the filter behaviour during a major electrical accident, a two-dimensional model is proposed. The main point is the use of a dedicated numerical scheme for a non-conservative hyperbolic problem. We present a numerical simulation of the process during the first 0.2 s when the safety valve bursts and we compare the numerical results with tests carried out in a high power test laboratory on real electrical apparatus.

  4. Two-dimensional modelling of internal arc effects in an enclosed MV cell provided with a protection porous filter

    Energy Technology Data Exchange (ETDEWEB)

    Rochette, D [Laboratoire Arc Electrique et Plasmas Thermiques, CNRS UMR 6069, Universite Blaise Pascal, IUT de Montlucon, Avenue Aristide Briand, BP 2235, 03101 Montlucon Cedex (France); Clain, S [Laboratoire de Mathematiques pour l' Industrie et la Physique, CNRS UMR 5640, Universite Paul Sabatier Toulouse 3, 118 route de Narbonne, 31062 Toulouse Cedex 4 (France); Andre, P [Laboratoire Arc Electrique et Plasmas Thermiques, CNRS UMR 6069, Universite Blaise Pascal, IUT de Montlucon, Avenue Aristide Briand, BP 2235, 03101 Montlucon Cedex (France); Bussiere, W [Laboratoire Arc Electrique et Plasmas Thermiques, CNRS UMR 6069, Universite Blaise Pascal, IUT de Montlucon, Avenue Aristide Briand, BP 2235, 03101 Montlucon Cedex (France); Gentils, F [Schneider Electric-Science and Technology Division-Research Center A2, 38050 Grenoble Cedex 9 (France)

    2007-05-21

    Medium voltage (MV) cells have to respect standards (for example IEC ones (IEC TC 17C 2003 IEC 62271-200 High Voltage Switchgear and Controlgear-Part 200 1st edn)) that define security levels against internal arc faults such as an accidental electrical arc occurring in the apparatus. New protection filters based on porous materials are developed to provide better energy absorption properties and a higher protection level for people. To study the filter behaviour during a major electrical accident, a two-dimensional model is proposed. The main point is the use of a dedicated numerical scheme for a non-conservative hyperbolic problem. We present a numerical simulation of the process during the first 0.2 s when the safety valve bursts and we compare the numerical results with tests carried out in a high power test laboratory on real electrical apparatus.

  5. Evaluation of tomato genotypes against tomato mosaic virus (ToMV) and its effect on yield contributing parameters

    International Nuclear Information System (INIS)

    Ullah, N.; Ali, A.; Ahmad, M.; Din, N.; Ahmad, F.; Fahim, M.

    2017-01-01

    The use of resistant varieties is an effective, economic and environment friendly management of plant diseases particularly those caused by viruses. This paper reports, evaluation of 21 different tomato genotypes to find out resistance sources against Tomato mosaic virus (ToMV) and to study effect of the virus on yield contributing parameters. The virus identity was confirmed both by Direct Antibody Coating Enzyme Linked Immunoassay (DAC-ELISA) and differential host assay. Characteristic necrotic lesions were observed on differential hosts viz., Nicotiana tabacum var. White burly and Chenopodium amaranticolor after 10 and 3-4 days of inoculation, respectively. Upon ToMV inoculation, plants of accession No. 017902 developed no symptoms and were rated as highly resistant. Its resistance was further confirmed by both DAC-ELISA and indicator host assay, while the remaining genotypes displayed a range of symptoms. Plants of accession No. 017883 showed lowest percent disease index (PDI) and were rated as resistant, while plants of cultivar Red jumbo showed maximum PDI (44.97%) and were rated as susceptible. In susceptible genotypes average ELISA absorbance A405 value (2.19) was found higher than resistant one (1.05), while in control healthy plants ELISA absorbance A405 was 0.18. Maximum virus titre 2.73 and 0.91 were found in leaf and root tissues of cultivar Red jumbo, respectively. Among tested genotypes, one was highly resistant, one resistant, four moderately susceptible and 15 were susceptible. The virus significantly (p<=0.05) reduced the yield contributing parameters i.e. plant height, fresh shoot and root weight, dry shoot and root weight in susceptible genotypes. (author)

  6. MCMEG: Simulations of both PDD and TPR for 6 MV LINAC photon beam using different MC codes

    International Nuclear Information System (INIS)

    Fonseca, T.C.F.; Mendes, B.M.; Lacerda, M.A.S.; Silva, L.A.C.; Paixão, L.

    2017-01-01

    The Monte Carlo Modelling Expert Group (MCMEG) is an expert network specializing in Monte Carlo radiation transport and the modelling and simulation applied to the radiation protection and dosimetry research field. For the first inter-comparison task the group launched an exercise to model and simulate a 6 MV LINAC photon beam using the Monte Carlo codes available within their laboratories and validate their simulated results by comparing them with experimental measurements carried out in the National Cancer Institute (INCA) in Rio de Janeiro, Brazil. The experimental measurements were performed using an ionization chamber with calibration traceable to a Secondary Standard Dosimetry Laboratory (SSDL). The detector was immersed in a water phantom at different depths and was irradiated with a radiation field size of 10×10 cm 2 . This exposure setup was used to determine the dosimetric parameters Percentage Depth Dose (PDD) and Tissue Phantom Ratio (TPR). The validation process compares the MC calculated results to the experimental measured PDD20,10 and TPR20,10. Simulations were performed reproducing the experimental TPR20,10 quality index which provides a satisfactory description of both the PDD curve and the transverse profiles at the two depths measured. This paper reports in detail the modelling process using MCNPx, MCNP6, EGSnrc and Penelope Monte Carlo codes, the source and tally descriptions, the validation processes and the results. - Highlights: • MCMEG is an expert network specializing in Monte Carlo radiation transport. • MCNPx, MCNP6, EGSnrc and Penelope Monte Carlo codes are used. • Exercise to model and simulate a 6 MV LINAC photon beam using the Monte Carlo codes. • The PDD 20,10 and TPR 20,10 dosimetric parameters were compared with real data. • The paper reports in the modelling process using different Monte Carlo codes.

  7. Functional properties and structural requirements of the plasmid pMV158-encoded MobM relaxase domain.

    Science.gov (United States)

    Fernández-López, Cris; Pluta, Radoslaw; Pérez-Luque, Rosa; Rodríguez-González, Lorena; Espinosa, Manuel; Coll, Miquel; Lorenzo-Díaz, Fabián; Boer, D Roeland

    2013-07-01

    A crucial element in the horizontal transfer of mobilizable and conjugative plasmids is the relaxase, a single-stranded endonuclease that nicks the origin of transfer (oriT) of the plasmid DNA. The relaxase of the pMV158 mobilizable plasmid is MobM (494 residues). In solution, MobM forms a dimer through its C-terminal domain, which is proposed to anchor the protein to the cell membrane and to participate in type 4 secretion system (T4SS) protein-protein interactions. In order to gain a deeper insight into the structural MobM requirements for efficient DNA catalysis, we studied two endonuclease domain variants that include the first 199 or 243 amino acid residues (MobMN199 and MobMN243, respectively). Our results confirmed that the two proteins behaved as monomers in solution. Interestingly, MobMN243 relaxed supercoiled DNA and cleaved single-stranded oligonucleotides harboring oriTpMV158, whereas MobMN199 was active only on supercoiled DNA. Protein stability studies using gel electrophoresis and mass spectrometry showed increased susceptibility to degradation at the domain boundary between the N- and C-terminal domains, suggesting that the domains change their relative orientation upon DNA binding. Overall, these results demonstrate that MobMN243 is capable of nicking the DNA substrate independently of its topology and that the amino acids 200 to 243 modulate substrate specificity but not the nicking activity per se. These findings suggest that these amino acids are involved in positioning the DNA for the nuclease reaction rather than in the nicking mechanism itself.

  8. Mutual influences of rated currents, short circuit levels, fault durations and integrated protective schemes for industrial distribution MV switchgears

    Energy Technology Data Exchange (ETDEWEB)

    Gaidano, G. (FIAT Engineering, Torino, Italy); Lionetto, P.F.; Pelizza, C.; Tommazzolli, F.

    1979-01-01

    This paper deals with the problem of integrated and coordinated design of distribution systems, as regards the definition of system structure and parameters together with protection criteria and schemes. Advantages in system operation, dynamic response, heavier loads with reduced machinery rating margins and overall cost reduction, can be achieved. It must be noted that MV switchgears installed in industrial main distribution substations are the vital nodes of the distribution system. Very large amounts of power (up to 100 MW and more) are conveyed through MV busbars, coming from Utility and from in-plant generators and outgoing to subdistribution substations, to step-down transformers and to main concentrated loads (big drivers, furnaces etc.). Criteria and methods already studied and applied to public distribution are examined to assess service continuity and economics by means of the reduction of thermal stresses, minimization of disturbances and improvement of system stability. The life of network components depends on sizing, on fault energy levels and on probability of fault occurrence. Constructional measures and protection schemes, which reduce probability and duration of faults, are the most important tools to improve overall reliability. The introduction of advanced techniques, mainly based on computer application, not only allows drastic reduction of fault duration, but also permits the system to operate, under any possible contingency, in the optimal conditions, as the computer provides adaptive control. This mode of system management makes it possible to size network components with reference to the true magnitude of system quantities, avoiding expensive oversizing connected to the unflexibility of conventional protection and control schemes.

  9. Reactions of guanine with methyl chloride and methyl bromide: O6-methylation versus charge transfer complex formation

    Science.gov (United States)

    Shukla, P. K.; Mishra, P. C.; Suhai, S.

    Density functional theory (DFT) at the B3LYP/6-31+G* and B3LYP/AUG-cc-pVDZ levels was employed to study O6-methylation of guanine due to its reactions with methyl chloride and methyl bromide and to obtain explanation as to why the methyl halides cause genotoxicity and possess mutagenic and carcinogenic properties. Geometries of the various isolated species involved in the reactions, reactant complexes (RCs), and product complexes (PCs) were optimized in gas phase. Transition states connecting the reactant complexes with the product complexes were also optimized in gas phase at the same levels of theory. The reactant complexes, product complexes, and transition states were solvated in aqueous media using the polarizable continuum model (PCM) of the self-consistent reaction field theory. Zero-point energy (ZPE) correction to total energy and the corresponding thermal energy correction to enthalpy were made in each case. The reactant complexes of the keto form of guanine with methyl chloride and methyl bromide in water are appreciably more stable than the corresponding complexes involving the enol form of guanine. The nature of binding in the product complexes was found to be of the charge transfer type (O6mG+ · X-, X dbond Cl, Br). Binding of HCl, HBr, and H2O molecules to the PCs obtained with the keto form of guanine did not alter the positions of the halide anions in the PCs, and the charge transfer character of the PCs was also not modified due to this binding. Further, the complexes obtained due to the binding of HCl, HBr, and H2O molecules to the PCs had greater stability than the isolated PCs. The reaction barriers involved in the formation of PCs were found to be quite high (?50 kcal/mol). Mechanisms of genotoxicity, mutagenesis and carcinogenesis caused by the methyl halides appear to involve charge transfer-type complex formation. Thus the mechanisms of these processes involving the methyl halides appear to be quite different from those that involve the

  10. Hovenia dulcis Thunb extract and its ingredient methyl vanillate activate Wnt/β-catenin pathway and increase bone mass in growing or ovariectomized mice.

    Directory of Open Access Journals (Sweden)

    Pu-Hyeon Cha

    Full Text Available The Wnt/β-catenin pathway is a potential target for development of anabolic agents to treat osteoporosis because of its role in osteoblast differentiation and bone formation. However, there is no clinically available anti-osteoporosis drug that targets this Wnt/β-catenin pathway. In this study, we screened a library of aqueous extracts of 350 plants and identified Hovenia dulcis Thunb (HDT extract as a Wnt/β-catenin pathway activator. HDT extract induced osteogenic differentiation of calvarial osteoblasts without cytotoxicity. In addition, HDT extract increased femoral bone mass without inducing significant weight changes in normal mice. In addition, thickness and area of femoral cortical bone were also significantly increased by the HDT extract. Methyl vanillate (MV, one of the ingredients in HDT, also activated the Wnt/β-catenin pathway and induced osteoblast differentiation in vitro. MV rescued trabecular or cortical femoral bone loss in the ovariectomized mice without inducing any significant weight changes or abnormality in liver tissue when administrated orally. Thus, natural HDT extract and its ingredient MV are potential anabolic agents for treating osteoporosis.

  11. Global DNA methylation of ischemic stroke subtypes.

    Directory of Open Access Journals (Sweden)

    Carolina Soriano-Tárraga

    Full Text Available Ischemic stroke (IS, a heterogeneous multifactorial disorder, is among the leading causes of mortality and long-term disability in the western world. Epidemiological data provides evidence for a genetic component to the disease, but its epigenetic involvement is still largely unknown. Epigenetic mechanisms, such as DNA methylation, change over time and may be associated with aging processes and with modulation of the risk of various pathologies, such as cardiovascular disease and stroke. We analyzed 2 independent cohorts of IS patients. Global DNA methylation was measured by luminometric methylation assay (LUMA of DNA blood samples. Univariate and multivariate regression analyses were used to assess the methylation differences between the 3 most common IS subtypes, large-artery atherosclerosis (LAA, small-artery disease (SAD, and cardio-aortic embolism (CE. A total of 485 IS patients from 2 independent hospital cohorts (n = 281 and n = 204 were included, distributed across 3 IS subtypes: LAA (78/281, 59/204, SAD (97/281, 53/204, and CE (106/281, 89/204. In univariate analyses, no statistical differences in LUMA levels were observed between the 3 etiologies in either cohort. Multivariate analysis, adjusted by age, sex, hyperlipidemia, and smoking habit, confirmed the lack of differences in methylation levels between the analyzed IS subtypes in both cohorts. Despite differences in pathogenesis, our results showed no global methylation differences between LAA, SAD, and CE subtypes of IS. Further work is required to establish whether the epigenetic mechanism of methylation might play a role in this complex disease.

  12. Inductive effect of methyl group in a series of methylated indoles: A ...

    Indian Academy of Sciences (India)

    Vol. 125, No. 4, July 2013, pp. 905–912. c Indian Academy of Sciences. Inductive effect of methyl group in a series of methylated indoles: A graph theoretical analysis in the light of density functional theory and correlation with experimental charge transfer transition energies. AMIT S TIWARYa,∗ and ASOK K MUKHERJEEb.

  13. Evidence for methyl group transfer between the methyl-accepting chemotaxis proteins in Bacillus subtilis

    International Nuclear Information System (INIS)

    Bedale, W.A.; Nettleton, D.O.; Sopata, C.S.; Thoelke, M.S.; Ordal, G.W.

    1988-01-01

    The authors present evidence for methyl (as methyl or methoxy) transfer from the methyl-accepting chemotaxis proteins H1 and possibly H3 of Bacillus subtilis to the methyl-accepting chemotaxis protein H2. This methyl transfer, which has been observed in vitro was strongly stimulated by the chemoattractant aspartate and thus may plan an important role in the sensory processing system of this organism. Although radiolabeling of H1 and H3 began at once after the addition of [ 3 H] methionine, radiolabeling of H2 showed a lag. Furthermore, the addition of excess nonradioactive methionine caused immediate exponential delabeling of H1 and H3 while labeling of H2 continued to increase. Methylation of H2 required the chemotactic methyltransferase, probably to first methylate H1 and H3. Aspartate caused increased labeling of H2 and strongly decreased labeling of H1 and H3 after the addition of nonradioactive methionine. Without the addition of nonradioactive methionine, aspartate caused demethylation of H1 and to a lesser extent H3, with an approximately equal increase of methylation of H2

  14. Methyl esters from vegetable oils with hydroxy fatty acids: Comparison of lesquerella and castor methyl esters

    Science.gov (United States)

    The search for alternative feedstocks for biodiesel as partial replacement for petrodiesel has recently extended to castor oil. In this work, the castor oil methyl esters were prepared and their properties determined in comparison to the methyl esters of lesquerella oil, which in turn is seen as alt...

  15. Modeling of the oxidation of methyl esters—Validation for methyl hexanoate, methyl heptanoate, and methyl decanoate in a jet-stirred reactor

    Science.gov (United States)

    Glaude, Pierre Alexandre; Herbinet, Olivier; Bax, Sarah; Biet, Joffrey; Warth, Valérie; Battin-Leclerc, Frédérique

    2013-01-01

    The modeling of the oxidation of methyl esters was investigated and the specific chemistry, which is due to the presence of the ester group in this class of molecules, is described. New reactions and rate parameters were defined and included in the software EXGAS for the automatic generation of kinetic mechanisms. Models generated with EXGAS were successfully validated against data from the literature (oxidation of methyl hexanoate and methyl heptanoate in a jet-stirred reactor) and a new set of experimental results for methyl decanoate. The oxidation of this last species was investigated in a jet-stirred reactor at temperatures from 500 to 1100 K, including the negative temperature coefficient region, under stoichiometric conditions, at a pressure of 1.06 bar and for a residence time of 1.5 s: more than 30 reaction products, including olefins, unsaturated esters, and cyclic ethers, were quantified and successfully simulated. Flow rate analysis showed that reactions pathways for the oxidation of methyl esters in the low-temperature range are similar to that of alkanes. PMID:23710076

  16. Modeling of the oxidation of methyl esters-Validation for methyl hexanoate, methyl heptanoate, and methyl decanoate in a jet-stirred reactor.

    Science.gov (United States)

    Glaude, Pierre Alexandre; Herbinet, Olivier; Bax, Sarah; Biet, Joffrey; Warth, Valérie; Battin-Leclerc, Frédérique

    2010-11-01

    The modeling of the oxidation of methyl esters was investigated and the specific chemistry, which is due to the presence of the ester group in this class of molecules, is described. New reactions and rate parameters were defined and included in the software EXGAS for the automatic generation of kinetic mechanisms. Models generated with EXGAS were successfully validated against data from the literature (oxidation of methyl hexanoate and methyl heptanoate in a jet-stirred reactor) and a new set of experimental results for methyl decanoate. The oxidation of this last species was investigated in a jet-stirred reactor at temperatures from 500 to 1100 K, including the negative temperature coefficient region, under stoichiometric conditions, at a pressure of 1.06 bar and for a residence time of 1.5 s: more than 30 reaction products, including olefins, unsaturated esters, and cyclic ethers, were quantified and successfully simulated. Flow rate analysis showed that reactions pathways for the oxidation of methyl esters in the low-temperature range are similar to that of alkanes.

  17. Histone Lysine Methylation in Diabetic Nephropathy

    Directory of Open Access Journals (Sweden)

    Guang-dong Sun

    2014-01-01

    Full Text Available Diabetic nephropathy (DN belongs to debilitating microvascular complications of diabetes and is the leading cause of end-stage renal diseases worldwide. Furthermore, outcomes from the DCCT/EDIC study showed that DN often persists and progresses despite intensive glucose control in many diabetes patients, possibly as a result of prior episode of hyperglycemia, which is called “metabolic memory.” The underlying mechanisms responsible for the development and progression of DN remain poorly understood. Activation of multiple signaling pathways and key transcription factors can lead to aberrant expression of DN-related pathologic genes in target renal cells. Increasing evidence suggests that epigenetic mechanisms in chromatin such as DNA methylation, histone acetylation, and methylation can influence the pathophysiology of DN and metabolic memory. Exciting researches from cell culture and experimental animals have shown that key histone methylation patterns and the related histone methyltransferases and histone demethylases can play important roles in the regulation of inflammatory and profibrotic genes in renal cells under diabetic conditions. Because histone methylation is dynamic and potentially reversible, it can provide a window of opportunity for the development of much-needed novel therapeutic potential for DN in the future. In this minireview, we discuss recent advances in the field of histone methylation and its roles in the pathogenesis and progression of DN.

  18. Prognostic DNA Methylation Markers for Prostate Cancer

    Directory of Open Access Journals (Sweden)

    Siri H. Strand

    2014-09-01

    Full Text Available Prostate cancer (PC is the most commonly diagnosed neoplasm and the third most common cause of cancer-related death amongst men in the Western world. PC is a clinically highly heterogeneous disease, and distinction between aggressive and indolent disease is a major challenge for the management of PC. Currently, no biomarkers or prognostic tools are able to accurately predict tumor progression at the time of diagnosis. Thus, improved biomarkers for PC prognosis are urgently needed. This review focuses on the prognostic potential of DNA methylation biomarkers for PC. Epigenetic changes are hallmarks of PC and associated with malignant initiation as well as tumor progression. Moreover, DNA methylation is the most frequently studied epigenetic alteration in PC, and the prognostic potential of DNA methylation markers for PC has been demonstrated in multiple studies. The most promising methylation marker candidates identified so far include PITX2, C1orf114 (CCDC181 and the GABRE~miR-452~miR-224 locus, in addition to the three-gene signature AOX1/C1orf114/HAPLN3. Several other biomarker candidates have also been investigated, but with less stringent clinical validation and/or conflicting evidence regarding their possible prognostic value available at this time. Here, we review the current evidence for the prognostic potential of DNA methylation markers in PC.

  19. Methylated genes as new cancer biomarkers

    DEFF Research Database (Denmark)

    Brunner, Nils; Duffy, M.J; Napieralski, R.

    2009-01-01

    Aberrant hypermethylation of promoter regions in specific genes is a key event in the formation and progression of cancer. In at least some situations, these aberrant alterations occur early in the formation of malignancy and appear to be tumour specific. Multiple reports have suggested that meas......Aberrant hypermethylation of promoter regions in specific genes is a key event in the formation and progression of cancer. In at least some situations, these aberrant alterations occur early in the formation of malignancy and appear to be tumour specific. Multiple reports have suggested...... that measurement of the methylation status of the promoter regions of specific genes can aid early detection of cancer, determine prognosis and predict therapy responses. Promising DNA methylation biomarkers include the use of methylated GSTP1 for aiding the early diagnosis of prostate cancer, methylated PITX2...... for predicting outcome in lymph node-negative breast cancer patients and methylated MGMT in predicting benefit from alkylating agents in patients with glioblastomas. However, prior to clinical utilisation, these findings require validation in prospective clinical studies. Furthermore, assays for measuring gene...

  20. Dynamic Alu Methylation during Normal Development, Aging, and Tumorigenesis

    Directory of Open Access Journals (Sweden)

    Yanting Luo

    2014-01-01

    Full Text Available DNA methylation primarily occurs on CpG dinucleotides and plays an important role in transcriptional regulations during tissue development and cell differentiation. Over 25% of CpG dinucleotides in the human genome reside within Alu elements, the most abundant human repeats. The methylation of Alu elements is an important mechanism to suppress Alu transcription and subsequent retrotransposition. Decades of studies revealed that Alu methylation is highly dynamic during early development and aging. Recently, many environmental factors were shown to have a great impact on Alu methylation. In addition, aberrant Alu methylation has been documented to be an early event in many tumors and Alu methylation levels have been associated with tumor aggressiveness. The assessment of the Alu methylation has become an important approach for early diagnosis and/or prognosis of cancer. This review focuses on the dynamic Alu methylation during development, aging, and tumor genesis. The cause and consequence of Alu methylation changes will be discussed.