The fragmentation of a 133 pps beam of 14Be ions at 35 MeV/A on targets of carbon and lead has been used to study the structure of the unbound nucleus 13Be. Neutrons and 12Be reaction products were measured in the DeMoN array and a detector telescope placed at 0° respectively. These coincidence measurements were used to reconstruct the 13Be particles. The beam energy was measured on a particle by particle basis from the time of flight. This was essential for momentum measurements which were made in the reference frame of the projectile. A significant contribution to the experimental background came from reactions in the detector telescope, which had to be subtracted. Relative velocity (arithmetic velocity difference) and invariant mass analyses both signify the existance of significant strength close to the 12Be + n threshold. Simulations including an experimental filter clearly show that this includes strength that is localised below 500 ke V in relative energy. Momentum distributions for 12Be, 10Be, neutrons and the reconstructed 13Be particle in the longitudinal direction have been measured. The 13Be distribution displays evidence for a two component structure. Calculations of the neutron stripping from 14Be have shown that this structure requires s-wave stripping to explain the narrow component. The wider component is consistent with d- wave stripping, and additional contributions from p-wave stripping cannot be excluded. The angular distribution of neutrons from 12Be + n breakup, measured in the 13Be reference frame is essentially isotropic. There is evidence for a weak asymmetry which could be due to broad over-lapping states of both positive and negative parity at energies below 2 MeV. This would support the inclusion of a P½ resonance in the low-lying structure of 13Be.

No description available.

No description available.

O veneno de C. d. terrificus tem sido descrito como sendo de pouca complexidade, tendo 4 frações caracterizadas, convulxina, giroxina. crotoxina e crotamina. O presente trabalho visou o isolamento e caracterização da Delta toxina cuja existência havia sido aventada em trabalhos anteriores. Após a realização de uma varredura de tampões em uma coluna de exclusão molecular Superdex-75 acoplada a um sistema FPLC, na presença de três diferentes tampões, chegou-se a uma condição ideal de fracionamento do veneno crotálico. Em seqüência realizou-se a segunda etapa de purificação em sistema HPLC em uma coluna C4, onde foi possível identificar o pico de interesse. O pico puro passou por análises em MALDI-ToF sendo sua massa estimada em 14.074,92 Da, Quando analisado por eletroforese em gel de poiiacrilamida, a delta toxina apresentou massa molecular de cerca de 14 kDa e uma migração anômala, Por eletroforese 2D, a proteína apresentou caráter ácido, com pl entre 4 e 5 e massa molecular de aproximadamente 42 kDa, revelando \"spots\" muito semelhantes podendo ser isoformas com características de uma proteína glicosiiada. Após digestão dos spots com tripsina, os fragmentos foram confrontados com o banco de dados do \"swissprot\", mostrando alto grau de homologia \"até 43% de cobertura\" com a troca ri na, um ativador de protrombina do veneno de Tropidechis carinatus, esses dados foram confirmados com a análise de aminoácidos. De posse desses resultados, optou-se por testar a capacidade da fração purificada de ativar fator X e II, usando substratos sintéticos. Os resultados apontaram para uma ativação direta do fator X, uma vez que não houve ativação do fator II, atividade que também não foi detectada no veneno total. A mesma se mostrou um potente ativador da agregação de forma direta, uma vez que os ensaios de agregação plaquetária foram realizados com plaquetas lavadas, logo na ausência de fatores séricos. Quando os ensaios de agregação foram realizados na presença de alguns inibidores observou-se que nem a atividade metalo proteinase, nem a serino proteinase, tampouco um domínio lectina estavam envolvidos no processo, uma vez que EDTA, benzamidina e D-galactose não inibiram a atividade da proteína. No presente trabalho isolamos a Delta toxina do veneno de C. d. terrificus. A mesma se comportou como previsto por Vital Brazil em 1980, eluindo na posição por ele aventada, sendo uma proteína ativadora de Fator X que ativa agregação plaquetária mesmo em concentrações muito baixas e de massa molecular de 40 kDa levando nos a crer se tratar de um homotrímero cujos componentes são unidos por ligações fracas. / The Crotalus durissus terrificus venom has been so far described as being of low complexity, with four major components described: convulxin, gyroxin, crotoxin and crotamine. In recent studies, other components of this venom were characterized as, for example, an analgesic factor. In 1980, Vital Brazil predicted the existence of a toxin which could be involved in platelet aggregation, and named it delta toxin. However, this toxin has never been isolated or characterized. The aim of the present work was to purify and characterize this toxin. After FPLC size exclusion chromatography followed by reverse phase HPLC, an homogeneous fraction was obtained, with a molecular weight of 14,074.92 Da. When analyzed by SOS-PAGE, this toxin presented an anomalous behavior, with a molecular weight of 14 kDa, while in 2D gels, spots around 40 kDa and with an isoelectrical point between 4 and 5 were observed suggesting isoforms with glicosilation microheterogeneity. After trypsin digestion, the fragments were submitted to the swissprot databank showing high homology (43% coverage, 15 matching peptides) with trocarin, a prothrombin activator from Tropidechis carinatus. These data were further confirmed by aminoacid analysis. The toxin was tested for its ability to activate factor II and X using synthetic substrates. Our data indicate a direct activation of factor X. The same toxin also behaved as a potent direct platelet aggregation activator on washed platelets. Assays with specific inhibitors indicate that neither metalloproteinase, nor serinoproteinase or t lectin domains are involved in the aggregating activity, since EDTA, benzamidin and D-galactose did not inhibit the toxin. In the present work, we were able to identify, purify and characterize a new toxin from the brazilian rattlesnake. It behaved as predicted by Vital-Brazil and displayed direct factor X activating properties, also inducing platelet aggregation, even at low concentrations. Our data also indicate that it is probably a homotrimer with the subunities linked by hydrophobic and/or electrostatic interactions.

O veneno de C. d. terrificus tem sido descrito como sendo de pouca complexidade, tendo 4 frações caracterizadas, convulxina, giroxina. crotoxina e crotamina. O presente trabalho visou o isolamento e caracterização da Delta toxina cuja existência havia sido aventada em trabalhos anteriores. Após a realização de uma varredura de tampões em uma coluna de exclusão molecular Superdex-75 acoplada a um sistema FPLC, na presença de três diferentes tampões, chegou-se a uma condição ideal de fracionamento do veneno crotálico. Em seqüência realizou-se a segunda etapa de purificação em sistema HPLC em uma coluna C4, onde foi possível identificar o pico de interesse. O pico puro passou por análises em MALDI-ToF sendo sua massa estimada em 14.074,92 Da, Quando analisado por eletroforese em gel de poiiacrilamida, a delta toxina apresentou massa molecular de cerca de 14 kDa e uma migração anômala, Por eletroforese 2D, a proteína apresentou caráter ácido, com pl entre 4 e 5 e massa molecular de aproximadamente 42 kDa, revelando \"spots\" muito semelhantes podendo ser isoformas com características de uma proteína glicosiiada. Após digestão dos spots com tripsina, os fragmentos foram confrontados com o banco de dados do \"swissprot\", mostrando alto grau de homologia \"até 43% de cobertura\" com a troca ri na, um ativador de protrombina do veneno de Tropidechis carinatus, esses dados foram confirmados com a análise de aminoácidos. De posse desses resultados, optou-se por testar a capacidade da fração purificada de ativar fator X e II, usando substratos sintéticos. Os resultados apontaram para uma ativação direta do fator X, uma vez que não houve ativação do fator II, atividade que também não foi detectada no veneno total. A mesma se mostrou um potente ativador da agregação de forma direta, uma vez que os ensaios de agregação plaquetária foram realizados com plaquetas lavadas, logo na ausência de fatores séricos. Quando os ensaios de agregação foram realizados na presença de alguns inibidores observou-se que nem a atividade metalo proteinase, nem a serino proteinase, tampouco um domínio lectina estavam envolvidos no processo, uma vez que EDTA, benzamidina e D-galactose não inibiram a atividade da proteína. No presente trabalho isolamos a Delta toxina do veneno de C. d. terrificus. A mesma se comportou como previsto por Vital Brazil em 1980, eluindo na posição por ele aventada, sendo uma proteína ativadora de Fator X que ativa agregação plaquetária mesmo em concentrações muito baixas e de massa molecular de 40 kDa levando nos a crer se tratar de um homotrímero cujos componentes são unidos por ligações fracas. / The Crotalus durissus terrificus venom has been so far described as being of low complexity, with four major components described: convulxin, gyroxin, crotoxin and crotamine. In recent studies, other components of this venom were characterized as, for example, an analgesic factor. In 1980, Vital Brazil predicted the existence of a toxin which could be involved in platelet aggregation, and named it delta toxin. However, this toxin has never been isolated or characterized. The aim of the present work was to purify and characterize this toxin. After FPLC size exclusion chromatography followed by reverse phase HPLC, an homogeneous fraction was obtained, with a molecular weight of 14,074.92 Da. When analyzed by SOS-PAGE, this toxin presented an anomalous behavior, with a molecular weight of 14 kDa, while in 2D gels, spots around 40 kDa and with an isoelectrical point between 4 and 5 were observed suggesting isoforms with glicosilation microheterogeneity. After trypsin digestion, the fragments were submitted to the swissprot databank showing high homology (43% coverage, 15 matching peptides) with trocarin, a prothrombin activator from Tropidechis carinatus. These data were further confirmed by aminoacid analysis. The toxin was tested for its ability to activate factor II and X using synthetic substrates. Our data indicate a direct activation of factor X. The same toxin also behaved as a potent direct platelet aggregation activator on washed platelets. Assays with specific inhibitors indicate that neither metalloproteinase, nor serinoproteinase or t lectin domains are involved in the aggregating activity, since EDTA, benzamidin and D-galactose did not inhibit the toxin. In the present work, we were able to identify, purify and characterize a new toxin from the brazilian rattlesnake. It behaved as predicted by Vital-Brazil and displayed direct factor X activating properties, also inducing platelet aggregation, even at low concentrations. Our data also indicate that it is probably a homotrimer with the subunities linked by hydrophobic and/or electrostatic interactions.

No description available.

Eine mit Polyethylen abgeschirmte Americium-Beryllium-Quelle wurde bzgl. ihres schnellen und thermischen Neutronenfeldes sowie Photonenfeldes durch Messungen und Simulationen quantifiziert. Dafür wurden Strahlungsfeldgrößen wie spektrale Teilchenflussdichten, Teilchenflussdichten, UmgebungsÄquivalentdosisleistungen und Richtungs-Äquivalentdosisleistungen für die jeweiligen Felder in unterschiedlichen Abständen der Strahlungsquelle bestimmt. Die ermittelten Ergebnisse werden verwendet, um einen neuen Bestrahlungsstand als Referenzfeld für Neutronen und Photonen zu errichten.:Einleitung 1. Theoretische Grundlagen 1.1. Strahlungsfeldgrößen 1.1.1. Radiometrische Größen 1.1.2. Interaktionskoeffizienten 1.1.3. Dosimetrische Größen 1.1.4. Fluenz-zu-Dosis-Konversionskoeffizienten 1.2. Photonen 1.2.1. Wechselwirkung mit Materie 1.2.2. Nachweis durch Szintillationsdetektoren 1.3. Neutronen 1.3.1. Klassifizierung 1.3.2. Wechselwirkung mit Materie 1.3.3. Nachweis schneller Neutronen durch organische Szintillationsdetektoren 1.3.4. Nachweis thermischer Neutronen durch ³He-Zählrohre 1.4. Americium-Beryllium-Quellen 1.4.1. Neutronenerzeugung 1.4.2. Abschirmung 1.5. Detektoren 1.5.1. Szintillationsdetektoren 1.5.2. ³He-Zählrohre 1.6. Digitale Pulsverarbeitung 1.6.1. Pulsformdiskriminierung mit organischen Szintillationsdetektoren 1.7. Monte-Carlo-Strahlungstransportsimulationen 2. Geräte und Materialien 3. Methoden 3.1. Quantifizierung des schnellen Neutronenfeldes 3.1.1. PFD-unterstützte Flugzeitmethode 3.1.2. Einfache Entfaltungstechnik 3.2. Quantifizierung des thermischen Neutronenfeldes 3.3. Quantifizierung des Photonenfeldes 4. Messungen 4.1. Messung 1 4.2. Messung 2 4.3. Messung 3 4.4. Messung 4 4.5. Messung 5 4.6. Messung 6 4.7. Messung 7 4.8. Messung 8 4.9. Messung 9 4.10. Messung 10 5. Simulationen mit FLUKA 5.1. Nachmodellierung der Versuchsaufbauten 5.2. Nachbildung der Strahlungsfelder 5.2.1. Bestimmung der Korrekturfaktoren 5.3. Simulierte Größen 6. Ergebnisse 6.1. Quantifizierung des schnellen Neutronenfeldes 6.1.1. Strahlungsfeldgrößen mittels des Stilbendetektors 6.1.2. Strahlungsfeldgrößen mittels der Plausibilitätsmessungen 6.1.3. Strahlungsfeldgrößen mittels der FLUKA-Simulationen 6.2. Quantifizierung des thermischen Neutronenfeldes 6.2.1. Strahlungsfeldgrößen mittels des ³He-Zählrohrs 6.2.2. Strahlungsfeldgrößen mittels der FLUKA-Simulationen 6.3. Quantifizierung des Photonenfeldes 6.3.1. Strahlungsfeldgrößen mittels des CeBr₃-Detektors 6.3.2. Strahlungsfeldgrößen mittels der Plausibilitätsmessungen 6.3.3. Strahlungsfeldgrößen mittels der FLUKA-Simulationen 7. Diskussion 7.1. Quantifizierung des schnellen Neutronenfeldes 7.1.1. Spektrale Teilchenflussdichten 7.1.2. Umgebungs-Äquivalentdosisleistungen 7.2. Quantifizierung des thermischen Neutronenfeldes 7.2.1. Teilchenflussdichten 7.3. Quantifizierung des Photonenfeldes 7.3.1. Teilchenflussdichten der Photonen mit den Energien 511 keV, 2,2 MeV und 4,4 MeV 7.3.2. Umgebungs-Äquivalentdosisleistungen 7.3.3. Richtungs-Äquivalentdosisleistungen 8. Zusammenfassung A. Bestimmte Strahlungsfeldgrößen A.1. Schnelles Neutronenfeld A.1.1. Spektrale Teilchenflussdichten A.1.2. Umgebungs-Äquivalentdosisleistungen A.2. Thermisches Neutronenfeld A.2.1. Teilchenflussdichten A.3. Photonenfeld A.3.1. Teilchenflussdichten der Photonen mit den Energien 511 keV, 2,2 MeV und 4,4 MeV A.3.2. Umgebungs-Äquivalentdosisleistungen A.3.3. Richtungs-Äquivalentdosisleistungen B. Zwischenergebnisse B.1. Quantifizierung des schnellen Neutronenfeldes B.1.1. Pulsladungshistogramme des Stilbendetektors für n₁-Neutronen B.1.2. Anzahlen der Rückstoßprotonen B.2. Quantifizierung des Photonenfeldes B.2.1. Simulierte und gemessene Größen zur Bestimmung der Teilchenflussdichten der Photonen mit den Energien 511 keV, 2,2 MeV und 4,4 MeV / An americium-beryllium source shielded with polyethylene was quantified in regards to its fast and thermal neutron field, as well as its photon field via measurements and simulations. Therefore, radiation field quantities like spectral fluence rates, fluence rates, ambient dose rate equivalents and directional dose rate equivalents of the respective fields were determined in different distances from the radiation source. The produced results will be used for establishing a new irradiation workbench as reference field for neutrons and photons.:Einleitung 1. Theoretische Grundlagen 1.1. Strahlungsfeldgrößen 1.1.1. Radiometrische Größen 1.1.2. Interaktionskoeffizienten 1.1.3. Dosimetrische Größen 1.1.4. Fluenz-zu-Dosis-Konversionskoeffizienten 1.2. Photonen 1.2.1. Wechselwirkung mit Materie 1.2.2. Nachweis durch Szintillationsdetektoren 1.3. Neutronen 1.3.1. Klassifizierung 1.3.2. Wechselwirkung mit Materie 1.3.3. Nachweis schneller Neutronen durch organische Szintillationsdetektoren 1.3.4. Nachweis thermischer Neutronen durch ³He-Zählrohre 1.4. Americium-Beryllium-Quellen 1.4.1. Neutronenerzeugung 1.4.2. Abschirmung 1.5. Detektoren 1.5.1. Szintillationsdetektoren 1.5.2. ³He-Zählrohre 1.6. Digitale Pulsverarbeitung 1.6.1. Pulsformdiskriminierung mit organischen Szintillationsdetektoren 1.7. Monte-Carlo-Strahlungstransportsimulationen 2. Geräte und Materialien 3. Methoden 3.1. Quantifizierung des schnellen Neutronenfeldes 3.1.1. PFD-unterstützte Flugzeitmethode 3.1.2. Einfache Entfaltungstechnik 3.2. Quantifizierung des thermischen Neutronenfeldes 3.3. Quantifizierung des Photonenfeldes 4. Messungen 4.1. Messung 1 4.2. Messung 2 4.3. Messung 3 4.4. Messung 4 4.5. Messung 5 4.6. Messung 6 4.7. Messung 7 4.8. Messung 8 4.9. Messung 9 4.10. Messung 10 5. Simulationen mit FLUKA 5.1. Nachmodellierung der Versuchsaufbauten 5.2. Nachbildung der Strahlungsfelder 5.2.1. Bestimmung der Korrekturfaktoren 5.3. Simulierte Größen 6. Ergebnisse 6.1. Quantifizierung des schnellen Neutronenfeldes 6.1.1. Strahlungsfeldgrößen mittels des Stilbendetektors 6.1.2. Strahlungsfeldgrößen mittels der Plausibilitätsmessungen 6.1.3. Strahlungsfeldgrößen mittels der FLUKA-Simulationen 6.2. Quantifizierung des thermischen Neutronenfeldes 6.2.1. Strahlungsfeldgrößen mittels des ³He-Zählrohrs 6.2.2. Strahlungsfeldgrößen mittels der FLUKA-Simulationen 6.3. Quantifizierung des Photonenfeldes 6.3.1. Strahlungsfeldgrößen mittels des CeBr₃-Detektors 6.3.2. Strahlungsfeldgrößen mittels der Plausibilitätsmessungen 6.3.3. Strahlungsfeldgrößen mittels der FLUKA-Simulationen 7. Diskussion 7.1. Quantifizierung des schnellen Neutronenfeldes 7.1.1. Spektrale Teilchenflussdichten 7.1.2. Umgebungs-Äquivalentdosisleistungen 7.2. Quantifizierung des thermischen Neutronenfeldes 7.2.1. Teilchenflussdichten 7.3. Quantifizierung des Photonenfeldes 7.3.1. Teilchenflussdichten der Photonen mit den Energien 511 keV, 2,2 MeV und 4,4 MeV 7.3.2. Umgebungs-Äquivalentdosisleistungen 7.3.3. Richtungs-Äquivalentdosisleistungen 8. Zusammenfassung A. Bestimmte Strahlungsfeldgrößen A.1. Schnelles Neutronenfeld A.1.1. Spektrale Teilchenflussdichten A.1.2. Umgebungs-Äquivalentdosisleistungen A.2. Thermisches Neutronenfeld A.2.1. Teilchenflussdichten A.3. Photonenfeld A.3.1. Teilchenflussdichten der Photonen mit den Energien 511 keV, 2,2 MeV und 4,4 MeV A.3.2. Umgebungs-Äquivalentdosisleistungen A.3.3. Richtungs-Äquivalentdosisleistungen B. Zwischenergebnisse B.1. Quantifizierung des schnellen Neutronenfeldes B.1.1. Pulsladungshistogramme des Stilbendetektors für n₁-Neutronen B.1.2. Anzahlen der Rückstoßprotonen B.2. Quantifizierung des Photonenfeldes B.2.1. Simulierte und gemessene Größen zur Bestimmung der Teilchenflussdichten der Photonen mit den Energien 511 keV, 2,2 MeV und 4,4 MeV

In the last 10-15 years there has been a renewed interest in amorphous Se (a-Se) and its alloys due to their application as photoconductor materials in the new fully digital direct conversion flat panel x-ray medical image detectors. For a number of reasons, the a-Se photoconductor layer in such x-ray detectors has to be operated at very high electric fields (up to 10 Volts per micron) and one of the most difficult problems related to such applications of a Se is the problem of the dark current (the current in the absence of any radiation) minimization in the photoconductor layer. <p>This PhD work has been devoted to researching the possibilities for dark current minimization in a-Se x-ray photoconductors devices through a systematic study of the charge transport (carrier mobility and carrier lifetimes) and dark currents in single and multilayered a-Se devices as a function of alloying, doping, deposition condition and other fabrication factors. The results of the studies are extensively discussed in the thesis. We have proposed a new technological method for dark current reduction in single and multilayered a-Se based photoconductor for x-ray detector applications. The new technology is based on original experimental findings which demonstrate that both hole transport and the dark currents in a-Se films are a very strong function of the substrate temperature (Tsubstrate) during the film deposition process. We have shown that the new technique reduces the dark currents to approximately the same levels as achievable with the previously existing methods for dark current reduction. However, the new method is simpler to implement, and offers some potential advantages, especially in cases when a very high image resolution (20 cycles/mm) and/or fast pixel readout (more than 30 times per second) are needed. <p>Using the new technology we have fabricated simple single and double (ni-like) photoconductor layers on prototype x-ray image detectors with CCD (Charge Coupled Device) readout circuits. Dark currents in the a-Se photoconductor layer were not a problem for detector operation at all tested electric fields. Compared to the currently available commercial systems for mammography, the prototype detectors have demonstrated an excellent imaging performance, in particular superior spatial resolution (20 cycles/mm). Thus, the newly proposed technology for dark current reduction has shown a potential for commercialization.

In the last 10-15 years there has been a renewed interest in amorphous Se (a-Se) and its alloys due to their application as photoconductor materials in the new fully digital direct conversion flat panel x-ray medical image detectors. For a number of reasons, the a-Se photoconductor layer in such x-ray detectors has to be operated at very high electric fields (up to 10 Volts per micron) and one of the most difficult problems related to such applications of a Se is the problem of the dark current (the current in the absence of any radiation) minimization in the photoconductor layer. <p>This PhD work has been devoted to researching the possibilities for dark current minimization in a-Se x-ray photoconductors devices through a systematic study of the charge transport (carrier mobility and carrier lifetimes) and dark currents in single and multilayered a-Se devices as a function of alloying, doping, deposition condition and other fabrication factors. The results of the studies are extensively discussed in the thesis. We have proposed a new technological method for dark current reduction in single and multilayered a-Se based photoconductor for x-ray detector applications. The new technology is based on original experimental findings which demonstrate that both hole transport and the dark currents in a-Se films are a very strong function of the substrate temperature (Tsubstrate) during the film deposition process. We have shown that the new technique reduces the dark currents to approximately the same levels as achievable with the previously existing methods for dark current reduction. However, the new method is simpler to implement, and offers some potential advantages, especially in cases when a very high image resolution (20 cycles/mm) and/or fast pixel readout (more than 30 times per second) are needed. <p>Using the new technology we have fabricated simple single and double (ni-like) photoconductor layers on prototype x-ray image detectors with CCD (Charge Coupled Device) readout circuits. Dark currents in the a-Se photoconductor layer were not a problem for detector operation at all tested electric fields. Compared to the currently available commercial systems for mammography, the prototype detectors have demonstrated an excellent imaging performance, in particular superior spatial resolution (20 cycles/mm). Thus, the newly proposed technology for dark current reduction has shown a potential for commercialization.