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Sample records for positrones unidad integral

  1. Tomography by positrons emission: integral unit to the service of Mexico; Tomografia por emision de positrones: unidad integral al servicio de Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Lopez D, F A [Unidad PET-Ciclotron, Facultad de Medicina, UNAM (Mexico)

    2005-07-01

    The applications of the Positron emission tomography (PET) together with the one radiopharmaceutical 2 - [{sup 18} F]-fluoro-2-deoxy-D-glucose in the area of the medical imaging is expanding quickly and it possesses a bigger impact at the moment in favor of those patient to who suffers an oncological, cardiac or neurological illness in Mexico. (Author)

  2. Positron astronomy with SPI/INTEGRAL

    International Nuclear Information System (INIS)

    Weidenspointner, G.; Diehl, R.; Strong, A.; Weidenspointner, G.; Skinner, G.K.; Skinner, G.K.; Jean, P.; Knoedlseder, J.; Von Ballmoos, P.; Cordier, B.; Schanne, S.; Winkler, C.

    2008-01-01

    We provide an overview of positron astronomy results that have been obtained using the INTEGRAL spectrometer SPI, and discuss their implications for the still mysterious origin of positrons in our Galaxy. It has long been known that the 511 keV positron annihilation emission is strongest from the central region of our Galaxy. Recently, it has been discovered with the SPI spectrometer that the weaker 511 keV line emission from the inner Galactic disk appears to be asymmetric, with the emission to the west of the Galactic center being about twice as strong than that to the east. This distribution of positron annihilation resembles that of low mass X-ray binaries as observed with the INTEGRAL imager IBIS at hard X-ray energies, suggesting that these systems could provide a significant portion of the positrons in our Galaxy. In addition, the spectrometer SPI has permitted unprecedented spectroscopy of annihilation radiation from the bulge and disk regions of the Galaxy, which commences to yield important insights into the conditions of the medium in which the positrons annihilate. (authors)

  3. Integral power evaluation in fossil fuel power plants; Evaluacion energetica integral en unidades de centrales termoelectricas

    Energy Technology Data Exchange (ETDEWEB)

    Figueroa I, Luis R; Sanchez H, Laura E; Rodriguez M, Jose H [Instituto de Investigaciones Electricas, Cuernavaca, Morelos (Mexico); Nebradt G, Jesus [Unidad de Investigacion y Desarrollo de la Subdireccion de Generacion de la Comision Federal de Electricidad, (Mexico)

    2006-07-01

    In this occasion, a methodology is presented that carries out an integral energy evaluation of fossil fuel power plants units (FFPPU) with the purpose of determining the root of the significant decrements of power produced soon after the annual maintenance service. This proposal, besides identifying the origin of the energy efficiency problems, offers information about the contributions of each one of the involved equipment in the total decrement of the unit. With this methodology, the maintenance focuses in the equipment that contributes to the greater energy loss. This document presents such methodology along with its application in a real case, results and necessary remedial actions, demonstrating that its application offers bases for the investment in corrective measures. [Spanish] En esta ocasion se presenta una metodologia que efectua una evaluacion energetica integral de las unidades de centrales termoelectricas (UCT) con el fin de determinar la raiz de los decrementos de potencia significativos producidos luego del servicio anual de mantenimiento. Dicha propuesta, ademas de identificar el origen de los problemas de eficiencia energetica, brinda informacion acerca de las aportaciones de cada uno de los equipos involucrados al decremento total de la unidad. Con esta metodologia, el mantenimiento se enfoca a los equipos que contribuyen a la mayor perdida de potencia. Este documento exhibe tal metodologia junto con su aplicacion en un caso real, resultados y las acciones correctivas necesarias, demostrando que su aplicacion ofrece bases para una inversion futura en medidas correctivas.

  4. Desarrollo del cuadro de mando integral para la unidad de mantenimiento de plantas de tratamiento de la EMAAP-Q

    OpenAIRE

    Ramírez, Jaime

    2010-01-01

    Este trabajo de investigación, formula y proporciona las pautas para la implementación del Cuadro de Mando Integral (CMI) en la Unidad de mantenimiento de Plantas. El CMI le servirá a la EMAAP-Q, como una herramienta de control estratégico que permitirá mejorar los niveles de calidad y productividad en la prestación del servicio de mantenimiento de Plantas de tratamiento. 1. NATURALEZA Y FUNDAMENTOS DEL CUADRO DE MANDO INTEGRAL 2. LA EMPRESA METROPOLITANA DE ALCANTARILLADO ...

  5. PETRIC - A positron emission tomography readout integrated circuit

    Energy Technology Data Exchange (ETDEWEB)

    Pedrali-Noy, Marzio; Gruber, Gregory; Krieger, Bradley; Mandelli, Emmanuele; Meddeler, Gerrit; Moses, William; Rosso, Valeria

    2000-11-05

    We present architecture, critical design issues and performance measurements of PETRIC, a 64-channel mixed signal front-end integrated circuit (IC) for reading out a photodiode (PD) array coupled with LSO scintillator crystals for a medical imaging application (PET). Each channel consists of a low noise charge sensitive pre-amplifier (CSA), an RC-CR pulse shaper and a winner-take-all (WTA) multiplexer that selects the channel with the largest input signal. Triggered by an external timing signal, a switch opens and a capacitor stores the peak voltage of the winner channel. The shaper rise and fall times are adjustable by means of external current inputs over a continuous range of 0.7 (mu)s to 9 (mu)s. Power consumption is 5.4 mW per channel, measured Equivalent Noise Charge (ENC) at 1 (mu)s peaking time. Zero leakage current is 33 rms electrons plus 7.3 rms electrons per pF of input capacitance. Design is fabricated in 0.5 (mu)m 3.3V CMOS technology.

  6. The use of running integrated difference curves for analysing momentum distributions from positron annihilation experiments

    International Nuclear Information System (INIS)

    Coleman, C.F.

    1979-01-01

    In positron annihilation measurements it is often necessary to compare annihilation line shapes or angular distributions obtained from a single sample subjected to different experimental conditions, or from a range of samples subjected to different mechanical or metallurgical treatments. The difference of the normalised distributions provides a convenient, easily visualised, and comprehensive summary of the experimental results. Changes in the shape of these difference curves can be shown to arise only when within the material under examination competition occurs between different types of positron trap. Some of the factors affecting the shape of these difference curves are discussed in terms of trapping model concepts. By using the running integrals of the difference curves (RID curves) a representation is obtained which is very little affected by the number of channels spanning the line, provided that there are enough, leads naturally to an optimised determination of the line shape parameter S, leads to the definition of a number of parameters related to the shape of the difference curve and has well defined statistical properties. Examples of RID curves show the range of shapes encountered, shape changes associated with competition between different types of positron trap, and artefact shapes associated with rate dependent effects in the detector and electronics. (orig.) [de

  7. Efficient Cryosolid Positron Moderators

    Science.gov (United States)

    2012-08-01

    table layout Figure 21 shows the integration of the IR spectroscopy optics with the positron Moderation and Annihilation vacuum chambers on the...Characterization of Cryogenic Moderators The application of Matrix Isolation Spectroscopy (MIS) to characterizing cryogenic solid positron ...Matrix Isolation Spectroscopy capability into our Positron Moderation apparatus, which enables spectroscopic characterization of the cryogenic

  8. Study of the electron-positron annihilation in the galactic center region with the Integral/SPI spectrometer

    International Nuclear Information System (INIS)

    Sizun, P.

    2007-04-01

    A spectral feature was detected in 1970 in the gamma-ray emission from the central regions of the Milky Way, during balloon flight observations. Located near 511 keV, this feature was soon attributed to the gamma-ray line tracing the annihilation of electrons with their anti-particles, positrons. However, none of the multiple astrophysical scenarios contemplated to explain the production of positrons in the Galactic bulge has been able to reproduce the high injection rate deduced from the flux of the 511 keV line, close to 10 43 positrons per second. Launched in 2002, the European gamma-ray satellite INTEGRAL was provided with a spectrometer, SPI, whose unprecedented imaging and spectral capabilities in this energy range enable us to further study the source of the 511 keV line detected in the Galactic centre region. Indeed, a better determination of the spatial extent of the source, the intrinsic width of the line and the fraction of positrons annihilating in-flight, directly or via the formation of ortho-Positronium atoms would improve our knowledge of both the annihilation medium and the initial source of positrons, and could allow us to discriminate between the various explanatory scenarios. The first part of this thesis deals with a key ingredient in the extraction of the annihilation spectrum: the optimization of the instrumental background model. New data screening and tracer selection procedures are presented. Classical multi-linear models are compared to neural and Bayesian networks. Finally, three years of observation are used to constrain the width of the source and derive its spectrum. The second part of the thesis focuses on one of the possible scenarios explaining the high positron injection rate deduced from the flux of the 511 keV line: the annihilation of light dark matter particles into electron-positron pairs. The various radiation mechanisms involved are modeled and confronted to observations in order to set an upper limit on the injection

  9. Positron annihilation lifetime spectroscopy (PALS) application in metal barrier layer integrity for porous low- k materials

    CERN Document Server

    Simon, Lin; Gidley, D W; Wetzel, J T; Monnig, K A; Ryan, E T; Simon, Jang; Douglas, Yu; Liang, M S; En, W G; Jones, E C; Sturm, J C; Chan, M J; Tiwari, S C; Hirose, M

    2002-01-01

    Positron Annihilation Lifetime Spectroscopy (PALS) is a useful tool to pre-screen metal barrier integrity for Si-based porous low-k dielectrics. Pore size of low-k, thickness of metal barrier Ta, positronium (Ps) leakage from PALS, trench sidewall morphology, electrical test from one level metal (1LM) pattern wafer and Cu diffusion analysis were all correlated. Macro-porous low-k (pore size >=200 AA) and large scale meso-porous low-k (>50~200 AA) encounter both Ps leakage and Cu diffusion into low-k dielectric in the 0.25 mu mL/0.3 mu mS structures when using SEMATECH in-house PVD Ta 250 AA as barrier layer. For small scale meso-porous (>20~50 AA) and micro- porous (<=20 AA) low-k, no Ps leakage and no Cu diffusion into low-k were observed even with PVD Ta 50 AA, which is proved also owing to sidewall densification to seal all sidewall pores due to plasma etch and ash. For future technology, smaller pore size of porous Si-based low-k (=<50 AA) will be preferential for dense low-k like trench sidewall to...

  10. Tomography by positrons emission: integral unit to the service of Mexico

    International Nuclear Information System (INIS)

    Lopez D, F.A.

    2005-01-01

    The applications of the Positron emission tomography (PET) together with the one radiopharmaceutical 2 - [ 18 F]-fluoro-2-deoxy-D-glucose in the area of the medical imaging is expanding quickly and it possesses a bigger impact at the moment in favor of those patient to who suffers an oncological, cardiac or neurological illness in Mexico. (Author)

  11. The Galactic 511 keV line: analysis and interpretation of Integral observations; L'annihilation des positrons galactiques: analyse et interpretation des donnees INTEGRAL

    Energy Technology Data Exchange (ETDEWEB)

    Lonjou, V

    2005-09-15

    Ever since the discovery of the 511 keV annihilation line emission from the galactic center region in the late seventies, the origin of galactic positrons has been the topic of a vivid scientific debate. It is also one of the prime scientific objectives of the imaging spectrometer SPI on board ESA's INTEGRAL observatory. In this thesis first a description of the most important SPI sub-system is given - the detector plane. Procedures for detector energy calibration and detector degradation analysis are developed. The determination of instrumental background models, a crucial aspect of data analysis, is elaborated. These background models are then applied to deriving sky maps and spectra of unprecedented quality of the Galactic positron annihilation radiation. The emission is centered on the galactic center with a spatial resolution of 8 degrees (FWHM), a second spatial component appears clearly: the galactic disc. The ray energy has been measured with unprecedented accuracy: 511.0 {+-} 0.03 keV for a full width at half maximum (FWHM) of 2.07 {+-} 0.1 keV. The total galactic flux ranges from 1.09 to 2.43 10{sup -3} ph.cm{sup -2}.s{sup -1} including uncertainties on spatial distribution. Finally, the implications of these observations for the production of positrons by various Galactic populations are discussed.

  12. Measurement of human blood brain barrier integrity using 11C-inulin and positron emission tomography

    International Nuclear Information System (INIS)

    Hara, Toshihiko; Iio, Masaaki; Tsukiyama, Takashi

    1988-01-01

    Positron emission tomography (PET) using 11 C-inulin was demonstrated to be applicable to the clinical measurement of blood brain barrier permeability and cerebral interstitial fluid volume. Kinetic data were analyzed by application of a two compartment model, in which blood plasma and interstitial fluid spaces constitute the compartments. The blood activity contribution was subtracted from the PET count with the aid of the 11 CO inhalation technique. The values we estimated in a human brain were in agreement with the reported values obtained for animal brains by the use of 14 C-inulin. (orig.)

  13. A Comparison of Endoscopic Ultrasound Guided Biopsy and Positron Emission Tomography with Integrated Computed Tomography in Lung Cancer Staging

    DEFF Research Database (Denmark)

    Larsen, Stine Schmidt; Vilmann, P; Krasnik, K

    2009-01-01

    BACKGROUND AND STUDY AIMS: Exact staging of patients with non-small-cell lung cancer (NSCLC) is important to improve selection of resectable and curable patients for surgery. Positron emission tomography with integrated computed tomography (PET/CT) and endoscopic ultrasound guided fine needle...... aspiration biopsy (EUS-FNA) are new and promising methods, but indications in lung cancer staging are controversial. Only few studies have compared the 2 methods. The aim of this study was to assess and compare the diagnostic values of PET/CT and EUS-FNA for diagnosing advanced lung cancer in patients, who...... had both procedures performed. PATIENTS AND METHODS: 27 patients considered to be potential candidates for resection of NSCLC underwent PET/CT and EUS-FNA. Diagnoses were confirmed either by open thoracotomy, mediastinoscopy or clinical follow-up. Advanced lung cancer was defined as tumour...

  14. Professional competences of nurse to work in Intensive Care Units: an integrative review Competencias profesionales de los enfermeros para trabajar en Unidades de Cuidados Intensivos: una revisión integradora Competência profissional do enfermeiro para atuar em Unidades de Terapia Intensiva: uma revisão integrativa

    Directory of Open Access Journals (Sweden)

    Silvia Helena Henriques Camelo

    2012-02-01

    Full Text Available This study aimed to identify and analyze nurses' competences to work at Intensive Care Units-ICU. An integrative review method was used, and data were collected in LILACS, SciELO and BDENF, from August to October 2010. Ten articles were identified, published in the last 12 years. Data grouping permitted the construction of thematic units related to nurses' competences: nursing care management, high-complexity nursing care delivery, decision making, leadership, communication, continuing/permanent education, human resource management, material resource management. The professional competences identified can support the outline of guidelines to constitute the profile of nursing working in intensive care units and drive/mobilize the improvement of nursing care practices.Este estudio tuvo como objetivo identificar y analizar las competencias de las enfermeras para actuar en Unidades de Cuidados Intensivos-UCI. Se utilizó el método de revisión integradora, y la recolección de datos se realizó a través de la base de datos LILACS, SciELO BDENF, entre agosto y octubre de 2010. Se identificaron 10 artículos, y el cotejo de los datos permitió la construcción de las siguientes unidades temáticas relacionadas con las habilidades de las enfermeras: gestionar los cuidados de enfermería, realizar los cuidados de enfermería más complejos, la toma de decisiones, el liderazgo, la comunicación, la educación continua y permanente y la gestión de recursos humanos y materiales. Las habilidades identificadas en este estudio sirven como una guía para formar el perfil de la enfermera que trabaja en unidades de cuidados intensivos-UCI y por lo tanto representan la línea de orientación que puede aumentar/movilizar la mejoría de las prácticas de atención recibidas por este profesional.Este estudo teve como objetivo analisar as competências profissionais dos enfermeiros em Unidades de Terapia Intensiva (UTI. Utilizou-se o método de revis

  15. Estudio controlado sobre la eficacia de una valoración e intervención integral en pacientes ancianos ingresados en una unidad de convalecencia geriátrica

    OpenAIRE

    Vázquez Ibar, Olga

    2016-01-01

    La valoración geriátrica integral es un proceso diagnóstico multidimensional e interdisciplinar que detecta necesidades y capacidades funcionales, cognitivas y sociales de ancianos, así como problemas médicos para establecer planes de intervención y seguimiento individualizados. Aunque se realiza en muchos entornos asistenciales, las unidades de convalecencia ofrecen intervenciones geriátricas intensas y prolongadas en el tiempo que generan efectos positivos en la salud de los ancianos. Ob...

  16. Relación entre el consumo abusivo de alcohol y la violencia ejercida por el hombre contra su pareja en la unidad de valoración integral de violencia de género (UVIVG) de Sevilla

    OpenAIRE

    C. Llopis Giménez; M.I. Rodríguez García; I. Hernández Mancha

    2014-01-01

    Se ha estudiado la posible relación entre el consumo de alcohol y la violencia ejercida por el hombre hacia la mujer con la que mantiene o ha mantenido relación sentimental, en una muestra de 50 parejas analizadas en la Unidad de Valoración Integral de Violencia de Género (UVIVG) de Sevilla, a lo largo de los años 2013 y 2014. Para ello se ha empleado una entrevista estructurada creada ad hoc, así como los cuestionarios MINI, MALT y CAGE. De las 50 parejas, en 25, las mujeres que denunciaron ...

  17. Integrated and automated data analysis for neuronal activation studies using positron emission tomography. Methodology and applications

    International Nuclear Information System (INIS)

    Minoshima, Satoshi; Arimizu, Noboru; Koeppe, R.A.; Kuhl, D.E.

    1994-01-01

    A data analysis method was developed for neuronal activation studies using [ 15 O] water positron emission tomography (PET). The method consists of several procedures including intra-subject head motion correction (co-registration), detection of the mid-sagittal plane of the brain, detection of the intercommissural (AC-PC) line, linear scaling and non-linear warping for anatomical standardization, pixel-by-pixel statistical analysis, and data display. All steps are performed in three dimensions and are fully automated. Each step was validated using a brain phantom, computer simulations, and data from human subjects, demonstrating accuracy and reliability of the procedure. The method was applied to human neuronal activation studies using vibratory and visual stimulations. The method detected significant blood flow increases in the primary sensory cortices as well as in other regions such as the secondary sensory cortex and cerebellum. The proposed method should enhance application of PET neuronal activation studies to the investigation of higher-order human brain functions. (author) 38 refs

  18. Positron sources

    International Nuclear Information System (INIS)

    Chehab, R.

    1994-01-01

    A tentative survey of positron sources is given. Physical processes on which positron generation is based are indicated and analyzed. Explanation of the general features of electromagnetic interactions and nuclear β + decay makes it possible to predict the yield and emittance for a given optical matching system between the positron source and the accelerator. Some kinds of matching systems commonly used - mainly working with solenoidal field - are studied and the acceptance volume calculated. Such knowledge is helpful in comparing different matching systems. Since for large machines, a significant distance exists between the positron source and the experimental facility, positron emittance has to be preserved during beam transfer over large distances and methods used for that purpose are indicated. Comparison of existing positron sources leads to extrapolation to sources for future linear colliders. Some new ideas associated with these sources are also presented. (orig.)

  19. Positron sources

    International Nuclear Information System (INIS)

    Chehab, R.

    1989-01-01

    A tentative survey of positron sources is given. Physical processes on which positron generation is based are indicated and analyzed. Explanation of the general features of electromagnetic interactions and nuclear β + decay makes it possible to predict the yield and emittance for a given optical matching system between the positron source and the accelerator. Some kinds of matching systems commonly used - mainly working with solenoidal fields - are studied and the acceptance volume calculated. Such knowledge is helpful in comparing different matching systems. Since for large machines, a significant distance exists between the positron source and the experimental facility, positron emittance has to be preserved during beam transfer over large distances and methods used for that purpose are indicated. Comparison of existing positron sources leads to extrapolation to sources for future linear colliders

  20. INTEGRAL SPI Limits on Electron-Positron Annihilation Radiation from the Galactic Plane

    DEFF Research Database (Denmark)

    Teegarden, B. J.; Watanabe, K.; Jean, P.

    2005-01-01

    ‐Ray Astrophysics Laboratory) mission, launched in 2002 October, is the detailed study of this radiation. The Spectrometer on INTEGRAL (SPI) is a high‐resolution, coded‐aperture gamma‐ray telescope with an unprecedented combination of sensitivity, angular resolution, and energy resolution. We report results from...... the first 10 months of observation. During this period a significant fraction of the observing time was spent in or near the Galactic plane. No positive annihilation flux was detected outside of the central region () of our Galaxy. In this paper we describe the observations and data analysis methods...

  1. Positron emission tomography in pediatric radiation oncology: integration in the treatment-planning process

    International Nuclear Information System (INIS)

    Krasin, M.J.; Hudson, M.M.; Kaste, S.C.

    2004-01-01

    The application of PET imaging to pediatric radiation oncology allows new approaches to targeting and selection of radiation dose based not only on the size of a tumor, but also on its metabolic activity. In order to integrate PET into treatment planning for radiation oncology, logistical issues regarding patient setup, image fusion, and target selection must be addressed. Through prospective study, the role of PET in pediatric malignancies will be established for diagnosis, treatment, and surveillance. To explore the potential role of PET and its incorporation into treatment planning in pediatric radiation oncology, an example case of pediatric Hodgkin's disease is discussed. (orig.)

  2. Positron emission tomography response criteria in solid tumours criteria for quantitative analysis of [18F]-fluorodeoxyglucose positron emission tomography with integrated computed tomography for treatment response assessment in metastasised solid tumours: All that glitters is not gold.

    Science.gov (United States)

    Willemsen, Annelieke E C A B; Vlenterie, Myrella; van Herpen, Carla M L; van Erp, Nielka P; van der Graaf, Winette T A; de Geus-Oei, Lioe-Fee; Oyen, Wim J G

    2016-03-01

    For solid tumours, quantitative analysis of [(18)F]-fluorodeoxyglucose positron emission tomography with integrated computed tomography potentially can have significant value in early response assessment and thereby discrimination between responders and non-responders at an early stage of treatment. Standardised strategies for this analysis have been proposed, and the positron emission tomography response criteria in solid tumours (PERCIST) criteria can be regarded as the current standard to perform quantitative analysis in a research setting, yet is not implemented in daily practice. However, several exceptions and limitations limit the feasibility of PERCIST criteria. In this article, we point out dilemmas that arise when applying proposed criteria like PERCIST on an expansive set of patients with metastasised solid tumours. Clinicians and scientists should be aware of these limitations to prevent that methodological issues impede successful introduction of research data into clinical practice. Therefore, to deliver on the high potential of quantitative imaging, consensus should be reached on a standardised, feasible and clinically useful analysis methodology. This methodology should be applicable in the majority of patients, tumour types and treatments. Copyright © 2015 Elsevier Ltd. All rights reserved.

  3. Study of the electron-positron annihilation in the galactic center region with the Integral/SPI spectrometer; Etude de l'annihilation electron-positon dans la region du centre galactique avec le spectrometre INTEGRAL/SPI

    Energy Technology Data Exchange (ETDEWEB)

    Sizun, P

    2007-04-15

    A spectral feature was detected in 1970 in the gamma-ray emission from the central regions of the Milky Way, during balloon flight observations. Located near 511 keV, this feature was soon attributed to the gamma-ray line tracing the annihilation of electrons with their anti-particles, positrons. However, none of the multiple astrophysical scenarios contemplated to explain the production of positrons in the Galactic bulge has been able to reproduce the high injection rate deduced from the flux of the 511 keV line, close to 10{sup 43} positrons per second. Launched in 2002, the European gamma-ray satellite INTEGRAL was provided with a spectrometer, SPI, whose unprecedented imaging and spectral capabilities in this energy range enable us to further study the source of the 511 keV line detected in the Galactic centre region. Indeed, a better determination of the spatial extent of the source, the intrinsic width of the line and the fraction of positrons annihilating in-flight, directly or via the formation of ortho-Positronium atoms would improve our knowledge of both the annihilation medium and the initial source of positrons, and could allow us to discriminate between the various explanatory scenarios. The first part of this thesis deals with a key ingredient in the extraction of the annihilation spectrum: the optimization of the instrumental background model. New data screening and tracer selection procedures are presented. Classical multi-linear models are compared to neural and Bayesian networks. Finally, three years of observation are used to constrain the width of the source and derive its spectrum. The second part of the thesis focuses on one of the possible scenarios explaining the high positron injection rate deduced from the flux of the 511 keV line: the annihilation of light dark matter particles into electron-positron pairs. The various radiation mechanisms involved are modeled and confronted to observations in order to set an upper limit on the injection

  4. Integration of Quantitative Positron Emission Tomography Absolute Myocardial Blood Flow Measurements in the Clinical Management of Coronary Artery Disease.

    Science.gov (United States)

    Gewirtz, Henry; Dilsizian, Vasken

    2016-05-31

    In the >40 years since planar myocardial imaging with(43)K-potassium was introduced into clinical research and management of patients with coronary artery disease (CAD), diagnosis and treatment have undergone profound scientific and technological changes. One such innovation is the current state-of-the-art hardware and software for positron emission tomography myocardial perfusion imaging, which has advanced it from a strictly research-oriented modality to a clinically valuable tool. This review traces the evolving role of quantitative positron emission tomography measurements of myocardial blood flow in the evaluation and management of patients with CAD. It presents methodology, currently or soon to be available, that offers a paradigm shift in CAD management. Heretofore, radionuclide myocardial perfusion imaging has been primarily qualitative or at best semiquantitative in nature, assessing regional perfusion in relative terms. Thus, unlike so many facets of modern cardiovascular practice and CAD management, which depend, for example, on absolute values of key parameters such as arterial and left ventricular pressures, serum lipoprotein, and other biomarker levels, the absolute levels of rest and maximal myocardial blood flow have yet to be incorporated into routine clinical practice even in most positron emission tomography centers where the potential to do so exists. Accordingly, this review focuses on potential value added for improving clinical CAD practice by measuring the absolute level of rest and maximal myocardial blood flow. Physiological principles and imaging fundamentals necessary to understand how positron emission tomography makes robust, quantitative measurements of myocardial blood flow possible are highlighted. © 2016 American Heart Association, Inc.

  5. Development of a data acquisition architecture with distributed synchronization for a Positron Emission Tomography system with integrated front-end.

    OpenAIRE

    Aliaga Varea, Ramón José

    2016-01-01

    [EN] Positron Emission Tomography (PET) is a non-invasive nuclear medical imaging modality that makes it possible to observe the distribution of metabolic substances within a patient's body after marking them with radioactive isotopes and arranging an annular scanner around him in order to detect their decays. The main applications of this technique are the detection and tracing of tumors in cancer patients and metabolic studies with small animals. The Electronic Design for Nuclear Applic...

  6. Planned Positron Factory project

    International Nuclear Information System (INIS)

    Okada, Sohei

    1990-01-01

    The Japan Atomic Energy Research Institute, JAERI, has started, drafting a construction plan for the 'Positron Factory', in which intense energy-controllable monoenergetic positron beams are produced from pair-production reactions caused by high-energy electrons from a linac. The JAERI organized a planning committee to provide a basic picture for the Positron Factory. This article presents an overview of the interactions of positrons, intense positron sources and the research program and facilities planned for the project. The interactions of positrons and intense positron sources are discussed focusing on major characteristics of positrons in different energy ranges. The research program for the Positron Factory is then outlined, focusing on advanced positron annihilation techniques, positron spectroscopy (diffraction, scattering, channeling, microscopy), basic positron physics (exotic particle science), and positron beam technology. Discussion is also made of facilities required for the Positron Factory. (N.K.)

  7. Additional benefit of 18F-fluorodeoxyglucose integrated positron emission tomography/computed tomography in the staging of oesophageal cancer

    International Nuclear Information System (INIS)

    Gillies, R.S.; Middleton, M.R.; Maynard, N.D.; Bradley, K.M.; Gleeson, F.V.

    2011-01-01

    18 F-fluorodeoxyglucose positron emission tomography (FDG PET) has been shown to improve the accuracy of staging in oesophageal cancer. We assessed the benefit of PET/CT over conventional staging and determined if tumour histology had any significant impact on PET/CT findings. A retrospective cohort study, reviewing the results from 200 consecutive patients considered suitable for radical treatment, undergoing routine PET/CT staging comparing the results from CT and endoscopic ultrasound, as well as multi-disciplinary team records. Adenocarcinoma and squamous cell carcinoma were compared for maximum Standardised Uptake Value (SUV max ), involvement of local lymph nodes and distant metastases. PET/CT provided additional information in 37 patients (18.5%) and directly altered management in 34 (17%): 22 (11%) were upstaged; 15 (7.5%) were downstaged, 12 of whom (6%) received radical treatment. There were 11 false negatives (5.5%) and 1 false positive (0.5%). SUV max was significantly lower for adenocarcinoma than squamous cell carcinoma (median 9.1 versus 13.5, p = 0.003). Staging with PET/CT offers additional benefit over conventional imaging and should form part of routine staging for oesophageal cancer. Adenocarcinoma and squamous cell carcinoma display significantly different FDG-avidity. (orig.)

  8. Transmission positron microscopes

    International Nuclear Information System (INIS)

    Doyama, Masao; Kogure, Yoshiaki; Inoue, Miyoshi; Kurihara, Toshikazu; Yoshiie, Toshimasa; Oshima, Ryuichiro; Matsuya, Miyuki

    2006-01-01

    Immediate and near-future plans for transmission positron microscopes being built at KEK, Tsukuba, Japan, are described. The characteristic feature of this project is remolding a commercial electron microscope to a positron microscope. A point source of electrons kept at a negative high voltage is changed to a point source of positrons kept at a high positive voltage. Positional resolution of transmission microscopes should be theoretically the same as electron microscopes. Positron microscopes utilizing trapping of positrons have always positional ambiguity due to the diffusion of positrons

  9. Positron emission tomography

    International Nuclear Information System (INIS)

    Iio, Masahiro

    1982-01-01

    Utilization of positron emission tomography was reviewed in relation to construction and planned construction of small-size medical cyclotrons, planned construction of positron cameras and utilization of short-lived radionuclides. (Chiba, N.)

  10. Positron emission tomography

    International Nuclear Information System (INIS)

    Reivich, M.; Alavi, A.

    1985-01-01

    This book contains 24 selections. Some of the titles are: Positron Emission Tomography Instrumentation, Generator Systems for Positron Emitters, Reconstruction Algorithms, Cerebral Glucose Consumption: Methodology and Validation, Cerebral Blood Flow Tomography Using Xenon-133 Inhalation: Methods and Clinical Applications, PET Studies of Stroke, Cardiac Positron Emission Tomography, and Use of PET in Oncology

  11. Positron scattering from vinyl acetate

    International Nuclear Information System (INIS)

    Chiari, L; Brunger, M J; Zecca, A; Blanco, F; García, G

    2014-01-01

    Using a Beer–Lambert attenuation approach, we report measured total cross sections (TCSs) for positron scattering from vinyl acetate (C 4 H 6 O 2 ) in the incident positron energy range 0.15–50 eV. In addition, we also report an independent atom model with screening corrected additivity rule computation results for the TCSs, differential and integral elastic cross sections, the positronium formation cross section and inelastic integral cross sections. The energy range of these calculations is 1–1000 eV. While there is a reasonable qualitative correspondence between measurement and calculation for the TCSs, in terms of the energy dependence of those cross sections, the theory was found to be a factor of ∼2 larger in magnitude at the lower energies, even after the measured data were corrected for the forward angle scattering effect. (paper)

  12. Positron-containing systems and positron diagnostics

    International Nuclear Information System (INIS)

    1978-01-01

    The results of the experimental and theoretical investigations are presented. Considered are quantum-mechanical calculations of wave functions describing the states of positron-containing atomic systems and of cross-sections of the processes characterizing different interactions, and also the calculations of the behaviour of positrons in gases in the presence of an electric field. The results of experimental tests are presented by the data describing the behaviour of positrons and positronium in liquids, polymers and elastomers, complex oxides and in different solids. New equipment and systems developed on the basis of current studies are described. Examined is a possibility of applying the methods of model and effective potentials for studying the bound states of positron systems and for calculating cross-sections of elementary processes of elastic and inelastic collisions with a positron involved. The experimental works described indicate new possibilities of the positron diagnosis method: investigation of thin layers and films of semiconductor materials, defining the nature of chemical bonds in semiconductors, determination of the dislocation density in deformed semiconductors, derivation of important quantitative information of the energy states of radiation defects in them

  13. Cardiac positron emission tomography

    International Nuclear Information System (INIS)

    Eftekhari, M.; Ejmalian, G.

    2003-01-01

    Positron emission tomography is an intrinsically tool that provide a unique and unparalleled approach for clinicians and researchers to interrogate the heart noninvasively. The ability to label substances of physiological interest with positron-emitting radioisotopes has permitted insight into normal blood flow and metabolism and the alterations that occur with disease states. Positron emission tomography of the heart has evolved as a unique, noninvasive approach for the assessment of myocardial perfusion, metabolism, and function. Because of the intrinsic quantitative nature of positron emission tomography measurements as well as the diverse compounds that can be labeled with positron- emitting radioisotopes, studies with positron emission tomography have provided rich insight into the physiology of the heart under diverse conditions

  14. Positron emission computed tomography

    International Nuclear Information System (INIS)

    Grover, M.; Schelbert, H.R.

    1985-01-01

    Regional mycardial blood flow and substrate metabolism can be non-invasively evaluated and quantified with positron emission computed tomography (Positron-CT). Tracers of exogenous glucose utilization and fatty acid metabolism are available and have been extensively tested. Specific tracer kinetic models have been developed or are being tested so that glucose and fatty acid metabolism can be measured quantitatively by Positron-CT. Tracers of amino acid and oxygen metabolism are utilized in Positron-CT studies of the brain and development of such tracers for cardiac studies are in progress. Methods to quantify regional myocardial blood flow are also being developed. Previous studies have demonstrated the ability of Positron-/CT to document myocardial infarction. Experimental and clinical studies have begun to identify metabolic markers of reversibly ischemic myocardium. The potential of Positron-CT to reliably detect potentially salvageable myocardium and, hence, to identify appropriate therapeutic interventions is one of the most exciting applications of the technique

  15. High resolution positron tomography

    International Nuclear Information System (INIS)

    Brownell, G.L.; Burnham, C.A.

    1982-01-01

    The limits of spatial resolution in practical positron tomography are examined. The four factors that limit spatial resolution are: positron range; small angle deviation; detector dimensions and properties; statistics. Of these factors, positron range may be considered the fundamental physical limitation since it is independent of instrument properties. The other factors are to a greater or lesser extent dependent on the design of the tomograph

  16. High energy positron imaging

    International Nuclear Information System (INIS)

    Chen Shengzu

    2003-01-01

    The technique of High Energy Positron Imaging (HEPI) is the new development and extension of Positron Emission Tomography (PET). It consists of High Energy Collimation Imaging (HECI), Dual Head Coincidence Detection Imaging (DHCDI) and Positron Emission Tomography (PET). We describe the history of the development and the basic principle of the imaging methods of HEPI in details in this paper. Finally, the new technique of the imaging fusion, which combined the anatomical image and the functional image together are also introduced briefly

  17. BEPC II positron source

    International Nuclear Information System (INIS)

    Pei Guoxi; Sun Yaolin; Liu Jintong; Chi Yunlong; Liu Yucheng; Liu Nianzong

    2006-01-01

    BEPC II-an upgrade project of the Beijing Electron Positron Collider (BEPC) is a factory type of e + e - collider. The fundamental requirements for its injector linac are the beam energy of 1.89 GeV for on-energy injection and a 40 mA positron beam current at the linac end with a low beam emittance of 1.6 μm and a low energy spread of ±0.5% so as to guarantee a higher injection rate (≥50 mA/min) to the storage ring. Since the positron flux is proportional to the primary electron beam power on the target, the authors will increase the electron gun current from 4A to 10A by using a new electron gun system and increase the primary electron energy from 120 MeV to 240 MeV. The positron source itself is an extremely important system for producing more positrons, including a positron converter target chamber, a 12kA flux modulator, the 7m focusing module with DC power supplies and the support. The new positron production linac from the electron gun to the positron source has been installed into the tunnel. In what follows, the authors will emphasize the positron source design, manufacture and tests. (authors)

  18. Positron-atom collisions

    International Nuclear Information System (INIS)

    Drachman, R.J.

    1984-01-01

    The past decade has seen the field of positron-atom collisions mature into an important sub-field of atomic physics. Increasingly intense positron sources are leading towards a situation in which electron and positron collision experiments will be on almost an equal footing, challenging theory to analyze their similarities and differences. The author reviews the advances made in theory, including dispersion theory, resonances, and inelastic processes. A survey of experimental progress and a brief discussion of astrophysical positronics is also included. (Auth.)

  19. Positron emission tomography

    International Nuclear Information System (INIS)

    Paans, A.M.J.

    1981-01-01

    Positron emitting radiopharmaceuticals have special applications in in-vivo studies of biochemical processes. The combination of a cyclotron for the production of radionuclides and a positron emission tomograph for the registration of the distribution of radioactivity in the body enables the measurement of local radioactivity concentration in tissues, and opens up new possibilities in the diagnosis and examination of abnormalities in the metabolism. The principles and procedures of positron emission tomography are described and the necessary apparatus considered, with emphasis on the positron camera. The first clinical applications using 55 Co bloemycine for tumor detection are presented. (C.F.)

  20. Positrons and positronium

    International Nuclear Information System (INIS)

    Jean, Y.C.; Lambrecht, R.M.

    1988-01-01

    This bibliography includes articles, proceedings, abstracts, reports and patents published between 1930 and 1984 on the subject of positrons, positron annihilation and positronium. The subject covers experimental and theoretical results in the areas of physics and chemistry of low and intermediate energy (< 0.6 MeV) positrons and positronium. The topics of interest are: fundamental properties, interactions with matter, nuclear technology, the history and philosophy of antimatter, the theory of the universe, and the applications of positrons in the chemical, physical, and biomedical sciences

  1. The role of positron emission tomography with 18F-fluorodeoxyglucose integrated with computed tomography in the evaluation of patients with multiple myeloma undergoing allogeneic stem cell transplantation.

    Science.gov (United States)

    Patriarca, Francesca; Carobolante, Francesca; Zamagni, Elena; Montefusco, Vittorio; Bruno, Benedetto; Englaro, Emanuaela; Nanni, Cristina; Geatti, Onelio; Isola, Miriam; Sperotto, Alessandra; Buttignol, Silvia; Stocchi, Raffaella; Corradini, Paolo; Cavo, Michele; Fanin, Renato

    2015-06-01

    Positron emission tomography (PET) integrated with computed tomography (PET/CT) has been reported to be useful for screening myelomatous lesions at diagnosis in patients with multiple myeloma (MM) and for monitoring response to autologous stem cell transplantation (auto-SCT). The aim of the study was to evaluate the prognostic significance of PET/CT in MM patients who received allogeneic stem cell transplantation (allo-SCT). Patients who underwent upfront auto-SCT followed by allo-SCT, either as consolidation or salvage treatment, were studied with PET/CT before and/or within 6 months after allo-SCT. The number, the maximum standard uptake value (SUV), and the location (medullary or extramedullary) of focal lesions (FLs) were recorded and investigated as predictors of progression-free survival (PFS) and overall survival (OS) by univariate and multivariate analyses. Fifty-four patients had a PET/CT scan before allo-SCT. Of these, 22 patients (41%) had a negative PET/CT scan, 11 patients (20%) showed 1 to 3 FLs, and 21 patients (39%) had either a diffuse bone marrow involvement or more than 3 FLs. SUV was >4.2 in 21 patients (39%) and extramedullary disease (EMD) was present in 6 patients (11%). Multivariate analysis of prognostic factors before allo-SCT showed that persistence of EMD at transplantation was an independent predictor of poor PFS, whereas OS was negatively influenced by unrelated donor and SUV > 4.2. Fifty-nine patients had a PET/CT scan within 6 months after allo-SCT. Multivariate analysis of post-treatment variables showed that persistence of EMD and failure to obtain complete response or very good partial response after allo-SCT were strongly associated with shorter PFS and OS. Of the 46 patients with evaluable PET/CT scans both before and 6 months after allo-SCT, the 23 patients who maintained or reached a PET complete remission showed a significantly prolonged PFS and OS compared with the 23 patients with persistence of any PET positivity (2-year

  2. Positron annihilation microprobe

    Energy Technology Data Exchange (ETDEWEB)

    Canter, K F [Brandeis Univ., Waltham, MA (United States)

    1997-03-01

    Advances in positron annihilation microprobe development are reviewed. The present resolution achievable is 3 {mu}m. The ultimate resolution is expected to be 0.1 {mu}m which will enable the positron microprobe to be a valuable tool in the development of 0.1 {mu}m scale electronic devices in the future. (author)

  3. Positrons in ionic crystals

    International Nuclear Information System (INIS)

    Pareja, R.

    1988-01-01

    Positron annihilation experiments in ionic crystals are reviewed and their results are arranged. A discussion about the positron states in these materials is made in the light of these results and the different proposed models. The positronium in alkali halides is specially considered. (Author)

  4. Positron emission tomography

    NARCIS (Netherlands)

    Paans, AMJ

    Positron Emission Tomography (PET) is a method for determining biochemical and physiological processes in vivo in a quantitative way by using radiopharmaceuticals labelled with positron emitting radionuclides as C-11, N-13, O-15 and F-18 and by measuring the annihilation radiation using a

  5. PF slow positron source

    International Nuclear Information System (INIS)

    Shirakawa, A.; Enomoto, A.; Kurihara, T.

    1993-01-01

    A new slow-positron source is under construction at the Photon Factory. Positrons are produced by bombarding a tantalum rod with high-energy electrons; they are moderated in multiple tungsten vanes. We report here the present status of this project. (author)

  6. Positron Factory project

    Energy Technology Data Exchange (ETDEWEB)

    Okada, Sohei; Sunaga, Hiromi; Kaneko, Hirohisa; Kawasuso, Atsuo; Masuno, Shin-ichi; Takizawa, Haruki; Yotsumoto, Keiichi [Japan Atomic Energy Research Inst., Takasaki, Gunma (Japan). Takasaki Radiation Chemistry Research Establishment

    1997-03-01

    We have started drafting a construction program for the Positron Factory, in which linac-based intense monoenergetic positron beams are planned to be applied for materials science, biotechnology and basic physics and chemistry. A technical survey study confirmed the feasibility of manufacturing a dedicated electron linac of 100 kW class with a beam energy of 100 MeV, which will produce a world-highest monoenergetic positron beam of more than 10{sup 10}/sec in intensity. A self-driven rotating converter (electrons to positrons and photons) suitable for the high power electron beam was devised and successfully tested. The practicability of simultaneous extraction of multi-channel monoenergetic positron beams with multiple moderator assemblies, which had been originated on the basis of a Monte Carlo simulation, was demonstrated by an experiment using an electron linac. An efficient moderator structure, which is composed of honeycomb-like assembled moderator foils and reflectors, is also proposed. (author)

  7. Positron-Induced Luminescence

    Science.gov (United States)

    Stenson, E. V.; Hergenhahn, U.; Stoneking, M. R.; Pedersen, T. Sunn

    2018-04-01

    We report on the observation that low-energy positrons incident on a phosphor screen produce significantly more luminescence than electrons do. For two different wide-band-gap semiconductor phosphors (ZnS:Ag and ZnO:Zn), we compare the luminescent response to a positron beam with the response to an electron beam. For both phosphors, the positron response is significantly brighter than the electron response, by a factor that depends strongly on incident energy (0-5 keV). Positrons with just a few tens of electron-volts of energy (for ZnS:Ag) or less (for ZnO:Zn) produce as much luminescence as is produced by electrons with several kilo-electron-volts. We attribute this effect to valence band holes and excited electrons produced by positron annihilation and subsequent Auger processes. These results demonstrate a valuable approach for addressing long-standing questions about luminescent materials.

  8. UNIDADES GEOMORFOLÓGICAS DE PORTUGAL CONTINENTAL

    Directory of Open Access Journals (Sweden)

    Diamantino Insua Pereira

    2014-12-01

    Full Text Available São representadas cartograficamente as unidades geomorfológicas identificadas para os 89015 km2 do território de Portugal Continental. A delimitação das unidades teve por base a análise dos padrões da textura fornecida por imagens SRTM, com revisão e adaptação posterior à altimetria e à geologia, para os quais foram usadas bases cartográficas digitais. Foram considerados três níveis taxionómicos que permitem descrever e caracterizar áreas homogéneas do ponto de vista geomorfológico. As três unidades de 1º nível baseiam-se nas unidades morfostruturais clássicas consideradas para a Península Ibérica. As dez unidades de 2º nível constituem, na sua maioria, divisões clássicas do relevo de Portugal Continental, agora agrupadas de acordo com a metodologia adoptada e designadas como unidades morfosculturais. As 56 unidades de 3º nível, ou subunidades morfosculturais, foram individualizadas com base nos padrões de relevo identificados nas imagens SRTM e na observação de campo e adquiriram uma designação baseada essencialmente nas geoformas que as individualizam e na toponímia local. As unidades geomorfológicas identificadas são descritas através de características do relevo, dissecação fluvial, estruturas, tipo de drenagem e base geológica, bem como de parâmetros numéricos gerados de forma automática, como classes de altitude e de declividade. Pretende-se que o mapa elaborado possa contribuir para a gestão territorial, em especial na tomada de decisões em conservação da natureza.

  9. High efficiency positron moderation

    International Nuclear Information System (INIS)

    Taqqu, D.

    1990-01-01

    A new positron moderation scheme is proposed. It makes use of electric and magnetic fields to confine the β + emitted by a radioactive source forcing them to slow down within a thin foil. A specific arrangement is described where an intermediary slowed-down beam of energy below 10 keV is produced. By directing it towards a standard moderator optimal conversion into slow positrons is achieved. This scheme is best applied to short lived β + emitters for which a 25% moderation efficiency can be reached. Within the state of the art technology a slow positron source intensity exceeding 2 x 10 10 e + /sec is achievable. (orig.)

  10. Positron emission tomography

    International Nuclear Information System (INIS)

    Wienhard, K.; Heiss, W.D.

    1984-01-01

    The principles and selected clinical applications of positron emission tomography are described. In this technique a chemical compound is labeled with a positron emitting isotope and its biochemical pathway is traced by coincidence detection of the two annihilation photons. The application of the techniques of computed tomography allows to reconstruct the spatial distribution of the radioactivity within a subject. The 18 F-deoxyglucose method for quantitative measurement of local glucose metabolism is discussed in order to illustrate the possibilities of positron emission tomography to record physiological processes in vivo. (orig.) [de

  11. Unidades fraseológicas y variación.

    Directory of Open Access Journals (Sweden)

    José Juan Batista Rodríguez

    2008-01-01

    Full Text Available ENGLISH: Phraseological units (PhU undoubtedly create problems in the translation of texts and they are of particular interest in the learning of a second foreign language, because they are used extensively in the spoken language. The difficulty that these PhU create during the translation from one language to another is influenced by two parameters which are their undefined origin and the diverse forms that they can take. This paper focuses on the diversities of PhU that exist in the Spanish language and how their frequent use has had an impact on their development. Their development is basically characterized by the lack, presence, integration or substitution of lexical items that can lead to the change of meaning or their disassociation from their origin. SPANISH: Las unidades fraseológicas (UFs plantean problemas en la traducción de textos ytienen un especial interés en la enseñanza del español como lengua extrajera debido a su alta frecuencia de uso en la lengua hablada. Las dificultades que presentan las unidades fraseológicas en el proceso de traducción de una lengua a otra están influidas por dos parámetros: la ausencia de relación con su fuente de origen y las diferentes variantes en las que pueden aparecer. El presente trabajo se centra en las variantes de las unidades fraseológicas pertenecientes al español y de cómo su frecuencia de uso ha impactado en su evolución. Esta evolución se caracteriza por la ausencia, presencia, incorporación o sustitución de formas léxicas que pueden conducir a un cambio de significado o a la disociación con su origen.

  12. Positron reemission microscopy

    International Nuclear Information System (INIS)

    Brandes, G.F.; Canter, K.F.; Mills, A.P. Jr.

    1991-01-01

    The positron reemission microscope (PRM), originally proposed by Hulett, Dale and Pendyala, operates on principles fundamentally different from those utilized in existing microscopes and offers sensitivity and contrast not available in conventional microscopes

  13. Solvated Positron Chemistry. II

    DEFF Research Database (Denmark)

    Mogensen, O. E.

    1979-01-01

    The reaction of the hydrated positron, eaq+ with Cl−, Br−, and I− ions in aqueous solutions was studied by means of positron The measured angular correlation curves for [Cl−, e+], [Br−, e+, and [I−, e+] bound states were in good agreement with th Because of this agreement and the fact...... that the calculated positron wavefunctions penetrate far outside the X− ions in the [X−, e+] sta propose that a bubble is formed around the [X−, e+] state, similar to the Ps bubble found in nearly all liquids. F−ions did not react w Preliminary results showed that CN− ions react with eaq+ while OH−ions are non...... in the Cl− case) at higher concentrations. This saturation and the high-concentration effects-in the angular correlation results were interpreted as caused by rather complicated spur effects, wh It is proposed that spur electrons may pick off the positron from the [X−, e+ states with an efficiency which...

  14. Positron annihilation spectroscopy

    International Nuclear Information System (INIS)

    Sundar, C.S.; Viswanathan, B.

    1996-01-01

    An overview of positron annihilation spectroscopy, the experimental techniques and its application to studies on defects and electronic structure of materials is presented. The scope of this paper is to present the requisite introductory material, that will enable a better appreciation of the subsequent specialized articles on the applications of positron annihilation spectroscopy to investigate various problems in materials science. (author). 31 refs., 3 figs

  15. Positron emission tomography

    International Nuclear Information System (INIS)

    Chandrasekhar, Preethi; Himabindu, Pucha

    2000-01-01

    Positron Emission Tomography (PET) is a non-invasive nuclear imaging technique used to study different molecular pathways and anatomical structures. PET has found extensive applications in various fields of medicine viz. cardiology, oncology, psychiatry/psychology, neuro science and pulmonology. This study paper basically deals with the physics, chemistry and biology behind the PET technique. It discusses the methodology for generation of the radiotracers responsible for emission of positrons and the annihilation and detection techniques. (author)

  16. Positron emission tomography

    International Nuclear Information System (INIS)

    Dvorak, O.

    1989-01-01

    The principle is briefly described of positron emission tomography, and its benefits and constraints are listed. It is emphasized that positron emission tomography (PET) provides valuable information on metabolic changes in the organism that are otherwise only very difficult to obtain, such as brain diagnosis including relationships between mental disorders and the physiology and pathophysiology of the brain. A PET machine is to be installed in Czechoslovakia in the near future. (L.O.)

  17. Desplazamiento forzado en Colombia. Análisis documental e informe de investigación en la Unidad deAtención Integral al Desplazado (UAID – Bogotá

    Directory of Open Access Journals (Sweden)

    Uva Falla Ramírez

    2003-01-01

    Full Text Available El fenómeno del desplazamiento forzado como consecuencia del conflicto armado ubica a Colombia como el país con la mayor crisis humanitaria en América Latina. Esta situación compromete al conjunto de estamentos de la sociedad en la búsqueda de soluciones, particularmente a la universidad colombiana, en cuyos propósitos se encuentra brindar respuestas a las problemáticas sociales. El artículo que a continuación se presenta recoge la experiencia de investigación —acción realizada por docentes y estudiantes de Trabajo Social durante dos años—, orientada, en primer lugar, a la elaboración de un análisis documental sobre el tema, el cual incluyó la revisión de 130 documentos ubicados en diversas fuentes de documentación de Bogotá, a través de un enfoque hermenéutico por medio del cual se logró una aproximación al desarrollo conceptual del tema. En segundo lugar, la investigación se orientó a un programa de atención interdisciplinario, ejecutado en la Unidad de Atención a población en situación de desplazamiento en Bogotá, en el cual se ofreció un portafolio de servicios acorde con los programas académicos de la Universidad Colegio Mayor de Cundinamarca. La reseña de este trabajo será objeto de otra presentación en próximos números de la revista. Los resultados de esta labor investigativa constituyen más aproximaciones e interrogantes sobre este complejo tema que conclusiones definitivas sobre el mismo.

  18. Positron studies in catalysis research

    International Nuclear Information System (INIS)

    1994-01-01

    During the past eight months, the authors have made progress in several areas relevant to the eventual use of positron techniques in catalysis research. They have come closer to the completion of their positron microscope, and at the same time have performed several studies in their non-microscopic positron spectrometer which should ultimately be applicable to catalysis. The current status of the efforts in each of these areas is summarized in the following sections: Construction of the positron microscope (optical element construction, data collection software, and electronic sub-assemblies); Doppler broadening spectroscopy of metal silicide; Positron lifetime spectroscopy of glassy polymers; and Positron lifetime measurements of pore-sizes in zeolites

  19. Unidades de Pediatría Ambiental

    OpenAIRE

    PARÍS M, ENRIQUE; MOLINA M, HELIA; RÍOS B, JUAN CARLOS

    2007-01-01

    Se considera que una Unidad de Pediatría Ambiental es una estructura con roles claramente definidos, situada preferentemente en un centro de salud, especializada en afecciones pediátricas, relacionadas al ambiente. Estos centros pueden proporcionar asesoramiento, información y tratamiento, promover la investigación, entrenar a profesionales, educar al público e informar a las autoridades responsables. Su personal, especialmente entrenado en problemas ambientales, incluye: pediatras, toxicólog...

  20. Unidad 4: Crear Polígonos

    OpenAIRE

    Gómez Trigueros, Isabel María

    2015-01-01

    En esta unidad aprenderéis a crear vuestros propios polígonos con Google Earth para delimitar un área geográfica. Podréis modificar el tamaño de los polígonos, el color del área y su perímetro, incluso elaborar polígonos en 3D para superponer distintas variables sobre un paisaje concreto.

  1. ENFERMAGEM DE UNIDADES CIRÚRGICAS

    Directory of Open Access Journals (Sweden)

    Monique Mendes Marinho

    2014-01-01

    Full Text Available Evaluar la cultura de la seguridad del paciente desde la perspectiva de las enfermeras de las unidades de hospitalización quirúrgica de un hospital universitario del Cuestionario de Actitudes de Seguridad (SAQ. Estudio con enfoque cuantitativo, de tipo encuesta transversal, realizada en dos unidades quirúrgicas de un hospital universitario de Florianópolis, SC, Brazil. Se aplicó el SAQ a 46 profesionales de enfermería. El análisis de datos utilizado la estadística descriptiva e inferencial. Los resultados muestran que todas las dimensiones de los valores medidos fueron inferiores a la cultura de seguridad mínima positiva, las dimensiones con puntuaciones más bajas fueron: “la percepción de la gestión” y las “condiciones laborales”. En cuanto a la edad de los profesionales, los más jóvenes se destacaron por obtener las puntuaciones más altas. En cuanto a las categorías profesionales, los puntajes más altos se relacionan con los auxiliares de enfermería. La evaluación de la cultura de la seguridad en las unidades de estudio demuestra debilidad en seis dimensiones evaluadas.

  2. Positron emission tomography

    International Nuclear Information System (INIS)

    Yamamoto, Y.L.; Thompson, C.J.; Diksic, M.; Meyer, E.; Feindel, W.H.

    1984-01-01

    One of the most exciting new technologies introduced in the last 10 yr is positron emission tomography (PET). PET provides quantitative, three-dimensional images for the study of specific biochemical and physiological processes in the human body. This approach is analogous to quantitative in-vivo autoradiography but has the added advantage of permitting non-invasive in vivo studies. PET scanning requires a small cyclotron to produce short-lived positron emitting isotopes such as oxygen-15, carbon-11, nitrogen-13 and fluorine-18. Proper radiochemical facilities and advanced computer equipment are also needed. Most important, PET requires a multidisciplinary scientific team of physicists, radiochemists, mathematicians, biochemists and physicians. The most recent trends are reviewed in the imaging technology, radiochemistry, methodology and clinical applications of positron emission tomography. (author)

  3. Digital positron annihilation spectrometer

    International Nuclear Information System (INIS)

    Cheng Bin; Weng Huimin; Han Rongdian; Ye Bangjiao

    2010-01-01

    With the high speed development of digital signal process, the technique of the digitization and processing of signals was applied in the domain of a broad class of nuclear technique. The development of digital positron lifetime spectrometer (DPLS) is more promising than the conventional positron lifetime spectrometer equipped with nuclear instrument modules. And digital lifetime spectrometer has many advantages, such as low noise, long term stability, flexible online or offline digital processing, simple setup, low expense, easy to setting, and more physical information. Digital constant fraction discrimination is for timing. And a new method of optimizing energy windows setting for digital positron lifetime spectrometer is also developed employing the simulated annealing for the convenient use. The time resolution is 220ps and the count rate is 200cps. (authors)

  4. 50 years of positrons

    International Nuclear Information System (INIS)

    Anon.

    1982-01-01

    This year marks the 50th anniversary of one of the major landmarks of modern physics - the discovery of the positron, the antimatter counterpart of the electron. This provided the first evidence for antimatter, and it was also unprecedented for the existence of a new particle to have been predicted by theory. The positron and the concepts behind it were to radically change our picture of Nature. It led to the rapid advancement or our understanding, culminating some fifteen years later with the formulation of quantum electrodynamics as we now know it. (orig./HSI).

  5. Positron emission tomography

    CERN Document Server

    Paans, A M J

    2006-01-01

    Positron Emission Tomography (PET) is a method for measuring biochemical and physiological processes in vivo in a quantitative way by using radiopharmaceuticals labelled with positron emitting radionuclides such as 11C, 13N, 15O and 18F and by measuring the annihilation radiation using a coincidence technique. This includes also the measurement of the pharmacokinetics of labelled drugs and the measurement of the effects of drugs on metabolism. Also deviations of normal metabolism can be measured and insight into biological processes responsible for diseases can be obtained. At present the combined PET/CT scanner is the most frequently used scanner for whole-body scanning in the field of oncology.

  6. The MEG positron spectrometer

    International Nuclear Information System (INIS)

    Nishiguchi, Hajime

    2007-01-01

    We have been developing an innovative spectrometer for the MEG experiment at the Paul Scherrer Institute (PSI) in Switzerland. This experiment searches for a lepton flavour violating decay μ + →e + γ with a sensitivity of 10 -13 in order to explore the region predicted by supersymmetric extensions of the standard model. The MEG positron spectrometer consists of a specially designed superconducting solenoidal magnet with a highly graded field, an ultimate low-mass drift chamber system, and a precise time measuring counter system. This innovative positron spectrometer is described here focusing on the drift chamber system

  7. LLNL pure positron plasma program

    International Nuclear Information System (INIS)

    Hartley, J.H.; Beck, B.R.; Cowan, T.E.; Howell, R.H.; McDonald, J.L.; Rohatgi, R.R.; Fajans, J.; Gopalan, R.

    1995-01-01

    Assembly and initial testing of the Positron Time-of-Flight Trap at the Lawrence Livermore National Laboratory (LLNL) Increase Pulsed Positron Facility has been completed. The goal of the project is to accumulate at high-density positron plasma in only a few seconds., in order to facilitate study that may require destructive diagnostics. To date, densities of at least 6 x 10 6 positrons per cm 3 have been achieved

  8. Simulation of the annihilation emission of galactic positrons

    International Nuclear Information System (INIS)

    Gillard, W.

    2008-01-01

    Positrons annihilate in the central region of our Galaxy. This has been known since the detection of a strong emission line centered on an energy of 511 keV in the direction of the Galactic center. This gamma-ray line is emitted during the annihilation of positrons with electrons from the interstellar medium. The spectrometer SPI, onboard the INTEGRAL observatory, performed spatial and spectral analyses of the positron annihilation emission. This thesis presents a study of the Galactic positron annihilation emission based on models of the different interactions undergone by positrons in the interstellar medium. The models are relied on our present knowledge of the properties of the interstellar medium in the Galactic bulge, where most of the positrons annihilate, and of the physics of positrons (production, propagation and annihilation processes). In order to obtain constraints on the positrons sources and physical characteristics of the annihilation medium, we compared the results of the models to measurements provided by the SPI spectrometer. (author)

  9. Impacto do programa de atenção integral à criança com asma em Unidade de Saúde na Cidade de Fortaleza, Ceará

    Directory of Open Access Journals (Sweden)

    Joelma Aurélio Sousa

    2016-12-01

    Full Text Available Nas últimas décadas, a asma tornou-se um importante problema de saúde pública, visto o significativo crescimento da prevalência e da mortalidade dessa doença. Desde 1996, as entidades médicas e governamentais promoveram a criação de consensos sobre o assunto com o objetivo de programar medidas para melhorar a assistência médica e reduzir a morbimortalidade dessa enfermidade. Objetivou-se avaliar a melhora clínica dos pacientes e correlacioná-la à adesão ao tratamento medicamentoso e/ou ambiental. Foi realizado estudo documental retrospectivo descritivo analítico, com dados coletados em prontuários de pacientes que participaram do PROAICA na Unidade de Saúde Lineu Jucá, em Fortaleza-Ceará, no período de 2009 a 2014. Esses dados foram armazenados e processados usando o programa Epi Info 7.0. Observou-se melhora clínica dos pacientes após o inicio da participação no programa, assim como melhora na classificação de gravidade da asma quando se compara a primeira à ultima consulta médica. Houve aumento de 28,06% nos pacientes classificados como intermitente, redução de 20,15% dos casos persistentes leves e diminuição de 10,79% nos classificados como persistente moderado. No entanto, ocorreu um aumento de 2,88% de pacientes graves. Verificou-se melhora na classificação de controle clinico nos pacientes com classificação parcialmente controlada e não controlada. Os dados analisados mostram a importância do programa e sua colaboração para o controle da asma, facilitando a melhor visualização das dificuldades ainda encontradas em sua implementação de modo a promover possíveis mudanças para garantir um melhor atendimento e maior efetividade do PROAICA.Impact of comprehensive care program for children with asthma in Health Unit in the City of Fortaleza, CearáAbstract: Introduction: In recent decades, asthma has become an important public health problem, since the significant growth of the prevalence and

  10. Positron annihilation near fractal surfaces

    International Nuclear Information System (INIS)

    Lung, C.W.; Deng, K.M.; Xiong, L.Y.

    1991-07-01

    A model for positron annihilation in the sub-surface region near a fractal surface is proposed. It is found that the power law relationship between the mean positron implantation depth and incident positron energy can be used to measure the fractal dimension of the fractal surface in materials. (author). 10 refs, 2 figs

  11. Update on nodal staging in non-small cell lung cancer with integrated positron emission tomography/computed tomography: a meta-analysis.

    Science.gov (United States)

    Pak, Kyoungjune; Park, Sohyun; Cheon, Gi Jeong; Kang, Keon Wook; Kim, In-Joo; Lee, Dong Soo; Kim, E Edmund; Chung, June-Key

    2015-06-01

    Nowadays, the number of primary studies on fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) has been increasing rapidly. Thus, we updated meta-analysis to evaluate the test performance of FDG PET/CT for nodal staging in non-small cell lung cancer (NSCLC) including the most recent studies. We performed a systematic search of MEDLINE and EMBASE for English publications using keywords "positron emission tomography", "lung cancer", and "lymph node". All searches were limited to human studies. Inclusion criteria were studies of the initial nodal staging of NSCLC with PET/CT. The reasons for exclusion are as follows: (1) studies with PET, (2) previous therapy before PET/CT, (3) nodal staging not confirmed by histology, and (4) reviews, abstracts, and editorial materials. 786 articles were identified through database searching. 28 studies including 3,255 patients and 11,887 lymph nodes (LN) were eligible for this study. The pooled sensitivity was 0.62 (95% CI 0.54-0.70), widely ranging from 0.13 to 0.98. The specificity ranged between 0.72 and 0.98 with an overall estimated specificity of 0.92 (0.88-0.95) for node-based data. The pooled sensitivity, specificity, positive and negative likelihood ratio were 0.67 (0.54-0.79), 0.87 (0.82-0.91), 5.20 (3.59-7.54), and 0.37 (0.25-0.55) for patient-based data. Studies from tuberculosis (Tb) endemic countries showed lower sensitivity (0.56 vs 0.68, p = 0.03) for node-based data and lower specificity (0.83 vs 0.89, p < 0.01) for patient-based ones. PET/CT has a high specificity, but low sensitivity for detecting LN metastasis in patients with NSCLC. Tb might be one of the main reasons for lower sensitivity of PET/CT in several countries. The primary clinicians of lung cancer should be aware of the possibility of hidden metastatic LNs in bilateral FDG uptake of mediastinal and hilar LNs, especially in the Tb endemic countries.

  12. Simulation of the annihilation emission of galactic positrons; Modelisation de l'emission d'annihilation des positrons Galactiques

    Energy Technology Data Exchange (ETDEWEB)

    Gillard, W

    2008-01-15

    Positrons annihilate in the central region of our Galaxy. This has been known since the detection of a strong emission line centered on an energy of 511 keV in the direction of the Galactic center. This gamma-ray line is emitted during the annihilation of positrons with electrons from the interstellar medium. The spectrometer SPI, onboard the INTEGRAL observatory, performed spatial and spectral analyses of the positron annihilation emission. This thesis presents a study of the Galactic positron annihilation emission based on models of the different interactions undergone by positrons in the interstellar medium. The models are relied on our present knowledge of the properties of the interstellar medium in the Galactic bulge, where most of the positrons annihilate, and of the physics of positrons (production, propagation and annihilation processes). In order to obtain constraints on the positrons sources and physical characteristics of the annihilation medium, we compared the results of the models to measurements provided by the SPI spectrometer. (author)

  13. Positron depth profiling

    International Nuclear Information System (INIS)

    Coleman, P.

    2001-01-01

    Wide-ranging studies of defects below the surface of semiconductor structures have been performed at the University of Bath, in collaboration with the University of Surrey Centre for Ion Beam Applications and with members of research teams at a number of UK universities. Positron implantation has been used in conjunction with other spectroscopies such as RBS-channeling and SIMS, and electrical characterisation methods. Research has ranged from the development of a positron-based technique to monitor the in situ annealing of near-surface open-volume defects to the provision of information on defects to comprehensive diagnostic investigations of specific device structures. We have studied Si primarily but not exclusively; e.g., we have investigated ion-implanted SiC and SiO 2 /GaAs structures. Of particular interest are the applications of positron annihilation spectroscopy to ion-implanted semiconductors, where by linking ion dose to vacancy-type defect concentration one can obtain information on ion dose and uniformity with a sensitivity not achievable by standard techniques. A compact, user-friendly positron beam system is currently being developed at Bath, in collaboration with SCRIBA, with the intention of application in an industrial environment. (orig.)

  14. Positron emission tomography

    Energy Technology Data Exchange (ETDEWEB)

    Lindback, Stig [GEMS PET Systems AB, Uppsala (Sweden)

    1995-07-15

    Positron Emission Tomography (PET) is an advanced nuclear medicine technique used for research at major centres. Unique diagnostic information is obtained from tomographic measurements of the biochemistry and physiology of tissues and organs. In theory, diseases are related to biochemical changes and these can be observed with PET long before any anatomical changes are detectable. In PET the radioactive component is a positron-emitting isotope or 'tracer'. The positrons annihilate with electrons in the body to produce two gamma rays 180° apart; coincidence detection of these gammas provides a very efficient method of determining the spatial distribution of the radioisotope tracer. Because physiological measurements are usually required in a single imaging session, very short-lived isotopes are used to label the tracer molecules; isotope production and labelling is usually carried out in situ. The most commonly used radionuclides are carbon- 11 (half-life 20 minutes), nitrogen-13 (10 minutes), oxygen-15 (2 minutes), and fluorine-18 (110 minutes). A PET system has three major components: - a particle accelerator with targets for production of the positron-emitting isotopes; - chemistry modules for synthesis and labelling of the desired tracers; - and a PET camera for in-vivo measurements of the distribution of the tracer in the body.

  15. Positron emission tomography

    International Nuclear Information System (INIS)

    Pavuk, M.

    2003-12-01

    The aim of this project is to provide a simple summary of new trends in positron emission tomography and its basic physical principles. It provides thereby compendious introduction of the trends of the present development in diagnostics using PET systems. A review of available literature was performed. (author)

  16. Positron emission tomography. Positronemisionstomografi

    Energy Technology Data Exchange (ETDEWEB)

    Bolwig, T G; Haunsoe, S; Dahlgaard Hove, J; Hesse, B; Hoejgard, L; Jensen, M; Paulson, O B; Hastrup Svendsen, J; Soelvsten Soerensen, S

    1994-10-01

    Positron emission tomography (PET) is a method for quantitative imaging of regional physiological and biochemical parameters. Positron emitting radioactive isotopes can be produced by a cyclotron, eg. the biologically important carbon ([sup 11]C), oxygen ([sup 15]O), and nitrogen ([sup 13]N) elements. With the tomographic principles of the PET scanner the quantitative distribution of the administered isotopes can be determined and images can be provided as well as dynamic information on blood flow, metabolism and receptor function. In neurology PET has been used for investigations on numerous physiological processes in the brain: circulation, metabolism and receptor studies. In Parkinson's disease PET studies have been able to localize the pathology specifically, and in early stroke PET technique can outline focal areas with living but non-functioning cells, and this could make it possible to intervene in this early state. With positron emission tomography a quantitative evaluation of myocardial blood flow, glucose and fatty acid metabolism can be made as well as combined assessments of blood flow and metabolism. Combined studies of blood flow and metabolism can determine whether myocardial segments with abnormal motility consist of necrotic or viable tissue, thereby delineating effects of revascularisation. In the future it will probably be possible to characterize the myocardial receptor status in different cardiac diseases. The PET technique is used in oncology for clinical as well as more basic research on tumor perfusion and metabolism. Further, tumor uptake of positron labelled cytotoxic drugs might predict the clinical benefit of treatment. (au) (19 refs.).

  17. Cardiac positron tomography

    International Nuclear Information System (INIS)

    Geltmann, E.M.; Roberts, R.; Sobel, B.E.

    1980-01-01

    Positron emission tomography (PET) performed after the administration of the positron-emitting radionuclides carbon-11 ( 11 C), nitrogen-13 ( 13 N), oxygen-15 ( 15 O) and fluorine-18 ( 18 F) has permitted the improved noninvasive assessment of the regional myocardial metabolism of normal physiologic substrates and intermediates and their cogeners. In experimental animals, the rate of oxidation of 11 C-palmitate correlates closely with other indexes of oxygen consumption, and the extraction of 11 C-palmitate (like that of 18 F-fatty acids and 18 F-fluoredoxyglucose) ist markedly diminished in regions of myocardial ischemia. In both experimental animals and in patients, myocardial infarct site and size, determined by positron emission tomography after the intravenous injection of 11 C-palmitate, correlate closely with the electrocardiographic infarct locus and enzymatically estimated infarct size as well as with the location and extent of regional left ventricular wall motion abnormalities. PET offers promise for assessment of flow as well despite the complexities involved. PET with 13 NH 3 appears to provide one useful qualitative index, although this tracer ist actively metabolized. Because of the quantitative capabilities of positron emission tomography and the rapid progress which is being made in the development of fast scan, multi-slice, and gated instrumentation, this technique is likely to facilitate improved understanding and characterization of regional myocardial metabolism and blood flow in man under physiological and pathophysiological conditions. (orig.) [de

  18. Positron emission tomography

    International Nuclear Information System (INIS)

    Lindback, Stig

    1995-01-01

    Positron Emission Tomography (PET) is an advanced nuclear medicine technique used for research at major centres. Unique diagnostic information is obtained from tomographic measurements of the biochemistry and physiology of tissues and organs. In theory, diseases are related to biochemical changes and these can be observed with PET long before any anatomical changes are detectable. In PET the radioactive component is a positron-emitting isotope or 'tracer'. The positrons annihilate with electrons in the body to produce two gamma rays 180° apart; coincidence detection of these gammas provides a very efficient method of determining the spatial distribution of the radioisotope tracer. Because physiological measurements are usually required in a single imaging session, very short-lived isotopes are used to label the tracer molecules; isotope production and labelling is usually carried out in situ. The most commonly used radionuclides are carbon- 11 (half-life 20 minutes), nitrogen-13 (10 minutes), oxygen-15 (2 minutes), and fluorine-18 (110 minutes). A PET system has three major components: - a particle accelerator with targets for production of the positron-emitting isotopes; - chemistry modules for synthesis and labelling of the desired tracers; - and a PET camera for in-vivo measurements of the distribution of the tracer in the body

  19. Positron emission tomography

    International Nuclear Information System (INIS)

    Bolwig, T.G.; Haunsoe, S.; Dahlgaard Hove, J.; Hesse, B.; Hoejgard, L.; Jensen, M.; Paulson, O.B.; Hastrup Svendsen, J.; Soelvsten Soerensen, S.

    1994-01-01

    Positron emission tomography (PET) is a method for quantitative imaging of regional physiological and biochemical parameters. Positron emitting radioactive isotopes can be produced by a cyclotron, eg. the biologically important carbon ( 11 C), oxygen ( 15 O), and nitrogen ( 13 N) elements. With the tomographic principles of the PET scanner the quantitative distribution of the administered isotopes can be determined and images can be provided as well as dynamic information on blood flow, metabolism and receptor function. In neurology PET has been used for investigations on numerous physiological processes in the brain: circulation, metabolism and receptor studies. In Parkinson's disease PET studies have been able to localize the pathology specifically, and in early stroke PET technique can outline focal areas with living but non-functioning cells, and this could make it possible to intervene in this early state. With positron emission tomography a quantitative evaluation of myocardial blood flow, glucose and fatty acid metabolism can be made as well as combined assessments of blood flow and metabolism. Combined studies of blood flow and metabolism can determine whether myocardial segments with abnormal motility consist of necrotic or viable tissue, thereby delineating effects of revascularisation. In the future it will probably be possible to characterize the myocardial receptor status in different cardiac diseases. The PET technique is used in oncology for clinical as well as more basic research on tumor perfusion and metabolism. Further, tumor uptake of positron labelled cytotoxic drugs might predict the clinical benefit of treatment. (au) (19 refs.)

  20. Additional benefit of {sup 18}F-fluorodeoxyglucose integrated positron emission tomography/computed tomography in the staging of oesophageal cancer

    Energy Technology Data Exchange (ETDEWEB)

    Gillies, R.S. [Oxford Cancer and Haematology Centre, Churchill Hospital, Department of Medical Oncology, Oxford (United Kingdom); Oxford Cancer and Haematology Centre, Churchill Hospital, Department of Oesophagogastric Surgery, Oxford (United Kingdom); Middleton, M.R. [Oxford Cancer and Haematology Centre, Churchill Hospital, Department of Medical Oncology, Oxford (United Kingdom); Maynard, N.D. [Oxford Cancer and Haematology Centre, Churchill Hospital, Department of Oesophagogastric Surgery, Oxford (United Kingdom); Bradley, K.M.; Gleeson, F.V. [Oxford Cancer and Haematology Centre, Churchill Hospital, Department of Radiology, Oxford (United Kingdom)

    2011-02-15

    {sup 18}F-fluorodeoxyglucose positron emission tomography (FDG PET) has been shown to improve the accuracy of staging in oesophageal cancer. We assessed the benefit of PET/CT over conventional staging and determined if tumour histology had any significant impact on PET/CT findings. A retrospective cohort study, reviewing the results from 200 consecutive patients considered suitable for radical treatment, undergoing routine PET/CT staging comparing the results from CT and endoscopic ultrasound, as well as multi-disciplinary team records. Adenocarcinoma and squamous cell carcinoma were compared for maximum Standardised Uptake Value (SUV{sub max}), involvement of local lymph nodes and distant metastases. PET/CT provided additional information in 37 patients (18.5%) and directly altered management in 34 (17%): 22 (11%) were upstaged; 15 (7.5%) were downstaged, 12 of whom (6%) received radical treatment. There were 11 false negatives (5.5%) and 1 false positive (0.5%). SUV{sub max} was significantly lower for adenocarcinoma than squamous cell carcinoma (median 9.1 versus 13.5, p = 0.003). Staging with PET/CT offers additional benefit over conventional imaging and should form part of routine staging for oesophageal cancer. Adenocarcinoma and squamous cell carcinoma display significantly different FDG-avidity. (orig.)

  1. Impact of incidental findings on integrated 2-[18F]-fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography in patients with gastric cancer.

    Science.gov (United States)

    Tae, Chung Hyun; Lee, Jun Haeng; Choi, Joon Young; Min, Byung-Hoon; Rhee, Poong-Lyul; Kim, Jae J

    2015-03-01

    Since positron emission tomography/computed tomography (PET/CT) has been introduced, many incidental findings have been identified. The aim of this study was to assess the clinical significance of incidental findings on PET/CT in patients with gastric cancer. A total of 421 patients with gastric cancer underwent PET/CT for initial staging. Incidental findings on PET/CT were classified into five categories according to clinical significance--normal variant, benign, probably benign, probably malignant, and definitely malignant. We obtained information regarding follow-up examinations, additional visits, final diagnosis of incidental findings and short-term medical costs for further evaluation. Eight hundred eighty-two incidental findings were detected in 386 (91.7%) patients. Of 274 incidental findings classified as probably benign, probably malignant or definitely malignant, 130 required one or more additional investigations. Finally, 12 (9.2%) were proved to be associated with second primary malignancy or metastasis of gastric cancer. One hundred twenty-nine additional outpatient visits and 10 additional hospitalizations were needed for evaluating the incidental findings. The treatment strategy for gastric cancer was changed in one patient. The estimated cost of additional investigations was $US283 (95% CI: $US248-$US311) per patient. Incidental findings on PET/CT were common. Although the incidental findings were suspicious of malignancy, most were benign with high costs for additional investigations. © 2015 Wiley Publishing Asia Pty Ltd.

  2. Positron effective mass in silicon

    International Nuclear Information System (INIS)

    Panda, B.K.; Shan, Y.Y.; Fung, S.; Beling, C.D.

    1995-01-01

    The positron effective mass in Si is obtained from the first-principles calculations along various crystallographic directions. The effect of electron-positron correlation on the band mass is examined in this work. A positron pseudopotential scheme is worked out to calculate the isotropic band mass without explicitly solving the band energy. The effective mass 1.46m obtained as a sum of band mass and the positron-plasmon interaction compares very well with 1.5m obtained from the positron mobility data

  3. High current pulsed positron microprobe

    International Nuclear Information System (INIS)

    Howell, R.H.; Stoeffl, W.; Kumar, A.; Sterne, P.A.; Cowan, T.E.; Hartley, J.

    1997-01-01

    We are developing a low energy, microscopically focused, pulsed positron beam for defect analysis by positron lifetime spectroscopy to provide a new defect analysis capability at the 10 10 e + s -l beam at the Lawrence Livermore National Laboratory electron linac. When completed, the pulsed positron microprobe will enable defect specific, 3-dimensional maps of defect concentrations with sub-micron resolution of defect location. By coupling these data with first principles calculations of defect specific positron lifetimes and positron implantation profiles we will both map the identity and concentration of defect distributions

  4. El mito de la unidad del pueblo.

    OpenAIRE

    Arenas, Nelly; Gómez Calcaño, Luis

    2007-01-01

    Presentación. Ramos Jiménez, Alfredo Los círculos bolivarianos. El mito de la unidad del pueblo. Arenas, Nelly y Gómez Calcaño, Luis Lo massmediático y las sociedades contemporáneas. Un acercamiento a la relación medios-democracia. Briceño Romero, Ysabel La economía ambiental y la política ambiental. Caraballo, Leonardo Javier Veinte años de democracia en la Argentina. ¿Qué democracia? Kers, Mercedes y Leiras, Santiago C. La ciencia de la política. Bolívar ...

  5. Positron emission tomography basic sciences

    CERN Document Server

    Townsend, D W; Valk, P E; Maisey, M N

    2003-01-01

    Essential for students, science and medical graduates who want to understand the basic science of Positron Emission Tomography (PET), this book describes the physics, chemistry, technology and overview of the clinical uses behind the science of PET and the imaging techniques it uses. In recent years, PET has moved from high-end research imaging tool used by the highly specialized to an essential component of clinical evaluation in the clinic, especially in cancer management. Previously being the realm of scientists, this book explains PET instrumentation, radiochemistry, PET data acquisition and image formation, integration of structural and functional images, radiation dosimetry and protection, and applications in dedicated areas such as drug development, oncology, and gene expression imaging. The technologist, the science, engineering or chemistry graduate seeking further detailed information about PET, or the medical advanced trainee wishing to gain insight into the basic science of PET will find this book...

  6. Polarized positron sources for the future linear colliders

    International Nuclear Information System (INIS)

    Chaikovska, I.

    2012-01-01

    This thesis introduces the polarized positron source as one of the key element of the future Linear Collider (LC). In this context, the different schemes of the polarized positron source are described highlighting the main issues in this technology. In particular, the main focus is on the Compton based positron source adopted by the CLIC as a preferred option for the future positron source upgrade. In this case, the circularly polarized high energy gamma rays resulting from Compton scattering are directed to a production target where an electromagnetic cascade gives rise to the production of positrons by e + -e - pair conversion. To increase the efficiency of the gamma ray production stage, a multiple collision point line integrated in energy recovery linac is proposed. The simulations of the positron production, capture and primary acceleration allow to estimate the positron production efficiency and provide a simple parametrization of the Compton based polarized positron source in the view of the future LC requirements. The storage ring based Compton source option, so-called Compton ring, is also described. The main constraint of this scheme is given by the beam dynamics resulting in the large energy spread and increased bunch length affecting the gamma ray production rate. An original theoretical contribution is shown to calculate the energy spread induced by Compton scattering. Moreover, an experiment to test the gamma ray production by Compton scattering using a state-of-art laser system developed at LAL has been conducted in the framework of the 'Mighty Laser' project at the ATF, KEK. The experimental layout as well as the main results obtained are discussed in details. The studies carried out in this thesis show that the polarized positron source based on Compton scattering is a promising candidate for the future LC polarized positron source. (author)

  7. Positron-molecule interactions and corresponding positron attachment to molecules. As a basis for positron emission tomography (PET)

    International Nuclear Information System (INIS)

    Tachikawa, Masanori; Kimura, Mineo; Pichl, Lukas

    2007-01-01

    Through positron and electron interactions, they annihilate emitting primarily two gamma rays with 180-degree opposite directions. Positron spectroscopy using the characteristics of these gamma rays has been employed for analyzing various properties of material as well as for positron emission tomography (PET). However, its fundamental physics of positron-electron interactions and resulting features of emitting gamma rays are not well understood. By obtaining better understanding of positron interactions, it should become possible to provide the firm bases for positron spectroscopy in finer accuracy and quality. Here, we propose a significant mechanism for positron annihilation through positron attachment process, which may help increase the quality of positron spectroscopy. (author)

  8. Electron-positron interactions

    International Nuclear Information System (INIS)

    Wiik, B.; Wolf, G.

    1979-01-01

    This book is an introduction into the physics of electron-positron interactions. After a description of electron-positron storage rings pure electromagnetic e + e - interactions, and the total cross section are considered. Then low energy processes, the production of the J/psi and psi' particles including their radiative decay as well as the search for other narrow vector states are described. Then after the quark model interpretation of J/psi and psi' charmed mesons, the heavy lepton t, and the upsilon resonances are described. Thereafter inclusive hadron production and jet formation is discussed. Finally the next generation of e + e - colliding rings is described, and the first results from PETRA are presented. This book is suited for all physicists, who want to get a general review about e + e - physics. (HSI) 891 HSI/HSI 892 RKD

  9. Tomography by positrons emission

    International Nuclear Information System (INIS)

    Mosconi, Sergio L.

    1999-01-01

    The tomography by positrons emission is a technology that allows to measure the concentration of positrons emission in a tri dimensional body through external measurements. Among the isotope emissions have carbon isotopes are ( 11 C), of the oxygen ( 15 O), of the nitrogen ( 13 N) that are three the element that constitute the base of the organic chemistry. Theses have on of the PET's most important advantages, since many biological interesting organic molecules can be tracer with these isotopes for the metabolism studies 'in vivo' through PET, without using organic tracers that modify the metabolism. The mentioned isotopes, also possess the characteristic of having short lifetime, that constitute on of PET's advantages from the dosimetric point of view. Among 11 C, 15 O, and 13 N, other isotopes that can be obtained of a generator as the 68 Ga and 82 Rb

  10. Positron emission tomography camera

    International Nuclear Information System (INIS)

    Anon.

    1986-01-01

    A positron emission tomography camera having a plurality of detector rings positioned side-by-side or offset by one-half of the detector cross section around a patient area to detect radiation therefrom. Each ring contains a plurality of scintillation detectors which are positioned around an inner circumference with a septum ring extending inwardly from the inner circumference along each outer edge of each ring. An additional septum ring is positioned in the middle of each ring of detectors and parallel to the other septa rings, whereby the inward extent of all the septa rings may be reduced by one-half and the number of detectors required in each ring is reduced. The additional septa reduces the costs of the positron camera and improves its performance

  11. Positron emission tomography camera

    International Nuclear Information System (INIS)

    Anon.

    1987-01-01

    A positron emission tomography camera having a plurality of detector rings positioned side-by-side or offset by one-half of the detector cross section around a patient area to detect radiation therefrom. Each detector ring or offset ring includes a plurality of photomultiplier tubes and a plurality of scintillation crystals are positioned relative to the photomultiplier tubes whereby each tube is responsive to more than one crystal. Each alternate crystal in the ring is offset by one-half or less of the thickness of the crystal such that the staggered crystals are seen by more than one photomultiplier tube. This sharing of crystals and photomultiplier tubes allows identification of the staggered crystal and the use of smaller detectors shared by larger photomultiplier tubes thereby requiring less photomultiplier tubes, creating more scanning slices, providing better data sampling, and reducing the cost of the camera. The offset detector ring geometry reduces the costs of the positron camera and improves its performance

  12. Development of a software tool for the management of quality control in a helical tomotherapy unit; Desarrollo de una herramienta de software para la gestion integral del control de calidad en una unidad de tomoterapia helicoidal

    Energy Technology Data Exchange (ETDEWEB)

    Garcia Repiso, S.; Hernandez Rodriguez, J.; Martin Rincon, C.; Ramos Pacho, J. A.; Verde Velasco, J. M.; Delgado Aparacio, J. M.; Perez Alvarez, M. e.; Gomez Gonzalez, N.; Cons Perez, V.; Saez Beltran, M.

    2013-07-01

    The large amount of data and information that is managed in units of external radiotherapy quality control tests makes necessary the use of tools that facilitate, on the one hand, the management of measures and results in real time, and on other tasks of management, file, query and reporting of stored data. This paper presents an application of software of own development which is used for the integral management of the helical TomoTherapy unit in the aspects related to the roles and responsibilities of the hospital Radiophysics. (Author)

  13. New techniques of positron annihilation

    International Nuclear Information System (INIS)

    1983-02-01

    Studies on new techniques of positron annihilation and its application to various fields are presented. First, production of slow positron and its characteristic features are described. The slow positron can be obtained from radioisotopes by using a positron moderator, proton beam bombardment on a boron target, and pair production by using an electron linear accelerator. Bright enhancement of the slow positron beam is studied. Polarized positron beam can be used for the study of the momentum distribution of an electron in ferromagnetic substances. Production of polarized positrons and measurements of polarization are discussed. Various phases of interaction between slow positrons and atoms (or molecules) are described. A comparative study of electron scavenging effects on luminescence and on positronium formation in cyclohexane is presented. The positron annihilation phenomena are applicable for the surface study. The microscopic information on the surface of porous material may be obtained. The slow positrons are also useful for the surface study. Production and application of slow muon (positive and negative) are presented in this report. (Kato, T.)

  14. Generation of monoenergetic positrons

    International Nuclear Information System (INIS)

    Hulett, L.D. Jr.; Dale, J.M.; Miller, P.D. Jr.; Moak, C.D.; Pendyala, S.; Triftshaeuser, W.; Howell, R.H.; Alvarez, R.A.

    1983-01-01

    Many experiments have been performed in the generation and application of monoenergetic positron beams using annealed tungsten moderators and fast sources of 58 Co, 22 Na, 11 C, and LINAC bremstrahlung. This paper will compare the degrees of success from our various approaches. Moderators made from both single crystal and polycrystal tungsten have been tried. Efforts to grow thin films of tungsten to be used as transmission moderators and brightness enhancement devices are in progress

  15. Positron emission tomography

    International Nuclear Information System (INIS)

    Marchenkov, N.S.

    2000-01-01

    The foundations of the positron emission tomography (PET), widely used for the medical diagnostics, are considered. The brief description of the cyclotron for production of radionuclides, applied in the PET, the target devices for manufacturing the position emitters, the moduli for the radiopharmaceuticals synthesis (RPS) for the PET is presented. The necessity and concept of complete automation of the RPS for the PET are discussed [ru

  16. A combined matrix isolation spectroscopy and cryosolid positron moderation apparatus

    Energy Technology Data Exchange (ETDEWEB)

    Molek, Christopher D.; Michael Lindsay, C.; Fajardo, Mario E. [Air Force Research Laboratory, Munitions Directorate, Ordnance Division, Energetic Materials Branch, AFRL/RWME, 2306 Perimeter Road, Eglin AFB, Florida 32542-5910 (United States)

    2013-03-15

    We describe the design, construction, and operation of a novel apparatus for investigating efficiency improvements in thin-film cryogenic solid positron moderators. We report results from solid neon, argon, krypton, and xenon positron moderators which illustrate the capabilities and limitations of our apparatus. We integrate a matrix isolation spectroscopy diagnostic within a reflection-geometry positron moderation system. We report the optical thickness, impurity content, and impurity trapping site structures within our moderators determined from infrared absorption spectra. We use a retarding potential analyzer to modulate the flow of slow positrons, and report positron currents vs. retarding potential for the different moderators. We identify vacuum ultraviolet emissions from irradiated Ne moderators as the source of spurious signals in our channel electron multiplier slow positron detection channel. Our design is also unusual in that it employs a sealed radioactive Na-22 positron source which can be translated relative to, and isolated from, the cryogenic moderator deposition substrate. This allows us to separate the influences on moderator efficiency of surface contamination by residual gases from those of accumulated radiation damage.

  17. Positron Annihilation in Insulating Materials

    International Nuclear Information System (INIS)

    Asoka-Kumar, P; Sterne, PA

    2002-01-01

    We describe positron results from a wide range of insulating materials. We have completed positron experiments on a range of zeolite-y samples, KDP crystals, alkali halides and laser damaged SiO 2 . Present theoretical understanding of positron behavior in insulators is incomplete and our combined theoretical and experimental approach is aimed at developing a predictive understanding of positrons and positronium annihilation characteristics in insulators. Results from alkali halides and alkaline-earth halides show that positrons annihilate with only the halide ions, with no apparent contribution from the alkali or alkaline-earth cations. This contradicts the results of our existing theory for metals, which predicts roughly equal annihilation contributions from cation and anion. We also present result obtained using Munich positron microprobe on laser damaged SiO 2 samples

  18. Applications of positron depth profiling

    International Nuclear Information System (INIS)

    Hakvoort, R.A.

    1993-01-01

    In this thesis some contributions of the positron-depth profiling technique to materials science have been described. Following studies are carried out: Positron-annihilation measurements on neon-implanted steel; Void creation in silicon by helium implantation; Density of vacancy-type defects present in amorphous silicon prepared by ion implantation; Measurements of other types of amorphous silicon; Epitaxial cobalt disilicide prepared by cobalt outdiffusion. Positron-annihilation experiments on low-pressure CVD silicon-nitride films. (orig./MM)

  19. Nonlinear positron acoustic solitary waves

    International Nuclear Information System (INIS)

    Tribeche, Mouloud; Aoutou, Kamel; Younsi, Smain; Amour, Rabia

    2009-01-01

    The problem of nonlinear positron acoustic solitary waves involving the dynamics of mobile cold positrons is addressed. A theoretical work is presented to show their existence and possible realization in a simple four-component plasma model. The results should be useful for the understanding of the localized structures that may occur in space and laboratory plasmas as new sources of cold positrons are now well developed.

  20. Applications of positron depth profiling

    Energy Technology Data Exchange (ETDEWEB)

    Hakvoort, R A

    1993-12-23

    In this thesis some contributions of the positron-depth profiling technique to materials science have been described. Following studies are carried out: Positron-annihilation measurements on neon-implanted steel; Void creation in silicon by helium implantation; Density of vacancy-type defects present in amorphous silicon prepared by ion implantation; Measurements of other types of amorphous silicon; Epitaxial cobalt disilicide prepared by cobalt outdiffusion. Positron-annihilation experiments on low-pressure CVD silicon-nitride films. (orig./MM).

  1. Positron emission tomography. Basic principles

    International Nuclear Information System (INIS)

    Rodriguez, Jose Luis; Massardo, Teresa; Gonzalez, Patricio

    2001-01-01

    The basic principles of positron emission tomography (PET) technique are reviewed. lt allows to obtain functional images from gamma rays produced by annihilation of a positron, a positive beta particle. This paper analyzes positron emitters production in a cyclotron, its general mechanisms, and the various detection systems. The most important clinical applications are also mentioned, related to oncological uses of fluor-l8-deoxyglucose

  2. Positron probes of the Ge(1 0 0) surface: The effects of surface reconstructions and electron-positron correlations on positron trapping and annihilation characteristics

    International Nuclear Information System (INIS)

    Fazleev, N.G.; Jung, E.; Weiss, A.H.

    2007-01-01

    Positron annihilation induced Auger electron spectroscopy (PAES) has been applied to study the Ge(1 0 0) surface. The high-resolution PAES spectrum from the Ge(1 0 0) surface displays several strong Auger peaks corresponding to M 4,5 N 1 N 2,3 , M 2,3 M 4,5 M 4,5 , M 2,3 M 4,5 V and M 1 M 4,5 M 4,5 Auger transitions. The integrated peak intensities of Auger transitions are used to obtain experimental annihilation probabilities for the Ge 3d and 3p core level electrons. These experimental results are analyzed by performing calculations of positron surface states and annihilation characteristics of surface trapped positrons with relevant Ge core-level electrons for the non-reconstructed and reconstructed Ge(1 0 0)-p(2 x 1), Ge(1 0 0)-p(2 x 2) and Ge(1 0 0)-c(4 x 2) surfaces. It is found that the positron surface state wave function extends into the Ge lattice in the regions where atoms are displaced from their ideal terminated positions due to reconstructions. Estimates of the positron binding energy and the positron annihilation characteristics reveal their sensitivity to the specific atomic structure of the topmost layers of Ge(1 0 0). A comparison with PAES data reveals an agreement with theoretical core annihilation probabilities for the Auger transitions considered

  3. Mining the bulk positron lifetime

    International Nuclear Information System (INIS)

    Aourag, H.; Guittom, A.

    2009-01-01

    We introduce a new approach to investigate the bulk positron lifetimes of new systems based on data-mining techniques. Through data mining of bulk positron lifetimes, we demonstrate the ability to predict the positron lifetimes of new semiconductors on the basis of available semiconductor data already studied. Informatics techniques have been applied to bulk positron lifetimes for different tetrahedrally bounded semiconductors in order to discover computational design rules. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. Positron implantation profile in kapton

    International Nuclear Information System (INIS)

    Plotkowski, K.; Panek, T.J.; Kansj, J.

    1988-01-01

    Measurements of positrons' implantation profile were made with geometry as in the majority of PAT experiments, making use of the difference in values of mean lifetimes of positrons in the absorber and in the detector. The function describing the absorption of positrons in the absorber taking into account measurement geometry was fitted to the experimental data. The correction to the exponential relation occurring in this function is the dominating factor for small thicknesses of the absorber. In this analysis various values of positrons' backscatter coefficients of the nickel and of the kapton were also taken into account

  5. Positron lifetimes in deformed copper

    International Nuclear Information System (INIS)

    Hinode, Kenji; Tanigawa, Shoichiro; Doyama, Masao

    1976-01-01

    Positron lifetime measurements were performed for Cu samples with different densities of lattice defects. The lifetime spectra were successfully resolved into two components with the help of the well established analysis program. Obtained results were quite consistent with those expected from the trapping model. The positron trapping mechanism from free to trapped states and the initial condition of the model were especially checked. Deduced values obtained for tau sub(c) (lifetime of free positrons) and tau sub(t) (lifetime of trapped positrons) were 122+-5 psec and 176+-5 psec, respectively. (auth.)

  6. Positron radiography of ignition-relevant ICF capsules

    Science.gov (United States)

    Williams, G. J.; Chen, Hui; Field, J. E.; Landen, O. L.; Strozzi, D. J.

    2017-12-01

    Laser-generated positrons are evaluated as a probe source to radiograph in-flight ignition-relevant inertial confinement fusion capsules. Current ultraintense laser facilities are capable of producing 2 × 1012 relativistic positrons in a narrow energy bandwidth and short time duration. Monte Carlo simulations suggest that the unique characteristics of such positrons allow for the reconstruction of both capsule shell radius and areal density between 0.002 and 2 g/cm2. The energy-downshifted positron spectrum and angular scattering of the source particles are sufficient to constrain the conditions of the capsule between preshot and stagnation. We evaluate the effects of magnetic fields near the capsule surface using analytic estimates where it is shown that this diagnostic can tolerate line integrated field strengths of 100 T mm.

  7. Positron-atom scattering using a modified Kohn variational technique

    International Nuclear Information System (INIS)

    Page, B.A.P.

    1976-01-01

    An analysis of the zero-energy positron-hydrogen and positron-helium systems using various approximations to the target ground-state wavefunction is presented. A modification of the normal Kohn variational method is used in which a quantity, asub(Q), which becomes the Kohn scattering length if the target wavefunction is exact, is related to the trial wavefunction psisub(t) through an integral expression. By comparing the results obtained with the definitive values for the positron-hydrogen system, it is conjectured that if the values of asub(Q) display a local minimum when all the nonlinear parameters of psisub(t) are varied, then this local minimum of asub(Q) is an upper bound on the exact scattering length. Using this criterion to analyse the positron-helium results, it is concluded that this method may be considered as an alternative to the 'method of models' procedure, since both methods give similar results. (author)

  8. On the Possibility of Accelerating Positron on an Electron Wake at SABER

    International Nuclear Information System (INIS)

    Ischebeck, R.; Joshi, C.; Katsouleas, T.C.; Muggli, P.; Wang, X.

    2008-01-01

    A new approach for positron acceleration in non-linear plasma wakefields driven by electron beams is presented. Positrons can be produced by colliding an electron beam with a thin foil target embedded in the plasma. Integration of positron production and acceleration in one stage is realized by a single relativistic, intense electron beam. Simulations with the parameters of the proposed SABER facility [1] at SLAC suggest that this concept could be tested there

  9. Semiempirical potentials for positron scattering by atoms

    Energy Technology Data Exchange (ETDEWEB)

    Assafrao, Denise; Walters, H. R. J.; Arretche, Felipe; Dutra, Adriano; Mohallem, J. R. [Departamento de Fisica, Universidade Federal do Espirito Santo, 29075-910, Vitoria, ES (Brazil); Department of Applied Mathematics and Theoretical Physics, Queen' s University, Belfast, BT7 1NN (United Kingdom); Departamento de Fisica, Universidade do Estado de Santa Catarina, 89223-100, Joinville, SC (Brazil); Laboratorio de Atomos e Moleculas Especiais, Departamento de Fisica, ICEx, Universidade Federal de Minas Gerais, PO Box 702, 30123-970, Belo Horizonte, MG (Brazil)

    2011-08-15

    We report calculations of differential and integral cross sections for positron scattering by noble gas and alkaline-earth atoms within the same methodology. The scattering potentials are constructed by scaling adiabatic potentials so that their minima coincide with the covalent radii of the target atoms. Elastic differential and integral cross sections are calculated for Ne, Ar, Be, and Mg, and the results are very close to experimental and best theoretical data. Particularly, elastic differential cross sections for Be and Mg at low energies are reported.

  10. Positron Emission Tomography (PET)

    International Nuclear Information System (INIS)

    Welch, M.J.

    1990-01-01

    Positron emission tomography (PET) assesses biochemical processes in the living subject, producing images of function rather than form. Using PET, physicians are able to obtain not the anatomical information provided by other medical imaging techniques, but pictures of physiological activity. In metaphoric terms, traditional imaging methods supply a map of the body's roadways, its, anatomy; PET shows the traffic along those paths, its biochemistry. This document discusses the principles of PET, the radiopharmaceuticals in PET, PET research, clinical applications of PET, the cost of PET, training of individuals for PET, the role of the United States Department of Energy in PET, and the futures of PET. 22 figs

  11. Positron Emission Tomography (PET)

    Energy Technology Data Exchange (ETDEWEB)

    Welch, M.J.

    1990-01-01

    Positron emission tomography (PET) assesses biochemical processes in the living subject, producing images of function rather than form. Using PET, physicians are able to obtain not the anatomical information provided by other medical imaging techniques, but pictures of physiological activity. In metaphoric terms, traditional imaging methods supply a map of the body's roadways, its, anatomy; PET shows the traffic along those paths, its biochemistry. This document discusses the principles of PET, the radiopharmaceuticals in PET, PET research, clinical applications of PET, the cost of PET, training of individuals for PET, the role of the United States Department of Energy in PET, and the futures of PET. 22 figs.

  12. Positron Emission Tomography (PET)

    Science.gov (United States)

    Welch, M. J.

    1990-01-01

    Positron emission tomography (PET) assesses biochemical processes in the living subject, producing images of function rather than form. Using PET, physicians are able to obtain not the anatomical information provided by other medical imaging techniques, but pictures of physiological activity. In metaphoric terms, traditional imaging methods supply a map of the body's roadways, its, anatomy; PET shows the traffic along those paths, its biochemistry. This document discusses the principles of PET, the radiopharmaceuticals in PET, PET research, clinical applications of PET, the cost of PET, training of individuals for PET, the role of the United States Department of Energy in PET, and the futures of PET.

  13. Cranial neuronavigation with direct integration of 11C methionine positron emission tomography (PET) data - results of a pilot study in 32 surgical cases

    International Nuclear Information System (INIS)

    Braun, V.; Dempf, S.; Richter, H.P.; Weller, R.; Reske, S.-N.; Schanchenmayr, W.

    2002-01-01

    MRI detects small intracranial lesions, but has difficulties in differentiating between tumor, gliosis and edema. 11 C methionine-PET may help to overcome this problem. For its appropriate intra-operative use, it must be integrated into neuronavigation. We present the results of our pilot study with this method. 32 patients with 34 intracranial lesions detected by MRI underwent additional 11 C methionine-PET, because the pathophysiological behavior or the tumor delineation was unclear. All lesions were treated surgically. In 25 patients PET data could be integrated directly into cranial neuronavigation. 11 C methionine uptake was observed in 27/34 lesions, 26 of them were tumors: 14 malignant and 7 benign gliomas, 3 gliomas without further histological typing, one Ewing sarcoma and one non-Hodgkin lymphoma. Only one 11 C methionine positive lesion was non-tumorous: it was staged as post-irradiation necrosis in a patient operated on for a malignant glioma. 3/7 11 C-methionine negative lesions were classified as gliosis (n = 2) and M. Whipple (n = 1), but 4/7 were tumors: 2 astrocytomas WHO o II, 1 DNT and one astrocytoma WHO o III. The sensitivity of 11 C methionine-PET was 87 %, the specificity 75 %, the positive predictive value 96 % and the negative predictive value 43 %. In all tumorous cases with positive tracer uptake the borderline area of the tumor was better defined by C methionine-PET than by MRI. Interpretation: A positive 11 C methionine-PET is highly suspicious of a tumor, a negative one does not exclude it. 11 C methionine-PET seems to be more sensitive than MRI for differentiating between tumor and edema or gliosis. Simultaneous integration MRI and 11 C methionine-PET into cranial neuronavigation can facilitate cross total tumor removal in glioma surgery. (author)

  14. Cyclotrons and positron emitting radiopharmaceuticals

    Energy Technology Data Exchange (ETDEWEB)

    Wolf, A.P.; Fowler, J.S.

    1984-01-01

    The state of the art of Positron Emission Tomography (PET) technology as related to cyclotron use and radiopharmaceutical production is reviewed. The paper discusses available small cyclotrons, the positron emitters which can be produced and the yields possible, target design, and radiopharmaceutical development and application. 97 refs., 12 tabs. (ACR)

  15. Cyclotrons and positron emitting radiopharmaceuticals

    International Nuclear Information System (INIS)

    Wolf, A.P.; Fowler, J.S.

    1984-01-01

    The state of the art of Positron Emission Tomography (PET) technology as related to cyclotron use and radiopharmaceutical production is reviewed. The paper discusses available small cyclotrons, the positron emitters which can be produced and the yields possible, target design, and radiopharmaceutical development and application. 97 refs., 12 tabs

  16. A Southern African positron beam

    International Nuclear Information System (INIS)

    Britton, D.T.; Haerting, M.; Teemane, M.R.B.; Mills, S.; Nortier, F.M.; Van der Walt, T.N.

    1997-01-01

    The first stage of a state of the art positron beam, being constructed at the University of Cape Town, is currently being brought into operation. This is the first positron beam on the African continent, as well as being the first positron beam dedicated to solid and surface studies in the southern hemisphere. The project also contains a high proportion of local development, including the encapsulated 22 Na positron source developed by our collaboration. Novel features in the design include a purely magnetic in-line deflector, working in the solenoidal guiding field, to eliminate unmoderated positrons and block the direct line of sight to the source. A combined magnetic projector and single pole probe forming lens is being implemented in the second phase of construction to achieve a spot size of 10 μm without remoderation

  17. Origin and annihilation physics of positrons in the Galaxy

    International Nuclear Information System (INIS)

    Alexis, Anthony

    2014-01-01

    A gamma radiation at 511 keV is observed since the early 1970's toward the Galactic bulge region. This emission is the signature of a large number of electron-positron annihilations, the positron being the electron's antiparticle. Unfortunately, the origin of the positrons responsible for this emission is still a mystery. Many positron-source candidates have been suggested but none of them can account for the galactic annihilation emission. The spatial distribution of this emission is indeed very atypical. Since 2002, the SPI spectrometer onboard the INTEGRAL space laboratory revealed an emission strongly concentrated toward the galactic bulge and a weaker emission from the galactic disk. This morphology is unusual because it does not correspond to any of the known galactic astrophysical-object or interstellar-matter distributions. The assumption that positrons annihilate close to their sources (i.e. the spatial distribution of the annihilation emission reflects the spatial distribution of the sources) has consequently been called into question. Recent studies suggest that positrons could propagate far away from their sources before annihilating. This physical aspect could be the key point to solve the riddle of the galactic positron origin. This thesis is devoted to the modelling of the propagation and annihilation of positrons in the Galaxy, in order to compare simulated spatial models of the annihilation emission with recent measurements provided by SPI/INTEGRAL. This method allows to put constraints on the origin of galactic positrons. We therefore developed a propagation Monte-Carlo code of positrons within the Galaxy in which we implemented all the theoretical and observational knowledge about positron physics (sources, transport modes, energy losses, annihilation modes) and the interstellar medium of our Galaxy (interstellar gas distributions, galactic magnetic fields, structures of the gaseous phases). Due to uncertainties in several physical parameters

  18. Low-energy positron-argon collisions by using parameter-free positron correlation polarization potentials

    International Nuclear Information System (INIS)

    Jain, A.

    1990-01-01

    We report differential, integral, and momentum-transfer cross sections and the scattering length (A 0 ) for positron (e + )-argon scattering at low energies below the positronium formation threshold. An optical-potential approach is employed in which the repulsive Coulombic interaction is calculated exactly at the Hartree-Fock level and the attractive polarization and correlation effects are included approximately via a parameter-free positron correlation polarization (PCP) potential recently proposed by us. The PCP model is based on the correlation energy var-epsilon corr of one positron in a homogeneous electron gas; in the outside region, the var-epsilon corr is joined smoothly with the correct asymptotic form of the polarization interaction (-α 0 /2r 4 , where α 0 is the target polarizability) where they cross each other for the first time. The total optical potential of the e + -argon system is treated exactly in a partial-wave analysis to extract the scattering parameters. It is found that the PCP potential gives much better qualitative results, particularly for the differential cross sections and the scattering length, than the corresponding results obtained from an electron polarization potential used as such for the positron case. We also discuss the ''critical'' points (representing the minima in the differential scattering) in the low-energy e + -Ar scattering. The present results involve no fitting procedure

  19. First image from a combined positron emission tomography and field-cycled MRI system.

    Science.gov (United States)

    Bindseil, Geron A; Gilbert, Kyle M; Scholl, Timothy J; Handler, William B; Chronik, Blaine A

    2011-07-01

    Combining positron emission tomography and MRI modalities typically requires using either conventional MRI with a MR-compatible positron emission tomography system or a modified MR system with conventional positron emission tomography. A feature of field-cycled MRI is that all magnetic fields can be turned off rapidly, enabling the use of conventional positron emission tomography detectors based on photomultiplier tubes. In this demonstration, two photomultiplier tube-based positron emission tomography detectors were integrated with a field-cycled MRI system (0.3 T/4 MHz) by placing them into a 9-cm axial gap. A positron emission tomography-MRI phantom consisting of a triangular arrangement of positron-emitting point sources embedded in an onion was imaged in a repeating interleaved sequence of ∼1 sec MRI then 1 sec positron emission tomography. The first multimodality images from the combined positron emission tomography and field-cycled MRI system show no additional artifacts due to interaction between the systems and demonstrate the potential of this approach to combining positron emission tomography and MRI. Copyright © 2010 Wiley-Liss, Inc.

  20. Los microbios en el agua de las unidades dentales

    Directory of Open Access Journals (Sweden)

    Chris H. Milleri

    1996-12-01

    Full Text Available Los microbios están presentes en el agua de las unidades dentales y existen en la biocapa que cubre las paredes de las tuberías de agua. El mejoramiento de la calidad microbiana del agua en las unidades dentales según estén disponibles los medios es una parte natural del mantenimiento de la calidad para la atención al paciente y al equipo de trabajo.

  1. Aspergilosis invasiva en unidad de cuidado intensivo

    Directory of Open Access Journals (Sweden)

    Mónica M. Toro-Lezcano

    Full Text Available La aspergilosis invasiva (AI es causada por la inhalación de conidias del moho Aspergillus spp. , el cual tiene como hábitat el suelo. Ha sido descrita en pacientes con trasplante de médula ósea y neutropenia grave (<500 neutrófilos/mm 3 . Los pacientes que ingresan a la unidad de cuidado intensivo (UCI también pueden ser susceptibles a la AI, con otros factores de riesgo tales como: enfermedad pulmonar obstructiva crónica (EPOC, cirrosis hepática, enfermedades autoinmunes en manejo inmunosupresor y trasplante de órgano sólido, en donde la mortalidad puede llegar al 80%. Se describe el caso de un hombre de 56 años con antecedente de tabaquismo, sin confirmación espirométrica de EPOC, que presentó AI pulmonar durante su estancia en UCI. El diagnóstico fue confirmado por histopatología de úlcera en carina, cultivo de aspirado traqueal y galactomanan en lavado broncoalveolar. Voriconazol fue su tratamiento, con buena respuesta clínica.

  2. The Effects of Surface Reconstruction and Electron-Positron Correlation on the Annihilation Characteristics of Positrons Trapped at Semiconductor Surfaces

    International Nuclear Information System (INIS)

    Fazleev, N. G.; Jung, E.; Weiss, A. H.

    2009-01-01

    Experimental positron annihilation induced Auger electron spectroscopy (PAES) data from Ge(100) and Ge(111) surfaces display several strong Auger peaks corresponding to M 4,5 N 1 N 2,3 , M 2,3 M 4,5 M 4,5 , M 2,3 M 4,5 V, and M 1 M 4,5 M 4,5 Auger transitions. The integrated peak intensities of Auger transitions have been used to obtain experimental annihilation probabilities for the Ge 3d and 3p core electrons. The experimental data were analyzed by performing theoretical studies of the effects of surface reconstructions and electron-positron correlations on image potential induced surface states and annihilation characteristics of positrons trapped at the reconstructed Ge(100) and Ge(111) surfaces. Calculations of positron surface states and annihilation characteristics have been performed for Ge(100) surface with (2x1), (2x2), and (4x2) reconstructions, and for Ge(111) surface with c(2x8) reconstruction. Estimates of the positron binding energy and annihilation characteristics reveal their sensitivity to the specific atomic structure of the topmost layers of the semiconductor and to the approximations used to describe electron-positron correlations. The results of these theoretical studies are compared with the ones obtained for the reconstructed Si(100)-(2x1) and Si(111)-(7x7) surfaces.

  3. Positrons in amorphous alloys

    International Nuclear Information System (INIS)

    Moser, Pierre.

    1981-07-01

    Positron annihilation techniques give interesting informations about ''empty spaces'' in amorphous alloys. The results of an extensive research work on the properties of either pre-existing or irradiation induced ''empty spaces'' in four amorphous alloys are presented. The pre-existing empty spaces appear to be small vacancy-like defects. The irradiation induced defects are ''close pairs'' with widely distributed configurations. There is a strong interaction between vacancy like and interstitial like components. A model is proposed, which explains the radiation resistance mechanism of the amorphous alloys. An extensive joint research work to study four amorphous alloys, Fe 80 B 20 ,Fe 40 Ni 40 P 14 B 6 , Cu 50 Ti 50 , Pd 80 Si 20 , is summarized

  4. Positron emission tomography camera

    International Nuclear Information System (INIS)

    Anon.

    1987-01-01

    A positron emission tomography camera having a plurality of detector planes positioned side-by-side around a patient area to detect radiation. Each plane includes a plurality of photomultiplier tubes and at least two rows of scintillation crystals on each photomultiplier tube extend across to adjacent photomultiplier tubes for detecting radiation from the patient area. Each row of crystals on each photomultiplier tube is offset from the other rows of crystals, and the area of each crystal on each tube in each row is different than the area of the crystals on the tube in other rows for detecting which crystal is actuated and allowing the detector to detect more inter-plane slides. The crystals are offset by an amount equal to the length of the crystal divided by the number of rows. The rows of crystals on opposite sides of the patient may be rotated 90 degrees relative to each other

  5. Defect identification using positrons

    International Nuclear Information System (INIS)

    Beling, C.D.; Fung, S.

    2001-01-01

    The current use of the lifetime and Doppler broadening techniques in defect identification is demonstrated with two studies, the first being the identification of carbon vacancy in n-6H SiC through lifetime spectroscopy, and the second the production of de-hydrogenated voids in α-Si:H through light soaking. Some less conventional ideas are presented for more specific defect identification, namely (i) the amalgamation of lifetime and Doppler techniques with conventional deep level transient spectroscopy in what may be called ''positron-deep level transient spectroscopy'', and (ii) the extraction of more spatial information on vacancy defects by means of what may be called ''Fourier transform Doppler broadening of annihilation radiation spectroscopy'' (orig.)

  6. Positron emitting pharmaceuticals

    International Nuclear Information System (INIS)

    Rajan, M.G.R.

    2012-01-01

    Positron Emission Tomography (PET) imaging of physiology at the molecular level bridges the gap between laboratory science and clinical medicine by providing the most specific and sensitive means for imaging molecular pathways and interactions in tissues of man. PET-imaging requires the use Positron Emitting Radiopharmaceuticals (PRPs), which are radioactively labeled 'true metabolites' i.e., sugars, amino acids, fatty acids etc., essentially made of H, C, N and O which the cells in the body can metabolize. The PET-isotopes: 11 C, 15 O, 13 N and 18 F (instead of H) are cyclotron produced and are short-lived, which places several constraints on the synthesis time for the PRPs, quality control and their clinical use as compared to the conventional 99m Tc- and other SPECT-RPs widely used in nuclear medicine. There are large number of published reports showing the utility of several PRPs labeled with 18 F (T 1/2 = 110 min) and 11 C (T 1/2 = 20 min). A few PRPs have been labeled with 13 N (T 1/2 = 10 min). 15 O (T 1/2 = 2min) is used mostly as H 2 15 O, C 15 or C 15 O 2 . 18 F-radiopharmaceuticals can be made at a medical cyclotron facility and sent to PET -imaging centres, which can be reached in a couple of hours. The sensitivity of PET -imaging has encouraged R and D in several other PRPs, labeled with viz., 68 Ga (generator produced, T 1/2 68 min), 124 I (cyclotron, T 1/2 4.2 d), 82 Rb (generator, T 1/2 75s), 64 Cu (cyclotron, T 1/2 12h), and 94m Tc (cyclotron, T 1/2 52 min). Due to its relevance in several diseases, particularly cancer, PET-imaging has made major scientific contribution to drug development, particularly for neurological diseases and cancer treatment. (author)

  7. Positron-acoustic waves in an electron-positron plasma with an electron beam

    International Nuclear Information System (INIS)

    Nejoh, Y.N.

    1996-01-01

    The nonlinear wave structures of large-amplitude positron-acoustic waves are studied in an electron-positron plasma in the presence of an electron beam with finite temperature and hot electrons and positrons. The region where positron-acoustic waves exist is presented by analysing the structure of the pseudopotential. The region depends sensitively on the positron density, the positron temperature and the electron beam temperature. It is shown that the maximum amplitude of the wave decreases as the positron temperature increases, and the region of positron-acoustic waves spreads as the positron temperature increases. 11 refs., 5 figs

  8. Defect characterization with positron annihilation

    International Nuclear Information System (INIS)

    Granatelli, L.; Lynn, K.G.

    1980-01-01

    Positron annihilation in metal crystals is reviewed. A brief introduction to the positron annihilation technique is presented first. Then the ability of the positron technique to perform microstructural characterization of four types of lattice defects (vacancies, voids, dislocations, grain boundaries) is discussed. It is frequently not possible to obtain samples that contain only one type of defect in nonnegligible concentrations. Such situations exist for some alloys and for fatigued metal samples. Finally, the current limitations and some future prospects of the technique are presented. 79 references, 14 figures, 1 table

  9. Fundamentals of positron emission tomography

    International Nuclear Information System (INIS)

    Ostertag, H.

    1989-01-01

    Positron emission tomography is a modern radionuclide method of measuring physiological quantities or metabolic parameters in vivo. The methods is based on: (1) Radioactive labelling with positron emitters; (2) the coincidence technique for the measurement of the annihilation radiation following positron decay; (3) analysis of the data measured using biological models. The basic aspects and problems of the method are discussed. The main fields of future research are the synthesis of new labelled compounds and the development of mathematical models of the biological processes to be investigated. (orig.) [de

  10. Cosmic Ray Positrons from Pulsars

    Science.gov (United States)

    Harding, Alice K.

    2010-01-01

    Pulsars are potential Galactic sources of positrons through pair cascades in their magnetospheres. There are, however, many uncertainties in establishing their contribution to the local primary positron flux. Among these are the local density of pulsars, the cascade pair multiplicities that determine the injection rate of positrons from the pulsar, the acceleration of the injected particles by the pulsar wind termination shock, their rate of escape from the pulsar wind nebula, and their propagation through the interstellar medium. I will discuss these issues in the context of what we are learning from the new Fermi pulsar detections and discoveries.

  11. Atomic collisions involving pulsed positrons

    DEFF Research Database (Denmark)

    Merrison, J. P.; Bluhme, H.; Field, D.

    2000-01-01

    Conventional slow positron beams have been widely and profitably used to study atomic collisions and have been instrumental in understanding the dynamics of ionization. The next generation of positron atomic collision studies are possible with the use of charged particle traps. Not only can large...... instantaneous intensities be achieved with in-beam accumulation, but more importantly many orders of magnitude improvement in energy and spatial resolution can be achieved using positron cooling. Atomic collisions can be studied on a new energy scale with unprecedented precion and control. The use...

  12. Parkinson disease and positron tomography

    International Nuclear Information System (INIS)

    Baron, J.C.

    1984-10-01

    Physiopathologic investigations of Parkinson disease and parkinsonian syndrome using positron tomography are briefly reviewed: study of cerebral blood flow and metabolism; effects of L-DOPA; study of dopaminergic receptors and of 18 F-Fluoro-L-DOPA incorporation [fr

  13. Deconvolution of Positrons' Lifetime spectra

    International Nuclear Information System (INIS)

    Calderin Hidalgo, L.; Ortega Villafuerte, Y.

    1996-01-01

    In this paper, we explain the iterative method previously develop for the deconvolution of Doppler broadening spectra using the mathematical optimization theory. Also, we start the adaptation and application of this method to the deconvolution of positrons' lifetime annihilation spectra

  14. Positron annihilation in superconductive metals

    Energy Technology Data Exchange (ETDEWEB)

    Dekhtjar, I.J.

    1969-03-10

    A correlation is shown between the parameters of superconductive metals and those of positron annihilation. Particular attention is paid to the density states obtained from the electron specific heat.

  15. Probing Positron Gravitation at HERA

    International Nuclear Information System (INIS)

    Gharibyan, Vahagn

    2015-07-01

    An equality of particle and antiparticle gravitational interactions holds in general relativity and is supported by indirect observations. Here I develop a method based on high energy Compton scattering to measure the gravitational interaction of accelerated charged particles. Within that formalism the Compton spectra measured at HERA rule out the positron's anti-gravity and hint for a positron's 1.3(0.2)% weaker coupling to the gravitational field relative to an electron.

  16. Probing Positron Gravitation at HERA

    Energy Technology Data Exchange (ETDEWEB)

    Gharibyan, Vahagn

    2015-07-15

    An equality of particle and antiparticle gravitational interactions holds in general relativity and is supported by indirect observations. Here I develop a method based on high energy Compton scattering to measure the gravitational interaction of accelerated charged particles. Within that formalism the Compton spectra measured at HERA rule out the positron's anti-gravity and hint for a positron's 1.3(0.2)% weaker coupling to the gravitational field relative to an electron.

  17. Ionization in positron- and positronium- collisions with atoms and molecules

    Energy Technology Data Exchange (ETDEWEB)

    Laricchia, G; Brawley, S; Cooke, D A; Murtagh, D J; Williams, A I [UCL Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom); Koever, A [permanent address: ATOMKI, Institute for Nuclear Research, Debrecen (Hungary)

    2009-11-15

    Recent progress in the experimental study of positron- and positronium-induced ionization of atoms and molecules is outlined. Investigations include integral and differential cross-sections, as well as formation of positronium in the first excited state. Future prospects are discussed.

  18. Simulation of the annihilation emission of galactic positrons; Modelisation de l'emission d'annihilation des positrons Galactiques

    Energy Technology Data Exchange (ETDEWEB)

    Gillard, W

    2008-01-15

    Positrons annihilate in the central region of our Galaxy. This has been known since the detection of a strong emission line centered on an energy of 511 keV in the direction of the Galactic center. This gamma-ray line is emitted during the annihilation of positrons with electrons from the interstellar medium. The spectrometer SPI, onboard the INTEGRAL observatory, performed spatial and spectral analyses of the positron annihilation emission. This thesis presents a study of the Galactic positron annihilation emission based on models of the different interactions undergone by positrons in the interstellar medium. The models are relied on our present knowledge of the properties of the interstellar medium in the Galactic bulge, where most of the positrons annihilate, and of the physics of positrons (production, propagation and annihilation processes). In order to obtain constraints on the positrons sources and physical characteristics of the annihilation medium, we compared the results of the models to measurements provided by the SPI spectrometer. (author)

  19. Positron Beam Characteristics at NEPOMUC Upgrade

    Science.gov (United States)

    Hugenschmidt, C.; Ceeh, H.; Gigl, T.; Lippert, F.; Piochacz, C.; Reiner, M.; Schreckenbach, K.; Vohburger, S.; Weber, J.; Zimnik, S.

    2014-04-01

    In 2012, the new neutron induced positron source NEPOMUC upgrade was put into operation at FRMII. Major changes have been made to the source which consists of a neutron-γ-converter out of Cd and a Pt foil structure for electron positron pair production and positron moderation. The new design leads to an improvement of both intensity and brightness of the mono-energetic positron beam. In addition, the application of highly enriched 113Cd as neutron-γ-converter extends the lifetime of the positron source to 25 years. A new switching and remoderation device has been installed in order to allow toggling from the high-intensity primary beam to a brightness enhanced remoderated positron beam. At present, an intensity of more than 109 moderated positrons per second is achieved at NEPOMUC upgrade. The main characteristics are presented which comprise positron yield and beam profile of both the primary and the remoderated positron beam.

  20. Endobronchial ultrasound-guided transbronchial needle aspiration for systematic nodal staging of lung cancer in patients with N0 disease by computed tomography and integrated positron emission tomography-computed tomography.

    Science.gov (United States)

    Ong, Philip; Grosu, Horiana; Eapen, George A; Rodriguez, Macarena; Lazarus, Donald; Ost, David; Jimenez, Carlos A; Morice, Rodolfo; Bandi, Venkata; Tamara, Luis; Cornwell, Lorraine; Green, Linda; Zhu, Angela; Casal, Roberto F

    2015-03-01

    Data regarding the sensitivity of endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) for staging of lung cancer in patients with radiographic N0 disease is scant and inconsistent. With increasing use of nonoperative ablative therapies, studies focusing on the performance characteristics of EBUS-TBNA in this population are important. To evaluate the sensitivity and negative predictive value (NPV) of EBUS-TBNA in patients with non-small cell lung cancer and radiographic N0 disease both by computed tomography (CT) and positron emission tomography (PET)-CT. This was a retrospective review of EBUS-TBNA performed for lung cancer staging at two major academic centers from 2009 to 2014. Patients with radiographic N0 disease (lymph nodes [LN]≤1 cm in the short axis and maximum standardized uptake value≤2.5 by PET-CT) were included. Primary outcome was sensitivity and NPV of EBUS-TBNA. Two hundred twenty patients with radiographic N0 disease underwent EBUS-TBNA, and 734 LN were sampled (median 3, range 1-6). Median LN diameter was 0.72 cm. One hundred patients (45.5%) underwent surgery, and 120 patients (54.5%) had nonsurgical therapy. N status was up-staged in 49 patients (22.3%): 18 by EBUS-TBNA (N1=11, N2=6, N3=1), 27 by surgery (N1 intralobar=16, N1 extralobar=3, N2=8 [5 LN in stations 4 and 7, and 3 LN in stations 5-6), and 4 by imaging follow-up (N1=2, N2=2). Overall false-negative rate of EBUS was 14.1% (sensitivity, 36.7%; specificity, 100%; and NPV, 84.7%). False-negative rate was 27 and 3.3% in surgical and nonsurgical populations, respectively. Excluding patients with occult disease "outside" the reach of EBUS, the overall false-negative rate of EBUS-TBNA was 5.5% (sensitivity, 60%; specificity, 100%; and NPV, 93.4%). This is the largest report of EBUS-TBNA in patients with N0 disease by "integrated" PET-CT. The majority of false-negative EBUS results were in LN stations outside its reach. In our study, both sensitivity and NPV of

  1. Positron probes of the Ge(1 0 0) surface: The effects of surface reconstructions and electron-positron correlations on positron trapping and annihilation characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Fazleev, N.G. [Department of Physics, University of Texas at Arlington, Box 19059, Arlington, TX 76019-0059 (United States) and Department of Physics, Kazan State University, Kazan 420008 (Russian Federation)]. E-mail: Fazleev@uta.edu; Jung, E. [Department of Physics, University of Texas at Arlington, Box 19059, Arlington, TX 76019-0059 (United States); Weiss, A.H. [Department of Physics, University of Texas at Arlington, Box 19059, Arlington, TX 76019-0059 (United States)

    2007-08-15

    Positron annihilation induced Auger electron spectroscopy (PAES) has been applied to study the Ge(1 0 0) surface. The high-resolution PAES spectrum from the Ge(1 0 0) surface displays several strong Auger peaks corresponding to M{sub 4,5}N{sub 1}N{sub 2,3}, M{sub 2,3}M{sub 4,5}M{sub 4,5}, M{sub 2,3}M{sub 4,5}V and M{sub 1}M{sub 4,5}M{sub 4,5} Auger transitions. The integrated peak intensities of Auger transitions are used to obtain experimental annihilation probabilities for the Ge 3d and 3p core level electrons. These experimental results are analyzed by performing calculations of positron surface states and annihilation characteristics of surface trapped positrons with relevant Ge core-level electrons for the non-reconstructed and reconstructed Ge(1 0 0)-p(2 x 1), Ge(1 0 0)-p(2 x 2) and Ge(1 0 0)-c(4 x 2) surfaces. It is found that the positron surface state wave function extends into the Ge lattice in the regions where atoms are displaced from their ideal terminated positions due to reconstructions. Estimates of the positron binding energy and the positron annihilation characteristics reveal their sensitivity to the specific atomic structure of the topmost layers of Ge(1 0 0). A comparison with PAES data reveals an agreement with theoretical core annihilation probabilities for the Auger transitions considered.

  2. Performance characterisation and optimisation of the HIPOS positron generator setup

    Energy Technology Data Exchange (ETDEWEB)

    Tucek, K., E-mail: kamil.tucek@ec.europa.eu [European Commission, Joint Research Centre, Institute for Energy and Transport, P.O. Box 2, NL-1755 ZG Petten (Netherlands); Zeman, A.; Daquino, G.; Debarberis, L. [European Commission, Joint Research Centre, Institute for Energy and Transport, P.O. Box 2, NL-1755 ZG Petten (Netherlands); Hogenbirk, A. [Nuclear Research and Consultancy Group (NRG), P.O. Box 25, NL-1755 ZG Petten (Netherlands)

    2012-01-01

    As part of an Exploratory Research Project at the Institute for Energy and Transport (Joint Research Centre of the European Commission), a feasibility assessment was performed for the construction and placement of a high-intensity positron facility (HIPOS) in a beam tube, HB9, at the High flux reactor (HFR) in Petten. This paper reports on the results of Monte Carlo simulations to optimise the concept of the HIPOS positron generator and to determine the performance characteristics of the chosen generator design. In the first step, a detailed model of the HFR reactor core, reflector, instrumentation and HB9 beam tube was prepared, and coupled neutron and photon transport calculations were carried out with the MCNP4C3 code to establish neutron and photon source terms on boundary surfaces of the HB9 beam tube. These sources were subsequently used with the MCNPX code to optimise the positron generator concept and geometry. The results showed that the positron beam can reach an integral intensity of 10{sup 13} e{sup +}/s before the moderation stage, easily meeting the specified target and confirming the hypothesis that very high positron yields can be obtained by using combined neutron and gamma radiation sources from a high flux reactor. Full details of the research work are reported in this study.

  3. Reconhecimento materno na Unidade de Cuidado Intensivo Neonatal

    Directory of Open Access Journals (Sweden)

    Monika Wernet

    2015-04-01

    Full Text Available RESUMO Objetivo: analisar experiências maternas em Unidade de Cuidado Intensivo Neonatal, com foco nas relações de reconhecimento. Método: estudo qualitativo, desenvolvido na perspectiva da hermenêutica gadameriana, fundamentado no conceito honnethiano de reconhecimento. Foram entrevistadas, em profundidade, dez mães de crianças internadas em Unidade de Cuidado Intensivo Neonatal. Resultados: há comprometimentos no processo de reconhecimento materno na unidade e, como desdobramento, surgem sentimentos de obrigação e insegurança para o cuidado do filho e fragilidades na autoestima. Conclusão: as interações com os profissionais de saúde e as normas e protocolos ali existentes promovem vulnerabilidades e comprometem o reconhecimento e a autonomia materna.

  4. Unidad de recuperación de azufre

    OpenAIRE

    Marqués Sancho, José Miguel

    2009-01-01

    En este proyecto se trata del diseño de una unidad de recuperación de azufre, dentro de una refinería de petróleo, ubicada cerca de Tarragona. En esta unidad se pretende recuperar gran parte del azufre generado en toda la planta, para evitar que se filtre en modo de dióxido de azufre a la atmosfera, evitando así la posible creación de lluvia acida. También se pretende aprovechar el azufre en estado líquido, y el vapor sobrantes, para diversas aplicaciones, dentro y fuera de la refinería. ...

  5. Los planetas: propuesta de unidad didáctica

    OpenAIRE

    Carbonell-Cano, Marc

    2016-01-01

    El trabajo que se expone a continuación se basa en el desarrollo de una unidad didáctica sobre los planetas con la intención que ésta sea extrapolable a las aulas y pueda ser llevada a cabo por un maestro de educación infantil. Se pretende que los alumnos adquieran unos conceptos determinados sobre el espacio que les rodea y a su vez, unas habilidades y unas competencias que les permitan desarrollarlos en otros ámbitos de la vida. Para lograr esto se plantea la unidad con un enfoque global...

  6. La Unidad Médica Nacional

    Directory of Open Access Journals (Sweden)

    Gilberto Rueda Pérez

    1995-04-01

    Full Text Available

    La medicina en Colombia y su ejercicio ético se encuentran frente a una encrucijada que se abre en caminos de difícil escogencia.

    La alta y avasalladora tecnología científica que, con la sistematización, la bioingeniería, la electrónica, la informática y la masificación, ha llevado los procedimientos, especialmente los de diagnóstico y los quirúrgicos, a metas no soñadas hace pocos años, pero que facilitan el diagnóstico y el tratamiento de procesos hasta hace poco incurables, han incrementado los costos operativos a niveles imposibles de alcanzar por la generalidad de las unidades médicas del país, reduciéndose a unos muy pocos, privilegiados, centros hospitalarios, entre nosotros llamados Clínicas, que pueden actualizarse a esos niveles.

    Mientras esta tecnología avanzada se ha logrado implementar para pequeños grupos de población que pueden acceder a ella, la medicina ofrecida a la población general del país, o sea la de menores recursos, ha ido bajando en calidad casi en la misma proporción en que la otra ha ascendido. Solamente es necesario observar la penuria de nuestros hospitales generales con dotaciones obsoletas imposibles de reparar y menos aún de reemplazar, con edificios al borde de la ruina por falta de mantenimiento; con plantas de personal congeladas desde hace 10 o más años, constituidas por trabajadores de la salud descontentos con el desempeño de sus funciones, sino, no menos grave, por los pobres resultados de su gestión.

    Esto ha ido creando en el estamento médico una sensación de insatisfacción, de malestar, de inconformidad, que se manifestar claramente en el ejercicio profesional y que lleva con frecuencia a fallas en la atención, a errores funestos ya manejos reñidos con la ética y no pocas veces con el código penal.

    Esto último se encargan de penalizarlo los innumerables tribunales y organizaciones éticas y administrativas creadas con el objeto de descubrir

  7. Positron spectroscopy for materials characterization

    International Nuclear Information System (INIS)

    Schultz, P.J.; Snead, C.L. Jr.

    1988-01-01

    One of the more active areas of research on materials involves the observation and characterization of defects. The discovery of positron localization in vacancy-type defects in solids in the 1960's initiated a vast number of experimental and theoretical investigations which continue to this day. Traditional positron annihilation spectroscopic techniques, including lifetime studies, angular correlation, and Doppler broadening of annihilation radiation, are still being applied to new problems in the bulk properties of simple metals and their alloys. In addition new techniques based on tunable sources of monoenergetic positron beams have, in the last 5 years, expanded the horizons to studies of surfaces, thin films, and interfaces. In the present paper we briefly review these experimental techniques, illustrating with some of the important accomplishments of the field. 40 refs., 19 figs

  8. Channeling crystals for positron production

    International Nuclear Information System (INIS)

    Decker, F.J.

    1991-05-01

    Particles traversing at small angles along a single crystal axis experience a collective scattering force of many crystal atoms. The enormous fields can trap the particles along an axis or plane, called channeling. High energy electrons are attracted by the positive nuclei and therefore produce strongly enhanced so called coherent bremsstrahlung and pair production. These effects could be used in a positron production target: A single tungsten crystal is oriented to the incident electron beam within 1 mrad. At 28 GeV/c the effective radiation length is with 0.9 mm about one quarter of the amorphous material. So the target length can be shorter, which yields a higher conversion coefficient and a lower emittance of the positron beam. This makes single crystals very interesting for positron production targets. 18 refs., 2 figs

  9. Positron emitter labeled enzyme inhibitors

    International Nuclear Information System (INIS)

    Fowler, J.S.; MacGregor, R.R.; Wolf, A.P.; Langstrom, B.

    1990-01-01

    This invention involves a new strategy for imagining and mapping enzyme activity in the living human and animal body using positron emitter-labeled suicide enzyme inactivators or inhibitors which become covalently bound to the enzyme as a result of enzymatic catalysis. Two such suicide inactivators for monoamine oxidase have been labeled with carbon-11 and used to map the enzyme subtypes in the living human and animal body using PET. By using positron emission tomography to image the distribution of radioactivity produced by the body penetrating radiation emitted by carbon-11, a map of functionally active monoamine oxidase activity is obtained. Clorgyline and L-deprenyl are suicide enzyme inhibitors and irreversibly inhibit monoamine oxidase. When these inhibitors are labeled with carbon-11 they provide selective probes for monoamine oxidase localization and reactivity in vivo using positron emission tomography

  10. Study of a positron generation

    International Nuclear Information System (INIS)

    Nakahara, Kazuo; Enomoto, A.; Ikeda, M.; Ohsawa, S.; Kamitani, T.; Hosoyama, K.; Takei, H.; Emoto, T.; Tani, S.

    1998-03-01

    In the Power Reactor and Nuclear Fuel Development Corporation (PNC), the following are examined as part of an application technology using a high power electron linac: monochromatic gamma ray sources, free electron lasers, and intense positron sources. This report presents the study of an intense positron source, which has been developed jointly by High Energy Accelerator Research Organization (KEK) and PNC. In this report, we describe following items for an adaptive estimate of a superconducting magnet in order to efficiently converge a positron beam. (1) The cryostat which included the superconducting magnet is manufactured. (2) An excitement test of the superconducting magnet is carried out with a magnetic substance such as the electromagnet yoke. (author)

  11. Instrumentation for positron emission tomography

    International Nuclear Information System (INIS)

    Budinger, T.F.; Derenzo, S.E.; Huesman, R.H.

    1984-01-01

    Positron emission tomography with a spatial resolution of 2 mm full width at half maximum for quantitation in regions of interest 4 mm in diameter will become possible with the development of detectors that achieve ultrahigh resolution. Improved resolution will be possible using solid-state photodetectors for crystal identification or photomultiplier tubes with many small electron multipliers. Temporal resolution of 2 seconds and gating of cyclic events can be accomplished if statistical requirements are met. The major physical considerations in achieving high-resolution positron emission tomography are the degradation in resolution resulting from positron range, emission angle, parallax error, detector sampling density, the sensitivity of various detector materials and packing schemes, and the tradeoff between temporal resolution and statistical accuracy. The accuracy of data required for physiological models depends primarily on the fidelity of spatial sampling independent of statistical constraints

  12. Positron creation in superheavy quasi-molecules

    International Nuclear Information System (INIS)

    Mueller, B.

    1976-01-01

    The review of positron creation in superheavy quasi-molecules includes spontaneous positron emission from superheavy atoms, supercritical quasi-molecules, background effects, and some implications of the new ground state. 66 references

  13. Positron emission tomography in oncology

    International Nuclear Information System (INIS)

    Anon.

    1988-01-01

    This report describes the current and potential uses of positron emission tomography in clinical medicine and research related to oncology. Assessment will be possible of metabolism and physiology of tumors and their effects on adjacent tissues. Specific probes are likely to be developed for target sites on tumors, including monoclonal antibodies and specific growth factors that recognize tumors. To date, most oncological applications of positron emission tomography tracers have been qualitative; in the future, quantitative metabolic measurements should aid in the evaluation of tumor biology and response to treatment

  14. NMF on positron emission tomography

    DEFF Research Database (Denmark)

    Bödvarsson, Bjarni; Hansen, Lars Kai; Svarer, Claus

    2007-01-01

    In positron emission tomography, kinetic modelling of brain tracer uptake, metabolism or binding requires knowledge of the cerebral input function. Traditionally, this is achieved with arterial blood sampling in the arm or as shown in (Liptrot, M, et al., 2004) by non-invasive K-means clustering....... We propose another method to estimate time-activity curves (TAC) extracted directly from dynamic positron emission tomography (PET) scans by non-negative matrix factorization (NMF). Since the scaling of the basis curves is lost in the NMF the estimated TAC is scaled by a vector alpha which...

  15. Development of an Electron-Positron Source for Positron Annihilation Lifetime Spectroscopy

    Science.gov (United States)

    2009-12-19

    REPORT Development of an electron- positron source for positron annihilation lifetime spectroscopy : FINAL REPORT 14. ABSTRACT 16. SECURITY...to generate radiation, to accelerate particles, and to produce electrons and positrons from vacuum. From applications using existing high-repetition...theoretical directions. This report reviews work directed toward the application of positron generation from laser interaction with matter 1. REPORT DATE

  16. 22 Na positron source for annihilation positron spectroscopy

    International Nuclear Information System (INIS)

    Cimpeanu, Catalina; Craciun, L.; Dragulescu, E.; Dudu, D.; Racolta, P.M.; Voiculescu, Dana; Miron, N.

    2002-01-01

    To extend the nuclear physics applications and to perform the study of vacancy - type defects in metals, semiconductors, polymers etc., we decided to promote positron annihilation techniques. In order to achieve this goal we started a project of dedicated positron sources produced at the IFIN-HH U-120 Cyclotron. We have used the nuclear reaction 24 Mg(d,α) 22 Na and deuterons of 13 MeV energy. The paper presents the main steps of this procedure like: general conditions required for 22 NaCl sources, reactive chamber and characteristics of Mg target, parameters for the irradiation, radiochemical procedures to separate Na from Mg after the irradiation and geometrical or mechanical requirements for dedicated NaCl source for positron annihilation spectrometry. In the e + lifetime measurements the e + 'death - stop' signals are always provided by γ - quanta generated by the e + e - annihilation and the 'birth - start' signals may be obtained from 'prompt' γ - quanta emitted from the NaCl source (the 1.275 MeV photons). The 22 NaCl stock solution obtained by radiochemical separation will be kept in the sealed quartz vials in dry places and will be dropped between the studied materials before use in positron spectrometry. (authors)

  17. 22 Na positron source for annihilation positron spectroscopy

    International Nuclear Information System (INIS)

    Cimpeanu, Catalina; Craciun, L.; Dragulescu, E.; Dudu, D.; Racolta, P. M.; Voiculescu, Dana; Miron, N.

    2003-01-01

    To extend the nuclear physics applications and to perform the study of vacancy - type defects in metals, semiconductors, polymers etc., we decided to promote positron annihilation techniques. In order to achieve this goal we started a project of dedicated positron sources produced at the IFIN-HH U-120 Cyclotron. We have used the nuclear reaction: 24 Mg(d,α) 22 Na with deuterons of 13 MeV energy. The paper presents the main characteristics of this procedure, as follows: general conditions asked for 22 NaCl sources, reactive chamber and characteristics of Mg target, parameters for the irradiation, radiochemical procedures for separating Na from Mg after the irradiation and geometrical or mechanical requirements for dedicated NaCl source for positron annihilation spectrometry. In the e + lifetime measurements, the e + end - start signals may be obtained from prompt γ -quanta emitted from the NaCl source (1. 275 MeV photons). The 22 NaCl stock solution obtained by radiochemical separation will be kept in quartz sealed ampoules in dry places and will be dropped between the study materials before the use in positron spectrometry. (authors)

  18. Positron Studies of Oxide-Semiconductor Structures

    OpenAIRE

    Uedono , A.; Wei , L.; Kawano , T.; Tanigawa , S.; Suzuki , R.; Ohgaki , H.; Mikado , T.

    1995-01-01

    The annihilation characteristics of positrons in SiO2 films grown on Si substrates were studied by using monoenergetic positron beams. Doppler broadening profiles of the annihilation radiation and lifetime spectra of positrons were measured as a function of incident positron energy for SiO2/Si structures fabricated by various oxidation techniques. From the measurements, it was found that the formation probability of positronium (Ps) atoms in SiO2 films strongly depends on the growth condition...

  19. A study of positron irradiated porous silicon

    International Nuclear Information System (INIS)

    Huang Yuanming; Xue Qing; Zhai Baogai; Xu Aijun; Liu Shewen; Yu Weizhong

    1998-01-01

    The effect of positron irradiation on photoluminescence (PL) of porous silicon has been studied. After four hour positron irradiation, the red PL spectrum of porous silicon blue shifts into greenish spectral region, and a higher energy luminescence band is introduced into this blueshifted spectrum. The fourier transform infrared absorption experiment shows that the positron irradiation can cause further oxidization of porous silicon. A possible mechanism causing this change of PL spectra after positron irradiation is suggested

  20. Positron probes for mechanical fatigue detection system

    International Nuclear Information System (INIS)

    Holt, W.H.; Mock, W. Jr.

    1976-01-01

    The invention comprises positron-emitting probes for use in testing samples of metals for fatique by positron annihilation techniques comprising a substrate made from the same material as the test sample, positron-emitting material supported by one surface of the substrate, and a cover for the emitting material, the cover is sealed to the substrate and is of such thinness and density as to provide a window through which positron passage is unimpeded

  1. Low-energy positron and electron scattering from nitrogen dioxide

    International Nuclear Information System (INIS)

    Chiari, Luca; Brunger, M J; Zecca, Antonio; García, Gustavo; Blanco, Francisco

    2013-01-01

    Total cross section (TCS) measurements for positron scattering from nitrogen dioxide (NO 2 ) are presented in the energy range 0.2–40 eV. The TCS, the elastic integral and differential cross sections, and the integral cross section accounting of all the inelastic processes (including positronium formation) have also been computed using the independent atom model with screening corrected additivity rule (IAM-SCAR) for incident energies from 1 to 1000 eV. A qualitative level of agreement is found between the present TCS experiment and theory at the common energies. As no previous measurements or calculations for positron–NO 2  scattering exist in the literature, we also computed the TCS for electron collisions with NO 2  employing the IAM-SCAR method. A comparison of those results to the present positron cross sections and the earlier electron-impact data and calculations is provided. To investigate the role that chemical substitution plays in positron scattering phenomena, we also compare the present positron–NO 2  data with the TCSs measured at the University of Trento for positron scattering from N 2 O and CO 2 . (paper)

  2. Studies of positron induced luminescence from polymers

    International Nuclear Information System (INIS)

    Xu, J.; Hulett, L.D. Jr.; Lewis, T.A.; Tolk, N.H.

    1994-01-01

    Light emission from polymers (anthracene dissolved in polystryrene) induced by low-energy positrons and electrons has been studied. Results indicate a clear difference between optical emissions under positron and electron bombardment. The positron-induced luminescence spectrum is believed to be generated by both collisional and annihilation processes

  3. Applications of Positron Annihilation Spectroscopy

    OpenAIRE

    Asoka-Kumar , P.; Lynn , K.

    1995-01-01

    We describe the application of Positron Annihilation Spectroscopy (PAS) to some selected technologically important systems. The method involves a nondestructive probe to detect low levels of open-volume defects. The discussion shows the application of PAS to a wide range of advanced material systems.

  4. WORKSHOP: Electron-positron mystery

    International Nuclear Information System (INIS)

    Bokemeyer, H.; Mueller, B.

    1989-01-01

    The tightly correlated electron-positron pairs seen in experiments at the GSI Darmstadt heavy ion Laboratory and elsewhere have yet to be explained. New particle or new effect? The question was highlighted at a recent Moriond workshop held at Les Arcs in the French Alps in January

  5. Positron annhilation in nonmetallic solids

    International Nuclear Information System (INIS)

    Cizek, A.; Sob, M.; Dekhtyar, I. Ya.

    1979-01-01

    In positron annihilation investigations of nonmetallic solids, the standard deviation of the gaussian component of the angular correlation curve is elucidated as material constant. It is related to the apparent radius of the chemical unit of the substance in question. (Auth.)

  6. Positron--Electron Project (PEP)

    International Nuclear Information System (INIS)

    Rees, J.R.

    1977-01-01

    PEP, an 18-GeV electron-positron colliding-beam storage ring facility at SLAC, is being built by a team from LBL and SLAC. Construction is under way and completion is scheduled for Fall of 1979. A summary is given of the design of the facility, and the status of the project is reported

  7. Positron computed tomography with fluorodeoxyglucose

    International Nuclear Information System (INIS)

    Hervouet, T.; Kraeber-Bodere, F.; Lamy, T.; Le Gouil, S.; Devillers, A.; Bodet-Milin, C.; Ansquer, C.; Cheze-le Rest, C.; Metges, J.P.; Teyton, P.; Lozach, P.; Volant, A.; Bizais, Y.; Visvikis, D.; Morel, O.; Girault, S.; Soulie, P.; Dupoiron, D.; Berthelot, C.; Lorimier, G.; Jallet, P.; Garin, E.; Prigent, F.; Lesimple, T.; Barge, M.L.; Rousseau, C.; Devillers, A.; Bernard, A.M.; Bouriel, C.; Bridji, B.; Resche, R.; Banayan, S.; Claret, M.; Ninet, J.; Janier, M.; Billotey, C.; Garin, E.; Devillers, A.; Becker, S.; Lecloirec, J.; Boucher, E.; Raoul, J.L.; Rolland, V.; Oudoux, A.; Valette, F.; Dupas, B.; Moreau, P.; Champion, L.; Anract, P.; Wartski, M.; Laurence, V.; Goldwasser, F.; Pecking, A.P.; Alberini, J.L.; Brillouet, S.; Caselles, O.; Allal, B.; Zerdoud, S.; Gansel, M.G.; Thomas, F.; Dierrickx, L.; Delord, J.P.; Marchand, C.; Resche, I.; Mahe, M.A.

    2006-01-01

    Several oral communications present the interest of positron computed tomography with fluorodeoxyglucose in the detection of cancers, or for the follow up of cancers treatments in order to detect early possible relapses.PET FDG is also used to optimize the definition of target volume in order to avoid side effects and to get a better control of the illness. (N.C.)

  8. O cuidado intensivo oferecido ao paciente no ambiente de Unidade de Terapia Intensiva El cuidado intensivo ofrecido al paciente en el ambiente de la Unidad de Cuidados Intensivos Intensive care provided to patients in the environment of Intensive Care Units

    Directory of Open Access Journals (Sweden)

    Marli Terezinha Stein Backes

    2012-12-01

    Full Text Available Estudo qualitativo, partiu da questão: como se dá o cuidado intensivo oferecido ao paciente no ambiente de Unidade de Terapia Intensiva? Teve como objetivo compreender o cuidado intensivo oferecido ao paciente no ambiente de Unidade de Terapia Intensiva Adulto. O método utilizado foi a Grounded Theory. Realizou-se 39 entrevistas com 47 sujeitos diferenciados (pacientes, profissionais da saúde, gestores, profissionais dos serviços de apoio, familiares de três Unidades de Terapia Intensiva Adulto, em Florianópolis/SC, Santa Maria/RS e Pelotas/RS, Brasil, entre junho de 2009 a setembro de 2010. A teoria "Sustentando a vida no ambiente complexo de cuidados em Unidade de Terapia Intensiva", foi delimitada por oito categorias, das quais será focalizada neste artigo a categoria "Cuidando e monitorando o paciente continuamente". Conclui-se que o cuidado intensivo requer um cuidado integral com os pacientes, que vai além do cuidado técnico e inclui as dimensões física, emocional, espiritual e social do ser humano.Este estudio cualitativo se basó en la pregunta: ¿Cómo funciona el cuidado intensivo ofrecido al paciente en el ambiente de la Unidad de Cuidados Intensivos? El artículo tuvo como objetivo comprender el cuidado intensivo ofrecido al paciente en la Unidad de Cuidados Intensivos de Adultos. El método utilizado fue la Grounded Theory. Se llevó a cabo 39 entrevistas con 47 personas de tres diferentes unidades de cuidados intensivos para adultos en Florianópolis/SC, Santa Maria/RS y Pelotas/RS, desde junio 2009 a septiembre de 2010. La teoría "Sosteniendo la vida en el complejo ambiente de cuidados en la Unidad de Cuidados Intensivos", fue delimitada por ocho categorías. En este artículo se centrará la categoría "Asistir y monitorear el paciente continuamente". Se concluye que el cuidado intensivo requiere una atención integral a los pacientes, más allá de la atención técnica e incluye la dimensión física, emocional

  9. The cryogenic source of slow monochromatic positrons

    International Nuclear Information System (INIS)

    Meshkov, I.N.; Pavlov, V.N.; Sidorin, A.O.; Yakovenko, S.L.

    2008-01-01

    The cryogenic source of slow monochromatic positrons based on the 22 Na isotope has been designed and constructed at JINR. Positrons emitted from radioactive source 22 Na have a very broad energy spectrum up to 0.5 MeV. To generate monochromatic beam of slow positrons the solid neon is used as a moderator. The solid neon allows forming slow positron beam of the energy of 1.2 eV at the spectrum width of 1 eV. The efficiency of moderation is 1 % of total positron flux

  10. High intensity positron program at LLNL

    International Nuclear Information System (INIS)

    Asoka-Kumar, P.; Howell, R.; Stoeffl, W.; Carter, D.

    1999-01-01

    Lawrence Livermore National Laboratory (LLNL) is the home of the world's highest current beam of keV positrons. The potential for establishing a national center for materials analysis using positron annihilation techniques around this capability is being actively pursued. The high LLNL beam current will enable investigations in several new areas. We are developing a positron microprobe that will produce a pulsed, focused positron beam for 3-dimensional scans of defect size and concentration with submicron resolution. Below we summarize the important design features of this microprobe. Several experimental end stations will be available that can utilize the high current beam with a time distribution determined by the electron linac pulse structure, quasi-continuous, or bunched at 20 MHz, and can operate in an electrostatic or (and) magnetostatic environment. Some of the planned early experiments are: two-dimensional angular correlation of annihilation radiation of thin films and buried interfaces, positron diffraction holography, positron induced desorption, and positron induced Auger spectroscopy

  11. High intensity positron program at LLNL

    International Nuclear Information System (INIS)

    Asoka-Kumar, P.; Howell, R.H.; Stoeffl, W.

    1998-01-01

    Lawrence Livermore National Laboratory (LLNL) is the home of the world's highest current beam of keV positrons. The potential for establishing a national center for materials analysis using positron annihilation techniques around this capability is being actively pursued. The high LLNL beam current will enable investigations in several new areas. We are developing a positron microprobe that will produce a pulsed, focused positron beam for 3-dimensional scans of defect size and concentration with submicron resolution. Below we summarize the important design features of this microprobe. Several experimental end stations will be available that can utilize the high current beam with a time distribution determined by the electron linac pulse structure, quasi-continuous, or bunched at 20 MHz, and can operate in an electrostatic or (and) magnetostatic environment. Some of the planned early experiments are: two-dimensional angular correlation of annihilation radiation of thin films and buried interfaces, positron diffraction holography, positron induced desorption, and positron induced Auger spectra

  12. Software correction of scatter coincidence in positron CT

    International Nuclear Information System (INIS)

    Endo, M.; Iinuma, T.A.

    1984-01-01

    This paper describes a software correction of scatter coincidence in positron CT which is based on an estimation of scatter projections from true projections by an integral transform. Kernels for the integral transform are projected distributions of scatter coincidences for a line source at different positions in a water phantom and are calculated by Klein-Nishina's formula. True projections of any composite object can be determined from measured projections by iterative applications of the integral transform. The correction method was tested in computer simulations and phantom experiments with Positologica. The results showed that effects of scatter coincidence are not negligible in the quantitation of images, but the correction reduces them significantly. (orig.)

  13. Variabilidade espacial de atributos de solos em unidades de manejo em área piloto de produção integrada de coco Soil spatial variation and properties as related to manegement units in an experimental area of integrated coconut production

    Directory of Open Access Journals (Sweden)

    João Bosco Vasconcellos Gomes

    2008-12-01

    para vários atributos, influenciados pela presença da depressão no extremo sul da área. Foram estabelecidas duas unidades de manejo para a área de estudo, as quais exigem práticas de manejo de água e solo diferenciadas.The objective of this work was to access spatial variations of soils from experimental plots for integrated coconut production based on the detailed mapping of soils and the construction of contour maps of soil properties. Observations and measurements were formed and samples collected in small trenches and soil profiles. The amount of soil clay from small trenches was evaluated in the field by finger touch feeling. Physical and chemical analyses were performed in all samples. Particle-size-distribution (profiles, Al, Ca and Mg, potential acidity, K and Na, pH, available P and organic C were determined. In samples from profiles Fe, Al, Ti, P and Si were determined by sulphuric acid digestion. Fe was also analyzed in the clay fraction by Na dithionite-citrate-bicarbonate extraction. X ray diffraction analysis was performed in the oxide-free clay fraction. The construction of semi-variograms made the classification possible, and the soil properties were compared based on the degree of spatial dependence. Contour maps were drawn using the kriging interpolator method. The mapped area is characterized by a broad summit of low coastal tablelands, with a closed depression in the far south of the area. From the depression center outwards we find, in sequence, a clayey Haplic Cambisol (Inceptsol, clay-laom Yellow Latosol (Oxisol and a sandy-loam Yellow Latosol. These Oxisols have cohesive subsurface horizons. Attributes with high heterogeneity degree predominate. Average values of P, K and Ca + Mg are influenced by liming and systematic fertilization of the planting area. Spatial dependence was observed for all analyzed variables, expressed by the semi-variogram models. The C0/(C0 + C1 ratio revealed a moderate to strong spatial dependence degree. The

  14. Positron annihilation in transparent ceramics

    Science.gov (United States)

    Husband, P.; Bartošová, I.; Slugeň, V.; Selim, F. A.

    2016-01-01

    Transparent ceramics are emerging as excellent candidates for many photonic applications including laser, scintillation and illumination. However achieving perfect transparency is essential in these applications and requires high technology processing and complete understanding for the ceramic microstructure and its effect on the optical properties. Positron annihilation spectroscopy (PAS) is the perfect tool to study porosity and defects. It has been applied to investigate many ceramic structures; and transparent ceramics field may be greatly advanced by applying PAS. In this work positron lifetime (PLT) measurements were carried out in parallel with optical studies on yttrium aluminum garnet transparent ceramics in order to gain an understanding for their structure at the atomic level and its effect on the transparency and light scattering. The study confirmed that PAS can provide useful information on their microstructure and guide the technology of manufacturing and advancing transparent ceramics.

  15. Electron-positron annihilation physics

    International Nuclear Information System (INIS)

    Foster, B.

    1990-01-01

    Electron-Positron Annihilation Physics is a detailed introduction to the main topics in e + e - annihilation, with particular emphasis on experimental work. Four main areas are covered, each in great detail, beginning with the Standard Model and its application to the production of lepton, quark and boson pairs. Secondly, the general features of fragmentation and different fragmentation models are explained. Chapter 3 is devoted to heavy quark and lepton physics, to which e + e - experiments have made an immense contribution. The final chapter, 'Where do we go from here?', looks for new phenomena beyond the Standard Model. Predictions of theory are compared with experimental results, highlighting shortcomings of some current theories. Details of instrumentation are included whenever possible. This ensures that the book is of maximum practical use to research workers. A comprehensive introduction to the major topics in the field, Electron-Positron Annihilation Physics is aimed at both graduate students studying high-energy physics and mature research workers. (author)

  16. Electron-Positron Accumulator (EPA)

    CERN Multimedia

    Photographic Service

    1986-01-01

    After acceleration in the low-current linac LIL-W, the electrons and positrons are accumulated in EPA to obtain a sufficient intensity and a suitable time-structure, before being passed on to the PS for further acceleration to 3.5 GeV. Electrons circulate from right to left, positrons in the other direction. Dipole bending magnets are red, focusing quadrupoles blue, sextupoles for chromaticity-control orange. The vertical tube at the left of the picture belongs to an optical transport system carrying the synchrotron radiation to detectors for beam size measurement. Construction of EPA was completed in spring 1986. LIL-W and EPA were conceived for an energy of 600 MeV, but operation was limited to 500 MeV.

  17. PEBS - Positron Electron Balloon Spectrometer

    CERN Document Server

    von Doetinchem, P.; Kirn, T.; Yearwood, G.Roper; Schael, S.

    2007-01-01

    The best measurement of the cosmic ray positron flux available today was performed by the HEAT balloon experiment more than 10 years ago. Given the limitations in weight and power consumption for balloon experiments, a novel approach was needed to design a detector which could increase the existing data by more than a factor of 100. Using silicon photomultipliers for the readout of a scintillating fiber tracker and of an imaging electromagnetic calorimeter, the PEBS detector features a large geometrical acceptance of 2500 cm^2 sr for positrons, a total weight of 1500 kg and a power consumption of 600 W. The experiment is intended to measure cosmic ray particle spectra for a period of up to 20 days at an altitude of 40 km circulating the North or South Pole. A full Geant 4 simulation of the detector concept has been developed and key elements have been verified in a testbeam in October 2006 at CERN.

  18. Positron annihilation in transparent ceramics

    International Nuclear Information System (INIS)

    Husband, P; Selim, F A; Bartošová, I; Slugeň, V

    2016-01-01

    Transparent ceramics are emerging as excellent candidates for many photonic applications including laser, scintillation and illumination. However achieving perfect transparency is essential in these applications and requires high technology processing and complete understanding for the ceramic microstructure and its effect on the optical properties. Positron annihilation spectroscopy (PAS) is the perfect tool to study porosity and defects. It has been applied to investigate many ceramic structures; and transparent ceramics field may be greatly advanced by applying PAS. In this work positron lifetime (PLT) measurements were carried out in parallel with optical studies on yttrium aluminum garnet transparent ceramics in order to gain an understanding for their structure at the atomic level and its effect on the transparency and light scattering. The study confirmed that PAS can provide useful information on their microstructure and guide the technology of manufacturing and advancing transparent ceramics. (paper)

  19. Unidades didácticas de matemáticas /

    OpenAIRE

    Caballero Gallego, Sheila

    2011-01-01

    La autora considera importante que se tenga en cuenta como docentes que no se debe únicamente fomentar la capacidad cognitiva del alumnado, ya que, las personas nos desarrollamos en más ámbitos que el estrictamente cognitivo. Por ello a la hora de diseñar unidades didácticas, especialmente de matemáticas, se deben tener en cuenta todos los aspectos que pueden influir, de una forma u otra, en nuestro alumnado.

  20. Positron confinement in embedded lithium nanoclusters

    Science.gov (United States)

    van Huis, M. A.; van Veen, A.; Schut, H.; Falub, C. V.; Eijt, S. W.; Mijnarends, P. E.; Kuriplach, J.

    2002-02-01

    Quantum confinement of positrons in nanoclusters offers the opportunity to obtain detailed information on the electronic structure of nanoclusters by application of positron annihilation spectroscopy techniques. In this work, positron confinement is investigated in lithium nanoclusters embedded in monocrystalline MgO. These nanoclusters were created by means of ion implantation and subsequent annealing. It was found from the results of Doppler broadening positron beam analysis that approximately 92% of the implanted positrons annihilate in lithium nanoclusters rather than in the embedding MgO, while the local fraction of lithium at the implantation depth is only 1.3 at. %. The results of two-dimensional angular correlation of annihilation radiation confirm the presence of crystalline bulk lithium. The confinement of positrons is ascribed to the difference in positron affinity between lithium and MgO. The nanocluster acts as a potential well for positrons, where the depth of the potential well is equal to the difference in the positron affinities of lithium and MgO. These affinities were calculated using the linear muffin-tin orbital atomic sphere approximation method. This yields a positronic potential step at the MgO||Li interface of 1.8 eV using the generalized gradient approximation and 2.8 eV using the insulator model.

  1. Positrons in biomolecular systems. II

    International Nuclear Information System (INIS)

    Glass, J.C.; Graf, G.; Costabal, H.; Ewert, D.H.; English, L.

    1982-01-01

    Pickoff-annihilation parameters, as related to the free volume model, are shown to be indicators of structural fluctuations in membranes and membrane bound proteins. Nitrous oxide anesthetic induces lateral rigidity in a membrane, and an anesthetic mechanism is suggested. Conformational changes of (Na + ,K + )ATPase in natural membrane are observed with ATP and Mg-ion binding. New positron applications to active transport and photosynthetic systems are suggested. (Auth.)

  2. Study of surface layer assessment of solids by ultra-slow and short-pulsed positron beams

    International Nuclear Information System (INIS)

    Suzuki, Ryouichi; Ohdaira, Toshiyuki; Mikado, Tomohisa; Yamada, Kawakatsu

    2004-01-01

    Thin films of insulators with low dielectric constant, as a candidate for next generation LSI (large scale integration), were assessed by two dimensional positron life time and wave height measurements using variable incident energy and also short pulsed positron beams. Linkages and openness of nano-scale voids in the films were evaluated by the measurements. Amorphous SiO 2 films were compared with SiCOH films synthesized by plasma CVD (Chemical Vapor Deposition) by measurements of the correlation between positron lifetime and momentum using short-pulsed positron beams. From the measurements, many hydrocarbons were found on void surface of SiCOH films. Positron lifetime measurement gives information about void sizes, and Doppler broadening due to annihilation γ-rays offers electron momentum distribution, which is a counterpart of positron annihilation. Two γ-rays are emitted on the positron annihilation. Coincident measurements of these two γ-rays provide the correlation spectra between positron lifetime and momentum. An instrument for positron annihilation excitation Auger electron spectroscopy (PAES) was improved, and a time-of-flight (TOF) PAES instrument was developed. Double counting rate and high resolution, compared with a conventional Auger electron spectrometer, were attained in elementary analysis using above TOF-PAES instrument. (Y. Kazumata)

  3. Design of a transmission electron positron microscope

    International Nuclear Information System (INIS)

    Doyama, Masao; Inoue, M.; Kogure, Y.; Hayashi, Y.; Yoshii, T.; Kurihara, T.; Tsuno, K.

    2003-01-01

    This paper reports the plans and design of positron-electron microscopes being built at KEK (High Energy Accelerator Research Organization), Tsukuba, Japan. A used electron microscope is altered. The kinetic energies of positrons produced by accelerators or by nuclear decays are not a unique value but show a spread over in a wide range. Positron beam is guided to a transmission electron microscope (JEM100SX). Positrons are moderated by a tungsten foil, are accelerated and are focused on a nickel sheet. The monochromatic focused beam is injected into an electron microscope. The focusing and aberration of positrons are the same as electrons in a magnetic system which are used in commercial electron microscopes. Imaging plates are used to record positron images for the transmission electron microscope. (author)

  4. Development of a transmission positron microscope

    Energy Technology Data Exchange (ETDEWEB)

    Matsuya, M., E-mail: matsuya@jeol.co.jp [JEOL Ltd., 1-2 Musashino, 3-Chome, Akishima, Tokyo 196-8558 (Japan); Jinno, S. [Department of Applied Chemistry, Chiba University, Yayoi, Inage, Chiba, Chiba 263-8552 (Japan); Ootsuka, T.; Inoue, M. [JEOL Ltd., 1-2 Musashino, 3-Chome, Akishima, Tokyo 196-8558 (Japan); Kurihara, T. [High Energy Accelerator Research Organization, Oho, Tsukuba, Ibaraki 305-0801 (Japan); Doyama, M.; Inoue, M. [Teikyo University of Science and Technology, Uenohara, Yamanashi 409-0913 (Japan); Fujinami, M. [Department of Applied Chemistry, Chiba University, Yayoi, Inage, Chiba, Chiba 263-8552 (Japan)

    2011-07-21

    A practical transmission positron microscope (TPM) JEM-1011B has been developed to survey differences in the interaction of positron and electron beams with materials, and is installed in the Slow Positron Facility of High Energy Accelerator Research Organization (KEK). The TPM can share positron and electron beams, and can also be used as a transmission electron microscope (TEM). Positron transmission images up to magnification 10,000x (resolution: 50 nm) and positron diffraction patterns up to 044 family were successfully obtained by the TPM comparing them with those of electrons. The differences in material transmittances for both beams have been measured, and can be explained by the calculated results of the Monte Carlo simulation code PENELOPE-2008.

  5. Positron emission tomography imaging--technical considerations

    International Nuclear Information System (INIS)

    Muehllehner, G.; Karp, J.S.

    1986-01-01

    Positron imaging instrumentation has improved rapidly in the last few years. Scanners currently under development are beginning to approach fundamental limits set by positron range and noncolinearity effects. This report reviews the latest developments in positron emission tomography (PET) instrumentation, emphasizing the development of coding schemes that reduce the complexity and cost of high-resolution scanners. The relative benefits of using time-of-flight (TOF) information is discussed as well. 68 references

  6. Positron Spectroscopy of Hydrothermally Grown Actinide Oxides

    Science.gov (United States)

    2014-03-27

    actinide oxides . The work described here is an attempt to characterize the quality of crystals using positron annihilation spectroscopy (PALS). The...Upadhyaya, R. V. Muraleedharan, B. D. Sharma and K. G. Prasad, " Positron lifetime studies on thorium oxide powders," Philosohical Magazine A, vol. 45... crystals . A strong foundation for actinide PALS studies was laid, but further work is required to build a more effective system. Positron Spectroscopy

  7. KEK-IMSS Slow Positron Facility

    Energy Technology Data Exchange (ETDEWEB)

    Hyodo, T; Wada, K; Yagishita, A; Kosuge, T; Saito, Y; Kurihara, T; Kikuchi, T; Shirakawa, A; Sanami, T; Ikeda, M; Ohsawa, S; Kakihara, K; Shidara, T, E-mail: toshio.hyodo@kek.jp [High Energy Accelerator Research Organization (KEK) 1-1 Oho, Tsukuba, Ibaraki, 305-0801 (Japan)

    2011-12-01

    The Slow Positron Facility at the Institute of Material Structure Science (IMSS) of High Energy Accelerator Research Organization (KEK) is a user dedicated facility with an energy tunable (0.1 - 35 keV) slow positron beam produced by a dedicated 55MeV linac. The present beam line branches have been used for the positronium time-of-flight (Ps-TOF) measurements, the transmission positron microscope (TPM) and the photo-detachment of Ps negative ions (Ps{sup -}). During the year 2010, a reflection high-energy positron diffraction (RHEPD) measurement station is going to be installed. The slow positron generator (converter/ moderator) system will be modified to get a higher slow positron intensity, and a new user-friendly beam line power-supply control and vacuum monitoring system is being developed. Another plan for this year is the transfer of a {sup 22}Na-based slow positron beam from RIKEN. This machine will be used for the continuous slow positron beam applications and for the orientation training of those who are interested in beginning researches with a slow positron beam.

  8. Toward a European Network of Positron Laboratories

    Directory of Open Access Journals (Sweden)

    Karwasz Grzegorz P.

    2015-12-01

    Full Text Available Some applications of controlled-energy positron beams in material studies are discussed. In porous organic polysilicates, measurements of 3γ annihilation by Doppler broadening (DB method at the Trento University allowed to trace pore closing and filling by water vapor. In silicon coimplanted by He+ and H+, DB data combined with positron lifetime measurements at the München pulsed positron beam allowed to explain Si blistering. Presently measured samples of W for applications in thermonuclear reactors, irradiated by W+ and electrons, show vast changes of positron lifetimes, indicating complex dynamics of defects.

  9. Electron-positron pair production in Coulomb collisions at ultrarelativistic energies

    International Nuclear Information System (INIS)

    Vane, C.R.; Datz, S.; Dittner, P.F.; Krause, H.F.; Bottcher, C.; Strayer, M.; Schuch, R.; Gao, H.; Hutton, R.

    1993-01-01

    We have measured angular and momentum distributions for electrons and positrons created as pairs in peripheral collisions of 6.4 TeV bare sulfur ions with fixed targets of Al, Pd, and Au. Singly- and doubly-differential cross sections have been determined for 1--17 MeV/c electrons and positrons detected independently and in coincidence as pairs. Integrated yields for pair production are found to vary as the square of the target nuclear charge. Relative angular and momentum differential cross sections are effectively target independent. Probability distributions for the pair total momentum, the positron fraction of the pair momentum, and the pair traverse momentum have been derived from the coincident electron-positron data

  10. Solvated Positron Chemistry - Positron Reactions with Pseudo-Halide Ions in Water

    DEFF Research Database (Denmark)

    Mogensen, O. E.; Pedersen, Niels Jørgen; Andersen, Jan Rud

    1982-01-01

    The hydrated positron e+aq reactions with SCN−, OCN−, CN−, S2− were studied by means of the angular correlation technique. The positron forms bound states with SCN−, CN−, and S2− but not with OCN−. Apparently, the e+aq reaction with SH− results in a positron bound state with S2−. It was difficult...

  11. 22 Na positron source for annihilation positron spectroscopy

    International Nuclear Information System (INIS)

    Cimpeanu, Catalina; Craciun, Liviu; Dragulescu, Emilian; Dudu, Dorin; Racolta, Petre Mihai; Voiculescu, Dana; Miron, N.

    2005-01-01

    To extend the nuclear physics applications and to perform the study of vacancy - type defects in metals, semiconductors, polymers, etc., we developed new positron annihilation techniques. In line with this goal we started a project for production of positron sources at the IFIN-HH U-120 Cyclotron. We made use of the nuclear reaction: 24 Mg(d,α) 22 Na with deuterons of 13 MeV energy. The paper present the main steps of this procedure which are: establishing the conditions required for 22 NaCl sources, for the parameters of reaction chamber and the characteristics of Mg target, parameters for the irradiation, radiochemical procedures for separation of Na from Mg after irradiation as well as the geometrical and mechanical requirements for the NaCl source. In the e + lifetime measurements the e + 'stop' signals are always provided by gamma - quanta generated by the e + e - annihilation and the 'start' signals are obtained from 'prompt' gamma - quanta emitted by the NaCl source (1.275 MeV photons). The 22 NaCl stock solution obtained by radiochemical separation will be kept in quartz sealed ampoules. (authors)

  12. Positron tomography. Methodology and applications

    International Nuclear Information System (INIS)

    Kellershohn, C.; Comar, D.

    1979-01-01

    Whereas single photon tomography provides a new and rewarding dimension to conventional nuclear medicine, positron tomography makes a new original approach possible of the analysis in vivo of fundamental biological and physiological processes. The main object of both is the sectional representation of the distribution of a radioactive indicator injected into the body system; compared with conventional detectors (gamma cameras and scintigraphic systems) they provide much greater accuracy in localization. The characteristics of these two methods can be presented schematically by comparing their respective advantages and drawbacks [fr

  13. Positron emission tomography takes lead

    International Nuclear Information System (INIS)

    Simms, R.

    1989-01-01

    Positron emission tomography (PET)'s ability to detect functional abnormalities before they manifest anatomically is examined and some of its most common applications are outlined. It is emphasised that when PET facility and Australian Nuclear Science and Technology Organization's national cyclotron are established at the Royal Prince Alfred Hospital, the availability of short-lived tracers such as oxygen 15, nitrogen 13 and fluorine 18 would improve the specificity of tests(e.g. for brain tumors or cardiac viability) further. Construction of the cyclotron will start shortly and is due to be completed and operating by the end of 1991

  14. Scattering data for modelling positron tracks in gaseous and liquid water

    International Nuclear Information System (INIS)

    Blanco, F; Roldán, A M; Krupa, K; García, G; McEachran, R P; Machacek, J R; Buckman, S J; Sullivan, J P; White, R D; Marjanović, S; Petrović, Z Lj; Brunger, M J; Chiari, L; Limão-Vieira, P

    2016-01-01

    We present in this study a self-consistent set of scattering cross sections for positron collisions with water molecules, in the energy range 0.1–10 000 eV, with the prime motivation being to provide data for modelling purposes. The structure of the database is based on a new model potential calculation, including interference terms, which provides differential and integral elastic as well as integral inelastic positron scattering cross sections for water molecules over the whole energy range considered here. Experimental and theoretical data available in the literature have been integrated into the database after a careful analysis of their uncertainties and their self-consistency. These data have been used as input parameters for a step-by-step Monte Carlo simulation procedure, providing valuable information on energy deposition, positron range, and the relative percentages of specific interactions (e.g. positronium formation, direct ionisation, electronic, vibrational and rotational excitations) in gaseous and liquid water. (paper)

  15. Theoretical aspects of positrons in imperfect solids

    International Nuclear Information System (INIS)

    Puska, M.J.

    1987-01-01

    The efficient use of positron annihilation in defect studies requires a deep understanding of the basic processes of positron-imperfect solid interaction. Three stages, i.e. thermalization, trapping by a defect, and the annihilation can be separated during the evolution of the interaction. The last two processes are the most relevant ones for the positron lifetime spectroscopy and they will be discussed in detail in this review. The complete solution of the problem of a localized positron interacting with the electrons around a defect requires the simultaneous self-consistent calculation of the electronic structure and the positron state. This is in principle possible in the two component density functional theory. However, the approximation, in which the electronic structure without the positron influence is used and the electron-positron correlation effects are described by local enhancement factors, has turned out to be feasible in practice and also accurate enough in predicting positron annihilation characteristics. Moreover, a non-self-consistent electron structure is sufficient in many cases. This enables an efficient calculation method in which the positron wave function can be solved in three dimensions for arbitrary defect geometries. Enhancement models for simple metals, transition metals, and semiconductors are represented. Thereafter, applications to vacancies, vacancy clusters, and vacancy-impurity complexes are shown. The positron trapping by defects is mediated by the transfer of the positron binding energy to the solid in the form of electron-hole pairs and phonons. The trapping phenomenon is discussed in the case of metals and semiconductors. Semiconductors are especially challenging because the existence of the energy gap makes the low energy electron-hole excitations impossible and because the defects have different charge states effecting strongly on the trapping rate. (author)

  16. Costo-beneficio en una unidad de cuidados intensivos neonatales

    OpenAIRE

    Rafael Amador Morán; Alberto Labrada Despaigne; Ana Campo González; Rosa Díaz Aguilar

    2011-01-01

    INTRODUCCIÓN. El Sistema Nacional de Salud de Cuba ha desarrollado un conjunto de reformas encaminadas a lograr una mayor eficiencia en la prestación de servicios, para preservar logros como la efectividad y la accesibilidad. El objetivo de esta investigación fue identificar los costos en la Unidad de Terapia Intensiva Neonatal del Hospital Ginecoobstétrico de Guanabacoa en el período de un año. MÉTODOS. Se realizó un estudio descriptivo prospectivo del período de enero a diciembre del 2009. ...

  17. Estado Confusional Agudo nas Unidades de Cuidados Intensivos

    OpenAIRE

    Santos, L; Alcântara, J

    1996-01-01

    As alterações do comportamento frequentemente observadas em doentes internados nas unidades de cuidados intensivos (UCI), podem ser adequadamente designadas, na maioria das vezes, por estado confusional agudo, o qual se caracteriza por: flutuação do estado de vigília, distúrbio do ciclo vigília-sono, défice de atenção e concentração, desorganização do pensamento, manifestado entre outras formas por discurso incoerente, distúrbios da percepção sob a forma de ilusões e/ou alucinações, desorient...

  18. Positrons trapped in polyethylene: Electric field effect

    International Nuclear Information System (INIS)

    Bertolaccini, M.; Bisi, A.; Gambarini, G.; Zappa, L.

    1978-01-01

    The intensity of the iot 2 -component of positrons annihilated in polyethylene is found to increase with increasing electric field, while the formation probability of the positron state responsible for this component remains independent of the field. (orig.) 891 HPOE [de

  19. Nanometer cavities studied by positron annihilation

    International Nuclear Information System (INIS)

    Mogensen, O.E.

    1992-01-01

    Positronium (Ps) is trapped in cavities in insulating solids, and the lifetime of ortho Ps is determined by the size of the cavity. The information on the properties of the cavities obtained by use of the standard slow positron beam and the 'normal' positron annihilation techniques is compared for several selected cases. (author)

  20. Positron prevacancy effects in pure annealed metals

    International Nuclear Information System (INIS)

    Smedskjaer, L.C.

    1981-06-01

    The low-temperature prevacancy effects sometimes observed with positrons in well-annealed high-purity metals are discussed. It is shown that these effects are not experimental artifacts, but are due to trapping of the positrons. It is suggested that dislocations are responsible for these trapping effects. 46 references, 5 figures

  1. Electron and Positron Stopping Powers of Materials

    Science.gov (United States)

    SRD 7 NIST Electron and Positron Stopping Powers of Materials (PC database for purchase)   The EPSTAR database provides rapid calculations of stopping powers (collisional, radiative, and total), CSDA ranges, radiation yields and density effect corrections for incident electrons or positrons with kinetic energies from 1 keV to 10 GeV, and for any chemically defined target material.

  2. LEP - Large Electron Positron Exhibition LEPFest 2000

    CERN Multimedia

    2000-01-01

    The Large Electron-Positron Collider (LEP) is 27 km long. Its four detectors (ALEPH, DELPHI, L3, OPAL) measure precisely what happens in the collisions of electrons and positrons. These conditions only exist-ed in the Universe when it was about 10 -10 sec old.

  3. Positron emission tomography of the heart

    International Nuclear Information System (INIS)

    Budinger, T.F.; Yano, Y.; Mathis, C.A.; Moyer, B.R.; Huesman, R.H.; Derenzo, S.E.

    1983-01-01

    Positron emission tomography (PET) offers the opportunity to noninvasively measure heart muscle blood perfusion, oxygen utilization, metabolism of fatty acids, sugars and amino acids. This paper reviews physiological principles which are basic to PET instrumentation for imaging the heart and gives examples of the application of positron emission tomography for measuring myocardial flow and metabolism. 33 references, 11 figures, 1 table

  4. Descriptions of positron defect analysis capabilities

    International Nuclear Information System (INIS)

    Howell, R.H.

    1994-10-01

    A series of descriptive papers and graphics appropriate for distribution to potential collaborators has been assembled. These describe the capabilities for defect analysis using positron annihilation spectroscopy. The application of positrons to problems in the polymer and semiconductor industries is addressed

  5. Applications of slow positrons to cancer research: Search for selectivity of positron annihilation to skin cancer

    International Nuclear Information System (INIS)

    Jean, Y.C.; Li Ying; Liu Gaung; Chen, Hongmin; Zhang Junjie; Gadzia, Joseph E.

    2006-01-01

    Slow positrons and positron annihilation spectroscopy (PAS) have been applied to medical research in searching for positron annihilation selectivity to cancer cells. We report the results of positron lifetime and Doppler broadening energy spectroscopies in human skin samples with and without cancer as a function of positron incident energy (up to 8 μm depth) and found that the positronium annihilates at a significantly lower rate and forms at a lower probability in the samples having either basal cell carcinoma (BCC) or squamous cell carcinoma (SCC) than in the normal skin. The significant selectivity of positron annihilation to skin cancer may open a new research area of developing positron annihilation spectroscopy as a novel medical tool to detect cancer formation externally and non-invasively at the early stages

  6. Applications of slow positrons to cancer research: Search for selectivity of positron annihilation to skin cancer

    Energy Technology Data Exchange (ETDEWEB)

    Jean, Y.C. [Department of Chemistry, University of Missouri-Kansas City, 205 Spenscer Chemistry Building, 5009 Rockhill Road, Kansas City, MO 64110 (United States)]. E-mail: jeany@umkc.edu; Li Ying [Department of Chemistry, University of Missouri-Kansas City, 205 Spenscer Chemistry Building, 5009 Rockhill Road, Kansas City, MO 64110 (United States); Liu Gaung [Department of Chemistry, University of Missouri-Kansas City, 205 Spenscer Chemistry Building, 5009 Rockhill Road, Kansas City, MO 64110 (United States); Chen, Hongmin [Department of Chemistry, University of Missouri-Kansas City, 205 Spenscer Chemistry Building, 5009 Rockhill Road, Kansas City, MO 64110 (United States); Zhang Junjie [Department of Chemistry, University of Missouri-Kansas City, 205 Spenscer Chemistry Building, 5009 Rockhill Road, Kansas City, MO 64110 (United States); Gadzia, Joseph E. [Dermatology, Department of Internal Medicine, University of Kansas Medical Center, Kansas City, KS 66103 (United States); Kansas Medical Clinic, Topeka, KS 66614 (United States)

    2006-02-28

    Slow positrons and positron annihilation spectroscopy (PAS) have been applied to medical research in searching for positron annihilation selectivity to cancer cells. We report the results of positron lifetime and Doppler broadening energy spectroscopies in human skin samples with and without cancer as a function of positron incident energy (up to 8 {mu}m depth) and found that the positronium annihilates at a significantly lower rate and forms at a lower probability in the samples having either basal cell carcinoma (BCC) or squamous cell carcinoma (SCC) than in the normal skin. The significant selectivity of positron annihilation to skin cancer may open a new research area of developing positron annihilation spectroscopy as a novel medical tool to detect cancer formation externally and non-invasively at the early stages.

  7. Positron annihilation studies on bulk metallic glass and high intensity positron beam developments

    International Nuclear Information System (INIS)

    Asoka-Kumar, P.; Stoeffl, W.

    2003-01-01

    Positron annihilation spectroscopy is an ideal probe to examine atomic scale open-volume regions in materials. Below, we summarize the recent results on studies of open-volume regions of a multicomponent Zr-Ti-Ni-Cu-Be bulk metallic glass. Our studies establish two types of open-volume regions, one group that is too shallow to trap positrons at room temperature and becomes effective only at low temperatures and the other group that localizes positrons at room temperature and is large enough to accommodate hydrogen. The second half of the paper will concentrate on the high intensity positron program at Lawrence Livermore National Laboratory. A new positron production target is under development and we are constructing two experimental end stations to accommodate a pulsed positron microprobe and an experiment on positron diffraction and holography. Important design considerations of these experiments will be described. (author)

  8. Positronic complexes with unnatural parity

    International Nuclear Information System (INIS)

    Bromley, M. W. J.; Mitroy, J.; Varga, K.

    2007-01-01

    The structure of the unnatural parity states of PsH, LiPs, NaPs, and KPs are investigated with the configuration interaction and stochastic variational methods. The binding energies (in hartree) are found to be 8.17x10 -4 , 4.42x10 -4 , 15.14x10 -4 , and 21.80x10 -4 , respectively. These states are constructed by first coupling the two electrons into a configuration which is predominantly 3 P e , and then adding a p-wave positron. All the active particles are in states in which the relative angular momentum between any pair of particles is at least L=1. The LiPs state is Borromean since there are no three-body bound subsystems (of the correct symmetry) of the (Li + , e - , e - , e + ) particles that make up the system. The dominant decay mode of these states will be radiative decay into a configuration that autoionizes or undergoes positron annihilation

  9. Integration

    DEFF Research Database (Denmark)

    Emerek, Ruth

    2004-01-01

    Bidraget diskuterer de forskellige intergrationsopfattelse i Danmark - og hvad der kan forstås ved vellykket integration......Bidraget diskuterer de forskellige intergrationsopfattelse i Danmark - og hvad der kan forstås ved vellykket integration...

  10. Positron annihilation spectroscopy in materials structure studies

    International Nuclear Information System (INIS)

    Grafutin, Viktor I; Prokop'ev, Evgenii P

    2002-01-01

    A relatively new method of materials structure analysis - positron annihilation spectroscopy (PAS) - is reviewed. Measurements of positron lifetimes, the determination of positron 3γ- and 2γ-annihilation probabilities, and an investigation of the effects of different external factors on the fundamental characteristics of annihilation constitute the basis for this promising method. The ways in which the positron annihilation process operates in ionic crystals, semiconductors, metals and some condensed matter systems are analyzed. The scope of PAS is described and its prospects for the study of the electronic and defect structures are discussed. The applications of positron annihilation spectroscopy in radiation physics and chemistry of various substances as well as in physics and chemistry of solutions are exemplified. (instruments and methods of investigation)

  11. Simulation of a Positron Source for CEBAF

    International Nuclear Information System (INIS)

    S. Golge; A. Freyberger; C. Hyde-Wright

    2007-01-01

    A positron source for the 6 GeV (or the proposed 12 GeV upgrade) recirculating linacs at Jefferson Lab is presented. The proposed 100nA CW positron source has several unique characteristics; high incident beam power (100kW), 10 MeV incident electron beam energy, CW incident beam and CW production. Positron production with 10 MeV electrons has several advantages; the energy is below neutron threshold so the production target will not become activated during use and the absolute energy spread is bounded by the low incident energy. These advantages are offset by the large angular distribution of the outgoing positrons. Results of simulations of the positron production, capture, acceleration and injection into the recirculating linac are presented. Energy flow and thermal management of the production target present a challenge and are included in the simulations

  12. Positron annihilation studies on high temperature superconductors

    International Nuclear Information System (INIS)

    Sundar, C.S.; Bharathi, A.

    1996-01-01

    A survey of the positron annihilation studies on high temperature superconductors (HTSC), with results drawn mainly from our work, is presented. These include results of the studies on the temperature dependence of positron lifetime across T c , which have been carried out in the whole gamut of oxide superconductors. These experimental results are discussed in conjunction with the results of theoretically calculated positron density distribution, and it is shown that the observed temperature dependence of lifetime is intimately linked to the probing of the Cu-O network by the positrons. Results on the investigation of oxygen defects, which play a crucial role in HTSC, are presented. The most significant contribution of positrons to HTSC relates to the investigation of Fermi surface and the results of these studies, drawn from literature, are indicated. Some of our recent results in other novel superconducting materials, viz., the fullerenes and borocarbides are also presented. (author). 69 refs., 15 figs

  13. Experimentation with low-energy positron beams

    International Nuclear Information System (INIS)

    Mills, A.P. Jr.

    1983-01-01

    The capability of studying the interactions of positrons with surfaces has recently been exploited by using ultra-high-vacuum techniques. The result has been a new understanding of how positrons interact with surfaces and because of this we are now able to make much stronger fluxes of slow positrons. The higher beam strengths in turn are opening up new possibilities for experimentation on surfaces and solids and for studying the atomic physics of positronium and positron-molecule scattering at low energies. The lectures are intended to review some of the history of this subject and to outline the present state of our knowledge of experimentation with low-energy positron beams. (orig./TW)

  14. Positron beam studies of transients in semiconductors

    International Nuclear Information System (INIS)

    Beling, C.D.; Ling, C.C.; Cheung, C.K.; Naik, P.S.; Zhang, J.D.; Fung, S.

    2006-01-01

    Vacancy-sensing positron deep level transient spectroscopy (PDLTS) is a positron beam-based technique that seeks to provide information on the electronic ionization levels of vacancy defects probed by the positron through the monitoring of thermal transients. The experimental discoveries leading to the concept of vacancy-sensing PDLTS are first reviewed. The major problem associated with this technique is discussed, namely the strong electric fields establish in the near surface region of the sample during the thermal transient which tend to sweep positrons into the contact with negligible defect trapping. New simulations are presented which suggest that under certain conditions a sufficient fraction of positrons may be trapped into ionizing defects rendering PDLTS technique workable. Some suggestions are made for techniques that might avoid the problematic electric field problem, such as optical-PDLTS where deep levels are populated using light and the use of high forward bias currents for trap filling

  15. Positron annihilation in vitreous silica glasses

    International Nuclear Information System (INIS)

    Uedono, Akira; Tanigawa, Shoichiro

    1993-01-01

    The annihilation characteristics of positrons in vitreous silica glasses (v-SiO 2 ) were studied by measurements of two-dimensional angular correlation of positron annihilation radiations and positron lifetime spectra. From the measurements, it was found that positrons and positronium (Ps) atoms mainly annihilate from trapped states by vacancy-type defects in v-SiO 2 . For v-SiO 2 specimens with cylindrical porous structures, annihilations of Ps with anisotropic momentum distributions were observed. This fact was attributed to the momentum uncertainty due to localization of Ps in a finite dimension of pores. This investigation showed possibilities for the detection of microstructures in v-SiO 2 by the positron annihilation technique. (author)

  16. O CUIDADO DE ENFERMAGEM EM UNIDADE DE TRANSPLANTE DE CÉLULAS-TRONCO HEMATOPOÉTICAS

    Directory of Open Access Journals (Sweden)

    Kaoana Lima

    2014-01-01

    Full Text Available En la unidad de trasplante de células madre hematopoyéticas cuidados de enfermería se presenta de manera diferente de otros servicios. Un enfoque descriptivo cualitativo tuvo como objetivo identificar las actividades de atención de enfermería de una unidad de trasplante clasificados de acuerdo con una referencia de funcións de la enfermera. La recolección de datos se realizó a través de la observación sistemática y el proceso de datos a través de análisis de contenido. Se identificaron tres posiciones para las enfermeras: clínica, de la gestión y de la visita, siendo la primera una gama más amplia de actividades de atención. El cuidado del mantenimiento de la vida se centran en la atención al paciente y el medio ambiente; le cuidado general técnico incluyen técnicas básicas como el manejo de instrumentos/medicamentos y la evaluación de los pacientes; y los especiales cubren determinadas actividades, como la recolección y la infusión de médula ósea, el cuidado del catéter central y de la transfusión de sangre y de la quimioterapia. Se concluyó que la atención sea integral, especializado y basado en los conocimientos adquiridos por formación complementaria y especialización.

  17. Comunidad universitaria de unidades de información especializadas en ciencias sociales: una experiencia exitosa

    Directory of Open Access Journals (Sweden)

    Carlos Eduard Cruz Meléndez

    2007-10-01

    Full Text Available Una de las características de los países de capitalismo dependiente – periférico es la escasa inversión en el campo de la investigación científica. En particular, en el ámbito de las ciencias sociales, esta situación se manifiesta en los muy limitados recursos para el desarrollo de centros de documentación y bibliotecas especializadas como soporte necesario para el desarrollo eficiente y eficaz de la investigación social sobre las realidades nacionales. La Comunidad Universitaria de Unidades de Información Especializadas en Ciencias Sociales es una experiencia exitosa en la educación superior, que provoca romper, a su vez, la lógica de mercantilizar la información, potenciando el uso de los limitados recursos que las universidades públicas costarricenses invierten en el campo de la información para investigación social, por medio de la coordinación de tareas y la integración de procesos técnicos entre distintas unidades de información participantes. Abstract One of the characeristics of peripherial capitalism dependant countries is the scant investment in scientific research particulary, in the field of Social Sciences; this situation is shown in the limited resources available for the development of specialized documentation centers and libraries as necessary support for the efficient and effective development of the social research on the national realities. The University Community of Specialized Information Units on Social Sciences is a successful experience in the university education field; this experience induces a break on the logic of commercialization of information by strengthening the use of the scarce resources that Costarican universities invest in this area. This action is carried out by means of coordinating the tasks and the integration of the technical processes between the different information units involved

  18. Performance analysis of the intense slow-positron beam at the NC State University PULSTAR reactor

    International Nuclear Information System (INIS)

    Moxom, J.; Hathaway, A.G.; Bodnaruk, E.W.; Hawari, A.I.; Xu, J.

    2007-01-01

    An intense positron beam, for application in nanophase characterization, is now under construction at the 1 MW PULSTAR nuclear reactor at North Carolina State University (NCSU). A tungsten converter/moderator is used, allowing positrons to be emitted from the surface with energies of a few electron volts. These slow positrons will be extracted from the moderator and formed into a beam by electrostatic lenses and then injected into a solenoidal magnetic field for transport to one of three experimental stations, via a beam switch. To optimize the performance of the beam and to predict the slow-positron intensity, a series of simulations were performed. A specialized Monte-Carlo routine was integrated into the charged-particle transport calculations to allow accounting for the probabilities of positron re-emission and backscattering from multiple-bank moderator/converter configurations. The results indicate that either a two-bank or a four-bank tungsten moderator/converter system is preferred for the final beam design. The predicted slow-positron beam intensities range from nearly 7x10 8 to 9x10 8 e + /s for the two-bank and the four-bank systems, respectively

  19. Positron transaxial emission tomograph with computerized image reconstruction

    International Nuclear Information System (INIS)

    Jatteau, Michel.

    1981-01-01

    This invention concerns a positron transaxial emission tomography apparatus with computerized image reconstruction, like those used in nuclear medicine for studying the metabolism of organs, in physiological examinations and as a diagnosis aid. The operation is based on the principle of the detection of photons emitted when the positrons are annihilated by impact with an electron. The appliance is mainly composed of: (a) - a set of gamma ray detectors distributed on a polygonal arrangement around the body area to be examined, (b) - circuits for amplifying the signals delivered by the gamma ray detectors, (c) - computers essentially comprising energy integration and discrimination circuits and provided at the output of the detectors for calculating and delivering, as from the amplified signals, information on the position and energy relative to each occurrence constituted by the detections of photons, (d) - time coincidence circuits for selecting by emission of detector validation signals, only those occurrences, among the ensemble of those detected, which effectively result from the annihilation of positrons inside the area examined, (e) - a data processing system [fr

  20. Positron deposition in plasmas by positronium beam ionization and transport of positrons in tokamak plasmas

    International Nuclear Information System (INIS)

    Murphy, T.J.

    1986-11-01

    In a recently proposed positron transport experiment, positrons would be deposited in a fusion plasma by forming a positronium (Ps) beam and passing it through the plasma. Positrons would be deposited as the beam is ionized by plasma ions and electrons. Radial transport of the positrons to the limiter could then be measured by detecting the gamma radiation produced by annihilation of positrons with electrons in the limiter. This would allow measurements of the transport of electron-mass particles and might shed some light on the mechanisms of electron transport in fusion plasmas. In this paper, the deposition and transport of positrons in a tokamak are simulated and the annihilation signal determined for several transport models. Calculations of the expected signals are necessary for the optimal design of a positron transport experiment. There are several mechanisms for the loss of positrons besides transport to the limiter. Annihilation with plasma electrons and reformation of positronium in positron-hydrogen collisions are two such processes. These processes can alter the signal and place restrictions ons on the plasma conditions in which positron transport experiments can be effectively performed

  1. [Integrity].

    Science.gov (United States)

    Gómez Rodríguez, Rafael Ángel

    2014-01-01

    To say that someone possesses integrity is to claim that that person is almost predictable about responses to specific situations, that he or she can prudentially judge and to act correctly. There is a closed interrelationship between integrity and autonomy, and the autonomy rests on the deeper moral claim of all humans to integrity of the person. Integrity has two senses of significance for medical ethic: one sense refers to the integrity of the person in the bodily, psychosocial and intellectual elements; and in the second sense, the integrity is the virtue. Another facet of integrity of the person is la integrity of values we cherish and espouse. The physician must be a person of integrity if the integrity of the patient is to be safeguarded. The autonomy has reduced the violations in the past, but the character and virtues of the physician are the ultimate safeguard of autonomy of patient. A field very important in medicine is the scientific research. It is the character of the investigator that determines the moral quality of research. The problem arises when legitimate self-interests are replaced by selfish, particularly when human subjects are involved. The final safeguard of moral quality of research is the character and conscience of the investigator. Teaching must be relevant in the scientific field, but the most effective way to teach virtue ethics is through the example of the a respected scientist.

  2. The proposed INEL intense slow positron source, beam line, and positron microscope facility

    International Nuclear Information System (INIS)

    Makowitz, H.; Denison, A.B.; Brown, B.

    1993-01-01

    A program is currently underway at the Idaho National Engineering Laboratory (INEL) to design and construct an Intense Slow Positron Beam Facility with an associated Positron Microscope. Positron beams have been shown to be valuable research tools and have potential application in industrial processing and nondestructive evaluation (microelectronics, etc.). The limit of resolution or overall usefulness of the technique has been limited because of lack of sufficient intensity. The goal of the INEL positron beam is ≥ 10 12 slow e+/s over a 0.03 cm diameter which represents a 10 3 to 10 4 advancement in beam current over existing beam facilities. The INEL is an ideal site for such a facility because of the nuclear reactors capable of producing intense positron sources and the personnel and facilities capable of handling high levels of radioactivity. A design using 58 Co with moderators and remoderators in conjunction with electrostatic positron beam optics has been reached after numerous computer code studies. Proof-of-principle electron tests have demonstrated the feasibility of the large area source focusing optics. The positron microscope development is occurring in conjunction with the University of Michigan positron microscope group. Such a Beam Facility and associated Intense Slow Positron Source (ISPS) can also be utilized for the generation and study of positron, and positron electron plasmas at ≤ 10 14 particles/cm 3 with plasma temperatures ranging from an eV to many keV, as well as an intense x-ray source via positron channeling radiation. The possibility of a tunable x-ray laser based on channeling positron radiation also exists. In this discussion the authors will present a progress report on various activities associated with the INEL ISPS

  3. Profilaxis para sangrado por ulceras de estrés en la unidad de cuidados intensivos

    Directory of Open Access Journals (Sweden)

    J.M. Avendaño-Reyes

    2014-01-01

    Conclusiones: La hospitalización en la unidad de cuidados intensivos por sí sola no justifica la profilaxis. Los IBP son por lo menos tan efectivos como los H2RA. Debemos individualizar el tratamiento de cada paciente en la unidad de cuidados intensivos, determinando el riesgo y evaluando la necesidad de comenzar la profilaxis.

  4. Improved positron emission tomography camera

    International Nuclear Information System (INIS)

    Mullani, N.A.

    1986-01-01

    A positron emission tomography camera having a plurality of rings of detectors positioned side-by-side or offset by one-half of the detector cross section around a patient area to detect radiation therefrom, and a plurality of scintillation crystals positioned relative to the photomultiplier tubes whereby each tube is responsive to more than one crystal. Each alternate crystal in the ring may be offset by one-half or less of the thickness of the crystal such that the staggered crystals are seen by more than one photomultiplier tube. This sharing of crystals and photomultiplier tubes allows identification of the staggered crystal and the use of smaller detectors shared by larger photomultiplier tubes thereby requiring less photomultiplier tubes, creating more scanning slices, providing better data sampling, and reducing the cost of the camera. (author)

  5. Positron emission tomography and migraine

    International Nuclear Information System (INIS)

    Chabriat, H.

    1992-01-01

    Positron emission tomography (PET) is a brain imaging technique that allows in vivo studies of numerous physiological parameters. There have been few PET studies in migraine patients. Cerebral blood flow changes with no variations in brain oxygen consumption have been reported in patients with prolonged neurologic manifestations during migraine attacks. Parenteral administration of reserpine during migraine headache has been followed by a fall in the overall cerebral uptake of glucose. The small sample sizes and a number of methodologic problems complicate the interpretation of these results. Recent technical advances and the development of new PET tracers can be expected to provide further insight into the pathophysiology of migraine. Today cerebral cortex 5 HT 2 serotonin receptors can be studied in migraine patients with PET

  6. High intensity positron program at LLNL

    International Nuclear Information System (INIS)

    Asoka-Kumar, P.; Howell, R.; Stoeffl, W.; Carter, D.

    1999-01-01

    Lawrence Livermore National Laboratory (LLNL) is the home of the world close-quote s highest current beam of keV positrons. The potential for establishing a national center for materials analysis using positron annihilation techniques around this capability is being actively pursued. The high LLNL beam current will enable investigations in several new areas. We are developing a positron microprobe that will produce a pulsed, focused positron beam for 3-dimensional scans of defect size and concentration with submicron resolution. Below we summarize the important design features of this microprobe. Several experimental end stations will be available that can utilize the high current beam with a time distribution determined by the electron linac pulse structure, quasi-continuous, or bunched at 20 MHz, and can operate in an electrostatic or (and) magnetostatic environment. Some of the planned early experiments are: two-dimensional angular correlation of annihilation radiation of thin films and buried interfaces, positron diffraction holography, positron induced desorption, and positron induced Auger spectroscopy. copyright 1999 American Institute of Physics

  7. Scintillators for positron emission tomography

    International Nuclear Information System (INIS)

    Moses, W.W.; Derenzo, S.E.

    1995-09-01

    Like most applications that utilize scintillators for gamma detection, Positron Emission Tomography (PET) desires materials with high light output, short decay time, and excellent stopping power that are also inexpensive, mechanically rugged, and chemically inert. Realizing that this ''ultimate'' scintillator may not exist, this paper evaluates the relative importance of these qualities and describes their impact on the imaging performance of PET. The most important PET scintillator quality is the ability to absorb 511 keV photons in a small volume, which affects the spatial resolution of the camera. The dominant factor is a short attenuation length (≤ 1.5 cm is required), although a high photoelectric fraction is also important (> 30% is desired). The next most important quality is a short decay time, which affects both the dead time and the coincidence timing resolution. Detection rates for single 511 keV photons can be extremely high, so decay times ≤ 500 ns are essential to avoid dead time losses. In addition, positron annihilations are identified by time coincidence so ≤5 ns fwhm coincidence pair timing resolution is required to identify events with narrow coincidence windows, reducing contamination due to accidental coincidences. Current trends in PET cameras are toward septaless, ''fully-3D'' cameras, which have significantly higher count rates than conventional 2-D cameras and so place higher demands on scintillator decay time. Light output affects energy resolution, and thus the ability of the camera to identify and reject events where the initial 511 keV photon has undergone Compton scatter in the patient. The scatter to true event fraction is much higher in fully-3D cameras than in 2-D cameras, so future PET cameras would benefit from scintillators with a 511 keV energy resolution < 10--12% fwhm

  8. High resolution computed tomography of positron emitters

    International Nuclear Information System (INIS)

    Derenzo, S.E.; Budinger, T.F.; Cahoon, J.L.; Huesman, R.H.; Jackson, H.G.

    1976-10-01

    High resolution computed transaxial radionuclide tomography has been performed on phantoms containing positron-emitting isotopes. The imaging system consisted of two opposing groups of eight NaI(Tl) crystals 8 mm x 30 mm x 50 mm deep and the phantoms were rotated to measure coincident events along 8960 projection integrals as they would be measured by a 280-crystal ring system now under construction. The spatial resolution in the reconstructed images is 7.5 mm FWHM at the center of the ring and approximately 11 mm FWHM at a radius of 10 cm. We present measurements of imaging and background rates under various operating conditions. Based on these measurements, the full 280-crystal system will image 10,000 events per sec with 400 μCi in a section 1 cm thick and 20 cm in diameter. We show that 1.5 million events are sufficient to reliably image 3.5-mm hot spots with 14-mm center-to-center spacing and isolated 9-mm diameter cold spots in phantoms 15 to 20 cm in diameter

  9. Amorphous silicon detectors in positron emission tomography

    Energy Technology Data Exchange (ETDEWEB)

    Conti, M. (Istituto Nazionale di Fisica Nucleare, Pisa (Italy) Lawrence Berkeley Lab., CA (USA)); Perez-Mendez, V. (Lawrence Berkeley Lab., CA (USA))

    1989-12-01

    The physics of the detection process is studied and the performances of different Positron Emission Tomography (PET) system are evaluated by theoretical calculation and/or Monte Carlo Simulation (using the EGS code) in this paper, whose table of contents can be summarized as follows: a brief introduction to amorphous silicon detectors and some useful equation is presented; a Tantalum/Amorphous Silicon PET project is studied and the efficiency of the systems is studied by Monte Carlo Simulation; two similar CsI/Amorphous Silicon PET projects are presented and their efficiency and spatial resolution are studied by Monte Carlo Simulation, light yield and time characteristics of the scintillation light are discussed for different scintillators; some experimental result on light yield measurements are presented; a Xenon/Amorphous Silicon PET is presented, the physical mechanism of scintillation in Xenon is explained, a theoretical estimation of total light yield in Xenon and the resulting efficiency is discussed altogether with some consideration of the time resolution of the system; the amorphous silicon integrated electronics is presented, total noise and time resolution are evaluated in each of our applications; the merit parameters {epsilon}{sup 2}{tau}'s are evaluated and compared with other PET systems and conclusions are drawn; and a complete reference list for Xenon scintillation light physics and its applications is presented altogether with the listing of the developed simulation programs.

  10. Amorphous silicon detectors in positron emission tomography

    International Nuclear Information System (INIS)

    Conti, M.; Perez-Mendez, V.

    1989-12-01

    The physics of the detection process is studied and the performances of different Positron Emission Tomography (PET) system are evaluated by theoretical calculation and/or Monte Carlo Simulation (using the EGS code) in this paper, whose table of contents can be summarized as follows: a brief introduction to amorphous silicon detectors and some useful equation is presented; a Tantalum/Amorphous Silicon PET project is studied and the efficiency of the systems is studied by Monte Carlo Simulation; two similar CsI/Amorphous Silicon PET projects are presented and their efficiency and spatial resolution are studied by Monte Carlo Simulation, light yield and time characteristics of the scintillation light are discussed for different scintillators; some experimental result on light yield measurements are presented; a Xenon/Amorphous Silicon PET is presented, the physical mechanism of scintillation in Xenon is explained, a theoretical estimation of total light yield in Xenon and the resulting efficiency is discussed altogether with some consideration of the time resolution of the system; the amorphous silicon integrated electronics is presented, total noise and time resolution are evaluated in each of our applications; the merit parameters ε 2 τ's are evaluated and compared with other PET systems and conclusions are drawn; and a complete reference list for Xenon scintillation light physics and its applications is presented altogether with the listing of the developed simulation programs

  11. Porous silicon investigated by positron annihilation

    International Nuclear Information System (INIS)

    Cruz, R.M. de la; Pareja, R.

    1989-01-01

    The effect of the anodic conversion in silicon single crystals is investigated by positron lifetime measurements. Anodization at constant current induces changes in the positron lifetime spectrum of monocrystalline silicon samples. It is found that theses changes are primarily dependent on the silicon resistivity. The annihilation parameter behaviour of anodized samples, treated at high temperature under reducing conditions, is also investigated. The results reveal that positron annihilation can be a useful technique to characterize porous silicon formed by anodizing as well as to investigate its thermal behaviour. (author)

  12. Positron emission tomography studies of brain receptors

    International Nuclear Information System (INIS)

    Maziere, B.; Maziere, M.

    1991-01-01

    Probing the regional distribution and affinity of receptors in the brain, in vivo, in human and non human primates has become possible with the use of selective ligands labelled with positron emitting radionuclides and positron emission tomography (PET). After describing the techniques used in positron emission tomography to characterize a ligand receptor binding and discussing the choice of the label and the limitations and complexities of the in vivo approach, the results obtained in the PET studies of various neurotransmission systems: dopaminergic, opiate, benzodiazepine, serotonin and cholinergic systems are reviewed

  13. High efficiency cyclotron trap assisted positron moderator

    OpenAIRE

    Gerchow, L.; Cooke, D. A.; Braccini, S.; Döbeli, M.; Kirch, K.; Köster, U.; Müller, A.; Van Der Meulen, N. P.; Vermeulen, C.; Rubbia, A.; Crivelli, P.

    2017-01-01

    We report the realisation of a cyclotron trap assisted positron tungsten moderator for the conversion of positrons with a broad keV- few MeV energy spectrum to a mono-energetic eV beam with an efficiency of 1.8(2)% defined as the ratio of the slow positrons divided by the $\\beta^+$ activity of the radioactive source. This is an improvement of almost two orders of magnitude compared to the state of the art of tungsten moderators. The simulation validated with this measurement suggests that usi...

  14. Characteristics of the positron annihilation process in the matter

    International Nuclear Information System (INIS)

    Dryzek, J.

    2000-01-01

    In this report the positrons annihilation spectroscopy, as a method for the matter study is described. The interaction of positrons of high as well as thermal energies are discussed and different models of mentioned interactions are presented. Special attention is paid for positrons interaction with crystal lattice and its defects. The influence of positron beams characteristics on measured values are also discussed

  15. Ações para o enfrentamento da violência contra a mulher em duas unidades de atenção primária à saúde no município do Rio de Janeiro

    Directory of Open Access Journals (Sweden)

    Tatiana dos Santos Borsoi

    2009-03-01

    Full Text Available Propôs-se conhecer e discutir ações voltadas para o enfrentamento da violência doméstica no âmbito do Programa de Assistência Integral à Saúde da Mulher. Para tanto, buscou-se levantar e comparar as práticas profissionais em duas unidades de saúde do município do Rio de Janeiro, sendo uma delas referência para o atendimento às vítimas de violência. Foram realizadas oito entrevistas em profundidade, semiestruturadas, com profissionais das equipes do Programa de Saúde da Mulher. Embora ambas as unidades identifiquem frequentemente usuárias vítimas de violência doméstica, na unidade de referência os profissionais se mostraram mais preparados para identificar o problema quando este não se apresenta de forma explícita e para desenvolver ações de acolhimento dentro da própria unidade de saúde. O que diferencia as duas unidades é o encaminhamento dado ao problema, relacionado com a forma como cada serviço entende a violência como demanda inerente também à esfera da saúde.

  16. Casuística de uma unidade de Ortogeriatria

    Directory of Open Access Journals (Sweden)

    Mónica Brinquinho

    2017-12-01

    Full Text Available A fratura do fémur está associada a importante morbimortalidade, sendo que menos de metade dos doentes regressam ao seu nível prévio de autonomia. Uma abordagem multidisciplinar permite uma reabilitação funcional imediata, bem como melhor gestão de comorbilidades, prevenção de fraturas secundárias e das quedas. Objetivos: apresentação da casuística de 3 meses de uma unidade de Ortogeriatria. Material e métodos: Descreve-se a demografia dos doentes admitidos, grau de dependência funcional, comorbilidades, intercorrências, tempo de internamento, mortalidade e destino à data de alta. O ganho de funcionalidade no internamento foi também avaliado. Resultados: De outubro/2015 a janeiro/2016 foram admitidos 66 doentes após cirurgia de fratura proximal do fémur. Média de idades foi 82,94±6,93 anos; 86% eram mulheres. O tempo de internamento foi de 7,8±4,68 dias, sendo o tempo médio para realizar cirurgia de 3±3,37 dias. Quanto ao grau de funcionalidade prévio 47% eram Katz A; à admissão 85% tinham mRankin ≤3. Identificaram-se várias comorbilidades em 89% dos doentes; nas intercorrências, a mais frequente foi a anemia (53%. Houve um ganho na funcionalidade relativamente à admissão na unidade de 75,8% e em relação ao estado funcional anterior ao evento de 19,7%. Setenta e um porcento dos doentes tiveram alta para o domicílio; a taxa de mortalidade foi de 1,52%. Conclusões: A unidade demonstrou eficiência no controlo das comorbilidades, reduzidas complicações e baixa mortalidade. Registou-se um ganho funcional comparando com a admissão em 3 em cada 4 doentes e em relação ao estado basal prévio em 1 em cada 5 doentes.

  17. Fatores associados à morte materna em unidade de terapia intensiva

    Directory of Open Access Journals (Sweden)

    Suzanne Vieira Saintrain

    Full Text Available RESUMO Objetivo: Identificar os fatores associados à morte materna em pacientes internadas em unidade de terapia intensiva. Métodos: Estudo do tipo transversal realizado em unidade de terapia intensiva materna. Foram selecionados todos os prontuários de pacientes admitidas no período de janeiro de 2012 a dezembro de 2014. O critério de inclusão foi todas as pacientes obstétricas e puérperas, e o de exclusão as com diagnóstico de mola hidatiforme, gravidez ectópica e anembrionada, e as internadas por causas não obstétricas. Foi realizada análise comparativa entre os desfechos óbito e alta hospitalar. Resultados: Foram incluídas 373 pacientes, com idade entre 13 a 45 anos. As causas de internação na unidade de terapia intensiva foram síndromes hipertensivas relacionadas à gestação, cardiopatias, insuficiência respiratória e sepse; as complicações foram lesão renal aguda (24,1%, hipotensão (15,5%, hemorragia (10,2% e sepse (6,7%. Ocorreram 28 óbitos (7,5%. As causas de óbito foram choque hemorrágico, falência múltipla de órgãos, insuficiência respiratória e sepse. Os fatores de risco independentes para óbito foram lesão renal aguda (OR = 6,77, hipotensão (OR = 15,08 e insuficiência respiratória (OR = 3,65. Conclusão: A frequência de óbitos foi baixa. Lesão renal aguda, hipotensão e insuficiência respiratória foram os fatores de risco independentes associados à mortalidade materna.

  18. On the average luminosity of electron positron collider and positron-producing energy

    International Nuclear Information System (INIS)

    Xie Jialin

    1985-01-01

    In this paper, the average luminosity of linac injected electron positron collider is investigated from the positron-producing energy point of view. When the energy of the linac injector is fixed to be less than the operating energy of the storage ring, it has been found that there exists a positron-producing energy to give optimum average luminosity. Two cases have been studied, one for an ideal storage ring with no single-beam instability and the other for practical storage ring with fast head-tail instability. The result indicates that there is a positron-producing energy corresponding to the minimum injection time, but this does not correspond to the optimum average luminosity for the practical storage rings. For Beijing Electron Positron Collider (BEPC), the positron-producing energy corresponding to the optimum average luminosity is about one tenth of the total injector energy

  19. Positron annihilation in a metal-oxide semiconductor studied by using a pulsed monoenergetic positron beam

    Science.gov (United States)

    Uedono, A.; Wei, L.; Tanigawa, S.; Suzuki, R.; Ohgaki, H.; Mikado, T.; Ohji, Y.

    1993-12-01

    The positron annihilation in a metal-oxide semiconductor was studied by using a pulsed monoenergetic positron beam. Lifetime spectra of positrons were measured as a function of incident positron energy for a polycrystalline Si(100 nm)/SiO2(400 nm)/Si specimen. Applying a gate voltage between the polycrystalline Si film and the Si substrate, positrons implanted into the specimen were accumulated at the SiO2/Si interface. From the measurements, it was found that the annihilation probability of ortho-positronium (ortho-Ps) drastically decreased at the SiO2/Si interface. The observed inhibition of the Ps formation was attributed to an interaction between positrons and defects at the SiO2/Si interface.

  20. A transmission positron microscope and a scanning positron microscope being built at KEK, Japan

    International Nuclear Information System (INIS)

    Doyama, M.; Inoue, M.; Kogure, Y.; Kurihara, T.; Yagishita, A.; Shidara, T.; Nakahara, K.; Hayashi, Y.; Yoshiie, T.

    2001-01-01

    This paper reports the plans of positron microscopes being built at KEK (High Energy Accelerator Research Organization), Tsukuba, Japan improving used electron microscopes. The kinetic energies of positron produced by accelerators or by nuclear decays have not a unique value but show a spread over in a wide range. Positron beam will be guided near electron microscopes, a transmission electron microscope (JEM100S) and a scanning electron microscope (JSM25S). Positrons are slowed down by a tungsten foil, accelerated and focused on a nickel sheet. The monochromatic focused beam will be injected into an electron microscope. The focusing of positrons and electrons is achieved by magnetic system of the electron microscopes. Imaging plates are used to record positron images for the transmission electron microscope. (orig.)

  1. Time-dependent behavior of positrons in noble gases

    International Nuclear Information System (INIS)

    Wadehra, J.M.

    1990-01-01

    Both equilibrium and nonequilibrium behaviors of positrons in several noble gases are reviewed. Our novel procedure for obtaining the time-dependent behavior of various swarm parameters -- such as the positron drift velocity, average positron energy, positron annihilation rate (or equivalently Z eff ) etc. -- for positrons in pure ambient gases subjected to external electrostatic fields is described. Summaries of time-dependent as well as electric field-dependent results for positron swarms in various noble gases are presented. New time-dependent results for positron swarms in neon are also described in detail. 36 refs., 4 figs., 3 tabs

  2. Positron imaging system with improved count rate and tomographic capability

    International Nuclear Information System (INIS)

    Muehllehner, G.; Buchin, M.P.

    1980-01-01

    Improvements to a positron camera imaging system are described. A pair of Angear-type scintillation cameras serve as the detectors, each camera being positioned on opposite sides of the organ of interest. Pulse shaping circuits reduce the pulse duration below 900 nanoseconds and the integration time below 500 noneseconds, improving the count rate capability and the counting statistics of the system and thus the image quality and processing speed. The invention also provides means for rotating the opposed camera heads about an axis which passes through the organ of interest. The cameras do not use collimators, and are capable of accepting radiation travelling in planes not perpendicular to the scintillation crystals. (LL)

  3. Application of mathematical removal of positron range blurring in positron emission tomography

    International Nuclear Information System (INIS)

    Haber, S.F.; Derenzo, S.E.; Uber, D.

    1990-01-01

    The range of positrons in tissue is an important limitation to the ultimate spatial resolution achievable in positron emission tomography. In this work the authors have applied a Fourier deconvolution technique to remove range blurring in images taken by the Donner 600-crystal positron tomograph. Using phantom data, the authors have found significant improvement in the image quality and the FWHM for both 68 Ga and 82 Rb. These were successfully corrected so that the images and FWHM almost matched those of 18 F which has negligible positron range. However, statistical noise was increased by the deconvolution process and it was not practical to recover the full spatial resolution of the tomograph

  4. Positron and positronium annihilation in silica-based thin films studied by a pulsed positron beam

    International Nuclear Information System (INIS)

    Suzuki, R.; Ohdaira, T.; Kobayashi, Y.; Ito, K.; Shioya, Y.; Ishimaru, T.

    2003-01-01

    Positron and positronium annihilation in silica-based thin films has been investigated by means of measurement techniques with a monoenergetic pulsed positron beam. The age-momentum correlation study revealed that positron annihilation in thermally grown SiO 2 is basically the same as that in bulk amorphous SiO 2 while o-Ps in the PECVD grown SiCOH film predominantly annihilate with electrons of C and H at the microvoid surfaces. We also discuss time-dependent three-gamma annihilation in porous low-k films by two-dimensional positron annihilation lifetime spectroscopy

  5. Generation of an intense pulsed positron beam and its applications

    International Nuclear Information System (INIS)

    Suzuki, Ryoichi; Mikado, Tomohisa; Ohgaki, Hideaki; Chiwaki, Mitsukuni; Yamazaki, Tetsuo; Kobayashi, Yoshinori.

    1994-01-01

    A positron pulsing system for an intense positron beam generated by an electron linac has been developed at the Electrotechnical Laboratory. The pulsing system generates an intense pulsed positron beam of variable energy and variable pulse period. The pulsed positron beam is used as a non destructive probe for various materials researches. In this paper, we report the present status of the pulsed positron beam and its applications. (author)

  6. Matrix Isolation Spectroscopy Applied to Positron Moderatioin in Cryogenic Solids

    Science.gov (United States)

    2011-07-01

    Current Positron Applications • 2-γ decay exploited in Positron Emission Tomography (PET) scanners. • Positrons localize & annihilate preferentially at...Air Force  Eglin Air Force Base AFRL-RW-EG-TP-2011-024 Matrix Isolation Spectroscopy Applied to Positron Moderation in Cryogenic Solids Distribution... Spectroscopy Applied to Positron Moderation in Cryogenic Solids 5a. CONTRACT NUMBER 5b. GRANT NUMBER 62602F 5c. PROGRAM ELEMENT NUMBER 6

  7. Bulk Materials Analysis Using High-Energy Positron Beams

    International Nuclear Information System (INIS)

    Glade, S C; Asoka-Kumar, P; Nieh, T G; Sterne, P A; Wirth, B D; Dauskardt, R H; Flores, K M; Suh, D; Odette, G.R.

    2002-01-01

    This article reviews some recent materials analysis results using high-energy positron beams at Lawrence Livermore National Laboratory. We are combining positron lifetime and orbital electron momentum spectroscopic methods to provide electron number densities and electron momentum distributions around positron annihilation sites. Topics covered include: correlation of positron annihilation characteristics with structural and mechanical properties of bulk metallic glasses, compositional studies of embrittling features in nuclear reactor pressure vessel steel, pore characterization in Zeolites, and positron annihilation characteristics in alkali halides

  8. Characterization of lacunar defects by positrons annihilation

    CERN Document Server

    Barthe, M F; Blondiaux, G

    2003-01-01

    Among the nondestructive methods for the study of matter, the positrons annihilation method allows to sound the electronic structure of materials by measuring the annihilation characteristics. These characteristics depend on the electronic density as seen by the positon, and on the electron momentums distribution which annihilate with the positon. The positon is sensible to the coulombian potential variations inside a material and sounds preferentially the regions away from nuclei which represent potential wells. The lacunar-type defects (lack of nuclei) represent deep potential wells which can trap the positon up to temperatures close to the melting. This article describes the principles of this method and its application to the characterization of lacunar defects: 1 - positrons: matter probes (annihilation of electron-positon pairs, annihilation characteristics, positrons sources); 2 - positrons interactions in solids (implantation profiles, annihilation states, diffusion and trapping, positon lifetime spec...

  9. Stress evaluation at the ILC positron source

    Energy Technology Data Exchange (ETDEWEB)

    Ushakov, Andriy; Moortgat-Pick, Gudrid [Universitaet Hamburg, II. Institut fuer Theoretische Physik, Luruper Chaussee 149, 22761 Hamburg (Germany); Riemann, Sabine; Dietrich, Felix [Deutsches Elektronen-Synchrotron (DESY), Standort Zeuthen, Platanenallee 6, 15738 Zeuthen (Germany); Aulenbacher, Kurt; Tyukin, Valery; Heil, Philipp [Johannes Gutenberg-Universitaet Mainz, Institut fuer Kernphysik, Johann-Joachim-Becher-Weg 45, 55128 Mainz (Germany)

    2016-07-01

    High luminosity is required at future Linear Colliders which is particularly challenging for all corresponding positron sources. At the International Linear Collider (ILC), polarized positrons are obtained from electron-positron pairs by converting high-energy photons produced by passing the high-energy main electron beam through a helical undulator. The conversion target undergoes cyclic stress with high peak values. To distribute the thermal load, the target is designed as wheel spinning in vacuum with 100 m/s. However, the cyclic stress over long time at high target temperatures could exceed the fatigue stress limit. In the talk, an overview of the ILC positron source is given. The prospects to study material parameters under conditions as expected at the ILC are discussed.

  10. Compact Positron Tomograph for Prostate Imaging

    National Research Council Canada - National Science Library

    Derenzo, Stephen

    2003-01-01

    The goal of this project is to construct a functioning compact positron tomography, whose geometry is optimized for detecting prostate tumors with molecular tracers such as 11Ccholine (carbon-11 choline...

  11. Compact Positron Tomograph for Prostate Imaging

    National Research Council Canada - National Science Library

    Huber, Jennifer

    2004-01-01

    The goal of this project is to construct a functioning compact positron tomograph, whose geometry is optimized for detecting prostate tumors with molecular tracers such as 11Ccholine (carbon-11 choline...

  12. Compact Positron Tomograph for Prostate Imaging

    National Research Council Canada - National Science Library

    Huber, Jennifer S

    2005-01-01

    The goal of this project is to construct a functioning compact positron tomograph, whose geometry is optimized for detecting prostate tumors with molecular tracers such as 11Ccholine (carbon-11 choline...

  13. A Magnetic Transport Middle Eastern Positron Beam

    International Nuclear Information System (INIS)

    Al-Qaradawi, I.Y.; Britton, D.T.; Rajaraman, R.; Abdulmalik, D.

    2008-01-01

    A magnetically guided slow positron beam is being constructed at Qatar University and is currently being optimised for regular operation. This is the first positron beam in the Middle East, as well as being the first Arabic positron beam. Novel features in the design include a purely magnetic in-line deflector, working in the solenoid guiding field, to eliminate un-moderated positrons and block the direct line of sight to the source. The impact of this all-magnetic transport on the Larmor radius and resultant beam characteristics are studied by SIMION simulations for both ideal and real life magnetic field variations. These results are discussed in light of the coupled effect arising from electrostatic beam extraction

  14. Polymeric membrane studied using slow positron beam

    International Nuclear Information System (INIS)

    Hung, W.-S.; Lo, C.-H.; Cheng, M.-L.; Chen Hongmin; Liu Guang; Chakka, Lakshmi; Nanda, D.; Tung, K.-L.; Huang, S.-H.; Lee, Kueir-Rarn; Lai, J.-Y.; Sun Yiming; Yu Changcheng; Zhang Renwu; Jean, Y.C.

    2008-01-01

    A radioisotope slow positron beam has been built at the Chung Yuan Christian University in Taiwan for the research and development in membrane science and technology. Doppler broadening energy spectra and positron annihilation lifetime have been measured as a function of positron energy up to 30 keV in a polyamide membrane prepared by the interfacial polymerization between triethylenetetraamine (TETA) and trimesoyl chloride (TMC) on modified porous polyacrylonitrile (PAN) asymmetric membrane. The multilayer structures and free-volume depth profile for this asymmetric membrane system are obtained. Positron annihilation spectroscopy coupled with a slow beam could provide new information about size selectivity of transporting molecules and guidance for molecular designs in polymeric membranes

  15. New Possibilities of Positron-Emission Tomography

    Science.gov (United States)

    Volobuev, A. N.

    2018-01-01

    The reasons for the emergence of the angular distribution of photons generated as a result of annihilation of an electron and a positron in a positron-emission tomograph are investigated. It is shown that the angular distribution of the radiation intensity (i.e., the probability of photon emission at different angles) is a consequence of the Doppler effect in the center-of-mass reference system of the electron and the positron. In the reference frame attached to the electron, the angular distribution of the number of emitted photons does not exists but is replaced by the Doppler shift of the frequency of photons. The results obtained in this study make it possible to extend the potentialities of the positron-emission tomograph in the diagnostics of diseases and to obtain additional mechanical characteristics of human tissues, such as density and viscosity.

  16. Positron lifetime experiments in indium selenide

    International Nuclear Information System (INIS)

    Cruz, R.M. de la; Pareja, R.

    1988-01-01

    Positron lifetime experiments have been performed on as-grown samples which had been isochronally annealed up to 820 K and plastically deformed and these experiments yield a constant lifetime of 282 ± 2 ps which is attributed to bulk positron states in InSe. Electron-irradiated samples exhibit a two-component spectrum, revealing the presence of positron traps which anneal out at about 330 K. The nature of the native shallow donors in InSe is discussed in the light of the results, which support the idea that native donor centres are probably interstitial In atoms rather than Se vacancies. Positron trapping observed in the electron-irradiated samples is attributed to defects related to In vacancies. (author)

  17. Positron kinetics in an idealized PET environment

    Science.gov (United States)

    Robson, R. E.; Brunger, M. J.; Buckman, S. J.; Garcia, G.; Petrović, Z. Lj.; White, R. D.

    2015-08-01

    The kinetic theory of non-relativistic positrons in an idealized positron emission tomography PET environment is developed by solving the Boltzmann equation, allowing for coherent and incoherent elastic, inelastic, ionizing and annihilating collisions through positronium formation. An analytic expression is obtained for the positronium formation rate, as a function of distance from a spherical source, in terms of the solutions of the general kinetic eigenvalue problem. Numerical estimates of the positron range - a fundamental limitation on the accuracy of PET, are given for positrons in a model of liquid water, a surrogate for human tissue. Comparisons are made with the ‘gas-phase’ assumption used in current models in which coherent scattering is suppressed. Our results show that this assumption leads to an error of the order of a factor of approximately 2, emphasizing the need to accurately account for the structure of the medium in PET simulations.

  18. Elastic scattering of slow positrons by helium

    International Nuclear Information System (INIS)

    Amusia, M.Ya.; Cherepkov, N.A.; Chernysheva, L.V.; Shapiro, S.G.

    1976-01-01

    The s-, p-, d- and f-wave phaseshifts for elastic scattering of slow positrons by He are calculated using a simplified version of the random phase approximation with exchange, with virtual positronium formation effect taken into account. (author)

  19. Radiopharmaceutical chemistry for positron emission tomography

    NARCIS (Netherlands)

    Elsinga, PH

    Radiopharmaceutical chemistry includes the selection, preparation, and preclinical evaluation of radiolabeled compounds. This paper describes selection criteria for candidates for positron emission tomography (PET) investigations. Practical aspects of nucleophilic and electrophilic

  20. Ionization and positron emission in giant quasiatoms

    International Nuclear Information System (INIS)

    Soff, G.; Reinhardt, J.; Reus, T. de; Wietschorke, K.H.; Schaefer, A.; Mueller, B.; Greiner, W.; Mueller, U.; Schlueter, P.

    1985-07-01

    Electron excitation processes in superheavy quasiatoms are treated within a relativistic framework. Theoretical results on K-hole production rates as well as delta-electron and positron spectra are compared with experimental data. It is demonstrated that the study of heavy ion collisions with nuclear time delay promises a signature for the spontaneous positron formation in overcritical systems. Corresponding experimental results are confronted with our theoretical hypothesis. Recent speculations on the origin of the observed peak structures in positron spectra are critically reviewed. Atomic excitations are also employed to obtain information on the course of a nuclear reaction. Using a semiclassical picture we calculate the emission of delta-electrons and positrons in deep-inelastic nuclear reactions. Furthermore some consequences of conversion processes in giant systems are investigated. (orig.)

  1. Radiation damage analysis by positron annihilation spectroscopy

    International Nuclear Information System (INIS)

    Siegel, R.W.

    1979-01-01

    The application of positron annihilation spectroscopy (PAS) to the characterization and study of defects in metals produced by radiation damage is discussed. The physical basis for the positron annihilation techniques (lifetime, Doppler broadening, angular correlation) is introduced and the techniques briefly described. Some examples of the application of PAS to radiation damage analysis are presented with a view toward elucidating the particular advantages of PAS over more traditional defect characterization techniques

  2. Design studies for the Positron Factory

    International Nuclear Information System (INIS)

    Okada, S.; Sunaga, H.; Kaneko, H.; Masuno, S.; Kawasuso, A.; Sakai, T.; Takizawa, H.; Yotsumoto, K.; Honda, Y.; Tagawa, S.

    1996-01-01

    In the design study for the Positron Factory, a feasibility of simultaneous extraction of multi-channel monoenergetic positron beams, which had been proposed at the previous conference (Linac 94), was demonstrated by an experiment using an electron linac. On the basis of the experimental result, an efficient moderator structure, which is composed of honeycomb-like assembled moderator foils and reflectors, is proposed. (author)

  3. Positron annihilation studies in lysozyme and catalase

    International Nuclear Information System (INIS)

    Rohilla, Y.; Singh, K.P.; Roy Choudhury, S.; Jain, P.C.

    1992-01-01

    Positron annihilation studies have been carried out in two enzymes, lysozyme and catalase. Temperature dependence of the positron lifetimes in these two enzymes has been investigated. The results explained in terms of the free volume model and fluctuations between different conformational micro states of enzyme structures provide a new insight into the mechanism of bio-activity of these enzymes. (author). 15 refs., 4 figs

  4. Radiation damage analysis by positron annihilation spectroscopy

    International Nuclear Information System (INIS)

    Siegel, R.W.

    1982-01-01

    Positron annihilation spectroscopy (PAS) has in recent years become a valuable new tool for investigating defects in metals. The ability of the positron to localize in a trapped state at various defect sites, in which the positron annihilates with unique characteristics, has enabled the positron to be used as a localized probe of these defect sites. Several reviews of the application of PAS to the study of defects in metals have been published, as have more general treatises on the applications of positron annihilation to the study of solids. PAS has made, and has considerably greater potential for, a significant contribution to radiation damage analysis in two areas of importance: (1) the determination of atomic-defect properties, a knowledge of which is necessary for the modeling required to couple the results of model experiments using electron and ion irradiation with the expected irradiation conditions of reactor systems, and (2) the monitoring and characterization of irradiation-induced microstructure development. A unique aspect of PAS for radiation damage analysis is the defect specificity of the annihilation characteristics of a trapped positron. In addition to its value as an independent analytical tool, PAS can be a useful complement to more traditional techniques for defect studies

  5. Positron annihilation studies on high temperature superconductors

    International Nuclear Information System (INIS)

    Sundar, C.S.; Bharathi, A.

    1991-01-01

    The results of positron annihilation measurements as a function of temperature, across Tc, in a variety of high temperature superconductors such as Y-Ba-Cu-O (Y1237), Y-Ba-Cu-O (Y1248), Bi-Sr-Ca-Cu-O, Tl-Ba-Ca-Cu-O, Ba-K-Bi-O and Nd-Ce-Cu-O are presented. It is shown that the variation of annihilation parameters in the superconducting state is correlated with the diposition of the positron density distribution with respect to the superconducting CuO planes. An increase in positron lifetime is observed below Tc when the positrons probe the CuO planes whereas a decrease in lifetime is observed when the positron density overlaps predominantly with the apical oxygen atom. With this correlation, the different temperature variation of annihilation parameters, seen in the various high temperature superconductors, is understood in terms of a local charge transfer from the planar oxygen atom to the apical oxygen atom. The significance of these results in the context of various theoretical models of high temperature superconductivity is discussed. In addition, the application of positron annihilation spectroscopy to the study of oxygen defects in the Y-Ba-Cu-O, Bi-Sr-Ca-Cu-O and Nd-Ce-Cu-O is presented. (author). 53 refs., 17 figs., 2 tabs

  6. Undulator-based production of polarized positrons

    Energy Technology Data Exchange (ETDEWEB)

    Alexander, G. [Tel-Aviv Univ. (Israel); Barley, J. [Cornell Univ., Ithaca, NY (United States); Batygin, Y. [SLAC, Menlo Park, CA (US)] (and others)

    2009-05-15

    Full exploitation of the physics potential of a future International Linear Collider will require the use of polarized electron and positron beams. Experiment E166 at the Stanford Linear Accelerator Center (SLAC) has demonstrated a scheme in which an electron beam passes through a helical undulator to generate photons (whose first-harmonic spectrum extended to 7.9 MeV) with circular polarization, which are then converted in a thin target to generate longitudinally polarized positrons and electrons. The experiment was carried out with a one-meter-long, 400-period, pulsed helical undulator in the Final Focus Test Beam (FFTB) operated at 46.6 GeV. Measurements of the positron polarization have been performed at five positron energies from 4.5 to 7.5 MeV. In addition, the electron polarization has been determined at 6.7MeV, and the effect of operating the undulator with a ferrofluid was also investigated. To compare the measurements with expectations, detailed simulations were made with an upgraded version of GEANT4 that includes the dominant polarization-dependent interactions of electrons, positrons, and photons with matter. The measurements agree with calculations, corresponding to 80% polarization for positrons near 6 MeV and 90% for electrons near 7 MeV. (orig.)

  7. Results on positron diffusion in Si

    International Nuclear Information System (INIS)

    Nielsen, B.; Lynn, K.G.; Vehanen, A.; Schultz, P.J.

    1984-10-01

    Positron diffusion in Si(100) and Si(111) has been measured using a variable energy positron beam. The diffusion related parameter, E 0 is found to be 4.2 +- 0.2 keV, significantly longer than previously reported values. The positron diffusion coefficient is estimated at D/sub +/ = 2.3 +- 0.4 cm 2 /sec, the uncertainty arising mainly from the characteristics of the assumed positron implantation profile. A drastic reduction in E 0 is found after heating the sample to 1300 0 K, showing that previously reported low values of E 0 are associated with the thermal history of the sample. A high sensitivity to defects introduced by low energy ion bombardment is found, and the defect recovery was followed during heat treatments. Reconstruction of the Si(111) surface into the so-called 7 x 7 structure had no detectable influence on the positron diffusion behavior. No changes in the positron diffusion was observed after covering the surface with atomic hydrogen. However the yield of positronium formation at the surface was enhanced, attributed to an increased density of states at the surface

  8. Production and applications of positron microbeams

    International Nuclear Information System (INIS)

    Brandes, G.R.; Canter, K.F.; Horsky, T.N.; Lippel, P.H.; Mills, A.P. Jr.

    1989-01-01

    The production of a positron microbeam using the high-brightness beam developed at Brandeis University and possible applications of this microbeam to spatially resolved defect studies and positron microscopy are reviewed. The high-brightness beam consists of a W(110) primary moderator and two remoderation stages which provide a 500-fold increase in brightness. With this brightness increase and microbeam optics, we are able to form a 12 μm FWHM beam (48 mrad pencil half-angle) at 5 keV beam energy. The well characterised small-diameter beam is particularly adaptable for determining defect concentration and structure, both laterally and in a depth-profiling mode. In the case of a transmission positron microscope or a positron re-emission microscope operating in a high-magnification mode, efficient image formation requires the use of a microbeam to maximise the number of positrons in the area being imaged. Results of the scanning microbeam tests and the application of a microbeam to positron microscopy and defect studies are reviewed. (author)

  9. Generation of a high-brightness pulsed positron beam for the Munich scanning positron microscope

    Energy Technology Data Exchange (ETDEWEB)

    Piochacz, Christian

    2009-11-20

    Within the present work the prerequisites for the operation of the Munich scanning positron microscope (SPM) at the high intense neutron induced positron source Munich (NEPOMUC) were established. This was accomplished in two steps: Firstly, a re-moderation device was installed at the positron beam facility NEPOMUC, which enhances the brightness of the positron beam for all connected experiments. The second step was the design, set up and initial operation of the SPM interface for the high efficient conversion of the continuous beam into a bunched beam. The in-pile positron source NEPOMUC creates a positron beam with a diameter of typically 7 mm, a kinetic energy of 1 keV and an energy spread of 50 eV. The NEPOMUC re-moderator generates from this beam a low energy positron beam (20 - 200 eV) with a diameter of less than 2 mm and an energy spread well below 2.5 eV. This was achieved with an excellent total efficiency of 6.55{+-}0.25 %. The re-moderator was not only the rst step to implement the SPM at NEPOMUc, it enables also the operation of the pulsed low energy positron beam system (PLEPS). Within the present work, at this spectrometer rst positron lifetime measurements were performed, which revealed the defect types of an ion irradiated uranium molybdenum alloy. Moreover, the instruments which were already connected to the positron beam facility bene ts considerably of the high brightness enhancement. In the new SPM interface an additional re-moderation stage enhances the brightness of the beam even more and will enable positron lifetime measurements at the SPM with a lateral resolution below 1 {mu}m. The efficiency of the re-moderation process in this second stage was 24.5{+-}4.5 %. In order to convert high efficiently the continuous positron beam into a pulsed beam with a repetition rate of 50 MHz and a pulse duration of less than 50 ps, a sub-harmonic pre-bucher was combined with two sine wave bunchers. Furthermore, the additional re-moderation stage of the

  10. Generation of a high-brightness pulsed positron beam for the Munich scanning positron microscope

    International Nuclear Information System (INIS)

    Piochacz, Christian

    2009-01-01

    Within the present work the prerequisites for the operation of the Munich scanning positron microscope (SPM) at the high intense neutron induced positron source Munich (NEPOMUC) were established. This was accomplished in two steps: Firstly, a re-moderation device was installed at the positron beam facility NEPOMUC, which enhances the brightness of the positron beam for all connected experiments. The second step was the design, set up and initial operation of the SPM interface for the high efficient conversion of the continuous beam into a bunched beam. The in-pile positron source NEPOMUC creates a positron beam with a diameter of typically 7 mm, a kinetic energy of 1 keV and an energy spread of 50 eV. The NEPOMUC re-moderator generates from this beam a low energy positron beam (20 - 200 eV) with a diameter of less than 2 mm and an energy spread well below 2.5 eV. This was achieved with an excellent total efficiency of 6.55±0.25 %. The re-moderator was not only the rst step to implement the SPM at NEPOMUc, it enables also the operation of the pulsed low energy positron beam system (PLEPS). Within the present work, at this spectrometer rst positron lifetime measurements were performed, which revealed the defect types of an ion irradiated uranium molybdenum alloy. Moreover, the instruments which were already connected to the positron beam facility bene ts considerably of the high brightness enhancement. In the new SPM interface an additional re-moderation stage enhances the brightness of the beam even more and will enable positron lifetime measurements at the SPM with a lateral resolution below 1 μm. The efficiency of the re-moderation process in this second stage was 24.5±4.5 %. In order to convert high efficiently the continuous positron beam into a pulsed beam with a repetition rate of 50 MHz and a pulse duration of less than 50 ps, a sub-harmonic pre-bucher was combined with two sine wave bunchers. Furthermore, the additional re-moderation stage of the SPM

  11. Intense low energy positron beams

    International Nuclear Information System (INIS)

    Lynn, K.G.; Jacobsen, F.M.

    1993-01-01

    Intense positron beams are under development or being considered at several laboratories. Already today a few accelerator based high intensity, low brightness e + beams exist producing of the order of 10 8 - 10 9 e + /sec. Several laboratories are aiming at high intensity, high brightness e + beams with intensities greater than 10 9 e + /sec and current densities of the order of 10 13 - 10 14 e + sec - 1 cm -2 . Intense e + beams can be realized in two ways (or in a combination thereof) either through a development of more efficient B + moderators or by increasing the available activity of B + particles. In this review we shall mainly concentrate on the latter approach. In atomic physics the main trust for these developments is to be able to measure differential and high energy cross-sections in e + collisions with atoms and molecules. Within solid state physics high intensity, high brightness e + beams are in demand in areas such as the re-emission e + microscope, two dimensional angular correlation of annihilation radiation, low energy e + diffraction and other fields. Intense e + beams are also important for the development of positronium beams, as well as exotic experiments such as Bose condensation and Ps liquid studies

  12. Positron emission tomography in neuropsychology.

    Science.gov (United States)

    Heiss, W D; Herholz, K; Pawlik, G; Wagner, R; Wienhard, K

    1986-01-01

    By positron emission tomography (PET) of 18F-2-fluoro-2-deoxy-D-glucose (FDG) local cerebral metabolic rate for glucose (LCMRGl) can be measured in man. Normal values in cerebral cortex and basal ganglia range from 35 to 50 mumol/100 g/min, the values in gray matter structures of the posterior fossa were 25-30 mumol/100 g/min, the lowest LCMRGl was found in the white matter (15-20 mumol/100 g/min). During sensory stimulation by various modalities functional activation increases LCMRGl in the respective special areas, while sleep decreases metabolic rate in all cortical and basal gray matter structures. In many neurological disorders CMRGl is altered in a disease-specific pattern. In dementia of the Alzheimer type CMRGl is impaired even in early stages with accentuation in the parieto-temporal cortex, while in multi-infarct dementia glucose uptake is mainly reduced in the multifocal small infarcts. In Huntington's chorea the most conspicuous changes are found in the caudate nucleus and putamen. In cases of focal lesions (e.g. ischemic infarcts) metabolic disturbances extend far beyond the site of the primary lesion and inactivation of metabolism is found in intact brain structures far away from the anatomical lesion. Additional applications of PET include determination of the metabolism of various substrates, of protein synthesis, of function and distribution of receptors, of tumor growth and of the distribution of drugs as well as the measurement of oxygen consumption, blood flow and blood volume.

  13. Positron emission tomography in epilepsy

    International Nuclear Information System (INIS)

    Hosokawa, Shinichi; Kato, Motohiro; Otsuka, Makoto; Kuwabara, Yasuo; Ichiya, Yuichi; Goto, Ikuo

    1989-01-01

    Positron emission tomography (PET) was performed with the 18 F-fluoro-deoxy-glucose method on 29 patients with epilepsy (generalized epilepsy, 4; partial epilepsy, 24; undetermined type, 1). The subjects were restricted to patients with epilepsy without focal abnormality on X-CT. All the patients with generalized epilepsy showed a normal pattern on PET. Fourteen out of the 24 patients with partial epilepsy and the 1 with epilepsy of undermined type showed focal hypometabolism on PET. The hypometabolic zone was localized in areas including the temporal cortex in 11 patients, frontal in 2 and thalamus in 1. The location of hypometabolic zone and that of interictal paroxysmal activity on EEG were well correlated in most patients. The patients with poorly-controlled seizure showed a higher incidence of PET abnormality (12 out of 13) than those with well-controlled seizures (2 out of 11). The incidence of abnormality on PET and MRI and the location of both abnormality were not necessarily coincident. These results indicated that the PET examination in epilepsy provides valuable information about the location of epileptic focus, and that the findings on PET in patients with partial epilepsy may be one of the good indicators about the intractability of partial epilepsy, and that PET and MRI provide complementary information in the diagnosis of epilepsy. (author)

  14. Positron emission tomography in oncology

    International Nuclear Information System (INIS)

    Lecomte, R.; Bentourkia, M.; Benard, F.

    2002-01-01

    Positron Emission Tomography is a sophisticated molecular imaging technique, using a special scanner, that displays the functional status of tissues in the body at the cellular level (their metabolism). It is a diagnostic scan that provides the physician with information not available with traditional anatomic studies such as CT or MRI. PET can detect changes in cell function (disease) long before they are evident as physical (anatomic) changes seen on CT or MRI. In this way PET can add important information about many diseases allowing the physician to make a diagnosis often much earlier than with anatomic imaging techniques such as CT or MRI alone. In addition, in cases where an abnormality is noted on CT or MRI, PET can help differentiate benign changes from changes due to disease. PET scanning also typically images the entire body, unlike CT/MRI which is usually broken up into specific limited body section scans. All cells use glucose as an energy source but cancer cells use much more since they are growing much faster and out of control. This is the basis of imaging with F-18 FDG glucose, the radiotracer agent use in a PET oncology study. The abnormal, accelerated glucose used by cancer cells is detected by the PET scanner that processes the emissions from the F-18 FDG glucose by abnormally high levels of metabolism (tumor)

  15. Positron in nuclear medicine imaging

    International Nuclear Information System (INIS)

    Basu, S.

    2012-01-01

    The last two decades have witnessed a rapid expansion of clinical indications of positron emission tomography (PET) based imaging in assessing a wide range of disorders influencing their clinical management. This is primarily based upon a large dataset of evidence that has been generated over the years. The impact has been most remarkable in the field of cancer, where it takes a pivotal role in the decision making (at initial diagnosis, early response assessment and following completion of therapeutic intervention) of a number of important malignancies. The concept of PET based personalized cancer medicine is an evolving and attractive proposition that has gained significant momentum in recent years. The non-oncological applications of PET and PET/CT are in (A) Cardiovascular Diseases (e.g. Myocardial Viability, Flow reserve with PET Perfusion Imaging and atherosclerosis imaging); (B) Neuropsychiatric disorders (e.g. Dementia, Epileptic Focus detection, Parkinson's Disease, Hyperkinetic Movement Disorders and Psychiatric diseases); (C) Infection and Inflammatory Disorders (e.g. Pyrexia of Unknown origin, complicated Diabetic Foot, Periprosthetic Infection, Tuberculosis, Sarcoidosis, Vasculitic disorders etc). Apart from these, there are certain novel clinical applications where it is undergoing critical evaluation in various large and small scale studies across several centres across the world. The modality represents a classical example of a successful translational research of recent times with a revolutionary and far-reaching impact in the field of medicine. (author)

  16. Angular correlation in positron annihilation

    International Nuclear Information System (INIS)

    Arponen, J.; Pajanne, E.

    1978-01-01

    The angular correlation of the two gamma quanta emitted when a thermalized positron annihilates with metallic conduction electrons is investigated by applying the newly developed theory of electron gas as a system of interacting collective excitations. The method leads in a natural way to the appearance of high-momentum components (i.e. pair momentum p>psub(F) in the annihilation radiation already in the case of annihilation with conduction electrons only. The amount of these components is significant approximately (10 %) in a dilute electron gas (like alkali metals), but fairly irrelevant for higher densities. The momentum-dependence of the enhancement factor for a dense system (with rsub(s) approximately equal to 2) agrees well both with the earlier theories due to Kahana and others, and also with recent accurate experimental observations. As rsub(s) increases into the alkali-metal region, the enhancement factor for p< psub(F) becomes relatively more and more constant, in contrast with the trend in the Kahana theory. In this density regime the experimental results seem to vary widely, although most of them desagree with the present prediction. We discuss the possible discrepancy and try to account for the effects of the core annihilation by a simple model. (author)

  17. Low energy scattering of positrons by H{sub 2}O

    Energy Technology Data Exchange (ETDEWEB)

    Arretche, F., E-mail: fsc1sem@fsc.ufsc.b [Departamento de Fisica, Universidade do Estado de Santa Catarina, 89223-100, Joinville, Santa Catarina (Brazil); Tenfen, W.; Mazon, K.T.; Michelin, S.E. [Departamento de Fisica, Universidade Federal de Santa Catarina, 88040-900, Florianopolis, Santa Catarina (Brazil); Lima, M.A.P. [Instituto de Fisica Gleb Wataghin, Universidade Estadual de Campinas, Unicamp, 13083-970, Campinas, Sao Paulo (Brazil); Lee, M.-T. [Departamento de Quimica, Universidade Federal de Sao Carlos, 13565-905, Sao Carlos, Sao Paulo (Brazil); Machado, L.E. [Departamento de Fisica, Universidade Federal de Sao Carlos, 13565-905, Sao Carlos, Sao Paulo (Brazil); Fujimoto, M.M. [Departamento de Fisica, Universidade Federal do Parana, 13565-905, Curitiba, Parana (Brazil); Pessoa, O.A. [Departamento de Fisica, Universidade do Estado de Santa Catarina, 89111-100, Sao Bento do Sul, Santa Catarina (Brazil)

    2010-01-15

    We present a theoretical investigation on elastic positron-H{sub 2}O collisions. More specifically, differential and integral cross sections in the 0-10 eV energy range are reported. The calculations were performed using two theoretical approaches, namely, the Schwinger multichannel method and the method of continued fractions. The positron-molecule interaction dynamics is described by using a potential composed of static and correlation-polarization contributions. Comparison of our calculated results with the recent experimental of Zecca et al. [J. Phys. B 39 (2006) 1597] and theoretical results is encouraging.

  18. Investigation of positron moderator materials for electron-linac-based slow positron beamlines

    International Nuclear Information System (INIS)

    Suzuki, Ryoichi; Ohdaira, Toshiyuki; Uedono, Akira

    1998-01-01

    Positron re-emission properties were studied on moderator materials in order to improve the positron moderation system of electron-linac-based intense slow positron beamlines. The re-emitted positron fraction was measured on tungsten, SiC, GaN, SrTiO 3 , and hydrogen-terminated Si with a variable-energy pulsed positron beam. The results suggested that tungsten is the best material for the primary moderator of the positron beamlines while epitaxially grown n-type 6H-SiC is the best material for the secondary moderator. Defect characterization by monoenergetic positron beams and surface characterization by Auger electron spectroscopy were carried out to clarify the mechanism of tungsten moderator degradation induced by high-energy electron irradiation. The characterization experiments revealed that the degradation is due to both radiation-induced vacancy clusters and surface carbon impurities. For the restoration of degraded tungsten moderators, oxygen treatment at ∼900degC is effective. Furthermore, it was found that oxygen at the tungsten surface inhibits positronium formation; as a result, it can increase the positron re-emission fraction. (author)

  19. Slow positron applications at slow positron facility of institute of materials structure science, KEK

    Science.gov (United States)

    Hyodo, Toshio; Mochizuki, Izumi; Wada, Ken; Toge, Nobukazu; Shidara, Tetsuo

    2018-05-01

    Slow Positron Facility at High Energy Accelerator Research Organization (KEK) is a user dedicated facility with an energy-tunable (0.1 - 35 keV) slow positron beam created by a dedicated ˜ 50 MeV linac. It operates in a short pulse (width 1-12 ns, variable, 5×106 e+/s) and a long pulse (width 1.2 µs, 5×107 e+/s) modes of 50 Hz. High energy positrons from pair creation are moderated by reemission after thermalization in W foils. The reemitted positrons are then electrostatically accelerated to a desired energy up to 35 keV and magnetically transported. A pulse-stretching section (pulse stretcher) is installed in the middle of the beamline. It stretches the slow positron pulse for the experiments where too many positrons annihilating in the sample at the same time has to be avoided. Four experiment stations for TRHEPD (total-reflection high-energy positron diffraction), LEPD (low-energy positron diffraction), Ps- (positronium negative ion), and Ps-TOF (positronium time-of-flight) experiments are connected to the beamline branches, SPF-A3, SPF-A4, SPF-B1 and SPF-B2, respectively. Recent results of these stations are briefly described.

  20. Solvated Positron Chemistry. Competitive Positron Reactions with Halide Ions in Water

    DEFF Research Database (Denmark)

    Christensen, Palle; Pedersen, Niels Jørgen; Andersen, J. R.

    1979-01-01

    It is shown by means of the angular correlation technique that the binding of positrons to halides is strongly influenced by solvation effects. For aqueous solutions we find increasing values for the binding energies between the halide and the positron with increasing mass of the halide...

  1. Theoretical calculations of positron lifetimes for metal oxides

    International Nuclear Information System (INIS)

    Mizuno, Masataka; Araki, Hideki; Shirai, Yasuharu

    2004-01-01

    Our recent positron lifetime measurements for metal oxides suggest that positron lifetimes of bulk state in metal oxides are shorter than previously reported values. We have performed theoretical calculations of positron lifetimes for bulk and vacancy states in MgO and ZnO using first-principles electronic structure calculations and discuss the validity of positron lifetime calculations for insulators. By comparing the calculated positron lifetimes to the experimental values, it wa found that the semiconductor model well reproduces the experimental positron lifetime. The longer positron lifetime previously reported can be considered to arise from not only the bulk but also from the vacancy induced by impurities. In the case of cation vacancy, the calculated positron lifetime based on semiconductor model is shorter than the experimental value, which suggests that the inward relaxation occurs around the cation vacancy trapping the positron. (author)

  2. Positron emission tomography with Positome, 2

    International Nuclear Information System (INIS)

    Nukui, Hideaki; Yamamoto, Y.L.; Thompson, C.J.; Feindel, W.

    1979-01-01

    Positron emission tomography with Positome II using 68 Ga-EDTA was performed in cases with brain tumor and cerebral arteriovenous malformation. A significant focal uptake in static study and hemodynamic changes in dynamic study were noted in all cases except one case with intracranial lipoma. Comparing this method with sup(99m) Tc-pertechnetate cerebral image study and computerized axial tomography, the diagnostic rate for detecting brain tumor was almost equal in all of these three methods. However, detecting and localizing was easier and clearer in static positron emission tomography with 68 Ga-EDTA than in sup(99m) Tc-pertechnetate cerebral image and computerized axial tomography without infusion of contrast medium. Furthermore, static positron emission tomography with 68 Ga-EDTA was superior to computerized axial tomography without infusion of contrast medium for detecting cerebral arteriovenous malformation. Concerning dynamic positron emission tomography with 68 Ga-EDTA, semiquantitative values obtained by this method correlated well with findings of computerized axial tomography and was thought to be more precise and in detail than the findings of sup(99m) Tc-pertechnetate cerebral image study. Summation of the previous studies about dynamic positron emission tomography with 77 Kr in occlusive cerebrovascular disease is also reported. In conclusion, static positron emission tomography with 68 Ga-EDTA is a very useful diagnostic method for detecting and localizing brain tumor and cerebral arteriovenous malformation without any attendant complications. Furthermore, a good combination of static and dynamic positron emission tomography and computerized axial tomography appear to be outstandingly effective for not only detecting the lesion but also understanding the pathophysiological aspect in cases with various intracranial lesions. (author)

  3. Positron annihilation induced Auger electron spectroscopy and its implementation at accelerator based low energy positron factories

    International Nuclear Information System (INIS)

    Weiss, A.; Koeymen, A.R.; Mehl, D.; Lee, K.H.; Yang Gimo; Jensen, K.

    1991-01-01

    Positron annihilation induced auger electron spectroscopy (PAES) makes use of a beam of low energy positrons to excite Auger transitions by annihilating core electrons. The large secondary electron background usually present in Auger spectra can be eliminated by setting the positron beam energy well below the Auger electron energy. This allows true Auger lineshapes to be obtained. Further, because the positron is localized just outside the surface before it annihilates, PAES is extremely sensitive to the topmost atomic layer. Recent PAES results obtained at the University of Texas at Arlington will be presented. In addition, the use of high resolution energy analyzers with multichannel particle detection schemes to prevent problems due to the high data rates associated with accelerator based positron beams will be discussed. (orig.)

  4. Positron sources for electron-positron colliders application to the ILC and CLIC

    CERN Multimedia

    CERN. Geneva

    2008-01-01

    The increased demanding qualities for positron sources dedicated to e+e- colliders pushed on investigations oriented on new kinds of e+ sources. The different kinds of positron sources polarized and no polarized are considered. Their main features (intensity, emittance) are described and analysed. Comparison between the different sources is worked out. The characteristics of the positron beam available in the collision point are greatly depending on the capture device and on the positron accelerator. Different kinds of capture systems are considered and their qualities, compared. Intense positron sources which are necessary for the colliders require intense incident beams (electrons or photons). The large number of pairs created in the targets leads to important energy deposition and so, thermal heating, which associated to temperature gradients provoke mechanical stresses often destructive. Moreover, the important Coulomb collisions, can affect the atomic structure in crystal targets and the radiation resist...

  5. Conceptual design of a slow positron source based on a magnetic trap

    CERN Document Server

    Volosov, V I; Mezentsev, N A

    2001-01-01

    A unique 10.3 T superconducting wiggler was designed and manufactured at BINP SB RAS. The installation of this wiggler in the SPring-8 storage ring provides a possibility to generate a high-intensity beam of photons (SR) with energy above 1 MeV (Ando et al., J. Synchrotron Radiat. 5 (1998) 360). Conversion of photons to positrons on high-Z material (tungsten) targets creates an integrated positron flux more than 10 sup 1 sup 3 particles per second. The energy spectrum of the positrons has a maximum at 0.5 MeV and the half-width about 1 MeV (Plokhoi et al., Jpn. J. Appl. Phys. 38 (1999) 604). The traditional methods of positron moderation have the efficiency epsilon=N sub s /N sub f of 10 sup - sup 4 (metallic moderators) to 10 sup - sup 2 (solid rare gas moderators) (Mills and Gullikson, Appl. Phys. Lett. 49 (1986) 1121). The high flux of primary positrons restricts the choice to a tungsten moderator that has epsilon approx 10 sup - sup 4 only (Schultz, Nuc. Instr. and Meth. B 30 (1988) 94). The aim of our pr...

  6. Numerical determination of elastic positron- and electron-atom scattering phaseshifts

    International Nuclear Information System (INIS)

    Page, B.A.P.

    1976-01-01

    Numerical investigations of both the positron- and electron-hydrogen systems in the elastic scattering energy region are presented. For the positron-hydrogen system, modifications of the Kohn variational method are used in which the quantities etasub(v) and etasub(Q) are related to the trial wavefunction PSIsub(t) through integral expressions using approximations to the target wavefunction psi. The quantities etasub(v) and etasub(Q) become the Kohn elastic phaseshifts when the exact target wavefunction is used. From the results obtained for the positron-hydrogen system it is conjectured that if the values of either etasub(v) or etasub(Q) display a local maximum when all the nonlinear parameters of PSIsub(t) are varied, then this local maximum value is a good approximation to the Kohn elastic phaseshifts that would be obtained by replacing the approximate psi with the exact psi in the particular PSIsub(t) used in the calculations. Application of this procedure to the positron-helium elastic scattering system is given using Hylleraas-type approximations to the helium ground-state wavefunction. Both the positron- and electron-hydrogen systems are analysed in the elastic scattering energy region using a modified optical potential method. The results suggest that the local maximum value of the modified optical potential phaseshift when all the nonlinear parameters of PSIsub(t) are varied, is reasonably close to the normal optical potential phaseshift obtained when the exact psi is used. (author)

  7. Relativistic total and differential cross section proton--proton electron--positron pair production calculation

    International Nuclear Information System (INIS)

    Rubinstein, J.E.

    1976-01-01

    Circle Feynman diagrams for a specific permutation of variables along with their corresponding algebraic expressions are presented to evaluate [H] 2 for proton-proton electron-positron pair production. A Monte Carlo integration technique is introduced and is used to set up the multiple integral expression for the total pair production cross section. The technique is first applied to the Compton scattering problem and then to an arbitrary multiple integral. The relativistic total cross section for proton-proton electron-positron pair production was calculated for eight different values of incident proton energy. A variety of differential cross sections were calculated for the above energies. Angular differential cross section distributions are presented for the electron, positron, and proton. Invariant mass differential cross section distributions are done both with and without the presence of [H] 2 . Both WGHT and log 10 (TOTAL) distributions were also obtained. The general behavioral trends of the total and differential cross sections for proton-proton electron-positron pair production are presented. The range of validity for this calculation is from 0 to about 200 MeV

  8. Clinical application of positron CT

    International Nuclear Information System (INIS)

    Takashima, Tsuneo; Yamaura, Akira; Shishido, Fumio; Tateno, Yukio.

    1981-01-01

    A newley designed positron CT has been applied for neurosurgical patients. The radiopharmaceuticals administered are 13 N-ammonia, 11 C-CO, and 18 F-fluorodeoxyglucose, which are produced and synthesized in the institute using the cyclotron. 13 N-ammonia and 18 F-fluorodeoxyglucose are administered by intravenous injection but 11 C-CO is administered by inhaling. 13 N-ammonia acts as a diffusible tracer and is readily metabolized to glutamine in the brain tissue, but the extraction fraction of the glutamine is so slow that the 13 N-ammonia imaging reflects the distribution of the crebral perfusion. 11 C-CO is combined with the hemoglobin and undiffusible in behavior. This makes the 11 C-CO images conduct the cerebral blood pooling distribution. 18 F-fluorodeoxyglucose is an analogous substance of glucose and is transported within the brain tissue competitively. Then, fluorodeoxyglucose is metabolized to fluorodeoxyglucose-6-phosphate but no further. This characteristic property of fluorodeoxyglucose let 18 F-fluorodeoxyglucose images convey the local cerebral metabolic rate of glucose. In normal volunteer subjects, the distribution of 13 N-ammonia and 18 F-fluorodeoxyglucose appeared in a similar fashion, and was in accordance with the brain tissue. Both tracers were accumulated in particularly high concentrations in the gray matter and the basal ganglia. 11 C-CO activity was prominently accumulated in various dural sinuses and the vascular areas. In stroke patients, old lesions showed a lack of perfusion but fresh lesions showed hyperperfusion surrounded by a decreased perfused area. 18 F-fluorodeoxyglucose activity was decreased in the lesion in spite of the hyperperfusion. (J.P.N.)

  9. Positron research in neuropsychiatric disorders

    International Nuclear Information System (INIS)

    Namura, Ikuro; Inoue, Osamu; Yamasaki, Toshiro.

    1984-01-01

    The principal findings revealed by our 18 F-fluoro-2-deoxyglucose ( 18 FDG) and 15 O-oxygen study were reviewed in the former part of this paper. (1) The effect of surgical severing of fiber connections on the terminal gray matter was clearly demonstrated in the following examples. A patient with the injured left optic radiation showed a markedly decreased 18 FDG uptake in the ipsilateral primary visual cortex. The extent of the decrease was larger in the secondary visual cortex (--60%). The patient with bilateral frontal leukotomy (lobotomy) showed about 30% decrease of oxygen accumulation not only in the frontal cortex but in the anterior half of the temporal cortex. (2) The effect of electrical stimulation of the left median nerve can be detected as an increased 18 FDG accumulation in the corresponding sensory and motor areas in the right precentral and postcentral cortices. The slight to moderate increase in the right striatal region was though to be related to the muscle movement caused by the stimulation. (3) The neuro-degenerative disorders such as Huntington's chorea and Parkinsonism could be diagnosed by demonstrating the decrease of 18 FDG in the degenerating focus or the increase in the secondarily affected area. An example was provided by a case of Huntington's chorea patient who showed a markedly decreased 18 FDG uptake in the striatal region in spite that 13 N-ammonia visualized this area. (4) Dementia gives another field where the 18 FDG and 15 O 2 studies are demonstrated to be quite useful. (5) The 18 FDG studies on the intrinsic psychoses are also reviewed. But consistent results seemed to be very difficult in this area by using labeled sugars and oxygens which are nonspecific gray matter imagers. Therefore, new tracers and new techniques in positron emission tomography are briefly described in the latter part of this paper. (author)

  10. Depth-dependent positron annihilation in different polymers

    Energy Technology Data Exchange (ETDEWEB)

    Yang, J.; Zhang, P.; Cheng, G.D.; Li, D.X.; Wu, H.B.; Li, Z.X.; Cao, X.Z. [Key Laboratory of Nuclear Analysis Techniques, Institute of High Energy Physics, Chinese Academy of Sciences, No. 19 Yuquan Lu, Beijing 100049 (China); Jia, Q.J. [Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, No. 19 Yuquan Lu, Beijing 100049 (China); Yu, R.S. [Key Laboratory of Nuclear Analysis Techniques, Institute of High Energy Physics, Chinese Academy of Sciences, No. 19 Yuquan Lu, Beijing 100049 (China); Wang, B.Y., E-mail: wangboy@ihep.ac.cn [Key Laboratory of Nuclear Analysis Techniques, Institute of High Energy Physics, Chinese Academy of Sciences, No. 19 Yuquan Lu, Beijing 100049 (China)

    2013-09-01

    Depth-dependent positron annihilation Doppler broadening measurements were conducted for polymers with different chemical compositions. Variations of the S parameter with respect to incident positron energy were observed. For pure hydrocarbons PP, HDPE and oxygen-containing polymer PC, S parameter rises with increasing positron implantation depth. While for PI and fluoropolymers like PTFE, ETFE and PVF, S parameter decreases with higher positron energy. For chlorine-containing polymer PVDC, S parameter remains nearly constant at all incident positron energies. It is suggested that these three variation trends are resulted from a competitive effect between the depth-dependent positronium formation and the influence of highly electronegative atoms on positron annihilation characteristics.

  11. Mineralogía y génesis de las arcillas de las unidades del Campo de Gibraltar. V. Unidad de Bolonia

    Directory of Open Access Journals (Sweden)

    Ruiz Cruz, M. D.

    1990-04-01

    Full Text Available The mineralogical results of the Bolonia Unit are analysed in the work. The Cabrito-l section is characterized by the mineralogical association kaolinite-illite-interestratified I-S, and is similar to the section of Punta Tarifa series of the Algeciras Unit. The Pulido section, characterized by the mineralogical association (kaolinite-illite-chlorite, may be considered as the most distal zone of the «areniscoso-micaceo» flysch of the Algeciras Unit. The most significant difference between the fine fractions of these Units is the remarkable development, in the Bolonia Unit, of authigenic chlorites, whose composition shows a diagenetic environment rich in Fe and Mg. On the other hand, the mineralogical composition of the fine fraction has made possible the identification in the Bolonia Unit, not only the «areniscas del Aljibe» levels, but also clay levels of Aljibe Unit, which has not been noticed until now. These mineralogical and lithological aspects lead to consider the Bolonia Unit as an intermediate Unit between the Algeciras and the Aljibe ones.En este trabajo se recogen los resultados obtenidos a partir del estudio mineralógico de la Unidad de Bolonia. De los perfiles estudiados, el del Cabrito, caracterizado por la asociación mineralógica caolinita-ilita, interestratificados I-E, es similar en gran medida a la serie tipo punta Tarifa de la Unidad de Algeciras. El perfil del Pulido, caracterizado por la asociación (caolinita-ilita-clorita puede interpretarse como la parte más distal del flysch areniscoso-micáceo de la Unidad de Algeciras. La diferencia más notable en la mineralogía de la fracción fina entre ambas Unidades se refiere al desarrollo notable, en Bolonia, de cloritas autigénicas, cuya composición indica un medio diagenético rico en Fe y Mg. Por otra parte, la mineralogía de la fracción fina ha permitido identificar en la Unidad de Bolonia no sólo los niveles de areniscas del Aljibe sino tambi

  12. Positron astrophysics and areas of relation to low-energy positron physics

    Science.gov (United States)

    Guessoum, Nidhal

    2014-05-01

    I briefly review our general knowledge of positron astrophysics, focusing mostly on the theoretical and modelling aspects. The experimental/observational aspects of the topic have recently been reviewed elsewhere [E. Churazov et al., Mon. Nat. R. Astron. Soc. 411, 1727 (2011); N. Prantazos et al., Rev. Mod. Phys. 83, 1001 (2011)]. In particular, I highlight the interactions and cross sections of the reactions that the positrons undergo in various cosmic media. Indeed, these must be of high interest to both the positron astrophysics community and the low-energy positron physics community in trying to find common areas of potential collaboration for the future or areas of research that will help the astrophysics community make further progress on the problem. The processes undergone by positrons from the moments of their birth to their annihilation (in the interstellar medium or other locations) are thus examined. The physics of the positron interactions with gases and solids (dust grains) and the physical conditions and characteristics of the environments where the processes of energy loss, positronium formation, and annihilation take place, are briefly reviewed. An explanation is given about how all the relevant physical information is taken into account in order to calculate annihilation rates and spectra of the 511 keV emission in the ISM; special attention is paid to positron interactions with dust and with polycyclic aromatic hydrocarbons. In particular, an attempt is made to show to what extent the interactions between positrons and interstellar dust grains are similar to laboratory experiments in which beams of low-energy positrons impinge upon solids and surfaces. Sample results are shown for the effect of dust grains on positron annihilation spectra in some phases of the ISM which, together with high resolution spectra measured by satellites, can be used to infer useful knowledge about the environment where the annihilation is predominantly taking place

  13. Evento adverso no idoso em Unidade de Terapia Intensiva

    Directory of Open Access Journals (Sweden)

    Larissa Chaves Pedreira

    Full Text Available Objetiva identificar a produção científica, na América Latina, sobre segurança do idoso na UTI e os eventos adversos trazidos pela literatura. Revisão sistemática quantitativa. A coleta, feita no banco de dados do LILACS e SCIELO, considerou descritores indexados e respeitou critérios de inclusão e exclusão. Foram selecionados vinte trabalhos para análise. Em sua maioria, esses trabalhos foram realizados após o ano de 2000, no Brasil, por profissionais enfermeiros e médicos, tratando principalmente de erros com medicação, retiradas acidentais de sondas e cateteres, infecção nosocomial, erro na técnica de procedimento e ocorrência de úlceras por pressão. A produção cientifica sobre a temática ainda é recente na América Latina, sendo preciso atentar para a população idosa nessas unidades, voltando-se para possíveis riscos a que estão expostos.

  14. A LIBERDADE EM SARTRE: UNIDADE ENTRE PROJETO E ENGAJAMENTO

    Directory of Open Access Journals (Sweden)

    Josiane Fátima Wambier

    2003-01-01

    Full Text Available O objetivo deste trabalho é refletir a liberdade em Sartre, tendo como base os textos: O existencialismo é um humanismo (1945 e Questão de método, a célebre introdução de Crítica da razão dialética (1960. A liberdade em Sartre é um tema filosófico e literário. No início do processo de sua trajetória intelectual, ela é encerrada dentro do cogito cartesiano: “penso, logo existo”. Apesar de ser concebida como uma pura subjetividade, ela também é entendida como projeto que se realiza na ação através do engajamento do homem no mundo. Posteriormente, ela é remetida para o plano histórico e relacionada com a necessidade no interior de uma tensão dialética entre objetividade e subjetividade. Mesmo nesta fase, o núcleo central do conceito sartreano de liberdade é conservado: a unidade entre projeto e engajamento.

  15. Costo-beneficio en una unidad de cuidados intensivos neonatales

    Directory of Open Access Journals (Sweden)

    Rafael Amador Morán

    2011-06-01

    Full Text Available INTRODUCCIÓN. El Sistema Nacional de Salud de Cuba ha desarrollado un conjunto de reformas encaminadas a lograr una mayor eficiencia en la prestación de servicios, para preservar logros como la efectividad y la accesibilidad. El objetivo de esta investigación fue identificar los costos en la Unidad de Terapia Intensiva Neonatal del Hospital Ginecoobstétrico de Guanabacoa en el período de un año. MÉTODOS. Se realizó un estudio descriptivo prospectivo del período de enero a diciembre del 2009. La muestra quedo constituida por 65 recién nacidos graves y críticos. Las variables independientes estudiadas fueron: antibióticos, inmunomoduladores, fármacos vasoactivos, soluciones para hidratación, yodo, peróxido de hidrógeno, vitaminas y minerales, oxígeno, material desechable, material de oficina y medios diagnósticos. La información recogida se introdujo en una base de datos, y se procesó con el programa Epidat 3.0. RESULTADOS. Existió un costo total de 70 605,83 CU, que representó unos 2 824,23 CUC, con costo total por paciente de 74,32 CUC. El mayor gasto correspondió al uso de materiales desechables, las soluciones para hidratación y los antibióticos.

  16. PACIENTE EM UNIDADES MÉDICO-CIRÚRGICAS

    Directory of Open Access Journals (Sweden)

    Gisele Hespanhol Dorigan

    2015-01-01

    Full Text Available Este estudio tuvo como objetivo identificar los factores predictivos de la experiencia y la satisfacción del paciente con la atención de enfermería y comparar las propiedades psicometricas de la versión brasileña y la versión original del Newcastle Satisfaction with Nursing Scales. Se trata de un estudio transversal con 351 pacientes en unidades médico-quirúrgicas de un hospital universitario. Para el análisis de los dados se utilizó el método de regresión lineal múltiple. La satisfacción con la atención de enfermería en general fue el predictor de las experiencias (p<0.0001 y la satisfacción con el internamiento (p<0,0001. Otros predictores de la satisfacción con la atención fueron la edad (p=0,027, el nivel de educación (p=0,024 y la satisfacción con la hospitalización (p=0,021. Llegamos a la conclusión de que la versión brasileña del instrumento demostró confiabilidad y validez satisfactorios, así como ser fácil de usar y menos costoso.

  17. Caracterização do atendimento de uma unidade de hemoterapia

    Directory of Open Access Journals (Sweden)

    Rodrigo Guimarães dos Santos Almeida

    2011-12-01

    Full Text Available O estudo objetivou descrever as características de atendimento de uma Unidade de Hemoterapia do interior do estado de São Paulo, no ano de 2009. Seguidos os preceitos éticos, foi realizado levantamento junto ao banco de dados da Unidade. No período observado a Unidade demonstra maior índice de doadores de repetição, com baixo índice de reações adversas e 100% de satisfação dos doadores. No serviço hospitalar cliente da Unidade, a clínica médica e a unidade de terapia intensiva foram os setores com maior consumo de transfusões. A Unidade descrita é autossuficiente no gerenciamento dos seus recursos. O presente estudo aponta para a necessidade de se explorar as dimensões dos papéis profissionais em hemoterapia, as possibilidades de captação de novos doadores, os motivos que levam os pacientes a doação de sangue, características, perfil epidemiológico e satisfação dos receptores.

  18. Positron transport: The plasma-gas interface

    International Nuclear Information System (INIS)

    Marler, J. P.; Petrovic, Z. Lj.; Bankovic, A.; Dujko, S.; Suvakov, M.; Malovic, G.; Buckman, S. J.

    2009-01-01

    Motivated by an increasing number of applications, new techniques in the analysis of electron transport have been developed over the past 30 years or so, but similar methods had yet to be applied to positrons. Recently, an in-depth look at positron transport in pure argon gas has been performed using a recently established comprehensive set of cross sections and well-established Monte Carlo simulations. The key novelty as compared to electron transport is the effect of positronium formation which changes the number of particles and has a strong energy dependence. This coupled with spatial separation by energy of the positron swarm leads to counterintuitive behavior of some of the transport coefficients. Finally new results in how the presence of an applied magnetic field affects the transport coefficients are presented.

  19. Present status of positron factory project

    International Nuclear Information System (INIS)

    Okada, S.; Sunaga, H.; Kaneko, H.; Tachibana, H.; Yotsumoto, K.; Okamoto, J.

    1992-01-01

    The Japan Atomic Energy Research Institute, JAERI, has been promoting design studies for the 'Positron Factory', in which linac-based intense monoenergetic positron beams are planned to be applied to advanced materials characterization and new fields of basic research. A tentative goal of the beam intensity is 10 10 s -1 , which is assumed to be realized with an electron linac of 100 kW class with a beam energy around 100 to 150 MeV. We performed a technical survey on the dedicated linac. It confirmed technical feasibility of manufacturing the state-of-the-art machine. We have been carrying out a design study of the target. A new concept of the target design is proposed, which is expected to supply intense slow positron beams simultaneously for multiple beam channels, on the basis of Monte Carlo simulations. (author)

  20. The positron accumulator ring for the APS

    International Nuclear Information System (INIS)

    Crosbie, E.A.

    1989-01-01

    The Positron Accumulator Ring (PAR) is designed to accumulate and damp positrons from the 450-MeV linac during the 0.5-s cycle time of the injector synchrotron for the APS 7-GeV storage ring. During 0.4 s of each synchrotron cycle, up to 24 linac pulses are injected into the horizontal phase space of the PAR at a 60-Hz rate. Each injected pulse occupies about 1.3 of the circumference of the accumulator ring. After 0.1 s for longitudinal damping, the single accumulated bunch is transferred to one of the 353-MHz buckets of the injector synchrotron RF system. The bunch is accelerated to 7 GeV and transferred to the storage ring, while the PAR accumulates the next bunch of positrons. 2 refs., 3 figs., 2 tabs

  1. The positron accumulator ring for the APS

    International Nuclear Information System (INIS)

    Crosbie, E.A.

    1989-01-01

    The Positron Accumulator Ring (PAR) is designed to accumulate and damp positrons from the 450-MeV linac during the 0.5-s cycle time of the injector synchrotron for the APS 7-GeV storage ring. During 0.4 s of each synchrotron cycle, up to 24 linac pulses are injected into the horizontal phase space of the PAR at a 60-Hz rate. Each injected pulse occupies about 1/3 of the circumference of the accumulator ring. After 0.1 s for longitudinal damping, the single accumulated bunch is transferred to one of the 353-MHz buckets of the injector synchrotron RF system. The bunch is accelerated to 7 GeV and transferred to the storage ring, while the PAR accumulates the next bunch of positrons. 2 refs., 3 figs., 2 tabs

  2. Positron Spectroscopy of Nanodiamonds after Hydrogen Sorption

    Directory of Open Access Journals (Sweden)

    Lyudmila Nikitina

    2018-01-01

    Full Text Available The structure and defects of nanodiamonds influence the hydrogen sorption capacity. Positronium can be used as a sensor for detecting places with the most efficient capture of hydrogen atoms. Hydrogenation of carbon materials was performed from gas atmosphere. The concentration of hydrogen absorbed by the sample depends on the temperature and pressure. The concentration 1.2 wt % is achieved at the temperature of 243 K and the pressure of 0.6 MPa. The hydrogen saturation of nanodiamonds changes the positron lifetime. Increase of sorption cycle numbers effects the positron lifetime, as well as the parameters of the Doppler broadening of annihilation line. The electron-positron annihilation being a sensitive method, it allows detecting the electron density fluctuation of the carbon material after hydrogen saturation.

  3. Positron spectroscopy studies of zeolites

    Science.gov (United States)

    Hung, Ku-Jung

    The lineshapes of two-dimensional angular correlation of electron-positron annihilation radiation (2D-ACAR) in alumina and several zeolites were measured as a function of internal surface areas. In all cases, the lineshape parameter S from 2D-ACAR spectra were found to vary proportionally with internal surface area. In order to investigate the Bronsted acidity in NaHY zeolite, the lineshape parameter evaluation from 2D-ACAR measurements for varied acidity in NaHY zeolites by ion-exchange and thermal desorption were presented. The result from this investigation has demonstrated that the Bronsted acidity in NaHY zeolite was found to vary linearly with the lineshape parameter of the angular correlation spectrum of the sample. The lineshapes of 2D-ACAR spectra were determined for different base adsorbed HY-zeolite samples under a temperature controlled heating system in order to investigate, in-situ, the acid strength and number of Bronsted acid sites in the sample. Results have shown that the lineshape parameter of the angular correlation spectrum of the sample increases with the strength of adsorbed base and decreases with the number of Bronsted acid sites in the sample. This indicated that the lineshape parameter is sensitive to all of the strengths and concentrations of Bronsted acid sites in the HY-zeolite samples. The result from this study has also demonstrated that the large size base, pyridine, would reduce the possibility of positronium formation in the sample by filling the cage to eliminate the internal surface areas where the positroniums are likely to form. However, the small size base, ammonia, did not show any effect on the internal surface areas. Owing to the fact that this technique monitors only the Bronsted acid sites that situate on the surface which relates to the catalytic activity, there is little ambiguity about the location of the source of information obtained. The findings presented in this dissertation point out the fact that such lineshape

  4. Integrated 18F-fluorodeoxyglucose positron emission tomography magnetic resonance imaging (18F-FDG PET/MRI), a multimodality approach for comprehensive evaluation of dementia patients: A pictorial essay

    International Nuclear Information System (INIS)

    Jena, Amarnath; Renjen, Pushpendra Nath; Taneja, Sangeeta; Gambhir, Aashish; Negi, Pradeep

    2015-01-01

    Dementia, caused by irreversible neurodegenerative disorders such as Alzheimer's disease or reversible non-degenerative conditions, is rapidly becoming one of the most alarming health problems in our aging society. This cognitive disorder associated with a multitude of clinical differentials with overlapping clinical, pathological, and imaging features is difficult to diagnose and treat, as it often presents late after significant neuronal damage has already occurred. Novel disease-modifying treatments being developed will have to be corroborated with innovative imaging biomarkers so that earlier reliable diagnosis can be made and treatment initiated upon. Along with new specific PET radiotracers, integrated PET/MRI with combined methodological advantage and simultaneously acquired structural-cum-functional information may help achieve this goal. The present pictorial essay details our experiences with PET/MRI in dementing disorders, along with reviewing recent advances and future scope

  5. 'Integration'

    DEFF Research Database (Denmark)

    Olwig, Karen Fog

    2011-01-01

    , while the countries have adopted disparate policies and ideologies, differences in the actual treatment and attitudes towards immigrants and refugees in everyday life are less clear, due to parallel integration programmes based on strong similarities in the welfare systems and in cultural notions...... of equality in the three societies. Finally, it shows that family relations play a central role in immigrants’ and refugees’ establishment of a new life in the receiving societies, even though the welfare society takes on many of the social and economic functions of the family....

  6. As unidades de conservação e a Floresta Ombrófila Mista no Estado do Paraná

    Directory of Open Access Journals (Sweden)

    Paulo de Tarso de Lara Pires

    2012-09-01

    Full Text Available http://dx.doi.org/10.5902/198050986625O intenso processo de ocupação territorial, uso desordenado dos recursos naturais e destruição de áreas verdes iniciadas no século XIX, são os principais motivos da intensa devastação das Florestas com Araucárias. Como meio de efetivação da proteção e desenvolvimento florestal, o Brasil adotou em sua política ambiental a criação do Sistema de Unidades de Conservação nas categorias, de proteção integral e uso sustentável. Uma alternativa viável é a regulação dos estoques de madeira no Estado por meio de Unidade de Conservação de Uso Sustentável. O que se pretende a partir deste ponto é analisar a possibilidade da criação de regulamentação do aproveitamento dos recursos naturais em espaços naturais protegidos. Para tanto, foram selecionadas e trabalhadas duas modalidades de Unidades de Conservação (UC, já existentes, e proposta a criação de uma nova modalidade, então denominada “Reservas Particulares de Desenvolvimento Sustentável (RPDS”. As Unidades de Proteção Integral têm desempenhado papel expressivo na preservação do Bioma Florestal com Araucária. Em contrapartida, as Unidades de Conservação de Uso Sustentável são inexpressivas no Bioma e necessitam de uma efetiva regulamentação para que desempenhem sua função ecológica e social. Medidas de incentivo à conservação das florestas particulares e ao uso sustentável dos recursos madeireiros e não madeireiros, somadas ao instrumental atualmente utilizado, podem contribuir com maior efetividade na conservação e recuperação do Bioma Florestal com Araucária.

  7. Theory, development, and applications of the scanning positron microbeam and positron reemission microscope

    International Nuclear Information System (INIS)

    Brandes, G.R.

    1990-01-01

    The theory, design, development, and applications of two new imaging instruments, the scanning positron microbeam (SPM) and positron reemission microscope (PRM), are discussed. The SPM consists of a sectored lens which focuses and rasters the positrons from the beam across the sample. The results of rastering the 10μm x 50μm beam across a test grid demonstrate the SPM's ability to scan a 500μm diameter region and to resolve features with ∼ 5μm resolution. The SPM was used to examine the location of defects in a Si-on-SiO 2 sample. Possible applications to three dimensional defect spectroscopy and the observation of small samples are considered. In the PRM, the positrons from the brightness-enhanced beam are focused at 5keV to an 8/Am diameter spot (FWHM) onto a thin metal single crystal. An image of the opposing side of the film is formed by accelerating and focusing the reemitted thermalized positrons with a cathode lens objective and a projector lens. The final image (real) is a record of the thermal positron emission intensity versus position. Images of surface and subsurface defect structures, taken at magnifications up to 4400x and with a resolution up to 80nm, are presented and discussed. The ultimate resolution capabilities and possible applications of the PRM are examined. The implantation and diffusion process of positrons was studied with the PRM by examining the positron emission profile of 3-9keV positrons implanted into a 2200 angstrom thick Ni single crystal

  8. Estimativa da população em unidades de conservação na Amazônia Legal brasileira: uma aplicação de grades regulares a partir da Contagem 2007

    Directory of Open Access Journals (Sweden)

    Álvaro de Oliveira D'Antona

    2013-12-01

    Full Text Available Neste artigo é testado um método para aumentar a resolução de dados censitários e apresentá-los agregados em uma grade regular. A metodologia empregada é composta pela agregação dos domicílios representados por suas coordenadas geográficas obtidas pela Contagem da População do Instituto Brasileiro de Geografia e Estatística (IBGE de 2007 e pela desagregação dos dados por setor censitário utilizando proporcionalidade de área. Os dados assim gerados foram usados para estimar a população residente em 114 unidades de conservação da Amazônia Legal brasileira, criadas até 2006, de modo a testar a metodologia em unidades territoriais que não seguem os limites político-administrativos, nem aqueles das unidades territoriais de coleta utilizados pelo IBGE. Esta metodologia também contribui para os estudos de população em áreas protegidas, dada a escassez de estimativas do volume da população em unidades de conservação. Os resultados mostraram uma população nas unidades selecionadas de 325.398 habitantes, sendo 297.693 em unidades de Uso Sustentável e 27.705 em unidades de Proteção Integral; no entorno estimou-se uma população de 1.020.237 habitantes. Apesar de limitações inerentes ao uso da Contagem 2007, a agregação de dados em grades revela-se como uma metodologia bastante promissora, tendo em vista os avanços no emprego das geotecnologias por parte do IBGE desde então. A grade minimiza problemas observados no uso de unidades administrativas ou de coleta para a espacialização dos dados censitários e apresenta-se como uma abordagem com grande potencial de aplicação na Demografia e em outras áreas do saber.

  9. Positron annihilation and perturbed angular correlation studies of radiation damage

    International Nuclear Information System (INIS)

    Zhu Jiazheng; Li Anli; Xu Yongjun; Wang Zhiqiang; Zhou Dongmei; Zheng Yongnan; Zhu Shengyun; Iwata, T.

    2002-01-01

    The positron annihilation and perturbed angular correlation techniques have been employed to study radiation damage in Si and Nb. The results obtained by the positron annihilation are consistent with those given by the perturbed angular correlation

  10. Automation of low temperature positron annihilation spectroscopy system

    International Nuclear Information System (INIS)

    Chaturvedi, T.P.; Venkiteswaran, S.; Pujari, P.K.

    1997-01-01

    This paper describes the automation implemented in the low temperature measurements in positron annihilation spectroscopic studies. This has not only widened the scope of the positron research, but also helps achieve result with better precision. (author). 3 refs., 1 fig

  11. Low-cost positron computed tomography

    International Nuclear Information System (INIS)

    Ott, R.J.; Batty, V.; Bateman, T.E.; Clack, R.; Flower, M.A.; Leach, M.O.; Marsden, P.; Webb, S.; McCready, V.R.

    1986-01-01

    After briefly describing the technique of positron emission tomography (PET) and the types of detectors used, the operational experience of a recently developed multi-wire proportional chamber positron camera which can be used to provide images using radionuclides such as 68 Ga, 124 I, 82 Rb, 55 Co, 18 F and 11 C is discussed. Clinical applications included PET imaging of the thyroid and the brain and possible future applications include PET imaging of the liver and tumour localization using antigen-specific monoclonal antibodies. Future developments to improve the sensitivity and spatial resolution of the detectors used in PET are discussed. (U.K.)

  12. Positron lifetime in vanadium oxide bronzes

    International Nuclear Information System (INIS)

    Dryzek, J.; Dryzek, E.

    2003-01-01

    The positron lifetime (PL) and Doppler broadening (DB) of annihilation line measurements have been performed in vanadium oxide bronzes M x V 2 O 5 . The dependence of these annihilation characteristics on the kind and concentration of the metal M donor has been observed. In the PL spectrum only one lifetime component has been detected in all studied bronzes. The results indicate the positron localization in the structural tunnels present in the crystalline lattice of the vanadium oxide bronzes. (copyright 2003 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  13. Features and applications of positron emission tomography

    International Nuclear Information System (INIS)

    Fan Mingwu

    1997-01-01

    Positron emission tomography, the so-called world's smartest camera, is based on a NaI or BGO detector and imaging of positron-emitting radioisotopes which are introduced as a tracer into the regional tissue or organ of interest. With the aid of a computer visual images of a series of these distributions can be built into a picture of the functional status of the tissue or organ being imaged. This highly accurate imaging technique is already widely used for clinical diagnostics heart disease, brain disorder, tumors and so on

  14. Observation of diffraction effects in positron channeling

    International Nuclear Information System (INIS)

    Palathingal, J.C.; Peng, J.P.; Lynn, K.G.; Wu, X.Y.; Schultz, P.J.

    1994-01-01

    An experimental investigation of positron channeling was made with a high-angular resolution apparatus, employing positrons of kinetic energy 1 MeV, derived from the Brookhaven National Laboratory Dynamitron. The pattern of transmission through a Si (100) single crystal of thickness 0.245 μm was investigated for a number of major planes. The authors have observed for the first time, in excellent detail, the fine structure of the channeling pattern expected to arise from the particle diffraction effects, theoretically explainable in terms of the quantum-mechanical many-beam calculations

  15. Positron Annihilation Study of Defects in Succinonitrile

    DEFF Research Database (Denmark)

    Eldrup, Morten Mostgaard; Pedersen, Niels Jørgen; Sherwood, J. N.

    1979-01-01

    Positron lifetime and angular correlation measurements have been made on the plastic crystal succinonitrile. They confirm the phase transition at 234 ± 1 K. In the plastic phase the average orthopositronium lifetime increases with temperature and saturates at the highest temperatures. This is int......Positron lifetime and angular correlation measurements have been made on the plastic crystal succinonitrile. They confirm the phase transition at 234 ± 1 K. In the plastic phase the average orthopositronium lifetime increases with temperature and saturates at the highest temperatures...

  16. Studies of glasses by positron annihilation

    International Nuclear Information System (INIS)

    Brauer, G.; Boden, G.

    1981-04-01

    Investigations of silica glasses, pyrocerams and metallic glasses by positron annihilation (lifetime, Doppler broadening) are presented. The measurements on silica glasses showed, that silica glass fused from naturally occuring quartz exhibits a higher order than that one produced from SiCl 4 . Furthermore it was found that the order of silica glasses increases after heat treatment above 900 0 C. Thus the X-amorphous state of silica glasses could be characterized by positron annihilation what is impossible at present by diffraction methods. (author)

  17. Intense positron beams and possible experiments

    International Nuclear Information System (INIS)

    Lynn, K.G.; Frieze, W.E.

    1983-07-01

    In this paper, we survey some of the ideas that have been proposed regarding the production of intense beams of low energy positrons. Various facilities to produce beams of this type are already under design or construction and other methods beyond those in use have been previously discussed. Moreover, a variety of potential experiments utilizing intense positron beams have been suggested. It is to be hoped that this paper can serve as a useful summary of some of the current ideas, as well as a stimulation for new ideas to be forthcoming at the workshop. 31 references

  18. Electrocardiographic gating in positron emission computed tomography

    International Nuclear Information System (INIS)

    Hoffman, E.J.; Phelps, M.E.; Wisenberg, G.; Schelbert, H.R.; Kuhl, D.E.

    1979-01-01

    Electrocardiographic (ECG) synchronized multiple gated data acquisition was employed with positron emission computed tomography (ECT) to obtain images of myocardial blood pool and myocardium. The feasibility and requirements of multiple gated data acquisition in positron ECT were investigated for 13NH3, ( 18 F)-2-fluoro-2-D-deoxyglucose, and ( 11 C)-carboxyhemoglobin. Examples are shown in which image detail is enhanced and image interpretation is facilitated when ECG gating is employed in the data collection. Analysis of count rate data from a series of volunteers indicates that multiple, statistically adequate images can be obtained under a multiple gated data collection format without an increase in administered dose

  19. Positron emission tomography imaging of gene expression

    International Nuclear Information System (INIS)

    Tang Ganghua

    2001-01-01

    The merging of molecular biology and nuclear medicine is developed into molecular nuclear medicine. Positron emission tomography (PET) of gene expression in molecular nuclear medicine has become an attractive area. Positron emission tomography imaging gene expression includes the antisense PET imaging and the reporter gene PET imaging. It is likely that the antisense PET imaging will lag behind the reporter gene PET imaging because of the numerous issues that have not yet to be resolved with this approach. The reporter gene PET imaging has wide application into animal experimental research and human applications of this approach will likely be reported soon

  20. Positron source based on the 48V isotope dedicated to positron lifetime spectroscopy

    International Nuclear Information System (INIS)

    Dryzek, Jerzy

    2009-01-01

    In the paper we consider application of the 48 V isotope as a source in the positron lifetime spectroscopy. The isotope was produced in the 48 Ti(p,n) 48 V reaction using 15 MeV proton beam. As a target the natural titanium thin plate was used. The measurements using the typical positron lifetime spectrometer have shown the usefulness of the source obtained for this application. Due to its properties, the source may be used for measurements of positron annihilation characteristics in high temperature or aggressive environments. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  1. Importance of non-local electron-positron correlations for positron annihilation characteristics in solids

    International Nuclear Information System (INIS)

    Rubaszek, A.

    2001-01-01

    Several methods to describe the electron-positron (e-p) correlation effects are used in calculations of positron annihilation characteristics in solids. The weighted density approximation (WDA), giving rise to the non-local, state-selective e-p correlation functions, is applied to calculate positron annihilation rates and e-p momentum densities in a variety of metals and silicon. The WDA results are compared to the results of other methods such as the independent particle model, local density approximation, generalised gradient approximation, and also to experiments. The importance of non-locality and state-dependence of the e-p correlation functions is discussed. (orig.)

  2. Positron annihilation studies of mesoporous silica films using a slow positron beam

    International Nuclear Information System (INIS)

    He Chunqing; Muramatsu, Makoto; Ohdaira, Toshiyuki; Kinomura, Atsushi; Suzuki, Ryoichi; Ito, Kenji; Kabayashi, Yoshinori

    2006-01-01

    Positron annihilation lifetime spectra were measured for mesoporous silica films, which were synthesized using triblock copolymer (EO 106 PO 70 EO 106 ) as a structure-directing agent. Different positron lifetime spectra for the deposited and calcined films indicated the formation of meso-structure after calcination, which was confirmed by Fourier transform infrared (FTIR) spectra and field emission-scanning electron microscopy (FE-SEM) observation. Open porosity or pore interconnectivity of a silica film might be evaluated by a two-dimensional positron annihilation lifetime spectrum of an uncapped film. Pore sizes and their distributions in the silica films were found to be affected by thermal treatments

  3. Positrons from supernova and the origin of the galactic-center positron-annihilation radiation

    International Nuclear Information System (INIS)

    Colgate, S.A.

    1983-01-01

    The emission of positrons from supernova ejecta is dicussed in terms of the galactic-center annihilation radiation. The positrons from the radioactive sequences 56 Ni→ 56 Co→ 56 Fe are the most numerous source from supernova. Only type I supernova will allow a significant fraction to escape the expanding ejecta. For a neutron star model of a type I SN a fraction 4 x 10 -3 of the escaped positron is enough to create the observed several year fluctuation of the annihilation radiation. The likelihood of this model is discussed in terms of other astrophysical evidence as well as the type I SN light curve

  4. Positron astrophysics and areas of relation to low-energy positron physics

    International Nuclear Information System (INIS)

    Guessoum, N.

    2014-01-01

    I briefly review our general knowledge of positron astrophysics, focusing mostly on the theoretical and modelling aspects. The experimental/observational aspects of the topic have recently been reviewed elsewhere [E. Churazov et al., Mon. Nat. R. Astron. Soc. 411, 1727 (2011); N. Prantazos et al., Rev. Mod. Phys. 83, 1001 (2011)]. In particular, I highlight the interactions and cross sections of the reactions that the positrons undergo in various cosmic media. Indeed, these must be of high interest to both the positron astrophysics community and the low-energy positron physics community in trying to find common areas of potential collaboration for the future or areas of research that will help the astrophysics community make further progress on the problem. The processes undergone by positrons from the moments of their birth to their annihilation (in the interstellar medium or other locations) are thus examined. The physics of the positron interactions with gases and solids (dust grains) and the physical conditions and characteristics of the environments where the processes of energy loss, positronium formation, and annihilation take place, are briefly reviewed. An explanation is given about how all the relevant physical information is taken into account in order to calculate annihilation rates and spectra of the 511 keV emission in the ISM; special attention is paid to positron interactions with dust and with polycyclic aromatic hydrocarbons. In particular, an attempt is made to show to what extent the interactions between positrons and interstellar dust grains are similar to laboratory experiments in which beams of low-energy positrons impinge upon solids and surfaces. Sample results are shown for the effect of dust grains on positron annihilation spectra in some phases of the ISM which, together with high resolution spectra measured by satellites, can be used to infer useful knowledge about the environment where the annihilation is predominantly taking place

  5. Positron emission tomography now and in the future

    International Nuclear Information System (INIS)

    Vaalburg, W.

    1987-01-01

    A survey is given of positron emission tomography used in nuclear medicine. The production of positron emitting radionuclides is discussed. The development of positron detectors is described. The application of positron emission tomography in cardiology, oncology and neurology is treated. The authors conclude that PET is a unique method to examine metabolic processes, although the method is still in its infancy. 7 refs.; 1 table

  6. Spectra of electrons emitted as a result of the sticking and annihilation of low energy positrons to the surfaces of graphene and highly oriented pyrolytic graphite (HOPG)

    Science.gov (United States)

    Chrysler, M.; Chirayath, V.; McDonald, A.; Lim, Z.; Shastry, K.; Gladen, R.; Fairchild, A.; Koymen, A.; Weiss, A.

    Positron annihilation induced Auger electron spectroscopy (PAES) was used to study the positron induced low energy electron spectra from HOPG and a sample composed of 6-8 layers of graphene grown on polycrystalline copper. A low energy (~2eV) beam of positrons was used to implant positrons into a surface localized state on the graphene and HOPG samples. Measurements of the energy spectra of the positron induced electrons obtained using a TOF spectrometer indicate the presence of an annihilation induced KLL C Auger peak (at ~263 eV) along with a narrow low energy secondary peak due to an Auger mediated positron sticking (AMPS) process. A broad spectral feature was also observed below ~15 eV which we believe may be due to a VVV C Auger transition not previously observed. The energy dependence of the integrated intensity of the AMPS peak was measured for a series of incident positron kinetic energies ranging from ~1.5 eV up to 11 eV from which the binding energy of the surface localized positron state on graphene and HOPG was estimated. The implication of our results regarding the applicability of AMPS and PAES to the study of graphene surfaces and interfaces will be discussed. This work was supported by NSF Grant No. DMR 1508719 and DMR 1338130.

  7. Initial results from the Donner 600 crystal positron tomograph

    International Nuclear Information System (INIS)

    Derenzo, S.E.; Huesman, R.H.; Cahoon, J.L.; Geyer, A.; Uber, D.; Vuletich, T.; Budinger, T.F.

    1986-10-01

    We describe a positron tomograph using a single ring of 600 close-packed 3 mm wide bismuth germanate (BGO) crystals coupled to 14 mm phototubes. The phototube preamplifier circuit derives a timing pulse from the first photoelectron, and sends it to address and coincidence circuits only if the integrated pulse height is within a pre-set window. The timing delays and pulse height windows for all 600 detectors and the coincidence timing windows are computer adjustable. An orbiting positron source is used for transmission measurements and a look-up table is used to reject scattered and random coincidences that do not pass through the source. Data can be acquired using a stationary mode for 1.57 mm lateral sampling or the two-position clam sampling mode for 0.79 mm lateral sampling. High maximum data rates are provided by 45 parallel coincidence circuits and 4 parallel histogram memory units. With two-position sampling and 1.57 mm bins, the reconstructed point spread function (PSF) of a 0.35 mm diam 22 Na wire source at the center of the tomograph is circular with 2.9 mm full-width at half-maximum (fwhm) and the PSF at a distance of 8 cm from the center is elliptical with a radial fwhm of 4.0 mm and tangential fwhm of 3.0 mm. 12 refs., 6 figs., 3 tabs

  8. Initial results from the Donner 600 crystal positron tomograph

    International Nuclear Information System (INIS)

    Derenzo, S.E.; Huesman, R.H.; Cahoon, J.L.; Geyer, A.; Uber, D.; Vuletich, T.; Budinger, T.F.

    1987-01-01

    The authors describe a positron tomography using a single ring of 600 close-packed 3 mm wide bismuth germanate (BGO) crystals coupled to 14 mm phototubes. The phototube preamplifier circuit derives a timing pulse from the first photoelectron, and sends it to address and coincidence circuits only if the integrated pulse height is within a pre-set window. The timing delays and pulse height windows for all 600 detectors and the coincidence timing windows are computer adjustable. An orbiting positron source is used for transmission measurements and look-up table is used to reject scattered and random coincidences that do not pass through the source. Data can be acquired using a stationary mode for 1.57 mm lateral sampling or the two-position clam sampling mode for 0.79 mm lateral sampling. High maximum data rates are provided by 45 parallel coincidence circuits and 4 parallel histogram memory units. With two-position sampling and 1.57 mm bins, the reconstructed point spread function (PSF) of a 0.35 mm diam /sup 22/Na wire source at the center of the tomograph is circular with 2.9 mm full-width at half-maximum (fwhm) and the PSF at a distance of 8 cm from the center is elliptical with a radial fwhm of 4.0 mm and tangential fwhm of 3.0 mm

  9. Positron studies of metal-oxide-semiconductor structures

    Science.gov (United States)

    Au, H. L.; Asoka-Kumar, P.; Nielsen, B.; Lynn, K. G.

    1993-03-01

    Positron annihilation spectroscopy provides a new probe to study the properties of interface traps in metal-oxide semiconductors (MOS). Using positrons, we have examined the behavior of the interface traps as a function of gate bias. We propose a simple model to explain the positron annihilation spectra from the interface region of a MOS capacitor.

  10. Production of slow-positron beams with an electron linac

    International Nuclear Information System (INIS)

    Howell, R.H.; Alvarez, R.A.; Stanek, M.

    1982-01-01

    Intense, pulsed beams of low-energy positrons have been produced by a high-energy beam from an electron linac. The production efficiency for low-energy positrons has been determined for electrons with 60 to 120 MeV energy, low-energy positron beams from a linac can be of much higher intensity than those beams currently derived from radioactive sources

  11. Positron collisions with helium and alkaline earth-like atoms

    International Nuclear Information System (INIS)

    Campbell, C.P.

    1998-09-01

    This doctoral thesis is subdivided into: 1. Theory of positron collisions with helium and alkaline earth-like atoms, 2. Positron collisions with helium, magnesium, calcium, zinc, 3. Intercomparison of positron scattering by all those elements. The appendix of this work gives details of the numerical calculations and expands on the wavefunctions used

  12. In-situ positron emission of CO oxidation

    NARCIS (Netherlands)

    Vonkeman, K.A.; Jonkers, G.; Wal, van der S.W.A.; Santen, van R.A.

    1993-01-01

    Using a Neuro ECAT positron tomog., the Positron Emission computed Tomog. (PET) was utilized to image the catalytic oxidn. of CO by using CO and CO2, labeled with short lived positron emitting nuclides. Studies were performed over highly dispersed CeO2/g-Al2O3 supported Pt and Rh catalysts. With a

  13. Positron Transport and Annihilation in the Galactic Bulge

    Directory of Open Access Journals (Sweden)

    Fiona Helen Panther

    2018-03-01

    Full Text Available The annihilation of positrons in the Milky Way Galaxy has been observed for ∼50 years; however, the production sites of these positrons remains hard to identify. The observed morphology of positron annihilation gamma-rays provides information on the annihilation sites of these Galactic positrons. It is understood that the positrons responsible for the annihilation signal originate at MeV energies. The majority of sources of MeV positrons occupy the star-forming thin disk of the Milky Way. If positrons propagate far from their sources, we must develop accurate models of positron propagation through all interstellar medium (ISM phases in order to reveal the currently uncertain origin of these Galactic positrons. On the other hand, if positrons annihilate close to their sources, an alternative source of MeV positrons with a distribution that matches the annihilation morphology must be identified. In this work, I discuss the various models that have been developed to understand the origin of the 511 keV line from the direction of the Galactic bulge, and the propagation of positrons in the ISM.

  14. Construction report of the PF slow-positron source. 1

    International Nuclear Information System (INIS)

    Enomoto, Atsushi; Kurihara, Toshikazu; Kobayashi, Hitoshi

    1993-12-01

    The slow positron source utilizing the electron beam of the 2.5 GeV electron beam accelerator which is the synchrotron radiation injector is being constructed. The outline of the project and the present state of construction are reported. As of November, 1993, by injecting the electron beam of about 10 W to the targets for producing positrons, the slow positrons of 4 x 10 4 e + /s has been obtained in the laboratory. Finally, with the electron beam of 30 kW, it is aimed at to obtain the slow positron beam of 2 x 10 9 e + /s. In the slow positron source, the electron beam from the 2.5 GeV linear accelerator is used as the primary beam. This beam is led to the target with electromagnets. Radiation shields were strengthened, and the electrostatic lens system was attached to efficiently extract and send out slow positrons. The conveying system for slow positrons is explained. Primary electron beam, target and moderator for producing slow positrons, the change to continuous current of pulsed slow positron beam and the heightening of luminance of slow positron beam, and the experiment on the utilization of slow positron beam, and the control system for positron conveyance path are reported. (K.I.)

  15. Positron emission tomography - a new approach to brain chemistry

    International Nuclear Information System (INIS)

    Jacobson, H.G.

    1988-01-01

    Positron emission tomography permits examination of the chemistry of the brain in living beings. Until recently, positron emission tomography had been considered a research tool, but it is rapidly moving into clinical practice. This report describes the uses and applications of positron emission tomography in examinations of patients with strokes, epilepsy, malignancies, dementias, and schizophrenia and in basic studies of synaptic neurotransmission

  16. Positron annihilation in metallic glasses - a general survey

    International Nuclear Information System (INIS)

    Brauer, G.; Kajcsos, Zs.; Kemeny, T.

    1981-08-01

    This report presents a review of the literature on positron annihilation studies concerning metallic glasses. After some general information and overview on structural models of metallic glasses as well as a short description of the positron annihilation method itself are added. Conclusions regarding information on the structure of metallic glasses obtainable by positron annihilation are also given. (author)

  17. Ingreso Temprano al Control Prenatal en una Unidad Materno Infantil

    Directory of Open Access Journals (Sweden)

    Delia Moya-Plata

    2010-12-01

    Full Text Available Introducción: El control prenatal se define como todas las acciones y procedimientos, sistemáticos y periódicos, destinados a la prevención, diagnostico y tratamiento de los factores que pueden coordinar la morbilidad y mortalidad materna y perinatal. La muerte de una madre es una tragedia evitable que afecta una vida joven llena de grandes esperanzas; es una de las experiencias más traumáticas que puede sufrir una familia y afecta seriamente el bienestar, la supervivencia y el desarrollo de los hijos, especialmente de los más pequeños. Todo lo anterior trae como consecuencia el debilitamiento de la estructura social en general. Materiales y Métodos: Es un estudio descriptivo de corte transversal, en el cual, se identificaron aspectos importantes como las variables sociodemográficas, clínicas, barreras de acceso y adherencia para el ingreso temprano al control prenatal de las gestantes que consultan a una unidad materno infantil. Resultados: El control prenatal representa una estrategia básica que permite identificar factores de riesgo y alteraciones fisiológicas en toda paciente gestante. Los resultados expresados en Le presente trabajo muestran el impacto favorable cuando no inciden las variables de riesgo. Discusión y Conclusiones: Queda demostrado que con un número suficiente de controles prenatales y efectuados en forma precoz, estas pacientes pueden ser contenidas en su situación y se llega a disminuir en forma muy importante la mortalidad perinatal. (Rev Cuid 2010;1(1:44-52.Palabras clave: Atención Prenatal, Factores Epidemiológicos, Accesibilidad a los Servicios de Salud. (Fuente: DeCS BIREME.

  18. Radiation damage of polymers studied by positron annihilation. Positron and gamma-ray irradiation effects

    International Nuclear Information System (INIS)

    Suzuki, T.; Oki, Y.; Numajiri, M.; Miura, T.; Kondo, K.; Ito, Y.

    1995-01-01

    Positron irradiation effects on polypropylene (PP) have been studied using positron sources ( 22 Na) during positron annihilation (PA) experiments. The irradiation effect was measured by the intensity (I 3 ) of the long-lived component of positronium (Ps). At a low temperature of around 100 K, I 3 for unirradiated PP samples increased due to a termination of the thermal motion of the -CH 3 groups. However, the increase in I 3 for γ-ray irradiated samples was reduced in inverse proportion to the amount of irradiation. Although no increase in I 3 was observed for 1 MGy-irradiated PP with γ-rays, an increase was observed again after a 48 h irradiation by positrons emitted from 22 Na. This may be due to a reconstructing of the polymer chains. (author)

  19. PAES: Positron annihilation induced Auger electron spectrometer

    OpenAIRE

    Hugenschmidt, Christoph

    2015-01-01

    Positron annihilation induced Auger electron spectroscopy (PAES) is a newly developed application for surface studies with high elemental selectivity and exceptional surface sensitivity. The instrument is operated by the Technische Universität München and is located at NEPOMUC.

  20. Characterization of lacunar defects by positrons annihilation

    International Nuclear Information System (INIS)

    Barthe, M.F.; Corbel, C.; Blondiaux, G.

    2003-01-01

    Among the nondestructive methods for the study of matter, the positrons annihilation method allows to sound the electronic structure of materials by measuring the annihilation characteristics. These characteristics depend on the electronic density as seen by the positon, and on the electron momentums distribution which annihilate with the positon. The positon is sensible to the coulombian potential variations inside a material and sounds preferentially the regions away from nuclei which represent potential wells. The lacunar-type defects (lack of nuclei) represent deep potential wells which can trap the positon up to temperatures close to the melting. This article describes the principles of this method and its application to the characterization of lacunar defects: 1 - positrons: matter probes (annihilation of electron-positon pairs, annihilation characteristics, positrons sources); 2 - positrons interactions in solids (implantation profiles, annihilation states, diffusion and trapping, positon lifetime spectrum: evolution with the concentration of defects); 3 - measurement of annihilation characteristics with two gamma photons (lifetime spectroscopy with the β + 22 Na isotope, spectroscopy of Doppler enlargement of the annihilation line); 4 - determination of the free volume of defects inside or at the surface of materials (annihilation signature in lacunar defects, lacuna, lacunar clusters and cavities, acceptors nature in semiconductors: ionic or lacunar, interface defects, precipitates in alloys); 5 - conclusions. (J.S.)

  1. PAES: Positron annihilation induced Auger electron spectrometer

    Directory of Open Access Journals (Sweden)

    Christoph Hugenschmidt

    2015-08-01

    Full Text Available Positron annihilation induced Auger electron spectroscopy (PAES is a newly developed application for surface studies with high elemental selectivity and exceptional surface sensitivity. The instrument is operated by the Technische Universität München and is located at NEPOMUC.

  2. Wake field in electron-positron plasmas

    International Nuclear Information System (INIS)

    Avinash, K.; Berezhiani, V.I.

    1993-03-01

    We study the creation of wake field in cold electron positron plasma by electron bunches. In the resulting plasma inhomogeneity we study the propagation of short electromagnetic pulse. In is found that wake fields can change the frequency of the radiation substantially. (author). 7 refs, 1 fig

  3. Positron annihilation in superconducting 123 compounds

    International Nuclear Information System (INIS)

    Peter, M.; Manuel, A.A.; Erb, A.

    1998-01-01

    After a brief review of the theory of angular correlation of positron annihilation radiation (ACAR), the authors illustrate experimental principles and give examples of successful determination of electron momentum density (EMD) and of positron lifetime in solids. The central question which the authors try to answer concerns the contribution of positron spectroscopy to the knowledge and understanding of the new high temperature superconducting oxides. They find that in these oxides also, partially filled bands exist and they can observe parts of their Fermi surface and measure lifetimes in accordance with band theoretical calculations. There are characteristic differences, however. The intensity of the anisotropy of the ACAR signal is below theoretical expectation and signals depend on sample preparation. Recent studies by the Geneva group have concerned dependence of the signals on impurities, on oxygen content and on the thermal history of preparation. Of particular interest are correlations between the variations of these signals and between the variations of structural and transport properties in these substances. Besides deliberate additions of impurities, the Geneva group also reports progress in the preparations of samples of highest purity (barium zirconate crucibles). The alloy series Pr x Y 1-x Ba 2 Cu 3 O 7-δ is of special interest because of exceptional transport properties. The recent positron results on these materials will be presented and commented in the light of theoretical models and in the light of the reported superconductivity of the Pr-compound

  4. Positron emission tomography in brain function study

    International Nuclear Information System (INIS)

    Wu Hua

    2006-01-01

    Little has been recognized about the advanced brain function. Recent years several new techniques such as event-related potentials, megnetoencephalography, functional magnetic resonance imaging and positron emission tomography (PET) have been used in the study of brain function. The methodology, application study in normal people and clinical patients of PET in brain function are reviewed. (authors)

  5. Positron emission tomography of the heart

    International Nuclear Information System (INIS)

    Budinger, T.F.; Yano, Y.; Moyer, B.R.; Mathis, C.A.; Ganz, E.; Huesman, R.H.; Derenzo, S.E.

    1982-01-01

    Positron emission tomography (PET) of the heart can measure blood perfusion, metabolism of fatty acids, metabolism of sugars, uptake of amino acids and can quantitate infarction volume. The principles which are basic to PET instrumentation and procedures for quantitative studies of the heart muscle with examples of measurements of myocardial flow and metabolism, are reviewed

  6. Positron emission tomography of the heart

    International Nuclear Information System (INIS)

    Budinger, T.F.; Yano, Y.; Huesman, R.H.; Derenzo, S.E.; Moyer, B.R.; Mathis, C.A.; Ganz, E.; Knittel, B.

    1983-01-01

    Positron emission tomography (PET) of the heart can measure blood perfusion, metabolism of fatty acids, metabolism of sugars, uptake of amino acids and can quantitate infarction volume. The principles are reviewed which are basic to PET instrumentation and procedures for quantitative studies of human physiology with examples of measurements of myocardial flow and metabolism

  7. Positron Interactions with Atoms and Ions

    Science.gov (United States)

    Bhatia, Anand K.

    2012-01-01

    Dirac, in 1928, combining the ideas of quantum mechanics and the ideas of relativity invented the well-known relativistic wave equation. In his formulation, he predicted an antiparticle of the electron of spin n-bar/2. He thought that this particle must be a proton. Dirac published his interpretation in a paper 'A theory of electrons and protons.' It was shown later by the mathematician Hermann Weyl that the Dirac theory was completely symmetric between negative and positive particles and the positive particle must have the same mass as that of the electron. In his J. Robert Oppenheimer Memorial Prize Acceptance Speech, Dirac notes that 'Blackett was really the first person to obtain hard evidence for the existence of a positron but he was afraid to publish it. He wanted confirmation, he was really over cautious.' Positron, produced by the collision of cosmic rays in a cloud chamber, was detected experimentally by Anderson in 1932. His paper was published in Physical Review in 1933. The concept of the positron and its detection were the important discoveries of the 20th century. I have tried to discuss various processes involving interactions of positrons with atoms and ions. This includes scattering, bound states and resonances. It has not been possible to include the enormous work which has been carried out during the last 40 or 50 years in theory and measurements.

  8. Tomography of positrons with SPECT systems

    International Nuclear Information System (INIS)

    Isoardi, Roberto A.

    1999-01-01

    The tomography for emissions of positrons (PET) demonstrate the clinical uses to provide information in the area of neurology, cardiology and principally, in oncology. This chapter describes the principles of the functioning and instrumentation, clinical applications and the state of the art

  9. Is positron emission tomography useful in stroke?

    NARCIS (Netherlands)

    DeReuck, J; Leys, D; DeKeyser, J

    Positron emission tomography (PET) has been widely used in the study of stroke and related cerebrovascular diseases. It has shown the various stages leading to cerebral infarction and defined the significance of the ischaemic penumbra. PET scan can predict the clinical outcome of patients with acute

  10. Positron emission tomography in malignant haematological disease

    NARCIS (Netherlands)

    Schot, Bartholomeus Wilhelmus

    2007-01-01

    Positron emission tomography (PET) is a diagnostic technique with a promising role especially in the haemato-oncology. Although its use in the management ; of malignant lymphoma seems to be established already, much about the true potential and drawbacks of FDG-PET in this disease are still unknown.

  11. Positron emission tomography applied to fluidization engineering

    NARCIS (Netherlands)

    Dechsiri, C; Ghione, A; van de Wiel, F; Dehling, HG; Paans, AMJ; Hoffmann, AC

    The movement of particles in a laboratory fluidized bed has been studied using Positron Emission Tomography (PET). With this non-invasive technique both pulses of various shapes and single tracer particles were followed in 3-D. The equipment and materials used made it possible to label actual bed

  12. Positron analysis of defects in metals

    NARCIS (Netherlands)

    van Veen, A.; Kruseman, A.C.; Schut, H.; Mijnarends, P.E.; Kooi, B.J.; de Hosson, J.T.M.; Jean, YC; Eldrup, M; Schrader, DM; West, RN

    1997-01-01

    New methods are discussed to improve defect analysis. The first method employs mapping of two shape parameters, S and W, of the positron annihilation photopeak. It is demonstrated that the combined use of S and W allows to a better discrimination of defects. The other method is based on background

  13. A positron annihilation study of hydrated DNA

    DEFF Research Database (Denmark)

    Warman, J. M.; Eldrup, Morten Mostgaard

    1986-01-01

    Positron annihilation measurements are reported for hydrated DNA as a function of water content and as a function of temperature (20 to -180.degree. C) for samples containing 10 and 50% wt of water. The ortho-positronium mean lifetime and its intensity show distinct variations with the degree...

  14. Positron annihilation spectroscopy in condensed matter

    International Nuclear Information System (INIS)

    Brauer, G.

    1982-09-01

    The topic of positron annihilation spectroscopy (PAS) is the investigation of all aspects connected with the annihilation of slow positrons. This work deals with the application of PAS to different problems of materials science. The first chapter is an introduction to fundamental aspects of positron annihilation, as far as they are important to the different experimental techniques of PAS. Chapter 2 is concerned with the information obtainable by PAS. The three main experimental techniques of PAS (2γ-angular correlation, positron lifetime and Doppler broadening) are explained and problems in the application of these methods are discussed. Chapter 3 contains experimental results. According to the different fields of application it was subgrouped into: 1. Investigations of crystalline solids. Detection of structural defects in Cu, estimation of defect concentrations, study of the sintering of Cu powders as well as lattice defects in V 3 Si. 2. Chemical investigations. Structure of mixed solvents, selective solvation of mixed solvents by electrolytes as well as the micellization of sodium dodecylsulphate in aqueous solutions. 3. Investigations of glasses. Influence of heat treatment and production technology on the preorder of X-amorphous silica glass as well as preliminary measurements of pyrocerams. 4. Investigations of metallic glasses. Demonstration of the influence of production technology on parameters measurable by PAS. Chapter 4 contains a summary as well as an outlook of further applications of PAS to surface physics, medicine, biology and astrophysics. (author)

  15. Positron lifetime studies of electron irradiated copper

    International Nuclear Information System (INIS)

    Hadnagy, T.D.

    1976-01-01

    Single-crystal copper was irradiated with 4.5-MeV electrons producing simple Frenkel defects as well as a significant concentration of divacancies. Mean positron lifetime characteristics, which are sensitive to the presence of vacancies and multivacancies in copper, was monitored after isochronal anneals between 80 and 800 0 K to determine the relative change of characteristic mean lifetimes and their associated intensities. Also a study of the dependence of the mean positron lifetime on the total electron fluence was made and compared with existing theories relating these lifetimes to vacancy or multivacancy concentrations. Numerical data from curve fitting procedures using a conventional trapping model for defect-induced changes in positron lifetimes indicate that upon irradiation with 4.5-MeV electrons at 80 0 K, about 8 percent of the defects produced are divacancy units. Divacancy units appear to be several times more effective in trapping positrons than are monovacancies. Further, the experimental data suggest that the stage III annealing processes in electron-irradiated copper most probably involve the motion and removal of both monovacancies and divacancies. A conglomerate (multivacancy) unit appears to exist as a stable entity even after annealing procedures are carried out at temperatures slightly above the stage III region. Such a stable unit could serve as a nucleation center for the appearance of voids

  16. Beta spectra. II-Positron spectra

    International Nuclear Information System (INIS)

    Grau, A.; Garcia-Torano, E.

    1981-01-01

    Using the Fermi theory of beta decay, the beta spectra for 30 positron emitters have been computed, introducing a correction factor for unique forbidden transitions. The spectra are ploted vs. energy, once normalised, and tabulated with the related Fermi functions. The average and median energies are calculated. (author)

  17. Advanced Instrumentation for Positron Emission Tomography [PET

    Science.gov (United States)

    Derenzo, S. E.; Budinger, T. F.

    1985-04-01

    This paper summarizes the physical processes and medical science goals that underlay modern instrumentation design for Positron Emission Tomography. The paper discusses design factors such as detector material, crystalphototube coupling, shielding geometry, sampling motion, electronics design, time-of-flight, and the interrelationships with quantitative accuracy, spatial resolution, temporal resolution, maximum data rates, and cost.

  18. Positron emission tomography of the lung

    International Nuclear Information System (INIS)

    Wollmer, P.

    1984-01-01

    Positron emission tomography enables the distribution of positron emitting isotopes to be imaged in a transverse plane through the body and the regional concentration of the isotope to be measured quantitatively. This thesis reports some applications of positron emission tomography to studies of pulmonary pathophysiology. Measurements in lung phantoms showed that regional lung density could be measured from a transmission tomogram obtained with an external source of positron emitting isotope. The regional, fractional blood volume was measured after labelling the blood with carbon-11-monoxide. Regional extravascular lung density (lung tissue and interstitial water per unit thoracic volume) was obtained by subtracting fractional blood volume from lung density. Measurements in normal subjects revealed large regional variations in lung density and fractional blood volume in the supine posture. Extravascular lung density showed a more uniform distribution. The technique has been used to study patients with chronic interstitial pulmonary oedema, pulmonary sarcoidosis and fibrosis, pulmonary arterial hypertension and patients with intracardiac, left-to-right shunt. Tomographic measurements of pulmonary tissue concentration of radionuclides are difficult, since corrections for the blood content and the inflation of the lung must be applied. A simultaneous measurement of lung density and fractional blood volume allows such corrections to be made and the extravascular tracer concentration to be calculated. This has been applied to measurements of the tissue penetration of carbon-11-labelled erythromycin in patients with lobar pneumonia. (author)

  19. Is the positron a light proton. Contrasts of positron/proton analogies in small molecules

    International Nuclear Information System (INIS)

    Cade, P.E.; Kao, C.-M.

    1982-01-01

    The nature of positron behavior in [M - :e + ] systems is explored. Here M - is a molecular anion which combines with a proton to form a stable system, HM. The sharp distinction between the positron and proton dynamics does not entirely remove common characteristics of these systems. Examples are given for HM versus [M - :e + ] systems with M - = (H - , SH - , CN - , and N 3- ). In addition, the possibilities of a 'positronium' bond versus a hydrogen bond are discussed. (Auth.)

  20. Projeto e desenvolvimento de uma unidade didática de apoio ao ensino da teoria clássica de controle PID

    OpenAIRE

    Kleber Batistela Pereira

    2012-01-01

    Este trabalho foi concebido inicialmente através de projeto, montagem e ensaios preliminares de uma unidade analógica, para propósito didático, composta de um servomecanismo controlado pelas clássicas estratégias Proporcional, Integral e Derivativa (PID). Com este equipamento foi demonstrado os conceitos fundamentais da engenharia de controle com seus ensaios e medidas que permitem exemplificar, de forma simples e bastante pedagógica, o funcionamento e os limites operacionais de um control...

  1. Aprendizagem e cultura organizacional na sa?de da fam?lia: an?lise e reflex?es em uma unidade docente-assistencial.

    OpenAIRE

    Moreira, Josicleide de Amorim Pereira

    2013-01-01

    A Estrat?gia Sa?de da Fam?lia enfrenta hoje o grande desafio de superar um modelo de aten??o biologicista, e consolidar-se como espa?o de cuidado integral, de inova??o, e de aprendizagem cont?nua. Reconhecer as diferentes subculturas nas organiza??es e potencializar a aprendizagem individual e coletiva ? essencial em espa?os como este. Nesta pesquisa estudamos a Aprendizagem e a Cultura Organizacional em uma unidade docente-assistencial, campo de pr?tica para alguns cursos de gradua??o...

  2. Positron deep level transient spectroscopy — a new application of positron annihilation to semiconductor physics

    Science.gov (United States)

    Beling, C. D.; Fung, S.; Au, H. L.; Ling, C. C.; Reddy, C. V.; Deng, A. H.; Panda, B. K.

    1997-05-01

    Recent positron mobility and lifetime measurements made on ac-biased metal on semi-insulating GaAs junctions, which have identified the native EL2 defect through a determination of the characteristic ionization energy of the donor level, are reviewed. It is shown that these measurements point towards a new spectroscopy, tentatively named positron-DLTS (deep level transient spectroscopy), that is the direct complement to conventional DLTS in that it monitors transients in the electric field of the depletion region rather than the inversely related depletion width, as deep levels undergo ionization. In this new spectroscopy, which may be applied to doped material by use of a suitable positron beam, electric field transients are monitored through the Doppler shift of the annihilation radiation resulting from the drift velocity of the positron in the depletion region. Two useful extensions of the new spectroscopy beyond conventional capacitance-DLTS are suggested. The first is that in some instances information on the microstructure of the defect causing the deep level may be inferred from the sensitivity of the positron to vacancy defects of negative and neutral charge states. The second is that the positron annihilation technique is intrinsically much faster than conventional DLTS with the capability of observing transients some 10 6 times faster, thus allowing deep levels (and even shallow levels) to be investigated without problems associated with carrier freeze-out.

  3. Positron annihilation in SiO 2-Si studied by a pulsed slow positron beam

    Science.gov (United States)

    Suzuki, R.; Ohdaira, T.; Uedono, A.; Kobayashi, Y.

    2002-06-01

    Positron and positronium (Ps) behavior in SiO 2-Si have been studied by means of positron annihilation lifetime spectroscopy (PALS) and age-momentum correlation (AMOC) spectroscopy with a pulsed slow positron beam. The PALS study of SiO 2-Si samples, which were prepared by a dry-oxygen thermal process, revealed that the positrons implanted in the Si substrate and diffused back to the interface do not contribute to the ortho-Ps long-lived component, and the lifetime spectrum of the interface has at least two components. From the AMOC study, the momentum distribution of the ortho-Ps pick-off annihilation in SiO 2, which shows broader momentum distribution than that of crystalline Si, was found to be almost the same as that of free positron annihilation in SiO 2. A varied interface model was proposed to interpret the results of the metal-oxide-semiconductor (MOS) experiments. The narrow momentum distribution found in the n-type MOS with a negative gate bias voltage could be attributed to Ps formation and rapid spin exchange in the SiO 2-Si interface. We have developed a two-dimensional positron lifetime technique, which measures annihilation time and pulse height of the scintillation gamma-ray detector for each event. Using this technique, the positronium behavior in a porous SiO 2 film, grown by a sputtering method, has been studied.

  4. Positron beam studies of solids and surfaces: A summary

    International Nuclear Information System (INIS)

    Coleman, P.G.

    2006-01-01

    A personal overview is given of the advances in positron beam studies of solids and surfaces presented at the 10th International Workshop on Positron Beams, held in Doha, Qatar, in March 2005. Solids studied include semiconductors, metals, alloys and insulators, as well as biophysical systems. Surface studies focussed on positron annihilation-induced Auger electron spectroscopy (PAES), but interesting applications of positron-surface interactions in fields as diverse as semiconductor technology and studies of the interstellar medium serve to illustrate once again the breadth of scientific endeavour covered by slow positron beam investigations

  5. Positron beam studies of solids and surfaces: A summary

    Science.gov (United States)

    Coleman, P. G.

    2006-02-01

    A personal overview is given of the advances in positron beam studies of solids and surfaces presented at the 10th International Workshop on Positron Beams, held in Doha, Qatar, in March 2005. Solids studied include semiconductors, metals, alloys and insulators, as well as biophysical systems. Surface studies focussed on positron annihilation-induced Auger electron spectroscopy (PAES), but interesting applications of positron-surface interactions in fields as diverse as semiconductor technology and studies of the interstellar medium serve to illustrate once again the breadth of scientific endeavour covered by slow positron beam investigations.

  6. Development of slow positron beam lines and applications

    Science.gov (United States)

    Mondal, Nagendra Nath

    2018-05-01

    A positron is an antiparticle of an electron that can be formed in diverse methods: natural or artificial β-decay process, fission and fusion reactions, and a pair production of electron-positron occurred in the reactor and the high energy accelerator centers. Usually a long-lifetime radio isotope is customized for the construction of a slow positron beam lines in many laboratories. The typical intensity of this beam depends upon the strength of the positron source, moderator efficiency, and guiding, pulsing, focusing and detecting systems. This article will review a few positron beam lines and their potential applications in research, especially in the Positronium Bose-Einstein Condensation.

  7. Ice and Atoms: experiments with laboratory-based positron beams

    International Nuclear Information System (INIS)

    Coleman, P G

    2011-01-01

    This short review presents results of new positron and positronium (Ps) experiments in condensed matter and atomic physics, as an illustration of the satisfying variety of scientific endeavours involving positron beams which can be pursued with relatively simple apparatus in a university laboratory environment. The first of these two studies - on ice films - is an example of how positrons and Ps can provide new insights into an important system which has been widely interrogated by other techniques. The second is an example of how simple positron beam systems can still provide interesting information - here on a current interesting fundamental problem in positron atomic physics.

  8. Study of radiation damage in metals by positron annihilation

    International Nuclear Information System (INIS)

    Gauster, W.B.

    1977-01-01

    Positron annihilation is a sensitive technique for probing defects in metals and it has recently been shown to be a valuable tool for the study of radiation damage. After an introduction to the three basic experimental methods (angular correlation, Doppler broadening, and lifetime measurements), the interaction of positrons with lattice defects is reviewed. Results for the annealing of damage after low temperature irradiation are used to show that positron annihilation has provided new information on annealing kinetics. The role of positron techniques in characterizing complex defect structures resulting from high-temperature neutron irradiation is reviewed and the possible utility of positron annihilation as a nondestructive monitor of property changes is pointed out

  9. UNIDADE MÓVEL PARA O BENEFICIAMENTO DE TOMATE/ITINERANT UNITY FOR TOMATOES HANDLING PROCESS

    Directory of Open Access Journals (Sweden)

    RICARDO RODRIGUES TEIXEIRA

    2008-11-01

    Full Text Available RESUMOAs perdas pós-colheita de tomate apresentam níveis bastante elevados, sendo proporcionais ao tempo de exposição dos frutos a condições climáticas adversas no período entre a colheita e o beneficiamento. Neste contexto, o presente trabalho propõe o desenvolvimento de uma unidade móvel para o beneficiamento de tomates em campo, visando reduzir o tempo entre a colheita e o beneficiamento de tomates e, conseqüentemente, reduzir as perdas pós-colheita. Para tal, foram identificados em campo os processos e tarefas necessários para o beneficiamento de tomates, empregados como base no desenvolvimento da unidade móvel. A unidade móvel foi então montada sobre uma carroceria do tipo baú. Foram avaliados os custos para a construção da unidade móvel e custos operacionais. A unidade móvel apresentou-se como uma solução de custo relativamente baixo para a redução das perdas pós-colheita do tomate.PALAVRAS-CHAVES: Perdas pós-Colheita, Qualidade dos Frutos, Qualidade do Tomate.

  10. UNIDADES DE FRIO PARA MACIEIRAS NA REGIÃO DE VACARIA – RS, BRASIL

    Directory of Open Access Journals (Sweden)

    LOANA SILVEIRA CARDOSO

    2015-06-01

    Full Text Available As macieiras necessitam de um período de acumulação de frio para a quebra da dormência das gemas. Neste estudo, as unidades de frioforam quantificadas por diferentes métodos de cálculo para a região de Vacaria-RS, Brasil, a fim de compará-las com as necessidades de macieiras ‘Gala’ e ‘Fuji’. As unidades de frio foram calculadas para o período de2000/2009, através dos seguintes métodos: Horas de Frio Ponderadas, Utah, Carolina do Norte, Utah Modificado e Carolina do Norte Modificado. Na região estudada, o número de unidades de frio apresenta altavariabilidade entre os anos, independentemente dos métodos de cálculo. Mesmo em anos com alta disponibilidade de horas de frio, o número de unidades de frio necessárias para a quebra de dormência em macieiras ‘Gala’ e ‘Fuji’ não é alcançado, naturalmente. Maio, junho e julho é o principal trimestre para acumular unidades de frio, durante o período de dormência de gemas de macieira.

  11. Detection of tokamak plasma positrons using annihilation photons

    Energy Technology Data Exchange (ETDEWEB)

    Guanying, Yu; Liu, Jian; Xie, Jinlin [University of Science and Technology, Hefei, Anhui, 230027 (China); Li, Jiangang, E-mail: j_li@ipp.ac.cn [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui 230031 (China)

    2017-05-15

    Highlights: • A design for detection of tokamak plasma positrons is given. • Identify the main obstacle toward experimental confirmation of fusion plasma positrons. • Signal to noise ratio in a plasma disruption is estimated. • Unique potential applications of fusion plasma positrons are discussed. - Abstract: A massive amount of positrons (plasma positrons), produced by the collision between runaway electrons and nuclei during fusion plasma disruption, was first predicted theoretically in 2003. To help confirm this prediction, we report here the design of an experimental system to detect tokamak plasma positrons. Because a substantial amount of positrons (material positrons) are produced when runaway electrons impact plasma-facing materials, we proposed maximizing the ratio of plasma to material positrons by inserting a thin carbon target at the plasma edge as a plasma positron bombing target and producing a plasma disruption scenario triggered by massive gas injection. Meanwhile, the coincidence detection of positron annihilation photons was used to filter out the noise of annihilation photons from locations other than the carbon target and that of bremsstrahlung photons near 511 keV. According to our simulation, the overall signal-to-noise ratio should be more than 10:1.

  12. Recent developments in the theory of positrons at surfaces

    International Nuclear Information System (INIS)

    Walker, A.B.

    1989-01-01

    Positron beams of ever brighter intensity are now establishing themselves as a novel surface probe enabling a wide variety of spectroscopies. The production of high positron intensities and exploitation of the beams depends critically on our understanding of the complex behaviour of positrons at and near surfaces. I will review progress on the theory of positron-surface interactions and of the implantation and diffusion of low energy positrons. Applications of this theory to a variety of experimental techniques such as ACAR (Angular Correlation by Annihilation Radiation) spectra, angle resolved positronium (Ps) spectroscopy, REPELS (Reemitted Positron Energy Loss Spectroscopy), LEPD (Low Energy Positron Diffraction) and measurements of defect profiles will be discussed. 24 refs. (author)

  13. Positron lifetime technique with applications in materials science

    International Nuclear Information System (INIS)

    Vries, J. de.

    1987-01-01

    This thesis deals with the positron lifetime technique as a method to measure extremely low concentrations of extremely small cavities in materials. The method is based upon the fact that the positron lieftime decreases as the electron density increases and upon the fact that a positron preferably annihilates in cavity-like defects in lattices. The theory of positron behaviour in materials and technical aspects of measuring positron liefetimes are described in ch.'s 2 and 3 respectively. Three methods for increasing the time resolution are discussed and some positron sources are described (ch.4). Some applications of the positron lifetime technique and experimental results are shown in chapter 5. 125 refs.; 61 figs.; 18 tabs

  14. PREFACE: The International Workshop on Positron Studies of Defects 2014

    Science.gov (United States)

    Sugita, Kazuki; Shirai, Yasuharu

    2016-01-01

    The International Workshop on Positron Studies of Defects 2014 (PSD-14) was held in Kyoto, Japan from 14-19 September, 2014. The PSD Workshop brought together positron scientists interested in studying defects to an international platform for presenting and discussing recent results and achievements, including new experimental and theoretical methods in the field. The workshop topics can be characterized as follows: • Positron studies of defects in semiconductors and oxides • Positron studies of defects in metals • New experimental methods and equipment • Theoretical calculations and simulations of momentum distributions, positron lifetimes and other characteristics for defects • Positron studies of defects in combination with complementary methods • Positron beam studies of defects at surfaces, interfaces, in sub-surface regions and thin films • Nanostructures and amorphous materials

  15. Experimental Study of a Positron\\\\ Source Using Channeling

    CERN Multimedia

    Gavrykov, V; Kulibaba, V; Baier, V; Beloborodov, K; Bojenok, A; Bukin, A; Burdin, S; Dimova, T; Druzhinin, V; Dubrovin, M; Seredniakov, S; Shary, V; Strakhovenko, V; Keppler, P; Major, J; Bogdanov, A V; Potylitsin, A; Vnoukov, I; Artru, X; Lautesse, P; Poizat, J-C; Remillieux, J

    2002-01-01

    Many simulations have predicted that the yield of positrons, resulting from the interaction of fast electrons in a solid target, increases if the target is a crystal oriented with a major axis parallel to the electron beam. Tests made at Orsay and Tokyo confirmed these expectations. The experiment WA 103 concerns the determination of the main characteristics (emittance, energy spread) of a crystal positron source which could replace advantageously the conventional positron converters foreseen in some linear collider projects. The main element of the set-up is a magnetic spectrometer, using a drift chamber, where the positron trajectories are reconstructed (see Figure 1) A first run has been operated in july 2000 and the first results showed, as expected, a significant enhancement in photon and positron generation along the $$ axis of the tungsten crystal. Indications about a significant increase in the number of soft photons and positrons were also gathered : this point is of importance for the positron colle...

  16. Positron annihilation in germanium in thermal equilibrium at high temperature

    Energy Technology Data Exchange (ETDEWEB)

    Uedono, Akira; Moriya, Tsuyoshi; Komuro, Naoyuki; Tanigawa, Shoichiro [Tsukuba Univ., Ibaraki (Japan). Inst. of Materials Science; Kawano, Takao; Ikari, Atsushi

    1996-09-01

    Annihilation characteristics of positrons in Ge in thermal equilibrium at high temperature were studied using a monoenergetic positron beam. Precise measurements of Doppler broadening profiles of annihilation radiation were performed in the temperature range between 300 K and 1211 K. The line shape parameters of Doppler broadening profiles were found to be almost constant at 300-600 K. The changes in these parameters were observed to start above 600 K. This was attributed to both the decrease in the fraction of positrons annihilating with core electrons and the lowering of the crystal symmetry around the region detected by positron-electron pairs. This suggests that behaviors of positrons are dominated by some form of positron-lattice coupling in Ge at high temperatures. The temperature dependence of the diffusion length of positrons was also discussed. (author)

  17. Investigation and realization of a slow-positron beam

    International Nuclear Information System (INIS)

    Ruiz, Nicolas

    2011-01-01

    This research thesis first proposes a presentation of the GBAR project (Gravitational Behaviour of Anti-hydrogen at Rest) within which this research took place, and which aims at performing the first direct test of the Weak Equivalence Principle on anti-matter by studying the free fall of anti-hydrogen atoms in the Earth gravitational field. The author presents different aspects of this project: scientific objective, experiment principle and structure, detailed structure (positron beam, positron trap, positron/positronium conversion, anti-proton beam, trapping, slowing down and neutralisation of anti-hydrogen ions). The author then reports the design of the positron beam: study of source technology, studies related to the fast positron source, design of the low positron line (approach, functions, simulations, technology). The two last chapters report the construction and the characterization of the slow-positron line [fr

  18. Ultrarelativistic electron and positron radiation in planar channeling

    International Nuclear Information System (INIS)

    Kalashnikov, N.P.; Olchack, A.S.

    1980-01-01

    The coherent electromagnetic radiation from channeling electrons and positrons is given by similar expression. However for the channeling positrons the close collisions are suppressed due to the fact that the positron wave function is exponentially small near the atoms of the crystal lattice. It follows that the coherent bremsstrahlung decreases for the channeling positrons. We have investigated the ultrarelativistic channeling electron and positron radiations, connected with the electromagnetic transitions from the continuum spectrum states to the quasi-bound spectrum states and between the different quasi-bound spectrum states. The radiation probabilities are calculated by using the model continuum planar potential. It is shown that the radiation from the channeling electrons is several orders of magnitude larger than the positron radiation, while the electron and positron radiation have similar characteristics such as frequency limitation and angular distribution of the radiation. (orig.)

  19. Diagnosis and evaluation of gastric cancer by positron emission tomography

    Science.gov (United States)

    Wu, Chen-Xi; Zhu, Zhao-Hui

    2014-01-01

    Gastric cancer is the second leading cause of cancer mortality worldwide. The diagnosis of gastric cancer has been significantly improved with the broad availability of gastrointestinal endoscopy. Effective technologies for accurate staging and quantitative evaluation are still in demand to merit reasonable treatment and better prognosis for the patients presented with advanced disease. Preoperative staging using conventional imaging tools, such as computed tomography (CT) and endoscopic ultrasonography, is inadequate. Positron emission tomography (PET), using 18F-fluorodeoxyglucose (FDG) as a tracer and integrating CT for anatomic localization, holds a promise to detect unsuspected metastasis and has been extensively used in a variety of malignancies. However, the value of FDG PET/CT in diagnosis and evaluation of gastric cancer is still controversial. This article reviews the current literature in diagnosis, staging, response evaluation, and relapse monitoring of gastric cancer, and discusses the current understanding, improvement, and future prospects in this area. PMID:24782610

  20. Effects of positron density and temperature on large amplitude ion-acoustic waves in an electron-positron-ion plasma

    International Nuclear Information System (INIS)

    Nejoh, Y.N.

    1997-01-01

    The nonlinear wave structures of large amplitude ion-acoustic waves are studied in a plasma with positrons. We have presented the region of existence of the ion-acoustic waves by analysing the structure of the pseudopotential. The region of existence sensitively depends on the positron to electron density ratio, the ion to electron mass ratio and the positron to electron temperature ratio. It is shown that the maximum Mach number increases as the positron temperature increases and the region of existence of the ion-acoustic waves spreads as the positron temperature increases. 12 refs., 6 figs

  1. Generation and application of slow positrons based on a electron LINAC

    International Nuclear Information System (INIS)

    Kurihara, Toshikazu

    2002-01-01

    History of slow positron in Institute of Materials Structure Science High Energy Accelerator Research Organization is explained. The principle of generation and application of intense positron beam is mentioned. Two sources of intense positron are radioactive decay of radioactive isotopes emitting positron and electron-positron pair creation. The radioactive decay method uses 58 Co, 64 Cu, 11 C, 13 N, 15 O and 18 F. The electron-positron pair creation method uses nuclear reactor or electron linear accelerator (LINAC). The positron experimental facility in this organization consists of electron LINAC, slow positron beam source, positron transport and experimental station. The outline of this facility is started. The intense slow positron beam is applied to research positronium work function, electron structure of surface. New method such as combination of positron lifetime measurement and slow positron beam or Auger electron spectroscopy by positron annihilation excitation and positron reemission microscope are developed. (S.Y.)

  2. Positron production in superheavy collisional systems - a sensitive probe for new atomic as well as nuclear physical phenomena

    International Nuclear Information System (INIS)

    Tsertos, H.

    1985-04-01

    In the present thesis a systematic study of the integral and spectral properties of the positron production in the collisional systems U+Pd, Pb+Th, U+Th and U+U for incident energies near the Coulomb threshold (5.9 MeV/u) was performed. Additionally for the system U+U the incident energy was varied between 5.7 MeV/u and 6.2 MeV/u with a constant step width of about 0.1 MeV/u. It could uniquely be shown that the positron production in the lighter system U+Pd can be solely explained by the nuclear production process while in the other three collisional systems both the dynamical and the nuclear positron production are experimentally verificable. The energy-integrated positron production in dependence both on the combined nuclear charge number of the collisional energy and on the impact parameter respectively the incident energy show the expected slope of a scattering process determined by the dynamics of the heavy ion collision which can be well described by the theoretical calculation. From this in the transition from the subcritical system Pb+Th to the supercritical systems U+Th and U+U no significant deviation can be observed, and so no statement about spontaneous positron emission in the supercritical system is possible. (orig./HSI) [de

  3. Compressive effect of the magnetic field on the positron range in commonly used positron emitters simulated using Geant4

    Science.gov (United States)

    Li, Chong; Cao, Xingzhong; Liu, Fuyan; Tang, Haohui; Zhang, Zhiming; Wang, Baoyi; Wei, Long

    2017-11-01

    The compressive effect of a magnetic field on the positron range from commonly used positron emitters in PET (Positron Emission Tomography) was simulated using the Geant4 toolkit with H2O as the environmental material. The compression of the positron range, which was different in the directions parallel and perpendicular to the magnetic field, showed finite final variation of relative change rate versus the magnetic field. The variation greatly depended on the positron-emission energy spectrum in the same medium. Furthermore, the volume of the positron annihilation point was dramatically compressed as the magnetic field was set in the range of 3-6T. It was more prominent for 82Rb , which is generally used as a positron source in PET technology.

  4. Analysis of defects near the surface and the interface of semiconductors by monoenergetic positron beam

    International Nuclear Information System (INIS)

    Uedono, Akira; Tanigawa, Shoichiro

    1989-01-01

    A monoenergetic low-speed positron beam line is constructed and a study is made on defects near the surface and the interface of semiconductors by using the beam line. Sodium-22 is used as beam source. Ion implantation, though being an essential technique for semiconductor integrated circuit production, can introduce lattice defects, affecting the yield and reliability of the resultant semiconductor devices. Some observations are made on the dependence of the Doppler broadening on the depth, and the ΔS-E relationship in P + -ion implanted SiO 2 (43nm)-Si. These observations demonstrate that monoenergetic positron beam is useful to detect hole-type defects resulting from ion implantation over a very wide range of defect density. Another study is made for the detection of defects near an interface. Positrons are expected to drift when left in an electric field with a gradient. Observations made here show that positrons can be concentrated at any desired interface by introducing an electric field intensity gradient in the oxide. This process also serves for accurate measurement of the electronic structure at the interface, and the effect of ion implantation and radiations on the interface. (N.K.)

  5. The non-destructive examination of reactor pressure vessel steels by positron annihilation

    International Nuclear Information System (INIS)

    Highton, J.P.

    1983-01-01

    The rapid radiation hardening of copper bearing reactor pressure vessel steels has been linked with microvoids that are associated with copper based complexes in the metal lattice. These microvoids are active in the sense that their size appears to be related to the temperature of irradiation, which thus determines their influence on dislocation mobility. These sites appear to grow by vacancy condensation which causes a reduction in the local lattice energy. Thus prolonged exposure to PWR temperatures, even in the absence of a neutron flux, may also cause embrittlement. It has been found that these sites, which represent a local negative charge, act as traps to positrons. The size of each site dictates its positron trapping potential. As the trapping potential increases so too does the probability that the positrons will annihilate with low momentum conduction electrons. The momentum of the annihilating electrons will determine the degree of Doppler broadening of the 511 keV annihilation gamma peak. Thus careful analysis of this peak can yield useful information on the degree of embrittlement caused by these active defect complexes. In this way positron annihilation offers a powerful non-destructive alternative to current methods of assessing the integrity of nuclear reactor pressure vessels. (author)

  6. La infección nosocomial. Un reto en las unidades de cuidados intensivos

    Directory of Open Access Journals (Sweden)

    Edwin Javier Gordon Zamora

    2018-01-01

    Full Text Available El estudio de la infección nosocomial en las unidades de cuidados intensivos deviene eje central de la asistencia médica y, un pilar del control de su calidad. Estas unidades asumen un elevado número de pacientes críticamente enfermos con comorbilidad, compromiso inmunológico y en contacto con dispositivos invasivos, factores estos que condicionan la diseminación de bacterias multirresistentes, por lo cual se requiere vigilancia e implementación eficiente de las medidas de prevención y control. En este trabajo se intenta abrir el debate en torno a un reto en las unidades de cuidados intensivos: las infecciones nosocomiales.

  7. Unidad y orden metafísicos del ordenamiento jurídico

    Directory of Open Access Journals (Sweden)

    Juan Carlos Riofrío Martínez-Villalba

    2014-01-01

    Full Text Available El trabajo analiza dos características constitutivas del ordenamiento jurídico: la unidad y el orden. se trabaja desde la perspectiva de una metafísica realista, bajo el método sistemático, deductivo y cualitativo. Para el efecto, se analizan los cuatro tipos de causas que pueden fundamentar la unidad y el orden del sistema jurídico. La amplitud de este esquema posibilita ir recogiendo al paso los aciertos de los neokantianos, de Kelsen, Austin, Luhmann y otros autores que han estudiado la materia. se muestran las diferentes nociones de ordenamiento jurídico y sus características principales. se estudia cómo las cuatro causas metafísicas dan unidad al ordenamiento jurídico y cómo le confieren orden. El artículo termina con unas conclusiones sintéticas.

  8. A multicrystal two dimensional BGO detector system for positron emission tomography

    International Nuclear Information System (INIS)

    Casey, M.E.; Nutt, R.

    1986-01-01

    This paper presents a discussion of a new multicrystal detector system as it is implemented in Positron Emission Tomography. The system consists of a 32 x 8 matrix of BGO crystals, a tuned light pipe, and four photomultipliers. The electronics that decodes the position consists of fast preamps, gated integrators, and level comparators. This detector represents a major development toward reducing the cost of PET

  9. O trabalho do dirigente de unidades de informação sob diferentes perspectivas administrativas

    Directory of Open Access Journals (Sweden)

    Simone de A.R. Branício

    Full Text Available O trabalho do dirigente de unidades de informação é discutido sob diferentes perspectivas administrativas, refletindo sobre novas formas de se entender o trabalho desse profissional à luz de abordagens que contemplam conceitos como gestão do aprendizado, competências e liderança. Em uma delas, as funções do administrador são definidas como planejar, organizar, dirigir e controlar, enquanto que outras evidenciam a avaliação das atividades rotineiras e a necessidade de uma visão integrada da unidade como forma de facilitar as tomadas de decisão.

  10. LA DECENA A TRAVÉS DE MATERIALES MANIPULATIVOS Propuesta de Unidad Didáctica

    OpenAIRE

    Moreno-Fernández, Mª del Mar

    2016-01-01

    Este Trabajo de Fin de Grado se realiza en el marco del Grado de Maestro en Educación Primaria de la Universidad Internacional de la Rioja. Se plantea como una unidad didáctica enfocada al uso de materiales de carácter manipulativo para el aprendizaje del concepto de la decena en alumnos de primer curso de Educación Primaria. El trabajo consta de una primera parte de contextualiza-ción teórica y de una segunda parte formada por la propuesta de unidad didáctica, donde se deta-llan competencias...

  11. Prevalência de interações medicamentosas em unidades de terapia intensiva no Brasil

    OpenAIRE

    Carvalho,Rhanna Emanuela Fontenele Lima de; Reis,Adriano Max Moreira; Faria,Leila Márcia Pereira de; Zago,Karine Santana de Azevedo; Cassiani,Silvia Helena De Bortoli

    2013-01-01

    OBJETIVO: Determinar a prevalência de interações medicamentosas em unidades de terapia intensiva e analisar a significância clínica das interações identificadas. MÉTODOS: Estudo multicêntrico, transversal e retrospectivo desenvolvido com 1124 pacientes em sete unidades de terapia intensiva (UTI) de hospitais de ensino no Brasil. As informações sobre os medicamentos administrados com 24 horas e 120 horas de internação foram obtidas nas prescrições. RESULTADOS: Em 24 horas 70,6% dos pacientes a...

  12. Transformación de un área de servicios corporativos en unidad de negocios

    OpenAIRE

    Bustamante Álvarez, América; Echeverri Granada, Lina María

    2013-01-01

    Interconexión Eléctrica S.A. –ISA– en su estrategia de internacionalización, ha identificado la necesidad de transformar la Gerencia Proyectos de Infraestructura (hasta ahora Área de Servicios Corporativos) en Unidad de Negocios -- Esta transformación tiene implicaciones en las personas, los procesos, la estructura y la cultura -- Por lo anterior, se propone un procedimiento que pueda servir de orientación, para construir el sistema de gestión de la nueva unidad de negocios, partiendo de ...

  13. Makey Makey y su posible aplicación en unidades de información

    OpenAIRE

    Itza Chaves Arias; Jonathan Esquivel Guillén; Ana Cristina Jiménez Varela; Hannia Sánchez López

    2018-01-01

    Esta revisión bibliográfica presenta el Makey Makey como un dispositivo que forma parte del Maker Movement y que puede utilizarse en las unidades de información. Por ello, se realizó una revisión de literatura que revisa el contexto histórico sobre el surgimiento de este recurso tecnológico; de hecho, en el apartado de Makey Makey se describen las principales características y usos del dispositivo; además, en la sociedad y en las unidades de información, el Makey Makey tiene diferentes caract...

  14. Positron annihilation spectroscopy in defects of semiconductors

    International Nuclear Information System (INIS)

    Fujinami, Masanori

    2002-01-01

    Interaction of positron and defects, application to research of defects of semiconductor and defects on the surface of semiconductor are explained. Cz (Czochralski)-Si single crystal with 10 18 cm -3 impurity oxygen was introduced defects by electron irradiation and the positron lifetime was measured at 90K after annealing. The defect size and recovery temperature were determined by the lifetime measurement. The distribution of defects in the depth direction is shown by S-E curve. The chemical state analysis is possible by CBS (Coincidence Doppler Broadening) spectra. The application to silicon-implanted (100 keV, 2x10 15 cm -2 ) silicon and oxygen-implanted (180 keV, 2x10 15 cm -2 ) silicon are stated. On the oxygen-implanted silicon, the main product was V2 after implantation, V 6 O 2 at 600degC and V 10 O 6 at 800degC. (S.Y.)

  15. Positron annihilation and Wheeler complexes in semiconductors

    International Nuclear Information System (INIS)

    Prokop'ev, E.P.

    1995-01-01

    Properties of Ps-Ex (positron-exciton) complex nature Wheeler complexes that may be formed at irradiation of semiconductors and ion crystals by positrons at low temperature under conditions of optical excitation by excitons are studied. Binding energy of similar and more complex systems regarding decomposition in Ps and Ex and/or Ex ± exceeds, at least, 0.1 eV, while lifetime regarding biquantum-self-annihilation constitutes τ 2γ ∼5.02x10 - 10 κ c 3 c (κ c -phenomenological parameter of the effective mass method). The lifetime estimations enabled to conclude that Ps-Ex complexes may be detected in some oxide semiconductors, in zinc sulfide, as well as, in alkaline-haloid crystals. At the same time, in silicon, gallium arsenide and in other semiconductors of A 3 B 5 and A 2 B 6 it is highly improbable to observe these complexes. 27 refs

  16. Positron Annihilation Characteristics in Polymer Composites

    International Nuclear Information System (INIS)

    Ashry, A.; Hemdan, M.; Ismail, A.; Ismail, H.; Osman, H.

    2000-01-01

    The effect of incorporation of GPF-carbon black on the free volume properties as well as the Doppler broadening parameters has been investigated for Natural rubber/Styrene Butadiene rubber (NR/SBR) blends. It is seen that, the free volume decreases with increasing of the GPF-black. Besides, as the size of the free volume decreases, the W-parameter, which corresponds to high momentum region, decreases and the S-parameter, which corresponds to low momentum one, shows an opposite behaviour. Furthermore, the d.c.electrical conductivity, mechanical and swelling behavior have been also investigated. Positron Annihilation Lifetime (PAL) and Doppler Broadening of the Annihilation Radiation (DBAR) results are compared with the other physical parameters measured. The analysis of positron annihilation parameters introduces a trusted support for the interpretations of the other macroscopic physical properties

  17. Study of tungsten based positron moderators

    Energy Technology Data Exchange (ETDEWEB)

    Lucio, O.G. de; Pérez, M.; Mendoza, U.; Morales, J.G.; Cruz, J.C. [Instituto de Física, Universidad Nacional Autónoma de México, Apartado Postal 20-364, 01000 México DF (Mexico); DuBois, R.D. [Missouri University of Science and Technology, Rolla, MO 65409 (United States)

    2015-07-01

    Positrons and how they interact with matter has a growing interest in many fields. Most of their uses require the production of slow positron beams with a well-defined energy, but since these particles are usually generated by means of a radioactive source, they are fast and with a broad distribution of energies. For this reason it is necessary to moderate them to lower energies via inelastic collisions. Then, they can be accelerated to the desired energies. This requires the use of a moderator. Tungsten is one of the most commonly used moderator materials because of its reasonable efficiency and relatively low cost. In this work we present different methods of producing transmission tungsten-based moderators, with particular interest in a combination of tungsten thin foils and grids. We also show results about the characterization of these moderators by ion beam analysis and microscopy techniques along with their relative moderation efficiencies.

  18. Positron annihilation studies in Hf doped YBCO

    International Nuclear Information System (INIS)

    Gopalan, P.; Priya, E.R.; Premila, M.; Sundar, C.S.; Gopinathan, K.P.

    1992-01-01

    The variation of positron lifetime and oxygen stoichiometry as a function of quench temperature has been measured in undoped and 0.5at%, 0.75at%, and 1.0 at% Hf doped YBCO. In both the undoped and Hf doped samples, the lifetime decreases and the oxygen content increases as the quench temperature is lowered from 900degC to 300degC. The lifetime in the tetragonal phase (900degC) decreases with the increase in Hf content, whereas in the orthorhombic phase (450degC) it increases. The difference in lifetime between the tetragonal and orthorhombic phases decreases with the increase in the Hf content. These trends are discussed in terms of the influence of Hf doping on the oxygen content and the positron density distribution in YBCO

  19. Positron scattering and annihilation from hydrogenlike ions

    International Nuclear Information System (INIS)

    Novikov, S.A.; Bromley, M.W.J.; Mitroy, J.

    2004-01-01

    The Kohn variational method is used with a configuration-interaction-type wave function to determine the J=0 and J=1 phase shifts and annihilation parameter Z eff for positron-hydrogenic ion scattering. The phase shifts are within 1-2% of the best previous calculations. The values of Z eff are small and do not exceed unity for any of the momenta considered. At thermal energies Z eff is minute with a value of order 10 -50 occurring for He + at k=0.05a 0 -1 . In addition to the variational calculations, analytic expressions for the phase shift and annihilation parameters within the Coulomb wave Born approximation are derived and used to help elucidate the dynamics of positron collisions with positive ions

  20. Application of positron annihilation in materials science

    International Nuclear Information System (INIS)

    Siegel, R.W.; Fluss, M.J.; Smedskjaer, L.C.

    1984-05-01

    Owing to the ability of the positron to annihilate from a variety of defect-trapped states, positron annihilation spectroscopy (PAS) has been applied increasingly to the characterization and study of defects in materials in recent years. In metals particularly, it has been demonstrated that PAS can yield defect-specific information which, by itself or in conjunction with more traditional experimental techniques, has already made a significant impact upon the determination of atomic-defect properties and the monitoring and characterization of vacancy-like microstructure development, as occurs during post-irradiation annealing. The applications of PAS are now actively expanding to the study of more complex defect-related phenomena in irradiated or deformed metals and alloys, phase transformations and structural disorder, surfaces and near-surface defect characterization. A number of these applications in materials science are reviewed and discussed with respect to profitable future directions

  1. Study of tungsten based positron moderators

    International Nuclear Information System (INIS)

    Lucio, O.G. de; Pérez, M.; Mendoza, U.; Morales, J.G.; Cruz, J.C.; DuBois, R.D.

    2015-01-01

    Positrons and how they interact with matter has a growing interest in many fields. Most of their uses require the production of slow positron beams with a well-defined energy, but since these particles are usually generated by means of a radioactive source, they are fast and with a broad distribution of energies. For this reason it is necessary to moderate them to lower energies via inelastic collisions. Then, they can be accelerated to the desired energies. This requires the use of a moderator. Tungsten is one of the most commonly used moderator materials because of its reasonable efficiency and relatively low cost. In this work we present different methods of producing transmission tungsten-based moderators, with particular interest in a combination of tungsten thin foils and grids. We also show results about the characterization of these moderators by ion beam analysis and microscopy techniques along with their relative moderation efficiencies

  2. Positron annihilation characterization of nanostructured ferritic alloys

    International Nuclear Information System (INIS)

    Alinger, M.J.; Glade, S.C.; Wirth, B.D.; Odette, G.R.; Toyama, T.; Nagai, Y.; Hasegawa, M.

    2009-01-01

    Nanostructured ferritic alloys (NFAs) were produced by mechanically alloying Fe-14Cr-3W-0.4Ti and 0.25Y 2 O 3 (wt%) powders followed by hot isostatic pressing consolidation at 850, 1000 and 1150 deg. C. Positron annihilation lifetime and orbital momentum spectroscopy measurements are in qualitative agreement with small angle neutron scattering, transmission electron microscopy and atom probe tomography observations, indicating that up to 50% of the annihilations occur at high densities of Y-Ti-O enriched nm-scale features (NFs). Some annihilations may also occur in small cavities. In Y-free control alloys, that do not contain NFs, positrons primarily annihilate in the Fe-Cr matrix and at features such as dislocations, while a small fraction annihilate in large cavities or Ar bubbles.

  3. Surface investigations by means of positrons annihilation

    International Nuclear Information System (INIS)

    Dryzek, J.; Stegemann, T.; Cleff, B.

    1996-01-01

    The aim of the report is a presentation of the positron annihilation studies performed on the Cu samples that surface was exposed to the friction and wear processes. Using the measurement of Doppler broadening of annihilation line, we were able to detect the profile of vacancies in the top layers of the defected metals. It was established that one could describe the profile by a simple exponential function of the depth in all cases. The range of vacancies concentration depth depends on the load, time and the speed of the defects creation processes on the surface of a sample. The outline of the positron annihilation method is also given. (author). 10 refs, 16 figs, 5 tabs

  4. Positron annihilation spectroscopy study of porous silicon

    International Nuclear Information System (INIS)

    Britkov, O.M.; Gavrilov, S.A.; Kalugin, V.V.; Timoshenkov, S.P.; Grafutin, V.I.; Ilyukhina, O.V.; Myasishcheva, G.G.; Prokop'ev, E.P.; Funtikov, Yu.V.

    2007-01-01

    Experimental studies of porous silicon by means of a standard positron annihilation technique based on measuring the angular distribution of annihilation photons, are reported. It was shown that the spectra of angular correlation of annihilation radiation in porous silicon are approximated well by a parabola (I p ) and two Gaussians (I g1 , I g2 ). The narrow Gaussian component I g1 is most likely due to the annihilation of localized para-positronium in pores. The full width at half maximum is on the order of 0.8 mrad, a value that corresponds to the kinetic energy of an annihilating positron-electron pair (0.079 ± 0.012 eV), and its intensity is about 1.5%. The total positronium yield in porous silicon reaches 6% in this case. The particle radius determined in the study is about 10-20 A [ru

  5. Image reconstruction methods in positron tomography

    International Nuclear Information System (INIS)

    Townsend, D.W.; Defrise, M.

    1993-01-01

    In the two decades since the introduction of the X-ray scanner into radiology, medical imaging techniques have become widely established as essential tools in the diagnosis of disease. As a consequence of recent technological and mathematical advances, the non-invasive, three-dimensional imaging of internal organs such as the brain and the heart is now possible, not only for anatomical investigations using X-ray but also for studies which explore the functional status of the body using positron-emitting radioisotopes. This report reviews the historical and physical basis of medical imaging techniques using positron-emitting radioisotopes. Mathematical methods which enable three-dimensional distributions of radioisotopes to be reconstructed from projection data (sinograms) acquired by detectors suitably positioned around the patient are discussed. The extension of conventional two-dimensional tomographic reconstruction algorithms to fully three-dimensional reconstruction is described in detail. (orig.)

  6. Positron annihilation study of hydrogen storage alloys

    International Nuclear Information System (INIS)

    Shirai, Yasuharu; Araki, Hideki; Sakaki, Kouji

    2003-01-01

    Some AB 5 and AB 2 hydrogen storage alloys have been characterized by using positron-annihilation lifetime spectroscopy. It has been shown that they contain no constitutional vacancies and that deviations from the stoichiometric compositions are all compensated by antistructure atoms. Positron lifetimes in fully-annealed LaNi 5-x Al x and MmNi 5-x Al x alloys show good correlation with their hydrogen desorption pressures. On the other hand, surprising amounts of vacancies together with dislocations have been found to be generated during the first hydrogen absorption process of LaNi 5 and ZrMn 2 . These lattice defects play important role in hydrogen absorption-desorption processes of hydrogen storage alloys. (author)

  7. Tomography by positrons: methodology and applications

    International Nuclear Information System (INIS)

    Kellershohn, C.; Comar, D.

    1979-01-01

    Whereas gamma tomography (single photon) provides a new and fruitful dimension to conventional nuclear medicine, tomography by positrons makes possible a novel approach to the in-vivo analysis of fundamental and biological processes. The main object of both is the cross sectional representation of the distribution of a radioactive marker injected into the organism and in comparison with conventional detectors (gamma cameras and scintigraphs) they afford a much improved accuracy in position finding. The characteristics of these two methods may be represented diagrammatically by comparing their respective advantages and drawbacks. The method of fabricating positron emitting radioelements, the preparation of the radopharmeutics and the detection appliances are then examined in turn. To conclude, the medical uses: anatomical autoradiographs, as well as physiological, metabolic and pharmacological autoradiographs are described [fr

  8. Measurement of high-Q2 deep inelastic scattering cross sections with a longitudinally polarised positron beam at HERA

    NARCIS (Netherlands)

    Chekanov, S.; Kooijman, P.

    2006-01-01

    The cross sections for charged and neutral current deep inelastic scattering in e+p collisions with a longitudinally polarised positron beam have been measured using the ZEUS detector at HERA. The results, based on data corresponding to an integrated luminosity of 23.8 pb−1 at , are given for both

  9. Nuclear-charge and positron-energy dependence of the single-quantum annihilation of positrons

    International Nuclear Information System (INIS)

    Palathingal, J.C.; Asoka-Kumar, P.; Lynn, K.G.; Wu, X.Y.

    1995-01-01

    We report an experimental study of the single-quantum annihilation of positrons in a number of elements having atomic numbers between 49 and 90, utilizing a monoenergetic positron beam. Measurements were made of the differential cross sections for the forward direction for the K, L, and M atomic shells in targets of Th, Pb, Au, Hf, Gd, and In, having thicknesses that vary between 2.7 and 4.4 mg/cm 2 . A shielded HPGe detector of high relative photopeak efficiency was used for recording the photon spectrum. Values for the individual atomic shells were obtained in the positron kinetic-energy range 1.02--2.24 MeV. It was observed that the differential cross sections measured for the forward direction varied with energy for each major shell almost alike so that the shell ratios appeared to remain constant while the positron energy varied. The dependence of the cross section on the atomic number Z of the target element was tested for each of the major shells at various energies of measurement. It was seen that the cross sections follow a Z ν relation with ν∼5.1 as the exponent for the K shell. For the higher shells, the exponent is approximately 6.4, which is significantly larger. It was also noted that this pattern is fairly independent of the positron energy. The results on the Z dependence are seen to be clearly at variance with the most updated theoretical predictions

  10. Positron spectroscopy of 2D materials using an advanced high intensity positron beam

    Science.gov (United States)

    McDonald, A.; Chirayath, V.; Lim, Z.; Gladen, R.; Chrysler, M.; Fairchild, A.; Koymen, A.; Weiss, A.

    An advanced high intensity variable energy positron beam(~1eV to 20keV) has been designed, tested and utilized for the first coincidence Doppler broadening (CDB) measurements on 6-8 layers graphene on polycrystalline Cu sample. The system is capable of simultaneous Positron annihilation induced Auger electron Spectroscopy (PAES) and CDB measurements giving it unparalleled sensitivity to chemical structure at external surfaces, interfaces and internal pore surfaces. The system has a 3m flight path up to a micro channel plate (MCP) for the Auger electrons emitted from the sample. This gives a superior energy resolution for PAES. A solid rare gas(Neon) moderator was used for the generation of the monoenergetic positron beam. The positrons were successfully transported to the sample chamber using axial magnetic field generated with a series of Helmholtz coils. We will discuss the PAES and coincidence Doppler broadening measurements on graphene -Cu sample and present an analysis of the gamma spectra which indicates that a fraction of the positrons implanted at energies 7-60eV can become trapped at the graphene/metal interface. This work was supported by NSF Grant No. DMR 1508719 and DMR 1338130.

  11. Assessment of cardiac sympathetic nerve integrity with positron emission tomography

    International Nuclear Information System (INIS)

    Raffel, David M.; Wieland, Donald M.

    2001-01-01

    The autonomic nervous system plays a critical role in the regulation of cardiac function. Abnormalities of cardiac innervation have been implicated in the pathophysiology of many heart diseases, including sudden cardiac death and congestive heart failure. In an effort to provide clinicians with the ability to regionally map cardiac innervation, several radiotracers for imaging cardiac sympathetic neurons have been developed. This paper reviews the development of neuronal imaging agents and discusses their emerging role in the noninvasive assessment of cardiac sympathetic innervation

  12. Integrated positron emission tomography/computed tomography for ...

    African Journals Online (AJOL)

    Methods. Patients who underwent both PET-CT and lymph node tissue sampling for the investigation of suspected NSCLC were prospectively included in this observational study. Results were analysed per patient and per lymph node stage. A post-hoc analysis was performed to test the validity of a maximum standardised ...

  13. The diagnostic accuracy of integrated positron emission tomography ...

    African Journals Online (AJOL)

    RESEARCH. 1049. December 2015, Vol. 105, No. 12 ... the management of pulmonary masses by preventing unnecessary .... from the data set to determine an SUVmax .... a mathematical model for predicting malignancy using age, diameter,.

  14. The diagnostic accuracy of integrated positron emission tomography ...

    African Journals Online (AJOL)

    The PET-CT findings, including maximum standardised uptake value (SUVmax), were compared with the gold standard (tissue or microbiological diagnosis). The sensitivity, specificity, positive and negative predictive values and diagnostic accuracy for malignant disease were calculated according to the SUVmax cut-off of ...

  15. Positron studies of defected metals, metallic surfaces

    International Nuclear Information System (INIS)

    Bansil, A.

    1991-01-01

    Specific problems proposed under this project included the treatment of electronic structure and momentum density in various disordered and defected systems. Since 1987, when the new high-temperature superconductors were discovered, the project focused extensively on questions concerning the electronic structure and Fermiology of high-T c superconductors, in particular, (i) momentum density and positron experiments, (ii) angle-resolved photoemission intensities, (iii) effects of disorder and substitutions in the high-T c 's

  16. Positron emission tomography in movement disorders

    International Nuclear Information System (INIS)

    Martin, W.R.W.

    1985-01-01

    Positron emission tomography provides a method for the quantitation of regional function within the living human brain. Studies of cerebral metabolism and blood flow in patients with Huntington's disease, Parkinson's disease and focal dystonia have revealed functional abnormalities within substructures of the basal ganglia. Recent developments permit assessment of both pre-synaptic and post-synaptic function ion dopaminergic pathways. These techniques are now being applied to studies of movement disorders in human subjects

  17. COSMIC-RAY POSITRONS FROM MILLISECOND PULSARS

    Energy Technology Data Exchange (ETDEWEB)

    Venter, C.; Kopp, A.; Büsching, I. [Centre for Space Research, North-West University, Potchefstroom Campus, Private Bag X6001, Potchefstroom 2520 (South Africa); Harding, A. K. [Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Gonthier, P. L. [Hope College, Department of Physics, Holland, MI (United States)

    2015-07-10

    Observations by the Fermi Large Area Telescope of γ-ray millisecond pulsar (MSP) light curves imply copious pair production in their magnetospheres, and not exclusively in those of younger pulsars. Such pair cascades may be a primary source of Galactic electrons and positrons, contributing to the observed enhancement in positron flux above ∼10 GeV. Fermi has also uncovered many new MSPs, impacting Galactic stellar population models. We investigate the contribution of Galactic MSPs to the flux of terrestrial cosmic-ray electrons and positrons. Our population synthesis code predicts the source properties of present-day MSPs. We simulate their pair spectra invoking an offset-dipole magnetic field. We also consider positrons and electrons that have been further accelerated to energies of several TeV by strong intrabinary shocks in black widow (BW) and redback (RB) systems. Since MSPs are not surrounded by pulsar wind nebulae or supernova shells, we assume that the pairs freely escape and undergo losses only in the intergalactic medium. We compute the transported pair spectra at Earth, following their diffusion and energy loss through the Galaxy. The predicted particle flux increases for non-zero offsets of the magnetic polar caps. Pair cascades from the magnetospheres of MSPs are only modest contributors around a few tens of GeV to the lepton fluxes measured by the Alpha Magnetic Spectrometer, PAMELA, and Fermi, after which this component cuts off. The contribution by BWs and RBs may, however, reach levels of a few tens of percent at tens of TeV, depending on model parameters.

  18. Positron emission tomography in movement disorders

    Energy Technology Data Exchange (ETDEWEB)

    Martin, W R.W.

    1985-02-01

    Positron emission tomography provides a method for the quantitation of regional function within the living human brain. Studies of cerebral metabolism and blood flow in patients with Huntington's disease, Parkinson's disease and focal dystonia have revealed functional abnormalities within substructures of the basal ganglia. Recent developments permit assessment of both pre-synaptic and post-synaptic function in dopaminergic pathways. These techniques are now being applied to studies of movement disorders in human subjects.

  19. Orbiting transmission source for positron tomography

    International Nuclear Information System (INIS)

    Huesman, R.H.; Derenzo, S.E.; Cahoon, J.L.; Geyer, A.B.; Moses, W.W.; Uber, D.C.; Vuletich, T.; Budinger, T.F.

    1988-01-01

    Accidental suppression and effective data rates have been measured for the orbiting transmission source as implemented in the Donner 600-Crystal Positron Tomograph. A mechanical description of the orbiting source and a description of the electronics used to discard scattered and accidental events is included. Since accidental coincidences were the rate-limiting factor in transmission data acquisition, the new method allows us to acquire sufficient transmission data in a shorter time with a more active transmission source

  20. Positron lifetime studies on thorium oxide powders

    International Nuclear Information System (INIS)

    Upadhyaya, D.D.; Muraleedharan, R.V.; Sharma, B.D.

    1982-01-01

    Positron lifetime spectra have been studied for ThO 2 powders, calcined at different temperatures and having different particle sizes. Three lifetime components could be resolved, the longest component being of low intensity. An observed strong dependence on the particle size of the annihilation process and the variation of positronium diffusion constant is explained on the basis of defect density variations in these powders. (author)

  1. Dark matter "transporting" mechanism explaining positron excesses

    Science.gov (United States)

    Kim, Doojin; Park, Jong-Chul; Shin, Seodong

    2018-04-01

    We propose a novel mechanism to explain the positron excesses, which are observed by satellite-based telescopes including PAMELA and AMS-02, in dark matter (DM) scenarios. The novelty behind the proposal is that it makes direct use of DM around the Galactic Center where DM populates most densely, allowing us to avoid tensions from cosmological and astrophysical measurements. The key ingredients of this mechanism include DM annihilation into unstable states with a very long laboratory-frame life time and their "retarded" decay near the Earth to electron-positron pair(s) possibly with other (in)visible particles. We argue that this sort of explanation is not in conflict with relevant constraints from big bang nucleosynthesis and cosmic microwave background. Regarding the resultant positron spectrum, we provide a generalized source term in the associated diffusion equation, which can be readily applicable to any type of two-"stage" DM scenarios wherein production of Standard Model particles occurs at completely different places from those of DM annihilation. We then conduct a data analysis with the recent AMS-02 data to validate our proposal.

  2. Advances in positron and electron scattering*

    Science.gov (United States)

    Limão-Vieira, Paulo; García, Gustavo; Krishnakumar, E.; Petrović, Zoran; Sullivan, James; Tanuma, Hajime

    2016-10-01

    The topical issue on Advances in Positron and Electron Scattering" combines contributions from POSMOL 2015 together with others devoted to celebrate the unprecedented scientific careers of our loyal colleagues and trusted friends Steve Buckman (Australian National University, Australia) and Michael Allan (University of Fribourg, Switzerland) on the occasion of their retirements. POSMOL 2015, the XVIII International Workshop on Low-Energy Positron and Positronium Physics and the XIX International Symposium on Electron-Molecule Collisions and Swarms, was held at Universidade NOVA de Lisboa, Lisboa, Portugal, from 17-20 July 2015. The international workshop and symposium allowed to achieve a very privileged forum of sharing and developing our scientific expertise on current aspects of positron, positronium and antiproton interactions with electrons, atoms, molecules and solid surfaces, and related topics, as well as electron interactions with molecules in both gaseous and condensed phases. Particular topics include studies of electron interactions with biomolecules, electron induced surface chemistry and the study of plasma processes. Recent developments in the study of swarms are also fully addressed.

  3. Development and applications of the positron microscope

    International Nuclear Information System (INIS)

    1991-01-01

    Progress on the positron microscope during the past year has been steady, and we currently project that initial microscope images can be collected during mid to late summer of 1992. Work during the year has mainly been divided among four areas of effort: hardware construction; power supply and control system development; radioactive source fabrication; and planning of initial experimental projects. Details of progress in these areas will be given below. An initial optical design of the microscope was completed during 1990, but during the past year, significant improvements have been made to this design, and several limiting cases of microscope performance have been evaluated. The results of these evaluations have been extremely encouraging, giving us strong indications that the optical performance of the microscope will be better than originally anticipated. In particular, we should be able to explore ultimate performance capabilities of positron microscopy using our currently planned optical system, with improvements only in the image detector system, and the positron-source/moderator configuration. We should be able to study imaging reemission microscopy with resolutions approaching 10 Angstrom and be able to produce beam spots for rastered microscope work with diameters below the 1000 Angstrom diffusion limit. Because of these exciting new possibilities, we have decided to upgrade several microscope subsystems to levels consistent with ultimate performance earlier in our construction schedule than we had previously intended. In particular, alignment facilities in the optical system, vibration isolation, and power supply and control system flexibility have all been upgraded in their design over the past year

  4. Higienização de unidade móvel de saúde | Hygiene mobile health unit

    Directory of Open Access Journals (Sweden)

    Evelise Pires Cogo Simão

    2016-07-01

    Full Text Available Introdução: Considerando a disseminação de micro-organismos no transporte e locomoção de pessoas por unidades móveis de saúde, não podemos deixar de prover a limpeza e desinfecção de todas as áreas destinadas à acomodação dos usuários e equipamentos. Objetivo: Identificar na literatura científica sobre higienização de Unidade Móvel de Saúde. Método: Trata-se de uma revisão integrativa da literatura nas bases de dados LILACS, SciELO, MEDLINE, PubMED, CINAHL, Embase, WoS, Scopus. A coleta de dados deu-se em março de 2015, incluindo artigos do período compreendido entre 2005 a 2015. Resultados: Foram selecionados 769 artigos. Destes, apenas seis artigos preencheram os critérios de inclusão. Ao caracterizar estes estudos percebe-se que todos descrevem estudos internacionais, dos quais três são da base de dados CINAHL, dois da Pubmed e um da LILACS. Conclusão: É necessária a realização de maiores investigações que subsidiem a higienização de unidades móveis de saúde, a partir da escolha do desinfetante adequado, frente à carga microbiana desses veículos, com o intuito de proporcionarem estratégias para prevenção da infecção relacionada à assistência à saúde, aumentando a adesão das boas práticas e inclusive elaboração de Protocolos Assistenciais ou Procedimentos Operacional Padrão (POP, no controle de infecção cruzada em unidades móveis de saúde. -------------------------------------------------------------------------------------------- Introduction: Considering the spread of microorganisms in the transport and mobility of people in mobile health units, the cleaning and disinfec tion of all areas for accommodation of users and equipment is crucial. Objective: To identify scientific literature related to the hygiene of mobile health units. Method: This is an integrative literature review in the databases LILACS, SciELO, MEDLINE, PubMed, CINAHL, Embase, WoS, and Scopus. The data collection

  5. Generation and application of slow positrons based on a electron LINAC

    CERN Document Server

    Kurihara, T

    2002-01-01

    History of slow positron in Institute of Materials Structure Science High Energy Accelerator Research Organization is explained. The principle of generation and application of intense positron beam is mentioned. Two sources of intense positron are radioactive decay of radioactive isotopes emitting positron and electron-positron pair creation. The radioactive decay method uses sup 5 sup 8 Co, sup 6 sup 4 Cu, sup 1 sup 1 C, sup 1 sup 3 N, sup 1 sup 5 O and sup 1 sup 8 F. The electron-positron pair creation method uses nuclear reactor or electron linear accelerator (LINAC). The positron experimental facility in this organization consists of electron LINAC, slow positron beam source, positron transport and experimental station. The outline of this facility is started. The intense slow positron beam is applied to research positronium work function, electron structure of surface. New method such as combination of positron lifetime measurement and slow positron beam or Auger electron spectroscopy by positron annihil...

  6. Low energy elastic scattering of positrons by CO: An application of continued fractions and Schwinger variational iterative methods

    Energy Technology Data Exchange (ETDEWEB)

    Arretche, F. [Departamento de Fisica, Universidade Federal de Santa Catarina, 88040-900, Florianopolis, Santa Catarina (Brazil)], E-mail: farretche@hotmail.com; Mazon, K.T.; Michelin, S.E. [Departamento de Fisica, Universidade Federal de Santa Catarina, 88040-900, Florianopolis, Santa Catarina (Brazil); Fujimoto, M.M. [Departamento de Fisica, Universidade Federal do Parana, 81531-990, Curitiba, Parana (Brazil); Iga, I.; Lee, M.-T. [Departamento de Quimica, Universidade Federal de Sao Carlos, 13565-905, Sao Paulo (Brazil)

    2008-02-15

    Iterative Schwinger variational methods and the method of continued fractions, widely used for electron-molecule scattering, are applied for the first time to investigate positron-molecule interactions. Specifically, integral and differential cross sections for elastic positron scattering by CO in the (0.5-20) eV energy range are calculated and reported. In our calculation, a static plus correlation-polarization potential is used to represent the collisional dynamics. Our calculated results are in general agreement with the theoretical and experimental data available in the literature.

  7. Positron emitting radionuclides for South Africa

    International Nuclear Information System (INIS)

    Wynchbank, S.; Van der Walt, T.N.; Sharpey-Shafer, J.

    2004-01-01

    Full text: In South Africa there are currently two projects underway to supply and utilise positron emitting radionuclides for imaging in clinical nuclear medicine facilities. The advantages and applications of such radio nuclides are numerous and well known. However the premier initial application will be to employ 1BF, at first in the compound fluorine-18 fluorodeoxyglucose ( 18 F)-FDG, for patients with cancers and neoplasms. The two projects are sited at iThemba LABS, where production of a generator supplying 66 Ga and the provision of ( 18 F]-FDG, are in an advanced state of planning; the former already fully financed by the Innovation Fund of the National Research Foundation. The two positron emitting radionuclides, 18 F and 68 Ge, will be produced using a cyclotron induced reaction on 1802 and Ga, respectively, at iThemba LABS. The 68 Ge/ 68 Ga generator consists of an anion exchanger loaded with 68 Ge, which decays to 68 Ga. The resulting radiopharmaceuticals, ( 18 F]-FDG and 68 Ga citrate, will be produced by the Radionuclide Production Group of iThemba LABS, using well described methods. However the structures and processes to be used in the generator to provide 68 Ga are novel and will be explained. Initially provision of the CBF]-FDG will be to selected clinical medicine facilities in the Western Cape and Gauteng. It should be noted that the logistical problems of providing this radiopharmaceutical (which are much complicated by its short half life of 109.7 min) to Gauteng, were shown to be surmountable in the 1970s, by a regular delivery of 18 F between Gauteng and Cape Town, after the advent of a commercial service using jet aircraft. The obvious requirement that there should be appropriate nuclear medicine facilities to image patients, at the sites to which the positron emitting radiopharmaceuticals will be supplied, has been addressed. Proposed solutions will be outlined, in terms of a dedicated positron emission tomography (PET) camera and a gamma

  8. Positron Annihilation in Thunderstorms Observed by ILDAS.

    Science.gov (United States)

    Kochkin, P.; Sarria, D., Sr.; Van Deursen, A.; de Boer, A.; Bardet, M.; Allasia, C.; Flourens, F.; Østgaard, N.

    2017-12-01

    Positron clouds within thunderstorms were for the first time reported in 2015 [Dwyer et al. 2015]. The observation was made by the Airborne Detector for Energetic Lightning Emissions (ADELE) in 2009 at 14.1 km altitude. Strong 511 keV line enhancement was recorded synchronously with nearby electrical activity. It lasted at least 0.2 s and was modeled as annihilation from disperse positron cloud more than a kilometer across. Different positron generation mechanisms were proposed in the paper. In January 2016 an Airbus A340 factory test aircraft was intentionally flying through thunderstorms over Northern Australia. The aircraft was equipped with a dedicated in-flight lightning detection system ILDAS (http://ildas.nlr.nl). The system contains two gamma-ray scintillation detectors each with 38x38 mm cylinder LaBr3 crystals. Total 9 video cameras were installed on-board to monitor the outer surfaces. When the aircraft flew at 12 km inside an active thundercloud, the ambient electric field was strong enough to trigger electrical discharges from the sharp edges. One sequence of such discharges was accompanied with enhancements of 511 keV line, each lasted for 0.5 - 1.0 s and total duration over 15 s. The video cameras recorded electrical discharges attached to the aircraft during this process. ILDAS reported brief 100 A current pulses in association with these discharges. Ground-based lightning location networks, i.e. WWLLN and local Australian LIAS, have not detected any sferics from this region. A detailed Geant4 model of the aircraft was created. The model was used to test different production mechanisms for the observed emission. In this presentation we will show a detailed reconstruction ofthe events with precise mapping on infrared cloud snapshot. Videos from the cameras at the positron detection moment will be shown. The results of the Geant4 simulation will be presented and discussed. References: 1. Dwyer, Joseph R., et al. "Positron clouds within thunderstorms

  9. Positrons annihilation and the Galactic center

    International Nuclear Information System (INIS)

    Wallyn, Pierre

    1992-01-01

    The Galactic center has been observed in gamma rays, many times since more than two decades and we do not still have a full comprehensive picture of this region. It is fairly well established that the 511 keV annihilation line has two origins: a steady diffuse emission, which follows more or less the type I supernovae distribution along the Galactic plane and a variable emission coming from the positrons emitted by (at least) one compact object and annihilating in a nearby cold molecular cloud. We present here an analysis of the profiles and intensifies of the 511 keV annihilation line observed in the direction of the Galactic center. We find that a warm medium (temperature of 8000 K) can describe the annihilation of positrons from the diffuse component of the line. The high state observations of the 511 keV line can be explained if the time-variable component is coming from the annihilation of the positrons in a cold medium (temperature around 80 K). This constraint on the annihilation medium temperature supports the association with the molecular cloud G-0.86-0.08 in the direction of 1E1740.7-2942. On may 22, 1989, HEXAGONE detected a narrow 511 keV line and also a broad emission around 170 keV in the direction of the Galactic center. Two weeks before, EXITE observed in the same direction a new transient source EXS 1737.9-2952 which showed a bump around 102 keV. We propose a simple semi-quantitative model which can mimic the bumps as well as its time variations and emphasize the strong similarities between EXS1737.9-2952 and Nova Muscae. We study the behaviour of positron annihilation by charge exchange in the cold phase of the interstellar medium. We calculate formula for the slowing-down time before thermalization of positrons of a given initial energy, for different medium densities. Our scenario explains the lack of detection of the recombination lines from positronium and gives new constraints on their possible observation. (author) [fr

  10. Positron lifetime measurements on electron irradiated amorphous alloys

    International Nuclear Information System (INIS)

    Moser, P.; Hautojaervi, P.; Chamberod, A.; Yli-Kauppila, J.; Van Zurk, R.

    1981-08-01

    Great advance in understanding the nature of point defects in crystalline metals has been achieved by employing positron annihilation technique. Positrons detect vacancy-type defects and the lifetime value of trapped positrons gives information on the size of submicroscopic vacancy aglomerates and microvoids. In this paper it is shown that low-temperature electron irradiations can result in a considerable increase in the positron lifetimes in various amorphous alloys because of the formation of vacancy-like defects which, in addition of the pre-existing holes, are able to trap positrons. Studied amorphous alloys were Fe 80 B 20 , Pd 80 Si 20 , Cu 50 Ti 50 , and Fe 40 Ni 40 P 14 B 6 . Electron irradiations were performed with 3 MeV electrons at 20 K to doses around 10 19 e - /cm 2 . After annealing positron lifetime spectra were measured at 77 K

  11. Measurement of positron range in matter in strong magnetic fields

    International Nuclear Information System (INIS)

    Hammer, B.E.; Christensen, N.L.

    1995-01-01

    Positron range is one factor that places a limitation on Positron Emission Tomography (PET) resolution. The distance a positron travels through matter before it annihilates with an electron is a function of its initial energy and the electron density of the medium. A strong magnetic field limits positron range when momentum components are transverse to the field. Measurement of positron range was determined by deconvolving the effects of detector response and radioactive distribution from the measured annihilation spread function. The annihilation spread function for a 0.5 mm bead of 68 Ga was measured with 0.2 and 1.0 mm wide slit collimators. Based on the annihilation spread function FWHM (Full Width at Half Maximum) for a 1.0 mm wide slit the median positron range in tissue equivalent material is 0.87, 0.50, 0.22 mm at 0, 5.0 and 9.4 T, respectively

  12. Intense positron beam and its application to surface science

    International Nuclear Information System (INIS)

    Ito, Y.; Hirose, M.; Kanazawa, I.; Sueoka, O.; Takamura, S.; Okada, S.

    1992-01-01

    Intense pulsed slow positron beam has been produced using the 100 MeV electron LINAC of JAERI · Tokai. In order to use the beam for surface studies such as positron diffraction and positron microscopy, it was transferred from the solenoid magnetic field to field free region and then was brightness-enhanced. The beam size was reduced from 10 mmφ (in the magnetic field) to 0.5 mmφ after two stages of re-moderation. Using the intense brightness-enhanced positron beam we have observed for the first time RHEPD (Reflection High-Energy Positron Diffraction) patterns. A design of re-emission positron microscopy is also described. (author)

  13. Techniques for slow positron beam generation and the applications

    International Nuclear Information System (INIS)

    Okada, Sohei

    1994-01-01

    Slow positron beams have been expected to be a powerful tool for observation of nature in wide range of research fields from materials science to basic physics, chemistry and biology. In this paper, at first, the beam technology is reviewed, which includes the positron generation, the transformation to slow positron beams and the beam manipulation such as beam stretching, bunching and brightness enhancement. Next, the present status of the slow positron beam applications to a variety of fields is demonstrated in terms of special characteristics of positron, that is, depth controllability, surface sensitivity, unique ionization channels and elemental anti-particle properties. Finally, prospects to produce intense slow positron beams are described. (author) 65 refs

  14. Positron Emission Tomography (PET) and breast cancer in clinical practice

    International Nuclear Information System (INIS)

    Lavayssiere, Robert; Cabee, Anne-Elizabeth; Filmont, Jean-Emmanuel

    2009-01-01

    The landscape of oncologic practice has changed deeply during the past few years and there is now a need, through a multidisciplinary approach, for imaging to provide accurate evaluation of morphology and function and to guide treatment (Image Guided Therapy). Increasing emphasis has been put on Position Emission Tomography (PET) role in various cancers among clinicians and patients despite a general context of healthcare expenditure limitation. Positron Emission Tomography has currently a limited role in breast cancer, but also general radiologists and specialists should be aware of these indications, especially when staging aggressive cancers and looking for recurrence. Currently, the hybrid systems associating PET and Computed Tomography (CT) and in the same device [Rohren EM, Turkington TG, Coleman RE. Clinical applications of PET in oncology. Radiology 2004;231:305-32; Blodgett TM, Meltzer CM, Townsend DW. PET/CT: form and function. Radiology 2007;242:360-85; von Schulthess GK, Steinert HC, Hany TF. Integrated PET/CT: current applications and futures directions. Radiology 2006;238(2):405-22], or PET-CT, are more commonly used and the two techniques are adding their potentialities. Other techniques, MRI in particular, may also compete with PET in some instance and as far as ionizing radiations dose limitation is considered, some breast cancers becoming some form of a chronic disease. Breast cancer is a very complex, non-uniform, disease and molecular imaging at large may contribute to a better knowledge and to new drugs development. Ongoing research, Positron Emission Mammography (PEM) and new tracers, are likely to bring improvements in patient care [Kelloff GJ, Hoffman JM, Johnson B, et al. Progress and promise of FDG-PET Imaging for cancer patient management and oncologic drug development. Clin Cancer Res 2005;1(April (8)): 2005

  15. Positron Emission Tomography (PET) and breast cancer in clinical practice

    Energy Technology Data Exchange (ETDEWEB)

    Lavayssiere, Robert [Centre d' Imagerie Paris-Nord, 1, avenue Charles Peguy, 95200 Sarcelles (France); Institut du Sein Henri Hartmann (ISHH), 1, rue des Dames Augustines, 92200 Neuilly sur Seine (France)], E-mail: cab.lav@wanadoo.fr; Cabee, Anne-Elizabeth [Centre d' Imagerie Paris-Nord, 1, avenue Charles Peguy, 95200 Sarcelles (France); Institut du Sein Henri Hartmann (ISHH), 1, rue des Dames Augustines, 92200 Neuilly sur Seine (France); Centre RMX, 80, avenue Felix Faure, 75105 Paris (France); Filmont, Jean-Emmanuel [Institut du Sein Henri Hartmann (ISHH), 1, rue des Dames Augustines, 92200 Neuilly sur Seine (France); American Hospital of Paris, Nuclear Medicine, 63, boulevard Victor Hugo - BP 109, 92202 Neuilly sur Seine Cedex (France)

    2009-01-15

    The landscape of oncologic practice has changed deeply during the past few years and there is now a need, through a multidisciplinary approach, for imaging to provide accurate evaluation of morphology and function and to guide treatment (Image Guided Therapy). Increasing emphasis has been put on Position Emission Tomography (PET) role in various cancers among clinicians and patients despite a general context of healthcare expenditure limitation. Positron Emission Tomography has currently a limited role in breast cancer, but also general radiologists and specialists should be aware of these indications, especially when staging aggressive cancers and looking for recurrence. Currently, the hybrid systems associating PET and Computed Tomography (CT) and in the same device [Rohren EM, Turkington TG, Coleman RE. Clinical applications of PET in oncology. Radiology 2004;231:305-32; Blodgett TM, Meltzer CM, Townsend DW. PET/CT: form and function. Radiology 2007;242:360-85; von Schulthess GK, Steinert HC, Hany TF. Integrated PET/CT: current applications and futures directions. Radiology 2006;238(2):405-22], or PET-CT, are more commonly used and the two techniques are adding their potentialities. Other techniques, MRI in particular, may also compete with PET in some instance and as far as ionizing radiations dose limitation is considered, some breast cancers becoming some form of a chronic disease. Breast cancer is a very complex, non-uniform, disease and molecular imaging at large may contribute to a better knowledge and to new drugs development. Ongoing research, Positron Emission Mammography (PEM) and new tracers, are likely to bring improvements in patient care [Kelloff GJ, Hoffman JM, Johnson B, et al. Progress and promise of FDG-PET Imaging for cancer patient management and oncologic drug development. Clin Cancer Res 2005;1(April (8)): 2005].

  16. Démarche estratégica em unidade materno infantil hospitalar Démarche estratégica en unidad materna infantil hospitalaria Strategic Démarche in a mother and child hospital unit

    Directory of Open Access Journals (Sweden)

    Maria Angélica Carvalho Andrade

    2009-02-01

    Full Text Available OBJETIVO: O enfoque démarche estratégica problematiza a dissociação entre direção estratégica da instituição e nível operacional, em busca do planejamento contínuo e flexível de projetos. O objetivo do trabalho foi descrever a aplicação deste enfoque na avaliação de unidade hospitalar. PROCEDIMENTOS METODOLÓGICOS: Foi realizada aplicação adaptada do enfoque na unidade materno-infantil de hospital público estadual, localizado no município da Serra, ES, como análise da gestão hospitalar, com envolvimento indireto dos atores institucionais que se constituíram nos informantes-chave no período de abril a julho de 2006. Além de reuniões com atores-chave, os dados foram obtidos nas fontes: livros de registros de internações do centro obstétrico, da maternidade e do berçário, faturamento do hospital, relatório estatísitico dos resultados perinatais da unidade materno infantil; livros de atendimento do ambulatório de aleitamento materno, considerando o ano de 2005. RESULTADOS: Os segmentos mais valorizados foram: unidade intensiva neonatal, centro cirúrgico obstétrico e centro obstétrico. Também obteve alta valorização o Programa de Atenção Humanizada à Mãe e ao Recém-nascido. Os principais pontos fracos evidenciados foram: baixa articulação com a rede (parceria com a rede municipal; insuficiência de leitos e de investimento tecnológico necessários para atender a demanda; rotatividade profissional devido aos vínculos temporários; e deficiente implementação da humanização comprometendo os fatores estratégicos de êxito dos segmentos. CONCLUSÕES: Os resultados mostram o potencial do método para problematizar a missão e para a análise da gestão hospitalar apontando estratégias para melhoria da qualidade e competitividade dos segmentos e para maior inserção e integração na rede de serviços.OBJETIVO: El enfoque démarche estratégica enfoca el problema de la disociación entre direcci

  17. A new slow positron beam facility using a compact cyclotron

    International Nuclear Information System (INIS)

    Hirose, Masafumi

    1998-01-01

    In 1993, Sumitomo Heavy Industries became the first in the world to successfully produce a slow positron beam using a compact cyclotron. Slow positron beam production using an accelerator had mainly consisted of using an electron linear accelerator (LINAC). However, the newly developed system that uses a compact cyclotron enabled cost reduction, downsizing of equipment, production of a DC slow positron beam, a polarized slow positron beam, and other benefits. After that, a genuine slow positron beam facility was developed with the construction of compact cyclotron No.2, and beam production in the new facility has already been started. The features of this new slow positron beam facility are explained below. 1) It is the world's first compact slow positron beam facility using a compact cyclotron. 2) It is the only genuine slow positron beam facility in the world which incorporates the production and use of a slow positron beam in the design stage of the cyclotron. To use a slow positron beam for non-destructive detection of lattice defects in semiconductor material, it is necessary to convert the beam into ultra-short pulses of several hundreds of pico-seconds. Sumitomo Heavy Industries has devised a new short-pulsing method (i.e. an induction bunching method) that enables the conversion of a slow positron beam into short pulses with an optimum pulsing electric field change, and succeeded in converting a slow positron beam into short pulses using this method for the first time in the world. Non-destructive detection of lattice defects in semiconductor material using this equipment has already been started, and some information about the depth distribution, size, density, etc. of lattice defects has already been obtained. (J.P.N.)

  18. Development of positron diffraction and holography at LLNL

    International Nuclear Information System (INIS)

    Hamza, A.; Asoka-Kumar, P.; Stoeffl, W.; Howell, R.; Miller, D.; Denison, A.

    2003-01-01

    A low-energy positron diffraction and holography spectrometer is currently being constructed at the Lawrence Livermore National Laboratory (LLNL) to study surfaces and adsorbed structures. This instrument will operate in conjunction with the LLNL intense positron beam produced by the 100 MeV LINAC allowing data to be acquired in minutes rather than days. Positron diffraction possesses certain advantages over electron diffraction which are discussed. Details of the instrument based on that of low-energy electron diffraction are described

  19. Preliminary results for positron emission mammography: real-time functional breast imaging in a conventional mammography gantry

    International Nuclear Information System (INIS)

    Weinberg, I.; Majewski, S.; Weisenberger, A.; Markowitz, A.; Aloj, L.; Majewski, L,; Danforth, D.; Mulshine, J.; Cowan, K.; Zujewski, J.; Chow, C.; Jones, E.; Chang, V.; Berg, W.; Frank, J.

    1996-01-01

    In order to optimally integrate radiotracer breast imaging within the breast clinic, anatomy and pathology should be easily correlated with functional nuclear medicine breast images. As a first step in the development of a hybrid functional/anatomic breast imaging platform with biopsy capability, a conventional X-ray mammography gantry was modified to image the compressed brest with positron emitters. Phantom studies with the positron emission mammography (PEM) device showed that a 1-cc hot spot could be detected within 5 min. A preliminary clinical trial demonstrated in vivo visualization of primary breast cancer within 4 min. For sites where positron-emitting radionuclides are available, PEM promises to achieve low-cost directed functional examination of breast abnormalities, with potential for achieving X-ray correlation and image-guided biopsy. (orig.)

  20. Unidades del paisaje de Puerto Rico: la influencia del clima, el substrato y la topografia

    Science.gov (United States)

    William Gould; Michael E. Jimenez; Gary Potts; Maya Quinones; Sebastian Martinuzzi

    2008-01-01

    El mapa de unidades del paisaje de Puerto Rico representa variaciones climaticas, topograficas y del substrato mediante la integracion de seis zonas climaticas (Ewel y Whitmore, 1973), seis substratos (Bawiec, 2001; USGS, 2005), cinco posiciones topograficas, o topoformas (Martinuzzi et al. 2007), y cuerpos de agua (USGS 2005). Los substratos representan el conjunto...

  1. Applications of positron annihilation spectroscopy to polymeric and biological systems

    International Nuclear Information System (INIS)

    Jean, Y.C.; Chen, Hongmin; Liu, Guang; Chakka, Lakshmi; Gadzia, Joseph E.

    2007-01-01

    Positron annihilation spectroscopy (PAS) is a novel radio-analytical technique which uses the positron (anti-electron) and is capable of probing the atomic and molecular scale (0.2-2 nm) free-volume and hole properties in polymeric and biological materials. Recently, we developed positron annihilation lifetime and Doppler broadening of energy spectroscopies coupled with a variable mono-energetic positron beam to measure the free-volume depth profile from the surface, interfaces, and to the bulk. This paper presents applications of PAS to determine multi-layer structures, glass transition temperatures in nano-scale polymeric films and to detect cancer in the human skin. (author)

  2. Positron annihilation study in La2CuO4

    International Nuclear Information System (INIS)

    Kubo, Y.; Asano, S.

    1992-01-01

    The positron annihilation study for La 2 CuO 4 are performed using the full-potential linearized augmented-plane-wave(FLAPW) calculated electron and positron densities. The electron-positron momentum density(EPMD) is computed, and the well known Lock-Crisp-West(LCW) zone folding of the EPMD is produced. In the LCW analysis, small residual variations of order about 3 % are observed. The calculations show that the relative weights of the Fermi surface discontinuities are substantially altered due to the positron preferentially sampling the Cu-O plane region

  3. Depth profiling of boron implanted silicon by positron beam

    International Nuclear Information System (INIS)

    Oevuenc, S.

    2004-01-01

    Positron depth profiling analyses of low energy implants of silicon aim to observe tbe structure and density of the vacancies generating by implantation and the effect of annealing. This work present the results to several set of data starting S and W parameters. Boron implanted Silicon samples with different implantation energies,20,22,24,and 26 keV are analyzed by Slow positron beam (0-40 keV and 10 5 e + /s )(Variable Energy Positron) at the Positron Centre Delf-HOLLAND

  4. Application of position-sensitive detectors to positron imaging

    International Nuclear Information System (INIS)

    Yamashita, Takaji; Uchida, Hiroshi; Watanabe, Mitsuo; Omura, Tomohide

    1994-01-01

    Positron imaging including positron emission tomography (PET) is expected to be a promising tool for basic and clinical research, because it makes possible the study of regional chemistry within multiple organs of the body in living human beings and experimental animals. New schemes of high resolution block detectors have been developed to improve the performance of positron imaging systems, which employ small segments of bismuth germanate (BGO) arrays and position-sensitive photomultiplier tubes (PS-PMT). The coincidence detector resolution of less than 2.0 mm in full width at half maximum was achieved with the detectors, which is very close to the theoretical resolution limit in positron imaging. (author)

  5. Positron lifetime study of neutron-irradiated molybdenum

    International Nuclear Information System (INIS)

    Hinode, Kenji; Tanigawa, Shoichiro; Kumakura, Hiroaki; Doyama, Masao; Shiraishi, Kensuke.

    1978-01-01

    Annealing behavior of fast-neutron-irradiated molybdenum was studied by means of positron lifetime technique. It was found that Stage III annealing can be mainly identified as the vacancy migration process from the detailed analyses of data. The void growth after successive high temperature annealings was clearly detected through the changes of positron lifetime parameters. An attempt to analyse the size distribution of voids from positron lifetime spectra was presented, and discussions on the evaluation of void concentration from positron data are also given. (author)

  6. Muon, positron and antiproton interactions with atoms and molecules

    Energy Technology Data Exchange (ETDEWEB)

    Armour, Edward A G, E-mail: edward.armour@nottingham.ac.u [School of Mathematical Sciences, University of Nottingham, Nottingham NG7 2RD (United Kingdom)

    2010-04-01

    In this paper, a description is given of some interesting processes involving the interaction of a muon, a positron, or an antiproton with atoms and molecules. The process involving a muon is the resonant formation of the muonic molecular ion, dt{mu}, in the muon catalyzed fusion cycle. In the case of a positron, the process considered is positron annihilation in low-energy positron scattering by the hydrogen molecule. The antiproton is considered as the nucleus of an antihydrogen atom interacting with simple atoms. Attention is given to antiproton annihilation through the strong interaction. An outline is given of proposed tests of fundamental physics to be carried out using antihydrogen.

  7. Positron lifetime spectroscopy of internally oxidised Ag-In alloys

    International Nuclear Information System (INIS)

    Wegner, D.; Lieb, K.P.

    1989-01-01

    The effects of In 2 O 3 precipitates on positron lifetimes after internal oxidation of α-Ag-In alloys have been investigated. A positron trap associated with the lifetime τ 205(3) ps was detected. On the basis of the experimental results obtained for different oxidation kinetics parameters, a trapping model is proposed according to which positrons thermalised in a dislocation field around oxide precipitates are trapped at the oxide/metal phase boundary. The transition from internal to external oxidation of Ag-In was also studied. The positron lifetime in In 2 O 3 was measured to be τ = 263(8) ps. (author)

  8. Caso clínico de la Unidad de Medicina Interna Integral: Neumonía

    Directory of Open Access Journals (Sweden)

    Analida E. Pinilla Roa

    1994-07-01

    Full Text Available Paciente masculino de 27 años, natural y procedente de Bogotá, indigente. Enfermedad actual. Consultó portos, con expectoración mucopurulenta y hemoptoica, dolor plurítico en hemitorax derecho, fiebre, diaforesis nocturna, astenia, adinamia y disnea progresiva de ocho días de evolución.

  9. Digital control for turbogas units; Control digital para unidades turbogas

    Energy Technology Data Exchange (ETDEWEB)

    Garcia Beltran, Carlos Daniel

    1997-02-01

    implementation and testing of several schemes of diffuse control: P, PD, PI and diffuse PID, of which the last one was selected for having a better answer. The results obtained in the simulations of the algebraic PI and of the diffuse PID, established that the second one improved the follow up indexes and reduced the starting period and the fuel consumption. [Espanol] La presente tesis trata sobre la rehabilitacion del sistema de control para las turbinas de gas W501 de la Central de Ciclo Combinado de Gomez Palacio, de Durango, Mexico. La primera parte del desarrollo trata sobre un proceso de reingenieria de software aplicado al sistema de control digital de las turbinas de gas de la central de ciclo combinado de Comez Palacio. Este proceso fue desarrollado utilizando conceptos de varias ramas de la ingenieria: a) involucro los conocimientos de la ingenieria de software, utilizando metodos formales para el analisis del sistema original y el rediseno del nuevo sistema: b) se utilizo la ingenieria de control en el analisis de diversas estrategias de control y automatizacion utilizados para el control de turbinas de gas, con el objetivo de verificar el tipo de instrucciones y rutinas presentes dentro del software. El producto final de esta etapa es un sistema programatico modularizado, basado en diseno estructurado, que es funcionalmente un espejo del sistema original. El sistema obtenido esta conformado por cinco modulos principales los cuales se basan en un modelo propuesto originalmente para control por lotes (batch) :i) Interfaz Hombre Maquina, ii) Control Regulatorio, iii) Protecciones, iv) Secuencias logicas y v) Supervision. La segunda etapa de desarrollo fue la mejora del control de velocidad de la turbina. Cuando se controla una unidad turbogas, debe tomarse en cuenta varias etapas de operacion tales como el arranque, el control en estado estable y el apagado. El comportamiento real de la turbina durante el arranque, y principalmente el gran numero de retrocesos

  10. TECNOLOGIA PARA GESTÃO DE UNIDADES DE INTERNAÇÃO HOSPITALARES

    Directory of Open Access Journals (Sweden)

    Jorge Lorenzetti

    2016-01-01

    Full Text Available En Brasil ocurren más de 18,5 millones de internaciones anuales. Las unidades de internación carecen de tecnologías de gestión que permitan mejores experiencias para pacientes y profesionales. El sistema de gestión PRAXIS suple esa brecha, el software recibió la patente 14196-6. El próposito de este artículo es describir la tacnología del PRAXIS y su proceso de contrucción y análisis de su solitud, después de un año de uso en una unidad hospitaria.El programa fue creado con soporte en la investigación metodológica, y de la cuasi-experimental para intervención en unidad de internación. Los resultados expresan la estructura de la tecnología y efectos de su implantación. Los aspectos evidenciados son beneficios de desempeño en la unidad, con planificación participativa, gestión de procesos de atención, gestión de personal, de materiales, de calidad, y uso de panel electrónico. La tecnología recibió apreciación positiva del equipo de enfermería y la comisión externa evaluadora. El proyecto precisa maduración para constituirse en recurso valioso e innovador para desempeño en las unidades de internación.

  11. MAPEAMENTO DE UNIDADES DE RELEVO NA MÉDIA SERRA DO ESPINHAÇO MERIDIONAL - MG

    Directory of Open Access Journals (Sweden)

    Éric Andrade Rezende

    2011-04-01

    Full Text Available O presente trabalho propõe um mapeamento de unidades de relevo para a porção sul do terço médio da Serra do Espinhaço Meridional. As unidades de relevo foram delimitadas a partir da análise integrada de cartas temáticas e imagens de satélite que permitiram observar variações na morfologia, na altimetria, na declividade, na litoestrutura e na organização da rede de drenagem. A etapa de cartografia digital, processada no software ArcGis 9.2, se baseou na utilização de produtos SRTM (Shuttle Radar Topography Mission. Os procedimentos metodológicos também incluíram trabalhos de campo e pesquisa bibliográfica. Foi empregada a taxonomia do mapeamento geomorfológico proposta pelo IBGE (2009, através da qual foram individualizadas quatorze Unidades Geomorfológicas. As unidades estão distribuídas entre cinco diferentes compartimentos do seguinte modo: dois planaltos, duas escarpas, seis depressões, três conjuntos de cristas e um conjunto de patamares. Foi possível observar que a disposição geral das unidades reflete o forte controle litoestrutural imposto ao relevo regional. Destaca-se a resistência diferenciada das diversas litologias frente aos processos denudacionais e a influência da neotectônica na geomorfogênese.

  12. Design and Characterization of a Three-Dimensional Positron Annihilation Spectroscopy System Using a Low-Energy Positron Beam

    Science.gov (United States)

    2012-03-22

    Technique Applied to Measure Oxygen -Atom Defects in 6H Silicon Carbide”. 2010. [31] Y. C. Jean , P. E. Mallon and D. M. Schrader. Principles and Applications...that result in β+ emission, by photon interactions with nuclei and subsequent pair production, or by β+ decays from radioactive isotopes made by...reactions for creating positrons [7], some of which are used to to create radioactive isotopes that β+ decay. Regardless of the positron source, positrons

  13. Theory of the temperature dependence of positron bulk lifetimes-implications for vacancy formation enthalpy measurements via positron experiments

    International Nuclear Information System (INIS)

    Tam, S.W.; Sinha, S.K.; Siegel, R.W.

    1977-02-01

    Temperature dependent effects, which may have a bearing on determinations of vacancy formation enthalpies in metals by positron annihilation, have been observed in certain metals. These effects have been observed to occur both at temperatures below those at which positron annihilation is most sensitive to equilibrium vacancies and at temperatures well within the vacancy-sensitive region. The effect of thermal lattice displacements on positron lifetimes in metals was investigated to help understand these phenomena

  14. Relevance of slow positron beam research to astrophysical studies of positron interactions and annihilation in the interstellar medium

    International Nuclear Information System (INIS)

    Guessoum, N.; Jean, P.; Gillard, W.

    2006-01-01

    The processes undergone by positrons in the interstellar medium (ISM) from the moments of their birth to their annihilation are examined. Both the physics of the positron interactions with gases and solids (dust grains), and the physical conditions and characteristics of the environments where the processes of energy loss, positronium formation, and annihilation taking place, are reviewed. An explanation is given as to how all the relevant physical information are taken into account in order to calculate annihilation rates and spectra of the 511 keV emission for the various phases of the ISM; special attention is paid to positron interactions with dust and with polycyclic aromatic hydrocarbons. An attempt is made to show to what extent the interactions between positrons and interstellar dust grains are similar to laboratory experiments in which beams of slow positrons impinge upon solids and surfaces. Sample results are shown for the effect of dust grains on positron annihilation spectra in some phases of the ISM which, together with high resolution spectra measured by satellites, can be used to infer useful knowledge about the environment where the annihilation is predominantly taking place and ultimately about the birth place and history of positrons in the Galaxy. The important complementarity between work done by the astrophysical and the solid-state positron communities is strongly emphasized and specific experimental work is suggested which could assist the modeling of the interaction and annihilation of positrons in the ISM

  15. Relevance of slow positron beam research to astrophysical studies of positron interactions and annihilation in the interstellar medium

    Energy Technology Data Exchange (ETDEWEB)

    Guessoum, N. [American University of Sharjah, Physics Department, P.O. Box 26666, Sharjah (United Arab Emirates)]. E-mail: nguessoum@aus.ac.ae; Jean, P. [Centre d' Etude Spatiale des Rayonnements, Toulouse (France); Gillard, W. [Centre d' Etude Spatiale des Rayonnements, Toulouse (France)

    2006-02-28

    The processes undergone by positrons in the interstellar medium (ISM) from the moments of their birth to their annihilation are examined. Both the physics of the positron interactions with gases and solids (dust grains), and the physical conditions and characteristics of the environments where the processes of energy loss, positronium formation, and annihilation taking place, are reviewed. An explanation is given as to how all the relevant physical information are taken into account in order to calculate annihilation rates and spectra of the 511 keV emission for the various phases of the ISM; special attention is paid to positron interactions with dust and with polycyclic aromatic hydrocarbons. An attempt is made to show to what extent the interactions between positrons and interstellar dust grains are similar to laboratory experiments in which beams of slow positrons impinge upon solids and surfaces. Sample results are shown for the effect of dust grains on positron annihilation spectra in some phases of the ISM which, together with high resolution spectra measured by satellites, can be used to infer useful knowledge about the environment where the annihilation is predominantly taking place and ultimately about the birth place and history of positrons in the Galaxy. The important complementarity between work done by the astrophysical and the solid-state positron communities is strongly emphasized and specific experimental work is suggested which could assist the modeling of the interaction and annihilation of positrons in the ISM.

  16. Positron Emission Tomography: Current Challenges and Opportunities for Technological Advances in Clinical and Preclinical Imaging Systems

    Science.gov (United States)

    Vaquero, Juan José; Kinahan, Paul

    2017-01-01

    Positron emission tomography (PET) imaging is based on detecting two time-coincident high-energy photons from the emission of a positron-emitting radioisotope. The physics of the emission, and the detection of the coincident photons, give PET imaging unique capabilities for both very high sensitivity and accurate estimation of the in vivo concentration of the radiotracer. PET imaging has been widely adopted as an important clinical modality for oncological, cardiovascular, and neurological applications. PET imaging has also become an important tool in preclinical studies, particularly for investigating murine models of disease and other small-animal models. However, there are several challenges to using PET imaging systems. These include the fundamental trade-offs between resolution and noise, the quantitative accuracy of the measurements, and integration with X-ray computed tomography and magnetic resonance imaging. In this article, we review how researchers and industry are addressing these challenges. PMID:26643024

  17. The electronics system for the LBNL positron emission mammography (PEM) camera

    CERN Document Server

    Moses, W W; Baker, K; Jones, W; Lenox, M; Ho, M H; Weng, M

    2001-01-01

    Describes the electronics for a high-performance positron emission mammography (PEM) camera. It is based on the electronics for a human brain positron emission tomography (PET) camera (the Siemens/CTI HRRT), modified to use a detector module that incorporates a photodiode (PD) array. An application-specified integrated circuit (ASIC) services the photodetector (PD) array, amplifying its signal and identifying the crystal of interaction. Another ASIC services the photomultiplier tube (PMT), measuring its output and providing a timing signal. Field-programmable gate arrays (FPGAs) and lookup RAMs are used to apply crystal-by-crystal correction factors and measure the energy deposit and the interaction depth (based on the PD/PMT ratio). Additional FPGAs provide event multiplexing, derandomization, coincidence detection, and real-time rebinning. Embedded PC/104 microprocessors provide communication, real-time control, and configure the system. Extensive use of FPGAs make the overall design extremely flexible, all...

  18. Positron Emission Tomography: Current Challenges and Opportunities for Technological Advances in Clinical and Preclinical Imaging Systems.

    Science.gov (United States)

    Vaquero, Juan José; Kinahan, Paul

    2015-01-01

    Positron emission tomography (PET) imaging is based on detecting two time-coincident high-energy photons from the emission of a positron-emitting radioisotope. The physics of the emission, and the detection of the coincident photons, give PET imaging unique capabilities for both very high sensitivity and accurate estimation of the in vivo concentration of the radiotracer. PET imaging has been widely adopted as an important clinical modality for oncological, cardiovascular, and neurological applications. PET imaging has also become an important tool in preclinical studies, particularly for investigating murine models of disease and other small-animal models. However, there are several challenges to using PET imaging systems. These include the fundamental trade-offs between resolution and noise, the quantitative accuracy of the measurements, and integration with X-ray computed tomography and magnetic resonance imaging. In this article, we review how researchers and industry are addressing these challenges.

  19. Mechanical design and development of a high power target system for the SLC Positron Source

    International Nuclear Information System (INIS)

    Reuter, E.; Mansour, D.; Porter, T.; Sax, W.; Szumillo, A.

    1991-12-01

    In order to bring the SLC Positron Source luminosity up to design specifications, the previous (stationary) positron target had to be replaced with a version which could reliably dissipate the higher power levels and cyclic pulsed thermal stresses of the high intensity 33GeV electron beam. In addition to this basic requirement, the new target system had to meet SLAC's specifications for Ultra High Vacuum, be remotely controllable, ''radiation hard,'' and designed in such a way that it could be removed and replaced quickly and easily with minimum personnel exposure to radiation. It was also desirable to integrate the target and collection components into a compact, easily manufacturable, and easily maintainable module. This paper briefly summarize the mechanical design and development of the new modular target system, its associated controls and software, alignment, and the quick removal system. Operational experience gained with the new system over the first running cycle is also summarized

  20. Investigation of the crystal lattice defects by means of the positrons annihilations

    International Nuclear Information System (INIS)

    Dryzek, J.

    1994-01-01

    In this report the positrons annihilation methods as a tool for the crystal defects studies is presented. The short description of the positron - crystal interactions and different positron capture models are discussed. 192 refs, 67 figs, 6 tabs

  1. Probing the positron moderation process using high-intensity, highly polarized slow-positron beams

    Science.gov (United States)

    Van House, J.; Zitzewitz, P. W.

    1984-01-01

    A highly polarized (P = 0.48 + or - 0.02) intense (500,000/sec) beam of 'slow' (Delta E = about 2 eV) positrons (e+) is generated, and it is shown that it is possible to achieve polarization as high as P = 0.69 + or - 0.04 with reduced intensity. The measured polarization of the slow e+ emitted by five different positron moderators showed no dependence on the moderator atomic number (Z). It is concluded that only source positrons with final kinetic energy below 17 keV contribute to the slow-e+ beam, in disagreement with recent yield functions derived from low-energy measurements. Measurements of polarization and yield with absorbers of different Z between the source and moderator show the effects of the energy and angular distributions of the source positrons on P. The depolarization of fast e+ transmitted through high-Z absorbers has been measured. Applications of polarized slow-e+ beams are discussed.

  2. Positron CT findings of chronic schizophrenics

    International Nuclear Information System (INIS)

    Toyoda, Junzo; Miyazaki, Chihiro; Sugai, Yuichi; Iio, Masaaki.

    1983-01-01

    Positron CT images of 15 chronic schizophrenics (2 females and 13 males) were examined in contrast to 5 male controls. Average age of controls was 36 years and that of schizophrenics was 42 years. Schizophrenic cases were ill over 6 years, averaging 17 years. All were under antipsychotic drug therapy. Tracer compounds were 11 C-CO2 and 11 C-glucose photosynthesised, the former being inhalated once just before and the latter being administered orally 10-15 minutes before examinations. On positron CT images of all normal controls, hyper-radioactivities in frontal regions were observed. Some asymmetries of activities were observed but not remarkable. There wes no difference between the images with 11 C-CO2 and those with 11 C-glucose. In schizophrenic cases, (1) 7 out of 15 cases showed hypo-activities in the frontal regions both with 11 C-CO2 and 11 C-glucose. (2) With 11 C-glucose, relative activities in the brain were lower than those in the soft tissues around the scalp, suggesting the lowered selective uptake of 11 C-glucose by the brain. (3) With 11 C-CO 2, 4 cases showed higher activities in the right temporal regions and their subcortex than the left. By consideration of relationships between these positron CT findings and clinical data such as present age, age of onset of illness, duration of illness, psychiatric symptoms, present drug amount, summed drug amount from administration, EEG and X-ray CT findings, significant correlation was recognized only between low frontal radioactivities and apathy-abulia as main symptom. Limitation on the explanation of the findings with the image alone was discussed. (author)

  3. Positron annihilation imaging device having movable collimator

    International Nuclear Information System (INIS)

    Thompson, C.J.

    1981-01-01

    This patent application relates to a positron annihilation imaging device comprising two circular arrays of detectors disposed in spaced apart parallel planes and circumferentially offset by half the detector spacing, axially movable annular outer collimator rings, generally disposed in a pair of opposite planes outside the associated planes of the detectors, each collimator being movable toward the opposite collimator. An inner collimator of annular configuration is disposed between the two rows of detectors and is formed in two rings which may be separated axially. The outer and inner collimators serve to enhance data readout and imaging. (author)

  4. Positron emission tomography of FDG in schizophrenia

    International Nuclear Information System (INIS)

    Sargent, T. III; Kusubov, N.

    1986-01-01

    The use of the Donner dynamic positron emission tomograph to study fluorodeoxyglucose labelled 18 F uptake in the brain of six patients with schizophrenia is reported. The glucose metabolic rate and the local cerebral metabolic rate were calculated. The dynamic brain uptake data and the blood input function were used to calculate rate constants by an iterative least squares fitting program for all regions of interest chosen in the brain. Although the number of patients was small, differences in k3 were statistically significant in several brain regions compared with normal controls

  5. Positron scattering from noble gases future prospects

    Energy Technology Data Exchange (ETDEWEB)

    Jones, A C L; Caradonna, P; Makochekanwa, C; Slaughter, D S; Sullivan, J P; Buckman, S J [Centre for Antimatter-Matter Studies, Research School of Physics and Engineering, Australian National University, Canberra, ACT (Australia); Mitroy, J, E-mail: acj107@rsphysse.anu.edu.a [Faculty of Education Health and Science, Charles Darwin University, NT (Australia)

    2009-11-01

    Recent results for positron scattering from noble gases over an energy range from 0.5 to 60eV are presented. Measurements include the grand total ({sigma}{sub GT}), Ps formation ({sigma}{sub Ps}) and Grand total - Ps formation (({sigma}{sub GT}-P{sub s}) cross sections. Some preliminary DCS results will also be presented. Work on a formulation of modified effective range theory (MERT) is being undertaken to determine the value of the scattering length which may be useful for identifying a bound state. Plans for experiments on metal atoms will be outlined.

  6. Positron Emission Tomography: Its 65 years

    International Nuclear Information System (INIS)

    Del Guerra, A.; Belcari, N.; Bisogni, M.

    2016-01-01

    Positron Emission Tomography (PET) is a well-established imaging technique for in vivo molecular imaging. In this review after a brief history of PET there are presented its physical principles and the technology that has been developed for bringing PET from a bench experiment to a clinical indispensable instrument. The limitations and performance of the PET tomographs are discussed, both as for the hardware and software aspects. The status of art of clinical, preclinical and hybrid scanners (i.e., PET/CT and PET/MR) is reported. Finally the actual trend and the recent and future technological developments are fully illustrated.

  7. Methods and instrumentation for positron emission tomography

    International Nuclear Information System (INIS)

    Mandelkern, M.A.; Phelps, M.E.

    1988-01-01

    This paper reports on positron emission tomography (PET), a technique for the noninvasive measurement of local tissue concentrations of injected radioactive tracers. Tracer kinetics techniques can be applied to this information to quantify physiologic function in human tissue. In the tracer method, a pharmaceutical is labeled by a radioactive atom. When introduced into the subject that molecule follows a physiologic pathway. The space- and time-dependent distribution of the radionuclide is obtained via an imaging technique. If the radiopharmaceutical is sufficiently analogous to a natural substrate or other substance of interest, a quantitative image can be translated into a physiologic measurement

  8. Three instruments for positron annihilation spectroscopy (PAS)

    International Nuclear Information System (INIS)

    Ivanov, E.A.; Plostinaru, D.; Catana, D.; Racolta, P.M.; Vata, I.

    2003-01-01

    The instruments presented here and dedicated to positron annihilation spectroscopy, PAS, are: 1. High Resolution Life Time Spectrometer (LTS) with time resolution τ = 260 ps, based on large BaF 2 scintillators; 2. Doppler Broadening Spectrometer (DBS) having a 1.6 keV resolution at 514 keV; 3. Positronium Life Time - Perturbed Angular Distribution Spectrometer ( PLT-PAD); positronium life time, in samples under high vacuum in magnetic field, is measured for time intervals up to 500 ns. Results of measurements are shown to illustrate performances of the instruments. (authors)

  9. DHCAL with Minimal Absorber: Measurements with Positrons

    CERN Document Server

    Freund, B; Repond, J.; Schlereth, J.; Xia, L.; Dotti, A.; Grefe, C.; Ivantchenko, V.; Antequera, J.Berenguer; Calvo Alamillo, E.; Fouz, M.C.; Marin, J.; Puerta-Pelayo, J.; Verdugo, A.; Brianne, E.; Ebrahimi, A.; Gadow, K.; Göttlicher, P.; Günter, C.; Hartbrich, O.; Hermberg, B.; Irles, A.; Krivan, F.; Krüger, K.; Kvasnicka, J.; Lu, S.; Lutz, B.; Morgunov, V.; Provenza, A.; Reinecke, M.; Sefkow, F.; Schuwalow, S.; Tran, H.L.; Garutti, E.; Laurien, S.; Matysek, M.; Ramilli, M.; Schroeder, S.; Bilki, B.; Norbeck, E.; Northacker, D.; Onel, Y.; Cvach, J.; Gallus, P.; Havranek, M.; Janata, M.; Kovalcuk, M.; Kvasnicka, J.; Lednicky, D.; Marcisovsky, M.; Polak, I.; Popule, J.; Tomasek, L.; Tomasek, M.; Sicho, P.; Smolik, J.; Vrba, V.; Zalesak, J.; van Doren, B.; Wilson, G.W.; Kawagoe, K.; Hirai, H.; Sudo, Y.; Suehara, T.; Sumida, H.; Takada, S.; Tomita, T.; Yoshioka, T.; Bilokin, S.; Bonis, J.; Cornebise, P.; Pöschl, R.; Richard, F.; Thiebault, A.; Zerwas, D.; Hostachy, J.Y.; Morin, L.; Besson, D.; Chadeeva, M.; Danilov, M.; Markin, O.; Popova, E.; Gabriel, M.; Goecke, P.; Kiesling, C.; Kolk, N.van der; Simon, F.; Szalay, M.; Corriveau, F.; Blazey, G.C.; Dyshkant, A.; Francis, K.; Zutshi, V.; Kotera, K.; Ono, H.; Takeshita, T.; Ieki, S.; Kamiya, Y.; Ootani, W.; Shibata, N.; Jeans, D.; Komamiya, S.; Nakanishi, H.

    2016-01-01

    In special tests, the active layers of the CALICE Digital Hadron Calorimeter prototype, the DHCAL, were exposed to low energy particle beams, without being interleaved by absorber plates. The thickness of each layer corresponded approximately to 0.29 radiation lengths or 0.034 nuclear interaction lengths, defined mostly by the copper and steel skins of the detector cassettes. This paper reports on measurements performed with this device in the Fermilab test beam with positrons in the energy range of 1 to 10 GeV. The measurements are compared to simulations based on GEANT4 and a standalone program to emulate the detailed response of the active elements.

  10. Movable collimator for positron annihilation imaging device

    International Nuclear Information System (INIS)

    Thompson, C.J.

    1982-01-01

    A positron annihilation imaging device has two or more rings of detectors from which three or more slices through the object being scanned can be determined at once. A technique is provided for adjusting the slice widths. One slice may be imaged by all detectors in adjacent planes simultaneously, and reconstructed as if all detectors were in the same plane. The single slice facility is provided without the necessity of rotating the detector array or moving it in any way during data collection, allowing the possibility of doing physiologically gated imaging of a single slice

  11. Positron annihilation study of polyphenylene dendrimers

    International Nuclear Information System (INIS)

    Marek, T.; Suevegh, K.; Vertes, A.; Ernst, A.; Bauer, R.; Weil, T.; Wiesler, U.; Klapper, M.; Muellen, K.

    2003-01-01

    The free volume of a series of rigid polyphenylene dendrimers was studied by positron lifetime spectroscopy and the experimental data were compared with results from molecular dynamics calculations. Contrary to dendrimers containing flexible repeat units rigid polyphenylene dendrimers proved to contain large stable 'inner' voids of a distinct size between their dendritic branches. The size of the 'inner' cavities increases with the size of the dendrimer. Due to these voids, polyphenylene dendrimers are potentially attractive with respect to the selective incorporation of guest molecules

  12. Contribution of positron emission tomography in neurology

    International Nuclear Information System (INIS)

    Salmon, E.; Franck, G.

    1992-01-01

    Positron Emission Tomography (PET) is a scanner technique using tracers labelled with shortlived radioisotopes which allows to study and quantify human metabolic processes or drug pharmacology in vivo. The technique is first applied in physiological studies. Sleep, normal brain metabolism or cerebral activations have been studied. The pharmacological approach concerns both drug distribution in the human brain and blood flow or metabolic variations under treatment. Main neurological applications in pathology are cerebrovascular disorders, diseases leading to dementia, epilepsy, movement disorders, and brain tumors. In each field of application, PET gives unique and frequently early informations. It nicely combines both dynamic informations and measurement precision. (author)

  13. Movable collimator for positron annihilation imaging device

    International Nuclear Information System (INIS)

    Thompson, C.J.

    1981-01-01

    A positron annihilation imaging device having two circular arrays of detectors disposed in spaced apart parallel planes wherein axially movable annular collimator rings are generally disposed in a pair of opposite planes outside the associated planes of the collimators to each collimator being movable toward the opposite collimator and a central collimator of annular configuration generally disposed between the two rows of detectors but being split into two rings which may be separated, the outer and inner collimators serving to enhance data readout and imaging

  14. Nonmedical applications of a positron camera

    International Nuclear Information System (INIS)

    Hawkesworth, M.R.; Parker, D.J.; Fowles, P.; Crilly, J.F.; Jefferies, N.L.; Jonkers, G.

    1991-01-01

    The positron camera in the School on Physics and Space Research, University of Birmingham, is based on position-sensitive multiwire γ-ray detectors developed at the Rutherford Appleton Laboratory. The current characteristics of the camera are discussed with particular reference to its suitability for flow mapping in industrial subjects. The techniques developed for studying the dynamics of processes with time scales ranging from milliseconds to days are described, and examples of recent results from a variety of industrial applications are presented. (orig.)

  15. Uma metodologia para especificação e síntese de unidades de controlo reconfiguráveis

    OpenAIRE

    Melo, Andreia Barbosa de

    2006-01-01

    Nesta tese toma-se um circuito digital estruturado de acordo com a comum divisão em unidade operacional (datapath) e unidade de controlo, e explora-se o projecto da unidade de controlo. Em concreto, explora-se o projecto de unidades de controlo complexas, que incluam reentrância e paralelismo. Além disso, explora-se a possibilidade de utilização de estruturas reutilizáveis que possam implementar diferentes unidades de controlo. A construção de arquitecturas de implementação que suportem a res...

  16. Mineralogía y génesis de las arcillas de las unidades del Campo de Gibraltar. IV. Unidad de Facinas

    Directory of Open Access Journals (Sweden)

    Ruiz Cruz, M. O.

    1989-08-01

    Full Text Available The Facinas Unit consists of a clayed flysch facies with quartzite and sandstone centimeter layers. According to paleontological data, two beds are distinguished, one lower of Albian-Aptian age, and another, hígher, Upper Cretaceous-Paleocene in age. The mineralogy of the Facinas Unit is very monotonous through all the sequences studied, especially for the concerning to less than 2 fraction. This unít is characterized by an abundance of chlorites of different composition and genesis: Authigenic chlorites are mainly Fe-rich members, whereas chlorites of inherited origin are magnesian. On the other hand, this míneralogical study reveals a common origin and/or evolution for the two beds of the Facinas Unít.Se recogen en este trabajo los resultados obtenidos a partir del estudio mineralógico de la Unidad de Facinas, que presenta dos tramos, uno inferior Albo-Aptense y otro superior Cretácico Superior-Paleoceno. Las secuencias estudiadas muestran una gran similitud litológica y, si bien en las muestras totales se observan ciertas diferencias mineralógicas, la fracción menor de 2 micras es muy homogénea. Caracterizan a esta Unidad la abundancia de cloritas de diferente composición y génesis: cloritas autigénicas, predominantemente ferrosas y cloritas heredadas, magnesianas. Por otra parte, este estudio mineralógico permite indicar un origen y/o evolución común para los dos tramos de la Unidad de Facínas.

  17. Applications of positron annihilation spectroscopy in materials research

    International Nuclear Information System (INIS)

    Singh, J.J.

    1988-01-01

    Positron Annihilation Spectroscopy (PAS) has emerged as a powerful technique for research in condensed matter. It has been used extensively in the study of metals, ionic crystals, glasses and polymers. The present review concentrates on applications of positron lifetime measurements for elucidation of the physicochemical structure of polymers. 10 references

  18. Applications of positron annihilation spectroscopy in materials research

    Science.gov (United States)

    Singh, Jag J.

    1988-01-01

    Positron Annihilation Spectroscopy (PAS) has emerged as a powerful technique for research in condensed matter. It has been used extensively in the study of metals, ionic crystals, glasses and polymers. The present review concentrates on applications of positron lifetime measurements for elucidation of the physicochemical structure of polymers.

  19. Metal/oxide/semiconductor interface investigated by monoenergetic positrons

    Science.gov (United States)

    Uedono, A.; Tanigawa, S.; Ohji, Y.

    1988-10-01

    Variable-energy positron-beam studies have been carried out for the first time on a metal/oxide/semiconductor (MOS) structure of polycrystalline Si/SiO 2/Si-substrate. We were successful in collecting injected positrons at the SiO 2/Si interface by the application of an electric field between the MOS electrodes.

  20. Short-lived positron emitter labeled radiotracers - present status

    International Nuclear Information System (INIS)

    Fowler, J.S.; Wolf, A.P.

    1982-01-01

    The preparation of labelled compounds is important for the application of positron emission transaxial tomography (PETT) in biomedical sciences. This paper describes problems and progress in the synthesis of short-lived positron emitter ( 11 C, 18 F, 13 N) labelled tracers for PETT. Synthesis of labelled sugars, amino acids, and neurotransmitter receptors (pimozide and spiroperidol tagged with 11 C) is discussed in particular

  1. Calculation of positron annihilation in high Tc copper oxides

    International Nuclear Information System (INIS)

    Barbiellini, B.; Jarlborg, T.; Gauthier, M.; Shukla, A.

    1992-01-01

    LMTO calculations have been done in order to obtain electronic and positronic states in YBaCuO compounds. The annihilation rates have been calculated including the enhancement effects. Folded momentum density spectra are calculated and used for prediction of Fermi surface signals. The influence of lattice defects on the spectra is studied by the comparison between experimental and calculated positron lifetimes. (orig.)

  2. Formation of a high intensity low energy positron string

    Science.gov (United States)

    Donets, E. D.; Donets, E. E.; Syresin, E. M.; Itahashi, T.; Dubinov, A. E.

    2004-05-01

    The possibility of a high intensity low energy positron beam production is discussed. The proposed Positron String Trap (PST) is based on the principles and technology of the Electron String Ion Source (ESIS) developed in JINR during the last decade. A linear version of ESIS has been used successfully for the production of intense highly charged ion beams of various elements. Now the Tubular Electron String Ion Source (TESIS) concept is under study and this opens really new promising possibilities in physics and technology. In this report, we discuss the application of the tubular-type trap for the storage of positrons cooled to the cryogenic temperatures of 0.05 meV. It is intended that the positron flux at the energy of 1-5 eV, produced by the external source, is injected into the Tubular Positron Trap which has a similar construction as the TESIS. Then the low energy positrons are captured in the PST Penning trap and are cooled down because of their synchrotron radiation in the strong (5-10 T) applied magnetic field. It is expected that the proposed PST should permit storing and cooling to cryogenic temperature of up to 5×109 positrons. The accumulated cooled positrons can be used further for various physics applications, for example, antihydrogen production.

  3. Formation of a high intensity low energy positron string

    International Nuclear Information System (INIS)

    Donets, E.D.; Donets, E.E.; Syresin, E.M.; Itahashi, T.; Dubinov, A.E.

    2004-01-01

    The possibility of a high intensity low energy positron beam production is discussed. The proposed Positron String Trap (PST) is based on the principles and technology of the Electron String Ion Source (ESIS) developed in JINR during the last decade. A linear version of ESIS has been used successfully for the production of intense highly charged ion beams of various elements. Now the Tubular Electron String Ion Source (TESIS) concept is under study and this opens really new promising possibilities in physics and technology. In this report, we discuss the application of the tubular-type trap for the storage of positrons cooled to the cryogenic temperatures of 0.05 meV. It is intended that the positron flux at the energy of 1-5 eV, produced by the external source, is injected into the Tubular Positron Trap which has a similar construction as the TESIS. Then the low energy positrons are captured in the PST Penning trap and are cooled down because of their synchrotron radiation in the strong (5-10 T) applied magnetic field. It is expected that the proposed PST should permit storing and cooling to cryogenic temperature of up to 5x10 9 positrons. The accumulated cooled positrons can be used further for various physics applications, for example, antihydrogen production

  4. Polarization Study for NLC Positron Source Using EGS4

    Energy Technology Data Exchange (ETDEWEB)

    Liu, James C

    2000-09-20

    SLAC is exploring a polarized positron source to study new physics for the NLC project. The positron source envisioned in this paper consists of a polarized electron source, a 50-MeV electron accelerator, a thin target less-than-or-equal-to 0.2 radiation length for positron production, and a capture system for high-energy, small angular divergence positrons. The EGS4 code was used to study the yield, energy spectra, emission-angle distribution, and the mean polarization of the positrons emanating from W-Re and Ti targets hit by longitudinally polarized electron and photon beams. To account for polarization within the EGS4 code a method devised by Flottmann was used, which takes into account polarization transfer for pair production, bremsstrahlung, and Compton interactions. A mean polarization of 0.85 for positrons with energies greater than 25 MeV was obtained. Most of the high-energy positrons were emitted within a forward angle of 20 degrees. The yield of positrons above 25 MeV per incident photon was 0.034, which was about 70 times higher than that obtained with an electron beam.

  5. Application of positron emitters to studies on plants

    Energy Technology Data Exchange (ETDEWEB)

    Ishioka, N S; Matsuoka, H [Japan Atomic Energy Research Inst., Takasaki, Gunma (Japan). Takasaki Radiation Chemistry Research Establishment; Sekine, T [and others

    1998-10-01

    A newly developed positron emitting tracer imaging system enables us to study dynamically the physiological function of plants, although this system covers, at present, a limited area in a plant. Production of the positron emitters {sup 11}C, {sup 13}N, {sup 18}F and {sup 48}V for this application, using an AVF cyclotron, is described. (author)

  6. Positron emission tomography in drug development and drug evaluation

    NARCIS (Netherlands)

    Paans, AMJ; Vaalburg, W

    2000-01-01

    Positron Emission Tomography (PET) is an imaging modality which can determine biochemical and physiological processes in vivo in a quantitative way by using radiopharmaceuticals labeled with positron emitting radionuclides as C-11, N-13, O-15 and F-18 and by measuring the annihilation radiation

  7. Positron imaging system with improved count rate and tomographic capability

    International Nuclear Information System (INIS)

    1979-01-01

    A system with improved count rate capability for detecting the radioactive distribution of positron events within an organ of interest in a living subject is described. Objects of the invention include improving the scintillation crystal and pulse processing electronics, avoiding the limitations of collimators and provide an Arger camera positron imaging system that avoids the use of collimators. (U.K.)

  8. Calculation of gamma spectra for positron annihilation on molecules

    Energy Technology Data Exchange (ETDEWEB)

    Green, Dermot G; Gribakin, G F [Centre for Theoretical Atomic, Molecular and Optical Physics, Queen' s University Belfast, BT7 1NN (United Kingdom); Wang, F [Centre for Molecular Simulation, Sinburne University of Technology, Melbourne, Victoria 3122 (Australia); Surko, C M, E-mail: dgreen09@qub.ac.u [Physics Department, University of California, San Diego, La Jolla, California 92093-0319 (United States)

    2009-11-01

    Gamma spectra for positron annihilation on molecules are calculated based on molecular electron momentum densities and using an atomic adjustment factor that accounts for the positron. Results for H{sub 2} agree well with experiment. Analysis of methane and larger alkanes and their substitutes is underway.

  9. Proposal for a slow positron facility at Jefferson National Laboratory

    Science.gov (United States)

    Mills, Allen P.

    2018-05-01

    One goal of the JPos-17 International Workshop on Physics with Positrons was to ascertain whether it would be a good idea to expand the mission of the Thomas Jefferson National Accelerator Facility (JLab) to include science with low energy (i.e. "slow") spin polarized positrons. It is probably true that experimentation with slow positrons would potentially have wide-ranging benefits comparable to those obtained with neutron and x-ray scattering, but it is certain that the full range of these benefits will never be fully available without an infrastructure comparable to that of existing neutron and x-ray facilities. The role for Jefferson Laboratory would therefore be to provide and maintain (1) a dedicated set of machines for making and manipulating high intensity, high brightness beams of polarized slow positrons; (2) a suite of unique and easily used instruments of wide utility that will make efficient use of the positrons; and (3) a group of on-site positron scientists to provide scientific leadership, instrument development, and user support. In this note some examples will be given of the science that might make a serious investment in a positron facility worthwhile. At the same time, the lessons learned from various proposed and successful positron facilities will be presented for consideration.

  10. Synthesis of the radiopharmaceuticals for positron emission tomography

    International Nuclear Information System (INIS)

    Biricova, V.; Kuruc, J.

    2007-01-01

    In this paper is shown a short overview of the biogenic positron radiopharmaceuticals production and a brief summary of some PET preparation synthesis. At the end the overview of some forward-looking positron radionuclides, which can be used for a preparation of the PET radiopharmaceuticals is said. A short review of diagnostic use of PET radiopharmaceuticals is presented (authors)

  11. Generation of slow positron beam and beam bunching

    International Nuclear Information System (INIS)

    Azuma, O.; Satoh, T.; Shitoh, M.; Kaneko, N.; Kawaratani, T.; Hara, O.

    1994-01-01

    Two items are described in this report. One is about the outline of our slow positron beam system, which has been fabricated as a commercial prototype. The other is about the calculation result of positron beam bunching, which will be an additional function to the system. (author)

  12. Positron annihilation studies on BeO powders

    International Nuclear Information System (INIS)

    Brauer, G.; Kerbe, F.; Kajcsos, Z.; Ashry, A.

    1984-01-01

    The sintering behaviour of two differently produced BeO powders is studied by positron annihilation. The positron lifetime in dislocations is found to be tau/sub d/ = (185 +- 2) ps, whereas for the perfect lattice tau/sub c/ = (130 +- 2) ps. (author)

  13. Recent developments in positron emission tomography (PET) instrumentation

    Energy Technology Data Exchange (ETDEWEB)

    Derenzo, S.E.; Budinger, T.F.

    1986-04-01

    This paper presents recent detector developments and perspectives for positron emission tomography (PET) instrumentation used for medical research, as well as the physical processes in positron annihilation, photon scattering and detection, tomograph design considerations, and the potentials for new advances in detectors. 117 refs., 4 figs., 4 tabs.

  14. Recent developments in positron emission tomography (PET) instrumentation

    International Nuclear Information System (INIS)

    Derenzo, S.E.; Budinger, T.F.

    1986-04-01

    This paper presents recent detector developments and perspectives for positron emission tomography (PET) instrumentation used for medical research, as well as the physical processes in positron annihilation, photon scattering and detection, tomograph design considerations, and the potentials for new advances in detectors. 117 refs., 4 figs., 4 tabs

  15. A question of balance: Kinetic balance for electrons and positrons

    International Nuclear Information System (INIS)

    Dyall, Kenneth G.

    2012-01-01

    Graphical abstract: Kinetic balance for both electrons and positrons is achieved by applying the correct relation for positive and negative energy states separately and then using the electron and positron eigensolutions from the separate diagonalizations of the Hamiltonian as a dual basis. Highlights: ► Kinetic balance for electrons and positrons is achieved in a dual atomic basis. ► Dual atomic balance alleviates, but does not eliminate, energy prolapse. ► Positron affinities converge quicker with basis set size with dual atomic balance. - Abstract: The kinetic balance criterion used in current relativistic basis set codes is satisfied by the electron solutions of the Dirac equation, but not the positron solutions. A proposal for applying kinetic balance to both sets of solutions is presented. The method is applied along with “normal” kinetic balance to one-electron systems, to investigate its possible relation to prolapse, and to the positron affinity of F − , to investigate the kinetic energy deficiency for positron solutions. The new method reduces but does not eliminate prolapse for energy-optimized basis sets, and provides faster and smoother convergence with basis set size for the positron affinity.

  16. Positron annihilation spectroscopy in defects of semiconductors

    CERN Document Server

    Fujinami, M

    2002-01-01

    Interaction of positron and defects, application to research of defects of semiconductor and defects on the surface of semiconductor are explained. Cz (Czochralski)-Si single crystal with 10 sup 1 sup 8 cm sup - sup 3 impurity oxygen was introduced defects by electron irradiation and the positron lifetime was measured at 90K after annealing. The defect size and recovery temperature were determined by the lifetime measurement. The distribution of defects in the depth direction is shown by S-E curve. The chemical state analysis is possible by CBS (Coincidence Doppler Broadening) spectra. The application to silicon-implanted (100 keV, 2x10 sup 1 sup 5 cm sup - sup 2) silicon and oxygen-implanted (180 keV, 2x10 sup 1 sup 5 cm sup - sup 2) silicon are stated. On the oxygen-implanted silicon, the main product was V2 after implantation, V sub 6 O sub 2 at 600degC and V sub 1 sub 0 O sub 6 at 800degC. (S.Y.)

  17. Positron annihilation and Wheeler complexes in semiconductors

    International Nuclear Information System (INIS)

    Prokob'ev, E.P.

    1995-01-01

    The Wheeler complexes Ps-Ex (positronium-exciton) were studied. These complexes are formed during irradiation of semiconductors and ionic crystals with positrons at low temperatures under optical excitation by excitons. The binding energy of these and more complex entities preventing dissociation into Ps and Ex and/or Ex ± is at least 0.1 eV, and the lifetime for the two-photon self-annihilation is τ 2γ ∼ 5.02 x 10 -10 x c 3 s (x c is the phenomenological parameter of the effective-mass method). The estimation of lifetimes τ 2γ and τ 2γ t (the total lifetime of Ps-Ex complexes with account for positron annihilation on valence electrons) led to the conclusion that Ps-Ex complexes can be observed in a number of oxide semiconductors, in zinc sulfide, and in alkali halide crystals; however, it was difficult to observe such complexes in silicon, gallium arsenide, and other A 3 B 5 and A 2 B 6 semiconductors

  18. Digital positron lifetime: the influence of noise

    International Nuclear Information System (INIS)

    Krille, Arnold; Krause-Rehberg, Reinhard; Anwand, Wolfgang

    2011-01-01

    In contrast to the world around where everything seems to go digital as soon as possible, positron lifetime spectrometers are kind of a 'last sanctuary' for analog measurements. Only a few of the newer spectrometers use the analog-digital-converters directly after the photomultipliers and extract the timing information via computer. Judging from their results it seems as if the current available converters and the timing mathematics are only as good as the conventional analog setup in the timing resolution. As it is decided that EPOS [1] will use digital positron lifetime, we try to find some reasons for limited timing resolution by simulating anode pulses from the photomultipliers and measuring the FWHM. We create pulses similar to current state-of-the-art 4GS/s digitizers but can control the level of noise and the bit-depth independently. We found that especially the noise (that would come from the analog electronics in/before the converters) has a great influence on the timing resolution. Also we try to use lowpass filtering to reduce that influence with great success.

  19. The Positron Emission Tomography. A diagnostic technique

    International Nuclear Information System (INIS)

    Salvadori, P.

    2001-01-01

    Positron Emission Tomography (PET) is a new imaging modality, which is able to assess non-invasively the biochemical mechanisms, underlying physiological and pathophysiological processes in vivo in humans. The technique relies on the administration of radioactive tracers labeled with short-lived positron emitters, which need to be produced on site via a particle accelerator (cyclotron). Radionuclides are produced upon request and formulated into biologically active organic molecules having precise pharmacokinetics and specificity. The radiotracer can be detected by the PET scanner and represented as tomographic sections (images of body sections) showing its regional distribution and concentration. This makes it possible to address clinical questions concerning occurrence and evolution of many diseases as well as their response to therapy. The ability to image (measure) biological processes and not only anatomy enables PET to explore diseases in the very early stage, including those diseases which are not related to modifications of organ structure (e.g. psychiatric diseases, metabolic disorders, biochemical disfunction). PET plays a major role, in conjunction with the other imaging modalities, to improve diagnosis capabilities and disease mechanism understanding [it

  20. Topics in electron-positron interactions

    International Nuclear Information System (INIS)

    Soeding, P.

    1983-01-01

    This chapter investigates the collision of an electron and a positron in a high energy storage ring in which a large energy Q=W=√s=2 E /SUB beam/ is dumped into a tiny region of space-time. If the electron and positron annihilate each other almost all of this energy becomes concentrated in a single field quantum. Points out 3 consequences: 1) all flavored particles existing in nature are expected to be pair-produced provided their mass is not larger than W/2; 2) the pair production process acts as an effective ''filter'' for fundamental (i.e. pointlike) particles; and 3) particles without flavor (i.e. the gluons) are not directly pair-produced in e - e + interactions. Discusses basic processes; probing QED and lepton structure; hadron production at high energies; resonances; e - e + storage rings; detectors; electroweak interaction and new particles (leptons, quarks); restrictions on a more general weak interaction scenario; limits on pair production of scalar particles; and jets and QCD tests