ABSTRACT
Cross-section calculations and transport models for Monte Carlo track structure codes are discussed as well as the simulation of secondary electron emission yields from thin metal foils. Inelastic cross sections for volume (bulk) and surface transport of electrons in copper are presented and implemented into PARTRAC. Simulations for the volume and surface excitation model are presented and analysed.
Subject(s)
Copper/chemistry , Copper/radiation effects , Electrons , Models, Statistical , Computer Simulation , Electron Transport , Monte Carlo Method , ProtonsABSTRACT
Differential and total inelastic cross sections are derived for the interaction between fast protons and Cu. The calculations are done under the non-relativistic plane-wave first-Born approximation and the dielectric theory. A semi-empirical optical oscillator strength density function and a simple linear-momentum dispersion algorithm are used to construct the energy loss function or Bethe surface of the medium. A transport model using these inelastic cross sections is implemented in the Monte Carlo code PARTRAC to simulate the spectra of secondary electron emissions from this homogeneous and isotropic thin copper foil target. Comparisons with experimental results show general agreement for impact energies >50 eV up to non-relativistic values. The model, however, overestimates the secondary electron yields at lower energies.
Subject(s)
Copper/chemistry , Copper/radiation effects , Electron Transport , Models, Chemical , Models, Statistical , Monte Carlo Method , Protons , Computer SimulationABSTRACT
Monte Carlo track simulation has become an important tool in radiobiology. Monte Carlo transport codes commonly rely on elastic and inelastic electron scattering cross sections determined using theoretical methods supplemented with gas-phase data; experimental condensed phase data are often unavailable or infeasible. The largest uncertainties in the theoretical methods exist for low-energy electrons, which are important for simulating electron track ends. To test the reliability of these codes to deal with low-energy electron transport, yields of low-energy secondary electrons ejected from thin foils have been measured following passage of fast protons. Fast ions, where interaction cross sections are well known, provide the initial spectrum of low-energy electrons that subsequently undergo elastic and inelastic scattering in the material before exiting the foil surface and being detected. These data, measured as a function of the energy and angle of the emerging electrons, can provide tests of the physics of electron transport. Initial measurements from amorphous solid water frozen to a copper substrate indicated substantial disagreement with MC simulation, although questions remained because of target charging. More recent studies, using different freezing techniques, do not exhibit charging, but confirm the disagreement seen earlier between theory and experiment. One now has additional data on the absolute differential electron yields from copper, aluminum and gold, as well as for thin films of frozen hydrocarbons. Representative data are presented.
Subject(s)
Algorithms , Electron Transport , Models, Chemical , Models, Statistical , Monte Carlo Method , Protons , Software , Computer Simulation , Phase Transition , Software ValidationABSTRACT
A case of rheumatoid-like arthritis as a symptom of primary agammaglobulinemia X-linked in a 24-month-old child is reported. The treatment protocol is also discussed.
Subject(s)
Agammaglobulinemia/diagnosis , Arthritis, Rheumatoid/diagnosis , Agammaglobulinemia/drug therapy , Agammaglobulinemia/genetics , Child, Preschool , Diagnosis, Differential , Genetic Linkage , Humans , Immunoglobulins, Intravenous/therapeutic use , Male , Sex Chromosome Aberrations/genetics , X ChromosomeABSTRACT
BACKGROUND: A clinician who deals with allergic patients needs the help of in vivo and in vitro allergometric tests in order to decide difficult therapeutic choices. METHODS: In the section of Clinical Immunology of the Institute of Paediatrics (Palermo University) two allergologic tests, prick and MAST-CLA, have been studied retrospectively, they were performed on patients observed for allergic disorders over 5 years. The aim of this study was to evaluate the diagnostic capacity of these tests "on the field". The study population is made of 459 patients (age range from 6 months to 16 years) affected with asthma, rhinitis, presumably allergic dermatitis, association of asthma and dermatitis, urticaria, selected on the basis of anamnesis and clinical examination. Eosynophils, basophils, total IgE, specific IgE with DHS-MAST-CLA and prick tests (Bayropharm) for the allergens most frequently responsible of allergic disease in our country, have been evaluated. A double controlled assay of 1040 pairs of allergens with MAST-CLA has been performed. RESULTS: The agreement between prick and MAST appeared to be satisfactory for inhaled allergens. Eosynophils count and total IgE levels showed a significative difference between patients negative versus patients positive for at least one allergen. CONCLUSIONS: The pattern of the allergens most frequently positive changes with age and patients positive for pollens showed positivity for vegetal food allergens with a frequency higher than expected.
