1,006 research outputs found
Simultaneous PIXE and RBS data analysis using Bayesian Inference with the DataFurnace code
The Rutherford Backscattering Spectroscopy (RBS) and Particle Induced X-ray
Emission (PIXE) techniques can be used to obtain complementary information
about the characteristics of a sample but, traditionally, a gap has separated
the available computer codes for analyzing data from each technique, being hard
to simultaneously analyze data from the same sample. The recent development of
a free and open source library, LibCPIXE, for PIXE simulation and analysis of
arbitrary multilayered samples, has permitted to integrate this technique into
the DataFurnace code which already handles many other IBA techniques such as
Rutherford and non-Rutherford backscattering, elastic recoil detection, and
non-resonant nuclear reaction analysis. The fitting capabilities of DataFurnace
can therefore now be applied to PIXE spectra as well, including the Bayesian
Inference analysis and the simultaneous and coherent fitting of multiple
spectra from different techniques. Various examples are presented in which the
simultaneous RBS and PIXE analysis allows us to obtain consistent results that
cannot be obtained by independent analysis of the data from each technique.Comment: 10 pages, 5 figures. Paper initially presented to IBA2005. Please
cite the published version (DOI:10.1016/j.nimb.2006.03.190
LibCPIXE: a PIXE simulation open-source library for multilayered samples
Most particle induced X-ray emission (PIXE) data analysis codes are not
focused on handling multilayered samples. We have developed an open-source
library called "LibCPIXE", for PIXE data analysis. It is written in standard C
and implements functions for simulating X-ray yields of PIXE spectra taken from
arbitrary samples, including multilayered targets. The library is designed to
be fast, portable, modular and scalable, as well as to facilitate its
incorporation into any existing program. In order to demonstrate the
capabilities of the library, a program called CPIXE was developed and used to
analyze various real samples involving both bulk and layered samples. Just as
the library, the CPIXE source code is freely available under the General Public
License. We demonstrate that it runs both under GNU/Linux systems as well as
under MS Windows. There is in principle no limitation to port it to other
platforms
High precision measurement of the hyperfine fields of substitutional and defect associated Cd in single crystalline hcp cobalt
The hyperfine fields of Cd in single crystalline hcp Co were measured after simultaneous implantation of 111mCd and 111In. High statistics measurements could be done separately for each parent isotope combining the e--g and g-g PAC techniques. The hyperfine coupling constants wL(CdCo)=422.8(1) Mrad/s and w0(CdCo)=6.14(11) Mrad/s are determined for Cd probes in undisturbed substitutional sites. Several defect associated sites in the hcp Co lattice are clearly seen in the data. Most of the radiation damage created by the ion implantation anneals out at temperatures below 503 K, with only one dominating component surviving at this temperature. This defect is assigned as a probe atom in an interstitial site, surrounded by a vacancy tetrahedron. The corresponding magnetic field and electric field gradient are collinear with the c-axis of the Co lattice, and the respective coupling constants are wL(defect)= 216.7(2) Mrad/s and w0(defect)= 45.3(6) Mrad/s
Annihilation of Dipolar Dark Matter to Photons
In this work we study the annihilation of fermionic dark matter, considering
it as a neutral particle with nonvanishing magnetic () and electric ()
dipole moments. Effective cross-section of the process is computed starting from a general form of coupling
in the framework of an extension of the Standard
Model. By taking into account annihilation of DM pairs into mono-energetic
photons, we found that for small masses, , an
electric dipole moment is required to satisfy
the current residual density inferences. Additionally, in order to pin down
models viable to describe the physics of dark matter at the early Universe we
also constrain our model according to recent measurements of the temperature
anisotropies of the cosmic background radiation, we report constraints to the
electric and magnetic dipole moments for a range of masses within our model.Comment: 20 pages, 6 figure
Analytical simulation of RBS spectra of nanowire samples
Almost all, if not all, general purpose codes for analysis of Ion Beam Analysis data have been originally developed to handle laterally homogeneous samples only. This is the case of RUMP, NDF, SIMNRA, and even of the Monte Carlo code Corteo. General-purpose codes usually include only limited support for lateral inhomogeneity. In this work, we show analytical simulations of samples that consist of a layer of parallel oriented nanowires on a substrate, using a model implemented in NDF. We apply the code to real samples, made of vertical ZnO nanowires on a sapphire substrate. Two configurations of the nanowires were studied: 40 nm diameter, 4.1 μm height, 3.5% surface coverage; and 55 nm diameter, 1.1 μm height, 42% surface coverage. We discuss the accuracy and limits of applicability of the analysisAuthors thank funding from projects CTQ2014-53334-C2-2-R (MINECO, Spain) and NANOAVANSENS S2013/MIT 3029 (Comunidad de Madrid). A.R.C. acknowledges Juan de la Cierva program (under contract number JCI-2012-14509). This work was partially funded by Fundação para a Ciência e Tecnologia under grant UID/Multi/04349/201
Hemoglobina versus reservas de ferro em dadores do sexo masculino
INTRODUÇÃO: Segundo aprovação dos critérios dos dadores do sexo masculino no nosso Serviço, são aceites para a dádiva homóloga de sangue, dadores com valores de Hemoglobina (Hb) iguais ou superiores a 13,5 g/dl. A Hb é determinada a todos os dadores pré-dádiva, através de hemograma. Verificámos que os valores de Hb nalguns dadores tendiam a diminuir com o número de dádivas. Estará essa diminuição relacionada com a depleção das reservas de ferro.
OBJECTIVOS: Apurar uma correlação entre diminuição do valor de Hb e a diminuição das reservas de ferro
MATERIAL E MÉTODOS: Analisámos, entre Agosto 2006 e Junho 2007, 18 dadores regulares do sexo masculino com valores de hemoglobina iguais ou inferiores a 13,5 g/dl. A estes dadores foi colhido sangue para determinação de Ferro, Ferritina e Transferrina.
REULTADOS: Dos 18 dadores analisados, 50% (9) tinham valores de Ferritina ou ferro diminuÃdos, 27,7% (5) dos dadores apresentavam valores de Ferritina e de Ferro dentro dos valores normais mas no limite inferior da normalidade. Os restantes 4 dadores que equivalem a 22,2% dos dadores analisados apresentavam valores dentro da normalidade. Se englobarmos no mesmo conjunto os dadores com valores de Ferro e Ferritina diminuÃdos com os dadores que tem valores dentro dos valores considerados normais, mas no limite inferior, temos 77,7% de dadores com valores de Ferro e Ferritina diminuÃdos. Os valores de Transferrina mantiveram-se em todos os dadores analisados dentro dos valores normais, 5 dadores apresentavam valores de MCH inferiores aos normais, sendo que destes, 4 (80%) apresentavam valores de Ferro e Ferritina diminuÃdos.
DISCUSSÃO: Prescrever suplemento de Ferro a todos os dadores regulares? Qual a dose e tempo de suplemento? DeverÃamos determinar o valor da Ferritina nos dadores regulares
CONCLUSÕES: ConcluÃmos que a diminuição dos valores de Hemoglobina está correlacionada com a descida dos valores da Ferritina, na maioria dos dadores estudados
Annihilation of Dipolar Dark Matter: χχ→γγ
In this work we study the annihilation of dark matter, considering it as a neutral particle with magnetic and/or electric moments not null. The calculation of the effective section of the process χχbar→γγ is made starting from a general form of coupling χ χbar γ in the framework of an extension of the Standard Model. We found, when taking into account an annihilation of DDM-antiDDM to monoenergetic photons, that for small masses, mχ ≤ 0 GeV, an electric dipole moment ~10–6 e cm is required to satisfy the current residual density, while for the range of greater sensitivity of HAWC, 10 TeV < Eg < 20 TeV, the electrical dipole moment must be of the order of 10–8 e cm
On the growth kinetics of Ni(Pt) silicide thin films
We report on the effect of Pt on the growth kinetics of δ-Ni2Si and Ni 1−xPtxSi thin films formed by solid phase reaction of a Ni(Pt) alloyed thin film on Si(100). The study was performed by real-time Rutherford backscattering spectrometry examining the silicide growth rates for initial Pt concentrations of 0, 1, 3, 7, and 10 at. % relative to the Ni content. Pt was found to exert a drastic effect on the growth kinetics of both phases. δ-Ni2Si growth is slowed down tremendously, which results in the simultaneous growth of this phase with Ni 1−xPtxSi. Activation energies extracted for the Ni 1−xPtxSi growth process exhibit an increase from Ea = 1.35 ± 0.06 eV for binary NiSi to Ea = 2.7 ± 0.2 eV for Ni 1−xPtxSi with an initial Pt concentration of 3 at. %. Further increasing the Pt content to 10 at. % merely increases the activation energy for Ni 1−xPtxSi growth to Ea = 3.1 ± 0.5 eV
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