Study of the stress intensity factors in the bulk of the material with synchrotron diffraction

Artículo de Proceedings de Congreso Internacional Fatigue2017In this work we present the results of a hybrid experimental and analytical approach for estimating the stress intensity factor. It uses the elastic strains within the bulk obtained by synchrotron X-ray diffraction data. The stress intensity factor is calculated using a multi-point overdeterministic method where the number of experimental data points is higher than the number of unknowns describing the elastic field surrounding the crack-tip. The tool is tested on X-ray strain measurements collected on a bainitic steel. In contrast to surface techniques the approach provides insights into the crack tip mechanics deep within the sample.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. The authors are grateful to the ESRF for ID15 beamtime awarded under MA-1483. Financial support of Universidad de Malaga through Plan Propio, Junta de Andalucía through Proyectos de Excelencia grant reference TEP-3244, Campus de Excelencia Internacional del Mar (CEIMAR) and Ministerio de Economia y Competitividad through grant reference MAT2016-76951-C2-2-P is also acknowledged. PJW acknowledges an ERC advanced grant

A novel method for unambiguous ion identification in mixed ion beams extracted from an EBIT

A novel technique to identify small fluxes of mixed highly charged ion beams extracted from an Electron Beam Ion Trap (EBIT) is presented and practically demonstrated. The method exploits projectile charge state dependent potential emission of electrons as induced by ion impact on a metal surface to separate ions with identical or very similar mass-to-charge ratio.Comment: 8 pages, 5 figure

Empirically Derived Integrated Stellar Yields of Fe-Peak Elements

We present here the initial results of a new study of massive star yields of Fe-peak elements. We have compiled from the literature a database of carefully determined solar neighborhood stellar abundances of seven iron-peak elements, Ti, V, Cr, Mn, Fe, Co, and Ni and then plotted [X/Fe] versus [Fe/H] to study the trends as functions of metallicity. Chemical evolution models were then employed to force a fit to the observed trends by adjusting the input massive star metallicity-sensitive yields of Kobayashi et al. Our results suggest that yields of Ti, V, and Co are generally larger as well as anticorrelated with metallicity, in contrast to the Kobayashi et al. predictions. We also find the yields of Cr and Mn to be generally smaller and directly correlated with metallicity compared to the theoretical results. Our results for Ni are consistent with theory, although our model suggests that all Ni yields should be scaled up slightly. The outcome of this exercise is the computation of a set of integrated yields, i.e., stellar yields weighted by a slightly flattened time-independent Salpeter initial mass function and integrated over stellar mass, for each of the above elements at several metallicity points spanned by the broad range of observations. These results are designed to be used as empirical constraints on future iron-peak yield predictions by stellar evolution modelers. Special attention is paid to the interesting behavior of [Cr/Co] with metallicity -- these two elements have opposite slopes -- as well as the indirect correlation of [Ti/Fe] with [Fe/H]. These particular trends, as well as those exhibited by the inferred integrated yields of all iron-peak elements with metallicity, are discussed in terms of both supernova nucleosynthesis and atomic physics.Comment: 27 pages, 6 figures; Accepted for Publication in the Astrophysical Journa

Detection of the 5p-4f orbital crossing and its optical clock transition in Pr9+

Recent theoretical works have proposed atomic clocks based on narrow optical transitions in highly charged ions. The most interesting candidates for searches of new physics are those which occur at rare orbital crossings where the shell structure of the periodic table is reordered. There are only three such crossings expected to be accessible in highly charged ions, and hitherto none have been observed as both experiment and theory have proven difficult. In this work we observe an orbital crossing in highly charged ions for the first time, in a system chosen to be tractable from both sides: Pr9+. We present electron beam ion trap measurements of its spectra, including the inter-configuration lines that reveal the sought-after crossing. The proposed nHz-wide clock line, found to be at 452.334(1) nm, proceeds through hyperfine admixture of its upper state with an E2-decaying level. With state-of-the-art calculations we show that it has a very high sensitivity to new physics and extremely low sensitivity to external perturbations, making it a unique candidate for proposed precision studies

Switching from a protease inhibitor-based regimen to a dolutegravir-based regimen : a randomized clinical trial to determine the effect on peripheral blood and ileum biopsies from antiretroviral therapy-suppressed human immunodeficiency virus-infected individuals

Background: Optimization of combination antiretroviral therapy (cART) can impact the human immunodeficiency virus (HIV) reservoir. We evaluated the effect on the HIV reservoir in peripheral blood and ileum biopsies in patients switching from boosted protease inhibitor (PI/r)-based therapy to dolutegravir (DTG)-based therapy. Methods: Impact of Integrase-inhibitor DOlutegravir On the viral Reservoir (INDOOR) is a phase 4 open-label clinical trial that randomly included 42 HIV type 1-infected individuals on effective cART: 20 who switched from PI/r-based to DTG-based cART (switch group), and 22 who remained in PI/r-based regimens (control group). We analyzed blood and ileum biopsies to quantify episomal, total, and integrated HIV DNA, cell-associated HIV RNA, residual plasma viremia, T-cell subsets, cell activation, and inflammation markers. Results: There were no related adverse events or treatment discontinuations due to drug intolerance. The HIV reservoir was consistently larger in ileal than in peripheral CD4(+) T cells in both groups (P <.01). Residual viremia in plasma decreased in the switch group (P =.03). However, we did not observe significant longitudinal changes in low-level viral replication, total and integrated HIV reservoir, HIV transcription, T-cell maturation subsets, immunoactivation markers, inflammatory soluble proteins, or cellular markers of latently infected cells. Conclusions: The INDOOR study is the first evaluation of changes in HIV reservoir size in ileum biopsies and in peripheral blood in individuals switched from PI/r- to DTG-based cART. Although this switch was safe and well tolerated, it had no impact on a large array of immunological and inflammatory markers or on HIV reservoir markers in peripheral or in ileal CD4(+) T cells

EUV spectroscopy of highly charged Sn13+-Sn15+ ions in an electron-beam ion trap

Extreme-ultraviolet (EUV) spectra of Sn13+-Sn15+ ions have been measured in an electron-beam ion trap (EBIT). A matrix inversion method is employed to unravel convoluted spectra from a mixture of charge states typically present in an EBIT. The method is benchmarked against the spectral features of resonance transitions in Sn13+ and Sn14+ ions. Three new EUV lines in Sn14+ confirm its previously established level structure. This ion is relevant for EUV nanolithography plasma but no detailed experimental data currently exist. We used the Cowan code for first line identifications and assignments in Sn15+. The collisional-radiative modeling capabilities of the Flexible Atomic Code were used to include line intensities in the identification process. Using the 20 lines identified, we have established 17 level energies of the 4p44d configuration as well as the fine-structure splitting of the 4p5 ground-state configuration. Moreover, we provide state-of-the-art ab initio level structure calculations of Sn15+ using the configuration-interaction many-body perturbation code ambit. We find that the here-dominant emission features from the Sn15+ ion lie in the narrow 2% bandwidth around 13.5 nm that is relevant for plasma light sources for state-of-the-art nanolithography

On the Transition Rate of the Fe X RED Coronal Line

We present a lifetime measurement of the 3s 23p 5 2 Po 1/2 first excited fine-structure level of the ground state configuration in chlorine-like Fe X, which relaxes to the ground state through a magnetic dipole (M1) transition (the so-called red coronal line) with a wavelength accurately determined to 637.454(1) nm. Moreover, the Zeeman splitting of line was observed. The lifetime of 14.2(2) ms is the most precise one measured in the red wavelength region and agrees well with advanced theoretical predictions and an empirically scaled interpolation based on experimental values from the same isoelectronic sequence

EUV spectroscopy of Sn5+-Sn(10+)ions in an electron beam ion trap and laser-produced plasmas

Emission spectra from multiply-charged Sn5+ –Sn10+ions are recorded from an electron beam ion trap (EBIT) and from laser-produced plasma (LPP) in the extreme ultraviolet range relevant for nanolithographic applications. Features in the wavelength regime between 12.6 and 20.8 nm are studied. Using the Cowan code, emission line features of the charge-state-resolved Sn ion spectra obtained from the EBIT are identified. Emission features from tin LPP either from a liquid micro-droplet or planar solid target are subsequently identified and assigned to specific charge states using the EBIT data. For the planar solid tin target, the 4d–5p transitions of Sn8+ –Sn10+ions are shown to dominate the long-wavelength part of the measured spectrum and transitions of type 4d–4f + 4p–4d are visible in absorption. For the droplet target case, a clear increase in the charge state distribution with increasing laser intensity is observed. This qualitatively demonstrates the potential of using long-wavelength out-of-band emission features to probe the charge states contributing to the strong unresolved transition array at 13.5 nm relevant for nanolithography

The AMS-RICH velocity and charge reconstruction

The AMS detector, to be installed on the International Space Station, includes a Ring Imaging Cerenkov detector with two different radiators, silica aerogel (n=1.05) and sodium fluoride (n=1.334). This detector is designed to provide very precise measurements of velocity and electric charge in a wide range of cosmic nuclei energies and atomic numbers. The detector geometry, in particular the presence of a reflector for acceptance purposes, leads to complex Cerenkov patterns detected in a pixelized photomultiplier matrix. The results of different reconstruction methods applied to test beam data as well as to simulated samples are presented. To ensure nominal performances throughout the flight, several detector parameters have to be carefully monitored. The algorithms developed to fulfill these requirements are presented. The velocity and charge measurements provided by the RICH detector endow the AMS spectrometer with precise particle identification capabilities in a wide energy range. The expected performances on light isotope separation are discussed.Comment: Contribution to the ICRC07, Merida, Mexico (2007); Presenter: F. Bara