35 research outputs found
Polarization of K-shell dielectronic recombination satellite lines of Fe XIX-XXV and its application for diagnostics of anisotropies of hot plasmas
We present a systematic measurement of the X-ray emission asymmetries in the
K-shell dielectronic, trielectronic, and quadruelectronic recombination of free
electrons into highly charged ions. Iron ions in He-like through O-like charge
states were produced in an electron beam ion trap, and the electron-ion
collision energy was scanned over the recombination resonances. Two identical
X-ray detectors mounted head-on and side-on with respect to the electron beam
propagation recorded X-rays emitted in the decay of resonantly populated
states. The degrees of linear polarization of X-rays inferred from observed
emission asymmetries benchmark distorted-wave predictions of the Flexible
Atomic Code (FAC) for several dielectronic recombination satellite lines. The
present method also demonstrates its applicability for diagnostics of energy
and direction of electron beams inside hot anisotropic plasmas. Both
experimental and theoretical data can be used for modeling of hot astrophysical
and fusion plasmas.Comment: 22 pages, 4 figures, 10 tables, accepted for publication in The
Astrophysical Journal Supplement Serie
MEDIÇÃO DE PROCESSOS DE COLISÃO ELETRÓNICA EM FE XVII DE INTERESSE ASTROFÍSICO
UID/FIS/04559/2020A análise de espectros de raios-X de alta resolução obtidos em observatórios espaciais requer uma boa compreensão dos processos físicos, nomeadamente os atómicos, que governam a emissão e dinâmica dos plasmas. O complexo de emissão Fe-L de Fe XVII, formado por riscas 3d→2p e 3s→2p, é frequentemente utilizado na referida análise e como diagnóstico de várias propriedades físicas como temperatura, opacidade e densidade do plasma. Neste trabalho, medimos as secções eficazes dos processos de colisão que levam à formação destas riscas, tanto as não-ressoantes (excitação por colisão), como ressoantes (recombinação dieletrónica). Acresce que os dados experimentais obtidos permitem uma validação dos valores teóricos destes processos atómicos.authorsversionpublishe
An Optical Atomic Clock Based on a Highly Charged Ion
Optical atomic clocks are the most accurate measurement devices ever
constructed and have found many applications in fundamental science and
technology. The use of highly charged ions (HCI) as a new class of references
for highest accuracy clocks and precision tests of fundamental physics has long
been motivated by their extreme atomic properties and reduced sensitivity to
perturbations from external electric and magnetic fields compared to singly
charged ions or neutral atoms. Here we present the first realisation of this
new class of clocks, based on an optical magnetic-dipole transition in
Ar. Its comprehensively evaluated systematic frequency uncertainty of
is comparable to that of many optical clocks in operation.
From clock comparisons we improve by eight and nine orders of magnitude upon
the uncertainties for the absolute transition frequency and isotope shift
(Ar vs. Ar), respectively. These measurements allow us to probe
the largely unexplored quantum electrodynamic nuclear recoil, presented as part
of improved calculations of the isotope shift which reduce the uncertainty of
previous theory by a factor of three. This work establishes forbidden optical
transitions in HCI as references for cutting-edge optical clocks and future
high-sensitivity searches for physics beyond the standard model.Comment: Main: 20 pages, 3 figures. Supplement: 19 pages, 2 figure
Detection of metastable electronic states by Penning trap mass spectrometry
State-of-the-art optical clocks achieve fractional precisions of
and below using ensembles of atoms in optical lattices or individual ions in
radio-frequency traps. Promising candidates for novel clocks are highly charged
ions (HCIs) and nuclear transitions, which are largely insensitive to external
perturbations and reach wavelengths beyond the optical range, now becoming
accessible to frequency combs. However, insufficiently accurate atomic
structure calculations still hinder the identification of suitable transitions
in HCIs. Here, we report on the discovery of a long-lived metastable electronic
state in a HCI by measuring the mass difference of the ground and the excited
state in Re, the first non-destructive, direct determination of an electronic
excitation energy. This result agrees with our advanced calculations, and we
confirmed them with an Os ion with the same electronic configuration. We used
the high-precision Penning-trap mass spectrometer PENTATRAP, unique in its
synchronous use of five individual traps for simultaneous mass measurements.
The cyclotron frequency ratio of the ion in the ground state to the
metastable state could be determined to a precision of , unprecedented in the heavy atom regime. With a lifetime of about 130
days, the potential soft x-ray frequency reference at has a linewidth of only , and one of the highest electronic quality factor
() ever seen in an experiment. Our low
uncertainty enables searching for more HCI soft x-ray clock transitions, needed
for promising precision studies of fundamental physics in a thus far unexplored
frontier
CIBERER : Spanish national network for research on rare diseases: A highly productive collaborative initiative
Altres ajuts: Instituto de Salud Carlos III (ISCIII); Ministerio de Ciencia e Innovación.CIBER (Center for Biomedical Network Research; Centro de Investigación Biomédica En Red) is a public national consortium created in 2006 under the umbrella of the Spanish National Institute of Health Carlos III (ISCIII). This innovative research structure comprises 11 different specific areas dedicated to the main public health priorities in the National Health System. CIBERER, the thematic area of CIBER focused on rare diseases (RDs) currently consists of 75 research groups belonging to universities, research centers, and hospitals of the entire country. CIBERER's mission is to be a center prioritizing and favoring collaboration and cooperation between biomedical and clinical research groups, with special emphasis on the aspects of genetic, molecular, biochemical, and cellular research of RDs. This research is the basis for providing new tools for the diagnosis and therapy of low-prevalence diseases, in line with the International Rare Diseases Research Consortium (IRDiRC) objectives, thus favoring translational research between the scientific environment of the laboratory and the clinical setting of health centers. In this article, we intend to review CIBERER's 15-year journey and summarize the main results obtained in terms of internationalization, scientific production, contributions toward the discovery of new therapies and novel genes associated to diseases, cooperation with patients' associations and many other topics related to RD research
Treatment with tocilizumab or corticosteroids for COVID-19 patients with hyperinflammatory state: a multicentre cohort study (SAM-COVID-19)
Objectives: The objective of this study was to estimate the association between tocilizumab or corticosteroids and the risk of intubation or death in patients with coronavirus disease 19 (COVID-19) with a hyperinflammatory state according to clinical and laboratory parameters.
Methods: A cohort study was performed in 60 Spanish hospitals including 778 patients with COVID-19 and clinical and laboratory data indicative of a hyperinflammatory state. Treatment was mainly with tocilizumab, an intermediate-high dose of corticosteroids (IHDC), a pulse dose of corticosteroids (PDC), combination therapy, or no treatment. Primary outcome was intubation or death; follow-up was 21 days. Propensity score-adjusted estimations using Cox regression (logistic regression if needed) were calculated. Propensity scores were used as confounders, matching variables and for the inverse probability of treatment weights (IPTWs).
Results: In all, 88, 117, 78 and 151 patients treated with tocilizumab, IHDC, PDC, and combination therapy, respectively, were compared with 344 untreated patients. The primary endpoint occurred in 10 (11.4%), 27 (23.1%), 12 (15.4%), 40 (25.6%) and 69 (21.1%), respectively. The IPTW-based hazard ratios (odds ratio for combination therapy) for the primary endpoint were 0.32 (95%CI 0.22-0.47; p < 0.001) for tocilizumab, 0.82 (0.71-1.30; p 0.82) for IHDC, 0.61 (0.43-0.86; p 0.006) for PDC, and 1.17 (0.86-1.58; p 0.30) for combination therapy. Other applications of the propensity score provided similar results, but were not significant for PDC. Tocilizumab was also associated with lower hazard of death alone in IPTW analysis (0.07; 0.02-0.17; p < 0.001).
Conclusions: Tocilizumab might be useful in COVID-19 patients with a hyperinflammatory state and should be prioritized for randomized trials in this situatio
Highly Charged Ions for High-Resolution Soft X-ray Grating Monochromator Optimisation
The energy-resolving performance of a synchrotron radiation monochromator can be characterised by measuring the fluorescence response of a gas in scans across characteristic absorption lines. Here, we describe a method using exceptionally narrow absorption features in the soft x-ray range. The features belong to helium-like ions and examples of the transition 1s → 2p in O and Ne are shown. We describe the instrument PolarX-EBIT and show typical data. A performance with ten times sharper effective feature width, when compared to neutral-gas absorption features, is demonstrated