20 research outputs found
High-resolution Laboratory Measurements of K-shell X-ray Line Polarization and Excitation Cross Sections in Heliumlike S XV Ions
We report measurements of electron-impact excitation cross sections for the
strong K-shell n=2-1 transitions in S XV using the LLNL EBIT-I electron beam
ion trap, two crystal spectrometers, and the EBIT Calorimeter Spectrometer. The
cross sections are determined by direct normalization to the well known cross
sections of radiative electron capture, measured simultaneously. Using
contemporaneous polarization measurements with the two crystal spectrometers,
whose dispersion planes are oriented parallel and perpendicular to the electron
beam direction, the polarization of the direct excitation line emission is
determined, and in turn the isotropic total cross sections are extracted. We
further experimentally investigate various line-formation mechanisms, finding
that radiative cascades and collisional inner-shell ionization dominate the
degree of linear polarization and total line-emission cross sections of the
forbidden line .Comment: 16 Pages, 9 Figures, published in Ap
Acute kidney injury in patients treated with immune checkpoint inhibitors
Background: Immune checkpoint inhibitor-associated acute kidney injury (ICPi-AKI) has emerged as an important toxicity among patients with cancer. Methods: We collected data on 429 patients with ICPi-AKI and 429 control patients who received ICPis contemporaneously but who did not develop ICPi-AKI from 30 sites in 10 countries. Multivariable logistic regression was used to identify predictors of ICPi-AKI and its recovery. A multivariable Cox model was used to estimate the effect of ICPi rechallenge versus no rechallenge on survival following ICPi-AKI. Results: ICPi-AKI occurred at a median of 16 weeks (IQR 8-32) following ICPi initiation. Lower baseline estimated glomerular filtration rate, proton pump inhibitor (PPI) use, and extrarenal immune-related adverse events (irAEs) were each associated with a higher risk of ICPi-AKI. Acute tubulointerstitial nephritis was the most common lesion on kidney biopsy (125/151 biopsied patients [82.7%]). Renal recovery occurred in 276 patients (64.3%) at a median of 7 weeks (IQR 3-10) following ICPi-AKI. Treatment with corticosteroids within 14 days following ICPi-AKI diagnosis was associated with higher odds of renal recovery (adjusted OR 2.64; 95% CI 1.58 to 4.41). Among patients treated with corticosteroids, early initiation of corticosteroids (within 3 days of ICPi-AKI) was associated with a higher odds of renal recovery compared with later initiation (more than 3 days following ICPi-AKI) (adjusted OR 2.09; 95% CI 1.16 to 3.79). Of 121 patients rechallenged, 20 (16.5%) developed recurrent ICPi-AKI. There was no difference in survival among patients rechallenged versus those not rechallenged following ICPi-AKI. Conclusions: Patients who developed ICPi-AKI were more likely to have impaired renal function at baseline, use a PPI, and have extrarenal irAEs. Two-thirds of patients had renal recovery following ICPi-AKI. Treatment with corticosteroids was associated with improved renal recovery
High Resolution Photoexcitation Measurements Exacerbate the Long-Standing Fe XVII Oscillator Strength Problem
For more than 40 years, most astrophysical observations and laboratory
studies of two key soft x-ray diagnostic transitions, and , in
Fe XVII ions found oscillator strength ratios disagreeing with
theory, but uncertainties had precluded definitive statements on this much
studied conundrum. Here, we resonantly excite these lines using synchrotron
radiation at PETRA III, and reach, at a millionfold lower photon intensities, a
10 times higher spectral resolution, and 3 times smaller uncertainty than
earlier work. Our final result of supports many of
the earlier clean astrophysical and laboratory observations, while departing by
five sigmas from our own newest large-scale ab initio calculations, and
excluding all proposed explanations, including those invoking nonlinear effects
and population transfers.Comment: Main text (6 pages, 3 figures), Supplmentary Material (8 pages, 4
figure), Published in Physical Review Letter
High-resolution Photo-excitation Measurements Exacerbate the Long-standing Fe XVII Emission Problem
We measured the L-shell soft X-ray fluorescence of Fe XVII ions in an electron beam ion trap following resonant photo-excitation using synchrotron radiation provided by the P04 beamline at PETRA III. Special attention is paid to two 2p-3d transitions, the 3C and 3D lines that are essential plasma diagnostics tools for astrophysics. Their resulting oscillator-strength ratio, f(3C)/f(3D) = 3.09(8)(6), is three times more accurate than previous results. The present ratio clearly departs by approximately 5-sigmas from the newest ab initio calculations but confirms previous laboratory measurements and astrophysical observations. A ten thousand-fold reduction in excitation-photon intensity and ten times higher spectral resolution allow us to exclude current explanations, reinstating a forty-year-old atomic-physics puzzle
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