Observation of Neutral Sodium Above Mercury During the Transit of November 8, 2006

We mapped the absorption of sunlight by sodium vapor in the exosphere of Mercury during the transit of Mercury on November 8, 2006, using the IBIS Interferometric BIdimensional Spectrometer at the Dunn Solar Telescope operated by the National Solar Observatory at Sunspot, New Mexico. The measurements were reduced to line-of-sight equivalent widths for absorption at the sodium D2 line around the shadow of Mercury. The sodium absorption fell off exponentially with altitude up to about 600 km. However there were regions around north and south polar-regions where relatively uniform sodium absorptions extended above 1000 km. We corrected the 0-600 km altitude profiles for seeing blur using the measured point spread function. Analysis of the corrected altitude distributions yielded surface densities, zenith column densities, temperatures and scale heights for sodium all around the planet. Sodium absorption on the dawn side equatorial terminator was less than on the dusk side, different from previous observations of the relative absorption levels. We also determined Earthward velocities for sodium atoms, and line widths for the absorptions. Earthward velocities resulting from radiation pressure on sodium averaged 0.8 km/s, smaller than a prediction of 1.5 km/s. Most line widths were in the range of 20 mA after correction for instrumental broadening, corresponding to temperatures in the range of 1000 K

Constraining the systematics of (acoustic) wave heating estimates in the solar chromosphere

Acoustic wave heating is believed to contribute significantly to the missing energy input required to maintain the solar chromosphere in its observed state. We studied the propagation of waves above the acoustic cutoff in the upper photosphere into the chromosphere with ultraviolet and optical spectral observations interpreted through comparison with three dimensional radiative magnetohydrodynamic (rMHD) \emph{Bifrost} models to constrain the heating contribution from acoustic waves in the solar atmosphere. Sit-and-stare observations taken with the Interface Region Imaging Spectrograph (IRIS) and data from the Interferometric BIdimensional Spectrograph (IBIS) were used to provide the observational basis of this work. We compared the observations with synthetic observables derived from the Bifrost solar atmospheric model. Our analysis of the \emph{Bifrost} simulations show that internetwork and enhanced network regions exhibit significantly different wave propagation properties, which are important for the accurate wave flux estimates. The inferred wave energy fluxes based on our observations are not sufficient to maintain the solar chromosphere. We point out that the systematics of the modeling approaches in the literature lead to differences which could determine the conclusions of this type of studies, based on the same observations.Comment: Accepted for publication in Ap

Solar Chromospheric Temperature Diagnostics: a joint ALMA-Hα\alpha analysis

We present the first high-resolution, simultaneous observations of the solar chromosphere in the optical and millimeter wavelength ranges, obtained with ALMA and the IBIS instrument at the Dunn Solar Telescope. In this paper we concentrate on the comparison between the brightness temperature observed in ALMA Band 3 (3 mm; 100 GHz) and the core width of the H$\alpha$ 656.3 nm line, previously identified as a possible diagnostic of the chromospheric temperature. We find that in the area of plage, network and fibrils covered by our FOV the two diagnostics are well correlated, with similar spatial structures observed in both. The strength of the correlation is remarkable, given that the source function of the mm-radiation obeys local thermodynamic equilibrium, while the H$\alpha$ line has a source function that deviates significantly from the local Planck function. The observed range of ALMA brightness temperatures is sensibly smaller than the temperature range that was previously invoked to explain the observed width variations in H$\alpha$. We employ analysis from forward modeling with the RH code to argue that the strong correlation between H$\alpha$ width and ALMA brightness temperature is caused by their shared dependence on the population number $n_2$ of the first excited level of hydrogen. This population number drives millimeter opacity through hydrogen ionization via the Balmer continuum, and H$\alpha$ width through a curve-of-growth-like opacity effect. Ultimately, the $n_2$ population is regulated by the enhancement or lack of downward Ly$\alpha$ flux, which coherently shifts the formation height of both diagnostics to regions with different temperature, respectively.Comment: Accepted for publication in Ap

Clinical impact of baseline chronic kidney disease in patients undergoing transcatheter or surgical aortic valve replacement

ObjectivesTo assess the treatment effect of TAVR versus SAVR on clinical outcomes to 3 years in patients stratified by chronic kidney disease (CKD) by retrospectively studying patients randomized to TAVR or SAVR.BackgroundThe impact of CKD on mid‐term outcomes of patients undergoing TAVR versus SAVR is unclear.MethodsPatients randomized to TAVR or SAVR in the CoreValve US Pivotal High Risk Trial were retrospectively stratified by eGFR: none/mild or moderate/severe CKD. To evaluate the impact of baseline CKD in TAVR patients only, all patients undergoing an attempted TAVR implant in the US Pivotal Trial and CAS were stratified by baseline eGFR into none/mild, moderate, and severe CKD. The primary endpoint was major adverse cardiovascular and renal events (MACRE), a composite of all‐cause mortality, myocardial infarction, stroke/TIA, and new requirement of dialysis.ResultsModerate/severe CKD was present in 62.7% and 60.7% of high‐risk patients randomized to TAVR or SAVR, respectively. Baseline characteristics were similar between TAVR and SAVR patients in both CKD subgroups, except for higher rates of diabetes and higher serum creatinine in SAVR patients. Among high‐risk patients with moderate/severe CKD, TAVR provided a lower 3‐year MACRE rate compared with SAVR: 42.1% vs. 51.0, P = .04. Of 3,733 extreme‐ and high‐risk TAVR patients, 39.9% had none/mild, 53.8% moderate, and 6.4% severe CKD. Worsening baseline CKD was associated with increased 3‐year MACRE rates [none/mild 51.5%, moderate 54.5%, severe 63.1%, P = .001].ConclusionsTAVR results in lower 3‐year MACRE versus SAVR in high‐risk patients with moderate/severe CKD. In patients undergoing TAVR, worsening CKD increases mid‐term mortality and MACRE. Randomized trials of TAVR vs. SAVR in patients with moderate‐severe CKD would help elucidate the best treatment for these complex patients.Trial RegistrationCoreValve US Pivotal Trial: NCT01240902.CoreValve Continued Access Study: NCT01531374.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/148361/1/ccd27928_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/148361/2/ccd27928.pd

The Effects of Atmospheric Dispersion on High-Resolution Solar Spectroscopy

We investigate the effects of atmospheric dispersion on observations of the Sun at the ever-higher spatial resolutions afforded by increased apertures and improved techniques. The problems induced by atmospheric refraction are particularly significant for solar physics because the Sun is often best observed at low elevations, and the effect of the image displacement is not merely a loss of efficiency, but the mixing of information originating from different points on the solar surface. We calculate the magnitude of the atmospheric dispersion for the Sun during the year and examine the problems produced by this dispersion in both spectrographic and filter observations. We describe an observing technique for scanning spectrograph observations that minimizes the effects of the atmospheric dispersion while maintaining a regular scanning geometry. Such an approach could be useful for the new class of high-resolution solar spectrographs, such as SPINOR, POLIS, TRIPPEL, and ViSP

Defining the Middle Corona

International audienceAbstract The middle corona, the region roughly spanning heliocentric distances from 1.5 to 6 solar radii, encompasses almost all of the influential physical transitions and processes that govern the behavior of coronal outflow into the heliosphere. The solar wind, eruptions, and flows pass through the region, and they are shaped by it. Importantly, the region also modulates inflow from above that can drive dynamic changes at lower heights in the inner corona. Consequently, the middle corona is essential for comprehensively connecting the corona to the heliosphere and for developing corresponding global models. Nonetheless, because it is challenging to observe, the region has been poorly studied by both major solar remote-sensing and in-situ missions and instruments, extending back to the Solar and Heliospheric Observatory (SOHO) era. Thanks to recent advances in instrumentation, observational processing techniques, and a realization of the importance of the region, interest in the middle corona has increased. Although the region cannot be intrinsically separated from other regions of the solar atmosphere, there has emerged a need to define the region in terms of its location and extension in the solar atmosphere, its composition, the physical transitions that it covers, and the underlying physics believed to shape the region. This article aims to define the middle corona, its physical characteristics, and give an overview of the processes that occur there

Integrated genomic characterization of pancreatic ductal adenocarcinoma

We performed integrated genomic, transcriptomic, and proteomic profiling of 150 pancreatic ductal adenocarcinoma (PDAC) specimens, including samples with characteristic low neoplastic cellularity. Deep whole-exome sequencing revealed recurrent somatic mutations in KRAS, TP53, CDKN2A, SMAD4, RNF43, ARID1A, TGFβR2, GNAS, RREB1, and PBRM1. KRAS wild-type tumors harbored alterations in other oncogenic drivers, including GNAS, BRAF, CTNNB1, and additional RAS pathway genes. A subset of tumors harbored multiple KRAS mutations, with some showing evidence of biallelic mutations. Protein profiling identified a favorable prognosis subset with low epithelial-mesenchymal transition and high MTOR pathway scores. Associations of non-coding RNAs with tumor-specific mRNA subtypes were also identified. Our integrated multi-platform analysis reveals a complex molecular landscape of PDAC and provides a roadmap for precision medicine

Factors Associated with Revision Surgery after Internal Fixation of Hip Fractures

Background: Femoral neck fractures are associated with high rates of revision surgery after management with internal fixation. Using data from the Fixation using Alternative Implants for the Treatment of Hip fractures (FAITH) trial evaluating methods of internal fixation in patients with femoral neck fractures, we investigated associations between baseline and surgical factors and the need for revision surgery to promote healing, relieve pain, treat infection or improve function over 24 months postsurgery. Additionally, we investigated factors associated with (1) hardware removal and (2) implant exchange from cancellous screws (CS) or sliding hip screw (SHS) to total hip arthroplasty, hemiarthroplasty, or another internal fixation device. Methods: We identified 15 potential factors a priori that may be associated with revision surgery, 7 with hardware removal, and 14 with implant exchange. We used multivariable Cox proportional hazards analyses in our investigation. Results: Factors associated with increased risk of revision surgery included: female sex, [hazard ratio (HR) 1.79, 95% confidence interval (CI) 1.25-2.50; P = 0.001], higher body mass index (fo