Diagnosing the Prominence-Cavity Connection

Prominences and cavities are ubiquitously observed together, but the physical link between these disparate structures has not been established. We address this issue by using dynamic emission in the extreme ultraviolet (EUV) to probe the connections of these structures. The SDO/AIA observations show that the cavity exhibits excessive emission variability compared to the surrounding quiet-sun streamer, particularly in the 171\AA bandpass. We find that this dynamic emission takes the form of coherent loop-like brightening structures which emanate from the prominence into the central cavity. The geometry of these structures, dubbed prominence horns, generally mimics the curvature of the cavity boundary. We use a space-time statistical analysis of two cavities in multiple AIA bandpasses to constrain the energetic properties of 45 horns. In general, we find there is a positive correlation between the light curves of the horns in the 171\AA and 193\AA bandpasses, however the 193\AA emission is a factor of 5 weaker. There is also a strong correlation between structural changes to the prominence as viewed in the He II 304\AA bandpass and the enhanced 171\AA emission. In that bandpass, the prominence appears to extend several megameters along the 171\AA horn where we observe co-spatial, co-temporal 304\AA and 171\AA emission dynamics. We present these observations as evidence of the magnetic and energetic connection between the prominence and the cavity. Further modeling work is necessary to explain the physical source and consequences of these events, particularly in the context of the traditional paradigm: the cavity is under dense because it supplies mass to the over dense prominence

Prominence Mass Supply and the Cavity

A prevalent but untested paradigm is often used to describe the prominence-cavity system: the cavity is under-dense because it is evacuated by supplying mass to the condensed prominence. The thermal non-equilibrium (TNE) model of prominence formation offers a theoretical framework to predict the thermodynamic evolution of the prominence and the surrounding corona. We examine the evidence for a prominence-cavity connection by comparing the TNE model with diagnostics of dynamic extreme ultraviolet emission (EUV) surrounding the prominence, specifically prominence horns. Horns are correlated extensions of prominence plasma and coronal plasma which appear to connect the prominence and cavity. The TNE model predicts that large-scale brightenings will occur in the SDO/AIA 171\AA\ bandpass near the prominence that are associated with the cooling phase of condensation formation. In our simulations, variations in the magnitude of footpoint heating lead to variations in the duration, spatial scale, and temporal offset between emission enhancements in the other EUV bandpasses. While these predictions match well a subset of the horn observations, the range of variations in the observed structures is not captured by the model. We discuss the implications of our one-dimensional loop simulations for the three-dimensional time-averaged equilibrium in the prominence and the cavity. Evidence suggests that horns are likely caused by condensing prominence plasma, but the larger question of whether this process produces a density-depleted cavity requires a more tightly constrained model of heating and better knowledge of the associated magnetic structure

Molecular absorption in transition region spectral lines

Aims: We present observations from the Interface Region Imaging Spectrograph (IRIS) of absorption features from a multitude of cool atomic and molecular lines within the profiles of Si IV transition region lines. Many of these spectral lines have not previously been detected in solar spectra. Methods: We examined spectra taken from deep exposures of plage on 12 October 2013. We observed unique absorption spectra over a magnetic element which is bright in transition region line emission and the ultraviolet continuum. We compared the absorption spectra with emission spectra that is likely related to fluorescence. Results: The absorption features require a population of sub-5000 K plasma to exist above the transition region. This peculiar stratification is an extreme deviation from the canonical structure of the chromosphere-corona boundary . The cool material is not associated with a filament or discernible coronal rain. This suggests that molecules may form in the upper solar atmosphere on small spatial scales and introduces a new complexity into our understanding of solar thermal structure. It lends credence to previous numerical studies that found evidence for elevated pockets of cool gas in the chromosphere.Comment: accepted by A&A Letter

Observed Variability of the Solar Mg II h Spectral Line

The Mg II h&k doublet are two of the primary spectral lines observed by the Sun-pointing Interface Region Imaging Spectrograph (IRIS). These lines are tracers of the magnetic and thermal environment that spans from the photosphere to the upper chromosphere. We use a double gaussian model to fit the Mg II h profile for a full-Sun mosaic dataset taken 24-Aug-2014. We use the ensemble of high-quality profile fits to conduct a statistical study on the variability of the line profile as it relates the magnetic structure, dynamics, and center-to-limb viewing angle. The average internetwork profile contains a deeply reversed core and is weakly asymmetric at h2. In the internetwork, we find a strong correlation between h3 wavelength and profile asymmetry as well h1 width and h2 width. The average reversal depth of the h3 core is inversely related to the magnetic field. Plage and sunspots exhibit many profiles which do not contain a reversal. These profiles also occur infrequently in the internetwork. We see indications of magnetically aligned structures in plage and network in statistics associated with the line core, but these structures are not clear or extended in the internetwork. The center-to-limb variations are compared with predictions of semi-empirical model atmospheres. We measure a pronounced limb darkening in the line core which is not predicted by the model. The aim of this work is to provide a comprehensive measurement baseline and preliminary analysis on the observed structure and formation of the Mg II profiles observed by IRIS.Comment: Accepted for publicatio

Development and Validation of a Risk Score for Chronic Kidney Disease in HIV Infection Using Prospective Cohort Data from the D:A:D Study

Ristola M. on työryhmien DAD Study Grp ; Royal Free Hosp Clin Cohort ; INSIGHT Study Grp ; SMART Study Grp ; ESPRIT Study Grp jäsen.Background Chronic kidney disease (CKD) is a major health issue for HIV-positive individuals, associated with increased morbidity and mortality. Development and implementation of a risk score model for CKD would allow comparison of the risks and benefits of adding potentially nephrotoxic antiretrovirals to a treatment regimen and would identify those at greatest risk of CKD. The aims of this study were to develop a simple, externally validated, and widely applicable long-term risk score model for CKD in HIV-positive individuals that can guide decision making in clinical practice. Methods and Findings A total of 17,954 HIV-positive individuals from the Data Collection on Adverse Events of Anti-HIV Drugs (D:A:D) study with >= 3 estimated glomerular filtration rate (eGFR) values after 1 January 2004 were included. Baseline was defined as the first eGFR > 60 ml/min/1.73 m2 after 1 January 2004; individuals with exposure to tenofovir, atazanavir, atazanavir/ritonavir, lopinavir/ritonavir, other boosted protease inhibitors before baseline were excluded. CKD was defined as confirmed (>3 mo apart) eGFR In the D:A:D study, 641 individuals developed CKD during 103,185 person-years of follow-up (PYFU; incidence 6.2/1,000 PYFU, 95% CI 5.7-6.7; median follow-up 6.1 y, range 0.3-9.1 y). Older age, intravenous drug use, hepatitis C coinfection, lower baseline eGFR, female gender, lower CD4 count nadir, hypertension, diabetes, and cardiovascular disease (CVD) predicted CKD. The adjusted incidence rate ratios of these nine categorical variables were scaled and summed to create the risk score. The median risk score at baseline was -2 (interquartile range -4 to 2). There was a 1: 393 chance of developing CKD in the next 5 y in the low risk group (risk score = 5, 505 events), respectively. Number needed to harm (NNTH) at 5 y when starting unboosted atazanavir or lopinavir/ritonavir among those with a low risk score was 1,702 (95% CI 1,166-3,367); NNTH was 202 (95% CI 159-278) and 21 (95% CI 19-23), respectively, for those with a medium and high risk score. NNTH was 739 (95% CI 506-1462), 88 (95% CI 69-121), and 9 (95% CI 8-10) for those with a low, medium, and high risk score, respectively, starting tenofovir, atazanavir/ritonavir, or another boosted protease inhibitor. The Royal Free Hospital Clinic Cohort included 2,548 individuals, of whom 94 individuals developed CKD (3.7%) during 18,376 PYFU (median follow-up 7.4 y, range 0.3-12.7 y). Of 2,013 individuals included from the SMART/ESPRIT control arms, 32 individuals developed CKD (1.6%) during 8,452 PYFU (median follow-up 4.1 y, range 0.6-8.1 y). External validation showed that the risk score predicted well in these cohorts. Limitations of this study included limited data on race and no information on proteinuria. Conclusions Both traditional and HIV-related risk factors were predictive of CKD. These factors were used to develop a risk score for CKD in HIV infection, externally validated, that has direct clinical relevance for patients and clinicians to weigh the benefits of certain antiretrovirals against the risk of CKD and to identify those at greatest risk of CKD.Peer reviewe

Diagnosing the Prominence-Cavity Connection in the Solar Corona

The corona is a unique layer in the solar atmosphere where the temperature rapidly increases as a function of radial height. While a majority of the corona exists at temperatures above one million degrees Kelvin, there are embedded regions of much cooler and denser plasma known as prominences. The formation mechanism and force balance of prominences are open questions in solar physics. The energetic equilibrium of the corona is described by a balance of heating, thermal conduction, and radiative cooling. Prominences can be described by the thermal instability of coronal energy balance which leads to the formation of cool condensations. For condensations to exist in force equilibrium in the corona, they must be supported against gravity by the magnetic field. Condensations will fall into the gravitational well provided on dipped magnetic field lines, but these field lines will also contain coronal plasma which surrounds the condensation. These formation and stability considerations require a hydrodynamic energetic connection and a magnetostatic structural connection between the prominence and the surrounding corona. Observationally, the prominence is surrounded by a density depleted elliptical structure known as a cavity. In this dissertation, we use extreme ultraviolet remote sensing observations of the prominence-cavity system to diagnose the static and dynamic properties of these structures. The observations are compared with numerical models for the time-dependent coronal condensation process and the time-independent corona-prominence magnetic field. To diagnose the density of the cavity, we construct a three-dimensional structural model of the corona. This structural model allows us to synthesize extreme ultraviolet emission in the corona in a way that incorporates the projection effects which arise from the optically thin plasma. This forward model technique is used to constrain a radial density profile simultaneously in the cavity and the streamer. We use a \u26chi2 minimization to find the density model which best matches a density sensitive line ratio (observed with Hinode/Extreme ultraviolet Imaging Spectrometer) and the white light scattered intensity (observed with Mauna Loa Solar Observatory MK4 coronagraph). This diagnostic finds that the observed cavity has a density depletion of 30\% relative to the streamer. The diagnosis of thermodynamic properties of the static cavity provides a measurement of the time-averaged equilibrium condition of the plasma. However, the coronal cooling model of prominence formation requires that there will be a time-dependent change in the coronal region which supplies mass to the prominence. We use extreme ultraviolet spectra and spectral images to diagnose the dynamics of the prominence and the surrounding corona. Based on the doppler shift of extreme ultraviolet coronal emission lines, we find that there are large regions of flowing plasma which appear to occur within cavities. These line of sight flows have speeds of 10 km/s and projected spatial scales of 100 Mm. Using the Solar Dynamics Observatory Atmospheric Imaging Assembly (SDO/AIA) dataset, we observe dynamic emission from the prominence-cavity system. The SDO/AIA dataset observes multiple spectral bandpasses with different temperature sensitivities. Time-dependent changes in the observed emission in these bandpass images represent changes in the thermodynamic properties of the emitting plasma. We find that the coronal region surrounding the prominence exhibits larger intensity variations (over tens of hours of observations) as compared to the streamer region. This variability is particularly strong in the cool coronal emission of the 171A bandpass. We identify the source of this variability as strong brightening events that resemble concave-up loop segments and extend from the cool prominence plasma. These features, referred to as prominence horns, are observed in multiple SDO/AIA bandpasses which allows us to determine how the characteristics of horns vary as a function of temperature. The most intriguing aspect of horn emission is the strong correlation between cool coronal emission and prominence emission and the weak correlation between hot coronal emission and cool coronal emission. Based on the dynamic observations, we suggest that horns are likely the signature thermal changes along magnetic field lines. Magnetic field lines are the basic structural building block of the corona. Energy and pressure balance in the corona occur along magnetic field lines. The large-scale extreme ultraviolet emission we observe in the corona is a conglomerate of many coronal loops projected along a line of sight. In order to calculate the plasma properties at a particular point in the corona, we use one-dimensional models for energy and pressure balance along field lines. In order to predict the extreme ultraviolet emission along a particular line of sight, we project these one-dimensional models onto the three-dimensional magnetic configuration provided by a MHD model for the coronal magnetic field. The thermal non-equilibrium model describes a method for inducing catastrophic cooling in a coronal loop by distributing chromospheric mass throughout the coronal region of the loop. This model results in the formation of a prominence along dipped magnetic loops. We find that the thermal non-equilibrium model matches our dynamic constraints of prominence horns. Loops undergoing cooling will brighten in the 171A bandpass in SDO/AIA and this coronal emission will be correlated with dynamic emission from prominence plasma. While prominence horns and prominence formation appear compatible based on the one-dimensional modeling, there is a discrepancy when we consider the projected spatial structure of horns. Horns project inside the density-depleted cavity, while the mechanism driving prominence formation requires density-enhancements. The three dimensional corona is composed of the projection of many distinct coronal loops. To diagnose the projection effects of prominence horns, we combine the one-dimensional hydrodynamic model with the three-dimensional flux rope model of the prominence-corona magnetic field. The flux rope model uses dipped and twisted magnetic field lines to support a prominence. The distribution of dipped field lines in the flux rope is not uniform. The segments of dipped field lines which would emit in the coronal bandpasses of SDO/AIA are volumetrically isolated along the topological surface which forms the boundary between the twisted flux rope and the near-potential arcade. The projected emission from these field lines would occur throughout the entirety of the flux rope cross section even though the field lines do not extend throughout most of the flux rope volume. Based on the flux rope model, prominence horns are an indication of prominence formation, but they do not occur within the cavity and they are not responsible for the density depletion in that structure. While the dipped field lines in the flux rope model can be linked to the prominence, they are not linked to the cavity. We use a one-dimensional hydrostatic model for coronal energy balance to solve for the plasma parameters throughout the volume of the flux rope model. Variations of plasma parameters between magnetic field lines occur due to geometric considerations for energy loss and column mass. Using this hydrostatic model, we find that the flux rope interior is density depleted relative to the surrounding arcade. Structurally, we find that the short field lines which dominate the flux rope volume can explain the density depletion of the cavity. By combining the hydrostatic and hydrodynamic results, we find that the flux rope model can describe the connection between prominence horns and the cavity. The cavity is formed by axial field lines which are circumscribed by high-density dipped field lines. The cavity is not directly connected to the prominence and does not supply mass to it. These results have allowed us to the establish the first comprehensive picture on the magnetic and energetic interaction of the prominence and the cavity. While the originally hypothesis that the cavity supplies mass to the prominence proved inaccurate, we cannot simply say that these structures are not related. Rather our findings suggest that the prominence and the cavity are distinct magnetic substructures that are complementary regions of a larger whole, specifically a magnetic flux rope

Array Mapping in Behavioral Synthesis

ing with credit is permitted. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. Request permissions from Publications Dept., ACM Inc., Fax: (212) 869-0481, or <[email protected]>. Array Mapping in Behavioral Synthesis Herman Schmit and Donald E. Thomas Dept. of ECE, Carnegie Mellon University Pittsburgh, PA, USA Abstract This paper discusses the mapping of arrays in a behavior to memories in an implementation. We introduce a design representation based on a variety of array grouping techniques and the binding of array groups to memory components with different dimensions, access times, and number of ports. The results of design actions are computed in terms of the number of memory components and the length of schedules in the behavior. We demonstrate the ability of a synthesis tool using this representation to generate designs that span the entire range of the memory design space. 1.0 Introductio..

Address generation for memories containing multiple arrays

Abstract—We present techniques for generating addresses for memories containing multiple arrays. Because these techniques rely on the inversion or rearrangement of address bits, they are faster and require less hardware to compute than the traditional technique of addition. Use of these techniques can improve performance and cost of application-specific memory subsystems by decreasing effective access time to arrays and by reducing address generation hardware. The primary drawback to this approach is that extra memory space is occasionally required, but in over a million tested cases, this extra memory space is on average only 2 % and no worse than 17.4 % of the utilized memory space. This amount of wasted address space is significantly less than the amount required by the only known similar technique [7] and rarely necessitates the allocation of additional memory components. These techniques provide a foundation for adderfree address generation for manually and automatically generated application-specific memory designs. Index Terms — Arrays, compilers (silicon), digital arithmetic, high-level synthesis, memory management, number theoretic transforms. I