Microfocal X-Ray Computed Tomography Post-Processing Operations for Optimizing Reconstruction Volumes of Stented Arteries During 3D Computational Fluid Dynamics Modeling

Restenosis caused by neointimal hyperplasia (NH) remains an important clinical problem after stent implantation. Restenosis varies with stent geometry, and idealized computational fluid dynamics (CFD) models have indicated that geometric properties of the implanted stent may differentially influence NH. However, 3D studies capturing the in vivo flow domain within stented vessels have not been conducted at a resolution sufficient to detect subtle alterations in vascular geometry caused by the stent and the subsequent temporal development of NH. We present the details and limitations of a series of post-processing operations used in conjunction with microfocal X-ray CT imaging and reconstruction to generate geometrically accurate flow domains within the localized region of a stent several weeks after implantation. Microfocal X-ray CT reconstruction volumes were subjected to an automated program to perform arterial thresholding, spatial orientation, and surface smoothing of stented and unstented rabbit iliac arteries several weeks after antegrade implantation. A transfer function was obtained for the current post-processing methodology containing reconstructed 16 mm stents implanted into rabbit iliac arteries for up to 21 days after implantation and resolved at circumferential and axial resolutions of 32 and 50 μm, respectively. The results indicate that the techniques presented are sufficient to resolve distributions of WSS with 80% accuracy in segments containing 16 surface perturbations over a 16 mm stented region. These methods will be used to test the hypothesis that reductions in normalized wall shear stress (WSS) and increases in the spatial disparity of WSS immediately after stent implantation may spatially correlate with the temporal development of NH within the stented region

Distributions of Pigments and Primary Production in a Gulf-Stream Meander

An investigation was made of physical effects of Gulf Stream meandering on the vertical and horizontal distributions of photosynthetic pigments and primary production. Cruises were conducted in the vicinity of a meander east of 73-degrees-W and north of 37-degrees-N from September 21 to October 5 (leg 1) and October 12-21, 1988 (leg 2), on the R/V Cape Hatteras. Relationships of photosynthesis (normalized to chlorophyll) to irradiance (P-1) did not show large horizontal variation, and water column composite P-I curves from leg 1 and leg 2 were similar. Therefore a single P-I curve derived from pooled data was used to model distributions of primary production. Distributions of photosynthetic pigments were characterized on the basis of in vivo fluorescence profiles and empirical relationships with extracted pigment concentrations. Subsurface irradiance was described using a spectral irradiance model. Cross sections of the Gulf Stream revealed consistently higher pigment concentrations and primary production on the slope water side. Along-stream variations in pigment distributions and primary production were apparently related to density structure influenced by meander circulation. Such variations were less pronounced during leg 2. which came after a transition from a well-defined meander interacting with a warm-core ring (leg 1) to a more linear stream (leg 2). Higher water-column-integrated primary production during leg 2 was attributed to mixing-induced nutrient injection and redistribution of chlorophyll in the photic zone

Influence of Type of Cigarette on Peripheral versus Central Lung Cancer

Objectives: Adenocarcinoma has replaced squamous cell carcinoma as the most common cell type of lung cancer in the United States. It has been proposed that this shift is due to the increased use of filter and lower-tar cigarettes, resulting in increased delivery of smoke to peripheral regions of the lungs, where adenocarcinoma usually occurs. We reviewed radiologic data to evaluate the hypothesis that tumors in smokers of cigarettes with lower-tar yield are more likely to occur peripherally than tumors in smokers of higher-yield cigarettes. Methods: At two urban academic medical centers, we reviewed computed tomographic scans, chest radiographs, and medical records to assign tumor location (peripheral or central) for 330 smokers diagnosed with carcinoma of the lung between 1993 and 1999. We compared the proportion of tumors in a peripheral versus central location by lifetime filter use and average lifetime tar rating (<21 and ≥21 mg). Results: Tumor location (69% peripheral and 31% central) was unrelated to cigarette filter use. Smokers of cigarettes with lower-tar ratings were more likely than those with higher ratings to have peripheral rather than central tumors (odds ratio, 1.76; 95% confidence interval, 0.89-3.47). When restricted to subjects with adenocarcinoma or squamous cell carcinoma, the odds ratio (95% confidence interval) was 2.31 (1.05-5.08). Conclusions: Among cigarette smokers with lung cancer, use of cigarettes with lower-tar yield was associated with preferential occurrence of tumors in peripheral sites. Our findings support the hypothesis that changes in smoking associated with lower-tar cigarettes have led to a shift in the location of smoking-related lung cancer

Mechanisms of deformation-induced trace element migration in zircon resolved by atom probe and correlative microscopy

The widespread use of zircon in geochemical and geochronological studies of crustal rocks is underpinned by an understanding of the processes that may modify its composition. Deformation during tectonic and impact related strain is known to modify zircon trace element compositions, but the mechanisms by which this occurs remain unresolved. Here we combine electron backscatter diffraction, transmission Kikuchi diffraction and atom probe microscopy to investigate trace element migration associated with a ~20 nm wide, 2° low-angle subgrain boundary formed in zircon during a single, high-strain rate, deformation associated with a bolide impact. The low-angle boundary shows elevated concentrations of both substitutional (Y) and interstitial (Al, Mg and Be) ions. The observed compositional variations reflect a dynamic process associated with the recovery of shock-induced vacancies and dislocations into lower energy low-angle boundaries. Y segregation is linked to the migration and localisation of oxygen vacancies, whilst the interstitial ions migrate in association with dislocations. These data represent the direct nanoscale observation of geologically-instantaneous, trace element migration associated with crystal plasticity of zircon and provide a framework for further understanding mass transfer processes in zircon

A Simple Coase-Like Mechanism that Transfers Control of Government Spending Levels from Politicians to Voters

Elected representatives have little incentive to pursue the interests of those electing them once they are elected. This well-known principle-agent problem leads, in a variety of theories of government, to nonoptimally large levels of government expenditure. An implication is that budgetary rules are seen as necessary to constrain politicians? tax and spending behavior. Popular among such constraints are various Balanced Budget Amendment proposals. These approaches, however, are shown here to have serious limitations, including failure to address the central concern of spending level. An alternative approach is advanced here that relies on a Coase-like mechanism that transfers control of government spending to the voter. Prisoner's dilemma incentives and political competition are seen to be critical to the superiority of the present mechanism to approaches requiring budget balance

Efficacy of Manipulating Reproduction of Common Ravens to Conserve Sensitive Prey Species: Three Case Studies

Expansion of human enterprise across western North America has resulted in an increase in availability of anthropogenic resource subsidies for generalist species. This has led to increases in generalists’ population numbers across landscapes that were previously less suitable for their current demographic rates. Of particular concern are growing populations of common ravens (Corvus corax; ravens), because predation by ravens is linked to population declines of sensitive species. Ecosystem managers seek management options for mitigating the adverse effects of raven predation where unsustainable predator–prey conflicts exist. We present 3 case studies examining how manipulating reproductive success of ravens influences demographic rates of 2 sensitive prey species. Two case studies examine impacts of removing raven nests or oiling raven eggs on nest survival of greater sage-grouse (Centrocercus urophasianus; sage-grouse) within Wyoming and the Great Basin of California and Nevada, USA, respectively. The third case study uses Mojave desert tortoise (Gopherus agassizii; tortoise) decoys to examine effects of oiling raven eggs on depredation rates of juvenile tortoises in the Mojave Desert in California. Initial trial years from all 3 case studies were consistent in finding improved vital rates associated with the application of strategies for reducing reproductive success of ravens. Specifically, removal of raven nests resulted in increased nest survival of sage-grouse within treatment areas where predation by ravens was the primary cause of nest failure. In addition, nest survival of sage-grouse and survival of juvenile tortoise decoys was higher following a treatment of oiling the eggs of ravens in their nests at 2 sites within the Great Basin and 4 tortoise conservation areas in the Mojave Desert in California. Along with specialized technologies that can make techniques such as egg-oiling more feasible, these findings support these management practices as important tools for managing ravens, especially in areas where breeding ravens have negative impacts on sensitive prey species

Microwave Spectroscopy of Thermally Excited Quasiparticles in YBa_2Cu_3O_{6.99}

We present here the microwave surface impedance of a high purity crystal of $YBa_2Cu_3O_{6.99}$ measured at 5 frequencies between 1 and 75 GHz. This data set reveals the main features of the conductivity spectrum of the thermally excited quasiparticles in the superconducting state. Below 20 K there is a regime of extremely long quasiparticle lifetimes, due to both the collapse of inelastic scattering below $T_c$ and the very weak impurity scattering in the high purity $BaZrO_3$-grown crystal used in this study. Above 20 K, the scattering increases dramatically, initially at least as fast as $T^4$.Comment: 13 pages with 10 figures. submitted to Phys Rev

Whole-Exome Sequencing and hiPSC Cardiomyocyte Models Identify \u3ci\u3eMYRIP\u3c/i\u3e, \u3ci\u3eTRAPPC11\u3c/i\u3e, and \u3ci\u3eSLC27A6\u3c/i\u3e of Potential Importance to Left Ventricular Hypertrophy in an African Ancestry Population

Background: Indices of left ventricular (LV) structure and geometry represent useful intermediate phenotypes related to LV hypertrophy (LVH), a predictor of cardiovascular (CV) disease (CVD) outcomes. Methods and Results: We conducted an exome-wide association study of LV mass (LVM) adjusted to height2.7, LV internal diastolic dimension (LVIDD), and relative wall thickness (RWT) among 1,364 participants of African ancestry (AAs) in the Hypertension Genetic Epidemiology Network (HyperGEN). Both single-variant and gene-based sequence kernel association tests were performed to examine whether common and rare coding variants contribute to variation in echocardiographic traits in AAs. We then used a data-driven procedure to prioritize and select genes for functional validation using a human induced pluripotent stem cell cardiomyocyte (hiPSC-CM) model. Three genes [myosin VIIA and Rab interacting protein (MYRIP), trafficking protein particle complex 11 (TRAPPC11), and solute carrier family 27 member 6 (SLC27A6)] were prioritized based on statistical significance, variant functional annotations, gene expression in the hiPSC-CM model, and prior biological evidence and were subsequently knocked down in the hiPSC-CM model. Expression profiling of hypertrophic gene markers in the knockdowns suggested a decrease in hypertrophic expression profiles. MYRIP knockdowns showed a significant decrease in atrial natriuretic factor (NPPA) and brain natriuretic peptide (NPPB) expression. Knockdowns of the heart long chain fatty acid (FA) transporter SLC27A6 resulted in downregulated caveolin 3 (CAV3) expression, which has been linked to hypertrophic phenotypes in animal models. Finally, TRAPPC11 knockdown was linked to deficient calcium handling. Conclusions: The three genes are biologically plausible candidates that provide new insight to hypertrophic pathways

The lifetime of nitrogen oxides in an isoprene-dominated forest

The lifetime of nitrogen oxides (NO_x) affects the concentration and distribution of NO_x and the spatial patterns of nitrogen deposition. Despite its importance, the lifetime of NO_x is poorly constrained in rural and remote continental regions. We use measurements from a site in central Alabama during the Southern Oxidant and Aerosol Study (SOAS) in summer 2013 to provide new insights into the chemistry of NO_x and NO_x reservoirs. We find that the lifetime of NO_x during the daytime is controlled primarily by the production and loss of alkyl and multifunctional nitrates (ΣANs). During SOAS, ΣAN production was rapid, averaging 90 ppt h^(−1) during the day, and occurred predominantly during isoprene oxidation. Analysis of the ΣAN and HNO_3 budgets indicate that ΣANs have an average lifetime of under 2 h, and that approximately 45 % of the ΣANs produced at this site are rapidly hydrolyzed to produce nitric acid. We find that ΣAN hydrolysis is the largest source of HNO_3 and the primary pathway to permanent removal of NO_x from the boundary layer in this location. Using these new constraints on the fate of ΣANs, we find that the NO_x lifetime is 11 ± 5 h under typical midday conditions. The lifetime is extended by storage of NO_x in temporary reservoirs, including acyl peroxy nitrates and ΣANs