The Formation, Structure, and Stability of a Shear Layer in a Fluid with Temperature-Dependent Viscosity

The presence of viscosity normally has a stabilizing effect on the flow of a fluid. However, experiments show that the flow of a fluid might form shear bands or shear layers, narrow bands in which the velocity of the fluid changes sharply. In general, adiabatic shear layers are observed not only in fluids but also in thermo-plastic materials subject to shear at a high-strain rate and in combustion. Therefore there is widespread interest in modeling the formation of shear layers. In this paper we investigate the basic system of conservation laws for a one-dimensional flow with temperature-dependent viscosity using a combination of analytical and numerical tools. We present results to substantiate the claim that the formation of shear layers is due to teh fact that viscosity decreases sufficiently quickly as temperature increases and analyze the structure and stability properties of the layers

Analysis of Shear Layers in a Fluid with Temperature-Dependent Viscosity

The presence of viscosity normally has a stabilizing effect on the flow of a fluid. Howerver, experiments show that the flow of a fluid in which viscosity decreases as temperature increases tends to form shear layers, narrow regions in which the velocity of the fluid changes sharply. In general, adiabatic shear layers are observed not only in fluids but also in thermo-plastic materials subject to shear at a high-strain rate and in combustion and there is widespread interest in modeling their formation. In this paper, we investigate a well-known model representing a basic system of conservation laws for a one-dimensional flow with temperature-dependent viscosity using a combination of analytical and numerical tools. We present results to substantiate the claim that the formation of shear layers can only occur in solutions of the model when the viscosity decreases sufficiently quickly as temperature increases and we further analyze the structure and stability properties of the layers

Characterization of the fecal microbiome in cats with inflammatory bowel disease or alimentary small cell lymphoma.

Feline chronic enteropathy (CE) is a common gastrointestinal disorder in cats and mainly comprises inflammatory bowel disease (IBD) and small cell lymphoma (SCL). Both IBD and SCL in cats share features with chronic enteropathies such as IBD and monomorphic epitheliotropic intestinal T-cell lymphoma in humans. The aim of this study was to characterize the fecal microbiome of 38 healthy cats and 27 cats with CE (13 cats with IBD and 14 cats with SCL). Alpha diversity indices were significantly decreased in cats with CE (OTU p = 0.003, Shannon Index p = 0.008, Phylogenetic Diversity p = 0.019). ANOSIM showed a significant difference in bacterial communities, albeit with a small effect size (P = 0.023, R = 0.073). Univariate analysis and LEfSE showed a lower abundance of facultative anaerobic taxa of the phyla Firmicutes (families Ruminococcaceae and Turicibacteraceae), Actinobacteria (genus Bifidobacterium) and Bacteroidetes (i.a. Bacteroides plebeius) in cats with CE. The facultative anaerobic taxa Enterobacteriaceae and Streptococcaceae were increased in cats with CE. No significant difference between the microbiome of cats with IBD and those with SCL was found. Cats with CE showed patterns of dysbiosis similar to those in found people with IBD

Measuring subaqueous progradation of the Wax Lake Delta with a model of flow direction divergence

Remotely sensed flow patterns can reveal the location of the subaqueous distal tip of a distributary channel on a prograding river delta. Morphodynamic feedbacks produce distributary channels that become shallower over their final reaches before the unchannelized foreset slopes basinward. The flow direction field over this morphology tends to diverge and then converge, providing a diagnostic signature that can be captured in flow or remote sensing data. A total of 21 measurements from the Wax Lake Delta (WLD) in coastal Louisiana and 317 measurements from numerically simulated deltas show that the transition from divergence to convergence occurs in a distribution that is centered just downstream of the channel tip, on average 132&thinsp;m in the case of the WLD. These data validate an inverse model for remotely estimating subaqueous channel tip location. We apply this model to 33 images of the WLD between its initiation in 1974 and 2016. We find that six of the primary channels grew at rates of 60–80&thinsp;m&thinsp;yr−1, while the remaining channel grew at 116&thinsp;m&thinsp;yr−1. We also show that the subaqueous delta planform grew at a constant rate (1.72&thinsp;km2&thinsp;yr−1). Subaerial land area initially grew at the same rate but slowed after about 1999. We explain this behavior as a gradual decoupling of channel tip progradation and island aggradation that may be common in maturing deltas.</p

Lump correction and identification in the combined thermal/epithermal neutron (CTEN) method

The authors present a model for self shielding in lumps of fissile material in active-neutron assays. The model combines the formula for self-attenuation of gamma-ray in lumpy sources with the multi-group analysis techniques used in neutron transport calculations. Models for thin foils and for spheres are examined in terms of error multiplication in determining lump corrections and the basic accuracy of the model

Static non-reciprocity in mechanical metamaterials

Reciprocity is a fundamental principle governing various physical systems, which ensures that the transfer function between any two points in space is identical, regardless of geometrical or material asymmetries. Breaking this transmission symmetry offers enhanced control over signal transport, isolation and source protection. So far, devices that break reciprocity have been mostly considered in dynamic systems, for electromagnetic, acoustic and mechanical wave propagation associated with spatio-temporal variations. Here we show that it is possible to strongly break reciprocity in static systems, realizing mechanical metamaterials that, by combining large nonlinearities with suitable geometrical asymmetries, and possibly topological features, exhibit vastly different output displacements under excitation from different sides, as well as one-way displacement amplification. In addition to extending non-reciprocity and isolation to statics, our work sheds new light on the understanding of energy propagation in non-linear materials with asymmetric crystalline structures and topological properties, opening avenues for energy absorption, conversion and harvesting, soft robotics, prosthetics and optomechanics.Comment: 19 pages, 3 figures, Supplementary information (11 pages and 5 figures

Variability Across Implanting Centers in Short and Long-Term Mortality and Adverse Events in Patients on HeartMate 3 Support: A Momentum 3 Secondary Analysis

Purpose: We aimed to characterize center-specific variability in HeartMate 3 (HM3) patient survival within the MOMENTUM 3 studies and to examine the correlation between implanting center survival and major adverse events (AEs). Methods: Center HM3 implant volume during the MOMENTUM 3 pivotal (n=515) and continued access protocol (n=1685) trials were tallied. Centers implanting ≤16 HM3 patients (25th percentile) were excluded. De-identified center variability in mortality was assessed at 90 days and 2 years using direct adjusted survival while accounting for key baseline risk factors. The 90-day frequency and 2-year rates of stroke, bleeding, and infection were compared across centers and correlations between survival and event rate variability were assessed. Results: Among 48 centers, 1957 HM3 patients were included in this analysis with site implants ranging between 17 to 103 patients. Patient cohorts differed across the sites by age (average 52-68 years), sex (60-95% male), destination therapy intent (25-100%), and %INTERMACS profile 1-2 (2-81%). At 90 days, center adjusted median mortality was 6.5%, nadiring at ≤3.2% (25th percentile) and peaking at ≥10.5% (75th percentile). Median 2-year center adjusted mortality was 18.6%, nadiring at ≤14.0% and peaking at ≥25.2% (figure A). AEs were also highly variable across centers; centers with low mortality tended to have lower AE rates at 2 years (figure B). Conclusion: Patient characteristics and outcomes were highly variable across MOMENTUM 3 centers despite trial preoperative inclusion/exclusion criteria. Many centers had exemplary risk-adjusted HM3 patient outcomes. Studies are needed to improve our understanding of top performing centers’ best practices as they relate to HM3 care in the pre, interoperative, and chronic support stages in an effort to further improve HM3 LVAD-associated clinical outcomes

Defining Metrics for Short Term Success After LVAD Implant: An Analysis of the Society of Thoracic Surgeons Intermacs Registry

Purpose: While clinical trials evaluating left ventricular assist device (LVAD) technology typically use composite outcomes to assess efficacy, composite outcomes including patient reported outcomes (PROs) have not been utilized as benchmarks for LVAD implant center performance improvement initiatives or quality ranking. The objective of the study was to assess the feasibility of generating a patient composite outcome measure including PROs from a real world registry. Methods: Short term (ST, 180 days) adverse events (AEs) and mortality were tallied for Intermacs patients undergoing LVAD implant between 1/2012 and 12/2019. ST postoperative events included mortality on first device and frequencies of stroke, reoperation (device malfunction/other), right heart failure (RHF), prolonged respiratory failure, and/or dialysis on first device. Logistic regression was used to generate odds ratios for mortality for each AE. Separately, the EuroQOL visual analog scale (VAS) was assessed at baseline and 180 days in ST survivors. Results: Of 20,115 patients, 37% suffered at least one event, most commonly death, reoperation and stroke (Table, column A). Stroke, prolonged respiratory failure, and dialysis attributed the most to ST mortality (Table, column B). Of the 16725 patients alive at 180 days, 43% completed a VAS with 82.0% showing VAS improvement. Renal failure and RHF contributed most to failure to improve VAS (Figure). Conclusion: Assessment of a ST composite outcome metric after LVAD implant from a real world data source is feasible but limited by incomplete PRO reporting. ST adverse events display differential effects on mortality and PROs that can be used in development of global rank outcome scores. While reoperation is common, stroke, prolonged respiratory failure and renal failure conferred highest risks of ST deaths within Intermacs. Assessment of PROs should become a priority for LVAD centers to allow the field to generate a complete assessment of patient-centered outcomes

In-beam spectroscopy using the (t,p) reaction: recent results near A = 100

Charged particle spectroscopy using the (t,p) reaction has been employed for more than two decades to study the low-energy structure of nuclei. This reaction has contributed significantly to the elucidation of single-particle and collective phenomena for neutron rich nuclei in virtually every mass region. We have begun to use the (t,p) reaction in conjunctionuclei with in-beam ..gamma..-ray and conversion-electron spectroscopy to bring additional understanding to low-energy nuclear structure. In this report we briefly discuss the experimental considerations in using this reaction for in-beam spectroscopy, and present some results for nuclei with mass near 100

Developing GIS-based eastern equine encephalitis vector-host models in Tuskegee, Alabama

<p>Abstract</p> <p>Background</p> <p>A site near Tuskegee, Alabama was examined for vector-host activities of eastern equine encephalomyelitis virus (EEEV). Land cover maps of the study site were created in ArcInfo 9.2^®from QuickBird data encompassing visible and near-infrared (NIR) band information (0.45 to 0.72 μm) acquired July 15, 2008. Georeferenced mosquito and bird sampling sites, and their associated land cover attributes from the study site, were overlaid onto the satellite data. SAS 9.1.4^®was used to explore univariate statistics and to generate regression models using the field and remote-sampled mosquito and bird data. Regression models indicated that <it>Culex erracticus </it>and Northern Cardinals were the most abundant mosquito and bird species, respectively. Spatial linear prediction models were then generated in Geostatistical Analyst Extension of ArcGIS 9.2^®. Additionally, a model of the study site was generated, based on a Digital Elevation Model (DEM), using ArcScene extension of ArcGIS 9.2^®.</p> <p>Results</p> <p>For total mosquito count data, a first-order trend ordinary kriging process was fitted to the semivariogram at a partial sill of 5.041 km, nugget of 6.325 km, lag size of 7.076 km, and range of 31.43 km, using 12 lags. For total adult <it>Cx. erracticus </it>count, a first-order trend ordinary kriging process was fitted to the semivariogram at a partial sill of 5.764 km, nugget of 6.114 km, lag size of 7.472 km, and range of 32.62 km, using 12 lags. For the total bird count data, a first-order trend ordinary kriging process was fitted to the semivariogram at a partial sill of 4.998 km, nugget of 5.413 km, lag size of 7.549 km and range of 35.27 km, using 12 lags. For the Northern Cardinal count data, a first-order trend ordinary kriging process was fitted to the semivariogram at a partial sill of 6.387 km, nugget of 5.935 km, lag size of 8.549 km and a range of 41.38 km, using 12 lags. Results of the DEM analyses indicated a statistically significant inverse linear relationship between total sampled mosquito data and elevation (R²= -.4262; p < .0001), with a standard deviation (SD) of 10.46, and total sampled bird data and elevation (R²= -.5111; p < .0001), with a SD of 22.97. DEM statistics also indicated a significant inverse linear relationship between total sampled <it>Cx. erracticus </it>data and elevation (R²= -.4711; p < .0001), with a SD of 11.16, and the total sampled Northern Cardinal data and elevation (R²= -.5831; p < .0001), SD of 11.42.</p> <p>Conclusion</p> <p>These data demonstrate that GIS/remote sensing models and spatial statistics can capture space-varying functional relationships between field-sampled mosquito and bird parameters for determining risk for EEEV transmission.</p