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

Atoms and the Law

Early in 1951 a group of interested members of the faculty of The University of Michigan Law School conceived the idea of a research project, the purpose of which would be to investigate the principal unique legal problems being created and likely to be created in the future by peaceful uses of atomic energy. The group planned the preparation and publication of a series of manuscripts which might ultimately emerge as one or more printed volumes dealing with the legal problems affecting this new form of energy. Many phases of the subject were scrutinized, including the rule-making and licensing powers of the Atomic Energy Commission, the censoring of scientific information, liability for radiation injuries to persons and property, patent rights, state regulatory activities, imd other areas of possible interest. In July 1951 the Michigan Memorial-Phoenix Project, the University\u27s major program of research in all phases of peaceful uses of the atom, made a substantial grant in support of the proposed study of legal problems. The law faculty group, consisting at the outset of Professors Samuel D. Estep, William ]. Pierce, and the undersigned, organized and embarked upon the program. Later Professors Eric Stein and William W. Bishop were added. A small research staff was recruited and the studies were commenced, beginning with an intensive examination of the legislative history of the Atomic Energy Act of 1946. In the summer of 1952, an Institute on Industrial and Legal Problems of Atomic Energy was organized and held in the Law Quadrangle in Ann Arbor. This proved to be one of the earliest of the many conferences held in this country resulting from the development of atomic enterprise, and it served to give very great stimulus to the research work being carried on within the staff of the Law School. The proceedings were published by the School and were widely distributed. In 1956 a second summer conference was held, this time a workshop, with a prepared agenda and working papers distributed in advance to the invited participants, who included not only lawyers but also engineers, A. E. C. staff members, scientists, health officials, and economists-a truly inter-disciplinary undertaking. The objective was to elicit concentrated thinking and interchange of ideas between knowledgeable people concerning atomic legal problems, and to precipitate these ideas in concrete form for the guidance of those responsible for current legal developments in the field. Again, proceedings were published and were widely distributed. Throughout the years manuscripts on various phases of the subject have been prepared by the research staff or by the members of the faculty engaged in the project. Little by little the materials, which now emerge as this volume entitled Atoms and the Law, took shape in manuscript ·form. Principal interest finally centered on tort liability for radiation injuries, workmen\u27s compensation for such injuries, federal statutory and administrative provisions regulating atomic activities, state regulation of atomic energy, and finally, in the later years, the international aspects of the subject. These became principal headings in the volume which is now being published. As the project unfolded, those of us who were participating in it became increasingly impressed with the feeling that here was something unique in legal research, for we were engaging in a task that involved not only frontiers of the law but also one which was ever so closely interwoven with the science and technology of tomorrow. In carrying out the project, it became necessary for us to proceed as far as possible to master a new scientific field, one with a new vocabulary and a radically different set of concepts. This certainly enhanced interest in the task, not to mention increasing the difficulty of carrying it forward. In addition, it afforded us an even more fascinating prospect, namely, the possibility of creation of a center for legal studies related to the new technological world, with its great variety of new facets-automation, water resources problems, aviation, etc., thus to make our contribution in providing the legal framework to facilitate the adjustment of scientific advances to the social order of which we are a part.https://repository.law.umich.edu/books/1025/thumbnail.jp

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

Risk Assessment and Comparative Effectiveness of Left Ventricular Assist Device and Medical Management in Ambulatory Heart Failure Patients The ROADMAP Study 2-Year Results

OBJECTIVES The authors sought to provide the pre-specified primary endpoint of the ROADMAP (Risk Assessment and Comparative Effectiveness of Left Ventricular Assist Device and Medical Management in Ambulatory Heart Failure Patients) trial at 2 years. BACKGROUND The ROADMAP trial was a prospective nonrandomized observational study of 200 patients (97 with a left ventricular assist device [LVAD], 103 on optimal medical management [OMM]) that showed that survival with improved functional status at 1 year was better with LVADs compared with OMM in a patient population of ambulatory New York Heart Association functional class IIIb/IV patients. METHODS The primary composite endpoint was survival on original therapy with improvement in 6-min walk distance \u3e= 75 m. RESULTS Patients receiving LVAD versus OMM had lower baseline health-related quality of life, reduced Seattle Heart Failure Model 1-year survival (78% vs. 84%; p = 0.012), and were predominantly INTERMACS (Interagency Registry for Mechanically Assisted Circulatory Support) profile 4 (65% vs. 34%; p \u3c 0.001) versus profiles 5 to 7. More LVAD patients met the primary endpoint at 2 years: 30% LVAD versus 12% OMM (odds ratio: 3.2 [95% confidence interval: 1.3 to 7.7]; p = 0.012). Survival as treated on original therapy at 2 years was greater for LVAD versus OMM (70 +/- 5% vs. 41 +/- 5%; p \u3c 0.001), but there was no difference in intent-to-treat survival (70 +/- 5% vs. 63 +/- 5%; p = 0.307). In the OMM arm, 23 of 103 (22%) received delayed LVADs (18 within 12 months; 5 from 12 to 24 months). LVAD adverse events declined after year 1 for bleeding (primarily gastrointestinal) and arrhythmias. CONCLUSIONS Survival on original therapy with improvement in 6-min walk distance was superior with LVAD compared with OMM at 2 years. Reduction in key adverse events beyond 1 year was observed in the LVAD group. The ROADMAP trial provides risk-benefit information to guide patient- and physician-shared decision making for elective LVAD therapy as a treatment for heart failure. (Risk Assessment and Comparative Effectiveness of Left Ventricular Assist Device and Medical Management in Ambulatory Heart Failure Patients [ROADMAP]; NCT01452802

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

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

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

Applied Mathematics at the U.S. Department of Energy: Past, Present and a View to the Future

Over the past half-century, the Applied Mathematics program in the U.S. Department of Energy's Office of Advanced Scientific Computing Research has made significant, enduring advances in applied mathematics that have been essential enablers of modern computational science. Motivated by the scientific needs of the Department of Energy and its predecessors, advances have been made in mathematical modeling, numerical analysis of differential equations, optimization theory, mesh generation for complex geometries, adaptive algorithms and other important mathematical areas. High-performance mathematical software libraries developed through this program have contributed as much or more to the performance of modern scientific computer codes as the high-performance computers on which these codes run. The combination of these mathematical advances and the resulting software has enabled high-performance computers to be used for scientific discovery in ways that could only be imagined at the program's inception. Our nation, and indeed our world, face great challenges that must be addressed in coming years, and many of these will be addressed through the development of scientific understanding and engineering advances yet to be discovered. The U.S. Department of Energy (DOE) will play an essential role in providing science-based solutions to many of these problems, particularly those that involve the energy, environmental and national security needs of the country. As the capability of high-performance computers continues to increase, the types of questions that can be answered by applying this huge computational power become more varied and more complex. It will be essential that we find new ways to develop and apply the mathematics necessary to enable the new scientific and engineering discoveries that are needed. In August 2007, a panel of experts in applied, computational and statistical mathematics met for a day and a half in Berkeley, California to understand the mathematical developments required to meet the future science and engineering needs of the DOE. It is important to emphasize that the panelists were not asked to speculate only on advances that might be made in their own research specialties. Instead, the guidance this panel was given was to consider the broad science and engineering challenges that the DOE faces and identify the corresponding advances that must occur across the field of mathematics for these challenges to be successfully addressed. As preparation for the meeting, each panelist was asked to review strategic planning and other informational documents available for one or more of the DOE Program Offices, including the Offices of Science, Nuclear Energy, Fossil Energy, Environmental Management, Legacy Management, Energy Efficiency & Renewable Energy, Electricity Delivery & Energy Reliability and Civilian Radioactive Waste Management as well as the National Nuclear Security Administration. The panelists reported on science and engineering needs for each of these offices, and then discussed and identified mathematical advances that will be required if these challenges are to be met. A review of DOE challenges in energy, the environment and national security brings to light a broad and varied array of questions that the DOE must answer in the coming years. A representative subset of such questions includes: (1) Can we predict the operating characteristics of a clean coal power plant? (2) How stable is the plasma containment in a tokamak? (3) How quickly is climate change occurring and what are the uncertainties in the predicted time scales? (4) How quickly can an introduced bio-weapon contaminate the agricultural environment in the US? (5) How do we modify models of the atmosphere and clouds to incorporate newly collected data of possibly of new types? (6) How quickly can the United States recover if part of the power grid became inoperable? (7) What are optimal locations and communication protocols for sensing devices in a remote-sensing network? (8) How can new materials be designed with a specified desirable set of properties? In comparing and contrasting these and other questions of importance to DOE, the panel found that while the scientific breadth of the requirements is enormous, a central theme emerges: Scientists are being asked to identify or provide technology, or to give expert analysis to inform policy-makers that requires the scientific understanding of increasingly complex physical and engineered systems. In addition, as the complexity of the systems of interest increases, neither experimental observation nor mathematical and computational modeling alone can access all components of the system over the entire range of scales or conditions needed to provide the required scientific understanding