Numerical comparison of pipe-column-separation models

Results comparing six column-separation numerical models for simulating localized vapor cavities and distributed vaporous cavitation in pipelines are presented. The discrete vapor-cavity model (DVCM) is shown to be quite sensitive to selected input parameters. For short pipeline systems, the maximum pressure rise following column separation can vary markedly for small changes in wave speed, friction factor, diameter, initial velocity, length of pipe, or pipe slope. Of the six numerical models, three perform consistently over a broad number of reaches. One of them, the discrete gas-cavity model, is recommended for general use as it is least sensitive to input parameters or to the selected discretization of the pipeline. Three models provide inconsistent estimates of the maximum pressure rise as the number of reaches is increased; however, these models do give consistent results provided the ratio of maximum cavity size to reach volume is kept below 10%.Angus R. Simpson and Anton Bergan

A bioprinted cardiac patch composed of cardiac-specific extracellular matrix and progenitor cells for heart repair

Congenital heart defects are present in 8 of 1000 newborns and palliative surgical therapy has increased survival. Despite improved outcomes, many children develop reduced cardiac function and heart failure requiring transplantation. Human cardiac progenitor cell (hCPC) therapy has potential to repair the pediatric myocardium through release of reparative factors, but therapy suffers from limited hCPC retention and functionality. Decellularized cardiac extracellular matrix hydrogel (cECM) improves heart function in animals, and human trials are ongoing. In the present study, a 3D-bioprinted patch containing cECM for delivery of pediatric hCPCs is developed. Cardiac patches are printed with bioinks composed of cECM, hCPCs, and gelatin methacrylate (GelMA). GelMA-cECM bioinks print uniformly with a homogeneous distribution of cECM and hCPCs. hCPCs maintain >75% viability and incorporation of cECM within patches results in a 30-fold increase in cardiogenic gene expression of hCPCs compared to hCPCs grown in pure GelMA patches. Conditioned media from GelMA-cECM patches show increased angiogenic potential (>2-fold) over GelMA alone, as seen by improved endothelial cell tube formation. Finally, patches are retained on rat hearts and show vascularization over 14 d in vivo. This work shows the successful bioprinting and implementation of cECM-hCPC patches for potential use in repairing damaged myocardium

The role of hydrogen sulfide in central cardiovascular regulation and cerebral artery tone

Hydrogen sulfide (H 2 S), traditionally known for its smell and toxicity, is now increasingly recognised as a gasotransmitter. It is produced endogenously by several enzymes and has biological effects, including neuromodulation, cardiovascular and antioxidant effects. In the peripheral cardiovascular system, H 2 S causes vasodilation and systemic administration of a H 2 S donor, sodium hydrogen sulfide (NaHS), reduces blood pressure in a dose dependent manner. The rostral ventrolateral medulla (RVLM) and the hypothalamic paraventricular nucleus (PVN) are brain nuclei with demonstrated involvement in increased sympathetic nerve activity observed in cardiovascular pathologies. The aim of this study was to investigate the possible role of H 2 S as a central cardiovascular regulator via the RVLM and PVN.. The presence of the H 2 S-producing enzyme, cystathionine β synthase (CBS) in the RVLM and PVN was demonstrated by western blotting and immunohistochemistry. Nerve recording studies were performed on anaesthetised male Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHR). Bilateral microinjections of NaHS (0.2 – 2000 pmol/side), or inhibitors of CBS (hydroxylamine, HA, 0.2 – 2.0 nmol/side; or amino-oxyacetate, AOA, 0.1 – 1.0 nmol/side) into the RVLM did not significantly affect blood pressure (BP), heart rate (HR) or lumbar sympathetic nerve activity (LSNA), compared to vehicle in WKY rats. Microinjections into the PVN of NaHS, HA and AOA had no consistent significant effects on BP, HR or LSNA compared to vehicle in WKY rats. NaHS microinjected into the PVN or RVLM of SHR rats did not significantly affect BP, HR or LSNA compared to vehicle. Together, these results suggest that H 2 S may not have a major cardiovascular regulatory role in the RVLM and PVN. H 2 S is produced in peripheral blood vessels via the enzyme cystathionine-γ-lyase (CSE). It is thought to be an important endogenous vasoactive mediator, since CSE gene deletion results in increased blood pressure. The aim of this study was to examine the mechanism of H 2 S-induced vasodilation of cerebral arteries. Vasorelaxation responses in middle cerebral arteries (MCA) from male Sprague-Dawley rats were examined using wire myography. Inhibiting K + conductance with KCl (50mM) significantly attenuated NaHS-induced relaxation, increasing the EC 50 by 4 fold. 4,4-diisothiocyanatostilbene-2,2-disulfonic acid (DIDS, 300µM) caused a significant 10-fold rightward shift of the NaHS concentration-response curve. Nifedipine (3µM), a blocker of L-type calcium channels, significantly reduced the maximum relaxation elicited by NaHS by 30%. These findings suggest that H 2 S mediated relaxation of MCA is DIDS sensitive and partly mediated by inhibition of L-type calcium channels with an additional contribution by potassium channels. H 2 S has antioxidant effects which may protect against endothelial dysfunction. The aim of this study was to examine the effect of streptozotocin-induced diabetes on the MCA response to H 2 S.. Diabetic MCA exhibited endothelial dysfunction, however, their response to NaHS was unaltered. L-cysteine-induced relaxation was enhanced in diabetic MCA. The lucigenin assay demonstrated increased superoxide generation from both aorta and cerebral vessels of diabetic animals. NaHS decreased superoxide generation from diabetic, but not control MCA. The results suggest that production of H2S is increased in diabetic MCA and H 2 S appears to act as an antioxidant in these vessels in vitro

Discovering Valuable Items from Massive Data

Suppose there is a large collection of items, each with an associated cost and an inherent utility that is revealed only once we commit to selecting it. Given a budget on the cumulative cost of the selected items, how can we pick a subset of maximal value? This task generalizes several important problems such as multi-arm bandits, active search and the knapsack problem. We present an algorithm, GP-Select, which utilizes prior knowledge about similarity be- tween items, expressed as a kernel function. GP-Select uses Gaussian process prediction to balance exploration (estimating the unknown value of items) and exploitation (selecting items of high value). We extend GP-Select to be able to discover sets that simultaneously have high utility and are diverse. Our preference for diversity can be specified as an arbitrary monotone submodular function that quantifies the diminishing returns obtained when selecting similar items. Furthermore, we exploit the structure of the model updates to achieve an order of magnitude (up to 40X) speedup in our experiments without resorting to approximations. We provide strong guarantees on the performance of GP-Select and apply it to three real-world case studies of industrial relevance: (1) Refreshing a repository of prices in a Global Distribution System for the travel industry, (2) Identifying diverse, binding-affine peptides in a vaccine de- sign task and (3) Maximizing clicks in a web-scale recommender system by recommending items to users

Evaluation of Two Implant Strategies, Revalor- XH or a Combination Revalor- IH/Revalor- 200 on Heifer Growth Performance and Carcass Characteristics

A commercial feedlot trial examined effects of two implant strategies (Revalor- IH on d 1 and re- implanted with Revalor- 200 on d 101 or Revalor- XH on d 1) on growth performance and carcass characteristics of heifers fed 183 days. Th ere were no differences between implant strategies for final body weight, dry matter intake, and average daily gain. Heifers implanted with the combination IH/200 treatment had improved carcassadjusted feed conversion, greater LM area, and lower calculated yield grade compared to heifers implanted with XH. Th e response in growth performance between the two implant strategies suggests that the partiallycoated Revalor- XH implant can be used in place of a more aggressive implant strategy when heifers are fed to similar days

Using Neural Networks for Aerodynamic Parameter Modeling

Neural networks are being developed at McDonnell Douglas Corporation to provide an onboard model of an aircraft\u27s aerodynamics to support advanced flight control systems. These flight control systems, constructed using neural networks and advanced controllers, have the potential to reduce flight control development costs and to improve inflight performance. Neural networks are useful in this situation because they can compactly represent the data and operate in real-tim

Pipeline column separation flow regimes

A generalized set of pipeline column separation equations is presented describing all conventional types of low-pressure regions. These include water hammer zones, distributed vaporous cavitation, vapor cavities, and shocks (that eliminate distributed vaporous cavitation zones). Numerical methods for solving these equations are then considered, leading to a review of three numerical models of column separation. These include the discrete vapor cavity model, the discrete gas cavity model, and the generalized interface vaporous cavitation model. The generalized interface vaporous cavitation model enables direct tracking of actual column separation phenomena (e.g., discrete cavities, vaporous cavitation zones), and consequently, better insight into the transient event. Numerical results from the three column separation models are compared with results of measurements for a number of flow regimes initiated by a rapid closure of a downstream valve in a sloping pipeline laboratory apparatus. Finally, conclusions are drawn about the accuracy of the modeling approaches. A new classification of column separation (active or passive) is proposed based on whether the maximum pressure in a pipeline following column separation results in a short-duration pressure pulse that exceeds the magnitude of the Joukowsky pressure rise for rapid valve closure.Anton Bergant and Angus R. Simpso

State Legislative Response to the Housing Crisis

Great public attention has recently been focused on the crisis in housing facing all major urban areas in this country. This article has been prepared to bring close attention to one segment of the hoped for solution-legislative action needed on the state level

Pilot, Rollout and Monte Carlo Tree Search Methods for Job Shop Scheduling

Greedy heuristics may be attuned by looking ahead for each possible choice, in an approach called the rollout or Pilot method. These methods may be seen as meta-heuristics that can enhance (any) heuristic solution, by repetitively modifying a master solution: similarly to what is done in game tree search, better choices are identified using lookahead, based on solutions obtained by repeatedly using a greedy heuristic. This paper first illustrates how the Pilot method improves upon some simple well known dispatch heuristics for the job-shop scheduling problem. The Pilot method is then shown to be a special case of the more recent Monte Carlo Tree Search (MCTS) methods: Unlike the Pilot method, MCTS methods use random completion of partial solutions to identify promising branches of the tree. The Pilot method and a simple version of MCTS, using the $\varepsilon$-greedy exploration paradigms, are then compared within the same framework, consisting of 300 scheduling problems of varying sizes with fixed-budget of rollouts. Results demonstrate that MCTS reaches better or same results as the Pilot methods in this context.Comment: Learning and Intelligent OptimizatioN (LION'6) 7219 (2012