A Compactness Theorem for Riemannian Manifolds with Boundary and Applications

In this paper we prove weak L^{1,p} (and thus C^{\alpha}) compactness for the class of uniformly mean-convex Riemannian n-manifolds with boundary satisfying bounds on curvature quantities, diameter, and (n-1)-volume of the boundary. We obtain two stability theorems from the compactness result. The first theorem applies to 3-manifolds (contained in the aforementioned class) that have Ricci curvature close to 0 and whose boundaries are Gromov-Hausdorff close to a fixed metric on S^2 with positive curvature. Such manifolds are C^{\alpha} close to the region enclosed by a Weyl embedding of the fixed metric into \R^3. The second theorem shows that a 3-manifold with Ricci curvature close to 0 (resp. -2, 2) and mean curvature close to 2 (resp. 2\sqrt 2, 0) is C^{\alpha} close to a metric ball in the space form of constant curvature 0 (resp -1, 1), provided that the boundary is a topological sphere.Comment: 17 pages; comments welcom

Chance-Constrained Efficiency Analysis

Data envelopment analysis (DEA) is extended to the case of stochastic inputs and outputs through the use of chance-constrained programming. The chance-constrained envelope envelops a given set of observations "most of the time." We show that the chance-constrained enveloping process leads to the definition of a conventional (certainty-equivalent) efficiency ratio (a ratio between weighted outputs and weighted inputs). Furthermore, extending the concept of Pareto and Koopmans efficiency to the case of chance-constrained dominance (to be defined), we establish the identity of the following two chance-constrained efficiency concepts: (i) the chance constrained DEA efficiency measure of a particular output-input point is unity, and all chance-constraints are binding; (ii) the point is efficient in the sense Pareto and Koopmans. Finally we discuss the implications of our approach for econometric frontier analysis.IC2 Institut

Severe idiopathic hypereosinophilic syndrome

SummaryHypereosinophilic syndrome (HES) is a systemic illness that usually presents with nonspecific symptoms. However, HES can be fatal, particularly when eosinophils infiltrate vital organs. We report a patient with HES who presented with a perforated viscus and sepsis-like syndrome and rapidly improved with drotrecogin-alfa and steroid therapy

Endemic mycosis

This article is made available for unrestricted research re-use and secondary analysis in any form or by any means with acknowledgement of the original source. These permissions are granted for the duration of the World Health Organization (WHO) declaration of COVID-19 as a global pandemi

Evaluating the financial risk involved in farmland investment decisions

Investing in farmland is one of the most important decisions that farmers face in their lifetimes. Usually, large amounts of debt are required to purchase a substantial tract of land, thereby reducing the farmer's liquidity position and future borrowing capacity. Fixed debt commitments must be met by highly variable future farm income. Variable cash flows are the most critical in the first three to five years after the land purchase. After that time, the financial position has improved as a result of the principal payments and possible appreciation in the value of new and existing land holdings. An incorrect decision in purchasing land may result in prolonged cash flow problems and force partial liquidation or possibly bankruptcy. Oregon farmers want to know how much can be paid for land considering their objectives relating to the return they desire on their investment and the risk they are willing to accept that debt can be serviced after the proposed farm expansion. Two models were developed in this study. The first is a net present value model to determine the effect of critical variables on the maximum economically feasible price that can be paid for farmland. The second model developed for this study is a risk analysis model to evaluate the decision maker's ability to meet fixed debt payments and other cash commitments given probability distributions for prices and yields The net present value of an acre of land is determined by summing the discounted cash flows after taxes over the planning horizon for the tract to be purchased. Whole firm analysis, or direct comparison between present and proposed expanded operation, is used to determine the exact effects of tax consequences associated with the land purchase. The discount factor used is the desired after-tax rate of return on equity capital. The model considers the case where the planning horizon is shorter in years than the loan repayment period. The risk model determines gross farm income, which consists of product prices and yields, stochastically using triangular probability distributions. Operating expenses, amortization payments for term debt, net capital purchases associated with depreciable items, living expenses and withdrawals, and all taxes are subtracted from gross receipts to determine yearly cash flow. Items given in the output include the low cash balance at the end of the number of years for which the program was run, the probability of a negative cash balance occurring, and the probability of financial failure. The models were applied to two case farm studies in Sherman and Marion Counties. Empirical results of these case studies indicate that given current production costs and gross farm receipts, farmland must continue to appreciate at an annual compound rate of 9 percent for the duration of the planning horizon to justify current land prices. Other variables having a sizable impact on the net present value include gross receipts and operating expenses for the newly purchased tract, the purchase price, and the discount factor Decision makers who own their farm operations and have low previous debt commitments are the most capable of generating adequate cash flows. Farmers who have large amounts of debt outstanding and who lease portions of their operation may have problems generating a positive cash balance within four years after the purchase What farmers pay for land is influenced by the amount of risk that they are willing to take

Developments in Atmosphere Revitalization Modeling and Simulation

"NASA's Advanced Exploration Systems (AES) program is pioneering new approaches for rapidly developing prototype systems, demonstrating key capabilities, and validating operational concepts for future human missions beyond Earth orbit" (NASA 2012). These forays beyond the confines of earth's gravity will place unprecedented demands on launch systems. They must not only blast out of earth's gravity well as during the Apollo moon missions, but also launch the supplies needed to sustain a crew over longer periods for exploration missions beyond earth's moon. Thus all spacecraft systems, including those for the separation of metabolic carbon dioxide and water from a crewed vehicle, must be minimized with respect to mass, power, and volume. Emphasis is also placed on system robustness both to minimize replacement parts and ensure crew safety when a quick return to earth is not possible. Current efforts are focused on improving the current state-of-the-art systems utilizing fixed beds of sorbent pellets by evaluating structured sorbents, seeking more robust pelletized sorbents, and examining alternate bed configurations to improve system efficiency and reliability. These development efforts combine testing of sub-scale systems and multi-physics computer simulations to evaluate candidate approaches, select the best performing options, and optimize the configuration of the selected approach, which is then implemented in a full-scale integrated atmosphere revitalization test. This paper describes the development of atmosphere revitalization models and simulations. A companion paper discusses the hardware design and sorbent screening and characterization effort in support of the Atmosphere Revitalization Recovery and Environmental Monitoring (ARREM) project within the AES program

Modeling of Atmosphere Revitalization

NASA's AES is pioneering new approaches for future human missions beyond Earth orbit. All spacecraft systems must be minimized with respect to mass, power, and volume. Here, we show work related to improving system efficiency and reliability for water separation systems on crewed vehicles and the initial development of COMSOL simulations in support of the Atmosphere Revitalization Recovery and Environmental Monitoring (ARREM) projec