Spot-on: Safe Fuel/Air Compression

The emission of fuel vapors into the atmosphere from underground storage tanks at filling stations is a common occurrence in many parts the world. The conditions of the vapor in the tanks vary significantly over a 24 hour period such that evaporation and excess air ingestion during the refueling process can cause tank over pressurization and subsequent emissions. At other times during a 24 hour cycle, pressures can fall below atmospheric pressure. The state of California has recognized this emissions problem and has enacted regulations to address it. Due to these low-emission environmental requirements in California, solutions must be implemented that do not entail release of these vapors into the atmosphere. One solution requires that the vapors fill a balloon during the appropriate times. However, the size of the balloon at typical inflation rates requires a significant amount of physical space (approximately 1000-2000 liters), which may not necessarily be available at filling stations in urban areas. Veeder-Root has a patent pending for a system to compress the vapors that are released to a 10:1 ratio, store this compressed vapor in a small storage tank, and then return the vapors to the original underground fuel tank when the conditions are thermodynamically appropriate (see Figure 1 for the schematic representation of this system). The limitation of the compressor, however, is that the compression phase must take place below the ignition temperature of the vapor. For a 10:1 compression ratio, however, the adiabatic temperature rise of a vapor would be above the ignition temperature. Mathematical modeling is necessary here to estimate the performance of the compressor, and to suggest paths in design for improvement. This report starts with a mathematical formulation of an ideal compressor, and uses the anticipated geometry of the compressor to state a simplified set of partial differential equations. The adiabatic case is then considered, assuming that the temporary storage tank is kept at a constant temperature. Next, the heat transfer from the compression chamber through the compressor walls is incorporated into the model. Finally, we consider the case near the valve wall, which is subject to the maximum temperature rise over the estimated 10,000 cycles that will be necessary for the process to occur. We find that for adiabatic conditions, there is a hot spot close to the wall where the vapor temperature can exceed the wall temperature. Lastly, we discuss the implications of our analysis, and its limitations

Enhanced Leak Detection

A key requirement for Veeder-Root’s Enhanced Leak Detection System is that it be able to test in situ for the presence of leaks at gasoline dispensing facilities. Aside from the obvious issues of safety and lost product, this functionality is obligatory for compliance with environmental standards mandated by federal and state oversight bodies, such as the California State Water Resources Control Board (SWRCB). The SWRCB demands a testing procedure that includes conditions as close to operational as possible, while still using environmentally safe gases as a test fluid. Although the test parameters (e.g., pressure) are allowed to deviate from operating conditions in order to facilitate the test procedure, a prescribed rescaling of the test thresholds must then be applied to account for the deviation. Whether the test is run at operation conditions or in a slightly different parameter regime, the fact that the testing must be done on the product and return lines after installation at a service station presents significant challenges in devising an effective test strategy

A Multicompartment Mathematical Model of Cancer Stem Cell-Driven Tumor Growth Dynamics

Tumors are appreciated to be an intrinsically heterogeneous population of cells with varying proliferation capacities and tumorigenic potentials. As a central tenet of the so-called cancer stem cell hypothesis, most cancer cells have only a limited lifespan and thus cannot initiate or re-initiate tumors. Longevity and clonogenicity are properties unique to the subpopulation of cancer stem cells. To understand the implications of the population structure suggested by this hypothesis - a hierarchy consisting of cancer stem cells and progeny non-stem cancer cells which experience a reduction in their remaining proliferation capacity per division - we set out to develop a mathematical model for the development of the aggregate population. We show that overall tumor progression rate during the exponential growth phase is identical to the growth rate of the cancer stem cell compartment. Tumors with identical stem cell proportions, however, can have different growth rates, dependent on the proliferation kinetics of all participating cell populations. Analysis of the model revealed that the proliferation potential of non-stem cancer cells is likely to be small to reproduce biologic observations. Furthermore, a single compartment of non-stem cancer cell population may adequately represent population growth dynamics only when the compartment proliferation rate is scaled with the generational hierarchy depth

Proteomic plasma membrane profiling reveals an essential role for gp96 in the cell surface expression of LDLR family members, including the LDL receptor and LRP6.

The endoplasmic reticulum chaperone gp96 is required for the cell surface expression of a narrow range of proteins, including toll-like receptors (TLRs) and integrins. To identify a more comprehensive repertoire of proteins whose cell surface expression is dependent on gp96, we developed plasma membrane profiling (PMP), a technique that combines SILAC labeling with selective cell surface aminooxy-biotinylation. This approach allowed us to compare the relative abundance of plasma membrane (PM) proteins on gp96-deficient versus gp96-reconstituted murine pre-B cells. Analysis of unfractionated tryptic peptides initially identified 113 PM proteins, which extended to 706 PM proteins using peptide prefractionation. We confirmed a requirement for gp96 in the cell surface expression of certain TLRs and integrins and found a marked decrease in cell surface expression of four members of the extended LDL receptor family (LDLR, LRP6, Sorl1 and LRP8) in the absence of gp96. Other novel gp96 client proteins included CD180/Ly86, important in the B-cell response to lipopolysaccharide. We highlight common structural motifs in these client proteins that may be recognized by gp96, including the beta-propeller and leucine-rich repeat. This study therefore identifies the extended LDL receptor family as an important new family of proteins whose cell surface expression is regulated by gp96

The travelling wave scheme for the Navier-Stokes equations.

The Travelling Wave (TW) scheme is developed for the one dimensional, compressible Navier-Stokes equations. The method is a deviation from traditional explicit methods in that the hyperbolic and parabolic parts are treated as a single entity and travelling waves are used as approximating tools. The scheme is used mainly for computation in the optimal regime where the mesh size is of the same order as the ratio of the viscosity $\varepsilon$ to the characteristic speed. A viscous Riemann solver is designed that solves the local Riemann problems by interpolating each adjacent data pair via three waves. The first and third in the genuinely nonlinear fields are travelling waves and the second in the linearly degenerate field is a diffusion wave. Viscous rarefactions are replaced by corresponding travelling waves, so a sonic entropy fix is incorporated. The solver is the viscous analogue of an approximate Riemann solver for the Euler equations. The TW scheme is second order accurate and TVD when $\varepsilon = {\cal O}(\Delta x)$. We analyze the scheme for the scalar problem and find an a priori estimate of the location and size of the TVD region. For values of $\varepsilon$ that lie in this region, the TW scheme is less dissipative than upwind schemes and resolves the near-discontinuities as well as and often better than centred difference schemes. Whereas the latter schemes become more oscillatory as $\varepsilon$ approaches zero, the TW scheme tends to the monotone Godunov's method in the limit of small viscosity. Our last topic is the initial-boundary value problem where we consider a shock being reflected from a rigid wall. A special Riemann solver which incorporates the no-slip boundary condition is used at the wall. The diffusion wave representation in this case is an extension of a scheme which we devised for the scalar convection-diffusion equation. The TW scheme gives good resolution of the boundary layer and the reflected shock. As $\varepsilon\to 0$, the Riemann solver still gives the correct behaviour in that the gas behind the reflected shock remains stationary and the temperature is discontinuous at the boundary.Ph.D.Mathematics and Scientific ComputingUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/104564/1/9527767.pdfDescription of 9527767.pdf : Restricted to UM users only

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NPS MedicineWise: 20 years of change

Abstract The cost and potential harms of medicines and other health technologies are issues of concern for governments and third party payers of health care. Various means have been demonstrated to promote appropriate evidence-based use of these technologies as a way to reduce waste and unintended variation. Since 1998, Australia has had a national organisation responsible for large scale programs to address safe, effective and cost effective use of health technologies. This article reviews 20 years of experience for NPS MedicineWise (NPS). NPS provides evidence-based information to health professionals and consumers using interventions that have been shown to be effective. A mix of academic detailing, audit and feedback and interactive learning is built into national programs designed to improve the use of medicines and medical tests. The target audiences have typically been general practitioners, pharmacists and nurses in primary care. Consumer programs, including mass media campaigns have supported the work with health professionals. NPS receives most of its income from the Australian Government and in return it is required to show saving for the Pharmaceutical Benefits Scheme and the Medical Benefits Schedule. Since 1998, total savings of AUD 1096.62 million have been demonstrated. In addition, changes in knowledge and attitudes, changes in prescribing and test ordering behaviours and improvements in health outcomes have been shown through annual evaluations