The rotation curves of dwarf galaxies: a problem for Cold Dark Matter?

We address the issue of accuracy in recovering density profiles from observations of rotation curves of galaxies. We ``observe'' and analyze our models in much the same way as observers do the real galaxies. We find that the tilted ring model analysis produces an underestimate of the central rotational velocity. In some cases the galaxy halo density profile seems to have a flat core, while in reality it does not. We identify three effects, which explain the systematic biases: (1) inclination (2), small bulge, and (3) bar. The presence of even a small non-rotating bulge component reduces the rotation velocity. In the case of a disk with a bar, the underestimate of the circular velocity is larger due to a combination of non-circular motions and random velocities. Signatures of bars can be difficult to detect in the surface brightness profiles of the model galaxies. The variation of inclination angle and isophote position angle with radius are more reliable indicators of bar presence than the surface brightness profiles. The systematic biases in the central ~ 1 kpc of galaxies are not large. Each effect separately gives typically a few kms error, but the effects add up. In some cases the error in circular velocity was a factor of two, but typically we get about 20 percent. The result is the false inference that the density profile of the halo flattens in the central parts. Our observations of real galaxies show that for a large fraction of galaxies the velocity of gas rotation (as measured by emission lines) is very close to the rotation of stellar component (as measured by absorption lines). This implies that the systematic effects discussed in this paper are also applicable both for the stars and emission-line gas.Comment: ApJ, in press, 30 pages, Latex, 21 .eps figure

Salt Loading from Efflorescence and Suspended Sediments in the Price River Basin

Salinity control is a major component of water management in arid climates and irrigated areas and one of particular concern in the Colorado River Basin. The alts enter the water as it flows over land or moves through the soil or geologic formations. The principal salt collection processes are 1) dissolution from the soil surface during runoff events, 2) transpiration of soil water leaving salt residuals, 3) efflorescence left by evaporating seepage and then dissolved by subsequent runoff, 4) dissolution with weathering of fixed bed channels, 5) salts released by sediments entering the channel from sheet, gulley, and bank erosion, and 6) deep percolation through saline aquifer reaching the stream as base flow. This study examined processes 3 and 5. Salt efflorescence was examined by field observation and instrumentation, laboratory experiments, and mathematical modeling. The field data showed near saturation conditions of sodium sulfate waters below crusts of densities between 0.14 and 0.36 g/cm^2 and which formed over abouta 10-day period following channel cleaning by storm runoff. Laboratory data on salt crusting in soil columns were also used in developing a model which when applied to the Price River Basin estimated that no more than 7.5 percent of the total salt loading comes from salt efflorescence being carried away in the stream flow. The conditions favorable to the accumulation of salt efflorescence are highly saline water just below the soil surface and a source of heat for vaporizing the water. Salt release from suspended sediments was studied by laboratory experimentation with sediment material obtained from various locations in the Price River Basin. The Buckinham Pi Theorem was employed to derive relationships expressing the EC of a sediment water system as a function o fthe controlling factors. The results were presented in two salt release equations, one excluding the effect of initial EC and the other providing for initially saline solutions. The salt release equations were incorporated into an adapted version of the Watershed Erosion and Sediment Transport (WEST) model and applied to a small tributary of Coal Creek. Extrapolation to the entire Price River Basin led to an estimate that about 0.50 percent of the total annual salt load is released from suspened sediments. This study concludes that surface salt sources produce a relatvely small fraction of the total loading. Future studies need to go underground. They need to quantify and examine the flow lines of water movement from mountain source and valley floow recharge areas to points of emergence as base flow in the larger stream channels. They need to investigate the aquifers and their soluble salt content

Impact of flow pulsatility on arterial drug distribution in stent-based therapy

Drug-eluting stents reside in a dynamic fluid environment where the extent to which drugs are distributed within the arterial wall is critically modulated by the blood flowing through the arterial lumen. Yet several factors associated with the pulsatile nature of blood flow and their impact on arterial drug deposition have not been fully investigated. We employed an integrated framework comprising bench-top and computational models to explore the factors governing the time-varying fluid dynamic environment within the vasculature and their effects on arterial drug distribution patterns. A custom-designed bench-top framework comprising a model of a single drug-eluting stent strut and a poly-vinyl alcohol-based hydrogel as a model tissue bed simulated fluid flow and drug transport under fully apposed strut settings. Bench-top experiments revealed a relative independence between drug distribution and the factors governing pulsatile flow and these findings were validated with the in silico model. Interestingly, computational models simulating suboptimal deployment settings revealed a complex interplay between arterial drug distribution, Womersley number and the extent of malapposition. In particular, for a stent strut offset from the wall, total drug deposition was sensitive to changes in the pulsatile flow environment, with this dependence increasing with greater wall displacement. Our results indicate that factors governing pulsatile luminal flow on arterial drug deposition should be carefully considered in conjunction with device deployment settings for better utilization of drug-eluting stent therapy.National Institutes of Health (U.S.) (grant NIH R01 GM-49039

LaScO3/SrTiO3: A conducting polar heterointerface of two 3d band insulating perovskites

This work reports a quasi-two-dimensional electron gas (q-2DEG) system at the interface of two wideband-gap insulators, (TiO2-terminated) SrTiO3 and LaScO3, with a minimum thickness of 4-unit cell (uc). The highly crystalline and abrupt heterointerface is confirmed with high-resolution electron microscopy. The mixed Ti4+ and Ti3+ valence states (for 4 uc of LaScO3) obtained from the x-ray photoelectron spectroscopy study suggest an intrinsic electronic reconstruction at the interface, leading to a metallic nature. This origin is well supported by density functional theory calculations that reveal an emergence of 3.3 states/eV/spin at the Fermi level for 4 uc in accordance with the polar catastrophe model. The study offers one more perovskite heterostructure, like LaAlO3/SrTiO3, for unraveling the q-2DEG phenomena toward a clear mechanism and futuristic applications

Study on the Drying Characteristics of Green Gram, Cowpea and Soybean

The study reveals the drying characteristics of Green gram, Cowpea and Soybean when exposed to two different drying mechanisms namely convective (i.e., Tray Drying) and a innovative method (i.e., microwave drying). The objective of the study is to come out with a most appropriate drying technique which gives the product a better keeping quality. In this study the drying characteristics i.e the amount of moisture removed for every 10min is calculated at different temperatures for the respective samples. The sample was dried in tray dryer and microwave at two temperatures

Digital control of force microscope cantilevers using a field programmable gate array

This report describes a cantilever controller for magnetic resonance force microscopy (MRFM) based on a field programmable gate array (FPGA), along with the hardware and software used to integrate the controller into an experiment. The controller is assembled from a low-cost commercially available software defined radio (SDR) device and libraries of open-source software. The controller includes a digital filter comprising two cascaded second-order sections ("biquads"), which together can implement transfer functions for optimal cantilever controllers. An appendix in this report shows how to calculate filter coefficients for an optimal controller from measured cantilever characteristics. The controller also includes an input multiplexer and adder used in calibration protocols. Filter coefficients and multiplexer settings can be set and adjusted by control software while an experiment is running. The input is sampled at 64 MHz; the sampling frequency in the filters can be divided down under software control to achieve a good match with filter characterisics. Data reported here were sampled at 500 kHz, chosen for acoustic cantilevers with resonant frequencies near 8 kHz. Inputs are digitized with 12 bits resolution, outputs with 14 bits. The experiment software is organized as a client and server to make it easy to adapt the controller to different experiments. The server encapusulates the details of controller hardware organization, connection technology, filter architecture, and number representation. The same server could be used in any experiment, while a different client encodes the particulars of each experiment.Comment: submitted to Review of Scientific Instrument

Cluster Algebra: A Query Language for Heterogeneous Databases

This report describes a query language based on algebra for heterogeneous databases. The database logic is used as a uniform framework for studying the heterogeneous databases. The data model based on the database logic is referred to as cluster data model in this report. Generalized Structured Query Language (GSQL) is used for expressing ad-hoc queries over the relational, hierarchical and network database uniformly. For the purpose of query optimization, a query language that can express the primitive heterogeneous database operations is required. This report describes such a query language for the clusters (i.e., heterogeneous databases). The cluster algebra consists of (a) generalized relational operations such as selection, union, intersection, difference, semi-join, rename and cross-product; (b) modified relational operations such as normal projection and normal join; and (c) new operations such as normalize, embed, and unembed

Hydrologic Evaluation of the Coastal Belt Water Project Sarir and Tazerbo Well Fields, Libya

Executive Summary: The basic purpose of this study was to conduct a finite-element computer model and give an dindependent appraisal of the reliability of the groundwater supply for the proposed Coastal Belt Water Project (CBWP_ Well Fields at Sarir and Tazerbo. There is no doubt that ample quantities of groundwater of acceptable quality occur at the sites selected for these well fields for the estimated 50-year life of the project and longer. Of major concern is the predicted drawdown of wells and total pumping lifts throughout the 50-year period. Excessive drawdowns could cause operating costs to become prohibitibely expensive. Average drawdown in wells not including well-field interference and hydraulic friction losses at the CBWP Well Field at Sarir is expected to be only about 30 m at the end of 50 years, but the static water level is relatively deep (56 m) which makes the total pumping lift fairly high when well-field interference and other losses are added. This optimistic estimate of drawdown is based upon computer analysis for almost 7 years of pumping history of the existing Sarir South agricultural well field nearby, where the subsurface geology is believed to be quite similar to that at the propsed CBWP Well Field at Sarir. The average dpumping lift, which includes many other factors besides aquifer drawdown, is estimated to be about 142 m. at the end of the 50-year pumping period at Sarir and should average about 136 m during the 50 years. Interference from pumpage at the existing agricultural well fields at Sarir may be responsible for about 10 m of this predicted pumping lift. Drawdown at Tazerbo is predicted to be about 90 m. at the end of 50 years, but the static water level is only about 9 m. there. Consequently its average pumping lift should be about 133 m at the end of the 50-year pumping period and should average about 118 m during the 50 years. no appreciable interference from nearby well fields is expected in the Tazerbo area based upon presently known conditions. Significatn reductions in pumping lifts at Tazerbo and in water-collection network costs at Sarir are possible by improved well field layout and well design. Suggested inprovements and estimated cost savings are presented in detail in Appendix A (especially see well-field design comparisons of Tables A-1 and A-4)

Stent Thrombogenicity Early in High Risk Interventional Settings is Driven by Stent Design and Deployment, and Protected by Polymer-Drug Coatings

Author Manuscript: 2012 April 5Background—Stent thrombosis is a lethal complication of endovascular intervention. Concern has been raised about the inherent risk associated with specific stent designs and drug-eluting coatings, yet clinical and animal support is equivocal. Methods and Results—We examined whether drug-eluting coatings are inherently thrombogenic and if the response to these materials was determined to a greater degree by stent design and deployment with custom-built stents. Drug/polymer coatings uniformly reduce rather than increase thrombogenicity relative to matched bare metal counterparts (0.65-fold; P=0.011). Thick-strutted (162 μm) stents were 1.5-fold more thrombogenic than otherwise identical thin-strutted (81 μm) devices in ex vivo flow loops (P<0.001), commensurate with 1.6-fold greater thrombus coverage 3 days after implantation in porcine coronary arteries (P=0.004). When bare metal stents were deployed in malapposed or overlapping configurations, thrombogenicity increased compared with apposed, length-matched controls (1.58-fold, P=0.001; and 2.32-fold, P<0.001). The thrombogenicity of polymer-coated stents with thin struts was lowest in all configurations and remained insensitive to incomplete deployment. Computational modeling–based predictions of stent-induced flow derangements correlated with spatial distribution of formed clots. Conclusions—Contrary to popular perception, drug/polymer coatings do not inherently increase acute stent clotting; they reduce thrombosis. However, strut dimensions and positioning relative to the vessel wall are critical factors in modulating stent thrombogenicity. Optimal stent geometries and surfaces, as demonstrated with thin stent struts, help reduce the potential for thrombosis despite complex stent configurations and variability in deployment

Effects of Fe substitution on the transport properties of the superconductor MgB2

A systematic study has been made on the effect of Fe substitution by means of resistivity, thermal conductivity, and Seebeck coefficient of the Mg1−xFexB2 superconductor involving 0%, 0.3%, 0.6%, 1.2%, and 3.0% Fe content. The superconducting transition has been found to be very sharp 0.2 K for a pristine sample and substitution of Fe results in the decrease of TC with the increase in the transition width. Thermal conductivity is found to decrease with Fe content in general, such that the shoulder present in the pristine sample tends to fade away with increasing Fe. An analysis has been made on the normal state resistivity in terms of a two-band model, and of the thermal conductivity in terms of the Wiedemann-Franz law and the lattice thermal conductivity,and the information obtained on the basis of this analysis has been discussed. Besides, the electronic density of states DOS near the Fermi level remains nearly unaffected upon Fe substitution, as evidenced by the Seebeck coefficient measurements. When compared with Mn, Fe behaves like a nonmagnetic element with a modest variation in TC and on the other hand, the TC depression is much stronger when compared with other elements like Al, Cu, etc. Therefore, the observed variation in TC for the presently investigated concentrations of Fe is attributed to the specific nature of the given substituent element Fe in altering the phonon frequency and/or electron-phonon coupling strength rather than spin-flip scattering or change in DOS or disorder