Fitting galactic rotation curves with conformal gravity and a global quadratic potential

We apply the conformal gravity theory to a sample of 111 spiral galaxies whose rotation curve data points extend well beyond the optical disk. With no free parameters other than galactic mass to light ratios, the theory is able to account for the systematics that is observed in this entire set of rotation curves without the need for any dark matter at all. In previous applications of the theory a central role was played by a universal linear potential term $V(r)=\gamma_0 c^2r/2$ that is generated through the effect of cosmology on individual galaxies, with the coefficient $\gamma_0=3.06\times 10^{-30} {\rm cm}^{-1}$ being of cosmological magnitude. Because the current sample is so big and encompasses some specific galaxies whose data points go out to quite substantial distances from galactic centers, we are able to identify an additional globally induced universal term in the data, a quadratic $V(r)=-\kappa c^2r^2/2$ term that is induced by inhomogeneities in the cosmic background. With $\kappa$ being found to be of magnitude $\kappa=9.54\times 10^{-54} {\rm cm}^{-2}$, through study of the motions of particles contained within galaxies we are thus able to both detect the presence of a global de Sitter-like component and provide a specific value for its strength. Our study suggests that invoking dark matter may be nothing more than an attempt to describe global physics effects such as these in purely local galactic terms.Comment: revtex4, 50 pages, 114 figures. Text expande

Spin Observables for Polarizing Antiprotons

The PAX project at GSI Darmstadt plans to polarize an antiproton beam by repeated interaction with a hydrogen target in a storage ring. Many of the beam particles are required to remain within the ring after interaction with the target, so small scattering angles are important. Hence we concentrate on low momentum transfer (small t), a region where electromagnetic effects dominate the hadronic effects. A colliding beam of polarized electrons with energy sufficient to provide scattering of antiprotons beyond ring acceptance may polarize an antiproton beam by spin filtering. Expressions for spin observables are provided and are used to estimate the rate of buildup of polarization of an antiproton beam.Comment: 4 pages, 2 figures, to be published in the Proceedings of the 17th International Spin Physics Symposium (SPIN 2006), Kyoto, Japan; October 2-7, 200

Locally Estimating Core Numbers

Graphs are a powerful way to model interactions and relationships in data from a wide variety of application domains. In this setting, entities represented by vertices at the "center" of the graph are often more important than those associated with vertices on the "fringes". For example, central nodes tend to be more critical in the spread of information or disease and play an important role in clustering/community formation. Identifying such "core" vertices has recently received additional attention in the context of {\em network experiments}, which analyze the response when a random subset of vertices are exposed to a treatment (e.g. inoculation, free product samples, etc). Specifically, the likelihood of having many central vertices in any exposure subset can have a significant impact on the experiment. We focus on using $k$-cores and core numbers to measure the extent to which a vertex is central in a graph. Existing algorithms for computing the core number of a vertex require the entire graph as input, an unrealistic scenario in many real world applications. Moreover, in the context of network experiments, the subgraph induced by the treated vertices is only known in a probabilistic sense. We introduce a new method for estimating the core number based only on the properties of the graph within a region of radius $\delta$ around the vertex, and prove an asymptotic error bound of our estimator on random graphs. Further, we empirically validate the accuracy of our estimator for small values of $\delta$ on a representative corpus of real data sets. Finally, we evaluate the impact of improved local estimation on an open problem in network experimentation posed by Ugander et al.Comment: Main paper body is identical to previous version (ICDM version). Appendix with additional data sets and enlarged figures has been added to the en

A Buffer Stocks Model for Stabilizing Price of Staple Food with Considering the Expectation of Non Speculative Wholesaler

This paper is a study of price stabilization in the staple food distribution system. All stakeholders experience market risks due to some possibility causes of price volatility. Many models of price stabilization had been developed by employing several approaches such as floor-ceiling prices, buffer funds, export or import taxes, and subsidies. In the previous researches, the models were expanded to increase the purchasing price for producer and decrease the selling price for consumer. Therefore, the policy can influence the losses for non-speculative wholesaler that is reflected by the descending of selling quantity and ascending of the stocks. The objective of this model is not only to keep the expectation of both producer and consumer, but also to protect non-speculative wholesaler from the undesirable result of the stabilization policy. A nonlinear programming model was addressed to determine the instruments of intervention program. Moreover, the result shows that the wholesaler behavior affects the intervention costs. Index Terms Buffer stocks, Price stabilization, Nonlinear programming, Wholesaler behavior

Dynamic muscle quality of the plantar flexors is impaired in claudicant patients with peripheral arterial disease and associated with poorer walking endurance

Objective Peripheral arterial disease and intermittent claudication (PAD-IC) negatively affects physical activity and function. There is evidence for plantarflexor muscle dysfunction and weakness; however, the extent to which this dysfunction can be attributed to reduced muscle size or quality, or both, is not yet known. This study investigated whether in vivo plantarflexor muscle quality during static and dynamic contractions is altered by PAD-IC and whether such changes are associated with impaired walking endurance according to initial and absolute claudication distances. Methods The study recruited 22 participants, consisting of 10 healthy controls and 12 claudicant patients with occlusion of the superficial femoral artery (seven unilateral and five bilateral). Muscle quality of the combined gastrocnemius muscles during static contractions was calculated by normalizing the estimated maximal potential muscle force to the physiological cross-sectional area of the lateral and medial gastrocnemius. Muscle quality during dynamic contractions of the combined plantarflexor muscles was calculated as the ratio of peak voluntary concentric plantarflexor power and the summed volume of lateral and medial gastrocnemius. Results Dynamic muscle quality was 24% lower in the claudicating-limb and asymptomatic-limb groups compared with controls (P = .017 and P = .023). The differences were most apparent at the highest contraction velocity (180°/s). Dynamic muscle quality was associated with reduced walking endurance (R = 0.689, P = .006 and R = 0.550, P = .042 for initial and absolute claudication distance, respectively). The claudicating-limb group demonstrated a trend toward reduced static muscle quality compared with controls (22%, P = .084). The relative contribution of the soleus muscle to plantarflexion maximum voluntary contraction was significantly higher in the claudicating-limb and asymptomatic-limb groups than in controls (P = .012 and P = .018). Conclusions The muscle strength of the plantarflexors in those with PAD-IC appears to be impaired at high contraction velocities. This may be explained by some reduction in gastrocnemii muscle quality and a greater reliance on the prominently type I-fibered soleus muscle. The reduced dynamic capability of the plantarflexor muscles was associated with disease severity and walking ability; therefore, efforts to improve plantarflexor power through dynamic exercise intervention are vital to maintain functional performance