An approximate Riemann solver for hypervelocity flows

We describe an approximate Riemann solver for the computation of hypervelocity flows in which there are strong shocks and viscous interactions. The scheme has three stages, the first of which computes the intermediate states assuming isentropic waves. A second stage, based on the strong shock relations, may then be invoked if the pressure jump across either wave is large. The third stage interpolates the interface state from the two initial states and the intermediate states. The solver is used as part of a finite-volume code and is demonstrated on two test cases. The first is a high Mach number flow over a sphere while the second is a flow over a slender cone with an adiabatic boundary layer. In both cases the solver performs well

The status of household food security targets in South Africa

This article investigates the conceptual and methodological challenges to develop a set of baseline indicators for South African food security targets. A food security target is a well-defined and measurable goal to reduce the numbers of people who lack enough food of the right quality to live healthy lives. To derive baseline indicators for household food security, the following question is asked: what is the average cost of a nutritionally adequate food basket per person? The cost of recommended nutrient intake is based on estimates of dietary energy costs. Reported food expenditure for each household based on 2005/2006 Income and Expenditure Survey data gets compared to two dietary energy cost baskets. The food expenditure shares of the poorest households vary between 38% and 71% according to different surveys. At food expenditure levels reported in the IES, one in five households meet their average dietary energy cost. Deep levels of food insecurity exist in rural areas with 85% of rural households unable to afford even the ‘below average dietary energy costs’. Food security policy based on refined baseline indicators can better target food insecure households. Another policy benefit is that robust indicators help to develop effective monitoring capabilities.food security, dietary energy cost, household expenditure, methodology, South Africa, Consumer/Household Economics,

The Importance of the Loss Function in Option Pricing

Which loss function should be used when estimating and evaluating option pricing models? Many different fucntions have been suggested, but no standard has emerged. We do not promote a partidular function, but instead emphasize that consistency in the choice of loss functions is crucial. First, for any given model, the loss function used in parameter estimation and model evaluation should be identical, otherwise suboptimal parameter estimates will be obtained. Second, when comparing models, the estimation loss function should be identical across models, otherwise unfair comparisons will be made. We illustrate the importance of these issues in an application of the so-called Practitioner Black-Scholes (PBS) model to S&P500 index options. We find reductions of over 50 percent in the root mean squared error of the PBS model when the estimation and evaluation loss functions are aligned. We also find that the PBS model outperforms a benchmark structural model when the estimation loss functions are identical across models, but otherwise not. The new PBS model with aligned loss functions thus represents a much tougher benchmark against which future structural models can be compared. Quelle fonction de pertes devrait être utilisée pour l'estimation et l'évaluation des modèles d'évaluation d'options? Plusieurs fonctions différentes ont été suggérées,0501s aucune norme ne s'est imposée. Nous ne promouvons aucune fonction,0501s soutenons que la cohérence dans le choix des fonctions est cruciale. Premièrement, pour n'importe quel modèle donné, la fonction de pertes utilisée dans l'estimation des paramètres et dans l'évaluation du modèle devrait être la même, sinon on obtient des estimations de paramètres sous-optimales. Deuxièmement, lors de la comparaison de modèles, la fonction de pertes pour l'estimation devrait être la même pour chaque modèle, autrement les comparaisons sont injustes. Nous illustrons l'importance de ces questions dans une application du modèle appelé Black-Scholes du praticien (PBS) aux options de l'index S&P500. Nous trouvons des réductions de plus de 50 pourcent de la racine de l'erreur quadratique moyenne du modèle PBS lorsque les fonctions de pertes d'estimation et d'évaluation sont alignées. Nous trouvons également que le modèle PBS dépasse un modèle de benchmark structurel quand les fonctions de pertes d'estimation sont identiques pour tous les modèles,0501s pas dans les autres cas. Le nouveau modèle PBS à fonctions de pertes alignées représente dès lors un benchmark bien plus robuste auquel les futurs modèles structurels pourront être comparés.Option pricing, implied volatility, practitioner Black-Scholes approach, pricing errors, loss functions, out-of-sample forecasting, parameter stability, Évaluation des options, volatilité implicite, approche Black-Scholes du praticien, erreurs d'évaluation, fonctions de perte, prévisions hors-échantillon, stabilité des paramètres

Matter in extremis: ultrarelativistic nuclear collisions at RHIC

We review the physics of nuclear matter at high energy density and the experimental search for the Quark-Gluon Plasma at the Relativistic Heavy Ion Collider (RHIC). The data obtained in the first three years of the RHIC physics program provide several lines of evidence that a novel state of matter has been created in the most violent, head-on collisions of $Au$ nuclei at $\sqrt{s}=200$ GeV. Jet quenching and global measurements show that the initial energy density of the strongly interacting medium generated in the collision is about two orders of magnitude larger than that of cold nuclear matter, well above the critical density for the deconfinement phase transition predicted by lattice QCD. The observed collective flow patterns imply that the system thermalizes early in its evolution, with the dynamics of its expansion consistent with ideal hydrodynamic flow based on a Quark-Gluon Plasma equation of state.Comment: 93 pages, 46 figures; final version for journal incorporating minor changes and correction

Modifications at the C-Terminus To Improve Pyrrole−Imidazole Polyamide Activity in Cell Culture

Pyrrole−imidazole (Py-Im) hairpin polyamides are a class of small molecule DNA minor groove binding compounds that have been shown to modulate endogenous gene expression in cell culture. Gene regulation by polyamides requires efficient cellular uptake and nuclear localization properties for candidate compounds. To further optimize Py-Im polyamides for enhanced potency in cell culture, a focused library of polyamides possessing various modifications at the C-terminus was synthesized and tested. Comparison of polyamide biological activity in two cell lines revealed tolerance for structural modifications and agreement in activity trends between cell lines. The use of an oxime linkage between the polyamide and an aromatic functionality on the C-terminus resulted in a ~20-fold increase in the potency of polyamides targeted to the androgen response element (ARE) in LNCaP cells by measuring AR-activated PSA expression

Jets and high pTp_T hadrons in dense matter: recent results from STAR

We review recent measurements of high transverse momentum (high $p_T$) hadron production in nuclear collisions by the STAR Collaboration at RHIC. The previously observed suppression in central Au+Au collisions has been extended to much higher $p_T$. New measurements from d+Au collisions are presented which help disentangle the mechanisms responsible for the suppression. Inclusive single hadron spectra are enhanced in d+Au relative to p+p, while two-particle azimuthal distributions are observed to be similar in p+p, d+Au and peripheral Au+Au collisions. The large suppression of inclusive hadron production and absence of the away-side jet-like correlations in central Au+Au collisions are shown to be due to interactions of the jets with the very dense medium produced in these collisions.Comment: 6 pages, 5 figures, joint proceedings for the CIPANP '03 Conferenc

Option Valuation with Long-run and Short-run Volatility Components

This paper presents a new model for the valuation of European options. In our model, the volatility of returns consists of two components. One of these components is a long-run component, and it can be modeled as fully persistent. The other component is short-run and has a zero mean. Our model can be viewed as an affine version of Engle and Lee (1999), allowing for easy valuation of European options. We investigate the model through an integrated analysis of returns and options data. The performance of the model is spectacular when compared to a benchmark single-component volatility model that is well-established in the literature. The improvement in the model’s performance is due to its richer dynamics which enable it to jointly model long-maturity and short-maturity options Ce papier présente un nouveau modèle d’évaluation d’options européennes. Dans notre modèle, la volatilité des rendements se décompose en deux parties. Une des composantes est une composante de long terme, et elle peut être modélisée comme permanente. L’autre composante porte sur le court terme et est de moyenne nulle. Notre modèle peut être considéré comme la version affine de Engle & Lee (1999), permettant l’évaluation simple d’options européennes. Nous étudions le modèle à travers une analyse intégrée de données de rendements et d’options. La performance du modèle est spectaculaire comparée à un benchmark tel qu’un modèle à une seule composante de volatilité bien connu dans la littérature. L’amélioration de la performance du modèle est due à une dynamique plus riche qui permet de modéliser conjointement des options à maturité longue et à maturité courteoption valuation, long-run component, short-run component, unobserved components, persistence, GARCH, out-of-sample, évaluation d’option, composante long terme, composante court terme, composantes non observables, persistance, GARCH, hors échantillon

People tracking by cooperative fusion of RADAR and camera sensors

Accurate 3D tracking of objects from monocular camera poses challenges due to the loss of depth during projection. Although ranging by RADAR has proven effective in highway environments, people tracking remains beyond the capability of single sensor systems. In this paper, we propose a cooperative RADAR-camera fusion method for people tracking on the ground plane. Using average person height, joint detection likelihood is calculated by back-projecting detections from the camera onto the RADAR Range-Azimuth data. Peaks in the joint likelihood, representing candidate targets, are fed into a Particle Filter tracker. Depending on the association outcome, particles are updated using the associated detections (Tracking by Detection), or by sampling the raw likelihood itself (Tracking Before Detection). Utilizing the raw likelihood data has the advantage that lost targets are continuously tracked even if the camera or RADAR signal is below the detection threshold. We show that in single target, uncluttered environments, the proposed method entirely outperforms camera-only tracking. Experiments in a real-world urban environment also confirm that the cooperative fusion tracker produces significantly better estimates, even in difficult and ambiguous situations