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

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,

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

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

Interaction between zeolites and cluster compounds. Part 2.—Thermal decomposition of iron pentacarbonyl on zeolites

Thermal decomposition in a thermobalance of Fe(CO)5 adsorbed on alkali-metal, hydrogen-Y, dealuminated Y, L and omega zeolites proceeds stepwise via slow decarbonylation at low and high temperatures, separated by a fast endothermic reaction. Average CO/Fe ratios have been determined after each step. From i.r. results the former intermediates are assigned to species bearing bridging CO, whereas reaction products with CO/Fe < 1 are associated with highly unsaturated carbonyl clusters in strong interaction with the zeolite.The thermal stability of zeolite/Fe(CO)5 adducts as well as of the intermediates increases with the electron-donor properties of the matrix and can be rationalized using the Sanderson electronegativity concept. Iron loadings ranging from 2.4 wt % in zeolite L up to 10 wt % with NaY and HY are obtained by decomposition in inert atmosphere. Under vacuum conditions loss of metal up to 50% is observed. Metallic iron clusters are the final decomposition products in alkali-metal zeolites, as probed by NO adsorption. In HY part of the metallic iron is oxidized to FeII ions, which are located at cation positions

Interaction between zeolites and cluster compounds. Part 1.—Adsorption of iron pentacarbonyl on zeolites

The adsorption isotherms of Fe(CO)5 on NaY, HY and Linde L zeolites obtained in McBain balances show micropore adsorption, whereas additional capillary condensation is found with zeolite omega and Na-mordenite. The pores and/or cages of the zeolites studied are completely filled with the complex upon saturation, with the exception of Na-mordenite. Their behaviour is explained, respectively, by pore blocking and the occurrence of channel openings that are too narrow. The silicalite channel system also is too narrow to accept Fe(CO)5 molecules.Infrared results show that an increasing interaction of the complex with faujasites exists in the sequence: dealuminated Y < CsY < HY < NaY. This is derived from the increasing band half-width of the adsorbed complex in the CO stretching region and from the increasing intensity of the v1 vibration, which upon adsorption becomes i.r. active. The interaction is assumed to be influenced mainly by electrostatic fields in the cages or pores, which can lead to a very restricted mobility for the encaged complex. The complex seems to remain intact upon adsorption at 293 K in all the zeolites studied

A descriptive analysis of general acute Trust star ratings

This paper examines the relationship between acute NHS Trust star ratings in England (generated by the Department of Health) in 2000/01 and 2001/02 with various other Trust characteristics and performance indicators from a Trust level database maintained by the Centre for Health Economics. The Trust star ratings system is a composite performance measure which places Trusts into one of four categories: from three stars, awarded to Trusts with the highest levels of performance to zero stars, awarded to Trusts showing the poorest levels of performance. We examine the descriptive statistics for the various variables in the dataset over the two years, according to each star rating as well as one-way Analysis of Variance (ANOVA) using zero star Trusts as the reference category and then least squares to fit a linear model to each of the variables in the dataset. Although zero star Trusts appear to perform better in terms of clinical outcomes such as death rates and readmissions, this is not statistically significant. However, zero star Trusts do worse than other Trusts across various patient satisfaction measures and financial and efficiency measures. Three star Trusts outperform others on two grounds fairly consistently: waiting times and financial balance suggesting either more efficient management or fewer capacity constraints. The labour market for consultants and nurses also appear to be utilised in different ways across the groups of Trusts. One hypothesis is that the different groups of Trusts focus on different elements of performance. The extent to which differences are due to exogenous factors or internal factors is a question for future research.analysis of variance (ANOVA), star rating, zero star Trusts

The Importance of the Loss Function in Option Valuation

Which loss function should be used when estimating and evaluating option valuation models? Many different functions have been suggested, but no standard has emerged. We 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 the same, otherwise suboptimal parameter estimates may be obtained. Second, when comparing models, the estimation loss function should be identical across models, otherwise inappropriate comparisons will be made. We illustrate the importance of these issues in an application of the so-called Practitioner Black-Scholes model to S&P 500 index options. Quelle devrait être la fonction de perte utilisée pour l'estimation et l'évaluation des modèles de valorisation des options? Plusieurs fonctions ont été suggérées, mais aucune norme ne s'est imposée. Dans ce travail, nous ne proposons pas une fonction en particulier, mais nous soutenons que la cohérence dans le choix des fonctions est cruciale. Premièrement, pour n'importe quel modèle donné, la fonction de perte utilisée dans l'estimation des paramètres et dans l'évaluation du modèle devrait être la même, sinon on obtient des estimations de paramètres sous-optimaux. Deuxièmement, lors de la comparaison des modèles, la fonction de perte utilisée 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'indice S&P500.implied volatility functions; valuation errors; out-of-sample forecasting; parameter stability, fonctions de volatilité implicite; évaluation des erreurs; prévision hors échantillon; stabilité des paramètres