Editor: S. DodelsonWe report a measurement of the flux of cosmic rays with unprecedented precision and statistics using the Pierre Auger Observatory. Based on fluorescence observations in coincidence with at least one surface detector we derive a spectrum for energies above 10 18 eV. We also update the previously published energy spectrum obtained with the surface detector array. The two spectra are combined addressing the systematic uncertainties and, in particular, the influence of the energy resolution on the spectral shape. 242Pierre Auger Collaboration / Physics Letters B 685 (2010) The spectrum can be described by a broken power law E −γ with index γ = 3.3 below the ankle which is measured at log 10 (E ankle /eV) = 18.6. Above the ankle the spectrum is described by a power law with index 2.6 followed by a flux suppression, above about log 10 (E/eV) = 19.5, detected with high statistical significance.

We report a study of the distributions of the depth of maximum, Xmax, of extensive air-shower profiles with energies above 10 17.8 eV as observed with the fluorescence telescopes of the Pierre Auger Observatory. The analysis method for selecting a data sample with minimal sampling bias is described in detail as well as the experimental cross-checks and systematic uncertainties. Furthermore, we discuss the detector acceptance and the resolution of the Xmax measurement and provide parameterizations thereof as a function of energy. The energy dependence of the mean and standard 4 deviation of the Xmax-distributions are compared to air-shower simulations for different nuclear primaries and interpreted in terms of the mean and variance of the logarithmic mass distribution at the top of the atmosphere.

The authors report on a large-scale study examining the effects of self-reported psychosocial factors on 1st-year college outcomes. Using a sample of 14,464 students from 48 institutions, the authors constructed hierarchical regression models to measure the predictive validity of the Student Readiness Inventory, a measure of psychosocial factors. Controlling for institutional effects and traditional predictors, the authors tested the effects of motivational and skill, social, and self-management measures on academic performance and retention. Academic Discipline was incrementally predictive of academic performance (grade-point average) and retention. Social Activity and Emotional Control also helped predict academic performance and retention, whereas Commitment to College and Social Connection offered incremental prediction of retention. This study elaborates recent meta-analytic findings (S. Robbins et al., 2004), demonstrating the salience of a subset of motivational, social, and self-management factors. Future research questions include how measures of psychosocial factors can be used to aid students, the salience of these measures over the entire college experience and for predicting job performance, and the need for testing theoretical models for explaining postsecondary educational outcomes incorporating traditional, motivational, self-management, and social engagement factors.With the scheduled revamping of the Higher Education Act, the accountability of postsecondary institutions for student academic performance and dropout has received much attention in professional reports as well as popular and research literatures (is concern that college students are ill prepared to meet the hurdles they face upon entry into college. To counter these problems, researchers have suggested the tying of federal (Stedman, 2003) and state (Hearn & Holdsworth, 2002) funding to outcomes of higher education.In practice, prediction of college success has largely centered on high-stakes testing. In many 4-year colleges and universities, there are many more applicants than spots, and high school academic performance and standardized achievement test scores are heavily weighted in admission decisions. A significant debate is occurring over how these indicators should be used. It has been argued that certain groups are disadvantaged by standardized test scores

Using data collected at the Pierre Auger Observatory during the past 3.7 years, we demonstrated a correlation between the arrival directions of cosmic rays with energy above 6 x 10(19) electron volts and the positions of active galactic nuclei (AGN) lying within approximately 75 megaparsecs. We rejected the hypothesis of an isotropic distribution of these cosmic rays with at least a 99% confidence level from a prescribed a priori test. The correlation we observed is compatible with the hypothesis that the highest-energy particles originate from nearby extragalactic sources whose flux has not been substantially reduced by interaction with the cosmic background radiation. AGN or objects having a similar spatial distribution are possible sources.

A. AAB et al. we have examined the implications of the distributions of depths of atmospheric shower maximum (X max ), using a hybrid technique, for composition and hadronic interaction models. We do this by fitting the distributions with predictions from a variety of hadronic interaction models for variations in the composition of the primary cosmic rays and examining the quality of the fit. Regardless of what interaction model is assumed, we find that our data are not well described by a mix of protons and iron nuclei over most of the energy range. Acceptable fits can be obtained when intermediate masses are included, and when this is done consistent results for the proton and iron-nuclei contributions can be found using the available models. We observe a strong energy dependence of the resulting proton fractions, and find no support from any of the models for a significant contribution from iron nuclei. However, we also observe a significant disagreement between the models with respect to the relative contributions of the intermediate components.