Azimuthal Correlations in p-p collisions

We report the analysis of experimental azimuthal correlations measured by STAR in p-p collisions at $\sqrt{s_{NN}}$ = 200 GeV. We conclude that for a fit of data using Pythia event generator we need to include two values of $k_{T}$.Comment: 4 page, 3 figures. Prepared for X Mexican Workshop on Particles and Fields. Morelia Mich. Nov 7-12, 200

Zero-energy peak of the density of states and localization properties of a one-dimensional Frenkel exciton: Off-diagonal disorder

We study a one-dimensional Frenkel Hamiltonian with off-diagonal disorder, focusing our attention on the physical nature of the zero-energy peak of the density of states. The character of excitonic states (localized or delocalized) is also examined in the vicinity of this peak. It is shown that the state being responsible for the peak is localized. A detailed comparison of the nearest-neighbor approach with the long-range dipole-dipole coupling is performed.Comment: 15 pages with 7 figures (REVTeX). To appear in Physical Review

Quark masses in QCD: a progress report

Recent progress on QCD sum rule determinations of the light and heavy quark masses is reported. In the light quark sector a major breakthrough has been made recently in connection with the historical systematic uncertainties due to a lack of experimental information on the pseudoscalar resonance spectral functions. It is now possible to suppress this contribution to the 1% level by using suitable integration kernels in Finite Energy QCD sum rules. This allows to determine the up-, down-, and strange-quark masses with an unprecedented precision of some 8-10%. Further reduction of this uncertainty will be possible with improved accuracy in the strong coupling, now the main source of error. In the heavy quark sector, the availability of experimental data in the vector channel, and the use of suitable multipurpose integration kernels allows to increase the accuracy of the charm- and bottom-quarks masses to the 1% level.Comment: Invited review paper to be published in Modern Physics Letters

Understanding delocalization in the Continuous Random Dimer model

We propose an explanation of the bands of extended states appearing in random one dimensional models with correlated disorder, focusing on the Continuous Random Dimer model [A.\ S\'{a}nchez, E.\ Maci\'a, and F.\ Dom\'\i nguez-Adame, Phys.\ Rev.\ B {\bf 49}, 147 (1994)]. We show exactly that the transmission coefficient at the resonant energy is independent of the number of host sites between two consecutive dimers. This allows us to understand why are there bands of extended states for every realization of the model as well as the dependence of the bandwidths on the concentration. We carry out a perturbative calculation that sheds more light on the above results. In the conclusion we discuss generalizations of our results to other models and possible applications which arise from our new insight of this problem.Comment: REVTeX 3.0, 4 pages, 4 figures (hard copy on request from [email protected]), Submitted to Phys Rev

Comparative study of the quality of risk disclosures in shareholders and stakeholder reports between developed and developing countries (case: oil industry)

The current global and competitive environment in which companies within the oil and gas (O&G) sector find themselves requires a greater degree of information that allows users to have a better understanding of the companies’ economic situation and risks they face. For that reason, there is a need to mitigate negative impacts that affect their activities. The objective of this research is to perform a comparative study between the quality of risk disclosures in shareholder and stakeholder reports of O&G companies, headquartered in developed (Canada, the UK and the US) and developing countries (Colombia, Brazil and Argentina) listed on their local stock exchange for the period 2016-2017; their size and its propensity to follow IPIECA (2015) as a voluntary industry guide to produce stakeholders' reports. Using the quantity of risk keywords as indicative of risk quality disclosures by following Bareta and Bonzolan, (2004) approach. The following findings were encountered: (a) companies based in developed countries tend to disclose high-quality risks in their shareholder reports, however the difference compared to developing countries is not significant due to the accounting globalized principles used. Stakeholder reports quality is highly associated with the adoption of industry-specific voluntary guidelines in both developed and developing countries. Additionally, the findings show that the quality of risk disclosures can also be influenced by stakeholder pressures that cause companies to change their reporting approach, in both developed and developing countries; (b) the size of the company in terms of total assets is not a determining factor that influences the company quality of risk disclosures nor for shareholders or stakeholder reports of the companies in developed or developing country; (c) The use of the voluntary guidelines of O&G (IPIECA), develops and improves risk disclosures quality in the shareholder and stakeholder reports of companies within the industry to enable good practices

Advance directives and communication styles in a lower Rio Grande Valley health facility

This study explores physicians\u27 decision-making communication styles at end-of-life and advance directives in a hospital. Participant observation, case studies and a survey questionnaire are used. Egalitarian communication style is found to have moderate reliability. A .6969 coefficient, is measured by Cronbach\u27s Alpha model. Authoritative communication style, yields a less than moderate alpha coefficient of .4278. Regression analysis using these two variables as the independent variables obtains insignificant results. However, sixty-three percent of the respondents speak Spanish moderately or very little. Eighty percent of the surveyed sample do not have training to administer advance directives. Twenty-two percent of the respondents have staff trained to administer advance directives. Policy recommendations call for training in advance directives for medical doctors in this particular facility