A Poisson Mixed Model with Nonnormal Random Effect Distribution

We propose in this paper a random intercept Poisson model in which the random effect distribution is assumed to follow a generalized log-gamma (GLG) distribution. We derive the first two moments for the marginal distribution as well as the intraclass correlation. Even though numerical integration methods are in general required for deriving the marginal models, we obtain the multivariate negative binomial model for a particular parameter setting of the hierarchical model. An iterative process is derived for obtaining the maximum likelihood estimates for the parameters in the multivariate negative binomial model. Residual analysis are proposed and two applications with real data are given for illustration.Comment: Submitted in the Computational Statistics & Data Analysis journa

Covariant Impulse Approximation for the study of the internal structure of composite particles

We present a brief review on the Impulse Approximation method to study processes of scattering off composite particles. We first construct the model in a non-relativistic fashion that enables us to extend the model to a covariant Impulse Approximation, which is needed for the study of high momentum transfer processes.Comment: 8 Page

The Privatization and Project Finance Adventure: Acquiring a Colombian Public Utility Company

Colombia is an exciting new arena for the international practitioner structuring project finance and privatization transactions. The sectors of the economy that are attractive targets for most multinationals (MNCs) entering Colombia are the energy, oil and gas, mining, water, and telecommunications sectors. In most cases, MNCs in these sectors consider investments in Colombia when the Colombian authorities announce a plan for the privatization or capitalization of state-run companies that have a monopoly on business. Often the MNC becomes aware of the privatization, concession, or capitalization project via an official announcement by the Colombian government calling for bids or an invitation informing the MNC that it is qualified for the particular project or a specific aspect of the project. When a client is interested in participating in the bid process, it will most certainly, unless it has participated in other bids in Colombia, approach counsel and its other advisors with assumptions of how the bid should be structured, from both a Colombian and U.S. angle. In these instances, the only option for counsel and other advisors is to listen and take note. The following key questions must be considered under this scenario: what type of restrictions exist under current privatization laws; what form of business association should be used; what is the tax treatment regarding business associations, dividend treatment, technical services and assistance contracts, and repatriation of profits; do foreign exchange regulations hinder the availability of using inter-company loans and foreign currency operations; how should the due diligence review be performed; and how should local counsel be chosen

The Privatization and Project Finance Adventure: Acquiring a Colombian Public Utility Company

Colombia is an exciting new arena for the international practitioner structuring project finance and privatization transactions. The sectors of the economy that are attractive targets for most multinationals (MNCs) entering Colombia are the energy, oil and gas, mining, water, and telecommunications sectors. In most cases, MNCs in these sectors consider investments in Colombia when the Colombian authorities announce a plan for the privatization or capitalization of state-run companies that have a monopoly on business. Often the MNC becomes aware of the privatization, concession, or capitalization project via an official announcement by the Colombian government calling for bids or an invitation informing the MNC that it is qualified for the particular project or a specific aspect of the project. When a client is interested in participating in the bid process, it will most certainly, unless it has participated in other bids in Colombia, approach counsel and its other advisors with assumptions of how the bid should be structured, from both a Colombian and U.S. angle. In these instances, the only option for counsel and other advisors is to listen and take note. The following key questions must be considered under this scenario: what type of restrictions exist under current privatization laws; what form of business association should be used; what is the tax treatment regarding business associations, dividend treatment, technical services and assistance contracts, and repatriation of profits; do foreign exchange regulations hinder the availability of using inter-company loans and foreign currency operations; how should the due diligence review be performed; and how should local counsel be chosen

An Empirical Study of Real-World SPARQL Queries

Understanding how users tailor their SPARQL queries is crucial when designing query evaluation engines or fine-tuning RDF stores with performance in mind. In this paper we analyze 3 million real-world SPARQL queries extracted from logs of the DBPedia and SWDF public endpoints. We aim at finding which are the most used language elements both from syntactical and structural perspectives, paying special attention to triple patterns and joins, since they are indeed some of the most expensive SPARQL operations at evaluation phase. We have determined that most of the queries are simple and include few triple patterns and joins, being Subject-Subject, Subject-Object and Object-Object the most common join types. The graph patterns are usually star-shaped and despite triple pattern chains exist, they are generally short.Comment: 1st International Workshop on Usage Analysis and the Web of Data (USEWOD2011) in the 20th International World Wide Web Conference (WWW2011), Hyderabad, India, March 28th, 201

Is type 2 diabetes really resolved after laparoscopic sleeve gastrectomy? Glucose variability studied by continuous glucose monitoring

The study was carried out on type 2 diabetic obese patients who underwent laparoscopic sleeve gastrectomy (LSG). Patients underwent regular glycemic controls throughout 3 years and all patients were defined cured from diabetes according to conventional criteria defined as normalization of fasting glucose levels and glycated hemoglobin in absence of antidiabetic therapy. After 3 years of follow-up, Continuous Glucose Monitoring (CGM) was performed in each patient to better clarify the remission of diabetes. In this study, we found that the diabetes resolution after LSG occurred in 40% of patients; in the other 60%, even if they showed a normal fasting glycemia and A1c, patients spent a lot of time in hyperglycemia. During the oral glucose tolerance test (OGTT), we found that 2 h postload glucose determinations revealed overt diabetes only in a small group of patients and might be insufficient to exclude the diagnosis of diabetes in the other patients who spent a lot of time in hyperglycemia, even if they showed a normal glycemia (<140 mg/dL) at 120 minutes OGTT. These interesting data could help clinicians to better individualize patients in which diabetes is not resolved and who could need more attention in order to prevent chronic complications of diabetes

A Copula-VAR-X Approach for Industrial Production Modelling and Forecasting

World economies, and especially European ones, have become strongly interconnected in the last decades and a joint modelling is required. We propose here the use of Copulas to build flexible multivariate distributions, since they allow for a rich dependence structure and more flexible marginal distributions that better fit the features of empirical data, such as leptokurtosis. We use our approach to forecast industrial production series in the core EMU countries and we provide evidence that the copula-VAR model outperforms or at worst compares similarly to normal VAR models, keeping the same computational tractability of the latter approach.Forecasting, Industrial Production, Copulas, VAR models.

On the generation of UHECRs in GRBs: a reappraisal

We re-examine critically the arguments raised against the theory that Ultra High Energy Cosmic Rays observed at Earth are produced in Gamma Ray Bursts. These include the limitations to the highest energy attainable by protons around the bursts' shocks, the spectral slope at the highest energies, the total energy released in non--thermal particles, the occurrence of doublets and triplets in the data reported by AGASA. We show that, to within the uncertainties in our current knowledge of GRBs, none of these objections is really fatal to the scenario. In particular, we show that the total energy budget of GRBs easily accounts for the energy injection rate necessary to account for UHECRs as observed at Earth. We also compute the expected particle spectrum at Earth, showing that it fits the HiRes and AGASA data to within statistical uncertainties. We consider the existence of multiplets in AGASA' data. To this end, we present a Langevin--like treatment for the motion of a charged particle in the IGM magnetic field, which allows us to estimate both the average and the rms timedelay for particles of given energy; we discuss when particles of identical energies reach the Earth in bunches, or spread over the rms timedelay, showing that multiplets pose no problem for an explosive model for the sources of UHECRs. We compare our model with a scenario where the particles are accelerated at internal shocks, underlining differences and advantages of particle acceleration at external shocks.Comment: Accepted for publication in the Astrophysical Journal; minor change