Quantile regression with clustered data

We show that the quantile regression estimator is consistent and asymptotically normal when the error terms are correlated within clusters but independent across clusters. A consistent estimator of the covariance matrix of the asymptotic distribution is provided and we propose a specification test capable of detecting the presence of intra-cluster correlation. A small simulation study illustrates the finite sample performance of the test and of the covariance matrix estimator

A cautionary note on tests for overidentifying restrictions

Tests of overidentifying restrictions are widely used in practice. However, there is often confusion about the nature of their null hypothesis and about the interpretation of their outcome. In this note we argue that these tests give little information on whether the instruments are correlated with the errors of the underlaying economic model and on whether they identify parameters of interest

Exogeneity in semiparametric moment condition models

The primary concern of this article is the provision of definitions and tests for exogeneity appropriate for models defined through sets of conditional moment restrictions. These forms of exogeneity are expressed as additional conditional moment constraints and may be equivalently formulated as a countably infinite number of unconditional restrictions. Consequently, tests of exogeneity may be seen as tests for an additional set of infinite moment conditions. A number of test statistics are suggested based on GMM and generalized empirical likelihood. The asymptotic properties of the statistics are described under both null hypothesis and a suitable sequence of local alternatives. An extensive set of simulation experiments explores the relative practical efficacy of the various test statistics in terms of empirical size and size-adjusted power

Pharmaceutical care in transplant patients in a university hospital: pharmaceutical interventions

A descriptive and prospective study was conducted on the pharmaceutical care in the post-transplant outpatient clinic of Hospital Universitario Walter Cantidio of Universidade Federal do Ceará (HUWC/UFC), in Fortaleza- Ceará in the period of April to October of 2011. The aim of the present study was to describe the pharmaceutical interventions performed in a Pharmaceutical Care service structured in the liver and kidney transplant outpatient clinic of an academic hospital. The Pharmaceutical interventions (PI) were classified according to Sabater et al.(2005), with significance based on Riba et al.(2000) and the Negative Outcomes associated with Medication (NOM) established at the Third Consensus of Granada. Statistical analyses were performed using the Epi Info v.3.5.1 program and hypothesis tests were done with the SigmaPlot v.10.0 program. A chi-squared (X²) test was utilized for statistical analysis of the sample. A total of 97 patients were followed, where 54 problems related to medications were identified and 139 PI performed. The main PI were in education of the patient about treatment (n=111; 80%) (p<0.05), while the significance of all interventions were appropriate, where 83.4% (n=116) of PI performed in the study period were shown to be "significant" (p<0.05). Through pharmaceutical care, the pharmacist is capable of monitoring the pharmacotherapeutic treatment and intervening when necessary, while being part of the multiprofessional team caring for the transplant patient

A search for ultra-high-energy photons at the Pierre Auger Observatory exploiting air-shower universality

The Pierre Auger Observatory is the most sensitive detector to primary photons with energies above ∼0.2 EeV. It measures extensive air showers using a hybrid technique that combines a fluorescence detector (FD) with a ground array of particle detectors (SD). The signatures of a photon-induced air shower are a larger atmospheric depth at the shower maximum (X$_{max}$) and a steeper lateral distribution function, along with a lower number of muons with respect to the bulk of hadron-induced background. Using observables measured by the FD and SD, three photon searches in different energy bands are performed. In particular, between threshold energies of 1-10 EeV, a new analysis technique has been developed by combining the FD-based measurement of X$_{max}$ with the SD signal through a parameter related to its muon content, derived from the universality of the air showers. This technique has led to a better photon/hadron separation and, consequently, to a higher search sensitivity, resulting in a tighter upper limit than before. The outcome of this new analysis is presented here, along with previous results in the energy ranges below 1 EeV and above 10 EeV. From the data collected by the Pierre Auger Observatory in about 15 years of operation, the most stringent constraints on the fraction of photons in the cosmic flux are set over almost three decades in energy

Study on multi-ELVES in the Pierre Auger Observatory

Since 2013, the four sites of the Fluorescence Detector (FD) of the Pierre Auger Observatory record ELVES with a dedicated trigger. These UV light emissions are correlated to distant lightning strikes. The length of recorded traces has been increased from 100 μs (2013), to 300 μs (2014-16), to 900 μs (2017-present), to progressively extend the observation of the light emission towards the vertical of the causative lightning and beyond. A large fraction of the observed events shows double ELVES within the time window, and, in some cases, even more complex structures are observed. The nature of the multi-ELVES is not completely understood but may be related to the different types of lightning in which they are originated. For example, it is known that Narrow Bipolar Events can produce double ELVES, and Energetic In-cloud Pulses, occurring between the main negative and upper positive charge layer of clouds, can induce double and even quadruple ELVES in the ionosphere. This report shows the seasonal and daily dependence of the time gap, amplitude ratio, and correlation between the pulse widths of the peaks in a sample of 1000+ multi-ELVES events recorded during the period 2014-20. The events have been compared with data from other satellite and ground-based sensing devices to study the correlation of their properties with lightning observables such as altitude and polarity