Generation of higher derivatives operators and electromagnetic wave propagation in a Lorentz-violation scenario

We study the perturbative generation of higher-derivative operators as corrections to the photon effective action, which are originated from a Lorentz violation background. Such corrections are obtained, at one-loop order, through the proper-time method, using the zeta function regularization. We focus over the lowest order corrections and investigate their influence in the propagation of electromagnetic waves through the vacuum, in the presence of a strong, constant magnetic field. This is a setting of experimental relevance, since it bases active efforts to measure non linear electromagnetic effects. After surprising cancellations of Lorentz violating corrections to the Maxwell's equation, we show that no effects of the kind of Lorentz violation we consider can be detected in such a context.Comment: v2: 13 pages, no figures, section IV considerably rewritten, main results unchanged and are now obtained in a simpler way. To appear in PL

Acute pancreatitis in children : a tertiary hospital report

INTRODUCTION: The incidence of acute pancreatitis (AP) in children has increased significantly in the past two decades. OBJECTIVE: All cases of AP, acute recurrent pancreatitis (ARP), and chronic pancreatitis examined between May 2002 and May 2012 at Hospital de Braga, Portugal, were reviewed. MATERIAL AND METHODS: Patients were identified by searching the hospital's electronic discharge records for the International Classification of Disease, Ninth Revision (ICD-9) code 577.0 (acute pancreatitis). ARP was considered as two or more episodes of AP per year or more than three episodes over a lifetime with intervening return to baseline. The following data were analyzed: demographic information, clinical, laboratory and imaging test results, etiology of pancreatitis, medical and surgical management, length of hospitalization, and outcome. The clinical and laboratory factors used in the pediatric acute pancreatitis severity score system and computed tomography severity index (CTSI) score were compared between patients with mild and severe disease. RESULTS: A total of 37 patients, 31 episodes of AP and 6 patients with ARP, were documented. The most prevalent etiologies were biliary stones/sludge (24.3%) and trauma (16.2%). Admission elevated white blood cell count (p=0.011), 48-h trough calcium (p=0.007), and 48-h rise in blood urea nitrogen (p=0.025) correlated significantly with disease severity. CTSI on admission had a score below 4 in three patients with severe disease. CONCLUSION: This Portuguese pediatric pancreatitis report highlights the multiple and complex etiology of this disease. Better pediatric scoring systems and management algorithms are needed

On the nature of Lithium-rich giant stars: constraints from Beryllium abundances

We have derived beryllium abundances for 7 Li-rich giant (A(Li) > 1.5) stars and 10 other Li-normal giants, with the aim of investigating the origin of the Lithium in the Li-rich giants. In particular, we test the predictions of the engulfment scenario proposed by Siess & Livio (1999), where the engulfment of a brown dwarf or one or more giant planets would lead to a simultaneous enrichment of 7Li and 9Be. We show that regardless their nature, none of the stars studied in this paper were found to have detectable beryllium. Using simple dilution arguments we show that the engulfment of an external object as the sole source of Li enrichment is ruled out by the Li and Be abundance data. The present results favor the idea that Li has been produced in the interior of the stars by a Cameron-Fowler process and brought up to the surface by an extra mixing mechanism.Comment: Accepted in A&

Comportamento de cultivares de Cynodon no Piauí.

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The role of bacteria in pine wilt disease: insights from microbiome analysis.

Pine Wilt Disease (PWD) has a significant impact on Eurasia pine forests. The microbiome of the nematode (the primary cause of the disease), its insect vector, and the host tree may be relevant for the disease mechanism. The aim of this study was to characterize these microbiomes, from three PWD-affected areas in Portugal, using Denaturing Gradient Gel Electrophoresis, 16S rRNA gene pyrosequencing, and a functional inference-based approach (PICRUSt). The bacterial community structure of the nematode was significantly different from the infected trees but closely related to the insect vector, supporting the hypothesis that the nematode microbiome might be in part inherited from the insect. Sampling location influenced mostly the tree microbiome (P < 0.05). Genes related both with plant growth promotion and phytopathogenicity were predicted for the tree microbiome. Xenobiotic degradation functions were predicted in the nematode and insect microbiomes. Phytotoxin biosynthesis was also predicted for the nematode microbiome, supporting the theory of a direct contribution of the microbiome to tree-wilting. This is the first study that simultaneously characterized the nematode, tree and insect-vector microbiomes from the same affected areas, and overall the results support the hypothesis that the PWD microbiome plays an important role in the disease's development