In this paper we present a full general relativistic one-dimensional hydro-code which incorporates a modern high-resolution shock-capturing algorithm, with an approximate Riemann solver, for the correct modelling of formation and propagation of strong shocks. The efficiency of this code in treating strong shocks is demonstrated by some numerical experiments. The interest of this technique in several astrophysical scenarios is discussed.

Background: Quarantine and stay-at-home orders are strategies that many countries used during the acute pandemic period of coronavirus disease 2019 (COVID-19) to prevent disease dissemination, health system overload, and mortality. However, there are concerns that patients did not seek necessary health care because of these mandates. Purpose: To evaluate the differences in the clinical presentation of acute appendicitis and CT findings related to these cases between the COVID-19 acute pandemic period and nonpandemic period. Materials and Methods: A retrospective observational study was performed to compare the acute pandemic period (March 23, 2020, to May 4, 2020) versus the same period the year before (March 23, 2019, to May 4, 2019). The proportion of appendicitis diagnosed by CT and level of severity of the disease were reviewed in each case. Univariate and bivariate analyses were performed to identify significant differences between the two groups. Results: A total of 196 abdominal CT scans performed due to suspected acute appendicitis were evaluated: 55 from the acute pandemic period and 141 from the nonpandemic period. The proportion of acute appendicitis diagnosed by abdominal CT was higher in the acute pandemic period versus the nonpandemic period: 45.5% versus 29.8% (P ¼ .038). The severity of the diagnosed appendicitis was higher during the acute pandemic period: 92% versus 57.1% (P ¼ .003). Conclusion: During the acute COVID-19 pandemic period, fewer patients presented with acute appendicitis to the emergency room, and those who did presented at a more severe stage of the disease.

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ElsevierChen Charpentier, BM.; Cortés, J.; Licea Salazar, JA.; Romero, J.; Roselló Ferragud, MD.; Santonja, F.; Villanueva Micó, RJ. (2015). Constructing adaptive generalized polynomial chaos method to measure the uncertainty in continuous models: A computational approach. AbstractDue to errors in measurements and inherent variability in the quantities of interest, models based on random differential equations give more realistic results than their deterministic counterpart. The generalized polynomial chaos (gPC) is a powerful technique used to approximate the solution of these equations when the random inputs follow standard probability distributions. But in many cases these random inputs do not have a standard probability distribution. In this paper, we present a step-by-step constructive methodology to implement directly a useful version of adaptive gPC for arbitrary distributions, extending the applicability of the gPC. The paper mainly focuses on the computational aspects, on the implementation of the method and on the creation of a useful software tool. This tool allows the user to easily change the types of distributions and the order of the expansions, and to study their the usefulness of the method are included.

The properties of the P-adrenergic receptor which regulates adenylate cyclase [ rapid decrease in the number of available receptors and in hormone-sensitive adenylate cyclase activity; conversely, lack of stimulation causes an increase in these parameters. It is suggested that these changes contribute to the phenomena of super-and subsensitivity in the pineal gland by regulating the capacity of the pineal to synthesize cyclic AMP in response to f-adrenergic stimulation.The pineal gland has proven to be a useful model in the study of the interaction between sympathetic nerves and the ,B-adrenergic receptors of responsive cells (1). Stimulation of the pineal ,B-adrenergic receptor results in increased levels of intracellular cyclic adenosine 3':5'-monophosphate (cyclic AMP) as a consequence of enhanced adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] activity (2, 3). In addition, through its influence on cyclic AMP levels, the f0-adrenergic receptor controls both the induction and maintenance of serotonin N-acetyl-transferase activity (= arylamine acetyltransferase; acetyl CoA:arylamine N-acetyltransferase, EC 2.3.1.5) (4, 5). Serotonin N-acetyltransferase forms N-acetylserotonin, a precursor for the synthesis of melatonin, the pineal hormone (1).Recent studies have shown that both the sensitivity and the magnitude of these biochemical responses of the pineal to f.-adrenergic stimulation are rapidly affected by the degree of prior stimulation of the receptor (6-8). Thus, following exposure of the pineal to either the noradrenergic neurotransmitter or to synthetic j3-adrenergic agonists, the subsequent responses are "subsensitive" in comparison with responses obtained from previously unstimulated glands. In contrast, after the reduction of sympathetic nerve firing by exposure of animals to light (9, 10), the responses are "supersensitive" (7,8). These changes in the sensitivity of the pineal to ,B-adrenergic stimulation can occur rapidly; subsensitivity has been shown to develop within hours and supersensitivity can be demonstrated within a day.Recently, competitive ,B-adrenergic antagonists of high specific activity have been used to characterize binding sites whose properties are similar to those of the f3-adrenergic receptor (11-13). In the rat pineal gland the sites which specifically bind 1-[3H]alprenololt were found to be indistinguishable from the fl-adrenergic receptor coupled to adenylate cyclase (14). The present study utilizes the binding of 1- [3H]alprenolol and the activity of hormone-sensitive adenylate cyclase to characterize changes in the properties of the ,B-adrenergic receptor which occur following stimulation of this receptor in vvo. We find that decreased ,B-adrenergic stimulation of the pineal results in both an increase in the hormone-sensitive adenylate cyclase activity and an increased number of specific l-[3H]alprenolol binding sites. In contrast, increased stimulation causes a decrease in both the amount of hormone-sensitive adenylate cyclase and the number of s...