Novel approach to the study of quantum effects in the early universe

We develop a theoretical frame for the study of classical and quantum gravitational waves based on the properties of a nonlinear ordinary differential equation for a function $\sigma(\eta)$ of the conformal time $\eta$, called the auxiliary field equation. At the classical level, $\sigma(\eta)$ can be expressed by means of two independent solutions of the ''master equation'' to which the perturbed Einstein equations for the gravitational waves can be reduced. At the quantum level, all the significant physical quantities can be formulated using Bogolubov transformations and the operator quadratic Hamiltonian corresponding to the classical version of a damped parametrically excited oscillator where the varying mass is replaced by the square cosmological scale factor $a^{2}(\eta)$. A quantum approach to the generation of gravitational waves is proposed on the grounds of the previous $\eta-$dependent Hamiltonian. An estimate in terms of $\sigma(\eta)$ and $a(\eta)$ of the destruction of quantum coherence due to the gravitational evolution and an exact expression for the phase of a gravitational wave corresponding to any value of $\eta$ are also obtained. We conclude by discussing a few applications to quasi-de Sitter and standard de Sitter scenarios.Comment: 20 pages, to appear on PRD. Already published background material has been either settled up in a more compact form or eliminate

Evaluation of appendicitis risk prediction models in adults with suspected appendicitis

Background Appendicitis is the most common general surgical emergency worldwide, but its diagnosis remains challenging. The aim of this study was to determine whether existing risk prediction models can reliably identify patients presenting to hospital in the UK with acute right iliac fossa (RIF) pain who are at low risk of appendicitis. Methods A systematic search was completed to identify all existing appendicitis risk prediction models. Models were validated using UK data from an international prospective cohort study that captured consecutive patients aged 16–45 years presenting to hospital with acute RIF in March to June 2017. The main outcome was best achievable model specificity (proportion of patients who did not have appendicitis correctly classified as low risk) whilst maintaining a failure rate below 5 per cent (proportion of patients identified as low risk who actually had appendicitis). Results Some 5345 patients across 154 UK hospitals were identified, of which two‐thirds (3613 of 5345, 67·6 per cent) were women. Women were more than twice as likely to undergo surgery with removal of a histologically normal appendix (272 of 964, 28·2 per cent) than men (120 of 993, 12·1 per cent) (relative risk 2·33, 95 per cent c.i. 1·92 to 2·84; P < 0·001). Of 15 validated risk prediction models, the Adult Appendicitis Score performed best (cut‐off score 8 or less, specificity 63·1 per cent, failure rate 3·7 per cent). The Appendicitis Inflammatory Response Score performed best for men (cut‐off score 2 or less, specificity 24·7 per cent, failure rate 2·4 per cent). Conclusion Women in the UK had a disproportionate risk of admission without surgical intervention and had high rates of normal appendicectomy. Risk prediction models to support shared decision‐making by identifying adults in the UK at low risk of appendicitis were identified

Geocronologia e geoquímica pelo método dos traços nucleares: alguns exemplos de utilização em geologia aplicada

On discute dans cet article un certain nombre d'applications typiques de la "méthode des traces nucléaires" en Géochronologie, en Géochimie et en Géophysique. En Géochronologie, après un rappel des principes de la datation par Traces de Fission (TF) et des types d'événements géologiques mesurables par cette méthode, on présente quelques applications typiques en métallogénie et dans les domaines de la Géologie du Pétrole. En Géochimie, les utilisations actuelles de la méthode des traces sont liées a la détection de gisements et au traitement de minéraux d'uranium, par l'emploi soit de techniques de cartographie de l'uranium sur lames pétrographiques, soit de techniques de prospection à l'échelle du terrain, basées sur la recherche d'émanations de radon-222 (222Rn). En Géophysique, une application importante concerne la détection et la prévision des tremblements de terre au moyen d'une surveillance continue des émanations en 222Rn au voisinage de zones à haut risqueDiscute-se, neste artigo, um certo número de aplicações típicas do "método dos traços nucleares" em Geocronologia, em Geoquímica e em Geofísica. Em Geocronologia, após uma revisão dos princípios da datação por Traços de Fissão (TF) e dos tipos de eventos geológicos passíveis de mensuração por este método, apresenta-se algumas aplicações típicas em metalogenia e nos domínios da Geologia do Petróleo. Em Geoquímica, as utilizações atuais do método dos traços estão ligadas à detecção de jazidas e ao tratamento de minerais de urânio, seja através do emprego de técnicas de cartografia do urânio sobre lâminas petrográficas, seja de técnicas de prospecção, em escala de campo, baseadas na detecção das emanações de radônio-222 (222Rn). Em Geofísica, uma aplicação importante diz respeito à detecção e previsão de tremores de terra através de uma vigilância contínua das emanações de 222Rn nas proximidades das zonas de alto riscoVarious applications of the "Nuclear Track Method" to Applied Geology and case studies are presented. In Geochronology, after a short review of the fission-track (FT) dating principles and main uses, one discuss some typical applications to Metallogeny and Petroleum Geology. In Applied Geochemistry, the track method is used for uranium prospection and uranium-ore studies, via, respectively, field measurements of radon-222 (222Rn) emanations and uranium- FT micromapping in petrographical thin sections. In Geophysics, important applications are the detection and prediction of earthquakes via the continuous record of 222Rn emanations along major fault

Dating Quartzose Sands of the Coastal Province of Rio Grande do Sul, Brazil, by Thermoluminescence

Recentemente ficou demonstrado que sedimentos eolicamente transportados perdem a maior parte de sua termoluminescência (TL) geológica quando expostos à luz solar (WINTLE e HUNTLEY, 1980; WINTLE, 1981; SINGHVI et al., 1982). Esta propriedade foi utilizada na tentativa de obterem-se idades de sistemas de dunas e de depósitos marinhos do quaternário costeiro do Rio Grande do Sul. Os resultados preliminares apresentados neste trabalho revelam que datações de areias quartzosas, oriundas destes tipos de depósitos, por termoluminescência, são viáveis, abrangendo o intervalo de tempo compreendido entre o presente e, pelo menos, 50.000 anos, sendo este tempo possivelmente extensível a mais de 100.000 anos