Entropy and Poincar\'e recurrence from a geometrical viewpoint

We study Poincar\'e recurrence from a purely geometrical viewpoint. We prove that the metric entropy is given by the exponential growth rate of return times to dynamical balls. This is the geometrical counterpart of Ornstein-Weiss theorem. Moreover, we show that minimal return times to dynamical balls grow linearly with respect to its length. Finally, some interesting relations between recurrence, dimension, entropy and Lyapunov exponents of ergodic measures are given.Comment: 11 pages, revised versio

Singularities in the Hamiltonian at electronic degeneracies

http://www.sciencedirect.com/science/article/B6TFM-414NVKS-4/1/a2e26328672bde0840300eafd471860

Rickettsia Conorii Infection Rare Form of Conjunctival Transmission

Mediterranean spotted fever (MSF) is a tick-borne rickettsial disease, endemic in Portugal. It is caused by Rickettsia conorii and clinically characterized by a vasculitic process with the classical clinical triad: fever, rash and lesion at the site of tick bite. It is accidentally transmitted to the human by its main vector, the Rhipicephalus sanguineus arthropod. Usually the disease develops after an infected tick bite but atypical forms of transmission such as mucosal contamination or inhalation have also been reportedinfo:eu-repo/semantics/publishedVersio

Malária Grave — Um Caso Clínico

Descreve-se um caso de malária grave por Plasmodium falciparum numa criança de raça negra, de 5 anos de idade, residente em Angola até 2 semanas antes do internamento. Apesar da terapêutica com quinino i.v. o quadro evoluiu com falência multiorgânica, nomeadamente coma, insuficiência renal, necrose hepática, diátese hemorrágica e rabdomiólise. Foi necessário instituir ventilação mecânica e na terapêutica de suporte recorreu-se à administração de derivados plasmáticos, aminas vasoactivas e diuréticos em altas doses, tendo havido regressão do quadro clínico. Discutem-se as complicações bem como os factores de mau prognóstico presentes neste caso

SENSITIVITY ANALYSIS OF TRACK VIBRATIONS DUE TO VERTICAL STIFFNESS VARIATION IN HIGH-SPEED RAILWAYS

High speed trains, when crossing regions with abrupt changes in vertical stiffness of the track and/or subsoil, may generate excessive ground and track vibrations. There is an urgent need for specific analyses of this problem so as to allow reliable esimates of vibration amplitude. Full understanding of these phenomena will lead to new construction solutions and mitigation of undesirable features. In this paper analytical transient solutions of dynamic response of one-dimensional systems with sudden change of foundation stiffness are derived. Results are expressed in terms of vertical displacement. Sensitivity analysis of the response amplitude is also performed. The analytical expressions presented herein, to the authors’ knowledge, have not been published yet. Although related to one-dimensional cases, they can give useful insight into the problem. Nevertheless, in order to obtain realistic response, vehicle- rail interaction cannot be omitted. Results and conclusions are confirmed using general purpose commercial software ANSYS. In conclusion, this work contributes to a better understanding of the additional vibration phenomenon due to vertical stiffness variation, permitting better control of the train velocity and optimization of the track design

Hospitalization of Children with Rotavirus Infection

Introdução. A infecção por rotavírus é a principal causa de diarreia aguda em todo o mundo. Nos países desenvolvidos não constitui uma causa importante de morte, mas cursa com uma alta morbilidade. Objectivo. Caracterizar a infecção por rotavírus em crianças hospitalizadas em dois Departamentos de Pediatria de Lisboa. Material e métodos. Revisão casuística dos internamentos com o diagnóstico de infecção por rotavírus, num hospital central especializado e num hospital geral na Zona Metropolitana de Lisboa, entre Janeiro e Dezembro de 2005. O diagnóstico foi efectuado através da identificação de antigénios virais nas fezes por “enzyme immunoassay”. Resultados. Foram analisados 92 casos; 82% ocorreram entre Dezembro e Março e 52,8% em crianças entre os três e os doze meses. Em metade dos casos registou-se bom nível socio-económico. Os factores de risco epidemiológicos encontrados foram: frequência de instituição de ensino ou ama em 21/38 (55%), contacto com pessoas com sintomatologia semelhante em 10/53 (19%) e irmãos com idade inferior a cinco anos em 25/76 (33%) das crianças. As infecções nosocomiais foram responsáveis por 26% dos casos estudados. A clínica cursou com: diarreia aquosa (96%), vómitos (87%) e febre (69%). Ocorreram complicações em 19/92 (21%) crianças e estas foram mais frequentes em lactentes com menos de seis meses de idade (35% vs. 16%, p=0,058). A mediana da duração de internamento foi cinco dias e o custo hospitalar directo variou entre 629,63 e 2342,38 euros. Discussão. O número de internamentos por infecção por rotavírus, especialmente em lactentes, a frequência de infecções nosocomiais por este agente, as complicações inerentes e os elevados custos, reflectem a importância da infecção por este agente em países desenvolvidos como Portugal

Vibrational energy transfer in N(2D)+N2 collisions: a quasiclassical trajectory study

Rate coefficients for the N(2D)+N2 collisions were calculated employing quasiclassical trajectories and the first available set of potential energy surfaces for such excited nitrogen interactions. The details of the vibrational energy transfer are discussed, such as the contributions from reactive and non-reactive trajectories as well as the contribution of each electronic symmetry. The calculated state-to-state and state-to-all rate coefficients show that deactivation is far more probable than excitation, and multi-quanta deactivation play an important role

From the lab to the river: Determination of ecological hosts of Anodonta anatina

1. Coextinction is the simplest form of secondary extinction and freshwater mussels (Bivalvia, Unionida) may be particularly prone to this phenomenon as their life cycle includes an obligatory parasitic larval stage on fish hosts. 2. The main aims of this study were to determine the possible ecological fish hosts of Anodonta anatina (Linnaeus, 1758) in several rivers of the Douro basin in north ern Portugal and to assess possible spatial and temporal differences in glochidial (larval) loads. In order to achieve this, electrofishing was conducted from December to April, the fish fauna was characterized, and levels of infestation with A. anatina glochidia were determined. 3. Native cyprinid species, mainly Luciobarbus bocagei (Iberian barbel) and Squalius carolitertii (northern Iberian chub), together with the non-native Lepomis gibbosus (pumpkinseed sunfish) and Alburnus alburnus (common bleak), were found to have the highest glochidial loads. Clear differences in infestation between rivers and throughout time were detected, with an infestation period from January to March, and with the Tâmega River having the highest prevalence. 4. Anodonta anatina is able to infest a variety of fish species, and this together with earlier studies showed that the metamorphosis into juveniles occurs mainly in native cyprinid species, although non-native species like common bleak can also be considered suitable hosts. However, the larvae infesting other non-native spe cies, such as the pumpkinseed sunfish, do not metamorphose and can be consid ered ‘dead ends’. 5. Overall, the results reported here are important for the conservation of A. anatina (and other unionoid species) because several Iberian rivers (and worldwide) have been subjected to the extirpation of native fish species and the introduction of non-native fish species. Therefore, careful assessments of fish communities should be conducted to assess possible negative interactions with freshwater musselsFundação para a Ciência e a Tecnologia, Grant/Award Number: PTDC/AGRFOR/1627/201