Large amplitude folding in finely layered viscoelastic rock structures

We analyze folding phenomena in finely layered viscoelastic rock. Fine is meant in the sense that the thickness of each layer is considerably smaller than characteristic structural dimensions. For this purpose we derive constitutive relations and apply a computational simulation scheme (a finite-element based particle advection scheme; see MORESI et al., 2001) suitable for problems involving very large deformations of layered viscous and viscoelastic rocks. An algorithm for the time integration of the governing equations as well as details of the finite-element implementation is also given. We then consider buckling instabilities in a finite, rectangular domain. Embedded within this domain, parallel to the longer dimension we consider a stiff, layered plate. The domain is compressed along the layer axis by prescribing velocities along the sides. First, for the viscous limit we consider the response to a series of harmonic perturbations of the director orientation. The Fourier spectra of the initial folding velocity are compared for different viscosity ratios. Turning to the nonlinear regime we analyze viscoelastic folding histories up to 40% shortening. The effect of layering manifests itself in that appreciable buckling instabilities are obtained at much lower viscosity ratios (1:10) as is required for the buckling of isotropic plates (1:500). The wavelength induced by the initial harmonic perturbation of the director orientation seems to be persistent. In the section of the parameter space considered here elasticity seems to delay or inhibit the occurrence of a second, larger wavelength. Finally, in a linear instability analysis we undertake a brief excursion into the potential role of couple stresses on the folding process. The linear instability analysis also provides insight into the expected modes of deformation at the onset of instability, and the different regimes of behavior one might expect to observe.

Outcomes after trans-tibial amputation: The relationship between quiet stance ability, strength of the hip abductor muscles and gait

Background and Purpose Previous research regarding the symmetry of trans-tibial amputees has examined weight distribution and various gait parameters between prosthetic and sound limbs. However, to date, no known research has determined if asymmetry is present in the strength of the hip abductor muscles or if correlations exist between these categories of symmetry. The purpose of the present study was, therefore, to document asymmetry present in stance, strength and gait measures, and to determine the relationship between these variables. Method Twenty-three elderly, unilateral trans-tibial amputees stood on two adjacent forceplates whilst the weight distribution and standard deviation (SD) of the anterior-posterior and the medio-lateral centre of pressure excursion (COPE) under each limb was recorded during four 40 s trials: quiet stance (QS), with eyes open and eyes closed; and even stance (ES), with eyes open and eyes closed. Gait measures (velocity, cadence, step and stride lengths, stance:swing ratio and period of double support) over 10 m of fast, yet safe walking and measures of the strength of hip abductor muscles were also obtained by use of a stride analyser and a dynamometer, respectively. Results No significant differences were found between QS and ES measures. However, significantly more weight was taken on the sound limb than on the amputated limb. Notably, more anterior-posterior movement occurred under the sound limb than the amputated limb, with this becoming more apparent with the eyes closed. Movement in the medio-lateral direction was found to be the same between sides. No differences in muscle strength or gait measures between limbs were demonstrated. However. strong hip abductor muscles were correlated with increased weight-bearing on the amputated limb, improved gait parameters and reduced medio-lateral COPE under the amputated limb. Conclusions This research confirms the asymmetrical nature of amputee stance and demonstrates symmetry of strength and gait measures between limbs. The correlations between hip abductor muscle strength, weight distribution and gait measures illustrates the importance of pre- and postoperative training of these muscles. Copyright © 2002 Whurr Publishers Ltd.

Estudo da função sistólica do ventrículo direito por ecocardiografia transtorácica: relatório de projecto

Mestrado em Tecnologia de Diagnóstico e Intervenção Cardiovascular. Área de especialização - Ultrassonografia Cardiovascular

Deformação miocárdica em atletas de diferentes modalidades – Um estudo por 2D Speckle Tracking: projecto de investigação

Mestrado em Tecnologia de Diagnóstico e Intervenção Cardiovascular. Área de Especialização: Ultrassonografia Cardiovascular

Avaliação ecocardiográfica da função sistólica ventricular direita em doentes com disfunção ventricular esquerda: parâmetros convencionais versus strain bidimensional

Mestrado em Tecnologia de Diagnóstico e Intervenção Cardiovascular.

Determinação dos valores de referência da excursão sistólica do plano do anel tricúspide (TAPSE) em crianças saudáveis

Mestrado em Tecnologia de Diagnóstico e Intervenção Cardiovascular - Área de especialização: Ultrassonografia cardiovascular

A teaching-learning sequence of colour informed by history and philosophy of science

In this work, we present a teaching-learning sequence on colour intended to a pre-service elementary teacher programme informed by History and Philosophy of Science. Working in a socio-constructivist framework, we made an excursion on the history of colour. Our excursion through history of colour, as well as the reported misconception on colour helps us to inform the constructions of the teaching-learning sequence. We apply a questionnaire both before and after each of the two cycles of action-research in order to assess students’ knowledge evolution on colour and to evaluate our teaching-learning sequence. Finally, we present a discussion on the persistence of deep-rooted alternative conceptions.

Autochthonous acute Chagas’ disease in São Paulo State, Brazil: Epidemiological aspects

Since the beginning of the seventies the natural transmission of Chagas’ infection has been considered to be under control in the State of São Paulo and not even a case of American Trypanosomiasis, transmitted by triatomine bugs, has been detected by the epidemiological surveillance system. This situation justifies the report of a case of acute Chagas’ disease that occurred in a forest area considered free of domiciliary triatomines along the Southern seacoast of São Paulo State. In May, 1995 the presence of trypomastigote forms of Trypanosoma cruzi had been diagnosed in a retired 57 year-old male patient, born and living in Santos (São Paulo State), complaining of fever, fatigue and malaise. The patient reported that 40 days before he had participated with 17 friends in a 7-day excursion in a forest area of the municipalities of Itanhaém and Peruíbe. During this period the group had been lodged in three houses located within the forest. Eight days after the end of the excursion the patient began to have fever, malaise and fatigue. During the next 31 days he had received medical care both as an inpatient and an outpatient, without any significant improvement. After the detection of T. cruzi trypomastigotes in his blood stream the patient began to be treated with benzonidazole in a hospital but died 8 days after the beginning of treatment. The epidemiological investigation carried out showed no signs of the presence of triatomine bugs in the three houses where the group had been lodged, or any indication of Chagas' infection in other excursionists

Utilidade do Doppler Tecidular na Predição de Eventos Arrítmicos em Adultos com Tetralogia de Fallot Corrigida

INTRODUCTION: Adults with repaired tetralogy of Fallot (TOF) may be at risk for progressive right ventricular (RV) dilatation and dysfunction, which is commonly associated with arrhythmic events. In frequently volume-overloaded patients with congenital heart disease, tissue Doppler imaging (TDI) is particularly useful for assessing RV function. However, it is not known whether RV TDI can predict outcome in this population. OBJECTIVE: To evaluate whether RV TDI parameters are associated with supraventricular arrhythmic events in adults with repaired TOF. METHODS: We studied 40 consecutive patients with repaired TOF (mean age 35 +/- 11 years, 62% male) referred for routine echocardiographic exam between 2007 and 2008. The following echocardiographic measurements were obtained: left ventricular (LV) ejection fraction, LV end-systolic volume, LV end-diastolic volume, RV fractional area change, RV end-systolic area, RV end-diastolic area, left and right atrial volumes, mitral E and A velocities, RV myocardial performance index (Tei index), tricuspid annular plane systolic excursion (TAPSE), myocardial isovolumic acceleration (IVA), pulmonary regurgitation color flow area, TDI basal lateral, septal and RV lateral peak diastolic and systolic annular velocities (E' 1, A' 1, S' 1, E' s, A' s, S' s, E' rv, A' rv, S' rv), strain, strain rate and tissue tracking of the same segments. QRS duration on resting ECG, total duration of Bruce treadmill exercise stress test and presence of exercise-induced arrhythmias were also analyzed. The patients were subsequently divided into two groups: Group 1--12 patients with previous documented supraventricular arrhythmias (atrial tachycardia, fibrillation or flutter) and Group 2 (control group)--28 patients with no previous arrhythmic events. Univariate and multivariate analysis was used to assess the statistical association between the studied parameters and arrhythmic events. RESULTS: Patients with previous events were older (41 +/- 14 vs. 31 +/- 6 years, p = 0.005), had wider QRS (173 +/- 20 vs. 140 +/- 32 ms, p = 0.01) and lower maximum heart rate on treadmill stress testing (69 +/- 35 vs. 92 +/- 9%, p = 0.03). All patients were in NYHA class I or II. Clinical characteristics including age at corrective surgery, previous palliative surgery and residual defects did not differ significantly between the two groups. Left and right cardiac chamber dimensions and ventricular and valvular function as evaluated by conventional Doppler parameters were also not significantly different. Right ventricular strain and strain rate were similar between the groups. However, right ventricular myocardial TDI systolic (Sa: 5.4+2 vs. 8.5 +/- 3, p = 0.004) and diastolic indices and velocities (Ea, Aa, septal E/Ea, and RV free wall tissue tracking) were significantly reduced in patients with arrhythmias compared to the control group. Multivariate linear regression analysis identified RV early diastolic velocity as the sole variable independently associated with arrhythmic history (RV Ea: 4.5 +/- 1 vs. 6.7 +/- 2 cm/s, p = 0.01). A cut-off for RV Ea of < 6.1 cm/s identified patients in the arrhythmic group with 86% sensitivity and 59% specificity (AUC = 0.8). CONCLUSIONS: Our results suggest that TDI may detect RV dysfunction in patients with apparently normal function as assessed by conventional echocardiographic parameters. Reduction in RV early diastolic velocity appears to be an early abnormality and is associated with occurrence of arrhythmic events. TDI may be useful in risk stratification of patients with repaired tetralogy of Fallot.

Transoesophageal Echocardiography for Monitoring Liver Surgery: Data from a Pilot Study

A pilot study aimed to introduce intraoperative monitoring of liver surgery using transoesophageal echocardiography (TEE) is described. A set of TEE measurements was established as a protocol, consisting of left atrial (LA) dimension at the aortic valve plane; mitral velocity flow integral, calculation of stroke volume and cardiac output (CO); mitral annular plane systolic excursion; finally, right atrial area. A total of 165 measurements (on 21 patients) were performed, 31 occurring during hypotension. The conclusions reached were during acute blood loss LA dimension changed earlier than CVP, and, in one patient, a dynamic left ventricular (LV) obstruction was observed; in 3 patients a transient LV systolic dysfunction was documented. The comparison between 39 CO paired measurements obtained by TEE and PiCCO2 revealed a statistically significant correlation (P < 0.001, r = 0.83). In this pilot study TEE successfully answered the questions raised by the anesthesiologists. Larger cohort studies are needed to address this issue.

Seasonal and spatial variations in limnological conditions of a floodplain lake (lake Catalão) connected to both the Solimões and Negro Rivers, Central Amazonia

Lakes play an important role in biogeochemical, ecological and hydrological processes in the river-floodplain system. The aim of this study was to evaluate the dynamics of the limnological conditions of Catalão Lake, an Amazon floodplain lake. Thus, some of the main limnological environment variables (O2, temperature, pH, nutrient, electrical conductivity) of the Catalão Lake were analyzed under temporal and spacial scales. The study was conducted between November/2004 and August/2005. Sampling excursion were carried out every three months; one excursion for each of the four different hydrological periods (low water, rising water, high water and falling water). Sampling points were chosen so that it could be obtained a gradient of the distance from Negro River. Limnological profiles in Catalão Lake showed generally acidic to slightly alcaline water, with low levels of dissolved oxygen and low concentrations of soluble reactive phosphorous. The Negro River seems to exert the main influence during the rising water period, while the Solimões River is the principal controlling river during peak water. The Principal Component Analysis (PCA) grouped the seasonal collections by hydrological period, showing the formation of a north-south spatial gradient within the lake in relation to the limnological variables. Multivariate dispersion analysis based on distance-to-centroid method demonstrated an increase in similarity over the course of the hydrological cycle, as the lake was inundated in response to the flood pulse of the main river channels. However, the largest spatial homogeneity in the lake was observed in the epilimnion layer, during the falling water period. The daily analysis of variation indicated an oligomitic pattern during the years in which the lake was permanently connected to the Negro River. Although Catalão Lake receives large quantities of both black water from the Negro River and sediment-filled water from the Solimões River, the physical and chemical characteristics of the lake are more similar to those of the Solimões (várzea lake) than the Negro (blackwater lake).

Effects of hyperglycemia on glucose metabolism before and after oral glucose ingestion in normal men.

The plasma glucose excursion may influence the metabolic responses after oral glucose ingestion. Although previous studies addressed the effects of hyperglycemia in conditions of hyperinsulinemia, it has not been evaluated whether the route of glucose administration (oral vs. intravenous) plays a role. Our aim was to determine the effects of moderately controlled hyperglycemia on glucose metabolism before and after oral glucose ingestion. Eight normal men underwent two oral glucose clamps at 6 and 10 mmol/l plasma glucose. Glucose turnover and cycling rates were measured by infusion of [2H7]glucose. The oral glucose load was labeled by D-[6,6-2H2]glucose to monitor exogenous glucose appearance, and respiratory exchanges were measured by indirect calorimetry. Sixty percent of the oral glucose load appeared in the systemic circulation during both the 6 and 10 mmol/l plasma glucose tests, although less endogenous glucose appeared during the 10 mmol/l tests before glucose ingestion (P &lt; 0.05). This inhibitory effect of hyperglycemia was not detectable after oral glucose ingestion, although glucose utilization was increased (+28%, P &lt; 0.05) due to increased nonoxidative glucose disposal [10 vs. 6 mmol/l: +20%, not significant (NS) before oral glucose ingestion; +40%, P &lt; 0.05 after oral glucose ingestion]. Glucose cycling rates were increased by hyperglycemia (+13% before oral glucose ingestion, P &lt; 0.001; +31% after oral glucose ingestion, P &lt; 0.05) and oral glucose ingestion during both the 6 (+10%, P &lt; 0.05) and 10 mmol/l (+26%, P &lt; 0.005) tests. A moderate hyperglycemia inhibits endogenous glucose production and contributes to glucose tolerance by enhancing nonoxidative glucose disposal. Hyperglycemia and oral glucose ingestion both stimulate glucose cycling.

Biostratigraphy, mineralogy and geochemistry of the Trabakua Pass and Ermua sections in Spain: Paleocene-Eocene transition

Isotopic, geochemical and bulk mineralogical analyses in the Trabakua and Ermua sections, Basque Basin, reveal major changes across the Paleocene-Eocene transition. Expanded sedimentary records exhibit a gradual decrease of 1.0 parts per thousand in delta(13)C values in the lower part of Zone P5 followed by a more rapid 3 parts per thousand negative excursion. The 3 parts per thousand delta(13)C excursion is associated with an abrupt decrease in carbonate sedimentation, increased detrital flux and decreased grain size which suggest changes in marine/atmospheric currents and/or size and structure of the ocean carbon reservoir. The clays recognized at Trabakua record a deep burial diagenesis as indicated by two generations of chlorite, the presence of mixed-layers chlorite-smectite and illite-smectite, the absence of smectite and the near absence of kaolinite. The very low delta(18)O values (<-3.5 parts per thousand) throughout the Trabakua and Ermua sections reflect diagenetic alteration rather than paleotemperatures. Because of deep burial diagenesis and very poorly preserved microfossils, the Trabakua Pass and Ermua sections are not optimal potential stratotypes for the Paleocene-Eocene boundary.

Trace-element and phosphorus contents in sediment associated with Cretaceous oceanic anoxic events

ABSTRACT : During my SNSF-funded Ph.D. thesis project, I studied the evolution of redox conditions and organic-carbon preservation in the western Tethyan realm during three major positive excursions in the Cretaceous δ13C record, corresponding to the Valanginian, Early Aptian and Late Cenomanian. These periods were characterized by important global environmental and climate change, which was associated with perturbations in the carbon cycle. For the period of the Valanginian δ13C excursion, total organic carbon (TOC) contents and the quality of preserved organic matter are typical of oxic pelagic settings in the western Tethys. This is confirmed by the absence of major excursions in the stratigraphic distribution of RSTE during the δ13C shift. Published TOC data from other parts of the Valanginian oceans indicate that dys- to anaerobic zones were restricted to marginal seas within the Atlantic and Southern Ocean, and to the Pacific. Phosphorus (P) and mineralogical contents suggest a stepwise climatic evolution during the Valanginian, with a humid and warm climate prior to the δ13C shift leading to an increase in continental runoff. During the δ13C shift, a decrease in detrital input and P contents suggests a change in the climate towards more and conditions. During the early Aptian oceanic anoxic event (OAE 1a), a general increase followed by a rapid decrease in P contents suggests enhanced nutrient input at the beginning of OAE 1a. The return to lower values during OAE 1 a, associated with an increase in RSTE contents, may have been related to the weakened capacity to retain P in the sedimentary reservoir due to bottom-water oxygen depletion. In basinal settings, the RSTE distribution indicates well-developed anoxic conditions during OAE la, whereas in the shallower-water environments, conditions were oxic to suboxic, rather than anoxic. Furthermore, in the deeper part of the Tethys, two distinct enrichments have been observed, indicating fluctuations in the intensity of water column anoxia during the δ73C excursion. We also studied the effect of the end-Cenomanian oceanic anoxic event (OAE 2) on an expanded section in the Chrummflueschlucht (E of Euthal, Ct Switzerland). The goal here was to identify paleoceanographic and paleoenvironmental conditions during OAE 2 in this part of the northern Tethyan margin. The results show that this section is one of the most complete sections for the Cenomanian-Turonian boundary interval known from the Helvetic realm, despite a small hiatus between sediments corresponding to peaks 1 and 2 in the δ13C record. The evolution of P contents points to an increase in the input of this nutrient at the onset of OAE 2. The trends in RSTE contents show, however, that this part of the Helvetic realm was not affected by a strong depletion in oxygen conditions during OAE 2, despite its hemipelagic position. A further goal of this project was to submit the samples to a total extraction method (a combined HF/HNO3/HCI acid digestion) and compare the results obtained by the partial HNO3 acid extraction in order to standardize the analytical prócedures in the extraction of RSTE. The obtained results for samples of OAE 1 a suggest that RSTE trends using the partial HNO3 digestion are very comparable to those obtained by the total digestion method and subsequently normalized with regards to AI contents. RÉSUMÉ : Durant ce projet de thèse, financé par le Swiss National Science Funding (SNSF), j'ai étudié l'évolution des conditions redox et de la préservation de carbone organique dans le domnaine ouesttéthysien pendant trois excursions majeures du δ13C au Crétacé correspondant au Valanginien, à l'Aptien inférieur et à la limite Cénomanien-Turonien. Ces périodes sont caractérisées par des changements climatiques et environnementaux globaux associés à des perturbations dans le cylce du carbone. Pour L'excursion positive en δ13C du Valanginien, les analyses du carbone organique total (COT) et les observations palynologiques du domaine téthysien ont présenté des indications d'environnement pélagique relativementbienoxygéné. L'absence d'enrichissements en éléments traces sensibles aux conditions redox (TE) pendant l'excursion positive en δ13C confirme ces interprétations. Les données publiées de COT dans d'autres partie du globe indiquent cependant l'existence de conditions dys- à anaérobiques dans certains bassins restreints de l'Atlantique, l'Océan Austral et du Pacifique. L'évolution du phosphore (P) et la composition minéralogique des sédiments semblent indiquer un climat relativement chaud et humide avant l'excursion en δ13C entraînant une augmentation de l'altération continentale. Pendant le shift isotopique, une diminution des apports détritiques et du P suggèrent une transition vers des conditions plus arides. À l'Aptien Inférieur, le début de l'événement anoxique (OAE 1a) est marqué par une augmentation générale du P dans les sédiments indiquant une augmentation du niveau trophique à la base de l'excursion isotopique. Durant l'événement anoxique, les sédiments sont relativement appauvris en P. Cette diminution rapide associée à des enrichissements en TE est probablement liée à une remobilisation plus importante du P lors de la mise en place de conditions anoxiques dans les eaux de fond. Dans les environnements de bassin, le comportement des TE (enrichissements bien marqués) attestent de conditions réductrices bien marquées alors que dans les environnements moins profonds, les conditions semblent plutôt oxiques à dysoxiques. De plus, deux niveaux d'enrichissement en TE ont été observés dans la partie plus profonde de la Téthys, indiquant des fluctuations assez rapides dans l'intensité de l'anoxie de la colonne d'eau. Nous avons ensuite étudié les effets de l'événement anoxique de la fin du Cenomanien (OAE 2) dans un basin marginal de la marge nord de la Téthys avec la coupe de Chrummflueschlucht (à l'est de Euthal, Ct Schwyz). Les résultats ont montré que cette coupe présente un des enregistrements sédimentaires des plus complets de l'OAE 2 dans le domaine helvétique malgré un hiatus entre le pic 1 et 2 de l'excursion en δ13C. L'évolution du P montre une augmentation au début de l'OAE 2. Cependant, la distribution des TE indique que cette région n'a pas été affectée par des conditions réductrices trop importantes. Un second aspect de ce travail a été l'étude des différentes méthodes sur l'analyse de la distribution des TE. Des échantillons de l'OAE 1a ont été soumis à deux types d'extractions, l'une dite «totale » (attaque combinée d'acides HF/HNO3/HCI) et l'autre dite partielle » (HNO3). Les résultats obtenus suggèrent que les courbes de tendances des TE acquises par extraction partielle sont semblables à celle obtenues par extraction totale et normalisées par l'AI.

Reserva online de Actividades

El Centre Excursionista de Terrassa (C.E.T.) necessita que els seus socis puguin apuntar-se a les sortides muntanyenques a través d'Internet, evitant el tediós desplaçament a la seu del CET. En un nou servidor Linux, s'executarà la nostra aplicació. En aquest servidor residiran Apatxe i MySQL.