Collapse of composite tubes under end moments

Cylindrical tubes of moderate wall thickness such as those proposed for the original space station truss, may fail due to the gradual collapse of the tube cross section as it distorts under load. Sometimes referred to as the Brazier instability, it is a nonlinear phenomenon. This paper presents an extension of an approximate closed form solution of the collapse of isotropic tubes subject to end moments developed by Reissner in 1959 to include specially orthotropic material. The closed form solution was verified by an extensive nonlinear finite element analysis of the collapse of long tubes under applied end moments for radius to thickness ratios and composite layups in the range proposed for recent space station truss framework designs. The finite element analysis validated the assumption of inextensional deformation of the cylindrical cross section and the approximation of the material as specially orthotropic

Inflection point inflation within supersymmetry

We propose to address the fine tuning problem of inflection point inflation by the addition of extra vacuum energy that is present during inflation but disappears afterwards. We show that in such a case, the required amount of fine tuning is greatly reduced. We suggest that the extra vacuum energy can be associated with an earlier phase transition and provide a simple model, based on extending the SM gauge group to SU(3)_C \times SU(2)_L\times U(1)_Y\times U(1)_{B-L}, where the Higgs field of U(1)_{B-L} is in a false vacuum during inflation. In this case, there is virtually no fine tuning of the soft SUSY breaking parameters of the flat direction which serves as the inflaton. However, the absence of radiative corrections which would spoil the flatness of the inflaton potential requires that the U(1)_{B-L} gauge coupling should be small with g_{B-L}\leq 10^{-4}.Comment: 6 pages, 1 figur

Design, synthesis, and biological evaluation of aryl piperazines with potential as antidiabetic agents via the stimulation of glucose uptake and inhibition of NADH:ubiquinone oxidoreductase

The management of blood glucose levels and the avoidance of diabetic hyperglycemia are common objectives of many therapies in the treatment of diabetes. An aryl piperazine compound 3a (RTC1) has been described as a promoter of glucose uptake, in part through a cellular mechanism that involves inhibition of NADH:ubiquinone oxidoreductase. We report herein the synthesis of 41 derivatives of 3a (RTC1) and a systematic structure-activity-relationship study where a number of compounds were shown to effectively stimulate glucose uptake in vitro and inhibit NADH:ubiquinone oxidoreductase. The hit compound 3a (RTC1) remained the most efficacious with a 2.57 fold increase in glucose uptake compared to vehicle control and micromolar inhibition of NADH:ubiquinone oxidoreductase (IC50 = 27 μM). In vitro DMPK and in vivo PK studies are also described, where results suggest that 3a (RTC1) would not be expected to provoke adverse drug-drug interactions, yet be readily metabolised, avoid rapid excretion, with a short half-life, and have good tissue distribution. The overall results indicate that aryl piperazines, and 3a (RTC1) in particular, have potential as effective agents for the treatment of diabetes

Theoretical description of deformed proton emitters: nonadiabatic coupled-channel method

The newly developed nonadiabatic method based on the coupled-channel Schroedinger equation with Gamow states is used to study the phenomenon of proton radioactivity. The new method, adopting the weak coupling regime of the particle-plus-rotor model, allows for the inclusion of excitations in the daughter nucleus. This can lead to rather different predictions for lifetimes and branching ratios as compared to the standard adiabatic approximation corresponding to the strong coupling scheme. Calculations are performed for several experimentally seen, non-spherical nuclei beyond the proton dripline. By comparing theory and experiment, we are able to characterize the angular momentum content of the observed narrow resonance.Comment: 12 pages including 10 figure

A tetragonal-to-monoclinic phase transition in a ferroelectric perovskite: the structure of PbZr(0.52)Ti(0.48)O3

The perovskite-like ferroelectric system PbZr(1-x)Ti(x)O3 (PZT) has a nearly vertical morphotropic phase boundary (MPB) around x=0.45-0.50. Recent synchrotron x-ray powder diffraction measurements by Noheda et al. [Appl. Phys. Lett. 74, 2059 (1999)] have revealed a new monoclinic phase between the previously-established tetragonal and rhombohedral regions. In the present work we describe a Rietveld analysis of the detailed structure of the tetragonal and monoclinic PZT phases on a sample with x= 0.48 for which the lattice parameters are respectively: at= 4.044 A, ct= 4.138 A, at 325 K, and am= 5.721 A, bm= 5.708 A, cm= 4.138 A, beta= 90.496 deg., at 20K. In the tetragonal phase the shifts of the atoms along the polar [001] direction are similar to those in PbTiO3 but the refinement indicates that there are, in addition, local disordered shifts of the Pb atoms of ~0.2 A perpendicular to the polar axis.. The monoclinic structure can be viewed as a condensation along one of the directions of the local displacements present in the tetragonal phase. It equally well corresponds to a freezing-out of the local displacements along one of the directions recently reported by Corker et al.[J. Phys. Condens. Matter 10, 6251 (1998)] for rhombohedral PZT. The monoclinic structure therefore provides a microscopic picture of the MPB region in which one of the "locally" monoclinic phases in the "average" rhombohedral or tetragonal structures freezes out, and thus represents a bridge between these two phases.Comment: REVTeX, 7 figures. Modifications after referee's suggestion: new figure (figure 5), comments in 2nd para. (Sect.III) and in 2nd & 3rd para. (Sect. IV-a), in the abstract: "...of ~0.2 A perpendicular to the polar axis.

Intramyocellular lipid content and lipogenic gene expression responses following a single bout of resistance type exercise differ between young and older men

The aim of this study was to examine the temporal relationship between intramyocellular lipid (IMCL) content and the expression of genes associated with IMCL turnover, fat metabolism, and inflammation during recovery from an acute bout of resistance type exercise in old versus young men. Seven healthy young (23 ± 2 years, 77.2±2.9 kg) and seven healthy older (72±1 years, 79.3±4.9 kg) males performed a single bout of resistance exercise involving 6 sets of 10 repetitions of leg press and 6 sets of 10 repetitions of leg extension at 75% one-repetition maximum (1-RM).Muscle biopsy samples were obtained before and 12, 24 and 48 h after the completion of exercise and analysed for IMCL content and the expression of 48 genes. The subjects refrained from further heavy physical exercise and consumed a standardized diet for the entire experimental period. The IMCL content was ~2-fold higher at baseline and 12 h post-exercise in old compared with young individuals. However, no differences between groups were apparent after 48 h of recovery. There was higher expression of genes involved in fatty acid synthesis (FASN and PPARγ) during the first 24 h of recovery. Differential responses to exercise were observed between groups for a number of genes indicating increased inflammatory response (IL6, IkBalpha, CREB1) and impaired fat metabolism and TCA cycle (LPL, ACAT1, SUCLG1) in older compared with younger individuals. A singe bout of resistance type exercise leads to molecular changes in skeletal muscle favouring reduced lipid oxidation, increased lipogenesis, and exaggerated inflammation during post-exercise recovery in the older compared with younger individuals, which may be indicative of a blunted response of IMCL turnover with ageing

Chronic disease prevention programs offered by Aboriginal Community Controlled Health Services in New South Wales, Australia

Objectives: To identify and describe chronic disease prevention programs offered by Aboriginal Community Controlled Health Services (ACCHSs) in New South Wales (NSW), Australia. Methods: ACCHSs were identified through the Aboriginal Health and Medical Research Council of NSW website. Chronic disease programs were identified from the Facebook page and website of each ACCHS. Characteristics, including regions, target population, condition, health behaviour, modality and program frequency were extracted and summarised. Results: We identified 128 chronic disease programs across 32 ACCHSs. Of these, 87 (68%) programs were broad in their scope, 20 (16%) targeted youth, three (2%) targeted Elders, 16 (12%) were for females only and five (4%) were for males only. Interventions included physical activity (77, 60%), diet and nutrition (74, 58%), smoking (70, 55%), and the Aboriginal and Torres Strait Islander Health Check (44, 34%), with 93 programs (73%) of ongoing duration. Conclusions: Chronic disease prevention programs address chronic conditions by promoting physical activity, diet and nutrition, smoking cessation and health screening. Most target the general Aboriginal community, a few target specific groups based on gender and age, and more than one‐quarter are time‐limited. Implications for public health: Chronic disease programs that are co‐produced with specific groups, based on age and gender, may be needed.Victoria Sinka, Pamela Lopez‐Vargas, Allison Tong, Michelle Dickson, Marianne Kerr, Noella Sheerin ... et al

Time-frequency scaling transformation of the phonocardiogram based of the matching pursuit method.

International audienceA time-frequency scaling transformation based on the matching pursuit (MP) method is developed for the phonocardiogram (PCG). The MP method decomposes a signal into a series of time-frequency atoms by using an iterative process. The modification of the time scale of the PCG can be performed without perceptible change in its spectral characteristics. It is also possible to modify the frequency scale without changing the temporal properties. The technique has been tested on 11 PCG's containing heart sounds and different murmurs. A scaling/inverse-scaling procedure was used for quantitative evaluation of the scaling performance. Both the spectrogram and a MP-based Wigner distribution were used for visual comparison in the time-frequency domain. The results showed that the technique is suitable and effective for the time-frequency scale transformation of both the transient property of the heart sounds and the more complex random property of the murmurs. It is also shown that the effectiveness of the method is strongly related to the optimization of the parameters used for the decomposition of the signals

Comportamento à flexão de vigas eco-eficientes de ultra elevada durabilidade

Atualmente, o ecossistema mundial tem vindo a ser confrontado com problemas de grande importância, a elevada poluição do meio ambiente e a limitação dos recursos energéticos. Estes problemas têm contribuído para que a sustentabilidade da construção seja uma prioridade cada vez maior no presente e no futuro. A manutenção e a reabilitação do património construído surge como uma das medidas mais eficazes para prevenir ou reduzir o consumo de energia no setor da construção. No caso da construção nova, a tendência é para verificar-se um aumento da utilização de elementos estruturais pré-fabricados com partes betonadas em obra, obtendose uma maior rapidez de execução associada a um maior controlo de qualidade. O betão de ultra elevada durabilidade, reforçado com fibras metálicas, é considerado um material inovador desenvolvido nas últimas décadas, apresentando um conjunto de caraterísticas especiais, como a durabilidade, a facilidade de aplicação, as elevadas resistências mecânicas, tornando-o num produto particularmente atraente para a reabilitação e reforço de estruturas de betão. No entanto, este betão não deve ser produzido em grandes quantidades devido ao elevado consumo de cimento e adições, resultando em elevados custos económicos e ambientais. Considerando estas desvantagens é proposto que o betão de ultra elevada durabilidade seja usado apenas na camada de recobrimento, formando-se assim uma superskin que protege o elemento estrutural dos ambientes mais agressivos, isto é, aumenta a durabilidade das estruturas de betão sem que, no entanto, seja criado um impacte ambiental muito significativo (a quantidade de CO2 libertada para a atmosfera é menor devido ao menor consumo de cimento e adições). A presente dissertação pretende explorar o conceito de superskin do ponto de vista do comportamento estrutural, nomeadamente, estudar o comportamento de vigas sujeitas a esforços de flexão, compostas por uma camada exterior de betão de ultra elevada durabilidade, associado a um núcleo com betão eco-eficiente, com baixa dosagem de cimento, de modo a obter uma solução mais durável e ao mesmo tempo, ecologicamente mais eficiente. Foram realizadas oito vigas com diferentes taxas de armadura: quatro vigas produzidas apenas com betão com baixa dosagem de cimento (usadas como vigas de referência) e quatro vigas produzidas com um betão de ultra elevada durabilidade na camada de recobrimento e com um betão com baixa dosagem de cimento no núcleo. As diferentes taxas de armadura longitudinal permitem avaliar a influência da superskin em vigas com roturas dúcteis e frágeis. Com base nos dados recolhidos durante os ensaios experimentais estudou-se: (i) relação cargadeslocamento; (ii) os valores teóricos e experimentais do momento resistente; (iii) a evolução da curvatura nas secções críticas; (iv) a evolução da rigidez à flexão com a carga aplicada; (v) a ductilidade; e (vi) a fendilhação e o tipo de rotura. Da análise de resultados foi possível verificar que o recobrimento em betão de ultra elevada durabilidade é uma solução com aspetos muito positivos, nomeadamente, aumenta a resistência à flexão das vigas