Essential spectrum in vibrations of thin shells in membrane approximation. Propagation of singularities

The spectral problem of thin elastic shells in membrane approximation does not satisfy the classical properties of compactness and so there exists an essential spectrum. In the first part, we propose to determinate this spectrum and the weakness directions in the shell. We particularly study the case of homogeneous and isotropic shells with some examples. In the second part, we consider an elementary model problem to study the propagation of singularities and their reflections at the boundary of the domain. In the last, we study the problem of propagation for an isotropic cylindrical shell and we show that the equation of propagation does not depend on the Poisson coefficient

Isomer triggering via nuclear excitation by electron capture

Triggering of long-lived nuclear isomeric states via coupling to the atomic shells in the process of nuclear excitation by electron capture (NEEC) is studied. NEEC occurring in highly-charged ions can excite the isomeric state to a triggering level that subsequently decays to the ground state. We present total cross sections for NEEC isomer triggering considering experimentally confirmed low-lying triggering levels and reaction rates based on realistic experimental parameters in ion storage rings. A comparison with other isomer triggering mechanisms shows that, among these, NEEC is the most efficient.Comment: minor changes - updated to the final version; 4 pages, 1 figur

Measure of combined effects of morphological parameters of inclusions within composite materials via stochastic homogenization to determine effective mechanical properties

In our previous papers we have described efficient and reliable methods of generation of representative volume elements (RVE) perfectly suitable for analysis of composite materials via stochastic homogenization. In this paper we profit from these methods to analyze the influence of the morphology on the effective mechanical properties of the samples. More precisely, we study the dependence of main mechanical characteristics of a composite medium on various parameters of the mixture of inclusions composed of spheres and cylinders. On top of that we introduce various imperfections to inclusions and observe the evolution of effective properties related to that. The main computational approach used throughout the work is the FFT-based homogenization technique, validated however by comparison with the direct finite elements method. We give details on the features of the method and the validation campaign as well. Keywords: Composite materials, Cylindrical and spherical reinforcements, Mechanical properties, Stochastic homogenization.Comment: 23 pages, updated figures, version accepted to Composite Structures 201

A RELAÇÃO ENTRE OS ESQUEMAS DESADAPTATIVOS INICIAIS E A DISPOSIÇÃO PARA SE COMUNICAR (WTC) EM ALUNOS IRANIANOS DO EFL

The current study set out to probe the relationship between Willingness to Communicate (WTC) and different components of Early Maladaptive Schemas (EMSs). Moreover, the study sought to discover whether any subcomponents of the EMSs significantly predicts the WTC of Iranian EFL learners. One hundred fifty intermediate EFL learners took a Nelson test, and 109 learners with scores within the range of ± one standard deviation from the mean were selected. The selected learners filled out two questionnaires measuring WTC and EMSs. The results of statistical analyses indicated that there was a statistically negative and significant relationship between WTC and the seclusion and defect/shyness components of EMSs. Moreover, it was revealed that none of the components of EMSs could significantly predict WTC. Based on the findings, the seclusion and defect/shame components of EMSs should be the focus of more attention if the target is to raise learners’ WTC.O presente estudo teve como objetivo investigar a relação entre a vontade de comunicar (WTC) e os diferentes componentes dos esquemas desadaptativos iniciais (EMSs). Além disso, o estudo procurou descobrir se algum subcomponente dos EMSs prevê significativamente o WTC dos alunos iranianos do EFL. Cento e cinquenta alunos intermediários de EFL fizeram um teste de Nelson, e 109 alunos com pontuações dentro da faixa de ± um desvio padrão da média foram selecionados. Os alunos selecionados preencheram dois questionários medindo WTC e EMSs. Os resultados das análises estatísticas indicaram que havia uma relação estatisticamente negativa e significativa entre o WTC e os componentes de reclusão e defeito / timidez dos EMSs. Além disso, foi revelado que nenhum dos componentes dos EMSs poderia prever significativamente o WTC. Com base nas descobertas, os componentes de isolamento e defeito / vergonha dos EMSs devem ser o foco de mais atenção se o objetivo for aumentar o WTC dos alunos

A unique Parthian sword in the Bonyad-e Mostazafan Museum

This study is going to introduce one of the unique and less known Parthian sword which have not been released to public for purpose of exhibit and study so far

Somatic embryogenesis and plantlet regeneration from protoplast culture of Muscari neglectum Guss

A protocol has been developed for plant regeneration from protoplast culture of Muscari neglectum using regenerable embryogenic calli obtained from bulb culture on Murashige and Skoog medium (MS) plant growth regulators (PGR)-free or containing lower 1-naphthaleneacetic acid (NAA) and 6- benzylaminopurine (BA) concentrations and 30 g/l sucrose. Protoplasts were isolated directly from embryogenic calli, embedded in Ca-alginate beads and cultured with nurse cells in MS medium supplemented with 1 mg/l each of NAA and BA, 100 mg/l ascorbic acid and 0.5 M mannitol at 25°C in darkness. After 4 weeks of culture, microcalli appeared on the surface of the Ca-alginate beads. Growth of microcalli in the medium with nurse cells (33.3%) was much better than those in the medium without nurse cells (6.5%). Transferring beads onto MS medium supplemented with 0.1 mg/l BA increased the growth of embryogenic calli. Somatic embryo development was observed either on half strength MS medium PGR-free or with 1 mg/l abscisic acid at 25°C under continuous illumination with fluorescent light. Maturated embryos germinated and then converted to plantlets on half strength MS medium containing 1 mg/l BA after 3 months. The plantlets left in the medium produced bulbs after 5 months.Key words: Ca-alginate beads, Muscari neglectum, nurse culture, plantlet regeneration, protoplast culture, somatic embryogenesis

Effects of TiO2 nanoparticles and spermine on antioxidant responses of Glycyrrhiza glabra L. to cold stress

Licorice (Glycyrrhiza glabra L.) is known as an important medicinal plant throughout the world. Glycyrrhizin is one of the most important specialized metabolites produced by licorice. In order to study the effect of TiO2 nanoparticles (TiO2 NPs) and spermine on physiological and biochemical traits of licorice under cold stress conditions, a factorial experiment was conducted in a completely randomized design with three replications. Plants were exposed to optimum temperature (26 ºC) as control and low temperature (4 ºC) as cold stress conditions and also treated with TiO2 NPs (2 and 5 ppm) and spermine (1 mM), separately. Results from physiological and biochemical analyses of the aerial parts of licorice seedlings showed that the growth parameters and the content of photosynthetic pigments decreased in response to low temperature. TiO2 NPs and spermine treatments increased plant resistance to cold stress and decreased the level of oxidative damage by reduction of alondialdehyde (MDA) and hydrogen peroxide (H2O2) contents. In other hand, TiO2 NPs and spermine caused increase of phenolics, total protein and osmolytes contents under cold stress conditions. An increase in glycyrrhizin content was significantly induced by low temperature, TiO2 NPs and spermine