The dynamic analysis of piping systems using pseudo-dynamic techniques

This paper describes an application of pseudo-dynamic techniques to the dynamic analysis of piping structures. Essentially it consists in coupling a direct time integration algorithm, such as the Newmark method, to an experimental step. At each time step the integration algorithm generates a displacement vector of the structure, which is prescribed for the test specimen. This is mounted in a rigid test rig fitted with a set of displacement actuators and load cells at the level of the structure degrees of freedom. The load cells allow the reading of the internal restoring force vector, which is fed back to the direct time integration algorithm in an actual time step. Further calculations for the velocity and acceleration vectors will define a new structure configuration by evaluating a new displacement vector referred to the next time step. This procedure makes it possible to assess experimentally a realistic stress distribution at sections of complex shape piping parts. The method is a precise tool in dynamic analysis and, on being carried out in a quasi-static procedure, it operates with less expensive equipment than is necessary in real dynamic test

Specifying Self-configurable Component-based Systems with FracToy

International audienceOne of the key research challenges in autonomic computing is to define rigorous mathematical models for specifying, analyzing, and verifying high-level self-* policies. This paper presents the FracToy formal methodology to specify self-configurable component-based systems, and particularly both their component-based architectural description and their self-configuration policies. This rigorous methodology is based on the first-order relational logic, and is implemented with the Alloy formal specication language. The paper presents the dierent steps of the FracToy methodology and illustrates them on a self-configurable component-based example

No evidence of break-up effects on the fusion of 9Be with medium-light nuclei

AbstractFusion cross sections were measured for the 9Be+27Al and 19F+9Be, 12C systems, at energies above the Coulomb barrier, in order to investigate the possible effect of fusion hindrance due to the break-up of the weakly bound nuclei. Comparisons with one-dimensional barrier penetration models and with other similar systems, where no break-up is expected to occur, show no evidence of fusion hindrance

RBCS1 expression in coffee: Coffea orthologs, Coffea arabica homeologs, and expression variability between genotypes and under drought stress

Background: In higher plants, the inhibition of photosynthetic capacity under drought is attributable to stomatal and non-stomatal (i.e., photochemical and biochemical) effects. In particular, a disruption of photosynthetic metabolism and Rubisco regulation can be observed. Several studies reported reduced expression of the RBCS genes, which encode the Rubisco small subunit, under water stress. Results: Expression of the RBCS1 gene was analysed in the allopolyploid context of C. arabica, which originates from a natural cross between the C. canephora and C. eugenioides species. Our study revealed the existence of two homeologous RBCS1 genes in C. arabica: one carried by the C. canephora sub-genome (called CaCc) and the other carried by the C. eugenioides sub-genome (called CaCe). Using specific primer pairs for each homeolog, expression studies revealed that CaCe was expressed in C. eugenioides and C. arabica but was undetectable in C. canephora. On the other hand, CaCc was expressed in C. canephora but almost completely silenced in non-introgressed ("pure") genotypes of C. arabica. However, enhanced CaCc expression was observed in most C. arabica cultivars with introgressed C. canephora genome. In addition, total RBCS1 expression was higher for C. arabica cultivars that had recently introgressed C. canephora genome than for "pure" cultivars. For both species, water stress led to an important decrease in the abundance of RBCS1 transcripts. This was observed for plants grown in either greenhouse or field conditions under severe or moderate drought. However, this reduction of RBCS1 gene expression was not accompanied by a decrease in the corresponding protein in the leaves of C. canephora subjected to water withdrawal. In that case, the amount of RBCS1 was even higher under drought than under unstressed (irrigated) conditions, which suggests great stability of RBCS1 under adverse water conditions. On the other hand, for C. arabica, high nocturnal expression of RBCS1 could also explain the accumulation of the RBCS1 protein under water stress. Altogether, the results presented here suggest that the content of RBCS was not responsible for the loss of photosynthetic capacity that is commonly observed in water-stressed coffee plants. Conclusion: We showed that the CaCe homeolog was expressed in C. eugenioides and non-introgressed ("pure") genotypes of C. arabica but that it was undetectable in C. canephora. On the other hand, the CaCc homeolog was expressed in C. canephora but highly repressed in C. arabica. Expression of the CaCc homeolog was enhanced in C. arabica cultivars that experienced recent introgression with C. canephora. For both C. canephora and C. arabica species, total RBCS1 gene expression was highly reduced with WS. Unexpectedly, the accumulation of RBCS1 protein was observed in the leaves of C. canephora under WS, possibly coming from nocturnal RBCS1 expression. These results suggest that the increase in the amount of RBCS1 protein could contribute to the antioxidative function of photorespiration in water-stressed coffee plants. (Résumé d'auteur

Adsorption of Cd, Cu, Ni and Zn in tropical soils under competitive and non-competitive systems

The adsorption of heavy metals in soils affects their behavior in the environment and their bioavailability to plants. The knowledge of the adsorption mechanisms in competitive systems allows a more realistic evaluation of the metals' behavior in the soil than the single metal adsorption. The objectives of this study were (i) to evaluate Cd, Cu, Ni, and Zn adsorption in 14 surface samples (0-0.2 m) of representative soils of the Brazilian humid-tropical region, in competitive and non-competitive systems, and (ii) to establish metal affinity sequences for each soil, based in the maximum adsorption capacity (MAC) estimated by the Langmuir model. The Rhodic Eutrudox, the Kandiudalf Eutrudox, the Arenic Hapludalf, the Arenic Hapludult and the Typic Argiudoll had the highest metals' adsorption capacity, whereas the Typic Quartzipsamment and the sandy-textured Arenic Hapludult had the lowest values. In general, the MAC values for metals were lower in the competitive than in the non-competitive system. In the non-competitive system, the most common affinity sequence was Cu > Zn > Ni > Cd, whereas the most common sequence was Cu > Cd > Zn > Ni in the competitive system. In general, the Langmuir model fitted well the adsorption data of metals on the studied soils.A adsorção de metais pesados em solos afeta seu comportamento e biodisponibilidade às plantas. O conhecimento dos mecanismos de adsorção em sistemas competitivos permite uma avaliação mais realista do comportamento dos metais no solo do que estudos com adsorção de cada metal, isoladamente. Os objetivos desse trabalho foram: (i) avaliar a adsorção de Cd, Cu, Ni e Zn em amostras superficiais (0-0,2 m) de 14 solos representativos da região tropical úmida, em sistema competitivo e não-competitivo, e (ii) estabelecer sequências de afinidade metálica para cada solo, com base nos valores de capacidade máxima de adsorção (CMA) dos metais estimados por meio do modelo de Langmuir. O Rhodic Eutrudox, o Kandiudalfic Eutrudox, o Arenic Hapludalf (Alf2), o Arenic Hapludult (Ult2) e o Typic Argiudoll apresentaram elevadas capacidades de adsorção dos metais, ocorrendo o inverso para o Typic Quartzipsamment e para o Arenic Hapludult textura arenosa. No geral, a CMA dos metais aos solos foi menor no sistema competitivo. A sequência de afinidade mais comumente encontrada no sistema não-competitivo foi Cu > Zn > Ni > Cd. No sistema competitivo, a sequência foi Cu > Cd > Zn > Ni. Em geral, o modelo de Langmuir simulou de maneira satisfatória a adsorção dos metais nas amostras de solo