Set based robust design of mechanical systems using the quantifier constraint satisfaction algorithm

Embodiment design is an important phase of the design process where the initial design parameters and their feasible solution spaces with design configurations are decided for the design problem. This article presents a new approach of embodiment design space exploration of the product based on set based design with integration of robustness for the mechanical systems. The approach presented addresses the initial design phase of the mechanical systems design and provides a three step approach based on a formal expression syntax, transformation and evaluation engine and a computational algorithm for performing a domain search for sets of robust solutions for the product designs by taking into the account the variations and uncertainties related to the manufacturing process and material. The approach is based on the design domain exploration and reduction techniques. This is achieved by the utilization and integration of existential and universal quantifiers from the quantifier constraint satisfaction problem (QCSP) for the expression of the parameters and variables related to the product design and robustness. The quantifier notion has been used to develop the consistency check for the existence of a design solution and existence of a robust design solution. In order to compute the developed quantifier approach, an algorithm based on the transformation of the quantifier with interval arithmetic has also been developed. In order to demonstrate the capability of the developed approach, this article includes three examples of mechanical systems from earlier research works that apply the quantifier model and the resolution algorithm to successfully explore the design domain for robust solutions while taking into account different types of variations such as variations in mechanical/material properties, manufacturing variations or variations in geometric dimensions which may be of continuous or discrete type.     

Nucleoside Analogues: Synthesis from Strained Rings

Nucleoside analogues are widely employed as bioactive compounds against cancer and viral infections. Consequently, it is important to develop efficient synthetic methods to access them with high efficiency and structural diversity. Herein, we present a full account of our work on the synthesis of nucleoside analogues via annulations of donor acceptor aminocyclopropanes and aminocyclobutanes. Thymine- and uracil-derived diester cyclopropanes were accessed from the corresponding nucleobases via vinylation and rhodium-catalyzed cyclopropanation, and were then used in (3+2) annulations with aldehydes, ketones and enol ethers. The obtained analogues could be transformed into important hydroxymethyl derivatives. Thymine and fluoro-uracil-derived diester cyclobutanes obtained from the nucleobases via vinylation and (2+2) cycloaddition could also be used in a (4+2) annulation with aldehydes. Finally, purine-derived diester cyclopropanes could be accessed using the condensation of nucleobases with chloromethyl ethylidene malonates, but annulation reactions with this class of substrates were not successful.     

Characterization of Liquid Resin Infusion (LRI) filling by fringe pattern projection and in situ thermocouples

Prepregs are not alone suited to the manufacturing of new types of aircraft structural parts that tend to be thicker and have more complex shapes. Direct processes called Liquid Composites Moulding (LCM), like Resin Transfer Moulding (RTM) or Resin Infusion Process (LRI: Liquid Resin Infusion, RFI: Resin Film Infusion) are now available. Particular attention is paid here to LRI process that looks very promising. In order to optimize both the design and manufacturing parameters in LRI processes, a general model to analyze the isothermal fluid flow through highly compressible porous media such as fibrous preforms has been recently proposed [1], [2], [3]. To validate the model and to improve the knowledge of the LRI process, an experimental approach is proposed. Two different measurement techniques, micro-thermocouple sensors and fringe projection technique, have been used to characterize the process. It appears that results derived from both techniques are in agreement and support the assumption that the resin flow occurs mainly transversely to the preform plane.     

Characterization of different promoters for designing a new expression vector in Saccharomyces cerevisiae

The widely used pESC vector series (Stratagene, La Jolla, CA, USA) with the bidirectional GAL1/GAL10 promoter provides the possibility of simultaneously expressing two different genes from a single vector in Saccharomyces cerevisiae. This system can be induced by galactose and is repressed by glucose. Since S. cerevisiae prefers glucose as a carbon source, and since its growth rate is higher in glucose than in galactose‐containing media, we compared and evaluated seven different promoters expressed during growth on glucose (pTEF1, pADH1, pTPI1, pHXT7, pTDH3, pPGK1 and pPYK1) with two strong galactose‐induced promoters (pGAL1 and pGAL10), using lacZ as a reporter gene and measuring LacZ activity in batch and continuous cultivation. TEF1 and PGK1 promoters showed the most constant activity pattern at different glucose concentrations. Based on these results, we designed and constructed two new expression vectors which contain the two constitutive promoters, TEF1 and PGK1, in opposite orientation to each other. These new vectors retain all the features from the pESC–URA plasmid except that gene expression is mediated by constitutive promoters. Copyright © 2010 John Wiley & Sons, Ltd.     

Skeletal System Biology and Smoke Damage: From Basic Science to Medical Clinic

Cigarette smoking has a negative impact on the skeletal system, as it reduces bone mass and increases fracture risk through its direct or indirect effects on bone remodeling. Recent evidence demonstrates that smoking causes an imbalance in bone turnover, making bone vulnerable to osteoporosis and fragility fractures. Moreover, cigarette smoking is known to have deleterious effects on fracture healing, as a positive correlation between the daily number of cigarettes smoked and years of exposure has been shown, even though the underlying mechanisms are not fully understood. It is also well known that smoking causes several medical/surgical complications responsible for longer hospital stays and a consequent increase in the consumption of resources. Smoking cessation is, therefore, highly advisable to prevent the onset of bone metabolic disease. However, even with cessation, some of the consequences appear to continue for decades afterwards. Based on this evidence, the aim of our review was to evaluate the impact of smoking on the skeletal system, especially on bone fractures, and to identify the pathophysiological mechanisms responsible for the impairment of fracture healing. Since smoking is a major public health concern, understanding the association between cigarette smoking and the occurrence of bone disease is necessary in order to identify potential new targets for intervention.