Design optimization of composite structures operating in acoustic environments

The optimal mechanical and geometric characteristics for layered composite structures subject to vibroacoustic excitations are derived. A Finite Element description coupled to Periodic Structure Theory is employed for the considered layered panel. Structures of arbitrary anisotropy as well as geometric complexity can thus be modelled by the presented approach. Damping can also be incorporated in the calculations. Initially, a numerical continuum-discrete approach for computing the sensitivity of the acoustic wave characteristics propagating within the modelled periodic composite structure is exhibited. The first- and second-order sensitivities of the acoustic transmission coefficient expressed within a Statistical Energy Analysis context are subsequently derived as a function of the computed acoustic wave characteristics. Having formulated the gradient vector as well as the Hessian matrix, the optimal mechanical and geometric characteristics satisfying the considered mass, stiffness and vibroacoustic performance criteria are sought by employing Newton׳s optimization method

Environmental determinants - The role of GSTP1 polymorphisms and tobacco smoke exposure in children with acute asthma

Background. The glutathione S-transferase enzymes (GSTs) play an important role in the detoxification of environmental tobacco smoke (ETS), which contributes to airway inflammation, a key component of asthma. Genetic variation in GST genes may influence individuals' ability to detoxify environmental pollutants. Objective. To examine the role of polymorphisms in GSTP1 (Ile105Val and Ala114Val), alone and in combination with ETS exposure, on atopy and asthma severity. Methods. GSTP1 Ile105Val and Ala114Val were genotyped and ETS exposure was assessed by parental questionnaire, which was validated by urinary cotinine measurements. Associations between ETS exposure, GSTP1 polymorphisms, and their interaction on atopy and asthma severity were investigated. Results. For the functional GSTP1 105 SNP, those with the Ile/Ile genotype had odds for atopy of 2.77 (p=.054) when assessed by genotype alone, which increased to 9.02 (p=.050) when ETS was included, relative to individuals with other genotypes. Likewise, compared to children with other GSTP1 114 genotypes, those with AlaAla genotype had a 5.47-fold (p=.002) increased risk of atopy (p=.020) when assessed by genotype alone, increasing to 9.17-fold when ETS was included. The 105 Ile/Ile individuals all had the AA (105 Ile/Ile and 114 AlaAla) haplotype group; therefore, the odds for atopy were the same. Individuals without any *C haplotype (105 Val and 114 Val allele) who were exposed to ETS had a 9.17-fold increased risk of atopy when compared with individuals with at least one *C haplotype and not exposed to ETS (p=.020). Conclusion. There were significant interactions between GSTP1 SNPs, atopy, and ETS exposure in this cohort. © 2010 Informa Healthcare USA, Inc