Sponge Gourd (Luffa Cylindrica) Reinforced Polyester Composites: Preparation and Properties

Increasing environmental concern along with the drive to find substitutes for synthetic fibers and value added applications for low cost and renewable plant fibers have led to the development of composites based on biomaterials. One of the drawbacks encountered in such exercise is the lack of adhesion between the incorporated plant fibers and synthetic polymeric matrices. Such drawback can be reduced by appropriate treatment of fibers. This paper describes the chemical treatments used on sponge gourd (Luffa cylindrica) fibers of Brazil to prepare their composites with polyester resin. Production of short fiber-polymer composite as well as mat-polyester composites is presented here. Characterization of the composites in respect of evaluation of density, water absorption, thermalstability, tensile properties and impact strength were made and the results are discussed. Observed impact strengthand tensile properties are discussed based on the fractographic studies of the composites.Defence Science Journal, Vol. 64, No. 3, May 2014, pp. 273-280, DOI:http://dx.doi.org/ 10.14429/dsj.64.732

Extracting Lyapunov exponents from the echo dynamics of Bose-Einstein condensates on a lattice

We propose theoretically an experimentally realizable method to demonstrate the Lyapunov instability and to extract the value of the largest Lyapunov exponent for a chaotic many-particle interacting system. The proposal focuses specifically on a lattice of coupled Bose-Einstein condensates in the classical regime describable by the discrete Gross-Pitaevskii equation. We suggest to use imperfect time-reversal of system's dynamics known as Loschmidt echo, which can be realized experimentally by reversing the sign of the Hamiltonian of the system. The routine involves tracking and then subtracting the noise of virtually any observable quantity before and after the time-reversal. We support the theoretical analysis by direct numerical simulations demonstrating that the largest Lyapunov exponent can indeed be extracted from the Loschmidt echo routine. We also discuss possible values of experimental parameters required for implementing this proposal

Efeito de tratamentos químicos nas propriedades de superfície de fibras de carbono via cromatografia gasosa inversa

Em aplicações aeroespaciais emprega-se o conjunto resina epóxi e fibras de carbono. Essa fibra apresenta baixa afinidade com diversos polímeros, resultando em pouca molhabilidade pelas resinas. Entretanto, pode-se utilizar tratamentos de superfície para introduzir grupos funcionais e/ou aumentar sua área superficial. Um método recente e pouco explorado para caracterizar a superfície de fibras de carbono é a cromatografia gasosa inversa (CGI). Quando comparada à cromatografia gasosa convencional, na CGI a superfície do substrato é o material a ser investigado, enquanto a fase móvel apresenta propriedades bem definidas. O objetivo deste trabalho é estudar o efeito de diversos agentes de tratamento químicos nas propriedades de superfície de fibras de carbono base PAN comerciais. As fibras foram pré-tratadas com acetona, para removem sua encimagem, e posteriormente tratadas com ácidos (HCl, HNO3, H2SO4 ou CH3COOH), NH4OH ou H2O2. Tais agentes de tratamento se mostraram eficazes para a modificação de superfície das fibras de carbono, em termos de promover distintos graus de interações físicas e ácido-base.info:eu-repo/semantics/publishedVersio

Influence of Stacking Sequence on the Mechanical and Dynamic Mechanical Properties of Cotton/Glass Fiber Reinforced Polyester Composites

This study focuses on the use of waste cotton fiber from the textile industry to produce composites with unsaturated polyester and to evaluate the performance of glass (G) / cotton (C) fiber laminates, particularly their mechanical and dynamic mechanical properties. Distinct stacking sequences were studied but the overall fiber content was kept constant. In general, hybrid laminates exhibited intermediate mechanical properties compared to those of the pure laminates, and optimum performance was obtained when the glass fiber mats were placed on the surfaces of the composite. Furthermore, some hybrid laminates exhibited superior dynamic mechanical performance, even compared to the pure glass laminate. Lower tan delta peak height (related to better fiber-matrix interaction) values and higher Tg were reported for the [C/G/Ḡ]s and [G/C/C]s samples which, together with the [G/C/Ḡ]s sample, exhibited the best results for reinforcement effectiveness and loss modulus peak height. Therefore, it is found possible to partially replace the glass fiber by waste cotton fiber considering that the final product may be optimized for mechanical property, which requires glass fiber at the surface of the laminate, or for dynamic mechanical properties, that allows higher cotton fiber content

ECLAPTE: Effective Closure of LAParoTomy in Emergency-2023 World Society of Emergency Surgery guidelines for the closure of laparotomy in emergency settings

Laparotomy incisions provide easy and rapid access to the peritoneal cavity in case of emergency surgery. Incisional hernia (IH) is a late manifestation of the failure of abdominal wall closure and represents frequent complication of any abdominal incision: IHs can cause pain and discomfort to the patients but also clinical serious sequelae like bowel obstruction, incarceration, strangulation, and necessity of reoperation. Previous guidelines and indications in the literature consider elective settings and evidence about laparotomy closure in emergency settings is lacking. This paper aims to present the World Society of Emergency Surgery (WSES) project called ECLAPTE (Effective Closure of LAParoTomy in Emergency): the final manuscript includes guidelines on the closure of emergency laparotomy

Identification of genetic variants associated with Huntington's disease progression: a genome-wide association study

Background Huntington's disease is caused by a CAG repeat expansion in the huntingtin gene, HTT. Age at onset has been used as a quantitative phenotype in genetic analysis looking for Huntington's disease modifiers, but is hard to define and not always available. Therefore, we aimed to generate a novel measure of disease progression and to identify genetic markers associated with this progression measure. Methods We generated a progression score on the basis of principal component analysis of prospectively acquired longitudinal changes in motor, cognitive, and imaging measures in the 218 indivduals in the TRACK-HD cohort of Huntington's disease gene mutation carriers (data collected 2008–11). We generated a parallel progression score using data from 1773 previously genotyped participants from the European Huntington's Disease Network REGISTRY study of Huntington's disease mutation carriers (data collected 2003–13). We did a genome-wide association analyses in terms of progression for 216 TRACK-HD participants and 1773 REGISTRY participants, then a meta-analysis of these results was undertaken. Findings Longitudinal motor, cognitive, and imaging scores were correlated with each other in TRACK-HD participants, justifying use of a single, cross-domain measure of disease progression in both studies. The TRACK-HD and REGISTRY progression measures were correlated with each other (r=0·674), and with age at onset (TRACK-HD, r=0·315; REGISTRY, r=0·234). The meta-analysis of progression in TRACK-HD and REGISTRY gave a genome-wide significant signal (p=1·12 × 10−10) on chromosome 5 spanning three genes: MSH3, DHFR, and MTRNR2L2. The genes in this locus were associated with progression in TRACK-HD (MSH3 p=2·94 × 10−8 DHFR p=8·37 × 10−7 MTRNR2L2 p=2·15 × 10−9) and to a lesser extent in REGISTRY (MSH3 p=9·36 × 10−4 DHFR p=8·45 × 10−4 MTRNR2L2 p=1·20 × 10−3). The lead single nucleotide polymorphism (SNP) in TRACK-HD (rs557874766) was genome-wide significant in the meta-analysis (p=1·58 × 10−8), and encodes an aminoacid change (Pro67Ala) in MSH3. In TRACK-HD, each copy of the minor allele at this SNP was associated with a 0·4 units per year (95% CI 0·16–0·66) reduction in the rate of change of the Unified Huntington's Disease Rating Scale (UHDRS) Total Motor Score, and a reduction of 0·12 units per year (95% CI 0·06–0·18) in the rate of change of UHDRS Total Functional Capacity score. These associations remained significant after adjusting for age of onset. Interpretation The multidomain progression measure in TRACK-HD was associated with a functional variant that was genome-wide significant in our meta-analysis. The association in only 216 participants implies that the progression measure is a sensitive reflection of disease burden, that the effect size at this locus is large, or both. Knockout of Msh3 reduces somatic expansion in Huntington's disease mouse models, suggesting this mechanism as an area for future therapeutic investigation

Effect of clay silylation on curing and mechanical and thermal properties of unsaturated polyester/montmorillonite nanocomposites

This workfocusesonthechemicalmodification ofmontmorillonite(MMT)(Cloisites Na) withcompa- tible silanes,vinyltriethoxysilane(CVTES)and γ-methacryloxypropyltrimethoxysilane(CMPS)inorderto preventagglomerationandtoimprovemontmorilloniteinteractionwithanunsaturatedpolyesterresin matrix seekingtoachieveamultifunctionalcomposite.Claysweredispersedintheresinbymechanical stirring andsonicationandthenanocompositeswerepreparedbyresintransferintoamold.Theme- chanical, morphological,thermaland flammability propertiesoftheobtainedcompositeswerecom- pared withthosepreparedusingcommercialCloisites 30B (C30B)andCloisites 15A(C15A)clays.Ad- vantagesofusingsilane-modified clays(CVTESandCMPS)ascomparedwithorganic-modified clays (C30B andC15A)canbesummarizedassimilar flexuralstrengthandlinearburningratebuthigher storagemodulusandimprovedadhesiontothepolyesterresinwithconsequenthigherthermalde- flection temperatureandreinforcementeffectivenessathighertemperatures.However,organicmodified claysshowedbetterdispersion(tendencytoexfoliate)andconsequentlydelayedthermalvolatilization due totheclaybarriereffect

Creep and residual properties of filament-wound composite rings under radial compression in harsh environments

This work focuses on the viscoelastic response of carbon/epoxy filament-wound composite rings under radial compressive loading in harsh environments. The composites are exposed to three hygro-thermo-mechanical conditions: (i) pure mechanical loading, (ii) mechanical loading in a wet environment and (iii) mechanical loading under hygrothermal conditioning at 40◦C. Dedicated equipment was built to carry out the creep experiments. Quasi-static mechanical tests are performed before and after creep tests to evaluate the residual properties of the rings. The samples are tested in (i) radial compression, (ii) axial compression, and (iii) hoop tensile strength. Different laminates wound at off-axis orientations are manufactured via filament winding and analyzed. Key results show that creep displacement is affected by both hygrothermal and mechanical conditionings, especially at a higher temperature. Moreover, residual properties are quantified showing that creep generates permanent damage in the cylinders.Peer reviewe

Curing and seawater aging effects on mechanical and physical properties of glass/epoxy filament wound cylinders

Polymer composites in marine structures that operate under seawater environment may be seriously affected, reducing durability estimates. This work aims at evaluating the effect of seawater exposure at 80 °C for 7–28 days on filament-wound glass fiber/epoxy composite cylinders partially cured by passing saturated steam through them just after winding seeking a faster curing route. The winding angle is varied (±55, ±65 and ± 75) and some of the cylinders are later post-cured for comparison. The unaged partially cured specimens do not reach complete curing, with a glass transition temperature (Tg) of 132 °C, below the Tg for the other samples (154–159 °C). Fully cured cylinders present mechanical properties slightly higher than partially cured ones. Moreover, aging in seawater for 7 days enhances the cross-linking degree of epoxy, with a positive effect on both hoop tensile strength and stiffness. Aging is, however, not critical for the radial compressive properties.Peer reviewe