3,405 research outputs found

    Yield anisotropy effects on buckling of circular tubes under bending

    Get PDF
    AbstractRelatively thin-walled tubes bent into the plastic range buckle by axial wrinkling. The wrinkles initially grow stably but eventually localize and cause catastrophic failure in the form of sharp local kinking. The onset of axial wrinkling was previously established by bifurcation analyses that use instantaneous deformation theory moduli. The curvatures at bifurcation were predicted accurately, but the wrinkle wavelengths were consistently longer than measured values. The subject is revisited with the aim of resolving this discrepancy. A set of new bending experiments is conducted on aluminum alloy tubes. The results are shown to be in line with previous ones. However, the tubes used were found to exhibit plastic anisotropy, which was measured and characterized through Hill’s quadratic anisotropic yield function. The anisotropy was incorporated in the flow theory used for prebuckling and postbuckling calculations as well as in the deformation theory used for bifurcation checks. With the anisotropy accounted for, calculated tube responses are found to be in excellent agreement with the measured ones while the predicted bifurcation curvatures and wrinkle wavelengths fall in line with the measurements also. The postbuckling response is established using a finite element model of a tube assigned an initial axisymmetric imperfection with the calculated wavelength. The response develops a limit moment that is followed by a sharp kink that grows while the overall moment drops. The curvature at the limit moment agrees well with the experimental onset of failure. From parametric studies of the various instabilities it is concluded that, for optimum predictions, anisotropy must be incorporated in both bifurcation buckling as well as in postbuckling calculations

    Factor-Loading Uncertainty and Expected Returns

    Get PDF
    Firm-specific information can affect expected returns if it affects investor uncertainty about risk-factor loadings. We show that a stock\u27s expected return is decreasing in factor-loading uncertainty, controlling for the average level of its factor loading. When loadings are persistent, learning by investors can induce time-series variation in price-dividend ratios, expected returns, and idiosyncratic volatility, even when the aggregate risk-premium is constant and fundamental shocks are homoscedastic. Consistent with our predictions, we estimate that average annual returns of a firm with the median level of factor-loading uncertainty are 400 to 525 basis points lower than a comparable firm without factor-loading uncertainty

    Historical roots and the evolving science of forest management under a systemic perspective

    Get PDF
    In recent history, both a growing awareness of how scientific and societal uncertainty impacts management decisions and of the intrinsic value of nature have suggested new approaches to forest management, with a growing debate in forest science over the need for a paradigmatic shift from the classic conventional world view, based on determinism, predictability, and output-oriented management, towards a world view that has roots in complex adaptive systems theory and is consistent with a nature-based ethic. A conceptual framework under this context is provided by systemic silviculture. In this discussion, we analyze how this approach can be linked to three fundamental moments of the history of forestry and forest science: the Dauerwald theory, Gurnaud's control method, and the origins of environmental ethics. Relationships with the recent history of forest management science and current research perspectives are also highlighted.4n

    Results from a meta-analysis of immune checkpoint inhibitors in first-line renal cancer patients: does PD-L1 matter?

    Get PDF
    Background: The aim of this study was to perform a literature-based meta-analysis to assess the efficacy of the novel immune checkpoint inhibitors (ICIs) in first-line metastatic renal cell carcinoma (RCC), focusing on the predictive role of PD-L1 expression. Methods: The primary outcome was overall survival, and secondary outcomes were progression-free survival (PFS) and objective response. We planned a subgroup analysis for overall survival according to PD-L1 status. Results: Five studies were included in the analysis for a total of 4063 cases. Overall survival was greater in PD-L1 positive tumours (HR = 0.49, 95% CI: 0.36\u20130.67; p < 0.001). The pooled analysis of the unselected cases showed a statistically significative improvement in PFS with the use of ICIs (HR = 0.85, 95% CI: 0.72\u20130.99; p = 0.04) and we found a greater PFS benefit (HR = 0.65, 95% CI: 0.57\u20130.74; p < 0.001) in patients with PD-L1 positive tumours. Conclusions: This study supports the efficacy of ICIs and, although a significant clinical benefit has been reported in PD-L1 negative patients, a greater efficacy of ICIs was observed in PD-L1 positive patients. More prospective randomized studies are needed to clarify the role of PDL-1 status in metastatic RCC treated with ICIs

    Synthesis and characterization of polymeric nanoparticles and their application in anticancer therapy

    Get PDF
    Motivation: Traditional and current chemotherapy used to treat cancer disease has always been characterized by the high prevalence of side effects. In order to avoid them, nanotechnology has raised as an acceptable solution to this problem by selectively targeting anticancer drugs to the tumoral cells. Within this project to antitumoral agents, tannic acid and amitriptyline, have been encapsulated in polymeric nanoparticles to allow their targeted delivery. Amitriptyline is a tricyclic antidepressant whose antitumoral activity against lung cancer was recently described [1], and this agent could be a good approach for treating other tumoral diseases.Methods: Tannic acid nanoparticles (TA) were synthetized according to a method previously described by our group [2], and PLGA-amitriptyline nanoparticles (PLGAMI) by emulsion solvent evaporation method. The so-obtained nanoparticles were characterized by dynamic light scattering (DLS), scanning electron microscopy (SEM) and FTIR spectroscopy.Results: Both nanoparticles, TA and PLGAMI, are small and spherical. TA nanoparticles showed a mean diameter of 60 nm (SEM), a hydrodynamic diameter of 500 nm and a zeta potential of -22 mV (DLS). PLGAMI nanoparticles showed a mean diameter of 25 nm, a hydrodynamic diameter of 110 nm and a zeta potential of -8 mV. The presence of the antitumoral agents in nanoparticles was confirmed by FTIR spectroscopy, and the entrapment efficiency determined by colorimetric methods, using an UV-Vis spectroscope.Conclusions: We have synthetized two polymeric nanoparticles bearing antitumoral agents as cargo. Our data confirm that these nanoparticles are suitable for continuing with the in-vitro assays, where we will compare the pro-apoptotic effect of both nanoparticles in cell cultures (H460 tumor cell line)

    Mono-dimensional blue native-PAGE and bi-dimensional blue native/urea-PAGE or /SDS-PAGE combined with nLC-ESI-LIT-MS/MS unveil membrane protein heteromeric and homomeric complexes in streptococcus thermophilus

    Get PDF
    Protein interactions are essential elements for the biological machineries underlying biochemical and physiological mechanisms indispensable for microorganism life. By using mono-dimensional blue native polyacrylamide gel electrophoresis (1D-BN-PAGE), two-dimensional blue native/urea-PAGE (2D-BN/urea-PAGE) and two-dimensional blue native/SDS-PAGE (2D-BN/SDS-PAGE), membrane protein complexes of Streptococcus thermophilus were resolved and visualized. Protein complex and oligomer constituents were then identified by nLC-ESI-LIT-MS/MS. In total, 65 heteromeric and 30 homomeric complexes were observed, which were then associated with 110 non-redundant bacterial proteins. Protein machineries involved in polysaccharide biosynthesis, molecular uptake, energy metabolism, cell division, protein secretion, folding and chaperone activities were highly represented in electrophoretic profiles; a number of homomeric moonlighting proteins were also identified. Information on hypothetical proteins was also derived. Parallel genome sequencing unveiled that the genes coding for the enzymes involved in exopolysaccharide biosynthesis derive from two separate clusters, generally showing high variability between bacterial strains, which contribute to a unique, synchronized and active synthetic module. The approach reported here paves the way for a further functional characterization of these protein complexes and will facilitate future studies on their assembly and composition during various growth conditions and in different mutant backgrounds, with important consequences for biotechnological applications of this bacterium in dairy productions. Biological significance Combined proteomic procedures have been applied to the characterization of heteromultimeric and homomeric protein complexes from the membrane fraction of S. thermophilus. Protein machineries involved in polysaccharide biosynthesis, molecular uptake, energy metabolism, cell division, protein secretion, folding and chaperone activities were identified; information on hypothetical and moonlighting proteins were also derived. This study is original in the lactic bacteria context and maybe considered as preliminary to a deeper functional characterization of the corresponding protein complexes. Due to the large use of S. thermophilus as a starter for dairy productions, the data reported here may facilitate future investigations on protein complex assembly and composition under different experimental conditions or for bacterial strains having specific biotechnological applications
    • …
    corecore