This contribution deals with some recent studies on numerical and analytical models for the evaluation of aeroelastic response of cross-section models of long span bridges. The time-domain indicial approach, whose validity has been only partially investigated in the past, is selected for the modeling of self-excited forces. Sets of indicial function coefficients are estimated for rectangular cross-sections, and their applicability is proven, through time-domain simulations and comparison with experimental tests. Critical flutter condition and dynamic pre-critical and post-critical behaviors are evaluated. 相似文献
Heat-labile toxin (LT) is a protein related to cholera toxin, produced by enterotoxigenic Escherichia coli strains, that is organized as an AB5 complex. A number of nontoxic derivatives of LT, useful for new or improved vaccines against diarrheal diseases or as mucosal adjuvants, have been constructed by site-directed mutagenesis. Here we have studied the biochemical properties of the nontoxic mutants LT-K7 (Arg-7-->Lys), LT-D53 (Val-53-->Asp), LT-K63 (Ser-63-->Lys), LT-K97 (Val-97-->Lys), LT-K104 (Tyr-104-->Lys), LT-K114 (Ser-114-->Lys), and LT-K7/K97 (Arg-7-->Lys and Val-97-->Lys). We have found that mutations in the A subunit may have profound effects on the ability to form the AB5 structure and on the stability and trypsin sensitivity of the purified proteins. Unstable mutants, during long-term storage at 4 degrees C, showed a decrease in the amount of the assembled protein in solution and a parallel appearance of soluble monomeric B subunit. This finding suggests that the stability of the B pentamer is influenced by the A subunit which is associated with it. Among the seven nontoxic mutants tested, LT-K63 was found to be efficient in AB5 production, extremely stable during storage, resistant to proteolytic attack, and very immunogenic. In conclusion, LT-K63 is a good candidate for the development of antidiarrheal vaccines and mucosal adjuvants. 相似文献
The synthesis of PMMA‐based nanoparticles (NPs) covalently labeled with a fluorescent dye is investigated for imaging applications such as cell uptake and biodistribution. Batch emulsion polymerization (BEP) and monomer‐starved semi‐batch emulsion polymerization (MSSEP) are adopted using SDS. Fluorescent properties are added to these NPs using Rhodamine‐B (RhB) as a fluorescent dye covalently bonded to 2‐hyroxyethyl‐acrylate. The resulting HEMA‐RhB monomer is copolymerized with MMA via BEP and MSSEP to synthesize fluorescent NPs. Subsequently, SDS is substituted with a biocompatible surfactant, Tween80, through ionic‐exchange resins. ζ‐Potential measurements confirmed the complete surfactant exchange that leads to biocompatible fluorescent NPs with tunable size and narrow size distribution.
Veiled virgin olive oil (VOO) samples of nine different olive cultivars are chosen to have a wide range of physicochemical and biological properties of colloidal dispersions. The contents of proteins and phospholipids range from 40 to 190 mg kg−1 and from 70 to 200 mg kg−1, respectively. The effect of lab-scale centrifugation on cloudy appearance is studied measuring the decrease of turbidity grade values. The time to obtain unveiled oils (20 NTU) is modeled by a logistic equation, and a clear relationship between the initial water content and the above time is observed with a different trend between two groups of the VOO samples. Four VOO samples are selected to study the aggregation phenomena of microdroplets of water, pulp particles, and olive stone fragments via optical microscopy and dynamic light scattering during lab-scale gravity sedimentation. All VOOs are unstable with the cloudiness disappearing within the 230 days of investigation due to an overall diameter increase of cloudy components which is modeled by a power-law equation. The VOO samples, characterized by both small diameter values of dispersed components (150–250 nm) and high values of water content, show the fastest aggregation kinetics, but they have the longest time of cloudiness stability. Practical Applications: Water content and size distribution of VOO cloudy components can be key factors to control the colloidal stability. If removal of cloudy appearance is required, centrifugation can be applied to obtain a fast oil clarification which shows a power law relationship of water content with time. Instead, if physical stability of the colloidal dispersion is required, the aggregation phenomena should be slow down through VOO processing to obtain small diameters of the cloudy components. Tuning both the water content and dispersed phase diameter in the VOO can be the first step towards the control of phenomena related to the colloidal dispersion for every olive oil processing organization, above and beyond the simple removal of cloudy appearance by filtration. 相似文献
Acidity at surface of cancer cells is a hallmark of tumor microenvironments, which does not depend on tumor perfusion, thus it may serve as a general biomarker for targeting tumor cells. We used the pH (low) insertion peptide (pHLIP) for decoration of liposomes and niosomes. pHLIP senses pH at the surface of cancer cells and inserts into the membrane of targeted cells, and brings nanomaterial to close proximity of cellular membrane. DMPC liposomes and Tween 20 or Span 20 niosomes with and without pHLIP in their coating were fully characterized in order to obtain fundamental understanding on nanocarrier features and facilitate the rational design of acidity sensitive nanovectors. The samples stability over time and in presence of serum was demonstrated. The size, ζ-potential, and morphology of nanovectors, as well as their ability to entrap a hydrophilic probe and modulate its release were investigated. pHLIP decorated vesicles could be useful to obtain a prolonged (modified) release of biological active substances for targeting tumors and other acidic diseased tissues. 相似文献
Selenoglutathione has been shown to have considerable potential as a catalyst of oxidative protein folding. Here we examine how this reagent modulates the folding pathway of bovine pancreatic trypsin inhibitor (BPTI) and show that the diselenide increases the efficiency of this process primarily by accelerating the conversion of a kinetically trapped folding intermediate. 相似文献
The isogeometric formulation of the boundary element method (IgA-BEM) is investigated within the adaptivity framework. Suitable weighted quadrature rules to evaluate integrals appearing in the Galerkin BEM formulation of 2D Laplace model problems are introduced. The proposed quadrature schemes are based on a spline quasi-interpolation (QI) operator and properly framed in the hierarchical setting. The local nature of the QI perfectly fits with hierarchical spline constructions and leads to an efficient and accurate numerical scheme. An automatic adaptive refinement strategy is driven by a residual-based error estimator. Numerical examples show that the optimal convergence rate of the Galerkin solution is recovered by the proposed adaptive method. 相似文献