Optimal laminations of thin underwater composite cylindrical vessels

This paper deals with the optimal design of deep submarine exploration housings and autonomous underwater vehicles. The structures under investigation are thin-walled laminated composite unstiffened vessels. Structural buckling failure due to the high external hydrostatic pressure is the dominant risk factor at exploitation conditions. The search of fiber orientations of the composite cylinders that maximize the stability limits is investigated. A genetic algorithm procedure coupled with an analytical model of shell buckling has been developed to determine numerically optimized stacking sequences. Characteristic lamination patterns have been obtained. FEM analyses have confirmed the corresponding significant increases of buckling pressures with respect to initial design solutions. Experiments on thin glass/epoxy and carbon/epoxy cylinders have been performed. The measured buckling pressures appear to be in good agreement with numerical results and demonstrate the gains due to the optimized laminations.     

Chain length dependent termination in radical cross-linking polymerization

The work presents an evidence in support of chain length dependent termination during cross-linking polymerization. It is based on the behavior of the ratio of the bimolecular termination coefficient to propagation rate coefficient k_p during the after-effect of a photo-induced polymerization. The chain-length dependence was manifested by a decrease of the ratio with the increase in dark reaction time faster than that resulting from the conversion increase. Two monomethacrylate/dimethacrylate and one dimethacrylate/dimethacrylate systems were chosen, which enabled to study the chain-length dependence as a function of cross-link density of the polymer being formed and physical properties of the initial composition. The ratios of the polymerization rate coefficients were calculated for various postpolymerization processes as a function of dark reaction conversion using the mixed termination model (concerning the bimolecular and monomolecular termination occurring parallel). A rapid drop of the ratio during the dark reaction was observed at the beginning of the after-effect and in slightly cross-linked systems suggesting a significant chain length dependence, but when the cross-link density increased with conversion or with cross-linking agent concentration in the feed, the drop of the ratio became much slower indicating that the chain length dependence decreased.     

Effect of knowledge above self-actualization on faking the Personal Orientation Inventory.

In a study with 90 undergraduates, factorially manipulated instructions (fake bad, be honest again control, fake good) and knowledge of self-actualization (naive, knowledgeable) were used to determine whether knowledge affects one's ability to (a) create a poor impression or (b) create a good impression in comparison with appropriate controls on a measure of self-actualization--the Personal Orientation Inventory (POI). Results show that both naive and knowledgeable Ss could lower their POI scores significantly when asked to do so; only knowledgeable Ss could fake good. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Multiscale characterization of nanostructured Al–Si–Zr alloys obtained by rapid solidification method

Properties of engineering metallic alloys (e.g., fracture toughness, corrosion resistance) are often limited by the presence of primary intermetallic particles which form during conventional solidification. Rapid solidification brings about much more homogenous amorphous and/or nanocrystalline structure with reduced density of primary particles. Rapidly solidified thin ribbons obtained by melt spinning are usually considered as intrinsically homogenous. However, due to different cooling conditions at the wheel surface and on the side exposed to the ambient environment, structure of such ribbons may vary significantly across its thickness. The materials studied in this study were 30–40 μm thickness ribbons of nanocrystalline hyper- and hypo-eutectic Al–Si–Zr alloys produced by melt-spinning method. Transmission electron microscopy and high resolution scanning transmission electron microscopy were used to characterize the structure homogeneity across the ribbons. Thin foils for transmission observations were prepared by focused ion beam system. Microstructural observations confirmed nanocrystalline character of Al–Si–Zr alloys. However, these observations revealed inhomogeneity of the structure across the ribbon width.     

Solvent-Induced Formation of Novel Ni(II) Complexes Derived from Bis-Thiosemicarbazone Ligand: An Insight from Experimental and Theoretical Investigations

In this work, we report solvent-induced complexation properties of a new N₂S₂ tetradentate bis-thiosemicarbazone ligand (H₂L^I), prepared by the condensation of 4-phenylthiosemicarbazide with bis-aldehyde, namely 2,2’-(ethane-1,2-diylbis(oxy)dibenzaldehyde, towards nickel(II). Using ethanol as a reaction medium allowed the isolation of a discrete mononuclear homoleptic complex [NiL^I] (1), for which its crystal structure contains three independent molecules, namely 1-I, 1-II, and 1-III, in the asymmetric unit. The doubly deprotonated ligand L^I in the structure of 1 is coordinated in a cis-manner through the azomethine nitrogen atoms and the thiocarbonyl sulfur atoms. The coordination geometry around metal centers in all the three crystallographically independent molecules of 1 is best described as the seesaw structure. Interestingly, using methanol as a reaction medium in the same synthesis allowed for the isolation of a discrete mononuclear homoleptic complex [Ni(L^II)₂] (2), where L^II is a monodeprotonated ligand 2-(2-(2-(2-(dimethoxymethyl)phenoxy)ethoxy)benzylidene)-N-phenylhydrazine-1-carbothioamide (HL^II). The ligand L^II was formed in situ from the reaction of L^I with methanol upon coordination to the metal center under synthetic conditions. In the structure of 2, two ligands L^II are coordinated in a trans-manner through the azomethine nitrogen atom and the thiocarbonyl sulfur atom, also yielding a seesaw coordination geometry around the metal center. The charge and energy decomposition scheme ETS-NOCV allows for the conclusion that both structures are stabilized by a bunch of London dispersion-driven intermolecular interactions, including predominantly N–H∙∙∙S and N–H∙∙∙O hydrogen bonds in 1 and 2, respectively; they are further augmented by less typical C–H∙∙∙X (where X = S, N, O, π), CH∙∙∙HC, π∙∙∙π stacking and the most striking, attractive long-range intermolecular C–H∙∙∙Ni preagostic interactions. The latter are found to be determined by both stabilizing Coulomb forces and an exchange-correlation contribution as revealed by the IQA energy decomposition scheme. Interestingly, the analogous long-range C–H∙∙∙S interactions are characterized by a repulsive Coulomb contribution and the prevailing attractive exchange-correlation constituent. The electron density of the delocalized bonds (EDDB) method shows that the nickel(II) atom shares only ~0.8|e| due to the σ-conjugation with the adjacent in-plane atoms, demonstrating a very weak σ-metalloaromatic character.     

The influence of inhomogeneous trap distribution on results of DLTS study

A model is developed to describe how a narrow distribution of deep traps adjacent to quantum dots (QDs) influences the trap-related signals measured by frequency scanned deep level transient spectroscopy (FS-DLTS). By comparison with experiment, it is demonstrated that traps with a steep concentration gradient, positioned in the so called transition layer close to the edge of the depletion region (“λ-effect”), have a strong influence on DLTS signal amplitudes. This is manifested by an extreme sensitivity to the change in the Fermi-level position when temperature is varied.     

Hydrogen production by direct injection of ethanol microdroplets into nitrogen microwave plasma flame

Liquid ethanol introduced as microdroplets into the tip of microwave nitrogen plasma, operating at 2.45 GHz under atmospheric pressure, has been investigated. Injection of ethanol outside the region of plasma generation eliminated a problem of soot formation at that region, which was responsible for short reactor lifetime. Using liquid ethanol allows to save energy needed for vaporization. Hydrogen, carbon monoxide and solid carbon were the main outlet products. Other products detected with gas chromatography were CH₄, C₂H₄ and C₂H₂. The best results concerning hydrogen production were as follows: concentration in the outlet gas up to 28%, production rate up to 1043 L/h, energy yield up to 209 L per kWh of microwave power, and were obtained for liquid C₂H₅OH flow rate of 3.7 L/h. A numerical 0D model was used to determine contributions of chemical reactions in formation of measured gaseous products. Simplified model involving only radical reactions without any ions and electrons predicts final concentrations of main compounds quite well for microwave power up to 4 kW.     

Fast-curing polyurethane adhesives derived from environmentally friendly hyperbranched polyglycerols - The effect of macromonomer structure

Transformation of glycerol to hyperbranched polyglycerols (HBPGs) and their further application as macromonomers for fast-curing polyurethane adhesives were described. An approach allowing for using of hyperbranched polyglycerols derived from renewable glycerol in adhesive technology was investigated. Four hyperbranched polyglycerols of different structures and functionalities were synthesized and crosslinked with polymeric methylenediphenyldiisocyanate (pMDI) and hexamethylenediisocyanate (HDI). Macromolecule functionality and functional group distribution were shown to be a critical factor in terms of the adhesive performance. The studied approach allowed to conclude that environmentally friendly polyglycerols - derived from renewable glycerol - when properly designed could successfully replace petroleum-based ones.     

Comparison of physicochemical and sensory changes in fresh and frozen herring (Clupea harrengus L.) during marinating

BACKGROUND: The influence of freezing on the changes during ripening is better described for salted fish than marinades. Therefore in the present study the effect of preliminary freezing of raw material on the ripening of carcasses and fillets marinated during 18 days at a temperature of 10 °C, in brine with 6% salt and 5% acetic acid was examined. RESULTS: In both cases the marinating of thawed frozen material resulted in larger mass losses and decrease of the value of meat colour parameters. The semi‐marinades from raw herring were characterised by higher values of total estimation based on sensory analysis. The statistical analysis showed weak correlation between the discriminants of sensory assessment and the studied physicochemical parameters of semi‐marinades. CONCLUSIONS: These results suggest that the semi‐marinades from raw fish are characterised by higher sensory quality, better colour parameters and higher yield than those from frozen thawed fish. Copyright © 2010 Society of Chemical Industry     

Lipopeptide Nanoparticles: Development of Vaccines against Hookworm Parasite

Necator americanus (hookworm) infects over half a billion people worldwide. Anthelminthic drugs are commonly used to treat the infection; however, vaccination is a more favorable strategy to combat this parasite. We designed new B‐cell peptide epitopes based on the aspartic protease of N. americanus (Na‐APR‐1). The peptides were conjugated to self‐adjuvanting lipid core peptide (LCP) systems via stepwise solid‐phase peptide synthesis (SPPS) and copper catalyst azide–alkyne cycloaddition (CuAAC) reactions. The LCP vaccine candidates were able to self‐assemble into nanoparticles, were administered to mice without the use of additional adjuvant, and generated antibodies that recognized the parent epitope. However, only one LCP derivative was able to produce a high titer of antibodies specific to Na‐APR‐1; circular dichroism analyses of this compound showed a β‐sheet conformation for the incorporated epitope. This study provides important insight in epitope and delivery system design for the development of a vaccine against hookworm infections.