Changes of colour and pH in fish musculature after ionizing radiation exposure

Irradiation of meat causes sensory changes as do other technological methods. The most significant sensory and quality indicator of meat is colour; therefore, the effect of irradiated pieces of fish was studied in relation to colour changes. Colour was measured at the musculature of Oncorhynchus mykiss. The parameters of colour, L*, a* and b*, were determined with the portable Superchroma S-Spex (Braive) spectrophotometer in the CIELAB system before irradiation (3 h post mortem) and after irradiation (⁶⁰Co source, a dose of 3 kGy and a dose rate of 3.33 kGy h^–1) (5 h post mortem). The change of L* was identical for both irradiated and nonirradiated samples. This change may be caused by maturation of fish flesh. a* was identical and b* decreased. This effect differs from that of irradiated pork. The decrease of the pH was identical for both irradiated and nonirradiated samples. This change may be caused by maturation of fish flesh.     

Crown ether bridged homo- and heterodinuclear copper(II) and nickel(II) cyclidene complexes: Interaction with anions

Homodinuclear (3CuCu, 3NiNi) and heterdionuclear (3CuNi) cyclidene complexes linked by two 1,10-diaza-18-crown-6 ethers were synthesized and their properties characterized. For the 3CuCu in the negative potential range the mixed-valence state Cu^I-Cu^II was observed and the comproportionation constants were determined. The redox potentials of M^II/III showed a good correlation with DN of the solvent. In acetonitrile solution containing 0.1 mol dm⁻³ Bu₄NPF₆ reversible M^II/III redox processes were observed. However, in the presence of stronger ion pairing anions (e.g. BF₄⁻ and ClO₄⁻) the “potential inversion” occurred. Redox potentials of dinuclear complexes were compared with mononuclear cyclidene complexes. The influence of selected anions (Cl⁻ and NO₃⁻) on the redox process M^II/III was studied. The effect of Cl⁻ anion was different for 3CuCu and 3NiNi. In 3CuCu coordination of two chloride anions took place after oxidation of copper centers. In the 3NiNi complex two Cl⁻ anions were coordinated to one of the nickel(II) centers facilitating oxidation, at different potentials, of both nickel(II) cations. The behaviour of heteronuclear complex with Cl⁻ anions was similar to 3NiNi. All dinuclear complexes interacted with NO₃⁻ anions and the observed potential shifts were larger for nickel(II) than for copper(II) cations.     

Exploration of the transition temperatures and crystal structure of highly crystalline poly(1,3-cyclohexadiene): An experimental and computational investigation

Experimental determination of transition temperatures for highly crystalline polymers such as poly-1,3-cyclohexadiene (PCHD) can be difficult due to reduced solubility and thermalization processes which occur during data acquisition. In order to facilitate further understanding of these processes for PCHD, density functional theory (DFT) and molecular dynamics (MD) were used in conjunction with differential scanning calorimetry (DSC) and powder X-ray diffraction (XRD) to explore the oligomer microstructures, the crystal structure, and the temperature dependence of the specific volume (1/ρ). DFT geometry minimizations on isolated oligomers were used to identify the lowest energy confirmer; revealing that alternating R,R and S,S chiral bonds between monomer units afford the lowest energy structure. MD simulations of crystalline PCHD were constructed so as to replicate the experimental XRD pattern of crystalline PCHD, with the best fit producing a monoclinic crystal structure. The temperature dependence of the specific volume derived from MD simulations provided insight into the glass/vitrification (T_g) and melting (T_m) transition temperatures. Comparison of the simulation transition temperatures with differential scanning calorimetry data of PCHD polymerized with Ni(acac)₂/MAO shows good agreement and solidifies the fidelity of the newly defined PCHD crystalline structure.     

Electrochemical behaviour of tetraazamacrocyclic nickel(II) complexes functionalized with crown ethers

Tetraazamacrocyclic nickel(II) complexes linked by the system of conjugated double bonds with one or two benzo-15-crown-5 moieties (2Ni and 3Ni) were synthesized and characterized. The CV of these complexes in acetonitrile (ACN) solution exhibited reversible Ni^II/III redox process. At more positive potentials oxidation of the bezno-15-crown-5 ether (B15C5) moiety was found. In complexes 2Ni and 3Ni redox potential of Ni^II/III did not change after the interactions of alkali and alkaline earth metal cations with B15C5 unit. However, the presence of guest cations caused a significant change of B15C5 oxidation potential. Complexation of two Cl⁻ anions to the coordinated Ni^II in 2Ni and 3Ni resulted in an appreciable shift of both Ni^II/III and B15C5 redox processes after addition of metal cations. Behaviour of complexes 2Ni and 3Ni was compared with behaviour of similar Cu^II complexes.     

Interaction of hydrocolloid networks with mono- and oligosaccharides

Summary The presented research covers the investigation on the interaction of basic mono- (D-glucose, D-fructose) and a disaccharide (saccharose) with two of the most used hydrocolloids, i.e. guar gum and xanthan. As a basic model the 50% water solution of an appropriate carbohydrate with 1%wt. of a hydrocolloid was chosen. Viscoelastic measurements were carried out at different temperatures. The analysis covered the time-temperature superposition method and fitting the continuous Maxwell model to the experimental data.     

Modeling supply and return line dynamics for an electrohydraulic actuation system

This paper presents a model of an electrohydraulic fatigue testing system that emphasizes components upstream of the servovalve and actuator. Experiments showed that there are significant supply and return pressure fluctuations at the respective ports of the servovalve. The model presented allows prediction of these fluctuations in the time domain in a modular manner. An assessment of design changes was done to improve test system bandwidth by eliminating the pressure dynamics due to the flexibility and inertia in hydraulic hoses. The model offers a simpler alternative to direct numerical solutions of the governing equations and is particularly suited for control-oriented transmission line modeling in the time domain.     

Polymer–leather composites. IV. Mechanical properties of selected acrylic polymer–leather composites

An extensive study was made of the mechanical properties of the polymer–leather composite materials reported in previous articles. Polymer was deposited into leather by both emulsion and bulk (or solution) polymerization. Either methyl methacrylate, n-butyl acrylate, or a fixed comonomer mixture of n-butyl acrylate and methyl methacrylate were used over the widest feasible range of composition. Tensile strengths, in analogy with many polymer-treated fibers, were generally smaller than untreated controls, but entensions to break remained fairly constant as composition changed. Polymer–leather composites prepared by both methods were rheologically similar when correlated against the volume fraction of the polymer used. Relative tensile and torsional moduli were greater than unity at small volume fractions of polymer, but higher compositions assumed more of the viscoelastic characteristics of the modifying polymer. The constancy of the glass transition temperature of the polymeric component as composition changed indicated poor domain interactions. However, residual porosity reduced low-temperature moduli anomalously. A modified Halpin–Tsai equation was proposed that qualitatively predicted moduli increase by incremental space filling as either fiber aggregation (from simple air drying of untreated controls) or polymer content increased. The simultaneous rheological dependence of polymer–fiber interactions in composites was also accounted for by the equation.     

Expectation and reality in freshman adjustment to college.

Earlier investigations of the "freshman myth" have focused on the differences between expectations and perceptions of the college environment and have shown that entering students typically anticipate more from that environment than is subsequently realized. The present study examined differences between expectations and perceptions of self-assessed adjustment to college to determine whether students also expect more of themselves than is subsequently realized. Occurrence of the myth in this new form was found among college freshmen at 2 colleges. A college adjustment scale was completed by 185 Ss before entering school, in the 8th wk of the 1st semester, and in the 5th wk of the 1st semester at one school. At the other school, an expectations scale was completed by 172 Ss during the orientation period prior to beginning the academic year. The adjustment scale was completed by 258 Ss in the 8th wk of the 2st semester. 123 Ss completed both scales. Differences in occurrence of the myth in various aspects of the adjustment are described, and the possibility of differences in occurrence at the 2 colleges is considered. Evidence concerning the course of the myth over time is presented, and individual differences in and behavioral correlates of the myth are identified. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modelling the movement of a two-link manipulator

An algorithm for optimizing the control signal for simple movements of a two-link manipulator with four degrees of freedom is described. Based on the typical movement and functions of upper human extremities, the manipulator (so-called anthropomorphic manipulator) is composed of two links. The motion of the links is developed by four driving motors. The mathematic model is based of the Lagrange equations of the IInd king. The minimization of the time of movement with initial limitation of accuracy is obtained and the error of the final position is minimized without changing the time-optimal criterion. The relations connected with minimalization of both quality factors are considered. At the same time, the algorithm optimizes the torque distribution between the actuators which drive each link of manipulator. As well the manipulator as its activity are modelled on the digital computer. The results of the computer simulation of the algorithm, and the modelling of the time and accuracy optimal control, are presented.     

Measuring adjustment to college.

A 52-item self-report Likert-type scale, yielding indices of 4 aspects of adjustment as well as a full-scale score, was developed and administered once each semester in each of 3 successive academic years to samples of freshman students (N?=?734). Reliability data for the scale as a whole and for the several subscales individually are presented, and validity was assessed through examination of the relationship between the subscales and several independent variables expected to be differentially relevant to the subscales. Implications for use of the scale in counseling and other remedial interventions are discussed. (46 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)