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Abstract  

Fibers drawn form poly[2,2'-(m-phenylene)-5,5'-bibenzimidazole] (PBI) were studied by DSC and DMA. PBI is a high temperature polymer T g is between 387 and450C depending on the measurement technique used. The as-spun fiber is free of orientation. The oriented fiber exhibits considerable dependence on whether the DSC measurements were carried out in free-to-shrink or fixed-length modes. The β-relaxation is at 290C, and was associated with loss of water. The γ-transition at 20C was not identified, while theδ-transition at –90C seems to correspond to rotation of the m-phenylene ring.

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The nuclear energy cycle requires the recycling of nuclear fuel, water, chemical reagents, and the volume reduction of radioactive liquid wastes. A fundamental technique for continuous recovery of water using a thin-film evaporator was examined. Appropriate recovery measurements were: an evaporator heat temperature of 323 K, a feed rate of 0.23 cm3s−1, a vacuum pressure of 15 mmHg (2 kPa), and impeller rotational speeds of 500–600 rpm (min−1). The concentration of trace technetium and rhenium in aqueous solutions was also studied. A decontamination factor of 105 for rhenium was obtained.

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Using the nephelometric sedimentation analytical method, the emulsions dispersity was investigated. These emulsions were formed in a centrifugal extractor mixing chamber with different extraction systems: TBP in kerosene—HNO3 and TBP in CCl4−HNO3. The TBP and HNO3 concentration, the speed of rotation and the supply of the mixing chamber with the phases stream influence on the histeresis loop of the emulsion type and the emulsion dispersity was described. The foaminess of extraction systems was investigated, and the stabilizing influence of w/o emulsions on the foaminess was confirmed.

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Abstract  

Soil desinfestation with methyl bromide increases the uptake of bromine by plants. According to the tolerance regulations in the FRG only 30–50 ppm Br are allowed. The bromine uptake by plants depends on: (a) the fumigation technique (applied amounts, reaction time, date of cultivation); (b) the growing conditions (soil type, climate and irrigation); (c) the plants (species, rotation, harvesting time etc.). The INAA is a simple and rapid method to analyse bromine in vegetables within a wide range using80Br and82Br. Since several years this method was also used to control imported crops.

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Thermal analysis by classical molecular dynamics simulations is discussed on hand of heat capacity of crystals of 9600 atoms. The differences between quantum mechanical and classical mechanical calculations are shown. Anharmonicity is proven to be an important factor. Finally, it is found that defects contribute to an increase in heat capacity before melting. The energy of conformational gauche defects within the crystal is only about 10% due to internal rotation. The other energy must be generated by cooperative strain. The conclusion is that the next generation of faster computers may permit wider use of molecular dynamics simulations in support of the interpretation of thermal analysis.

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Abstract  

Rotating disc reactor (RDR) was constructed to conduct gas–liquid–solid reactions with controlled reagent transfer from gaseous to liquid phase. The concept is based on continuous formation of thin liquid films at a surface of rotating discs where the mass transfer proceed in diffusion–convective way. The reactor was employed to run precipitation reaction of CaCO3 via carbon dioxide absorption in lime slurry. During each reaction pH changes and Ca2+ concentration in time were measured. Disc rotations and gas flows were changed during the experiment and their influence on the obtained CaCO3 powders has been examined and fully discussed.

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Abstract  

The thermally induced structural transformation of a hydrogen-bonded crystal formed from an amphoteric molecule of 6-[2-methoxy-4-(pyridylazo)phenoxy]hexanoic acid MeO was studied using differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction measurement (XRD). Crystal form of the hydrogen-bonded crystal was measured by single crystal four circle diffractometer (Mo-Kα radiation). As a result, the crystal of MeO was stabilized by many C–H⋅⋅⋅O hydrogen bonds, and the C–H⋅⋅⋅O hydrogen bonds were broken by thermal energy reversibly. After transformation the supramolecular architecture was composed of supramolecular polymer including free-rotation pentamethylene main chains.

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Lymnaea are capable of learning an association between light and rotation. The conditioning paradigm to produce this association and the unconditioned escape response are the same for both Lymnaea and Hermissenda , but the underlying neural mechanisms appear to differ between the two species due to differences in the organization and function of their visuo-and vestibular-sensory systems. The RPeD11 interneuron in Lymnaea controls withdrawal behavior. We analyzed the electrophysiologic characteristics of the RPeD11 and observed an increase in cell excitability; that is, spontaneous activity of the postsynaptic potential in the RpeD11 was increased in conditioned animals after learning acquisition.

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Abstract  

Force generation in muscle during contraction arises from direct interaction of the two main protein components of the muscle, myosin and actin. The process is driven by the energy liberated from the hydrolysis of ATP. In the presence of CaATP the energy released from hydrolysis produces conformational changes in myosin and actin, which can be manifested as an internal motion of myosin head while bound to actin. It is suggested that myosin heads attached to actin produce conformational changes during the hydrolysis process of ATP, which results in a strain in the head portion of myosin in an ATP-dependent manner. These structural changes lead to a large rotation of myosin neck region relieving the strain. Paramagnetic probes and EPR spectroscopy provide direct method in which the rotation and orientation of specifically labelled proteins can be followed during muscle activity. In order to find correlation between local and global structural changes in the intermediate states of the ATPase cycle, the spectroscopic measurements were combined with DSC measurements that report domain stability and interactions. In the review a detailed description of the application of EPR and DSC techniques in muscle protein research will be given. The measurements show that the small local structural changes detected by EPR after nucleotide binding influence the global structure of protein system responsible for muscle contraction.

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The relaxation spectra in polymers arise from the existence of many possible modes for dissipating the strain energy raised by the imposed force. These modes are made up by coupling the simplest and fastest mode of relaxation involving the rotation of a conformer, typically represented by the picosecond rotation of the carbon to carbon bond. This fast relaxation process cannot take place easily in the condensed state crowded by the densely packed conformers, necessitating cooperativity among them. The domain of cooperativity grows at lower temperatures, toward the infinite size at the Kauzman zero entropy temperature. From the temperature dependence of the domain size, the well-known Vogel equation is derived, which is numerically equivalent to the empirical WLF and free volume equations. The molar volume is a crucial factor in determining the molar free volume and, therefore, in determining theT g of a material. The molar ΔC P is proportional to the logarithmic molar volume, and is greater for a polymer with a higherT g, but ΔC P per gram for it is smaller, as it is proportional to (logM) divided byM, whereM is the molecular weight of the conformer.

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