Ferromagnetic shape memory flapper

A new method for propulsion using a Ni₂MnGa ferromagnetic shape memory flapper is introduced. We optically examine the magnetic field induced strain of pure shear by means of a state of the art generator that provides alternating magnetic fields of 7000 Oe at frequencies of up to 100 Hz. Preliminary measurements show local shear deformation of about 5%, which open new frontiers in propulsion mechanisms.     

Changes in chemical constituents during the maturation and ripening of two commercially important pomegranate accessions

Pomegranate juice is well known for its health beneficial compounds. This study was undertaken to investigate changes in the major chemical composition in arils and peels during fruit maturation in two Israeli commercial accessions, ‘Wonderful’ and ‘Rosh-Hapered.’ In both accessions, the levels of total phenolic, antioxidant activity and hydrolysable tannins were reduced in the peels during maturation, while the anthocyanin level increased. The results show that the sugar content in the aril juice increased in both accessions while the levels of acidity and of citric acid decreased. However, these two accessions differed in other parameters in the aril juice, i.e., while the antioxidant and total phenolic contents significantly decreased in ‘Rosh-Hapered’, these changes were not observed in ‘Wonderful’. The anthocyanin level, however, increased in ‘Wonderful’ but did not change in ‘Rosh-Hapered.’ This knowledge could help establish the optimum harvest date ensuring the maximum nutritional properties of pomegranates.     

The peak sidelobe of the phased array having randomly located elements

A formula is derived for the peak sidelobe level of a phased array in which the elements are randomly located. The parameters of the formula are the number and size of the array elements, size of the array, wavelength, beamsteering angle, and signal bandwidth. The theory is tested by measurement of the peak sidelobe of several hundred computer-simulated random arrays. Unlike the case for the conventional array the effect of spatial taper (nonuniform density of element location) upon the peak sidelobe level is minor. The peak sidelobe of the two-dimensional planar array is approximately 3 dB higher than that of the linear array of the same length and same number of elements.     

Synthetic fuels and fusion

The decreasing availability of fossil fuels emphasizes the need to develop systems which will produce synthetic fuel to substitute for and supplement the natural supply. An important first step in the synthesis of liquid and gaseous fuels is the production of hydrogen. Thermonuclear fusion offers an inexhaustible source of energy for the production of hydrogen from water. Depending on design, electric generation efficiencies of 40–60% and hydrogen production efficiencies by high temperature electrolysis of 50–70% are projected for fusion reactors using high temperature blankets. Fusion/coal symbiotic systems appear economically promising for the first generation of commercial fusion synfuels plants. Coal production requirements and the environmental effects of large-scale coal usage would be greatly reduced by a fusion/coal system. In the long-term, there could be a gradual transition to an inexhaustible energy system based solely on fusion.     

Impact of natural organic matter (NOM) on freshwater amphipods

Natural organic matter (NOM) isolated from the eutrophic Sanctuary Pond (Point Pelee National Park, Canada) has an adverse impact on amphipod species (Gammarus tigrinus and Chaetogammarus ischnus from Lake Müggelsee, Germany, and Eulimnogammarus cyaneus, from Lake Baikal, Russia). Increases in amphipod mortality, changes in peroxidase activity and increases of heat shock protein (hsp70) expression were observed upon exposure to NOM. The highest resistance to the adverse impact of NOM was observed with the endemic Baikalian amphipod E. cyaneus. However, the mechanisms behind this finding remains obscure. If differences in the sensitivity of the hsp70 antibody may be excluded, different modes of action may be postulated: because the adverse impact of NOM may be caused by reactive oxygen species (ROS) and the NOM itself, the observed differences may be due to the action of ROS alone (with E. cyaneus) and a combination of both adverse modes of action (European species).     

Sensitivity analysis of narrowband photonic crystal filters and waveguides to structure variations and inaccuracy

Photonic crystal microcavities, formed by local defects within an otherwise perfectly periodic structure, can be used as narrowband optical resonators and filters. The coupled-cavity waveguide (CCW) is a linear array of equally spaced identical microcavities. Tunneling of light between microcavities forms a guiding effect, with a central frequency and bandwidth controlled by the local defects' parameters and spacing, respectively. We employ cavity perturbation theory to investigate the sensitivity of microcavities and CCWs to random structure inaccuracies. For the microcavity, we predict a frequency shift that is due to random changes in the lattice structure and show an approximate linear dependence between the standard deviation of the structure inaccuracy and that of the resonant frequency. The effect of structural inaccuracy on the CCW devices, however, is different; it has practically no effect on the CCW performance if it is below a certain threshold but may destroy the CCW if this threshold is exceeded.     

Chiasma interference as a function of genetic distance

For many organisms, meiotic double crossing over is less frequent than expected on the assumption that exchanges occur at random with respect to each other. This "interference," which can be almost total for nearby intervals, diminishes as the intervals in which the double crossovers are scored are moved farther apart. Most models for interference have assumed, at least implicitly, that the intensity of interference depends inversely on the physical distance separating the intervals. However, several observations suggest that interference depends on genetic distance (Morgans) rather than physical distance (base pairs or micrometers). Accordingly, we devise a model in which interference is related directly to genetic distance. Its central feature is that recombinational intermediates (C's) have two fates--they can be resolved with crossing over (Cx) or without (Co). We suppose that C's are distributed at random with respect to each other (no interference); interference results from constraints on the resolution of C's. The basic constraint is that each pair of neighboring Cx's must have between them a certain number of Co's. The required number of intervening Co's for a given organism or chromosome is estimated from the fraction of gene conversions that are unaccompanied by crossover of flanking markers. The predictions of the model are compared with data from Drosophila and Neurospora.     

The thrombin receptor elevates intracellular calcium in adult rat ventricular myocytes

While there is evidence that thrombin receptor activation leads to contractile dysfunction and induces arrhythmias in ischemic/reperfused cardiac tissue, thrombin is variably reported to modulate intracellular calcium in cardiomyocytes. The present study demonstrates that thrombin receptor activation leads to a rise in intracellular calcium in adult ventricular myocytes and serves to reconcile previous discrepant findings. The thrombin receptor-derived agonist peptide (SFLLRN, a portion of the tethered ligand created by thrombin's proteolytic actions) increases cytosolic calcium and twitch amplitude in cardiomyocytes isolated from adult ventricles. The truncated control peptide FLLRN has no effect, establishing that the response to SFLLRN results from a specific agonist peptide-receptor interaction. However, the response to SFLLRN occurs only at high agonist peptide concentrations and thrombin itself is inactive. This result is not compatible with an action of SFLLRN at a distinct protease-activated receptor (PAR-2; which is activated by SFLLRN, but not by thrombin), since SLIGRL (a ligand which is selective for PAR-2, but not the thrombin receptor) has no effect. Rather, the enzyme-based cell isolation procedure may partially cleave the thrombin receptor and influence cell responses, since concentrations of SFLLRN which are sub-threshold in enzymatically disaggregated myocytes significantly increase the force of isometric contraction of intact rat papillary muscles. These studies provide the first evidence that thrombin receptor activation leads to a change in intracellular calcium and a positive inotropic response in adult ventricular myocardium.