Modeling of the electrostrictive, dielectric, and piezoelectric properties of ceramic PbTiO(3)

The upper and lower limits of the electrostrictive constants, dielectric permittivities, spontaneous polarizations, and piezoelectric coefficients were calculated for ceramic PbTiO(3) from theoretical single-crystal constants. Experimental ceramic data fall between these upper and lower limits. The large piezoelectric anisotropy d(33)/d(31) of ceramic PbTiO(3 ) was shown to be related to the single-crystal PbTiO(3) electrostrictive anisotropies Q(11)/Q(12 ) and Q(44)/Q(12). The possibility of a change in sign of the ceramic d(31) coefficient due to a slight variation in the single-crystal electrostrictive anisotropies was discussed. The single-crystal and predicted ceramic hydrostatic electrostrictive constants were found to be equal. Using this result the ceramic hydrostatic g(h ) coefficient is always smaller than the single-crystal g (h), but the ceramic hydrostatic d(h) coefficient can be either larger or smaller than the single-crystal d(h) depending on the dielectric anisotropy (epsilon (11)/epsilon(33)) of the single-crystal.     

The effects of various post-mortem treatments on certain physical and sensory properties of three different bovine muscles

Sixty crossbred steers with chronological ages approximating 15 months, carcass weights approximating 270 kg and subcutaneous fat thickness measurements approximating 1·2 cm, were maintained for approximately 210 days on a constantly increasing concentrate ration (13 to 75%, according to NAS nutrient requirements for beef cattle; NAS, 1976). These animals were utilized to evaluate the effects of delayed chilling, hot-boning and electrical stimulation on certain physical, histological, biochemical and sensory properties of three different muscles (Semimembranosus, SM; Longissimus dorsi, LD; and Triceps brachii, TB). Results indicated that neither delayed chilling nor electrical stimulation produced consistent meaningful alterations in any of the physical, cooking or palatability attributes evaluated. However, early post-mortem excision of muscle (hot-boning) consistently produced toughening in all of the muscles evaluated. This was observed to a much greater degree in the TB than in either the SM or LD. Based upon sarcomere length determinations, such toughening could be attributed to cold shortening only in the TB. Electrical stimulation of excised muscle was ineffective in preventing or offsetting this toughening. The delayed chilling treatment imposed (2 h at 12·5°C) was ineffective in enhancing potential effects of electrical stimulation on tenderness.     

First Identification of a Putative Sex Pheromone in a Praying Mantid

Praying mantids are models for a wide variety of behavioral, physiological, and ecological studies, and sex pheromones have been assumed to be important components of their biology. However, no mantid pheromone has ever been identified. We collected volatiles emitted by females of the mantid, Sphodromantis lineola, via solid phase microextraction (SPME). Mass spectral analysis revealed the collected volatiles to be a mixture of pentadecanal and tetradecanal. We prepared a synthetic mixture of these compounds, and found that males were both attracted to this mixture and stimulated to exhibit typical precopulatory behavior. We then examined male antennae with scanning electron microscopy, and confirmed the presence of porous antennal sensilla typical of insect pheromone receptors, i.e., that male mantids are equipped with the appropriate morphological apparatus to receive volatile chemical signals. Pheromones, in conjunction with visual and tactile cues, are thus an important feature of the reproductive biology of this, and undoubtedly other species of mantids. In addition to adding a crucial aspect of behavioral biology to our knowledge of this group, identification and synthesis of mantid pheromones may be a first step in attracting and aggregating these generalist predators for use in pest control.     

Effects of molasses grass,Melinis minutiflora volatiles on the foraging behavior of the cereal stemborer parasitoid,Cotesia sesamiae

Olfactory responses of the cereal stemborer parasitoid Cotesia sesamiae to volatiles emitted by gramineous host and nonhost plants of the stemborers were studied in a Y-tube olfactometer. The host plants were maize (Zea mays) and sorghum ( Sorghum bicolor), while the nonhost plant was molasses grass (Melinis minutiflora). In single-choice tests, females of C. sesamiae chose volatiles from infested and uninfested host plants and molasses grass over volatiles from the control (soil). In dual-choice tests, the wasp preferred volatiles from infested host plants to those from uninfested host plants. There was no discrimination between molasses grass volatiles and those of uninfested maize, uninfested sorghum, or infested maize. The wasp preferred sorghum volatiles over maize. Combining uninfested maize or sorghum with molasses grass did not make volatiles from the combination more attractive as compared to only uninfested host plants. Infested maize alone was as attractive as when combined with molasses grass. Infested sorghum was preferred over its combination with molasses grass. Local growth conditions of the molasses grasses influenced attractiveness to the parasitoids. Volatiles from Thika molasses grass were attractive, while those from Mbita molasses grass were not. Growing the Thika molasses grass in Mbita rendered it unattractive and vice versa with the Mbita molasses grass. This is a case of the same genotype expressing different phenotypes due to environmental factors.