Vision-based flight control in the hawkmoth Hyles lineata

Vision is a key sensory modality for flying insects, playing an important role in guidance, navigation and control. Here, we use a virtual-reality flight simulator to measure the optomotor responses of the hawkmoth Hyles lineata, and use a published linear-time invariant model of the flight dynamics to interpret the function of the measured responses in flight stabilization and control. We recorded the forces and moments produced during oscillation of the visual field in roll, pitch and yaw, varying the temporal frequency, amplitude or spatial frequency of the stimulus. The moths’ responses were strongly dependent upon contrast frequency, as expected if the optomotor system uses correlation-type motion detectors to sense self-motion. The flight dynamics model predicts that roll angle feedback is needed to stabilize the lateral dynamics, and that a combination of pitch angle and pitch rate feedback is most effective in stabilizing the longitudinal dynamics. The moths’ responses to roll and pitch stimuli coincided qualitatively with these functional predictions. The moths produced coupled roll and yaw moments in response to yaw stimuli, which could help to reduce the energetic cost of correcting heading. Our results emphasize the close relationship between physics and physiology in the stabilization of insect flight.     

Copper Oxide Precipitates in NBS Standard Reference Material 482

Copper oxide has been detected in the copper containing alloys of NBS Standard Reference Material (SRM) 482. This occurrence is significant because it represents heterogeneity within a standard reference material that was certified to be homogeneous on a micrometer scale. Oxide occurs as elliptically to spherically shaped precipitates whose size differs with alloy composition. The largest precipitates occur in the Au20-Cu80 alloy and range in size from submicrometer up to 2 μm in diameter. Precipitates are observed using light microscopy, electron microscopy, and secondary ion mass spectrometry (SIMS). SIMS has demonstrated that the precipitates are present within all the SRM 482 wires that contain copper. Only the pure gold wire is precipitate free. Initial results from the analysis of the Au20-Cu80 alloy indicate that the percentage of precipitates is less than 1 % by area. Electron probe microanalysis (EPMA) of large (2 μm) precipitates in this same alloy indicates that precipitates are detectable by EPMA and that their composition differs significantly from the certified alloy composition. The small size and low percentage of these oxide precipitates minimizes the impact that they have upon the intended use of this standard for electron probe microanalysis. Heterogeneity caused by these oxide precipitates may however preclude the use of this standard for automated EPMA analyses and other microanalysis techniques.     

Time-course and reversibility of the hypoxia-induced alterations in cerebral vascularity and cerebral capillary glucose transporter density

The adult rat adapts to prolonged moderate hypobaric hypoxia by polycythemia, increased brain vascularity, and increased density of the brain capillary glucose transporter (GLUT-1). We now report on the time-course and reversibility of these adaptive alterations. Adult male Wistar rats were subjected to hypobaric hypoxia at 0.5 atmosphere for periods of 4 days or 1, 2 or 3 weeks, and compared to normoxic littermate controls. Reversibility of the effects of hypoxia was studied in rats subjected to hypobaric hypoxia for 3 weeks and then allowed to recover at normobaric conditions for 3 additional weeks. Cerebral vascularity was studied in cross-sections of the cerebral cortex that were immunocytochemically stained with a GLUT-1 antibody. The density of GLUT-1 was determined in isolated cerebral microvessels by quantitative autoradiography of immunoblots. Blood hematocrit and cerebral microvascularity did not significantly increase after 4 days of hypoxia, but were significantly increased at 1, 2 and 3 weeks of hypoxia. Three weeks of normoxic recovery after 3 weeks of hypoxia reversed the polycythemia and cerebral hypervascularity. However, the density of GLUT-1 in isolated cerebral microvessels, which was significantly increased after 1 and 3 weeks of hypoxia, remained elevated after 3 weeks of normoxia.     

Alteration of oestradiol metabolism in myc oncogene-transfected mouse mammary epithelial cells

Targeted overexpression of the c-myc oncogene induces neoplastic transformation in immortalized, non-tumorigenic mouse mammary epithelial cells (MMEC). Experiments in the present study were conducted to examine whether cellular transformation induced by c-myc oncogene is associated with altered metabolism of 17beta-oestradiol (E2). The parental, MMEC and the stable c-myc transfectant (MMEC/myc3) cell lines were compared for major oestrogen metabolic pathways, namely E2 and E1 interconversion, and C2- and C16alpha-hydroxylation by both high-pressure liquid chromatography (HPLC) analysis and the 3H release assay using specifically labelled [C2-3H]E2 or [C16alpha-3H]E2. The reductive conversion of E1 to E2 was about 14-fold and 12-fold higher than the oxidative conversion of E2 to E1 in MMEC and MMEC/myc3 cells respectively. However, in MMEC/myc3 cells, both reductive and oxidative reactions were decreased by about 32% and 12% relative to those seen in the parental MMEC cells (P = 0.0028). The extent of C16alpha-hydroxylation was increased by 164.3% (P < 0.001), with a concomitant 48.4% decrease (P < 0.001) in C2-hydroxylation in MMEC/myc3 cells; this resulted in a fourfold increase in the C16alpha/C2 hydroxylation ratio in this cell line. Thus, a persistent c-myc expression, leading to aberrant hyperproliferation in vitro and tumorigenesis in vivo, is associated with an altered oestrogen metabolism. However, it remains unclear whether this represents a result of oncogene expression/activation or is rather a consequence of phenotypic transformation of the cells.     

Comparison of three DNA extraction methods on bone and blood stains up to 43 years old and amplification of three different gene sequences

The objective of this study was to determine the effects of cellobiose and monensin on the in vitro fermentation of organic acids (L-aspartate, fumarate, and DL-malate) by mixed ruminal bacteria. Ruminal fluid was collected from a steer fed 36.7 kg of forage and 4.5 kg of concentrate supplement once per day. Ruminal fluid was centrifuged to sediment feed particles and protozoa, and the resulting supernatant, which contained bacteria, was added (33%, vol/vol) to anaerobic media (500 ml). Incubations (n = 2) were performed in batch culture at 39 degrees C and sampled at 0, 2, 4, 6, 8, 12, and 24 h. Organic acids were added to achieve a final concentration of 7.5 mM. Cellobiose was added to obtain a final concentration of 5 mM, and monensin dissolved in ethanol was included at concentrations of 0 or 5 ppm. Addition of cellobiose to organic acid fermentations increased the rate of organic acid utilization by the mixed bacterial population. Total concentrations of volatile fatty acids were increased by the addition of cellobiose to all fermentations. A lag period (< or = 8 h) occurred in fermentations that were treated with monensin before organic acids were utilized. Total concentrations of volatile fatty acids were increased, and the acetate to propionate ratio was decreased, by monensin treatment. When cellobiose and monensin were added together, propionate production and organic acid utilization were increased. Both cellobiose and monensin affected the in vitro fermentation of organic acids by mixed ruminal bacteria by providing a carbon and energy source and by influencing electron disposal.     

Effect of Substructure on the Thermoelectric Power of aβ-Quenched ZrCrFe Alloy

β-quenching a Zr-1.15 wt％Cr-0.10 wt％Fe alloy produces a martensitic or a Widmanst(a|¨)tten transforma-tion morphology,or a mixture of the two,depending on the cooling rate.For the Widmanst(a|¨)tten structure,orthe mixed martensitic-Widmanst(a|¨)itten structure,a grain boundary phase is observed at most prior-β grainboundaries.X-ray line broadening analysis and the thermoelectric power(TEP)measurements of thesequenched samples show that not only the solubility of alloying elements in α-Zr matrix,but also substructure(microstrain,crystallite size and dislocation density)have an effect on TEP.Thus,TEP measurements are verywell suited for following the structural transformations taking place in Zr alloys during fabrication.     

The effect of cooking temperature and applied pressure on the release of liquor from fish

The effect of cooking temperature and applied pressure was investigated to determine the condition for optimum release of liquor from fish normally used in the manufacture of fish meal in the UK. Fish was cooked at 60, 80 and 100°C and the release of liquor during cooking was measured. The cooked material was subjected to pressures of 1–2, 50 and 100 kg/cm² and the amount of liquor released during each stage of pressing was also measured. Analyses for moisture, oil and solids content of the liquors and resulting press cake are recorded and also the reduction in volume occurring after pressing. The results show that an increase in the cooking temperature increases the release of liquor and the magnitude of the increase is dependent on the species and its quality. Also up to 80% of the total liquor was released by applying a pressure of 1–2 kg/cm².