ALBERT

Notes: Summary Chitosan-acetic acid complex membrane and several chitosan-polymer complex membranes have been prepared and the gas permeabilities of these membranes have been examined. It has been found that chitosan-acetic acid complex membrane shows high permselectivities for oxygen and carbon dioxide, and synthetic polymers can modify the permeation behavior of chitosan membrane for oxygen and carbon dioxide. The separation factor αCO2/O2 of these membranes were much smaller than unity, indicating possible applications for the preservations of fruits and vegetables. It has been noticed that the permeation behaviors of these membranes are markedly influenced by metal ions added into the membranes and the membranes have good mechanical strength.

Notes: Abstract Green peach aphids Myzus persicae from the Beijing region, maintained on greenhouse tobacco plants, were reared on modified artificial diet; sinigrin, tomatine, nicotine, gossypol, phlorizin, inulin and malic acid were added separately in concentrations of 0.1% or 0.2%. In preference tests none of the diets enriched by secondary substances was more acceptable than the basal diet. Diet uptake during larval development was determined quantitatively by using C14 glycine in the diets. For the basal diet the total uptake during larval development was about 1.16 μl/aphid. The addition of secondary plant substances to the diet caused reductions of uptake to different degrees in the order: nicotine〉phlorizin〉gossypol〉tomatine〉malic acid〉inulin〉sinigrin. The larvae feeding on diets containing sinigrin or tomatine from the second day after birth seemed to have a much higher tolerance for sinigrin than tomatine, with a mortality of 9.6% within 7 days of rearing for the former and 89.4% for the latter. Hence this aphid differs from that occurring in the Netherlands in that the latter has a higher tolerance towards tomatine. The addition of inulin, malic acid or sinigrin did not cause a significant difference in the rate of larval development or in adult longevity. Diets containing these substances could support the aphid's development and reproduction for at least three generations.

Notes: Abstract We make use of Chern-Simons cohomology and the family index theorem to deal with two-dimensional anomalies, infinite-dimensional algebras and their relations. We also take advantage of Zweibein formulation to treat the world sheet trace anomaly and Virasoro algebra in Polyakov string and to show how the anaomaly-free condition gives rise to the critical dimensions.

Notes: Abstract Mean projected ranges of Hg+ implanted at energies from 50 to 400 keV in aluminium are measured by MeV4He+ Rutherford backscattering. The obtained projected ranges and other previous results of Br+ and Hg+ implanted in silicon, quartz crystal and glass are compared with Biersack's angular diffusion model. The results show that there is good agreement between the experimental and calculated mean projected ranges to within experimental error.

Notes: Abstract The space chages formed in the process of photorefraction in LiNbO3 crystals is visualised by charged powder techniques. The results confirmed the existence of space charge carriers at the periphery of the illuminated region with negative charge carriers in the +z periphery and positive in the −z. The observed patterns on the surface of LiNbO3-Fe (0.05%) crystal illuminated with higher light intensities presented discharge-like features, namely traces of discharge in the medium at the crystal surface. The correlation between the kinetics curves of birefringence changeΔn(t) and the revealed surface patterns indicated that electric breakdown of the medium at the surfaces was responsible for the periodic reduction ofΔn(t).

Notes: Abstract It is shown that Ω(n 2) distinct moves may be necessary to move a line segment (a “ladder”) in the plane from an initial to a final position in the presence of polygonal obstacles of a total ofn vertices, and that Ω(n 4) moves may be necessary for the same problem in three dimensions. These two results establish lower bounds on algorithms that solve the motion-planning problems by listing the moves of the ladder. The best upper bounds known areO(n 2 logn) in two dimensions, andO(n 5 logn) in three dimensions.

Notes: Summary Two species of feather mites, Alloptes (A.) sp. and Laronyssus martini, coexisted on the flight feathers of kittiwakes, while Alloptes (C.) sp. occurred alone on murres. All three species were found mostly on the ventral surface of mid-wing regions. On individual feathers, the mites were attached to the distal sides of barbs on the trailing vanes. The two species coexisted on kittiwakes but occupied different portions of feathers. The results suggest that the two species compete for the attachment site on the feather and Alloptes (A.) sp. is excluded by L. martini from the preferred microhabitat.

Notes: Abstract The visual system of the fly is able to extract different types of global retinal motion patterns as may be induced on the eyes during different flight maneuvers and to use this information to control visual orientation. The mechanisms underlying these tasks were analyzed by a combination of quantitative behavioral experiments on tethered flying flies (Musca domestica) and model simulations using different conditions of oscillatory large-field motion and relative motion of different segments of the stimulus pattern. Only torque responses about the vertical axis of the animal were determined. The stimulus patterns consisted of random dot textures (“Julesz patterns”) which could be moved either horizontally or vertically. Horizontal rotatory large-field motion leads to compensatory optomotor turning responses, which under natural conditions would tend to stabilize the retinal image. The response amplitude depends on the oscillation frequency: It is much larger at low oscillation frequencies than at high ones. When an object and its background move relative to each other, the object may, in principle, be discriminated and then induce turning responses of the fly towards the object. However, whether the object is distinguished by the fly depends not only on the phase relationship between object and background motion but also on the oscillation frequency. At all phase relations tested, the object is detected only at high oscillation frequencies. For the patterns used here, the turning responses are only affected by motion along the horizontal axis of the eye. No influences caused by vertical motion could be detected. The experimental data can be explained best by assuming two parallel control systems with different temporal and spatial integration properties: TheLF-system which is most sensitive to coherent rotatory large-field motion and mediates compensatory optomotor responses mainly at low oscillation frequencies. In contrast, theSF-system is tuned to small-field and relative motion and thus specialized to discriminate a moving object from its background; it mediates turning responses towards objects mainly at high oscillation frequencies. The principal organization of the neural networks underlying these control systems could be derived from the characteristic features of the responses to the different stimulus conditions. The input to the model circuits responsible for the characteristic sensitivity of the SF-system to small-field and relative motion is provided by retinotopic arrays of local movement detectors. The movement detectors are integrated by a large-field element, the output cell of the network. The synapses between the detectors and the output cells have nonlinear transmission characteristics. Another type of large-field elements (“pool cells”) which respond to motion in front of both eyes and have characteristic direction selectivities are assumed to interact with the local movement detector channels by inhibitory synapses of the shunting type, before the movement detectors are integrated by the output cells. The properties of the LF-system can be accounted for by similar model circuits which, however, differ with respect to the transmission characteristic of the synapses between the movement detectors and the output cell; moreover, their pool cells are only monocular. This type of network, however, is not necessary to account for the functional properties of the LF-system. Instead, intrinsic properties of single neurons may be sufficient. Computer simulations of the postulated mechanisms of the SF-and LF-system reveal that these can account for the specific features of the behavioral responses under quite different conditions of coherent large-field motion and relative motion of different pattern segments.