PHOTOMORPHOGENESIS IN Penicillium isariaeforme: EXOGENOUS CALCIUM SUBSTITUTES FOR LIGHT

Abstract— Penicillium isariaeforme is a photomorphogenic fungus which produces upright bundles of conidia-bearing mycelia (called coremia) when grown on a defined medium in visible (450–500 nm) light. We found that exogenous Ca²⁺ ions could substitute for light. In the dark 1–2 m M Ca²⁺ triggered coremia formation. Dark induction of coremia was specific for Ca²⁺ in that it could not be duplicated by 50 m M Ba²⁺, Fe²⁺, Mg²⁺, Mn²⁺, Sr²⁺, or Zn²⁺. Additionally, light-induced coremia formation was inhibited by both KI (2.5 m M ) and phenylacetic acid (0.25 m M ).     

MODELING THE MOVEMENTS OF COWBIRDS: APPLICATION TOWARDS MANAGEMENT AT THE LANDSCAPE SCALE

ABSTRACT. Brood parasitism by brown‐headed cowbirds (Molothrus ater) reduces the reproductive success of two endangered bird species at Fort Hood, Texas. A successful management program has focused on trapping cowbirds at feeding locations, grassland areas almost always associated with the presence of cattle. To enhance the efficacy of this effort, we developed an individual‐based model that predicted visitation rates by cowbirds to all potential feeding locations at Fort Hood and the surrounding landscape. Utilizing GRASS‐GIS and SWARM, the model incorporated the spatial arrangement of habitats, daily movements of cattle, and daily movements of cowbirds from their breeding sites to feeding locations. We simulated four types of movements by cow‐birds as they searched for cattle: 1) random walk, 2) direct return to previous locations (i.e., memory), 3) return to previous locations with en route assessment (i.e., memory with limited perception of the current state of the system), and 4) omniscience. Straight‐line distances between breeding and feeding locations for cowbirds that used the memory‐with‐perception rule were similar to independent telemetry results, and total search distances for this movement type approached those of omniscience. Both movement distance measures were inversely related to perception distance. Maps of cowbird visits to feeding areas differed among movement rules but were not strongly affected by the density of breeding cow‐birds. Maps also identified locations where trapping efforts could reduce parasitism within specific areas known to support endangered species. While it seems plausible that cowbirds are able to remember foraging locations and to perceive their surroundings as they travel, additional studies are needed to document their cognitive abilities. By simulating movements of individual cowbirds across a dynamic landscape, model results may help to strengthen ongoing cowbird control efforts.     

CELL LOSS QUALITY OF SERVICE IN AN INTEGRATED TRAFFIC ATM NETWORK

This paper explores and evaluates several aspects of quality of service (QOS) in an integrated traffic ATM network. Specifically, we consider the relationships between service class definitions, usage parameter control (UPC) or policing of customer traffic, network resource allocation mechanisms, and specific network conditions under which realistic QOS limits on cell loss ratio (CLR) can be met. Traffic consists of a mixture of voice, video, image and data divided into two service classes for UPC and network resource allocation. The block oriented network simulator (BONeS) tool is used for performance evaluations. Limitations associated with evaluating very low CLR values (e.g. 10⁻⁸ and 10⁻⁶) via simulation are overcome by a hybrid simulation and extrapolation technique. It is found that these stringent QOS limits on CLR can be met for most traffic with the techniques used here, reasonable backbone trunk loads (75 per cent) and reasonable buffer sizes (200–250 cell buffers per queue). However, meeting similar limits for extremely bursty traffic (such as our image traffic model) would require extra care in network design and operation, including judicious segregation of traffic.     

Hidden symmetries of energy-conserving differential equations

Hidden symmetries of second-order differential equations whichare invariant under a one-parameter Lie point group and areof the energy-conserving form are analysed as an inverse problemfor some particular cases. These hidden symmetries occur asadditional one-parameter lie point group symmetries in the reducedfirst-order differential equations.     

INFLUENCES OF AVAILABILITY ON PARAMETER ESTIMATES FROM SITE OCCUPANCY MODELS WITH APPLICATION TO SUBMERSED AQUATIC VEGETATION

Site occupancy models are commonly used by ecologists to estimate the probabilities of species site occupancy and of species detection. This study addresses the influence on site occupancy and detection estimates of variation in species availability among surveys within sites. Such variation in availability may result from temporary emigration, nonavailability of the species for detection, and sampling sites spatially when species presence is not uniform within sites. We demonstrate, using Monte Carlo simulations and aquatic vegetation data, that variation in availability and heterogeneity in the probability of availability may yield biases in the expected values of the site occupancy and detection estimates that have traditionally been associated with low‐detection probabilities and heterogeneity in those probabilities. These findings confirm that the effects of availability may be important for ecologists and managers, and that where such effects are expected, modification of sampling designs and/or analytical methods should be considered. Failure to limit the effects of availability may preclude reliable estimation of the probability of site occupancy.     

THE STEPWISE BIPHOTONIC PHOTOIONIZATION OF CHLORPROMAZINE AS SEEN BY LASER FLASH PHOTOLYSIS

It is generally accepted that both promazine (PZ) and chlorpromazine (CPZ) photionize monophotonically to their respective cation radicals and the corresponding hydrated electrons. It is also supposed that this photoinization has a role in the phototoxic effects of these drugs. However, using laser flash photolysis, we have observed that photoionization of CPZ during S1 excitation (lambda greater than 300 nm) is a stepwise biphotonic process. In the case of PZ our flash photolysis results are less clearcut, but are consistent with stepwise biphotonic photoionization for S1 excitation. We demonstrate, using computer simulation of the intramolecular kinetics, that the estimated triplet state lifetime of CPZ is sufficiently long (23 ns at room temperature) to account for the apparent monophotonic photoionization that has been observed by others at high light intensities and short pulse times. Our laser flash photolysis results also suggest that the photo-ionization mechanism of PZ and CPZ is wavelength-dependent. Both drugs exhibit apparent monophotonic photoionization when they are excited at 266 nm under conditions of laser pulse width and intensity similar to those at 355 nm. We suggest that photoionization is not an important mechanism in the observed phototoxic and photoallergic effects of PZ and CPZ in sunlight.     

Loss and Birefringence for Arbitrarily Bent Optical Fibres

We present a calculation to determine the radiation losses forarbitrarily bent, weakly guiding optical fibres. Our resultsare derived for the full set of vector Maxwell's equations,and show that the rate of energy loss due to radiation differsfor the various modes. These results are different from thatcalculated from a scalar theory, where the so-called linearlypolarized (LP) modes are used to approximate the electromagneticfield distributions, showing that in this case scalar theoriesgive incorrect loss rates. We also show that different rangesfor the size of the curvature and torsion produce quite differenteffects. In particular, we show that, for smaller amounts ofcurvature and torsion, the modes retain the basic structureof the modes in the straight fibre while losing energy slowlyat differing rates, while, for larger amounts of curvature andtorsion, the modes become distorted by the bending.