No abstract
Cephalopods are well known for their diverse, quickchanging camouflage in a wide range of shallow habitats worldwide. However, there is no documentation that cephalopods use their diverse camouflage repertoire at night. We used a remotely operated vehicle equipped with a video camera and a red light to conduct 16 transects on the communal spawning grounds of the giant Australian cuttlefish Sepia apama situated on a temperate rock reef in southern Australia. Cuttlefish ceased sexual signaling and reproductive behavior at dusk and then settled to the bottom and quickly adapted their body patterns to produce camouflage that was tailored to different backgrounds. During the day, only 3% of cuttlefish were camouflaged on the spawning ground, but at night 86% (71 of 83 cuttlefish) were camouflaged in variations of three body pattern types: uniform ( ), mottled ( ), or disruptive ( ) colorn p 5 n p 33 n p 34 ation. The implication is that nocturnal visual predators provide the selective pressure for rapid, changeable camouflage patterning tuned to different visual backgrounds at night.
The fungus Verticillium lecanii has previously been shown to be capable of inverting the chirality of ibuprofen and 2-phenylpropionic acid from the (R)-enantiomer to the corresponding (S)-antipode, a phenomenon also observed in mammalian systems including man. An investigation is reported here into the substrate specificity of the enzyme system present in V. lecanii using the following 2-arylpropionic acids : ibuprofen, ketoprofen, indoprofen, suprofen, flurbiprofen and fenoprofen, together with the structurally related compounds 2-phenylbutyric acid, 2-phenoxypropionic acid, mandelic acid, atrolactic acid, etodolac and amethoxyphenylpropionic acid. The results demonstrated that V. lecanii is capable of inverting the chirality of all the 2-arylpropionic acids investigated. All were inverted in the (R) to (S) direction with the exception of ketoprofen, where inversion was observed in the reverse direction. Using the structurally related compounds as substrates, the size of the alkyl substituent at the a-carbon at the methyl group, and the presence of the methyl group at the chiral centre, were found to be critical. These results suggest that V. lecanii could be used as a basis for the production of pure enantiomers of the 2-arylpropionic acids in commercial biotransformations.
A Vector Inversion Generator, VIG, consists of two parallel plate transmission lines, sharing a common conductor that have been wound on a mandrel [1,2]. These units can be made highly efficient and are capable of developing high transient voltages in a time that is determined by the two way transit time for an electromagnetic wave to propagate up the "active" line. Heretofore, the active line in a VIG device was switched using a spark gap because of the extremely high dl/dt and large values of current, I. Spark gap switches have limited life due to electrode erosion, are difficult to trigger with precision and have limited pulse repetition rate. Further, spark switches are usually pressurized to increase operating voltage and to present an inert gas to the electrodes in the switch. By contrast, solid state switches have none of the undesirable characteristics of spark switches and gas plumbing but are limited in dl/dt, I and standoff voltage. In this paper, we will describe the results of our efforts to produce a solid state, precision switched, VIG for applications at high repetition rate and at modest energies. We will present VIG design methodology that determines the maximum value of both I and dl/dt that a switch will see as a function of line length and line impedance. In order to test our methodology, we purchased a solid state switch available from Applied Pulsed Power, Inc. This switch is capable of dl/dt on the order of 30 kA/ ts, peak operating voltage of 4.7 kV, and a peak repetitive current of 10 kA. Test data at voltages greater than 1 kV at a repetition rate up to 500 Hz will be presented. At these voltages, the VIG erected to greater than 60 kV. Due to controller and reverse diode issues, we conducted limited testing at higher voltages producing VIG erected voltages on the order of 100 kV. From these tests, we designed a switch for custom fabrication by Applied Pulsed Power. The switch is to be capable of peak repetitive currents greater than 30 kA, with dl/dt greater than 100 kA/ps. Performance and characterization of this switch will be presented and discussed in terms of VIG design constraints.
The market squid (Loligo opalescens) supports the largest commercial marine fishery in Califomia, both in terms of quantity landed and dollars paid ex-vessel. The fishery is presently being managed without an estimate ofpopulation abundance, which is critical to establishing catch limits. Preliminq findings fiom a cruise with in Monterey Bay, 5-12 May 2003, may change th~s situation by allowing quantification of the spawning products. Imagingthe spawning grounds by means of sidescan sonar at 420 kHz has revealed characteristic markings that are very suggestive of the size and distribution of clumps of market-squid benthic egg beds, each composed of groups of gelatinous egg capsules. The hypothesis that these are due to squid egg beds has been tested by means of video surveys conducted by scuba divers over comparable seafloor areas with and without egg beds.
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