Chaetognath ecology in relation to hydrographic conditions in the Australian sector of the Antarctic Ocean

Chaetognath ecology in relation to hydrographic conditions was investigated during austral summer in the Antarctic Ocean with two cruises conducted seven years apart. Time series samples were collected at a total of five stations along 140_E in the region of the Antarctic Divergence (AD). The numerically dominant species was Eukrohnia hamata, averaging over 80% of the collected specimens. This species was most abundant north of the AD where bi-modal distribution was common. No species displayed regular diel vertical migration nor were their vertical distribution restricted by hydrographic clines. Breeding of E. hamata appeared unaffected by water conditions-the same maturity stages were present in similar percentages across the water masses. Vertical segregation of size classes among E. hamata was clearest north of the AD in a more stratified water column. In other locations, the size classes overlapped considerably; this is likely due to physical forcing from mixing water. Feeding activity of E. hamata was lowest within the AD and increased both north and south on the edges of the front. Feeding activity appeared continuous with no recognizable diel pattern. E. hamata containing prey items were smaller north of the AD compared to the south, suggesting two separate populations. The percentage of predators with food in their gut was much larger in this study than previously reported work. Often times nearly 50% of the E. hamata collected had highly digested contents in the posterior of the gut

Life history strategy of the chaetognath Sagitta elegans in the World Oceans

Sagitta elegans is the best-studied chaetognatha in the world ocean. This species typically inhabits the upper 100 to 150m in the arctic and subarctic area of both the Atlantic and Pacific. S. elegans was also reported from the North Pacific Intermediate Water and the meso- and bathypleagic layer in the Sea of Japan. Diurnal vertical migration is recognized in the various waters. The size and number of grasping spines and teeth of S. elegans in the Sea of Japan are greater than those from the Pacific. They also have developed intestinal tissue containing oil droplets similar to meso- and bathypelagic species. These features are adaptations to the deep-water environment. Number of generations per year, life span and growth rate depend on the waters inhabited. In general, S. elegans mature at large sizes in lower temperatures and life span is short in warm regions. Food is also an important factor controlling their growth. Feeding activity of S. elegans in the various waters of the Pacific is high during the night time. The major food organisms are copepods. S. elegans inhabiting the open sea consume larger copepods compared to those in coastal waters. The percentage of secondary production consumed daily by S. elegans, was 36% in Bedford Basin, Nova Scotia, 10% in the Bering Sea and 4% in the western North Pacific, respectively

Thioureas as Highly Active Catalysts for Biomimetic Bromocyclization of Geranyl Derivatives

Thioureas bearing electron-deficient aryl groups show high catalytic activity in the biomimetic bromocyclization of geranyl derivatives. The reaction of geranyl derivatives with N-bromosuccinimide (NBS) proceeds rapidly in CH2Cl2 to give the corresponding bromocyclization products in high yields as a ca. 1:1 mixture of endo- and exo-isomers. The reactivity of geranyl derivatives highly depends on the terminal substituent: electron-donating substituents increase the reactivity, while electron-withdrawing substituents decrease the reactivity

Microfabrication of Microchannels for Fuel Cell Plates

Portable electronic devices such as notebook computers, PDAs, cellular phones, etc., are being widely used, and they increasingly need cheap, efficient, and lightweight power sources. Fuel cells have been proposed as possible power sources to address issues that involve energy production and the environment. In particular, a small type of fuel-cell system is known to be suitable for portable electronic devices. The development of micro fuel cell systems can be achieved by the application of microchannel technology. In this study, the conventional method of chemical etching and the mechanical machining method of micro end milling were used for the microfabrication of microchannel for fuel cell separators. The two methods were compared in terms of their performance in the fabrication with regards to dimensional errors, flatness, straightness, and surface roughness. Following microchannel fabrication, the powder blasting technique is introduced to improve the coating performance of the catalyst on the surface of the microchannel. Experimental results show that end milling can remarkably increase the fabrication performance and that surface treatment by powder blasting can improve the performance of catalyst coating

Community structure and vertical distribution of chaetognaths in the Celebes and Sulu Seas

Chaetognath community structure, vertical distribution and migration patterns were investigated in two marginal basins-the Celebes and Sulu Seas. The two seas are part of an island arc located in the southeastern Asia region of the western equatorial Pacific Ocean. The Sulu Sea had higher species diversity (Shannon Index, H\u27) and higher overall chaetognath abundance than the Celebes Sea. Twenty-two species from 4 genera were collected from the Sulu Sea and 19 species from 4 genera were collected from the Celebes Sea. Three species were collected exclusively in the Sulu Sea: Sagitta bipunctata, Sagitta nagae and an unidentified Sagitta species. Sagitta enflata was the numerically dominant species at both locations. Species diversity in the Celebes Sea was fairly even between the surface and 1000m. However, in the Sulu Sea substantial drops in diversity occurred at 175-200m-below the oxycline, thermocline and halocline-as well as at 900-1000m. The drop at 175-200m and 900-1000m was largely due to the numerical dominance of the species Sagitta decipiens and Sagitta macrocephala, respectively. In the Celebes Sea only, a large portion of the overall chaetognath population migrated downwards during the day into the 125-200m layer. Cluster analysis using Ward\u27s method, along with weighted mean depth values, revealed that this migration was largely attributable to the species Sagitta pacifica, Sagitta ferox-robusta, Sagitta neglecta and Pterosagitta draco. A similar migration of the overall population was blocked in the Sulu Sea-apparently by the oxycline. It seems the group of migrating chaetognaths in the Celebes Sea prevented the numerical dominance of S. decipiens at the lower edge of the epipelagic region, possibly through competition, and consequently prevented the same drop in diversity (H\u27) at 175-200m as was recorded in the Sulu Sea

Observation of a non-uniform current distribution in stacked high temperature superconducting tapes

High Temperature Superconductors (HTS) improve upon low temperature superconductors in many ways and the ability to cope with a non-uniform current distribution might be one of those improvements. To put this to the test, an experimental setup is designed to force a non-uniform current upon a stack of 5 HTS tapes, using a worst case current feeding method. The experiment can help determine the potential of this conductor design and is part of the ongoing effort to develop a non-transposed stacked HTS conductor for the nuclear fusion reactor FFHR. The results clearly show that the conductor sample is able to stably conduct a current equal to its critical current, although at an elevated electric field of roughly 5 mV/m. This means non-transposed stacked tape conductors remain stable, even if a worst case nonuniform current is constantly forced upon them. A hypothesis to explain this abnormally high electric field is formulated on the basis of the results, however additional research is needed to verify it. It states that the electric field is necessary for the tapes to share current and would mean that in a properly engineered application, these losses due to the electric field, would only occur during start-up. Overall it is clear that this experiment proves the excellent stability of non-transposed stacked HTS tapes and their ability to conduct a non-uniform current

First record of a leptocephalus larva ingested by a chaetognath

An approximately 17mm Nemichthys scolopaceus leptocephalus was found in the gut of a 25mm chaetognath, Sagitta (Flacdsagitta) hexaptera, collected in the North Equatorial Current region of the western North Pacific. The chaetognath was photographed before preservation. The leptocephalus was folded in half and was positioned deep within the hindgut. Although the chaetognath was caught during sampling for leptocephali, its location in the hindgut suggests that the leptocephalus could have been ingested prior to capture by the net. This first record of ingestion of this unique type of fish larva suggests that if contact is made with small leptocephali, it is possible for them to be ingested by relatively large sized chaetognaths that may identify them as potential prey