An extension of the characteristic angle method to the easy-plane spin-3/2 ferromagnet

The Characteristic Angle (CA) method [Lei Zhou and Ruibao Tao, J. Phys. A, {\bf 27} 5599] developed previously for the easy-plane spin-1 magnetic systems has been successfully extended to the spin-3/2 case. A compact form of the CA spin-3/2 operator transformation is given, then the ground state energy, the magnon dispersion relation and the spontaneous magnetization are discussed for an easy-plane spin-3/2 ferromagnet by using the CA method. Comparisons with the old theoretical methods are made in the end.Comment: LaTex formatted. To be published in the forthcoming issue of Physics Letters A (1996). 3 figures. Email address: [email protected]

Development of monotonic neuronal tuning in the monkey inferotemporal cortex through long-term learning of fine shape discrimination

Visual expertise in discriminating fine differences among a group of similar objects can be obtained through extensive long-term training. Here we investigated the neural bases of this superior capability. The inferotemporal cortex, located at the final stage along the ventral visual pathway, was a candidate site in monkeys because cells there respond to various complex features of objects. To identify the changes that underlie the development of visual expertise in fine discrimination, we created a set of parametrically designed object stimuli and compared the stimulus selectivity of inferotemporal cells between two different training histories. One group of recordings was conducted after the monkeys had been extensively trained for fine discrimination (fine-discrimination period) and the other after the monkeys had been exposed only for coarse discrimination (coarse-discrimination period). We found that the tuning of responses recorded in the fine-discrimination period was more monotonic in the stimulus parameter space. The stimuli located at the extreme in the parameter space evoked the maximum responses in a larger proportion of cells and the direction of response decrease in the parameter space was more consistent. Moreover, the stimulus arrangement reconstructed from the responses recorded during the fine-discrimination period was more similar to the original stimulus arrangement. These results suggest that visual expertise could be based on the development, in the inferotemporal cortex, of neuronal selectivity monotonically tuned over the parameter space of the object images

Stock Assessment of Norwegian Atlantic Halibut North of 62°N Latitude Using a Data-Limited Approach

Landings of Atlantic halibut (Hippoglossus hippoglossus) have increased significantly in later years. More fishing boats are joining the open-access fishery, with an ever-increasing number of fishing gear. The Atlantic halibut is also a popular tourist and recreational fishery target species. Atlantic halibut is a large, late-maturing flatfish with life history traits that make the stock sensitive to overfishing. The stock has a long history of exploitation, and historical fisheries show that increased landings over time have been followed by significant reductions in landings. The current regulations of the Norwegian Atlantic halibut fishery north of 62°N consist of input regulations (minimum catch size, no-catch periods, and fishing gear restrictions). Management authorities suggest new management actions to ensure a sustainable fishery of the Atlantic halibut stock in a long-term perspective. The aim of this study was to perform a stock assessment of the Norwegian Atlantic halibut stock north of 62°N using a data-limited approach. The purpose was to use the Stochastic Surplus Production Model in Continuous Time (SPiCT) and empirical approaches (with Data Limited Methods Toolkit (DLMtool)) on the limited data to assess the stock status and propose a management advice. The potential effects of tourist- and recreational fisheries were also examined through alternative landings (+20% and +40%) scenarios. Landings in Norway north of 62°N and Norwegian coastal scientific survey data were used. Four survey indices were developed from the scientific survey, of which one was used in the full assessment. The SPiCT assessment fulfilled the technical criteria, and the halibut stock was given ICES (International Council for the Exploration of the Sea) category 2 MSY (maximum sustainable yield) advice. The DLMtool gave similar results and provided estimates of a new minimum catch size. The assessment showed that the stock is close to optimal levels and utilized around MSY. The stock is probably declining due to overfishing in recent years. The management advice for the Norwegian halibut stock north of 62°N is to reduce fishing by implementing a TAC at 2000-2424 tons. An increased minimum catch size of around 90-106 cm should be implemented (together with or independently of other measures) to fit the species' life-history traits better. Tourist- and recreational fisheries might have a negative effect on the halibut stock, especially locally. The findings in this thesis can contribute to better management of the Norwegian halibut stock north of 62°N.Landingene av atlantisk kveite (Hippoglossus hippoglossus) har økt signifikant de siste årene. Flere båter har blitt med i det åpne fiskeriet, og et stadig større antall fiskeredskaper er i bruk. Atlantisk kveite er også en populær målart for turist- og fritidsfiskerier. Arten atlantisk kveite er en stor flatfisk som blir sent kjønnsmoden, og som har livshistorietrekk som gjør at den er sensitiv for overfiske. Kveitefiske har en lang historie, og statistikk viser at økte landinger over tid følges av store reduksjoner i landinger. Dagens forvaltning av norsk atlantisk kveite nord for 62°N består av innsatsreguleringer (minstemål, fredningsperioder og restriksjoner av fiskeredskap). Nye forvaltningstiltak er blitt foreslått av fiskerimyndighetene for å sikre et bærekraftig fiske av kveitebestanden i et langtidsperspektiv. Formålet med denne studien var å gjennomføre en bestandsvurdering av den norske atlantiske kveitebestanden nord for 62°N ved bruk av en databegrenset tilnærming. Målet var å teste og tilpasse en anerkjent stokastisk produksjonsmodell (Stochastic Surplus Production Model in Continuous Time - SPiCT) samt en empirisk tilnærming (med Data-Limited Methods Toolkit - DLMtool) for å vurdere bestandsstatus og foreslå et forvaltningsråd. De mulige effektene av turist- og fritidsfiske ble også undersøkt gjennom alternative scenarioer for landinger (+20% and +40%). Landingene for at atlantisk kveite i Norge nord for 62°N og data fra kysttoktet ble brukt. Fire indekser ble utviklet fra toktdataene, hvorav en ble brukt i hele bestandsvurderingen. Bestandsvurderingen med SPiCT oppfylte de tekniske kriteriene, og kveitebestanden ble gitt MSY-råd (maksimal bærekraftig fangst) etter det internasjonale havforskningsrådets (ICES) bestandskategori 2. DLMtool ga tilsvarende resultater og forslag til nytt økt minstemål. Bestandsvurderingen viste at bestanden er i tilnærmet optimal tilstand og utnyttet rundt MSY. Bestanden minsker trolig på grunn av overfiske de siste årene. Forvaltningsrådet for den norske atlantiske kveitebestanden nord for 62°N er å redusere fiske ved å innføre en kvote på mellom 2000-2424 tonn i fiskeriet. I tillegg foreslås det å øke minstemålet til mellom 90-106 cm (i tillegg til, eller uavhengig av andre forvaltningstiltak) som er bedre tilpasset arten. Turist- og fritidsfiske kan ha en negativ effekt på kveitebestanden, særlig lokalt. Funnene i denne oppgaven kan bidra til en bedre forvaltning av dem norske atlantiske kveitebestanden nord for 62°N

The RILEM Approach to Mitigate Alkali Aggregate Reactions (AAR) in Concrete

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