A Bioeconomic Model for Management of Orange Roughy Stocks

The paper reports the results of a bioeconomic analysis of the exploitation of a recently discovered orange roughy stock located off Tasmania. The parameters of the model are based on the experience derived from the orange roughy fisheries in New Zealand where stocks have been heavily exploited. The model is used to predict the open-access equilibrium stock, and to calculate the stock which maximizes the net present value and the stock level consistent with the F,,, Rule. Assuming a linear approach path, the net present value of the fishery at each of these stocks is calculated. The results are used to estimate the benefit of management and the cost of a conservative stock policy. It is suggested that the results will contribute to the development of a management policy for the Tasmanian stock, and for stocks which are likely to be discovered elsewhereFishery management, bioeconomic model, orange roughy, Environmental Economics and Policy, Production Economics,

The Turnip mosaic virus and its effects on Arabidopsis thaliana gene expression

Utilizing natural and engineered viruses is an accepted approach to studying plant-virus interactions as it relates to symptomology. The majority of the research topics were generated by deciphering where short-comings in the literature existed. Specifically, how Turnip mosaic virus (TuMV) helper component protease (HC-Pro) small RNA (sRNA) binding affinity affects expression of genes correlated with disease phenotypes and studying debilitated viruses in a variety of RNA silencing deficient Arabidopsis thaliana plants. Taken as a whole, the research presented addressed the susceptibility of A. thaliana to TuMV. The first study was conducted to monitor genes implicated in symptomology in various RNA silencing pathway mutant backgrounds. I hypothesized that an in vitro approach, in conjunction with an in silico study would reveal the mechanism TuMV utilizes to regulate sRNA expression, post-infection. The second study focused on severe, moderate, and weak TuMV strains, versus A. thaliana response to pathogen challenge. I hypothesized that TuMV HC-Pro FRNK box mutants that differed in their ability to infect plants affected the function of host sRNA in graduated steps. I also postulated that these mutants might allow me to uncouple developmental abnormalities associated with disease progression and accumulation of the virus itself. In the final study, I combined my passion for plant pathology and molecular techniques to explore a topic unrelated to potyviruses. Conclusions based on analyzing the transcripts and sRNAs of genes correlated with TuMV disease symptomology, quantifying their expression in wild-type and RNA silencing defective A. thaliana plants, and characterizing various TuMV viruses lacking RNA silencing suppressor activity will be discussed. Future directions will also be introduced

Accumulation of BEL1-like transcripts in solanaceous species

Although numerous RNAs have been detected in the phloem, few have been confirmed to move long distances. In potato, full-length mRNA of the BEL1-like transcription factor, StBEL5, moves from leaf veins through the phloem to stolon tips to activate tuber formation. BEL1-like transcription factors are ubiquitous in plants and interact with KNOTTED1-types to regulate numerous developmental processes. To explore the range of KNOTTED1- and BEL1-like mRNAs present in phloem, an analysis of the transcript profile of phloem sap was undertaken. Using a modified technique for the collection of phloem-enriched exudate from excised stems, numerous RNAs encoding these transcription factors were detected in the phloem sap from several solanceous species. All seven known BEL1-like RNAs of potato were detected in the phloem-enriched exudates of stem whereas, several stolon-abundant RNAs were not. After refining the technique to minimize contamination from wounded cells, KNOTTED1-like RNAs were detected in phloem-enriched sap of potato and BEL5 RNA was detected in sap collected from two closely related nontuber-bearing potato species and tomato. BEL5 RNA was also detected in RNA extracted from leaf veins of tobacco. The detection of these full-length mRNAs from the KNOTTED1- and BEL1-like families in phloem sap indicates that their potential role as long-distance signals seems to be much more extensive than previously known

Collision and pursuit course terminal closures for spacecraft to satellite rendezvous

Collision and pursuit course closure maneuvers were studied for correcting position and velocity errors in the terminal phase of spacecraft to satellite rendezvous. Minimum values of the ratio of initial range to velocity necessary to achieve rendezvous were determined for collision closures as a function of the initial line of sight. The time and velocity increment required for rendezvous were computed as a function of initial conditions. Pursuit closure maneuvers were analyzed and time and velocity increments defined as a function of initial range, closing velocity, line of sight angle and angular velocity. The velocity increments required were significantly higher than for a collision closure under similar initial conditions. In addition, the pursuit closure was shown to require very precise control of the initial angular velocity in order to achieve rendezvous. The collision closure maneuver was recommended because the pursuit closure required a greater velocity increment and precise control of the initial angular velocity. An example was presented to illustrate the analysis of a collision closure maneuver i n a rendezvous mission --Abstract, page ii

Barriers to Offering Vasectomy at Publicly Funded Family Planning Organizations in Texas

Few publicly funded family planning clinics in the United States offer vasectomy, but little is known about the reasons this method is not more widely available at these sources of care. Between February 2012 and February 2015, three waves of in-depth interviews were conducted with program administrators at 54 family planning organizations in Texas. Participants described their organization’s vasectomy service model and factors that influenced how frequently vasectomy was provided. Interview transcripts were coded and analyzed using a theme-based approach. Service models and barriers to providing vasectomy were compared by organization type (e.g., women’s health center, public health clinic) and receipt of Title X funding. Two thirds of organizations did not offer vasectomy on-site or pay for referrals with family planning funding; nine organizations frequently provided vasectomy. Organizations did not widely offer vasectomy because they could not find providers that would accept the low reimbursement for the procedure or because they lacked funding for men’s reproductive health care. Respondents often did not perceive men’s reproductive health care as a service priority and commented that men, especially Latinos, had limited interest in vasectomy. Although organizations of all types reported barriers, women’s health centers and Title X-funded organizations more frequently offered vasectomy by conducting tailored outreach to men and vasectomy providers. A combination of factors operating at the health systems and provider level influence the availability of vasectomy at publicly funded family planning organizations in Texas. Multilevel approaches that address key barriers to vasectomy provision would help organizations offer comprehensive contraceptive services.Population Research Cente

A study on the water chemistry and plankton in blackwater lakelets of the south-western Cape

Includes bibliographies.Blackwater lakelets in the south-western Cape are amongst the most darkly coloured humic waters in the world. In addition the aquatic invertebrate fauna of this region represents a relict and highly endemic group of the South Temperate Gondwanian fauna. The major environmental and biological variables were investigated over a period of fifteen months in six south-western Cape vleis (Suurdam, Gillidam, Sirkelsvlei, Grootrondevlei, Grootwitvlei and Rondevlei), which range in colour from a very dark brown to only slightly stained and vary in pH from 3.7 to 10.1. Using absorbance and fluorescence measurements and the Folin-Ciocallteu reagent, relative measures of the quantity and quality of humic compounds were obtained. Suurdam, Gillidam and Sirkelsvlei contained waters of greatest humic content (Suurdam mean A₂₉₀ = 6.561), with a common mid-winter to spring minimum; levels were lower in Grootrondevlei and Grootwitvlei (Grootrondevlei mean A₂₉₀ = 0.996), with a common mid-winter to spring maximum; and lowest in Rondevlei (mean A₂₉₀ = 0.284), with a slight peak in winter. Maxima were related to increased inflow of water with winter rain. Humic compounds in Suurdam, Gillidam and Grootrondevlei were of relatively high molecular weight and phenolic content, indicating an allochthonous origin. In Sirkelsvlei humic compounds were of lower molecular weight and phenolic content, possibly as a result of precipitation of the higher molecular weight fraction due to the high total salinity. Grootwitvlei and Rondevlei had lower molecular weight fractions probably as a result of autochthonous humic production, precipitation with calcium and greater rates of humic degradation; a higher molecular weight allochthonous fraction was present in winter in these two vleis. Buffering at low pH and the complexation of both iron and soluble reactive phosphorous were evident in Suurdam and Gillidam. Catchment geology, atmospheric precipitation, evaporation and the input of vertebrate excreta explain the inorganic chemical environments of the vleis. Acid, well-leached soils and calcareous sands resulted in mean pH values of 3.8 and 4.2 in Suurdam and Gillidam and 8.0 and 8.6 in Grootwitvlei and Rondevlei. The cation composition of the vleis on well-leached acid soils was primarily determined by the atmospheric precipitation of marine salt; evaporation and calcareous sands increased the salinity or relative calcium concentrations in some vleis. Animal excreta in Grootwitvlei and Rondevlei also alter the cation composition slightly, and increase the load of major nutrients. Nitrogen and phosphorous are largely of biological origin. Nutrient levels in the vleis are variously affected by marginal macrophytes, the sediments, primary production and the levels of humics. Chlorophyll a levels indicated low phytoplankton biomass in Suurdam, Gillidam and Grootrondevlei (Suurdam, mean chlorophyll a = 0.9ug1-¹ ) and no distinct seasonality; intermediate levels in Sirkelsvlei (mean chlorophyll a = 11.6ug1-¹ ) and high levels in Grootwitvlei and Rondevlei (Rondevlei, mean chlorophyll a = 60.4ug1-¹ ) displayed a common mid- to late-summer peak. Summer stratification was present only in Suurdam and Gillidam. Maximum phytoplankton biomass of the different vleis related to pH, the quantity and quality of the humic substances, and the nutrient loading. Chlorophyll b: chlorophyll a ratios and chlorophyll c: chlorophyll a ratios indicated a dominance of b- and c-containing species in Suurdam, Gillidam and Grootrondevlei and a dominance of species containing only chlorophyll a in Grootwitvlei and Rondevlei. Multi-dimensional scaling showed four distinct zooplankton community groupings. In Suurdam, the community was dominated by Microcyclops crassipes and was characterised by low zooplankton abundance (mean no.m-³ = 1783), a low species richness, an absence of limnetic cladocerans, and high species diversity (H') and evenness (J') indices. The community appeared to be limited by the low pH and the pH-dependent humic toxicity of the water. The communities in Gillidam, Grootrondevlei and Grootwitvlei were dominated by Metadiaptomus purcelli; otherwise that of Gillidam showed similar characteristics to that of Suurdam and was probably limited by the same factors. Both communities contained individuals of small mean size, more likely a result of limitation by the chemical environment rather than of predation pressure. A number of large-bodied limnetic cladoceran species and Lovenula simplex were present in Grootrondevlei, but absent from Grootwitvlei, possibly as a result of a visual predation pressure. In Sirkelsvlei the community was dominated by Metadiaptomus capensis and Lovenula simplex was present in lower numbers. Species richness, species diversity (H') and evenness (J') were low, with few limnetic cladoceran species present. High total salinity probably determines the community composition and seasonal variation. The eutrophic Rondevlei contains a community dominated by cosmopolitan and common Pan-Ethiopian species, in contrast to the endemic south temperate Gondwanian species of the other vleis. The community was dominated by Thermocyclops oblongatus, Brachionus calyciflorus and Brachionus rubens, and was characterized by greater species richness, and high species diversity (H') and evenness (J'). Total zooplankton abundances were much greater than in the other vleis (mean no.m-³ = 618944). Size-selective predation and the quantity and quality of the phytoplankton probably determine community composition. It is concluded that zooplankton diversity and abundance are influenced, both directly and indirectly, by the concentration and character of the humic substances and the pH, particularly at high concentration and low pH