EXPERIMENTAL INVESTIGATION OF THE SLOSH-DAMPING EFFECTIVENESS OF POSITIVE-EXPULSION BAGS AND DIAPHRAGMS IN SPHERICAL TANKS

Slosh damping effectiveness of positive expulsion bags and diaphragms in spherical tank

AGRICULTURAL TRADE RELATIONS BETWEEN CANADA AND THE UNITED STATES

International Relations/Trade,

Experimental investigation of liquid sloshing in a scale-model Centaur liquid-hydrogen tank

Liquid sloshing in scale model Centaur liquid hydrogen tan

Gamma-Ray Burst and Relativistic Shells: The Surface Filling Factor

The variability observed in many complex gamma-ray bursts (GRBs) is inconsistent with causally connected variations in a single, symmetric, relativistic shell interacting with the ambient material ("external shocks"). Rather, the symmetry of the shell must be broken on an angular scale much smaller than Gamma^{-1} where Gamma is the bulk Lorentz factor for the shell. The observed variability in the external shock models arises from the number of causally connected regions that (randomly) become active. We define the "surface filling factor" to be the ratio of the area of causally connected regions that become active to the observable area of the shell. From the observed variability in 52 BATSE bursts, we estimate the surface filling factor to be typically 0.005 although some values are near unity. We find that the surface filling factor is about 0.1 Delta T/T in both the constant Gamma phase (which probably produces the GRB) and the deaccelerating phase (which probably produces the x-ray afterglows). Here, \Delta T is a typical time scale of variability and T is the time since the initial signal. We analyze the 2 hr flare seen by ASCA 36 hr after the GRB and conclude that the surface filling factor must be small (0.001) in the x-ray afterglow phase as well. Explanations for low surface filling factor can either require more or less energy (by a factor of about 1000) compared to that expected for a symmetric shell.Comment: 26 pages, 5 embedded figures, Latex, revised version as in press, ApJ, added figure to show the possible expanding shell geometries that can give low filling facto

Which Triggers Produce the Most Erosive, Frequent, and Longest Runout Turbidity Currents on Deltas?

Subaerial rivers and turbidity currents are the two most voluminous sediment transport processes on our planet, and it is important to understand how they are linked offshore from river mouths. Previously, it was thought that slope failures or direct plunging of river floodwater (hyperpycnal flow) dominated the triggering of turbidity currents on delta fronts. Here we reanalyze the most detailed time‐lapse monitoring yet of a submerged delta; comprising 93 surveys of the Squamish Delta in British Columbia, Canada. We show that most turbidity currents are triggered by settling of sediment from dilute surface river plumes, rather than landslides or hyperpycnal flows. Turbidity currents triggered by settling plumes occur frequently, run out as far as landslide‐triggered events, and cause the greatest changes to delta and lobe morphology. For the first time, we show that settling from surface plumes can dominate the triggering of hazardous submarine flows and offshore sediment fluxes

Experimental Investigation of Optimized Cold-formed Steel Compression Members

In the past, standard C - shaped metal studs have been the only option for designers and contractors when selecting a cross section for load bearing compression members. T he sigma shaped section has recently emerged as an alternative to the C - section. The sigma shaped section is very similar to the C - shape, with the exception of having an intermediate web return and complex stiffeners. The experimental results of concentric axial compression tests of fifty - eight sigma shaped members are reported. Specimen s were tested at various lengths to force global, distortional, and local buckling failure modes. Additionally, the test program contained members with and without web holes. Comparisons of experimental results with the American Iron and Steel Institute ( AISI) design methods, Effective Width Method (EWM) and Direct Strength Method (DSM), are discussed

Oral language at school entry: dimensionality of speaking and listening skills

There has been a resurgence in concern about the levels of pupils’ oral language skills at school entry. To support and develop these skills effectively an understanding of the key components of oral language is required. We examined the oral language skills of monolingual children in Reception (MAge = 57.9 months; n = 126) and Year 1 (MAge = 69.07; n = 124) classes in England. Children were recruited from schools that were representative of London primary schools and were assessed on measures designed to tap phonology, core language skills (vocabulary and grammar) and discourse skills, both in the receptive and expressive modalities. Using confirmatory factor analyses, we examined the associations between oral language skills by component and modality for each age group. Oral language was best represented by four dimensions in Reception (receptive core language skills, receptive discourse, expressive core language skills, and expressive discourse). By contrast in Year 1, three dimensions were identified, irrespective of modality: phonology, core language skills and discourse. Our data speak to the importance of capturing these dimensions in assessments and teaching and monitoring their development at school entry. The results also highlighted the foundational role of discourse skills at the start of school

The temporal pattern and lifestyle associations of respiratory virus infection in a cohort study spanning the first two years of life

Background: Respiratory virus infection is common in early childhood, and children may be symptomatic or symptom-free. Little is known regarding the association between symptomatic/asymptomatic infection and particular clinical factors such as breastfeeding as well as the consequences of such infection. Method: We followed an unselected cohort of term neonates to two years of age (220 infants at recruitment, 159 who remained in the study to 24 months), taking oral swabs at birth and oropharyngeal swabs at intervals subsequently (at 1.5, 6, 9, 12, 18 and 24 months and in a subset at 3 and 4.5 months) while recording extensive metadata including the presence of respiratory symptoms and breastfeeding status. After 2 years medical notes from the general practitioner were inspected to ascertain whether doctor-diagnosed wheeze had occurred by this timepoint. Multiplex PCR was used to detect a range of respiratory viruses: influenza (A&B), parainfluenza (1–4), bocavirus, human metapneumovirus, rhinovirus, coronavirus (OC43, 229E, NL63, HKU1), adenovirus, respiratory syncytial virus (RSV), and polyomavirus (KI, WU). Logistic regression and generalised estimating equations were used to identify associations between clinical factors and virus detection. Results: Overall respiratory viral incidence increased with age. Rhinovirus was the virus most frequently detected. The detection of a respiratory virus was positively associated with respiratory symptoms, male sex, season, childcare and living with another child. We did not observe breastfeeding (whether assessed as the number of completed months of breastfeeding or current feed status) to be associated with the detection of a respiratory virus. There was no association between early viral infection and doctor-diagnosed wheeze by age 2 years. Conclusion: Asymptomatic and symptomatic viral infection is common in the first 2 years of life with rhinovirus infection being the most common. Whilst there was no association between early respiratory viral infection and doctor-diagnosed wheeze, we have not ruled out an association of early viral infections with later asthma, and long-term follow-up of the cohort continues

THE URUGUAY ROUND AGREEMENT ON AGRICULTURE: AN EVALUATION

Contact for this paper: Laura Bipes/University of Minnesota/Department of Applied Economics/ 1994 Buford Avenue./ St. Paul, MN 55108 USA. From the start, agriculture played a central role in the Uruguay Round of GATT trade negotiations. The Punta del Este Declaration called for a solution to the problems facing agricultural trade through modified trade rules and an agreement to lower protection levels. It was recognized that such an improvement implied negotiations on the national farm policies as well as just trade policies. The time that it took to reach agreement reflected the political sensitivity and technical complexity of this task. The Agreement embodied in the Final Act of the Uruguay Round breaks new ground for agriculture, and takes a big step towards placing this sector of world trade under rules more consistent with those in operation in other areas. However, the degree of liberalization of markets is modest, and much remains to be done in future rounds of negotiations. The most far-reaching element in the Agreement is a change in the rules regarding market access. With very few exceptions, all participating countries have agreed to convert all existing non-tariff barriers (along with unbound tariffs) into bound duties and not to introduce new non-tariff measures. Negotiations agreed to reduce these new bound tariffs, as well as tariffs already bound earlier, according to Schedules included as a part of the Agreement. "Tariffication" will impose changes in import policies for a number of countries. Canada will replace import quotas for dairy and poultry products with tariffs, initially at a high level. The European Union will replace its variable levy with tariffs, though a maximum duty-paid price for cereals has been negotiated which puts a limit on the tariff charged. Latin American countries have generally engaged in tariffication in recent years in advance of the Uruguay Round Agreement: for these, and other countries their tariffs will now be bound. The US will forgo the use of Section 22 import quotas and the negotiation of voluntary export restraint agreements with beef suppliers, but the impact on these markets is likely to be small. Japan and Korea have been allowed to delay tariffication in the case of rice for the next few years. The Agreement provides in cases of tariffication for "minimum access opportunities", to guard against the impact of high initial tariff rates. This will open up reduced-tariff quotas for a number of products including beef, cereals and fruits and vegetables. The quotas will be expanded to about 5 percent of consumption over the 6 year period. Japan and Korea have agreed to a greater expansion of market access for rice in compensation for the delay in introducing tariffs. The ability of countries to control export subsidies in agricultural markets was one of the main issues under discussion in the negotiation. Under the Agreement, countries accept commitments on reducing expenditure on export subsidies as well on the quantity of subsidized exports. This will limit export subsidies by the EU and other countries, for such products as wheat, dairy products and beef, and should lead to firmer world market prices in these commodities. These quantities are also expressed in the Schedules which form part of the Agreement. Countries have also agreed not to apply export subsidies to commodities not subsidized in the base period. The Agreement also sets rules and commitments for domestic support policies. It defines a set of policies which are deemed to be less trade-distorting than others, and allocates them to a "green box" which is broadly immune to challenge. Other policies not sheltered in this way are subject to reduction through a limit on the total support given by domestic subsidies and administered prices. It was decided that neither the U.S. deficiency payments (under current legislation) nor the new hectarage compensation payments under the reformed Common Agricultural Policy of the EU need to be reduced. It was also agreed that subsidies that conform to the new rules are sheltered from international challenge under the GATT. Developing Countries generally face less stringent commitments, having 10 years rather than six to make the changes, and having to meet only two-thirds of the reduction targets. In addition, development policies are included broadly in the "green box". Along with the provisions on domestic and trade policies in the Agreement, participants also concluded an Agreement on Sanitary and Phytosanitary Measures (SPS Agreement). The goal was to make it easier to distinguish between genuine health and safety issues and disguised protection. The right of countries to set their own safety and health standards is reaffirmed, but with the provision that such standards should be based on scientific justification and that use be made of international standards where possible. The extent to which the Agreement will lead to greater market access, curb export subsidies and modify domestic policies in the next few years can only be determined from a detailed inspection of the Schedule of commitments made by the individual countries. Paradoxically, the immediate impact on national policies is likely in most cases to be small. Many countries have been engaged in a process of reducing government support to agriculture, and making such support more closely targetted to needs, in advance of the outcome of the Round. Policy reforms in the EU, Canada, Sweden, Australia and New Zealand, along with much of Latin America, have been strongly influenced by the negotiations in the Uruguay Round. The Agreement thus takes on the task of supporting and locking-in such reforms, and encouraging them in other countries. In some aspects the Agreement falls short of expectations (or at least initial demands). It does not constitute a major move toward free trade in agricultural products: the cost of changing the rules has been to give up some degree of liberalization. The tariffs which countries will impose in place of non-tariff barriers are in many cases so high that trade will be restricted to the agreed access quantities. Export subsidy programs will continue though at a reduced level. The major pressure to reinstrument farm policies will continue to be from domestic budget constraints. It will take further rounds of negotiations to reduce protection in agricultural markets to a level comparable to that for most manufactured products. However, with the rule changes and the new types of country commitments agreed, a much more promising basis bas been created for future negotiations.International Relations/Trade,