The optical potential of 6^{6}He in the eikonal approximation

The new data of the elastic scattering of $^{6}$He+$^{12}$C at about 40 MeV/nucleon are analyzed in the eikonal approximation. The $^{6}$He+$^{12}$C phase-shift function is evaluated completely without any {\it ad hoc} assumption by a Monte Carlo integration, which makes it possible to use a realistic 6-nucleon wave function for a halo nucleus $^{6}$He. The effect of the breakup of $^6$He on the elastic differential cross sections as well as the optical potential is studied at different energies from 40 to 800 MeV/nucleon. PACS number(s): 24.10.-i; 21.60.Ka; 25.60.Bx; 25.10.+s Keywords: Eikonal; Glauber; Monte Carlo; Halo; BreakupComment: 13 pages, 9 figure

Boat and ship engravings at Al Zubarah, Qatar: the dāw exposed?

This is the author accepted manuscript. The final version is available from ArchaeopressOn-going excavations at the site of the 18th–19th century walled town of Al Zubarah, Qatar, have uncovered a number of engravings of seagoing craft etched into the dry plasterwork of buildings within the settlement. The engravings are essentially graffiti, carved into the interiors of rooms without aesthetic reference to the original decorative schema of their settings. The resulting images are of varying sophistication and detail — dependent, no doubt, on the skill and inclination of their executors. While the crudest images are rudimentary outlines of hulls, others show detail that demonstrates the familiarity of their creators with boat construction and type — not surprising in a settlement whose raison d’être was the livings to be made from the sea. This iconographic vestige provides an insight into the types of vessel their creators used and encountered, and allows us to venture our own identifications of them. It also prompts us to reflect on the nature of the relationship between Al Zubarah’s some-time residents and the sea: the vessels depicted are for the most part a mixture of ocean-going types built within the Gulf or western Indian Ocean region. One, however, is of a European naval vessel, perhaps suggesting the shadow of British imperial power in the Gulf. Finally, the process of identification of these watercraft inspires renewed reflection on the word ‘dhow’ and its variants, from both a typological and an etymological perspective; these new reflections are presented at the end of this paper

Soil-transmitted helminth infections and nutritional status in Ecuador: findings from a national survey and implications for control strategies.

OBJECTIVE: The estimation of prevalence and intensity of soil-transmitted helminth (STH) infections at a country-level is an essential prerequisite for the implementation of a rational control programme. The aim of this present study was to estimate the prevalence and distribution of STH infections and malnutrition in school-age children in rural areas of Ecuador. DESIGN: Cross-sectional study from October 2011 to May 2012. SETTING: Eighteen rural schools were randomly selected from the three ecological regions of Ecuador (coastal, highlands and Amazon basin). PARTICIPANTS: 920 children aged 6-16 years. MAIN OUTCOME MEASURES: Prevalence and intensity of STH infections associated with malnutrition (thinness/wasting or stunting). RESULTS: The results showed that 257 (27.9%) children were infected with at least one STH parasite. The prevalence of Trichuris trichiura, Ascaris lumbricoides and hookworm was 19.3%, 18.5% and 5.0%, respectively. Malnutrition was present in 14.2% of children and most common was stunting (12.3%). Compared with other regions, schoolchildren in the Amazon region had the highest STH prevalence (58.9%) of which a greater proportion of infections were moderate/heavy intensity (45.6%) and had the highest prevalence of malnutrition (20.4%). A positive association was observed between moderate to heavy infections with A. lumbricoides and malnutrition (adjusted OR 1.85, 95% CI 1.04 to 3.31, p=0.037). CONCLUSIONS: Our estimate of the prevalence of STH infections of 27.9% at a national level in Ecuador is lower than suggested by previous studies. Our data indicate that schoolchildren living in the Amazon region have a greater risk of STH infection and stunting compared with children from other regions. The implementation of school-based preventive chemotherapy and nutritional supplement programmes within the Amazon region should be prioritised. Long-term control strategies require improvements in water, sanitation and hygiene

Assessing ballast treatment standards for effect on rate of establishment using a stochastic model of the green crab

This paper describes a stochastic model used to characterize the probability/risk of NIS establishment from ships' ballast water discharges. Establishment is defined as the existence of a sufficient number of individuals of a species to provide for a sustained population of the organism. The inherent variability in population dynamics of organisms in their native or established environments is generally difficult to quantify. Muchqualitative information is known about organism life cycles and biotic and abiotic environmental pressures on the population, but generally little quantitative data exist to develop a mechanistic model of populations in such complex environments. Moreover, there is little quantitative data to characterize the stochastic fluctuations of population size over time even without accounting for systematic responses to biotic and abiotic pressures. This research applies an approach using life-stage density and fecundity measures reported in research to determine a stochastic model of an organism's population dynamics. The model is illustrated withdata from research studies on the green crab that span a range of habitats of the established organism and were collected over some years to represent a range of time-varying biotic and abiotic conditions that are expected to exist in many receiving environments. This model is applied to introductions of NIS at the IMO D-2 and the U.S. ballast water discharge standard levels designated as Phase Two in the United States Coast Guard'sNotice of Proposed Rulemaking. Under a representative range of ballast volumes discharged at U.S. ports, the average rate of establishment of green crabs for ballast waters treated to the IMO-D2 concentration standard (less than 10 organisms/m3) is predicted to be reduced to about a third the average rate from untreated ballast water discharge. The longevity of populations from the untreated ballast water discharges is expected to be reducedby about 90% by treatment to the IMO-D2 concentration standard

The continuous p-centre problem: An investigation into variable neighbourhood search with memory

A VNS-based heuristic using both a facility as well as a customer type neighbourhood structure is proposed to solve the p-centre problem in the continuous space. Simple but effective enhancements to the original Elzinga-Hearn algorithm as well as a powerful ‘locate-allocate’ local search used within VNS are proposed. In addition, efficient implementations in both neighbourhood structures are presented. A learning scheme is also embedded into the search to produce a new variant of VNS that uses memory. The effect of incorporating strong intensification within the local search via a VND type structure is also explored with interesting results. Empirical results, based on several existing data set (TSP-Lib) with various values of p, show that the proposed VNS implementations outperform both a multi-start heuristic and the discrete-based optimal approach that use the same local search