479 research outputs found
Wheat forecast economics effect study
A model to assess the value of improved information regarding the inventories, productions, exports, and imports of crop on a worldwide basis is discussed. A previously proposed model is interpreted in a stochastic control setting and the underlying assumptions of the model are revealed. In solving the stochastic optimization problem, the Markov programming approach is much more powerful and exact as compared to the dynamic programming-simulation approach of the original model. The convergence of a dual variable Markov programming algorithm is shown to be fast and efficient. A computer program for the general model of multicountry-multiperiod is developed. As an example, the case of one country-two periods is treated and the results are presented in detail. A comparison with the original model results reveals certain interesting aspects of the algorithms and the dependence of the value of information on the incremental cost function
PUFA content of silages prepared from tuna cannery wastes
Ensiling as one of the best methods for utilization of tuna wastes was investigated. docosahexaenoic acid [DHA C22:6(n-3)]- rich products were obtained from the wastes (viscera and dark meat) of four tuna species, namely longtail, skipjack, yellowfin and kawakawa by a procedure involving ensiling in organic acids followed by neutralization. Identification of fatty acids in the samples was performed by comparison with chromatograms of fatty acids standard.
Total lipid content of silages varied from 10.41% in skipjack dark meat silage to 22.01% in kawakawa viscera silage, but all lipids contained high percentages of DHA and EPA [eicosapanteoneic acid C20:5(n-3)]. The highest DHA ratio (15% of total lipids) was found in the lipid of skipjack viscera silage and the highest ratio of EPA (11% of total lipids) belonged to the lipids of kawakawa dark meat silage.
ANOVA test results indicated that DHA ratio was significantly high before silage preparation and linolenic acid [C18:3(n-3)] content significantly differed between the species (p<0.05)
Abelian Gauge Theory in de Sitter Space
Quantization of spinor and vector free fields in 4-dimensional de Sitter
space-time, in the ambient space notation, has been studied in the previous
works. Various two-points functions for the above fields are presented in this
paper. The interaction between the spinor field and the vector field is then
studied by the abelian gauge theory. The U(1) gauge invariant spinor field
equation is obtained in a coordinate independent way notation and their
corresponding conserved currents are computed. The solution of the field
equation is obtained by use of the perturbation method in terms of the Green's
function. The null curvature limit is discussed in the final stage.Comment: 10 pages, typos corrected, reference adde
Watersheds are Schramm-Loewner Evolution curves
We show that in the continuum limit watersheds dividing drainage basins are
Schramm-Loewner Evolution (SLE) curves, being described by one single parameter
. Several numerical evaluations are applied to ascertain this. All
calculations are consistent with SLE, with ,
being the only known physical example of an SLE with . This lies
outside the well-known duality conjecture, bringing up new questions regarding
the existence and reversibility of dual models. Furthermore it constitutes a
strong indication for conformal invariance in random landscapes and suggests
that watersheds likely correspond to a logarithmic Conformal Field Theory (CFT)
with central charge .Comment: 5 pages and 4 figure
"Massless" vector field in de Sitter Universe
In the present work the massless vector field in the de Sitter (dS) space has
been quantized. "Massless" is used here by reference to conformal invariance
and propagation on the dS light-cone whereas "massive" refers to those dS
fields which contract at zero curvature unambiguously to massive fields in
Minkowski space. Due to the gauge invariance of the massless vector field, its
covariant quantization requires an indecomposable representation of the de
Sitter group and an indefinite metric quantization. We will work with a
specific gauge fixing which leads to the simplest one among all possible
related Gupta-Bleuler structures. The field operator will be defined with the
help of coordinate independent de Sitter waves (the modes) which are simple to
manipulate and most adapted to group theoretical matters. The physical states
characterized by the divergencelessness condition will for instance be easy to
identify. The whole construction is based on analyticity requirements in the
complexified pseudo-Riemanian manifold for the modes and the two-point
function.Comment: 33 pages, 3 figure
The modalities of Iranian soft power: from cultural diplomacy to soft war
Through exploring Iran's public diplomacy at the international level, this article demonstrates how the Islamic Republic's motives should not only be contextualised within the oft-sensationalised, material or âhardâ aspects of its foreign policy, but also within the desire to project its cultural reach through âsofterâ means. Iran's utilisation of culturally defined foreign policy objectives and actions demonstrates its understanding of soft power's potentialities. This article explores the ways in which Iran's public diplomacy is used to promote its soft power and craft its, at times, shifting image on the world stage
Acceptability, feasibility and cost of point of care testing for sexually transmitted infections among South African adolescents where syndromic management is standard of care
BACKGROUND: Young people (YP) in southern Africa are at substantial risk of HIV and sexually transmitted infections (STIs). Despite the epidemiological and biological link between STIs and HIV transmission and acquisition, infections such as Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) remain widely undiagnosed. Syndromic STI management is the standard of care in low- and middle-income countries (LMICs) despite a high prevalence of asymptomatic infections. We conducted an observational study to explore the acceptability, feasibility, and cost of a STI test-and-treat service for YP in Cape Town. METHODS: YP attending a mobile clinic (MC) and a youth centre clinic (YC) were offered STI screening. Urine testing for CT and NG using a 90-min molecular point-of-care (POC) test on the GeneXpert platform was conducted and treatment provided. Data were collated on demographics, sexual behaviour, presence of symptoms, uptake of same-day treatment, prevalence of CT/NG, and service acceptability. RESULTS: Three hundred sixty six participants were enrolled (median age 20, 83% female).57% (209/366) of participants tested positive for either CT (126/366, 34%) or NG (57/366, 16%) or co-infection (26/366, 7%). Clinical symptoms were a poor predictor of GeneXpert diagnosed CT or NG, with a sensitivity of 46.8% and 54.0% for CT and NG respectively. Although half of participants initially chose to receive same day results and treatment, only a third waited for results on the day. The majority of participants (91%) rated the service highly via a post-visit acceptability questionnaire. CONCLUSION: Curable STIs are highly prevalent in this population. STI screening using POC testing was feasible and acceptability was high. The study provides further impetus for moving policy beyond syndromic management of STIs in South Africa
Anomaly and quantum corrections to solitons in two-dimensional theories with minimal supersymmetry
We reexamine the issue of the soliton mass in two-dimensional models with N
=1 supersymmetry. The superalgebra has a central extension, and at the
classical level the soliton solution preserves 1/2 of supersymmetry which is
equivalent to BPS saturation. We prove that the property of BPS saturation,
i.e. the equality of the soliton mass to the central charge, remains intact at
the quantum level in all orders of the weak coupling expansion. Our key finding
is an anomaly in the expression for the central charge. The classical central
charge, equal to the jump of the superpotential, is amended by an anomalous
term proportional to the second derivative of the superpotential. The anomaly
is established by various methods in explicit one-loop calculations. We argue
that this one-loop result is not affected by higher orders. We discuss in
detail how the impact of the boundary conditions can be untangled from the
soliton mass calculation. In particular, the soliton profile and the energy
distribution are found at one loop. A "supersymmetry" in the soliton mass
calculations in the non-supersymmetric models is observed.Comment: 50 pages, LaTex, 2 figures. The version exactly matching that
published in Phys.Rev. D. The most essential addition is a footnote,
clarifying multiplet shortenin
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