835 research outputs found
Purpose and potential for commodity exchanges in African economies:
This paper reviews the purpose and potential of commodity exchanges in Africa. Drawing from the existing literature and using indicative empirics, it examines the conditions that enable successful exchanges, highlights the special challenges to setting up exchanges in Africa, and reviews alternatives to domestic exchanges. We argue that many critical preconditions for the successful establishment of commodity exchanges in Africa remain binding in the short to medium term. The development of commodity exchanges in the region is impeded by the relatively small size of domestic commodity markets, the weak physical and communication infrastructure, a lack of supportive legal and regulatory environments, and the likelihood of policy interventions, particularly in the staple cereals market. Meanwhile, the demand for a domestic commodity exchange for export crops may be limited due to the availability of well-established exchanges abroad and functioning auction floors. The paper highlights three points: (a) efforts to launch exchanges in Africa should realistically assess whether basic conditions for success can be met, (b) if the pre-conditions cannot be met, the use of existing exchanges abroad or the development of regional exchanges may be more feasible than the establishment of national commodity exchanges, and (c) the goals of risk management and reduced transaction costs might be achieved more effectively by improving market fundamentals through investments in transportation, information services, or other financial institutions.commodity exchanges, Risk management, Market development,
Analysis of close encounters with Ganymede and Callisto using a genetic n-body algorithm
In this work we describe a genetic algorithm which is used in order to study
orbits of minor bodies in the frames of close encounters. We find that the
algorithm in combination with standard orbital numerical integrators can be
used as a good proxy for finding typical orbits of minor bodies in close
encounters with planets and even their moons, saving a lot of computational
time compared to long-term orbital numerical integrations. Here, we study close
encounters of Centaurs with Callisto and Ganymede in particular. We also
perform n-body numerical simulations for comparison. We find typical impact
velocities to be between and for
Ganymede and between and for
Callisto.Comment: 18 pages, 3 figure
The Partnered Core of a Game With Side Payments
SIGLEAvailable from Bibliothek des Instituts fuer Weltwirtschaft, ZBW, Duesternbrook Weg 120, D-24105 Kiel W 109 (258) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman
Stability of spikes in the shadow Gierer-Meinhardt system with Robin boundary conditions
We consider the shadow system of the Gierer-Meinhardt system in a smooth bounded domain RN,At=2AāA+,x, t>0, ||t=ā||+Ardx, t>0 with the Robin boundary condition +aAA=0, x, where aA>0, the reaction rates (p,q,r,s) satisfy 1<p<()+, q>0, r>0, s0, 1<<+, the diffusion constant is chosen such that 1, and the time relaxation constant is such that 0. We rigorously prove the following results on the stability of one-spike solutions: (i) If r=2 and 1<p<1+4/N or if r=p+1 and 1<p<, then for aA>1 and sufficiently small the interior spike is stable. (ii) For N=1 if r=2 and 1<p3 or if r=p+1 and 1<p<, then for 0<aA<1 the near-boundary spike is stable. (iii) For N=1 if 3<p<5 and r=2, then there exist a0(0,1) and Āµ0>1 such that for a(a0,1) and Āµ=2q/(s+1)(pā1)(1,Āµ0) the near-boundary spike solution is unstable. This instability is not present for the Neumann boundary condition but only arises for the Robin boundary condition. Furthermore, we show that the corresponding eigenvalue is of order O(1) as 0. Ā©2007 American Institute of Physic
How to contribute research results to Internet standarization
The development of new technology is driven by scientific
research. The Internet, with its roots in the ARPANET and
NSFNet, is no exception. Many of the fundamental, long-term
improvements to the architecture, security, end-to-end protocols
and management of the Internet originate in the related academic
research communities. Even shorter-term, more commercially
driven extensions are oftentimes derived from academic research.
When interoperability is required, the IETF standardizes such new
technology. Timely and relevant standardization benefits from
continuous input and review from the academic research
community.
For an individual researcher, it can however by quite puzzling
how to begin to most effectively participate in the IETF and -
arguably to a much lesser degree - in the IRTF. The interactions
in the IETF are much different than those in academic
conferences, and effective participation follows different rules.
The goal of this document is to highlight such differences and
provide a rough guideline that will hopefully enable researchers
new to the IETF to become successful contributors more quicklyThis research was supported by Trilogy (http://www.trilogy-project.org), a research project (ICT-216372) partially funded by the European Community under its Seventh Framework Programme. European Community's Seventh Framework ProgramPublicad
The Many Faces of ProteināProtein Interactions: A Compendium of Interface Geometry
A systematic classification of proteināprotein interfaces is a valuable resource for understanding the principles of molecular recognition and for modelling protein complexes. Here, we present a classification of domain interfaces according to their geometry. Our new algorithm uses a hybrid approach of both sequential and structural features. The accuracy is evaluated on a hand-curated dataset of 416 interfaces. Our hybrid procedure achieves 83% precision and 95% recall, which improves the earlier sequence-based method by 5% on both terms. We classify virtually all domain interfaces of known structure, which results in nearly 6,000 distinct types of interfaces. In 40% of the cases, the interacting domain families associate in multiple orientations, suggesting that all the possible binding orientations need to be explored for modelling multidomain proteins and protein complexes. In general, hub proteins are shown to use distinct surface regions (multiple faces) for interactions with different partners. Our classification provides a convenient framework to query genuine gene fusion, which conserves binding orientation in both fused and separate forms. The result suggests that the binding orientations are not conserved in at least one-third of the gene fusion cases detected by a conventional sequence similarity search. We show that any evolutionary analysis on interfaces can be skewed by multiple binding orientations and multiple interaction partners. The taxonomic distribution of interface types suggests that ancient interfaces common to the three major kingdoms of life are enriched by symmetric homodimers. The classification results are online at http://www.scoppi.org
Increased expression of a microRNA correlates with anthelmintic resistance in parasitic nematodes
Resistance to anthelmintic drugs is a major problem in the global fight against parasitic nematodes infecting humans and animals. While previous studies have identified mutations in drug target genes in resistant parasites, changes in the expression levels of both targets and transporters have also been reported. The mechanisms underlying these changes in gene expression are unresolved. Here, we take a novel approach to this problem by investigating the role of small regulatory RNAs in drug resistant strains of the important parasite Haemonchus contortus. microRNAs (miRNAs) are small (22 nt) non-coding RNAs that regulate gene expression by binding predominantly to the 3ā² UTR of mRNAs. Changes in miRNA expression have been implicated in drug resistance in a variety of tumor cells. In this study, we focused on two geographically distinct ivermectin resistant strains of H. contortus and two lines generated by multiple rounds of backcrossing between susceptible and resistant parents, with ivermectin selection. All four resistant strains showed significantly increased expression of a single miRNA, hco-miR-9551, compared to the susceptible strain. This same miRNA is also upregulated in a multi-drug-resistant strain of the related nematode Teladorsagia circumcincta. hco-miR-9551 is enriched in female worms, is likely to be located on the X chromosome and is restricted to clade V parasitic nematodes. Genes containing predicted binding sites for hco-miR-9551 were identified computationally and refined based on differential expression in a transcriptomic dataset prepared from the same drug resistant and susceptible strains. This analysis identified three putative target mRNAs, one of which, a CHAC domain containing protein, is located in a region of the H. contortus genome introgressed from the resistant parent. hco-miR-9551 was shown to interact with the 3ā² UTR of this gene by dual luciferase assay. This study is the first to suggest a role for miRNAs and the genes they regulate in drug resistant parasitic nematodes. miR-9551 also has potential as a biomarker of resistance in different nematode species
Less sensitive oxygen-rich organic peroxides containing geminal hydroperoxy groups
Tetranitratoethane (C2H2N4O12), which has an oxygen content of 70.1% was synthesized by nitration of monomeric glyoxal using N2O5 and purified by sublimation. Single crystals could be grown from CH2Cl2/pentane and were used to determine the structure by X-ray diffraction. Several energetic parameters and values were also established
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