5,635 research outputs found
Three-quark exchange operators, crossing matrices and Fierz transformations in SU(2) and SU(3)
We give explicit expressions for the three-quark exchange operators, crossing
matrices and Fierz transforms for the SU(2) and SU(3) groups. We identify the
invariant terms in these operators and express them in terms of Casimir
operators.Comment: 8 pages, RevTex, to appear in Jour. Math. Phy
Cubic Casimir operator of SU(3) and confinement in the nonrelativistic quark model
Only two-body [] confining potentials have
been considered, thus far, in the quark model without gluons, which by
construction can only depend on the quadratic Casimir operator of the colour
SU(3) group. A three-quark potential that depends on the cubic Casimir operator
is added to the quark model. This results in improved properties of
colour non-singlet states, which can now be arranged to have (arbitrarily)
higher energy than the singlet, and the "colour dissolution/anticonfinement"
problem of the model is avoided.Comment: 10 pages, 2 tables, RevTex, to appear in Phys. Lett.
Coral tumor-like growth anomalies induce an immune response and reduce fecundity
Coral growth anomalies (GAs) are chronic diseases that adversely affect organism health and fitness. We investigated immunity and fecundity within and among GA-affected and visually healthy control colonies of the reef-building coral Acropora hyacinthus. Compared to controls, GAs had higher activity of the key immunity enzyme phenoloxidase (PO), suggesting a localised immune response within the GA. Both GAs and healthy tissue of GA-affected colonies had significantly greater total potential PO (tpPO)-PO activity inclusive of the activated latent PO, prophenoloxidase - than control colonies. Higher tpPO activity in GA-affected corals suggests elevated constitutive immunity compared to visually healthy controls. Additionally, fewer GA-affected colonies produced gametes, fewer polyps had oocytes (p < 0.001) and the number of oocytes per polyp was lower. Therefore, GAs in A. hyacinthus might induce, or represent a shift in resource investment towards immunity and away from reproduction. While the effect on population growth is likely to be small, reduced fecundity in GA-affected colonies does suggest a selective pressure against GAs
Syzygies in equivariant cohomology for non-abelian Lie groups
We extend the work of Allday-Franz-Puppe on syzygies in equivariant
cohomology from tori to arbitrary compact connected Lie groups G. In
particular, we show that for a compact orientable G-manifold X the analogue of
the Chang-Skjelbred sequence is exact if and only if the equivariant cohomology
of X is reflexive, if and only if the equivariant Poincare pairing for X is
perfect. Along the way we establish that the equivariant cohomology modules
arising from the orbit filtration of X are Cohen-Macaulay. We allow singular
spaces and introduce a Cartan model for their equivariant cohomology. We also
develop a criterion for the finiteness of the number of infinitesimal orbit
types of a G-manifold.Comment: 28 pages; minor change
Challenges in the Control and Elimination of Plasmodium vivax Malaria
The human malaria parasite Plasmodium vivax imposes unique challenges to its control and elimination. Primary among those is the hypnozoite reservoir of infection in endemic communities. It is the dominant source of incident malaria and exceedingly difficult to attack due to both inability to diagnose latent carriers and the potentially life-threatening toxicity of primaquine in patients with an inborn deficiency of G6PD, the only therapeutic option against hypnozoites. Large segments of endemic populations are not eligible for primaquine, and alternative strategies for managing the threat of relapse in any group have not been optimized or validated. Association of risk of primaquine failure against latent P. vivax with impaired alleles of P450 2D6 exacerbates the substantial pool of primaquine ineligibles. Resistance to chloroquine against acute P. vivax malaria commonly occurs; alternative therapies like ACTs are effective but seldom evaluated as a partner drug to primaquine in the essential radical cure. Many of the Anopheles mosquito vector of P. vivax in South and Southeast Asia, where >90% of infections occur, thrive in a diversity of habitats and exhibit wide ranges of feeding and breeding behavior. This chapter explores many of these challenges and possible approaches in controlling and eliminating endemic vivax malaria
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Proposal to Allow Treasury to Buy Mortgage-Related Assets to Address Financial Instability
Financial markets underwent severe stress during the week of September 15 - 22, 2008. After Lehman Brothers declared bankruptcy and AIG received a bridge loan from the Federal Reserve, policymakers reassessed their case-by-case approach to resolving financial problems. Secretary of the Treasury Paulson announced a plan to allow Treasury to purchase mortgage-related assets from U.S. financial institutions. The announced intent of the plan is to unclog financial markets, increase the health of the banking sector, and reduce ongoing risks to the economy. This report discusses a draft
of the proposal as it stood on September 21, 2008, and analyzes frequently asked questions
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