KLT-type relations for QCD and bicolor amplitudes from color-factor symmetry

Color-factor symmetry is used to derive a KLT-type relation for tree-level QCD amplitudes containing gluons and an arbitrary number of massive or massless quark-antiquark pairs, generalizing the expression for Yang-Mills amplitudes originally postulated by Bern, De Freitas, and Wong. An explicit expression is given for all amplitudes with two or fewer quark-antiquark pairs in terms of the (modified) momentum kernel. We also introduce the bicolor scalar theory, the "zeroth copy" of QCD, containing massless biadjoint scalars and massive bifundamental scalars, generalizing the biadjoint scalar theory of Cachazo, He, and Yuan. We derive KLT-type relations for tree-level amplitudes of biadjoint and bicolor theories using the color-factor symmetry possessed by these theories.Comment: 24 pages, 2 figures; v2: added referenc

Some implications of increased cooperation in world oil conservation

Petroleum industry and trade

Generic advertising impacts on demands for orange juice in fifty Nielsen metropolitan regions

Agribusiness, Demand and Price Analysis,

Triple-crown advertising impacts on demands for orange juice in fifty Nielsen metropolitan regions

Agribusiness, Demand and Price Analysis,

Some implications of increased cooperation in world oil conservation

In this article, Stephen Brown and Hillard Huntington combine recent studies of world oil markets and the nascent literature on damage estimates from carbon dioxide (CO2) emissions to derive cost and benefit curves for the reduction of these emissions through cooperative programs of oil conservation. Their analysis shows that the desirability of extending cooperation in global energy conservation policies is essentially an empirical issue rather than a conceptual one. The current evidence suggests that over the next two decades, the Organization for Economic Cooperation and Development will have an incentive to reduce its oil consumption and the associated CO2 emissions by more than is optimal from a world perspective. During this period, extending cooperation to the oil-importing developing countries may push oil conservation too far.Petroleum industry and trade

Assessing the economic cost of unilateral oil conservation

Power resources ; Petroleum industry and trade

Simultaneous measurement of multiple parameters of a subwavelength structure based on the weak value formalism

A mathematical extension of the weak value formalism to the simultaneous measurement of multiple parameters is presented in the context of an optical focused vector beam scatterometry experiment. In this example, preselection and postselection are achieved via spatially-varying polarization control, which can be tailored to optimize the sensitivity to parameter variations. Initial experiments for the two-parameter case demonstrate that this method can be used to measure physical parameters with resolutions at least 1000 times smaller than the wavelength of illumination

How University Endowments Respond to Financial Market Shocks: Evidence and Implications

Endowment payouts have become an increasingly important component of universities’ revenues in recent decades. We test two leading theories of endowment payouts: (1) universities smooth endowment payouts, or (2) universities use endowments as self-insurance against financial shocks. In contrast to both theories, endowments actively reduce payouts relative to their stated payout policies following negative, but not positive, shocks. This asymmetric behavior is consistent with “endowment hoarding,” especially among endowments with values close to the benchmark value at the start of the university president’s tenure. We also document the effect of negative endowment shocks on university operations, including personnel cuts.

Human sperm ion channel (dys)function:implications for fertilization

BACKGROUND: Intensive research on sperm ion channels has identified members of several ion channel families in both mouse and human sperm. Gene knock-out studies have unequivocally demonstrated the importance of the calcium and potassium conductances in sperm for fertility. In both species, the calcium current is carried by the highly complex cation channel of sperm (CatSper). In mouse sperm, the potassium current has been conclusively shown to be carried by a channel consisting of the pore forming subunit SLO3 and auxiliary subunit leucine-rich repeat-containing 52 (LRRC52). However, in human sperm it is controversial whether the pore forming subunit of the channel is composed of SLO3 and/or SLO1. Deciphering the role of the proton-specific Hv1 channel is more challenging as it is only expressed in human sperm. However, definitive evidence for a role in, and importance for, human fertility can only be determined through studies using clinical samples.OBJECTIVE AND RATIONALE: This review aims to provide insight into the role of sperm ion channels in human fertilization as evidenced from recent studies of sperm from infertile men. We also summarize the key discoveries from mouse ion channel knock-out models and contrast the properties of mouse and human CatSper and potassium currents. We detail the evidence for, and consequences of, defective ion channels in human sperm and discuss hypotheses to explain how defects arise and why affected sperm have impaired fertilization potential.SEARCH METHODS: Relevant studies were identified using PubMed and were limited to ion channels that have been characterized in mouse and human sperm. Additional notable examples from other species are included as appropriate.OUTCOMES: There are now well-documented fundamental differences between the properties of CatSper and potassium channel currents in mouse and human sperm. However, in both species, sperm lacking either channel cannot fertilize in vivo and CatSper-null sperm also fail to fertilize at IVF. Sperm-lacking potassium currents are capable of fertilizing at IVF, albeit at a much lower rate. However, additional complex and heterogeneous ion channel dysfunction has been reported in sperm from infertile men, the causes of which are unknown. Similarly, the nature of the functional impairment of affected patient sperm remains elusive. There are no reports of studies of Hv1 in human sperm from infertile men.WIDER IMPLICATIONS: Recent studies using sperm from infertile men have given new insight and critical evidence supporting the supposition that calcium and potassium conductances are essential for human fertility. However, it should be highlighted that many fundamental questions remain regarding the nature of molecular and functional defects in sperm with dysfunctional ion channels. The development and application of advanced technologies remains a necessity to progress basic and clinical research in this area, with the aim of providing effective screening methodologies to identify and develop treatments for affected men in order to help prevent failed ART cycles. Conversely, development of drugs that block calcium and/or potassium conductances in sperm is a plausible strategy for producing sperm-specific contraceptives.</p

Trends in antibacterial resistance among Streptococcus pneumoniae isolated in the USA: update from PROTEKT US Years 1–4

© 2008 Jenkins et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens