Top quark forward-backward asymmetry and W^prime bosons

The top quark forward-backward asymmetry measured at the Fermilab Tevatron collider deviates from the standard model prediction. A W^prime boson model is described, where the coupling W^prime-t-d is fixed by the tt_bar forward-backward asymmetry and total cross section at the Tevatron. We show that such a W^prime boson would be produced in association with a top quark at the CERN Large Hadron Collider (LHC), thus inducing additional tt_bar+j events. We use measurements of tt_bar+n-jet production from the LHC to constrain the allowed W^prime-t-d couplings as a function of W^prime boson mass. We find that this W^prime model is constrained at the 95% C.L. using 0.7 fb^{-1} of data from the LHC, and could be fully excluded with 5 fb^{-1} of data.Comment: 6 pgs., 4 PS figure

The Evolutionary Origin of the Runx/CBFbeta Transcription Factors – Studies of the Most Basal Metazoans

BACKGROUND. Members of the Runx family of transcriptional regulators, which bind DNA as heterodimers with CBFβ, are known to play critical roles in embryonic development in many triploblastic animals such as mammals and insects. They are known to regulate basic developmental processes such as cell fate determination and cellular potency in multiple stem-cell types, including the sensory nerve cell progenitors of ganglia in mammals. RESULTS. In this study, we detect and characterize the hitherto unexplored Runx/CBFβ genes of cnidarians and sponges, two basal animal lineages that are well known for their extensive regenerative capacity. Comparative structural modeling indicates that the Runx-CBFβ-DNA complex from most cnidarians and sponges is highly similar to that found in humans, with changes in the residues involved in Runx-CBFβ dimerization in either of the proteins mirrored by compensatory changes in the binding partner. In situ hybridization studies reveal that Nematostella Runx and CBFβ are expressed predominantly in small isolated foci at the base of the ectoderm of the tentacles in adult animals, possibly representing neurons or their progenitors. CONCLUSION. These results reveal that Runx and CBFβ likely functioned together to regulate transcription in the common ancestor of all metazoans, and the structure of the Runx-CBFβ-DNA complex has remained extremely conserved since the human-sponge divergence. The expression data suggest a hypothesis that these genes may have played a role in nerve cell differentiation or maintenance in the common ancestor of cnidarians and bilaterians.National Science Foundation (IBN-0212773, FP-91656101-0); Boston University SPRInG (20-202-8103-9); Israel Science Foundation (825/07

The Draft Restatement: A Critique from a Securities Regulation Perspective

For the past several years, the American Law Institute has been preparing a proposed revision of the Restatement (Second) of the Foreign Relations Law of the United States (“Draft Restatement”). This article is a critique from a securities regulation perspective of the Draft Restatement\u27s sections 402, 403, 416, 418, 419, 420 and 431.1 In short, the Draft Restatement departs substantially from existing law. It would add dangerous vagueness and uncertainty to the jurisdictional analysis used to determine whether the United States securities laws will be applied to transnational securities activities. In particular, the complicated balancing inquiry required under the Draft would increase litigation by introducing new issues into the jurisdictional analysis and by removing the certainty created by past court decisions. The Draft would make it substantially more difficult to apply United States securities laws where their application is necessary, appropriate and noncontroversial. In addition, the Draft\u27s restrictions on access to information located abroad could impair effective and even-handed enforcement of the securities laws. The Draft Restatement would also make it more difficult for the Securities and Exchange Commission to take summary action which may be necessary for the protection of securities markets in the United States. Section 1905 of the American Law Institute\u27s Federal Securities Code (“Code”), by contrast, retains the benefits of current judicial analysis by substantially codifying that reasoning, while eliminating the drawback of its case-by-case development. Although Section 1905 of the Code was drafted in the context of a general revision of the securities laws, it is a more accurate and workable “restatement” of foreign relations law. The Code also furthers the investor protection purposes of the securities laws because it takes a broader view of the appropriate application of United States securities laws than the Draft Restatement. This article compares and contrasts the analysis used under current law with the analysis that would be used under the Code and under the Draft Restatement. Part I consists of a summary review of current judicial analysis of application of United States law, a comparison of that analysis with that of the Code and the Draft Restatement and illustrations of the differences using five examples. Part II sets forth our principal concerns about the Draft Restatement\u27s approach to application of United States law. Part III critically reviews the Draft\u27s approach to access to information located abroad and the judicial and administrative enforcement mechanisms available to the Commission

A Certificateless Ring Signature Scheme and An ID-Based Multisignature Scheme from Multilinear Forms

数字签名是密码学的重要问题之一，它用来保护数据的完整性和身份识别及认证。基于公钥密码体制和私钥密码体制都可以获得数字签名，特别是公钥密码体制的诞生为数字签名的研究和应用开辟了一条广阔的道路。对于公钥密码体制需要把用户和他的公钥捆绑在一起，才能保证公钥的真实性。传统的公钥密码体制采用证书方式，虽然这样保证了用户公钥的真实性，但是对证书的管理和支持及结构上的配置是传统公钥体制的一个比较麻烦的问题之一。基于身份的公钥密码体制（简记ID-PKC）免除了证书问题，即在该体制中用户的公钥直接从用户身份的某一方面获取，但是ID-PKC有一个内在的缺点就是用户密钥托管问题，正是这个缺点严重地阻止了ID-PKC...Digital signature, one of the important applications of public key cryptosystem, can be used to protect data integrity and authenticate the identity of the sender of a message. It plays an important role in the electronic transactions. Public Key Cryptography (PKC)is gaining a considerable attention because it can assure the security requirements of many applications. To guarantee the authenticity...学位：理学硕士院系专业：数学系_基础数学学号：20022301

The Conservation Reserve Program: Economic Implications for Rural America

This report estimates the impact that high levels of enrollment in the Conservation Reserve Program (CRP) have had on economic trends in rural counties since the program's inception in 1985 until today. The results of a growth model and quasi-experimental control group analysis indicate no discernible impact by the CRP on aggregate county population trends. Aggregate employment growth may have slowed in some high-CRP counties, but only temporarily. High levels of CRP enrollment appear to have affected farm-related businesses over the long run, but growth in the number of other nonfarm businesses moderated CRP's impact on total employment. If CRP contracts had ended in 2001, simulation models suggest that roughly 51 percent of CRP land would have returned to crop production, and that spending on outdoor recreation would decrease by as much as $300 million per year in rural areas. The resulting impacts on employment and income vary widely among regions having similar CRP enrollments, depending upon local economic conditions.Community/Rural/Urban Development, Land Economics/Use,

The critical detection distance for passively tracking tagged fish using a fixed radio telemetry station in a small stream

Background: Fixed radio telemetry stations are used to study the movement ecology of fishes in streams and rivers. A common assumption of such studies is that detection efficiency remains constant through space and time. The objective of this study was to understand how site characteristics and tag distance can influence the detection efficiency of a fixed receiver when used for fisheries research in a small stream. Field tests included a fixed receiver station on Forty Mile Creek, in Banff National Park, AB, Canada that recorded signals from radio tags over specified distances (i.e., 0 m, 27 m, 53 m, 80 m) within the expected detection range from July to October, 2016. Model selection was used to test which parameters may influence detection efficiency. Results: The fixed receiver was able to record an average of 89% of transmissions over the study period. Detection efficiency was greater or equal to 0.97 at tag di