3,598 research outputs found
Statistical Mechanics of 2+1 Gravity From Riemann Zeta Function and Alexander Polynomial:Exact Results
In the recent publication (Journal of Geometry and Physics,33(2000)23-102) we
demonstrated that dynamics of 2+1 gravity can be described in terms of train
tracks. Train tracks were introduced by Thurston in connection with description
of dynamics of surface automorphisms. In this work we provide an example of
utilization of general formalism developed earlier. The complete exact solution
of the model problem describing equilibrium dynamics of train tracks on the
punctured torus is obtained. Being guided by similarities between the dynamics
of 2d liquid crystals and 2+1 gravity the partition function for gravity is
mapped into that for the Farey spin chain. The Farey spin chain partition
function, fortunately, is known exactly and has been thoroughly investigated
recently. Accordingly, the transition between the pseudo-Anosov and the
periodic dynamic regime (in Thurston's terminology) in the case of gravity is
being reinterpreted in terms of phase transitions in the Farey spin chain whose
partition function is just a ratio of two Riemann zeta functions. The mapping
into the spin chain is facilitated by recognition of a special role of the
Alexander polynomial for knots/links in study of dynamics of self
homeomorphisms of surfaces. At the end of paper, using some facts from the
theory of arithmetic hyperbolic 3-manifolds (initiated by Bianchi in 1892), we
develop systematic extension of the obtained results to noncompact Riemannian
surfaces of higher genus. Some of the obtained results are also useful for 3+1
gravity. In particular, using the theorem of Margulis, we provide new reasons
for the black hole existence in the Universe: black holes make our Universe
arithmetic. That is the discrete Lie groups of motion are arithmetic.Comment: 69 pages,11 figures. Journal of Geometry and Physics (in press
United States Food Law Update: Moving Toward a More Balanced Food Regulatory Regime
For decades, the federal government has played a significant role in promoting healthy eating. In the early 1900s, the United States Department of Agriculture (USDA) promoted a foundational diet of milk, proteins, fruits and vegetables, and grains. Most Americans are at least somewhat familiar, although perhaps confused, with the more nuanced healthy eating recommendations contained in the food pyramid - first employed in 1992. And virtually every American has experienced the federally supported school lunch program. In the first half of 2011, these two iconic programs underwent significant change as part of a stepped-up effort to improve the health of the country through better food choices. Part I of this article describes the MyPlate initiative that replaces the iconic USDA food pyramid and menu revisions to the national school lunch and school breakfast programs. This section also profiles administrative decisions in two school districts to ban, on health grounds, brown- bag lunches in favor of school- provided lunches. Finally, this section describes some of the challenges of implementing a rule for chain restaurant menu labeling under the Patient Protection and Affordable Care Act
United States Food Law Update: The FDA Food Safety Modernization Act, Obesity and Deceptive Labeling Enforcement
The long-awaited enactment of the FDA Food Safety Modernization Act (FSMA), the most significant amendment to the Federal Food, Drug, and Cosmetic Act in several decades, provides the Food and Drug Administration (FDA) with significantly enhanced jurisdiction to close some of the gaps in the domestic food safety system. The enhanced FDA authority, however, will have little impact on the shared governance system at the federal level that involves multiple agencies, as the Act does not address the U.S. General Accounting Office\u27s (GAO) repeated calls for consolidation of the fragmented federal food safety system. Rather, the Act perpetuates the division of authority between the FDA and the U.S. Department of Agriculture (USDA), as well as the potential for jurisdictional gaps, overlaps and inefficiencies. Part I of this article explores not only the FSMA, but a second piece of federal legislation, the Healthy, Hunger-Free Kids Act of 2010, which inter alia provides support for serving locally grown food in the school lunch program. Part II provides a brief update on three ongoing food law issues: the Pelman v. McDonald\u27s Corp. obesity litigation and associated local initiatives directed at the fast food restaurant industry, legal challenges to the raw almond pasteurization rule, and an update on the FDA\u27s review of genetically engineered salmon. Part III explores in greater depth a series of public and private enforcement actions directed toward allegedly deceptive labeling
The Rb binding domain of HPV31 E7 is required to maintain high levels of DNA repair factors in infected cells
Human papillomaviruses (HPV) exhibit constitutive activation of ATM and ATR DNA damage response (DDR) pathways, which are required for productive viral replication. Expression of HPV31 E7 alone is sufficient to activate the DDR through an unknown mechanism. Here, we demonstrate that the E7 Rb binding domain is required to increase levels of many DDR proteins, including ATM, Chk2, Chk1, the MRN components MRE11, Rad50, and NBS1, as well as the homologous recombination repair proteins BRCA1 and Rad51. Interestingly, we have found that the increase in these DNA repair proteins does not occur solely at the level of transcription, but that E7 broadly increases the half-life of these DDR factors, a phenotype that is lost in the E7 Rb binding mutant. These data suggest that HPV-31 upregulates DNA repair factors necessary for replication by increasing protein half-life in a manner requiring the E7 Rb binding domain
In vivo nuclear magnetic resonance imaging
A number of physiological changes have been demonstrated in bone, muscle and blood after exposure of humans and animals to microgravity. Determining mechanisms and the development of effective countermeasures for long duration space missions is an important NASA goal. The advent of tomographic nuclear magnetic resonance imaging (NMR or MRI) gives NASA a way to greatly extend early studies of this phenomena in ways not previously possible; NMR is also noninvasive and safe. NMR provides both superb anatomical images for volume assessments of individual organs and quantification of chemical/physical changes induced in the examined tissues. The feasibility of NMR as a tool for human physiological research as it is affected by microgravity is demonstrated. The animal studies employed the rear limb suspended rat as a model of mucle atrophy that results from microgravity. And bedrest of normal male subjects was used to simulate the effects of microgravity on bone and muscle
G-Ruption: The Third International Meeting On G-Quadruplex And G-Assembly
A three and a half day conference focusing on nucleic acid structures called G-quadruplexes (G4s) and other guanine-based assemblies was held in Sorrento. Italy (June 28-July 1, 2011) and featured 35 invited talks and over 89 posters. The G-quadruplex field continues to expand at an explosive rate with the emergence of new connections to biology, chemistry, physics, and nanotechnology. Following the trend established by the previous two international G4 meetings, the conference touched upon all these areas and facilitated productive exchanges of ideas between researchers from all over the world
Viral metagenomics, protein structure, and reverse genetics: Key strategies for investigating coronaviruses
Viral metagenomics, modeling of protein structure, and manipulation of viral genetics are key approaches that have laid the foundations of our understanding of coronavirus biology. In this review, we discuss the major advances each method has provided and discuss how future studies should leverage these strategies synergistically to answer novel questions
United States Food Law Update: Health Care Reform, Preemption, Labeling Claims and Unpaid Interns: The Latest Battles in Food Law
This edition of the Food Law Update explores four legal issues arising in the first half of 2010 reflective of the diverse nature of the food law specialist. As the national debate surrounding the merits of health care reform dominated the legislative agenda, this article first will discuss the food labeling rules embedded within section 4205 of the Patient Protection and Affordable Care Act of 2010. The authors then analyze the preemptive reach of the Federal Food, Drug, and Cosmetic Act and the Meat Inspection Act with respect to three separate California statutes regarding animal welfare standards, retail labels on meat packages and state-based mislabeling claims for natural products. Section three further discusses litigation concerning allegedly misleading label claims of health benefits, nutritional composition, natural foods and Country-of-Origin. The final section of this Update explores an increasingly important legal issue common in the local foods/small scale production content - the use of unpaid interns as labor and potential changes in regulatory oversight
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The Influence of Government Regulations on Content Management Systems: An Exploratory Study
The primary focus of this study was to determine why and how small businesses implement content management and to clarify the relationship of content management to regulatory compliance issues presented by the Health Insurance Portability and Accountability and Sarbanes-Oxley Act
Ozone profile observations in Houston, Texas (1994 - 2010) from aircraft, balloons, and satellites
Houston, Texas has long been an urban area plagued with high levels of surface ozone, particularly in spring and late summer. The combination of a large commuter population and one of the largest concentrations of petrochemical plants in the world results in abundant and nearly co-located sources of NOx and hydrocarbons. The location of Houston on the South Coast of the United States in a subtropical climate results in meteorological conditions that favor ozone production. Using MOZAIC (1994 - 2004), ozonesonde (2000, 2004 - 2010), and TES (2005 – 2010) data, we examine the evolution of ozone profiles over Houston during a period in which various strategies have been implemented to alleviate the ozone pollution problem. Using meteorological data from associated soundings and analyses, we identify and evaluate influences on the ozone profiles from natural and anthropogenic sources, as well as local and remote sources. We further investigate how these various influences have changed with time
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