Cyclic Statistics In Three Dimensions

While 2-dimensional quantum systems are known to exhibit non-permutation, braid group statistics, it is widely expected that quantum statistics in 3-dimensions is solely determined by representations of the permutation group. This expectation is false for certain 3-dimensional systems, as was shown by the authors of ref. [1,2,3]. In this work we demonstrate the existence of ``cyclic'', or $Z_n$, {\it non-permutation group} statistics for a system of n > 2 identical, unknotted rings embedded in $R^3$. We make crucial use of a theorem due to Goldsmith in conjunction with the so called Fuchs-Rabinovitch relations for the automorphisms of the free product group on n elements.Comment: 13 pages, 1 figure, LaTex, minor page reformattin

Analytical Challenges and Metrological Approaches to Ensuring Dietary Supplement Quality: International Perspectives

The increased utilization of metrology resources and expanded application of its’ approaches in the development of internationally agreed upon measurements can lay the basis for regulatory harmonization, support reproducible research, and advance scientific understanding, especially of dietary supplements and herbal medicines. Yet, metrology is often underappreciated and underutilized in dealing with the many challenges presented by these chemically complex preparations. This article discusses the utility of applying rigorous analytical techniques and adopting metrological principles more widely in studying dietary supplement products and ingredients, particularly medicinal plants and other botanicals. An assessment of current and emerging dietary supplement characterization methods is provided, including targeted and non-targeted techniques, as well as data analysis and evaluation approaches, with a focus on chemometrics, toxicity, dosage form performance, and data management. Quality assessment, statistical methods, and optimized methods for data management are also discussed. Case studies provide examples of applying metrological principles in thorough analytical characterization of supplement composition to clarify their health effects. A new frontier for metrology in dietary supplement science is described, including opportunities to improve methods for analysis and data management, development of relevant standards and good practices, and communication of these developments to researchers and analysts, as well as to regulatory and policy decision makers in the public and private sectors. The promotion of closer interactions between analytical, clinical, and pharmaceutical scientists who are involved in research and product development with metrologists who develop standards and methodological guidelines is critical to advance research on dietary supplement characterization and health effects

The imperative for controlled mechanical stresses in unraveling cellular mechanisms of mechanotransduction

BACKGROUND: In vitro mechanotransduction studies are designed to elucidate cell behavior in response to a well-defined mechanical signal that is imparted to cultured cells, e.g. through fluid flow. Typically, flow rates are calculated based on a parallel plate flow assumption, to achieve a targeted cellular shear stress. This study evaluates the performance of specific flow/perfusion chambers in imparting the targeted stress at the cellular level. METHODS: To evaluate how well actual flow chambers meet their target stresses (set for 1 and 10 dyn/cm(2 )for this study) at a cellular level, computational models were developed to calculate flow velocity components and imparted shear stresses for a given pressure gradient. Computational predictions were validated with micro-particle image velocimetry (μPIV) experiments. RESULTS: Based on these computational and experimental studies, as few as 66% of cells seeded along the midplane of commonly implemented flow/perfusion chambers are subjected to stresses within ±10% of the target stress. In addition, flow velocities and shear stresses imparted through fluid drag vary as a function of location within each chamber. Hence, not only a limited number of cells are exposed to target stress levels within each chamber, but also neighboring cells may experience different flow regimes. Finally, flow regimes are highly dependent on flow chamber geometry, resulting in significant variation in magnitudes and spatial distributions of stress between chambers. CONCLUSION: The results of this study challenge the basic premise of in vitro mechanotransduction studies, i.e. that a controlled flow regime is applied to impart a defined mechanical stimulus to cells. These results also underscore the fact that data from studies in which different chambers are utilized can not be compared, even if the target stress regimes are comparable

Neuroserpin polymorphisms and stroke risk in a biracial population: the stroke prevention in young women study

<p>Abstract</p> <p>Background</p> <p>Neuroserpin, primarily localized to CNS neurons, inhibits the adverse effects of tissue-type plasminogen activator (tPA) on the neurovascular unit and has neuroprotective effects in animal models of ischemic stroke. We sought to evaluate the association of neuroserpin polymorphisms with risk for ischemic stroke among young women.</p> <p>Methods</p> <p>A population-based case-control study of stroke among women aged 15–49 identified 224 cases of first ischemic stroke (47.3% African-American) and 211 age-matched control subjects (43.1% African-American). Neuroserpin single nucleotide polymorphisms (SNPs) chosen through HapMap were genotyped in the study population and assessed for association with stroke.</p> <p>Results</p> <p>Of the five SNPs analyzed, the A allele (frequency; Caucasian = 0.56, African-American = 0.42) of SNP rs6797312 located in intron 1 was associated with stroke in an age-adjusted dominant model (AA and AT vs. TT) among Caucasians (OR = 2.05, p = 0.023) but not African-Americans (OR = 0.71, p = 0.387). Models adjusting for other risk factors strengthened the association. Race-specific haplotype analyses, inclusive of SNP rs6797312, again demonstrated significant associations with stroke among Caucasians only.</p> <p>Conclusion</p> <p>This study provides the first evidence that neuroserpin is associated with early-onset ischemic stroke among Caucasian women.</p

Correction to: Cluster identification, selection, and description in Cluster randomized crossover trials: the PREP-IT trials

An amendment to this paper has been published and can be accessed via the original article

Nanofiber-Based Expansion and Differentiation Technology for High-Volume Ex Vivo Production of Reticulocytes for P. Vivax Malaria Research

Abstract Abstract 2357 Infection by Plasmodium Vivax (P. Vivax) is the most common cause of Sleeping Malaria. P. Vivax and other plasmodia have grown increasingly resistant to antimalarial drugs. Introduced by mosquito bite, P. vivax sporozoites enter circulation and preferentially penetrate reticulocytes by attaching to the Fya and Fyb Duffy antigen/chemokine receptor (DARC) via PvRBP-1 and PvRBP-2 proteins located at their apical poles. Once in a reticulocyte, the parasite begins to reproduce asexually, releasing of thousands of merozoites into circulation. At this point, merozoites can also enter the liver and triggering relapses months or years later. The emergence of drug-resistant strains of p. vivax has stimulated development of new vaccines and treatments, but progress has been slowed by the dearth of reliable screening platforms. Many vaccine candidates have been developed to act upon vivax merozoites by preventing binding of PvRBP-1 and 2 to DARC, thereby arresting reproduction. However, there is a distinct lack of in vitro models to evaluate candidates that employ this mechanism. We are addressing this issue with a novel ex vivo expansion and differentiation technology for large-scale production of DARC expressing reticulocytes for in vitro P. vivax infection studies. This technology comprises an expansion system that can produce high yields of hematopoietic precursors (CD133+/CD34+ cells) from a variety of sources (marrow, peripheral blood, and cord blood), and a differentiation system to produce a relatively pure population of enucleated erythrocytes. In this study, we have refined the polyethersulfone (PES) nanofiber-based culturing system containing growth factors and cytokines in a serum-free media, to expand hematopoietic stem and progenitor cells (HSPC) ex vivo. This expansion technology allows rapid 200-fold ex vivo proliferation within 7 days of umbilical cord blood derived CD133+/CD34+ HSPCs from a DARC+ donor. Following expansion, over 50% of these cells retained HSPC phenotype (expression of CD34+). We have subsequently demonstrated that feeder layer free three-step differentiation of nanofiber-expanded cells using cytokines results in a population containing predominately enucleated reticulocyte-like cells. At 21 days of differentiation, cells had expanded 50-fold. Around 41% of cells were enucleated reticulocytes. These cells expressed glycophorin-A, a major sialoglycoprotein present on the human erythrocyte membrane. ∼28% of cells were CD36+, and ∼70% were CD71+ indicating an erythroid lineage. These results suggest that this technology can produce a population of DARC+ reticulocytes that is ∼5,000-fold greater than the starting population of HSPCs. We are partnering with leading malaria vaccine researchers to demonstrate that these reticulocytes can be parasitized by p. vivax. We believe that this will provide a unique platform to jumpstart research of malaria parasites and enable rapid development of effective vaccines. Further development of this technology may also have significant implications for large-scale ex vivo production of erythrocytes for general use. Reticulocyte-like cells and expelled nuclei during differentiation of nanofiber-expanded HSPC. Disclosures: No relevant conflicts of interest to declare. </jats:sec

Urban Safety, Anti-Social Behaviour and the Night-Time Economy

The contemporary city is a contested space and its governance is the subject of complex global economic forces, local interests and political struggles as well as a response to the changing face of governing alliances in residential and commercial areas, forms of consumption, commercially-generated crime and disorder and cultural expressions of leisure. This article seeks to provide a thematic introduction to the manner in which the regulation of contemporary British cities has been influenced by concerns with tackling anti-social behaviour and promoting civility. It argues that in governing urban safety, the normative governmental agendas that seek to remoralise and cleanse city spaces and promote certain values of appropriate consumer-citizen, often clash with commercially-driven imperatives to (excessive) consumption and the allure of cities, for some, as places of difference that exhibit relaxed normative constraints; most notably in the night-time economy. It argues that the manner in which these forces are played out is conditioned by the interplay between different actors and organisations, as both regulators and regulated, some of whom have assumed new responsibilities in the governance of urban safety. The resultant pressures have produced mixed experiences of the city as a meeting place for loosely connected strangers, as a place of indulgence and as a place of cultural expression