The physical basis for Parrondo's games

Several authors have implied that the original inspiration for Parrondo's games was a physical system called a ``flashing Brownian ratchet''. The relationship seems to be intuitively clear but, surprisingly, has not yet been established with rigor. In this paper, we apply standard finite-difference methods of numerical analysis to the Fokker-Planck equation. We derive a set of finite difference equations and show that they have the same form as Parrondo's games. Parrondo's games, are in effect, a particular way of sampling a Fokker-Planck equation. Physical Brownian ratchets have been constructed and have worked. It is hoped that the finite element method presented here will be useful in the simulation and design of flashing Brownian ratchets.Comment: 10 pages and 2 figure

Agreement between mothers and children with malocclusion in rating children's oral health-related quality of life

Introduction: The aim of this study was to compare the assessment of oral health-related quality of life (OH-QoL) between children with malocclusion and their mothers, by using responses to the child perceptions questionnaire and the parental-caregivers perceptions questionnaire. Methods: The study was conducted in 90 children, aged 11 to 14 years, with a malocclusion grade of 4 or 5 according to the index of orthodontic treatement need dental health component. The children and their mothers completed the questionnaires independently. Results: The mean ratings were similar for total scores (children, 20.4; mothers, 20.1), oral symptoms (children, 5.2; mothers, 4.7), and social well-being (children, 4.3; mothers, 4.8). However, the mothers group had a lower mean score for functional limitations (children, 5.3; mothers, 3.6) and a higher mean score for emotional well-being (children, 5.6; mothers, 7.1). The correlations between children's and mothers' responses ranged from rs = 0.545 for total score and emotional well-being to rs = 0.357 for functional limitations. There were good correlations between their responses to global (rs = 0.466) and life overall (rs = 0.427) questions, but poor correlations between the 2 questions, suggesting that these concepts were considered differently. Conclusions: Maternal opinions were similar to those of their children for the overall impact on OH-QoL of malocclusion, but mothers were more dissatisfied with the appearance of their children's teeth and overestimated the emotional impact of malocclusion. It would be useful to develop a specific measure to assess OH-QoL in children with malocclusion. (Am J Orthod Dentofacial Orthop 2010;137:631-8

Photonic Quantum Logic with Narrowband Light from Single Atoms

Increasing control of single photons enables new applications of photonic quantum-enhanced technology and further experimental exploration of fundamental quantum phenomena. Here, we demonstrate quantum logic using narrow linewidth photons that are produced under nearly perfect quantum control from a single ^87Rb atom strongly coupled to a high-finesse cavity. We use a controlled- NOT gate integrated into a photonic chip to entangle these photons, and we observe non-classical correlations between events separated by periods exceeding the travel time across the chip by three orders of magnitude. This enables quantum technology that will use the properties of both narrowband single photon sources and integrated quantum photonics, such as networked quantum computing, narrow linewidth quantum enhanced sensing and atomic memories.Comment: 5 pates, 3 figure

Heterometallic cobalt(ii) calix[6 and 8]arenes: synthesis, structure and electrochemical activity

Heterometallic cobalt p-tert-butylcalix[6 and 8]arenes have been generated from the in situ reaction of lithium reagents (n-BuLi or t-BuOLi) or NaH with the parent calix[n]arene and subsequent reaction with CoBr2. The reverse route, involving the addition of in situ generated Li[Co(Ot-Bu)3] to p-tert-butylcalix[6 and 8]arene, has also been investigated. X-ray crystallography reveals the formation of complicated products incorporating differing numbers of cobalt and lithium or sodium centers, often with positional disorder, as well as, in some cases, the retention of halide. The electrochemical analysis revealed several oxidation events related to the subsequent oxidation of Co(ii) centers and the reduction of the metal cation at negative potentials. Moreover, the electrochemical activity of the phenol moieties of the parent calix[n]arenes resulted in dimerized products or quinone derivatives, leading to insoluble oligomeric products that deposit and passivate the electrode. Preliminary screening for electrochemical proton reduction revealed good activity for a number of these systems. Results suggest that [Co6Na(NCMe)6(μ-O)(p-tert-butylcalix[6]areneH)2Br]·7MeCN (6·7MeCN) is a promising molecular catalyst for electrochemical proton reduction, with a mass transport coefficient, catalytic charge transfer resistance and current magnitude at the catalytic turnover region that are comparable to those of the reference electrocatalyst (Co(ii)Cl2)

American Ginseng Modifies 137Cs-Induced DNA Damage and Oxidative Stress in Human Lymphocytes

The multifold bioactive medicinal properties of ginseng have been closely linked to its antioxidative ability, which is related to its ginsenoside content. Since the key mechanism of radiation-induced cell death and tissue damage is the generation of reactive oxygen species (ROS) that attack cellular DNA, this study focuses on the impact of a standardized North American ginseng extract (NAGE) on 137Cs-induced oxidative stress in human peripheral lymphocytes (PBL) obtained from 10 healthy individuals (6M/4F), 42.7 ± 4.6 years of age. At two different time points (0 h and 24 h before irradiation), we applied NAGE (250 - 1000 µg ml-1) to mononuclear cell cultures for cytokinesisblock micronuclei (MN) assay and determination of the state of oxidative stress in PBL. We found that at both time points, NAGE significantly reduced the MN yields in PBL after irradiation (1 and 2 Gy) in a concentration-dependent manner (P<0.001). Compared with radiation alone, the maximum reduction rate of MN yield were 51.1% and 49.1% after 1 Gy and 2 Gy exposures, respectively. We also found that before irradiation the presence of NAGE in the culture medium resulted in a significant increased intracellular total antioxidant capacity (TAC) in PBL. At both time points, the increment of 137Cs-induced MN yields in PBL was positively correlated with the increment of intracellular ROS production (R = 0.6 - 0.7, P = 0.002), but negatively correlated with the reduction of TAC levels (R = -0.4 - 0.5, P = 0.02 - 0.004). However, the presence of NAGE in the culture medium significantly increased the TAC levels, while concomitantly decreasing both ROS production and MN yields in PBL (P<0.001). Our findings that NAGE is effective in protecting human PBL against radiation-induced oxidative stress should encourage further in vivo study of dietary supplementation with NAGE as an effective natural radiation countermeasure. Originally published Open Nuclear Medicine Journal Vol 1 No. 1, 2009

Self-reported health and cardiovascular reactions to psychological stress in a large community sample: Cross-sectional and prospective associations

Exaggerated cardiovascular reactions to acute psychological stress have been implicated in a number of adverse health outcomes. This study examined, in a large community sample, the cross-sectional and prospective associations between reactivity and self-reported health. Blood pressure and heart rate were measured at rest and in response to an arithmetic stress task. Self-reported health was assessed concurrently and five years later. In cross-sectional analyses, those with excellent/good self-reported health exhibited larger cardiovascular reactions than those with fair/poor subjective health. In prospective analyses, participants who had larger cardiovascular reactions to stress were more likely to report excellent/good health five years later, taking into account their reported health status at the earlier assessment. The findings suggest that greater cardiovascular reactivity may not always be associated with negative health outcomes

Radioprotective Effect of American Ginseng on Human Lymphocytes at 90 Minutes Post-irradiation: A Study of 40 Cases

Backgroundâ Ionizing radiation (IR) initiates intracellular oxidative stress through enhanced formation of reactive oxygen species (ROS) that attack DNA leading to cell death. As the diversity of IR applied in medicine, agriculture, industry, and the growing threats of global terrorism, the acquisition of radioprotectors is an urgent need for the nation. However, the applicability of radioprotectors currently under investigation is limited due to their inherent toxicity. Objectiveâ This study investigated the effect of a standardized North American ginseng extract (NAGE, total ginsenoside content: 11.7%) on DNA damage in human lymphocytes at 90 min postirradiation. Designâ With the application of NAGE (250 â 1000 μg mlâ 1) at 90 min post-irradiation (1 and 2 Gy), DNA damage in lymphocytes obtained from 40 healthy individuals was evaluated by cytokinesis-block micronucleus (CBMN) assay. Similar experiments were also performed in lymphocytes treated with WR-1065 (1 mM or 3mM). In addition, before and after irradiation, lymphocytes obtained from 10 individuals were measured for their total antioxidant capacity (TAC) and the reactive oxygen species (ROS). Resultsâ The significant effect of NAGE against 137Cs-induced MN in lymphocytes is concentration-dependent. NAGE (750 μg mlâ 1) reduced MN yield by 50.7% after 1 Gy and 35.9% after 2 Gy exposures, respectively; these results were comparable to that of WR-1065. Further, we also found that NAGE reduces MN yield and ROS but increases TAC in lymphocytes. Conclusionsâ Our results suggest that NAGE is a relatively non-toxic natural compound that holds radioprotective potential in human lymphocytes even when applied at 90 min post-irradiation. One of the radioprotective mechanisms may be mediated through the scavenging of free radicals and enhancement of the intracellular TAC. Originally published Journal of Alternative and Complementary Medicine Vol. 16, No. 5 2010

Islet β-Cells Deficient in Bcl-xL Develop but Are Abnormally Sensitive to Apoptotic Stimuli

OBJECTIVE: Bcl-xL is an antiapoptotic member of the Bcl-2 family of proteins and a potent regulator of cell death. We investigated the importance of Bcl-xL for beta-cells by deleting the Bcl-x gene specifically in beta-cells and analyzing their survival in vivo and in culture. RESEARCH DESIGN AND METHODS: Islets with beta-cells lacking the Bcl-x gene were assessed in vivo by histology and by treatment of mice with low-dose streptozotocin (STZ). Islets were isolated by collagenase digestion and treated in culture with the apoptosis inducers staurosporine, thapsigargin, gamma-irradiation, proinflammatory cytokines, or Fas ligand. Cell death was assessed by flow cytometric analysis of subgenomic DNA. RESULTS: Bcl-xL-deficient beta-cells developed but were abnormally sensitive to apoptosis induced in vivo by low-dose STZ. Although a small proportion of beta-cells still expressed Bcl-xL, these did not have a survival advantage over their Bcl-xL-deficient neighbors. Islets appeared normal after collagenase isolation and whole-islet culture. They were, however, abnormally sensitive in culture to a number of different apoptotic stimuli including cytotoxic drugs, proinflammatory cytokines, and Fas ligand. CONCLUSIONS: Bcl-xL expression in beta-cells is dispensible during islet development in the mouse. Bcl-xL is, however, an important regulator of beta-cell death under conditions of synchronous stress. Bcl-xL expression at physiological levels may partially protect beta-cells from apoptotic stimuli, including apoptosis because of mediators implicated in type 1 diabetes and death or degeneration of transplanted islets

The Empirical Landscape of Trade Policy

This chapter surveys empirically the broad features of trade policy in goods for 31 major economies that collectively represented 83 percent of the world's population and 91 percent of the world's GDP in 2013. We address five questions: Do some countries have more liberal trading regimes than others? Within countries, which industries receive the most import protection? How do trade policies change over time? Do countries discriminate among their trading partners when setting trade policy? Finally, how liberalized is world trade? Our analysis documents the extent of cross-sectional heterogeneity in applied commercial policy across countries, their economic sectors, and their trading partners, over time. We conclude that substantial trade policy barriers remain as an important feature of the world economy.antidumpin