Site Percolation and Phase Transitions in Two Dimensions

The properties of the pure-site clusters of spin models, i.e. the clusters which are obtained by joining nearest-neighbour spins of the same sign, are here investigated. In the Ising model in two dimensions it is known that such clusters undergo a percolation transition exactly at the critical point. We show that this result is valid for a wide class of bidimensional systems undergoing a continuous magnetization transition. We provide numerical evidence for discrete as well as for continuous spin models, including SU(N) lattice gauge theories. The critical percolation exponents do not coincide with the ones of the thermal transition, but they are the same for models belonging to the same universality class.Comment: 8 pages, 6 figures, 2 tables. Numerical part developed; figures, references and comments adde

Broken scaling in the Forest Fire Model

We investigate the scaling behavior of the cluster size distribution in the Drossel-Schwabl Forest Fire model (DS-FFM) by means of large scale numerical simulations, partly on (massively) parallel machines. It turns out that simple scaling is clearly violated, as already pointed out by Grassberger [P. Grassberger, J. Phys. A: Math. Gen. 26, 2081 (1993)], but largely ignored in the literature. Most surprisingly the statistics not seems to be described by a universal scaling function, and the scale of the physically relevant region seems to be a constant. Our results strongly suggest that the DS-FFM is not critical in the sense of being free of characteristic scales.Comment: 9 pages in RevTEX4 format (9 figures), submitted to PR

Gas filaments of the cosmic web located around active galaxies in a protocluster

Cosmological simulations predict the Universe contains a network of intergalactic gas filaments, within which galaxies form and evolve. However, the faintness of any emission from these filaments has limited tests of this prediction. We report the detection of rest-frame ultraviolet Lyman-alpha radiation from multiple filaments extending more than one megaparsec between galaxies within the SSA 22 proto-cluster at a redshift of 3.1. Intense star formation and supermassive black-hole activity is occurring within the galaxies embedded in these structures, which are the likely sources of the elevated ionizing radiation powering the observed Lyman-alpha emission. Our observations map the gas in filamentary structures of the type thought to fuel the growth of galaxies and black holes in massive proto-clusters

Rethinking ecosystem service indicators for their application to intermittent rivers

In these times of strong pressure on aquatic ecosystems and water resources due to climate change and water abstraction, intermittent rivers and ephemeral streams (IRES) (rivers that periodically cease to flow and/or dry) have become valuable assets. Indeed, not only do they supply water but they also offer services for humanity. Despite a growing recognition towards IRES, information for assessing their ecosystem services (ES) remains scarce. In a first step, an international interdisciplinary group of researchers developed a methodological framework to acknowledge ES provided by IRES using 109 indicators. A subset of selected ES indicators was then applied to two case studies: the Rio Seco in the Algarve (Portugal) and the Giofyros River in Crete (Greece). This paper discusses the applicability of these indicators, including the temporal and spatial variability of IRES flow regimes. Aspects of the framework, such as the methods and time required for data collection, the nature (demand or supply) and functionality of each indicator are discussed. The new framework accounts for flow intermittence in ES analyses and can help scientists and water managers to i) increase the ease and justification for IRES use in management approaches and ii) improve their conservation and restoration with a comprehensive set of appropriate indicators for IRES. In addition, the comprehensive nature of the proposed indicators ensures that they can be understood by a broad audience and easily applicable. Since they were designed through a public participation process, the setting has been prepared for holistic stakeholder analysis and education around IRES functions and associated ES. From a management point of view, it would be particularly relevant to perform an economic evaluation with this new framework to understand the value of each ES category and their trade-offs. For the scientific community, however, it is important to consider public preferences to design socially accepted policies. The proposed indicators can successfully bridge these elements, hereby establishing a solid basis for the assessment of ES provided by IRES.info:eu-repo/semantics/publishedVersio

Apple peel and flesh contain pro-neurogenic compounds

As mammals evolved with exposure to particular diets, naturally abundant compounds may have become part of the set of environmental co-determinants that shaped brain structure and function. Here we investigated whether bioactive factors found in apples directly affect hippocampal neurogenesis in the adult mouse. We found that quercetin, the most abundant flavanol in apple peel, was anti-proliferative at high concentrations but pro-neurogenic at low concentrations. This was confirmed in vivo, with intraperitoneally delivered quercetin promoting survival and neuronal differentiation, without affecting proliferation. Using a bioassay-guided fractionation approach we also identified additional pro-neurogenic compounds in apple flesh that were not related to flavonoids. We found that 3,5-dihydroxybenzoic acid significantly increased neural precursor cell proliferation and neurogenesis. This work shows that both flavonoids and 3,5-dihydroxybenzoic acid are pro-neurogenic, not only by activating precursor cell proliferation but also by promoting cell-cycle exit, cellular survival, and neuronal differentiation

Food insecurity is associated with lower levels of antiretroviral drug concentrations in hair among a cohort of women living with human immunodeficiency virus in the United States

Background. Food insecurity is a well-established determinant of suboptimal, self-reported antiretroviral therapy (ART) adherence, but few studies have investigated this association using objective adherence measures. We examined the association of food insecurity with levels of ART concentrations in hair among women living with human immunodeficiency virus (WLHIV) in the United States. Methods. We analyzed longitudinal data collected semiannually from 2013 through 2015 from the Women's Interagency HIV Study, a multisite, prospective, cohort study of WLHIV and controls not living with HIV. Our sample comprised 1944 person-visits from 677 WLHIV. Food insecurity was measured using the US Household Food Security Survey Module. ART concentrations in hair, an objective and validated measure of drug adherence and exposure, were measured using high-performance liquid chromatography with mass spectrometry detection for regimens that included darunavir, atazanavir, raltegravir, or dolutegravir. We conducted multiple 3-level linear regressions that accounted for repeated measures and the ART medication(s) taken at each visit, adjusting for sociodemographic and clinical characteristics. Results. At baseline, 67% of participants were virally suppressed and 35% reported food insecurity. In the base multivariable model, each 3-point increase in food insecurity was associated with 0.94-fold lower ART concentration in hair (95% confidence interval, 0.89 to 0.99). This effect remained unchanged after adjusting for self-reported adherence. Conclusions. Food insecurity was associated with lower ART concentrations in hair, suggesting that food insecurity may be associated with suboptimal ART adherence and/or drug absorption. Interventions seeking to improve ART adherence among WLHIV should consider and address the role of food insecurity

Therapeutic Potential of a Novel Vitamin D3 Oxime Analogue, VD1-6, with CYP24A1 Enzyme Inhibitory Activity and Negligible Vitamin D Receptor Binding

Abstract: The regulation of vitamin D3 actions in humans occurs mainly through the Cytochrome P450 24-hydroxylase (CYP24A1) enzyme activity. CYP24A1 hydroxylates both 25-hydroxycholecalciferol (25(OH)D3) and 1,25-dihydroxycholecalciferol (1,25(OH)2D3), which is the first step of vitamin D catabolism. An abnormal status of the upregulation of CYP24A1 occurs in many diseases, including chronic kidney disease (CKD). CYP24A1 upregulation in CKD and diminished activation of vitamin D3 contribute to secondary hyperparathyroidism (SHPT), progressive bone deterioration, and soft tissue and cardiovascular calcification. Previous studies have indicated that CYP24A1 inhibition may be an effective strategy to increase endogenous vitamin D activity and decrease SHPT. This study has designed and synthesized a novel C-24 O-methyloxime analogue of vitamin D3 (VD1-6) to have specific CYP24A1 inhibitory properties. VD1-6 did not bind to the vitamin D receptor (VDR) in concentrations up to 10-7 M, assessed by a VDR binding assay. The absence of VDR binding by VD1-6 was confirmed in human embryonic kidney HEK293T cultures through the lack of CYP24A1 induction. However, in silico docking experiments demonstrated that VD1-6 was predicted to have superior binding to CYP24A1, when compared to that of 1,25(OH)2D3. The inhibition of CYP24A1 by VD1-6 was also evident by the synergistic potentiation of 1,25(OH)2D3-mediated transcription and reduced 1,25(OH)2D3 catabolism over 24 h. A further indication of CYP24A1 inhibition by VD1-6 was the reduced accumulation of the 24,25(OH)D3, the first metabolite of 25(OH)D catabolism by CYP24A1. Our findings suggest the potent CYP24A1 inhibitory properties of VD1-6 and its potential for testing as an alternative therapeutic candidate for treating SHPT.Ali K. Alshabrawy, Yingjie Cui, Cyan Sylvester, Dongqing Yang, Emilio S. Petito, Kate R. Barratt, Rebecca K. Sawyer, Jessica K. Heatlie, Ruhi Polara, Matthew J. Sykes, Gerald J. Atkins, Shane M. Hickey, Michael D. Wiese, Andrea M. Stringer, Zhaopeng Liu, and Paul H. Anderso

Steering self-organisation through confinement

Self-organisation is the spontaneous emergence of spatio-temporal structures and patterns from the interaction of smaller individual units. Examples are found across many scales in very different systems and scientific disciplines, from physics, materials science and robotics to biology, geophysics and astronomy. Recent research has highlighted how self-organisation can be both mediated and controlled by confinement. Confinement occurs through interactions with boundaries, and can function as either a catalyst or inhibitor of self-organisation. It can then become a means to actively steer the emergence or suppression of collective phenomena in space and time. Here, to provide a common framework for future research, we examine the role of confinement in self-organisation and identify overarching scientific challenges across disciplines that need to be addressed to harness its full scientific and technological potential. This framework will not only accelerate the generation of a common deeper understanding of self-organisation but also trigger the development of innovative strategies to steer it through confinement, with impact, e.g., on the design of smarter materials, tissue engineering for biomedicine and crowd management

An analytical approach to the dynamic topology problem

Currently, it is possible to modify (say, hourly) the topology of a data communications network by adding or deleting network links and/or by increasing or decreasing bandwidth on existing links in response to changing traffic loads and/or projected network conditions. The intent of this paper is to study a Markov decision process (MDP) model of the dynamic topology problem (DTP), the problem of activating and/or deleting links, as a function of the current traffic in the network and of the most recent network topology design. We present a decomposition of this model and structural results for the decomposition. The decomposition and structural results enhance the tractability of procedures for determining optimal link control policies. A numerical example is used to illustrate these results.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47986/1/11235_2005_Article_BF02110313.pd