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Isotope effects and possible pairing mechanism in optimally doped cuprate superconductors

We have studied the oxygen-isotope effects on T_{c} and in-plane penetration depth \lambda_{ab}(0) in an optimally doped 3-layer cuprate Bi_{1.6}Pb_{0.4}Sr_{2}Ca_{2}Cu_{3}O_{10+y} (T_{c} \sim 107 K). We find a small oxygen-isotope effect on T_{c} (\alpha_{O} = 0.019), and a substantial effect on \lambda_{ab} (0) (\Delta \lambda_{ab} (0)/\lambda_{ab} (0) = 2.5\pm0.5%). The present results along with the previously observed isotope effects in single-layer and double-layer cuprates indicate that the isotope exponent \alpha_{O} in optimally doped cuprates is small while the isotope effect on the in-plane effective supercarrier mass is substantial and nearly independent of the number of the CuO_{2} layers. A plausible pairing mechanism is proposed to explain the isotope effects, high-T_{c} superconductivity and tunneling spectra in a consistent way.Comment: 5 pages, 4 figure

Renormalization of composite operators

The blocked composite operators are defined in the one-component Euclidean scalar field theory, and shown to generate a linear transformation of the operators, the operator mixing. This transformation allows us to introduce the parallel transport of the operators along the RG trajectory. The connection on this one-dimensional manifold governs the scale evolution of the operator mixing. It is shown that the solution of the eigenvalue problem of the connection gives the various scaling regimes and the relevant operators there. The relation to perturbative renormalization is also discussed in the framework of the $\phi^3$ theory in dimension $d=6$.Comment: 24 pages, revtex (accepted by Phys. Rev. D), changes in introduction and summar

Changes in epidermal radiosensitivity with time associated with increased colony numbers

Epidermal clonogenic cell survival and colony formation following irradiation were investigated and related to radiosensitivity. A rapid in vivo/in vitro assay was developed for the quantification of colonies arising from surviving clonogenic cells in pig epidermis after irradiation. Bromodeoxyuridine (BrdU)-labelled cells in full thickness epidermal sheets were visualized using standard immunohistochemistry. In unirradiated skin, approximately 900 BrdU-positive cells mm(-2) were counted. In a time sequence experiment, BrdU-positive cell numbers increased from an average of 900 cells mm(-2) to approximately 1400 cells mm(-2) after BrdU-labelling for 2-24 h. In irradiated skin, colonies containing >/=16 BrdU-positive cells were seen for the first time at days 14/15 after irradiation. The number of these colonies per cm(2) as a function of skin surface dose yielded a cell survival curve with a D(0)-value (+/-SE) of 3.9+/-0.6 Gy. This relatively high D(0)-value is possibly due to a rapid fall off in depth dose distribution for the iridium-192 source and consequently a substantial contribution of hair follicular epithelium to colony formation. At 14/15 days after irradiation, the ED(50) level of 33.6 Gy for the in vivo response of moist desquamation corresponded with 2.7 colonies cm(-2). Surprisingly, the number of colonies increased with time after irradiation with an estimated doubling time of approximately 4 days, while the D(0)-value remained virtually unchanged. This increase in colony numbers could be due to migration of clonogenic cells, to the recruitment of dormant clonogenic cell survivors by elevated levels of cytokines, or to both. Although frequent biopsying caused increased cytokine levels, which had a systemic effect on unirradiated skin, it had no influence on colony formation in irradiated skin. Smaller colonies, containing 4-8 cells or 9-15 cells, were abundant, particularly after higher doses, which resulted in higher D(0)-values. The majority of these small colonies were abortive and did not progress to larger colonies. There was no statistical evidence for significant variations in the interanimal responses

Experiential contributions to social dominance in a rat model of Fragile-X syndrome

Social withdrawal is one phenotypic feature of the monogenic neurodevelopmental disorder Fragile-X. Using a ‘knock-out’ rat model of Fragile-X, we examined whether deletion of the Fmr1 gene that causes this condition would affect the ability to form and express a social hierarchy as measured in a tube-test. Male Fragile-X ‘knock-out’ rats living together could successfully form a social dominance hierarchy, but were significantly subordinate to wild-type animals in mixed group cages. Over 10 days of repeated testing, the Fragile-X mutant rats gradually showed greater variance and instability of rank during their tube-test encounters. This affected the outcome of future encounters with stranger animals from other cages, with the initial phenotype of wild-type dominance lost to a more complex picture that reflected, regardless of genotype, the prior experience of winning or losing. Our findings offer a novel insight into the complex dynamics of social interactions between laboratory living groups of Fragile X and wild-type rats. Even though this is a monogenic condition, experience has an impact upon future interactions with other animals. Gene/environment interactions should therefore be considered in the development of therapeutics

Langzeitpotenzierung im Hippokampus:Entdeckung, Mechanismen und Funktion

In diesem Übersichtsartikel blicken wir auf unsere Beiträge zur Erforschung der Eigenschaften und Mechanismen der Langzeitpotenzierung (LTP) zurück und beschreiben die wichtigsten Einflüsse auf unsere Arbeit. Wir fahren dann fort abzuwägen, ob diese Forschung ihre frühen Versprechungen erfüllt hat, eine überzeugende Darstellung der synaptischen Grundlage der Gedächtnisspeicherung zu liefern

A Compact Beam Stop for a Rare Kaon Decay Experiment

We describe the development and testing of a novel beam stop for use in a rare kaon decay experiment at the Brookhaven AGS. The beam stop is located inside a dipole spectrometer magnet in close proximity to straw drift chambers and intercepts a high-intensity neutral hadron beam. The design process, involving both Monte Carlo simulations and beam tests of alternative beam-stop shielding arrangements, had the goal of minimizing the leakage of particles from the beam stop and the resulting hit rates in detectors, while preserving maximum acceptance for events of interest. The beam tests consisted of measurements of rates in drift chambers, scintilation counter hodoscopes, a gas threshold Cherenkov counter, and a lead glass array. Measurements were also made with a set of specialized detectors which were sensitive to low-energy neutrons, photons, and charged particles. Comparisons are made between these measurements and a detailed Monte Carlo simulation.Comment: 39 pages, 14 figures, submitted to Nuclear Instruments and Method

The therapeutic ratio in BNCT: Assessment using the Rat 9L gliosarcoma brain tumor and spinal cord models

During any radiation therapy, the therapeutic tumor dose is limited by the tolerance of the surrounding normal tissue within the treatment volume. The short ranges of the products of the {sup 10}B(n,{alpha}){sup 7}Li reaction produced during boron neutron capture therapy (BNCT) present an opportunity to increase the therapeutic ratio (tumor dose/normal tissue dose) to levels unprecedented in photon radiotherapy. The mixed radiation field produced during BNCT comprises radiations with different linear energy transfer (LET) and different relative biological effectiveness (RBE). The short ranges of the two high-LET products of the `B(n,a)`Li reaction make the microdistribution of the boron relative to target cell nuclei of particular importance. Due to the tissue specific distribution of different boron compounds, the term RBE is inappropriate in defining the biological effectiveness of the {sup 10}B(n,{alpha}){sup 7}Li reaction. To distinguish these differences from true RBEs we have used the term {open_quotes}compound biological effectiveness{close_quotes} (CBE) factor. The latter can be defined as the product of the true, geometry-independent, RBE for these particles times a {open_quotes}boron localization factor{close_quotes}, which will most likely be different for each particular boron compound. To express the total BNCT dose in a common unit, and to compare BNCT doses with the effects of conventional photon irradiation, multiplicative factors (RBEs and CBEs) are applied to the physical absorbed radiation doses from each high-LET component. The total effective BNCT dose is then expressed as the sum of RBE-corrected physical absorbed doses with the unit Gray-equivalent (Gy-Eq)

A simple mathematical model for Ebola in Africa

We deal with the following question: Can the consumption of contaminated bush meat, the funeral practices and the environmental contamination explain the recurrence and persistence of Ebola virus disease outbreaks in Africa? We develop an SIR-type model which, incorporates both the direct and indirect transmissions in such a manner that there is a provision of Ebola viruses. We prove that the full model has one (endemic) equilibrium which is locally asymptotically stable whereas, it is globally asymptotically stable in the absence of the Ebola virus shedding in the environment. For the sub-model without the provision of Ebola viruses, the disease dies out or stabilizes globally at an endemic equilibrium. At the endemic level, the number of infectious is larger for the full model than for the sub-model without provision of Ebola viruses. We design a nonstandard finite difference scheme, which preserves the dynamics of the model. Numerical simulations are provided.The South African Research Chairs Initiative (SARChI chair) in Mathematical Models and Methods in Bioengineering and Biosciences.https://www.tandfonline.com/loi/tjbd20hj2021Forensic MedicineMathematics and Applied Mathematic

Initial insights into the impact and implementation of Creating Active Schools in Bradford, UK

YesFew whole-school physical activity programmes integrate implementation science frameworks within the design, delivery, and evaluation. As a result, knowledge of the key factors that support implementation at scale is lacking. The Creating Active Schools (CAS) programme was co-designed and is underpinned by the Capability, Opportunity, Motivation and Behaviour (COM-B) model and the Consolidated Framework for Implementation Research (CFIR). The study aims to understand the initial impact and implementation of CAS in Bradford over 9 months using McKay's et al.'s (2019) implementation evaluation roadmap. Focus groups and interviews were conducted with school staff (n = 30, schools = 25), CAS Champions (n = 9), and the CAS strategic lead (n = 1). Qualitative data were analysed both inductively and deductively. The deductive analysis involved coding data into a priori themes based on McKay et al's implementation evaluation roadmap, using a codebook approach to thematic analysis. The inductive analysis included producing initial codes and reviewing themes before finalising. Identified themes aligned into three categories: (i) key ingredients for successful adoption and implementation of CAS, (ii) CAS implementation: challenges and solutions, and (iv) the perceived effectiveness of CAS at the school level. This included the willingness of schools to adopt and implement whole-school approaches when they are perceived as high quality and aligned with current school values. The programme implementation processes were seen as supportive; schools identified and valued the step-change approach to implementing CAS long-term. Formal and informal communities of practice provided "safe spaces" for cross-school support. Conversely, challenges persisted with gaining broader reach within schools, school staff's self-competence and shifting school culture around physical activity. This resulted in varied uptake between and within schools. This study provides novel insights into the implementation of CAS, with outcomes aligning to the adoption, reach, and sustainability. Successful implementation of CAS was underpinned by determinants including acceptability, intervention complexity, school culture and school stakeholders' perceived self-efficacy. The combination of McKay's evaluation roadmap and CFIR establishes a rigorous approach for evaluating activity promotion programmes underpinned by behavioural and implementation science. Resultantly this study offers originality and progression in understanding the implementation and effectiveness of whole-school approaches to physical activity.Higher Education Innovation Fund (UKRI), Sport England’s Local Delivery Pilot in Bradford, Bradford District Metropolitan Council via the Living Well Programm