672 research outputs found

    Sieve weights and their smoothings

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    We obtain asymptotic formulas for the 2k2kth moments of partially smoothed divisor sums of the M\"obius function. When 2k2k is small compared with AA, the level of smoothing, then the main contribution to the moments come from integers with only large prime factors, as one would hope for in sieve weights. However if 2k2k is any larger, compared with AA, then the main contribution to the moments come from integers with quite a few prime factors, which is not the intention when designing sieve weights. The threshold for "small" occurs when A=12k(2kk)−1A=\frac 1{2k} \binom{2k}{k}-1. One can ask analogous questions for polynomials over finite fields and for permutations, and in these cases the moments behave rather differently, with even less cancellation in the divisor sums. We give, we hope, a plausible explanation for this phenomenon, by studying the analogous sums for Dirichlet characters, and obtaining each type of behaviour depending on whether or not the character is "exceptional".Comment: Final version, 85 pages, to appear in Ann. Sci. \'Ec. Norm. Sup\'er.. Added abstract in French and made several minor changes compared to the previous versio

    The effects of hypnosis on flow states and three-point shooting performance in basketball players.

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    This study examined the effects of hypnosis on flow states and three-point shooting performance in 5 collegiate basketball players. The investigation uti- lized an ideographic single-subject multiple baselines across subjects design combined with a procedure that monitors the internal experience of the par- ticipants (Wollman, 1986). The method of intervention utilized in this study involved relaxation, imagery, hypnotic induction, hypnotic regression, and trigger control procedures. The results indicated that all five participants in- creased both their mean basketball three-point shooting performance and their mean flow scores from baseline to intervention. There were no overlapping data points between the baseline and intervention for either performance or flow state. Additionally, each participant indicated that they had felt the inter- vention was useful in keeping them confident, relaxed, and calm. These re- sults support the hypothesis that a hypnosis intervention can improve three- point shooting performance in basketball players and increase feelings and cognitions that are associated with flow

    The cornerstone of Labour's 'New NHS': reforming primary care

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    Two remarkable aspects of the Thatcher ‘internal market’ reforms of the NHS were the focus on creating a market for hospital services and the way in which primary care was treated almost peripherally in the 1989 White Paper (Department of Health 1989a). The 1991 NHS reforms introduced general practitioner (GP) fundholding almost as an afterthought, and the revision of the GP contract in 1990 Paper (Department of Health 1989b) was conducted separately from the implementation of other health care reforms. In contrast the principal focus of Labour’s ‘new NHS’ reform is primary care (Department of Health 1997). The intention of the government is both to improve the efficiency and equity of primary care provision and to develop Primary Care Groups and Primary Care Trusts which both provide care efficiently and act as agents who purchase secondary and tertiary care on behalf of patients. This is an ambitious agenda. This paper explores the policy context of Primary Care Groups in sections 1 and 2, describes and appraises the government proposals in section 3, and identifies major issues involved in the implementation of change in section 4.fundholding, rationing

    Using group supervision for undergraduate dissertations: a preliminary enquiry into the student experience

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    This paper explores the student experience of the use of individual and group supervisory strategies with students undertaking their undergraduate dissertation on a social work programme. The findings indicate that small, supervisor led groups may be an effective mode for undergraduate dissertation supervision. This preliminary study suggests that there may be advantages of the peer group approach including: a higher rate for completion on time; greater student engagement maintained during the process and less ‘failure driven’ learning. The students’ results suggest that there is no detrimental effect on performance

    Queen control of a key life-history event in a eusocial insect

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    In eusocial insects, inclusive fitness theory predicts potential queen–worker conflict over the timing of events in colony life history. Whether queens or workers control the timing of these events is poorly understood. In the bumble-bee Bombus terrestris, queens exhibit a ‘switch point’ in which they switch from laying diploid eggs yielding females (workers and new queens) to laying haploid eggs yielding males. By rearing foundress queens whose worker offspring were removed as pupae and sexing their eggs using microsatellite genotyping, we found that queens kept in the complete absence of adult workers still exhibit a switch point. Moreover, the timing of their switch points relative to the start of egg-laying did not differ significantly from that of queens allowed to produce normal colonies. The finding that bumble-bee queens can express the switch point in the absence of workers experimentally demonstrates queen control of a key life-history event in eusocial insects. In addition, we found no evidence that workers affect the timing of the switch point either directly or indirectly via providing cues to queens, suggesting that workers do not fully express their interests in queen–worker conflicts over colony life history

    The newly developed CRF1-receptor antagonists, NGD 98-2 and NGD 9002, suppress acute stress-induced stimulation of colonic motor function and visceral hypersensitivity in rats.

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    Corticotropin releasing factor receptor 1 (CRF1) is the key receptor that mediates stress-related body responses. However to date there are no CRF1 antagonists that have shown clinical efficacy in stress-related diseases. We investigated the inhibitory effects of a new generation, topology 2 selective CRF1 antagonists, NGD 98-2 and NGD 9002 on exogenous and endogenous CRF-induced stimulation of colonic function and visceral hypersensitivity to colorectal distension (CRD) in conscious rats. CRF1 antagonists or vehicle were administered orogastrically (og) or subcutaneously (sc) before either intracerebroventricular (icv) or intraperitoneal (ip) injection of CRF (10 µg/kg), exposure to water avoidance stress (WAS, 60 min) or repeated CRD (60 mmHg twice, 10 min on/off at a 30 min interval). Fecal pellet output (FPO), diarrhea and visceromotor responses were monitored. In vehicle (og)-pretreated rats, icv CRF stimulated FPO and induced diarrhea in >50% of rats. NGD 98-2 or NGD 9002 (3, 10 and 30 mg/kg, og) reduced the CRF-induced FPO response with an inhibitory IC50 of 15.7 and 4.3 mg/kg respectively. At the highest dose, og NGD 98-2 or NGD 9002 blocked icv CRF-induced FPO by 67-87% and decreased WAS-induced-FPO by 23-53%. When administered sc, NGD 98-2 or NGD 9002 (30 mg/kg) inhibited icv and ip CRF-induced-FPO. The antagonists also prevented the development of nociceptive hyper-responsivity to repeated CRD. These data demonstrate that topology 2 CRF1 antagonists, NGD 98-2 and NGD 9002, administered orally, prevented icv CRF-induced colonic secretomotor stimulation, reduced acute WAS-induced defecation and blocked the induction of visceral sensitization to repeated CRD

    NASA 2018 Green Propulsion Roadmap

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    The Green Propulsion Working Group (GPWG) is a technical guidance working group formed April 2017 under the Agency's Capability Leadership Team The GPWG was tasked with recommending an agency road map and providing guidance to NASA on green propulsion technology development and infusion The GPWG's efforts focus on ionic liquid propellants and related technologies The GPWG was chartered with three representatives from NASA Centers currently exploring green propulsion technologies As other Centers may explore programs that utilize green propulsion, membership of the working group can be expanded to include more interested parties Working group also solicits and coordinates with other government agencies (e.g. AFRL, MDA) In 2015, JANNAF hosted a Technical Interchange Meeting (TIM) on Green Monopropellant Alternatives to Hydrazine (GMAH) Included both Government and non-Government contributions on the State-of-the-Art in Green Propulsion Technology Following the TIM, a Government-only session (USAF/AFRL/NASA/MDA/DLA) reviewed and identified remaining technical gaps in Green Propulsion In 2016, an inter-agency team (AFRL/NASA/MDA) worked together to develop an informal inter-agency "roadmap" based on the outcome of the TIM Approach consisted of near-term, mid-term, and long-term technology advancement areas, approaching incrementally larger thrust classes The NASA Green Propulsion Working Group reviewed the work of the 2016 Inter-Agency Working Group, and concurs that the identified technical gaps and technology development areas are still relevant and necessary to see green propulsion technology advanced The GPWG recommends the 2016 roadmap be adopted as baseline for NASA needs, with some additions The focus of the 2016 inter-agency roadmap was primarily on the thruster technology. The Agency must also invest in understanding the broader propulsion system-level technology gaps in parallel. Timeframes are considered suggested from a priority standpoint, but are also flexible as some efforts will need to occur in the nearer term or concurrently in order to meet specific mission requirements The GPWG developed 2018 roadmap breaks down the technology development goals into Technology Development Areas (TDA's), and identifies the near-, mid, and long-term sub-goals within those areas. Those TDA's are: Thruster Hardware Development Modeling & Tools Development Materials Properties and Compatibility Propellant Development

    Green Propulsion Advancement and Infusion

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    All space missions benefit from increased propulsion system performance allowing lower spacecraft launch mass, larger scientific payloads, or extended on-orbit lifetimes. Likewise, propellant candidates that offer significant reduction in personnel hazards and shorter payload processing present a more attractive propulsion subsystem solution. Aiming to reduce risk to potential infusion missions and fully comprehend the alternative propellant performance, the work presented herein represents many years of development and collaborative efforts to successfully align higher performance, low toxicity hydrazine alternatives into NASA Goddard Space Flight Center (GSFC) missions. The High Performance Green Propulsion (HPGP) technology is being considered for Science Mission Directorate (SMD) missions

    Green Propulsion Advancement and Infusion

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    All space missions benefit from increased propulsion system performance, allowing lower spacecraft launch mass, larger scientific payloads, or extended on-orbit lifetimes. Likewise, long-term storable liquid propellant candidates that offer significant reduction in personnel hazards and shorter payload processing schedules present a more attractive propulsion subsystem solution to spacecraft builders. Aiming to reduce risk to potential infusion missions and fully comprehend the alternative propellant performance, the work presented herein represents many years of development and collaborative efforts to successfully align higher performance, low toxicity green propellants into NASA Goddard Space Flight Center (GSFC) missions. High Performance Green Propulsion (HPGP), and the associated propellant technology, has advanced significantly in maturity with increased familiarity with LMP-103S propellant handling, the proven reduction in loading hazards, successful launches conducted at multiple international Ranges, and HPGP on-orbit flight heritage. As science missions move forward to the potential infusion of HPGP technology, the National Aeronautics and Space Administration (NASA) and its partners are working to address gaps in system performance and operational considerations
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