4,535 research outputs found
Cylindrical Algebraic Sub-Decompositions
Cylindrical algebraic decompositions (CADs) are a key tool in real algebraic
geometry, used primarily for eliminating quantifiers over the reals and
studying semi-algebraic sets. In this paper we introduce cylindrical algebraic
sub-decompositions (sub-CADs), which are subsets of CADs containing all the
information needed to specify a solution for a given problem.
We define two new types of sub-CAD: variety sub-CADs which are those cells in
a CAD lying on a designated variety; and layered sub-CADs which have only those
cells of dimension higher than a specified value. We present algorithms to
produce these and describe how the two approaches may be combined with each
other and the recent theory of truth-table invariant CAD.
We give a complexity analysis showing that these techniques can offer
substantial theoretical savings, which is supported by experimentation using an
implementation in Maple.Comment: 26 page
Deriving bases for Abelian functions
We present a new method to explicitly define Abelian functions associated
with algebraic curves, for the purpose of finding bases for the relevant vector
spaces of such functions. We demonstrate the procedure with the functions
associated with a trigonal curve of genus four. The main motivation for the
construction of such bases is that it allows systematic methods for the
derivation of the addition formulae and differential equations satisfied by the
functions. We present a new 3-term 2-variable addition formulae and a complete
set of differential equations to generalise the classic Weierstrass identities
for the case of the trigonal curve of genus four.Comment: 35page
Re-evaluating the Relevance of Vegetation Trimlines in the Canadian Arctic as an Indicator of Little Ice Age Paleoenvironments
The origin of trimlines associated with the so-called âlichen-freeâ areas in the Canadian Arctic has been attributed both to perennial snowfield expansion during the Little Ice Age (LIA) and to seasonally persistent snow cover in more recent times. Because of the disparate hypotheses (ecological versus paleoclimatic) regarding the formation of these trimlines, their use as a paleoclimatic indicator has been abandoned for more than two decades. We re-examine this debate and the validity of the opposing hypotheses in the light of new regional mapping of trimlines across the Queen Elizabeth Islands (QEI). The ecological hypothesisâinsufficient duration of the growing season resulting from seasonally persistent snow coverâfails to account for the poikilohydric nature of lichens and their ability to endure short growing seasons. It cannot adequately explain the existence of sharp trimlines or account for the occurrence of those trimlines on sparsely vegetated carbonate terrain. Furthermore, trimlines outlining the former extent of thin plateau ice caps are accordant with trimlines associated with former perennial snowfields, indicating that these trimlines record snow and ice expansion during the LIA rather than the seasonal persistence of more recent snow cover. We suggest that these features represent an important LIA climate indicator and should therefore be used for paleoclimatic reconstruction.Lâorigine des Ă©paulements propres aux zones dites sans lichen de lâArctique canadien a Ă©tĂ© attribuĂ©e tant Ă lâexpansion des champs de neige pĂ©renne pendant le petit Ăąge glaciaire quâĂ la couverture de neige longĂ©vive dâĂ©poques plus rĂ©centes. Puisquâil existe des hypothĂšses disparates (Ă©cologiques par opposition Ă palĂ©oclimatiques) quant Ă la formation de ces Ă©paulements, on a arrĂȘtĂ© de sâen servir Ă titre dâindicateur palĂ©oclimatique depuis plus dâune vingtaine dâannĂ©es. Ici, ce dĂ©bat fait lâobjet dâun nouvel examen oĂč lâon se penche sur la validitĂ© des hypothĂšses divergentes Ă la lumiĂšre du nouveau mappage rĂ©gional des Ă©paulements des Ăźles de la Reine-Ălisabeth. LâhypothĂšse dâordre Ă©cologique âdurĂ©e insuffisante de la saison de croissance dĂ©coulant de la couverture de neige longĂ©vive en saison âomet de tenir compte de la nature poecilitique du lichen et de son aptitude Ă endurer de courtes saisons de croissance. Cette hypothĂšse ne permet pas dâexpliquer adĂ©quatement lâexistence dâĂ©paulements prĂ©cis ou de tenir compte de la prĂ©sence de ces Ă©paulements en terrain carbonatĂ© Ă vĂ©gĂ©tation Ă©parse. Par ailleurs, les Ă©paulements qui dĂ©limitent lâancienne Ă©tendue des minces calottes glaciaires des plateaux correspondent aux Ă©paulements associĂ©s aux anciens champs de neige pĂ©renne, ce qui indique que ces Ă©paulements dĂ©notent les expansions de neige et de glace du petit Ăąge glaciaire et non pas de la couverture de neige longĂ©vive saisonniĂšre plus rĂ©cente. On suggĂšre que ces caractĂ©ristiques reprĂ©sentent un important indicateur climatique du petit Ăąge glaciaire et par consĂ©quent, quâon devrait sâen servir Ă des fins de reconstruction palĂ©oclimatique
Veterinary practitionersâ selection of diagnostic tests for the primary evaluation of colic in the horse
The aim of this study was to survey veterinary practitionersâ selection of diagnostic tests for horses with clinical signs of abdominal pain. A questionnaire was distributed to veterinary surgeons involved in the primary evaluation of horses with abdominal pain, including the respondent's demographics, selection of diagnostic tests and factors affecting decision-making. Data analysis included descriptive analysis, categorisation of free text and simple univariable correlations to explore the relationships between independent variables and the relative self-estimated frequency that diagnostic tests were performed. A total of 228 responses were analysed. Participants worked in mixed practice (55.7 per cent), first opinion equine (22.8 per cent), first and second opinion equine (17.9 per cent) and referral practice (3.1 per cent). The majority (48.2 per cent, 105/218) were very confident managing a colic case (confidence level 4/5). The most frequently used diagnostic tests were âresponse to analgesiaâ (87.2±24.0 per cent cases), rectal examination (75.9±21.2 per cent) and nasogastric intubation (43.8±27.6 per cent). Approach varied between practitioners, and for all diagnostic tests with frequency of use ranging from 0 to 100 per cent of cases. âRisk to personal safetyâ was the most common reason for not using rectal examination. Practitioner's opinion of their confidence level in managing a colic case was associated with how frequently they used different diagnostic tests. There was marked variation in practitionersâ approaches, highlighting the need for further evidence to support decision-making
Reviewing research evidence and the case of participation in sport and physical recreation by black and minority ethnic communities
The paper addresses the implications of using the process of systematic review in the many areas of leisure where there is a dearth of material that would be admitted into conventional Cochrane Reviews. This raises important questions about what constitutes legitimate knowledge, questions that are of critical import not just to leisure scholars, but to the formulation of policy. The search for certainty in an area that lacks conceptual consensus results in an epistemological imperialism that takes a geocentric form. While clearly, there is a need for good research design whatever the style of research, we contend that the wholesale rejection of insightful research is profligate and foolhardy. A mechanism has to be found to capitalise on good quality research of whatever form. In that search, we draw upon our experience of conducting a review of the material available on participation in sport and physical recreation by people from Black and minority ethnic groups. The paper concludes with a proposal for a more productive review process that makes better use of the full panoply of good quality research available. © 2012 © 2012 Taylor & Francis
Abelian functions associated with a cyclic tetragonal curve of genus six
We develop the theory of Abelian functions defined using a tetragonal curve of genus six, discussing in detail the cyclic curve y^4 = x^5 + λ[4]x^4 + λ[3]x^3 + λ[2]x^2 + λ[1]x + λ[0]. We construct Abelian functions using the multivariate sigma-function associated with the curve, generalizing the theory of theWeierstrassâ-function.
We demonstrate that such functions can give a solution to the KP-equation, outlining how a general class of solutions could be generated using a wider class of curves. We also present the associated partial differential equations
satisfied by the functions, the solution of the Jacobi inversion problem, a power series expansion for Ï(u) and a new addition formula
Truth table invariant cylindrical algebraic decomposition
When using cylindrical algebraic decomposition (CAD) to solve a problem with
respect to a set of polynomials, it is likely not the signs of those
polynomials that are of paramount importance but rather the truth values of
certain quantifier free formulae involving them. This observation motivates our
article and definition of a Truth Table Invariant CAD (TTICAD).
In ISSAC 2013 the current authors presented an algorithm that can efficiently
and directly construct a TTICAD for a list of formulae in which each has an
equational constraint. This was achieved by generalising McCallum's theory of
reduced projection operators. In this paper we present an extended version of
our theory which can be applied to an arbitrary list of formulae, achieving
savings if at least one has an equational constraint. We also explain how the
theory of reduced projection operators can allow for further improvements to
the lifting phase of CAD algorithms, even in the context of a single equational
constraint.
The algorithm is implemented fully in Maple and we present both promising
results from experimentation and a complexity analysis showing the benefits of
our contributions.Comment: 40 page
Cannabinoids in experimental stroke: a systematic review and meta-analysis
Cannabinoids (CBs) show promise as neuroprotectants with some agents already licensed in humans for other conditions. We systematically reviewed CBs in preclinical stroke to guide further experimental protocols. We selected controlled studies assessing acute administration of CBs for experimental stroke, identified through systematic searches. Data were extracted on lesion volume, outcome and quality, and analyzed using random effect models. Results are expressed as standardized mean difference (SMD) with 95% confidence intervals (CIs). In all, 144 experiments (34 publications) assessed CBs on infarct volume in 1,473 animals. Cannabinoids reduced infarct volume in transient (SMD â1.41 (95% CI â1.71), â1.11) P<0.00001) and permanent (â1.67 (â2.08, â1.27), P<0.00001) ischemia and in all subclasses: endocannabinoids (â1.72 (â2.62, â0.82), P=0.0002), CB1/CB2 ligands (â1.75 (â2.19, â1.31), P<0.00001), CB2 ligands (â1.65 (â2.09, â1.22), P<0.00001), cannabidiol (â1.20 (â1.63, â0.77), P<0.00001), Î9-tetrahydrocannabinol (â1.43 (â2.01, â0.86), P<0.00001), and HU-211 (â2.90 (â4.24, â1.56), P<0.0001). Early and late neuroscores significantly improved with CB use (â1.27 (â1.58, â0.95), P<0.00001; â1.63 (â2.64, â0.62), P<0.002 respectively) and there was no effect on survival. Statistical heterogeneity and publication bias was present, median study quality was 4 (range 1 to 6/8). Overall, CBs significantly reduced infarct volume and improve functional outcome in experimental stroke. Further studies in aged, female and larger animals, with other co-morbidities are required
An evaluation of a short course in mindfulness for Health Visitor Practice Teachers
Practice Teachers (PTs) participated in an 8 week course, Mindfulness Based Cognitive for well-being and resilience. The evaluation was undertaken using three (3) evidenced based questionnaires: Perceived stress(PSS) (Cohen et al 1983), Self-Compassion Score SCS (Neff 2003) and Five Facet Mindfulness Questionnaire (FFMQ) (Baer et al 2006) to identify outcomes for the mindfulness training. Findings indicate the impact on personal wellbeing and professional practice with recommendations for retention of students & Health Visitor (HV) workforce.
Summary
Mindfulness skills to support top performance and good mental health were offered in eight two-hour sessions to 18 Practice Teachers from September- December 2014 and was evaluated. The course drew on the approach of Mindfulness Based Cognitive Therapy, where participants learn to focus their attention and develop the possibility of creating the space for reflection and response rather than reacting to lifeâs difficulties. Participants had the opportunity to develop selfâcare and self-compassion in the sessions as well as in between sessions and which research has shown can have a positive effect on others. Compassion is a contemporary theme in the CNOâs strategy to return to the fundamentals of nursing; mindfulness enables the foundation of practising compassion on self and ultimately to practice compassion with others we work and care for.
The attendees were encouraged to review and refresh their practice through with the ultimate planned outcome, to reduce student attrition and prevent breakdown of the practice placement. However, this is a the complex area of adult learning and the nature of student attrition from courses as well as from the workforce cannot necessarily be reduced to one factor.
The practice of mindfulness can have an influential effect on health, well-being and resilience, as shown by scientific and medical evidence. This experiential course was neither therapy nor religious instruction but an effective means of helping to alleviate stress and promoting well-being, resilience and flourishing. The course was delivered at a time when practitioners, including PTs were experiencing an increase of student numbers and service delivery changes with associated imperative data collection. The perception of practitioners about the declared increase in the HV workforce (DH 2011) to support and implement these changes was not evident and the evaluation indicates the need for self-care and resilience in the workforce which includes students and practitioners.
The project outcomes make recommendations based on the impact of this mindfulness training with PTs to inform future developments within the programme and practice education as well as the HV workforce where a number of interventions call for 'mindfulness' with infants, children and families
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To be or not to be an auctioneer: Some thoughts on the legal nature of online eBay auctions and the protection of consumers
This paper discusses the legal classification of online âeBayâ auctions. The discussion has key implications on the scope of consumer protection law as sale by auctions are, for example, excluded from the scope of the Consumer Protection (Distance Selling) Regulations 2000. The paper uncovers that online âeBayâ auctions cannot always be considered as traditional auctions and that eBay, as an intermediary, is not to be considered as an auctioneer. This creates difficulties associated with a distributive application of consumer protection laws such as the Consumer Protection (Distance Selling) Regulations 2000. Another set of difficulties is associated with a lenient legal regime applicable to the liability of eBay under the Electronic Commerce (EC Directive) Regulations 2002 . The paper concludes that there is an urgent need to clarify the legal classification of online auctions and to rethink the liability of online auction sites to better protect consumers
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