14,381 research outputs found

    Energy Conversion Alternatives Study (ECAS), General Electric Phase 1. Volume 3: Energy conversion subsystems and components. Part 1: Bottoming cycles and materials of construction

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    Energy conversion subsystems and components were evaluated in terms of advanced energy conversion systems. Results of the bottoming cycles and materials of construction studies are presented and discussed

    A product formula and combinatorial field theory

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    We treat the problem of normally ordering expressions involving the standard boson operators a, ay where [a; ay] = 1. We show that a simple product formula for formal power series | essentially an extension of the Taylor expansion | leads to a double exponential formula which enables a powerful graphical description of the generating functions of the combinatorial sequences associated with such functions | in essence, a combinatorial eld theory. We apply these techniques to some examples related to specic physical Hamiltonians

    Hopf Algebras in General and in Combinatorial Physics: a practical introduction

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    This tutorial is intended to give an accessible introduction to Hopf algebras. The mathematical context is that of representation theory, and we also illustrate the structures with examples taken from combinatorics and quantum physics, showing that in this latter case the axioms of Hopf algebra arise naturally. The text contains many exercises, some taken from physics, aimed at expanding and exemplifying the concepts introduced

    Haematological Indices in Three Genotypes (Naked Neck, Frizzled Feather, Normal Feathered) of Nigerian Local Chicken

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    A study was designed to evaluate the haematological parameters and body weights of three genotypes (naked neck, frizzled feather and normal feathered) of Nigerian chicken. Chickens were managed intensively for 2 months before blood samples were collected for analysis. Body weights and 2ml of capillary blood samples were collected from the right side of the neck of each bird into a syringe and collected in a test tube containing EDTA (Ethylene diaminetetra acetic acid) as an anticoagulant. These blood samples were taken to Animal Science Department Laboratory where haematological parameters in the 3 varieties of local chickens were evaluated within 2 days. Haematological parameters evaluated were Packed Cell Volume, Haemoglobin Concentration, Platelets Counts and White Blood Counts. Hematological parameters and body weights were compared between varieties using Multivariate General Linear model of SPSS version 7.0 for ANOVA. Significant means were separated using Duncan Multiple Range Test. Comparison of cockerels of the 3 varieties revealed that frizzled feather cockerels performed best in Platelets Counts (33.20x109l), Haemoglobin Concentration (9.9g/dl), Packed Cell Volume (29.40%), ranked second in White Blood Counts (4.29 x 109ml) and body weight (1.12kg). Naked neck cockerels had the best mean body weight (1.15kg), White Blood Counts (4.71 x 109ml), ranked second in Platelets Counts (22.90 x 109l), Haemoglobin Concentration (3.82g/dl) and Packed Cell Volume (25.80%). Normal feathered cockerels performed worst in all the haematological parameters and body weight with the values of Packed Cell Volume (28.30%), White Blood Counts (3.20 x 109ml), Platelets Counts (203.60 x 109l), Haemoglobin Concentration (7.74g/dl) and body weight (0.91kg). There were significant differences (P<0.05) in haematological parameters and body weights among the 3 varieties of local chicken cockerels. Comparison of pullets of the 3 varieties revealed that frizzled feather pullets had the best Platelets Counts (30.80 x 109l), White Blood Counts (3.64 x 109ml), ranked third in mean body weight (0.98kg), Haemoglobin Concentration (8.05g/dl) and Packed Cell Volume (25.80%). Naked neck pullets performed best in mean body weight (2.43kg), Packed Cell Volume (29.80%), ranked second in Haemoglobin Concentration (8.91g/dl), third in Platelets Counts (29.00 x 109l) and White Blood Counts (3.51 x 109ml). Normal feathered pullets performed best in Haemoglobin Concentration (9.27g/dl), ranked second in mean body weight (1.01kg), White Blood Counts (3.34 x 109ml), Packed Cell Volume (28.30%) and Platelets Counts (29.20 x 109l). There were no significant differences (P>0.05) in haematological parameters and body weight of pullets in the 3 varieties of local chickens. Best results in haematological parameters were obtained from cockerels of naked neck and frizzled feather varieties. Generally, naked neck and frizzled feather varieties performed better than the normal feathered variety. It is recommended that the naked neck and frizzled feather cockerels be characterized, conserved and crossed with normal feathered pullets to enhance their haemtological profiles and body weights. Keywords: Local Chickens, haematology, body weight, management, genetic improvement

    Micro, meso and macro issues emerging from focus group discussions: Contributions to a physiotherapy HIV curriculum

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    Background. Physiotherapy in South Africa has not defined its contribution to the management of HIV. As part of developing an appropriate HIV/AIDS physiotherapy curriculum, focus group discussions (FGDs) with physiotherapy clinicians and educators were undertaken.Objectives. To understand the perceptions and experiences of HIV management in refining an HIV physiotherapy curriculum.Methods. Six focus groups chosen using purposive sampling ensured representation from experienced and newly qualified academics and clinicians. Interpretive content analysis strengthened the knowledge areas required in practice and attitudes based on the groups’ experiences of HIV management. Concepts were identified, and de- and recontextualised to develop categories and themes.Results and discussion. Five themes emerged: the need to include HIV in the physiotherapy curriculum; a physiotherapy-specific HIV curriculum; co-ordinated curriculum design; underlying concerns relating to HIV management and inclusion in the curriculum; and the need for professional development. Further analysis and abstraction highlighted micro, meso and macro issues. Micro issues included content, while meso-level concerns included perceived gaps in the curriculum and recommendations to respond to issues such as therapists’ coping and burnout, therapists’ attitude to HIV, and organisational problems threatening the application of knowledge regarding this condition. At a macro level, participants felt that the political nature of HIV and curriculum structure were problematic and that there was a need for continuous staff development.Conclusion. A list of topics related to HIV, which tallied well with evidence in the literature and patients’ clinical presentations, emerged. The need for a complex, well-designed programme for the physiotherapy management of HIV emerged and was informed by the difficulties experienced at the micro, meso and macro levels of the curriculum

    Laguerre-type derivatives: Dobinski relations and combinatorial identities

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    We consider properties of the operators D(r,M)=a^r(a^\dag a)^M (which we call generalized Laguerre-type derivatives), with r=1,2,..., M=0,1,..., where a and a^\dag are boson annihilation and creation operators respectively, satisfying [a,a^\dag]=1. We obtain explicit formulas for the normally ordered form of arbitrary Taylor-expandable functions of D(r,M) with the help of an operator relation which generalizes the Dobinski formula. Coherent state expectation values of certain operator functions of D(r,M) turn out to be generating functions of combinatorial numbers. In many cases the corresponding combinatorial structures can be explicitly identified.Comment: 14 pages, 1 figur

    Hopf algebras: motivations and examples

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    This paper provides motivation as well as a method of construction for Hopf algebras, starting from an associative algebra. The dualization technique involved relies heavily on the use of Sweedler's dual
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