61,763 research outputs found

    Preliminary flight prototype silver ion monitoring system, addendum

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    A number of electrode fabrication techniques are investigated, to achieve an electrode meeting shuttle mission requirements for functional life and stability as well as accuracy and precision of measurement. The instability of a silver bromide column when employed in a closed loop calibration scheme is discussed

    Evaluation of 2 possible further developments of the UK in-flight radiation warning meter for SSTS

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    A mass reduction of the moderator and the response to the nucleon flux, responsible for the tissue-star component of the total-dose equivalent rate using a high atomic number material, are discussed. Radiation situations at SST cruising altitudes (approximately 20 km) due to solar proton flares were simulated in the stratosphere and on the ground. Actual stratospheric situations due to galactic cosmic radiation with a limited range of quality factor values (2-4) were encountered during slow ascents by balloons to 36 km. Synthetic situations obtained from high and low energy acclerator radiations were used to obtain radiation distributions having a larger range of quality factor values (11/2-9) than experienced in the stratosphere. The measurements made in these simulations related to the directly ionizing, neutron and tissue-star components of dose-equivalent rate. Due to the restricted range of neutron spectra encountered in the stratosphere, a significant mass reduction of the moderator by 4 kg was made, with the moderator clad with cadmium or some other slow neutron absorber

    Quasideterminants

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    The determinant is a main organizing tool in commutative linear algebra. In this review we present a theory of the quasideterminants defined for matrices over a division algebra. We believe that the notion of quasideterminants should be one of main organizing tools in noncommutative algebra giving them the same role determinants play in commutative algebra.Comment: amstex; final version; to appear in Advances in Mat

    Profinite completion of Grigorchuk's group is not finitely presented

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    In this paper we prove that the profinite completion G^\mathcal{\hat G} of the Grigorchuk group G\mathcal{G} is not finitely presented as a profinite group. We obtain this result by showing that H^2(\mathcal{\hat G},\field{F}_2) is infinite dimensional. Also several results are proven about the finite quotients G/StG(n)\mathcal{G}/ St_{\mathcal{G}}(n) including minimal presentations and Schur Multipliers

    In vitro effect of canine hyperimmune sera on TNFa activity

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    [Introduction]: Septic shock in dogs is caused by cardiovascular and vasomotor failure associated with an uncontrolled intrinsic release of inflammatory mediators [1–5]. The syndrome is characterized by cardiovascular dysfunction, vascular permeability alterations, pulmonary oedema and tissue hypoxia resulting from microthrombi which may culminate in disseminated intravascular coagulation and catastrophic multiple organ failure [6,7]. Systemic bacterial infection, particularly by Gram-negative enterobacteria, haemorrhagic trauma, gastric dilation/volvulus and pancreatitis are the major underlying causes leading tosepsis [8,9]. Because of haemodynamic instability and associated hypovolemia, fluid replacement therapy is generally applied to restore effective circulating volume. The use of fresh frozen plasma has been recommended in cases of coagulopathies as it has been recognized to assist restoration of haemodynamic stability [1,5,10,11]. There is increasing evidence that the drivers of the haemodynamic instability are inflammatory mediators (particularly TNFa) activated primarily by bacterial endotoxin [3,4,12,13]

    Renormalization Group Treatment of Nonrenormalizable Interactions

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    The structure of the UV divergencies in higher dimensional nonrenormalizable theories is analysed. Based on renormalization operation and renormalization group theory it is shown that even in this case the leading divergencies (asymptotics) are governed by the one-loop diagrams the number of which, however, is infinite. Explicit expression for the one-loop counter term in an arbitrary D-dimensional quantum field theory without derivatives is suggested. This allows one to sum up the leading asymptotics which are independent of the arbitrariness in subtraction of higher order operators. Diagrammatic calculations in a number of scalar models in higher loops are performed to be in agreement with the above statements. These results do not support the idea of the na\"ive power-law running of couplings in nonrenormalizable theories and fail (with one exception) to reveal any simple closed formula for the leading terms.Comment: LaTex, 11 page
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