26,005 research outputs found

    Process for glass coating an ion accelerator grid Patent

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    Helium outgassing process for fused glass coating on ion accelerator gri

    Method of making an ion beam sputter-etched ventricular catheter for hydrocephalus shunt

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    The centricular catheter comprises a multiplicity of inlet microtubules. Each microtubule has both a large opening at its inlet end and a multiplicity of microscopic openings along its lateral surfaces. The microtubules are perforated by an ion beam sputter etch technique. The holes are etched in each microtubule by directing an ion beam through an electro formed mesh mask producing perforations having diameters ranging from about 14 microns to about 150 microns. This structure assures a reliable means for shunting cerebrospinal fluid from the cerebral ventricles to selected areas of the body

    Ion beam sputter-etched ventricular catheter for hydrocephalus shunt

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    A cerebrospinal fluid shunt in the form of a ventricular catheter for controlling the condition of hydrocephalus by relieving the excessive cerebrospinal fluid pressure is described. A method for fabrication of the catheter and shunting the cerebral fluid from the cerebral ventricles to other areas of the body is also considered. Shunt flow failure occurs if the ventricle collapse due to improper valve function causing overdrainage. The ventricular catheter comprises a multiplicity of inlet microtubules. Each microtubule has both a large openings at its inlet end and a multiplicity of microscopic openings along its lateral surfaces

    Method of making dished ion thruster grids

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    A pair of flat grid blanks are clamped together at their edges with an impervious metal sheet on top. All of the blanks and sheets are dished simultaneously by forcing fluid to inflate an elastic sheet which contacts the bottom grid blank. A second impervious metal sheet is inserted between the two grid blanks if the grids have high percentage open areas. The dished grids are stress relieved simultaneously

    Towards a quantum theory of de Sitter space

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    We describe progress towards constructing a quantum theory of de Sitter space in four dimensions. In particular we indicate how both particle states and Schwarzschild de Sitter black holes can arise as excitations in a theory of a finite number of fermionic oscillators. The results about particle states depend on a conjecture about algebras of Grassmann variables, which we state, but do not prove.Comment: JHEP3 LaTex - 19 page

    Electromagnetic flow rate meter

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    A liquid metal, whose flow rate is to be determined, is directed through a chamber made of electrically-insulating material on which there is impressed a magnetic field perpendicular to the direction of flow of the liquid metal. The magnetic field is made to increase in strength in a downstream direction of the flow of liquid metal. At least a pair of electrodes are disposed in the chamber traversely and perpendicular to the direction of flow and an ammeter is connected between the electrodes. Electrodes may be disposed in the top or the bottom of the chamber and each may be segmented. Oppositely disposed electrodes may be used with at least one dividing wall extending from each electrode to cause reversal of the direction of flow of the liquid metal. The magnetic field may be provided by electromagnets or permanent magnets such as shaded pole permanent magnets

    Intercalated graphite electrical conductors

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    For years NASA has wanted to reduce the weight of spacecraft and aircraft. Experiments are conducted to find a lightweight synthetic metal to replace copper. The subject of this paper, intercalated graphite, is such a material. Intercalated graphite is made by heating petroleum or coal to remove the hydrogen and to form more covalent bonds, thus increasing the molecular weight. The coal or petroleum eventually turns to pitch, which can then be drawn into a fiber. With continued heating the pitch-based fiber releases hydrogen and forms a carbon fiber. The carbon fiber, if heated sufficiently, becomes more organized in parallel layers of hexagonally arranged carbon atoms in the form of graphite. A conductor of intercalated graphite is potentially useful for spacecraft or aircraft applications because of its low weight

    Decoupling a Fermion Whose Mass Comes from a Yukawa Coupling: Nonperturbative Considerations

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    Perturbative analyses seem to suggest that fermions whose mass comes solely from a Yukawa coupling to a scalar field can be made arbitrarily heavy, while the scalar remains light. The effects of the fermion can be summarized by a local effective Lagrangian for the light degrees of freedom. Using weak coupling and large N techniques, we present a variety of models in which this conclusion is shown to be false when nonperturbative variations of the scalar field are considered. The heavy fermions contribute nonlocal terms to the effective action for light degrees of freedom. This resolves paradoxes about anomalous and nonanomalous symmetry violation in these models. Application of these results to lattice gauge theory imply that attempts to decouple lattice fermion doubles by the method of Swift and Smit cannot succeed, a result already suggested by lattice calculations.Comment: 31 page

    Emerging Alternatives to the Impact Factor

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    Purpose: The authors document the proliferating range of alternatives to the impact factor that have arisen within the past five years, coincident with the increased prominence of open access publishing. Methodology/Approach: This paper offers an overview of the history of the impact factor as a measure for scholarly merit; a summary of frequent criticisms of the impact factor’s calculation and usage; and a framework for understanding some of the leading alternatives to the impact factor. Findings: This paper identifies five categories of alternatives to the impact factor: a. Measures that build upon the same data that informs the impact factor. b. Measures that refine impact factor data with “page rank” indices that weight electronic resources or Web sites through the number of resources that link to them. c. Measures of article downloads and other usage factors. d. Recommender systems, in which individual scholars rate the value of articles and a group’s evaluations pool together collectively. e. Ambitious measures that attempt to encompass the interactions and influence of all inputs in the scholarly communications system. Value of Paper: Librarians can utilize the measures described in this paper to support more robust collection development than is possible through reliance on the impact factor alone
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