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1

Charged Polytropic Stars and a Generalization of Lane-Emden Equation  

NASA Astrophysics Data System (ADS)

In this paper we discuss charged stars with polytropic equation of state, where we derive an equation analogous to the Lane-Endem equation. We assume that these stars are spherically symmetric, and the electric field have only the radial component. First we review the field equations for such stars and then we proceed with the analog of the Lane-Emden equation for a polytropic Newtonian fluid and their relativistic equivalent (Tooper, 1964).1 These kind of equations are very interesting because they transform all the structure equations of the stars in a group of differential equations which are much more simple to solve than the source equations. These equations can be solved numerically for some boundary conditions and for some initial parameters. For this we assume that the pressure caused by the electric field obeys a polytropic equation of state too.

Picanço, Rodrigo; Malheiro, Manoel; Ray, Subharthi

2

Composite magnetic polytropes  

NASA Astrophysics Data System (ADS)

Using the homological Milne variables and the phase portrait of the Lane-Emden equation in these variables we determine the boundary between layers of different polytropic indices. We argue about the homological properties of the equilibrium equation of a polytrope in the presence of a weak poloidal magnetic field and obtain the field distribution in a sequence of composite polytropic stars with uniform density throughout the core (n=0) and an envelope with polytropic index (n=1).

Blaga, Cristina

2007-03-01

3

Polytropic, differentially rotating cylinders  

Microsoft Academic Search

Infinite cylinders composed of polytropic material can possess nearly arbitrary rotation fields while retaining the fundamental simplicity of one-dimensional structures. The physical properties of these objects can be easily calculated and understood by junior-senior level physics students even without access to a large computing facility. Analytical results are presented here for polytropic index 0 and 1 as well as numerical

Sheridan A. Simon; Michael F. Czysz; Karen Everett; Christopher Field

1981-01-01

4

A Polytropic solar model  

NASA Astrophysics Data System (ADS)

We develop a composite polytropic solar model characterized by three ploytropic indices. This phenomenological model can represent some of the main features of the standard solar model (SSM). It is used to study neutrino production and various solar properties. Three solar models with lower core temperatures than that predicted by the SSM are considered. We find that lowering the core temperature by 3 percent requires changes of the opacity of the middle layer by 32-35 percent, a factor of three larger than the current uncertainty. Thus, one does not expect that the solar neutrino puzzle can be solved within the framework of the SSM. The calculation of the asymptotic p-mode frequencies reveal the need to modify the polytropic solar model. We also find that the p-mode frequencies are not sensitive to the changes of the central temperature. Finally, the Mikheyev-Smirnov-Wolfenstein effect is studied and considered as a solution to the solar neutrino problem.

Tsai, Jongni

5

Stability of polytropes  

SciTech Connect

This paper is an investigation of the stability of some ideal stars. It is intended as a study in general relativity, with emphasis on the coupling to matter, aimed at a better understanding of strong gravitational fields and 'black holes'. This contrasts with the usual attitude in astrophysics, where Einstein's equations are invoked as a refinement of classical thermodynamics and Newtonian gravity. Our work is based on action principles for systems of metric and matter fields, well-defined relativistic field models that we hope may represent plausible types of matter. The thermodynamic content must be extracted from the theory itself. When the flow of matter is irrotational, and described by a scalar density, we are led to differential equations that differ little from those of Tolman, but they admit a conserved current, and stronger boundary conditions that affect the matching of the interior solution to an external metric and imply a relation of mass and radius. We propose a complete revision of the treatment of boundary conditions. An ideal star in our terminology has spherical symmetry and an isentropic equation of state, p=a{rho}{sup {gamma}}, a and {gamma} piecewise constant. In our first work it was assumed that the density vanished beyond a finite distance from the origin and that the metric is to be matched at the boundary to an exterior Schwartzchild metric. But it is difficult to decide what the boundary conditions should be and we are consequently skeptical of the concept of a fixed boundary. We investigate the double polytrope, characterized by a polytropic index n{<=}3, in the bulk of the star and a value larger than five in an outer atmosphere that extends to infinity. It has no fixed boundary but a region of critical density where the polytropic index changes from a value that is appropriate for the bulk of the star to a value that provides a crude model for the atmosphere. The boundary conditions are now natural and unambiguous. The existence of a relation between mass and radius is confirmed, as well as an upper limit on the mass. The principal conclusion is that all the static configurations are stable. There is a solution that fits the Sun. The masses of white dwarfs respect the Chandrasekhar limit. The application to neutron stars has surprising aspects.

Froensdal, Christian [Physics Department, University of California, Los Angeles, California 90095-1547 (United States)

2008-05-15

6

Computing polytropic models obeying specific metrics  

NASA Astrophysics Data System (ADS)

We apply zatrikean pregeometry to polytropic stars, finding the corresponding zatrikean Lane-Emden equations, solving them numerically and presenting the results on the boundary conditions and the interior structure of the zatrikean polytropes.

Dallas, Th.; Geroyannis, V. S.

2013-09-01

7

Dynamic voids surrounded by shocked conventional polytropic gas envelopes  

NASA Astrophysics Data System (ADS)

With proper physical mechanisms of energy and momentum input from around the centre of a self-gravitating polytropic gas sphere, a central spherical 'void' or 'cavity' or 'bubble' of very much less mass contents may emerge and then dynamically expand into a variety of surrounding more massive gas envelopes with or without shocks. We explore self-similar evolution of a self-gravitating polytropic hydrodynamic flow of spherical symmetry with such an expanding 'void' embedded around the centre. The void boundary supporting a massive envelope represents a pressure-balanced contact discontinuity where drastic changes in mass density and temperature occur. We obtain numerical void solutions that can cross the sonic critical surface either smoothly or by shocks. Using the conventional polytropic equation of state, we construct global void solutions with shocks travelling into various envelopes including static polytropic sphere, outflow, inflow, breeze and contraction types. In the context of supernovae, we discuss the possible scenario of separating a central collapsing compact object from an outgoing gas envelope with a powerful void in dynamic expansion. Initially, a central bubble is carved out by an extremely powerful neutrinosphere. After the escape of neutrinos during the decoupling, the strong electromagnetic radiation field and/or electron-positron pair plasma continue to drive the cavity expansion. In a self-similar dynamic evolution, the pressure across the contact discontinuity decreases with time to a negligible level for a sufficiently long lapse, and eventually the gas envelope continues to expand by inertia. We describe model cases of polytropic index ?= 4/3 -? with ? > 0 and discuss pertinent requirements to justify our proposed scenario.

Lou, Yu-Qing; Wang, Lile

2012-03-01

8

The Effect of a Radial Electric Field in The Structure of a Polytropic Star  

NASA Astrophysics Data System (ADS)

In this work we show how a radial electric field can affect the structure of a relativistic star. For this, we assumed that the star is spherically symmetric. We see that this kind of electric field introduces a change in the gravitational force generated by the star, and consequently in the structure of the star. We also assume that the pressure caused by the electric field obeys a polytropic equation of state, and then we derive an equation analogous to the Lane - Emden equation for a charged polytropic star.

Picanço, Rodrigo; Malheiro, Manuel; Ray, Subharthi

2004-12-01

9

The boundary conditions for polytropic gas spheres  

NASA Astrophysics Data System (ADS)

Numerical solutions are obtained for the Emden equation of polytropic density and the associated zero-order Emden functions psi(0) of Chandrasekhar (1933) and presented in a table for values of the index n between 0 and 5. These computer results (to 10 decimal places) are shown to be more accurate than those hand-calculated by Comrie and Sadler (1930) and are to be applied to a quantitative investigation of the effects of axial rotation on the shape and density distribution of polytropic gas spheres, using the method of Kopal (1983) in Clairaut coordinates.

Jabbar, J. R.

1984-03-01

10

Compact electron beam ion trap for spectroscopy of moderate charge state ions  

SciTech Connect

A compact electron beam ion trap (EBIT) has been constructed for spectroscopic studies of moderate charge state ions. The electron beam energy range of the present EBIT is 100-1000 eV, for which it is rather difficult to operate an ordinary EBIT which used to be designed for operation with higher electron energy ({approx}10 keV or more). To cut down the running costs, a superconducting wire with a high critical temperature is used for the central magnet so that it can be operated without liquid helium. The performance of the compact EBIT has been investigated through visible spectroscopy of highly charged krypton and iron ions.

Nakamura, Nobuyuki; Kikuchi, Hiroyuki [Institute for Laser Science, University of Electro-Communications, Chofu, Tokyo 182-8585 (Japan); Sakaue, Hiroyuki A. [National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan); Watanabe, Tetsuya [National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan)

2008-06-15

11

Compact electron beam ion trap for spectroscopy of moderate charge state ions.  

PubMed

A compact electron beam ion trap (EBIT) has been constructed for spectroscopic studies of moderate charge state ions. The electron beam energy range of the present EBIT is 100-1000 eV, for which it is rather difficult to operate an ordinary EBIT which used to be designed for operation with higher electron energy (~10 keV or more). To cut down the running costs, a superconducting wire with a high critical temperature is used for the central magnet so that it can be operated without liquid helium. The performance of the compact EBIT has been investigated through visible spectroscopy of highly charged krypton and iron ions. PMID:18601394

Nakamura, Nobuyuki; Kikuchi, Hiroyuki; Sakaue, Hiroyuki A; Watanabe, Tetsuya

2008-06-01

12

Rapidly rotating polytropes in general relativity  

Microsoft Academic Search

We construct an extensive set of equilibrium sequences of rotating polytropes in general relativity. We determine a number of important physical parameters of such stars, including maximum mass and maximum spin rate. The stability of the configurations against quasi-radial perturbations is diagnosed. Two classes of evolutionary sequences of fixed rest mass and entropy are explored: normal sequences which behave very

Gregory B. Cook; Stuart L. Shapiro; Saul A. Teukolsky

1994-01-01

13

Cosmological Constraints on Polytropic Gas Model  

NASA Astrophysics Data System (ADS)

We study the polytropic gas scenario as the unification of dark matter and dark energy. We fit the model parameters by using the latest observational data including type Ia supernovae, baryon acoustic oscillation, cosmic microwave background, and Hubble parameter data. At 68.3 % and 95.4 % confidence levels, we find the best fit values of the model parameters as and . Using the best fit values of the model, we obtain the evolutionary behaviors of the equation of state parameters of the polytropic gas model and dark energy, the deceleration parameter of the universe, the dimensionless density parameters of dark matter and dark energy as well as the growth factor of structure formation. Then, we investigate different energy conditions in the polytropic gas model and obtain that only the strong energy condition is violated for the special ranges of the redshift. We also conclude that in the this model, the universe starts from the matter dominated epoch and approaches a de Sitter phase at late times, as expected. Further, the universe begins to accelerate at redshift z t=0.74. Furthermore, in contrary to the ?CDM model, the cosmic coincidence problem is solved naturally in the polytropic gas scenario. Moreover, this model fits the data of the growth factor well as the ?CDM model.

Asadzadeh, S.; Safari, Z.; Karami, K.; Abdolmaleki, A.

2014-04-01

14

Low power, compact charge coupled device signal processing system  

NASA Technical Reports Server (NTRS)

A variety of charged coupled devices (CCDs) for performing programmable correlation for preprocessing environmental sensor data preparatory to its transmission to the ground were developed. A total of two separate ICs were developed and a third was evaluated. The first IC was a CCD chirp z transform IC capable of performing a 32 point DFT at frequencies to 1 MHz. All on chip circuitry operated as designed with the exception of the limited dynamic range caused by a fixed pattern noise due to interactions between the digital and analog circuits. The second IC developed was a 64 stage CCD analog/analog correlator for performing time domain correlation. Multiplier errors were found to be less than 1 percent at designed signal levels and less than 0.3 percent at the measured smaller levels. A prototype IC for performing time domain correlation was also evaluated.

Bosshart, P. W.; Buss, D. D.; Eversole, W. L.; Hewes, C. R.; Mayer, D. J.

1980-01-01

15

Incompressible relativistic spheres: Electrically charged stars, compactness bounds, and quasiblack hole configurations  

NASA Astrophysics Data System (ADS)

We investigate the properties of relativistic star spheres made of an electrically charged incompressible fluid, generalizing, thus, the Schwarzschild interior solution. The investigation is carried by integrating numerically the hydrostatic equilibrium equation, i.e., the Tolman-Oppenheimer-Volkoff (TOV) equation, with the hypothesis that the charge distribution is proportional to the energy density. We match the interior to a Reissner-Nordström exterior, and study some features of these star spheres such as the total mass M, the radius R, and the total charge Q. We also display the pressure profile. For star spheres made of a perfect fluid there is the Buchdahl bound, R/M?9/4, a compactness bound found from generic principles. For the Schwarzschild interior solution there is also the known compactness limit, the interior Schwarzschild limit where the configurations attain infinite central pressure, given by R/M=9/4, yielding an instance where the Buchdahl bound is saturated. We study this limit of infinite central pressure for the electrically charged stars and compare it with the Buchdahl-Andréasson bound, a limit that, like the Buchdahl bound for the uncharged case, is obtained by imposing some generic physical conditions on charged configurations. We show that the electrical interior Schwarzschild limit of all but two configurations is always below the Buchdahl-Andréasson limit, i.e., we find that the electrical interior Schwarzschild limit does not generically saturate the Buchdahl-Andréasson bound. We also find that the quasiblack hole limit, i.e., the extremal most compact limit for charged incompressible stars, is reached when the matter is highly charged and the star's central pressure tends to infinity. This is one of the two instances where the Buchdahl-Andréasson bound is saturated, the other being the uncharged, interior Schwarzschild solution.

Arbañil, José D. V.; Lemos, José P. S.; Zanchin, Vilson T.

2014-05-01

16

Effective geometries in self-gravitating polytropes  

NASA Astrophysics Data System (ADS)

Perturbations of a perfect barotropic and irrotational Newtonian self-gravitating fluid are studied using a generalization of the so-called “effective geometry” formalism. The case of polytropic spherical stars, as described by the Lane-Emden equation, is studied in detail in the known cases of existing explicit solutions. The present formulation gives a natural scenario in which the acoustic analogy has relevance for both stellar and galactic dynamics.

Bini, D.; Cherubini, C.; Filippi, S.

2008-09-01

17

Polytropic dark haloes of elliptical galaxies  

NASA Astrophysics Data System (ADS)

The kinematics of stars and planetary nebulae in early-type galaxies provide vital clues to the enigmatic physics of their dark matter haloes. We fit published data for 14 such galaxies using a spherical, self-gravitating model with two components: (i) a Sérsic stellar profile fixed according to photometric parameters, and (ii) a polytropic dark matter halo that conforms consistently to the shared gravitational potential. The polytropic equation of state can describe extended theories of dark matter involving self-interaction, non-extensive thermostatistics or boson condensation (in a classical limit). In such models, the flat-cored mass profiles widely observed in disc galaxies are due to innate dark physics, regardless of any baryonic agitation. One of the natural parameters of this scenario is the number of effective thermal degrees of freedom of dark matter (Fd) which is proportional to the dark heat capacity. By default, we assume a cosmic ratio of baryonic and dark mass. Non-Sérsic kinematic ideosyncrasies and possible non-sphericity thwart fitting in some cases. In all 14 galaxies, the fit with a polytropic dark halo improves or at least gives similar fits to the velocity dispersion profile, compared to a stars-only model. The good halo fits usually prefer Fd values from six to eight. This range complements the recently inferred limit of 7 < Fd < 10, derived from constraints on galaxy cluster core radii and black hole masses. However, a degeneracy remains: radial orbital anisotropy or a depleted dark mass fraction could shift our models' preference towards lower Fd; whereas a loss of baryons would favour higher Fd.

Saxton, Curtis J.; Ferreras, Ignacio

2010-06-01

18

Charge-state dependent compaction and dissociation of protein complexes: insights from ion mobility and molecular dynamics.  

PubMed

Collapse to compact states in the gas phase, with smaller collision cross sections than calculated for their native-like structure, has been reported previously for some protein complexes although not rationalized. Here we combine experimental and theoretical studies to investigate the gas-phase structures of four multimeric protein complexes during collisional activation. Importantly, using ion mobility-mass spectrometry (IM-MS), we find that all four macromolecular complexes retain their native-like topologies at low energy. Upon increasing the collision energy, two of the four complexes adopt a more compact state. This collapse was most noticeable for pentameric serum amyloid P (SAP) which contains a large central cavity. The extent of collapse was found to be highly correlated with charge state, with the surprising observation that the lowest charge states were those which experience the greatest degree of compaction. We compared these experimental results with in vacuo molecular dynamics (MD) simulations of SAP, during which the temperature was increased. Simulations showed that low charge states of SAP exhibited compact states, corresponding to collapse of the ring, while intermediate and high charge states unfolded to more extended structures, maintaining their ring-like topology, as observed experimentally. To simulate the collision-induced dissociation (CID) of different charge states of SAP, we used MS to measure the charge state of the ejected monomer and assigned this charge to one subunit, distributing the residual charges evenly among the remaining four subunits. Under these conditions, MD simulations captured the unfolding and ejection of a single subunit for intermediate charge states of SAP. The highest charge states recapitulated the ejection of compact monomers and dimers, which we observed in CID experiments of high charge states of SAP, accessed by supercharging. This strong correlation between theory and experiment has implications for further studies as well as for understanding the process of CID and for applications to gas-phase structural biology more generally. PMID:22280183

Hall, Zoe; Politis, Argyris; Bush, Matthew F; Smith, Lorna J; Robinson, Carol V

2012-02-22

19

Rapidly rotating polytropes in general relativity  

NASA Technical Reports Server (NTRS)

We construct an extensive set of equilibrium sequences of rotating polytropes in general relativity. We determine a number of important physical parameters of such stars, including maximum mass and maximum spin rate. The stability of the configurations against quasi-radial perturbations is diagnosed. Two classes of evolutionary sequences of fixed rest mass and entropy are explored: normal sequences which behave very much like Newtonian evolutionary sequences, and supramassive sequences which exist solely because of relativistic effects. Dissipation leading to loss of angular momentum causes a star to evolve in a quasi-stationary fashion along an evolutionary sequence. Supramassive sequences evolve towards eventual catastrophic collapse to a black hole. Prior to collapse, the star must spin up as it loses angular momentum, an effect which may provide an observational precursor to gravitational collapse to a black hole.

Cook, Gregory B.; Shapiro, Stuart L.; Teukolsky, Saul A.

1994-01-01

20

Universal Charge-Radius Relation for Subatomic and Astrophysical Compact Objects  

SciTech Connect

Electron-positron pair creation in supercritical electric fields limits the net charge of any static, spherical object, such as superheavy nuclei, strangelets, and Q balls, or compact stars like neutron stars, quark stars, and black holes. For radii between 4x10{sup 2} and 10{sup 4} fm the upper bound on the net charge is given by the universal relation Z=0.71R{sub fm}, and for larger radii (measured in femtometers or kilometers) Z=7x10{sup -5}R{sub fm}{sup 2}=7x10{sup 31}R{sub km}{sup 2}. For objects with nuclear density the relation corresponds to Z{approx_equal}0.7A{sup 1/3} (10{sup 8}10{sup 12}), where A is the baryon number. For some systems this universal upper bound improves existing charge limits in the literature.

Madsen, Jes [Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C (Denmark)

2008-04-18

21

Optimization of a compact multicusp He+ ion source for double-charge-exchanged He- beam  

NASA Astrophysics Data System (ADS)

Preliminary test bench results to study the beam quality extracted from a compact multicusp He+ ion source for He- beam production are reported. The bench is a part of the beam diagnostic system equipped with energy analyzers, emittance meters, focusing beam optics, an alkali-metal charge-exchange cell, a neutral particle energy analyzer, a double focusing magnetic momentum analyzer, a postaccelerator, and a drift tube. Utilizing the front end of the bench, the transverse emittance and the energy distribution function of a He+ beam extracted from a multi-line-cusp magnetic-field ion source 8 cm in diameter and 9 cm in length were measured. The results indicated that improvements in both formation of the plasma meniscus and reinforcement of pumping in the extraction region are necessary to produce a higher brightness He+ beam.

Shinto, K.; Sugawara, H.; Takenaga, M.; Takeuchi, S.; Tanaka, N.; Okamoto, A.; Kitajima, S.; Sasao, M.; Nishiura, M.; Wada, M.

2006-03-01

22

( N+1)-dimensional Lorentzian evolving wormholes supported by polytropic matter  

NASA Astrophysics Data System (ADS)

In this paper we study ( N+1)-dimensional evolving wormholes supported by energy satisfying a polytropic equation of state. The considered evolving wormhole models are described by a constant redshift function and generalizes the standard flat Friedmann-Robertson-Walker spacetime. The polytropic equation of state allows us to consider in (3+1)-dimensions generalizations of the phantom energy and the generalized Chaplygin gas sources.

Cataldo, Mauricio; Aróstica, Fernanda; Bahamonde, Sebastian

2013-08-01

23

Fast-charging compact seed source for magnetic flux compression generators.  

PubMed

Flux compression generators (FCGs) are some of the most attractive sources of single-use compact pulsed power available today due to their high energy density output and mobility. Driving FCGs requires some seed energy, which is typically provided by applying a high seed current, usually in the kiloampere range for midsized helical FCGs. This initial current is supplied by a high-current seed source that is capable of driving an inductive load. High-current seed sources have typically been comprised of discharging large capacitors using spark gaps and overvoltage triggering mechanisms to provide the prime power for FCGs. This paper will discuss a recent design of a self-contained (battery powered with full charge time less than 40 s), single-use compact seed source (CSS) using solid-state components for the switching scheme. The CSS developed is a system (0.005 m(3) volume and weighing 3.9 kg) capable of delivering over 360 J ( approximately 12 kA) into a 5.20 muH load with a trigger energy of microjoules at the TTL triggering level. The newly designed solid-state switching scheme of the CSS incorporates off-the-shelf high-voltage semiconductor components that minimize system cost and size as necessary for a single-use application. A detailed evaluation of the CSS is presented primarily focusing on the switching mechanics and experimental characterization of the solid-state components used in the system. PMID:19123584

Elsayed, M; Kristiansen, M; Neuber, A

2008-12-01

24

Fast-charging compact seed source for magnetic flux compression generators  

NASA Astrophysics Data System (ADS)

Flux compression generators (FCGs) are some of the most attractive sources of single-use compact pulsed power available today due to their high energy density output and mobility. Driving FCGs requires some seed energy, which is typically provided by applying a high seed current, usually in the kiloampere range for midsized helical FCGs. This initial current is supplied by a high-current seed source that is capable of driving an inductive load. High-current seed sources have typically been comprised of discharging large capacitors using spark gaps and overvoltage triggering mechanisms to provide the prime power for FCGs. This paper will discuss a recent design of a self-contained (battery powered with full charge time less than 40 s), single-use compact seed source (CSS) using solid-state components for the switching scheme. The CSS developed is a system (0.005 m3 volume and weighing 3.9 kg) capable of delivering over 360 J (~12 kA) into a 5.20 ?H load with a trigger energy of microjoules at the TTL triggering level. The newly designed solid-state switching scheme of the CSS incorporates off-the-shelf high-voltage semiconductor components that minimize system cost and size as necessary for a single-use application. A detailed evaluation of the CSS is presented primarily focusing on the switching mechanics and experimental characterization of the solid-state components used in the system.

Elsayed, M.; Kristiansen, M.; Neuber, A.

2008-12-01

25

An ultra compact 10 GHz electron-cyclotron-resonance ion source (ECRIS) for multiply charged ions production  

Microsoft Academic Search

There is considerable current interest in the use of beams of highly charged ions for a wide variety of applications. In particular, there is a need for sources with low power consumption for installation in high voltage terminals where typically only a few hundred Watts of electrical power is available. An ultra-compact (200 mm long and 120 mm outside diameter)

M. Schlapp; R. Trassl; E. Salzborn; R. W. McCullough; T. K. McLaughlin; H. B. Gilbody

1995-01-01

26

Autogravity waves in a polytropic layer  

NASA Astrophysics Data System (ADS)

The mystery of the spiral arms in galaxies is investigated. Since B. Lindblad, a few theories have come up that partially explain the spiral arms. One theory is due to C. C. Lin and F. H. Shu. They interpret the spiral arms as a density wave. This theory has been partially supported by observations. However it has also generated some criticism. A major weakness of this theory is its dispersiveness. That is, after a long enough time, there will be no localized structure in the system, which is contrary to the observations. The remedy for this defect is to include the nonlinear term that balances the dispersive term. With this in mind, we explore the nonlinear properties of a simple model of galactic slab. The model was originally studied by Ledoux in 1952. We consider here a polytropic gas slab under the influence of both self-gravitational and external potential. Physically, the external force can be thought of as a compound effect of the halo surrounding the whole galaxy. We then study the development of gravitational instability. To get to the nonlinear regime, we choose mild instability; that is to say the control parameters are near the critical point. In the long wavelength limit, we found that the waves obey the nonlinear evolution equations similar to the Bousinesq and K.d.V. equations if we choose the appropriate scalings. On the other hand, if we choose the scalings similar to the shallow water theory, the equations will be modified shallow water equations in a projected dimension. The possibility of some nonlinear solutions is also discussed.

Qian, Zhongshan

27

New type of compact electrostatic energy analyzer adequate to measurement of charge exchange neutral particles with a low counting yield  

NASA Astrophysics Data System (ADS)

A new type of compact electrostatic cylindrical energy analyzer originally providing a deflection angle of ?/22 has been designed with the aim of measuring energy spectra of charge exchange neutral particles in the tandem mirror GAMMA10. The essential advantage of the use of this analyzer is that a large entrance aperture can be adopted with high energy resolution so that high incident current is analyzed, while the radius of the cylindrical electrodes remain compact. Characteristics of the analyzer are discussed using computer simulations of ion trajectories including an effect of fringing field obtained by finite-element method as well as small-angle scattering in stripping collisions of hydrogen atoms.

Goto, T.; Ishii, K.; Katsuki, Y.; Kikuno, N.; Goi, Y.; Nagasaki, M.; Ishibashi, N.; Ono, Y.; Yamanashi, M.; Ichimura, M.; Tamano, T.; Yatsu, K.

1999-01-01

28

The structure of the tidally and rotationally distorted polytropes  

NASA Astrophysics Data System (ADS)

It is noted that Chandrasekhar (1933), in his pioneer work on the tidally and rotationally distorted polytropes, assumed the ratio of the mean radii of the components to their distance apart to be so small that quantities of the sixth-order in the ratio could be neglected. On this assumption, he considered one of the configurations of the system as a mass point. The perturbation method of Chandrasekhar, however, fails near the surface of a polytrope. With this failure in mind, Naylor and Anand (1970) calculated these models using the method of Monaghan and Roxburgh (1965) at the interfacial points chosen by Monaghan and Roxburgh. The models are recalculated here for the polytropic index n = 1.5, 2.0, and 3.0 at new interfacial points to ensure more accurate results. In addition, the structure of these models is studied in more detail for different values of q.

Singh, M.; Singh, G.

1983-10-01

29

An ultra compact 10 GHz electron-cyclotron-resonance ion source (ECRIS) for the production of multiply charged ions  

Microsoft Academic Search

There is a growing interest in the use of beams of multiply charged ions produced in special environments like high voltage platforms, Dynamitrons, Van-de-Graaff accelerators or on-line production systems for radioactive beam facilities. A compact 10 GHz ECR ion source (200 mm long, 170 mm diameter) has been developed and tested. The complete magnetic structure made from permanent magnet material

M. Schlapp; R. Trassl; P. Hathiramani; E. Salzborn; R. W. McCullough; J. B. Greenwood

1996-01-01

30

An ultra compact 10 GHz electron-cyclotron-resonance ion source (ECRIS) for the production of multiply charged ions  

Microsoft Academic Search

There is a growing interest in the use of beams of multiply charged ions produced in special environments like high voltage platforms, Dynamitrons, Van-de-Graaff accelerators or on-line production systems for radioactive beam facilities. A compact 10 GHz ECR ion source (200 mm long, 170 mm diameter) has been developed and tested. The complete magnetic structure made from permanent magnet material

M. Schlapp; R. Trassl; P. Hathiramani; R. W. McCullough; J. B. Greenwood; E. Salzborn

1997-01-01

31

Numerical Modeling of Tidal Effects in Polytropic Accretion Discs  

NASA Technical Reports Server (NTRS)

A two-dimensional time-dependent hybrid Fourier-Chebyshev method of collocation is developed and used for the study of tidal effects in accretion discs, under the assumption of a polytropic equation of state and a standard alpha viscosity prescription.

Godon, P.

1996-01-01

32

Polytrope-Black Hole simulations in full GR  

NASA Astrophysics Data System (ADS)

The characteristic formulation of GR has succesfully been used by us to evolve single black hole spacetimes stably. We here extend this implementation to handle non-vacuum spacetimes targeting one containing a black hole and a polytrope. Preliminar results will be shown and the challenges faced for an accurate simulation under this formulation discussed.

Lehner, Luis; Bishop, Nigel; Winicour, Jeffrey; Gomez, Roberto; Maharaj, Manoj

2002-04-01

33

Compact modeling of charge carrier mobility in organic thin-film transistors  

NASA Astrophysics Data System (ADS)

Finding the common points in theoretical models for mobility in thin-film transistors (TFTs), we demonstrate that there exists a generic analytical model for the mobility in organic TFTs (OTFTs), and the generic model is then converted into a TFT Compact Mobility Model, which is physically derivable from one perspective, and properly arranged to be suitable for compact modeling of OTFTs from another perspective, by separation and proper interfacing of temperature and bias dependence of the mobility, both significant for OTFTs, with the compact models for electrical current in OTFT. The proposed TFT Compact Mobility Model is verified theoretically and against experimental data, and the model is applicable even for high temperatures T>To, above the characteristic temperature To of the distribution of states in the organic material, a condition at which other models diverge in principle. The improvement is achieved by the identification of a temperature ``shaping'' function, which contains a diverging function when derived theoretically elsewhere at idealized assumptions, and we suggest an approach to remedy the problem, since divergence in characteristic equations of compact models is not allowed. However, an open question remains for the bias enhancement in mobility at high temperatures, for which case no physical model is available at present. Another essential practical feature of the TFT Compact Mobility Model is that the model is both upgradable and reducible, allowing for easier implementation, modifications and independence of characterization techniques, enabling a systematic fitting of experimental data with large scattering in the values, which is the case for OTFT nowadays.

Marinov, O.; Deen, M. J.; Datars, R.

2009-09-01

34

Demonstration of charge breeding in a compact room temperature electron beam ion trap  

NASA Astrophysics Data System (ADS)

For the first time, a small room-temperature electron beam ion trap (EBIT), operated with permanent magnets, was successfully used for charge breeding experiments. The relatively low magnetic field of this EBIT does not contribute to the capture of the ions; single-charged ions are only caught by the space charge potential of the electron beam. An over-barrier injection method was used to fill the EBIT's electrostatic trap with externally produced, single-charged potassium ions. Charge states as high as K19+ were reached after about a 3 s breeding time. The capture and breeding efficiencies up to 0.016(4)% for K17+ have been measured.

Vorobjev, G.; Sokolov, A.; Thorn, A.; Herfurth, F.; Kester, O.; Quint, W.; Stöhlker, Th.; Zschornack, G.

2012-05-01

35

Supersymmetric formulation of polytropic gas dynamics and its invariant solutions  

SciTech Connect

In this paper, a supersymmetric extension of the polytropic gas dynamics equations is constructed through the use of a superspace involving two independent fermionic variables and two bosonic superfields. A superalgebra of symmetries of the proposed extended model is determined and a systematic classification of the one-dimensional subalgebras of this superalgebra is performed. Through the use of the symmetry reduction method, a number of invariant solutions of the supersymmetric polytropic gas dynamics equations are found. Several types of solutions are obtained including algebraic-type solutions and propagation waves (simple and double waves). Many of the obtained solutions involve arbitrary functions of one or two bosonic or fermionic variables. In the case where the arbitrary functions involve only the independent fermionic variables, the solutions are expressed in terms of Taylor expansions.

Grundland, A. M. [Centre de Recherches Mathematiques, Universite de Montreal, C. P. 6128, Succ. Centre-ville, Montreal, (QC) H3C 3J7 (Canada); Universite du Quebec, Trois-Rivieres, CP500 (QC) G9A 5H7 (Canada); Hariton, A. J. [Centre de Recherches Mathematiques, Universite de Montreal, C. P. 6128, Succ. Centre-ville, Montreal, (QC) H3C 3J7 (Canada)

2011-04-15

36

Uniformly rotating homogeneous and polytropic rings in Newtonian gravity  

NASA Astrophysics Data System (ADS)

An analytical method is presented for treating the problem of a uniformly rotating, self-gravitating ring without a central body in Newtonian gravity. The method is based on an expansion about the thin ring limit, where the cross-section of the ring tends to a circle. The iterative scheme developed here is applied to homogeneous rings up to the 20th order and to polytropes with the index n = 1 up to the third order. For other polytropic indices no analytic solutions are obtainable, but one can apply the method numerically. However, it is possible to derive a simple formula relating mass to the integrated pressure to leading order without specifying the equation of state. Our results are compared with those generated by highly accurate numerical methods to test their accuracy.

Petroff, David; Horatschek, Stefan

2008-09-01

37

Consistency of f(R) gravity models around solar polytropes  

NASA Astrophysics Data System (ADS)

It is stated that a class of f(R) gravity models seem to obtain ?CDM behavior for high redshifts and general relativistic behavior locally at high curvatures. In the present Letter, we numerically study polytropic configurations that resemble stars like young sun with Hu and Sawicki's f(R) gravity field equations and compare the spacetime at the boundary to the general relativistic counterpart. These polytropes are stationary spherically symmetric configurations and have regular metrics at the origin. Since Birkhoff's theorem does not apply for modified gravity, the solution outside may deviate from Schwarzschild-de Sitter spacetime. At the boundary, Post-Newtonian parametrization was used to determine how much the studied model deviates from the general relativistic ?CDM model.

Henttunen, K.; Vilja, I.

2014-04-01

38

Emden-Chandrasekhar axisymmetric, solid-body rotating polytropes  

Microsoft Academic Search

The basic theory on polytorpes is revisited and EC polytropes are defined. The first-order approximation theory of Chandrasekhar (1933a, b, c) and Chandrasekhar and Lebovitz (1962) is reviewed, refined and extended in such a way that better results are obtained without involving hard analytical or numerical techniques. A more precise equation is given in defining non-outer equipotential surfaces, and a

R. Caimmi

1980-01-01

39

A study of massive classical polytropes in general relativity  

Microsoft Academic Search

A detailed study of classical polytropes in general relativity is presented for chi(0) (equivalent to (dP\\/dE)-sub0) no greater than 1.0 and sigma(0) (equivalent to P\\/E-sub0) less than or equal to chi(0), where E is the coordinate density and P is the pressure. The behavior of various structural parameters is studied with mu(0) (equivalent to sigma(0)\\/chi(0), where sigma(0) and chi(0) are

S. C. Pandey; M. C. Durgapal; A. K. Pande

1989-01-01

40

Oblique radiative shocks, including their interactions with nonradiative polytropic shocks  

SciTech Connect

A theory of shocks dominated by radiation energy flux in optically mixed thin-upstream thick-downstream systems, in which the temperature immediately ahead and some short distance behind the shock front are equilibrated by radiation transport, is presented. This theory is applied to determine properties of the normal and oblique radiative shock, followed by applications to interactions when radiative and polytropic shocks are present in the same system. Comparison with experimental data is presented.

Doss, F. W.; Drake, R. P.; Myra, E. S. [Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, Michigan 48109-2143 (United States)

2011-05-15

41

Sinuous oscillations and steady warps of polytropic disks  

SciTech Connect

In an asymptotic development of the equations governing the equilibria and linear stability of rapidly rotating polytropes we employed the slender aspect of these objects to reduce the three-dimensional partial differential equations to a somewhat simpler, ordinary integro-differential form. The earlier calculations dealt with isolated objects that were in centrifugal balance, that is the centrifugal acceleration of the configuration was balanced largely by self gravity with small contributions from the pressure gradient. Another interesting situation is that in which the polytrope rotates subject to externally imposed gravitational fields. In astrophysics, this is common in the theory of galactic dynamics because disks are unlikely to be isolated objects. The dark halos associated with disks also provide one possible explanation of the apparent warping of many galaxies. If the axis of the highly flattened disk is not aligned with that of the much less flattened halo, then the resultant torque of the halo gravity on the disk might provide a nonaxisymmetric distortion or disk warp. Motivated by these possibilities we shall here build models of polytropic disks of small but finite thickness which are subjected to prescribed, external gravitational fields. First we estimate how a symmetrical potential distorts the structure of the disk, then we examine its sinuous oscillations to confirm that they freely decay, hence suggesting that a warp must be externally forced. Finally, we consider steady warps of the disk plane when the axis of the disk does not coincide with that of the halo.

Balmforth, N.J. [Texas Univ., Austin, TX (United States). Fusion Research Center; Spiegel, E.A. [Columbia Univ., New York, NY (United States). Astronomy Dept.

1995-05-01

42

Caloric curves fitted by polytropic distributions in the HMF model  

NASA Astrophysics Data System (ADS)

We perform direct numerical simulations of the Hamiltonian mean field (HMF) model starting from non-magnetized initial conditions with a velocity distribution that is (i) Gaussian; (ii) semi-elliptical, and (iii) waterbag. Below a critical energy E c , depending on the initial condition, this distribution is Vlasov dynamically unstable. The system undergoes a process of violent relaxation and quickly reaches a quasi-stationary state (QSS). We find that the distribution function of this QSS can be conveniently fitted by a polytrope with index (i) n = 2; (ii) n = 1; and (iii) n = 1/2. Using the values of these indices, we are able to determine the physical caloric curve T kin ( E) and explain the negative kinetic specific heat region C kin = dE/ d T kin < 0 observed in the numerical simulations. At low energies, we find that the system has a "core-halo" structure. The core corresponds to the pure polytrope discussed above but it is now surrounded by a halo of particles. In case (iii), we recover the "uniform" core-halo structure previously found by Pakter and Levin [Phys. Rev. Lett. 106, 200603 (2011)]. We also consider unsteady initial conditions with magnetization M 0 = 1 and isotropic waterbag velocity distribution and report the complex dynamics of the system creating phase space holes and dense filaments. We show that the kinetic caloric curve is approximately constant, corresponding to a polytrope with index n 0 ? 3.56 (we also mention the presence of an unexpected hump). Finally, we consider the collisional evolution of an initially Vlasov stable distribution, and show that the time-evolving distribution function f( ?,v,t) can be fitted by a sequence of polytropic distributions with a time-dependent index n( t) both in the non-magnetized and magnetized regimes. These numerical results show that polytropic distributions (also called Tsallis distributions) provide in many cases a good fit of the QSSs. They may even be the rule rather than the exception. However, in order to moderate our message, we also report a case where the Lynden-Bell theory (which assumes ergodicity or efficient mixing) provides an excellent prediction of an inhomogeneous QSS. We therefore conclude that both Lynden-Bell and Tsallis distributions may be useful to describe QSSs depending on the efficiency of mixing.

Campa, Alessandro; Chavanis, Pierre-Henri

2013-04-01

43

A study of massive classical polytropes in general relativity  

Microsoft Academic Search

A detailed study of classical polytropes in general relativity has been presented for ?O (=(dP\\/dE)O)= 1.0 and sO(=(P\\/EO)=?O. The behaviour of various structural parameters with =sO\\/?O, sO and ?O are the values ofP\\/E and dP\\/dE at the centre) has been studied. The most important result of this study is the fact the qualitative behaviour of all the structural parameters depends

S. C. Pandey; M. C. Durgapal; A. K. Pande

1989-01-01

44

Newtonian polytropes for anisotropic matter: General framework and applications  

NASA Astrophysics Data System (ADS)

We set up the general formalism to model polytropic Newtonian stars with anisotropic pressure. We obtain the corresponding Lane-Emden equation. A heuristic model based on an ansatz to obtain anisotropic matter solutions from known solutions for isotropic matter is adopted to illustrate the effects of the pressure anisotropy on the structure of the star. In particular, we calculate the Chandrasekhar mass for a white dwarf. It is clearly displayed how the Chandrasekhar mass limit changes depending on the anisotropy. Prospective astrophysical applications of the proposed approach are discussed.

Herrera, L.; Barreto, W.

2013-04-01

45

A Compact Charge-Based Propagation Delay Model for Submicronic CMOS Buffers  

Microsoft Academic Search

We provide an accurate analytical expression for the propagation delayand the output transition time of submicron CMOS buffers\\u000a that takes into account the short-circuit current, the input-output coupling capacitance, and the carrier velocitysaturation\\u000a effects, of increasing importance in deep-submicron technologies. The model is based on the nth-power law MOSFET model and\\u000a computes the propagation delayfrom the charge delivered to the

José Luis Rosselló; Jaume Segura

2002-01-01

46

An ultra compact 10 GHz electron-cyclotron-resonance ion source (ECRIS) for the production of multiply charged ions  

SciTech Connect

There is a growing interest in the use of beams of multiply charged ions produced in special environments like high voltage platforms, Dynamitrons, Van-de-Graaff accelerators or on-line production systems for radioactive beam facilities. A compact 10 GHz ECR ion source (200 mm long, 170 mm diameter) has been developed and tested. The complete magnetic structure made from permanent magnet material is comprised of four ring magnets producing an asymmetric axial magnetic field with a mirror ratio of 2.5 and a 24 piece hexapole magnet with a maximum radial field of 0.94 T inside the plasma chamber of 25 mm inner diameter. The coupling of the microwave to the plasma using a resonant transition line from rectangular to circular waveguide shows efficient ECR plasma heating at microwave power levels around 10 watts. Charge state distributions for various elements with intensities up to 320 e{mu}A and their dependence on operation parameters will be presented as well as VUV spectra in the wavelength region down to 15 nm.

Schlapp, M. [Argonne National Lab., IL (United States); Trassl, R.; Hathiramani, P.; Salzborn, E. [Giessen Univ. (Germany). Inst. fuer Kernphysik im Strahlenzentrum; McCullough, R.W.; Greenwood, J.B. [Queen`s Univ., Belfast, Northern Ireland (United Kingdom). Dept. of Pure and Applied Physics

1996-12-31

47

Polytropic equilibrium and normal modes in cold atomic traps  

NASA Astrophysics Data System (ADS)

The compressibility limit of a cold gas confined in a magneto-optical trap due to multiple scattering of light is a long-standing problem. This scattering mechanism induces long-range interactions in the system, which are responsible for the occurrence of plasma-like phenomena. In the present paper, we investigate the importance of the long-range character of the mediated atom-atom interaction in the equilibrium and dynamical features of a magneto-optical trap. Making use of a hydrodynamical formulation, we derive a generalized Lane-Emden equation modeling the polytropic equilibrium of a magneto-optical trap, allowing us to describe the crossover between the two limiting cases: temperature-dominated and multiple-scattering-dominated traps. The normal collective modes of the system are also computed.

Terças, H.; Mendonça, J. T.

2013-08-01

48

Accelerated power series solution of polytropic and isothermal gas spheres  

NASA Astrophysics Data System (ADS)

In this paper, a power series solution for the Lane-Emden equation has been developed. We construct a recurrence relation for the coefficients ak in the power series expansion ?( x)=? akxk of the solution of the Lane-Emden equation. For a polytrope with index n?1.9 the series appear to converge everywhere inside the star. For n>1.9 the series converges in the inner radii, but then diverges. To improve the convergence radii of the series we used a combination of two accelerating techniques, Euler-Abel transformation and Padé approximation. These transformed series converge everywhere for n?5. A comparison with the isothermal sphere reveals a good fit with both the numerical and four terms optimized model developed by Hunter [MNRAS 328 (2001) 839].

Nouh, M. I.

2004-07-01

49

A polytropic approach to semi-relativistic isothermal gas spheres at arbitrary temperature  

NASA Astrophysics Data System (ADS)

We use the standard polynomial expansion technique to show the existence of a relation between the polytropic model and the description of gas spheres at finite temperature. A numerical analysis is performed concerning the obtained perturbative parameters. It is shown that there is a correspondence between polytropic and gas sphere thermal models for fermions and bosons. For instance, the polytropic index n displays evident correlation with temperature and chemical potential. The behaviour of sample configurations is illustrated, considering neutrons as fermions and Z0 bosons. Boson and fermion stars presented similar graphics for the parameters used in this model, but with very different temperature regimes.

de Sousa, Claudio M. G.; de Araujo, Evandro A.

2011-07-01

50

Compact multichannel neutral particle analyzer for measurement of energetic charge-exchanged neutrals in Alcator C-Mod  

SciTech Connect

A four-channel compact neutral particle analyzer (CNPA) based on operating small Si diode detectors in pulse-height analysis (PHA) mode is used to measure energetic hydrogen minority ions with energies between {approx}50 and 350 keV stemming from ion-cyclotron range-of-frequency heated D(H) Alcator C-Mod plasmas with both active and passive charge exchange (CX). First core minority ion distribution results from Alcator C-Mod discharges and a detailed description of the diagnostic are presented. The diagnostic employs integrated electronics and fast digitization of the shaping amplifier voltage. The digitized data are stored for postshot PHA, which removes the constraints of real-time PHA and allows for improved performance via elimination of base line shift effects and potentially relieving pileup through Gaussian fitting routines. The CNPA is insensitive to the large gamma and neutron background in Alcator C-Mod discharges but is susceptible to the plasma's soft x-ray flux. The soft x-ray flux limits the CNPA energy resolution to {approx}15-20 keV. A simple model is used to interpret the active CNPA data which permits rapid estimates of the core hydrogen minority temperatures and anisotropy with a time resolution of {approx}100 ms. Hydrogenlike boron is identified as an important electron donor for the CX signal.

Tang, V.; Liptac, J.; Parker, R. R.; Bonoli, P. T.; Fiore, C. L.; Granetz, R. S.; Irby, J. H.; Lin, Y.; Wukitch, S. J.; Frenje, J. A.; Leiter, R.; Mcduffee, S.; Petrasso, R. D. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2006-08-15

51

Study of polytropic exponent based on high pressure switching expansion reduction  

NASA Astrophysics Data System (ADS)

Switching expansion reduction (SER) uses a switch valve to substitute the throttle valve to reduce pressure for high pressure pneumatics. The experiments indicate that the simulation model well predicts the actual characteristics. The heat transfers and polytropic exponents of the air in expansion tank and supply tanks of SER have been studied on the basis of the experiments and the simulation model. Through the mathematical reasoning in this paper, the polytropic exponent can be calculated by the air mass, heat, and work exchanges of the pneumatic container. For the air in a constant volume tank, when the heat-absorption is large enough to raise air temperature in discharging process, the polytropic exponent is less than 1; when the air is experiencing a discharging and heat-releasing process, the polytropic exponent exceeds the specific heat ratio (the value of 1.4).

Wang, Xuanyin; Luo, Yuxi; Xu, Zhipeng

2011-10-01

52

Polytropic neutron star - black hole merger simulations with a Paczy?ski-Wiita potential  

NASA Astrophysics Data System (ADS)

Context. Mergers of neutron stars (NS) and black holes (BH) are among the strongest sources of gravitational waves and are potential central engines for short gamma-ray bursts. Aims: We aim to compare the general relativistic (GR) results of other groups with Newtonian calculations of models with equivalent parameters. We vary the mass ratio of the NS to BH and the compactness of the NS. The mass of the NS is 1.4 M_?. We compare the dynamics in the parameter-space regions where the NS is expected to reach the innermost stable circular orbit (ISCO) before being tidally disrupted (mass shedding, MS), and vice versa. Methods: The hydrodynamics is evolved by a Newtonian PPM scheme with four levels of nested grids. We use a polytropic EoS (? = 2), as adopted in the GR simulations. However, instead of full GR we use a Newtonian potential supplemented by a Paczy?ski-Wiita-Artemova potential for the BH, both disregarding and including rotation of the BH. Results: If the NS is compact (C = 0.18), it is accreted by the BH more quickly, and only a small amount of mass remains outside the BH. If the mass ratio is small (Q = 2 or 3) or the NS is less compact (C = 0.16 or less), the NS is tidally torn apart before being accreted. Although most of the mass is absorbed by the BH, some 0.1 M_? remain in a tidal arm. For small mass ratios (Q = 2 and 3), the tidal arm can wrap around the BH to form a thick disk. When including the effects of either BH spin-up or spin-down by the accreted matter, more mass remains in the surroundings (0.2-0.3 M_?). Conclusions: Although details and quantitative results differ, the general trends of our Newtonian calculations are similar to the GR calculations. A clear delimiting line separating the ISCO from the MS cases is not found. Inclusion of BH rotation as well as sufficient numerical resolution are extremely important.

Ruffert, M.; Janka, H.-Th.

2010-05-01

53

Critical rotation of general-relativistic polytropic models revisited  

NASA Astrophysics Data System (ADS)

We develop a perturbation method for computing the critical rotational parameter as a function of the equatorial radius of a rigidly rotating polytropic model in the "post-Newtonia approximation" (PNA). We treat our models as "initial value problems" (IVP) of ordinary differential equations in the complex plane. The computations are carried out by the code dcrkf54.f95 (Geroyannis and Valvi 2012 [P1]; modified Runge-Kutta-Fehlberg code of fourth and fifth order for solving initial value problems in the complex plane). Such a complex-plane treatment removes the syndromes appearing in this particular family of IVPs (see e.g. P1, Sec. 3) and allows continuation of the numerical integrations beyond the surface of the star. Thus all the required values of the Lane-Emden function(s) in the post-Newtonian approximation are calculated by interpolation (so avoiding any extrapolation). An interesting point is that, in our computations, we take into account the complete correction due to the gravitational term, and this issue is a remarkable difference compared to the classical PNA. We solve the generalized density as a function of the equatorial radius and find the critical rotational parameter. Our computations are extended to certain other physical characteristics (like mass, angular momentum, rotational kinetic energy, etc). We find that our method yields results comparable with those of other reliable methods. REFERENCE: V.S. Geroyannis and F.N. Valvi 2012, International Journal of Modern Physics C, 23, No 5, 1250038:1-15.

Geroyannis, V.; Karageorgopoulos, V.

2013-09-01

54

A compact charge-based model to study the nanoscale undoped double gate MOSFETs for nanoelectronic circuit design using genetic algorithms  

NASA Astrophysics Data System (ADS)

The analytical modeling of nanoscale devices is an important area of computer-aided design for fast and accurate nanoelectronic design and optimization. In the present paper, a new approach for modeling semiconductor devices, nanoscale double gate DG MOSFETs, by use of the gradual channel approximation (GC) approach and genetic algorithm optimization technique (GA) is presented. The proposed approach combines the universal optimization and fitting capability of GA and the cost-effective optimization concept of quantum correction, to achieve reliable, accurate and simple compact models for nanoelectronic circuit simulations. Our compact models give good predictions of the quantum capacitance, threshold voltage shift, quantum inversion charge density and drain current. These models have been verified with 2D self-consistent results from numerical calculations of the coupled Poisson-Schrödinger equations. The developed models can also be incorporated into nanoelectronic circuit simulators to study the nanoscale CMOS-based devices without impact on the computational time and data storage.

Bendib, T.; Djeffal, F.; Arar, D.

2013-04-01

55

Fluorescence lifetime imaging microscope consisting of a compact picosecond dye laser and a gated charge-coupled device camera for applications to living cells.  

PubMed

An inverted microscope was combined with a compact dye laser with a pulse width of <190 ps and an intensified charge-coupled device (ICCD) camera with a minimum gate width of 200 ps. The resulting fluorescence lifetime imaging microscope, which has a temporal resolution of 340 ps, was used to measure the fluorescence lifetime of polymer microspherers. The results indicated a fluorescence lifetime of 0.9 ns. The present analytical instrument was also employed in an evaluation of biological cells after labeling them with SYTO 13, a fluorescent dye. PMID:17038764

Uchimura, Tomohiro; Kawanabe, Satoshi; Maeda, Yuki; Imasaka, Totaro

2006-10-01

56

The global polytropic model for the solar and jovian systems revisited  

NASA Astrophysics Data System (ADS)

The "global polytropic model" (Geroyannis) 1993 [P1]; Geroyannis and Valvi 1994 [P2]) is based on the assumption of hydrostatic equilibrium for the solar/jovian system, described by the Lane-Emden differential equation. A polytropic sphere of polytropic index n and radius R1 represents the central component S1 (Sun/Jupiter) of a polytropic configuration with further components the polytropic spherical shells S2, S3, ..., defined by the pairs of radii (R1,R2), (R2,R3), ..., respectively. R1, R2, R3, ..., are the roots of the real part Re(theta(R)) of the complex Lane-Emden function theta(R). Each polytropic shell is assumed to be an appropriate place for a planet/satellite to be "born" and "live". This scenario has been studied numerically for the case of the solar system (P1) and the jovian system (P2). In the present paper, the Lane-Emden differential equation is solved numerically in the complex plane by using the Fortran code dcrkf54.f95 (Geroyannis and Valvi 2012; modified Runge-Kutta- Fehlberg code of fourth and fifth order for solving initial value problems in the complex plane). We include in our numerical study some trans-Neptunian objects. We emphasize on computing distances and comparing with previous results. REFERENCES: V.S. Geroyannis 1993, Earth, Moon, and Planets, 61, 131-139. V.S. Geroyannis and F.N. Valvi 1994, Earth, Moon, and Planets, 64, 217-225. V.S. Geroyannis and F.N. Valvi 2012, International Journal of Modern Physics C, 23, No 5, 1250038:1-15.

Geroyannis, V.; Valvi, F.; Dallas, T.

2013-09-01

57

Compact Analytic Expression for the Electric Field of a 2DElliptical Charge Distribution Inside a Perfectly Conducting CircularCylinder  

SciTech Connect

By combining the method of images with calculus of complex variables, we provide a simple expression for the electric field of a two-dimensional (2D) static elliptical charge distribution inside a perfectly conducting cylinder. The charge distribution need not be concentric with the cylinder.

Furman, M.A.

2007-05-29

58

Investigation of high resolution compact gamma camera module based on a continuous scintillation crystal using a novel charge division readout method  

NASA Astrophysics Data System (ADS)

The objective of this study is to investigate a high performance and lower cost compact gamma camera module for a multi-head small animal SPECT system. A compact camera module was developed using a thin Lutetium Oxyorthosilicate (LSO) scintillation crystal slice coupled to a Hamamatsu H8500 position sensitive photomultiplier tube (PSPMT). A two-stage charge division readout board based on a novel sub-tractive resistive readout with a truncated center-of-gravity (TCOG) positioning method was developed for the camera. The performance of the camera was evaluated using a flood 99mTc source with a four-quadrant bar-mask phantom. The preliminary experimental results show that the image shrinkage problem associated with the conventional resistive readout can be effectively overcome by the novel subtractive resistive readout with an appropriate fraction subtraction factor. The response output area (ROA) of the camera shown in the flood image was improved up to 34%, and an intrinsic spatial resolution better than 2 mm of detector was achieved. In conclusion, the utilization of a continuous scintillation crystal and a flat-panel PSPMT equipped with a novel subtractive resistive readout is a feasible approach for developing a high performance and lower cost compact gamma camera.

Dai, Qiu-Sheng; Zhao, Cui-Lan; Zhang, Hua-Lin; Qi, Yu-Jin

2010-08-01

59

A compact tetrathiafulvalene-benzothiadiazole dyad and its highly symmetrical charge-transfer salt: ordered donor ?-stacks closely bound to their acceptors.  

PubMed

A compact and planar donor-acceptor molecule 1 comprising tetrathiafulvalene (TTF) and benzothiadiazole (BTD) units has been synthesised and experimentally characterised by structural, optical, and electrochemical methods. Solution-processed and thermally evaporated thin films of 1 have also been explored as active materials in organic field-effect transistors (OFETs). For these devices, hole field-effect mobilities of ?FE = (1.3±0.5)×10(-3) and (2.7±0.4)×10(-3) ?cm(2) ?V?s(-1) were determined for the solution-processed and thermally evaporated thin films, respectively. An intense intramolecular charge-transfer (ICT) transition at around 495?nm dominates the optical absorption spectrum of the neutral dyad, which also shows a weak emission from its ICT state. The iodine-induced oxidation of 1 leads to a partially oxidised crystalline charge-transfer (CT) salt {(1)2I3}, and eventually also to a fully oxidised compound {1I3}?1/2I2. Single crystals of the former CT compound, exhibiting a highly symmetrical crystal structure, reveal a fairly good room temperature electrical conductivity of the order of 2?S?cm(-1). The one-dimensional spin system bears compactly bonded BTD acceptors (spatial localisation of the LUMO) along its ridge. PMID:24737663

Geng, Yan; Pfattner, Raphael; Campos, Antonio; Hauser, Jürg; Laukhin, Vladimir; Puigdollers, Joaquim; Veciana, Jaume; Mas-Torrent, Marta; Rovira, Concepció; Decurtins, Silvio; Liu, Shi-Xia

2014-06-01

60

a Runge-Kutta Code for the Complex Plane: Comparing with Similar Codes by Applying to Polytropic Models  

NASA Astrophysics Data System (ADS)

In this paper, we modify the Runge-Kutta-Fehlberg code of fourth and fifth order with the purpose of solving initial value problems established on ordinary differential equations involving complex-valued functions of one complex variable, which are allowed to have high complexity in their definition, when integration along prescribed complex paths is required. Such initial value problems arise in certain astrophysical issues, like the polytropic models, applied to polytropic stars, and the general-relativistic polytropic models, applied to neutron stars. Comparison with similar codes is made by applying to these models.

Geroyannis, V. S.; Valvi, F. N.

2012-05-01

61

A compact electron beam ion source with integrated Wien filter providing mass and charge state separated beams of highly charged ions.  

PubMed

A Wien filter was designed for and tested with a room temperature electron beam ion source (EBIS). Xenon charge state spectra up to the charge state Xe46+ were resolved as well as the isotopes of krypton using apertures of different sizes. The complete setup consisting of an EBIS and a Wien filter has a length of less than 1 m substituting a complete classical beamline setup. The Wien filter is equipped with removable permanent magnets. Hence total beam current measurements are possible via simple removal of the permanent magnets. In dependence on the needs of resolution a weak (0.2 T) or a strong (0.5 T) magnets setup can be used. In this paper the principle of operation and the design of the Wien filter meeting the requirements of an EBIS are briefly discussed. The first ion beam extraction and separation experiments with a Dresden EBIS are presented. PMID:19566197

Schmidt, M; Peng, H; Zschornack, G; Sykora, S

2009-06-01

62

Compact, accurate description of diagnostic neutral beam propagation and attenuation in a high temperature plasma for charge exchange recombination spectroscopy analysis  

NASA Astrophysics Data System (ADS)

Charge exchange recombination spectroscopy on Alcator C-Mod relies on the use of the diagnostic neutral beam injector as a source of neutral particles which penetrate deep into the plasma. It employs the emission resulting from the interaction of the beam atoms with fully ionized impurity ions. To interpret the emission from a given point in the plasma as the density of emitting impurity ions, the density of beam atoms must be known. Here, an analysis of beam propagation is described which yields the beam density profile throughout the beam trajectory from the neutral beam injector to the core of the plasma. The analysis includes the effects of beam formation, attenuation in the neutral gas surrounding the plasma, and attenuation in the plasma. In the course of this work, a numerical simulation and an analytical approximation for beam divergence are developed. The description is made sufficiently compact to yield accurate results in a time consistent with between-shot analysis.

Bespamyatnov, Igor O.; Rowan, William L.; Granetz, Robert S.

2008-10-01

63

Structure of external electromagnetic field around a slowly rotating compact object and charged-particle trajectories therein  

Microsoft Academic Search

The authors have discussed the trajectories of a charged particle in a dipole magnetic field and quadrupole electric field superposed on the external space-time of a very slowly rotating mass represented by a first-order correction to the Schwarzschild geometry. The metric, which is an approximate form of the Hartle-Thorne metric, includes corrections of the linear order in (omega = 2J\\/gamma3)

A. R. Prasanna; A. Gupta

1997-01-01

64

Local pellet based and line-integrated nonperturbing charge exchange measurements with a compact neutral particle analyzer on Large Helical Device  

NASA Astrophysics Data System (ADS)

Experiments on suprathermal ion physics are carried out on the Large Helical Device (LHD) with a 40 channel compact neutral particle analyzer (CNPA). The analyzer is used both in passive nonperturbing chord-integral neutral particle flux measurements and for local probing with an impurity pellet. The analyzer observes trapped particles with |v?/v|<0.25 and the pitch angle cosine value v?/v changes sign along the diagnostic sight line. The measurable energy range for H0 is 1-170 keV. Radially resolved data on local H0 atomic energy spectra have been obtained on LHD by the pellet charge exchange method with CNPA, as well as chord-integral atomic energy distribution data for electron cyclotron heated, neutral beam injected, and high power ion cyclotron heated plasma. The article addresses the diagnostic technical background and the analysis scheme of measurement results taking into account the helical geometry and the species and densities of the charge exchange targets.

Goncharov, P. R.; Ozaki, T.; Sudo, S.; Tamura, N.; Tespel Group; LHD Experimental Group; Veshchev, E. A.; Sergeev, V. Yu.; Krasilnikov, A. V.

2006-10-01

65

Free boundary value problem of the one-dimensional model of polytropic ideal gas  

Microsoft Academic Search

In this paper the free boundary value problem of the one-dimensional model of polytropic ideal gas is discussed. Under some\\u000a smallness assumption on the initial data, the global weak solution of our problem is obtained. Furthermore the solution decays\\u000a inL\\u000a ?-sense as time goes to infinity (Theorem 2.1).

Sadamu Inaishi

1991-01-01

66

Effective geometry of the n=1 uniformly rotating self-gravitating polytrope  

SciTech Connect

The ''effective geometry'' formalism is used to study the perturbations of a perfect barotropic Newtonian self-gravitating rotating and compressible fluid coupled with gravitational backreaction. The case of a uniformly rotating polytrope with index n=1 is investigated, due to its analytical tractability. Special attention is devoted to the geometrical properties of the underlying background acoustic metric, focusing, in particular, on null geodesics as well as on the analog light cone structure.

Bini, D.; Cherubini, C.; Filippi, S.; Geralico, A. [Istituto per le Applicazioni del Calcolo 'M. Picone', CNR, I-00185 Rome (Italy) and ICRA, University of Rome 'La Sapienza', I-00185 Rome (Italy); Nonlinear Physics and Mathematical Modeling Lab, Engineering Faculty, University Campus Bio-Medico, I-00128 Rome (Italy) and ICRA, University of Rome 'La Sapienza', I-00185 Rome (Italy); Physics Department and ICRA, University of Rome 'La Sapienza', I-00185 Rome (Italy)

2010-08-15

67

ROSSBY WAVE INSTABILITY IN LOCALLY ISOTHERMAL AND POLYTROPIC DISKS: THREE-DIMENSIONAL LINEAR CALCULATIONS  

SciTech Connect

Numerical calculations of the linear Rossby wave instability (RWI) in global three-dimensional (3D) disks are presented. The linearized fluid equations are solved for vertically stratified, radially structured disks with either a locally isothermal or polytropic equation of state, by decomposing the vertical dependence of the perturbed hydrodynamic quantities into Hermite and Gegenbauer polynomials, respectively. It is confirmed that the RWI operates in 3D. For perturbations with vertical dependence assumed above, there is little difference in growth rates between 3D and two-dimensional (2D) calculations. Comparison between 2D and 3D solutions of this type suggests the RWI is predominantly a 2D instability and that 3D effects, such as vertical motion, can be interpreted as a perturbative consequence of the dominant 2D flow. The vertical flow around corotation, where vortex formation is expected, is examined. In locally isothermal disks, the expected vortex center remains in approximate vertical hydrostatic equilibrium. For polytropic disks, the vortex center has positive vertical velocity, whose magnitude increases with decreasing polytropic index n.

Lin, Min-Kai, E-mail: mklin924@cita.utoronto.ca [Canadian Institute for Theoretical Astrophysics, 60 St. George Street, Toronto, ON M5S 3H8 (Canada)

2012-07-20

68

Pair production of heavy MSSM charged and neutral Higgs bosons in multi-TeV e{sup +}e{sup -} collisions at the Compact Linear Collider  

SciTech Connect

In the theoretical framework of the minimal supersymmetric extension of the standard model (MSSM), we study the pair production of heavy charged and neutral Higgs bosons in e{sup +}e{sup -} collisions with a center-of-mass energy of 3 TeV, at the Compact Linear Collider (CLIC). The high-energy beam-beam effects at the interaction point are taken into account in our simulations. With an integrated luminosity of 3000 fb{sup -1}, the hadronic cascade decays of H{sup +}H{sup -} and A{sup 0}H{sup 0} pairs can be observed over a wide range of Higgs boson masses, extending beyond 1 TeV. The Higgs mass parameter m{sub A} can be derived from a {chi}{sup 2}-analysis, and the corresponding statistical error was found to be smaller than 1%. In addition, by comparing the signal rates of different decay channels, one can determine the ratio between the vacuum expectation values tan{beta} with a good accuracy in the intermediate region, i.e. when tan{beta} lies between 6 and 11 typically.

Coniavitis, Elias; Ferrari, Arnaud [Uppsala University, box 535, 75121 Uppsala (Sweden)

2007-01-01

69

VISCOUS ACCRETION OF A POLYTROPIC SELF-GRAVITATING DISK IN THE PRESENCE OF WIND  

SciTech Connect

Self-similar and semi-analytical solutions are found for the height-averaged equations governing the dynamical behavior of a polytropic, self-gravitating disk under the effects of winds around the nascent object. In order to describe the time evolution of the system, we adopt a radius-dependent mass loss rate, then highlight its importance on both the traditional {alpha} and innovative {beta} models of viscosity prescription. In agreement with some other studies, our solutions represent that the Toomre parameter is less than one in most regions on the {beta}-disk, which indicates that in such disks gravitational instabilities can occur at various distances from the central accretor. So, the {beta}-disk model might provide a good explanation of how the planetary systems form. The purpose of the present work is twofold: examining the structure of a disk with wind in comparison to a no-wind solution and seeing whether the adopted viscosity prescription significantly affects the dynamical behavior of the disk-wind system. We also considered the temperature distribution in our disk by a polytropic condition. The solutions imply that, under our boundary conditions, the radial velocity is larger for {alpha}-disks and increases as wind becomes stronger in both viscosity models. Also, we noticed that the disk thickness increases by amplifying the wind or adopting larger values for the polytropic exponent {gamma}. It also may globally decrease if one prescribes a {beta}-model for the viscosity. Moreover, in both viscosity models, the surface density and mass accretion rate diminish as the wind gets stronger or {gamma} increases.

Abbassi, Shahram; Nourbakhsh, Erfan [School of Physics, Damghan University, P.O. Box 36715-364, Damghan (Iran, Islamic Republic of); Shadmehri, Mohsen, E-mail: abbassi@ipm.ir, E-mail: e.nourbakhsh@mail.sbu.ac.ir, E-mail: m.shadmehri@gu.ac.ir [Department of Physics, Golestan University, Basij Square, Gorgan (Iran, Islamic Republic of)

2013-03-10

70

Vortex laws and field line invariants in polytropic field-aligned MHD flow  

NASA Astrophysics Data System (ADS)

The consequences of conservation of angular momentum in, single- or double-polytropic, steady, compressible, magnetohydrodynamic (MHD) flow parallel to the magnetic field are examined, the principal result being the MHD counterparts of Crocco's theorem and Lord Kelvin's theorem, both expressed in terms of a generalized vorticity. Under special assumptions concerning geometry and/or homogeneity of the general field line invariants, these vortex laws lead to additional field line invariants which describe the conservation of generalized angular momentum in the plasma, taking into account torques produced by j x B forces and Coriolis forces.

Sonnerup, B. U. O.; Hau, L.-N.

1994-01-01

71

The structure of synchronously rotating close binaries built on polytropic model nu = 3  

NASA Technical Reports Server (NTRS)

Mathematical procedures are developed which can provide an exact solution for the structure of synchronously rotating close binaries built on the polytropic model with nu equal to 3. Results are discussed for separations of centers of 10.0, 4.0, 3.0, and 2.8 solar radii. For the present discussion, both components are assumed to have the solar mass and, in the zeroth approximation, the solar radius. The present results are compared with those obtained by Chandrasekhar (1933) using first-order perturbation theory.

Green, L. C.; Kolchin, E. K.

1974-01-01

72

Closure of the hierarchy of fluid equations by means of the polytropic-coefficient function (PCF)  

NASA Astrophysics Data System (ADS)

The continuity and momentum equations of a fluid plasma component may be viewed as four scalar evolution equations for the four scalar fluid variables n(xvec ,t) (density) and u(xvec ,t) (fluid velocity), which are zeroth- and first order velocity moments of the velocity distribution function (VDF). However, the momentum equation in addition contains the gradient of the pressure p(xvec ,t), which is a second-order velocity moment for which another equation, the ``closure equation'', is needed. In the present work, closure by means of the polytropic-coefficient function (PCF) is discussed which, by analogy with the well-known polytropic coefficient (also called the ``polytropic index'' or ``polytropic exponent'') in macroscopic thermodynamic systems, is formally defined by ?(xvec ,t) = (nDp/Dt)(pDn/Dt) = (n/p)(Dp/Dn), with D/Dt = ?/?t+uvec .?/?xvec , which amounts to the closure equation if ?(xvec ,t) is known. In fluid problems, however, the PCF is usually unknown and hence must be assumed or guessed, but in kinetic problems it can be calculated exactly. These general concepts are first developed and then applied specifically to the basic Tonks-Langmuir (TL) model [L. Tonks and I. Langmuir, Phys. Rev. 34, 876, 1929]. It is shown for the first time that results obtained from the fluid equations closed with the correct PCF coincide with the corresponding results calculated on the basis of the exact kinetic solution [K.-U. Riemann, Phys. Plasmas 13, 063508 (2006)], but differ visibly from those obtained from the approximate fluid equations closed with the zero-pressure approximation [Riemann et al., Plasma Phys. Control. Fusion 47, 1949 (2005)]. Also, it is again confirmed that the correct PCF may be a strongly varying function of position, so that the simple constant values of ? usually assumed [K.-U. Riemann, XXVIII International Conference on Phenomena in Ionized Gases, 479 (2007)] may lead to markedly erroneous results especially near material walls. All of these findings lead us to conclude that better approximations to the PCF are needed for closing fluid equations in an appropriate manner.

Kuhn, S.; Kamran, M.; Jeli?, N.; Kos, L.; Tskhakaya, D.

2010-12-01

73

Application of the BPES to Lane-Emden equations governing polytropic and isothermal gas spheres  

NASA Astrophysics Data System (ADS)

We apply the Boubaker Polynomials Expansion Scheme (BPES) in order to obtain analytical-numerical solutions to two separate Lane-Emden problems: the Lane-Emden initial value problem of the first kind (describing the gravitational potential of a self-gravitating spherically symmetric polytropic gas), the Lane-Emden initial value problem of the second kind (describing isothermal gas spheres embedded in a pressurized medium at the maximum possible mass allowing for hydrostatic equilibrium). Both types of problems are simultaneously singular and nonlinear, and hence can be challenging to solve either numerically or analytically. We find that the BPES allows us to compute numerical solutions to both types of problems, and an error analysis demonstrates the accuracy of the method. In all cases, we demonstrate that relative error can be controlled to less than 1%. Furthermore, we compare our results to those of Hunter (2001). [Hunter, C., 2001. Series solutions for polytropes and the isothermal sphere. Monthly Notices of the Royal Astronomical Society, 328 839-847] and Mirza (2009). Approximate analytical solutions of the Lane-Emden equation for a self-gravitating isothermal gas sphere. Monthly Notices of the Royal Astronomical Society, 395 2288-2291. in order to demonstrate the accuracy of our method.

Boubaker, K.; Van Gorder, Robert A.

2012-08-01

74

A brief analysis of self-gravitating polytropic models with a non-zero cosmological constant  

NASA Astrophysics Data System (ADS)

Context. We investigate the equilibrium and stability of polytropic spheres in the presence of a non-zero cosmological constant. Aims: We solve the Newtonian gravitational equilibrium equation for a system with a polytropic equation of state of the matter P = K?? introducing a non-zero cosmological constant ?. Methods: We consider the cases of n = 1, 1.5, 3 and construct series of solutions with a fixed value of ?. For each value of n, the non-dimensional equilibrium equation has a family of solutions, instead of the unique solution of the Lane-Emden equation at ? = 0. Results: The equilibrium state exists only for central densities ?0 higher than the critical value ?c. There are no static solutions at ?0 < ?c. We investigate the stability of equilibrium solutions in the presence of a non-zero ? and show that dark energy reduces the dynamic stability of the configuration. We apply our results to the analysis of the properties of the equilibrium states of clusters of galaxies in the present universe with non-zero ?.

Merafina, M.; Bisnovatyi-Kogan, G. S.; Tarasov, S. O.

2012-05-01

75

Analytical families of two-component anisotropic polytropes and their relativistic extensions  

NASA Astrophysics Data System (ADS)

In this paper, we study a family of two-component anisotropic polytropes which model a wide range of spherically symmetric astrophysical systems such as early-type baryonic galaxies. This family is found to contain a large class of models such as the hypervirial family (which satisfy the virial theorem locally), the Plummer and Hernquist models and Navarro-Frenk-White (NFW) like models. The potential-density pair for these models are derived, as well as their velocity dispersions and anisotropy parameters. The projected quantities are computed and found to reduce to analytical expressions in some cases. The first section of this paper presents an extension of the two-term anisotropic polytropes to encompass a very wide range of potential-density pairs. In the next section, we present the general relativistic extension of the potential-density pair and calculate the stress-energy tensor, the relativistic anisotropy parameter, the velocity of circular orbits and the angular momentum. Remarkably, for the case of the hypervirial family, the relativistic pressure in the Newtonian limit and the relativistic anisotropy parameter are found to coincide with the corresponding Newtonian expressions. The weak, dominant and strong energy conditions are found to be satisfied only for a certain range of the free parameters. We show that the relativistic hypervirial family also has a finite total mass like its Newtonian counterpart. In the first appendix, a relativistic extension of a different hypervirial family of models is studied and the relativistic anisotropy parameter is found to coincide with the Newtonian one. Finally, we present a family of models obtained from our distribution function that are similar to the Ossipkov-Merritt models; by computing their anisotropy parameters, we show that they model systems with isotropic cores and radially anisotropic exteriors.

Nguyen, Phuc H.; Lingam, Manasvi

2013-12-01

76

An empirical polytrope law for solar wind thermal electrons between 0.45 and 4.76 AU: Voyager 2 and Mariner 10  

NASA Technical Reports Server (NTRS)

Empirical evidence is presented that solar wind thermal electrons obey a polytrope law with polytrope index gamma = 1.175 plus or minus 0.03. The Voyager 2 and Mariner 10 data used as evidence are compared and discussed. The theoretical predictions that solar wind thermal electrons in the asymptotic solar wind should obey a polytrope law with polytrope index gamma = 1.16 plus or minus. The widespread impressions in the literature that solar wind electrons behave more like an isothermal than adiabatic gas, and the arguments that Coulomb collisions are the dominant stochastic process shaping observed electron distribution functions in the solar wind are reexamined, reviewed and evaluated. The assignment of the interplanetary potential as equal to approximately seven times the temperature of the thermal electrons is discussed.

Sittler, E. C., Jr.; Scudder, J. D.

1979-01-01

77

Compact monolithic capacitive discharge unit  

DOEpatents

A compact monolithic capacitive discharge unit (CDU) is disclosed in which a thyristor switch and a flyback charging circuit are both sandwiched about a ceramic energy storage capacitor. The result is a compact rugged assembly which provides a low-inductance current discharge path. The flyback charging circuit preferably includes a low-temperature co-fired ceramic transformer. The CDU can further include one or more ceramic substrates for enclosing the thyristor switch and for holding various passive components used in the flyback charging circuit. A load such as a detonator can also be attached directly to the CDU.

Roesler, Alexander W. (Tijeras, NM); Vernon, George E. (Rio Rancho, NM); Hoke, Darren A. (Albuquerque, NM); De Marquis, Virginia K. (Tijeras, NM); Harris, Steven M. (Albuquerque, NM)

2007-06-26

78

Investigation of the Polytropic Relationship Between Density and Temperature Within Interplanetary Coronal Mass Ejections Using Numerical Simulations  

NASA Technical Reports Server (NTRS)

Single-point spacecraft measurements within coronal mass ejections (CMEs) often exhibit a negative correlation between electron density and temperature. At least two opposing interpretations have been suggested for this relationship. If, on one hand, these single spacecraft observations provide direct measures of the polytropic properties of the plasma, then they imply that the polytropic index for the electrons gamma(sub e) is often < 1. Moreover, since the electrons carry the bulk of the pressure (via their significantly higher temperature), this further implies that the dynamics of CME evolution are dominated by an effective polytropic index gamma(sub e)ff < 1. On the other hand, gamma < 1 implies that as the ejecta propagate away from the Sun and expand, they also heat up; a result clearly at odds with in situ observations. In contrast to these CME intervals, many studies have shown that the quiescent solar wind exhibits a positive correlation between electron density and temperature, suggesting that gamma(sub e) > 1. In this study we simulate the evolution of a variety of CME-like disturbances in the solar wind using a one-dimensional, single-fluid model, to address the interpretation of the relationship between electron density and temperature within CMEs at fixed locations in space. Although we strictly impose a polytropic relationship (with gamma = constant) throughout our simulations, we demonstrate that a variety of correlations can exist between density and temperature at fixed points. Furthermore, we demonstrate that the presence of only local uncorrelated random fluctuations in density and temperature can produce a negative correlation. Consequently, we conclude that these single-point observations of negative correlations between electron density and temperature cannot be used to infer the value of gamma(sub e). Instead, we suggest that entropy variations, together with the plasma's tendency to achieve pressure balance with its surroundings, are responsible for the observed profiles.

Riley, Pete; Gosling, J. T.; Pizzo, V. J.

2001-01-01

79

Receptor choice determinants in the envelope glycoproteins of amphotropic, xenotropic, and polytropic murine leukemia viruses.  

PubMed Central

The envelope glycoproteins (SU) of mammalian type C retroviruses possess an amino-terminal domain of about 200 residues, which is involved in binding a cell surface receptor. In this domain, highly conserved amino acid sequences are interrupted by two segments of variable length and sequence, VRA and VRB. We have studied the role of these variable regions in receptor recognition and binding by constructing chimeric molecules in which portions of the amino-terminal domains from amphotropic (4070A), xenotropic (NZB), and polytropic (MCF 247) murine leukemia virus SU proteins were permuted. These chimeras, which exchanged either one or two variable regions, were expressed at the surface of replication-defective viral particles by a pseudotyping assay. Wild-type or recombinant env genes were transfected into a cell line producing Moloney murine leukemia virus particles devoid of envelope glycoproteins in which a retrovirus vector genome carrying an Escherichia coli lacZ gene was packaged. The host range and sensitivity to interference of pseudotyped virions were assayed, and we observed which permutations resulted in receptor switch or loss of function. Our results indicate that the determinants of receptor choice are found within the just 120 amino acids of SU proteins. Downstream sequences contribute to the stabilization of the receptor-specific structure.

Battini, J L; Heard, J M; Danos, O

1992-01-01

80

Decay of electric charge on corona charged polyethylene  

Microsoft Academic Search

This paper describes a study on the surface potential decay of corona charged low density polyethylene (LDPE) films. A conventional corona charging process is used to deposit charge on the surface of film and surface potential is measured by a compact JCI 140 static monitor. The results from corona charged multilayer sample reveal that the bulk process dominates charge decay.

Zhiqiang Xu; Linwen Zhang; George Chen

2007-01-01

81

Compaction managed mirror bend achromat  

DOEpatents

A method for controlling the momentum compaction in a beam of charged particles. The method includes a compaction-managed mirror bend achromat (CMMBA) that provides a beamline design that retains the large momentum acceptance of a conventional mirror bend achromat. The CMMBA also provides the ability to tailor the system momentum compaction spectrum as desired for specific applications. The CMMBA enables magnetostatic management of the longitudinal phase space in Energy Recovery Linacs (ERLs) thereby alleviating the need for harmonic linearization of the RF waveform.

Douglas, David (Yorktown, VA) [Yorktown, VA

2005-10-18

82

The Homologousness of Polytropic Gaseous Spheres in the General-Relativistic Case  

NASA Astrophysics Data System (ADS)

TOV equations in the polytropic case (P = K?1+1/N) are represented by the homologous invariants of U, V, and an additional one of w = P / ( ?c2), where P and ?c2 are the pressure and the static energy density. The homologous core solutions form a curved surface in the space of (U, V, w), and they are distinguished by the asymptotic surface values of E ( = UV N ) and D ( = wV ). U, V, and w lead the invariant variables of x and ?, expressing the radius and the mass function. The solution of x and ? with a central value of wc, called the core bundle solution (CB), well describes the extreme general-relativistic state. Core solutions are represented by the usual Emden variables, defined by ? = ? ? N and P = K ?1+1/N ? N+1, as the general-relativistic E-solution (gE), which are determined by the two parameters ?c and ? ( = K ? 1/N ). However, these two parameters change into each other by a homologous transformation, under the condition of wc = ?c?. Hence, the gE solutions form a continuous group of one-parameter families, one of which is a CB solution corresponding to the gE solution with ? = 1, and another of which the general-relativisitic Lane-Emden solutions (gLE), defined by gE solutions with ?c = 1. A gLE solution changes into a CB solution by homologous transformation between each other. In gLE, three ways of ? = ( K-1? )N, ?c, and pc?-1 render the normalization by K N/2, ?c-1/2, and pc-1/2, respectively, so that three kinds of mass-radius relations, derived from each normalization, weave the mass-radius textile in the (M, R, ?) space, where it stands up besides the Schwarzschild-radius wall.

Kondo, Masa-Aki

2008-08-01

83

GRAVITATIONAL INSTABILITY OF ROTATING, PRESSURE-CONFINED, POLYTROPIC GAS DISKS WITH VERTICAL STRATIFICATION  

SciTech Connect

We investigate the gravitational instability (GI) of rotating, vertically stratified, pressure-confined, polytropic gas disks using a linear stability analysis as well as analytic approximations. The disks are initially in vertical hydrostatic equilibrium and bounded by a constant external pressure. We find that the GI of a pressure-confined disk is in general a mixed mode of the conventional Jeans and distortional instabilities, and is thus an unstable version of acoustic-surface-gravity waves. The Jeans mode dominates in weakly confined disks or disks with rigid boundaries. On the other hand, when the disk has free boundaries and is strongly pressure confined, the mixed GI is dominated by the distortional mode that is surface-gravity waves driven unstable under their own gravity and thus incompressible. We demonstrate that the Jeans mode is gravity-modified acoustic waves rather than inertial waves and that inertial waves are almost unaffected by self-gravity. We derive an analytic expression for the effective sound speed c{sub eff} of acoustic-surface-gravity waves. We also find expressions for the gravity reduction factors relative to a razor-thin counterpart that are appropriate for the Jeans and distortional modes. The usual razor-thin dispersion relation, after correcting for c{sub eff} and the reduction factors, closely matches the numerical results obtained by solving a full set of linearized equations. The effective sound speed generalizes the Toomre stability parameter of the Jeans mode to allow for the mixed GI of vertically stratified, pressure-confined disks.

Kim, Jeong-Gyu; Kim, Woong-Tae [Center for the Exploration of the Origin of the Universe (CEOU), Astronomy Program, Department of Physics and Astronomy, Seoul National University, Seoul 151-742 (Korea, Republic of); Seo, Young Min; Hong, Seung Soo, E-mail: jgkim@astro.snu.ac.kr, E-mail: wkim@astro.snu.ac.kr, E-mail: seo3919@email.arizona.edu, E-mail: sshong@astro.snu.ac.kr [FPRD, Department of Physics and Astronomy, Seoul National University, Seoul 151-742 (Korea, Republic of)

2012-12-20

84

Application of AN Empirically-Derived Polytropic Index for the Solar Wind to a Solar Wind Shock Propagation Model.  

NASA Astrophysics Data System (ADS)

Data from the Helios 1 spacecraft have been used to determine an empirical value for the polytropic index for the free-streaming solar wind. Application of this non-adiabatic polytropic index to a two-dimensional solar wind computer model to simulate the effects of thermal heat conduction has been investigated. The current project involves the insertion of this empirically-derived polytropic index into a magnetohydrodynamic model of solar wind propagation. This computer model is used to predict the time for shocks originating at the Sun to travel to Earth. This information is important for the protection of Earth-orbiting satellites. The model is a two and one-half-dimensional numerical code that solves the magnetohydrodynamic equations using the two-step Lax -Wendroff scheme. The shock jump ratios of the plasma parameters are determined using the Rankine-Hugoniot relations. In addition, the shock model requires a representative background solar wind as an initial condition. The original background solar wind is similar to the results obtained by Parker (Astrophysical Journal, 1958) and Weber and Davis (Astrophysical Journal, 1967). Changes to this initial condition are made by applying the non-adiabatic polytropic index to a three-dimensional, steady-state, magnetohydrodynamic model of the solar wind. The adjustments to the steady -state model produce a background solar wind that compares well to Helios 1 data. This new background solar wind is used as the initial condition for the 2D shock model. The shock model is also adjusted to include the effects of heat conduction. Comparison of model results with observational data indicate that these changes produce average transit times that are only 45 minutes late. Before the changes to the 2D shock model and its initial solar wind condition were made, the average prediction time was two hours late. Adjusting the shock model to include the effects of heat conduction but using the original background solar wind produces an average transit time that is less than one hour early. A few specific events are discussed in greater detail.

Totten, Tracy Lynn

85

Baryon currents in QCD with compact dimensions  

SciTech Connect

On a compact space with nontrivial cycles, for sufficiently small values of the radii of the compact dimensions, SU(N) gauge theories coupled with fermions in the fundamental representation spontaneously break charge conjugation, time reversal, and parity. We show at one loop in perturbation theory that a physical signature for this phenomenon is a nonzero baryonic current wrapping around the compact directions. The persistence of this current beyond the perturbative regime is checked by lattice simulations.

Lucini, B. [Physics Department, Swansea University, Singleton Park, Swansea SA2 8PP (United Kingdom); Patella, A. [Scuola Normale Superiore, Piazza dei Cavalieri 27, 56126 Pisa (Italy); Istituto Nazionale Fisica Nucleare Sezione di Pisa, Largo Pontecorvo 3, 56126 Pisa (Italy); Pica, C. [Physics Department, Brookhaven National Laboratory, Upton, New York 11973 (United States)

2007-06-15

86

Linear stability analysis of nonaxisymmetric instabilities in self-gravitating polytropic disks  

NASA Astrophysics Data System (ADS)

An important problem in astrophysics involves understanding the formation of planetary systems. When a star-forming cloud collapses under gravity its rotation causes it to flatten into a disk. Only a small percentage of the matter near the rotation axis falls inward to create the central object, yet our Sun contains over 99% of the matter of our Solar System. We examine how global hydrodynamic instabilities transport angular momentum through the disk causing material to accrete onto the central star. We analyze the stability of polytropic disks in the linear regime. A power law angular velocity of power q is imposed, and the equilibrium disk structure is found through solution of the time-independent hydrodynamic equations via the Hachisu self-consistent field method. The disk is perturbed, and the time-dependent linearized hydrodynamic equations are used to evolve it. If the system is unstable, the characteristic growth rate and frequency of the perturbation are calculated. We consider modes with azimuthal e im[varphi] dependence, where m is an integer and [varphi] is the azimuthal angle. We map trends across a wide parameter space by varying m , q and the ratios of the star-to-disk mass M* /Md and inner-to-outer disk radius r - /r + . We find that low m modes dominate for small r - /r + , increasing to higher r - /r + as M* /Md increases, independent of q . Three main realms of behavior are identified, for M* << Md , M* ? Md and M* >> Md , and analyzed with respect to the I, J and P mode types as discussed in the literature. Analysis shows that for M* << Md , small r - /r + disks are dominated by low m I modes, which give way to high m J modes at high r - /r + . Low m J modes dominate M* ? Md disks for small r - /r + , while higher m I modes dominate for high r - /r + . Behavior diverges with q for M* >> Md systems with high q models approximating M* ? Md characteristics, while low q models exhibit m = 2 I modes dominating where r - /r + < 0.60.

Hadley, Kathryn Z.

87

Ceramic powder compaction.  

National Technical Information Service (NTIS)

With the objective of developing a predictive model for ceramic powder compaction we have investigated methods for characterizing density gradients in ceramic powder compacts, reviewed and compared existing compaction models, conducted compaction experime...

S. J. Glass K. G. Ewsuk F. M. Mahoney

1995-01-01

88

MOSFET Electric-Charge Sensor  

NASA Technical Reports Server (NTRS)

Charged-particle probe compact and consumes little power. Proposed modification enables metal oxide/semiconductor field-effect transistor (MOSFET) to act as detector of static electric charges or energetic charged particles. Thickened gate insulation acts as control structure. During measurements metal gate allowed to "float" to potential of charge accumulated in insulation. Stack of modified MOSFET'S constitutes detector of energetic charged particles. Each gate "floats" to potential induced by charged-particle beam penetrating its layer.

Robinson, Paul A., Jr.

1988-01-01

89

Compact magnetograph  

NASA Technical Reports Server (NTRS)

A compact magnetograph system based on solid Fabry-Perot interferometers as the spectral isolation elements was studied. The theory of operation of several Fabry-Perot systems, the suitability of various magnetic lines, signal levels expected for different modes of operation, and the optimal detector systems were investigated. The requirements that the lack of a polarization modulator placed upon the electronic signal chain was emphasized. The PLZT modulator was chosen as a satisfactory component with both high reliability and elatively low voltage requirements. Thermal control, line centering and velocity offset problems were solved by a Fabry-Perot configuration.

Title, A. M.; Gillespie, B. A.; Mosher, J. W.

1982-01-01

90

A Three-dimensional Numerical Solution for the Shape of a Rotationally Distorted Polytrope of Index Unity  

NASA Astrophysics Data System (ADS)

We present a new three-dimensional numerical method for calculating the non-spherical shape and internal structure of a model of a rapidly rotating gaseous body with a polytropic index of unity. The calculation is based on a finite-element method and accounts for the full effects of rotation. After validating the numerical approach against the asymptotic solution of Chandrasekhar that is valid only for a slowly rotating gaseous body, we apply it to models of Jupiter and a rapidly rotating, highly flattened star (? Eridani). In the case of Jupiter, the two-dimensional distributions of density and pressure are determined via a hybrid inverse approach by adjusting an a priori unknown coefficient in the equation of state until the model shape matches the observed shape of Jupiter. After obtaining the two-dimensional distribution of density, we then compute the zonal gravity coefficients and the total mass from the non-spherical model that takes full account of rotation-induced shape change. Our non-spherical model with a polytropic index of unity is able to produce the known mass of Jupiter with about 4% accuracy and the zonal gravitational coefficient J 2 of Jupiter with better than 2% accuracy, a reasonable result considering that there is only one parameter in the model. For ? Eridani, we calculate its rotationally distorted shape and internal structure based on the observationally deduced rotation rate and size of the star by using a similar hybrid inverse approach. Our model of the star closely approximates the observed flattening.

Kong, Dali; Zhang, Keke; Schubert, Gerald; Anderson, John

2013-02-01

91

NEAR- AND FAR-FIELD RESPONSE TO COMPACT ACOUSTIC SOURCES IN STRATIFIED CONVECTION ZONES  

SciTech Connect

The role of the acoustic continuum associated with compact sources in the Sun's interior wave field is explored for a simple polytropic model. The continuum produces a near-field acoustic structure-the so-called acoustic jacket-that cannot be represented by a superposition of discrete normal modes. Particular attention is paid to monochromatic point sources of various frequency and depth, and to the surface velocity power that results, both in the discrete f- and p-mode spectrum and in the continuum. It is shown that a major effect of the continuum is to heal the surface wave field produced by compact sources, and therefore to hide them from view. It is found that the continuous spectrum is not a significant contributor to observable inter-ridge seismic power.

Cally, Paul S., E-mail: paul.cally@monash.edu [Monash Centre for Astrophysics and School of Mathematical Sciences, Monash University, Clayton, Victoria 3800 (Australia)

2013-05-01

92

Compact spaces, compact cardinals, and elementary submodels  

Microsoft Academic Search

If M is an elementary submodel and X a topological space, then XM denotes the set X?M given the topology generated by the open subsets of X which are members of M. Call a compact space squashable iff for some M, XM is compact and XM?X. The first supercompact cardinal is the least ? such that all compact X with

Kenneth Kunen

2003-01-01

93

Ceramic powder compaction  

SciTech Connect

With the objective of developing a predictive model for ceramic powder compaction we have investigated methods for characterizing density gradients in ceramic powder compacts, reviewed and compared existing compaction models, conducted compaction experiments on a spray dried alumina powder, and conducted mechanical tests and compaction experiments on model granular materials. Die filling and particle packing, and the behavior of individual granules play an important role in determining compaction behavior and should be incorporated into realistic compaction models. These results support the use of discrete element modeling techniques and statistical mechanics principals to develop a comprehensive model for compaction, something that should be achievable with computers with parallel processing capabilities.

Glass, S.J.; Ewsuk, K.G. [Sandia National Labs., Albuquerque, NM (United States); Mahoney, F.M. [Norton Co., Worcester, MA (United States)

1995-12-31

94

Polytropic star structure analysis under Bonnor-Ebert gas sphere astrophysical configuration thorough investigating analytical solutions to the related Lane-Emden equation  

NASA Astrophysics Data System (ADS)

In this paper, Bonnor-Ebert gas sphere model of polytropic stars has been investigated through an analytical approach. Two confirmed and well-established methods have been used: the Enhanced Lagrangian Formulation Method ELFM and the Boubaker Polynomials Expansion Scheme BPES. Solutions to the related generalized Lane-Emden equation of the second kind have been expressed and plotted. Results have given evidence to the relevance of the dimensionless Bonnor-Ebert radius, in good agreement with some recently proposed profiles.

Boubaker, K.; Bhrawy, A. H.

2012-03-01

95

The Compact for Education.  

ERIC Educational Resources Information Center

The Compact for Education is not yet particularly significant either for good or evil. Partly because of time and partly because of unreasonable expectations, the Compact is not yet a going concern. Enthusiasts have overestimated Compact possibilities and opponents have overestimated its dangers, so if the organization has limited rather than…

Harrington, Fred Harvey

96

Prediction of compaction curves  

Microsoft Academic Search

Compaction of soil is one of the major activities in geotechnical engineering involving earthworks. Compaction curve generally features an inverted parabolic shape and is used to find the optimum water content that maximises dry density. Since its introduction by Proctor in 1933, several researchers have provided qualitative explanations for the general shape of the compaction curve. Furthermore, there is a

Nurses Kurucuk; Australia Jayantha Kodikara; Australia Delwyn Fredlund

97

Soil Compaction and Drainage  

NSDL National Science Digital Library

This bulletin, authored by N.R. Fausey and B.H. Nolte for Ohio State University, describes soil compaction and its effect on drainage and crops in situations of surface soil compaction and deep soil compaction. Contains links to research, discussions and conclusions.

Fausey, N. R.; Nolte, B. H.

2008-02-07

98

Compact plasma accelerator  

NASA Technical Reports Server (NTRS)

A compact plasma accelerator having components including a cathode electron source, an anodic ionizing gas source, and a magnetic field that is cusped. The components are held by an electrically insulating body having a central axis, a top axial end, and a bottom axial end. The cusped magnetic field is formed by a cylindrical magnet having an axis of rotation that is the same as the axis of rotation of the insulating body, and magnetized with opposite poles at its two axial ends; and an annular magnet coaxially surrounding the cylindrical magnet, magnetized with opposite poles at its two axial ends such that a top axial end has a magnetic polarity that is opposite to the magnetic polarity of a top axial end of the cylindrical magnet. The ionizing gas source is a tubular plenum that has been curved into a substantially annular shape, positioned above the top axial end of the annular magnet such that the plenum is centered in a ring-shaped cusp of the magnetic field generated by the magnets. The plenum has one or more capillary-like orifices spaced around its top such that an ionizing gas supplied through the plenum is sprayed through the one or more orifices. The plenum is electrically conductive and is positively charged relative to the cathode electron source such that the plenum functions as the anode; and the cathode is positioned above and radially outward relative to the plenum.

Foster, John E. (Inventor)

2004-01-01

99

High-frequency behavior of w-mode pulsations of compact stars  

NASA Astrophysics Data System (ADS)

We study the asymptotic behavior of the quasinormal modes (QNMs) of w-mode pulsations of compact stars in the high-frequency regime. We observe that both the axial and polar w-mode QNMs attain similar asymptotic behaviors in spite of the fact that they are described by two totally different differential equation systems. We obtain robust asymptotic formulas relating w-mode QNMs of different polarities and different angular momenta. To explore the physical reason underlying such similarity, we first derive a high-frequency approximation for the polar w-mode oscillations to unify the descriptions for both cases. Then, we develop WKB-type analyses for them and quantitatively explain the observed asymptotic behaviors for polytropic stars and quark stars. We also point out that such asymptotic behaviors for realistic stars are strongly dependent on the equation of state near the stellar surface.

Zhang, Y. J.; Wu, J.; Leung, P. T.

2011-03-01

100

Reversible DNA compaction.  

PubMed

In this review we summarize and discuss the different methods we can use to achieve reversible DNA compaction in vitro. Reversible DNA compaction is a natural process that occurs in living cells and viruses. As a result these process long sequences of DNA can be concentrated in a small volume (compacted) to be decompacted only when the information carried by the DNA is needed. In the current work we review the main artificial compacting agents looking at their suitability for decompaction. The different approaches used for decompaction are strongly influenced by the nature of the compacting agent that determines the mechanism of compaction. We focus our discussion on two main artificial compacting agents: multivalent cations and cationic surfactants that are the best known compacting agents. The reversibility of the process can be achieved by adding chemicals like divalent cations, alcohols, anionic surfactants, cyclodextrins or by changing the chemical nature of the compacting agents via pH modifications, light induced conformation changes or by redox-reactions. We stress the relevance of electrostatic interactions and self-assembly as a main approach in order to tune up the DNA conformation in order to create an on-off switch allowing a transition between coil and compact states. The recent advances to control DNA conformation in vitro, by means of molecular self-assembly, result in a better understanding of the fundamental aspects involved in the DNA behavior in vivo and serve of invaluable inspiration for the development of potential biomedical applications. PMID:24444152

González-Pérez, Alfredo

2014-01-01

101

Compact matrix pseudogroups  

Microsoft Academic Search

The compact matrix pseudogroup is a non-commutative compact space endowed with a group structure. The precise definition is given and a number of examples is presented. Among them we have compact group of matrices, duals of discrete groups and twisted (deformed)SU(N) groups. The representation theory is developed. It turns out that the tensor product of representations depends essentially on their

S. L. Woronowicz

1987-01-01

102

Compact Polarimetry Potentials  

NASA Technical Reports Server (NTRS)

The goal of this study is to show the potential of a compact-pol SAR system for vegetation applications. Compact-pol concept has been suggested to minimize the system design while maximize the information and is declined as the ?/4, ?/2 and hybrid modes. In this paper, the applications such as biomass and vegetation height estimates are first presented, then, the equivalence between compact-pol data simulated from full-pol data and compact-pol data processed from raw data as such is shown. Finally, a calibration procedure using external targets is proposed.

Truong-Loi, My-Linh; Dubois-Fernandez, Pascale; Pottier, Eric

2011-01-01

103

Stability of polytropes  

Microsoft Academic Search

This paper is an investigation of the stability of some ideal stars. It is intended as a study in general relativity, with emphasis on the coupling to matter, aimed at a better understanding of strong gravitational fields and ``black holes.'' This contrasts with the usual attitude in astrophysics, where Einstein's equations are invoked as a refinement of classical thermodynamics and

Christian Frønsdal

2008-01-01

104

Stability of polytropes  

Microsoft Academic Search

This paper is an investigation of the stability of some ideal stars. It is intended as a study in general relativity, with emphasis on the coupling to matter, aimed at a better understanding of strong gravitational fields and 'black holes'. This contrasts with the usual attitude in astrophysics, where Einstein's equations are invoked as a refinement of classical thermodynamics and

Froensdal; Christian

2008-01-01

105

The compact genetic algorithm  

Microsoft Academic Search

This paper introduces the compact genetic algorithm (cGA) which represents the population as a probability distribu- tion over the set of solutions and is operationally equivalent to the order-one behavior of the simple GA with uniform crossover. It processes each gene independently and requires less memory than the simple GA. The development of the compact GA is guided by a

Georges R. Harik; Fernando G. Lobo; David E. Goldberg

1999-01-01

106

Compact emergency lamp  

Microsoft Academic Search

This paper presents a compact emergency lamp using light emitting diodes (LEDs). The goal is to develop a compact and low cost electronic circuit to drive and control the current of LEDs arranged in a single enclosure. The proposed idea allows using the same equipment in the daily activities, supplied by mains, and under a possible failure of it. The

Rafael A. Pinto; Marcelo R. Cosetin; Alexandre Campos; Ricardo N. do Prado

2009-01-01

107

Core Compactness of Progenitors  

NASA Astrophysics Data System (ADS)

The compactness of the core of a pre-supernova star is one of the important unexplored issues in progenitor evolution. Recent studies have found the core compactness to be varying non-monotonically as a function of ZAMS mass. In this work we have calculated a large grid of 1D full stellar and naked C/O core models using the implicit hydrodynamic code KEPLER and the open source stellar evolution code MESA, in order to gain a better insight in core compactness' dependence on the stellar mass and convection physics. We find the complicated evolution during C, O and Si burning phases act as the main cause of the non-monotonic variation of compactness, and the whole compactness curve as a function of mass to be quite dependent on the treatment of semiconvection. We also conclude that the C/O core mass is the main discriminant of pre-supernova structure.

Sukhbold, Tuguldur; Woosley, S. E.; Paxton, B.; Heger, A.

2013-04-01

108

Core Compactness of Progenitors  

NASA Astrophysics Data System (ADS)

The compactness of the core of a pre-supernova star is one of the important unexplored issues in progenitor evolution. Recent studies have found the core compactness to be varying non-monotonically as a function of ZAMS mass. In this work we have calculated a large grid of 1D full stellar and naked C/O core models using the implicit hydrodynamic code KEPLER and the open source stellar evolution code MESA, in order to gain a better insight in core compactness' dependence on the stellar mass and convection physics. We find the complicated evolution during C burning acts as the main cause of the non-monotonic variation of compactness, and the whole compactness curve as a function of mass to be quite dependent on the treatment of semiconvection. We also conclude that the C/O core mass is the main discriminant of pre-supernova structure.

Sukhbold, Tuguldur; Woosley, S. E.; Paxton, B.; Heger, A.

2013-01-01

109

Nonconformally flat initial data for binary compact objects  

SciTech Connect

A new method is described for constructing initial data for a binary neutron-star system in quasiequilibrium circular orbit. Two formulations for nonconformally flat data, waveless and near-zone helically symmetric, are introduced; in each formulation, the Einstein-Euler system, written in 3+1 form on an asymptotically flat spacelike hypersurface, is exactly solved for all metric components, including the spatially nonconformally flat potentials, and for irrotational flow. A numerical method applicable to both formulations is explained with an emphasis on the imposition of a spatial gauge condition. Results are shown for solution sequences of irrotational binary neutron-stars with matter approximated by parametrized equations of state that use a few segments of polytropic equations of state. The binding energy and total angular momentum of solution sequences computed within the conformally flat--Isenberg-Wilson-Mathews--formulation are closer to those of the third post-Newtonian (3PN) two point particles up to the closest orbits, for the more compact stars, whereas sequences resulting from the waveless/near-zone helically symmetric formulations deviate from the 3PN curve even more for the sequences with larger compactness. We think it likely that this correction reflects an overestimation in the Isenberg-Wilson-Mathews formulation as well as in the 3PN formula, by {approx}1 cycle in the gravitational-wave phase during the last several orbits. The work suggests that imposing spatial conformal flatness results in an underestimate of the quadrupole deformation of the components of binary neutron-star systems in the last few orbits prior to merger.

Uryu, Koji [Department of Physics, University of the Ryukyus, Senbaru, Nishihara, Okinawa 903-0213 (Japan); Limousin, Francois; Gourgoulhon, Eric [Laboratoire Univers et Theories, UMR 8102 du CNRS, Observatoire de Paris, Universite Paris Diderot, F-92190 Meudon (France); Friedman, John L. [Department of Physics, University of Wisconsin-Milwaukee, P.O. Box 413, Milwaukee, Wisconsin 53201 (United States); Shibata, Masaru [Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502 (Japan)

2009-12-15

110

Thermodynamics of magnetized binary compact objects  

NASA Astrophysics Data System (ADS)

Binary systems of compact objects with electromagnetic field are modeled by helically symmetric Einstein-Maxwell spacetimes with charged and magnetized perfect fluids. Previously derived thermodynamic laws for helically symmetric perfect-fluid spacetimes are extended to include the electromagnetic fields, and electric currents and charges; the first law is written as a relation between the change in the asymptotic Noether charge ?Q and the changes in the area and electric charge of black holes, and in the vorticity, baryon rest mass, entropy, charge and magnetic flux of the magnetized fluid. Using the conservation laws of the circulation of magnetized flow found by Bekenstein and Oron for the ideal magnetohydrodynamic fluid, and also for the flow with zero conducting current, we show that, for nearby equilibria that conserve the quantities mentioned above, the relation ?Q=0 is satisfied. We also discuss a formulation for computing numerical solutions of magnetized binary compact objects in equilibrium with emphasis on a first integral of the ideal magnetohydrodynamic-Euler equation.

Ury?, K?ji; Gourgoulhon, Eric; Markakis, Charalampos

2010-11-01

111

Reply to "Comment on the Paper ''On the Determination of Electron Polytrope Indices Within Coronal Mass Ejections in the Solar Wind'"'. Appendix 5  

NASA Technical Reports Server (NTRS)

We strongly disagree with the essence of the Osherovich (hereafter Osherovich) comment on one of our papers. The following paragraphs provide the basis of our disagreement and elaborate on why we believe that none of the concluding statements in his Comment are true. Our most important point is that one can apply the model developed by Osherovich and colleagues to real data obtained at a single point in space to determine the polytropic index within magnetic clouds if and only if the highly idealized assumptions of that model conform to physical reality. There is good reason to believe that those assumptions do not provide an accurate physical description of real magnetic clouds in the spherically expanding solar wind.

Gosling, J. T.; Riley, P.; Skoug, R. M.

2001-01-01

112

Computational compact torus experiment  

SciTech Connect

We describe a typical 2D magnetohydrodynamic (MHD) calculation of rundown of plasma in a coaxial, magnetized gun and injection of the plasma and reconnection of the embedded magnetic fields to form a compact toroidal plasma.

Eddleman, J.L.; McNamara, B.; Nash, J.K.; Shearer, J.W.; Turner, W.C.

1980-12-24

113

Compact Acoustic Recorder.  

National Technical Information Service (NTIS)

This paper discusses the design and operation of a portable compact acoustic recorder. Designed to be used in arctic conditions for applications that require portable equipment, the device is configured to fit into a lightweight briefcase. It will operate...

R. Stein

1989-01-01

114

Compact turbidity meter  

NASA Technical Reports Server (NTRS)

Proposed monitor that detects back-reflected infrared radiation makes in situ turbidity measurements of lakes, streams, and other bodies of water. Monitor is compact, works well in daylight as at night, and is easily operated in rough seas.

Hirschberg, J. G.

1979-01-01

115

Topological charges in monopole theories  

NASA Astrophysics Data System (ADS)

Let us consider a monopole theory with a compact, simply connected gauge group and the Higgs field in the adjoint representation. Using root theory we show that. (i) The homotopy class of the Higgs field is a p-tuple of integers where p is the dimension of the centre of the residual symmetry group. These “Higgs charges” can be expressed as surface integrals of differential forms. (ii) To any invariant polynomial on the Lie algebra is associated a topological invariant which turns out to be a combination of the Higgs charges. (iii) Electric charge is quantized. The monopole's magnetic charge is a combination — with the Higgs charges as coefficients — of p basic magnetic charges which satisfy generalized Dirac conditions. The example of G=SU( N) is worked out in detail.

Horváthy, P. A.; Rawnsley, J. H.

1984-12-01

116

Physically detached 'compact groups'  

NASA Technical Reports Server (NTRS)

A small fraction of galaxies appear to reside in dense compact groups, whose inferred crossing times are much shorter than a Hubble time. These short crossing times have led to considerable disagreement among researchers attempting to deduce the dynamical state of these systems. In this paper, we suggest that many of the observed groups are not physically bound but are chance projections of galaxies well separated along the line of sight. Unlike earlier similar proposals, ours does not require that the galaxies in the compact group be members of a more diffuse, but physically bound entity. The probability of physically separated galaxies projecting into an apparent compact group is nonnegligible if most galaxies are distributed in thin filaments. We illustrate this general point with a specific example: a simulation of a cold dark matter universe, in which hydrodynamic effects are included to identify galaxies. The simulated galaxy distribution is filamentary and end-on views of these filaments produce apparent galaxy associations that have sizes and velocity dispersions similar to those of observed compact groups. The frequency of such projections is sufficient, in principle, to explain the observed space density of groups in the Hickson catalog. We discuss the implications of our proposal for the formation and evolution of groups and elliptical galaxies. The proposal can be tested by using redshift-independent distance estimators to measure the line-of-sight spatial extent of nearby compact groups.

Hernquist, Lars; Katz, Neal; Weinberg, David H.

1995-01-01

117

'Stutter timing' for charge decay time measurement  

NASA Astrophysics Data System (ADS)

The paper describes the approach of 'stutter timing' that has been developed to improve the accuracy of measuring charge decay times in the presence of noise in compact and portable charge decay test instrumentation. The approach involves starting and stopping the timing clock as the noisy signal rises above and falls below the target threshold voltage level.

Chubb, John; Harbour, John; Pavey, Ian

2011-06-01

118

Compact vacuum insulation embodiments  

Microsoft Academic Search

An ultra-thin compact vacuum insulation panel is comprised of two hard, but bendable metal wall sheets closely spaced apart from each other and welded around the edges to enclose a vacuum chamber. Glass or ceramic spacers hold the wall sheets apart. The spacers can be discrete spherical beads or monolithic sheets of glass or ceramic webs with nodules protruding therefrom

D. K. Benson; T. F. Potter

1992-01-01

119

Compact vacuum insulation  

Microsoft Academic Search

An ultra-thin compact vacuum insulation panel is comprised of two hard, but bendable metal wall sheets closely spaced apart from each other and welded around the edges to enclose a vacuum chamber. Glass or ceramic spacers hold the wall sheets apart. The spacers can be discrete spherical beads or monolithic sheets of glass or ceramic webs with nodules protruding therefrom

David K. Benson; Thomas F. Potter

1993-01-01

120

Compact vacuum insulation  

Microsoft Academic Search

Improved compact insulation panel is provided which is comprised of two adjacent metal sheets spaced close together with a plurality of spherical, or other discretely shaped, glass or ceramic beads optimally positioned between the sheets to provide support and maintain the spacing between the metal sheets when the gases there between are evacuated to form a vacuum. These spherical glass

D. K. Benson; T. F. Potter

1992-01-01

121

Compact vacuum insulation  

Microsoft Academic Search

Improved compact insulation panel is provided which is comprised of two adjacent metal sheets spaced close together with a plurality of spherical, or other discretely shaped, glass or ceramic beads optimally positioned between the sheets to provide support and maintain the spacing between the metal sheets when the gases therebetween are evacuated to form a vacuum. These spherical glass beads

David K. Benson; Thomas F. Potter

1992-01-01

122

Compact, Integrated Photoelectron Linacs  

Microsoft Academic Search

The innovative compact high energy iniector which has been developed by DULY Research Inc., will have wide scientific industrial and medical applications. The new photoelectron injector integrates the photocathode directly into a multicell linear accelerator with no drift space between the injector and the linac. By focusing the beam with solenoid or permanent magnets, and producing high current with low

David Yu

2000-01-01

123

Fast, Compact Assignment Algorithm.  

National Technical Information Service (NTIS)

The m x n assignment problem is solved by a modified Hungarian algorithm in which the data matrix is built up column by column. Many of the usual bookkeeping operations are thereby avoided, leading to a compact FORTRAN code that requires only four vectors...

D. P. Laurie

1983-01-01

124

Handmade compact disc spectroscope  

NASA Astrophysics Data System (ADS)

Astronomy data center held some programs for the open house day of 2005, and a program of handmade compact disc spectroscope in craft corner received a favorable review. We report a summary of the program and the product in this article.

Kawanomoto, Satoshi

2006-10-01

125

Compact explosion diagrams  

Microsoft Academic Search

This paper presents a system to automatically generate compact explosion diagrams. Inspired by handmade illustrations, our approach reduces the complexity of an explosion diagram by rendering an exploded view only for a subset of the assemblies of an object. However, the exploded views are chosen so that they allow inference of the remaining unexploded assemblies of the entire 3D model.

Markus Tatzgern; Denis Kalkofen; Dieter Schmalstieg

2010-01-01

126

Compact, Rugged Temperature Recorder  

NASA Technical Reports Server (NTRS)

Solid-state temperature recorder is compact, lightweight, and rugged. Records 2,048 temperature readings over period of up to nearly a year and retains them at least another 4 months using batteries. Battery-operated recorder has no moving parts--is completely solid-state electronic.

Westbrook, R. M.; Bennett, L. D.; Steinhauer, R. A.; Deboo, G. J.

1982-01-01

127

A Compact Acoustic Recorder  

Microsoft Academic Search

The design and operation of a portable compact acoustic recorder is discussed. Designed to be used in arctic conditions for applications that require portable equipment, the device is configured to fit into a lightweight briefcase. It will operate for eight hours at -40 F with heat provided by a hot water bottle. It has proven to be an effective scientific

Ronald Stein

1989-01-01

128

Compact antenna range analysis  

Microsoft Academic Search

This preliminary design study (methodology investigation) established the feasibility and cost of the reflector for an outdoor compact range with 50 foot diameter quiet zone. The U.S. Army at Ft. Huachuca, Arizona would use the range to measure patterns of microwave antennas mounted on vehicles and aircraft. Considerations included reflector configuration, size, focal length, surface accuracy, edge treatment, feed, quiet

R. W. Moody; O. D. Asbell; E. B. Joy

1986-01-01

129

Compact fusion reactors  

SciTech Connect

Compact, high-power-density approaches to fusion power are proposed to improve economic viability through the use of less-advanced technology in systems of considerably reduced scale. The rationale for and the means by which these systems can be achieved are discussed, as are unique technological problems.

Krakowski, R.A.; Hagenson, R.L.

1983-01-01

130

The compact genetic algorithm  

Microsoft Academic Search

This paper introduces the “compact genetic algorithm” (cGA). The cGA represents the population as a probability distribution over the set of solutions, and is operationally equivalent to the order-one behavior of the simple GA with uniform crossover. It processes each gene independently and requires less memory than the simple GA

G. R. Harik; Fernando G. Lobo; D. E. Goldberg

1998-01-01

131

Compact routing schemes  

Microsoft Academic Search

We describe several compact routing schemes for general weighted undirected networks. Our schemes are simple and easy to implement. The routing tables stored at the nodes of the network are all very small. The headers attached to the routed messages, including the name of the destination, are extremely short. The routing decision at each node takes constant time. Yet, the

Mikkel Thorup; Uri Zwick

2001-01-01

132

Local Microcode Compaction Techniques  

Microsoft Academic Search

Microcode compaction is an essential tool for the compilation of high-level language microprograms into microinstructions with parallel microoperations. Although guaranteeing minimum execution time is an exponentially complex problem, recent research indicates that it is not difficult to obtain practical results. This paper, which assumes no prior knowledge of microprogramming on the part of the reader, surveys the approaches that have

David Landskov; Scott Davidson; Bruce Shriver; Patrick W. Mallett

1980-01-01

133

Soil Compaction Investigation.  

ERIC Educational Resources Information Center

Describes a lab investigation designed to introduce students to soil compaction and help them to learn to design and adapt procedures that scientists use when they plan and conduct controlled investigations. Provided are objectives, a list of materials, procedures, and a sample student handout. (CW)

Turski, Mark P.

1988-01-01

134

Compact, Integrated Photoelectron Linacs  

NASA Astrophysics Data System (ADS)

The innovative compact high energy iniector which has been developed by DULY Research Inc., will have wide scientific industrial and medical applications. The new photoelectron injector integrates the photocathode directly into a multicell linear accelerator with no drift space between the injector and the linac. By focusing the beam with solenoid or permanent magnets, and producing high current with low emittance, extremely high brightness is achieved. In addition to providing a small footprint and improved beam quality in an integrated structure, the compact system considerably simplifies external subsystems required to operate the photoelectron linac, including rf power transport, beam focusing, vacuum and cooling. The photoelectron linac employs an innovative Plane-Wave-Transformer (PWT) design, which provides strong cell-to-cell coupling, relaxes manufacturing tolerance and facilitates the attachment of external ports to the compact structure with minimal field interference. DULY Research Inc. under the support of the DOE Small Business Innovation Research (SBIR) program, has developed, constructed and installed a 20-MeV, S-band compact electron source at UCLA. DULY Research is also presently engaged in the development of an X-band photoelectron linear accelerator in another SBIR project. The higher frequency structure when completed will be approximately three times smaller, and capable of a beam brightness ten times higher than the S-band structure.

Yu, David

2000-12-01

135

Compact rotating cup anemometer  

NASA Technical Reports Server (NTRS)

Compact, collapsible rotating cup anemometer is used in remote locations where portability and durability are factors in the choice of equipment. This lightweight instrument has a low wind-velocity threshold, is capable of withstanding large mechanical shocks while in its stowed configuration, and has fast response to wind fluctuations.

Wellman, J. B.

1968-01-01

136

Diffusion in Compacted Betonite.  

National Technical Information Service (NTIS)

The objective of this report is to collect the literature bearing on the diffusion in compacted betonite, which has been suggested as possible buffer material for the disposal of spent fuel. Diffusion in a porous, water-saturated material is usually descr...

A. Muurinen J. Rantanen

1985-01-01

137

Compact finger imager  

NASA Astrophysics Data System (ADS)

We present the design of a compact, low-cost finger imager, to be used for enrolling and recognizing individuals based upon their finger ridge patterns. The optical system employs viewing beyond the critical angle and darkfield illumination for maximum image contrast. The optical system is afocal and telecentric, achieving corrected distortion with oblique viewing.

Clark, Peter P.; Goodman, Douglas S.; Plummer, William T.

1999-10-01

138

Compact Artificial Hand.  

National Technical Information Service (NTIS)

A compact and relatively simple artificial hand includes hooks pivotally mounted on a first frame to move together and apart. The first frame is rotatably mounted on a second frame to enable 'turning at the wrist' movements without limitation, and the sec...

G. A. Wiker W. A. Mann

1977-01-01

139

Videos on Compact Objects  

NSDL National Science Digital Library

This site has three videos on X-ray binary systems, black hole M87, and neutron stars using either AVI or quicktime format. The videos are less than a minute long, but effectively portray these compact objects and how they behave.

2005-06-07

140

Progress in Compact Toroid Experiments  

SciTech Connect

The term "compact toroids" as used here means spherical tokamaks, spheromaks, and field reversed configurations, but not reversed field pinches. There are about 17 compact toroid experiments under construction or operating, with approximate parameters listed in Table 1.

Dolan, Thomas James

2002-09-01

141

Dynamic Compaction Facility Test Report  

SciTech Connect

The primary objective for the Dynamic Compaction Facility (DCF) test was to determine if dynamic compaction of buried low-level waste trenches would cause damage or failure to the adjacent Mixed Waste Management Facility (MWMF) closure system. A second objective was to quantify the success of dynamic compaction in consolidated buried B-25 boxes containing low-level waste.

McMullin, S.R.; Dendler, S.A.

2000-11-03

142

Super-Compact Laser  

NASA Technical Reports Server (NTRS)

Microcosm, Inc. produced the portable Farfield-2 laser for field applications that require high power pulsed illumination. The compact design was conceived through research at Goddard Space Flight Center on laser instruments for space missions to carry out geoscience studies of Earth. An exclusive license to the key NASA patent for the compact laser design was assigned to Microcosm. The FarField-2 is ideal for field applications, has low power consumption, does not need water cooling or gas supplies, and produces nearly ideal beam quality. The properties of the laser also make it effective over long distances, which is one reason why NASA developed the technology for laser altimeters that can be toted aboard spacecraft. Applications for the FarField-2 include medicine, biology, and materials science and processing, as well as diamond marking, semiconductor line-cutting, chromosome surgery, and fluorescence microscopy.

1997-01-01

143

Take Charge!  

NSDL National Science Digital Library

Students come to understand static electricity by learning about the nature of electric charge, and different methods for charging objects. In a hands-on activity, students induce an electrical charge on various objects, and experiment with electrical repulsion and attraction.

Integrated Teaching And Learning Program

144

Compaction and particle segregation in myelin membrane arrays  

PubMed Central

Compacted membrane arrays are formed in the nerve myelin sheath by lowering the water activity (through evaporation or immersion in hypertonic solutions of nonelectrolytes or monovalent salts) or by binding specific cations (Ca(++), La(+++), and tetracaine at concentrations above 5-10 mM). X-ray diffraction observations on intact, hydrated nerves treated to induce compaction provide a control to assess the significance of structural changes seen by freeze-fracture electron microscopy. Compaction inevitably leads to lateral segregation of particles away from the closely packed membrane arrays into contiguous normal, or slightly expanded, period arrays. In the particle-enriched layers, the E fracture face is more particle-dense than the P face, whereas no particles are found on either face in the compacted layers. Morphologically, compaction induced by the all-or-nothing, relatively irreversible action of specific cations cannot be distinguished from compaction to the same extent induced by the graded, reversible effects of nonelectrolytes. Compaction by sodium chloride resembles that by specific- cation binding in that the repeat period is independent of reagent concentration; but, like dehydration by nonelectrolytes, the extent of compaction is reversibly related to reagent concentration. Sodium chloride-compacted myelin can be distinguished morphologically by a lack of the elongated border particles at the boundary between smooth and particle-enriched membrane observed for other compacting treatments. Fracture faces in compacted arrays are not always smooth, but the unusual appearances can be duplicated in purified myelin lipid multilayers subjected to similar treatments, which indicates that the particle-free membrane fracture faces are uninterrupted lipid hydrocarbon layers. Correlation of x-ray diffraction and electron microscopy observations provides a direct basis for identifying the intramembrane particles with transmembrane protein. The transmembrane protein appears to play a significant role in maintaining the normal membrane separation; swelling of the particle-enriched arrays in myelin compacted by tetracaine at low ionic strength provides information about the charge distribution on the transmembrane protein. Swelling of the compacted arrays following irreversible particle segregation shows that the interaction properties of the particle-free membranes are similar to those of pure lipid multilayers. Compaction and the consequent particle segregation in lyelin results from conditions stabilizing close apposition of the lipid bilayers. Particle segregation in areas of close contact between other cell membranes may also be driven by interbilayer attractive forces.

Hollingshead, CJ; Caspar, DLD; Melchior, V; Kirschner, DA

1981-01-01

145

Hydraulic conductivity of compacted zeolites.  

PubMed

Hydraulic conductivities of compacted zeolites were investigated as a function of compaction water content and zeolite particle size. Initially, the compaction characteristics of zeolites were determined. The compaction test results showed that maximum dry unit weight (?(dmax)) of fine zeolite was greater than that of granular zeolites. The ?(dmax) of compacted zeolites was between 1.01 and 1.17 Mg m(-3) and optimum water content (w(opt)) was between 38% and 53%. Regardless of zeolite particle size, compacted zeolites had low ?(dmax) and high w(opt) when compared with compacted natural soils. Then, hydraulic conductivity tests were run on compacted zeolites. The hydraulic conductivity values were within the range of 2.0 × 10(-3) cm s(-1) to 1.1 × 10(-7) cm s(-1). Hydraulic conductivity of all compacted zeolites decreased almost 50 times as the water content increased. It is noteworthy that hydraulic conductivity of compacted zeolite was strongly dependent on the zeolite particle size. The hydraulic conductivity decreased almost three orders of magnitude up to 39% fine content; then, it remained almost unchanged beyond 39%. Only one report was found in the literature on the hydraulic conductivity of compacted zeolite, which is in agreement with the findings of this study. PMID:23460541

Oren, A Hakan; Ozdamar, Tu?çe

2013-06-01

146

Do charge state signatures guarantee protein conformations?  

PubMed

The extent to which proteins in the gas phase retain their condensed-phase structure is a hotly debated issue. Closely related to this is the degree to which the observed charge state reflects protein conformation. Evidence from electron capture dissociation, hydrogen/deuterium exchange, ion mobility, and molecular dynamics shows clearly that there is often a strong correlation between the degree of folding and charge state, with the most compact conformations observed for the lowest charge states. In this article, we address recent controversies surrounding the relationship between charge states and folding, focussing also on the manipulation of charge in solution and its effect on conformation. 'Supercharging' reagents that have been used to effect change in charge state can promote unfolding in the electrospray droplet. However for several protein complexes, supercharging does not appear to perturb the structure in that unfolding is not detected. Consequently, a higher charge state does not necessarily imply unfolding. Whilst the effect of charge manipulation on conformation remains controversial, there is strong evidence that a folded, compact state of a protein can survive in the gas phase, at least on a millisecond timescale. The exact nature of the side-chain packing and secondary structural elements in these compact states, however, remains elusive and prompts further research. PMID:22562394

Hall, Zoe; Robinson, Carol V

2012-07-01

147

Compact LINAC for deuterons  

SciTech Connect

We are developing a compact deuteron-beam accelerator up to the deuteron energy of a few MeV based on room-temperature inter-digital H-mode (IH) accelerating structures with the transverse beam focusing using permanent-magnet quadrupoles (PMQ). Combining electromagnetic 3-D modeling with beam dynamics simulations and thermal-stress analysis, we show that IHPMQ structures provide very efficient and practical accelerators for light-ion beams of considerable currents at the beam velocities around a few percent of the speed of light. IH-structures with PMQ focusing following a short RFQ can also be beneficial in the front end of ion linacs.

Kurennoy, S S [Los Alamos National Laboratory; O' Hara, J F [Los Alamos National Laboratory; Rybarcyk, L J [Los Alamos National Laboratory

2008-01-01

148

Compact Plasma Accelerator  

NASA Technical Reports Server (NTRS)

A plasma accelerator has been conceived for both material-processing and spacecraft-propulsion applications. This accelerator generates and accelerates ions within a very small volume. Because of its compactness, this accelerator could be nearly ideal for primary or station-keeping propulsion for spacecraft having masses between 1 and 20 kg. Because this accelerator is designed to generate beams of ions having energies between 50 and 200 eV, it could also be used for surface modification or activation of thin films.

Foster, John E.

2004-01-01

149

Compaction of Titanium Powders  

NASA Astrophysics Data System (ADS)

Accurate modeling of powder densification has been an area of active research for more than 60 years. The earliest efforts were focused on linearization of the data because computers were not readily available to assist with curve-fitting methods. In this work, eight different titanium powders (three different sizes of sponge fines <150 ?m, <75 ?m, and < 45 ?m; two different sizes of a hydride-dehydride [HDH] <75 ?m and < 45 ?m; an atomized powder; a commercially pure [CP] Ti powder from International Titanium Powder [ITP]; and a Ti 6 4 alloy powder) were cold pressed in a single-acting die instrumented to collect stress and deformation data during compaction. From these data, the density of each compact was calculated and then plotted as a function of pressure. The results show that densification of all the powders, regardless of particle size, shape, or chemistry, can be modeled accurately as the sum of an initial density plus the sum of a rearrangement term and a work-hardening term. These last two terms are found to be a function of applied pressure and take the form of an exponential rise.

Gerdemann, Stephen J.; Jablonski, Paul D.

2011-05-01

150

Compact electrostatic comb actuator  

DOEpatents

A compact electrostatic comb actuator is disclosed for microelectromechanical (MEM) applications. The actuator is based upon a plurality of meshed electrostatic combs, some of which are stationary and others of which are moveable. One or more restoring springs are fabricated within an outline of the electrostatic combs (i.e. superposed with the moveable electrostatic combs) to considerably reduce the space required for the actuator. Additionally, a truss structure is provided to support the moveable electrostatic combs and prevent bending or distortion of these combs due to unbalanced electrostatic forces or external loading. The truss structure formed about the moveable electrostatic combs allows the spacing between the interdigitated fingers of the combs to be reduced to about one micron or less, thereby substantially increasing the number of active fingers which can be provided in a given area. Finally, electrostatic shields can be used in the actuator to substantially reduce unwanted electrostatic fields to further improve performance of the device. As a result, the compact electrostatic comb actuator of the present invention occupies only a fraction of the space required for conventional electrostatic comb actuators, while providing a substantial increase in the available drive force (up to one-hundred times).

Rodgers, M. Steven (Albuquerque, NM); Burg, Michael S. (Albuquerque, NM); Jensen, Brian D. (Albuquerque, NM); Miller, Samuel L. (Albuquerque, NM); Barnes, Stephen M. (Albuquerque, NM)

2000-01-01

151

Compact Flares and CMEs  

NASA Technical Reports Server (NTRS)

From a search of the SOHO/LASCO CME Catalog, we found several flares that were strong but short-lived in GOES X-ray flux (peak flux > C5, duration compact (brightened only a small part of the active region). From the magnetic location and magnetic surroundings determined from MDI magnetograms, it appears that the non-CME flares were confined deep within surrounding strong closed magnetic fields, while the CME-producing flares either triggered neighboring sheared fields to erupt into a CME, or were able to erupt out of the active region and directly drive a CME. Compact ejective flares of this last type may produce a large CME by driving the eruption of a large coronal loop such as a trans-equatorial loop. We present an example of such a flare and CME.

Moore, Ronald; Sterling, Alphonse

2004-01-01

152

Compaction of Titanium Powders  

SciTech Connect

Accurate modeling of powder densification has been an area of active research for more than 60 years. The earliest efforts were focused on linearization of the data because computers were not readily available to assist with curve-fitting methods. In this work, eight different titanium powders (three different sizes of sponge fines<150 {micro}m,<75 {micro}m, and<45 {micro}m; two different sizes of a hydride-dehydride [HDH]<75 {micro}m and<45 {micro}m; an atomized powder; a commercially pure [CP] Ti powder from International Titanium Powder [ITP]; and a Ti 6 4 alloy powder) were cold pressed in a single-acting die instrumented to collect stress and deformation data during compaction. From these data, the density of each compact was calculated and then plotted as a function of pressure. The results show that densification of all the powders, regardless of particle size, shape, or chemistry, can be modeled accurately as the sum of an initial density plus the sum of a rearrangement term and a work-hardening term. These last two terms are found to be a function of applied pressure and take the form of an exponential rise.

Gerdemann, Stephen,J; Jablonski, Paul, J

2011-05-01

153

Compact Infrasonic Windscreen  

NASA Technical Reports Server (NTRS)

A compact windscreen has been conceived for a microphone of a type used outdoors to detect atmospheric infrasound from a variety of natural and manmade sources. Wind at the microphone site contaminates received infrasonic signals (defined here as sounds having frequencies <20 Hz), because a microphone cannot distinguish between infrasonic pressures (which propagate at the speed of sound) and convective pressure fluctuations generated by wind turbulence. Hence, success in measurement of outdoor infrasound depends on effective screening of the microphone from the wind. The present compact windscreen is based on a principle: that infrasound at sufficiently large wavelength can penetrate any barrier of practical thickness. Thus, a windscreen having solid, non-porous walls can block convected pressure fluctuations from the wind while transmitting infrasonic acoustic waves. The transmission coefficient depends strongly upon the ratio between the acoustic impedance of the windscreen and that of air. Several materials have been found to have impedance ratios that render them suitable for use in constructing walls that have practical thicknesses and are capable of high transmission of infrasound. These materials (with their impedance ratios in parentheses) are polyurethane foam (222), space shuttle tile material (332), balsa (323), cedar (3,151), and pine (4,713).

Zuckerwar, Allan J.; Shams, Qamar A.; Sealey, Bradley S.; Comeaux, Toby

2005-01-01

154

Design of a compact structure cancer therapy synchrotron  

NASA Astrophysics Data System (ADS)

HIMM, a new compact accelerator facility dedicated to carbon cancer therapy, has been designed and is presently under construction. The synchrotron has a compact structure that exhibits a circumference of only 56.2 m. The charge exchange injection (CEI) method is adopted for synchrotron injection with a carbon-ion energy of 7 MeV/u. The third-order resonance and RF-Knock Out scheme are adopted in this machine. The general design of the machine and injection/extraction simulation results is discussed in this paper.

Yang, J. C.; Shi, J.; Chai, W. P.; Xia, J. W.; Yuan, Y. J.; Li, Y.

2014-08-01

155

Electric Fields and Monopole Currents in Compact QED  

NASA Astrophysics Data System (ADS)

The confinement in compact QED is known to be related to magnetic monopoles. Magnetic currents form a solenoid around electric flux lines between a pair of electric charges. This behaviour can be described by the dual version of Maxwell—London equations including a fluctuating string. We use a definition of magnetic monopole currents adjusted to the definition of the electric field strength on a lattice and get good agreement for field and current distributions between compact QED and the predictions of dual Maxwell—London equations. Further we show that the monopole fluctuations in the vacuum are suppressed by the flux tube.

Zach, Martin; Faber, Manfried; Kainz, Wolfgang; Skala, Peter

1995-04-01

156

Compact Groups of Galaxies  

NASA Astrophysics Data System (ADS)

Compact groups of galaxies typically contain fewer than ten galaxies, separated from one another on the plane of the sky by a galaxy diameter or less. A continuing question about these groups is why we see so many of them even though galaxy interactions should quickly destroy the individual galaxies and result in a single merger remnant. The presence of tidally distorted galaxies in these groups implies that they are not simply projections of unrelated galaxies on the sky. Hickson compact groups (HCGs) form a well-defined sample that can be examined for clues to this puzzle. We used deep X-ray (ROSAT PSPC) and optical observations of twelve Hickson groups to explore their interaction histories. Diffuse X-ray emission (of luminosity 10^{41 -42} erg s^{-1} is seen primarily in elliptical-rich HCGs, implying that these groups contain gas at a temperature of k {rm T}~0.9 keV. Total and gas masses obtained from the X-ray data show that these groups have baryon fractions similar to those of clusters of galaxies, but gas-to-stellar-mass ratios two orders of magnitude smaller. Deep, multicolor photometry of the same sample shows no correlation between the presence of tidal features in group galaxies and X-ray emission in a group; however, two bright ellipticals in the sample not previously thought to be merger remnants have peculiar color structures and extremely low X-ray luminosities which may result from mergers. HCG 94 is an exceptional group: extremely X-ray -luminous, it is the only group in our sample with diffuse optical light in the group potential (the other groups have an upper limit of 1/3 L*, while the light in HCG 94 has a luminosity of 7 L*). High-resolution X-ray observations show that the diffuse hot gas and the diffuse light trace the same potential in this group, implying that this potential is changing slowly. Galaxy-formation simulations in a cold-dark-matter-dominated universe create groups that have properties similar to X-ray-bright HCGs; however, the simulated groups are not physically compact for most of the time that they are X-ray-luminous.

Pildis, Rachel Ann

1995-01-01

157

Electrosintering of iron powder compacts  

NASA Astrophysics Data System (ADS)

The influence of a nominal external electric fieldE=3 to 10 kV/cm on the sintering of iron powder compacts for 30 minutes at 1140°C in a vacuum of ˜10-6 torr was investigated. It was found that the field reduced the porosity by as much as 29 to 73 pct compared to sintering without a field, the magnitude depending on the procedure employed to measure the density of the specimen. Optical microscopy revealed that the specimen electrosintered withE=10 kV/cm had a skin of ˜0.2 mm in thickness, where the porosity was significantly less than in the interior. This was also the depth of carburization that was obtained upon carburizing the electrosintered specimens. It is proposed that the decrease in porosity produced by the field results from a decrease in the chemical potential of vacancies at or just below the charged external surface. Vacancy flux equations employed to calculate the porosity as a function of distance below the external surface showed that the porosity becomes approximately zero at a distance ofx c=0.4 to 0.5 mm below the surface, which is in reasonable accord with the microscopy measurements. Similar values ofx c were obtained by assuming that the entire porosity decrease given by the density measurements occurred in a ring of thickness ofx c below the external surface. The difference in the density measured by two Archimedes-principle procedures and microscopy observations suggests that the cavities open to the external surface of the electrosintered specimens are smaller or narrower than those for specimens sintered without a field.

Fahmy, Yusef; Conrad, Hans

2001-03-01

158

Chandrasekhar's perturbation method-oriented theories Third-order results for uniformly and differentially rotating polytropic stars; reliability and accuracy of first- and second-order results for uniform rotation  

NASA Astrophysics Data System (ADS)

The aim of this investigation is the computation, by implementation of algorithms of a third-order perturbation theory developed in an earlier paper, of numerical results that represent quantitatively the distortion of the structure of a polytropic star, distortion owing to either uniform or differential rapid rotation. The results presented are systematically compared with those of previous investigations. Reliability and accuracy of firstand second-order results are also discussed. The FORTAN program implementing the codes of the theory is extensively described and specifically documented.

Geroyannis, V. S.; Valvi, F. N.

1985-12-01

159

Multipurpose Compact Spectrometric Unit  

SciTech Connect

A new standalone compact spectrometer was developed. The device consists of analog (peamplifier, amplifier) and digital parts. The digital part is based on the 160 MIPS Digital Signal Processor. It contains 20 Msps Flash-ADC, 1 MB RAM for spectra storage, 128 KB Flash/ROM for firmware storage, Real Time Clock and several voltage regulators providing the power for user peripherals (e.g. amplifier, temperature sensors, etc.). Spectrometer is connected with a notebook via high-speed USB 2.0 bus. The spectrometer is multipurpose device, which is planned to be used for measurements of Rn activities, energy of detected particles by CdTe pixel detector or for coincidence measurements.

Bocarov, Viktor; Cermak, Pavel; Mamedov, Fadahat; Stekl, Ivan [Institute of Experimental and Applied Physics, Czech Technical University in Prague, Horska 3a/22, CZ-12800 Prague 2 (Czech Republic)

2009-11-09

160

Compact artificial hand  

NASA Technical Reports Server (NTRS)

A relatively simple, compact artificial hand, is described which includes hooks pivotally mounted on first frame to move together and apart. The first frame is rotatably mounted on a second frame to enable "turning at the wrist" movement without limitation. The second frame is pivotally mounted on a third frame to permit 'flexing at the wrist' movement. A hook-driving motor is fixed to the second frame but has a shaft that drives a speed reducer on the first frame which, in turn, drives the hooks. A second motor mounted on the second frame, turns a gear on the first frame to rotate the first frame and the hooks thereon. A third motor mounted on the third frame, turns a gear on a second frame to pivot it.

Wiker, G. A.; Mann, W. A. (inventors)

1979-01-01

161

Compact acoustic refrigerator  

DOEpatents

A compact acoustic refrigeration system actively cools components, e.g., electrical circuits (22), in a borehole environment. An acoustic engine (12, 14) includes first thermodynamic elements (12) for generating a standing acoustic wave in a selected medium. An acoustic refrigerator (16, 26, 28) includes second thermodynamic elements (16) located in the standing wave for generating a relatively cold temperature at a first end of the second thermodynamic elements (16) and a relatively hot temperature at a second end of the second thermodynamic elements (16). A resonator volume (18) cooperates with the first and second thermodynamic elements (12, 16) to support the standing wave. To accommodate the high heat fluxes required for heat transfer to/from the first and second thermodynamic elements (12, 16), first heat pipes (24, 26) transfer heat from the heat load (22) to the second thermodynamic elements (16) and second heat pipes (28, 32) transfer heat from first and second thermodynamic elements (12, 16) to the borehole environment.

Bennett, Gloria A. (Los Alamos, NM)

1992-01-01

162

Atacama compact array antennas  

NASA Astrophysics Data System (ADS)

The ACA (Atacama Compact Array) system is an important element of ALMA and consists of four ACA 12-m antennas and twelve ACA 7-m antennas. The ACA system aims to acquire the total power data with four 12-m antennas and the short baseline interferometer data with 7-m antennas. The ACA system also increases reliability of the interferometer maps of astronomical sources larger than the field view of the 12-m antenna. The science performance of these antennas has been extensively verified at OSF (operation support facility) at an elevation of 2900 m in Atacama desert in northern Chile since 2007. The pointing performance has been verified with a dedicated optical pointing telescope, the servo performance is tested with angle encoders, and the surface accuracy has been measured with a radio holography method. Both ACA 12-m antennas and 7-m antennas have been successfully demonstrated to meet the very stringent ALMA specifications.

Saito, M.; Inatani, J.; Nakanishi, K.; Saito, H.; Iguchi, S.

2012-09-01

163

Compact vacuum insulation  

DOEpatents

An ultra-thin compact vacuum insulation panel is comprised of two hard, but bendable metal wall sheets closely spaced apart from each other and welded around the edges to enclose a vacuum chamber. Glass or ceramic spacers hold the wall sheets apart. The spacers can be discrete spherical beads or monolithic sheets of glass or ceramic webs with nodules protruding therefrom to form essentially point'' or line'' contacts with the metal wall sheets. In the case of monolithic spacers that form line'' contacts, two such spacers with the line contacts running perpendicular to each other form effectively point'' contacts at the intersections. Corrugations accommodate bending and expansion, tubular insulated pipes and conduits, and preferred applications are also included.

Benson, D.K.; Potter, T.F.

1993-01-05

164

Compact vacuum insulation embodiments  

DOEpatents

An ultra-thin compact vacuum insulation panel is comprised of two hard, but bendable metal wall sheets closely spaced apart from each other and welded around the edges to enclose a vacuum chamber. Glass or ceramic spacers hold the wall sheets apart. The spacers can be discrete spherical beads or monolithic sheets of glass or ceramic webs with nodules protruding therefrom to form essentially point' or line' contacts with the metal wall sheets. In the case of monolithic spacers that form line' contacts, two such spacers with the line contacts running perpendicular to each other form effectively point' contacts at the intersections. Corrugations accommodate bending and expansion, tubular insulated pipes and conduits, and preferred applications are also included. 26 figs.

Benson, D.K.; Potter, T.F.

1992-04-28

165

Charge-pump voltage converter  

DOEpatents

A charge-pump voltage converter for converting a low voltage provided by a low-voltage source to a higher voltage. Charge is inductively generated on a transfer rotor electrode during its transit past an inductor stator electrode and subsequently transferred by the rotating rotor to a collector stator electrode for storage or use. Repetition of the charge transfer process leads to a build-up of voltage on a charge-receiving device. Connection of multiple charge-pump voltage converters in series can generate higher voltages, and connection of multiple charge-pump voltage converters in parallel can generate higher currents. Microelectromechanical (MEMS) embodiments of this invention provide a small and compact high-voltage (several hundred V) voltage source starting with a few-V initial voltage source. The microscale size of many embodiments of this invention make it ideally suited for MEMS- and other micro-applications where integration of the voltage or charge source in a small package is highly desirable.

Brainard, John P. (Albuquerque, NM); Christenson, Todd R. (Albuquerque, NM)

2009-11-03

166

A nonrecursive list compacting algorithm  

Microsoft Academic Search

A simple nonrecursive list structure compacting scheme or garbage collector suitable for both compact and LISP-like list structures is presented. The algorithm avoids the need for recursion by using the partial structure as it is built up to keep track of those lists that have been copied.

C. J. CI-IENEY

1970-01-01

167

Variational analysis of deconfinement in compact U(1) gauge theory  

NASA Astrophysics Data System (ADS)

A variational method is used to analyze compact U(1) gauge theory in 2+1 dimensions at finite temperature T, weak coupling g, and where the fundamental magnetic monopoles have magnetic charge 2?n/g. The theory undergoes a critical transition from a confining phase at temperatures below Tc=2g2/n2? to a deconfined phase at temperatures above Tc. The free energy and all its derivatives are continuous at Tc, indicative of the Berezinski-Kosterlitz-Thouless phase transition. The relevant gauge-invariant correlation functions decay exponentially at large distances. The spatial Wilson loop obeys the area law at all finite temperatures, even for the noncompact theory. The case n=2 corresponds to the compact U(1) theory considered as a low energy effective theory for the spontaneously broken Georgi-Glashow model. The results in this case agree with those derived previously for compact U(1) in this model using dimensional reduction of the Lagrangian.

Gripaios, B. M.

2003-01-01

168

Wild Mouse Variants of Envelope Genes of Xenotropic/Polytropic Mouse Gammaretroviruses and Their XPR1 Receptors Elucidate Receptor Determinants of Virus Entry?  

PubMed Central

Mouse xenotropic and polytropic leukemia viruses (XMVs and PMVs) are closely related gammaretroviruses that use the XPR1 receptor for entry. To identify amino acid residues in XPR1 important for virus entry, we tested mouse cells derived from evolutionarily divergent species for susceptibility to prototypical PMVs, XMVs, and the wild mouse isolate CasE#1. CasE#1 has a variant XMV/PMV host range, and sequence analysis of the CasE#1 env gene identifies segments related to PMVs and XMVs. Cells from the Asian mouse species Mus pahari show a unique pattern of susceptibility to these three viruses; these cells are susceptible to XMVs and CasE#1 but are resistant to PMVs, whereas NIH 3T3 cells show the reciprocal pattern, susceptibility to only PMVs. The M. pahari XPR1 gene differs from that of NIH 3T3 in the two extracellular loops (ECLs) previously shown to mediate virus entry (M. Marin, C. S. Tailor, A. Nouri, S. L. Kozak, and D. Kabat, J. Virol. 73:9362-9368, 1999, and N. S. Van Hoeven and A. D. Miller, Retrovirology 2:76, 2005). Using transfected hamster cells expressing chimeric and mutated XPR1s, we demonstrated that the susceptibility differences between NIH 3T3 and M. pahari cells are receptor mediated, that PMV entry requires residues in ECL3, that the CasE#1 entry determinant is in ECL4, and that determinants for XMV entry are in both ECL3 and ECL4. Additional substitutions in ECL3 and ECL4 modulate virus susceptibility and suggest that ECL3 and ECL4 may contribute to the formation of a single virus receptor site. The position of M. pahari at the base of the Mus phylogenetic tree indicates that XPR1-mediated susceptibility to XMVs is the ancestral type in this genus and that the phenotypic variants of mouse XPR1 likely arose in conjunction with exposure to gammaretrovirus infections and coevolutionary adaptations in the viral envelope.

Yan, Yuhe; Knoper, Ryan C.; Kozak, Christine A.

2007-01-01

169

Topological charges and the genus of surfaces  

Microsoft Academic Search

We show that the topological charge of the n-soliton solution of the sine-Gordon equation n[?] = (12?)[? dx?x?] is related to the genus g > 1 of a constant negative curvature compact orientable surface described by this configuration. The relation is n = 2(g ? 1), where n = 2? is even. The moduli space of complex dimension Bg =

Luis J. Boya; Antonio J. Segui-Santonja

1997-01-01

170

Zinc-air batteries for field charging  

Microsoft Academic Search

In order to realize the operational and service cost savings through the use of rechargeable batteries, the dismounted soldier is burdened with the weight, volume and\\/or charging logistics of the batteries. By providing the soldier with a high energy density source and a light weight compact battery charger the burden imposed by rechargeable batteries in the forward field can be

T. B. Atwater

1998-01-01

171

Relativistic Charged Star Solutions in Higher Dimensions  

NASA Astrophysics Data System (ADS)

We present a class of relativistic solutions of the Einstein-Maxwell equations for a spherically symmetric charged static fluid sphere in higher dimensions. The interior space at t= constant considered here possess ( D-1) dimensional spheroidal geometry described by a higher dimensional Vaidya-Tikekar metric. A class of new static solutions of coupled Einstein-Maxwell equations is obtained in a D-dimensional space-time by prescribing the geometry of a ( D-1) dimensional hyper spheroid in hydrostatic equilibrium. The solutions of the Einstein-Maxwell field equations are employed to obtain relativistic models for charged compact stars with a suitable law for variation of electric field in terms of the charged fluid content in the interior of the sphere. The central density is found to depend on the space-time dimensions and a physically realistic model is permitted for ( D?4). The validity of both Strong Energy Condition (SEC), Weak Energy Condition (WEC) are studied for a given configuration and compactness of compact objects. We found new class of solutions with interesting stellar models where it permits a star with a core having different property than the rest which however disappears in higher dimensions. The effect of dimensions on the Electric charge of the compact object is studied. We note that the upper limit of the electric field is determined by the space-time dimensions which are determined.

Chattopadhyay, P. K.; Deb, R.; Paul, B. C.

2014-05-01

172

CHARGE syndrome  

Microsoft Academic Search

CHARGE syndrome was initially defined as a non-random association of anomalies (Coloboma, Heart defect, Atresia choanae, Retarded growth and development, Genital hypoplasia, Ear anomalies\\/deafness). In 1998, an expert group defined the major (the classical 4C's: Choanal atresia, Coloboma, Characteristic ears and Cranial nerve anomalies) and minor criteria of CHARGE syndrome. Individuals with all four major characteristics or three major and

Kim D Blake; Chitra Prasad

2006-01-01

173

Investigation of Continuous Compaction Control Systems.  

National Technical Information Service (NTIS)

Continuous Compaction Control (CCC) systems have demonstrated great promise for improving the efficiency of field compaction and revolutionizing the compaction control process. To evaluate the effectiveness and reliability of CCC systems in the State of D...

C. Meehan F. S. Tehrani

2009-01-01

174

Compact vacuum insulation  

DOEpatents

Improved compact insulation panel is provided which is comprised of two adjacent metal sheets spaced close together with a plurality of spherical, or other discretely shaped, glass or ceramic beads optimally positioned between the sheets to provide support and maintain the spacing between the metal sheets when the gases there between are evacuated to form a vacuum. These spherical glass beads provide the maximum support while minimizing thermal conductance. In its preferred embodiment; these two metal sheets are textured with ribs or concave protrusions in conjunction with the glass beads to maximize the structural integrity of the panels while increasing the spacing between beads, thereby reducing the number of beads and the number of thermal conduction paths. Glass or porcelain-enameled liners in combination with the glass spacers and metal sidewalls effectively decrease thermal conductivity, and various laminates, including wood, porcelain-enameled metal, and others effectively increase the strength and insulation capabilities of the panels. Also, a metal web is provided to hold the spacers in place, and strategic grooves are shown to accommodate expansion and contraction or shaping of the panels. 35 figs.

Benson, D.K.; Potter, T.F.

1992-10-27

175

Compact vacuum insulation  

DOEpatents

Improved compact insulation panel is provided which is comprised of two adjacent metal sheets spaced close together with a plurality of spherical, or other discretely shaped, glass or ceramic beads optimally positioned between the sheets to provide support and maintain the spacing between the metal sheets when the gases therebetween are evacuated to form a vacuum. These spherical glass beads provide the maximum support while minimizing thermal conductance. In its preferred embodiment; these two metal sheets are textured with ribs or concave protrusions in conjunction with the glass beads to maximize the structural integrity of the panels while increasing the spacing between beads, thereby reducing the number of beads and the number of thermal conduction paths. Glass or porcelain-enameled liners in combination with the glass spacers and metal sidewalls effectively decrease thermal conductivity, and variious laminates, including wood, porcelain-enameled metal, and others effectively increase the strength and insulation capabilities of the panels. Also, a metal web is provided to hold the spacers in place, and strategic grooves are shown to accommodate expansion and contraction or shaping of the panels.

Benson, David K. (Golden, CO); Potter, Thomas F. (Denver, CO)

1992-01-01

176

A compact acoustic recorder  

NASA Astrophysics Data System (ADS)

The design and operation of a portable compact acoustic recorder is discussed. Designed to be used in arctic conditions for applications that require portable equipment, the device is configured to fit into a lightweight briefcase. It will operate for eight hours at -40 F with heat provided by a hot water bottle. It has proven to be an effective scientific tool in the measurement of underwater acoustic signals in arctic experiments. It has also been used successfully in warmer climates, e.g., in recording acoustic signals from small boats with no ac power. The acoustic recorder's cost is moderate since it is based on a Sony Walkman Professional (WM-D6C) tape recorder playback unit. A speaker and battery assembly and a hydrophone interface electronic assembly complete the system electronics. The interface assembly supplies a number of functions, including a calibration tone generator, an audio amplifier, and a hydrophone interface. Calibrated acoustic recordings can be made by comparing the calibration tone amplitude with the acoustic signal amplitude. The distortion of the recording is minimized by using a high quality, consumer tape recorder.

Stein, Ronald

1989-09-01

177

Compact THz imaging detector  

NASA Astrophysics Data System (ADS)

We describe preliminary design, modeling and test results for the development of a monolithic, high pixel density, THz band focal plane array (FPA) fabricated in a commercial CMOS process. Each pixel unit cell contains multiple individual THz band antennae that are coupled to independent amplifiers. The amplified signals are summed either coherently or incoherently to improve detection (SNR). The sensor is designed to operate at room temperature using passive or active illumination. In addition to the THz detector, a secondary array of Visible or SWIR context imaging pixels are interposed in the same area matrix. Multiple VIS/SWIR context pixels can be fabricated within the THz pixel unit cell. This provides simultaneous, registered context imagery and "Pan sharpening" MTF enhancement for the THz image. The compact THz imaging system maximizes the utility of a ~ 300 ?m x 300 ?m pixel area associated with the optical resolution spot size for a THz imaging system operating at a nominal ~ 1.0 THz spectral frequency. RF modeling is used to parameterize the antenna array design for optimal response at the THz frequencies of interest. The quarter-wave strip balanced bow-tie antennae are optimized based on the semiconductor fabrication technology thin-film characteristics and the CMOS detector input impedance. RF SPICE models enhanced for THz frequencies are used to evaluate the predicted CMOS detector performance and optimal unit cell design architecture. The models are validated through testing of existing CMOS ROICs with calibrated THz sources.

Newman, J. Daniel; Lee, Paul P. K.; Sacco, Andrew P.; Chamberlain, Thomas B.; Willems, Dave A.; Fiete, Robert D.; Bocko, Mark V.; Ignotovic, Zeljko; Pipher, Judith L.; McMurtry, Craig W.; Zhang, Xi-Cheng; Rhodes, David B.; Ninkov, Zoran

2013-05-01

178

Compact optical interconnect module  

NASA Astrophysics Data System (ADS)

The results of a design study for the development of an eye- safe (near-infrared wavelength), compact, multichannel optical interconnect system appropriate for integration with electronics and to be used for short distance communication are discussed. There are potential advantages to using optical interconnects instead of current hardwire interconnections for data transmission over short distances. This technology also has potential applications to data transmission for computing applications. This design study focused on the development of an optical interconnect module to function much like a conventional data cable. The module must be rugged, small, easily integrated into current data transfer, and must have the potential to be produced in volume and at lost cost. The desired system level performance of the optical interconnects was evaluated and design specifications were determined for the optical design. Trade studies involving current technologies were performed to determine suitable hardware configurations. These requirements pointed toward the application of microfabrication technology and micro-optics in order to accomplish the design goals. A pseudo-monolithic silicon-based optical system has been proposed involving diffractive and microrefractive optics along with integrated sensors and emitters. The device emphasizes the use of existing technologies gathered from different disciplines and integrated into one system.

Peters, Bruce R.; Reardon, Patrick J.; Reardon, Janine V.

1997-09-01

179

Compact Dexterous Robotic Hand  

NASA Technical Reports Server (NTRS)

A compact robotic hand includes a palm housing, a wrist section, and a forearm section. The palm housing supports a plurality of fingers and one or more movable palm members that cooperate with the fingers to grasp and/or release an object. Each flexible finger comprises a plurality of hingedly connected segments, including a proximal segment pivotally connected to the palm housing. The proximal finger segment includes at least one groove defining first and second cam surfaces for engagement with a cable. A plurality of lead screw assemblies each carried by the palm housing are supplied with power from a flexible shaft rotated by an actuator and output linear motion to a cable move a finger. The cable is secured within a respective groove and enables each finger to move between an opened and closed position. A decoupling assembly pivotally connected to a proximal finger segment enables a cable connected thereto to control movement of an intermediate and distal finger segment independent of movement of the proximal finger segment. The dexterous robotic hand closely resembles the function of a human hand yet is light weight and capable of grasping both heavy and light objects with a high degree of precision.

Lovchik, Christopher Scott (Inventor); Diftler, Myron A. (Inventor)

2001-01-01

180

A compact 1 MV multi-element AMS system  

Microsoft Academic Search

HVE has designed and built a compact 1MV multi-element AMS system with a footprint of 3.8m×6.3m. The system is primarily designed for the analysis of light elements like beryllium, carbon and aluminium, but it also supports the measurement of heavy ions like iodine and plutonium. The analysis of 14C is done using the charge state 1. For this, the accelerator

M. G. Klein; D. J. W. Mous; A. Gottdang

2006-01-01

181

A compact 1 MV multi-element AMS system  

Microsoft Academic Search

HVE has designed and built a compact 1 MV multi-element AMS system with a footprint of 3.8 m × 6.3 m. The system is primarily designed for the analysis of light elements like beryllium, carbon and aluminium, but it also supports the measurement of heavy ions like iodine and plutonium. The analysis of 14C is done using the charge state

M. G. Klein; D. J. W. Mous; A. Gottdang

2006-01-01

182

Compact stars and the symmetry energy  

NASA Astrophysics Data System (ADS)

The effect of the symmetry energy on some properties of compact stars which contain strange degrees of freedom is discussed. Both the onset of hyperons or kaon condensation will be considered. The hyperon-meson couplings are chosen according to experimental values of the hyperon nuclear matter potentials and possible uncertainties are considered. It is shown that a softer symmetry energy affects the onset of strangeness, namely neutral (negatively charged) strange particles set on at larger (smaller) densities, and gives rise to a smaller strangeness fraction as a function of density. A softer symmetry energy will possibily give rise to maximum mass configurations with larger masses. Hyperon-meson couplings have a strong effect on the mass of the star. It is shown that, for stars with masses above 1 Msolar, the radius of the star varies linearly with the symmetry energy slope L.

Providência, Constana; Cavagnoli, Rafael; Menezes, Debora P.; Panda, Prafulla K.; Rabhi, Aziz

2013-02-01

183

Compact, Reliable EEPROM Controller  

NASA Technical Reports Server (NTRS)

A compact, reliable controller for an electrically erasable, programmable read-only memory (EEPROM) has been developed specifically for a space-flight application. The design may be adaptable to other applications in which there are requirements for reliability in general and, in particular, for prevention of inadvertent writing of data in EEPROM cells. Inadvertent writes pose risks of loss of reliability in the original space-flight application and could pose such risks in other applications. Prior EEPROM controllers are large and complex and do not provide all reasonable protections (in many cases, few or no protections) against inadvertent writes. In contrast, the present controller provides several layers of protection against inadvertent writes. The controller also incorporates a write-time monitor, enabling determination of trends in the performance of an EEPROM through all phases of testing. The controller has been designed as an integral subsystem of a system that includes not only the controller and the controlled EEPROM aboard a spacecraft but also computers in a ground control station, relatively simple onboard support circuitry, and an onboard communication subsystem that utilizes the MIL-STD-1553B protocol. (MIL-STD-1553B is a military standard that encompasses a method of communication and electrical-interface requirements for digital electronic subsystems connected to a data bus. MIL-STD- 1553B is commonly used in defense and space applications.) The intent was to both maximize reliability while minimizing the size and complexity of onboard circuitry. In operation, control of the EEPROM is effected via the ground computers, the MIL-STD-1553B communication subsystem, and the onboard support circuitry, all of which, in combination, provide the multiple layers of protection against inadvertent writes. There is no controller software, unlike in many prior EEPROM controllers; software can be a major contributor to unreliability, particularly in fault situations such as the loss of power or brownouts. Protection is also provided by a powermonitoring circuit.

Katz, Richard; Kleyner, Igor

2010-01-01

184

Compact Holographic Data Storage  

NASA Technical Reports Server (NTRS)

NASA's future missions would require massive high-speed onboard data storage capability to Space Science missions. For Space Science, such as the Europa Lander mission, the onboard data storage requirements would be focused on maximizing the spacecraft's ability to survive fault conditions (i.e., no loss in stored science data when spacecraft enters the 'safe mode') and autonomously recover from them during NASA's long-life and deep space missions. This would require the development of non-volatile memory. In order to survive in the stringent environment during space exploration missions, onboard memory requirements would also include: (1) survive a high radiation environment (1 Mrad), (2) operate effectively and efficiently for a very long time (10 years), and (3) sustain at least a billion write cycles. Therefore, memory technologies requirements of NASA's Earth Science and Space Science missions are large capacity, non-volatility, high-transfer rate, high radiation resistance, high storage density, and high power efficiency. JPL, under current sponsorship from NASA Space Science and Earth Science Programs, is developing a high-density, nonvolatile and rad-hard Compact Holographic Data Storage (CHDS) system to enable large-capacity, high-speed, low power consumption, and read/write of data in a space environment. The entire read/write operation will be controlled with electrooptic mechanism without any moving parts. This CHDS will consist of laser diodes, photorefractive crystal, spatial light modulator, photodetector array, and I/O electronic interface. In operation, pages of information would be recorded and retrieved with random access and high-speed. The nonvolatile, rad-hard characteristics of the holographic memory will provide a revolutionary memory technology meeting the high radiation challenge facing the Europa Lander mission. Additional information is contained in the original extended abstract.

Chao, T. H.; Reyes, G. F.; Zhou, H.

2001-01-01

185

Novelties in physics of explosive welding and powder compaction  

NASA Astrophysics Data System (ADS)

Widely known technologies of explosive (X) welding and explosive (X) powder compaction are based on applications of porous composite solid or liquid explosives. Recent results on dynamics of X-welding and X-powder compaction are presented and discussed in this paper in the conceptual context of an orderly oscillating detonation wave (DW), a synergetic phenomenon observed in detonation of all classes of composite energetic materials, that was discovered in LEDAP in last eight years. Regular instabilities that are induced by oscillating DW, are transmitted through the interface of the impacted materials, causing the local instability and fluctuations in both processes, formation of the interfacial waves (X-welding mechanism) and in an initial phase of powder compaction. Application of high resolution optical probes (spatial resolution 250 ?m, temporal resolution 1 ns, 96 independent channels) allowed the simultaneous registration of the oscillating DW in the X-charge and transmission of oscillations, through the flyer plate, up to the welding zone. Similar measurements have been made in experiments with X-compaction of tungsten powder providing the continuos registration of shock wave velocity inside the compacted powder, its geometrical shape, their instabilities and irregularities.

Plaksin, I.; Campos, J.; Ribeiro, J.; Mendes, R.; Direito, J.; Braga, D.; Pruemmer, R.

2003-09-01

186

Mesoscale Simulations of Powder Compaction  

NASA Astrophysics Data System (ADS)

Mesoscale 3D simulations of shock compaction of metal and ceramic powders have been performed with an Eulerian hydrocode GEODYN. The approach was validated by simulating a well-characterized shock compaction experiment of a porous ductile metal. Simulation results using the Steinberg material model and handbook values for solid 2024 aluminum showed good agreement with experimental compaction curves and wave profiles. Brittle ceramic materials are not as well studied as metals, so a simple material model for solid ceramic (tungsten carbide) has been calibrated to match experimental compaction curves. Direct simulations of gas gun experiments with ceramic powders have been performed and showed good agreement with experimental data. The numerical shock wave profile has same character and thickness as that measured experimentally using VISAR. The numerical results show reshock states above the single-shock Hugoniot line as observed in experiments. We found that for good quantitative agreement with experiments 3D simulations are essential.

Lomov, Ilya.; Fujino, Don; Antoun, Tarabay; Liu, Benjamin

2009-12-01

187

NRL Compact Accelerator Theory Studies.  

National Technical Information Service (NTIS)

NRL compact accelerator theory studies in support of the Spiral Line Induction Accelerator (SLIA) and the Recirculating Linear Accelerator (RLA) are summarized in a series of short papers. The first of these papers describes the ELBA three-dimensional bea...

A. W. Ali F. Mako G. Joyce J. Krall R. F. Hubbard

1990-01-01

188

Compact Toroid Refueling of Reactors.  

National Technical Information Service (NTIS)

The feasibility of refueling fusion reactors and devices such as the International Thermonuclear Engineering Reactor (ITER) with high-velocity compact toroids is investigated. For reactors with reasonable limits on recirculating power, it is concluded tha...

M. J. Gouge J. T. Hogan S. L. Milora C. E. Thomas

1988-01-01

189

Compact Adaptive Optics Systems (CAOS).  

National Technical Information Service (NTIS)

As feasibility study has been conducted to investigate whether compact adaptive optical (AO) systems based on the use of transparent wavefront modulators are viable. The results presented here consider the generic properties of suitable wavefront sensor t...

A. H. Greenway

2002-01-01

190

Compaction with Automatic Jog Introduction.  

National Technical Information Service (NTIS)

This paper presents a novel polynomial-time algorithm for compacting a VLSI layout. Compared to previous algorithms, the algorithm promises to produce higher quality output while reducing the need for designer intervention. The performance gain is realize...

F. M. Maley

1985-01-01

191

MESOSCALE SIMULATIONS OF POWDER COMPACTION  

SciTech Connect

Mesoscale 3D simulations of shock compaction of metal and ceramic powders have been performed with an Eulerian hydrocode GEODYN. The approach was validated by simulating a well-characterized shock compaction experiment of a porous ductile metal. Simulation results using the Steinberg material model and handbook values for solid 2024 aluminum showed good agreement with experimental compaction curves and wave profiles. Brittle ceramic materials are not as well studied as metals, so a simple material model for solid ceramic (tungsten carbide) has been calibrated to match experimental compaction curves. Direct simulations of gas gun experiments with ceramic powders have been performed and showed good agreement with experimental data. The numerical shock wave profile has same character and thickness as that measured experimentally using VISAR. The numerical results show reshock states above the single-shock Hugoniot line as observed in experiments. We found that for good quantitative agreement with experiments 3D simulations are essential.

Lomov, Ilya; Fujino, Don; Antoun, Tarabay; Liu, Benjamin [Lawrence Livermore National Laboratory, P. O. Box 808, Livermore CA 94551 (United States)

2009-12-28

192

Compaction in Igneous Rocks (Invited)  

NASA Astrophysics Data System (ADS)

There is increasing evidence that compaction happens in a variety of igneous rocks during solidification, having been described in rocks ranging from thick basaltic flows to layered intrusions. The evidence includes 1) bent mineral grains, 2) development of foliations without a lineation consistent with pure shear, 3) reverse fractionation trends observed at the base of many layered intrusions, and 4) geochemical evidence of progressive loss of elements with increasing incompatibility as pore space is reduced by the combined effects of compaction and solidification of interstitial liquid. Modeling shows that a variety of apparently non-intuitive phenomenon besides simple loss of pore space can occur during compaction. For example, in a compacting pile that is cooling and solidifying from above, compaction becomes more effective with distance below the top owing to higher permeability away from the cooling contact and can lead to dilation of the solid matrix in the mush. This can express itself in the formation of segregation sheets in thick lava flows to possibly the formation of modal layering in thick sills and layered intrusions. Alternatively, compaction in a mush zone that has a density change in the solid assemblage, such as across an ultramafic-mafic contact, can lead to higher porosity zones within the rock with the higher density difference between solid and liquid. These also tend to be areas where platinum-group element and sulfide enrichments can also occur. The observation that compaction occurs in a wide variety of igneous rocks suggests that “cumulate” rocks are nothing more than partly crystallized basalts that have undergone extensive textural and compositional modification during compaction. This can explain why plagioclase, a mineral that otherwise has a neutral to positive buoyancy in most basaltic liquid, is actually the most commonly observed "settled" mineral in layered intrusions.

Boudreau, A. E.

2009-12-01

193

Charge Falling Through a Charged Ring Model  

NSDL National Science Digital Library

The Charge Falling Through a Charged Ring shows dynamics of a charged ball as it is released and falls through a ring of charge. The ball and the ring can be charged with a positive blue) or a (red) negative charge.

Krizaj, Dejan

2010-11-09

194

Compact Optoelectronic Compass  

NASA Technical Reports Server (NTRS)

A compact optoelectronic sensor unit measures the apparent motion of the Sun across the sky. The data acquired by this chip are processed in an external processor to estimate the relative orientation of the axis of rotation of the Earth. Hence, the combination of this chip and the external processor finds the direction of true North relative to the chip: in other words, the combination acts as a solar compass. If the compass is further combined with a clock, then the combination can be used to establish a threeaxis inertial coordinate system. If, in addition, an auxiliary sensor measures the local vertical direction, then the resulting system can determine the geographic position. This chip and the software used in the processor are based mostly on the same design and operation as those of the unit described in Micro Sun Sensor for Spacecraft (NPO-30867) elsewhere in this issue of NASA Tech Briefs. Like the unit described in that article, this unit includes a small multiple-pinhole camera comprising a micromachined mask containing a rectangular array of microscopic pinholes mounted a short distance in front of an image detector of the active-pixel sensor (APS) type (see figure). Further as in the other unit, the digitized output of the APS in this chip is processed to compute the centroids of the pinhole Sun images on the APS. Then the direction to the Sun, relative to the compass chip, is computed from the positions of the centroids (just like a sundial). In the operation of this chip, one is interested not only in the instantaneous direction to the Sun but also in the apparent path traced out by the direction to the Sun as a result of rotation of the Earth during an observation interval (during which the Sun sensor must remain stationary with respect to the Earth). The apparent path of the Sun across the sky is projected on a sphere. The axis of rotation of the Earth lies at the center of the projected circle on the sphere surface. Hence, true North (not magnetic North), relative to the chip, can be estimated from paths of the Sun images across the APS. In a test, this solar compass has been found to yield a coarse estimate of the North (within tens of degrees) in an observation time of about ten minutes. As expected, the accuracy was found to increase with observation time: after a few hours, the estimated direction of the rotation axis becomes accurate to within a small fraction of a degree.

Christian, Carl

2004-01-01

195

A Compact Polarization Imager  

NASA Technical Reports Server (NTRS)

A new type of image detector has been designed to analyze the polarization of light simultaneously at all picture elements (pixels) in a scene. The Integrated Dual Imaging Detector (IDID) consists of a polarizing beamsplitter bonded to a custom-designed charge-coupled device with signal-analysis circuitry, all integrated on a silicon chip. The IDID should simplify the design and operation of imaging polarimeters and spectroscopic imagers used, for example, in atmospheric and solar research. Other applications include environmental monitoring and robot vision. Innovations in the IDID include two interleaved 512 x 1024 pixel imaging arrays (one for each polarization plane), large dynamic range (well depth of 10(exp 6) electrons per pixel), simultaneous readout and display of both images at 10(exp 6) pixels per second, and on-chip analog signal processing to produce polarization maps in real time. When used with a lithium niobate Fabry-Perot etalon or other color filter that can encode spectral information as polarization, the IDID can reveal tiny differences between simultaneous images at two wavelengths.

Thompson, Karl E.; Rust, David M.; Chen, Hua

1995-01-01

196

Charged holostars  

Microsoft Academic Search

A charged holostar is an exact solution of the Einstein field equations. Its interior matter distribution rho = 1 \\/ (8 pi r^2) is singularity free with an overall string equation of state. It has a boundary membrane of tangential pressure (but no mass-energy) situated roughly a Planck coordinate distance outside of the outer horizon of the RN-solution with the

Michael Petri

2003-01-01

197

Theoretical modelling of the compaction curve  

Microsoft Academic Search

Soil compaction is one of the major activities in geotechnical engineering involving earthworks. The compaction curve is used to find the optimum water content that maximizes dry density. Since its introduction by Proctor in 1933, several researchers have provided qualitative explanations for the inverted parabolic shape of the compaction curve. However, fundamental research on the compaction process and the evolution

N. Kurucuk; J. Kodikara; D. G. Fredlund

2008-01-01

198

Blue ellipticals in compact groups  

NASA Technical Reports Server (NTRS)

By studying galaxies in compact groups, the authors examine the hypothesis that mergers of spiral galaxies make elliptical galaxies. The authors combine dynamical models of the merger-rich compact group environment with stellar evolution models and predict that roughly 15 percent of compact group ellipticals should be 0.15 mag bluer in B - R color than normal ellipticals. The published colors of these galaxies suggest the existence of this predicted blue population, but a normal distribution with large random errors can not be ruled out based on these data alone. However, the authors have new ultraviolet blue visual data which confirm the blue color of the two ellipticals with blue B - R colors for which they have their own colors. This confirmation of a population of blue ellipticals indicates that interactions are occurring in compact groups, but a blue color in one index alone does not require that these ellipticals are recent products of the merger of two spirals. The authors demonstrate how optical spectroscopy in the blue may distinguish between a true spiral + spiral merger and the swallowing of a gas-rich system by an already formed elliptical. The authors also show that the sum of the luminosity of the galaxies in each group is consistent with the hypothesis that the final stage in the evolution of compact group is an elliptical galaxy.

Zepf, Stephen E.; Whitmore, Bradley C.

1990-01-01

199

Compact orthogonal NMR field sensor  

DOEpatents

A Compact Orthogonal Field Sensor for emitting two orthogonal electro-magnetic fields in a common space. More particularly, a replacement inductor for existing NMR (Nuclear Magnetic Resonance) sensors to allow for NMR imaging. The Compact Orthogonal Field Sensor has a conductive coil and a central conductor electrically connected in series. The central conductor is at least partially surrounded by the coil. The coil and central conductor are electrically or electro-magnetically connected to a device having a means for producing or inducing a current through the coil and central conductor. The Compact Orthogonal Field Sensor can be used in NMR imaging applications to determine the position and the associated NMR spectrum of a sample within the electro-magnetic field of the central conductor.

Gerald, II, Rex E. (Brookfield, IL); Rathke, Jerome W. (Homer Glen, IL)

2009-02-03

200

Charged poles?  

NSDL National Science Digital Library

A significant portion of the recent work in the field of physics education research has been concerned with the identification of alternate conceptions (Driver and Easley, 1978) that students have about physical systems. Most of this work has been concentrated in the area of mechanics. There has been some work done in the area of electricity and magnetism but, by comparison, this area has received relatively little attention. The author reports on a study designed to determine if student difficulties in understanding the interactions of electric charges with magnetic fields might be caused, at least in part, by an alternate conception. In discussions among physics teachers one often hears several reasons proposed for these difficulties. One reason given is that magnetic force situations are three dimensional. A second one is that the right hand rule is an unusual procedure which is often misunderstood. These matters are almost certainly involved, but might there not also be some alternate conception causing students difficulty? The purpose of the study was to determine whether the students thought of magnetic poles as exerting forces directly on electric charges, in a manner similar to the behaviour of electrostatic charges.

Maloney, David

2006-05-24

201

Compact intermediates in RNA folding  

SciTech Connect

Large noncoding RNAs fold into their biologically functional structures via compact yet disordered intermediates, which couple the stable secondary structure of the RNA with the emerging tertiary fold. The specificity of the collapse transition, which coincides with the assembly of helical domains, depends on RNA sequence and counterions. It determines the specificity of the folding pathways and the magnitude of the free energy barriers to the ensuing search for the native conformation. By coupling helix assembly with nascent tertiary interactions, compact folding intermediates in RNA also play a crucial role in ligand binding and RNA-protein recognition.

Woodson, S.A. (JHU)

2011-12-14

202

VARIABLE MOMENTUM COMPACTION LATTICE STUDIES.  

SciTech Connect

The VUV storage ring at the National Synchrotron Light Source was used to study the impact of changes in the momentum compaction factors over a large range from positive to negative values. Changes in bunch length and synchrotron tune were measured versus current and RF parameters for these different lattices. By controlling both the first and second-order momentum compaction factors, a lattice was developed in which a pair of alpha buckets was created within the energy aperture of the vacuum chamber and beam was stored simultaneously in both buckets.

KRAMER,S.; MURPHY,J.B.

1999-03-29

203

Stability competition between the layered and compact Cu16 clusters  

NASA Astrophysics Data System (ADS)

Copper clusters experience a shape variation from layered to compact at the aggregation number of N = 16. Based on an extensive search for the structures of the low-lying neutral and charged isomers of Cu16 clusters, we address in this study the challenge in a structure search for clusters at shape-variation sizes, which arises from the structural diversity of the low-lying isomers. In order to reduce the bias on the structures with different shapes, a multi-step approach with a large number of candidates is applied to screen the structure pools which are necessarily larger than usual structure search of other sizes. In addition to the previously reported layered and compact structures, a third kind of structure, which can be recognized as a hybrid of layered and compact structures, is identified. Moreover, one of these hybrid structures is predicted to be most stable among the isomers. These hybrid structures not only bridge the structural and electronic properties of the distinct layered and compact structures, but also help understand the growth pattern of copper clusters. A set of new structures of anionic and cationic Cu16 isomers is also presented, starting from the newly established structure pool. The computed properties based on the identified neutral and ionic ground-state structures agree well with the available experimental data.

Zhu, W. H.; Yang, F.; Zeng, Q.; Yang, M. L.; Jackson, K. A.

2012-08-01

204

ULTRA-COMPACT ACCELERATOR TECHNOLOGIES FOR APPLICATION IN NUCLEAR TECHNIQUES  

SciTech Connect

We report on compact accelerator technology development for potential use as a pulsed neutron source quantitative post verifier. The technology is derived from our on-going compact accelerator technology development program for radiography under the US Department of Energy and for a clinic sized compact proton therapy systems under an industry sponsored Cooperative Research and Development Agreement. The accelerator technique relies on the synchronous discharge of a prompt pulse generating stacked transmission line structure with the beam transit. The goal of this technology is to achieve approx10 MV/m gradients for 10 s of nanoseconds pulses and approx100 MV/m gradients for approx1 ns systems. As a post verifier for supplementing existing x-ray equipment, this system can remain in a charged, stand-by state with little or no energy consumption. We describe the progress of our overall component development effort with the multilayer dielectric wall insulators (i.e., the accelerator wall), compact power supply technology, kHz repetition-rate surface flashover ion sources, and the prompt pulse generation system consisting of wide-bandgap switches and high performance dielectric materials.

Sampayan, S.; Caporaso, G.; Chen, Y.-J.; Falabella, S.; Guethlein, G.; Harris, J. R.; Hawkins, S.; Holmes, C.; Nelson, S.; Paul, A. C.; Poole, B.; Sanders, D.; Sitaraman, S.; Sullivan, J.; Wang, L.; Watson, J. [Beam Research Program, Lawrence Livermore National Laboratory, P.O. Box 808, L-645 Livermore, CA 94551 (United States); Carazo, V. [MMech, State College, PA 16803 (United States); Guse, S.; Pearson, D.; Schmidt, R. [CPAC Inc., Livermore, CA 94550 (United States)

2009-12-02

205

Mesoscale simulations of powder compaction  

NASA Astrophysics Data System (ADS)

Mesoscale 3D simulations of metal and ceramic powder compaction in shock waves have been performed with an Eulerian hydrocode GEODYN. The approach was validated by simulating shock compaction of porous well-characterized ductile metal using Steinberg material model. Results of the simulations with handbook values for parameters of solid 2024 aluminum have good agreement with experimental compaction curves and wave profiles. Brittle ceramic materials are not so well studied as metals, so material model for ceramic (tungsten carbide) has been fitted to shock compression experiments of non-porous samples and further calibrated to experimental match compaction curves. Direct simulations of gas gun experiments with ceramic powder have been performed and showed good agreement with experimental data. Numerical shock wave profile has same character and thickness as measured with VISAR. Numerical results show evidence of hard-to-explain reshock states above the single-shock Hugoniot line, which have also been observed in the experiments. We found that to receive good quantitative agreement with experiment it is essential to perform 3D simulations, since 2D results tend to underpredict stress levels for high-porosity powders regardless of material properties. We developed a process to extract macroscale information for the simulation which can be directly used in calibration of continuum model for heterogeneous media.

Lomov, Ilya; Antoun, Tarabay; Liu, Benjamin

2009-06-01

206

Compact Marx generator test system  

Microsoft Academic Search

Marx generators have been built with a wide span of physical size and output capability, ranging from circuit board scale devices of a few stages up to systems capable of producing many Megavolts and occupying entire buildings. Our focus in this paper is the development of a capability to explore compact Marx generator (CMG) devices, where we arbitrarily define a

F. E. Peterkin; B. J. Hankla; J. L. Stevens; J. F. Sharrow; D. C. Stoudt

2002-01-01

207

Compact Microscope Imaging System Developed.  

National Technical Information Service (NTIS)

The Compact Microscope Imaging System (CMIS) is a diagnostic tool with intelligent controls for use in space, industrial, medical, and security applications. The CMIS can be used in situ with a minimum amount of user intervention. This system, which was d...

M. McDowell

2001-01-01

208

Compact range techniques and measurements  

Microsoft Academic Search

Compact range techniques for measuring the gain patterns of full-size microwave antennas and for making radar reflectivity measurements are described. The basic principle of this technique is the use of a large collimating device to generate a uniform plane wave across the aperture of a target or antenna without requiring the normal far-field separation. Two different collimating devices were used

R. Johnson; H. Ecker; R. Moore

1969-01-01

209

Compact high-voltage structures.  

National Technical Information Service (NTIS)

A basic understanding of the critical issues limiting the compactness of high-voltage systems is required for the next generation of impulse generators. In the process of optimizing the design of a highly reliable solid-dielectric over-voltage switch, an ...

M. Wilson D. A. Goerz

1997-01-01

210

Modelling of compact fluorescent lamps  

Microsoft Academic Search

Compact fluorescent lamps (CFLs) are increasingly being used in households and commercial buildings because of the desire to reduce electricity usage. CFLs are nonlinear, which raises concerns over the widespread use of CFLs due to possible adverse effects on harmonic voltage levels in the distribution system. Laboratory tests were performed on more than 23 brands of CFLs sold in New

Z. Wei; N. R. Watson; L. P. Frater

2008-01-01

211

Oil Shale Compaction Experimental Results.  

National Technical Information Service (NTIS)

Oil shale compaction reduces the void volume available for gas flow in vertical modified in situ (VMIS) retorts. The mechanical forces caused by the weight of the overlying shale can equal 700 kPa near the bottom of commercial retorts. Clear evidence of s...

L. J. Fahy

1985-01-01

212

Compact color schlieren optical system  

NASA Technical Reports Server (NTRS)

A compact optical system for use with rainbow schlieren deflectometry is described. Both halves of the optical system consist of well-corrected telescopes whose refractive elements are all from manufacturer's stock catalogs, with the reflective primary being a spherical surface. As a result, the system is relatively easy to construct and meets the requirement of long focal length for quantitative rainbow schlieren measurements.

Buchele, Donald R.; Griffin, Devon W.

1993-01-01

213

Mesoscale Simulations of Power Compaction  

SciTech Connect

Mesoscale 3D simulations of metal and ceramic powder compaction in shock waves have been performed with an Eulerian hydrocode GEODYN. The approach was validated by simulating shock compaction of porous well-characterized ductile metal using Steinberg material model. Results of the simulations with handbook values for parameters of solid 2024 aluminum have good agreement with experimental compaction curves and wave profiles. Brittle ceramic materials are not so well studied as metals, so material model for ceramic (tungsten carbide) has been fitted to shock compression experiments of non-porous samples and further calibrated to match experimental compaction curves. Direct simulations of gas gun experiments with ceramic powder have been performed and showed good agreement with experimental data. Numerical shock wave profile has same character and thickness as measured with VISAR. Numerical results show reshock states above the single-shock Hugoniot line also observed in experiments. They found that to receive good quantitative agreement with experiment it is essential to perform 3D simulations.

Lomov, I; Fujino, D; Antoun, T; Liu, B

2009-08-06

214

High flux compact neutron generators.  

National Technical Information Service (NTIS)

Compact high flux neutron generators are developed at the Lawrence Berkeley National Laboratory. The neutron production is based on D-D or D-T reaction. The deuterium or tritium ions are produced from plasma using either a 2 MHz or 13.56 MHz radio frequen...

J. Reijonen T. P. Lou B. Tolmachoff K. N. Leung J. Verbeke

2001-01-01

215

Compact Circuit Preprocesses Accelerometer Output  

NASA Technical Reports Server (NTRS)

Compact electronic circuit transfers dc power to, and preprocesses ac output of, accelerometer and associated preamplifier. Incorporated into accelerometer case during initial fabrication or retrofit onto commercial accelerometer. Made of commercial integrated circuits and other conventional components; made smaller by use of micrologic and surface-mount technology.

Bozeman, Richard J., Jr.

1993-01-01

216

Colloid diffusion coefficients in compacted and consolidated clay barriers: Compaction density and colloid size effects  

NASA Astrophysics Data System (ADS)

An experimental methodology applying the nuclear ion beam technique Rutherford Backscattering Spectrometry (RBS) is used to measure colloid diffusion profiles within three different types of clay: consolidated Opalinus clay (Switzerland), Callovo-Oxfordian clay (France) and FEBEX bentonite (Spain) compacted at different densities. The RBS technique is widely applied in materials science and it was selected because it allows the measurement of concentration profiles at short range distances (?m). The effects of colloid size, clay type and clay density were analyzed with negatively charged Au colloids of 2, 20 and 40 nm. Apparent diffusion coefficients ( Da) for gold colloids could be measured and Da values ranged from (10 -18 to 10 -19 m 2/s). The larger diffusion coefficient was measured for 2 nm colloids in the Opalinus clay with Da(Au 2 nm) = (2.1 ± 0.5) × 10 -18 m 2/s. The accessible porosity for colloids is even lower than that measured for anions, since not only anion exclusion but also size exclusion hinders diffusion. For example, 40 nm colloids did not accede at all to bentonite compacted at higher densities.

Alonso, Ursula; Missana, Tiziana; Garcia-Gutierrez, Miguel; Patelli, Alessandro; Albarran, Nairoby; Rigato, Valentino

217

Compact merons and skyrmions in thin chiral magnetic films  

SciTech Connect

A meron is a controversial topological excitation because it carries just one-half of the skyrmion number. A vortex in thin magnetic films has been argued to be a half-skyrmion, i.e., a meron. We present another type of merons, investigating the two-dimensional nonlinear sigma model together with the Dzyaloshinskii-Moriya interaction. Here, the vortex number of a meron is zero. Basic topological excitations are merons and skyrmions. They behave as if they were free particles. A prominent feature is that the topological charge density is strictly confined within compact domains. We propose an analytic approach for these compact excitations, and construct a phase diagram. It is comprised of the helix, meron, skyrmion-crystal, skyrmion-gas, and ferromagnet phases. It captures the essential nature of the experimental data recently performed in chiral magnets such as MnSi and FeCoSi thin films.

Ezawa, Motohiko [Department of Applied Physics, University of Tokyo, Hongo 7-3-1, 113-8656 (Japan)

2011-03-01

218

Effect of Compaction and Increase of Saturation after Compaction on the Engineering Properties of Compacted Clay.  

National Technical Information Service (NTIS)

Laboratory test specimens of kaolin clay were prepared at four levels of impact compaction effort over a wide range of moisture contents. The specimens were than wetted by capillarity either to their plastic limit (36 percent) under 2 to 4 psi lateral con...

C. A. Pagen C. L. Wang B. N. Jagannath

1968-01-01

219

Dynamic Compaction of Metal and Ceramic Powders.  

National Technical Information Service (NTIS)

The state of the art and the technological potential for the dynamic consolidation of metal and ceramic powders were assessed. Fundamental consideration of dynamic consolidation, consolidation phenomena during dynamic compaction, dynamic compaction and co...

V. D. Linse O. R. Bergmann C. F. Cline J. D. Mote H. Palmour

1983-01-01

220

Branched Nanowire Architectures for Compact Power Sources.  

National Technical Information Service (NTIS)

Efficient compact power sources are critical to future mobile technologies, yet limitations with existing sources have restricted development. The objective of this research is to exploit advances in nanoscience to enable new capabilities in compact biofu...

C. M. Lieber

2009-01-01

221

Tank farms compacted low level waste  

SciTech Connect

This report describes the process of Low Level Waste (LLW) volume reduction by compaction. Also included is the data used for characterization of LLW destined for compaction. Scaling factors (ratios) are formed based on data contained in this report.

Waters, M.S., Westinghouse Hanford

1996-07-01

222

Compact Process Development at Babcock and Wilcox.  

National Technical Information Service (NTIS)

Multiple process approaches have been used historically to manufacture cylindrical nuclear fuel compacts. Scale-up of fuel compacting was required for the Next Generation Nuclear Plant to achieve an economically viable automated production process capable...

E. Shaber J. Phillips

2012-01-01

223

Lithium ion source for satellite charge control  

NASA Astrophysics Data System (ADS)

A lithium ion source using thermal emission from mineral beta-eucryptite was investigated as a possible control device for spacecraft charging. This source can be used for control of positively charged spacecraft potentials in sunlight and differentially charged spacecraft surfaces in shadow. The dependence is studied of the emitted ion current on several parameters: source temperature (power input), source bias potentials and potentials applied to simulated spacecraft geometries. Saturation current of about 5.8 micro amp were measured at an extraction potentials of 100 Volts from a source of 0.317 sq cm surface area with a power input of 18 Watts. The lifetime due to ion exhaustion was found to be approx. 200 hours for this compact source. The results indicate that this type of ion source may represent an effective charge control device for spacecraft.

Song, Tae I.

1990-06-01

224

Charged particle distributions in Jupiter's magnetosphere  

Microsoft Academic Search

In situ data from the Pioneer and Voyager spacecraft, supplemented by earth-based observations and theoretical considerations, are used as the basis for the present quantitative, compact model of the 1 eV-several MeV charged particle distribution in the Jovian magnetosphere. The thermal plasma parameters of convection speed, number density, and characteristic energy, are specified as functions of position for electrons and

Neil Divine; H. B. Garrett

1983-01-01

225

Charged Membranes  

NSDL National Science Digital Library

This Teaching Resource provides three animated lessons that describe the storage and utilization of energy across plasma membranes. The “Na,K ATPase” animation explains how these pumps establish the electrochemical gradient that stores energy across plasma membranes. The “ATP synthesizing complexes” animation shows how these complexes transfer energy from the inner mitochondrial membrane to adenosine triphosphate (ATP). The “action potential” lesson explains how charged membranes are used to propagate signals along the axons of neurons. These animations serve as valuable resources for any collegiate-level course that describes these important factors. Courses that might employ them include introductory biology, biochemistry, biophysics, cell biology, pharmacology, and physiology.

Jack D. Thatcher (Lewisburg;West Virginia School of Osteopathic Medicine REV)

2013-04-16

226

The hot compaction of polyethylene terephthalate  

Microsoft Academic Search

A process is described for the successful compaction of polyethylene terephthalate fibres. The measurement of mechanical properties shows that a very high proportion of the original fibre properties are retained and that the compacted samples have a good degree of coherence. Electron microscopy studies of suitably etched samples reveals the effect of the compaction temperature on the structure of the

J. Rasburn; P. J. Hine; I. M. Ward; R. H. Olley; D. C. Bassett; M. A. Kabeel

1995-01-01

227

Effect of {zeta} potential on the strength of compacted coal logs  

SciTech Connect

Coal can be compacted into solid cylinders called coal logs to facilitate handling and transportation. It is hypothesized and proved experimentally herein that by altering the {zeta} potential of coal to achieve the isoelectric point, the strength and abrasion resistance of compacted coal logs can be significantly improved. Experimental data providing the evidence are reported herein. It is theorized that by zeroing the {zeta} potential of the coal, the charges on coal particles are neutralized, and the electrostatic repelling force between coal particles containing like charges is eliminated. This brings the particles closer together with less compaction pressure and force. This method to improve coal agglomerate strength may be applicable to briquetting and pelletizing of fine particles of materials wetted by water.

Liu, H.; Lin, Y.; Marrero, T.R. [Univ. of Missouri, Columbia, MO (United States). Capsule Pipeline Research Center] [Univ. of Missouri, Columbia, MO (United States). Capsule Pipeline Research Center

1996-01-01

228

Compact torus studies: Final report  

SciTech Connect

The compact torus (CT) device has been proposed for use in some applications which are of interest in Laboratory programs in the areas of pulsed power and inertial confinement fusion. These applications involve compression and acceleration of CT plasmas. The RACE (Ring Accelerator Experiment) experimental program at Livermore has been initiated to study these applications. The work reported here involves studies of plasma physics and other aspects of these compact torus applications. The studies conducted identify specific problem areas associated with the CT device and examine these areas in some detail. This report contains studies of three particular problem areas of the CT applications. These three areas are: the general nonlinear properties of the CT as a magnetohydrodynamic (MHD) equilibrium, particle simulation of the compression of the CT, with a focus on the non-MHD effects, and nonlinear RF interaction problems in the CT.

Morse, E.C.

1987-06-01

229

Compact lanthanum hexaboride hollow cathode  

NASA Astrophysics Data System (ADS)

A compact lanthanum hexaboride hollow cathode has been developed for space applications where size and mass are important and research and industrial applications where access for implementation might be limited. The cathode design features a refractory metal cathode tube that is easily manufactured, mechanically captured orifice and end plates to eliminate expensive e-beam welding, graphite sleeves to provide a diffusion boundary to protect the LaB6 insert from chemical reactions with the refractory metal tube, and several heater designs to provide long life. The compact LaB6 hollow cathode assembly including emitter, support tube, heater, and keeper electrode is less than 2 cm in diameter and has been fabricated in lengths of 6-15 cm for different applications. The cathode has been operated continuously at discharge currents of 5-60 A in xenon. Slightly larger diameter versions of this design have operated at up to 100 A of discharge current.

Goebel, Dan M.; Watkins, Ronald M.

2010-08-01

230

Compact lanthanum hexaboride hollow cathode.  

PubMed

A compact lanthanum hexaboride hollow cathode has been developed for space applications where size and mass are important and research and industrial applications where access for implementation might be limited. The cathode design features a refractory metal cathode tube that is easily manufactured, mechanically captured orifice and end plates to eliminate expensive e-beam welding, graphite sleeves to provide a diffusion boundary to protect the LaB6 insert from chemical reactions with the refractory metal tube, and several heater designs to provide long life. The compact LaB(6) hollow cathode assembly including emitter, support tube, heater, and keeper electrode is less than 2 cm in diameter and has been fabricated in lengths of 6-15 cm for different applications. The cathode has been operated continuously at discharge currents of 5-60 A in xenon. Slightly larger diameter versions of this design have operated at up to 100 A of discharge current. PMID:20815605

Goebel, Dan M; Watkins, Ronald M

2010-08-01

231

The Atacama Compact Array (ACA)  

NASA Astrophysics Data System (ADS)

For realizing high fidelity of imaging with mosaicing observations, the Atacama Large Millimeter/submillimeter Array (ALMA) consists of a homogeneous array of 12 m antennas (12 m Array) and the Atacama Compact Array (ACA) in order to cover all spatial frequency Fourier components of the brightness distribution of observed sources. The array is located at an altitude site of about 5000m with an operating wavelength range of 0.3 to 3mm. ACA is an array composed of four 12 m dishes [TP (Total Power) Array] and twelve 7 m dishes (7 m Array). The 7 m Array has a very compact configuration to take short-baseline data corresponding to the low spatial frequency Fourier components. The 7 m Array has two configurations extended over 30--50m to avoid shadowing at low elevation. The scientific importances and operation concepts of ACA, and the system design of ACA and its performance are presented in this paper.

Iguchi, Satoru; Morita, Koh-Ichiro; Sugimoto, Masahiro; Vila Vilaró, Baltasar; Saito, Masao; Hasegawa, Tetsuo; Kawabe, Ryohei; Tatematsu, Ken'ichi; Seiichi, Seiichi; Kiuchi, Hitoshi; Okumura, Sachiko K.; Kosugi, George; Inatani, Junji; Takakuwa, Shigehisa; Iono, Daisuke; Kamazaki, Takeshi; Ogasawara, Ryusuke; Ishiguro, Masato

2009-02-01

232

High flux compact neutron generators  

Microsoft Academic Search

Compact high flux neutron generators are developed at the Lawrence Berkeley National Laboratory. The neutron production is based on D-D or D-T reaction. The deuterium or tritium ions are produced from plasma using either a 2 MHz or 13.56 MHz radio frequency (RF) discharge. RF-discharge yields high fraction of atomic species in the beam which enables higher neutron output. In

J. Reijonen; T.-P. Lou; B. Tolmachoff; K.-N. Leung; J. Verbeke; J. Vujic

2001-01-01

233

Compact optical microfiber phase modulator.  

PubMed

A compact optical microfiber phase modulator with MHz bandwidth is presented. A micrometer-diameter microfiber is wound on a millimeter-diameter piezoelectric ceramic rod with two electrodes. When a voltage is applied to the piezoelectric ceramic, the rod is strained, leading to a phase change along the microfiber; because of the small size, the optical microfiber phase modulator can have as high as a few MHz bandwidth response. PMID:22297339

Zhang, Xueliang; Belal, M; Chen, G Y; Song, Zhangqi; Brambilla, G; Newson, T P

2012-02-01

234

Compact solid state laser projector  

NASA Astrophysics Data System (ADS)

Industrial, consumer and military requirements for high resolution large screen data displays are taxing the capabilities of current display technologies,, such as cathode ray tubes, liquid crystal devices, digital mirror devices and plasma. Solid state laser projection provides a variety of advantages when used in displays with more than 1000 lines of resolution and measuring over 40 to 300 inches diagonally. Solid state laser technology can provide the best image quality in a compact package.

Gibeau, Frank C.; McKinney, Kerry K.

1997-07-01

235

Compact planar microwave blocking filters  

NASA Technical Reports Server (NTRS)

A compact planar microwave blocking filter includes a dielectric substrate and a plurality of filter unit elements disposed on the substrate. The filter unit elements are interconnected in a symmetrical series cascade with filter unit elements being organized in the series based on physical size. In the filter, a first filter unit element of the plurality of filter unit elements includes a low impedance open-ended line configured to reduce the shunt capacitance of the filter.

U-Yen, Kongpop (Inventor); Wollack, Edward J. (Inventor)

2012-01-01

236

CIT (Compact Ignition Tokamak) fueling  

SciTech Connect

A series of viewgraphs present issues related to the conceptual design of the Compact Ignition Tokamak. The presentation includes discussions of fueling issues, pellet injector technology, pellet ablation and penetration, particle confinement, and fueling scenarios. The author concludes that existing technology should be used for the basic injector while several options for enhanced velocity injectors are under development; adequate models exist for pellet ablation; and improvements in confinement models can come from the TFTR and JET programs. (DWL)

Houlberg, W.A.

1988-01-01

237

Compact portable diffraction moire interferometer  

DOEpatents

A compact and portable moire interferometer used to determine surface deformations of an object. The improved interferometer is comprised of a laser beam, optical and fiber optics devices coupling the beam to one or more evanescent wave splitters, and collimating lenses directing the split beam at one or more specimen gratings. Observations means including film and video cameras may be used to view and record the resultant fringe patterns. 7 figs.

Deason, V.A.; Ward, M.B.

1988-05-23

238

Nanotaper for compact mode conversion  

Microsoft Academic Search

We propose and demonstrate an efficient coupler for compact mode conversion between a fiber and a submicrometer waveguide. The coupler is composed of high-index-contrast materials and is based on a short taper with a nanometer-sized tip. We show that the micrometer-long silicon-on-insulator-based nanotaper coupler is able to efficiently convert both the mode field profile and the effective index, with a

Vilson R. Almeida; Roberto R. Panepucci; Michal Lipson

2003-01-01

239

Compact magnetic energy storage module  

DOEpatents

A superconducting compact magnetic energy storage module in which a plurality of superconducting toroids, each having a toroidally wound superconducting winding inside a poloidally wound superconducting winding, are stacked so that the flow of electricity in each toroidally wound superconducting winding is in a direction opposite from the direction of electrical flow in other contiguous superconducting toroids. This allows for minimal magnetic pollution outside of the module. 4 figures.

Prueitt, M.L.

1994-12-20

240

Compact Color Schlieren Optical System  

NASA Technical Reports Server (NTRS)

Compact, rugged optical system developed for use in rainbow schlieren deflectometry. Features unobscured telescope with focal-length/aperture-width ratio of 30. Made of carefully selected but relatively inexpensive parts. All of lenses stock items. By-product of design is optical system with loose tolerances on interlens spacing. One of resulting advantages, insensitivity to errors in fabrication of optomechanical mounts. Another advantage is ability to compensate for some of unit-to-unit variations inherent in stock lenses.

Buchele, Donald R.; Griffin, Devon W.

1996-01-01

241

Compact magnetic energy storage module  

DOEpatents

A superconducting compact magnetic energy storage module in which a plurality of superconducting toroids, each having a toroidally wound superconducting winding inside a poloidally wound superconducting winding, are stacked so that the flow of electricity in each toroidally wound superconducting winding is in a direction opposite from the direction of electrical flow in other contiguous superconducting toroids. This allows for minimal magnetic pollution outside of the module.

Prueitt, Melvin L. (Los Alamos, NM)

1994-01-01

242

A tandem-based compact dual-energy gamma generator  

NASA Astrophysics Data System (ADS)

A dual-energy tandem-type gamma generator has been developed at E. O. Lawrence Berkeley National Laboratory and Sandia National Laboratories. The tandem accelerator geometry allows higher energy nuclear reactions to be reached, thereby allowing more flexible generation of MeV-energy gammas for active interrogation applications. Both positively charged ions and atoms of hydrogen are created from negative ions via a gas stripper. In this paper, we show first results of the working tandem-based gamma generator and that a gas stripper can be utilized in a compact source design. Preliminary results of monoenergetic gamma production are shown.

Persaud, A.; Kwan, J. W.; Leitner, M.; Leung, K.-N.; Ludewigt, B.; Tanaka, N.; Waldron, W.; Wilde, S.; Antolak, A. J.; Morse, D. H.; Raber, T.

2010-02-01

243

Compaction with automatic jog introduction  

NASA Astrophysics Data System (ADS)

This thesis presents an algorithm for one-dimensional compaction of VLSI layouts. It differs from older methods in treating wires not as objects to be moved, but as constraints on the positions of other circuit components. These constraints are determined for each wiring layer using the theory of planar routing. Assuming that the wiring layers can be treated independently, the algorithm minimizes the width of a layout, automatically inserting as many jogs in wires as necessary. It runs in time 0(n4) on input of size n. Several heuristics are suggested for improving the algorithm's practical performance. The compaction algorithm takes as input a data structure called a sketch, which explicitly distinguishes between flexible components (wires) and rigid components (modules). The algorithm first finds constraints on the positions of modules that ensure enough space is left for wires. Next, it solves the system of constraints by a standard graph-theoretic technique, obtaining a placement for the modules. It then relies on a single-layer router to restore the wires to each circuit layer. An efficient single-layer router is already known; it is able to minimize the length of every wire, though not the number of jogs. As given, the compaction algorithm applies only to a VLSI model that requires wires to run a rectilinear grid. This restriction is needed only because the theory of planar routing (and single-layer routers) has not yet been extended to other models.

Maley, F. M.

1986-05-01

244

Analysis of compact and sealed RPCs feasibility  

NASA Astrophysics Data System (ADS)

In this article, the feasibility of developing compact and portable float glass sealed Resistive Plate Chambers, sRPCs, is analyzed. For this purpose, several small (80 cm2) sealed chambers have been constructed using inexpensive materials like windows float glass, copper tape and nylon fishing line. For the sake of simplicity, during this first development stage, only R134a has been used as ionizing gas. In order to distinguish gas leakage from internal gas degradation, a couple of sRPCs were tested inside a box with flowing gas: one with R134a and another with N2. Prompt charge, signal rising slope and operational current were used to assess chambers performance degradation during a two-week period. Regarding these variables, small leakages were spotted as the main reason for the performance degradation observed after about one week of steady operation at the sRPC working in N2 environment. The sRPC working in an R134a environment did not show any significative degradation during the whole test. A discussion on merits and limitations of the proposed design is provided.

Morales, M.; Rodríguez-Sánchez, J. L.; Garzón, J. A.

2013-03-01

245

Electron Strippers for Compact Neutron Generators  

NASA Astrophysics Data System (ADS)

The next generation of compact tandem-type DD or DT neutron generators requires a robust electron stripper with high charge exchange efficiency. In this study, stripping foils of various types were tested, and the H- to H+ conversion efficiency, endurance to the heat load, and durability were investigated in terms of suitability in the tandem-type neutron generator. In the experiments, a H- beam was accelerated to about 180 keV, passes through a stripping foil, and produces a mixed beam of H-, H0, and H+. These ions were separated by an electric field, and detected by a movable Faraday cup to determine the conversion efficiency. The experimental results using thin foils of diamond-like carbon, gold, and carbon nano-tubes revealed issues on the robustness. As a new concept, a H- beam was injected onto a metal surface with an oblique angle, and reflected H+ ions are detected. It was found that the conversion efficiency, H+ fraction in the reflected particles, depends on the surface condition, with the maximum value of about 90%.

Terai, K.; Tanaka, N.; Kisaki, M.; Tsugawa, K.; Okamoto, A.; Kitajima, S.; Sasao, M.; Takeno, T.; Antolak, A. J.; Leung, K. N.; Wada, M.

2011-09-01

246

Electron Strippers for Compact Neutron Generators  

SciTech Connect

The next generation of compact tandem-type DD or DT neutron generators requires a robust electron stripper with high charge exchange efficiency. In this study, stripping foils of various types were tested, and the H{sup -} to H{sup +} conversion efficiency, endurance to the heat load, and durability were investigated in terms of suitability in the tandem-type neutron generator. In the experiments, a H{sup -} beam was accelerated to about 180 keV, passes through a stripping foil, and produces a mixed beam of H{sup -}, H{sup 0}, and H{sup +}. These ions were separated by an electric field, and detected by a movable Faraday cup to determine the conversion efficiency. The experimental results using thin foils of diamond-like carbon, gold, and carbon nano-tubes revealed issues on the robustness. As a new concept, a H{sup -} beam was injected onto a metal surface with an oblique angle, and reflected H{sup +} ions are detected. It was found that the conversion efficiency, H{sup +} fraction in the reflected particles, depends on the surface condition, with the maximum value of about 90%.

Terai, K.; Tanaka, N.; Kisaki, M.; Tsugawa, K.; Okamoto, A.; Kitajima, S.; Sasao, M. [Graduate school of Engineering, Tohoku University, Aoba, Sendai, Miyagi 980-8579 (Japan); Takeno, T. [Tohoku University International Advanced Research and Education Organization, Aoba, Sendai, Miyagi 980-8578 (Japan); Antolak, A. J. [Sandia National Laboratories, Livermore, California 94550 (United States); Leung, K. N. [Lawrence Berkeley National Laboratory and Nuclear Engineering Dept., University of California, Berkeley (United States); Wada, M. [Doshisha University, Kyotanabe, Kyoto, 610-0321 (Japan)

2011-09-26

247

Weakly Charged Cationic Nanoparticles Induce DNA Bending and Strand Separation  

SciTech Connect

The understanding of interactions between double stranded (ds) DNA and charged nanoparticles will have a broad bearing on many important applications from drug delivery [ 1 4 ] to DNAtemplated metallization. [ 5 , 6 ] Cationic nanoparticles (NPs) can bind to DNA, a negatively charged molecule, through a combination of electrostatic attraction, groove binding, and intercalation. Such binding events induce changes in the conformation of a DNA strand. In nature, DNA wraps around a cylindrical protein assembly (diameter and height of 6 nm) [ 7 ] with an 220 positive charge, [ 8 ] creating the complex known as chromatin. Wrapping and bending of DNA has also been achieved in the laboratory through the binding of highly charged species such as molecular assemblies, [ 9 , 10 ] cationic dendrimers, [ 11 , 12 ] and nanoparticles. [ 13 15 ] The charge of a nanoparticle plays a crucial role in its ability to induce DNA structural changes. If a nanoparticle has a highly positive surface charge density, the DNA is likely to wrap and bend upon binding to the nanoparticle [ 13 ] (as in the case of chromatin). On the other hand, if a nanoparticle is weakly charged it will not induce dsDNA compaction. [ 9 , 10 , 15 ] Consequently, there is a transition zone from extended to compact DNA conformations which depends on the chemical nature of the nanoparticle and occurs for polycations with charges between 5 and 10. [ 9 ] While the interactions between highly charged NPs and DNA have been extensively studied, the processes that occur within the transition zone are less explored.

Railsback, Justin [North Carolina State University; Singh, Abhishek [North Carolina State University; Pearce, Ryan [North Carolina State University; McKnight, Timothy E [ORNL; Collazo, Ramon [North Carolina State University; Sitar, Zlatko [ORNL; Yingling, Yaroslava [North Carolina State University; Melechko, Anatoli Vasilievich [ORNL

2012-01-01

248

A compact 1 MV multi-element AMS system  

NASA Astrophysics Data System (ADS)

HVE has designed and built a compact 1 MV multi-element AMS system with a footprint of 3.8 m × 6.3 m. The system is primarily designed for the analysis of light elements like beryllium, carbon and aluminium, but it also supports the measurement of heavy ions like iodine and plutonium. The analysis of 14C is done using the charge state 1. For this, the accelerator terminal is designed for high stripper gas thickness to efficiently destroy the interfering molecules like 13CH and 12CH 2. For the analysis of 10Be, suppression of the isobaric 10B is achieved using an absorber foil that can be inserted in front of the electrostatic analyser. The analysis of 26Al can be done using charge-state 1 or 3. The rare isotopes are identified in a dual-anode high-resolution detector and a two-dimensional data acquisition system.

Klein, M. G.; Mous, D. J. W.; Gottdang, A.

2006-08-01

249

Simple, compact, high-repetition rate XeCl laser  

NASA Astrophysics Data System (ADS)

Operation of a compact corona-preionized XeCl excimer laser, simple in construction and utilizing all commercial components, is reported. The laser comprises a stainless-steel-tube vacuum/pressure vessel with a total gas volume of about 4.5 l, an excitation circuit of the capacitor charge transfer type, and two water-cooled copper pipe heat exchangers. An average output power in excess of 1 W was obtained at pulse repetition frequencies (PRF) of up to 750 Hz. A maximum efficiency of 0.15 percent is reported for PRF of 400 at a charging voltage of 25 kV. Finally, considerably longer gas lifetime is noted when helium was used as a buffer gas, as compared with that of neon, yielding a 10-percent reduction in power after more than 1 million firings.

Armandillo, E.; Grasso, G.; Salvetti, G.; Penco, E.

1985-05-01

250

Soil-water characteristic curves for compacted clays  

Microsoft Academic Search

Soil-water characteristic curves (SWCCs) are presented for four compacted clay barrier soils that were prepared at different compaction water contents (dry, wet, and optimum water content) and compactive efforts (standard and modified Proctor). The SWCCs were measured in the laboratory using pressure plate extractors. The shape of the SWCC depends on compaction water content and compactive effort, but compaction water

James M. Tinjum; Craig H. Benson; Lisa R. Blotz

1997-01-01

251

Charged gravastars admitting conformal motion  

NASA Astrophysics Data System (ADS)

We propose a new model of a gravastar admitting conformal motion. While retaining the framework of the Mazur-Mottola model, the gravastar is assumed to be internally charged, with an exterior defined by a Reissner-Nordström instead of a Schwarzschild line element. The solutions, obtained by exploiting an assumed conformal Killing vector, involve (i) the interior region, (ii) the shell, and (iii) the exterior region of the sphere. Of these three cases the first one is of primary interest since the total gravitational mass here turns out to be an electromagnetic mass under some specific conditions. This suggests that the interior de Sitter vacuum of a charged gravastar is essentially an electromagnetic mass model that must generate gravitational mass which provides a stable configuration by balancing the repulsive pressure arising from charge with its attractive gravity to avert a singularity. Therefore the present model, like the Mazur-Mottola model, results in the construction of a compact astrophysical object, as an alternative to a black hole. We have also analyzed various other aspects such as the stress energy tensor in the thin shell and the entropy of the system.

Usmani, A. A.; Rahaman, F.; Ray, Saibal; Nandi, K. K.; Kuhfittig, Peter K. F.; Rakib, Sk. A.; Hasan, Z.

2011-07-01

252

Compact Video Microscope Imaging System Implemented in Colloid Studies  

NASA Technical Reports Server (NTRS)

Long description Photographs showing fiber-optic light source, microscope and charge-coupled discharge (CCD) camera head connected to camera body, CCD camera body feeding data to image acquisition board in PC, and Cartesian robot controlled via PC board. The Compact Microscope Imaging System (CMIS) is a diagnostic tool with intelligent controls for use in space, industrial, medical, and security applications. CMIS can be used in situ with a minimum amount of user intervention. This system can scan, find areas of interest in, focus on, and acquire images automatically. Many multiple-cell experiments require microscopy for in situ observations; this is feasible only with compact microscope systems. CMIS is a miniature machine vision system that combines intelligent image processing with remote control. The software also has a user-friendly interface, which can be used independently of the hardware for further post-experiment analysis. CMIS has been successfully developed in the SML Laboratory at the NASA Glenn Research Center and adapted for use for colloid studies and is available for telescience experiments. The main innovations this year are an improved interface, optimized algorithms, and the ability to control conventional full-sized microscopes in addition to compact microscopes. The CMIS software-hardware interface is being integrated into our SML Analysis package, which will be a robust general-purpose image-processing package that can handle over 100 space and industrial applications.

McDowell, Mark

2002-01-01

253

Compaction of Space Mission Wastes  

NASA Technical Reports Server (NTRS)

The current solid waste management system employed on the International Space Station (ISS) consists of compaction, storage, and disposal. Wastes such plastic food packaging and trash are compacted manually and wrapped in duct tape footballs by the astronauts. Much of the waste is simply loaded either into the empty Russian Progress vehicle for destruction on reentry or into Shuttle for return to Earth. This manual method is wasteful of crew time and does not transition well to far term missions. Different wastes onboard spacecraft vary considerably in their characteristics and in the appropriate method of management. In advanced life support systems for far term missions, recovery of resources such as water from the wastes becomes important. However waste such as plastic food packaging, which constitutes a large fraction of solid waste (roughly 21% on ISS, more on long duration missions), contains minimal recoverable resource. The appropriate management of plastic waste is waste stabilization and volume minimization rather than resource recovery. This paper describes work that has begun at Ames Research Center on development of a heat melt compactor that can be used on near term and future missions, that can minimize crew interaction, and that can handle wastes with a significant plastic composition. The heat melt compactor takes advantage of the low melting point of plastics to compact plastic materials using a combination of heat and pressure. The US Navy has demonstrated successful development of a similar unit for shipboard application. Ames is building upon the basic approach demonstrated by the Navy to develop an advanced heat melt type compactor for space mission type wastes.

Fisher, John; Pisharody, Suresh; Wignarajah, K.

2004-01-01

254

Gravitational Waves from Compact Objects  

NASA Astrophysics Data System (ADS)

This thesis addresses problems in the generation and detection of gravitational waves from two types of sources: inspiraling compact binaries and rapidly rotating young neutron stars. Chapters 2 and 3 estimate the computational costs of a basic matched filtering strategy to search for inspiraling compact binaries. Chapter 2 (written in 1995) sets up the machinery for calculating costs and makes a rough estimate based on the waveforms and noise spectra available at the time. It also systematizes previously published methods of choosing the filters. Chapter 3 (written with B. S. Sathyaprakash in 1998) fine-tunes the machinery and updates the estimates of Chapter 2 using more current waveforms and noise spectra. Chapter 4 (written with Hideyuki Tagoshi and Akira Ohashi) concerns the post-Newtonian generation of gravitational waveforms from inspiraling compact binaries whose component objects spin about their own axes. It lays out a method of calculating post-Newtonian spin effects and calculates the lowest-order such effect not previously known (the second-post-Newtonian spin-orbit contribution to the waveforms in the absence of precession). Chapters 5 and 6 concern the Chandrasekhar-Friedman-Schutz (CFS) gravitational radiation instability as it applies to the r-modes of rapidly rotating young neutron stars. Chapter 5 (written with Lee Lindblom and Sharon M. Morsink) computes the viscous damping and gravitational radiation timescales of the r-modes and shows that viscosity does not suppress the CFS instability in hot young neutron stars. Chapter 6 (written with Lee Lindblom, Curt Cutler, Bernard F. Schutz, Alberto Vecchio, and Nils Andersson) computes approximate gravitational waveforms from young neutron stars spinning down due to the r-mode instability and estimates that these gravitational waves can be detected by the 'enhanced' LIGO interferometers if a suitable data analysis strategy is developed.

Owen, Benjamin James

255

Compact inertial confinement multireactor concepts  

SciTech Connect

Inertial confinement fusion (ICF) commercial-applications plant-optimum driver pulse repetition rates may exceed reactor pulse-repetition-rate capabilities. Thus, more than one reactor may be required for low-cost production of electric power, process heat, fissionable fuels, etc., in ICF plants. Substantial savings in expensive reactor containment cells and blankets can be realized by placing more than one reactor in a cell and by surrounding more than one reactor cavity with a single blanket system. There are also some potential disadvantages associated with close coupling in compact multicavity blankets and multireactor cells. Tradeoffs associated with several scenarios have been studied.

Pendergrass, J.H.

1985-01-01

256

Compact Airborne Spectral Sensor (COMPASS)  

NASA Astrophysics Data System (ADS)

The COMPACT Airborne Spectral Sensor (COMPASS) design is intended to demonstrate a new design concept for solar reflective hyper spectral systems for the Government. Capitalizing from recent focal plane developments, the COMPASS system utilizes a single FPA to cover the 0.4-2.35micrometers spectral region. This system also utilizes an Offner spectrometer design as well as an electron etched lithography curved grating technology pioneered by NASA/JPL. This paper also discusses the technical trades, which drove the design selection of COMPASS. When completed, the core COMPASS spectrometer design could be used in a large variety of configurations on a variety of aircraft.

Simi, Christopher G.; Winter, Edwin M.; Williams, Mary M.; Driscoll, David C.

2001-08-01

257

Shock compaction of molybdenum powder  

NASA Technical Reports Server (NTRS)

Shock recovery experiments which were carried out in the 9 to 12 GPa range on 1.4 distension Mo and appear adequate to compact to full density ( 45 (SIGMA)m) powders were examined. The stress levels, however, are below those calculated to be from 100 to approx. 22 GPa which a frictional heating model predicts are required to consolidate approx. 10 to 50 (SIGMA)m particles. The model predicts that powders that have a distension of m=1.6 shock pressures of 14 to 72 GPa are required to consolidate Mo powders in the 50 to 10 (SIGMA)m range.

Ahrens, T. J.; Kostka, D.; Vreeland, T., Jr.; Schwarz, R. B.; Kasiraj, P.

1983-01-01

258

Exceptionally bright, compact starburst nucleus  

SciTech Connect

Observations are reported of a remarkably bright (V about 13) starburst nucleus, 0833 + 652, which has been detected at radio, infrared, optical, ultraviolet, and X-ray wavelengths. Despite an observed flux at each of these wavelengths which is comparable to that of NGC 7714, often considered the 'prototypical' example of the starburst phenomenon, 0833 + 652 appears to be a previously uncataloged object. Its ease of detectability throughout the electromagnetic spectrum should make it useful for a variety of problems in the study of compact emission-line galaxies. 30 references.

Margon, B.; Anderson, S.F.; Mateo, M.; Fich, M.; Massey, P.

1988-11-01

259

Compact Radiometers Expand Climate Knowledge  

NASA Technical Reports Server (NTRS)

To gain a better understanding of Earth's water, energy, and carbon cycles, NASA plans to embark on the Soil Moisture Active and Passive mission in 2015. To prepare, Goddard Space Flight Center provided Small Business Innovation Research (SBIR) funding to ProSensing Inc., of Amherst, Massachusetts, to develop a compact ultrastable radiometer for sea surface salinity and soil moisture mapping. ProSensing incorporated small, low-cost, high-performance elements into just a few circuit boards and now offers two lightweight radiometers commercially. Government research agencies, university research groups, and large corporations around the world are using the devices for mapping soil moisture, ocean salinity, and wind speed.

2010-01-01

260

Intense Pulsed Neutron Emission from a Compact Pyroelectric Driven Accelerator  

SciTech Connect

Intense pulsed D-D neutron emission with rates >10{sup 10} n/s during the pulse, pulse widths of {approx}100's ns, and neutron yields >10 k per pulse are demonstrated in a compact pyroelectric accelerator. The accelerator consists of a small pyroelectric LiTaO{sub 3} crystal which provides the accelerating voltage and an independent compact spark plasma ion source. The crystal voltage versus temperature is characterized and compare well with theory. Results show neutron output per pulse that scales with voltage as V{approx}1.7. These neutron yields match a simple model of the system at low voltages but are lower than predicted at higher voltages due to charge losses not accounted for in the model. Interpretation of the data against modeling provides understanding of the accelerator and in general pyroelectric LiTaO{sub 3} crystals operated as charge limited negative high voltage targets. The findings overall serve as the proof-of-principle and basis for pyroelectric neutron generators that can be pulsed, giving peak neutron rates orders of magnitude greater than previous work, and notably increase the potential applications of pyroelectric based neutron generators.

Tang, V; Meyer, G; Falabella, S; Guethlein, G; Sampayan, S; Kerr, P; Rusnak, B; Morse, J

2008-10-08

261

The Telomere Binding Protein TRF2 Induces Chromatin Compaction  

PubMed Central

Mammalian telomeres are specialized chromatin structures that require the telomere binding protein, TRF2, for maintaining chromosome stability. In addition to its ability to modulate DNA repair activities, TRF2 also has direct effects on DNA structure and topology. Given that mammalian telomeric chromatin includes nucleosomes, we investigated the effect of this protein on chromatin structure. TRF2 bound to reconstituted telomeric nucleosomal fibers through both its basic N-terminus and its C-terminal DNA binding domain. Analytical agarose gel electrophoresis (AAGE) studies showed that TRF2 promoted the folding of nucleosomal arrays into more compact structures by neutralizing negative surface charge. A construct containing the N-terminal and TRFH domains together altered the charge and radius of nucleosomal arrays similarly to full-length TRF2 suggesting that TRF2-driven changes in global chromatin structure were largely due to these regions. However, the most compact chromatin structures were induced by the isolated basic N-terminal region, as judged by both AAGE and atomic force microscopy. Although the N-terminal region condensed nucleosomal array fibers, the TRFH domain, known to alter DNA topology, was required for stimulation of a strand invasion-like reaction with nucleosomal arrays. Optimal strand invasion also required the C-terminal DNA binding domain. Furthermore, the reaction was not stimulated on linear histone-free DNA. Our data suggest that nucleosomal chromatin has the ability to facilitate this activity of TRF2 which is thought to be involved in stabilizing looped telomere structures.

Baker, Asmaa M.; Fu, Qiang; Hayward, William; Victoria, Samuel; Pedroso, Ilene M.; Lindsay, Stuart M.; Fletcher, Terace M.

2011-01-01

262

Compact electron beam ion sources/traps: review and prospects.  

PubMed

The Dresden electron beam ion trap (EBIT)/electron beam ion source (EBIS) family are very compact and economically working table-top ion sources. We report on the development of three generations of such ion sources, the so-called Dresden EBIT, Dresden EBIS, and Dresden EBIS-A, respectively. The ion sources are classified by different currents of extractable ions at different charge states and by the x-ray spectra emitted by the ions inside the electron beam. We present examples of x-ray measurements and measured ion currents extracted from the ion sources at certain individual operating conditions. Ion charge states of up to Xe(48+) but also bare nuclei of lighter elements up to nickel have been extracted. The application potential of the ion sources is demonstrated via proof-of-concept applications employing an EBIT in a focused ion beam (FIB) column or using an EBIT for the production of nanostructures by single ion hits. Additionally we give first information about the next generation of the Dresden EBIS series. The so-called Dresden EBIS-SC is a compact and cryogen-free superconducting high-B-field EBIS for high-current operation. PMID:18315151

Zschornack, G; Kreller, M; Ovsyannikov, V P; Grossman, F; Kentsch, U; Schmidt, M; Ullmann, F; Heller, R

2008-02-01

263

Dense and Homogeneous Compaction of Fine Ceramic and Metallic Powders: High-Speed Centrifugal Compaction Process  

SciTech Connect

High-Speed Centrifugal Compaction Process (HCP) is a variation of colloidal compacting method, in which the powders sediment under huge centrifugal force. Compacting mechanism of HCP differs from conventional colloidal process such as slip casting. The unique compacting mechanism of HCP leads to a number of characteristics such as a higher compacting speed, wide applicability for net shape formation, flawless microstructure of the green compacts, etc. However, HCP also has several deteriorative characteristics that must be overcome to fully realize this process' full potential.

Suzuki, Hiroyuki Y. [Graduate School of Engineering, Hiroshima University, 1-4-1 Kagamiayma, Higashi-Hiroshima, Hiroshima, 739-8527 (Japan)

2008-02-15

264

Zinc-air batteries for forward field charging  

Microsoft Academic Search

In order to realize the operational and service cost savings through the use of rechargeable batteries, the dismounted soldier is burdened with the weight, volume and\\/or charging logistics of the batteries. By providing the soldier with a high energy density source and a lightweight compact battery charger, the burden imposed by rechargeable batteries in the forward field can be minimized.

T. B. Atwater

1998-01-01

265

Combined Velocity/Charge-To-Mass-Ratio Analyzer  

NASA Technical Reports Server (NTRS)

Instrument analyzes ions according to velocity and ratio of mass to electric charge. State-of-the-art combination of two instruments: time-of-flight analyzer and electrostatic analyzer functioning as mass spectrometer. Features include compactness, light weight, and low power. Terrestrial versions useful in chemical analysis, chromatography, and analysis of plasmas.

Chutjian, Ara; Orient, Otto J.; Bernius, Mark T.; Hodges, R. Richard

1992-01-01

266

Structural properties of compact groups  

NASA Technical Reports Server (NTRS)

We report the results of a systematic study of galaxies in the regions of Hickson compact groups. Our sample is composed of the 22 Hickson groups which are located in the southern hemisphere and have cz less than 9000 km/s. Making use of digitized images of IIIa-J plates that cover an area of 0.5 x 0.5 deg around each group, we were able to detect and classify images down to a magnitude limit of 19.5 in the B band. This limit is typically three magnitudes fainter than previous studies. Most groups show a statistically significant excess of fainter galaxies compared to the background. These fainter galaxies typically have a somewhat more extended spatial distribution than the brighter galaxies originally classified by Hickson. Our data suggest that Hickson groups have a wide range in density and radius, ranging from very compact structures with overdensities of the order of 10(exp 2) and crossing times of roughly 0.01 H(sub 0 sup -1), to much more diffuse structures, similar to loose groups, with overdensities of about 3 and crossing times of roughly 0.5 H(sub 0 sup -1).

De Carvalho, R. R.; Ribeiro, A. L. B.; Zepf, Stephen E.

1994-01-01

267

Incompletely compacted equilibrated ordinary chondrites  

SciTech Connect

We document the size distributions and locations of voids present within five highly porous equilibrated ordinary chondrites using high-resolution synchrotron X-ray microtomography ({mu}CT) and helium pycnometry. We found total porosities ranging from {approx}10 to 20% within these chondrites, and with {mu}CT we show that up to 64% of the void space is located within intergranular voids within the rock. Given the low (S1-S2) shock stages of the samples and the large voids between mineral grains, we conclude that these samples experienced unusually low amounts of compaction and shock loading throughout their entire post accretionary history. With Fe metal and FeS metal abundances and grain size distributions, we show that these chondrites formed naturally with greater than average porosities prior to parent body metamorphism. These materials were not 'fluffed' on their parent body by impact-related regolith gardening or events caused by seismic vibrations. Samples of all three chemical types of ordinary chondrites (LL, L, H) are represented in this study and we conclude that incomplete compaction is common within the asteroid belt.

Sasso, M.R.; Macke, R.J.; Boesenberg, J.S.; Britt, D.T.; Rovers, M.L.; Ebel, D.S.; Friedrich, J.M.; (Fordham)

2010-01-22

268

Compact Microscope Imaging System Developed  

NASA Technical Reports Server (NTRS)

The Compact Microscope Imaging System (CMIS) is a diagnostic tool with intelligent controls for use in space, industrial, medical, and security applications. The CMIS can be used in situ with a minimum amount of user intervention. This system, which was developed at the NASA Glenn Research Center, can scan, find areas of interest, focus, and acquire images automatically. Large numbers of multiple cell experiments require microscopy for in situ observations; this is only feasible with compact microscope systems. CMIS is a miniature machine vision system that combines intelligent image processing with remote control capabilities. The software also has a user-friendly interface that can be used independently of the hardware for post-experiment analysis. CMIS has potential commercial uses in the automated online inspection of precision parts, medical imaging, security industry (examination of currency in automated teller machines and fingerprint identification in secure entry locks), environmental industry (automated examination of soil/water samples), biomedical field (automated blood/cell analysis), and microscopy community. CMIS will improve research in several ways: It will expand the capabilities of MSD experiments utilizing microscope technology. It may be used in lunar and Martian experiments (Rover Robot). Because of its reduced size, it will enable experiments that were not feasible previously. It may be incorporated into existing shuttle orbiter and space station experiments, including glove-box-sized experiments as well as ground-based experiments.

McDowell, Mark

2001-01-01

269

Hydrostatic compaction of Microtherm HT.  

SciTech Connect

Two samples of jacketed Microtherm{reg_sign}HT were hydrostatically pressurized to maximum pressures of 29,000 psi to evaluate both pressure-volume response and change in bulk modulus as a function of density. During testing, each of the two samples exhibited large irreversible compactive volumetric strains with only small increases in pressure; however at volumetric strains of approximately 50%, the Microtherm{reg_sign}HT stiffened noticeably at ever increasing rates. At the maximum pressure of 29,000 psi, the volumetric strains for both samples were approximately 70%. Bulk modulus, as determined from hydrostatic unload/reload loops, increased by more than two-orders of magnitude (from about 4500 psi to over 500,000 psi) from an initial material density of {approx}0.3 g/cc to a final density of {approx}1.1 g/cc. An empirical fit to the density vs. bulk modulus data is K = 492769{rho}{sup 4.6548}, where K is the bulk modulus in psi, and {rho} is the material density in g/cm{sup 3}. The porosity decreased from 88% to {approx}20% indicating that much higher pressures would be required to compact the material fully.

Broome, Scott Thomas; Bauer, Stephen J.

2010-09-01

270

Compact submanifolds supporting singular interactions  

SciTech Connect

A quantum particle moving under the influence of singular interactions on embedded surfaces furnish an interesting example from the spectral point of view. In these problems, the possible occurrence of a bound-state is perhaps the most important aspect. Such systems can be introduced as quadratic forms and generically they do not require renormalization. Yet an alternative path through the resolvent is also beneficial to study various properties. In the present work, we address these issues for compact surfaces embedded in a class of ambient manifolds. We discover that there is an exact bound state solution written in terms of the heat kernel of the ambient manifold for a range of coupling strengths. Moreover, we develop techniques to estimate bounds on the ground state energy when several surfaces, each of which admits a bound state solution, coexist. -- Highlights: •Schrödinger operator with singular interactions supported on compact submanifolds. •Exact bound-state solution in terms of the heat kernel of the ambient manifold. •Generalization of the variational approach to a collection of submanifolds. •Existence of a lower bound for a unique ground state energy.

Kaynak, Burak Tevfik, E-mail: burak.kaynak@boun.edu.tr; Teoman Turgut, O., E-mail: turgutte@boun.edu.tr

2013-12-15

271

NRL compact accelerator theory studies  

NASA Astrophysics Data System (ADS)

NRL compact accelerator theory studies in support of the Spiral Line Induction Accelerator (SLIA) and the Recirculating Linear Accelerator (RLA) are summarized in a series of short papers. The first of these papers describes the ELBA 3-D beam simulation code, a particle code which was used to model beam stability and transport in both accelerators. The second paper presents and analytical model for the dangerous three-wave electromagnetic instability and defines parameter regimes for the SLIA where the instability can be completely stabilized. ELBA simulations of the SLIA in the various stability regimes, described by the analytical mode, are described in the next paper. The fourth paper includes additional ELBA simulations of beam transport in the SLIA, demonstrating that high eccentricity equilibria can lead to serious emittance growth. The effects of axisymmetric ion channel motion on beam transport in the RLA are discussed in the next paper. The sixth paper describes ELBA simulations of erosion and off-axis drifts in both straight and curved sections of the RLA. The final paper discusses the various atomic and surface plasma processes which may occur in compact accelerators.

Hubbard, Richard F.; Ali, A. Wahab; Joyce, Glenn; Krall, J.; Mako, F.; Serafim, P.; Slinker, S. P.; Sprangle, P.; Tang, C. M.

1990-08-01

272

Compacted carbon for electrochemical cells  

SciTech Connect

This invention provides compacted carbon that is useful in the electrode of an alkali metal/carbon electrochemical cell of improved capacity selected from the group consisting of: (a) coke having the following properties: (i) an x-ray density of at least 2.00 grams per cubic centimeters, (ii) a closed porosity of no greater than 5%, and (iii) an open porosity of no greater than 47%; and (b) graphite having the following properties: (i) an x-ray density of at least 2.20 grams per cubic centimeters, (ii) a closed porosity of no greater than 5%, and (iii) an open porosity of no greater than 25%. This invention also relates to an electrode for an alkali metal/carbon electrochemical cell comprising compacted carbon as described above and a binder. This invention further provides an alkali metal/carbon electrochemical cell comprising: (a) an electrode as described above, (b) a non-aqueous electrolytic solution comprising an organic aprotic solvent and an electrolytically conductive salt and an alkali metal, and (c) a counterelectrode.

Greinke, Ronald Alfred (Medina, OH); Lewis, Irwin Charles (Strongsville, OH)

1997-01-01

273

Compacted carbon for electrochemical cells  

DOEpatents

This invention provides compacted carbon that is useful in the electrode of an alkali metal/carbon electrochemical cell of improved capacity selected from the group consisting of: (a) coke having the following properties: (1) an x-ray density of at least 2.00 grams per cubic centimeters, (2) a closed porosity of no greater than 5%, and (3) an open porosity of no greater than 47%; and (b) graphite having the following properties: (1) an x-ray density of at least 2.20 grams per cubic centimeters, (2) a closed porosity of no greater than 5%, and (3) an open porosity of no greater than 25%. This invention also relates to an electrode for an alkali metal/carbon electrochemical cell comprising compacted carbon as described above and a binder. This invention further provides an alkali metal/carbon electrochemical cell comprising: (a) an electrode as described above, (b) a non-aqueous electrolytic solution comprising an organic aprotic solvent and an electrolytically conductive salt and an alkali metal, and (c) a counter electrode. 10 figs.

Greinke, R.A.; Lewis, I.C.

1997-10-14

274

Compact pulse forming line using barium titanate ceramic material.  

PubMed

Ceramic material has very high relative permittivity, so compact pulse forming line can be made using these materials. Barium titanate (BaTiO(3)) has a relative permittivity of 1200 so it is used for making compact pulse forming line (PFL). Barium titanate also has piezoelectric effects so it cracks during high voltages discharges due to stresses developed in it. Barium titanate is mixed with rubber which absorbs the piezoelectric stresses when the PFL is charged and regain its original shape after the discharge. A composite mixture of barium titanate with the neoprene rubber is prepared. The relative permittivity of the composite mixture is measured to be 85. A coaxial pulse forming line of inner diameter 120 mm, outer diameter 240 mm, and length 350 mm is made and the composite mixture of barium titanate and neoprene rubber is filled between the inner and outer cylinders. The PFL is charged up to 120 kV and discharged into 5 ? load. The voltage pulse of 70 kV, 21 ns is measured across the load. The conventional PFL is made up of oil or plastics dielectrics with the relative permittivity of 2-10 [D. R. Linde, CRC Handbook of Chemistry and Physics, 90th ed. (CRC, 2009); Xia et al., Rev. Sci. Instrum. 79, 086113 (2008); Yang et al., Rev. Sci. Instrum. 81, 43303 (2010)], which increases the length of PFL. We have reported the compactness in length achieved due to increase in relative permittivity of composite mixture by adding barium titanate in neoprene rubber. PMID:22129008

Kumar Sharma, Surender; Deb, P; Shukla, R; Prabaharan, T; Shyam, A

2011-11-01

275

Compact pulse forming line using barium titanate ceramic material  

NASA Astrophysics Data System (ADS)

Ceramic material has very high relative permittivity, so compact pulse forming line can be made using these materials. Barium titanate (BaTiO3) has a relative permittivity of 1200 so it is used for making compact pulse forming line (PFL). Barium titanate also has piezoelectric effects so it cracks during high voltages discharges due to stresses developed in it. Barium titanate is mixed with rubber which absorbs the piezoelectric stresses when the PFL is charged and regain its original shape after the discharge. A composite mixture of barium titanate with the neoprene rubber is prepared. The relative permittivity of the composite mixture is measured to be 85. A coaxial pulse forming line of inner diameter 120 mm, outer diameter 240 mm, and length 350 mm is made and the composite mixture of barium titanate and neoprene rubber is filled between the inner and outer cylinders. The PFL is charged up to 120 kV and discharged into 5 ? load. The voltage pulse of 70 kV, 21 ns is measured across the load. The conventional PFL is made up of oil or plastics dielectrics with the relative permittivity of 2-10 [D. R. Linde, CRC Handbook of Chemistry and Physics, 90th ed. (CRC, 2009); Xia et al., Rev. Sci. Instrum. 79, 086113 (2008); Yang et al., Rev. Sci. Instrum. 81, 43303 (2010)], which increases the length of PFL. We have reported the compactness in length achieved due to increase in relative permittivity of composite mixture by adding barium titanate in neoprene rubber.

Kumar Sharma, Surender; Deb, P.; Shukla, R.; Prabaharan, T.; Shyam, A.

2011-11-01

276

Charge interactions can dominate the dimensions of intrinsically disordered proteins  

PubMed Central

Many eukaryotic proteins are disordered under physiological conditions, and fold into ordered structures only on binding to their cellular targets. Such intrinsically disordered proteins (IDPs) often contain a large fraction of charged amino acids. Here, we use single-molecule Förster resonance energy transfer to investigate the influence of charged residues on the dimensions of unfolded and intrinsically disordered proteins. We find that, in contrast to the compact unfolded conformations that have been observed for many proteins at low denaturant concentration, IDPs can exhibit a prominent expansion at low ionic strength that correlates with their net charge. Charge-balanced polypeptides, however, can exhibit an additional collapse at low ionic strength, as predicted by polyampholyte theory from the attraction between opposite charges in the chain. The pronounced effect of charges on the dimensions of unfolded proteins has important implications for the cellular functions of IDPs.

Muller-Spath, Sonja; Soranno, Andrea; Hirschfeld, Verena; Hofmann, Hagen; Ruegger, Stefan; Reymond, Luc; Nettels, Daniel; Schuler, Benjamin

2010-01-01

277

Health monitoring during vibratory compaction of soil  

Microsoft Academic Search

Vibratory compaction is a proven and commonly adopted densification technique applicable for a wide variety of soil types and compositions. There is a clear need to develop performance-based intelligent vibratory soil compaction techniques wherein the state of the soil is determined during compaction (i.e., health monitoring, continuous quality control). The application of vibration-based structural health monitoring strategies utilized in damage

Michael A. Mooney; Essam F. Tawfik; Godfrey B. Chan; Jie L. Pan

2002-01-01

278

Combined method of compaction of collapsible soils  

SciTech Connect

The writer proposes a combined method of compaction of collapsible soils. He presents results of investigations carried out to study compacted zones of pads punched (tamped-out) by rammers 10 and 20 tons in mass, as well as a comparative analysis of the pads over against compacted zones obtained by means of plane rammers. The analysis results are illustrated by the {open_quotes}arch effect{close_quotes} on the stress conditions of the soaked soil mass.

Bagdasarov, Yu.A.

1994-07-01

279

Crack prevention in shock compaction of powders  

SciTech Connect

The occurrence of macro-cracks in compacts fabricated by shock compaction of powders is a severe problem preventing this consolidation technique from commercial applications. In this paper the sources of important failure types that typically occur in the cylindrical configuration i.e. radial, transverse, and spiral cracks and the Mach stem are described. Subsequently, solutions for their prevention are given supported by experimental results and/or computer simulations. Some conflicting requirements for obtaining bonded crack-free compacts are discussed.

Carton, E. P. [TNO Prins Maurits Laboratory, P.O. Box 45, 2280 AA, Rijswijk (Netherlands); Delft University of Technology, Laboratory for Applied Inorganic Chemistry, P.O. Box 5045, 2600 Georgia, Delft (Netherlands); Stuivinga, M.; Verbeek, H. J. [TNO Prins Maurits Laboratory, P.O. Box 45, 2280 AA, Rijswijk (Netherlands)

1998-07-10

280

Method for preparing porous metal hydride compacts  

DOEpatents

A method for preparing porous metallic-matrix hydride compacts which can be repeatedly hydrided and dehydrided without disintegration. A mixture of a finely divided metal hydride and a finely divided matrix metal is contacted with a poison which prevents the metal hydride from dehydriding at room temperature and atmospheric pressure. The mixture of matrix metal and poisoned metal hydride is then compacted under pressure at room temperature to form porous metallic-matrix hydride compacts.

Ron, Moshe (Haifa, IL) [Haifa, IL; Gruen, Dieter M. (Downers Grove, IL) [Downers Grove, IL; Mendelsohn, Marshall H. (Woodridge, IL) [Woodridge, IL; Sheft, Irving (Oak Park, IL) [Oak Park, IL

1981-01-01

281

Compact Process Development at Babcock & Wilcox  

Microsoft Academic Search

Multiple process approaches have been used historically to manufacture cylindrical nuclear fuel compacts. Scale-up of fuel compacting was required for the Next Generation Nuclear Plant (NGNP) project to achieve an economically viable automated production process capable of providing a minimum of 10 compacts\\/minute with high production yields. In addition, the scale-up effort was required to achieve matrix density equivalent to

Eric Shaber; Jeffrey Phillips

2012-01-01

282

Influence of space charge on the scale-up of multiplexed electrosprays  

Microsoft Academic Search

The effect of the space charge of the homopolarly charged droplets in a system of multiplexed electrosprays is investigated. The system consists of a microfabricated liquid distributor with multiple electrospray sources held at a high voltage, a nearby extractor electrode plate held at an intermediate voltage, and a grounded electrode further downstream. The system is very compact, with a spatial

Weiwei Deng; Alessandro Gomez

2007-01-01

283

Production of highly charged ions for ion–surface interaction studies  

Microsoft Academic Search

We give an overview of the production of highly charged ions in the room-temperature Dresden EBIT and its successors, the Dresden EBIS and Dresden EBIS-A, and their application in different areas. Due to their compact design they are favored for the study and use of the interaction of ions with surfaces. In particular, interaction processes with highly charged ions are

G. Zschornack; F. Großmann; R. Heller; U. Kentsch; M. Kreller; S. Landgraf; V. P. Ovsyannikov; M. Schmidt; F. Ullmann

2007-01-01

284

The flow field behind an unsteady shock wave generated by an exploding spherical charge  

Microsoft Academic Search

The paper deals with an experimental investigation and numerical analysis of the parameters of an unsteady shock wave and a flow field, both generated by an exploding compacted powder charge of spherical shape. The study is carried out for distances not greater than 20 charge diameters. The density distribution behind the shock wave was measured with a Mach Zehnder interferometer,

V. T. Markin; N. I. Nosenko; N. N. Sysoev

1979-01-01

285

Characteristics of solid-target charge-exchange analyzers for energetic ion diagnostics on tokamaks  

SciTech Connect

Compact electrostatic charge-exchange analyzers have been constructed for installation in areas of high magnetic fields and restricted access near tokamak fusion devices. The analyzers employed carbon stripping foils, and have been calibrated for proton energies between 1 and 70 keV. They have been successfully used to study charge-exchange losses in auxiliary-heated tokamak plasmas.

Beiersdorfer, P.; Roquemore, A.L.; Kaita, R.

1987-05-01

286

Comprehensive Evaluation of Compaction of Asphalt Pavements and Development of Compaction Monitoring System.  

National Technical Information Service (NTIS)

This study aimed to conduct a comprehensive evaluation of compaction of asphalt pavements and develop software for monitoring field compaction in real time. In the first phase of this study, the researchers built several test sections that were constructe...

A. Chowdhury E. Kassem E. Masad T. Scullion W. Liu

2012-01-01

287

Experimental studies of compact toroids  

SciTech Connect

The Berkeley Compact Toroid Experiment (BCTX) device is a plasma device with a Marshall-gun generated, low aspect ratio toroidal plasma. The device is capable of producing spheromak-type discharges and may, with some modification, produce low-aspect ratio tokamak configurations. A unique aspect of this experimenal devie is its large lower hybrid (LH) heating system, which consists of two 450MHz klystron tubes generating 20 megawatts each into a brambilla-type launching structure. Successful operation with one klystron at virtually full power (18 MW) has been accomplished with 110 {mu}s pulse length. A second klystron is currently installed in its socket and magnet but has not been added to the RF drive system. This report describes current activities and accomplishments and describes the anticipated results of next year's activity.

Not Available

1991-01-01

288

Compact high-voltage structures  

SciTech Connect

A basic understanding of the critical issues limiting the compactness of high-voltage systems is required for the next generation of impulse generators. In the process of optimizing the design of a highly reliable solid-dielectric over-voltage switch, an understanding of the limiting factors found are shown. Results of a l3O kV operating switch, having a modest field enhancement of 16% above the average field stress in the switching region, are reported. The resulting high reliability is obtained by reducing the standard deviation of the switch to 6.8%. The total height of the switch is 1 mm. The resulting operating parameters are obtained by controlling field distribution across the entire switch package and field shaping the desired point of switch closure. The disclosed field management technique provides an approach to improve other highly stressed components and structures.

Wilson, M. J.; Goerz, D.A.

1997-06-09

289

THE MOST DISTANT COMPACT GROUPS  

SciTech Connect

We present photometric and spectroscopic observations of the members of three previously cataloged compact group (CG) candidates at redshifts z > 0.3. These confirm spectroscopic redshifts compatible with being gravitationally bound structures at redshifts 0.3112, 0.3848, and 0.3643, respectively, and then they are the most distant CGs known with spectroscopic confirmation for all their members. The morphological and spectroscopic properties of all their galaxies indicate early types dominated by an old population of stars, with little star formation or nuclear activity. Most of the physical properties derived for the three groups are quite similar to the average properties of CGs at lower redshifts. In particular, from the velocities and positions of the respective members of each CG, we estimate short dynamic times. These leave open the questions of identifying the mechanism for forming CGs continuously and the nature of the final stages of these structures.

Gutierrez, C. M., E-mail: cgc@iac.es [Instituto de Astrofisica de Canarias, E-38205 La Laguna, Tenerife (Spain)] [Departamento de Astrofisica, Universidad de la Laguna, E-38200 Tenerife (Spain)

2011-08-10

290

Compact Microwave Fourier Spectrum Analyzer  

NASA Technical Reports Server (NTRS)

A compact photonic microwave Fourier spectrum analyzer [a Fourier-transform microwave spectrometer, (FTMWS)] with no moving parts has been proposed for use in remote sensing of weak, natural microwave emissions from the surfaces and atmospheres of planets to enable remote analysis and determination of chemical composition and abundances of critical molecular constituents in space. The instrument is based on a Bessel beam (light modes with non-zero angular momenta) fiber-optic elements. It features low power consumption, low mass, and high resolution, without a need for any cryogenics, beyond what is achievable by the current state-of-the-art in space instruments. The instrument can also be used in a wide-band scatterometer mode in active radar systems.

Savchenkov, Anatoliy; Matsko, Andrey; Strekalov, Dmitry

2009-01-01

291

Compact Quantum Cascade Laser Transmitter  

SciTech Connect

): In this paper we present design considerations, thermal and optical modeling results, and device performance for a ruggedized, compact laser transmitter that utilizes a room temperature quantum cascade (QC) laser source. The QC laser transmitter is intended for portable mid-infrared (3-12 µm) spectroscopy applications, where the atmospheric transmission window is relatively free of water vapor interference and where the molecular rotational vibration absorption features can be used to detect and uniquely identify chemical compounds of interest. Initial QC laser-based sensor development efforts were constrained by the complications of cryogenic operation. However, improvements in both QC laser designs and fabrication processes have provided room-temperature devices that now enable significant miniaturization and integration potential for national security, environmental monitoring, atmospheric science, and industrial safety applications.

Anheier, Norman C.; Hatchell, Brian K.; Gervais, Kevin L.; Wojcik, Michael D.; Krishnaswami, Kannan; Bernacki, Bruce E.

2009-04-01

292

Ductile compaction in volcanic conduits  

NASA Astrophysics Data System (ADS)

Silicic magmas typically outgas through connected pore and crack networks with a high gas permeability without the need for decoupled movement of pores in the melt. It is the efficiency with which this process can occur which governs the pressure in the pore network. However, such a connected coupled network is generally mechanically unstable and will relax until volume equilibrium when the pores become smaller and isolated. Consequently, gas permeability can be reduced during densification. Cycles of outgassing events recorded in gas monitoring data show that permeable flow of volatiles is often transient, which is interpreted to reflect magma densification and the closing of pore-networks. Understanding the timescale over which this densification process occurs is critical to refining conduit models that seek to predict the pressure evolution in a pore-network leading to eruptions. We conduct uniaxial compaction experiments to parameterize non-linear creep and relaxation processes that occur in magmas with total pore fractions 0.2-0.85. We analyze our results by applying both viscous sintering and viscoelastic deformation theory to test the applicability of currently accepted models to flow dynamics in the uppermost conduit involving highly porous magmas. We show that purely ductile compaction can occur rapidly and that pore networks can close over timescales analogous to the inter-eruptive periods observed during classic cyclic eruptions such as those at Soufriere Hills volcano, Montserrat, in 1997. At upper-conduit axial stresses (0.1-5 MPa) and magmatic temperatures (830-900 oC), we show that magmas can evolve to porosities analogous to dome lavas erupted at the same volcano. Such dramatic densification events over relatively short timescales and in the absence of brittle deformation show that permeable flow will be inhibited at upper conduit levels. We therefore propose that outgassing is a key feature at many silicic volcanoes and should be incorporated into conduit flow models.

Wadsworth, Fabian; Vasseur, Jeremie; Lavallée, Yan; Scheu, Bettina; Dingwell, Donald

2014-05-01

293

Urban Regimes and School Compacts: The Development of the Detroit Compact.  

ERIC Educational Resources Information Center

Examines the development and implementation of a school compact program in the Detroit (Michigan) Public School System. Demonstrates its initiation by corporate leaders; and highlights some issues faced by elected officials, schools, and the community while making compact agreements. Problems still faced by the Detroit Compact are reviewed. (SLD)

Orr, Marion

1993-01-01

294

The Effect of Laboratory Compaction on the Compressibility of a Compacted Highly Plastic Clay.  

National Technical Information Service (NTIS)

The compressibility of the plastic St. Croix clay is to be studied for both laboratory and field compaction. This interim report deals with the laboratory-compacted phase. The clay was compacted to three levels of kneading type effort and at water content...

A. DiBernardo C. W. Lovell

1979-01-01

295

Ultrasonic Characterization of Iron Powder Metallurgy Compacts during and after Compaction  

Microsoft Academic Search

Ultrasonic measurements in powder metallurgy (PM) compacts at various stages of production are presented both as a practical means of improving PM production and as a method of providing a fuller understanding of PM materials. Ultrasonic monitoring during powder compaction, a novel process instrumentation technique to follow powder densification, is reviewed. Measurements taken during the compaction of simple PM disk

Andrew Lerossignol Dawson; Jean François Bussière

1998-01-01

296

Morphology of galaxies in compact groups  

Microsoft Academic Search

We present the results of an isophotal analysis of 140 early-type galaxies and a visual inspection of images of an additional 202 galaxies in compact groups. This is essentially the entire sample of galaxies in the subset of 92 Hickson compact groups which have at least three accordant members. About 12% of the elliptical galaxies have larger characteristic radii and

Claudia Mendes de Oliveira; Paul Hickson

1994-01-01

297

Compact, solid-state femtosecond source  

Microsoft Academic Search

The goal of this program was to demonstrate that femtosecond laser sources (1 femtosecond = 10(exp -15) sec) can be made to be extremely compact and robust. We demonstrated the generation of ultrashort pulses using compact diode-pumped lasers. Our latest pump source is 300 times smaller and weighs only a fraction of today's commercial equivalent. It runs on 110 VAC

Philippe Bado

1993-01-01

298

Hydrodynamic Modeling and Explosive Compaction of Ceramics.  

National Technical Information Service (NTIS)

High-density ceramics with high-strength microstructure were achieved by explosive compaction. Well-characterized Al sub 2 O sub 3 , AlN, and boron powders were explosively compacted in both cylindrical and flat plate geometries. In cylindrical geometries...

C. Hoenig A. Holt M. Finger W. Kuhl

1977-01-01

299

Compact reflective imaging spectrometer utilizing immersed gratings  

Microsoft Academic Search

A compact imaging spectrometer comprising an entrance slit for directing light, a first mirror that receives said light and reflects said light, an immersive diffraction grating that diffracts said light, a second mirror that focuses said light, and a detector array that receives said focused light. The compact imaging spectrometer can be utilized for remote sensing imaging spectrometers where size

Chrisp; Michael P

2006-01-01

300

Ceramic granule strength variability and compaction behavior.  

National Technical Information Service (NTIS)

Diametral compression strength distributions and the compaction behavior and of irregular shape 150--200 (mu)m ceramic granules and uniform-size 210 (mu)m glass spheres were measured to determine how granule strength variability relates to compaction beha...

S. J. Glass K. G. Ewsuk M. J. Readey

1995-01-01

301

Physics of compact ignition tokamak designs  

SciTech Connect

Models for predicting plasma performance in compact ignition experiments are constructed on the basis of theoretical and empirical constraints and data from tokamak experiments. Emphasis is placed on finding transport and confinement models which reproduce results of both ohmically and auxiliary heated tokamak data. Illustrations of the application of the models to compact ignition designs are given.

Singer, C.E.; Ku, L.P.; Bateman, G.; Seidl, F.; Sugihara, M.

1986-03-01

302

Compact reactor\\/ORC power source  

Microsoft Academic Search

A compact power source that combines an organic Rankine Cycle (ORC) electric generator with a nuclear reactor heat source is being designed and fabricated. Incorporating existing ORC technology with proven reactor technology, the compact reactor\\/ORC power source offers high reliability while minimizing the need for component development. Thermal power at 125 kWt is removed from the coated particle fueled, graphite

K. L. Meier; W. L. Kirchner; G. J. Willcutt

1986-01-01

303

Compact emergency lamp using power LEDs  

Microsoft Academic Search

This paper presents a compact emergency lamp using light emitting diodes (LEDs). The goal is to develop a compact and low cost electronic circuit to drive and control the current of LEDs arranged in a single enclosure. The proposed idea allows using the same equipment in the daily activities, supplied by mains, and under a possible failure of it. The

R. A. Pinto; M. R. Cosetin; M. F. da Silva; G. W. Denardin; J. Fraytag; A. Campos; R. N. do Prado

2009-01-01

304

Compact Process Development at Babcock & Wilcox  

SciTech Connect

Multiple process approaches have been used historically to manufacture cylindrical nuclear fuel compacts. Scale-up of fuel compacting was required for the Next Generation Nuclear Plant (NGNP) project to achieve an economically viable automated production process capable of providing a minimum of 10 compacts/minute with high production yields. In addition, the scale-up effort was required to achieve matrix density equivalent to baseline historical production processes, and allow compacting at fuel packing fractions up to 46% by volume. The scale-up approach of jet milling, fluid-bed overcoating, and hot-press compacting adopted in the U.S. Advanced Gas Reactor (AGR) Fuel Development Program involves significant paradigm shifts to capitalize on distinct advantages in simplicity, yield, and elimination of mixed waste. A series of compaction trials have been completed to optimize compaction conditions of time, temperature, and forming pressure using natural uranium oxycarbide (NUCO) fuel at packing fractions exceeding 46% by volume. Results from these trials are included. The scale-up effort is nearing completion with the process installed and operable using nuclear fuel materials. Final process testing is in progress to certify the process for manufacture of qualification test fuel compacts in 2012.

Eric Shaber; Jeffrey Phillips

2012-03-01

305

Compact copper coil ignition tokamak devices  

SciTech Connect

This report discusses the compact copper ignition studies being presently carried out in the USA. Scoping and preconceptual design studies during FY85 and early FY86 have focused on a minimum cost compact copper coil ignition device. The mission of this program is to develop and optimize ignited plasma operation. Secondary objectives include the development of some plasma interactive components. 2 figures.

Schmidt, J.A.

1986-03-01

306

Compaction of TiH sub 1. 65 \\/KClO sub 4 pyrotechnic powder during confined burn  

Microsoft Academic Search

The burning behavior of titanium subhydride potassium perchlorate (TiH{sub 1.65}\\/KClOâ) is currently under investigation. The research is presently aimed at studying the dynamic compaction of the material as a confined cylindrical charge of the pyrotechnic burns. Flash radiography equipment, optical fibers, and piezoelectric pressure transducers are used to study this phenomenon. The length to diameter ratio of the test charge

S. L. Hingorani-Norenberg; A. Razani; M. Shahinpoor

1990-01-01

307

Charge Accumulation Type Hydrogen Ion Image Sensor with High pH Resolution  

Microsoft Academic Search

We propose a charge transfer type ion image sensor operated using a charge accumulation technique that accumulates the output signal and integrates it temporally. This technique is expected to image hydrogen ion distributions with a high signal-to-noise (S\\/N) ratio. The sensor was fabricated using large-scale integration technology, so that its size was very compact, and its specialized charge transfer characteristics

Shoko Takenaga; Yui Tamai; Makoto Ishida; Kazuaki Sawada

2011-01-01

308

National Crime Prevention and Privacy Compact: Resource Materials.  

National Technical Information Service (NTIS)

This report consists of several informational resources relating to the proposed National Crime Prevention and Privacy Compact (Compact). Adoption of the Compact by the U.S. Congress and the States will facilitate the full implementation of the Interstate...

1998-01-01

309

A compact tritium AMS system  

NASA Astrophysics Data System (ADS)

Tritium ( 3H) is a radioisotope that is extensively utilized in biological and environmental research. For biological research, 3H is generally quantified by liquid scintillation counting requiring gram-sized samples and counting times of several hours. For environmental research, 3H is usually quantified by 3He in-growth which requires gram-sized samples and in-growth times of several months. In contrast, provisional studies at LLNL's Center for Accelerator Mass Spectrometry have demonstrated that accelerator mass spectrometry (AMS) can be used to quantify 3H in milligram-sized biological samples with a 100 to 1000-fold improvement in detection limits when compared to scintillation counting. This increased sensitivity is expected to have great impact on the biological and environmental research community. However, in order to make the 3H AMS technique more broadly accessible, smaller, simpler, and less expensive AMS instrumentation must be developed. To meet this need, a compact, relatively low cost prototype 3H AMS system has been designed and built based on an LLNL ion source/sample changer and an AccSys Technology radio frequency quadrupole (RFQ) linac. With the prototype system, 3H/ 1H ratios ranging from 1×10 -10 to 1×10 -13 have be measured from milligram-sized samples. With improvements in system operation and sample preparation methodology, the sensitivity limit of the system is expected to increase to approximately 1×10 -15.

Roberts, M. L.; Hamm, R. W.; Dingley, K. H.; Chiarappa-Zucca, M. L.; Love, A. H.

2000-10-01

310

Compact drilling and sample system  

NASA Technical Reports Server (NTRS)

The Compact Drilling and Sample System (CDSS) was developed to drill into terrestrial, cometary, and asteroid material in a cryogenic, vacuum environment in order to acquire subsurface samples. Although drills were used by the Apollo astronauts some 20 years ago, this drill is a fraction of the mass and power and operates completely autonomously, able to drill, acquire, transport, dock, and release sample containers in science instruments. The CDSS has incorporated into its control system the ability to gather science data about the material being drilled by measuring drilling rate per force applied and torque. This drill will be able to optimize rotation and thrust in order to achieve the highest drilling rate possible in any given sample. The drill can be commanded to drill at a specified force, so that force imparted on the rover or lander is limited. This paper will discuss the cryo dc brush motors, carbide gears, cryogenic lubrication, quick-release interchangeable sampling drill bits, percussion drilling and the control system developed to achieve autonomous, cryogenic, vacuum, lightweight drilling.

Gillis-Smith, Greg R.; Petercsak, Doug

1998-01-01

311

Compact binaries, hypernovae, and GRBs  

NASA Astrophysics Data System (ADS)

The collapse of a massive stellar core may lead to the production of a black hole surrounded by a torus of material. Such a system is a potential source for the so-called long gamma-ray bursts (GRBs). A torus will form around the black hole if the infalling material contains sufficient angular momentum. This however requires that the core of the massive star rotates extremely rapidly prior to collapse. Here we explore whether tidal locking within binaries can spin stars up sufficiently. We show that the binaries are required to have separations ?3-4 R ?, hence the massive star would have lost its outer envelope (for example in a common envelope phase). In addition, the companions to the massive stars must themselves be compact. Comparison with observed tight binaries, which contain either two neutron stars or a neutron star and a white dwarf, shows that angular momentum is likely to have played an important role during the core collapse of the secondary in about half the systems, including the recently-discovered neutron star binary J0737-3039. Even if these systems failed to produce a GRB, as they do not contain a black hole, they are relevant to the problem of GRB production as a very similar evolutionary pathway (but with a slightly more massive helium star core) may well produce a GRB.

Davies, Melvyn B.; Levan, Andrew

2010-03-01

312

A compact high power pulsed modulator based on spiral Blumlein line.  

PubMed

A compact high power pulsed modulator based on spiral water Blumlein line, which consists of primary storage capacitors, a Tesla transformer, a spiral Blumlein line of water dielectric, and a field-emission diode, is described. The experimental results showed that the diode voltage is more than 500 kV, the electron beam current of diode is about 32 kA, and the pulse duration is about 180 ns. The distributions for electrical field in the spiral water Blumlein line were obtained by the simulations. In addition, the process of the charging a spiral Blumlein line was simulated through the PSPICE software to get the wave form of charging voltage of pulse forming line, the diode voltage, and diode current of modulator. The theoretical and simulated results are in agreement. This accelerator is very compact and works stably and reliably. PMID:17979411

Liu, Jinliang; Yin, Yi; Ge, Bin; Cheng, Xinbing; Feng, Jiahuai; Zhang, Jiande; Wang, Xinxin

2007-10-01

313

Field performance of compacted clay liners  

SciTech Connect

A database consisting of 85 full-scale compacted clay liners was assembled to evaluate field hydraulic conductivity K{sub F}. Large-scale field hydraulic conductivity tests were conducted on each liner. All of the clay liners were intended to achieve K{sub F} {le} 1 {times} 10{sup {minus}7} cm/s, but only 74% succeeded in meeting this objective. The important factors affecting K{sub F} are the soil wetness relative to the line of optimums and the number of lifts or the thickness of the liner. Poor correlation exists between K{sub F} and hydraulic conductivities measured in the laboratory (K{sub L}) on field-compacted samples (especially for liners with K{sub F} > 10{sup {minus}7} cm/s compacted at lower water contents relative to the line of optimums), percent compaction, and index properties representative of composition (e.g., Atterberg limits and particle size fractions). The findings indicate that (1) compacted clay liners having K{sub F} {le} 10{sup {minus}7} cm/s can be constructed with a broad variety of clayey soils; (2) the primary emphasis should be ensuring compaction is primarily wet of the line of optimums; (3) less emphasis should be placed on other traditional measures such as percent compaction, K{sub L}, and index properties; and (4) liners that are thicker or have a greater number of lifts tend to have lower K{sub F}.

Benson, C.H. [Univ. of Wisconsin, Madison, WI (United States). Dept. of Civil and Environmental Engineering] [Univ. of Wisconsin, Madison, WI (United States). Dept. of Civil and Environmental Engineering; Daniel, D.E. [Univ. of Illinois, Urbana, IL (United States). Dept. of Civil Engineering] [Univ. of Illinois, Urbana, IL (United States). Dept. of Civil Engineering; Boutwell, G.P. [Soil Testing Engineers, Inc., Baton Rouge, LA (United States)] [Soil Testing Engineers, Inc., Baton Rouge, LA (United States)

1999-05-01

314

Compact Dielectric Wall Accelerator Development For Intensity Modulated Proton Therapy And Homeland Security Applications  

SciTech Connect

Compact dielectric wall (DWA) accelerator technology is being developed at the Lawrence Livermore National Laboratory. The DWA accelerator uses fast switched high voltage transmission lines to generate pulsed electric fields on the inside of a high gradient insulating (HGI) acceleration tube. Its high electric field gradients are achieved by the use of alternating insulators and conductors and short pulse times. The DWA concept can be applied to accelerate charge particle beams with any charge to mass ratio and energy. Based on the DWA system, a novel compact proton therapy accelerator is being developed. This proton therapy system will produce individual pulses that can be varied in intensity, energy and spot width. The system will be capable of being sited in a conventional linac vault and provide intensity modulated rotational therapy. The status of the developmental new technologies that make the compact system possible will be reviewed. These include, high gradient vacuum insulators, solid dielectric materials, SiC photoconductive switches and compact proton sources. Applications of the DWA accelerator to problems in homeland security will also be discussed.

Chen, Y -; Caporaso, G J; Guethlein, G; Sampayan, S; Akana, G; Anaya, R; Blackfield, D; Cook, E; Falabella, S; Gower, E; Harris, J; Hawkins, S; Hickman, B; Holmes, C; Horner, A; Nelson, S; Paul, A; Pearson, D; Poole, B; Richardson, R; Sanders, D; Stanley, J; Sullivan, J; Wang, L; Watson, J; Weir, J

2009-06-17

315

A compact solid-state detector for small angle particle tracking  

NASA Astrophysics Data System (ADS)

MIcrostrip Detector Array System (MIDAS) is a compact silicon-tracking telescope for charged particles emitted at small angles in intermediate energy photonuclear reactions. It was realized to increase the angular acceptance of the DAPHNE detector and used in an experimental program to check the Gerasimov-Drell-Hearn sum rule at the Mainz electron microtron (MAMI). MIDAS provides a trigger for charged hadrons, p/? ± identification and particle tracking in the region 7°< ?<16°. In this paper we present the main characteristics of MIDAS and its measured performances.

Altieri, S.; Barnaba, O.; Braghieri, A.; Cambiaghi, M.; Lanza, A.; Locatelli, T.; Panzeri, A.; Pedroni, P.; Pinelli, T.; Jennewein, P.; Lang, M.; Preobrazhensky, I.; Annand, J. R. M.; Sadiq, F.

2000-09-01

316

Compact vs. Exponential-Size LP Relaxations  

SciTech Connect

In this paper we introduce by means of examples a new technique for formulating compact (i.e. polynomial-size) LP relaxations in place of exponential-size models requiring separation algorithms. In the same vein as a celebrated theorem by Groetschel, Lovasz and Schrijver, we state the equivalence of compact separation and compact optimization. Among the examples used to illustrate our technique, we introduce a new formulation for the Traveling Salesman Problem, whose relaxation we show equivalent to the subtour elimination relaxation.

Carr, R.D.; Lancia, G.

2000-09-01

317

A compact range RCS measurement system  

NASA Astrophysics Data System (ADS)

This paper discusses a compact range radar cross-section measurement system. The system consists of a dual-shaped offset Cassegrain antenna system and a short pulse coherent radar cross-section instrumentation system. The combination of a highly focused antenna beam and a short pulse radar system with high performance time domain gating allows a considerable improvement of the compact range performance as compared with front-fed offset parabolic antenna systems. The paper also presents some of the results obtained in a scaled-down EHF compact range set up in a small room with no microwave absorbing material on the ceiling, floor, and sidewalls.

Pasqualucci, F.; Paul, J. A.; Andrews, J. H.; Conn, J. K.; Gans, L. S.

318

Compaction of TiO 2 suspension by using dual ionic thermosensitive polymers  

Microsoft Academic Search

The compaction of TiO2 suspension as a negatively charged model suspension by using dual ionic thermosensitive polymers was investigated. First, a cationic thermosensitive polymer, poly (N-isopropylacrylamide-co-N,N-dimethylaminopropylacrylamide) was added to the TiO2 suspension, followed by an anionic thermosensitive polymer, poly (N-isopropyl-acrylamide-co-acrylic acid). By adding the latter, a polymer complex with the cationic thermosensitive polymer adsorbed on the particle is formed, and

Shuji Sakohara; Ryosuke Hinago; Hidenori Ueda

2008-01-01

319

The RADAN series of compact pulsed power Generators and their applications  

Microsoft Academic Search

This paper presents results of development of a compact pulsed power high-voltage generators and high-current electron accelerators of the RADAN series. The basic high-voltage units of RADAN instruments are built around coaxial pulsed forming lines and efficient charging device represented by a Tesla transformer. The fields of applications in science and in practice are rather wide and include formation of

GENNADY A. MESYATS; SERGEI D. KOROVIN; VLADISLAV V. ROSTOV; VALERY G. SHPAK; MICHAEL I. YALANDIN

2004-01-01

320

Dynamic-Carrier-Distribution-Based Compact Modeling of p--i--n Diode Reverse Recovery Effects  

NASA Astrophysics Data System (ADS)

This paper presents a compact model of the diode reverse recovery effect for the simulation program with integrated circuit emphasis (SPICE) simulation. We found that the reverse recovery effect can be described with the dynamic carrier distribution within the lightly-doped N- drift layer of a p--i--n power diode. The proposed model is verified with two-dimensional (2D) device simulation results and compared with a lumped-charge-based conventional model.

Nakashima, Junichi; Miyake, Masataka; Miura-Mattausch, Mitiko

2012-02-01

321

Towards a classification of static electrovacuum spacetimes containing an asymptotically flat spacelike hypersurface with compact interior  

NASA Astrophysics Data System (ADS)

We show that static electrovacuum black hole spacetimes containing an asymptotically flat spacelike hypersurface with compact interior and with both degenerate and non-degenerate components of the event horizon do not exist, under the supplementary hypothesis that all degenerate components of the event horizon have charges of the same sign. This extends previous uniqueness theorems of Simon and Masood-ul-Alam (where only non-degenerate horizons were allowed) and Heusler (where only degenerate horizons were allowed).

Chrusciel, Piotr T.

1999-03-01

322

Compact 14.5 GHz all-permanent magnet ECRIS for experiments with slow multicharged ions  

Microsoft Academic Search

A compact 14.5 GHz electron cyclotron resonance ion source (ECRIS) for production of multiply charged ions (MCI) with a plasma-confining magnetic field generated by permanent magnets has been constructed. Microwave power with frequency between 12.75 and 14.5 GHz is transmitted from ground potential via an insulating window into the watercooled plasma chamber fitted with an aluminium liner. The HF coupling

E. Galutschek; R. Trassl; E. Salzborn; F. Aumayr; Hp Winter

2007-01-01

323

Explosive compaction of Li-ion battery components  

NASA Astrophysics Data System (ADS)

The compaction behavior of Li-ion battery components was studied by using explosive dynamic compaction. Dynamic compaction experiments were conducted on the cathode material LiMn2O4 and the ceramic electrolyte Li-doped BPO4. The compaction caused by the shock wave was studied by varying the compaction pressure and the compaction assembly. Densities up to 93.4% of the theoretical mass density were obtained without any heat treatment. A comparison between explosive compaction and magnetic pulse compaction as well as static pressing has been made.

Jak, M. J. G.; Kelder, E. M.; Schoonman, J.; Lashkov, V. N.; Strikanov, A. V.; Selezenev, A. A.; Potanin, A. A.

1999-11-01

324

Application of compact electron cyclotron resonance ion source  

SciTech Connect

The compact electron cyclotron resonance (ECR) ion source with a permanent magnet configuration (Kei2 source) has been developed at National Institute of Radiological Sciences for a new carbon therapy facility. The Kei2 source was designed for production of C{sup 4+} ions; its performance such as beam intensity and stability has already reached the medical requirements. Therefore, the prototype development of the source for medical use is essentially finished. Recently, we have started a few studies on other applications of the source. One is the production of fullerenes in the ECR plasma and modified fullerenes with various atoms for new materials. A second application is the production of multiply charged ions (not only carbon) for ion implantation. In this paper, some basic experiments for these applications are reported.

Muramatsu, M.; Kitagawa, A.; Iwata, Y.; Ogawa, H.; Hojo, S.; Kubo, T.; Kato, Y.; Biri, S.; Fekete, E.; Yoshida, Y.; Drentje, A. G. [Graduate School of Mechanical Engineering, Toyo University, Tokyo 112-8606, Japan and National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage, Chiba 263-8555 (Japan); National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage, Chiba 263-8555 (Japan); Department of Electrical, Electronic and Information Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871 (Japan); Institute of Nuclear Research (ATOMKI), H-4026 Debrecen, Bem ter 18/c (Hungary); Department of Mechanical Engineering, Toyo University, 2100 Kujirai, Kawagoe, Saitama 350-0815 (Japan); National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage, Chiba 263-8555, Japan and K.V.I. University of Groningen, 9747 AA Groningen (Netherlands)

2008-02-15

325

Charge Islands Through Tunneling.  

National Technical Information Service (NTIS)

It has been recently reported that the electrical charge in a semiconductive carbon nanotube is not evenly distributed, but rather it is divided into charge 'islands'. This paper links the aforementioned phenomenon to tunneling and provides further insigh...

D. C. Robinson

2002-01-01

326

Finding an Unknown Charge  

NSDL National Science Digital Library

Four charges are shown (one is unknown) given in 10-10C that form what is known as a quadrupole. You can measure the potential at any point by dragging the test charge around. Distance is measured in m.

Christian, Wolfgang; Belloni, Mario

2007-01-26

327

Compaction of DNA by gemini surfactants: effects of surfactant architecture.  

PubMed

The interaction between bacteriophage T4 DNA and cationic gemini surfactants was studied by the use of fluorescence microscopy. Upon addition of surfactant, DNA undergoes a transition from random coil to globule, with an intermediate coexistence region. The state behavior of a DNA-gemini surfactant system was found to depend on spacer length, valency, head group size, and tail length. A series of alkanediyl-alpha,omega-bis-(dimethylalkylammonium bromide) surfactants with fixed tail length and variable spacer length s showed a minimum of compaction efficiency at s=6 due to the competition between entropy loss and enthalpy gain. This occurs at roughly the same spacer length at which the critical micellization concentration shows a maximal value (at s=5). In comparison with a single-tailed divalent surfactant (12-3-1) it was shown that the two-tailed equivalent (12-3-12) was more efficient in compacting DNA. A series of gemini surfactants based on cationic peptides with a alpha,omega-diamino alkyl spacer showed similar behavior upon changing the spacer length. Additionally, two surfactants based on diastereomers of tartaric acid with hexadecanoic acid tails and alpha,omega-diaminopropanyl and spermidine head groups, respectively, showed effects of head group size that depended strongly on entropy effects. The dependence on valency of the head group is found to be similar to what is known for mono- and multivalent ions, the latter being more efficient per unit of charge. PMID:16290792

Karlsson, Lisa; van Eijk, Marcel C P; Söderman, Olle

2002-08-15

328

Our compact with tomorrow's doctors.  

PubMed

In recent years, the image of medicine as a caring profession has been badly tarnished by a rash of critical reports in the media. In the face of this negative publicity, do young people still want to be doctors? The author reviews conventional reasons given for the declining applicant pool (e.g., issues of declining income, loss of autonomy, etc.) and posits that an additional reason may be perceptions that doctors no longer command respect and that they are being oppressed by, rather than being guardians of, the health care system. Such views challenge academic medicine to broadcast to the world a realistic picture of the fabulous opportunities and gratifications that lie ahead for the next generation of physicians. However, academic medicine must also address some current realities within medical education, such as the admission process (where at present there is a tendency to overemphasize indices of academic achievement and underemphasize the personal characteristics sought in applicants) and the acculturation process in medical school (which can often dehumanize students and convert idealistic ones into cynics). The author acknowledges that these are tough challenges. He suggests as a first step that leaders of academic medicine prepare and disseminate an explicit statement of their commitments, a kind of compact between teachers and learners of medicine. He outlines these commitments, and states his hope that by fulfilling them, the academic medicine community can make clear that medicine-which at its core is still about the doctor-patient relationship-is a true calling, not just beleaguered occupation. PMID:12063190

Cohen, Jordan J

2002-06-01

329

Performance of a compact injector for heavy-ion medical accelerators  

NASA Astrophysics Data System (ADS)

A compact injector, designed for a heavy-ion medical accelerator complex, was constructed. It consists of an Electron-Cyclotron-Resonance Ion-Source (ECRIS) and two linacs, which are a Radio-Frequency-Quadrupole linac and an Interdigital H-mode Drift-Tube-Linac (IH-DTL) having the same operating frequency of 200 MHz. For beam focusing of the IH-DTL, the method of Alternating-Phase-Focusing (APF) was employed. The compact injector can accelerate heavy ions having a charge-to-mass ratio of {q}/{m}={1}/{3} up to 4.0 MeV/u. Use of the APF IH-DTL and operating frequency of 200 MHz allowed us to design compact linacs; the total length of the two linacs is less than 6 m. Beam-acceleration tests of the compact injector system were performed. The measured intensity of accelerated C4+12 beams with the compact injector was 380 e?A. Beam transmission of the APF IH-DTL was estimated to be as high as 96%, which is comparable to the value calculated by a simulation code. Transverse phase-space and energy distributions of accelerated beams were measured and compared with those calculated by the simulation code, and we found that they were agreed well with each other.

Iwata, Y.; Yamada, S.; Murakami, T.; Fujimoto, T.; Fujisawa, T.; Ogawa, H.; Miyahara, N.; Yamamoto, K.; Hojo, S.; Sakamoto, Y.; Muramatsu, M.; Takeuchi, T.; Mitsumoto, T.; Tsutsui, H.; Watanabe, T.; Ueda, T.

2007-03-01

330

Design and Build a Compact Raman Sensor for Identification of Chemical Composition  

NASA Technical Reports Server (NTRS)

A compact remote Raman sensor system was developed at NASA Langley Research Center. This sensor is an improvement over the previously reported system, which consisted of a 532 nm pulsed laser, a 4-inch telescope, a spectrograph, and an intensified charge-coupled devices (CCD) camera. One of the attractive features of the previous system was its portability, thereby making it suitable for applications such as planetary surface explorations, homeland security and defense applications where a compact portable instrument is important. The new system was made more compact by replacing bulky components with smaller and lighter components. The new compact system uses a smaller spectrograph measuring 9 x 4 x 4 in. and a smaller intensified CCD camera measuring 5 in. long and 2 in. in diameter. The previous system was used to obtain the Raman spectra of several materials that are important to defense and security applications. Furthermore, the new compact Raman sensor system is used to obtain the Raman spectra of a diverse set of materials to demonstrate the sensor system's potential use in the identification of unknown materials.

Garcia, Christopher S.; Abedin, M. Nurul; Ismail, Syed; Sharma, Shiv K.; Misra, Anupam K.; Sandford, Stephen P.; Elsayed-Ali, Hani

2008-01-01

331

Environmental Assessment for the Compact Ignition Tokamak.  

National Technical Information Service (NTIS)

The Compact Ignition Tokamak (CIT) is the proposed next step in the US magnetic confinement fusion energy program. The US Department of Energy (DOE) has chosen the Princeton Plasma Physics Laboratory (PPPL) as the preferred location for this ignition rese...

M. A. McKenzie-Carter J. R. Stencel

1987-01-01

332

Diagnostics for the National Compact Stellarator Experiment  

SciTech Connect

The status of planning of the National Compact Stellarator Experiment (NCSX) diagnostics is presented, with the emphasis on resolution of diagnostics access issues and on diagnostics required for the early phases of operation.

B.C. Stratton; D. Johnson; R. Feder; E. Fredrickson; H. Neilson; H. Takahashi; M. Zarnstorf; M. Cole; P. Goranson; E. Lazarus; B. Nelson

2003-09-16

333

Compact Microwave Cavity for Hydrogen Atomic Clock.  

National Technical Information Service (NTIS)

A summary is presented that introduces the compact microwave cavity used in the hydrogen atomic clock. Special emphasis is placed on derivation of theoretical calculating equations of main parameters of the microwave cavity. A brief description is given o...

D. Zhang Y. Zhang Y. Fu Y. Zhang

1992-01-01

334

Compaction Studies of Palladium/Aluminum Powders.  

National Technical Information Service (NTIS)

A compaction study has been performed comparing predicted and experimentally determined density gradients in palladium/aluminum mixtures of differing weight fractions. A modified constitutive equation for porous media was used to predict the density gradi...

O. L. Burchett M. R. Birnbaum C. T. Oien

1978-01-01

335

ACTIVELY CONTROLLED AFTERBURNER FOR COMPACT WASTE INCINERATION  

EPA Science Inventory

In a continuing research program directed at developing technology for compact shipboard incinerators, active control of fluid dynamics has been used to enhance mixing in incinerator afterburner (AB) experiments and increase the DRE for a waste surrogate. Experiments were conduc...

336

Sequence Compaction to Preserve Transition Frequencies.  

National Technical Information Service (NTIS)

Simulation-based power estimation is commonly used for its high accuracy despite excessive computation times. Techniques have been proposed to speed it up by compacting an input sequence while preserving its power-consumption characteristics; We propose a...

A. Pinar C. L. Liu

2002-01-01

337

Complete Clinical Evaluation of Compact Travel Hemodialyzer.  

National Technical Information Service (NTIS)

Field testing of a compact travel dialysis system was successfully completed. Effective solute clearance and water extraction was accomplished during 187 hemodialyses performed by 32 patients on 39 trips. Problems encountered consisted of difficulty in at...

E. A. Friedman

1977-01-01

338

Compact Fast Analyzer of Rotary Cuvette Type.  

National Technical Information Service (NTIS)

A compact fast analyzer of the rotary cuvette type is provided for simultaneously determining concentrations in a multiplicity of discrete samples using either absorbance or fluorescence measurement techniques. A rigid, generally rectangular frame defines...

L. H. Thacker

1976-01-01

339

Active compaction of crosslinked driven filament networks*  

PubMed Central

The contractile ability of active materials relies on the interplay of force-exerting and force-bearing structures. However, the complexity of interactions and limited parameter control of many model systems are major obstacles in advancing our understanding of the underlying fundamental principles. To shed light on these principles we introduce and analyse a minimal reconstituted system, consisting of highly concentrated actin filaments that are crosslinked by ?-actinin and actively transported in the two-dimensional geometry of a motility assay. This minimal system actively compacts and evolves into highly compact fibres that exceed the length of the individual filaments by two orders of magnitude. We identify the interplay between active transport and crosslinking to be responsible for the observed active compaction. This enables us to control the structure and the length scale of active compaction.

Schaller, V.; Hammerich, B.; Bausch, A.R.

2013-01-01

340

Radionuclide Diffusion and Mobilities in Compacted Bentonite.  

National Technical Information Service (NTIS)

Transport rates of the fission products strontium, technetium, iodide and cesium as well as the actinides thorium, protactinium, uranium, neptunium, plutonium and americium in compacted bentonite have been studied. A sodium bentonite, Wyoming Bentonite MX...

B. Torstenfelt B. Allard K. Andersson H. Kipatsi L. Eliasson

1983-01-01

341

Steady state compact toroidal plasma production  

DOEpatents

Apparatus and method for maintaining steady state compact toroidal plasmas. A compact toroidal plasma is formed by a magnetized coaxial plasma gun and held in close proximity to the gun electrodes by applied magnetic fields or magnetic fields produced by image currents in conducting walls. Voltage supply means maintains a constant potential across the electrodes producing an increasing magnetic helicity which drives the plasma away from a minimum energy state. The plasma globally relaxes to a new minimum energy state, conserving helicity according to Taylor's relaxation hypothesis, and injecting net helicity into the core of the compact toroidal plasma. Controlling the voltage so as to inject net helicity at a predetermined rate based on dissipative processes maintains or increases the compact toroidal plasma in a time averaged steady state mode.

Turner, William C. (Livermore, CA)

1986-01-01

342

Extended Compact Genetic Algorithm in Matlab  

Microsoft Academic Search

This report provides documentation for matlab R ? implementation of the extended compact genetic algorithm (eCGA). The implementation works for integer decision variables where each variable can be of differing cardinality.

Kumara Sastry; Albert Orriols-Puig

2007-01-01

343

Temperature evolution during compaction of pharmaceutical powders.  

PubMed

A numerical approach to the prediction of temperature evolution in tablet compaction is presented here. It is based on a coupled thermomechanical finite element analysis and a calibrated Drucker-Prager Cap model. This approach is capable of predicting transient temperatures during compaction, which cannot be assessed by experimental techniques due to inherent test limitations. Model predictions are validated with infrared (IR) temperature measurements of the top tablet surface after ejection and match well with experiments. The dependence of temperature fields on speed and degree of compaction are naturally captured. The estimated transient temperatures are maximum at the end of compaction at the center of the tablet and close to the die wall next to the powder/die interface. PMID:17969108

Zavaliangos, Antonios; Galen, Steve; Cunningham, John; Winstead, Denita

2008-08-01

344

Dirt depreciation of compact fluorescent lamp downlights.  

National Technical Information Service (NTIS)

An experimental protocol and apparatus was developed to assess the relative differences in dirt depreciation between vented and unvented compact fluorescent recessed downlights under simulated conditions. A simulated plenum/ceiling chamber is designed to ...

M. Siminovitch A. Hamilton C. Zhang R. Verderber

1993-01-01

345

More about Charging Things  

NSDL National Science Digital Library

In the first chapter, you charged things up with excess electrons and saw what could happen as a result. Now we're going to get an idea of how to measure how much charge something has, figure out whether an object is positively or negatively charged, and make up a new concept called the electric field.

Robertson, William C.

2005-01-01

346

Spacecraft Charging Technology, 1980  

NASA Technical Reports Server (NTRS)

The third Spacecraft Charging Technology Conference proceedings contain 66 papers on the geosynchronous plasma environment, spacecraft modeling, charged particle environment interactions with spacecraft, spacecraft materials characterization, and satellite design and testing. The proceedings is a compilation of the state of the art of spacecraft charging and environmental interaction phenomena.

1981-01-01

347

Compact reflective imaging spectrometer utilizing immersed gratings  

DOEpatents

A compact imaging spectrometer comprising an entrance slit for directing light, a first mirror that receives said light and reflects said light, an immersive diffraction grating that diffracts said light, a second mirror that focuses said light, and a detector array that receives said focused light. The compact imaging spectrometer can be utilized for remote sensing imaging spectrometers where size and weight are of primary importance.

Chrisp, Michael P. (Danville, CA)

2006-05-09

348

A compact range RCS measurement system  

Microsoft Academic Search

This paper discusses a compact range radar cross-section measurement system. The system consists of a dual-shaped offset Cassegrain antenna system and a short pulse coherent radar cross-section instrumentation system. The combination of a highly focused antenna beam and a short pulse radar system with high performance time domain gating allows a considerable improvement of the compact range performance as compared

F. Pasqualucci; J. A. Paul; J. H. Andrews; J. K. Conn; L. S. Gans

1986-01-01

349

Dynamic Compaction Modeling of Porous Silica Powder  

Microsoft Academic Search

A computational analysis of the dynamic compaction of porous silica is presented and compared with experimental measurements. The experiments were conducted at Cambridge University's one-dimensional flyer plate facility. The experiments shock loaded samples of silica dust of various initial porous densities up to a pressure of 2.25 GPa. The computational simulations utilized a linear Us-Up Hugoniot. The compaction events were

John P. Borg; Larry Schwalbe; John Cogar; D. J. Chapman; K. Tsembelis; Aaron Ward; Andrew Lloyd

2006-01-01

350

Stylolite compaction and stress models  

NASA Astrophysics Data System (ADS)

Stylolites are rough dissolution seams that develop during pressure solution in the Earth's crust. Especially in limestone quarries they exhibit a spectacular roughness with spikes and large columns. They are visible as dark lines of residual clays and other non-dissolvable components in the white limestone. The roughening phenomena seems to be universal since stylolites can also be found in quarzites, mylonites and all kinds of rocks that undergo pressure solution. The genesis of stylolites is not well understood even though they have been used to estimate compaction and to determine the direction of the main compressive stress. We have developed a numerical model to study the dynamic development of the roughness and its dependence on stress. Based on the model we present estimates of finite strain and depth of burial. The numerical stylolites are studied in two ways: the temporal evolution of the roughness on one hand and the fractal characteristics of the roughness on the other hand. In addition we vary the noise in the model and illustrate the importance of the grain size on the roughening process. Surface energies are dominant for small wavelengths and the initial stylolite growth is non-linear and as slow as a diffusive process. However, once a critical wavelength is reached the elastic regime becomes dominant and the growth is still non-linear but not as strong as in the surface energy dominated case. The growth of the roughness speeds up and teeth structures develop. Depending on the system size the growth will reach a third regime where saturation is reached and the roughness stays constant. We will present a scaling law based on these findings that can be used to estimate finite strain from natural stylolites. The roughness of the stylolite itself is self-affine with two different roughness exponents. The switch from one exponent to the other is dependent on stress. We show how stylolites can thus be used as palaeo-stress-gauges. A variation of the initial noise in the system does only change the stylolite growth significantly, if the absolute size of the noise is changed, for example the grain size in a sample. The roughness exponents do not change but the switch from slow to fast growth comes earlier so that the finial stylolite will look different.

Koehn, D.; Ebner, M.; Renard, F.; Toussaint, R.

2009-04-01

351

Nanodots formation with slow highly charged ions  

NASA Astrophysics Data System (ADS)

We have been developing a compact electron beam ion source with a high-Tcsuperconductor as a solenoid magnet, which can be operated at liquid nitrogen temperature, and can deliver slow highly-charged ions as high as q = 42. With this ion source together with other ion sources, nanodot formation processes were studied for a highly oriented pyrolytic graphite (HOPG) plate as a target. The impact site was observed with both the scanning tunnelling microscope (STM) mode and non-contact atomic force microscope (NCAFM) mode. It was found that protrusion-like dots were observed for both modes at the same position, and one HCI induced one dot. The dot size (diameter) and height were observed to be more or less the same for both modes, i.e, an HCI impact induces topographic modification on the HOPG surface. The dot size and height were measured as functions of the charge state (q = 8-46) and the kinetic energy (E = 1-300 keV) of highly-charged ions. It was found that the dot size increased linearly with the charge state, although the dependence on the kinetic energy was very weak if any.

Yamazaki, Yasunori

2007-06-01

352

The EBIT charge breeder at NSCL  

NASA Astrophysics Data System (ADS)

The National Superconducting Cyclotron Laboratory (NSCL) is finalizing ReA to reaccelerate rare-isotope beams to energies of ˜0.3-20 MeV/u. ReA consists of an electron-beam ion source / trap (EBIS/T), a mass separator, a radio-frequency quadrupole (RFQ) pre-accelerator, and a superconducting radio-frequency linear accelerator (SRF-LINAC). By increasing the charge of ions injected into the RFQ and SRF-LINAC, this charge breeder is a key component to provide a compact and cost-efficient reaccelerator. The ReA EBIT has started producing highly charged ion beams. It is equipped with an electron gun yielding a few amperes and a magnet configuration made of Helmholtz coils and a solenoid, providing a maximum magnetic field strength of 6 T. The solenoid magnet configuration will guarantee high beam acceptance. The combination of a high-current gun and strong magnetic field will allow this EBIS/T to reach high electron current densities suitable to rapidly increase the charge of short-lived isotopes within tens of milliseconds. The status of the EBIT will be presented.

Lapierre, Alain; Schwarz, Stefan; Kittimanapun, Kritsada; Bollen, Georg; Kester, Oliver

2011-10-01

353

Using the interstate compact to control acid deposition  

Microsoft Academic Search

Interstate compacts between states which generate and those which receive acid rain are a promising way to reduce a problem with regional differences. The author examines the applicability of the interstate compact to control acid rain, suggests a structure for the compact, and outlines restrictions resulting from Section 102 of the Clean Air Act. Such a compact would not be

1985-01-01

354

Coulombic charge ice  

NASA Astrophysics Data System (ADS)

We consider a classical model of charges ±q on a pyrochlore lattice in the presence of long-range Coulomb interactions. This model first appeared in the early literature on charge order in magnetite [P. W. Anderson, Phys. Rev. 102, 1008 (1956), 10.1103/PhysRev.102.1008]. In the limit where the interactions become short ranged, the model has a ground state with an extensive entropy and dipolar charge-charge correlations. When long-range interactions are introduced, the exact degeneracy is broken. We study the thermodynamics of the model and show the presence of a correlated charge liquid within a temperature window in which the physics is well described as a liquid of screened charged defects. The structure factor in this phase, which has smeared pinch points at the reciprocal lattice points, may be used to detect charge ice experimentally. In addition, the model exhibits fractionally charged excitations ±q/2 which are shown to interact via a 1/r potential. At lower temperatures, the model exhibits a transition to a long-range ordered phase. We are able to treat the Coulombic charge ice model and the dipolar spin ice model on an equal footing by mapping both to a constrained charge model on the diamond lattice. We find that states of the two ice models are related by a staggering field which is reflected in the energetics of these two models. From this perspective, we can understand the origin of the spin ice and charge ice ground states as coming from a dipolar model on a diamond lattice. We study the properties of charge ice in an external electric field, finding that the correlated liquid is robust to the presence of a field in contrast to the case of spin ice in a magnetic field. Finally, we comment on the transport properties of Coulombic charge ice in the correlated liquid phase.

McClarty, P. A.; O'Brien, A.; Pollmann, F.

2014-05-01

355

Charge-ordering transitions without charge differentiation  

NASA Astrophysics Data System (ADS)

The distorted perovskite nickelate system RNiO3 (R=rare earth except La) undergoes a metal-insulator transition (MIT) at a temperature that varies smoothly with the R ionic radius. This MIT is accompanied by structural transition which leads to two inequivalent Ni sites in the cell, and has been explained by charge ordering (CO): charge is transferred between the Ni1 and Ni2 sites in a long-range ordered fashion. Experimental data on core binding energies, ionic radii, and Mossbauer shifts are interpreted in terms of Ni cation charges of 3±? with, for example, ? 0.3 for YNiO3. Making use of first principles DFT results and a new approach not invoking integration of the charge density, we findfootnotetextY. Quan, V. Pardo, and W. E. Pickett, Phys. Rev. Lett. (2012, in press) that the Ni 3d occupation is identical (to high accuracy) for the two Ni sites. We also present results for other compounds (La2VCuO6, YNiO3, CaFeO3, AgNiO2, V4O7), all of which have distinct ``charge states'' that have identical 3d occupation. This quantitative procedure will be discussed and some implications will be outlined.

Quan, Yundi; Pardo, Victor; Pickett, Warren

2013-03-01

356

Evaluation of Laboratory Compaction Techniques for Simulating Field Soil Compaction (Phase 2).  

National Technical Information Service (NTIS)

The primary objective of this project was to further the Phase I study, which was to investigate the potential of using gyratory compaction for field simulation, and try to establish the standard test procedure for compacting silty and sandy soils. The ob...

W. V. Ping G. Xing M. Leonard Z. Yang

2003-01-01

357

Diagnostics of soil compaction in steppe zone  

NASA Astrophysics Data System (ADS)

Land degradation and desertification are among the major challenges in steppe zone, and leads the risks of food security in affected areas. Soil compaction is one of the basic reasons of degradation of arable land. The processes of soil compaction have different genesis. Knowledge of soil compaction mechanisms and their early diagnostics permit to accurately forecast velocity and degree of degradation processes as well as to undertake effective preventive measures and land reclamation activities. Manifestations of soil compaction and degradation of soil structure due to vertic, alkaline and and mechanical (agro-) compaction, as well as caused by combination of these processes in irrigated and rainfed conditions were studied in four model plots in Krasnodar and Saratov regions of Russia. Typic chernozems, solonetz and kashtanozem solonetz, south chernozem and dark-kashtanozem soils were under investigation. Morphological (mesomorphological, micromorphological and microtomographic) features, as well as number of physical (particle size analyses, water-peptizable clays content (WPC), swelling and shrinking, bulk density and moisture), chemical (humus, pH, CAC, EC), and mineralogical (clay fraction) properties were investigated. Method for grouping soil compaction types by morphological features was proposed. It was shown that: - overcompacted chernozems with vertic features has porosity close to natural chernozems (about 40%), but they had the least pore diameter (7-12 micron) among studied soils. Solonetzic soils had the least amount of "pore-opening" (9%). - irrigation did not lead to the degradation of soil structure on micro-level. - "mechanically" (agro-) compacted soils retained an intra-aggregate porosity. - studied soils are characterized by medium and heavy particle size content (silt [<0.1mm] of 30-60%). Subsoil horizons of chernozems with vertic and alkaline features were the heaviest by particle size content. - the share of WPC to clay ratio was 40% in average, this ratio in vertic and alkaline soils was up to more than 70%. - overcompacted chernozems with vertic features has the swelling degree of 17-25%, all studied soils have the maximum value of swelling degree in subsoil compacted horizon. - humus content varied from 2 to 4%, pH - from 6.9 to 8.2. Studied soils were saturated with basics, Ca of 30 mg*eq/100g and more, Na was more relevant to compacted solonetz and solonetz-like soils (up to 4.3 mg*eq/100g)

Sorokin, Alexey; Kust, German

2014-05-01

358

Relativistic structure, stability, and gravitational collapse of charged neutron stars  

SciTech Connect

Charged stars have the potential of becoming charged black holes or even naked singularities. We present a set of numerical solutions of the Tolman-Oppenheimer-Volkov equations that represents spherical charged compact stars in hydrostatic equilibrium. The stellar models obtained are evolved forward in time integrating the Einstein-Maxwell field equations. We assume an equation of state of a neutron gas at zero temperature. The charge distribution is taken as being proportional to the rest mass density distribution. The set of solutions present an unstable branch, even with charge-to-mass ratios arbitrarily close to the extremum case. We perform a direct check of the stability of the solutions under strong perturbations and for different values of the charge-to-mass ratio. The stars that are in the stable branch oscillate and do not collapse, while models in the unstable branch collapse directly to form black holes. Stars with a charge greater than or equal to the extreme value explode. When a charged star is suddenly discharged, it does not necessarily collapse to form a black hole. A nonlinear effect that gives rise to the formation of a shell of matter (in supermassive stars), is negligible in the present simulations. The results are in agreement with the third law of black hole thermodynamics and with the cosmic censorship conjecture.

Ghezzi, Cristian R. [Instituto de Matematica, Estatistica e Computacao Cientifica, Universidade Estadual de Campinas, Campinas, Sao Paulo (Brazil)

2005-11-15

359

Structure of water at charged interfaces: a molecular dynamics study.  

PubMed

The properties of water molecules located close to an interface deviate significantly from those observed in the homogeneous bulk liquid. The length scale over which this structural perturbation persists (the so-called interfacial depth) is the object of extensive investigations. The situation is particularly complicated in the presence of surface charges that can induce long-range orientational ordering of water molecules, which in turn dictate diverse processes, such as mineral dissolution, heterogeneous catalysis, and membrane chemistry. To characterize the fundamental properties of interfacial water, we performed molecular dynamics (MD) simulations on alkali chloride solutions in the presence of two types of idealized charged surfaces: one with the charge density localized at discrete sites and the other with a homogeneously distributed charge density. We find that, in addition to a diffuse region where water orientation shows no layering, the interface region consists of a "compact layer" of solvent next to the surface that is not described in classical electric double layer theories. The depth of the diffuse solvent layer is sensitive to the type of charge distributions on the surface and the ionic strength. Simulations of the aqueous interface of a realistic model of negatively charged amorphous silica show that the water orientation and the distribution of ions strongly depend on the identity of the cations (Na(+) vs Cs(+)) and are not well represented by a simplistic homogeneous charge distribution model. While the compact layer shows different solvent net orientation and depth for Na(+) vs Cs(+), the depth (?1 nm) of the diffuse layer of oriented waters is independent of the identity of the cation screening the charge. The details of interfacial water orientation revealed here go beyond the traditionally used double and triple layer models and provide a microscopic picture of the aqueous/mineral interface that complements recent surface specific experimental studies. PMID:24979659

Dewan, Shalaka; Carnevale, Vincenzo; Bankura, Arindam; Eftekhari-Bafrooei, Ali; Fiorin, Giacomo; Klein, Michael L; Borguet, Eric

2014-07-15

360

Charge Islands Through Tunneling  

NASA Technical Reports Server (NTRS)

It has been recently reported that the electrical charge in a semiconductive carbon nanotube is not evenly distributed, but rather it is divided into charge "islands." This paper links the aforementioned phenomenon to tunneling and provides further insight into the higher rate of tunneling processes, which makes tunneling devices attractive. This paper also provides a basis for calculating the charge profile over the length of the tube so that nanoscale devices' conductive properties may be fully exploited.

Robinson, Daryl C.

2002-01-01

361

Induction spray charging apparatus  

US Patent & Trademark Office Database

Induction charging apparatus for HVLP spray guns includes an air cap having a central fluid exit orifice for receiving the spray gun nozzle. The cap includes one or more charging electrodes surrounding the orifice and carrying a voltage sufficiently large to induce on the spray droplets charges of a polarity opposite to that on the electrodes. The cap includes a rotatable electrical connector to enable the cap to rotate 360.degree., while maintaining electrical connections between the electrodes and a power supply.

1995-04-25

362

Spacecraft Charging Interactive Handbook  

Microsoft Academic Search

Recent spacecraft failures have brought into focus the need for increased understanding and modeling of spacecraft charging by spacecraft designers. Spacecraft charging assessments are needed for designing all geosynchronous, mid-altitude, and polar, low-earth orbit spacecraft. Under contract to the Spacecraft Environment Effects Program office at NASA\\/Marshall, we are developing a CD-ROM\\/web based multimedia interactive Spacecraft Charging Handbook with integrated, updated

V. A. Davis; I. Katz; M. J. Mandell; B. M. Gardner

1998-01-01

363

Battery formation charging apparatus  

SciTech Connect

An apparatus is describe for charging electric storage batteries, the apparatus comprising: (a) a host computer for providing charging information to and receiving status information from at least one slave computer by means of a data link; and (b) at least one control module coupled to the slave computer for applying charging current to at least one electric storage battery in response to instructions received from the slave computer, and for providing feedback and status information to the slave computer.

Stewart, J.L.

1987-08-04

364

Activation analysis of the compact ignition tokamak  

SciTech Connect

The US fusion program has completed the conceptual design of a compact tokamak device that achieves ignition. The high neutron wall loadings associated with this compact deuterium-tritium-burning device indicate that radiation-related issues may be significant considerations in the overall system design. Sufficient shielding will be requied for the radiation protection of both reactor components and occupational personnel. A close-in igloo shield has been designed around the periphery of the tokamak structure to permit personnel access into the test cell after shutdown and limit the total activation of the test cell components. This paper describes the conceptual design of the igloo shield system and discusses the major neutronic concerns related to the design of the Compact Ignition Tokamak.

Selcow, E.C.

1986-01-01

365

The birthplace of compact groups of galaxies  

NASA Technical Reports Server (NTRS)

We use complete redshift surveys to study the redshift neighborhoods of 38 Hickson compact groups (HCGs). Twenty-nine of these HCGs (76%) are embedded in rich looser systems which we call HCG associations. Analysis of the redshift neighborhood of HCGs outside the CfA survey suggests that most HCGs are embedded in more extended physical systems. Rich loose groups extracted from the CfA survey (Ramella et al. (1994)) have physical properties similar to those of the HCG associations. These rich loose groups often contain compact configurations. N-body experiments (Diaferio (1994)) suggest that compact configurations analogous to HCGs form continually during the collapse of rich loose groups. These observational and numerical results suggest that rich loose groups are the birthplace of HCGs.

Ramella, Massimo; Diaferio, Antonaldo; Geller, Margaret J.; Huchra, John P.

1994-01-01

366

FUZZY C-MEANS WITH VARIABLE COMPACTNESS  

PubMed Central

Fuzzy c-means (FCM) clustering has been extensively studied and widely applied in the tissue classification of biomedical images. Previous enhancements to FCM have accounted for intensity shading, membership smoothness, and variable cluster sizes. In this paper, we introduce a new parameter called “compactness” which captures additional information of the underlying clusters. We then propose a new classification algorithm, FCM with variable compactness (FCMVC), to classify three major tissues in brain MRIs by incorporating the compactness terms into a previously reported improvement to FCM. Experiments on both simulated phantoms and real magnetic resonance brain images show that the new method improves the repeatability of the tissue classification for the same subject with different acquisition protocols.

Roy, Snehashis; Agarwal, Harsh; Carass, Aaron; Bai, Ying; Pham, Dzung L.; Prince, Jerry L.

2009-01-01

367

FUZZY C-MEANS WITH VARIABLE COMPACTNESS.  

PubMed

Fuzzy c-means (FCM) clustering has been extensively studied and widely applied in the tissue classification of biomedical images. Previous enhancements to FCM have accounted for intensity shading, membership smoothness, and variable cluster sizes. In this paper, we introduce a new parameter called "compactness" which captures additional information of the underlying clusters. We then propose a new classification algorithm, FCM with variable compactness (FCMVC), to classify three major tissues in brain MRIs by incorporating the compactness terms into a previously reported improvement to FCM. Experiments on both simulated phantoms and real magnetic resonance brain images show that the new method improves the repeatability of the tissue classification for the same subject with different acquisition protocols. PMID:20126427

Roy, Snehashis; Agarwal, Harsh; Carass, Aaron; Bai, Ying; Pham, Dzung L; Prince, Jerry L

2008-01-01

368

Settlement of footing on compacted ash bed  

SciTech Connect

Compacted coal ash fills exhibit capillary stress due to contact moisture and preconsolidation stress due to the compaction process. As such, the conventional methods of estimating settlement of footing on cohesionless soils based on penetration tests become inapplicable in the case of footings on coal ash fills, although coal ash is also a cohesionless material. Therefore, a method of estimating load-settlement behavior of footings resting on coal ash fills accounting for the effect of capillary and preconsolidation stresses is presented here. The proposed method has been validated by conducting plate load tests on laboratory prepared compacted ash beds and comparing the observed and predicted load-settlement behavior. Overestimation of settlement greater than 100% occurs when capillary and preconsolidation stresses are not accounted for, as is the case in conventional methods.

Ramasamy, G.; Pusadkar, S.S. [IIT Roorkee, Roorkee (India). Dept. of Civil Engineering

2007-11-15

369

Injector Study for Compact Hard X-Ray Source via Laser Compton Scattering  

NASA Astrophysics Data System (ADS)

Compact hard X-ray source via laser Compton sattering has been developed in SHI and AIST. Our system has the injector and the linac and the high power laser system. The injector has a photo-cathode rf gun with a solenoid magnet. To enhance the X-ray yeild, we are planning to increase electron beam charge up to 5 nC/bunch and to make multi-bunch beam. The beam tracking simulation in the injector have been performed by changing laser spot size, laser pulse width, rf phase and solenoid field to optimize the distance between the injector and the linac for 5 nC/bunch high charge beam. In addition, high charge multi-bunch beam simulation in rf-gun cavity have been carried out to investigate the influence by the beam loading and the wake field.

Kuroda, Ryunosuke; Toyokawa, Hiroyuki; Sei, Norihiro; Yasumoto, Masato; Ogawa, Hiroshi; Koike, Masaki; Yamada, Kawakatsu; Nakajyo, Terunobu; Sakai, Fumio; Yanagida, Tatsuya

370

Observational properties of compact groups of galaxies  

NASA Technical Reports Server (NTRS)

Compact groups are small, relatively isolated, systems of galaxies with projected separations comparable to the diameters of the galaxies themselves. Two well-known examples are Stephan's Quintet (Stephan, 1877) and Seyfert's Sextet (Seyfert 1948a,b). In groups such as these, the apparent space density of galaxies approaches 10(exp 6) Mpc(sub -3), denser even than the cores of rich clusters. The apparent unlikeliness of the chance occurrence of such tight groupings lead Ambartsumyan (1958, 1975) to conclude that compact groups must be physically dense systems. This view is supported by clear signs of galaxy interactions that are seen in many groups. Spectroscopic observations reveal that typical relative velocities of galaxies in the groups are comparable to their internal stellar velocities. This should be conducive to strong gravitational interactions - more so than in rich clusters, where galaxy velocities are typically much higher. This suggests that compact groups could be excellent laboratories in which to study galaxy interactions and their effects. Compact groups often contain one or more galaxies whose redshift differs greatly from those of the other group members. If these galaxies are at the same distance as the other members, either entire galaxies are being ejected at high velocities from these groups, or some new physical phenomena must be occurring. If their redshifts are cosmological, we must explain why so many discordant galaxies are found in compact groups. In recent years much progress has been made in addressing these questions. Here, the author discusses the current observational data on compact groups and their implications.

Hickson, Paul

1990-01-01

371

Experimental Compaction in a Growing Dendritic Zone  

NASA Astrophysics Data System (ADS)

The Earth inner core is thought to be in a state of dynamical equilibrium between dendritic solidification and compaction of the resulting solid-liquid region (or 'mushy zone') (Sumita et al.,1996). One important question is how much liquid can be trapped in the inner core, or how efficient is compaction to squeeze out the liquid phase. While this can be estimated theoretically in the case of non-reacting liquid and solid phases, this problem is somewhat more complicated in the case of a crystallizing mushy zone, as it involves a continuous mass transfer between the two phases as the system evolves. Consequences on the evolution of the connectivity of the melt as solidification proceed are difficult to assess, making the dependence of the permeability on porosity difficult to predict theoretically, particularly when the liquid fraction becomes small. Other open questions includes how does compaction and convection compete in the mushy zone? What are the effects of compaction on the thickness of the convecting zone? on the interdendritic spacing? on the structure and dimensions of chimneys? We present here preliminary results of an experiment devoted to the study of compaction during the dendritic crystallization of a model material. In our experimental set-up, compaction is promoted by a high apparent gravity, which is imposed by putting the crystallizing sample in a standard lab centrifuge, where the centrifuge acceleration can reach a few thousand g. While solidification proceed, the sample is scanned in situ with ultrasounds, allowing us to follow the propagation of the solidification front and to investigate the variations of ultrasound velocity and attenuation in the liquid, mush and solid domains.

Deguen, R.; Alboussière, T.; Brito, D.; La Rizza, P.; Masson, J.

2007-12-01

372

The effect of laser irradiance on the charge loss in expanding tungsten plasma  

NASA Astrophysics Data System (ADS)

The charge loss in tungsten plasma produced by 1064 nm wavelength Nd:YAG laser was investigated by a compact ion collector. In particular the influence of laser irradiance on the critical distance, beyond which charge state of ions are frozen, was studied. For the range of laser irradiance, 3-10 × 108 W/cm2, we found critical distance in the range of 2.2-2.8 cm. The charge state distribution of tungsten ions in far expansion zone measured with the help of time-of-flight ion energy analyzer showed that maximum attainable change state and intensity of highly charged ions increases with the laser irradiance. The increase of critical distance with laser irradiance is attributed to rise of ions charge state in the plasma. Highly charged ions are more energetic as compared to low charge state ions, consequently they recombine at larger distances from the target.

Ilyas, B.; Dogar, A. H.; Qayyum, A.

2013-10-01

373

Momentum compaction and phase slip factor  

SciTech Connect

Section 2.3.11 of the Handbook of Accelerator Physics and Engineering on Landau damping is updated. The slip factor and its higher orders are given in terms of the various orders of the momentum compaction. With the aid of a simplified FODO lattice, formulas are given for the alteration of the lower orders of the momentum compaction by various higher multipole magnets. The transition to isochronicity is next demonstrated. Formulas are given for the extraction of the first three orders of the slip factor from the measurement of the synchrotron tune while changing the rf frequency. Finally bunch-length compression experiments in semi-isochronous rings are reported.

Ng, K.Y.; /Fermilab

2010-10-01

374

THETA CONSTANTS, MODULI, AND COMPACT RIEMANN SURFACES  

PubMed Central

One of the classical tools for the study of moduli of compact Riemann surfaces is the Riemann theta function. Preliminary results were announced earlier1 which established relations between two kinds of theta constants on a compact Riemann surface of genus 2. In this note we generalize the results there obtained. The main theorem is as follows: A sufficient condition for [Formula: see text] to be independent of [Formula: see text] is that [Formula: see text] for the 2g-2(2g-1 - 1) characteristics [Formula: see text] where [Formula: see text] ranges over all odd g - 1 characteristics.

Farkas, H. M.

1969-01-01

375

Remote vacuum compaction of compressible hazardous waste  

DOEpatents

A system is described for remote vacuum compaction and containment of low-level radioactive or hazardous waste comprising a vacuum source, a sealable first flexible container, and a sealable outer flexible container for receiving one or more first flexible containers. A method for compacting low level radioactive or hazardous waste materials at the point of generation comprising the steps of sealing the waste in a first flexible container, sealing one or more first containers within an outer flexible container, breaching the integrity of the first containers, evacuating the air from the inner and outer containers, and sealing the outer container shut. 8 figs.

Coyne, M.J.; Fiscus, G.M.; Sammel, A.G.

1998-10-06

376

Remote vacuum compaction of compressible hazardous waste  

DOEpatents

A system for remote vacuum compaction and containment of low-level radioactive or hazardous waste comprising a vacuum source, a sealable first flexible container, and a sealable outer flexible container for receiving one or more first flexible containers. A method for compacting low level radioactive or hazardous waste materials at the point of generation comprising the steps of sealing the waste in a first flexible container, sealing one or more first containers within an outer flexible container, breaching the integrity of the first containers, evacuating the air from the inner and outer containers, and sealing the outer container shut.

Coyne, Martin J. (Pittsburgh, PA); Fiscus, Gregory M. (McMurray, PA); Sammel, Alfred G. (Pittsburgh, PA)

1998-01-01

377

Constructing ``non-Kerrness'' on compact domains  

NASA Astrophysics Data System (ADS)

Given a compact domain of a three-dimensional hypersurface on a vacuum spacetime, a scalar (the ``non-Kerrness'') is constructed by solving a Dirichlet problem for a second order elliptic system. If such scalar vanishes, and a set of conditions are satisfied at a point, then the domain of dependence of the compact domain is locally isometric to a portion of a member of the Kerr family of solutions to the Einstein field equations. This construction is expected to be of relevance in the analysis of numerical simulations of black hole spacetimes.

Bäckdahl, Thomas; Kroon, Juan A. Valiente

2012-04-01

378

Coarsening and Slow Dynamics in Granular Compaction  

NASA Astrophysics Data System (ADS)

We address the problem of the microscopic reorganization of a granular medium under a compaction process in the framework of Tetris-like models. We point out the existence of regions of spatial organization which we call domains, and study their time evolution. It turns out that after an initial transient, most of the activity of the system is concentrated on the boundaries between domains. One can then describe the compaction phenomenon as a coarsening process for the domains, and a progressive reduction of domain boundaries. We discuss the link between the coarsening process and the slow dynamics in the framework of a model of active walkers on active substrates.

Baldassarri, A.; Krishnamurthy, S.; Loreto, V.; Roux, S.

2001-11-01

379

Coarsening and slow dynamics in granular compaction.  

PubMed

We address the problem of the microscopic reorganization of a granular medium under a compaction process in the framework of Tetris-like models. We point out the existence of regions of spatial organization which we call domains, and study their time evolution. It turns out that after an initial transient, most of the activity of the system is concentrated on the boundaries between domains. One can then describe the compaction phenomenon as a coarsening process for the domains, and a progressive reduction of domain boundaries. We discuss the link between the coarsening process and the slow dynamics in the framework of a model of active walkers on active substrates. PMID:11736401

Baldassarri, A; Krishnamurthy, S; Loreto, V; Roux, S

2001-11-26

380

Quantizations of compact Lie group actions  

NASA Astrophysics Data System (ADS)

In this paper we describe quantizations in the monoidal categories of unitary representations of compact connected Lie groups. For the n-dimensional torus T we show that the set Q(T) of quantizations is isomorphic to the (n2)-dimensional torus. For connected compact Lie groups G of rank n, we get the result that the set QE(G) of extendible quantizations of G-modules is isomorphic to the set of quantizations of its maximal torus T invariant under action by its Weyl group. For all these cases we give explicit formulae for quantizations and apply these to quantize Hilbert–Schmidt operators.

Huru, Hilja L.; Lychagin, Valentin V.

2014-06-01

381

Compact Focal Plane Assembly for Planetary Science  

NASA Technical Reports Server (NTRS)

A compact radiometric focal plane assembly (FPA) has been designed in which the filters are individually co-registered over compact thermopile pixels. This allows for construction of an ultralightweight and compact radiometric instrument. The FPA also incorporates micromachined baffles in order to mitigate crosstalk and low-pass filter windows in order to eliminate high-frequency radiation. Compact metal mesh bandpass filters were fabricated for the far infrared (FIR) spectral range (17 to 100 microns), a game-changing technology for future planetary FIR instruments. This fabrication approach allows the dimensions of individual metal mesh filters to be tailored with better than 10- micron precision. In contrast, conventional compact filters employed in recent missions and in near-term instruments consist of large filter sheets manually cut into much smaller pieces, which is a much less precise and much more labor-intensive, expensive, and difficult process. Filter performance was validated by integrating them with thermopile arrays. Demonstration of the FPA will require the integration of two technologies. The first technology is compact, lightweight, robust against cryogenic thermal cycling, and radiation-hard micromachined bandpass filters. They consist of a copper mesh supported on a deep reactive ion-etched silicon frame. This design architecture is advantageous when constructing a lightweight and compact instrument because (1) the frame acts like a jig and facilitates filter integration with the FPA, (2) the frame can be designed so as to maximize the FPA field of view, (3) the frame can be simultaneously used as a baffle for mitigating crosstalk, and (4) micron-scale alignment features can be patterned so as to permit high-precision filter stacking and, consequently, increase the filter bandwidth and sharpen the out-of-band rolloff. The second technology consists of leveraging, from another project, compact and lightweight Bi0.87Sb0.13/Sb arrayed thermopiles. These detectors consist of 30-layer thermopiles deposited in series upon a silicon nitride membrane. At 300 K, the thermopile arrays are highly linear over many orders of magnitude of incident IR power, and have a reported specific detectivity that exceeds the requirements imposed on future mission concepts. The bandpass filter array board is integrated with a thermopile array board by mounting both boards on a machined aluminum jig.

Brown, Ari; Aslam, Shahid; Huang, Wei-Chung; Steptoe-Jackson, Rosalind

2013-01-01

382

Dynamic Compaction Modeling of Porous Silica Powder  

NASA Astrophysics Data System (ADS)

A computational analysis of the dynamic compaction of porous silica is presented and compared with experimental measurements. The experiments were conducted at Cambridge University's one-dimensional flyer plate facility. The experiments shock loaded samples of silica dust of various initial porous densities up to a pressure of 2.25 GPa. The computational simulations utilized a linear Us-Up Hugoniot. The compaction events were modeled with CTH, a 3D Eulerian hydrocode developed at Sandia National Laboratory. Simulated pressures at two test locations are presented and compared with measurements.

Borg, John P.; Schwalbe, Larry; Cogar, John; Chapman, D. J.; Tsembelis, K.; Ward, Aaron; Lloyd, Andrew

2006-07-01

383

Compact, Robust Chips Integrate Optical Functions  

NASA Technical Reports Server (NTRS)

Located in Bozeman, Montana, AdvR Inc. has been an active partner in NASA's Small Business Innovation Research (SBIR) and Small Business Technology Transfer (STTR) programs. Langley Research Center engineers partnered with AdvR through the SBIR program to develop new, compact, lightweight electro-optic components for remote sensing systems. While the primary customer for this technology will be NASA, AdvR foresees additional uses for its NASA-derived circuit chip in the fields of academic and industrial research anywhere that compact, low-cost, stabilized single-frequency lasers are needed.

2010-01-01

384

Compaction Scale Up and Optimization of Cylindrical Fuel Compacts for the Next Generation Nuclear Plant  

SciTech Connect

Multiple process approaches have been used historically to manufacture cylindrical nuclear fuel compacts. Scale-up of fuel compacting was required for the Next Generation Nuclear Plant (NGNP) project to achieve an economically viable automated production process capable of providing a minimum of 10 compacts/minute with high production yields. In addition, the scale-up effort was required to achieve matrix density equivalent to baseline historical production processes, and allow compacting at fuel packing fractions up to 46% by volume. The scale-up approach of jet milling, fluid-bed overcoating, and hot-press compacting adopted in the U.S. Advanced Gas Reactor (AGR) Fuel Development Program involves significant paradigm shifts to capitalize on distinct advantages in simplicity, yield, and elimination of mixed waste. A series of designed experiments have been completed to optimize compaction conditions of time, temperature, and forming pressure using natural uranium oxycarbide (NUCO) fuel. Results from these experiments are included. The scale-up effort is nearing completion with the process installed and operational using nuclear fuel materials. The process is being certified for manufacture of qualification test fuel compacts for the AGR-5/6/7 experiment at the Advanced Test Reactor (ATR) at the Idaho National Laboratory (INL).

Jeffrey J. Einerson; Jeffrey A. Phillips; Eric L. Shaber; Scott E. Niedzialek; W. Clay Richardson; Scott G. Nagley

2012-10-01

385

Charge-depletion meter  

SciTech Connect

This invention relates to a charge-depletion meter apparatus having a current-to-frequency converter to sense and convert the current drain of a battery source to a digital signal which is divided and then accumulated in a counter. An LCD display unit displays the accumulated charge which is received from the counter.

Schneider, J.F.

1984-11-27

386

Rocket Motor Charging Experiments.  

National Technical Information Service (NTIS)

A study of the effect of rocket engines on electrostatic charge accumulation was made. Experiments were conducted to measure short-circuit charging current and open-circuit voltage produced by 5-inch solid-fuel rocket motors during static firings at sea l...

E. F. Vance J. E. Nanevicz

1966-01-01

387

Percussion Initiated Spotting Charge.  

National Technical Information Service (NTIS)

In accordance with this invention, a solid propellant rocket motor is provided with a motor closure head and with a percussion initiated spotting charge mounted on the motor closure head. The percussion initiated spotting charge includes a body made of a ...

R. E. Betts

1983-01-01

388

Nondissipative optimum charge regulator  

NASA Technical Reports Server (NTRS)

Optimum charge regulator provides constant level charge/discharge control of storage batteries. Basic power transfer and control is performed by solar panel coupled to battery through power switching circuit. Optimum controller senses battery current and modifies duty cycle of switching circuit to maximize current available to battery.

Rosen, R.; Vitebsky, J. N.

1970-01-01

389

Differential compaction behaviour of roller compacted granules of clopidogrel bisulphate polymorphs.  

PubMed

In the present work, in-die and out-of-die compaction behaviour of dry-granulated powders of clopidogrel bisulphate (CLP) polymorphs, form I and form II, was investigated using a fully instrumented rotary tablet press. Each polymorph was compacted at three different roller pressures [70.3 (S1), 105.5 (S2) and 140.6 (S3)kgf/cm(2)], and obtained granules were characterized for their physico-mechanical properties. Compaction data were analyzed for out-of-die compressibility, tabletability and compactibility profiles, and in-die Heckel, Kawakita and Walker analysis. The roller compacted granules of both forms showed markedly different tabletting behaviour. Roller pressure exhibited a trend on compaction behaviour of form I granules, whereas, in case of form II, the effect was insignificant. Tabletability of the six granule batches follows the order; I_S1>I_S2>I_S3>II_S1?II_S2?II_S3. In case of form I, the reduced tabletability of the granules compacted at higher roller pressure was attributed to the decreased compressibility and plastic deformation. This was confirmed by compressibility plot and various mathematical parameters derived from Heckel (Py), Kawakita (1/b) and Walker (W) equations. The reduced tabletability of form I granules was due to 'granule hardening' during roller compaction. On the other hand, insignificant effect of roller compaction on tabletting behaviour of form II granules was attributed to brittle fragmentation. The extensive fragmentation of granules offered new 'clean' surfaces and higher contact points that negated the effect of granule hardening. PMID:24971694

Khomane, Kailas S; Bansal, Arvind K

2014-09-10

390

Compact soft x-ray transmission microscopy with sub-50 nm spatial resolution.  

PubMed

In this paper, the development of compact transmission soft x-ray microscopy (XM) with sub-50 nm spatial resolution for biomedical applications is described. The compact transmission soft x-ray microscope operates at lambda = 2.88 nm (430 eV) and is based on a tabletop regenerative x-ray source in combination with a tandem ellipsoidal condenser mirror for sample illumination, an objective micro zone plate and a thinned back-illuminated charge coupled device to record an x-ray image. The new, compact x-ray microscope system requires the fabrication of proper x-ray optical devices in order to obtain high-quality images. For an application-oriented microscope, the alignment procedure is fully automated via computer control through a graphic user interface. In imaging studies using our compact XM system, a gold mesh image was obtained with 45 nm resolution at x580 magnification and 1 min exposure. Images of a biological sample (Coscinodiscus oculoides) were recorded. PMID:16510949

Kim, Kyong Woo; Kwon, Youngman; Nam, Ki-Yong; Lim, Jong-Hyeok; Kim, Kyu-Gyum; Chon, Kwon Su; Kim, Byoung Hoon; Kim, Dong Eon; Kim, JinGon; Ahn, Byoung Nam; Shin, Hyun Joon; Rah, Seungyu; Kim, Ki-Ho; Chae, Jin Seok; Gweon, Dae Gab; Kang, Dong Woo; Kang, Sung Hoon; Min, Jin Young; Choi, Kyu-Sil; Yoon, Seong Eon; Kim, Eun-A; Namba, Yoshiharu; Yoon, Kwon-Ha

2006-03-21

391

Space charge measurement techniques and space charge in polyethylene  

Microsoft Academic Search

Recently, several new techniques such as LIPP, PIPS, PEA and TP methods have been developed to measure directly the space charge distributions in insulating polymers. Many papers have been published on space charge in insulating materials. In this paper, the space charge measurement techniques and space charge in polyethylene are reviewed. The space charge distributions in polyethylene depend strongly upon

T. Mizutani

1994-01-01

392

Environmental assessment for the compact ignition Tokamak  

Microsoft Academic Search

The Compact Ignition Tokamak (CIT) is the proposed next step in the U.S. magnetic confinement fusion energy program. DOE has chosen the Princeton Plasma Physics Laboratory (PPPL) as the preferred location for this ignition research device. The site at PPPL is adjacent to the existing Tokamak Fusion Test Reactor (TFTR) test cell. One of the necessary early planning steps in

M. A. McKenzie-Carter; J. R. Stencel

1987-01-01

393

High-level test compaction techniques  

Microsoft Academic Search

Available register-transfer level (RTL) test generation techniques do not make a concerted effort to reduce the test application time associated with the derived tests. Chip tester memory limitations, increasing tester costs, etc., make it imperative that the issue of generating compact tests at the RTL be addressed and consolidated with the known gains of high-level testing. In this paper, the

Srivaths Ravi; Ganesh Lakshminarayana; Niraj K. Jha

2002-01-01

394

Ultra Compact Back-Lighted Thyratron.  

National Technical Information Service (NTIS)

An ultra-compact Back-Lighted Thyratron (BLT) holds the promise in high voltage (above 30 kV), high current (peak current > 10 kA) switching at high repetition rates (>1 kHz) in a small volume (100 cm3 or less). A helium- filled mini-BLT with the effectiv...

C. Jiang E. B. Sozer

2011-01-01

395

Concentric decomposition during rapid compact growth  

Microsoft Academic Search

We study the propagation of compact superheated solid in the large undercooling limit using the phase-field model. Below a critical undercooling, the superheated solid decomposes into solid and liquid domains, either in the form of liquid droplets or in periodic structures of concentric rings. For the latter, a one-dimensional analysis provides an excellent estimate for the propagation velocity and for

Menahem Zukerman; Raz Kupferman; Ofer Shochet; Eshel Ben-Jacob

1996-01-01

396

Compacting of Biomass for Energy Densification  

Microsoft Academic Search

Biomass waste materials such as crop dust, fruit, and agricultural residues can be used as solid fuel sources. The energy use of these waste materials is limited because of their low densities. Compacting or briquetting of biomass waste materials can be done through various techniques. For example, the squeezing and stabilization of crop straw may have a mechanism that differs

K. Demirbas; A. Sahin-Demirbas

2009-01-01

397

Novel compact microstrip interdigital bandstop filters  

Microsoft Academic Search

A novel compact microstrip interdigital band-stop filter is designed and implemented. The structure is similar to that of an interdigital capacitor. The input port and output ports are connected to form the bandstop characteristic. This proposed filter with microstrip interdigital geometry not only exhibits good bandstop characteristics and a tunable central frequency, but it also is easy to fabricate and

Ru-Yuan Yang; Min-Hung Weng; Cheng-Yuan Hung; Han-Jan Chen; Mau-phon Houng

2004-01-01

398

Non-compaction of the ventricular myocardium  

PubMed Central

Non-compaction of the left ventricle (LVNC) is a disorder of endomyocardial morphogenesis that results in multiple trabeculations in the left ventricular (LV) myocardium. This rare disorder is characterized by an excessively prominent trabecular meshwork and deep intratrabecular recesses. This idiopathic cardiomyopathy is characterized by an altered structure of the myocardial wall as a result of intrauterine arrest of compaction of the myocardial fibers in the absence of any coexisting congenital lesion. It can be associated with neuromuscular disorders and can co-exist with other cardiac malformations, and it is accompanied by depressed ventricular function, systemic embolism and ventricular arrhythmia. Echocardiography is the method of choice for diagnosing LVNC, but the correct diagnosis is often missed or delayed due to a lack of knowledge concerning this uncommon disease and its similarity to other diseases of the myocardium and endocardium. There is a two-layered structure of the myocardial wall consisting of a thin compacted epicardial layer and a thick non-compacted endocardial layer with prominent trabeculations and deep recesses.

VIZZARDI, ENRICO; NODARI, SAVINA; METRA, MARCO; DEI CAS, LIVIO

2006-01-01

399

Compact imaging spectrometer utilizing immersed gratings  

Microsoft Academic Search

A compact imaging spectrometer with an immersive diffraction grating that compensates optical distortions. The imaging spectrometer comprises an entrance slit for transmitting light, means for receiving the light and directing the light, an immersion grating, and a detector array. The entrance slit, the means for receiving the light, the immersion grating, and the detector array are positioned wherein the entrance

Michael P. Chrisp; Scott A. Lerner; Paul J. Kuzmenko; Charles L. Bennett

2007-01-01

400

Compact Imaging Spectrometer Utilizing Immersed Gratings  

Microsoft Academic Search

A compact imaging spectrometer with an immersive diffraction grating that compensates optical distortions. The imaging spectrometer comprises an entrance slit for transmitting light, a system for receiving the light and directing the light, an immersion grating, and a detector array. The entrance slit, the system for receiving the light, the immersion grating, and the detector array are positioned wherein the

Michael P. Chrisp; Scott A. Lerner; Paul J. Kuzmenko; Charles L. Bennett

2006-01-01

401

A COMPACT 100 KV NANOSECOND PULSER  

Microsoft Academic Search

The Pichugin pulser (named after its Russian inventor) has not only the potential to be very compact, but also very reliable. This is because the device uses magnetic coupliig between stages and, therefore, only one erection switch is needed, independent of the number of voltage multiplication stages used. Compared with other voltage multiplier designs, the Pichugin pulser makes efficient use

T. G. Engel; M. Kristiansen; J. Bridges

1993-01-01

402

Physics issues of compact drift optimized stellarators  

Microsoft Academic Search

Physics issues are discussed for compact stellarator configurations which achieve good confinement by the fact that the magnetic field modulus |B| in magnetic co-ordinates is dominated by poloidally symmetric components. Two distinct configuration types are considered: (1) those which achieve their drift optimization and rotational transform at low ? and low bootstrap current by appropriate plasma shaping; and (2) those

D. A. Spong; S. P. Hirshman; L. A. Berry; J. F. Lyon; R. H. Fowler; D. J. Strickler; M. J. Cole; B. N. Nelson; D. E. Williamson; A. S. Ware; D. Alban; G. Y. Fu; D. A. Monticello; W. H. Miner; P. M. Valanju

2001-01-01

403

Compact range for variable-zone measurements  

DOEpatents

A compact range for testing antennas or radar targets includes a source for directing energy along a feedline toward a parabolic reflector. The reflected wave is a spherical wave with a radius dependent on the distance of the source from the focal point of the reflector. 2 figs.

Burnside, W.D.; Rudduck, R.C.; Yu, J.S.

1987-02-27

404

Compact Reconfigurable HF-UHF Antennas.  

National Technical Information Service (NTIS)

The development of a compact reconfigurable HF-UHF antenna is of great practical importance in mobile military communications where low visibility and high mobility are required Variations of monopole and diPOLE ANTENNAS IN USE TODAY ARE NARROWBAND AND AR...

K. Sarabandi

2004-01-01

405

Compact, Lightweight Servo-Controllable Brakes  

NASA Technical Reports Server (NTRS)

Compact, lightweight servo-controllable brakes capable of high torques are being developed for incorporation into robot joints. A brake of this type is based partly on the capstan effect of tension elements. In a brake of the type under development, a controllable intermediate state of torque is reached through on/off switching at a high frequency.

Lovchik, Christopher S.; Townsend, William; Guertin, Jeffrey; Matsuoka, Yoky

2010-01-01

406

STEIN COMPACTS IN LEVI-FLAT HYPERSURFACES  

Microsoft Academic Search

We explore connections between geometric properties of the Levi foliation of a Levi-flat hypersurface M and holomorphic convex- ity of compact sets in M, or bounded in part by M. Applications include extendability of Cauchy-Riemann functions, solvability of the @b-equation, approximation of Cauchy-Riemann and holomorphic func- tions, and global regularity of the @-Neumann operator.

CHRISTINE LAURENT-THIEBAUT

407

A PLASTICITY MODEL FOR POWDER COMPACTION PROCESSES  

Microsoft Academic Search

An endochronic constitutive model for cold powder compaction processes is developed. Although the concept of yield surface has not been explicitly assumed in the endochronic theory, it is demonstrated that the cone-cap yield surface can be derived as a special case of the proposed endochronic model. The plastic flow rule and the dilatancy condition of the model are derived and

A. Bakhshiani; M. Mofid; A. R. Khoei

408

Compact Electric- And Magnetic-Field Sensor  

NASA Technical Reports Server (NTRS)

Compact sensor measures both electric and magnetic fields. Includes both short electric-field dipole and search-coil magnetometer. Three mounted orthogonally providing triaxial measurements of electromagnetic field at frequencies ranging from near 0 to about 10 kHz.

Winterhalter, Daniel; Smith, Edward

1994-01-01

409

Compaction and Wear Concerns on Sports Fields.  

ERIC Educational Resources Information Center

Describes relatively simple measures athletic-facility managers can use to alleviate the turf destruction and compaction of athletic fields including seed and soil amendments and modifications on team practice. Ways of enhancing surface traction and lessen surface hardness are explored. (GR)

Gillan, John

1999-01-01

410

VLA Neutral Hydrogen Imaging of Compact Groups.  

National Technical Information Service (NTIS)

Images of the neutral hydrogen (H I) in the direction of the compact groups of galaxies, HCG 31, HCG 44, and HCG 79 are presented. The authors find in HCG 31 and HCG 79, emission contained within a cloud much larger than the galaxies as well as the entire...

B. A. Williams P. M. Mcmahon J. H. Vangorkom

1990-01-01

411

Compaction in sandstones: influence on reservoir quality  

Microsoft Academic Search

Primary porosity that is lost during burial through cementation by carbonate, evaporite, and some clay minerals can be regenerated during the stage of secondary porosity development that is typical of most basins. However, primary porosity that is lost through compaction is forever lost and cannot be regenerated. Thus, it is desirable to be able to predict the amount of porosity

1984-01-01

412

Feuilletages holomorphes sur les surfaces complexes compactes  

Microsoft Academic Search

In this work we study nonsingular holomorphic foliations on compact complex surfaces and we obtain a classification of these objects. Mainly, there are two different cases: foliations on surfaces admitting a rational or elliptic fibering, and foliations on surfaces of general type. In the first case the method consists in comparing the foliation and the fibration, for exemple looking at

Marco Brunella

1997-01-01

413

Incompatible mechanical properties in compact bone  

Microsoft Academic Search

The covariation of a number of mechanical of properties, and some physical characteristics, of compact bones from a wide range of bones were examined. Young's modulus was well predicted by a combination of mineral content and porosity. Increasing Young's modulus was associated with: increasing stress at yield, increasing bending strength, and a somewhat higher resilience, tensile strength and fatigue strength.

John Currey

2004-01-01

414

Realisation of a compact methane optical clock  

SciTech Connect

A compact optical clock based on a double-mode He-Ne/CH{sub 4} optical frequency standard and a femtosecond Er{sup 3+} fibre laser is realised and its stability against a commercial hydrogen frequency standard is measured. (letters)

Gubin, M A; Kireev, A N; Konyashchenko, A V; Kryukov, P G; Tausenev, A V; Tyurikov, D A; Shelkovnikov, A S [P. N. Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2008-07-31

415

Compact reconditioner for Ni/Cd cells  

NASA Technical Reports Server (NTRS)

Extension of life of multiple-cell nickel-cadium battery packs is accomplished by reconditioning method requiring discharge of each battery cell. Compact and lightweight dc-to-dc converter replaces relay-sensor system, protecting against voltage-reversal damage, and monitors overall cell condition.

Kapustka, R. E.

1976-01-01

416

Compact range for variable-zone measurements  

DOEpatents

A compact range for testing antennas or radar targets includes a source for directing energy along a feedline toward a parabolic reflector. The reflected wave is a spherical wave with a radius dependent on the distance of the source from the focal point of the reflector.

Burnside, Walter D. (Columbus, OH); Rudduck, Roger C. (Columbus, OH); Yu, Jiunn S. (Albuquerque, NM)

1988-01-01

417

On the cold compaction of powders  

Microsoft Academic Search

Constitutive models are developed for stage I cold compaction of powders under general loading. Densification is assumed to occur by plastic deformation at the isolated contacts between particles. The shape of the yield surface is found to be sensitive to the cohesive strength between particles and to be less sensitive to the degree of inter-particle friction. An internal state variable

N. A. Fleck

1995-01-01

418

Compact Apparatus For Growth Of Protein Crystals  

NASA Technical Reports Server (NTRS)

Compact apparatus proposed specifically for growth of protein crystals in microgravity also used in terrestrial laboratories to initiate and terminate growth at prescribed times automatically. Has few moving parts. Also contains no syringes difficult to clean, load, and unload and introduces contaminant silicon grease into crystallization solution. After growth of crystals terminated, specimens retrieved and transported simply.

Carter, Daniel C.; Miller, Teresa Y.

1991-01-01

419

Exponential approximations to compacted sediment porosity profiles  

Microsoft Academic Search

Sediment compaction and corresponding porosity variations can be modeled by a simple exponential with depth. The porosity solution is derived analytically as a complicated function of pore water pressure, but the underlying form is shown to approximate an exponential except near the surface where the behavior is linear. Even though the analytical simplifications ignore some of the detailed effects of

David B. Bahr; Eric W. H. Hutton; James P. M. Syvitski; Lincoln F. Pratson

2001-01-01

420

Sound scattering by a compact circular pore  

Microsoft Academic Search

The aim of this paper is to study the three-dimensional scattering of an oblique wave incident on a flanged circular compact pore of finite depth. The multipole structure with the scattering is resolved by the method of matched asymptotic expansion, where we assume smallness of ?=ka, the product of the incident wavenumber k and the pore radius a. Two distinguished

C. Y. Kuo; R. L. Chern; C. C. Chang

2009-01-01

421

Sound scattering by a compact circular pore  

Microsoft Academic Search

The aim of this paper is to study the three-dimensional scattering of an oblique wave incident on a flanged circular compact pore of finite depth. The multipole structure with the scattering is resolved by the method of matched asymptotic expansion, where we assume smallness of ?=k*a*, the product of the incident wavenumber k* and the pore radius a*. Two distinguished

C. Y. Kuo; R. L. Chern; C. C. Chang

2009-01-01

422

Compact embedded antenna design and its applications  

Microsoft Academic Search

This work proposes a compact antenna design for various terminal devices application. Good agreement between the simulated and measured results validates the design. I. Introduction A known challenge in designing the embedded antenna for terminal devices application is always the compromise between the antenna size and its performance under a specified working scenario. More specifically, users have come to expect

Cheng-Nan Hu; Jing-Wei Huang; D. C. Chang

2011-01-01

423

Compact Five-Gun Cathode Ray Tube.  

National Technical Information Service (NTIS)

The objective of this contract was to develope a compact five-gun cathode ray tube similar to thE JAN-7YP2, but restricted to an overall length of 12 inches. Initial efforts during this period were directed towards design and tooling of a suitable glass e...

G. E. Hassler

1970-01-01

424

Compact Tactile Sensors for Robot Fingers  

NASA Technical Reports Server (NTRS)

Compact transducer arrays that measure spatial distributions of force or pressure have been demonstrated as prototypes of tactile sensors to be mounted on fingers and palms of dexterous robot hands. The pressure- or force-distribution feedback provided by these sensors is essential for the further development and implementation of robot-control capabilities for humanlike grasping and manipulation.

Martin, Toby B.; Lussy, David; Gaudiano, Frank; Hulse, Aaron; Diftler, Myron A.; Rodriguez, Dagoberto; Bielski, Paul; Butzer, Melisa

2004-01-01

425

Compact, integrateddynamic holographic memory with refreshed holograms  

Microsoft Academic Search

An innovative architecture for compact, integrated volume holographic memories is described. It is based on phase-conjugate readout and on a modulator -detector - memory array implemented in a silicon integrated circuit. The lensless memory module sustains dynamic read-write holograms by periodic refreshing. The integrated circuit is described and experimentally characterized. Holograms were stored in a prototype storage module that uses

Jean-Jacques P. Drolet; Ernest Chuang; George Barbastathis; Demetri Psaltis

1997-01-01

426

Compact Digital Compass with PCB Fluxgate Sensors  

Microsoft Academic Search

The new compact digital compass with PCB fluxgate sensors and accelerometers will be introduced in this contribution. Competitive low-cost, low-accuracy compasses are dedicated for measurement in horizontal plane only. The main advantage of developed compass is that it is able to determine azimuth in every position. The compass module consists of a tri axial fluxgate magnetometer and tri axial MEMS

J. Vcelak; V. Petrucha; P. Kaspar

2006-01-01

427

Investigation of HMA compactability using GPR technique  

NASA Astrophysics Data System (ADS)

In-situ field density is often regarded as one of the most important controls used to ensure that an asphalt pavement being placed is of high quality. The achieved density results from the effectiveness of the applied compaction mode on the Hot Mix Asphalt (HMA) layer. It is worthwhile mentioning that the proper compaction of HMA increases pavement fatigue life, decreases the amount of permanent deformation or rutting, reduces the amount of oxidation or aging, decreases moisture damage or stripping, increases strength and internal stability, and may decrease slightly the amount of low-temperature cracking that may occur in the mix. Conventionally, the HMA density in the field is assessed by direct destructive methods, including through the cutting of samples or drilling cores. These methods are characterized by a high accuracy, although they are intrusive and time consuming. In addition, they provide local information, i.e. information only for the exact test location. To overcome these limitations, the use of non-intrusive techniques is often recommended. The Ground Penetrating Radar (GPR) technique is an example of a non-intrusive technique that has been increasingly used for pavement investigations over the years. GPR technology is practical and application-oriented with the overall design concept, as well as the hardware, usually dependent on the target type and the material composing the target and its surroundings. As the sophistication of operating practices increases, the technology matures and GPR becomes an intelligent sensor system. The intelligent sensing deals with the expanded range of GPR applications in pavements such as determining layer thickness, detecting subsurface distresses, estimating moisture content, detecting voids and others. In addition, the practice of using GPR to predict in-situ field density of compacted asphalt mixture material is still under development and research; however the related research findings seem to be promising. Actually, the prediction is not regulated by any standards or specifications, although the practice is considered to be workable. In view of the above, an extensive experiment was carried out in both the laboratory and the field based on a trial asphalt pavement section under construction. In the laboratory, the study focused on the estimation of the density of HMA specimens achieved through three different roller compaction modes (static, vibratory and a combination of both) targeted to simulate field compaction and assess the asphalt mix compactability. In the field, the different compaction modes were successively implemented on three subsections of the trial pavement section. Along each subsection, GPR data was collected in order to determine the new material's dielectric properties and based on that, to predict its density using proper algorithm. Thus, cores were extracted to be used as ground truth data. The comparison of the new asphalt material compactability as obtained from the laboratory specimens, the predictions based on GPR data and the field cores provided useful information that facilitated the selection of the most effective compaction mode yielding the proper compaction degree in the field. This work benefited from networking activities carried out within the EU funded COST Action TU1208 "Civil Engineering Applications of Ground Penetrating Radar."

Plati, Christina; Georgiou, Panos; Loizos, Andreas

2014-05-01

428

Influence of phase-transition scenarios on the abrupt changes in the characteristics of compact stars  

NASA Astrophysics Data System (ADS)

We study the abrupt changes in the characteristics of compact stars due to the quark deconfinement phase transition. The hadronic phase is described within the relativistic mean-field theory, including a scalar-isovector ?-meson effective field. To describe the quark phase, we use the MIT bag model, in which the interactions between u, d and s quarks inside the bag are taken into account in the one-gluon exchange approximation. We analyze catastrophic changes of the parameters of the near-critical configuration of compact star and compute the amount of the energy released by a corequake for the two extreme cases of the deconfinement phase transition scenarios. The first one corresponds to the ordinary first-order phase transition (Maxwell scenario) and the second one corresponds to the phase transition calculated using the bulk Gibbs equilibrium conditions and global charge neutrality (Glendenning scenario).

Alaverdyan, G. B.

2014-03-01

429

Folding without charges  

PubMed Central

Surface charges of proteins have in several cases been found to function as “structural gatekeepers,” which avoid unwanted interactions by negative design, for example, in the control of protein aggregation and binding. The question is then if side-chain charges, due to their desolvation penalties, play a corresponding role in protein folding by avoiding competing, misfolded traps? To find out, we removed all 32 side-chain charges from the 101-residue protein S6 from Thermus thermophilus. The results show that the charge-depleted S6 variant not only retains its native structure and cooperative folding transition, but folds also faster than the wild-type protein. In addition, charge removal unleashes pronounced aggregation on longer timescales. S6 provides thus an example where the bias toward native contacts of a naturally evolved protein sequence is independent of charges, and point at a fundamental difference in the codes for folding and intermolecular interaction: specificity in folding is governed primarily by hydrophobic packing and hydrogen bonding, whereas solubility and binding relies critically on the interplay of side-chain charges.

Kurnik, Martin; Hedberg, Linda; Danielsson, Jens; Oliveberg, Mikael

2012-01-01

430

Charge breeding techniques  

NASA Astrophysics Data System (ADS)

The numerous newly built and forthcoming post-accelerators for radioactive ions, produced with the isotope separator on-line (ISOL) technique, all have a need for an efficient method to accelerate the precious primary ions. The traditional foil or gas stripping technique was challenged some five to ten years ago by a novel scheme called charge breeding. The transformation from 1 + to n + charged ions takes place inside an Electron Beam Ion Source/Trap (EBIS/T) or Electron Cyclotron Resonance Ion Source/Trap (ECRIS/T) by electron-ion collisions. These charge breeders are located in the low-energy part of the machine before the accelerating structures. Because of the capability of these devices to produce highly charged ions, charge-to-mass ratios between 1/9 and 1/4 are easily obtained. In this article the performance and the features of the two charge breeding concepts will be compared and discussed. An outlook on charge breeders for the next generation of radioactive ion beam facilities is also given.

Wenander, Fredrik

2004-12-01

431

Relativistically spinning charged sphere  

NASA Astrophysics Data System (ADS)

When the equatorial spin velocity v of a charged conducting sphere approaches c, the Lorentz force causes a remarkable rearrangement of the total charge q. Charge of that sign is confined to a narrow equatorial belt at latitudes b??(3)(1-v2/c2)1/2 while charge of the opposite sign occupies most of the sphere’s surface. The change in field structure is shown to be a growing contribution of the “magic” electromagnetic field of the charged Kerr-Newman black hole with Newton’s G set to zero. The total charge within the narrow equatorial belt grows as (1-v2/c2)-(1/4) and tends to infinity as v approaches c. The electromagnetic field, Poynting vector, field angular momentum, and field energy are calculated for these configurations. Gyromagnetic ratio, g factor, and electromagnetic mass are illustrated in terms of a 19th century electron model. Classical models with no spin had the small classical electron radius e2/mc2˜ a hundredth of the Compton wavelength, but models with spin take that larger size but are so relativistically concentrated to the equator that most of their mass is electromagnetic. The method of images at inverse points of the sphere is shown to extend to charges at points with imaginary coordinates.

Lynden-Bell, D.

2004-11-01

432

Relativistically spinning charged sphere  

SciTech Connect

When the equatorial spin velocity v of a charged conducting sphere approaches c, the Lorentz force causes a remarkable rearrangement of the total charge q. Charge of that sign is confined to a narrow equatorial belt at latitudes b{<=}{radical}(3)(1-v{sup 2}/c{sup 2}){sup 1/2} while charge of the opposite sign occupies most of the sphere's surface. The change in field structure is shown to be a growing contribution of the 'magic' electromagnetic field of the charged Kerr-Newman black hole with Newton's G set to zero. The total charge within the narrow equatorial belt grows as (1-v{sup 2}/c{sup 2}){sup -(1/4)} and tends to infinity as v approaches c. The electromagnetic field, Poynting vector, field angular momentum, and field energy are calculated for these configurations. Gyromagnetic ratio, g factor, and electromagnetic mass are illustrated in terms of a 19th century electron model. Classical models with no spin had the small classical electron radius e{sup 2}/mc{sup 2}{approx} a hundredth of the Compton wavelength, but models with spin take that larger size but are so relativistically concentrated to the equator that most of their mass is electromagnetic. The method of images at inverse points of the sphere is shown to extend to charges at points with imaginary coordinates.

Lynden-Bell, D. [Institute of Astronomy, The Observatories, Madingley Road, Cambridge, CB3 0HA (United Kingdom) and Clare College, Cambridge (United Kingdom)

2004-11-15

433

Charged particle detection using swept charge devices  

NASA Astrophysics Data System (ADS)

Airless planetary bodies like the Moon allow us to remotely sense their surface elemental composition using the technique of X-Ray Fluorescence (XRF) spectroscopy. An array of twenty four Swept Charge Devices (SCDs) will form the Chandrayaan-2 Large Area Soft X-ray Spectrometer (CLASS) to be flown on Chandrayaan-2 for XRF studies of the lunar surface. The innovative SCD can provide better X-ray spectroscopic performance at higher operating temperatures compared to X-ray CCDs. However the fluorescent spectra produced by X-rays from the sun can also be contaminated by Particle Induced X-ray Emissions (PIXE). In order to estimate the PIXE contribution to the observed X-ray spectrum, it is required to have a simultaneous measurement of charged particle flux in the lunar orbit. Tests are being conducted in this regard to test the feasibility of using one of the SCDs of CLASS for charged particle detection. Experiments have been carried out where a scintillator of suitable thickness is placed over an SCD to convert it into a particle detector. Preliminary results of these experiments will be presented in this work.

Unnikrishnan, Uma; Sudhakar, M.; Tyagi, A.; Bug, M.; Radhakrishna, V.; Athiray, P. S.

434

The effect of temperature of magnetic pulsed compaction on the characteristics of nanostructured aluminum compacts  

Microsoft Academic Search

Magnetic pulse compaction (MPC) allows one to maintain a nanostructured state in nano powder metallic compacts and to achieve\\u000a near theoretical density. In this study, nano Al powders of about 80 nm in diameter were prepared with the Pulse Wire Evaporation\\u000a (PWE) method and passivated with a thin Al2O3 layer on a surface about 2 nm thick to prevent further

Geun Hee Lee; Chang Kyu Rhee; Whung Whoe Kim; Victor V. Ivanov

2003-01-01

435

Charge gradient microscopy  

PubMed Central

Here we present a simple and fast method to reliably image polarization charges using charge gradient microscopy (CGM). We collected the current from the grounded CGM probe while scanning a periodically poled lithium niobate single crystal and single-crystal LiTaO3 thin film on the Cr electrode. We observed current signals at the domains and domain walls originating from the displacement current and the relocation or removal of surface charges, which enabled us to visualize the ferroelectric domains at a scan frequency above 78 Hz over 10 ?m. We envision that CGM can be used in high-speed ferroelectric domain imaging and piezoelectric energy-harvesting devices.

Hong, Seungbum; Tong, Sheng; Park, Woon Ik; Hiranaga, Yoshiomi; Cho, Yasuo; Roelofs, Andreas

2014-01-01

436

Fluid-Assisted Compaction and Deformation of Reservoir Lithologies.  

National Technical Information Service (NTIS)

The compaction and diagenesis of sandstones that form reservoirs to hydrocarbons depend on mechanical compaction processes, fluid flow at local and regional scales, and chemical processes of dissolution, precipitation and diffusional solution transport. T...

A. K. Kronenberg F. M. Chester J. S. Chester A. Hajash W. He S. Karner S. Lenz

2002-01-01

437

Computed tomography of INEL New Production Reactor target compacts.  

National Technical Information Service (NTIS)

Gamma-ray computed tomography (CT) is a potentially powerful nondestructive method for assessing New Production Reactor (NPR) target compacts and assemblies at Idaho National Engineering Laboratory. These target compacts are made up of numerous compressed...

G. P. Roberson H. E. Martz D. R. Rikard L. O. Hester T. J. Roney

1993-01-01

438

18 CFR 420.23 - Exempt uses under the Compact.  

...23 Conservation of Power and Water Resources DELAWARE RIVER BASIN COMMISSION ADMINISTRATIVE MANUAL BASIN REGULATIONS-WATER...under the Compact. (a) Section 15.1(b) of the Delaware River Basin Compact provides that “no provision of...

2014-04-01

439

Chemical Compaction Aids for Fine-Grained Soils. Volume 1.  

National Technical Information Service (NTIS)

Soil is man's cheapest and most abundant construction material, and compaction is the most widely used method of strengthening soils and making them suitable for construction uses. The technology of compaction, while improving, remains largely in a trial ...

J. M. Hoover R. L. Handy

1979-01-01

440

Effect of Compaction and Preforming Parameters on the Compaction Behavior of Bindered Textile Preforms for Automated Composite Manufacturing  

NASA Astrophysics Data System (ADS)

The effect of compaction and preforming parameters on the Fiber Volume Fraction (FVF) and the Residual Preform Thickness (RPT) of bindered textile preforms during a compaction experiment was investigated by using Taguchi method. Four compaction and preforming parameters of compaction temperature (A), binder activation temperature (B), binder content (C) and binder activation time (D) were selected and optimized with respect to the FVF at specified compaction pressure (0.2 MPa) and the RPT after compaction. The results reveal that the compaction behavior of bindered textile preforms has been significantly influenced due to the presence of preforming binder. From all the selected experiment parameters the compaction temperature is the most influential factors on the FVF and RPT. The significant sequence of the parameters for the resulting FVF can be concluded as ABDC, which represents compaction temperature, binder activation temperature, binder activation time and binder content respectively, while this sequence is changed as ADCB as far as the RPT is concerned. The FVF during compaction and RPT during release were correlated with the compaction and preforming parameters using a modified four-parameter-compaction-model which has been proposed for describing the compaction behavior of bindered textile preforms.

Wu, Wangqing; Jiang, Binyan; Xie, Lei; Klunker, Florian; Aranda, Santiago; Ziegmann, Gerhard

2013-10-01

441

Methodology for modeling viscoelastic, uniaxial, and roller compacted pharmaceutical powders  

Microsoft Academic Search

Roller compaction is a pharmaceutical unit operation typically scaled-up and controlled through trial and error to produce compacted powders with specific qualities. The goal of this research was to develop a methodology to predict final roller compact properties based on raw material properties and process conditions for use in scale-up and control. Uniaxial compacts were created with an Instron\\/Sintech universal

Anna Rose Alsman Hayes

2008-01-01

442

Porosity effect on the electrical conductivity of sintered powder compacts  

Microsoft Academic Search

A new equation for calculating the electrical conductivity of sintered powder compacts is proposed. In this equation, the\\u000a effective resistivity of porous compacts is a function of the fully dense material conductivity, the porosity of the compact\\u000a and the tap porosity of the starting powder. The new equation is applicable to powder sintered compacts from zero porosity\\u000a to tap porosity.

J. M. Montes; F. G. Cuevas; J. Cintas

2008-01-01

443

The influence of crushed rock salt particle gradation on compaction  

SciTech Connect

This paper presents results of laboratory compaction testing to determine the influence of particle size, size gradation and moisture-content on compaction of crushed rock salt. Included is a theoretical analysis of the optimum size gradation. The objective is to evaluate the relative densities that can be achieved with tamping techniques. Initial results indicate that compaction increases with maximum particle size and compaction energy, and varies significantly with article size gradation and water content.

Ran, C.; Daemen, J.J.K. [Univ. of Nevada, Reno, NV (United States)

1994-12-31

444

Uncertainty analysis of basin scale compaction processes  

NASA Astrophysics Data System (ADS)

The dynamic evolution of porosity distribution in sedimentary basins has been typically interpreted by assuming that mechanical compaction is the dominant process. While mechanical compaction is particularly relevant during the early burial phase and has been often assumed to play a key role in the diagenesis even at the largest depths, temperature-activated geochemical compaction has been recognized as a major component driving the evolution of the basin characteristics and of the compaction process at least within the deepest layers. As a consequence, modeling basin evolution requires solving a coupled system involving partial differential equations and algebraic relationships between state variables. In this framework, quartz cementation and smectite-illite transformation are recognized to be the most relevant processes affecting sedimentary basins evolution. Spatial and temporal scales of basin evolution are intrinsically very large and it is often difficult to provide reliable estimates for the parameters included in the selected geochemical and compaction models. In this study we focus on the effects that the coupling between the quartz cementation process and mechanical compaction have on the distribution of porosity, pressure and temperature in the evolving sedimentary basin in the presence of uncertain model parameters and boundary conditions. We quantify uncertainty associated with the system state variables by means of a Global Sensitivity Analysis (GSA). The methodology is framed within the context of a generalized Polynomial Chaos Expansion (GPCE) approximation of a basin-scale evolution scenario. Sparse grids sampling techniques are employed to improve the computational efficiency of the methodology. The theoretical and computational framework adopted allows an efficient computation of the variance-based Sobol indices, exploiting a polynomial interpolation over the sparse grid collocation points. An additional advantage of the GPCE is that it yields a surrogate model of the system behavior. This can be exploited within the context of uncertainty propagation studies, e.g., based on numerical Monte Carlo simulations. It allows observing the space-time evolution of the probability density distribution (and its statistical moments) of target problem variables. The approach is illustrated through a one-dimensional example involving the process of quartz cementation in sandstones and the resulting effects on the dynamics of porosity, temperature and pressure.

Formaggia, L.; Guadagnini, A.; Imperiali, I.; Lever, V.; Porta, G.; Riva, M.; Scotti, A.; Tamellini, L.

2012-04-01

445

Structural and electronic properties of neutral and charged Ca 8C 12 metal carbides  

NASA Astrophysics Data System (ADS)

This Letter reports our detailed first-principles study on neutral and charged Ca 8C 12 clusters. Except a compact structure owning geometrical characters of the CaC 2 bulk, all the other low-lying structures within 0.2 eV in relative total energy are hollow configurations. Most of the low-lying structures are calculated to be magnetic. The ground states are a D3d flat structure, a compact structure, and a D3d hollow cage-like structure for Ca 8C 12, CaC12-, and CaC12+ clusters, respectively. The net charge on Ca ion, except the dangling one of the compact structure, is calculated to be around +1.4e.

Chen, Gang; Peng, Qi; Kawazoe, Yoshiyuki

2011-05-01

446

Photoinduced Charge Transfer Process  

NASA Astrophysics Data System (ADS)

The photoinduced charge transfer process is the fundamental process in a photovoltaic system. Organic photovoltaics contain a donor-acceptor molecular system which undergoes photoinduced charge transfer leading to a large dipole moment. Often the charge transfer properties of such donor-acceptor systems are measured in solution. The dipole moments on the solvent molecules creates a reaction field. To simulate this reaction field we adopt an approach similar to the explicit solvent model proposed by Washel and co-workers. We use Monte Carlo simulations to determine various possible solvent structures. We use a carotenoid-porphyrin-C60 molecular triad as the light-harvesting system. This molecular triad has a very large dipole moment (153 Debye) in the charge separated state. The resulting solvent structures and the reaction field as a function of temperature will be presented.

Basurto, Luis; Baruah, Tunna; Zope, Rajendra; Rodriguez, Jose

2011-10-01

447

Charged Current Review.  

National Technical Information Service (NTIS)

Experimental measurements of the pi lifetime and leptonic branching ratios are combined to give updated world averages for these quantities. The results are then used to test the university of the electroweak charged current couplings to the three lepton ...

S. H. Robertson

2001-01-01

448

Benchmark Airport Charges  

NASA Technical Reports Server (NTRS)

The Netherlands Directorate General of Civil Aviation (DGCA) commissioned Hague Consulting Group (HCG) to complete a benchmark study of airport charges at twenty eight airports in Europe and around the world, based on 1996 charges. This study followed previous DGCA research on the topic but included more airports in much more detail. The main purpose of this new benchmark study was to provide insight into the levels and types of airport charges worldwide and into recent changes in airport charge policy and structure, This paper describes the 1996 analysis. It is intended that this work be repeated every year in order to follow developing trends and provide the most up-to-date information possible.

deWit, A.; Cohn, N.

1999-01-01

449

The Punch Charge.  

National Technical Information Service (NTIS)

The punch charge is a novel metal-explosive configuration used to produce relatively large-diameter holes through steel target plates. The report treats several design configurations and describes the corresponding target response patterns in steel plates...

J. Pearson

1973-01-01

450

Can Water Store Charge?  

PubMed Central

Previous work from this and other laboratories has demonstrated large pH gradients in water. Established by passing current between immersed electrodes, pH gradients between electrodes were found to disappear slowly, persisting for tens of minutes after the current had been turned off. We find here that these pH gradients reflect a genuine separation of charge: at times well after disconnection of the power supply, current could be drawn through a resistor placed between the charging electrodes or between pairs of electrodes positioned on either side of the midline between original electrodes. In some experiments, it was possible to recover the majority of charge that had been imparted to the water. It appears, then, that water has the capacity to store and release substantial amounts of charge.

Ovchinnikova, Kate; Pollack, Gerald H.

2010-01-01

451

Uniqueness of charged static asymptotically flat black holes in dynamical Chern-Simons gravity  

NASA Astrophysics Data System (ADS)

Making use of the conformal positive energy theorem, we prove the uniqueness of four-dimensional static electrically charged black holes being the solution of Chern-Simons modified gravity equations of motion. We assume that black hole spacetime contains an asymptotically flat spacelike hypersurface with compact interior and nondegenerate components of the event horizon.

Rogatko, Marek

2013-07-01

452

Particle-Charge Spectrometer  

NASA Technical Reports Server (NTRS)

An instrument for rapidly measuring the electric charges and sizes (from approximately 1 to approximately 100 micrometers) of airborne particles is undergoing development. Conceived for monitoring atmospheric dust particles on Mars, instruments like this one could also be used on Earth to monitor natural and artificial aerosols in diverse indoor and outdoor settings for example, volcanic regions, clean rooms, powder-processing machinery, and spray-coating facilities. The instrument incorporates a commercially available, low-noise, ultrasensitive charge-sensing preamplifier circuit. The input terminal of this circuit--the gate of a field-effect transistor--is connected to a Faraday-cage cylindrical electrode. The charged particles of interest are suspended in air or other suitable gas that is made to flow along the axis of the cylindrical electrode without touching the electrode. The flow can be channeled and generated by any of several alternative means; in the prototype of this instrument, the gas is drawn along a glass capillary tube (see upper part of figure) coaxial with the electrode. The size of a particle affects its rate of acceleration in the flow and thus affects the timing and shape of the corresponding signal peak generated by the charge-sensing amplifier. The charge affects the magnitude (and thus also the shape) of the signal peak. Thus, the signal peak (see figure) conveys information on both the size and electric charge of a sensed particle. In experiments thus far, the instrument has been found to be capable of measuring individual aerosol particle charges of magnitude greater than 350 e (where e is the fundamental unit of electric charge) with a precision of +/- 150 e. The instrument can sample particles at a rate as high as several thousand per second.

Fuerstenau, Stephen; Wilson, Gregory R.

2008-01-01

453

Electrically charged targets  

DOEpatents

Electrically chargeable laser targets and method for forming such charged targets in order to improve their guidance along a predetermined desired trajectory. This is accomplished by the incorporation of a small amount of an additive to the target material which will increase the electrical conductivity thereof, and thereby enhance the charge placed upon the target material for guidance thereof by electrostatic or magnetic steering mechanisms, without adversely affecting the target when illuminated by laser energy.

Goodman, Ronald K. (Livermore, CA); Hunt, Angus L. (Alamo, CA)

1984-01-01

454

Modeling of spacecraft charging  

NASA Technical Reports Server (NTRS)

Three types of modeling of spacecraft charging are discussed: statistical models, parametric models, and physical models. Local time dependence of circuit upset for DoD and communication satellites, and electron current to a sphere with an assumed Debye potential distribution are presented. Four regions were involved in spacecraft charging: (1) undisturbed plasma, (2) plasma sheath region, (3) spacecraft surface, and (4) spacecraft equivalent circuit.

Whipple, E. C., Jr.

1977-01-01

455

On Haar Measure in Locally Compact T2 Spaces.  

National Technical Information Service (NTIS)

Let G be a group of homeomorphisms of a locally compact Hausdorff space X onto itself. If for each disjoint pair of compact sets there is a non-empty open set, no image of which meets both of the compact sets simultaneously, then there is a non-trivial re...

R. C. Steinlage

1971-01-01

456

Suction and water uptake in unsaturated compacted bentonite  

Microsoft Academic Search

Suction is an important process dominating water movement in unsaturated compacted bentonite. Suction measurements were carried out to investigate the characteristics of suction in unsaturated compacted bentonite for the buffer of a HLW repository. The suction values decreased with increasing the water content at a given dry density, and it revealed higher value at the higher dry density of compacted

Jae Owan Lee; Won Jin Cho; Sangki Kwon

2011-01-01

457

A large deformation finite element model for soil compaction  

Microsoft Academic Search

Soil compaction involves a reduction in volume of the soil mass, which has been considered as one of the most important methods to increase geomaterials' strength in geotechnical engineering practice. This paper presents a numerical model to simulate soil compaction using a finite deformation finite element approach. The fundamental formulations for soil compaction are introduced first. Then the model is

Kaiming Xia

2011-01-01

458

A large deformation finite element model for soil compaction  

Microsoft Academic Search

Soil compaction involves a reduction in volume of the soil mass, which has been considered as one of the most important methods to increase geomaterials' strength in geotechnical engineering practice. This paper presents a numerical model to simulate soil compaction using a finite deformation finite element approach. The fundamental formulations for soil compaction are introduced first. Then the model is

Kaiming Xia

2012-01-01

459

Applied mechanics modeling of granulated ceramic powder compaction  

Microsoft Academic Search

In ceramic manufacturing processes such as dry-pressing, correlations between applied compacting pressure and resultant powder compact density are essential for defining reliable process conditions for ceramic components. Pressure-density diagrams have been developed as a tool for both process control and for understanding the compaction behavior of different powders. These types of diagrams, however, pertain only to the averag@ properties of

F. M. Mahoney; M. J. Readey

1995-01-01

460

Soil-water characteristic curves for compacted clays  

SciTech Connect

Soil-water characteristic curves (SWCCs) are presented for four compacted clay barrier soils that were prepared at different compaction water contents (dry, wet, and optimum water content) and compactive efforts (standard and modified Proctor). The SWCCs were measured in the laboratory using pressure plate extractors. The shape of the SWCC depends on compaction water content and compactive effort, but compaction water content is more important. Compaction at higher compaction water content or with greater compactive effort results in larger air entry. Also, clays with higher plasticity index have greater air-entry suction. Changes in the shape of the SWCC are consistent with changes in pore size that occur by varying compaction conditions and with the mineralogical composition of the soils. These changes in the SWCC also are reflected in the van Genuchten and Brooks-Corey parameters, which were obtained from least-squares fits to the SWCC data. Regression equations are presented that can be used to estimate the van Genuchten parameters {alpha} and n from compaction water content, compactive effort, and plasticity index.

Tinjum, J.M. [CH2M Hill, Inc., Denver, CO (United States); Benson, C.H.; Blotz, L.R. [Univ. of Wisconsin, Madison, WI (United States). Dept. of Civil and Environmental Engineering

1997-11-01

461

Regeneration of compacted soil aggregates by earthworm activity  

Microsoft Academic Search

Soil compaction is a problem of modern agriculture, caused by heavy machinery when used in unsuitable, especially moist, conditions. Some regeneration processes in compacted loess soil were studied in a field experiment near Relliehausen, at the edge of the Solling mountains in Lower Saxony, Germany. Conventional tillage (CT) and conservation tillage (CS) systems were compared. The compaction was induced by

O. Larink; D. Werner; M. Langmaack; S. Schrader

2001-01-01

462

ON b-WEAKLY COMPACT OPERATORS ON BANACH LATTICES  

Microsoft Academic Search

In this paper every b-weakly compact operator is shown to factor through a KB-space. Also we give some necessary and sufficient conditions for a continuous operator T : E ? X from a Banach lattice into a Banach space to be a b-weakly compact. Moreover, we investigated the order structure of b-weakly compact operator.

Birol Altin

463

Multifunctional graded index TiO2 compact layer for performance enhancement in dye sensitized solar cell  

NASA Astrophysics Data System (ADS)

A specially tailored index TiO2 compact layer (arc-TiO2) has been successfully deposited to serve as photoanode of a dye-sensitized solar cell (DSSC) by radio-frequency magnetron sputtering. The employment of the TiO2 compact layer in the DSSC was systematically investigated by means of UV-absorption spectra, incident photon to current efficiency (IPCE), open-circuit voltage decay (OCVD) and electrochemical impedance spectroscopy (EIS). The higher and red-shifted transmittance spectra of the ITO/arc-TiO2 electrode mimic the IPCE spectra of the DSSC, in a specific wavelength region. Furthermore, the blue-shift of the UV-absorption spectra and lower R1 value obtained from EIS measurements implied the decrease of the charge interfacial resistance, and this consequently facilitates the charge transport from the nanocrystalline-TiO2 to the ITO. The integrated effects of the arc-TiO2 compact layer originate the remarkable improvement in this type of DSSC applications. As a result, the arc-TiO2-based DSSC showed higher conversion efficiency of about 4.38%, representing almost 53% increment compared to bare ITO cell. This work also discuss the fundamental insight of the compact layer that determines the origin of such improvement in the DSSC performance.

Abdullah, M. H.; Rusop, M.

2013-11-01

464

Compact F-theory GUTs with U(1)PQ  

NASA Astrophysics Data System (ADS)

We construct semi-local and global realizations of SU(5) GUTs in F-theory that utilize a U(1)PQ symmetry to protect against dimension four proton decay. Symmetries of this type, which assign charges to H u and H d that forbid a tree level ? term, play an important role in scenarios for neutrino physics and gauge mediation that have been proposed in local F-theory model building. As demonstrated in [1], the presence of such a symmetry implies the existence of non-GUT exotics in the spectrum, when hypercharge flux is used to break the GUT group and to give rise to doublet-triplet splitting. These exotics are of precisely the right type to solve the unification problem in such F-theory models and might also comprise a non-standard messenger sector for gauge mediation. We present a detailed description of models with U(1)PQ in the semi-local regime, which does not depend on details of any specific Calabi-Yau four-fold, and then specialize to the geometry of [2] to construct three-generation examples with the minimal allowed number of non-GUT exotics. Among these, we find a handful of models in which the D3-tadpole constraint can be satisfied without requiring the introduction of anti-D3-branes, though this analysis does not incorporate contributions from additional fluxes that will ultimately be needed for moduli stabilization. Finally, because SU(5) singlets that carry U(1)PQ charge may serve as candidate right-handed neutrinos or can be used to lift the exotics, we study their origin in compact models and motivate a conjecture for how to count their zero modes in a semi-local setting.

Marsano, Joseph; Saulina, Natalia; Schäfer-Nameki, Sakura

2010-04-01

465

Role of electric charge in shaping equilibrium configurations of fluid tori encircling black holes  

NASA Astrophysics Data System (ADS)

Astrophysical fluids may acquire nonzero electrical charge because of strong irradiation or charge separation in a magnetic field. In this case, electromagnetic and gravitational forces may act together and produce new equilibrium configurations, which are different from the uncharged ones. Following our previous studies of charged test particles and uncharged perfect fluid tori encircling compact objects, we introduce here a simple test model of a charged perfect fluid torus in strong gravitational and electromagnetic fields. In contrast to ideal magnetohydrodynamic models, we consider here the opposite limit of negligible conductivity, where the charges are tied completely to the moving matter. This is an extreme limiting case which can provide a useful reference against which to compare subsequent more complicated astrophysically motivated calculations. To clearly demonstrate the features of our model, we construct three-dimensional axisymmetric charged toroidal configurations around Reissner-Nordström black holes and compare them with equivalent configurations of electrically neutral tori.

Ková?, Ji?í; Slaný, Petr; Stuchlík, Zden?k; Karas, Vladimír; Cremaschini, Claudio; Miller, John C.

2011-10-01

466

Compact airborne staring FPA sensor with microscanning  

NASA Astrophysics Data System (ADS)

As staring focal plane array (FPA) detectors become more readily available, imaging IR sensors can be constructed in more compact packages that are lighter and consume less power than first or second generation scanning IR sensor packages. However, FPA detector-based imagers typically demonstrate reduced resolution when compared to scanning systems with similar instantaneous-field-of-view. This resolution limitation is created by a the active pixel size and the spatially synchronous scene sampling native to staring FPA systems. A technique called microscanning can be used to improve the resolution of staring systems by over-sampling the scene; moving the image of the scene on the detector in a controlled fashion. This paper presents a compact MWIR staring FPA airborne forward looking infrared sensor design using microscanning for resolution improvement.

Sanders, John; Wan, William H.; Harris, Van; Newton, Dave; Tylinski, George; Wolschon, Mark; Imamura, Joe

1996-06-01

467

Compact AMS System At Yamagata University  

SciTech Connect

A new compact accelerator mass spectrometry (AMS) system has been installed in the Kaminoyama research institute at Yamagata University. The AMS system is based on a 0.5 MV Pelletron accelerator developed by National Electrostatics Corp. The performance of the system was investigated using C series samples (C1-C8), standard samples (HOxII), and reagent graphite without any chemical treatment. The precision of {sup 14}C measurements for the standard samples is typically higher than 0.3%. The ratio of {sup 14}C to {sup 12}C is less than 6x10{sup -16} for the reagent graphite. In this paper, we present the performance of the new compact AMS system, as well as of the fully automated 20-reactor graphite lines equipped at the research institute.

Tokanai, Fuyuki; Kato, Kazuhiro; Anshita, Minoru; Izumi, Akihiro; Sakurai, Hirohisa [Department of Physics, Faculty of Science, Yamagata University, Yamagata 990-8560 (Japan); Saito, Tsugio [Electronics equipment division, Hakuto Co., Ltd., Tokyo 160-8910 (Japan)

2011-06-01

468

Metagratings for Diffraction Based, Compact, Holographic Imaging  

NASA Astrophysics Data System (ADS)

Recent developments in semiconductor technology brought to life a new generation of highly-compact visible-frequency cameras. Unfortunately, straight forward extension of this progress to low-frequency domains (such as mid-IR imaging) is impossible since the pixel size at these frequencies is limited by free-space diffraction limit. Here we present an approach to realize highly-compact imaging systems at lower frequencies. Our approach takes advantage of high refractive index of materials commonly utilized in semiconductor detectors of mid-IR radiation, accompanied by metagratings, structures with engineered diffraction properties, to achieve a 10-fold reduction in the pixel size. In contrast to conventional refraction-based imaging, the approach essentially produces a digital hologram -- a 2D projection of the 3D optical field, enabling a post-imaging ``refocusing'' of the picture. The perspectives of numerical recovery of the optical field and the stability of such recovery are discussed.

Inampudi, Sandeep; Podolskiy, Viktor A.

2013-03-01

469

Compact fluorescence spectroscopic tool for cancer detection  

NASA Astrophysics Data System (ADS)

We describe a compact fluorescence spectroscopic tool for in vivo point monitoring of aminolaevulinic acid (ALA)-induced protoporphyrin IX (PpIX) fluorescence and autofluorescence, as a non-invasive method of differentiating normal and cancerous tissue. This instrument incorporates a 405nm diode laser with a shutter to prevent exposure of tissue to harmful light doses and reduce photobleaching, a bifurcated optical fibre to allow illumination of tissue and collection of fluorescence with a single fibre, a compact grating spectrometer for collection of spectra and a PC for system control. We present spectra obtained using this system both during routine gastro-intestinal (GI) endoscopy for cancer detection and during photodynamic therapy (PDT) of anal intraepithelial neoplasia (AIN) for monitoring of treatment progress. These results illustrate the potential of the system to be used for fluorescence monitoring in a variety of clinical applications.

Nadeau, Valerie; Hamdan, Khaled; Hewett, Jacqueline; Makaryceva, Juljia; Tait, Iain; Cuschieri, Alfred; Padgett, Miles J.

2002-05-01

470

Dense Quark Matter in Compact Stars  

NASA Astrophysics Data System (ADS)

According to quantum chromodynamics (QCD), matter at ultra-high densities will take the form of a color-superconducting quark liquid, in which there is a condensate of Cooper pairs of quarks near the Fermi surface. I present a review of the physics of color superconductivity, and discuss possible signatures by which it might be detected in compact stars. I give a detailed discussion of the effects of color superconductivity on the mass-radius relationship of compact stars, showing that one would have to fix the bag constant by other measurements in order to see the effects of color superconductivity. An additional parameter in the quark matter equation of state connected with perturbative corrections allows quark matter to imitate nuclear matter over the relevant density range, so that hybrid stars can show a mass-radius relationship very similar to that of nuclear matter, and their masses can reach 1.9 M?.

Alford, M. G.

2004-04-01

471

A compact, high-performance cryogenic stage  

NASA Astrophysics Data System (ADS)

This paper describes the design concept and performance for a compact, high performance cryogenic upper stage. The design concept, developed during the Compact LOX Feed System Study, involves a toroidal liquid oxygen tank for both high-thrust and low-thrust STS launched OTV's. Study results show that a 17,000 lbm payload having a 38.5 ft maximum length can be delivered by the stage to geosynchronous orbit following deployment from the Orbiter cargo bay. Detailed design and analysis of the storage vessel, fluid management, and thermal control hardware were performed in support of the overall integrated tank design. A single tank configuration was eva